Direct-current bus capacitor discharging circuit and method, electronic equipment and storage medium
By forming an electrical loop with the bus capacitor using an ANPC-type three-level circuit and an inductor circuit, the switching sequence of the switching devices and the resistance and capacitance losses of the inductor circuit are controlled. This solves the problem of energy leakage from the bus capacitor after the energy storage converter stops, achieving safe and low-cost bus voltage discharge and enhancing the product's competitiveness.
Patent Information
- Application Number
- CN202511069496.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-31
- Publication Date
- 2025-11-14
AI Technical Summary
In existing technologies, the design of the bus capacitor to discharge energy after the energy storage converter is shut down leads to increased costs and larger product size, while also posing a high voltage risk. Existing solutions cannot effectively solve this problem.
An ANPC-type three-level circuit, an inductor circuit, and a filter circuit are used to form an electrical loop with the bus capacitor. By controlling the switching sequence of the switching devices and the resistance and capacitance losses of the inductor circuit, the bus voltage can be discharged, avoiding the need to add additional circuits and devices.
It achieves safe discharge of bus voltage, reduces the risk of high voltage after equipment shutdown, reduces product cost and size, and improves product power density and competitiveness.
Smart Images
Figure CN120956050A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of bus capacitor discharge technology, and in particular to a DC bus capacitor discharge circuit, method, electronic device and storage medium. Background Technology
[0002] In energy storage converters, bus capacitors provide transient energy and perform DC-side filtering. After the energy storage converter shuts down, the energy in the bus capacitors typically needs a discharge path to ensure the safety of operators.
[0003] In existing technologies, most methods involve adding extra control circuitry, such as controllers and load resistors, to discharge voltage. However, this method increases cost and product size, thus reducing the product's overall competitiveness. In practice, bus voltage discharge is necessary, therefore, a discharge path is indispensable in the design process. Summary of the Invention
[0004] The main objective of this application is to provide a DC bus capacitor discharge circuit, method, electronic device, and storage medium to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.
[0005] To achieve the above objectives, one aspect of this application provides a DC bus capacitor discharge circuit, the circuit comprising: a bus capacitor, an ANPC type three-level circuit, an inductor circuit, a filter circuit, and a three-phase AC interface terminal;
[0006] One end of the three bridge arms of the ANPC-type three-level circuit is connected to the bus capacitor, the other end of the three bridge arms of the ANPC-type three-level circuit is connected to one end of the inductor circuit, and the other end of the inductor circuit is connected to the three-phase AC interface terminal.
[0007] One end of the filter circuit is connected to the other end of the inductor circuit and the three-phase AC interface, and the other end of the filter circuit is connected to the midpoint of the bus capacitor to form an electrical circuit.
[0008] To achieve the above objectives, another aspect of this application provides a method for discharging a DC bus capacitor, the method comprising:
[0009] The bus voltage of the bus capacitor is detected; wherein the bus capacitor includes a positive bus capacitor and a negative bus capacitor;
[0010] When the bus voltage is greater than the set safety voltage, the inductance of the inductor circuit is obtained. Based on the bus voltage and the inductance, the three bridge arms in the ANPC type three-level circuit are cyclically opened and closed in a set order until the voltage of the positive bus capacitor drops to the set safety voltage.
[0011] When the voltage of the positive bus capacitor drops to the set safe voltage, the three bridge arms in the ANPC type three-level circuit are switched on and off in the set sequence again until the voltage of the negative bus capacitor drops to the set safe voltage, so as to discharge the bus voltage.
[0012] Furthermore, the method of cyclically switching the three bridge arms in the ANPC-type three-level circuit in the predetermined order includes:
[0013] The current drive bridge arm is determined according to the set order; wherein the current drive bridge arm includes the first switching device, the second switching device, the third switching device, the fourth switching device, the fifth switching device, and the sixth switching device;
[0014] Based on the bus voltage and the inductance, the corresponding turn-on time and the corresponding turn-off time for each cycle are determined, and the first switching device is turned on and off cyclically based on the corresponding turn-on time and the corresponding turn-off time.
[0015] The second switching device is controlled to be normally open, and the third, fourth, fifth and sixth switching devices are all controlled to be normally closed.
