31results about How to "Solve the three-phase unbalance problem" patented technology

A reactive power compensation device based on novel modular multilevel topology and a control method thereof relate to a high-voltage and large-power reactive power compensation device. In the prior art, compensation in a high-voltage and large-power field is limited and an inhibiting ability to circulation is insufficient. The invention aims at solving the above problems. A three-phase alternating-current power supply, a resistance-inductance load, a MMC converter, a signal detection circuit, a control circuit and a driving circuit are included. The MMC converter comprises three bridge arms which share a same structure and are connected in parallel. Each bridge arm comprises an upper bridge arm and a lower bridge arm which are symmetrical about a middle point of the bridge arm and are connected in series. Each upper bridge arm comprises a resistor, an inductor, several half-bridge units and an H bridge unit which are connected in series. The inductor of each upper bridge arm and an inductor of each lower bridge arm are connected in series. The middle points of the three bridge arms of the converter are connected in parallel between the three-phase alternating-current power supply and the load through a lead. By using the device and the method in the invention, power-grid reactive power can be compensated; a three-phase imbalance problem of a system is solved; effects of supporting a power grid voltage and inhibiting the circulation are achieved.

The invention discloses an intelligent power distribution and utilization flexible control system. The intelligent power distribution and utilization flexible control system comprises a transformer, a three-phase rectifier, at least one single-phase inverter and at least one three-phase inverter. The three-phase rectifier converts a three-phase alternating current produced by the transformer into a direct current which is output to the inverters, the single-phase inverters convert the direct current into single-phase alternating currents with adjustable frequency and amplitude, and the three-phase inverters convert the direct current into three-phase alternating currents with adjustable frequency and amplitude. According to the intelligent power distribution and utilization flexible control system, the method that the three-phase alternating current is rectified and then inverted is adopted, the problem that a great deal of single-phase electric equipment is directly connected to a power supply grid to cause three-phase unbalance is solved, damage to power transmission and distribution equipment and the electric equipment is reduced, and reliability, economical efficiency and power quality of power supply are improved. Besides, the intelligent power distribution and utilization flexible control system achieves clear work division of modules, is easy to design, build and maintain, operates easily, and achieves convenient system expansion and upgrading.

The invention discloses a site optimization method of a three-phase unbalanced power switching device. The three-phase unbalancing problem in a power system brings about a series of problems of excessively high neutral current, increasing line loss and increasing electric energy loss of a distribution transformer. The problems can be effectively solved by reasonably installing the three-phase unbalanced power switching device. An overall suppression strategy is put forward through time characteristic analysis of the three-phase unbalanced load to perform site optimization of the three-phase unbalanced power switching device. The main characteristics are that the unbalancing characteristics of the load are obtained by using the power data of acquisition points, then the power data of multiple key load points are obtained by the unbalancing characteristics, and the power data are substituted in an objective function and enabled to meet the corresponding constraint conditions so that the optimal site scheme is obtained by using the stepwise optimization method.

The invention relates to a UPFC (unified power flow controller) three-phase imbalance optimization method based on nonlinear control. The method comprises steps as follows: 1), a modularized multi-level UPFC is constructed; 2), an inner current loop in a parallel side current converter adopts a passive sliding mode variable structure control mode, reactive regulation is performed through q-axis component, and active regulation is performed through d-axis component; 3), an inner current loop in a series side current converter adopts the passive sliding mode variable structure control mode, voltage with controllable amplitude and phase angle is injected by a series side transformer, positive sequence component is used for realizing phase shift adjustment and series compensation of alternating voltage, negative sequence component is used for offsetting negative sequence voltage component of an imbalanced part of an electric transmission line, and three-phase imbalance optimization is realized. Compared with the prior art, the method has the advantages of being high in dynamic response speed, high in robustness, safe, economic and stable and inhibiting zero-sequence current, and parameters are easy to adjust.

