Control method and related device for realizing zero-pressure-difference suction of input relay

Abstract

The present application provides a control method and related device for realizing zero-voltage-difference suction of an input relay. The method includes: determining a target energy transfer strategy according to the working mode of the control system; controlling a post-stage voltage conversion circuit to transmit electric energy to a DC bus according to the target energy transfer strategy; sending a driving signal to a pre-stage controller to instruct the pre-stage controller to invert the electric energy on the DC bus into a three-phase AC voltage by controlling the pre-stage voltage conversion circuit, and controlling the input relay to suck in when it is detected that the phase and amplitude of the three-phase AC voltage are the same as those of the grid voltage. In this way, when controlling the input relay to suck in, the voltage states at both ends of its contacts are the same, realizing zero-voltage-difference suction of the input relay, avoiding damage and failure of the input relay due to the existence of a voltage difference at both ends of the contacts during suction, and improving safety and reliability.

Description

Technical Field

[0001] This application relates to the field of electronic power, and particularly to a control method and related device for achieving zero-voltage-difference closing of an input relay. Background Art

[0002] With the rapid development of electronic power technology, the application scenarios of bidirectional AC-DC conversion control systems are increasing, such as in new energy vehicles for implementing V2G (Vehicle-to-Grid) technology. Among them, the input relays are respectively located in the inputs of each phase of the three-phase. The traditional control method usually directly closes the input relay at startup. However, since the grid voltage at the front end of the input relay changes instantaneously, there will be a voltage difference across the contacts when the input relay closes, which is likely to cause phenomena such as arcing and sparking, sharply reducing the life of the relay and affecting the reliability of the relay. Summary of the Invention

[0003] Embodiments of this application provide a control method and related device for achieving zero-voltage-difference closing of an input relay, in order to achieve zero-voltage-difference closing of the input relay, avoid damage to the relay caused by the voltage difference across the contacts when the input relay closes, and improve safety.

[0004] In a first aspect, embodiments of this application provide a control method for achieving zero-voltage-difference closing of an input relay, which is applied to a post-stage controller in a control system. The control system includes the post-stage controller, a post-stage voltage conversion circuit, a pre-stage controller, and a pre-stage voltage conversion circuit. The post-stage voltage conversion circuit is connected to the pre-stage voltage conversion circuit through a DC bus. The pre-stage voltage conversion circuit is connected to the grid through an input relay. The post-stage voltage conversion circuit is connected to a DC power supply terminal. The method includes:

[0005] Determine a target energy transfer strategy according to the working mode of the control system. The working mode includes a rectification mode and a grid connection mode. The rectification mode refers to a working mode of taking power from the grid and converting it into direct current. The grid connection mode refers to a working mode of taking power from the DC power supply terminal and converting it into alternating current;

[0006] Control the post-stage voltage conversion circuit to transfer electrical energy to the DC bus according to the target energy transfer strategy;

[0007] Send a driving signal to the pre-stage controller to instruct the pre-stage controller to control the pre-stage voltage conversion circuit to invert the electrical energy on the DC bus into a three-phase AC voltage, and control the input relay to close when the phase and amplitude of the three-phase AC voltage are detected to be the same as those of the grid voltage.

[0008] In a second aspect, an embodiment of the present application provides a control device for realizing zero-voltage-difference closing of an input relay, which is applied to a post-stage controller in a control system. The control system includes the post-stage controller, a post-stage voltage conversion circuit, a pre-stage controller, and a pre-stage voltage conversion circuit. The post-stage voltage conversion circuit is connected to the pre-stage voltage conversion circuit through a DC bus. The pre-stage voltage conversion circuit is connected to the power grid through an input relay. The post-stage voltage conversion circuit is connected to a DC power supply terminal. The device includes:

[0009] A determination unit, configured to determine a target energy transfer strategy according to the working mode of the control system. The working mode includes a rectification mode and a grid connection mode. The rectification mode refers to a working mode of taking power from the power grid and converting it into direct current. The grid connection mode refers to a working mode of taking power from the DC power supply terminal and converting it into alternating current.

[0010] A control unit, configured to control the post-stage voltage conversion circuit to transfer electric energy to the DC bus according to the target energy transfer strategy.

[0011] A signal sending unit, configured to send a driving signal to the pre-stage controller to instruct the pre-stage controller to control the pre-stage voltage conversion circuit to invert the electric energy on the DC bus into a three-phase AC voltage, and control the input relay to close when it is detected that the phase and amplitude of the three-phase AC voltage are the same as those of the grid voltage.

[0012] In a third aspect, an embodiment of the present application provides a controller, including a processor, a memory, and one or more programs. The one or more programs are stored in the memory and are configured to be executed by the processor. The programs include instructions for performing the steps in the first aspect of the embodiment of the present application.

[0013] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, on which a computer program / instruction is stored. When the computer program / instruction is executed by a processor, the steps in the first aspect of the embodiment of the present application are implemented.

