Failure detection circuit of converter current sensor and failure detection method thereof

Abstract

The embodiment of the invention discloses a failure detection circuit of a converter current sensor and a failure detection method thereof. The circuit comprises a grid-side switch, a grid-side filtering unit, a converter power unit, a machine-side filtering unit, a machine-side switch, a generator and a plurality of current sensors. The input end of the grid-side converter unit is connected with an alternating-current power grid or an alternating-current load through the current sensor, the grid-side filter unit and the grid-side switch which are connected in series; and the output end of the machine-side converter unit is connected with the generator through the current sensor, the machine-side filter unit and the machine-side switch which are connected in series. In this way, whether the converter sensor fails or not can be accurately detected, the method is simple, and the cost is low.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of converters, and in particular to a failure detection circuit of a converter current sensor and a failure detection method thereof. Background Art

[0002] A converter is a power electronic device used to convert direct current into alternating current (DC / AC), or to convert alternating current into direct current (AC / DC), or to convert alternating current into direct current and then convert direct current into another alternating current of another frequency, voltage, and phase (AC / DC / AC). It is widely used in the fields of renewable energy generation, motor drive, power storage, etc. Current sensors are very important to converters because converters need to accurately sense current signals in order to control the output current. Specifically, current sensors can sense parameters such as current size, direction, and waveform in real time, and then feed these parameters back to the converter control system. The control system uses these parameters for current control and protection to ensure the safety and stable operation of the system. If the current sensor fails or malfunctions, the system cannot sense the current signal normally, resulting in system loss of control or damage.

[0003] In order to improve the reliability of the converter, before connecting to the grid or starting, the converter will perform self-tests on key components to determine whether the key components are in normal working condition. In the prior art, the failure detection of the current sensor needs to be determined by comparing the loop current calculated by the parameters of other components in the circuit with the current sensor sampling current to determine whether the current sensor has failed, or by adding additional components to form a short-circuit loop, and by comparing the short-circuit current with the current sensor sampling current, it is determined whether other current sensors in the converter have failed. Both the device parameters and the short-circuit current may change with changes in the external environment, which will affect the accuracy of the current sensor failure detection. Summary of the invention

[0004] In view of the above problems, an embodiment of the present invention provides a failure detection circuit of a current sensor of a converter and a failure detection method thereof, which overcome the above problems or at least partially solve the above problems.

[0005] According to one aspect of an embodiment of the present invention, a failure detection circuit of a converter current sensor is provided, comprising: a grid-side switch, a grid-side filter unit, a converter power unit, a machine-side filter unit, a machine-side switch, a generator and a plurality of current sensors; the input end of the grid-side converter unit is connected to an AC grid or an AC load through the current sensor, the grid-side filter unit and the grid-side switch connected in series; the output end of the machine-side converter unit is connected to the generator through the current sensor, the machine-side filter unit and the machine-side switch connected in series.

[0006] Optionally, one current sensor is connected to each of the three phases A, B, and C at the input end of the grid-side converter unit to respectively detect the current of the corresponding phase lines; one current sensor is connected to each of the three phases U, V, and W at the output end of the machine-side converter unit to respectively detect the current of the corresponding phase lines.

[0007] Optionally, one current sensor is connected to each of the three-phase lines A, B, and C at the input end of the grid-side converter unit to detect the current of the three-phase lines A, B, and C respectively.

[0008] Optionally, one current sensor is connected to each of the U, V, and W three-phase lines at the output end of the machine-side converter unit to respectively detect the current of the U, V, and W three-phase lines.

[0009] Optionally, the grid-side filtering unit includes: 3 filter inductors and 3 filter capacitors, one end of the 3 filter capacitors are connected together, and the other ends are respectively connected to the three-phase lines A, B, and C, and the 3 filter inductors are respectively connected in series to the three-phase lines A, B, and C.

[0010] Optionally, the converter power unit includes: a grid-side converter unit, a supporting capacitor and a machine-side converter unit; the output end of the grid-side converter unit is connected to the machine-side converter unit, and a supporting capacitor is connected in parallel between the grid-side converter unit and the machine-side converter unit.

[0011] Optionally, the failure detection circuit also includes: a pre-charging circuit and a chopping branch, the pre-charging circuit is connected in parallel to the output end of the grid-side converter unit to charge the support capacitor, and the chopping circuit is connected in parallel to the input end of the machine-side converter unit to chop the input signal of the machine-side converter unit.

