Design Of 10kW Lead Acid Battery Charging System

With the increasing demand for energy in the current society,some unstable situations appear in the peak period of power supply.The problem could be alleviate by the high-power lead-acid battery energy storage system which can achieve peak load shifting.However,due to the unreasonable charging strategy of the lead-acid battery during charging,the batteries may be overcharged,undercharged,heated excessively,so that the cycle life of the battery may decrease drastically.In this thesis,a lead-acid battery charging system with a rated power of 10 kW is designed for the charging characteristics of lead-acid batteries and actual requirements.The three-stage charging method is selected as the charging control strategy of the system through the comparison and analysis of the five battery charging strategies.The high-power charging system consists of two parts: the pre-power factor correction circuit and the post-stage DC conversion circuit.A three-stage interleaved Boost topology is adopted to correct grid-side current distortion and reduce the impact of input current ripple.As the control chip,FAN9673 is capable of implementing channel management of the three parallel Boost circuits.A startup protection circuit is designed to suppress the inrush current generated at the moment of power-up.The compensating circuit of the double-closed-loop control strategy is designed to ensure that the high-voltage output of the preceding stage is stable.The ZVS phase-shifted full-bridge topology is selected as the post-stage DC conversion circuit by comparing several DC topologies.Soft switching can be achieved through resonance to reduce the switching losses and current stress of MOSFETs.UCC28950 is able to generate two pairs of complementary drive output signals,through UCC27324 enhanced current drive capability with the built-in totem pole structure.The gate drive transformer is designed to achieve drive isolation for MOSFETs on the same bridge.Overcurrent,overvoltage,overheat protection circuits and charge control circuit by three-stage charging strategy are well designed.Finally,the 10kW lead-acid battery charging experimental prototype is powered on.According to the key waveforms and data analysis of the debugging process,the measured batteries can achieve the designed three-stage charging and there is no abnormal heating occurs.The power factor up to 0.99 and the peak efficiency of the system is 91.5%,which meets the expected requirements and at the same time verifies the correctness of the circuit design.