Reactive power compensator topology circuit and double closed loop control method based on double rotating phase shifter synthesized phase principle

Abstract

The application discloses a double closed loop control of a reactive power compensator based on a phase quantity synthesis principle of double rotating phase shifters, and the double closed loop control is characterized in that: by measuring a voltage of a reactive power compensator access point, a load current, an inductance current and a total current of a primary side of two rotating phase shifters, the total current is converted to a dq0 coordinate system, and instantaneous power of a line is calculated by using an instantaneous power theory; reactive power of the load is taken as a feedback value, and an expected value of power closed loop control is determined by combining a power factor preset value of a power grid, the expected value and the given value are compared to form a given value of the reactive current; d and q axis components of the instantaneous current are taken as feedback values, and the closed loop control quantity is formed by comparing the d and q axis components with the given value; by using a rotating vector synthesis principle, a rotor mechanical angle instruction of each rotating phase shifter is obtained, the rotor mechanical angle instruction is adjusted through a servo controller, and then the reactive power absorbed or emitted by the reactive power compensator is changed; and the application provides a new reactive power compensation control scheme which is low in cost, strong in impact resistance, high in reliability, convenient in maintenance, omni-directional in compensation and continuous in adjustment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of power transmission and distribution network and grid-connection of distributed power supply, and particularly relates to the reactive power regulation of active distribution network with high penetration of distributed power supply, the reactive power regulation of urban power network with high cable rate, and the reactive power regulation of extra-high voltage line with excessive charging power. BACKGROUND

[0002] With the increasing penetration of new energy, the characteristics of its immediate output will cause the problem of complex voltage and reactive power distribution of active distribution network with high penetration of distributed power supply, and further put forward higher requirements for the reactive power and voltage regulation strategy and equipment performance of active distribution network.

[0003] Meanwhile, with the acceleration of urban cable rate in China and the rapid development of extra-high voltage power grid, the charging power of 100km long cable line in 500kV extra-high voltage power grid is about 961-1611MVar, which is 3-4 times of 220kV cable line of the same length and 11-16 times of overhead line of the same length and voltage level. Especially when the load is light or the grid construction in some areas is ahead of the grid scale and the load is light, the effect of capacity increase is more obvious, the reactive power of the grid is seriously excessive, which has a great impact on the safe and stable operation of the grid, and the problems of grid reactive power and dynamic voltage stability are increasingly prominent. Fast and efficient dynamic reactive power compensation is of increasing importance to improve the power factor and transmission efficiency of the grid side, reduce power loss and ensure the safe and stable operation of the grid.

[0004] Thyristor-switchable shunt capacitor is one of the traditional reactive power compensation methods, which has the advantages of flexible operation and low investment. However, it can only compensate in single polarity and cannot continuously adjust the compensated reactive power. Switching of the capacitor will cause fluctuations in the grid and even unnecessary impact on the grid. The adjustment effect is poor and the reliability is poor. Although thyristor-controlled capacitor can continuously adjust the reactive power, it also has the disadvantage of single-polarity reactive power compensation.

[0005] Flexible AC transmission system devices such as static reactive power compensator, static synchronous compensator and unified power flow controller can continuously adjust the compensated reactive power and have fast control response speed. However, they are all power electronic devices, which generally have the disadvantages of small thermal capacity, poor tolerance, weak impact resistance and high cost, and are difficult to adapt to the conditions of active distribution network or extra-high voltage network and line, such as snowstorm disaster and severe cold weather, complex load properties and other conditions. The control strategy is complex and cannot avoid the problem of introducing harmonics into the system, which is greatly limited in the application of the grid.

[0006] The reactive power compensator based on the traditional mechanical tap changer phase-shifting transformer cannot meet the continuous adjustment of the compensation of reactive power, the frequent switching of the mechanical switch increases the device loss, is easy to be damaged, increases the maintenance and maintenance cost to some extent, reduces the device reliability, and the adjustment speed is slow.

[0007] The reactive power compensator based on the principle of synthesizing phase quantities of double rotary phase shifters does not need mechanical tap switches, has a faster response speed than the traditional phase-shifting transformer, can continuously adjust the reactive power, has good stability and high reliability, and has the advantages of low cost, high reliability, durability, small loss, relatively simple control method, no harmonic problem, no electromagnetic interference problem and the like compared with the power electronic type reactive power compensator.

[0008] Therefore, it is urgent to invent a reactive power compensator control strategy based on the principle of synthesizing phase quantities of double rotary phase shifters with high reliability and low cost to realize accurate regulation and control of the compensation of reactive power, ensure that no overcurrent occurs in the internal regulation and control process, thereby effectively improving the power factor of the power grid to a set value, reducing power loss, and improving power supply quality. SUMMARY

[0009] The application discloses a double closed-loop control of a reactive power compensator based on the principle of synthesizing phase quantities of double rotary phase shifters, measures the voltage of a reactive power compensator access point, load and inductance currents and total currents of primary sides of two rotary phase-shifting transformers, converts the currents to a dq0 coordinate system, calculates the instantaneous power of the line by using the instantaneous power theory, takes the reactive power absorbed by the inductance as a feedback value, determines the expected value of power closed-loop control in combination with a preset power factor of the power grid, compares the two to form a given value of the reactive current, compares the d and q axis components of the instantaneous current with the given value to form a closed-loop control amount, uses the principle of rotary vector synthesis to obtain the rotor mechanical angle instructions of the rotary phase shifters, adjusts the instructions by a servo controller, and changes the reactive power absorbed or emitted by the reactive power compensator, and the application provides a new reactive power compensation control scheme with low cost, strong impact resistance, high reliability, easy maintenance, omnidirectional compensation and continuous adjustment.

