Hi, I am doing a project on three phase rectifier with dc-link capacitor. In order to fit the theory to matlab simulations, I will need to calculate the voltage ripple by finding the output minimum voltage and maximum voltage. In order to get the minimum, I will need Time interval segment II. I’m using a star connected supply with 100V phase voltage. Thank you
hi
you can find it here:
power electronics (circuits,devices and applications) M.H.Rashid _3rd edition
chapter3
Dear Wuxin,
generally speaking, we calculate the voltage stress on the DC-link capacitor from the topology and the applied switching sequence as it is a very established approach. You can find it for three-phase two-level VSIs in:
1) J.W. Kolar and S.D. Round: Analytical calculation of the RMS current stress on the DC-link capacitor of voltage-PWM converter systems
2) Gohil et al.: Analytical Method to Calculate the DC-Link Current Stress in Voltage Source Converters
If you really want to take the measurement approach you should consider the following:
1) Check if during the applied zero vector the discharging current is constant (wL > R, f_el < < f_pwm and C_dc large)
2) If 1) holds consider a linear discharge of the capacitor
3) Calculate V_dcMin = V_dcMax - 1/C_dc * I_rms * (t_2-t_1)
Take into consideration this value holds only for the modulation index and the load angle you calculated it for. As you will find in 1) and 2) distortions are functions of M_i and phi.
Cheers
Pascal
FIRST YOU HAVE THE FREQUENCY AND YOU CAN GET THE PERIOD
SECOND WE ASSUME WE ARE AT THE TOP OF THE SIN WAVE.
AT THIS POINT WE EQUATE
THE DAMPENING EXPONENTIAL FROM THE TOP OF THE SIN WAVE
TO THE SIN WAVE
AND FIND THE POINT THEY MEET .
THE TIME THEY MEET IS THIS INTERVAL .
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