[0014] It can be seen that in the embodiment of the present application, the post-stage controller determines a target energy transfer strategy according to the working mode of the control system, controls the post-stage voltage conversion circuit to transfer electric energy to the DC bus according to the target energy transfer strategy, and finally sends a driving signal to the pre-stage controller, so that the pre-stage controller controls the pre-stage voltage conversion circuit to invert the electric energy on the DC bus into a three-phase AC voltage, and controls the input relay to close when it is detected that the phase and amplitude of the three-phase AC voltage are the same as those of the grid voltage. In this way, when controlling the input relay to close, the voltage states at both ends of its contacts are the same, realizing zero-voltage-difference closing of the input relay, avoiding damage and failure of the input relay due to the existence of a voltage difference at both ends of the contacts when the input relay closes, and improving safety and reliability. Brief Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 is a structural block diagram of a control system provided by an embodiment of the present application;

[0017] Figure 2 is a structural block diagram of another control system provided by an embodiment of the present application;

[0018] Figure 3 is a schematic flowchart of a control method for realizing zero-pressure-difference suction of an input relay provided by an embodiment of the present application;

[0019] Figure 4 is a structural block diagram of a DC power supply terminal provided by an embodiment of the present application;

[0020] Figure 5 is a structural block diagram of a control device for realizing zero-pressure-difference suction of an input relay provided by an embodiment of the present application;

[0021] Figure 6 is a structural block diagram of another control device for realizing zero-pressure-difference suction of an input relay provided by an embodiment of the present application;

[0022] Figure 7 is a structural block diagram of a controller provided by an embodiment of the present application. Detailed Description of the Embodiments

[0023] In order to enable those skilled in the art to better understand the solution of the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0024] The terms "first", "second", etc. in the description, claims and the above-mentioned drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0025] Reference to "embodiment" herein means that a particular feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0026] Currently, in order to achieve zero-voltage-difference closing of the input relay in the prior art, the common solution is to collect the voltage of each phase and control the relay of that phase to close when the voltage of each phase passes through the zero point. However, due to the influence of the sampling circuit and the accuracy of the analog-to-digital converter (ADC), there will be errors in the determination when the voltage passes through the zero point, and there is also a certain delay in the operation of the input relay itself. Due to the coupling of various factors, there will still be a voltage difference across the contacts of the input relay when it closes. Therefore, it is extremely idealistic to achieve zero-voltage-difference closing based on the existing solutions.

[0027] To solve the above problems, the embodiments of this application provide a control method and related device for achieving zero-voltage-difference closing of the input relay, aiming to invert the electrical energy on the DC bus into three-phase AC voltage with the same amplitude and phase as the grid voltage through a pre-stage voltage conversion circuit, so that the voltage difference across the contacts of the input relay is zero.

[0028] Please refer to Figure 1 , Figure 1 which is a structural block diagram of a control system provided by the embodiments of this application. As Figure 1As shown, the control system 10 includes a post-stage controller 11, a post-stage voltage conversion circuit 12, a pre-stage controller 13, and a pre-stage voltage conversion circuit 14. The post-stage voltage conversion circuit 12 is connected to the pre-stage voltage conversion circuit 14 through a DC bus 15. The pre-stage voltage conversion circuit 14 is connected to the power grid 17 through an input relay 16. The post-stage voltage conversion circuit 12 is connected to a DC power supply terminal 18. The post-stage controller 11 is communicatively connected to the pre-stage controller 13. In an embodiment of the present application, the control system 10 further includes a soft start circuit 19. One end of the soft start circuit 19 is connected to the power grid 17, and the other end is connected to the DC bus 15. It is used to draw power from the power grid 17 and rectify it into direct current to supply power to the DC bus 15 in the standby state, so as to support the power consumption requirements of devices such as the pre-stage controller 13 and the post-stage controller 11 in the standby state. Among them, the post-stage controller 11 and the pre-stage controller 13 can be specifically implemented as a DSP (Digital Signal Processor, digital signal processor). The post-stage voltage conversion circuit 12 can be specifically implemented as a bidirectional DC-DC (direct current-direct current) main power topology such as a dual active bridge DAB (Dual Active Bridge) or a bidirectional full-bridge CLLC (Capacitor-Inductor-Inductor-Capacitor). The pre-stage voltage conversion circuit 14 can be specifically implemented as a bidirectional AC-DC (alternating current-direct current) main power topology such as a three-phase four-leg, a three-phase three-leg, or an active neutral point clamped three-level topology ANPC (ActiveNeutral Point Clamped).

