• Journal of Korea Multimedia Society
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• v.23 no.9
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• pp.1171-1180
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• 2020

The number of the PV systems installed in south korea has been gradually increasing. Interest of operation & management of PV System is rising up as PV System installation trends to increase. The vital function of operation & management is the monitoring system. Most monitoring systems are only available for equipment of suppliers and manufacturers. In this study, a monitoring system was implemented to support multi-domain equipment (inverter, junction box, water distribution board, environmental sensors) that are not limited to specific manufacturers. Monitoring system includes a visualization function, which makes it easy for users to check the power generation and the operation status of the equipment of PV System. In the future, this monitoring system will be utilized as an operation & maintenance foundation element in the PV system industry.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1398-1408
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• 2018

In order to further improve the steady-state control performance of model predictive torque control (MPTC), a double-vector-based model predictive torque control without a weighting factor is proposed in this paper. The extended voltage vectors synthesized by two basic voltage vectors are used to increase the number of feasible voltage vectors. Therefore, the control precision of the torque and the stator flux along with the steady-state performance can be improved. To avoid testing all of the feasible voltage vectors, the solution of deadbeat torque control is calculated to predict the reference voltage vector. Thus, the candidate voltage vectors, which need to be evaluated by a cost function, can be reduced based on the sector position of the predicted reference voltage vector. Furthermore, a cost function, which only includes a reference voltage tracking error, is designed to eliminate the weighting factor. Moreover, two voltage vectors are applied during one control period, and their durations are calculated based on the principle of reference voltage tracking error minimization. Finally, the proposed method is tested by simulations and experiments.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1169-1170
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• 2006

Grid connected PV(Photovoltic) generation systems are becoming and actual and general. The power output of PV system is directly affected by the weather conditions. And when AC power supply is needed, power conversion by an inverter and a MPPT control are necessary. The PV power generation system can be treated to a harmonics source for the power distribution system. So, the PV system combined the function of active filter system can be useful applied in power distribution system. AF(Active Filters) intended for harmonic solutions are expending their functions from harmonic compensation of nonlinear loads into harmonic isolation between utilities and consumer. With the test analysis of the proposed control strategy of PV-AF system, the outcome of the test shows the stability and effectiveness of the proposed PV-AF system. The various capability of AF has been proved in previous research and usage. In this paper, authors present a DSP controlled PV-AF system for power conditioning in three-phase industrial or commercial power systems and verify it through experimental results.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1855-1865
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• 2018

This paper presents a control strategy for voltage-controlled multi-function distributed generation (DG) combined with an active power filter (APF) and a reactive power compensator. The control strategy is based on droop control. As a result of local nonlinear loads, the voltages of the point of common coupling (PCC) and the currents injecting into the grid by the DG are distorted. The power quality of the PCC voltage can be enhanced by using PCC harmonic compensation. In addition, with the PCC harmonic compensation, the DG offers a low-impedance path for harmonic currents. Therefore, the DG absorbs most of the harmonic currents generated by local loads, and the total harmonic distortion (THD) of the grid connected current is dramatically reduced. Furthermore, by regulating the reactive power of the DG, the magnitude of the PCC voltage can be maintained at its nominal value. The performance of the DG with the proposed control strategy is analyzed by bode diagrams. Finally, simulation and experimental results verify the proposed control strategy.

• Journal of Power Electronics
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• v.17 no.2
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• pp.533-541
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• 2017

This paper presents a novel Parameter-Independent Fictive-Axis (PIFA) approach for the Voltage-Oriented Control (VOC) algorithm used in grid-tied single-phase inverters. VOC is based on the transformation of the single-phase grid current into the synchronous reference frame. As a result, an orthogonal current signal is needed. Traditionally, this signal has been obtained from fixed time delays, digital filters or a Hilbert transformation. Nevertheless, these solutions present stability and transient drawbacks. Recently, the Fictive Axis Emulation (FAE) VOC has emerged as an alternative for the generation of the quadrature current signal. FAE requires detailed information of the grid current filter along with its transfer function for signal creation. When the transfer function is not accurate, the direct and quadrature current components present steady-state oscillations as the fictive two-phase system becomes unbalanced. Moreover, the digital implementation of the transfer function imposes an additional computing burden on the VOC. The PIFA VOC presented in this paper, takes advantage of the reference current to create the required orthogonal current, which effectively eliminates the need for the filter transfer function. Moreover, the fictive signal amplitude and phase do not change with a frequency drift, which results in an increased reliability. This yields a fast, linear and stable system that can be installed without fine tuning. To demonstrate the good performance of the PIFA VOC, simulation and experimental results are presented.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.10
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• pp.52-62
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• 2003

