Power grid test system and method

Abstract

The invention provides a power grid test system and method. The power grid test system comprises a switch assembly, a first link and a second link, the resistance / inductive reactance value of the first link is different from the resistance / inductive reactance value of the second link, and the switch assembly is used for selecting one of the first link and the second link to be connected with a power grid; therefore, the power grid test system can be suitable for test requirements of different resistance / inductive reactance values, and when the test requirements of different resistance / inductive reactance values are met, only switching needs to be carried out through the switch assembly, so that the test performance of the power grid test system is improved.

Description

Technical Field

[0001] The present application belongs to the field of power grid technology, and in particular, relates to a power grid testing system and method. Background Art

[0002] In the power system, a weak grid refers to a scenario where the short-circuit capacity of the grid is relatively small and the grid strength is relatively weak. This scenario usually occurs when long-distance power transmission or distributed power sources are connected to the grid. The characteristics of a weak grid will have a significant impact on the stability of the power system and the operating performance of the inverter. Therefore, it is necessary to test the inverter in a weak grid environment.

[0003] In the related art, since the resistance-inductance value of the resistance-inductance component in the power grid test system is a fixed value, when the resistance-inductance value required for the test changes, it is necessary to replace the resistance-inductance component or manually adjust the wiring position to perform the test.

[0004] Therefore, how to improve the test performance of the power grid test system is a problem that those skilled in the art currently need to solve. Summary of the invention

[0005] The purpose of the present application is to provide a power grid testing system and method, aiming to solve the problem of low testing performance of the power grid testing system in traditional technologies.

[0006] A first aspect of an embodiment of the present application provides a power grid testing system, wherein the power grid testing system is used to be arranged between a power grid and a conversion device, and the power grid testing system includes:

[0007] A switch assembly, used for connecting to the power grid;

[0008] a first link, wherein a link start point of the first link is connected to the switch component, and a link end point of the first link is used to connect to the conversion device;

[0009] a second link, wherein a link start point of the second link is connected to the switch component, and a link end point of the second link is used to connect to the conversion device;

[0010] The impedance value of the first link is different from the impedance value of the second link, and / or the inductive reactance value of the first link is different from the inductive reactance value of the second link; the switch component is configured to select one of the first link and the second link to be connected to the power grid.

[0011] In some embodiments of the present application, the first link is used to short-circuit the switch component and the conversion device, and a resistance-inductance component is provided between the link start point and the link end point of the second link;

[0012] The switch component is configured to connect the first link to a strong power grid when the switch component is connected to the strong power grid; and is configured to connect the second link to a weak power grid when the switch component is connected to the weak power grid.

[0013] In some embodiments of the present application, the resistance-inductance component includes a plurality of resistance-inductance elements arranged in series, and the resistance-inductance elements are selected from at least one of resistance and inductance.

[0014] In some embodiments of the present application, the resistance-sensing component includes at least one bypass switch, and at least one of the plurality of resistance-sensing elements is connected in parallel with the bypass switch.

[0015] In some embodiments of the present application, the plurality of resistance-sensing elements include a first resistance-sensing element and a second resistance-sensing element, the first resistance-sensing element is a variable resistance resistor, and the second resistance-sensing element is a variable inductor.

[0016] In some embodiments of the present application, the switch assembly includes:

[0017] a first switch element, wherein the first switch element is provided with an input pin and a plurality of output pins, the input pin is used to connect to the power grid, and the first switch element is configured to select at least one of the plurality of output pins to be connected to the input pin; the plurality of output pins include a first output pin and a second output pin;

[0018] a second switch element, arranged between the first output pin and the first link;

[0019] The third switch is arranged between the second output pin and the second link.

[0020] In some embodiments of the present application, a resistance-inductive component is provided on the second link, and the resistance-inductive component includes a plurality of resistance-inductive elements; the conversion device includes a plurality of converters;

[0021] The power grid testing system comprises a third link, one end of the third link is connected to the switch assembly, and the other end of the third link is connected between the plurality of the resistance-sensing elements on the second link, and the plurality of the resistance-sensing elements are divided into a first sub-link and a second sub-link along a direction from a link start point to a link end point of the second link;

[0022] The first sub-link and the second sub-link are used to connect to different converters.

