Jordi Espina

Reduction of Output Common Mode Voltage Using a Novel SVM Implementation in Matrix Converters for Improved Motor Lifetime

This paper presents the study of an alternative space vector modulation (SVM) implementation for matrix converters (MCs), which reduces the output common mode (CM) voltage. The strategy is based on replacing the MC zero vectors with rotating ones. In doing this, the CM voltage (CMV) can be reduced, which, in turn, reduces the CM leakage current. By reducing the CM current, which flows inside the motor through the bearings and windings, the induction motor (IM) deterioration can be slowed down. This paper describes the SVM pattern and analyzes the CMV and the leakage current paths. Simulation and experimental results based on an MC-IM drive are provided to corroborate the presented approach.

Speed Anti-Windup PI strategies review for Field Oriented Control of Permanent Magnet Synchronous Machines

The work presented in this paper addresses the unwanted windup phenomenon reviewing and comparing different PI anti-windup strategies employed in speed control of electric drives. The tuning process of PI controllers is usually carried out considering the system as linear and therefore disregarding its physical limits such as maximum current and voltage. To safeguard the systems integrity, the PI output is normally limited eventually causing the windup phenomenon characterized by long periods of overshoots which may even result in instability.

Common Mode EMI Model for a Direct Matrix Converter

This paper presents an electromagnetic interference (EMI) model to evaluate the conducted common mode (CM) disturbances produced by matrix converters (MCs). The model is based on obtaining a high frequency (HF) equivalent circuit with HF sources representing the switching devices. The circuit resolution in the frequency domain allows the calculation of any EMI parameter with very low computational burden and avoids convergence problems, which are common in time domain methods. The original contribution lies in the source model implementation and placement. The simulation and experimental results for CM leakage currents validate the EMI model.

Predictive Direct Torque Control of Matrix Converter fed Permanent Magnet Synchronous Machines

A predictive Direct Torque Control method for Matrix Converters fed Permanent Magnet Synchronous Machines drives is proposed in this paper. The voltage vector from the Matrix Converter which ensures minimum torque ripple is selected based on a predictive algorithm. A look-up table for Direct Torque Control using Matrix Converters has been developed which delivers a set of three vectors, at every sample period, that fulfil the torque and flux demands. The predictive algorithm computes the torque error that would be present applying each vector and selects the one that contributes with the minimum error. Simulation results, which confirm the good performance of the proposed predictive Direct Torque Control using Matrix Converters are shown.

Predictive vector selector for Direct Torque Control of Matrix Converter fed Induction Motors

In this paper, a Direct Torque Control method for Matrix Converters fed Induction Motors is proposed. A predictive algorithm which ensures minimum torque ripple is employed for the selection of the appropriate voltage vector from the Matrix Converter. A new look-up table for Direct Torque Control using Matrix Converters has been developed which delivers a set of three vectors, at every sample period, that fulfil the torque and flux demands. The predictive algorithm computes the torque error that would be present applying each vector and selects the one that contributes with the minimum error. Simulation results, which confirm the good performance of the novel predictive Direct Torque Control using Matrix Converters are shown.

EMI model of an AC/AC power converter

This paper deals with the validation of an EMI model to predict electromagnetic interferences (EMI) produced by power converters. A direct AC to AC matrix converter (MC) has been selected as experimental setup for the paper, but the modeling method can be applied to other converter topologies. The method is based on obtaining a high frequency equivalent circuit, using a combined time and frequency domain approach based on: “EMI source identification→ propagation path impedance→ derived disturbance”. The advantages of the proposed procedure are the computational time reduction and the lack of convergence problems, which may arise when using pure time domain procedures. The paper is focused on the prediction of common mode (CM) EMI of a matrix converter. The simulation results of this case will permit the calculation of currents which leak through the ground connections. Two different EMI sources are compared: one based on PWM waveforms obtained from MATLAB® model and a second one where these data are obtained experimentally from a MC prototype. This procedure allows the comparison of EMI spectra when using simulated waveforms or real source waveforms.

Efficiency Evaluation of Fully Integrated On-Board EV Battery Chargers With Nine-Phase Machines

A fully integrated on-board battery charger for future electric vehicles (EVs) has been recently introduced. It reutilizes all the propulsion components of an EV in charging/vehicle-to-grid (V2G) modes, it does not require any additional components or hardware reconfiguration, and charging/V2G modes are realized with zero electromagnetic torque production. Both fast (three-phase) and slow (single-phase) chargings are possible, with unity power factor operation at the grid side. The solution is based on the use of a triple three-phase machine and a nine-phase inverter/rectifier. This paper reports on the results of efficiency evaluation for the said system. Testing is performed using both a nine-phase induction machine and a nine-phase permanent magnet machine for a range of operating conditions in charging/V2G modes, with both three-phase and single-phase grid connection. Additionally, the impact of converter interleaving on the losses and efficiency is also studied. Losses are separated for different subsystems, thus providing an insight into the importance of optimization of different EV power train components from the efficiency point of view. Promising efficiencies, in the order of 90%, are achieved although none of the system components have been optimized.

Design and Initial Testing of a High-Speed 45-kW Switched Reluctance Drive for Aerospace Application

This paper presents innovative research toward the development of a 45-kW high-speed switched reluctance drive as an alternative starter-generator for future aeroengines. To perform such a function, the machine had to be designed with a very wide constant power-speed range. During engine-start/motoring mode, a peak torque demand of 54 N · m at 8 kr/min was met, while in generating mode, 19.2-32 kr/min, the machine was designed to deliver a constant power of 45 kW. The key enabling feature of the design lies in the novel rotor structure developed so as to allow for such a wide speed range. The results presented are those measured during the initial testing phase and validate the system design and performance in the low-speed region with the machine operated in starting mode. The measured machine power density is at 9.8 kW/L, while the global system efficiency is at 82%.

Space Vector Modulation strategy to reduce the Common Mode perturbations in Matrix Converters

An alternative Space Vector Modulation (SVM) strategy which reduces the Common Mode (CM) perturbations when using Matrix Converters (MC) is presented in this work. The proposed method maintains the conventional SVM pattern but the zero vectors, which have been shown to introduce not only high CM voltage values but also high CM voltage time derivative. Hence the three zero vectors are replaced by three rotating ones, in such a way that the fundamental output voltage vector and the input current direction remains both unchanged. Results of the proposed SVM strategy driving a Permanent Magnet Synchronous Machine (PMSM) are provided to confirm the effectiveness of the method.

Highly-integrated power cell for high-power wide band-gap power converters

The fast switching speeds and low specific conduction losses of wide band-gap semiconductors allow the realisation of high-frequency, high power-density switching converters with dramatically reduced passive component requirements compared to Silicon technology. However, careful attention must be paid to switching cell design to mitigate the effects of circuit parasitics and fast voltage transitions which would otherwise limit the attainable switching speed and lead to increased levels of EMI. This paper presents a modular, power-cell solution which allows the creation of any two-level topology converter. The cell structure enables fast switching of wide bandgap semiconductor devices while allowing high power converters to be fabricated using multiple, smaller commutation cells. Close integration of semiconductor dies, decoupling capacitors, gate drives and an output filter with a single ceramic substrate to act as the thermal path allows dramatic increases in power density without compromising converter performance.