A three-phase voltage regulator and its control method under wide voltage variation

Abstract

This invention discloses a three-phase voltage regulator and its control method under wide voltage variations, relating to the field of voltage regulation technology. It includes a controller, a mechanical bypass switch, an input switch, an output switch, an independent electronic bypass switch for each phase, an input filter, two sets of series power supplies, a parallel power supply, and an output filter. After commissioning, the mechanical bypass switch, input switch, and output switch are closed, and then the electronic bypass switch is turned on. During normal operation, the mechanical bypass switch is disconnected, the electronic bypass switch is turned off, and robust voltage regulation control is activated to ensure normal user voltage. In case of a fault, the series and parallel power supplies are turned off, the electronic bypass switch is quickly turned on, and the mechanical bypass switch is closed. Then, the input and output switches are disconnected, and the user voltage is supplied by the mechanical bypass switch, achieving seamless power supply switching. Finally, the device exits operation and triggers an alarm. This invention has advantages such as high output voltage accuracy, good dynamic stability, and independent three-phase regulation.

Description

Technical Field

[0001] This invention relates to the field of voltage stabilization technology, and more specifically to a three-phase voltage stabilization device and its control method under a wide range of voltage variations. Background Technology

[0002] Distribution network voltage quality is a technical indicator that measures the deviation between the actual voltage and the ideal voltage in a power system. Voltage fluctuations, in particular, directly affect power supply reliability and user satisfaction. Excessively high voltage can lead to malfunctions and damage to electrical equipment in the distribution area, affecting users' normal power consumption, causing abnormal operation of electrical equipment, and in severe cases, even damaging user equipment. Insufficiently low voltage increases line losses and can also cause users' electrical appliances to malfunction. With the improvement of people's living standards, especially in vast rural areas, low voltage frequently occurs at night, affecting users' normal power consumption.

[0003] With the large-scale integration of distributed photovoltaic (PV) power into low-voltage rural distribution networks, the characteristic of rural distribution network voltage monotonically decreasing with electrical distance has changed. This has led to reverse power flow phenomena caused by distributed PV integration, resulting in severe voltage exceeding-limit problems. Overvoltages caused by improper PV integration by numerous users pose a serious threat to personal safety and the stable operation of power equipment.

[0004] Therefore, how to provide a three-phase voltage regulator and its control method under a wide range of voltage variations is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a three-phase voltage stabilizing device and its control method under large voltage fluctuations. Through power electronics technology and robust control technology, the voltage fluctuation problem is solved and high-quality power is provided to users.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A three-phase voltage regulator for a wide range of voltage variations includes: a controller, a three-phase mechanical bypass switch, a three-phase input switch, a three-phase output switch, an independent electronic bypass switch for each phase, two sets of series power units and parallel power units;

[0008] One end of the electronic bypass switch for each phase is connected to one end of the input switch for that phase, and the other end is connected to one end of the output switch for that phase; the other ends of the three-phase input switches are connected to the input terminal of the three-phase mechanical bypass switch; the other ends of the three-phase output switches are connected to the output terminal of the three-phase mechanical bypass switch.

[0009] For each phase, one end of the first set of series power units is connected to the connection point of the phase input switch and the phase electronic bypass switch; the other end of the first set of series power units, one end of the second set of series power units, and one end of the phase parallel power unit are all connected to a node; the other end of the second set of series power units is connected to the connection point of the phase output switch and the phase electronic bypass switch; the other end of the parallel power unit is connected to the neutral line.

[0010] The controller's input ports are used to acquire three-phase input voltage, three-phase output voltage, and three-phase output current. Its output ports are used to control the on / off state of the three-phase mechanical bypass switch, three-phase input switch, three-phase output switch, and electronic bypass switch of each phase. Its PWM output ports are used to control the two sets of series power units and parallel power units of each phase.

[0011] Preferably, it also includes independent input filter circuits and output filter circuits for each phase;

[0012] For each phase, the input filter circuit is located between the connection point of the first set of series power units of that phase and the connection point of the phase input switch and electronic bypass switch; the output filter circuit is located between the connection point of the second set of series power units of that phase and the connection point of the phase output switch and electronic bypass switch.

