Modern Power Electronic Systems Research Articles

Design of a Low Inductance Power Module Based on Low Temperature Co-fired Ceramic

Abstract Efficient, compact, and reliable power electronic modules are building blocks of modern day power electronic systems. In recent times, wide bandgap semiconductor devices, such as, silicon carbide (SiC) and gallium nitride (GaN), are widely investigated and used in the power electronic modules to realize power dense, highly efficient, and fast switching modules for various applications. For high power applications is it required to parallel and series several devices to achieve high current and high voltage specifications, which results in larger current conducting traces. One of the major obstacles in using these wideband gap power semiconductor devices are the internal module stray inductance that is associated with these current conducting traces. With increasing demand for higher switching frequency, the internal module parasitic inductance must be reduced to as minimum as possible in order to utilize the full potential of the wide bandgap devices. A multi-layer approach of low-temperature co-fired ceramic (LTCC) to package the wide bandgap devices is investigated. The multi-layer design freedom by using LTCC can be utilized to reduce the footprint of the overall power module, electrical interconnects, hence, reducing the package parasitic inductance. LTCC also facilitates high temperature operations and has a coefficient of thermal expansion matching with wide bandgap devices. In this paper, we report on a LTCC based power module design where LTCC is utilized as an isolation layer between the source and the drain of the power devices. A simulation based parasitic inductance analysis and electro-thermal-mechanical study is performed using ANSYS Workbench Tools to investigate the feasibility of this LTCC based design.

Dryout avoidance control for multi-evaporator vapor compression cycle cooling

Two-phase cooling systems (e.g., pump-loops, vapor compression cycles) present a promising approach to the cooling of modern high power electronic systems. Such systems can achieve high coefficient of heat transfer but may incur dangerously high temperature when the imposed heat flux exceeds the critical heat flux (CHF). This paper presents a new control strategy that provides robust CHF avoidance in two-phase cooling for multiple evaporators under dynamic heat loads. This approach operates near the CHF to allow reduced coolant flow rates and greater system efficiency compared with the typical, and more conservative, open-loop or worst-case control strategies. The control architecture consists of two loops: an outer loop to determine evaporator mass flow rate demand, and an inner loop to supply and distribute the coolant using system actuators. Each control loop is implemented with feedforward based on static models as well as proportional–integral (PI) feedback controllers, and the decentralized approach allows scalable control design without the need for high fidelity nonlinear dynamic models. Simulations and corresponding experimental controller validations were conducted using a three-evaporator vapor compression cycle (VCC) testbed with transient imposed heat flux. The full closed-loop system is shown to be able to operate near CHF while avoiding CHF under transient heat flux, demonstrating both efficiency and robustness.

Tailoring the dipole properties in dielectric polymers to realize high energy density with high breakdown strength and low dielectric loss

High energy density polymer materials are desirable for a broad range of modern power electronic systems. Here, we report the development of a new class of polymer dielectrics based on polyurea and polythiourea, which possess high thermal stability. By increasing the dipole density, the dielectric constant of meta-phenylene polyurea and methylene polythiourea can be increased to 5.7, compared with aromatic polyurea and aromatic polythiourea, which have a dielectric constant in the range of 4.1–4.3. The random dipoles with high dipolar moment and amorphous structure of these polyurea and polythiourea based polymers provide strong scattering to the charge carriers, resulting in low losses even at high electric fields. Consequently, this new class of polymers exhibit a linear dielectric response to the highest field measured (>700 MV/m) with a high breakdown strength, achieving high energy density (>13 J/cm3) with high efficiency (>90%).

Design and Implementation of Digital Control in a Fuel Cell System

Digital control implementation is crucial in modern power electronic converters and energy conversion systems, as more complex control and friendly user interface are required. The fuel cell (FC) is a promising clean energy source and a reliable technology for niche applications providing high conversion efficiency. In this paper, a digitally controlled FC system is documented based on the boost-inverter topology that achieves both boosting and inversion functions in a single-stage. A digital signal processor TMS320F28335 is used to implement the control of the FC system in order to provide a number of benefits including low-cost, good performance, an easy implementation of a relatively complicated algorithm, and user friendly interface. The control design, analysis, simulation and experimental results are presented in the paper to confirm the performance of the digitally controlled FC system.

