Test current generating device of converter grid-connected cabinet

Abstract

The utility model discloses a test current generating device of a converter grid-connected cabinet, and relates to the technical field of power electronics. The test current generating device of the converter grid-connected cabinet comprises an alternating current source and a transformer, wherein the input end of the alternating current source is configured as the input end of the test current generating device, and the output end of the alternating current source is connected with the primary winding of the transformer; a secondary winding of the transformer is configured as an output end of the test current generating device and is connected with a machine side of the converter grid-connected cabinet; the number of turns of the primary winding is N times that of the secondary winding, so that the voltage output by the alternating current source can be reduced to 1 / N through the transformer; due to energy conservation, under the condition that loss is ignored, the current output by the alternating current source can be expanded to N times through the transformer and then serves as the test current, namely, the amplitude of the test current received by the converter grid-connected cabinet can be improved, and then the large-current test requirement exceeding the set capacity of the alternating current source can be met.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a test current generating device for a converter grid-connected cabinet. Background Technology

[0002] Converters, such as wind power converters, are usually connected to the power grid through grid-connected cabinets. As the power level of their application systems gradually increases, the rated current on the grid-connected cabinet connected to the converter side is also constantly increasing. However, the ever-increasing current level also puts forward higher requirements for the testing equipment of the grid-connected cabinet. Traditional current source testing equipment is limited by its own design capacity and cannot meet the high current testing needs that exceed its set capacity. Utility Model Content

[0003] In view of the above problems, this application provides a test current generating device for a converter grid-connected cabinet to improve the amplitude of the test current. The specific solution is as follows:

[0004] The first aspect of this application provides a test current generating device for a converter grid-connected cabinet, comprising: an AC source and a transformer; wherein,

[0005] The input terminal of the AC source is configured as the input terminal of the test current generating device;

[0006] The output terminal of the AC source is connected to the primary winding of the transformer;

[0007] The secondary winding of the transformer is configured as the output terminal of the test current generating device and is used to connect to the machine side of the converter grid-connected cabinet.

[0008] In the transformer, the number of turns in the primary winding is N times the number of turns in the secondary winding; N is a positive number greater than 1.

[0009] In one possible implementation, the AC source includes at least one power conversion circuit;

[0010] The input terminal of the power conversion circuit is configured as the input terminal of the AC source, and the output terminal of the power conversion circuit is configured as the output terminal of the AC source.

[0011] When the number of power conversion circuits is greater than 1, the two sides of each power conversion circuit are connected in parallel.

[0012] In one possible implementation, the test current generating device further includes: a current sensor and a driving circuit;

[0013] The current sensor is disposed at the output terminal of the test current generating device;

[0014] The output terminal of the current sensor is used to connect to the input terminal of the control device;

[0015] The input terminal of the drive circuit is used to connect to the output terminal of the controller;

[0016] The output terminal of the drive circuit is connected to the control terminal of the power conversion circuit.

[0017] In one possible implementation, the test current generating device further includes: a controller;

[0018] The controller is configured as the control device.

[0019] In one possible implementation, the controller's communication or setting terminal receives: an input command for the amplitude of the test current;

[0020] And / or, the communication terminal or setting terminal of the controller receives: the frequency input command of the test current.

[0021] In one possible implementation, the power conversion circuit includes: a DC / AC conversion circuit;

[0022] The DC side of the DC / AC conversion circuit is configured as the input terminal of the power conversion circuit;

[0023] The AC side of the DC / AC conversion circuit is configured as the output terminal of the power conversion circuit.

[0024] In one possible implementation, the test current generating device further includes: a DC source connected to the DC side of the DC / AC conversion circuit;

[0025] Alternatively, the test current generating device may further include: a rectifier, wherein the AC side of the rectifier receives AC power, and the DC side of the rectifier is connected to the DC side of the DC / AC conversion circuit.

[0026] In one possible implementation, the power conversion circuit includes: an AC / AC conversion circuit;

[0027] The first side of the AC / AC conversion circuit is configured as the input terminal of the power conversion circuit;

[0028] The second side of the AC / AC conversion circuit is configured as the output terminal of the power conversion circuit.

[0029] In one possible implementation, the test current generating device further includes: a capacitor;

[0030] The capacitor is located at the input terminal of the AC source.

[0031] In one possible implementation, the test current generating device further includes a filter circuit;

[0032] The filter circuit is located between the output terminal of the AC source and the primary winding of the transformer.

