(19)
(11)EP 3 276 814 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
06.05.2020 Bulletin 2020/19

(21)Application number: 17168815.3

(22)Date of filing:  28.04.2017
(51)Int. Cl.: 
H02M 7/487  (2007.01)
H02J 3/38  (2006.01)

(54)

METHOD AND DEVICE FOR CONTROLLING OPERATION OF INVERTER

VERFAHREN UND VORRICHTUNG ZUR STEUERUNG DES BETRIEBS EINES WECHSELRICHTERS

PROCÉDÉ ET DISPOSITIF POUR COMMANDER LE FONCTIONNEMENT D'UN INVERSEUR


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 25.07.2016 CN 201610591490

(43)Date of publication of application:
31.01.2018 Bulletin 2018/05

(73)Proprietor: Sungrow Power Supply Co., Ltd.
Hefei, Anhui 230088 (CN)

(72)Inventors:
  • XU, Jun
    HEFEI, Anhui 230088 (CN)
  • CAO, Jinhu
    HEFEI, Anhui 230088 (CN)
  • CHEN, Peng
    HEFEI, Anhui 230088 (CN)
  • WANG, Peng
    HEFEI, Anhui 230088 (CN)

(74)Representative: Eisenführ Speiser 
Patentanwälte Rechtsanwälte PartGmbB Postfach 31 02 60
80102 München
80102 München (DE)


(56)References cited: : 
EP-A1- 2 611 021
EP-A2- 2 784 926
EP-A1- 3 010 137
CN-A- 105 141 158
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD



    [0001] The present disclosure relates to a field of inverter control, and more particularly to a method and a device for controlling an operation of an inverter.

    BACKGROUND



    [0002] With development of a photovoltaic industry, a system voltage of a photovoltaic assembly increases from 1000V to 1500V. In order to fit a photovoltaic assembly with a system voltage being 1500V, an inverter connected to the photovoltaic assembly generally adopts a five level topology structure.

    [0003] When the inverter with the five level topology structure normally operates, the inverter operates in a five level operation mode, that is, the inverter alternately outputs five different levels in different switching state combinations of switching transistors. As shown in Figure 2, a floating capacitor voltage Ufc is Udc/4 when the inverter with the five level topology structure normally operates. For an output voltage UAN of the inverter, the output voltage has five levels respectively being +Udc/2 (S1 and S7 are switched on), +Udc/4 (S1 and S8 are switched on or S4, S5 and S7 are switched on), 0 (S2, S3 and S7 are switched on or S4, S5 and S8 are switched on), -Udc/4 (S6 and S7 are switched on or S2, S3 and S8 are switched on) and -Udc/2 (S6 and S8 are switched on). S1, S2, S3, S4, S5, S6, S7 and S8 are all switching transistors, Udc is an operation voltage setting threshold when the inverter with the five level topology structure normally operates, Udc is less than 1500V and Udc generally ranges from 800V to 1300V.

    [0004] However, when the inverter starts operation, a direct current side voltage of the inverter is an open-circuit voltage which is 1500V, in order to avoid voltage stresses of the switching transistors S1 and S6 exceeding a withstanding range, the floating capacitor voltage Ufc is pre-charged to a preset value (such as 450V). In this case, the inverter alternately outputs seven different levels in different switching state combinations of switching transistors. For example, the floating capacitor voltage Ufc is pre-charged to 450V that is 3Udc'/10, the output voltage UAN of the inverter in Figure 2 may have seven levels respectively being +Udc'/2 (S1 and S7 are switched on), +Udc'/5 (S1 and S8 are switched on), +3Udc'/10 (S4, S5 and S7 are switched on), 0 (S2, S3 and S7 are switched on or S4, S5 and S8 are switched on), -2Udc'/10 (S6 and S7 are switched on), -3Udc'/10 (S2, S3 and S8 are switched on) and -Udc'/2 (S6 and S8 are switched on), Udc' is 1500V. In this case, if the inverter is still controlled to operate in the five level operation mode, an output current of the inverter may be severely distorted, thereby affecting an operation stability of a whole photovoltaic system.

    [0005] European patent application EP 2 611 021 A1 discloses a power conversion apparatus including a power converter that is configured to perform three-level operation or two-level operation. The power conversion apparatus includes a comparison circuit which compares a determination element related to a loss in the power converter with a switching reference value and outputs a determination instruction when a difference has occurred between the determination element and the switching reference value, a determination circuit which determines whether the determination element is greater or less than the switching reference value when having received a determination instruction from the comparison circuit, and outputs a two-level operation switching instruction when the determination element is greater than or equal to the switching reference value, and a switching circuit which, when having received a two-level operation switching instruction from the determination circuit, turns off the alternating-current switch and turns on the valve devices in the arm sequentially, thereby bringing the power converter into a two-level operation state. Since the characteristics of the photovoltaic cells vary, depending on insolation or temperature conditions, a maximum power point tracking method has been employed to constantly obtain the maximum power.

    [0006] Chinese patent application CN 105141158 A discloses a control method, a device and a system for a five-level inverter. The method comprises the steps of detecting the DC bus voltage of the five-level inverter to be larger than a preset threshold; improving the voltage applied at the two ends of a second energy storage unit; during the high voltage start-up process or the low voltage ride-through process of the five-level inverter, controlling the five-level inverter to run in a two-level or three-level operating mode. In the five-level inverter, the second energy storage unit is connected in parallel with a series circuit composed of a first switch tube and a second switch tube. The voltage applied across the first/second switch tube in the turn-off state is equal to the voltage applied at the two ends of the second energy storage unit. Therefore, when the DC bus voltage of the five-level inverter is comparatively high, the voltage applied at the two ends of the second energy storage unit is improved. In this way, the voltage applied at the two ends of the tube stack composed of the first and second switch tubes is decreased.

    [0007] European patent application EP 3 010 137 A1 discloses a multilevel inverter. The multilevel inverter is possible to safely cut off a voltage output from a main circuit, when a cut-off command is generated, without causing an increase in the size of a cut-off circuit or an increase in the number of wires. A cut-off circuit, when given a first cut-off signal, turns OFF a set of a switching element directly connected to a positive voltage terminal, of an output circuit section, and reverse blocking type switching element, the collector of which is connected to a neutral point of the output circuit section, in a main circuit. Also, the cut-off circuit, when given a second cut-off signal, turns OFF a set of a switching element directly connected to a negative voltage terminal, of the output circuit section, and reverse blocking type switching element, the emitter of which is connected to the neutral point, in the main circuit.