[0010] The application is achieved by the following technical solutions:

[0011] In the dual closed-loop control of the reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters proposed in this invention, the primary windings of the dual rotating phase shifters are connected in parallel and simultaneously connected in parallel with the three-phase capacitors; the secondary windings of the dual rotating phase shifters are connected in series with corresponding phases to form a three-phase star or delta connection, and are connected in parallel with the three-phase energy storage inductors of the three-phase connection; both rotating phase shifters are composed of a closed iron core magnetic circuit, primary windings, secondary windings, controllers, servo motors, worm gears, worm shafts, and housings, accessories, etc. The reactive power compensation mechanism of a reactive power compensator based on a dual rotating phase shifter is as follows: First, energy is extracted from the primary side of the reactive power compensator (dual rotating phase shifter transformer) through parallel connection; then, the inductive voltage regulation principle of the rotating phase shifter transformer is used to change the relative angular displacement of the primary and secondary (stator and rotor) winding axes, i.e., the stator and rotor position angles. While completing the energy transfer between the primary and secondary windings through magnetic field induction, the phase of the secondary winding voltage is adjusted (relative to the primary voltage phase). When the effective turns ratio of the primary and secondary windings of the two rotating phase shifter transformers is equal, the amplitude of their secondary voltages is equal, and the phase is determined by their respective rotor position angles; the dual rotating phase shifter... The secondary windings of the phase transformer are connected in series with the corresponding phase ends to form a three-phase connection and are connected in parallel with the three-phase energy storage inductor. At this time, the voltage applied across the three-phase energy storage inductor is actually a composite voltage of two voltage phasors with equal amplitude and 360° adjustable phase. According to the rotating vector synthesis method, this composite voltage phasor can achieve arbitrary adjustment of amplitude from 0 to maximum voltage (twice the amplitude of the secondary voltage) and phase angle from 0° to 360°, thereby steplessly and continuously changing the reactive power absorbed by the three-phase energy storage inductor, and thus realizing bidirectional and continuous adjustment of reactive power compensation to the grid by the reactive power compensator based on the principle of composite phasor of dual rotating phase shifters.

[0012] This invention proposes a dual-closed-loop control system for reactive power compensators based on the principle of synthesized phasors using dual rotating phase shifters. It mainly comprises six parts: a main circuit for reactive power compensation using dual rotating phase shifters, a detection module, a signal processing module, a power outer loop control module, a direct current inner loop control module, and a phase angle control module. The input terminal of the detection module is connected to the secondary voltage output terminal of a voltage transformer that measures the three-phase voltage at the reactive power compensator connection point of the dual rotating phase shifters, and the secondary current output terminal of a current transformer that measures the three-phase current flowing through the load and inductor, and the total primary current of the two rotating phase shifters. The processing results of the detection module are transmitted to the signal processing module. The converted and calculated data results of the signal processing module are transmitted to the power outer loop control module, the direct current inner loop control module, and the phase angle control module. The calculation results of the power outer loop control module are transmitted to the direct current inner loop control module, and the calculation results of the direct current inner loop control module are transmitted to the phase angle control module. The results of the phase angle control module are then transmitted to the servo controllers of the two rotating phase shifters.

[0013] The main circuit of the dual rotating phase-shifting transformer can essentially be considered as a controlled power source. Its magnitude depends only on the amplitude of the synthesized voltage phasor on the secondary side and is independent of the phase angle. Therefore, in the dual closed-loop control of the reactive power compensator based on the synthesized phasor principle of the dual rotating phase shifter proposed in this invention, the rotor position angles of the two rotating phase-shifting transformers are set to opposite numbers. By controlling only one variable, the synthesized voltage amplitude can be arbitrarily adjusted from 0 to its maximum value. This control strategy is also applicable to reactive power compensators with two coaxially rotating phase-shifting transformers.

[0014] The detection module uses voltage transformers and current transformers to collect the electrical physical quantities required to establish a dual closed-loop control model of the reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters. These quantities include: the three-phase voltage at the reactive power compensator connection point, the three-phase current flowing through the load and inductor, and the total primary current of the two rotating phase shifters. The module then transmits the collected electrical physical quantities to the signal processing module.

[0015] The signal processing module performs coordinate transformation on the three-phase voltage and current input from the detection module. It uses a phase-locked loop (PLL) to obtain the phase of the voltage at the access point and fixes it on the d-axis as a reference phasor. Other electrical physical quantities are transformed from the abc coordinate system to the dq0 coordinate system based on the synchronous rotating coordinate transformation theory. The phase of the voltage at the access point is then transmitted to the direct current inner loop control module and the phase angle control module. At the same time, the calculated d and q axis components of each physical quantity are transmitted to the direct current inner loop control module and the phase angle control module. The three-phase instantaneous reactive power flowing through the load, capacitor, and inductor, as well as the three-phase instantaneous active power of the load, calculated using instantaneous power theory, are transmitted to the power outer loop control module.

[0016] The power outer loop control module, in conjunction with the power factor preset on the grid side, determines the setpoint for the power closed loop control based on the three-phase reactive power of the capacitor and the instantaneous active and reactive power of the three-phase load. Then, the three-phase instantaneous reactive power consumed by the inductor is used as the feedback value, and the compensation amount for the power outer loop closed loop control is formed through the PI controller. Based on its direct relationship with the energy storage inductor current, the reactive component of the direct current is obtained and transmitted to the direct current inner loop control module.

[0017] The direct current inner loop control module uses the reactive component of the inductor current input from the power outer loop control module after limiting it as the given value of the reactive current; it uses the d and q axis components of the inductor current input from the signal processing module as feedback quantities, and compares the deviation with the given values ​​of active and reactive current respectively. After passing through the PI controller, it forms the compensation quantities for the d and q axis current closed loop control respectively. Combined with the phase of the access point voltage input from the signal processing module, it is transformed into the abc coordinate system, and the obtained inductor current phasor is transmitted to the phase angle control module.

