Parameter control method of bidirectional power conversion circuit for alternating current and direct current electric energy exchange

Abstract

The invention discloses a parameter control method for a bidirectional power conversion circuit with alternating current and direct current electric energy interchange, which relates to the technical field of circuit parameter control, and comprises the following steps: respectively carrying out electric energy conversion on an alternating current side and electric energy adjustment on a direct current side by adopting a topological structure in which a three-phase voltage source type converter and a direct current circuit bidirectional converter are connected in series; collecting parameters of the AC-DC bidirectional power converter in real time; switching among three working modes of rectification, inversion and shutdown is realized; the DC bus voltage is kept at a rated value when supply and demand in the DC subnet are balanced, and bidirectional flow of power is realized when supply and demand are unbalanced; performing coordinate transformation on the acquired voltage and current; and separating positive and negative sequence components of the voltage by using a second-order generalized integrator algorithm. By adopting a specific topological structure and utilizing the droop characteristic to realize working mode switching, the adaptability and the control precision of the bidirectional power converter in the alternating current and direct current hybrid micro-grid are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit parameter control, and in particular to a method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange. Background Art

[0002] With the increasing number of distributed energy sources, AC / DC hybrid microgrids have attracted more and more attention as an effective means of efficiently utilizing distributed energy sources. In AC / DC hybrid microgrids, bidirectional power converters are the core devices for achieving energy control.

[0003] Traditional bidirectional power converter control strategies often use traditional control methods of converters, such as dual closed-loop control, constant power control, V / F control, etc. However, these methods do not fully consider the characteristics of AC / DC hybrid microgrids, so there are certain limitations in practical applications. Traditional bidirectional power converter control strategies are often only applicable to specific application scenarios. They are not adaptable enough to complex and changeable system environments such as AC / DC hybrid microgrids, and may be inflexible in switching working modes. Under unbalanced grid conditions, traditional bidirectional power converters may not be able to effectively handle voltage and current imbalances. Summary of the invention

[0004] In order to solve the above technical problems, a method for controlling parameters of a bidirectional power conversion circuit for AC / DC power interchange is provided. This technical solution solves the problems raised in the above background technology.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is: A method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange, comprising: A topology structure in which a three-phase voltage source converter and a DC circuit bidirectional converter are connected in series is used to perform power conversion on the AC side and power regulation on the DC side respectively; By installing sensors, the input and output voltage and current parameters of the AC / DC bidirectional power converter are collected in real time; By utilizing the droop characteristics of the DC output side and judging the operating status of the system according to the DC microgrid bus voltage, the AC / DC bidirectional power converter can be switched between the three working modes of rectification, inversion and shutdown. By adjusting the active power droop coefficient, the DC bus voltage and transmission power are controlled, the DC bus voltage is kept at the rated value when the supply and demand are balanced within the DC subnet, and bidirectional power flow is achieved when the supply and demand are unbalanced; Under balanced working conditions, the collected voltage and current are transformed into coordinates, and their coordinate components are controlled by a proportional-integral controller, and the output current command value enters the current inner loop; Under unbalanced working conditions, the second-order generalized integrator algorithm is used to separate the positive and negative sequence components of the voltage, and the separated positive and negative sequence components are synchronously controlled respectively; Monitor the system's operating status and parameters in real time. When an abnormality or fault is found, cut off the source of the fault and start the backup power supply.

[0006] Preferably, the topology structure of a three-phase voltage source converter and a DC circuit bidirectional converter connected in series to respectively perform power conversion on the AC side and power regulation on the DC side specifically includes: The three-phase voltage source converter adopts a dual closed-loop control structure with voltage outer loop and current inner loop to track and control the grid-connected current; The three-phase voltage source converter receives three-phase AC power from the grid or generator; Inside the three-phase voltage source converter, the unidirectional conductivity of the diode is used to convert AC power into DC power through a rectifier circuit; The three-phase voltage source converter controls the output voltage and current by adjusting the pulse width and frequency, and realizes the smooth conversion of electric energy; The DC circuit bidirectional converter adopts a double closed-loop structure, with the inductor current as the control variable in the inner control loop and the capacitor voltage as the control variable in the outer control loop to control the stability of the DC bus voltage. The DC circuit bidirectional converter receives DC power from the three-phase voltage source converter; Based on the load demand and the requirements of the energy storage system, the DC circuit bidirectional converter accurately regulates the DC power; When energy flows from a DC source to another DC load, the voltage reduction or voltage increase function is realized by controlling the on and off of the switch tube, converting the DC power into DC power of a preset voltage level; The regulated DC power is converted back to AC power via an additional inverter circuit; The regulated DC power is supplied to the energy storage system for charging or discharging.