[0029] Further, please refer to Figure 2 , Figure 2 which is a structural block diagram of another control system provided by an embodiment of the present application. As shown in Figure 2As shown in the figure, the input relay 16 includes a first relay S1, a second relay S2, and a third relay S3, which are respectively located in the inputs of each phase of the three-phase to connect the power grid 17 and the front-stage voltage conversion circuit 14. Among them, corresponding capacitors and inductors are also provided at the rear end of each phase input relay 16. For example, a first capacitor C1 and a first inductor L1 are provided at the rear end of the first relay S1, a second capacitor C2 and a second inductor L2 are provided at the rear end of the second relay S2, and a third capacitor C3 and a third inductor L3 are provided at the rear end of the third relay S3. The above-mentioned first capacitor C1, second capacitor C2, and third capacitor C3 are used to store the alternating current inverted by the front-stage voltage conversion circuit 14 to characterize the voltage conditions at the rear end of each phase input relay 16. The DC bus 15 includes a fourth capacitor C4 and a fifth capacitor C5. It can be understood that the power transmission to the DC bus involved in the embodiments of the present application is specifically to charge the fourth capacitor C4 and / or the fifth capacitor C5. The soft start circuit 19 can specifically be composed of a first resistor R1, a second resistor R2, a fourth relay S4, a fifth relay S5, and a rectifier bridge D1~D4. It can be understood that when the system is in the standby state, the first relay S1, the second relay S2, and the third relay S3 are all in the off state, the fourth relay S4 and the fifth relay S5 are normally closed, and the soft start circuit 19 supplies power to the fourth capacitor C4 and / or the fifth capacitor C5 on the DC bus side by taking power from the power grid 17 and rectifying it into direct current to support the power consumption requirements of some devices in the system in the standby state.

[0030] It should be noted that the DC bus voltage that can be theoretically obtained by the current soft start circuit through the rectifier bridge is , where U1 refers to the DC bus voltage and U2 refers to the root mean square voltage, that is, the effective value of the grid phase voltage at the front end of the input relay. For example, assuming that the grid phase voltage U2 at the front end of the input relay is 220V, then the DC bus voltage obtained through the soft start circuit is 622V. However, because there are resistors on the soft start circuit and the DC bus capacitor also needs to supply power to loads such as the front and rear stage controllers through the step-down of the auxiliary source transformer, the actual DC bus voltage cannot reach the theoretical value. In this way, the DC bus voltage obtained by rectifying the grid voltage through the soft start circuit is not sufficient to invert and establish a three-phase AC voltage with the same amplitude as the grid voltage. Therefore, in order to ensure that there is enough energy on the DC bus capacitor to invert the AC voltage, it is necessary to transmit energy to the DC bus capacitor by the rear-stage voltage conversion circuit to reverse the wave, supporting the DC bus voltage to invert the three-phase AC voltage.

[0031] Please refer to Figure 3 , Figure 3 which is a schematic flow chart of a control method for realizing zero-voltage-difference suction of the input relay provided by the embodiments of the present application, and is applied to the rear-stage controller 11 as shown in Figure 1 the figure, such as Figure 3As shown, the method includes:

[0032] S301, determining a target energy transfer strategy according to the working mode of the control system.

[0033] Among them, the working mode includes a rectification mode and a grid connection mode. The rectification mode refers to the working mode of taking power from the power grid and converting it into direct current. The grid connection mode refers to the working mode of taking power from the DC power supply terminal and converting it into alternating current. Specifically, the post-stage controller can continuously monitor the start-up instruction when the control system is in the standby state. When receiving the start-up instruction, it determines the working mode of the control system according to the start-up instruction.

[0034] S302, controlling the post-stage voltage conversion circuit to transfer electric energy to the DC bus according to the target energy transfer strategy.

[0035] S303, sending a drive signal to the pre-stage controller to instruct the pre-stage controller to control the pre-stage voltage conversion circuit to invert the electric energy on the DC bus into a three-phase AC voltage, and controlling the input relay to close when detecting that the phase and amplitude of the three-phase AC voltage are the same as those of the grid voltage.

[0036] Among them, after receiving the drive signal, the pre-stage controller collects the grid voltage at the front end of the input relay through a hardware circuit and performs operations such as phase locking, and then enables the pre-stage voltage conversion circuit to invert a three-phase AC voltage on the X capacitor using the DC bus voltage, and collects the AC instantaneous voltage on the X capacitor through a hardware circuit for loop control and determination of amplitude and phase. When detecting that the grid voltage is the same as the phase and amplitude of the three-phase AC voltage, the pre-stage controller issues a control signal, thereby realizing zero-voltage difference closing of the input relay.

[0037] Among them, after the post-stage controller controls the post-stage voltage conversion circuit to transfer electric energy to the DC bus according to the target energy transfer strategy, it can collect the DC bus voltage in real time through a voltage sampling circuit. After detecting that the DC bus voltage reaches a preset standard value, it sends a drive signal to the pre-stage controller. Among them, the preset standard value is used to represent the state that the electric energy on the DC bus is sufficient to support inversion into a three-phase AC voltage.

[0038] It can be seen that in the embodiment of the present application, the post-stage controller determines the target energy transfer strategy according to the working mode of the control system, controls the post-stage voltage conversion circuit to transfer electric energy to the DC bus according to the target energy transfer strategy, and finally sends a driving signal to the pre-stage controller, so that the pre-stage controller controls the pre-stage voltage conversion circuit to invert the electric energy on the DC bus into a three-phase AC voltage, and controls the input relay to close when it detects that the phase and amplitude of the three-phase AC voltage are the same as those of the grid voltage. In this way, when the input relay is controlled to close, the voltage states at both ends of its contacts are the same, realizing zero-voltage-difference closing of the input relay, avoiding damage and failure of the input relay due to the voltage difference at both ends of the contacts during closing, and improving safety and reliability.

