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TIDM-1000: Neutral requirement in 3 phase 6 switch pfc converter

Anoop kumar N
Intellectual 908 points
Part Number: TIDM-1000

Hello, Experts,

This is for my customer; the front-end converter is 3 phase PFC with 3 PFC chokes and 6 Mosfet operated using SVPWM without neutral. But customer asking for neutral line, they argued that neutral can bypass unbalanced current in case of any disturbance happened. 

Qn1: Incase if there is no neutral if an unblance happen; what will be the after effect ?

Qn2: if the grid is unbalanced (say RY phase 420Vac, YB phase 400Vac) and there is no neutral. weather my controller will taken care ? (by making proper adjustments in the modulating signal ) ?

Qn3: If i am taking neutral? how it is being connected to the converter without changing the topology. ? Spitted DC link capacitor with neutral at the middle point. ?

Thanks and regards

Anoop kumar 

  • 0
    TI__Genius 15685 points

    Hi Anoop,

    Anoop kumar N said:
    Qn1: Incase if there is no neutral if an unblance happen; what will be the after effect ?

    For build 1~3 the neutral line needs to be connected due to DC voltage balance. Pls check below comments in the user guide.

    "In this build 4,  the board is operated as a three-wire system, that is, the neutral of the power supply is not connected to the DC midpoint of the output. To maintain the DC bus balance, a balance loop with a simple proportional gain is added in the control structure as shown in Figure 44. In this build a third harmonic injection is also carried out, which helps in stabilizing the DC bus balance point."

    Anoop kumar N said:
    Qn2: if the grid is unbalanced (say RY phase 420Vac, YB phase 400Vac) and there is no neutral. weather my controller will taken care ? (by making proper adjustments in the modulating signal ) ?

    The current ref design code does not have the algorithm to deal with the severe unbalance at the AC input. 

    Anoop kumar N said:
    Qn3: If i am taking neutral? how it is being connected to the converter without changing the topology. ? Spitted DC link capacitor with neutral at the middle point. ?

    Pls refer to the TIDM-1000 user guide which shows how to create the virtual neutral point and how to add the neutral line. 

    Regards,

    Chen