37results about How to "Reduce the impact of power quality" patented technology

The invention discloses an active power filter of a 380V system, including an active filter branch 1, a current sensor CT1 connected to the three-phase current of the active filter branch 1, a current sensor CT2 connected to the three-phase current of the load, a voltage sensor PT connected to the three-phase voltage, as well as a digital signal processor 2 connected to the sasid four components; The apparatus also comprises a display and man-machine interaction control equipment communicating with the digital signal processor 2 through the system bus. The fast response characteristic and the high controllability of the invention have guaranteed the real-time of reactive power compensation; the invention raises the dynamic ability of eliminating harmonic, and reduces the adverse effect to the system electrical energy quality produced after the compensating input; and the invention also plays the role of stabilizing the voltage, compensation of the reactive power, and raising the efficiency factor.

The invention discloses an islanding detecting method which comprises the following steps: acquiring a voltage waveform of a common coupling point and measuring a frequency value, calculating the average change rate in a certain period to obtain a judging signal, comparing the judging signal with the preset change rate threshold value, outputting a control signal, selecting an outputted reference signal of an inverter by the control signal, introducing reference current after phase deviation under the condition that islanding possibly exists by a frequency change rate detection method, realizing further detection according to a sliding mode frequency deviation method, otherwise, introducing non-deviation reference current, and achieving normal operation of the system. The islanding detecting method has the advantages of reducing detection blind zones and impact on the system power quality and increasing the detection speed.

The invention discloses a microgrid non-destructive island detection method based on harmonic current injection and harmonic impedance measurement. The method comprises the steps of utilizing an FFT algorithm to real-timely measure a harmonic voltage, a harmonic current and a system frequency at a PCC, comparing the harmonic voltage and the system frequency with a preset voltage threshold value and a preset frequency threshold value in real time, and if the harmonic voltage and the system frequency exceed the threshold values, judging as an island state directly; otherwise, utilizing the harmonic voltage and the harmonic current to calculate an equivalent harmonic impedance amplitude and a phase angle, calculating a ratio of the harmonic impedance amplitude to the last harmonic impedance amplitude, judging whether the ratio of the harmonic impedance amplitude is greater than a proportionality coefficient or not, if so, judging whether the impedance phase angle is less than zero or not,and if not, judging as an island. According to the method, the amplitude change and phase change of the harmonic impedance are used as the island detection criteria, so that the island detection accuracy is improved, the island detection can be realized without needing to force the voltage and frequency to exceed the threshold values, and the island detection method is non-destructive.

The embodiment of the invention discloses a new energy storage system scheduling optimization method considering demand response resources, and the method comprises the steps: training an intelligentload neural network model, so as to obtain a function of controllable active power of a residence with respect to a demand response control signal; based on the function of the controllable active power, optimizing by utilizing a new energy storage scheduling optimization model to obtain a demand response control signal; calculating controllable active power by utilizing a function of the controllable active power at least based on the demand response control signal; and obtaining a scheduling strategy of the new energy storage system by utilizing the new energy storage scheduling optimizationmodel at least based on the controllable active power.

The present invention discloses an optimization planning method of a power distribution network comprising new energy power generation systems and special load. Models are established for new energy power generation systems and a special load, and a photovoltaic charging station employs a direct current charging mode. A power distribution network comprising a single new energy power generation system or the special load is subjected to modeling analysis, and access points having the least influence on the electric energy quality of the power distribution network are taken as subsystem optimal arrangement points. A power distribution network comprising a plurality of new energy power generation systems or the special load is subjected to modeling analysis, and subsystems capable of offsetting electric energy quality influence are intensively arranged; each subsystem is ranked according to the influence on the electric energy quality, and each subsystem is arranged according to the arrangement rule of the power distribution network comprising the single new energy power generation system or the special load. The optimization planning method of a power distribution network comprising the new energy power generation systems and the special load have features such as initiative, integrity and the like on the electric energy quality of the power distribution network comprising the new energy power generation systems and the special load, and can be used for planning and management of the power distribution network comprising the new energy power generation systems and the special load.

The invention provides an FIR band-pass filter and parameter adaptive AFDPF combined island detection method, and belongs to the field of anti-island protection of distributed power grid-connected systems. By real-time sampling and analysis of common coupling point voltage, an FIR band-pass filter is used for extracting island features as a pre-judgment condition for island generation, which avoids harmonic pollution caused by introduction of disturbance by an active frequency shift algorithm with positive feedback during normal grid connection. In order to solve the problem that an FIR band-pass filter extraction feature analysis method is easy to misjudge the non-island disturbance, through combination with power grid synchronization features of an AFDDP algorithm, the AFDDP algorithm isstarted after the FIR band-pass filter extracts the features to predict the island generation, AFDDP algorithm positive feedback coefficients are set to achieve the purpose of eliminating detection dead zones according to the frequency and loading condition adaptive adjustment, and finally the PCC point voltage frequency triggers over-frequency protection under the action of APFPF disturbance toachieve island detection.

