| With the shortage of energy and the increasing prominence of environmental problems,distributed generation and energy storage technology have been developed rapidly.At present,distributed power and energy storage units usually form a microgrid first,and then merge into the grid through the microgrid.In order to improve the power utilization rate better,on the basis of the microgrid,the active distribution network is proposed.The active distribution network adopts the mode of actively managing distributed power,energy storage equipment and customer bidirectional load.The topology structure is flexible and the power supply utilization rate is high.However,compared with the traditional distribution network,there are a large number of power electronic devices in the active distribution network,lacking damping and inertia,and the system is prone to unstable operation.The energy storage converter using the Virtual Synchronous Generator(VSG)control strategy increases the inertia of the system by simulating the characteristics of the synchronous generator,which is of great significance for the stable and reliable operation of the active distribution network.In this paper,the control strategy of energy storage converter based on VSG algorithm is studied,which mainly aims at the problems of power configuration,harmonic suppression and smooth impact of active distribution network under the condition of grid-connected.While solving the above problems,the energy storage converter can still maintain its own good inertia and damping characteristics.On the other hand,considering the abnormality of the grid voltage,the influence of the grid voltage anomaly on the grid-connected current of the energy storage converter based on the VSG algorithm is reduced,and the grid-connected current quality of the energy storage converter is guaranteed to be good.Firstly,the control principle of current-mode VSG is expounded.The structure of power loop and frequency modulation and voltage regulation characteristics in VSG algorithm are analyzed.And the influence of the main parameters of power ring of VSG algorithm on the system is studied.Then the working principle of proportional integral(PI)controller,proportional resonance(PR)controller and quasi-proportional resonance(QPR)controller is analyzed.The working characteristics of different controllers are analyzed and the QPR controller is selected as the current inner loop controller of the energy storage converter in this paper.Secondly,according to the different load conditions in the active distribution network,this paper focuses on the reactive power compensation strategy based on the VSG algorithm,discusses in detail the calculation method of the instantaneous reactive energy of the load,gives the way of reactive power compensation,and verifies the feasibility of the VSG power storage converter for reactive power compensation under different loads through simulation.Based on the harmonic suppression strategy of the non-linear load by the energy storage converter of VSG algorithm,the simulation results of harmonic suppression are given.In addition,the method of smoothing motor grid-connected current based on VSG algorithm is proposed in this paper,and the VSG can maintain the original inertia and damping characteristics.And the relevant simulation verification is given.Aiming at the grid-connected current anomaly of energy storage converter based on VSG algorithm when the grid is abnormal,the control strategy based on VSG algorithm is proposed.Firstly,it analyzes the influence and cause of the grid voltage containing harmonics and the grid three-phase voltage imbalance on the VSG grid-connected current quality.Secondly,the control strategy for improving the grid-connected current quality is proposed.When the voltage contains harmonics,the current feedforward compensation control is carried out.When the voltage is unbalanced,the positive and negative sequence separation and the negative sequence current control are performed to solve the negative impact of voltage abnormality.Finally,the correctness and validity of the proposed control strategy are verified by simulation.Finally,in this paper,the smooth control and reactive power compensation of motor grid-connected current based on VSG energy storage converter are verified experimentally on 30kW experimental platform,and the results show that the method used in this paper is effective. |
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