A DC energy-consuming valve current-carrying test circuit and method

Abstract

The present invention relates to a through-flow test circuit for a DC energy-consuming valve and a test method for the through-flow test circuit of the DC energy-consuming valve. The test circuit includes a voltage source, a first isolation valve, a current-limiting resistor, a test valve, a second isolation valve, an auxiliary valve, and a current source. By providing the through-flow test circuit and method for the DC energy-consuming valve, electrical stress equivalent to the actual working conditions is provided for the DC energy-consuming valve to achieve the purpose of assessing its through-flow performance.

Description

Technical Field

[0001] The present invention relates to the field of high-power power electronics, and particularly to a direct-current energy-consuming valve current-carrying test device and method. Background Art

[0002] In a system for transmitting offshore wind power through a flexible direct-current (DC) transmission system, an offshore converter station generally operates in an island mode. The converter station is responsible for controlling the AC voltage, and the power flowing into the flexible DC system is determined by the output power of the wind farm. When a fault occurs in the onshore converter station or the receiving-end AC grid, the power sent out by the wind farm cannot be consumed in time, resulting in the input power of the DC system being greater than the output power. This will inevitably cause the DC voltage to continuously rise, endangering the safety of the system. The DC energy-consuming device is connected in parallel with the DC bus. When the above situation occurs, the surplus power during the grid fault can be discharged through the DC energy-consuming device to assist the system in crossing the fault.

[0003] The core device in the DC energy-consuming device is the DC energy-consuming valve. One technical route is to use MMC sub-modules connected in series to form the DC energy-consuming valve. Although the DC energy-consuming valve uses MMC sub-modules, its actual working conditions are very different from those of the MMC, and the test standard IEC 62501 for flexible DC converter valves cannot be directly applied to test the DC energy-consuming valve. When the above-mentioned fault occurs, the DC energy-consuming valve consumes the surplus power of the system and will bear the corresponding voltage and current stresses. Summary of the Invention

[0004] Based on the above situation of the prior art, in order to evaluate the electrical tolerance of the DC energy-consuming valve under different energy-consuming conditions, the present invention provides a parameter-adjustable and easy-to-implement solution. The present invention provides a DC energy-consuming valve current-carrying test circuit and method to provide electrical stress equivalent to the actual working conditions for the DC energy-consuming valve, so as to achieve the purpose of evaluating its current-carrying performance.

[0005] To achieve the above object, according to one aspect of the present invention, a DC energy-consuming valve current-carrying test circuit is provided, including: a voltage source, a first isolation valve 1, a current-limiting resistor R, a test valve, a second isolation valve 2, an auxiliary valve, and a current source; wherein, the voltage source is connected in series with the first isolation valve 1, the current-limiting resistor R, and the test valve; the second isolation valve 2 is connected in series with the auxiliary valve and then connected in parallel with the test valve, and the current source is connected in parallel with the auxiliary valve.

[0006] Further, the positive pole of the voltage source is connected to the anode of the first isolation valve 1, the cathode of the first isolation valve 1 is connected to one end of the current-limiting resistor R, the positive pole of the test valve is connected to the other end of the current-limiting resistor R, and the negative pole of the test valve is connected to the negative pole of the voltage source and then grounded.

[0007] Further, the cathode of the second isolation valve 2 is connected to the positive pole of the test valve, the anode of the second isolation valve 2 is connected to the positive pole of the auxiliary valve, and the negative pole of the auxiliary valve is connected to the negative pole of the test valve.

[0008] Further, the positive pole of the current source is connected to the positive pole of the auxiliary valve, and the negative pole of the current source is connected to the negative pole of the auxiliary valve.

[0009] Further, the current source is a DC current source, the voltage source is a DC voltage source, and the outputs of the current source and the voltage source are adjustable.