The invention discloses a current-voltage compensation system combining a compensation transformer and an energy storage module, and the system comprises a multi-tap compensation transformer module which is used for taking power from a power grid and then compensating the voltage of a power supply line so as to enable the voltage of the tail end of the line to meet the standard; an energy storagemodule which is connected with a three-phase line and a neutral line of a power supply line and is used for realizing peak-valley load adjustment; and a control module which is connected with the multi-tap compensation transformer module and the energy storage module and is used for detecting voltage and current information of the power supply line, generating a control instruction and controllingthe multi-tap compensation transformer module and the energy storage module according to the control instruction. The independent adjustment of the three-phase voltage can be realized, the adjustmentis bidirectional, the compensation transformer can be supported to work normally at the peak of power utilization through the peak regulation effect of the energy storage module, and the applicability is higher.

The invention discloses a household energy management optimization method based on a renewable energy sharing model. The method comprises the steps that: uniformly dividing one-day time into 48 time periods, and obtaining a scheduling space; dividing intelligent electric appliances into rigid electric appliances and flexible electric appliances according to the working modes of the intelligent electric appliances expected by a user, and setting the day-ahead working data of the flexible electric appliances, including the start-stop time of each flexible electric appliance and the time requiredfor completing the work; enabling an operator to acquire the working data of the electric appliances of the user through an intelligent electric meter and calculate the total power of electricity utilization of the user; predicting a day-ahead photovoltaic power generation amount by using an Ostwald physical prediction strategy, and obtaining a real-time electricity price and a peak power limit published by a power grid to generate an optimal scheduling model; and optimizing and solving the optimal scheduling model by utilizing an improved binary particle swarm algorithm to obtain an optimalhousehold energy management solution. According to the improved binary particle swarm algorithm, the next generation of particles are directly updated by adopting a dynamic probability method on the basis of integrating individual and global optimal particle positions, so that the algorithm convergence speed is higher, and the optimization effect is better.

The present invention relates to an islanding detection method, device and system based on hybrid power feedback disturbance, including real-time acquisition of local load consumption power, power grid transmission power and distributed power output power, and judging whether the operating state of the microgrid falls into overvoltage and undervoltage and The detection blind area of ​​the over-under-frequency detection method, if not, use the over-under-voltage and over-under-frequency detection method to perform island detection on the microgrid; if so, determine the dominant feedback disturbance and calculate the active voltage feedback coefficient and reactive frequency feedback coefficient; Simultaneously inject active voltage feedback disturbance and reactive frequency feedback disturbance into the microgrid; first judge whether islanding occurs according to the grid-connected point voltage within the first preset time or the grid-connected point frequency within the second preset time, and if so, calculate the grid equivalent Resistance and judge whether real islanding occurs again according to the grid equivalent resistance. The invention is based on the mixed power feedback disturbance, has a small detection blind area, and realizes higher reliability, accuracy and adaptability.

The invention relates to a wind farm anti-islanding identification method and system based on a harmonic impedance matrix. By collecting the voltage and current of the grid-connected point of the wind farm, analyzing the magnitude of each harmonic impedance, calculating the harmonic impedance matrix modulus, and judging wind power Whether there is an island in the wind farm, so as to realize the island protection of the wind farm. Islanding is identified by using the change of circuit impedance at the grid-connected point before and after the grid is disconnected. Under grid-connected conditions, the system impedance is equivalent to the parallel connection of wind farm impedance and grid impedance. Since the main grid is close to an ideal voltage source, the system impedance is very small. After the island occurs, the main grid circuit is disconnected, and the system impedance is equal to the power station system impedance, and its value is generally much greater than the impedance when connected to the grid, so that the island state can be identified.

The invention discloses a hybrid island detection method based on the combination of wavelet neural network and SMS. The technical scheme of the method is: in the first stage, a voltage signal is obtained by detecting the voltage signal on the common coupling point in a period and performing wavelet transformation. The average value of the absolute value of the wavelet coefficients in the period is used as the input signal of the BP neural network, and finally the BP neural network is used for pattern recognition; the second stage introduces the phase disturbance in the SMS algorithm, so that whether the frequency of the common coupling point voltage exceeds Threshold, and through frequency detection to determine whether the islanding phenomenon really occurs, so as to take corresponding islanding protection measures when the grid-connected power generation system is in the islanding state. The invention greatly improves the reliability of the isolated island detection, and greatly reduces the influence of the detection method on the power quality of the system under the premise of ensuring the identification rate of the isolated island.

