Control of Photovoltaic Plants Interconnected via VSC to Improve Power Oscillations in a Power System

This paper presents an integrated methodology applied to photovoltaic (PV) plants for improving the dynamic performance of electric power systems. The proposed methodology is based on primary frequency control, which adds an ancillary signal to the voltage reference of the DC-link for the voltage source converter (VSC) in order to reduce power oscillations. This ancillary signal is computed by relating the energy stored in the VSC of the DC-link and the energy stored in the synchronous machine's shaft In addition, the methodology considers the operating limits of the VSC, which prioritizes active power over reactive power. Furthermore, the VSC control is assessed with interconnection and damping assignment passivity-based control (IDA-PBC), as well as compared to conventional PI control. IDA-PBC is employed to design a Lyapunov asymptotically stable controller using the Hamiltonian structural properties of the open-loop model of the VSC. A 12-bus test system that considers PV plants is employed to compare the proposed IDA-PBC control with a classical proportional-integral control approach. The impact of the proposed methodology is analyzed in four scenarios with different PV penetration levels (10%, 30%, 50%, and 80%) and four large disturbances in the test power system. In addition, a decrease in the inertia of the synchronous machines from 100 to 25% is analyzed. The time-domain simulation results show that the frequency oscillations are reduced by 16.8%, 38.43%, 37.53%, and 76.94% in comparison with the case where the proposed methodology was not implemented. The simulations were conducted using the SimPowerSystems toolbox of the MATLAB/Simulink software.