CN117424194A - Flexible interconnection equipment of fault blocking type isolation-free transformer, control method and storage medium - Google Patents
Flexible interconnection equipment of fault blocking type isolation-free transformer, control method and storage medium Download PDFInfo
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- CN117424194A CN117424194A CN202311381807.XA CN202311381807A CN117424194A CN 117424194 A CN117424194 A CN 117424194A CN 202311381807 A CN202311381807 A CN 202311381807A CN 117424194 A CN117424194 A CN 117424194A
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- 230000000903 blocking effect Effects 0.000 title claims abstract description 64
- 238000000034 method Methods 0.000 title claims abstract description 17
- 239000003990 capacitor Substances 0.000 claims abstract description 22
- 238000002955 isolation Methods 0.000 claims abstract description 16
- 230000002159 abnormal effect Effects 0.000 claims description 7
- 230000009466 transformation Effects 0.000 claims description 6
- 238000003908 quality control method Methods 0.000 claims description 4
- 238000004146 energy storage Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000004590 computer program Methods 0.000 claims 2
- 238000010586 diagram Methods 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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Classifications
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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
- H02J1/106—Parallel operation of dc sources for load balancing, symmetrisation, or sharing
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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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
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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
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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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
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
The invention discloses fault blocking type non-isolation transformer flexible interconnection equipment, a control method and a storage medium. The midpoint of the direct current bus capacitor of the isolation-free transformer type flexible interconnection device is grounded through a resistor. The fault blocking type direct current power distribution cabinet comprises a direct current fault blocking unit and a direct current power distribution unit. The control method is that a four-leg power module of the isolation-free transformer type flexible interconnection device adopts a four-leg Pulse Width Modulation (PWM) control algorithm, and a coordination controller self-adaptively starts and stops flexible interconnection devices at all ends according to three-phase unbalance, power factors and heavy overload conditions of a power distribution area. The invention solves the problems of common-mode voltage and ground wire circulation in the prior art and the problem of large light load or no-load loss of the multi-terminal flexible interconnection system; the fault blocking type direct current power distribution cabinet enables the direct current system to have fault ride-through capability on the basis of considering direct current power distribution efficiency.
Description
Technical Field
The invention relates to the technical field of power electronics and power distribution, in particular to fault blocking type isolation-free transformer flexible interconnection equipment, a control method and a storage medium.
Background
The flexible interconnection device is formed by connecting two groups of voltage source converters consisting of fully-controlled power electronic devices back to back, compared with a traditional tie switch, the flexible interconnection device is free from the limitation of the action times of the traditional mechanical switch, has longer service life, can not only regulate the power flow between the power distribution stations on two sides in real time within the self capacity regulation range, but also can avoid the problem of power interruption caused by switching operation of the traditional tie switch, and ensures reliable operation of power supply.
At present, the flexible interconnection device can be divided into an isolation type and an isolation-free type, an isolation transformer is omitted in an isolation-free topology, the overall efficiency is improved, the cost is reduced, but a traditional three-bridge arm power module does not have zero line current independent control capability, when three-phase voltage of a transformer area is unbalanced or unbalanced current of the transformer area is compensated, a common mode voltage and ground wire circulation are generated in an interconnection system due to the fact that neutral points of the transformer area are grounded, and the system is unstable and even fails. And secondly, the coordination controller mainly adjusts the transfer power of the flexible interconnection devices according to the heavy overload condition of the station area, and the plurality of groups of flexible interconnection devices are in a hot standby state, so that no-load and light-load loss of equipment is large. In addition, the direct current port causes abnormal work and even damage of direct current load due to the problem of high-frequency common mode voltage and external EMC disturbance. Meanwhile, when a single pole to ground fault or an interelectrode short circuit fault occurs at the positive and negative poles of the direct current distribution system, even if the semiconductor power device is quickly locked, the diode anti-parallel connection of the semiconductor power device of the flexible interconnection device can be burst due to long action time (more than 30 ms) of the mechanical direct current breaker. Therefore, how to combine the cost, efficiency and reliability of the flexible interconnection device of the distribution network and the dc distribution system is an important problem to be solved.
