Method and apparatus for detecting relay fault condition in power take-off system

Abstract

The invention provides a method for detecting a fault state of a relay in a power take-off system, which comprises the following steps of: respectively setting a first sampling point and a second sampling point at a non-voltage converter side terminal and a voltage converter side terminal of a first relay, a third sampling point and a fourth sampling point are respectively arranged at a non-voltage converter side terminal and a voltage converter side terminal of the second relay, and a first voltage between the first sampling point and the third sampling point and a second voltage between the second sampling point and the fourth sampling point are sampled; the closed loop forming condition among the first sampling point, the second sampling point and the fourth sampling point is analyzed at least based on the first voltage and the second voltage, so that the respective fault states of the first relay and the second relay are judged, and the judgment at least comprises the following steps: under the condition that the first relay and / or the second relay is in the fault state; it is determined whether the occurring fault condition relates to an adhesion fault or a clamping stagnation fault. The invention further provides a device for detecting the fault state of the relay in the power output system.

Description

Technical Field

[0001] The present invention relates to a method for detecting a relay fault state in a power output system. The present invention also relates to a device for detecting a relay fault state in a power output system and a machine-readable storage medium. Background Art

[0002] At present, electric vehicles generally use high-voltage discharge circuits to provide power output for vehicle driving. For safety purposes, the discharge circuit is connected to relays in the power lines on the positive and negative sides to control the on-off between the DC power supply and the load. For example, when the vehicle is driven, the relay is turned on to provide the battery voltage to the motor, and when the vehicle is not driven or when the battery or other circuit components fail, the relay is turned off to cut off the power output.

[0003] However, in actual applications, due to the impact of high current in the circuit or due to mechanical damage, the relay contacts may become stuck or stuck, and thus cannot be normally controlled to open or close. Once the relay's shutdown or connection function fails, the entire high-voltage system may be energized or unable to be powered on normally. This will cause a lot of inconvenience to personnel during driving, parking or maintenance, and may even cause serious life-threatening consequences.

[0004] In existing solutions, it has been proposed to identify the fault status of a single relay or a group of relays as a whole by sampling an index voltage or an index current. However, it is not possible to quickly confirm the fault status of each relay in a group of relays in a simple and effective way. In addition, the current diagnostic scheme mainly focuses on the identification of adhesion faults, but lacks the means to identify the stuck state of relay contacts.

[0005] In this context, it is desirable to provide an improved relay fault diagnosis scheme to efficiently detect the contact state of each relay in a multi-way relay. Summary of the invention

[0006] The object of the present invention is to provide a method for detecting a relay fault state in a power output system, a device for detecting a relay fault state in a power output system and a machine-readable storage medium, so as to at least solve some of the problems in the prior art.

[0007] According to a first aspect of the present invention, a method for detecting a relay fault state in a power output system is provided, wherein the power output system comprises: a power battery; a voltage converter that steps up or steps down an output voltage of the power battery; a relay that is arranged on an input side or an output side of the voltage converter, wherein the relay comprises a first relay arranged in a positive bus and a second relay arranged in a negative bus, wherein the method comprises the following steps:

[0008] A first sampling point and a second sampling point are respectively set at the non-voltage converter side terminal and the voltage converter side terminal of the first relay, a third sampling point and a fourth sampling point are respectively set at the non-voltage converter side terminal and the voltage converter side terminal of the second relay, and a first voltage between the first sampling point and the third sampling point and a second voltage between the second sampling point and the fourth sampling point are sampled; and

[0009] The closed loop formation between the first to fourth sampling points is analyzed based on at least the first voltage and the second voltage to determine the respective fault states of the first relay and the second relay, wherein the determination at least includes: in the case where a fault state occurs in the first relay and / or the second relay, determining whether the fault state occurs involves a sticking fault or a jamming fault.

[0010] The present invention particularly includes the following technical concepts: by setting multiple sampling points at two relays and analyzing the closed loop formation between specific sampling points, the voltage-dividing principle can be used to cleverly analyze the equivalent circuit formed by different combinations of on-off states of multiple relays, without the need to equip each relay with an additional detection circuit. As a result, the contact states of the positive and negative side relays can be easily and efficiently determined. In addition, through a unified detection method, a two-way evaluation of relay adhesion and jamming can be achieved at the same time, and on the basis of saving detection costs, more targeted remedial measures can be taken when any fault occurs.

[0011] Optionally, the method further comprises the following steps: asynchronously controlling the on and off of the first relay and the second relay according to a preset operation sequence, wherein after the on and off state of one of the first relay and the second relay is changed, the first voltage and the second voltage are sampled.

[0012] This allows the operation sequence to create multiple combinations of on and off states of the two relays, and then determine whether the detected voltage changes as expected. This dynamic operation method can independently determine the contact state of each relay without introducing complex detection circuits.

[0013] Optionally, the operation sequence includes a power-on operation and a power-off operation, and the one that is first closed in the power-on operation and the one that is first opened in the power-off operation involve the same one of the first relay and the second relay.

[0014] Therefore, the correlation between each operation step in the operation sequence can be fully utilized to avoid redundantly performing the same type of fault diagnosis on the same relay, which can greatly improve the diagnostic efficiency.

[0015] Optionally, the first relay and the second relay respectively have an initial state of being disconnected, and the operation sequence includes: operation a: controlling the first relay to close and keeping the second relay disconnected; operation b: controlling the second relay to close and keeping the first relay closed; operation c: controlling the first relay to open and keeping the second relay closed; operation d: controlling the second relay to open and keeping the first relay open; or, operation a: controlling the second relay to close and keeping the first relay open; operation b: controlling the first relay to close and keeping the second relay closed; operation c: controlling the second relay to open and keeping the first relay closed; operation d: controlling the first relay to open and keeping the second relay open.

[0016] Therefore, by performing the on-off action on only one of the relays in each operation step, it is possible to more reliably identify which specific relay has failed based on voltage detection, effectively reducing the ambiguity of the fault conclusion.

[0017] Optionally, after performing operation a, if the comparison result between the first voltage and the second voltage reflects that a closed loop is formed between the first to fourth sampling points, it is determined that the first relay or the second relay that has not been closed in operation a has a sticking fault; after performing operation b, if the comparison result between the first voltage and the second voltage reflects that a closed loop is not formed between the first to fourth sampling points, it is determined that at least one of the first relay and the second relay has a stuck fault; and / or, after performing operation c, if the comparison result between the first voltage and the second voltage reflects that a closed loop is formed between the first to fourth sampling points, it is determined that the first relay or the second relay that is disconnected in operation c has a sticking fault.

[0018] Therefore, it is possible to determine whether the actual closed loop change is consistent with the specific on-off action of the relay based on the detected voltage. Therefore, the relay fault state can be logically judged very clearly and concisely.

[0019] Optionally, after operation c is performed, the first voltage and the second voltage are sampled after a predetermined period of time.

[0020] Thus, the non-sudden change characteristic of the voltage on the capacitive element in the circuit is taken into account, thereby avoiding erroneous conclusions drawn when the measurement is performed when the discharge time is too short.

