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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.
Kim, Kiryong,Shin, Dongsul,Lee, Jaecheol,Lee, Jong-Pil,Yoo, Dong-Wook,Kim, Hee-Je The Korean Institute of Power Electronics 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.
Kim, Kiryong,Shin, Dongsul,Kim, Hee-Je,Lee, Jong-Pil The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2
A circulating current is a major problem caused by directly connecting voltage-source inverters (VSIs) in parallel. This circulating current occurs as a zero-sequence current between the inverters by specific switch states. Several studies have presented alternatives using hardware and software methods. When coupled inductors (CIs) are employed for the high-frequency circulating current, a controller is required to prevent the low-frequency circulating current from saturating the CIs. In this study, the zero-sequence circulating current and its alternatives are investigated using hardware and mathematical description. A high-performance circulating current controller is proposed by applying a repetitive controller to the zero-sequence current control loop. The proposed controller can effectively minimize the low-frequency circulating current without any data sharing between the inverters in unfavorable conditions. It can also be applicable to the modular configuration of parallel three-phase VSIs. Experimental results verify the performance of the proposed controller.
Kiryong Kim,Dongsul Shin,Hee-Je Kim,Jong-Pil Lee 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2
A circulating current is a major problem caused by directly connecting voltage-source inverters (VSIs) in parallel. This circulating current occurs as a zero-sequence current between the inverters by specific switch states. Several studies have presented alternatives using hardware and software methods. When coupled inductors (CIs) are employed for the high-frequency circulating current, a controller is required to prevent the low-frequency circulating current from saturating the CIs. In this study, the zero-sequence circulating current and its alternatives are investigated using hardware and mathematical description. A high-performance circulating current controller is proposed by applying a repetitive controller to the zero-sequence current control loop. The proposed controller can effectively minimize the low-frequency circulating current without any data sharing between the inverters in unfavorable conditions. It can also be applicable to the modular configuration of parallel three-phase VSIs. Experimental results verify the performance of the proposed controller.
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.
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.
Lee, Seul Gi,Kim, Da Hyun,Lee, Young Seok,Cho, Seung-Yong,Chung, Myung-Sub,Cho, MinJa,Kang, YoungWoon,Kim, HyeJung,Kim, DongSul,Lee, Kwang-Won Elsevier 2018 Journal of food composition and analysis Vol.69 No.-
<P><B>Abstract</B></P> <P>Rice can be the major contributor to exposure of inorganic arsenic (iAs). A total of 485 domestic rice (polished rice, n = 368; husked rice, n = 117) samples produced in 2014 were determined for total arsenic (tAs) and As species. The determination of As species was conducted by HPLC-ICP-MS. AsIII was the major detected species. AsV, DMA, and MMA were occurred in lower level in both types of rice. In polished rice, iAs represented 43–91% of tAs: tAs = 0.088 ± 0.021 mg/kg; iAs = 0.060 ± 0.013 mg/kg. In husked rice, iAs ranged from 55% to 91% of tAs; tAs = 0.160 ± 0.042 mg/kg, iAs = 0.114 ± 0.029 mg/kg. The iAs level of polished rice samples was below the current maximum limit of the Chinese and German standard (0.2 mg/kg for inorganic arsenic in milled rice). Also, husked rice samples did not exceed the standard for iAs. Average dietary exposure to iAs from polished rice consumption was calculated as 0.17 ± 0.21 μg/kg·bw/day which was 8.09% level of Provisional Tolerable Weekly Intake. The result obtained in the present study provide a reference data of iAs in Korean rice for the establishment of safety standards.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Korean polished and husked rice were analyzed for total and inorganic arsenic. </LI> <LI> In rice AsIII was the major detected species, and iAs represents 43–91%. </LI> <LI> The level of iAs of polished rice was below the current maximum limit of standard. </LI> <LI> Safety standards depend on the As characteristic in rice and other foods. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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>