Multifunctional micro power grid interconnection equipment

Abstract

The invention discloses multifunctional micro-grid interconnection equipment which comprises a host inversion module, a slave inversion module, a sampling detection module, an MCU core processing module, a transformer module, a protection circuit module and an auxiliary power supply module. Based on the micro-grid interconnection requirement, intelligent switching of three working modes including an independent working mode, a parallel working mode and a grid-connected working mode is supported, and the micro-grid interconnection system is suitable for interconnection work of a micro-grid interconnection system and multi-purpose electric appliances. In an independent working mode, the equipment provides a function of converting 30-50V direct current into 24V alternating current, and has a closed-loop control stable output voltage; in the parallel working mode, the host inversion module and the slave inversion module are in phase-locked parallel connection to form a micro-grid system; in the grid-connected mode, the transformer module transforms 220V alternating current commercial power into 24V alternating current, and performs phase synchronization and power control with the inversion module to realize grid connection. The invention provides a brand new solution for interconnection and combination of the new energy electric appliance and the micro-grid.

Description

Technical Field

[0001] The invention relates to the fields of switching power supply technology, digital control technology, electric energy conversion and electrical automation, and is a multifunctional microgrid interconnection device specially used for ensuring the safety and stability of multi-electrical appliances in parallel operation and microgrid interconnection. Background Art

[0002] With the rapid economic development, the power electronics industry is actively integrating into the construction of the Internet of Things. The power electronics system is developing towards both independent working mode and collaborative working mode, which requires more intelligent control and switching. The core issue lies in the combination of switching power supply power conversion and phase-locked synchronous control technology. High-efficiency switching power supply power conversion is based on hardware to realize functional circuits, and high-performance phase-locked synchronous control technology is based on software and hardware to realize phase-locked loops.

[0003] In addition, considering the importance that society attaches to the new energy industry, the new energy vehicle industry has received much attention. Its internal power conversion system and external adaptation working environment are also development directions worthy of attention. In order to achieve the reasonable conversion and controllable output of the battery power of new energy vehicles, the effective combination of switching power supply and synchronization technology is also required.

[0004] In summary, in order to meet the needs of different application fields, it is necessary to design a multifunctional microgrid interconnection device with safe and reliable working performance. Summary of the invention

[0005] The purpose of the present invention is to provide a multifunctional microgrid interconnection device, which combines switching power supply, synchronization technology and automatic control technology, and proposes a new solution for the microgrid interconnection power supply system that can work in coordination, in order to solve the problem of combining high-efficiency power conversion with high-performance phase-locked control. The present invention has three working mode switching: independent-parallel-grid-connected. Each power module uses dual closed-loop control and phase-locked loop control. The operation effect is monitored in real time through the sampling detection module, and the protection circuit module enhances the safety performance of the equipment.

[0006] The specific technical solution for achieving the purpose of the present invention is:

[0007] A multifunctional microgrid interconnection device, characterized in that: the device includes a host inverter module, a slave inverter module, a sampling detection module, an MCU core processing module, a transformer module, a protection circuit module and an auxiliary power supply module;

[0008] The host inverter module is respectively connected to the slave inverter module, the sampling detection module, the MCU core processing module, the transformer module, the protection circuit module and the auxiliary power supply module;

[0009] The slave inverter module is respectively connected to the host inverter module, the sampling detection module, the MCU core processing module, the transformer module, the protection circuit module and the auxiliary power supply module;

[0010] The sampling detection module is respectively connected to the host inverter module, the slave inverter module, the MCU core processing module, the transformer module and the auxiliary power supply module.

[0011] The MCU core processing module is respectively connected to the host inverter module, the slave inverter module, the sampling detection module, the protection circuit module and the auxiliary power supply module;

[0012] The transformer module is connected to the host inverter module, the slave inverter module and the sampling detection module respectively.

