 DEPARTMENT OF ELECTRICAL POWER ENGINEERING

COLLEGE OF ENGINEERING

POWER ELECTRONICS Fourier Series and THD for a Square-Wave Inverter Example: The full bridge inverter shown has a switching frequency sequence that produces a square wave voltage across a series RL load. .

Determine:

• a. Amplitudes of the Fourier series terms for the square wave load voltage
• b.Amplitudes of the Fourier series terms for load current
• c.Power absorbed by the load
• d. Total harmonic distortion (THD) of the load voltage and the load current

 Please enter the input value: Input voltage (positive value only): V Resistance: ohm Inductor: mH Switching Frequency: Hz

The amplitude of load voltage is determined from

Vn = (4 Vdc) / n ¦Đ

The amplitude of each current is determined from

In = Vn /Zn

Power at each frequency is determined from

Pn = I2rms R See Fourier Series Analysis

a)and b) Fourier series quantities

 n fn(Hz) Vn(V) Zn(¦¸) In(A) Pn(W) 1 3 5 7 9

c)

 Power absorbed by the load P = ¦˛Pn = W

d)

 THDv = = %

 THDI = = %