[0039] In a possible example, the working mode of the control system is the grid-connected mode, the DC power supply terminal includes a DC-side capacitor, a pre-charge relay, and a DC battery in an energy-sufficient state. Determining the target energy transfer strategy according to the working mode of the control system includes: determining that the target energy transfer strategy is the first energy transfer strategy, and the first energy transfer strategy is used to represent that the post-stage controller controls the pre-charge relay to close and controls the post-stage voltage conversion circuit to extract part of the energy of the DC battery and transfer it to the DC bus.

[0040] Among them, when the control system operates in the grid-connected mode, its service control process is that the post-stage voltage conversion circuit extracts the energy of the DC battery and inverts it into alternating current through the pre-stage voltage conversion circuit, and is connected to the grid after the input relay closes. Therefore, there must be an energy-sufficient DC battery connected to its DC side. As Figure 4 shown, the DC power supply terminal 18 includes a DC-side capacitor C6, a pre-charge relay S6, and a DC battery 181, and the DC battery 181 is in an energy-sufficient state. Further, the DC power supply terminal 18 further includes a third resistor R3 and a diode D5. As described above, in order to realize zero-voltage-difference closing of the input relay, it is necessary for the post-stage voltage conversion circuit to draw power from the DC power supply terminal 18 and send a reverse wave to charge the DC bus, so as to support the pre-stage voltage conversion circuit to invert and establish a three-phase AC voltage with the same phase and amplitude as the grid voltage on the X capacitor. In this example, since the DC power supply terminal 18 in the grid-connected mode must include a DC battery 181 in an energy-sufficient state, the post-stage controller can directly determine that the target energy transfer strategy is the first energy transfer strategy, that is, control the pre-charge relay S6 to close, and control the post-stage voltage conversion circuit to extract part of the energy of the DC battery 181 and transfer enough electric energy to the DC bus to support the inversion of three-phase alternating current.

[0041] It can be seen that in this example, when the operating mode of the control system is the grid-connected mode, the DC power supply terminal must include a DC battery in an energy-sufficient state. At this time, the post-stage controller can directly determine that the target energy transfer strategy is the first energy transfer strategy, so as to control the pre-charge relay to close and extract part of the energy from the DC battery to charge the DC bus, so as to support the front-stage voltage conversion circuit to invert and establish a three-phase AC voltage, and finally realize the zero-voltage-difference closing of the input relay, improving the safety performance.

[0042] In a possible example, the operating mode of the control system is the rectification mode. Determining the target energy transfer strategy according to the operating mode of the control system includes: obtaining a first sampled voltage, where the first sampled voltage is used to characterize the battery state of the DC power supply terminal, and the battery state includes a first state and a second state. The first state means that the DC power supply terminal includes a DC battery in an energy-sufficient state, and the second state means that the DC power supply terminal does not include a DC battery in an energy-sufficient state; determining the target energy transfer strategy according to the battery state of the DC power supply terminal.

[0043] Among them, when the control system operates in the rectification mode, its service control process is that after the input relay closes, the front-stage voltage conversion circuit takes power from the power grid and rectifies it into direct current to supply power to the DC bus. In the rectification mode, there are two battery states at the DC power supply terminal, namely the above-mentioned first state and second state. Among them, the fact that the DC power supply terminal does not include a DC battery in an energy-sufficient state may specifically refer to that the DC power supply terminal does not include a DC battery, or the DC power supply terminal includes a DC battery with insufficient energy. In this example, after the post-stage controller determines that the operating mode of the control system is the rectification mode, it obtains the first sampled voltage to determine the battery state of the DC power supply terminal. Specifically, when the first sampled voltage is greater than or equal to a first preset voltage, it is determined that the battery state of the DC power supply terminal is the first state; when the first sampled voltage is less than the first preset voltage, it is determined that the battery state of the DC power supply terminal is the second state.

[0044] It can be seen that in this example, when the operating mode of the control system is the rectification mode, the post-stage controller obtains the first sampled voltage to determine the battery state of the DC power supply terminal, and then determines the target energy transfer strategy according to the battery state of the DC power supply terminal, so as to be able to adaptively determine the optimal energy transfer method according to different battery states of the DC power supply terminal, improving the reliability.

[0045] In a possible example, the battery state of the DC power supply terminal is the first state. The DC power supply terminal includes a DC-side capacitor, a pre-charge relay, and a DC battery in an energy-sufficient state. Determining a target energy transfer strategy according to the battery state of the DC power supply terminal includes: obtaining a second sampling voltage, where the second sampling voltage is used to characterize the energy state of the DC-side capacitor; and determining a target energy transfer strategy according to the first sampling voltage and the second sampling voltage.

[0046] Among them, when the battery state of the DC power supply terminal is the first state, its circuit configuration can be equivalent to Figure 4 an example, that is, the DC power supply terminal includes a DC-side capacitor C6, a pre-charge relay S6, and a DC battery 181 in an energy-sufficient state. At this time, in order to avoid damage to the pre-charge relay S6 due to a large voltage difference across the contacts when it is closed, it is necessary to detect and compare the voltages across its contacts to further determine the energy transfer strategy. It can be understood that the first sampling voltage is also used to characterize the voltage at the back end of the pre-charge relay S6, and the second sampling voltage is also used to characterize the voltage at the front end of the pre-charge relay S6. By comparing the first sampling voltage and the second sampling voltage, it is determined whether to close the pre-charge relay S6 during energy transfer, thereby determining the energy transfer strategy.