[0007] Preferably, the method of utilizing the droop characteristics of the DC output side, judging the operating state of the system according to the DC microgrid bus voltage, and realizing the switching of the AC / DC bidirectional power converter between the three working modes of rectification, inversion and shutdown specifically includes: During system operation, the DC microgrid bus voltage and AC / DC subgrid load conditions are continuously monitored, and the working mode of the AC / DC bidirectional power converter is dynamically adjusted based on real-time data; Determine whether the DC subnet load power is greater than the rated power, or whether the DC microgrid bus voltage is lower than a first preset threshold value. If so, switch the working mode of the AC / DC bidirectional power converter to the rectification mode, and transfer power from the AC subnet to the DC subnet. If not, do not output; Determine whether the load power of the AC subgrid is greater than the rated power, or the bus voltage of the DC microgrid is higher than the second preset threshold. If so, switch the working mode of the AC / DC bidirectional power converter to the inverter mode, and transfer power from the DC subgrid to the AC subgrid. If not, the output DC microgrid bus voltage is within a stable range, and the power output of the internal power supply of the AC / DC subgrid meets the load requirements. No power exchange is performed, and the working mode of the AC / DC bidirectional power converter is switched to the shutdown mode.

[0008] Preferably, the controlling of the DC bus voltage and the transmission power by adjusting the active power droop coefficient, maintaining the DC bus voltage at a rated value when the supply and demand in the DC subnet are balanced, and realizing the bidirectional flow of power when the supply and demand are unbalanced specifically includes: S101: Based on the design requirements of the DC subnet, determine the rated value of the DC bus voltage and set the initial active power droop coefficient, which determines the response speed and amplitude of the bus voltage when the power changes; S102: When the supply and demand are balanced, that is, the load demand is equal to the output power of the micro-source, the DC bus voltage is kept near the rated value through a droop control strategy; S103: When the actual DC bus voltage deviates from the rated value, the output power of the micro source is adjusted according to the droop coefficient to maintain voltage stability; S104: monitoring the actual value of the DC bus voltage in real time through a voltage sensor, calculating the imbalance degree of the current system supply and demand state according to the difference between the real-time monitored bus voltage and the rated voltage, and outputting it as a power deviation; S105: obtaining the output power of the distributed power source that needs to be adjusted by calculating the product of the power deviation and the droop coefficient, and adjusting the output power of the distributed power source by controlling the switching device of the distributed power source to respond to the power deviation; S106: Determine whether the difference between the adjusted bus voltage value and the rated value is greater than a preset difference threshold value, if so, return to step S104, if not, do not output; S107: Based on the real-time monitoring of system load changes, dynamically adjust the droop coefficient to improve the response speed to load changes and the stability of the bus voltage.

[0009] Preferably, under the balanced working condition, coordinate transformation is performed on the collected voltage and current, and the coordinate components are controlled by a proportional integral controller, and the output current command value enters the current inner loop, specifically comprising: The voltage or current signal in the three-phase circuit is collected by the sensor, and the three-phase voltage or current signal is placed on the A, B, and C axes of the three-phase ABC coordinate system respectively; Using the first coordinate transformation formula, the three-phase voltage or current signal is transformed from the three-phase ABC coordinate system to the two-phase Stationary coordinate system; The DQ rotating coordinate system is determined by obtaining the angle between the electronic rotor and the stator reference axis. The rotation angle between the stationary coordinate systems; Based on the rotation angle, the two phases are transformed using the second coordinate transformation formula. The voltage or current component in the stationary coordinate system is transformed into the two-phase DQ rotating coordinate system to obtain the voltage or current component in the two-phase DQ rotating coordinate system; The voltage and current components in the DQ coordinate system after coordinate transformation are input into the proportional-integral controller; Design proportional-integral controller based on system requirements and control objectives; The proportional-integral controller calculates the required control quantity based on the input voltage and current components and the preset reference value, adjusts the output voltage and current of the distributed power supply or inverter, and maintains the stability of the DC bus voltage; The first coordinate transformation formula is: , In the formula, They are the coordinate components of the voltage or current signal in the three-phase circuit in the three-phase ABC coordinate system, Two-phase The coordinate components of the voltage or current signal in the stationary coordinate system; The second coordinate transformation formula is: , In the formula, They are the coordinate components of the voltage or current signal in the two-phase DQ rotating coordinate system, The DQ rotation coordinate system is The rotation angle between the stationary coordinate systems.

