66results about How to "Guaranteed voltage quality" patented technology

The invention provides an intelligent reactive compensation comprehensive control device, wherein a judging process of a judging module in a central processing unit is as follows: 1, judging whether to switch on or switch off according to reactive power or power factor of an electric grid; 2, judging whether voltages in three phases are all in a range of allowing the switching on or the switchingoff; 3, calculating a vacancy value or an excess value of total reactive power, and selecting a total compensation capacitor group; 4, calculating the vacancy value or the excess value of the reactive power of each phase, and selecting an individual compensation capacitor group; 5, judging whether the capacitor group is in blocking state; and 6, outputting switching on or switching off instructions to a switching outlet driving unit of the compensation capacitor. The control device uses the reactive power or the power factor of the electric grid as criterion for controlling the switching on or the switching off of the capacitor groups, uses the voltage as a constraint condition, and uses the vacancy or the excess of the reactive power to preferentially select a reactive power compensationpolicy and the capacitor groups to be switched, so that the power factor of the electric grid can be effectively improved, losses of the electric grid can be reduced, and voltage quality of the electric grid is ensured.

The invention relates to a low voltage load online phase modulation device and a phase modulation method thereof. According to the invention, optimization selection is performed to phase sequence state combination of electric load of users in a power distribution area, and then the electric load of the users is switched freely among phases A, B and C via a controllable switch, so that loads of the three phases of the power distribution area can be balanced. The low voltage load online phase modulation device fully integrates advantages of a mechanical switch and an electronic switch, so that the function of zero passage seamless switching of voltage and current can be realized, the impacts on a low voltage power grid and the electric load of the users are avoided, and the reliability of power supply and the voltage quality are guaranteed. The low voltage load online phase modulation device ensures that the load of the three phases of the power distribution area realizes minimum unbalance degree, the switching times of the switch is minimum, and the service life of the low voltage load online phase modulation device is improved. The low voltage load online phase modulation device has the function of three-phase load adjustment, and moreover, has functions of fault protection for over-current and over-voltage and leakage protection.

The invention relates to a hierarchical control method for an ad / dc microgrid with the direct voltage recovery character. The method comprises two layers of control, wherein in the first layer of control, a direct voltage-active power droop control method is adopted, and even load allocation is achieved; in the second layer of control, a method for compensating for the direct current bus voltage reference value is adopted for the direct current bus voltage drop caused by the droop control, the recovery of the bus voltage is achieved, and the quality of the direct current bus voltage is guaranteed. According to the method, the even power distribution during load changing of a local power source is achieved while the quality of the direct current bus voltage is guaranteed.

The present invention relates to a power distribution network reactive power compensation planning method. Through the setting of a reactive power compensation planning target, condition constraint and selected typical region calculation and the expansion to an entire network, the optimal compensation capacity and economic efficiency of reactive power compensation planning are obtained, the network loss is effectively reduced by using the reactive power compensation planning, the reasonable configuration of a reactive power compensation capacity is realized, and the safe and economic operation of a power system is ensured.

The invention discloses a distributed power quality conditioner and a method for controlling the same. The distributed power quality conditioner comprises one or more series compensation devices and parallel compensation devices, wherein each of the series compensation devices and the parallel compensation devices comprises a central controller; the series compensation devices and the parallel compensation devices do not share a direct current bus; and when the series compensation devices and the parallel compensation devices are used together, a management center is configured for acquiring the voltage of an electric network and load current information to determine the failure type of the electric network, and coordinately operating all series compensation devices and all parallel compensation devices.

The invention provides a voltage threshold probability-based reactive power optimizing method for a grid containing a wind power plant, which aims to solve the problem that under the condition of wind power networking, the effect of the voltage optimizing control to an automatic voltage control system is not ideal. The method comprises the steps as follows: firstly, collecting grid operation parameters, basic parameters of each wind power generator in the wind power plant, and active power output data of the wind power plant; secondly, acquiring voltage impact factor, power conversion coefficient of the wind power generators and wind power plant active power probability distribution equation through the above parameters, and further obtaining voltage threshold probability; and lastly, establishing a reactive power optimizing model on the basis of the voltage threshold probability, adopting genetic algorithm to solve the model, and obtaining a control instruction of a reactive power device. According to the invention, the voltage threshold probability-based reactive power optimizing method substitutes a conventional reactive power optimizing method for the automatic voltage control system, can enable the voltage optimizing control to the automatic voltage control system to effectively control the reactive power device in the grid under the condition of wind power networking, and ensure the safe and economic operation of the grid.

