PV Modules Interfacing Isolated Triple Active Bridge for Nanogrid Applications

Abstract

DC nanogrid architectures with Photovoltaic (PV) modules are expected to grow significantly in the next decades. Therefore, the integration of multi-port power converters and high-frequency isolation links are of increasing interest. The Triple Active Bridge (TAB) topology shows interesting advantages in terms of isolation, Zero Voltage Switching (ZVS) over wide load and input voltage ranges and high frequency operation capability. Thus, controlling PV modules is not an easy task due to the complexity and control stability of the system. In fact, the TAB power transfer function has many degrees of freedom, and the relationship between any of two ports is always dependent on the third one. In this paper we analyze the interfacing of photovoltaic arrays to the TAB with different solar conditions. A simple but effective control solution is proposed, which can be implemented through general purpose microcontrollers. The TAB is applied to an islanded DC nanogrid, which can be useful and readily implemented in locations where the utility grid is not available or reliable, and applications where isolation is required as for example More Electric Aircraft (MEA). Different conditions have been simulated and the control loops are proved for a reliable bus voltage control on the load side and a good maximum power point tracking (MPPT).

Triple active bridge converter in nanogrid applications: A direct interface for photovoltaic modules and storage

“…For the DC bus voltage control, a proportional‐integral block has been used and its constants have been defined through MATLAB SISOtool and analytical analyses as shown in [38]. The DC bus voltage control loop aims to have a good rejection of step disturbance, considering that the voltage must be kept constant on the DC bus with a low ripple even in the case of high load changes.…”

“…This feed‐forward acts on the phase shifts as a power flow decoupling system. The regulator parameters for this control are defined considering the derivative of the power extracted from the PV modules side with both phase shifts as shown in [38]. The added feed‐forward control is highly related to the presence of the solar PV modules.…”

“…Anyway, usually the control strategies applied to the TAB converter are related to the DC devices attached to the three ports. When considering a direct interface of PV arrays, the TAB should be able to achieve both good Maximum Power Point Tracking (MPPT) and bus voltage regulation [38]. The most important power transfer limitation of the TAB is the intrinsic trade‐off between port voltages and switching frequency.…”

A Survey on Multi-Active Bridge DC-DC Converters: Power Flow Decoupling Techniques, Applications, and Challenges

“…The work in [173] proposed a TAB converter for the integration of hydrogen-based fuel cells with a traction power system, where singleloop PI controllers are implemented to maintain the currents at each port. The research presented in [68], proposes a TAB converter for the integration of PV modules with the battery storage system in a nanogrid. A linear simple PI controller is implemented to regulate the DC bus voltage and a maximum power point tracking algorithm is developed for power sharing between three ports, then a current control loop is assigned to the load side port.…”

“…The features and capability of the MAB converter have made it a suitable candidate for a wide range of applications and it has gained the interest of many researchers. MAB converters with different numbers of ports and their combination with other converters have been proposed for the following applications: hybrid energy storage (HESS) [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]; more electric aircraft (MEA) [19][20][21][22][23][24][25]; monopolar and bipolar DC grids [26][27][28][29][30][31][32][33][34]; Solid state transformer (SST) and modular transformer in microgrids, locomotive traction, EV charging, shipboards ; doubly fed induction generators (DFIG) in wind turbines [58]; unified power quality conditioner (UPQC) [59][60][61][62]; electric vehicle (EV) charging [63][64][65][66][67]; renewable energy systems (RES) such as PV modules integration with energy storage systems (ESS), microgrids or EV charging stations [68][69]…”