Grid-connected control circuit for bidirectional energy storage inverter

Abstract

The utility model relates to a grid-connected control circuit for a bidirectional energy storage inverter. The grid-connected control circuit comprises a grid-connected loop, a sampling circuit and a protection loop, the grid-connected loop is connected with the power grid side input loop and the user side output loop at the same time, and on-off control of the power grid side and the user side is carried out through a relay. The sampling loop comprises a step-down transmitting circuit, a step-up transmitting circuit, a voltage division filter circuit and a linear amplification circuit, the step-down transmitting circuit converts an input voltage signal of a power grid side into a voltage transmitting signal, and the step-up transmitting circuit generates a voltage step-up signal; the two signals are simultaneously sent to the voltage division filter circuit, are amplified by the linear amplification circuit, and then are sent to the protection loop; the two electrical parameter acquisition alarm chips of the protection loop carry out voltage division sampling and output alarm signals to the four input AND gates, and the four input AND gates output signals to the relay to control the on-off of the relay. According to the grid-connected control circuit, grid-connected control is simplified, the system operation efficiency and stability are improved, and the energy conversion loss is reduced.

Description

Technical Field

[0001] The utility model relates to the field of bidirectional energy storage inverters, and in particular to a user-unaware grid-connected control circuit for bidirectional energy storage inverters. Background Art

[0002] As a core component of energy storage systems, bidirectional energy storage inverters are capable of bidirectionally converting DC and AC power between energy storage devices (such as batteries) and the grid or loads. In charging mode, the bidirectional energy storage inverter rectifies the grid's AC power into DC power for storage in the battery. In discharging mode, the bidirectional energy storage inverter converts the DC power in the battery into AC power to supply the load or feed it back to the grid.

[0003] In the existing technology, bidirectional energy storage inverters usually use fully controlled inverters for grid-connected control. Their working principle is to achieve bidirectional conversion of DC and AC by controlling power electronic devices, and to manage the power flow between the grid and the energy storage equipment through complex control algorithms. Although bidirectional energy storage inverters can achieve bidirectional power conversion between the energy storage system and the grid, they still have the following disadvantages in practical applications: 1. Large conversion losses: In existing solutions, the inverter must continue to work during grid-connected operation, resulting in frequent conversion of energy between DC and AC, which increases the overall loss of the system. 2. High switching complexity: The switching process between grid-connected and off-grid modes relies on the complex control logic of the main control system, which increases the response time and control difficulty of the system, and may lead to untimely switching under special circumstances. 3. Insufficient reliability: Existing protection mechanisms mostly rely on software control, and there is a risk of hardware damage due to control failure or delay, making it difficult to ensure the stability and safety of the system.

[0004] Patent CN114362578A discloses a grid-connected inverter control method, controller, and grid-connected inverter. The method first determines the inverter state based on grid-side electrical signal parameters. When the inverter is unstable, the method then determines the feedforward coefficient of the voltage feedforward controller and the control parameters of the repetitive controller in the grid-connected current controller based on the electrical signal parameters. Finally, the voltage feedforward controller is adjusted based on the feedforward coefficient, and the repetitive controller is adjusted based on the control parameters. Therefore, the grid-connected inverter control method performs related control on the voltage feedforward controller and the repetitive controller, stabilizing the inverter and improving the inverter's stability. Furthermore, compared to real-time detection methods, the present invention adjusts the parameters of the related controllers only when the inverter is unstable, reducing harmonic disturbances applied to the grid-connected current side and thereby ensuring good grid-connected current quality. Patent CN106130387A discloses a grid-connected control method for an inverter with an LCL filter. This method is based on a voltage outer loop, a power loop, and a current dual loop in an αβ coordinate system. The method is implemented by a voltage transformer, a current transformer, and a controller equipped with the inverter. The controller includes a PI controller, a quasi-PR controller, and a P controller. The method includes the following steps: ① collecting voltage and current signals; ② constructing a voltage outer loop and stabilizing the inverter DC side voltage using a PI controller; ③ constructing a power loop and controlling the inverter's grid-connected power factor by controlling the reactive power of the input grid; and ④ constructing a current dual loop consisting of a grid-side current outer loop and a capacitor current inner loop to control the grid-side current output to increase system stability. The present invention does not require complex coordinate rotation transformations or cumbersome feedforward decoupling control. The control method is simple, can achieve unity power factor operation, and has good stability. The above patents all disclose technologies related to inverter grid-connected control. However, these grid-connected control technologies easily lead to frequent switching of the inverter during operation, resulting in large conversion losses. In addition, the switching process relies on the complex control logic and software control of the main control system, which is highly complex and affects the efficiency and stability of system operation. Utility Model Content

