Study On Medium Voltage MW-Scale Cascaded H-bridge Battery Storage System Based On VSG

The current electrical grid wastes large quantities of electricity,so it is inefficient because of the separation between the amount of energy produced from the generation sources and the number of energy consumers needed.Natural power generators such as wind turbines and photovoltaic cells are the most effective technologies to solve energy problems.Natural energy generators rely on renewable energy resources,which depend on the weather conditions and the natural environment,which causes deterioration in the quality of energy and the instability of the electrical grid because of the fluctuation of their output,which results in a negative impact on the grid voltage and frequency stabilization.Through the utilization of energy storage within the grid,many of these shortcomings can be removed.The battery energy storage system(BESS)is an important technology option to enhance grid connections to a large renewable source of energy and to incorporate a large proportion of renewable energy into large power grids.BESS is being considered as a countermeasure to offset energy fluctuations.With industrial progress and development in recent years,electrical applications have been urgently needed with a higher level of medium voltage and high energy.As a result,the control strategy of the battery storage system based on the topology of a cascaded H-bridge multilevel inverter has been widely sought since its launch.This type of multilevel inverter is one of the topologies suitable for modern battery storage systems.The virtual synchronous generator(VSG)control concept is discussed in this dissertation,which is a recently developed control strategy based on mimicking the swing equation of synchronous generators for familiar integration of distributed generations(DGs).The main contributions of this dissertation are summarized as follows:(1)Makes power electronics multilevel inverters to achievement the static and dynamic performance of conventional synchronous generators which are needed in future.(2)Aiming at achieving stable operation VSGs,this dissertation proposed the design criteria for the characteristic parameters of VSGs(inertia,damping factor,and droop coefficients).Different rotating inertia and damping factor set values shows the system frequency response.The system was subjected to increase in the active and reactive load power in different steps change.(3)The study discussed the operational performance of BESS.One of the effective tools to solve the grid-connection problem of renewable energy has been studied from the aspects of modeling,analyzing and control.The balancing control of the state of charge(SOC)is proposed to achieve output power balancing.The improved control approach,simply base on proportional-resonant(PR)regulator and decoupled current control,achieves an efficient performance.The effectiveness of the method is verified by MATLAB/SIMULINK.(4)The work described a control strategy of BESS,with focus on cell and phase balancing control.Then,the control model is used to study balancing for three phase output power and energy.