• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.560-564
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• 2003

This paper proposes a simple control strategy based on the discontinuous PWM(DPWM) to balance the DC-link voltage of three-level Neutral-Point-Clamped(WPC) inverters at low modulation index. New DPWM methods in multi-level inverter are also introduced. The proposed DPWM method changes the path and duration to flow the neutral point current out of or into neutral point of the DC-link and it makes the overall fluctuation of the DC-link voltage zero during a sampling time of reference voltage vector. Therefore, the voltage of the DC-link can be balanced fairly well and also the voltage ripple of the DC-link is reduced significantly. Moreover, comparing with conventional methods, the proposed strategy is very simple. The validity of the proposed DPWM method is verified by experiment

• Journal of Power Electronics
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• v.19 no.2
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• pp.529-539
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• 2019

The modular multilevel converter (MMC) has become a promising topology for high-voltage direct current (HVDC) transmission systems. To control a MMC system properly, the ac-side current, circulating current and submodule (SM) capacitor voltage are taken into consideration. This paper proposes a low-computation indirect model predictive control (IMPC) strategy that takes advantages of the conventional MPC and has no weighting factors. The cost function and duty cycle are introduced to minimize the tracking error of the ac-side current and to eliminate the circulating current. An optimized merge sort (OMS) algorithm is applied to keep the SM capacitor voltages balanced. The proposed IMPC strategy effectively reduces the controller complexity and computational burden. In this paper, a discrete-time mathematical model of a MMC system is developed and the duty ratio of switching state is designed. In addition, a simulation of an eleven-level MMC system based on MATLAB/Simulink and a five-level experimental setup are built to evaluate the feasibility and performance of the proposed low-computation IMPC strategy.

• Analyses & Alternatives
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• v.6 no.1
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• pp.69-114
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• 2022

This paper analyzes Taiwan's 「New Southbound Policy」 from the perspective of 'balancing' and 'bandwagoning' in international politics. Specifically, it examines the changes and characteristics of 'Southbound policies' that have continued since the period of the Lee Teng-hui(李登輝) administration, and examines the meaning of the New Southbound Policy promoted by the Tsai Ing-wen(蔡英文) administration. Taiwan's foreign policy has been strongly influenced by external variables such as U.S.-China relations. Previous Taiwanese governments have actively promoted Southbound policies to advance to Southeast Asian countries such as ASEAN with the aim of 'De-Sinicization', but have not achieved much results. This is because variables such as cooperative U.S.-China relations and strong checks from China played a role at the time. In this environment, Taiwan had to pursue an appropriate 'balancing' between the United States, China, and Southeast Asian countries. However, since the inauguration of the Trump administration, strategic competition between the U.S. and China has been maximized, creating a new space for Taiwan's foreign policy. This is because the U.S. valued cooperation with Taiwan in the process of embodying the 'Indo-Pacific Strategy' to curb China's rise. The New Southbound Policy promoted by the Tsai Ing-won administration is different from the existing Southbound policies in that it seeks to link with the U.S. India-Pacific Strategy and attempts to advance to South Asian countries such as India. From an international political point of view, the Tsai Ing-won administration's New Southbound Policy can be interpreted as a 'bandwagoning' to the United States, not a balanced strategy between the U.S. and China. Strategic competition between the U.S. and China is expected to intensify for a considerable period of time in the future, and honeymoon between Taiwan and the U.S. are also expected to continue. Taiwan's bandwagoning strategy, which actively pursues a link between the New Southbound Policy and the India-Pacific Strategy, is also expected to be maintained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.211-219
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• 2014

This paper studies the technology management strategy for activating the industry-academia cooperation in open innovation environment. For this, the importance and concept of technology management balancing the internal innovation and utilization of external innovation resources, and industry-academia cooperation were theoretically reviewed. For the successful technology management in open innovation environment firms should adopt the industry-academia cooperation strategy. The technology management strategy for activating the industry-academia cooperation of the firm can be summarized as follows; Firstly, technology strategy for academia-industry cooperation utilizing the strategic technology roadmap should be prepared and executed. Secondly, the firm should adopt the open innovation system and transform their NIH(Not-Invented-Here) culture for open culture. Finally, for activating the networking with various innovation actors, industry-academia cooperation supporting system should be prepared.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.114-123
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• 2018

Recently, as one of the countermeasures to reduce carbon dioxide($CO_2$) for global warming problems, operation methods in micro-grid systems replacing diesel generator with renewable energy sources including wind power(WP) and photovoltaic(PV) system have been studied and presented in energetic manners. However, it is reported that some operation problems in micro-grid systems without diesel generator for carbon-free island are being occurred when large scaled WP systems are at start-up. To overcome these problems, this paper proposes an operation strategy in micro-grid systems by adapting control devices such as CVCF(constant voltage constant frequency) ESS(energy storage system) for constant frequency and voltage regulation, load control ESS for balancing demand and supply and SVC(static-var compensator) for reactive power compensation. From the simulation results based on the various operation scenarios, it is confirmed that the proposed operation strategy in micro-grid systems without diesel generators is a useful tool to perform a stable operation in micro-grid systems without diesel generator and also make a contribution to reduce carbon dioxide in micro-grid systems.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.247-249
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• 2007

