Power conversion device and method for detecting failure thereof

Abstract

The application discloses a power conversion device and a fault detection method thereof. The power conversion device comprises a power conversion unit, a filter capacitor and a voltage sampling module. The filter capacitor is used for filtering the voltage of the power conversion unit, and the voltage sampling module is used for sampling the voltage of the filter capacitor. The power conversion device further comprises a controller configured to acquire the voltage of the filter capacitor and determine whether the power conversion unit is abnormal based on the voltage of the filter capacitor and a preset threshold. The application multiplexes the voltage sampling at the filter capacitor without adding any hardware circuit, realizes the fault detection of the power conversion unit, and effectively avoids the further expansion of the fault. Compared with the prior art, the application has lower cost, higher reliability, simpler detection logic and is easier to implement.

Description

Technical Field

[0001] This application relates to the field of converter technology, and in particular to a power conversion device and a fault detection method thereof. Background Technology

[0002] When a converter reaches a certain service life or is subjected to extremely harsh environments, its internal components will become contaminated to varying degrees. This contamination poses a significant risk to the reliability of the converter and the system. This is because: firstly, the sealing media, such as dust plugs, may deteriorate over time, leading to a decline in the converter's sealing performance. This allows rainwater, dust, and other impurities to enter the converter, contaminating its internal environment. Secondly, when the ambient temperature drops rapidly, the converter's metal casing also cools down quickly. Since air and metal have significantly different specific heat capacities, the temperature change of the air inside the converter is relatively slow. This creates a temperature difference between the internal air and the inner wall of the metal casing. The warmer air condenses into water droplets upon contact with the cooler metal casing, further contaminating the converter's internal environment.

[0003] Regardless of the reason, when the internal environment of the converter becomes contaminated to a certain extent, it can easily lead to the failure of the power switching transistors. Alternatively, the power switching transistors may fail after reaching a certain service life or due to poor reliability. After failure, they are in an uncontrolled state and can no longer perform their switching function. If the converter is restarted at this time, the fault will be amplified, potentially leading to a breakdown or even a fire.

[0004] Therefore, it is necessary to test the power switches in the converter before it is put into operation, detect any failed power switches, and then issue an alarm to prevent the converter from operating. Summary of the Invention

[0005] This application provides a power conversion device and a fault detection method thereof to detect faulty power switching transistors and prevent the fault from escalating.

[0006] This application provides a power conversion device, which includes a power conversion unit, a filter capacitor, and a voltage sampling module;

[0007] The filter capacitor is used to filter the voltage of the power conversion unit, and the voltage sampling module is used to sample the voltage of the filter capacitor.

[0008] The power conversion device further includes a controller configured to acquire the voltage of the filter capacitor and determine whether there is an abnormality in the power conversion unit based on the voltage of the filter capacitor and a preset threshold value.

[0009] Another aspect of this application provides a fault detection method for a power conversion device, the power conversion device including a power conversion unit, a filter capacitor, and a voltage sampling module;

[0010] The filter capacitor is used to filter the voltage of the power conversion unit, and the voltage sampling module is used to sample the voltage of the filter capacitor.

[0011] The fault detection method includes:

[0012] Obtain the voltage of the filter capacitor;

[0013] Based on the voltage of the filter capacitor and the preset threshold value, it is determined whether there is an abnormality in the power conversion unit.

[0014] The power conversion device and fault detection method provided in this application, without adding any hardware circuits, reuse the voltage sampling at the filter capacitor to realize fault detection of the power conversion unit, effectively preventing the fault from further expanding; compared with the prior art, it has lower cost, higher reliability, simpler detection logic, and is easier to implement. Attached Figure Description

[0015] Figure 1 A schematic diagram of a power conversion device provided in an embodiment of this application;

[0016] Figure 2 A first specific circuit diagram of the power conversion device provided in the embodiments of this application;

[0017] Figure 3 This is a second specific circuit diagram of the power conversion device provided in the embodiments of this application;

