A method for detecting insulation resistance of electric vehicles

Abstract

The invention discloses a method for detecting insulation resistance of an electric vehicle. When in a static state, obtain the equivalent capacitance Cp of the positive pole to the ground and the equivalent capacitance Cn of the negative pole to the ground; respectively obtain the predicted steady-state voltage Up' of the positive pole and the predicted steady-state voltage Un' of the negative pole; based on the voltage value of the positive pole to the place Up and the positive predicted steady-state voltage Up' to obtain the final insulation resistance value Rp of the positive electrode to ground; based on the equivalent capacitance Cn of the negative electrode to ground and the negative predicted steady-state voltage Un', the final insulation resistance value Rn of the negative electrode to ground is obtained. The insulation impedance detection method of the electric vehicle of the present invention avoids the influence of the Y capacitor on the insulation detection function of the whole vehicle, improves the insulation detection accuracy, greatly reduces the insulation detection time, and improves the safety level of the whole vehicle.

Description

technical field [0001] The invention belongs to the technical field of new energy vehicle safety detection, and more specifically relates to an insulation resistance detection method of an electric vehicle. Background technique [0002] Electric vehicles generally detect the insulation resistance between the high-voltage positive and negative poles of the power battery system and the ground in real time to ensure that no electric shock or other high-voltage safety accidents will occur. The two detection methods widely adopted at present are: 1. Bridge type: by incorporating and paralleling a large resistor with a certain resistance value between the positive and negative poles of the high-voltage system and the ground, real-time monitoring is performed according to the changes in the voltage of the high-voltage system before and after the ground. Calculate the current resistance value. 2. Low-frequency AC voltage injection method: By injecting a low-frequency and low-amplit...

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Problems solved by technology

But because there is no clear limit on the size of the Y capacitor of the whole vehicle, when the Y capacitor is relatively large, it takes a long time to stabilize (up to tens of seconds), and the requirement for the insulation detection cycle of the whole vehicle is unacceptable

Another method is to measure the size of the Y capacitor by means of offline measurement, and then perform corresponding compensation on the software algorithm. Although this method has certain effects, it lacks versatility and robustness. There is a certain difference in the size of the vehicle. In addition, with the use of the whole vehicle, the Y capacitor will age, and when the working condition changes (AC / DC charging), the Y capacitor of the external load (such as DC charger, etc.) It will also be introduced, which will further increase the calculation error

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