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CN-122000981-A - Multi-port direct current breaker with current limiting and power flow control functions and control method thereof

CN122000981ACN 122000981 ACN122000981 ACN 122000981ACN-122000981-A

Abstract

The invention discloses a multi-port direct current breaker which comprises a plurality of parallel circuits, a main breaker, a lightning arrester, a mode switching switch, a current limiting inductor, a power flow capacitor, a current limiting capacitor, a first thyristor, a second thyristor and a third thyristor, wherein each circuit comprises a first current transfer switch, a first mechanical switch, a second current transfer switch, a second mechanical switch, an isolating switch and a reactor which are sequentially connected, the first current transfer switch is connected with a first direct current bus, the second mechanical switch is connected with a second direct current bus, the isolating switch is connected with the first mechanical switch and the second current transfer switch after being connected in series, the main breaker is connected with the lightning arrester in parallel and then connected with the first thyristor in series, the second thyristor is connected with the current limiting capacitor in series and then connected with the first thyristor in parallel, the mode switching switch is connected with the power flow capacitor in series and then connected with the plurality of circuits in parallel, and the mode switching switch is connected with the first direct current bus and the power flow capacitor is connected with the second direct current bus.

Inventors

  • XIAO HUANGQING
  • HUANG YUNFENG

Assignees

  • 华南理工大学

Dates

Publication Date
20260508
Application Date
20260112

Claims (10)

  1. 1. The multi-port direct current breaker with the current limiting and the power flow control functions is characterized by comprising a plurality of parallel circuits, a main breaker, a lightning arrester, a mode switching switch, a current limiting inductor, a power flow capacitor, a current limiting capacitor, a first thyristor, a second thyristor and a third thyristor, wherein each circuit comprises a first bridge arm, a second bridge arm, an isolating switch and a reactor, the first bridge arm comprises a first current transfer switch and a first mechanical switch, and the second bridge arm comprises a second current transfer switch and a second mechanical switch; The first end of the first current transfer switch is connected with the first direct current bus, the second end of the first current transfer switch is connected with the first end of the first mechanical switch, the second end of the first mechanical switch is connected with the first end of the second current transfer switch, the second end of the second current transfer switch is connected with the first end of the second mechanical switch, the second end of the second mechanical switch is connected with the second direct current bus, and after the isolating switch and the reactor are connected in series, the second end of the reactor is respectively connected with the second end of the first mechanical switch and the first end of the second current transfer switch; The main breaker is connected with the lightning arrester in parallel and then connected with the first thyristor in series, the second thyristor is connected with the current-limiting capacitor in series and then connected with the first thyristor in parallel, the third thyristor is connected with the current-limiting inductor in series and then connected with the first thyristor in parallel, the mode switching switch is connected with the power flow capacitor in series and then connected with a plurality of circuits in parallel, the first end of the mode switching switch is connected with the first direct current bus, and the second end of the power flow capacitor is connected with the second direct current bus; The first end of the main breaker and the first end of the arrester are respectively connected with a first direct current bus, the second end of the main breaker and the second end of the arrester are respectively connected with anodes of the first thyristor, the second thyristor and the third thyristor, the first end of the current-limiting capacitor is connected with a cathode of the second thyristor in series, the first end of the current-limiting inductor is connected with a cathode of the third thyristor in series, and the cathode of the first thyristor, the second end of the current-limiting capacitor and the second end of the current-limiting inductor are respectively connected with a second direct current bus.
  2. 2. The multi-port dc circuit breaker with current limiting and flow control of claim 1 wherein the current transfer switch and the main breaker each use multiple insulated gate bipolar transistors in series-parallel.
  3. 3. The multi-port dc circuit breaker with current limiting and flow control of claim 2 wherein the mode switch comprises two structures, one is formed using a third mechanical switch and the other is formed using a third current transfer switch in series with a third mechanical switch.
  4. 4. The multi-port dc circuit breaker with current limiting and flow control of claim 3 wherein the first mechanical switch, the second mechanical switch and the third mechanical switch are all ultra-fast mechanical switches.
  5. 5. The multi-port dc circuit breaker with current limiting and flow control according to claim 2, wherein the lightning arrester is a metal oxide lightning arrester, the number of parallel lines is m, and m is an integer greater than or equal to 3.
  6. 6. A power flow control method of a multi-port dc circuit breaker with current limiting and power flow control, characterized by being applied to the multi-port dc circuit breaker with current limiting and power flow control according to any one of claims 1 to 5, comprising the steps of: S11, when a system in which the direct current circuit breaker is positioned normally operates, the direct current circuit breaker is in a power flow control mode, and a mode change-over switch and mechanical switches of all lines are in a closed state; S12, collecting the tide capacitor voltage and each line current through an external voltage sampling circuit, and transmitting the collected tide capacitor voltage and each line current to a microcontroller; S13, the microcontroller calculates the difference value between the voltage of the power flow capacitor and the reference value thereof, generates a pair of complementary PWM signals through modulation, controls the first current transfer switch and the second current transfer switch which are connected with the MMC circuit, and controls the first current transfer switch and the second current transfer switch of the relaxation circuit; And S14, respectively calculating the difference value between the current of the other lines and the reference value of the current of the other lines by the microcontroller, generating a pair of complementary PWM signals through modulation, and respectively controlling the first current transfer switch and the second current transfer switch of the other lines.
  7. 7. A method for processing a dc fault of a multi-port dc circuit breaker with current limiting and power flow control, which is applied to the multi-port dc circuit breaker with current limiting and power flow control according to any one of claims 1 to 5, and is used for realizing fast mode switching, current limiting and dc fault clearing.
  8. 8. The method for handling dc faults in a multi-port dc circuit breaker with current limiting and flow control of claim 7 comprising the steps of: s21, after a system in which the direct current breaker is located detects that a line fault occurs, controlling the main breaker and the first thyristor to be conducted; S22, after the main circuit breaker is completely conducted, controlling the first current transfer switch and the second current transfer switch of the normal circuit to be conducted, and controlling the first current transfer switch and the second current transfer switch of the fault circuit to be conducted; s23, after the current transfer switch is completely switched on or off, the second mechanical switch of the normal line, the first mechanical switch of the fault line and the third mechanical switch of the mode switching are controlled to be switched off; S24, after the mechanical switch is completely disconnected, the first thyristor is controlled to be disconnected, the second thyristor and the third thyristor are controlled to be conducted, the negative pressure of the current-limiting capacitor enables the current in the first thyristor to be reduced to 0, the current-limiting capacitor completes primary current limiting, the negative pressure at two ends of the current-limiting capacitor is reduced and then positive pressure is increased to system voltage in the process of putting the current-limiting capacitor into operation, the current in the current-limiting capacitor is reduced to 0, and the current-limiting inductor is completely put into operation; s25, after the current limiting inductor is completely put into operation, the main circuit breaker is controlled to be disconnected, so that fault current is transferred to the lightning arrester, and the fault current is consumed energy through the lightning arrester and is rapidly reduced to 0; And S26, after the line fault current is reduced to 0, the isolating switch of the fault line is controlled to be opened, so that the line fault clearing is thoroughly realized, and the normal power flow of the rest normal lines is restored.
  9. 9. The method according to claim 8, wherein in step S22, if the mode switching switch is formed by connecting a third current transfer switch in series with a third mechanical switch, the third current transfer switch for mode switching is turned off.
  10. 10. The method according to claim 8, wherein in step S22, if the mode switch is configured by only one third mechanical switch, the mode switch is not required to be operated.