[0018] The phase angle control module calculates the composite voltage phasor of the secondary side of the rotating phase-shifting transformer using the inductor current phasor input from the direct current inner loop control module. Combined with the access point voltage phase input from the signal processing module, this phasor is transformed from the abc coordinate system to the dq0 coordinate system. Using the principle of rotating vector synthesis and the access point voltage input from the detection module, the rotor electrical angle commands of the two rotating phase-shifting transformers are calculated. Then, combined with the number of pole pairs of the two rotating phase-shifting transformers, the rotor mechanical angle control commands of the two rotating phase-shifting transformers are calculated. The calculation results are then transmitted to the servo controllers of the two rotating phase-shifting transformers in the reactive power compensator. The servo controllers of the two rotating phase-shifting transformers adjust the rotor position angle according to the rotor mechanical angle control commands transmitted from the phase angle control module, thereby changing the amplitude of the composite voltage phasor on the secondary side. This achieves precise control of the power output or absorption by the reactive power compensator and the secondary side current, forming a dual closed-loop control of current and power.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. This invention provides a dual closed-loop control method for power and current of a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters. On the one hand, it enables precise regulation of reactive power, achieving bidirectional and dynamic compensation for the reactive power required by the load without introducing harmonic problems. On the other hand, while adjusting the absorbed or generated reactive power, the current within the device is simultaneously controlled according to the expected value, preventing internal overcurrent and insulation damage. Therefore, it improves the reliability and adaptability of the reactive power compensator, effectively enhances the power factor on the grid side, improves power supply efficiency and power quality, and reduces power loss. Thus, it has a wider range of applications and better prospects.

[0021] 2. This invention obtains the instantaneous reactive power required for control at various points through coordinate transformation and instantaneous reactive power theory calculation, and achieves the purpose of controlling reactive current by controlling reactive power; based on the given values ​​of reactive power and reactive current, the combined voltage on the secondary side of the two rotating phase-shifting transformers is obtained; using the principle of rotating vector synthesis, the phase angle of two phasors with the same amplitude is obtained to determine the rotor position angle of the two rotating phase-shifting transformers, and the adjustment is performed by a servo controller, thereby realizing dual closed-loop control of power and current. This method solves the technical problem of promoting the application of reactive power compensators based on the principle of phasor synthesis of dual rotating phase shifters.

[0022] 3. This invention provides a dual closed-loop control of power and current of reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters. It also provides a new reactive power compensation control scheme with low cost, strong impact resistance, high reliability, and convenient maintenance, which is omnidirectional and continuously adjustable. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the main circuit wiring of a preferred embodiment of the reactive power compensator dual closed-loop control based on the principle of synthesized phasors of dual rotating phase shifters provided by the present invention.

[0024] Figure 2 This is a schematic diagram of a single-phase equivalent circuit of a preferred embodiment of the dual-closed-loop control of a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters, provided by the present invention.

[0025] Figure 3 This is a control structure design diagram of a preferred embodiment of the dual closed-loop control of a reactive power compensator based on the principle of synthesized phasors by dual rotating phase shifters provided by the present invention.

[0026] Figure 4 This is a control principle diagram of a preferred embodiment of the dual closed-loop control of a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters provided by the present invention.

[0027] Figure 5 This invention provides a simulation waveform diagram showing the reactive power compensation of a reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters, as well as the reactive power generated and absorbed by capacitors and inductors, as the rotor electrical angle of the rotating phase shifter changes.

[0028] Figure 6 This is a graph showing the change in rotor electrical angle of the two rotating phase-shifting transformers during dynamic reactive power compensation in the dual closed-loop control of the reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters, provided by this invention.

[0029] Figure 7 This invention provides a tracking curve of the real-time power value versus the given value in the power outer loop control of a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters, as well as a compensation curve of the device for the reactive power required by the load during dynamic reactive power compensation.

[0030] Figure 8 This invention provides a tracking curve of the real-time values ​​of the active and reactive current components versus the given values ​​in the direct current inner loop control of a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters during dynamic reactive power compensation.

[0031] Figure 9 This invention provides a curve showing the change in the power factor on the grid side during dynamic reactive power compensation using a dual-loop control system for a reactive power compensator based on the principle of synthesized phasors from dual rotating phase shifters.

[0032] Figure 10 The present invention provides a diagram showing the voltage and current waveforms of phase A on the grid side after reactive power compensation is achieved by implementing dual closed-loop control of a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters.

[0033] The symbols for each component in the attached diagram are as follows: The voltage at the connection point of the reactive power compensator; The reactive power of the equivalent load at the connection point; The reactive power compensated by the reactive power compensation device; It is used to compensate for the reactive power consumed by the equivalent inductor in the device, and it is also the feedback quantity of the power outer loop closed-loop control. To compensate for the reactive power generated by the parallel capacitors in the compensation device; The current flowing through the load, The current flowing through the parallel capacitor. This represents the total current on the primary side of the two rotating phase-shifting transformers. A represents the current on the secondary side of a two-phase-shifting transformer. l B l, C l For each live wire terminal of the line, the reactive power compensator based on the double rotating phase-shifting transformer is connected in parallel. , , These are the terminals at the beginning of a three-phase capacitor. , , These are the terminals at the end of the three-phase capacitor; , , , , , This is the starting end of the primary winding of a two-rotating phase-shifting transformer; , , , , , These are the ends of the primary windings of the two rotating phase-shifting transformers, respectively. , , , , , These are the starting ends of the secondary windings of the two rotating phase-shifting transformers, respectively. , , , , , These are the ends of the secondary windings of the two rotating phase-shifting transformers, respectively. , , , , , These are the terminals of each phase at both ends of the three-phase energy storage inductor. For the parallel capacitor in the compensation device, To compensate for the energy storage inductor in the device, To compensate for the equivalent inductance of the internal inductance and energy storage inductance of the two rotating phase-shifting transformers in the device, The equivalent resistance of the internal resistance of the two rotating phase-shifting transformers and the line resistance of the compensation device. ; This represents the turns ratio of a two-phase-shifting transformer. This represents the number of pole pairs of the rotating phase-shifting transformer. These are the secondary voltages of two rotating phase-shifting transformers, both of which are rotating phasors with equal amplitude and variable phase angle. These correspond to the electrical angles of the two rotating phasors, respectively. These correspond to the rotor position angles of the two rotating phase-shifting transformers, i.e., the servo controller angles. The combined voltage on the secondary sides of the two rotating phase-shifting transformers determines the magnitude of reactive power consumption by the inductor in the reactive power compensator. Obtained by superposition and synthesis; Voltage at the access point The phase of the phase is used as the reference phase during coordinate transformation, so that the voltage at the connection point can be fixed on the d-axis. These are the voltages at the access points. The d-axis and q-axis components in the dq0 coordinate system; Secondary current The active and reactive components in the dq0 coordinate system are also the feedback values ​​of the d and q axes in the direct current inner loop closed-loop control, respectively. These are the load currents respectively The d-axis and q-axis components in the dq0 coordinate system; The total series current on the primary side is respectively The d-axis and q-axis components in the dq0 coordinate system; They are respectively The d-axis and q-axis components in the dq0 coordinate system; This represents the expected value of reactive power consumed by the inductor in the reactive power compensator. It is the compensation amount for reactive power closed-loop control formed by the PI controller of the power outer loop control module; These are the expected values ​​of the active current and reactive current on the secondary side of the rotating phase-shifting transformer, respectively. These are the compensation quantities for the d-axis and q-axis current closed-loop control formed by the PI controller of the direct current inner loop control module. This is the compensation amount for current closed-loop control. Detailed Implementation

