• Journal of Power Electronics
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• 제9권3호
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• pp.410-417
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• 2009

This paper represents a design and implementation of a digital controller for a multi-phase synchronous buck converter (SBC) using a digital signal processor (DSP). The multi-phase SBC has generally been used for a voltage regulation module (VRM) of a microprocessor because of its high current handling capability at a low output voltage. The VRM requires high control performance of tight output regulation, high slew rate, and load sharing capability of multiple converters. In order to achieve these requirements, the design and implementation of a digital control system for a multi-phase SBC are presented in this paper. The digital PWM generation, current sensing, and voltage and current controller using a DSP TMS320F2812 are considered. The experimental results are provided to show the validity of the implemented digital control system.

• Journal of Power Electronics
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• 제15권1호
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• pp.116-122
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• 2015

This paper presents a new current sharing control strategy for parallel-connected, synchronised three-phase DC-AC converters employing space vector pulse width modulation (SVPWM) without current sharing reactors. Unlike conventional control methods, the proposed method breaks the paths of the circulating current by dividing the switching cycle evenly between parallel connected equally rated converters. Accordingly, any inter-module reactors or circulating current control will be redundant, leading to reductions in system costs, size, and control algorithm complexity. Each converter in the new scheme employs a synchronous dq current regulator that uses only local information to attain a desired converter current. A stability analysis of the current controller is included together with a simulation of the converter and load current waveforms. Experimental results from a 2.5kVA test rig are included to verify the proposed control method.

• Journal of Power Electronics
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• 제19권6호
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• pp.1575-1581
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• 2019

Due to the mismatched line impedance among distributed generation units (DGs) and uncontrolled harmonic current, the droop controller has a number of problems such as inaccurate reactive power sharing and voltage distortion at the point of common coupling (PCC). To solve these problems, this paper proposes a resistive-capacitive virtual impedance control method. The proposed control method modifies the DG output impedance at the fundamental and harmonic frequencies to compensate the mismatched line impedance among DGs and to regulate the harmonic current. Finally, reactive power sharing is accurately achieved, and the PCC voltage distortion is compensated. In addition, adaptively controlling the virtual impedance guarantees compensation performance in spite of load changes. The effectiveness of the proposed control method was verified by experimental results.

• Journal of Power Electronics
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• 제5권2호
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• pp.160-165
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• 2005

In a parallel operation of UPS, there are two types of circulating currents between UPS. One is the low order circulating current with a fundamental frequency caused by the amplitude and phase differences of UPS output voltages, and the other is the harmonic circulating current with PWM switching frequency caused by non-synchronized PWM waveforms among UPS. The elimination of the low order circulating current is essential for optimal load sharing in parallel operations of UPS, which can be accomplished by the phase and magnitude control at each UPS. The harmonic circulating current may cause troubles and deteriorate in performance of the controller for optimal load sharing in parallel operation of UPS. This paper presents a PWM synchronizing method to eliminate the harmonic circulation current in parallel operation of UPS. The effectiveness of the proposed scheme has been investigated and verified through experiments by a 50kVA UPS.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2801-2803
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• 1999

An unified controller for emergency generator is presented to control AVR and Governor and l00kVA power conditioner. This controller is operated to compensate current harmonics and asymmetries caused by nonlinear load and unbalance loads. The power conditioner shapes the source current sinusoidal in phase with source voltage and allows the generator to maximum power even to the single phase load. Also this power conditioner allows that three phase generator synchronizes with single phase main source and load sharing. An l00kVA generator system was built and the unified controller is realized with DSP(TMS320C32PCMA). Experimental results for many load conditions are presented to verify the performance of the unified controller.

