167 results about "Reactive power theory" patented technology

An integral method for realizing parallel generation and network reactive power compensation at the same time is based on the transient reactive power theory applying park transfer to transform a three phase inverter output current to a rotation dq coordinate to realize separation of active current and reactive current to convert the DC current of the photovoltaic to AC current by controlling the currents and directions carry out reactive power compensation to the local network. When a photovoltaic battery has enough energy to output, it realizes parallel generation and reactive compensation at the same time, when it stops the output, the inverter compensates the network independently.

The invention discloses a control method of an alternating voltage sensorless high voltage direct current transmission converter, belonging to the technical field of electrical equipment and comprising the following steps: establishing a stator resistor and an inductor for a virtual motor; building relative position relationships among a current vector, a voltage vector and a flux linkage vector, and analyzing a vectorgram; establishing a converter and flux linkage mathematic model, and calculating a virtual flux linkage vector of a system to obtain a power feedback quantity of the system; acquiring an active control signal and a reactive control signal of the system through a direct power control algorithm, and generating a PWM trigger converter for respectively and independently controlling the active power and reactive power of the system; and utilizing MATLAB simulation software to set up a system model for verifying, and obtaining a systematic selection device when the verification is successful. By utilizing Matlab/Simulink to set up a corresponding simulation model, the designed method is verified to have rapid response speed, the voltage and power after startup can still reach stable values after about 2 power frequency periods and have high steady state precision.

The invention discloses an improved droop control method based on a communication network for a distributed power source in a parallel connection operation mode in a micro power grid system. The defect of a traditional droop control method is overcome, the performance of the distributed power source in the parallel connection operation mode is improved, the stability of the system is improved, and the improved droop control method is suitable for control over the parallel connection operation mode in the micro power grid system which integrates with new energy resource distributed power generation. According to the improved droop control method, a communication network is used as the basis, a central controller in the micro power grid system and controllers of all inverter units form an entire control system, the active power and the reactive power of public loads are calculated, and the droop control scheme of each distributed power source is corrected. The scheme is used, a better power flow equalizing effect can be achieved, smaller deviation of busbar voltage frequency and amplitude is achieved, and a good application prospect is achieved.

A reactive power compensation and harmonic governance system and a control method for realizing power compensation and harmonic governance by using the same belong to the field of an electric system and solve the problems that the prior reactive power compensation technique cannot synchronously realize the full compensation for the electric network while meeting the reactive power compensation of continuous change, compensating capacity has waste and system cost is high. The system of the invention uses the structure that M groups of TSCs are connected to the electric network in parallel, the three-phase output ends of SVG are respectively connected to one end of an inductor, the other end of each of three inductors is respectively connected the three phases of the electric network. The control method of the reactive power compensation and the harmonic governance comprises: processing the collected electric current values and voltage values by a controller, obtaining the control parameters of the TSC according to a switching rule for realizing stage reactive power compensation, obtaining the control parameters of the SVG by combining with an instantaneous reactive power theory for realizing the compensation of the residual reactive power between each two stages. The invention realizes the quick and continuous reactive power compensation and the harmonic governance under the condition that load contains harmonic current, and is used for the reactive power compensation of the electric system.

The invention discloses an optimized control method for wind power field reactive power compensation capacity considering wind power distribution rule; according to the method, a reactive power compensation capacity optimization model is utilized to carry out an optimized treatment, and the optimization target is that investment cost of reactive power compensation and operation cost of wind power system caused by reactive power are minimized; operation cost and investment cost are calculated; the operation cost comprises the affect of wind power distribution result and power property; and an optimized calculation is carried out by utilizing a particle swarm optimization algorithm combined with a power flow calculation program. The method has the beneficial effects that according to the optimization decision method of the compensation capacity, the reactive power compensation of a wind power field has the best economical efficiency and the strongest pertinency on the premise of adequately ensuring continuity of reactive power adjustment by wind power system.