The invention provides a bidirectional droop control method for an IC (Interlinking Converter) in an AC-DC (Alternating Current-Direct Current) mixed microgrid for performing Udc-f-P bidirectional droop control and recovery control of the IC in the AC-DC mixed microgrid. With the method, bidirectional flow of electric energy is controlled; the maximum utilization of distributed energy is achieved; the voltage quality is ensured; drop of direct current voltage and frequency is prevented; uniform load distribution among interlinking converters is achieved; and the stability of the AC-DC mixed microgrid is improved.

The invention discloses a grid-connected converter series virtual impedance method for virtual inertia control. The method comprises the steps that a direct current micro-grid system is established; signal measurement and processing are carried out; small signal analysis is carried out on a reference current equation; small signal analysis is carried out on a grid-connected converter mathematicalmodel and a current inner loop control model; small signal analysis is carried out a power equation; output impedance Zo(s) is calculated; a spike function is extracted and multiplied with a low-passfilter to form a compensation amount; series virtual impedance is applied to a current reference value; PI control and feedforward decoupling control are carried out; alpha beta transform and SVPWM modulation are carried out. According to the invention, the method has the advantages of simple structure and high efficiency; when the direct current micro-grid system is unstable, the control goals ofincreasing system damping, suppressing direct current voltage oscillation, and ensuring voltage quality during steady-state operation are realized.

The invention discloses an energy-storage system-based self-starting control method for a double-fed induction generator. The control method particularly comprises the steps as follows: (1) when a power network is in a low-voltage fault, a self-starting controller of the double-fed induction generator cuts off a network side load; an energy-storage system is merged into two ends of a direct-current capacitor; the energy-storage system charges the direct-current capacitor; and the control system adopts a PV voltage control strategy; (2) after network side voltage reaches the control range of rated voltage, a system load is connected; meanwhile, a frequency controller is started; the self-starting frequency of the generator is further controlled to ensure that the frequency of the system is stabilized within the rated frequency; and (3) after the controller detects stable frequency and voltage of the system, the system stably runs, cuts off the energy storage system, and is converted into a PQ power control mode to stably run; and the self-starting process of the generator is ended. Under the direct-current voltage support of the energy storage system, self-starting and running with the load of the generator are achieved; and stable voltage and frequency are ensured.

The invention discloses a joint coordination method for automatic voltage control (AVC) of master stations and voltage reactive power control (VQC) of plant stations, which relates to the technical field of power dispatching automation systems. The method aims to solve the problems of simultaneously deploying AVC and plant-station VQC in the same area and using a decision tree method with data mining to solve the technical problems of joint coordination equipment between the two. The method has the following implementation processes: 1) preparing data and establishing a data-mining knowledge base; 2) establishing node attributes; 3) testing samples; 4) adjusting the node attributes; 5) verifying the samples; and 6) generating a coordination strategy. The data mining method based on decision trees has the characteristics of high intuitionistic property, easy operation and capability of flexibly expanding the node attributes. The method can extract results to be predicted from a great amount of relevant information, which provides bases for power dispatching automatic control decision.

The invention relates to a method for suppressing voltage fluctuation and harmonic distortion through a static synchronous compensator in a distribution network. The method comprises: detecting electric parameters at a PCC of the distribution network; calculating a positive-sequence reactive output, a negative-sequence reactive output, and a t-order harmonic active output of a DSTATCOMi connected to the same PCC; calculating a positive-sequence voltage, a negative-sequence voltage , and a t-order harmonic voltage compensation reference value of the PCC; calculating a virtual positive-sequence susceptance, a negative-sequence susceptance, and a harmonic conductance of the DSTATCOMi based on universal impedance shape; calculating a positive-sequence, negative-sequence, and harmonic output current reference value of the DSTATCOMi; synthesizing the output current reference value of the DSTATCOMi to perform proportional current limitation according to priorities; and synthesizing PWM signals from the DSTATCOMi control system to perform pulse width modulation. The invention can achieve a reasonable cooperation between overall control over PCC electric energy quality and protection of the distribution network, enhance both local and regional voltage quality in the distribution network, and ensure the security and the stable operation of the distribution network.

