Ionut Trintis

A new modular multilevel converter with integrated energy storage

This paper introduces a new modular converter with integrated energy storage based on the cascaded half-bridge modular multilevel converter with common DC bus. It represents a complete modular solution with power electronics and energy storage building blocks, for medium and high voltage applications. Furthermore, this solution can interconnect a DC and AC grid with bidirectional power flow, where both of them can receive or generate excess power to the third source integrated in each converter sub-module. This particularity enables the converter usage as a high voltage UPS system in the future HVDC meshed grids. Its functionality and flexibility makes the converter independent on the energy storage unit characteristic. The converter concept with its basic functions and control schemes are described and evaluated in this paper.

Design and construction of a test bench to characterize efficiency and reliability of high voltage battery energy storage systems

Stationary battery energy storage systems are widely used for uninterruptible power supply systems. Furthermore, they are able to provide grid services. This yields in rising installed power and capacity. One possibility uses high voltage batteries. This results in an improvement of the overall system efficiency. High voltage batteries may be advantageous for future medium voltage DC-grids as well. In all cases, high availability and reliability is indispensable. Investigations on the operating behavior of such systems are needed. For this purpose, a test bench for high voltage storage systems was built to analyze these processes for different battery technologies. A special safety infrastructure for the test bench was developed due to the high voltage and the storable energy of approximately 120 kWh. This paper presents the layout of the test bench for analyzing high voltage batteries with about 4,300 volts including all components, the safety requirements with the resultant safety circuit and the aim of the investigations to be performed with the test bench.

Test setup for accelerated test of high power IGBT modules with online monitoring of V ce and V f voltage during converter operation

Several accelerated test methods exist in order to study the failures mechanisms of the high power IGBT modules like temperature cycling test or power cycles based on DC current pulses. The main drawback is that the test conditions do not represent the real performance and stress conditions of the device in real application. The hypothesis is that ageing of power modules closer to real environment including cooling system, full dc-link voltage and continuous PWM operation could lead to more accurate study of failure mechanism. A new type of test setup is proposed, which can create different real load conditions like in the field. Furthermore, collector-emitter voltage (Vce) has been used as indicator of the wear-out of the high power IGBT module. The innovative monitoring system implemented in the test setup is capable of measure the Vce and forward voltage of the antiparallel diode (Vf) during converter operation, which is also demonstrated.

Overview of multi-DC-bus solutions for DC microgrids

DC Microgrids have recently received a lot of attention in the last years due to high penetration of renewable energy sources as well as distributed energy storage systems. In the future DC microgrids could be preferable respect to AC microgrids in terms of redundancy since multi-DC-Bus solutions could provide a continuative power supply to the loads. An overview of Multi-DC-Bus solutions is presented in this paper. The performances are compared on the basis of possible DC microgrid configurations, redundancy, different DC voltage levels.

Online chip temperature monitoring using υ ce -load current and IR thermography

This paper presents on-state collector-emitter voltage (υce, on)-load current (Ic) method to monitor chip temperature on power insulated gate bipolar transistor (IGBT) modules in converter operation. The measurement method is also evaluated using infrared (IR) thermography. Temperature dependencies of υce, on at load current is measured and temperature dependency calibration factor is formulated. This method needs a correction to compensate a deviation in the interconnection resistance from homogeneous temperature field in calibration to non-homogeneous field in loading. The correction parameter is obtained from a static calibration and the method is proposed in the paper. Ageing compensation in estimating the temperature is illustrated. The correction parameter is also analysed in finite element model and also investigated experimentally superimposing heat by conducting device for a longer time in the calibration.

Comparison of the dielectric electroactive polymer generator energy harvesting cycles

The Dielectric ElectroActive Polymer (DEAP) generator energy harvesting cycles have been in the spotlight of the scientific interest for the past few years. Indeed, several articles have demonstrated thorough and comprehensive comparisons of the generator fundamental energy harvesting cycles, namely Constant Charge (CC), Constant Voltage (CV) and Constant E-field (CE), based on average theoretical models. Yet, it has not been possible until present to validate the outcome of those comparisons via respective experimental results. In this paper, all three primary energy harvesting cycles are experimentally compared, based upon the coupling of a DEAP generator with a bidirectional non-isolated power electronic converter, by means of energy gain, energy harvesting efficiency and energy conversion efficiency.

Advanced power cycling test for power module with on-line on-state V CE measurement

Recent research has made an effort to improve the reliability of power electronic systems to comply with more stringent constraints on cost, safety, predicted lifetime and availability in many applications. For this, studies about failure mechanisms of power electronic components and lifetime estimation of power semiconductor devices and capacitors have been done. Accelerated power cycling test is one of the common tests to assess the power device module and develop the lifetime model considering the physics of failure. In this paper, a new advanced power cycling test setup is proposed for power module. The proposed concept can perform various stress conditions which is valid in a real mission profile and it is using a real power converter application with small loss. The concept of the proposed test setup is first presented. Then, the on-line on-state collector-emitter voltage VCE measurement for condition monitoring of the test device is discussed. Finally, a characterization method of test device regarding on-state VCE for junction temperature estimation is proposed. The experimental results of the prototype confirm the validity and the effectiveness of proposed test setup.

SiC heat pump converters with support for voltage unbalance in distribution grids

This paper studies the impact of involving the demand side of the LV grid into the grid conditioning process. Heat pumps are distribution loads with a substation capacity increase in the last years, with expectancy of growth in the coming years. Controlling the loads is the first step in the transition to smart grids, and heat pumps are to be the first promising smart loads. They can be used for load shedding but also for unbalance compensation purposes. When they are equipped with a back to back compressor drive and a proper control strategy, grid support can be provided to reduce the negative sequence component in the voltage at the installation point. Two control strategies are proposed and investigated experimentally on a SiC heat pump converter prototype.

Efficiency and reliability improvement in wind turbine converters by grid converter adaptive control

This paper presents a control method that reduces the losses in wind turbine converters adaptively controlling the grid converter. The dc-link voltage adapts its reference based on the system state and therefore reduces the stored energy, and is therefore kept at the minimum necessary for the grid and generator side. Operating in this way, the electrical and thermal stress factors are decreased on the power electronic devices, increasing their lifetime. The simulation results using this method show efficiency increase and devices temperature cycles slightly decreased. Experimental results on a wind turbine power stack shows efficiency increase in the high power region.

Energy harvesting cycles of Dielectric ElectroActive Polymer Generators

Energy harvesting via Dielectric ElectroActive Polymer (DEAP) generators has attracted much of the scientific interest over the past few years, mainly due to the advantages that these smart materials offer against competing technologies, as electromagnetic generators and piezoelectrics. Their higher energy density, superior low-speed performance, light-weighted nature as well as their shapely structure have rendered DEAPs candidate solutions for various actuation and energy harvesting applications. In this paper, a thoroughly analysis of all energy harvesting operational cycles of a DEAP generator, coupled to a non-isolated power electronics converter, is conducted and for the first time experimental results for each one of them are presented.