[0034] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention, but this should not be used to limit the scope of protection of the present invention.

[0035] See Figure 1 , Figure 1 This is a schematic diagram of the main circuit of a preferred embodiment of the dual closed-loop control of a reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters provided by the present invention. The control objective is to improve the power factor on the grid side to a set value, that is, to control the reactive power generated by the rotating reactive power compensator to be close to the reactive power required by the load.

[0036] See Figure 2 , Figure 2 This is a single-phase equivalent circuit diagram of a preferred embodiment of the dual-closed-loop control of a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters, provided by the present invention. The reactive power generated by the three-phase capacitors in the reactive power compensator... The equivalent inductance that consumes reactive power in the device remains almost unchanged, and is equivalent to a reactive power source. The magnitude of this reactive power source is determined by the secondary-side synthesized voltage. The determination is made by the rotor electrical angle of the two rotating phase-shifting transformers. Influenced by rotor position angle control.

[0037] See Figure 3 , Figure 3 This invention provides a preferred embodiment of the dual-closed-loop control structure for a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters. It mainly comprises six parts: a main circuit for the reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters, a detection module, a signal processing module, a power outer loop control module, a direct current inner loop control module, and a phase angle control module. The input terminal of the detection module is connected to the secondary voltage output terminal of the voltage transformer that measures the three-phase voltage at the reactive power compensator connection point, and the secondary current output terminal of the current transformer that measures the three-phase current flowing through the load and inductor, and the total primary current of the two rotating phase-shifting transformers. The processing result of the detection module is transmitted to the signal processing module. The converted and calculated data results of the signal processing module are transmitted to the power outer loop control module, the direct current inner loop control module, and the phase angle control module. The calculation results of the power outer loop control module are transmitted to the direct current inner loop control module, and the calculation results of the direct current inner loop control module are transmitted to the phase angle control module. The results of the phase angle control module are transmitted to the servo controllers of the two rotating phase-shifting transformers, and the reactive power and current are adjusted and controlled by the servo motors adjusting the rotor angle.

[0038] See Figure 4 , Figure 4This is a control principle diagram of a preferred embodiment of the dual closed-loop control of a reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters, provided by the present invention. It includes a reactive power compensation main circuit based on the rotating phase shift principle, a detection module, a signal processing module, a power outer loop control module, a direct current inner loop control module, and a phase angle control module. A dual closed-loop control of power and current for a reactive power compensator based on the rotating phase shift principle includes the following specific steps:

[0039] A. The detection module acquires the electrical physical quantities required to establish a dual-closed-loop control model for the reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters, including: the three-phase voltage at the reactive power compensator connection point. Three-phase current flowing through the load Three-phase current of inductor and the total primary current of the two rotating phase-shifting transformers The detected electrical physical quantities are transmitted to the signal processing module; the load-absorbed reactive power can be indirectly measured through the signal processing module. and merit Capacitors generate reactive power and inductor absorption of reactive power And all of them are passed to the power outer loop control module.

[0040] B. The signal processing module will perform coordinate transformation on the three-phase voltage and current input from the detection module, and use a phase-locked loop (PLL) to obtain the phase of the voltage at the connection point. This is used as a reference phasor fixed on the d-axis. Other electrical physical quantities are then transformed from the abc coordinate system to the dq0 coordinate system based on the synchronous rotating coordinate transformation theory. The results before and after the transformation are as follows: Become ; Become ; Become ; Become ; the transformed direct current The voltage is transmitted to the direct current inner loop control module; the transformed access point voltage is then transferred. The data is passed to the phase angle processing module; the instantaneous reactive power calculated using instantaneous power theory in the dq0 coordinate system will then be transferred. and load active power The signal is transmitted to the power outer loop control module; and the phase of the voltage at the connection point is... It is transmitted to the direct current inner loop control module and the phase angle control module.

[0041] C. The power outer loop control module determines the setpoint for power closed loop control based on the power factor setting value on the grid side and the instantaneous power input from the signal processing module. ,by As a real-time feedback value, the compensation amount for reactive power closed-loop control is formed by comparing the feedback value with the setpoint. Based on its direct relationship with the inductor current, the reactive component of the direct current is obtained and transmitted to the direct current inner loop control module.

[0042] D. The direct current inner loop control module uses the direct current reactive component input from the power outer loop control module as the reactive current setpoint. Simultaneously read the internally stored active current setpoint. ; Input via signal processing module These values ​​are used as feedback values ​​for active and reactive current, respectively, and their deviations are compared with the given values ​​for active and reactive current. These deviations are then processed by a PI controller to form compensation values ​​for the d-axis and q-axis current closed-loop control. This compensation is then combined with the phase voltage at the access point input from the signal processing module. Transform it to the abc coordinate system. The results before and after the transformation are as follows: Become ; Transformed current phasors It is passed to the phase angle control module.

