T Thomas Gerrits

Dual voltage source inverter topology extending machine operating range

Field weakening operation of an electrical machine is a conventional method to extend the angular velocity range of a system above the peak output voltage of the inverter. A downside, however, is that an increased reactive current is required that creates losses but no output torque. A dual voltage source inverter topology is proposed, capable of driving an electrical machine without weakening its field in an extended speed range. For this purpose, a second inverter fed by a capacitor only is connected to the open-end side of the machine windings. Charging the floating capacitors is realized by adding an AC zero sequence current to the regular machine currents. The operating principles of the presented topology are demonstrated, showing their possible advantages when driving an electrical machine. Simulation results confirm the proposed ideas.

Loss minimization of boost mode dual inverter drive system

A dual inverter drive system is proposed, which is capable of boosting the phase voltages applied to an open-winding electric machine. A zero sequence current at the third harmonic of the intended output frequency is added to increase the supply voltage of one inverter, thereby extending the operating range of the machine. The need for a reactive current to weaken the machine field is avoided as a result. A method is introduced for simultaneously optimizing the inverter voltages and minimizing the required boost current, to maximize the overall system efficiency. The analysis is explained and verified by simulation.

Development of a linear position independent Inductive Energy Transfer system

An inductively coupled contactless energy transfer system for translating motion that is able to transfer 1 kW of power is proposed in this paper. The system consists of a gapped transformer with multiple secondary coils and a single primary one. Using this approach a long stroke energy transfer system can be constructed. No active control for switching on the moving side of the transformer is required. The magnetic design of the transformer is such, that the position dependency of the transformer parameters is minimized. This allows a fixed capacitor value to be used to operate the system close to resonant mode. The magnetic design procedure of the core is described and analyzed. The design has been implemented and measurements on the prototype have been conducted.

Fault-tolerant operation of a fully electric gearbox equivalent

A fault-tolerant operation method for a dynamic electric vehicle (EV) propulsion system using variable torque/speed characteristics is presented. With this method, the electrically powered vehicle can continue driving with a minimum performance reduction, and without the need for redundant systems on machine or electronics level. One of the possible single module fault scenarios, during which the system must continue operation, is shown. The accompanying theoretical analysis of the fault scenario is presented, and simulations and preliminary measurements are executed to demonstrate the presented solution.

Operating Range Advancement of a Dual-Inverter Driven Machine Through Voltage Range Enhancement

Speed range maximization of a traction drive is one of the main focus points in transportation electrification research. This paper presents a range improvement method, suitable for each type of open-winding three-phase electric machine. A dual-inverter drive system is proposed, which is capable of enhancing the phase voltages applied to the open-winding electrical machine. A common-mode current at the third-harmonic of the intended output frequency is deliberately generated to boost the supply voltage of one inverter, thereby extending the operating range of the machine above the base angular velocity. The need for a reactive fundamental frequency current to weaken the machine field is avoided as a result. A method is introduced for simultaneously optimizing the inverter voltages and minimizing the required boost current, thereby maximizing the speed range and the overall efficiency. The analysis is explained and verified by experiments. A relative angular velocity advancement of a factor 1.6 is achieved using voltage range enhancement.

Twelve-phase open-winding SPMSM development for speed dependent reconfigurable traction drive

Commercially available electrical machines are generally not optimized for a broad operating range, as required in e.g. vehicle traction applications. The required mechanical angular velocity of the wheels for electrical vehicle propulsion is relatively low (around 1,000 rpm), while the torque demand is high (around 500 Nm). This combination requires an adequate solution in the mechanical, electromechanical or electrical domain. No cheap, reliable, lightweight and efficient solution has been invented yet. This paper presents an operation method for a dynamic electric vehicle propulsion system using variable torque/speed characteristics. With this method, the speed range of an electrical machine can be extended. The twelve-phase open-winding surface permanent magnet synchronous machine presented in this paper is developed to verify the different dynamic drive operation modes in practice.

Dynamic Machine Operation Transitions

Wide angular velocity operation of an electrical machine is demonstrated by partitioning each of the stator coils of a three-phase configuration. An open-winding machine drive circuit is proposed with which dynamic transitions between machine operating modes can be executed. The principle of operation and the design choices of the required bidirectional series switch are explained and motivated. The behavior of the proposed system is analysed, and verified by simulations. Finally, the results of a configuration (gear) transition are compared to a state-of-the-art mechanical twin-clutch transmission, showing that both the angular jerk and transition time are much smaller with the proposed system.