Energy storage PCS AC relay power supply switching circuit, control circuit and method

Abstract

The invention discloses an energy storage PCS alternating current relay power supply switching circuit, a control circuit and a method, and belongs to the technical field of energy storage converters. Wherein the power supply switching circuit is used for reducing the maintaining voltage while maintaining reliable closing of the relay, and on / off of the first field effect transistor Q2 and the second field effect transistor Q3 is based on the state of the switching tube Q1; the first field effect transistor Q2 controls the state of the Zener diode ZD1 through state switching and is used for controlling the potential of one end of the coil when the alternating current relay is in the pull-in and holding state. And the main control module is used for outputting an alternating-current relay control signal and controlling the power supply switching circuit. According to the power supply switching circuit, reliable closing of the alternating-current relay is ensured, and meanwhile, the maintaining voltage of the coil is reduced, so that the power supply loss of the alternating-current relay is reduced; and meanwhile, load impact current and impact voltage during actuation of the alternating-current relay are reduced through a control method, so that adhesion of the alternating-current relay and interference on voltage of a power supply are avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage converters, and in particular relates to an energy storage PCS AC relay power supply switching circuit and a control method. Background Art

[0002] As a key device connecting the energy storage battery system and the power grid, the power storage converter (PCS) plays a vital role in the modern power system. It can not only realize the efficient conversion and storage of electric energy, but also improve the stability and reliability of the power grid. The PCS usually uses AC relays as switching elements to control the charging and discharging process of the battery and perform AC-DC conversion.

[0003] However, when the switch is in operation, the relay will generate very high voltage and current spikes at the moment of power on and off. These spikes will form transient arcs between the contacts, causing contact erosion and adhesion, affecting the reliability and service life of the relay. At the same time, in the case of interference such as overvoltage during relay operation, it is easy to cause instability of the system power supply, resulting in malfunction of sensitive devices in the system.

[0004] In order to solve these problems, the existing technology usually adopts the soft start method of "pre-charging resistor + pre-charging relay" to limit the current spike that occurs at the moment of attraction to reduce the heat generated by the contacts. This soft start method controls the switch signal to achieve safe and smooth power startup, which improves the service life of the power supply to a certain extent. The main function of the pre-charging relay is to protect the power supply capacitor and internal components to prevent damage to the components when the capacitor voltage rises.

[0005] However, the above prior art has the following problems: Due to the introduction of the pre-charging circuit, additional components are required, such as pre-charging resistors and relays for controlling pre-charging. These components require additional PCB space, making the product layout more complicated and increasing the cost. After the relay is energized, its coil needs to maintain a certain voltage to keep the contacts closed, but this will cause continuous power consumption. Especially in large-capacity relays, this coil maintains a large power consumption, causing the relay to heat up significantly, thereby increasing the thermal management burden of the converter system. Summary of the invention

[0006] In order to solve the problems existing in the above-mentioned background technology, the present application provides a power supply switching circuit and control method of an energy storage PCS AC relay. The method uses a power supply switching circuit to reduce the holding voltage of the coil while ensuring the reliable closure of the AC relay, thereby reducing the power supply loss of the AC relay; at the same time, the control method is used to reduce the load impact current and impact voltage when the AC relay is energized, thereby avoiding adhesion of the AC relay and interference with the power supply voltage.

[0007] The technical solution is as follows:

[0008] On the one hand, a power switching circuit of an energy storage PCS AC relay is provided, comprising a main control module, and a power switching circuit corresponding to the AC relay, wherein the power switching circuit is connected to the main control module;

[0009] The power switching circuit is used to control the coil voltage in the closed and held state of the AC relay to reduce power supply loss, and includes: a first capacitor C1, a fourth resistor R4, a first voltage regulator ZD1, a fifth resistor R5 and a first field effect transistor Q2.

[0010] The first capacitor C1 and the fourth resistor R4 are connected in series.