The invention discloses a multi-time-scale province-region-county integrated reactive power optimization method of an electric system. The method considers the yearly rule, the season rule, the monthly rule, the day rule, super-short-time built-in inertia rules and random components. The method can achieve multi-time-scale province-region-county integrated reactive power optimization, provides multi-time-scale continuous reactive voltage optimal configuration strategies, achieves reactive voltage optimal operation between various voltage classes in long periods, intermediate periods and short periods, improves the voltage qualified rate of the whole network, guarantees continuous, safe and stable operation of the power grid, provides theoretical foundations for setting up the operation mode of the power grid and reasonably and optimally utilizing electricity generation resources, and can effectively guarantee safe, stable and continuous operation of the power grid.

The invention relates to a low-voltage regulation method for a power distribution network. The low-voltage regulation method comprises the steps of obtaining data parameters of a main transformer, an SVR feeder line automatic voltage regulator, a power distribution transformer and a load circuit; analyzing low-voltage reasons and low-voltage positions of the power grid through the data parameters; if the SVR feeder line automatic voltage regulator, the power distribution transformer and the load circuit terminal all suffer from lower voltages, performing voltage regulation by adjusting a main transformer tap gear; if the power distribution transformer and the load circuit terminal both suffer from lower voltages, performing voltage regulation by adjusting a tap switch position of the SVR feeder line automatic voltage regulator to change the transformation ratio of an auto-transformer; and if only the load circuit terminal suffers from a lower voltage, performing voltage regulation by adjusting the tap position of the power distribution transformer and switching a reactive compensation capacitor. By adoption of the low-voltage regulation method, the voltage at the tail end of a city and town power grid is improved, the reactive current flow of the circuit is lowered, the electric energy loss is reduced, and the power supply voltage quality of rural power grids is improved.

The invention relates to a new-type urbanization-based low voltage treatment measures optimization method, which comprises the steps as follows: system parameters of a power distribution network are obtained; the maximum load as shown in the specification of a distribution transformer is calculated according to the distribution transformer capacity; eta represents the load rate of the distribution transformer; S represents the capacity of the distribution transformer; rhi represents a power factor; the current power load of a load terminal is counted; the reason of a low voltage is judged according to the system parameters, and the power load, namely the maximum load of the distribution transformer; if the current power load is greater than the maximum load P of the distribution transformer, voltage adjustment is carried out through a power distribution device; and if the current power load is smaller than the maximum load P of the distribution transformer and when terminal voltage fluctuation of a to-be-tested circuit is greater than a standard value, voltage adjustment is carried out through a wire with a relatively large wire diameter. The terminal voltage of an urban power grid is improved; the reactive current flow of the circuit is reduced; the electric energy loss is reduced; and the quality of a power supply voltage of a rural power grid is improved.

A coordinated control method for multiple converters in the AC / DC section in a hybrid micro grid comprises the following steps: a mathematical model is built according to the structure and parameters of an AC / DC micro grid, specifically, a mathematical model of boost circuits is built through an average state method according to the numerical theory under the premise of considering the switching nonlinearity of the boost circuits; in view of the characteristics of the multiple boost circuits, photovoltaic power generation and micro grid load in an AC / DC hybrid micro grid and multiple converters in the AC section, input variables influencing the micro grid control effect are separated and divided into controllable variables and disturbance variables (namely, adjustable electrical variables and unadjustable electrical variables) according to an H<infinite> design method of the weighted mixed sensitivity problem, and a state space is established; and an AC / DC hybrid micro grid DC power flow section multi-converter K<infinite> coordinated controller is designed based on the H<infinite> method of the weighted mixed sensitivity problem. The performance of the controller can be continuously improved by adjusting a weight function flexibly according to performance indicators to be designed, in order to ensure the voltage quality of a DC system.