[0013] Preferably, the input filter circuit consists of an inductor L 1x With capacitor C 1x The output filter circuit consists of inductor L. 2x With capacitor C 2x Composition, where x represents phase A, phase B, or phase C;

[0014] For each phase, the inductance L 1x One end of the inductor L is connected to the connection point between the output terminal of the phase input switch and the phase electronic bypass switch. 1x The other end is connected to the input terminal of the first group of series power units in this phase, capacitor C 1x One end is connected to inductor L 1x The input terminal, capacitor C 1x The other end is connected to the neutral line; inductor L 2x One end is connected to the output terminal of the second series power unit of this phase, and the inductor L 2x The other end is connected to the connection point between the input terminal of the phase output switch and the phase electronic bypass switch, capacitor C 2x One end is connected to inductor L 2x At the output terminal, capacitor C 2x The other end is connected to the center line.

[0015] Preferably, the electronic bypass switch consists of a pair of anti-parallel thyristors, the two sets of series power units are each composed of two silicon carbide power devices connected in reverse series, and the parallel power unit is composed of two silicon carbide power devices connected in reverse series.

[0016] A control method for a three-phase voltage regulator under a wide voltage variation includes:

[0017] S1 system startup and initialization, including:

[0018] S101: After receiving the start command, the controller controls the three-phase mechanical bypass switch, three-phase input switch and three-phase output switch to close completely, establishing a direct power supply path from the power grid to the user's load;

[0019] S102: The controller turns on the electronic bypass switch for each phase;

[0020] S103: After the system stabilizes, the controller disconnects the three-phase mechanical bypass switch;

[0021] S104: Turn off the electronic bypass switch of each phase and enter the voltage regulation mode;

[0022] S2 three-phase independent precision voltage regulation operation includes:

[0023] S201: The controller continuously collects the grid input voltage, output voltage, and output current of each phase through the input port;

[0024] S202: Calculate the deviation between the output voltage of each phase and the rated voltage of the power grid, and generate the basic duty cycle of each phase based on the deviation value;

[0025] The controller determines whether the output voltage is greater than the grid rated voltage. If so, it applies the basic duty cycle of the phase to the two silicon carbide power devices in the first series power unit of the phase and adjusts their duty cycle through the PWM signal to increase the voltage. At the same time, it ensures that the two silicon carbide power devices in the second series power unit of the phase are continuously conducting. Otherwise, the controller applies the basic duty cycle of the phase to the two silicon carbide power devices in the second series power unit of the phase and adjusts their duty cycle to decrease the voltage. At the same time, it keeps the two silicon carbide power devices in the first series power unit of the phase continuously conducting.

[0026] The controller calculates the complementary duty cycle of each phase and applies it to the two silicon carbide power devices in the parallel power unit of that phase;

[0027] The PID control coefficients for each phase are automatically adjusted based on the deviation value.

[0028] Preferably, the duty cycle of phase A foundation The calculation formula is:

[0029] ;

[0030] Where U0 is the rated voltage of the power grid, U La The measured value of phase A output voltage, k pa1 k ia1 k da1 The PID control coefficient for phase A voltage;

[0031] A. Complementary duty cycles D. a2 The calculation formula is:

[0032] ;

[0033] The formula for calculating the PID control coefficient of phase A voltage is:

[0034] ;

[0035] Where, k p0 k i0 k d0 is the initial value of the robust control coefficient, and k is the droop coefficient.

[0036] Preferably, the duty cycle of phase B foundation The calculation formula is:

[0037] ;

[0038] Where U0 is the rated voltage of the power grid, U Lb The measured value of the output voltage of phase B, k pb1 k ib1 k db1 The PID control coefficients for phase B voltage;

[0039] B. Complementary duty cycles D. b2 The calculation formula is:

[0040] ;

[0041] The formula for calculating the PID control coefficient of phase B voltage is:

[0042] ;

[0043] Where, k p0 k i0 k d0 is the initial value of the robust control coefficient, and k is the droop coefficient.

[0044] Preferably, the duty cycle of the C-phase foundation The calculation formula is:

[0045] ;

[0046] Where U0 is the rated voltage of the power grid. The measured value of the C-phase output voltage, k pc1 k ia1 k da1 The PID control coefficients for phase C voltage;

[0047] C. Mutually complementary duty cycles D. c2 The calculation formula is:

[0048] ;

[0049] The formula for calculating the PID control coefficient of phase C voltage is:

[0050] ;

[0051] Where, k p0 k i0 k d0 is the initial value of the robust control coefficient, and k is the droop coefficient.