The invention provides a static voltage stabilization device and a voltage stabilization method of a three-phase intelligent line. In recent years, various non-linear loads in the power grid have beenincreasing; because of load volatility, nonlinearity and unbalanced power consumption characteristics, harmonic, reactive power, transient shock and three-phase unbalance problems in the power grid become series increasingly. The static voltage stabilization device is composed of a housing; and an alternating-current / direct-current sampling module, a main circuit module, a control module, a driving module, a power supply module and a protection module are installed inside the housing. The alternating-current / direct-current sampling module includes one group of voltage transformers and two groups of current transformers; and the two groups of current transformers are connected with a system side (1) and a load side (2) respectively. The main circuit module includes a rectifier circuit (3),an inverter circuit (4) and a filter circuit (5) and is connected with the system side and the load side; and the control module is connected to the main circuit module via the driving module. The invention provides a static voltage stabilization device and a voltage stabilization method for a three-phase intelligent line.

The invention discloses a low-voltage single-phase power supply system of 10 kV transformer and 220 V, which comprises 10 kV-220 V three-phase-to-two-phase transformer, an electric energy collection unit, an unbalance control unit, a reactive power control unit and an AC-DC-AC module connected in sequence At first, that three-phase voltage is convert into two-phase voltages by use a transformer, the electric quantity is collected by connected with an electric energy acquisition unit, and the collected electric quantity is sent to an unbalanced control unit and a reactive power control unit, the unbalanced control unit is used for monitoring the current unbalance degree between the alpha phase and the beta phase, and the AC-DC-AC module regulates the two-phase current, and the reactive power control unit is used to monitor the power, the AC-DC-AC module regulates the power in the circuit; Compared with the power supply mode of the two-inlet single-phase transformer, the power supply system provided by the invention can solve the three-phase unbalance problem of the 10kV side, greatly reduce the probability of the three-phase current unbalance of the 220V side, reduce the capacity ofthe three-phase unbalance treatment device, reduce the line loss, and improve the power supply quality.

The invention relates to the technical field of power supply and distribution devices, and discloses a three-phase imbalance automatic commutation system. Current information of each phase of a three-phase branch in a power grid system is collected through a collection module, a main control module obtains the three-phase unbalance degree of the system according to the current information, and when the three-phase unbalance degree is larger than a preset threshold value, it is judged that phase change processing needs to be carried out. And the main control module compares the circuit information of each phase to judge an overload phase in the three phases. A current zero-crossing detection module detects a current zero-crossing point of three phases, and the main control module outputs acorresponding commutation control signal when the current of an overload phase crosses zero. And an automatic commutation module completes an automatic commutation process according to the commutationcontrol signal. By means of the three-phase imbalance automatic commutation system, an operator can complete automatic commutation under the condition that the tail end load is not powered off, the problem of three-phase imbalance of the tail end load is fundamentally solved, the tedious process of manual commutation is avoided, and the commutation efficiency and the power supply reliability of the system are greatly improved.

The invention discloses a charging pile power grid balancing automatic phase selection device. The device comprises a court transformer, the output end of the court transformer is connected with a number of electromobile alternate current charging piles respectively, the outlet side of the transformer is provided with a signal acquisition module, the inlet wire of the power supply of each alternate current charging pile of the electromobile is provided each with an automatic phase selection switch. According to the automatic phase selection device, the problem of unbalanced three-phase power system arising out of the charging pile is solved; so that when the charging pile is being charged, the impact of high current load on the unbalanced three-phase power grid is reduced, and harm to the power distribution network in the use process by the charging pile is decreased.

