PEM fuel cell system control: A review

The area of modeling and simulation is a critical aspect in the basic research to commercialization and instantiation cycle. This paper reports on modeling and simulation in the context of verification, validation, and experimentation of power and energy systems and associated electrical apparatus via the utilization of power hardware in the loop (PHIL)-based strategies. PHIL is a powerful technique for testing and demonstration of systems in a rigorous and dynamic manner that is not achievable with other methodologies; however, it must only be conducted with foreknowledge of the technique and its challenges in order to realize its significant benefits. This paper reports on the state of the art in PHIL and its challenges and presents sample case studies illustrating its impact.

Role of Power Hardware in the Loop in Modeling and Simulation for Experimentation in Power and Energy Systems

The area of modeling and simulation is a critical aspect in the basic research to commercialization and instan- tiation cycle. This paper reports on modeling and simulation in the context of verification, validation, and experimentation of power and energy systems and associated electrical apparatus via the utilization of power hardware in the loop (PHIL)-based strategies. PHIL is a powerful technique for testing and de- monstration of systems in a rigorous and dynamic manner that is not achievable with other methodologies; however, it must only be conducted with foreknowledge of the technique and its challenges in order to realize its significant benefits. This paper reports on the state of the art in PHIL and its challenges and presents sample case studies illustrating its impact.

Role of Power Hardware in the Loop in Modeling and Simulation for Experimentation in Power and Energy Systems This paper reports on the development and benefits for modeling and simulation in ship power systems and how this is used for verification, validation, and experimentation of power components and integration using power hardware in the loop for testing and demonstration of the system.

Microgrids (MGs) are seen today as the solution to the challenge of meeting the ever-increasing demand of energy which is clean. A variety of challenges need to be overcome for these MGs to be successful varying from stability, power quality to protection, and management. Since the various control strategies are actively being researched and emerging challenges still being addressed, there has been a lot of interest related to the aspect of testing. The ever-increasing complexity of control mechanisms invokes the need for safer, faster yet reliable testing methods, which do not compromise on the degree of detail and at the same time are economical and require the minimum testing time. Off-line simulation, real-time (RT) simulation, hardware in the loop simulation, RT emulation, hardware test beds, pilot plants, and other integrated approaches are the major methods for testing in MGs. This paper gives an overview of the testing techniques and discusses the trends in the various technologies employed for testing MGs. First, the various methods are briefly discussed and a comparison is provided. Next, the various research efforts carried out on the aspect of MG testing are categorized and presented one-by-one. Furthermore, new methodologies and emerging approaches for the testing have also been highlighted, and the challenges and future research avenues have been presented.

Real-Time Testing Approaches for Microgrids

Electric vehicles (EVs) have remarkably emerged as an alternative for internal combustion engines. With high penetration levels of the EVs, its addition to the existing distribution line infrastructure affects the power quality and grid stability. Additionally, EV charging loads are characteristically different as they are mobile compared to other fixed node-connected loads. Proposing solutions without considering these factors may result in grid congestion and subsequent over/under compensations. Another emerging dynamics co-occurring in the distribution system is high penetration levels of renewable energy in the utility grid. Although these dynamics pose challenges in stable grid operation, it also gives opportunities for solving some of the grid integration issues of EV loads. Thus, the effect of adding EV charging load to the existing low voltage distribution system must be analyzed by considering different criteria such as grid impact with different EV chargers, mobile nature of EV load, power quality, voltage profile, and spread/peak demand of load curve. This paper presents a detailed report on the impact analysis of EV integration on the component and system levels. For analyzing the effect on power quality (component level), grid pollution contributed by EV chargers along with possible solutions is elucidated. Detailed discussion on the significance of EV load location, existing load distribution, and nature of EV charging load distribution is presented by considering different feeders and different load curves. These discussions are supported with simulated case studies followed by a review of existing literature for enhanced understanding. Finally, techniques employed to effectively model the mobile nature of EV load and distributed EVs potential to provide ancillary solutions are also explained.

