Abstract
This paper investigates a combined resonant–repetitive (RR) control structure for a three-phase four-leg dc/ac converter power supply. The RR control configuration is composed by a resonant controller tuned at the system fundamental frequency working in conjunction with a plug-in-type repetitive controller. The resonant part of the control scheme is used to assure prompt tracking of the inverter output voltage and to achieve as fast as possible system response to load variations; to this purpose, it is tuned at the fundamental frequency. At the same time, the resonant controller is able to stabilize the system without the necessity of any further additional controller; the repetitive part of the scheme is implemented for the fine regulation at the system harmonic frequencies. The proposed control configuration is used to regulate the power supply output voltage, providing very good tracking of the output voltage reference even in the presence of a nonlinear load. Experimental validation from a 40-kVA converter prototype is presented to validate the operation of the proposed converter and control.
Highlights
Distributed generation is being developed worldwide to meet the increasing energy demand as well to reduce the environmental impact of fossil-fuel based centralized generation
resonant control (RSC) is devoted to provide tracking of the fundamental harmonic, whereas repetitive control (RC) is used to cancel the output voltages harmonic contents introduced by distortive loads
Comprehensive analysis has been performed through a full switching model, which includes the single-precision floating-point 32-bit arithmetic, as in the selected Digital Signal Processor (DSP), synchronized sampling and PWM unit
Summary
Distributed generation is being developed worldwide to meet the increasing energy demand as well to reduce the environmental impact of fossil-fuel based centralized generation. On the contrary, distributed generation systems are accomplished by using renewable energy generating units (e.g., photovoltaic arrays and wind turbines) which have relatively low power rating and are suitably connected to the power grid at the voltage level of the electricity distribution network, so that the significant investment in electric transmission infrastructure can be substantially reduced. A DC-AC converter with 4-wire output is used for connecting the generating system to the distribution network and the user loads. Such a converter is required to provide both active and reactive power output depending on whether it is operated on-grid or off-grid. The paper refers to the off-grid mode of operation of the DC-AC converter with 4-wire output in order to investigate, in particular, the control issues
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