[0012] Based on the same inventive concept, a failure detection method for a converter current sensor is provided, comprising: controlling the grid-side switch to disconnect, starting the pre-charging circuit to charge the supporting capacitor; starting the converter power unit, forming a first single-phase current circuit through any two phase lines respectively provided with current sensors, the converter power unit and the grid-side filter unit, and determining whether the two current sensors have failed according to a first current difference detected by the two current sensors in the first single-phase current circuit; forming a second single-phase current circuit through any two phase lines respectively provided with current sensors, the converter power unit, the machine-side filter unit and the generator, and determining whether the two current sensors have failed according to a second current difference detected by the two current sensors in the first single-phase current circuit.

[0013] Optional,

[0014] The starting of the converter power unit forms a first single-phase current loop through any two phase lines respectively provided with current sensors, the converter power unit and the grid-side filter unit, and determines whether the two current sensors fail according to a first current difference detected by the two current sensors in the first single-phase current loop, including: starting the grid-side converter so that the grid-side converter, the grid-side filter unit and any two phase lines respectively provided with current sensors form a first single-phase current loop; obtaining current values ​​detected by the two current sensors in the first single-phase current loop, and calculating a first current difference between the two; judging whether the first current difference exceeds a first preset threshold; if the first current difference exceeds the first preset threshold, determining that at least one of the two current sensors fails; otherwise, the two current sensors are normal.

[0015] Optionally, a second single-phase current loop is formed by any two phase lines respectively provided with current sensors, the converter power unit, the machine-side filter unit and the generator, and whether the two current sensors fail is determined according to the second current difference detected by the two current sensors in the first single-phase current loop, including: starting the machine-side converter to form a second single-phase current loop by the machine-side converter, the machine-side filter unit, the generator and any two phase lines respectively provided with current sensors; obtaining the current values ​​detected by the two current sensors in the second single-phase current loop, and calculating the second current difference between the two; judging whether the second current difference exceeds a second preset threshold; if the second current difference exceeds the second preset threshold, determining that at least one of the two current sensors has failed; otherwise, the two current sensors are normal.

[0016] The failure detection circuit of the converter current sensor in the embodiment of the present invention includes: a grid-side switch, a grid-side filter unit, a converter power unit, a machine-side filter unit, a machine-side switch, a generator and multiple current sensors; the input end of the grid-side converter unit is connected to the AC grid or the AC load through the current sensor, the grid-side filter unit and the grid-side switch connected in series; the output end of the machine-side converter unit is connected to the generator through the current sensor, the machine-side filter unit and the machine-side switch connected in series, so as to accurately detect whether the converter sensor fails, and the method is simple and low-cost.

[0017] The above description is only an overview of the technical solution of the embodiment of the present invention. In order to more clearly understand the technical means of the embodiment of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0019] Figure 1 A schematic structural diagram of a failure detection circuit of a current sensor of a current transformer provided by an embodiment of the present invention is shown;

[0020] Figure 2 A schematic structural diagram of a failure detection circuit of a current sensor of a current transformer according to an embodiment of the present invention is shown;

[0021] Figure 3 A schematic diagram of failure detection of a grid-side current sensor according to an embodiment of the present invention is shown;

[0022] Figure 4 A schematic diagram showing failure detection of a generator-side current sensor according to an embodiment of the present invention is shown;

[0023] Figure 5 A schematic flow chart of a method for detecting failure of a current sensor of a current transformer provided in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0024] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0025] Figure 1 FIG. 1 is a schematic diagram showing a structure of a failure detection circuit of a current transformer current sensor provided by an embodiment of the present invention. Figure 1 As shown, the failure detection circuit of the converter current sensor includes: a grid-side switch, a grid-side filter unit, a converter power unit, a machine-side filter unit, a machine-side switch, a generator and multiple current sensors; the input end of the grid-side converter unit is connected to the AC grid or the AC load through the current sensor, the grid-side filter unit and the grid-side switch connected in series; the output end of the machine-side converter unit is connected to the generator through the current sensor, the machine-side filter unit and the machine-side switch connected in series.

[0026] Any two phases of the A, B, and C phases at the input end of the grid-side converter unit are connected to a current sensor to detect the current of the corresponding phase line; any two phases of the U, V, and W phases at the output end of the generator-side converter unit are connected to a current sensor to detect the current of the corresponding phase line. Figure 1 In the embodiment, a current sensor BC1 is arranged on the A phase line of the input end of the grid-side converter unit, and a current sensor BC2 is arranged on the C phase line. A current sensor BC3 is arranged on the U phase line of the output end of the grid-side converter unit, and a current sensor BC4 is arranged on the W phase line.

