WO2022088554A1 - 一种多端口交流电网柔性互联装置及其控制方法和系统 - Google Patents

一种多端口交流电网柔性互联装置及其控制方法和系统 Download PDF

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WO2022088554A1
WO2022088554A1 PCT/CN2021/076799 CN2021076799W WO2022088554A1 WO 2022088554 A1 WO2022088554 A1 WO 2022088554A1 CN 2021076799 W CN2021076799 W CN 2021076799W WO 2022088554 A1 WO2022088554 A1 WO 2022088554A1
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Prior art keywords
voltage
feeder
port
flexible
interconnection
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PCT/CN2021/076799
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English (en)
French (fr)
Inventor
张建文
冯欣
施刚
周剑桥
黄玉辉
蔡旭
金之俭
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上海交通大学
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Priority to US18/251,233 priority Critical patent/US20230396065A1/en
Publication of WO2022088554A1 publication Critical patent/WO2022088554A1/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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • 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
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
    • 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
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/10—Flexible AC transmission systems [FACTS]
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

Definitions

  • the invention relates to the flexible interconnection of alternating current power grids and the technical fields of power electronics, in particular to a flexible interconnection device of a multi-port alternating current power grid with active power flow control capability suitable for alternating current power grids, and a control method and system thereof.
  • the traditional AC power grid has significant advantages in system stability and reliability. However, due to insufficient control ability, it cannot effectively solve the problem of feeder blockage, and the problem of unbalanced feeder load is prominent. Therefore, the actual capacity of the distribution network system is limited by the single feeder that first reaches the upper limit of the capacity, which is much lower than the design capacity, which seriously affects the economic operation of the AC power grid.
  • the first solution is to build or upgrade existing feeders, which is expensive and time-consuming;
  • the second solution is to adjust through primary equipment, such as through an on-load voltage regulator Adjust the voltage and reconstruct the network through the action of the tie switch to achieve the load balance of the feeder.
  • traditional adjustment methods such as on-load voltage regulators and feeder switching operations have limited adjustment capabilities, slow response speed, and insufficient adjustment accuracy.
  • the third solution is to provide interconnection ports of different AC feeders through the Flexible Alternative Current Interconnector (FACI) to realize flexible interconnection and active power flow control between feeders.
  • FACI Flexible Alternative Current Interconnector
  • the mainstream topology of the existing flexible AC interconnection devices mainly adopts back-to-back voltage source inverters, which are formed by multiple voltage source inverters through a shared DC bus, which can realize multi-directional power flow operation and decoupling of active power and reactive power. control.
  • this topology is constituted by a full-power voltage source inverter, so it has the disadvantages of high price, high loss, large volume, and high failure rate.
  • the present invention is proposed in view of the problems existing in the prior art.
  • the present invention provides a multi-port flexible AC interconnection device with active power flow control capability suitable for an AC power grid.
  • the multi-port flexible AC interconnection device includes a static synchronous compensator (Static Synchronous Compensator, STATCOM) and is connected in series with it.
  • STATCOM Static Synchronous Compensator
  • the static synchronous compensator is a medium-voltage level voltage source converter, which has the function of two-way compensation for reactive power, can absorb reactive power from the system, and can also provide reactive power compensation for the system;
  • the multi-port flexible interconnection module includes a plurality of first single-phase converters that share the same common connection bus and are connected in parallel with each other.
  • the AC output ports of the first single-phase converters are connected in series with the feeder.
  • the amplitude and phase of the voltage at the AC output port of the first single-phase converter realizes the active control of the active power and reactive power of the feeder; the AC component of the AC output port voltage of the first single-phase converter connected in series on the feeder is referred to below as the AC component is the series equivalent voltage.
  • the above-mentioned common connection bus is a DC bus
  • the first single-phase converter is a voltage source type single-phase inverter.
  • the medium-voltage-level voltage source converter is a three-phase inverter with a withstand voltage level of a medium-voltage level (eg, 10 kV), and an output voltage of bipolar.
  • a medium-voltage level eg, 10 kV
  • the topology of the medium-voltage stage voltage source converter can be a two-level voltage source inverter, a three-level voltage source inverter, or other level voltage source inverter.
  • the multi-port flexible interconnection module may further include a second single-phase converter connected in parallel with the first single-phase converter; the medium-voltage stage voltage source converter may It is connected to the AC output port of the second single-phase converter, and can also be directly connected to the positive or negative pole of the common connection bus of the multi-port flexible interconnection module.
  • Both of these two methods can realize the static synchronous compensator and the multi-port flexible
  • the series connection of interconnection modules specifically, when the multi-port flexible interconnection module only includes the first single-phase converter, the medium-voltage-level voltage source converter is directly connected to the positive or negative pole of the common connection bus, which can realize the above
  • the series connection of the static synchronous compensator and the multi-port flexible interconnection module when the multi-port flexible interconnection module includes the first single-phase converter and the second single-phase converter at the same time, the medium-voltage stage voltage source converter
  • the AC output port can be connected to the AC output port of the second single-phase converter, and the static synchronous compensator and the multi-port flexible interconnection module can also be connected in series, and at this time, the second single-phase converter can be adjusted by adjusting the AC output port.
  • the amplitude and phase of the AC output port voltage of the inverter can be adjusted, so that the voltage of the common connection bus of the multi-port flexible interconnection module can be stabilized.
  • the first single-phase converter and the second single-phase converter in the above are both voltage source type single-phase converters; the voltage source type single-phase converter is rated output voltage compared to medium voltage Voltage Source Converters Low, single-phase converters with a unipolar output voltage.
  • the topology of the single-phase converter that constitutes the multi-port flexible interconnection module can be a two-level half-bridge inverter, a three-level half-bridge inverter, or other power-achievable inverters. Bi-directional flow half-bridge inverter.
  • the present invention provides a control method suitable for the multi-port flexible AC interconnection device, the control method includes a line power flow control loop, a static synchronous compensator control loop and a common connection bus voltage balance control loop;
  • the active power of one and only one feeder is determined by the requirement of the system's active power balance, and only the reactive power of the feeder needs to be controlled, and the feeder is called The feeder is controlled by constant reactive power, and the active power and reactive power of other feeders need to be controlled, which is called the power flow control feeder;
  • the phase-locked loop locks the three-phase voltage of the node of the constant reactive power control feeder, and the phase angle of the output of the phase-locked loop provides the angle for the Park transformation matrix from the abc coordinate system to the dq coordinate system; the three control loops are described below. Describe in order:
  • the control objective of the line power flow control loop is that the active power of the power flow control feeder reaches the reference value and reactive power reaches the reference value Set the line power flow control loop output as
  • the subscript i indicates that the ith feeder is a constant reactive power control feeder, and the subscript j indicates the first j power flow control feeders;
  • the line power flow control loop first calculates the reference value of the d-axis component of the power flow control feeder current according to the active power reference value and the reactive power reference value of the power flow control feeder and q-axis component reference values
  • the calculation method is to solve the following system of equations:
  • the line power flow control loop is carried out in the dq coordinate system and is controlled by a proportional integral controller.
  • the mathematical equation is:
  • V is the node voltage of the feeder
  • I is the current of the feeder
  • ⁇ is the AC frequency of the feeder
  • L is the equivalent inductance and inductance of the feeder
  • R is the equivalent resistance value of the feeder
  • R is the equivalent resistance value of the feeder
  • the subscript j represents the parameter of the jth power flow control feeder
  • the subscript d represents the d-axis component
  • the subscript q represents the q-axis component
  • the superscript * represents is the reference value
  • k p is the proportional-integral controller proportional gain coefficient
  • k i is the proportional-integral controller integral gain coefficient
  • the control objective of the static synchronous compensator control loop is that the reactive power of the constant reactive power control feeder reaches the reference value
  • the sum of the three-phase capacitor voltage of the static synchronous compensator is stable as a reference value Its output is the reference value of the AC component of the voltage at the AC output port of the static synchronous compensator
  • the static synchronous compensator control loop is composed of a voltage control outer loop, a reactive power control outer loop and a current control inner loop;
  • the voltage control outer loop uses a proportional-integral controller to control the sum of the three-phase capacitor voltages of the static synchronous compensator, the input is the difference between the reference value and the instantaneous value of the sum of the three-phase capacitor voltages of the static synchronous compensator, and the output is a constant Reference value for the d-axis component of the feeder current for power control
  • the mathematical equation is:
  • k p1 is the proportional-integral controller proportional gain coefficient
  • k i1 is the proportional-integral controller integral gain coefficient
  • ⁇ VC proportional-integral controller integral gain coefficient
  • STATCOM is the instantaneous value of the sum of the three-phase capacitor voltages of the static synchronous compensator, is the sum of the reference values of the current d-axis components of the power flow control feeder
  • the reactive power control outer loop controls the reactive power reference value of the feeder according to the constant reactive power Calculate the reference value of the q-axis component of the constant reactive power control feeder current
  • the calculation formula is:
  • the current control inner loop is controlled in the dq coordinate system, and the proportional integral controller is used to control the d-axis component and the q-axis component of the constant reactive power control feeder current respectively.
