WO2022252095A1 - 一种多逆变器并联系统以及逆变器的控制并网方法 - Google Patents

一种多逆变器并联系统以及逆变器的控制并网方法 Download PDF

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Publication number
WO2022252095A1
WO2022252095A1 PCT/CN2021/097533 CN2021097533W WO2022252095A1 WO 2022252095 A1 WO2022252095 A1 WO 2022252095A1 CN 2021097533 W CN2021097533 W CN 2021097533W WO 2022252095 A1 WO2022252095 A1 WO 2022252095A1
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WIPO (PCT)
Prior art keywords
bus
inverter
inverter circuit
voltage
controller
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PCT/CN2021/097533
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English (en)
French (fr)
Inventor
于心宇
李俊杰
辛凯
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华为数字能源技术有限公司
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Application filed by 华为数字能源技术有限公司 filed Critical 华为数字能源技术有限公司
Priority to EP21943470.1A priority Critical patent/EP4344009A1/en
Priority to CN202180098311.4A priority patent/CN117337525A/zh
Priority to PCT/CN2021/097533 priority patent/WO2022252095A1/zh
Priority to AU2021449495A priority patent/AU2021449495A1/en
Publication of WO2022252095A1 publication Critical patent/WO2022252095A1/zh
Priority to US18/523,539 priority patent/US20240106351A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/123—Suppression of common mode voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation

Definitions

  • the present application relates to the field of electronic technology, and in particular to a multi-inverter parallel system and a grid-connected method for controlling the inverters.
  • the inverter is the key device to realize the conversion of direct current into alternating current.
  • a common implementation method is to connect multiple inverters in series and parallel to form a multi-inverter parallel system to transmit greater power.
  • a relay is usually designed on its AC side. By controlling the closing and association of the relay, the inverter can be connected to and disconnected from the grid.
  • the connection mode between multiple inverters due to the problem of system communication delay, it is often difficult for multiple inverters in the system to achieve simultaneous grid connection.
  • a certain time sequence is connected to the grid sequentially, because it is difficult to control multiple relays to be closed at the same time.
  • the present application provides a multi-inverter parallel system and a method for controlling grid connection of the inverters, so as to avoid the problem of impulsive circulation when the inverters are connected to the grid in the multi-inverter parallel system, and improve system reliability.
  • the embodiment of the present application provides a multi-inverter parallel system, the system includes a first inverter and a second inverter; wherein, the first inverter includes a first inverter circuit, a first control The input end of the first inverter circuit is used to connect to the first DC bus, and the output end is used to connect to the first relay; the second inverter includes a second inverter circuit, a second controller and a second inverter circuit.
  • each phase of the output end of the first inverter circuit is connected with each phase of the output end of the second inverter circuit respectively Corresponding connection;
  • the first controller is used to control the closing of the first relay;
  • the second controller is used to control the DC bus voltage of the second inverter circuit and the DC voltage of the first inverter circuit when the first relay is closed when the second relay is disconnected.
  • the bus voltage is the same and the common-mode voltage injection mode of the second inverter circuit is the same as the common-mode voltage injection mode of the first inverter circuit when the first relay is closed, and the second relay is controlled to be closed.
  • the second controller can control the DC bus voltage of the second inverter circuit to be consistent with the DC bus voltage of the first inverter circuit (for example, both are the first voltage value or approach to the first voltage value) before the second relay is closed. first voltage value), and control the common-mode voltage injection method of the second inverter circuit to be consistent with the common-mode voltage injection method of the first inverter circuit (for example, both are the first common-mode voltage injection method), so that the first inverter circuit
  • the common-mode voltage output by the inverter circuit is the same or similar to that of the second inverter circuit.
  • the second relay is controlled to close to realize the grid-connected operation of the second inverter, which can effectively avoid a large common-mode circulation impact at the moment the second relay is closed and affect the reliability of the system.
  • the first controller is further configured to: receive a first bus voltage command from the second controller, where the first bus voltage command is used to indicate the initial DC voltage of the second inverter circuit bus voltage; determine the first voltage value according to the initial DC bus voltage of the first inverter circuit and the initial DC bus voltage of the second inverter circuit; send a second bus voltage instruction to the second controller, and the second bus voltage instruction Used to indicate the first voltage value.
  • the second controller is further configured to: receive a third bus voltage command from the first controller, where the third bus voltage command is used to indicate the initial DC voltage of the first inverter circuit bus voltage; determine the first voltage value according to the initial DC bus voltage of the first inverter circuit and the initial DC bus voltage of the second inverter circuit; send a fourth bus voltage instruction to the first controller, and the fourth bus voltage instruction Used to indicate the first voltage value.
  • the first controller and the second controller can negotiate to determine the first voltage value through information interaction (such as interactive bus voltage command), so as to control the DC bus voltage of the second inverter circuit and the first inverter
  • the DC bus voltage of the transformer circuit is the same.
  • the second controller is further configured to: receive common-mode voltage injection mode information from the first controller, where the common-mode voltage injection mode information is used to instruct the first inverter circuit to adopt The first common-mode voltage injection method; according to the first common-mode voltage injection method, the common-mode voltage output by the second inverter circuit is controlled.
  • the first controller can inform the second controller of the common-mode voltage injection mode adopted by the first inverter circuit through information interaction with the second controller, so that the second controller can control the second inverter
  • the transformer circuit adopts the same common-mode voltage injection method.
  • the second controller is also used to: when the second relay is disconnected, control the effective value of the differential mode line voltage output by the second inverter circuit and the effective value of the grid line voltage same.
  • the second controller can control the differential mode line voltage output by the second inverter circuit to be consistent with the grid line voltage, or both approach the grid line voltage before the second relay is closed. After that, the second relay is controlled to be closed to realize the grid-connected operation of the second inverter, which can effectively avoid a large differential-mode circulating current impact at the moment the second relay is closed, which will affect the reliability of the system.
  • the first DC bus includes a first positive DC bus and a first negative DC bus, wherein the first positive DC bus is used to connect the positive pole of the input end of the first inverter circuit, and the first A negative DC bus is used to connect the negative pole of the input terminal of the first inverter circuit;
  • the second DC bus includes a second positive DC bus and a second negative DC bus, wherein the second positive DC bus is used to connect the input of the second inverter circuit
  • the positive pole of the terminal, the second negative DC bus is used to connect the negative pole of the input end of the second inverter circuit; the first negative DC bus is connected to the second positive DC bus, or the first positive DC bus is connected to the second negative DC bus.
  • the multi-inverter parallel system in the above technical solution may specifically be a bipolar series-parallel multi-inverter parallel system.
  • the embodiment of the present application provides another multi-inverter parallel system, the system includes a first inverter and a second inverter; wherein, the first inverter includes a first inverter circuit, a first The controller and the first relay, the input end of the first inverter circuit is used to connect to the first DC bus, and the output end is used to connect to the first relay; the second inverter includes a second inverter circuit, a second controller and For the second relay, the input end of the second inverter circuit is used to connect the second DC bus, and the output end is used to connect the second relay; each phase of the output end of the first inverter circuit is connected to each phase of the output end of the second inverter circuit respectively.
  • the first DC bus is connected to the second DC bus, the first controller is used to control the closing of the first relay; the second controller is used to control the common mode voltage of the second inverter circuit when the second relay is disconnected
  • the injection method is the same as the common-mode voltage injection method of the first inverter circuit when the first relay is closed, and the second relay is controlled to be closed.
  • the second controller can control the common-mode voltage injection mode of the second inverter circuit to be consistent with the common-mode voltage injection mode of the first inverter circuit (for example, both are the first common-mode voltage injection mode) before the second relay is closed. ), so that the common-mode voltages output by the first inverter circuit and the second inverter circuit are the same or similar. After that, control the second relay to close to realize the grid-connected operation of the second inverter, which can effectively avoid the large common-mode circulating current impact at the moment the second relay is closed, which will affect the reliability of the system.
  • the second controller is further configured to: receive common-mode voltage injection mode information from the first controller, where the common-mode voltage injection mode information is used to instruct the first inverter circuit to adopt The first common-mode voltage injection method; according to the first common-mode voltage injection method, the common-mode voltage output by the second inverter circuit is controlled.
  • the second controller is also used to: when the second relay is disconnected, control the effective value of the differential mode line voltage output by the second inverter circuit and the effective value of the grid line voltage same.
  • the second controller before the second relay is closed, can control the differential mode line voltage output by the second inverter circuit to be consistent with the grid line voltage, or to be close to the grid line voltage. After that, the second relay is controlled to be closed to realize the grid-connected operation of the second inverter, which can effectively avoid a large differential-mode circulating current impact at the moment the second relay is closed, which will affect the reliability of the system.
  • the first DC bus includes a first positive DC bus and a first negative DC bus, wherein the first positive DC bus is used to connect the positive pole of the input end of the first inverter circuit, and the first A negative DC bus is used to connect the negative pole of the input terminal of the first inverter circuit;
  • the second DC bus includes a second positive DC bus and a second negative DC bus, wherein the second positive DC bus is used to connect the input of the second inverter circuit The positive pole of the terminal, the second negative DC bus is used to connect the negative pole of the input end of the second inverter circuit; the first positive DC bus is connected to the second positive DC bus, and the first negative DC bus is connected to the second negative DC bus.
  • the multi-inverter parallel system in the above technical solution may specifically be a common DC bus multi-inverter parallel system.
  • an embodiment of the present application provides a grid-connected method for controlling inverters in a multi-inverter parallel system, the method is applied to the second controller of the second inverter in the multi-inverter parallel system,
  • the second inverter is an inverter to be connected to the grid in a multi-inverter parallel system, wherein the second inverter includes a second controller, a second inverter circuit and a second relay, and the second inverter circuit
  • the input terminal is connected to the second DC bus, and the output terminal is connected to the second relay;
  • the method includes: the second controller determines the first inverter, and the first inverter is a grid-connected inverter in a multi-inverter parallel system Inverter, the first inverter includes a first controller, a first inverter circuit and a first relay, the input end of the first inverter circuit is connected to the first DC bus, the output end is connected to the first relay, and the first relay is closed , the phases of the output terminals of the
  • the second controller controls the DC bus voltage of the second inverter circuit to be the same as the DC bus voltage of the first inverter circuit, including: the second The controller controls the difference between the DC bus voltage of the second inverter circuit and the first voltage value to be smaller than the first voltage threshold when the second relay is turned off.
  • the method further includes: the second controller determines the first voltage value according to the initial DC bus voltage of the first inverter circuit and the initial DC bus voltage of the second inverter circuit; Alternatively, the second controller receives a second bus voltage command from the first controller, and the second bus voltage command is used to indicate the first voltage value.
  • the second controller controls the common-mode voltage injection mode of the second inverter circuit and the common-mode voltage injection mode of the first inverter circuit when the second relay is turned off. Same, including: the second controller receives the common-mode voltage injection mode information from the first controller, and the common-mode voltage injection mode information is used to indicate the first common-mode voltage injection mode adopted by the first inverter circuit; the second control The converter controls the common-mode voltage output by the second inverter circuit according to the first common-mode voltage injection mode.
  • the method further includes: when the second relay is disconnected, the second controller controls the effective value of the differential mode line voltage output by the second inverter circuit and the effective value of the grid line voltage. same value.
  • the second DC bus includes a second positive DC bus and a second negative DC bus, the second positive DC bus is connected to the positive pole of the input end of the second inverter circuit, and the second negative DC bus Connect the negative pole of the input end of the second inverter circuit;
  • the first DC bus bar includes a first positive DC bus bar and a first negative DC bus bar, the first positive DC bus bar is connected to the positive pole of the input end of the first inverter circuit, and the first negative DC bus bar Connect the negative pole of the input end of the first inverter circuit; wherein, the first negative DC bus is connected to the second positive DC bus, or the first positive DC bus is connected to the second negative DC bus.
  • the embodiment of the present application provides a grid-connected method for inverter control in a multi-inverter parallel system, the method is applied to a second controller of a second inverter, and the second inverter is a multi-inverter
  • the method includes: the second controller determines the first inverter, the first inverter is a grid-connected inverter in a multi-inverter parallel system, and the first inverter includes the first inverter A controller, a first inverter circuit and a first relay, the input end of the first inverter circuit is connected to the first DC bus, the output end is connected to the first relay, the first relay is closed, the first DC bus and the second DC The bus bars are connected, and
  • the second controller controls the common-mode voltage injection mode of the second inverter circuit to be the same as the common-mode voltage injection mode of the first inverter circuit, It includes: the second controller receives common-mode voltage injection mode information from the first controller, and the common-mode voltage injection mode information is used to indicate the first common-mode voltage injection mode adopted by the first inverter circuit; the second controller according to The first common-mode voltage injection mode controls the common-mode voltage output by the second inverter circuit.
  • the method further includes: when the second relay is disconnected, the second controller controls the effective value of the differential mode line voltage output by the second inverter circuit and the effective value of the grid line voltage. same value.
