Converter

Abstract

The invention provides a converter, and relates to the technical field of power electronics. The converter comprises a bleeder circuit which comprises a first resistor and a power switch which are connected in series; the current detection circuit comprises a first capacitor; the input end of the isolation unit is connected with the first capacitor in series; wherein the input end of the current detection circuit is connected in parallel to one of the first resistor and the power switch, and the current detection circuit detects the direction of current flowing through the first capacitor and outputs a current detection signal; the signal conditioning circuit is electrically connected to the output end of the current detection circuit and is used for receiving the current detection signal and outputting a working state signal of the bleeder circuit; and the controller is electrically connected to the signal conditioning circuit, receives the working state signal of the bleeder circuit, and judges whether the bleeder circuit is in an on state or an off state, thereby realizing rapid detection of the working state of the bleeder circuit.

Description

Technical Field

[0001] The present disclosure relates to the field of power electronics technology, and in particular to a converter. Background Art

[0002] In wind power converters, frequency converters, SVG (Static Var Generator), STATCOM (Static Synchronous Compensator), and flexible DC transmission equipment, a chopper circuit needs to be installed to discharge the energy of the DC bus during transient grid overvoltage or energy backflow. In high-availability applications, the controller needs to understand the working status of the chopper circuit. Otherwise, once the chopper circuit malfunctions or refuses to operate, causing circuit damage, the availability of the entire system will be affected.

[0003] like Figure 1 As shown, in the prior art 1, the DC bus voltage is detected to determine the working state of the discharge circuit. Using an AD converter to detect the DC bus voltage is an indirect way to determine the working state of the discharge circuit. This solution has some difficulties in the following aspects:

[0004] (1) Slow response speed. One reason for the slow response speed is that the state of the discharge circuit needs to be reflected on the DC bus voltage, which requires an integration process of the discharge circuit current on the DC bus capacitor. Another reason is that the analog signal obtained by sampling the DC bus voltage needs to be filtered, and the filter will produce a certain delay. Combining the above reasons, the response speed of the solution using DC bus voltage detection is slow.

[0005] (2) The bus voltage drops, and the indirect detection scheme using the DC bus voltage has the limitation of not being able to accurately determine the working status of the discharge circuit.

[0006] like Figure 2 As shown, in the prior art 2, a current detection device is used to detect the current of the discharge circuit to determine the working state of the discharge circuit. Specifically, a current detection device is installed in the discharge circuit to determine the working state of the discharge circuit. This solution can directly determine the working state of the discharge circuit, but due to the high DC bus voltage, a current sensor with a relatively large rated current is required, such as a large current Hall device, which has a high cost and a large volume, and is not easy to integrate with the drive circuit of the discharge circuit.

[0007] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0008] The present disclosure provides a converter, which at least to some extent overcomes the problems of slow response speed, large size and high cost in related technologies.

[0009] Other features and advantages of the present disclosure will become apparent from the following detailed description, or may be learned in part by the practice of the present disclosure.

[0010] According to one aspect of the present disclosure, there is provided a converter, comprising:

[0011] The discharge circuit includes a first resistor and a power switch connected in series, wherein the power switch includes a control terminal, a first terminal and a second terminal;

[0012] Current detection circuit, including:

[0013] a first capacitor;

[0014] An isolation unit, wherein an input terminal of the isolation unit is connected in series with the first capacitor;

[0015] Wherein, the input end of the current detection circuit is connected in parallel to one of the first resistor and the power switch, and the current detection circuit detects the direction of the current flowing through the first capacitor and outputs a current detection signal;

[0016] A signal conditioning circuit is electrically connected to the output end of the current detection circuit, receives the current detection signal, and outputs a discharge circuit working state signal;

[0017] The controller is electrically connected to the signal conditioning circuit, receives the working state signal of the discharge circuit, and determines whether the discharge circuit is in the on state or the off state.

[0018] According to another aspect of the present disclosure, there is also provided a converter, comprising:

[0019] The discharge circuit includes a first resistor and a power switch connected in series, wherein the power switch includes a control terminal, a first terminal and a second terminal;

[0020] The first current detection circuit comprises:

[0021] a first capacitor;

[0022] A first isolation unit, wherein an input terminal of the first isolation unit is connected in series with a first capacitor;

[0023] Wherein, the first current detection circuit detects the direction of the current flowing through the first capacitor and outputs a first current detection signal;

[0024] The second current detection circuit comprises:

[0025] A second capacitor;

[0026] A second isolation unit, wherein an input terminal of the second isolation unit is connected in series with a second capacitor;

[0027] Wherein, the second current detection circuit detects the direction of the current flowing through the second capacitor and outputs a second current detection signal;

[0028] Wherein, the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel to the first resistor, or the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel to the power switch;

[0029] A signal conditioning circuit is electrically connected to an output end of the first current detection circuit and an output end of the second current detection circuit, receives one of the first current detection signal and the second current detection signal, and outputs a discharge circuit working state signal;

[0030] The controller is electrically connected to the signal conditioning circuit, receives the working state signal of the discharge circuit, and determines whether the discharge circuit is in the on state or the off state.

[0031] The converter of the present invention determines whether the discharge circuit is in the on state or the off state by detecting the direction of the current flowing through the first capacitor. Since the voltage across the first resistor or the power switch will change when the discharge circuit is in different working states or when the working state changes, the current detection circuit is connected in parallel to the first resistor or the power switch of the discharge circuit. When the voltage changes, the current of the first capacitor will change. The current detection circuit is used to detect the direction of the current flowing through the first capacitor, and the controller determines whether the discharge circuit is in the on state or the off state. Compared with the prior art one, the circuit of the present invention has a faster response speed and can clearly distinguish the working state of the discharge circuit; compared with the prior art two, the converter of the present invention has a simple structure, does not require auxiliary voltage, does not require active devices, can achieve isolation, has a lower implementation cost, and has a smaller volume, and is easy to integrate with the drive circuit of the discharge circuit. By detecting the working state of the discharge circuit, the present invention can understand the cause of the fault and prevent the accident from expanding when the working state of the discharge circuit is abnormal.

[0032] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0034] Figure 1 A circuit diagram of prior art 1 is shown.

[0035] Figure 2 A circuit diagram of the second prior art is shown.

[0036] Figure 3 A circuit diagram of an H-bridge converter with two discharge circuit structures is shown.

[0037] Figure 4 A first circuit diagram of a converter in an embodiment of the present disclosure is shown.

[0038] Figure 5 A second circuit diagram of a converter according to an embodiment of the present disclosure is shown.

[0039] Figure 6 A first circuit diagram of a first embodiment of a converter in an embodiment of the present disclosure is shown.

[0040] Figure 7 A second circuit diagram of a first embodiment of a converter in the embodiments of the present disclosure is shown.

[0041] Figure 8 A first circuit diagram of a second embodiment of a converter in the embodiments of the present disclosure is shown.

[0042] Fig. 9 A second circuit diagram of a second embodiment of a converter in the embodiments of the present disclosure is shown.

[0043] Fig.10 A first circuit diagram of a third embodiment of a converter in the embodiments of the present disclosure is shown.

[0044] Fig.11 A second circuit diagram of a third embodiment of a converter in the embodiments of the present disclosure is shown.

[0045] Fig.12 A first circuit diagram of a converter in another embodiment of the present disclosure is shown.

[0046] Fig.13 A second circuit diagram of a converter according to another embodiment of the present disclosure is shown.

