A three-port power flow controller for HVDC grids

Abstract

This work proposes a three-port converter structure for high-voltage dc (HVDC) applications to facilitate power flow routing between a controlled dc bus and two independent dc networks. Control of line power flows is achieved via the series injection of incremental dc voltages between the networks, thus the converter structure is only rated for a fraction of the rated power and voltage of the connecting dc networks. Unlike previously proposed dc power flow devices, a significant advantage of the presented structure is that the incremental dc voltages are generated without requiring power exchange with an external ac network. As a result, the proposed converter structure offers a highly cost-effective means of routing and controlling dc power flows within emerging HVDC grids.

Investigate on a Simplified Multi-Port Interline DC Power Flow Controller and Its Control Strategy

“…This kind of control scheme is simple to implement, but it can only adjust the equivalent resistance of the line in one direction, which limits its power flow control ability. (2) For the DC voltage control type DCPFC, according to the voltage regulation means, it can be further divided into three main types, which are 1 a DC transformer type [6][7][8][9][10], 2 an auxiliary voltage source type [11][12][13][14][15]] and 3 a capacitor-based interline energy-exchanged type [3,[16][17][18][19][20][21][22][23][24]. In comparison, the DCPFC of capacitor-based interline energy-exchanged type has more advantages and better application prospects.…”

“…Based on the concept depicted in Figure 1b, by increasing the DC capacitor number and introducing coupled inductors, a novel type of IDCPFCs with independent connections of the capacitor in two lines were respectively investigated in references [3,[21][22][23]. In reference [24], the application modular multilevel converter (MMC) device was also considered, and an MMC-based IDCPFC was proposed. These schemes in reference [3,[21][22][23][24] avoided the capacitor switching in the line.…”

“…In reference [24], the application modular multilevel converter (MMC) device was also considered, and an MMC-based IDCPFC was proposed. These schemes in reference [3,[21][22][23][24] avoided the capacitor switching in the line. However, it should be noted that all the above existing topologies are characterized by two-port characteristics, which can only assist in regulating the current on one line.…”

“…If the power flow control of multiple lines is required at the same time, the corresponding multi-port topology should be developed, and this problem is also an area that this paper deals with. in references [16][17][18][19][20]; (b) The dual-capacitor control type in references [3,[21][22][23][24].…”

“…In addition, with the controlled line Currently, the research on multi-port IDCPFC (MI-DCPFC) is still in its infancy. Based on the MMC-based IDCPFC proposed in reference [24], a MI-DCPFC topology based on MMC was developed in reference [25]. However, it requires multi-winding transformers and needs to connect MMC in each control line, which leads to higher system costs.…”