Power electronic voltage regulating device with reclosing function

Abstract

A high-efficiency power electronic voltage regulating device with a reclosing function is connected in series with a low-voltage line and comprises a silicon controlled bypass switch, a series power unit, a parallel power unit, an input filtering unit, an output filtering unit, a controller, a topology change-over switch, a mechanical bypass switch, an input switch, an output switch and the like. Under a normal working condition, power is supplied to a user through the silicon controlled bypass switch; through an AI pre-judgment technology, a power grid voltage drop or increase trend is pre-judged, and a series power unit is conducted in advance; a topology change-over switch is connected to form a boost or buck topology, and when the voltage of a power grid is too low or too high, the normal voltage of a user is ensured through PR closed-loop control; when the rear-end line / load breaks down, reclosing control is carried out; and voltage upper and lower limits are adjusted remotely. The device utilizes the AI pre-judgment technology, has the characteristics of stable voltage, no need of input / output commutation and the like, solves the problems of over-high and over-low voltage and automatic reclosing in fault, and improves the high power supply quality and the power supply reliability of users.

Description

Technical Field

[0001] This invention relates to the fields of power electronics and voltage regulation, and in particular to a power electronic voltage regulator with reclosing function. Background Technology

[0002] The power distribution network is a crucial link in energy production, conversion, and consumption. It also serves as a support platform for renewable energy integration, a platform for diverse and massive information data, and a trading platform for multiple market participants, occupying a core position in the entire smart grid system. Currently, the country is increasing investment in the construction and upgrading of the power distribution network, primarily addressing the challenges faced by traditional distribution networks in the face of increasingly complex electricity demands and the integration of new energy sources. These challenges include: insufficient transformer capacity leading to increased load causing long-term (heavy) and short-term (heavy) overloads of transformers; seasonal electricity demand during peak agricultural seasons and summer peak demand; and low voltage issues caused by long terminal lines.

[0003] With economic development and social progress, people have increasingly higher requirements for voltage quality. Excessive voltage can cause user equipment to burn out, resulting in economic losses, while insufficient voltage can prevent user equipment from functioning properly, and in severe cases, cause equipment damage. Voltage quality problems not only cause significant economic losses to users but also lead to serious production and operational accidents.

[0004] With the large-scale integration of distributed photovoltaic (PV) systems in rural areas, excessive daytime PV power transmission causes backflow, resulting in excessively high voltage; at night, increased electricity consumption causes excessively low voltage. As the economy develops and people's living standards improve, electricity consumption has increased significantly, especially in vast rural areas, where existing infrastructure cannot keep up with the growing demand.

[0005] Currently, the main measures to solve the above problems include traditional methods such as replacing large-capacity distribution transformers and upgrading lines. However, these methods involve large investments, long cycles, and are difficult to adapt to dynamic problems such as instantaneous voltage fluctuations. In addition, traditional voltage stabilization devices mostly use mechanical voltage regulation or simple electronic voltage regulation methods, which have disadvantages such as slow response speed, low efficiency, large size, and limited functionality. They cannot meet the high voltage quality requirements of modern distribution networks, especially in terms of rapid isolation and restoration of power supply in the face of instantaneous voltage drops, surges, and temporary faults on the user side, where there is still considerable room for improvement.

[0006] Therefore, there is an urgent need for a power electronic voltage regulating device that integrates high-efficiency voltage regulation, rapid dynamic response, fault self-recovery and remote control to meet the voltage management needs in complex power distribution network environments. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a high-efficiency power electronic voltage regulator with reclosing function and its control technology. The invention provides a corresponding topology and control method, which simultaneously solves the problems of excessively high and low voltage and suppresses voltage drops and surges through AI prediction technology, AC chopping technology and single-pole commutation control.

[0008] The technical solution of the present invention is as follows:

[0009] On the one hand, the present invention provides a power electronic voltage regulating device with reclosing function, which is connected in series in a low-voltage power distribution line. Its features include a main power circuit, a mechanical bypass branch, and a control unit.

[0010] The main power circuit includes:

[0011] A thyristor bypass switch consists of a pair of anti-parallel thyristors and is used to conduct when the mains voltage is normal, so as to supply power to the load with low loss.

