Laurent Rambault

Linear Feedback Control of a Parallel Active Harmonic Conditioner in Power Systems

Harmonics are one of the major quality concerns. The increasing use of power semiconductor devices (i.e., nonlinear loads) is keeping harmonic distortion in electrical installations on the rise. Harmonics generally cause the distortions of voltage and current waveforms, which result in many harmful effects on both utilities and customers. A parallel active harmonic conditioner can be used to compensate current harmonics demanded by nonlinear devices so that the supply current remains quasi-sinusoidal. In principle, this conditioner consists of a voltage-source inverter connected in parallel between the utility system and the customer. The control of such an inverter is an essential step in harmonic compensation. Most of the existing control methods are formulated as a classical tracking problem that requires reference generation. In a previous work, a parallel active harmonic conditioner was formulated as a perturbation rejection problem rather than a reference tracking one, and a linear state feedback H infin controller was synthesized in order to drive the inverter. The objective of this paper is to reduce the number of measured outputs, and therefore to design a linear output feedback H infin controller by noniterative means. The robustness of such a controller with respect to the system impedance uncertainties is investigated. Moreover, the validity of the synthesized output feedback control law is revealed through both simulation and experimental results.

Linear closed-loop control of active power filter

This paper presents a parallel active power filter which is intended for eliminating the unwanted harmonics. A novel linear model of a three-phase network is proposed and allows the use of tools developed for linear control theory. Moreover, with the same tools, uncertainties of physical parameters can be taken into account. Theoretical analysis, complete simulation of the system and experimental results are presented to confirm the validity of the proposed technique

IP Controlled Three-Phase Shunt Active Power Filter for Power Improvement Quality

The simulation and experimental study of new IP (integrator proportional) controlled DC bus voltage of three phase shunt active power filter (APF), to improve power quality by compensating harmonics and reactive power required by nonlinear load is proposed. The compensation process is based on sensing mains currents only, an approach different from conventional methods, which require harmonics or reactive volt-ampere values of the load. The not sinusoidal mains voltage form problem is resolved by using PLL system. PWM signal generation is based on hysteresis control comparators to obtain the switching signals. Various simulation and experimental results are presented under steady state and transient conditions

H Control Design Methodology for a Three-Phase Active Power Filter

In this paper, an Hinfin control design methodology is presented in order to synthesize a full-order dynamic output feedback controller for an active power filter connected in parallel to a three-phase voltage distribution system. A shunt active filter is usually used to improve power quality by eliminating harmonic distortion generated by non-linear and switching loads. In order to be able to extract desired harmonics, the multivariable system is described by a linear coupled state space representation in a rotating two-phase framework. The originality of this paper is that axes decoupling is achieved by representing the system in a new complex framework in which the model is mathematically decoupled and therefore physical decoupling can be avoided. Moreover, the validity and efficiency of the proposed methodology are proved through numerical simulations.

Frequency measurement with high accuracy and method for harmonics identification in polluted distribution power networks

As demands for high quality, reliability and usability of electrical power source are increasing and essential, many studies investigate algorithms of harmonic source detection. To evaluate the quality of electrical network, a method for fundamental frequency and harmonics characteristics with high accuracy is proposed. The interest of this work is to control the stability, safety and efficiency of an electrical network with fast and accurate estimation of the fundamental frequency and harmonic distorsion. In practical cases, the fundamental frequency is considered uncertain. Its deviation induces large perturbation on high range harmonics. To alleviate this drawback, we consider the fundamental frequency as an uncertain frequency and suggest a method to evaluate its value with high degree of accuracy. From this correct numerical value of the fundamental frequency, all magnitude and phase of harmonics are estimated with higher precision. Thus, this paper deals with the identification of fundamental frequency and selective harmonic identification. The method developed is derived with the Fourier series for fundamental frequency and on the Discrete Fourier Transform (DFT) for harmonics. Outset, we will focus just on the first coefficient of the Fourier series not to perform the magnitude and phase, but to explain a condition that allows to reach the real value of fundamental frequency. The algorithm is an iterative one. The result is presented in continuous case and in discrete case. After, the DFT method is applied to obtain magnitude and phase of fundamental and harmonics. The simulation and experimental results show the ability of the developed algorithm.

Direct power control of shunt active filter

This paper presents a new control method entitled direct power control (DPC) for shunt active power filtering, which is applied to eliminate line current harmonics and compensate reactive power. Its main goal is to rebuild active and reactive powers to be compared to references values using hysteresis control. The outputs of hysteresis controllers associated with a switching table, control the instantaneous active and reactive power by selecting the optimum switching state of the voltage source inverter (VSI). A theoretical analysis with a complete simulation of the system and experimental results are presented to prove the excellent performance of the proposed technique.

A Novel Control System for a Three-Phase Shunt Active Power Filter

In this paper, the validity of a linear complex-valued model proposed for describing a three-phase shunt active filter used to improve the quality of the electrical energy, and the ability of the Hinfin control design tool to provide a robust controller capable of compensating current harmonics demanded by switching loads are confirmed through numerical simulations. At a first time, ideal ones are performed by considering the pulse-width modulated voltage source inverter of the active filter as a simple gain. Then, a prototype of an active filtered three-phase power distribution network is built in Simulink in order to reveal difficulties that may be encountered in a real implementation and how one can overcome them. After taking into consideration the modifications required to avoid these difficulties, experimental results based on a laboratory prototype are provided to verify the effectiveness of the control algorithm.

Multivariable output feedback stabilisation with structure constraint: application to a gyrometer

In this paper, the problem of static output feedback control of a linear system is considered. This method allows to design a PID controller in order to taking into account the industrial context. The proposed algorithm is used to perform a multivariable PID controller applied to design a sensor. The system, a gyrometer, is an angular velocity sensor used as instrument of navigation for aeronautics. The numerical results presented are obtained from real system and real time board.

Linearizing Control of an Induction Motor Subjected to Parameter Variation

A linearized feedback system with a reference model is designed for a nonlinear squirrel induction motor subjected to resistance and inductance deviations. The use of a reference model maintains the decoupling between the rotor speed regulation and that of the rotor flux modulus despite parameter variation, which yields the independence of their dynamics. A comparison test is carried out to illustrate the usefulness of the reference model.A linearized feedback system with a reference model is designed for a nonlinear squirrel induction motor subjected to resistance and inductance deviations. The use of a reference model maintains the decoupling between the rotor speed regulation and that of the rotor flux modulus despite parameter variation, which yields the independence of their dynamics. A comparison test is carried out to illustrate the usefulness of the reference model.

H∞ Static Control Law for a Three-phase Shunt Active Power Filter

Abstract The aim of this work is to design a static feedback gain used to force a three-phase shunt active power filter to act as a current source capable of delivering the appropriate harmonics demanded by non-linear loads. This filter is connected in parallel to a three-phase power distribution system in order to keep the current supplied by the latter almost sinusoidal. The control design is performed using the H ∞ suboptimal control theory based on linear matrix inequalities (LMIs), with both partial and full state feedback. Numerical simulations will be presented in order to investigate the advantages of the full state feedback structure over the partial state feedback one, and to compare the performances of the corresponding H ∞ static control laws.