Urban dynamometer driving schedule(FTP-75 mode) plays very significant role on automotive emission test, due to reference point. The overall system energy efficiency of a HEV(Hybrid Electric Vehicle) is highly dependent on the energy management strategy employed. An energy source is the heart of a HEV. In order to applicable to a vehicle component, it must be need to real world test result. But, the present state of things have numerous problems. In this paper, be studied performed based on HEV simulation software in virtual world and chassis dynamometer test in real world and the result make a comparative. Toyota Prius vehicle was adapted as a modeling and real testing to evaluate the hybrid components and energy balancing management. The point at issue is voltage and current analysis for HEV battery SOC(State of Charge), and verification for energy.

• Journal of Ecology and Environment
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• v.35 no.2
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• pp.61-71
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• 2012

Recent conditions in North Sulawesi Province (NSP) have become favorable for the development of tourism. In this paper, we present the recent status of biodiversity and tourism in NSP as a basic consideration towards integrative biodiversity conservation strategy. Overall, biological accounts suggest that NSP is important for the world biodiversity conservation program. NSP's biodiversity makes the area a major nature-based tourism (ecotourism) site in the world. Development of diverse tourism programs in NSP has provided new opportunities for balancing development and conservation of regional ecosystems. However, the excessive tourism growth in some particular areas in NSP has been identified as the primary factor of environmental degradation. Nowadays, biodiversity of North Sulawesi regions are suffering from the number of tourist impacts and facilities. Based on those conditions, tourism planning and development in NSP is needed to formulate a proper strategy to protect the ecosystem and biodiversity from degradation and extinction. This will be a new challenge of sustainable island tourism development and biodiversity conservation in NSP.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1173-1185
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• 2017

In this paper, a new single phase multilevel inverter topology with a single DC source is presented. The proposed topology is developed based on the concepts of the L-Z source inverter and the switched capacitor multilevel inverter. The input voltage to the proposed inverter is boosted by two steps: the first step by an impedance network and the second step by switched capacitor units. Compared to other existing topologies, the presented topology can produce a higher boosted multilevel output voltage while using a smaller number of components. In addition, it provides more flexibility to control boosting factor, size, cost and complexity of the inverter. The proposed inverter possesses all the advantages of the L-Z source inverter and the switched capacitor multilevel inverter like controlling the start-up inrush current and capacitor voltage balancing using a simple switching strategy. The operating principle and general expression for the different parameters of the proposed topology are presented in detail. A phase disposition pulse width modulation strategy has been developed to switch the inverter. The effectiveness of the topology is verified by extensive simulation and experimental studies on a 7-level inverter structure.

• Journal of Power Electronics
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• v.14 no.5
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• pp.946-956
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• 2014

Cascaded H-Bridge (CHB) converters can be directly connected to medium-voltage grids without using transformers and they possess the advantages of large capacity and low harmonics. They are significant tools for providing grid connections in large-capacity renewable energy systems. However, the reliability of a grid-connected CHB converter can be seriously influenced by the number of power switching devices that exist in the structure. This paper proposes a fault-tolerant control strategy based on double zero-sequence voltage injection and DC voltage optimization to improve the reliability of star-connected CHB converters after one or more power units have been bypassed. By injecting double zero-sequence voltages into each phase cluster, the DC voltages of the healthy units can be rapidly balanced after the faulty units are bypassed. In addition, optimizing the DC voltage increases the number of faulty units that can be tolerated and improves the reliability of the converter. Simulations and experimental results are shown for a seven-level three-phase CHB converter to validate the efficiency and feasibility of this strategy.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.576-588
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• 2014

The superiority of CMI (Cascaded Multilevel Inverter) is unparalleled in high power and high voltage STATCOM (Static Synchronous Compensator). However, the parameters and operating conditions of each individual power unit composing the cascaded STATCOM differ from unit to unit, causing unit voltage disequilibrium on the DC side. This phenomenon seriously impairs the operation performance of STATCOM, and thus maintaining the DC voltage balance and stability becomes critical for cascaded STATCOM. This paper analyzes the case of voltage disequilibrium, combines the operation characteristics of the cascaded STATCOM, and proposes a new DC voltage control scheme with the advantages of good control performance and stability. This hierarchical control method uses software to achieve the total active power control and also uses chopper controllers to enable that the imbalance power can flow among the capacitors in order to keep DC capacitor voltages balance. The operating principle of the chopper controllers is analyzed and the implementation is presented. The major advantages of the proposed control strategy are that the number of PI regulators has been decreased remarkably and accordingly the blindness of system design and debugging also reduces obviously. The simulation reveals that the proposed control scheme can achieve the satisfactory control goals.