AC interface circuit of bidirectional energy storage inverter

Abstract

The utility model discloses an AC interface circuit of a bidirectional energy storage inverter, which comprises an AC input circuit, a bypass unit and a control circuit, the control circuit comprises a single chip microcomputer, a bypass current sampling circuit, a calibration-free electric energy metering chip and a bypass relay, and the AC input circuit comprises an AC input end and an inverter circuit connecting end. The bypass unit comprises a bypass connecting end and an alternating current output end, and the bypass connecting end is connected between the alternating current input end and the inverter circuit connecting end; a contact of the bypass relay is connected between the bypass connecting end and the alternating current output end, and a control end of the bypass relay is connected with the single chip microcomputer; the sampling signal output end of the bypass current sampling circuit is connected with the current sampling signal input end of the calibration-free electric energy metering chip, and the alarm signal output end of the calibration-free electric energy metering chip is connected with the single-chip microcomputer. According to the utility model, when overcurrent occurs in the bypass unit, the bypass relay can cut off the output of the bypass unit in time, so that the safety performance of the bidirectional energy storage inverter is improved.

Description

Technical Field

[0001] The utility model relates to a bidirectional energy storage inverter, and particularly to an AC interface circuit of a bidirectional energy storage inverter. Background Art

[0002] A bidirectional energy storage inverter is a device that can achieve bidirectional conversion and storage of electric energy. Its structure includes an inverter, an energy storage unit, and a control system. The inverter is the core component, which can convert direct current into alternating current and also convert alternating current into direct current. The energy storage unit usually adopts a battery or a supercapacitor to store electric energy. The control system is responsible for monitoring and controlling the operation of the entire system to ensure efficient conversion and storage of energy.

[0003] The working principle of a bidirectional energy storage inverter is to convert electric energy into a form suitable for storage through the inverter, and then convert the stored electric energy into power supply to the system according to needs. This device can be applied to fields such as power grid frequency modulation, energy storage systems, and electric vehicle charging, and has high practical value.

[0004] With the development of technology and the expansion of applications, people's requirements for inverters are no longer limited to basic power conversion functions, but also hope that it can provide more advanced functions. These advanced functions include:

[0005] UPS (Uninterruptible Power Supply) function: The UPS system can provide a short-term power supply when the grid power supply is interrupted to protect electronic devices from the sudden interruption of the power supply. This function usually requires the inverter to quickly switch to the backup power supply when the power fails, and the bypass unit plays a key role in this process.

[0006] Charge and discharge simultaneously function: This means that the inverter can charge the energy storage device (such as a battery) while supplying power to the load. This function is particularly useful in some renewable energy applications, such as solar power generation systems, which can charge the battery during the day while generating electricity, so as to continue to supply power at night or on cloudy days.

[0007] The realization of these functions often depends on the bypass unit. The bypass unit allows bypassing the inverter under specific circumstances, directly connecting the power supply and the load, or maintaining the continuous supply of power during the maintenance or troubleshooting of the inverter.

[0008] The invention with the application number CN202111330998.8 discloses an automatic continuous power supply and system. The automatic continuous power supply includes: a bypass unit, the input end of the bypass unit is connected to the commercial power, and the output end of the bypass unit is connected to the load; a bidirectional inverter, the bidirectional inverter is connected to the output end of the bypass unit and to the load; an energy storage battery, the energy storage battery is connected to the bidirectional inverter, and when the commercial power is cut off, the energy storage battery supplies power to the load via the bidirectional inverter. The automatic continuous power supply and system of this invention lack overcurrent protection for the bypass unit. When the bypass unit has overcurrent or over-power, it is easy for circuit devices to be damaged, and even a fire may be triggered. [Summary of the Invention]

[0009] The technical problem to be solved by the present utility model is to provide an AC interface circuit for a bidirectional energy storage inverter that can improve the safety performance of the bidirectional energy storage inverter.