The invention discloses a reactive power optimization method for a photovoltaic reactive power partition pricing power distribution network, and the method comprises the steps: proposing a controllable photovoltaic reactive power partition pricing model, taking the minimum reactive comprehensive cost and the minimum deviation between active power loss and voltage as optimization targets, and constructing a power distribution network active-reactive power optimization model including response PV inverter reactive partition electricity price, static Var compensator (SVC) dynamic compensation, on-load voltage regulation equipment OLTC tap and capacitor bank switching; and processing nonlinear terms in the model by adopting mathematical means such as second-order cone programming and a large Mmethod, finally obtaining a mixed integer second-order cone programming model of active-reactive coordination optimization of the power distribution network containing controllable photovoltaic in the power market environment, and segmenting and solving the model by adopting a Benders decomposition method. According to the invention, the reactive capacity of a photovoltaic inverter and the reactive support capability of original discrete equipment of a distribution network are reasonably and coordinately utilized, the active power loss is reduced, and the user voltage quality is ensured.

The invention relates to a dry-type electric power transformer and belongs to the technical field of transformers. The invention improves the structure of the prior dry-type electric power transformer and is characterized in that each phase winding of a high voltage winding consists of two independent windings of an upper winding and a lower winding, and the upper winding is separated from the lower winding by an insulating pad into two independent upper and lower windings of 10KV. By changing the structure of the high-voltage winding, the invention does not affect the mechanical and electrical performances of products, and plays a connecting role during the transformation of the transition from a 10KV power grid to a 20KV power grid; primary side voltage of the 10KV power grid and the 20KV power grid can be freely switched, without any effect on the secondary side; compared with a 10KV transformer, the invention increases the power supply capacity, ensures the voltage quality, reduces the electric energy loss of the power grid and saves the construction cost of the power grid, and the invention has all the functions of a 20KV transformer simultaneously and is well in line with the distribution of the town power grid.

The invention discloses a double-end power supply structure applicable to a low-voltage distribution network with direct current microgrid access. A first power distribution cabinet and a second power distribution cabinet are connected through a dual-power-supply automatic transfer switch (ATS); the low-voltage buses of the first low-voltage power distribution cabinet and the second low-voltage power distribution cabinet are connected through a soft normally open point (SNOP); a direct current microgrid is connected through the direct current side of the SNOP; and the SNOP is connected with the dual-power-supply ATS in parallel. By adoption of the double-end power supply structure, the following technical problems can be solved: the low-voltage parallel power supply system comprising the direct current microgrid in the prior art is instable in alternating current system frequency and has reactive power-caused loss; the power supply may suffer from a reverse-power operating condition caused by influences from values of a power supply voltage, phase, equivalent impedance, an impedance angle, a load, a power factor and the like; and furthermore, the service life and the like of the ATS are influenced by deformation of a mechanical switch contact due to frequent switching of the conventional ATS.

The invention discloses an on-load capacity-regulation distributing transformer, comprising a transformer body, a detection unit, a control unit and a capacity regulation device, wherein the detection unit is connected with the transformer body, a signal output end of the detection unit is connected with a signal input end of the control unit, a signal output end of the control unit is connected with a signal control end of the capacity regulation device, and a signal output end of the capacity regulation device is respectively connected with a high-voltage coil and a low-voltage coil of the transformer body; the capacity regulation device comprises a contactor and a combination switch, wherein the combination switch has 5KW or below 5KW voltage class and is connected in parallel to an electronic switch of a thyristor; and the control unit can be used for eliminating overcurrent on a high-voltage side and overvoltage on a low-voltage side by selecting a control strategy of nonsynchronous actions on the high-voltage side and the low-voltage side. The invention solves the problems on the voltage class, cost, volume and reliability of the on-load capacity-regulation combination switch of the distributing transformer, and provides the on-load capacity-regulation transformer with the advantages of high automation degree, low cost and easiness in implementation, so as to realize the reliable and economic capacity-regulation operation of the distributing transformer.

The invention discloses a cascade energy storage system and method for improving power quality of a power grid. The system comprises distributed energy storage units, a low-voltage module group and ahigh-voltage module group, wherein the low-voltage module group comprises a plurality of cascaded H-bridge circuits; the low-voltage module group is connected to a low-voltage alternating current busthrough a filter; the high-voltage module group comprises a plurality of the cascaded H-bridge circuits; the high-voltage module group is connected in parallel between a low-voltage bus and a high-voltage bus through the filter; each distributed energy storage unit is connected to the low-voltage module group or the high-voltage module group through one of the H-bridge circuits; and each distributed energy storage unit is connected to the corresponding module group through the H-bridge circuit to form a three-phase independent structure. Through the cascade H-bridge series structure, the energy storage system can be directly connected to the medium-voltage or even high-voltage power grid without isolation of a transformer, and the voltage of the direct-current side of CHB connected to theenergy storage system does not need to be very high, and thus the flexibility and reliability of the operation of the energy storage system are improved.