  • the second DC bus includes a second positive DC bus and a second negative DC bus, the second positive DC bus is connected to the positive pole of the input end of the second inverter circuit, and the second negative DC bus Connect the negative pole of the input end of the second inverter circuit;
  • the first DC bus bar includes a first positive DC bus bar and a first negative DC bus bar, the first positive DC bus bar is used to connect the positive pole of the input end of the first inverter circuit, and the first negative DC bus bar is used to connect the positive pole of the input end of the first inverter circuit.
  • the DC bus is connected to the negative pole of the input end of the first inverter circuit; wherein, the first positive DC bus is connected to the second positive DC bus, and the first negative DC bus is connected to the second negative DC bus.
  • FIG. 1 is a schematic diagram of a relay connected to a single inverter in the embodiment of the present application
  • FIG. 2 is a schematic structural diagram of a multi-inverter parallel system provided by an embodiment of the present application
  • Figure 3a, Figure 3b and Figure 3c are schematic diagrams of several ways in which the first controller and the second controller interact with the bus voltage command to determine the first voltage value in the embodiment of the present application;
  • FIG. 4 is a schematic diagram of a bipolar series-parallel multi-inverter parallel system provided by an embodiment of the present application
  • Fig. 5 is a schematic diagram of a parallel system of multiple inverters with a common DC negative pole provided by an embodiment of the present application;
  • FIG. 6 is a schematic diagram of a parallel system of multiple inverters with a common DC positive pole provided by an embodiment of the present application
  • FIG. 7 is a schematic flowchart of a method for controlling grid connection of an inverter provided in an embodiment of the present application.
  • FIG. 8 is another schematic flowchart of a method for controlling grid connection of an inverter provided in an embodiment of the present application.
  • FIG. 9 is a schematic diagram of a parallel system of multiple inverters with a common DC bus provided by an embodiment of the present application.
  • FIG. 10 is another schematic flowchart of a method for controlling grid connection of an inverter provided in an embodiment of the present application.
  • An embodiment of the present application provides a multi-inverter parallel system. As shown in FIG. 2 , the system includes a first inverter 210 and a second inverter 220 .
  • the present application does not specifically limit the number of inverters included in the multi-inverter parallel system.
  • the first inverter is only an inverter that has been connected to the grid in the multi-inverter parallel system
  • the second inverter is the inverter that has not yet been connected to the grid but will be paralleled in the multi-inverter parallel system.
  • One inverter of the grid is taken as an example to illustrate the grid-connection mechanism (or called the start-up mechanism) in the multi-inverter parallel system provided by the embodiment of the present application.
  • the first inverter may be an inverter that is first connected to the grid in the multi-inverter parallel system, or an inverter that has recently completed grid connection in the multi-inverter parallel system , it can also be any inverter that has been connected to the grid in the multi-inverter parallel system, which is not limited in this application.
  • the system may include a larger number of inverters. For example, as shown in FIG. The second inverter 220 , . . . until the Nth transformer 2N0 , where N is an integer greater than or equal to 2.
  • the first inverter 210 includes a first controller 211 , a first inverter circuit 212 and a first relay 213 , and the first controller 211 is used to control the first inverter circuit 212 and the first relay 213 .
  • the input terminal of the first inverter circuit 212 (also referred to as the DC outlet terminal) is connected to the first DC bus bar.
  • the first DC bus bar includes a first positive DC bus bar and a first negative DC bus bar.
  • it also includes a first DC bus bar.
  • the DC bus wherein the first positive DC bus is connected to the positive pole of the input end of the first inverter circuit 212
  • the first negative DC bus is connected to the negative pole of the input end of the first inverter circuit 212 .
  • Each output end (also known as an AC outlet) of the first inverter circuit 212 is connected to one end of a first relay 213, and the other end of the first relay 213 is connected to a first transformer, and the output of the first transformer can be further connected to an AC For the grid, in this way, the first inverter 210 can be connected to and disconnected from the grid by controlling the closing and opening of the first relay 213 .
  • the second inverter 220 includes a second controller 221 , a second inverter circuit 222 and a second relay 223 , and the second controller 221 is used to control the second inverter circuit 222 and the second relay 223 .
  • the input terminal of the second inverter circuit 222 (also referred to as the DC outlet terminal) is connected to the second DC bus
  • the second DC bus includes a second positive DC bus and a second negative DC bus, and optionally, also includes a second medium DC bus , wherein the second positive DC bus is connected to the positive pole of the input end of the second inverter circuit 222 , and the second negative DC bus is connected to the negative pole of the input end of the second inverter circuit 222 .
  • Each output end (also known as an AC outlet) of the second inverter circuit 222 is connected to one end of a second relay 223, and the other end of the second relay 223 is connected to a second transformer, and the output of the second transformer is further connected to the AC grid In this way, the second inverter 220 can be connected to and disconnected from the grid by controlling the closing and opening of the second relay 223 .
  • Each phase of the output terminal of the first inverter circuit 212 is respectively connected to each phase of the output terminal of the second inverter circuit 222 , thereby forming a form in which multiple inverters are connected in parallel.
  • the input end of the first inverter circuit 212 and the input end of the second inverter circuit 222 can be connected in many possible ways, for example, in a bipolar series-parallel multi-inverter parallel system, if the second inverter circuit
  • the inverter 220 corresponds to the first inverter 210, and the negative pole of the input end of the first inverter circuit 212 is connected to the positive pole of the input end of the second inverter circuit 222 (that is, the first negative DC bus is connected to the second positive DC bus) , or the positive pole of the input terminal of the first inverter circuit 212 may be connected to the negative pole of the input terminal of the second inverter circuit 222 (that is, the first positive DC bus is connected to the second negative DC bus).
  • the negative pole of the input terminal of the first inverter circuit 212 can be connected with the negative pole of the input terminal of the second inverter circuit 222 (that is, the first negative DC bus and the second negative connected to the DC bus).
  • the positive pole of the input terminal of the first inverter circuit 212 can be connected with the positive pole of the input terminal of the second inverter circuit 222 (that is, the first positive DC bus is connected to the second positive pole). flow bus connection).
  • first transformer and the second transformer may be the same transformer or the same winding of the same transformer, or may be different transformers or different windings of the same transformer, which is not limited in this application.
  • the first controller 211 can provide voltage control instructions to the first inverter circuit 212, thereby controlling the DC bus voltage of the first inverter circuit 212 or The AC voltage output by the first inverter circuit 212 is controlled.
  • the first controller 211 can provide a high-level or low-level control signal to the first relay 213, thereby controlling the first relay 213 to close or open .
  • the first inverter 210 is a three-phase inverter.
  • the first inverter circuit 212 has a three-phase AC outlet, and each phase of the AC outlet is connected to the first transformer through a first relay 213 , and there are three first relays 213 in total.
  • the first controller 211 can control the three first relays 213 synchronously, that is, when the first controller 211 controls the first relays 213 to close, it means that the first controller 211 controls the three first relays 213 to close together, When the first controller 211 controls the first relays 213 to be turned off, it means that the first controller 211 controls the three first relays 213 to be turned off together.
  • the first controller 211 can set a potential connected to the three first relays 213 to a high level, thereby providing high-level control signals to the three first relays 213 at the same time to control the three first relays 213. All the first relays 213 are closed.
  • the first controller 211 can also set a potential connected to the three first relays 213 as a low level, so as to provide a low level control signal to the three first relays 213 at the same time to control The three first relays 213 are all turned off.
  • the second controller 221 can provide voltage control instructions to the second inverter circuit 222, thereby controlling the DC bus voltage of the second inverter circuit 222 or The AC voltage output by the second inverter 222.
  • the second controller 221 can provide a high-level signal or a low-level control signal to the second relay 223, thereby controlling the second relay 223 to close or break. open.
  • the second inverter 220 is a three-phase inverter.
  • the second inverter circuit 222 has a three-phase AC outlet, and each phase of the AC outlet is connected to the second transformer through a second relay 223 , and there are three second relays 223 in total.
  • the second controller 221 can control the three second relays 223 synchronously, that is, when the second controller 221 controls the second relays 223 to close, it means that the second controller 221 controls the three second relays 223 to close together, When the second controller 221 controls the second relays 223 to be turned off, it means that the second controller 221 controls the three second relays 223 to be turned off together.
  • the second controller 221 can set a potential connected to the three second relays 223 to a high level, thereby providing high-level control signals to the three second relays 223 at the same time to control the three second relays 223. All the second relays 223 are closed.
  • the second controller 221 can also set a potential connected to the three second relays 223 as a low level, so as to provide a low level control signal to the three second relays 223 at the same time to control The three second relays 223 are all turned off.
  • the communication connection may be a wired connection (such as a wired cable), or a wireless connection (such as a fifth generation (the 5th generation, 5G) network, etc.), which is not limited in this application.
  • the first controller may be used to: control the first relay to close.
  • the first controller may control the DC bus voltage of the first inverter circuit to be the first voltage value (or control the difference between the DC bus voltage of the first inverter circuit and the first voltage value) when the first relay is closed. The difference between them is less than the first voltage threshold), and the common-mode voltage injection mode of the first inverter circuit is controlled to be the first common-mode voltage injection mode.
  • the first controller is further configured to send common-mode voltage injection mode information to the second controller, where the common-mode voltage injection mode information is used to indicate the first common-mode voltage injection mode adopted by the first inverter circuit.
  • the first controller can also control the common-mode voltage output by the first inverter circuit according to the first common-mode voltage injection mode.
  • the first common-mode voltage injection method may be continuous pulse width modulation (continuous pulse width modulation, CPWM) or discontinuous pulse width modulation (discontinuous pulse width modulation, DPWM), which is not limited in this application. Both the CPWM mode and the DPWM mode may have multiple possible specific implementation modes, which will not be described in detail in this application.
  • the "common-mode voltage injection method" is a certain preset rule to increase the common-mode voltage component in the three-phase voltage output by the three-phase inverter. It can also be called a modulation method or a common-mode voltage modulation method or has other names. , this application is not limited.
  • the second controller can be used for: when the second relay is disconnected, the DC bus voltage of the second inverter circuit is controlled to be the same as the DC bus voltage of the first inverter circuit when the first relay is closed, and the common voltage of the second inverter circuit is The injection mode of the mode voltage is the same as that of the common mode voltage injection mode of the first inverter circuit when the first relay is closed, and then the second relay is controlled to be closed.
  • the second controller can control the DC bus voltage of the second inverter circuit to be the first voltage value (or control the difference between the DC bus voltage of the second inverter circuit and the first voltage value) when the second relay is closed.
  • the difference between them is less than the first voltage threshold
  • the common-mode voltage injection mode of the second inverter circuit is controlled to be the first common-mode voltage injection mode, and then the second relay is controlled to close.
  • the first common-mode voltage injection mode is the common-mode voltage injection mode adopted by the first inverter circuit above
  • the second controller can receive the common-mode voltage injection mode information from the first controller, and according to the common-mode voltage injection mode The voltage injection mode information determines the first common-mode voltage injection mode, and then controls the common-mode voltage output by the second inverter circuit according to the first common-mode voltage injection mode.
  • the second controller may control the common-mode voltage output by the second inverter circuit according to the first common-mode voltage injection manner.
  • the first controller controls the difference between the DC bus voltage of the first inverter circuit and the first voltage value to be smaller than the first voltage threshold, which can be understood as: the first controller controls the first inverter circuit The DC bus voltage is equal to or close to the first voltage value.
  • the fact that the second controller controls the difference between the DC bus voltage of the second inverter circuit and the first voltage value to be smaller than the first voltage threshold can be understood as: the second controller controls the DC bus voltage of the second inverter circuit equal to or close to the first voltage value.
  • the second controller can control the DC bus voltage of the second inverter circuit to be consistent with the DC bus voltage of the first inverter circuit (for example, both are at the first voltage value or approach to the first voltage value) before the second relay is closed. at the first voltage value), and control the common-mode voltage injection method of the second inverter circuit to be consistent with the common-mode voltage injection method of the first inverter circuit (for example, both are the first common-mode voltage injection method), so that the second The common-mode voltage output by the first inverter circuit is the same or similar to that of the second inverter circuit.
  • the second relay is controlled to close to realize the grid-connected operation of the second inverter, which can effectively avoid a large common-mode circulation impact at the moment the second relay is closed and affect the reliability of the system.
  • the first voltage value is greater than or equal to the initial DC bus voltage of the first inverter circuit, and greater than or equal to the initial DC bus voltage of the second inverter circuit.
  • the initial DC bus voltage of the first inverter circuit refers to the DC bus voltage of the first inverter circuit before the second relay is closed.
  • the initial DC bus voltage of the second inverter circuit refers to the DC bus voltage of the second inverter circuit before the second relay is closed.
  • the first controller and the second controller can negotiate to determine the above-mentioned first voltage value through information interaction (such as an interactive bus voltage command), so that the first inverter and the second inverter can control the first voltage
  • the first voltage value may be the initial DC bus voltage of the first inverter circuit, may also be the initial DC bus voltage of the second inverter circuit, or may be another value different from the two.
  • the first controller may receive a first bus voltage command from the second controller, and the first bus voltage command is used to indicate an initial DC bus voltage of the second inverter circuit.
