Study Of Hierarchical Modulation And Control Of Multi-DC Port Hybrid ANPC Inverter

Energy storage systems can improve the strong volatility and uncertainty of high permeability new energy grid connection,and are one of the important technical routes to achieve the national "dual carbon strategy".The energy storage grid connected converter,as a key component of the energy storage system to achieve energy conversion,has significant research value.However,due to the high correlation between energy storage voltage and state of charge(SOC),current energy storage grid connected converters mostly use a two-stage structure of DC-DC and inverter to achieve a wide range of voltage input.The two-stage structure requires two transformations of energy from energy storage to the power grid,resulting in additional energy loss.Therefore,this thesis proposes an efficient energy storage grid connected converter structure and designs a modulation strategy for this structure.The specific research content is as follows:1.This thesis analyzes the common problems of two-stage structures in energy storage power conversion.To address the low efficiency of the two-stage structure,this thesis proposes a multi-DC port inverter topology.Chapter 2 analyzes the six power paths of the proposed topology structure,establishes two operating modes: "independent power supply" and "common power supply",and designs a switching state where the inverter can achieve decoupling of high and low frequency switches.In addition,this thesis also established a Si/GaN hybrid inverter model based on active midpoint clamping(ANPC)topology.Based on PLECS,loss simulation and efficiency analysis were conducted on the Si/GaN hybrid inverter model,demonstrating the advantages of the proposed topology.2.This thesis proposes a simplified SVPWM hierarchical modulation strategy for scenarios where voltage imbalance between various ports,uneven distribution of 64 voltage space vectors,dynamic changes in amplitude and phase angles,and difficulty in vector synthesis are caused by real-time changes in SOC.The first stage adopts a virtual two-level space vector modulation strategy to avoid judging sectors and calculating complex trigonometric functions,achieving undistorted current control;The second stage redistributes the duty cycle of each port based on the volt-second balance theory,maximizing the output power of the main port and achieving efficient modulation goals.In addition,this thesis also simulated and implemented the modulation algorithm based on MATLAB/Simulink environment,verifying the effectiveness of the proposed modulation strategy from the perspective of power quality and efficiency comparison.3.A physical platform for the multi-DC port hybrid Si/GaN inverter used in the experiment was built at the hardware level,and a d SPACE controller was configured at the software level.Different output waveform data were collected through experimental debugging under various operating conditions.The feasibility of the proposed topology structure and the effectiveness of the proposed modulation strategy were demonstrated through analysis and comparison of the waveform and data in the experimental results.The multi-DC port hybrid inverter topology and modulation strategy proposed in this thesis can achieve low-cost,high power quality,and high efficiency output,which has important scientific value and broad application prospects in the field of new energy generation.