WO2018126822A1 - 分布式电源发电系统的控制方法和控制系统 - Google Patents

分布式电源发电系统的控制方法和控制系统 Download PDF

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Publication number
WO2018126822A1
WO2018126822A1 PCT/CN2017/113582 CN2017113582W WO2018126822A1 WO 2018126822 A1 WO2018126822 A1 WO 2018126822A1 CN 2017113582 W CN2017113582 W CN 2017113582W WO 2018126822 A1 WO2018126822 A1 WO 2018126822A1
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port
isolated
sub
converter
output
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PCT/CN2017/113582
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English (en)
French (fr)
Inventor
孙凯
陆杨军
吴红飞
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清华大学
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Priority to US16/475,636 priority Critical patent/US11283260B2/en
Publication of WO2018126822A1 publication Critical patent/WO2018126822A1/zh

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    • 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
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/12—Parallel operation of dc generators with converters, e.g. with mercury-arc rectifier
    • 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
    • H02M1/0077—Plural converter units whose outputs are connected in series
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33561—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having more than one ouput with independent control
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Definitions

  • the present invention relates to the field of DC power supply systems, and in particular to a control method and control system for a distributed power generation system.
  • the medium voltage DC distribution network corresponding to the existing medium voltage AC distribution network will have a bus voltage of about 15kV, and multiple DC/DC (DC/DC) interface converters can be used to reduce the output side series.
  • DC/DC DC/DC
  • Device voltage stress on the output side of the small interface converter For example, "AI Bratcu, I. Titanu, S. Bacha, D. Picault, and B. Raison, "Cascaded DC-DC Converter Photovoltaic Systems: Power Optimization Issues," IEEE Transactions on Industrial Electronics, vol. 58, no. 2 , pp. 403-411, February, 2011."
  • a plurality of DC/DC interface converters are used in series on the output side.
  • the input ports of each interface converter are respectively connected to independent distributed power sources, and theoretically, independent control of each distributed power source can be realized.
  • the output ports of the interface converters are connected in series, the output voltage of each module is proportional to its input power, so independent control of the distributed power supply will cause the output ports of the interface converters to be non-uniform. Therefore, in order to avoid excessive voltage stress on the output side of the interface converter, it is impossible to implement independent control for each distributed power supply, and the entire system cannot be output at maximum power.
  • Patent application with the publication number CN105553273A Please also adopt a structure in which a plurality of converter outputs are connected in series, although it simultaneously realizes independent control of the distributed power supply connected to the input ports of the converters and equalization control of the output ports, but in the technical solution disclosed in the above application At each moment, only one converter output port transmits power to the DC bus. The anti-parallel diodes of the output ports of all other converters are turned on and do not transmit power to the DC bus. Therefore, the voltage stress of the device on the output side of each converter is equal to DC.
  • the bus voltage, the loss of the output side series structure can reduce the voltage stress of the device, and is not suitable for the application of distributed power supply to the medium voltage DC distribution network.
  • the distributed power generation system includes N sub-isolated three-port converters and N independent distributed DC power supplies corresponding to the N sub-isolated three-port converters, N being a natural number greater than 1; each sub-isolation three
  • the port converter includes an input port, a bidirectional port and an output port, wherein an output port of each sub-isolated three-port converter is electrically isolated from an input port, and an output port and a bidirectional port of each sub-isolated three-port converter are Electrically isolated; the input port of each sub-isolated three-port converter is connected to a corresponding distributed DC power source, and the bidirectional ports of the N sub-isolated three-port converters are connected in parallel and constitute a low-voltage DC bus, and the N sub-isolated three-port conversion
  • the output ports of the device are connected in series and connected to the medium voltage DC distribution network;
  • the control method includes:
  • Step S1 for each of the N sub-isolated three-port converters, independently controlling the input port voltage and the input port current obtained by sampling at the input port of the sub-isolated three-port converter Input power of the sub-isolated three-port converter;
  • Step S2 For each of the N sub-isolated three-port converters, calculate the input power of the sub-isolated three-port converter according to the input port voltage and the input port current of the sub-isolated three-port converter ;
  • Step S3 obtaining an average output power of the N sub-isolated three-port converters
  • Step S4 Calculating a new output port reference voltage of each of the N sub-isolated three-port converters according to the following formula:
  • V o_nrefi V o_refi -k 1_i ⁇ P avg ,
  • V o_nrefi is the new output port reference voltage of the i-th sub-isolated three-port converter
  • Vo_refi is the preset output port reference voltage of the i-th sub-isolated three-port converter
  • k 1_i is a first preset proportional coefficient corresponding to the i-th sub-isolated three-port converter
  • P avg is the average output power
  • Step S5 Calculating a difference between an input power of the sub-isolated three-port converter and the average output power for each of the N sub-isolated three-port converters to obtain the sub-isolated three-port Bidirectional port power of the converter;
  • Step S6 Calculate a new bidirectional port reference voltage of each of the N sub-isolated three-port converters according to the following formula:
  • V b_nrefi V b_refi -k 2_i ⁇ P b_i ,
  • V b_nrefi is the new bidirectional port reference voltage of the i-th sub-isolated three-port converter
  • V b_refi is the preset bidirectional port reference voltage of the i-th sub-isolated three-port converter
  • k 2_i is a second preset proportional coefficient corresponding to the i-th sub-isolated three-port converter
  • P b_i is a bidirectional port power of the i-th sub-isolated three-port converter
  • Step S7 for each of the N sub-isolated three-port converters, the output port voltage obtained by sampling at the output port of the sub-isolated three-port converter and the sub-isolated three-port converter The new output port reference voltage is compared to obtain an output port error signal;
  • Step S8 for each of the N sub-isolated three-port converters, the bidirectional port voltage obtained by sampling at the bidirectional port of the sub-isolated three-port converter and the sub-isolated three-port converter Comparing the new bidirectional port reference voltage to obtain a bidirectional port error signal;
  • Step S9 adjusting, for each of the N sub-isolated three-port converters, the output port error signal and the bidirectional port error signal of the sub-isolated three-port converter to adjust the sub-isolated three-port converter Bidirectional port voltage and output port voltage.
  • step S9 includes:
  • the output port error signal of the sub-isolated three-port converter is used as an input of an output voltage regulator corresponding to the sub-isolated three-port converter
  • the bidirectional port error signal of the sub-isolated three-port converter is used as a bidirectional port voltage adjustment corresponding to the sub-isolated three-port converter Input of the device;
  • the bidirectional port voltage and the output port voltage of the sub-isolated three-port converter are adjusted by the control signal.
  • the step S3 includes:
  • the input power of the N sub-isolated three-port converters is averaged to obtain the average output power.
  • the step S3 includes:
  • the sub-isolated three-port transform is calculated based on the output port voltage and the output port current sampled at the output port of the sub-isolated three-port converter. Output power of the device;
  • the output power of the N sub-isolated three-port converters is averaged to obtain the average output power.
  • the step S1 includes:
  • a maximum power point tracking is performed according to an input port voltage and an input port current of the sub-isolated three-port converter to independently control the sub-isolated three-port The input power of the converter.
  • the preset output port reference voltages of the N sub-isolated three-port converters are the same, and the preset bidirectional port reference voltages of the N sub-isolated three-port converters are the same, the N sub-isolated three-port converters
  • the corresponding first preset proportional coefficients are the same, and the second preset proportional coefficients corresponding to the N sub-isolated three-port converters are the same.
  • step S3 is implemented in the following manner:
  • a voltage signal representing the input power of each of the sub-isolated three-port converters is output through a resistor to the same average output power bus, and a voltage signal representative of the average output power output from the average power bus is received.
  • step S3 is implemented in the following manner:
  • a voltage signal representative of the input power of each of the sub-isolated three-port converters is transmitted to the second layer controller and receives the average output power returned by the second layer controller.
  • a control system for a distributed power generation system includes N sub-isolated three-port converters and N independent distributed DC power supplies corresponding to the N sub-isolated three-port converters, N being a natural number greater than 1; each sub- The isolated three-port converter includes an input port, a bidirectional port, and an output port, wherein an output port of each sub-isolated three-port converter is electrically isolated from an input port, and an output port of each sub-isolated three-port converter is bidirectional
  • the ports are electrically isolated; the input ports of each of the sub-isolated three-port converters are connected to corresponding distributed DC power sources, and the bidirectional ports of the N sub-isolated three-port converters are connected in parallel and constitute a low voltage DC bus, and the N sub-isolations are three
  • the output ports of the port converter are connected in series and connected to the medium voltage DC distribution network;
  • the control system includes N sub-isolated three-port converter controllers that are in one-to-one correspondence with the N sub-isolated three-port converters, wherein each sub-isolated three-port converter controller includes:
  • An input power control device for independently controlling an input power of the corresponding sub-isolated three-port converter according to an input port voltage and an input port current sampled at an input port of the corresponding sub-isolated three-port converter;
  • An input power calculation device configured to calculate an input power of the corresponding sub-isolated three-port converter according to an input port voltage and an input port current of the corresponding sub-isolated three-port converter
  • An average power obtaining device for obtaining an average output power of the N sub-isolated three-port converters
  • a new output port reference voltage calculation device for calculating a new output port reference voltage of the corresponding sub-isolated three-port converter according to the following formula:
  • V o_nrefi V o_refi -k 1_i ⁇ P avg ,
  • V o_nrefi is the new output port reference voltage of the corresponding sub-isolated three-port converter
  • V o_refi is the preset output port reference voltage of the corresponding sub-isolated three-port converter
  • k 1_i is a first preset proportional coefficient corresponding to the corresponding sub-isolated three-port converter
  • P avg is the average output power
  • a bidirectional port power calculation device configured to calculate a difference between an input power of the corresponding sub-isolated three-port converter and the average output power to obtain a bidirectional port power of the corresponding sub-isolated three-port converter
  • a new bidirectional port reference voltage calculation device for calculating a new bidirectional port reference voltage of a corresponding sub-isolated three-port converter according to the following formula:
  • V b_nrefi V b_refi -k 2_i ⁇ P b_i ,
  • V b_nrefi is the new bidirectional port reference voltage of the corresponding sub-isolated three-port converter
  • V b_refi is the preset bidirectional port reference voltage of the corresponding sub-isolated three-port converter
  • k 2_i is a second preset proportional coefficient corresponding to the corresponding sub-isolated three-port converter
  • P b_i is a bidirectional port power of the corresponding sub-isolated three-port converter
  • Output port error signal obtaining means for comparing the output port voltage obtained by sampling at the output port of the corresponding sub-isolated three-port converter with the new output port reference voltage of the corresponding sub-isolated three-port converter to obtain an output port Error signal
  • a bidirectional port error signal obtaining device for comparing a bidirectional port voltage sampled at a bidirectional port of a corresponding sub-isolated three-port converter with a new bidirectional port reference voltage of a corresponding sub-isolated three-port converter to obtain a bidirectional Port error signal;
  • a voltage regulating device configured to adjust a bidirectional port voltage and an output port voltage of the corresponding sub-isolated three-port converter based on an output port error signal and a bidirectional port error signal of the corresponding sub-isolated three-port converter.
