Research On Active Power Control Strategy Of Photovaltaic Power Station

With more and more large scale photovoltaic power stations connecting to thegrid，the output power fluctuations caused by intermittency and randomness of solarlight resources have a more serious impact on the stability of the grid. Therefore, thegrid starts to make a detailed technical requirments to regulate the photovoltaic powerstation connecting to the grid，and also put forward a clear rule to regulate the activepower output of the PV power station. In order to improve the stability andschedulability of the output power of the PV power station and to increase power grid’scapacity to accept photovoltaic power station， active power control strategy ofphotovoltaic power station is studied in this paper.1. Based on the influcences on the grid caused by the large-scale photovoltaicpower station access to the grid, this paper analyzes the necessity of active powercontrol of the photovoltaic power station. And according to the requirement of theactive power control of the photovoltaic power station ruled by the grid, this paper alsoanalyzes the principles of the active power control of the photovoltaic power station.Due to the analysis of these principles, this paper proposes the active power controlsystem with two-level control architecture, which consists of the top centralized controllevel and the local control level.2. For the local control level, based on the analysis of the basic theory ofphotovoltaic cell, the realization method of constrained production of photovoltaic cellsis studied. A perturbation and observation control algorithm is proposed to realise theconstrained output power control of the photovotaic cell.The essence of the method is asearch algorithm which makes the output move toward the target value.The method cansolve the difficulty caused by the fact that the P-V character is nolinear, and can switchto MPPT output seamlessly.3. For the upper control level, fisrtly, due to the control mode under the gridscheduling and plan, an algorithm is studied to set the expected output of thephotovotaic power station. Secondly, based on the consideration of icreacing the lifespan of PV inverter, a power allocation strategy is proposed, whose control objective is to minimize the number of running inverter, and whose constraint condition is the ruleproposed by the grid, the output range of each inverter and launching or stopinginverters in turn. This strategy also takes the PV power prediction and the condition ofeach inverter into account.Based on all the studies above, the simulation and analysis of PV station activepower control is done. The result shows that the control strategy this paper proposed canachieve the output power tracking the value that is dispatched by the grid schedulingand planning, and can improve the stability of the output power of PV sation.