[0013] The protection circuit module is respectively connected to the host inverter module, the slave inverter module, the MCU core processing module and the auxiliary power supply module;

[0014] The auxiliary power supply module is respectively connected to the host inverter module, the slave inverter module, the sampling detection module, the MCU core processing module and the protection circuit module;

[0015] The host inverter module, the slave inverter module and the transformer module are closed and disconnected through air switches and relays to achieve intelligent switching between independent, parallel and grid-connected working modes;

[0016] The sampling detection module collects the output voltage amplitude phase and inductor current of the host inverter module and the slave inverter module, and collects the mains power grid amplitude and phase information of the transformer module;

[0017] The MCU core processing module obtains data from the sampling detection module, is connected to the host inverter module, the slave inverter module and the protection circuit module, and provides control signals therefor;

[0018] The protection circuit module enhances the safety performance of human-machine interaction of the device;

[0019] The auxiliary power supply module supplies power to each module;

[0020] In the independent working mode, the host inverter module works alone, calling the voltage and current double closed-loop control algorithm in the MCU core processing module to stabilize the output voltage and adjust the output current;

[0021] In the parallel working mode, the host and slave inverter modules use master-slave control. The slave inverter module calls the improved SOGI phase-locked loop algorithm in the MCU core processing module to track the host inverter module. After detecting that the phase error is within 2%, the MCU core processing module enables the slave inverter module control signal and calls the voltage and current dual closed-loop control algorithm in the MCU core processing module to stabilize the output voltage and adjust the output current of the host and slave inverter modules to achieve the parallel function.

[0022] In the grid-connected working mode, the host and slave inverter modules are connected to the mains through the transformer module, and droop control is selected. The host and slave inverter modules first call the improved SOGI phase-locked loop algorithm in the MCU core processing module to track the mains phase. The MCU core processing module enables the control signals of the host and slave to complete the grid-connected phase conditions, and then sets the power output limit of the host and slave inverter modules, and calls the voltage and current dual closed-loop control algorithm in the MCU core processing module to ensure that their output does not exceed the demand of the power grid and maintain the stable operation of the power grid.

[0023] Furthermore, the host inverter module and the slave inverter module have the same structure, including an optocoupler isolation circuit, a gate drive circuit, a full-bridge inverter circuit and a filter circuit connected in sequence, wherein the full-bridge inverter circuit and the filter circuit constitute the power part of the module, and the optocoupler isolation circuit and the gate drive circuit constitute the control part of the module; in the power part, a 30-50V DC power input is used as the bus voltage of the full-bridge inverter circuit, and a square wave signal of a corresponding level of 30-50V between the bridge arms is obtained by diagonally switching the switch tube, and the filter circuit uses a first-order LC filter with a cut-off frequency of 2KHz to filter out the high-frequency components of the square wave level signal between the bridge arms to obtain a 24V 50Hz sine wave output; in the control part, the optocoupler isolation circuit includes a TLP250 chip, the gate drive circuit includes an IR2104 chip, the bipolar pulse width modulation SPWM control signal generated by the MCU core processing module received by the optocoupler isolation circuit is electrically isolated from the front and back stages through the TLP250 chip, the output of the TLP250 chip is transmitted to the gate drive circuit, and two pairs of mutually inverted SPWM control signals are generated through the IR2104 chip, which are then connected between the gate-source electrodes of the four MOSFET switch tubes in the full-bridge inverter circuit of the power part to control the full-bridge switch tube to switch to diagonal conduction.

[0024] Furthermore, the sampling detection module includes a voltage signal acquisition circuit and a current signal acquisition circuit. The voltage signal acquisition circuit includes an isolation op amp chip AMC1200BDWVR and a precision op amp chip GS8552-SR. The voltage signal to be sampled is proportionally amplified by a resistor divider and then input into the isolation op amp chip. The output of the isolation op amp chip is then sent to the precision op amp chip, and the corresponding conversion output voltage range of the voltage signal to be sampled is controlled within 0-3.3V; the current signal acquisition circuit includes a current transformer chip CC6920SO-5A and a precision op amp chip GS8552-SR. The current signal to be sampled is first sent to the current transformer chip connected in series in the circuit, and the output of the current transformer chip is then sent to the precision op amp chip, and the corresponding conversion output voltage range of the current signal to be sampled is controlled within 0-3.3V.