Disclosure of Invention
The invention aims to: the invention aims to provide fault blocking type isolation-free transformer flexible interconnection equipment, a control method and a storage medium, wherein the fault blocking type isolation-free transformer flexible interconnection equipment enables a direct current distribution system to have fault ride-through capability and improves stability of the direct current distribution system
The technical scheme is as follows: in order to achieve the above purpose, the fault blocking type non-isolation transformer flexible interconnection equipment comprises a plurality of groups of non-isolation transformer flexible interconnection devices and a fault blocking type direct current power distribution cabinet;
the direct current sides of the plurality of groups of isolation-free transformer type flexible interconnection devices are respectively connected together through direct current terminals, and the alternating current sides are connected to low-voltage buses of corresponding distribution areas through alternating current terminals; the incoming line terminal of the fault blocking type direct current power distribution cabinet is connected to the direct current terminal of the isolation-free transformer type flexible interconnection device;
the isolation-free transformer type flexible interconnection device adopts a four-leg power module, and the four-leg power module adopts a four-leg pulse width modulation PWM algorithm; the device also comprises a coordination controller for carrying out flexible interconnection control on the four-bridge arm power modules.
The isolation-free transformer type flexible interconnection device further comprises an LCL filter circuit and a direct current bus capacitor; the alternating-current terminal is connected to the LCL filter circuit, the LCL filter circuit is connected to the four-bridge arm power module, the four-bridge arm power module is connected to the direct-current bus capacitor, and the direct-current bus capacitor is connected to the direct-current terminal; the midpoint of a direct current bus capacitor of the isolation-free transformer type flexible interconnection device is grounded through a resistor; the coordination controller is arranged on a cabinet door panel of the flexible interconnection device.
The fault blocking type direct current power distribution cabinet comprises a direct current fault blocking unit and a direct current power distribution unit; the output terminal of the direct current fault blocking unit is connected to the input terminal of the direct current power distribution unit.
The direct current fault blocking unit adopts a symmetrical three-level BUCK circuit and comprises an input fuse, a direct current capacitor, an IGBT, a current limiting reactor, a current sensor and an output fuse; the input fuse is connected to the direct current capacitor, the direct current capacitor is connected to the IGBT, the IGBT is connected to the current limiting reactor, the current limiting reactor is connected to the current sensor, the current sensor is connected to the output fuse, and the output fuse is connected with the input terminal of the direct current distribution unit.
The direct-current power distribution unit comprises a direct-current incoming line breaker and a direct-current outgoing line breaker, an upper port of the direct-current incoming line breaker is connected to the rear end of an input terminal of the direct-current power distribution unit, a lower port of the direct-current incoming line breaker is connected with an upper port of the direct-current outgoing line breaker, and the direct-current outgoing line breaker integrates a leakage protection function; the direct current outgoing line breaker is used for accessing direct current photovoltaics, energy storage, charging piles and other direct current loads.
The fault blocking type isolation-free transformer flexible interconnection control method is applied to the equipment, and the four-bridge arm power module realizes the function of converting alternating current into direct current and comprises a direct current voltage control mode, a power control mode and an alternating current voltage frequency control mode;
the four-bridge arm Pulse Width Modulation (PWM) algorithm comprises four current closed-loop regulation control algorithm loops, namely a three-phase positive sequence current closed-loop control loop, a three-phase negative sequence current closed-loop control loop, a three-phase zero sequence current closed-loop control loop and an N-phase current closed-loop control loop; the N-phase current closed-loop control loop takes the ground wire circulation equal to zero as a target;
the coordination controller adjusts the starting, stopping, active power target value, reactive power target value, direct current voltage target value, alternating current voltage target value and alternating current frequency target value of the four-bridge arm power module according to the control requirement of the distribution area;
the fault blocking type direct current power distribution cabinet regulates the internal IGBT unit to rapidly chopper or block according to the abnormal condition of the output current, and achieves fault current limiting and blocking.
In the four-bridge arm pulse width modulation PWM algorithm, a three-phase positive sequence current closed-loop control loop takes a positive sequence active current instruction and a positive sequence reactive current instruction as target values, outputs positive sequence active voltage and positive sequence reactive voltage through a PID regulator, and then generates a three-phase positive sequence voltage instruction through coordinate transformation;
the three-phase negative sequence current closed-loop control loop takes a negative sequence active current instruction and a negative sequence reactive current instruction as targets, outputs a negative sequence active voltage and a negative sequence reactive voltage through a PID regulator, and generates a three-phase negative sequence voltage instruction through coordinate transformation;
the three-phase zero-sequence current closed-loop control loop takes a zero-sequence current instruction as a target value and outputs a zero-sequence voltage instruction through a PR regulator;
the N-phase current closed-loop control loop takes an N-line current instruction as a target value, and outputs an N-line voltage instruction through a PR regulator;
and adding the three-phase positive sequence voltage command, the three-phase negative sequence voltage command, the zero sequence voltage command and the N line voltage command to generate UA, UB, UC and UN, and generating a four-bridge arm PWM pulse driving signal through PWM modulation.
