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Does a 3-phase phase-locked loop diagram possible for an AC to DC battery charger?

Discussion in 'Power Electronics' started by Hasan2019, Aug 18, 2021.

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  1. Hasan2019


    Sep 11, 2019
    Hi there,

    In order to achieve unity power factor control, the phase of the AC voltage needs to be obtained. The phase is obtained through a phase-locked loop (PLL).

    Take a look for single phase control structure of the PLL ,

    For such similar way I want to mention some of 3-phase equations, could you kindly elaborate it more ?

    VSa = 1/3*(VSab-VSca);
    VSb = 1/3*(VSbc-VSab);
    VSc = 1/3*(VSca-VSbc);

    VSalpha = 2/3*(VSa - (0.5*VSb) - (0.5*VSc));
    VSbeta = 2/3 *(SQRT3_2*VSb - SQRT3_2*VSc);

    VSq = VSalpha*COS_theta + VSbeta*SIN_theta;
    VSd = -VSalpha*SIN_theta + VSbeta*COS_theta;

    VSd_error = (VSd - VSd_ref);

    freq_delta += (Kp_PLL*(VSd_error-AC_FREQ_PERR) + Ki_PLL*VSd_error);


    p_VSd_error = VSd_error;

    if(freq_delta > 5.) freq_delta = 5.;
    if(freq_delta < -5.) freq_delta = -5.;

    freq = ((AC_FREQ_NORMAL ? 50 : 60) + freq_delta);

    freq_filtered = 0.99*freq_filtered + 0.01*freq;

    theta += (PI2*freq_filtered*AC_TSW);
    AC_TSW= 0.000033

    Lets angle theta goes pi to 2*pi.
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