[0025] Furthermore, the MCU core processing module is an STM32F407ZGT6 core board, which contains interconnected functional modules ADC module, timer module and OLED display module; the MCU core processing module is embedded with a voltage and current dual closed-loop control algorithm and an improved SOGI phase-locked loop algorithm, the voltage and current dual closed-loop control algorithm uses a current inner loop based on a PI controller and a voltage outer loop based on a PR controller, and an S domain model is obtained according to the topological structure of the host and slave inverter modules, and then the continuous system is discretized, the MCU core processing module obtains the voltage amplitude information of the master and slave inverter modules collected by the sampling detection module, and sends it to the PI and PR controllers in the dual loops, and compares it with the preset value. The modulation ratio of the SPWM control signal is corrected by line feedback to achieve voltage stabilization and current control; the improved SOGI phase-locked loop algorithm includes a SOGI generator, a dq rotating coordinate transformation, a PI controller and a resonant feedback integral link. The SOGI generator obtains the voltage amplitude and phase information of the host inverter module and the amplitude and phase AC quantity information of the main power grid collected by the sampling detection module, and can generate an alpha-axis component of the measured AC voltage with a phase difference of 90° and a beta-axis component with a phase difference of 90° from the measured AC voltage. The dq rotating coordinate transformation requires two sinusoidal signals with a phase difference of 90° as input signals. The two orthogonal components alpha and beta generated by SOGI are transformed by Park to obtain the d-axis component of the rotating coordinate system. and the q-axis component , where the phase value required for Park transformation is the phase value feedback output by the resonant feedback integral link; the PI regulator obtains The value is output, and the instantaneous angular frequency value of the sampled signal is obtained by the resonant feedback integral link. The improved version replaces the preset resonant frequency in the integral link with the output voltage of the host inverter module or the angular frequency of the mains grid obtained by real-time sampling, and then the required phase value is obtained by integrating the angular frequency.

[0026] In the data collection and processing stage, the input port of the MCU core processing module is connected to the sampling detection module, the sampling detection module collects the amplitude and phase information of the host inverter module, the slave inverter module output and the mains, and sends them to the ADC module of the MCU core processing module, and displays the real-time detection data through the OLED display module; in the control signal output stage, the output port of the MCU core processing module is connected to the host inverter module and the slave inverter module, and the voltage and current dual closed-loop control algorithm and the improved SOGI phase-locked loop algorithm are called through the timer module to adjust the SPWM control signal output by the core board in real time.

[0027] Furthermore, the transformer module is only used in the mains grid-connected working mode, and the mains 220V AC is reduced to 24V AC and then connected to the main and slave inverter modules; the winding ratio is calculated in combination with the transformer step-down ratio, that is, the ratio of the number of turns on the high-voltage side and the low-voltage side. The theoretical winding ratio is 220 / 24 = 9.17, and the winding ratio of 10:1 is selected in the actual design.

[0028] Furthermore, the protection circuit module is used for safety confirmation and risk protection of function switching. In the three working modes, fuses and thermistors are used to prevent overcurrent and overheating of the inverter module; in the parallel and grid-connected working modes, infrared transmitting tubes are used for secondary confirmation of phase tracking; in the intelligent switching of working modes, air switches and relays are used for safe operation.

[0029] Furthermore, the auxiliary power supply module includes a three-way linear regulator chip and an isolated power supply chip. The DC input of the power part of the host and slave inverter modules passes through the three-way linear regulator chip to convert the 30-50V DC input into three outputs of 3.3V, 5V and 12V. The three voltages are electrically isolated from each other through the isolated power supply chip to power each module.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1) The present invention uses the STM32 series core board to control the output of the bipolar SPWM control signal, drives the full-bridge inverter circuit through optical coupling isolation, and is connected to the power grid through transformer boosting, so as to have a strong ability to drive the inductive load.

[0032] 2) The present invention uses a voltage-current dual closed-loop control algorithm and an improved SOGI phase-locked loop algorithm. The voltage-current dual closed-loop algorithm is designed based on the circuit topology, and the voltage feedforward is added to improve the response speed, thereby achieving a stable control effect of the inverter output voltage. The improved SOGI phase-locked loop algorithm uses real-time sampling angular frequency resonant feedback to improve phase tracking performance.

[0033] 3) The present invention uses the optocoupler isolation chip TLP250 and the gate drive chip IR2104 to achieve safe electrical isolation while providing a new gate drive solution for the combination of MOSFET and single-chip microcomputer under the premise of ensuring performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural block diagram of the present invention;

[0035] Figure 2 The main inverter module and the slave inverter module circuit block diagram of the present invention;

[0036] Figure 3 This is the voltage and current dual closed-loop algorithm control block diagram;

[0037] Figure 4 This is the control block diagram of the improved SOGI phase-locked loop algorithm;

[0038] Figure 5 It is the work flow chart of the present invention. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0040] See also Figure 1 The present invention includes a host inverter module 1, a slave inverter module 2, a sampling detection module 3, an MCU core processing module 4, a transformer module 5, a protection circuit module 6 and an auxiliary power supply module 7.