[0010] Preferably, under the unbalanced working condition, the positive and negative sequence components of the voltage are separated by using a second-order generalized integrator algorithm, and the separated positive and negative sequence components are synchronously controlled respectively, specifically including: In two phases In the stationary coordinate system, the grid phase voltage is subjected to a 90° phase shift operation to calculate the positive and negative sequence components of the grid phase voltage; Use power conversion equipment to synchronously control positive and negative sequence components, and quickly adjust the grid voltage amplitude through voltage and current dual-loop control; inputting the extracted positive sequence component into the positive sequence control system; The positive sequence control system adjusts the control strategy based on the amplitude and phase information of the positive sequence component to maintain the stability and balance of the grid voltage; inputting the extracted negative sequence component into a negative sequence control system; The negative sequence control system reduces the impact of unbalanced grid voltage on the power system by compensating or suppressing the negative sequence component.

[0011] Preferably, the real-time monitoring of the operating status and parameters of the system, and upon finding an abnormality or fault, cutting off the fault source and starting the backup power supply specifically include: The sensors deployed on the equipment collect the equipment's operating status and parameters in real time, and the collected data is transmitted wirelessly to the central monitoring center; When an abnormality or failure is detected, the system automatically triggers the alarm mechanism; Determine the location and nature of the fault source through comparative analysis; If the fault source poses a threat to the safety of the system or equipment, shut down the faulty equipment, disconnect the power supply, isolate the faulty area and start the backup power supply.

[0012] Compared with the prior art, the present invention has the following beneficial effects: By adopting a topological structure in which a three-phase voltage source converter is connected in series with a DC circuit bidirectional converter, it can better adapt to the characteristics of AC / DC hybrid microgrids, realize the interchange and regulation of electric energy, and use droop control and proportional integral control methods to accurately control parameters, thereby improving the control accuracy and stability of the system, realizing flexible switching of the AC / DC bidirectional power converter between the three working modes of rectification, inversion and shutdown, and effectively solving the voltage and current control problems under unbalanced working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flow chart of the parameter control method of the bidirectional power conversion circuit for AC / DC power interchange of the present invention; Figure 2 A flow chart of a method for converting electric energy on the AC side and regulating electric energy on the DC side according to the present invention; Figure 3 A flow chart of a method for switching an AC / DC bidirectional power converter between three working modes: rectification, inversion and shutdown; Figure 4 A flow chart of a method for controlling DC bus voltage and transmission power by adjusting active power droop coefficient of the present invention; Figure 5 The flowchart of the method for performing coordinate transformation on the collected voltage and current of the present invention; Figure 6 A flow chart of a method for separating positive and negative sequence components of voltage using a second-order generalized integrator algorithm according to the present invention; Figure 7 It is a flow chart of the method for real-time monitoring of the operating status and parameters of the system of the present invention. DETAILED DESCRIPTION