[0043] E. The phase angle control module receives the current phasor from the direct current inner loop control module. The resultant voltage phasor of the secondary side of the rotating phase-shifting transformer was calculated. Combined with the access point voltage phase input from the signal processing module The voltage phasors are transformed from the abc coordinate system to the dq0 coordinate system. The results before and after the transformation are as follows: Become Using the principle of rotational vector synthesis, combined with the access point voltage input from the signal processing module... The rotor electrical angle commands of the two rotating phase-shifting transformers were calculated. Combined with the number of pole pairs of the rotating phase-shifting transformer The two rotor electrical angle commands transmitted from the phase angle control module Converted into two rotor mechanical angle commands The servo controllers of the two rotating phase-shifting transformers receive the rotor mechanical angle control command transmitted by the phase angle control module and adjust the rotor position angle, thereby changing the size of the equivalent power source of the device, realizing real-time tracking and precise control of power and current, and achieving the purpose of reactive power compensation.

[0044] F. The detection module, signal processing module, power outer loop control module, direct current inner loop control module, phase angle control module, and the servo controllers of the voltage transformer and current transformer secondary sides of the reactive power compensator main circuit based on the principle of synthesized phasors of dual rotating phase shifters, as well as the two rotating phase shifting transformers, constitute a dual closed-loop control loop based on the outer loop three-phase instantaneous reactive power and the inner loop active and reactive current decoupling control. The calculation is specifically performed in the following steps:

[0045] 1) The signal processing module uses Park transform, with the device's input voltage as the reference phasor, to transform all physical quantities input from the detection module into the dq0 coordinate system. Furthermore, since a constant amplitude transformation is used in the coordinate transformation, a correction factor of 1.5 is required when calculating the instantaneous power using instantaneous power theory. Therefore, the active and reactive power consumed on each line can be expressed as follows:

[0046] (1)

[0047] (2)

[0048] The reactive power flowing through the load, parallel capacitors, and inductors includes... They can be calculated using the following formulas:

[0049] (3)

[0050] (4)

[0051] (5)

[0052] Active power consumed by the load for:

[0053] (6)

[0054] 2) To ensure that the power factor on the grid side is at the set value The reactive power consumed by the inductor needs to be adjusted, therefore the setpoint for the reactive power consumed by the inductor should be:

[0055] (7)

[0056] The power outer loop control module receives instantaneous active and reactive power input from the signal processing module and determines the setpoint for the power closed loop control by combining it with the preset power factor on the grid side. and the reactive power consumed by the inductor As feedback, the two are compared in real time, and the instantaneous value of the controlled variable is adjusted without error from the given value through PI control. This is combined with the proportional and integral coefficients of the PI controller in the power outer loop control module. , The compensation amount for power closed-loop control is formed. :

[0057] (8)

[0058] 3) The relationship between the reactive power consumed by the inductor and the secondary current is as follows:

[0059] (9)

[0060] in It is the total inductance of the energy storage inductor and the internal inductance of the rotating phase-shifting transformer, which is equivalent to the secondary side.

[0061] Equation (9) shows that the reactive power consumed by the inductor is only related to the reactive component of the inductor current. Therefore, the reactive power can be independently adjusted by regulating the reactive current. The power outer loop control module reads the total reactance of the energy storage inductor and the inductance of the rotating phase-shifting transformer on the secondary side. Combined with its own power closed-loop control compensation amount Substituting into the above formula for calculation, since the current of the inductor always lags behind the voltage by 90°, its q-axis component is less than zero. The component of the direct current coupled to the q-axis is obtained as shown in formula (10), which is used as the reactive current setpoint in the current inner loop control. .

[0062] (10)

[0063] 4) The direct current inner loop control module reads the internally stored active current setpoint. The reactive current setpoint input from the power outer loop control module is received. And limit the amplitude; receive the instantaneous inductor current after coordinate transformation input from the signal processing module. As the feedback input signal, it is compared with the given values ​​of active and reactive current respectively. A PI controller is used to achieve instantaneous current tracking control of the given value, preventing overcurrent in the device. This is achieved by combining the proportional and integral coefficients of the active and reactive PI controllers. , This forms the compensation amount for d-axis and q-axis current closed-loop control. :

[0064] (11)

[0065] The direct current inner loop control module, combined with the signal processing module, inputs the access point voltage phase. The compensation amount is then converted to the abc coordinate system.

[0066] 5) Secondary side composite voltage The relationship with the inductor current is as follows:

[0067] (12)

[0068] The phase angle control module reads circuit parameters, including the energy storage inductor and the internal impedance of the rotating phase-shifting transformer, and calculates the total impedance to the secondary side. It receives the current closed-loop control compensation input from the direct current inner loop control module, and calculates the combined voltage on the secondary side of the two rotating phase-shifting transformers using the above formula. Combined with the access point voltage phase input from the signal processing module ,Will Transformed to the dq0 coordinate system, this forms the d-axis component of the control voltage. .

[0069] Essentially, it is synthesized from two rotating vectors with equal amplitude and adjustable phase. Based on the principle of rotational vector synthesis, the relationship between the control voltage and the rotor electrical angle can be obtained:

[0070] (13)

[0071] The phase angle control module receives the access point voltage from the signal processing module. Combined with the d-axis component of the control voltage obtained from its own calculations The rotor electrical angle that the two rotating phase-shifting transformers should move can then be calculated. Combined with the number of pole pairs of the rotating phase-shifting transformer The mechanical angle command of the rotor of the two rotating phase-shifting transformers is calculated by equation (14). Based on this, the position angles of the two rotors are adjusted by the servo controllers of the two rotating phase-shifting transformers. Adjusting the rotor position angles changes the magnitude of the secondary side composite voltage, alters the inductor current, and consequently changes the reactive power absorbed or generated by the device. This forms a closed-loop control of power and current, ultimately enabling real-time tracking and precise control of reactive power and current, achieving the purpose of reactive power compensation.

[0072] (14)

[0073] Please see Figures 5 to 10To verify the dynamic compensation performance and effectiveness of the dual closed-loop control of the reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters proposed in this invention, reference was made. Figure 1 A circuit model under 690V was built in the MATLAB / SIMULINK simulation platform, and the control strategy was designed as a reference. Figure 4 The simulation design and verification of the dual closed-loop control of the reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters includes the following specific steps:

[0074] A. The main circuit parameters of the reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters are set as follows: the capacity of each of the two rotating phase shifting transformers is 1.5MW, and the three-phase capacitors... Three-phase energy storage inductor .

