Insulation resistance detecting method for electric vehicle

Abstract

The invention discloses an insulation resistance detecting method for an electric vehicle, and the method comprises the following steps of respectively obtaining an initial insulation resistance valueRp' of a positive pole to ground and an initial insulation resistance value Rn' of a negative pole to ground; determining whether the vehicle is in a standing state, and respectively obtaining an equivalent capacitance Cp of the positive pole to the ground and an equivalent capacitance Cn of the negative pole to the ground when the vehicle is in a static state; respectively obtaining a positive predicted steady state voltage Up' and a negative predicted steady state voltage Un'; obtaining a final insulation resistance value Rp of the positive electrode to the ground based on the voltage valueUp of the positive pole to the ground and the positive predicted steady-state voltage Up'; and obtaining a final insulation resistance value Rn of the negative electrode to the ground based on the equivalent capacitance Cn of the negative electrode to the ground and the negative predicted the steady-state voltage Up'. The insulation resistance detecting method for the electric vehicle provided bythe invention avoids the influence of the Y capacitor on the insulation detecting function of the whole vehicle, improves the insulation detection precision, greatly reduces the time of the insulation detection, 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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