[0018] Figure 4 A third specific circuit diagram of the power conversion device provided in the embodiments of this application;

[0019] Figure 5 This is a fourth specific circuit diagram of the power conversion device provided in the embodiments of this application;

[0020] Figure 6 A fifth specific circuit diagram of the power conversion device provided in the embodiments of this application;

[0021] Figure 7 A sixth specific circuit diagram of the power conversion device provided in the embodiments of this application;

[0022] Figure 8 A seventh specific circuit diagram of the power conversion device provided in the embodiments of this application;

[0023] Figure 9This application provides an eighth specific circuit diagram of a power conversion device.

[0024] Figure 10 A ninth specific circuit diagram of the power conversion device provided in the embodiments of this application;

[0025] Figure 11 This is a schematic diagram of a fault detection method for a power conversion device provided in an embodiment of this application.

[0026] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0028] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] The power conversion device provided in this application includes a power conversion unit, a filter capacitor, and a voltage sampling module.

[0030] In some examples, the power conversion unit includes at least one of a DC / AC unit, a DC / DC unit, an AC / DC unit, and an AC / AC unit.

[0031] In some examples, the filter capacitor is used to filter the voltage of the power conversion unit, and the voltage sampling module is used to sample the voltage of the filter capacitor.

[0032] Taking the power conversion unit as a DC / AC unit as an example, such as Figure 1 As shown, the power conversion device may specifically include an inverter unit (i.e., a DC / AC unit), a DC bus capacitor B, an AC filter capacitor C, and a voltage sampling module; the DC bus capacitor B is connected between the positive DC terminal VBUS+ and the negative DC terminal VBUS- of the inverter unit, the AC terminal of the inverter unit is connected to the AC power grid, the AC filter capacitor C is used to filter the AC voltage of the inverter unit, and the voltage sampling module is used to sample the voltage of the AC filter capacitor C.

[0033] In some examples, the voltage sampling module is used to sample the phase voltage and / or line voltage of the AC filter capacitor.

[0034] In some examples, the power conversion device further includes a filter inductor L and / or a grid-connected switch K; the filter inductor L is disposed between the AC terminal of the inverter unit and the AC filter capacitor C; the grid-connected switch K is disposed between the AC filter capacitor C and the AC power grid.

[0035] Figures 2-4 yes Figure 1 Some specific circuit diagrams. For example... Figures 2-4 As shown, the DC bus capacitor B includes a first DC bus capacitor C1 and a second DC bus capacitor C2. The first DC bus capacitor C1 and the second DC bus capacitor C2 can be a single set of capacitors, or multiple sets of capacitors connected in series or parallel; the filter inductor L includes a first filter inductor L... A Second filter inductor L B Third filter inductor L C The AC filter capacitor C includes the first AC filter capacitor C. A Second AC filter capacitor C B Third AC filter capacitor C C .

[0036] The positive DC terminal VBUS+ of the inverter unit is connected to one end of the first DC bus capacitor C1, the negative DC terminal VBUS- of the inverter unit is connected to one end of the second DC bus capacitor C2, and the midpoint VBUSN of the inverter unit is connected to the other end of both the first DC bus capacitor C1 and the second DC bus capacitor C2.

[0037] The AC terminal A of the inverter unit is connected to the first filter inductor L. A The inverter unit is connected to phase A of the AC power grid, and its AC terminal B is connected to the second filter inductor L. B The inverter unit is connected to phase B of the AC power grid, and its AC terminal C is connected to the third filter inductor L. C It is connected to phase C of the AC power grid. It can be understood that the AC terminal A of the inverter unit is the midpoint of the bridge arm, i.e., the connection point between the upper and lower bridge arms; the other AC terminals are similar.

