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This paper presents the analysis and validation of a real-time ac drive simulator. Real-time simulation has been used for over a decade in power systems engineering to test controllers thoroughly, efficiently, and safely. The development and testing of large ac drives could benefit from this type of simulation, but real-time power system simulators have modeling restrictions preventing stable and accurate simulation of isolated drives switching at high frequencies. These restrictions can be overcome by combining in a single model both the power converter and motor models. After discussing the salient issues related to the real-time simulation of ac drives, a prototype real-time simulator for drives is described. Its ability to accurately emulate the behavior of large drives is demonstrated through two case studies. A first case study demonstrates the feasibility of simulating a drive of typical complexity in real-time. The second case study demonstrates how the controller for a PWM VSI fed induction motor, switching at 4 kHz, is designed, implemented in a microcontroner and tested in real-time using a simulated inverter, motor and load. Comparisons against results obtained with another simulation tool, which uses extremely accurate variable-step integration algorithms, demonstrates the validity of our approach. Index Terms--AC motor drives, hardware-in-the-loop testing, real time simulation, state space methods.

The three-phase dual active bridge (3p-DAB) converter is widely considered in dc-grid applications. Because of the higher number of switches in the 3p-DAB, it can be argued that the reliability of the 3p-DAB is reduced when compared to other isolated-bidirectional dc–dc converter topologies. The previous work has shown that the 3p-DAB can be operated in a frozen leg fault-tolerant mode, i.e., with the two transistors of the same phase being opened by their gate driver internal protections. Because the free-wheeling diodes are left self-commutated, the analytical characterization of the converter for all voltage and loading conditions is not trivial. In this article, it is proposed to open the faulty phase such as it eliminates the interaction with the faulty-phase free-wheeling diodes. This allows the converter to fall in a characterizable operating mode for all voltage and loading conditions. The results further show that the open-phase operation provides advantages over the frozen leg operation in terms of current stress and power transfer capability. Experimental results on a small-scale closed-loop gallium nitride-based prototype as well as time-domain simulation results are provided to support the theoretical analyses. [ABSTRACT FROM AUTHOR]

Developing a general and stable numerical interface for power hardware-in-the-loop (PHIL) applications is a major challenge. This paper proposes a stable, robust and precise implementation of a multi-time-step interface for a PHIL simulator based on the Bergeron transmission line model (BTLM). Two limitations of the transmission-line-based interface were identified, and remedial strategies were formulated in order to ensure that the interface was compatible with the PHIL application. Stability and passivity analyses were then conducted on the resulting interface to verify its performance. The proposed interface was implemented in an experimental 3-kVA PHIL setup, using a custom-made switching power amplifier (PA). Multiple tests were performed in order to demonstrate the stability and accuracy of the closed-loop system under a wide range of operating conditions and with various devices under test (DUTs). Experimental results were obtained from islanding tests involving different simulated load configurations and solar inverter responses to network disturbance while operating in a closed-loop configuration. [ABSTRACT FROM AUTHOR]

The three-phase dual active bridge (3p-DAB) converter is widely addressed in emerging power systems applications such as solid-state transformer and dc microgrids. Its successful integration requires accurate modeling of its small-signal characteristics. Due to its dc–ac–dc structure, the DAB converter brings many challenges to small-signal modeling. The state-space averaging (SSA) has been the first proposed methodology to approximate the control-to-output and line-to-output transfer functions of the 3p-DAB. However, as shown in this paper, SSA is not precise for the stability analysis of 3p-DAB converters. A generalized state-space averaging (GSSA) model based on the dynamic phasor concept is developed in this paper for the Y-Δ 3p-DAB. A hybrid SSA and GSSA model representation is then proposed for the evaluation of all the converter transfer functions. The developed models are validated with detailed time-domain switch-level simulations in an electromagnetic transient-type (EMT-type) program. They are also used for the accelerated stability prediction in an EMT-type program. [ABSTRACT FROM PUBLISHER]

This study establishes a new basis for understanding the stability of power hardware‐in‐the‐loop (PHIL) systems considering their hybrid (analogue/digital) nature. Such systems are known to have closed‐loop stability issues due to delays between the simulator and the power amplifier (PA). This work demonstrates that the conventional method for determining the stability criterion, which considers the system as a continuous model, is not appropriate. A new method of assessing the stability of a PHIL system based on discrete‐time impedance frequency responses is thus presented. Hydro‐Québec's Research Institute will use this innovative approach for the development of its own PHIL system, which will involve connecting the institute's real‐life experimental distribution test line to its large‐scale real‐time digital simulator through a 25‐kV, 10‐MVA PA. The validity of the new method is demonstrated for simulation models of a well‐known inductive system and of a distribution feeder connected to a large‐scale power system. [ABSTRACT FROM AUTHOR]

