Analysis And Control Of DC-AC Dual Active Bridge Multiport Converter

With the reduction of nonrenewable energy sources and the more serious situation of environmental pollution,many countries are adjusting the energy structure to cope with the challenges,in which new energy power generation has become the focus of research.Multi-port converter as a converter integrated multiple energy ports that with the advantages of less switching devices,the simplified topology and the optimized control methods,so in the field of renewable has a very broad application prospects.Firstly,the principle of the main circuit topology of the multi-port converter is studied.The working mode of the DC-DC part of the main circuit,the transmission power and the principle of the dual frequency ripple in the circuit are analyzed.To the double frequency ripple of the circuit that a new method is proposed to suppress by the LC power decoupling circuit,and the feasibility of the LC branch suppression ripple is proved by theoretical method.Then,according to the principle of the circuit,the parameters of Boost circuit,resonant tank circuit,LC ripple suppression branch and LCL grid-connected filter are designed.The two parts that the DC-DC dual active bridge converter and the DC-AC inverter are modeled respectively and on which the controller can be designed.After that,the two implementation methods of MPPT are compared with the multi-stage PV grid-connected structure,and the scheme of decoupling control strategy of the dual active bridge converter and the inverter is proposed.The MPPT control,the ripple power suppression control and the secondary-side DC bus voltage control are realized for the dual active bridge converter.The regulator PI controller are designed for the controller of DC bus voltage which can be verified the correctness by the Bode plot of the voltage regulator system which before and after the compensation.Aiming at the existence of resonant spikes in the LCL filter of the inverter,the double closed-loop control strategy of the outer current and the inner current of the capacitor current under active damping is studied.The parameters of the outer loop PR controller and the inner loop proportional controller are designed and a variety of passive damping methods are also compared to analyze the capacitor parallel resistance has the best damping effect of which control strategy of the single current loop and the design of the PR controller are studied.The two control strategies and the parameters of active damping and passive damping controller are verified the correctness by the Bode plot of inverter system which before and after system compensation.Finally,the coordination control of the system and the proposed LC branch active power decoupling method are simulated.The effects of the new power decoupling branch on the ripple of the circuit are verified by Matlab simulation result of the photovoltaic cell port,the battery port and the DC bus voltage respectively.The harmonic suppression effect of the grid-connected inverter is simulated by comparing the active damping and passive damping in Matlab.It can be seen from the simulation results that the proposed LC branch active power decoupling method and the coordinated control of the whole system are correct and feasible.