[0005] The utility model aims to provide a grid-connected control circuit for a bidirectional energy storage inverter, which simplifies grid-connected control, improves system operation efficiency and stability, and reduces energy conversion losses.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a grid-connected control circuit for a bidirectional energy storage inverter, comprising a grid-connected circuit, a sampling circuit, and a protection circuit; the grid-connected circuit is connected to both the grid-side input circuit and the user-side output circuit, and the on / off control of the grid-side input circuit and the user-side output circuit is performed by a relay; the sampling circuit comprises a step-down transmission circuit, a step-up transmission circuit, a voltage divider filter circuit, and a linear amplifier circuit; the step-down transmission circuit is connected to the grid-side input circuit and converts the input voltage signal of the grid-side input circuit into a voltage transmission signal; the step-up transmission circuit generates a voltage increase signal; the voltage transmission signal and the voltage increase signal are simultaneously fed into the voltage divider filter circuit to generate an AC voltage signal, which is then fed into the linear amplifier circuit for signal amplification to generate a sampled voltage signal and fed into the protection circuit; the protection circuit comprises two electrical parameter acquisition and alarm chips and a four-input AND gate; the two electrical parameter acquisition and alarm chips respectively perform voltage sampling and output alarm signals to the four-input AND gate; the four-input AND gate outputs a signal to the relay to control its switching.

[0007] Furthermore, the grid-connected circuit includes a relay RY1, a diode D1, a resistor R1 and a capacitor C1. The diode D1 performs circuit breaking and continuous current flow, and the capacitor C1 performs signal filtering. The output end of the four-input AND gate is simultaneously connected to one end of the capacitor C1 and one end of the resistor R1, and the other end of the capacitor C1 is grounded. The other end of the resistor R1 is simultaneously connected to the cathode of the diode D1 and one end of the coil of the relay RY1, and the anode of the diode D1 and the other end of the coil of the relay RY1 are connected and then grounded; the switch of the relay RY1 is connected between the grid-side input circuit and the user-side output circuit.

[0008] Furthermore, the relay RY1 is a HF140FF relay.

[0009] Furthermore, the step-down voltage transmitter circuit converts the 220V AC voltage signal input from the grid-side input circuit into a 3.8V voltage transmitter signal. The step-down voltage transmitter circuit includes a current-type voltage transmitter U1, a resistor R2, and a resistor R6. The live wire of the grid-side input circuit is connected to one end of the primary side of the current-type voltage transmitter U1 via the resistor R2, and the neutral wire is connected to the other end of the primary side. One end of the secondary side of the current-type voltage transmitter U1 is grounded and connected to the other end of the secondary side via the resistor R6, and then connected to the voltage divider filter circuit to output a 3.8V voltage transmitter signal.

[0010] The lifting transmission circuit generates a 1.66V voltage lifting signal. The lifting transmission circuit includes a resistor R3, a resistor R4, a resistor R5, a capacitor C2, a capacitor C3 and an operational amplifier U2. One end of the resistor R3 is connected to the +5V voltage signal, and the other end of the resistor R3 is simultaneously connected to one end of the resistor R4, one end of the capacitor C2 and the negative input terminal of the operational amplifier U2. The other end of the resistor R4 and the other end of the capacitor C2 are connected and then grounded. The positive power connection terminal of the operational amplifier U2 is connected to the +5V voltage signal and is grounded through the capacitor C3. The negative power connection terminal of the operational amplifier U2 is grounded. The output terminal of the operational amplifier U2 is connected to the voltage divider filter circuit to output a 1.66V voltage lifting signal and is connected to the positive input terminal of the operational amplifier U2 through the resistor R5.

