Calculation method of inverter bus current

Abstract

The invention provides a method for calculating inverter bus current. By accumulating the charge of the upper and lower half bridges on the AC side of the inverter, according to the principle of charge conservation, the charge of the positive electrode of the DC bus is equal to the charge of the upper bridge, and the charge of the negative electrode of the DC bus is equal to the charge of the upper bridge. The amount of charge is equal to the amount of lower bridge charge. In this way, the DC current on the bus side can be calculated according to the charge amount of the upper bridge or the lower bridge accumulated on the AC side of the inverter in a calculation cycle and the duration of the calculation cycle. The busbar current calculation scheme avoids the dispersion characteristics of the physical sensor and the failure of the sensor, saves the DC current sensor, and reduces the product cost. In addition, the calculation accuracy is comparable to that of physical sensors, and the accuracy is stable, and the accuracy is not degraded under fault conditions, avoiding the complex calculation of losses in the power balance method.

Description

technical field [0001] The invention relates to the technical field of new energy vehicles, in particular to a method for calculating inverter bus current. Background technique [0002] In the electric drive system of new energy vehicles, signals such as voltage and current are important inputs required by the motor controller. The DC side current of the inverter is one of them. It can be used for inverter control and derating protection, power calculation, and can be used for mutual verification with the current signal of the battery management system to ensure the safety of the system. The DC bus current can be acquired directly by placing a DC current sensor, but this increases the hardware cost, and there is a problem of physical sensor failure and a decrease in accuracy in the case of a fault. The use of software calculations instead of physical sensors can not only reduce product costs, but also avoid problems such as sensor dispersion and failure. A feasible calcula...

AI Technical Summary

Problems solved by technology

However, this method needs to calibrate the inverter loss under different working conditions, and the calibration work is complicated

In addition, the loss of the inverter is related to multiple factors such as DC voltage, AC current, switching frequency, power factor, and modulation degree. It is difficult to take all these factors into consideration during application, resulting in limited accuracy of the calculated bus current.

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