• The Transactions of the Korean Institute of Power Electronics
• /
• v.5 no.5
• /
• pp.443-450
• /
• 2000

A PWM inverter for an induction motor often has a problem with a high frequency leakage current that flows through stray capacitors between stator windings and a motor frame to ground. This paper proposes a new type of Active Common Mode Voltage Canceler circuit for the reduction of common mode voltage and high frequency leakage current generated by the PWM VSI-fed induction motor drives. The compensating voltage applied by the common made voltage canceler has the same amplitude as, hut the opposite polarity to, the common mode voltage by PWM Inverter. Therefore, common mode voltage and high frequency leakage current can be canceled. The proposed circuit consists of four-level half-bridge inverter and common-mode transformer. Simulated and experimental results show that common mode voltage canceler makes significant contributions to reducing a high frequency leakage current.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.6
• /
• pp.478-487
• /
• 2003

In this paper, a type and special feature of Multi-level inverter used in medium-voltage and high-capacity motor driver is introduced. Especially, a power quality and structural advantages of H-Bridge Multi-level inverter is described. It presented the specific structure of power circuit, design method, controller composition and PWM techniques of the cascaded H-Bridge Multi-level inverter which is developed. The feasibility of the developed product based on 3,300V lMVA 7-level H-bridge inverter was studied by experiments and we get conclusion that 1)generate of near-sinusoidal output voltage; 2)is low dv/dt at output voltage; 3)reduce the harmonic injection at input; Experiment demonstrate that it is very economical in productivity because of using the existing production technique and examination equipment, and has the reliability and a good maintenance due to the structure of Power Cell unit combination as well as low cost IGBT.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.11 no.4
• /
• pp.313-320
• /
• 2006

In this paper, a design approach of LC trap filter for output side harmonic reduction of single phase NPC multilevel inverter is proposed, and THD of the output voltage and harmonic FFT of the output current are analyzed. The proposed filter consists of a conventional LCR filter cascaded with an LC trap filter and it is tuned to inverter switching frequency. A NPC multilevel inverter inverter is used an inverter system for high power application and DSP(TMS320C31) is used for the controller. The effectiveness of the proposed system confirmed through simulation and experimental results.

• Proceedings of the KIEE Conference
• /
• 1998.07f
• /
• pp.1957-1959
• /
• 1998

본 연구에서는 단상 인버터에서 출력 고조파 성분을 억제하기 위해 3레벨 PWM 인버터의 전력회로를 제안하였다. 이 제안된 전력회로를 이용하여 정현적 PWM전압을 발생하기 위한 스위칭함수를 구현하였다. 또한 부하변동에 따른 동특성을 개선시키고, 인덕터의 편자현상을 보상하기 위해 인덕터의 전류제어기를 구성하였다.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.5
• /
• pp.438-447
• /
• 2004

A new multilevel PWM inverter using a half-bridge and full-bridge cells is proposed for the use of stand-alone photovoltaic inverters. The configuration of the proposed multilevel PWM inverter is based on a prior 11-level shaped PWM inverter. Among three full-bridge cells employed in the prior inverter, one cell is substituted by a half-bridge cell. Owing to this simple alteration, the proposed inverter has three promising merits. First it increases the number of output voltage levels resulted in high quality output voltages. Second, it reduces two power switching devices by means of employing a half-bridge cell. Third, it reduces power imposed on a transformer connected with the half-bridge unit. That is to say, most power is transferred to loads via cascaded transformers connected with low switching inverters, which are used to synthesize the fundamental output voltage levels whereas the output of a transformer linked to a high switching inverter is used to improve the final output voltage waves; thus, it is desirable in the point of the improvement of the system efficiency. By comparing to the prior 11-level PWM inverter, it assesses the performance of the proposed inverter as a stand-alone photovoltaic inverter. The validity of the proposed inverter is verified by computer-aided simulations and experimental results.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.6
• /
• pp.469-477
• /
• 2003