[0023] In some embodiments of the present application, the resistance-sensing elements on the first sub-link and the second sub-link both include a first resistance-sensing element and a second resistance-sensing element, the first resistance-sensing element is a variable resistance resistor, and the second resistance-sensing element is a variable inductor.

[0024] In some embodiments of the present application, the plurality of output pins further include a third output pin, the switch component further includes a fourth switch element, and the fourth switch element is disposed between the third output pin and the third link.

[0025] In some embodiments of the present application, the switch assembly further includes a fifth switch element, and the fifth switch element is arranged between a link start point of the first link and a link start point of the second link;

[0026] The fifth switch is configured to be closed when the third output pin is conductively connected to the third link, so as to connect the first sub-link to the conversion device.

[0027] In some embodiments of the present application, the switch assembly further includes a sixth switch element, which is disposed between different converters and is configured to be disconnected when the third output pin is conductively connected to the third link.

[0028] A second aspect of the present application further provides a power grid testing method, which is applied to the power grid testing system as described above; the power grid testing method comprises:

[0029] Obtaining a target impedance value or a target inductive reactance value;

[0030] At least one of the first link, the second link, and the third link is switched on or off according to the target impedance value or the target inductance value.

[0031] In some embodiments of the present application, obtaining a target impedance value or a target inductive reactance value includes:

[0032] Obtaining a target short-circuit capacity ratio, and obtaining the target impedance value or the target inductive reactance value according to the target short-circuit capacity ratio;

[0033] Alternatively, the cable parameters between the conversion device and the power grid are acquired, and the impedance value or the target inductive reactance value is obtained according to the cable parameters.

[0034] The beneficial effects of the present application are as follows: in the power grid testing system and method of the present application, the power grid testing system includes a switch component, a first link and a second link; the resistance / inductance value of the first link is different from the resistance / inductance value of the second link, and the switch component is used to select one of the first link and the second link to connect to the power grid; therefore, the power grid testing system in the present application can be suitable for testing needs with different resistance / inductance values, and when dealing with testing needs with different resistance / inductance values, it only needs to switch through the switch component, which is beneficial to improving the testing performance of the power grid testing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the framework structure of a power grid testing system provided in one embodiment of the present application;

[0036] Figure 2 A schematic diagram of the framework structure of a power grid testing system provided in one embodiment of the present application;

[0037] Figure 3 A schematic diagram of the circuit structure of a power grid testing system provided in one embodiment of the present application;

[0038] Figure 4 A schematic diagram of the structure of a resistive-sensing element provided in one embodiment of the present application;

[0039] Figure 5 Another schematic diagram of the structure of a resistive-sensing element provided in one embodiment of the present application;

[0040] Figure 6 A schematic diagram of the structure of a power grid testing system provided in one embodiment of the present application;

[0041] Figure 7 Another structural schematic diagram of a power grid testing system provided in one embodiment of the present application;

[0042] Figure 8 Another structural schematic diagram of a power grid testing system provided in one embodiment of the present application;

[0043] Fig. 9 A further structural schematic diagram of a power grid testing system provided in one embodiment of the present application.

[0044] Explanation of specific element symbols: 100-power grid, 110-strong power grid, 120-weak power grid, 200-switch assembly, 300-first link, 400-second link, 500-conversion device, SW-first switch element, SW1-second switch element, SW2-third switch element, SW3-fourth switch element, SW4-fifth switch element, SW5-sixth switch element, S1-regulating switch, S2-bypass switch. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0046] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0048] It should be noted that in the power system, a weak power grid refers to a power grid structure with relatively small short-circuit capacity and weak overall power grid strength. For example, the end of a long-distance transmission line or the access point where a distributed power source (such as solar and wind power generation facilities) is connected to the power grid. Since the characteristics of the power grid in these scenarios are relatively fragile, they will have a significant impact on the overall stability of the power system and the operating performance of key equipment such as inverters. However, with the continuous increase in the penetration rate of new energy (such as solar and wind energy) worldwide, the widespread application of long and medium-sized transmission lines in power systems, and the complex influence of factors such as transformer leakage inductance, the impedance characteristics of the power grid have begun to show a wide range of variations. After the distributed generation system is connected to the power grid, the current fed into it will produce a significant voltage drop when flowing through the grid impedance, and this voltage drop forms a close coupling relationship with the inverter; therefore, the power grid can no longer be regarded as an ideal power source, but the existence of impedance should be taken into account.