  • each sub-isolated three-port converter controller includes:
  • An input module configured to use an output port error signal of the corresponding sub-isolated three-port converter as an input of an output voltage regulator corresponding to the sub-isolated three-port converter, and to isolate a bidirectional port of the corresponding sub-isolated three-port converter
  • the error signal acts as an input to the bidirectional port voltage regulator corresponding to the sub-isolated three-port converter
  • a superimposing module configured to superimpose an output signal of the output voltage regulator corresponding to the sub-isolated three-port converter and an output signal of the bidirectional port voltage regulator corresponding to the sub-isolated three-port converter to obtain a control signal
  • an adjustment module configured to adjust a bidirectional port voltage and an output port voltage of the sub-isolated three-port converter by the control signal.
  • the average power obtaining means of each sub-isolated three-port converter controller comprises:
  • An input averaging module for averaging input powers of the N sub-isolated three-port converters to obtain the average output power.
  • the average power obtaining means of each sub-isolated three-port converter controller comprises:
  • An output power calculation module for calculating an output power of the corresponding sub-isolated three-port converter according to an output port voltage and an output port current sampled at an output port of the corresponding sub-isolated three-port converter;
  • an output averaging module for averaging output powers of the N sub-isolated three-port converters to obtain the average output power.
  • the input power control device of each sub-isolated three-port converter controller includes:
  • the maximum power point tracking module is configured to perform maximum power point tracking according to the input port voltage and the input port current of the corresponding sub-isolated three-port converter to independently control the input power of the sub-isolated three-port converter.
  • the preset output port reference voltages of the N sub-isolated three-port converters are the same, and the preset bidirectional port reference voltages of the N sub-isolated three-port converters are the same, the N sub-isolated three-port converters
  • the corresponding first preset proportional coefficients are the same, and the second preset proportional coefficients corresponding to the N sub-isolated three-port converters are the same.
  • the average power obtaining means of each sub-isolated three-port converter controller includes an output and receive module for outputting a voltage signal representing the input power of the corresponding sub-isolated three-port converter to the same average output power through the resistor a bus bar and receiving a voltage signal representative of the average output power output by the average power bus.
  • the average power obtaining means of each sub-isolated three-port converter controller includes a transmitting and receiving module for transmitting a voltage signal representing the input power of the corresponding sub-isolated three-port converter to the second layer controller, And receiving the average output power returned by the second layer controller.
  • the control method and control system of the distributed power generation system can realize independent power control of each distributed power source, stable control of bidirectional port voltage of each sub-isolated three-port converter, and voltage equalization of output port voltage Control enables each distributed power supply to operate at maximum power output while effectively reducing device voltage stress on the output side.
  • FIG. 1 shows a schematic diagram of a distributed power generation system and a control system thereof for accessing a medium voltage DC distribution network according to an embodiment of the present invention
  • FIG. 2 shows a schematic diagram of a manner of obtaining an average output power according to an embodiment of the present invention
  • FIG. 3 exemplarily shows an equivalent schematic diagram of a distributed power generation system that performs control using a control method according to an embodiment of the present invention
  • FIG. 4 is a diagram showing a manner of obtaining an average output power according to another embodiment of the present invention.
  • FIG. 5 is a schematic structural diagram of a distributed power generation system for accessing a medium voltage DC distribution network according to an embodiment of the present invention
  • FIG. 6 shows a circuit schematic of a sub-isolated three-port converter in accordance with one embodiment of the present invention
  • FIG. 7a illustrates a simulation result diagram of controlling a distributed power source power generation system using a control method according to an embodiment of the present invention, according to an example
  • FIG. 7b shows a simulation result diagram of controlling a distributed power source power generation system using a control method according to an embodiment of the present invention, according to another example.
  • the present invention provides a control method for a distributed power generation system that is connected to a medium voltage DC distribution network. Through the control method, independent control of each distributed power source and voltage equalization control of the output ports of the respective converters can be realized.
  • the form of the voltage signal can be used to represent a certain data, for example, the average output power P avg can be represented by the voltage signal v Pavg . Therefore, it can be understood that in the drawing, the meaning represented by the voltage signal v Pavg coincides with the average output power P avg . Other similar voltage signals are the same, not to be repeated.
  • the distributed power generation system includes N sub-isolated three-port converters (such as 1# sub-isolated three-port converter, 2# sub-isolated three-port converter, etc. N# sub-isolated three-port converter) N independent distributed DC power sources (V in_1 , V in_2 ... V in_N as shown in FIG. 1 ) corresponding to N sub-isolated three-port converters, N being a natural number greater than 1.
  • Each sub-isolated three-port converter includes an input port, a bidirectional port, and an output port, wherein an output port of each sub-isolated three-port converter is electrically isolated from an input port, and an output port of each sub-isolated three-port converter It is electrically isolated from the bidirectional port.
  • the input ports of each sub-isolated three-port converter are connected to corresponding distributed DC power sources, and the bidirectional ports of the N sub-isolated three-port converters are connected in parallel to form a low-voltage DC bus, and the output ports of the N sub-isolated three-port converters are connected in series and connected. Into the medium voltage DC distribution network.
  • a plurality of sub-isolated three-port converters and respective corresponding control systems are shown.
  • the control method of the distributed power generation system according to the embodiment of the present invention is implemented by all sub-isolated three-port converter control systems. All sub-isolated three-port converter control systems implement the same control process for their respective sub-isolated three-port converters.
  • step S1 may include: for each of the N sub-isolated three-port converters, the maximum power is input according to the input port voltage V in — i and the input port current I in — i of the sub-isolated three-port converter Point tracking to independently control the input power P in — i of the sub-isolated three-port converter.
  • voltage sampling and current sampling are respectively performed at their input ports to obtain an input port voltage V in_1 and an input port current I in_1 .
  • Maximum power point tracking can be performed based on the input port voltage V in_1 obtained by sampling and the input port current I in_1 .
  • the maximum power point tracking mode is used to independently control the input power P in_1 of the 1# sub-isolated three-port converter.
  • Step S2 For each of the N sub-isolated three-port converters, calculate the sub-isolated three-port converter according to the input port voltage V in_i and the input port current I in_i of the sub-isolated three-port converter Input power P in_i .
  • Step S3 Obtain an average output power P avg of the N sub-isolated three-port converters.
  • step S3 may include averaging input power P in — i of the N sub-isolated three-port converters to obtain an average output power P avg , ie,
  • the sum of the output powers of all sub-isolated three-port converters is equal to the sum of the input powers, so the average output power can be obtained by input power to all sub-isolated three-port converters. Average to get.
  • step S3 can include: for each of the N sub-isolated three-port converters, the output port voltage V o_i obtained by sampling at the output port of the sub-isolated three-port converter and output port sub-current I o calculating the three-port isolation transformer output power P o_i; and isolation of the N sub-three-port converter output power P o_i averaged to obtain an average output power P avg.
  • the average output power in this example is calculated as follows:
  • FIG. 2 shows only a schematic diagram of a controller corresponding to a 1# sub-isolated three-port converter (and a control method implemented thereby), and a controller corresponding to the other sub-isolated three-port converter (and a control method implemented thereby)
  • the principle is similar to the controller corresponding to the 1# sub-isolated three-port converter (and its implemented control method), and will not be described again.
  • voltage sampling and current sampling can be separately performed at the output port of the 1# sub-isolated three-port converter to obtain an output port voltage V o_1 and an output port current I o .
  • the output power P o_1 of the 1# sub-isolated three-port converter can be calculated from the output port voltage V o_1 and the output port current I o . It can be understood that since the output ports of the N sub-isolated three-port converters are connected in series, the output port currents of all the sub-isolated three-port converters are the same, and the output port current can be measured only once for the N sub-isolated three-port converters. The average output power calculated directly from the output power of all sub-isolated three-port converters is relatively accurate.
  • Step S4 Calculate the new output port reference voltage of each of the sub-isolated three-port converters of the N sub-isolated three-port converters according to the following formula:
  • V o_nrefi V o_refi -k 1_i ⁇ P avg (3)
  • V o_nrefi is the new output port reference voltage of the i-th sub-isolated three-port converter
  • Vo_refi is the preset output port reference voltage of the i-th sub-isolated three-port converter
  • k 1_i is the first preset proportional coefficient corresponding to the i-th sub-isolated three-port converter
  • P avg is the average output power.
  • the first predetermined scale factor k 1 — i is a fixed coefficient greater than zero.
  • the sum of the output powers of all sub-isolated three-port converters is equal to the sum of the input powers, ie,
  • an equivalent schematic diagram of the distributed power source power generation system controlled by the control method according to the embodiment of the present invention as shown in FIG. 3 can be obtained, where r is an equivalent virtual resistance.
  • r is an equivalent virtual resistance.
  • the preset output port reference voltages V o_refi of the N sub-isolated three-port converters are the same, and are uniformly represented by Vo_ref .
  • the control method of the output port voltage of each sub-isolated three-port converter can be summarized as a power-voltage droop control method based on virtual resistance.
  • Step S5 Calculating a difference between an input power and an average output power of the sub-isolated three-port converter for each of the three sub-isolated three-port converters to obtain a bidirectional of the sub-isolated three-port converter Port power.
  • the bidirectional port power of each of the sub-isolated three-port converters of the N sub-isolated three-port converters is calculated according to the following formula:
  • P b_i is the bidirectional port power of the i-th sub-isolated three-port converter.
  • Step S6 Calculate the new bidirectional port reference voltage of each of the sub-isolated three-port converters of the N sub-isolated three-port converters according to the following formula:
  • V b_nrefi V b_refi -k 2_i ⁇ P b_i , (9)
  • V b_nrefi is the new bidirectional port reference voltage of the i-th sub-isolated three-port converter
  • V b_refi is the preset bidirectional port reference voltage of the i-th sub-isolated three-port converter
  • k 2_i is the second preset proportional coefficient corresponding to the i-th sub-isolated three-port converter.
  • the second predetermined scale factor k 2 — i is a fixed coefficient greater than zero.
  • the regulated bidirectional port voltage is:
  • V b_i is the bidirectional port voltage of the i-th sub-isolated three-port converter
  • V b is the low-voltage DC bus voltage
  • I b_i is the bidirectional of the i-th sub-isolated three-port converter Port current
  • r b is a virtual resistor.
