• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.123-126
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• 1996

In this paper, optimal modulation controller is designed to improve the stability of A.C. and A.C.-D.C. power system, and optimal theory is applied to select optimal modulation controller input signal Optimal modulation controller for speed governor and exciter controller system is constructed in A.C. power system, while the controller is constructed to the both control systems like AC. power system, considering ACR-AVR, APR-$A{\gamma}R$ as the control method of direct current system. It is considered that the stability of A.C. power system only and A.C.-D.C. power system against load fluctuations and disturbances under case of optimal modulation control.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1413-1421
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• 2017

In order to control the output voltage in a dual active bridge converter, this paper establishes a theoretical inductor current equation for a dual-pulse-width-modulation scheme that ensures low switching loss. It also proposes a modulation strategy that minimizes conduction loss. When compared to the conventional single-pulse-width-modulation strategy, the proposed approach can reduce the inductor current RMS and improve efficiency in the low power region, as verified through simulation and experimental results.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1978-1987
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• 2014

Power requirement to the induction heating system varies during the heating process. A closed loop control is required to have a smooth control over the power. In this work, a constant frequency pulse density modulation based power tracking control scheme for domestic induction heating system is developed using the Fuzzy Logic Controller. In the conventional power modulation schemes, the switching losses increase with the change in the load. The proposed pulse density modulation scheme maintains minimum switching losses for the entire load range. This scheme is implemented for the class-D series resonant inverter system. Fuzzy logic controller based power tracking control scheme is developed for domestic induction heating power supply for various power settings. The open loop and closed loop simulation studies are done using the MATLAB/Simulink simulation tool. The control logic is implemented in hardware using the PIC16F877A microcontroller. Fuzzy controller tracks the set power by changing the pulse density of the gate pulses applied to the inverter. The results obtained are used to know the effectiveness of the fuzzy logic controller to achieve the set power.

• Journal of Advanced Navigation Technology
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• v.28 no.1
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• pp.116-122
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• 2024

In this paper, course structure and course width were studied among the main performances of the system to derive the required performance of the modulation index, output power, and phase change specifications of the instrument landing system (ILS) localizer power amplifier. To satisfy the course structure's deviation standard (± 5 uA), the difference in depth of modulation (DDM) deviation standard of the carrier with sideband (CSB) amplifier was standardized to ± 1 uA(0.001 DDM). CSB 30 W power amplifier was designed, and through the modulation compensation circuit, sum in depth of modulation (SDM) is 40% ± 0.1% and DDM is ± 0.0005 DDM in the operating output range(45 dBm ~ 35 dBm). In addition, the course width and displacement sensitivity specifications were analyzed through simulation, and the ± 0.1° change applied during comissioning inspection, which is the most stringent standard, was applied. The output variation of the suppressed with sideband only ( SBO) amplifier was ± 2 mW or less, The phase was standardized to within ± 3 ° and the characteristics were satisfied. By applying a compensation circuit according to output power and temperature, stable modulation index, output, and phase characteristics were obtained.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2129-2138
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• 2016

The full-bridge inverter, widely used for single-phase photovoltaic grid-connected applications, presents a leakage current issue. Therefore, an AC bypass branch is introduced to overcome this challenge. Nevertheless, existing modulation strategies entail drawbacks that should be addressed. One is the zero-crossing distortion (ZCD) of the AC current caused by neglecting the AC filter inductor voltage. Another is that the system cannot deliver reactive power because the AC bypass branch switches at the power frequency. To address these problems, this work proposes an optimized hybrid modulation strategy. To reduce ZCD, the phase angle of the inverter output voltage reference is shifted, thereby compensating for the neglected leading angle. To generate the reactive power, the interval of the negative power output is calculated using the power factor. In addition, the freewheeling switch is kept on when power is flowing into the grid and commutates at a high frequency when power is fed back to the DC side. In this manner, the dead-time insertion in the high-frequency switching area is minimized. Finally, the performances of the proposed modulation strategy and traditional strategies are compared on a universal prototype inverter. Experimental results validate the theoretical analysis.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.32-32
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• 2009

