A short-circuit current power supply for DC circuit breaker disconnection test and its control method

Abstract

The present invention relates to a short-circuit current power supply for DC circuit breaker disconnection test and its control method. In the power supply, a DC adjustable regulated power supply DCPS is connected to an energy storage capacitor bank through a DC switch Ks. The energy storage capacitor bank is composed of multiple capacitor monomers C1, C2 to C n in parallel, and each energy storage capacitor monomer is connected in series with a contactor switch, which are K c1 , K c2 to K cn in sequence. One end of the positive pole of the energy storage capacitor bank is connected in series with multiple series-connected DC reactors L1, L2 to L n , and then connected in series with one end of an auxiliary switch K H . The other end of the auxiliary switch K H is connected to one end of the DC circuit breaker Q Z , and the other end of the DC circuit breaker Q Z is connected to the negative end of the energy storage capacitor bank. Among them, each of the DC reactors L1, L2 to L n is connected in parallel with a bypass switch K L1 , K L2 to K Ln in sequence. The power supply of the present invention can meet the high requirements of various large-current capacity DC circuit breakers for test conditions.

Description

Technical Field

[0001] The present invention relates to the cut-off test of a DC circuit breaker, and in particular to a short-circuit current power supply for DC circuit breaker cut-off test and its control method. Background Art

[0002] DC circuit breakers are used to provide system protection for short-circuit accidents in DC systems and cut off the accident current generated by short-circuits. To perform this system protection reliably, it is required that the DC circuit breaker has a specified cut-off performance according to the DC system used. During the process of testing the cut-off performance of the circuit breaker before installation and application, a DC power supply device capable of providing a sufficiently large short-circuit current is needed. Since the DC resistance of the circuit loop in the DC system is very small, once a short-circuit fault occurs, the short-circuit current that needs to be cut off by the DC circuit breaker is very large. Especially for large-capacity DC circuit breakers applied to medium- and high-voltage DC systems, when performing short-circuit current cut-off tests on them, the short-circuit current capacity provided by the power supply needs to be even greater. In addition, in order to verify sufficiently and simulate the actual application situation as much as possible, it is required that the duration of the short-circuit current provided by the power supply is long enough. Currently, DC circuit breakers mainly include mechanical circuit breakers, all-solid-state circuit breakers based on semiconductor switches, and hybrid DC circuit breakers composed of a combination of mechanical switches and semiconductor switches. Since the cut-off times of these several types of circuit breakers are long or short, in order to truly simulate the cut-off situation of the DC circuit breaker under short-circuit faults in the DC line, it is necessary that the magnitude and duration of the short-circuit test current of the power supply capable of providing short-circuit current can be set according to actual needs. For example, for a certain mechanical DC circuit breaker with a rated working voltage of 4000V, it is required that the short-circuit current of the test power supply is greater than 70kA, and the maximum peak current may reach more than 100kA, and it is desired that the duration of the short-circuit current is more than 40ms.

[0003] For the short-circuit current cut-off test of DC circuit breakers applied to low voltage and small current capacity, in order to simulate the short-circuit current flowing through the DC circuit breaker during a short-circuit fault in the actual DC power grid system circuit, a DC power supply obtained by directly rectifying the power taken from the AC power grid can be used for power supply. However, for large-capacity DC circuit breakers applied to medium- and high-voltage DC systems, because the short-circuit current is too large, it will affect the normal operation of the power grid and the electrical equipment on the same grid. Summary of the Invention

[0004] To meet the needs of the cut-off performance test of large-current DC circuit breakers, based on the basic principle of generating test short-circuit current by discharging energy storage capacitors, this patent proposes a main circuit structure of a DC test power supply that can provide a large short-circuit current for a sufficiently long time, and proposes a basic system structure and control method in which the magnitude range and maintenance time of the short-circuit current can be accurately and arbitrarily set and controlled, so that this test power supply can meet the high requirements of various large-current capacity DC circuit breakers for test conditions.

