Research On Passivity-based Control Of Photovoltaic Inverter

With the increase of the PV penetration, the stiff grid works in a more complex environment, which brings some obstacles in the control of PV inverters. Firstly, the stiff gird features more like the weak grid, where large grid impedance may deteriorate the power quality. Secondly, the grid voltage may fluctuate. If the control parameters of linear control strategies do not change accordingly, the output power quality cannot be guaranteed. Lastly, in the island mode, the load maybe unknown and it may change randomly, which make the design of the control system complex. So it is significant to investigate a control strategy with strong robustness.The passivity-based control(PBC) has attracted many investigations due to its simple algorithm and strong robustness. The essence of PBC is energy regulation. It utilizes damping injection and energy shaping to realize the object tracking.This paper designs PBC algorithm for the single-phase PV inverter under the stiff grid, weak grid and island-mode condition. And it would focus on the EulerLagrange(EL) model based PBC algorithm. Firstly this paper would analyze the structure of the inverter and define the control objective. Then the EL model of the system would be built, and the passivity property of the system would be identified. Next the PBC algorithm would be designed through damping injection. Then the control performance would be discussed in three aspects, steady-state performance, transient performance and robustness. In the stiff grid, this paper would focus on the effect of the damping coefficients and give the guidance of choosing them. And this paper would analyze the system robustness of the output filter inductance estimation error. In the weak grid, this paper would focus on the grid line impedance. In the island mode, this paper would focus on the load and analyze the robustness of the load estimation error. Lastly, the proposed PBC algorithm would be tested in simulations to verify its effectiveness and robustness of the system parameters change and the external disturbance.The Port Controlled Hamilton(PCH) model of the inverter would be built and the PBC algorithm would be designed through Interconnection and Damping Assignment Passivity Based Control(IDA-PBC). Then in the simulations, this paper would compare the control performance of these two k inds of PBC algorithms.In the end, the single-phase PV inverter platform would be built to verify the effectiveness and the strong robustness of the proposed PBC strategy.