• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.153-156
• /
• 2003

Many researchers have tried to develop the piezoelectric shell element and verified them with the benchmarking problem of the piezoelectric bimorph beam since there is no experimental result for the control of shell structure with piezoelectric sensor/actuator. In this paper, the experiments are designed and performed to verify the control Performance of piezoelectric sensor/actuator on the shell structure. PVDF is easy to be attached on the surface of a shell structure but makes weak control forces. On the contrary, PZT makes control forces large enough to control the structure, but it is not easy to make a PZT element with curvature. To use PVDF as an actuator, the structure should be designed as flexible as possible and the voltage amplifier could make high control voltage. PVDF actuator powered by a voltage amplifier that generates output voltage from -200 to +200 volts, shows little control performance to control the vibration of an arch type shell structure. The performance of sensor looks good and the negative velocity feedback control works perfectly. The actuator voltage seems to be too small to verify the control effect Quantitatively. An experiment with high voltage amplifier is scheduled to verify the control effect Quantitatively.

• 조명전기설비학회논문지
• /
• 제23권2호
• /
• pp.103-107
• /
• 2009

PI제어기는 발전기의 전압제어 시스템에 널리 쓰이고 있다. 하지만 발전 시스템의 특성이 연속적으로 변화할 때, 새로운 PI매개변수를 결정하는 것이 쉽지 않다. 이를 해결하기 위하여 본 논문에서는 발전기의 전압제어에 신경망자율 적응 제어를 이용하는 제어 방법을 제안하였다. 전압제어 시스템의 적절한 연속적인 궤환 제어 이득은 델타학습 규칙에 의해서 결정된다. 제안된 제어 방법의 기능은 직류 발전기 전압제어 실험에 의해 확인하였다.

• 전기학회논문지
• /
• 제67권11호
• /
• pp.1512-1516
• /
• 2018

The power system and control system constantly reveals surge voltage such as switching surge of lighting devices and power conversion devices, operating and stops surge of rotating devices, charge & discharge surge, opening & closing surge of circuit breakers and the like. Such a surge voltages can cause damage or malfunction of the element such as CPU, Memory, semiconductor etc. In the industry, in order to protect the system from the surge voltage, a surge protector with low discharge starting voltage, fast response time, and low capacitance is required, and technical development research for that is ongoing. In this paper, in order to solve the problem of the existing GDT discharge tube not discharging from the transient voltage which is higher than the commercial voltage and lower than the discharge voltage of the discharge element, we have developed a discharge element having the control electrode & control circuit. The discharge element having the control electrode and the control circuit can control the discharge voltage according to the needs of the consumer and can satisfy the requirement of the discharge element and the technology of the surge protector downsizing technology and the surge protection technology. It is judged to be effective for development.

• Journal of Power Electronics
• /
• 제16권1호
• /
• pp.329-339
• /
• 2016

Owing to mismatched feeder impedances in an islanded microgrid, the conventional droop control method typically results in errors in reactive power sharing among distributed generation (DG) units. In this study, an improved droop control strategy based on secondary voltage control is proposed to enhance the reactive power sharing accuracy in an islanded microgrid. In a DG local controller, an integral term is introduced into the voltage droop function, in which the voltage compensation signal from the secondary voltage control is utilized as the common reactive power reference for each DG unit. Therefore, accurate reactive power sharing can be realized without any power information exchange among DG units or between DG units and the central controller. Meanwhile, the voltage deviation in the microgrid common bus is removed. Communication in the proposed strategy is simple to implement because the information of the voltage compensation signal is broadcasted from the central controller to each DG unit. The reactive power sharing accuracy is also not sensitive to time-delay mismatch in the communication channels. Simulation and experimental results are provided to validate the effectiveness of the proposed method.