[0005] For this purpose, a short-circuit current power supply for DC breaker cutting test is provided, including a DC adjustable regulated power supply DCPS, a DC switch Ks, an energy storage capacitor bank, a DC reactor, and an auxiliary switch K H , and a controller;

[0006] The DC adjustable regulated power supply DCPS is connected to the energy storage capacitor bank through the DC switch Ks. The energy storage capacitor bank is composed of multiple capacitor monomers from C1, C2 to C n in parallel. Each energy storage capacitor monomer is connected in series with a contactor switch, which are K c1 , K c2 to K cn in sequence. One end of the positive pole of the energy storage capacitor bank is connected in series with multiple series-connected DC reactors from L1, L2 to L n and then connected to one end of the auxiliary switch K H . The other end of the auxiliary switch K H is connected to one end of the measured DC breaker Q Z . The other end of the DC breaker Q Z is connected to the negative end of the energy storage capacitor bank. Among them, each of the DC reactors from L1, L2 to L n is connected in parallel with a bypass switch K L1 , K L2 to K Ln ;

[0007] The controller is used to control the on / off and detect the status of switches K c1 , K c2 to K cn , K L1 , K L2 to K Ln as well as Ks and K R , and to control the on / off and detect the status of the protection breaker Q1, and is used to detect the DC voltage on the energy storage capacitor, the voltage on the measured DC breaker switch, and the current flowing through the measured DC breaker in real time.

[0008] Furthermore, the capacitance values of the capacitor monomers of the energy storage capacitor bank are arranged and taken according to a geometric sequence with a common ratio of 2, and / or the inductance values of the DC reactors from L1, L2 to L n are arranged and taken according to a geometric sequence with a common ratio of 2.

[0009] Furthermore, it also includes a protection breaker Q1. One end of the positive pole of the energy storage capacitor bank is connected in series with multiple series-connected DC reactors from L1, L2 to L n through the protection breaker Q1.

[0010] Furthermore, a varistor MOV is connected in parallel at both ends of the protection breaker Q1.

[0011] Further, a resistor Rc is connected in parallel with the energy storage capacitor bank, and the resistor Rc is connected to the energy storage capacitor bank through a series switch K R to discharge the energy storage capacitor bank.

[0012] Further, a design method for the capacitance value C of the energy storage capacitor bank and the parameter L of the DC reactor includes:

[0013] 1) According to the given target values i low and i max , calculate to obtain θ low with the unit of radian;

[0014] 2) Calculate the intermediate variable

[0015] 3) Calculate the intermediate variable

[0016] 4) Based on the initial value U C of the energy storage capacitor and the pre-detected line resistance R, calculate the reactor parameter with the unit of H;

[0017] 5) Calculate the energy storage capacitance value with the unit of F.

[0018] A control method for the DC circuit breaker to cut off the short-circuit current power supply for testing is also provided, including:

[0019] 1) Before the test, control all switches to be in the off state;

[0020] 2) Control the protection circuit breaker Q1 to close, control the auxiliary switch K H to close, and control the bypass switches of all reactors to close to test the DC resistance R of the line;

[0021] 3) Disconnect the auxiliary switch k H , and according to the rated operating voltage of the tested DC circuit breaker, take the initial discharge voltage U C of the energy storage capacitor to be greater than the rated voltage;

[0022] 4) According to the short-circuit current parameters i low , i max and T Hold required for the test of the tested DC circuit breaker, as well as U C and the tested line resistance R, calculate the total capacitance value C of the energy storage capacitors and the total inductance L of the reactors to be configured, and control the corresponding capacitor monomers and reactors to be put into operation according to the total capacitance value C of the energy storage capacitors and the total inductance L of the reactors;

[0023] 5) Close the control switch Ks, start the DC adjustable regulated power supply DCPS, and charge the energy storage capacitor bank in constant current mode until the voltage on the energy storage capacitor is charged to the initial discharge voltage U C and then stop charging and disconnect the switch Ks;

[0024] 6) Control the closing of the measured DC circuit breaker Q Z switch, and control the closing of the auxiliary switch K H so that when the short-circuit current rises to reach the minimum value i required for the cut-off test low at time T Hold within the time period of, conduct the cut-off performance test of the measured DC circuit breaker Q Z ;

[0025] 7) During the test of the measured DC circuit breaker Q Z , the controller collects the line loop current in real time. If an abnormal fault is found, control the protective circuit breaker Q1 to trip;

[0026] 8) After the test is completed, control the discharge branch switch K of the energy storage capacitor R to close until it is judged that the voltage on the energy storage capacitor bank is zero volts, then control to disconnect K R , and then control all switches to the off state.