The coordination controller carries out electric energy quality control and interconnection area power transfer according to the working condition of the distribution area, and the self-adaptive start-stop multi-group flexible interconnection device comprises the following specific steps:
selecting an isolation-free transformer type flexible interconnection device of a light-load power distribution station area as a direct-current voltage control mode, wherein the isolation-free transformer type flexible interconnection devices of the rest power distribution station areas adopt a power control mode;
when the three-phase unbalance of the distribution area is higher than a set threshold value, starting the isolation-free transformer type flexible interconnection device, adjusting the split-phase active power instruction of the isolation-free transformer type flexible interconnection device, and carrying out three-phase unbalance current compensation;
when the power factor of the distribution transformer area is lower than a set threshold value, starting the non-isolation transformer type flexible interconnection device, adjusting a reactive power instruction of the non-isolation transformer type flexible interconnection device, and performing reactive current compensation;
when the load rate of a certain distribution transformer area exceeds a set threshold value, starting the isolation-free transformer type flexible interconnection device, adjusting an active power instruction of the flexible interconnection device, and carrying out power transfer of the interconnection transformer area;
when the voltage frequency of the distribution station is abnormal, the total incoming line switch of the distribution station is disconnected, the isolation-free transformer type flexible interconnection device is started, and an alternating voltage instruction and an alternating frequency instruction of the flexible interconnection device are regulated to supply power to the radio loss station;
when the three-phase unbalance degree, the power factor, the load ratio and the voltage frequency of the distribution area are all in the qualified range, the coordination controller sends a shutdown instruction to the four-bridge arm power module of the isolation-transformer-free flexible interconnection device, and the isolation-transformer-free flexible interconnection device is in cold standby and only remains a control power supply.
The fault blocking type direct current power distribution cabinet has the capability of fast blocking direct current faults, namely when the current sensor of the positive electrode or the negative electrode detects that the current exceeds a protection threshold value, the fault blocking type direct current power distribution cabinet judges that a single pole to ground fault or an interelectrode short circuit fault occurs in a direct current system, and the IGBT is controlled to fast chopper and lock, so that millisecond blocking and current limiting are realized.
And the direct current distribution unit integrates a leakage protection algorithm, and when detecting that the zero sequence current of a certain direct current outlet exceeds a protection threshold value, the direct current outlet with single pole to ground fault is positioned, and the corresponding direct current outlet breaker is cut off.
And the direct current distribution unit collects current data of each direct current outgoing line in real time, and when detecting that the current of a certain direct current outgoing line exceeds a protection threshold value, positions the direct current outgoing line with interelectrode faults, and cuts off the corresponding direct current outgoing line breaker.
The beneficial effects are that: the invention has the following advantages: 1. the isolation transformer-free flexible interconnection device provided by the invention has no isolation transformer, saves the volume and cost of the isolation transformer, and reduces the loss of the isolation transformer part; the device adopts a four-bridge arm power module and a four-bridge arm Pulse Width Modulation (PWM) control algorithm, so that the problems of high-frequency common mode voltage and ground wire circulation are solved; 2. the coordination controller is used for starting and stopping the flexible interconnection device in a self-adaptive mode according to power transfer and power quality control requirements of the distribution area, PWM pulse of the flexible interconnection device is turned off in the self-adaptive mode when the power is stopped, no-load switching loss is reduced, and the system operation efficiency is improved on the basis of considering peak load bearing capacity of the distribution area; 3. the fault blocking type direct current power distribution cabinet provided by the invention enables the direct current power distribution system to have fault ride-through capability on the basis of considering the direct current power distribution efficiency, and improves the stability of the direct current power distribution system.