The embodiment of the invention discloses a phase recognition method based on a clustering algorithm and network search, and the method comprises the steps: S1, carrying out the data collection, and carrying out the data collection of data of a phase recognition model; s2, performing data processing, processing missing data in the sample data in a data deleting or complementing manner, and removing abnormal values from abnormal data by adopting a 3 sigma criterion; s3, establishing a phase recognition model, judging the connectivity between the samples from the perspective of sample density based on a density-based clustering algorithm DBSCAN, and forming a clustering cluster based on the connectable samples to obtain a final cluster; and S4, performing model evaluation and prediction, performing cross validation on the data set for phase identification model evaluation, finding out optimal parameters of the model, and adding a new data set into the model to perform model prediction. According to the invention, the problems of three-phase imbalance and inaccurate line loss calculation of the existing electric energy meter are solved.

The invention provides a controllable zero sequence compensator of a low-voltage power grid. The controllable zero sequence compensator comprises a zigzag transformer and a single-phase inverter, wherein the zigzag transformer is connected with the low-voltage power grid, one end of the output end of the single-phase inverter is connected with the neutral line of the zigzag transformer, the other end of the output end of the single-phase inverter is used for being connected with the neutral line of the low-voltage power grid, and the single-phase inverter is used for outputting compensation currents to the neutral line of the low-voltage power grid according to the currents of the neutral line of the zigzag transformer, the currents of the neutral line of the low-voltage power grid and the currents of the neutral line of a load. By the controllable zero sequence compensator, zero sequence currents form a loop among the zigzag transformer, the single-phase inverter and the load, the currents of the neutral line of the low-voltage power grid is allowed to drop to zero, compensation of the zero sequence currents of the low-voltage power grid is completed, and the three-phase unbalance problem of the low-voltage power grid is solved.

The invention discloses a zero-millisecond three-phase unbalanced control commutation switch and a commutation timing control method thereof. The switch comprises an upper circuit board, three thyristors, three magnetic holding relays and a lower circuit board. The thyristors and the magnetic holding relays are inserted into the lower circuit board through pins, the three thyristors comprise a A-phase thyristor, a B-phase thyristor and a C-phase thyristor, the three magnetic holding relays comprise an A-phase magnetic holding relay, a B-phase magnetic holding relay and a C-phase magnetic holding relay, the lower circuit board is further provided with a commutation unit circuit for commutation, and the upper circuit board is provided with a digital tube. The invention has the advantages that the load power supply is not interrupted when a load is switched from a current connection phase to a light carrier phase through the cooperation of a power electronic device and the magnetic holding relays. The three-phase unbalance problem of a power distribution network is solved, and the power consumption of a user is not adversely affected.

The invention discloses a method for electromagnetic ultrahigh-voltage DC remote power transmission and distribution of an ocean controllable source. A power generator provides electric energy for thewhole method and is then is connected with a deck power-end large-power rectification device and an inversion device to provide an intermediate-frequency alternating current with an adjustable voltage, the voltage is converted to a ultrahigh-voltage direct current by a deck power-end boost transformer and the deck power-end rectification device, the electric energy loss is reduced to the minimumby a long-distance ultrahigh-voltage DC power transmission and distribution ocean cable and then the electric energy is converted to an ultrahigh-voltage alternating current to be transmitted to a reactor and an underwater transformation device by an underwater power-end large-power inversion device, the electric energy is converted to a low-voltage alternating current by an underwater transformation device and then is supplied to an underwater emitter rectification inversion unit for use. By the method, the electric energy loss of traditional long-distance AC power transmission is greatly reduced, the power and the efficiency of long-distance electric energy transmission are improved, the electric energy demand of an ocean controllable source electromagnetic emitter at the bottom of sea is effectively guaranteed, and meanwhile, the problem of three-phase unbalance is thoroughly solved.

