A power conversion system and a method for detecting short circuit of a main switch thereof

Abstract

The application provides a power conversion system and a main switch short circuit detection method thereof. In the short circuit fault detection method, when all the first side main switches in the power conversion system do not have short circuit faults, the power converter in the power conversion system is used to charge the second side bus capacitor in the power conversion system. Therefore, when the second side voltage of the power conversion system is equal to zero, the second bus capacitor can also be charged, so that the voltage across the second bus capacitor always keeps consistent with the second side voltage, and false judgment in the process of detecting the short circuit fault of the second side main switch is avoided. Since the power conversion system can also be a direct current conversion system, and the second side main switch can also be a contactor, the main switch short circuit detection method of the power conversion system provided by the application can avoid false judgment in the process of detecting the sticking fault of the contactor on one side of the direct current conversion system when the voltage of the one side is equal to zero.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to a power conversion system and a main switch short circuit detection method thereof. BACKGROUND

[0002] At present, in order to ensure the safe operation of the DC conversion system, the contactors on both sides of the DC conversion system are detected for sticking fault before the DC conversion system is started. Generally, before the contactor on one side is detected for sticking fault, the bus capacitor on the side needs to be charged by using the voltage on the side of the DC conversion system.

[0003] However, when the operation mode of the DC conversion system is the constant bus voltage operation mode, since the voltage on one side of the DC conversion system is equal to zero, the charging of the bus capacitor on the side of the DC conversion system cannot be realized, so that the voltage across the bus capacitor on the side is always consistent with the voltage on the side, which further leads to misjudgment of the sticking fault detection, i.e. the DC conversion system cannot be started normally.

[0004] Therefore, how to avoid misjudgment in the process of detecting the contactor on one side of the DC conversion system for sticking fault when the voltage on the side is equal to zero is a technical problem to be solved. SUMMARY

[0005] Therefore, the present application provides a power conversion system and a main switch short circuit detection method thereof to avoid misjudgment in the process of detecting the contactor on one side of the DC conversion system for sticking fault when the voltage on the side is equal to zero.

[0006] To achieve the above object, the embodiments of the present application provide the following technical solutions:

[0007] In one aspect, the present application provides a main switch short circuit detection method of a power conversion system, the first side of the power conversion system is connected with a power supply, and the second side of the power conversion system is a DC side; the main switch short circuit detection method comprises:

[0008] determining whether all the first side main switches in the power conversion system have not occurred short circuit fault;

[0009] if all the first side main switches have not occurred short circuit fault, charging the second side bus capacitor in the power conversion system by using the first side voltage of the power conversion system and a power converter in the power conversion system;

[0010] after the charging is completed, detecting each second side main switch for short circuit fault in turns.

[0011] Optionally, detecting one second side main switch for short circuit fault comprises:

[0012] By controlling each of the second side main switches, the second side main switch to be detected is in an off state, and the remaining second side main switches are in a conductive state.

[0013] It is judged whether the voltage across the second side bus capacitor after charging is equal to the second side voltage of the power conversion system.

[0014] If the voltage across the second side bus capacitor after charging is equal to the second side voltage of the power conversion system, it is determined that the second side main switch to be detected has a short circuit fault.

[0015] Optionally, if the power converter is used as a voltage source, the voltage across the second side bus capacitor is charged to a first preset value, which is less than or equal to the set voltage value of the second side bus capacitor.

[0016] Optionally, if the power converter is used as a current source, the voltage across the second side bus capacitor is charged to a second preset value; the difference between the second side voltage of the power conversion system and the second preset value is less than or equal to a first preset overvoltage.

[0017] Optionally, charging the second side bus capacitor in the power conversion system by using the power converter in the power conversion system comprises:

[0018] All the first side main switches are closed, and the power converter is controlled to perform power conversion.

[0019] Optionally, if the first side of the power conversion system is a direct current side and each of the first side main switches is parallelly connected with a slow start circuit, it is judged whether all the first side main switches in the power conversion system have a short circuit fault, comprising:

[0020] The first side bus capacitor in the power conversion system is charged by using the first side voltage of the power conversion system and all the slow start circuits;

[0021] After charging is completed, each of the first side main switches is detected for a short circuit fault and a corresponding detection result is obtained;

[0022] If each of the detection results is that the first side main switch to be detected does not have a short circuit fault, the step of charging the second side bus capacitor in the power conversion system by using the power converter in the power conversion system is executed.

