Test method and system for verifying selective protection of DC busbar system or device

Abstract

The present invention discloses a test method and system for verifying the selective protection of a DC common bus system or device, the method comprising: determining two adjacent branches in the DC common bus system or device as short-circuit fault branches and selective protection verification branches respectively; using an IGBT full-bridge circuit single-phase upper and lower tubes to directly pass through to create a short-circuit fault to verify the selective protection. The system is used to execute the above method. The present invention has the advantages of simple principle, easy operation, safety and reliability.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of detection of power electrical systems, and in particular to a test method and system for verifying selective protection of a DC common bus system or device. Background Art

[0002] Compared with traditional AC power distribution methods, systems or devices using DC common bus have the advantages of low reactive power consumption, high system efficiency, small overall equipment size and light weight. Therefore, more and more power and electrical systems or devices are beginning to regard DC common bus technology as the development direction of the future power and electrical system field.

[0003] In the DC busbar technology, each grid-connected branch has a high degree of independence from each other, so the DC busbar system or device is required to have a selective protection function, which can timely remove the faulty branch and ensure the continued normal operation of other branches. However, after the system protection function design is completed, it is often faced with the problem of verifying the selective protection function. In addition, the switchgear that can withstand large impact currents is often large and bulky, and it is often difficult to perform short-circuit tests at the operation site of some devices with limited space. Therefore, how to ensure that the test process is safe and reliable, will not harm the operator and the operating equipment, and is convenient for the operator to conduct field verification at the equipment operation site are all issues that the tester needs to consider. Summary of the invention

[0004] The technical problem to be solved by the present invention is: in view of the technical problems existing in the prior art, the present invention provides a test method and system for verifying the selective protection of a DC common bus system or device which has a simple principle, is easy to operate, and is safe and reliable.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A test method for verifying selective protection of a DC common bus system or device, comprising:

[0007] In a DC busbar system or device, two adjacent branches are determined as a short-circuit fault branch and a selective protection verification branch respectively;

[0008] The single-phase upper and lower tubes of the IGBT full-bridge circuit are directly connected to create a short-circuit fault to verify the selective protection.

[0009] As a further improvement of the method of the present invention: the method of using the IGBT full-bridge circuit to directly connect the upper and lower tubes of the single-phase to create a short-circuit fault includes:

[0010] a. Short-circuit the upper tube or lower tube of the selected test short-circuit phase of the IGBT full-bridge circuit;

[0011] b. Shield fault feedback signal;

[0012] c. Send an opening signal to the non-short-circuited pipe in the test short-circuited phase to create a direct-through fault between the upper and lower pipes.

[0013] As a further improvement of the method of the present invention: short-circuiting the upper tube or the lower tube of the selected test short-circuit phase of the IGBT full-bridge circuit is to short-circuit the busbar positive electrode with the selected fault phase output outside the power module, or to connect the busbar negative electrode with the selected fault phase output terminal outside the module.

[0014] As a further improvement of the method of the present invention: the short-circuiting of the upper tube or the lower tube of the selected test short-circuit phase of the IGBT full-bridge circuit is performed by using a short-circuiting tool inside the module.

[0015] As a further improvement of the method of the present invention: the shielding of the fault feedback signal is to shield the tube fault signal fed back by the IGBT on the selected fault phase driving board, to ensure that the start-up instruction will not be unable to be issued due to the tube fault after startup.

[0016] As a further improvement of the method of the present invention: sending an opening signal to the non-short-circuited pipe in the test short-circuited phase to create a direct connection fault between the upper and lower pipes means: sending an opening instruction to the selected faulty phase through a network cable or a WiFi signal in a safe operating area to achieve the purpose of direct connection between the upper and lower pipes.

[0017] As a further improvement of the method of the present invention: the short-circuit fault branch includes a first IGBT full-bridge circuit, and the positive and negative poles on the DC side of the IGBT full-bridge circuit are connected to the positive and negative poles of the DC bus through a first relay protection device.

