Efficient Grounding for Modular Multilevel HVDC Converters
(MMC) on the AC Side
Abstract:
In wished-for means a zigzag transformer has been proposed to erect an artificial
neutral point and keep voltage balance between the positive pole and the negative pole. An
efficient grounding system consists of the zigzag transformer and the impartial grounding
resistor. In this dissertation the different impedances, including positive-, negative-, zerosequence impedance, and dc current impedance, boast been analyzed, in the same way. Then, the
computer simulations have been performed to evaluate the characteristic of the zigzag
transformer under normal voltage, zero-sequence voltage and un- balanced dc voltage,
respectively. The simulation results show that1) the zigzag transformer can in fact balance the
unbalanced voltage in dc side of the MMC below different work conditions; 2) the zero-sequence
impedance is low and zero-sequence current is convenient for the detection of a single-phase
fault; 3) the power consumption of the neutral grounding resistor is of a light rating, and the
cooling of the resistor is unnecessary.
Existing method:
In vacant method an unbalance voltage between a positive pole and negative pole will
exist for a long time in an ungrounded modular multilevel converter (MMC) HVDC transmission
system.
Proposed method:
The anticipated MMC HVDC method safe operation, a zero potential point must be
provided for the control and protect systems. The foundation device can be installed either on the
dc side or ac side. On the dc side, it can use the high-resistance grounding device; however, it
has several disadvantages, such as high power loss, low reliability, and high cost. The grounding
device installed on the ac side may be a favored pick.
Further Details Contact: A Vinay 9030333433, 08772261612
Email: takeoffstudentprojects@gmail.com | www.takeoffprojects.com
Block diagram:
Schematic diagram of the MMC-HVDC system with grounding
This project developed in Matlab/simlink soft ware and the results have been studied.
Advantages:
1) the grounding technique of the zigzag transformer has many advantages, such as low
installation area, low loss, low reactive power burning up, low impedance for dc current and
zero-sequence current, enduring high voltage, and low cost of research and development.
2) A zigzag transformer has been future to construct an artificial neutral point and keep voltage
balance between the positive dowel and the negative dowel.
Applications:
The Modular Multilevel HVDC Converters are applicable in HVDC transmission
systems and power generating systems etc.
Further Details Contact: A Vinay 9030333433, 08772261612
Email: takeoffstudentprojects@gmail.com | www.takeoffprojects.com