Innovation recovers power lost due to solar panel variability

According to ST, the SPV1020 chip will allow multi-panel arrays, ranging from domestic rooftop-type equipment to larger installations, to deliver more energy at a lower cost per Watt. The chip has been designed to allow 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 aging. Without MPPT, the power from a solar panel can fall by 10 to 20% 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. ST says that the SPV1020 enables distributed MPPT (DMPPT), which compensates each panel individually, in contrast to a centralised MPPT scheme that applies a 'best-fit' compensation to all the panels in the array. The company believes DMPPT to be the most promising technique to improve the energy productivity of photovoltaic systems because it maximises 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 is said to reduce part counts. ST has integrated all of the required functions in a monolithic chip using its 0.18-micron BCD8 multipower process technology. BCD8 is designed to combine power and analogue functions for the dc/dc converter on the same chip as the digital logic performing the MPPT algorithm. According to ST, this technology enables a smaller, more reliable and longer-lasting solution than an alternative built with discrete components. "Maximising 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 industrialisation of renewable-energy technologies."