This paper investigates the use of the norm criteria in the electromagnetic time reversal (EMTR) technique to locate faults in transmission lines. The energy root criterion and amplitude peak criterion, derived from 2-norm and ∞-norm, are considered and discussed contrastively. It is shown that both considered norm criteria can effectively be used in an EMTR method to locate faults. The ∞-norm originates from temporal and spatial variation of norm quantity of voltage/current wave propagation in the EMTR process. It is proven that the ∞-norm criterion makes use of the EMTR refocusing property of voltage/current waves propagating along transmission lines. In the extremely noisy circumstances, the ∞-norm criterion shows better robustness against noise compared to the 2-norm. It can locate the fault accurately even when the time-domain features of a strongly interfered signal cannot be identified. To validate the performance of the proposed criteria, two experimental tests on a reduced-scale network composed of coaxial cables and a real power grid are performed. The fault position is located accurately by the two criteria using one-terminal measurement data. It is suggested that the two criteria can be used complementarily to enhance the fault location efficiency.

The insertion of dead-time will lead to the distortion of output waveforms, which seriously affects the characteristics of the AC induction motor (ACIM) control system. In order to reduce the output distortion of three-level T-type inverters caused by dead-time insertion, an online feedback dead-time compensation method is developed. In this method, the compensation time is obtained and further corrected by online feedback of duty cycle. Meanwhile, Current polarity judgment is accurately realized by sampling the neutral point potential (NP) and three phase output terminal voltage potentials. In addition, this paper takes the neutral point potential fluctuation into account to approximate the true situation. The developed method can be applied to both open-loop and closed-loop motor drive systems. To verify the effectiveness of the method, essential simulation and experiments are carried out. Compared with the traditional methods, the developed method can prominently reduce the output waveform distortion. Simulation results emphasize that the proposed scheme can significantly improve the performance of three-level inverters, and the identical conclusion is obtained on 210V/2.24kW motor platform.

The application of electric motor emulators (EME) has been prosperous in recent years along with the advancement in power hardware-in-the-loop technology. However, EME design methods based on a typical modeling approach and control structure tend to be invalid in promising a clear, dynamic accuracy objective and a robust dynamic accuracy performance over wide working points, especially at high operating speed. Hence, a new EME design method based on multi-input multioutput (MIMO) modeling and a MIMO closed-loop current control (MCLCC) structure is proposed in this article. Singular values of the MIMO motor model are analyzed to clarify the influence of the rotor speed on the dynamic accuracy objective of EME for the first time, based on which an unknown input observer is designed in the MCLCC structure to compensate for disturbance voltages caused by modeling errors. The transient tracking errors of both current and torque responses can thus be remarkably reduced at 300-Hz electrical speed in the experiment even if 35% modeling errors exist, verifying the superiority of the proposed EME design method in dynamic accuracy.

Resolvers are universally employed as absolute angle sensors in motor control systems. Detecting the synchronous envelopes is an essential step during the resolver-to-digital conversion (RDC) process when calculating the angle. However, conventional filter-based envelope detection could introduce enormous angle delay and peak capturing-based detection could lead to apparent quantization angle error. A novel all-digital RDC system is proposed in this article with the synchronous envelopes detected based on numerical synchronous integration method. The sine and cosine signals are oversampled and then multiplied by the excitation signal before integration to derive the envelopes. The angle delay and quantization errors could thus be largely reduced compared with RDC systems based on conventional envelop detections. In the experiment, angle error is limited to less than 30 arc min at the angular speed of 1000 r/min.

Electric motor emulator (EME) is being increasingly utilized during the development and test process of motor drive units (MDUs) for electric vehicle applications. However, the high-speed instability issue, without sufficient corresponding theoretical analysis currently, limits its further application. Hence, a comprehensive modeling and stability analysis approach for the high-speed EME is presented here to enrich the understanding of this special power hardware-in-the-loop testing scenario. A detailed model of the EME testing system with MDU included is developed in complex vector (CV) form for the first time, the poles loci of which are then plotted for accurately predicting the system stability. Influences of various factors including control bandwidth, time delay, and control structure on the speed limit of the EME are investigated, with parameter nonlinearities in the motor model also considered to demonstrate the extended applicability of the CV-based modeling approach. The maximum error between the predicted speed limits and the experimental results is less than 20 Hz, and the EME running up to 800 Hz is also experimentally achieved by adopting the internal model control structure, both validating the effectiveness and accuracy of the presented CV modeling and stability analysis approach for the high-speed EME.

An electric motor emulator (EME) is being prevalently used during the testing process of the motor drive unit for electric vehicle applications. Most of the existing research works focus on the improvement and analysis of the terminal current emulation accuracy of the EME, whereas research on the emulation accuracy of the EME terminal voltage is rare. The purpose of this article is to cope with the distortion of the EMEs terminal voltage at high modulation index due to the parasitic capacitance and deadtime of the emulator converter. A novel control scheme based on an active circulation regulation approach and a switched-mode modulation strategy is proposed in this article. The proposed control scheme is aimed at the commercial EME with the parallel-branch converter. Both simulations and experiments are carried out based on a prototype power topology, validating the effectiveness of the proposed control scheme in improving the voltage emulation accuracy of the EME.