Design Of Power Conversion System Research Articles

Design and performance comparisons of power converters for battery energy storage systems

SummaryThe use of grid‐connected battery energy storage systems (BESSs) has increased around the world. In the scenario of high penetration level of renewable energy sources in distributed generation, BESS plays an important role to combine a sustainable power supply with a reliable dispatched energy source. Different power converter topologies are employed to connect the batteries to the grid, generally using single‐stage converters. However, the battery voltage changes according to its state of charge, which can introduce great variations in the dc‐link voltage. Therefore, the dc/ac stage converter must have its power switches designed to support this voltage variation. A controllable dc‐link voltage is achieved by inserting a dc/dc converter stage to connect the batteries to the dc/ac stage. Among the dc/dc converters, the interleaved bidirectional converter has been widely used due to the low input current ripple. However, the trade‐off of the insertion of the dc/dc stage is barely explored in the literature. Therefore, this work presents a methodology of analysis, considering the battery voltage variation and its influence on BESS power conversion system design and efficiency. Furthermore, it is proposed a power conversion system design oriented toward the voltage class of power switches and efficiency. The analysis in this study are conducted through the use of a case study approach, incorporating both simulated and experimental results.

Analyzing the engineering feasibility of the direct fusion drive

The Direct Fusion Drive (DFD) and its terrestrial counterpart, the Princeton Field Reversed Configuration (PFRC) reactor, have seen significant developments in the past decade. Various groups conducted detailed research on the required specifications of the engine and associated technology for power delivery to onboard avionics and payloads. Multiple studies have also addressed the thrust generation mechanism using empirical specific power scaling relations and plasma flow simulations. Recent studies have designed spacecraft for missions to Earth’s second Lagrange point, Mars, transneptunian bodies like Pluto, and the neighboring star systems Alpha Centauri A and B. However, significant work is needed to design the engine components in detail using scientific scaling relations and ab inito calculations to develop the physical systems for prototyping and testing. After critically analyzing the reference design of the DFD and the underlying fusion reactor, this paper addresses the technological gaps and suggests avenues to improve specifications toward targets outlined in previous studies while considering costs. Further, the authors present a prototype engine and magnetohydrodynamic power conversion system design to study the engineering hurdles relevant to the practical implementation of the DFD.

Design of an Integrated Power Module for Silicon Carbide MOSFET with Self-Compensation of the Magnetic Field

Compactness, efficiency, and light weight are the key topics in the design of power conversion systems for transportation applications. This demand is achievable by using wide band gap devices such as SiC devices, characterized by the high switching speed and low on-resistance. However, this trend imposes new challenges and the effect of parasitic elements of power package during switching transient becomes significant. Hence, new packaging solutions should be investigated for addressing this concern. This paper presents a new multichip power module architecture, where its design considering capacitive and inductive stray elements is carried out. Using Ansys Q3D Extractor, electromagnetic simulations are achieved to extract the inductive and capacitive parasitic element of one leg of a three-phase inverter.

A Comparison of Power Conversion Systems for Modular Battery-Based Energy Storage Systems

A modular battery-based energy storage system is composed by several battery packs distributed among different modules or parts of a power conversion system (PCS). The design of such PCS can be diverse attending to different criteria such as reliability, efficiency, fault tolerance, compactness and flexibility. The present paper proposes a quantitative and qualitative comparison among the most widely proposed PCSs for modular battery-based energy storage systems in literature. The obtained results confirm the high performance of those PCSs based on the parallel connection of different modules to a single point of common coupling, also identifying those based on modular multilevel cascaded converters as promising concepts according to the assumptions of the present paper.

The use of multi-objective optimization to improve the design process of nuclear power plant systems

Multi-objective optimization is proposed to address the problem of design optimality in the nuclear power plant design process. This is done via the creation/development of the Optimization and Preference Tool for the Improvement of Nuclear Systems (OPTIONS). This work details applications of multi-objective optimization methods (in Python 3) to two different nuclear system design problems: the flash-Rankine power conversion system (PCS) of the I2S-LWR and the Passive Endothermic Reaction Cooling System (PERCS) attached to a standard PWR primary system (in RELAP5). The PCS design problem is first solved for three configurations using a specific particle swarm optimization method, achieving a thermodynamic efficiency of 34.81%. A new method, the Mixed-Integer Non-dominated Sorting Genetic Algorithm (MI-NSGA), is created and then used, solving a PCS superstructure of 22 configurations and achieving an efficiency of 35.63%. The OPTIONS tool is finally used to optimize the PERCS, improving cost, core temperature control, and cooling longevity.

