Comparative Analysis of Sub-Synchronous Oscillations With Various Grid-Forming Control Schemes Under Series-Compensated Line

Abstract

This paper presents a comparative study of various grid-forming control strategies under different series compensation levels to suggest the optimal control scheme for compensated lines. Series compensation is a technique used to insert a fixed capacitor in transmission line to maximize its power-transfer capacity and enhance the stability of the power system, however it may result in sub-synchronous oscillations issues. Virtual oscillator control and matching control schemes are recently proposed grid forming control strategies to ensure the power-sharing and synchronization capability of inverters under parallel operation. The mentioned schemes are designed for grid-forming control of inverter-based resources, with keeping traditionally used droop control as a benchmark for comparison. The IEEE first-benchmarked test model is modified by inserting series capacitance and energizing it with 1000MW grid forming inverter-based source in MATLAB/ Simulink. Distinct grid forming schemes, namely droop, matching, and dispatchable virtual oscillator control are implemented and critically analyzed for sub-synchronous oscillations under the same specifications as the test model. The simulation response of subsynchronous oscillations are investigated in time domain, frequency domain, and by calculating performance indices to verify the results in every aspect. The overall analysis justifies the damped, low transient overshoot and fast settling of sub-synchronous oscillations with the virtual oscillator control scheme at various compensation levels.

Keywords

• Renewable energy resources
• converter-based plant
• grid-forming control schemes
• series compensation
• optimization
• sub-synchronous oscillations