  • the mathematical equation is:
  • V Cid and V Ciq are the d-axis component and the q-axis component of the AC component of the AC output port voltage of the first single-phase converter connected to the constant reactive power control feeder
  • V SMd and V SMq are the d-axis and q-axis components of the AC output port voltage of the second single-phase converter connected to the static synchronous compensator
  • k p2 is the proportional-integral controller proportional gain coefficient
  • k i2 is the integral link gain coefficient of the proportional-integral controller
  • V id , V iq , V Cid , V Ciq , V SMd , V SMq are feedforward terms, which are used to enhance the anti-interference ability of the control loop and speed up the response speed
  • the control objective of the common connection bus voltage balance control loop is to stabilize the common connection bus voltage to a reference value Its output is a common connection bus balanced reference voltage
  • the control of the common connection bus voltage balance control loop is carried out in the abc coordinate system, and the proportional integral controller is used to control the abc three-phase common connection bus voltage, and the mathematical equation is:
  • V linka , V linkb , and V linkc are the three-phase common connection bus voltages
  • I pa , I pb , and I pc are the three-phase currents of the static synchronous compensator branch
  • k p3 is the proportional-integral controller proportional gain coefficient
  • k i3 is the proportional-integral controller integral gain coefficient
  • the topology of the multi-port flexible AC interconnection device includes a second single-phase converter connected to the medium-voltage-level voltage source converter, the output reference voltage of the line power flow control loop is obtained Then, the reference voltage of the AC output port of the first single-phase converter is:
  • V common ,dc is the reference value of the common DC component in the output voltage of the AC output port of the single-phase converter, the reference value is greater than zero and less than the common connection bus voltage;
  • the topology of the multi-port flexible AC interconnection device includes a second single-phase converter connected to a medium-voltage stage voltage source converter, the feedforward three-phase reference voltage in the common connection bus voltage balance control loop equal to zero, the reference voltage of the AC output port of the second single-phase converter is:
  • the reference voltage of the AC output port of the medium-voltage-level voltage source converter is:
  • the output reference voltage of the line power flow control loop is obtained.
  • the reference voltage of the AC output port of the first single-phase converter is:
  • the feedforward three-phase reference voltage in the common connection bus voltage balance control loop is the AC component of the reference voltage of the AC output port of the first single-phase converter connected to the constant reactive power control feeder, calculated according to any one of the series equivalent voltage distribution methods described in the third aspect of the present invention
  • the feedforward terms V SMd and V SMq in the current control inner loop of the static synchronous compensator control loop equal to zero
  • the reference voltage of the AC output port of the static synchronous compensator is:
  • the plus sign is taken when the AC output port of the static synchronous compensator is connected to the negative pole of the common connection bus, and the minus sign is taken when the AC output port of the static synchronization compensator is connected to the positive pole of the common connection bus.
  • the present invention provides a method for distributing the equivalent voltage of the multi-port flexible AC interconnection device in series on the distribution network feeder, and the voltage distribution method satisfies the following basic condition equations:
  • the first feeder is a constant reactive power control feeder
  • the vector expression of the AC component of the equivalent voltage in series on the kth feeder of the multi-port flexible AC interconnection device In order to achieve the target power flow on the kth feeder, the vector expression of the series equivalent voltage between the first feeder and the kth feeder is required, is the vector expression of the AC component of the AC output port voltage of the second single-phase converter in the multi-port flexible interconnection module connected to the static synchronous compensator, is the conjugate vector expression of the alternating current on the kth feeder, is the conjugate vector expression of the AC current of the static synchronous compensator branch, and n is the number of feeders interconnected through the multi-port flexible AC interconnection device;
  • the distribution method of the series equivalent voltage of the multi-port flexible AC interconnection device with active power flow control capability suitable for the AC power grid on the distribution network feeder is any group that satisfies the basic condition equation. solution.
  • a method for distributing the equivalent voltage of the multi-port flexible AC interconnection device with active power flow control capability suitable for the AC power grid in series on the distribution network feeder is: Its characteristic is simplicity.
  • another distribution method of the series equivalent voltage is selection satisfies Taking the minimum value, the amplitude of the AC component of the output voltage required by the single-phase converter can be minimized.
  • the distribution method of the series equivalent voltage can also be any selection method that satisfies the basic condition equation.
  • the voltage components of the AC output ports of the single-phase converter in the multi-port flexible interconnection module contain the same magnitude of DC components and different AC components required for control.
  • the DC component of the AC output port voltage of the single-phase converter may be half of the voltage of the common connection bus, or may be other values smaller than the voltage of the common connection bus and greater than zero.
  • the present invention provides an AC power grid multi-feeder flexible interconnection system using the multi-port flexible AC interconnection device.
  • the core equipment of the AC power grid multi-feeder flexible interconnection system is the multi-port flexible AC interconnection device.
  • Other components can also include AC feeders, AC loads, energy storage devices, etc.;
  • the multi-port flexible AC interconnection device is installed at the gathering place of a plurality of AC feeders, and the AC feeder is connected to the multi-port flexible AC interconnection device.
  • the step-down transformer is connected to the low-voltage AC system, and the low-voltage AC system can be connected to a low-voltage AC load or an energy storage device or an electric vehicle fast charging station.
  • the AC power grid multi-feeder flexible interconnection system may include one of the multi-port flexible AC interconnection devices, as shown in FIG. 4; or may include a plurality of the multi-port flexible AC interconnection devices, as shown in FIG. 5; when the When the AC power grid multi-feeder flexible interconnection system includes more than two multi-port flexible AC interconnection devices, the multi-port flexible AC interconnection devices are installed at the convergence of multiple AC feeders in their respective areas, and the multi-port flexible AC interconnection devices pass through the connection between the multi-port flexible AC interconnection devices. Interconnection interconnects multiple areas to form a more complex ring/mesh system topology.
  • the invention provides an overvoltage protection method for the voltage of the multi-port flexible AC interconnection device connected in series on the feeder.
  • a protection device is connected in parallel between the output ports.
  • the protection device is composed of a metal-oxide varistors (MOV) and a thyristor bypass switch in parallel.
  • MOV metal-oxide varistors
  • the metal-oxide voltage limiter limits the voltage to the protection level.
  • the thyristor bypass switch realizes overvoltage protection by bypassing the AC output port of the first single-phase converter;
  • the thyristor bypass switch is composed of an anti-parallel thyristor, a resistance-capacitance loop, a static resistance in parallel, and then a saturable reactor in series.
  • the present invention provides a startup method of the multi-port flexible AC interconnection device, and the startup method of the multi-port flexible AC interconnection device can be composed of three stages:
  • the first stage is an uncontrolled rectification stage.
  • the AC output port is connected in series with a current limiting resistor and then connected to the grid. All switches are locked, and the capacitors in the multi-port flexible AC interconnection device are charged through a rectifier circuit formed by diodes;
  • the second stage is a controlled rectification stage.
  • the multi-port flexible AC interconnection device is connected to the multi-port flexible AC interconnection device by switching the capacitors in or out of the charging circuit in turn, but the total number of capacitors in the charging circuit is constant.
  • the capacitor voltage is charged to near the rated value;
  • the third stage is a ramp-up stage. After the second stage is charged, the capacitor voltage is charged to a rated value by a given ramp-up reference voltage, and the voltage control loop includes the first step of the present invention.
  • the present invention provides a control system suitable for the multi-port flexible AC interconnection device.
  • the control system of the multi-port flexible AC interconnection device can adopt a centralized control structure, that is, the line power flow control loop, the static synchronous compensator control Both the loop and the common connection bus voltage balance control loop are implemented in the same controller; a distributed control architecture can also be used, and the control is realized by multiple controllers of the same level, and there is no communication between the controllers at the same level, such as line flow control loop, static synchronous compensator control loop and common connection bus voltage balance control loop are implemented in three different controllers respectively; a layered control architecture combining centralized control and distributed control can also be used, through multiple different The level of controller realizes control, there is information communication between different levels of control, and there is no communication between controllers at the same level.
  • the line power flow control loop and the calculation of the series equivalent voltage distribution are controlled in the first-level controller, and the static synchronous compensator is controlled.
  • the loop and the common connection bus voltage balance control loop are controlled in two secondary controllers respectively, and there is communication and interaction of control information between the primary controller and the secondary control, and the controller is capable of realizing the control loop.
  • Hardware devices such as controllers based on digital signal processing chips and controllers based on field programmable logic gate array chips.
  • the present invention has the following beneficial effects:
  • the existing static synchronous compensator only has the function of reactive power compensation, and does not have the functions of multi-AC feeder interconnection and feeder active power flow decoupling control.
  • the present invention provides multiple AC interconnection ports by introducing a multi-port flexible interconnection module. The interconnection of multiple AC feeders is realized, and the active control of the decoupling of active power and reactive power of the feeder can be realized by adjusting the amplitude and phase of the series equivalent voltage connected in series on the feeder.
  • the present invention does not need to use full power, but uses a series voltage source to realize active power flow control, and the converter device has low cost and covers an area of Small, low loss, fast control speed.
  • the multi-port flexible interconnection module in the present invention has the characteristics of modularization, and by increasing the number of the first single-phase converters connected in parallel in the interconnection module, the expansion of interconnection ports can be realized quickly and economically.
  • Fig. 1 is the topological structure of the multi-port flexible AC interconnection device according to the present invention and the system schematic diagram of interconnecting multi-feeders;
  • FIG. 2 is a system schematic diagram of the multi-port flexible AC interconnection device according to the present invention omitting the topology structure of the second single-phase converter connected to the static synchronous compensator and interconnecting multiple feeders;
  • FIG. 3 is a schematic diagram of a typical topology example of a medium-voltage stage voltage source converter and a second single-phase converter in the multi-port flexible AC interconnection device according to the present invention
  • Fig. 4 is a kind of AC power grid multi-feeder flexible interconnection system whose core equipment is the multi-port flexible AC interconnection device of the present invention
  • FIG. 5 is an AC power grid multi-feeder flexible interconnection system comprising a plurality of the multi-port flexible AC interconnection devices according to the present invention
  • FIG. 6 is a wiring diagram and a schematic diagram of a protection device for an overvoltage protection method for the voltage of the multi-port flexible AC interconnection device connected in series on the feeder according to the present invention
  • Fig. 7 shows the topology structure of the dual-port flexible AC interconnection device in which the multi-port flexible interconnection module adopts parallel two-level half-bridge inverters and the static synchronous compensator adopts cascaded full-bridge topology and realizes two feeders in the first embodiment Schematic diagram of the interconnected system;
  • FIG. 8 is a block diagram of a control method of a dual-port flexible AC interconnection device in which the multi-multi-port flexible interconnection module adopts parallel two-level half-bridge inverters and the static synchronous compensator adopts cascaded full-bridge topology in the first embodiment;
  • FIG. 9 is a waveform diagram of the simulated power flow of each feeder, the voltage of each capacitor in the device, and the current of each feeder under the first working condition in the first embodiment;
  • FIG. 10 is a waveform diagram of the simulated power flow of each feeder, the voltage of each capacitor in the device, and the current of each feeder under the second working condition in the first embodiment;
  • 11 is a waveform diagram of the simulated power flow of each feeder, the voltage of each capacitor in the device, and the current of each feeder under the third working condition in the first embodiment;
  • Fig. 13 shows that the multi-port flexible interconnection module in the second embodiment adopts a parallel two-level half-bridge inverter and omits the half-bridge inverter connected with the static synchronous compensator.
