Jean-Marie Rétif

Permanent Magnet Synchronous Machine Hybrid Torque Control

This paper presents a control scheme suitable for systems composed of a continuous process modulated in energy by a power converter with a finite number of topologies. To track the continuous reference values, a topology of the power converter is determined from a criterion based on a process state variable model and taking into account the possible topologies of the power converter. The proposed hybrid control scheme is applied to an electrical motor drive composed of an inverter coupled to a permanent magnet synchronous machine. An evolution which insures a fixed modulation frequency is also proposed. Experimental results validate the feasibility and effectiveness of the proposed schemes.

A Digital-Controller Parameter-Tuning Approach, Application to a Switch-Mode Power Supply

Analogue control of monolithic DC/DC converters is technologically coming to a limit due to high switching frequency and a request for large regulation bandwidth. Digital control is now experimented for low-power low-voltage switch-mode power supply. Digital implementation of analogue solutions does not prove real performances. This paper compares a classical digital controller to a candidate alternative strategy. Sensitivity functions are used to compare controller performances. An off-line approach using fuzzy logic to quantify controller performances and a genetic algorithm to obtain an optimal controller is presented. A so-called RST algorithm optimized with this approach shows better performances.

A predictive control for a matrix converter-fed permanent magnet synchronous machine

Many research efforts have been dedicated to matrix converters for several years. As major technological issues are now solved, this structure will widespread in industrial applications, in particular with AC motors. Current control is a key issue for AC motor drives, so many control schemes have been proposed. Some of them proposed at first for inverters, were applied to matrix converters. Among algorithms used with inverters, predictive control shows very good performances. In this paper a new control scheme is proposed for a matrix converter- fed permanent magnet synchronous machine. Literature about matrix converter technology and control and about predictive control for inverter-fed AC machines is reviewed. The proposed predictive control principle, the model of the whole machine - converter and the cost-function are detailed. The method offers a trade-off between the quality of motor currents and input power factor. Finally experimental results are reported. The feasibility and the effectiveness of the proposed method is assessed.

Hybrid control of a three-cell converter associated to an inductive load

This paper presents a control scheme for a multilevel multi-cell converter. For this type of converters, load current and capacitor voltages must be jointly controlled. Moreover the real-time constraint is important. This constraint leads us to propose a control based on a simplified state-space model. The model allows predicting the state vector evolution for every converter configuration. The control algorithm directly determines the converter switching state which minimizes a simple cost function. A normalization of the state variables is proposed for the cost function calculation in order to ensure a trade-off between the tracking of the load current and the tracking of the capacitor voltages. The proposed control scheme is detailed and compared with a classical control scheme with simulations. Finally, experimental results are presented to show the effectiveness of the proposed method.

Comparative study of two Predictive Current Controls for a Permanent Magnet Synchronous Machine drive

This paper presents the experimental results-based comparison of two predictive current controls (PCC) for permanent magnet synchronous machines (PMSM) drives. The first tested control scheme is based on a model including the inverter and the PMSM and taking into account the discrete nature of the inverter leg states. It predicts the future evolution of the currents for each possible configuration of the inverter. The switching state which minimizes a given cost function is selected. The selected inverter state is applied during the next sampling time. The second tested control scheme uses a model of the PMSM to predict the output voltages which allow to reach desired currents after one modulation period. A new algebraic method is presented to directly compute the duty cycle of each leg. Then a modulator generates the corresponding gate drive pulses of the inverter. These two control schemes are tested with a 1.6 kW PMSM drive at several operating points during steady state and transient operation. A detailed comparison of results is given. Advantages and drawbacks of each method are discussed.

Predictive Current Control for an Induction Motor

This paper presents a predictive current control (PCC) strategy applied to an induction motor (IM) drive. In contrast to conventional vector control, where the inverter is not taken into account by the controller, the PCC considers the state of the inverter as a discrete control variable. Based on a simplified state space model of the IM and the inverter, the proposed control scheme calculates the state vector evolution direction in the d- and q-reference frame for all possible switching states of the inverter. The switching state which minimizes a given cost function is selected and is applied during an adapted duration which is calculated for each computation cycle. As the control requires the knowledge of the instantaneous rotor fluxes and in order to improve the control robustness, a reduced-order extended high gain observer is proposed for estimation of rotor fluxes and inverse rotor time constant. The simulation results validate the observer. The controller is implemented on a 5.5 kW IM drive with a digital-signal-processor (DSP) on a DSpace1103 board. Experimental results show the effectiveness and the performances of the proposed control.

A PWM ASIC using stochastic coding

The authors describe an application-specific integrated circuit (ASIC) design implementing a novel pulse width modulation (PWM) technique. This PWM function is based on the stochastic coding of the driving pulses. This approach allows a small IC area and high-speed generation of pulse sequences. The validity of the proposed PWM has been studied with simulation and experiment. Several limiting operation conditions of the ASIC are also defined. Using the stochastic PWM a three-voltage inverter is shown to be a more efficient solution than the classical PWM and a dual-voltage inverter; fewer harmonics are generated in current and voltage.<<ETX>>

A New Direct Current Control for a Permanent Magnet Synchronous Machine

Abstract In this article, a new direct current control (DCC) is presented. Currents directly control the torque in a permanent magnet synchronous machine (PMSM). As with conventional direct-torque control (DTC), the control variable of the proposed DCC is directly the inverter switching state, so similar fast torque dynamics are obtained. However, hysteresis controllers and switching tables are not used here. Based on a simplified state-space model of a PMSM, including the inverter switching states, the proposed control scheme selects a set of three configurations and calculates their respective application times in order to obtain the desired state vector with a fixed switching frequency. The design of the proposed controller is fully discussed. Comparative studies with DTC are performed on a 1.6-kW PMSM drive with a digital signal processor (DSP) system. Experimental results prove the superior performances of the proposed control.

Non-linear control design for a boost converter using bond graphs

Abstract The bond graph technique is applied to model a boost converter in order to derive an averaged model. The obtained averaged model is non-ideal as it takes into account most of the converter non-linearities introduced by power semiconductor devices. An ideal averaged model of the converter can be deduced easily for computing a non-linear control law in a real-time control context. The current-mode control of the boost converter is considered. The zero dynamics are studied by both classical theory and the bond graph approach. A modified version of a conventional nonlinear control law is proposed in order to improve the dynamic behaviour and to reduce the sensitivity to control model errors. The non-ideal averaged model is used firstly for simulation analyses of the proposed control law and then for comparison with experimental results.

Modeling and Implementation for Embedded DC Motor Ethernet Control System

In this paper, a model of Embedded DC Motor Ethernet Control System is proposed with analysis on transmission time delay and data packet dropout. Based on this model, the ECS is described as a two-state asynchronous dynamical system with output feedback control and then implemented on a platform which uses a PC as a central controller and an ARM9 kit as a remote controller. As a key part of developments, embedded programs including client program and Linux Module are realized on the kit. The platform is proved to be flexible to run different control algorithms and extensibility to add nodes. The experiments and results demonstrate the validity of the system.