[0014] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0015] Reference Figure 1 As shown, a method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange comprises: A topology structure in which a three-phase voltage source converter and a DC circuit bidirectional converter are connected in series is adopted to respectively perform power conversion on the AC side and power regulation on the DC side; By installing sensors, the input and output voltage and current parameters of the AC / DC bidirectional power converter are collected in real time; By utilizing the droop characteristics of the DC output side and judging the operating status of the system according to the DC microgrid bus voltage, the AC / DC bidirectional power converter can be switched between the three working modes of rectification, inversion and shutdown. By adjusting the active power droop coefficient, the DC bus voltage and transmission power are controlled, the DC bus voltage is kept at the rated value when the supply and demand are balanced within the DC subnet, and bidirectional power flow is achieved when the supply and demand are unbalanced; Under balanced working conditions, the collected voltage and current are transformed into coordinates, and their coordinate components are controlled by a proportional-integral controller, and the output current command value enters the current inner loop; Under unbalanced working conditions, the second-order generalized integrator algorithm is used to separate the positive and negative sequence components of the voltage, and the separated positive and negative sequence components are synchronously controlled respectively; Monitor the system's operating status and parameters in real time. When an abnormality or fault is found, cut off the source of the fault and start the backup power supply.

[0016] Reference Figure 2 As shown, a topology structure in which a three-phase voltage source converter and a DC circuit bidirectional converter are connected in series is used to perform power conversion on the AC side and power regulation on the DC side, respectively. Specifically, the following are included: The three-phase voltage source converter adopts a dual closed-loop control structure with voltage outer loop and current inner loop to track and control the grid-connected current; The three-phase voltage source converter receives three-phase AC power from the grid or generator; Inside the three-phase voltage source converter, the unidirectional conductivity of the diode is used to convert AC power into DC power through a rectifier circuit; The three-phase voltage source converter controls the output voltage and current by adjusting the pulse width and frequency, and realizes the smooth conversion of electric energy; The DC circuit bidirectional converter adopts a double closed-loop structure, with the inductor current as the control variable in the inner control loop and the capacitor voltage as the control variable in the outer control loop to control the stability of the DC bus voltage. The DC circuit bidirectional converter receives DC power from the three-phase voltage source converter; Based on the load demand and the requirements of the energy storage system, the DC circuit bidirectional converter accurately regulates the DC power; When energy flows from a DC source to another DC load, the voltage reduction or voltage increase function is realized by controlling the on and off of the switch tube, converting the DC power into DC power of a preset voltage level; The regulated DC power is converted back to AC power via an additional inverter circuit; The regulated DC power is supplied to the energy storage system for charging or discharging.

[0017] Inside the three-phase voltage source converter, the unidirectional conductivity of the diodes in the rectifier circuit, such as the diode bridge rectifier, is used to convert AC power into DC power. This process includes a filtering circuit to reduce harmonics. The three-phase voltage source converter adjusts the width and frequency of the pulse through pulse width modulation technology to accurately control the output voltage and current to achieve smooth conversion of electrical energy. The pulse width modulation strategy can include sinusoidal pulse width modulation and space vector pulse width modulation.

[0018] Reference Figure 3 As shown in the figure, the droop characteristics of the DC output side are used to judge the operating state of the system according to the DC microgrid bus voltage, and the AC / DC bidirectional power converter is switched between the three working modes of rectification, inversion and shutdown. Specifically, the following are included: During system operation, the DC microgrid bus voltage and AC / DC subgrid load conditions are continuously monitored, and the working mode of the AC / DC bidirectional power converter is dynamically adjusted based on real-time data; Determine whether the DC subnet load power is greater than the rated power, or whether the DC microgrid bus voltage is lower than a first preset threshold value. If so, switch the working mode of the AC / DC bidirectional power converter to the rectification mode, and transfer power from the AC subnet to the DC subnet. If not, do not output; Determine whether the load power of the AC subgrid is greater than the rated power, or the bus voltage of the DC microgrid is higher than the second preset threshold. If so, switch the working mode of the AC / DC bidirectional power converter to the inverter mode, and transfer power from the DC subgrid to the AC subgrid. If not, the output DC microgrid bus voltage is within a stable range, and the power output of the internal power supply of the AC / DC subgrid meets the load requirements. No power exchange is performed, and the working mode of the AC / DC bidirectional power converter is switched to the shutdown mode.

[0019] Ensure that the AC / DC bidirectional power converter and its control system are installed and connected to the DC microgrid bus and the AC subgrid. The bidirectional converter has the ability to receive external control signals, monitor input and output voltage and current, and adjust its own working mode. According to the design specifications of the DC microgrid and based on the safe and stable operation range of the system, the rated power, the first preset threshold, i.e. the lower voltage limit, and the second preset threshold, i.e. the upper voltage limit, are set.