[0041] The host inverter module 1 is connected to the slave inverter module 2, the sampling detection module 3, the MCU core processing module 4, the transformer module 5, the protection circuit module 6, and the auxiliary power supply module 7 respectively.

[0042] The slave inverter module 2 is connected to the host inverter module 1, the sampling detection module 3, the MCU core processing module 4, the transformer module 5, the protection circuit module 6, and the auxiliary power supply module 7 respectively.

[0043] The sampling detection module 3 is connected to the host inverter module 1, the slave inverter module 2, the MCU core processing module 4, the transformer module 5, and the auxiliary power supply module 7 respectively.

[0044] The MCU core processing module 4 is connected to the host inverter module 1 , the slave inverter module 2 , the sampling detection module 3 , the protection circuit module 6 , and the auxiliary power supply module 7 respectively.

[0045] The transformer module 5 is connected to the host inverter module 1 , the slave inverter module 2 , and the sampling detection module 3 respectively.

[0046] The protection circuit module 6 is connected to the host inverter module 1 , the slave inverter module 2 , the MCU core processing module 4 , and the auxiliary power supply module 7 respectively.

[0047] The auxiliary power supply module 7 is connected to the host inverter module 1, the slave inverter module 2, the sampling detection module 3, the MCU core processing module 4, and the protection circuit module 6.

[0048] See also Figure 2 The host inverter module 1 of the present invention includes a full-bridge inverter circuit, an optocoupler isolation circuit, a gate drive circuit, and a filter circuit. The MCU core processing module 4 generates a bipolar SPWM control signal, and controls the MOSFET switch tube in the full-bridge inverter circuit to switch diagonal conduction through the conversion of the optocoupler isolation chip TLP250 and the gate drive chip IR2104. The filter circuit converts the electrical level between the bridge arms into a standard sine wave output. The host inverter module 1 includes two function switching interfaces, the parallel interface is connected to the slave inverter module 2, and the grid-connected interface is connected to the transformer module 5. The two interfaces are respectively connected to an air switch. In the independent working mode, both interface switches are disconnected. In the parallel working mode, only the parallel interface switch is closed. In the grid-connected working mode, both the grid-connected interface switch and the parallel interface switch are closed.

[0049] The hardware structure of the slave inverter module 2 of the present invention is the same as that of the host inverter module 1. The module includes two function switching interfaces, the parallel interface is connected to the host inverter module 1, and the grid interface is connected to the transformer module 5. The two interfaces are respectively connected to an air switch. In the independent working mode, both interface switches are disconnected. In the parallel working mode, only the parallel interface switch is closed. In the grid-connected working mode, both the grid-connected interface switch and the parallel interface switch are closed.

[0050] The sampling detection module 3 of the present invention comprises an isolation amplifier chip AMC1200BDWVR, a precision amplifier chip GS8552-SR and a current transformer chip CC6920SO-5A, which isolates the voltage and current signals and converts them into small voltage signals within 0-3.3V. The input is connected to the host inverter module 1, the output of the slave inverter module 2, and the transformer module 5. The output is connected to the ADC sampling module of the MCU core processing module.

[0051] The MCU core processing module 4 of the present invention includes an STM32F407ZGT6 core board. The input interface is connected to the sampling detection module 3, and the output and power grid information of the collected host inverter module 1 and the slave inverter module 2 are obtained. Through the voltage and current double closed-loop control algorithm and the improved SOGI phase-locked loop algorithm, the inverter voltage stabilization control and the inverter parallel grid control are completed. The output interface is connected to the host inverter module 1, the slave inverter module 2, and the protection circuit module 6, and the SPWM control signal is output to the optical coupler isolation drive of the host inverter module 1 and the slave inverter module 2, and the output enable signal is output to the protection circuit module 6.

[0052] The transformer module 5 of the present invention includes two function switching interfaces. Both interfaces are grid-connected function interfaces, each of which is connected to an air switch and is in a closed state in the grid-connected working mode.

