46 research outputs found
Grid Converters for Stationary Battery Energy Storage Systems
No full textThe integration of renewable energy sources in the power system, with high percentage, is a well known challenge nowadays. Power sources like wind and solar are highly volatile, with uctuations on various time scales. One long term solution is to build a continentwide or worldwide supergrid. Another solution is to use distributed energy storage units, and create virtual power plants. Stationary energy storage is a complementary solution, which can postpone the network expansion and can be optimized for dierent kind of grid services. As an energy storage solution with timing for few seconds to hours, rated at MW and MWh, battery energy storage systems are suitable and ecient solutions.Grid connection of the storage system can be done at dierent voltage levels, depending on the location and application scenario. For high power and energy ratings, increase in the battery and converter voltage ratings can enhance the overall system eciency.This work is divided in two parts, "Control of DC-AC Grid Converters" and "Medium Voltage Grid Converters for Energy Storage". The rst part starts with a brief review of control strategies applied to grid connected DC-AC converters. A control implementation was realized for a 100 kW active rectier to be used in a 6 kV battery energy storage test bench. In the second part, dierent solutions for power converters to interface energy storage units to medium voltage grid are given. A new modular multilevel converter concept is introduced, where the energy storage units are integrated in each converter cell.The control of DC-AC grid converters has been a research subject for more than a century, and there is still place for improvements. A review of the main control principles is given in the rst part. The stationary frame control was implemented for a low-voltage 100 kW bidirectional grid converter, to be used in a high voltage battery energy storage test bench. The control structure proved to be stable without damping. The converter was tested in the test bench and the experimental results are presented.Multilevel converters are replacing the classical two-level converters more and more, on a large variety of applications. For medium voltage applications, multilevel converters are a necessity. The second part presents a review of hard-switched and soft-switched multilevel converter topologies for medium voltage. Four converter topologies were chosen as potential solutions for direct connection of battery energy storage systems to the grid. An evaluation is done, in terms of semiconductors requirements and losses, output voltage quality and common mode voltage.The main advantage of batteries direct connection to the grid is the high efficiency potential. However, this solution is suitable only for battery technologies with low voltage variation. It is also necessary to build a battery system with high amount of serial connected cells, and the knowledge in this eld is still limited nowadays. Therefore, twostage converters solutions were introduced to overcome these disadvantages. Modular multilevel converters can make use of battery voltage technologies where the maturity and reliability is well proven in industry.Cascaded H-bridge topology with bidirectional boost converters is proposed to interface low voltage batteries to the medium voltage grid. A control structure based on single phase control is proposed. It balances the capacitor voltages and the state of charge of batteries from dierent cells. A semiconductor loss analysis is performed and it shows the loss distribution in the converter cell and the eciency over a wide battery voltage variation.A new modular multilevel converter structure with integrated energy storage is introduced.This converter structure is suitable to interface low and medium voltage energy storage units to medium and high voltage grids. It can also interconnect a DC and AC grid with bidirectional power ow, were both can be backed-up for the distributed energy storage units installed in each converter cell. The converter operation and control methods are presented, and the energy storage system construction concept and challenges are addressed
Grid Converters for Stationary Battery Energy Storage Systems
No full textThe integration of renewable energy sources in the power system, with high percentage, is a well known challenge nowadays. Power sources like wind and solar are highly volatile, with uctuations on various time scales. One long term solution is to build a continentwide or worldwide supergrid. Another solution is to use distributed energy storage units, and create virtual power plants. Stationary energy storage is a complementary solution, which can postpone the network expansion and can be optimized for dierent kind of grid services. As an energy storage solution with timing for few seconds to hours, rated at MW and MWh, battery energy storage systems are suitable and ecient solutions.Grid connection of the storage system can be done at dierent voltage levels, depending on the location and application scenario. For high power and energy ratings, increase in the battery and converter voltage ratings can enhance the overall system eciency.This work is divided in two parts, "Control of DC-AC Grid Converters" and "Medium Voltage Grid Converters for Energy Storage". The rst part starts with a brief review of control strategies applied to grid connected DC-AC converters. A control implementation was realized for a 100 kW active rectier to be used in a 6 kV battery energy storage test bench. In the second part, dierent solutions for power converters to interface energy storage units to medium voltage grid are given. A new modular multilevel converter concept is introduced, where the energy storage units are integrated in each converter cell.The control of DC-AC grid converters has been a research subject for more than a century, and there is still place for improvements. A review of the main control principles is given in the rst part. The stationary frame control was implemented for a low-voltage 100 kW bidirectional grid converter, to be used in a high voltage battery energy storage test bench. The control structure proved to be stable without damping. The converter was tested in the test bench and the experimental results are presented.Multilevel converters are replacing the classical two-level converters more and more, on a large variety of applications. For medium voltage applications, multilevel converters are a necessity. The second part presents a review of hard-switched and soft-switched multilevel converter topologies for medium voltage. Four converter topologies were chosen as potential solutions for direct connection of battery energy storage systems to the grid. An evaluation is done, in terms of semiconductors requirements and losses, output voltage quality and common mode voltage.The main advantage of batteries direct connection to