Drawings
FIG. 1 is a topological structure diagram of a non-isolated transformer type flexible interconnect device of the present invention;
FIG. 2 is a schematic block diagram of a flexible interconnection four-leg Pulse Width Modulation (PWM) control algorithm without an isolation transformer according to the present invention;
fig. 3 is a schematic block diagram of a fault blocking type direct current power distribution cabinet according to the present invention.
Detailed Description
The technical scheme of the present invention will be described in detail with reference to the following examples and the accompanying drawings.
As shown in fig. 1, the fault blocking type isolation-free transformer flexible interconnection device topology structure of the present invention is: the isolation-transformer-free flexible interconnection device comprises a plurality of groups of flexible direct current interconnections and 1 set of fault blocking type direct current power distribution cabinet.
The isolation-free transformer type flexible interconnection device adopts a four-bridge arm power module;
the direct current sides of the plurality of groups of isolation-free transformer type flexible interconnection devices are respectively connected together through direct current terminals, and the alternating current sides are connected to low-voltage buses of corresponding distribution areas through alternating current terminals;
the incoming line terminal of the fault blocking type direct current power distribution cabinet is connected to the direct current terminal of the isolation-free transformer type flexible interconnection device;
the flexible interconnection device without the isolation transformer adopts a four-bridge arm pulse width modulation PWM algorithm, is applied to a four-bridge arm power module, and comprises four current closed-loop regulation control algorithm loops, namely a three-phase positive sequence current closed-loop control loop, a three-phase negative sequence current closed-loop control loop, a three-phase zero sequence current closed-loop control loop and an N-phase current closed-loop control loop; the N-phase current closed-loop control loop aims at the ground wire circulation equal to zero.
The isolation-free transformer type flexible interconnection device comprises an alternating current terminal, an LCL filter circuit, a four-bridge arm power module, a direct current bus capacitor and a direct current terminal; the alternating-current terminal is connected to the LCL filter circuit, the LCL filter circuit is connected to the four-bridge arm power module, the four-bridge arm power module is connected to the direct-current bus capacitor, and the direct-current bus capacitor is connected to the direct-current terminal; the midpoint of the direct current bus capacitor of the isolation-free transformer type flexible interconnection device is grounded through a resistor.
The isolation-free transformer type flexible interconnection device comprises a coordination controller for flexible interconnection control of a plurality of groups of flexible interconnection devices, and the coordination controller is mounted on a cabinet door panel of the flexible interconnection device.
The fault blocking type direct current power distribution cabinet comprises a direct current fault blocking unit and a direct current power distribution unit; the output terminal of the direct current fault blocking unit is connected to the input terminal of the direct current power distribution unit.
The direct current fault blocking unit adopts a symmetrical three-level BUCK circuit and comprises an input fuse, a direct current capacitor, an IGBT, a current limiting reactor, a current sensor and an output fuse; the input fuse is connected to the direct current capacitor, the direct current capacitor is connected to the IGBT, the IGBT is connected to the current limiting reactor, the current limiting reactor is connected to the current sensor, the current sensor is connected to the output fuse, and the output fuse is connected with the input terminal of the direct current distribution unit.
The direct-current power distribution unit comprises a direct-current incoming line breaker and a direct-current outgoing line breaker, an upper port of the direct-current incoming line breaker is connected to the rear end of an input terminal of the direct-current power distribution unit, a lower port of the direct-current incoming line breaker is connected with an upper port of the direct-current outgoing line breaker, and the direct-current outgoing line breaker integrates a leakage protection function; the direct current outgoing line breaker is used for accessing direct current photovoltaics, energy storage, charging piles and other direct current loads.
The four-bridge arm power module of the isolation-free flexible interconnection device realizes the function of converting alternating current into direct current, and comprises a direct current voltage control mode, a power control mode and an alternating current voltage frequency control mode; the current inner loop in the control algorithm adopts a four-bridge arm Pulse Width Modulation (PWM) algorithm.
The coordination controller of the isolation-free flexible interconnection device adjusts the starting and stopping of the four-bridge arm power module, the active power target value, the reactive power target value, the direct current voltage target value, the alternating current voltage target value and the alternating current frequency target value according to the control requirements of the distribution area.
The fault blocking type direct current power distribution cabinet regulates the internal IGBT unit to rapidly chopper or block according to the abnormal condition of the output current, and achieves fault current limiting and blocking.