[0047] Fig.14 A first circuit diagram of a fourth embodiment of a converter in another embodiment of the present disclosure is shown.

[0048] Fig.15 A second circuit diagram of a fourth embodiment of a converter in another embodiment of the present disclosure is shown.

[0049] Fig.16 A first circuit diagram of a fifth embodiment of a converter in another embodiment of the present disclosure is shown.

[0050] Fig.17 A second circuit diagram of a fifth embodiment of a converter in another embodiment of the present disclosure is shown.

[0051] Fig.18 A schematic diagram showing a first simulation result of a converter in an embodiment of the present disclosure is shown.

[0052] Fig.19 A schematic diagram showing a second simulation result of a converter in an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0053] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0054] In addition, the accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0055] The terms "first", "second", etc. used in the present disclosure do not specifically refer to the order or sequence, nor are they used to limit the present disclosure. They are only used to distinguish between elements or operations described with the same technical terms. Secondly, the terms "comprise", "include", "have", "contain", etc. used in the present disclosure are all open terms, that is, they mean including but not limited to. In addition, "coupled" or "connected" used in the present disclosure may refer to two or more elements making direct physical or electrical contact, or making indirect physical or electrical contact with each other. In addition, in the disclosure, unless the text specifically limits the articles, "one" and "the" may refer to a single or multiple elements.

[0056] The specific implementation of the embodiment of the present disclosure is described in detail below with reference to the accompanying drawings.

[0057] In the present disclosure, a chopper circuit refers to a circuit structure in which a resistor is connected in series with a power switch and then connected in parallel to a DC bus; wherein the power switch may be an IGBT (Insulated Gate Bipolar Transistor), or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or other active switches, and the present disclosure does not limit this.

[0058] Figure 3 (a) and (b) in the figure respectively show an H-bridge converter with two discharge circuit structures; the resistor on the right side of the middle DC bus capacitor and the power switch form a discharge circuit. Figure 3 In (a), the power devices S1, S2, S3 and S4 form an H-bridge circuit, the DC bus capacitor C0 is connected in parallel on the DC side of the H-bridge circuit, the resistor R1 is connected in series with the power switch K1, and then connected in parallel to the DC bus capacitor. Figure 3 In (b), an H-bridge circuit is formed by power devices S1, S2, S3 and S4, a DC bus capacitor C0 is connected in parallel on the DC side of the H-bridge circuit, a power switch K1 is connected in series with a resistor R1, and then connected in parallel to the DC bus capacitor.

[0059] This disclosure Figure 3 An embodiment of a converter is provided based on the structure in (a) of FIG. Figure 3 The same functions and effects can also be achieved in (b), and also fall within the protection scope of the present disclosure.

[0060] Figure 4 A first circuit diagram of a converter according to an embodiment of the present disclosure is shown. Figure 5 A second circuit diagram of a converter according to an embodiment of the present disclosure is shown. Figure 4 and Figure 5 As shown, the converter provided in the embodiment of the present disclosure includes:

[0061] The discharge circuit includes a first resistor R1 and a power switch K1 connected in series, wherein the power switch K1 includes a control terminal, a first terminal and a second terminal;

[0062] A current detection circuit, comprising: a first capacitor C1; an isolation unit M, wherein an input end of the isolation unit M is connected in series with the first capacitor C1; wherein the input end of the current detection circuit is connected in parallel to the first resistor R1, or the input end of the current detection circuit is connected in parallel to the power switch K1, and the current detection circuit detects the direction of the current flowing through the first capacitor C1 and outputs a current detection signal;

[0063] The signal conditioning circuit S is electrically connected to the output end of the current detection circuit, receives the current detection signal, and outputs a discharge circuit working state signal;

[0064] The controller C is electrically connected to the signal conditioning circuit, receives the working state signal of the discharge circuit, and determines whether the discharge circuit is in the on state or the off state.

[0065] exist Figure 4 In the first circuit diagram of the converter, the input end of the current detection circuit is connected in parallel to the first resistor R1; Figure 5 In the second circuit diagram of the converter, the input end of the current detection circuit is connected in parallel to the power switch K1.

[0066] When the voltage across the first resistor R1 or the power switch K1 changes, the capacitive current of the first capacitor C1 will change. The working state of the discharge circuit can be determined by detecting the direction of the current flowing through the first capacitor using the current detection circuit.

[0067] When the power switch K1 is turned on, the discharge circuit is in an on state; when the power switch K1 is turned off, the discharge circuit is in an off state.

[0068] In some embodiments, the signal conditioning circuit S uses different circuit forms such as a comparator and a triode circuit to convert the current detection signal in the form of an analog signal into a discharge circuit working state signal in the form of a digital signal. The output digital signal corresponds to the input analog signal, but the correspondence is not unique. The discharge circuit working state signal output by the signal conditioning circuit S represents the first signal and the second signal in the form of high and low level values. For example, the first signal is a high level signal and the second signal is a low level signal.

[0069] like Figure 6 As shown, a first embodiment of a current transformer is provided. Referring to the first circuit diagram of the first embodiment, the current detection circuit further includes: a second resistor R2, which is connected in series with the first capacitor C1 and the input end of the first isolation unit, and the input end of the current detection circuit is connected in parallel to the first resistor R1. The first isolation unit includes a transformer T, wherein the primary side of the transformer T is the input end of the first isolation unit, and the secondary side of the transformer is the output end of the first isolation unit.

[0070] In this embodiment, the first capacitor C1, the primary side of the transformer T and the second resistor R2 are connected in series and then connected in parallel with the first resistor R1. The secondary side of the transformer T is connected to the signal conditioning circuit S, and the signal conditioning circuit S is connected to the controller C.

[0071] If the current direction of the first capacitor C1 is the first direction, that is, the capacitor current is from left to right, the first capacitor C1 is charged, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high-level signal, then the controller C determines that the discharge circuit is in the on state; if the current direction of the first capacitor C1 is the second direction, that is, the capacitor current is from right to left, the first capacitor C1 is discharged, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a low-level signal, then the controller C determines that the discharge circuit is in the off state.

[0072] This embodiment uses a set of detection circuits to detect the working state of the discharge circuit, and the charging and discharging processes of the first capacitor C1 correspond to different working states of the discharge circuit.

[0073] In order to achieve a wider coverage, a converter embodiment is also provided that uses two sets of detection circuits to detect the working state of the discharge circuit, which can detect the high voltage condition when the DC bus is working normally, and can also detect the low voltage test condition of the module during field maintenance. This method has a slightly increased cost. Compared with the second prior art, one set of detection circuits is about 4% of the cost of the Hall device. Then the two sets of detection circuits increase the cost by about 4% relative to the Hall device of the second prior art, which is equivalent to the cost of the two sets of detection circuits being 8% of the Hall device of the second prior art. In essence, the cost is greatly reduced, and a smaller volume is achieved compared to the second prior art. This detection method has a wide working voltage range and reliable detection signals.

[0074] like Figure 7 As shown, a second circuit diagram of a first embodiment of a converter is provided as another circuit connection method. Figure 6 As shown in the circuit diagram, Figure 7 The input end of the current detection circuit is connected in parallel to the power switch K1.

[0075] In this embodiment, the first capacitor C1, the primary side of the transformer T and the second resistor R2 are connected in series and then connected in parallel with the power switch K1. The secondary side of the transformer T is connected to the signal conditioning circuit S, and the signal conditioning circuit S is connected to the controller C.