[0021] Optionally, when the voltage difference between the first voltage and the second voltage is less than a preset deviation, it is determined that a closed loop is formed between the first to fourth sampling points.

[0022] Therefore, the closed loop formation situation can be quickly determined through voltage analysis, thus improving the efficiency of fault diagnosis.

[0023] Optionally, the power output system also includes an input capacitor arranged on the input side and an output capacitor arranged on the output side of the voltage converter, and the method also includes the following steps: pre-charging the input capacitor or the output capacitor of the voltage converter so that a predetermined voltage difference is formed between the first voltage and the second voltage when the first relay and the second relay are not fully closed.

[0024] Therefore, the fault diagnosis process of the relay can be implemented regardless of whether the fuel cell is started or not.

[0025] Optionally, the upper limit value of the predetermined voltage difference is determined in relation to the following factors: when a closed loop is formed between the first to fourth sampling points by closing the first relay or the second relay, the life loss suffered by the first relay or the second relay that performs the closure; and / or, the lower limit value of the predetermined voltage difference is determined in relation to the following factors: when a closed loop is not formed between the first to fourth sampling points in an overcharge state of the input capacitor or the output capacitor, the voltage difference between the first voltage and the second voltage.

[0026] Thus, the relay is prevented from actively closing under excessive voltage difference to form a loop, causing the normally normal relay to stick. In addition, the predetermined voltage difference is prevented from being too small, so as to avoid further reduction of the voltage difference in the event of pre-overcharge, resulting in misjudgment of the fault.

[0027] Optionally, the method further includes the following steps: detecting a third voltage between the first sampling point and the fourth sampling point and a fourth voltage between the second sampling point and the third sampling point; and, in the step of determining the fault state, additionally determining the fault state of each of the first relay and the second relay based on the third voltage and the fourth voltage.

[0028] Therefore, through the cross-voltage sampling method, the current circuit topology can be accurately determined, and the fault state of each relay can be accurately distinguished without controlling the first and second relays to repeatedly switch on and off states.

[0029] Optionally, in the step of determining the fault state, conditions that the first to fourth voltages should satisfy in each combined on-off state of the first relay and the second relay are predetermined and stored, the actual on-off state of the first relay and the second relay is determined by checking which of all the conditions the current first to fourth voltages satisfy, and the fault state of each of the first relay and the second relay is determined by comparing the controlled on-off state of the first relay and the second relay with the actual on-off state.

[0030] Therefore, by comparing the consistency between the actual on-off state and the controlled on-off state, it is possible not only to check whether the relay is faulty, but also to directly determine the fault location and type.

[0031] Optionally, when the first relay and the second relay are both controlled to be disconnected, whether the first relay and / or the second relay has a sticking fault is determined based on the first to fourth voltages; when the first relay and the second relay are both controlled to be closed, whether the first relay and / or the second relay has a sticking fault is determined based on the first to fourth voltages; when the first relay is controlled to be closed and the second relay is controlled to be disconnected, whether the first relay has a sticking fault and whether the second relay has a sticking fault is determined based on the first to fourth voltages; and / or, when the first relay is controlled to be disconnected and the second relay is controlled to be closed, whether the first relay has a sticking fault and whether the second relay has a sticking fault is determined based on the first to fourth voltages.

[0032] Therefore, by purposefully controlling the initial on / off states of the first and second relays, specific types of fault diagnosis can be performed more specifically, thereby improving the efficiency of fault identification.

[0033] Optionally, the relay is a main relay arranged between the power battery and the voltage converter, the first relay is connected between the positive terminal of the power battery and the positive terminal of the voltage converter on the positive bus, and the second relay is connected between the negative terminal of the power battery and the negative terminal of the voltage converter on the negative bus.

[0034] In this way, the fault status of the main relay can be effectively checked to ensure reliable connection and disconnection between the power battery and the load circuit.

[0035] Optionally, the power output system further comprises a secondary battery connected in parallel with the voltage converter at the output side of the voltage converter;

[0036] The relay is an auxiliary relay arranged between the voltage converter and the secondary battery. The first relay is connected between the positive terminal of the voltage converter and the positive terminal of the secondary battery on the positive bus, and the second relay is connected between the negative terminal of the voltage converter and the negative terminal of the secondary battery on the negative bus.

[0037] Thereby, the fault state of the auxiliary relay can be effectively checked to ensure reliable connection and disconnection between the secondary battery and the voltage converter.

[0038] According to a second aspect of the present invention, there is provided a device for detecting a relay fault state in a power output system, the device being used to execute the method according to the first aspect of the present invention, the device comprising:

[0039] a voltage detection unit configured to be able to set a first sampling point and a second sampling point at a non-voltage converter side terminal and a voltage converter side terminal of the first relay, respectively, set a third sampling point and a fourth sampling point at a non-voltage converter side terminal and a voltage converter side terminal of the second relay, respectively, and sample a first voltage between the first sampling point and the third sampling point and a second voltage between the second sampling point and the fourth sampling point; and

[0040] A control unit is configured to analyze the closed loop formation between the first to fourth sampling points based on at least the first voltage and the second voltage to determine the respective fault states of the first relay and the second relay, wherein the determination at least includes: in the case where a fault state occurs in the first relay and / or the second relay, determining whether the fault state occurs involves a sticking fault or a jamming fault.

[0041] According to a third aspect of the present invention, there is provided a machine-readable storage medium, on which a computer program is stored, wherein the computer program is used to execute the method according to the first aspect of the present invention when executed on a computer. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be described in more detail below with reference to the accompanying drawings, so that the principles, features and advantages of the present invention can be better understood. The accompanying drawings include:

[0043] Figure 1 shows a structural block diagram of a power output system according to an exemplary embodiment of the present invention;

[0044] Figure 2a A schematic diagram showing sampling point positions and sampling voltages in a main relay configuration according to an exemplary embodiment of the present invention is shown;

[0045] Figure 2b A schematic diagram showing the sampling point position and the sampling voltage under the auxiliary relay configuration according to an exemplary embodiment of the present invention is shown;

[0046] Figure 3 A flow chart showing a method for detecting a relay failure in a power output system implemented in a main relay configuration according to an exemplary embodiment of the present invention;

[0047] Figure 4a and Figure 4b A schematic diagram showing a sampling point position and a sampling voltage in a main relay configuration according to another exemplary embodiment of the present invention is shown;

[0048] Figure 5a-5d A schematic diagram showing four combined on-off states of the first relay and the second relay in a main relay configuration; and

[0049] Figure 6 A flow chart showing a method for detecting a relay failure in a power output system implemented in a main relay configuration according to another exemplary example of the present invention is shown. DETAILED DESCRIPTION

[0050] In order to make the technical problems, technical solutions and beneficial technical effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the scope of protection of the present invention.

