Improved Damping Control Method for Grid-Forming Converters Using LQR and Optimally Weighted Feedback Control Loops

Abstract

Power grid pattern is expected to evolve from generator-based power systems towards converter-based systems in the forthcoming decades. Therefore, grid-forming converters will be pertinent to interconnected power grids in pursuance of enhancement their resilience against disturbances. This paper introduces a new efficient damping control method for gridforming converters that provides a smooth power modulation and an efficient damping response against frequency and voltage deviations. First, an averaged state-space representation for a grid forming application in dq synchronization frame is derived. Based on this model, a new hybrid damping controller, including the concept of state feedback control and PI control, is proposed to address the main issues in existing controllers. The state feedback controller is optimally designed using a linearquadratic regulator (LQR) approach to optimize the system performance. Moreover, the PI controller is optimally designed using the pattern search algorithm. The proposed damping control method integrates optimally between the control loops through a mapping matrix to rapidly synchronize with the grid and efficiently damp the oscillations. Simulations are carried out to prove the proposed method robustness. Finally, a comparative study using controller hardware-in-the-loop (CHiL) is employed against conventional system to validate the proposed damping method.INDEX TERMS Grid-forming converters, inverter dominated grid, weak grid, virtual inertia, damping emulation, distributed generation, LQR design, pattern search.

LQR controller design for portable power supply based on flyback converter

“…The block diagram of the LQR optimized control system for the Flyback converter is shown in Figure 4, where k1 and k2 are the state feedback parameters, k3 refers to the feedback control parameter of the integration gain, and KPWM represents the gain from the modulation circuit to the main power circuit. Since the LQR controller has sufficient amplitude margin and phase angle margin [6], it can ensure that the output voltage of the Flyback converter has good dynamic performance under different disturbances.…”