[0018] As a further improvement of the method of the present invention: the selective protection verification branch includes a second IGBT full-bridge circuit, and the positive and negative poles on the DC side of the second IGBT full-bridge circuit are connected to the positive and negative poles of the DC bus through a second relay protection device.

[0019] As a further improvement of the method of the present invention: the IGBT full-bridge circuits all include a DC side support capacitor and a buffer resistor.

[0020] As a further improvement of the method of the present invention: when verifying the selective protection, one or more of the following methods are adopted:

[0021] A. Determine whether the overcurrent protection action occurs in each branch relay protection device;

[0022] B. Observe the short-circuit current change trend of the fault branch;

[0023] C. Observe the voltage changes of the selective protection verification branch.

[0024] As a further improvement of the method of the present invention: when verifying the selective protection, if only the relay protection device of the short-circuit fault branch is overcurrent-activated while other branches are not protected, and the voltage of the branch verified by the selective protection is never lower than the undervoltage protection threshold value, then it is proved that the DC busbar system or device meets the selective protection requirements.

[0025] The present invention further provides a test system for verifying the selective protection of a DC common bus system or device, comprising:

[0026] The power module is used for the power input / output of the system. It converts the fixed-frequency and fixed-amplitude AC power into the required DC power through four-quadrant rectification, or it can invert the DC power into variable-frequency and variable-amplitude AC power for resistive and inductive loads.

[0027] Fast fuse, used to protect the branch circuit;

[0028] The DC busbar is used for power transfer of the inverter. While receiving the output power from the power supply, it outputs the power in the system to the load.

[0029] Bus tie switch, used for connection between different inverter cabinets, with overcurrent protection function;

[0030] High-voltage differential probe, used to collect voltage waveforms;

[0031] Current probe, used to collect current waveform.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] 1. The test method and system for verifying the selective protection of a DC busbar system or device of the present invention are simple in principle, easy to operate, safe and reliable. They can not only ensure a safe and reliable short-circuit test method, but also verify that the DC busbar system or device meets the requirements of the selective protection function.

[0034] 2. The test method and system for verifying the selective protection of a DC common bus system or device of the present invention fully considers the current difficulty of short-circuit test technology, difficulty in selecting tooling, and limited on-site operating conditions. Local materials are used, and short-circuit tooling is pre-embedded in the module to short-circuit the upper or lower tube of the selected faulty phase; the short-circuit tooling is manufactured using power modules, which is simple, safe, and reliable to operate.

[0035] 3. The present invention verifies the test method and system for selective protection of a DC common bus system or device, shields the tube fault signal received by the driver board from the IGBT to ensure the sending of the opening signal; and uses the upper and lower tubes of a certain phase of the IGBT full-bridge circuit to directly create a branch short circuit to verify the selective protection function. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the process of the present invention.

[0037] Figure 2 It is a schematic diagram of a test system of the present invention in a specific application example.

[0038] Figure 3 It is a schematic diagram of control topology of the present invention in a specific application example.

[0039] Figure 4 It is a short circuit test wiring diagram of the present invention in a specific application example.

[0040] Figure 5 It is a C-phase drive board interface diagram in a specific application example of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] The present invention provides the following description of the components involved. The busbar involved in the present invention refers to a copper busbar or aluminum busbar connecting the main switch in the distribution cabinet and the switches in each branch circuit in the power supply system. The surface is insulated and its main function is to serve as a conductor. The DC common busbar involved in the present invention is mainly used in multi-transmission systems. It can connect multiple groups of power supplies and loads in the intermediate DC link through the DC side of the converter unit, which is beneficial to the rational distribution of system energy and the rational utilization and recovery of renewable energy. The selective protection involved in the present invention refers to the mutual coordination of the action characteristics of two or more protection devices. When a short circuit, grounding or other overcurrent occurs within a specified range, the device specified to act within this range acts to cut off the fault and control the impact of the fault to the minimum range.