[0051] Figure 1 FIG. 1 shows a structural block diagram of a power output system according to an exemplary embodiment of the present invention. The power output system 1 can be installed in a pure electric vehicle or a hybrid vehicle and used to provide driving power to the vehicle. Figure 1 As shown, the power output system 1 includes a fuel cell 10 as a power battery, a voltage converter 11, an inverter 12, a traction motor 13, an auxiliary mechanical component 14, a secondary battery 15, an input capacitor C1, an output capacitor C2, a first pre-charging circuit 16, a second pre-charging circuit 17, a fuse 18, a main relay 21, and an auxiliary relay 22. In addition, the power output system 1 also includes a device 30 for detecting a relay fault in the power output system 1, and the device 30 includes a voltage detection unit 31 and a control unit 32.

[0052] The fuel cell 10 is a power generation device that generates direct current power, receives a supply of hydrogen and air from the outside, and generates power through an electrochemical reaction between hydrogen and oxygen.

[0053] The voltage converter 11 steps up or steps down the output voltage of the fuel cell 10 and supplies it to the inverter 12 on the output side. Thus, the electric power generated by the fuel cell 10 is transmitted to the inverter 12 via the voltage converter 11 .

[0054] The inverter 12 converts the power supplied from the fuel cell 10 and the secondary battery 15 in a direct current form into an alternating current form, and supplies the converted power to the traction motor 13 to drive the vehicle.

[0055] The secondary battery 15 is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, or a large-capacity capacitor can also be used as a secondary battery. The secondary battery 15 is connected in parallel to the output side of the voltage converter 11. In this embodiment, the secondary battery 15 is used together with the fuel cell 10 as a power source for the power output system 1, and the secondary battery 15 can also be charged with the power generated by the fuel cell 10. In addition, the secondary battery 15 can also output the charged power to loads such as the auxiliary mechanical components 14 and the traction motor 13.

[0056] The auxiliary mechanical component 14 is also connected in parallel to the output side of the voltage converter 11, for example, between the output side of the voltage converter 11 and the auxiliary relay 22. Figure 1 As shown, the auxiliary mechanical components 14 are connected to the output side of the voltage converter 11 by a set of fuses 18, and can be operated by the power provided by the fuel cell 10 and the secondary battery 15. The auxiliary mechanical components 14 include, for example, an air compressor, a hydrogen circulation pump, a cooling water pump, and a high-pressure cooling fan.

[0057] exist Figure 1 In the illustrated embodiment, two relay configurations are shown, which may exist in one or the other or both at the same time in the power output system 1 .

[0058] In the main relay configuration, the power output system 1 includes a relay in the form of a main relay 21, which is provided between the fuel cell 10 and the voltage converter 11 and is used to perform connection and disconnection between the fuel cell 10 and the voltage converter 11. The main relay 21 includes, for example, a first relay 211 provided in the positive bus and a second relay 212 provided in the negative bus, the first relay 211 being connected between the positive terminal of the fuel cell 10 and the positive terminal of the voltage converter 11 on the positive bus, and the second relay 212 being connected between the negative terminal of the fuel cell 10 and the negative terminal of the voltage converter 11 on the negative bus.

[0059] In the auxiliary relay configuration, the power output system 1 includes a relay in the form of an auxiliary relay 22, which is arranged between the voltage converter 11 and the secondary battery 15, and is used to perform the connection and disconnection between the voltage converter 11 and the secondary battery 15 and the inverter 12. When the auxiliary relay 22 is disconnected, the entire vehicle can directly drive the inverter 12 and the traction motor 13 by the secondary battery 15 to ensure power output. The auxiliary relay 22, for example, includes a first relay 221 arranged in the positive bus and a second relay 222 arranged in the negative bus. The first relay 221 is connected between the positive terminal of the voltage converter 11 and the positive terminal of the secondary battery 15 on the positive bus, and the second relay 222 is connected between the negative terminal of the voltage converter 11 and the negative terminal of the secondary battery 15 on the negative bus.

[0060] The input capacitor C1 is connected between the positive and negative bus bars on the input side of the voltage converter 11 and is used to smooth the DC voltage on the input side of the voltage converter 11. The output capacitor C2 is connected between the positive and negative bus bars on the output side of the voltage converter 11 and is used to reduce and smooth the AC component in the output voltage of the voltage converter 11. It should be noted that in this context, the capacitors C1 and C2 are shown and described in a manner independent of the voltage converter 11, but they can also be defined as being part of the voltage converter 11 and are therefore shown as a whole with it.

[0061] The first and second pre-charging circuits 16 , 17 are respectively arranged in parallel with the input capacitor C1 and the output capacitor C2 to pre-charge the input capacitor C1 and the output capacitor C2 during the fault diagnosis of the main relay 21 or the auxiliary relay 22 .

[0062] The device 30 for detecting relay failure in the power output system 1 includes a voltage detection unit 31 and a control unit 32. The voltage detection unit 31 is used to set different sampling points at the main relay 21 or the auxiliary relay 22 and selectively sample the voltage between the two sampling points, which can be done by arranging a voltage sensor at an appropriate position of the power output system 1. For the sake of simplicity, the arrangement of the specific sampling points and the related voltage sensors is described in detail below. Figure 1 It is not explicitly shown and will be further explained below.

[0063] The control unit 32 obtains the various sampled voltages from the voltage detection unit 31, and analyzes the closed loop formation between different sampling points set at the main relay 21 or the auxiliary relay 22. Through this analysis, the control unit 32 can determine the fault state of the first relay and the second relay included in the main relay 21 or the auxiliary relay 22, and this determination at least includes: when the first relay and / or the second relay has a fault state, determine whether the fault state involves a sticking fault or a stuck fault. In the sense of the present invention, "stuck fault" means that the relay cannot be normally attracted due to an open coil or mechanical abnormality; "sticking fault" means that the relay's moving contact and fixed contact are welded, and thus cannot be opened normally.

[0064] To this end, the control unit 32 can, for example, output a control instruction to the main relay 21 or the auxiliary relay 22 to control the first and second relays to be alternately disconnected and connected according to the operation sequence. In addition, the control unit 32 can also control the working states of the first and second pre-charging circuits 16 and 17 to pre-charge the input capacitor C1 and the output capacitor C2.

[0065] Figure 2a A schematic diagram showing sampling point positions and sampling voltages in a main relay configuration according to an exemplary embodiment of the present invention is shown.

[0066] like Figure 2a As shown, in the main relay configuration, the main relay 21 is connected in series between the power battery in the form of the fuel cell 10 and the voltage converter 11. In this case, the main relay 21 includes a first relay 211 and a second relay 212 respectively arranged in the positive busbar and the negative busbar.

[0067] In this embodiment, a first sampling point a1 and a second sampling point a2 are respectively set at the non-voltage converter side terminal and the voltage converter side terminal of the first relay 211, and a third sampling point a3 and a fourth sampling point a4 are respectively set at the non-voltage converter side terminal and the voltage converter side terminal of the second relay 212.