[0010] To solve the above technical problem, the technical solution adopted by the present utility model is that an AC interface circuit for a bidirectional energy storage inverter includes an AC input circuit, a bypass unit, and a control circuit. The control circuit includes a single-chip microcomputer, a bypass current sampling circuit, a calibration-free electric energy metering chip, and a bypass relay. The AC input circuit includes an AC input end and an inverter circuit connection end. The bypass unit includes a bypass connection end and an AC output end. The bypass connection end is connected between the AC input end and the inverter circuit connection end; the contact of the bypass relay is connected between the bypass connection end and the AC output end, and the control end of the bypass relay is connected to the single-chip microcomputer; the sampling signal output end of the bypass current sampling circuit is connected to the current sampling signal input end of the calibration-free electric energy metering chip, and the alarm signal output end of the calibration-free electric energy metering chip is connected to the single-chip microcomputer.

[0011] For the above-mentioned AC interface circuit, the control circuit includes a bypass voltage sampling circuit, and the sampling signal output end of the bypass voltage sampling circuit is connected to the voltage sampling signal input end of the calibration-free electric energy metering chip.

[0012] For the above-mentioned AC interface circuit, it includes a pre-charge circuit. The pre-charge circuit includes an input end and an AC input voltage sampling end. The input end of the pre-charge circuit is connected between the AC input end and the bypass connection end; the control circuit includes an AC input relay, the contact of the AC input relay is connected between the AC input end and the bypass connection end, and the control end of the AC input relay is connected to the single-chip microcomputer; the AC input voltage sampling end is connected to the single-chip microcomputer.

[0013] For the above-mentioned AC interface circuit, it includes a self-recovery fuse, and the self-recovery fuse is connected between the AC input end and the contact of the AC input relay.

[0014] For the AC interface circuit described above, the AC input terminals of the AC input circuit include a live wire input terminal and a neutral wire input terminal, and the inverter circuit connection terminals of the AC input circuit include a PFC input positive terminal and a PFC input negative terminal; the input terminals of the pre-charge circuit include a pre-charge circuit live wire input terminal and a pre-charge circuit neutral wire input terminal; the AC input voltage sampling terminals of the pre-charge circuit include an AC input voltage sampling live wire terminal and an AC input voltage sampling neutral wire terminal; the AC input voltage sampling live wire terminal is connected to the pre-charge circuit live wire input terminal through a first current-limiting resistor, and the AC input voltage sampling neutral wire terminal is connected to the pre-charge circuit neutral wire input terminal through a second current-limiting resistor. The AC input voltage sampling live wire terminal and the AC input voltage sampling neutral wire terminal of the pre-charge circuit are respectively connected to the AC input voltage sampling signal input terminals of the microcontroller for the pre-charge circuit.

[0015] For the AC interface circuit described above, the AC output terminals of the bypass unit include a live wire output terminal and a neutral wire output terminal; the bypass connection terminals of the bypass unit include a bypass live wire connection terminal and a bypass neutral wire connection terminal; the bypass live wire connection terminal of the bypass of the bypass unit is connected to the live wire input terminal of the AC input terminal through the first contact of the AC input relay and the self-resetting fuse; the bypass neutral wire connection terminal of the bypass of the bypass unit is connected to the neutral wire input terminal of the AC input terminal through the second contact of the AC input relay.

[0016] For the AC interface circuit described above, the bypass current sampling circuit includes a bypass current sampling resistor, a bypass current sampling signal output terminal and a ground terminal; the first end of the bypass current sampling resistor is connected to the bypass neutral wire connection terminal of the bypass of the bypass unit, and the second end of the bypass current sampling resistor is connected to the neutral wire output terminal of the AC output terminal through the second contact of the bypass relay; the second end of the bypass current sampling resistor is connected to the bypass current sampling signal output terminal, and the first end of the bypass current sampling resistor is connected to the ground terminal; the bypass current sampling signal output terminal of the bypass current sampling circuit is connected to the first pin of the current channel analog input of the calibration-free energy metering chip, and the ground terminal of the bypass current sampling circuit is connected to the second pin of the current channel analog input of the calibration-free energy metering chip.