[0043] like Figure 1 and Figure 2 As shown, a test method for verifying the selective protection of a DC busbar system or device, the test method comprises:

[0044] In a DC busbar system or device, two adjacent branches are determined as a short-circuit fault branch and a selective protection verification branch respectively;

[0045] The single-phase upper and lower tubes of the IGBT full-bridge circuit are directly connected to create a short-circuit fault to verify the selective protection.

[0046] In a specific application example, the present invention uses an IGBT full-bridge circuit with single-phase upper and lower tubes connected directly to create a short-circuit fault, including:

[0047] a. Short-circuit the upper tube or lower tube of the selected test short-circuit phase of the IGBT full-bridge circuit;

[0048] b. Shield fault feedback signal;

[0049] c. Send an opening signal to the non-short-circuited pipe in the test short-circuited phase to create a direct-through fault between the upper and lower pipes.

[0050] The control topology diagram is as follows Figure 3 shown.

[0051] In specific applications, for the above operation a, short-circuiting the upper tube or lower tube of the selected test short-circuit phase of the IGBT full-bridge circuit can be performed as follows: short-circuiting the positive pole of the busbar with the selected fault phase output outside the power module (such as short-circuiting the upper tube) or connecting the negative pole of the busbar with the selected fault phase output terminal outside the module (such as short-circuiting the lower tube). Similarly, short-circuiting can also be performed inside the module using a short-circuiting tool.

[0052] In specific applications, for the above operation b, the tube fault signal fed back by the IGBT on the selected fault phase driver board can be shielded to ensure that the start-up command cannot be issued due to the tube fault after startup.

[0053] In specific applications, for the above-mentioned operation c, an opening instruction can be issued to the selected faulty phase through a network cable or WiFi signal in a safe operating area to achieve the purpose of direct connection between the upper and lower pipes.

[0054] In a specific application example, the short-circuit fault branch includes a first IGBT full-bridge circuit, and the positive and negative poles of the DC side of the IGBT full-bridge circuit are connected to the positive and negative poles of the DC bus through a first relay protection device.

[0055] In a specific application example, the selective protection verification branch includes a second IGBT full-bridge circuit, and the positive and negative poles of the DC side of the second IGBT full-bridge circuit are connected to the positive and negative poles of the DC bus through a second relay protection device.

[0056] As a preferred embodiment, the first IGBT full-bridge circuit and the second IGBT full-bridge circuit both include a DC side support capacitor and a buffer resistor.

[0057] In specific application examples, when verifying the selective protection, one or more of the following methods may be used:

[0058] A. Determine whether the overcurrent protection action occurs in each branch relay protection device;

[0059] B. Observe the short-circuit current change trend of the fault branch;

[0060] C. Observe the voltage changes of the selective protection verification branch.

[0061] Furthermore, in a specific application example, if the test results show that only the relay protection device of the short-circuit fault branch is overcurrent-activated while other branches are not protected, and the selective protection verifies that the branch voltage is never lower than the undervoltage protection threshold, then it proves that the DC busbar system or device meets the selective protection requirements.

[0062] The present invention uses a specific application to illustrate its main working principle. In this embodiment, its test wiring diagram is as follows Figure 4 As shown in the figure, it is a typical DC common bus system, the intermediate DC nominal voltage is DC1050V, the short-circuit fault branch is selected in the side thrust unit, and the selective protection verification branch is selected in the daily use unit. Both units detect the branch voltage and current.

[0063] The status of each module and important test parameters during the test are shown in Table 1 below.

[0064] Table 1 Parameters of each functional unit in the selective protection verification test

[0065]

[0066]

[0067] It can be seen from the above table that the total capacitance in the test system is 29.5mF, of which the side pusher acts as a short-circuit branch and its 2mF capacitance does not contribute to the melting of the branch fuse.

[0068] Combination Figure 3 It can be seen that the short-circuit control signal is generated by the PC controlling the DCU. The DCU can send the pulse command to the pulse distribution board through the optical fiber. The pulse distribution board controls the IGBT through the driver board using its internal pulse program. In this embodiment, the short-circuit test selects the C phase as the fault phase, short-circuits the lower tube of the C phase through external wiring in advance, and controls the upper tube of the IGBT to close. The schematic diagram of the driver board potential is as follows Figure 5 shown.