[0016] Furthermore, determining the corresponding start time and corresponding stop time for each cycle includes:
[0017] In the current loop, the set conduction time is obtained, and the set conduction time is used as the corresponding turn-on time of the first switching device in the current loop;
[0018] Based on the turn-on time, the bus voltage, and the inductance, the corresponding turn-off time of the first switching device in the current cycle is determined so that the turn-on current of the first switching device in the next cycle is lower than the set specification threshold.
[0019] Furthermore, determining the corresponding start time and corresponding stop time for each cycle includes:
[0020] In the current loop, the set conduction time is obtained, and the set conduction time is used as the corresponding turn-on time of the first switching device in the current loop;
[0021] Obtain the current parameters of the inductor circuit, and determine the corresponding turn-off time based on the inductance and the current parameters, so that the turn-on current of the first switching device in the next cycle is lower than the set specification threshold.
[0022] Furthermore, the three bridge arms in the ANPC-type three-level circuit are cyclically switched on and off again in the predetermined order, including:
[0023] The current drive bridge arm is determined according to the set order; wherein the current drive bridge arm includes the first switching device, the second switching device, the third switching device, the fourth switching device, the fifth switching device, and the sixth switching device;
[0024] Based on the bus voltage and the inductance, the corresponding turn-on time and the corresponding turn-off time for each cycle are determined, and the fourth switching device is turned on and off cyclically based on the corresponding turn-on time and the corresponding turn-off time.
[0025] The third switching device is controlled to be normally open, and the first, second, fifth, and sixth switching devices are all controlled to be normally closed.
[0026] Furthermore, the DC bus capacitor discharge method also includes:
[0027] The bus voltage is further discharged through the inductor circuit and the filter circuit.
[0028] Furthermore, the set conduction time is less than 10µs.
[0029] To achieve the above objectives, another aspect of this application provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described method.
[0030] To achieve the above objectives, another aspect of the embodiments of this application proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method.
[0031] The embodiments of this application include at least the following beneficial effects: This application provides a DC bus capacitor discharge circuit, method, electronic device, and storage medium. This solution is based on an ANPC-type three-level circuit. Through an inductor circuit and a filter circuit, an electrical loop is formed with the midpoint of the bus capacitor, creating a current path for the switching device to turn on and a freewheeling path for the switching device to turn off. The initial voltage loss caused by the switching sequence of the ANPC-type three-level circuit, and the subsequent voltage loss caused by the inductor circuit and filter circuit, consume the energy of the bus voltage, discharging the bus voltage of the product. This reduces the risk of operators coming into contact with high voltage after equipment shutdown, ensuring operator safety. Furthermore, it eliminates the need for additional circuits and components, effectively reducing product cost, further compressing product size, increasing the size of internal control components, and improving product power density, thus giving the product a competitive edge. Attached Figure Description
[0032] Figure 1 This is a circuit diagram of the DC bus capacitor discharge circuit provided in an embodiment of this application;
[0033] Figure 2 This is a flowchart of the DC bus capacitor discharge method provided in the embodiments of this application;
[0034] Figure 3 This is a schematic diagram of the current path when the first switching device is turned on, provided in an embodiment of this application.
[0035] Figure 4 This is a schematic diagram of the signal sent to the current drive bridge arm when the positive bus capacitor is discharged, provided in an embodiment of this application.
[0036] Figure 5 This is a graph showing the relationship between the conduction current and voltage of the switching device provided in the embodiments of this application;
[0037] Figure 6 This is a schematic diagram of the freewheeling path when the first switching device is turned off, provided in an embodiment of this application.
[0038] Figure 7 This is a schematic diagram of the signal sent to the current drive bridge arm when the negative bus capacitor is discharged, provided in an embodiment of this application.
[0039] Figure 8 This is a schematic diagram of the current path when the fourth switching device is turned on, provided in an embodiment of this application;
[0040] Figure 9 This is a schematic diagram of the freewheeling path when the fourth switching device is turned off, provided in an embodiment of this application.
[0041] Figure label: ANPC type three-level circuit 100, inductor circuit 200, filter circuit 300, AC circuit breaker 400. Detailed Implementation
[0042] To make the objectives, technical solutions, and advantages of this application clearer, 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 it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.
[0043] It is understood that the terms “first,” “second,” etc., used in this application may be used herein to describe various concepts, but unless otherwise stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the words “if,” “when,” or “in response to a determination” as used herein may be interpreted as “when…” or “when…” or “in response to a determination.”