[0023] Optionally, detecting a short circuit fault of one of the first side main switches and obtaining a corresponding detection result, comprising:

[0024] By controlling each of the first side main switches, the first side main switch to be detected is in an off state, and the remaining first side main switches are in a conductive state.

[0025] determining whether the first side voltage of the power conversion system is equal to the voltage across the first side bus capacitor after charging;

[0026] If the first side voltage of the power conversion system is not equal to the voltage across the first side bus capacitor after charging, the detection result is that the first side main switch to be detected does not have a short circuit fault.

[0027] Another aspect of the present application provides a power conversion system, comprising: a controller, a power converter, a first side bus capacitor, a second side bus capacitor, at least one first side main switch and at least one second side main switch; wherein:

[0028] The first side bus capacitor is connected between two poles of the first side of the power converter;

[0029] The second side bus capacitor is connected between two poles of the second side of the power converter;

[0030] The first side of the power converter is connected to the first side of the power conversion system, and the second side of the power converter is connected to the second side of the power conversion system;

[0031] The first side main switch is arranged between the first port of the first side of the power converter and the first port of the first side of the power conversion system, or between the second port of the first side of the power converter and the second port of the first side of the power conversion system;

[0032] The second side main switch is arranged between the positive pole of the second side of the power converter and the positive pole of the second side of the power conversion system, or between the negative pole of the second side of the power converter and the negative pole of the second side of the power conversion system;

[0033] The power converter and all the main switches are controlled by the controller, and the controller is configured to execute the main switch short circuit detection method according to any one of the preceding aspects.

[0034] Optionally, the first side of the power conversion system is a direct current side or an alternating current side.

[0035] Optionally, if the first side of the power conversion system is a direct current side, the power conversion system further comprises: at least one slow start circuit; wherein:

[0036] Each slow start circuit is connected across a corresponding first side main switch.

[0037] All the soft start circuits are controlled by the controller.

[0038] Optionally, if the first side of the power conversion system is a DC side, the first side main switch is a circuit breaker, a contactor, a MOS tube or an IGBT.

[0039] If the first side of the power conversion system is an AC side, the first side main switch is a circuit breaker or a contactor.

[0040] Optionally, the second side main switch is a circuit breaker, a contactor, a MOS tube or an IGBT.

[0041] As can be seen from the above technical solution, the present application provides a main switch short circuit detection method for a power conversion system, which is suitable for a power conversion system with a power supply connected to the first side and a DC side as the second side. In the short circuit fault detection method, when all the first side main switches in the power conversion system do not have short circuit faults, the power converter in the power conversion system is used to charge the second bus capacitor in the power conversion system. Therefore, the second bus capacitor can also be charged when the voltage of the second side of the power conversion system is equal to zero, so that the voltage across the second bus capacitor always keeps consistent with the voltage of the second side, and thus false judgment in the process of detecting the short circuit fault of the second side main switch is avoided. Since the power conversion system can also be a DC conversion system and the second side main switch can also be a contactor, the main switch short circuit detection method provided by the present application can avoid false judgment in the process of detecting the sticking fault of the contactor on one side of the DC conversion system when the voltage of the side is equal to zero. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0043] Figure 1 Flowchart of an embodiment of the main switch short circuit detection method for a power conversion system provided by the present application;

[0044] Figure 2 Flowchart of a specific example of the main switch short circuit detection method for a power conversion system provided by the present application;

[0045] Figure 3 Flowchart of a specific embodiment of detecting a short circuit fault of a second side main switch provided by the present application;

[0046] Figure 4 A flow chart of another embodiment of the main switch short circuit detection method of the power conversion system provided by the present application;

[0047] Figure 5 A flow chart of one specific embodiment of the short circuit fault detection of a first side main switch provided by the present application;

[0048] Figure 6 A structure diagram of the power conversion system provided by the present application.

[0049] Figure 7 and Figure 8 Structure diagrams of two specific examples of the power conversion system provided by the present application. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be described clearly and completely below with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative work fall within the scope of protection of the present application.

[0051] In the present application, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms “include”, “contain” or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement “including a…” does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0052] In order to avoid misjudgment in the process of sticking fault detection of the contactor on one side of the direct current conversion system when the voltage of the side is equal to zero, the present application provides a main switch short circuit detection method of the power conversion system, which is suitable for the power conversion system with a power supply connected to the first side and a direct current side connected to the second side.

