Jan Doutreloigne

Reconfigurable Topologies for Smarter PV Modules: Simulation, Evaluation and Implementation

In a reconfigurable PV panel, the connections between groups of cells (cell-strings) can be rearranged in order to increase the overall power output under non-uniform conditions. In a traditional PV panel, current mismatch between the series-connected cells (due to irradiation differences of differential aging) limits the generated power output by either reducing the overall current or by bypassing the substring containing the limiting cells. A reconfigurable panel can respond to such a situation by changing the connections to a more favorable configuration, allowing the majority of the cells to operate at their MPP. This paper elaborates on such a topology and its components (high current switches, wiring). To get a clearer picture of the added value of such a reconfigurable panel, a detailed energy yield analysis was performed which includes the performance of those added components. The simulation model used for this analysis is calibrated with extensive measurement results. A comparison of that model and corresponding measurements will be discussed. The analysis shows that a reconfigurable PV panel can outperform the traditional panels when suboptimal conditions are predominant, as encountered for instance in BIPV. As a demonstration of the principle, a small-scale prototype was created and will be presented in this paper.

A double-pole single-throw latching MEMS switch for reconfigurable distribution frames

A double-pole single-throw latching MEMS switch is presented, which could be used as reconfiguration switches in telecommunication networks. The switch can latch into a closed state so that no energy is needed to stay in that state. The latching mechanism was operated using thermal actuators which use a polysilicon heater underneath the structural layer. Using the MetalMUMPs technology, the switch was successfully fabricated and was able to latch into the closed state. Cycling tests of 105 latching cycles showed that the switch resistance remains below 3Ω.

Integrated switch for substring reconfiguration to optimize module power under partial shading

The output power of a PV module can drop significantly if there is a current mismatch between the series-connected individual cells. This current mismatch can arise due to differences in temperatures of the cells or simply because of partial shading of the PV panel. The most common solution to this problem is by bypassing those limiting cells (in practice, the entire substring containing them is bypassed) and in doing so, ensuring a higher output power. The problem with this approach is that there might still be a lot of power available in those bypassed cells, both in those who are actually shaded (when it is not a 100% shade) and in those still fully illuminated, but merely belonging to that bypassed substring. A reconfigurable module topology might be more efficient. In such a topology the connections between the substrings can be rearranged during operation in order to maximize the module power output. For this topology to be effective, a network of very low-ohmic (not exceeding a few m) switches are needed, capable of communication from anywhere in the panel. This paper describes the design of such a reconfiguration switch.