  • control method of the bidirectional port voltage of each sub-isolated three-port converter can be summarized as a virtual resistance-based power-voltage droop control method.
  • Step S7 For each of the N sub-isolated three-port converters, the output port voltage V o_i obtained by sampling at the output port of the sub-isolated three-port converter and the sub-isolated three-port converter The new output port reference voltage V o — nrefi is compared to obtain an output port error signal.
  • Step S8 for each of the N sub-isolated three-port converters, the bidirectional port voltage V b_i obtained by sampling at the bidirectional port of the sub-isolated three-port converter and the sub-isolated three-port converter The new bidirectional port reference voltage V b_nrefi is compared to obtain a bidirectional port error signal.
  • Step S9 For each of the N sub-isolated three-port converters, adjust the bidirectional port of the sub-isolated three-port converter based on the output port error signal and the bidirectional port error signal of the sub-isolated three-port converter Voltage and output port voltage.
  • step S9 may include: for each of the N sub-isolated three-port converters, the output port error signal of the sub-isolated three-port converter is corresponding to the sub-isolated three-port converter An input voltage regulator input, and the bidirectional port error signal of the sub-isolated three-port converter is used as an input of a bidirectional port voltage regulator corresponding to the sub-isolated three-port converter; and the sub-isolated three-port converter An output signal of the corresponding output voltage regulator is superimposed with an output signal of the bidirectional port voltage regulator corresponding to the sub-isolated three-port converter to obtain a control signal; and the bidirectional of the sub-isolated three-port converter is adjusted by the control signal Port voltage and output port voltage.
  • sampling is performed at the output port of the 1# sub-isolated three-port converter to obtain its output port voltage V o_1 .
  • the V o_1 is compared with Vo_nref1 to obtain an output port error signal.
  • the output port error signal can then be input to an output voltage regulator (OVR).
  • OVR output voltage regulator
  • sampling is performed at the bidirectional port of the 1# sub-isolated three-port converter to obtain its bidirectional port voltage V b_1 .
  • V b_1 Comparing V b_1 with V b_nref1 to obtain a bidirectional port error signal.
  • This bidirectional port error signal can then be input into a bidirectional port voltage regulator (BVR).
  • BVR bidirectional port voltage regulator
  • control signal v D_1 of the input power and the control signal of the bidirectional port voltage and the output port voltage are shown.
  • the driving circuit is input, and the driving circuit generates corresponding driving signals.
  • the sub-isolated three-port converter can change the voltage and/or current of each port under the control of the driving signal.
  • the preset output port reference voltage V o_refi of the N sub-isolated three-port converters is the same, and the preset bidirectional port reference voltages V b — refi of the N sub-isolated three-port converters are the same, and the N sub-isolated three-port converters correspond to
  • the first preset proportional coefficients k 1_i are the same, and the second preset proportional coefficients k 2_i corresponding to the N sub-isolated three-port converters are the same.
  • each sub-isolated three-port converter can speed up the related operation process of each sub-isolated three-port converter, and conveniently realize the control of the input power and the output port voltage of each sub-isolated three-port converter.
  • the distributed power generation system shown corresponds to the present example, that is, the preset output port reference voltage V o_refi of the N sub-isolated three-port converters is the same, and the V o_ref is uniformly used to represent the bidirectional port.
  • the reference voltage V b_refi is the same, and is uniformly represented by V b — ref .
  • the first preset proportional coefficients k 1 — i are the same, and are uniformly represented by k 1
  • the second preset proportional coefficients k 2 — i are the same, and are uniformly represented by k 2 .
  • step S3 can be implemented by outputting a voltage signal representing the input power of each sub-isolated three-port converter through a resistor to the same average output power bus and receiving an average power bus output representing the average output power. Voltage signal.
  • step S3 can be implemented by transmitting a voltage signal representative of the input power of each sub-isolated three-port converter to the second layer controller and receiving the average output power returned by the second layer controller.
  • Each sub-isolated three-port converter controller transmits a voltage signal v Pin_i representing the input power of the corresponding sub-isolated three-port converter to the second layer controller through communication, and the second layer controller is operated to obtain an average output. The power is then communicated to each of the isolated three-port converter controllers, a schematic of which is shown in FIG.
  • each sub-isolated three-port converter is connected to an independent distributed power source, which can realize independent power control of each distributed power source, and can make each distributed power source work in a maximum power output state;
  • each sub-isolated three-port converter is connected in series, which can reduce the voltage stress of the device on the output side, and the control method provided by the invention can realize the voltage equalization of the output ports of all the sub-isolated three-port converters. Control so that the voltage stress of the device on the output side of each sub-isolated three-port converter is consistent.
  • FIG. 5 is a block diagram showing the structure of a distributed power generation system for accessing a medium voltage DC distribution network according to an embodiment of the present invention.
  • 6 shows a circuit schematic of a sub-isolated three-port converter in accordance with one embodiment of the present invention.
  • Figure 5 exemplarily shows a distributed power generation system consisting of three sub-isolated three-port converters, wherein each sub-isolated three-port converter can employ a circuit topology as shown in Figure 6.
  • the input ports of each of the sub-isolated three-port converters are respectively connected to the solar photovoltaic cells by adjusting the duty ratios of the first to fourth switching tubes (S 1 to S 4 ) in the sub-isolated three-port converter shown in FIG.
  • FIGS 7a and 7b are diagrams showing simulation results of controlling a distributed power source power generation system using a control method according to an embodiment of the present invention.
  • W/div is “watts/division”, which means how many watts of power each grid corresponds to
  • V/div is “volts/division”, which means how many volts per grid corresponds to
  • the ms/div is “milliseconds/division”, which indicates how many milliseconds each cell corresponds to.
  • Time t 1 is introduced at the start of the control strategies described herein, each sub-isolated output port of the three-port power converter voltage quickly reach equilibrium automatically, indicating the effectiveness of the method described herein.
  • the distributed power generation system is always controlled using the control methods described herein. It can be seen from Fig. 7b that, in the case of controlling the distributed power generation system by the control method described herein, when the input power of a sub-isolated three-port converter is abrupt, the output ports of the respective sub-isolated three-port converters The voltage is still well balanced, further illustrating the effectiveness of the control method described herein.
  • control system of the distributed power generation system and each of the sub-isolated three-port converter controllers can be implemented using any suitable hardware, software, and/or firmware.
  • control system of the distributed power generation system and each of the sub-isolated three-port converter controllers thereof may employ a field programmable gate array (FPGA), a digital signal processor (DSP), and a complex programmable logic device (CPLD). ), micro control unit (MCU) or central processing unit (CPU) implementation.
  • FPGA field programmable gate array
  • DSP digital signal processor
  • CPLD complex programmable logic device
  • MCU micro control unit
  • CPU central processing unit
  • a control system for a distributed power generation system includes N sub-isolated three-port converters and N independent one-to-one correspondences with N sub-isolated three-port converters.
  • N is a natural number greater than 1; each sub-isolated three-port converter includes an input port, a bidirectional port, and an output port, wherein the output port and the input port of each sub-isolated three-port converter are electrically The isolated output port of each sub-isolated three-port converter is electrically isolated from the bidirectional port; the input port of each sub-isolated three-port converter is connected to a corresponding distributed DC power supply, and the bidirectional ports of the N sub-isolated three-port converters are connected in parallel Connected and formed a low-voltage DC bus, the output ports of the N sub-isolated three-port converters are connected in series and connected to the medium voltage DC distribution network.
  • the control system includes N sub-isolated three-port converter controllers one-to-one corresponding to the N sub-isolated three-port converters, wherein each sub-isolated three-port converter controller includes: an input power control device, an input power calculation device, and an average power Obtaining device, new output port reference voltage calculating device, bidirectional port power calculating device, new bidirectional port reference voltage calculating device, output port error signal obtaining device, bidirectional port error signal obtaining device and voltage adjusting device.
  • the input power control means is for independently controlling the input power of the corresponding sub-isolated three-port converter based on the input port voltage and the input port current sampled at the input port of the corresponding sub-isolated three-port converter.
  • the input power calculation means is configured to calculate an input power of the corresponding sub-isolated three-port converter according to an input port voltage and an input port current of the corresponding sub-isolated three-port converter.
  • the average power obtaining device is used to obtain the average output power of the N sub-isolated three-port converters.
  • the new output port reference voltage calculation means is for calculating a new output port reference voltage of the corresponding sub-isolated three-port converter according to the following formula:
  • V o_nrefi V o_refi -k 1_i ⁇ P avg ,
  • V o_nrefi is the new output port reference voltage of the corresponding sub-isolated three-port converter
  • V o_refi is the preset output port reference voltage of the corresponding sub-isolated three-port converter
  • k 1_i is the first preset proportional coefficient corresponding to the corresponding sub-isolated three-port converter
  • P avg is the average output power.
  • the bidirectional port power calculation device is configured to calculate a difference between an input power and an average output power of the corresponding sub-isolated three-port converter to obtain a bidirectional port power of the corresponding sub-isolated three-port converter.
  • the new bidirectional port reference voltage calculation device is used to calculate the new bidirectional port reference voltage of the corresponding sub-isolated three-port converter according to the following formula:
  • V b_nrefi V b_refi -k 2_i ⁇ P b_i ,
  • V b_nrefi is the new bidirectional port reference voltage of the corresponding sub-isolated three-port converter
  • V b_refi is the preset bidirectional port reference voltage of the corresponding sub-isolated three-port converter
  • k 2_i is the second preset proportional coefficient corresponding to the corresponding sub-isolated three-port converter
  • P b_i is the bidirectional port power of the corresponding sub-isolated three-port converter.
  • the output port error signal obtaining means is configured to compare the output port voltage obtained by sampling at the output port of the corresponding sub-isolated three-port converter with the new output port reference voltage of the corresponding sub-isolated three-port converter to obtain an output port error signal.
  • the bidirectional port error signal obtaining means is for comparing the bidirectional port voltage sampled at the bidirectional port of the corresponding sub-isolated three-port converter with the new bidirectional port reference voltage of the corresponding sub-isolated three-port converter to obtain a bidirectional port Error signal.
  • the voltage regulating device is configured to adjust a bidirectional port voltage and an output port voltage of the corresponding sub-isolated three-port converter based on an output port error signal and a bidirectional port error signal of the corresponding sub-isolated three-port converter.
  • the voltage regulating device of each sub-isolated three-port converter controller includes: an input module for using an output port error signal of the corresponding sub-isolated three-port converter as an output corresponding to the sub-isolated three-port converter
  • the input of the voltage regulator, and the bidirectional port error signal of the corresponding sub-isolated three-port converter is used as an input of the bidirectional port voltage regulator corresponding to the sub-isolated three-port converter
  • an overlay module for isolating the sub-port An output signal of the output voltage regulator corresponding to the three-port converter is superimposed with an output signal of the bidirectional port voltage regulator corresponding to the sub-isolated three-port converter to obtain a control signal
  • an adjustment module for adjusting by the control signal
  • the sub-isolated three-port converter has a bidirectional port voltage and an output port voltage.
