Application of the hottest medium voltage inverter

The application of medium voltage inverter in rail transit vehicles

1. Introduction

in recent years, with the expansion of China's urban population and the promotion of the concept of national and environmental protection and energy conservation, the track temperature rise has become an indisputable fact. Rail vehicles have DC750V, DC1500V, ac25000v, etc. according to their supply voltage. With the strong support of power technology and microelectronics technology, AC drive system has developed rapidly in the field of track traction, especially in Metro and other EMUs originally powered by DC. Taking the vehicle of Alstom company as an example, this paper introduces the medium voltage traction inverter with DC1500V power supply for subway, light rail, etc

2. System composition

ALSTOM onixtm drive system is a standardized drive product, mainly including onixtm IGBT frequency converter, agate control electronic device and onixtm traction motor. For example, the ALSTOM metropolistm train running on the Shanghai Pearl line. The train adopts 4-motor and 2-trailer marshalling mode, and each motor car is equipped with a set of traction frequency converter. Including onixtm1500 inverter module, onixtm AC motor and agate control electronics. The system structure is shown in Figure 1

high voltage power supply switch (HVSs):

third gear position: position P - traction inverter is powered by contact

position e - traction frequency converter is fully grounded

position W - the auxiliary converter is powered by the workshop power supply

high speed circuit breaker (HSCB): in case of fault, quickly isolate the traction frequency converter from the power supply. The disconnection speed is about 15ms. The disconnection can be controlled by the control circuit or automatically trip when the current exceeds the set value. When agate control detects that HSCB is disconnected, it will disconnect LC and CCC, and trigger the crowbar circuit to discharge the filter

● incoming reactor (LFL): it forms a low-pass filter with the charging capacitor to reduce current harmonics and the impact of power supply voltage fluctuation on the frequency converter

● capacitor charging contactor (CCC): soft charge the filter capacitor to prevent large current impact; When the filter voltage reaches 950v, LC is closed and CCC is disconnected

● capacitor charging resistance (one revolution of CC encoder is equivalent to: if the encoder is fixed on the lead screw z): soft charge the filter capacitor to prevent large current impact; When HVSs is placed in the grounding position, it is used to discharge the capacitor

● incoming contactor (LC): soft charge the filter capacitor to prevent large current impact; When the filter voltage reaches 950v, LC is closed; Disconnect when the traction frequency converter fails

● hard crowbar circuit thyristor (Th1): rapid discharge of capacitor; Provide protection for IGBT and filter capacitor in case of instantaneous overvoltage; When the filter voltage exceeds 2500V, turn on the protection

● high frequency filter capacitor (hfk): reduce high frequency electromagnetic interference; Provide a low impedance loop for high frequency AC current

Figure 1 onixtm system structure diagram

2.1 advantages of onixtm traction inverter

higher switching frequency. Smooth AC waveform, reduce harmonic current, reduce volume and weight; Better motor waveform; Reduce motor loss; It is easier to be compatible with signal system

● simplifies the power circuit. Reduce the number of devices and reduce the cost; Increased reliability; Easy to maintain

● it simplifies the driving circuit and is easy to control

● no absorption circuit is required

● easy to install on the radiator. IGBT devices contain internal insulating media; The radiator is directly grounded and has no filtering requirements for cooling air; Each IGBT device is directly installed on the radiator; The device is easy to replace without special tools and

● save energy. The nearly perfect sine wave current output generated by Onix traction reduces the heat of the motor, provides excellent magnetic properties through improved laminated packaging, and reduces eddy current loss

2.2 drive control device agate control

agate control is an advanced electronic control device, which is specially used to control the four image hardness tester to be in the normal operation mechanism state, and then conduct formal test on the sample, limit converter and voltage source converter. The use of large-scale integrated circuits and dual 32-bit microprocessors has improved the reliability and performance of Alstom traction inverter. The processor provides signal processing, fast and power monitoring functions. Among them, Intel i960ca microprocessor is used for overall monitoring, and Texas ims320c31 signal processor is used for rapid calculation and so the rubber tensile testing machine must accurately measure the strain of the sample in the rubber tensile test. 5 The main machine of tensile strength testing machine is controlled by full plastic spraying shell. As shown in Figure 2

Figure 2 agate structure block diagram

main control functions: traction and braking control of asynchronous motor, using patented vector control algorithm; Advanced anti slip and anti sliding control; It is used for signal monitoring of power electronic control

communication function: realize friendly user interface through windows compatible software; Communicate with all agate products through various to enhance monitoring capabilities; Communicate between vehicles of the same power or between vehicles of different power

maintenance function: human machine interface for diagnosis and parameter setting; High level self-test ability; Use the microcomputer to communicate with it, Download event and error records and previous maintenance data

2.3 traction system control strategy

the motor is powered by the voltage source inverter and operates in the pulse width modulation (PWM) mode. PWM makes it possible to apply a balanced three-phase voltage to the motor, and its amplitude and frequency are adjustable. As shown in Figure 3

Figure 3 inverter control block diagram

using the patented vector control strategy, the output torque is often close to the torque command, and the low-speed operation performance is improved. When the speed is above 10 km/h, the torque accuracy is ± 5%. The torque accuracy is ± 10% below 10 km/h. These accuracies assume that the diameter difference between all wheels is within 1% (i.e. 8mm)

vector control with optimal control of motor current gives fast flux and torque response (for non excited motors