Abstract
Research and/or Engineering Question/Object
On board charger is used for charging thehigh voltage battery in PHEVs and EVs and it usually employs a boost converter as PFC(Power factor correction). PFC regulates theDC-Link voltage and shapes sinusoidal current. For high power charging, an interleaved boost converter is useful since this topology has several benefits such as current ripple cancellation, and electromagnetic-interference reduction. However, the current of each phase might do not flow equally due to different parameter or duty cycle and it causes current unbalancing. It occurs harmful effects on the power components.
Methodology
The control structure of an interleaved boost PFC is consist of voltage and current control. The multi-phase interleaved converter is controlled by either multiple or single current control. The latter is simpler and it controls a single current loop and to apply the same duty cycle on the other phases by duplicating the result. But it has a drawback that is a current unbalancing. To overcome it, this paper proposed current balancing control. The controller adjusts the duty cycle based on current differences among phases. The current sensing value is an input of the controller and the original duty cycle of the current control is multiplied by the correction value.
Results
The proposed current balancing control is simulated and experimented on 6.6kW boost PFC converter and it is evaluated under inductance mismatching condition.The experimental result was almost same as the simulation. Current unbalancing was disappeared with the balancing control. The difference of each phase existed without balancing control, but it was reduced upto 90% with the balancing control.
Limitation of this study
The single current control is chosen and its benefit is not to require a single current sensor for each phase. However the current sensors are necessary for balancing control. Instead of reducing microcontroller load,extra hardware is needed for balancing control. So developing the method that does not require extra circuits or one more current sensor is challenging for size reduction.
What does this paper offer that is new in the field including in comparison to other work by the authors?
The common control method is to control each phase independently of multiphase interleaved converter. But the proposed method is helpful not only microcontroller speed but also simplicity of the controller.
Conclusions
The proposed current balancing control approach is verified by the simulation and experiment. As the control scheme is simple, it realizes balancing control without high speed microcontroller. The approach can help keeping the boost PFC converter from the critical dangers such as over current. Furthermore, it would reduce maintenance cost on the parameter deviations.
Keywords : OBC, Multiphase Interleaved Converter, Balancing control