[0044] As used in this application, the terms "at least one", "multiple", "each", "any", etc., "at least one" includes one, two or more, "multiple" includes two or more, "each" refers to each of the corresponding multiples, and "any" refers to any one of the multiples.
[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.
[0046] Figure 1 This is a circuit diagram of a DC bus capacitor discharge circuit provided in one embodiment of this application. The DC bus capacitor discharge circuit includes: a bus capacitor, an ANPC type three-level circuit 100, an inductor circuit 200, a filter circuit 300, an AC circuit breaker 400, and a three-phase AC interface terminal.
[0047] The bus capacitor includes a positive bus capacitor and a negative bus capacitor. The connection point between the positive bus capacitor and the negative bus capacitor is called the midpoint of the bus capacitor.
[0048] One end of the three bridge arms of the ANPC type three-level circuit 100 is electrically connected to the bus capacitor, that is, one end of the three bridge arms is connected to the positive bus capacitor and the negative bus capacitor respectively. The other end of the three bridge arms of the ANPC type three-level circuit 100 is connected to one end of the inductor circuit 200. The other end of the inductor circuit 200 is connected to the three-phase AC interface terminal through the AC circuit breaker 400.
[0049] The other end of the inductor circuit 200 is connected to the AC circuit breaker 400 via a filter circuit 300, which brings out the virtual neutral point of the three-phase AC side. That is, one end of the filter circuit 300 is electrically connected to the other end of the inductor circuit 200, and another end of the filter circuit 300 is also connected to the three-phase AC interface terminal via the AC circuit breaker 400. The other end of the filter circuit 300 is electrically connected to the midpoint of the bus capacitor, thus connecting the virtual neutral point of the three-phase AC side with the midpoint of the bus capacitor, forming an electrical loop.
[0050] The ANPC type three-level circuit 100 includes: a first bridge arm, a second bridge arm, and a third bridge arm.
[0051] Each bridge arm consists of six connected switching devices, which can be composed of IGBT modules, IGBT half-bridge modules, or power MOSFETs.
[0052] The filter circuit 300 includes: a first RC parallel circuit, a second RC parallel circuit, and a third RC parallel circuit.
[0053] The inductor circuit 200 includes: a first inductor, a second inductor, and a third inductor.
[0054] One end of the first inductor is connected to the first bridge arm of the ANPC type three-level circuit 100, and the other end of the first inductor is connected to one end of the first RC parallel circuit. The other end of the first RC parallel circuit is electrically connected to the midpoint of the bus capacitor. The first inductor leads out the virtual midpoint of phase A AC through the first RC parallel circuit.
[0055] One end of the second inductor is connected to the second bridge arm of the ANPC type three-level circuit 100, and the other end of the second inductor is connected to one end of the second RC parallel circuit. The other end of the second RC parallel circuit is electrically connected to the midpoint of the bus capacitor. The second inductor leads out the virtual midpoint of phase B AC through the second RC parallel circuit.
[0056] One end of the third inductor is connected to the third bridge arm of the ANPC type three-level circuit 100, and the other end of the third inductor is connected to one end of the third RC parallel circuit. The other end of the third RC parallel circuit is electrically connected to the midpoint of the bus capacitor. The third inductor leads out the virtual midpoint of the C-phase AC circuit through the third RC parallel circuit.
[0057] in, Figure 1In the diagram, r1 represents the internal resistance of the first inductor, r2 represents the internal resistance of the second inductor, and r3 represents the internal resistance of the third inductor.
[0058] Figure 2 This is an optional flowchart of a DC bus capacitor discharge method provided in another embodiment of this application. The DC bus capacitor discharge method is applied to the DC bus capacitor discharge circuit provided in another embodiment of this application. Figure 2 The method may include, but is not limited to, steps S100 to S300.
[0059] Step S100: Detect the bus voltage of the bus capacitor.
[0060] Step S200: When the bus voltage is greater than the set safety voltage, obtain the inductance of the inductor circuit. Based on the bus voltage and the inductance, cyclically open and close the three bridge arms in the ANPC type three-level circuit in the set order until the voltage of the positive bus capacitor drops to the set safety voltage.
[0061] Step S300: When the voltage of the positive bus capacitor drops to the set safe voltage, the three bridge arms in the ANPC type three-level circuit are switched on and off in the set sequence again until the voltage of the negative bus capacitor drops to the set safe voltage to discharge the bus voltage.