  • the static synchronous compensator adopts a cascaded full bridge Topological structure of the dual-port flexible AC interconnection device and a schematic diagram of the system for realizing the interconnection of two feeders;
  • FIG. 14 shows that the multi-port flexible interconnection module in the second embodiment adopts a parallel two-level half-bridge inverter and omits the half-bridge inverter connected to the static synchronous compensator.
  • the static synchronous compensator adopts a cascaded full-bridge A block diagram of a control method of a topology dual-port flexible AC interconnection device;
  • Fig. 16 shows the topology structure of the three-port flexible AC interconnection device in which the multi-port flexible interconnection module adopts parallel two-level half-bridge inverters and the static synchronous compensator adopts the cascaded full-bridge topology and realizes the interconnection of three feeders in the third embodiment Schematic diagram of the system;
  • 17 is a block diagram of a control method of a three-port flexible AC interconnection device in which the multi-port flexible interconnection module adopts a parallel two-level half-bridge inverter and the static synchronous compensator adopts a cascaded full-bridge topology in the third embodiment;
  • 18 to 19 are waveform diagrams of the simulation of the power flow of each feeder, the voltage of each capacitor in the device, and the current of each feeder according to the third embodiment.
  • the present invention provides a multi-port flexible AC interconnection device with active power flow control capability suitable for an AC power grid.
  • the multi-port flexible AC interconnection device includes a static synchronous compensator and a multi-port serial connection therewith.
  • Flexible interconnection module ;
  • the static synchronous compensator is a medium-voltage level voltage source converter, which has the function of two-way compensation for reactive power, which can absorb reactive power from the system and provide reactive power compensation for the system;
  • the multi-port flexible interconnection module includes a plurality of first single-phase converters that share the same common connection bus and are connected in parallel with each other.
  • the AC output ports of the first single-phase converters are connected in series with the feeder.
  • the amplitude and phase of the AC output port voltage of the single-phase converter realizes the active control of the active power and reactive power of the feeder; the invention defines the AC component of the AC output port voltage of the first single-phase converter connected in series on the feeder as Equivalent voltage in series.
  • the multi-port flexible interconnection module may further include a second single-phase converter connected in parallel with the first single-phase converter, and the medium-voltage stage voltage source converter and the second single-phase converter are connected in parallel.
  • the AC output ports are connected to realize the series connection of the static synchronous compensator and the multi-port flexible interconnection module; by adjusting the amplitude and phase of the AC output port voltage of the second single-phase converter, the multi-port flexible interconnection module is realized.
  • the common connection bus voltage is stable.
  • the medium-voltage-level voltage source converter is directly connected to the positive or negative pole of the common connection bus, so that the static synchronous compensator and the multi-port converter can be realized.
  • Serial connection of flexible interconnect modules is directly connected to the positive or negative pole of the common connection bus, so that the static synchronous compensator and the multi-port converter can be realized.
  • the AC output port of the medium-voltage stage voltage source converter can be connected to the AC output port of the second single-phase converter.
  • the ports are connected, and the series connection of the static synchronous compensator and the multi-port flexible interconnection module can also be realized.
  • the present invention uses a multi-port flexible AC interconnection device to realize the device topology and system connection of dual feeder interconnection;
  • the multi-port flexible AC interconnection device includes a three-phase cascaded full bridge Topological static synchronous compensator and multi-port flexible interconnection module in series with it.
  • the multi-port flexible interconnection module includes three two-level half-bridge inverters that share the same common connection bus, and the three half-bridge inverters are respectively connected with the two AC feeders and the static synchronous compensator one by one; Adjust the series equivalent voltage connected in series on the feeder, the AC component of the AC output port voltage of the half-bridge inverter connected in series with the static synchronous compensator, and the amplitude and phase of the AC component of the AC output port voltage of the static synchronous compensator.
  • the internal energy balance of the multi-port flexible AC interconnection device is realized;
  • the internal energy balance of the multi-port flexible AC interconnection device is manifested in that the capacitor voltage of the common connection bus remains stable and the capacitor voltage in the static synchronous compensator remains stable. , the active power flowing into the above capacitor is required to remain zero, namely:
  • a multi-port flexible AC interconnection device is used to realize dual feeder interconnection.
  • the multi-port flexible AC interconnection device includes a three-phase cascaded full-bridge topology static synchronous compensator and a multi-port flexible interconnection module connected in series with it.
  • the multi-port flexible interconnection module includes two two-level half-bridge inverters that share the same common connection bus, the two half-bridge inverters are respectively connected to the two AC feeders one by one, and the static synchronous compensator directly Connect to the negative terminal of the common connection bus.
  • the internal energy balance of the multi-port flexible AC interconnection device is realized, and on the other hand, the AC feeder is realized.
  • Active control of active power and reactive power that is, to achieve decoupling control of line power flow.
  • a multi-port flexible AC interconnection device is used to realize the interconnection of three feeders.
  • the multi-port flexible AC interconnection device includes a three-phase cascaded full-bridge topology static synchronous compensator and a multi-port flexible interconnection module connected in series with it.
  • the multi-port flexible interconnection module includes four two-level half-bridge inverters sharing the same common connection bus, and the four half-bridge inverters are respectively connected with three AC feeders and static synchronous compensators one by one.
  • MATLAB/Simulink software is used to perform simulation verification on the system below, and the simulation parameters are shown in Table 1.
  • the multi-port flexible AC interconnection device includes three half-bridge inverters, of which the two half-bridge inverters connected to the AC feeder control the active power and reactive power on the feeder 2, and the corresponding control loop is line power flow control ring.
  • the half-bridge inverter connected with the static synchronous compensator controls the voltage balance of the common connection bus, and the corresponding control loop is the common connection bus voltage balance control loop.
  • the static synchronous compensator compensates the reactive power on the feeder 1, and the corresponding control loop is the static synchronous compensator control loop.
  • Condition 1 node 1 absorbs 0.3p.u. reactive power, node 2 emits 0.95p.u. active power, absorbs 0.3p.u. reactive power, simulating the situation of active power heavy load and reactive power light load.
  • node 1 absorbs 0.3p.u. reactive power
  • node 2 absorbs 0.95p.u. active power
  • absorbs 0.3p.u. reactive power simulating the situation that the active power is overloaded and reversed, and the reactive power is lightly loaded.
  • Condition 4 node 1 emits 0.95p.u. reactive power, node 2 absorbs 0.3p.u. active power, and emits 0.95p.u. reactive power, simulating the situation of active power light load, reactive power heavy load and direction.
  • each graph contains 8 waveform graphs, from left to right, from top to bottom is feeder 1 Active power P 1 waveform, feeder 1 reactive power Q 1 waveform, feeder 2 active power P 2 waveform, feeder 2 reactive power Q 2 waveform, three-phase common connection bus voltage Vlink_abc waveform, three-phase static synchronization Compensator sub-module capacitor voltage VCHB_capacitor_abc waveform, feeder 1 three-phase current I1abc waveform, feeder 2 three-phase current I2abc waveform.
  • the simulation waveform results show that the multi-port flexible AC interconnection device can realize the active power flow control of the active power and reactive power decoupling on the port interconnection feeder under the condition of maintaining the internal energy balance, that is, the capacitor voltage is stable.
  • the multi-port flexible AC interconnection device includes two half-bridge inverters, of which the half-bridge inverter connected to the AC feeder 2 controls the active power and reactive power on the feeder 2, and the corresponding control loop is the line power flow control loop .
  • the half-bridge inverter connected with the AC feeder 1 controls the voltage balance of the common connection bus, and the corresponding control loop is the common connection bus voltage balance control loop.
  • the static synchronous compensator compensates the reactive power on the feeder 1, and the corresponding control loop is the static synchronous compensator control loop.
  • the DC component in the output voltage of the half-bridge inverter is now output by the static synchronous compensator.
  • the output voltage is overshoot, and the capacitor voltage of the static synchronous compensator sub-module in the second embodiment is 1000V.
  • the working condition set by the simulation is the same as the working condition 2 of the first embodiment, namely: node 1 absorbs 0.3p.u. reactive power, node 2 absorbs 0.95p.u. active power, and absorbs 0.3p.u. reactive power.
  • Figure 15 shows the simulation results of the working conditions, including a total of 8 waveforms, from left to right, top to bottom: feeder 1 active power P 1 waveform, feeder 1 reactive power Q 1 waveform, feeder 2 active power P 2 waveform, feeder 2 reactive power Q 2 waveform, three-phase common connection bus voltage Vlink_abc waveform, three-phase static synchronous compensator sub-module capacitor voltage VCHB_capacitor_abc waveform, feeder 1 three-phase current I1abc waveform, feeder 2 Three-phase current I2abc waveform diagram.
