Alexandru Onea

Fast calculating PWM techniques of voltage source inverter

The control of a three phase AC motor is performed with a three phase inverter. A key role in the correct functioning of the inverter is the used modulation technique. In this paper is proposed a class of modulation algorithms for the three phase inverters which have the advantage of a very simple implementation. The equivalence between a modulation strategy from this class and classical space vector pulse width modulation is demonstrated using simulation environment Matlab/Simulink. A comparative study of different modulation techniques was done referring to power losses of semiconductors.

Phase resistance estimation and monitoring of PMSM used in electrical vehicles

Permanent magnet synchronous motors (PMSM) are widely used in electric vehicle application due to their high power density, high efficiency and very good performance at low speeds. Safety concerns in automotive industry require monitoring of the system to ensure a correct and safe operation of the electric vehicle. This paper presents three software methods for estimating the winding electrical resistance and detecting an open phase failure during torque control operation of a PMSM. All three methods can be applied online. Differences between these methods are reflected into computational effort and efficiency. The described methods were numerically simulated and tested in MATLAB. The first two methods monitor the electrical resistance of the stator windings which are estimated through an Extended Kalman Filter (EKF) and an Unscented Kalman Filter (UKF). Hence, the three phase model and the rotating reference frame model are both used as internal models for the proposed Kalman filters and the estimation performance is evaluated in each case. In order to detect an open phase fault, the gradient of the estimated electrical resistance is monitored. The third method which is independent of the motor parameters calculates the Discrete Fourier Transformation (DFT) coefficients of the fundamental frequency in the phase currents signals. Hence, due to the low computational effort and good performance, the Goertzel algorithm is proposed. Conclusions are drawn based on estimation accuracy, time response and complexity of each method.

Passivity Based Torque Control of PMSM used in electrical vehicles

This paper presents a passivity based torque control structure for a high power Permanent Magnet Synchronous Motor (PMSM) used in Electric Vehicles (EV). A comparative study is done with a parallel PI algorithm in terms of response time, settling time, stationary error and required input electrical energy to reach the desired operating point. Moreover, parameters variations are simulated in order to evaluate the performance of the Passivity Based Control (PBC) scheme. In both control structures, the angular speed loop is controlled through a parallel PI algorithm. First, the mathematical model of PMSM is obtained in terms of Euler-Lagrange (EL) formalism which is the starting point for the passivity based torque controller design. This is followed by the damping injection and the re-modeling of the closed loop energy storage function in order to achieve passivity and asymptotic stability. Finally, the desired currents are derived from the torque request provided in the outer speed control loop. The algorithms are numerically simulated in MATLAB-Simulink.

Robust control of externally excited synchronous machine based on passivity theory

This paper proposes a robust Passivity Based Control (PBC) strategy for an Externally Excited Synchronous Machine (EESM) used in high power applications. The mathematical model of the EESM is obtained in Euler-Lagrange (EL) formalism which is the basis for the PBC control design. Variations of parameters are modelled as external perturbations and are compensated by pre-control actions determined by disturbance observers. The reference current are calculated considering Maximum Torque Per Ampere (MTPA) and Field Weakening (FW) strategies. The proposed control structure is compared with a Field Oriented Control (FOC) algorithm based on PI current and speed controllers. Numerical simulations are carried out in Matlab-Simulink.

Distributed control of voltage supply system used in electric vehicles

The actual trend in automotive is to reduce as much as possible pollution caused by motor vehicle emissions. This could be achieved by using electrical propulsion systems which usually contains: electrical machine, three phase voltage source inverter (VSI), voltage supply system. The main problem of the full electric vehicles represents the autonomy due to low energy capacity of batteries. This issue could be solved by using a hydrogen fuel cell in parallel with a battery pack to extend the range of the electrical vehicles. This paper presents a voltage supply system which connects to a DC bus a battery, a fuel cell, and a supercapacitor using DCDC converters. The focus of this work is on keeping controlling the voltage level of DC bus and on energy distribution between elements of voltage supply system. The proposed algorithm is validated using a close loop model which contains simulation of: fuel cell, battery pack, supercapacitor, DCDC converter, distributed control strategy of voltage supply system, DC Link capacitor, VSI, electrical machine, vehicle dynamics, and driver. The model is developed in Matlab/Simulink.

