Jonatan Roberto Fischer

Adaptive Dead-Time Compensation for Grid-Connected PWM Inverters of Single-Stage PV Systems

This study presents a new software-based plug-in dead-time compensator for grid-connected pulsewidth modulated voltage-source inverters of single-stage photovoltaic (PV) systems using predictive current controllers (PCCs) to regulate phase currents. First, a nonlinear dead-time disturbance model is reviewed, which is then used for the generation of a feed-forward compensation signal that eliminates the current distortion associated with current clamping effects around zero-current crossing points. A novel closed-loop adaptive adjustment scheme is proposed for fine tuning in real time the compensation model parameters, thereby ensuring accurate results even under the highly varying operating conditions typically found in PV systems due to insolation, temperature, and shadowing effects, among others. The algorithm implementation is straightforward and computationally efficient, and can be easily attached to an existent PCC to enhance its dead-time rejection capability without modifying its internal structure. Experimental results with a 5-kW PV system prototype are presented.

Calculation-Delay Tolerant Predictive Current Controller for Three-Phase Inverters

This work presents an improved deadbeat predictive current controller for grid-tie inverters that addresses issues related to implementation delays. The total delay is composed of the integer computational delay and a fractional delay, which is taken into account in the design of the controller algorithm, to improve its performance and robustness. The control strategy, based on a model that includes these delays, employs state feedback and a prediction observer in order to obtain a true two-sample ripple-free deadbeat response. System robustness can be adjusted with an appropriate selection of the location of the observer poles, at the expense of reducing control bandwidth. The proposed control scheme is both simple and computationally efficient since only few operations are required to include the delay in the algorithm. Experimental results show an improvement of the dynamic response even when mismatch in the load-inductance value estimation occurs.

Robust Predictive Control of Grid-Tied Converters Based on Direct Power Control

This study focuses on the control of instantaneous complex power of a grid-connected voltage-source inverter (VSI). In this study, a new space-vector-modulation-based direct power control approach is proposed: the robust predictive direct power control (RP-DPC). The proposed predictive control algorithm ensures that both, instantaneous real and imaginary powers, track the reference with high speed and accuracy reducing steady-state errors. In order to reduce the total harmonic distortion (THD) in the output currents, a fundamental frequency positive sequence detector is used in conjunction with a prediction grid voltage observer. Comparative simulations and experimental results of a 10-kW three-phase grid-connected VSI showing the steady-state and transient performance of the proposed RP-DPC are given. A low THD and balanced output currents are maintained even under severe voltage unbalance conditions.

Repetitive Control With Adaptive Sampling Frequency for Wind Power Generation Systems

This paper presents a novel repetitive control (RC) for wind power generation systems (WPGS), which achieves optimal performance in steady-state conditions due to a variable sampling/switching period technique (VSPT). The main objective of VSPT is to obtain an integer number of samples per grid period, which solves the main problem of RC, i.e., the loss of rejection to periodic disturbances due to grid frequency drift. The sampling/switching frequency is adjusted with a variable sampling period filter phase-locked loop, which also adds robustness to the system due to its inherent tolerance to grid voltage distortion and unbalances, and events such as frequency steps and faults. The control and synchronism subsystems are described, designed, and verified experimentally in a 10-kW WPGS. The results obtained prove the accuracy of the proposed control even under severe disturbances, typical in grids with high WPGS penetration, providing ancillary functions to enhance reliability and reduce operational costs.

Generalized Predictive Current Control (GPCC) for Grid-Tie Three-Phase Inverters

This work proposes a linear generalized predictive current control (GPCC) for grid-connected voltage-source inverters, which presents a fast response to current reference step changes, parameter variation robustness, and low distortion at the output currents, with reduced computational effort. Experimental results on a 10-kW converter connected to a real grid are shown, and the proposed controller is compared against a classical proportional resonant controller.

A Robust Model Predictive Control For Grid-Connected Voltage-Source Inverters

Model predictive control is a new alternative in the control of power converters. The practical application of this controller demands a correct compensation of the computation delay. This compensation requires an estimation of the load current, usually attained in an open-loop manner, i. e. without error feedback of the model parameters. However, this strategy gives rise to diverse perturbations in the waveform, when there is a certain amount of parameter variation. In this work, the effects of this variation are analyzed and a way to reduce the distortion is proposed, using a Luenberger observer. This new approach is called Robust Model Predictive Control. The proposal is applied to a grid-connected voltage-source inverter. To validate the proposal, simulations are included in the paper.

Filtro notch digital para la conformación del espectro en control predictivo basado en modelo

This paper presents the evaluation of different types of digital filter in Finite Control Set Model Predictive Control (FCS-MPC), in order to control the injected current spectrum of a power converter, and fix it to a narrow band around an arbitrary switching frequency. In FCS-MPC, a cost function in which there are included system variables to be controlled, is minimized. With the use of a current error filter, the current spectrum can also be controlled. Simulations are presented to show the obtained results.

Control de corriente Predictivo Robusto y Auto-Ajustable

This paper presents a self tuning robust predictive current controller that can be applied to both single and three phase grid tie voltage source inverters. Due to its adaptive capability, this control has a great robustness to paremetric variations, presents low steady-state current error and lowers dead time distortion in contrast with its nonadaptive variant (RPCC). Both simulation and experimental results were carried out in order to asses the proposed technique.