  • the first controller can determine the first voltage value according to the initial DC bus voltage of the first inverter circuit and the initial DC bus voltage of the second inverter circuit determined according to the first bus voltage command, and then send the first voltage value to the second controller Sending a second bus voltage command, where the second bus voltage command is used to indicate the first voltage value.
  • the first controller may determine the larger voltage value of the initial DC bus voltage of the first inverter circuit and the initial DC bus voltage of the second inverter circuit as the first voltage value, or may determine a value greater than The initial DC bus voltage of the first inverter circuit is determined as the first voltage value by a voltage value greater than the initial DC bus voltage of the second inverter circuit, which is not limited in this application.
  • the second controller may receive a third bus voltage command from the first controller, the third bus voltage command is used to indicate the initial DC bus voltage of the first inverter circuit.
  • the second controller can determine the first voltage value according to the initial DC bus voltage of the second inverter circuit and the initial DC bus voltage of the first inverter circuit determined according to the third bus voltage command, and then provide the first voltage value to the first controller Sending a fourth bus voltage command, where the fourth bus voltage command is used to indicate the first voltage value.
  • the second controller may determine the larger voltage value of the initial DC bus voltage of the first inverter circuit and the initial DC bus voltage of the second inverter circuit as the first voltage value, or may determine a value greater than The initial DC bus voltage of the first inverter circuit is determined as the first voltage value by a voltage value greater than the initial DC bus voltage of the second inverter circuit, which is not limited in this application.
  • the first controller may send a fifth bus voltage command to the second controller, and the initial DC bus voltage of the first inverter circuit is indicated to the second controller through the fifth bus voltage command.
  • the second controller receives the fifth bus voltage command, it can determine the initial DC bus voltage of the first inverter circuit as the first voltage value, and then, as described above, the second controller can control the fifth bus voltage.
  • the second relay is controlled to close.
  • the second controller can also control the effective value of the differential mode line voltage output by the second inverter circuit to be the same as the effective value of the grid line voltage when the second relay is turned off (or control the second inverter circuit The difference between the effective value of the output differential mode line voltage and the effective value of the grid line voltage is less than the second voltage threshold), and then control the second relay to close.
  • the second controller can control the DC bus voltage of the second inverter circuit to be the same as the DC bus voltage of the first inverter circuit when the first relay is closed, and the effective value of the differential mode line voltage output by the second inverter circuit After the effective value of the grid line voltage is the same and the common-mode voltage injection mode of the second inverter circuit is the same as the common-mode voltage injection mode of the first inverter circuit when the first relay is closed, the second relay is controlled to be closed.
  • the second controller can control the differential mode line voltage output by the second inverter circuit to be consistent with the grid line voltage or approach the grid line voltage before the second relay is closed.
  • the second relay is controlled to be closed to realize the grid-connected operation of the second inverter, which can effectively avoid a large differential-mode circulating current impact at the moment the second relay is closed, which will affect the reliability of the system.
  • Figure 4 shows a bipolar series-parallel multi-inverter parallel system, which includes 2M inverters, where M is a positive integer.
  • the 2M inverters can be divided into two groups, each group has M inverters, and the inverters in the two groups correspond one-to-one.
  • the negative pole of the input terminal of the inverter circuit of the i-th inverter in the first group is connected to the positive pole of the input terminal of the i-th inverter in the second group.
  • the phases of the output terminals of the inverter circuits of the first group of inverters are connected to each other, and the phases of the output terminals of the inverter circuits of the second group of inverters are also connected to each other.
  • the first group of inverters and the second group of inverters The output terminals of the inverter circuit are respectively connected to different transformers or different windings of the same transformer, and then connected to the three-phase AC power grid. Since the negative electrode potential of the input terminal of the inverter circuit of the first group of inverters is higher than the negative electrode potential of the input terminal of the inverter circuit of the second group of inverters, the first group of inverters can be called positive inverters, The second set of inverters are negative inverters.
  • each inverter is a three-phase inverter, and may include a controller, an inverter circuit , relays and related capacitors, inductors and other circuit components.
  • the positive pole inverter 410 includes a controller 411, a positive pole inverter circuit 412, and three relays 413
  • the negative pole inverter 420 includes a controller 421, a negative pole inverter circuit 422, and three relays 423.
  • the inverter 430 includes a controller 431 , a positive inverter circuit 432 and three relays 433
  • the negative inverter 440 includes a controller 441 , a negative inverter circuit 442 and three relays 443 .
  • the positive inverter 410 and the positive inverter 430 belong to the first group of inverters
  • the negative inverter 420 and the negative inverter 440 belong to the second group of inverters. It can be understood that the number of inverters in each group can be expanded according to the above-mentioned connection method according to actual needs, which will not be repeated here.
  • the grid-connected mechanism of inverters applicable to the bipolar series-parallel multi-inverter parallel system in Figure 5 may include:
  • one inverter (such as the positive inverter 410 ) can be designated to be connected to the grid first. Since there is no grid-connected inverter in the system before the positive inverter 410 is connected to the grid, when the three relays 413 of the positive inverter 410 are closed, the bus voltage only needs to be guaranteed not to be lower than the grid-connected The minimum required bus voltage is enough, and the common-mode voltage injection method can be adopted in any way.
  • the positive inverter 410 can also control the differential mode line voltage output by itself to be consistent with the grid line voltage, and then the positive inverter 410 controls to close three relays 413 to realize the grid connection of the positive inverter 410 run.
  • the negative inverter 420 can communicate with the positive inverter 410 (for example, exchange bus voltage command ), control the DC bus voltage of the negative inverter 420 to be connected to the grid to be consistent with the positive inverter 410 that has been connected to the grid, and control the voltage of the negative inverter 420 to be connected to the grid and the positive inverter 410 to be connected to the grid
  • the common mode voltage injection method is the same.
  • the negative inverter 420 to be connected to the grid can also control the differential mode line voltage output by itself to be consistent with the grid line voltage, and according to the same common mode voltage injection method as the positive inverter 410, control The common-mode voltage of its own output. Subsequently, the negative inverter 420 controls to close the three relays 423 to realize the grid-connected operation of the negative inverter 423 .
  • the grid-connected operation of other inverters is successively realized by referring to the above-mentioned method.
  • the positive inverter 430 can communicate with the positive inverter 410 (for example, exchange the bus voltage command), Control the DC bus voltage of the positive inverter 430 to be connected to the grid to be consistent with the positive inverter 410 that has been connected to the grid, and control the common mode of the positive inverter 430 to be connected to the grid and the positive inverter 420 to be connected to the grid
  • the voltage injection method is the same.
  • the positive inverter 430 to be connected to the grid can control its output differential mode line voltage to be consistent with the grid line voltage, and control itself according to the same common mode voltage injection method as the positive inverter 410. output common-mode voltage. Subsequently, the positive inverter 430 controls and closes three relays 433 to realize the grid-connected operation of the positive inverter 430 .
  • the positive inverter 430 can also communicate with the negative inverter 420 (for example, exchange the bus voltage command), and control the DC bus voltage of the positive inverter 430 to be connected to the grid to be consistent with that of the negative inverter 420 that has been connected to the grid.
  • the positive inverter 430 controls and closes three relays 433 to realize the grid-connected operation of the positive inverter 430 .
  • the slow rise of the common mode voltage and the slow rise of the differential mode voltage when the inverter is connected to the grid can be realized, so as to avoid the huge common mode circulating current and differential mode circulating current in the system at the moment the inverter is connected to the grid. Effectively improve the reliability of the system.
  • This application does not specifically limit the order in which multiple inverters are connected to the grid in a multi-inverter parallel system. Understandably, if the positive inverter 410 is connected to the grid first, and then the negative inverter 420 is connected to the grid, when the positive inverter 410 has been connected to the grid and the negative inverter 420 is to be connected to the grid, the positive inverter 410 can be used as The above-mentioned first inverter, the negative inverter 420 can be used as the above-mentioned second inverter to implement the above-mentioned inverter grid-connected mechanism.
  • the negative inverter 420 is connected to the grid first, and then the positive inverter 410 is connected to the grid, when the negative inverter 420 has been connected to the grid and the positive inverter 410 is to be connected to the grid, the negative inverter 420 can be used as the upper The first inverter mentioned above, the positive inverter 410 can be used as the second inverter mentioned above to implement the inverter grid-connected mechanism above.
  • Figure 5 shows a parallel system of multiple inverters with a common negative DC bus, which may also be called a parallel system with multiple inverters with a common negative DC bus.
  • the system may include multiple inverters, the negative poles of the input terminals of the inverter circuits of the multiple inverters are connected to each other, and the phases of the output terminals are connected to each other. Since the potentials of these inverters are all positive for the parallel point of the DC side, these inverters can be called positive inverters.
  • each inverter is a three-phase inverter, and may include a controller, an inverter circuit, a relay, and related circuits such as capacitors and inductors element. As shown in FIG.
  • the positive inverter 510 includes a controller 511 , a positive inverter circuit 512 and three relays 513
  • the positive inverter 520 includes a controller 521 , a positive inverter circuit 522 and three relays 523 .
  • the present application does not specifically limit the number of inverters included in the system, for example, the system may also include other positive inverters.
  • the grid-connected mechanism of the inverter in this system and the corresponding description in FIG. 4 details are not repeated here.
  • Figure 6 shows a parallel system of multi-inverters with a common positive DC bus, which can also be called a parallel system with multi-inverters with a common positive DC bus.
  • the system may include multiple inverters, the positive poles of the input terminals of the inverter circuits of the multiple inverters are connected to each other, and the phases of the output terminals are connected to each other. Since the potentials of these inverters are all negative for the DC side parallel point, these inverters are called negative inverters.
  • each inverter is a three-phase inverter, and may include a controller, an inverter circuit, a relay, and related circuits such as capacitors and inductors element. As shown in FIG.
  • the negative inverter 610 includes a controller 611 , a negative inverter circuit 612 and three relays 613
  • the negative inverter 620 includes a controller 621 , a negative inverter circuit 622 and three relays 623 .
  • the present application does not specifically limit the number of inverters included in the system, for example, the system may also include other negative inverters.
  • the grid-connected mechanism of the inverter in this system and the corresponding description in FIG. 4 details are not repeated here.
  • the embodiment of the present application also provides a grid-connected method for inverter control, as shown in FIG. 7 , the method includes:
  • Step 701 determine the grid-connected inverter and the grid-connected inverter.
  • Step 702 the grid-connected inverters and the grid-connected inverters exchange bus voltage commands, so that the DC bus voltages of all inverters are consistent, that is, the grid-connected inverters control their DC bus voltages to the first voltage value ( Or control the difference between its DC bus voltage and the first voltage value to be less than the first voltage threshold), and at the same time, the grid-connected inverter also controls its DC bus voltage to the first voltage value (or also controls its DC bus The difference between the voltage and the first voltage value is less than the first voltage threshold).
  • Step 703 the grid-connected inverter and the grid-connected inverter exchange common-mode voltage injection mode information, so that all inverters adopt the same common-mode voltage injection mode.
  • step 702 does not specifically limit the execution sequence between step 702 and step 703 .
  • Step 704 the inverter to be connected to the grid controls its differential mode line voltage to be consistent with the grid line voltage before the relay is closed, that is, the effective value of the differential mode line voltage output by the inverter to be connected to the grid is controlled to be the same as the effective value of the grid line voltage (or control the deviation between the effective value of the differential mode line voltage output and the effective value of the grid line voltage to be less than the second voltage threshold), and inject the common mode voltage according to the above common mode voltage injection method;
  • step 705 the grid-connected inverter closes the grid-connected relay to realize power-on.
  • the inverter control grid connection method corresponding to the above-mentioned multi-inverter parallel system provided by the embodiment of the present application can be shown in Figure 8, and this method is applied to the multi-inverter parallel system
  • the second controller of the second inverter in the second inverter is an inverter to be connected to the grid in a multi-inverter parallel system.
  • the method includes:
  • step 801 the second controller determines the first inverter, and the first inverter is an inverter connected to the grid in a multi-inverter parallel system.
  • the second controller can use a certain preset rule to select an inverter that has been connected to the grid in the multi-inverter parallel system as the first inverter.
  • the second controller can select the multi-inverter In the parallel system of inverters, the first inverter that has been connected to the grid can be used as the first inverter, or the inverter that has been connected to the grid recently in the multi-inverter parallel system can be selected as the first inverter. Any inverter that has been connected to the grid in the multi-inverter parallel system can also be selected as the first inverter, which is not limited in this application.
  • Step 802 when the second relay is turned off, the second controller controls the DC bus voltage of the second inverter circuit to be the same as the DC bus voltage of the first inverter circuit, and the common-mode voltage injection mode of the second inverter circuit is the same as The common-mode voltage injection method of the first inverter circuit is the same.
  • the second controller can also control the effective value of the differential mode line voltage output by the second inverter circuit to be the same as the effective value of the grid line voltage when the second relay is turned off.
  • Step 803 the second controller controls the second relay to close.