  • the average power obtaining means of each sub-isolated three-port converter controller includes An input averaging module is used to average the input power of the N sub-isolated three-port converters to obtain an average output power.
  • the average power obtaining means of each sub-isolated three-port converter controller includes: an output power calculation module for outputting the output port voltage and output port according to sampling at an output port of the corresponding sub-isolated three-port converter The current calculates the output power of the corresponding sub-isolated three-port converter; and an output averaging module for averaging the output power of the N sub-isolated three-port converters to obtain an average output power.
  • the input power control device of each sub-isolated three-port converter controller includes a maximum power point tracking module for performing maximum power point tracking according to input port voltages and input port currents of corresponding sub-isolated three-port converters, The input power of the sub-isolated three-port converter is independently controlled.
  • the preset output port reference voltages of the N sub-isolated three-port converters are the same, the preset bidirectional port reference voltages of the N sub-isolated three-port converters are the same, and the first preset corresponding to the N sub-isolated three-port converters
  • the scaling factors are the same, and the second preset proportional coefficients corresponding to the N sub-isolated three-port converters are the same.
  • the average power obtaining means of each sub-isolated three-port converter controller includes an output and receive module for outputting a voltage signal representing the input power of the corresponding sub-isolated three-port converter to the same average output power through the resistor
  • the busbar receives the voltage signal representing the average output power of the average power bus output.
  • the average power obtaining means of each sub-isolated three-port converter controller includes a transmitting and receiving module for transmitting a voltage signal representing the input power of the corresponding sub-isolated three-port converter to the second layer controller, And receive the average output power returned by the second layer controller.
  • the input power of each sub-isolated three-port converter is independently controlled, and the bidirectional port and the output port adopt a power-voltage droop control strategy based on a virtual resistor to realize the bidirectional port voltage of each sub-isolated three-port converter.
  • the stable control and the equalization control of the output port voltage realize modular design and provide a feasible technical solution for connecting the distributed power generation system to the medium voltage DC distribution network.

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Abstract

一种分布式电源发电系统的控制方法和控制系统。所述分布式电源发电系统包括N个子隔离三端口变换器和与N个子隔离三端口变换器一一对应的N个独立的分布式直流电源，N为大于1的自然数；每个子隔离三端口变换器的输入端口连接对应的分布式直流电源，双向端口并联连接、构成低压直流母线，输出端口串联连接、再接入中压直流配电网；该控制方法包括：独立控制每个子隔离三端口变换器的输入功率，双向端口和输出端口采用基于虚拟电阻的功率-电压下垂控制策略，实现每个子隔离三端口变换器的双向端口电压的稳定控制和输出端口电压的均压控制，实现模块化设计，为将分布式电源发电系统接入中压直流配电网提供一种可行的技术方案。

Description

分布式电源发电系统的控制方法和控制系统 技术领域
本发明涉及直流供电系统领域，具体地，涉及一种分布式电源发电系统的控制方法和控制系统。
背景技术
近年来，光伏、风电等分布式新能源成为缓解能源危机和改善环境污染问题的有效途径，但是由于光伏等分布式电源的输出为直流且电压较低，因此将其接入交流大电网需要经过多级的功率变换并且需要笨重的工频变压器。而与交流大电网相比，中压直流配电网可以更好地接纳分布式直流电源和直流负荷。将分布式电源发电系统输出的直流电接入中压直流配电网，不仅可以减少功率变换环节，提高电力系统中新能源发电渗透率和运行效率，而且可以显著提高配电网的可靠性和设备利用率，降低并网系统的复杂性，因此接入中压直流配电网的分布式电源发电系统得到了越来越多的关注。
与现有中压交流配电网相对应的中压直流配电网，其母线电压将达到15kV左右，可以采用多个直流/直流(DC/DC)接口变换器输出侧串联的结构，来减小接口变换器输出侧的器件电压应力。如文献“A.I.Bratcu，I.Munteanu，S.Bacha，D.Picault，and B.Raison，“Cascaded DC-DC Converter Photovoltaic Systems：Power Optimization Issues，”IEEE Transactions on Industrial Electronics，vol.58，no.2，pp.403-411，February，2011.”就采用了多个DC/DC接口变换器输出侧串联的结构。在上述文献所公开的技术方案中，每个接口变换器的输入端口分别连接独立的分布式电源，理论上可以实现各分布式电源的独立控制。然而，由于各接口变换器的输出端口串联连接，每个模块的输出电压正比于其输入功率，因此分布式电源的独立控制将会导致各接口变换器的输出端口不均压。因此，为了避免接口变换器输出侧的器件电压应力过高，就不能对每个分布式电源实施独立控制，也就无法使得整个系统以最大功率输出。公开号为CN105553273A的专利申 请中也采用了多个变换器输出串联的结构，虽然其同时实现了各变换器输入端口连接的分布式电源的独立控制和输出端口的均压控制，但是在上述申请所公开的技术方案中，每一时刻只有一个变换器输出端口向直流母线传递功率，其他所有变换器的输出端口的反并联二极管导通、不向直流母线传递功率，因此每个变换器输出侧的器件电压应力等于直流母线电压，失去了输出侧串联结构可以减小器件电压应力的优势，不适用于分布式电源接入中压直流配电网的应用场合。
因此，需要提供一种接入中压直流配电网的分布式电源发电系统的控制方法，以至少部分地解决现有技术中存在的上述问题。
发明内容
为了至少部分地解决现有技术中存在的问题，根据本发明的一个方面，提供一种分布式电源发电系统的控制方法。所述分布式电源发电系统包括N个子隔离三端口变换器和与所述N个子隔离三端口变换器一一对应的N个独立的分布式直流电源，N为大于1的自然数；每个子隔离三端口变换器包括一个输入端口、一个双向端口和一个输出端口，其中，每个子隔离三端口变换器的输出端口与输入端口是电气隔离的，每个子隔离三端口变换器的输出端口与双向端口是电气隔离的；每个子隔离三端口变换器的输入端口连接对应的分布式直流电源，所述N个子隔离三端口变换器的双向端口并联连接并构成低压直流母线，所述N个子隔离三端口变换器的输出端口串联连接并接入中压直流配电网；
所述控制方法包括：
步骤S1：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，根据在该子隔离三端口变换器的输入端口处采样获得的输入端口电压和输入端口电流，独立控制该子隔离三端口变换器的输入功率；
步骤S2：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，根据该子隔离三端口变换器的输入端口电压和输入端口电流计算该子隔离三端口变换器的输入功率；
步骤S3：获得所述N个子隔离三端口变换器的平均输出功率；