    [0008] European patent application EP 2 784 926 A2 discloses a method of operating a flying capacitor multilevel converter. The multilevel converter has a direct current link and a plurality of phase legs each having a plurality of flying capacitors includes employing redundant states to balance flying capacitor voltages by charging or discharging flying capacitors. The redundant states are employed by obtaining a load current of the flying capacitor multilevel converter. If a load current value is lower than a threshold value then a capacitor current of a phase terminal capacitor is utilized to determine redundant states else a load current direction is utilized to determine the redundant states.

    SUMMARY



    [0009] In order to solve the above technical problem, a method and a device, according to independent method claim 1 and independent apparatus claim 6, respectively for controlling an operation of an inverter is provided according to embodiments of the disclosure to achieve an objection of preventing an output current of an inverter from being distorted caused by the inverter still being controlled according to a five level control strategy in a case that a floating capacitor voltage of the inverter being not in a preset range, thereby improving an operation stability of a whole photovoltaic system. Specific preferred further details of the embodiments are claimed in the dependent claims. Technical solutions are described as follows.

    [0010] A method for controlling an operation of an inverter includes:

    determining whether a direct current side voltage of the inverter is greater than an operation voltage setting threshold; and

    in a case that the direct current side voltage of the inverter is not greater than the operation voltage setting threshold, controlling the inverter to operate according to a five level control strategy;

    and

    in a case that the direct current side voltage of the inverter is greater than the operation voltage setting threshold:

    adjusting the direct current side voltage by using a maximum power tracking algorithm;

    adjusting linearly a floating capacitor voltage of the inverter based on the adjusted direct current side voltage;

    determining whether the adjusted floating capacitor voltage is in a preset range, where the preset range ranges from a quarter of the operation voltage setting threshold minus a preset threshold to a quarter of the operation voltage setting threshold plus the preset threshold; and

    controlling the inverter to operate according to a five level control strategy in a case that the adjusted floating capacitor voltage is in the preset range; and

    controlling the inverter to operate according to a seven level control strategy in a case that the adjusted floating capacitor voltage is not in the preset range.



    [0011] Preferably, after controlling the inverter to operate according to the five level control strategy, the method further includes:

    determining whether the direct current side voltage is greater than a first preset voltage, where the first preset voltage is greater than the operation voltage setting threshold; and

    executing a step of adjusting the direct current side voltage by using the maximum power tracking algorithm in a case that the direct current side voltage is greater than the first preset voltage; and

    controlling the inverter to operate according to the five level control strategy in a case that the direct current side voltage is not greater than the first preset voltage.



    [0012] Preferably, the adjusting linearly the floating capacitor voltage of the inverter based on the adjusted direct current side voltage includes:

    substituting the adjusted direct current side voltage into a preset linear relation formula to obtain a to-be-used floating capacitor voltage; and

    adjusting the floating capacitor voltage to the to-be-used floating capacitor voltage.



    [0013] Preferably, the preset linear relation formula is

    where Udc1 is a direct current side open-circuit voltage of the inverter, Ufc1 is a floating capacitor voltage corresponding to the direct current side open-circuit voltage of the inverter, Udc2 is the operation voltage setting threshold, Ufc2 a floating capacitor voltage corresponding to the operation voltage setting threshold, X is the direct current side voltage of the inverter and Y is the floating capacitor voltage of the inverter.

    [0014] A device for controlling an operation of an inverter includes:

    a first determining unit, configured to determine whether a direct current side voltage of the inverter is greater than an operation voltage setting threshold, where a first controlling unit is executed in a case that the direct current side voltage of the inverter is not greater than the operation voltage setting threshold, and a first adjusting unit is executed in a case that the direct current side voltage of the inverter is greater than the operation voltage setting threshold;

    the first controlling unit, configured to control the inverter to operate according to a five level control strategy;

    the first adjusting unit, configured to adjust the direct current side voltage by using a maximum power tracking algorithm;

    a second adjusting unit, configured to adjust linearly a floating capacitor voltage of the inverter based on the adjusted direct current side voltage;

    a second determining unit, configured to determine whether the adjusted floating capacitor voltage is in a preset range, where the preset range ranges from a quarter of the operation voltage setting threshold minus a preset threshold to a quarter of the operation voltage setting threshold plus the preset threshold, and where the first controlling unit is executed in a case that the adjusted floating capacitor voltage is in the preset range, and a second controlling unit is executed in a case that the adjusted floating capacitor voltage is not in the preset range; and

    the second controlling unit, configured to control the inverter to operate according to a seven level control strategy.



    [0015] Preferably, the device further includes a third determining unit, configured to determine whether the direct current side voltage is greater than a first preset voltage, where the first preset voltage is greater than the operation voltage setting threshold, and where the first adjusting unit is executed in a case that the direct current side voltage is greater than the first preset voltage, and the first controlling unit is executed in a case that the direct current side voltage is not greater than the first preset voltage.

    [0016] Preferably, the second adjusting unit includes:

    a calculating subunit, configured to substitute the adjusted direct current side voltage into a preset linear relation formula to obtain a to-be-used floating capacitor voltage; and

    an adjusting subunit, configured to adjust the floating capacitor voltage to the to-be-used floating capacitor voltage.



    [0017] Preferably, the calculating subunit is specifically configured to substitute the adjusted direct current side voltage into

    to obtain a to-be-used floating capacitor voltage, where Udc1 is a direct current side open-circuit voltage of the inverter, Ufc1 is a floating capacitor voltage corresponding to the direct current side open-circuit voltage of the inverter, Udc2 is the operation voltage setting threshold, Ufc2 a floating capacitor voltage corresponding to the operation voltage setting threshold, X is the direct current side voltage of the inverter and Y is the floating capacitor voltage of the inverter.

    [0018] An inverter includes any one of the above devices for controlling an operation of an inverter.

    [0019] A photovoltaic power generation system includes the above inverter.

    [0020] Compared with the conventional technology, the disclosure has the following advantages. In the disclosure, it is firstly determined whether a direct current side voltage of an inverter is greater than an operation voltage setting threshold. In a case that it is determined that the direct current side voltage is greater than the operation voltage setting threshold, the direct current side voltage of the inverter may be an open-circuit voltage which is 1500V (for example when the inverter starts operation, the direct current side voltage of the inverter is the open-circuit voltage). The inverter alternatively outputs seven different levels. Since a normal operation mode of the inverter is a five level operation mode, in this case, the direct current side voltage is adjusted by using a maximum power tracking algorithm and a floating capacitor voltage of the inverter is linearly adjusted based on the adjusted direct current side voltage, the floating capacitor voltage is adjusted to be in a preset range so to convert the inverter from a seven level operation mode to the five level operation mode. In a case that the floating capacitor voltage is adjusted to be in the preset range, the inverter is controlled to operate according to the five level control strategy. In a case that the floating capacitor voltage is not adjusted to be in the preset range, the inverter is controlled to operate according to the seven level control strategy rather than the five level control strategy to prevent an output current of the inverter from being distorted caused by the inverter still being controlled according to the five level control strategy in a case that the floating capacitor voltage of the inverter being not in the preset range, thereby improving an operation stability of a whole photovoltaic system.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0021] In order to describe technical solutions in embodiments of the present disclosure more clearly, hereinafter drawings to be used in the description of the embodiments are introduced simply. Apparently, the drawings described below only describe some embodiments of the present disclosure. Those skilled in the art can obtain other drawings based on these drawings without any creative work.

