Stand-alone Pv Power Generation System Control Strategy And Its Application

As the shortage of conventional energy, the technology of new energy has been paid a lot of attention, especially the clean and non-pollution-free photovoltaic technology, such as the independent photovoltaic power generation system, which is widely used. However, the conventional control strategy of independent photovoltaic power system results in low efficiency, lead-acid batteries aging and some other problems. So, this thesis addresses this problem to find a control strategy for independent photovoltaic power system, which will greatly promote its development and application.Firstly, to solve the problem that lead-acid battery is difficult to completely absorb the energy converted by photovoltaic cell arrays, the three-stage charging method based on discharge pulse is proposed in this thesis. This method utilizes lead-acid battery's self-discharging to increase its acceptable charging current and makes lead-acid battery fully absorb the energy converted by photovoltaic cell arrays.Then, a coordinated control strategy of charging is proposed to deal with the matching problem between photovoltaic cell arrays and lead-acid battery match unreasonable in the independent photovoltaic power generation system. The discharge pulse based three-stage charging method is used when charging. Meanwhile, to increase photovoltaic cell arrays'output, the maximum power point tracking algorithm is employed. Then, small constant current charging is used before finishing charging, which can make the lead-acid battery's terminal voltage increase to the overcharge point voltage and determine the lead-acid battery's state of chare(SOC). The discharging course is protected by measuring its voltage and estimating its SOC.Finally, the control strategy proposed in this thesis is applied in independent photovoltaic power experimental system. The experimental results show that this strategy improves the efficiency of independence photovoltaic power experiment system and provides a way to use solar energy efficiently.