Bachir Kedjar

DSP-Based Implementation of an LQR With Integral Action for a Three-Phase Three-Wire Shunt Active Power Filter

This paper presents the design and implementation of a linear quadratic regulator (LQR) with integral action (LQRI) for a three-phase three-wire shunt active filter (SAF). The integral action is added so as to cancel the steady-state errors for reference tracking or disturbance rejection, knowing that the standard LQR provides only proportional gains. The controller is designed to achieve DC bus voltage regulation and harmonics and reactive power compensation. The converter model is set in the d-q rotating reference frame. The latter is augmented with the integral of the q component of the SAF currents and DC bus voltage to achieve integral action. The controllers performance depends on the weighting matrix, which is chosen to ensure satisfactory response. The converter is controlled as a whole, i.e., a multi-input-multioutput system and a fixed pulsewidth modulation at 10 kHz is used to generate the gating signals of the power devices. The system is tested for harmonics, reactive power, and load unbalance compensation for balanced/unbalanced loads. The experimental results obtained with a digital signal processor-based implementation of the controller on the DS1104 of dSPACE show good performance in terms of DC bus voltage regulation (small overshoot and very fast time response) and a low total harmonic distortion of AC line currents.

Vienna Rectifier With Power Quality Added Function

The aim of this paper is to introduce power quality added function to the standard Vienna rectifier in order to compensate reactive power and to cancel current-type harmonics drawn by nonlinear loads connected to the same point of common coupling. A theoretical investigation that demonstrates the ability of such topology to compensate harmonics and limited reactive power is first presented. Then, the design and implementation of a linear quadratic regulator with integral action is presented. The converter is controlled as a whole i.e., a multiple-input-multiple-output system, and uses an augmented model that was developed in the d- q frame. Experimental results obtained with a digital-signal-processor-based DS1103 controller and the converter operating at a 20-kHz switching frequency proved the effectiveness of the theoretical study and the high performance of the proposed control strategy in compensating load harmonics and limited reactive power.

Modeling, control and simulation of DFIG for maximum power point tracking

This paper deals with the modeling, analysis, control and simulation of a doubly-fed induction generator (DFIG) driven by a wind turbine. This grid connected wind energy conversion system (WECS) is composed of DFIG and two back-to-back PWM voltage-source converters in the rotor circuit. A mathematical model of the machine, derived in an appropriate dq reference frame is established. The grid voltage oriented vector control is used for the grid side converter (GSC) in order to maintain a constant DC bus voltage and to compensate for reactive power at the power network. The stator voltage orientated vector control is adopted in the rotor side converter (RSC) control strategy, providing efficient handling of active and reactive power at the stator, as well as a maximum power point tracking (MPPT) method for the DFIG-based wind turbine. The proposed system is simulated for different operating conditions to illustrate the reliability of the control technique. Corresponding system simulation results under nonlinear load variations and wind speed transients are presented to demonstrate the significance of MPPT in WECS, and the effectiveness of adopted control technique.

LQ control of a three-phase four-wire shunt active power filter based on three-level NPC inverter

This paper presents the design and implementation of a linear quadratic regulator (LQR) with Integral action (LQIR) for a three-phase four-wire shunt active power filter using a three-level neutral point clamped inverter (SAF-NPC). The integral action is added so as to cancel the steady state errors for reference tracking or disturbance rejection knowing that the standard LQR provides only proportional gains. The controller is designed to achieve overall DC bus voltage regulation, unbalance voltage between the upper and lower capacitors, harmonics, reactive power and loadpsilas neutral current compensations. The converter model is set in the d-q-o rotating reference frame. The latter is augmented with the integral of the q component of the SAF-NPC currents, DC bus voltage unbalance and overall DC bus voltage to achieve integral action. The controllerpsilas performance depends on the weighting matrix, which is chosen to ensure satisfactory responses. The converter is controlled as a multi-input multi-output (MIMO) system and a fixed PWM at 2.34 kHz is used to generate the gating signals of the power devices. The system is tested for harmonics, reactive power and load unbalance compensation for balanced/unbalanced loads. The simulation results obtained with SPS and Simulink of Matlab show good performance in terms of overall DC bus voltage regulation, DC bus voltage unbalance compensation (small overshoot and very fast time response) and a low total harmonic distortion (THD) of ac line currents.

LQR with Integral Action to Enhance Dynamic Performance of Three-Phase Three-Wire Shunt Active Filter

This paper presents the design of a Linear Quadratic Regulator (LQR) with Integral action (LQIR) to improve dynamic performance of a three-phase three-wire shunt active power filter (SAF). The integral action is added to cancel the steady state errors knowing that the standard LQR provides only proportional gains. The controller is designed to achieve DC bus voltage regulation, harmonics and reactive power compensation. The converter model is set in the dq rotating reference frame augmented with the integral of q component of the SAF currents and DC bus voltage. The performance of the controller depends on the weightening matrix which is chosen to guaranty satisfactory responses. The converter is controlled as a whole and a fixed PWM at 2.34 kHz is used to generate the gating signals of the power devices. The system is tested for both active and reactive power variations of the combined linear and non-linear load, for a distorted/unbalanced voltage source, and for unbalanced loads. The Simulation results obtained show good performance in terms of the DC bus voltage regulation (small overshoot and very fast time response) and low total harmonic distortion (THD) of ac line currents.