[0011] The gate of the first field effect transistor Q2 is connected to the resistor R3 and the first capacitor C1 in sequence;

[0012] The source of the first field effect transistor Q2 is connected to the drain of the second field effect transistor Q3, and the on / off of the first field effect transistor Q2 and the second field effect transistor Q3 is based on the state of the switch tube Q1;

[0013] The drain of the first field effect transistor Q2 is connected to one end of the coil of the AC relay, and the source and drain of the first field effect transistor Q2 are connected to a fifth resistor R5 and a voltage-stabilizing diode ZD1. The first field effect transistor Q2 controls the state of the voltage-stabilizing diode ZD1 by switching the state, so as to control the potential of one end of the coil of the AC relay in the pull-in and hold states;

[0014] The main control module is used to output an AC relay control signal 500 to control the power switching circuit.

[0015] A further technical solution is that the switch tube Q1 is turned on or off based on the AC relay control signal 500 output by the main control module. The switch tube Q1 is a triode, and the collector of the switch tube is connected to the other end of the first capacitor C1 and to the gate of the second field effect tube Q3 through the sixth resistor R6. The base of the switch tube Q1 is connected in series with the first resistor R1 and inputs the AC relay control signal 500. The emitter of the switch tube Q1 is connected to the power supply voltage, and a second resistor R2 is connected between the emitter and the base.

[0016] As a further technical solution, the first capacitor C1 is further connected to a fourth resistor R4, the other end of the fourth resistor R4 is connected to the source of the first field effect transistor Q2, and a second voltage regulator ZD2 is connected between the gate and source of the first field effect transistor Q2.

[0017] According to a further technical solution, the source of the second field effect transistor Q3 is grounded, and a seventh resistor R7 and a third voltage regulator tube ZD3 are connected between the gate and the source of the second field effect transistor Q3.

[0018] On the other hand, an energy storage PCS control circuit is provided, including the above-mentioned energy storage PCS AC relay power switching circuit, which also includes an inverter module, a bus capacitance load BUS_C on the DC side of the inverter module, and an LC load on the AC side of the inverter module. The inverter module converts the DC side battery voltage into an AC voltage, and outputs a three-phase AC voltage with the same frequency, phase and amplitude as the power grid. AC relays are respectively configured on the three-phase AC bus, and the energy storage PCS AC relay power switching circuit corresponds one-to-one to the AC relays.

[0019] According to a further technical solution, the main control module samples the grid voltage, the AC side voltage of the inverter module, the battery voltage and the DC bus voltage through a voltage sampling circuit.

[0020] According to a further technical solution, the main control module is an MCU of an energy management system or a converter.

[0021] On the other hand, a control method of an energy storage PCS control circuit is provided, which is applied to the control circuit of the energy storage PCS, comprising:

[0022] Step S1: The main control module samples the grid voltage value and calculates the AC voltage, frequency and phase required by the AC output terminal of the inverter module according to the voltage phase lock;

[0023] Step S2: the inverter module outputs a three-phase AC voltage with the same frequency and amplitude as the power grid;

[0024] Step S3: When the difference between the voltage at point A and the grid voltage is detected to be less than 5V, the main control module performs inverter module blocking and outputs a relay closing control signal.

[0025] In a further technical solution, step S3 comprises:

[0026] Step S301: At the moment when the AC relay coil is closed, the main control module outputs a closing signal, the transistor Q1 is turned on, and the second effect transistor Q3 is turned on, and a closed loop I is formed at this time;

[0027] When the second field effect transistor Q3 is turned on, the power supply voltage charges the first capacitor C1 to drive the first field effect transistor Q2;

[0028] When the voltage at the input terminal of the first field effect tube Q2 is greater than the conduction voltage, the first field effect tube Q2 is turned on. At this time, the AC relay coil and the second field effect tube Q3 are turned on, the voltage regulator diode ZD1 and the fifth resistor R5 are short-circuited, and the AC relay coil driving voltage is 12V;

[0029] Step S302: After the AC relay coil is closed, the first capacitor C1 is used to isolate the power supply voltage, and the fourth resistor R4 is discharged. When the GS voltage of the second field effect transistor Q2 is lower than the conduction threshold, the second field effect transistor Q2 is turned off, and the voltage across the relay coil is reduced to 12-V. ZD1 , V ZD1 is the voltage difference across the Zener diode ZD1.

