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Z-소스 인버터를 이용한 계통연계형 PV 시스템용 PCS 설계
This research gives the analysis and design for grid-connected PV system using Z-source inverter. Instead of the traditional inverter, such as voltage source or current source, this research use the Z-source inverter with the low frequency transformer type. The PLL control for detection of source voltage information, the ac current control algorithm for grid side, the current control algorithm for MPPT by shoot-through time and the voltage control algorithm for dc link voltage. Through the simulation, we conformed the algorithms work well with excellent characteristics. The energy form solar cell is heavily dependent on the environment such as radiation and temperature. The MPPT control is required to extract maximum energy from solar cell. In this paper, the MPPT technique using the perturbation and observation method(P&O) and shoot-through time of Z-source inverter. The Z-source inverter has bed current condition for MPPT of PV-array. And we have to control the Z-source input current continuously. we can overcome this adding the LC filter. This paper constructed the PCS for PV system and analysis of the high efficient and reliable control algorithm for the construction of Z-source inverter.
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Cultural Industry is able to do the OSMU (One Source Multi Use), which could recreate the one successful content and use it in the other various areas. Therefore, it has been regarded as a higher value-added industry. Moreover, it is also highly noticed as one of the leading economy industry in 21th century due to its high economic and culture impacts. However, the current Cultural Industry in Korea is lack of Human Resource Development program. Especially, the structure of Cultural Industry is more and more centered on creating process recently. The demand for creative producer is increasing magnificently nowadays, so it is indicates that the recent education program is required to have more concrete construction with an emphasis on creativity. To develop the creative producer development education program, it is needed four important processes. First of all, do the prior research on the teaching method for producing and Creative enhancement. Through this research, it could be suggested the most appropriate method for education program. Secondly, the necessity of creative producer development and the process to diagnose the problems are required. Through this process, we are able to check the matters and find ways to solve the problems. Thirdly, work on the case study to solve problems. Do research to figure out what educational program domestic and foreign institutions have for the creative producer development. Lastly, interview with the educational experts related to the cultural industry. We try to get their opinion on the educational program for the desirable creative producer development. Through the four processes mentioned above, we could conclude that the educational program for the creative producer of cultural industry are as follows. The purposes of the education for the creative producer development are enhancing creativity, understanding the cultural industry, acquiring know-hows to plan, processing the project and so on. The important points of the field are conceiving an idea, reinforcing creativity, providing the opportunity for communication, improving expertise, developing ability to plan the cultural contents, and supporting with practical business affairs and training. Also, the educational program for the creative producer development can be classified in two parts. One of them is the educational program to improve the creativity. Discussion-centered education can be constituted in order to augment the creativity. And it also provides the chances to communicate freely. The program consists of three steps such as “expectation”, “profound comprehension”and “idea expression”. In order to do the Creative Producer Development, it is highly needed the education program including projects and practices. Therefore, our Education Program for Creative Producer Development includes the Project education method and the theory of Torrance and Safter as its basic structure. Till now, we did the researches on the educational program for the creative producer development of cultural industry. I expect that this scrutiny would be the driving force to improve the Creative Producer Development in the near future.