[0052] Preferred options also include:

[0053] If overvoltage protection, overcurrent protection, or overtemperature protection is triggered, the controller immediately shuts down all series and parallel power units of all phases, and at the same time, quickly turns on the electronic bypass switch of each phase.

[0054] Close the three-phase mechanical bypass switch. After the three-phase mechanical bypass switch is confirmed to be closed, the controller turns off the electronic bypass switch of each phase.

[0055] Disconnect the three-phase input switch and the three-phase output switch to shut down the device.

[0056] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a three-phase voltage stabilizing device and its control method under large voltage fluctuations, which can suppress large voltage fluctuations in the power grid, ensure stable voltage for users, and has the characteristics of high output voltage accuracy, good dynamic stability, wide adjustment range, and independent three-phase adjustment, providing users with high-precision voltage. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0058] Figure 1 This is a schematic diagram of a three-phase voltage stabilizing device for a wide range of voltage variations provided by the present invention.

[0059] Figure 2 The present invention provides a flowchart of a control method for a three-phase voltage stabilizing device under a wide range of voltage variations. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] This invention discloses a three-phase voltage stabilizing device for large voltage variations, such as... Figure 1 As shown, it includes:

[0062] The system includes a controller, a three-phase mechanical bypass switch, a three-phase input switch, a three-phase output switch, an independent electronic bypass switch for each phase, two sets of series power units, and a parallel power unit.

[0063] One end of the electronic bypass switch for each phase is connected to one end of the input switch for that phase, and the other end is connected to one end of the output switch for that phase. The other ends of the three-phase input switches are connected to the input terminal of the three-phase mechanical bypass switch. The other ends of the three-phase output switches are connected to the output terminal of the three-phase mechanical bypass switch. At the same time, one end of the three-phase input switch serves as the three-phase input terminal of the device for connecting to the power grid, and one end of the three-phase output switch serves as the three-phase output terminal of the device for connecting to the user load.

[0064] For each phase, one end of the first set of series power units is connected to the connection point of the phase input switch and the phase electronic bypass switch; the other end of the first set of series power units, one end of the second set of series power units, and one end of the phase parallel power unit are all connected to a node; the other end of the second set of series power units is connected to the connection point of the phase output switch and the phase electronic bypass switch; the other end of the parallel power unit is connected to the neutral line.

[0065] The controller's input ports are used to acquire three-phase input voltage, three-phase output voltage, and three-phase output current. Its output ports are used to control the on / off state of the three-phase mechanical bypass switch, three-phase input switch, three-phase output switch, and electronic bypass switch of each phase. Its PWM output ports are used to control the two sets of series power units and parallel power units of each phase.

[0066] In this embodiment, an independent input filter circuit and an output filter circuit for each phase are also included;

[0067] For each phase, the input filter circuit is located between the connection point of the first set of series power units of that phase and the connection point of the phase input switch and electronic bypass switch; the output filter circuit is located between the connection point of the second set of series power units of that phase and the connection point of the phase output switch and electronic bypass switch. The input filter circuit consists of an inductor L. 1x With capacitor C 1x The output filter circuit consists of inductor L. 2x With capacitor C 2x The composition is defined as follows, where x represents phase A, phase B, or phase C.

[0068] More specifically, in the A-phase structure, the A-phase input filter circuit A consists of inductor L 1A With capacitor C 1A The A-phase output filter circuit consists of inductor L. 2A With capacitor C 2A Composition: One end of the A-phase electronic bypass switch A is connected to one end of the corresponding phase input switch, and the other end of the A-phase electronic bypass switch A is connected to one end of the corresponding phase output switch; one end of the first group of series power units IA in phase A is connected to one end of the input filter circuit A, and the other end of the input filter circuit A is connected to the connection node between the A-phase electronic bypass switch A and the A-phase input switch; the other end of the first group of series power units IA in phase A is connected to one end of the A-phase parallel power unit A and one end of the A-phase second group of series power units IIA; the other end of the A-phase second group of series power units IIA is connected to one end of the A-phase output filter A, and the other end of the A-phase output filter A is connected to the connection node between the A-phase electronic bypass switch A and the A-phase output switch; the other end of the A-phase parallel power unit A and capacitor C... 1A Common terminal, capacitor C 2A The common terminal is connected to the center line N;