    Figure 1 is a flowchart of a method for controlling an operation of an inverter according to the disclosure;

    Figure 2(a) to Figure 2(h) are schematic diagrams of an current flowing path in a case that an inverter operates in a seven level operation mode according to the disclosure;

    Figure 3 is another flowchart of a method for controlling an operation of an inverter according to the disclosure;

    Figure 4 is a sub-flowchart of a method for controlling an operation of an inverter according to the disclosure;

    Figure 5 is a schematic logic structural diagram of a device for controlling an operation of an inverter according to the disclosure;

    Figure 6 is another schematic logic structural diagram of a device for controlling an operation of an inverter according to the disclosure; and

    Figure 7 is a schematic logic structural diagram of an adjusting unit according to the disclosure.


    DETAILED DESCRIPTION OF EMBODIMENTS



    [0022] Technical solutions of embodiments of the present disclosure will be described clearly and completely below in conjunction with the drawings of the embodiments of the disclosure. Apparently, the described embodiments are some rather than all of the embodiments of the present disclosure. Any other embodiments obtained based on the embodiments of the present disclosure by those skilled in the art without any creative work fall within the protection scope of the present disclosure.

    Embodiment 1



    [0023] Reference is made to Figure 1, which is a flowchart of a method for controlling an operation of an inverter according to the disclosure. The method may include steps S11 to S16.

    [0024] In step S11, it is determined whether a direct current side voltage of the inverter is greater than an operation voltage setting threshold. Step S12 is executed in a case that the direct current side voltage of the inverter is not greater than the operation voltage setting threshold. And step S13 is executed in a case that the direct current side voltage of the inverter is greater than the operation voltage setting threshold.

    [0025] It should be noted that, in a case that the direct current side voltage of the inverter is not greater than the operation voltage setting threshold, a voltage stress of each switching transistor in the inverter is in a withstanding range. The inverter operates in a five level operation mode, so step S12 is executed.

    [0026] In a case that the direct current side voltage of the inverter is greater than the operation voltage setting threshold, the voltage stress of the switching transistor in the inverter may exceed the withstanding range of the switching transistor. In this case, in order to prevent the voltage stress of the switching transistor from exceeding the withstanding range of the switching transistor, the inverter does not operate in the five level operation mode (For example, when the inverter starts operation, the direct current side voltage of the inverter is an open-circuit voltage which is 1500V. In order to prevent voltage stresses of the switching transistor S1 and the switching transistor S6 exceeding the withstanding range, a floating capacitor voltage Ufc is pre-charged to a preset value (such as 450V). In this case, the inverter alternately outputs seven different levels in different switching state combinations of switching transistors. So the inverter is not controlled to operate according to a five level control strategy and step S13 is executed.

    [0027] The operation voltage setting threshold is generally 1200V.

    [0028] In step S12, the inverter is controlled to operate according to a five level control strategy.

    [0029] In this embodiment, in a case that the inverter is controlled to operate according to the five level control strategy, the inverter operates in the five level operation mode.

    [0030] A specific process of controlling the inverter to operate according to the five level control strategy includes: adjusting a duty cycle of the inverter according to Ufc=1/4Udc1 to make the inverter alternately output five levels respectively being 0, ±1/4Udc1, ±1/2Udc1 in different switching state combinations of switching transistors. Udc1 is the direct current side voltage of the inverter.

    [0031] In step 13, the direct current side voltage is adjusted by using a maximum power tracking algorithm.

    [0032] In this embodiment, adjusting the direct current side voltage by using the maximum power tracking algorithm includes: tracking an output power of the inverter by using the maximum power tracking algorithm until a maximum output power of the inverter is tracked, and adjusting the direct current side voltage based on the tracked output power.

    [0033] A specific process of tracking an output power of the inverter by using the maximum power tracking algorithm until a maximum output power of the inverter is tracked and adjusting the direct current side voltage based on the tracked output power in the disclosure is the same as a process of tracking an output power of the inverter by using the maximum power tracking algorithm until a maximum output power of the inverter is tracked and adjusting the direct current side voltage based on the tracked output power in the conventional technology, which is not described here.

    [0034] In step S14, a floating capacitor voltage of the inverter is linearly adjusted based on the adjusted direct current side voltage.

    [0035] In step S15, it is determined whether the adjusted floating capacitor voltage is in a preset range. The preset range ranges from a quarter of the operation voltage setting threshold minus a preset threshold to a quarter of the operation voltage setting threshold plus the preset threshold. Step S12 is executed in a case that the adjusted floating capacitor voltage is in the preset range,or step S16 is executed in a case that the adjusted floating capacitor voltage is not in the preset range.

    [0036] In a case that the adjusted floating capacitor voltage is not in the preset range, in order to prevent the voltage stress of the switching transistor from exceeding the withstanding range of the switching transistor, the inverter has to operate in a seven level operation mode, so step S16 is executed.

    [0037] In step S16, the inverter is controlled to operate according to a seven level control strategy.

    [0038] In this embodiment, in a case that the inverter is controlled to operate in the seven level control strategy, the inverter operates in a seven level operation mode.

    [0039] A specific process of controlling the inverter to operate according to the seven level control strategy includes: adjusting a duty cycle of the inverter according to a requirement of the seven level operation mode to make the inverter alternately output seven different levels in different switching state combinations of switching transistors. For example, when the inverter starts operation, the direct current side voltage of the inverter is an open-circuit voltage which is 1500V. In order to prevent a voltage stress of the switching transistor from exceeding the withstanding range, a floating capacitor voltage Ufc is pre-charged to 450V which is 3Udc2/10. A voltage outputted by the inverter may be respectively +Udc2/2, +Udc2/5, +3Udc2/10, 0, -2Udc2/10, -3Udc2/10 and -Udc2/2. Udc2 is the open-circuit voltage which is 1500V.

    [0040] A current flowing path in a case that the inverter operates in the seven level operation mode is the same as a current flowing path in a case that the inverter operates in the five level operation mode.