[0010] Further, the test valve is composed of n MMC half-bridge sub-modules connected in series. The half-bridge sub-module includes a capacitor C, a first IGBT T1 and a first diode D1 anti-parallel to the first IGBT T1, a second IGBT T2 and a second diode D2 anti-parallel to the second IGBT T2. The first IGBT T1 and the second IGBT T2 are connected in series and then connected in parallel with the capacitor C. The connection point between the first IGBT T1 and the second IGBT T2 is the positive pole, and the other end of the second IGBT T2 is the negative pole. The positive pole of the phase unit is consistent with the positive pole of the sub-module, and the negative pole of the phase unit is consistent with the negative pole of the sub-module.

[0011] Further, n is a natural number greater than or equal to 5.

[0012] Further, the auxiliary valve is a fully controlled switch, and the first isolation valve 1 and the second isolation valve 2 are semi-controlled switches.

[0013] According to another aspect of the present invention, the present invention provides a test method for a DC energy-consuming valve current-carrying test circuit, including the following steps:

[0014] (1) Turn on the auxiliary valve, start the current source and adjust the output current of the current source to reach the test requirement value;

[0015] (2) Start the voltage source and charge the test valve to the test requirement value;

[0016] (3) Block the voltage source;

[0017] (4) Turn on the second IGBT (T2) in all sub-modules of the test valve, turn off the auxiliary valve, so that the test current transfers from the auxiliary valve to the test valve;

[0018] (5) Turn off the second IGBT (T2) in all sub-modules of the test valve, turn on the auxiliary valve, so that the test current transfers from the test valve to the auxiliary valve;

[0019] (6) Repeat steps (4) and (5) according to the switching frequency required by the test, and continue the test for the required time until the test ends.

[0020] In summary, the present invention provides a DC energy-consuming valve current-carrying test circuit composed of a voltage source, a first isolation valve, a current-limiting resistor, a test valve, a second isolation valve, an auxiliary valve, and a current source, as well as a test method for the DC energy-consuming valve current-carrying test circuit.

[0021] The present invention has the following beneficial technical effects:

[0022] (1) The combined operation of the voltage source and the current source provides the electrical stress required by the test for the test valve, greatly reducing the demand for the test power supply capacity and the test cost.

[0023] (2) The outputs of the voltage source and the current source are adjustable to meet the different current-carrying test requirements of the DC energy-consuming valve.

[0024] (3) When the voltage source is working, the second isolation valve bears high voltage to protect the current source; when the current source is working, the first isolation valve isolates the voltage source to protect the current source. Description of the Drawings

[0025] Figure 1 is the circuit diagram of the DC energy-consuming valve current-carrying test of the present invention;

[0026] Figure 2 is the electrical schematic diagram of the half-bridge sub-module of the present invention;

[0027] Figure 3 is the flowchart of the DC energy-consuming valve current-carrying test method of the present invention;

[0028] Figure 4 is the commutation control diagram of the test valve and the auxiliary valve in the DC energy-consuming valve current-carrying test of the present invention. Detailed Embodiments

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0030] The present invention provides a DC energy-consuming valve current-carrying test circuit composed of a voltage source, a first isolation valve, a current-limiting resistor, a test valve, a second isolation valve, an auxiliary valve, and a current source, as well as a test method for the DC energy-consuming valve current-carrying test circuit.

[0031] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. The present invention provides a DC energy-consuming valve through-flow test circuit, as Figure 1 shown. The DC energy-consuming valve through-flow test circuit includes: a voltage source, a first isolation valve 1, a current-limiting resistor R, a test valve, a second isolation valve 2, an auxiliary valve, and a current source. Among them, the voltage source is a DC voltage source with adjustable output, which is used to charge the test valve and provide a test voltage; the current source is a DC current source, which is adjustable and used to provide a test current for the test valve.