[0053] The power conversion system includes two sides, which are referred to as a first side and a second side respectively; optionally, the first side of the power conversion system can be a direct current side, at this time, the power conversion system is a direct current conversion system, and the power converter in the power conversion system is a direct current converter; the first side of the power conversion system can also be an alternating current side, at this time, the power conversion system is an ACDC conversion system, and the power converter is an ACDC converter; in actual application, it includes but is not limited to this, which is not specifically limited here, and can be determined according to specific conditions, all of which are within the protection scope of the present application.

[0054] If the first side of the power conversion system is a direct current side, that is, the power conversion system is a direct current conversion system, then in the power conversion system, the first side bus capacitor is connected between the two poles of the first side of the power converter; the second side bus capacitor is connected between the two poles of the second side of the power converter; the first side main switch can be arranged between the positive pole of the first side of the power converter and the positive pole of the first side of the power conversion system, or between the negative pole of the first side of the power converter and the negative pole of the first side of the power conversion system; the second side main switch is arranged between the positive pole of the second side of the power converter and the positive pole of the second side of the power conversion system, or between the negative pole of the second side of the power converter and the negative pole of the second side of the power conversion system.

[0055] The specific flow of the main switch short circuit detection method of the power conversion system is as shown in Figure 1 The specific flow of the main switch short circuit detection method of the power conversion system is as shown in

[0056] S110, judge whether all the first side main switches in the power conversion system have not occurred short circuit failure.

[0057] If all the first side main switches have not occurred short circuit failure, then step S120 and S130 are executed in turn; if at least one first side main switch has occurred short circuit failure, then the main switch short circuit detection method of the power conversion system is stopped.

[0058] Optionally, the first side main switch can be a mechanical switch such as a contactor or a circuit breaker, or an electronic switch such as a MOS tube or an IGBT, which is not specifically limited here, and can be determined according to specific conditions, all of which are within the protection scope of the present application.

[0059] It should be noted that when the power conversion system is a direct current conversion system, the first side main switch can be a mechanical switch or an electronic switch; when the power conversion system is an ACDC conversion system, the first side main switch can only be a mechanical switch.

[0060] In practical applications, if the first side main switch is a mechanical switch, the short-circuit fault of the first side main switch is usually caused by the sticking of the contact in the mechanical switch; if the first side main switch is an electronic switch, the short-circuit fault of the first side main switch is usually caused by the destruction of the PN junction in the electronic switch.

[0061] S120, charging the second side bus capacitor in the power conversion system by using the first side voltage of the power conversion system and the power converter in the power conversion system.

[0062] In practical applications, the specific implementation of step S120 is that all the first side main switches are closed, and the power converter is controlled to perform power conversion, that is, the first side voltage is converted into a corresponding voltage by power conversion to charge the second side bus capacitor; specifically, when the power conversion system is a direct current conversion system, that is, the power converter is a direct current converter, the second side bus capacitor is charged by chopper.

[0063] In a specific example, the second side voltage of the power conversion system is equal to zero before starting, that is, the power converter acts as a voltage source, and the voltage across the second side bus capacitor after charging is charged to a first preset value, wherein the first preset value is less than or equal to the set voltage value of the second side bus capacitor; in addition, if the power conversion system is a direct current conversion system, the operating mode of the power conversion system at this time is a constant bus voltage operating mode.

[0064] The set voltage value of the second side bus capacitor is pre-set according to actual needs, which is not limited here and is within the protection scope of the present application.

[0065] It should be noted that, in general, after it is determined that all the second side main switches do not have short-circuit faults, the power conversion system will be grid-connected, and therefore, in practical applications, a lower limit value is set for the voltage across the second side bus capacitor after charging, which is set according to actual grid-connection needs and is not limited here.

[0066] In another specific example, the second side voltage of the power conversion system is not equal to zero before starting, that is, the power converter acts as a current source, and the voltage across the second side bus capacitor after charging is charged to a second preset value, wherein the difference between the second side voltage of the power conversion system and the second preset value is less than or equal to the first preset overvoltage; in addition, if the power conversion system is a direct current conversion system, the operating mode of the power conversion system at this time is a constant current operating mode or a constant power operating mode.

[0067] The first preset overvoltage is determined according to actual working requirements of the second-side main switch and an impact capacity range that can be borne by the second-side bus capacitor, so as to avoid a large impact on the second-side main switch when the second-side main switch is closed, that is, to avoid damage to the second-side main switch and the second-side bus capacitor, which are not limited here and are within the protection scope of the present application.