[0011] The voltage divider filter circuit generates an AC voltage signal of 0.3V to 1.4V. The voltage divider filter circuit includes a resistor R7, a resistor R9 and an inductor U4. The voltage transmission signal output by the step-down transmission circuit is connected to the linear amplifier circuit via the resistor R7. The voltage boost signal output by the boost transmission circuit is connected to the linear amplifier circuit via the resistor R9 and the inductor U4 in turn.

[0012] The linear amplifier circuit amplifies the AC voltage signal to generate a sampling voltage signal of 1.5V to 6.9V. The linear amplifier circuit includes an operational amplifier U5, a resistor R8, a resistor R10 and a capacitor C4. The negative input terminal of the operational amplifier U5 is connected to the voltage divider filter circuit. The positive connection terminal of the operational amplifier U5 is divided into two paths, one path is grounded through the resistor R8, and the other path is connected to the output terminal of the operational amplifier U5 through the resistor R10. The positive power connection terminal of the operational amplifier U5 is connected to the +5V voltage signal and is grounded through the capacitor C4. The negative power connection terminal of the operational amplifier U2 is grounded. The output terminal of the operational amplifier U5 is connected to the protection circuit.

[0013] Furthermore, the current-type voltage transmitter adopts a ZMPT101B voltage transformer.

[0014] Furthermore, the protection circuit includes two electrical parameter acquisition alarm chips U6 and U8, a four-input AND gate U7, and resistors R11, R13 and R14. The sampling voltage signal output by the linear amplification circuit is connected to resistors R11, R13 and R14 in sequence and then grounded. The electrical parameter acquisition alarm chip U6 is connected to both ends of the resistor R11, and the electrical parameter acquisition alarm chip U8 is connected to both ends of the resistor R13 to perform voltage division sampling through resistors R11 and R13; the output ends of the two electrical parameter acquisition alarm chips U6 and U8 are respectively connected to two input ends of the four-input AND gate, and the third input end of the four-input AND gate is also connected to the user switch signal. The output end of the four-input AND gate is connected to the grid-connected circuit.

[0015] Furthermore, the two electrical parameter acquisition alarm chips U6 and U8 both use INA226 chips, and the four-input AND gate uses 74LS21 chips.

[0016] Furthermore, the protection circuit also includes a resistor R12, a resistor R15, a resistor R16, a capacitor C5, a capacitor C6 and a capacitor C7; one end of the resistor R11 is connected to the VIN+ pin of the electrical parameter acquisition alarm chip U6, and the other end of the resistor R11 is simultaneously connected to the VIN- pin and the VBUS pin of the electrical parameter acquisition alarm chip U6, the GND pin of the electrical parameter acquisition alarm chip U6 is grounded, the VS+ pin is connected to the +5V voltage signal and is grounded through the capacitor C5, the A0 pin and the A1 pin are both grounded, the Alert pin is divided into two paths, one path is connected to the +5V voltage signal through the resistor R12, and the other path is connected to the 1B pin of the four-input AND gate; one end of the resistor R13 is connected to the electrical parameter acquisition alarm chip U8 The other end of the resistor R13 is connected to the VIN- pin and VBUS pin of the electrical parameter acquisition alarm chip U8 at the same time, the GND pin of the electrical parameter acquisition alarm chip U8 is grounded, the VS+ pin is connected to the +5V voltage signal and is grounded through the capacitor C7, the A0 pin and the A1 pin are both connected to the +5V voltage signal, the Alert pin is divided into two paths, one path is connected to the +5V voltage signal through the resistor R15, and the other path is connected to the 1A pin of the four-input AND gate; the 1C pin and 1D pin of the four-input AND gate are user switch signals at the same time, and are connected to the +5V voltage signal through the resistor R15, the 1Y pin is connected to the grid-connected loop, the GND pin is grounded, and the VCC pin is connected to the +5V voltage signal and is grounded through the capacitor C6.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a grid-connected control circuit for a bidirectional energy storage inverter, simplifies the grid-connected control, realizes a user-unaware grid-connected control circuit, avoids complex main control logic switching, and makes the system transition between grid-connected and off-grid modes smoother and faster, thereby improving the response speed and stability of the system; the circuit directly connects the power grid and the user side to achieve efficient transmission of electric energy, reduces the loss caused by frequent switching of the inverter, and improves the overall energy efficiency of the system; in addition, through an independent hardware protection mechanism, accurate detection and rapid response to input voltage anomalies are achieved, effectively avoiding system failures caused by control failures, and improving the reliability and safety of system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a circuit diagram of a grid-connected control circuit according to an embodiment of the present utility model;