[0033] Using the above technical solution, the test current generating device for the converter grid-connected cabinet provided in this application includes: an AC source and a transformer; wherein, the input terminal of the AC source is configured as the input terminal of the test current generating device, and the output terminal of the AC source is connected to the primary winding of the transformer; the secondary winding of the transformer is configured as the output terminal of the test current generating device, outputting a test current and connected to the machine side of the converter grid-connected cabinet; moreover, in the transformer, the number of turns of the primary winding is N times the number of turns of the secondary winding; N is a positive number greater than 1, and thus the voltage output by the AC source can be reduced to 1 / N by the transformer; and due to the conservation of energy, the current output by the AC source can be amplified to N times by the transformer to serve as the test current, which means that the amplitude of the test current received by the converter grid-connected cabinet can be increased, thereby meeting the high current test requirements exceeding the set capacity of the AC source. Attached Figure Description

[0034] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0035] Figure 1 A schematic diagram of a doubly fed converter and its grid-connected cabinet provided in an embodiment of this application;

[0036] Figure 2 A schematic diagram of a test current generating device for a converter grid-connected cabinet provided in an embodiment of this application;

[0037] Figure 3 A schematic diagram of a specific structure of a test current generating device for a converter grid-connected cabinet provided in an embodiment of this application;

[0038] Figure 4 Another specific structural schematic diagram of the test current generating device for the converter grid-connected cabinet provided in the embodiments of this application;

[0039] Figure 5 Another specific structural schematic diagram of the test current generating device for the converter grid-connected cabinet provided in the embodiments of this application;

[0040] Figure 6 Another specific structural schematic diagram of the test current generating device for the converter grid-connected cabinet provided in the embodiments of this application;

[0041] Figure 7Another specific structural schematic diagram of the test current generating device for the converter grid-connected cabinet provided in the embodiments of this application;

[0042] Figure 8 The control block diagram of the controller in the test current generating device of the converter grid-connected cabinet provided in the embodiments of this application. Detailed Implementation

[0043] The embodiments of this application are described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is for explaining specific embodiments only and is not intended to limit the scope of this application.

[0044] The embodiments of this application are described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Those skilled in the art will understand that with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0045] The terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of units is not necessarily limited to those units, but may include other units not explicitly listed or inherent to those processes, methods, products, or apparatuses.

[0046] Figure 1 Taking a doubly-fed induction generator (DFIG) converter as an example, the structure and connection relationship of converters commonly used in wind power generation are illustrated. As shown in the figure, the DFIG converter 10 mainly includes: a generator-side converter 11, a grid-side converter 12, and a first contactor KM1. The AC side of the generator-side converter 11 is connected to the rotor of the DFIG generator G, and the DC side of the generator-side converter 11 is connected to the DC side of the grid-side converter 12. The AC side of the grid-side converter 12 is connected via the first contactor KM1. The grid-connected cabinet 21 is connected to the generator side. The grid-connected cabinet 21 mainly includes a second contactor KM2 and a main circuit breaker Q1. One side of the second contactor KM2 is connected to one side of the main circuit breaker Q1, and the connection point is configured as the generator side of the grid-connected cabinet 21. The other side of the second contactor KM2 is configured as the stator side of the grid-connected cabinet 21, which is used to connect to the stator of the doubly-fed generator G. The other side of the main circuit breaker Q1 is configured as the grid side of the grid-connected cabinet 21, which is used to connect to the power grid through a transformer.

[0047] With continuous technological advancements, wind turbine unit capacities are increasingly trending towards higher power outputs. As a key component of wind turbines, the rated current of the wind power converter is also continuously increasing with the overall power rating of the turbine. Figure 1 The rated current on the machine side of the grid-connected cabinet 21 shown in the diagram is constantly increasing. The ever-increasing current level places higher demands on the testing equipment of the grid-connected cabinet 21. Traditional current source testing equipment is limited by its own design capacity and cannot meet the high current testing requirements that exceed its set capacity.

[0048] Therefore, this application provides a test current generating device for a converter grid-connected cabinet to increase the amplitude of the test current received by the converter grid-connected cabinet. The specific solution is as follows:

[0049] The converter grid-connected cabinet can be Figure 1 The grid-connected cabinet 21 of the doubly fed converter 10 shown in the figure, Figure 2 It is marked as 20 in the text.