[0038] First AC filter capacitor C A One end is connected to the filter inductor L A Between the AC power grid and phase A, for example, point A1 in the diagram; the second AC filter capacitor C B One end is connected to the filter inductor L B Between phase B of the AC power grid, for example, point B1 in the diagram; the third AC filter capacitor C C One end is connected to the filter inductor L C Between the AC power grid and phase C, for example, point C1 in the diagram; the first AC filter capacitor C A The other end, the second AC filter capacitor C BThe other end and the third AC filter capacitor C C The other end is connected together (as shown at point N in the diagram) and shorted to the midpoint VBUSN of the inverter unit. Understandably, in some examples, the filter inductor L is not configured. A L B L C That is also feasible.

[0039] The voltage sampling module is used to sample the voltage of the AC filter capacitor, such as sampling the line voltage and / or phase voltage of the AC filter capacitor. For example, the phase voltage V... A1N V B1N V C1N Line voltage V A1B1 V B1C1 V C1A1 etc.

[0040] In some examples, the grid-connected switch K includes a first grid-connected switch, a second grid-connected switch, and a third grid-connected switch. The first grid-connected switch is, for example, M1 and / or S1 in the figure; the second grid-connected switch is, for example, M2 and / or S2 in the figure; and the third grid-connected switch is, for example, M3 and / or S3 in the figure. The AC terminal A of the inverter unit is connected to AC grid A through the first grid-connected switch; the AC terminal B of the inverter unit is connected to AC grid B through the second grid-connected switch; and the AC terminal C of the inverter unit is connected to AC grid C through the third grid-connected switch.

[0041] In some examples, the inverter unit includes one of the following: a type I three-level inverter circuit, an ANPC three-level inverter circuit, and a type T three-level inverter circuit.

[0042] The Type I three-level inverter circuit consists of power switching transistors TA1~TA4, TB1~TB4, TC1~TC4, and power diodes DA1~DA6, DB1~DB6, and DC1~DC6.

[0043] The ANPC type three-level inverter circuit consists of power switching transistors TA1~TA6, TB1~TB6, TC1~TC6, and power diodes DA1~DA6, DB1~DB6, and DC1~DC6.

[0044] The T-type three-level inverter circuit consists of power switching transistors TA1~TA4, TB1~TB4, TC1~TC4, and power diodes DA1~DA4, ​​DB1~DB4, and DC1~DC4.

[0045] It should be noted that the power switching transistor can be a silicon device, a silicon carbide device, or a gallium nitride device.

[0046] The following explanation will first take a type I three-level inverter circuit as an example:

[0047] In standby mode, i.e., when the bus is powered on and none of the power switches are driven to conduct, and when there are no short-circuit faults in all the power switches and power diodes in the inverter unit, taking phase A bridge arm as an example, TA1, TA2, TA3, and TA4 are connected in series to share the full bus voltage. Therefore, A1 and the midpoint N of the AC filter capacitor are at the same potential, and the phase voltage V... A1N That is, 0, and similarly, V B1N V C1N It is also 0, so the line voltage V at this time A1B1 V B1C1 V C1A1 All of them are 0.

[0048] However, when TA1 or DA1 fails due to a short circuit, they can be considered equivalent to conductors. For phase A bridge arm, only TA2, TA3, and TA4 are connected in series and receive the full bus voltage. Therefore, the voltage of A1 to VBUS- is (2 / 3)*V. BUS V BUS This represents the total bus voltage at this point. However, because point N is short-circuited to the bus midpoint VBUSN, its voltage relative to BUS- is still (1 / 2)*V. BUS Then the phase voltage V A1N It then becomes (1 / 6)*V BUS Since the power transistors (including power switches and power diodes) in both phase B and phase C bridge arms are functioning normally, then V B1N V C1N If it is still 0, then the line voltage V A1B1 It becomes (1 / 6)*V BUS V C1A1 It becomes (-1 / 6)*V BUS Therefore, by observing the amplitude changes of the phase voltage and / or line voltage at the AC filter capacitor, it is possible to detect whether a power transistor has experienced a short circuit failure. Combining this with the voltage direction, the location of the short-circuited power transistor can even be determined. Since each power switching transistor is paired with a power diode connected in parallel, the power switching transistors mentioned below will be treated as a single unit with the diode connected in parallel. For example, describing TA1 as short-circuited means that TA1 and / or DA1 are short-circuited; describing TA1 as normal means that both TA1 and DA1 are normal. A power transistor short circuit includes a direct short circuit, an impedance-based short circuit, or a short-circuit impedance less than the impedance value corresponding to the normal transistor characteristics.