As shown in fig. 2, in the four-bridge arm pulse width modulation PWM algorithm, a three-phase positive sequence current closed-loop control loop takes a positive sequence active current instruction and a positive sequence reactive current instruction as target values, outputs a positive sequence active voltage and a positive sequence reactive voltage through a PID regulator, and then generates a three-phase positive sequence voltage instruction through coordinate transformation; the three-phase negative sequence current closed-loop control loop takes a negative sequence active current instruction and a negative sequence reactive current instruction as targets, outputs a negative sequence active voltage and a negative sequence reactive voltage through a PID regulator, and generates a three-phase negative sequence voltage instruction through coordinate transformation; the three-phase zero-sequence current closed-loop control loop takes a zero-sequence current instruction as a target value and outputs a zero-sequence voltage instruction through a PR regulator; the N-phase current closed-loop control loop takes the N-line current instruction as a target value, and outputs the N-line voltage instruction through the PR regulator. And adding the three-phase positive sequence voltage command, the three-phase negative sequence voltage command, the zero sequence voltage command and the N line voltage command to generate UA, UB, UC and UN, and generating a four-bridge arm PWM pulse driving signal through PWM modulation.
Assuming that three-phase current of alternating-current side of isolation-free transformer type flexible interconnection device is I A 、I B 、I C The earth wire circulation of PE grounding point of power distribution station AC system is I PE . If the agreed three-phase current inflow device is positive, according to the Kill Hall current law, the earth wire circulates I PE =-(I A +I B +I C +I N ) If the ground current I is to be caused PE =0, then I N =-(I A +I B +I C )。
The N-phase current control loop adopts a PR controller and comprises a proportional controller P, a fundamental resonance controller R1 and a triple resonance controller R3. Given value of PR controller is I N_ref =-(I A +I B +I C ) The feedback value is I N Output U of PR controller N * I.e. the Pulse Width Modulation (PWM) voltage command of the fourth leg.
The coordination controller carries out electric energy quality control and interconnection area power transfer according to the working condition of the distribution area, and the self-adaptive start-stop multi-group flexible interconnection device comprises the following specific steps: selecting a flexible interconnection device of a light-load power distribution station area as a direct-current voltage control mode, wherein the flexible interconnection devices of the rest power distribution station areas adopt a power control mode; when the three-phase unbalance of the distribution area is higher than a set threshold value, starting the flexible interconnection device, adjusting the split-phase active power instruction of the flexible interconnection device, and carrying out three-phase unbalance current compensation; when the power factor of the distribution transformer area is lower than a set threshold value, starting the flexible interconnection device, adjusting a reactive power instruction of the flexible interconnection device, and performing reactive current compensation; when the load rate of a certain distribution area exceeds a set threshold value, starting a flexible interconnection device, adjusting an active power instruction of the flexible interconnection device, and carrying out power transfer of the interconnection area; when the voltage frequency of the distribution station is abnormal, the total incoming line switch of the distribution station is disconnected, the flexible interconnection device is started, and an alternating voltage instruction and an alternating frequency instruction of the flexible interconnection device are regulated to supply power to the radio-loss station; when the three-phase unbalance degree, the power factor, the load factor and the voltage frequency of the distribution area are all in the qualified range, the coordination controller sends a shutdown instruction to the four-bridge arm power module of the flexible interconnection device, and the flexible interconnection device is in cold standby and only remains a control power supply.
The fault blocking type direct current power distribution cabinet has the capability of fast blocking direct current faults, namely when the current sensor of the positive electrode or the negative electrode detects that the current exceeds a protection threshold value, the fault blocking type direct current power distribution cabinet judges that a single pole to ground fault or an interelectrode short circuit fault occurs in a direct current system, and the IGBT is controlled to fast chopper and lock, so that millisecond blocking and current limiting are realized.
As shown in fig. 3, it is assumed that current signals detected by the positive and negative current sensors of the dc fault blocking unit are IDC1 and IDC2, respectively, and it is assumed that the positive current IDC1 outflow terminal is positive and the negative current IDC2 inflow terminal is positive. When a single pole to ground fault or an interelectrode short circuit fault occurs in the direct current system, the positive pole or negative pole current sensor detects that the current exceeds a protection threshold IDCth, and the IGBT1 or the IGBT2 is controlled to be rapidly chopped and locked.
