Integral‐resonant control for stand‐alone voltage source inverters

Abstract

This study deals with a newly-conceived voltage control method for three-phase four-leg voltage source inverters\ud (VSIs) which are being required in autonomous power generating units devoted to supply both three-phase and single-phase electrical loads in four-wire electric power distribution systems. To deal with VSI operating conditions providing three-phase voltage supply of both unbalanced loads and non-linear loads, an integral + resonant (I + R) voltage control structure is discussed and experimentally verified by means of a 25 kVA rated power converter prototype. It is shown that the proposed voltage control allows simplifying the overall control configuration, achieving zero-overhead power factor regulation and fast compensation of load unbalances. Further to that, a complete current limiting strategy is described and tested under different load conditions

Direct repetitive control with gain scheduling feature for stand-alone generating applications

“…Several stationary control strategies have been considered in previous work to achieve the phase-to-neutral voltage regulation of the 4-leg VSI. A multi-resonant control solution was first reported in [1]- [3], which enables a fine parameters tuning of the controller gain and phase at each harmonic frequency to achieve better performance, although the computational requirement is relatively high. In [4], an effective use of the resonant + repetitive combined control strategy was demonstrated for the output voltage regulation.…”

Load adaptive zero-phase-shift direct repetitive control for stand-alone four-leg VSI

“…The inverter is seen from the control algorithm mainly as a gain with a delay due to the discretization caused by the PWM unit as shown in (1), where K m is the gain depending to the modulation strategy, V dc and F sw are respectively the input DC-link voltage and the inverter switching frequency. Output phase voltages are filtered by means of a second order low-pass Butterworth filter having the transfer function as in (2), where  f is the filter cut-off frequency. Inverter output filters are necessary to remove the switching components from the output voltage and current waveforms.…”

“…One of the Repetitive Control (RC) main competitors is the Multi Resonant Control (MRC) structure, which is able to locate a harmonic compensator at each desired harmonic with almost independent gain and phase [1,2]. However, MRC main drawback is the difficult implementation and the requirement in terms of control platform memory and computational performance.…”

Single-Phase Inverter for Grid-Connected and Intentional Islanding Operations in Electric Utility Systems

“…From the SW point of view, in order to assure a low current-total harmonic distortion (THD) in the grid-tied mode, as well as a low voltage-THD when supplying non-linear loads in the intentional islanding mode, resonant controllers were demonstrated to be more effective [3], [4] with respect to standard PI controllers in the synchronous frame. This paper describes solutions for a hardware topology as well as a control architecture for a single phase inverter in order to achieve low current THD during grid-tied operation and low voltage distortion in the islanding mode.…”

“…A voltage and current low THD control strategy is also presented. It is composed of a single control loop that is continuously tuned to follow grid frequency variations in order to overcome the potential degradation of the regulation performance [4]. The same control structure is proposed for used in both the grid-tied and islanding modes of operation.…”