    [0041] An example is taken to illustrate the current flowing path in a case that the inverter operates in the seven level operation mode. For example, when the inverter starts operation, the direct current side voltage of the inverter is an open-circuit voltage which is 1500V. In order to prevent voltage stresses of the switching transistor S1 and the switching transistor S6 from exceeding the withstanding range, a floating capacitor voltage Ufc is pre-charged to 450V which is 3Udc2/10. Reference is made to Figure 2(a) to Figure 2(h). As shown in Figure 2(a), the switching transistors S1 and S7 are switched on, the output voltage of the inverter is UAN=Udc2/2. As shown in Figure 2(b), the switching transistors S4, S5 and S7 are switched on, the output voltage of the inverter is UAN=Ufc, i.e., (+3Udc2/10). As shown in Figure 2(c), the switching transistors S1 and S8 are switched on, the output voltage of the inverter is UAN=Udc2/2-Ufc. As shown in Figure 2(d), the switching transistors S2, S3 and S7 are switched on, the output voltage of the inverter is UAN=0. As shown in Figure 2(e), the switching transistors S4, S5 and S8 are switched on, the output voltage of the inverter is UAN=0. As shown in Figure 2(f), the switching transistors S6 and S7 are switched on, the output voltage of the inverter is UAN=-Udc2/2+Ufc. As shown in Figure 2(g), the switching transistors S2, S3 and S8 are switched on, the output voltage of the inverter is UAN=-Ufc. As shown in Figure 2(h), the switching transistors S6 and S8 are switched on, the output voltage of the inverter is UAN=-Udc2/2.

    [0042] In the disclosure, it is firstly determined whether a direct current side voltage of an inverter is greater than an operation voltage setting threshold. In a case that it is determined that the direct current side voltage is greater than the operation voltage setting threshold, the direct current side voltage of the inverter may be an open-circuit voltage which is 1500V (for example when the inverter starts operation, the direct current side voltage of the inverter is the open-circuit voltage). The inverter alternatively outputs seven different levels. Since a normal operation mode of the inverter is a five level operation mode, in this case, the direct current side voltage is adjusted by using a maximum power tracking algorithm and a floating capacitor voltage of the inverter is linearly adjusted based on the adjusted direct current side voltage, the floating capacitor voltage is adjusted to be in a preset range so to convert the inverter from a seven level operation mode to the five level operation mode. In a case that the floating capacitor voltage is adjusted to be in the preset range, the inverter is controlled to operate according to the five level control strategy. In a case that the floating capacitor voltage is not adjusted to be in the preset range, the inverter is controlled to operate according to the seven level control strategy rather than the five level control strategy to prevent an output current of the inverter from being distorted caused by the inverter still being controlled according to the five level control strategy in a case that the floating capacitor voltage of the inverter being not in the preset range, thereby improving an operation stability of a whole photovoltaic system.

    Embodiment 2



    [0043] In this embodiment, another method for controlling an operation of an inverter is provided based on the method for controlling an operation of an inverter shown in Figure 1. Reference is made to Figure 3, the method may include steps S31 to S37.

    [0044] In step S31, it is determined whether a direct current side voltage of the inverter is greater than an operation voltage setting threshold. Step S32 is executed in a case that the direct current side voltage of the inverter is not greater than the operation voltage setting threshold. And step S33 is executed in a case that the direct current side voltage of the inverter is greater than the operation voltage setting threshold.

    [0045] In step S32, the inverter is controlled to operate according to a five level control strategy.

    [0046] In step 33, the direct current side voltage is adjusted by using a maximum power tracking algorithm.

    [0047] In step S34, a floating capacitor voltage of the inverter is linearly adjusted based on the adjusted direct current side voltage.

    [0048] In step S35, it is determined whether the adjusted floating capacitor voltage is in a preset range. The preset range ranges from a quarter of the operation voltage setting threshold minus a preset threshold to a quarter of the operation voltage setting threshold plus the preset threshold. Step S32 is executed in a case that the adjusted floating capacitor voltage is in the preset range and step S36 is executed in a case that the adjusted floating capacitor voltage is not in the preset range.

    [0049] In step S36, the inverter is controlled to operate according to a seven level control strategy.

    [0050] A specific process of step S31 to step S36 is the same as a process of step S11 to step S16 of the method for controlling an operation of an inverter shown in Figure 1, which is not described here.

    [0051] In step S37, it is determined whether the direct current side voltage is greater than a first preset voltage. The first preset voltage is greater than the operation voltage setting threshold. Step S33 is executed in a case that the direct current side voltage is greater than the first preset voltage, and step S32 is executed in a case that the direct current side voltage is not greater than the first preset voltage.

    [0052] After the inverter is controlled to operate in the five level operation mode according to the five level control strategy, it is considered that a low temperature makes an effect on a photovoltaic assembly, which may cause an output voltage of the inverter rise from an operation voltage setting threshold (such as 1200 V) to a first preset voltage (such as 1300V) or more. When the output voltage of the inverter rises from the operation voltage setting threshold to the first preset voltage or more, regarding an influence of a voltage spike under full power, a voltage stress of the switching transistor in the inverter rises and may even exceed a voltage stress withstanding range of the switching transistor. In this case, a floating capacitor voltage of the inverter needs to be adjusted to lower the voltage stress of the switching transistor and further ensure an operation stability of a photovoltaic system. Specifically, step S37 is executed after step S32.

    [0053] The above preset threshold is influenced by a specific circuit of an inverter or a photovoltaic system, the preset threshold may be variable. The above preset threshold may be, but not limited to, 20V.

    [0054] In the embodiment 1 and the embodiment 2, a process of adjusting linearly the floating capacitor voltage of the inverter based on the adjusted direct current side voltage may be referred to Figure 4 and may include steps S41 and S42.

    [0055] In step S41, the adjusted direct current side voltage is substituted into a preset linear relation formula to calculate a to-be-used floating capacitor voltage.

    [0056] The preset linear relation formula is obtained based on the above operation voltage setting threshold, a floating capacitor voltage corresponding to the above operation voltage setting threshold, the direct current side voltage of the inverter (that is the open-circuit voltage) when the inverter starts operation and a floating capacitor voltage corresponding to the direct current side voltage of the inverter when the inverter starts operation.

    [0057] In particular, the preset linear relation formula may be

    where Udc1 is a direct current side open-circuit voltage of the inverter, Ufc1 is a floating capacitor voltage corresponding to the direct current side open-circuit voltage of the inverter, Udc2 is the operation voltage setting threshold, Ufc2 a floating capacitor voltage corresponding to the operation voltage setting threshold, X is the direct current side voltage of the inverter and Y is the floating capacitor voltage of the inverter.

    [0058] In step S42, the floating capacitor voltage is adjusted to the to-be-used floating capacitor voltage.

    Embodiment 3



    [0059] Corresponding to the above method embodiments, a device for controlling an operation of an inverter is provided according to this embodiment. Referring to Figure 5, the device for controlling an operation of an inverter includes: a first determining unit 51, a first controlling unit 52, a first adjusting unit 53, a second adjusting unit 54, a second determining unit 55 and a second controlling unit 56.