Electric Resistance Welding (ERW) process is the most efficient process to manufacture the linepipe. To develop the high performance ERW linepipe using the high strength and the high alloy steels, the modulation of input power waveform such as sinusoidal waveform is introduced because the conventional ERW technology is not sufficient enough to produce the high quality linepipe due to its strength and high alloy contents (high Ceq). In this article, the material used for the experiment was API X60 with 8.2mm thickness, and ERW simulator at POSCO was used to develop a waveform control system for the power modulation. The frequency of power modulation was varied from 50Hz to 150Hz with the fixed amplitude of ${\pm}2%$ power. The non-modulated power input and the modulated power input cases are conducted to demonstrate the variation of the narrow gap length and the arcing frequency due to power modulation. From results of the non-modulated power input case, the excessive power causes the longer narrow gap length and the low arcing frequency due to the large heat input and the strong electro magnetic force that increase the weld defect. On the contrary, the small narrow gap length and the high arcing frequency reduce the weld defect. After modulating the power input with 50Hz and 100Hz at the fixed power, the arcing frequency increases, but the narrow gap length does not change much. The high arcing frequency prevents the formation of weld defect because the sweeping frequently cleans the oxides on the narrow gap edges. As a result, the manufacturing window can be expanded by the power modulation that provides the stable ERW process for the quality improvement of the linepipe made from the high strength/high alloy steels.

• Journal of Power Electronics
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• v.10 no.4
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• pp.374-381
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• 2010

Typical power electronic converters employ only pulse width modulation (PWM) to generate specific switching patterns. In this paper, a novel control strategy combining both pulse-width and amplitude modulation strategies (PWAM) has been proposed for power converters. The Pulse Amplitude Modulation (PAM), used in communication systems, has been applied to power electronic converters. This increases the degrees of freedom in eliminating or mitigating harmonics when compared to the conventional PWM strategies. The role of PAM in the novel PWAM strategy is based on the control of the converter's dc sources values. Software implementation of the conventional PWM and the PWAM control strategies has been applied to a five-level inverter for mitigating selective harmonics. Results show the superiority of the proposed strategy from the THD point of view along with a reduction in the inverter power dissipation.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.299-306
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• 2002

The load frequency control(LFC) of power system is one of important subjects in view of system operation and control. That is, even though the rapid load disturbances are applied to the given power system, the stable and reliable power should be supplied to the users, converging unconditionally and rapidly the frequency deviations and the tie-line power flow ones of each area into allowable boundary limits. Nonetheless of such needs, if the internal parameter perturbation and the sudden load variation are given, the unstable phenomena of power systems can be often brought out because of the large frequency deviation and the unsuppressible power line one. So, an optimal modulation controller for UC of multi-area power system is designed by a recursive algorithm that determines the state weighting matrix Q of a linear quadratic performance criterion. The optimal modulation controller is based on optimal control and can obtain the exact dynamic response of the UC of multi-area power system in the time domain. The performances of the resultant optimal modulation control, that is, the steady-state deviations of frequency and tie-line power flow and the related dynamics, were investigated and analyzed in detail by being applied to the UC of multi-area power system in the perturbations of predetermined internal parameters. Through the simulation results tried variously in this paper for disturbance of stepwise load changes, the superiorities of the proposed optimal modulation controller in robustness and stability were proved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.951-959
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• 2011

The low power consumption modulation is required for short range communication. In this paper, we analyze performance of low power consumption modulation scheme such as PSPM, PSSK and QAPM using OFDM transmission in AWGN channel. A PSPM, PSSK and QAPM modulation scheme are decrease in bandwidth efficiency but improved power efficiency than existing PSK and QAM. These modulation schemes can achieve power efficiency because every symbol of modulations has a zero-envelope period like PPM techniques. The OFDM system is high bandwidth efficiency than single carrier system. In this paper, we are propose the frequency domain mapping method for OFDM transmission using low power consumption modulation method. Also, we compare low power OFDM communication system regard to BER performance, throughput and PAPR.

• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.434-438
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• 2009

In this paper, a 12.5-Gb/s optical transmitter is implemented using 0.13-${\mu}m$ CMOS technology. The optical transmitter that we constructed compensates temperature effects of VCSEL (Vertical cavity surface emitting laser) using auto-power control (APC) and auto-modulation control (AMC). An external monitoring photodiode (MPD) detects optical power and modulation. The proposed APC and AMC demonstrate 5$\sim$20-mA of bias-current control and 5$\sim$20-mA of modulation-current control, respectively. To enhance the bandwidth of the optical transmitter, an active feedback amplifier with negative capacitance compensation is exploited. The whole chip consumes only 140.4-mW of DC power at a single 1.8-V supply under the maximum modulation and bias currents, and occupies the area of 1280-${\mu}m$ by 330-${\mu}m$ excluding bonding pads.