[0027] In the embodiment of the present invention, the grid-side switch is first controlled to be disconnected, and the pre-charging loop is started to charge the supporting capacitor. Then the converter power unit is started, and a first single-phase current loop is formed through any two phase lines respectively provided with current sensors, the converter power unit and the grid-side filter unit, and whether the two current sensors are failed is determined according to the first current difference detected by the two current sensors in the first single-phase current loop. Figure 1 In the process, after charging the supporting capacitor, the converter power unit is started to form a first single-phase current loop between the AC phases. The current sensors BC1 and BC2 detect the current in the loop and calculate the first current difference between the two. If the first current difference is greater than the first preset threshold, it can be determined that at least one of the current sensors BC1 and BC2 has failed.

[0028] In the embodiments of the present invention, see Figure 2 , the converter power unit includes: a grid-side converter unit, a support capacitor and a machine-side converter unit; the output end of the grid-side converter unit is connected to the machine-side converter unit, and the support capacitor is connected in parallel between the grid-side converter unit and the machine-side converter unit. The failure detection circuit also includes: a pre-charging circuit and a chopping branch, the pre-charging circuit is connected in parallel to the output end of the grid-side converter unit to charge the support capacitor, and the chopping circuit is connected in parallel to the input end of the machine-side converter unit to chop the input signal of the machine-side converter unit.

[0029] In this way, if it is necessary to detect whether the current sensor located at the input end of the converter power unit fails, the grid-side converter is started, so that the grid-side converter, the grid-side filter unit and any two phase lines respectively provided with current sensors form a first single-phase current loop; the current values ​​detected by the two current sensors in the first single-phase current loop are obtained, and the first current difference between the two is calculated; it is determined whether the first current difference exceeds the first preset threshold; if the first current difference exceeds the first preset threshold, it is determined that at least one of the two current sensors fails; otherwise, the two current sensors are normal. If it is necessary to detect whether the current sensor located at the input end of the converter power unit fails, the generator-side converter is started, so that the generator-side converter, the generator-side filter unit, the generator and any two phase lines respectively provided with current sensors form a second single-phase current loop; the current values ​​detected by the two current sensors in the second single-phase current loop are obtained, and the second current difference between the two is calculated; it is determined whether the second current difference exceeds the second preset threshold; if the second current difference exceeds the second preset threshold, it is determined that at least one of the two current sensors fails; otherwise, the two current sensors are normal.

[0030] The grid-side filtering unit includes: 3 filter inductors and 3 filter capacitors, one end of the 3 filter capacitors is connected together, and the other end is connected to the three-phase lines A, B, and C respectively, and the 3 filter inductors are connected in series to the three-phase lines A, B, and C respectively. That is, the 3 filter capacitors are connected in a star shape, and when any first single-phase current loop is connected, 2 filter capacitors are connected to the loop.

[0031] In an embodiment of the present invention, the input end of the grid-side converter unit, that is, the grid side, can use two current sensors, which are respectively set on any two phases of the three phases A, B, and C, or three current sensors can be used, which are respectively set on the three phases A, B, and C. Similarly, the output end of the grid-side converter unit, that is, the machine side, can use two current sensors, which are respectively set on any two phases of the three phases U, V, and W, or three current sensors can be used, which are respectively set on the three phases U, V, and W. The current sensors on the grid side and the machine side of the grid-side converter unit can be arranged in any combination. That is, two current sensors can be set on the grid side, and three current sensors can be set on the machine side at the same time; three current sensors can also be set on the grid side, and two current sensors can be set on the machine side at the same time.