[0062] Steps S100 to S300 of the embodiments of this application, by adjusting the switching sequence of the switching devices and the duty cycle of the PWM signal of the ANPC type three-level circuit, and in conjunction with the inductor circuit and filter circuit on the AC side of the converter, are connected to the midpoint of the bus capacitor to form an electrical circuit. This allows the energy of the bus capacitor to be initially discharged through the conduction and turn-off losses of the switching devices during the continuous switching process, and then discharged again through inductance and resistance losses. This solves the problem of the high voltage of the bus capacitor after the converter is shut down, which may pose a certain danger to the operators. It also solves the problems of increased product cost and size caused by adding an additional discharge circuit.
[0063] In some embodiments of S100, after the energy storage converter is shut down, the bus capacitance is detected to obtain the bus voltage. It is then determined whether the bus voltage is greater than a set safety voltage.
[0064] The bus capacitors include positive bus capacitors and negative bus capacitors.
[0065] In some embodiments of S200, when it is determined that the bus voltage is greater than the set safety voltage, a signal is sent to the switching devices of the three bridge arms in the ANPC type three-level circuit, so that the three bridge arms are opened and closed in sequence according to the set order to discharge the voltage of the positive bus capacitor.
[0066] When the bus voltage is determined to be greater than the set safety voltage, the inductance of the current inductor circuit is obtained. Based on the bus voltage and the inductance, the PWM signal to be sent to the three bridge arms of the ANPC type three-level circuit is determined. According to the set sequence, the driving sequence of the three bridge arms in the ANPC type three-level circuit is determined, and the three bridge arms are driven to open and close in sequence.
[0067] As the switching devices in the three bridge arms open and close, the energy dissipates gradually during the opening and closing process, and the voltage of the positive bus capacitor gradually decreases.
[0068] In another embodiment, in the current path, some energy is consumed again by the internal resistance of the inductor in the inductor circuit and the resistance of the resistor and capacitor in the filter circuit, thereby reducing the voltage of the positive bus capacitor again until the voltage of the positive bus capacitor drops to the set safe voltage, and the drive signal is stopped.
[0069] In some embodiments of S300, when it is determined that the voltage of the positive bus capacitor has dropped to the set safe voltage, a signal is sent again to the switching devices of the three bridge arms in the ANPC type three-level circuit, so that the three bridge arms open and close in sequence according to the set order to discharge the voltage of the negative bus capacitor.
[0070] When the voltage of the positive bus capacitor drops to the set safe voltage, the inductance of the current inductor circuit is obtained. Based on the bus voltage and the inductance, the PWM signal to be sent to the three bridge arms of the ANPC type three-level circuit is determined. According to the set sequence, the driving sequence of the three bridge arms in the ANPC type three-level circuit is determined, and the three bridge arms are driven to open and close in sequence.
[0071] As the switching devices in the three bridge arms open and close, the energy dissipates gradually during the opening and closing process, and the voltage of the negative bus capacitor gradually decreases.
[0072] In another embodiment, in the current path, the internal resistance of the inductor in the inductor circuit and the resistance values of the resistors and capacitors in the filter circuit are used to consume some energy again, thereby further reducing the voltage of the negative bus capacitor until the voltage of the negative bus capacitor drops to the set safe voltage, at which point the drive signal is stopped. This achieves the discharge of the bus voltage, making the bus voltage lower than the set safe voltage.
[0073] In another embodiment, the negative bus voltage can be discharged first, and then the positive bus voltage can be discharged to discharge the bus voltage so that the bus voltage is lower than the set safety voltage.
[0074] Reference Figures 3 to 5 In another embodiment of this application, the DC bus capacitor discharge method, step S200, specifically includes the process of discharging the voltage of the positive bus capacitor:
[0075] S210, determine the current drive axle arm according to the set sequence;
[0076] S220 determines the corresponding turn-on time and corresponding turn-off time for each cycle based on the bus voltage and inductance, and cycles the first switching device on and off according to the corresponding turn-on time and corresponding turn-off time.
[0077] S230 controls the second switching device to be normally open, and controls the third, fourth, fifth and sixth switching devices to be normally closed.
[0078] In some embodiments of S210, the current drive arm is determined by a set sequence.
