| Photovoltaic (PV) power generation is paid great attention by the power industry because of its environmental characteristics as a common distributed power supply. However, the power of PV has obvious intermittent influenced by the light intensity, temperature and other environmental factors. In order to solve this problem, hybrid energy storage system (HESS) is usually needed in the PV system. Lithium battery as a large capacity device in HESS can realize peak shaving and valley filling to ensure the reliability of electricity. And supercapacitor as a large power device in HESS can respond to a frequency adjustment to improve the quality of power supply. Therefore, the coordinated control of PV and HESS was studied in this paper. The main research contents are as follows:First of all, the only distributed power generation was a PV array in this paper. Based on the signal diode equivalent circuit model, a PV array that the peak power was 180kW was modeled. A new control algorithm--"incremental conductance plus integral regulation" control algorithm was presented in this paper based on the analysis of the two traditional maximum power point tracking algorithm, and simulated in the Simulink environment. The results showed that the algorithm could not only accurately track the PV array, but also fast response to the change of light intensity.Secondly, considering the effect of filter circuits at both ends of bi-directional DC-DC converter (BDC), the large signal model and small signal model of a half bridge Buck/Boost converter for the output and the input both with a filter circuit were modeled respectively by using the state space averaging method, and transfer functions from the duty ratio disturbance, the inductor current disturbance to the output voltage disturbance were given. The small signal model and the control system of a half bridge Buck/Boost converter were established in Simulink. The simulation results showed that the small signal model was correct, and the control method could realize the constant voltage control and constant current control.Finally, according to the real-time condition of PV array, LiFeP4(LFP) lithium iron battery stack and supercapacitor stack, energy management scheme was presented to achieve the coordinated work of them by the coordinated control of a Boost converter and two BDCs. According to the complementary characteristics of LFP lithium iron battery stack and supercapacitor stack, low pass filter control was using to smooth the hybrid energy storage power. On those basis, a PV and HESS coordinated control model was modeled. The simulation results showed that the coordinated control scheme used in this paper could make the Boost converter and two BDCs switch in different operating modes, which completed the energy management of the whole system to ensure the system fast and stable response. Meanwhile, Low pass filter control avoided the impact of high current fluctuation of the battery stack to extend the life of it, and the power output capacity of the system was also improved. |
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