A coaxial type rotary reactive compensator topology circuit

Abstract

The application discloses a coaxial rotating type reactive power compensator (CA-RVC) topological circuit, which is used for solving the reactive power compensation problems of power distribution networks with high penetration rate distributed power supply, urban power cable networks with high cable rate, and ultra-high voltage lines, etc. The application comprises a main circuit composed of two coaxially rotating phase-shifting transformers, capacitors and inductors, and a controller, a servo motor, a worm gear, a shell, accessories and the like; the primary winding and the capacitors are commonly connected in parallel at a compensation point, the secondary winding is connected in series in one group of three-phase connection and in series in another group of three-phase reverse connection, the phase windings at the corresponding positions of the phase shifters are connected in series at the head and tail, and then connected in parallel with the inductors. The technical method of the CA-RVC provided by the application is to change the inductive reactive power by controlling the rotor position angle of the coaxially rotating phase-shifting transformer and adjusting the amplitude of the synthesized voltage at the secondary side, so as to realize the adjustment of the quality and size of the reactive power at the compensation point, meanwhile, the number of servo motors and drivers is reduced, and the strict synchronization of the rotating phase-shifting of the two phase shifters is improved.

Description

TECHNICAL FIELD

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

[0002] Under the background of implementing renewable energy alternative action and constructing new power system mainly based on new energy in China, the random output characteristics of distributed power cause the voltage and reactive power distribution of active power distribution network containing high penetration rate distributed power to be complicated. When the power of load node is less than the power generated by distributed power, reactive power will be sent back, which will cause the voltage of power system to rise and even voltage to exceed the limit. There may be bidirectional power flow on the line, which will cause the power transmission loss to increase, affect the voltage and power supply quality, and further put forward higher requirements on the reactive power and voltage regulation strategy of active power distribution network and the performance of its equipment.

[0003] At the same time, with the acceleration of urban cable rate process 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 the same length 220kV cable line and 11-16 times of the same length and voltage grade overhead line. 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 capacitive effect is more obvious, the power grid is seriously over-reactive, which has a great impact on the safe and stable operation of the power grid, and the reactive power and voltage regulation problem of the power grid is increasingly prominent.

[0004] Reactive power compensation device can emit a certain amount of inductive or capacitive reactive power, which can support the voltage of line node through parallel reactive power compensation device. Configuring reactive power compensation device at appropriate position will effectively reduce the transmission of reactive power in the system, reduce network loss, and then improve the economy of the system. Shunt capacitor bank is one of the most traditional reactive power compensation devices, which has low production cost, flexible regulation and wide application range, but can only compensate in one direction, i.e. can only emit inductive reactive power, and has the disadvantage of being unable to continuously adjust reactive power. When the groups are turned on and off, it may cause unnecessary disturbance to the system.

[0005] Flexible AC transmission technology can compensate for reactive power and improve system stability, such as phase-shifting transformer, static var compensator, static synchronous compensator and unified power flow controller. Static var compensator mainly includes thyristor switched capacitor and thyristor controlled reactor. Among them, thyristor switched capacitor can only be adjusted in stages, and cannot accurately and fully compensate for the reactive power required by the load; thyristor controlled reactor continuously adjusts the compensation reactive power by changing the triggering angle of the thyristor, but it can only compensate for capacitive reactive power in one direction, so it is often used with thyristor switched capacitor, but there is a serious harmonic problem; static synchronous compensator and unified power flow controller can realize bidirectional compensation of reactive power, and have the characteristics of fast control response speed (10-20 ms) and continuous adjustment of reactive power, but these devices with power electronic devices as the core components of the converter circuit generally have small heat capacity, poor resistance, weak impact resistance, high cost, complex control strategy, and are difficult to adapt to the extreme weather of thunderstorms and snowstorms and the harsh natural environment of scorching heat and severe cold faced by distribution or high-voltage power grids and lines, as well as complex load properties, and it is difficult to meet the accuracy, economy and safety goals and needs, and it is difficult to be widely used.

[0006] The traditional mechanical tap changer in the phase-shifting transformer cannot meet the continuous and accurate adjustment of reactive power compensation, and frequent changes of the mechanical switch not only increase the wear and tear of the device, but also easily cause damage, to some extent, increase the maintenance cost of the device, and have poor reliability.

