The Research On Signal Detection And Control Method Of H-Bridge Cascaded STATCOM

With the accelerating pace of industrialization in my country,the proportion of non-linear devices connected to the power grid has gradually increased,resulting in increasingly serious power quality problems.Static synchronous compensator(STATCOM)has good dynamic performance and compensation effect,and has an irreplaceable role in the management of power quality.The STATCOM with H-type cascade structure has the advantages of modularity,high compensation accuracy,and easy expansion.It is a major direction for contemporary scholars to study STATCOM devices.The thesis selects H-bridge cascaded STATCOM as the research object,and conducts research on its command signal detection method,AC side output control,and DC side voltage balance stability.The thesis first analyzes the switching function model and working status of the H-bridge power unit module,discusses the level superposition principle of the H-bridge module,and deduces the mathematical model of the H-bridge cascaded STATCOM;then,The pq detection method,ip-iq detection method,and dq detection method based on the instantaneous reactive power theory are discussed,and the advantages and disadvantages of the traditional command signal detection method are compared and analyzed.An ip-iq detection method without phase-locked loop is proposed as the thesis signal detection method;According to the characteristics of H-bridge cascaded STATCOM nonlinear strong coupling,the control principle of AC side output is analyzed.According to the established mathematical model,an AC side output internal model decoupling controller is designed to solve the traditional feedforward decoupling Difficulties in setting control parameters,low compensation accuracy,etc.;from the perspective of energy balance,analyze the causes and influencing factors of DC-side capacitor voltage imbalance,and demonstrate the main factors that cause DC-side voltage imbalance through mathematical derivation,from the overall capacitor voltage The three aspects of stability,phase-to-phase balance,and phase-to-phase balance were studied,and a three-level balance control method for the DC-side capacitor voltage was proposed.The overall balance and stability of the DC-side capacitor voltage was achieved using a control method in which the average value of the global capacitor voltage is equal to the reference value The zero-sequence voltage injection method is used to adjust the active power balance in the phase to achieve phase-to-phase voltage equalization control,and the DC voltage of the H-side power unit module in the phase is balanced by controlling the active power distribution of the sub-modules in the phase.Finally,the main circuit parameters of H-bridge cascaded STATCOM is analyzed and calculated,and a simulation model is built in MATLAB/Simulink to simulate and analyze the balanced and unbalanced working conditions.The simulation results show that the detection method and control method proposed in the thesis can be used to perform real-time dynamic reactive power compensation of the power grid under two operating conditions,and the DC side voltage fluctuation range is always maintained in the allowable range,which verifies the detection proposed in the thesis The correctness and effectiveness of the method and control method provide a theoretical basis for the subsequent experimental prototype production and device development.