[0049] Specifically, as shown in Table 1 below, for cases where only a single bridge arm has a short-circuited power transistor, besides directly causing a half-bus or full-bus short circuit (which can be directly detected by using bus voltage as a characteristic quantity), the remaining fault states will generally cause changes in phase voltage and line voltage. By detecting the amplitude and direction of the phase voltage and / or line voltage, the specific faulty bridge arm and faulty power transistor can be easily located. For cases where multiple bridge arms simultaneously experience power transistor short-circuit faults, since the phase voltages are independent of each phase and do not cross-influence each other, the changes in phase voltage are completely consistent with the case of a single bridge arm with a short-circuited power transistor. However, line voltages are interconnected. If we want to locate the specific faulty bridge arm and faulty power transistor using only line voltage as a characteristic quantity, we need to arrange and combine the following scenarios: simultaneous faults of bridge arm A and bridge arm B, simultaneous faults of bridge arm B and bridge arm C, simultaneous faults of bridge arm C and bridge arm A, and simultaneous faults of all three bridge arms. We need to list the line voltages for each scenario in Table 1. Finally, by looking up the table, we can match the detected voltages with the voltages in the table to determine the location of the faulty bridge arm and faulty power transistor. Since there are too many possible combinations, this application only provides the general idea and will not elaborate further.

[0050] Table 1. Amplitude and direction of phase voltage and line voltage when a power transistor in a single bridge arm is short-circuited.

[0051]

[0052] V in Table 1 BUS This is the real-time bus voltage, which can be obtained through the bus voltage sampling module of the inverter unit. The negative sign indicates that the voltage direction is negative, and the absence of a negative sign indicates that the voltage is positive.

[0053] For the ANPC type three-level inverter circuit, when a short-circuited power transistor exists in a single bridge arm, the amplitude and direction of the phase voltage and line voltage are almost exactly the same as in Table 1, except that DA5 is replaced with TA5 and DA6 is replaced with TA6. The same applies to the B-phase bridge arm and the C-phase bridge arm.

[0054] For a T-type three-level inverter circuit, the amplitude and direction of the phase voltage and line voltage when a short-circuited power transistor exists in a single bridge arm are shown in Table 2 below. Similarly, the bridge arm with a short-circuited power transistor can be detected based on the phase voltage and / or line voltage, preventing power-on. Finally, the short-circuited power transistor can be located based on the voltage direction.

[0055] Table 2. Amplitude and direction of phase voltage and line voltage when a short-circuited power transistor exists in a single bridge arm.

[0056]

[0057] Figures 5-7 yes Figure 1 Other specific circuit diagrams. In Figures 5-7In the examples, the inverter unit includes a type I three-level inverter circuit, an ANPC three-level inverter circuit, and a T-type three-level inverter circuit. (And...) Figures 2-4 The difference in the example is that the connection point N of the AC filter capacitor is not shorted to the midpoint BVBUSN of the inverter unit.

[0058] exist Figure 5 In the example, in standby mode, i.e., when the bus is powered on and none of the power switches are driven to conduct, when all the power switches and power diodes in the inverter unit are fault-free, TA1, TA2, TA3, and TA4 are connected in series to obtain the full bus voltage, i.e., the voltage at point A1 to BUS- is (1 / 2)*VBUS. TB1, TB2, TB3, and TB4 are connected in series to obtain the full bus voltage, i.e., the voltage at point B1 to BUS- is (1 / 2)*VBUS. TC1, TC2, TC3, and TC4 are connected in series to obtain the full bus voltage, i.e., the voltage at point C1 to BUS- is (1 / 2)*VBUS. Therefore, the voltage of the filter capacitor is 0V.