步骤S4：根据以下公式计算所述N个子隔离三端口变换器中的每个子隔离三端口变换器的新输出端口基准电压：
Vo_nrefi＝Vo_refi-k1_i·Pavg，
其中，i＝1，2，...N，Vo_nrefi是第i个子隔离三端口变换器的新输出端口基准电压，Vo_refi是第i个子隔离三端口变换器的预设输出端口基准电压，k1_i是第i个子隔离三端口变换器所对应的第一预设比例系数，Pavg是所述平均输出功率；
步骤S5：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，计算该子隔离三端口变换器的输入功率与所述平均输出功率之差，以获得该子隔离三端口变换器的双向端口功率；
步骤S6：根据以下公式计算所述N个子隔离三端口变换器中的每个子隔离三端口变换器的新双向端口基准电压：
Vb_nrefi＝Vb_refi-k2_i·Pb_i，
其中，i＝1，2，...N，Vb_nrefi是第i个子隔离三端口变换器的新双向端口基准电压，Vb_refi是第i个子隔离三端口变换器的预设双向端口基准电压，k2_i是第i个子隔离三端口变换器所对应的第二预设比例系数，Pb_i是第i个子隔离三端口变换器的双向端口功率；
步骤S7：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，将在该子隔离三端口变换器的输出端口处采样获得的输出端口电压和该子隔离三端口变换器的新输出端口基准电压相比较，以获得输出端口误差信号；
步骤S8：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，将在该子隔离三端口变换器的双向端口处采样获得的双向端口电压和该子隔离三端口变换器的新双向端口基准电压相比较，以获得双向端口误差信号；以及
步骤S9：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，基于该子隔离三端口变换器的输出端口误差信号和双向端口误差信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
示例性地，所述步骤S9包括：
对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，将该子隔离三端口变换器的输出端口误差信号作为与该子隔离三端口变换器对应的输出电压调节器的输入，并将该子隔离三端口变换器的双向端口误差信号作为与该子隔离三端口变换器对应的双向端口电压调节 器的输入；
将与该子隔离三端口变换器对应的输出电压调节器的输出信号和与该子隔离三端口变换器对应的双向端口电压调节器的输出信号相叠加，以获得控制信号；以及
通过所述控制信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
示例性地，所述步骤S3包括：
对所述N个子隔离三端口变换器的输入功率求平均，以获得所述平均输出功率。
示例性地，所述步骤S3包括：
对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，根据在该子隔离三端口变换器的输出端口处采样获得的输出端口电压和输出端口电流计算该子隔离三端口变换器的输出功率；以及
对所述N个子隔离三端口变换器的输出功率求平均，以获得所述平均输出功率。
示例性地，所述步骤S1包括：
对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，根据该子隔离三端口变换器的输入端口电压和输入端口电流进行最大功率点跟踪，以独立控制该子隔离三端口变换器的输入功率。
示例性地，所述N个子隔离三端口变换器的预设输出端口基准电压相同，所述N个子隔离三端口变换器的预设双向端口基准电压相同，所述N个子隔离三端口变换器所对应的第一预设比例系数相同，所述N个子隔离三端口变换器所对应的第二预设比例系数相同。
示例性地，所述步骤S3采用以下方式实现：
将代表每个子隔离三端口变换器的输入功率的电压信号通过电阻输出到同一平均输出功率母线，并接收所述平均功率母线输出的、代表所述平均输出功率的电压信号。
示例性地，所述步骤S3采用以下方式实现：
将代表每个子隔离三端口变换器的输入功率的电压信号传送至第二层控制器，并接收所述第二层控制器返回的所述平均输出功率。
根据本发明的另一方面，提供一种分布式电源发电系统的控制系统， 其中，所述分布式电源发电系统包括N个子隔离三端口变换器和与所述N个子隔离三端口变换器一一对应的N个独立的分布式直流电源，N为大于1的自然数；每个子隔离三端口变换器包括一个输入端口、一个双向端口和一个输出端口，其中，每个子隔离三端口变换器的输出端口与输入端口是电气隔离的，每个子隔离三端口变换器的输出端口与双向端口是电气隔离的；每个子隔离三端口变换器的输入端口连接对应的分布式直流电源，所述N个子隔离三端口变换器的双向端口并联连接并构成低压直流母线，所述N个子隔离三端口变换器的输出端口串联连接并接入中压直流配电网；
所述控制系统包括与所述N个子隔离三端口变换器一一对应的N个子隔离三端口变换器控制器，其中，每个子隔离三端口变换器控制器包括：
输入功率控制装置，用于根据在对应的子隔离三端口变换器的输入端口处采样获得的输入端口电压和输入端口电流，独立控制对应的子隔离三端口变换器的输入功率；
输入功率计算装置，用于根据对应的子隔离三端口变换器的输入端口电压和输入端口电流计算对应的子隔离三端口变换器的输入功率；
平均功率获得装置，用于获得所述N个子隔离三端口变换器的平均输出功率；
新输出端口基准电压计算装置，用于根据以下公式计算对应的子隔离三端口变换器的新输出端口基准电压：
Vo_nrefi＝Vo_refi-k1_i·Pavg，
其中，i＝1，2，...N，Vo_nrefi是对应的子隔离三端口变换器的新输出端口基准电压，Vo_refi是对应的子隔离三端口变换器的预设输出端口基准电压，k1_i是对应的子隔离三端口变换器所对应的第一预设比例系数，Pavg是所述平均输出功率；
双向端口功率计算装置，用于计算对应的子隔离三端口变换器的输入功率与所述平均输出功率之差，以获得对应的子隔离三端口变换器的双向端口功率；
新双向端口基准电压计算装置，用于根据以下公式计算对应的子隔离三端口变换器的新双向端口基准电压：
Vb_nrefi＝Vb_refi-k2_i·Pb_i，
其中，i＝1，2，...N，Vb_nrefi是对应的子隔离三端口变换器的新双向 端口基准电压，Vb_refi是对应的子隔离三端口变换器的预设双向端口基准电压，k2_i是对应的子隔离三端口变换器所对应的第二预设比例系数，Pb_i是对应的子隔离三端口变换器的双向端口功率；
输出端口误差信号获得装置，用于在对应的子隔离三端口变换器的输出端口处采样获得的输出端口电压和对应的子隔离三端口变换器的新输出端口基准电压相比较，以获得输出端口误差信号；
双向端口误差信号获得装置，用于将在对应的子隔离三端口变换器的双向端口处采样获得的双向端口电压和对应的子隔离三端口变换器的新双向端口基准电压相比较，以获得双向端口误差信号；以及
电压调节装置，用于基于对应的子隔离三端口变换器的输出端口误差信号和双向端口误差信号调节对应的子隔离三端口变换器的双向端口电压和输出端口电压。
示例性地，每个子隔离三端口变换器控制器的电压调节装置包括：
输入模块，用于将对应的子隔离三端口变换器的输出端口误差信号作为与该子隔离三端口变换器对应的输出电压调节器的输入，并将对应的子隔离三端口变换器的双向端口误差信号作为与该子隔离三端口变换器对应的双向端口电压调节器的输入；
叠加模块，用于将与该子隔离三端口变换器对应的输出电压调节器的输出信号和与该子隔离三端口变换器对应的双向端口电压调节器的输出信号相叠加，以获得控制信号；以及
调节模块，用于通过所述控制信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
示例性地，每个子隔离三端口变换器控制器的平均功率获得装置包括：
输入平均模块，用于对所述N个子隔离三端口变换器的输入功率求平均，以获得所述平均输出功率。
示例性地，每个子隔离三端口变换器控制器的平均功率获得装置包括：
输出功率计算模块，用于根据在对应的子隔离三端口变换器的输出端口处采样获得的输出端口电压和输出端口电流计算对应的子隔离三端口变换器的输出功率；以及
输出平均模块，用于对所述N个子隔离三端口变换器的输出功率求平均，以获得所述平均输出功率。
示例性地，每个子隔离三端口变换器控制器的输入功率控制装置包括：
最大功率点跟踪模块，用于根据对应的子隔离三端口变换器的输入端口电压和输入端口电流进行最大功率点跟踪，以独立控制该子隔离三端口变换器的输入功率。
示例性地，所述N个子隔离三端口变换器的预设输出端口基准电压相同，所述N个子隔离三端口变换器的预设双向端口基准电压相同，所述N个子隔离三端口变换器所对应的第一预设比例系数相同，所述N个子隔离三端口变换器所对应的第二预设比例系数相同。
示例性地，每个子隔离三端口变换器控制器的平均功率获得装置包括输出和接收模块，用于将代表对应的子隔离三端口变换器的输入功率的电压信号通过电阻输出到同一平均输出功率母线，并接收所述平均功率母线输出的、代表所述平均输出功率的电压信号。
示例性地，每个子隔离三端口变换器控制器的平均功率获得装置包括发送和接收模块，用于将代表对应的子隔离三端口变换器的输入功率的电压信号传送至第二层控制器，并接收所述第二层控制器返回的所述平均输出功率。
根据本发明实施例的分布式电源发电系统的控制方法和控制系统，可以实现各分布式电源的独立功率控制、每个子隔离三端口变换器的双向端口电压的稳定控制和输出端口电压的均压控制，能够使各分布式电源工作在最大功率输出状态，同时能够有效减小输出侧的器件电压应力。
在发明内容中引入了一系列简化的概念，这些概念将在具体实施方式部分中进一步详细说明。本发明内容部分并不意味着要试图限定所要求保护的技术方案的关键特征和必要技术特征，更不意味着试图确定所要求保护的技术方案的保护范围。
以下结合附图，详细说明本发明的优点和特征。
附图说明
本发明的下列附图在此作为本发明的一部分用于理解本发明。附图中示出了本发明的实施方式及其描述，用来解释本发明的原理。在附图中，
图1示出根据本发明一个实施例的、接入中压直流配电网的分布式电源发电系统及其控制系统的示意图；
图2示出根据本发明一个实施例的平均输出功率的获得方式的示意图；
图3示例性地示出采用根据本发明实施例的控制方法进行控制的分布式电源发电系统的等效示意图；
图4示出根据本发明另一个实施例的平均输出功率的获得方式的示意图；
图5示出根据本发明一个实施例的、接入中压直流配电网的分布式电源发电系统的结构示意图；
图6示出根据本发明一个实施例的子隔离三端口变换器的电路原理图；以及
图7a示出根据一个示例的、采用根据本发明实施例的控制方法控制分布式电源发电系统的仿真结果图；以及
图7b示出根据另一个示例的、采用根据本发明实施例的控制方法控制分布式电源发电系统的仿真结果图。