The invention provides an electric principle-based wind power plant cluster reactive power sharing method. The method comprises the following steps: calculating real-time voltage of hubs; calculating voltage difference of the hubs; calculating the reactive power demand quantity of the hubs; calculating equivalent electric impedance of the wind powder plant from the wind plant to the hubs according to regional tidal stream information and wind power plant access circuit parameters; calculating the reactive sharing quantity of the wind power plant; and sending a reactive adjusting command to a wind power plant monitoring system to enter the next control. In the method, the hub voltage in the wind power plant access region is used as a regulating object, the actual condition of the wind power plant access region is concerned, and local region operation information is utilized so that equivalence is performed to the impedance of a wind power plant power passing circuit according to the basic electric principle; the reactive power is optimized by using the minimum active power loss of the access region as a target to ensure that the power grid operation and economic benefit of reactivepower adjustment are concerned while the wind power plant cluster provides reactive power support, and the reactive power coordinating distribution control of the wind power plant cluster can be improved conveniently.

The invention relates to a power network model-based wind power field automatic voltage control method which comprises the following steps of: 1, reading original data and building a wind power field power network mathematical model; 2, reading a wind power field real-time running working condition and a voltage target value released by the power grid dispatching; 3, carrying out load flow calculation to obtain initial load flow distribution on the basis of the former two steps; 4, distributing and releasing the reactive power reference value of a wind driven generator according to a sensitivity ordering strategy; 5, distributing and issuing the reactive power reference value of a dynamic reactive compensation device according to the sequence; and 6, confirming and releasing the tapping point gear reference value of an on-load tap changing transformer according to a step-by step adjustment strategy. According to the power network model-based wind power field automatic voltage control method, the unified coordination control among the reactive power of the wind power field wind driven generator, the reactive power of the dynamic reactive compensation device and the tapping joint of the on load tap changing transformer can be realized.

Embodiments of the invention relate to devices and methods and systems for controlling a reactive power contribution to reactive power flowing in an electricity distribution network, so as to optimise this reactive power flow. Conventional methods of controlling reactive power flow focus on minimising a reactive power contribution by power provision and power consumption devices connected to the electricity distribution network, in accordance with, for example, regulations governing a maximum allowed power factor and/or under the control of a central controlling entity. However, such methods are slow to react to changing network conditions, and do not take account of local variations in reactive power. In an embodiment of the present invention, there is provided a reactive power control device for use with a power consumption and/or provision device. The reactive power control device comprises detecting means for detecting, at the power device, a reactive power characteristic of electrical power flowing in the electric power distribution network, the reactive power characteristic relating to a reactive power component of electricity flowing in the network. The reactive power control device further comprises control means for controlling, on the basis of the detected reactive power characteristic a reactive power contribution to the electricity distribution device so as to adjust a value of the detected reactive power characteristic. This enables individual power consumption and/or provision devices to react autonomously to local variations in the electricity distribution network, and to provide a reactive power contribution, to drive the detected reactive power characteristic towards a desired value.

The invention discloses control method and system for selectively compensating wattless power by an active filter. The method comprises the following steps of: generating fundamental wave factors by electric network load current or electric network voltage; and then, multiplying the fundamental wave factors by the output of a voltage controller to generate control signals of the electric network current so that the active filter can selectively compensate the wattless power while filtering harmonic waves. The wattless compensation or wattless uncompensation can be selected through regulating the fundamental wave factors, the defect that the traditional wattful balance control method can only realize the simultaneous compensation of the harmonic waves and the wattless power but is not applicable to the large-capacitance wattless power load, the control method can be applicable to more application occasions, and in addition, the method of the invention does not need coordinate transformation and the phase locked loop and has , has simple algorithm and low hardware cost, thereby being capable of replacing the harmonic wave detection method based on the instantaneous wattless power theory in the active filter.

