• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.56 no.2
• /
• pp.90-98
• /
• 2007

More and All-Electric Aircraft (AEA) carry many loads with varied functions. In particular, there may be large pulsed loads with short duty ratio, which can affect the normal operation of other loads. In this paper, a bi-directional converter with inductive storage is used as a voltage bus conditioner (VBC) to mitigate voltage transients on the bus. In addition, the constant frequency hysteresis control technique for a VBC is presented. A simple and fast prediction of the hysteresis band-width is implemented by the phase-lock loop control, keeping constant switching frequency. This technique offers the excellent dynamic response in load or parameter variation. The control performance is illustrated by simulated results with the SABER package, The proposed hysteresis control results in the shortest and the smallest excursions.

• Proceedings of the KIPE Conference
• /
• 2012.11a
• /
• pp.205-206
• /
• 2012

A general method to measure the inverter DC bus capacitor current is described. It is an indirect estimated method. By measuring the input and out voltage and current can calculate DC bus capacitor current. This paper will develope the theory that describes the indirect method. It will discuss and verify the feasibility of this approach through the use of the PSIM. Using SPWM control method will be simulated and compared.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.27 no.2
• /
• pp.126-133
• /
• 2022

This study proposes a suppression of zero sequence current (ZSC), which is caused by zero sequence voltage (ZSV) for a dual two-level inverter with single DC bus. Large output voltages enable the dual inverter with single DC bus to improve a system efficiency compared with single inverter. However, the structure of dual inverter with single DC bus inevitably generates ZSC, which reduces the system efficiency and causes a current ripple. ZSV is also produced by dead time, and its magnitude is determined by the DC bus and current direction. This study presents a novel space vector modulation method that allows the instantaneous suppression of ZSC. Based on a condition where a switching period is twice a sampling (control) period, the proposed control method is implemented by injecting the offset voltage at the primary inverter. This offset voltage is injected in half of the switching period to suppress the ZSC. Simulation and experiments are used to compare the proposed and conventional methods to determine the ZSC suppression performance.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.23 no.5
• /
• pp.345-351
• /
• 2018

A distributed control method is proposed to improve the power sharing performance of bidirectional distributed generators and the voltage regulation performance of a DC bus in a DC microgrid. Voltage sensitivity analysis based on power flow analysis is conducted to analyze the structural characteristics of a DC microgrid. A distributed control method using a voltage sensitivity matrix is proposed on the basis of this analysis. The proposed method uses information received through the communication system and performs the droop gain variation method and voltage shift method without additional PI controllers. This approach achieves improved power sharing and voltage regulation performance without output transient states. The proposed method is implemented through a laboratory-scaled experimental system consisting of two bidirectional distributed generators, namely, a load and a non-dispatchable distributed generator in a four-bus ring-type model. The experimental results show improved power sharing accuracy and voltage regulation performance.

• Proceedings of the KIPE Conference
• /
• 2007.07a
• /
• pp.196-198
• /
• 2007

In the substations for traction systems and the large-scale discharging system of secondary batteries, the voltage of DC bus line goes up by the regenerated energy and the energy is usually wasted in resistor for system stability. This paper proposes the DC power regenerating system using a three phase PWM inverter. The proposed system can regenerate the excessive DC power from DC bus line to AC supply and control the power factor of AC supply to unity. To implement unity power factor, the magnitude of the inverter output voltage should be higher than that of AC supply and therefore SVPWM technique is adopted. Computer simulations are carried out to verify the validity of the proposed system.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.23 no.5
• /
• pp.313-320
• /
• 2018

This study proposes a new voltage balancer with bidirectional DC-DC converter function. The proposed balancer can serve as a voltage balancer and a bidirectional DC-DC converter. Thus, the balancer can be applied to battery management systems or fast chargers in electric vehicles (EVs) charging stations while balancing bipolar DC bus voltages. The proposed system has unlimited voltage balancing range unlike the conventional voltage balancing control using a three-level DC-DC converter. A comparison of the voltage balancing range between the proposed and conventional scheme is explored to confirm this superiority. Simulation and experimental results are provided to validate the effectiveness of the proposed system.

• Proceedings of the KIPE Conference
• /
• 2019.07a
• /
• pp.467-468
• /
• 2019

This paper proposes an improved bus voltage regulation scheme in filter-based reference current generation of power management for DC home grid with photovoltaics (PV), battery, and ultracapacitor (ultracap) by using feedforward terms instead of the filter output to produce the ultracap reference current. Simulation results have proved the effectiveness of the proposed scheme.

• Journal of Power Electronics
• /
• v.15 no.3
• /
• pp.806-818
• /
• 2015

Based on the inherent relationship between dc-bus voltage and grid feeding active power, two dc-bus voltage regulators with different references are adopted for a grid-connected PV inverter operating in both normal grid voltage mode and low grid voltage mode. In the proposed scheme, an additional dc-bus voltage regulator paralleled with maximum power point tracking controller is used to guarantee the reliability of the low voltage ride-through (LVRT) of the inverter. Unlike conventional LVRT strategies, the proposed strategy does not require detecting grid voltage sag fault in terms of realizing LVRT. Moreover, the developed method does not have switching operations. The proposed technique can also enhance the stability of a power system in case of varying environmental conditions during a low grid voltage period. The operation principle of the presented LVRT control strategy is presented in detail, together with the design guidelines for the key parameters. Finally, a 3 kW prototype is built to validate the feasibility of the proposed LVRT strategy.

• Proceedings of the KIEE Conference
• /
• 2007.04c
• /
• pp.97-99
• /
• 2007

This paper presents a fuzzy logical control method to implement an on-line optimum efficiency control for Permanent Magnet Synchronous Motor. This method real-timely adjusts the output voltage of the inverter system to achieve the optimum running efficiency of the whole system. At first, the input power is calculated during the steady state in the process of efficiency optimizing. To exactly estimate the steady state of the system, this section needs check up the speed setting on timely. The second section is to calculate input power of dc-bus. The exact measurement of the voltage and current is the vital point to acquire the input power. The third section is the fuzzy logic control unit, which is the key of the whole drive system. Based on the change of input power of dc-bus and output voltage, the variable of output voltage is gained by the fuzzy logical unit. With the on-line optimizing. the whole system call fulfill the minimum input power of dc-bus on the running state. The experimental result proves that the system applied the adjustable V/f control method and the efficiency-optimizing unit possesses optimum efficiency, and it is a better choice for simple variable speed applications such as fans and pump.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2005.11a
• /
• pp.429-432
• /
• 2005

This paper investigates how the PCB power-bus structure's characteristics are influenced by the loading of decoupling capacitors that are placed close to vias, on purpose or not. It is worthwhile to see the correlated effects of the aforementioned lumped elements in that when they inevitably share one DC power-bus they will result in positive or negative changes in the PCB EMC design. The EM fields and impedance profiles are rigously calculated on the PCB power-bus cases loaded with the above components and their effects will be given to bring better PCB EMC countermeasures.