Power output method of alternating current asynchronous transmission system

Abstract

The invention discloses a power output method of an alternating current asynchronous transmission system, which is a method for implementing maximum power output of a transmission system within a total speed regulation range. Udc=Udc0 is relative to a rated power point P2N of the transmission system; in a low-voltage region, a peak feature curve cluster of the transmission system takes extreme value output voltage of an inverter as an inflection point to promote the maximum output power of a motor; in a high-voltage region, the peak feature curve cluster of the transmission system fully utilizes high voltage to expand a boost constant power region and takes the extreme value output voltage of the inverter as a constant voltage inflection point to expand a constant voltage and constant power region, thereby lowering a working current of the motor. The invention fully utilizes the inherent output characteristic of an asynchronous motor within an effective power voltage range and particularly under lower or higher power voltage, has both the inverter safety and the system reliability, promotes the power output capability of the transmission system to the maximum in the premise of no enhancement of the maximum output current of the inverter and the keeping of stable running of the asynchronous motor and satisfies the power needs of loading.

Description

technical field [0001] The present invention relates to a power output control method of a transmission system, in particular to an electric transmission system composed of an inverter and an AC asynchronous drive motor. In the case of frequent voltage fluctuations, a strategy and method to improve the power output capability of the AC asynchronous electric drive system. The invention is especially suitable for places where the capacity of the power supply is small and the voltage of the power supply fluctuates frequently during load, such as urban rail passenger cars, pure electric vehicles, hybrid electric vehicles, and field mobile operating vehicles. Background technique [0002] In electric transmission vehicles, the asynchronous transmission system consists of two major components, the inverter 1 and the asynchronous motor 4, and adopts frequency conversion speed regulation, such as figure 1 As shown: Inverter 1 adopts VVVF control, its input side is DC power supply 5...

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Problems solved by technology

Press (U dc / U dcN ) 2 The multiplier reduces the torque in the constant power area, which can also ensure the safe operation of the asynchronous motor and the system, but the output capacity of the motor is reduced too much, and even the output of the transmission system may not be able to meet the power demand of the load.

Moreover, these two adjustment methods cannot transition smoothly, and the phenomenon of discontinuous output power (or torque) often occurs during speed adjustment, which generally needs to be determined point by point through ground tests.

The direct consequence of applying this strategy is that it is often necessary to expand the capacity of the motor and inverter during system design to meet the minimum power performance requirements of the load for the drive system when the power supply is at low voltage, which directly leads to the increase in the size of the motor and inverter. The system cost increases and the operating efficiency decreases; at the rated voltage, the asynchronous motor and inverter have too much power margin, the system does not operate in the high efficiency area, and the overall efficiency is low

[0009] Take the chopping method and press U dcN Characteristic line output, drive system at DC side bus voltage U dc When it is higher, its advantages are not fully utilized—reducing the output current of the inverter to make the asynchronous motor work at a high efficiency point. At the same time, because the constant voltage and constant power area is compressed, the conversion efficiency of the inverter 1 is not optimal, that is, the electric energy underutilized

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