    [0060] The first determining unit 51 is configured to determine whether a direct current side voltage of the inverter is greater than an operation voltage setting threshold. The first controlling unit 52 is executed in a case that the direct current side voltage of the inverter is not greater than the operation voltage setting threshold, and the first adjusting unit 53 is executed in a case that the direct current side voltage of the inverter is greater than the operation voltage setting threshold.

    [0061] The first controlling unit 52 is configured to control the inverter to operate according to a five level control strategy.

    [0062] The first adjusting unit 53 is configured to adjust the direct current side voltage by using a maximum power tracking algorithm.

    [0063] The second adjusting unit 54 is configured to adjust linearly a floating capacitor voltage of the inverter based on the adjusted direct current side voltage.

    [0064] The second determining unit 55 is configured to determine whether the adjusted floating capacitor voltage is in a preset range, where the preset range ranges from a quarter of the operation voltage setting threshold minus a preset threshold to a quarter of the operation voltage setting threshold plus the preset threshold. The first controlling unit 52 is executed in a case that the adjusted floating capacitor voltage is in the preset range, and the second controlling unit 56 is executed in a case that the adjusted floating capacitor voltage is not in the preset range.

    [0065] The second controlling unit 56 is configured to control the inverter to operate according to a seven level control strategy.

    [0066] In this embodiment, the device for controlling the operation of the inverter shown in Figure 5 may further include a third determining unit 57 as shown in Figure 6. The third determining unit 57 is configured to determine whether the direct current side voltage is greater than a first preset voltage, where the first preset voltage is greater than the operation voltage setting threshold. The first adjusting unit 53 is executed in a case that the direct current side voltage is greater than the first preset voltage, and the first controlling unit 52 is executed in a case that the direct current side voltage is not greater than the first preset voltage.

    [0067] In this embodiment, the second adjusting unit 54 further includes: a calculating subunit 541 and an adjusting subunit 542, as shown in Figure 7.

    [0068] The calculating subunit 541 is configured to substitute the adjusted direct current side voltage into a preset linear relation formula to obtain a to-be-used floating capacitor voltage.

    [0069] In this embodiment, the preset linear relation formula may be

    where Udc1 is a direct current side open-circuit voltage of the inverter, Ufc1 is a floating capacitor voltage corresponding to the direct current side open-circuit voltage of the inverter, Udc2 is the operation voltage setting threshold, Ufc2 a floating capacitor voltage corresponding to the operation voltage setting threshold, X is the direct current side voltage of the inverter and Y is the floating capacitor voltage of the inverter.

    [0070] The calculating subunit 541 is configured to substitute the adjusted direct current side voltage into

    to obtain a to-be-used floating capacitor voltage.

    [0071] The adjusting subunit 542 is configured to adjust the floating capacitor voltage to the to-be-used floating capacitor voltage.

    [0072] The above preset threshold is influenced by a specific circuit of an inverter or a photovoltaic system, the preset threshold may be variable. The above preset threshold may be, but not limited to, 20V.

    Embodiment 4



    [0073] In this embodiment, it is further provided an inverter including the device for controlling the operation of the inverter illustrated in the embodiment 3.

    [0074] Of course, in this embodiment, it is further provided a photovoltaic power generation system including the above inverter.

    [0075] It should be noted that, the various embodiments in the disclosure are described progressively. Each embodiment focuses on the difference from other embodiments. The same or similar parts of the various embodiments can be referred mutually. The device provided by the embodiment is described simply since it corresponds to the method provided by the embodiment, and part of the method description can be referred to, to explain the corresponding parts of the device.

    [0076] Finally, it should be noted that, in the disclosure, relationship terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, which does not require or indicate there exist any real relationships or sequences among those entities or operations. And terms "include", "contain" or any other variants mean to cover non-exclusive containing so to make a process, a method, a product or a device including a series of essential factors not only include these essential factors but also include those essential factors not clearly listed or further include fixed essential factors of the process, the method, the product or the device. In a situation without many limits, an essential factor limited by a sentence "include a ..." does not exclude another same essential factor existing in a process, a method, a product or a device including the descried essential factor.

    [0077] Above, a method and a device for controlling an operation of an inverter provided by the disclosure are specifically illustrated. A principle and the embodiments of the disclosure are illustrated by using specific examples in the description. The above description of the embodiments is used to help understanding a method and a core idea of the disclosure. In addition, for those skilled in the arts, according to the idea of the disclosure, a change is made in the specific embodiments and an applying filed. In summary, contents of the specification should not be understood to limit the disclosure.

    [0078] The present application claims the priority to Chinese Patent Application No. 201610591490.6, titled "METHOD AND DEVICE FOR CONTROLLING OPERATION OF INVERTER", filed on July 25, 2016 with the State Intellectual Property Office of the PRC.


    Claims

    1. A method for controlling an operation of an inverter, comprising:

    determining (S31) whether a direct current side voltage of the inverter is greater than an operation voltage setting threshold; and

    in a case that the direct current side voltage of the inverter is not greater than the operation voltage setting threshold, controlling (S32) the inverter to operate according to a five level control strategy; and

    in a case that the direct current side voltage of the inverter is greater than the operation voltage setting threshold:

    adjusting (S33) the direct current side voltage by using a maximum power tracking algorithm;

    adjusting (S34) linearly a floating capacitor voltage of the inverter based on the adjusted direct current side voltage;

    determining (S35) whether the adjusted floating capacitor voltage is in a preset range, wherein the preset range ranges from a quarter of the operation voltage setting threshold minus a preset threshold to a quarter of the operation voltage setting threshold plus the preset threshold; and

    controlling (S32) the inverter to operate according to a five level control strategy in a case that the adjusted floating capacitor voltage is in the preset range; and

    controlling (S36) the inverter to operate according to a seven level control strategy in a case that the adjusted floating capacitor voltage is not in the preset range.


     
    2. The method according to claim 1, wherein after controlling (S32) the inverter to operate according to the five level control strategy, the method further comprises:

    determining (S37) whether the direct current side voltage is greater than a first preset voltage, wherein the first preset voltage is greater than the operation voltage setting threshold; and

    executing a step of adjusting (S33) the direct current side voltage by using the maximum power tracking algorithm in a case that the direct current side voltage is greater than the first preset voltage; and

    controlling (S32) the inverter to operate according to the five level control strategy in a case that the direct current side voltage is not greater than the first preset voltage.