[0079] Based on the bridge arm structure of the ANPC type three-level circuit, each bridge arm is equipped with six switching devices. The currently driven bridge arm includes the first switching device, the second switching device, the third switching device, the fourth switching device, the fifth switching device, and the sixth switching device.
[0080] The sequence can be the switching devices of the first bridge arm, the second bridge arm and the third bridge arm being turned on and off in sequence, or the switching devices of the second bridge arm, the first bridge arm and the third bridge arm being turned on and off in sequence. In this case, the currently driven bridge arm can be the first bridge arm, the second bridge arm or the third bridge arm. No specific restrictions are made on the sequence in this application.
[0081] In some embodiments of S220, reference is made to... Figure 4 When discharging the voltage of the positive bus capacitor, the first switching device is driven to open and close. Based on the bus voltage and inductance, the corresponding turn-on time and turn-off time of the first switching device in the current cycle are determined on the current drive bridge arm. A PWM signal is generated based on the corresponding turn-on time and turn-off time to execute the opening and closing action of the first switching device in the current cycle for the initial discharge.
[0082] In order to discharge the voltage of the positive bus capacitor, the three bridge arms will cycle open and close in a set order. For the current driving bridge arm, the corresponding opening time and corresponding closing time for each cycle are determined to realize multiple opening and closing actions of the first switching device, so as to cycle open and close the current driving bridge arm, that is, cycle open and close the first switching device.
[0083] Reference Figure 3 When the first switching device is turned on, the current path flows from the positive bus capacitor through the first switching device, the second switching device, and the corresponding inductor in the inductor circuit. Since the switching frequency of the first switching device is at a high frequency, it can also pass through the resistor and capacitor in the filter circuit, and finally return to the positive bus capacitor.
[0084] Reference Figure 5During the turn-on and turn-off process of the first switching device, as the Ic turn-on current increases and the Vce voltage decreases, when the two overlap, this part represents the energy consumed by the first switching device during the turn-on and turn-off process. As the first switching device repeatedly turns on and off, the energy is gradually consumed, and the voltage of the positive bus capacitor gradually decreases.
[0085] In some embodiments of S230, reference is made to... Figure 4 A fixed high level is sent to the second switching device to control it to be in the normally open state, and a fixed low level is sent to the third, fourth, fifth and sixth switching devices to control them to be in the normally closed state.
[0086] Reference Figure 6 When the first switching device is turned off, the inductor current in the inductor circuit will not change abruptly. The inductor in the inductor circuit will form a new freewheeling path with the switching device, and will pass through the anti-parallel diode of the fifth switching device, the second switching device, the inductor in the inductor circuit, and the resistor and capacitor in the filter circuit in sequence.
[0087] Reference Figures 5 to 8 In another embodiment of this application, the DC bus capacitor discharge method, step S300, specifically includes the process of discharging the voltage of the negative bus capacitor:
[0088] S310, determine the current drive axle arm according to the set sequence;
[0089] S320 determines the corresponding turn-on time and corresponding turn-off time for each cycle based on the bus voltage and inductance, and cycles the fourth switching device on and off according to the corresponding turn-on time and corresponding turn-off time.
[0090] S330 controls the third switching device to be normally open, and controls the first, second, fifth and sixth switching devices to be normally closed.
[0091] In some embodiments of S310, the current drive arm is determined by a set sequence.
[0092] Based on the bridge arm structure of the ANPC type three-level circuit, each bridge arm is equipped with six switching devices. The currently driven bridge arm includes the first switching device, the second switching device, the third switching device, the fourth switching device, the fifth switching device, and the sixth switching device.
[0093] The sequence can be the switching devices of the first bridge arm, the second bridge arm and the third bridge arm being turned on and off in sequence, or the switching devices of the second bridge arm, the first bridge arm and the third bridge arm being turned on and off in sequence. In this case, the currently driven bridge arm can be the first bridge arm, the second bridge arm or the third bridge arm. No specific restrictions are made on the sequence in this application.
[0094] In some embodiments of S320, refer to Figure 7 When discharging the voltage of the negative bus capacitor, the fourth switching device is driven to open and close. The corresponding turn-on time and corresponding turn-off time of the fourth switching device in the current cycle are determined by the bus voltage and inductance. The corresponding turn-on time and corresponding turn-off time are used to form a PWM signal to perform the opening and closing action of the fourth switching device in the current cycle for the initial discharge.