[0017] For the AC interface circuit described above, the bypass voltage sampling circuit includes a bypass voltage sampling circuit output terminal and the ground terminal described above. The bypass voltage sampling circuit output terminal is connected to the bypass live wire connection terminal of the bypass unit; the bypass voltage sampling circuit output terminal is connected to the voltage sampling signal input pin of the calibration-free energy metering chip through a third current-limiting resistor; the alarm signal output terminals of the calibration-free energy metering chip include two alarm signal output pins, and the two alarm signal output pins are respectively connected to the microcontroller.

[0018] When an overcurrent occurs in the bypass unit of the AC interface circuit of the bidirectional energy storage inverter of the present utility model, the bypass relay can timely cut off the output of the bypass unit, improving the safety performance of the bidirectional energy storage inverter. Brief Description of Drawings

[0019] The present utility model will be further described in detail below in conjunction with the drawings and specific embodiments.

[0020] Figure 1 It is a circuit diagram of the AC interface circuit of the bidirectional energy storage inverter according to an embodiment of the present utility model.

[0021] Figure 2 It is a wiring diagram of the calibration-free electric energy metering chip according to an embodiment of the present utility model. Specific Embodiments

[0022] The AC interface circuit of the bidirectional energy storage inverter according to an embodiment of the present utility model is as Figure 1 and Figure 2 shown, and includes an AC input circuit, a pre-charge circuit, a bypass unit, a first EMC circuit, a second EMC circuit, a third EMC circuit, and a control circuit.

[0023] The control circuit includes a single-chip microcomputer (not shown in the figure), a bypass current sampling circuit, a bypass voltage sampling circuit, a calibration-free electric energy metering chip, a self-resetting fuse, a bypass relay, and an AC input relay.

[0024] The AC input circuit includes an AC input terminal and an inverter circuit connection terminal. The bypass unit includes a bypass connection terminal and an AC output terminal. The bypass connection terminal is connected between the AC input terminal and the inverter circuit connection terminal. The contact of the bypass relay is connected between the bypass connection terminal and the AC output terminal, and the control end of the bypass relay is connected to the single-chip microcomputer. The sampling signal output terminal of the bypass current sampling circuit is connected to the current sampling signal input terminal of the calibration-free electric energy metering chip, and the sampling signal output terminal of the bypass voltage sampling circuit is connected to the voltage sampling signal input terminal of the calibration-free electric energy metering chip. The alarm signal output terminal of the calibration-free electric energy metering chip is connected to the single-chip microcomputer.

[0025] The pre-charge circuit includes an input terminal and an AC input voltage sampling terminal. The input terminal of the pre-charge circuit is connected between the AC input terminal and the bypass connection terminal. The contact of the AC input relay is connected between the AC input terminal and the bypass connection terminal, and the control end of the AC input relay is connected to the single-chip microcomputer. The AC input voltage sampling terminal is connected to the single-chip microcomputer. The self-resetting fuse is connected between the AC input terminal and the contact of the AC input relay.

[0026] The first EMC circuit is connected between the self-resetting fuse and the contact of the AC input relay, the second EMC circuit is connected between the bypass connection terminal and the inverter circuit connection terminal, and the third EMC circuit is connected between the contact of the bypass relay and the AC output terminal.

[0027] As Figure 1As shown, the AC input terminal of the AC input circuit includes an AC input terminal J1, and the AC input terminal J1 includes a live wire input terminal IN-L and a neutral wire input terminal IN-N. The inverter circuit connection terminal of the AC input circuit includes a PFC input positive terminal IPOUT and a PFC input negative terminal INV-N. IPOUT and INV-N are the inputs of the PFC circuit during charging and the outputs of the AC inverter during inversion.

