High-speed, variable-speed drive system in megawatt power range

IEEE Trans. on Ind. Applicat.

Toliyat

2006

A multilevel power-converter topology based on two types of current-source inverters (CSIs) has been proposed for large induction motor drives. The topology utilizes the combination of the load-commutated inverter (LCI) using thyristors and the CSI using gate turn-off thyristors (GTOs). As a result, the multilevel-inverter operation takes advantage of a soft switching of the LCI and hard switching of the CSI. The output capacitor is required to generate the leading power factor for load commutation of the LCI. It is shown that the proposed multilevel operation contributes to the leading-power-factor generation by providing the effective phase shift. Thus, the leading power factor required for the load commutation of the LCI is obtained with significantly smaller capacitors at the inverter's output terminals. As a result, the proposed approach can employ the LCI and utilize its softswitching operation, yielding a cost-effective solution compared with the conventional multilevel CSI using two GTO CSIs. The switching losses are curtailed due to the natural commutation of the LCI and the six-step operation of the GTO CSI. Therefore, the proposed multilevel inverter can both increase the output power level and decrease the output capacitor size for LCI. The simulation and experimental results have been shown to verify the feasibility of the proposed multilevel topology and its operation.Index Terms-Gate turn-off thyristor (GTO) inverter, loadcommutated inverter (LCI), multilevel converter.

Section: Multilevel Converter Topology Using Two Types Of Current-soumentioning

confidence: 99%

Multilevel Converter Topology Using Two Types of Current-Source Inverters

IEEE Trans. on Ind. Applicat.

Toliyat

2006

“…The LCI-based drive employs converter grade thyristors and utilizes soft switching by natural commutation of the thyristors. Therefore, it provides simplicity, robustness, cost effectiveness, and very low switching losses, resulting in a favorable topology in high-power areas [6], [11]. Moreover, because it Manuscript has the current-source inverter (CSI) topology, it has inherent advantages of CSI, such as embedded short-circuit protection, improved converter reliability, and instantaneous regeneration ability [1].…”

Section: Introductionmentioning

confidence: 99%

A Hybrid Converter System for High-Performance Large Induction Motor Drives

IEEE Trans. On Energy Conversion

Toliyat

2005

A hybrid converter system employing a combination of a load-commutated inverter (LCI), a dc-dc buck converter, and a voltage-source inverter (VSI) is proposed for the large induction motor drives. The VSI ensures the safe commutation of the LCI with active commutation angle control over all speed regions. By replacing capacitor banks and a forced dc-commutation circuit, this system can eliminate all drawbacks related to these circuits in the conventional LCI-based induction motor drives. Sinusoidal motor current and voltage waveforms are achieved with the VSI providing the reactive and harmonic power to the motor, resulting in high-performance drives. The buck converter enables both the VSI and the LCI to be fed from the single-diode rectifier. As a result, the dc-link inductor size can be reduced and the LCI is operated without the controlled rectifier. In addition, faster dynamic response can be obtained through the VSI and the buck converter operation. Finally, the buck converter performs the dc-link current control to ensure minimum VSI rating. The feasibility of the proposed hybrid circuit for the high-power drive systems is verified by computer simulation for a 500-hp induction motor. Experimental results are also included for a 1-hp induction motor laboratory setup controlled by the proposed hybrid system.

“…Along with their slow response, the CSI-based drives find favor in high power conversion areas, where regeneration capability and reliability are more advantageous than fast dynamic responses. Especially, load-commutated inverters (LCIs) employing high-power, low-cost thyristors as switching devices Manuscript have traditionally been used in high-power induction motor drives, such as fans, pumps, and compressors [1], [2]. The conventional LCI-based drives with commutation constraints of their switching components operate with capacitors in parallel with the load terminals.…”

Section: Introductionmentioning

confidence: 99%

An Integrated Current Source Inverter With Reactive and Harmonic Power Compensators

IEEE Trans. Power Electron.

Kim

2009

An integrated current source converter system is presented based on an assembly of a thyristor-based current source inverter (CSI) in parallel with an insulated-gate-bipolar-transistorbased voltage source inverter (VSI) along with passive capacitors for high-power induction motor drive applications. The proposed configuration installs the VSI and the capacitor in such a way that both provide reactive power for generating the leading power factor required to accomplish natural commutations of the CSI. Based on the collaborative operation of the VSI and the parallel capacitor, the proposed system can be designed with a compromise between the VSI power capacity and the capacitor size. In addition, the VSI compensates harmonic current components from the thyristor-based CSI, while the capacitor filters out the voltage spikes during commutation of the thyristors. As a result, sinusoidal motor currents with improved harmonic spectrum can be drawn from this system. The proposed system utilizes the highpower capability of the thyristor-based CSI to supply high real power, while the VSI with easy controllability regulates the induction motor. Theoretical analyses based on mathematical modeling are presented in detail for the relationship between the inverter rating and the capacitor size, design considerations of the capacitor size, and the loss performances.Index Terms-Capacitor filter, current source inverter (CSI), voltage source inverter (VSI).