Multi-Port DC-DC and DC-AC Converters for Large-Scale Integration of Renewable Power Generation

Abstract

Numerous research studies on high capacity DC-DC converters have been put forward in recent years, targeting multi-terminal medium-voltage direct current (MVDC) and high-voltage direct current (HVDC) systems, in which renewable power plants can be integrated at both medium-voltage (MV) and high-voltage (HV) DC and AC terminals; hence, leading to complex hybrid AC-DC systems. Multi-port converters (MPCs) offer the means to promote and accelerate renewable energy and smart grids applications due to their increased control flexibilities. In this paper, a family of MPCs is proposed in order to act as a hybrid hub at critical nodes of complex multi-terminal MVDC and HVDC grids. The proposed MPCs provide several controllable DC voltages from constant or variable DC or AC voltage sources. The theoretical analysis and operation scenarios of the proposed MPC are discussed and validated with the aid of MATLAB-SIMULINK simulations, and further corroborated using experimental results from scale down prototype. Theoretical analysis and discussions, quantitative simulations, and experimental results show that the MPCs offer high degree of control flexibilities during normal operation, including the capacity to reroute active or DC power flow between any arbitrary AC and DC terminals, and through a particular sub-converter with sufficient precision. Critical discussions of the experimental results conclude that the DC fault responses of the MPCs vary with the topology of the converter adopted in the sub-converters. It has been established that a DC fault at high-voltage DC terminal exposes sub-converters 1 and 2 to extremely high currents; therefore, converters with DC fault current control capability are required to decouple the healthy sub-converters from the faulted one and their respective fault dynamics. On the other hand, a DC fault at the low-voltage DC terminal exposes the healthy upper sub-converter to excessive voltage stresses; therefore, sub-converters with bipolar cells, which possess the capacity for controlled operation with variable and reduced DC voltage over wide range are required. In both fault causes, continued operation without interruption to power flow during DC fault is not possible due to excessive over-current or over-voltage during fault period; however, it is possible to minimize the interruption. The above findings and contributions of this work have been further elaborated in the conclusions.

Parameter extraction and selection for a scalable N-type SiC MOSFETs model and characteristic verification along with conventional dc-dc buck converter integration

“…In the above (5), the Coulomb charge can be explained in terms of inversion charge (Q inv ) defined by (7) and located at any point y in a cartesian coordinate system and perpendicular to the surface. Assuming the fixed charge distribution, the μ C is related by the following equation…”

“…These days, DC-DC power applications are widely explored in both low and high power applications [2][3][4]. These DC-DC converters are integrated with renewable energy sources (RESs), microgrids (MGs), high frequency (HF), high voltage direct current (HVDC) and electric vehicle (EV) like similar applications [5][6][7][8]. The driving element of these applications is mostly a MOSFETs.…”

A novel multiport converter switching scheme to integrate multiple renewable energy sources

“…MPCs have been taking much attention since last decade due to their capability in integrating multiple sources/loads in a cost‐efficient way 7 . Depending on the type of integrated sources/loads, MPCs can be divided into three categories: (a) DC MPCs, 8–10 (b) AC MPCs, 11–13 and (c) hybrid MPCs 14–17 . As shown in Figure 2A, the DC‐based RESs suffering from the intermittency are the main application for DC MPCs, where these sources are integrated with energy storage systems to create a smooth and programmable power generation at output.…”

“…7 Depending on the type of integrated sources/loads, MPCs can be divided into three categories: (a) DC MPCs, [8][9][10] (b) AC MPCs, [11][12][13] and (c) hybrid MPCs. [14][15][16][17] As shown in Figure 2A, the DC-based RESs suffering from the intermittency are the main application for DC MPCs, where these sources are integrated with energy storage systems to create a smooth and programmable power generation at output. In DC MPCs, the DC-based RESs are directly connected to DC ports, although AC-based sources have to be connected using an individual rectifier.…”

Power Flow Management by Active Nodes: A Case Study in Real Operating Conditions

“…The inclusion of DC sub-networks is becoming attractive in recent years due to the possibility to integrate, at a different power level, RES and energy storage, enabling a meshed hybrid AC/DC distribution grid [15]. The DC sub-networks can be operated in LV [16], MV [17,18] or both [19,20] and can be connected to the AC network via multi-port power electronics converters [21,22]. A hybrid configuration can further improve the flexibility of the entire system in terms of active and reactive power flow controllability [20].…”