High Temperature Silicon Carbide Power Modules for High Performance Systems

The demands of modern high-performance power electronics systems are rapidly surpassing the power density, efficiency, and reliability limitations defined by the intrinsic properties of silicon-based semiconductors. The advantages of silicon carbide (SiC) are well known, including high temperature operation, high voltage blocking capability, high speed switching, and high energy efficiency. In this discussion, APEI, Inc. presents two newly developed high performance SiC power modules for extreme environment systems and applications. These power modules are rated to 1200V, are operational at currents greater than 100A, can perform at temperatures in excess of 250 °C, and are designed to house various SiC devices, including MOSFETs, JFETs, or BJTs.

Improved Core-Loss Calculation for Magnetic Components Employed in Power Electronic Systems

In modern power electronic systems, voltages across inductors/transformers generally show rectangular shapes, as the voltage across an inductor/transformer can be positive, negative or zero. In the stage of zero applied voltage (constant flux) core losses are not necessarily zero. At the beginning of a period of constant flux, losses still occur in the material. This is due to relaxation processes. A physical explanation about magnetic relaxation is given and a new core loss modeling approach that takes such relaxation effects into consideration is introduced. The new loss model is called i2GSE and has been verified experimentally.

High Temperature Silicon Carbide Power Modules for High Performance Systems

The demands of modern high-performance power electronics systems are rapidly surpassing the power density, efficiency, and reliability limitations defined by the intrinsic properties of silicon-based semiconductors. The advantages of silicon carbide (SiC) are well known, including high temperature operation, high voltage blocking capability, high speed switching, and high energy efficiency. In this discussion, APEI, Inc. presents two newly developed high performance SiC power modules for extreme environment systems and applications. These power modules are rated to 1200V, are operational at currents greater than 100A, can perform at temperatures in excess of 250 °C, and are designed to house various SiC devices, including MOSFETs, JFETs, or BJTs. One newly developed module is designed for high performance, ultra-high reliability systems such as aircraft and spacecraft, and features a hermetically sealed package with a ring seal technology capable of sustaining temperatures in excess of 400°C. The second module is designed for high performance commercial and industrial systems such as hybrid electric vehicles or renewable energy applications, implements a novel ultra-low parasitic packaging approach that enables high switching frequencies in excess of 100 kHz, and weighs in at just over 130 grams (offering ~5× mass reduction and ~3× size reduction in comparison with industry standard power brick packaging technology). It is configurable as either a half or full bridge converter. In this discussion, APEI, Inc. introduces these products and presents practical testing of each.

Optimized Design of Stationary Frame Three Phase AC Current Regulators

Current regulation plays an important role in modern power electronic AC conversion systems. The most direct strategy to regulate such currents is to use a simple closed loop proportional-integral (PI) regulator, which has no theoretical stability limits as the proportional and integral gains are increased, since it is only a second order system. However, pulsewidth modulation (PWM) transport and controller sampling delays limit the gain values that can be achieved in practical systems. Taking these limitations into account, this paper presents an analytical method to determine the best possible gains that can be achieved for any class of practical linear AC current controller. The analysis shows that the maximum possible proportional gain is determined by the plant series inductance, the DC bus voltage and the transport and sampling delays, while the maximum possible integral gain is determined primarily by the transport and sampling delays. The work is applicable to stationary frame PI regulators, stationary frame controllers with back electromotive force compensation, stationary frame P+ resonant (PR) controllers, and synchronous d- q frame controllers, since they all have identical proportional and integral gains that must be optimized for any particular application.

High-Speed Real-Time Simulation for Power Electronic Systems

Real-time simulators have been used as an aid to power system design for many years. Over time, scaled-down physical models and analog computer-based simulators have given way to real-time simulators based on digital technology. Another trend has been the need for shorter and shorter frame times for these digital real-time simulators. Modern power electronic systems use highfrequency Pulse-Width Modulated (PWM) controllers. Indications are that frame times of 2 μS are needed for PWM switching frequencies of 10 KHz. As frequencies increase further it is possible that frame times of less than 1 μS may be required. In order to achieve these very short frame times, the implementation of this type of simulator requires careful selection of the methods and technologies used. The first involves thorough analysis of the integration method chosen, to ensure that it provides the performance, stability and accuracy required. Additionally, the choice of computing platform is crucial to provide the computational support to meet these very aggressive timing requirements.