[0007] The rotating phase-shifting transformer is controlled by a servo motor, and the response speed of hundreds of milliseconds is faster than that of the traditional phase-shifting transformer, and for most applications of the power system, the response speed of hundreds of milliseconds can meet the requirements, in addition, it can realize stepless continuous adjustment, has good stability and high reliability; compared with power electronic devices, it will not produce harmonic distortion or phase shift, and has the advantages of being rugged, durable, low cost, relatively simple control method, small loss and no electromagnetic interference problem, etc., and the application prospect of the rotating phase-shifting transformer in the power grid research and application is very promising, therefore, a coaxial rotating phase-shifting transformer is considered to realize reactive power regulation.

[0008] Therefore, in view of the problems existing in the prior art, there is an urgent need to invent a coaxial rotating reactive power compensator topology circuit specially solving the problems of active power distribution network flexible reactive power regulation, high cable rate urban power grid and excessive charging power of ultra-high voltage line, etc., which has strong resistance, high reliability, low cost, bidirectional continuous regulation and no harmonic introduction; at the same time, the regulation mechanism and method of the coaxial rotating reactive power compensator are researched, so that it can dynamically and accurately compensate for reactive power, thereby effectively improving the power supply efficiency and power supply quality of the power grid, reducing the transmission of reactive power in the system and reducing power loss. SUMMARY

[0009] The application discloses a coaxial rotating type reactive power compensator (CA-RVC) topological circuit, which is used for solving the reactive power compensation problems of power distribution networks with high penetration rate of distributed power supply, urban power grids with high cable rate, and ultra-high voltage lines, etc. The CA-RVC topological circuit comprises a main circuit composed of two coaxially rotating phase-shifting transformers, capacitors and inductors, and a controller, a servo motor, a worm gear, a shell, accessories and the like. The primary windings and the capacitors are commonly connected in parallel at a compensation point, the secondary windings are connected in series in a group of three-phase forward connection and a group of three-phase reverse connection, the phase windings corresponding to the phase shifter are connected in series at the head and tail, and then connected in parallel with the inductors. The CA-RVC topological circuit provided by the application adjusts the amplitude of the synthesized voltage at the secondary side by controlling the rotor position angle of the coaxially rotating phase-shifting transformer, changes the reactive power absorbed by the inductor, and thus adjusts the size of the compensated reactive power. Meanwhile, the number of servo motors and drivers is reduced, and the strict synchronization of the rotating phase-shifting of the two phase shifters is improved.

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

[0011] The CA-RVC topological circuit provided by the application mainly comprises three-phase capacitors, two coaxially rotating phase-shifting transformers and three-phase energy storage inductors. The primary windings of the two coaxially rotating phase-shifting transformers are connected in parallel and connected in parallel with the three-phase capacitors at a compensation point. The secondary windings of the two coaxially rotating phase-shifting transformers are connected in series in a group of three-phase forward connection and a group of three-phase reverse connection, and the phase windings corresponding to the phase shifter are connected in series at the head and tail to form a three-phase star or angle connection, which is connected in parallel with the three-phase energy storage inductors of the three-phase star or angle connection. The two coaxially rotating phase-shifting transformers are composed of a common closed magnetic circuit, primary windings, two groups of secondary windings, a controller, a servo motor, a turbine, a worm gear, a shell and accessories. The method features voltage regulation and power conversion by using the electromagnetic induction principle and the rotating vector synthesis method, adjusting the amplitude of the voltage across the three-phase energy storage inductor to change the reactive power absorbed by the inductor, and realizing the adjustment and control of the reactive power compensated by the CA-RVC.

[0012] The coaxial type rotating reactive power compensator topology circuit firstly takes power for the reactive power compensator (the primary side of two coaxial rotating phase shift transformers) in parallel; then the primary and secondary (stator and rotor) winding axis relative angular displacement, namely the stator and rotor position angle, is changed; according to the induction voltage regulation principle of the rotating phase shift transformer, the electric energy transmission between the primary and secondary is completed through the magnetic field induction, at the same time, the secondary winding voltage phase is adjusted (relative to the primary voltage phase); the secondary voltage amplitudes of the two coaxial rotating phase shift transformers are equal, and the phases are opposite to each other; after the two groups of secondary windings of the two coaxial rotating phase shift transformers corresponding to the phase shifter positions are connected in series, three-phase connection is formed, and the three-phase energy storage inductance is connected in parallel; at this time, the voltage across the three-phase energy storage inductance is the combined voltage of two vectors with equal amplitude and opposite phase angle; according to the rotating vector synthesis method, the amplitude of the combined voltage can be adjusted arbitrarily between 0 and the maximum voltage (twice the secondary voltage amplitude), so as to change the reactive power absorbed by the inductance, and then continuously and bidirectionally adjust and control the reactive power compensation of the coaxial type rotating reactive power compensator provided by the application.