The present invention discloses a hybrid modulation strategy for improving the electric energy quality of MMC-UPFC series connection side compensation voltage and smooth switching. Based on nearest level modulation (NLM) and carrier disposition CD-SPWM-VLM modulation with the introduction of virtual cyclic mapping, a hybrid modulation strategy is proposed, combined with Nanjing UPFC actual engineering parameters, the relationship between grid voltage harmonic content and an inverter modulation ratio is analyzed, and thus a control threshold of the hybrid modulation strategy is determined to achieve smooth switching as much as possible. First of all, an average modulation ratio m of three periods of the series connection side compensation voltage is read and calculated, the NLM is employed when m is larger than 0.5, otherwise, the CD-SPWM-VLM is employed. In the operation process, when detected m is larger than or equal to 0.6, the NLM is employed, when the detected m is smaller than or equal to 0.4, the CD-SPWM-VLM is employed, while the harmonic characteristics of MMC output series connection compensation voltage is improved well, no excessive device switching loss is generated, and the validity of the control strategy is verified in a UPFC engineering simulation model.

The invention discloses a joint deployment method for distributed power supplies and intelligent parking lots. The method includes the steps that a first-stage model is established, wherein the control variables of the first-stage model include a first vector representing candidate station locations in the distributed power supplies and the number of distributed power supplies configured at the candidate station locations, and a second vector representing candidate station locations in the intelligent parking lots and the number of bidirectional charging piles configured at the candidate station locations; a second-stage model is established, wherein the control variable of the second-stage model is a third vector representing active power and reactive power in the intelligent parking lots; the first-stage model and the second-stage model are solved with a preset algorithm, the optimal solutions of the first vector and the second vector are obtained, and the optimal solutions serve as the joint deployment scheme of the distributed power supplies and the intelligent parking lots, wherein the optimal solutions are obtained by carrying out repeated iteration on the solving results of the first-stage model and the second-stage model. The invention further discloses a joint deployment device for the distributed power supplies and the intelligent parking lots.

The invention relates to a voltage reactive power comprehensive control method of an extra-high voltage transformer substation. The process include a first of calculating changing situations of extra-high voltage medium voltage and reactive power when reactive power output changes in a machine group, a second step of calculating changing situations of the extra-high voltage medium voltage and reactive power in the process of switching changes in low capacity and low resistance in the extra-high valve station, a third step of calculating changing situations of the extra-high voltage medium voltage and reactive power when different active power flows are sent downwards by an extra-high main transformer, a fourth step of drawing a voltage reactive power comprehensive control nine-zone diagram according to the calculating results of the first step and the third step, and a fifth step of controlling the system and enabling the system to run in an normal operation area according to the corresponding position of a present operating point in the nine-zone diagram. Compared with the prior art, according to the voltage reactive power comprehensive control method of the extra-high voltage transformer substation, the problems that opposite voltage regulating measures are repeatedly adopted, and the system vibrates in the adjacent area are effectively solved. Operation times of reactive power voltage regulating equipment are reduced, and the voltage reactive power comprehensive control method of the extra-high voltage transformer substation has the advantages of guaranteeing the quality of network voltage and controlling fast and efficiently.

The invention discloses a wind turbine generator set black start capability verification system and method. The system comprises an external power supply G1, a wind turbine generator set, an SVG system, a simulation load L1, a matching load L2, a box type transformer T1, a box type transformer T2, a load transformer T3 and an engine room transformer T5. The external power supply G1 is connected with the wind turbine generator set. The wind turbine generator set is connected with the box type transformer T1. The box type transformer T1 is connected with a bus F1. The SVG system is connected with the bus F1. The simulation load L1 is connected with the load transformer T3. The matching load L2 is connected with the engine room transformer T5. The load transformer T3 and the engine room transformer T5 are connected with the box type transformer T2. The box type transformer T2 is connected with the bus F1. The matching load L2 is connected with an energy management system. The wind turbine generator set is connected with the energy management system through a wind turbine generator monitoring system. The real black start is simulated so as to verify the black start capability of the wind turbine generator set.

