• Journal of Power Electronics
• /
• v.15 no.5
• /
• pp.1235-1243
• /
• 2015

This paper presents a modified Space Vector Pulse Width Modulation Technique (SVPWM), which solves the well-known problem of voltage imbalance in the capacitors of a single-phase multilevel inverter. The proposed solution is based on the measurement of DC voltage levels at each capacitor of the inverter DC bus. The measurements are then used to adjust the size of the active vectors within the SVPWM algorithm to keep the voltage waveform sinusoidal regardless of any voltage imbalance on the DC link capacitors. When a voltage deviation exceeds a predetermined hysteresis band, the correspondent voltage vector is restricted to restore the voltage level to an acceptable threshold. Hence, the need for external voltage regulators for the voltage capacitors is eliminated. The functionality of the proposed algorithm is successfully demonstrated through simulations and experiments on a grid tied application.

• Proceedings of the KIPE Conference
• /
• 2017.07a
• /
• pp.216-218
• /
• 2017

The imbalance at the 3-phase side at the railway power supply substation has been a well-known issue. Due to the difference in status of loads at each phase at any given moment, it is difficult to maintain the balance in the 2-phase side of the transformer. Consequently, the 3-phase side also presents a certain level of imbalance as well. A co-phase power supply was proposed as a solution. The real application of such system is gradually expanding, proving the effectiveness of the system. In this paper, the application of the single phase D-Q rotating frame theory was applied to the control of the co-phase power supply system. In addition, the power stack of the system was composed of MMC valves, which offers superior operational characteristics. The effectiveness of the system was verified with a real-time simulation, and the results are presented.

• International Journal of Internet, Broadcasting and Communication
• /
• v.13 no.3
• /
• pp.25-33
• /
• 2021

Energy-harvesting wireless sensor networks(EH-WSNs) can collect energy from the environment and overcome the technical limitations of existing power. Since the transmission distance in a wireless sensor network is limited, the data are delivered to the destination node through multi-hop routing. In EH-WSNs, the routing protocol should consider the power situations of nodes, which is determined by the remaining power and energy-harvesting rate. In addition, in applications such as environmental monitoring, when there are urgent data, the routing protocol should be able to transmit it stably and quickly. This paper proposes an adaptive routing protocol that satisfies different requirements of normal and urgent data. To extend network lifetime, the proposed routing protocol reduces power imbalance for normal data and also minimizes transmission latency by controlling the transmission power for urgent data. Simulation results show that the proposed adaptive routing can improve network lifetime by mitigating the power imbalance and greatly reduce the transmission delay of urgent data.

• Journal of Power Electronics
• /
• v.17 no.2
• /
• pp.422-431
• /
• 2017

The equivalent circuit of a three-leg, four-wire voltage source converter (VSC) is derived using switching functions. Simulations and experiments are conducted (i) to investigate the effects of the zero sequence on VSCs when a three-phase imbalance exists and (ii) to use the consistency of simulations and laboratory experiments to validate the equivalent circuit. The impact of a three-phase imbalance on the VSC has yet to be fully investigated because of the lack of an equivalent circuit to show rigorously how the zero sequence currents flow through the VSC.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.7
• /
• pp.757-765
• /
• 2007

OFDM system is an excellent high speed transmission method but it is seriously sensitive to the phase noise and IQ imbalance. Therefore, in this paper, we analyze the communication performance of the OFDM communication system with IQ imbalance and phase noise. Phase noise's variance can be calculated by integral calculus of phase noise power spectrum. From simulation results, it can be shown that the BER performances show different change according to the phase noise variance and IQ imbalance amount. When amplitude imbalance is ${\varepsilon}$=0.2; 0.3; 0.4 and phase imbalance is ${\phi}=10^0$, and distribution of phase noise is ${\sigma}^2=0.012$, BER is degraded by 2.88 dB, 3.61 dB, 4.09 dB in $10^{-5}$ in the respect of the SNR penalty.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.1
• /
• pp.21-28
• /
• 2009