[0049] As one of the most important devices in the power system, the inverter is responsible for converting DC power into AC power and ensuring the stability and efficiency of power supply. Since weak power grids will seriously affect the stability and output quality of inverter operation, the operating performance of the inverter under weak power grids has become one of the important characteristics of the inverter. Therefore, it is necessary to conduct targeted tests on the performance of the inverter under weak power grids during the research and development process.

[0050] However, in existing power grid test systems, the resistance and inductance values ​​of resistance and inductance components are usually fixed. This means that when the resistance and inductance values ​​required for the test change, testers often have to replace components with different resistance and inductance values, or manually adjust the wiring position of the test system to meet the new test requirements. Such operations are not only time-consuming and labor-intensive, but also increase the complexity and uncertainty of the test process, affecting the accuracy and efficiency of the test.

[0051] Based on this, the present application improves the power grid testing system and method in the related art.

[0052] See also Figure 1 , Figure 1 A schematic diagram of the framework structure of the power grid 100 test system of this embodiment is shown; the power grid 100 test system of this embodiment is used to be arranged between the power grid 100 and the conversion device 500.

[0053] It should be explained that the power grid 100 generally refers to a large-scale power transmission and distribution network, which is responsible for transmitting electric energy from power stations to various power consumption points. Exemplarily, the power grid 100 can be divided into a strong power grid 110 and a weak power grid 120. The conversion device 500 is generally used for converting electric energy, such as from high voltage to low voltage, or from direct current to alternating current, to meet the power demand of different devices or systems. Exemplarily, the conversion device 500 can be an inverter or a rectifier.

[0054] Please continue reading Figure 1 In this embodiment, the power grid 100 test system includes a switch component 200, a first link 300 and a second link 400; the switch component 200 is used to connect the power grid 100; the link starting point of the first link 300 is connected to the switch component 200, and the link end point of the first link 300 is used to connect the conversion device 500; the link starting point of the second link 400 is connected to the switch component 200, and the link end point of the second link 400 is used to connect the conversion device 500; wherein, the impedance value of the first link 300 is different from the impedance value of the second link 400, and / or, the inductive reactance value of the first link 300 is different from the inductive reactance value of the second link 400; the switch component 200 is configured to select one of the first link 300 and the second link 400 to connect to the power grid 100.

[0055] It should be explained that the impedance value of the first link 300 is different from the impedance value of the second link 400, which can be understood as the resistance / reactance on the first link 300 is different from the resistance / reactance on the second link 400. The inductive reactance value of the first link 300 is different from the inductive reactance value of the second link 400, which can be understood as the degree of obstruction of the electronic components on the first link 300 and the second link 400 to the passage of alternating current is different.

[0056] It is understandable that the electric energy of the power grid 100 can be transmitted to the conversion device 500 through the first link 300 and the second link 400. The first link 300 and the second link 400 have different inductance / impedance values, and the switch component 200 can select the first link 300 or the second link 400 to transmit electric energy to select the required inductance / impedance value.

[0057] The resistance-inductance values ​​(impedance value and inductance value) of the resistance-inductance components in the current power grid 100 test system are fixed values ​​and cannot adapt to different test needs; however, in the present application, the switch component 200 is used to switch to the first link 300 or the second link 400 for testing, so that the power grid 100 test system can be suitable for testing needs with different resistance / inductance values, and when responding to testing needs with different resistance / inductance values, it is only necessary to switch through the switch component 200, which is beneficial to improving the test performance of the power grid 100 test system.

[0058] In some embodiments of this application, please refer to Figure 2 , Figure 2 The schematic diagram of the framework structure of the power grid 100 test system provided in this embodiment is shown. The first link 300 of this embodiment is used to short-circuit the switch component 200 and the conversion device 500, and a resistance-inductance component is provided between the link start point and the link end point of the second link 400; the switch component 200 is configured to connect the first link 300 to the strong power grid 110 when the switch component 200 is connected to the strong power grid 110; and is configured to connect the second link 400 to the weak power grid 120 when the switch component 200 is connected to the weak power grid 120.

[0059] It should be explained that the resistance-inductance component may include a resistor and an inductor, and the resistor and the inductor together constitute a circuit with a specific impedance value and inductance value.