[0019] Figure 2It is a schematic diagram of the grid-connected control circuit of an embodiment of the utility model applied to a bidirectional energy storage inverter.

[0020] In the figure: 1-grid-connected circuit; 2-sampling circuit; 3-protection circuit; 4-energy storage battery; 5-bidirectional DC / DC; 6-full-bridge inverter; 7-rectifier bridge; 8-grid; 9-user load. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] like Figure 1-2 As shown, this embodiment provides a grid-connected control circuit for a bidirectional energy storage inverter, comprising a grid-connected circuit 1, a sampling circuit 2, and a protection circuit 3. The grid-connected circuit 1 connects both the grid-side input circuit and the user-side output circuit, and controls the on / off of the grid-side input circuit and the user-side output circuit via a relay. The sampling circuit 2 connects both the grid-side input circuit and the protection circuit. The sampling circuit comprises a step-down transmission circuit, a step-up transmission circuit, a voltage divider filter circuit, and a linear amplifier circuit. The step-down transmission circuit connects to the grid-side input circuit and converts the input voltage signal of the grid-side input circuit into a voltage transmission signal. The step-up transmission circuit generates a voltage increase signal. The voltage transmission signal and the voltage increase signal are simultaneously fed into the voltage divider filter circuit to generate an AC voltage signal, which is then fed into the linear amplifier circuit for signal amplification to generate a sampled voltage signal that is fed into the protection circuit. The protection circuit 3 comprises two electrical parameter acquisition and alarm chips and a four-input AND gate. The two electrical parameter acquisition and alarm chips perform voltage sampling and output alarm signals to the four-input AND gate, which then outputs signals to the relay to control its on / off.

[0025] In this embodiment, the grid-connected circuit 1 includes a relay RY1, a diode D1, a resistor R1, and a capacitor C1. The diode D1 provides circuit breakers and continuous current, while the capacitor C1 performs signal filtering. The output of the four-input AND gate is connected to both one end of the capacitor C1 and one end of the resistor R1. The other end of the capacitor C1 is grounded. The other end of the resistor R1 is connected to both the cathode of the diode D1 and one end of the coil of the relay RY1. The anode of the diode D1 is connected to the other end of the coil of the relay RY1 and then to ground. The switch of the relay RY1 is connected between the grid-side input circuit and the user-side output circuit. The relay RY1 is an HF140FF relay.

[0026] The grid-connected circuit is sampled and completed using an HF140FF relay, with diode D1 used for circuit-breaking and continuous current, and capacitor C1 for signal filtering. When the grid input circuit is connected, it is directly connected to the user-side output circuit via relay RY1, eliminating the need to activate the fully controlled inverter for output. This allows for simultaneous battery charging and user-side power supply, reducing conversion losses incurred during operation of the bidirectional energy storage inverter.

[0027] Figure 1 In the figure, NETL and NETN are the grid-side live and neutral wires of the bidirectional energy storage inverter, while UERTL and USERN are the user-side live and neutral wires. With this circuit, when the grid is connected and the user has output requirements, there's no need for a rectifier bridge, full-bridge inverter, or active DC-DC converter to deliver power, effectively reducing losses during inverter operation.