A complete class of PWM techniques for voltage source inverter

A propulsion system for hybrid electric vehicles and electric vehicles contains DC voltage supply, DC link capacitor, three phase voltage source inverter and a three phase AC machine. The key role of the inverter is to convert DC voltage to three AC voltages which commands the motor. The electrical machine is chosen to have the phase voltages in star connection and the common node of the phase voltages unconnected to ground. This paper contains a complete class of modulation techniques used to command the voltage source inverter. It consists in variation of potential of common node of electrical machine phases. This class of modulation techniques is simple to be implemented, offers a complete description of all possibilities to command the voltage source inverter and includes all other modulation techniques that could be found in literature. It is demonstrated analytically the inclusion in this class of some modulation techniques which could be found in literature such as sinusoidal pulse width modulation, third harmonic injection, and space vector pulse width modulation with sector selection.

Determination of stator temperature for thermal protection in a Permanent Magnet Synchronous Machine

This paper presents an on-line method for determining the hottest spot temperature of the copper windings of a Permanent Magnet Synchronous Machine (PMSM). The purpose is to protect the Electrical Machine (EM) from high temperatures which reduces the lifetime of the machine and can eventually lead to insulation faults of the motor. The method relies on experimental data acquired from a network of thermocouples placed around the stator windings of an actual PMSM. A mathematical model is proposed and the parameters are derived from the measurement data. Finally, the temperature of the hottest spot is determined on-line based on a single, fixed, temperature sensor placed in an accessible area of the stator (It is assumed that this is not the hottest temperature spot) and on the operating point of the PMSM. The data is combined in a Particle Filter (PF). The described method can be used with minor changes to any type of EM. The algorithm is executed in an offline environment with experimental data from a real motor-load test bench.

Simple adaptive voltage control of permanent magnet synchronous machine

This paper presents a voltage control strategy for a DC load powered by a three phase inverter connected to a Permanent Magnet Synchronous Generator (PMSG). The DC load consists of a DC capacitor in parallel with the inverter and the unknown current load. The control strategy is designed based on Simple Adaptive Control (SAC) technique. The structure is a cascade controller designed in rotor reference frame. In the inner loop the torque control is performed while, in the outer loop, the voltage of the DC link capacitor is regulated. Disturbance observers are used to increase the robustness of the control system. Parameter variations are simulated in order to asses the performance of the control strategy. Simulations are performed in Matlab-Simulink.

Simple adaptive control of externally excited synchronous machine

This paper proposes a control strategy for a high power Externally Excited Synchronous Machine (EESM) based on Simple Adaptive Control technique. A cascade control scheme is designed in the rotor reference frame. In the current control loop a SAC approach is described, while for the speed control loop a robust controller is proposed. The rotor and stator reference currents are determined based on a Maximum Torque per Ampere (MTPA) and Field Weakening (FW) strategies. Variations of parameters are simulated in order to evaluate the performance of the control method. Numerical simulations are performed in Matlab-Simulink.

Temperature estimation for condition monitoring of PMSM used in electric vehicles

This paper proposes an estimation approach based on Kalman filtering for determining the temperature of the stator windings of a Permanent Magnet Synchronous Motor (PMSM). Two schemes based on the Extended Kalman Filter (EKF) and the Unscented Kalman Filter (UKF) are investigated. The estimation is performed in a closed loop currents control scheme for a surface mounted PMSM. The temperature behavior is derived from the estimated dq axis electrical resistance and from the three phase resistance. Conclusions underline the estimation performance of each of the proposed methods.