[0053] The protection circuit module 6 of the present invention has an input interface and two output interfaces. The input interface is connected to the MCU core processing module 4 to obtain the enable control signal. The output interface is connected to the host inverter module 1 and the slave inverter module 2 to control the drive signal and the parallel grid-connected switch.

[0054] The auxiliary power supply module 7 of the present invention can output mutually isolated 3.3V, 5V, and 12V voltages to supply power to each module.

[0055] See also Figure 5 , the present invention works like this:

[0056] First, the configuration of each module in the MCU core processing module is initialized and the submodule is called, and the clock and timer are initialized. Among them, the TIM2 timer is responsible for ADC sampling, the TIM3 timer is responsible for calling the SOGI phase-locked loop, and the TIM4 is responsible for the generation of the SPWM control signal. The TIM2 timer generates interrupts at a frequency of 20kHz, and each interrupt obtains an ADC sampling value. The sampling value of each sine wave cycle (50Hz) is converted into the effective value of the sine wave output signal of the cycle by the corresponding sampling point level conversion calculation; the TIM3 timer generates interrupts at a frequency of 5kHz, and the TIM2 timer ADC sampling value is used as the input of the SOGI phase-locked loop algorithm. The sampling value in each sine wave cycle is calculated by SOGI-dq phase locking, and 100 phase values ​​are output in one sine wave cycle; the TIM4 timer generates interrupts at a frequency of 20kHz, and the comparison value is set according to the preset sine table data at this frequency to realize the generation of the SPWM wave. At this time, the preset modulation ratio of the SPWM wave is 0.6, and this modulation ratio is limited to between 0.35-0.95. It runs at a frequency of 10ms and is responsible for the real-time display of the OLED. The displayed parameters include output voltage amplitude and grid information.

[0057] After all configurations and initializations are completed, the interrupt in the While loop is triggered. In the interrupt service function, the input voltage signal is first sampled, and the coordinate conversion is performed, and the SOGI phase-locked loop program is executed to phase-lock the parallel inverter grid voltage; then the voltage loop and current loop are controlled, and the target value obtained by the loop control is modified to the SPWM modulation ratio; finally, the output SPWM control signal is enabled.

[0058] The external 30-50V DC input host inverter module 1 and slave inverter module 2, the external AC effective value 220V input transformer module 5. In the single inverter independent working mode, the auxiliary power supply module 7 supplies power to the host inverter module 1, the sampling detection module 3, the MCU core processing module 4 and the protection circuit module 6. The sampling detection module 3 collects the output voltage amplitude of the host inverter module 1, and sends it to the MCU core processing module 4 to call the voltage and current dual closed-loop control algorithm, and adjusts the modulation ratio of the SPWM output signal in real time to achieve the voltage stabilization output of the host inverter module 1; in the multi-inverter parallel working mode, the host inverter module 1 and the slave inverter module 2 respectively call the voltage and current dual closed-loop control algorithm in the independent working mode to achieve voltage stabilization. At the same time, the sampling detection module 3 collects the output voltage amplitude phase of the host inverter module 1, and sends it to the MCU core processing module 4 to call the improved SOGI phase-locked loop algorithm. After obtaining the accurate phase, the start number table position set by the sine table data is adjusted to complete the slave inverter module 2. The phase tracking of the host inverter module 1 determines that the phase difference between the host inverter module 1 and the slave inverter module 2 is less than 2%, and enables the SPWM output signal of the slave inverter module 2, and at the same time enables the control signal of the protection circuit module 6, closes the relay switch between the host inverter module 1 and the slave inverter module 2, and completes the parallel function; in the mains grid-connected working mode, such as calling the dual closed-loop and phase-locked loop algorithms in the independent and parallel working modes, the host inverter module 1 and the slave inverter module 2 perform phase-locked tracking on the voltage module 5, and at the same time achieve output voltage regulation through the dual closed-loop algorithm, and set power output limits for the host inverter module 1 and the slave inverter module 2 through droop control. After the current sharing and phase-locked tracking are completed, the control signal of the protection circuit module 6 is enabled to close the relays between the host inverter module 1, the slave inverter module 2 and the transformer module 5 to complete the grid-connected function.