Comprehensive review & impact analysis of integrating projected electric vehicle charging load to the existing low voltage distribution system

The significance of harmonics in power systems has increased substantially due to the use of solid state controlled loads and other high frequency producing devices. An important consideration when evaluating the impact of harmonics is their effect on power system components and loads. Transformers are major components in power systems. Supplying non-linear loads by transformer leads to higher losses, early fatigue of insulation, and reduction of the useful life of transformer. To prevent these problems rated capacity of transformer supplying non-linear loads must be reduced. This paper reviews the non linear loads effects on the transformers and the standard IEEE procedures for derating of the transformers which are under distorted currents. The equivalent losses and capacity of a typical 25 KVA single phase transformer is then evaluated using analysis and simulations in MATLAB/Simulink-based on useful model of transformer under harmonic condition- and results are compared.

Comparison of distribution transformer losses and capacity under linear and harmonic loads

In power hardware in the loop (PHIL) simulations, a real-time simulated power system is interfaced to a piece of hardware, usually called hardware under test (HuT). A PHIL test can be realized using several simulation tools. Among them Real Time Digital Simulator (RTDS) is an ideal tool to perform complex power system simulations in near real-time. Stable operation of the entire system, along with the accuracy of simulation results are the main concerns regarding a PHIL simulation. In this paper, a simulated power network on RTDS will be interfaced to HuT through a voltage source converter (VSC). Issues around stability and other interface problems are studied and a new method to stabilize some unstable PHIL cases is proposed. PHIL simulation results in PSCAD and RSCAD are presented.

Studies in power hardware in the loop (PHIL) simulation using real-time digital simulator (RTDS)

Transformers are normally designed and built for utilizing at rated frequency and prefect sinusoidal loads. Supplying non-linear loads by transformer leads to higher losses, early fatigue of insulation, and reduction of the useful life of transformer. To prevent these problems rated capacity of transformer supplying non-linear loads must be reduced. In this paper, at first, a useful model of transformer under harmonic condition is presented. The model in addition to ordinary parameters includes a potential difference defined as the second derivative of the load current that represents eddy current losses in windings and the other stray losses represented as a resistor in series with the leakage inductance and dc resistance. Finally, losses and capacity of 50 KVA transformer under harmonic load current is calculated. This model simulated in MATLAB/Simulink and then its results are compared with losses and capacity calculated by standard.

Derating of transformers under non-sinusoidal loads

A virtual power system can be interfaced with a physical system to form a power hardware-in-the-loop (PHIL) simulation. In this scheme, the virtual system can be simulated in a fast parallel processor to provide near real-time outputs, which then can be interfaced to a physical hardware that is called the hardware under test (HuT). Stable operation of the entire system, while maintaining acceptable accuracy, is the main challenge of a PHIL simulation. In this paper, after an extended stability analysis for voltage and current type interfaces, some guidelines are provided to have a stable PHIL simulation. The presented analysis have been evaluated by performing several experimental tests using a Real Time Digital Simulator (RTDS™) and a voltage source converter (VSC). The practical test results are consistent with the proposed analysis.

Stability synthesis of power hardware-in-the-loop (PHIL) simulation

Ability of fuel cell systems to produce power is limited So it is necessary to force the system to operate in conditions which correspond to fuel cell maximum power point (MPP) Since fuel cell MPP is a unique and fixed point of operation, load power requirements are not taken into account and output voltage will vary with variations of load resistance In this paper, a new configuration for fuel cell / battery hybrid power system with required controller is proposed and analyzed This system works in the way that, fuel cell operates in its MPP and output voltage is kept constant The proposed system is simulated and results show acceptable operation of the system under different conditions

M. Dargahi

Papers

Comparison of distribution transformer losses and capacity under linear and harmonic loads

Studies in power hardware in the loop (PHIL) simulation using real-time digital simulator (RTDS)

Derating of transformers under non-sinusoidal loads

Stability synthesis of power hardware-in-the-loop (PHIL) simulation

Maximum power point tracking for fuel cell in fuel cell/battery hybrid systems