     
    3. The method according to claim 1 or 2, wherein the adjusting (S34) linearly the floating capacitor voltage of the inverter based on the adjusted direct current side voltage comprises:

    substituting (S41) the adjusted direct current side voltage into a preset linear relation formula to obtain a to-be-used floating capacitor voltage; and

    adjusting (S42) the floating capacitor voltage to the to-be-used floating capacitor voltage.


     
    4. The method according to claim 3, wherein the preset linear relation formula is

    wherein Udc1 is a direct current side open-circuit voltage of the inverter, Ufc1 is a floating capacitor voltage corresponding to the direct current side open-circuit voltage of the inverter, Udc2 is the operation voltage setting threshold, Ufc2 a floating capacitor voltage corresponding to the operation voltage setting threshold, X is the direct current side voltage of the inverter and Y is the floating capacitor voltage of the inverter.
     
    5. A device for controlling an operation of an inverter, comprising:

    a first determining unit (51), configured to determine whether a direct current side voltage of the inverter is greater than an operation voltage setting threshold, and configured to handover control to a first controlling unit (52) in a case that the direct current side voltage of the inverter is not greater than the operation voltage setting threshold, and configured to handover control to a first adjusting unit (53) in a case that the direct current side voltage of the inverter is greater than the operation voltage setting threshold;

    the first controlling unit (52), configured to control the inverter to operate according to a five level control strategy;

    the first adjusting unit (53), configured to adjust the direct current side voltage by using a maximum power tracking algorithm;

    a second adjusting unit (54), configured to adjust linearly a floating capacitor voltage of the inverter based on the adjusted direct current side voltage;

    a second determining unit (55), configured to determine whether the adjusted floating capacitor voltage is in a preset range, wherein the preset range ranges from a quarter of the operation voltage setting threshold minus a preset threshold to a quarter of the operation voltage setting threshold plus the preset threshold, and configured to handover control to the first controlling unit (52) in a case that the adjusted floating capacitor voltage is in the preset range, and configured to handover control to a second controlling unit (56) in a case that the adjusted floating capacitor voltage is not in the preset range; and

    the second controlling unit (56), configured to control the inverter to operate according to a seven level control strategy.


     
    6. The device according to claim 5, further comprising:
    a third determining unit (57), configured to determine whether the direct current side voltage is greater than a first preset voltage, wherein the first preset voltage is greater than the operation voltage setting threshold, and configured to handover control to the first adjusting unit (53) in a case that the direct current side voltage is greater than the first preset voltage, and configured to handover control to the first controlling unit (52) in a case that the direct current side voltage is not greater than the first preset voltage.
     
    7. The device according to claim 5 or 6, wherein the second adjusting unit (54) comprises:

    a calculating subunit (541), configured to substitute the adjusted direct current side voltage into a preset linear relation formula to obtain a to-be-used floating capacitor voltage; and

    an adjusting subunit (542), configured to adjust the floating capacitor voltage to the to-be-used floating capacitor voltage.


     
    8. The device according to claim 7, wherein the calculating subunit (541) is specifically configured to substitute the adjusted direct current side voltage into

    to obtain a to-be-used floating capacitor voltage, wherein Udc1 is a direct current side open-circuit voltage of the inverter, Ufc1 is a floating capacitor voltage corresponding to the direct current side open-circuit voltage of the inverter, Udc2 is the operation voltage setting threshold, Ufc2 a floating capacitor voltage corresponding to the operation voltage setting threshold, X is the direct current side voltage of the inverter and Y is the floating capacitor voltage of the inverter.
     
    9. An inverter comprising the device for controlling an operation of an inverter according to any one of claims 5 to 8.
     
    10. A photovoltaic power generation system comprising the inverter according to claim 9.
     


    Ansprüche

    1. Verfahren zum Steuern eines Betriebs von einem Wechselrichter, umfassend:

    Bestimmen (S31), ob eine gleichstromseitige Spannung des Wechselrichters größer ist als ein Betriebsspannungseinstellschwellenwert; und

    in einem Fall, in dem die gleichstromseitige Spannung des Wechselrichters nicht größer ist als der Betriebsspannungseinstellschwellenwert, Steuern (S32) des Wechselrichters, so dass dieser gemäß einer fünfstufigen Steuerungsstrategie arbeitet; und

    in einem Fall, in dem die gleichstromseitige Spannung des Wechselrichters größer ist als der Betriebsspannungseinstellschwellenwert:

    Anpassen (S33) der gleichstromseitigen Spannung durch Verwenden eines Maximalleistungs- Tracking-Algorithmus;

    lineares Anpassen (S34) einer schwebenden Kondensatorspannung des Wechselrichters, basierend auf der angepassten gleichstromseitigen Spannung;

    Bestimmen (S35), ob die angepasste schwebende Kondensatorspannung in einem voreingestellten Bereich liegt, wobei der voreingestellte Bereich von einem Viertel des Betriebsspannungseinstellschwellenwertes minus einem voreingestellten Schwellenwert bis zu einem Viertel des Betriebsspannungseinstellschwellenwertes plus dem voreingestellten Schwellenwert reicht; und

    Steuern (S32) des Wechselrichters, so dass dieser gemäß einer fünfstufigen Steuerungsstrategie arbeitet, in einem Fall, in dem die angepasste schwebende Kondensatorspannung in dem voreingestellten Bereich liegt, und

    Steuern (S36) des Wechselrichters, so dass dieser gemäß einer siebenstufigen Steuerungsstrategie arbeitet, in einem Fall, in dem die angepasste schwebende Kondensatorspannung nicht in dem voreingestellten Bereich liegt.


     
    2. Verfahren nach Anspruch 1, wobei das Verfahren nach einem Steuern (S32) des Wechselrichters, so dass dieser gemäß der fünfstufigen Steuerungsstrategie arbeitet, des Weiteren umfasst:

    Bestimmen (S37), ob die gleichstromseitige Spannung größer ist als eine erste voreingestellte Spannung, wobei die erste voreingestellte Spannung größer ist als der Betriebsspannungseinstellschwellenwert; und

    Ausführen eines Schrittes des Anpassens (S33) der gleichstromseitigen Spannung durch Verwenden des Maximalleistungs-Tracking-Algorithmus, in einem Fall, in dem die gleichstromseitige Spannung größer ist als die erste voreingestellte Spannung; und

    Steuern (S32) des Wechselrichters, so dass dieser nach der fünfstufigen Steuerungsstrategie arbeitet, in einem Fall, in dem die gleichstromseitige Spannung nicht größer ist als die erste voreingestellte Spannung.


     
    3. Verfahren nach Anspruch 1 oder 2, wobei das lineare Anpassen (S34) der schwebenden Kondensatorspannung des Wechselrichters, basierend auf der angepassten gleichstromseitigen Spannung, umfasst:

    Einsetzen (S41) der angepassten gleichstromseitigen Spannung in eine vorgegebene lineare Beziehungsformel, um eine zu verwendende schwebende Kondensatorspannung zu erhalten; und

    Anpassen (S42) der schwebenden Kondensatorspannung an die zu verwendende schwebende Kondensatorspannung.