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The power conversion circuit of the grid-connected PV system using a Quasi Z-source inverter was analyzed in this paper. The MPPT (Maximum Power Point Tracking) control and inverter output current control of the Quasi Z-source inverter was realized using photovoltaic source simulator and real grid. And the method for power quality improvement is suggested and proved the performance through simulation and experiment. The use of the renewable-energy generating system recently increased because of the exhaustion of fossil fuel and the influence of the environment. As such, the inverter, which converts variable energy sources like photovoltaic energy, wind, and fuel cell to acceptable electrical sources, has gained importance of late. The traditional inverters, such as the voltage-source and the current-source inverter, cannot satisfy the requirements of the variable energy source mentioned above. As such, one more separate DC/DC converter was used. This cascaded arrangement of two power converters, however, increases not only the complexity of the circuitry and control but the cost and the space requirement as well. Moreover, the increased number of power switches brings about power loss. The Z-source inverter and the Quasi Z-source inverter have a unique impedance network. Thus, the circuit configuration is changed from that of a voltage source to that of an impedance source. The Quasi Z-source inverter system is more suitable for PV system application in terms of structure and control. Since the input current is continuous the Quasi Z-source inverter system does not cause inconvenience to lifespan of a PV array. Moreover withstanding voltage of capacitor and diode is reduced. Since this inverter provides a common ground it is easy to manufacture the system. The inverter for the grid-connected PV system must satisfy the following conditions. First, the inverter must drive MPPT (maximum power point tracking) control because of the PI or PV characteristic of the PV array. Second, it must be able to control the PCC (point of common coupling) current. In other words, the magnitude and phase of the inverter output current should be controlled. Moreover, the current wave form must be AC sinusoidal. In this paper, the shoot-through state was used to control the MPPT, and the output current was controlled through DC link voltage regulation. With the Quasi Z-source inverter, the longer the shoot-through time, the higher the increase in the Quasi Z-source output voltage. In this paper, however, the output voltage was constantly controlled; as such, the boost effect did not occur. Otherwise, the inverter output power would have progressively increased. As such, the increase in the shoot-through time appeared to have increased the inverter output current, and this is equal to the requirement of the current from the PV array and occurred due to the decrease in the PV array output voltage due to the V-I characteristic of the PV array. Consequently, the increase in the shoot-through time caused the decrease in the PV array output voltage. Therefore, the shoot-through time can be controlled by sensing the PV array output current and voltage using the P&O method.In case of capacitor voltage control, since the capacitor voltage of the Quasi Z-source impedance network is equal to the average of the DC link voltage, instead of the DC-link voltage, the capacitor voltage is used for control. If the voltage is more than the reference voltage, the difference between the voltages becomes the power reference. Based on this power reference, the current reference increases; thus, the output current also increases and the capacitor voltage decreases. Consequently, the capacitor voltage is regulated. For higher efficiency of the system, if possible, the reference voltage of the capacitor should be set at a lower value. On the other hand, the reference voltage of capacitor has to be set at a higher value to have margin for a shoot-through reference and to inject a current into the grid. Although the capacitor voltage of an impedance network is controlled to be constant, the output voltage of an impedance network varies according to the shoot-through time ratio. This may result in an unstable operation. To overcome these matters, in this paper, a method to keep the output voltage of an impedance network constant is proposed. This results in an expansion of MPPT range and a higher efficiency of QZSI. The impedance network parameters of the Quasi Z-source inverter system can be designed using a ripple ratio of voltage and current with other specifications of the system. Through the design, five modes which are caused by large ripple ratio of inductor current are simplified only two modes which are shoot-through mode and active mode. This simplified design makes the system control easy. Through a LCL filter design, the THD of grid injected current can be reduced with compact volume of the system. Also using a resonant controller lower order harmonics of the grid are compensated. Through these power quality improvement methods, the requirement of grid connected inverter can be satisfied.
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선형 안정성 이론 기반 극초음속 경계층 천이 지연을 위한 다공 표면 설계
비행체 표면에서의 마찰항력과 열전달은 경계층의 상태와 매우 밀접하게 연관되기 때문에 극초음속 비행체의 열공력성능, 임무성능을 향상시키기 위한 경계층 천이 제어 연구가 큰 관심을 받고 있다. 본 연구에서는 다공 표면이 극초음속 경계층 안정화와 천이에 미치는 영향을 분석하기 위해 선형 안정성 이론 기반의 안정성 해석기법을 구 축하였다. 구축한 해석기법으로 날카로운 원뿔 위 극초음속 경계층에 대한 Mack 2차 모드의 증폭률을 계산하고 선행연구 결과와의 비교를 통해 검증을 수행하였다. 검증해 석 결과 다공 표면 적용에 따라 최대 증폭률이 감소하였으며, 불안정한 영역이 상류로 이동함을 확인하였다. 기공 반경, 간격, 깊이, 단면 형상과 같이 다공 형상 파라미터에 따른 효과를 분석하였으며, 기공 내의 희박효과와 표면에서의 열적 어드미턴스가 해석 결과에 미치는 영향을 평가하였다. 또한, 반경험적 천이 예측 기법을 기반으로 다공 표 면의 천이 지연 효과를 분석하였다. 이를 바탕으로 최적 제어 효과를 가지는 다공 표 면 설계 방법을 탐색/제시하였다.
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