The invention discloses a source-load coordinated voltage control method and device based on multiple agents. The method comprises the following steps of: acquiring a preset prediction curve; solving a maximum peak clipping objective function constructed by a preset prediction curve according to the first optimization constraint condition to obtain an ideal load scheduling curve; realizing charging active power regulation control according to the ideal load scheduling curve; if the first node voltage is lower than the preset lower limit value, performing adaptive reactive power control according to the acquired total reactive power demand, the total active power output of distributed power supplies and the maximum total reactive power output of an inverter; and performing out-of-limit monitoring on the voltage of the second node in the partition, and executing a preset feeder line automatic compensation strategy when the voltage of the second node exceeds a preset voltage range. The technical problems that an existing distributed control technology lacks pertinence and reliability, so that the distributed control effect of the voltage of the power distribution network is poor, and the voltage quality and the absorption capacity of the distributed power supply cannot be guaranteed can be solved.

The invention relates to an oil-filled power transformer, belonging to the field of transformer technique. The invention improves the existing oil-filled power transformer structure and is mainly characterized in that each phase of winding of a high-voltage winding consists of an upper independent winding and a lower independent winding; the upper winding and the lower winding are separated into two independent 10KV windings by a cross-over block; by changing the high-voltage winding structure, the mechanical and electric performance of the product is not affected, and wiring can be carried out inside an oil tank; the structure of the invention does not affect the mechanical strength and electric performance of the product; furthermore, during the transitional reconstruction from 10KV power network to 20KV power network, the transformer of the invention has a transition effect; primary side voltages of 10KV transformer and 20KV transformer can be freely switched and the secondary side is not affected; compared with 10KV transformer, the power supply capability is increased, the quality of the voltage is ensured, the power energy dissipation of the power network is reduced, the construction expense of the power network is saved, meanwhile, all functions of 20KV transformer are provided, and the distribution of town power network is complied with more.

The invention relates to a photovoltaic grid-connected inverter control method, in particular to a photovoltaic grid-connected inverter control method for preventing voltage out-of-limit of a low-voltage distribution network by considering the influence of line impedance and operating environments on a photovoltaic inverter. Voltage out-of-limit of a grid connection point of the inverter can be prevented, and light discarding amount can be decreased as far as possible by the aid of the residual capacity of the inverter on the premise of ensuring the voltage quality of the grid connection point when voltage exceeds upper limit. Compared with a traditional method, when the voltage of the grid connection point exceeds the upper limit, an active and reactive power matching method is designed by reverse thinking on the premise of ensuring the voltage quality, and the light discarding amount is decreased by the residual capacity of the inverter.

The invention belongs to the electrical network voltage idle work automatic control technology area, its characteristic lies in based on the electrical power system network parameter and various generatrixes pitch point voltage, current, the merit and the reactive power actual value formed the Jacobian matrix, find out the actual sum lose value; again construct the optimization objective function to obtain the minimum value of the system sum active lose; then formed the discrete logic event, solved the optimization objective function to get the voltage value, the voltage value of idle work compensation node and the transformation ratio value on load tap changing transformer as the control command output, in order to adjust the above node parameter. The invention guarantees the voltage quality and simultaneously enhances the movement efficiency.

The invention discloses an active distribution network voltage coordination control system and method based on sensitivity analysis. The system comprises: a voltage overrun target screening module forselecting a node with the largest voltage overrun in the active distribution network system; ; a FCE active power regulation selection module for selecting the best active power device according to the voltage sensitivity matrix; a reactive power equipment selection module for seleting the optimal reactive power equipment according to the voltage sensitivity matrix; an FCE active power regulatingmodule for completing the distribution of the active power target value; a reactive power regulating module for completing reactive power target value transmission; a synergistic interactive controlis used for carrying out active PID regulation and reactive PID regulation on an intelligent manager according to an active target value and a reactive target value, respectively, and completing fastcomputation of FCE control; an intelligent management controller is used for setting the active power target value of the active power equipment and the reactive power equipment respectively. The invention achieves the requirements of multi-objective coordination and optimization control of an active distribution network.