Research On Microgrid Inverter Based On Virtual Synchronous Generator

In recent years,various distributed power generation methods using clean energy have risen rapidly under the pressure of energy shortage and environmental degradation.As a micro-grid technology to solve the distributed power generation access to the large power grid,the key equipment is the inverter that realizes the energy conversion between the distributed power supply and the large power grid.Because the traditional inverter cannot meet the inherent rotational inertia and frequency and voltage regulation capabilities required by the power system,the virtual synchronous generator(VSG)technology uses a control algorithm to make the inverter simulate the rotor motion equation of the synchronous generator and The electromagnetic transient equation makes it have the characteristics of voltage and frequency regulation of the synchronous generator,provides inertial support to the system,and solves the problems of small inertia and small damping of the distributed power supply.At the same time,the VSG has flexible inverter control and fast response The advantages of fully ensure that the frequency of the distributed power supply will not change suddenly,and the output is more stable.VSG technology has become one of the control strategies with good control effect and wider and wider range of application in distributed generation technology.This article first describes the research status of microgrid and virtual synchronous generator technology,and points out the problems and challenges faced by microgrid,and comprehensively introduces the common control strategies of microgrid inverters and existing domestic and foreign Classic model of virtual synchronous generator.The research status of resonance problems of traditional grid-connected inverters and virtual synchronous generators is summarized.Then,based on the traditional grid-connected model of the inverter and the second-order mathematical model of the synchronous generator,the overall structure of the virtual synchronous generator is established,and the specific implementation method of the virtual synchronous generator control is designed.Then,by decomposing the control variables of VSG,the instantaneous power of the system is obtained,and a small signal model of active power and reactive power is established.The law between the resonance peak and the virtual moment of inertia when a single virtual synchronous generator resonates is analyzed.The simulation verifies the correctness of the derivation.The design and verification of the control strategy can not only simulate the external characteristics of the synchronous motor,but also stabilize the output.Resonance suppression can also be achieved by changing the parameters of the control loop.Next,the Norton equivalent model is used to establish the equivalent output impedance model of two inverters in parallel.The resonance function of the parallel system is analyzed by the transfer function of the current-voltage relationship and its corresponding bode diagram,and it is proposed to increase the virtual rotational inertia and The virtual resonance suppression method of virtual synchronous generators with series virtual impedances is verified by matlab simulation.Finally,build a virtual synchronous generator experiment platform,design experiment circuits and write software programs,and verify the feasibility and effectiveness of the designed experiment platform and control strategy through laboratory low-voltage environment experiments.