• International Journal of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.161-167
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• 2021

This paper proposes a new personalized HRTF estimation method which is based on a deep neural network (DNN) model and improved elevation reproduction using a notch filter. In the previous study, a DNN model was proposed that estimates the magnitude of HRTF by using anthropometric measurements [1]. However, since this method uses zero-phase without estimating the phase, it causes the internalization (i.e., the inside-the-head localization) of sound when listening the spatial sound. We devise a method to estimate both the magnitude and phase of HRTF based on the DNN model. Personalized HRIR was estimated using the anthropometric measurements including detailed data of the head, torso, shoulders and ears as inputs for the DNN model. After that, the estimated HRIR was filtered with an appropriate notch filter to improve elevation reproduction. In order to evaluate the performance, both of the objective and subjective evaluations are conducted. For the objective evaluation, the root mean square error (RMSE) and the log spectral distance (LSD) between the reference HRTF and the estimated HRTF are measured. For subjective evaluation, the MUSHRA test and preference test are conducted. As a result, the proposed method can make listeners experience more immersive audio than the previous methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.169-180
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• 2019

Grid codes for grid-connected inverters are essential considerations for bulk grid systems. In particular, a low-voltage ride-through (LVRT) function, which can contribute to the grid system's stabilization with the occurrence of voltage sag, is required by such inverters. However, when the grid voltage is under zero-voltage condition due to a grid accident, a zero-voltage ride-through (ZVRT) function is required. Grid-connected inverters typically have phase-locked loop (PLL) control to synchronize the phase of the grid voltage with that of the inverter output. In this study, the LVRT regulations of Germany, the United States, and Japan are analyzed. Then, three major PLL methods of grid-connected single-phase inverters, namely, notch filter-PLL, dq-PLL using an active power filter, and second-order generalized integrator-PLL, are reviewed. The proposed PLL method, which controls inverter output under ZVRT condition, is suggested. The proposed PLL operates better than the three major PLL methods under ZVRT condition in the simulation and experimental tests.

• Journal of Power Electronics
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• v.12 no.4
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• pp.654-663
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• 2012

In this paper, a digital control strategy based on equivalent fundamental and odd harmonic resonators is proposed for single-phase DVRs. By using a delay block, which can be equivalent to a bank of resonators, it rejects the fundamental and odd harmonic disturbances effectively. The structure of the single closed-loop control system consists of a delay block, a proportional gain and a set of zero phase notch filters. The principle of the controller design is discussed in detail to ensure the stability of the system. Both the supply voltage and the load current feedforwards are used to improve the response speed and the ability to eliminate disturbances. The proposed controller is simple in terms of its structure and implementation. It has good performances in harmonic compensation and dynamic response. Experimental results from a 2kW DVR prototype confirm the validity of the design procedure and the effectiveness of the control strategy.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.150-152
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• 2018

계통 사고 시 계통연계형 인버터에 대한 각국의 계통 규정(Grid Code)이 더욱 엄격해 지고 있다. 계통 규정은 특히, 계통 내 저전압 사고로 인한 인버터 운전계속성(Low Voltage Ride Through, LVRT)뿐만 아니라 0 전압 사고 시 운전계속성(Zero Voltage Ride Through, ZVRT)을 통해 인버터가 계통 안정화에 기여할 것을 요구하고 있다. 계통연계형 인버터는 계통전압과 인버터 출력 위상을 일치시키는 PLL제어가 적용되며 본 논문에서는 위상 추종이 어려운 0 전압 상황에서도 안정적인 위상 추종 및 인버터 출력이 가능한 PLL 방법을 제안한다. 단상 인버터에 Notch filter-PLL, APF를 이용한 dq-PLL, 및 SOGI-PLL(Second-order Generalized Intergrator)을 적용하고 독일, 미국, 및 일본의 0 전압 상황에 대해 시뮬레이션과 실험을 진행하여 제안한 PLL 기법의 ZVRT 유효성을 확인하였다.