[0060] It is understandable that the theoretical resistance-inductance value of the first link 300 can be set to 0, that is, even the actual resistance-inductance value on the first link 300 in the actual structure is set to be sufficiently small. In this way, the first link 300 can be used to connect the strong power grid 110 and the conversion device 500 when the power grid 100 is a strong power grid 110. In addition, the resistance-inductance value on the second link 400 is relatively large to meet the testing needs of the weak power grid 120. Therefore, in this embodiment, the first link 300 or the second link 400 can be selectively accessed through the switch assembly 200 to meet the testing needs of the strong power grid 110 or the weak power grid 120.

[0061] In other embodiments, the first link 300 and the second link 400 are both used to connect to the weak power grid 120, and are connected to the weak power grid 120 with different test requirements. The test requirements can be determined according to the target short circuit capacity ratio (SCR) required to be achieved by the weak power grid 120 test or the actual cable parameters from the conversion device 500 to the power grid 100.

[0062] In some embodiments of this application, please refer to Figure 3 , Figure 3 FIG. 1 shows a circuit structure diagram of a power grid 100 test system provided in this embodiment; Figure 3 SALM-1, SALM-2, SAL1-1 and SAL1-2 are resistors, SARN-1, SARN-2, SAR2-1 and SAR2-2 are inductors. The resistance-sensing component of this embodiment includes a plurality of resistance-sensing elements arranged in series, and the resistance-sensing elements are selected from at least one of resistance and inductance.

[0063] In some embodiments, Figure 3 As shown, the resistor and the inductor in the resistive-inductive element are both connected in series.

[0064] In some embodiments of this application, please continue to refer to Figure 3 Also see Figure 4 and Figure 5 , Figure 4 FIG. 4 shows a schematic diagram of the structure of the resistive-sensing element provided in this embodiment. Figure 5 Another structural schematic diagram of the resistance-inductance element provided in this embodiment is shown; the resistance-inductance component of this embodiment includes at least one bypass switch S2, and at least one of the multiple resistance-inductance elements is connected in parallel with the bypass switch S2.

[0065] Specifically, if Figure 4 As shown, if the bypass switch S2 is closed, the current flows through the bypass switch S2, and the inductor is bypassed; if the bypass switch S2 is open, the current can flow through the inductor. Figure 5 As shown, if the bypass switch S2 is closed, the current flows through the bypass switch S2, and the resistor is bypassed; if the bypass switch S2 is open, the current can flow through the resistor. It can be understood that the resistance and inductance of the second link 400 can be adjusted by selectively bypassing one or more resistors and / or inductors.

[0066] In some embodiments, Figure 4 and Figure 5 The inductor / resistor is connected in series with an adjustment switch S1, and the inductor / resistor can be set to three states by controlling the adjustment switch S1 and the bypass switch S2.

[0067] The first state is the disconnected state, at which time the regulating switch S1 and the bypass switch S2 are both disconnected. When the power grid 100 test system is in power-off, standby or strong network mode, the power grid 100 test system needs to access any impedance, so the regulating switch S1 and the bypass switch S2 are both disconnected.

[0068] The second state is the on-state, in which the regulating switch S1 is closed and the bypass switch S2 is disconnected. When the grid 100 test system needs to simulate a weak grid 120 or different cables between parallel machines, impedance needs to be put into operation. In this case, the regulating switch S1 is closed and the bypass switch S2 is disconnected, so that the impedance is in the on-state.

[0069] The third state is the bypass state, in which the regulating switch S1 is disconnected and the bypass switch S2 is closed. When the power grid 100 test system needs to simulate a weak power grid 120 or different cables between parallel machines, but does not need to invest in impedance, or the impedance needs to be bypassed due to a fault, the regulating switch S1 is disconnected and the bypass switch S2 is closed, then the single device will be bypassed and will not be physically connected to the impedance circuit.

[0070] In some embodiments of this application, please continue to refer to Figure 3In this embodiment, the plurality of resistance-sensing elements include a first resistance-sensing element and a second resistance-sensing element, wherein the first resistance-sensing element is a variable resistance resistor and the second resistance-sensing element is a variable inductor. Thus, the impedance value of the second link 400 can be adjusted by adjusting the resistance of the first resistance-sensing element, and similarly, the inductive reactance value of the second link 400 can be adjusted by adjusting the inductance of the second resistance-sensing element.