[0068] In order to realize the fault state determination of the first relay 211 and the second relay 212, for example, a voltage sensor may be arranged between the first sampling point a1 and the third sampling point a3 to sample the first voltage U1 therebetween. In addition, a voltage sensor may be arranged between the second sampling point a2 and the fourth sampling point a4 to sample the second voltage U2 therebetween. Figure 2a In the main relay configuration shown, the first voltage U1 corresponds to the output voltage of the fuel cell 10, for example, and the second voltage U2 corresponds to the input voltage of the voltage converter 11 (that is, the voltage on the input capacitor C1). Figure 1The voltage sampling unit 31 in the embodiment can collect voltage signals from these voltage sensors and provide them to the control unit 32 for closed loop formation situation analysis.

[0069] Figure 2b A schematic diagram showing sampling point positions and sampling voltages in an auxiliary relay configuration according to an exemplary embodiment of the present invention is shown.

[0070] like Figure 2b As shown, in the auxiliary relay configuration, the auxiliary relay 22 is connected in series between the voltage converter 11 and the secondary battery 15. In this case, the auxiliary relay 22 includes a first relay 221 and a second relay 222 respectively provided in the positive bus and the negative bus.

[0071] In this embodiment, a first sampling point a1 and a second sampling point a2 are respectively set at the non-voltage converter side terminal and the voltage converter side terminal of the first relay 221, and a third sampling point a3 and a fourth sampling point a4 are respectively set at the non-voltage converter side terminal and the voltage converter side terminal of the second relay 222.

[0072] In order to realize the fault state determination of the first relay 211 and the second relay 222, for example, a voltage sensor may be arranged between the first sampling point a1 and the third sampling point a3 to sample the first voltage U1 therebetween. In addition, a voltage sensor may be arranged between the second sampling point a2 and the fourth sampling point a4 to sample the second voltage U2 therebetween. Figure 2b In the auxiliary relay configuration shown, the first voltage U1 corresponds to the output voltage of the secondary battery 15 , for example, and the second voltage U2 corresponds to the output voltage of the voltage converter 11 (ie, the voltage on the output capacitor C2 ).

[0073] Next, we will combine Figure 3 right Figure 2a The fault determination process of the first and second relays in the circuit shown is described. In this embodiment, Figure 3 The method shown exemplarily includes steps S300-S317, and these steps can be used, for example, in Figure 1 The device 30 shown is implemented in the case.

[0074] In step S300, before starting the fault determination process, Figure 2a The first and second relays 211, 212 are shown in the disconnected state to ensure that the entire power output system 1 is in the power-off state. At this time, the fuel cell 10 can be started to start generating electricity, or the fuel cell 10 can be in the shutdown state.

[0075] In step S301, the first pre-charging circuit 16 is controlled to pre-charge the input capacitor C1 on the input side of the voltage converter 11, so that a predetermined voltage difference is formed between the first voltage U1 and the second voltage U2 before the first relay 211 and the second relay 212 are fully closed. The predetermined voltage difference means that there is a voltage deviation within a specified value range between the first voltage U1 at the output end of the fuel cell 10 and the second voltage U2 on the input capacitor C1.

[0076] On the one hand, if the voltage difference between the first voltage U1 and the second voltage U2 is too large (for example, greater than 100V), then when a closed loop is formed between the first to fourth sampling points a1, a2, a3, and a4 by controlling the first or second relay 211, 212 to close, a large amount of charge will flow at both ends of the relay that performs the closing action, thereby forming a large current shock, which will cause the relay contacts to heat up rapidly and melt. In this way, even if the relay is originally normal, it may be more likely to fail due to being attracted under a large voltage difference. Taking this influence into account, the upper limit value of the predetermined voltage difference can be determined in relation to the following factors: when a closed loop is formed between the first to fourth sampling points a1, a2, a3, and a4 by closing one of the first relay 211 and the second relay 212, the life loss suffered by the first relay 211 or the second relay 212 that performs the closing.

[0077] On the other hand, if the voltage difference between the first voltage U1 and the second voltage U2 is too small (for example, less than 50V), then if the input capacitor C1 is overcharged, the voltage difference between the first voltage U1 and the second voltage U2 will be further reduced, so that the following situation may occur: even if a closed loop is not formed between the first to fourth sampling points a1, a2, a3, and a4, the deviation between the first voltage U1 and the second voltage U2 cannot be identified due to the instrument accuracy limitation of the voltage sensor, resulting in a false judgment that the relay has a sticking fault. Taking this influence into account, the lower limit value of the predetermined voltage difference can be determined in relation to the following factors: the voltage difference between the first voltage U1 and the second voltage U2 when a closed loop is not formed between the first to fourth sampling points a1, a2, a3, and a4 in the overcharge state of the input capacitor C1 or the output capacitor C2.

[0078] In a specific example, assuming that the output voltage of the fuel cell 10 is 500V, the voltage across the input capacitor C1 can be made to reach about 400V-450V through this pre-charging process to ensure that there is a predetermined voltage difference of 50V-100V between the first voltage U1 and the second voltage U2. The specific value of the predetermined voltage difference can be obtained through the pre-calibration process, and the two aspects mentioned above (i.e., the adverse effects caused by too large or too small voltage difference) should be considered in a compromise.

[0079] In step S302, the on and off of the first and second relays 211 and 212 are asynchronously controlled according to a preset operation sequence. Specifically, operation a is performed in step S302: the first relay 211 is controlled to be closed, and the second relay 212 is kept open. After the on and off state of the first relay 211 is changed in step S302, the first voltage U1 and the second voltage U2 are sampled in step S303.

[0080] In step S304, the first voltage U1 is compared with the second voltage U2, and it is checked whether the result of the comparison reflects the formation of a closed loop between the first to fourth sampling points a1, a2, a3, and a4. Specifically, it can be checked whether the voltage difference between the first voltage U1 and the second voltage U2 is less than the preset deviation. In the simplest case, the preset deviation can be set to be directly equal to the predetermined voltage difference mentioned above. However, in order to more reliably distinguish the formation state and the non-formation state of the closed loop, the preset deviation here can be set to 15V, for example, so that it is less than the predetermined voltage difference of 50V-100V actively formed in the open circuit state through the pre-charging process.

[0081] At this time, if the contact of the second relay 212 is stuck, since the first relay 211 has been controlled to be closed, the two relays 211 and 212 are in a closed state, thereby forming a closed loop between the first to fourth sampling points a1, a2, a3, and a4. In this case, the second voltage U2 is forced to be clamped to be substantially the same as the first voltage U1, so that the voltage difference between the first voltage U1 and the second voltage U2 is less than a preset deviation (for example, 15V), so it can be determined in step S305 that the second relay 212 has a sticking fault.

[0082] On the contrary, if the contact of the second relay 212 is normal, the second relay 212 should be in an open state, and a closed loop cannot be formed between the first sampling point to the fourth sampling point a1, a2, a3, and a4. The voltage difference between the first voltage U1 and the second voltage U2 will still maintain a predetermined voltage difference of 50V-100V, which is greater than the preset deviation 15V. In this case, it can be temporarily determined in step S306 that the second relay 212 has no adhesion failure.

[0083] If it is determined in step S306 that no adhesion fault of the second relay 212 is found, operation b may be continued in step S307: the second relay 212 is controlled to be closed, and the first relay 211 is kept closed. Then, the first voltage U1 and the second voltage U2 are sampled again in step S308.

