Research On VSG Control Method For Frequency Stability Improvement Of Microgrid

When virtual synchronous generator technology is used to improve the phenomenon of inertia loss caused by high proportion distributed power consumption,it is easily affected by line parameter perturbation,long frequency transient oscillation period and low precision of phase-locked loop,which will decrease the output performance of inverter and even cause system stability collapse.Aiming at the above problems,this paper makes some improvements to the virtual synchronous generator technology.The main innovations and work are as follows:In order to solve the problem that the perturbation of circuit filter parameters may affect the output performance of virtual synchronous generator due to the change of external environment in actual operation,the influence degree of the perturbation of circuit filter parameters on the output performance is analyzed quantitatively.Virtual synchronous generator controlled frequency modulation not only provides inertia and damping,but also brings a long time of frequency transient adjustment.Control strategy based on the analysis of the present several virtual synchronous generator,for its share of a time period of oscillation frequency transient process,and there are multiple disturbance to the limit of the frequency problem,put forward the adaptive frequency control strategy based on negative moment of inertia,flexible features using virtual synchronous generator parameters,real-time adjust the moment of inertia,not only eliminates the time period of oscillation,Moreover,the effect of damping coefficient is weakened and the complexity of parameter design is reduced.The proposed strategy is verified by simulation from the perspective of stability.When a microgrid is faced with a disturbance condition,it uses a virtual synchronous generator to modulate frequency,which requires more stringent real-time frequency information collection than a large grid.Simulation comparison indicates that the traditional phase-locked loop is difficult to meet the requirements on both phase-locked accuracy and dynamic response performance.A frequency acquisition method based on dual Fourier transform is designed.By using the improved sliding window Fourier transform as the PLL phase discriminator for wave power grid information,keep the advantage of Fourier transform,reduce bring spectrum leakage due to the sampling period is not synchronized,so that they can quickly and accurately to provide real-time virtual synchronous generator power grid frequency,the simulation verified the help of virtual synchronous generator frequency modulation performance improvement.Finally,the virtual synchronous generator frequency modulation method is verified by experiments on the semi-physical experiment platform.The paper has 78 figures,10 tables,and 93 references.