[0030] A further technical solution is that before step S1, the main control module detects whether the voltage and frequency on the AC side meet the grid-connected conditions and issues instructions. When the grid-connected conditions are met, the DC side pre-charges and soft-starts to connect to the battery system.

[0031] The technical solution includes at least the following technical effects:

[0032] 1. Through a power switching circuit, the holding voltage of the AC side relay can be reduced, reducing the DC loss of the relay coil, thereby reducing energy consumption and heat generation. The circuit is simple and easy to implement, without adding multiple power supplies, simplifying system design and reducing costs.

[0033] 2. By utilizing the power switch components of the energy storage converter PCS itself and changing the closing and disconnecting control logic of the relay, the impact overvoltage and overcurrent problems when the relay is energized can be reduced without adding any components, thus avoiding the adhesion of the relay.

[0034] It is to be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0036] Figure 1 A functional schematic diagram of an energy storage PCS control circuit provided by the preferred embodiment is shown;

[0037] Figure 2 The topology diagram of the energy storage PCS AC relay power switching circuit is shown. Figure 1 Schematic diagram of the power switching circuit corresponding to any AC Relay in the three-phase line;

[0038] Figure 3 Shows Figure 2 Schematic diagram of the component circuit operation at the moment when the AC relay coil is energized;

[0039] Figure 4 Shown based on Figure 1 Logic diagram of the topological control method;

[0040] Figure 5 The figure shows a voltage waveform diagram when the AC relay is closed when the control circuit and method of the present embodiment are not used. The dropped AC voltage shown in the figure is any one phase of the three-phase voltage;

[0041] Figure 6 The voltage waveform diagram when the AC relay is closed after adopting the control method of this embodiment is shown, and the three colors of linearity in the figure represent the waveform of the three-phase AC power;

[0042] Description of reference numerals:

[0043] 100, battery voltage sampling; 200, bus voltage sampling; 300, inverter module voltage sampling;

[0044] 400, grid voltage sampling; 500, relay control signal;

[0045] 1. Loop I; 2. Loop II; 3. Loop III; 4. Loop IV;

[0046] C1, first capacitor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor;

[0047] R7, the seventh resistor; Q1, the transistor; Q2, the first field effect transistor; Q3, the second field effect transistor; R3, the third resistor;

[0048] ZD1, the first voltage regulator; ZD2, the second voltage regulator; ZD3, the third voltage regulator; Relay, AC relay. DETAILED DESCRIPTION

[0049] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0050] This embodiment proposes a power switching circuit for an energy storage PCS AC relay, which effectively reduces the holding voltage of the relay coil, thereby reducing the DC loss of the coil; at the same time, a control method is used to reduce the load impact current and impact voltage when the AC relay is energized, thereby avoiding the AC relay from sticking and interfering with the power supply voltage.

[0051] Figure 2 , Figure 3The energy storage PCS AC relay power switching circuit shown is adapted to the AC relay one by one, and is used to control the coil voltage of the AC relay at the moment of closure and in the holding state. The power switching circuit is connected to the main control module;

[0052] The power switching circuit is used to keep the relay reliably closed while reducing the maintenance voltage to reduce power supply loss. It includes: a first capacitor C1, a fourth resistor R4, a first voltage regulator ZD1, a fifth resistor R5 and a second field effect transistor Q2. In the power switching circuit, the second field effect transistor Q2 is used as a switch tube, and its on and off states control the circuit in which the relay coil is located and the voltage difference across the coil.