[0095] In order to discharge the voltage of the negative bus capacitor, the three bridge arms will cycle open and close in the set sequence. For the current driving bridge arm, the corresponding opening time and closing time for each cycle are determined to realize the multiple opening and closing actions of the fourth switching device, so as to cycle open and close the current driving bridge arm, that is, cycle open and close the fourth switching device.
[0096] Reference Figure 8 When the fourth switching device is turned on, since the switching frequency of the fourth switching device is at a high frequency, the current path flows from the midpoint of the bus capacitor through the resistor and capacitor in the filter circuit, the corresponding inductor in the inductor circuit, the third switching device and the fourth switching device in sequence, and finally returns to the negative bus capacitor.
[0097] Reference Figure 5 During the turn-on and turn-off process of the fourth switching device, as the Ic turn-on current increases and the Vce voltage decreases, when the two overlap, this part represents the energy consumed by the fourth switching device during the turn-on and turn-off process. As the fourth switching device repeatedly turns on and off, the energy is gradually consumed, and the voltage of the negative bus capacitor gradually decreases.
[0098] In some embodiments of S230, reference is made to... Figure 7 A fixed high level is sent to the third switching device to control it to be in the normally open state, and a fixed low level is sent to the first, second, fifth, and sixth switching devices to control them to be in the normally closed state.
[0099] Reference Figure 9When the fourth switching device is turned off, the inductor current in the inductor circuit will not change abruptly. There will be a freewheeling path that passes through the midpoint of the bus capacitor, the resistor and capacitor in the filter circuit, the inductor in the inductor circuit, the anti-parallel diode of the third and sixth switching devices, and then returns to the midpoint of the bus capacitor.
[0100] In another embodiment of the DC bus capacitor discharge method provided in this application, the process of determining the corresponding turn-on time and the corresponding turn-off time in S220 specifically includes:
[0101] S221, In the current loop, obtain the set conduction time and use the set conduction time as the corresponding turn-on time of the first switching device in the current loop;
[0102] S222: Based on the turn-on time, bus voltage, and inductance, determine the corresponding turn-off time of the first switching device in the current cycle, so that the turn-on current of the first switching device in the next cycle is lower than the set specification threshold.
[0103] In this embodiment, the positive bus capacitor is discharged in the current drive bridge arm of one cycle.
[0104] Normally, the time before the first switching device turns on is consistent with the dead time of the product's normal operation. Based on the set conduction time, the corresponding turn-on time of the first switching device in this cycle is determined to keep the switching frequency of the switching device at a high frequency, greater than 100kHz.
[0105] The set conduction time is less than 10µs. That is, the corresponding turn-on time is less than 10µs.
[0106] The corresponding shutdown time is determined by the current startup time, bus voltage, and inductance to ensure that the startup current Ic of the next startup does not exceed the set threshold, so that the current drive arm has enough time to eliminate the risk of heat accumulation in the current cycle.
[0107] Specifically, using the inductance formula U = L * di / dt, the bus voltage U gradually decreases with each turn of the first switching device, reaching a maximum value that is the half-bus voltage when the energy storage converter just stops operating; this is a known quantity. L is the inductance of the inductor connected to the current drive bridge arm, and is a fixed value.
[0108] The turn-on time t is adjusted to control the value of i to be less than the maximum value given in the switching transistor's datasheet, i.e., the set threshold value. Similarly, the current i value during this turn-on is calculated using the same formula. Based on the established empirical formula, the corresponding turn-off time is selected to be approximately 10 times the previous turn-on time for initial determination. Based on the bus voltage U and inductance L from the inductance formula, the corresponding turn-off time is determined again to reduce the current on the inductor connected to the current drive bridge arm to below 10A, so that the next cycle can begin.
[0109] Similarly, in the subsequent loops, the corresponding turn-on time and corresponding turn-off time of the first switching device in the current drive bridge arm can be obtained.
[0110] In another embodiment, the negative bus capacitor is discharged in the current drive bridge arm during one cycle.
[0111] Normally, the time before the fourth switching device turns on is consistent with the dead time of the product's normal operation. Based on the set conduction time, the corresponding turn-on time of the current fourth switching device in this cycle is determined to keep the switching frequency of the switching device at a high frequency, greater than 100kHz.