[0012] The series power unit is composed of a first silicon carbide MOSFET (T1) and a second silicon carbide MOSFET (T2) connected in reverse series;

[0013] The parallel power unit consists of a third silicon carbide MOSFET (T3) and a fourth silicon carbide MOSFET (T4) connected in reverse series;

[0014] A topology switching switch has one moving terminal and two stationary terminals. The moving terminal is connected to one end of the parallel power unit, the first stationary terminal is connected to the first end (A) of the series power unit, and the second stationary terminal is connected to the second end (B) of the series power unit. By switching the conduction path of the topology switching switch, the series power unit is located on different sides of the parallel power unit, thereby configuring the main power circuit as a boost topology or a buck topology.

[0015] The input filter unit, consisting of an input inductor (L1) and an input capacitor (C1), is connected between the mains input terminal and the first terminal (A) of the series power unit.

[0016] The output filter unit, consisting of an output inductor (L2) and an output capacitor (C2), is connected between the second terminal (B) of the series power unit and the load output terminal.

[0017] The mechanical bypass branch includes a mechanical bypass switch, which is connected in parallel with the main power circuit;

[0018] The control unit, signal-connected to the thyristor bypass switch, the series power unit, the parallel power unit, the topology switching switch, and the mechanical bypass switch, is configured to perform the following operations:

[0019] Based on real-time sampling of the grid voltage and AI algorithms, the changing trend of the grid voltage is predicted, and the switching of the topology switching switch and the thyristor bypass switch is controlled in advance based on the prediction results.

[0020] When the grid voltage is abnormal, the PR closed-loop control algorithm based on virtual impedance adjusts the duty cycle of the series power unit and the parallel power unit to stabilize the output voltage.

[0021] When a load-side fault is detected, an automatic reclosing logic sequence is executed.

[0022] Furthermore, when the control unit executes the advance control, it is specifically configured as follows:

[0023] When it is predicted that the grid voltage is likely to drop below the lower voltage limit or experience a sudden drop, before the voltage actually exceeds the limit, the topology switching switch is controlled to connect its moving end with the first stationary end to form a boost topology, while the thyristor bypass switch is turned off and the series and parallel power modules are turned on.

[0024] When it is predicted that the grid voltage is likely to rise above the upper voltage limit or experience a sudden increase, before the voltage actually exceeds the limit, the topology switching switch is controlled to connect its moving end with the second stationary end to form a step-down topology, while the thyristor bypass switch is turned off and the series and parallel power modules are turned on.

[0025] Furthermore, when the control unit executes the PR closed-loop control algorithm based on virtual impedance for voltage reduction, the duty cycle D of the first silicon carbide MOSFET (T1) and the second silicon carbide MOSFET (T2) of the series power unit... 12 The formula is as follows:

[0026]

[0027] In the formula, U ref U is the output voltage setpoint. L i represents the actual measured value of the output voltage of this device. L This is the actual measured value of the output current of this device, R is the virtual impedance, and k is the control coefficient. p1 k i1 The value range is 0.1 <k p1 <1000, 0.01 <k i1 <10;;

[0028] The duty cycle D of the third silicon carbide MOSFET (T3) and the fourth silicon carbide MOSFET (T4) in the parallel power unit 34 The formula is as follows:

[0029] D 34 = 1-D 12 .

[0030] Furthermore, when the control unit executes the PR closed-loop control algorithm based on virtual impedance for boosting, the duty cycle D of the first silicon carbide MOSFET (T1) and the second silicon carbide MOSFET (T2) of the series power unit... 12 The formula is as follows:

[0031] D 12 = 1-D 34 .

[0032] The duty cycle D of the third silicon carbide MOSFET (T3) and the fourth silicon carbide MOSFET (T4) in the parallel power unit 34 The formula is as follows:

[0033]

[0034] In the formula, U ref U is the output voltage setpoint. L i represents the actual measured value of the output voltage of this device. L This is the actual measured value of the output current of this device, R is the virtual impedance, and k is the control coefficient. p1 k i1 The value range is 0.1 <k p1 <1000, 0.01 <k i1 <10.