[0059] However, when TA1 or DA1 fails due to a short circuit, they can be considered equivalent to wires. In this case, only TA2, TA3, and TA4, connected in series, share the full bus voltage. Therefore, the voltage at point A1 relative to BUS- is (2 / 3)*VBUS. Similarly, TB1, TB2, TB3, and TB4, connected in series, share the full bus voltage, meaning the voltage at point B1 relative to BUS- is still (1 / 2)*VBUS. Likewise, TC1, TC2, TC3, and TC4, connected in series, share the full bus voltage, meaning the voltage at point C1 relative to BUS- is still (1 / 2)*VBUS. Therefore, the line voltage of the filter capacitor is V. A1B1 =(1 / 6)*VBUS、V B1C1 =0、V C1A1 =(-1 / 6)*VBUS, the phase voltage of the filter capacitor is V A1N =(1 / 9)*VBUS、V B1N =(-1 / 18)*VBUS、V C1N =(-1 / 18)*VBUS. Based on the obvious change in voltage compared to 0V, it can be determined that there is a power transistor fault, that is, an inverter unit fault, and the start-up of waveform generation is prohibited.

[0060] Specifically, when a power transistor in a single bridge arm experiences a short circuit fault, the filter capacitor voltage is shown in Table 3. The simultaneous faulting of multiple bridge arms represents a combination of single-arm faults. Besides short-circuit faults, open-circuit faults can also be detected; refer to the calculation methods described later.

[0061] Table 3 shows the amplitude and direction of the phase voltage and line voltage of the filter capacitor when a short-circuited power transistor is present.

[0062]

[0063] exist Figure 6 In the example, when a short-circuited power transistor exists in a single bridge arm, the magnitude and direction of the phase voltage and line voltage are almost identical to those in Table 3, except that DA5 is replaced with TA5 and DA6 is replaced with TA6, and the same applies to B and C.

[0064] exist Figure 7 In the example, the magnitude and direction of the phase voltage and line voltage when a short-circuited power transistor exists in a single bridge arm can be calculated with reference to Table 2. Similarly, the bridge arm with a short-circuited power transistor can be detected based on the phase voltage and / or line voltage, preventing power-on, and finally, the short-circuited power transistor can be located based on the voltage direction.

[0065] It should be noted that, in Figures 5-7 The examples all have three bridge arms, and the same applies to the case of four bridge arms.

[0066] Figure 8 yes Figure 1 Another specific circuit diagram. For example... Figure 8 As shown, the DC bus capacitor B is C1 in the diagram, and it is connected between the positive DC terminal VBUS+ and the negative DC terminal VBUS- of the inverter unit. The filter inductor L is L1 in the diagram. The AC terminal A of the inverter unit is connected to the AC power grid through the filter inductor L1, and the AC terminal B of the inverter unit is directly connected to the AC power grid. The AC filter capacitor C is C2 in the diagram, connected between A1 and B1. The voltage sampling module is used to sample the voltage of the AC filter capacitor C2. M1 and S1 in the diagram are the first grid-connected switches, and M2 and S2 are the second grid-connected switches. The inverter unit includes a single-phase full-bridge circuit, composed of power switches TA1~TA2, TB1~TB2, and power diodes DA1~DA2, DB1~DB2.

[0067] exist Figure 8 In the example, in the standby state, that is, when the bus is powered on and none of the power switches are driven to conduct, when all the power switches and power diodes in the inverter unit are fault-free, TA1 and TA2 are connected in series to obtain the full bus voltage, that is, the voltage of point A1 to BUS- is (1 / 2)*VBUS, TB1 and TB2 are connected in series to obtain the full bus voltage, that is, the voltage of point B1 to BUS- is (1 / 2)*VBUS, then the voltage of the filter capacitor is 0V.

