The paper focuses on estimating the rectifier current in slim DC-Link AC drives, known for their reduced DC-Link capacitance. Particularly, at full load, the capacitor’s filtering effect on the input voltage diminishes. This allows the estimation of the input voltage from DC-Link voltage measurements. We adopt a simplified model, treating the drive as a DC-Link that supplies a constant power load. Notably, the model accounts for the equivalent series resistance (ESR) of the capacitor, adding intricacy to the design. We propose an adaptive observer to estimate both the rectification current and the input voltage. We design a Luenberger state observer with output injection terms. The study on the observer stability is based on decoupling the state estimation errors from the input estimation errors through swapping design. Theoretical developments are validated through numerical simulations.

This paper proposes a fundamental-model-based observer to estimate the state and load torque of an induction motor. It relies on a novel representation of the motor model, namely a cascade of two linear-time varying systems with known input terms, to which a "true" Kalman filter is applicable. The interest is that the global convergence of the observer can be guaranteed, moreover without any two-time-scale assumption. The good behavior of the observer is illustrated on numerical and experimental data of a motor startup with a soft starter.

We propose a novel observer for speed and torque estimation in induction motors, using only electrical measurements and assuming the parameters known. The design is based on a novel representation of the motor model taking the form of a cascade of a flux subsystem and a velocity subsystem with known injection terms. After giving sufficient conditions for the uniform strong observability of those subsystems, we exploit the KKL approach to design a globally asymptotically stable observer without relying on any time-scale separation. We provide a method to optimize the observer parameters and illustrate its performance on simulation in a realistic scenario.

This chapter addresses the estimation of the Total Harmonic Distortion (THD) of the drive input current, which is an interesting performance indicator of the variable speed drive. The analysis of the complete drive system is done (study of the dynamic model of the DC bus and its stability, frequency analysis of the input signals). A simplified estimator of the THD is proposed to be able to embed the calculation algorithm in real-time Drive control load with good accuracy and depending on the conduction mode of the DC choke (continuous or discontinuous).

Variable speed drives often contains a DC link with a passive filter to decrease the Total Harmonic Distortion of the input currents. Unfortunately the interaction of the motor with this filter may yield an undesirable sustained oscillation in the DC link. We propose a simple yet effective strategy to avoid this phenomenon, by suitably manipulating the inverter duty cycles. The stability analysis, based on the mathematical theory of averaging, is interesting in itself as a means to study oscillations in power systems.

We revisit higher-order averaging and ripple computation for DC-DC converters in Continuous Conduction Mode, following the modern treatment of periodic averaging theory. We give a much simpler treatment of second-order averaging and ripple computation than usually found in the power electronics literature. We also extend it to third-order averaging, thus significantly improving the accuracy of the approximations, which is useful in particular when the switching frequency is not very high.

SummaryA gradient descent‐based nonlinear observer for surface‐mount permanent magnet synchronous motors with remarkable stability properties was recently proposed. A key assumption for the derivation of the observer is the knowledge of the electrical parameters, which are usually uncertain. In the present paper, we propose a robust adaptive flux observer adding immersion and invariance parameter adaptation algorithms to estimate the stator resistance. Global boundedness of all signals and convergence to a residual set of the flux estimation error is guaranteed. The performance of the new adaptive observer is assessed with realistic simulations. Copyright © 2015 John Wiley & Sons, Ltd.

Operation of induction machines in the high-speed and/or high-torque range requires field-weakening to comply with voltage and current physical limitations. This paper presents an anti-windup approach to this problem: rather than developing an ad-hoc field weakening strategy in the high-speed region, we equip an unconstrained vector-control design with an anti-windup module that automatically adjusts the current and flux set-points so that voltage and current constraints are satisfied at every operating point. The anti-windup module includes a feedforward modification of the set point aimed at maximizing the available torque in steady-state and a feedback modification of the controller based on an internal model-based antiwindup scheme. This paper includes a complete stability analysis of the proposed solution and presents encouraging experimental results on an industrial drive.

A gradient descent-based nonlinear observer for surface-mount permanent magnet synchronous motors (PMSMs) with remarkable stability properties was recently proposed in [7]. A key assumption for the derivation of the observer is the absence of rotor saliency, which is the case in surface-mount PMSMs. Practically, PMSMs have saliencies from low level for surface-mount PMSMs to high level for internal-mount PMSMs. A question of great practical interest is to firstly assess the performance of the observer in the presence of saliency, and secondly to propose way of enhancement to take this effect into account. This is the topic of study of the present paper. We show in simulation the performance of the different observers.

Energy saving is a concern of increasing importance in the operation of electrical drives and has become a primary motivation to equip pumps and fans with inverters, that allow speed operation away from the nominal set point. The present paper underlines the merits of extremum seeking, a popular adaptive control method, for online optimization of energy efficiency by adapting the flux to the motor speed. The benefits of the method are illustrated experimentally on a commercially available inverter.