Research On Control Strategy Of Virtual Synchronous Generator Based On LADRC

Due to the limitation of traditional energy storage capacity and the impact on environmental pollution,people are paying more and more attention to distributed generation(DG).Distributed energy can affect the stability of the entire system.Virtual Synchronous Generators(VSG)make high-power electronics elements simulate external output characteristics that have the inertia and damping of synchronous generators by control algorithms.Firstly,the mathematical model of the traditional synchronous generator and the active frequency and reactive voltage regulation characteristics are analyzed.The mathematical model of the three-phase inverter controlled by the virtual synchronous generator is established,and the working principle of the model is analyzed.The principle of value selection,the tuning method and the design of the original parameters of the main circuit filter are given.Secondly,the Linear Active Disturbance Rejection Control(LADRC)is introduced into the VSG,which is applied in two aspects of VSG control.First,it is applied to the rotor equation in the VSG active frequency modulation characteristic,which is used to deal with system frequency fluctuation caused by load imbalance caused by distributed switching in the independent microgrid.A LADRC model with simulated generator secondary frequency modulation to reduce frequency variation is established.According to the frequency fluctuation,the VSG output is changed by the linear auto disturbance rejection control,thereby changing the VSG output power given value to reduce the frequency fluctuation.Second,during the grid voltage imbalance,the VSG output current is not sinusoidal.An improved balanced current method for VSG control is designed,which uses LADRC in the current loop to make the VSG output current approximately sinusoidal and better to traverse faults.Finally,the above control strategy is simulated in the MATLAB/Simulinkenvironment.It is verified that the proposed control strategy makes the VSG have better performance in improving the grid frequency regulation under island conditions and in the case of crossing unbalanced voltage faults under grid-connected conditions.