[0050] like Figure 2 As shown, the test current generating device 30 of the converter grid-connected cabinet 20 includes: an AC source 101 and a transformer 102; wherein:

[0051] The input terminal of AC source 101 is configured as the input terminal of the test current generating device 30 for connecting to a corresponding power supply, such as a DC power supply or an AC power supply. This is not limited here, but depends on the specific application environment, and all are within the protection scope of this application.

[0052] The output terminal of AC source 101 is connected to the primary winding of transformer 102; the secondary winding of transformer 102 is configured as the output terminal of test current generating device 30, outputting test current and connected to the generator side of converter grid-connected cabinet 20. Taking the grid side of converter grid-connected cabinet 20 connected to a three-phase (ABC) power grid as an example, the generator side, grid side, and stator side of converter grid-connected cabinet 20 are all three-phase structures, and the primary and secondary sides of transformer 102 are also three-phase structures. The stator side of converter grid-connected cabinet 20 can be short-circuited to form a current path, enabling converter grid-connected cabinet 20 to undergo high-current testing, thereby simulating the high-current operation condition of converter grid-connected cabinet 20 when a doubly-fed wind turbine generator is running at full power. Moreover, the working time of the test current generating device can exceed the preset time, so that converter grid-connected cabinet 20 can be tested under long-term operation, thereby verifying that the design of converter grid-connected cabinet 20 meets the operating requirements of the connected unit. In addition, the connection method of the primary and secondary windings of the transformer 102 can be any of the following: Y / Y, Y / Yn, Y / △, Yn / △, △ / Y, △ / Yn and △ / △; where the part before the ' / ' indicates the connection method of the primary winding, and the part after the ' / ' indicates the connection method of the secondary winding, Y refers to star connection, Y refers to star connection with neutral point lead-out, and △ refers to delta connection; the specific connection method can be determined according to its application environment, and is not limited here.

[0053] Furthermore, in the transformer 102, the number of turns in the primary winding is N times the number of turns in the secondary winding; N is a positive number greater than 1, meaning the primary voltage of the transformer 102 is N times the secondary voltage. Considering energy conservation, i.e., the primary power of the transformer 102 equals the sum of the secondary power and the power loss, we have: neglecting losses, the power of the transformer 102 before and after transformation is equal. Therefore, when the primary voltage of the transformer 102 is N times the secondary voltage, we can conclude that the primary current of the transformer 102 is 1 / N of the secondary current, meaning the secondary current of the transformer 102 is N times the primary current. Therefore, the current output from the AC source 101 is amplified to N times its value by the transformer 102. Consequently, the converter grid-connected cabinet 20 can use the AC source 101 with its small current output capability as a test current source, and achieve a large current output function through the transformer 102.

[0054] The test current generating device 30 provided in this embodiment amplifies the current output by the AC source 101 to N times its value as the test current through the transformer 102. This can increase the amplitude of the test current received by the converter grid-connected cabinet 20, enabling the test current generating device 30 to meet the high current test requirements exceeding the set capacity of the AC source 101. In other words, the test current generating device 30 can meet the high current test requirements of high-power converters, and it has a simple structure that is easy to implement.

[0055] Based on the previous embodiment, this embodiment provides some exemplary descriptions of the specific structure of the test current generating device 30, such as:

[0056] like Figure 3 As shown, its AC source 101 may include at least one ( Figure 3 (Multiple examples are shown below) Power conversion circuit 111; the input terminal of the power conversion circuit 111 is configured as the input terminal of AC source 101, and the output terminal of the power conversion circuit 111 is configured as the output terminal of AC source 101.

[0057] See Figure 3 When the number of power conversion circuits 111 is greater than one, the two sides of each power conversion circuit 111 are connected in parallel. In this case, the power conversion circuit 111 serves as a power module of the AC source 101. By connecting multiple power modules in parallel, the power setting of the AC source 101 can be realized. The more power modules connected in parallel, the greater the power that the AC source 101 can achieve. In practical applications, the number of power modules connected in parallel can be flexibly configured according to test requirements, making it easy to expand and upgrade the capacity of the test current generating device 30.

[0058] In addition, the power conversion circuit 111 contains at least one power switching device. By controlling its on / off state, the state of the power conversion circuit 111 and its specific output voltage and current can be controlled. In a structure in which multiple power conversion circuits 111 are connected in parallel, the state of each power conversion circuit 111 can be set according to the required test current; the larger the required test current, the more power conversion circuits 111 will be in operation.

