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This paper analyses the formation mechanism of the transmission distortion of electronic voltage transformer, and points out that the integrator will magnify the transient transfer error and superimpose the dynamic additional component on the output signal, which may cause the transfer distortion of voltage signal in serious cases. To restrict the electronic transformer transient variable error effect on distance relay, a distance relay method using instantaneous value after equal transfer processes is proposed. It directly uses output differential signals of the capacitor voltage divider and Rogowski coil. The capacitor voltage divider and Rogowski coil are decomposed into several typical variable link in series. The virtual digital transfer link, which is constructed by the digital filter, is used to compensate for the difference parts of the transfer link, so that the voltage and current signals pass through the same transfer link. It can mitigate the influence of voltage and current signal transfer difference on the calculation accuracy of distance relay. The simulation results show that the proposed distance relay method has fast operation speed and is less affected by abnormal voltage and current signal transfer, and its performance is better than existing distance relay methods. [ABSTRACT FROM AUTHOR]

SUMMARY Recently, in Japan, large-scale introduction of photovoltaics (PVs) has been under way. This development increases the likelihood of system voltage increase and fluctuations, which can be prevented by employing PV output prediction. In this study, we focus our attention on applying PV output prediction to system operation with the objective of system voltage control. In this paper, 30-min ahead prediction is assumed according to prior research with prediction error consideration. System voltages of 30 min ahead are estimated and are controlled in advance by using transformer taps and static capacitors. In this paper, voltage control is proposed for coordinating control, which is based on one of the games in the game theory, potential game. The validity of the proposed method is confirmed by running simulations using a modified IEEE 30 bus system. By applying the proposed method, both the voltage deviations and control counts improved considerably compared to a conventional method. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents an experimental discussion on modular multilevel cascade converters based on double-star chopper cells (MMCC-DSCC). Hereinafter, a single MMCC-DSCC is referred to simply as a 'DSCC'. A couple of DSCCs are used to form a front-to-front (FTF) system capable of dc voltage matching and galvanic isolation between two dc grids. The FTF system can be considered as a dc-ac-dc power conversion system including an ac-link high-power transformer. The higher the ac-link frequency, the smaller and lighter are the ac-link transformer and dc capacitors. When the so-called 'phase-shifted-carrier PWM' is applied to the DSCC, theoretical analysis and computer simulation have confirmed that a ratio of the carrier frequency with respect to the ac-link frequency can be reduced to 5/2. This paper designs, constructs, and tests a 400-Vdc 10-kW downscaled FTF system with a carrier frequency of 450 Hz and an ac-link frequency of 180 Hz, where their ratio is 5/2. Experimental waveforms obtained from the downscaled system are compared with simulated ones obtained from a software package, PSCAD/EMTDC, under the same operating and circuit conditions. They agree well each other not only under steady states but also under transient states. [ABSTRACT FROM AUTHOR]

SUMMARY The Japanese government has set 53 GW as the target level of PV deployment by 2030. However, the large-scale introduction of PV will cause several problems in power systems. One of these problems is the increase in voltage due to decreased load demands associated with large PV active power output. Another problem is voltage variations caused by fluctuations in PV system output. In this paper, we focus our attention on the voltage and reactive power control for large-scale PV deployment and propose voltage control using the PF (PV power factor), SC (static capacitor), and TAP (transformer tap). In the proposed method, the SC and TAP controls consider voltage stability through the use of VMPI-i and VMPI-i sensitivity, and the PF control suppresses voltage variation and voltage spikes. Finally, we simulate these controls using the Ward-Hale system to verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]