[0069] The B-phase structure, the B-phase input filter circuit consists of inductor L 1B With capacitor C 1B The B-phase output filter circuit consists of inductor L 2B With capacitor C 2B Composition: One end of the B-phase electronic bypass switch B is connected to one end of the corresponding phase input switch, and the other end of the B-phase electronic bypass switch B is connected to one end of the corresponding phase output switch; one end of the first group of series power units IB in phase B is connected to one end of the input filter circuit B, and the other end of the input filter circuit B is connected to the connection node between the B-phase electronic bypass switch B and the B-phase input switch; the other end of the first group of series power units IB in phase B is connected to one end of the B-phase parallel power unit B and one end of the B-phase second group of series power units IIB; the other end of the B-phase second group of series power units IIB is connected to one end of the B-phase output filter B, and the other end of the B-phase output filter B is connected to the connection node between the B-phase electronic bypass switch B and the B-phase output switch; the other end of the B-phase parallel power unit B and capacitor C... 1B Common terminal, capacitor C 2B The common terminal is connected to the center line N;

[0070] The C-phase structure, the C-phase input filter circuit C consists of an inductor L 1C With capacitor C 1C The C-phase output filter circuit consists of inductor L 2C With capacitor C 2C Composition: One end of the C-phase electronic bypass switch C is connected to one end of the corresponding phase input switch, and the other end of the C-phase electronic bypass switch C is connected to one end of the corresponding phase output switch; one end of the first group of series power ICs in phase C is connected to one end of the input filter circuit C, and the other end of the input filter circuit C is connected to the connection node between the C-phase electronic bypass switch C and the C-phase input switch; the other end of the first group of series power ICs in phase C is connected to one end of the C-phase parallel power IC and one end of the C-phase second group of series power ICs; the other end of the C-phase second group of series power ICs is connected to one end of the C-phase output filter C, and the other end of the C-phase output filter C is connected to the connection node between the C-phase electronic bypass switch C and the C-phase output switch; the other end of the C-phase parallel power IC and capacitor C... 1C Common terminal, capacitor C 2C The common terminal is connected to the center line N.

[0071] In this embodiment, the electronic bypass switch consists of a pair of anti-parallel thyristors, the two sets of series power units are each composed of two silicon carbide power devices connected in reverse series, and the parallel power unit is composed of two silicon carbide power devices connected in reverse series.

[0072] This invention provides a control method for a three-phase voltage regulator under a wide voltage variation, such as... Figure 2 As shown, it includes:

[0073] S1 system startup and initialization, including:

[0074] S101: After receiving the start command, the controller controls the three-phase mechanical bypass switch, three-phase input switch and three-phase output switch to close completely, establishing a direct power supply path from the power grid to the user's load;

[0075] S102: The controller turns on the electronic bypass switch for each phase;

[0076] S103: After the system stabilizes, the controller disconnects the three-phase mechanical bypass switch;

[0077] S104: Turn off the electronic bypass switch of each phase and enter the voltage regulation mode;

[0078] S2 three-phase independent precision voltage regulation operation includes:

[0079] S201: The controller continuously collects the grid input voltage, output voltage, and output current of each phase through the input port;

[0080] S202: Calculate the deviation between the output voltage of each phase and the rated voltage of the power grid, and generate the basic duty cycle of each phase based on the deviation value;

[0081] The controller determines whether the output voltage is greater than the grid rated voltage. If so, it applies the basic duty cycle of the phase to the two silicon carbide power devices in the first series power unit of the phase and adjusts their duty cycle through the PWM signal to increase the voltage. At the same time, it ensures that the two silicon carbide power devices in the second series power unit of the phase are continuously conducting. Otherwise, the controller applies the basic duty cycle of the phase to the two silicon carbide power devices in the second series power unit of the phase and adjusts their duty cycle to decrease the voltage. At the same time, it keeps the two silicon carbide power devices in the first series power unit of the phase continuously conducting.

[0082] The controller calculates the complementary duty cycle of each phase and applies it to the two silicon carbide power devices in the parallel power unit of that phase;

[0083] The PID control coefficients for each phase are automatically adjusted based on the deviation value.

[0084] More specifically, 1) A-phase voltage closed-loop robust proportional-integral-derivative (PID) control

[0085] Voltage closed-loop PID control is adopted, as shown below:

[0086] (1)

[0087] In the above formula, U0 is the rated voltage of the power grid, U La The measured value of the output voltage of phase A of this device, and the voltage PID control coefficient k. pa1 k ia1 k da1 ;

[0088] When the pressure is reduced, D a1 The duty cycle of the two silicon carbide power devices IA in the first series power group of phase A is set, and the two silicon carbide power devices IIA in the second series power group of phase A are in the on state.

