Stefan George Rosu

Maximum Efficiency per Torque Direct Flux Vector Control of Induction Motor Drives

In this paper, a loss-minimizing strategy is proposed for induction motor drives to ensure maximum efficiency operation for a given torque demand. The proposed strategy directly regulates the machine stator flux, according to the desired torque, using an optimal stator flux reference. Therefore, the proposed strategy is suitable for motor control schemes that are based on direct flux regulation, such as direct torque control or direct flux vector control. The maximum efficiency per torque (MEPT) stator flux map is computed offline using the traditional no-load and short-circuit test data. An iron loss model based on the stator flux and frequency is also proposed for the calibration of the machine loss model and also for online monitoring of the iron losses during motor operation. The proposed MEPT strategy has been validated on a 2.2-kW induction machine, and the motor efficiency has been measured for different speed values and variable load conditions. The experimental results confirm the effectiveness of the proposed solution.

Identification of the Magnetic Model of Permanent-Magnet Synchronous Machines Using DC-Biased Low-Frequency AC Signal Injection

This paper proposes a simple procedure for accurate identification of the magnetic model of permanent-magnet synchronous machines through inverter supply. The proposed method accounts for the magnetic saturation and the cross-saturation effects. The identification methods reported in the literature may require a servomotor to drive the motor under test at controlled constant speed or the motor itself must accelerate and decelerate. The technique proposed here can be applied at standstill with or without rotor locking and uses a dc+ac injection strategy to identify the machine inductances to construct its magnetic model. The direct current sets the operating point, whereas the superimposed ac component estimates the inductance at that particular point. Small ac signal is injected to ensure local linearity of the magnetic characteristic. Saturation effects are automatically accounted for by the dc bias level, and cross-saturation effects are quantified through maintaining a constant current along the cross-axis. The magnetic model thus obtained can be used for optimal control of the machine and for accurate torque estimation in vector-controlled drives.

Implementation of a three-phase active power filter with sliding mode control

In this paper a three-phase shunt active power filter with sliding mode control is presented. The reference current is determined in a simple manner by multiplying each phase voltage with a factor depending on the power absorbed by the nonlinear load. Sliding mode is analyzed on each phase considering the interactions between the three phases. The system was simulated and implemented. The experimental results confirm the simulation results.

Performance evaluation of wireless power transfer systems for electric vehicles using the opposition method

The present paper proposes the use of the opposition method to evaluate the performance of a wireless power transfer system. The work is focused on the effect related to the insertion of conductive or ferromagnetic components that are materials typically adopted in the realization of this kind of systems.

Load identification in dynamic wireless power transfer system utilizing current injection in the transmitting coil

In this paper, a load identification approach for dynamic wireless power transfer for electric vehicles is introduced. In the proposed method, determination of the load parameters and position are achieved without requiring any communication link between the transmitter and receiver or using any extra coil. The load detection procedure is achievable using two modes: the energy injection mode and the free resonant mode. The operating principles and theoretical analysis of this method are presented in this paper, together with experimental results.

A dynamic wireless charging system for electric vehicles based on DC/AC converters with SiC MOSFET-IGBT switches and resonant gate-drive

This paper presents a high-performance dynamic Wireless Power Transfer (WPT) system for electric vehicles, which has high efficiency and the potential for large scale deployment. The detailed single stage 22kW DC/AC converter design of the transmitter side is presented. The converter is connected to a series-series WPT compensated system and has features like hybrid switches with fast 0-Ω gate-drive circuit for the SiC MOSFET and resonant gate-drive circuit for the IGBT, which allows operation without ZVS switching. Experimental results are presented to confirm the correct operation of the converter with two test cases: 1) a DC current imposed through an inductive load for converter efficiency measurements in hard-switching and 2) an AC output current imposed in a full scale static laboratory WPT system, similar to the dynamic one.

Multi-N-phase SMPM drives

The paper presents an SMPM multi-n-phase electric drive for traction application. The whole drive, motor structure, converter structure and a PWM control strategy is proposed. In particular the drive control and the DC-link advantage of a multi-phase structure is investigated in a specific machine design. The possibility to strongly reduce the DC-link capacitor stress is presented thanks to a phase shift in the PWM carriers of different converters. A comparison analysis is given for the same motor wounded and supplied in three different ways also considering fault conditions.

Virtual load with common mode active filtering for power hardware-in-the-loop testing of power electronic converters

This paper presents an industrial platform for the testing of power converters for variable speed electrical drives at the end of the production line. For this purpose, the converter under test does not supply a real electrical machine but another power electric converter acting as a load emulator that regenerates the power into the grid. The testing platform is intended to emulate all necessary tests needed to stress the converter under test for different operating conditions and also for special identification procedures. Simulation and experimental results are presented for the testing of an 150 kVA power converter at the end of the production line.

Performance analysis of slope and frequency modulated carrier PWM methods for grid connected converters

A detailed analysis of two Pulse-Width Modulation (PWM) methods is performed in this paper for grid connected converters. The considered methods are: sinusoidal carrier regulated by the slope of a trapezoidal waveform PWM (SLPWM) and frequency modulated triangular carrier PWM (HIPWM-FMTC). The analysis of the two PWM methods is realized with four performance indicators: standard and weighted total harmonic distortion (THD and WTHD), fulfillment of the grid connection requirements and minimum pulse width. The results are compared with those obtained for the Space Vector Modulation (SVPWM) and Selective Harmonic Elimination PWM (SHE-PWM). Experimental results are presented for a 1 kVA inverter prototype to validate the paper conclusions.

A simple method for power loss estimation in PWM inverter-fed motors

This paper presents a simple power loss estimation method for inverter-fed low power AC asynchronous and synchronous motors. The method uses a simulation based DC/AC converter power loss estimation based on datasheet parameters and load characteristics like measured phase resistance and current phase delay. A current control scheme is used to impose a constant current at various speeds. Using this approach both asynchronous and synchronous motors can be used as a load. Total power loss is measured as the DC Link current by an amperemeter avoiding the use of complicated measurement systems.