[0028] The pre-charge circuit input terminal includes a pre-charge circuit live wire input terminal BYPASS_L and a pre-charge circuit neutral wire input terminal BYPASS_N. The AC input voltage sampling terminals of the pre-charge circuit include an AC input voltage sampling live wire terminal L_IN and an AC input voltage sampling neutral wire terminal N_IN. The AC input voltage sampling live wire terminal L_IN is connected to the pre-charge circuit live wire input terminal BYPASS_L through current-limiting resistors R72, R316, and R314, and the AC input voltage sampling neutral wire terminal N_IN is connected to the pre-charge circuit neutral wire input terminal BYPASS_N through current-limiting resistors R311, R313, and R315. The AC input voltage sampling live wire terminal L_IN and the AC input voltage sampling neutral wire terminal N_IN of the pre-charge circuit are respectively connected to the AC input voltage sampling signal input terminals of the single-chip microcomputer for the pre-charge circuit.

[0029] The contact of the bypass relay RLY2-A is connected between the bypass connection terminal and the AC output terminal, and the contact of the AC input relay RLY1-A is connected between the AC input terminal and the bypass connection terminal. The control terminals of the bypass relay and the AC input relay are respectively connected to the relay control signal output terminal of the single-chip microcomputer. The self-resetting fuse F2 is connected between the AC input terminal and the contact of the AC input relay RLY1-A.

[0030] The AC output terminal of the bypass unit includes an AC output terminal J2, and the AC output terminal J2 includes a live wire output terminal VL and a neutral wire output terminal OUT-N. The bypass connection terminal of the bypass unit includes a bypass live wire connection terminal and a bypass neutral wire connection terminal. The bypass live wire connection terminal of the bypass of the bypass unit is connected to the live wire input terminal IN-L of the AC input terminal J1 through the first contact of the AC input relay RLY1-A and the self-resetting fuse F2. The bypass neutral wire connection terminal of the bypass of the bypass unit is connected to the neutral wire input terminal IN-N of the AC input terminal J1 through the second contact of the AC input relay RLY1-A.

[0031] The bypass current sampling circuit includes a bypass current sampling resistor R81, a bypass current sampling signal output terminal OUT-N1, and a ground terminal VSS. The first end of the bypass current sampling resistor R81 is connected to the bypass neutral connection end of the bypass unit. The second end of the bypass current sampling resistor R81 is connected to the neutral output terminal OUT-N of the AC output terminal J2 through the second contact of the bypass relay RLY2-A. The second end of the bypass current sampling resistor R81 is connected to the bypass current sampling signal output terminal OUT-N1, and the first end of the bypass current sampling resistor R81 is connected to the ground terminal VSS. As Figure 2 shown, the bypass current sampling signal output terminal OUT-N1 of the bypass current sampling circuit is connected to the first pin IP of the current channel analog input of the calibration-free electric energy metering chip BL094210L, and the ground terminal VSS of the bypass current sampling circuit is connected to the second pin IN of the current channel analog input of the calibration-free electric energy metering chip BL094210L.

[0032] The bypass voltage sampling circuit includes a bypass voltage sampling circuit output terminal VL1 and a ground terminal VSS. The bypass voltage sampling circuit output terminal VL1 is connected to the bypass live wire connection end of the bypass unit. As Figure 2 shown, the bypass voltage sampling circuit output terminal VL1 is connected to the voltage sampling signal input pin VP of the calibration-free electric energy metering chip BL094210L through a current limiting resistor. The alarm signal output pin TX_SDO and the RX_SDI of the calibration-free electric energy metering chip are respectively connected to the single-chip microcomputer.

[0033] The first EMC circuit is connected between the self-recovery fuse F2 and the contact of the AC input relay RLY1-A, and includes a capacitor CX1, capacitors CY2 and CY3, inductors L8-A and L8-B, and M1.

[0034] The second EMC circuit is connected between the bypass connection end and the inverter circuit connection end, and includes a capacitor CX4, capacitors CY5 and CY6, and inductors L7-A and L7-B.

[0035] The third EMC circuit is connected between the contact of the bypass relay RLY2-A and the AC output end, and includes a capacitor CY1, a capacitor CY4, and inductors L3-A and L3-B.

