Design Of A Multi-port PV DC/DC Converter Based On Combined Pulse Unit

In order to accommodate multiple of energy utilized in combination and free flow of energy between various units, a variety of novel converters emerged. In this dissertation, various types of converter in photovoltaic system are deeply studied. On this basis of the study, a multi-port PV DC/DC converter based on combined pulse unit is proposed. Then, theoretical and experimental study are conducted and circuit is desiged using ARM chip.Firstly, various types of DC/DC converter for photovoltaic conversion are studied and a improved three-port converter based on combined pulse unit (Multi-port converter based, MPC) is proposed. The improved MPC optimizes the DC-link to achieve MPPT better, which effectively meets the satisfaction of multi-port and maximum power point tracking (MPPT). Theoretical analysis is illustrated under various operating conditions and the key components is designed detailedly.Secondly, the electrical characteristics of photovoltaic cell is necessarily narrated and its engineering mode is presented. Based on platform of Matlab/Simulink, the simulation model of the PV cell is established, computing to testify the commonly used MPPT methods and its comparative characristics are summerized.Besides, Buck converter which can achieve MPPT is researched and the MPPT (perturbation and observation method) used in improved MPC is identified and analized. The control strategy is discussed, namely MPPT control for the photovoltaic panelarrays and phase-shifted control cycle control for the full-bridge converter, which makes independent control of solar photovoltaic cells and full-bridge converter is easily implemented. Model built on Matlab/Simulink computs the operating conditions of MPC in a typical use, and the simulation results show that the proposed MPC can coordinately operate.Finally, the main power circuit is conducted with LPC2131 as the core of the control circuit, and other hardware and software is also designed including drive circuit, sampling circuit, Phase-shifted signal generative circuit and signal conditioning circuits. A prototype is achieced and the system get its experimental verification.