Loss of off-site power transient analysis for a sodium-cooled fast reactor equipped with a gas power conversion system and preliminary optimisation of its operation

The French Commission for Atomic Energy and Alternative Energy (CEA) in collaboration with its industrial partners develops Sodiumcooled Fast Reactors (SFR) as industrial-scale demonstrators mainly guided by safety and operability objectives. In this paper, a SFR reactor associated to a nitrogen closed Brayton cycle for the Power Conversion System (PCS) is considered. This paper is dedicated to an alternative procedure to control a Loss Of Off-site Power (LOOP). Usually, in case of LOOP, the SFR standard procedure relies on passive Decay Heat Removal (DHR) systems to cool down the primary circuit. In this paper, an alternative solution substitutes the use of the latter by the gas Power Conversion System (PCS). This aims at reducing the delay to reach the cold shutdown state while fulfiling safety criteria dealing with thermal stress issues.The aim of this paper is to study the potential of the alternative sequence to cool down the reactor for a LOOP. It is interesting to integrate the alternative procedure to the reactor operation, in order to improve the reliability of the DHR function, by adding a medium strength safety defence line. Nevertheless, the high level of complexity associated to the gas PCS design makes its qualification as a safety grade system impossible. For this reason, the DHR systems cannot be replaced by the gas PCS and remain the main safety grade systems.The actuator of the sodium temperature regulation of the secondary circuit is chosen thanks to a global sensitivity analysis performed with a metamodel-based methodology. The setting of the controller associated to the TM rotation speed regulation is justified by the study of different proportional-integral-derivative (PID) controllers.A comparison of this alternative sequence with the reference one, based on simulations with the system thermalhydraulic code CATHARE2, is presented in this paper. The study indicates that the passive DHR systems allow the reactor to reach the cold shutdown state only after 24 h, whereas the procedure with the gas PCS required few hours to lead the reactor in this safety state. A Multiobjective Optimisation Problem (MOP) is solved in order to minimize simultaneously the delay to reach the cold shutdown state and the thermal stresses on the main vessel during the alternative procedure. These two objectives are conflicting, thus optimal compromises between them are required to solve the MOP and define a Pareto front.In this way, the alternative procedure allows the reactor to reach the cold shutdown state in a time ranging from around 36 min to 3 h and 52 min. The shortest observed time to reach the safety state induces a maximum of the thermal gradient through the main vessel around 40 percent higher than the procedure with passive DHR systems whereas a long delay to reach the safety state can divide the higher thermal gradient observed by 6.7.Thanks to the regulation of the TM rotation speed, the gas PCS is hence an adaptable system to optimize the thermalhydraulic behaviour of a SFR during a LOOP.

Guest Editorial: Special Section on Modeling, Design, and Application of Next-Generation Power Components

Power electronics, characterized by impressive technology advancement over the last two decades, has become a more complex and multidisciplinary research field. Power semiconductor devices, passive components and power conversion systems are undergoing significant performance improvement, but meanwhile facing challenges in efficiency, flexibility and reliability. While new wide-bandgap semiconductor devices are now establishing new efficiency and switching speed standards in the market, silicon power devices keep improving in terms of both manufacturing technology, package materials and design. Both call for new modeling methods and design efforts at device, component, and system levels, in order to accurately predict device characteristics, losses, EMI, hence allow design of power conversion systems with more precise margins. Furthermore, there is a lack of understanding of new phenomena and failure mechanisms associated with the new component technologies. From a system point of view, condition monitoring for high reliability is nowadays a musthave part in the overall application development process, demanding accurate and trustable models.

Mitigation of high harmonicity and design of a battery charger for a new piezoelectric wind energy harvester

A new piezoelectric wind energy harvester (PWEH) implementation and its power conversion system design have been studied. The new PWEH is a portable, economic, easy-mounted, and contactless machine exerting the elastic piezoelectric layers with permanent magnets (PMs). Although a single piezoelectric layer has an ideal sinusoidal waveform from its output terminals, the combined rotating system having multiple layers give complicated responses due to the electromechanical damping, high frequency mechanical vibrations and electromagnetic nonlinearities. In the current work, for instance, three layers generate three different waveforms with high harmonics. Thus, the output waveforms of such multiple layer low power-scale systems require special attention to gain the maximal power from such low-scale harvesters. Indeed, electrical power generation from complicated voltage waveforms and charging efficiency have become main tasks for those low power systems. The proposed rectifier is joined to a capacitor-inductor output filter to ensure high quality DC – bus voltage by ripple mitigation function. An effective control strategy is also carried out for the voltage – mode control (VMC) method in order to control the DC-DC buck converter in such a way that it may guarantee a smooth output DC voltage. Then the later can be applied to charge storage unit such as a lead-acid type electrochemical battery for the future numerous low power applications. The proposed circuitry is successful to mitigate the harmonics of the voltage waveforms from the terminals of three piezoelectric layers with high THD values (i.e. 169.16%, 51.75% and 42.64%). In addition, the proposed PWEH has an ability to charge the battery with a stable output rectified voltage at 40 V by enabling a linear increase in the State-Of-Charge (SOC) from 0% to 18% after 4 s till the battery is fully charged.