[0075] B. In the simulation, the rotor angles of the two rotating phase-shifting transformers are continuously changed from small to large. The simulated waveforms showing the change in reactive power absorbed or emitted by the reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters are observed. (Refer to...) Figure 5 .from Figure 5 We see that when At that time, the reactive power absorbed by the equivalent power source in the device It has a maximum value because it is greater than the power output of the capacitor. At this point, the device exhibits inductive behavior, providing maximum capacitive reactive power to the grid; as... Increase Gradually decrease to equal The capacitive reactive power provided by the device also decreases until it reaches zero; if When it increases further, Less than The device exhibits capacitive behavior, providing inductive reactive power to the grid, and when At this time, the device provides the grid with the maximum inductive reactive power; at this time, the reactive power compensation adjustment range of the device is -1.088~1.045Mvar (- for output, + for absorption).

[0076] C. Based on the adjustment range of the reactive power compensation device, a reactive power disturbance is applied to the load in the main circuit: the load reactive power is initially set to capacitive reactive power of 0.8 Mvar, then suddenly decreases to 0.3 Mvar at 3 seconds; at 6 seconds, the load nature abruptly changes to inductive, with reactive power at 0.3 Mvar; and at 9 seconds, it suddenly increases to inductive reactive power of 0.8 Mvar. The load active power is set to 0.6 MW and remains unchanged; it is set that the power factor on the grid side can be improved to 0.97 after control.

[0077] D. See also Figure 6 , Figure 6This is a graph showing the change in rotor electrical angle of the two rotating phase-shifting transformers during dynamic reactive power compensation simulation, based on the principle of synthesized phasors of dual rotating phase shifters, after applying reactive power disturbance to the load. The simulation results show that the rotating phase-shifting transformers respond quickly to disturbance signals and can be smoothly and continuously adjusted.

[0078] E. See also Figure 7 and Figure 8 , Figure 7 It is the tracking curve of the real-time power value and the given value in the power outer loop control under the dual closed-loop control of the reactive power compensator based on the principle of synthesized phasors of dual rotating phase shifters provided by this invention after applying reactive power disturbance to the load, as well as the compensation curve of the device for the reactive power required by the load. Figure 8 This is a tracking curve of the real-time values ​​of the active and reactive components of the current versus the given value in the direct current inner loop control. This verifies that the power current dual closed-loop control strategy provided by this invention can effectively track and adjust the instantaneous reactive power absorbed by the inductive equivalent power source to the given value without error, thereby achieving dynamic adjustment and compensation of the reactive power required by the load for the entire device, thus achieving the preset power factor. Simultaneously, it demonstrates that the power current dual closed-loop control strategy provided by this invention can effectively track the inductor current to its given value, ensuring that overcurrent does not occur inside the device and damage the device insulation, thus improving the reliability of the reactive power compensator's operation.

[0079] F. After applying a reactive power disturbance to the load, refer to the diagram showing the change in the grid-side power factor under the dual closed-loop control of the reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters provided in this invention. Figure 9 Simulation results verify that the proposed control strategy can achieve rapid and continuous unidirectional and bidirectional reactive power adjustment and compensation, ensuring that the reactive power compensated by the entire device is consistent with the reactive power required by the load, thereby improving the grid-side power factor to the preset value of 0.97 with high adjustment accuracy, thus achieving the goal of reducing power transmission losses and improving grid power supply efficiency.

[0080] G. See also Figure 10 , Figure 10 This invention presents the voltage and current waveforms of phase A on the grid side after reactive power compensation, based on the dual-loop control principle of a reactive power compensator using a dual-rotating phase shifter. The results show that after compensation, the grid-side voltage and current are in phase, and the harmonic content of both voltage and current is almost zero. This verifies that the dual-loop control strategy for power and current of the reactive power compensator based on the rotating phase shift principle provided by this invention does not introduce harmonics into the grid and can improve power quality.