[0047] It can be seen that in this example, when the working mode of the control system is the rectification mode and the battery state of the DC power supply terminal is the first state, the post-stage controller obtains the second sampling voltage to determine the energy state of the DC-side capacitor, and determines the target energy transfer strategy according to the first sampling voltage and the second sampling voltage, so that the energy transfer method can be determined according to the voltage state across the contacts of the pre-charge relay, improving safety.

[0048] In a possible example, determining the target energy transfer strategy according to the first sampling voltage and the second sampling voltage includes: detecting that the difference between the first sampling voltage and the second sampling voltage is less than a preset value, and determining that the target energy transfer strategy is the first energy transfer strategy.

[0049] Among them, when the difference between the first sampling voltage and the second sampling voltage is less than the preset value, it indicates that the voltage difference across the contacts of the pre-charge relay is not large. Then, the post-stage controller can control the pre-charge relay to close, so as to control the post-stage voltage conversion circuit to draw power from the DC battery and reverse-wave to supply power to the DC bus. The preset value is an empirical value obtained through historical data statistical analysis. That is, in this example, when the working mode of the control system is the rectification mode, the battery state of the DC power supply terminal is the first state, and the difference between the first sampling voltage and the second sampling voltage is less than the preset value, the energy transfer strategy of the post-stage controller is the same as the energy transfer strategy when the working mode of the control system is the grid-connected mode, both of which are the first energy transfer strategy.

[0050] It can be seen that in this example, when the difference between the first sampling voltage and the second sampling voltage is less than the preset value, it can be determined that the pre-charge relay meets the closing condition. The subsequent-stage controller determines that the target energy transfer strategy is the first energy transfer strategy, controls the pre-charge relay to close, and controls the subsequent-stage voltage conversion circuit to extract part of the energy of the DC battery and transfer electric energy to the DC bus, so as to support the inverter of the previous-stage voltage conversion circuit to establish a three-phase AC voltage, and finally realizes the zero-voltage-difference closing of the input relay, improving the safety performance.

[0051] In a possible example, the determining the target energy transfer strategy according to the first sampling voltage and the second sampling voltage includes: detecting that the difference between the first sampling voltage and the second sampling voltage is greater than the preset value, and determining that the target energy transfer strategy is the second energy transfer strategy, where the second energy transfer strategy is used to represent that the subsequent-stage controller controls the subsequent-stage voltage conversion circuit to extract the energy of the DC side capacitor and transfer electric energy to the DC bus.

[0052] Among them, when the difference between the first sampling voltage and the second sampling voltage is greater than the preset value, it indicates that the voltage difference across the contacts of the pre-charge relay is large. If it is closed at this time, it may cause damage to the pre-charge relay. Therefore, the subsequent-stage controller determines that the target energy transfer strategy is the second energy transfer strategy, that is, does not close the pre-charge relay, and directly extracts the energy of the DC side capacitor and transfers electric energy to the DC bus. It can be understood that in this example, the DC battery charges the DC side capacitor C6 through the diode D5 and the third resistor R3, and the subsequent-stage controller controls the subsequent-stage voltage conversion circuit to reverse-wave and extract the energy of the DC side capacitor C6 and transfer electric energy to the DC bus.

[0053] It can be seen that in this example, when the difference between the first sampling voltage and the second sampling voltage is greater than the preset value, it can be determined that the pre-charge relay does not meet the closing condition. The subsequent-stage controller determines that the target energy transfer strategy is the second energy transfer strategy, controls the subsequent-stage voltage conversion circuit to extract the energy of the DC side capacitor and transfer electric energy to the DC bus, so as to support the inverter of the previous-stage voltage conversion circuit to establish a three-phase AC voltage, and finally realizes the zero-voltage-difference closing of the input relay, improving the safety performance.

[0054] In a possible example, the battery state of the DC power supply end is the second state, the DC power supply end includes a DC side capacitor, and the determining the target energy transfer strategy according to the battery state of the DC power supply end includes: determining that the target energy transfer strategy is the third energy transfer strategy, where the third energy transfer strategy is used to represent that the subsequent-stage controller extracts the energy on the DC bus and charges the DC side capacitor, and extracts the energy of the DC side capacitor and transfers electric energy to the DC bus when detecting that the second sampling voltage reaches the target voltage.

[0055] Among them, when the battery state of the DC power supply end is in the second state, the DC power supply end does not include a DC battery in a fully charged state, that is, power cannot be taken from the DC battery to support the DC bus. At this time, the post-stage controller determines that the target energy transfer strategy is the third energy transfer strategy, that is, first controls the post-stage voltage conversion circuit to transfer energy forward, extracts the energy on the DC bus to charge the DC-side capacitor, and when it is detected that the second sampling voltage reaches the target voltage, controls the post-stage voltage conversion circuit to transfer energy backward, extracts the energy of the DC-side capacitor and transmits electrical energy to the DC bus. Among them, the target voltage is used to represent the state where the DC-side capacitor reaches sufficient energy. It can be understood that during the forward energy transfer stage, the energy on the DC bus is the energy rectified by the soft start circuit, and this part of the energy theoretically cannot be inverted into a three-phase AC voltage. Therefore, the post-stage controller first controls the post-stage voltage conversion circuit to transfer energy forward, continuously transmits the energy rectified by the soft start circuit to the DC-side capacitor, and then transfers energy backward to charge the DC bus, so as to support the front-stage voltage conversion circuit to invert and establish a three-phase AC voltage, and finally realize the zero-voltage-difference suction of the input relay.

