Boost Converter for high voltage electric vehicles

[cts_casemod]

According to the simulations a frequency of 40KHz produces good results, with a current swing of 6A. This can be easily achieved by most fast IGBT's.

The Plots below are for an output power of 5KW and input voltage of 248VAC.



Here, I implemented the PFC pre-converter as a constant current source. There's no voltage loop, for simplicity, although the real thing has one.

With F= 40KHz, Max duty = 97% and a current limit of 26A, the inductor works in CCM for most of the time.

Blue Plot = Inductor current
Green Plot = battery current (Follows input voltage)
Red plot = Battery voltage (Rbat = 0.5Ohm)


Here a further detail during the AC supply peak



During the AC supply zero crossing. There's a blanking period of 0.7ms after each zero crossing. There's also a bit of noise (I didn't smooth the input signal for the simulation to run faster)



Also a test at 120VAC. The inductor current is discontinuous and peaks at 12.5A, however the output current is only 2.1Apeak or 1.5ARMS = 660W. This is to show how the peak currents and hence losses double when the converter operates in DCM.



This one is for 300V DC supply: 18A Average input current (22A peak), with an output current of 11.7A (5.15KW). This is what can be expected for the inverter boost converter, although with higher currents, which should allow a lower inductance value for the inductor.

[e*clipse]

This is an excellent, pragmatic range for a charger - exactly what I want to do.

What drives the converter into DCM? Is it the voltage difference between the battery voltage and the peak rectified AC voltage?

What happens in the situation of DC input, with limited current (solar). Would it be possible to stay near the maximum power point of the solar panels? Maybe not a perfect mppt set-up, but close?

Also, to do the pulsed charging near the end of the charge cycle, what do these controllers do? The Infineon one I used had a "sleep" mode.

Thanks a bunch,

E*clipse

[cts_casemod]

Originally Posted by e*clipse

This is an excellent, pragmatic range for a charger - exactly what I want to do.

What drives the converter into DCM? Is it the voltage difference between the battery voltage and the peak rectified AC voltage?

What happens in the situation of DC input, with limited current (solar). Would it be possible to stay near the maximum power point of the solar panels? Maybe not a perfect mppt set-up, but close?

Also, to do the pulsed charging near the end of the charge cycle, what do these controllers do? The Infineon one I used had a "sleep" mode.

Thanks a bunch,

E*clipse

For a given inductance, the slope of the current on an inductor is more or less constant. If the frequency, current or duty cycle are low, for a given slope the inductor current will quickly ramp back to zero.

At low voltages, or loads, to keep the input sinusoidal the current must be reduced in phase with the voltage, therefore it goes into DCM.

For a limited DC, one needs a large input capacitor to reduce the source impedance. The converter then can work in burst mode or DCM with reduced output frequency.

I'm not familiar with the pulse charging setup. How does it work?