• Journal of Power Electronics
• /
• v.19 no.1
• /
• pp.158-167
• /
• 2019

This research comparatively studies three kinds of flux regulation methods, namely, stored capacitor discharge pulse (SCDP), constant current source pulse (CCSP), and quantitative flux regulation pulse (QFRP), which are used for hybrid permanent magnet (PM) axial field flux-switching memory machines (HPM-AFFSMMs). Through an analysis of the operation principle and the series hybrid PM flux regulation mechanism of the objective machine, the circuit topologies and flux regulation process of these flux regulation methods are addressed in detail. On the basis of a simulation, the flux regulation characteristics of the researched machine during the magnetization and demagnetization processes are comparatively evaluated. Then, machine performance, including back EMF, direct and quadrature axis inductances, and magnetization and demagnetization characteristics, is quantitatively investigated. Results show that the QFRP enables the HPM-AFFSMM to achieve a less harmonic component of back EMF by approximately 7.28% and 7.97% at the magnetization and demagnetization states, respectively, and a more complete magnetization process than the SCDP and CCSP.

• International Area Studies Review
• /
• v.13 no.1
• /
• pp.445-464
• /
• 2009

Many countries in the world have regulated cross-border supply in basic telecommunications services based on GATS exception rule for telecommunications because of anti-competition behavior control, domestic consumer protection, tax levy, national security, etc. Korea partially regulates cross-border supply in telecommunications service through the WTO and the domestic law and regulation. However, WTO and FTA negotiations, cross-border supply regulation are strongly demanded to deregulation. Therefore, it is required to review the effectiveness of cross-border supply regulation to prepare the counter plan for that regulation. Thus, the major countries of the telecommunication services regulation regarding the cross-border supply are reviewed. In addition, it is retrieved some implications for Korean regulation policy by reviewing the actual regulation of many countries cases.

• Journal of Power Electronics
• /
• v.16 no.4
• /
• pp.1324-1335
• /
• 2016

This article explores the speed regulation problem of permanent magnet synchronous motor (PMSM) systems subjected to unknown time-varying disturbances. A continuous sliding mode control (CSMC) technique is introduced for the speed loop to enhance the robustness of PMSM systems and eliminate the chattering phenomenon caused by high-frequency switch function in the conventional control law. However, the high control gain of the CSMC law in the presence of strong disturbances leads to large steady-state speed fluctuations for PMSM systems. In many application fields, PMSM systems are affected by time-varying disturbances instead of constant disturbances. For example, electric bicycles are usually affected by changing environmental disturbances, including wind speeds, road conditions, etc. These disturbances may be in the form of constant, ramp, and parabolic disturbances. Hence, a generalized proportional integral (GPI) observer is employed to estimate these types of disturbances. Then, the disturbance estimation method and the aforementioned CSMC method are combined to establish a composite sliding mode control method called the CSMC+GPI method for the speed loop of PMSM systems. Contrary to the conventional sliding mode control technique, the proposed method completely eliminates the chattering phenomenon caused by the switching function in the conventional control law. Moreover, a small control gain for the CSMC+GPI method is chosen by feed-forwarding estimated values to the speed controller. Hence, the steady-state speed fluctuations are small. The effectiveness of the proposed control scheme is verified by simulation and experimental result.

• Proceedings of the KIEE Conference
• /
• 2003.11b
• /
• pp.87-90
• /
• 2003

There are generally two temperature control methods using ac voltage regulators - the phase control method and the on-off control method. The phase control method uses thyristor's angles of extinction for the output power regulation and the on-off control method uses the control of on and off times for the output power regulation. Both of methods have the problems that are the unbalance of the three phase and surge current caused system's destruction. The main object of this study proposes a solution of problems of surge currents and unbalance of three phase when thyristor voltage regulator is switching. To solve the problem, It is proposes that the solution of surge currents is using a tap transformer and an additional switch with adjustable resistance and applies zero crossing of switching voltage of two input line to power load. This method is discuss and verified by computer simulations and experiments.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.9 no.2
• /
• pp.6-11
• /
• 2010

For the purpose of reducing the energy consumption in the house heating, the various devices have been developed. One of these is to control the flow in the heat pipe and the flow control valve using shape memory alloy(SMA) spring is proposed in our study. The proposed house heating system is to save the gas consumption and the remote control system is designed for the convenience of using the proposed valve. The developed valve consists of SMA spring, disk, return spring, and regulation handle. The regulation handle is for supplying the additional hot water and is controlled by remote-control-motor. In order to design the remote control system, the Zigbee wireless communication protocol is used. The performance of the proposed valve structure is shown through the experimental result.