[0076] If the current direction of the first capacitor C1 is the first direction, that is, the capacitor current is from left to right, the first capacitor C1 is charged, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high-level signal, then the controller C determines that the discharge circuit is in the off state; if the current direction of the first capacitor C1 is the second direction, that is, the capacitor current is from right to left, the first capacitor C1 is discharged, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a low-level signal, then the controller C determines that the discharge circuit is in the on state.

[0077] like Figure 8 As shown, a second embodiment of a converter is provided. Referring to the first circuit diagram of the second embodiment, the current detection circuit further includes a second resistor R2, and the isolation unit M includes:

[0078] A first transformer T1, wherein the primary side of the first transformer T1 is connected in series with the first capacitor C1 and the second resistor R2, and the secondary side of the first transformer T1 is electrically connected to the signal conditioning circuit S;

[0079] A second transformer T2, wherein the primary side of the second transformer T2 is connected in series with the first capacitor C1 and the second resistor R2, the primary side of the second transformer T2 is connected in parallel with the primary side of the first transformer T1, and the secondary side of the second transformer T2 is electrically connected to the signal conditioning circuit S;

[0080] A first diode D1, wherein a cathode of the first diode D1 is electrically connected to a second end of the primary side of the first transformer T1;

[0081] The second diode D2, wherein the anode of the second diode D2 is electrically connected to the second end of the primary side of the second transformer T2, the cathode of the second diode D2 is electrically connected to the anode of the first diode D1, and the first end of the second transformer T2 and the first end of the first transformer T1 are the same end.

[0082] The first capacitor C1 is connected in series with the primary side of the first transformer T1 and the second resistor R2, and then connected in parallel with the first resistor R1. The first diode D1 is connected between the first capacitor C1 and the primary side of the first transformer T1.

[0083] The first capacitor C1 is connected in series with the primary side of the second transformer T2 and the second resistor R2, and then connected in parallel with the first resistor R1. The second diode D2 is connected between the first capacitor C1 and the primary side of the second transformer T2.

[0084] In this embodiment, the current detection signal includes a first current detection signal and a second current detection signal, wherein the first transformer T1 outputs the first current detection signal, and the second transformer T2 outputs the second current detection signal.

[0085] In this embodiment, the signal conditioning circuit S includes two signal conditioning sub-circuits, the first signal conditioning sub-circuit receives the first current detection signal and outputs a discharge circuit working state signal to the controller; the second signal conditioning sub-circuit receives the second current detection signal and outputs a discharge circuit working state signal to the controller. The controller can determine the on state or off state of the discharge circuit according to the discharge circuit working state signal output by the first signal conditioning sub-circuit or the second signal conditioning sub-circuit.

[0086] When the current direction of the first capacitor C1 is the first direction, that is, the current of the first capacitor C1 is from left to right, the first capacitor C1 is charged, the first diode D1 is turned on, the first transformer T1 outputs the first current detection signal, the second diode D2 is turned off, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high level signal, and the controller C determines that the discharge circuit is in the on state;

[0087] When the current direction of the first capacitor C1 is the second direction, that is, the current of the first capacitor C1 is from right to left, the first capacitor C1 is discharged, the second diode D2 is turned on, the second transformer T2 outputs a second current detection signal, the first diode D1 is turned off, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a high level signal, and the controller C determines that the discharge circuit is in the off state.

[0088] like Fig. 9 As shown, a second circuit diagram of a second embodiment of a converter is provided as another circuit connection method. Figure 8 As shown in the circuit diagram, Fig. 9 The input end of the current detection circuit is connected in parallel to the power switch K1.

[0089] In this embodiment, the current detection circuit further includes: a second resistor R2, and the isolation unit M includes:

[0090] A first transformer T1, wherein the primary side of the first transformer T1 is connected in series with the first capacitor C1 and the second resistor R2, and the secondary side of the first transformer T1 is electrically connected to the signal conditioning circuit S;

[0091] A second transformer T2, wherein the primary side of the second transformer T2 is connected in series with the first capacitor C1 and the second resistor R2, the primary side of the second transformer T2 is connected in parallel with the primary side of the first transformer T1, and the secondary side of the second transformer T2 is electrically connected to the signal conditioning circuit S;

[0092] A first diode D1, wherein a cathode of the first diode D1 is electrically connected to a second end of the primary side of the first transformer T1;

[0093] The second diode D2, wherein the anode of the second diode D2 is electrically connected to the second end of the primary side of the second transformer T2, the cathode of the second diode D2 is electrically connected to the anode of the first diode D1, and the first end of the second transformer T2 and the first end of the first transformer T1 are the same end.

[0094] The first capacitor C1 is connected in series with the primary side of the first transformer T1 and the second resistor R2, and then connected in parallel with the power switch K1. The first diode D1 is connected between the first capacitor C1 and the primary side of the first transformer T1.

[0095] The first capacitor C1 is connected in series with the primary side of the second transformer T2 and the second resistor R2, and then connected in parallel with the power switch K1. The second diode D2 is connected between the first capacitor C1 and the primary side of the second transformer T2.

[0096] In this embodiment, the current detection signal includes a first current detection signal and a second current detection signal, wherein the first transformer T1 outputs the first current detection signal, and the second transformer T2 outputs the second current detection signal.

[0097] In this embodiment, the signal conditioning circuit S includes two signal conditioning sub-circuits, the first signal conditioning sub-circuit receives the first current detection signal and outputs a discharge circuit working state signal to the controller; the second signal conditioning sub-circuit receives the second current detection signal and outputs a discharge circuit working state signal to the controller. The controller can determine the on state or off state of the discharge circuit according to the discharge circuit working state signal output by the first signal conditioning sub-circuit or the second signal conditioning sub-circuit.

[0098] When the current direction of the first capacitor C1 is the first direction, that is, the capacitor current is from left to right, the first capacitor C1 is charged, the first diode D1 is turned on, the first transformer T1 outputs the first current detection signal, the second diode D2 is turned off, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high level signal, and the controller C determines that the discharge circuit is in the off state;

[0099] When the current direction of the first capacitor C1 is the second direction, that is, the capacitor current is from right to left, the first capacitor C1 is discharged, the second diode D2 is turned on, the second transformer T2 outputs a second current detection signal, the first diode D1 is turned off, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a high level signal, and the controller C determines that the discharge circuit is in the on state.

[0100] like Fig.10 As shown, a third embodiment of a converter is provided. Referring to the first circuit diagram of the third embodiment, the current detection circuit further includes: a second resistor R2, and the isolation unit includes:

[0101] A first optical coupler O11, wherein a first capacitor C1, an input end of the first optical coupler O11 and a second resistor R2 are connected in series, and an output end of the first optical coupler O11 is electrically connected to a signal conditioning circuit S;

[0102] The second optocoupler O12, wherein the first capacitor C1, the input end of the second optocoupler O12 and the second resistor R2 are connected in series, the first end of the input end of the second optocoupler O12 is electrically connected to the second end of the input end of the first optocoupler O11, the second end of the input end of the second optocoupler O12 is electrically connected to the first end of the input end of the first optocoupler O11, the first end of the input end of the second optocoupler O12 has the same polarity as the first end of the input end of the first optocoupler O11, and the output end of the second optocoupler O12 is electrically connected to the signal conditioning circuit S.

[0103] In this embodiment, the first capacitor C1 is connected in series with the input end of the first optocoupler O11 and the second resistor R2, and then connected in parallel with the first resistor R1, wherein the input end of the first optocoupler O11 is the light emitting device D11, and the output end of the first optocoupler O11 is the photosensor Q11.