[0069] In this embodiment, the points of the A and B phase driver boards do not need to be specially processed. The C phase driver board needs to remove the X2:3 point wiring and short-circuit X2:3 and X2:6 to shield the driver board itself from detecting IGBT tube failures. During the test phase, the Vge voltage of the upper tube IGBT at points X2:4 and X2:6 of the test phase driver board is measured to determine the on / off instructions of the IGBT upper tube.

[0070] The specific test steps of this embodiment are as follows:

[0071] 1. Before the test, short-circuit the two lower tube IGBTs of the C phase of the thrust module using a shorting busbar, and pre-process the driver board (as described above) to shield the fault signal fed back by the detection board;

[0072] 2. After all power modules are in place, Figure 3 Arrange the positions of the medium voltage probe and current probe and connect them to the oscilloscope, correctly set the range, ratio and other parameters of each probe, set the DC bus voltage as the trigger source, and the trigger threshold is 900V;

[0073] 3. Use a multimeter to measure the resistance of each branch fuse and record it;

[0074] 4. After the preparation work is completed, start the generator and the rectifier unit in turn to raise the intermediate voltage of the DC network to DC1050V;

[0075] 5. Send a signal to open the upper tube of phase C of the thrust module to realize direct connection between the upper and lower tubes of the branch module;

[0076] 6. Record test data: including oscilloscope waveform and measured resistance of each branch fuse.

[0077] Test verification results:

[0078] 1. The resistance values ​​of each branch fuse before and after the test are shown in the table below.

[0079] Table 2 Resistance value before and after fast fuse test

[0080] Fuse location Push+ Side Push Daily Use+ Daily use- DC / DC+ DC / DC- Rectification 1+ Resistance before test 0.3 0.2 0.2 0.2 0.2 0.3 0.2 Resistance after test Circuit Breaker Circuit Breaker 0.2 0.2 0.2 0.3 0.2 Fuse location Rectification 1- Rectification 2+ Rectification 2- Inverter 1+ Inverter 1- Inverter 2+ Inversion 2- Resistance before test 0.2 0.2 0.3 0.2 0.2 0.2 0.2 Resistance after test 0.2 0.2 0.3 0.2 0.2 0.2 0.2

[0081] 2. The peak value of the short-circuit fault branch fault current can reach about 10kA;

[0082] 3. During the test, the selective protection verified that the branch voltage never fell below the 600V undervoltage protection threshold.

[0083] Test conclusion: The DC common bus system meets the selective protection requirements.

[0084] The present invention further provides a test system for verifying the selective protection of a DC common bus system or device, comprising:

[0085] Power module 1 is used for power input / output of the system, converting the fixed-frequency and fixed-amplitude AC power into the required DC power through four-quadrant rectification, or converting the DC power into variable-frequency and variable-amplitude AC power through inversion for use by resistive and inductive loads;

[0086] The fast fuse 2 is used to protect the branch where it is located. When a large impact current flows through the branch, it can be quickly blown to prevent the fault area from expanding to the DC bus and other branches;

[0087] DC busbar 3 is used for power transfer of the inverter. While receiving the output power from the power supply, it outputs the power in the system to the load, which facilitates the power distribution of the system.

[0088] The bus tie switch 4 is used to connect different inverter cabinets and has an overcurrent protection function. When a large current flows through the bus tie switch, the bus tie switch will be quickly disconnected to protect other inverters from being affected by the faulty inverter;

[0089] A high voltage differential probe 5, used for collecting voltage waveforms;

[0090] The current probe 6 is used to collect the current waveform.

