Control Strategy Research Of Cascade SVG Used In Electrified Railway

In this article, the application background of this research topic is electrified railway reactive governance, it gives detailed design principles of SVG cascaded by the single-phase H-bridge unit and its industrial implementation, which has important application value. In this article,it Carries out a detailed analysis of the single-phase H-bridge cascade topology, covering the transfer analysis based on quasi-PR regulator inner current loop state, the unit suspended capacitor voltage balance control method, a cascade SVG overall control strategy, as well as industrial prototype control-platform design.First, it analyses carrier phase shift PWM modulation strategy used in H-bridge cascaded topology, quantitatively calculates output voltage harmonics of the natural sampling carrier phase shift PWM modulation.Because of the system delay caused by Traditional single-phase PLL algorithm using low-pass filter, a new single-phase PLL algorithm based on output feedback is gived. This algorithm uses the angle output of the PLL to construct a two-octave component in order to offset middle part of the two frequency components and achieve the purpose of eliminating the delay of the low-pass filter. Low Voltage Ride Through experiments and Grid voltage flicker experiment prove the stability and faster speed response of this single-phase PLL algorithm.It constructs state space mathematical model of H-bridge unit based on the quasi-PR regulator inner current loop, and analyzes the impact of the quasi-PR regulator with parameter changes to the state of the entire inner current loop status,the state transition of the quasi-PR regulator, the steady-state error and stability of the system. It provides a strong reference to the Parameter s selection of the quasi-PR regulator.It analyzes charging and discharging rules of the bus capacitor with Single H-bridge running at the rectifier conditions and reactive conditions, and analyzes the differents of charging and discharging rules of the bus capacitor between the rectifier conditions and reactive conditions, thus it proposed a suspended capacitor voltage balance control algorithms of single-phase cascade SVG unit based on the flying capacitor charging and discharging rules. Simulation and experimental results verify the feasibility of the algorithm. It designs the hardware and software control platform, which could be used in single-phase cascaded SVG. Detailed analysis of the system hardware design is given, it covers the designs of FPGA system and power unit sampling system. It also analyzes software design methods for the overall control of the device, gives the file structure of the control software to provide a reference for the software design of power electronic devices.Finally, it provides some experimental results and analysis of these experimental results.