Alfred Hayek

Modeling and Control of a Single-Phase Sheppard-Taylor Based Power Factor Corrector

In this paper, a single-phase power factor corrector (PFC) based on the Sheppard-Taylor topology is presented. Compared to conventional buck, boost or buck-boost PFCs, this topology allows a better current tracking at the AC side, with a relatively reduced voltage at the DC side. Consequently, the high frequency AC filters required by the buck PFCs are avoided, and the voltage stresses on the boost switches are significantly reduced. Furthermore, the control detuning phenomenon from which suffer most of the conventional PFCs, especially at very low input voltage, is avoided. This yields major improvements in the source current waveform. The proposed converter is integrated as a PFC at the DC-end of a single-phase diode bridge. A pulse-width-modulated (PWM) control is developed in order to ensure a unity power factor at the AC-source side and a regulated voltage at the DC-load side. In order to verify the performance of the proposed control scheme, simulation experiments are carried out on a numerical version of the converter with its control circuit. The implemented model of the converter is obtained by using the switching function technique. The control system is tested under both rated and disturbed operating conditions. The system performance is evaluated in terms of source current total harmonic distortion (THD), voltage regulation, robustness and dynamic time response to a set point offset.

Small-Signal Average Modeling, Simulation and Carrier-Based Linear Control of a Three-Phase Four-Leg Shunt Active Power Filter

Current harmonics caused by nonlinear loads yield major power quality related problems in the utility. Such harmonics are commonly reduced by employing static compensators known as active power filters (APF). APF topologies are of various types, depending on technical and economical requirements; and their performance is intimately related to the applied control algorithm. In this paper, a new constant-frequency linear control scheme is proposed for a shunt three-phase four-leg APF. The APF is used to compensate the current distortion and the reactive power created by a typical industrial load. The elaboration of the control law is based on a small-signal averaged model of the converter, computed in the (d,q,0) synchronous frame. The control scheme consists of multiple-loops PI controllers that ensure voltage regulation at the DC side of the filter, and current wave shaping at the AC side. The control system is implemented numerically using the Matlab/Simulink tool. The performance of the proposed control approach is finally discussed through the obtained simulation results.

Small-Signal Averaged Model and Carrier-Based Linear Control of a Sheppard-Taylor PFC

In this paper, the small-signal averaged model of a Sheppard-Taylor DC-DC converter, used in single-phase Power Factor Correction (PFC) applications, is derived. Compared to conventional buck, boost or buck-boost PFCs, this topology allows a better current tracking at the AC side, with a relatively reduced voltage at the DC side. Based on this model, a carrier- based Pulse-Width-Modulation (PWM) linear control system is developed in order to ensure a unity power factor at the rectifier AC-side and a regulated voltage at the rectifier DC-side. Both current and voltage regulators are Pi-type. The performance of the proposed control scheme is tested through simulations. The system performance is evaluated in terms of source current Total Harmonic Distortion (THD), input power factor and DC-voltage regulation.

A new single-phase power factor corrector based on the sepic and Sheppard-Taylor topologies

In this paper, a new single-phase power factor corrector (PFC) based on the Sheppard-Taylor topology is proposed. Compared to conventional buck, boost or buck-boost PFCs, this topology allows a better current tracking at the AC side, with a relatively reduced voltage at the DC side. Consequently, the high frequency AC filters required by the buck PFCs are avoided, and the voltage stresses on the boost switches are significantly reduced. Furthermore, the control detuning phenomenon, from which suffer most of the conventional PFCs, especially at very low input voltage, is avoided. This yields major improvements in the source current waveform. The proposed converter is integrated as a PFC at the DC-end of a single-phase diode bridge. A pulse-width-modulated (PWM) control is developed in order to ensure a unity power factor at the AC-source side and a regulated voltage at the DC-load side. In order to verify the performance of the proposed control scheme, simulation experiments are carried out on a numerical version of the converter with its control circuit. The implemented model of the converter is obtained by using the switching function technique. The control system is tested under both rated and disturbed operating conditions. The system performance is evaluated in terms of source current total harmonic distortion (THD), voltage regulation, robustness and dynamic time response to a set point offset.

Averaged Model Based Control of a Sheppard-Taylor PFC with Nonlinearity Compensation

In this paper, a nonlinearity compensation control is developed and applied for the single-phase Sheppard-Taylor power factor corrector (PFC). Compared to conventional buck, boost or buck-boost PFCs, this topology allows a better current tracking at the AC side, with a relatively reduced voltage at the DC side. Based on the exact linearization of the converters averaged model, and on the use of a fixed-frequency carrier to generate the Pulse-Width-Modulated (PWM) gate signal, the control system is designed to ensure unity power factor at the rectifier AC-side and regulated voltage at the rectifier DC-side. The performance of the proposed control scheme is tested through simulations, and evaluated in terms of source current total harmonic distortion (THD), input power factor and DC-voltage regulation.

