Research On Detection And Control Technology Of Unified Power Quality Conditioner With Micro-grid

Developing new energies is an important way to solve the contradiction between energy and environment.As a large number of new energies such as solar energy,wind energy and biomass energy are connected to the distribution network,they are bound to affect the voltage and frequency of the distribution network.New energies like photovoltaic,wind power generation have the features of intermittent,volatility which cause instability to the grid voltage.What's more,many of new energy power electronic transformation equipment connected to the distribution network,and a variety of nonlinear and impact loads,both of them bring serious voltage and current distortion to the distribution network.A mass of harmonic current deteriorates the normal operation of normal electrical equipment,especially precision equipment.At present,most of the power improvement equipment can match the requirements when the distribution network is relatively stable.However,it appears challenge to the existing power quality detection and control technology with the power quality problem brought by new energies accessed to the distribution network.With the support of the national natural fund project “Power quality analysis and control method research in the distribution system with micro-grid”(51477070),the unified power quality conditioner(UPQC)considering micro-grid is taken as the research object.According to its topology and function,the contents that include voltage detection and controlin series active power filter,harmonic detection and control method in parallel active power filter,new topology voltage control in the DC side,and the reactive power coordinated control between the series and parallel filters are studied.The research achievements are as follows:(1)The micro-grid likely causes the voltage drop of the grid at point of common coupling because it is influenced by natural conditions like light,temperature.In view of the problem that the traditional PI controller can't conduct better dynamic performance and accuracy of voltage detection in the UPQC,the decoupling control is presented at the cross coupling between dq axis of the UPQC,and it improves the control performance.Furtherly,the voltage drop detection algorithm that chaos immune genetic algorithm is combined with PI control is proposed.Due to the randomicity,ergodicity and regularity of chaotic variables,the chaos immune genetic algorithm combined the immune genetic algorithm is used to optimize the controller parameters.The dynamic response performance and robust performance of control system are further improved,which meet the requirements of voltage detection accuracy and compensation performance of the UPQC.Simulation results show that the proposed method is effective and feasible.(2)Compared to the normal power system,the distribution system with micro-grid is more difficult to detect and compensate harmonic because of the affections caused by the factors such as randomicity,stability.This paper proposes a harmonic current detection method based on the ultra-short feedback controller.According to human hormones regulating feedback mechanism,the ultrashort feedback controller based on feedback mechanism endocrine hormone is formed.It is performed to detect harmonic current of distribution network containing micro-grid.It solves the power problems caused by the micro-grid fluctuations and load parameters variations in the distribution network,and improves the anti-interference performance of the UPQC harmonic detection.As for the traditional hysteresis control method,the compensation current signal is fixed when tracking the error signal.In order to overcome this shortcoming,the control strategy with variable loop width hysteresis is proposed to compensate harmonic,which makes sure that the compensation current signal accurately track the change of the instruction current signal in real-time.Then it enhances the dynamic performance of the UPQC harmonic compensation and control precision.The simulations verify the effectiveness of the harmonic detection method and the proposed control strategy.(3)The energy coupling between the series and parallel filters of the UPQC reduces the stability of the DC bus voltage.In order to keep the voltage stability,the new topology is constructed by integrating PV module in the DC side,and it increases its versatility in the same time.Since photovoltaic power generation is easy to cause instability of bus voltage,the control strategy combined chaotic particle swarm optimization algorithm based on multi-agent voltage is put forward.The intelligent of agent is applied into search of particle swarm,which enhances internal information diversity and transitivity of the particle swarm optimization.These characteristics combine the optimization ability in whole solution space about chaotic local search algorithm,and improve the optimization velocity of particle swarm.So the parameters of PI controller can be optimized dynamically on-line,which improves the robustness,rapidity and dynamic of voltage control.The defects that large parameters fluctuation and disturbance of the DC voltage exists in new topology is desolved.Simulations verify the feasibility of the proposed bus voltage control strategy in the DC side and the compensation effect of the UPQC.(4)Due to the independent functions and low utilization ratio between parallel active power filter(PAPF)and series active power filter(SAPF)in the normal operation of the UPQC,the control strategy that the voltage vector is perpendicular to the current vector to output reactive power by SAPF is put forward.The control strategy is proposed to the dynamic cooperative task solving mechanism based on multi-agent system(MAS)of UPQC coordinated control.The dynamic collaboration task based on MAS solving organization model is given,and the complex task decomposition principle of UPQC is designed.The reactive power compensation implementation mechanism based on dynamic collaboration tasks solving is presented.Especially when no voltage distortion is in the series side,the SAPF is used for reactive power compensation coorperatively,the PAFP is used for harmonic compensation.The efficiency of comprehensive compensation is improved by the UPQC coordinated control.The simulations verify the feasibility of the reactive power coordinate control strategy in the UPQC.(5)The overall experiment platform of the UPQC including micro-grid is built,and the software and hardware of the UPQC are designed.Then the experimental prototype is developed.The proposed voltage sag detection method,harmonic detection and control strategy of the UPQC are experimentally studied.The experiments verify the feasibility of the detection and control strategy of the UPQC.