Research On Independent Operation Of Photovoltatic Inverter And Control Of Multiple Modules In Parallel Operation

With the rapid social progress and economic development, the requirement of reliability of power supply and the quality of power supply in all fields has been higher and higher. On the one hand, parallel operation of multi-inverters can solve the shortcomings of low reliability in centralized power supply; on the other hand, the system is easy to expand capacity with high flexibility, and it is considered to be one of the current direction of the power technology development. Digital control technology with higher integration has stronger adaptability and more flexibility compared to analog control, so the digital control is also the main direction of the future development of the power industry.The main study of this paper is the single-phase inverter and its parallel control technology, and the digital control is achieved through DSP. The work topology adopted in this paper is analyzed in the first place: taking the instability of battery output voltage into consideration, the front-end DC/DC conversion part to stable the wide range of changes in battery voltage at a constant value is designed, which has electrical isolation function. On the basis of drawing control strategy, the research of control methods of the single phase inverter is carried out, and a double closed loop control method with load feed forward is adopted, and the inverter mathematical model has been established.Secondly, the mathematical model of two parallel single-phase inverter system is established, and the load-sharing principle and circulation characteristics are analyzed; then, the corresponding relationship between the output voltage amplitude; next, phase and output power of the inverter is obtained; and then the conclusion that the suppression of circulating current is realized by adjusting the given voltage come out. On the base of above theoretical analysis and existing parallel technology, the parallel control strategy implemented which is competitive in synchronization and CAN-Bus is adopted to achieve current-sharing in this paper. Only data connection is used in this scheme, so the control algorithm is easy to implement and has better performance in current-sharing. It also has a easy way to expand its system capacity and improves power supply reliability greatly.Finally, a parallel system composed by two inverters is established, and the analysis and design of hardware and software are carried out. A digital control circuit with DSP as its core is drawn, and system program flow chart is given. The scheme is verified on the 3k W experimental platform, and the results show that this method can achieve reliable parallel with smaller circulation current.