[0068] S130, after the charging is completed, short-circuit fault detection is performed on each second-side main switch in turns.

[0069] For example, assuming that the power conversion system includes two second-side main switches, which are respectively referred to as a positive second-side main switch and a negative second-side main switch, the short-circuit fault detection is performed on each second-side main switch in turns, specifically, the short-circuit fault detection is performed on the positive second-side main switch for the first time, and the short-circuit fault detection is performed on the negative second-side main switch for the second time.

[0070] At this time, in an example, as shown in FIG. 13, Figure 2 the step S130 includes the following steps.

[0071] S131, the short-circuit fault detection is performed on the positive second-side main switch.

[0072] S132, the short-circuit fault detection is performed on the negative second-side main switch.

[0073] Optionally, the second-side main switch can be a mechanical switch such as a contactor or a circuit breaker, or an electronic switch such as a MOS tube or an IGBT, which is not limited here and can be determined according to specific conditions and is within the protection scope of the present application.

[0074] In actual application, if the second-side main switch is a mechanical switch, the short-circuit fault of the second-side main switch is usually caused by adhesion of contacts in the mechanical switch; if the second-side main switch is an electronic switch, the short-circuit fault of the second-side main switch is usually caused by damage of PN junctions in the electronic switch.

[0075] Since the second-side bus capacitor in the power conversion system is charged by the power converter in the power conversion system when all the first-side main switches in the power conversion system do not have short-circuit faults, the second-side bus capacitor can also be charged when the second-side voltage of the power conversion system is equal to zero, thereby avoiding that the voltage across the second-side bus capacitor always keeps consistent with the second-side voltage, and further avoiding misjudgment in the process of performing short-circuit fault detection on the second-side main switch; since the power conversion system can also be a direct-current conversion system and the second-side main switch can also be a contactor, the main switch short-circuit detection method of the power conversion system provided by the present application can avoid misjudgment in the process of performing adhesion fault detection on the contactor on one side of the direct-current conversion system when the voltage on the side is equal to zero.

[0076] Another embodiment of the present application provides a specific implementation of short-circuit fault detection for a second-side main switch, which includes the following steps: Figure 3 Figure 3 As shown in FIG. 6 (only for the purpose of illustration of short-circuit fault detection for a second-side main switch), the specific implementation includes the following steps:

[0077] S210. By controlling each second-side main switch, the second-side main switch to be detected is in an off state, and the remaining second-side main switches are in an on state.

[0078] For example, assuming that the power conversion system includes two second-side main switches, which are referred to as a positive second-side main switch and a negative second-side main switch, and the short-circuit fault detection is performed for the positive second-side main switch, the positive second-side main switch is the second-side main switch to be detected.

[0079] In actual application, the short-circuit fault detection method is performed before the power conversion system is started. Therefore, if the short-circuit fault detection is performed for the first time, each second-side main switch is in a default state, i.e., an off state, before the short-circuit fault detection is performed. If the short-circuit fault detection is not performed for the first time, the last second-side main switch to be detected is in an off state, and the other second-side main switches are in an on state before the short-circuit fault detection is performed.

[0080] In a specific example, the short-circuit fault detection is performed for the first time. If the number of second-side main switches included in the power conversion system is greater than 1, the second-side main switch to be detected is kept in a current state, and the remaining second-side main switches are turned on, so that the second-side main switch to be detected is in an off state, and the remaining second-side main switches are in an on state. If the number of second-side main switches included in the power conversion system is equal to 1, the second-side main switch to be detected is kept in a current state, so that the second-side main switch to be detected is in an off state, and the remaining second-side main switch is in an on state.

[0081] In a specific example, the short-circuit fault detection is not performed for the first time. If the number of second-side main switches included in the power conversion system is greater than 1, the second-side main switch to be detected is turned off, the last second-side main switch to be detected is turned on, and the other second-side main switches are kept in a current state, so that the second-side main switch to be detected is in an off state, and the remaining second-side main switches are in an on state.

[0082] S220. It is determined whether the voltage across the second-side bus capacitor after the capacitor is charged is equal to the second-side voltage of the power conversion system.