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 2003년도 학술대회 논문집
• /
• pp.193-195
• /
• 2003

In superconductor power systems, a quench detector can misrecognize oscillation about current or voltage control as a quench. So, for the correct detection of a quench, it seems need to guarantee a smooth control of current or voltage. In this paper, we have studied a control function and control parameter for smooth control of current or voltage.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1997년도 전력전자학술대회 논문집
• /
• pp.269-275
• /
• 1997

This paper presents real time digital signal processor(DSP) control of UPS system feeding processor(DSP) control of UPS system feeding nonlinear loads to provide sinusoidal inverter output voltage. The control scheme is composed of an rms voltage compensator, the load current harmonics feed-forward loop for the cancellation of output voltage harmonics, and the output voltage harmonics feedback loop for system stability. The controller employs a Texas Instruments TMS320C40GFL50 DSP.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.425-428
• /
• 2000

A new dead time compensation method using time delay control approach is presented. The dead time in switching pattern cause the voltage distortion and it can be considered as the disturbance voltage. In this paper the disturbance voltage is estimated using time delay control and the estimated disturbance voltage is summed with voltage command in predictive current control by a feed-forward. The proposed scheme is implemented on a PMSM and the effectiveness is verified through comparative simulation.

• 전기의세계
• /
• 제15권5호
• /
• pp.6-12
• /
• 1966

As a power system gets complicated and the number of regulating points increases, the voltage reactive power control tends to be more complex and more difficult. In the past, we took only the voltage regulation into account for this voltage control problem. pay attention not only to the voltage regulation but also to the rational system operation which minimizes transmission losses. Considering the rehuirements mentioned above we aim developing a method of coordination of these regulating equipments and also present some preliminary discussions aboutcomputer control of power systems which is now frequently available with the progress of digital computer technique.

• Journal of Electrical Engineering and Technology
• /
• 제13권4호
• /
• pp.1459-1473
• /
• 2018

This paper focuses on voltage control schemes for multi-terminal low-voltage direct current (LVDC) distribution systems. In a multi-terminal LVDC distribution system, there can be multiple AC/DC converters that connect the LVDC distribution system to the AC grids. This configuration can provide enhanced reliability, grid-supporting functionality, and higher efficiency. The main applications of multi-terminal LVDC distribution systems include flexible power exchange between multiple power grids and integration of distributed energy resources (DERs) using DC voltages such as photovoltaics (PVs) and battery energy storage systems (BESSs). In multi-terminal LVDC distribution systems, voltage regulation is one of the most important issues for maintaining the electric power balance between demand and supply and providing high power quality to end customers. This paper focuses on a voltage control method for multi-terminal LVDC distribution system that can efficiently coordinate multiple control units, such as AC/DC converters, PVs and BESSs. In this paper, a control hierarchy is defined for undervoltage (UV) and overvoltage (OV) problems in LVDC distribution systems based on the control priority between the control units. This paper also proposes methods to determine accurate control commands for AC/DC converters and DERs. By using the proposed method, we can effectively maintain the line voltages in multi-terminal LVDC distribution systems in the normal range. The performance of the proposed voltage control method is evaluated by case studies.

• 전기학회논문지
• /
• 제67권7호
• /
• pp.824-832
• /
• 2018

According to the government's policy to demonstrate and expand the renewable energy sources, distributed generators such as PV and WP are installed and operated in distribution systems. However, there are many issues related to power quality problems including over voltage and under voltage of customers. In order to overcome these problems, the electric power company have installed a step voltage regulator (SVR) in primary feeders interconnected with distributed generators, and also have established the technical guidelines for the distributed generators to stabilize the customer voltages in distribution systems. However, it is difficult to maintain the customer voltages within allowable limit. Therefore, this paper reviews the problems of voltage control by SVR in a distribution systems interconnected with a large amount of PV systems, and proposes characteristics of operating range and voltage control limit of the small hydropower generators. Also, with the estimation of the influence to the power system voltages from the voltage control mode of generators, this paper proposes the optimal voltage control algorithm of the small hydropower generators. By programming the proposed algorithm into control simulator of exciter, it is confirmed that the proposed algorithm can contribute the voltage stabilization in distribution systems interconnected with large scaled PV systems.