PV inverter -- innovations and market trends

France's Yole Développement, recently organized a seminar on PV inverter - technical innovations and market trends. The speakers were Brice Legouic, Power Electronics Market & Technology Analyst, Yole and Paul Kleistead, Cree.

What are the trends for 2011-12? According to Legouic, one, a first step of standardization should take place at the added functionalities level. This includes MPP positioning with advanced solutions, monitoring, and anti-theft and protection. Two, players with a higher level of product quality will enter the EU market. These include Japanese players focusing on efficiency and reliability, but with more expensive inverters.

Yole also anticipates a double speed business to take place. If the residential segment is opened to Chinese manufacturers and industrial/solar farms are dedicated to high-end products, the PV inverter market would become two different markets.

Speaking about market trends, he said that trends will be driven by reduction of feed-in tariff, which hurries the end users to sign contracts. Over 2 million are likely to be sold in 2012. The total market in 2010 was slightly below €3.3 billion, and will overpass €3.5 billion by 2012.

Over 75 percent of the market is owned by the top 10 PV inverter players. Five of these are German, eight are European, and two are American. Eighty percent of EU inverters are made in Europe and 20 percent are made in the USA. Asian players will likely increase their supply for the EU market. Japanese players currently have very small implantation in the EU. However, Yole believes that their market share would reach 15 percent within the next three years.

On technological trends, Legouic touched upon the neutral-point-clamped (NPC) architecture. The NPC architecture uses diode to clamp the DC bus voltage in two equal voltages. The benefits are:
* allowing the use of lower 600V devices instead of 1200V,
* reducing dynamic losses, and
* SJ MOS can be used for outer switches for their higher frequency performances.

The NPC architecture is nearly always used for 10-50kW inverters.

Using the SiC free-wheeling diode can increase efficiency from up to 2 percent. More and more are used for low- to medium-power range. Benefits include much better recovery time and reduction in IGBT switching losses.

On the DC/DC stage component chart, he added that according to STMicroelectronics, we can assume that when the maximum input voltage of an inverter is below 650V, the DC/DC stage is MOSFET-based. Over 650V, the inverter can be considered to be built with a 1200V IGBT.

As for implementation of new technologies, such as SiC vs. GaN, 900-1200V will be the targeted range for over 10kW inverters. SiC diodes are already implemented in residential and commercial inverters.

In 2012, silicon will represent more than 90 percent of the modules market, and about 75 percent of the wafer market. SiC will be mostly driven by diodes. Components will be at an early stage of adoption.

Brice Legouic concluded that micro-inverters are also a place for technical innovation. Enphase is a global leader with about 30 percent market share in the US residential segment. The conversion architecture is totally different from standard inverters. The SiC diodes are implemented and represent a huge market for device makers as micro-inverter quantities are important.

Other expected products have shown significant improvements in the integration of the same silicon chip of several functions, such as command and driver IC, power conversion and RF components for communications in a PV plant.