[0083] ​If the voltage across the second-side bus capacitor after charging is equal to the second-side voltage of the power conversion system, step S230 is performed; if the voltage across the second-side bus capacitor after charging is not equal to the second-side voltage of the power conversion system, step S240 is performed.

[0084] S230, determining that the second-side main switch to be detected has a short-circuit fault.

[0085] S240, determining that the second-side main switch to be detected has no short-circuit fault.

[0086] In this embodiment, since the voltage across the second-side bus capacitor after charging is not equal to the second-side voltage of the power conversion system after step S210 is performed, if the voltage across the second-side bus capacitor after charging is equal to the second-side voltage of the power conversion system, it can be determined that the second-side main switch to be detected has a short-circuit fault, and thus this embodiment can realize short-circuit fault detection of the second-side main switch to be detected.

[0087] The present application provides a specific implementation of step S110, which is applicable to the case that the first side of the power conversion system is a direct current side and each first-side main switch is connected in parallel with a slow-start circuit, i.e., the case that the power conversion system is a direct current conversion system and each first-side main switch is connected in parallel with a slow-start circuit; the specific process of this embodiment can be seen from Figure 4 (only on the basis of Figure 1 ) and specifically includes the following steps:

[0088] S310, charging the first-side bus capacitor in the power conversion system by using the first-side voltage of the power conversion system and all slow-start circuits.

[0089] The voltage across the first-side bus capacitor is charged to a third preset value; wherein the difference between the first-side voltage of the power conversion system and the third preset value is less than or equal to a second preset overvoltage.

[0090] In addition, the second preset overvoltage is determined according to the actual working requirement of the first-side main switch and the impact capacity range that can be borne by the first-side bus capacitor, so as to avoid a large impact on the first-side main switch when it is closed, i.e., to avoid damage to the first-side main switch and the first-side bus capacitor, which are not specifically limited here and are within the protection scope of the present application.

[0091] S320, after charging is completed, performing short-circuit fault detection on each first-side main switch in batches and obtaining corresponding detection results.

[0092] The present embodiment also provides a specific implementation of performing short-circuit fault detection on one first-side main switch and obtaining corresponding detection results; the specific process of this embodiment can be seen from Figure 5 (Figure 5 only on the basis of Figure 4 For example, the short-circuit fault detection of a first side main switch is demonstrated, which comprises the following steps:

[0093] S410, by controlling each first side main switch, the first side main switch to be detected is in an off state, and the rest of the first side main switches are in an on state.

[0094] For example, assuming that the power conversion system comprises two first side main switches, which are respectively referred to as a positive first side main switch and a negative first side main switch, and the short-circuit fault detection is performed on the positive first side main switch, the positive first side main switch is the first side main switch to be detected.

[0095] It should be noted that the first side main switch to be detected is in an off state, and the rest of the first side main switches are in an on state, which is the same as the second side main switch to be detected being in an off state and the rest of the second side main switches being in an on state, which will not be described here.

[0096] S420, whether the first side voltage of the power conversion system is equal to the voltage across the first side bus capacitor after charging.

[0097] If the first side voltage of the power conversion system is not equal to the voltage across the first side bus capacitor after charging, step S430 is performed; if the first side voltage of the power conversion system is equal to the voltage across the first side bus capacitor after charging, step S440 is performed.

[0098] S430, the corresponding detection result is that the first side main switch to be detected does not have a short-circuit fault.

[0099] S440, the corresponding detection result is that the first side main switch to be detected has a short-circuit fault.

[0100] In this embodiment, since the first side voltage of the power conversion system is not equal to the voltage across the first side bus capacitor after charging after step S410 is performed, when the first side voltage of the power conversion system is equal to the voltage across the first side bus capacitor after charging, it can be determined that the first side main switch to be detected has a short-circuit fault, thereby realizing the short-circuit fault detection of the first side main switch.

[0101] S330, after all the first side main switches have been detected for short-circuit faults, whether each detection result is that the first side main switch to be detected does not have a short-circuit fault.

[0102] If each detection result is that the first side main switch to be detected does not have a short-circuit fault, step S120 is performed; if each detection result is not that the first side main switch to be detected does not have a short-circuit fault, the main switch short-circuit detection method is stopped.

[0103] The above is only one specific embodiment of step S110. In actual applications, the above is not limited, and the specific embodiments are not limited here. The specific embodiments are within the protection scope of the present application.