  • the simulation waveform results show that, after the half-bridge inverter connected with the static synchronous compensator is omitted from the topology, the multi-port flexible AC interconnection device can also maintain the internal energy balance, that is, the capacitor voltage is stable. Active power flow control by decoupling active power and reactive power on port interconnected feeders.
  • the connection diagram of the three-feeder interconnection system in which flexible interconnection is realized by the multi-port flexible AC interconnection device is shown in FIG. 16
  • the control method of the third embodiment is shown in FIG. 17 .
  • the multi-port flexible AC interconnection device includes four half-bridge inverters, of which the three half-bridge inverters connected to the AC feeder control the active power and reactive power on feeder 2 and feeder 3, and the corresponding control loops are Line flow control loop.
  • the half-bridge inverter connected with the static synchronous compensator controls the voltage balance of the common connection bus, and the corresponding control loop is the common connection bus voltage balance control loop.
  • the static synchronous compensator compensates the reactive power on the feeder 1, and the corresponding control loop is the static synchronous compensator control loop.
  • the method for distributing the equivalent voltage in series with the multi-port flexible AC interconnection device on the distribution network feeder in the third embodiment considering that the optimization goal is to minimize the amplitude of the AC component of the output voltage required by the half-bridge inverter, that is, selection satisfies Take the minimum value.
  • node 1 emits 0.2p.u. reactive power
  • node 2 emits 0.5p.u. active power
  • node 3 emits 0.5p.u. active power
  • Figures 18 to 19 are the simulation results of the working conditions, including a total of 11 waveforms, from left to right, top to bottom: feeder 1 active power P 1 waveform, feeder 1 reactive power Q 1 waveform, feeder 2 Active power P2 waveform, feeder 2 reactive power Q2 waveform, feeder 3 active power P3 waveform, feeder 3 reactive power Q3 waveform, three-phase common connection bus voltage Vlink_abc waveform, three-phase static synchronization Compensator sub-module capacitor voltage VCHB_capacitor_abc waveform, feeder 1 three-phase current I1abc waveform, feeder 2 three-phase current I2abc waveform, feeder 3 three-phase current I3abc waveform.
  • the simulation waveform results show that the multi-port flexible AC interconnection device not only realizes active power flow control by decoupling the active power and reactive power on the port interconnected feeder, but also maintains the internal energy balance of the device when three feeders are interconnected. That is, the capacitor voltage is stable and has port expansion capability.

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Abstract

发明公开一种适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，包括一个静止同步补偿器以及与之串联的一个多端口柔性互联模块，多端口柔性互联模块由多个共享直流母线的电压源型单相逆变器组成，每个端口与不同的交流电网馈线相联，通过调节串联在馈线上单相逆变器交流侧输出电压的幅值相位，实现馈线之间有功功率的灵活交互，并且馈线上有功、无功功率解耦控制。本发明通过引入多端柔性互联模块，提供多个可控交流端口与多条馈线相联，实现了馈线之间柔性互联，即馈线之间有功功率灵活交互，达到了馈线之间潮流主动控制的效果，可实现多端互联的柔性交流电网，同时为各个馈线提供相应的无功功率。

Description

一种多端口交流电网柔性互联装置及其控制方法和系统 技术领域
本发明涉及交流电网柔性互联、电力电子技术领域，特别是一种适用于交流电网的具备主动潮流控制能力的多端口交流电网柔性互联装置及其控制方法和系统。
背景技术
传统交流电网在系统稳定性和可靠性上具备着显著的优势，然而由于控制能力不足，无法有效解决馈线堵塞问题，馈线负荷不均衡问题突出。因此，配网系统实际容量受最先达到容量上限的单条馈线限制，远低于设计容量，严重影响交流电网经济运行。
另一方面，由于全球变暖和化石燃料的枯竭问题，发展风能和太阳能成为了全球共识。作为分布式能源，风能和太阳能具有间歇性、不确定性、波动性等特点，并网时给交流电网在电压控制、暂稳态稳定性、振荡阻尼等方面带来了严峻的技术挑战。
为解决上述问题，通常有三种方案：第一种方案为新建或升级现有馈线，这种方案成本高昂且耗时长久；第二种方案为通过一次设备进行调节，例如通过有载调压器调节电压、通过联络开关动作重构网络实现馈线负荷均衡。然而，有载调压器、馈线开关动作等传统调节方式调节能力受限，响应速度较慢，且调节精度不足，网络重构方式则受开关动作次数及时间、合闸冲击电流、器件寿命的影响；第三种方案为通过柔性交流互联装置(Flexible Alternative Current Interconnector,FACI)提供不同交流馈线的互联端口，实现馈线之间的柔性互联和主动潮流控制。该方案充分利用电力电子装置控制的实时性和快速性，实现相邻网络间的功率调节，从而优化潮流分布，配合电力电子装置的无功调节能力，同时通过电力电子装置控制的快速性，能够进行快速的网架结构重构，提供供电可靠性，从而极大地改善供电质量。
现有柔性交流互联装置主流拓扑主要采用背靠背电压源型逆变器，由多个电压源型逆变器通过共用直流母线形成，能够实现多向的潮流运行与有功功率和无功功率的解耦控制。然而，该拓扑结构采用全功率电压源型逆变器的方式构成，因此具有价格昂贵、损耗高、体积大、故障率高等缺点。
发明内容
本部分的目的在于概述本发明的实施例的一些方面以及简要介绍一些较佳实施例。在本部分以及本申请的说明书摘要和发明名称中可能会做些简化或省略以避免使本部分、说明书摘要和发明名称的目的模糊，而这种简化或省略不能用于限制本发明的范围。
鉴于现有技术中存在的问题，提出了本发明。
一、本发明提供一种适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，所述多端口柔性交流互联装置包括一个静止同步补偿器(Static Synchronous Compensator,STATCOM)以及与之串联的一个多端口柔性互联模块；
所述静止同步补偿器为中压级电压源型变流器，其具备无功功率双向补偿功能，可以从系统吸收无功，也可以为系统提供无功补偿；
所述多端口柔性互联模块包括多个共享同一公共连接母线且彼此互相并联的第一单相变 流器，第一单相变流器的交流输出端口与馈线串联，通过调节串联在馈线上的第一单相变流器交流输出端口电压的幅值相位，实现馈线有功功率和无功功率的主动控制；以下将串联在馈线上的第一单相变流器交流输出端口电压的交流成分称为串联等效电压。
进一步优选的，上述中的公共连接母线为直流母线，第一单相变流器为电压源型单相逆变器。
进一步优选的，所述中压级电压源型变流器是耐压等级为中压等级的(如10kV)、三相的、输出电压为双极性的逆变器。
