A. Hodder

Double-fed asynchronous motor-generator equipped with a 3-level VSI cascade

The present paper investigates the complete regulation strategy for a large double-fed asynchronous motor-generator equipped with a 3-level VSI cascade for applications mainly in the field of pumped storage plant. For the present application, the specific problem of the DC link capacitors voltage balancing is investigated. Also a sensorless method for the determination of the rotor angle is proposed and verified in practice. Measurements of the system performed on a laboratory low power system are discussed and compared to simulations.

An analytical determination of the torque-speed and efficiency-speed characteristics of a BLDC motor

The paper presents a complete mathematical analysis of a BLDC motor commutation which results in the motor static characteristics torque-speed and efficiency-speed. The motor, having a sinusoidal back emf, is supplied from a DC source via a 6-leg inverter using the 120°ON operation. The formulas for the phase currents and voltages are derived. The first harmonic of the phase voltage is determined, which is used in combination with the classical BLDC motor theory to obtain simple formulas for the motor torque and efficiency. The model is verified using a measurement on a small industrial BLDC motor.

Optimal design of an in-wheel BLDC motor for a kick scooter

The paper presents an optimization design of an in-wheel BLDC motor for a kick scooter. The optimization is performed using a genetic optimization tool combined with a FEM commercial software. The new contributions of the paper are: i) introduction of three operating modes for which the motor is optimized with a reduced number of FEM simulations and ii) new approach to simultaneously maximize the energetic efficiency, minimize the cogging and respect the thermal constraint.

HIL Simulation of a mixed islanded power network with external DSP regulator

The present paper describes the implementation of an industrial regulator in a real time Hardware-In-the-Loop simulation of a mixed islanded power network including precise models of the hydraulic system. The studied network is composed of three different types of electrical power generation systems and a consumer.

Benchmark test of a variable speed unit for teaching purposes

Variable speed pump-turbine units have become nowadays an interesting way to increase stability of electrical power networks due to their high level of operating flexibility. Different advantages offered by variable speed pump-turbine units for both pumping and generating modes can be pointed out by means of either reliable simulation models or benchmark test devices. This paper presents a benchmark test of 3.3 kVA of a variable speed unit for teaching purposes. The control strategies for the transformer section and for the machine section are described. Comparisons between simulated and test results performed on this low power system are presented for different cases of operation (SVC effect, reactive power compensation, flywheel effect).

A new electrically assist scooter

The present paper addresses the study of a new electrically assist scooter. Nowadays, every electrical scooter found in the market works with human action, either by using a throttle handle or pedal, to control the electrical motor speed and no one offers a real assistance. For proper design, the scooter behavior, with different users, has to be analyzed by way of speed measurements. From this, an ideal and a worst case can be established leading to the knowledge of the power, torque and energy required by the electrical assistance. A topology is proposed and an algorithm for proper assistance is presented. Finally, measurements performed on the real prototype illustrate the behavior of the assistance.

Simulating real DSP code using a DLL, application to a 3-level VSI SVC

The present paper addresses the use of a Windows™ DLL to simulate the real code of a DSP for faster development time and advanced testing, especially in high power systems. The development of power system control usually starts with simulations and the development of the control is done with the simulation tool native blocs. Once the control is validated in simulation it is usually C coded into a DSP and real test can be performed. The present paper introduces a way of simulating the real DSP code to fill the gap between simulation and reality. By generating a DLL, the DSP C Code can be called by the simulation tool (in our case SIMSEN). The power part is ‘analogically’ simulated with a small integration step, and the DLL is called ‘digitally’ at a given sampling time. A 3-level VSI SVC is used as a guideline to illustrate the concepts presented.

Start-up of a varspeed group in pump mode, practical implementations and tests

The present paper addresses the practical implementation in a test bench of different control strategies for the start-up of a varspeed group in pump mode. In varspeed groups using a double-fed induction machine supplied by back to back voltage source inverters (VSI), the possibility exists of using the rotor side VSI to start up the group. The current paper focuses on the start-up strategy and its implementation in a test bench of 3.3 kVA. After presenting the hardware composing the test bench, two different start-up strategies are detailed, which are the field oriented control and critical torque. Those two strategies are then implemented in practice, tested, measured and compared.

Teaching lab on the DSP implementation of the speed control of a DC machine

The present paper addresses the speed control of a DC machine in the context of an advanced teaching lab consisting in setting up an islanded production unit. The different steps followed by the student to design and implement the speed control of the DC machine used in this islanded production unit are explained. A hardware specifically designed for this teaching and consisting of a DSP and an Analog to Digital (A/D) converter is presented. The major steps for the design of the PI (Proportional-Integral) regulator are recalled, whereas different improvement techniques such as the Anti-Reset Windup (ARW) or the set value corrector are presented in details. The corresponding code implemented in a DSP is given and detailed. Different tests performed on the test bench are then discussed mainly in terms of response time and overshoot.