  • the embodiment of the present application also provides another multi-inverter parallel system.
  • the multi-inverter parallel system includes a first inverter and a second inverter, wherein the first inverter includes a first controller and a second inverter.
  • An inverter circuit and a first relay the first controller is used to control the first inverter circuit and the first relay
  • the second inverter includes a second controller, the second inverter circuit and the second relay
  • the second controller is used for controlling the second inverter circuit and the second relay.
  • the input terminal of the first inverter circuit (also referred to as the DC outlet terminal) is connected to the first DC bus bar, and the first DC bus bar includes a first positive DC bus bar and a first negative DC bus bar, and optionally, a second DC bus bar.
  • a DC bus bar wherein the first positive DC bus bar is connected to the positive pole of the input end of the first inverter circuit, and the first negative DC bus bar is connected to the negative pole of the input end of the first inverter circuit.
  • the output end of the first inverter circuit (also known as the AC outlet end) is connected to one end of the first relay, and the other end of the first relay is connected to a transformer, and the output of the transformer can be further connected to the AC power grid, thus, by controlling the first relay Closing and disconnecting can realize the grid connection and disconnection of the first inverter.
  • the input terminal of the second inverter circuit (also referred to as the DC outlet terminal) is connected to the second DC bus bar, the second DC bus bar includes a second positive DC bus bar and a second negative DC bus bar, and optionally, also includes a second medium DC bus bar, wherein, the second positive DC bus is connected to the positive pole of the input end of the second inverter circuit, and the second negative DC bus is connected to the negative pole of the input end of the second inverter circuit.
  • the output end of the second inverter circuit (also called the AC outgoing line end) is connected to one end of the second relay, and the other end of the second relay is connected to the same transformer, and the transformer is further connected to the AC grid. Disconnection can realize grid connection and disconnection of the second inverter.
  • Each phase of the output end of the first inverter circuit is connected to each phase of the output end of the second inverter circuit, and the first DC bus of the first inverter circuit is connected to the second DC bus of the second inverter circuit.
  • the positive pole of the input end of the first inverter circuit is connected to the positive pole of the input end of the second inverter circuit (that is, the first positive DC bus bar is connected to the second positive DC bus bar), and the negative pole of the input end of the first inverter circuit is connected to the second positive DC bus bar.
  • the negative poles of the input ends of the second inverter circuit are connected (that is, the first negative DC bus is connected to the second negative DC bus).
  • the first controller can be used to: control the first relay to close.
  • the first controller can be used to control the common-mode voltage injection mode of the first inverter circuit to be the first common-mode voltage injection mode, and send common-mode voltage injection mode information to the second controller without controlling the first The DC bus voltage of the inverter circuit.
  • the common-mode voltage injection mode information is used to indicate the first common-mode voltage injection mode adopted by the first inverter circuit.
  • the first controller can also control the common-mode voltage output by the first inverter circuit according to the first common-mode voltage injection method.
  • the second controller can be used to: control the common-mode voltage injection mode of the second inverter circuit to be the same as the common-mode voltage injection mode of the first inverter circuit when the first relay is closed when the second relay is off, and thereafter Then control the second relay to close.
  • the second controller may be configured to receive common-mode voltage injection mode information from the first controller, and control the common-mode voltage injection mode of the second inverter circuit to be the first common-mode voltage injection mode according to the common-mode voltage injection mode information. The way of voltage injection, and after that, controlling the closing of the second relay also does not need to control the DC bus voltage of the second inverter circuit.
  • the second controller can also control the common-mode voltage output by the second inverter circuit according to the first common-mode voltage injection method.
  • the second controller can also control the effective value of the differential mode line voltage output by the second inverter circuit to be the same as the effective value of the grid line voltage when the second relay is turned off (or control the second inverter circuit The difference between the effective value of the output differential mode line voltage and the effective value of the grid line voltage is smaller than the second voltage threshold), and then the second relay is controlled to close.
  • Figure 9 shows an example of another multi-inverter parallel system provided by the embodiment of the present application.
  • This example is specifically a common DC bus multi-inverter parallel system, and the common DC bus multi-inverter parallel system Including multiple inverters, the positive poles of the input terminals of the inverter circuits of the multiple inverters are connected to each other, the negative poles of the input terminals are connected to each other, and the phases of the output terminals are connected to each other and connected to the same transformer, which is further connected to three interphase AC grid.
  • This application does not specifically limit the number of inverters included in the multi-inverter parallel system of the common DC bus. For the convenience of illustration, only two inverters are shown in Fig.
  • each inverter is Three-phase inverters, and may include controllers, inverter circuits, relays, and related circuit components such as capacitors and inductors.
  • the inverter 910 includes a controller 911 , an inverter circuit 912 and three relays 913
  • the inverter 920 includes a controller 921 , an inverter circuit 922 and three relays 923 .
  • the number of inverters in the system can be expanded according to the above-mentioned connection methods according to requirements, and details will not be repeated here.
  • the inverter grid-connection mechanism applicable to the multi-inverter parallel system with common DC bus in Figure 9 may include:
  • inverter 910 there is no inverter connected to the grid in the system, and one inverter (such as inverter 910 ) may be designated to be connected to the grid first. Since there is no grid-connected inverter in the system before the inverter 910 is connected to the grid, when the three relays 913 of the inverter 910 are closed, the bus voltage only needs to be guaranteed not to be lower than the minimum required for grid connection. The bus voltage is enough, and the common-mode voltage injection method can adopt any method. Before the three relays 913 are closed, the inverter 910 controls the differential mode line voltage output by itself to be consistent with the grid line voltage. Subsequently, the inverter 910 controls and closes the three relays 913 to realize the grid-connected operation of the inverter 910 .
  • the inverter 920 can communicate with the inverter 910 to control the inverter to be connected to the grid 920 is consistent with the common-mode voltage injection method of the grid-connected inverter 910 . Since the inverter 910 and the inverter 920 are connected in parallel with the same DC bus, the DC bus voltages of the two are naturally consistent, and there is no need to control the DC bus voltages of the two to be consistent through communication.
  • the inverter 920 to be connected to the grid can also control the differential mode line voltage output by itself to be consistent with the grid line voltage, and control its own output according to the same common mode voltage injection method as the inverter 910 common-mode voltage. Subsequently, the inverter 920 controls and closes three relays 923 to realize grid-connected operation of the inverter 920 .
  • the inverter control grid connection method corresponding to another multi-inverter parallel system provided by the embodiment of the present application can be shown in Figure 10, and this method is applied to multi-inverter A second controller of the second inverter in the parallel system, where the second inverter is an inverter to be grid-connected in the multi-inverter parallel system.
  • the method includes:
  • Step 1001 the second controller determines the first inverter, and the first inverter is an inverter connected to the grid in a multi-inverter parallel system.
  • the second controller can use a certain preset rule to select an inverter that has been connected to the grid in the multi-inverter parallel system as the first inverter.
  • the second controller can select the multi-inverter In the parallel system of inverters, the first inverter that has been connected to the grid can be used as the first inverter, or the inverter that has been connected to the grid recently in the multi-inverter parallel system can be selected as the first inverter. Any inverter that has been connected to the grid in the multi-inverter parallel system can also be selected as the first inverter, which is not limited in this application.
  • Step 1002 the second controller controls the common-mode voltage injection mode of the second inverter circuit to be the same as the common-mode voltage injection mode of the first inverter circuit when the second relay is turned off.
  • the second controller can also control the effective value of the differential mode line voltage output by the second inverter circuit to be the same as the effective value of the grid line voltage when the second relay is turned off.
  • Step 1003 the second controller controls the second relay to close.
  • the embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.
  • computer-usable storage media including but not limited to disk storage, CD-ROM, optical storage, etc.
  • These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions
  • the device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

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Abstract

一种多逆变器并联系统以及逆变器的控制并网方法，其中系统包括第一逆变器和第二逆变器，第一逆变器包括第一控制器、第一逆变电路和第一继电器，第二逆变器包括第二控制器、第二逆变电路和第二继电器，第一逆变电路的输出端的各相分别与第二逆变电路的输出端的各相对应连接；第一控制器可控制第一继电器闭合，第二控制器可在第二继电器断开时，控制第二逆变电路的与第一逆变电路的直流母线电压相同，且第二逆变电路与第一逆变电路的共模电压注入方式相同，然后再控制第二继电器闭合，实现第二逆变器的并网运行，从而使得第一逆变电路与第二逆变电路输出的共模电压一致，避免第二继电器闭合瞬间产生较大的共模环流冲击，影响系统的可靠性。

Description

一种多逆变器并联系统以及逆变器的控制并网方法 技术领域
本申请涉及电子技术领域，尤其涉及一种多逆变器并联系统以及逆变器的控制并网方法。
背景技术
逆变器是实现直流电转换为交流电的关键装置。为提升逆变器的功率容量，常用的实现方式是将多个逆变器通过串、并联的方式连接在一起，构成多逆变器并联系统，以传输更大功率。
对于单个逆变器，如图1所示，其交流侧通常设计有继电器，通过控制继电器的闭合与关联，可以实现逆变器的并网和脱网。但是在多逆变器并联系统中，不论多个逆变器之间的接线方式关系如何，由于系统通信延时的问题，系统中的多个逆变器往往难以实现同时并网，而是以一定的时序进行先后并网，因为难以控制多个继电器同时闭合。如此，如果时序上后并网(即继电器后闭合)的逆变器输出的交流三相电压与时序上先并网(即继电器先闭合)的逆变器输出的交流三相电压不同，就会在环流路径上形成环流，导致很大的并网电流冲击，从而影响系统的可靠性。
发明内容
本申请提供一种多逆变器并联系统以及逆变器的控制并网方法，用以避免多逆变器并联系统中逆变器并网瞬间产生冲击环流的问题，提高系统可靠性。
第一方面，本申请实施例提供一种多逆变器并联系统，该系统包括第一逆变器和第二逆变器；其中，第一逆变器包括第一逆变电路、第一控制器和第一继电器，第一逆变电路的输入端用于连接第一直流母线，输出端用于连接第一继电器；第二逆变器包括第二逆变电路、第二控制器和第二继电器，第二逆变电路的输入端用于连接第二直流母线，输出端用于连接第二继电器；第一逆变电路的输出端的各相分别与第二逆变电路的输出端的各相对应连接；第一控制器用于控制第一继电器闭合；第二控制器用于在第二继电器断开时，控制第二逆变电路的直流母线电压与第一继电器闭合时第一逆变电路的直流母线电压相同且第二逆变电路的共模电压注入方式与第一继电器闭合时第一逆变电路的共模电压注入方式相同，以及控制第二继电器闭合。
上述技术方案中，第二控制器可在第二继电器闭合前，控制第二逆变电路的直流母线电压与第一逆变电路的直流母线电压一致(例如均为第一电压值或趋近于第一电压值)，且控制第二逆变电路的共模电压注入方式与第一逆变电路的共模电压注入方式一致(例如均为第一共模电压注入方式)，从而使得第一逆变电路与第二逆变电路输出的共模电压相同或相近。在此之后，再控制第二继电器闭合，实现第二逆变器的并网运行，可有效避免第二继电器闭合的瞬间产生较大的共模环流冲击，影响系统的可靠性。
在第一方面的一种可能的设计中，第一控制器还用于：接收来自第二控制器的第一母线电压指令，该第一母线电压指令用于指示第二逆变电路的初始直流母线电压；根据第一逆变电路的初始直流母线电压和第二逆变电路的初始直流母线电压，确定第一电压值；向 第二控制器发送第二母线电压指令，该第二母线电压指令用于指示第一电压值。
在第一方面的一种可能的设计中，第二控制器还用于：接收来自第一控制器的第三母线电压指令，该第三母线电压指令用于指示第一逆变电路的初始直流母线电压；根据第一逆变电路的初始直流母线电压和第二逆变电路的初始直流母线电压，确定第一电压值；向第一控制器发送第四母线电压指令，该第四母线电压指令用于指示第一电压值。
上述技术方案中，第一控制器与第二控制器可通过进行信息交互(例如交互母线电压指令)，协商确定上述第一电压值，从而控制第二逆变电路的直流母线电压与第一逆变电路的直流母线电压一致。
在第一方面的一种可能的设计中，第二控制器还用于：接收来自第一控制器的共模电压注入方式信息，该共模电压注入方式信息用于指示第一逆变电路采用的第一共模电压注入方式；根据第一共模电压注入方式，控制第二逆变电路输出的共模电压。
上述技术方案中，第一控制器可通过与第二控制器进行信息交互，从而将第一逆变电路采用的共模电压注入方式通知给第二控制器，以便第二控制器控制第二逆变电路采用相同的共模电压注入方式。
在第一方面的一种可能的设计中，第二控制器还用于：在第二继电器断开时，控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
上述技术方案中，第二控制器可在第二继电器闭合前，控制第二逆变电路输出的差模线电压与电网线电压一致，或者均趋近于电网线电压。在此之后，再控制第二继电器闭合，实现第二逆变器的并网运行，可有效避免在第二继电器闭合的瞬间产生较大的差模环流冲击，影响系统的可靠性。
在第一方面的一种可能的设计中，第一直流母线包括第一正直流母线和第一负直流母线，其中第一正直流母线用于连接第一逆变电路的输入端的正极，第一负直流母线用于连接第一逆变电路的输入端的负极；第二直流母线包括第二正直流母线和第二负直流母线，其中第二正直流母线用于连接第二逆变电路的输入端的正极，第二负直流母线用于连接第二逆变电路的输入端的负极；第一负直流母线与第二正直流母线相连，或者第一正直流母线与第二负直流母线相连。
上述技术方案中的多逆变器并联系统具体可以为双极式串并联多逆变器并联系统。
第二方面，本申请实施例提供另一种多逆变器并联系统，该系统包括第一逆变器和第二逆变器；其中，第一逆变器包括第一逆变电路、第一控制器和第一继电器，第一逆变电路的输入端用于连接第一直流母线，输出端用于连接第一继电器；第二逆变器包括第二逆变电路、第二控制器和第二继电器，第二逆变电路的输入端用于连接第二直流母线，输出端用于连接第二继电器；第一逆变电路的输出端的各相分别与第二逆变电路的输出端的各相对应连接；第一直流母线与第二直流母线相连，第一控制器用于控制第一继电器闭合；第二控制器用于在第二继电器断开时，控制第二逆变电路的共模电压注入方式与第一继电器闭合时第一逆变电路的共模电压注入方式相同，以及控制第二继电器闭合。
上述技术方案中，由于第一直流母线与第二直流母线并联，第一逆变电路的直流母线电压与第二逆变电路的直流母线电压天然一致。因此，第二控制器可在第二继电器闭合前，控制第二逆变电路的共模电压注入方式与第一逆变电路的共模电压注入方式一致(例如均为第一共模电压注入方式)，从而使得第一逆变电路与第二逆变电路输出的共模电压相同或相近。在此之后，再控制第二继电器闭合，实现第二逆变器的并网运行，可有效避免第 二继电器闭合的瞬间产生较大的共模环流冲击，影响系统的可靠性。
在第二方面的一种可能的设计中，第二控制器还用于：接收来自第一控制器的共模电压注入方式信息，该共模电压注入方式信息用于指示第一逆变电路采用的第一共模电压注入方式；根据第一共模电压注入方式，控制第二逆变电路输出的共模电压。
在第二方面的一种可能的设计中，第二控制器还用于：在第二继电器断开时，控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
上述技术方案中，第二控制器可在第二继电器闭合前，控制第二逆变电路输出的差模线电压设置为与电网线电压一致，或者均趋近于电网线电压。在此之后，再控制第二继电器闭合，实现第二逆变器的并网运行，可有效避免在第二继电器闭合的瞬间产生较大的差模环流冲击，影响系统的可靠性。