The application provides a zero sequence current compensation system of a low voltage distribution network. The zero sequence current compensation system of the low voltage distribution network comprises a zigzag transformer connected with the low voltage distribution network, a single phase inverter, an electric current detection device used to detect an electric current of a neutral line of the zigzag transformer, an electric current of a neutral line of the low voltage distribution network and an electric current of a neutral line of a load and an inverter controller used to control the single phase inverter according to detection results of the electric current detection device, wherein one output end of the single phase inverter is connected with the neutral line of the zigzag transformer, and the other output end of the single phase inverter is connected with the neutral line of the load and the neutral line of the low voltage distribution network. The zero sequence current compensation system of the low voltage distribution network can enable a zero sequence current to form a loop circuit among the zigzag transformer, the single phase inverter and the load, and then reduces the electric current of the neutral line of the low voltage distribution network to zero, and thereby achieves compensation for the zero sequence current of the low voltage distribution network, and furthermore solves the problem that three phases of the low voltage distribution network are imbalanced.

The invention relates to a comprehensive treatment device used for solving three-phase imbalance of a distribution network, which comprises an SVG branch, intelligent phase-change switch branches, anelectrically operated circuit breaker and a controller, wherein the SVG branch is hooked to a 380V bus through the electrically operated circuit breaker, a plurality of intelligent phase-change switchbranches are arranged and directly connected to the 380V bus, the input is three-phase four-wire 380V, the output is single-phase 220V, the controller is connected with the SVG branch through electric signals and monitors the intelligent phase-change switch branches, and the controller adjusts the output of the intelligent phase-change switch branches and the SVG branch when the three phases of the distribution network are unbalanced. Compared with the prior art, the comprehensive treatment device in small in configured capacity of the SVG branch. The SVG branch operates at a zero-output state most of the time, and is low in loss, small heat generation and higher in reliability.

The invention discloses a three-phase equilibrium single-double pole electric slag furnace. The three-phase equilibrium single-double pole electric slag furnace is characterized in that a rectification device 1 is connected with a power grid three-phase power source 6 through a three-phase inlet wire, and a two-phase passing transformer 7 in the power grid three-phase power source 6 is connected with an ordinary electric slag furnace 2. An output end of an insulated gate bipolar translator (IGBT) flow variable module 9 in the rectification device 1 is connected with the three-phase inlet wire through a lower control limit (LCL) filter circuit 8, and an a end in a secondary coil of the transformer 7 is connected with the upper end of an electrode 4 inside a boiler 5 through an A short net impedance 3. The bottom of the boiler 5 is connected with a b end in the secondary coil of the transformer 7 through a B short net impedance 10. The three-phase equilibrium single-double pole electric slag furnace has the advantages that compared with the prior art, the problem that a single-phase electric slag furnace causes three-phase imbalance to a power grid is solved, the laden power factor is improved, a series of impacts brought by the problem of the unbalanced power grid are reduced, the investment cost of a steel making enterprise is saved, simultaneously the purposes of energy conservation and emission reduction are achieved, the utilization rate of electric energy is improved, and the pollution to the power grid is reduced.

The invention discloses a depth adjustment method and device for a distributed photovoltaic inverter. The adjustment method comprises the following steps: calculating a reference current instruction according to a system power reference instruction; extracting a reference current instruction and positive-sequence, negative-sequence and zero-sequence components of the output current of the inverter based on a reduced-order resonance regulator; independently carrying out closed-loop control on the positive sequence component, the negative sequence component and the zero sequence component; performing Park inverse transformation on a closed-loop control result to obtain an inverter output reference voltage; generating an inverter power device trigger pulse in response to the resulting reference voltage; acquiring three-phase voltage and current information of each feeder line in the power distribution area; and calculating three-phase power information of each feeder line, performing regulation and control by taking three-phase power balance as a target, generating a three-phase power reference instruction of each distributed photovoltaic inverter in the transformer area, and issuing the three-phase power reference instruction to the corresponding inverter. According to the technical scheme, deep adjustment of the distributed photovoltaic inverter is realized, and a new way is provided for operation control of a power distribution network.

