Zhiming Lan

Large power three-level voltage source inverter with IGCTs and the experiment

IGCTs have the features of high current, high voltage, high reliability, compact structure and low loss. They have been widely used in large power voltage source inverter systems now, and they have extensive application prospect. In the paper, the large power three-level converter with IGCTs is introduced. Then with a series experiments, the converter is tested. The efficiency of the converter is also investigated. The experiment result shows that the output power of the large power three-level converter with IGCTs is in the same level as the similar converters in the world. And the converter shows excellent performance in driving a linear motor in a traction system.

The investigation on a novel IGCT-based cascade high voltage large capacity converter

Large capacity converter is widely used in various national economic fields. The novel topology and new emerging device with high voltage and current are the ways to get large capacity converter. In media and high voltage large capacity AC-DC-AC converter systems, the Integrated Gate Commutated Thyristor (IGCT) takes the place of gate turn off thyristor (GTO) duo to its excellent performance. In this paper, the investigation on a novel IGCT-based cascade high voltage large capacity converter is presented. The base unit of the converter is IGCT-based three-level neutral point clamped (NPC) H-bridge converter. Its output voltage has five levels. One phase circuit of the converter this paper presented consists of two base units and its output phase voltage has nine levels. The converter adopts phase shift input transformer to reduce the harmonics in grid side. The output line root-mean-square (RMS) voltage can reach 10kV ant its power capacity can reach 30MW. Three types of carrier-based PWM strategy based on cascaded carriers and phase shift consideration are proposed. The comparison analysis among three types of strategy by simulation result is implemented.

Investigation on large power AC drive system

The performance of the large power AC drive system for rolling mills should meet the need of production technology and adapt to the requirement of the electric network. In the paper, the cycloconverter system is introduced. With the development of large power electronics, application of the large power converter using the self-controllable devices such as IGCT becomes the trend. The three-level AC-DC-AC converter system with IGCTs whose rated power is 16MVA has been developed and put into use. And it is estimated that the AC-DC-AC converter system will be used in the drive for rolling mills in the near future.

Investigation on the protection system of the large power converter with IGCT

Large power three-level voltage source converters with IGCT are being used in medium or large power drive systems now and have prospective future. The protection system is very important to the safe operation of the converter. Method should be carefully taken to protect the converter when fault takes place in the converter, especially over-current due to short circuits in the load or in the converter itself. The converter system is introduced. With software simulation and experiment, the short circuit process of the converter is investigated. Then the schematic diagram of the inverter with protection system is designed. System experiment shows the converter has excellent performance.

Investigation on IGCT-based NPC/H-bridge large power converter

Nowadays the medium and high voltage large power AC-DC-AC converters are widely used in various industrial fields. The integrated gate commutated thyristor (IGCT) is applied to these converters on a large scale due to its high rated voltage and current and other excellent characteristics. In this paper the investigation on IGCT-based NPC/H-bridge large power converter is proposed. The converter is composed of two IGCT-based five-level NPC/H-bridge converters and their outputs are in parallel connection. Each phase of the five-level NPC/H-bridge converter is composed of two IGCT-based three-level neutral point clamped (NPC) legs in an H-bridge form. The converter adopts modular design and the module of IGCT-based three-level NPC legs has been developed. The turn off characteristics of IGCT are investigated and tested. At last one type of carrier-based modified in-phase disposition (IPD) modulation scheme is simulated.

Investigation on the 16MVA voltage source converter with IGCTs

With the development of large power electronics, application of the large power converter using the self-controllable devices such as IGCT becomes the trend. The large power high performance AC-DC-AC converters with high output frequency and less harmonic component are widely required in many fields such as metallurgy and transportation. The 16MVA voltage source converter with IGCTs is introduced. And the working process of the 16MVA converter is studied with simulation. Then the property of the back-to-back converter unit is examined with a series of experiments. The experiment results show that the converter has excellent performance.

Research on the transient state of large power voltage source inverter with IGCTs

IGCTs have the features of high current, high voltage, high reliability, compact structure and low loss. They have been widely used in large power voltage source inverter systems now, and they have extensive application prospect. In the paper, the switching property of IGCT used in large power voltage source inverter is investigated. And part of the simulation results are verified with experiment results. The switching process of IGCT will cause the mutation of current and voltage in the inverter. And the short circuit process of the inverter is analyzed. If short circuit occurs in the inverter, resonance current and voltage will appear in the inverter. So, during the design of the inverter, EMC should be carefully considered.

Investigation on the 7.5MVA IGCT-based three-level NPC convertor

In this paper an investigation and development on a set of 7.5MVA large power three-level neutral point clamped convertor system is introduced. The convertor include five parts: rectifier, discharge circuit, chopper, dc-link, inverter. The rectifier of the convertor consist of the three phases diode rectifier bridge in series with thyristor rectifier bridge. The discharge circuit consists of one thyristor bridge in series with a resistor. The chopper consists of one IGCT bridge in series of resistors. The dc-link consists of multiple capacitors. The inverter of the convertor used a kind of topology of each power bridge having a separate snubber circuit. The convertor used modularization design to reduce the stray inductance and its bulk. The control system of the convertor adopted the VMIC core system based on VME bus and DSP microcomputer control board to generate the three-level voltage space vector modulation pulse. The protection system of the convertor could take fast and effective protection action aim at overvoltage and overcurrent and other faults occurred. The experiment of the convertor performance showed that the maximum of the direct voltage was 5000V and the maximum of the output current was 2500A.