[0104] In this embodiment, the first capacitor C1 is connected in series with the input end of the second optocoupler O12 and the second resistor R2, and then connected in parallel with the first resistor R1, wherein the input end of the second optocoupler O12 is the light emitting device D12, and the output end of the second optocoupler O12 is the photosensitive device Q12. Including but not limited to, the light emitting device D11 and the light emitting device D12 may be light emitting diodes, and the photosensitive device Q11 and the photosensitive device Q12 may be phototransistors.

[0105] The first end of the light emitting device D11 has the same polarity as the first end of the light emitting device D12, for example, they can be an anode; the second end of the light emitting device D11 has the same polarity as the second end of the light emitting device D12, for example, they can be a cathode. The light emitting device D11 and the photosensitive device Q11 are arranged relative to each other in a closed space. The light emitting device D11 emits light when it is forward-conducted, and the photosensitive signal generated by the light irradiating the photosensitive device Q11 is used as a current detection signal. The light emitting device D12 and the photosensitive device Q12 are arranged relative to each other in a closed space. The light emitting device D12 emits light when it is forward-conducted, and the photosensitive signal generated by the light irradiating the photosensitive device Q12 is used as a current detection signal.

[0106] When the current direction of the first capacitor C1 is the first direction, that is, the current of the first capacitor C1 is from left to right, the first capacitor C1 is charged, and the light-emitting device D11 at the input end of the first optocoupler device O11 is forward-conducted, emitting light to the photosensitive device Q11, and the photosensitive device Q11 generates a photosensitive signal as a first current detection signal. Therefore, the first optocoupler device O11 outputs the first current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high-level signal, and the controller C determines that the discharge circuit is in the on state; the light-emitting device D12 at the input end of the second optocoupler device O12 is reversely cut off.

[0107] When the current direction of the first capacitor C1 is the second direction, that is, the current of the first capacitor C1 is from right to left, the first capacitor C1 is discharged, the light-emitting device D12 at the input end of the second optocoupler device O12 is forward-conducted, and emits light to the photosensitive device Q12. The photosensitive device Q12 generates a photosensitive signal as a second current detection signal. Therefore, the second optocoupler device O12 outputs a second current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a high-level signal, and the controller C determines that the discharge circuit is in the off state; the light-emitting device D11 at the input end of the first optocoupler device O11 is reversely cut off.

[0108] In this embodiment, the signal conditioning circuit S includes two signal conditioning sub-circuits, the first signal conditioning sub-circuit receives the first current detection signal and outputs a discharge circuit working state signal to the controller; the second signal conditioning sub-circuit receives the second current detection signal and outputs a discharge circuit working state signal to the controller. The controller can determine the on state or off state of the discharge circuit according to the discharge circuit working state signal output by the first signal conditioning sub-circuit or the second signal conditioning sub-circuit.

[0109] like Fig.11 As shown, a second circuit diagram of a third embodiment of a converter is provided as another circuit connection method. Fig.10 As shown in the circuit diagram, Fig.11 The input end of the current detection circuit is connected in parallel to the power switch K1.

[0110] In this embodiment, the current detection circuit includes: a first capacitor C1, a second resistor R2, a first optocoupler device O11, and a second optocoupler device O12.

[0111] The first capacitor C1 is connected in series with the input end of the first optocoupler O11 and the second resistor R2, and then connected in parallel with the power switch K1. The output end of the first optocoupler O11 is electrically connected to the signal conditioning circuit S, wherein the input end of the first optocoupler O11 is the light-emitting device D11, and the output end of the first optocoupler O11 is the photosensor Q11.

[0112] The first capacitor C1 is connected in series with the input end of the second optocoupler O12 and the second resistor R2, and then connected in parallel with the power switch K1. The output end of the second optocoupler O12 is electrically connected to the signal conditioning circuit S, wherein the input end of the second optocoupler O12 is the light emitting device D12, and the output end of the second optocoupler O12 is the photosensitive device Q12. Including but not limited to, the above-mentioned light emitting device D11 and the light emitting device D12 can be light emitting diodes, and the above-mentioned photosensitive device Q11 and the photosensitive device Q12 can be phototransistors.

[0113] The first end of the light emitting device D11 has the same polarity as the first end of the light emitting device D12, for example, they can be an anode; the second end of the light emitting device D11 has the same polarity as the second end of the light emitting device D12, for example, they can be a cathode. The light emitting device D11 and the photosensitive device Q11 are arranged relative to each other in a closed space. The light emitting device D11 emits light when it is forward-conducted, and the photosensitive signal generated by the light irradiating the photosensitive device Q11 is used as a current detection signal. The light emitting device D12 and the photosensitive device Q12 are arranged relative to each other in a closed space. The light emitting device D12 emits light when it is forward-conducted, and the photosensitive signal generated by the light irradiating the photosensitive device Q12 is used as a current detection signal.

[0114] When the current direction of the first capacitor C1 is the first direction, that is, the current of the first capacitor C1 is from left to right, the first capacitor C1 is charged, and the light-emitting device D11 at the input end of the first optocoupler device O11 is forward-conducted, emitting light to the photosensitive device Q11, and the photosensitive device Q11 generates a photosensitive signal as a first current detection signal. Therefore, the first optocoupler device O11 outputs the first current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high-level signal, and the controller C determines that the discharge circuit is in the off state; the light-emitting device D12 at the input end of the second optocoupler device O12 is reversely cut off.

[0115] When the current direction of the first capacitor C1 is the second direction, that is, the current of the first capacitor C1 is from right to left, the first capacitor C1 is discharged, the light-emitting device D12 at the input end of the second optocoupler device O12 is forward-conducted, and emits light to the photosensitive device Q12. The photosensitive device Q12 generates a photosensitive signal as a second current detection signal. Therefore, the second optocoupler device O12 outputs a second current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a high-level signal, and the controller C determines that the discharge circuit is in the on state; the light-emitting device D11 at the input end of the first optocoupler device O11 is reversely cut off.

[0116] In this embodiment, the signal conditioning circuit S includes two signal conditioning sub-circuits, the first signal conditioning sub-circuit receives the first current detection signal and outputs a discharge circuit working state signal to the controller; the second signal conditioning sub-circuit receives the second current detection signal and outputs a discharge circuit working state signal to the controller. The controller can determine the on state or off state of the discharge circuit according to the discharge circuit working state signal output by the first signal conditioning sub-circuit or the second signal conditioning sub-circuit.

[0117] Fig.12 A first circuit diagram of a converter in another embodiment of the present disclosure is shown. Fig.13 A second circuit diagram of a converter in another embodiment of the present disclosure is shown. Fig.12 and Fig.13As shown, a converter provided in another embodiment of the present disclosure includes:

[0118] The discharge circuit includes a first resistor R1 and a power switch K1 connected in series, wherein the power switch K1 includes a control terminal, a first terminal and a second terminal;

[0119] The first current detection circuit comprises: a first capacitor C1; a first isolation unit M1, wherein an input end of the first isolation unit M1 is connected in series with the first capacitor C1; wherein the first current detection circuit detects a direction of a current flowing through the first capacitor C1 and outputs a first current detection signal;

[0120] The second current detection circuit comprises: a second capacitor C2; a second isolation unit M2, wherein an input end of the second isolation unit M2 is connected in series with the second capacitor C2; wherein the second current detection circuit detects a direction of a current flowing through the second capacitor C2 and outputs a second current detection signal;

[0121] The input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel to the first resistor R1, or the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel to the power switch K1;

[0122] A signal conditioning circuit S is electrically connected to an output end of the first current detection circuit and an output end of the second current detection circuit, receives one of the first current detection signal and the second current detection signal, and outputs a discharge circuit working state signal;

[0123] The controller C is electrically connected to the signal conditioning circuit S, receives the working state signal of the discharge circuit, and determines whether the discharge circuit is in the on state or the off state.