在第二方面的一种可能的设计中，第一直流母线包括第一正直流母线和第一负直流母线，其中第一正直流母线用于连接第一逆变电路的输入端的正极，第一负直流母线用于连接第一逆变电路的输入端的负极；第二直流母线包括第二正直流母线和第二负直流母线，其中第二正直流母线用于连接第二逆变电路的输入端的正极，第二负直流母线用于连接所述第二逆变电路的输入端的负极；第一正直流母线与第二正直流母线相连，第一负直流母线与第二负直流母线相连。
上述技术方案中的多逆变器并联系统具体可以为共直流母线多逆变器并联系统。
第三方面，本申请实施例提供一种多逆变器并联系统中逆变器的控制并网方法，该方法应用于多逆变器并联系统中的第二逆变器的第二控制器，该第二逆变器为多逆变器并联系统中待并网的逆变器，其中，第二逆变器包括第二控制器、第二逆变电路和第二继电器，第二逆变电路的输入端连接第二直流母线，输出端连接第二继电器；该方法包括：第二控制器确定第一逆变器，该第一逆变器为多逆变器并联系统中已并网的逆变器，第一逆变器包括第一控制器、第一逆变电路和第一继电器，第一逆变电路的输入端连接第一直流母线，输出端连接第一继电器，第一继电器闭合，第一逆变电路的输出端的各相分别与第二逆变电路的输出端的各相对应连接；第二控制器在第二继电器断开时，控制第二逆变电路的直流母线电压与第一逆变电路的直流母线电压相同，且第二逆变电路的共模电压注入方式与第一逆变电路的共模电压注入方式相同；第二控制器控制第二继电器闭合。
在第三方面的一种可能的设计中，第二控制器在第二继电器断开时，控制第二逆变电路的直流母线电压与第一逆变电路的直流母线电压相同，包括：第二控制器在第二继电器断开时，控制第二逆变电路的直流母线电压与第一电压值之间的差值小于第一电压阈值。
在第三方面的一种可能的设计中，该方法还包括：第二控制器根据第一逆变电路的初始直流母线电压和第二逆变电路的初始直流母线电压，确定第一电压值；或者，第二控制器接收来自第一控制器的第二母线电压指令，该第二母线电压指令用于指示第一电压值。
在第三方面的一种可能的设计中，第二控制器在第二继电器断开时，控制第二逆变电路的共模电压注入方式与所述第一逆变电路的共模电压注入方式相同，包括：第二控制器接收来自第一控制器的共模电压注入方式信息，该共模电压注入方式信息用于指示第一逆变电路采用的第一共模电压注入方式；第二控制器根据第一共模电压注入方式，控制第二逆变电路输出的共模电压。
在第三方面的一种可能的设计中，该方法还包括：第二控制器在第二继电器断开时，控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
在第三方面的一种可能的设计中，第二直流母线包括第二正直流母线和第二负直流母线，第二正直流母线连接第二逆变电路的输入端的正极，第二负直流母线连接第二逆变电路的输入端的负极；第一直流母线包括第一正直流母线和第一负直流母线，第一正直流母线连接第一逆变电路的输入端的正极，第一负直流母线连接第一逆变电路的输入端的负极；其中，第一负直流母线与第二正直流母线相连，或者第一正直流母线与第二负直流母线相连。
第三方面和第三方面的任一种可能的设计中的有益效果可参考第一方面中的相应描述，不再赘述。
第四方面，本申请实施例提供一种多逆变器并联系统中逆变器的控制并网方法，该方法应用于第二逆变器的第二控制器，该第二逆变器为多逆变器并联系统中待并网的逆变器，第二逆变器包括第二控制器、第二逆变电路和第二继电器，第二逆变电路的输入端连接第二直流母线，输出端连接第二继电器；该方法包括：第二控制器确定第一逆变器，该第一逆变器为多逆变器并联系统中已并网的逆变器，第一逆变器包括第一控制器、第一逆变电路和第一继电器，第一逆变电路的输入端连接第一直流母线，输出端连接第一继电器，第一继电器闭合，第一直流母线与第二直流母线相连，第一逆变电路的输出端的各相分别与第二逆变电路的输出端的各相对应连接；第二控制器在第二继电器断开时，控制第二逆变电路的共模电压注入方式与第一逆变电路的共模电压注入方式相同；第二控制器控制第二继电器闭合。
在第四方面的一种可能的设计中，第二控制器在第二继电器断开时，控制第二逆变电路的共模电压注入方式与第一逆变电路的共模电压注入方式相同，包括：第二控制器接收来自第一控制器的共模电压注入方式信息，该共模电压注入方式信息用于指示第一逆变电路采用的第一共模电压注入方式；第二控制器根据第一共模电压注入方式，控制第二逆变电路输出的共模电压。
在第四方面的一种可能的设计中，该方法还包括：第二控制器在第二继电器断开时，控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
在第四方面的一种可能的设计中，第二直流母线包括第二正直流母线和第二负直流母线，第二正直流母线连接第二逆变电路的输入端的正极，第二负直流母线连接第二逆变电路的输入端的负极；第一直流母线包括第一正直流母线和第一负直流母线，第一正直流母线用于连接第一逆变电路的输入端的正极，第一负直流母线连接第一逆变电路的输入端的负极；其中，第一正直流母线与第二正直流母线相连，第一负直流母线与第二负直流母线相连。
第四方面和第四方面的任一种可能的设计中的有益效果可参考第二方面中的相应描述，不再赘述。
附图说明
图1为本申请实施例中单个逆变器连接的继电器的示意图；
图2为本申请实施例提供的一种多逆变器并联系统的结构示意图；
图3a、图3b和图3c为本申请实施例中第一控制器与第二控制器交互母线电压指令确定第一电压值的几种方式的示意图；
图4为本申请实施例提供的一种双极式串并联多逆变器并联系统的示意图；
图5为本申请实施例提供的一种共直流负极多逆变器并联系统的示意图；
图6为本申请实施例提供的一种共直流正极多逆变器并联系统的示意图；
图7为本申请实施例提供的一种逆变器的控制并网方法的流程示意图；
图8为本申请实施例提供的一种逆变器的控制并网方法的另一流程示意图；
图9为本申请实施例提供的一种共直流母线多逆变器并联系统的示意图；
图10为本申请实施例提供的一种逆变器的控制并网方法的又一流程示意图。
具体实施方式
为了使本申请的目的、技术方案和优点更加清楚，下面将结合附图对本申请作进一步地详细描述。
需要说明的是，在本申请的描述中“至少一个”是指一个或多个，“多个”是指两个或两个以上。鉴于此，本申请实施例中也可以将“多个”理解为“至少两个”。“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，字符“/”，如无特殊说明，一般表示前后关联对象是一种“或”的关系。另外，需要理解的是，在本申请的描述中，“第一”、“第二”等词汇，仅用于区分描述的目的，而不能理解为指示或暗示相对重要性，也不能理解为指示或暗示顺序。
本申请实施例提供一种多逆变器并联系统，如图2所示，该系统包括第一逆变器210和第二逆变器220。
应注意，本申请对多逆变器并联系统中包括的逆变器的数量不作具体限定。本申请仅以第一逆变器为该多逆变器并联系统中已并网的一台逆变器，第二逆变器为该多逆变器并联系统中还未并网但是将要进行并网的一台逆变器为例来说明本申请实施例所提供的多逆变器并联系统中的并网机制(或者称为开机启动机制)。其中，第一逆变器可以是该多逆变器并联系统中最先完成并网的一台逆变器，也可以是该多逆变器并联系统中最近完成并网的一台逆变器，也可以是该多逆变器并联系统中已完成并网的任一台逆变器，本申请均不限定。
可选的，该系统可包括数量更多的逆变器，例如，如图2所示，该系统共包括N个逆变器，所述N个逆变器包括第一逆变器210、第二逆变器220、…直至第N变压器2N0，N为大于或等于2的整数。
具体的，第一逆变器210包括第一控制器211、第一逆变电路212和第一继电器213，第一控制器211用于控制第一逆变电路212和第一继电器213。第一逆变电路212的输入端(也称直流出线端)连接第一直流母线，第一直流母线包括第一正直流母线和第一负直流母线，可选的，还包括第一中直流母线，其中，第一正直流母线连接第一逆变电路212的输入端的正极，第一负直流母线连接第一逆变电路212的输入端的负极。第一逆变电路212的每个输出端(也称交流出线端)连接一个第一继电器213的一端，第一继电器213的另一端连接第一变压器，该第一变压器的输出可进一步连接到交流电网，如此，通过控制第一继电器213的闭合与断开可实现第一逆变器210的并网与脱网。
类似的，第二逆变器220包括第二控制器221、第二逆变电路222和第二继电器223，第二控制器221用于控制第二逆变电路222和第二继电器223。第二逆变电路222的输入端(也称直流出线端)连接第二直流母线，第二直流母线包括第二正直流母线和第二负直 流母线，可选的，还包括第二中直流母线，其中，第二正直流母线连接第二逆变电路222的输入端的正极，第二负直流母线连接第二逆变电路222的输入端的负极。第二逆变电路222的每个输出端(也称交流出线端)连接一个第二继电器223的一端，第二继电器223的另一端连接第二变压器，该第二变压器的输出进一步连接到交流电网，如此，通过控制第二继电器223的闭合与断开可实现第二逆变器220的并网与脱网。
第一逆变电路212的输出端的各相分别与第二逆变电路222的输出端的各相对应连接，从而形成多个逆变器并联的形式。第一逆变电路212的输入端与第二逆变电路222的输入端可通过多种可能的方式进行连接，例如，在双极式串并联多逆变器并联系统中，若第二逆变器220与第一逆变器210相对应，则第一逆变电路212的输入端的负极与第二逆变电路222的输入端的正极连接(即第一负直流母线与第二正直流母线相连)，或者第一逆变电路212的输入端的正极可与第二逆变电路222的输入端的负极连接(即第一正直流母线与第二负直流母线相连)。再例如，在共负极直流母线多逆变器并联系统中，第一逆变电路212的输入端的负极可与第二逆变电路222的输入端的负极连接(即第一负直流母线与第二负直流母线相连)。再例如，在共正极直流母线多逆变器并联系统中，第一逆变电路212的输入端的正极可与第二逆变电路222的输入端的正极连接(即第一正直流母线与第二正直流母线相连)。
应注意，上述第一变压器和第二变压器可以是同一变压器或者同一变压器的相同绕组，也可以是不同变压器或者是同一变压器的不同绕组，本申请并不限定。
第一控制器211与第一逆变电路212和第一继电器213之间具有控制连接(如图2中虚线所示)。基于第一控制器211与第一逆变电路212之间的控制连接，第一控制器211可向第一逆变电路212提供电压控制指令，从而控制第一逆变电路212的直流母线电压或者控制第一逆变电路212输出的交流电压。基于第一控制器211与第一继电器213之间的控制连接，第一控制器211可向第一继电器213提供高电平或低电平的控制信号，从而控制第一继电器213闭合或断开。
示例性地，如图2所示，第一逆变器210为三相逆变器。第一逆变电路212具有三相交流出线端，每相交流出线端均通过一个第一继电器213与第一变压器连接，共存在三个第一继电器213。第一控制器211可对该三个第一继电器213进行同步控制，即当第一控制器211控制第一继电器213闭合时，表示第一控制器211控制该三个第一继电器213一起闭合，当第一控制器211控制第一继电器213断开时，表示第一控制器211控制该三个第一继电器213一起断开。例如，第一控制器211可以将与该三个第一继电器213都连接的一处电位设置为高电平，从而向三个第一继电器213同时提供高电平的控制信号，以控制该三个第一继电器213都闭合。再例如，第一控制器211也可以将与该三个第一继电器213都连接的一处电位设置为低电平，从而向三个第一继电器213同时提供低电平的控制信号，以控制该三个第一继电器213都断开。
第二控制器221与第二逆变电路222和第二继电器223之间具有控制连接(如图2中虚线所示)。基于第二控制器221与第二逆变电路222之间的控制连接，第二控制器221可向第二逆变电路222提供电压控制指令，从而控制第二逆变电路222的直流母线电压或者第二逆变电222路输出的交流电压。基于第二控制器221与第二继电器223之间的控制连接，第二控制器221可向第二继电器223提供高电平信号或低电平的控制信号，从而控制第二继电器223闭合或断开。
示例性地，如图2所示，第二逆变器220为三相逆变器。第二逆变电路222具有三相交流出线端，每相交流出线端均通过一个第二继电器223与第二变压器连接，共存在三个第二继电器223。第二控制器221可对该三个第二继电器223进行同步控制，即当第二控制器221控制第二继电器223闭合时，表示第二控制器221控制该三个第二继电器223一起闭合，当第二控制器221控制第二继电器223断开时，表示第二控制器221控制该三个第二继电器223一起断开。例如，第二控制器221可以将与该三个第二继电器223都连接的一处电位设置为高电平，从而向三个第二继电器223同时提供高电平的控制信号，以控制该三个第二继电器223都闭合。再例如，第二控制器221也可以将与该三个第二继电器223都连接的一处电位设置为低电平，从而向三个第二继电器223同时提供低电平的控制信号，以控制该三个第二继电器223都断开。
第一控制器211与第二控制器221之间具有通信连接(通信连接暂未在图2中示出)，第一控制器211与第二控制器221可通过该通信连接交互必要的指令或信息，从而支持逆变器进行并网或脱网。所述通信连接可以是有线连接(例如有线线缆)，也可以是无线连接(例如第五代(the 5th generation，5G)网络等)，本申请并不限定。
具体的，第一控制器可用于：控制第一继电器闭合。可选的，第一控制器可在第一继电器闭合时，控制第一逆变电路的直流母线电压为第一电压值(或者说控制第一逆变电路的直流母线电压与第一电压值之间的差值小于第一电压阈值)，以及控制第一逆变电路的共模电压注入方式为第一共模电压注入方式。可选的，第一控制器还可用于向第二控制器发送共模电压注入方式信息，该共模电压注入方式信息用于指示第一逆变电路采用的第一共模电压注入方式。第一控制器还可根据该第一共模电压注入方式，控制第一逆变电路输出的共模电压。
第一共模电压注入方式可以为连续脉冲宽度调制(continuous pulse width modulation，CPWM)方式或者不连续脉冲宽度调制(discontinuous pulse width modulation，DPWM)方式，本申请并不限定。CPWM方式和DPWM方式均可具有多种可能的具体实现方式，本申请不再详述。所述“共模电压注入方式”是指令三相逆变器输出的三相电压中增加共模电压分量的某种预设规律，也可称为调制方式或共模电压调制方式或者具有其它名称，本申请均不限制。
第二控制器可用于：在第二继电器断开时，控制第二逆变电路的直流母线电压与第一继电器闭合时第一逆变电路的直流母线电压相同，且第二逆变电路的共模电压注入方式与第一继电器闭合时第一逆变电路的共模电压注入方式相同，此后再控制第二继电器闭合。
可选的，第二控制器可在第二继电器闭合时，控制第二逆变电路的直流母线电压为第一电压值(或者说控制第二逆变电路的直流母线电压与第一电压值之间的差值小于第一电压阈值)，以及控制第二逆变电路的共模电压注入方式为第一共模电压注入方式，并在此后控制第二继电器闭合。其中，该第一共模电压注入方式即为上文中第一逆变电路采用的共模电压注入方式，第二控制器可接收来自第一控制器的共模电压注入方式信息，根据该共模电压注入方式信息，确定第一共模电压注入方式，进而根据该第一共模电压注入方式，控制第二逆变电路输出的共模电压。可选的，第二控制器在控制第二继电器闭合之前，可按照第一共模电压注入方式，控制第二逆变电路输出的共模电压。
本申请实施例中，第一控制器控制第一逆变电路的直流母线电压与第一电压值之间的差值小于第一电压阈值可以理解为：第一控制器控制第一逆变电路的直流母线电压等于或 趋近于第一电压值。类似的，第二控制器控制第二逆变电路的直流母线电压与第一电压值之间的差值小于第一电压阈值可以理解为：第二控制器控制第二逆变电路的直流母线电压等于或趋近于第一电压值。
如此，通过上述方式，第二控制器可在第二继电器闭合前，控制第二逆变电路的直流母线电压与第一逆变电路的直流母线电压一致(例如均为第一电压值或趋近于第一电压值)，且控制第二逆变电路的共模电压注入方式为与第一逆变电路的共模电压注入方式一致(例如均为第一共模电压注入方式)，从而使得第一逆变电路与第二逆变电路输出的共模电压相同或相近。在此之后，再控制第二继电器闭合，实现第二逆变器的并网运行，可有效避免第二继电器闭合的瞬间产生较大的共模环流冲击，影响系统的可靠性。