[0053] like Figure 2 The gate of the first field effect tube Q2 is connected in series with a resistor R3, the other end of the resistor R3 is connected to one end of the first capacitor C1 and one end of the fourth resistor R4, and the other end of the capacitor C1 is connected to the switch tube Q1;

[0054] The source of the first field effect transistor Q2 is also connected to the other end of the fourth resistor R4 and the drain of the second field effect transistor Q3. The on / off of the first field effect transistor Q2 and the second field effect transistor Q3 is based on the state of the switch tube Q1.

[0055] When the switch tube Q1 is turned on, the second field effect tube Q3 is turned on to form the I loop 1. At this time, the II loop 2 forms a closed loop at the moment when the second field effect tube Q3 is turned on, and the power supply voltage charges the first capacitor C1; and as the gate voltage of the first field effect tube Q2 continues to increase, when Vgs meets the turn-on threshold, the first field effect tube Q2 is turned on;

[0056] The drain of the first field effect transistor Q2 is connected to one end of the coil of the AC relay, and the other end of the coil is connected to the driving voltage source. When the first field effect transistor Q2 and the second field effect transistor Q3 are turned on and the relay is energized, the current flows through the relay coil, the first field effect transistor Q2, and the second field effect transistor Q3 in sequence to form a III loop 3.

[0057] A second voltage regulator ZD2 is connected between the source and gate of the first field effect transistor Q2, and a fifth resistor R5 and a voltage regulator diode ZD1 are connected between the source and drain. The first field effect transistor Q2 controls the state of the voltage regulator diode ZD1 by switching the state. When the first field effect transistor Q2 is turned on, the fifth resistor R5 and the voltage regulator diode ZD1 are short-circuited; when the first field effect transistor Q2 is turned off, the current flows through the relay coil, the first and fifth resistors R5, and the second field effect transistor Q3 in sequence to form a IV loop 4.

[0058] The switching of the power switching circuit is based on the AC relay control signal 500 output by the main control module, specifically: the switch tube Q1 uses a triode, the collector of the switch tube is connected to the other end of the first capacitor C1, and is connected to the gate of the second field effect tube Q3 through the sixth resistor R6, the base of the switch tube Q1 is connected in series with the first resistor R1 and inputs the AC relay control signal 500, the emitter of the switch tube Q1 is connected to the 12v power supply voltage, and a second resistor R2 is connected between the emitter and the base. When the main control module outputs the AC relay closing signal, the switch tube Q1 is based on the The signal is turned on, the second field effect transistor Q3 is turned on, and the first field effect transistor Q2 is turned on when the conduction condition is met, and the current flows through the relay coil, the first field effect transistor Q2, and the second field effect transistor Q3 in sequence; due to the discharge of the resistor R4, when the Vgs of the first field effect transistor Q2 is less than the conduction threshold, the first field effect transistor Q2 is turned off, so that the current flows through the relay coil, the first and fifth resistors R5, and the second field effect transistor Q3 in sequence. The switching circuit realizes the switching of the loop in which the relay coil is located. As the circuit is switched, the voltage difference of the AC relay at both ends of the coil changes accordingly.

[0059] Preferably, a seventh resistor R7 and a third voltage regulator tube ZD3 are connected between the gate and source of the second field effect tube Q3, and the source of the second field effect tube Q3 is grounded.

[0060] Preferably, the relay driving voltage source adopts a 12V DC voltage, the voltage source is connected to the positive electrode of the charging capacitor EC1, and the negative electrode of the charging capacitor EC1 is grounded.

[0061] Preferably, two ends of the relay coil are connected with a diode D1, and the diode D1 is used to prevent the reverse voltage from burning out components when the relay is disconnected.

[0062] Preferably, the first voltage regulator tube ZD1, the second voltage regulator tube ZD2, and the third voltage regulator tube ZD3 are voltage regulator diodes; the switch tube Q1 is a PNP transistor, and the first field effect tube Q2 and the second field effect tube Q3 are N-MOS tubes, that is, depletion-type N-channel MOSFET tubes.