[0059] The power conversion circuit 111 can be a DC / AC conversion circuit or an AC / AC conversion circuit, with at least one AC side configured as the output terminal of the power conversion circuit 111, and the other side used to connect to the corresponding power supply. For example, the DC side of the DC / AC conversion circuit is used to connect to a DC power supply, and the other AC side of the AC / AC conversion circuit is used to connect to an AC power supply. There is no limitation here, and it depends on the specific application environment. All of them are within the protection scope of this application.

[0060] Figure 4 The example shown is an AC source 101 including a power conversion circuit 111, which includes a DC / AC conversion circuit. The DC side of the DC / AC conversion circuit is configured as the input terminal of the power conversion circuit 111 for connecting to a DC power supply. The AC side of the DC / AC conversion circuit is configured as the output terminal of the power conversion circuit 111.

[0061] In this case, the test current generating device 30 may further include: a DC source; the DC source is connected to the DC side of the DC / AC conversion circuit. In practical applications, the DC source can be a battery or other device, and there is no limitation here. Alternatively, the test current generating device 30 may further include: a rectifier; the AC side of the rectifier receives AC power. In practical applications, the rectifier can be a single-phase rectifier or a three-phase rectifier, depending on the AC power it receives, and there is no limitation here; the DC side of the rectifier is connected to the DC side of the DC / AC conversion circuit.

[0062] The aforementioned DC source or rectifier can provide DC power to the DC / AC conversion circuit. No limitation is made here, depending on the specific application environment, and all are within the protection scope of this application.

[0063] The power conversion circuit 111 can also be an AC / AC conversion circuit. The first side of the AC / AC conversion circuit is configured as the input terminal of the power conversion circuit 111 for connecting to an AC power source, and the second side of the AC / AC conversion circuit is configured as the output terminal of the power conversion circuit 111.

[0064] In practical applications, the input terminal of the AC source 101 can also be equipped with a corresponding capacitor; for example, when the power conversion circuit 111 adopts a DC / AC conversion circuit, a capacitor can also be connected between the positive and negative terminals of its DC side. Figure 4 The capacitor Cd shown is used to filter the connected DC power supply and to support the input voltage of the power conversion circuit 111.

[0065] When the power conversion circuit 111 adopts an AC / AC conversion circuit, if the AC power supply connected to its first side outputs single-phase AC power, a corresponding capacitor can also be set between the two poles of the AC power supply to achieve the filtering function; if the AC power supply outputs three-phase AC power, a corresponding capacitor can be set between any two phases of the AC power supply.

[0066] Furthermore, regardless of the structure of the AC source 101, the test current generating device 30 may also include Figure 5 (like Figure 5 The filter circuit 103 shown in the figure (taking the AC source 101 using a DC / AC conversion circuit as an example) is located between the output terminal of the AC source 101 and the primary winding of the transformer 102.

[0067] In practical applications, the filter circuit 103 can be any form of hardware filter circuit, such as an LC (Inductance-Capacitance) circuit or an LCL (Inductance-Capacitance-Inductance) circuit, depending on the specific application environment, and all are within the protection scope of this application.

[0068] This embodiment provides specific examples of some optional structures of the test current generating device 30, but it is not intended to limit the test current generating device 30. Regardless of the specific structure adopted, any scheme that amplifies the current output by the AC source 101 through the transformer 102 to increase the amplitude of the test current received by the converter grid-connected cabinet 20 is within the protection scope of this application.

[0069] Based on the above embodiments, this embodiment provides another example of the optional structure of the test current generating device 30, such as:

[0070] It may also include Figure 6 (in order to be in) Figure 5 (Based on the structure shown, for example) As shown: a current sensor 104 and a drive circuit 105; the current sensor 104 is disposed at the output terminal of the test current generating device 30 to sample the test current; the output terminal of the current sensor 104 is used to connect to a controller with arithmetic processing function, so that the current sensor 104 can output the sampled value of the test current to the controller; in practical applications, the controller can be a controller, control device, or host computer, etc., which can generate a modulation signal for the power conversion circuit 111 after processing the sampled value. When at least two power conversion circuits 111 in the AC source 101 need to be in working state, these power conversion circuits 111 can receive the same modulation signal.

