Julian Wölfle

Efficiency analysis of three-level NPC and T-Type voltage source inverter for various operation modes optimizing the overall drive train efficiency by an operating mode selection

For drive train efficiency estimation, three-level inverters are analyzed regarding different modulation techniques and switching frequencies. In this paper an optimized operating mode selector is proposed to choose a loss optimal modulation technique and switching frequency for each operating point. Energy savings due to the operating mode selector are validated on a driving cycle.

A novel control method to improve the reliability of traction inverters for permanent magnet synchronous machines

In automotive applications system reliability is of major importance. The Voltage Source Inverter (VSI) of a traction system is a reliability and lifetime limiting factor due to the limited temperature cycle capability of its switching devices, commonly IGBT-modules. Temperature swings caused by varying load conditions on the motor cause mechanical stress in the switching modules due to change in power dissipation. This paper presents a novel control method, which achieves a reduction of temperature swing during low load conditions by increasing the conduction losses of the switching devices. A temperature controller increases the motor current without affecting the mechanical output power of the supplied motor. This is possible, as a specific motor torque and power can be achieved with different current values as long as certain lower and upper current limits are observed which are defined by system parameters and operation conditions.

A hybrid discontinuous modulation technique to influence the switching losses of three phase inverters

This paper presents a modulation technique, which combines the known space-vector-pulse-width-modulation (SVPWM) and the discontinuous-pulse-width-modulation (DPWM). This enables the possibility to set the switching losses freely within a certain border band. A possible area of application is the reliability of IGBT-inverters modules, where junction temperature swings can be reduced by influencing the power losses. The functionality is underlined by the analytical derivation of the switching and conduction mean power loss equations which are verified by measurements in certain operation points.

Handling of disturbance variables within a multi-phase interleaved-switched inverter by a discrete-time decoupling network

This paper presents investigations on the control block diagram of a multi-phase interleaved-switched inverter. Disturbing influences caused by the interleaved switching affect the desired simplicity of the block diagram. A possibility to eliminate these disturbances by a novel discrete-time decoupling network is presented and its functionality and advantage are approved by measurements.

Simple but accurate loss modelling of an IPMSM considering harmonic losses and saturation effects

For drive train efficiency optimization, an accurate but simple loss model of an interior permanent magnet synchronous machine (IPMSM) is proposed. In order to analyze different inverter topologies, switching frequencies and modulation techniques it is necessary that the loss model of the machine takes losses caused by harmonics into account. Considering harmonics and saturation effects, loss characteristics of the IPMSM are shown. Furthermore, loss calculations are opposed to test bench measurements in order to validate the loss models accuracy.

Temperature control system using a hybrid discontinuous modulation technique to improve the lifetime of IGBT power modules

This paper presents a model based junction temperature control system to increase the expected lifetime of IGBT power modules by using a hybrid discontinuous modulation technique. This modulation technique offers the possibility to influence the switching losses and is therefore used as a correcting variable for controlling the junction temperatures of IGBT power modules.

Control Method to Increase the Reliability of IGBT Power Modules Validated on a Three Phase Inverter

This paper presents a junction temperature controller which increases the reliability of IGBT power modules in power electronic applications without affecting the demanded output power. Power electronic applications have to deal with varying load conditions. These varying load conditions lead to temperature swings which lead to mechanical stress of common IGBT power modules. At low load conditions the switching losses are increased by increasing the switching frequency. This leads to reduced temperature swings resulting in a higher reliability. The functionality of the control system is verified on a three phase two level inverter connected to a passive load.

Optimal control of power electronic converters for traction applications

Energy flow and consumption are critical in modern electric drive applications within the transportation industry. Reducing losses and hardware requirements ultimately lowers a vehicles overall cost while improving performance. This paper presents an optimal control solution to reduce energy losses by limiting the peak power demands on the battery by using the power electronic converter and bus capacitor as a power buffer. From the optimal control solution, a sub-optimal proportional control method is proposed due to its ease of implementation and reduced complexity.