[0089] During boost, D a1 The duty cycle of the two silicon carbide power devices IIA in the second series power group of phase A is set, and the two silicon carbide power devices IA in the first series power group of phase A are in the on state.

[0090] The duty cycles of the two power devices connected in parallel in phase A are shown below:

[0091] D a2 = 1-D a1 (2)

[0092] Among them, D a2The duty cycle of the two silicon carbide power devices connected in parallel in phase A;

[0093] The voltage PID control coefficient is automatically adjusted based on the deviation between the A-phase output voltage of this device and the rated voltage of the power grid to obtain the best robust control performance.

[0094] k pa1 = k p0 + k*|U0-U La | (3)

[0095] k ia1 = k i0 + k*|U0-U La | (4)

[0096] k da1 = k d0 + k*d(U La ) / dt (5)

[0097] Where, k p0 k i0 k d0 Here are the initial values ​​for the robust control coefficients, and k is the droop coefficient.

[0098] 2) Robust PID control of B-phase voltage closed loop

[0099] Voltage closed-loop PID control is adopted, as shown below:

[0100] (6)

[0101] In the above formula, U0 is the rated voltage of the power grid, U Lb The measured value of the output voltage of phase B of this device, and the voltage PID control coefficient k. pb1 k ib1 k db1 ;

[0102] When the pressure is reduced, D b1 The duty cycle of the two silicon carbide power devices IB in the first series power group of phase B is set, and the two power devices IIB in the second series power group of phase B are in the on state.

[0103] During boost, D b1 The duty cycle of the two silicon carbide power devices IIB in the second series power group of phase B is set, and the two power devices IB in the first series power group of phase B are in the on state.

[0104] The duty cycles of the two power devices connected in parallel in phase B are shown below:

[0105] D b2 =1-D b1 (7)

[0106] Among them, D b2 The duty cycle of the two silicon carbide power devices connected in parallel for phase B;

[0107] The voltage PID control coefficient is automatically adjusted based on the deviation between the output voltage of phase B of this device and the rated voltage of the power grid to obtain the best robust control performance.

[0108] k pb1 = k p0 + k*|U0-U Lb | (8)

[0109] k ib1 = k i0 + k*|U0-U Lb | (9)

[0110] k db1 = k d0 + k*d(U Lb ) / dt (10)

[0111] 3) Robust closed-loop PID control of C-phase voltage

[0112] Voltage closed-loop PID control is adopted, as shown below:

[0113] (11)

[0114] In the above formula, U0 is the rated voltage of the power grid, U Lc The measured value of the C-phase output voltage of this device, and the voltage PID control coefficient k. pc1 k ia1 k da1 ;

[0115] When the pressure is reduced, D c1 The duty cycle of the two silicon carbide power devices IC in the first series of C phase is set, and the two silicon carbide power devices IIC in the second series of C phase are in the on state.

[0116] During boost, D c1 The duty cycle of the two silicon carbide power devices IIC in the second series of C phase is set, and the two power devices IC in the first series of C phase are in the on state.

[0117] The power C of the parallel-connected silicon carbide power devices is shown below:

[0118] D c2 = 1-D c1 (12)

[0119] Among them, D c2 The duty cycle of the two power devices connected in parallel in phase C is the power of phase C.

[0120] The voltage PID control coefficient is automatically adjusted based on the deviation between the C-phase output voltage of this device and the rated voltage of the power grid to obtain the best robust control performance.

[0121] k pc1 = k p0 + k*|U0-U Lc | (13)

[0122] k ic1 = k i0 + k*|U0-U Lc | (14)

[0123] k dc1 = k d0 + k*d(U Lc ) / dt (15)

[0124] This embodiment also includes a fault detection and protection switching mechanism, specifically:

[0125] Fault Trigger Judgment: The controller continuously monitors protection signals such as overvoltage, overcurrent, and overtemperature. Once any protection condition is triggered, the fault handling process is immediately initiated.

[0126] Emergency shutdown and rapid bypass:

[0127] The controller immediately shuts down all series and parallel power units of all phases, cutting off the main power circuit.

[0128] At the same time, the electronic bypass switch of each phase is quickly activated to achieve millisecond-level current bypass, ensuring uninterrupted power supply to users.

