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"OBRIGADO DEUS PELA VIDA,PELA MINHA FAMILIA,PELO TRABALHO,PELO PÃO DE CADA DIA,PROTEGENOS DO MAL"

"OBRIGADO DEUS PELA VIDA,PELA MINHA FAMILIA,PELO TRABALHO,PELO PÃO DE CADA DIA,PROTEGENOS  DO MAL"

“SE SEUS PROJETOS FOREM PARA UM ANO,SEMEIE O GRÂO.SE FOREM PARA DEZ ANOS,PLANTE UMA ÁRVORE.SE FOREM PARA CEM ANOS,EDUQUE O POVO.”

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segunda-feira, 27 de dezembro de 2021

3-phase Dynamic Voltage Restorer with Switching Cell Structured Direct AC-AC Converter Using Interphase Voltage* Hyeongmin Lee School of Electronic and Electrical Engineering Graduate School, Kyungpook National University Daegu, Korea (Supervised by Professor Heung-Geun Kim)



 

3-phase Dynamic Voltage Restorer with Switching Cell Structured Direct AC-AC Converter Using Interphase Voltage* Hyeongmin Lee School of Electronic and Electrical Engineering Graduate School, Kyungpook National University Daegu, Korea (Supervised by Professor Heung-Geun Kim) 


 (Abstract) Instantaneous voltage sag account for the largest proportion of various grid accidents, and the economic losses resulting from them are enormous. To solve this problem, various dynamic voltage restorer(DVR) systems are being researched and developed. Most of these are back-to-back(BTB) types and energy storage(ES) types. Since the BTB type uses the distribution voltage as a voltage source, it can be compensated continuously without a separate storage device, but energy conversion loss occurs because energy conversion must be performed in two or more stages. Also, in order to secure the DC-link voltage, the controller must be complicatedly configured. The ES type utilizes an extra energy storage device and uses it as a voltage source. This results in energy conversion in one stage, resulting in small conversion losses. However, since the unit cost of the energy storage device is high, there is a disadvantage that a lot of cost is incurred to construct the system. Also, due to the capacity limitations of energy storage devices, the compensation time is limited. If additional storage devices are configured to extend the compensation time, the cost will be higher, and this will determine the performance of the system. In this paper, a DVR system consisting of a direct AC-AC converter with a switching cell structure and using an interphase voltage source is presented. The switching cell structure overcomes the current commutation problem, which is a disadvantage of the conventional AC switch, and can prevent damage to the switch due to the short circuit and open of the conventional switch leg. In addition, it can be operated with a high switching frequency because it can be configured as a diode with a fast reverse recovery time instead of a body diode with poor performance. This can reduce the volume and unit cost of passive filters, which are costly in the system configuration. And by using the interphase voltage as a voltage source, it overcomes the disadvantage that the compensation range of the DVR using an ac-ac converter is limited to 50%. This can also compensate for phase jump situations. Compared with the BTB type, the efficiency is good due to energy conversion in one stage, and the time to secure the DC-link voltage is not required, so the dynamic characteristics are better. In addition, control is simple because it is driven through DC reference. Compared with the ES type, there is no limit to the storage device, so the compensation duration is long and the system configuration is economical. Above all, unlike the two conventional compensators that use a voltage source inverter(VSI), the system reliability is excellent and there is no need to apply a bulky and lossy filter. Finally, to prove the feasibility of this paper, we performed a simulation and directly configured the hardware to prove that it is compensable under various voltage sag situations.
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