[0091] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A test method for verifying the selective protection of a DC busbar system or device, characterized in that: include: In a DC busbar system or device, two adjacent branches are determined as a short-circuit fault branch and a selective protection verification branch respectively; The single-phase upper and lower tubes of the IGBT full-bridge circuit are directly connected to create a short-circuit fault to verify the selective protection; The method of using the IGBT full-bridge circuit to directly connect the upper and lower tubes of the single-phase to create a short-circuit fault includes: a. Short-circuit the upper tube or lower tube of the selected test short-circuit phase of the IGBT full-bridge circuit; b. Shield fault feedback signal; c. Send an opening signal to the non-short-circuited pipe in the test short-circuited phase to create a direct-through fault between the upper and lower pipes.

2. The test method for verifying the selective protection of a DC busbar system or device according to claim 1, characterized in that: The short-circuiting of the upper tube or the lower tube of the selected test short-circuit phase of the IGBT full-bridge circuit is to short-circuit the positive electrode of the busbar with the selected fault phase output outside the power module.

3. The test method for verifying the selective protection of a DC busbar system or device according to claim 1, characterized in that: The short-circuiting of the upper tube or the lower tube of the test short-circuit phase selected by the IGBT full-bridge circuit is performed by using a short-circuiting tool inside the module.

4. The test method for verifying the selective protection of a DC busbar system or device according to claim 1, characterized in that: The shielding of the fault feedback signal is to shield the tube fault signal fed back by the IGBT on the selected fault phase driving board, so as to ensure that the start-up instruction cannot be issued due to the tube fault after startup.

5. The test method for verifying the selective protection of a DC busbar system or device according to claim 1, characterized in that: The sending of an opening signal to the non-short-circuited pipe in the test short-circuited phase to create a direct connection fault between the upper and lower pipes means: sending an opening instruction to the selected faulty phase through a network cable or a WiFi signal in a safe operating area to achieve the purpose of direct connection between the upper and lower pipes.

6. The test method for verifying the selective protection of a DC busbar system or device according to any one of claims 1 to 5, characterized in that: The short-circuit fault branch includes a first IGBT full-bridge circuit, and the positive and negative poles on the DC side of the IGBT full-bridge circuit are connected to the positive and negative poles of the DC bus through a first relay protection device.

7. The test method for verifying the selective protection of a DC busbar system or device according to any one of claims 1 to 5, characterized in that: The selective protection verification branch includes a second IGBT full-bridge circuit, and the positive and negative poles on the DC side of the second IGBT full-bridge circuit are connected to the positive and negative poles of the DC bus through a second relay protection device.

8. The test method for verifying the selective protection of a DC busbar system or device according to any one of claims 1 to 5, characterized in that: The IGBT full-bridge circuits all include a DC side support capacitor and a buffer resistor.

9. The test method for verifying the selective protection of a DC busbar system or device according to any one of claims 1 to 5, characterized in that: When verifying selective protection, one or more of the following methods are used: A. Determine whether the overcurrent protection action occurs in each branch relay protection device; B. Observe the short-circuit current change trend of the fault branch; C. Observe the voltage changes of the selective protection verification branch.

10. The test method for verifying the selective protection of a DC busbar system or device according to claim 9, characterized in that: When verifying the selective protection, if only the relay protection device of the short-circuit fault branch is overcurrent-activated while other branches are not protected, and the voltage of the branch verified by the selective protection is never lower than the undervoltage protection threshold, it proves that the DC busbar system or device meets the selective protection requirements.

11. A test system for implementing any test method of claims 1-10, characterized in that: include: The power module (1) is used for the power input / output of the system, converting the fixed-frequency and fixed-amplitude AC power into the required DC power through four-quadrant rectification, or converting the DC power into variable-frequency and variable-amplitude AC power through inversion for use by resistive and inductive loads; A fast fuse (2), used for protecting the branch circuit; The DC busbar (3) is used for power transfer of the inverter, and outputs the power in the system to the load while receiving the output power from the power supply; A busbar switch (4), used for connecting different inverter cabinets, and having an overcurrent protection function; A high voltage differential probe (5), used for collecting voltage waveforms; The current probe (6) is used to collect the current waveform.

Images