可选的，第一电压值大于或等于第一逆变电路的初始直流母线电压，且大于或等于第二逆变电路的初始直流母线电压。其中，第一逆变电路的初始直流母线电压是指，在第二继电器闭合前第一逆变电路的直流母线电压。类似的，第二逆变电路的初始直流母线电压是指，在第二继电器闭合前第二逆变电路的直流母线电压。
示例性地，第一控制器和第二控制器可通过信息交互(如交互母线电压指令)，协商确定上述第一电压值，从而使得第一逆变器与第二逆变器对第一电压值的理解保持一致。也就是说，第一电压值可以是第一逆变电路的初始直流母线电压，也可以是第二逆变电路的初始直流母线电压，也可以是区别于二者的另一值。
在一个示例中，如图3a所示，第一控制器可接收来自第二控制器的第一母线电压指令，该第一母线电压指令用于指示第二逆变电路的初始直流母线电压。如此，第一控制器可根据第一逆变电路的初始直流母线电压以及根据第一母线电压指令确定的第二逆变电路的初始直流母线电压，确定第一电压值，进而向第二控制器发送第二母线电压指令，该第二母线电压指令用于指示第一电压值。例如，第一控制器可将第一逆变电路的初始直流母线电压和第二逆变电路的初始直流母线电压中较大的那个电压值，确定为第一电压值，或者也可以将一个大于第一逆变电路的初始直流母线电压，同时大于第二逆变电路的初始直流母线电压的电压值，确定为第一电压值，本申请并不限定。
在另一个示例中，如图3b所示，第二控制器可接收来自第一控制器的第三母线电压指令，该第三母线电压指令用于指示第一逆变电路的初始直流母线电压。如此，第二控制器可根据第二逆变电路的初始直流母线电压以及根据第三母线电压指令确定的第一逆变电路的初始直流母线电压，确定第一电压值，进而向第一控制器发送第四母线电压指令，该第四母线电压指令用于指示第一电压值。例如，第二控制器可将第一逆变电路的初始直流母线电压和第二逆变电路的初始直流母线电压中较大的那个电压值，确定为第一电压值，或者也可以将一个大于第一逆变电路的初始直流母线电压，同时大于第二逆变电路的初始直流母线电压的电压值，确定为第一电压值，本申请并不限定。
在另一个示例中，如果已并网的逆变器的逆变电路的直流母线电压默认比未并网的逆变电路的直流母线电压要大，在这种情形下，如图3c所示，第一控制器可向第二控制器发送第五母线电压指令，通过该第五母线电压指令将第一逆变电路的初始直流母线电压指示给第二控制器。如此，第二控制器接收到该第五母线电压指令后，可将第一逆变电路的初始直流母线电压确定为第一电压值，进而，如上文中所述，第二控制器可在控制第二逆变电路的直流母线电压等于或趋近于第一电压值后，控制第二继电器闭合。
可选的，第二控制器还可在第二继电器断开时，控制第二逆变电路输出的差模线电压 的有效值与电网线电压的有效值相同(或者说控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值之间的差值小于第二电压阈值)，进而再控制第二继电器闭合。即，第二控制器可在控制第二逆变电路的直流母线电压与第一继电器闭合时第一逆变电路的直流母线电压相同、且第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同、且第二逆变电路的共模电压注入方式与第一继电器闭合时第一逆变电路的共模电压注入方式相同之后，控制第二继电器闭合。
如此，通过上述方式，第二控制器可在第二继电器闭合前，控制第二逆变电路输出的差模线电压设置为与电网线电压一致，或者趋近于电网线电压。在此之后，再控制第二继电器闭合，实现第二逆变器的并网运行，可有效避免在第二继电器闭合的瞬间产生较大的差模环流冲击，影响系统的可靠性。
下面给出本申请实施例提供的多逆变器并联系统的几个具体示例。上文中所介绍的逆变器的并网机制均可适用于下述几种具体的多逆变器并联系统。
图4所示为一种双极式串并联多逆变器并联系统，该系统中包括2M个逆变器，M为正整数。2M个逆变器可分为两组，每组M个逆变器，两组之间逆变器一一对应。其中，第一组的第i个逆变器的逆变电路的输入端的负极与第二组中第i个逆变器的逆变电路的输入端的正极相连。第一组逆变器的逆变电路的输出端的各相彼此相连，第二组逆变器的逆变电路的输出端的各相也彼此相连，第一组逆变器与第二组逆变器的逆变电路的输出端分别连接到不同的变压器或同一变压器的不同绕组，进而连接到三相交流电网。由于第一组逆变器的逆变电路的输入端的负极电位高于第二组逆变器的逆变电路的输入端的负极电位，因此，可称第一组逆变器为正极逆变器，第二组逆变器为负极逆变器。
为了图示方便，图4中仅画出了4个逆变器(即每组2个逆变器)，每个逆变器均为三相逆变器，并可包括控制器、逆变电路、继电器以及相关的电容、电感等电路元件。如图4所示，正极逆变器410包括控制器411、正极逆变电路412以及3个继电器413，负极逆变器420包括控制器421、负极逆变电路422以及3个继电器423，正极逆变器430包括控制器431、正极逆变电路432以及3个继电器433，负极逆变器440包括控制器441、负极逆变电路442以及3个继电器443。其中，正极逆变器410和正极逆变器430属于第一组逆变器，负极逆变器420和负极逆变器440属于第二组逆变器。可以理解地，每组逆变器的数量均可根据实际需要按照上述连接方式进行扩展，不再赘述。
图5中的双极式串、并联多逆变器并联系统适用的逆变器的并网机制可包括：
初始时，该系统中尚无逆变器并网，可指定一台逆变器(如正极逆变器410)最先并网。由于在正极逆变器410并网前，该系统中无已并网逆变器，因此，在正极逆变器410的3个继电器413闭合时，其母线电压只需保证不低于并网所需的最低母线电压即可，共模电压注入方式可以采取任意一种方式。在继电器413闭合前，正极逆变器410还可控制自身输出的差模线电压与电网线电压一致，随后，正极逆变器410控制闭合3个继电器413，实现正极逆变器410的并网运行。
在正极逆变器410并网后，后续逆变器要并网时，例如负极逆变器420要并网时，负极逆变器420可通过与正极逆变器410通信(例如交互母线电压指令)，控制待并网的负极逆变器420与已并网的正极逆变器410的直流母线电压一致，以及控制待并网的负极逆变器420与已并网的正极逆变器410的共模电压注入方式一致。在3个继电器420闭合前， 待并网的负极逆变器420还可控制自身输出的差模线电压与电网线电压一致，并按照与正极逆变器410相同的共模电压注入方式，控制自身输出的共模电压。随后，负极逆变器420控制闭合3个继电器423，实现负极逆变器423的并网运行。
进而，参照上述方式陆续实现其他逆变器的并网运行。例如，在正极逆变器410和负极逆变器430并网后，正极逆变器430要并网时，正极逆变器430可通过与正极逆变器410通信(例如交互母线电压指令)，控制待并网的正极逆变器430与已并网的正极逆变器410的直流母线电压一致，以及控制待并网的正极逆变器430与已并网的正极逆变器420的共模电压注入方式一致。在3个继电器433闭合前，待并网的正极逆变器430可控制自身输出的差模线电压与电网线电压一致，并按照与正极逆变器410相同的共模电压注入方式，控制自身输出的共模电压。随后，正极逆变器430控制闭合3个继电器433，实现正极逆变器430的并网运行。或者，正极逆变器430也可通过与负极逆变器420通信(例如交互母线电压指令)，控制待并网的正极逆变器430与已并网的负极逆变器420的直流母线电压一致，以及控制待并网的正极逆变器430与已并网的负极逆变器420的共模电压注入方式一致。在3个继电器433闭合前，待并网的正极逆变器430可控制自身输出的差模线电压与电网线电压一致，并按照与负极逆变器420相同的共模电压注入方式，控制自身输出的共模电压。随后，正极逆变器430控制闭合3个继电器433，实现正极逆变器430的并网运行。
通过上述并网机制，可实现逆变器并网时的共模电压缓起和差模电压缓起，从而避免在逆变器并网瞬间系统中产生极大的共模环流和差模环流，有效提升系统的可靠性。
本申请对多逆变器并联系统中多台逆变器并网的先后顺序不作具体限定。可以理解地，如果先并网正极逆变器410，后并网负极逆变器420，当正极逆变器410已并网，负极逆变器420要并网时，正极逆变器410可作为上文中所述的第一逆变器，负极逆变器420可作为上文中所述的第二逆变器执行上文中的逆变器并网机制。类似的，如果先并网负极逆变器420，后并网正极逆变器410，当负极逆变器420已并网，正极逆变器410要并网时，负极逆变器420可作为上文中所述的第一逆变器，正极逆变器410可作为上文中所述的第二逆变器执行上文中的逆变器并网机制。
图5所示为一种共负极直流母线多逆变器并联系统，也可称为共直流母线负极多逆变器并联系统。该系统中可包括多个逆变器，多个逆变器的逆变电路的输入端的负极彼此相连，输出端的各相彼此相连。由于这些逆变器对于直流侧并机点的电位均为正，因此，可称这些逆变器为正极逆变器。为了图示方便，图5中仅画出了两个逆变器，每个逆变器均为三相逆变器，并可包括控制器、逆变电路、继电器以及相关的电容、电感等电路元件。如图5所示，正极逆变器510包括控制器511、正极逆变电路512以及3个继电器513，正极逆变器520包括控制器521、正极逆变电路522以及3个继电器523。但应注意，本申请对该系统中包括的逆变器的数量不作具体限定，例如，该系统中还可包括其他正极逆变器。该系统中逆变器的并网机制与可参考图4中的相应描述，不再赘述。
图6所示为一种共正极直流母线多逆变器并联系统，也可称为共直流母线正极多逆变器并联系统。该系统中可包括多个逆变器，多个逆变器的逆变电路的输入端的正极彼此相连，输出端的各相彼此相连。由于这些逆变器对于直流侧并机点的电位均为负，因此称这些逆变器为负极逆变器。为了图示方便，图6中仅画出了两个逆变器，每个逆变器均为三相逆变器，并可包括控制器、逆变电路、继电器以及相关的电容、电感等电路元件。如图 6所示，负极逆变器610包括控制器611、负极逆变电路612以及3个继电器613，负极逆变器620包括控制器621、负极逆变电路622以及3个继电器623。但应注意，本申请对该系统中包括的逆变器的数量不作具体限定，例如，该系统中还可包括其他负极逆变器。该系统中逆变器的并网机制与可参考图4中的相应描述，不再赘述。
基于上述各种可能的多逆变器并联系统，本申请实施例还提供一种逆变器的控制并网方法，如图7所示，该方法包括：
步骤701，确定待并网逆变器和已并网逆变器。
步骤702，待并网逆变器与已并网逆变器交互母线电压指令，使得全部逆变器的直流母线电压一致，即待并网逆变器控制其直流母线电压为第一电压值(或者说控制其直流母线电压与第一电压值之间的差值小于第一电压阈值)，同时已并网逆变器也控制其直流母线电压为第一电压值(或者说也控制其直流母线电压与第一电压值之间的差值小于第一电压阈值)。
步骤703，待并网逆变器与已并网逆变器交互共模电压注入方式信息，使得全部逆变器采用相同的共模电压注入方式。
应注意，本申请对步骤702与步骤703之间的执行顺序不作具体限定。
步骤704，待并网逆变器在继电器闭合前，控制其差模线电压与电网线电压一致，即待并网逆变器控制其输出的差模线电压有效值与电网线电压有效值相同(或者说控制其输出的差模线电压有效值与电网线电压有效值之间的偏差小于第二电压阈值)，并按照上述共模电压注入方式，注入共模电压；
步骤705，待并网逆变器闭合并网继电器，实现开机启动。
从第二逆变器的角度，与本申请实施例提供的上述多逆变器并联系统对应的逆变器的控制并网方法可如图8所示，该方法应用于多逆变器并联系统中的第二逆变器的第二控制器，该第二逆变器为多逆变器并联系统中待并网的逆变器。该方法包括：
步骤801，第二控制器确定第一逆变器，该第一逆变器为多逆变器并联系统中已并网的逆变器。
本申请实施例中，第二控制器可采用某种预设规则选择多逆变器并联系统中已并网的一台逆变器作为第一逆变器，例如第二控制器可选择多逆变器并联系统中最先完成并网的一台逆变器作为第一逆变器，也可以选择多逆变器并联系统中最近完成并网的一台逆变器作为第一逆变器，也可以选择多逆变器并联系统中已完成并网的任一台逆变器作为第一逆变器，本申请均不限定。
步骤802，第二控制器在第二继电器断开时，控制第二逆变电路的直流母线电压与第一逆变电路的直流母线电压相同，且第二逆变电路的共模电压注入方式与第一逆变电路的共模电压注入方式相同。
可选的，第二控制器还可在第二继电器断开时，控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
步骤803，第二控制器控制第二继电器闭合。
本申请实施例还提供另一种多逆变器并联系统，该多逆变器并联系统包括第一逆变器和第二逆变器，其中，第一逆变器包括第一控制器、第一逆变电路和第一继电器，第一控制器用于控制第一逆变电路和第一继电器，第二逆变器包括第二控制器、第二逆变电路和 第二继电器，第二控制器用于控制第二逆变电路和第二继电器。
具体的，第一逆变电路的输入端(也称直流出线端)连接第一直流母线，第一直流母线包括第一正直流母线和第一负直流母线，可选的，还包括第一中直流母线，其中，第一正直流母线连接第一逆变电路的输入端的正极，第一负直流母线连接第一逆变电路的输入端的负极。第一逆变电路的输出端(也称交流出线端)连接第一继电器的一端，第一继电器的另一端连接变压器，该变压器的输出可进一步连接到交流电网，如此，通过控制第一继电器的闭合与断开可实现第一逆变器的并网与脱网。
第二逆变电路的输入端(也称直流出线端)连接第二直流母线，第二直流母线包括第二正直流母线和第二负直流母线，可选的，还包括第二中直流母线，其中，第二正直流母线连接第二逆变电路的输入端的正极，第二负直流母线连接第二逆变电路的输入端的负极。第二逆变电路的输出端(也称交流出线端)连接第二继电器的一端，第二继电器的另一端连接同一变压器，该变压器进一步连接到交流电网，如此，通过控制第二继电器的闭合与断开可实现第二逆变器的并网与脱网。
第一逆变电路的输出端的各相分别与第二逆变电路的输出端的各相对应连接，且第一逆变电路的第一直流母线与第二逆变电路的第二直流母线相连。具体的，第一逆变电路的输入端的正极与第二逆变电路的输入端的正极连接(即第一正直流母线与第二正直流母线相连)，第一逆变电路的输入端的负极与第二逆变电路的输入端的负极连接(即第一负直流母线与第二负直流母线相连)。
在该多逆变器并联系统中，由于第一逆变电路的第一直流母线与第二逆变电路的第二直流母线相连，第一逆变电路的直流母线电压与第二逆变电路的直流母线电压天然一致。因此，在第二逆变器并网的过程中，第一控制器可用于：控制第一继电器闭合。可选的，第一控制器可用于控制第一逆变电路的共模电压注入方式为第一共模电压注入方式，以及向第二控制器发送共模电压注入方式信息，而无需控制第一逆变电路的直流母线电压。该共模电压注入方式信息用于指示第一逆变电路采用的第一共模电压注入方式。可选的，第一控制器还可根据第一共模电压注入方式，控制第一逆变电路输出的共模电压。
相应的，第二控制器可用于：在第二继电器断开时，控制第二逆变电路的共模电压注入方式与第一继电器闭合时第一逆变电路的共模电压注入方式相同，此后再控制第二继电器闭合。可选的，第二控制器可用于，接收来自第一控制器的共模电压注入方式信息，根据该共模电压注入方式信息控制第二逆变电路的共模电压注入方式为第一共模电压注入方式，以及在此之后，控制第二继电器闭合，同样无需控制第二逆变电路的直流母线电压。
可选的，第二控制器还可根据第一共模电压注入方式，控制第二逆变电路输出的共模电压。
可选的，第二控制器还可在第二继电器断开时，控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同(或者说控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值之间的差值小于第二电压阈值)，此后再控制第二继电器闭合。
图9所示为本申请实施例提供的另一种多逆变器并联系统的一个示例，该示例具体为一种共直流母线多逆变器并联系统，该共直流母线多逆变器并联系统中包括多个逆变器，多个逆变器的逆变电路的输入端的正极彼此相连，输入端的负极彼此相连，输出端的各相彼此相连，并连接到相同的变压器，该变压器进一步连接到三相交流电网。本申请对该共直流母线多逆变器并联系统中包括的逆变器的数量不作具体限定，为了图示方便，图9中 仅画出了两个逆变器，每个逆变器均为三相逆变器，并可包括控制器、逆变电路、继电器以及相关的电容、电感等电路元件。如图9所示，逆变器910包括控制器911、逆变电路912以及3个继电器913，逆变器920包括控制器921、逆变电路922以及3个继电器923。实际中，可根据需求按照上述连接方式对系统中逆变器的数量进行扩展，不再赘述。