[0035] Furthermore, when the control unit executes the automatic reclosing logic sequence, it is specifically configured as follows:

[0036] Upon detecting a fault, first shut off the thyristor bypass switch and all power modules, and disconnect the output switch;

[0037] After a preset delay, the mechanical bypass switch is first closed to tentatively restore power supply;

[0038] After the fault current is detected to have disappeared, the output switch is closed sequentially, the thyristor bypass switch is turned on, and finally the mechanical bypass switch is turned off, so that the device returns to normal working mode.

[0039] Furthermore, the topology switching switch is a single-pole double-throw solid-state relay or is implemented by a combination of two independent single-pole single-throw relays.

[0040] Furthermore, the silicon carbide MOSFET can be replaced by a gallium nitride high electron mobility transistor.

[0041] Secondly, the present invention also provides a three-phase power electronic voltage regulating system, characterized in that it is composed of the above three power electronic voltage regulating devices in a star or delta connection manner, and each phase device is independently controlled.

[0042] Compared with the prior art, the features of the present invention are as follows:

[0043] 1) Applying AI prediction algorithms to voltage trend assessment represents a leap from "passive response" to "active intervention," significantly reducing the impact of voltage fluctuations on the load and improving power quality.

[0044] 2) Introducing the concept of virtual impedance into the PR control of AC voltage regulation improves the damping characteristics of the system, effectively suppresses the resonance that may be caused by the LC filter circuit, and makes the dynamic process of the system more stable and reliable.

[0045] 3) It highly integrates efficient AC chopper voltage regulation, voltage transient event suppression and user-side automatic reclosing functions into a single device, providing a complete solution for low-voltage line voltage quality problems, solving overvoltage and undervoltage problems, suppressing voltage drops and surges, and clearing temporary user faults with automatic reclosing. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the topology of Embodiment 1 of the power electronic voltage regulating device with reclosing function of the present invention.

[0047] Figure 2 This is the PR control block diagram in this invention.

[0048] Figure 3 This is the main logic block diagram of the present invention. Detailed Implementation

[0049] The present invention will be further described below with reference to the embodiments and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0050] Example 1: Single-phase voltage regulating device

[0051] Please see Figure 1 , Figure 1 This is a schematic diagram of the topology of Embodiment 1 of the power electronic voltage regulator with reclosing function of the present invention. As can be seen from the figure, this embodiment provides a single-phase power electronic voltage regulator with reclosing function, including a thyristor bypass switch, a series power unit, a parallel power unit, an input filter unit, an output filter unit, a controller, a DC commutator switch, a mechanical bypass switch, an input switch, an output switch, etc.; by switching the boost (DC commutator switch connected to point A) and buck topologies (DC commutator switch connected to point B) through the DC commutator switch, the boost and buck functions are realized.

[0052] The thyristor bypass switch consists of a pair of anti-parallel thyristors;

[0053] The series power unit is composed of two silicon carbide power devices T1 and T2 connected in reverse series.

[0054] The parallel power unit is composed of two silicon carbide power devices T3 and T4 connected in reverse series.

[0055] The input filtering unit is composed of an inductor L1 and a capacitor C1, and the output filtering unit is composed of an inductor L2 and a capacitor C2.

[0056] The topology switching switch has three single-terminal terminals. The middle terminal of the DC commutation switch is connected to one end of the parallel power unit, and the other two ends of the DC commutation switch are respectively connected to the two ends of the series power unit.

[0057] The other end of the input switch is connected to the input terminal of the mechanical bypass switch, and the other end of the output switch is connected to the output terminal of the mechanical bypass switch.

[0058] One end of the series power unit is connected to one end of inductor L1 and one end of capacitor C1, and the other end of inductor L1 is connected to one end of the thyristor bypass switch. The other end of the series power unit is connected to one end of inductor L2 and capacitor C2, and the other end of inductor L2 is connected to the other end of the thyristor bypass switch. The other ends of the parallel power unit, capacitor C1, and capacitor C2 are connected to the neutral line N. The mechanical bypass switch is connected to the input and output terminals of the device of the present invention.

[0059] The control unit has the following functions:

[0060] 1) Topology switching switch

[0061] The topology switch is connected to one end of inductor L2 (point B), meaning the series power unit is located at the front end of the parallel power unit, and the device is a step-down topology; the topology switch is connected to one end of inductor L1 (point A), meaning the series power unit is located at the rear end of the parallel power unit, and the device is a step-up topology.