[0084] In step S309 , the first voltage U1 and the second voltage U2 are compared, and it is checked whether the comparison result reflects that a closed loop is formed between the first to fourth sampling points a1 , a2 , a3 , and a4 .

[0085] If the closing operation of the second relay 212 is normally implemented in step S307, then since the first relay 211 has been placed in a closed state by operation a before, both relays 211 and 212 should be in a closed state. At this time, the voltage converter 11 is driven to perform a step-up or step-down operation on the output voltage U1 of the fuel cell 10. Therefore, it can be determined in step S309 that the voltage difference between the first voltage U1 and the second voltage U2 is less than the preset deviation 15V, which means that a closed loop is formed between the first to fourth sampling points a1, a2, a3, and a4. In this case, it can be determined in step S311 that neither the first nor the second relays 211 nor 212 has a stuck fault. On the contrary, if the closing operation of any one of the first relay 211 and the second relay 212 is not normally implemented, a closed loop cannot be formed between the first to fourth sampling points a1, a2, a3, and a4, so it is determined in step S309 that there is a predetermined voltage difference greater than the preset deviation (15V) between the output voltage U1 of the fuel cell 10 and the input voltage U2 of the voltage converter 11, and even the discharge process of the input side capacitor C1 will cause this predetermined voltage difference to increase further. In this case, it can be determined in step S310 that at least one of the first relay 211 and the second relay 212 has a stuck fault.

[0086] If it is confirmed in step S311 that neither the first relay 211 nor the second relay 212 has a stuck fault, operation c can be continued in step S312: the first relay 211 is controlled to be disconnected and the second relay 212 is kept closed. Then, the first voltage U1 and the second voltage U2 are sampled again in step S313.

[0087] Here, in order to avoid repeated detection of the sticking state of the same relay, the first relay 211 needs to be disconnected first in the power-off operation implemented in step S311, so as to ensure that the relay that is first closed in the power-on operation in step S302 and the relay that is first disconnected in the power-off operation in step S311 are the same as the first relay 211 and the second relay 212. In this way, the sticking diagnosis of one of the first and second relays 211 and 212 (the second relay 212) can be implemented in the power-on operation, and the sticking diagnosis of the other of the first and second relays 211 and 212 (the first relay 211) can be implemented in the power-off operation.

[0088] In step S314, it is checked again based on the comparison result of the first voltage U1 and the second voltage U2 whether a closed loop is formed between the first to fourth sampling points a1, a2, a3, and a4. If it is found in step S314 that the voltage difference between the first voltage U1 and the second voltage U2 is less than the preset deviation, it means that the previously formed closed loop has not been destroyed by the active disconnection of the first relay 211 in operation c. In this case, it can be determined in step S315 that the first relay has a sticking fault.

[0089] On the contrary, if it is found in step S314 that the voltage difference between the first voltage U1 and the second voltage U2 is greater than the preset deviation, it means that the previously formed closed loop has been destroyed, so the charge accumulated in the input side capacitor C1 is forced to discharge (or passively discharge) so that the voltage difference increases to exceed the preset deviation. In this case, it means that the disconnection operation of the first relay 211 is successfully implemented in operation c, so that it can be determined in step S316 that the first relay 211 has no adhesion failure.

[0090] It should be noted that, considering that the forced discharge (or passive discharge) process of the input side capacitor C1 requires a certain target discharge time, for example, a preset deviation of 15V can be generated between the second voltage U2 and the first voltage U1 only after a target discharge time of 1.4 seconds, so after the operation c is performed in step S311, the first voltage U1 and the second voltage U2 can be sampled in step S312 after a predetermined time period. The predetermined time period is, for example, set to be greater than 1.4 seconds, especially greater than 2.5 seconds.

[0091] Finally, if it is confirmed in step S316 that neither the first relay 211 nor the second relay 212 has a sticking fault, operation d may be performed in step S317: the second relay 212 is controlled to be disconnected, and the first relay 211 is kept disconnected. Thus, the complete power-off process ends.

[0092] In an embodiment not shown, if it is determined in any of steps S305, S310 and S315 that the first relay 211 and / or the second relay 212 fails, the corresponding response measures can also be triggered in time. For example, for a relay adhesion failure, a safety alarm can be triggered to notify the possible high voltage risk. For a relay jam failure, the entire vehicle can be notified that energy conversion cannot be performed, and the user can be prompted to replace the faulty relay as soon as possible.

[0093] It should be noted that although the reference Figure 3The operation sequence of first controlling the first relay 211 to close during the power-on process and first controlling the first relay 211 to open during the power-off process is described, but it is also conceivable that another operation sequence of first controlling the second relay 212 to close during the power-on process and correspondingly first controlling the second relay 212 to open during the power-off process is controlled. The relay fault analysis process based on another operation sequence can be compared with Figure 3 The process shown is carried out by analogy and will not be described in detail here.

[0094] It should also be noted that although reference Figure 3 The process of performing relay fault diagnosis when the fuel cell 10 is started is described, but it is also conceivable that the relay fault diagnosis process is performed when the fuel cell 10 is not started. In the case where the fuel cell 10 is not started, in step S301, only the first pre-charging circuit 16 is used to increase the second voltage on the input capacitor C1 to 100V to form a predetermined voltage difference between the first voltage U1 and the second voltage U2. The remaining steps are the same as Figure 3 The processes shown are the same and will not be repeated here.

[0095] In an embodiment not shown, the Figure 2b The auxiliary relay configuration shown in the figure is used for fault determination. Figure 3 In the determination process described, it should be noted that the second pre-charging circuit 17 should be controlled to pre-charge the output capacitor C2 on the output side of the voltage converter 11 before the voltage sampling is performed, so that a predetermined voltage difference is formed between the first voltage U1 and the second voltage U2 before the first relay 221 and the second relay 222 are fully closed. Here, the output voltage of the secondary battery 15 is, for example, 550V. In order to form a predetermined voltage difference of 50V-100V, the output capacitor C2 can be charged to a voltage of 450V across the capacitor C2.

[0096] Figure 4a and Figure 4b A schematic diagram showing sampling point positions and sampling voltages in a main relay configuration according to another exemplary embodiment of the present invention is shown.

[0097] and Figure 2a By comparison, Figure 4a In addition to collecting the first voltage U1 between the first sampling point a1 and the third sampling point a3 and the second voltage U2 between the second sampling point a2 and the fourth sampling point a4 by means of the voltage sensor, voltage sensors are additionally arranged between the first sampling point a1 and the fourth sampling point a4 and between the second sampling point a2 and the third sampling point a3 to sample the third voltage U3 and the fourth voltage U4.