This paper presents a generic electrothermal model for Li-ion battery. The model is developed with the objective to simplify the parameter identification procedure, while representing adequately the thermal effects on the battery performance. Most of the well-accepted electrothermal Li-ion battery models require in-depth and proprietary battery data or dedicated test environments for parameter identification. The dedicated test bench usually involves expensive thermal test chambers, calorimeters, and temperatures sensors, and challenges associated with their installations. This makes the electrical and thermal simulation of Li-ion batteries difficult to achieve. This paper proposes a generic electrothermal model with a simpler parameter identification process. The parameters identification process is solely based on datasheet discharge curves and simple experiments at room temperature. The model is validated experimentally using a 12 V 40 Ah LiFePO4 battery module. The performance of the model is tested with constant current discharges, constant current–constant voltage charges, as well as with a Simplified Federal Urban Driving Schedule dynamic driving cycle, at different operating temperatures. As expected, the simulation results show an error within $\pm$1% and $\pm$1.3% compared to experimental results, for both steady and dynamic states, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a sliding-mode control (SMC)-based scheme for the variable-speed direct-driven wind energy conversion systems (WECS) equipped with a permanent magnet synchronous generator connected to the grid. In this paper, diode rectifier, boost converter, neutral point clamped inverter, and L filter are used as the interface between the wind turbine and grid. This topology has abundant features such as simplicity for low- and medium-power wind turbine applications. It is also less costly than back-to-back two-level converters in medium-power applications. The SMC approach demonstrates great performance in complicated nonlinear systems control such as WECS. The proposed control strategy modifies reaching law (RL) of the sliding mode technique to reduce chattering issue and to improve total harmonic distortion property compared to conventional RL SMC. The effectiveness of the proposed control strategy is explored by simulation study on a 4-kW wind turbine, and then verified by experimental tests for a 2-kW setup. [ABSTRACT FROM PUBLISHER]

In this letter, the authors present an approach for designing discrete packaging of a bidirectional power switch used in matrix converter applications. The study is based on computing the magnetic field inside a specific resonant switching cell in order to incorporate low-voltage control circuits inside the compact space volume of the power module. The novelty of the proposed configuration is the creation of an oriented magnetic field area, which has very low impact on the low-level control signals of the power devices. Numerical analyses as well as experimental results are presented to demonstrate the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

At high frequency, AC resistance of a printed circuit board (PCB) winding becomes important and accounts for a large proportion of planar transformer losses. The winding is then influenced by both skin and proximity phenomenon, which makes the current distribution uneven resulting in an increased resistance. The study of improving AC resistance of a PCB winding has been tackled by many researchers. However, the lack of an overview and comparison among improvements has made it difficult to apply those methods to a specific winding. To overcome the above limitations, this paper investigates the pros and cons of three popular AC resistance optimizing methods: optimizing track width of a solid PCB winding, using multi-strands and using Litz style PCB winding. To verify the theoretical analysis, a total of 12 PCBs are simulated by finite element (FEM) and tested in the laboratory. Five criteria are analyzed, including skin resistance, proximity resistance, AC to DC ratio, total AC resistance and complexity are taken into consideration. The results of this study show that optimizing track width method has a significant improvement on AC resistance while the use of Litz PCB is effective for applications that need stable AC resistance in a wide frequency range. The use of parallel strands winding should be carefully considered as there is not significant benefit in both reducing the AC resistance and AC to DC ratio. [ABSTRACT FROM AUTHOR]

At high frequency, power losses of a winding due to eddy currents becomes significant. Moreover, the skin and proximity AC resistances are influenced by the width of printed circuit board (PCB) conductors and distance between the adjacent tracks which causes many difficulties to design windings with lowest AC resistances. To clarify this phenomenon, this paper focuses on modeling the influence of skin and proximity effects on AC resistance of planar PCB winding, thereby providing guidelines to reduce the winding AC resistance. An approximate electromagnetic calculation method is proposed and it shows that when the winding proximity AC to DC ratio (F p r o x i m i t y) is equal to 1 3 the AC on DC ratio caused by skin effect (F s k i n) , the winding is optimized and it has lowest AC resistance. 3-D finite element simulations of 3, 7 and 10-Turn windings, which are divided into 3 groups with the same footprint, are presented to investigate the lowest AC resistance when the track width varies from 3 mm to 5 mm and the frequency range is up to 700 kHz. In order to verify the theoretical analysis and simulation results, an experiment with 3 simulated groups, (9 prototypes in total) is built and has a very good fit with simulation results. Experimental results show that at the optimal width, the AC resistance of the windings can be reduced up to 16.5 % in the frequency range from 200 kHz to 700 kHz. [ABSTRACT FROM AUTHOR]