Claims

1. A multifunctional microgrid interconnection device, It is characterized in that The device includes a host inverter module, a slave inverter module, a sampling detection module, an MCU core processing module, a transformer module, a protection circuit module and an auxiliary power supply module; The host inverter module is respectively connected to the slave inverter module, the sampling detection module, the MCU core processing module, the transformer module, the protection circuit module and the auxiliary power supply module; The slave inverter module is respectively connected to the host inverter module, the sampling detection module, the MCU core processing module, the transformer module, the protection circuit module and the auxiliary power supply module; The sampling detection module is respectively connected to the host inverter module, the slave inverter module, the MCU core processing module, the transformer module and the auxiliary power supply module; The MCU core processing module is respectively connected to the host inverter module, the slave inverter module, the sampling detection module, the protection circuit module and the auxiliary power supply module; The transformer module is respectively connected to the host inverter module, the slave inverter module, and the sampling detection module; The protection circuit module is respectively connected to the host inverter module, the slave inverter module, the MCU core processing module and the auxiliary power supply module; The auxiliary power supply module is respectively connected to the host inverter module, the slave inverter module, the sampling detection module, the MCU core processing module and the protection circuit module; The host inverter module, the slave inverter module and the transformer module are closed and disconnected through air switches and relays to achieve intelligent switching between independent, parallel and grid-connected working modes; The sampling detection module collects the output voltage amplitude phase and inductor current of the host inverter module and the slave inverter module, and collects the mains power grid amplitude and phase information of the transformer module; The MCU core processing module obtains data from the sampling detection module, is connected to the host inverter module, the slave inverter module and the protection circuit module, and provides control signals therefor; The protection circuit module enhances the safety performance of human-machine interaction of the device; The auxiliary power supply module supplies power to each module; In the independent working mode, the host inverter module works alone, calling the voltage and current double closed-loop control algorithm in the MCU core processing module to stabilize the output voltage and adjust the output current; In the parallel working mode, the host and slave inverter modules use master-slave control. The slave inverter module calls the improved SOGI phase-locked loop algorithm in the MCU core processing module to track the host inverter module. After detecting that the phase error is within 2%, the MCU core processing module enables the slave inverter module control signal and calls the voltage and current dual closed-loop control algorithm in the MCU core processing module to stabilize the output voltage and adjust the output current of the host and slave inverter modules to achieve the parallel function. In the grid-connected working mode, the host and slave inverter modules are connected to the mains through the transformer module, and droop control is selected. The host and slave inverter modules first call the improved SOGI phase-locked loop algorithm in the MCU core processing module to track the mains phase. The MCU core processing module enables the control signals of the host and slave to complete the grid-connected phase conditions, and then sets the power output limit of the host and slave inverter modules, and calls the voltage and current dual closed-loop control algorithm in the MCU core processing module to ensure that their output does not exceed the demand of the power grid and maintain the stable operation of the power grid.

2. The device according to claim 1, It is characterized in that The host inverter module and the slave inverter module have the same structure, including an optocoupler isolation circuit, a gate drive circuit, a full-bridge inverter circuit and a filter circuit connected in sequence. The full-bridge inverter circuit and the filter circuit constitute the power part of the module, and the optocoupler isolation circuit and the gate drive circuit constitute the module control part; in the power part, the power input 30-50V DC is used as the bus voltage of the full-bridge inverter circuit, and the square wave signal of the corresponding level of 30-50V between the bridge arms is obtained by diagonally switching the switch tube. The filter circuit uses a first-order LC filter with a cut-off frequency of 2KHz to filter out the high-frequency components of the square wave level signal between the bridge arms to obtain 24V 50Hz sine wave output; in the control part, the optocoupler isolation circuit includes a TLP250 chip, the gate drive circuit includes an IR2104 chip, the bipolar pulse width modulation SPWM control signal generated by the MCU core processing module received by the optocoupler isolation circuit is electrically isolated from the front and back stages through the TLP250 chip, the output of the TLP250 chip is transmitted to the gate drive circuit, and two pairs of mutually inverted SPWM control signals are generated through the IR2104 chip, which are then connected between the gate-source electrodes of the four MOSFET switch tubes in the full-bridge inverter circuit of the power part to control the full-bridge switch tube to switch to diagonal conduction.

