• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.12
• /
• pp.2402-2409
• /
• 2009

This paper proposed a simple and helpful analysis model of voltage variation in order to predict the voltage variation at PCC (Point of Common Coupling), when a wind turbine is connected in an isolated grid. The PCC voltage flucuates when the wind turbine outputs active power to an isolated grid. This voltage variation is proportional to the product of the line impedance from the ideal generator to the PCC and the wind turbine output current. And It is different according as where wind turbine is connected. To solve the problem of voltage variation, this paper proposed the reactive power control. To verify the proposed analysis model, this paper utilized PSCAD/EMTDC Simulation and the field measurement data of the voltage variation during the wind power generation.

• Journal of Information Processing Systems
• /
• v.7 no.1
• /
• pp.93-102
• /
• 2011

In deeply scaled CMOS technologies, two major non-ideal factors are threatening the survival of the CMOS; i) PVT (process, voltage, and temperature) variations and ii) leakage power consumption. In this paper, we propose a novel post-silicon tuning methodology to scale optimum voltage and frequency "dynamically". The proposed design technique will use our PVT sensor circuits to monitor the variations and based on the monitored variation data, voltage and frequency will be compensated "automatically". During the compensation process, supply voltage is dynamically adjusted to guarantee the minimum total power consumption without violating the frequency requirement. The simulation results show that the proposed technique can reduce the total power by 85% and the static power by 53% on average for the selected ISCAS'85 benchmark circuits with 45 nm CMOS technology compared to the results of the traditional PVT compensation method.

• Journal of Power Electronics
• /
• v.17 no.2
• /
• pp.464-475
• /
• 2017

This study examines a P+multi resonant-based voltage control for voltage harmonics compensation under the islanded mode of a microgrid. In islanded mode, the inverter is defined as a voltage source to supply the full local load demand without the connection to the grid. On the other hand, the output voltage waveform is distorted by the negative and zero sequence components and current harmonics due to the unbalanced and nonlinear loads. In this paper, the P+multi resonant controller is used to compensate for the voltage harmonics. The gain tuning method is assessed by the tendency analysis of the controller as the variation of gain. In addition, this study analyzes the slight voltage magnitude drop due to the practical form of the P+multi resonant and proposes a counter method to solve this problem by adding the PI-based voltage restoration method. The proposed P+multi resonant controller to compensate for the voltage harmonics is verified through the PSIM simulation and experimental results.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.40 no.4
• /
• pp.42-50
• /
• 2003

This paper presents an embedded RC oscillator which has temperature compensation circuits. The conventional RC oscillator has frequency deviation about 15%, which is caused by variation of resistors and the reference voltage of schmitt trigger from the temperature condition. In this paper, the proposed circuit use a CMOS bandgap reference having balanced current temperature coefficients as a triggering voltage of schmitt trigger. The constant current sources consist of current mirror circuit with the positive and negative temperature coefficient. The proposed circuit shows less 3% frequency deviation for variation of temperature, supply voltage and process parameters.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.5 no.6
• /
• pp.544-551
• /
• 2000

In this paper, 3-phase hybrid series active power filter for compensate current harmonics, voltage drop and unbalanced voltage in the network presented. The proposed system is implemented with a space vector modulation voltage source inverter and a high pass filter connected in parallel to the power system. Here the load is six-pulses thyristor rectifier. The phase angle detected in order to generation reference voltage at load terminal is synchronized with the positive sequence component of the unbalanced source by using symmetrical component transformation. The proposed system has an function harmonic isolation between source and load, voltage regulation, and unbalance compensation. Therefore, what the power system is improved quality, the source current is maintained as a nearly sinusoidal waveform and the load voltage is regulated with a rated voltage regardless of the source variation condition. To verify the validity of the proposed compensating system, the computer simulation and experiment are carried out.

• Proceedings of the KIPE Conference
• /
• 2017.07a
• /
• pp.180-181
• /
• 2017

Recently as distributed source has increased, the distribution system has changed from unidirectional power flow to bi-directional power flow. This power flow causes the PCC voltage variation, which can adversely affect voltage sensitive loads. In this paper, the relation between the active power, reactive power and PCC voltage of the distributed source is analyzed, and the PCC voltage control scheme by reactive power compensation is proposed in the distributed source itself. In addition, limitations and conditions according to the standard for interconnecting distributed resources are specified and verified through simulation.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.11
• /
• pp.1584-1590
• /
• 2017

This paper presents a implementation method of reliable speed limitation controller considering motor parameter variation in high speed operation. In spinning process of drum washing machine, speed increase has to be limited when unallowable imbalance mass is detected. Otherwise, severe noise and vibration can happen because noise and vibration are proportional to imbalance mass. To detect imbalance mass, d-axis current magnitude is used. However, we have to compensate for back-emf and power supply variation by means of detecting them because d-axis current is affected by both of them. On the other hand, we have to carefully estimate back-emf because back-emf is affected by stator resistance variation and inverter voltage error. Stator resistance variation can happen by manufacturing process for mass production or temperature variation in running. And there are inverter voltage errors between command voltage from micro-computer to inverter and real voltage from inverter to motor because of rising and falling time delay and turn-on resistance of power semiconductor switch. To solve this problem, we propose 2-step align current injection method which is to inject step-wise current right before starting. By this method, we can simply obtain stator resistance by ratio of voltage without inverter voltage error and current, and we can measure inverter voltage error. So we can obtain more exact model current, and then by simple calculation with compensation gain, we can estimate more accurate motor back-emf. We show that this method works well. It is verified through experiments.

• Journal of Power Electronics
• /
• v.5 no.4
• /
• pp.329-334
• /
• 2005

The DSTATCOM(Distribution Static Synchronous Compensator) is one of the Custom Power Devices that can regulate voltage. The DSTATCOM operates as a shunt connected static var compensator whose capacitive or inductive output current can be controlled independent of the system voltage. The magnitude of the compensated voltage is limited by characteristics of the system and the load. Compensation capability of the DSTATCOM which can inject 1 MVAR reactive power was simulated by EMTDC under several conditions. This paper analyzes the effect of the DSTATCOM's compensation considering the length and kind of distribution line, the power factor and magnitude of the load, and the duration and magnitude of the voltage variation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.3
• /
• pp.223-228
• /
• 2010

In this paper, temperature compensation circuit for the X-band voltage controlled oscillator(VCO) is presented by using the temperature sensor with the OP-AMP circuit. The frequency drifting by the temperature could be compensated by applying the tuning voltage which include the linearly changing output voltage of the temperature sensor. As a result, the frequency variation is reduced to 6.6~4.4 MHzfrom the 71~73 MHz variation with the compensation circuit over -30~+$60^{\circ}C$ range, when VCO is operated in the frequency range of 9.95~10.05 GHz.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.1271-1278
• /
• 2010

High-speed traction has voltage source variation because the electric power of tractions is supplied by difference traction power system according to operating section. This paper proposes the robust control maintaining constant output performance against voltage source variation for PWM converters of the high speed traction. The proposed scheme consists of feed-forward compensation for current controller by on-line calculating the rms voltage of voltage source. Total dynamic performance of high speed traction can be improved by the reduction of the output voltage ripple which is resulted from voltage source sag and variation. The superior performance and validity of the proposed scheme is proved through the simulation.