[0013] The reactive power absorbed by the three-phase energy storage inductance is only related to the amplitude of the combined voltage, and is irrelevant to the phase of the combined voltage; compared with two independent rotating phase shift transformers, the two coaxial rotating phase shift transformers reduce the number of servo motors and drivers required by the device while ensuring that the adjustment range of the secondary combined voltage amplitude meets the requirements, thereby reducing the cost and size of the reactive power compensator and improving the strict synchronization of the rotating phase shift angles of the two rotating phase shift transformers, so that the regulation and control of the reactive power is more accurate.

[0014] The three-phase capacitor emits reactive power Q C which almost remains unchanged; the three-phase energy storage inductance has a constant current characteristic, and the two coaxial rotating phase shift transformers and the energy storage inductance connected in parallel can be essentially equivalent to a controlled power source Q L , the size of which is related to the amplitude of the combined voltage at the secondary side and depends on the rotor position angle of the two coaxial rotating phase shift transformers. By continuously changing the reactive power absorbed by the inductance, the reactive power compensated by the entire device to the power grid can be continuously changed; when the equivalent inductance of the two coaxial rotating phase shift transformers and the energy storage inductance absorbs reactive power Q L greater than Q C , the entire device is inductive, and the capacitive reactive power is compensated to the power grid; otherwise, the device is capacitive, and the inductive reactive power is compensated to the power grid; by adjusting and controlling the compensation reactive power of the entire device, the power factor of the power grid side can be improved to a preset value. The reactive power compensation adjustment range of the coaxial type rotating reactive power compensator provided by the application is determined by the size of the three-phase capacitor, the three-phase energy storage inductance and the capacity of the rotating phase shift transformer, and the bidirectional adjustment of the compensation reactive power of the device can be realized by reasonably setting the parameters.

[0015] The present application has the advantages of:

[0016] 1. The present application provides a coaxial rotating type reactive power compensator topology circuit, which can continuously adjust the amplitude of the synthesized voltage or the voltage on both sides of the inductor after electromagnetic induction conversion and rotation vector synthesis, to change the reactive power absorbed by the equivalent inductor in the reactive power compensator, thereby realizing continuous adjustment and conversion of the size and polarity of the reactive power compensated by the coaxial rotating type reactive power compensator.

[0017] 2. The present application provides a simple control mechanism for the coaxial rotating type reactive power compensator topology circuit: only one variable, the rotor position angle of the two coaxially rotating phase-shifting transformers, needs to be adjusted and controlled, and the compensated reactive power monotonically changes with it; according to the rotation vector synthesis method, when , the amplitude of the synthesized voltage is maximum, and the coaxial rotating type reactive power compensator absorbs the maximum reactive power; as increases, the absorbed reactive power decreases accordingly, until it is 0; as further increases, the nature of the compensated reactive power changes, and when , the coaxial rotating type reactive power compensator emits the maximum reactive power.

[0018] 3. The present application provides a coaxial rotating type reactive power compensator topology circuit, the adjustment range of which has a quantitative constraint relationship with the size of the three-phase capacitor and the three-phase energy storage inductor and the capacity of the rotating phase-shifting transformer, and reasonable parameter setting can realize bidirectional compensation of reactive power by the reactive power compensator; when the reactive power compensator is inductive, it compensates capacitive reactive power to the power grid, which is suitable for scenarios such as ultrahigh-voltage power grids, urban high-cable-rate power grids, and light-load holidays; when the reactive power compensator is capacitive, it is suitable for active distribution network scenarios of high-penetration distributed power sources.

[0019] 4. The present application provides a coaxial rotating type reactive power compensator topology circuit that can work in under-compensation, over-compensation, and full-compensation modes, achieve a preset power factor, improve power supply efficiency, reduce line loss, and improve power supply voltage quality; it is suitable for reactive power compensation of power grids at various AC voltage levels.

[0020] 5. The coaxial rotating type reactive power compensator topology circuit provided by the present application has larger thermal capacity, stronger impact resistance, better durability, lower cost, and higher reliability compared to reactive power compensators with power electronic converters as the core, and is more suitable for the lightning and snow weather disasters and harsh natural environments faced by transmission and distribution networks and lines, as well as complex electrical load properties and behaviors, etc.