[0062] 2) Voltage over-limit detection technology

[0063] Set the upper and lower limits of the voltage. The upper limit is the grid rated voltage U0 + 5% U0 by default, and the lower limit is the grid rated voltage U0 - 5% U0 by default.

[0064] Calculate the effective value U of the grid voltage based on the Discrete Fourier Transform formula. in Output voltage RMS value U L The calculation formula is as follows:

[0065] (1)

[0066] (2)

[0067] (3)

[0068] The N sine function values ​​and N cosine function values ​​from equations (1) and (2) are compiled into a table and stored in the controller's memory. U is then calculated using the table lookup method. R U I ;

[0069] Where N is the number of sampling points within the period, which can be set to N=128, m is the sampling sequence from 0 to N-1, U m U represents the voltage value at the instantaneous sampling point. R U I These are the real and imaginary parts of the voltage, respectively, and U is the voltage amplitude.

[0070] 3) Voltage sag surge detection technology

[0071] Instantaneous detection method: When the instantaneous value of the grid voltage is lower than the corresponding value of the same phase point of the previous cycle by 10% for 5 consecutive sampling points, it is determined that the grid voltage has dropped; when the grid voltage is higher than the corresponding value of the same phase point of the previous cycle by 10% for 5 consecutive sampling points, it is determined that the grid voltage has surged.

[0072] 4) Output voltage PR closed-loop control based on virtual impedance

[0073] When the effective value of the grid voltage U in When the voltage limit is exceeded, the series power unit and the parallel power unit are controlled to step down the voltage. A closed-loop control based on the output voltage PR is adopted. The duty cycles of the two power devices T3 and T4 in the series power unit are shown below:

[0074] (4)

[0075] In the above formula, U ref U is the output voltage setpoint. L i represents the actual measured value of the output voltage of this device. L D represents the actual measured value of the output current of this device. 12 The duty cycles of the two power devices T1 and T2 in the series power unit; the control coefficient k p1 k i1 Its value range is 0.1 <k p1 <1000, 0.01 <k i1 <10; R is the virtual impedance;

[0076] The duty cycles of the two power devices T3 and T4 in the parallel power unit are shown below:

[0077] D 34 = 1-D 12 (5)

[0078] Among them, D 34The duty cycles of the two power devices T3 and T4 in the parallel power unit;

[0079] grid voltage RMS value U in When the voltage is below the lower limit, the series and parallel power units are controlled to boost the voltage. A closed-loop control based on the output voltage PR is adopted. The duty cycles of the two power devices T3 and T4 in the parallel power unit are shown below:

[0080] (6)

[0081] The duty cycle D of the two power devices T1 and T2 in the series power unit 12 The formula is as follows:

[0082] D 12 = 1-D 34 (7)

[0083] 5) Controller

[0084] Based on a domestically produced ARM chip, programmable control is implemented, and the control logic is as follows:

[0085] i) Initialization: Close the DC commutator switch and connect it to inductor L2. The device topology is a boost structure. Turn on the thyristor bypass switch and turn off the mechanical bypass switch. Set the number of sampling points, upper voltage limit, lower voltage limit, rated grid voltage, setpoint output voltage, grid frequency, and set the sine and cosine function tables.

[0086] ii) Sample voltage and current, and calculate grid voltage, output voltage, and current;

[0087] iii) Within the normal range of the grid voltage, the thyristor bypass switch is turned on, the series power unit and the parallel power unit are turned off, and the control DC commutation switch is connected. The default device topology is a boost structure.

[0088] iv) Based on AI technology, predict the voltage change trend, predict that the grid voltage change is close to the lower voltage limit, or there is a sign of a sudden voltage drop, turn on the series power unit, turn off the thyristor bypass switch, and control the DC commutation switch connection, so that the device topology is a boost structure.

[0089] v) Based on AI technology, predict voltage change trends, predict that the grid voltage change is close to the voltage upper limit, or there are signs of a sudden voltage rise, turn on the series power unit, turn off the thyristor bypass switch, and control the DC commutation switch connection to make the device topology a step-down structure.