[0071] Furthermore, the input terminal of the drive circuit 105 is connected to the output terminal of the controller to receive the modulation signal from the power conversion circuit 111; the output terminal of the drive circuit 105 is connected to the control terminal of the power conversion circuit 111. That is, the controller can output a modulation signal to the drive circuit 105, thereby controlling the power conversion circuit 111 through the drive circuit 105. When at least two power conversion circuits 111 in the AC source 101 need to be in operation, these power conversion circuits 111 can share the same drive circuit 105, or they can each be equipped with a corresponding drive circuit 105 and receive the same modulation signal.

[0072] In practical applications, the aforementioned control device can be externally mounted on the test current generating device 30. Of course, the test current generating device 30 can also include corresponding equipment to realize the aforementioned control function.

[0073] In one example, the test current generating device 30 may further include Figure 7 As shown: Controller 106; Controller 106 is configured as the aforementioned control device, its input terminal is connected to the output terminal of current sensor 104 to receive the aforementioned sampled value; In practical applications, if controller 106 has an analog-to-digital conversion function, it can directly receive the sampled value, perform analog-to-digital conversion on the sampled value, and then further process the resulting digital signal; If controller 106 does not have an analog-to-digital conversion function, an additional current sampling circuit can perform analog-to-digital conversion on the sampled value, and then controller 106 can perform further processing based on the digital signal obtained from the analog-to-digital conversion. Furthermore, the output terminal of controller 106 is connected to the input terminal of drive circuit 105, so that drive circuit 105 can control power conversion circuit 111.

[0074] Figure 8 The diagram shown illustrates the principle of closed-loop control of the AC source 101 by the aforementioned control device, such as controller 106. The specific control principle is as follows:

[0075] After receiving the digital signals of the three-phase test current samples, the controller 106 first decomposes them into current feedback quantities in a two-phase rotating coordinate system through coordinate transformation. These current feedback quantities include the d-axis feedback component i. d * and q-axis feedback component i q * .

[0076] The controller 106 also performs coordinate transformation on the amplitude input command of the test current to obtain the current input command in a two-phase rotating coordinate system. This current input command includes the d-axis current input command i. d_ref ( Figure 8 China and Israel i d_ref (Using 0 as an example for demonstration) and q-axis current input command i q_ref Set the d-axis current input command i d_ref With d-axis feedback component i d * The comparison output results, and the q-axis current input command i q_ref With q-axis feedback component i q * The comparison output is processed by the current control module 161 in the controller 106 to generate a modulation voltage in a two-phase rotating coordinate system. This modulation voltage includes a d-axis modulation voltage component u. d *and q-axis modulated voltage component u q * .

[0077] Then, the d-axis modulated voltage component u d * and q-axis modulated voltage component u d * and u q * Park in controller 106 -1 Module 162 performs an inverse Park transform to generate the modulation voltage u in a two-phase stationary coordinate system. α and u β The signal is input to the voltage vector generation module 163 in the controller 106, thereby generating a modulation signal for the power conversion circuit 111.

[0078] The modulation signal is sent to the drive circuit 105, which drives the corresponding power conversion circuit 111 to work, thereby regulating the output voltage of the AC source 101 and generating current in the loop. This causes the test current generator 30 to output current according to the amplitude input command of the test current, forming a closed-loop control.

[0079] To facilitate direct control of the test current amplitude, only the d-axis or q-axis amplitude of the test current can be controlled. In this case, the output test current amplitude will match the command value; for example... Figure 8 i in d_ref =0, meaning that only the q-axis amplitude of the test current is controlled at this time. Alternatively, in practical applications, the d-axis current input command i can also be issued simultaneously. d_ref and q-axis current input command i q_ref This allows for the simultaneous control of the d-axis and q-axis amplitudes of the test current. At this point, the amplitude of the output three-phase test current is equal to the square root of the sum of the squares of the d-axis and q-axis amplitudes.

[0080] in addition, Figure 8 f_ref in the code represents the frequency input command for the test current. It is converted into an angular frequency by the angular frequency conversion module 164, and then integrated by the integration module 165 to obtain the angle information θ. p The angle information θ p It is mainly used to assist in the coordinate transformation in the above control process. For example, the angle information θ is required in both the Park transformation and the inverse Park transformation. p . Figure 8 In the angular frequency conversion module 164, π represents the value of a circle, and s represents the complex frequency in the integration module 165.

