Research On Control Strategy Of Cascaded H-bridge Energy Storage Power Conversion System

The volatility and intermittence of renewable energy power generation presents a huge challenge to the stable operation of the power system.The Power Conversion System(PCS)is required to provide spare capacity to achieve dynamic supply and demand balance.Cascade H-bridge energy storage power conversion system is used in high-voltage large-capacity system in the main topology,with different energy storage media combined in large-capacity energy storage occasions have a wide application space.In this paper,the cascade H-bridge energy storage power conversion system as the research object,its control strategy in-depth study,and the experimental device hardware and software design.In this paper,the cascaded H-bridge converter single-phase equivalent circuit as an example to analyze the cascade H bridge PCS works.The mathematic model of the cascaded H-bridge PCS is the basis of the control strategy design.The mathematical model of the abc,?? and dq coordinate systems is established,and the expression under the complex frequency domain is given.In this paper,the horizontal carrier phase shift modulation strategy is used to describe the modulation law in detail,and the output voltage of the cascaded H-bridge single-phase AC side is analyzed concretely.This paper focuses on the storage control strategy of the cascade H-bridge of the storage medium,and gives a brief overview of the PCS control strategy of cascade H-bridge with super storage capacity.Based on the mathematical model of the cascaded H-bridge PCS,the active power of the system is controlled by the current feedforward decoupling control strategy based on the PI regulator to realize the charge and discharge of the battery pack.The phase-to-phase SOC equalization is realized by zero-sequence voltage injection method,and SOC equalization is realized by fundamental voltage injection method.In this paper,we analyze the reason why the two methods can achieve equilibrium,and give the form of zero sequence voltage and fundamental voltage.The fault-tolerant control can ensure that the system can run reliably under the fault condition.This paper analyzes the output voltage symmetry and the non-faulty unit SOC balance from the fault condition,and briefly introduces the fault-tolerant control strategy.Based on the design principle of the industrial platform,a lOkW small experimental prototype is built,and the design of the driving plate circuit is completed.The function of driving the power device and sampling the voltage of the DC side of each power unit is realized.Completed the design of the voltage sampling board circuit,to achieve the AD7656 timing control,battery voltage and drive signal codec function.The hardware design of the main control board and the bottom board circuit is completed.The function of SOC acquisition,control algorithm and modulation strategy is realized by dual "DSP + FPGA" architecture.Finally,the effectiveness of the control strategy is verified by MATLAB simulation.