Finding the Line Harmonic Current of Two Multiphase Dc–dc Converters with an Input Filter

A dc separately excited motor is controlled by two multiphase dc–dc converters. The average armature current is $I_a = 100 A$ . A simple LC-input filter with $L_e = 0.3 mH$ and $C_e = 4500 µF$ is used. Each dc–dc converter is operated at a frequency of $f = 350 Hz$ . Determine the rms fundamental component of the dc–dc converter-generated harmonic current in the supply.

Question

Finding the Line Harmonic Current of Two Multiphase Dc–dc Converters with an Input Filter

A dc separately excited motor is controlled by two multiphase dc–dc converters. The average armature current is [latex]I_a = 100 A[/latex]. A simple LC-input filter with [latex]L_e = 0.3 mH[/latex] and [latex]C_e = 4500 µF[/latex] is used. Each dc–dc converter is operated at a frequency of [latex]f = 350 Hz[/latex]. Determine the rms fundamental component of the dc–dc converter-generated harmonic current in the supply.

Accepted Answer

[latex]I_a = 100 A, u = 2, L_e = 0.3 mH, C_e = 4500 µF[/latex], and [latex]f_0=1/(2\pi \sqrt{L_eC_e} )=136.98 Hz[/latex]. The effective dc–dc converter frequency is [latex]f_e = 2 × 350 = 700 Hz[/latex]. From the results of Example 5.9, the rms value of the fundamental component of the dc–dc converter current is [latex]I_{1h} = 45.02 A[/latex]. From Eq. (14.50),

[latex]I_{ns}=\frac{1}{1+(nuf/f_0)^2}I_{nh}[/latex] (14.50)

the fundamental component of the dc–dc converter-generated harmonic current is

[latex]I_{1s}=\frac{45.02}{1+(2 imes 350/136.98)^2}=1.66 A[/latex]

Question 14.12: Finding the Line Harmonic Current of Two Multiphase Dc–dc Co...

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