[0032] Among them, the DC voltage source is connected in series with the first isolation valve 1, the current-limiting resistor R, and the test valve. The positive pole of the DC voltage source is connected to the anode of the first isolation valve 1, the cathode of the first isolation valve 1 is connected to one end of the current-limiting resistor R, the positive pole of the test valve is connected to the current-limiting resistor R, and the negative pole of the test valve is connected to the negative pole of the DC voltage source and then grounded; the second isolation valve 2 is connected in series with the auxiliary valve and then connected in parallel with the test valve. The cathode of the second isolation valve 2 is connected to the positive pole of the test valve, the anode of the second isolation valve 2 is connected to the positive pole of the auxiliary valve, and the negative pole of the auxiliary valve is connected to the negative pole of the test valve; the DC current source is connected in parallel with the auxiliary valve, the positive pole of the DC current source is connected to the positive pole of the auxiliary valve, and the negative pole of the DC current source is connected to the negative pole of the auxiliary valve.

[0033] The test valve is composed of n MMC half-bridge sub-modules connected in series. In an optional embodiment, the half-bridge sub-module includes a capacitor C, a first IGBT T1 and a first diode D1 anti-parallel to the first IGBT T1, a second IGBT T2 and a second diode D2 anti-parallel to the second IGBT T2; wherein the first IGBT T1 and the second IGBT T2 are connected in series and then connected in parallel with the capacitor C. The connection point between the first IGBT T1 and the second IGBT T2 is the positive pole, and the other end of the second IGBT T2 is the negative pole. The positive pole of the phase unit is the same as the positive pole of the sub-module, the negative pole of the phase unit is the same as the negative pole of the sub-module, and the circuit schematic diagram of the sub-module is as Figure 2 shown. When the first IGBT T1 is turned on and the second IGBT T2 is turned off, the sub-module is in the input state; when the second IGBT T2 is turned on and the first IGBT T1 is turned off, the sub-module is in the cut-off state.

[0034] In another optional embodiment of the present invention, a method for testing the over-current turn-off of the MMC valve IGBT is also provided, which can be used for the commutation valve over-current turn-off test circuit. The flow chart of this test method is as Figure 3 shown, and specifically includes the following steps:

[0035] Step 1: Turn on the auxiliary valve, start the current source and adjust the output current of the current source to reach the test requirement value;

[0036] Step 2: Start the voltage source and charge the test valve to the test requirement value;

[0037] Step 3: Block the voltage source;

[0038] Step 4: Turn on the second IGBT T2 in all sub-modules of the test valve, turn off the auxiliary valve, so that the test current transfers from the auxiliary valve to the test valve;

[0039] Step 5: Turn off the second IGBT T2 in all sub-modules of the test valve, turn on the auxiliary valve, so that the test current transfers from the test valve to the auxiliary valve;

[0040] Step 6: Repeat steps 4 and 5 according to the switching frequency required by the test, and continue for the test required time, and the test ends.

[0041] Specifically, after the test starts, first turn on the auxiliary valve and start the current source, and adjust the current source so that the output current of the current source reaches the test requirement; then start the voltage source to charge the test valve, and control it according to a predetermined voltage equalization strategy during the charging process of the test valve; during the operation of the voltage source, due to the existence of the second isolation valve 2, the current source is protected from high voltage intrusion; after the test valve is charged, block the voltage source and the test valve, and then control the second IGBT T2 in the test valve to turn on according to the predetermined commutation timing, block the auxiliary valve, so that the current source current commutes from the auxiliary valve to the test valve to form a test current. After the test valve conducts current for a certain time, turn on the auxiliary valve and block the test valve, so that the current source current commutes from the test valve to the auxiliary valve. During the above commutation process, in order to ensure a smooth load switching of the current source, there must be a certain overlap time Δt for the opening and closing of the auxiliary valve and the test valve, as Figure 4 shown. Repeat the above current conduction process according to the required switching frequency and continue for the test-specified time to complete the current conduction test of the DC energy-consuming valve.

[0042] In summary, the present invention relates to a current conduction test circuit for a DC energy-consuming valve, including a voltage source, a first isolation valve, a current-limiting resistor, a test valve, a second isolation valve, an auxiliary valve and a current source. And a method for testing the over-current turn-off of the MMC valve IGBT, which can be used for the over-current turn-off test circuit of the energy-consuming valve, provides an electrical stress equivalent to the actual working condition for the DC energy-consuming valve to achieve the purpose of evaluating its current conduction performance. And it has the following beneficial technical effects:

[0043] (1) The combined operation of the voltage source and the current source is used to provide the electrical stress required by the test for the test valve, which greatly reduces the demand for the capacity of the test power supply and reduces the test cost.