[0032] Continue to see Figure 2, one current sensor is connected to each of the three-phase lines A, B, and C at the input end of the grid-side converter unit to detect the current of the three-phase lines A, B, and C respectively. One current sensor is connected to each of the three-phase lines U, V, and W at the output end of the machine-side converter unit to detect the current of the three-phase lines U, V, and W respectively. If it is to be detected whether the current sensor located at the input end of the converter power unit fails, start the grid-side converter so that the grid-side converter, the grid-side filter unit, and any two phase lines therein form a first single-phase current loop. The currents in the same series loop should be equal, therefore, the current values ​​detected by the two current sensors in the first single-phase current loop are obtained, and the first current difference between the two is calculated. If the first current difference exceeds the first preset threshold value, it can be determined that at least one of the two current sensors has failed. Otherwise, the two current sensors are normal. For example, see Figure 3 The grid-side converter, the grid-side filter unit and the two-phase lines AB form a first single-phase current loop (such as Figure 3 The circuit in bold) can detect whether the current sensors BC1 and BC2 are failed. Through a first single-phase current circuit, it can only be detected whether the two current sensors on the first single-phase current circuit are failed, and it cannot be determined which current sensor is failed. Further, the same method can be applied to detect whether the current sensors BC2 and BC3 on the first single-phase current circuit formed by the grid-side converter, the grid-side filter unit, and the BC two-phase line are failed. Theoretically, the currents in the above two first single-phase circuits should be consistent. In this way, if it is determined that the current sensors BC1 and BC2 are failed based on the detection of the previous two first single-phase current circuits, the current sensors BC2 and BC3 are also failed, and the current values ​​detected by the current sensors BC1 and BC3 are equal, it can be determined that the current sensor BC2 is failed and the current sensors BC1 and BC3 are normal. The embodiment of the present invention can also detect whether the current sensors BC1 and BC3 on the grid-side converter, the grid-side filter unit, and the AC two-phase line are failed. Combining the detection results of the above three first single-phase circuits, it can be determined which current sensor is failed. The first preset threshold can be set as needed and is not specifically limited here.

[0033] If you want to detect whether the current sensor located at the output end of the converter power unit fails, start the machine-side converter so that the machine-side converter, the machine-side filter unit, the generator and any two phase lines form a second single-phase current loop, and close the machine-side switch in the second single-phase current loop; obtain the current values ​​detected by the two current sensors in the second single-phase current loop, and calculate the second current difference between the two. If the second current difference exceeds the second preset threshold, it can be determined that at least one of the two current sensors has failed. Otherwise, the two current sensors are normal. For example, see Figure 4The machine-side converter, the machine-side filter unit and the UV two-phase line form a second single-phase current loop (such as Figure 4 Bold loop), it is possible to detect whether current sensors BC4 and BC5 have failed. Through a second single-phase current loop, it can only be detected whether the two current sensors on the second single-phase current loop have failed, and it cannot be determined which current sensor has failed. Furthermore, the same method can be applied to detect whether the current sensors BC5 and BC6 on the second single-phase current loop formed by the machine-side converter, the machine-side filter unit, and the VW two-phase line therein have failed, and to detect whether the current sensors BC4 and BC6 on the second single-phase current loop formed by the machine-side converter, the machine-side filter unit, and the UW two-phase line therein have failed. Theoretically, the currents in the above three second single-phase loops should be consistent. In this way, it can be determined which current sensor has failed in combination with the detection results of the above three second single-phase loops. The second preset threshold value can be set as needed, and is not specifically limited here.

[0034] The embodiment of the present invention utilizes the current sensor of the converter itself, which is mutually redundant in the current loop formed under a specific output mode, and determines whether the current sensor fails through redundant comparison, which is independent of the parameters of other components of the converter, making the failure detection of the current sensor more accurate. In the current sensor failure detection, only the function of the converter itself is utilized, without increasing any hardware cost and without relying on other sensors in the circuit, whether the converter sensor fails can be accurately detected before the converter is connected to the grid, which greatly increases the reliability of the converter, does not require the addition of additional hardware, and the method is simpler and the cost is lower.

[0035] To summarize, the failure detection circuit of the converter current sensor in the embodiment of the present invention includes: a grid-side switch, a grid-side filter unit, a converter power unit, a machine-side filter unit, a machine-side switch, a generator and multiple current sensors; the input end of the grid-side converter unit is connected to the AC grid or the AC load through the current sensor, the grid-side filter unit and the grid-side switch connected in series; the output end of the machine-side converter unit is connected to the generator through the current sensor, the machine-side filter unit and the machine-side switch connected in series, so as to accurately detect whether the converter sensor fails, and the method is simple and low-cost.

[0036] Based on the same concept, an embodiment of the present invention also provides a failure detection method for a current sensor of a current transformer, such as Figure 5 As shown, the failure detection method of the converter current sensor is applied to the failure detection circuit of the converter current sensor mentioned above, and the method includes:

[0037] Step S11: Control the grid-side switch to be disconnected, and start the pre-charging circuit to charge the supporting capacitor.