• Journal of Power Electronics
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• 제17권2호
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• pp.551-560
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• 2017

The present study proposes an angle droop controller for converter interfaced (dispatchable) distributed generation (DG) resources in the islanded mode of operation. Due to the necessity of proper real and reactive power sharing between different types of resources in microgrids and the ability of systems to respond properly to abnormal conditions (sudden load changes, load uncertainty, load current disturbances, transient conditions, etc.), it is necessary to produce appropriate references for all of the mentioned above conditions. The proposed control strategy utilizes a current controller in addition to an angle droop controller in the discrete time domain to generate appropriate responses under transient conditions. Furthermore, to reduce the harmonics caused by switching at converters' output, a LCL filter is used. In addition, a comparison is done on the effects that LCL filters and L filters have on the performance of DG units. The performance of the proposed control strategy is demonstrated for multi islanded grids with various types of loads and conditions through simulation studies in the DigSilent Power Factory software environment.

• Journal of Power Electronics
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• 제11권5호
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• pp.639-654
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• 2011

This paper presents a Current Distribution Control design for Paralleled Positive Output Elementary Super Lift Luo Converters (PPOESLLCs) operated in Continuous Conduction Mode using a Sliding Mode Controller (SMC). Manipulating the higher current requirement of the load through the paralleling of POESLLCs, results in a current inequality. This is mainly due to dissimilarities in the power semiconductor switches and circuit components used in POESLLCs, which may lead to converter failures. In order to balance the proper load current sharing and the load voltage regulation of PPOESLLCs, a SMC is developed. The SMC is designed for the inherently variable-structured of POESLLCs by using the state-space average based model. The static and dynamic performance of the developed controller with PPOESLLCs is validated for its robustness to perform over a wide range of operating conditions through both a laboratory prototype and MatLab/Simulink models, which are compared with a Proportional-Integral (PI) controller. Theoretical analysis, simulation and experimental results are presented to demonstrate the feasibility of the developed SMC along with the complete design procedure.

• Journal of Power Electronics
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• 제15권2호
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• pp.327-337
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• 2015

This study discusses the design of a parallel-operated DC-DC single-ended primary-inductor converter (SEPIC) for low-voltage application and current sharing with a constant output voltage. A coupled inductor is used for parallel-connected SEPIC topology. Generally, two separate inductors require different ripple currents, but a coupled inductor has the advantage of using the same ripple current. Furthermore, tightly coupled inductors require only half of the ripple current that separate inductors use. In this proposed work, tightly coupled inductors are used. These produce an output that is more efficient than that from separate inductors. Two SEPICs are also connected in parallel using the coupled inductors with a single common controller. An analog control circuit is designed to generate pulse width modulation (PWM) signals and to fulfill the closed-loop control function. A stable output current-sharing strategy is proposed in this system. An experimental setup is developed for a 18.5 V, 60 W parallel SEPIC (PSEPIC) converter, and the results are verified. Results indicate that the PSEPIC provides good response for the variation of input voltage and sudden change in load.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.274-276
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• 2007

In this paper, a low cost and high reliability control scheme is proposed for 400Hz UPS system operated in parallel. The proposed control scheme is consisted of two parts which are synchronization and load sharing control. The synchronization control is achieved by discrete logic ICs and analog circuit. The load sharing control is realized by current transformers (CTs) without any controller. Therefore, This proposed control scheme is rather simple and the cost may be decreased, compared with control scheme using expensive controller such as DSP and CAN. The practical feasibility of the proposed control scheme is proved by analysis and simulation.

• 전기학회논문지
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• 제58권9호
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• pp.1706-1713
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• 2009

In this paper, a parallel operation algorithm for high power PEMFC generation systems is proposed. According to increasing the capacity of fuel cell systems with several fuel cell stacks, the different dynamic characteristics of each fuel cell stack effect on imbalance of load sharing and current distribution, so that a robust parallel operation algorithm is desired. Therefore, a power-sharing technique is developed and explained in order to design an optimal distributed PEMFC generation system. In addition, an optimal controller design procedure for the proposed parallel operation algorithm is introduced, along with informative simulations and experimental results.