3. The device according to claim 1, It is characterized in that The sampling detection module includes a voltage signal acquisition circuit and a current signal acquisition circuit. The voltage signal acquisition circuit includes an isolation amplifier chip AMC1200BDWVR and a precision amplifier chip GS8552-SR. The voltage signal to be sampled is proportionally amplified by a resistor divider and then input into the isolation amplifier chip. The output of the isolation amplifier chip is then sent to the precision amplifier chip, and the corresponding conversion output voltage range of the voltage signal to be sampled is controlled within 0-3.3V; the current signal acquisition circuit includes a current transformer chip CC6920SO-5A and a precision amplifier chip GS8552-SR. The current signal to be sampled is first sent to the current transformer chip connected in series in the circuit, and the output of the current transformer chip is then sent to the precision amplifier chip, and the corresponding conversion output voltage range of the current signal to be sampled is controlled within 0-3.3V.

4. The device according to claim 1, It is characterized in that The MCU core processing module is an STM32F407ZGT6 core board, which contains interconnected functional modules ADC module, timer module and OLED display module; the MCU core processing module is embedded with a voltage and current dual closed-loop control algorithm and an improved SOGI phase-locked loop algorithm, the voltage and current dual closed-loop control algorithm uses a current inner loop based on a PI controller and a voltage outer loop based on a PR controller, and derives an S domain model according to the topological structure of the host and slave inverter modules, and then discretizes the continuous system, the MCU core processing module obtains the voltage amplitude information of the master and slave inverter modules collected by the sampling detection module, and sends it to the PI and PR controllers in the dual loops, and feedback corrects the modulation ratio of the SPWM control signal by comparing it with the preset value to achieve voltage stabilization and current control; the improved SOGI phase-locked loop algorithm includes a SOGI generator, a dq rotation coordinate transformation, a PI controller and a resonant feedback integral link, S The OGI generator obtains the voltage amplitude and phase information of the host inverter module and the amplitude and phase AC quantity information of the mains power grid collected by the sampling detection module, and can generate the alpha axis component of the measured AC voltage with a phase difference of 90° and the beta axis component with a phase difference of 90°. The dq rotating coordinate transformation requires two sinusoidal signals with a phase difference of 90° as input signals. The two orthogonal components alpha and beta generated by SOGI are transformed by Park to obtain the d axis component and q axis component of the rotating coordinate system, wherein the phase value required by the Park transformation is the phase value feedback output by the resonant feedback integral link; the PI regulator obtains the value and outputs the value of the instantaneous angular frequency of the sampled signal, and the resonant feedback integral link obtains the instantaneous angular frequency value. The improved version replaces the preset resonant frequency in the integral link with the output voltage of the host inverter module or the angular frequency of the mains power grid obtained by real-time sampling, and then integrates the angular frequency to obtain the required phase value; In the data collection and processing stage, the input port of the MCU core processing module is connected to the sampling detection module, the sampling detection module collects the amplitude and phase information of the host inverter module, the slave inverter module output and the mains, and sends them to the ADC module of the MCU core processing module, and displays the real-time detection data through the OLED display module; in the control signal output stage, the output port of the MCU core processing module is connected to the host inverter module and the slave inverter module, and the voltage and current dual closed-loop control algorithm and the improved SOGI phase-locked loop algorithm are called through the timer module to adjust the SPWM control signal output by the core board in real time.

5. The device according to claim 1, It is characterized in that The transformer module is only used in the mains grid-connected working mode, and the mains 220V AC is reduced to 24V AC and then connected to the main and slave inverter modules. The winding ratio is calculated based on the transformer step-down ratio, that is, the ratio of the number of turns on the high-voltage side and the low-voltage side. The theoretical winding ratio is 220 / 24 = 9.17, and the actual design chooses a winding ratio of 10:

1.

6. The device according to claim 1, It is characterized in that The protection circuit module is used for safety confirmation and risk protection of function switching. In the three working modes, fuses and thermistors are used to prevent overcurrent and overheating of the inverter module; in the parallel and grid-connected working modes, infrared transmitting tubes are used for secondary confirmation of phase tracking; in the intelligent switching of working modes, air switches and relays are used for safe operation.

7. The device according to claim 1, It is characterized in that The auxiliary power supply module includes a three-way linear regulator chip and an isolated power supply chip. The DC input of the power part of the master and slave inverter modules is converted into three outputs of 3.3V, 5V and 12V through the three-way linear regulator chip. The three voltages are electrically isolated from each other through the isolated power supply chip to power each module.

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