And the direct current distribution unit integrates a leakage protection algorithm, and when detecting that the zero sequence current of a certain direct current outlet exceeds a protection threshold value, the direct current outlet with single pole to ground fault is positioned, and the corresponding direct current outlet breaker is cut off.
And the direct current distribution unit collects current data of each direct current outgoing line in real time, and when detecting that the current of a certain direct current outgoing line exceeds a protection threshold value, positions the direct current outgoing line with interelectrode faults, and cuts off the corresponding direct current outgoing line breaker.
Claims (10)
1. A fault blocking type no-isolation transformer flexible interconnection device is characterized in that: the system comprises a plurality of groups of isolation-free transformer type flexible interconnection devices and fault blocking type direct current power distribution cabinets; the direct current sides of the plurality of groups of isolation-free transformer type flexible interconnection devices are respectively connected together through direct current terminals, and the alternating current sides are connected to low-voltage buses of corresponding distribution areas through alternating current terminals; the incoming line terminal of the fault blocking type direct current power distribution cabinet is connected to the direct current terminal of the isolation-free transformer type flexible interconnection device;
the isolation-free transformer type flexible interconnection device comprises an LCL filter circuit, a four-leg power module, a direct current bus capacitor and a coordination controller for flexible interconnection control of the four-leg power module, wherein the four-leg power module adopts a four-leg pulse width modulation PWM algorithm; the alternating current terminal is connected to the LCL filter circuit, the LCL filter circuit is connected to the four-bridge arm power module, the four-bridge arm power module is connected to the direct current bus capacitor, the direct current bus capacitor is connected to the direct current terminal, and the midpoint of the direct current bus capacitor is grounded through a resistor.
2. The fault blocking type isolation-free transformer flexible interconnection apparatus of claim 1, wherein: the fault blocking type direct current power distribution cabinet comprises a direct current fault blocking unit and a direct current power distribution unit; the output terminal of the direct current fault blocking unit is connected to the input terminal of the direct current power distribution unit.
3. The fault blocking type isolation-free transformer flexible interconnection apparatus of claim 2, wherein: the direct current fault blocking unit adopts a symmetrical three-level BUCK circuit and comprises an input fuse, a direct current capacitor, an IGBT, a current limiting reactor, a current sensor and an output fuse; the input fuse is connected to the direct current capacitor, the direct current capacitor is connected to the IGBT, the IGBT is connected to the current limiting reactor, the current limiting reactor is connected to the current sensor, the current sensor is connected to the output fuse, and the output fuse is connected with the input terminal of the direct current distribution unit.
4. The fault blocking type isolation-free transformer flexible interconnection apparatus of claim 2, wherein: the direct-current power distribution unit comprises a direct-current incoming line breaker and a direct-current outgoing line breaker, an upper port of the direct-current incoming line breaker is connected to the rear end of an input terminal of the direct-current power distribution unit, a lower port of the direct-current incoming line breaker is connected with an upper port of the direct-current outgoing line breaker, and the direct-current outgoing line breaker integrates a leakage protection function; the direct current outgoing line breaker is used for accessing direct current photovoltaics, energy storage, charging piles and other direct current loads.
5. A fault blocking type isolation-free transformer flexible interconnection control method applied to the equipment of claim 1, which is characterized in that: the four-bridge arm power module realizes the function of converting alternating current into direct current, and comprises a direct current voltage control mode, a power control mode and an alternating current voltage frequency control mode;
the four-bridge arm Pulse Width Modulation (PWM) algorithm comprises four current closed-loop regulation control algorithm loops, namely a three-phase positive sequence current closed-loop control loop, a three-phase negative sequence current closed-loop control loop, a three-phase zero sequence current closed-loop control loop and an N-phase current closed-loop control loop; the N-phase current closed-loop control loop takes the ground wire circulation equal to zero as a target;
the coordination controller adjusts the starting, stopping, active power target value, reactive power target value, direct current voltage target value, alternating current voltage target value and alternating current frequency target value of the four-bridge arm power module according to the control requirement of the distribution area;
the fault blocking type direct current power distribution cabinet regulates the internal IGBT unit to rapidly chopper or block according to the abnormal condition of the output current, and achieves fault current limiting and blocking.