Optimal control of a grid connected variable speed wind energy conversion system based on squirrel cage induction generator

This paper presents the design of a Linear Quadratic Regulator (LQR) with Integral action (LQRI) applied to a grid connected wind energy conversion system (WECS) based on squirrel cage induction generator (SCIG) with full-capacity power converter (WECS-SCIG). The controller is used to achieve speed regulation for maximum power extraction from the wind turbine, DC bus voltage regulation and to keep the power factor at unity for the grid-side converter. The model of this latter is set in the d-q rotating reference frame synchronized with phase a of grid voltages while rotor flux oriented vector control is used for the machine-side converter. Knowing that the standard LQR provide essentially proportional gains, the system dynamic is augmented with the integral of the q component of the grid currents, the rotor flux, the DC bus voltage and the generator speed in order to cancel steady-state errors. The WECS-SCIG is controlled as a whole i.e. a multi-input-multi-output (MIMO) system and a fixed PWM at 2.7 kHz is used to generate the gating signals of the two back to back converters. The system is tested for both steady-state and in transient for a sudden variation in wind speed. The simulation results obtained with SimPowerSystems (SPS) and Simulink of Matlab implementation of the controller proved the effectiveness of the control strategy.

LQR with integral action applied to a wind energy conversion system based on doubly fed induction generator

This paper presents the design of a Linear Quadratic Regulator (LQR) with Integral action (LQRI) applied to a wind energy conversion system (WECS) based on doubly fed induction generator (DFIG). The controller is used to achieve speed regulation for maximum power extraction from the wind turbine, DC bus voltage regulation, to make the machine draw its magnetizing current only from the stator and to keep the power factor at unity for the grid-side converter. The model of this latter is set in the d-q rotating reference frame synchronized with phase a of grid voltages while stator flux oriented vector control is used for the rotor-side converter. Knowing that the standard LQR provide essentially proportional gains, the DFIG dynamic is augmented with the integral of the q component of the grid-side converter currents, the d component of the machine-side converter currents, DC bus voltage and machines speed in order to cancel steady-state errors. The DFIG is controlled as a whole i.e. a multi-input-multi-output (MIMO) system and a fixed PWM at 5 kHz is used to generate the gating signals of the two back to back converters. The system is tested for both sub-synchronous and super-synchronous speed and the simulation results obtained with Sim Power System (SPS) and Simulink of Matlab implementation of the controller proved the effectiveness of the control strategy.

LQR with Integral Action for Phase Current Control of Constant Switching Frequency Vienna Rectifier

This paper deals with the design of a linear quadratic regulator (LQR) with integral action (LQIR) to improve dynamic performance of a three-phase Vienna rectifier. The integral action is added to cancel the steady state errors knowing that the standard LQR controller provides only proportional gains. The controller is designed to achieve overall output voltage regulation, DC load unbalance compensation and unity power factor. The converter small-signal model is in the dq rotating reference frame augmented with the integral of the q-component of input currents; overall output voltage and DC load unbalance. The performance of the controller depends on the weightening matrix which is chosen to guaranty satisfactory responses. The converter is controlled as a whole which provides the input current references and a fixed PWM at 2.04 kHz is used to generate the gating signals of the power semiconductors. Simulation results obtained using Matlabreg/Simulink are presented to confirm the validity of the proposed controller design. The system is tested for a balanced load at rated power, in case of unbalanced load and for mains voltages perturbations and shows good performance in terms of the overall DC output voltage regulation, DC load unbalance compensation (small overshoot and very fast time response) and small total harmonic distortion (THD) of line currents

A simple control method for modular multilevel converters

In this paper a simple control method involving new insertion index selection scheme for control of Modular Multilevel Converters (MMC) is proposed. In contrast with classical closed-loop methods, where all available arm voltages are measured and used in the generation process of insertion indices, this method uses available average voltage, i.e. the arithmetic mean of available upper and lower arm voltages per leg. Thus, number of measured signals to be fed back are reduced to half. Moreover, development of available arm voltage ripple expressions along with the thorough evaluation of the proposed insertion method impact on arm voltages driving input- and output-currents are presented and discussed. Finally, analytical findings along with simulation results proved the effectiveness of the proposed method.

D-Q frame optimal control of single phase grid connected inverter with LCL filter

The aim of this paper is to present the design of a linear quadratic regulator (LQR) based on optimal control of single phase grid connected inverter with an LCL output filter used in solar applications. The converter model is set in the D-Q rotating reference frame where integral action is added to the grid current in order to cancel steady state error. The controller is tested in steady state, dynamic regime and for parameter variations. The simulation results carried out showed good performance and robustness of the adopted controller.