[0027] Among them, the test method of the line DC resistance R further includes:

[0028] Control the bypass switches of all reactors to close, short-circuit the measured DC circuit breaker with a thick wire, and use a high-precision resistance test instrument to measure the line DC resistance R; or

[0029] Use the external load test function of the DC adjustable regulated power supply DCPS, close Ks, accurately output a constant current, detect the accurate output voltage of the DC adjustable power supply, and obtain the line DC resistance R by using the ratio of the output voltage to the output current.

[0030] 1) The method for designing the parameters of the energy storage capacitor and reactor of the short-circuit current power supply proposed by the present invention is highly practical, meets the requirements of engineering design, and creates conditions for automatically configuring the test condition parameters (the magnitude range and duration of the short-circuit current).

[0031] 2) The scheme proposed by the present invention of paralleling multiple energy storage capacitor monomers, with the capacitance values distributed in a geometric progression with a common ratio of 2, and series-connected reactor monomers, with the inductance values also distributed in a geometric progression with a common ratio of 2, can achieve precise adjustment and control of the short-circuit current range and duration required for the test.

[0032] 3) Since during the test, the energy storage capacitor is actually charged and then supplies power to the DC circuit breaker under test, and at this time, the energy storage capacitor is isolated from the power grid and the DC voltage regulator power supply through a switch, this structure avoids the impact on the external power grid during the test of the high-current-capacity DC circuit breaker.

[0033] 4) The energy storage capacitor is charged using a DC adjustable power supply instead of the conventional method of directly rectifying the power grid power supply for charging. The advantage is that the initial voltage of the energy storage capacitor can be any voltage within the rated output voltage range of the DC adjustable power supply, which is convenient for further optimizing the initial voltage before the short-circuit discharge of the energy storage capacitor, for calculating and optimizing the parameters of the energy storage capacitor and the reactor inductance, so as to reduce the system cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The main circuit electrical schematic diagram of the present invention is shown.

[0035] Figure 2 Shows Figure 1 The equivalent RLC series circuit of the circuit.

[0036] Figure 3 The schematic diagram of the key parameters of the short-circuit current is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The technical solutions of the present invention will be further described below with reference to the drawings and specific embodiments.

[0038] Figure 1 For the main circuit electrical schematic diagram of the power supply system, the DC adjustable regulated power supply DCPS is connected to the energy storage capacitor bank through the DC switch Ks. The energy storage capacitor bank is composed of multiple capacitor monomers from C1, C2 to C n in parallel. Each energy storage capacitor monomer is connected in series with a contactor switch, which are Kc1, Kc2 to Kcn in sequence. A resistor Rc is connected in parallel with the energy storage capacitor bank, and it can discharge the energy storage capacitor bank through the series switch K R . One end of the positive pole of the energy storage capacitor bank is connected in series with a protective circuit breaker Q1. After passing through the protective circuit breaker Q1, it is then connected in series with multiple series-connected DC reactors from L1, L2 to L n in sequence, and then connected in series with the auxiliary switch K H , and finally connected to one end of the DC circuit breaker Q Z . The other end of the DC circuit breaker Q Z is connected to the negative end of the energy storage capacitor bank. Each of the DC reactors from L1, L2 to L n is connected in parallel with a bypass switch K L1 , K L2 to K Ln in sequence. To prevent overvoltage generated when the protective circuit breaker switch is turned off, a varistor MOV is connected in parallel across the two ends of the protective circuit breaker Q1.

[0039] To facilitate the implementation of the required capacitance and inductance parameters, the capacitance values of the individual capacitors in the energy storage capacitor bank are arranged and taken according to a geometric sequence with a common ratio of 2, and the inductance values of the DC reactors from L1, L2 to L n are also arranged and taken according to a geometric sequence with a common ratio of 2.

