Method and system for improving DC voltage utilization ratio of three-phase and four-switch fault-tolerant inverter

Abstract

The invention discloses a method and system for improving the DC voltage utilization ratio of a three-phase and four-switch fault-tolerant inverter. The method comprises the steps of (S1) calculating and judging whether an unbalanced coefficient epsilon of capacitor voltage at a DC side is zero or not, if so, executing the step (S3), or else, executing the step (S2); (S2) correcting four effective voltage vectors of the four-switch fault-tolerant inverter and calculating corrected voltage vector amplitudes respectively; (S3) calculating a reference voltage vector amplitude; (S4) calculating a modulation ratio parameter M on the basis of the reference voltage vector amplitude; (S5) carrying out modulation area division on a complex plane formed by the four voltage vectors; (S6) setting overmodulation algorithms corresponding to various areas respectively and selecting corresponding vectors to synthesize corresponding compensation voltage vectors; and (S7) calculating action time of two effective voltage vectors corresponding to the compensation voltage vectors and an equivalent zero vector to finish PWM modulation. By the method and the system, the DC voltage utilization rate of the inverter is improved; meanwhile, electromagnetic torque is improved; output harmonics are reduced; and the method is simple and easy to implement in engineering.

Description

technical field [0001] The invention belongs to the technical field of motor control, and in particular relates to a method and system for improving the DC voltage utilization rate of a four-switch fault-tolerant inverter. Background technique [0002] Voltage source inverters have been widely used in metal rolling, mine hoisting, ship propulsion, locomotive traction and military and other fields, and are the main equipment for AC-DC conversion. However, it is inevitable that some failures will occur during the operation of the system, such as open circuit and short circuit of power electronic switching devices. Industrial production can cause catastrophic events and endanger personal safety. Therefore, in order to obtain higher reliability, it is required that the system can continue to operate when the inverter fails, that is, the system must have fault-tolerant operation capability. [0003] After the switching tube of the three-phase six-switch inverter fails, the topo...

AI Technical Summary

Problems solved by technology

The maximum DC voltage utilization rate of the four-switch fault-tolerant inverter is only half of that of the six-switch inverter, which greatly reduces the load capacity

This method improves the output voltage of the four-switch inverter to a certain extent, thereby increasing the output torque, but the calculation of the control angle and the holding angle is either performed by complex mathematical operations online or stored offline, which limits the algorithm Accuracy is not conducive to engineering implementation, and this method does not consider the imbalance of the DC side bus capacitor voltage, so it is not suitable for the occasions where there are capacitor voltage fluctuations on the DC side of the fault-tolerant four-switch inverter

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