[0056] It can be seen that in this example, when the battery state of the DC power supply end is in the second state, the post-stage controller determines that the target energy transfer strategy is the third energy transfer strategy, first controls the post-stage voltage conversion circuit to transfer energy forward, extracts the energy on the DC bus to charge the DC-side capacitor, and then transfers energy backward to extract the energy of the DC-side capacitor and transmit electrical energy to the DC bus, so that the energy on the DC bus is sufficient to support the front-stage voltage conversion circuit to invert and establish a three-phase AC voltage, realize the zero-voltage-difference suction of the input relay, and improve safety.

[0057] Consistent with the above-described embodiments, please refer to Figure 5 , Figure 5 is a structural block diagram of a control device for realizing zero-voltage-difference suction of an input relay provided by an embodiment of the present application. The device is applied to the post-stage controller 11 as shown in Figure 1 The control device 50 for realizing zero-voltage-difference suction of the input relay includes: a determination unit 501, configured to determine a target energy transfer strategy according to the working mode of the control system, where the working mode includes a rectification mode and a grid connection mode. The rectification mode refers to a working mode of taking power from the power grid and converting it into direct current, and the grid connection mode refers to a working mode of taking power from the DC power supply end and converting it into alternating current; a control unit 502, configured to control the post-stage voltage conversion circuit to transmit electrical energy to the DC bus according to the target energy transfer strategy; a signal sending unit 503, configured to send a driving signal to the front-stage controller to instruct the front-stage controller to control the front-stage voltage conversion circuit to invert the electrical energy on the DC bus into a three-phase AC voltage, and control the input relay to suck in when it is detected that the phase and amplitude of the three-phase AC voltage are the same as those of the grid voltage.

[0058] In a possible example, the operating mode of the control system is the grid-connected mode. The DC power supply terminal includes a DC-side capacitor, a pre-charge relay, and a DC battery in an energy-sufficient state. In terms of determining the target energy transfer strategy according to the operating mode of the control system, the determining unit 501 is specifically configured to: determine that the target energy transfer strategy is the first energy transfer strategy, and the first energy transfer strategy is used to represent that the post-stage controller controls the pre-charge relay to close and controls the post-stage voltage conversion circuit to extract part of the energy of the DC battery and transfer electric energy to the DC bus.

[0059] In a possible example, the operating mode of the control system is the rectification mode. In terms of determining the target energy transfer strategy according to the operating mode of the control system, the determining unit 501 is specifically configured to: obtain a first sampling voltage, where the first sampling voltage is used to represent the battery state of the DC power supply terminal, and the battery state includes a first state and a second state. The first state means that the DC power supply terminal includes a DC battery in an energy-sufficient state, and the second state means that the DC power supply terminal does not include a DC battery in an energy-sufficient state; determine the target energy transfer strategy according to the battery state of the DC power supply terminal.

[0060] In a possible example, the battery state of the DC power supply terminal is the first state. The DC power supply terminal includes a DC-side capacitor, a pre-charge relay, and a DC battery in an energy-sufficient state. In terms of determining the target energy transfer strategy according to the battery state of the DC power supply terminal, the determining unit 501 is specifically configured to: obtain a second sampling voltage, where the second sampling voltage is used to represent the energy state of the DC-side capacitor; determine the target energy transfer strategy according to the first sampling voltage and the second sampling voltage.

[0061] In a possible example, in terms of determining the target energy transfer strategy according to the first sampling voltage and the second sampling voltage, the determining unit 501 is specifically configured to: when it is detected that the difference between the first sampling voltage and the second sampling voltage is less than a preset value, determine that the target energy transfer strategy is the first energy transfer strategy.

[0062] In a possible example, in terms of determining the target energy transfer strategy according to the first sampling voltage and the second sampling voltage, the determining unit 501 is specifically configured to: when it is detected that the difference between the first sampling voltage and the second sampling voltage is greater than a preset value, determine that the target energy transfer strategy is the second energy transfer strategy, and the second energy transfer strategy is used to represent that the post-stage controller controls the post-stage voltage conversion circuit to extract the energy of the DC-side capacitor and transfer electric energy to the DC bus.

[0063] In a possible example, the battery state of the DC power supply terminal is the second state. The DC power supply terminal includes a DC-side capacitor. In terms of determining the target energy transfer strategy according to the battery state of the DC power supply terminal, the determining unit 501 is specifically configured to: determine that the target energy transfer strategy is the third energy transfer strategy, and the third energy transfer strategy is used to characterize that the post-stage controller extracts the energy on the DC bus to charge the DC-side capacitor, and extracts the energy of the DC-side capacitor to transmit electric energy to the DC bus when it is detected that the second sampling voltage reaches the target voltage.

