Electric current reconstructing and over-modulating device of air conditioning frequency converter and method thereof

Abstract

The invention relates to an electric current reconstructing and over-modulating device of an air conditioning frequency converter, which is characterized by comprising an electric current reconstructing device, a vector controller, a pulse width modulation (PWM) frequency converter, a direct current side electric current sensor, an electric motor and a coder. The electric current reconstructing device comprises an SVPWM over-modulating module, a pulse width modulation (PWM) signal adjusting module, a direct current sampling module and an alternating current reconstructing module. An electric current reconstructing and over modulating method of the air conditioning frequency converter comprises the steps: sampling the direct current side electric current of the pulse width modulation (PWM)frequency converter at twice by the electric current reconstructing device; counting an approach vector switch action time which meets a minimum sampling time request according to the two sampling values; sampling the direct current side electric current at twice again in the approach vector switch action time; and reconstructing three phase alternating current according to the sampling values ofthe direct current at twice, thereby realizing the closed loop control of the pulse width modulation (PWM) frequency converter. The modulating method can be widely used for the field in reconstructingand over-modulating the electric current of the frequency converter in air conditionings and electric vehicles.

Description

technical field [0001] The invention relates to a modulation device and method for a motor and a frequency converter, in particular to a current reconstruction overmodulation device and method for an air conditioner frequency converter. Background technique [0002] With the active promotion of energy-saving and consumption-reducing technologies worldwide, inverter air conditioners are gradually attracting the attention of the market because of their power-saving features. At present, the motors of frequency conversion air conditioners mainly use permanent magnet synchronous motors, which have the characteristics of simple structure, small size, light weight, low loss and high efficiency. However, in the traditional vector control system of the permanent magnet synchronous motor, since the AC current signal needs to be measured as feedback to realize the closed-loop control of the current, three current sensors are required on the AC side of the inverter. In addition, in or...

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Problems solved by technology

In this way, the whole system requires a total of four current sensors, resulting in high cost, complex structure, and large volume of the entire frequency conversion device, which is not conducive to integration

[0003] In addition, since most air-conditioning compressors need to operate in the medium-high speed area, and the performance of the compressor speed control system is affected by the output voltage of the inverter, the current three-phase bridge voltage inverter adopts SPWM (sinusoidal Voltage Pulse Width Modulation, Sine Pulse Width Modulation) and SVPWM (Space Vector Voltage Pulse Width Modulation, Space Vector Pulse Width Modulation) to generate PWM (Pulse Width Modulation, Pulse Width Modulation) signal, and although the SPWM algorithm is simple in structure and easy to implement, but The fundamental wave amplitude of the output phase voltage of the inverter is relatively low. In contrast, the SVPWM algorithm has the characteristics of high voltage utilization, that is, the fundamental wave amplitude of the maximum output voltage is high.

However, the SVPWM algorithm still has the problem of not fully utilizing the DC bus voltage, so it is necessary to over-modulate the frequency converter to improve the utilization of the power supply voltage

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