[0068] However, when TA1 or DA1 fails due to a short circuit, they can be considered equivalent to wires. Point A1 is equivalent to being connected to BUS+, so the voltage of point A1 to BUS- is VBUS. TB1 and TB2 are connected in series to share the full bus voltage, meaning the voltage of point B1 to BUS- is still (1 / 2)*VBUS. Therefore, the voltage across the filter capacitor is V. A1B1 =(1 / 2)*VBUS、VB1A1 =(-1 / 2)*VBUS. Based on the obvious change in voltage compared to 0V, it can be determined that there is a power transistor fault, that is, an inverter unit fault, and the start-up of waveform generation is prohibited.

[0069] Specifically, the filter capacitor voltage for a power transistor short-circuit fault is shown in Table 4. In addition to short-circuit faults, open-circuit faults can also be detected. The impedance of an open-circuit power transistor is many orders of magnitude larger than that of a normal power transistor. Therefore, the normal power transistor can be considered to be short-circuited, and the voltage drop is entirely on the open-circuit transistor. Therefore, following this approach, the filter capacitor voltage for a power transistor open-circuit fault is shown in Table 5.

[0070] Table 4 shows the amplitude and direction of the filter capacitor voltage when a short-circuited power transistor is present.

[0071]

[0072] Table 5 shows the amplitude and direction of the filter capacitor voltage when an open-circuit power transistor is present.

[0073]

[0074] Figure 9 yes Figure 1 Another specific circuit diagram. (And...) Figure 8 The example differs in that the inverter unit consists of power switches TA1~TA2, TB1~TB2, TC1~TC2, and power diodes DA1~DA2, DB1~DB2, and DC1~DC2. The amplitude and direction of the filter capacitor voltage when a short circuit or open circuit occurs in the power switches can be found in Tables 4 and 5. Fault detection methods can be found in [reference needed]. Figure 8 To understand.

[0075] Figure 10 yes Figure 1 Another specific circuit diagram. For example... Figure 10 As shown, the DC bus capacitor B is C1 in the figure, and DC bus capacitor C1 is connected between the positive DC terminal VBUS+ and the negative DC terminal VBUS- of the inverter unit. The filter inductor L includes the first filter inductor L... A Second filter inductor L B Third filter inductor L C The AC filter capacitor C includes the first AC filter capacitor C. A Second AC filter capacitor C B Third AC filter capacitor C CThe grid-connected switch K includes a first grid-connected switch, a second grid-connected switch, and a third grid-connected switch. The first grid-connected switch is, for example, M1 and / or S1 in the diagram; the second grid-connected switch is, for example, M2 and / or S2 in the diagram; and the third grid-connected switch is, for example, M3 and / or S3 in the diagram. The inverter unit includes a three-phase full-bridge circuit, composed of power switching transistors TA1~TA2, TB1~TB2, TC1~TC2, and power diodes DA1~DA2, DB1~DB2, and DC1~DC2.

[0076] exist Figure 10 In the example, in the standby state, that is, when the bus is powered on and none of the power switches are driven to conduct, when all the power switches and power diodes in the inverter unit are fault-free, TA1 and TA2 are connected in series to obtain the full bus voltage, that is, the voltage of point A1 to BUS- is (1 / 2)*VBUS, TB1 and TB2 are connected in series to obtain the full bus voltage, that is, the voltage of point B1 to BUS- is (1 / 2)*VBUS, TC1 and TC2 are connected in series to obtain the full bus voltage, that is, the voltage of point C1 to BUS- is (1 / 2)*VBUS, then the voltage of the filter capacitor is 0V.