[0064] It can be understood that since the method embodiment and the device embodiment are different presentation forms of the same technical concept, the content of the method embodiment part in this application should be synchronously adapted to the device embodiment part, and will not be elaborated here.

[0065] In the case of adopting an integrated unit, as Figure 6 shown, Figure 6 FIG. is a structural block diagram of another control device for realizing zero-voltage-difference suction of an input relay provided by an embodiment of the present application. In Figure 6 it, the control device 50 for realizing zero-voltage-difference suction of the input relay includes: a processing module 52 and a communication module 51. The processing module 52 is used to control and manage the actions of the control device for realizing zero-voltage-difference suction of the input relay. For example, it executes the steps of the determining unit 501, the control unit 502, and the signal sending unit 503, and / or is used to execute other processes of the technologies described herein. The communication module 51 is used to support the interaction between the control device for realizing zero-voltage-difference suction of the input relay and other devices. As Figure 6 shown, the control device for realizing zero-voltage-difference suction of the input relay may further include a storage module 53, and the storage module 53 is used to store the program code and data of the control device 50 for realizing zero-voltage-difference suction of the input relay.

[0066] Among them, all relevant contents of each scenario involved in the above method embodiment can be cited in the function description of the corresponding functional module, and will not be elaborated here. The above control device 50 for realizing zero-voltage-difference suction of the input relay can execute the above Figure 2 shown control method for realizing zero-voltage-difference suction of the input relay.

[0067] Please refer to Figure 7 , Figure 7 FIG. is a structural block diagram of a controller provided by an embodiment of the present application. As Figure 7As shown, the controller may include one or more of the following components: a processor 701, and a memory 702 coupled to the processor 701. The memory 702 may store one or more computer programs, and the one or more computer programs may be configured to implement the methods described in the above embodiments when executed by the one or more processors 701. Specifically, the controller may refer to the subsequent-stage controller 11 involved in the above embodiments.

[0068] It can be understood that the DC-DC converter may include more or fewer structural elements than those shown in the above structural block diagram, which will not be limited herein.

[0069] An embodiment of the present application further provides a computer storage medium, on which computer programs / instructions are stored. When the computer programs / instructions are executed by a processor, part or all of the steps of any method described in the above method embodiments are implemented.

[0070] It should be understood that in various embodiments of the present application, the magnitudes of the serial numbers of the above processes do not mean the order of execution. The execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0071] In several embodiments provided in the present application, it should be understood that the disclosed methods and apparatuses may be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for example, the division of the units is only a logical function division, and there may be other division methods in actual implementation; for example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other may be through some interfaces, and the indirect couplings or communication connections of the devices or units may be in electrical, mechanical or other forms.

[0072] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0073] In addition, in each embodiment of the present invention, the functional units may be integrated into one processing unit, or each unit may be physically included separately, or two or more units may be integrated into one unit. The above integrated units may be implemented in the form of hardware, or in the form of a combination of hardware and software functional units.

[0074] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can easily conceive of changes or substitutions without departing from the spirit and scope of the present invention, and can make various modifications and alterations, including combinations of the above different functions and implementation steps, including software and hardware implementation manners, all within the protection scope of the present invention.

Claims

1. A control method for realizing zero-voltage differential pickup of an input relay, characterized in that: A rear-stage controller applied to a control system, the control system comprising the rear-stage controller, a rear-stage voltage conversion circuit, a front-stage controller and a front-stage voltage conversion circuit, the rear-stage voltage conversion circuit being connected to the front-stage voltage conversion circuit via a DC bus, the front-stage voltage conversion circuit being connected to a power grid via an input relay, the rear-stage voltage conversion circuit being connected to a DC power supply terminal, the method comprising: Determine the target energy transmission strategy according to the working mode of the control system, the working mode includes a rectification mode and a grid-connected mode, the rectification mode refers to a working mode of taking power from the grid and converting it into direct current, and the grid-connected mode refers to a working mode of taking power from the DC power supply terminal and converting it into alternating current; Controlling the subsequent voltage conversion circuit to transmit electric energy to the DC bus according to the target energy transfer strategy; Sending a driving signal to the front-stage controller to instruct the front-stage controller to control the front-stage voltage conversion circuit to invert the electric energy on the DC bus into a three-phase AC voltage, and controlling the input relay to be attracted when it is detected that the phase and amplitude of the three-phase AC voltage are the same as the phase and amplitude of the grid voltage; Wherein, when the working mode is the grid-connected mode, the DC power supply end includes a DC side capacitor, a pre-charge relay and a DC battery in a sufficient energy state, and the target energy transmission strategy is determined according to the working mode of the control system, including: determining that the target energy transmission strategy is a first energy transmission strategy, and the first energy transmission strategy is used to characterize that the post-stage controller controls the pre-charge relay to be attracted, and controls the post-stage voltage conversion circuit to extract part of the energy of the DC battery to transmit electric energy to the DC bus; Wherein, when the working mode is the rectification mode, determining the target energy transmission strategy according to the working mode of the control system includes: Acquire a first sampled voltage, where the first sampled voltage is used to characterize a battery state of the DC power supply end, where the battery state includes a first state and a second state, where the first state means that the DC power supply end includes a DC battery in a sufficient energy state, and the second state means that the DC power supply end does not include a DC battery in a sufficient energy state; If the battery state of the DC power supply end is the first state, and the DC power supply end includes a DC side capacitor, a pre-charge relay, and a DC battery in a sufficient energy state, then a second sampling voltage is obtained, and the second sampling voltage is used to characterize the energy state of the DC side capacitor; If the difference between the first sampling voltage and the second sampling voltage is less than a preset value, determining that the target energy transfer strategy is the first energy transfer strategy; If the difference between the first sampling voltage and the second sampling voltage is greater than a preset value, determining that the target energy transfer strategy is the second energy transfer strategy, the second energy transfer strategy is used to indicate that the subsequent controller controls the subsequent voltage conversion circuit to extract energy from the DC link capacitor and transmit electrical energy to the DC bus; If the battery state of the DC power supply end is the second state, the DC power supply end includes a DC side capacitor, and the target energy transmission strategy is determined according to the battery state of the DC power supply end, then the target energy transmission strategy is determined to be a third energy transmission strategy, and the third energy transmission strategy is used to characterize that the post-stage controller extracts energy from the DC bus to charge the DC side capacitor, and extracts energy from the DC side capacitor to transmit electrical energy to the DC bus when it is detected that the second sampling voltage reaches the target voltage.