Description

Multi-port direct current breaker with current limiting and power flow control functions and control method thereof Technical Field The invention relates to the technical field of power electronics, in particular to a multi-port direct current breaker with current limiting and power flow control functions and a control method thereof. Background The direct current power grid has two basic networking modes, namely a first mode of adopting a modularized multi-level converter (MMC) plus direct current breaker scheme based on a half-bridge sub-module and being suitable for the direct current power grid with any end number, and a second mode of adopting an MMC with direct current fault self-clearing capacity, such as an MMC based on Quan Qiaozi modules, without a direct current breaker, and being suitable for the small-scale direct current power grid with the end number smaller than 10. When the networking mode of the half-bridge submodule MMC and the direct-current circuit breaker is adopted, the converter station is usually required to continue to operate during the fault period of the direct-current circuit, the blocking cannot be realized, the fault line is rapidly cut off by the direct-current circuit breaker, and the fault processing principle is similar to that of an alternating-current power grid. When the network construction mode without the direct current circuit breaker is adopted, the related converter in the network is locked during the direct current line fault period, the fault current is reduced to zero and kept stable about 10 ms after the locking, the fault line is isolated through the isolating switch, the related converter is unlocked to restore the power transmission, the power transmission from the fault start to the power transmission restoration is generally about 20 ms, and the impact on the alternating current power grid is generally within the bearable range. When a direct current power grid is formed by adopting a half-bridge submodule MMC and a direct current breaker, the direct current breaker becomes a critical element. At present, three types of high-voltage direct-current circuit breakers mainly comprise a traditional mechanical circuit breaker based on a conventional switch, a solid-state circuit breaker based on a pure electric electronic device and a hybrid circuit breaker combining the two types of circuit breakers. Although technically feasible solutions have been developed, they are expensive and bulky and difficult to use widely in the grid as ac circuit breakers, and thus dc circuit breakers remain a fundamental technical bottleneck for developing dc grids. Meanwhile, as the development speed of the fault current of the direct-current power grid is extremely high, larger smoothing reactors are required to be installed at two ends of a line so as to inhibit the rise of the fault current. However, when a larger smoothing reactor is selected for better current limiting, the dynamic characteristics of the flexible dc system are affected. In order to solve the contradiction, fault current limiters can be arranged at two ends of the line to replace a common smoothing reactor, and the current limiters are in a low-impedance state in normal operation and are switched to a high-impedance state in fault. In addition, in the direct current power grid with the number of the power transmission lines larger than that of the converter stations, the power flow cannot be effectively regulated only by the converter stations, and the degree of freedom of power flow control is insufficient. At this time, a dc power flow controller needs to be introduced to enhance the regulation capability, and the controller is also a key device for the development of a dc power grid. In the future, the direct current power grid comprises a large number of direct current lines, and if the whole system needs to be provided with a plurality of discrete direct current breakers, fault current limiters and power flow controllers, the cost is high, the volume is huge, and huge economic and technical challenges are formed for the development of the direct current power grid. Disclosure of Invention The invention aims to overcome the defects and shortcomings of the prior art, and provides a multi-port direct current breaker with current limiting and power flow control and a control method thereof, the multiport direct current breaker integrates multiport direct current breaker, fault current limiting and power flow control functions into a whole by utilizing topological structure similarity so as to reduce the number of required components, thereby obviously reducing engineering cost. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: A multi-port direct current breaker with current limiting and power flow control comprises a plurality of parallel circuits, a main breaker, a lightning arrester, a mode change-over switch, a current limiting inductor, a power flow cap