The invention provides a method and a device for optimizing the reactive power of a power distribution network containing distributed generation. The method comprises the steps of setting up a power distribution network reactive power optimization genetic algorithm model according to the preset control parameters of the power distribution network containing distributed generation and a genetic algorithm model, performing load flow calculation on the preset control parameters of the power distribution network to determine the equality constraints of the reactive power optimization of the power distribution network reactive power optimization genetic algorithm model, determining the inequality constraints of the power distribution network reactive power optimization genetic algorithm model according to the positions of controllable transformer taps, each node voltage, the output power of parallel reactive compensation capacity generators and the power factor of the high voltage side of each node distribution transformer in the control parameters of the power distribution network, and generating a reactive power optimization result according to a preset priority parameter, the equality and inequality constraints of the reactive power optimization and the reactive power optimization genetic algorithm model. The method and the device for optimizing the reactive power of the power distribution network containing distributed generation in real time have the advantages that less information is requested for solving problems, the solving process is simple and the optimal solution or the second-belt solution can be obtained with a great probability.

The invention discloses an excitation state analysis-based low-voltage ride-through control method of a virtual synchronous power generator. The method comprises the steps of improving designs of droop characteristic, a reactive power ring and an active power ring by means of a reactive power adjustment principle of the synchronous power generator and a power grid which are connected in parallel,and the problems of excessive large reactive power increment, difficulty in preventing impact current and loop coupling reinforcement are effectively dealt with; and on the basis of no change on characteristic of the state analysis-based low-voltage ride-through control method of virtual synchronous power generator (VSG) system, an additional current ring is designed again, the under-excitation state running of an auxiliary system can be assisted during power grid fault period, an output current is adjusted, and a reactive power support is given out. A new directional method is employed, the transient process is accelerated, a control algorithm is not needed to be switched during the power grid fault period, a smooth switching strategy among states is also not needed to be added, and the low-voltage ride-through problem and the asymmetric drop of the power grid can be simultaneously dealt with.

A compensation circuitry for providing reactive power to a network includes an inductance means and a capacitor means associated with switching appliances and with a controlling mechanism. The compensation circuitry is used for delivering reactive power compensation to electrical networks of either low or high voltage. The inductance means and the capacitor means are connected serially, thereby bringing the circuitry to a virtual gain selected from a group consisting of virtual inductance gain (VIG) or virtual capacitance gain (VCG), and wherein the virtual gain selected from the group is above the absolute value of 1.5.

The invention relates to an adjusting method based on comprehensive considering of voltage and reactive power for an SVG (Static Var generator) of a wind power plant, belonging to the technical field of automatic voltage and reactive power adjusting of a wind power plant. The method comprises the following steps: correcting target voltage values into an upper limit value and a lower limit value according to emergency upper and lower limits of voltage, a qualified bandwidth of voltage and a voltage adjusting dead zone; determining whether to carry out "constant-voltage" adjusting or "constant reactive power" adjusting according to the condition whether the current voltage is beyond the range of the lower limit value to the upper limit value or not; when carrying out "constant-voltage" adjusting, determining the reactive power adjusting variable according to the out-of-limit amount; when carrying out "constant-voltage" adjusting, determining the reactive power adjusting variable according to a target reactive power value; and verifying the reactive power adjusting variable according to the upper and lower limits of voltage and a reactive power adjusting step length. According to the adjusting method, the voltage of a point of common coupling is given a priority to be controlled between the upper and lower limits required as dispatching; therefore, the voltage qualified rate of the wind power plant is improved, the accurate adjustment of reactive power output can be realized under the condition of qualified voltage, and the operation safety and reliability of the wind power plant can be improved.

The invention belongs to the technical area of compensating the delayed time in the harmonic current detection. It is characterized by that it improves the conventional instant space vector method based on the theory of instant reactive power. When the coordinate transformation is carried out, the "delta" "theta" angle is added to the conversion matrix in order to compensate the delayed time, "delta" "theta"=n "omega" "delta" T here n is harmonic degree, "omega" is the angular frequency of the principal wave, "dlta" T is the delay time. Thus, the issue of the delayed time of the digital controller is solved. The invention realizes the real-time compensating the harmonic current, guarantees the compensation characteristic of the active filter as well as avoids the need of the device with high calculating speed so as to reduce the cost.

