Research On Photovoltaic Pump System Of Variable Frequency Control And Group Control Technology

Photovoltaic pump system using solar energy as an input, do not relay on the power grid and work independently. It could be a good solution to domestic water and agricultural water problems that using photovoltaic pump system in those remote areas lacking electricity but having abundant sunlight resources. Therefore photovoltaic pump system is widely used around world.In this paper, variable frequency control technologies and group control technologies of photovoltaic pump system which adopts three-phase asynchronous motor as drive were studied and analyzed.1) The paper established a mathematical model of photovoltaic pump system. Two kinds of speed regulation, including VVVF and vector control, were introduced and were also compared on the stability of PV array voltage by Matlab.2) A sensorless vector control method which can be applied in photovoltaic pump system was introduced. This paper focuses on the design method of full order observation and speed estimation convergent algorithm. The simulation results show that the multiple iterations can improve the convergence of the algorithm.3) A parameter identification method of induction motors under the static state was proposed. Instead of the traditional current loop controller, an open-loop control strategy was adopted at the single-phase test.The stator current was upraised by adding DC offset voltage until the DC component of stator current is greater than the amplitude of the fundamental component, which effectively solved the influence of dead zone and other nonlinear factors.4) A flow optimization algorithm was proposed for photovoltaic pump centralized group control system which multiple pumps operating in parallel. Group control system can run all day at the optimal flow conditions through the way of reasonable distributing system power, and controlling start and stop of each unit by estimating the flow optimal value. The paper established a mathematical model of pump parallel device and system conditions was solved by using the Newton iterative method. Finally, the corresponding control strategies were proposed.5) The performance parameters of head curve and power curve were obtained from experiments by setting up the experimental platform of photovoltaic pump centralized group control system. Experiments prove that the equalization is the best way of power allocation. Finally, the group control experiments verify the validity of the method described above.