• Journal of Power Electronics
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• v.9 no.1
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• pp.43-50
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• 2009

This paper deals with a novel solid state controller (NSSC) for an isolated asynchronous generator (IAG) feeding 3-phase 4-wire loads driven by constant power prime movers, such as uncontrolled pico hydro turbines. AC capacitor banks are used to meet the reactive power requirement of the asynchronous generator. The proposed NSSC is realized using a set of IGBTs (Insulated gate bipolar junction transistors) based current controlled 2-leg voltage source converters (CC- VSC) and a DC chopper at its DC bus, which keeps the generated voltage and frequency constant in spite of changes in consumer loads. The neutral point of the load is created using aT-configuration of the transformers. The IAG system is modeled in MATLAB along with Simulink and PSB (power system block set) toolboxes. The simulated results are presented to demonstrate the capability of the isolated generating system consisting of NSSC and IAG driven by uncontrolled pico hydro turbine and feeding 3-phase 4-wire loads.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.125-128
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• 2002

In this paper, a novel on-line do capacitance estimation method for the PWM converter is proposed. At no load, Input current at a low frequency is injected, which causes do voltage ripple. With the ac voltage and current ripple components of the dc side, the capacitance can be calculated. Experimental result shows that the estimation error is less than $2\%$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.340-343
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• 2003

This paper presents characteristics of piezo transformer for AC-DC converter. This transformer uses transverse vibration mode and the origin of the structure was the ring dot type transformer. Because, the ring dot type transformers produce only step-up phenomenon, we made a multi-layered ring dot structure for a step-down output. The characteristics of the transformer were simulated by using the ANSYS. And frequency and voltage were measured by changing the load resistance and current. Frequencies that have the maximum output voltage and current were gradually increased, when the resistance were increased. Output voltage and current show a stable linearity according to the input voltage. The maximum output power was expected greater than 20 [W]. So, we expect that this type of multi-layered step-down ring dot transformer can be adopted for a small AC adapters.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.766-776
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• 2015

It is well known that series arc faults in Low Voltage DC (LVDC) distribution system occur at unintended points of discontinuity within an electrical circuit. These faults can make circuit breakers not respond timely due to low fault current. It, therefore, is needed to detect the series fault for protecting circuits from electrical fires. This paper proposes a novel scheme to detect the series arc fault using Wavelet Singular Value Decomposition (WSVD) and state diagram. In this paper, the fault detector developed is designed by using three criterion factors based on the RMS value of Singular value of Approximation (SA), Sum of the absolute value of Detail (SD), and state diagram. LVDC distribution system including AC/DC and DC/DC converter is modeled to verify the proposed scheme using ElectroMagnetic Transient Program (EMTP) software. EMTP/MODELS is also utilized to implement the series arc model and WSVD. Simulation results according to various conditions clearly show the effectiveness of the proposed scheme.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.530-532
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• 2007

This paper presents the design, development and performance of a power conditioning system (PCS) for application to a 250kW Molten Carbonate Fuel Cell (MCFC) generation system. A DSP controller was used to control the dc-dc and dc-ac converter operation for grid connection and power injection to the grid. The controller must also supervise the total PCS operation while communicating with the fuel cell system controller. A control method for parallel operation of dc-dc converters was proposed and verified. A 250kW prototype was successfully built and tested. Experimental performances are compared to minimum target requirements of the PCS for MCFC.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.13-14
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• 2011

The power conversion converter for driving the wireless power transfer system is can be into the two part of the DC power conversion rectifier and the high frequency dc-ac power conversion inverter. In this paper, The operating characteristics of the Class-${\Phi}_2$ resonant inverter have been investigated through by simulation and by experiment. It can be switched at a high frequency without the switching losses and the harmonics are reduced effectively due to the input LC filter. Its switching frequency is 1MHz and the input voltage is 96V which is the output voltage of LLC resonant converter. And its output peak voltage is 170V. The resonant inverter module operated at the commercial power source of 220V was built. And also the electromagnetic coupled resonance coils were designed for wireless power transfer with a 1MHz operating frequency. As a experimental result, the wireless power transmission was confirmed and it is varified the validity of the experiment.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.765-768
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• 2003

In the end of a production line a new built power converter has to undergo a series of stress tests. This can be achieved by connecting it to a dynamometer consisting of a three-phase machine joined by a rigid shaft to a DC load machine. The latter is controlled to create some specific load characteristic needed for the test. In this paper a test method is proposed, in which no mechanical equipment is needed. The suggested test stand consists only of a converter to be tested and a simulator converter. Both devices are connected back-to-back on the AC-side via smoothing reactors. The simulator operates in real-time as an equivalent load circuit, so that the device under test will only notice the behaviour of a three-phase machine under consideration of the load.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.11
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• pp.635-644
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• 2002

Many generating units can be in parallel connection to one battery and inverter. However, one of the biggest problems we encountered is that wind speed is fluctuated sharply in accordance with the unstable weather conditions. To solve this problem, we need energy storage equipment such as storage lead-acid battery. We design a system and analyze its modeling so that it supplies a stable power to the load through DC-AC inverter part. In this paper, we applied dual step-up/down buck-boost converter and dual high-frequency half-bridge converter to the proposed system. These converters are used to store energy in the battery regardless of the change of the wind speed. The operation process of two proposed types of converters for high-power battery charging is discussed along with simulation and experimental result. We design a charging circuit which is applicable in the actual wind power generation system for 30kw and confirm the circuit's validity.

• Journal of Power Electronics
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• v.16 no.1
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• pp.163-172
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• 2016

The modular multilevel converter (MMC) has been receiving increased attentions in recent years. The new modular multilevel converter is a derivative topology from the traditional MMC in which the number of sub-modules (SMs) necessitated by each phase can be reduced by one. This paper presents a phase-shifted carrier pulse-width modulation (PSC-PWM) for the new MMC with an optimal phase-shifted angle to suppress the harmonics of the output voltage. Further, the harmonic features when the capacitor voltage of the middle SM is selected as two different values are also investigated. Moreover, in order to avoid introducing an unnecessary dc offset current at the ac terminals of the new MMC, a novel capacitor voltage balancing scheme is proposed by adjusting the amplitude of the reference signals rather than the offset. Finally, the validity and effectiveness of the proposed modulation and balancing schemes have been verified by experimental results based on a three-phase prototype of the new MMC.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1796-1801
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• 2008

In this paper, a new current based maximum power point tracking (CMPPT) method is proposed for a single phase photovoltaic power conditioning system and the current based MPPT modifies incremental conductance method. The current based MPPT method makes the entire control structure of the power conditioning system simple and uses an inherent current source characteristic of solar cell array. In addition, digital phase locked loop using an all pass filter is introduced to detect phase of grid voltage as well as peak voltage. Controllers about dc/dc boost converter, dc-link voltage, dc/ac inverter is designed for a coordinated operation. Furthermore, PI current control using a pseudo synchronous d-q transformation is employed for grid current control with unity power factor. 3kW prototype photovoltaic power conditioning system is built and its experimental results are given to verify the effectiveness of the proposed control schemes.