[0036] When the bidirectional energy storage inverter works in the charging mode, J1 is the AC input terminal, and the pre-charge circuit is powered by BYPASS_L and BYPASS_N. Then the auxiliary power supply starts, and the single-chip microcomputer works normally. The single-chip microcomputer samples the AC input voltage through L_IN and N_IN, and then turns on the AC input relay RLY1-A. The AC input end of the AC input circuit supplies power to the inverter circuit connection end and reaches the PFC input. At this time, the inverter works normally. When the bypass function is turned on, the single-chip microcomputer sends a signal to make the bypass relay RLY2-A close, and there is AC output at the J2 terminal. If the output at the J2 terminal is short-circuited, due to the excessive instantaneous current, the signal sampled by the calibration-free electric energy metering chip BL094210L reacts slowly and is too late to send a signal to make the bypass relay RLY2-A disconnect. At this time, the current flowing through the self-recovery fuse F2 is also very large, causing the self-recovery fuse F2 to disconnect, thereby protecting the AC input relay RLY1-A from damage. In the case of overload, since the three signals VL1, OUT-N1, and VSS detect the voltage and current of the J2 terminal, the single-chip microcomputer can know the power output by J2. When the output power is too large, the bypass relay RLY2-A is disconnected, thereby protecting the circuit of the input terminal J1.

[0037] In Figure 2 , VL1 is the voltage sampling signal of the calibration-free electric energy metering chip BL094210L, OUT-N1 is the current sampling signal of the calibration-free electric energy metering chip BL094210L, VSS is the sampling ground wire of the calibration-free electric energy metering chip BL094210L, DVCC is the power supply pin of the calibration-free electric energy metering chip BL094210L, and TX_SDO and RX_SDI are the alarm pins that provide the output voltage and current information to the single-chip microcomputer.

[0038] The output voltage of J2 can be sampled through VL1 and VSS, and the output current can be sampled through OUT-N1 and VSS. When the voltage and current of the circuit are determined, the output power of J2 can be calculated from the data sent to the single-chip microcomputer through TX_SDO and RX_SDI. When the power reaches the threshold, the relay RLY2-A can be disconnected to achieve protection.

[0039] When the bypass function is turned on and during normal operation, due to the user's incorrect operation, bypass overcurrent may occur. When the current is not high and the load is 2 to 3 times the normal load, within the tolerance range of the power supply, through the calibration-free power metering chip BL094210L, VLN samples the L line of the inverter output, and OUT-N1 samples the voltage of the sampling resistor with VSS to know the output current. Then, the power is transmitted to the single-chip microcomputer through TX_SDO and RX_SDI to turn off the bypass relay. When the current is too high or there is a short circuit, at this time, through the calibration-free power metering chip BL094210L, it may not have enough time to react. At this time, the self-resetting fuse F2 quickly shuts off and disconnects the input. When the user realizes the operation error and removes the bypass overcurrent, the self-resetting fuse F2 self-resets and the circuit resumes normal use.

Claims

1. An AC interface circuit of a bidirectional energy storage inverter, comprising an AC input circuit, a bypass unit and a control circuit. The control circuit includes a single-chip microcomputer. The AC input circuit includes an AC input end and an inverter circuit connection end. The bypass unit includes a bypass connection end and an AC output end. The bypass connection end is connected between the AC input end and the inverter circuit connection end; it is characterized in that, The control circuit includes a bypass current sampling circuit, a calibration-free electric energy metering chip, and a bypass relay. The contact of the bypass relay is connected between the bypass connection terminal and the AC output terminal, and the control terminal of the bypass relay is connected to the single-chip microcomputer. The sampling signal output terminal of the bypass current sampling circuit is connected to the current sampling signal input terminal of the calibration-free electric energy metering chip, and the alarm signal output terminal of the calibration-free electric energy metering chip is connected to the single-chip microcomputer.

2. The AC interface circuit according to claim 1, wherein The control circuit includes a bypass voltage sampling circuit, and the sampling signal output terminal of the bypass voltage sampling circuit is connected to the voltage sampling signal input terminal of the calibration-free electric energy metering chip.

