Research On Photovoltaic Power Optimized System And Power Line Communication

In recent years,with the technology progress and the cost reduction of Photovoltaic(PV)power generation,PV generation is increasingly commercially competitive.However,there remain problems such as mismatch PV modules and power generating efficiency reduction,which affect the instability and reliability of the system.With the IOT era coming,the expectation for intelligence of PV system has been raised.The communication technology can be applicable to condition monitoring and control optimization.The dissertation studies two kinds of P V power optimized system and the corresponding communication solutions,power optimizer system with multiplexing power line communication(PLC)and single-phase cascaded H-bridge(CHB)inverter system with conventional PLC.The detailed circuit and algorithm for the two solutions are analyzed contrastively.Firstly,the dissertation analyses the cause and consequence of PV module and PV string mismatch,on this base,studies the topology of PV optimizer.For centralized system with multiplexed parallel-connected strings,the structure of Buck optimizer and phase-shifted full-bridge compensator are researched.The system solves the mismatch problems and keeps the optimizers in cut-through mode as possible.For household single string system,the topology structure,modulation strategy and control strategy of CHB inverter are studied.Secondly,the principle of multiplexing PLC is analyzed.Based on different signal modulating position in DC PWM controller,the multiplexing PLC is divided into the modulation wave based dual modulation and the carrier wave based dual modulation.Then the common phase dual modulation(CPDM)and the orthogonal frequency division multiplexing(OFDM)are discussed.Thirdly,the dissertation analyses multiplexing PLC and conventional PLC for different applications.The multiplexing PLC can be used in the DC system of compensator and optimizers,with the advantages of simple hardware and low cost.The signal condition circuits and DFT coherent demodulation algorithm are studied.For CHB inverter,because of the high communication speed demand,the dissertation adopts conventional PLC to meet the communicating requirement.Finally,the PV emulator platform is designed for laboratory environment.On this base,the Buck optimizer and full-bridge compensator experiment is implemented.For single-phase CHB inverter,the high speed PLC is also verified.