[0020] Reference Figure 4 As shown in the figure, by adjusting the active power droop coefficient, controlling the DC bus voltage and transmission power, the DC bus voltage is kept at the rated value when the supply and demand are balanced within the DC subnet, and the bidirectional flow of power is achieved when the supply and demand are unbalanced. Specifically, the following steps are included: S101: Based on the design requirements of the DC subnet, determine the rated value of the DC bus voltage and set the initial active power droop coefficient, which determines the response speed and amplitude of the bus voltage when the power changes; S102: When the supply and demand are balanced, that is, the load demand is equal to the output power of the micro-source, the DC bus voltage is kept near the rated value through a droop control strategy; S103: When the actual DC bus voltage deviates from the rated value, the output power of the micro source is adjusted according to the droop coefficient to maintain voltage stability; S104: monitoring the actual value of the DC bus voltage in real time through a voltage sensor, calculating the imbalance degree of the current system supply and demand state according to the difference between the real-time monitored bus voltage and the rated voltage, and outputting it as a power deviation; S105: obtaining the output power of the distributed power source that needs to be adjusted by calculating the product of the power deviation and the droop coefficient, and adjusting the output power of the distributed power source by controlling the switching device of the distributed power source to respond to the power deviation; S106: Determine whether the difference between the adjusted bus voltage value and the rated value is greater than a preset difference threshold value, if so, return to step S104, if not, do not output; S107: Based on the real-time monitoring of system load changes, dynamically adjust the droop coefficient to improve the response speed to load changes and the stability of the bus voltage.

[0021] Based on real-time monitoring of system load changes, dynamic adjustment of the droop coefficient can be achieved by analyzing the trend and rate of load changes, using algorithms such as sliding average filters or Kalman filters to predict future load demands, and dynamically adjusting the droop coefficient according to the predicted load demand to improve the response speed to load changes and the stability of the bus voltage. When the load increases rapidly, the droop coefficient can be appropriately reduced to increase the voltage recovery speed; when the load is stable, the droop coefficient can be maintained or appropriately increased to improve the stability of the system.

[0022] Reference Figure 5As shown, under the balanced working condition, the collected voltage and current are transformed into coordinates, and their coordinate components are controlled by the proportional integral controller. The output current command value enters the current inner loop, specifically including: The voltage or current signal in the three-phase circuit is collected by the sensor, and the three-phase voltage or current signal is placed on the A, B, and C axes of the three-phase ABC coordinate system respectively; Using the first coordinate transformation formula, the three-phase voltage or current signal is transformed from the three-phase ABC coordinate system to the two-phase Stationary coordinate system; The DQ rotating coordinate system is determined by obtaining the angle between the electronic rotor and the stator reference axis. The rotation angle between the stationary coordinate systems; Based on the rotation angle, the two phases are transformed using the second coordinate transformation formula. The voltage or current component in the stationary coordinate system is transformed into the two-phase DQ rotating coordinate system to obtain the voltage or current component in the two-phase DQ rotating coordinate system; The voltage and current components in the DQ coordinate system after coordinate transformation are input into the proportional-integral controller; Design proportional-integral controller based on system requirements and control objectives; The proportional-integral controller calculates the required control quantity based on the input voltage and current components and the preset reference value, adjusts the output voltage and current of the distributed power supply or inverter, and maintains the stability of the DC bus voltage; The first coordinate transformation formula is: , In the formula, They are the coordinate components of the voltage or current signal in the three-phase circuit in the three-phase ABC coordinate system, Two-phase The coordinate components of the voltage or current signal in the stationary coordinate system; The second coordinate transformation formula is: , In the formula, They are the coordinate components of the voltage or current signal in the two-phase DQ rotating coordinate system, The DQ rotation coordinate system is The rotation angle between the stationary coordinate systems.