以下是附图中的符号的意义：Vin_1～Vin_N为第1～N个子隔离三端口变换器的输入端口电压；Iin_1～Iin_N为第1～N个子隔离三端口变换器的输入端口电流；Vb_1～Vb_N为第1～N个子隔离三端口变换器的双向端口电压；Vo_1～Vo_N为第1～N个子隔离三端口变换器的输出端口电压；Io为接入中压直流配电网的分布式电源发电系统的输出电流，即，第1～N个子隔离三端口变换器的输出端口电流；VDC为中压直流配电网电压；vVin_1～vVin_N为代表第1～N个子隔离三端口变换器的输入端口电压的电压信号；vIin_1～vIin_N为代表第1～N个子隔离三端口变换器的输入端口电流的电压信号；vPin_1～vPin_N为代表第1～N个子隔离三端口变换器的输入功率的电压信号；vPavg为代表平均输出功率的电压信号；vVb_1～vVb_N为代表第1～N个子隔离三端口变换器的双向端口电压的电压信号；vVo_1～vVo_N为代表第1～N个子隔离三端口变换器的输出端口电压的电压信号；vIo为代表接入中压直流配电网的分布式电源发电系统的输出电流的电压信号；vPo_1～vVo_N为代表第1～N个子隔离三端口变换器的输出功率的电压信号；vVb_ref为代表每个子隔离三端口变换器的预设双向端口基准电压的电压信号；vVb_nref1～vVb_nrefN为代表第1～N个子隔离三端口变换器的新双向端口基准电压的电压信号；vVo_ref为代表每个子隔离三端口变换器的预设输出端口基准电压的电压信号；vVo_nref1～vVo_nrefN为代表第1～N个子隔离三端口变换器的新输出端口基 准电压的电压信号；k1为第一预设比例系数；k2为第二预设比例系数；OVR为输出电压调节器；BVR为双向端口电压调节器；vD_1～vD_N为第1～N个子隔离三端口变换器的输入功率的控制信号；
Figure PCTCN2017113582-appb-000001
为第1～N个子隔离三端口变换器的双向端口电压和输出端口电压的控制信号；R为电阻；r为虚拟电阻；RL为等效的线路电阻；S1、S2、S3、S4、S5和S6为开关管；D1、D2为二极管；L1、L2和LE为电感；Cin、Cb、Ca1、Ca2、Co1和Co2为电容；T为变压器；Pin1、Pin2和Pin3分别为第1个、第2个和第3个子隔离三端口变换器的输入功率；t1和t2为时间。
具体实施方式
在下文的描述中，提供了大量的细节以便能够彻底地理解本发明。然而，本领域技术人员可以了解，如下描述仅涉及本发明的较佳实施例，本发明可以无需一个或多个这样的细节而得以实施。此外，为了避免与本发明发生混淆，对于本领域公知的一些技术特征未进行描述。
为了解决上述问题，本发明提出一种接入中压直流配电网的分布式电源发电系统的控制方法。通过该控制方法可以实现各分布式电源的独立控制和各变换器的输出端口的均压控制。
下面结合附图1至7b对本发明作进一步说明。需注意的是，在信号传递过程中，可以使用电压信号的形式来代表某个数据，例如平均输出功率Pavg可以用电压信号vPavg表示。因此，可以理解，在附图中，电压信号vPavg所代表的含义与平均输出功率Pavg一致。其他类似的电压信号也是一样，不一一赘述。
图1示出根据本发明一个实施例的、接入中压直流配电网的分布式电源发电系统及其控制系统的示意图。所述分布式电源发电系统包括N个子隔离三端口变换器(如图1所示的1#子隔离三端口变换器、2#子隔离三端口变换器……N#子隔离三端口变换器)和与N个子隔离三端口变换器一一对应的N个独立的分布式直流电源(如图1所示的Vin_1、Vin_2……Vin_N)，N为大于1的自然数。每个子隔离三端口变换器包括一个输入端口、一个双向端口和一个输出端口，其中，每个子隔离三端口变换器的输出端口与输入端口是电气隔离的，每个子隔离三端口变换器的输出端口与双向端口是电气隔离的。每个子隔离三端口变换器的输入端口连接对应的分布式直流 电源，N个子隔离三端口变换器的双向端口并联连接并构成低压直流母线，N个子隔离三端口变换器的输出端口串联连接并接入中压直流配电网。
参考图1，示出多个子隔离三端口变换器及各自对应的控制系统。根据本发明实施例的分布式电源发电系统的控制方法由所有子隔离三端口变换器控制系统共同实现。所有子隔离三端口变换器控制系统均针对各自对应的子隔离三端口变换器实现相同的控制过程。
根据本发明实施例的分布式电源发电系统的控制方法包括以下步骤：
步骤S1：对于N个子隔离三端口变换器中的每个子隔离三端口变换器，根据在该子隔离三端口变换器的输入端口处采样获得的输入端口电压Vin_i(i＝1，2，…，N)和输入端口电流Iin_i(i＝1，2，…，N)，独立控制该子隔离三端口变换器的输入功率Pin_i(i＝1，2，…，N)。
示例性地，步骤S1可以包括：对于N个子隔离三端口变换器中的每个子隔离三端口变换器，根据该子隔离三端口变换器的输入端口电压Vin_i和输入端口电流Iin_i进行最大功率点跟踪，以独立控制该子隔离三端口变换器的输入功率Pin_i。
参考图1所述的1#子隔离三端口变换器，在其输入端口处分别进行电压采样和电流采样，以获得输入端口电压Vin_1和输入端口电流Iin_1。可以基于采样获得的输入端口电压Vin_1和输入端口电流Iin_1进行最大功率点跟踪。利用最大功率点跟踪方式来独立控制1#子隔离三端口变换器的输入功率Pin_1。
步骤S2：对于N个子隔离三端口变换器中的每个子隔离三端口变换器，根据该子隔离三端口变换器的输入端口电压Vin_i和输入端口电流Iin_i计算该子隔离三端口变换器的输入功率Pin_i。
步骤S3：获得N个子隔离三端口变换器的平均输出功率Pavg。
在一个示例中，步骤S3可以包括：对N个子隔离三端口变换器的输入功率Pin_i求平均，以获得平均输出功率Pavg，即，
Figure PCTCN2017113582-appb-000002
在忽略系统的损耗的情况下，根据功率守恒原理，所有子隔离三端口变换器的输出功率之和等于输入功率之和，因此平均输出功率可以通过对所有子隔离三端口变换器的输入功率求平均来获得。
在另一个示例中，步骤S3可以包括：对于N个子隔离三端口变换器 中的每个子隔离三端口变换器，根据在该子隔离三端口变换器的输出端口处采样获得的输出端口电压Vo_i和输出端口电流Io计算该子隔离三端口变换器的输出功率Po_i；以及对N个子隔离三端口变换器的输出功率Po_i求平均，以获得平均输出功率Pavg。本示例中平均输出功率的计算公式如下：
Figure PCTCN2017113582-appb-000003
基于本示例的平均输出功率的获得方式的示意图如附图2所示。图2仅示出1#子隔离三端口变换器所对应的控制器(及其实现的控制方法)的示意图，其他子隔离三端口变换器所对应的控制器(及其实现的控制方法)的原理与1#子隔离三端口变换器所对应的控制器(及其实现的控制方法)类似，不做赘述。
参考图2，可以在1#子隔离三端口变换器的输出端口处分别进行电压采样和电流采样，以获得输出端口电压Vo_1和输出端口电流Io。根据输出端口电压Vo_1和输出端口电流Io可以计算1#子隔离三端口变换器的输出功率Po_1。可以理解，由于N个子隔离三端口变换器的输出端口串联连接，因此所有子隔离三端口变换器的输出端口电流是相同的，可以针对N个子隔离三端口变换器仅测量一次输出端口电流。直接根据所有子隔离三端口变换器的输出功率所计算的平均输出功率比较准确。
步骤S4：根据以下公式计算N个子隔离三端口变换器中的每个子隔离三端口变换器的新输出端口基准电压：
Vo_nrefi＝Vo_refi-k1_i·Pavg  (3)
其中，i＝1，2，...N，Vo_nrefi是第i个子隔离三端口变换器的新输出端口基准电压，Vo_refi是第i个子隔离三端口变换器的预设输出端口基准电压，k1_i是第i个子隔离三端口变换器所对应的第一预设比例系数，Pavg是平均输出功率。
第一预设比例系数k1_i是一个固定的、大于零的系数。
如上文所述，忽略系统的损耗，根据功率守恒原理，所有子隔离三端口变换器的输出功率之和等于输入功率之和，即，
Po＝Pin_1+Pin_2+…+Pin_N  (4)
Po＝Io·VDC  (5)
其中，Po为N个子隔离三端口变换器的总输出功率，VDC为中压直流配电网电压。根据公式(1)～(5)，可确定在以新输出端口基准电压为基准调 节第i个子隔离三端口变换器的输出端口电压时，经调节的输出端口电压为：
Figure PCTCN2017113582-appb-000004
则有
Figure PCTCN2017113582-appb-000005
根据公式(7)，可以获得如附图3所示的采用根据本发明实施例的控制方法进行控制的分布式电源发电系统的等效示意图，其中r为等效的虚拟电阻。在图3中，假设N个子隔离三端口变换器的预设输出端口基准电压Vo_refi相同，统一用Vo_ref表示。从公式(7)及图3可知，每个子隔离三端口变换器的输出端口电压的控制方法可以总结为基于虚拟电阻的功率-电压下垂控制方法。
步骤S5：对于N个子隔离三端口变换器中的每个子隔离三端口变换器，计算该子隔离三端口变换器的输入功率与平均输出功率之差，以获得该子隔离三端口变换器的双向端口功率。
根据以下公式计算N个子隔离三端口变换器中的每个子隔离三端口变换器的双向端口功率：
Pb_i＝Pin_i-Pavg，  (8)
其中，i＝1，2，...N，Pb_i是第i个子隔离三端口变换器的双向端口功率。
步骤S6：根据以下公式计算N个子隔离三端口变换器中的每个子隔离三端口变换器的新双向端口基准电压：
Vb_nrefi＝Vb_refi-k2_i·Pb_i，  (9)
其中，i＝1，2，...N，Vb_nrefi是第i个子隔离三端口变换器的新双向端口基准电压，Vb_refi是第i个子隔离三端口变换器的预设双向端口基准电压，k2_i是第i个子隔离三端口变换器所对应的第二预设比例系数。
第二预设比例系数k2_i是固定的、大于零的系数。
在以新双向端口基准电压为基准调节第i个子隔离三端口变换器的双向端口电压时，经调节的双向端口电压为：
Vb_i＝Vb_nrefi＝Vb_refi-k2_i·Vb·Ib_i＝Vb_refi-Ib_i·rb  (10)
其中，i＝1，2，...N，Vb_i为第i个子隔离三端口变换器的双向端口电压，Vb为低压直流母线电压，Ib_i为第i个子隔离三端口变换器的双向端口电流，rb为虚拟电阻。
与输出端口电压类似地，每个子隔离三端口变换器的双向端口电压的控制方法可以总结为基于虚拟电阻的功率-电压下垂控制方法。
步骤S7：对于N个子隔离三端口变换器中的每个子隔离三端口变换器，将在该子隔离三端口变换器的输出端口处采样获得的输出端口电压Vo_i和该子隔离三端口变换器的新输出端口基准电压Vo_nrefi相比较，以获得输出端口误差信号。
步骤S8：对于N个子隔离三端口变换器中的每个子隔离三端口变换器，将在该子隔离三端口变换器的双向端口处采样获得的双向端口电压Vb_i和该子隔离三端口变换器的新双向端口基准电压Vb_nrefi相比较，以获得双向端口误差信号。
步骤S9：对于N个子隔离三端口变换器中的每个子隔离三端口变换器，基于该子隔离三端口变换器的输出端口误差信号和双向端口误差信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
示例性地，步骤S9可以包括：对于N个子隔离三端口变换器中的每个子隔离三端口变换器，将该子隔离三端口变换器的输出端口误差信号作为与该子隔离三端口变换器对应的输出电压调节器的输入，并将该子隔离三端口变换器的双向端口误差信号作为与该子隔离三端口变换器对应的双向端口电压调节器的输入；将与该子隔离三端口变换器对应的输出电压调节器的输出信号和与该子隔离三端口变换器对应的双向端口电压调节器的输出信号相叠加，以获得控制信号；以及通过控制信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
参考图1，在1#子隔离三端口变换器的输出端口处进行采样，获得其输出端口电压Vo_1。将Vo_1与Vo_nref1相比较，获得输出端口误差信号。随后，可以将该输出端口误差信号输入输出电压调节器(OVR)中。
此外，在1#子隔离三端口变换器的双向端口处进行采样，获得其双向端口电压Vb_1。将Vb_1与Vb_nref1相比较，获得双向端口误差信号。随后，可以将该双向端口误差信号输入双向端口电压调节器(BVR)中。