An all-round soft-switching AC-DC hybrid energy router, including a three-phase bidirectional rectifier unit, a dual active full-bridge conversion unit, an all-round zero-voltage soft-switching unit, an interleaved parallel Boost unit, a four-switch Buck-Boost unit, a single-phase Full-bridge bidirectional inverter unit, high-voltage DC bus, low-voltage DC bus, Hall current sampling, voltage sampling, DSP control board, drive circuit, auxiliary power supply. The all-round zero-voltage soft switching unit used in the dual active full-bridge converter in this device is divided into 7 modes in one cycle, which greatly reduces the switching loss of the dual active full-bridge converter. The new structure improves SST's ability to support the distribution network and improve power quality. The DC bus is drawn out so that DC loads, energy storage devices, and photovoltaic equipment can be connected to the local energy Internet, realizing distributed equipment and distribution in the region. The power exchange between grids solves the problem of local consumption of new energy and lays a hardware foundation for the optimization of power economy.

The invention discloses a three-phase-equilibrium electroslag refining furnace which comprises a modular-multilevel-based correction device, a normal electroslag furnace, a three-phase power supply and a transformer, wherein the modular-multilevel-based correction device is connected with the three-phase power supply through a three-phase incoming line; two phases of the three-phase power supply are connected with the normal electroslag furnace through the transformer; the modular-multilevel-based correction device is of a three-phase half-bridge topological structure; and each bridge arm in the three-phase half-bridge topological structure is characterized in that two converter sub-modules are serially connected and then are connected with one phase of the three-phase power supply through an electric reactor. The three-phase-equilibrium electroslag refining furnace disclosed by the invention solves the problem of three-phase nonequilibrium of the power grid caused by the single-phase electroslag furnace, and improves power factor of the load, reduces a series of influences caused by the problem of grid nonequilibrium, and saves investment cost of steel-making enterprise; and meanwhile, the electroslag refining furnace achieves the purpose of energy conservation and emission reduction, improves utilization rate of electric energy and reduces pollution on the power grid.

The invention discloses a vertical electrode hot water boiler device. The device is characterized in that a three-petal-shaped opening is formed in the middle of an insulation shell and serves as a water guide opening, and the insulation shell is provided with three heating spaces with the inner sides communicated; three electrode plates are bent rectangular plates and are used for being attached to the inner side wall of an electrode supporting plate; a movable shield central pipe is connected with three shield plates which are in a rectangular plate shape, form an included angle of 120 degrees and are used for isolating the electrode plates; and the upper end of a lead screw which penetrates through a nut coaxially arranged with the central pipe and is in threaded fit with the nut penetrates out of a large tank and is connected with a stepping motor. The problem that the electrode structure is unstable is solved through a new structural form, and a zero electrode is omitted; by optimizing the electrode design, the total height of equipment is reduced, the size is reduced, and the applicability of the equipment is improved; the problem of electrification of a tank body is solved, the safety of the equipment is improved, and the equipment cost is reduced; the installation difficulty of internal parts is reduced, the installation cost is saved, and the quality assurance capability is improved; and by optimizing the sealing structure, the sealing reliability is improved.

The invention discloses a low-voltage single-phase power supply system from 10kV to 220V. The system includes a three-phase-two-phase transformer connected in sequence from 10kV to 220V, an electric energy collection unit, an unbalance control unit, a reactive power control unit, and an AC- DC‑AC module, this application first uses the transformer to convert the three-phase voltage into two-phase voltage, and collects the electrical quantity by connecting the electric energy collection unit, and sends the collected electrical quantity to the unbalance control unit and the reactive power control unit, and the unbalance control unit The unit is used to monitor the current unbalance between the α phase and the β phase, the AC‑DC‑AC module regulates the two-phase current, the reactive power control unit is used to monitor the power, and the AC‑DC‑AC module regulates the current in the line The power is adjusted; compared with the power supply mode of single-phase transformer with two incoming lines, the power supply system provided by the present invention can solve the problem of three-phase unbalance on the 10kV side, and can greatly reduce the probability of three-phase current unbalance on the 220V side, reducing The capacity of the three-phase unbalance control device can reduce line loss and improve the quality of power supply.