进一步优选的，如图3，所述中压级电压源型变流器的拓扑可以是两电平电压源型逆变器，也可以三电平电压源型逆变器，还可以是其他多电平电压源型逆变器。
进一步优选的，如图1，所述多端口柔性互联模块还可以包括与所述第一单相变流器并联的第二单相变流器；所述中压级电压源型变流器可以与第二单相变流器的交流输出端口相连，也可以与所述多端口柔性互联模块公共连接母线的正极或负极直接相连，通过该两种方式均能够实现静止同步补偿器与多端口柔性互联模块的串联连接；具体的，当多端口柔性互联模块仅包括第一单相变流器时，中压级电压源型变流器与公共连接母线的正极或负极直接相连，能够实现所述静止同步补偿器与所述多端口柔性互联模块的串联；当多端口柔性互联模块同时包括第一单相变流器以及第二单相变流器时，中压级电压源型变流器的交流输出端口可以与第二单相变流器的交流输出端口相连，也能够实现所述静止同步补偿器与所述多端口柔性互联模块的串联，且此时可以通过调节第二单相变流器交流输出端口电压的幅值相位，实现所述多端口柔性互联模块的公共连接母线电压稳定。
进一步优选的，上述中的第一单相变流器和第二单相变流器均为电压源型单相变流器；电压源型单相变流器为额定输出电压相比中压级电压源型变流器低、单相的、输出电压为单极性的变流器。
进一步优选的，组成所述多端口柔性互联模块的单相变流器的拓扑可以是两电平半桥型逆变器，也可以是三电平半桥型逆变器，或者其他可实现功率双向流动的半桥型逆变器。
二、本发明提供一种适用于所述多端口柔性交流互联装置的控制方法，所述控制方法包括线路潮流控制环、静止同步补偿器控制环和公共连接母线电压平衡控制环；
所述多端口柔性交流互联装置互联了多条馈线时，其中有且仅有一条馈线的有功功率大小由系统有功功率平衡的需求决定，仅需控制该馈线的无功功率大小，该馈线称为定无功功率控制馈线，其他馈线的有功功率和无功功率均需控制，称为潮流控制馈线；
锁相环锁定所述定无功功率控制馈线的节点三相电压，锁相环输出的相角为abc坐标系到dq坐标系的帕克转换矩阵提供角度；下面对各所述三个控制环依次进行描述：
1、所述线路潮流控制环的控制目标为潮流控制馈线的有功功率达到参考值
Figure PCTCN2021076799-appb-000001
和无功功率达到参考值
Figure PCTCN2021076799-appb-000002
设定线路潮流控制环输出为
Figure PCTCN2021076799-appb-000003
Figure PCTCN2021076799-appb-000004
为与定无功功率控制馈线相连的第一单相变流器交流输出端口的输出电压的交流成分的参考值；
Figure PCTCN2021076799-appb-000005
为与潮流控制馈线相连的第一单相变流器交流输出端口的输出电压的交流成分的参 考值；其中，下标i表示第i条馈线为定无功功率控制馈线，下标j表示第j条潮流控制馈线；
所述线路潮流控制环首先根据潮流控制馈线的有功功率参考值和无功功率参考值计算潮流控制馈线电流的d轴分量参考值
Figure PCTCN2021076799-appb-000006
和q轴分量参考值
Figure PCTCN2021076799-appb-000007
计算方法为解如下方程组：
Figure PCTCN2021076799-appb-000008
线路潮流控制环在dq坐标系下进行，利用比例积分控制器进行控制，数学方程为：
Figure PCTCN2021076799-appb-000009
Figure PCTCN2021076799-appb-000010
和
Figure PCTCN2021076799-appb-000011
乘以帕克逆转换矩阵，得到abc坐标系下的线路潮流控制环输出参考电压
Figure PCTCN2021076799-appb-000012
即
Figure PCTCN2021076799-appb-000013
其中，V表示馈线的节点电压，I表示馈线的电流，ω表示馈线的交流频率，L表示馈线的等效电感感值，R表示馈线的等效电阻阻值，V,I,L,R的下标i表示为定无功功率控制馈线的参数，下标j表示为第j条潮流控制馈线的参数，下标d表示为d轴分量，下标q表示为q轴分量，上标*表示为参考值；k p为比例积分控制器比例环节增益系数，k i为比例积分控制器积分环节增益系数；V id,V iq,V jd,V jq,I id(ωL i+R i),I iq(ωL i+R i)为前馈项，作用是增强控制环抗干扰能力，加快控制环响应速度，I jqωL j,I jdωL j,I iqωL i,I idωL i为解耦项，作用是实现d轴和q轴的解耦控制。
2、所述静止同步补偿器控制环的控制目标为定无功功率控制馈线的无功功率达到参考值
Figure PCTCN2021076799-appb-000014
和静止同步补偿器三相电容电压之和稳定为参考值
Figure PCTCN2021076799-appb-000015
其输出为静止同步补偿器交流输出端口的电压的交流成分的参考值
Figure PCTCN2021076799-appb-000016
所述静止同步补偿器控制环由电压控制外环、无功功率控制外环和电流控制内环组成；
所述电压控制外环使用比例积分控制器对静止同步补偿器三相电容电压之和进行控制，输入为静止同步补偿器三相电容电压之和的参考值与瞬时值之差，输出为定无功功率控制馈线电流d轴分量的参考值
Figure PCTCN2021076799-appb-000017
数学方程为：
Figure PCTCN2021076799-appb-000018
其中，k p1为比例积分控制器比例环节增益系数，k i1为比例积分控制器积分环节增益系数，ΣV C,STATCOM为静止同步补偿器三相电容电压之和瞬时值，
Figure PCTCN2021076799-appb-000019
为潮流控制馈线的电流d轴分量的参考值之和；
所述无功功率控制外环根据定无功功率控制馈线的无功功率参考值
Figure PCTCN2021076799-appb-000020
计算定无功功率控制馈线电流q轴分量参考值
Figure PCTCN2021076799-appb-000021
计算公式为：
Figure PCTCN2021076799-appb-000022
所述电流控制内环在dq坐标系下进行控制，利用比例积分控制器，对定无功功率控制馈线电流的d轴分量和q轴分量分别控制，数学方程为：
Figure PCTCN2021076799-appb-000023
Figure PCTCN2021076799-appb-000024
和
Figure PCTCN2021076799-appb-000025
乘以帕克逆转换矩阵，再乘以-1反相后，得到abc坐标系下的静止同步补偿器控制环输出参考电压
Figure PCTCN2021076799-appb-000026
即V pa,V pb,V pc；其中，V Cid和V Ciq为与定无功功率控制馈线相连的第一单相变流器交流输出端口电压的交流成分的d轴分量和q轴分量，V SMd和V SMq为与静止同步补偿器相连的第二单相变流器交流输出端口电压的交流成分的d轴分量和q轴分量，k p2为比例积分控制器比例环节增益系数，k i2为比例积分控制器积分环节增益系数，V id,V iq,V Cid,V Ciq,V SMd,V SMq为前馈项，作用是增强控制环抗干扰能力，加快控制环响应速度，I idωL i,I iqωL i为解耦项，作用是实现d轴和q轴的解耦控制。
3、所述公共连接母线电压平衡控制环的控制目标为公共连接母线电压稳定为参考值
Figure PCTCN2021076799-appb-000027
其输出为公共连接母线平衡参考电压
Figure PCTCN2021076799-appb-000028
所述公共连接母线电压平衡控制环的控制在abc坐标系下进行，利用比例积分控制器对abc三相的公共连接母线电压进行控制，数学方程为：
Figure PCTCN2021076799-appb-000029
其中，V linka,V linkb,V linkc为三相公共连接母线电压，I pa,I pb,I pc为静止同步补偿器支路三相电流，
Figure PCTCN2021076799-appb-000030
为前馈的三相参考电压，k p3为比例积分控制器比例环节增益系数，k i3为比例积分控制器积分环节增益系数；
若所述多端口柔性交流互联装置拓扑中包含与中压级电压源型变流器相连的第二单相变流器，得到线路潮流控制环的输出参考电压
Figure PCTCN2021076799-appb-000031
后，第一单相变流器交流输出端口的参考电压为：
Figure PCTCN2021076799-appb-000032
其中，
Figure PCTCN2021076799-appb-000033
为与定无功功率控制馈线相连的第一单相变流器交流输出端口的参考电压，
Figure PCTCN2021076799-appb-000034
为与第j条潮流控制馈线相连的第一单相变流器交流输出端口的参考电压，
Figure PCTCN2021076799-appb-000035
为按照本发明第三方面所述的任意一种串联等效电压分配方式计算得到的与定无功功率控制馈线相连的第一单相变流器交流输出端口的参考电压的交流成分，V common,dc为单相变流器交流输出端口输出电压中共有的直流成分参考值，该参考值大于零且小于公共连接母线电压；
若所述多端口柔性交流互联装置拓扑中包含中压级电压源型变流器相连的第二单相变流器，则所述公共连接母线电压平衡控制环中的前馈三相参考电压
Figure PCTCN2021076799-appb-000036
等于零，第二单相变流器交流输出端口的参考电压为：
Figure PCTCN2021076799-appb-000037
若所述多端口柔性交流互联装置拓扑中包含与静止同步补偿器相连的第二单相变流器，中压级电压源型变流器的交流输出端口的参考电压为：
Figure PCTCN2021076799-appb-000038
若所述多端口柔性交流互联装置拓扑中不包含与中压级电压源型变流器相连的第二单相变流器，得到线路潮流控制环的输出参考电压
Figure PCTCN2021076799-appb-000039
后，第一单相变流器交流输出端口的参考电压为：
Figure PCTCN2021076799-appb-000040
其中，
Figure PCTCN2021076799-appb-000041
为与定无功功率控制馈线相连的第一单相变流器交流输出端口的参考电压，
Figure PCTCN2021076799-appb-000042
为与第j条潮流控制馈线相连的第一单相变流器交流输出端口的参考电压；
若所述多端口柔性交流互联装置拓扑中不包含与静止同步补偿器相连的第二单相变流器，则所述公共连接母线电压平衡控制环中的前馈三相参考电压
Figure PCTCN2021076799-appb-000043