[0071] In some embodiments, the first resistance-sensing element is a sliding resistor, and the second resistance-sensing element is a sliding resistor.

[0072] In some embodiments, the grid 100 test system can automatically calculate the corresponding impedance value required based on the target short-circuit capacity ratio to be achieved or the actual cable parameters from the inverter to the grid 100. If it is within the upper limit of the impedance capacity, the grid 100 test system can automatically switch on and off after the user confirms the switch on.

[0073] Specifically, taking the conversion device 500 as an inverter as an example, if impedance switching is performed according to the target short-circuit capacity ratio. At this time, the parameters that the user needs to set include the target short-circuit capacity ratio (SCR), the number of inverters, the rated power of the inverter, the voltage of the test grid 100, and the frequency of the grid 100. The grid 100 test system in this embodiment can automatically calculate the required impedance value and automatically match the impedance that can be put into use. The calculation formula for calculating the inductance based on the SCR and the rated capacity is as follows: Among them, P is the rated capacity of the inverter connected to the device, U is the effective value of the rated voltage at the grid-connected point, f is the rated voltage frequency at the grid-connected point, and SCR is the short-circuit capacity ratio.

[0074] Specifically, the cable parameters may include cable length, cable material, number of cable cores, cable model and other related parameters. The power grid 100 test system can store parameters of common power cables, such as the common 4*240mm2 cables of different materials and models and their related parameters. If a common power cable is used, the user only needs to enter the required cable length, and the power grid 100 test system can automatically match the corresponding resistance and inductance value. If a power cable not stored in the power grid 100 test system is used, the user is required to enter the cable material, cross-sectional area, winding method, length and other parameters, and the power grid 100 test system automatically matches the corresponding resistance and inductance value according to the above parameters.

[0075] In some embodiments of this application, please continue to refer to Figure 3The switch assembly 200 of this embodiment includes a first switch element SW, a second switch element SW1 and a third switch element SW2; the first switch element SW is provided with an input pin and a plurality of output pins, the input pin is used to connect to the power grid 100, and the first switch element SW is configured to select at least one of the plurality of output pins to be connected to the input pin; the plurality of output pins include a first output pin and a second output pin; the second switch element SW1 is provided between the first output pin and the first link 300; the third switch element SW2 is provided between the second output pin and the second link 400.

[0076] It can be understood that when it is necessary to test the performance of the conversion device 500 under the condition of the strong power grid 110, the first output pin of the first switch element SW is connected to the input pin, and the second switch element SW1 is closed, so that the first output pin is connected to the first link 300, thereby connecting the conversion device 500 directly or through low impedance to the strong power grid 110. When it is necessary to test the performance of the conversion device 500 under the condition of the weak power grid 120, the second output pin of the first switch element SW is connected to the input pin, and the third switch element SW2 is closed, so that the second output pin is connected to the second link 400, thereby connecting the conversion device 500 to the weak power grid 120 through the resistance-inductance component.

[0077] In some embodiments, the first switch element SW is a rotary adjustment switch S1.

[0078] In some embodiments of this application, please continue to refer to Figure 3 In this embodiment, a resistance-inductive component is provided on the second link 400, and the resistance-inductive component includes a plurality of resistance-inductive elements; the conversion device 500 includes a plurality of converters; the power grid 100 test system includes a third link, one end of the third link is connected to the switch component 200, and the other end is connected between the plurality of resistance-inductive elements on the second link 400, and the plurality of resistance-inductive elements are divided into a first sub-link and a second sub-link along the direction from the link start point to the link end point of the second link 400; wherein the first sub-link and the second sub-link are used to connect to different converters.

[0079] It is understandable that the power grid 100 can be connected to the first converter via the third link and the first sub-link, and can also be connected to the second converter via the third link and the second sub-link, so as to simulate a parallel operation scenario with different cable lengths between different converters.

[0080] In some embodiments, the resistance-inductance value of the first sub-link is different from the resistance-inductance value of the second sub-link.

[0081] In some embodiments of this application, please continue to refer to Figure 3In this embodiment, the resistance-sensing elements on the first sub-link and the second sub-link both include a first resistance-sensing element and a second resistance-sensing element, the first resistance-sensing element is a variable resistance resistor, and the second resistance-sensing element is a variable inductor. In this way, the resistance-sensing values ​​of the first sub-link and the second sub-link can be adjusted to meet different test needs.