[0028] In this embodiment, the step-down voltage transmitter circuit converts the 220V AC voltage signal input from the grid-side input circuit into a 3.8V voltage transmission signal. The step-down voltage transmitter circuit includes a current-type voltage transmitter U1, resistors R2, and resistors R6. The live wire of the grid-side input circuit is connected to one end of the primary side of the current-type voltage transmitter U1 via resistor R2, and the neutral wire is connected to the other end of the primary side. One end of the secondary side of the current-type voltage transmitter U1 is grounded and connected to the other end of the secondary side via resistor R6. The secondary side is then connected to a voltage divider and filter circuit to output a 3.8V voltage transmission signal. The current-type voltage transmitter uses a ZMPT101B voltage transformer.

[0029] The lifting transmission circuit generates a 1.66V voltage lifting signal. The lifting transmission circuit includes a resistor R3, a resistor R4, a resistor R5, a capacitor C2, a capacitor C3 and an operational amplifier U2. One end of the resistor R3 is connected to the +5V voltage signal, and the other end of the resistor R3 is simultaneously connected to one end of the resistor R4, one end of the capacitor C2 and the negative input end of the operational amplifier U2. The other end of the resistor R4 and the other end of the capacitor C2 are connected to ground. The positive power connection end of the operational amplifier U2 is connected to the +5V voltage signal and is grounded through the capacitor C3. The negative power connection end of the operational amplifier U2 is grounded. The output end of the operational amplifier U2 is connected to the voltage divider filter circuit, outputs a 1.66V voltage lifting signal, and is connected to the positive input end of the operational amplifier U2 through the resistor R5.

[0030] The voltage divider filter circuit generates an AC voltage signal of 0.3V to 1.4V. The voltage divider filter circuit includes a resistor R7, a resistor R9 and an inductor U4. The voltage transmission signal output by the step-down transmission circuit is connected to the linear amplifier circuit via the resistor R7, and the voltage boost signal output by the boost transmission circuit is connected to the linear amplifier circuit via the resistor R9 and the inductor U4 in turn.

[0031] The linear amplifier circuit amplifies the AC voltage signal to generate a sampling voltage signal of 1.5V to 6.9V. The linear amplifier circuit includes an operational amplifier U5, a resistor R8, a resistor R10 and a capacitor C4. The negative input terminal of the operational amplifier U5 is connected to the voltage divider filter circuit. The positive connection terminal of the operational amplifier U5 is divided into two paths, one path is grounded through the resistor R8, and the other path is connected to the output terminal of the operational amplifier U5 through the resistor R10. The positive power connection terminal of the operational amplifier U5 is connected to the +5V voltage signal and is grounded through the capacitor C4. The negative power connection terminal of the operational amplifier U2 is grounded. The output terminal of the operational amplifier U5 is connected to the protection circuit.

[0032] The sampling circuit primarily utilizes a ZMPT101B current-to-voltage transmitter. This transmitter, along with R2 and R6 on the left and right ends, forms a step-down transmitter circuit, converting the 220V AC voltage signal into a 3.8V AC voltage signal. Since the protection circuit's input voltage is limited to 0-30V, it requires a voltage greater than 0V. Therefore, resistors R3 and R4 divide the voltage to produce a 1.66V signal. This signal is then passed through the transmitter circuit, which consists of feedback resistor R5, filter capacitor C3, and operational amplifier U2, to generate a stable 1.66V voltage-step-up signal. The 1.66V voltage-step-up signal and the 3.8V voltage signal are then divided by R7 and R9 and filtered by the filter inductor of U4 to produce an AC voltage signal between 0.3V and 1.4V. Finally, this signal passes through a linear amplifier circuit, consisting of input resistor R8, feedback resistor R10, filter capacitor C4, and operational amplifier U5, amplifying it to a 1.5V to 6.9V AC voltage signal for subsequent sampling.