R&D on the power conversion system for gas turbine high temperature reactors

JAERI is conducting R&D on the power conversion system of the GTHTR300 plant, in parallel with plant design work. The design of the power conversion system is based on a regenerative, non-intercooled, closed Brayton cycle with helium gas as the working fluid. A single-shaft, axial-flow turbo-compressor and a directly coupled electric generator run on magnetic bearings. Major R&D issues for the power conversion system are aerodynamic performance of the helium gas compressor, high load capacity magnetic bearings and performance of magnetic bearing supported rotor, and operability and controllability of the closed-cycle gas turbine system. Three test plans were set up to address theses issues, aiming at verifying the design of the GTHTR300 power conversion system and establishing key technologies of a closed-cycle helium gas turbine system. The compressor aerodynamic performance test is aiming at verifying the aerodynamic performance and design method of the helium compressor. A 1/3-scale, four-stage compressor test model and a helium gas loop were designed and fabricated. The model was designed to simulate the repeating stage flow, and at the same time have satisfactorily high machining precision, Reynolds number and measurement accuracy. The helium gas operating pressure is varied to investigate the effects of the Reynolds number on the efficiency and surge margin. Two sets of blades were fabricated to evaluate the effects of the end-wall over-camber angle. Test results will provide the basis for further improvement in the GTHTR300 compressor design. The magnetic bearing development test is aiming at developing the technology of the magnetic bearing supported rotor system. The test rig composed of 1/3-scale turbo-compressor and generator rotor models that are connected together by a flexible coupling. Each rotor models are supported by two radial magnetic bearings with a high load capacity that is about 1/10 of the GTHTR300 design. The rotor models were designed so that both the critical speeds and vibration modes are matched to those of the actual rotors. A 1/3-scale test model of a turbo-machine rotor system and magnetic bearings were designed and fabrication of the test model was started. Testing of magnetic bearing performance, unbalance response, stability, and auxiliary bearing reliability will be carried out together with development of advanced control method in the program. The test will validate the design methods of the rotor system and magnetic bearing control system. The test will verify the rotor design of GTHTR300 and the results will identify technical issues in scaling up of magnetic bearings. The gas-turbine system operation and control test is aiming to demonstrate operability and controllability of the closed-cycle gas-turbine system. Preliminary design was made for the test facility that is an integrated scaled model of the GTHTR300 power conversion system. Pressurized helium gas at around 1 MPa is used as the working fluid, and an electric heater simulates the reactor. Planned test modes are normal operation, start-up, shutdown, load change, loss of load, and emergency shutdown. Specifications of the system operation and control were defined to fulfill the test requirements. The test will verify the design of the GTHTR300 control system and establish the operation and control method. Development and verification of a plant dynamics analysis code will be made based on the test results. Major components of the facility, such as a turbine, a heater, a recuperator, and a pre-cooler, were designed to meet the specifications. Preliminary transient analyses were made for the test facility design. It was confirmed from the results of the analyses that the test facility can be operated to meet the requirements of the test plan and controlled satisfactorily. A revision of the design is underway for purposes of the reduction in the power demands and the improvement in the control system. These scaled tests will surely validate the GTHTR300 power conversion system design and the results will be incorporated in the design in the upgrading stage. The R&D program as a whole will well demonstrate the technical feasibility of the high-efficiency gas-turbine system for high-temperature gas-cooled reactor plants.

Cost and performance design approach for GTHTR300 power conversion system

Japan Atomic Energy Research Institute (JAERI) has been carrying out a design and developmental program for the gas turbine high temperature reactor of 300 MWe nominal-capacity (GTHTR300) power plant, aiming at prototype demonstration in Japan during 2010s. This paper introduces overall objectives of the program and describes the plant design and development approach taken to achieve these goals. A detailed description is focused on the power conversion system design and associated component research and development undertaken in the present program. The power conversion system incorporates unique design approach of non-intercooled cycle to attain economical performance at minimal system complexity, intrinsic cycle flow provision for reactor pressure vessel cooling, simplified and high-performance turbomachine in a horizontal design, and modularity of maintenance for all major power conversion equipment. This paper reports extensive technical evaluation related to these significant system design features, which are shown to offer the optimum solution of plant cost, efficiency potential, reliability and maintainability in addition to near-term commercial deployment.

A Reverse Conduction Static Induction Thyristor Model for Circuit Simulation

In a field of simulation concerning semiconductor power devices, there are process simulation, device simulation, circuit simulation. These simulations are selected for their purpose. In order to analyze static and dynamic phenomena of semiconductor power devices or passive devices, and to support the design of power conversion systems, many circuit simulation models of semiconductor power devices such as GTOs, IGBTs, Thyristors are fabricated.In this paper, a reverse coducting static induction thyristor model is proposed. The model is made up of SI thyristor model with two transistor analogue and diode model with SPICE internal diode, capacitance and resistance. For confirming the accuracy of this circuit model, some experiments are carried out. As a result, good agreement are shown between the measured and calculated results.

95/01463 GT-MHR hellum gas turbine power conversion system design and development

Highly integrated Gallium Arsenide (GaAs) chips of preamplifiers and summing amplifiers have been exposed to high fluence of fast neutrons and γ-dose at the IBR-2 reactor in Dubna. A stable performance of the electronics has been demonstrated up to a fluence of 5×1014ncm-2 and a γ-dose of 55 kGy. The radiation hardness tests confirm the applicability of the preamplifiers for more than 10 years operation in the ATLAS hadronic end-cap calorimeter at LHC.