the grid is the high efficiency potential. However, this solution is suitable only for battery technologies with low voltage variation. It is also necessary to build a battery system with high amount of serial connected cells, and the knowledge in this eld is still limited nowadays. Therefore, twostage converters solutions were introduced to overcome these disadvantages. Modular multilevel converters can make use of battery voltage technologies where the maturity and reliability is well proven in industry.Cascaded H-bridge topology with bidirectional boost converters is proposed to interface low voltage batteries to the medium voltage grid. A control structure based on single phase control is proposed. It balances the capacitor voltages and the state of charge of batteries from dierent cells. A semiconductor loss analysis is performed and it shows the loss distribution in the converter cell and the eciency over a wide battery voltage variation.A new modular multilevel converter structure with integrated energy storage is introduced.This converter structure is suitable to interface low and medium voltage energy storage units to medium and high voltage grids. It can also interconnect a DC and AC grid with bidirectional power ow, were both can be backed-up for the distributed energy storage units installed in each converter cell. The converter operation and control methods are presented, and the energy storage system construction concept and challenges are addressed
Energy Harvesting Cycles of Dielectric ElectroActive Polymer Generators
No full textEnergy 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
Simple DCM or CRM analog peak current controller for HV capacitor charge-discharge applications
No full textThis paper presents a simple analog current controller suitable for buck and boost converter topologies. The controller operates in DCM or CRM, depending on the setup. The experimental results are presented to validate the proposed controller functionality for a high voltage capacitor charge-discharge application
Performance assessment of commercial gallium nitride-on-silicon discrete power devices with figure of merit
No full textThere have been various technical developments of commercial gallium nitride on silicon power devices over the last couple of years since the initial appearance. Efforts have been made to increase threshold voltage and power density, while reducing stray impedance to improve the efficiency of the power conversion systems. In this paper, seven types of gallium nitride-on-silicon discrete power devices on the market are electrically analyzed and compared in the same test environment. To objectively understand the performance of power semiconductor devices, the figure of merit is derived from the measurements to enable a quantitative comparison. The results demonstrate that the power density of the current commercially available gallium nitride power components already goes beyond the theoretical limitation of the silicon material. Moreover, switching capability of commercial gallium nitride-on-silicon devices are found to be fourteen-times-better than that of a state-of-the-art silicon device from the same category.</p
Unbalanced Voltage Compensation in Low Voltage Residential AC Grids
No full textThis paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The controlalgorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling. The voltage control was evaluated with either active or reactive independent phase load current control. The control performance in field operation in a residential grid situated in Bornholm, Denmark was investigated for different use cases
Failure mechanism analysis of a discrete 650V enhancement mode GaN-on-Si power device with reverse conduction accelerated power cycling test
No full textA commercial discrete enhancement mode gallium nitride power component employing advanced package technology without conventional bond wire possesses the ability for bidirectional conduction. The gallium nitride power components can provide not only higher forward conductivity but also superior reverse conductivity. For the most part recent critical debates about the reverse conductivity of a GaN device have tended to center around their performance. However, the reliability of the device under reverse operation should be assessed in order for the advantages to be fully utilized in real applications. We present the results of reverse conduction power cycling test of a discrete 650-volt gallium nitride power device with novel package technology at temperature swings of 100 K. The result shows degradation of thermal conductivity and raising leakage current drain to source as reaching the number of cycles to failure. In physical failure analysis, delamination of a solder joint between a chip and a copper layer of an aluminum print circuit board is observed with a scanning acoustic microscope
A New Modular Multilevel Converter with Integrated Energy Storage
No full textThis 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 bench tests of converter driven 1kW underwater induction generator for the deep wind project
No full textThis paper presents a 1 kW generator and converter applied to a floating Darreius type wind turbine system [1], 121, 131. The completed system is floated in the sea with the generator 5m below the surface. The present paper sketches the design and presents the laboratory bench test results, as well as the environment where the turbine was placed
Voltage Unbalance Compensation with Smart Three-phase Loads
No full textThis paper describes the design, proof-of-concept simulations and laboratory test of an algorithm for controlling active front-end rectifiers to reduce voltage unbalance. Usinginputs of RMS voltage, the rectifier controller allocates load unevenly on its 3 phases to compensate for voltage unbalance originating in the power supply network. Two variants of the algorithm are tested: first, using phase-neutral voltage as input, second, using phase-phase voltage. The control algorithm is described, and evaluated in simulations and laboratory tests. Two metrics for quantifying voltage unbalance are evaluated: one metric based on the maximum deviation of RMS phaseneutral voltage from the average voltage and one metric based on negative sequence voltage. The tests show that controller that uses phase-neutral voltage as input can in most cases eliminatethe deviations of phase voltage from the average voltage, but it does not reduce the negative sequence voltage. The controller that uses phase-phase voltage as input eliminates negative sequence voltage, and reduces voltage deviations from the average to approximately half their initial value. Current unbalance is reduced when the voltage unbalance is caused by asymmetrical loads. These results suggest that the optimal algorithm to reduce system unbalance depends on which system parameter is most important: phase-neutral voltage unbalance, phase-phase voltage unbalance, or current unbalance