The invention discloses an automatic analysis system for the wind power plant reactive power regulation capacity based on WAMS dynamic data. The system comprises a real-time monitor module, an evaluation and examination module, a safety pre-warning module and an accident analysis module. The real-time monitor module monitors changes between active power and reactive power of wind power equipment in real time. The evaluation and examination module counts the three-phase current unbalance degree, operation conditions and dynamic reactive power response capacity of a reactive compensation device, counts voltage deviation, variation in voltage, the three-phase voltage unbalance degree, frequency and active power changes, and counts the reactive power supporting capacity when in high-low voltage ride-through and low voltage ride-through of a wind turbine generator. The safety pre-warning module analyzes the voltage stability index and high-low voltage ride-through events. The accident analysis module analyzes the active power recovery situation of offline events. According to the technical scheme, the automatic analysis system is used for achieving the purpose of estimating reactive power regulation operation capacity in an intelligent power grid dispatching technical support system, and an assisting tool and a convenience means are provided for power grid dispatching operation personnel to locate draught fan offline reasons rapidly.

The invention discloses an intelligent electric power parameter tester, which comprises a zero-crossing comparison circuit, a phase locking synchronous circuit, a signal conditioning circuit, an A/D conversion module, a control module, a power supply, an input module, a data display module and a USB interface module. Multiple electric power parameters are measured by adopting a DSP digital processing chip, and the intelligent electric power parameter tester has the unique advantages in aspects of improvement on measurement accuracy, real-time digital signal processing and intellectualization. In the intelligent electric power parameter tester, voltage and current at the same phase are respectively used as a real part and an imaginary part of a complex sequence to perform Fourier transform, and the intelligent electric power parameter tester has the maximal advantage that various electric power parameters (voltage effective values, current effective values, frequency, harmonic waves, power factors, active power, reactive power and the like) in a power grid can be solved simultaneously by only one-time the Fourier transform of the complex sequence, so the calculated amount is reduced, and the real-time and accuracy of measurement are improved. The intelligent electric power parameter tester can be widely applied in occasions such as electric power departments, industrial and mining enterprises and the like where the multiple parameters of an electric power system are needed to be measured automatically.

The invention discloses a triangular connection type comprehensive compensation system integrated with a cascaded active filter and a reactive compensator. The system comprises triangular connection type N-grade cascaded converters and a three-phase filter inductor connected with each N-grade cascaded converter; triangular connection type thyristor reactors and star-shaped connection type thyristors are used for switching the reactive compensator composed of fixed capacitors; and the triangular connection type N-grade cascaded converters and the reactive compensator are connected in parallel between a connection node and a ground node of an input power grid voltage and a load. According to the system provided by the invention, reactive power and harmonic current in a medium-voltage power grid are subjected to dynamic compensation and the efficiency of the power grid is improved; when the system is used for compensating, the system has no negative influences on the power grid, and has advantages of stable system, simple structure, strong stability and flexibility in compensation.

The invention relates to a non-intrusive identification method of a non-variable frequency air conditioner based on a second harmonic wave of current and reactive power. The method comprises the following steps of (1) sampling voltage and current of a main power supply incoming line of an indoor power grid to form a voltage sampling sequence and a current sampling sequence; (2) setting a time window, calculating real-time average reactive power and the second harmonic wave of the current, corresponding to the time window, of the main power supply incoming line according to the voltage sampling sequence and the current sampling sequence for forming a real-time average reactive power sequence and a second harmonic wave sequence of the current; and (3) judging whether the non-variable frequency air conditioner is started or exits or not in the indoor power grid according to the real-time average reactive power sequence and the second harmonic wave sequence of the current, and if not, returning to the step (2). Fast and accurate non-intrusive identification is carried out on starting and exiting of the non-variable frequency air conditioner on the basis of the second harmonic wave of the current and the reactive power, and the non-intrusive identification method has the advantages of being simple, economical and easy to popularize and apply.