[0124] When the power switch K1 is turned on, the discharge circuit is in an on state; when the power switch K1 is turned off, the discharge circuit is in an off state.

[0125] In this embodiment, the signal conditioning circuit S includes two signal conditioning sub-circuits, the first signal conditioning sub-circuit receives the first current detection signal and outputs a discharge circuit working state signal to the controller; the second signal conditioning sub-circuit receives the second current detection signal and outputs a discharge circuit working state signal to the controller. The controller can determine the on state or off state of the discharge circuit according to the discharge circuit working state signal output by the first signal conditioning sub-circuit or the second signal conditioning sub-circuit.

[0126] Fig.12 In the first circuit diagram of the converter, the input end of the first current detection circuit is connected in parallel to the first resistor R1, and the input end of the second current detection circuit is connected in parallel to the first resistor R1; Fig.13In the second circuit diagram of the converter, the input end of the first current detection circuit is connected in parallel to the power switch K1, and the input end of the second current detection circuit is connected in parallel to the power switch K1.

[0127] When the voltage across the first resistor R1 or the power switch K1 changes, the capacitive current of the first capacitor C1 and the second capacitor C2 changes. The first current detection circuit is used to detect the direction of the current flowing through the first capacitor C1, and the second current detection circuit is used to detect the direction of the current flowing through the second capacitor C2, so as to determine the working state of the discharge circuit.

[0128] like Fig.12 As shown, when the input ends of the first current detection circuit and the second current detection circuit are connected in parallel with the first resistor R1, if it is detected that the current direction of the first capacitor C1 is the first direction, that is, the current of the first capacitor C1 is from left to right, and the first capacitor C1 is charged, the controller C determines that the discharge circuit is in the on state; if it is detected that the current direction of the second capacitor C2 is the second direction, that is, the current of the second capacitor is from right to left, and the second capacitor C2 is discharged, the controller C determines that the discharge circuit is in the off state.

[0129] like Fig.13 As shown, when the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel with the power switch K1, if it is detected that the current direction of the second capacitor C2 is the second direction, that is, the current of the second capacitor C2 is from right to left, and the second capacitor C2 is discharged, the controller C determines that the discharge circuit is in the on state; if it is detected that the current direction of the first capacitor C1 is the first direction, that is, the current of the first capacitor C1 is from left to right, and the first capacitor C1 is charged, the controller C determines that the discharge circuit is in the off state.

[0130] The signal conditioning circuit S converts the first current detection signal of the current direction of the first capacitor C1 or the second current detection signal of the second capacitor C2 received in the form of an analog signal into a discharge circuit working state signal in the form of a digital signal. The discharge circuit working state signal includes a first signal and a second signal. The first signal corresponds to the first direction, and the second signal corresponds to the second direction.

[0131] In this embodiment, the signal conditioning circuit S includes two signal conditioning sub-circuits, the first signal conditioning sub-circuit receives the first current detection signal and outputs a discharge circuit working state signal to the controller; the second signal conditioning sub-circuit receives the second current detection signal and outputs a discharge circuit working state signal to the controller. The controller can determine the on state or off state of the discharge circuit according to the discharge circuit working state signal output by the first signal conditioning sub-circuit or the second signal conditioning sub-circuit.

[0132] like Fig.14As shown, a fourth embodiment of a converter in another embodiment is provided. Referring to the first circuit diagram of the fourth embodiment, the first current detection circuit further includes: a second resistor R2; the first isolation unit includes: a first transformer T1, wherein the first capacitor C1, the primary side of the first transformer T1 and the second resistor R2 are connected in series, and the secondary side of the first transformer T1 is electrically connected to the signal conditioning circuit S; a first voltage regulator tube ZD1, wherein the anode of the first voltage regulator tube ZD1 is electrically connected to the first end of the primary side of the first transformer T1, and the cathode of the first voltage regulator tube ZD1 is electrically connected to the second end of the primary side of the first transformer T1;

[0133] The second current detection circuit also includes: a third resistor R3; the second isolation unit includes: a second transformer T2, wherein the second capacitor C2, the primary side of the second transformer T2 and the third resistor R3 are connected in series, the first end of the primary side of the second transformer T2 and the first end of the primary side of the first transformer T1 are the same-name terminals, and the secondary side of the second transformer T2 is electrically connected to the signal conditioning circuit S; a second voltage regulator tube ZD2, the anode of the second voltage regulator tube ZD2 is electrically connected to the second end of the primary side of the second transformer T2, and the cathode of the second voltage regulator tube ZD2 is electrically connected to the first end of the primary side of the second transformer T2.

[0134] In this embodiment, the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel to the first resistor R1.

[0135] like Fig.15 As shown, a second circuit diagram of a fourth embodiment of a converter in another embodiment is provided as another circuit connection method. Fig.14 As shown in the circuit diagram, Fig.15 The input end of the first current detection circuit and the input end of the second detection circuit are connected in parallel to the power switch K1.

[0136] like Fig.15 As shown, in this embodiment, the first capacitor C1, the primary side of the first transformer T1 and the second resistor R2 are connected in series, and then connected in parallel with the power switch K1, the first voltage regulator ZD1 is connected in parallel with the primary side of the first transformer T1, and the secondary side of the first transformer T1 is electrically connected to the signal conditioning circuit S, wherein the anode 1 of the first voltage regulator ZD1 is electrically connected to the first end of the primary side of the first transformer T1, and the cathode 2 of the first voltage regulator ZD1 is electrically connected to the second end of the primary side of the first transformer T1. The second capacitor C2, the primary side of the second transformer T2 and the third resistor R3 are connected in series, and then connected in parallel with the power switch K1, the second voltage regulator ZD2 is connected in parallel with the primary side of the second transformer T2, and the secondary side of the second transformer T2 is electrically connected to the signal conditioning circuit S, wherein the anode 1 of the second voltage regulator ZD2 is electrically connected to the second end of the primary side of the second transformer T2, and the cathode 2 of the second voltage regulator ZD2 is electrically connected to the first end of the primary side of the second transformer T2.

[0137] like Fig.14 and Fig.15 In the embodiment shown, the forward bias voltage of the first voltage regulator tube ZD1 and the second voltage regulator tube ZD2 is about 0.3V-0.7V, and the reverse bias voltage breaks down at about 20V.

[0138] like Fig.14 As shown, when the current direction of the first capacitor C1 and the second capacitor C2 is the first direction, the capacitor current is from left to right, the first capacitor C1 and the second capacitor C2 are charged, and the primary side of the first transformer T1 has a voltage of about 20V due to the first voltage regulator ZD1, which exceeds the threshold set by the signal conditioning circuit S, so the signal output by the secondary side of the first transformer T1 can be recognized by the signal conditioning circuit S, the first transformer T1 outputs a first current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high-level signal, and the controller C determines that the discharge circuit is in the on state. The primary side of the second transformer T2 has a voltage of about 0.3V-0.7V due to the forward bias of the second voltage regulator ZD2, which is lower than the threshold set by the signal conditioning circuit S, so the signal output by the secondary side of the second transformer T2 cannot be recognized by the signal conditioning circuit S.