Averaged-Model-Based Nonlinear Control of a PWM Three-Phase Four-Leg Shunt Active Power Filter

Current harmonics caused by nonlinear loads yield major power quality related problems in the utility. Such harmonics are commonly reduced by employing static compensators known as Active Power Filters (APF). APF topologies are of various types, depending on technical and economical requirements. In this paper, a new constant-frequency nonlinear control scheme for a shunt three-phase four-leg APF is proposed. The APF is used to compensate the current distortion and the reactive power created by a typical industrial load. The elaboration of the control law is based on the state-space averaged model of the converter, computed in the (d,q,0) synchronous frame. The multiple-loop control scheme consists, first, of inner controllers that ensures current shaping and reactive power compensation, and second, an outer loop to allow voltage regulation at the DC side of the filter. In addition, a nonlinearity compensation block is integrated in the inner sub-controller in order to ensure perfect cross-decoupling and linearity between the inner inputs and outputs. The control system is implemented numerically using Matlab/Simulink tool. The performance of the proposed control approach is finally discussed through the obtained simulation results.

Small-signal averaged model and carrier-based linear control of a new Sheppard-Taylor-based PFC

In this paper, the small-signal averaged model of a new Sheppard-Taylor-based DC-DC converter, used in single-phase power factor correction (PFC) applications, is derived. Compared to the conventional Sheppard-Taylor converter, this topology allows lower voltage stresses across the capacitors and larger output voltage range for the same operating area. Based on the proposed model, a carrier-based Pulse-Width-Modulation (PWM) linear control system is developed in order to ensure a unity power factor at the rectifier AC-side and a regulated voltage at the rectifier DC-side. Both current and voltage regulators are PI-type. The performance of the proposed control scheme is tested through simulations. The system performance is evaluated in terms of source current total harmonic distortion (THD), input power factor and DC-voltage regulation.

A linear decoupling control for a PWM three-phase four-wire shunt Active Power Filter

The presence of current harmonics in the grid causes major problems such as overheating and electromagnetic emissions. Active Power Filters (APF) have been presented as alternative to reduce such harmonics. In this paper, a new constant-frequency control scheme based on the linear decoupling principle is proposed for a shunt three-phase fourwire APF. The APF is used to compensate the current distortion and the reactive power created by a typical industrial load. The elaboration of the control law is based on a small-signal averaged model of the converter, computed in the (d,q,0) synchronous frame. The control scheme consists of multiple-loops regulators that ensure voltage regulation at the DC side of the filter, and current wave shaping at the AC side. The control system is implemented numerically using Matlab/Simulink tool. The performance of the proposed control approach is finally discussed through the obtained simulation results.

Comparative Study of Two Average-Model-Based PWM Control Schemes for a Sheppard-Taylor PFC

In this paper, a comparative evaluation of two control strategies applied on the single-phase Sheppard-Taylor power factor corrector (PFC) is proposed. Both control laws generate fixed-frequency carrier-based pulse-width-modulation (PWM) gate signals, and are designed on the basis of the nonlinear averaged model of the converter, which is established using the well-known state-space averaging technique. The first control approach employs linear PI regulators for both input current wave-shaping and output voltage regulation. For this purpose, the derivation of the converters small-signal transfer functions was required. The second control uses the input-output feedback linearization strategy in order to compensate the systems nonlinearity and simply, thus, the controllers design. The performance of both control schemes is tested through simulations. The comparison is conducted in terms of source current total harmonic distortion (THD), input power factor and DC-voltage regulation.

Carrier-Based Linear Decoupling Control of a Three-Phase Four-Leg Shunt Active Power Filter

Current harmonics caused by nonlinear loads yield major power quality related problems in the utility. Such harmonics are commonly reduced by employing static compensators known as active power filters (APF). APF topologies are of various types, depending on technical and economical requirements; and their performance is intimately related to the applied control algorithm. In this paper, a new constant-frequency linear decoupling control scheme is proposed for a shunt three-phase four-leg APF. The APF is used to compensate the current distortion and the reactive power created by a typical industrial load. The elaboration of the control law is based on a small-signal averaged model of the converter, computed in the (d,q,0) synchronous frame. The control scheme consists of embedded current and voltage loops that ensure respectively current wave shaping at the AC side of the filter, and voltage regulation at the DC side. The control system is implemented numerically using the Matlab/Simulink tool. The performance of the proposed control approach is finally discussed through the obtained simulation results.