图9中的共直流母线多逆变器并联系统适用的逆变器的并网机制可包括：
初始时，该系统中尚无逆变器并网，可指定一台逆变器(如逆变器910)最先并网。由于在逆变器910并网前，该系统中无已并网逆变器，因此，逆变器910的3个继电器913闭合时，其母线电压只需保证不低于并网所需的最低母线电压即可，共模电压注入方式可以采取任意一种方式。在3个继电器913闭合前，逆变器910控制自身输出的差模线电压与电网线电压一致。随后，逆变器910控制闭合3个继电器913，实现逆变器910的并网运行。
在逆变器910并网后，当后续逆变器要并网时，例如逆变器920要并网时，逆变器920可通过与逆变器910通信，控制待并网的逆变器920与已并网的逆变器910的共模电压注入方式一致。由于逆变器910与逆变器920共直流母线并联，因此两者直流母线电压天然一致，不需要通过通信控制两者的直流母线电压一致。在3个继电器923闭合前，待并网的逆变器920还可控制自身输出的差模线电压与电网线电压一致，并按与逆变器910相同的共模电压注入方式，控制自身输出的共模电压。随后，逆变器920控制闭合3个继电器923，实现逆变器920的并网运行。
进而，如果该系统中还包括更多的逆变器，则可按照上述方式，陆续实现其他逆变器的并网运行，不再赘述。
从第二逆变器的角度，与本申请实施例提供的另一种多逆变器并联系统相应的逆变器的控制并网方法可如图10所示，该方法应用于多逆变器并联系统中的第二逆变器的第二控制器，该第二逆变器为多逆变器并联系统中待并网的逆变器。该方法包括：
步骤1001，第二控制器确定第一逆变器，该第一逆变器为多逆变器并联系统中已并网的逆变器。
本申请实施例中，第二控制器可采用某种预设规则选择多逆变器并联系统中已并网的一台逆变器作为第一逆变器，例如第二控制器可选择多逆变器并联系统中最先完成并网的一台逆变器作为第一逆变器，也可以选择多逆变器并联系统中最近完成并网的一台逆变器作为第一逆变器，也可以选择多逆变器并联系统中已完成并网的任一台逆变器作为第一逆变器，本申请均不限定。
步骤1002，第二控制器在第二继电器断开时，控制第二逆变电路的共模电压注入方式与第一逆变电路的共模电压注入方式相同。
可选的，第二控制器还可在第二继电器断开时，控制第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
步骤1003，第二控制器控制第二继电器闭合。
本领域内的技术人员应明白，本申请的实施例可提供为方法、系统、或计算机程序产品。因此，本申请可采用完全硬件实施例、完全软件实施例、或结合软件和硬件方面的实施例的形式。而且，本申请可采用在一个或多个其中包含有计算机可用程序代码的计算机可用存储介质(包括但不限于磁盘存储器、CD-ROM、光学存储器等)上实施的计算机程 序产品的形式。
本申请是参照根据本申请的方法、设备(系统)、和计算机程序产品的流程图和/或方框图来描述的。应理解可由计算机程序指令实现流程图和/或方框图中的每一流程和/或方框、以及流程图和/或方框图中的流程和/或方框的结合。可提供这些计算机程序指令到通用计算机、专用计算机、嵌入式处理机或其他可编程数据处理设备的处理器以产生一个机器，使得通过计算机或其他可编程数据处理设备的处理器执行的指令产生用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的装置。
这些计算机程序指令也可存储在能引导计算机或其他可编程数据处理设备以特定方式工作的计算机可读存储器中，使得存储在该计算机可读存储器中的指令产生包括指令装置的制造品，该指令装置实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能。
这些计算机程序指令也可装载到计算机或其他可编程数据处理设备上，使得在计算机或其他可编程设备上执行一系列操作步骤以产生计算机实现的处理，从而在计算机或其他可编程设备上执行的指令提供用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的步骤。
显然，本领域的技术人员可以对本申请进行各种改动和变型而不脱离本申请的保护范围。这样，倘若本申请的这些修改和变型属于本申请权利要求及其等同技术的范围之内，则本申请也意图包含这些改动和变型在内。

Claims (21)

  1. 一种多逆变器并联系统，其特征在于，包括第一逆变器和第二逆变器；
    所述第一逆变器包括第一控制器、第一逆变电路和第一继电器，所述第一逆变电路的输入端用于连接第一直流母线，输出端用于连接所述第一继电器；
    所述第二逆变器包括第二控制器、第二逆变电路和第二继电器，所述第二逆变电路的输入端用于连接第二直流母线，输出端用于连接所述第二继电器；所述第一逆变电路的输出端的各相分别与所述第二逆变电路的输出端的各相对应连接；
    所述第一控制器，用于控制所述第一继电器闭合；
    所述第二控制器，用于在所述第二继电器断开时，控制所述第二逆变电路的直流母线电压与所述第一继电器闭合时所述第一逆变电路的直流母线电压相同且所述第二逆变电路的共模电压注入方式与所述第一继电器闭合时所述第一逆变电路的共模电压注入方式相同，以及控制所述第二继电器闭合。
  2. 根据权利要求1所述的系统，其特征在于，所述第一控制器具体用于，在所述第一继电器闭合时，控制所述第一逆变电路的直流母线电压与第一电压值之间的差值小于第一电压阈值；
    所述第二控制器具体用于，在所述第二继电器断开时，控制所述第二逆变电路的直流母线电压与所述第一电压值之间的差值小于所述第一电压阈值。
  3. 根据权利要求2所述的系统，其特征在于，所述第一控制器还用于：
    接收来自所述第二控制器的第一母线电压指令，所述第一母线电压指令用于指示所述第二逆变电路的初始直流母线电压；
    根据所述第一逆变电路的初始直流母线电压和所述第二逆变电路的初始直流母线电压，确定所述第一电压值；
    向所述第二控制器发送第二母线电压指令，所述第二母线电压指令用于指示所述第一电压值。
  4. 根据权利要求2所述的系统，其特征在于，所述第二控制器还用于：
    接收来自所述第一控制器的第三母线电压指令，所述第三母线电压指令用于指示所述第一逆变电路的初始直流母线电压；
    根据所述第一逆变电路的初始直流母线电压和所述第二逆变电路的初始直流母线电压，确定所述第一电压值；
    向所述第一控制器发送第四母线电压指令，所述第四母线电压指令用于指示所述第一电压值。
  5. 根据权利要求1至4中任一项所述的系统，其特征在于，所述第二控制器还用于：
    接收来自所述第一控制器的共模电压注入方式信息，所述共模电压注入方式信息用于指示所述第一逆变电路采用的第一共模电压注入方式；
    根据所述第一共模电压注入方式，控制所述第二逆变电路输出的共模电压。
  6. 根据权利要求1至5中任一项所述的系统，其特征在于，所述第二控制器还用于：
    在所述第二继电器断开时，控制所述第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
  7. 根据权利要求1至6中任一项所述的系统，其特征在于，所述第一直流母线包括第 一正直流母线和第一负直流母线，所述第一正直流母线用于连接所述第一逆变电路的输入端的正极，所述第一负直流母线用于连接所述第一逆变电路的输入端的负极；
    所述第二直流母线包括第二正直流母线和第二负直流母线，所述第二正直流母线用于连接所述第二逆变电路的输入端的正极，所述第二负直流母线用于连接所述第二逆变电路的输入端的负极；
    其中，所述第一负直流母线与所述第二正直流母线相连，或者所述第一正直流母线与所述第二负直流母线相连。
  8. 一种多逆变器并联系统，其特征在于，所述系统包括第一逆变器和第二逆变器；
    所述第一逆变器包括第一控制器、第一逆变电路和第一继电器，所述第一逆变电路的输入端用于连接第一直流母线，输出端用于连接第一继电器；
    所述第二逆变器包括第二控制器、第二逆变电路和第二继电器，所述第二逆变电路的输入端用于连接第二直流母线，输出端用于连接第二继电器；所述第一直流母线与所述第二直流母线相连，所述第一逆变电路的输出端的各相分别与所述第二逆变电路的输出端的各相对应连接；
    所述第一控制器，用于控制所述第一继电器闭合；
    所述第二控制器，用于在所述第二继电器断开时，控制所述第二逆变电路的共模电压注入方式与所述第一继电器闭合时所述第一逆变电路的共模电压注入方式相同，以及控制所述第二继电器闭合。
  9. 根据权利要求8所述的系统，其特征在于，所述第二控制器还用于：
    接收来自所述第一控制器的共模电压注入方式信息，所述共模电压注入方式信息用于指示所述第一逆变电路采用的第一共模电压注入方式；
    根据所述第一共模电压注入方式，控制所述第二逆变电路输出的共模电压。
  10. 根据权利要求8或9所述的系统，其特征在于，所述第二控制器还用于：
    在所述第二继电器断开时，控制所述第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
  11. 根据权利要求8至10中任一项所述的系统，其特征在于，所述第一直流母线包括第一正直流母线和第一负直流母线，所述第一正直流母线用于连接所述第一逆变电路的输入端的正极，所述第一负直流母线用于连接所述第一逆变电路的输入端的负极；
    所述第二直流母线包括第二正直流母线和第二负直流母线，所述第二正直流母线用于连接所述第二逆变电路的输入端的正极，所述第二负直流母线用于连接所述第二逆变电路的输入端的负极；
    其中，所述第一正直流母线与所述第二正直流母线相连，所述第一负直流母线与所述第二负直流母线相连。
  12. 一种逆变器的控制并网方法，其特征在于，所述方法应用于第二逆变器的第二控制器，所述第二逆变器为多逆变器并联系统中待并网的逆变器，所述第二逆变器包括所述第二控制器、第二逆变电路和第二继电器，所述第二逆变电路的输入端连接第二直流母线，输出端连接所述第二继电器；所述方法包括：
    所述第二控制器确定第一逆变器，所述第一逆变器为所述多逆变器并联系统中已并网的逆变器，所述第一逆变器包括第一控制器、第一逆变电路和第一继电器，所述第一逆变电路的输入端连接第一直流母线，输出端连接所述第一继电器，所述第一继电器闭合，所 述第一逆变电路的输出端的各相分别与所述第二逆变电路的输出端的各相对应连接；
    所述第二控制器在所述第二继电器断开时，控制所述第二逆变电路的直流母线电压与所述第一逆变电路的直流母线电压相同，且所述第二逆变电路的共模电压注入方式与所述第一逆变电路的共模电压注入方式相同；
    所述第二控制器控制所述第二继电器闭合。
  13. 根据权利要求12所述的方法，其特征在于，所述第二控制器在所述第二继电器断开时，控制所述第二逆变电路的直流母线电压与所述第一逆变电路的直流母线电压相同，包括：
    所述第二控制器在所述第二继电器断开时，控制所述第二逆变电路的直流母线电压与第一电压值之间的差值小于所述第一电压阈值。
  14. 根据权利要求13所述的方法，其特征在于，所述方法还包括：
    所述第二控制器根据所述第一逆变电路的初始直流母线电压和所述第二逆变电路的初始直流母线电压，确定所述第一电压值；或者，
    所述第二控制器接收来自所述第一控制器的第二母线电压指令，所述第二母线电压指令用于指示所述第一电压值。
  15. 根据权利要求12至14中任一项所述的方法，其特征在于，所述第二控制器在所述第二继电器断开时，控制所述第二逆变电路的共模电压注入方式与所述第一逆变电路的共模电压注入方式相同，包括：
    所述第二控制器接收来自所述第一控制器的共模电压注入方式信息，所述共模电压注入方式信息用于指示所述第一逆变电路采用的第一共模电压注入方式；
    所述第二控制器根据所述第一共模电压注入方式，控制所述第二逆变电路输出的共模电压。
  16. 根据权利要求12至15中任一项所述的方法，其特征在于，所述方法还包括：
    所述第二控制器在所述第二继电器断开时，控制所述第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
  17. 根据权利要求12至16中任一项所述的方法，其特征在于，所述第二直流母线包括第二正直流母线和第二负直流母线，所述第二正直流母线连接所述第二逆变电路的输入端的正极，所述第二负直流母线连接所述第二逆变电路的输入端的负极；
    所述第一直流母线包括第一正直流母线和第一负直流母线，所述第一正直流母线连接所述第一逆变电路的输入端的正极，所述第一负直流母线连接所述第一逆变电路的输入端的负极；
    其中，所述第一负直流母线与所述第二正直流母线相连，或者所述第一正直流母线与所述第二负直流母线相连。
  18. 一种逆变器的控制并网方法，其特征在于，所述方法应用于第二逆变器的第二控制器，所述第二逆变器为多逆变器并联系统中待并网的逆变器，所述第二逆变器包括所述第二控制器、第二逆变电路和第二继电器，所述第二逆变电路的输入端连接第二直流母线，输出端连接所述第二继电器；所述方法包括：
    所述第二控制器确定第一逆变器，所述第一逆变器为所述多逆变器并联系统中已并网的逆变器，所述第一逆变器包括第一控制器、第一逆变电路和第一继电器，所述第一逆变电路的输入端连接第一直流母线，输出端连接所述第一继电器，所述第一继电器闭合，所 述第一直流母线与所述第二直流母线相连，所述第一逆变电路的输出端的各相分别与所述第二逆变电路的输出端的各相对应连接；
    所述第二控制器在所述第二继电器断开时，控制所述第二逆变电路的共模电压注入方式与所述第一逆变电路的共模电压注入方式相同；
    所述第二控制器控制所述第二继电器闭合。
  19. 根据权利要求18所述的方法，其特征在于，所述第二控制器在所述第二继电器断开时，控制所述第二逆变电路的共模电压注入方式与所述第一逆变电路的共模电压注入方式相同，包括：
    所述第二控制器接收来自所述第一控制器的共模电压注入方式信息，所述共模电压注入方式信息用于指示所述第一逆变电路采用的第一共模电压注入方式；
    所述第二控制器根据所述第一共模电压注入方式，控制所述第二逆变电路输出的共模电压。
  20. 根据权利要求18或19所述的方法，其特征在于，所述方法还包括：
    所述第二控制器在所述第二继电器断开时，控制所述第二逆变电路输出的差模线电压的有效值与电网线电压的有效值相同。
  21. 根据权利要求18至20中任一项所述的方法，其特征在于，所述第二直流母线包括第二正直流母线和第二负直流母线，所述第二正直流母线用于连接所述第二逆变电路的输入端的正极，所述第二负直流母线用于连接所述第二逆变电路的输入端的负极；
    所述第一直流母线包括第一正直流母线和第一负直流母线，所述第一正直流母线用于连接所述第一逆变电路的输入端的正极，所述第一负直流母线用于连接所述第一逆变电路的输入端的负极；
    其中，所述第一正直流母线与所述第二正直流母线相连，所述第一负直流母线与所述第二负直流母线相连。
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ZHANG ZHENYAN, GAO LEI; ZHANG JIN: "Leakage Current and Circulating Current Reduction for Parallel Non-isolated Grid-connected Inverters", DIANQI CHUANDONG - ELECTRIC DRIVE, TIANJIN DIANQI CHUANDONG SHEJI YANJIUSUO, CN, vol. 46, no. 11, 31 December 2016 (2016-12-31), CN , pages 24 - 28, XP093009384, ISSN: 1001-2095, DOI: 10.19457/j.1001-2095.20161106 *

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