6. The fault blocking type isolation-free transformer flexible interconnection control method according to claim 5, wherein the fault blocking type isolation-free transformer flexible interconnection control method comprises the following steps: in the four-bridge arm pulse width modulation PWM algorithm, a three-phase positive sequence current closed-loop control loop takes a positive sequence active current instruction and a positive sequence reactive current instruction as target values, outputs positive sequence active voltage and positive sequence reactive voltage through a PID regulator, and then generates a three-phase positive sequence voltage instruction through coordinate transformation;
the three-phase negative sequence current closed-loop control loop takes a negative sequence active current instruction and a negative sequence reactive current instruction as targets, outputs a negative sequence active voltage and a negative sequence reactive voltage through a PID regulator, and generates a three-phase negative sequence voltage instruction through coordinate transformation;
the three-phase zero-sequence current closed-loop control loop takes a zero-sequence current instruction as a target value and outputs a zero-sequence voltage instruction through a PR regulator;
the N-phase current closed-loop control loop takes an N-line current instruction as a target value, and outputs an N-line voltage instruction through a PR regulator;
and adding the three-phase positive sequence voltage command, the three-phase negative sequence voltage command, the zero sequence voltage command and the N line voltage command to generate UA, UB, UC and UN, and generating a four-bridge arm PWM pulse driving signal through PWM modulation.
7. The fault blocking type isolation-free transformer flexible interconnection control method according to claim 5, wherein the fault blocking type isolation-free transformer flexible interconnection control method comprises the following steps: the coordination controller carries out electric energy quality control and interconnection area power transfer according to the working condition of the distribution area, and the self-adaptive start-stop multi-group flexible interconnection device comprises the following specific steps:
selecting an isolation-free transformer type flexible interconnection device of a light-load power distribution station area as a direct-current voltage control mode, wherein the isolation-free transformer type flexible interconnection devices of the rest power distribution station areas adopt a power control mode;
when the three-phase unbalance of the distribution area is higher than a set threshold value, starting the isolation-free transformer type flexible interconnection device, adjusting the split-phase active power instruction of the isolation-free transformer type flexible interconnection device, and carrying out three-phase unbalance current compensation;
when the power factor of the distribution transformer area is lower than a set threshold value, starting the non-isolation transformer type flexible interconnection device, adjusting a reactive power instruction of the non-isolation transformer type flexible interconnection device, and performing reactive current compensation;
when the load rate of a certain distribution transformer area exceeds a set threshold value, starting the isolation-free transformer type flexible interconnection device, adjusting an active power instruction of the flexible interconnection device, and carrying out power transfer of the interconnection transformer area;
when the voltage frequency of the distribution station is abnormal, the total incoming line switch of the distribution station is disconnected, the isolation-free transformer type flexible interconnection device is started, and an alternating voltage instruction and an alternating frequency instruction of the flexible interconnection device are regulated to supply power to the radio loss station;
when the three-phase unbalance degree, the power factor, the load ratio and the voltage frequency of the distribution area are all in the qualified range, the coordination controller sends a shutdown instruction to the four-bridge arm power module of the isolation-transformer-free flexible interconnection device, and the isolation-transformer-free flexible interconnection device is in cold standby and only remains a control power supply.
8. The fault blocking type isolation-free transformer flexible interconnection control method according to claim 5, wherein the fault blocking type isolation-free transformer flexible interconnection control method comprises the following steps: the fault blocking type direct current power distribution cabinet has the capability of fast blocking direct current faults, namely when the current sensor of the positive electrode or the negative electrode detects that the current exceeds a protection threshold value, the fault blocking type direct current power distribution cabinet judges that a single pole to ground fault or an interelectrode short circuit fault occurs in a direct current system, and the IGBT is controlled to fast chopper and lock, so that millisecond blocking and current limiting are realized.
9. The fault blocking type isolation-free transformer flexible interconnection control method according to claim 5, wherein the fault blocking type isolation-free transformer flexible interconnection control method comprises the following steps: and the direct current distribution unit integrates a leakage protection algorithm, and when detecting that the zero sequence current of a certain direct current outlet exceeds a protection threshold value, the direct current outlet with single pole to ground fault is positioned, and the corresponding direct current outlet breaker is cut off.
And the direct current distribution unit collects current data of each direct current outgoing line in real time, and when detecting that the current of a certain direct current outgoing line exceeds a protection threshold value, positions the direct current outgoing line with interelectrode faults, and cuts off the corresponding direct current outgoing line breaker.
10. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the method according to any of claims 6-9.
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