[0081] Furthermore, the amplitude input command for the aforementioned test current can be pre-set by the tester through the setting terminal of the controller 106, such as via buttons or a touchscreen, or it can be sent by the tester to the communication terminal of the controller 106 via a host computer or a handheld device in the field. As long as the controller 106 can receive the amplitude input command, the amplitude of the test current can be adjusted, making the current level of the test current generator 30 easily expandable and applicable to application scenarios with various current amplitude requirements. Similarly, the frequency input command f_ref for the aforementioned test current can also be received by the controller 106 through its own setting terminal or communication terminal, thereby enabling the frequency adjustment of the test current and giving the test current generator 30 a current frequency modulation function, making it applicable to application scenarios with various current frequency requirements.

[0082] The test current generating device 30 provided in this embodiment can not only meet the high current testing requirements of high-power converters, but also control the amplitude and frequency of the test current, and realize the controllable output of test current with different amplitudes over a wide frequency band, thus meeting the testing requirements of multiple scenarios and multiple working conditions.

[0083] Similar or identical parts between the various embodiments in this specification can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0084] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0085] The features described above regarding the disclosed embodiments can be substituted for or combined with each other to enable those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A test current generating device for a converter grid-connected cabinet, characterized in that, include: AC power source (101) and transformer (102); among which, The input terminal of the AC source (101) is configured as the input terminal of the test current generating device; The output terminal of the AC source (101) is connected to the primary winding of the transformer (102); The secondary winding of the transformer (102) is configured as the output terminal of the test current generating device and is used to connect to the machine side of the converter grid-connected cabinet. In the transformer (102), the number of turns in the primary winding is N times the number of turns in the secondary winding; N is a positive number greater than 1.

2. The test current generating device for the converter grid-connected cabinet according to claim 1, characterized in that, The AC source (101) includes: at least one power conversion circuit (111); The input terminal of the power conversion circuit (111) is configured as the input terminal of the AC source (101), and the output terminal of the power conversion circuit (111) is configured as the output terminal of the AC source (101). When the number of power conversion circuits (111) is greater than 1, the two sides of each power conversion circuit (111) are connected in parallel.

3. The test current generating device for the converter grid-connected cabinet according to claim 2, characterized in that, Also includes: Current sensor (104) and driving circuit (105); The current sensor (104) is disposed at the output end of the test current generating device; The output terminal of the current sensor (104) is used to connect to the input terminal of the control device; The input terminal of the driving circuit (105) is used to connect to the output terminal of the controller; The output terminal of the drive circuit (105) is connected to the control terminal of the power conversion circuit (111).

4. The test current generating device for the converter grid-connected cabinet according to claim 3, characterized in that, Also includes: Controller (106); The controller (106) is configured as the control device.

5. The test current generating device for the converter grid-connected cabinet according to claim 4, characterized in that, The controller (106) receives the following input command: amplitude of the test current; And / or, the communication terminal or setting terminal of the controller (106) receives: the frequency input command of the test current.

6. The test current generating device for the converter grid-connected cabinet according to any one of claims 2 to 5, characterized in that, The power conversion circuit (111) includes: a DC / AC conversion circuit; The DC side of the DC / AC conversion circuit is configured as the input terminal of the power conversion circuit (111); The AC side of the DC / AC conversion circuit is configured as the output terminal of the power conversion circuit (111).

7. The test current generating device for the converter grid-connected cabinet according to claim 6, characterized in that, The test current generating device further includes: a DC source, which is connected to the DC side of the DC / AC conversion circuit; Alternatively, the test current generating device may further include: a rectifier, wherein the AC side of the rectifier receives AC power, and the DC side of the rectifier is connected to the DC side of the DC / AC conversion circuit.

8. The test current generating device for a converter grid-connected cabinet according to any one of claims 2 to 5, characterized in that, The power conversion circuit (111) includes: an AC / AC conversion circuit; The first side of the AC / AC conversion circuit is configured as the input terminal of the power conversion circuit (111); The second side of the AC / AC conversion circuit is configured as the output terminal of the power conversion circuit (111).

9. The test current generating device for a converter grid-connected cabinet according to any one of claims 1 to 5, characterized in that, Also includes: Capacitance (Cd); The capacitor (Cd) is located at the input terminal of the AC source (101).

10. The test current generating device for a converter grid-connected cabinet according to any one of claims 1 to 5, characterized in that, Also includes: Filter circuit (103); The filter circuit (103) is located between the output terminal of the AC source (101) and the primary winding of the transformer (102).

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