[0077] However, when TA1 or DA1 fails due to a short circuit, they can be considered equivalent to wires. Point A1 is equivalent to being connected to BUS+, so the voltage of point A1 to BUS- is VBUS. TB1 and TB2, connected in series, share the full bus voltage, meaning the voltage of point B1 to BUS- is still (1 / 2)*VBUS. TC1 and TC2, connected in series, share the full bus voltage, meaning the voltage of point C1 to BUS- is still (1 / 2)*VBUS. Therefore, the line voltage of the filter capacitor is V. A1B1 =(1 / 2)*VBUS、V B1C1 =0、V C1A1 =(-1 / 2)*VBUS, the phase voltage of the filter capacitor is V A1N =(1 / 3)*VBUS、V B1N =(-1 / 6)*VBUS、V C1N =(-1 / 6)*VBUS. Based on the obvious change in voltage compared to 0V, it can be determined that there is a power transistor fault, that is, an inverter unit fault, and the start-up of waveform generation is prohibited.

[0078] Specifically, the filter capacitor voltage for a single bridge arm with a power transistor experiencing a short circuit fault is shown in Table 6. The simultaneous faulting of multiple bridge arms constitutes a permutation of single-arm faults. In addition to short-circuit faults, open-circuit faults can also be detected; the filter capacitor voltage for a single bridge arm with a power transistor experiencing a short circuit fault is shown in Table 7.

[0079] Table 6 shows the amplitude and direction of the phase voltage and line voltage of the filter capacitor when a short-circuited power transistor is present.

[0080]

[0081] Table 7 shows the amplitude and direction of the phase voltage and line voltage of the filter capacitor when an open-circuit power transistor is present.

[0082]

[0083] It should be noted that, in Figure 10 The example shows three bridge arms, but the same applies to the case of four bridge arms.

[0084] It should also be noted that DC / DC units, AC / DC units, and AC / AC units can be some common circuit topologies, which will not be elaborated here, but can be understood by referring to existing technologies.

[0085] Accordingly, the power conversion device further includes a controller configured to execute the steps of the fault detection method of the power conversion device. Specifically, as Figure 11 As shown, the fault detection method includes the following steps:

[0086] S11. Obtain the voltage of the filter capacitor;

[0087] S12. Based on the voltage of the filter capacitor and the preset threshold value, determine whether there is an abnormality in the power conversion unit.

[0088] In some examples, the preset threshold value is a single-point value;

[0089] The determination of whether the power conversion unit is abnormal based on the voltage of the filter capacitor and a preset threshold value includes:

[0090] If the amplitude of the voltage of the filter capacitor is greater than the preset threshold, then the power conversion unit is determined to be abnormal; otherwise, the power conversion unit is not abnormal.

[0091] Wherein, the preset threshold value is not less than the maximum sampling error of the voltage sampling module. For example, Figure 2 As shown, both line voltage and phase voltage are 0V when there is no short circuit fault in the power transistor. However, after a fault occurs, the amplitude will change, increasing to varying degrees. Therefore, the threshold voltage can be selected based on 0V plus the error of the sampling circuit to avoid false alarms. The amplitude represents the absolute value of the voltage. The threshold voltage can be a specific numerical value or a range.

[0092] It should be noted that the abnormality of the power conversion unit is not limited to the aforementioned power transistor short circuit or open circuit fault. Other factors, such as the external environment, can also cause the power conversion unit to malfunction, which can also be determined by the above judgment method.

[0093] In some examples, the preset threshold value includes a lower threshold value and a higher threshold value;

[0094] The determination of whether the power conversion unit is abnormal based on the voltage of the filter capacitor and a preset threshold value includes:

[0095] If the amplitude of the filter capacitor voltage is between the lower threshold and the upper threshold, then the power conversion unit is determined to be abnormal; otherwise, the power conversion unit is not abnormal.

[0096] In some examples, the fault detection method further includes:

[0097] The specific location of the anomaly can be determined based on the direction of the voltage across the filter capacitor.

