| With the increasing consumption of fossil fuels, the development and utilization of new energy has been widely concerned. Cleanliness, extensive distribution and other characteristics of photovoltaic energy, make it rapidly developed and widely used. Because of the fluctuation of photovoltaic energy, the alone photovoltaic power generation system has a huge interference on the power network. It needs to configure a certain capacity of the storage medium. That can smooth the PV’s fluctuation. In the storage medium, the energy type storage and the power type storage has its advantages and disadvantages. And the lithium battery and the super capacitor respectively is a typical representative of the two kinds of storage modes. If both mix use, it can optimize the storage energy. In the photovoltaic power generation system with hybrid storage energy, there are a variety of connection mode. The system, which uses the DC bus in parallel connection mode, can realize the bidirectional current control of the super capacitor and the lithium battery. If it uses some hybrid storage energy control strategy, it can optimization the hybrid storage energy.This paper describes the design of a controller, which is used in photovoltaic power generation system with hybrid storage energy. In the system, photovoltaic, super capacitor and lithium battery use the DC bus in parallel connection mode. The controller is consists of the power module and the control module. The power module plays a role in energy conversion between the various power supplies. Its main circuit topology uses the non isolated bidirectional DC-DC converter. The control module controls the size and direction of energy flow between the various power supplies. This paper proposes a hybrid storage energy control strategy that super capacitor to absorb the short-term PV fluctuation and lithium battery to absorb the long-time PV fluctuation. Using this control strategy, the super capacitor as the filtering unit to balance the short-term PV fluctuation and stabilize the DC voltage, the lithium battery as the main energy storage unit to absorb the long-time PV fluctuation. This control strategy can achieve the optimization of the super capacitor and the lithium battery, also realize the value maximization. This paper also proposes a new photovoltaic power prediction algorithm to achieve smooth PV fluctuation effect, which is a mathematical model based on the trend of moving average method. The algorithm has little influence factors, it only needs a small amount of historical data to establish the model. It is easy to implement and also has a good smooth effect.This paper completes the design of software and hardware and obtains the control system based on the DSP28335. The simulation results verify the accuracy of the main circuit parameter design. This paper also completes the prototype machine. The experiment results show that, the power module has fast starting and stopping performance. When starting, the voltage and current waveform both have not overshoot and oscillation. When stopping, the voltage and current waveform is both smooth and have no shock. The voltage ripple is±0.5%,the current ripple is±0.8%,the full load efficient is97.25%and the MPPT efficient is99.81%. When the equipment has been working in long time, the temperature range of the IGBT, inductance and capacitor are all more reasonable. Therefore, all the indexes of performance meet the design requirement. When the photovoltaic power generation system with hybrid storage energy running, the photovoltaic power predict smooth effect is obvious and the output power curve of the controller are smooth optimization. It reduces the charge and discharge times of the lithium battery and prolongs its service life. It also reduces the capacity of the required configuration storage unit. So it is verification that this photovoltaic power prediction algorithm join to the controller can improve storage utilization rate and reduce the cost of the system. |
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