[0098] exist Figure 4bIn the illustrated embodiment, the voltage sensor may not be directly connected between the corresponding sampling points, but the voltage sensor may be connected in series with two voltage-dividing resistors Rd1 and Rd2 on the branch between the first and fourth sampling points a1 and a4. The voltage sensor is, for example, arranged between the two voltage-dividing resistors Rd1 and Rd2, so that the third voltage U3 may be indirectly derived through the relationship between the reading Ud of the voltage sensor and the voltage-dividing resistors Rd1 and Rd2. For example, there is U3=Ud / k2, where k2 is a sampling coefficient related to Rd1, Rd2 and the internal resistance of the voltage sensor. In other embodiments, it may also be approximately considered that U3≈Ud. Similarly, the reading Us of the voltage sensor on the branch between the second and third sampling points a2 and a3 and the voltage-dividing resistors Rs1 and Rs2 arranged in series therewith may also be used to derive the corresponding fourth voltage U4=Us / k1, where k1 is a sampling coefficient related to Rs1, Rs2 and the internal resistance of the voltage sensor. Alternatively, it may also be approximately considered that U4≈Us. The role of the voltage divider resistors Rd1, Rd2, Rs1, and Rs2 is to protect the voltage sensor to prevent the measured voltage from exceeding the voltage sensor range. The specific values ​​of these voltage divider resistors can be flexibly selected according to actual conditions. Figure 4a Just omit it as shown.

[0099] Therefore, in addition to using Figure 1 In addition to analyzing the closed loop formation between the first to fourth sampling points a1, a2, a3, and a4 based on the first and second voltages U1 and U2, the control unit 32 can also additionally determine the actual on-off state of the first relay 211 and the second relay 212 based on the sampling results of the third voltage U3 and the fourth voltage U4, and then determine the respective fault states of the first relay 211 and the second relay 212 by comparing the controlled on-off state of the first relay 211 and the second relay 212 with the actual on-off state.

[0100] Figure 5a-5d Schematic diagram showing four combined on-off states of the first relay and the second relay in the main relay configuration. In the illustrated embodiment, as described above, using Figure 4b The third voltage U3 and the fourth voltage U4 are characterized by the voltage sensor readings Us and Ud in and the appropriate sampling coefficients k1 and k2. For the sake of brevity, only Us and Ud appear in the description below.

[0101] exist Figure 5a In the embodiment, the first relay 211 and the second relay 212 are both in the disconnected state. For example, the actual on-off state of the first and second relays 211 and 212 can be determined when the measured first to fourth voltages meet the following conditions: Figure 5a Combined on-off status shown:

[0102] |(U1+U4) / 2-Us / k1|≤U thres

[0103] |(U1+U4) / 2-Ud / k2|≤U thres

[0104] |Us / k1-Ud / k2|≤U thres

[0105] Among them, U thres The predetermined voltage difference between the first voltage U1 and the second voltage U2 when the first and second relays 211 and 212 are not fully closed can be determined in the manner described above. In addition, U can also be determined in relation to the accuracy and range of the voltage sensor used to measure Ud and Us. thres For example, U thres It can be 20V.

[0106] In this embodiment, if the control on / off states of the first relay 211 and the second relay 212 are Figure 5a If the actual on-off state shown does not match, it can be inferred that the first relay 211 and / or the second relay 212 has a stuck fault. For example, if the first relay 211 is controlled to be closed and the second relay 212 is closed, it is determined that both the first relay 211 and the second relay 212 have a stuck fault. For another example, if the first relay 211 is controlled to be closed and the second relay 212 is disconnected, it is determined that the first relay 211 has a stuck fault. For another example, if the first relay 211 is controlled to be disconnected and the second relay 212 is closed, it is determined that the second relay 212 has a stuck fault.

[0107] exist Figure 5b In the embodiment, the first relay 211 and the second relay 212 are both in a closed state. For example, the actual on-off state of the first and second relays 211 and 212 can be determined when the measured first to fourth voltages meet the following conditions: Figure 5b Combined on-off status shown:

[0108] |U1-U2|≤U thres

[0109] exist Figure 5b In the circuit topology shown, the closed loop condition can be estimated by analyzing only the first voltage and the second voltage, so the redundant check of the third voltage and the fourth voltage can be omitted in the corresponding judgment conditions, thereby saving fault diagnosis time.

[0110] In this embodiment, if the control on / off states of the first relay 211 and the second relay 212 are Figure 5bIf the actual on-off state shown does not match, it can be inferred that the first relay 211 and / or the second relay 212 have a sticking fault. For example, if the first relay 211 is controlled to be disconnected and the second relay 212 is disconnected, it is determined that both the first relay 211 and the second relay 212 have a sticking fault. For another example, if the first relay 211 is controlled to be closed and the second relay 212 is disconnected, it is determined that the second relay 212 has a sticking fault. For another example, if the first relay 211 is controlled to be disconnected and the second relay 212 is closed, it is determined that the first relay 211 has a sticking fault.

[0111] exist Figure 5c In the embodiment, the first relay 211 is in a closed state and the second relay 212 is in an open state. For example, the actual on-off states of the first and second relays 211 and 212 can be determined to be: Figure 5c Combined on-off status shown:

[0112] |U1-Us / k1|≤U thres

[0113] |U2-Ud / k2|≤U thres

[0114] |Us / k1-Ud / k2|>U thres

[0115] In this embodiment, if the control on / off states of the first relay 211 and the second relay 212 are Figure 5c If the actual on-off state shown does not match, it can be inferred that the first relay 211 has a sticking fault, and / or the second relay 212 has a stuck fault. For example, if the first relay 211 is controlled to be closed and the second relay is closed 211, it is determined that the second relay 212 has a stuck fault. If the first relay 211 is controlled to be disconnected and the second relay 212 is disconnected, it is determined that the first relay 211 has a sticking fault. For another example, if the first relay 211 is controlled to be disconnected and the second relay 212 is closed, it is determined that the first relay 211 has a sticking fault and the second relay 212 has a stuck fault.

[0116] exist Figure 5d In the embodiment, the first relay 211 is in an open state and the second relay 212 is in a closed state. For example, the actual on-off states of the first and second relays 211 and 212 can be determined to be: Figure 5d Combined on-off status shown:

[0117] |U2-Us / k1|≤U thres

[0118] |U1-Ud / k2|≤U thres

[0119] |Us / k1-Ud / k2|>U thres

[0120] In this embodiment, if the control on / off states of the first relay 211 and the second relay 212 are Figure 5d If the actual on-off state shown does not match, it can be inferred that the first relay 211 has a stuck fault, and / or the second relay 212 has a sticking fault. For example, if the first relay 211 is controlled to be closed and the second relay 212 is closed, it is determined that the first relay 211 has a stuck fault. If the first relay 211 is controlled to be disconnected and the second relay 212 is disconnected, it is determined that the second relay 212 has a sticking fault. For another example, if the first relay 211 is controlled to be closed and the second relay 212 is disconnected, it is determined that the first relay 211 has a stuck fault and the second relay 212 has a sticking fault.

[0121] Figure 6 A flowchart of a method for detecting a relay failure in a power output system in a main relay configuration according to another exemplary embodiment of the present invention is shown. In this embodiment, the method exemplarily includes steps S600-S606, and these steps can be used, for example, in a Figure 1 The device 30 shown is implemented in the case.