[0090] vi) If the grid voltage is lower than the lower voltage limit / a voltage drop occurs, the duty cycle of the series power unit and the parallel power unit is controlled through the output voltage PR closed-loop control to perform boost control / drop suppression;

[0091] vii) If the grid voltage is higher than the voltage limit or a voltage surge occurs, the duty cycle of the series power unit and the parallel power unit is controlled through the output voltage PR closed-loop control to perform voltage reduction control / surge suppression.

[0092] viii) If overvoltage protection, overcurrent protection, or overtemperature protection is triggered, the series power unit and the parallel power unit shall be shut down immediately, the thyristor bypass switch shall be closed, and the mechanical bypass switch shall be closed; then the thyristor bypass switch, input switch, and output switch shall be shut down, the device shall be taken out of operation, and an alarm signal shall be issued at the same time.

[0093] ix) If a fault occurs in the back-end line / user end, the thyristor bypass switch, series power unit and parallel power unit are turned off, the output switch and mechanical bypass switch are turned off; after 1 second, the mechanical bypass switch is closed again. If the fault current is cleared, the output switch is closed and the thyristor bypass switch is turned on, and the device continues to work; if the fault current continues to exist, the mechanical bypass switch is opened, the device exits operation, and an alarm signal is issued.

[0094] Figure 3 This is the control logic block diagram of the present invention. Upon startup, the input / output switches are closed, the thyristor bypass switch is turned on, and the DC commutator switch is controlled. The device topology is set to a boost structure by default. The mechanical bypass switch is then disconnected. When the grid voltage is normal, the thyristor bypass switch supplies power to the user, allowing the device to operate at its highest efficiency. Using AI prediction technology, the device predicts grid voltage changes. If the grid voltage is predicted to be close to the lower voltage limit or show signs of a sudden drop, the series power unit is turned on, and the thyristor bypass switch is turned off. If the grid voltage is predicted to be close to the lower voltage limit or show signs of a sudden drop, the DC commutator switch is controlled, enabling the device to operate in a buck topology. In the boost topology, when the grid voltage is below the lower voltage limit or a voltage drop occurs, the series and parallel power units are controlled for boost control / drop suppression. In the buck topology, when the grid voltage is above the upper voltage limit or a voltage surge occurs, the series and parallel power units are controlled for buck control / surge suppression. When a user fault occurs, the device performs reclosing. If reclosing is successful, the device continues to operate; otherwise, it exits operation due to the fault and triggers an alarm.

[0095] In this implementation, the upper and lower voltage limits, output voltage setpoint, and reclosing time can be remotely adjusted and set according to the actual site conditions. The domestically produced ARM chip can be replaced by a domestically produced DSP or other CPUs. The power unit can be composed of gallium nitride or other low-loss, high-frequency power devices.

[0096] Example 2: Three-phase voltage regulation system

[0097] For a three-phase four-wire system, it consists of three independent single-phase voltage regulating devices as described in Example 1. Each device is connected between the three-phase live wires (A, B, and C) and the neutral wire. The controllers of the three devices communicate via CAN bus or Ethernet, enabling data aggregation and collaborative management. However, the voltage regulation and reclosing logic are executed completely independently, thereby achieving regulation of the three-phase voltage.

[0098] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A power electronic voltage regulating device with reclosing function, connected in series in a low-voltage distribution line, characterized in that, Includes main power circuit, mechanical bypass branch and control unit; The main power circuit includes: A thyristor bypass switch consists of a pair of anti-parallel thyristors and is used to conduct when the mains voltage is normal, so as to supply power to the load with low loss. The series power unit is composed of a first silicon carbide MOSFET (T1) and a second silicon carbide MOSFET (T2) connected in reverse series; The parallel power unit consists of a third silicon carbide MOSFET (T3) and a fourth silicon carbide MOSFET (T4) connected in reverse series; A topology switching switch has one moving terminal and two stationary terminals. The moving terminal is connected to one end of the parallel power unit, the first stationary terminal is connected to the first end (A) of the series power unit, and the second stationary terminal is connected to the second end (B) of the series power unit. By switching the conduction path of the topology switching switch, the series power unit is located on different sides of the parallel power unit, thereby configuring the main power circuit as a boost topology or a buck topology. The input filter unit, consisting of an input inductor (L1) and an input capacitor (C1), is connected between the mains input terminal and the first terminal (A) of the series power unit. The output filter unit, consisting of an output inductor (L2) and an output capacitor (C2), is connected between the second terminal (B) of the series power unit and the load output terminal. The mechanical bypass branch includes a mechanical bypass switch, which is connected in parallel with the main power circuit; The control unit, signal-connected to the thyristor bypass switch, the series power unit, the parallel power unit, the topology switching switch, and the mechanical bypass switch, is configured to perform the following operations: Based on real-time sampling of the grid voltage and AI algorithms, the changing trend of the grid voltage is predicted, and the switching of the topology switching switch and the thyristor bypass switch is controlled in advance based on the prediction results. When the grid voltage is abnormal, the PR closed-loop control algorithm based on virtual impedance adjusts the duty cycle of the series power unit and the parallel power unit to stabilize the output voltage. When a load-side fault is detected, an automatic reclosing logic sequence is executed.