[0021] 6.The coaxial rotating type reactive power compensator topology circuit provided by the application is more accurate in adjusting compensation reactive power, has better power supply quality, and has lower device maintenance cost compared with the way of adjusting tap to control reactive power of the discrete phase-shifting transformer topology circuit; compared with two independent rotating phase-shifting transformers, the coaxial rotating type reactive power compensator topology circuit reduces the number of servo motors and drivers required by the reactive power compensation device, reduces the cost and size of the device, improves the strict synchronization of the phase-shifting angle, and is more accurate in controlling reactive power. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is an electrical system application schematic diagram of a preferred embodiment of the coaxial rotating type reactive power compensator topology circuit provided by the application.

[0023] Figure 2 is an electrical principle connection schematic diagram of a preferred embodiment of the coaxial rotating type reactive power compensator topology circuit provided by the application.

[0024] Figure 3 is a main circuit connection schematic diagram of a preferred embodiment of the coaxial rotating type reactive power compensator topology circuit provided by the application after being connected to a power grid.

[0025] Figure 4 is a single-phase equivalent circuit schematic diagram of the main circuit of a preferred embodiment of the coaxial rotating type reactive power compensator topology circuit provided by the application.

[0026] Figure 5 is a single-phase equivalent circuit schematic diagram of a preferred embodiment of the coaxial rotating type reactive power compensator topology circuit provided by the application.

[0027] Figure 6 is a simulation change waveform diagram of the reactive power and the capacitance, inductance, reactive power emission and absorption of the coaxial rotating type reactive power compensator provided by the application changing with the rotor angle of the rotating phase-shifting transformer.

[0028] The symbols of components in the drawings are as follows: is an equivalent power source of a power distribution system, and the capacity is S s1 ; R l1 , X l1 is an equivalent resistance and reactance of a power supply side power supply line; CA-RVC is a coaxial rotating type reactive power compensator, and the capacity is S CA-RVC ; P load , Q load is active and reactive power of an equivalent load at an access point; Q Σ is total capacitive reactive power compensated by the reactive power compensator to the power grid; is a voltage at the access point of the new reactive power compensation device. A, B, and C are each-phase live line terminals of the coaxial rotating type reactive power compensator connected in parallel to the line.C A, B, C C A, B, C C A, B, C C A, B, C C A, B, C C A, B, C L1 A, B, C L1 A, B, C L1 A, B, C L2 A, B, C L2 A, B, C L2 A, B, C g A, B, C Σ A, B, C Σ A, B, C Σ A, B, C S A, B, C L A, B, C C A, B, C Σ A, B, C load A, B, C A, B, C A, B, C A, B, C

[0029] The numerical labels for each component in the attached diagram are as follows: 1, a three-phase capacitor; 2, a coaxial connection structure of two three-phase rotating phase-shifting transformers; 3, a three-phase energy storage inductor.

[0030] 301, 302, and 303 are the primary windings of each phase shared by the two coaxial rotating phase-shifting transformers; 401, 402, and 403 are the core magnetic circuits of each phase shared by the coaxial rotating phase-shifting transformers; 501, 502, and 503 are the secondary windings of each phase of the first group of the coaxial rotating phase-shifting transformers; 701, 702, and 703 are the secondary windings of each phase of the second group of the coaxial rotating phase-shifting transformers; 601, 602, and 603 are the phase-shifting mechanisms of each phase of the two coaxial rotating phase-shifting transformers; the three-phase primary windings, core magnetic circuits, secondary windings, and phase-shifting mechanisms constitute the two coaxial rotating phase-shifting transformers of the coaxial type rotating reactive power compensator; the secondary windings 501, 502, and 503 and 701, 702, and 703 of the first group of rotating phase-shifting transformers are connected in series at the corresponding phase shifter positions to form the coaxial connection structure 2 of the double rotating phase-shifting transformer. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0032] Depend on Figure 1 As shown, a coaxial rotating reactive power compensator topology circuit is connected in parallel to a line, suitable for dynamically compensating the reactive power of the load, improving the power factor and power supply efficiency on the power supply side, and effectively reducing power transmission losses. It is suitable for dynamically compensating the charging power in ultra-high voltage lines and urban power grids with high cable penetration rates, avoiding the capacitive rise effect that could lead to high voltage at the end of the line damaging equipment insulation and other adverse events, ensuring the safe and stable operation of the power grid and improving the power supply environment. Simultaneously, it can not only achieve continuous stepless adjustment of reactive power compensation, but also perform bidirectional compensation of inductive and capacitive reactive power, and ensure that it does not introduce harmonic problems into the power grid, improving power quality and having a wide range of applications. Using a non-power electronic rotating phase-shifting transformer, it has low cost, stronger impact resistance and endurance, and high power supply reliability. The use of a coaxial rotating phase-shifting transformer reduces the size and cost of the device, improves the strict synchronization of the two phase shifters, and makes control simpler and more precise. The coaxial rotating reactive power compensator topology circuit provided by this invention is a good embodiment suitable for this scenario.