[0023] Use high-precision sensors such as Hall sensors to collect the voltage and current signals in the three-phase circuit respectively, ensure that the sensors are connected to the A, B, and C phases of the three-phase circuit respectively, obtain the position information of the motor rotor through the motor position sensor, and calculate the angle between the rotor and the stator reference axis. Based on system requirements and control objectives such as maintaining DC bus voltage stability and optimizing current waveforms, design the parameters of the PI controller, including the proportional coefficient and integral coefficient. These parameters can be determined through experimental debugging or system identification methods.

[0024] Reference Figure 6 As shown, under unbalanced working conditions, the second-order generalized integrator algorithm is used to separate the positive and negative sequence components of the voltage, and the separated positive and negative sequence components are synchronously controlled, specifically including: In two phases In the stationary coordinate system, the grid phase voltage is subjected to a 90° phase shift operation to calculate the positive and negative sequence components of the grid phase voltage; Use power conversion equipment to synchronously control positive and negative sequence components, and quickly adjust the grid voltage amplitude through voltage and current dual-loop control; inputting the extracted positive sequence component into the positive sequence control system; The positive sequence control system adjusts the control strategy based on the amplitude and phase information of the positive sequence component to maintain the stability and balance of the grid voltage; inputting the extracted negative sequence component into a negative sequence control system; The negative sequence control system reduces the impact of unbalanced grid voltage on the power system by compensating or suppressing the negative sequence component.

[0025] Through the output of the second-order generalized integrator, we can get the orthogonal signal, that is, the signal after 90° phase shift. Using these orthogonal signals, we can calculate the positive and negative sequence components of the grid phase voltage. The specific calculation involves the symmetrical component method, that is, using The voltage components and their orthogonal components in the coordinate system are transformed into positive and negative sequence components through the transformation matrix.

[0026] Reference Figure 7 As shown, the system's operating status and parameters are monitored in real time. When an abnormality or fault is found, the fault source is cut off and the backup power supply is started. Specifically, it includes: The sensors deployed on the equipment collect the equipment's operating status and parameters in real time, and the collected data is transmitted wirelessly to the central monitoring center; When an abnormality or failure is detected, the system automatically triggers the alarm mechanism; Determine the location and nature of the fault source through comparative analysis; If the fault source poses a threat to the safety of the system or equipment, shut down the faulty equipment, disconnect the power supply, isolate the faulty area and start the backup power supply.

[0027] Sensors are deployed at key locations of key equipment. These sensors can monitor the operating status and key parameters of the equipment, such as temperature, pressure, vibration, current, voltage, etc., in real time to ensure that the connection between the sensors and the data acquisition module is stable and reliable. The data acquisition module is responsible for converting the analog signals collected by the sensors into digital signals and performing preliminary processing. Wireless transmission equipment is configured to wirelessly transmit the data processed by the data acquisition module to the central monitoring center to ensure the stability of wireless transmission and the security of the data.

[0028] Furthermore, the present solution also proposes a computer-readable storage medium on which a computer-readable program is stored. When the computer-readable program is called, the above-mentioned method for controlling parameters of a bidirectional power conversion circuit for AC / DC power interchange is executed.

[0029] It is understandable that the storage medium may be a magnetic medium, such as a floppy disk, a hard disk, or a magnetic tape; an optical medium, such as a DVD; or a semiconductor medium, such as a solid state drive (SSD).

[0030] In summary, the advantages of the present invention are: by adopting a topological structure in which a three-phase voltage source converter is connected in series with a DC circuit bidirectional converter, it can better adapt to the characteristics of an AC / DC hybrid microgrid, realize the interchange and regulation of electric energy, and use droop control and proportional-integral control methods to accurately control parameters, thereby improving the control accuracy and stability of the system, realizing flexible switching of the AC / DC bidirectional power converter between the three working modes of rectification, inversion and shutdown, and effectively solving the voltage and current control problems under unbalanced working conditions.

