| Distributed optical storage system can reduce the phenomenon of light abandoning and power limiting to a certain extent and make full use of solar energy resources.However,the output efficiency of photovoltaic cells is limited to a certain extent,and the output energy is greatly affected by the environment.In addition,the cost of energy storage device is also high.Therefore,improving the output efficiency of photovoltaic energy storage system and extending the working life of energy storage device are the core technologies to improve the working performance of whole system.In this thesis,the performance of the system is improved by improving the output power of photovoltaic cells and reducing the current or voltage ripple of the battery.Firstly,the maximum power point tracking algorithm of single sensor based on impedance matching is proposed,which uses dichotomy to adjust the duty ratio and step size to avoid the contraction between the tracking speed and tracking accuracy of traditional conductance increment method.Only the output current is used as the feedback quantity,so as to reduce the sampling error,simplify the hardware circuit and improve the operation accuracy.Then a novel model predictive control algorithm based on three phase stagger buck-boost circuit is proposed.In order to maintain the DC bus voltage constant,the charging and discharging mode of the battery is determined according to the output power of the photovoltaic cell and the rated load power.Then the model predictive control is implemented in different working modes.Specifically,the sampling period is divided into two parts with different length in one sampling period,and the total on-off state of all switches in the next period is determined according to the simplified mathematical model,and then the specific on-off state is determined according to the three-phase uniform flow,so as to complete the two-step prediction of variable step size.This algorithm can not only reduce the ripple size of the output current and voltage of the battery,but also reduce the ripple size and overshoot of the DC bus voltage.This paper builds simulation models on the MATLAB/SIMULINK simulation platform.The simulation results of the new MPPT algorithm and the model predictive control algorithm are analyzed and compared with the simulation results of the traditional algorithm,which proves the feasibility and reliability of the two algorithms.Finally,this paper builds an experimental platform for cogeneration of distributed photovoltaic energy storage system,and completes the system’s hardware design including BUCK circuit,buck-boost circuit,feedback acquisition circuit,temperature detection circuit,PWM processing circuit and relay control circuit.The PWM wave production,sampling data processing,LCD display,and the main circuit control are completed by the main control chip of stm32.The experiment verified the effectiveness of the single sensor MPPT algorithm based on impedance matching of hardware circuit,realized the adjustment of different operating modes of the system by changing the temperature detection module under the premise of stable DC bus voltage,and completed the system’s cogeneration and output adjustable functions. |
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