STMicroelectronics Innovation Recovers Power Lost Due To Solar-Panel Variability

ST’s new SPV1020 chip allows Maximum Power-Point Tracking (MPPT) to be applied individually for each panel. MPPT automatically adjusts a solar generator’s output circuitry to compensate for power fluctuations resulting from varying solar intensity, shadowing, temperature change, panel mismatch, or ageing. Without MPPT, the power from a solar panel can fall by 10 to 20 percent if even a small percentage of its surface is in shadow. This disproportionate decrease may restrict the choice of site or force the use of a smaller array to avoid shadows. In some cases, it can challenge the viability of the project.



The SPV1020 enables Distributed MPPT (DMPPT), which compensates each panel individually, in contrast to a centralized MPPT scheme that applies a ‘best-fit’ compensation to all the panels in the array. DMPPT is the most promising technique to improve the energy productivity of photovoltaic systems because it maximizes the power extracted from each panel regardless of adjacent module performance, even if a module has failed.



Implementing DMPPT usually requires a network of discrete components for each panel in an array. The SPV1020 replaces this network with a single chip and also integrates the DC/DC converter to step-up the panel’s low-voltage DC output to a larger DC voltage from which line-quality AC power is produced. By integrating MPPT and the DC/DC converter, the SPV1020 dramatically simplifies design and reduces part count, making DMPPT economical for solar generators across a range of power ratings and price points.



ST has integrated all of the required functions in a monolithic chip using its advanced 0.18-micron BCD8 multi-power process technology. BCD8 holds the key to combining power and analog functions for the DC/DC converter on the same chip as the digital logic performing the MPPT algorithm. This technology enables a smaller, more reliable and longer-lasting solution than an alternative built with discrete components. The IC also has an advanced DC/DC converter architecture that minimizes the size and number of external passive components needed.



“Maximizing efficiency and reliability are key elements to deliver cost-competitive power from renewable sources,” said Pietro Menniti, General Manager of ST’s Industrial and Power Conversion Division. “The development of innovative products such as the SPV1020, which implements MPPT and power conversion circuitry in a single chip, will maintain ST’s position at the forefront of the industrialization of renewable-energy technologies.”



Major features of SPV1020:



* Integrated DC/DC converter bypass and cut-off diodes

* Fully compatible with widely used DC/AC inverters

* Enables independent output-voltage adjustment per panel

* Narrow output voltage range improves inverter performance

* Reduces over-voltage during DC-bus disconnection



The SPV1020 is available in a 36-pin PowerSSO (PSSO-36) package. Engineering samples and evaluation kits are already available. Volume production is scheduled for November 2010. The projected price is around $5.00 for a minimum order of 1000 units. Alternative pricing options are available for larger quantities.