[0038] Before performing current sensor failure detection, the converter power unit is disconnected and the pre-charging loop is started to charge the support capacitor to provide power for the first single-phase current loop and the second single-phase current loop formed subsequently.

[0039] Step S12: Start the converter power unit, form a first single-phase current loop through any two phase lines respectively provided with current sensors, the converter power unit and the grid-side filter unit, and determine whether the two current sensors fail according to a first current difference detected by the two current sensors in the first single-phase current loop.

[0040] In an embodiment of the present invention, if it is necessary to detect whether the current sensor located at the input end of the converter power unit fails, the grid-side converter is started so that the grid-side converter, the grid-side filter unit and any two phase lines respectively provided with current sensors form a first single-phase current loop; the current values ​​detected by the two current sensors in the first single-phase current loop are obtained, and the first current difference between the two is calculated; it is determined whether the first current difference exceeds the first preset threshold; if the first current difference exceeds the first preset threshold, it is determined that at least one of the two current sensors fails; otherwise, the two current sensors are normal. For example, by forming a first single-phase current loop with the grid-side converter, the grid-side filter unit and the two phase lines AB, it is possible to detect whether the current sensors BC1 and BC2 fail.

[0041] Through a first single-phase current loop, only whether the two current sensors on the first single-phase current loop have failed can be detected, and it cannot be determined which current sensor has failed. Furthermore, the same method can be applied to detect whether the current sensors BC2 and BC3 on the first single-phase current loop formed by the grid-side converter, the grid-side filter unit, and the BC two-phase line therein have failed. And detect whether the current sensors BC1 and BC3 on the first single-phase current loop formed by the grid-side converter, the grid-side filter unit, and the AC two-phase line therein have failed. Theoretically, the currents in the above first single-phase loops should be consistent, so the detection results of the above three first single-phase loops can be combined to determine which current sensor has failed.

[0042] Step S13: forming a second single-phase current loop through any two phase lines respectively provided with current sensors, the converter power unit, the machine-side filter unit and the generator, and determining whether the two current sensors fail according to the second current difference detected by the two current sensors in the first single-phase current loop.

[0043] In an embodiment of the present invention, if it is necessary to detect whether the current sensor located at the output end of the converter power unit fails, start the machine-side converter so that the machine-side converter, the machine-side filter unit, the generator and any two phase lines respectively provided with current sensors form a second single-phase current loop; obtain the current values ​​detected by the two current sensors in the second single-phase current loop, and calculate the second current difference between the two; determine whether the second current difference exceeds the second preset threshold; if the second current difference exceeds the first preset threshold, it is determined that at least one of the two current sensors fails; otherwise, the two current sensors are normal. For example, by forming a second single-phase current loop with the machine-side converter, the machine-side filter unit and the UV two-phase lines, it is possible to detect whether current sensors BC4 and BC5 fail.

[0044] Through a second single-phase current loop, it can only be detected whether the two current sensors on the second single-phase current loop have failed, and it cannot be determined which current sensor has failed. Furthermore, the same method can be applied to detect whether the current sensors BC5 and BC6 on the second single-phase current loop formed by the machine-side converter, the machine-side filter unit, and the VW two-phase line therein have failed, and to detect whether the current sensors BC4 and BC6 on the second single-phase current loop formed by the machine-side converter, the machine-side filter unit, and the UW two-phase line therein have failed. Theoretically, the currents in the above three second single-phase loops should be consistent. In this way, combining the detection results of the above three second single-phase loops can determine which current sensor has failed.

[0045] The embodiment of the present invention utilizes the current sensor of the converter itself, which is mutually redundant in the current loop formed under a specific output mode, and determines whether the current sensor fails through redundant comparison, which is independent of the parameters of other components of the converter, thereby making the failure detection of the current sensor more accurate and greatly improving the reliability of the converter. In this process, no hardware cost needs to be increased and it does not rely on other sensors in the circuit. The method is simpler and the cost is lower.

[0046] The above specific embodiments of the present invention are described. In some cases, the actions or steps recorded in the embodiments of the present invention can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the process depicted in the accompanying drawings does not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0047] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure is limited to these examples. Based on the concept of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0048] This application is intended to cover all such substitutions, modifications and variations that fall within the broad scope of all embodiments. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the scope of protection of this disclosure.

