Two-motor driving type cascading multi-level inverter system without active front end and control method thereof

Abstract

The invention discloses a two-motor driving type cascading multi-level inverter system without an active front end and a control method thereof. The system comprises an energy feedback coupling unit arranged between a power unit of a first cascading multi-level inverter and a power unit of a second cascading multi-level inverter, wherein the energy feedback coupling unit comprises a first inverter circuit, a second inverter circuit, a middle direct voltage capacitor, a current reversible chopper circuit, a buffering inductor, a buffering resistor and a storage battery, the current reversible chopper circuit comprises a buck chopper circuit part and a boost chopper circuit part, the switching between the buck chopping mode and the boost chopping mode is achieved according to the voltage between the two ends of the middle direct voltage capacitor, and then energy can be fed back to the storage battery and recycled to drive motors to run. According to the system, a bidirectional transducer based on a three-phase PWM rectifying circuit is not needed, winding remaking of a phase-shifting transformer is avoided, the energy feedback coupling unit does not need to be connected with a power grid, the complexity and cost of the system can be reduced, energy feeding and harmonic wave injection to the power grid are avoided, and the system is suitable for large-scale application.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a two-motor-driven cascaded multi-level inverter system without an active front end and a control method. Background technique [0002] With the development of power electronics technology, high-voltage inverters, as one of the main achievements of power electronics technology development, have been widely used in production, life, transportation, medical and health due to their high power factor, high efficiency, high precision, and wide speed range. And other fields, to drive the motor to run, and play an increasingly important role. [0003] At present, most of the common high-voltage inverters on the market are cascaded multi-level inverter circuit structures composed of power units based on three-phase uncontrolled rectification circuits. For the circuit topology of traditional cascaded high-voltage inverters, see figure 1 , the circuit topology result...

AI Technical Summary

Problems solved by technology

Although it can meet the performance requirements of bidirectional flow of energy, the introduction of PWM rectification circuit requires a phase-shifting transformer with a more complex winding structure, and the cost of the phase-shifting transformer is high, which is not conducive to large-scale industrial application

In addition, the PWM rectifier control circuit needs to detect the amount of information such as the AC side current and the DC side voltage to implement the PWM rectification control algorithm, which not only increases the cost of the detection link, but also increases the complexity of the control system

In addition, the three-phase PWM rectifier circuit (that is, the active front end) is connected to the grid, and while feeding energy back to the grid, it also injects some harmonics into the grid, which has a negative impact on the reliability of the system.

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