A Power Control Method With Simple Structure and Fast Dynamic Response for Single-Phase Grid-Connected DG Systems

Abstract

This paper presents a new method for controlling the exchange of power between a single-phase distributed generation system and the grid. Rather than controlling the active and reactive powers separately and through the media of current signal as is done by the conventional techniques, the proposed controller acts directly on the instantaneous power. This eliminates the conventional need for calculating the active and reactive powers; a calculation that involves filtering/phase-shifting and slows down the system responses and adds to computational complexity. This paper first formulates a nonlinear structure from a purely mathematical approach based on minimizing a cost function. The minimization procedure generates a reference for the current signal which is subsequently used in the current control loop. This paper then derives an equivalent linear counterpart for the nonlinear structure. Moreover, it is also shown that the idea of controlling the instantaneous power does not require a separate loop for the current. Having replaced the nonlinear part with its linear equivalent, a control loop that comprises linear time-varying elements is obtained. This paper further develops a linear time-invariant model of the loop for stability and design purposes. The proposed control system is successfully applied to a photovoltaic system and performance evaluation results (using computer simulations and a laboratory experimental setup) are presented. Desired performance and robustness of the proposed method is verified by testing it within different operating conditions. Index Terms-Distributed generation (DG), enhanced phaselocked loop (EPLL), instantaneous power control, photovoltaic, renewable energy, single-phase power control.

Three-phase phase-locked loop synchronization algorithms for grid-connected renewable energy systems: A review

“…The three-phase enhanced PLL (3EPLL) proposed in [70] is a three-phase version of the EPLL [71][72][73][74] and is developed by utilizing four individual EPLL blocks. The EPLL is actually an adaptive band pass filter that is capable of adjusting the transfer function according to the error signal, as depicted in Fig.…”

Three-Phase Photovoltaic Systems: Structures, Topologies, and Control

“…There are other control solutions available for single-phase grid-connected PV systems [76]- [78]. For example, the instantaneous power is controlled in [77], where the synthesis of the power reference is a challenge; in [78], a onecycle control method has been applied to single-stage single-phase grid-connected PV inverters for low power applications. It should be noted that the injected grid current is demanded to be synchronized with the grid voltage as required by the standards in this field [68].…”

Overview of Single-phase Grid-connected Photovoltaic Systems

“…For example, the instantaneous power is controlled in [77], where the synthesis of the power reference is a challenge; in [78], a onecycle control method has been applied to single-stage single-phase grid-connected PV inverters for low power applications.…”