为按照本发明第三方面所述的任意一种串联等效电压分配方式计算得到的与定无功功率控制馈线相连的第一单相变流器交流输出端口的参考电压的交流成分；
若所述多端口柔性交流互联装置拓扑中不包含与静止同步补偿器相连的第二单相变流器，静止同步补偿器控制环中的电流控制内环中的前馈项V SMd和V SMq等于零，静止同步补偿器的交流输出端口的参考电压为：
Figure PCTCN2021076799-appb-000044
当静止同步补偿器交流输出端口与公共连接母线负极相连时取加号，当静止同步补偿器交流输出端口与公共连接母线正极相连时取减号。
三、本发明提供一种所述多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，所述电压分配方法满足以下基本条件方程：
Figure PCTCN2021076799-appb-000045
上述中，假设第1条馈线为定无功功率控制馈线，
Figure PCTCN2021076799-appb-000046
为所述多端口柔性交流互联装置在第k条馈线上串联等效电压交流成分的矢量表达式，
Figure PCTCN2021076799-appb-000047
为实现第k条馈线上目标潮流时所需串联在第1条馈线和第k条馈线之间的串联等效电压矢量表达式，
Figure PCTCN2021076799-appb-000048
为与所述静止同步补偿器相连的所述多端口柔性互联模块中的第二单相变流器交流输出端口电压交流成分的矢量表达式，
Figure PCTCN2021076799-appb-000049
为第k条馈线上的交流电流的共轭矢量表达式，
Figure PCTCN2021076799-appb-000050
为所述静止同步补偿器支路的交流电流的共轭矢量表达式，n为通过所述多端口柔性交流互联装置互联的馈线数量；
所述适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法为满足所述基本条件方程的任何一组
Figure PCTCN2021076799-appb-000051
的解。
进一步优选的，所述适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置在配网馈线上串联等效电压的一种分配方法是
Figure PCTCN2021076799-appb-000052
其特点为简化性。
进一步优选的，如图2，串联等效电压的另一种分配方法是
Figure PCTCN2021076799-appb-000053
即
Figure PCTCN2021076799-appb-000054
的选取满足
Figure PCTCN2021076799-appb-000055
从而能够在拓扑上省去与所述静止同步补偿器连接的第二单相变流器。
进一步优选的，串联等效电压的另一种分配方法是
Figure PCTCN2021076799-appb-000056
的选取满足
Figure PCTCN2021076799-appb-000057
取到最小值，从而能够使得单相变流器所需输出电压交流成分幅值最小。
进一步优选的，串联等效电压的分配方法还可以是任何一种满足所述基本条件方程的选取方式。
进一步优选的，所述多端口柔性互联模块中的单相变流器交流输出端口电压成分中含有相同大小的直流成分和控制所需的不同交流成分。
进一步优选的，所述单相变流器交流输出端口电压的直流成分可以是公共连接母线电压值的一半，也可以是其他小于公共连接母线电压值且大于零的值。
四、本发明提供一种采用所述多端口柔性交流互联装置的交流电网多馈线柔性互联系统，如图4，所述交流电网多馈线柔性互联系统核心设备为所述多端口柔性交流互联装置，其他组成还可以包括交流馈线、交流负载、储能设备等；
所述多端口柔性交流互联装置安装于多条交流馈线汇集处，交流馈线与多端口柔性交流互联装置相连，交流馈线可以接入交流负载，也可以经升压变压器接入高压系统，还可以经降压变压器接入低压交流系统，低压交流系统可以接入低压交流负载或储能设备或电动汽车快充站等。
进一步优选的，所述交流电网多馈线柔性互联系统可以包含一个所述多端口柔性交流互联装置，如图4；也可以包含多个所述多端口柔性交流互联装置，如图5；当所述交流电网多馈线柔性互联系统包括两个以上的多端口柔性交流互联装置时，所述多端口柔性交流互联装置安装于各自区域中多条交流馈线汇集处，通过多端口柔性交流互联装置之间的互联将多片区域互联，形成更复杂的环状/网状系统拓扑。
五、发明提供一种所述多端口柔性交流互联装置串联在馈线上的电压的过压保护方法，该方法为：通过在所述多端口柔性互联模块中的第一单相变流器的交流输出端口间并联一个保护装置实现，所述保护装置由金属氧化物限压器(Metal-oxide Varistors,MOV)和晶闸管旁路开关并联组成，所述金属氧化物限压器将电压限制在保护水平，所述晶闸管旁路开关通过将第一单相变流器的交流输出端口旁路，实现过压保护；
所述晶闸管旁路开关由反并联晶闸管、阻容回路、静态电阻并联后再与一个饱和电抗器串联构成。
六、本发明提供一种所述多端口柔性交流互联装置的启动方法，所述多端口柔性交 流互联装置的启动方法可以由三个阶段构成：
所述第一阶段为不控整流阶段，交流输出端口串联限流电阻后并网，所有开关闭锁，经过二极管构成的整流电路对多端口柔性交流互联装置内电容进行充电；
所述第二阶段为受控整流阶段，所述第一阶段充电结束后，通过将电容轮流切入或切除充电回路但总投入充电回路电容个数一定的方式，将多端口柔性交流互联装置内电容电压充至额定值附近；
所述第三阶段为斜坡升压阶段，所述第二阶段充电结束后，通过给定斜坡上升的参考电压，利用电压控制环将电容电压充电至额定值，所述电压控制环包括本发明第二方面所述的公共连接母线电压平衡控制环和本发明第二方面所述的静止同步补偿器控制环中的电压控制外环。
七、本发明提供一种适用于所述多端口柔性交流互联装置的控制系统，所述多端口柔性交流互联装置的控制系统可以采用集中式控制架构，即线路潮流控制环、静止同步补偿器控制环和公共连接母线电压平衡控制环都在同一个控制器中实现；也可以采用分布式控制架构，通过多个同一级别的控制器实现控制，同级控制器之间无通讯，例如线路潮流控制环、静止同步补偿器控制环和公共连接母线电压平衡控制环分别在三个不同的控制器中实现；还可以采用集中式控制和分布式控制相结合的分层式控制架构，通过多个不同级别的控制器实现控制，不同级别控制间有信息通讯，同级别控制器间无通讯，例如线路潮流控制环和串联等效电压分配的计算在一级控制器中实现控制，静止同步补偿器控制环和公共连接母线电压平衡控制环分别在两个二级控制器中实现控制，并且一级控制器与二级控制之间有控制信息的通讯交互，所述控制器为具备实现控制环能力的硬件设备，如基于数字信号处理芯片的控制器、基于现场可编程逻辑门阵列芯片的控制器。
与现有柔性互联装置相比，本发明具有如下有益效果：
1、现有的静止同步补偿器只具备无功功率补偿功能，不具备多交流馈线互联和馈线主动潮流解耦控制功能，而本发明通过引入多端口柔性互联模块，提供多个交流互联端口，实现多交流馈线互联，并通过调节串联在馈线上的串联等效电压的幅值相位，可实现馈线有功功率和无功功率解耦的主动控制。
2、本发明和现有常用柔性互联装置，即背靠背电压源型变流器相比，不需要通过全功率，采用串联电压源的方式实现主动潮流控制，变流器装置成本低、占地面积小、损耗低、控制速度快。
3、本发明中的多端口柔性互联模块具备模块化的特点，通过增加互联模块中并联的第一单相变流器数量，可快速、经济地实现互联端口的拓展。
附图说明
为了更清楚地说明本发明实施例的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其它的附图。 其中：
图1为本发明所述多端口柔性交流互联装置的拓扑结构及其互联多馈线的系统示意图；
图2为本发明所述多端口柔性交流互联装置省去与静止同步补偿器相连的第二单相变流器的拓扑结构及其互联多馈线的系统示意图；
图3为本发明所述多端口柔性交流互联装置中的中压级电压源型变流器和第二单相变流器的典型拓扑举例示意图；
图4为本发明一种核心设备为所述多端口柔性交流互联装置的交流电网多馈线柔性互联系统；
图5为本发明一种包含多个所述多端口柔性交流互联装置的交流电网多馈线柔性互联系统；
图6为本发明所述多端口柔性交流互联装置串联在馈线上的电压的过压保护方法接线图及保护装置示意图；
图7为实施方案一中多端口柔性互联模块采用并联两电平半桥型逆变器、静止同步补偿器采用级联全桥拓扑的双端口柔性交流互联装置的拓扑结构及其实现两条馈线互联的系统示意图；
图8为实施方案一中的多多端口柔性互联模块采用并联两电平半桥型逆变器、静止同步补偿器采用级联全桥拓扑的双端口柔性交流互联装置的控制方法框图；
图9为实施方案一中第一种工况的仿真各馈线潮流、装置内各电容电压、各馈线电流波形图；
图10为实施方案一中第二种工况的仿真各馈线潮流、装置内各电容电压、各馈线电流波形图；
图11为实施方案一中第三种工况的仿真各馈线潮流、装置内各电容电压、各馈线电流波形图；
图12为实施方案一中第四种工况的仿真各馈线潮流、装置内各电容电压、各馈线电流波形图；
图13为实施方案二中的多端口柔性互联模块采用并联两电平半桥型逆变器且省去与静止同步补偿器相连的半桥型逆变器、静止同步补偿器采用级联全桥拓扑的双端口柔性交流互联装置的拓扑结构及其实现两条馈线互联的系统示意图；
图14为实施方案二中的多端口柔性互联模块采用并联两电平半桥型逆变器且省去与静止同步补偿器相连的半桥型逆变器、静止同步补偿器采用级联全桥拓扑的双端口柔性交流互联装置的控制方法框图；
图15为实施方案二的仿真各馈线潮流、装置内各电容电压、各馈线电流波形图；
图16为实施方案三中多端口柔性互联模块采用并联两电平半桥型逆变器、静止同步补偿器采用级联全桥拓扑的三端口柔性交流互联装置的拓扑结构及其实现三条馈线互联的系统示意图；
图17为实施方案三中的多端口柔性互联模块采用并联两电平半桥型逆变器、静止同步补偿器采用级联全桥拓扑的三端口柔性交流互联装置的控制方法框图；
图18～19为实施方案三的仿真各馈线潮流、装置内各电容电压、各馈线电流波形图。
具体实施方式
为使本发明的上述目的、特征和优点能够更加明显易懂，下面结合说明书附图对本发明的具体实施方式做详细的说明。
参照图1～3，本发明提供了一种适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，所述多端口柔性交流互联装置包括静止同步补偿器以及与之串联的多端口柔性互联模块；
静止同步补偿器为中压级电压源型变流器，其具备无功功率双向补偿功能，可以从系统吸收无功，也可以为系统提供无功补偿；
多端口柔性互联模块包括多个共享同一公共连接母线且彼此互相并联的第一单相变流器，第一单相变流器的交流输出端口与馈线串联，通过调节串联在馈线上的第一单相变流器交流输出端口电压的幅值相位，实现馈线有功功率和无功功率的主动控制；本发明将串联在馈线上的第一单相变流器交流输出端口电压的交流成分定义为串联等效电压。