[0104] The present application provides a power conversion system. The second side of the power conversion system is a DC side. The specific structure can be seen from Figure 6 . Specifically, the power conversion system includes a controller (not shown in the figures for simplifying the view), a power converter 10, a first side bus capacitor 20, a second side bus capacitor 30, at least one first side main switch S1 (only two first side main switches S1 are shown in the figures as an example), at least one second side main switch S2 (only two second side main switches S2 are shown in the figures as an example), and at least one soft start circuit 40 (only two soft start circuits 40 are shown in the figures as an example). Figure 6 Figure 7 Figure 6 Figure 6 Figure 6

[0105] In actual applications, the power source can be a DC power source or an AC power source. The specific embodiments are not limited here. The specific embodiments are within the protection scope of the present application. However, the type of the power source should match the type of the first side. For example, if the first side is a DC side, the power source is a DC power source.

[0106] Optionally, the first side of the power conversion system can be a DC side. In this case, the power conversion system is a DC conversion system, and the power converter 10 in the power conversion system is a DC converter. The first side of the power conversion system can also be an AC side. In this case, the power conversion system is an ACDC conversion system, and the power converter 10 is an ACDC converter. The specific embodiments are not limited here. The specific embodiments are within the protection scope of the present application.

[0107] Optionally, the first side main switch S1 can be a mechanical switch such as a contactor or a circuit breaker, or an electronic switch such as a MOS tube or an IGBT. The specific embodiments are not limited here. The specific embodiments are within the protection scope of the present application.

[0108] It should be noted that when the power conversion system is a DC conversion system, the first side main switch S1 can be a mechanical switch or an electronic switch. When the power conversion system is an ACDC conversion system, the first side main switch S1 can only be a mechanical switch.

[0109] ​​​​​Optionally, the second-side main switch S2 can be a mechanical switch such as a contactor or circuit breaker, or an electronic switch such as a MOSFET or IGBT. No specific limitation is made here, and it can be determined according to the specific situation. All of them are within the protection scope of this application.

[0110] The first-side bus capacitor 20 and the second-side bus capacitor 30 each include one capacitor, or at least two capacitors connected in series; no specific limitation is made here, and it can be determined according to the specific situation, all of which are within the protection scope of this application; in practical applications, it is preferred that the first-side bus capacitor 20 and the second-side bus capacitor 30 each include two capacitors connected in series, for example Figure 6 Capacitors C1 and C2 are included.

[0111] The soft-start circuit 40 can be any soft-start circuit found in existing technology, such as... Figure 6 As shown, the structure formed by the slow-start resistor and the MOSFET connected in series has many implementation methods in the existing technology, which will not be elaborated here.

[0112] The specific connection relationships between the various components are as follows:

[0113] The first-side bus capacitor 20 is connected between the two poles on the first side of the power converter 10; the second-side bus capacitor 30 is connected between the two poles on the second side of the power converter 10.

[0114] The first side of the power converter 10 is connected to the first side of the power conversion system, and the second side of the power converter 10 is connected to the second side of the power conversion system.

[0115] The first-side main switch S1 can be located between the first port of the first side of the power converter 10 and the first port of the first side of the power conversion system, or between the second port of the first side of the power converter 10 and the second port of the first side of the power conversion system.

[0116] It should be noted that if the first side of the power conversion system can be the DC side, then the first port and the second port are the positive and negative terminals, respectively.

[0117] The second-side main switch S2 is located between the positive terminal of the second side of the power converter 10 and the positive terminal of the second side of the power conversion system, or between the negative terminal of the second side of the power converter 10 and the negative terminal of the second side of the power conversion system.

[0118] In practical applications, the number of first-side main switches S1 and the number of second-side main switches S2 can be determined according to specific circumstances, and no specific limitation is made here, all of which are within the protection scope of this application; preferably, the number of first-side main switches S1 is equal to 2 and the number of second-side main switches S2 is equal to 2.

[0119] In a specific example, as shown in Figure 6 the number of the first side main switches S1 is equal to 2, one first side main switch S1 is arranged between the positive pole of the first side of the power converter 10 and the positive pole of the first side of the power conversion system, and is recorded as the positive pole first side main switch; the other first side main switch S1 is arranged between the negative pole of the first side of the power converter 10 and the negative pole of the first side of the power conversion system, and is recorded as the negative pole first side main switch.