The invention discloses an integrated controlled system and an integrated controlled method for dynamic reactive power compensation based on a touch screen, a PLC and a DSP. The system consists of an integrated control arithmetic unit, a TSC and an HVC. The control method comprises the following steps: firstly acquiring the voltage and current of a three-phase power grid and receiving related parameters from the touch screen; computing reactive capacity required by the system at the moment according to a instantaneous reactive power theory and utilizing the PLC to check a target power factor to obtain a most rational compensation loop combination plan; and finally utilizing thyristor cross-zero trigger technology to control a corresponding compensation loop for switching. The system and the method effectively solve the problems that the conventional compensation system cannot perform frequent switching and is low in response speed, low in compensation accuracy and the like, and greatly improve the stability of the system and reduce the running cost simultaneously.

A thyristor controlled LC (TCLC) compensator for compensating dynamic reactive power in a power grid system, with an advantage of mitigating harmonic current injection from solid-state switches during switching on or off is provided. Exemplarily, the TCLC compensator is shunt-connected to the three-phase power grid and comprises an electronic controller, a coupling inductor (L_c), a first branch of circuit with a parallel inductor (L_PF) and a solid-state switch, and a second branch of circuit with a parallel capacitor (C_PF), wherein the coupling inductor (L_c) is connected in series with a parallel combination of the first and second branch of circuit. The electronic controller for the TCLC compensator is configured in accordance to the generalized instantaneous reactive power theory for improving the response speed instead of using traditional average reactive power concept.

This invention discloses a SPWM inversion supply automatic master-slave parallel control method applying transient reactive power theory and parallel inversion supply output power performance, that is to control the output active power by converting frequency of its output voltage to control the output reactive power by converting its amplitude so as to uncouple the output active power P and reactive power Q to control the invented power source frequency/phase and amplitude. Although the system exists interlink signal line, the signal transferred by it is DC which can conveniently suppress interference of long distance transmission, so, the automatic master-slave control way is available in the distributed generation and UPS systems.

The invention discloses an comprehensive compensation instruction current obtaining method of an angle-shaped chain-type SVG of a power distribution network. The method comprises the following steps of detecting load currents of ila, ilb and ilc; obtaining load current fundamental active components through ip-iq conversion based on an instantaneous reactive power theory and LPF (lowpass filtering); subtracting the load current fundamental active components from the load current and negating the calculation result to obtain line current compensation instruction signal load currents ia*, ib*, ic* which contain fundamental reactive components, fundamental negative sequence components and reactive components; performing matrix transformation and LPF on the line current compensation instruction signal load currents to obtain a fundamental negative sequence active component and a fundamental negative sequence negative component; and multiplying the fundamental negative sequence active component and the fundamental negative sequence negative component with cos (omega t) and sin (omega t) respectively to obtain a zero sequence loop current instruction i0*, and combining the line current compensation instruction with the zero sequence loop current instruction to obtain an angle-shaped chain-type SVG phase current instruction iab*, ibc* and ica*. The comprehensive compensation instruction current obtaining method of the angle-shaped chain-type SVG of the power distribution networkload current instantaneous value takes load current instantaneous value to achieve simple calculation and can be effectively combined with an existing single-phase chain-type SVG control strategy to achieve an angle-shaped chain-type SVG comprehensive compensation function.