[0033] The electrical wiring diagram of a preferred embodiment of a coaxial rotary reactive power compensator topology is as follows: Figure 2 As shown, 1 is a three-phase parallel capacitor, with each terminal A at the beginning. C B C C C Connected in parallel to the corresponding live wire terminals A, B, and C of the line connected to the power grid, and to the terminal X of each of the three-phase capacitors. C, Y C , Z C The neutral point N1 is connected to the three-phase star connection; 2 is the coaxial connection of two rotating phase-shifting transformers, wherein: the first ends A1, B1, C1 of the primary side windings of the two coaxial rotating phase-shifting transformers are connected in parallel to the corresponding phase line terminals A, B, C of the line at the access point of the power grid, the end terminals A2, B2, C2 of the primary side windings are connected to the neutral point N2 to realize the star connection of the three-phase power taking windings, and the three-phase power taking windings can also be connected in delta connection according to the application occasion; one set of secondary side windings of the two coaxial rotating phase-shifting transformers is connected in positive connection mode, and the other set of secondary side windings is connected in reverse connection mode, the secondary side windings of the two rotating phase-shifting transformers are connected in series according to the corresponding positions of the phase-shifting devices, that is, the end terminals a2, b2, c2 of the first set of secondary side windings of the two coaxial rotating phase-shifting transformers are connected to the first end terminals a3, c3, b3 of the second set of secondary side windings of the two coaxial rotating phase-shifting transformers; the end terminals a4, b4, c4 of the second set of secondary side windings of the two coaxial rotating phase-shifting transformers are connected to the neutral line N3 to form a three-phase star connection; the voltage and power transformation between the primary windings and the secondary windings of the phase-shifting devices is realized through the closed three-phase magnetic circuit of the coaxial rotating phase-shifting transformers, and the voltage phase of each secondary winding is adjusted through the phase-shifting adjustment mechanism; the output voltage of the secondary side of the coaxial rotating phase-shifting transformers is a voltage vector synthesized by two rotating vectors with the same amplitude and opposite phase angles, and the amplitude of the vector can be adjusted by controlling the phase-shifting angle. The first end terminals A L1 , B L1 , C L1 of the three-phase energy storage inductors are connected to the first end terminals a1, b1, c1 of the first set of secondary side windings of the two coaxial rotating phase-shifting transformers, and the end terminals A L2 , B L2 , C L2 of the three-phase energy storage inductors are connected in star connection to the neutral line N3; at this time, the two coaxial rotating phase-shifting transformers of the three-phase star connection are connected in parallel with the three-phase energy storage inductors which are also connected in three-phase star connection, the synthesized voltage with adjustable amplitude of the secondary side is applied to the two ends of the energy storage inductor, so that the reactive power absorbed by the inductor can be adjusted, and the control of the reactive power compensated by the coaxial rotating type reactive power compensator to the power grid is realized.

[0034] Referring to Figure 3 , Figure 3 is a main circuit connection diagram of a coaxial type rotating reactive power compensator topological circuit according to the present application, according to the power conservation theorem, the power relationship at the point where the compensator is connected to the power grid is:

[0035] Q S = Q Σ + Q load = Q C + Q loadQ L (1)

[0036] From the above formula, if the power factor of the power grid side is to be improved to a preset value λ, the reactive power of the power supply side is reduced, at which time the reactive power compensated by the reactive power compensator and the reactive power absorbed by the equivalent inductance should respectively satisfy:

[0037]

[0038]

[0039] Referring to Figure 4 and Figure 5 , Figure 4 and Figure 5 are respectively a single-phase equivalent circuit and a single-phase equivalent circuit schematic diagram of a main circuit of a coaxial rotary reactive power compensator topological circuit preferred embodiment provided by the present application. The reactive power Q C emitted by the three-phase capacitor in the coaxial rotary reactive power compensator topological circuit almost remains unchanged, and the equivalent inductance consuming reactive power in the device is equivalent to a reactive power source Q L , the size of the reactive power source is determined by the rotor-side synthesized voltage ΔU, is affected by the rotor electrical angle of the coaxial rotating shift-phase transformer, is controlled by the rotor position angle β, and the internal resistance of the rotating shift-phase transformer is ignored. Their relationship is as follows:

[0040]

[0041]

[0042]

[0043]

[0044] Among them, the reactive power Q RPST absorbed by the rotating shift-phase transformer is 5% to 25% of its own capacity; is a branch coefficient, Q Lmax is the maximum value of the equivalent inductance absorbing reactive power of the internal reactance and energy storage inductance of the two rotating shift-phase transformers; p is the pole pair number of the rotating shift-phase transformer. It can be known that for a multi-pole rotating shift-phase transformer, only a very small mechanical angle of the rotor angle needs to be moved to change the synthesized voltage phasor amplitude added to the inductance;

[0045] By adjusting to change ΔU, the size and properties of the overall compensated reactive power are controlled. When , ΔU max = 2kU S has a maximum value, Q L is maximum, at which time the coaxial rotary reactive power compensator absorbs the maximum reactive power; when​ When ΔU min =0 has a minimum value, Q L is minimum, and the coaxial rotary type reactive power compensator emits reactive power with a maximum value.

[0046] When Q Σ >0, i.e. , the device presents inductive and can absorb the extra inductive reactive power of the power grid, compensate for capacitive reactive power, solve the problem of excessive charging reactive power caused by high penetration of distributed power or long ultra-high voltage cable lines; when Q Σ <0, i.e. , the device presents capacitive and can compensate for inductive reactive power to the power grid; when , i.e. , it can compensate for certain reactive power to the power grid, improve power supply efficiency and voltage quality, and improve the power factor of the power grid side to a preset value λ.

[0047] To realize the reactive power compensation range -Q ΣCmax ~Q ΣLmax (-emission, + absorption) of the coaxial rotary type reactive power compensator proposed in the application, the capacitance and energy storage inductance need to be reasonably designed:

[0048] When , the entire device emits reactive power Q ΣCmax is:

[0049]

[0050] In the actual circuit, in addition to Q RPST , there is also a certain amount of reactive power loss, so in order to ensure the required reactive power compensation range of the power grid, considering a 1.1 times margin, the three-phase capacitor C is set to:

[0051]

[0052] When , the entire device absorbs reactive power Q ΣLmax is:

[0053]

[0054] Therefore, the energy storage inductance L should be:

[0055]

[0056] The branch coefficient at this time is The energy storage inductance can be simplified as:

[0057]

[0058] In order to verify the compensation adjustment mechanism and performance of the coaxial type rotary reactive compensator topological circuit provided in the application, reference is made to Figure 3 The circuit model under 690V is built in the MATLAB / SIMULINK simulation platform, and the simulation change waveform diagram of the reactive power absorbed or emitted by the coaxial type rotary reactive compensator provided in the application and the change of the reactive power emitted and absorbed by the capacitor and the inductor with the rotor angle of the rotary phase shifting transformer is as shown in Figure 6 The coaxial type rotary reactive compensator topological circuit simulation design and verification includes the following specific steps:

[0059] 1. Assuming that the capacity of the rotary phase shifting transformer in the coaxial type rotary reactive compensator is 1.5MW, and the required reactive power adjustment range is-1Mvar~+1Mvar (- for emission, + for absorption). First, determine the size of the parallel capacitor and the energy storage inductor in the coaxial type rotary reactive compensator topological circuit provided in the application:

[0060] When , the device emits reactive power with a maximum value Q ΣCmax =1Mvar, at this time only the two coaxial rotary phase shifting transformers themselves need to consume reactive power, and Q RPST is 25% of its capacity, the parallel capacitor should emit reactive power Q C :

[0061] Q C =Q ΣCmax +Q RPST =1.75Mvar (13)

[0062] According to formula (9), the three-phase capacitor C should be set as:

[0063]

[0064] Wherein U S =690V

[0065] When , the device absorbs reactive power with a maximum value Q ΣLmax =1Mvar, and according to formula (11), the energy storage inductor L is:

[0066]

[0067] 2. In the simulation, by continuously changing the rotor angle of the two coaxial rotary phase shifting transformers in the coaxial type rotary reactive compensator from 0~90°, the simulation waveform diagram of the change of the reactive power compensated by the reactive power compensator is observed, and reference is made to Figure 6 .