This paper discusses ternary logic gate, ternary D flip-flop, and ternary four-digit parallel input/output register. The ternary logic gates consist of n-channel pass transistors and neuron MOS(νMOS) threshold inverters on voltage mode. They are designed with a transmission function using threshold inverter that are in turn, designed using Down Literal Circuit(DLC) that has various threshold voltages. The νMOS pass transistor is very suitable gate to the multiple-valued logic(MVL) and has the input signal of the multi-level νMOS threshold inverter. The ternary D flip-flop uses the storage element of the ternary data. The ternary four-digit parallel input/output register consists of four ternary D flip-flops which can temporarily store four-digit ternary data. In this paper, these circuits use 3.3V low power supply voltage and 0.35m process parameter, and also represent HSPICE simulation result.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.3
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• pp.275-284
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• 2004

This paper discusses how to control the compensation voltages in dynamic voltage restorers (DVR). On analyzing the power circuit of a DVR system, control limitations and control targets are presented for the voltage compensation in DVRs. Based on the preceded power stage analysis, a novel controller for the compensation voltages of DVRs is proposed by a feed forward control scheme. This paper discusses also the time delay problems in the control system of DVRs. Digitally controlled DVR systems normally have control delay at amount of one sampling time of the control system and a half of the switching period of the DVR inverter. The control delay in digital controllers increases the dimension of the system transfer function one degree higher, which makes the control system more complicate and more unstable. This paper proposes a guide line to design the control gain, appropriate output filter parameters and inverter switching frequency for DVRs with digital controllers. Proposed theory is verified by an experimental DVR system with a full digital controller.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.59-68
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• 2009

Fuel cell generators as the distributed generation system with a few hundred watt$\sim$a few hundred kilowatt capacity, can supply the high quality electric power to user as compared with conventional large scale power plants. In this paper, PEMFC(polymer electrolyte membrane fuel cell) generator as micro-source is modelled by using PSIM simulation software and DSP based fuel cell hardware simulator based on the PSIM simulation model is implemented. The relation of fuel cell voltage and current(V-I curve) is linearized by first order function on the ohmic area in voltage-current curve of fuel cell. The implemented system is composed of a PEMFC hardware simulator, an isolated full bridge dc boost converter, and a 60[Hz] voltage source PWM inverter. The voltage-current-power(V-I-P) characteristics of the implemented fuel cell hardware simulator are verified in load variation and transient state and the 60[Hz] output voltage sinusoidal waveform of the PWM inverter is investigated under the resistance load and nonlinear diode load.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.2
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• pp.179-184
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• 2016

The electrical load testing system developed from this study was designed to control rated-capacity-testing or variable-load-testing in an active and precise manner and save electric energy during testing, and also to convert the saved electric energy through the electrical load testing system to grid line. As for the device under testing, it was designed to be applied to not only transformer, rectifier, voltage regulator, inverter which require grid voltage source but, also applied to electric power, aerogenerator, photovoltaic, hybrid generator, battery, etc. which do not require grid voltage source. The system was designed to return the power consumed during the testing to the grid line by connecting the synchronizing pwm inverter circuit to the grid voltage source, and was also made to enable the being-tested system from disuse of approximately 93.4% energy when compared to the conventional load testing system which has used the passive resistor.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.1
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• pp.1-11
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• 2007

In this paper, a new fully digital control method for UPS inverter, which is based on the double control loop such as the outer voltage control loop and inner current control loop, is proposed. In the proposed control system, overshoots and oscillations due to the computation time-delay are compensated by explicit incorporation of the time-delay in the current control loop transfer function. The inner current control loop is adopted by an internal model controller. The internal model controller is designed to a second order deadbeat reference-to-output response which means that its response reaches the reference in two sampling time including computational time-delays. The outer voltage control loop employing P-Resonance controller is proposed. The resonance controller has an infinite gain at resonant frequency, and the resonant frequency is set to the fundamental frequency of the reference voltage in this paper. Thus the outer voltage control loop causes no steady state error as regard to both magnitude and phase. The effectiveness of the proposed control system has been verified by the simulation and experimental results respectively.