[0098] For example, Figure 2 As shown, it is possible to determine which preset range the phase voltage amplitude of the AC filter capacitor falls within, thereby initially selecting potentially abnormal power transistors. The preset range is divided based on the real-time bus voltage amplitude; then, the abnormal power transistor is finally located based on the phase voltage direction. One recommended method for dividing the preset range is as follows: the first range is [0, V...]. th1 ], second interval [V th1 V th2 ], third interval [V th2 V th3 ], while V th1 =0 + maximum sampling error, V th2 =(1 / 6)*V BUS +Maximum sampling error, V th3 =(1 / 2)*V BUS +Maximum sampling error. For example, Figure 2 As shown, the voltage of phase A of the AC filter capacitor is in the second interval. It can be determined that either TA1, TA2, or DA6 are short-circuited, or TA3, TA4, or DA5 are short-circuited. If it is further determined that the direction is positive, that is, the potential at point A is higher than that at point N, then an alarm can be triggered to indicate that TA1, TA2, or DA6 are short-circuited and operation is prohibited.

[0099] In some examples, due to the first interval [0, V] th1 The existence of [the voltage] allows us to directly determine which range the phase voltage amplitude falls within in order to pinpoint whether there is an abnormality in the power device, or even its specific location.

[0100] In some examples, the fault detection method further includes:

[0101] If an anomaly is detected in the power conversion unit, the power conversion unit's wave transmission action is prohibited; if no anomaly is detected in the power conversion unit, the power conversion unit is allowed to perform subsequent wave transmission actions.

[0102] In some specific examples, such as Figure 2 As shown, the fault detection method further includes: when the bus voltage reaches the bus voltage threshold, performing the step of determining whether the power conversion unit is abnormal based on the voltage of the filter capacitor and a preset threshold value.

[0103] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.

Claims

1. A power conversion device, characterized in that, The power conversion device includes a power conversion unit, a filter capacitor, and a voltage sampling module; The filter capacitor is used to filter the voltage of the power conversion unit, and the voltage sampling module is used to sample the voltage of the filter capacitor. The power conversion device further includes a controller configured to acquire the voltage of the filter capacitor; Based on the voltage of the filter capacitor and the preset threshold value, it is determined whether there is an abnormality in the power conversion unit.

2. The power conversion device as described in claim 1, characterized in that, The controller is configured to prohibit the power conversion unit from transmitting waves when it is determined that there is an abnormality in the power conversion unit; and to allow the power conversion unit to perform subsequent transmission waves when it is determined that there is no abnormality in the power conversion unit.

3. The power conversion device as described in claim 1, characterized in that, The preset threshold value is a single-point value; The controller is configured to determine that the power conversion unit is malfunctioning if the amplitude of the voltage of the filter capacitor is greater than the preset threshold value. Otherwise, the power conversion unit is not malfunctioning.

4. The power conversion device as described in claim 3, characterized in that, The preset threshold value is not less than the maximum sampling error of the voltage sampling module.

5. The power conversion device as described in claim 1, characterized in that, The preset threshold values ​​include a lower threshold value and a higher threshold value; The controller is configured to determine that the power conversion unit is abnormal if the amplitude of the filter capacitor voltage is between the lower threshold and the upper threshold. Otherwise, the power conversion unit is not malfunctioning.

6. The power conversion device as described in claim 5, characterized in that, The controller is configured to locate the specific location of the anomaly point based on the direction of the voltage of the filter capacitor.

7. The power conversion device as described in claim 1, characterized in that, The voltage sampling module is used to sample the phase voltage and / or line voltage of the filter capacitor.

8. The power conversion device as described in claim 1, characterized in that, The power conversion unit includes at least one of a DC / AC unit, a DC / DC unit, an AC / DC unit, and an AC / AC unit.

9. A fault detection method for a power conversion device, characterized in that, The power conversion device includes a power conversion unit, a filter capacitor, and a voltage sampling module; The filter capacitor is used to filter the voltage of the power conversion unit, and the voltage sampling module is used to sample the voltage of the filter capacitor. The fault detection method includes: Obtain the voltage of the filter capacitor; Based on the voltage of the filter capacitor and the preset threshold value, it is determined whether there is an abnormality in the power conversion unit.

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