[0112] The corresponding shutdown time is determined by the current startup time, bus voltage, and inductance to ensure that the startup current Ic of the next startup does not exceed the set threshold, so that the current drive arm has enough time to eliminate the risk of heat accumulation in the current cycle.
[0113] Specifically, using the inductance formula U = L * di / dt, the bus voltage U gradually decreases with each turn of the fourth switching device, reaching a maximum value that is the half-bus voltage when the energy storage converter just stops operating; this is a known quantity. L is the inductance of the inductor connected to the current drive bridge arm, and is a fixed value.
[0114] The turn-on time t is adjusted to control the value of i to be less than the maximum value given in the switching transistor's datasheet, i.e., the set threshold value. Similarly, the current i value during this turn-on is calculated using the same formula. Based on the established empirical formula, the corresponding turn-off time is selected to be approximately 10 times the previous turn-on time for initial determination. Based on the bus voltage U and inductance L from the inductance formula, the corresponding turn-off time is determined again to reduce the current on the inductor connected to the current drive bridge arm to below 10A, so that the next cycle can begin.
[0115] Similarly, in the subsequent loops, the corresponding turn-on time and corresponding turn-off time of the fourth switching device in the current drive bridge arm can be obtained.
[0116] In another embodiment of the DC bus capacitor discharge method provided in this application, the process of determining the corresponding turn-on time and the corresponding turn-off time in S220 specifically includes:
[0117] S221, In the current loop, obtain the set conduction time and use the set conduction time as the corresponding turn-on time of the first switching device in the current loop;
[0118] S222: Obtain the current parameters of the inductor circuit, and determine the corresponding turn-off time based on the inductance and current parameters, so that the turn-on current of the first switching device in the next cycle is lower than the set specification threshold.
[0119] In this embodiment, the positive bus capacitor is discharged in the current drive bridge arm of one cycle.
[0120] Normally, the time before the first switching device turns on is consistent with the dead time of the product's normal operation. Based on the set conduction time, the corresponding turn-on time of the first switching device in this cycle is determined to keep the switching frequency of the switching device at a high frequency, greater than 100kHz.
[0121] The set conduction time is less than 10µs. That is, the corresponding turn-on time is less than 10µs.
[0122] To obtain the current parameters of an inductor circuit, use the current parameters and inductance value, and then apply the following formula.
[0123] t = -L / r * [ln(It / Io)]
[0124] Calculate the corresponding turn-off time of the first switching device in this cycle to ensure that the turn-on current Ic of the next turn-on does not exceed the set specification threshold. Here, t is the time to be calculated, L is the inductance of the inductor connected to the current drive bridge arm, which is a fixed value, r is the internal resistance of the inductor connected to the current drive bridge arm, It is the safety value of the required reduction of the inductor current, and Io is the initial current of the i value measured above.
[0125] The current parameters include the safety value It for the required reduction of the inductor current and the initial current Io measured at the top.
[0126] In another embodiment of this application, the DC bus capacitor discharge method further includes:
[0127] The bus voltage is discharged again through inductor circuits and filter circuits.
[0128] In this embodiment, as can be seen from S200 and S300, the voltage of the bus capacitor is initially discharged by cyclically opening and closing the three bridge arms in the ANPC type three-level circuit in a set sequence.
[0129] Reference Figure 5During the opening and closing process of the first or fourth switching device, as the Ic turn-on current increases and the Vce voltage decreases, when the two overlap, this part represents the energy consumed by the first or fourth switching device during the opening and closing process. As the first or fourth switching device repeatedly turns on, the energy is gradually consumed, and the voltage of the positive or negative bus capacitor gradually decreases to initially discharge the voltage of the bus capacitor.
[0130] In the current path, the inductor's internal resistance and the resistors and capacitors in the filter circuit will also consume some energy to further reduce the voltage of the positive or negative bus capacitor until the voltage of the positive or negative bus capacitor drops to the set safe voltage, at which point the drive signal will stop being sent, thus realizing the discharge of the bus voltage and making the bus voltage lower than the set safe voltage.
[0131] This application also provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the aforementioned DC bus capacitor discharge method. This electronic device can be any smart terminal, including tablet computers, in-vehicle computers, etc.
[0132] It is understood that the content of the above method embodiments is applicable to this device embodiment. The specific functions implemented by this device embodiment are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.
