Nicolas Patin

A New PWM Strategy to Reduce the Inverter Input Current Ripples

This paper deals with an innovating pulsewidth modulation (PWM) strategy allowing reduction of the DC input current ripples in classical operating area of adjustable-speed drives, and also maintaining a good quality of AC current waveforms and limited switching losses in the inverter. Thus, such a strategy is an interesting solution within embedded systems. Theoretical principles of the proposed method are introduced. Then, simulation results highlight the benefits of this algorithm compared to classical PWM control. Finally, a DSP-base implementation has been performed, and effectiveness of this strategy is confirmed by experiments for a starter-generator application.

A Direct Digital Technique Implementation of General Discontinuous Pulse Width Modulation Strategy

This paper presents direct digital technique-generalized discontinuous pulse width modulation (PWM) - a new implementation method for an optimal discontinuous PWM (DPWM) in terms of switching losses of the inverter on an embedded system. At each sampling period, an optimal choice is done in order to clamp one of the three half-bridges. Its advantages compared to classic ones (DPWM) are as follows: needless to know the load power factor, operational under steady-state and dynamic operating conditions, and low computation time. The proposed algorithm is then verified by simulation. Experimental results, based on a resistance-inductance load and a starter-generator application, are provided to show its effectiveness.

Modeling and Control of a Cascaded Doubly Fed Induction Generator Dedicated to Isolated Grids

This paper deals with the control of an autonomous cascaded doubly fed induction generator (CDFIG) operating in a variable speed constant frequency (VSCF) mode. The proposed structure is a full stand-alone generating system dedicated to isolated grids for embedded systems such as aircraft or small-scale renewable-energy systems such as microhydropower generators. Compared to a traditional VSCF system based on a single DFIG, CDFIG allows suppressing brushes, leading to an easier maintenance. However, the main difficulty when working with such a structure is its inherent complexity. The major issue is to synthesize an efficient global-control strategy for these two strongly connected machines. To overcome this problem, a modeling methodology based on dynamical equivalent circuits is given in this paper for the design of the CDFIG controller. Presented simulations and experimental results validate the proposed design approach.

Modeling and control of a cascaded doubly-fed induction generator based on dynamical equivalent circuits

This paper deals with the control of an autonomous cascaded doubly-fed induction generator operating in a variable speed constant frequency mode. The proposed structure is a full stand-alone generating system dedicated to isolated grids in embedded systems or in small-scale renewable energy systems such as windmill and hydropower generators. The study is focused on the CDFIG. Its behavior against several design parameters (numbers of pole pairs and rotor interconnection) is recalled. A model, based on dynamical equivalent circuits, is also given for the design of the controller. Finally, the synthesized controller is validated by simulations and experimental results.

PWM strategy dedicated to the reduction of DC bus capacitor stress in embedded three phase inverter

This article proposes a new PWM strategy, called Unified Double Carrier PWM (Uni-DCPWM), which allows one to reduce DC link capacitor RMS current value of an embedded low voltage three phase voltage source inverter. Instead of using 2 adjacent active vectors and zero vectors to balance the reference vector in terms of volt-second at each switching period as in most of PWM strategies in the literature, this strategy uses 3 consecutive active vectors (at high voltage level) or 2 non-adjacent active vectors and a zero vector to reproduce the reference vector. Analytical calculations show that this strategy effectively reduces DC link capacitor RMS current value comparing to Space Vector PWM (SVPWM) for high power factor loads. However, RMS value of load current harmonics due to switching of this strategy is higher than SVPWM. This strategy is adapted to volume constrained environment such as automobile.

Active filtering applied to a doubly-fed induction generator supplying nonlinear loads on isolated grid

Variable speed and constant frequency (VSCF) generators are widely used in industry (e.g. embedded applications and renewable energy systems). Doubly-fed induction generators (DFIG) allow a such operation. Moreover, this kind of machines can be driven by a low power converter in comparison to the power provided to the grid. But on isolated grid, a efficient controller is needed in order to maintain quasi-sinusoidal voltages with an important amount of nonlinear load and with a small passive filter. The aim of this paper is to present a new design methodology based on the inversion of the dynamical model of the system. It also uses an original representation of the system called dynamical equivalent circuit. Thus, a hierarchical controller is designed and validated by simulation

A methodology for studying aluminum electrolytic capacitors wear-out in automotive cases

Electrolytic aluminum capacitors used in electric drive for automotive are deemed to be the weakest components of static power converters. A lot of studies have been made to estimate their aging but only for a nominal point. This paper presents a specific operation cycle implementation to study the impact of a variable and more realistic thermal cycling. Moreover, an improvement of the classical electrical model for an electrolytic capacitor is proposed by adding a diffusion-relative element called “anomalous diffusion”. Experimental results show the interest of this element for an impedance-fitting. Finally, thermal measurements validate thermal cycling simulations.