[0031] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange, characterized in that: include: A topology structure in which a three-phase voltage source converter and a DC circuit bidirectional converter are connected in series is used to perform power conversion on the AC side and power regulation on the DC side respectively; By installing sensors, the input and output voltage and current parameters of the AC / DC bidirectional power converter are collected in real time; By utilizing the droop characteristics of the DC output side and judging the operating status of the system according to the DC microgrid bus voltage, the AC / DC bidirectional power converter can be switched between the three working modes of rectification, inversion and shutdown. By adjusting the active power droop coefficient, the DC bus voltage and transmission power are controlled, the DC bus voltage is kept at the rated value when the supply and demand are balanced within the DC subnet, and bidirectional power flow is achieved when the supply and demand are unbalanced; Under balanced working conditions, the collected voltage and current are transformed into coordinates, and their coordinate components are controlled by a proportional-integral controller, and the output current command value enters the current inner loop; Under unbalanced working conditions, the second-order generalized integrator algorithm is used to separate the positive and negative sequence components of the voltage, and the separated positive and negative sequence components are synchronously controlled respectively; Monitor the system's operating status and parameters in real time. When an abnormality or fault is found, cut off the source of the fault and start the backup power supply.

2. The method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange according to claim 1, characterized in that: The topology structure of a three-phase voltage source converter and a DC circuit bidirectional converter in series, respectively performing AC side power conversion and DC side power regulation, specifically includes: The three-phase voltage source converter adopts a dual closed-loop control structure with voltage outer loop and current inner loop to track and control the grid-connected current; The three-phase voltage source converter receives three-phase AC power from the grid or generator; Inside the three-phase voltage source converter, the unidirectional conductivity of the diode is used to convert AC power into DC power through a rectifier circuit; The three-phase voltage source converter controls the output voltage and current by adjusting the pulse width and frequency, and realizes the smooth conversion of electric energy; The DC circuit bidirectional converter adopts a double closed-loop structure, with the inductor current as the control variable in the inner control loop and the capacitor voltage as the control variable in the outer control loop to control the stability of the DC bus voltage. The DC circuit bidirectional converter receives DC power from the three-phase voltage source converter; Based on the load demand and the requirements of the energy storage system, the DC circuit bidirectional converter accurately regulates the DC power; When energy flows from a DC source to another DC load, the voltage reduction or voltage increase function is realized by controlling the on and off of the switch tube, converting the DC power into DC power of a preset voltage level; The regulated DC power is converted back to AC power via an additional inverter circuit; The regulated DC power is supplied to the energy storage system for charging or discharging.

3. The method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange according to claim 2, characterized in that: The method of utilizing the droop characteristics of the DC output side and judging the operating state of the system according to the DC microgrid bus voltage to realize the switching of the AC / DC bidirectional power converter between the three working modes of rectification, inversion and shutdown specifically includes: During system operation, the DC microgrid bus voltage and AC / DC subgrid load conditions are continuously monitored, and the working mode of the AC / DC bidirectional power converter is dynamically adjusted based on real-time data; Determine whether the DC subnet load power is greater than the rated power, or whether the DC microgrid bus voltage is lower than a first preset threshold value. If so, switch the working mode of the AC / DC bidirectional power converter to the rectification mode, and transfer power from the AC subnet to the DC subnet. If not, do not output; Determine whether the load power of the AC subgrid is greater than the rated power, or the bus voltage of the DC microgrid is higher than the second preset threshold. If so, switch the working mode of the AC / DC bidirectional power converter to the inverter mode, and transfer power from the DC subgrid to the AC subgrid. If not, the output DC microgrid bus voltage is within a stable range, and the power output of the internal power supply of the AC / DC subgrid meets the load requirements. No power exchange is performed, and the working mode of the AC / DC bidirectional power converter is switched to the shutdown mode.