Claims

1. A dual-closed-loop control method for a reactive power compensator based on the phasor principle of dual rotating phase shifters. The reactive power compensator comprises six parts: a main circuit for reactive power compensation using dual rotating phase shifters, a detection module, a signal processing module, a power outer loop control module, a direct current inner loop control module, and a phase angle control module. The input terminal of the detection module is connected to the secondary voltage output terminal of a voltage transformer that measures the three-phase voltage at the reactive power compensator connection point, and the secondary current output terminal of a current transformer that measures the three-phase current flowing through the load and inductor, and the total primary current of the two rotating phase shifters. The processing result of the detection module is transmitted to the signal processing module. The converted and calculated data results of the signal processing module are transmitted to the power outer loop control module, the direct current inner loop control module, and the phase angle control module. The calculation result data of the power outer loop control module is transmitted to the direct current inner loop control module, the calculation result data of the direct current inner loop control module is transmitted to the phase angle control module, and the result data of the phase angle control module is transmitted to the servo controllers of the two rotating phase shifters respectively. The detection module, signal processing module, power outer loop control module, direct current inner loop control module, phase angle control module, and the servo controllers of the voltage transformer and current transformer secondary sides of the reactive power compensation main circuit based on the principle of synthesized phasors of dual rotating phase shifters, as well as the two rotating phase shifting transformers, constitute a dual closed-loop control loop based on outer loop three-phase instantaneous reactive power and inner loop active and reactive current decoupling control. The calculations are performed in the following steps: 1) The signal processing module uses Park transform, with the device's input voltage as the reference phasor, to transform all physical quantities input from the detection module into the dq0 coordinate system. Furthermore, since a constant amplitude transformation is used in the coordinate transformation, a correction factor of 1.5 is required when calculating the instantaneous power using instantaneous power theory. Therefore, the reactive and active power consumed on each line can be expressed as follows: (1) (2) Among them, U Sd U Sq These are the voltages at the access points. The d-axis and q-axis components in the dq0 coordinate system, I d , I q Secondary current Active and reactive components in the dq0 coordinate system; reactive power flowing through the load, parallel capacitor, and inductor. They can be calculated using the following formulas: (3) (4) (5) Among them, I loadq For the load current The q-axis component in the dq0 coordinate system, I Lq Total series current on the primary side The q-axis component in the dq0 coordinate system; Active power consumed by the load for: (6) Among them, I loadd For the load current The d-axis components in the dq0 coordinate system; 2) To ensure that the power factor on the grid side is at the set value The reactive power consumed by the inductor needs to be adjusted, therefore the setpoint for the reactive power consumed by the inductor should be: (7) Among them, Q C To compensate for the reactive power generated by the parallel capacitor in the compensation device, Q load The reactive power of the equivalent load at the connection point; The power outer loop control module receives instantaneous reactive power input from various points from the signal processing module and combines it with the preset power factor on the grid side to determine the setpoint for the power closed loop control. and the reactive power consumed by the inductor As feedback, the two are compared in real time, and the instantaneous value of the controlled variable is adjusted without error from the given value through PI control. This is combined with the proportional and integral coefficients of the PI controller in the power outer loop control module. , The compensation amount for power closed-loop control is formed. : (8) 3) The relationship between the reactive power consumed by the inductor and the secondary current is as follows: (9) in It is the total reactance of the energy storage inductor and the inductance of the rotating phase-shifting transformer equivalent to the secondary side; it can be seen from equation (9) that the reactive power consumed by the inductor at this time is only related to the reactive component of the inductor current, so the reactive power can be independently adjusted by adjusting the reactive current; the power outer loop control module reads the total reactance of the energy storage inductor and the inductance of the rotating phase-shifting transformer equivalent to the secondary side. Combined with its own power closed-loop control compensation amount Substituting into the above formula for calculation, the component of the direct current coupled to the q-axis is obtained, as shown in equation (10), which is used as the reactive current setpoint in the current inner loop control. ; (10) 4) The direct current inner loop control module reads the internally stored active current setpoint. The reactive current setpoint input from the power outer loop control module is received. The instantaneous inductor current after coordinate transformation is received from the signal processing module. As the feedback input signal, it is compared with the given values ​​of active and reactive current respectively. A PI controller is used to achieve instantaneous current tracking control of the given value, preventing overcurrent in the device. This is achieved by combining the proportional and integral coefficients of the active and reactive PI controllers. , This forms the compensation amount for d-axis and q-axis current closed-loop control. : (11) The direct current inner loop control module, combined with the signal processing module, inputs the access point voltage phase. The compensation amount is then transformed into the abc coordinate system. 5) Secondary side composite voltage The relationship with the inductor current is as follows: (12) The phase angle control module reads the circuit parameters, including the energy storage inductor and the internal impedance of the RPST, and calculates the total impedance on the secondary side. It receives the current closed-loop control compensation input from the direct current inner loop control module, and calculates the combined voltage of the two RPST secondary sides using the above formula. Combined with the access point voltage phase input from the signal processing module ,Will Transformed to the dq0 coordinate system, this forms the d-axis component of the control voltage. ; Essentially, it is synthesized from two rotating vectors with equal amplitude and adjustable phase. Based on the principle of rotational vector synthesis, the relationship between the control voltage and the rotor electrical angle can be obtained: (13) The phase angle control module receives the access point voltage from the signal processing module. Combined with the d-axis component of the control voltage obtained from its own calculations The rotor electrical angle that the two rotating phase-shifting transformers should move can then be calculated. ; (14) Combining the number of pole pairs p of the rotating phase-shifting transformer, the rotor mechanical angle command β of the two rotating phase-shifting transformers is calculated using equation (14). 1, β2, and based on this, the position angles of the two rotors are adjusted by the servo controllers of the two rotating phase-shifting transformers; by adjusting the rotor position angles, the magnitude of the secondary side composite voltage is changed, the inductor current is changed, and the reactive power absorbed or generated by the device is also changed accordingly, thus forming a closed-loop control of power and current, and finally realizing real-time tracking and precise control of reactive power and current, achieving the purpose of reactive power compensation.

2. The dual-closed-loop control method for reactive power compensators based on the principle of synthesized phasors using dual rotating phase shifters according to claim 1, characterized in that, The main circuit of the dual rotating phase-shifting transformer can essentially be considered as a controlled power source. Its magnitude and direction are only related to the amplitude of the synthesized voltage phasor on the secondary side, and are independent of the phase angle. It is determined by the servo controller adjusting the rotor position angle. Therefore, in the dual closed-loop control method of the reactive power compensator based on the synthesized phasor principle of the dual rotating phase shifter proposed in this invention, the rotor position angles of the two rotating phase-shifting transformers are set to opposite numbers. By controlling only one variable, the amplitude of the synthesized voltage can be arbitrarily adjusted from 0 to the maximum value, thereby achieving precise control of reactive power compensation by the reactive power compensator. The inductor reactive current is directly related to the reactive power, thus enabling real-time tracking of the reactive current and ensuring that the device does not experience overcurrent.

3. The dual-closed-loop control method for reactive power compensators based on the principle of synthesized phasors using dual rotating phase shifters according to claim 1, characterized in that, The detection module uses voltage transformers and current transformers to collect the electrical physical quantities required to establish a model of the reactive power compensator dual closed-loop control method based on the principle of synthesized phasors of dual rotating phase shifters. These quantities include: the three-phase voltage at the connection point of the reactive power compensator, the three-phase current flowing through the load and inductor, and the total primary current of the two rotating phase shifters; and transmits the collected electrical physical quantities to the signal processing module.

4. The dual-closed-loop control method for reactive power compensators based on the principle of synthesized phasors using dual rotating phase shifters according to claim 1, characterized in that, The signal processing module performs coordinate transformation on the three-phase voltage and current input from the detection module. It uses a phase-locked loop (PLL) to obtain the phase of the voltage at the access point and fixes it on the d-axis as a reference phasor. Other electrical physical quantities are transformed from the abc coordinate system to the dq0 coordinate system based on the synchronous rotating coordinate transformation theory. The phase of the voltage at the access point is then transmitted to the direct current inner loop control module and the phase angle control module. At the same time, the calculated d and q axis components of each physical quantity are transmitted to the direct current inner loop control module and the phase angle control module. The instantaneous three-phase reactive power flowing through the load, capacitor, and inductor, as well as the instantaneous three-phase active power of the load, calculated using instantaneous power theory, are transmitted to the power outer loop control module.