[0082] In some embodiments of this application, please continue to refer to Figure 3 In this embodiment, the plurality of output pins further include a third output pin, and the switch component 200 further includes a fourth switch element SW3 , which is disposed between the third output pin and the third link.

[0083] It is understandable that when parallel connection is required, the third output pin can be connected to the input pin, the fourth switch SW3 is closed, and the current of the grid 100 flows along the third link to the first sub-link and the second sub-link.

[0084] In some embodiments of this application, please continue to refer to Figure 3 The switch component 200 of this embodiment also includes a fifth switch element SW4, which is arranged between the link starting point of the first link 300 and the link starting point of the second link 400; the fifth switch element SW4 is configured to be closed when the third output pin is connected to the third link to connect the first sub-link to the conversion device 500.

[0085] It can be understood that when parallel connection is required, the fifth switch SW4 can be closed so that the first sub-link can be directly connected to the conversion device 500, and when parallel connection is not required, the fifth switch SW4 can be disconnected, and the current can flow through the entire second link 400 and then flow to the conversion device 500.

[0086] In some embodiments of this application, please continue to refer to Figure 3 The switch assembly 200 of this embodiment further includes a sixth switch element SW5, which is disposed between different converters and is configured to be disconnected when the third output pin is connected to the third link.

[0087] It is understandable that when parallel connection is required, the sixth switch SW5 can be opened to divide the conversion device 500 into two converters. When parallel connection is not required, the sixth switch SW5 can be closed to integrate all converters in the conversion device 500 for testing.

[0088] In some embodiments of this application, please continue to refer to Figure 3In this embodiment, four inverters can be connected, respectively connected to switches FS1-FS4. The access point of the power grid 100 is at the line port (input pin) of the first switch SW. The supported line voltage levels include 380 / 400 / 440 / 480 / 660 / 690 / 1140V, which can basically meet the weak network test scenario of the mainstream inverter power segment. The power grid 100 can be a simulated power grid 100 or a real power grid 100. The power grid 100 can also be connected to the first switch SW after connecting to the transformer. Without replacing the test inverter, the power grid 100 can also be unchanged. The power grid 100 test system can quickly switch between strong and weak network states without replacing the test device and the inverter terminal, thereby reducing the workload during the test process.

[0089] Specifically, the power grid 100 test system of this embodiment may have four modes, including a power failure mode, a strong network mode, a weak network mode, and a parallel test mode.

[0090] Please continue reading Figure 3 and see Figure 6 , Figure 6 FIG. 1 shows a schematic diagram of the structure of the power grid 100 test system provided in this embodiment; Figure 6 INV is an inverter. In the power-off mode, the first switch element SW is switched to the "0" position, and all input pins and output pins of the first switch element SW are disconnected. At this time, the grid 100 and the inverter are disconnected.

[0091] Please continue reading Figure 3 and see Figure 7 , Figure 7 FIG. 1 shows a schematic diagram of the structure of the power grid 100 test system provided in this embodiment; Figure 7 INV is the inverter. In the strong grid mode, the first switch SW is set to the "1" position. At this time, the second switch SW1 and the sixth switch SW5 are closed, and the third switch SW2, the fourth switch SW3 and the fifth switch SW4 are disconnected. The power grid 100 is directly short-connected to the inverter under the switches FS1-FS4 (corresponding to the first link 300) through the switch assembly 200. That is to say, the internal impedance of the test system of the power grid 100 is in a disconnected state.

[0092] Please continue reading Figure 3 and see Figure 8 , Figure 8 FIG. 1 shows a schematic diagram of the structure of the power grid 100 test system provided in this embodiment; Figure 8INV is the inverter. In the weak grid mode, the first switch SW is switched to the "2" position. At this time, the third switch SW2 and the sixth switch SW5 are closed, the second switch SW1, the fourth switch SW3 and the fifth switch SW4 are disconnected, and the power grid 100 is connected to the inverter under the switches FS1-FS4 (corresponding to the second link 400) through the third switch SW2 and the resistance-inductive element.