     
    4. Verfahren nach Anspruch 3, wobei die vorgegebene lineare Beziehungsformel

    lautet,
    wobei Udc1 eine gleichstromseitige Leerlaufspannung des Wechselrichters ist, Ufc1 eine der gleichstromseitigen Leerlaufspannung des Wechselrichters zugehörige schwebende Kondensatorspannung ist, Udc2 der Betriebsspannungseinstellschwellenwert ist, Ufc2 eine dem Betriebsspannungseinstellschwellenwert zugehörige schwebende Kondensatorspannung ist, X die gleichstromseitige Spannung des Wechselrichters ist und Y die schwebende Kondensatorspannung des Wechselrichters ist.
     
    5. Gerät zum Steuern eines Betriebs von einem Wechselrichter, umfassend:

    eine erste Bestimmungseinheit (51), die konfiguriert ist, um zu bestimmen, ob eine gleichstromseitige Spannung des Wechselrichters größer ist als ein Betriebsspannungseinstellschwellenwert, und die konfiguriert ist, um eine Steuerung an eine erste Steuerungseinheit (52) in einem Fall zu übergeben, in dem die gleichstromseitige Spannung des Wechselrichters nicht größer ist als der Betriebsspannungseinstellschwellenwert, und die konfiguriert ist, um eine Steuerung an eine erste Anpassungseinheit (53) in einem Fall zu übergeben, in dem die gleichstromseitige Spannung des Wechselrichters größer ist als der Betriebsspannungseinstellschwellenwert;

    die erste Steuerungseinheit (52), die konfiguriert ist, um den Wechselrichter zu steuern, so dass dieser gemäß einer fünfstufigen Steuerungsstrategie arbeitet;

    die erste Anpassungseinheit (53), die konfiguriert ist, um die gleichstromseitige Spannung durch Verwenden eines Maximalleistungs-Tracking-Algorithmus anzupassen;

    eine zweite Anpassungseinheit (54), die konfiguriert ist, um eine schwebende Kondensatorspannung des Wechselrichters, basierend auf der angepassten gleichstromseitigen Spannung, linear anzupassen;

    eine zweite Bestimmungseinheit (55), die konfiguriert ist, um zu bestimmen, ob die angepasste schwebende Kondensatorspannung in einem voreingestellten Bereich liegt, wobei der voreingestellte Bereich von einem Viertel des Betriebsspannungseinstellschwellenwertes minus einem voreingestellten Schwellenwert bis zu einem Viertel des Betriebsspannungseinstellschwellenwertes plus dem voreingestellten Schwellenwert reicht, und die konfiguriert ist, um eine Steuerung an die erste Steuerungseinheit (52) in einem Fall zu übergeben, in dem die angepasste schwebende Kondensatorspannung in dem voreingestellten Bereich liegt, und die konfiguriert ist, um eine Steuerung an eine zweite Steuerungseinheit (56) in einem Fall zu übergeben, in dem die angepasste schwebende Kondensatorspannung nicht in dem voreingestellten Bereich liegt; und

    die zweite Steuerungseinheit (56), die konfiguriert ist, um den Wechselrichter zu steuern, so dass dieser gemäß einer siebenstufigen Steuerungsstrategie arbeitet.


     
    6. Gerät nach Anspruch 5, des Weiteren umfassend:
    eine dritte Bestimmungseinheit (57), die konfiguriert ist, um zu bestimmen, ob die gleichstromseitige Spannung größer ist als eine erste voreingestellte Spannung, wobei die erste voreingestellte Spannung größer ist als der Betriebsspannungseinstellschwellenwert, und die konfiguriert ist, um eine Steuerung an die erste Anpassungseinheit (53) in einem Fall zu übergeben, in dem die gleichstromseitige Spannung größer ist als die erste voreingestellte Spannung, und die konfiguriert ist, um eine Steuerung an die erste Steuerungseinheit (52) in einem Fall zu übergeben, in dem die gleichstromseitige Spannung nicht größer ist als die erste voreingestellte Spannung.
     
    7. Gerät nach Anspruch 5 oder 6, wobei die zweite Anpassungseinheit (54) umfasst:

    eine Berechnungs-Untereinheit (541), die konfiguriert ist, um die angepasste gleichstromseitige Spannung in eine vorgegebene lineare Beziehungsformel einzusetzen, um eine zu verwendende schwebende Kondensatorspannung zu erhalten; und

    eine Anpassungs-Untereinheit (542), die konfiguriert ist, um die schwebende Kondensatorspannung an die zu verwendende schwebende Kondensatorspannung anzupassen.


     
    8. Gerät nach Anspruch 7, wobei die Berechnungs-Untereinheit (541) speziell konfiguriert ist, um die angepasste gleichstromseitige Spannung in

    einzusetzen, um eine zu verwendende schwebende Kondensatorspannung zu erhalten, wobei Udc1 eine gleichstromseitige Leerlaufspannung des Wechselrichters ist, Ufc1 eine der gleichstromseitigen Leerlaufspannung des Wechselrichters zugehörige schwebende Kondensatorspannung ist, Udc2 der Betriebsspannungseinstellschwellenwert ist, Ufc2 eine dem Betriebsspannungseinstellschwellenwert zugehörige schwebende Kondensatorspannung ist, X die gleichstromseitige Spannung des Wechselrichters ist und Y die schwebende Kondensatorspannung des Wechselrichters ist.
     
    9. Wechselrichter, der das Gerät zum Steuern eines Betriebs von einem Wechselrichter nach einem der Ansprüche 5 bis 8 umfasst.
     
    10. Photovoltaisches Stromerzeugungssystem, das den Wechselrichter nach Anspruch 9 umfasst.
     


    Revendications

    1. Procédé de commande du fonctionnement d'un onduleur, comprenant :

    déterminer (S31) si une tension du côté du courant continu de l'onduleur est plus haute qu'un seuil de fixation d'une tension de fonctionnement ; et

    dans le cas où la tension du côté du courant continu de l'onduleur n'est pas plus haute que le seuil de fixation d'une tension de fonctionnement, commander (S32) l'onduleur pour qu'il fonctionne suivant une stratégie de commande à cinq niveaux ; et

    dans le cas où la tension du côté du courant continu de l'onduleur est plus haute que le seuil de fixation d'une tension de fonctionnement :

    régler (S33) la tension du côté du courant continu en utilisant un algorithme de suivi de puissance maximum ;

    régler (S34) linéairement une tension flottante de condensateur de l'onduleur sur la base de la tension réglée du côté du courant continu ;

    déterminer (S35) si la tension flottante réglée de condensateur est dans une plage fixée à l'avance, la plage fixée à l'avance allant d'un quart du seuil de fixation d'une tension de fonctionnement diminué d'un seuil fixé à l'avance à un quart du seuil de fixation d'une tension de fonctionnement plus le seuil fixé à l'avance ; et

    commander (S32) l'onduleur pour qu'il fonctionne suivant une stratégie de commande à cinq niveaux dans le cas où la tension flottante réglée de condensateur est dans la plage fixée à l'avance ; et

    commander (S36) l'onduleur pour qu'il fonctionne suivant une stratégie de commande à sept niveaux dans le cas où la tension flottante réglée de condensateur n'est pas dans la plage fixée à l'avance.