[0120] In another specific example, as shown in Figure 6 the number of the second side main switches S2 is equal to 2, one second side main switch S2 is arranged between the positive pole of the second side of the power converter 10 and the positive pole of the second side of the power conversion system, and is recorded as the positive pole second side main switch; the other second side main switch S2 is arranged between the negative pole of the second side of the power converter 10 and the negative pole of the second side of the power conversion system, and is recorded as the negative pole second side main switch.

[0121] Each slow start circuit 40 is connected across a corresponding first side main switch S1.

[0122] In a specific example, as shown in Figure 7 both sides of the power conversion system are DC sides and are connected with power supplies, and are recorded as A side and B side respectively, wherein the first side of the power conversion system is the A side and the second side is the B side, the A side is provided with two main switches recorded as SA, and the B side is provided with two main switches recorded as SB, and each main switch SA is connected with a slow start circuit 40 in parallel across the two ends.

[0123] In another specific example, as shown in Figure 8 both sides of the power conversion system are DC sides and are connected with power supplies, and are recorded as A side and B side respectively, wherein the first side of the power conversion system is the B side and the second side is the A side, the A side is provided with two main switches recorded as SA, and the B side is provided with two main switches recorded as SB, and each main switch SB is connected with a slow start circuit 40 in parallel across the two ends.

[0124] In actual application, if the power conversion system is provided with a slow start circuit, the power conversion system is also provided with at least one fuse Fu, wherein the fuse Fu and the slow start circuit are arranged on the same side of the power conversion system; the specific connection relationship of the fuse Fu is as follows:

[0125] In a specific example, as shown in Figure 7 the power conversion system is provided with two fuses Fu, one fuse Fu is arranged between the positive pole of the A side of the power converter 10 and the positive pole of the A side of the power conversion system, and the other fuse Fu is arranged between the negative pole of the A side of the power converter 10 and the negative pole of the A side of the power conversion system.

[0126] In another specific example, such as Figure 8 As shown, the power conversion system is equipped with two fuses Fu. One fuse Fu is located between the positive terminal of the B side of the power converter 10 and the positive terminal of the B side of the power conversion system, and the other fuse Fu is located between the negative terminal of the B side of the power converter 10 and the negative terminal of the B side of the power conversion system.

[0127] The power converter 10, all main switches, and all soft-start circuits 40 are all controlled by the controller, which is used to execute the main switch short-circuit detection method provided in the above embodiment.

[0128] It should be noted that in practical applications, the controller can be set independently or integrated into the power converter 10. No specific limitation is made here, and it can be determined according to the specific situation. All of these are within the protection scope of this application.

[0129] In existing technology, a non-board-mounted circuit is required to connect a soft-start circuit in parallel across the two ends of a contactor on one side of the DC-DC converter system. However, non-board-mounted circuits are susceptible to incorrect connections. For example, suppose that in the DC-DC converter system, the positive contactor on this side is positioned between the positive terminal of the DC-DC converter system and the positive terminal of the DC-DC converter, and the negative contactor on this side is positioned between the negative terminal of the DC-DC converter system and the negative terminal of the DC-DC converter. One end of the positive soft-start circuit is connected to the positive terminal of the DC-DC converter and the other end is connected to the negative terminal of the DC-DC converter, and one end of the negative soft-start circuit is connected to the negative terminal of the DC-DC converter and the other end is connected to the positive terminal of the DC-DC converter. When such incorrect connections occur, if the existing short-circuit fault detection method is used to detect short circuit faults in the two contactors on this side, the voltage on this side will be directly applied across the two ends of the soft-start circuit, causing the soft-start resistor in the soft-start circuit to overheat, which in turn leads to the scrapping of the PCB board and causes significant losses.

[0130] In the power conversion system provided in this application, if the soft-start circuit is placed on the first side of the power conversion system, the problem of misconnection of the above-mentioned non-board circuit can be solved, thus reducing economic losses and optimizing the overall cost of the power conversion system. Therefore, placing the soft-start circuit on the first side of the power conversion system is the preferred embodiment.

[0131] The above description of the disclosed embodiments is merely exemplary and not limiting. Since modifications and changes can be made to the disclosed embodiments without departing from the spirit and scope of the application, it is intended that such modifications and changes be included within the scope of the application as defined in the claims.

Claims

1. A method of detecting a short circuit of a main switch of a power conversion system, characterized by, The first side of the power conversion system is connected with a power supply, and the second side of the power conversion system is a direct current side; the main switch short circuit detection method comprises: judging whether all the first side main switches in the power conversion system have not occurred short circuit fault; if all the first side main switches have not occurred short circuit fault, charging the second side bus capacitor in the power conversion system by using the first side voltage of the power conversion system and the power converter in the power conversion system; after the charging is completed, detecting the short circuit fault of each second side main switch in turns.