3. The AC interface circuit according to claim 2, wherein It includes a pre-charge circuit. The pre-charge circuit includes an input terminal and an AC input voltage sampling terminal. The input terminal of the pre-charge circuit is connected between the AC input terminal and the bypass connection terminal. The control circuit includes an AC input relay. The contact of the AC input relay is connected between the AC input terminal and the bypass connection terminal, and the control terminal of the AC input relay is connected to the single-chip microcomputer. The AC input voltage sampling terminal is connected to the single-chip microcomputer.

4. The AC interface circuit according to claim 3, wherein It includes a self-resetting fuse, and the self-resetting fuse is connected between the AC input terminal and the contact of the AC input relay.

5. The AC interface circuit according to claim 4, wherein It includes a first EMC circuit, a second EMC circuit, and a third EMC circuit. The first EMC circuit is connected between the self-resetting fuse and the contact of the AC input relay. The second EMC circuit is connected between the bypass connection terminal and the inverter circuit connection terminal. The third EMC circuit is connected between the contact of the bypass relay and the AC output terminal.

6. The AC interface circuit according to claim 3, wherein The AC input terminal of the AC input circuit includes a live wire input terminal and a neutral wire input terminal. The inverter circuit connection terminal of the AC input circuit includes a PFC input positive terminal and a PFC input negative terminal. The input terminal of the pre-charge circuit includes a pre-charge circuit live wire input terminal and a pre-charge circuit neutral wire input terminal. The AC input voltage sampling terminal of the pre-charge circuit includes an AC input voltage sampling live wire terminal and an AC input voltage sampling neutral wire terminal. The AC input voltage sampling live wire terminal is connected to the pre-charge circuit live wire input terminal through a first current-limiting resistor. The AC input voltage sampling neutral wire terminal is connected to the pre-charge circuit neutral wire input terminal through a second current-limiting resistor. The AC input voltage sampling live wire terminal and the AC input voltage sampling neutral wire terminal of the pre-charge circuit are respectively connected to the AC input voltage sampling signal input terminals of the pre-charge circuit of the single-chip microcomputer.

7. The AC interface circuit according to claim 6, wherein The AC output terminal of the bypass unit includes a live wire output terminal and a neutral wire output terminal. The bypass connection terminal of the bypass unit includes a bypass live wire connection terminal and a bypass neutral wire connection terminal. The bypass live wire connection terminal of the bypass of the bypass unit is connected to the live wire input terminal of the AC input terminal through the first contact of the AC input relay and the self-resetting fuse. The bypass neutral wire connection terminal of the bypass of the bypass unit is connected to the neutral wire input terminal of the AC input terminal through the second contact of the AC input relay.

8. The AC interface circuit according to claim 7, characterized in that, The bypass current sampling circuit includes a bypass current sampling resistor, a bypass current sampling signal output terminal, and a grounding terminal; the first end of the bypass current sampling resistor is connected to the bypass neutral wire connection end of the bypass of the bypass unit, and the second end of the bypass current sampling resistor is connected to the neutral wire output end of the AC output terminal through the second contact of the bypass relay; the second end of the bypass current sampling resistor is connected to the bypass current sampling signal output terminal, and the first end of the bypass current sampling resistor is connected to the grounding terminal; the bypass current sampling signal output terminal of the bypass current sampling circuit is connected to the first pin of the current channel analog input of the calibration-free electric energy metering chip, and the grounding terminal of the bypass current sampling circuit is connected to the second pin of the current channel analog input of the calibration-free electric energy metering chip.

9. The AC interface circuit according to claim 8, characterized in that, The bypass voltage sampling circuit includes a bypass voltage sampling circuit output terminal and the grounding terminal, and the bypass voltage sampling circuit output terminal is connected to the bypass live wire connection end of the bypass unit; the bypass voltage sampling circuit output terminal is connected to the voltage sampling signal input pin of the calibration-free electric energy metering chip through a third current limiting resistor; the alarm signal output terminal of the calibration-free electric energy metering chip includes two alarm signal output pins, and the two alarm signal output pins are respectively connected to the single-chip microcomputer.

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