[0044] (2) The outputs of the voltage source and the current source are adjustable to meet the different current-carrying test requirements of the DC energy-consuming valve.

[0045] (3) When the voltage source is working, the second isolation valve bears high voltage to protect the current source; when the current source is working, the first isolation valve isolates the voltage source to protect the current source.

[0046] It should be understood that the above specific embodiments of the present invention are only used for exemplary illustration or explanation of the principle of the present invention, and do not constitute a limitation to the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present invention shall be included within the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all variations and modifications that fall within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A test method for a current-carrying test circuit of a DC energy-consuming valve, characterized in that, the current-carrying test circuit of the DC energy-consuming valve includes: a voltage source, a first isolation valve (1), a current-limiting resistor (R), a test valve, a second isolation valve (2), an auxiliary valve, and a current source; wherein, the voltage source is connected in series with the first isolation valve (1), the current-limiting resistor, and the test valve; the second isolation valve (2) is connected in series with the auxiliary valve and then connected in parallel with the test valve, and the current source is connected in parallel with the auxiliary valve; the test valve is composed of n MMC half-bridge sub-modules connected in series, and the half-bridge sub-module includes a first IGBT and a second IGBT connected in series; the test method includes the steps of: (1) Turn on the auxiliary valve, start the current source and adjust the output current of the current source to reach the test requirement value; (2) Start the voltage source and charge the test valve to the test requirement value; (3) Block the voltage source; (4) Turn on the second IGBT (T2) in all sub-modules of the test valve, turn off the auxiliary valve, so that the test current transfers from the auxiliary valve to the test valve; (5) Turn off the second IGBT (T2) in all sub-modules of the test valve, turn on the auxiliary valve, so that the test current transfers from the test valve to the auxiliary valve; (6) Repeat steps (4) and (5) according to the switching frequency required by the test, and continue for the test required time, and the test ends.

2. The test method according to claim 1, characterized in that, the positive pole of the voltage source is connected to the anode of the first isolation valve (1), the cathode of the first isolation valve (1) is connected to one end of the current-limiting resistor (R), the positive pole of the test valve is connected to the other end of the current-limiting resistor (R), and the negative pole of the test valve is connected to the negative pole of the voltage source and then grounded.

3. The test method according to claim 1, characterized in that, the cathode of the second isolation valve (2) is connected to the positive pole of the test valve, the anode of the second isolation valve (2) is connected to the positive pole of the auxiliary valve, and the negative pole of the auxiliary valve is connected to the negative pole of the test valve.

4. The test method according to claim 1, characterized in that, the positive pole of the current source is connected to the positive pole of the auxiliary valve, and the negative pole of the current source is connected to the negative pole of the auxiliary valve.

5. The test method according to claim 1, characterized in that, the current source is a DC current source, the voltage source is a DC voltage source, and the current source and the voltage source are adjustable.

6. The test method according to claim 1, characterized in that, The half-bridge sub-module further includes a capacitor (C), a first diode (D1) anti-parallel to the first IGBT (T1), and a second diode (D2) anti-parallel to the second IGBT (T2); wherein the first IGBT (T1) and the second IGBT (T2) are connected in series and then connected in parallel with the capacitor (C), the connection point between the first IGBT (T1) and the second IGBT (T2) is the positive pole, the other end of the second IGBT (T2) is the negative pole, the positive pole of the phase unit is the same as the positive pole of the sub-module, and the negative pole of the phase unit is the same as the negative pole of the sub-module.

7. The test method according to claim 6, characterized in that, the n is a natural number greater than or equal to 5.

8. The test method according to claim 1, characterized in that, the auxiliary valve is a fully controlled switch, and the first isolation valve (1) and the second isolation valve (2) are semi-controlled switches.

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