[0040] The controller is used to control the on / off and perform status detection on the switching devices such as Kc1, Kc2 to Kcn, K L1 , K L2 to K Ln as well as Ks and K R etc., and also detect the on / off state of the protection circuit breaker Q1. The controller also continuously detects the DC voltage across the energy storage capacitor, the voltage across the measured DC circuit breaker switch, and the current flowing through the measured DC circuit breaker.

[0041] Figure 1 The essence of the circuit is in the form of Figure 2 the RLC series circuit shown. The fully charged energy storage capacitor, through the series reactor, forms a short - circuit loop after the measured DC circuit breaker is closed, so that the energy storage capacitor releases the short - circuit current required by the required magnitude.

[0042] The reactor is used to limit the magnitude of the short - circuit peak current and extend the duration. Since there is inevitably a line DC resistance in the actual current loop, Figure 2 it is represented by a unified resistor R in . This is a second - order RLC series circuit. The capacitor C discharges through the series inductor L and resistor R, and the discharge current flows through the DC circuit breaker.

[0043] In this architecture, let the minimum value of the test - required test short - circuit current be i low , the maximum value be i max , and the duration greater than the minimum short - circuit current be T Hold . Therefore, for the specified test requirements, through engineering approximation and detailed derivation, a parameter design method and calculation steps for the capacitance value C of the energy storage capacitor bank and the parameter L of the reactor are proposed as follows:

[0044] 1) First, according to the given target values i low (unit: A) and i max (unit: A), calculate to obtain where the unit of θ low is radians;

[0045] 2) Calculate the intermediate variable

[0046] 3) Calculate the intermediate variable

[0047] 4) Based on the initial value U of the energy storage capacitorC (Unit: V), and the line resistance R (Unit: Ω) that can be pre-detected. Further calculation yields the reactor parameters as follows: The unit is H;

[0048] 5) Connect and further calculate the energy storage capacitance value: The unit is F.

[0049] Referring to the parameter design method proposed above, the following is a comparative analysis of the calculation and simulation results for various cases:

[0050] Table 1 below shows the total inductance of the reactor L and the total capacitance value of the energy storage capacitor C calculated based on the minimum short-circuit current i low , the maximum value i max , the duration T Hold greater than the minimum short-circuit current, the initial voltage U of the energy storage capacitor C and the total line resistance R.

[0051] Table 1 Calculated values of L and C

[0052] <![CDATA[i max (A)]]> <![CDATA[i low (A)]]> <![CDATA[t Hold (ms)]]> <![CDATA[U C (V)]]> R (Ω) L (H) C (F) 110000 80000 40.0 4400 0.015 0.0007172 0.974658 100000 80000 30.0 4000 0.018 0.000566 0.960059 80000 50000 40.0 4000 0.018 0.0007727 0.645265 50000 30000 20.0 4000 0.018 0.0007019 0.165697

[0053] Table 2 Simulated values of short-circuit current parameters

[0054]

[0055]

[0056] Comparing Table 2 with Table 1, it can be seen that the parameters designed according to the method of this patent application can make the relative error between the realized short-circuit peak current and the set target peak current not exceed 5%. The relative error between the duration of the short-circuit current greater than the set current value i low and the set requirement for this time also does not exceed about 5%. Therefore, from the perspective of engineering applications, the proposed parameter design method for the energy storage capacitor and the reactor is feasible.

[0057] As can be seen from Table 1, for different requirements of the minimum test short-circuit current of i low , the maximum value (i.e., the peak value) of i max , and the duration T Hold greater than the minimum short-circuit current, the range of the sizes of the energy storage capacitor C and the reactor inductance L that need to be configured varies greatly. In order to achieve relatively accurate i max and T Hold , there are also high requirements for the accuracy of C and L. Therefore, this patent proposal proposes to connect multiple capacitor units in parallel for the energy storage capacitor, and also connect multiple in series for the reactor. Moreover, the capacitance values of the individual capacitors in the energy storage capacitor bank are arranged and taken according to a geometric sequence with a common ratio of 2, L1, L2 to Ln The inductance values of the DC reactors are also arranged and taken according to a geometric progression with a common ratio of 2.