[0122] In step S600, control Figure 1 The first pre-charging circuit 16 shown pre-charges the input capacitor C1 on the input side of the voltage converter 11, so that when the first relay 211 and the second relay 212 are not fully closed, a predetermined voltage difference is formed between the first voltage U1 and the second voltage U2. The formation process and specific value range of the predetermined voltage difference can be referred to Figure 3 Step S301 of the method shown is not described in detail here.

[0123] In step S601, the control on-off state of the first and second relays 211, 212 is obtained. The control on-off state is understood as the target on-off state to be achieved by controlling the first relay 211 and the second relay 212 by an electrical signal. This target on-off state can be recorded in the software as a control signal, but does not reflect the actual state of the relay contacts. The actual on-off state is understood as the mechanical on-off state of the first and second relays 211, 212 in the real circuit. In specific applications, since the first and second relays 211, 212 may fail, their actual on-off states are not always consistent with the control on-off states.

[0124] In step S602, the first voltage U1, the second voltage U2, the third voltage U3 and the fourth voltage U4 are sampled. A variety of voltage sensors capable of measuring the first to fourth voltages U1, U2, U3 and U4 may be used, and are not specifically limited here. In addition, depending on the accuracy and range of the relevant voltage sensors, the voltage sensors may be selected as needed. Figure 4a or Figure 4b Alternatively to the arrangement of the voltage sensors shown, other numbers of voltage sensors or other arrangements of the voltage sensors may also be selected.

[0125] In step S603, the first to fourth voltages U1, U2, U3, U4 are analyzed to check whether the first to fourth voltages U1, U2, U3, U4 meet the above combination Figure 5a-5d Which of all the conditions described, and thereby determine the actual on-off state of the first relay 211 and the second relay 212. For example, the first to fourth voltages U1, U2, U3, U4 of the first and second relays 211, 212 in each combined on-off state can be measured in advance by software simulation or experimental process, and then the conditions that the first to fourth voltages U1, U2, U3, U4 must meet in each combined on-off state are set and stored. As described above, corresponding voltage conditions can be set and stored for the states of "both the first relay 211 and the second relay 212 are disconnected", "both the first relay 211 and the second relay 212 are closed", "the first relay 211 is closed and the second relay 212 is disconnected", and "the first relay 211 is disconnected and the second relay 212 is closed".

[0126] In step S604, it is checked whether the controlled on / off state of the first relay 211 and the second relay 212 is consistent with the actual on / off state, and the fault state of each of the first relay 211 and the second relay 212 is determined in step S605 or step S606 according to the consistency check result.

[0127] Specifically, if it is determined in step S604 that the control on-off state of the first relay 211 and the second relay 212 is consistent with the actual on-off state, it is determined in step S605 that no faults of the first and second relays 211 and 212 are currently found. In combination with the control on-off state of the first and second relays 211 and 212, a more specific conclusion about the fault-free state of the first and second relays 211 and 212 can also be drawn in this step. For example, if the control on-off state of the first and second relays 211 and 212 is "the first and second relays 211 and 212 are both disconnected", it can be concluded in step S605 that no adhesion fault occurs in the first and second relays 211 and 212. For another example, if the control on-off state of the first and second relays 211 and 212 is "the first and second relays 211 and 212 are both closed", it can be concluded in step S605 that no stuck fault occurs in the first and second relays 211 and 212.

[0128] If it is determined in step S604 that the control on-off state of the first relay 211 and the second relay 212 is inconsistent with the actual on-off state, it can be determined in step S606 that there is a fault in the first relay and the second relay 211, 212. In combination with the control on-off state of the first and second relays 211, 212, a more specific conclusion about the fault state of the first and second relays 211, 212 can also be drawn in this step. For example, if the actual on-off state of the first and second relays 211, 212 is "the first relay 211 is closed and the second relay 212 is open", and the control on-off state of the first and second relays 211, 212 is "the first relay 211 is open and the second relay 212 is closed", it can be concluded in step S606 that the first relay 211 has a sticking fault, and the second relay 212 has a stuck fault. For another example, if the actual on-off state of the first and second relays 211 and 212 is "the first relay 211 is off and the second relay 212 is closed", and the controlled on-off state of the first and second relays 211 and 212 is "the first relay 211 is closed and the second relay 212 is off", it can be concluded in step S606 that the first relay 211 has a stuck fault and the second relay 212 has a sticking fault.

[0129] It should be noted that although the reference Figure 4a-4b , Figure 5a-5d as well as Figure 6 Only the relay fault diagnosis process in the main relay configuration is described, but similar diagnosis processes are also applicable to Figure 2b The auxiliary relay configuration shown also falls within the scope of the present invention.

[0130] It can be understood that the methods of various embodiments of the present disclosure can be implemented by computer programs / software. These software can be loaded into the working memory of the processor and used to execute the methods according to various embodiments of the present disclosure when running.

[0131] According to another embodiment of the present disclosure, a machine-readable storage medium is provided, such as a CD-ROM, which includes a computer program, which, when executed, causes a computer or a processor to perform a method according to each embodiment of the present disclosure. The machine-readable storage medium is, for example, an optical storage medium or a solid-state medium supplied together with other hardware or as part of other hardware.

[0132] Although specific embodiments of the present invention are described in detail herein, they are provided for the purpose of explanation only and should not be considered to limit the scope of the present invention. Various substitutions, changes and modifications may be conceived without departing from the spirit and scope of the present invention.

Claims

1. A method for detecting a relay fault state in a power output system (1), the power output system (1) comprising: A power battery (10); a voltage converter (11) which increases or decreases the output voltage of the power battery (10); a relay which is arranged on the input side or the output side of the voltage converter (11), the relay comprising a first relay (211, 221) arranged in the positive bus and a second relay (212, 222) arranged in the negative bus, the method comprising the following steps: A first sampling point (a1) and a second sampling point (a2) are respectively set at the non-voltage converter side terminal and the voltage converter side terminal of the first relay (211, 221), a third sampling point (a3) ​​and a fourth sampling point (a4) are respectively set at the non-voltage converter side terminal and the voltage converter side terminal of the second relay (212, 222), and a first voltage between the first sampling point (a1) and the third sampling point (a3) ​​and a second voltage between the second sampling point (a2) and the fourth sampling point (a4) are sampled; and A closed loop formation situation between the first to fourth sampling points is analyzed based at least on the first voltage and the second voltage to determine the respective fault states of the first relay (211, 221) and the second relay (212, 222), wherein the determination at least includes: when a fault state occurs in the first relay (211, 221) and / or the second relay (212, 222), determining whether the fault state occurs involves a sticking fault or a jamming fault.

2. The method according to claim 1, wherein: The method further comprises the following steps: asynchronously controlling the on and off of the first relay (211, 221) and the second relay (212, 222) according to a preset operation sequence, wherein after the on and off state of one of the first relay (211, 221) and the second relay (212, 222) is changed, sampling the first voltage and the second voltage.

3. The method according to claim 2, wherein: The operation sequence includes a power-on operation and a power-off operation, and the one that is closed first in the power-on operation and the one that is opened first in the power-off operation involve the same one of the first relay (211, 221) and the second relay (212, 222).

