Study On The Power Decoupling Control Strategy Of Synchronverter

With the continuous depletion of traditional fossil energy,it has promoted the vigorous development of renewable energy.By simulating the internal mechanism and external characteristics of the synchronous generator,the synchronverter can realize friendly grid-connected distributed energy and improve the reliability and stability of distributed energy access to the microgrid.In the microgrid,when the power angle is small,the active power and reactive power output from the synchronverter are approximately decoupled,but in reality,this situation cannot be satisfied at all times.When the power angle is large,the active power and reactive power output from the synchronverter has a strong coupling relationship,so that the active and reactive power cannot be individually adjusted.At the same time,due to the resistive nature of the lines in the microgrid,there will be strong coupling between the active and reactive power output from the synchronous inverter,which will easily generate power oscillations and affect the practical application of the synchronverter in the microgrid..This paper proposes a decoupling control strategy for output power of synchronverters for the power coupling problem of synchronverters in microgrids.The specific work of the study is as follows:(1)The principle and process of synchronverter synchronous generator simulation are analyzed,and the mathematical model of active and reactive power output from synchronverter is established.The mechanism of power coupling of synchronverter is analyzed.Based on the simulation platform of Matlab,a simulation model of grid-connected synchronverters was built.Under different operating conditions,the active power,reactive power,output voltage amplitude and frequency waveform of the synchronverter were obtained,verifying that the synchronverter was built.The correctness of the module and the coupling of the active and reactive power output from the synchronous inverter.(2)When the power angle is large,the coupling problem of the active and reactive power output of the synchronverter is analyzed.The small signals of the active and reactive power are analyzed and the corresponding coupling quantities are separated.The coupling states of P-V and Q-? are corresponding to each other.A decoupling control strategy based on current feedback is proposed.By adding a feedback current loop,the dynamic current needed to eliminate the power coupling amount is compensated to reduce the output power oscillation of the synchronverter.By building a simulation model,the effectiveness of the method is verified.(3)Analyze the decoupling control strategy of synchronverter current feedback and establish a dynamic small signal model for the output power of synchronverter.According to the transfer function of active power-power angle and reactive power-voltage amplitude,the original system and current feedback The decoupled control system performs the stability analysis and compares the Bode diagrams of the two systems.It can be known that adding the decoupling control can make the system more stable.(4)For the incorporation of a synchronverter into a microgrid with distributed power supply,due to the resistive characteristics of the circuit,the traditional virtual impedance method is used for decoupling.When the virtual impedance is selected,the actual output voltage amplitude of the DG is relatively high.For the problem of large deviation,an improved decoupling control strategy for synchroverter based on virtual impedance is proposed.The virtual impedance loop is added to realize the power decoupling control,and considering that the virtual impedance is large,the command voltage rating needs to be adjusted accordingly,and a method for adjusting the command voltage rating is established.Finally,the simulation model is built to verify the superiority and feasibility of the method.