[0139] When the current direction of the first capacitor C1 and the second capacitor C2 is the second direction, the capacitor current is from right to left, the first capacitor C1 and the second capacitor C2 are discharged, and the primary side of the second transformer T2 has a voltage of about 20V due to the second voltage regulator ZD2, which exceeds the threshold set by the signal conditioning circuit S, so the signal output by the secondary side of the second transformer T2 can be recognized by the signal conditioning circuit S, the second transformer outputs a second current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a high-level signal, and the controller C determines that the discharge circuit is in the off state. The primary side of the first transformer T1 has a voltage of about 0.3V-0.7V due to the forward bias of the first voltage regulator ZD1, which is lower than the threshold set by the signal conditioning circuit S, so the signal output by the secondary side of the first transformer T1 cannot be recognized by the signal conditioning circuit S.

[0140] like Fig.15As shown, when the current direction of the first capacitor C1 and the second capacitor C2 is the first direction, the capacitor current is from left to right, the first capacitor C1 and the second capacitor C2 are charged, and the primary side of the first transformer T1 has a voltage of about 20V due to the first voltage regulator ZD1, which exceeds the threshold set by the signal conditioning circuit S, so the signal output by the secondary side of the first transformer T1 can be recognized by the signal conditioning circuit S, the first transformer T1 outputs a first current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high-level signal, and the controller C determines that the discharge circuit is in the off state. The primary side of the second transformer T2 has a voltage of about 0.3V-0.7V due to the forward bias of the second voltage regulator ZD2, which is lower than the threshold set by the signal conditioning circuit S, so the signal output by the secondary side of the second transformer T2 cannot be recognized by the signal conditioning circuit S.

[0141] When the current direction of the first capacitor C1 and the second capacitor C2 is the second direction, the capacitor current is from right to left, the first capacitor C1 and the second capacitor C2 are discharged, and the primary side of the second transformer T2 has a voltage of about 20V due to the second voltage regulator ZD2, which exceeds the threshold set by the signal conditioning circuit S, so the signal output by the secondary side of the second transformer T2 can be recognized by the signal conditioning circuit S, the second transformer outputs a second current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a high-level signal, and the controller C determines that the discharge circuit is in the on state. The primary side of the first transformer T1 has a voltage of about 0.3V-0.7V due to the forward bias of the first voltage regulator ZD1, which is lower than the threshold set by the signal conditioning circuit S, so the signal output by the secondary side of the first transformer T1 cannot be recognized by the signal conditioning circuit S.

[0142] like Fig.16 As shown, a fifth embodiment of a converter in another embodiment is provided. Referring to the first circuit diagram of the fifth embodiment, the first current detection circuit further includes:

[0143] A second resistor R2;

[0144] The first isolation unit includes: a first optocoupler device O21, wherein a first capacitor C1, an input end of the first optocoupler device O21 and a second resistor R2 are connected in series, and an output end of the first optocoupler device O21 is electrically connected to a signal conditioning circuit S; a first diode D31, wherein a cathode of the first diode D31 is electrically connected to a first end of the input end of the first optocoupler device O21, and an anode of the first diode D31 is electrically connected to a second end of the input end of the first optocoupler device O21;

[0145] The second current detection circuit also includes:

[0146] a third resistor R3; a second isolation unit comprises: a second optocoupler O22, wherein a second capacitor C2, an input end of the second optocoupler O22 and a third resistor R3 are connected in series, a first end of the input end of the second optocoupler O22 is electrically connected to a second end of the input end of the first optocoupler O21, a second end of the input end of the second optocoupler O22 is electrically connected to a first end of the input end of the first optocoupler O21, a first end of the input end of the second optocoupler O22 has the same polarity as a first end of the input end of the first optocoupler O21, and an output end of the second optocoupler O22 is electrically connected to a signal conditioning circuit S; a second diode D32, an anode of the second diode D32 is electrically connected to a second end of the input end of the second optocoupler O22, and a cathode of the second diode D32 is electrically connected to a first end of the input end of the second optocoupler O22.

[0147] In this embodiment, the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel to the first resistor R1.

[0148] In the first current detection circuit, the first capacitor C1, the input end of the first optocoupler device O21 and the second resistor R2 are connected in series and then connected in parallel with the first resistor R1, wherein the input end of the first optocoupler device O21 is the light-emitting device D21, and the output end of the first optocoupler device O21 is the photosensitive device Q21.

[0149] In the second current detection circuit, the second capacitor C2, the input end of the second optocoupler O22 and the third resistor R3 are connected in series and then connected in parallel with the first resistor R1, wherein the input end of the second optocoupler O22 is the light-emitting device D22, and the output end of the second optocoupler O22 is the photosensitive device Q22.

[0150] The first end of the light emitting device D21 has the same polarity as the first end of the light emitting device D22, for example, they may be anodes; the second end of the light emitting device D21 has the same polarity as the second end of the light emitting device D22, for example, they may be cathodes.

[0151] like Fig.17 As shown, a second circuit diagram of a fifth embodiment of a converter in another embodiment is provided as another circuit connection method. Fig.16 As shown in the circuit diagram, Fig.17 The input end of the first current detection circuit and the input end of the second detection circuit are connected in parallel to the power switch K1.

[0152] In the first current detection circuit, the first capacitor C1, the input end of the first optocoupler device O21 and the second resistor R2 are connected in series and then connected in parallel with the power switch K1, wherein the input end of the first optocoupler device O21 is the light-emitting device D21, and the output end of the first optocoupler device O21 is the photosensor Q21.

[0153] In the second current detection circuit, the second capacitor C2, the input end of the second optocoupler O22 and the third resistor R3 are connected in series and then connected in parallel with the power switch K1. The input end of the second optocoupler O22 is the light-emitting device D22, and the output end of the second optocoupler O22 is the photosensor Q22.

[0154] The first end of the light emitting device D21 has the same polarity as the first end of the light emitting device D22, for example, they may be anodes; the second end of the light emitting device D21 has the same polarity as the second end of the light emitting device D22, for example, they may be cathodes.

[0155] like Fig.16 As shown, when the current direction of the first capacitor and the second capacitor is the first direction, the capacitor current is from left to right, the first capacitor C1 and the second capacitor C2 are charged, the light-emitting device D21 at the input end of the first optocoupler device O21 is forward-conducted, and emits light to the photosensitive device Q21, and the photosensitive device Q21 generates a photosensitive signal as a first current detection signal. Therefore, the first optocoupler device O21 outputs the first current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high-level signal, and the controller C determines that the discharge circuit is in the on state; the light-emitting device D22 at the input end of the second optocoupler device O22 is reversely cut off, and the signal output by the photosensitive device Q22 cannot be recognized by the signal conditioning circuit S.

[0156] When the current direction of the first capacitor and the second capacitor is the second direction, the capacitor current is from right to left, the first capacitor C1 and the second capacitor C2 are discharged, the light emitting device D22 at the input end of the second optocoupler O22 is forwardly conducted, and emits light to the photosensitive device Q22, and the photosensitive device Q22 generates a photosensitive signal as a second current detection signal, so the second optocoupler O22 outputs the second current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a high-level signal, and the controller C determines that the discharge circuit is in the off state. The light emitting device D21 at the input end of the first optocoupler O21 is reversely cut off, and the signal output by the photosensitive device Q21 cannot be recognized by the signal conditioning circuit S.