2. The main switch short-circuit detection method according to claim 1, characterized by, detecting the short circuit fault of one second side main switch, comprising: controlling each second side main switch, so that the to-be-detected second side main switch is in an off state and the remaining second side main switches are in a conductive state; judging whether the voltage across the second side bus capacitor after charging is equal to the second side voltage of the power conversion system; if the voltage across the second side bus capacitor after charging is equal to the second side voltage of the power conversion system, it is determined that the to-be-detected second side main switch has occurred short circuit fault.

3. The main switch short detection method according to claim 1, wherein if the power converter is used as a voltage source, the voltage across the second side bus capacitor is charged to a first preset value, and the first preset value is less than or equal to the set voltage value of the second side bus capacitor.

4. The main switch short detection method according to claim 1, characterized by, if the power converter is used as a current source, the voltage across the second side bus capacitor is charged to a second preset value; the difference between the second side voltage of the power conversion system and the second preset value is less than or equal to a first preset overvoltage.

5. The main switch short-circuit detection method according to any one of claims 1 to 4, characterized by, charging the second side bus capacitor in the power conversion system by using the power converter in the power conversion system, comprising: closing all the first side main switches and controlling the power converter to perform power conversion.

6. The main switch short-circuit detection method according to any one of claims 1 to 4, characterized by, if the first side of the power conversion system is a direct current side and each first side main switch is connected with a slow start circuit in parallel, judging whether all the first side main switches in the power conversion system have not occurred short circuit fault, comprising: charging the first side bus capacitor in the power conversion system by using the first side voltage of the power conversion system and all the slow start circuits; after the charging is completed, detecting the short circuit fault of each first side main switch in turns and obtaining corresponding detection results; if each detection result is that the to-be-detected first side main switch has not occurred short circuit fault, performing the step of charging the second side bus capacitor in the power conversion system by using the power converter in the power conversion system.

7. The main switch short detection method according to claim 6, wherein detecting the short circuit fault of one first side main switch and obtaining a corresponding detection result, comprising: controlling each first side main switch, so that the to-be-detected first side main switch is in an off state and the remaining first side main switches are in a conductive state; judging whether the first side voltage of the power conversion system is equal to the voltage across the first side bus capacitor after charging; if the first side voltage of the power conversion system is not equal to the voltage across the first side bus capacitor after charging, the corresponding detection result is that the to-be-detected first side main switch has not occurred short circuit fault.

8. A power conversion system, comprising: The power conversion system comprises: a controller, a power converter, a first side bus capacitor, a second side bus capacitor, at least one first side main switch and at least one second side main switch; wherein: the first side bus capacitor is connected between two poles of a first side of the power converter; the second side bus capacitor is connected between two poles of a second side of the power converter; the first side of the power converter is connected to a first side of the power conversion system, and the second side of the power converter is connected to a second side of the power conversion system; the first side main switch is arranged between a first port of the first side of the power converter and a first port of the first side of the power conversion system, or between a second port of the first side of the power converter and a second port of the first side of the power conversion system; the second side main switch is arranged between a positive pole of the second side of the power converter and a positive pole of the second side of the power conversion system, or between a negative pole of the second side of the power converter and a negative pole of the second side of the power conversion system; the power converter and all the main switches are controlled by the controller, and the controller is configured to perform the main switch short circuit detection method according to any one of claims 1 to 7.

9. The power conversion system of claim 8, wherein, The first side of the power conversion system is a direct current side or an alternating current side.

10. The power conversion system of claim 9, wherein, If the first side of the power conversion system is a direct current side, the power conversion system further comprises at least one slow start circuit; wherein: each slow start circuit is connected across a corresponding first side main switch; all the slow start circuits are controlled by the controller.

11. The power conversion system of claim 9, wherein, If the first side of the power conversion system is a direct current side, the first side main switch is a circuit breaker, a contactor, a MOS tube or an IGBT. If the first side of the power conversion system is an alternating current side, the first side main switch is a circuit breaker or a contactor.

12. The power conversion system of any one of claims 8 to 11, wherein, The second side main switch is a circuit breaker, a contactor, a MOS tube or an IGBT.

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