[0129] Establish a mechanical bypass:

[0130] The controller closes the three-phase mechanical bypass switch to establish a reliable, low-impedance mechanical power supply path.

[0131] Exiting operation and isolation:

[0132] After the mechanical bypass switch is confirmed to be closed, the controller shuts off the electronic bypass switch for each phase to prevent the thyristor from being turned on for a long time.

[0133] Subsequently, the three-phase input switch and the three-phase output switch were disconnected to safely isolate the faulty device from the power grid and the load.

[0134] The device is shut down, and the controller sends an alarm signal to prompt maintenance personnel to carry out repairs.

[0135] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0136] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a three-phase voltage regulator under a wide voltage variation, the method being based on a three-phase voltage regulator under a wide voltage variation, comprising: The system includes a controller, a three-phase mechanical bypass switch, a three-phase input switch, a three-phase output switch, an independent electronic bypass switch for each phase, two sets of series power units, and a parallel power unit. One end of the electronic bypass switch for each phase is connected to one end of the input switch for that phase, and the other end is connected to one end of the output switch for that phase; the other ends of the three-phase input switches are connected to the input terminal of the three-phase mechanical bypass switch; the other ends of the three-phase output switches are connected to the output terminal of the three-phase mechanical bypass switch. For each phase, one end of the first set of series power units is connected to the connection point of the phase input switch and the phase electronic bypass switch; the other end of the first set of series power units, one end of the second set of series power units, and one end of the phase parallel power unit are all connected to a node; the other end of the second set of series power units is connected to the connection point of the phase output switch and the phase electronic bypass switch; the other end of the parallel power unit is connected to the neutral line. The controller's input ports are used to acquire three-phase input voltage, three-phase output voltage, and three-phase output current. Its output ports are used to control the on / off states of the three-phase mechanical bypass switch, three-phase input switch, three-phase output switch, and electronic bypass switches for each phase. Its PWM output ports are used to control the two sets of series power units and parallel power units for each phase. The controller is characterized by including: S1 system startup and initialization, including: S101: After receiving the start command, the controller controls the three-phase mechanical bypass switch, three-phase input switch and three-phase output switch to close completely, establishing a direct power supply path from the power grid to the user's load; S102: The controller turns on the electronic bypass switch for each phase; S103: After the system stabilizes, the controller disconnects the three-phase mechanical bypass switch; S104: Turn off the electronic bypass switch of each phase and enter the voltage regulation mode; S2 three-phase independent precision voltage regulation operation includes: S201: The controller continuously collects the grid input voltage, output voltage, and output current of each phase through the input port; S202: Calculate the deviation between the output voltage of each phase and the rated voltage of the power grid, and generate the basic duty cycle of each phase based on the deviation value; The controller determines whether the output voltage is greater than the grid rated voltage. If so, it applies the basic duty cycle of the phase to the two silicon carbide power devices in the first series power unit of the phase and adjusts their duty cycle through the PWM signal to reduce the voltage. At the same time, it ensures that the two silicon carbide power devices in the second series power unit of the phase are continuously conducting. Otherwise, the controller applies the basic duty cycle of the phase to the two silicon carbide power devices in the second series power unit of the phase and adjusts their duty cycle to increase the voltage. At the same time, it keeps the two silicon carbide power devices in the first series power unit of the phase continuously conducting. The controller calculates the complementary duty cycle of each phase and applies it to the two silicon carbide power devices in the parallel power unit of that phase; The PID control coefficients for each phase are automatically adjusted based on the deviation value.

2. The control method for a three-phase voltage regulator under a wide voltage range according to claim 1, characterized in that, A-phase base duty cycle The calculation formula is: ； in, U 0 represents the rated voltage of the power grid. U La This is the measured value of the output voltage of phase A. k pa1 , k ia1 , k da1 The PID control coefficient for phase A voltage; A. Complementary duty cycles The calculation formula is: ； The formula for calculating the PID control coefficient of phase A voltage is: ； in, k p0 , k i0 , k d0 These are the initial values ​​for the robust control coefficients. k This is the droop coefficient.

3. The control method for a three-phase voltage stabilizing device under a wide voltage range according to claim 1, characterized in that, Phase B base duty cycle The calculation formula is: ； in, U 0 represents the rated voltage of the power grid. U Lb This is the measured value of the output voltage of phase B. k pb1 , k ib1 , k db1 The PID control coefficients for phase B voltage; B complements each other's duty cycle D b2 The calculation formula is: ； The formula for calculating the PID control coefficient of phase B voltage is: ； in, k p0 , k i0 , k d0 These are the initial values ​​for the robust control coefficients. k This is the droop coefficient.