This paper proposes a Carrier-Rotation (CR) PWM technique that is a new solution for the voltage unbalancing problem of flying capacitors in the Flying Capacitor Multi-level Inverter (FCMI). The proposed technique equalizes the utilization of phase leg voltage redundancies corresponding to the charging and the discharging state of individual flying capacitors during each switching period of all the switches. Therefore, the charging and the discharging quantity of flying capacitors are equal, which makes the average variation of flying capacitor voltages become zero and keeps their voltage stable during minimum specified period. It also has the reduced harmonic contents of output voltage and the same switch utilization since all the carrier signals are in phase and the switching frequency of each switch is identical. The proposed technique is analyzed precisely in flying capacitor 3-level inverter and then it has expanded to the FCMI (N-level, N>3). Experimental results on the laboratory prototype flying capacitor 3-level inverter confirm the validity of the proposed technique.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.1193-1195
• /
• 2004

Ozone gas is one of the strongest oxidizing and bleaching agents which leave no residues harmful to the global environment. In recent years, the ozone generator has been widely utilized, However, it has been known that a broader application of ozone is hindered primarily because of its low efficiency of generation. Thus, it is more indispensable to improve actual system efficiency of the silent discharge type ozonizer using high frequency inverter. This paper presents a multi level resonant ozone power regulation by association of high frequency transformers and full bridge invert. And proposed resonant inverter system can generate continuous output voltage. can control linearly quantity of ozone gas. This invert that add PWM forms within square forms of output voltage about one level range. The power regulation characteristics and operating performances of silent discharge (SD)type ozone generating tube load driven by this load proposed inverter using FET modules are illustrated from a practical point of view, which can operate under stable conditions of basic level and PWM hybrid control strategy implemented DSP(2406). The effectoveness of propsed invert type ozonizer is proved by experiment results.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.18 no.5
• /
• pp.422-428
• /
• 2013

Recently, we use a static synchronous compensator(STATCOM) with cascaded H-bride topologies, because it is easy to increase capacity and to reduce total harmonic distortion(THD). When we use equipment for reactive power compensation, dc-link voltage unbalances occur from several reasons although loads are balanced. In the past, switching pattern change of single phase inverter and reference voltage magnitude change of inverter equipped with power sensor have been used for dc-link voltage balance. But previous methods are more complicated and expensive because of additional component costs. Therefore, this paper explains reasons of dc-link voltage unbalance and proposes solution. This solution is complex method that is composed of reference voltage magnitude change of inverter without additional hardware and shifted phase angle of inverter reference voltages change. It proves possibility through 1000[KVA] system simulation.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.4 no.6
• /
• pp.547-553
• /
• 1999

A new multi-step voltage source inverter is proposed in this paper. The proposed scheme is composed of t the double-connected 12-step inverter with an auxiliary circuit. The auxiliary circuit includes two voltage d dividing capacitors, two switching devices and a low KV A autotransformer. The resultant system is shown to b be a 24-step inverter suitable for medium power level SVC applications in which the PWM method can not be e employed. A 36-step operation can also be 이)tained by the addition of a bidirectional switch to the ProlXlsed I inverter. The design parameters are derived from the analysis of voltages and currents by means of switching f functions. The validity of the proposed scheme is confirmed by the simulated and experimental results.

• Journal of Power Electronics
• /
• v.13 no.2
• /
• pp.296-303
• /
• 2013

This paper proposes a high efficiency three-phase cascaded phase shifted H-bridge multi-level inverter without DC/DC converters for grid-tied multi string photovoltaic (PV) applications. The cascaded H-bridge topology is suitable for PV applications since each PV module can act as a separate DC source for each cascaded H-bridge module. The proposed phase shifted H-bridge multi-level topology offers advantages such as operation at a lower switching frequency and a lower current ripple when compared to conventional two level topologies. It is also shown that low ripple sinusoidal current waveforms are generated with a unity power factor. The control algorithm permits the independent control of each DC link voltage with a maximum power point for each string of PV modules. The use of the controller area network (CAN) communication protocol for H-bridge multi-level inverters, along with localized PWM generation and PV voltage regulation are implemented. It is also shown that the expansion and modularization capabilities of the H-bridge modules are improved since the individual inverter modules operate more independently. The proposed topology is implemented for a three phase 240kW multi-level PV power conditioning system (PCS) which has 40kW H-bridge modules. The experimental results show that the proposed topology has good performance.