[0058] Let Figure 1 The capacitance value of C1 in n is Cp method, the capacitance value of C2 is 2 × Cp (unit: F), and the capacitance value of C n is 2 n × Cp (unit: F). Then, when all the switches of the capacitor branches are fully closed, the total capacitance that can be achieved is (2

[0059] Similarly, let Figure 1 The inductance value of L1 in n is p (unit: H), the inductance value of L2 is 2 × p (unit: H), and the inductance value of L n is 2 n+1 × p (unit: H). Then, when all the parallel switches of the reactor branches are fully opened, the total inductance that can be achieved is (2 max - 1) × p (unit: H). If the minimum inductance p is 10 μH, when n takes the maximum value of 6, the maximum total inductance can reach 1270 μH, and the inductance adjustment accuracy is 10 μH. The simulation shows that the total capacitance accuracy of 20 μF and the total inductance accuracy of 10 μH have little influence on the short-circuit current peak value i low and the short-circuit current holding time T Hold of the short-circuit current greater than the set i

[0060] The system configuration and control method are as follows:

[0061] 1) Before the test, all the switches of the system are in the open state.

[0062] 2) Close the protection circuit breaker Q1 and the KH auxiliary switch. The controller controls all the bypass switches of the reactors to be closed, short-circuit the DC circuit breaker under test with a thick wire, and use a high-precision resistance test instrument to measure the DC resistance R of the line. It should be noted that a subsequent improved method is to use the external load test function of the DC adjustable regulated power supply DCPS, close Ks, accurately output a constant current, detect the accurate output voltage of the DC adjustable regulated power supply DCPS, and obtain the DC resistance of the external line by using the ratio of the output voltage to the output current.

[0063] 3) Disconnect the short-circuit wire of the DC circuit breaker under test. Open the auxiliary switch k H , refer to the rated working voltage of the DC circuit breaker under test, and take the initial discharge voltage U of the energy storage capacitorC Slightly greater than the rated voltage.

[0064] 4) The control system of the power supply automatically calculates the total capacitance value of the energy storage capacitors and the total inductance of the reactors to be configured according to the short-circuit current parameters i low , i max and T Hold , U C required for the test of the DC circuit breaker under test and the measured line resistance R according to the method in Section 5.2 above, and automatically decides which energy storage capacitor monomers and which reactor monomers need to be put into operation, then controls the series switch of the capacitor monomer to close and the bypass switch of the reactor monomer to open. For example, for the second row of Table 1, when a capacitor of 0.960059 F (i.e., 960059 uF) needs to be configured and an inductor of 0.000566 H (i.e., 566 uH) is configured, with the capacitor and inductor accuracies being 20 uF (i.e., C1 is designed as 20 uF) and 10 uH (i.e., L1 is designed as 10 uH) respectively, for the capacitor, since 960059 / 20≈48003, the corresponding binary number is 1011 1011 1000 0011, that is, it is necessary to control switches Kc1, Kc2, Kc8, Kc9, Kc 10 , Kc 12 , Kc 13 , Kc4 and Kc 16 to close simultaneously, while the switch of other capacitor branches is open. For the reactor, since 566 / 10≈57, the corresponding binary number is 111001, and it is necessary to control switches K L1 , K L4 , K L5 and K L6 to open simultaneously, while the bypass switches of other reactor monomers are closed.

[0065] 5) The controller controls switch Ks to close and conduct, then starts the DC adjustable regulated power supply DCPS, and charges the energy storage capacitor bank in constant current mode until the voltage on the energy storage capacitor is charged to the set target value, i.e., the initial discharge voltage U C , and then stops charging and opens switch Ks.

