Research On Non-isolated Buck-boost Converters For Photovoltaic Electric Water Heaters

Solar water heaters are widely loved by users because of the advantages of energy saving,but traditional solar water heaters generally have the problems of fragile and bursting collector tubes,aging and leaking pipes,difficult maintenance,and limited installation scope to meet only some users.The rapid development of the photovoltaic industry has brought new opportunities for solar water heaters,and photovoltaic electric water heaters were born.Photovoltaic electric water heaters have the characteristics of environmental protection and energy saving of traditional solar water heaters.At the same time,they can also complement "Gudian" for complementary heating in rainy weather.Because they do not have the disadvantages of traditional solar water heaters,they are flexible and convenient to install,safe and easy to maintain,and have a long service life.The advantages such as longevity are outstanding,and they are now increasingly valued by people.This paper studies the DC/DC converters of photovoltaic electric water heaters,analyzes the advantages and disadvantages of different types of DC/DC converters in photovoltaic electric water heaters,and proposes that non-isolated buck-boost DC/DC converters are most suitable for photovoltaic power generation.Water heater,and select the most suitable Cuk circuit for detailed analysis and experiment.First,the equivalent model of the selected converter is analyzed,and the control-output relationship formula and the input-output relationship formula are obtained,which provides a theoretical basis for the following parameter design and maximum power point tracking optimization;second,through the formula Derivation,the inductor,switch,diode,capacitance and load parameters of the converter are designed;finally,by combining the photovoltaic cell model with the non-isolated buck-boost converter model under study,an improved Maximum Power Point Tracking control method,and based on ds PIC30F2020 single-chip microcomputer,completed the design of the control program.This paper uses MATLAB software to simulate the main circuit and the Maximum Power Point Tracking,and build a test prototype with a maximum power of 540 W,and verify it experimentally.Both simulation and experimental results show that applying a non-isolated Buck-boost converter to a photovoltaic electric water heater system can not only achieve the maximum utilization of light energy,but also has the advantages of high transmission efficiency and simple control,and is very suitable for photovoltaic electric water heaters.Promote use.