将1#子隔离三端口变换器对应的OVR和BVR的输出信号相叠加，获得控制信号
Figure PCTCN2017113582-appb-000006
用于调节该子隔离三端口变换器的双向端口电压和输出端口电压，以最终实现双向端口的电压稳定控制和输出端口的均压控制。
如图1所示，输入功率的控制信号vD_1以及双向端口电压和输出端口 电压的控制信号
Figure PCTCN2017113582-appb-000007
均输入驱动电路，驱动电路生成相应的驱动信号，子隔离三端口变换器可以在驱动信号的控制下改变各端口的电压和/或电流大小。
示例性地，N个子隔离三端口变换器的预设输出端口基准电压Vo_refi相同，N个子隔离三端口变换器的预设双向端口基准电压Vb_refi相同，N个子隔离三端口变换器所对应的第一预设比例系数k1_i相同，N个子隔离三端口变换器所对应的第二预设比例系数k2_i相同。将各子隔离三端口变换器的上述参数设置为相同，可以加快各子隔离三端口变换器的相关运算过程，方便实现对各子隔离三端口变换器的输入功率和输出端口电压的控制。在图1和图2中，所示的分布式电源发电系统与本示例对应，即N个子隔离三端口变换器的预设输出端口基准电压Vo_refi相同，统一采用Vo_ref表示，预设双向端口基准电压Vb_refi相同，统一采用Vb_ref表示，第一预设比例系数k1_i相同，统一采用k1表示，第二预设比例系数k2_i相同，统一采用k2表示。
根据一个示例，步骤S3可以采用以下方式实现：将代表每个子隔离三端口变换器的输入功率的电压信号通过电阻输出到同一平均输出功率母线，并接收平均功率母线输出的、代表平均输出功率的电压信号。
也就是说，可以将每个子隔离三端口变换器的输入功率的电压信号VPin_i(i＝1，2，…N)通过电阻连接在一起，组成平均输出功率母线。所有子隔离三端口变换器对应的电阻大小一致。
根据另一个示例，步骤S3可以采用以下方式实现：将代表每个子隔离三端口变换器的输入功率的电压信号传送至第二层控制器，并接收第二层控制器返回的平均输出功率。
每个子隔离三端口变换器控制器将代表其所对应的子隔离三端口变换器的输入功率的电压信号vPin_i通过通信方式传送至第二层控制器，第二层控制器经过运算得到平均输出功率，再以通信方式传送至每个隔离三端口变换器控制器，本示例的示意图如附图4所示。
根据本发明实施例的控制方法具有如下有益效果：
(1)、每个子隔离三端口变换器的输入端口连接独立的分布式电源，可以实现各分布式电源的独立功率控制，可以使得各分布式电源工作在最大功率输出状态；
(2)、每个子隔离三端口变换器的输出端口串联连接，可以减小输出侧的器件电压应力，同时采用本发明提供的控制方法可以实现所有子隔离三端口变换器的输出端口的均压控制，使得每个子隔离三端口变换器输出侧的器件电压应力一致。
图5示出根据本发明一个实施例的、接入中压直流配电网的分布式电源发电系统的结构示意图。图6示出根据本发明一个实施例的子隔离三端口变换器的电路原理图。
图5示例性地示出由三个子隔离三端口变换器构成的分布式电源发电系统，其中，每个子隔离三端口变换器可以采用如图6所示的电路拓扑结构。每个子隔离三端口变换器的输入端口分别连接太阳能光伏电池，通过调节图6所示的子隔离三端口变换器中的第一至第四开关管(S1～S4)的占空比来实现太阳能光伏电池的最大功率点跟踪控制，通过调节第五和第六开关管(S5、S6)相对于第一至第四开关管(S1～S4)驱动信号的移相角来实现每个子隔离三端口变换器的双向端口的电压稳定控制和输出端口的均压控制。
图7a和7b示出采用根据本发明实施例的控制方法控制分布式电源发电系统的仿真结果图。在图7a和7b中，“W/div”是“瓦/格”，表示每格对应多少瓦特的功率，“V/div”是“伏/格”，表示每格对应多少伏特的电压，“ms/div”是“毫秒/格”，表示每格对应多少毫秒。
在图7a所示的示例中，在时刻t1之前并未采用本文所述的控制方法，而从时刻t1开始采用本文所述的控制方法控制分布式电源发电系统。从图7a中可以看到，由于各个太阳能光伏电池的输出功率(即对应的子隔离三端口变换器的输入功率)是独立控制的、可以工作在最大功率点，因此每个子隔离三端口变换器所连接的太阳能光伏电池的输出功率是不相同的。如图7a所示，在时刻t1之前，没有应用本文所述的控制方法，此时每个子隔离三端口变换器的输出端口电压与所连接的太阳能光伏电池的输出功率成正比，输出端口电压不能均衡。在时刻t1开始引入本文所述的控制策略，每个子隔离三端口功率变换器的输出端口电压很快达到自动均衡，表明了本文所述的控制方法的有效性。在图7b所示的示例中，始终采用本文所述的控制方法控制分布式电源发电系统。从图7b可以看到，在采用本文所述的控制方法控制分布式电源发电系统的情况下，当某个子隔离三端口变换 器的输入功率发生突变时，各个子隔离三端口变换器的输出端口电压仍然能够很好地保持均衡，进一步说明了本文所述控制方法的有效性。
分布式电源发电系统的控制系统及其中的每个子隔离三端口变换器控制器可以采用任何合适的硬件、软件和/或固件实现。示例性地，分布式电源发电系统的控制系统及其中的每个子隔离三端口变换器控制器可以采用现场可编程门阵列(FPGA)、数字信号处理器(DSP)、复杂可编程逻辑器件(CPLD)、微控制单元(MCU)或中央处理单元(CPU)等实现。
根据本发明另一方面，提供一种分布式电源发电系统的控制系统，其中，分布式电源发电系统包括N个子隔离三端口变换器和与N个子隔离三端口变换器一一对应的N个独立的分布式直流电源，N为大于1的自然数；每个子隔离三端口变换器包括一个输入端口、一个双向端口和一个输出端口，其中，每个子隔离三端口变换器的输出端口与输入端口是电气隔离的，每个子隔离三端口变换器的输出端口与双向端口是电气隔离的；每个子隔离三端口变换器的输入端口连接对应的分布式直流电源，N个子隔离三端口变换器的双向端口并联连接并构成低压直流母线，N个子隔离三端口变换器的输出端口串联连接并接入中压直流配电网。控制系统包括与N个子隔离三端口变换器一一对应的N个子隔离三端口变换器控制器，其中，每个子隔离三端口变换器控制器包括：输入功率控制装置、输入功率计算装置、平均功率获得装置、新输出端口基准电压计算装置、双向端口功率计算装置、新双向端口基准电压计算装置、输出端口误差信号获得装置、双向端口误差信号获得装置和电压调节装置。
输入功率控制装置用于根据在对应的子隔离三端口变换器的输入端口处采样获得的输入端口电压和输入端口电流，独立控制对应的子隔离三端口变换器的输入功率。
输入功率计算装置用于根据对应的子隔离三端口变换器的输入端口电压和输入端口电流计算对应的子隔离三端口变换器的输入功率。
平均功率获得装置用于获得N个子隔离三端口变换器的平均输出功率。
新输出端口基准电压计算装置用于根据以下公式计算对应的子隔离三端口变换器的新输出端口基准电压：
Vo_nrefi＝Vo_refi-k1_i·Pavg，
其中，i＝1，2，...N，Vo_nrefi是对应的子隔离三端口变换器的新输出端口 基准电压，Vo_refi是对应的子隔离三端口变换器的预设输出端口基准电压，k1_i是对应的子隔离三端口变换器所对应的第一预设比例系数，Pavg是平均输出功率。
双向端口功率计算装置用于计算对应的子隔离三端口变换器的输入功率与平均输出功率之差，以获得对应的子隔离三端口变换器的双向端口功率。
新双向端口基准电压计算装置用于根据以下公式计算对应的子隔离三端口变换器的新双向端口基准电压：
Vb_nrefi＝Vb_refi-k2_i·Pb_i，
其中，i＝1，2，...N，Vb_nrefi是对应的子隔离三端口变换器的新双向端口基准电压，Vb_refi是对应的子隔离三端口变换器的预设双向端口基准电压，k2_i是对应的子隔离三端口变换器所对应的第二预设比例系数，Pb_i是对应的子隔离三端口变换器的双向端口功率。
输出端口误差信号获得装置用于在对应的子隔离三端口变换器的输出端口处采样获得的输出端口电压和对应的子隔离三端口变换器的新输出端口基准电压相比较，以获得输出端口误差信号。
双向端口误差信号获得装置用于将在对应的子隔离三端口变换器的双向端口处采样获得的双向端口电压和对应的子隔离三端口变换器的新双向端口基准电压相比较，以获得双向端口误差信号。
电压调节装置用于基于对应的子隔离三端口变换器的输出端口误差信号和双向端口误差信号调节对应的子隔离三端口变换器的双向端口电压和输出端口电压。
示例性地，每个子隔离三端口变换器控制器的电压调节装置包括：输入模块，用于将对应的子隔离三端口变换器的输出端口误差信号作为与该子隔离三端口变换器对应的输出电压调节器的输入，并将对应的子隔离三端口变换器的双向端口误差信号作为与该子隔离三端口变换器对应的双向端口电压调节器的输入；叠加模块，用于将与该子隔离三端口变换器对应的输出电压调节器的输出信号和与该子隔离三端口变换器对应的双向端口电压调节器的输出信号相叠加，以获得控制信号；以及调节模块，用于通过控制信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
示例性地，每个子隔离三端口变换器控制器的平均功率获得装置包括 输入平均模块，用于对N个子隔离三端口变换器的输入功率求平均，以获得平均输出功率。
示例性地，每个子隔离三端口变换器控制器的平均功率获得装置包括：输出功率计算模块，用于根据在对应的子隔离三端口变换器的输出端口处采样获得的输出端口电压和输出端口电流计算对应的子隔离三端口变换器的输出功率；以及输出平均模块，用于对N个子隔离三端口变换器的输出功率求平均，以获得平均输出功率。
示例性地，每个子隔离三端口变换器控制器的输入功率控制装置包括最大功率点跟踪模块，用于根据对应的子隔离三端口变换器的输入端口电压和输入端口电流进行最大功率点跟踪，以独立控制该子隔离三端口变换器的输入功率。
示例性地，N个子隔离三端口变换器的预设输出端口基准电压相同，N个子隔离三端口变换器的预设双向端口基准电压相同，N个子隔离三端口变换器所对应的第一预设比例系数相同，N个子隔离三端口变换器所对应的第二预设比例系数相同。
示例性地，每个子隔离三端口变换器控制器的平均功率获得装置包括输出和接收模块，用于将代表对应的子隔离三端口变换器的输入功率的电压信号通过电阻输出到同一平均输出功率母线，并接收平均功率母线输出的、代表平均输出功率的电压信号。
示例性地，每个子隔离三端口变换器控制器的平均功率获得装置包括发送和接收模块，用于将代表对应的子隔离三端口变换器的输入功率的电压信号传送至第二层控制器，并接收第二层控制器返回的平均输出功率。
上文已经结合图1至7b描述了根据本发明实施例的分布式电源发电系统的控制方法的原理、实现方式和优点，本领域技术人员可以结合关于分布式电源发电系统的控制方法的描述理解相应的控制系统，不再赘述。
根据上述控制方法和控制系统，独立控制每个子隔离三端口变换器的输入功率，双向端口和输出端口采用基于虚拟电阻的功率-电压下垂控制策略，实现每个子隔离三端口变换器的双向端口电压的稳定控制和输出端口电压的均压控制，实现模块化设计，为将分布式电源发电系统接入中压直流配电网提供一种可行的技术方案。
本发明已经通过上述实施例进行了说明，但应当理解的是，上述实施 例只是用于举例和说明的目的，而非意在将本发明限制于所描述的实施例范围内。此外本领域技术人员可以理解的是，本发明并不局限于上述实施例，根据本发明的教导还可以做出更多种的变型和修改，这些变型和修改均落在本发明所要求保护的范围以内。本发明的保护范围由附属的权利要求书及其等效范围所界定。

Claims (16)