[0063] like Figure 2 As shown, the power switching circuit provided in this embodiment adds a loop consisting of a first capacitor C1, a fourth resistor R4, a first voltage regulator ZD1, a fifth resistor R5 and a first field effect transistor Q2 on the basis of a commonly used circuit. The circuit can simply control the relay to have a voltage of +12V at the moment of closure. After closing, in the holding state, as the first field effect transistor Q2 is turned off, the reverse-connected voltage regulator diode ZD1 can maintain the rated stable voltage output, thereby adjusting the holding voltage value of the relay coil to be reduced to 12-V, and the voltage across the coil is reduced by 12-V. ZD1 Volts, thereby effectively reducing the power consumption of the coil, V ZD1 Indicates the voltage value of the first voltage regulator tube ZD1.

[0064] like Figure 1 The functional principle diagram of an energy storage PCS control circuit provided by the preferred embodiment shown in FIG. Figure 2 Shows Figure 1 The power switching circuit schematic diagram corresponding to any AC Relay in the three-phase line. Figure 2 There are three circuit arrangements in Figure 1 The three AC Relays on the three-phase line correspond to each other.

[0065] Figure 1 In the system, the main control module is the energy management system or the converter microcontroller.

[0066] like Figure 1 The energy storage PCS control circuit shown includes Figure 2 The energy storage PCS AC relay power switching circuit shown also includes an inverter module, a bus capacitance load BUS_C on the DC side of the inverter module, and an LC load on the AC side of the inverter module. The energy storage battery is located on the DC side of the inverter module, and outputs DC power to the inverter module through the DC bus. The bus capacitance load BUS_C is connected between the positive and negative poles of the DC bus. The AC side of the inverter module is a three-phase AC line, and the three-phase AC line is respectively connected with an LC load and an AC Relay. When the AC Relay is closed, the inverter module converts the DC side battery voltage into an AC voltage and outputs a three-phase AC voltage with the same frequency, phase and amplitude as the power grid.

[0067] The main control module samples the grid voltage 400 , the inverter module voltage 300 , the battery voltage 100 and the bus voltage 200 respectively through the voltage sampling circuit, and outputs an AC relay control signal 500 .

[0068] like Figure 1-Figure 4 As shown, the control method of the energy storage PCS control circuit includes the following steps:

[0069] Step S1: The main control module samples the voltage and frequency values ​​of the power grid, and calculates the AC voltage, frequency and phase required by the AC output terminal of the inverter module according to the voltage phase lock;

[0070] In this embodiment, before closing the AC Relay, the DC voltage connected to the battery system is soft-started: the main control module first detects whether the voltage frequency on the AC side of the inverter module meets the grid-connected conditions. If the grid-connected conditions are met, the DC side is pre-charged and soft-started to connect to the battery system. The main control module calculates the PWM to be output based on the sampled grid voltage phase-locked.

[0071] Step S2: The inverter module inverts and outputs a three-phase AC voltage with the same frequency and amplitude as the power grid, and the inverter module outputs the voltage to charge and store energy for the LC load.

[0072] Step S3: When the difference between the voltage at point A between the LC loads and the grid voltage is less than 5V, the main control module performs inverter module blocking, and the main control module outputs an output AC relay closing control signal. If the difference between the voltage at point A and the grid voltage is greater than or equal to 5V, it returns to step S2.

[0073] At this time, the bus capacitance load BUS_C and LC load already have energy due to the connection of the DC side battery and the inverter output charging. Therefore, when the AC relay is closed, it is equivalent to zero load connection, and the impact voltage and current values ​​generated are much smaller than the impact values ​​when the relay is directly energized.

[0074] Step S301: AC Relay coil closing moment: Figure 1 The schematic diagram of component circuit operation when the relay coil is energized is shown. The main control module sends an AC relay closing signal, the transistor Q1 is turned on, and the second field effect transistor Q3 in the I loop 1 is turned on. At this time, the II loop 2 forms a closed loop at the moment when the second field effect transistor Q3 is turned on, and the 12V power supply voltage charges the first capacitor C1; when the gate-source voltage difference Vgs of the first field effect transistor Q2 is greater than the turn-on threshold, the first field effect transistor Q2 is turned on, and the first voltage regulator tube ZD1 and the fifth resistor R5 are short-circuited, and the relay coil, the first field effect transistor Q2, and the second field effect transistor Q3 are turned on to form the III loop 3. At this time, the relay coil driving voltage is +12V, which can meet the relay closing voltage requirement.