• International Journal of Control, Automation, and Systems
• /
• v.3 no.spc2
• /
• pp.302-307
• /
• 2005

A novel neuro controller based simple neuro-structure with modified error function is introduced in this paper. This controller consists of two independent controllers, known as the voltage regulator and the angular controller. The voltage regulator is used to modify terminal voltage for the purpose of tracking a reference voltage. The angular controller is utilized to guarantee the stability of the system. In this structure each neuron uses a linear hard limit activation function that depends on the controlled variable and its derivatives. There is no need for parameter identification or any off-line training data. Two proposed controllers are merged by a smooth switch to build a complete controller. The effectiveness of the proposed novel control action is demonstrated through some computer simulations on a Single-Machine Infinite-Bus (SMIB) power system.

• Journal of Biosystems Engineering
• /
• v.21 no.2
• /
• pp.155-166
• /
• 1996

A direct injection sprayer was designed using the concepts of injection mixing and total flow control, flowrate-based system compensating for the variation of forwarding speed. A metered rate, proportionally to the actual diluent flow rate, of a tracer chemical was injected directly into the diluent stream. The injection of chemical may improve the precision and safety of chemical application process. The control system was evaluated for the variables of the control interval, tolerances and sensitivities of flow regulation valve and injection pump. Performance of the system was assessed as that the response time of flow rate, response time of injection rate, absolute steady state error, and the coefficient of variance(C.V.) of concentration were 8.5 and -0.53 seconds, 0.067 lpm(0.8%) and 3.15%, respectively, at optimal parameters of control interval of 1.0 sec, fast sensitivity of flow regulation valve, medium sensitivity of injection pump and medium tolerance of flow rate. Performance of the system can be improved by increasing the sensitivity of flow regulating valve and employing a high resolution velocimeter, such as Doppler radar.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.54 no.11
• /
• pp.540-547
• /
• 2005

One of the roles of AGC is to regulate the frequency of power systems. AGC is also used to control the frequency of Korean Power System. AGC control strategies depend on system characteristics and the requirements of the systems to which those are applied. Korean Power System consists of one control area and does not have tie-lines. In this research, an AGC control strategy is suggested to avoid conflict with governor dynamics and to enhance frequency recovery It shows good performance for regulation and frequency recovery. This control strategy is expected to be applied to New EMS in KPX to get reasonable AGC regulation and frequency recovery performance.

• Journal of Korean Academy of Nursing
• /
• v.26 no.2
• /
• pp.413-427
• /
• 1996

This study was conducted to test the effect of a self regulation education program as a nursing intervention with chronically ill patients. A quasi experimental research(non equivalent control group pretest-posttest design) was used in this study. The subjects were 30 non insulin dependent diabetic patients(experimental group : 14 patients, control group : 16 patients). The study was carried out from May, 1995 to February, 1996. Data were collected before the education program, immediately after ＆ 2 menths later and were analyzed with repeated measure ANCOVA, paired t-test and t-test. The results are as follows : 1. There was a significant difference in self efficacy between the two groups（F＝27.61, P＝0.000）. There was a significant difference according to experimental stages（F＝33.09, P＝0.000） and interaction between education and experimental stages（F＝30.21, P＝0.000）. 2. There was a significant difference in self care behavior between the two groups（F＝27.05, P＝0. 000). There was a significant difference according to experimental stages（F＝31.14, P＝0.000） and interaction between education and experimental stages（F＝28.88, P＝0.000）. 3. There was a significant difference in glycemic control between before the education program and 2 months iater in the experimental group （t＝2.88, P＝0.013）. But there was no significant difference between before the education program and 2 months later in the control group. These results suggest that a self regulation education program is effective in promoting ＆ maintaining self care behavior and in improving glycemic control.. Thus this program can be recommended as an effective nursing intervention for chronically ill patients including diabetic patients.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.7
• /
• pp.809-815
• /
• 2018

Distributed generations (DGs) using renewable energy resources in power systems have been widely integrated, and many of these DGs have intermittency. DGs can significantly affect the overall voltage profile of the system through the reactive power control for a voltage support. Therefore, in the planning stage of the optimal operation and dispatch of voltage regulation devices, DGs' hosting capacity with the reactive power control scheme should be considered. In this paper, we model the IEEE 34-bus test feeder, including all essential equipment. An optimization method is utilized to determine the optimal siting and operation of the voltage regulation devices in the presence of DGs with reactive power control scheme. Finally, we compare the optimal results of the each case to analyze the relationship among the hosting capacity of the DGs and voltage regulation devices operation.