  1. 一种分布式电源发电系统的控制方法，其中，所述分布式电源发电系统包括N个子隔离三端口变换器和与所述N个子隔离三端口变换器一一对应的N个独立的分布式直流电源，N为大于1的自然数；每个子隔离三端口变换器包括一个输入端口、一个双向端口和一个输出端口，其中，每个子隔离三端口变换器的输出端口与输入端口是电气隔离的，每个子隔离三端口变换器的输出端口与双向端口是电气隔离的；每个子隔离三端口变换器的输入端口连接对应的分布式直流电源，所述N个子隔离三端口变换器的双向端口并联连接并构成低压直流母线，所述N个子隔离三端口变换器的输出端口串联连接并接入中压直流配电网；
    所述控制方法包括：
    步骤S1：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，根据在该子隔离三端口变换器的输入端口处采样获得的输入端口电压和输入端口电流，独立控制该子隔离三端口变换器的输入功率；
    步骤S2：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，根据该子隔离三端口变换器的输入端口电压和输入端口电流计算该子隔离三端口变换器的输入功率；
    步骤S3：获得所述N个子隔离三端口变换器的平均输出功率；
    步骤S4：根据以下公式计算所述N个子隔离三端口变换器中的每个子隔离三端口变换器的新输出端口基准电压：
    Vo_nrefi＝Vo_refi-k1_i·Pavg，
    其中，i＝1，2，...N，Vo_nrefi是第i个子隔离三端口变换器的新输出端口基准电压，Vo_refi是第i个子隔离三端口变换器的预设输出端口基准电压，k1_i是第i个子隔离三端口变换器所对应的第一预设比例系数，Pavg是所述平均输出功率；
    步骤S5：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，计算该子隔离三端口变换器的输入功率与所述平均输出功率之差，以获得该子隔离三端口变换器的双向端口功率；
    步骤S6：根据以下公式计算所述N个子隔离三端口变换器中的每个子隔离三端口变换器的新双向端口基准电压：
    Vb_nrefi＝Vb_refi-k2_i·Pb_i，
    其中，i＝1，2，...N，Vb_nrefi是第i个子隔离三端口变换器的新双向端口基准电压，Vb_refi是第i个子隔离三端口变换器的预设双向端口基准电压，k2_i是第i个子隔离三端口变换器所对应的第二预设比例系数，Pb_i是第i个子隔离三端口变换器的双向端口功率；
    步骤S7：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，将在该子隔离三端口变换器的输出端口处采样获得的输出端口电压和该子隔离三端口变换器的新输出端口基准电压相比较，以获得输出端口误差信号；
    步骤S8：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，将在该子隔离三端口变换器的双向端口处采样获得的双向端口电压和该子隔离三端口变换器的新双向端口基准电压相比较，以获得双向端口误差信号；以及
    步骤S9：对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，基于该子隔离三端口变换器的输出端口误差信号和双向端口误差信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
  2. 根据权利要求1所述的控制方法，其特征在于，所述步骤S9包括：
    对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，
    将该子隔离三端口变换器的输出端口误差信号作为与该子隔离三端口变换器对应的输出电压调节器的输入，并将该子隔离三端口变换器的双向端口误差信号作为与该子隔离三端口变换器对应的双向端口电压调节器的输入；
    将与该子隔离三端口变换器对应的输出电压调节器的输出信号和与该子隔离三端口变换器对应的双向端口电压调节器的输出信号相叠加，以获得控制信号；以及
    通过所述控制信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
  3. 根据权利要求1所述的控制方法，其特征在于，所述步骤S3包括：
    对所述N个子隔离三端口变换器的输入功率求平均，以获得所述平均输出功率。
  4. 根据权利要求1所述的控制方法，其特征在于，所述步骤S3包括：
    对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，根 据在该子隔离三端口变换器的输出端口处采样获得的输出端口电压和输出端口电流计算该子隔离三端口变换器的输出功率；以及
    对所述N个子隔离三端口变换器的输出功率求平均，以获得所述平均输出功率。
  5. 根据权利要求1所述的控制方法，其特征在于，所述步骤S1包括：
    对于所述N个子隔离三端口变换器中的每个子隔离三端口变换器，根据该子隔离三端口变换器的输入端口电压和输入端口电流进行最大功率点跟踪，以独立控制该子隔离三端口变换器的输入功率。
  6. 根据权利要求1所述的控制方法，其特征在于，所述N个子隔离三端口变换器的预设输出端口基准电压相同，所述N个子隔离三端口变换器的预设双向端口基准电压相同，所述N个子隔离三端口变换器所对应的第一预设比例系数相同，所述N个子隔离三端口变换器所对应的第二预设比例系数相同。
  7. 根据权利要求1所述的控制方法，其特征在于，所述步骤S3采用以下方式实现：
    将代表每个子隔离三端口变换器的输入功率的电压信号通过电阻输出到同一平均输出功率母线，并接收所述平均功率母线输出的、代表所述平均输出功率的电压信号。
  8. 根据权利要求1所述的控制方法，其特征在于，所述步骤S3采用以下方式实现：
    将代表每个子隔离三端口变换器的输入功率的电压信号传送至第二层控制器，并接收所述第二层控制器返回的所述平均输出功率。
  9. 一种分布式电源发电系统的控制系统，其中，所述分布式电源发电系统包括N个子隔离三端口变换器和与所述N个子隔离三端口变换器一一对应的N个独立的分布式直流电源，N为大于1的自然数；每个子隔离三端口变换器包括一个输入端口、一个双向端口和一个输出端口，其中，每个子隔离三端口变换器的输出端口与输入端口是电气隔离的，每个子隔离三端口变换器的输出端口与双向端口是电气隔离的；每个子隔离三端口变换器的输入端口连接对应的分布式直流电源，所述N个子隔离三端口变换器的双向端口并联连接并构成低压直流母线，所述N个子隔离三端口变换器的输出端口串联连接并接入中压直流配电网；
    所述控制系统包括与所述N个子隔离三端口变换器一一对应的N个子隔离三端口变换器控制器，其中，每个子隔离三端口变换器控制器包括：
    输入功率控制装置，用于根据在对应的子隔离三端口变换器的输入端口处采样获得的输入端口电压和输入端口电流，独立控制对应的子隔离三端口变换器的输入功率；
    输入功率计算装置，用于根据对应的子隔离三端口变换器的输入端口电压和输入端口电流计算对应的子隔离三端口变换器的输入功率；
    平均功率获得装置，用于获得所述N个子隔离三端口变换器的平均输出功率；
    新输出端口基准电压计算装置，用于根据以下公式计算对应的子隔离三端口变换器的新输出端口基准电压：
    Vo_nrefi＝Vo_refi-k1_i·Pavg，
    其中，i＝1，2，...N，Vo_nrefi是对应的子隔离三端口变换器的新输出端口基准电压，Vo_refi是对应的子隔离三端口变换器的预设输出端口基准电压，k1_i是对应的子隔离三端口变换器所对应的第一预设比例系数，Pavg是所述平均输出功率；
    双向端口功率计算装置，用于计算对应的子隔离三端口变换器的输入功率与所述平均输出功率之差，以获得对应的子隔离三端口变换器的双向端口功率；
    新双向端口基准电压计算装置，用于根据以下公式计算对应的子隔离三端口变换器的新双向端口基准电压：
    Vb_nrefi＝Vb_refi-k2_i·Pb_i，
    其中，i＝1，2，...N，Vb_nrefi是对应的子隔离三端口变换器的新双向端口基准电压，Vb_refi是对应的子隔离三端口变换器的预设双向端口基准电压，k2_i是对应的子隔离三端口变换器所对应的第二预设比例系数，Pb_i是对应的子隔离三端口变换器的双向端口功率；
    输出端口误差信号获得装置，用于在对应的子隔离三端口变换器的输出端口处采样获得的输出端口电压和对应的子隔离三端口变换器的新输出端口基准电压相比较，以获得输出端口误差信号；
    双向端口误差信号获得装置，用于将在对应的子隔离三端口变换器的双向端口处采样获得的双向端口电压和对应的子隔离三端口变换器的 新双向端口基准电压相比较，以获得双向端口误差信号；以及
    电压调节装置，用于基于对应的子隔离三端口变换器的输出端口误差信号和双向端口误差信号调节对应的子隔离三端口变换器的双向端口电压和输出端口电压。
  10. 根据权利要求9所述的控制系统，其特征在于，每个子隔离三端口变换器控制器的电压调节装置包括：
    输入模块，用于将对应的子隔离三端口变换器的输出端口误差信号作为与该子隔离三端口变换器对应的输出电压调节器的输入，并将对应的子隔离三端口变换器的双向端口误差信号作为与该子隔离三端口变换器对应的双向端口电压调节器的输入；
    叠加模块，用于将与该子隔离三端口变换器对应的输出电压调节器的输出信号和与该子隔离三端口变换器对应的双向端口电压调节器的输出信号相叠加，以获得控制信号；以及
    调节模块，用于通过所述控制信号调节该子隔离三端口变换器的双向端口电压和输出端口电压。
  11. 根据权利要求9所述的控制系统，其特征在于，每个子隔离三端口变换器控制器的平均功率获得装置包括：
    输入平均模块，用于对所述N个子隔离三端口变换器的输入功率求平均，以获得所述平均输出功率。
  12. 根据权利要求9所述的控制系统，其特征在于，每个子隔离三端口变换器控制器的平均功率获得装置包括：
    输出功率计算模块，用于根据在对应的子隔离三端口变换器的输出端口处采样获得的输出端口电压和输出端口电流计算对应的子隔离三端口变换器的输出功率；以及
    输出平均模块，用于对所述N个子隔离三端口变换器的输出功率求平均，以获得所述平均输出功率。
  13. 根据权利要求9所述的控制系统，其特征在于，每个子隔离三端口变换器控制器的输入功率控制装置包括：
    最大功率点跟踪模块，用于根据对应的子隔离三端口变换器的输入端口电压和输入端口电流进行最大功率点跟踪，以独立控制该子隔离三端口变换器的输入功率。
  14. 根据权利要求9所述的控制系统，其特征在于，所述N个子隔离三端口变换器的预设输出端口基准电压相同，所述N个子隔离三端口变换器的预设双向端口基准电压相同，所述N个子隔离三端口变换器所对应的第一预设比例系数相同，所述N个子隔离三端口变换器所对应的第二预设比例系数相同。
  15. 根据权利要求9所述的控制系统，其特征在于，每个子隔离三端口变换器控制器的平均功率获得装置包括输出和接收模块，用于将代表对应的子隔离三端口变换器的输入功率的电压信号通过电阻输出到同一平均输出功率母线，并接收所述平均功率母线输出的、代表所述平均输出功率的电压信号。
  16. 根据权利要求9所述的控制系统，其特征在于，每个子隔离三端口变换器控制器的平均功率获得装置包括发送和接收模块，用于将代表对应的子隔离三端口变换器的输入功率的电压信号传送至第二层控制器，并接收所述第二层控制器返回的所述平均输出功率。
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