Claims

1. A failure detection circuit for a current sensor of a current transformer, characterized in that: The failure detection circuit includes: a grid-side switch, a grid-side filter unit, a converter power unit, a machine-side filter unit, a machine-side switch, a generator and multiple current sensors; the input end of the grid-side converter unit is connected to the AC grid or the AC load through the current sensor, the grid-side filter unit and the grid-side switch connected in series; the output end of the machine-side converter unit is connected to the generator through the current sensor, the machine-side filter unit and the machine-side switch connected in series.

2. The failure detection circuit according to claim 1, characterized in that: One current sensor is connected to each of the three phases A, B, and C at the input end of the grid-side converter unit to respectively detect the current of the corresponding phase line; one current sensor is connected to each of the three phases U, V, and W at the output end of the machine-side converter unit to respectively detect the current of the corresponding phase line.

3. The failure detection circuit according to claim 2, characterized in that: A current sensor is respectively connected to the three-phase lines A, B, and C at the input end of the grid-side converter unit to detect the current of the three-phase lines A, B, and C respectively.

4. The failure detection circuit according to claim 2, characterized in that: The three-phase lines U, V, and W at the output end of the generator-side converter unit are each connected with a current sensor to detect the current of the three-phase lines U, V, and W respectively.

5. The failure detection circuit according to any one of claims 2 to 4, characterized in that: The grid-side filtering unit includes: 3 filter inductors and 3 filter capacitors, one end of the 3 filter capacitors are connected together, and the other ends are respectively connected to the A, B, and C three-phase lines, and the 3 filter inductors are respectively connected in series to the A, B, and C three-phase lines.

6. The failure detection circuit according to claim 1, characterized in that: The converter power unit comprises: a grid-side converter unit, a supporting capacitor and a machine-side converter unit; the output end of the grid-side converter unit is connected to the machine-side converter unit, and the supporting capacitor is connected in parallel between the grid-side converter unit and the machine-side converter unit.

7. The failure detection circuit according to claim 1, characterized in that: The failure detection circuit also includes: a pre-charging circuit and a chopping branch, the pre-charging circuit is connected in parallel to the output end of the grid-side converter unit to charge the support capacitor, and the chopping circuit is connected in parallel to the input end of the machine-side converter unit to chop the input signal of the machine-side converter unit.

8. A method for detecting failure of a current sensor of a current transformer, characterized in that: The failure detection method comprises: The switch on the control grid side is disconnected, and the pre-charging circuit is started to charge the supporting capacitor; Starting the converter power unit, forming a first single-phase current loop through any two phase lines respectively provided with current sensors, the converter power unit and the grid-side filter unit, and determining whether the two current sensors fail according to a first current difference detected by the two current sensors in the first single-phase current loop; A second single-phase current loop is formed by any two phase lines respectively provided with current sensors, the converter power unit, the machine-side filter unit and the generator, and whether the two current sensors fail is determined according to a second current difference detected by the two current sensors in the first single-phase current loop.

9. The method according to claim 8, characterized in that: The starting of the converter power unit, forming a first single-phase current loop through any two phase lines respectively provided with current sensors, the converter power unit and the grid-side filter unit, and determining whether the two current sensors fail according to a first current difference detected by the two current sensors in the first single-phase current loop, includes: Starting the grid-side converter so that the grid-side converter, the grid-side filter unit, and any two phase lines respectively provided with current sensors form a first single-phase current loop; Obtaining current values ​​detected by two current sensors in the first single-phase current loop, and calculating a first current difference between the two; Determining whether the first current difference exceeds a first preset threshold; If the first current difference exceeds the first preset threshold, it is determined that at least one of the two current sensors is failed; otherwise, the two current sensors are normal.

10. The method according to claim 8, characterized in that: The method forms a second single-phase current loop through any two phase lines respectively provided with current sensors, the converter power unit, the machine-side filter unit and the generator, and determines whether the two current sensors fail according to a second current difference detected by the two current sensors in the first single-phase current loop, including: Starting the machine-side converter so that the machine-side converter, the machine-side filter unit, the generator, and any two phase lines respectively provided with current sensors form a second single-phase current loop; Obtaining current values ​​detected by two current sensors in the second single-phase current loop, and calculating a second current difference between the two; Determining whether the second current difference exceeds a second preset threshold; If the second current difference exceeds the second preset threshold, it is determined that at least one of the two current sensors is failed; otherwise, the two current sensors are normal.

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