4. The method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange according to claim 3, characterized in that: The method of controlling the DC bus voltage and transmission power by adjusting the active power droop coefficient, maintaining the DC bus voltage at a rated value when the supply and demand in the DC subnet are balanced, and realizing the bidirectional flow of power when the supply and demand are unbalanced specifically includes: S101: Based on the design requirements of the DC subnet, determine the rated value of the DC bus voltage and set the initial active power droop coefficient, which determines the response speed and amplitude of the bus voltage when the power changes; S102: When the supply and demand are balanced, that is, the load demand is equal to the output power of the micro-source, the DC bus voltage is kept near the rated value through a droop control strategy; S103: When the actual DC bus voltage deviates from the rated value, the output power of the micro source is adjusted according to the droop coefficient to maintain voltage stability; S104: monitoring the actual value of the DC bus voltage in real time through a voltage sensor, calculating the imbalance degree of the current system supply and demand state according to the difference between the real-time monitored bus voltage and the rated voltage, and outputting it as a power deviation; S105: obtaining the output power of the distributed power source that needs to be adjusted by calculating the product of the power deviation and the droop coefficient, and adjusting the output power of the distributed power source by controlling the switching device of the distributed power source to respond to the power deviation; S106: Determine whether the difference between the adjusted bus voltage value and the rated value is greater than a preset difference threshold value, if so, return to step S104, if not, do not output; S107: Based on the real-time monitoring of system load changes, dynamically adjust the droop coefficient to improve the response speed to load changes and the stability of the bus voltage.

5. The method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange according to claim 4, characterized in that: Under the balanced working condition, the collected voltage and current are subjected to coordinate transformation, and their coordinate components are controlled by a proportional integral controller, and the output current command value enters the current inner loop, specifically including: The voltage or current signal in the three-phase circuit is collected by the sensor, and the three-phase voltage or current signal is placed on the A, B, and C axes of the three-phase ABC coordinate system respectively; Using the first coordinate transformation formula, the three-phase voltage or current signal is transformed from the three-phase ABC coordinate system to the two-phase Stationary coordinate system; The DQ rotating coordinate system is determined by obtaining the angle between the electronic rotor and the stator reference axis. The rotation angle between the stationary coordinate systems; Based on the rotation angle, the two phases are transformed using the second coordinate transformation formula. The voltage or current component in the stationary coordinate system is transformed into the two-phase DQ rotating coordinate system to obtain the voltage or current component in the two-phase DQ rotating coordinate system; The voltage and current components in the DQ coordinate system after coordinate transformation are input into the proportional-integral controller; Design proportional-integral controller based on system requirements and control objectives; The proportional-integral controller calculates the required control quantity based on the input voltage and current components and the preset reference value, adjusts the output voltage and current of the distributed power supply or inverter, and maintains the stability of the DC bus voltage; The first coordinate transformation formula is: , In the formula, They are the coordinate components of the voltage or current signal in the three-phase circuit in the three-phase ABC coordinate system, Two-phase The coordinate components of the voltage or current signal in the stationary coordinate system; The second coordinate transformation formula is: , In the formula, They are the coordinate components of the voltage or current signal in the two-phase DQ rotating coordinate system, The DQ rotation coordinate system is The rotation angle between the stationary coordinate systems.

6. A method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange according to claim 5, characterized in that: In the unbalanced working condition, the positive and negative sequence components of the voltage are separated by using a second-order generalized integrator algorithm, and the separated positive and negative sequence components are synchronously controlled respectively, specifically including: In two phases In the stationary coordinate system, the grid phase voltage is subjected to a 90° phase shift operation to calculate the positive and negative sequence components of the grid phase voltage; Use power conversion equipment to synchronously control positive and negative sequence components, and quickly adjust the grid voltage amplitude through voltage and current dual-loop control; inputting the extracted positive sequence component into the positive sequence control system; The positive sequence control system adjusts the control strategy based on the amplitude and phase information of the positive sequence component to maintain the stability and balance of the grid voltage; inputting the extracted negative sequence component into a negative sequence control system; The negative sequence control system reduces the impact of unbalanced grid voltage on the power system by compensating or suppressing the negative sequence component.

7. The method for controlling parameters of a bidirectional power conversion circuit for AC / DC power exchange according to claim 6, characterized in that: The real-time monitoring system's operating status and parameters, upon finding an abnormality or fault, cutting off the fault source and starting the backup power supply specifically include: The sensors deployed on the equipment collect the equipment's operating status and parameters in real time, and the collected data is transmitted wirelessly to the central monitoring center; When an abnormality or failure is detected, the system automatically triggers the alarm mechanism; Determine the location and nature of the fault source through comparative analysis; If the fault source poses a threat to the safety of the system or equipment, shut down the faulty equipment, disconnect the power supply, isolate the faulty area and start the backup power supply.

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