2. A control device for realizing zero-pressure difference pickup of an input relay, characterized in that: A rear-stage controller used in a control system, the control system comprising the rear-stage controller, a rear-stage voltage conversion circuit, a front-stage controller and a front-stage voltage conversion circuit, the rear-stage voltage conversion circuit being connected to the front-stage voltage conversion circuit via a DC bus, the front-stage voltage conversion circuit being connected to a power grid via an input relay, the rear-stage voltage conversion circuit being connected to a DC power supply terminal, the device comprising: A determination unit, used to determine a target energy transmission strategy according to an operating mode of the control system, wherein the operating mode includes a rectification mode and a grid-connected mode, wherein the rectification mode refers to an operating mode in which power is taken from the grid and converted into direct current, and the grid-connected mode refers to an operating mode in which power is taken from the DC power supply terminal and converted into alternating current; A control unit, configured to control the subsequent voltage conversion circuit to transmit electric energy to the DC bus according to the target energy transmission strategy; a signal sending unit, configured to send a driving signal to the front-stage controller to instruct the front-stage controller to control the front-stage voltage conversion circuit to invert the electric energy on the DC bus into a three-phase AC voltage, and control the input relay to be attracted when it is detected that the phase and amplitude of the three-phase AC voltage are the same as the phase and amplitude of the grid voltage; Wherein, when the working mode is the grid-connected mode, the DC power supply end includes a DC side capacitor, a pre-charge relay and a DC battery in a sufficient energy state, and the target energy transmission strategy is determined according to the working mode of the control system, including: determining that the target energy transmission strategy is a first energy transmission strategy, and the first energy transmission strategy is used to characterize that the post-stage controller controls the pre-charge relay to be attracted, and controls the post-stage voltage conversion circuit to extract part of the energy of the DC battery to transmit electric energy to the DC bus; Wherein, when the working mode is the rectification mode, determining the target energy transmission strategy according to the working mode of the control system includes: Acquire a first sampled voltage, where the first sampled voltage is used to characterize a battery state of the DC power supply end, where the battery state includes a first state and a second state, where the first state means that the DC power supply end includes a DC battery in a sufficient energy state, and the second state means that the DC power supply end does not include a DC battery in a sufficient energy state; If the battery state of the DC power supply end is the first state, and the DC power supply end includes a DC side capacitor, a pre-charge relay, and a DC battery in a sufficient energy state, then a second sampling voltage is obtained, and the second sampling voltage is used to characterize the energy state of the DC side capacitor; If the difference between the first sampling voltage and the second sampling voltage is less than a preset value, determining that the target energy transfer strategy is the first energy transfer strategy; If the difference between the first sampling voltage and the second sampling voltage is greater than a preset value, determining that the target energy transfer strategy is the second energy transfer strategy, the second energy transfer strategy is used to indicate that the subsequent controller controls the subsequent voltage conversion circuit to extract energy from the DC link capacitor and transmit electrical energy to the DC bus; If the battery state of the DC power supply end is the second state, the DC power supply end includes a DC side capacitor, and the target energy transmission strategy is determined according to the battery state of the DC power supply end, then the target energy transmission strategy is determined to be a third energy transmission strategy, and the third energy transmission strategy is used to characterize that the post-stage controller extracts energy from the DC bus to charge the DC side capacitor, and extracts energy from the DC side capacitor to transmit electrical energy to the DC bus when it is detected that the second sampling voltage reaches the target voltage.

3. A controller, characterized in that: The method comprises a processor, a memory and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the processor, and the programs include instructions for executing the steps in the method according to claim 1.

4. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: The computer program / instructions implement the steps of the method of claim 1 when executed by a processor.

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