4. The method according to claim 2 or 3, wherein: The first relay (211, 221) and the second relay (212, 222) respectively have an initial state of disconnection, and the operation sequence includes: Operation a: controlling the first relay (211, 221) to close and keeping the second relay (212, 222) open; Operation b: controlling the second relay (212, 222) to close and keeping the first relay (211, 221) closed; Operation c: controlling the first relay (211, 221) to open and keeping the second relay (212, 222) closed; Operation d: controlling the second relay (212, 222) to open and keeping the first relay (211, 221) open; or Operation a: control the second relay (212, 222) to close and keep the first relay (211, 221) open; Operation b: control the first relay (211, 221) to close and keep the second relay (212, 222) closed; Operation c: control the second relay (212, 222) to open and keep the first relay (211, 221) closed; Operation d: control the first relay (211, 221) to open and keep the second relay (212, 222) open.

5. The method according to claim 4, wherein: After performing operation a, if the comparison result between the first voltage and the second voltage reflects that a closed loop is formed between the first to fourth sampling points, it is determined that a first relay (211, 221) or a second relay (212, 222) that has not been closed in operation a has a sticking fault; After performing operation b, if the comparison result between the first voltage and the second voltage reflects that a closed loop is not formed between the first to fourth sampling points, it is determined that at least one of the first relay (211, 221) and the second relay (212, 222) has a stuck fault; and / or After performing operation c, if the comparison result between the first voltage and the second voltage reflects that a closed loop is formed between the first to fourth sampling points, it is determined that a first relay (211, 221) or a second relay (212, 222) disconnected in operation c has a sticking fault.

6. The method according to claim 4 or 5, wherein: After operation c is performed, the first voltage and the second voltage are sampled after a predetermined period of time.

7. The method according to any one of claims 1 to 6, wherein: When the voltage difference between the first voltage and the second voltage is less than the preset deviation, it is determined that a closed loop is formed between the first to fourth sampling points.

8. The method according to any one of claims 1 to 7, wherein: The power output system (1) further comprises an input capacitor (C1) arranged on the input side of the voltage converter (11) and an output capacitor (C2) arranged on the output side of the voltage converter (11), and the method further comprises the following steps: precharging the input capacitor (C1) or the output capacitor (C2) of the voltage converter (11) so that a predetermined voltage difference is formed between the first voltage and the second voltage before the first relay (211, 221) and the second relay (212, 222) are fully closed.

9. The method according to claim 8, wherein: The upper limit value of the predetermined voltage difference is determined in relation to the following factors: When a closed loop is formed between the first to fourth sampling points by closing the first relay (211, 221) or the second relay (212, 222), the life loss suffered by the first relay (211, 221) or the second relay (212, 222) performing the closing; and / or The lower limit value of the predetermined voltage difference is determined in relation to the following factors: A voltage difference between the first voltage and the second voltage when a closed loop is not formed between the first to fourth sampling points in an overcharge state of the input capacitor (C1) or the output capacitor (C2).

10. The method according to any one of claims 1 to 9, wherein: The method further comprises the following steps: detecting a third voltage between the first sampling point (a1) and the fourth sampling point (a4) and a fourth voltage between the second sampling point (a2) and the third sampling point (a3); and In the step of determining the fault state, the fault state of each of the first relay (211, 221) and the second relay (212, 222) is additionally determined based on the third voltage and the fourth voltage.

11. The method according to claim 10, wherein: In the step of determining the fault state, the conditions that the first to fourth voltages should satisfy in each combined on-off state of the first relay (211, 221) and the second relay (212, 222) are predetermined and stored, the actual on-off state of the first relay (211, 221) and the second relay (212, 222) is determined by checking which of all the conditions the first to fourth voltages currently satisfy, and the fault state of each of the first relay (211, 221) and the second relay (212, 222) is determined by comparing the controlled on-off state and the actual on-off state of the first relay (211, 221) and the second relay (212, 222).

12. The method according to claim 10 or 11, wherein: When both the first relay (211, 221) and the second relay (212, 222) are controlled to be disconnected, determining whether a sticking fault occurs in the first relay (211, 221) and / or the second relay (212, 222) based on the first to fourth voltages; Under the condition that both the first relay (211, 221) and the second relay (212, 222) are controlled to be closed, determining whether a stuck fault occurs in the first relay (211, 221) and / or the second relay (212, 222) based on the first to fourth voltages; When the first relay (211, 221) is controlled to be closed and the second relay (212, 222) is controlled to be open, determining whether a stuck fault occurs in the first relay (211, 221) and / or a sticking fault occurs in the second relay (212, 222) based on the first to fourth voltages; and / or When the first relay (211, 221) is controlled to be disconnected and the second relay (212, 222) is controlled to be closed, it is determined based on the first to fourth voltages whether a sticking fault occurs in the first relay (211, 221) and / or a stuck fault occurs in the second relay (212, 222).

13. The method according to any one of claims 1 to 12, wherein: The relay is a main relay (21) arranged between a power battery (10) and a voltage converter (11); the first relay (211) is connected between a positive terminal of the power battery (10) and a positive terminal of the voltage converter (11) on a positive bus bar; and the second relay (212) is connected between a negative terminal of the power battery (10) and a negative terminal of the voltage converter (11) on a negative bus bar.

14. The method according to any one of claims 1 to 13, wherein: The power output system (1) further comprises a secondary battery (15) which is connected in parallel with the voltage converter (11) at the output side of the voltage converter (11); The relay is an auxiliary relay (22) arranged between a voltage converter (11) and a secondary battery (15), wherein the first relay (221) is connected between the positive terminal of the voltage converter (11) and the positive terminal of the secondary battery (15) on a positive bus bar, and the second relay (222) is connected between the negative terminal of the voltage converter (11) and the negative terminal of the secondary battery (15) on a negative bus bar.

15. A device (30) for detecting a relay fault state in a power output system (1), the device (30) being used to perform a method according to any one of claims 1 to 14, the device (30) comprising: A voltage detection unit (31) is configured to be able to set a first sampling point (a1) and a second sampling point (a2) at a non-voltage converter side terminal and a voltage converter side terminal of a first relay (211, 221), respectively, set a third sampling point (a3) ​​and a fourth sampling point (a4) at a non-voltage converter side terminal and a voltage converter side terminal of a second relay (212, 222), respectively, and sample a first voltage between the first sampling point (a1) and the third sampling point (a3) ​​and a second voltage between the second sampling point (a2) and the fourth sampling point (a4); as well as A control unit (32) is configured to analyze the closed loop formation between the first to fourth sampling points based on at least the first voltage and the second voltage to determine the fault state of each of the first relay (211, 221) and the second relay (212, 222), wherein the determination at least includes: when a fault state occurs in the first relay (211, 221) and / or the second relay (212, 222), determining whether the fault state occurs involves a sticking fault or a jamming fault. 16 . A machine-readable storage medium having a computer program stored thereon, the computer program being configured to execute the method according to claim 1 when executed on a computer.

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