5. The dual-closed-loop control method for reactive power compensators based on the principle of synthesized phasors using dual rotating phase shifters according to claim 1, characterized in that, The power outer loop control module, in conjunction with the power factor preset on the grid side, determines the setpoint for the power closed loop control based on the three-phase reactive power of the capacitor and the instantaneous active and reactive power of the three-phase load. Then, the three-phase instantaneous reactive power consumed by the inductor is used as the feedback value, and the compensation amount for the power outer loop closed loop control is formed through the PI controller. Based on its direct relationship with the energy storage inductor current, the reactive component of the direct current is obtained and transmitted to the direct current inner loop control module.

6. The dual-closed-loop control method for reactive power compensators based on the principle of synthesized phasors using dual rotating phase shifters according to claim 1, characterized in that, The direct current inner loop control module uses the reactive component of the inductor current input from the power outer loop control module after limiting it as the given value of the reactive current; it uses the d and q axis components of the inductor current input from the signal processing module as feedback quantities, and compares the deviation with the given values ​​of active and reactive current respectively. After passing through the PI controller, it forms the compensation quantities for the d and q axis current closed loop control respectively. Combined with the phase of the access point voltage input from the signal processing module, it is transformed into the abc coordinate system, and the obtained inductor current phasor is transmitted to the phase angle control module.

7. The dual-closed-loop control method for reactive power compensators based on the principle of synthesized phasors using dual rotating phase shifters according to claim 1, characterized in that, The phase angle control module calculates the composite voltage phasor of the secondary side of the rotating phase-shifting transformer using the inductor current phasor input from the direct current inner loop control module. Combined with the access point voltage phase input from the signal processing module, this phasor is transformed from the abc coordinate system to the dq0 coordinate system. Using the principle of rotating vector synthesis and the access point voltage input from the detection module, the rotor electrical angle commands of the two rotating phase-shifting transformers are calculated. Then, combined with the number of pole pairs of the two rotating phase-shifting transformers, the rotor mechanical angle control commands of the two rotating phase-shifting transformers are calculated. The calculation results are then transmitted to the servo controllers of the two rotating phase-shifting transformers in the reactive power compensator. The servo controllers of the two rotating phase-shifting transformers adjust the rotor position angle according to the rotor mechanical angle control commands transmitted from the phase angle control module, thereby changing the amplitude of the composite voltage phasor on the secondary side. This achieves precise control of the power output or absorption by the reactive power compensator and the secondary side current, forming a dual closed-loop control of current and power.

8. The dual closed-loop control method for reactive power compensators based on the principle of synthesized phasors using dual rotating phase shifters according to claim 1, characterized in that... The control method includes the following specific steps: A. The detection module acquires the electrical physical quantities required to establish a dual-closed-loop control method model for the reactive power compensator based on the principle of synthesized phasors using dual rotating phase shifters, including: the three-phase voltage at the reactive power compensator connection point. Three-phase current flowing through the load Three-phase current of inductor and the total primary current of the two rotating phase-shifting transformers The detected electrical physical quantities are transmitted to the signal processing module; the load-absorbed reactive power can be indirectly measured through the signal processing module. and merit Capacitors generate reactive power and inductor absorption of reactive power And all of them are passed to the power outer loop control module; B. The signal processing module will perform coordinate transformation on the three-phase voltage and current input from the detection module, and use a phase-locked loop (PLL) to obtain the phase of the voltage at the connection point. This is used as a reference phasor fixed on the d-axis. Other electrical physical quantities are then transformed from the abc coordinate system to the dq0 coordinate system based on the synchronous rotating coordinate transformation theory. The results before and after the transformation are as follows: Become ; Become ; Become ; Become ; the transformed direct current The voltage is transmitted to the direct current inner loop control module; the transformed access point voltage is then transferred. The data is passed to the phase angle processing module; the instantaneous reactive power calculated using instantaneous reactive power theory in the dq0 coordinate system will then be transferred. and load active power The signal is transmitted to the power outer loop control module; and the phase of the voltage at the connection point is... The signal is transmitted to the direct current inner loop control module and the phase angle control module; C. The power outer loop control module determines the setpoint for power closed loop control based on the power factor setting value on the grid side and the instantaneous power input from the signal processing module. ,by As a real-time feedback value, the compensation amount for reactive power closed-loop control is formed by comparing the feedback value with the setpoint. Based on its direct relationship with the inductor current, the reactive component of the direct current is obtained and transmitted to the direct current inner loop control module. D. The direct current inner loop control module uses the direct current reactive component input from the power outer loop control module as the reactive current setpoint. Simultaneously read the internally stored active current setpoint. ; Input via signal processing module These values ​​are used as feedback values ​​for active and reactive current, respectively, and their deviations are compared with the given values ​​for active and reactive current. These deviations are then processed by a PI controller to form compensation values ​​for the d-axis and q-axis current closed-loop control. This compensation is then combined with the phase voltage at the access point input from the signal processing module. Transform it to the abc coordinate system. The results before and after the transformation are as follows: Become ; Transformed current phasors Passed to the phase angle control module; E. The phase angle control module receives the current phasor from the direct current inner loop control module. The resultant voltage phasor of the secondary side of the rotating phase-shifting transformer was calculated. Combined with the access point voltage phase input from the signal processing module The voltage phasors are transformed from the abc coordinate system to the dq0 coordinate system. The results before and after the transformation are as follows: Become Using the principle of rotational vector synthesis, combined with the access point voltage input from the signal processing module... The rotor electrical angle commands of the two rotating phase-shifting transformers were calculated. Combined with the number of pole pairs of the rotating phase-shifting transformer The two rotor electrical angle commands transmitted from the phase angle control module Converted into two rotor mechanical angle commands The servo controllers of the two rotating phase-shifting transformers receive the rotor mechanical angle control command transmitted by the phase angle control module and adjust the rotor position angle, thereby changing the size of the equivalent power source of the device, realizing real-time tracking and precise control of power and current, and achieving the purpose of reactive power compensation.

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