2. The power electronic voltage regulating device with reclosing function according to claim 1, characterized in that, When the control unit executes the advance control, it is specifically configured as follows: When it is predicted that the grid voltage is likely to drop below the lower voltage limit or experience a sudden drop, before the voltage actually exceeds the limit, the topology switching switch is controlled to connect its moving end with the first stationary end to form a boost topology, while the thyristor bypass switch is turned off and the series and parallel power modules are turned on. When it is predicted that the grid voltage is likely to rise above the upper voltage limit or experience a sudden increase, before the voltage actually exceeds the limit, the topology switching switch is controlled to connect its moving end with the second stationary end to form a step-down topology, while the thyristor bypass switch is turned off and the series and parallel power modules are turned on.

3. The power electronic voltage regulating device with reclosing function according to claim 1, characterized in that, When the control unit executes the PR closed-loop control algorithm based on virtual impedance for voltage reduction, the duty cycle D of the first silicon carbide MOSFET (T1) and the second silicon carbide MOSFET (T2) in the series power unit is... 12 The formula is as follows: ； In the formula, U ref U is the output voltage setpoint. L i represents the actual measured value of the output voltage of this device. L This is the actual measured value of the output current of this device, R is the virtual impedance, and k is the control coefficient. p1 k i1 The value range is 0.1 <k p1 <1000, 0.01 <k i1 <10;; The duty cycle D of the third silicon carbide MOSFET (T3) and the fourth silicon carbide MOSFET (T4) in the parallel power unit 34 The formula is as follows: D 34 = 1-D 12 。 4. The power electronic voltage regulating device with reclosing function according to claim 1, characterized in that, When the control unit executes the PR closed-loop control algorithm based on virtual impedance for voltage boosting, the duty cycle D of the first silicon carbide MOSFET (T1) and the second silicon carbide MOSFET (T2) in the series power unit is... 12 The formula is as follows: D 12 = 1-D 34 The duty cycle D of the third silicon carbide MOSFET (T3) and the fourth silicon carbide MOSFET (T4) in the parallel power unit. 34 The formula is as follows: ； In the formula, U ref U is the output voltage setpoint. L i represents the actual measured value of the output voltage of this device. L This is the actual measured value of the output current of this device, R is the virtual impedance, and k is the control coefficient. p1 k i1 The value range is 0.1 <k p1 <1000, 0.01 <k i1 <10.

5. The power electronic voltage regulating device with reclosing function according to claim 1, characterized in that, When the control unit executes the automatic reclosing logic sequence, it is specifically configured as follows: Upon detecting a fault, first shut off the thyristor bypass switch and all power modules, and disconnect the output switch; After a preset delay, the mechanical bypass switch is first closed to tentatively restore power supply; After the fault current is detected to have disappeared, the output switch is closed sequentially, the thyristor bypass switch is turned on, and finally the mechanical bypass switch is turned off, so that the device returns to normal working mode.

6. The power electronic voltage regulating device with reclosing function according to claim 1, characterized in that, The topology switching switch is a single-pole double-throw solid-state relay or a combination of two independent single-pole single-throw relays.

7. The power electronic voltage regulating device with reclosing function according to claim 1, characterized in that, The silicon carbide MOSFET can be replaced by a gallium nitride high electron mobility transistor.

8. A three-phase power electronic voltage regulating system, characterized in that, It is composed of three power electronic voltage regulating devices as described in any one of claims 1 to 7, which are combined in a star or delta connection, and each phase device is independently controlled.

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