[0093] Please continue reading Figure 3 and see Fig. 9 , Fig. 9 FIG. 1 shows a schematic diagram of the structure of the power grid 100 test system provided in this embodiment; Fig. 9 In the figure, INV is the inverter. In the parallel test mode, the first switch SW is set to the "3" position. At this time, the fourth switch SW3 and the fifth switch SW4 are closed, and the second switch SW1, the third switch SW2 and the sixth switch SW5 are disconnected. The power grid 100 is connected to the inverter under the switches FS3 and FS4 through the fourth switch SW3 and the resistance-sensing element on the right (corresponding to the third link and the first sub-link); the power grid 100 is connected to the inverter under the switches FS1 and FS2 through the fourth switch SW3 and the resistance-sensing element on the left (corresponding to the third link and the second sub-link).

[0094] It is understandable that in the parallel test mode, the cable length between the inverters will affect the inverter's circulating current, resonance and other factors. Therefore, simulating different cable lengths between inverters to avoid repeated cable setup is an activity that is often required in inverter testing but has a complicated testing process. In the parallel test mode, the Grid 100 test system can divide the impedance into two parts. The user only needs to set the cable length and cable type from the inverters at both ends to the grid connection point.

[0095] In some embodiments, the inductive reactance value range of the power grid 100 test system of this embodiment is 0-6mH, and can be adjusted in real time according to the test requirements. The inductive elements include 10uH / 20uH / 50uH / 100uH / 200uH and 2 adjustable inductors of up to 10uH per phase.

[0096] In some embodiments, the impedance value range of the power grid 100 test system of this embodiment is 0-4Ω, and the resistance elements include 0.5mΩ / 1mΩ / 2mΩ / 5mΩ / 10mΩ / 20mΩ / 50mΩ / 100mΩ and 2 adjustable resistors with a maximum of 1mΩ per phase.

[0097] In some embodiments, the maximum simulated cable length supported in this embodiment is 8-10km.

[0098] In some embodiments, the resistive and inductive elements in the power grid 100 test system are connected in a cascaded distributed connection manner. In the power grid 100 test system, top air cooling can be used to dissipate heat.

[0099] In some embodiments, the power grid 100 test system can be controlled by local control and / or remote control. Among them, local control can be controlled by a touch screen on the power grid 100 test device. Remote control can be controlled by a host computer, by connecting the computer and the power grid 100 test device with a network cable, and then directly connecting the device through the host computer. Input data viewing, parameter setting, equipment start and stop, switch opening and closing, and alarm query can be performed on the host computer.

[0100] In some embodiments, the communication protocol in the remote control supports Modbus TCP.

[0101] Further, in order to better implement the power grid 100 test system in any of the above embodiments, based on the above power grid 100 test system, this embodiment further provides a power grid 100 test method, which is applied to the above power grid 100 test system; the power grid 100 test method includes:

[0102] S100: Obtain a target impedance value or a target inductive reactance value;

[0103] Specifically, the target impedance value or the target inductive reactance value may be obtained by calculation or may be directly input.

[0104] In some embodiments, the target impedance value or the target inductive reactance value can be calculated according to the target short-circuit capacity ratio as described in the above embodiments, or calculated according to input cable parameters.

[0105] S200: switching on or off at least one of the first link 300 , the second link 400 , and the third link according to the target impedance value or the target inductance value.

[0106] Specifically, when it is necessary to connect to the strong power grid 110, the first link 300 is turned on, and the second link 400 and the third link are disconnected. When it is necessary to connect to the weak power grid 120 and multiple inverters are tested together, the second link 400 is turned on, and the first link 300 and the third link are disconnected. When it is necessary to connect to a weak network and multiple inverters are divided into two groups for parallel testing, the third link is turned on, and the second link 400 is divided into a first sub-link and a second sub-link, and the first sub-link and the second sub-link are connected to inverters of different groups to achieve parallel testing.

[0107] In some embodiments of the present application, step S100 includes: obtaining a target short-circuit capacity ratio, and obtaining a target impedance value or a target inductance value based on the target short-circuit capacity ratio; or, obtaining cable parameters between the conversion device 500 and the power grid 100, and obtaining an impedance value or a target inductance value based on the cable parameters.

[0108] In some embodiments, the cable parameters include cable length, model, number of cores, type, etc.

