Direct current inner feedback test method for micro-grid or energy storage device test

Abstract

The present application relates to a kind of direct current inner feedback test methods for micro-grid or energy storage device test, by direct current bus and AC-DC bidirectional converter simulator, energy is flowed through loop when charging and discharging test is carried out to micro-grid or energy storage device, grid only needs to supplement AC-DC bidirectional converter simulator and the self loss of test equipment, improve the utilization of energy;Compared with traditional test scheme, this technology does not need additional battery auxiliary, reduces the construction cost of test system;Test system is isolated to grid in the test process, and will not pollute the grid, reliably guarantee the safety of grid;Using direct current inner feedback technology, main power is limited between test end equipment, reduces the requirement of external grid, not only can greatly save the investment of test system, also makes it possible to build large-capacity test system under general grid condition, provides greater room for equipment inspection, technical development verification and other aspects.

Description

Technical Field

[0001] This invention relates to a testing technique, and more particularly to a DC internal feedback test method for testing microgrids or energy storage devices. Background Technology

[0002] Generally, the rated power of microgrid equipment is at least several hundred kilowatts. In order to ensure that these devices can operate normally after being connected to the grid, they must be subjected to full-function tests at a power level no less than the rated power. This is to prevent such high-power devices from impacting the power system due to equipment issues after being connected to the grid.

[0003] In traditional experimental methods, such as Figure 1 The charging test path shown illustrates that during the charging test, contactors K1 and K2 are turned on, and the power grid needs to provide all the energy, including the rated power of the tested energy storage converter and the energy storage system losses. During the discharging test, as in the discharging test path, contactor K1 is turned off, and contactors K2 and K3 are turned on. All the energy within the energy storage system needs to be consumed by the test load. For a typical 500kW energy storage converter test, one cycle takes approximately 4 hours (2 hours of charging test + 2 hours of discharging test). Generally, about 4 cycles are required. Thus, the energy consumption alone (without considering system losses) is 8 hours × 500kW = 4000kWh, resulting in high test costs. Furthermore, factors such as distribution capacity, operating costs, and grid pollution control must also be considered. Summary of the Invention

[0004] To address the issue of high energy consumption during testing of microgrid equipment connected to the power grid, a DC internal feedback test method for testing microgrids or energy storage devices is proposed.

[0005] The technical solution of the present invention is: a DC internal feedback test method for testing microgrids or energy storage devices, wherein a DC bus is established at the test end, and the AC grid is connected to the DC bus through a series isolation transformer, contactor and rectifier equipment, and the AC grid provides the DC bus with electrical energy at the test end;

[0006] The DC bus is connected to the DC internal feedback test system. When the DC internal feedback test system is conducting a charging test, the AC / DC bidirectional conversion simulator absorbs the DC energy output from the converter under test from the DC bus as a simulated power source and converts it into the AC power signal required by the converter under test for the converter under test to use. The converter under test converts the power signal into DC power and injects it into the shared DC bus.

[0007] When the DC internal feedback test system is conducting a discharge test, the tested converter absorbs energy from the DC bus and converts it into AC power signal. The AC / DC bidirectional conversion simulator, as an electronic load, absorbs energy from the AC side of the tested converter and converts it into DC energy to continuously replenish the DC bus.

[0008] Furthermore, the DC bus serves as a connection channel between the converter under test and the DC side of the AC / DC bidirectional conversion simulator, and only provides the internal power consumption of the converter under test and the AC / DC bidirectional conversion simulator during operation.

[0009] Furthermore, when the AC / DC bidirectional conversion simulator acts as a power source for the power grid, it absorbs energy from the DC bus and controls the response characteristics of the simulated AC power grid under various conditions by the control unit, thus establishing a virtual power grid to test the working status and response parameters of the tested converter equipment after it is connected to the power grid.

[0010] Furthermore, when the AC / DC bidirectional converter simulator is used as an electronic load, it operates in a controllable rectification mode, absorbing energy from the AC side of the converter under test. The load size is adjusted by controlling the conduction state of the rectifier circuit to form a controllable load for the converter under test, so as to test the response characteristics of the converter under test under different load conditions.

[0011] The beneficial effects of this invention are as follows: The DC internal feedback test method for testing microgrids or energy storage devices limits the main power between devices within the test system, reducing the requirements of the external power grid. This not only greatly saves investment in the test system, but also makes it possible to build a large-capacity test system under general power grid conditions, providing greater flexibility for equipment inspection, technology development and verification, etc. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the functional test of energy storage devices in a traditional microgrid;

[0013] Figure 2 This is a diagram of the DC internal feedback test system for testing microgrids or energy storage devices according to the present invention. Detailed Implementation

[0014] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0015] This invention incorporates a simulated load based on power electronics technology in a DC internal feedback test system for microgrid or energy storage device testing. This device can also be used as a simulated power supply for the power grid. The specific structure is as follows: Figure 2As shown, the AC power grid is connected to the DC bus via an isolation transformer, contactor K1, and rectifier connected in series. The DC internal feedback loop unit consists of an AC / DC bidirectional conversion simulator, contactor K2, contactor K3, and the converter under test connected in series. The DC side of the AC / DC bidirectional conversion simulator and the converter under test is connected to the DC bus.