The invention provides a safety constraint economic dispatching method for embedded reactive power and voltage, and belongs to the field of electric power system safety constraint economic dispatching. According to the method, first an optimal power flow model of safety constraint economic dispatching formed by an objective function and a constraint condition is built; after the model is iteratively solved, a per unit error is checked for all branch lines; if a line exists which does not meet the per unit error, a power flow equation constraint is updated, iteration of a next time is performedtill all the lines meet the per unit error, the model converges, iteration ends, and a whole set of electric power system safety constraint economic dispatching scheme containing node voltage amplitude, a voltage phase angle, unit active power output and reactive power output is obtained. The safety constraint economic dispatching method for embedded reactive power and voltage can maximally meetelectric power system economic operation requirements, and reduce electric power system operation cost; and is high in precision, is good in convergence, and has very high practical application value.

The invention discloses an implementation method of a novel software phase-locked loop used for a signaling virtual channel (SVC) control system. The implementation method of the novel software phase-locked loop used for the SVC control system utilizes a phase-locked principle based on an instantaneous reactive power theory, achieves a software phase-locked module by coding in a digital signal processer (DSP) unit, replaces a complex integration link by a field programmable gate array (FPGA) counter, produces a phase-locked angle theta, enables the software phase-locked module to match with a phase-locked counter and achieves a phase-locked function. Under the conditions of voltage unbalance, voltage dropping and frequency discontinuity, the implementation method of the novel software phase-locked loop used for the SVC control system is still capable of rapidly and reliably achieving phase locking. A software phase-locked loop module calculates a correction angle of each phase according to a system sample and a condition of calculating delay and unbalanced three-phase voltage. The SVC control system triggers the control on the basis of each phase correction angle, reduces trigger error of a thyristor and improves system control accuracy. The implementation method of the novel software phase-locked loop used for the SVC control system is easy to achieve, is capable of being conveniently connected with other modules in the SVC control system, is simple and enables parameters to be conveniently modified and possesses good generality and expandability.

The invention relates to a detection control method of a self-adapting tuning passive power filter and provides a self-adapting tuning passive power filter, which comprises a single tuning LC passive filter and an inverter connected with the LC passive filter. The inverter is provided with a controller, and a drive unit is connected between the inverter and the controller; the voltage of the LC passive filter is detected in real time and input to a measuring unit of the controller; the measuring unit uses an instantaneous symmetrical component method and instantaneous reactive power theory to calculate tuning secondary voltage component that is then input to a compensation unit of the controller; the compensation unit uses a space vector modulation method to calculate the duty ratio required for generating compensating voltage and input the duty ratio to the drive unit; and the drive unit generates trigger pulse to control the work of the inverter to realize the self-adapting tuning, thus realizing the automatic follow-up tuning of electrical network frequency fluctuation and element parameter change. Besides, the inverter is small in volume, low in cost, adjustable in parameters and easy for being implemented industrially.

A method regulates voltages of a power distribution system that includes a substation transformer, at least one distributed energy resource (DER) for generating reactive power into the power distribution system, at least one DER controller operatively connected to the DER for controlling an amount of the generated reactive power, and a monitoring controller for monitoring a voltage violation on at least one phase of a monitored bus. The method determines an amount of reactive power required to compensate a voltage violation on the monitored bus using equivalent impedances of a path of the power distribution system between the substation transformer and the monitored bus and a shift of phase angle on the path, and transmits a request to provide the reactive power to compensate the voltage violation.

The invention provides a method for detecting harmonic current of power grid current. The method for detecting the harmonic current of the power grid current relates to a harmonic current detecting part, a harmonic current decomposing part, a harmonic current scale factor calculating part and a harmonic wave content calculating part. The method for detecting the harmonic current of the power grid current is based on the instantaneous reactive power theory and combined with Fourier transform, can rapidly and accurately calculate the harmonic current each time, the harmonic current at a certain time or certain times can be conveniently compensated according to calculated harmonic current values each time, the difficulty for implementing the method for detecting the harmonic current of the power grid current is reduced, the harmonic current can be rapidly detected, therefore, stability and reliability of an active power filter governing device are effectively improved, and then cost of the active power filter governing device is effectively lowered, market competition advantages of the active power filter governing device using the technology is beneficially improved, and power quality of a clean power grid is further beneficially improved.