DFT-spread OFDM(Discrete Fourier Transform-Spread Orthogonal Frequency Division Multiplexing) is very effective for solving the PAPR(Peak-to-Average Power Ratio) problem. Therefore, the SC-FDMA(Single Carrier-Frequency Division Multiple Access) which is basically same to the DFT spread OFDM was adopted as the uplink standard of the 3GPP LTE ($3^{rd}$ Generation Partnership Project Long Term Evolution). Unlike the ordinary OFDM system, the SC-FDMA using DFT spreading method is vulnerable to the ICI(Inter-Carrier Interference) problem caused by the phase noise and IQ(In-phase/Quadrature) imbalance and effected FDE(Frequency Domain Equalizer). In this paper, the ICI effects from the phase noise and IQ imbalance which can be problems in uplink transmission are analyzed according the back-off level of HPA. Next, we propose the equalizer algorithm to remove the ICI effects. This proposed equalizer based on the FDE can be considered as up-graded and improved version of PNS(Phase Noise Suppression) algorithm. This proposed equalizer effectively compensates the ICI resulting from the phase noise and IQ imbalance. Finally, through the computer simulation, it can be shown that about SNR=14 dB is required for the $BER=10^{-4}$ after ICI compensation when the back-off is 4.5 dB, $\varepsilon=0.005$, $\phi=5^{\circ}$, and $pn=0.06\;rad^2$.

• East Asian Economic Review
• /
• v.16 no.3
• /
• pp.227-247
• /
• 2012

This paper investigates the source of bilateral trade imbalance at industry level. We build a simple model based on gravity theory and derive the prediction that the bilateral trade balance in an industry is increasing in the difference between trading partners in the output share of the industry. We test this prediction and find that the difference in industry share is highly significant in predicting both the sign and the magnitude of trade balance at industry level. We also find that FTAs tend to enlarge trade imbalance at industry level. However, the overall predictive power of the model is rather limited, suggesting that factors other than production specialization are important in determining trade balance at industry level. Another finding of the paper is that the influence of the difference in industry share on trade balance increases as we move to industries that produce more homogeneous products. This finding calls into question monopolistic competition as the main driver of gravity in international trade.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.27 no.4
• /
• pp.348-355
• /
• 2022

A bipolar DC distribution system suffers from an imbalance in voltages when asymmetric loads are connected at the outputs. Dedicated voltage balancers are required to address the imbalance in bipolar voltage levels. However, additional components eventually increase the cost and decrease the efficiency and power density of the system. Therefore, to deal with the imbalance in output voltages without adding any extra components, this study presents a coupled inductor-based voltage balancing technique with a dual-output CLL resonant converter. The proposed coupled inductor does not require extra magnetic components to balance the output voltages because it is the result of resonant inductors of the CLL tank circuit. It can also avoid complex control schemes applied to voltage balancing. Moreover, with the proposed coupled inductor, the CLL converter acquires good features including zero voltage and zero current switching. Detailed analysis of the proposed coupled inductor is presented with different load conditions. A 3.6-kW hardware prototype was built and tested to validate the performance of the proposed coupled inductor-based voltage balancing technique.

• Journal of Advanced Marine Engineering and Technology
• /
• v.30 no.4
• /
• pp.505-513
• /
• 2006

A linear power amplifier is particularly emphasized on the system using a linear modulations, such as 16QAM and QPSK with pulse shaping. because intermodulation distortion which causes adjacent channel interference and co-channel interference is mostly generated in a nonlinear power amplifier. In this paper, parameters of a linearization loop, such as an amplitude imbalance a phase imbalance and a delay mismatch, are briefly analyzed to get a specific cancellation performance and linearization bandwidth. Experimental results are presented for IMT-2000 frequency band. The center frequency of the feedforward amplifier is 2140 MHz with 60 MHz bandwidth. When the average output power of feedforward amplifier is 20 Watt. the intermodulation cancellation performance is more than 21 dB. In this case, the output power of feedforward amplifier reduced 3.5 dB because of extra delay line loss and coupling loss. The feedforward amplifier efficiency is more than 7.2 % for multicarrier signals, 59 dBc for ACPR.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2005.06a
• /
• pp.1176-1185
• /
• 2005

A linear power amplifier is particularly emphasized on the system using a linear modulations, such as 16QAM and QPSK with pulse shaping, because intermodulation distortion which causes adjacent channel interference and co-channel interference is mostly generated in a nonlinear power amplifier. In this paper, parameters of a linearization loop, such as an amplitude imbalance, a phase imbalance and a delay mismatch, are briefly analyzed to get a specific cancellation performance and linearization bandwidth. Experimental results are presented for IMT-2000 frequency band. The center frequency of the feedforward amplifier is 2140 MHz with 60 MHz bandwidth. When the average output power of feedforward amplifier is 20 Watt, the intermodulation cancellation performance is more than 21 dB. In this case, the output power of feedforward amplifier reduced 3.5 dB because of extra delay line loss and coupling loss. The feedforward amplifier efficiency is more than 7.2 % for multicarrier signals, 59 dBc for ACPR.