Photovoltaic (PV) System Design, Control, and Optimization

Sponsor: National Science Foundation

PV systems have been widely deployed in electronic and electrical systems of various scales, such as embedded systems, hybrid electric vehicles, home appliances, satellites and power plants. Due to the intermittent nature of solar energy, power management techniques are imperative for maximizing the output power of a PV system.

Maximum Power Transfer Tracking for PV Systems

The PV panel exhibits a nonlinear output current-voltage (I-V) relationship, and under a given solar irradiance level there is an operating point (V, I) where the PV panel output power is maximized. We propose the maximum power transfer tracking technique, which considers the converter efficiency variation to maximize the output power of the whole PV system.Related work:

  • Y. Kim, N. Chang, Y. Wang, and M. Pedram, “Maximum power transfer tracking for a photovoltaic-supercapacitor energy system,” in Proc. ISLPED, 2010.

Reconfigurable PV Panel to Combat Partial Shading Effect

The solar irradiance levels on PV cells in a PV panel may be different from each other, and this is what we call partial shading effect. Partial shading effect significantly degrades the output power of a PV panel. For example, if one fourth of the PV panel is completely shaded, the PV panel will suffer from power loss of nearly 50%. To improve the output power of a PV panel under partial shading, we propose a reconfigurable PV panel structure and a dynamic programming algorithm to reconfigure the PV panel dynamically under partial shading. Simulation results demonstrate that our method can improve the PV system output power by up to 2.31X. We have also built reconfigurable PV prototypes and demonstrated the effectiveness of PV panel reconfiguration technique.Related work:

  • X. Lin, Y. Wang, S. Yue, D. Shin, N. Chang, and M. Pedram, “Near-optimal, dynamic module reconfiguration in a photovoltaic system to combat partial shading effects,” in Proc. DAC, 2012.
  • Y. Wang, X. Lin, Y. Kim, N. Chang, and M. Pedram, “Architecture and control algorithms for combating partial shading in photovoltaic systems,” IEEE TCAD, vol. 33, no. 6, 2014, pp. 917-930.

Online Fault Detection and Tolerance for PV Systems

A PV system may suffer from PV cell faults, which are caused by contact failure, corrosion of wire, hail impact, moisture, etc. When some of the PV cells in a PV panel become defective, it can lead to lower output power and shorter lifespan for the PV system. Unfortunately, manual fault detection and elimination are expensive and almost impossible for remote PV systems (e.g., PV systems in orbital or deep space mission). We present design principles and runtime control algorithms for a fault-tolerant PV panel, which can detect and bypass PV cell faults in situ without manual interventions.Related work:

  • X. Lin, Y. Wang, D. Zhu, N. Chang, and M. Pedram, “Online fault detection and tolerance for photovoltaic energy harvesting systems,” in Proc. ICCAD, 2012.
  • X. Lin, Y. Wang, M. Pedram, J. Kim, and N. Chang, “Designing fault-tolerant photovoltaic systems,” IEEE Design & Test, vol. 31, no. 3, 2014, pp. 76-84.

PV System on HEV/EV

On top of regenerative braking-based battery charging scheme, a PV system mounted on the HEV/EV can collect energy to charge vehicle batteries whenever there is solar irradiance. To fully make use of the vehicle surface areas, PV cells will be mounted on the hood, rooftop, door panels, etc. However, due to the uneven distributions of the solar irradiance and temperature on different vehicle surface areas, the actual output power of the vehicle PV system may be depressed. We propose a dynamic PV panel reconfiguration algorithm, which updates the PV panel configuration according to the change of irradiance and temperature distributions on the PV panel to enhance the output power. Furthermore, we investigate the customization of the PV panel installation on HEV/EV and implement a high-speed, high-voltage PV reconfiguration switch network with IGBT and a controller. We derive the optimal reconfiguration period based on the driving profiles, taking into account the on/off delay of IGBT, computation overhead, and energy overhead.Related work:

  • Y. Wang, X. Lin, N. Chang, and M. Pedram, “Dynamic reconfiguration of photovoltaic energy harvesting system in hybrid electric vehicles,” in Proc. ISLPED, 2012.
  • J. Kim, Y. Wang, M. Pedram and N. Chang, “Fast photovoltaic array reconfiguration for partial solar powered vehicles,” in Proc. ISLPED, 2014. (Best Paper Award)