| Solar energy and wind energy are affected by environmental factors,which have intermittent and unstable characteristics,making it difficult to predict power generation.When such new energy is incorporated into the traditional power grid in large quantities,the uncertainty of output power will affect the power quality of the system,such as harmonics,voltage fluctuations,flickers,and even lead to the collapse of the whole system.Electric Spring(ES)is a new type of power compensation device proposed for such kind of problem.It changes the operation mode of the traditional power system in which the power generation is determined by the power consumption,realizes the new operation mode of automatic matching between power generation and power consumption,and effectively solves the impact of power fluctuation on the system when photovoltaic and wind energy are connected to the grid in a large scale.Taking single phase ACES as the research object,the typical problems of the application of ES in the new energy power generation system is studied.It covers operation principle,mathematic model,control strategy and software and hardware platform.The main work of this paper is as follows:(1)The background and significance of the topic are briefly described,and the research status at home and abroad is described in detail from three aspects of topology,control methods and other related research.(2)A power control method based on feedforward decoupling is proposed,and the mathematical model of single-phase ES in different coordinate systems is established.Aiming at the particularity of ES structure,the filter capacitor voltage inner loop is introduced into the traditional power decoupling control to achieve the purpose of decoupling PCC input active and reactive power.At the same time,the design methods of controller parameters are described in detail.Finally,the accuracy of the proposed algorithm is verified by simulations on MATLAB/Simulink platform and TMS320F28335 DSP experimental platform.(3)A compound control method based on repetitive control and state feedback is proposed.The repetitive controller is used to improve the steady-state performance of the state feedback system and the state feedback is used to improve the dynamic performance of the repetitive controller.The mathematic model of ES in discrete domain is given,and the design method of parameters in compound control algorithm based on repetitive control and pole control is described in detail.Finally,the accuracy of the algorithm is verified by MATLAB/Simulink simulation platform and TMS320F28335 DSP experimental platform.(4)A coordinated control strategy of multiple ESs is proposed,and the disadvantages of multiple ESs running independently are analyzed.Power decoupling control algorithm is improved for islanding operation of microgrid,which increases voltage and frequency regulation.Dropping control is introduced to dynamically modify the reference voltage of each ES to achieve coordinated operation of multiple ESs.Finally,the accuracy of the algorithm is verified by MATLAB/Simulink simulation platform.(5)An experimental platform of ES based on TMS320F28335 DSP with 110 V voltage rating is built in lab,which includes a single-phase PWM rectifier,a single-phase AC ES and a power grid simulator.In order to realize the bi-directional operation of ES,a PWM rectifier based on PI plus PR controller is used as the bi-directional DC power supply of ES.In order to verify the control performance of the proposed composite controller based on repetitive control and state feedback in the case of distorted grid,a power grid distortion simulator is built to simulate the abrupt amplitude change and a large number of harmonics of grid.Finally,the performance test of each module is completed in the laboratory. |
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