The Voltage Doubler Circuit Has A Larger Boost Ratio Than The Double Buck Grid-connected Inverter

The environmental pollution and energy shortage problems caused by traditional energy sources are becoming more and more serious.Solar energy has become a key research object in renewable energy due to its clean and rich advantages.At the same time,solar power generation technology is efficient,pollution-free,and not subject to resource distribution in regions.Limitations and other advantages have received widespread attention.This paper aims at the problem that the output voltage of a single photovoltaic panel in a photovoltaic grid-connected system is too low to be boosted to obtain a DC bus voltage that is connected to the grid of the mains.This paper proposes a method to convert the 20 V output voltage of a single photovoltaic panel through a large step-up ratio DC/DC The converter is connected to the 400 V DC bus,and then the 400 V DC bus voltage is realized by the inverter circuit to realize the two-stage grid-connected inverter circuit topology of grid-connected inverter.The top stage of this topology adopts a staggered structure and a diode-capacitor multiplier(DCM)combination voltage multiplier circuit with a large boost ratio DC/DC structure to achieve high gain and maximum power point tracking point tracking(MPPT)control;the rear stage adopts a double Buck inverter structure without bridge arm through risk,and uses voltage and current double closed loop and digital phase-locked control methods to achieve inverter grid connection.In addition,the topology uses high-frequency switching control to comply with the development trend of inverters with high switching frequency and high power density.This article will carry out in-depth research and analysis from the issues of circuit topology and control strategy.The specific content includes:Firstly,a detailed analysis of the working principle of the front-stage high-gain high-efficiency circuit topology is carried out,and the correctness of the circuit with a gain of 20 times is preliminarily verified through the calculation of voltage gain;a mathematical model of the photovoltaic cell is established and a simulation is built under the PSIM environment Model,simulation and analysis of the output characteristics under different lighting and temperature conditions;introduced several typical and intelligent algorithms of maximum power point tracking control method,in which,after simulation analysis of traditional conductance increment method and variable step conductance increment method,The superior performance of the latter is verified.Secondly,the selection and working principle of the topology of the double Buck inverter circuit in the latter stage are elaborated.The modulation method is asymmetric unipolar SPWM modulation technology.The circuit has a high-frequency drive signal without dead time and a small output current distortion rate.Advantages;In order to maintain the stability of the DC bus voltage and realize the power factor control of the grid-connected current,the double Buck circuit uses a double closed-loop control strategy of voltage outer loop PI control and current inner loop PR control;For the problem of small gain in the non-fundamental frequency region,a voltage feed-forward link is introduced to suppress the effect of grid voltage on grid-connected current.At the same time,the control strategy is modeled and analyzed,and the control parameters are designed.In addition,the principle and phase-locked loop technology are introduced.The realization method of digital phase-locked loop is given.Finally,based on the control chip TMS32F28335,the design and selection of the main circuit parameters and the design of the hardware and software parts of the control system are introduced in detail.According to the previous theoretical analysis,a simulation model of a double-buck photovoltaic grid-connected system with a large boost ratio based on a 20 V input voltage doubler circuit of the photovoltaic panel is built.Simulation verification was carried out,and the simulation results verified the superiority of the inverter system proposed in this paper in terms of high transformation ratio and high-quality grid connection.In addition,a 400 W experimental prototype was built,and the feasibility of theoretical analysis was further verified by the experimental results.