[0075] Step S302: The AC Relay coil is closed and maintained: When the II loop 2 enters a steady state, the first capacitor C1 acts to isolate 12V, and the fourth resistor R4 discharges. When the gate-source voltage difference Vgs of the first field effect transistor Q2 is lower than the conduction threshold, the first field effect transistor Q2 is turned off. At this time, 12V, the relay coil Relay1, the first voltage regulator ZD1, the fifth resistor R5 and the second field effect transistor Q3 constitute the IV loop 4. Due to the action of the first voltage regulator ZD1, the voltage across the relay coil is reduced to 12-V. ZD1 , and higher than the coil maintenance voltage. By selecting Zener diodes with different voltage values ​​and resistors with different resistance values, the relay coil voltage can be made 12V at the moment of energization, and the voltage during maintenance can be reduced to <9V, V ZD1 is the voltage difference across the Zener diode ZD1.

[0076] In this embodiment, the second field effect transistor Q3 and the first field effect transistor Q2 are depletion-type N-channel MOSFETs, the transistor Q1 is a PNP transistor, and ZD1 and ZD2 are voltage-stabilizing diodes.

[0077] Figure 5The voltage waveform diagram when the relay is closed is shown when the control method of this embodiment is not adopted. It can be seen that the AC voltage drops significantly at the moment of closing.

[0078] Figure 6 The voltage waveform diagram when the relay is closed after adopting the control method of this embodiment is shown. Figure 6 From the instantaneous three-line voltage at closing, it can be concluded that the voltage does not drop at the instant of closing and the current increases slowly.

[0079] The present invention provides a power supply switching circuit, control circuit and control method for an energy storage PCS AC relay. Through a power supply switching circuit, the holding voltage of the AC side relay can be reduced. The circuit can reduce the holding voltage of the coil after the relay is energized, thereby reducing the power supply loss of the relay coil. The circuit is simple and easy to implement, and does not require the addition of multiple power supplies. By using the power switch components of the energy storage converter PCS itself, by changing the closing and disconnecting control logic of the relay, and by managing the closing and disconnecting of the relay through innovative control logic, the impact overvoltage and overcurrent problems when the relay is energized can be reduced without adding components, and the relay can be prevented from sticking.

[0080] The terms such as "first", "second", "third", etc. cited in this specification are only for the convenience of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships should be regarded as within the scope of the invention without substantially changing the technical content.

[0081] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention invented herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not invented by the present invention. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present invention are indicated by the appended claims.

[0082] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. An energy storage PCS AC relay power switching circuit, characterized in that: It includes a main control module and a power switching circuit corresponding to the AC relay, wherein the power switching circuit is connected to the main control module; The power switching circuit includes: a first capacitor C1, a first voltage regulator ZD1, a fifth resistor R5 and a first field effect transistor Q2; The gate of the first field effect transistor Q2 is connected to the resistor R3 and the first capacitor C1 in sequence; The source of the first field effect transistor Q2 is connected to the drain of the second field effect transistor Q3, and the on / off of the first field effect transistor Q2 and the second field effect transistor Q3 is based on the state of the switch tube Q1; The drain of the first field effect transistor Q2 is connected to one end of the coil of the AC relay, and the source and drain of the first field effect transistor Q2 are connected to a fifth resistor R5 and a voltage-stabilizing diode ZD1. The first field effect transistor Q2 controls the state of the voltage-stabilizing diode ZD1 by switching the state, so as to control the potential of one end of the coil of the AC relay in the pull-in and hold states; The main control module is used to output an AC relay control signal (500) to control the power switching circuit.

