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

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 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 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.

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 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 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 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.