[0157] like Fig.17As shown, when the current direction of the first capacitor and the second capacitor is the first direction, the capacitor current is from left to right, the first capacitor C1 and the second capacitor C2 are charged, the light-emitting device D21 at the input end of the first optocoupler device O21 is forward-conducted, and emits light to the photosensitive device Q21, and the photosensitive device Q21 generates a photosensitive signal as a first current detection signal. Therefore, the first optocoupler device O21 outputs the first current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the first signal, wherein the first signal is a high-level signal, and the controller C determines that the discharge circuit is in the off state; the light-emitting device D22 at the input end of the second optocoupler device O22 is reversely cut off, and the signal output by the photosensitive device Q22 cannot be recognized by the signal conditioning circuit S.

[0158] When the current direction of the first capacitor and the second capacitor is the second direction, the capacitor current is from right to left, the first capacitor C1 and the second capacitor C2 are discharged, the light emitting device D22 at the input end of the second optocoupler O22 is forwardly turned on, and emits light to the photosensitive device Q22, and the photosensitive device Q22 generates a photosensitive signal as a second current detection signal, so the second optocoupler O22 outputs the second current detection signal, and the discharge circuit working state signal output by the signal conditioning circuit S is the second signal, wherein the second signal is a high-level signal, and the controller C determines that the discharge circuit is in the on state. The light emitting device D21 at the input end of the first optocoupler O21 is reversely cut off, and the signal output by the photosensitive device Q21 cannot be recognized by the signal conditioning circuit S.

[0159] Taking a STATCOM project as an example, the system availability design target is 99%, and the transient overvoltage is 2.0pu 50ms; in order to reduce cost and volume, the first resistor R1 of the selected discharge circuit has a small margin for thermal shock resistance; since the discharge circuit operation frequency may be high, the detection of the discharge circuit working status needs to be completed in a relatively short time; the bus voltage range is wide, and the bus voltage is about 1000V during normal operation. Not only does it need to detect the working status of the discharge circuit for normal operation, but it also needs to detect the working status of the discharge circuit during shutdown self-test (DC bus voltage 24V).

[0160] In one example, the DC bus voltage Vdc_bus=1000V is used for simulation, and the Figure 6 or Figure 7 The converter shown in the figure detects the working state of the discharge circuit; Fig.18 As shown in the figure, the circuit simulation waveforms are as follows from top to bottom: the voltage of the first resistor of the discharge circuit, the current of the first capacitor, the output voltage of the secondary side of the transformer, and the output of the signal conditioning circuit. Fig.18It can be concluded that the output of the signal conditioning circuit can very accurately determine the working state of the discharge circuit. The discharge circuit state signal is a high-level signal at 5-10ms and 20-25ms, indicating that the discharge circuit is in the on state, and the discharge circuit is in the off state at other times.

[0161] In another example, the DC bus voltage Vdc_bus=1300V is used for simulation, and the Fig.14 or Fig.15 The converter shown in the figure detects the working state of the discharge circuit; Fig.19 As shown, (a) represents the first current detection circuit, (b) represents the second current detection circuit, and the circuit simulation waveforms are as follows from top to bottom: the voltage of the first resistor of the discharge circuit, the input of the signal conditioning circuit, and the output of the signal conditioning circuit; Fig.19 It can be concluded from (a) that the discharge circuit state signal output by the signal conditioning circuit is the first signal, which is a high-level signal. Fig.19 It can be concluded from (b) that the discharge circuit status signal output by the signal conditioning circuit is the second signal, and the second signal is a high-level signal. By observing the output signal of the signal conditioning circuit, the working status of the discharge circuit can be judged very accurately.

[0162] The converter provided by the present invention can be used in devices that withstand short-term and severe fluctuations in the power grid, such as new energy power generation equipment, high and low voltage reactive power compensation equipment, energy storage and other power grid power smoothing equipment; another example is devices that withstand short-term energy backflow and uncontrolled rectifier-type inverters.

[0163] The present invention connects a detection device containing a capacitor in parallel at both ends of a resistor or a power device of a discharge circuit, and determines the working state of the discharge circuit by detecting the capacitor current; the method of detecting the current of the parallel capacitor has a fast response speed and low cost.

[0164] It should be noted that the acquisition, storage, use, and processing of data in the technical solution disclosed in this disclosure are in compliance with the relevant provisions of national laws and regulations, and various types of data such as personal identity data, operation data, behavioral data, etc. related to individuals, customers, and groups obtained in the embodiments of this disclosure have all been authorized.

[0165] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. The present disclosure is intended to cover any variations, uses or adaptations of the present disclosure, which follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The description and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A converter, characterized in that: include: A discharge circuit includes a first resistor and a power switch connected in series, wherein the power switch includes a control terminal, a first terminal, and a second terminal; Current detection circuit, including: a first capacitor; an isolation unit, wherein an input terminal of the isolation unit is connected in series with the first capacitor; The input end of the current detection circuit is connected in parallel to the first resistor and one of the power switch, and the current detection circuit detects the direction of the current flowing through the first capacitor and outputs a current detection signal; A signal conditioning circuit, electrically connected to the output end of the current detection circuit, receives the current detection signal, and outputs a discharge circuit working state signal; The controller is electrically connected to the signal conditioning circuit, receives the working state signal of the discharge circuit, and determines whether the discharge circuit is in the on state or the off state.

2. The converter according to claim 1, characterized in that: The current detection circuit also includes: a second resistor, connected in series with the first capacitor and the input end of the isolation unit; The isolation unit comprises: A transformer, wherein the primary side of the transformer is the input end of the isolation unit, the secondary side of the transformer is the output end of the isolation unit, and the secondary side of the transformer outputs the current detection signal.

3. The converter according to claim 2, characterized in that: When the input end of the current detection circuit is connected in parallel with the first resistor, if it is detected that the current direction of the first capacitor is a first direction, the controller determines that the discharge circuit is in the on state; If it is detected that the current direction of the first capacitor is the second direction, the controller determines that the discharge circuit is in the off state; When the input end of the current detection circuit is connected in parallel with the power switch, if it is detected that the current direction of the first capacitor is the second direction, the controller determines that the discharge circuit is in the on state; if it is detected that the current direction of the first capacitor is the first direction, the controller determines that the discharge circuit is in the off state; The first direction is opposite to the second direction.

4. The converter according to claim 3, characterized in that: The signal conditioning circuit converts the current detection signal received in the form of an analog signal into the discharge circuit working status signal in the form of a digital signal, wherein the discharge circuit working status signal includes a first signal and a second signal, wherein the first signal corresponds to the first direction and the second signal corresponds to the second direction.

5. The converter according to claim 1, characterized in that: The current detection circuit also includes: A second resistor; The isolation unit comprises: a first transformer, wherein the first capacitor, the primary side of the first transformer and the second resistor are connected in series, and the secondary side of the first transformer is electrically connected to the signal conditioning circuit; a second transformer, wherein the first capacitor, the primary side of the second transformer and the second resistor are connected in series, the primary side of the second transformer is connected in parallel with the primary side of the first transformer, and the secondary side of the second transformer is electrically connected to the signal conditioning circuit; a first diode, wherein a cathode of the first diode is electrically connected to the second end of the primary side of the first transformer; A second diode, wherein an anode of the second diode is electrically connected to the second end of the primary side of the second transformer, a cathode of the second diode is electrically connected to the anode of the first diode, and a first end of the second transformer is a same-name end as a first end of the first transformer.