此外，多端口柔性互联模块还可以包括与所述第一单相变流器并联的第二单相变流器，中压级电压源型变流器与所述第二单相变流器的交流输出端口相连，实现所述静止同步补偿器与所述多端口柔性互联模块的串联；通过调节第二单相变流器交流输出端口电压的幅值相位，实现所述多端口柔性互联模块的公共连接母线电压稳定。
当多端口柔性互联模块仅包括第一单相变流器时，中压级电压源型变流器与公共连接母线的正极或负极直接相连，能够实现所述静止同步补偿器与所述多端口柔性互联模块的串联。
当多端口柔性互联模块同时包括第一单相变流器以及第二单相变流器时，中压级电压源型变流器的交流输出端口可以与第二单相变流器的交流输出端口相连，同样能够实现所述静止同步补偿器与所述多端口柔性互联模块的串联。
以下结合具体三种实施例进行具体说明：
一、在第一种实施例中，如图7，本发明使用多端口柔性交流互联装置实现双馈线互联的装置拓扑和系统连接；所述多端口柔性交流互联装置包括一个三相级联全桥拓扑的静止同步补偿器和与之串联的多端口柔性互联模块。该多端口柔性互联模块包含三个共享同一公共连接母线的两电平半桥型逆变器，该三个半桥型逆变器分别与两条交流馈线以及静止同步补偿器一一相连；通过调节串联在馈线上的串联等效电压、与静止同步补偿器串联的半桥型逆变器交流输出端口电压的交流成分、静止同步补偿器的交流输出端口电压的交流成分的幅值相位，一方面实现多端口柔性交流互联装置的内部能量平衡，另一方面实现交流馈线上的有功功率和无功功率的主动控制，即实现线路潮流的解耦控制。
对于图7所示的多端口柔性交流互联装置实现的双馈线互联系统，多端口柔性交流互联装置内部能量平衡的表现为公共连接母线的电容电压保持稳定以及静止同步补偿器 内的电容电压保持稳定，则要求流入上述电容的有功功率保持为零，即：
Figure PCTCN2021076799-appb-000058
其中，第一行的方程表示为流入公共连接母线电容的有功功率为零，第二行的方程表示为流入静止同步补偿器电容的有功功率为零，
Figure PCTCN2021076799-appb-000059
表示与馈线1相连的半桥型变流器交流输出端口的电压的交流成分矢量表达式，
Figure PCTCN2021076799-appb-000060
表示与馈线2相连的半桥型变流器交流输出端口的电压的交流成分矢量表达式，
Figure PCTCN2021076799-appb-000061
表示与静止同步补偿器相连的半桥型变流器交流输出端口的电压的交流成分矢量表达式，
Figure PCTCN2021076799-appb-000062
表示静止同步补偿器交流输出端口的电压的交流成分矢量表达式，
Figure PCTCN2021076799-appb-000063
表示馈线1电流的共轭矢量表达式，
Figure PCTCN2021076799-appb-000064
表示馈线2电流的共轭矢量表达式，
Figure PCTCN2021076799-appb-000065
表示静止同步补偿器支路电流的共轭矢量表达式。通过调节
Figure PCTCN2021076799-appb-000066
与
Figure PCTCN2021076799-appb-000067
的幅值及大小，使得上述方程成立，即实现多端口柔性交流互联装置的内部能量平衡。
二、在第二种实施例中，参照图13，使用多端口柔性交流互联装置实现双馈线互联。该实施例中，多端口柔性交流互联装置包括一个三相级联全桥拓扑的静止同步补偿器和与之串联的多端口柔性互联模块。该多端口柔性互联模块包含两个共享同一公共连接母线的两电平半桥型逆变器，该两个半桥型逆变器分别与两条交流馈线一一相连，而静止同步补偿器直接与公共连接母线负极相连。通过调节串联在馈线上的串联等效电压和静止同步补偿器的交流输出端口电压的交流成分的幅值相位，一方面实现多端口柔性交流互联装置的内部能量平衡，另一方面实现交流馈线上的有功功率和无功功率的主动控制，即实现线路潮流的解耦控制。
该实施例中，实现多端口柔性交流互联装置的内部能量平衡的原理与上述实施例相同，此处不赘述。
三、在第三种实施例中，参照图16，使用多端口柔性交流互联装置实现三条馈线互联。该实施例中，多端口柔性交流互联装置包括一个三相级联全桥拓扑的静止同步补偿器和与之串联的多端口柔性互联模块。该多端口柔性互联模块包含四个共享同一公共连接母线的两电平半桥型逆变器，该四个半桥型逆变器分别与三条交流馈线以及静止同步补偿器一一相连。通过调节串联在馈线上的串联等效电压、与静止同步补偿器串联的半桥型逆变器的交流输出端口电压的交流成分、静止同步补偿器的交流输出端口电压的交流成分的幅值相位，一方面实现多端口柔性交流互联装置的内部能量平衡，另一方面实现交流馈线上的有功功率和无功功率的主动控制，即实现线路潮流的解耦控制。
该实施例中，实现多端口柔性交流互联装置的内部能量平衡的原理与上述实施例相同，此处不赘述。
以下结合具体的仿真实例来对上述三个实施例中的结构和方法的应用分别进行进一步说明。
结合上述实施例，以下采用MATLAB/Simulink软件针对系统进行仿真验证，仿真参数如表1所示。
Figure PCTCN2021076799-appb-000068
仿真实例一：
由多端口柔性交流互联装置实现柔性互联的双馈线互联系统，其连接示意图参照图7，实施方案一的控制方法如图8所示。多端口柔性交流互联装置包含三个半桥型逆变器，其中与交流馈线相连的两个半桥型逆变器控制馈线2上的有功功率和无功功率，对应的控制环为线路潮流控制环。与静止同步补偿器相连的半桥型逆变器控制公共连接母线电压平衡，对应的控制环为公共连接母线电压平衡控制环。静止同步补偿器对馈线1上的无功功率进行补偿，对应的控制环为静止同步补偿器控制环。
实施方案一的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，考虑简化性取
Figure PCTCN2021076799-appb-000069
为验证多端口柔性交流互联装置的主动潮流控制能力，仿真设定了四种运行工况。
工况一：节点1吸收0.3p.u.无功功率，节点2发出0.95p.u.有功功率，吸收0.3p.u.无功功率，仿真有功功率重载，无功功率轻载的情况。
工况二：节点1吸收0.3p.u.无功功率，节点2吸收0.95p.u.有功功率，吸收0.3p.u.无功功率，仿真有功功率重载且反向，无功功率轻载的情况。
工况三：节点1吸收0.95p.u.无功功率，节点2吸收0.3p.u.有功功率，吸收0.95p.u.无功功率，仿真有功功率轻载，无功功率重载的情况。
工况四：节点1发出0.95p.u.无功功率，节点2吸收0.3p.u.有功功率，发出0.95p.u.无功功率，仿真有功功率轻载，无功功率重载且方向的情况。
图9、图10、图11、图12分别为实施方案一中工况一到工况四的仿真结果，每幅图包含8幅波形图，从左到右、从上到下依次为馈线1有功功率P 1波形图，馈线1无功功率Q 1波形图，馈线2有功功率P 2波形图，馈线2无功功率Q 2波形图，三相公共连接母线电压Vlink_abc波形图，三相静止同步补偿器子模块电容电压VCHB_capacitor_abc波形图，馈线1三相电流I1abc波形图，馈线2三相电流I2abc波形图。
仿真波形结果表明，多端口柔性交流互联装置在保持内部能量平衡，即电容电压稳定的情况下，可实现端口互联馈线上的有功功率与无功功率解耦的主动潮流控制。
仿真实例二：
由多端口柔性交流互联装置实现柔性互联的双馈线互联系统，其连接示意图参照图13，实施方案二的控制方法如图14所示。多端口柔性交流互联装置包含两个半桥型逆变器，其中与交流馈线2相连的半桥型逆变器控制馈线2上的有功功率和无功功率，对应的控制环为线路潮流控制环。与交流馈线1相连的半桥型逆变器控制公共连接母线电压平衡，对应的控制环为公共连接母线电压平衡控制环。静止同步补偿器对馈线1上的无功功率进行补偿，对应的控制环为静止同步补偿器控制环。
实施方案二的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，
Figure PCTCN2021076799-appb-000070
的选取满足
Figure PCTCN2021076799-appb-000071
因此在拓扑上省去与所述静止同步补偿器连接的半桥型逆变器。
由于拓扑上省去与所述静止同步补偿器连接的半桥型逆变器，该半桥型逆变器输出电压中的直流成分现由静止同步补偿器输出，为防止静止同步补偿器子模块输出电压超调，实施方案二中静止同步补偿器子模块电容电压为1000V。
仿真设定的工况与实施方案一种的工况二相同，即：节点1吸收0.3p.u.无功功率，节点2吸收0.95p.u.有功功率，吸收0.3p.u.无功功率。
图15为工况仿真结果，总共包含8幅波形图，从左到右、从上到下依次为：馈线1有功功率P 1波形图、馈线1无功功率Q 1波形图、馈线2有功功率P 2波形图、馈线2无功功率Q 2波形图、三相公共连接母线电压Vlink_abc波形图、三相静止同步补偿器子模块电容电压VCHB_capacitor_abc波形图、馈线1三相电流I1abc波形图、馈线2三相电流I2abc波形图。
仿真波形结果表明，在拓扑上省去与所述静止同步补偿器连接的半桥型逆变器后，多端口柔性交流互联装置也可以在保持内部能量平衡，即电容电压稳定的情况下，实现端口互联馈线上的有功功率与无功功率解耦主动潮流控制。
实施方案三：
由多端口柔性交流互联装置实现柔性互联的三条馈线互联系统，其连接示意图参照图16，实施方案三的控制方法如图17所示。多端口柔性交流互联装置包含四个半桥型逆变器，其中与交流馈线相连的三个半桥型逆变器控制馈线2、馈线3上的有功功率和无功功率，对应的控制环为线路潮流控制环。与静止同步补偿器相连的半桥型逆变器控制公 共连接母线电压平衡，对应的控制环为公共连接母线电压平衡控制环。静止同步补偿器对馈线1上的无功功率进行补偿，对应的控制环为静止同步补偿器控制环。
实施方案三的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，考虑优化目标为半桥型逆变器所需输出电压交流成分幅值最小，即
Figure PCTCN2021076799-appb-000072
的选取满足
Figure PCTCN2021076799-appb-000073
取到最小值。
仿真设定的工况如下：节点1发出0.2p.u.无功功率，节点2发出0.5p.u.有功功率，吸收0.1p.u.无功功率，节点3发出0.5p.u.有功功率，发出0.1p.u.无功功率。
图18～19为工况仿真结果，总共包含11幅波形图，从左到右、从上到下依次为：馈线1有功功率P 1波形图、馈线1无功功率Q 1波形图、馈线2有功功率P 2波形图、馈线2无功功率Q 2波形图、馈线3有功功率P 3波形图、馈线3无功功率Q 3波形图、三相公共连接母线电压Vlink_abc波形图、三相静止同步补偿器子模块电容电压VCHB_capacitor_abc波形图、馈线1三相电流I1abc波形图、馈线2三相电流I2abc波形图、馈线3三相电流I3abc波形图。