4. The control method for a three-phase voltage regulator under a wide voltage range according to claim 1, characterized in that, C-phase base duty cycle The calculation formula is: ； in, U 0 represents the rated voltage of the power grid. This is the measured value of the C-phase output voltage. k pc1 , k ia1 , k da1 The PID control coefficients for phase C voltage; C mutually complement duty cycle D c2 The calculation formula is: ； The formula for calculating the PID control coefficient of phase C voltage is: ； in, k p0 , k i0 , k d0 These are the initial values ​​for the robust control coefficients. k This is the droop coefficient.

5. The control method for a three-phase voltage stabilizing device under a wide voltage range according to claim 1, characterized in that, Also includes: If overvoltage protection, overcurrent protection, or overtemperature protection is triggered, the controller immediately shuts down all series and parallel power units of all phases, and at the same time, quickly turns on the electronic bypass switch of each phase. Close the three-phase mechanical bypass switch. After the three-phase mechanical bypass switch is confirmed to be closed, the controller turns off the electronic bypass switch of each phase. Disconnect the three-phase input switch and the three-phase output switch to shut down the device.

6. A three-phase voltage stabilizing device for a wide range of voltage variations, the device being used to implement the method described in any one of claims 1-5, characterized in that, include: The system includes a controller, a three-phase mechanical bypass switch, a three-phase input switch, a three-phase output switch, an independent electronic bypass switch for each phase, two sets of series power units, and a parallel power unit. One end of the electronic bypass switch for each phase is connected to one end of the input switch for that phase, and the other end is connected to one end of the output switch for that phase; the other ends of the three-phase input switches are connected to the input terminal of the three-phase mechanical bypass switch; the other ends of the three-phase output switches are connected to the output terminal of the three-phase mechanical bypass switch. For each phase, one end of the first set of series power units is connected to the connection point of the phase input switch and the phase electronic bypass switch; the other end of the first set of series power units, one end of the second set of series power units, and one end of the phase parallel power unit are all connected to a node; the other end of the second set of series power units is connected to the connection point of the phase output switch and the phase electronic bypass switch; the other end of the parallel power unit is connected to the neutral line. The controller's input ports are used to acquire three-phase input voltage, three-phase output voltage, and three-phase output current. Its output ports are used to control the on / off state of the three-phase mechanical bypass switch, three-phase input switch, three-phase output switch, and electronic bypass switch of each phase. Its PWM output ports are used to control the two sets of series power units and parallel power units of each phase.

7. A three-phase voltage stabilizing device under a wide voltage range according to claim 6, characterized in that, It also includes independent input and output filter circuits for each phase; For each phase, the input filter circuit is located between the connection point of the first set of series power units of that phase and the connection point of the phase input switch and electronic bypass switch; the output filter circuit is located between the connection point of the second set of series power units of that phase and the connection point of the phase output switch and electronic bypass switch.

8. A three-phase voltage stabilizing device under a wide voltage range according to claim 7, characterized in that, The input filter circuit consists of inductor L 1x With capacitor C 1x The output filter circuit consists of inductor L. 2x With capacitor C 2x Composition, where x represents phase A, phase B, or phase C; For each phase, the inductance L 1x One end of the inductor L is connected to the connection point between the output terminal of the phase input switch and the phase electronic bypass switch. 1x The other end is connected to the input terminal of the first group of series power units in this phase, capacitor C 1x One end is connected to inductor L 1x The input terminal, capacitor C 1x The other end is connected to the neutral line; inductor L 2x One end is connected to the output terminal of the second series power unit of this phase, and the inductor L 2x The other end is connected to the connection point between the input terminal of the phase output switch and the phase electronic bypass switch, capacitor C 2x One end is connected to inductor L 2x At the output terminal, capacitor C 2x The other end is connected to the center line.

9. A three-phase voltage stabilizing device under a wide voltage range according to claim 6, characterized in that, The electronic bypass switch consists of a pair of anti-parallel thyristors, and each of the two sets of series power units is composed of two silicon carbide power devices connected in reverse series. The parallel power unit is composed of two silicon carbide power devices connected in reverse series.

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