[0033] In this embodiment, the protection circuit 3 includes two electrical parameter acquisition and alarm chips U6 and U8, a four-input AND gate U7, and resistors R11, R12, R13, R14, R15, R16, capacitors C5, C6, and C7. The sampled voltage signal output by the linear amplifier circuit is connected to resistors R11, R13, and R14 in sequence and then grounded. The electrical parameter acquisition and alarm chip U6 is connected to both ends of resistor R11, and the electrical parameter acquisition and alarm chip U8 is connected to both ends of resistor R13 to perform voltage division sampling through resistors R11 and R13. The output ends of the two electrical parameter acquisition and alarm chips U6 and U8 are respectively connected to two input ends of the four-input AND gate. The third input end of the four-input AND gate is also connected to the user switch signal. The output end of the four-input AND gate is connected to the grid-connected circuit. The two electrical parameter acquisition and alarm chips U6 and U8 both use INA226 chips, and the four-input AND gate uses a 74LS21 chip.

[0034] Specifically, one end of the resistor R11 is connected to the VIN+ pin of the electrical parameter acquisition alarm chip U6, and the other end of the resistor R11 is simultaneously connected to the VIN- pin and VBUS pin of the electrical parameter acquisition alarm chip U6. The GND pin of the electrical parameter acquisition alarm chip U6 is grounded, the VS+ pin is connected to the +5V voltage signal and is grounded through the capacitor C5, the A0 pin and the A1 pin are both grounded, the Alert pin is divided into two paths, one path is connected to the +5V voltage signal through the resistor R12, and the other path is connected to the 1B pin of the four-input AND gate; one end of the resistor R13 is connected to the VIN+ pin of the electrical parameter acquisition alarm chip U8, and the other end of the resistor R13 is simultaneously connected The VIN- pin and VBUS pin of the electrical parameter acquisition alarm chip U8, the GND pin of the electrical parameter acquisition alarm chip U8 is grounded, the VS+ pin is connected to the +5V voltage signal and is grounded through the capacitor C7, the A0 pin and the A1 pin are both connected to the +5V voltage signal, the Alert pin is divided into two paths, one path is connected to the +5V voltage signal through the resistor R15, and the other path is connected to the 1A pin of the four-input AND gate; the 1C pin and 1D pin of the four-input AND gate are user switch signals at the same time, and are connected to the +5V voltage signal through the resistor R15, the 1Y pin is connected to the grid-connected loop, the GND pin is grounded, and the VCC pin is connected to the +5V voltage signal and is grounded through the capacitor C6.

[0035] The protection circuit consists of two INA226 electrical parameter acquisition and alarm chips (U6 and U8), a 74LS21 four-input AND gate (U7), and its associated voltage transmitter and sampling circuit. The two chips sample the voltages of resistors R11 and R13, respectively, and, in conjunction with filter capacitors C5 and C7 and return resistor R14, form a voltage overvoltage and undervoltage detection and alarm circuit. If the voltage is too high or too low, pins 3 of the electrical parameter acquisition and alarm chips U6 and U8, respectively, will output a low level, signaling an alarm. This alarm signal is fed into pins 2 and 1 of the four-input AND gate U7. Simultaneously, a user switch signal is fed into pins 4 and 5. If there is no alarm signal, meaning the voltage is normal and the user closes the switch, all four inputs of the AND gate will be high. At this point, pin 6 of the AND gate U7 will also output a high level, which is used to open the RY1 circuit relay mentioned above. If any of the alarm signals is triggered, pin 6 of the four-input AND gate U7 will output a low level, closing the circuit relay, thus implementing hardware protection. Resistors R12, R15, and R16 are used to ensure that the alarm signal is not falsely triggered and to ensure smooth operation of the system.

[0036] This utility model provides a grid-connected control circuit for a bidirectional energy storage inverter. It utilizes an HF140FF relay to directly connect to the user's load side during grid access, avoiding the frequent switching of fully controlled inverters. This enables seamless grid-connected control and improves system operating efficiency and stability. Furthermore, through optimized grid-connected circuit design, the circuit enables direct power supply to the user side and battery charging, eliminating the inverter's DC-to-AC conversion process and reducing energy conversion losses during inverter operation. Furthermore, the circuit combines the INA226 chip with the 74LS21 AND gate chip to create an independent hardware protection mechanism, ensuring rapid system response and output shutdown in abnormal situations. The ZMPT101B current-type voltage transmitter enables precise voltage sampling, ensuring accurate and reliable protection.