[0066] 6) When the switch of the DC circuit breaker under test is closed and the controller detects that the system is normal, it controls the auxiliary switch K H to close. At this time, the voltage on the energy storage capacitor is applied across the switch of the DC circuit breaker Qz under test through Q1, the reactor, and the auxiliary switch. Since the DC circuit breaker Qz under test is closed and conducts directly, a short-circuit current is formed. When the short-circuit current rises to reach the minimum value i low required for the cut-off test, within the time period of T Hold , the cut-off performance test of the DC circuit breaker under test can be carried out.

[0067] 7) During the test of the DC circuit breaker under test, the controller real-time collects the line loop current. If an abnormal fault is detected, the protection circuit breaker Q1 automatically trips to cut off the power supply loop on the DC circuit breaker Qz under test.

[0068] 8) During the above entire process, the voltage across the switch of the DC circuit breaker under test and the current data flowing through it are real-time sampled and detected and sent to the controller for storage, so as to finally form a test data report and for data analysis.

[0069] 9) After the test is completed, the controller controls the discharge branch switch K of the energy storage capacitor R to close, releasing the electrical energy on the energy storage capacitor. When it is judged that the voltage on the energy storage capacitor is zero volts, then it controls to disconnect K R . Then, the controller controls all switches (including the protection circuit breaker Q1) to be in the off state, restoring to the initial switch state before the test.

[0070] Compared with the prior art, the present invention has the following advantages:

[0071] 1) The method for designing the parameters of the energy storage capacitor and reactor of the short-circuit current power supply proposed by the present invention is highly practical, meeting the engineering design requirements, and creating conditions for automatically configuring the test condition parameters (the magnitude range and continuous maintenance time of the short-circuit current).

[0072] 2) The scheme proposed by the present invention of parallel connection of multiple energy storage capacitor monomers with the capacitance values distributed in a geometric progression with a common ratio of 2 and series connection of reactor monomers with the inductance values also distributed in a geometric progression with a common ratio of 2 can achieve precise adjustment and control of the short-circuit current range and maintenance time required for the test.

[0073] 3) Since during the test, it is actually the energy storage capacitor after being fully charged that supplies power to the DC circuit breaker under test, and at this time the energy storage capacitor is isolated from the power grid and the DC voltage regulating power supply through the switch, this structure avoids the influence on the external power grid during the test process of high-current capacity DC circuit breakers.

[0074] 4) The energy storage capacitor is charged by a DC adjustable regulated power supply DCPS instead of directly rectifying and charging using the power grid power in the conventional way. The advantage is that the initial voltage of the energy storage capacitor can be any voltage within the rated output voltage range of the DC adjustable regulated power supply DCPS, which is convenient for further optimizing the initial voltage before the short-circuit discharge of the energy storage capacitor for the calculation and optimization of the energy storage capacitor parameters and the reactor inductance parameters, so as to facilitate the reduction of the system cost. The design method for optimizing the parameter configuration according to the unit price of the capacitor and reactor materials to reduce the system cost will not be elaborated here.

[0075] The above specific embodiments are merely several preferred embodiments of the present invention. Based on the technical solution of the present invention and the relevant revelations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A short-circuit current power supply for DC circuit breaker disconnection test, characterized in that: including a DC adjustable regulated power supply DCPS, a DC switch Ks, an energy storage capacitor bank, a DC reactor, and an auxiliary switch K H , and a controller; The DC adjustable regulated power supply DCPS is connected to the energy storage capacitor bank through the DC switch Ks. The energy storage capacitor bank is composed of multiple capacitor monomers from C1, C2 to C n in parallel. Each energy storage capacitor monomer is connected in series with a contactor switch, which are K c1 , K c2 to K cn in sequence. One end of the positive pole of the energy storage capacitor bank is connected in series with multiple series-connected DC reactors from L1, L2 to L n , and then connected in series with one end of the auxiliary switch K H . The other end of the auxiliary switch K H is connected to one end of the DC circuit breaker Q Z . The other end of the DC circuit breaker Q Z is connected to the negative end of the energy storage capacitor bank. Among them, each DC reactor from L1, L2 to L n is connected in parallel with a bypass switch K L1 , K L2 to K Ln ; The controller is used to control the on / off and perform state detection of switches K c1 , K c2 to K cn , K L1 , K L2 to K Ln as well as Ks and K R , and perform on / off control and state detection of the protection circuit breaker Q1, and is used to detect in real time the DC voltage on the energy storage capacitor, the voltage on the measured DC circuit breaker switch, and the current flowing through the measured DC circuit breaker; The design method of the capacitance value C of the energy storage capacitor bank and the parameter L of the DC reactor further includes: 1) Calculate according to the given target value i low and i max to obtain θ low The unit of which is radian; 2) Calculate intermediate variables 3) Calculate intermediate variables 4) Based on the initial value U of the energy storage capacitor C and the line resistance R obtained by pre-detection, calculate the reactor parameters The unit is H; 5) Calculate the energy storage capacitance value The unit is F.

