Christoph H. van der Broeck

A thermal modeling methodology for power semiconductor modules

Abstract This work presents a flexible thermal modeling methodology for power semiconductor modules. It allows time efficient simulation of temperature cycling for different module designs and operation profiles. To keep the model compact and flexible as well as accurate, the solid state heat conduction paths of the power modules are modeled by a 3D finite difference model. It is combined with an analytical heat sink model describing convective cooling. The temperature gradient of the cooling fluid is captured by a mass transportation model. The resulting linear state space model can be easily formulated in discrete time domain to allow a fast and detailed simulation of thermal load transients. With the balanced truncation based model reduction technique, the thermal state space model is efficiently reduced to allow fast analysis of thermal cycling and reliability issues. Finally, the thermal model is validated with measurements and data from the manufacture.

Dynamic control of a dual active bridge for bidirectional AC charging

The dynamic control of a bidirectional charger based on a dual active bridge (DAB) cascaded with a singlephase grid inverter is the scope of this work. Due to a small dc-link capacitance the power fluctuation of the grid at twice the grid frequency is transferred to the battery. To compensate this ac-power fluctuation it is demonstrated how the switching pattern must be selected to achieve a continuous power transfer and improve the dynamic control of the dc-link voltage. For the control it is also taken into account that depending on the voltage ratio and the transferred power certain switching patterns can improve the efficiency of the DAB. Furthermore, a repetitive controller is proposed to enhance the performance of the controller. Finally the control design is presented and measurements on a prototype demonstrating the functionality of the proposed concepts are shown.

Discrete time modeling, implementation and design of current controllers

This work addresses discrete time modeling, implementation and design options for the current control of three phase grid tied PWM converters. Based on an accurate discrete time model of the PWM converter, closed loop current control is reviewed from the perspective of the synchronous and stationary reference frame. Then, implementation options for the synchronous frame proportional integral (SFPI) regulator and the proportional resonant (PR) regulator are discussed leading to the formulation of a general controller framework based on space vector resonators: the Resonant Space Vector (RSV) regulator. It can embody multiple SFPI regulators on different frequencies and allows a consistent design of state feedback controllers as well as an efficient implementation. For this control framework an insightful design procedure based on the root locus method for complex system models is introduced. Finally, the performance of the presented control design and implementation concepts is demonstrated experimentally.

Unified Control of a Buck Converter for Wide-Load-Range Applications

A new discrete-time state feedback controller is presented, which allows high-bandwidth voltage control of a buck converter for any load condition, whether it operates in discontinuous conduction mode (DCM), continuous conduction mode (CCM), or at the boundary of these regions. This makes the buck converter applicable for a wide range of applications. For the control design process, two large-signal models, which represent the buck converters discrete time dynamics in CCM and DCM, are developed. A simple proportional-integral regulator is used for the voltage control of the converter. The operation mode is detected and the voltage controller is connected in cascade to a current controller in CCM or to a nonlinear state feedback decoupling structure in DCM. In this paper, the modeling and design of the proposed control topology are introduced and its performance is demonstrated in simulation and experiment.

Unified control of a buck converter for wide load range applications

A new discrete time state feedback controller is presented, which allows high bandwidth voltage control of a buck converter for any load condition whether it operates in discontinuous conduction mode (DCM), continuous conduction mode (CCM) or in the boundary of these regions. This makes the buck converter applicable for a wide range of applications. For the control design process two large signal models are developed, which represent the buck converters discrete time dynamics in CCM and DCM. A simple PI regulator is used for the voltage control of the converter. The operation mode is detected and the voltage controller is connected in cascade to a current controller in CCM or to a nonlinear state feedback decoupling structure in DCM. In this work, the modeling and design of the proposed control topology are introduced and its performance is demonstrated in simulation and experiment.

Spatial electro-thermal modeling and simulation of power electronic modules

In this work the spatial electro-thermal modeling of power electronic modules is discussed. It is shown how physical and mathematical modeling techniques can be combined to obtain a compact time efficient electro-thermal simulation framework for power electronic modules. The framework can be used to evaluate the transient temperature distribution of a power module in an electric vehicle over driving cycles. Based on the simulated temperature distribution the lifetime of the power module can be estimated using various aging laws. The simulation and lifetime estimation is demonstrated as an example for a Hybridpack2 inverter module. Finally, a design parameter study is carried out, which evaluates different module design options with respect to their impact on reliability.

A generalized control design approach for a repetitive controller on current harmonics

This paper proposes a generalized design procedure for repetitive current controllers to obtain good disturbance rejection properties and well behaved and robust system dynamics. Based on an accurate discrete time model different implementation options for repetitive controllers are discussed leading to an intuitive control structure, which allows a simple control design. It will be shown that any desirable dynamics can be achieved by adjusting one parameter only. Even dead beat design is theoretical possible. The impact of model inaccuracies and numerical errors on the dynamics and stability of the system will be investigated. Based on the analysis methods are reviewed to handle these challenges. Simulations and experiments verify the proposed control structure and design concept.

Analysis and Design of Repetitive Controllers for Applications in Distorted Distribution Grids

This paper proposes a generalized design procedure for repetitive current controllers in distorted distribution grids to obtain good disturbance rejection properties and well behaved and robust system dynamics. Different implementation options for repetitive controllers (RCs) are discussed based on an accurate discrete time model. A simple control design is derived, which allows any desirable dynamics to be adjusted by one single parameter. Even a deadbeat design is possible. The impact of model inaccuracies and numerical errors on the dynamic and stability of the system is investigated. It is shown that the RC leads to low damping or even instability at high switching frequencies caused by modeling errors or numerical inaccuracies. Based on the stability analysis, it is discussed how to handle these design challenges, which exist especially for RCs of high order. The proposed control structure and control design concept is verified by simulations and experiments.

Spatial Electro-Thermal Modeling and Simulation of Power Electronic Modules

In this work, the spatial electro-thermal modeling and simulation of power electronic modules is discussed. It is shown how physical and mathematical modeling techniques can be combined to obtain a compact time-efficient electro-thermal simulation framework for power electronic modules. The accuracy of the modeling framework is demonstrated based on experiments. It can be used for the fast calculation of the temperature distribution of a power module in an electric vehicle over driving cycles. The spatial temperature information allows to effectively estimate the lifetime of the power module.

Electro-thermal simulation of bond wires in power modules for realistic mission profiles

For the successful electrification of global transportation, the reliability of power electronic modules is of major importance. Today, one of the main reasons for module failure is the thermo-mechanically induced fatigue of bond wires as a result of strong load variations. A multitude of studies have been conducted to analyze the operational stress of bond wires based on thermal simulations using simple repetitive load patterns. This paper proposes a compact electro-thermal model for detailed time-efficient simulations of the thermal stress within bond wires. It incorporates the impact of parasitic electromagnetic coupling effects for an accurate loss determination over a wide frequency range. Finally, the bond wire model is embedded into a system simulation of the drive train of an electric vehicle. This allows to determine the realistic temperature distribution along the bond wires over time for specific mission profiles.