[0068] From Figure 6 we can see that when ,Figure 6 reactive Q absorbed by the equivalent power source in L max, because it is greater than the power Q emitted by the capacitor C At this time, the reactive compensator presents inductive and absorbs the maximum inductive reactive power, 1.045 Mvar, and provides capacitive reactive power to the power grid; as increases, Q L gradually decreases, and the capacitive reactive power provided by the reactive compensator also decreases, until when Q L decreases to equal Q C , the reactive compensator provides zero reactive power; if further increases, Q L is less than Q C , the device presents capacitive and provides inductive reactive power to the power grid, and when , the reactive compensator provides the maximum inductive reactive power to the power grid, 1.088 Mvar; this is consistent with the theoretical analysis result of the compensation adjustment mechanism of a coaxial rotary reactive compensator provided by the present application, verifying the correctness of the reactive compensation adjustment mechanism;

[0069] In the simulation result, the adjustment range of the reactive compensator is -1.088 Mvar~1.045 Mvar, which meets the required adjustment range, verifying the rationality of the design of the capacitive and inductive parameters of the coaxial rotary reactive compensator; at the same time, it is verified that the coaxial rotary reactive compensator provided by the present application has the ability of continuous and bidirectional adjustment and compensation of reactive power, can make the reactive power compensated by the coaxial rotary reactive compensator close to the required reactive power of the load, thereby reducing the reactive power provided by the power source, improving the power factor of the power grid side to the preset value, and improving the power supply efficiency of the power grid.

Claims

1. A coaxial rotating reactive power compensator topology circuit, comprising three subsystems: a three-phase capacitor, two coaxial rotating phase-shifting transformers, and a three-phase energy storage inductor; the primary windings of the two coaxial rotating phase-shifting transformers are connected in parallel, and simultaneously connected in parallel with the three-phase capacitors at the compensation point; the secondary windings of the two coaxial rotating phase-shifting transformers are configured such that one set is connected in sequence (a, b, c) and the other set is connected in opposite directions (a, c, b), with the corresponding phase windings of the phase-shifting transformers connected in series to form a three-phase star or delta connection, and simultaneously connected in parallel with the three-phase energy storage inductor connected in a three-phase star or delta connection; the two coaxial rotating phase-shifting transformers consist of a common closed core magnetic circuit and primary windings, two sets of secondary windings, a controller, a servo motor, a turbine, a worm gear, and a housing and accessories; the method is characterized by... By utilizing the principles of electromagnetic induction and the rotating vector synthesis method, voltage regulation and power conversion are performed. The voltage amplitude across the three-phase energy storage inductor is adjusted to change the reactive power absorbed by the inductor, thereby realizing the regulation and control of reactive power compensation by the coaxial rotating reactive power compensator.

2. The coaxial rotary reactive power compensator topology circuit according to claim 1, characterized in that, First, energy is extracted from the primary side of two coaxially rotating phase-shifting transformers in parallel. Then, the relative angular displacement of the primary and secondary winding axes, i.e., the stator and rotor position angles, is changed. Based on the induction voltage regulation principle of the rotating phase-shifting transformer, while completing the energy transfer between the primary and secondary windings through magnetic field induction, the phase of the secondary winding voltage is adjusted. The secondary voltage amplitudes of the two coaxially rotating phase-shifting transformers are equal, and their phases are opposites. The two sets of secondary windings of the two coaxially rotating phase-shifting transformers are connected in series at the corresponding phase shifter positions to form a three-phase connection, which is then connected in parallel with a three-phase energy storage inductor. At this point, the voltage across the three-phase energy storage inductor is a composite voltage of two vectors with equal amplitudes and opposite phase angles. According to the rotating vector synthesis method, the amplitude of this composite voltage can be arbitrarily adjusted from 0 to twice the secondary voltage amplitude, thereby changing the reactive power absorbed by the inductor. This allows for stepless, continuous, and bidirectional adjustment and control of reactive power compensation by the coaxial rotating reactive power compensator.

3. The coaxial rotary reactive power compensator topology circuit according to claim 2, characterized in that, The reactive power absorbed by the three-phase energy storage inductor is only related to the amplitude of the synthesized voltage, and not to the phase of the synthesized voltage. Compared with two independent rotating phase-shifting transformers, using two coaxial rotating phase-shifting transformers can ensure that the amplitude adjustment range of the secondary side synthesized voltage meets the requirements, while also reducing the number of servo motors and drivers required by the device, reducing the cost and size of the reactive power compensator, improving the strict synchronization of the phase shift angle of the two rotating phase shifters, and making the control of reactive power more precise.