[0109] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0110] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0111] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0112] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this application, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0113] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A power grid testing system, characterized in that: The power grid testing system is used to be arranged between the power grid and the conversion device, and the power grid testing system includes: A switch assembly, used for connecting to the power grid; a first link, wherein a link start point of the first link is connected to the switch component, and a link end point of the first link is used to connect to the conversion device; a second link, wherein a link start point of the second link is connected to the switch component, and a link end point of the second link is used to connect to the conversion device; The impedance value of the first link is different from the impedance value of the second link, and / or the inductive reactance value of the first link is different from the inductive reactance value of the second link; the switch component is configured to select one of the first link and the second link to be connected to the power grid.

2. The power grid testing system according to claim 1, characterized in that: The first link is used to short-circuit the switch component and the conversion device, and a resistance-inductance component is provided between the link start point and the link end point of the second link; The switch component is configured to connect the first link to a strong power grid when the switch component is connected to the strong power grid; and is configured to connect the second link to a weak power grid when the switch component is connected to the weak power grid.

3. The power grid testing system according to claim 2, characterized in that: The resistance-inductance component includes a plurality of resistance-inductance elements arranged in series, and the resistance-inductance elements are selected from at least one of resistance and inductance.

4. The power grid testing system according to claim 3, characterized in that: The resistance-inductive component includes at least one bypass switch, and at least one of the plurality of resistance-inductive elements is connected in parallel with the bypass switch.

5. The power grid testing system according to claim 3, characterized in that: The plurality of resistance-sensing elements include a first resistance-sensing element and a second resistance-sensing element. The first resistance-sensing element is a variable resistance resistor, and the second resistance-sensing element is a variable inductor.

6. The power grid testing system according to any one of claims 1 to 5, characterized in that: The switch assembly comprises: a first switch element, wherein the first switch element is provided with an input pin and a plurality of output pins, the input pin is used to connect to the power grid, and the first switch element is configured to select at least one of the plurality of output pins to be connected to the input pin; the plurality of output pins include a first output pin and a second output pin; a second switch element, arranged between the first output pin and the first link; The third switch is arranged between the second output pin and the second link.

7. The power grid testing system according to claim 6, characterized in that: The second link is provided with a resistance-inductance component, and the resistance-inductance component includes a plurality of resistance-inductance elements; the conversion device includes a plurality of converters; The power grid testing system comprises a third link, one end of the third link is connected to the switch assembly, and the other end of the third link is connected between the plurality of the resistance-sensing elements on the second link, and the plurality of the resistance-sensing elements are divided into a first sub-link and a second sub-link along a direction from a link start point to a link end point of the second link; The first sub-link and the second sub-link are used to connect to different converters.

8. The power grid testing system according to claim 7, characterized in that: The resistance-sensing elements on the first sub-link and the second sub-link both include a first resistance-sensing element and a second resistance-sensing element. The first resistance-sensing element is a variable resistance resistor, and the second resistance-sensing element is a variable inductor.

9. The power grid testing system according to claim 7, characterized in that: The plurality of output pins further include a third output pin, and the switch assembly further includes a fourth switch element, wherein the fourth switch element is disposed between the third output pin and the third link.

10. The power grid testing system according to claim 9, characterized in that: The switch assembly further includes a fifth switch element, the fifth switch element being arranged between a link start point of the first link and a link start point of the second link; The fifth switch is configured to be closed when the third output pin is conductively connected to the third link, so as to connect the first sub-link to the conversion device.

11. The power grid testing system according to claim 9, characterized in that: The switch assembly further includes a sixth switch element, which is disposed between different converters and is configured to be disconnected when the third output pin is conductively connected to the third link.

12. A power grid testing method, characterized in that: The power grid testing method is applied to the power grid testing system according to any one of claims 1 to 11; the power grid testing method comprises: Obtaining a target impedance value or a target inductive reactance value; At least one of the first link, the second link, and the third link is switched on or off according to the target impedance value or the target inductance value.

13. The power grid testing method according to claim 12, characterized in that: The obtaining of the target impedance value or the target inductive reactance value comprises: Obtaining a target short-circuit capacity ratio, and obtaining the target impedance value or the target inductive reactance value according to the target short-circuit capacity ratio; Alternatively, the cable parameters between the conversion device and the power grid are acquired, and the impedance value or the target inductive reactance value is obtained according to the cable parameters.

Images