The invention discloses an intelligent power distribution and utilization flexible control system. The intelligent power distribution and utilization flexible control system comprises a transformer, a three-phase rectifier, at least one single-phase inverter and at least one three-phase inverter. The three-phase rectifier converts a three-phase alternating current produced by the transformer into a direct current which is output to the inverters, the single-phase inverters convert the direct current into single-phase alternating currents with adjustable frequency and amplitude, and the three-phase inverters convert the direct current into three-phase alternating currents with adjustable frequency and amplitude. According to the intelligent power distribution and utilization flexible control system, the method that the three-phase alternating current is rectified and then inverted is adopted, the problem that a great deal of single-phase electric equipment is directly connected to a power supply grid to cause three-phase unbalance is solved, damage to power transmission and distribution equipment and the electric equipment is reduced, and reliability, economical efficiency and power quality of power supply are improved. Besides, the intelligent power distribution and utilization flexible control system achieves clear work division of modules, is easy to design, build and maintain, operates easily, and achieves convenient system expansion and upgrading.

The invention relates to a device and method for treating three-phase imbalance of a distribution transformer district. The device comprises a control panel and an IGBT unit. The control panel comprises a current collection unit used for collecting the current data and current phase information of an outlet side of a transformer, a main control unit connected with the current collection unit and used for receiving the current data and the current phase information and acquiring calculation data and a driving signal, a driving unit and a communication unit, wherein the driving unit is electrically connected with the main control unit, and the driving unit enables the IGBT unit to work according to a driving signal; and one end of the communication unit is electrically connected with the main control unit, the other end of the communication unit is connected with a single-phase new energy power supply, and the communication unit is used for interacting the calculation data and the current phase information with the single-phase new energy power supply. The treating device is simple in structure and reasonable in layout, the phenomenon of three-phase imbalance can be avoided, damage to related equipment is avoided, and the operation stability of the related equipment is improved.

The invention is suitable for a low-voltage management device and method at the end of a long-distance 10kV distribution network, and relates to the technical field of distribution network power management devices. The invention includes an active compensation unit, a passive compensation unit, and a control unit. The active compensation unit and the passive compensation unit are connected in series to the end of the 10kV power distribution line, and the active compensation unit is set at the front end of the passive compensation unit and located at the power distribution line. line power side. Aiming at the deficiencies of existing low-voltage treatment devices, the invention achieves the goals of simple structure, increased power density, reduced capacity requirements of compensation devices, and improved equipment cost performance.

A three-phase unbalanced phase-change molded case circuit breaker comprises a circuit breaker body, a contact module, a transmission mechanism, an arc extinguish chamber and a phase-change switch, the contact module comprises a static contact and a moving contact, the static contact is located in the arc extinguish chamber, the static contact is connected with a first wiring board, and the moving contact is connected with a second wiring board; the second wiring board is connected to the input end of the phase-change switch; the transmission mechanism comprises a pull rod, a connecting plate and a rotating support, the moving contact is located at one end of the rotating support, one end of the pull rod is located at the other end of the rotating support, the other end of the pull rod is connected with the connecting plate, and the connecting plate is matched with a permanent magnet fixed to the circuit breaker body.

The invention discloses a parallel-connection active power filter suitable for a three-phase four-wire power grid system, which mainly comprises a three-phase full-bridge inverter circuit, a half-bridge chopper circuit and two capacitors; the three-phase full-bridge inverter circuit is electrically connected with the three-phase four-wire power grid system and connected in parallel with the half-bridge chopper circuit; and the other side of the half-bridge chopper circuit is electrically connected with a midpoint of the two capacitors at a direct-current side through an inductance, and the half-bridge chopper circuit is used for controlling the direct-circuit side voltage of the parallel-connection active power filter. A double close-loop control mode is adopted in the invention, wherein the inner ring is a voltage ring which is used for providing energy feedforward for controlling the direct-current end voltage stabilization and restraining zero-sequence current perturbance; and the outer ring is a current ring which is used for controlling the output current of the parallel-connection active power filter. Compared with the prior art, the parallel-connection active power filter with the double close-loop control structure can be used for preferably compensating the power grid harmonic current and restraining three-phase imbalance.