4. The coaxial rotary reactive power compensator topology circuit according to claim 1, characterized in that: It consists of a series-parallel structure of three-phase capacitors, two coaxial rotating phase-shifting transformers, and a three-phase energy storage inductor, wherein: ① In the topology of the coaxial rotary var compensator, the three-phase capacitors form a three-phase star connection for connection to the power grid: Terminals A at the beginning of the circuit. C B C C C Connected in parallel to the corresponding live wire terminals A, B, and C of each phase of the grid-side line, and to the terminal X of each phase of the three-phase capacitor. C Y C Z C The convergence point is neutral point N1, if the power supply side voltage U S If it remains unchanged, then the reactive power generated by the three-phase capacitors is constant; ② Coaxial connection method of two rotating phase-shifting transformers in the topology circuit of coaxial rotating reactive power compensator: The first ends A1, B1, and C1 of the primary windings shared by the two coaxial rotating phase-shifting transformers are connected in parallel to the corresponding live wire terminals A, B, and C of the line at the grid connection point. The last ends A2, B2, and C2 of the primary windings converge to form the neutral point N2, realizing the star connection of the three-phase power extraction windings. Alternatively, depending on the application requirements, the three-phase power extraction windings can be connected in a delta configuration. One set of secondary windings of the coaxial rotating phase-shifting transformers is connected in the correct order (a, b, c), and the other set of secondary windings is connected in the reverse order (a, c, b). The secondary windings of the two rotating phase-shifting transformers are connected in series at the corresponding phase ends of the phase shifter, i.e., the two coaxial rotating phase-shifting transformers are connected in series. The ends a2, b2, c2 of the first set of secondary windings of the phase shifter are connected to the beginning ends a3, c3, b3 of the second set of secondary windings of the two coaxially rotating phase shifters, respectively. The ends a4, b4, c4 of the second set of secondary windings of the two coaxially rotating phase shifters converge at the neutral line N3, forming a three-phase star connection. The voltage and power conversion between the primary and secondary windings of the phase shifter is realized through the closed three-phase core magnetic circuit of the coaxially rotating phase shifter. The voltage phase of each secondary winding is adjusted by the phase shift adjustment mechanism. The output voltage of the secondary series side of the coaxially rotating phase shifter is a voltage phasor synthesized by two rotating vectors with the same amplitude and opposite phase angle. The amplitude of this phasor can be adjusted by controlling the phase shift angle. ③ In the coaxial rotary var compensator topology circuit, the three-phase energy storage inductor forms a three-phase star connection, and the secondary side also forms a three-phase star connection. The coaxial rotary var compensator is connected in parallel: the first terminal A of the three-phase energy storage inductor... L1 B L1 C L1 The first two sets of secondary windings of two coaxial rotating phase-shifting transformers are connected to the beginning terminals a1, b1, and c1 respectively, and the end terminal A of the three-phase energy storage inductor is connected to the end terminal A. L2 B L2 C L2 The neutral line N3, which is formed by the convergence of the two coaxial rotating phase-shifting transformers in a three-phase star connection at the end of the second secondary winding, is connected in parallel with the three-phase energy storage inductor, which is also in a three-phase star connection. The adjustable amplitude of the composite voltage on the secondary side of the inductor is applied to the two ends of the energy storage inductor, thereby adjusting the reactive power absorbed by the inductor and thus realizing the control of the reactive power compensation to the grid by the coaxial rotating reactive power compensator.

5. The coaxial rotary reactive power compensator topology circuit according to claim 1, characterized in that, The reactive power Q generated by the three-phase capacitor C It remains almost unchanged; the three-phase energy storage inductor has constant current characteristics, and the two coaxial rotating phase-shifting transformers and the energy storage inductor connected in parallel with them can essentially be equivalent to a controlled power source Q. L The magnitude is related to the amplitude of the secondary-side synthesized voltage, which depends on the rotor position angle of the two rotating phase-shifting transformers; by steplessly changing the reactive power absorbed by the three-phase energy storage inductor, the reactive power compensated to the grid by the entire device can be continuously changed; when Q L Greater than Q C If the current is not high enough, the entire device will be inductive, compensating for capacitive reactive power to the grid; otherwise, the device will be capacitive, compensating for inductive reactive power to the grid. When the reactive power compensation of the entire device is close to the reactive power required by the load, the power factor on the grid side can be increased to the preset value. The adjustment range of the coaxial rotating reactive power compensator is determined by the size of the three-phase capacitor, the three-phase energy storage inductor, and the capacity of the rotating phase-shifting transformer. Reasonable parameter setting can realize bidirectional adjustment of reactive power.

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