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Parallel Operation of Trans-Z-Source Inverter
Dongsul Shin,Honnyong Cha,Jong-Pil Lee,Dong-Wook Yoo,Fang Z. Peng,Heung-Geun Kim 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
Recently, there is a strong demand for high power conversion system in power electronics area especially in photovoltaic (PV) power conditioning system (PCS), wind power generation, and fuel cell power generation system. However, there is a limit in increasing power level mainly due to the limitations in switching device’s voltage and current rating. One way to solve this problem is to connect power converters in parallel. Parallel operation of inverter has many advantages such as modularity, ease of maintenance, (n+1) redundancy, high reliability, etc. This paper presents parallel operation of voltage-fed-trans-Z-source inverter. A 2.6 ㎾ prototype inverter is built and tested to verify performances of the proposed inverter.
Dongsul Shin,Jong-Pil Lee,Dong-Wook Yoo,Hee-Je Kim Institute of Electrical and Electronics Engineers 2015 IEEE transactions on industrial electronics Vol. No.
<P>A merit of the interleaving reducing the switching harmonics allows for the reduction of the filter inductance. However, in the case of direct parallel voltage source inverters (VSIs), a severe circulating current occurs. To suppress the high frequency circulating current, coupled inductors (CIs) for the high impedance is inserted. However, the employed CIs induce a positive- or negative-sequence circulating current (i.e., a cross current) besides the zero-sequence circulating current already mentioned in the other papers. Due to different impedances developed by the current characteristics and the cross current in the CIs, VSIs becomes unstable when the resonant controllers are applied for the harmonic compensation such as 5, and 7th harmonics. In this paper, the cross currents and the impedances of CIs varying with the current characteristics are mathematically analyzed, and a novel current controller is proposed to solve this stability problem. The experimental results validate the proposed control scheme.</P>
Comparative Evaluation of Coupling L-CL Filter for Interleaved Three-Phase Voltage Source Inverters
Dongsul Shin,Jong-Pil Lee,Tae-Jin Kim,Dong-Wook Yoo,Hee-Je Kim 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In this paper, the combinations of coupled inductors (CIs) and LCL filters are comparatively investigated for gridconnected interleaved three-phase voltage source inverters (VSIs) in terms of the resonance phenomenon. In current-controlled direct parallel VSIs, two current controllers are required for the power flow and the circulating currents. Therefore, the stability of both current controllers are evaluated for three possible configurations of CIs and LCL filters. As a result, the resonance frequencies vary with the placement of the parallel capacitors and the grid-side inductors. A configuration for reducing the effect of the resonance on the system stability is proposed, and the stable operation of the proposed configuration is simply achieved without additional losses by passive or the controller complexity by active damping. The three possible combinations of CIs and LCL filters are simulated and the proposed configuration is experimentally verified.
인터리브드 PWM 컨버터에서의 Coupled Inductor 해석
신동설(Dongsul Shin),차헌녕(Honnyong Cha),이종필(Jong-Pil Lee),유동욱(Dong-Wook Yoo),김희제(Heeje Kim) 전력전자학회 2011 전력전자학술대회 논문집 Vol.2011 No.7
The interleaving method is usually used to reduce the ripple of output current of filter inductor in parallel operation of PWM DC/DC converter. Although the current ripple of filter inductor decreases, each current ripple of filter inductor is not decreased. In this study, the operation of interleaved buck converter with coupled inductor is analyzed in each operation mode. It is verified through experiment. The possibility of application to grid connected inverter with parallel operation is identified.
Kiryong Kim,Dongsul Shin,Jaecheol Lee,Jong-Pil Lee,Dong-Wook Yoo,Hee-Je Kim 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4
This paper proposes a control strategy based on the frequency detection method, comprising a current control and a feed-forward voltage control loop, is proposed for grid-interactive power conditioning systems (PCS). For continuous provision of power to critical loads, PCS should be able to check grid outages instantaneously. Hence, proposed in the present paper are a frequency detection method for detecting abnormal grid conditions and a controller, which consists of a current controller and a feedforward voltage controller, for different operation modes. The frequency detection method can detect abnormal grid conditions accurately and quickly. The controller which has current and voltage control loops rapidly helps in load voltage regulation when grid fault occurs by changing reference and control modes. The proposed seamless transfer control strategy is confirmed by experimental results.
Parallel operation of inverter using trans-Z-source network
Aleem, Zeeshan,Dongsul Shin,Honnyong Cha,Jong-Pil Lee,Dong-Wook Yoo,Peng, Fang Z. IET 2015 IET power electronics Vol.8 No.11
<P>There is strong demand for high-power application for photovoltaic and wind power generation systems. The realisation of a high power conversion system is usually limited by the available switching devices because of the maximum voltage and current ratings, losses and switching frequency. Thus, utilising parallel-connected power converters rated at more minute power levels are highly desirable. A robust approach for such a realisation would result in many advantages, such as modularity, ease of maintenance, (<I>n</I> + 1) redundancy and high reliability. The parallel operation of a voltage-fed (VF) trans-Z-source inverter (ZSI) is presented. A two parallel connected VF-trans-ZSI is introduced and a similar concept is extended to N-parallel connected inverter. A 2.9 kW prototype inverter is built and tested to verify the performance of the proposed inverter.</P>
Kiryong Kim,Dongsul Shin,Jong-Pil Lee,Tae-Jin Kim,Dong-Wook Yoo,Hee-Je Kim 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper proposes a control strategy for grid interactive Power Conditioning System (PCS) which has a feedforward voltage control based on grid frequency detection. The PCS should supply the power to the critical load, regardless of the grid condition. In order to provide the power to the critical load continuously, the PCS should operate two modes. One is Grid-Connected mode and the other is Stand-Alone mode. It is important to know the grid condition to decide operation modes. This paper proposes a control method based on the grid frequency to detect the grid condition and consists of a current controller and a feedforward voltage controller. The grid frequency detection is able to reduce the grid fault detection time and a feedforward voltage controller helps voltage regulation fast. This proposed control strategy is verified by the simulation and experimental results.