A reactive power compensation device based on novel modular multilevel topology and a control method thereof relate to a high-voltage and large-power reactive power compensation device. In the prior art, compensation in a high-voltage and large-power field is limited and an inhibiting ability to circulation is insufficient. The invention aims at solving the above problems. A three-phase alternating-current power supply, a resistance-inductance load, a MMC converter, a signal detection circuit, a control circuit and a driving circuit are included. The MMC converter comprises three bridge arms which share a same structure and are connected in parallel. Each bridge arm comprises an upper bridge arm and a lower bridge arm which are symmetrical about a middle point of the bridge arm and are connected in series. Each upper bridge arm comprises a resistor, an inductor, several half-bridge units and an H bridge unit which are connected in series. The inductor of each upper bridge arm and an inductor of each lower bridge arm are connected in series. The middle points of the three bridge arms of the converter are connected in parallel between the three-phase alternating-current power supply and the load through a lead. By using the device and the method in the invention, power-grid reactive power can be compensated; a three-phase imbalance problem of a system is solved; effects of supporting a power grid voltage and inhibiting the circulation are achieved.

The invention discloses a vertical electrode hot water boiler device. The middle part of the insulating shell has a three-lobed opening as a water guide, and the insulating shell has three heating spaces connected on the inside; the three electrode plates are bent rectangular plates. It is used to fit the inner side wall of the electrode support plate; the central tube of the movable shield is connected with three rectangular plates with an angle of 120° and is used to isolate the shield plate of the electrode plate; it passes through the nut coaxially arranged with the central tube and is connected with the The upper end of the lead screw that the nut thread fits passes through the large tank and is connected with a stepping motor. The problem of unstable electrode structure is solved through a new structural form, and the zero electrode is canceled; by optimizing the electrode design, the overall height of the equipment is reduced, the size is reduced, and the applicability of the equipment is improved; the problem of tank electrification is solved, and the The equipment is safe, and the cost of the equipment is reduced; the difficulty of installing internal parts is reduced, the installation cost is saved, and the quality assurance ability is improved; and the sealing reliability is improved by optimizing the sealing structure.

The invention provides a reactive power compensation device, and the device comprises a main circuit, wherein the main circuit is a compensation current generation loop and comprises an LCL unit and athree-level conversion module group which are connected in sequence; the main circuit is connected to a power grid through an LCL unit and a three-level converter module which are connected in sequence; by adjusting the phase and amplitude of the output voltage in real time, the reactive current absorbed or emitted by the circuit can be changed, and dynamic reactive compensation is realized. Dynamic compensation is tracked in real time through a control system, harmonic current is detected in real time through the harmonic current compensation technology based on the instantaneous reactive power theory, dynamic compensation of the harmonic current is achieved through instantaneous current tracking control, load harmonic changes are automatically tracked, and high controllability and rapidresponsiveness are achieved. And the compensation performance is excellent, and is not influenced by the system impedance; the risk of resonance with the system impedance can be eliminated, and system resonance caused by harmonic waves in a power supply system can also be suppressed.

The invention discloses a transformer area system for governing three-phase imbalance and a control method. The system comprises a transformer area centralized controller, a dynamic compensation device, a phase-change switch, a collector and other devices, and the collector collects the current of each branch and communicates with the phase-change switch in each branch. The transformer area centralized controller and the collector are communicated with each other, and the transformer area centralized controller and the dynamic compensation device are communicated with each other. The transformer area centralized controller is adopted to control the phase change switch and the dynamic compensation device, and the problem of three-phase imbalance caused by high-proportion single-phase photovoltaic access to a low-voltage transformer area is solved.