6. The converter according to claim 5, characterized in that The current detection signal includes a first current detection signal and a second current detection signal. When the current direction of the first capacitor is a first direction, the first transformer outputs the first current detection signal; when the current direction of the first capacitor is a second direction, the second transformer outputs the second current detection signal.

7. The converter according to claim 1, characterized in that: The current detection circuit also includes: A second resistor; The isolation unit comprises: A first optocoupler device, wherein the first capacitor, the input end of the first optocoupler device and the second resistor are connected in series, and the output end of the first optocoupler device is electrically connected to the signal conditioning circuit; A second optocoupler device, wherein the first capacitor, the input end of the second optocoupler device and the second resistor are connected in series, the output end of the second optocoupler device is electrically connected to the signal conditioning circuit, and the first end of the input end of the second optocoupler device is electrically connected to the second end of the input end of the first optocoupler device, the second end of the input end of the second optocoupler device is electrically connected to the first end of the input end of the first optocoupler device, and the first end of the input end of the second optocoupler device has the same polarity as the first end of the input end of the first optocoupler device.

8. The converter according to claim 7, characterized in that: The current detection signal includes a first current detection signal and a second current detection signal. When the current direction of the first capacitor is a first direction, the first optocoupler device outputs the first current detection signal; when the current direction of the first capacitor is a second direction, the second optocoupler device outputs the second current detection signal.

9. The converter according to claim 6 or 8, characterized in that: When the input end of the current detection circuit is connected in parallel with the first resistor, if it is detected that the current direction of the first capacitor is a first direction, the controller determines that the discharge circuit is in the on state; If it is detected that the current direction of the first capacitor is the second direction, the controller determines that the discharge circuit is in the off state; When the input end of the current detection circuit is connected in parallel with the power switch, if it is detected that the current direction of the first capacitor is the second direction, the controller determines that the discharge circuit is in the on state; if it is detected that the current direction of the first capacitor is the first direction, the controller determines that the discharge circuit is in the off state; The first direction is opposite to the second direction.

10. The converter according to claim 9, characterized in that The signal conditioning circuit converts the first current detection signal or the second current detection signal received in the form of an analog signal into the discharge circuit working status signal in the form of a digital signal, and the discharge circuit working status signal includes a first signal and a second signal, the first signal corresponds to the first direction, and the second signal corresponds to the second direction.

11. A converter, characterized in that: include: A discharge circuit includes a first resistor and a power switch connected in series, wherein the power switch includes a control terminal, a first terminal, and a second terminal; The first current detection circuit comprises: a first capacitor; A first isolation unit, wherein an input terminal of the first isolation unit is connected in series with the first capacitor; Wherein, the first current detection circuit detects the direction of the current flowing through the first capacitor and outputs a first current detection signal; The second current detection circuit comprises: A second capacitor; A second isolation unit, wherein an input terminal of the second isolation unit is connected in series with the second capacitor; Wherein, the second current detection circuit detects the direction of the current flowing through the second capacitor and outputs a second current detection signal; Wherein, the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel to the first resistor, or the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel to the power switch; a signal conditioning circuit, electrically connected to an output end of the first current detection circuit and an output end of the second current detection circuit, receiving one of the first current detection signal and the second current detection signal, and outputting a discharge circuit working state signal; The controller is electrically connected to the signal conditioning circuit, receives the working state signal of the discharge circuit, and determines whether the discharge circuit is in the on state or the off state.

12. The converter according to claim 11, characterized in that When the input end of the first current detection circuit and the input end of the second current detection circuit are connected in parallel with the first resistor, if it is detected that the current direction of the first capacitor is a first direction, the controller determines that the discharge circuit is in the on state; if it is detected that the current direction of the second capacitor is a second direction, the controller determines that the discharge circuit is in the off state; When the input end of the first current detection circuit and the input end of the second current detection circuit are respectively connected in parallel with the power switch, if it is detected that the current direction of the second capacitor is the second direction, the controller determines that the discharge circuit is in the on state; if it is detected that the current direction of the first capacitor is the first direction, the controller determines that the discharge circuit is in the off state; The first direction is opposite to the second direction.

13. The converter according to claim 12, characterized in that The signal conditioning circuit converts the first current detection signal or the second current detection signal received in the form of an analog signal into the discharge circuit working status signal in the form of a digital signal, and the discharge circuit working status signal includes a first signal and a second signal, the first signal corresponds to the first direction, and the second signal corresponds to the second direction.

14. The converter according to claim 12, characterized in that: The first current detection circuit further includes: a second resistor, connected in series with the first capacitor and the input end of the first isolation unit; The first isolation unit comprises: A first transformer, wherein a primary side of the first transformer is the input end of the first isolation unit, and a secondary side of the first transformer is the output end of the first isolation unit; a first voltage regulator tube, wherein an anode of the first voltage regulator tube is electrically connected to a first end of the primary side of the first transformer, and a cathode of the first voltage regulator tube is electrically connected to a second end of the primary side of the first transformer; The second current detection circuit further includes: a third resistor, connected in series with the second capacitor and the input end of the second isolation unit; The second isolation unit comprises: a second transformer, wherein the primary side of the second transformer is the input end of the second isolation unit, the secondary side of the second transformer is the output end of the second isolation unit, and the first end of the primary side of the second transformer and the first end of the primary side of the first transformer are the same-named ends; A second voltage regulator tube, wherein an anode of the second voltage regulator tube is electrically connected to the second end of the primary side of the second transformer, and a cathode of the second voltage regulator tube is electrically connected to the first end of the primary side of the second transformer.

15. The converter according to claim 14, characterized in that When the current direction of the first capacitor is the first direction, the first transformer outputs the first current detection signal; When the current direction of the second capacitor is the second direction, the second transformer outputs the second current detection signal.

16. The converter according to claim 12, characterized in that The first current detection circuit further includes: a second resistor, connected in series with the first capacitor and the input end of the first isolation unit; The first isolation unit comprises: A first optocoupler device, wherein an input end of the first optocoupler device is the input end of the first isolation unit, and an output end of the first optocoupler device is the output end of the first isolation unit; a first diode, wherein a cathode of the first diode is electrically connected to a first end of the input end of the first optocoupler device, and an anode of the first diode is electrically connected to a second end of the input end of the first optocoupler device; The second current detection circuit further includes: a third resistor, connected in series with the second capacitor and the input end of the second isolation unit; The second isolation unit comprises: a second optocoupler device, wherein the input end of the second optocoupler device is the input end of the second isolation unit, the output end of the second optocoupler device is the output end of the second isolation unit, the first end of the input end of the second optocoupler device is electrically connected to the second end of the input end of the first optocoupler device, the second end of the input end of the second optocoupler device is electrically connected to the first end of the input end of the first optocoupler device, and the first end of the input end of the second optocoupler device has the same polarity as the first end of the input end of the first optocoupler device; A second diode, wherein an anode of the second diode is electrically connected to the second end of the input end of the second optocoupler device, and a cathode of the second diode is electrically connected to the first end of the input end of the second optocoupler device.

17. The converter according to claim 16, characterized in that When the current direction of the first capacitor is the first direction, the first optocoupler device outputs the first current detection signal; When the current direction of the second capacitor is the second direction, the second optocoupler device outputs the second current detection signal.

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