仿真波形结果表明，多端口柔性交流互联装置在互联了三条馈线的情况下，既实现了端口互联馈线上的有功功率与无功功率解耦主动潮流控制，同时又保持了装置内部内部能量平衡，即电容电压稳定，具备端口拓展能力。

Claims (20)

  1. 一种适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，其特征在于：所述多端口柔性交流互联装置包括静止同步补偿器以及与之串联的多端口柔性互联模块；
    所述静止同步补偿器为中压级电压源型变流器，其具备无功功率双向补偿功能，可以从系统吸收无功，也可以为系统提供无功补偿；
    所述多端口柔性互联模块，包括多个共享同一公共连接母线且彼此互相并联的第一单相变流器，所述第一单相变流器的交流输出端口与馈线串联，通过调节串联在馈线上的第一单相变流器交流输出端口电压的幅值相位，实现馈线有功功率和无功功率的主动控制；将串联在馈线上的第一单相变流器交流输出端口电压的交流成分定义为串联等效电压。
  2. 如权利要求1所述的适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，其特征在于：所述中压级电压源型变流器与所述公共连接母线线的正极或负极直接相连，实现所述静止同步补偿器与所述多端口柔性互联模块的串联。
  3. 如权利要求1或2所述的适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，其特征在于：所述中压级电压源型变流器是耐压等级为中压等级的、三相的、输出电压为双极性的逆变器。
  4. 如权利要求1或2所述的适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，其特征在于：所述中压级电压源型变流器的拓扑为两电平电压源型逆变器，或者是三电平电压源型逆变器，或者是多电平电压源型逆变器。
  5. 如权利要求1所述的适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，其特征在于：所述多端口柔性互联模块还包括与所述第一单相变流器并联的第二单相变流器，所述中压级电压源型变流器与所述第二单相变流器的交流输出端口相连，实现所述静止同步补偿器与所述多端口柔性互联模块的串联；
    通过调节第二单相变流器交流输出端口电压的幅值相位，实现所述多端口柔性互联模块的公共连接母线电压稳定。
  6. 如权利要求1、2、5任一所述的适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，其特征在于：所述单相变流器为电压源型单相逆变器；电压源型单相逆变器为耐压等级相比中压级电压源型变流器低的、单相的、输出电压为单极性的逆变器。
  7. 如权利要求1、2、5任一所述的适用于交流电网的具备主动潮流控制能力的多端口柔性交流互联装置，其特征在于：所述单相变流器的拓扑为两电平半桥型逆变器，或者是三电平半桥型逆变器，或者是能够实现功率双向流动的半桥型逆变器。
  8. 一种如权利要求1～7任一所述的多端口柔性交流互联装置的控制方法，其特征在于：所述控制方法包括线路潮流控制环、静止同步补偿器控制环和公共连接母线电压平衡控制环；
    所述多端口柔性交流互联装置互联了多条馈线时，其中有且仅有一条馈线的有功功率大小由系统有功功率平衡的需求决定，仅需控制该馈线的无功功率大小，该馈线称为定无功功率控制馈线，其他馈线的有功功率和无功功率均需控制，称为潮流控制馈线；
    锁相环锁定所述定无功功率控制馈线的节点三相电压，锁相环输出的相角为abc坐标系到dq坐标系的帕克转换矩阵提供角度。
  9. 如权利要求8所述的多端口柔性交流互联装置的控制方法，其特征在于：所述线路潮流控制环的控制目标为潮流控制馈线的有功功率达到参考值
    Figure PCTCN2021076799-appb-100001
    和无功功率达到参考值
    Figure PCTCN2021076799-appb-100002
    所述静止同步补偿器控制环的控制目标为定无功功率控制馈线的无功功率达到参考值
    Figure PCTCN2021076799-appb-100003
    和静止同步补偿器三相电容电压之和稳定为参考值
    Figure PCTCN2021076799-appb-100004
    其输出为静止同步补偿器交流输出端口的电压的交流成分的参考值
    Figure PCTCN2021076799-appb-100005
    所述公共连接母线电压平衡控制环的控制目标为公共连接母线电压稳定为参考值
    Figure PCTCN2021076799-appb-100006
    其输出为公共连接母线平衡参考电压
    Figure PCTCN2021076799-appb-100007
  10. 一种如权利要求1～7任一所述的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，其特征在于：所述分配方法满足以下基本条件方程：
    Figure PCTCN2021076799-appb-100008
    假设第1条馈线为所述定无功功率控制馈线，
    Figure PCTCN2021076799-appb-100009
    为所述多端口柔性交流互联装置在第k条馈线上串联等效电压交流成分的矢量表达式；
    Figure PCTCN2021076799-appb-100010
    为实现第k条馈线上目标潮流时所需串联在第1条馈线和第k条馈线之间的串联等效电压矢量表达式；
    Figure PCTCN2021076799-appb-100011
    为与所述静止同步补偿器相连的多端口柔性互联模块中的第一单相变流器交流输出端口电压中的交流成分的矢量表达式；
    Figure PCTCN2021076799-appb-100012
    为第k条馈线上的交流电流的共轭矢量表达式；
    Figure PCTCN2021076799-appb-100013
    为所述静止同步补偿器支路的交流电流的共轭矢量表达式；n为通过所述多端口柔性交流互联装置互联的馈线数量；
    所述多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法为满足所述基本条件方程的任何一组
    Figure PCTCN2021076799-appb-100014
    的解。
  11. 如权利要求10所述的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，其特征在于：令
    Figure PCTCN2021076799-appb-100015
  12. 如权利要求10所述的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，其特征在于：令
    Figure PCTCN2021076799-appb-100016
    即
    Figure PCTCN2021076799-appb-100017
    的选取满足：
    Figure PCTCN2021076799-appb-100018
  13. 如权利要求10所述的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，其特征在于：
    Figure PCTCN2021076799-appb-100019
    的选取满足
    Figure PCTCN2021076799-appb-100020
    取到最小值。
  14. 如权利要求10～13任一所述的多端口柔性交流互联装置在配网馈线上串联等效电压的分配方法，其特征在于：所述多端口柔性互联模块中的单相变流器交流输出端口电压成分中含有相同大小的直流成分和控制所需的不同交流成分；
    所述单相变流器交流输出端口电压的直流成分为所述公共连接母线电压值的一半。
  15. 一种采用权利要求1～7任一所述多端口柔性交流互联装置的交流电网多馈线柔性互联系统，其特征在于：包括至少一个如权利要求1～7任一所述的多端口柔性交流互联装置以及交流馈线；
    所述多端口柔性交流互联装置安装于多条交流馈线汇集处，所述交流馈线与所述多端口柔性交流互联装置相连；
    当所述交流电网多馈线柔性互联系统包括两个以上的多端口柔性交流互联装置时，所述多端口柔性交流互联装置安装于各自区域中多条交流馈线汇集处，并通过多端口柔性交流互联装置之间的互联将多片区域互联，形成环状/网状系统拓扑。
  16. 如权利要求15所述的交流电网多馈线柔性互联系统，其特征在于：所述交流馈线能够接入交流负载。
  17. 如权利要求15所述的交流电网多馈线柔性互联系统，其特征在于：所述交流馈线能够经升压变压器接入高压系统，或者能够经降压变压器接入低压交流系统。
  18. 一种如权利要求1～7任一所述的多端口柔性交流互联装置串联在馈线上的电压的过压保护方法，其特征在于：在所述多端口柔性互联模块中的第一单相变流器的交流输出端口间并联一个保护装置；
    所述保护装置由金属氧化物限压器和晶闸管旁路开关并联组成，所述金属氧化物限压器将电压限制在保护水平，所述晶闸管旁路开关通过将第一单相变流器的交流输出端口旁路，实现过压保护；
    所述晶闸管旁路开关由反并联晶闸管、阻容回路以及静态电阻并联后再与一个饱和电抗器串联构成。
  19. 一种如权利要求1～7任一所述的多端口柔性交流互联装置的启动方法，其特征在于：由以下三个阶段构成，
    所述第一阶段为不控整流阶段，交流输出端口串联限流电阻后并网，所有开关闭锁，经过二极管构成的整流电路对多端口柔性交流互联装置内电容进行充电；
    所述第二阶段为受控整流阶段，所述第一阶段充电结束后，通过将电容轮流切入或切除充电回路但总投入充电回路电容个数一定的方式，将多端口柔性交流互联装置内电容电压充至额定值附近；
    所述第三阶段为斜坡升压阶段，所述第二阶段充电结束后，通过给定斜坡上升的参考电压，利用电压控制环将电容电压充电至额定值，所述电压控制环包括权利要求9所述的公共连接母线电压平衡控制环和静止同步补偿器控制环中的电压控制外环。
  20. 一种如权利要求1～7任一所述的多端口柔性交流互联装置的控制系统，其特征在于：所述多端口柔性交流互联装置的控制系统采用集中式控制架构，或者采用分布式控制架构，或者采用集中式控制和分布式控制相结合的分层式控制架构；
    当采用集中式控制架构时，权利要求9所述的线路潮流控制环、静止同步补偿器控制环和公共连接母线电压平衡控制环都在同一个控制器中实现；当采用分布式控制架构时，通过多个同一级别的控制器实现控制，同级控制器之间无通讯；当采用集中式控制和分布式控制相结合的分层式控制架构时，通过多个不同级别的控制器实现控制，不同级别控制间有信息通讯，同级别控制器间无通讯。
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