Hilton Abílio Gründling

Adaptive Current Control for Grid-Connected Converters With LCL Filter

This paper presents a discrete-time adaptive current controller for grid-connected voltage source PWM converters with LCL-filter. The main attribute of the proposed current controller is that, in steady state, the damping of the LCL resonance does not depend on the grid characteristic since the adaptive feedback gains ensure a predefined behavior for the closed-loop current control. Simulation and experimental results are presented to validate the analysis and to demonstrate the good performance of the proposed controller for grid-connected converters subjected to large grid impedance variation and grid voltage disturbances.

Comparison of digital control techniques with repetitive integral action for low cost PWM inverters

This paper presents a comparison among digital control techniques with repetitive integral action applied to voltage-source PWM inverters. As a result of the repetitive integral action, these digital control schemes can reduce steady-state errors and distortions caused by unknown periodic disturbances, which usually result from the input source and output load. Moreover, these digital control schemes measure only the output voltage, decreasing the amount of sensors and the overall system cost. The control laws, stability analysis, common and distinguishing features of these control algorithms are discussed. Experimental results from a PWM inverter (110 V/sub RMS/, 1 kVA) controlled by a low cost microcontroller are presented to demonstrate the control techniques performance under different load conditions, output filters and command strategies.

Discrete-Time Sliding Mode Observer for Sensorless Vector Control of Permanent Magnet Synchronous Machine

This paper proposes a sensorless vector control that combines two discrete-time observers to estimate the rotor speed and position of permanent magnet synchronous machines (PMSM). The first one is a sliding mode (DSM) current observer and the second one is an adaptive electromotive force (EMF) observer. Initially, the sliding conditions that assure the sliding motion around the sliding surface are derived and a design procedure to the DSM current observer is developed. Moreover, using discrete-time adaptive Lyapunov based EMF observer the rotor speed and position are obtained. Experimental results validate the theoretical analysis and demonstrate the very good performance of the proposed discrete-time sensorless vector control.

Space vector modulation for voltage-source inverters: a unified approach

This paper presents a unified approach of the space vector modulation for voltage-source inverters. To demonstrate the proposed unified approach, five fundamental inverters topologies are analyzed: single-phase full-bridge, three-phase three-wire, three-phase four-wire, three-phase four-leg and three-phase three-level inverters. Switching vectors, separation and boundary planes in the inverter output space as well as decomposition matrices and possible switching sequences are derived for each one of these inverters. Experimental results are shown to validate the proposed unified approach.

Control strategy of an interleaved boost power factor correction converter

Power factor correction interleaved boost converters provide a reduction of the inductor volume and weight when compared with the conventional PFC boost converter. However, to achieve these benefits, proper current sharing and current ripple minimization must be ensured. This paper proposes a controller based on the Lyapunov-likelihood control technique for interleaved boost converters (IBC) that ensures output voltage regulation and proper current share for each boost cell. In addition, a switching logic scheme for the IBC is developed to guarantee the input current ripple minimization. Extensive simulations are presented to demonstrate the performance of the proposed control and switching logic scheme.

Adaptive current control for grid-connected converters with LCL-filter

This paper presents a discrete-time adaptive current controller for grid-connected pulse width modulation voltage source converters with LCL filter. The main attribute of the proposed current controller is that, in steady state, the damping of the LCL resonance does not depend on the grid characteristic since the adaptive feedback gains ensure a predefined behavior for the closed-loop current control. An overview of model reference adaptive state feedback theory is presented aiming to give the reader the required background for the adaptive current control design. The digital implementation delay is included in the model, and the stability concerning the variation of the grid parameters is analyzed in detail. Furthermore, current distortions due to the grid background voltage are rejected without using the conventional stationary resonant controllers or the synchronous proportional-plus-integral controllers. Simulation and experimental results are presented to validate the analysis and to demonstrate the good performance of the proposed controller for grid-connected converters subjected to large grid impedance variation and grid voltage disturbances.

Analysis and comparison of hybrid multilevel voltage source inverters

This paper analyzes different hybrid multilevel inverters for high-power applications. With these hybrid topologies, it is possible to minimize the number of series-connected inverters for a given number of levels and, consequently, to reduce the THD of output voltage. Moreover, this paper develops a comparison among different hybrid multilevel inverters, especially between binary and trinary hybrid multilevel inverters. Several points are discussed, taking into account number of levels, spectral performance and power processing of hybrid multilevel inverters. Finally, a design procedure to obtain the number of H-bridge cells and DC voltage source of each cell for a given number of levels is proposed, so that few H-bridge cells synthesize a voltage waveform with a large number of levels, in order to minimize the circulating energy among cells.

Analysis and design of a repetitive predictive-PID controller for PWM inverters

This paper presents a predictive PID controller including a feedforward control and a repetitive controller for UPS applications. This digital control scheme can minimize periodic distortions resulted from nonlinear cyclic loads. Design procedure and stability analysis of the control scheme are discussed. Simulation and experimental results for a single-phase PWM inverter (110 V/sub RMS/, 1 kVA) controlled by a low cost microcontroller are presented to demonstrate the performance of the proposed control approach under periodic load disturbances.

Dual output three-level boost power factor correction converter with unbalanced loads

In this paper, a control strategy for three-level boost power factor correction converter with fully regulated two outputs is proposed. Beyond two outputs which are completely regulated, a switching logic law is established to minimize the input current ripple. Besides the features of the three-level boost power converter already known, the proposed approach has the advantage of regulating two output voltages for unbalanced loads, guaranteeing voltage sharing across the semiconductor device independent of the load, based on a Lyapunov-like technique. The robustness of the feedback control system is investigated, and experimental results are reported.

Isolated interleaved-phase-shift-PWM DC-DC ZVS converters

This paper describes the operation principles of an isolated ZVS DC-DC converter, which is composed by two half-bridge converters. Soft-switching is achieved for a wide load range. This ZVS DC-DC converter operates at constant frequency and it is phase-shift modulated. The main advantage of the phase-shift interleaving is the equalization of the input capacitor voltage, where each capacitor shares one-quarter of the total input voltage. The converter can be an alternative for ZVS phase-shift full-bridge DC-DC converter for high voltage applications, as result of the series arrangement in one of the two half-bridge converters. Analysis, operating principle and design procedures are presented in the paper. Experimental results from a 1.5 kW prototype converter operating at 100 kHz with isolated 60 V/25 A output are presented to validate the theoretical analysis.