Pre-charging circuit in energy storage system

How does a precharge circuit work?

A precharge circuit charges the DC-link capacitor to the battery voltage, minimizing the inrush current caused when the main contactors close. For the health of the main contactors the inrush is minimized as too high of inrush can cause the contacts to weld together, rendering them defective. Figure 1-1. Precharge Configurations

How long does the precharge circuit take?

The precharge circuit's goal is to limit inrush current at system power-up. Depending on the system voltage, capacitance value, and intended design, precharge can take as little as a few milliseconds or as long as several seconds.

When is a precharge circuit necessary?

In hybrid or electric vehicles, a precharge circuit is used every time the vehicle is turned on. This is necessary for the following reasons, which are discussed in this paper.

What is a smart precharge circuit?

A smart precharge circuit is a circuit that includes a timer and/or counter to monitor the precharge process. It aborts the precharge if the voltage does not reach a certain level within a prescribed period of time or if a certain number of precharge events occur within a specific window of time to prevent overheating.

Where is the precharge circuit typically found?

The precharge circuit is commonly found on the positive leg of the circuit. However, it could also be installed on the negative leg. Since the precharge circuit is directly connected to the battery, both the contactor and the resistor must be rated for full battery voltage.

What is a passive precharge circuit?

This design must charge a 2mF DC-Link capacitor up to the system voltage of 800V in 0.5 seconds. However, 800V EVs can carry as much as 1000V at full charge, so the components in the design must be sized accordingly. At a high level, a passive precharge circuit is a simple RC circuit that can be represented as an exponentially decaying function.