Virtual Resistor Active Damping with Selective Harmonics Control of LCL-Filtered VSCs

Abstract

LCL filter is widely adopted for strict standard compliance of grid-tied voltage source converters (VSCs). The third order low-pass filtering provides great attenuation for the high frequency harmonics generated by the power electronics guaranteeing low output currents noise injection into the grid. A major concern of the implementation of the LCL-filter is to safeguard the system stability by providing effective damping of the filter resonances. Active damping methods are preferred because it does not result in substantial power losses as it would result by the utilization of passive damping circuits. Capacitor-current active damping (CCAD) technique can be effective while realizing only a proportional feedback. However, the suitable feedback gain for maintaining stability remains to be identified. Another control issue related to the grid-tied VSC is the harmonics compensation of the currents due to the grid voltage distortion. Therefore, this paper proposes an improved resonator with phase compensation to suppress the harmonics distortion while maintaining stability with properly design capacitor current feedback. The capacitor feedback gain for stability is analytically derived in this paper. The proposed control scheme is verified by both simulation and experimental results.

Virtual Shifting Impedance Method for Extended Range High-Fidelity PHIL Testing

“…With the software impedance reduced, the voltage after the original system impedance Z 1 is to be emulated by the PA to realise the virtual shift in impedance and ensure accurate simulation. In fact, the voltage V A can be obtained by subtracting the voltage drop across the shifted impedance R sh = aR 1 and X sh = aX 1 from V D as described in [23] V…”

Virtual Shifting Impedance Method for Extended Range High-Fidelity PHIL Testing

“…4: Virtual Shifting Impedance algorithm implementation system impedance Z 1 is to be emulated by the PA to realise the virtual shift in impedance and ensure accurate simulation. In fact, the voltage V A can be obtained by subtracting the voltage drop across the shifted impedance R sh = aR 1 and X sh = aX 1 from V D as described in [26] V…”

ZVS Turn-on integrated Triangular Current Mode Three-phase PFC for EV On-board Chargers

“…Passive damping is the simplest method but would cause extra loss. Several active damping methods exist to stabilize the system without adding extra components [8].…”

“…The capacitor-current-feedback control is one of the active damping methods used for damping the input filter. The capacitor current is fed back to the current loop by a proportional gain, which can be considered as a virtual resistor parallel to the capacitor due to a time delay [8]. Moreover, the current i b should be fed back to the main loop damping the LC branch resonance as shown in Fig.…”

“…In [6], only the passive damping method is applied to suppress the LCL and LC branch resonances. This method is simple and reliable but at the cost of extra losses [8]. In this paper, an iTCM modulated three-phase grid-connected AC-DC PFC converter is proposed, and the active damping method is developed to stabilize the system.…”