2. The energy storage PCS AC relay power switching circuit according to claim 1, characterized in that: The switch tube Q1 is turned on or off based on the AC relay control signal (500) output by the main control module. The switch tube Q1 is a triode. The collector of the switch tube is connected to the other end of the first capacitor C1 and to the gate of the second field effect tube Q3 via a sixth resistor R6. The base of the switch tube Q1 is connected in series with the first resistor R1 and inputs the AC relay control signal (500). The emitter of the switch tube Q1 is connected to the power supply voltage, and a second resistor R2 is connected between the emitter and the base.

3. The energy storage PCS AC relay power switching circuit according to claim 1, characterized in that: The first capacitor C1 is also connected to the fourth resistor R4. The other end of the fourth resistor R4 is connected to the source of the first field effect transistor Q2. A second voltage regulator ZD2 is connected between the gate and source of the first field effect transistor Q2.

4. The energy storage PCS AC relay power switching circuit according to claim 2, characterized in that: The source of the second field effect transistor Q3 is grounded, and the seventh resistor R7 and the third voltage regulator tube ZD3 are connected between the gate and the source of the second field effect transistor Q3.

5. An energy storage PCS control circuit, characterized in that: The energy storage PCS AC relay power switching circuit comprises the energy storage PCS AC relay power switching circuit as described in any one of claims 1 to 4, and further comprises an inverter module, a bus capacitance load BUS_C on the DC side of the inverter module, and an LC load on the AC side of the inverter module. The inverter module converts the DC side battery voltage into an AC voltage, and outputs a three-phase AC voltage with the same frequency, phase and amplitude as the power grid. AC relays are respectively arranged on the three-phase AC busbars, and the energy storage PCS AC relay power switching circuit corresponds one-to-one to the AC relays.

6. The energy storage PCS control circuit according to claim 5, characterized in that: The main control module samples the grid voltage, the AC side voltage of the inverter module, the battery voltage and the DC bus voltage through the voltage sampling circuit.

7. The energy storage PCS control circuit according to claim 5, characterized in that: The main control module is the MCU of the energy management system or converter.

8. A control method for an energy storage PCS control circuit, applied to the control circuit of the energy storage PCS according to any one of claims 5 to 7, characterized in that: include: Step S1: The main control module samples the grid voltage value and calculates the AC voltage, frequency and phase required by the AC output terminal of the inverter module according to the voltage phase lock; Step S2: the inverter module outputs a three-phase AC voltage with the same frequency and amplitude as the power grid; Step S3: When the difference between the voltage at point A and the grid voltage is detected to be less than 5V, the main control module performs inverter module blocking and outputs an AC relay closing control signal.

9. The control method according to claim 8, characterized in that: Step S3 comprises, Step S301: At the moment when the AC relay coil is closed, the main control module outputs a closing signal, the transistor Q1 is turned on, and the second effect transistor Q3 is turned on, and a closed loop I is formed at this time; When the second field effect transistor Q3 is turned on, the power supply voltage charges the first capacitor C1 to drive the first field effect transistor Q2; When the voltage at the input terminal of the first field effect tube Q2 is greater than the conduction voltage, the first field effect tube Q2 is turned on. At this time, the AC relay coil and the second field effect tube Q3 are turned on, the voltage regulator diode ZD1 and the fifth resistor R5 are short-circuited, and the AC relay coil driving voltage is 12V; Step S302: After the AC relay coil is closed, the first capacitor C1 is used to isolate the power supply voltage, and the fourth resistor R4 is discharged. When the GS voltage of the second field effect transistor Q2 is lower than the conduction threshold, the second field effect transistor Q2 is turned off, and the voltage across the relay coil is reduced to 12-V. ZD1 , V ZD1 is the voltage difference across the Zener diode ZD1.

10. The control method according to claim 8, characterized in that: Before step S1, the main control module detects whether the voltage and frequency on the AC side meet the grid connection conditions and issues instructions. When the grid connection conditions are met, the DC side pre-charge soft start is connected to the battery system.

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