     
    2. Procédé suivant la revendication 1, dans lequel, après avoir commandé (S32) l'onduleur pour qu'il fonctionne suivant la stratégie de commande à cinq niveaux, le procédé comprend, en outre :

    déterminer (S37) si la tension du côté du courant continu est plus haute qu'une première tension fixée à l'avance, la première tension fixée à l'avance étant plus haute que le seuil de fixation d'une tension de fonctionnement ; et

    exécuter un stade de réglage (S33) de la tension du côté du courant continu en utilisant l'algorithme suivi de puissance maximum dans le cas où la tension du côté du courant continu est plus haute que la première tension fixée à l'avance ; et

    commander (S32) l'onduleur pour qu'il fonctionne suivant la stratégie de commande à cinq niveaux dans le cas où la tension du côté du courant continu n'est pas plus haute que la première tension fixée à l'avance.


     
    3. Procédé suivant la revendication 1 ou 2, dans lequel le réglage (S34) de manière linéaire de la tension flottante de condensateur de l'onduleur sur la base de la tension réglée du côté du courant continu comprend :

    substituer (S41) la tension réglée du côté du courant continu dans une formule de relation linéaire fixée à l'avance pour obtenir une tension flottante de condensateur à utiliser; et

    régler (S42) la tension flottante de condensateur à la tension flottante de condensateur à utiliser.


     
    4. Procédé suivant la revendication 3, dans lequel la formule de relation linéaire fixée à l'avance est

    dans laquelle Udc1 est une tension en circuit ouvert du côté du courant continu de l'onduleur, Ufc1 est une tension flottante de condensateur correspondant à la tension en circuit ouvert du côté du courant continu de l'onduleur, Udc2 est le seuil de fixation d'une tension de fonctionnement, Ufc2 est une tension flottante de condensateur correspondant au seuil de fixation d'une tension de fonctionnement, X est la tension du côté du courant continu de l'onduleur et Y est la tension flottante de condensateur de l'onduleur.
     
    5. Dispositif pour commander un fonctionnement d'un onduleur, comprenant :

    une première unité (51) de détermination, configurée pour déterminer si une tension du côté du courant continu de l'onduleur est plus haute qu'un seuil de fixation d'une tension de fonctionnement et configurée pour passer la commande à une première unité (52) de commande dans le cas où la tension du côté du courant continu de l'onduleur n'est pas plus haute que le seuil de fixation d'une tension de fonctionnement et configurée pour passer la commande à une première unité (53) de réglage dans le cas où la tension du côté du courant continu de l'onduleur est plus haute que le seuil de fixation d'une tension de fonctionnement ;

    la première unité (52) de commande étant configurée pour commander l'onduleur afin qu'il fonctionne suivant une stratégie de commande à cinq niveaux ;

    la première unité (53) de réglage étant configurée pour régler la tension du côté du courant continu en utilisant un algorithme de suivi de puissance maximum ;

    une deuxième unité (54) de réglage, configurée pour régler linéairement une tension flottante de condensateur de l'onduleur sur la base de la tension réglée du côté du courant continu ;

    une deuxième unité (55) de détermination, configurée pour déterminer si la tension flottante réglée de condensateur est dans une plage fixée à l'avance, la plage fixée à l'avance allant d'un quart du seuil de fixation d'une tension de fonctionnement moins un seuil fixé à l'avance à un quart du seuil de fixation d'une tension de fonctionnement plus le seuil fixé à l'avance, et configurée pour passer la commande à la première unité (52) de commande dans le cas où la tension flottante réglée de condensateur est dans la plage fixée à l'avance, et configurée pour passer la commande à une deuxième unité (56) de commande dans le cas où la tension flottante réglée de condensateur n'est pas dans la plage fixée à l'avance ; et

    la deuxième unité (56) de commande est configurée pour commander l'onduleur afin qu'il fonctionne suivant une stratégie de commande à sept niveaux.


     
    6. Dispositif suivant la revendication 5, comprenant, en outre :
    une troisième unité (57) de détermination, configurée pour déterminer si la tension du côté du courant continu est plus haute qu'une première tension fixée à l'avance, la première tension fixée à l'avance étant plus haute que le seuil de fixation d'une tension de fonctionnement, et configurée pour passer la commande à la première unité (53) de réglage dans le cas où la tension du coté du courant continu est plus haute que la première tension fixée à l'avance, et configurée pour passer la commande à la première unité (52) de commande dans le cas où la tension du côté du courant continu n'est pas plus haute que la première tension fixée à l'avance.
     
    7. Dispositif suivant la revendication 5 ou 6, dans lequel la deuxième unité (54) de réglage comprend :

    une sous-unité (541) de calcul, configurée pour substituer la tension réglée du côté du courant continu dans une formule de relation linéaire fixée à l'avance pour obtenir une tension flottante à utiliser de condensateur ; et

    une sous-unité (542) de réglage configurée pour régler la tension flottante de condensateur à la tension flottante à utiliser de condensateur.


     
    8. Dispositif suivant la revendication 7, dans lequel la sous-unité (541) de calcul est configurée spécifiquement pour substituer la tension réglée du côté du courant continu dans


    pour obtenir une tension flottante à utiliser de condensateur, Udc1 est une tension en circuit ouvert du côté du courant continu de l'onduleur, Ufc1 est une tension flottante de condensateur correspondant à la tension en circuit ouvert du côté du courant continu de l'onduleur, Udc2 est le seuil de fixation d'une tension de fonctionnement, Ufc2 est une tension flottante de condensateur correspondant au seuil de fixation d'une tension de fonctionnement, X est la tension du côté du courant continu de l'onduleur et Y est la tension flottante de condensateur de l'onduleur.
     
    9. Onduleur comprenant le dispositif de commande d'un fonctionnement d'un onduleur suivant l'une quelconque des revendications 5 à 8.
     
    10. Système photovoltaïque de production d'électricité comprenant l'onduleur suivant la revendication 9.
     




    Drawing



























    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description