[0016] An AC / DC bidirectional converter simulator was set up in the test system. This simulator, based on power electronics technology, can be used as either a simulated power supply or an electronic load. The DC side of the converter under test is connected to the DC side of the simulated power supply in a loop via a DC bus, thus forming the basic structure of "DC internal feedback".

[0017] The AC / DC bidirectional converter simulator in this system is essentially a power electronic device that can realize AC / DC bidirectional conversion. The AC / DC bidirectional converter simulator is composed of a three-phase bridge inverter circuit with IGBTs as switching devices, along with drive, acquisition, and control modules.

[0018] When used as a power grid simulation power source, the AC / DC bidirectional converter simulator absorbs energy from the DC bus and controls the response characteristics of the simulated AC power grid under various conditions by the control unit, establishing a virtual power grid to test the operating status and response parameters of the tested converter equipment after it is connected to the power grid. When used as an electronic load, the AC / DC bidirectional converter simulator operates in controlled rectification mode, absorbing energy from the AC side of the tested converter. The load size is adjusted by controlling the conduction state of the rectifier circuit to form a controllable load for the tested converter, so as to test the response characteristics of the tested converter under different load conditions.

[0019] During the charging test ( Figure 2 In the charging path (loop direction), the AC / DC bidirectional conversion simulator acts as a simulated power source, absorbing DC energy from the DC bus output by the converter under test and converting it into AC power signals required by the converter under test for its use. The converter under test performs work from the power signals and converts them into DC power, which is then injected into the shared DC bus. The energy lost in the process is converted back into DC power by a controllable rectifier device from the external AC power grid and replenished to the shared DC bus.

[0020] During the discharge test ( Figure 2 In the discharge path (loop direction), the tested converter absorbs energy from the DC bus and converts it into AC power signal. At this time, the AC / DC bidirectional conversion simulator, as an electronic load, absorbs energy from the AC side of the tested converter (to serve as the load of the tested converter) and converts it into DC energy to continuously replenish the DC bus.

[0021] Because energy flows through a loop in both charging and discharging test modes, the power grid only needs to compensate for the losses of the AC / DC bidirectional converter simulator and the converter under test, improving energy utilization (generally only 15% of the required test capacity). This significantly reduces energy loss during testing and lowers equipment operating costs. Compared to traditional testing methods, this technology requires no additional battery assistance, reducing the cost of building the test system. The test system isolates the power grid during testing, preventing grid pollution and reliably ensuring grid safety. Generally, load testing environments have high power requirements, but the power grid support within the test site is limited, making it difficult to build large-capacity test systems. By employing DC internal feedback technology, the main power is limited to the equipment within the test site, reducing the requirements of the external power grid. This not only significantly saves on test system investment but also makes it possible to build large-capacity test systems under general power grid conditions, providing greater flexibility for equipment inspection and technology development verification.

[0022] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A DC inner feedback test method for micro-grid or energy storage device test, characterized in that, The DC bus is established at the test end, and the AC power grid is connected with the DC bus through a series isolation transformer, a contactor K1 and a rectifier device, and the AC power grid supplies the test end with electric energy; The DC bus is connected with a DC internal feedback test system, which is composed of a bidirectional AC / DC converter simulator, a contactor K2, a contactor K3 and the tested converter in series, and the DC bus is connected with the DC side of the bidirectional AC / DC converter simulator and the tested converter, when the DC internal feedback test system performs a charging test, the bidirectional AC / DC converter simulator absorbs the DC energy output by the tested converter from the DC bus and converts the DC energy into an AC power signal required by the tested converter to supply the tested converter, and the tested converter converts the AC power signal into DC power to inject into the shared DC bus; When the DC internal feedback test system performs a discharging test, the tested converter absorbs energy from the DC bus and converts the energy into an AC power signal, and the bidirectional AC / DC converter simulator absorbs the energy from the AC side of the tested converter and converts the energy into DC energy to continuously supplement the DC bus; When the bidirectional AC / DC converter simulator is used as a grid simulation power source, the bidirectional AC / DC converter simulator absorbs energy from the DC bus, and a control unit controls the response characteristics of the simulated AC grid in various states to establish a virtual grid for testing the working state and response parameters of the tested converter when the converter is connected to the grid. When the bidirectional AC / DC converter simulator is used as an electronic load, the bidirectional AC / DC converter simulator works in a controllable rectification mode, absorbs energy from the AC side of the tested converter, adjusts the load size by controlling the conduction state of the rectification circuit, forms a controllable load of the tested converter, and tests the response characteristics of the tested converter under different load conditions.

2. The DC internal feedback test method for micro-grid or energy storage device test according to claim 1, characterized in that, The DC bus is used as a communication channel for the DC sides of the tested converter and the bidirectional AC / DC converter simulator, and only provides the working internal consumption energy of the tested converter and the bidirectional AC / DC converter simulator.

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