2. The short-circuit current power supply for DC circuit breaker disconnection test according to claim 1, characterized in that: The capacitance values of the individual capacitors in the energy storage capacitor bank are arranged and taken according to a geometric sequence with a common ratio of 2, and / or the inductance values of the DC reactors from L1 and L2 to L n are arranged and taken according to a geometric sequence with a common ratio of 2.

3. The short-circuit current power supply for DC circuit breaker disconnection test according to claim 1, characterized in that: It further includes a protection circuit breaker Q1. One end of the positive pole of the energy storage capacitor bank is connected in series to L through L1 and L2 in sequence via the protection circuit breaker Q1 n for a plurality of series-connected DC reactors.

4. The short-circuit current power supply for DC circuit breaker cutting test according to claim 3, characterized in that: A varistor MOV is connected in parallel at both ends of the protection circuit breaker Q1.

5. The short-circuit current power supply for DC circuit breaker disconnection test according to claim 1, characterized in that: The energy storage capacitor bank is connected in parallel with a resistor Rc, and the resistor Rc is connected in series with a switch K R to discharge the energy storage capacitor bank.

6. The control method of the short-circuit current power supply for DC circuit breaker cut-off test according to any one of claims 1-5, characterized in that, Including: 1) Before the test, control all switches to be in the off state; 2) Control and protect the closing of circuit breaker Q1, control the closing of auxiliary switch K H Close, control the closing of the bypass switches of all reactors, and test the DC resistance R of the line; 3) Disconnect the auxiliary switch k H , according to the rated operating voltage of the DC circuit breaker under test, take the initial discharge voltage U C of the energy storage capacitor to be greater than this rated operating voltage; 4) According to the short-circuit current parameters i low , i max and T Hold , as well as U C and the measured line resistance R, calculate the total capacitance value C of the energy storage capacitor and the total inductance L of the reactor that need to be configured. According to the total capacitance value C of the energy storage capacitor and the total inductance L of the reactor, control the corresponding capacitor monomers and reactors to be put into operation; 5) Close the control switch Ks, start the DC adjustable regulated power supply DCPS, and charge the energy storage capacitor bank in constant current mode until the voltage on the energy storage capacitor reaches the initial discharge voltage U C and then stop charging and disconnect the switch Ks; 6) Control the DC circuit breaker Q under test Z Close the switch, and control to close the auxiliary switch K H So that when the short-circuit current rises to reach the minimum value i required for the cut-off test low At time T Hold During the time period, perform the cut-off performance test on the DC circuit breaker Q under test Z ; 7) During the test of the DC circuit breaker Q under test Z in the test process, the controller collects the line loop current in real time. If an abnormal fault is found, it controls the protection circuit breaker Q1 to trip; 8) After the test is completed, control the discharge branch switch K of the energy storage capacitor R to close it until the voltage across the energy storage capacitor bank is judged to be zero volts, and then control to open K R , and then control all switches to the off state.

7. The control method according to claim 6, wherein The test method of the line DC resistance R further includes: Control the bypass switches of all reactors to be closed, short-circuit the measured DC circuit breaker with a thick wire, and use a high-precision resistance test instrument to measure the line DC resistance R; or Use the external load test function of the DC adjustable regulated power supply DCPS, close Ks, accurately output a constant current, detect the accurate output voltage of the DC adjustable power supply, and obtain the line DC resistance R by using the ratio of the output voltage to the output current.

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