[0133] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described DC bus capacitor discharge method.
[0134] It is understood that the content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented in this storage medium embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.
[0135] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.
[0136] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.
[0137] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.
[0138] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.
[0139] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0140] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of the units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.
[0141] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.
Claims
1. A DC bus capacitor discharge circuit, characterized in that, include: Bus capacitor, ANPC type three-level circuit, inductor circuit, filter circuit and three-phase AC interface terminal; One end of the three bridge arms of the ANPC-type three-level circuit is connected to the bus capacitor, the other end of the three bridge arms of the ANPC-type three-level circuit is connected to one end of the inductor circuit, and the other end of the inductor circuit is connected to the three-phase AC interface terminal. One end of the filter circuit is connected to the other end of the inductor circuit and the three-phase AC interface, and the other end of the filter circuit is connected to the midpoint of the bus capacitor to form an electrical circuit.
2. A method for discharging a DC bus capacitor, characterized in that, The method, applied to the DC bus capacitor discharge circuit of claim 1, comprises: The bus voltage of the bus capacitor is detected; wherein the bus capacitor includes a positive bus capacitor and a negative bus capacitor; When the bus voltage is greater than the set safety voltage, the inductance of the inductor circuit is obtained. Based on the bus voltage and the inductance, the three bridge arms in the ANPC type three-level circuit are cyclically opened and closed in a set order until the voltage of the positive bus capacitor drops to the set safety voltage. When the voltage of the positive bus capacitor drops to the set safe voltage, the three bridge arms in the ANPC type three-level circuit are switched on and off in the set sequence again until the voltage of the negative bus capacitor drops to the set safe voltage, so as to discharge the bus voltage.
3. The DC bus capacitor discharge method according to claim 2, characterized in that, The three bridge arms in the ANPC-type three-level circuit that are cyclically switched on and off in a predetermined order include: The current drive bridge arm is determined according to the set order; wherein the current drive bridge arm includes the first switching device, the second switching device, the third switching device, the fourth switching device, the fifth switching device, and the sixth switching device; Based on the bus voltage and the inductance, the corresponding turn-on time and the corresponding turn-off time for each cycle are determined, and the first switching device is turned on and off cyclically based on the corresponding turn-on time and the corresponding turn-off time. The second switching device is controlled to be normally open, and the third, fourth, fifth and sixth switching devices are all controlled to be normally closed.
4. The DC bus capacitor discharge method according to claim 3, characterized in that, Determining the corresponding start time and corresponding stop time for each cycle includes: In the current loop, the set conduction time is obtained, and the set conduction time is used as the corresponding turn-on time of the first switching device in the current loop; Based on the turn-on time, the bus voltage, and the inductance, the corresponding turn-off time of the first switching device in the current cycle is determined so that the turn-on current of the first switching device in the next cycle is lower than the set specification threshold.
5. The DC bus capacitor discharge method according to claim 3, characterized in that, Determining the corresponding start time and corresponding stop time for each cycle includes: In the current loop, the set conduction time is obtained, and the set conduction time is used as the corresponding turn-on time of the first switching device in the current loop; Obtain the current parameters of the inductor circuit, and determine the corresponding turn-off time based on the inductance and the current parameters, so that the turn-on current of the first switching device in the next cycle is lower than the set specification threshold.
6. The DC bus capacitor discharge method according to claim 2, characterized in that, Repeatedly switch the three bridge arms of the ANPC-type three-level circuit on and off in the set order, including: The current drive bridge arm is determined according to the set order; wherein the current drive bridge arm includes the first switching device, the second switching device, the third switching device, the fourth switching device, the fifth switching device, and the sixth switching device; Based on the bus voltage and the inductance, the corresponding turn-on time and the corresponding turn-off time for each cycle are determined, and the fourth switching device is turned on and off cyclically based on the corresponding turn-on time and the corresponding turn-off time. The third switching device is controlled to be normally open, and the first, second, fifth, and sixth switching devices are all controlled to be normally closed.
7. The DC bus capacitor discharge method according to claim 2, characterized in that, Also includes: The bus voltage is further discharged through the inductor circuit and the filter circuit.
8. The DC bus capacitor discharge method according to claim 4, characterized in that, The set conduction time is less than 10µs.
9. An electronic device, characterized in that, The electronic device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method according to any one of claims 2 to 8.
10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 2 to 8.