Current-limiting droop control with virtual inertia and self-synchronization properties

Abstract

Abstract-In this paper a current-limiting droop control of grid-tied inverters that introduces virtual inertia and operates without a phase locked loop unit is proposed. The proposed controller inherits a self-synchronization function and can guarantee tight bounds for the inverter frequency. In addition, using nonlinear Lyapunov theory, it is analytically proven that the inverter current never violates a given maximum value. Compared to the original current-limiting droop controller, the maximum capacity of the inverter is utilized at all times using the proposed strategy, even under grid faults. It is also proven that the proposed controller significantly reduces the resonance problem of the LCL filter. Extended simulation results are presented to verify the performance of the proposed controller under normal and faulty grid conditions.

Analysis and design of gradient descent based pre‐synchronization control for synchronverter

“…The variable J in (14) is the total moment of inertia referred to rotor. SV frequency syn being the important variable of SV control, is obtained by the active power loop and upon integrating it, the phase output of SV control syn is obtained.…”

“…The mechanical torque T m is calculated by dividing reference value Figure 5 Proposed pre-synchronisation control for the basic SV scheme of active power P * g with nominal angular frequency n . Hence, based on (14) and expression of electrical torque T e , the active power loop is implemented as shown in Figure 5. The reactive power control in SV is implemented using an integral control, with inputs of either difference between reference and actual reactive power, or difference between nominal RMS voltage and measured RMS grid voltage.…”

“…The self‐synchronisation concept in [11] was also applied to the universal droop control scheme in [13]. A current‐limiting droop control for a single‐phase system was proposed in [14], along with the self‐synchronisation ability based on virtual current concept in [11]. However, the synchronisation performance with initial phase difference beyond or has not been addressed in [12–14].…”

“…A current‐limiting droop control for a single‐phase system was proposed in [14], along with the self‐synchronisation ability based on virtual current concept in [11]. However, the synchronisation performance with initial phase difference beyond or has not been addressed in [12–14]. In [15], a single‐phase SV with current limitation capability has been proposed and the virtual current concept of [11] was used for self‐synchronisation.…”

SRF-based Current-Limiting Droop Controller for Three-Phase Grid-Tied Inverters

“…The control of the power electronic interfaced DERs connected to the main grid or a microgrid represents an active topic and among different control approaches, droop control represents the most widely used control technique for DERs since it has the ability to regulate to grid voltage and frequency [2]. In this context, enhanced droop controllers have been proposed with improved stability properties by either mimicking the frequency inertia of the conventional synchronous generators [3], [4], [5], [6] or by introducing robust control methods for better voltage and frequency regulation and increased protection [7], [8]. These droop control approaches are mostly implemented in a multi-loop structure with inner current and voltage control loops and the outer power loop (droop control) to improve the power quality [9].…”