[0037] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. Any person skilled in the art may utilize the above disclosure to modify or remodel the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention shall remain within the scope of protection of the present invention.

Claims

1. A grid-connected control circuit for a bidirectional energy storage inverter, characterized in that: It includes a grid-connected circuit, a sampling circuit and a protection circuit; the grid-connected circuit is connected to the grid-side input circuit and the user-side output circuit at the same time, and the on-off control of the grid-side input circuit and the user-side output circuit is performed through a relay; the sampling circuit includes a step-down transmission circuit, a lifting transmission circuit, a voltage divider filter circuit and a linear amplifier circuit, the step-down transmission circuit is connected to the grid-side input circuit, and converts the input voltage signal of the grid-side input circuit into a voltage transmission signal, the lifting transmission circuit generates a voltage lifting signal, the voltage transmission signal and the voltage lifting signal are simultaneously sent to the voltage divider filter circuit to generate an AC voltage signal, and then sent to the linear amplifier circuit for signal amplification to generate a sampling voltage signal and send it to the protection circuit; the protection circuit includes two electrical parameter acquisition alarm chips and a four-input AND gate, the two electrical parameter acquisition alarm chips perform voltage division sampling respectively, and output alarm signals to the four-input AND gate, and the four-input AND gate outputs signals to the relay to control its switch.

2. A grid-connected control circuit for a bidirectional energy storage inverter according to claim 1, characterized in that: The grid-connected circuit includes a relay RY1, a diode D1, a resistor R1 and a capacitor C1. The diode D1 performs circuit breaking and continuous current flow, and the capacitor C1 performs signal filtering. The output end of the four-input AND gate is simultaneously connected to one end of the capacitor C1 and one end of the resistor R1, and the other end of the capacitor C1 is grounded. The other end of the resistor R1 is simultaneously connected to the cathode of the diode D1 and one end of the coil of the relay RY1, and the anode of the diode D1 and the other end of the coil of the relay RY1 are connected and then grounded; the switch of the relay RY1 is connected between the grid-side input circuit and the user-side output circuit.

3. A grid-connected control circuit for a bidirectional energy storage inverter according to claim 2, characterized in that: The relay RY1 adopts HF140FF relay.

4. The grid-connected control circuit for a bidirectional energy storage inverter according to claim 1, characterized in that: The step-down voltage transmitter circuit converts the 220V AC voltage signal input from the grid-side input circuit into a 3.8V voltage transmitter signal. The step-down voltage transmitter circuit includes a current-type voltage transmitter U1, a resistor R2, and a resistor R6. The live wire of the grid-side input circuit is connected to one end of the primary side of the current-type voltage transmitter U1 via the resistor R2, and the neutral wire is connected to the other end of the primary side. One end of the secondary side of the current-type voltage transmitter U1 is grounded and connected to the other end of the secondary side via the resistor R6, and then connected to the voltage divider filter circuit to output a 3.8V voltage transmitter signal. The lifting transmission circuit generates a 1.66V voltage lifting signal. The lifting transmission circuit includes a resistor R3, a resistor R4, a resistor R5, a capacitor C2, a capacitor C3 and an operational amplifier U2. One end of the resistor R3 is connected to the +5V voltage signal, and the other end of the resistor R3 is simultaneously connected to one end of the resistor R4, one end of the capacitor C2 and the negative input terminal of the operational amplifier U2. The other end of the resistor R4 and the other end of the capacitor C2 are connected and then grounded. The positive power connection terminal of the operational amplifier U2 is connected to the +5V voltage signal and is grounded through the capacitor C3. The negative power connection terminal of the operational amplifier U2 is grounded. The output terminal of the operational amplifier U2 is connected to the voltage divider filter circuit to output a 1.66V voltage lifting signal and is connected to the positive input terminal of the operational amplifier U2 through the resistor R5. The voltage divider filter circuit generates an AC voltage signal of 0.3V to 1.4V. The voltage divider filter circuit includes a resistor R7, a resistor R9 and an inductor U4. The voltage transmission signal output by the step-down transmission circuit is connected to the linear amplifier circuit via the resistor R7. The voltage boost signal output by the boost transmission circuit is connected to the linear amplifier circuit via the resistor R9 and the inductor U4 in turn. The linear amplifier circuit amplifies the AC voltage signal to generate a sampling voltage signal of 1.5V to 6.9V. The linear amplifier circuit includes an operational amplifier U5, a resistor R8, a resistor R10 and a capacitor C4. The negative input terminal of the operational amplifier U5 is connected to the voltage divider filter circuit. The positive connection terminal of the operational amplifier U5 is divided into two paths, one path is grounded through the resistor R8, and the other path is connected to the output terminal of the operational amplifier U5 through the resistor R10. The positive power connection terminal of the operational amplifier U5 is connected to the +5V voltage signal and is grounded through the capacitor C4. The negative power connection terminal of the operational amplifier U2 is grounded. The output terminal of the operational amplifier U5 is connected to the protection circuit.