The invention relates to an alternating current and direct current hybrid power supply system and method. The system comprises current transformers C1, C2, C3, C4 and C5, diodes D1, D2 and D3, intelligent control switches S1, S2 and S3 and a direct current bus. A principle of prioritizing usage of a local DG is adopted, and a self-adaptive power control strategy based on direct current bus voltage signals is employed; the intelligent control switches S1, S2 and S3 for a three-phase alternating current power grid, the local DG and a local energy storage component are automatically controlled according to a state of the direct current bus voltage signals; supply and demand power balance between the three-phase alternating current power grid, the local DG as well as the local energy storage component and electricity consumption of loads can be effectively regulated and controlled. The method is well compatible with traditional alternating current systems; problems of alternating current stability, voltage and frequency synchronization, reactive power and the like caused by the local DG being connected to a power grid in an alternating current form can be prevented; continuous and high-reliability power supply for local loads can be realized; influence exerted on user side electric energy quality can be reduced, local DG energy utilization efficiency can be improved, and an environment friendliness property is fulfilled.

The invention relates to a self-adaptation positive sequence current quick break protection method for a distribution network containing inverter-based distributed generations (IBDGs), in particular to an island detection method suitable for a micro-grid including multiple inverter-based distributed generations (IBDGs). The island detection method includes the steps that segmented reactive power perturbations, frequency boundary values of the segmented reactive power perturbations and starting criteria used when the segmented reactive power perturbations are switched are set in an initialized mode, wherein the starting criteria comprise the first starting criterion which is set according to the situation that the first segment reactive power perturbations of the different IBDGs are synchronous, the second starting criterion which is set according to the situation that the first segment reactive power perturbations of the different IBDGs are not synchronous, but overlapping exists and the starting criterion which is set according to the situation that the first segment reactive power perturbations of the different IBDGs are not synchronous, and overlapping does not exist; whether system frequency meets the three starting criteria or not is detected, and the reactive power perturbations are exerted according to a detection result; whether the criteria for determining an island are met is detected. Reactive power perturbations when a system operates normally in a grid-connected mode are reduced.

The invention discloses a multi-target planning method for power grids of wind farms based on improved NSGA-II. The multi-target planning method includes the steps of building an output force model of the wind farms, calculating the flicker value of a wind turbine generator system at a common connection point, creating a target function with shortest line length and minimal flicker value of a wind farm at a common access point, and realizing multi-target planning of the power grid of the wind farm based on NSGA-II algorithm of NDX operators, the output force model and the target function. The multi-target planning method overcome the defects of subjectivity of conventional multi-target optimization and obtaining one solution in one time, enhances overall searching capability than routine NSGA-II algorithm, and improves convergence.

The invention discloses an islanding detecting method which comprises the following steps: acquiring a voltage waveform of a common coupling point and measuring a frequency value, calculating the average change rate in a certain period to obtain a judging signal, comparing the judging signal with the preset change rate threshold value, outputting a control signal, selecting an outputted reference signal of an inverter by the control signal, introducing reference current after phase deviation under the condition that islanding possibly exists by a frequency change rate detection method, realizing further detection according to a sliding mode frequency deviation method, otherwise, introducing non-deviation reference current, and achieving normal operation of the system. The islanding detecting method has the advantages of reducing detection blind zones and impact on the system power quality and increasing the detection speed.

The invention discloses an energy storage converter with an automatically adjustable switching frequency. A DC buffer circuit is arranged at a DC side, thereby guaranteeing the use stability of a battery; an EMI filter is arranged at an AC side, so the electric energy quality of alternating-current output is improved; the switching frequency of an IGBT in the converter is adjusted by monitoring the electric energy quality of a power grid side in real time, thereby reducing the working loss of equipment, and achieving the purposes of reducing the electric energy consumption of the equipment andprolonging the service life of the equipment.

The invention discloses an electric power supply inserting-connecting apparatus. The electric power supply inserting-connecting apparatus comprises a plug and a socket; the plug comprises a plug hand-held part, an inserting sheet box, a wedge-shaped block and inserting sheets; the inserting sheet box is fixedly mounted at the lower end of the plug hand-held part; an inserting sheet cavity is formed in the inserting sheet box; the inner top end of the inserting sheet cavity is elastically connected with the wedge-shaped block; the two ends of the wedge-shaped block are glidingly clamped with two inserting sheets through a key slot structure; the two inserting sheets run through the two ends of the inserting sheet box respectively; the inserting sheet box movably runs through a through holein the top end of the socket; a contact piece groove is formed in the socket at the lower end of the through hole; and contact pieces are fixed at the two ends of the contact piece groove. Through limiting rods, up and down movement of positioning blocks can be controlled; the limiting rods perform downward thrust on the positioning blocks under the effect of a torsional spring, wherein the thrustis greater than sum of elastic force provided by a spring and a compression spring, so that the positioning blocks can be tightly extruded and pressed at the top end of the socket, and sliding of theplug can be avoided; and therefore, only when the symmetrical limiting rods are pressed downwards, the plug can be inserted into the socket, so that a certain protection effect is achieved.