Abstract
Photovoltaic (PV) systems are the most promising technology for residential installation as an alternative source of energy. To interface the primary source of PV to the electrical grid, an LCL-filtered inverter is being broadly adopted due to its low volume compared to the L-filtered one and the superior ability to filter high-frequency harmonics. In this context, this paper proposes highly accurate digital current controllers for single-phase LCL-filtered grid-connected inverters. The proposed controllers are: Integral-single-lead, integral double-lead, integral double-lead taking into account the effect of pulse width modulation (PWM) delay and the proportional-resonant (PR). These controllers are different from the traditional Proportional-Integral (PI), Proportional-Derivative (PD), and Proportional-Integral-Derivative (PID). One of the novelties of this paper is the detailed, step-by-step procedure for tuning each parameter of the proposed digital controllers considering the dynamic behavior of the LCL filter. The proposed PR has a different and more straightforward tuning methodology than those procedures commonly found in the literature. Therefore, this paper is an attractive tool for a fast, accurate, and reliable way to tune digital current controllers for a single-phase LCL-filtered grid-connected inverter. The controllers were verified in the digital signal controller (DSC) TMS320F28335 while the power structure runs in a hardware-in-loop (HIL device). Results show the efficacy of the proposed controllers.
Highlights
Several concerns never worried about before are causing severe problems, obliging utilities to impose restrictions on the customers. One such issue is the injection of high frequencies components generated by the pulse width modulation (PWM) of the electronics’ converters used in PV systems [1,2]
For low power and limited availability, several PV systems with LCL-filtered inverter are connected to single-phase distribution system around the world
Current controllers for LCL-filtered grid-connected inverter are continually being proposed in the literature [3]
Summary
The high penetration of PV system in residences brought new challenges to the distribution utilities. Several concerns never worried about before are causing severe problems, obliging utilities to impose restrictions on the customers One such issue is the injection of high frequencies components generated by the pulse width modulation (PWM) of the electronics’ converters used in PV systems [1,2]. Regarding the power distribution system, the LCL-filter inverter usually can be connected to singleor three-phase systems. For low power and limited availability, several PV systems with LCL-filtered inverter are connected to single-phase distribution system around the world. Current controllers for LCL-filtered grid-connected inverter are continually being proposed in the literature [3]. Regarding controllers for a single-phase LCL-filtered grid-connected inverter, the most dominant is the PR. The idea behind that is to preserve the features and simplicity of three-phase in single-phase systems In this case, simplified controllers can be adopted to make the output current follow its reference signal with negligible steady-state error. Since the controlled current is AC, the controller needs to have high accuracy
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