5. The grid-connected control circuit for a bidirectional energy storage inverter according to claim 4, characterized in that: The current-type voltage transmitter adopts ZMPT101B voltage transformer.

6. The grid-connected control circuit for a bidirectional energy storage inverter according to claim 1, characterized in that: The protection circuit includes two electrical parameter acquisition alarm chips U6 and U8, a four-input AND gate U7, and resistors R11, R13 and R14. The sampling voltage signal output by the linear amplification circuit is connected to resistors R11, R13 and R14 in sequence and then grounded. The electrical parameter acquisition alarm chip U6 is connected to both ends of the resistor R11, and the electrical parameter acquisition alarm chip U8 is connected to both ends of the resistor R13 to perform voltage division sampling through resistors R11 and R13; the output ends of the two electrical parameter acquisition alarm chips U6 and U8 are respectively connected to two input ends of the four-input AND gate, and the third input end of the four-input AND gate is also connected to the user switch signal. The output end of the four-input AND gate is connected to the grid-connected circuit.

7. A grid-connected control circuit for a bidirectional energy storage inverter according to claim 6, characterized in that: The two electrical parameter acquisition alarm chips U6 and U8 both use INA226 chips, and the four-input AND gate uses 74LS21 chips.

8. A grid-connected control circuit for a bidirectional energy storage inverter according to claim 7, characterized in that: The protection circuit also includes a resistor R12, a resistor R15, a resistor R16, a capacitor C5, a capacitor C6 and a capacitor C7; one end of the resistor R11 is connected to the VIN+ pin of the electrical parameter acquisition alarm chip U6, and the other end of the resistor R11 is simultaneously connected to the VIN- pin and the VBUS pin of the electrical parameter acquisition alarm chip U6, the GND pin of the electrical parameter acquisition alarm chip U6 is grounded, the VS+ pin is connected to the +5V voltage signal and is grounded through the capacitor C5, the A0 pin and the A1 pin are both grounded, the Alert pin is divided into two paths, one path is connected to the +5V voltage signal through the resistor R12, and the other path is connected to the 1B pin of the four-input AND gate; one end of the resistor R13 is connected to the VI of the electrical parameter acquisition alarm chip U8 N+ pin, the other end of the resistor R13 is simultaneously connected to the VIN- pin and VBUS pin of the electrical parameter acquisition alarm chip U8, the GND pin of the electrical parameter acquisition alarm chip U8 is grounded, the VS+ pin is connected to the +5V voltage signal and is grounded through the capacitor C7, the A0 pin and the A1 pin are both connected to the +5V voltage signal, the Alert pin is divided into two paths, one path is connected to the +5V voltage signal through the resistor R15, and the other path is connected to the 1A pin of the four-input AND gate; the 1C pin and 1D pin of the four-input AND gate are user switch signals at the same time, and are connected to the +5V voltage signal through the resistor R15, the 1Y pin is connected to the grid-connected loop, the GND pin is grounded, and the VCC pin is connected to the +5V voltage signal and is grounded through the capacitor C6.

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