Tech focus: A novel circuit topology for the largest central inverter system
A maximum uptime is especially important for large commercial and utility-scale solar plants. Herein the inverter system plays a key role, being responsible for the maximum energy harvest. In order to meet the requirements of large solar parks even better, Dr. Marco Trova from Power-One and his team developed a new circuit topology and cooling concept for the company's AURORA ULTRA central inverter system, which is one of the largest systems available on the market. For PES, he explains the new technologies and how plant operators can benefit from them.
The poor ratio between the DC input and AC output voltage is one of the biggest disadvantages most utility-scale inverter systems entail. PV plants are usually based on a maximum DC input voltage of 1000V. In the past, it was not possible to achieve an AC line voltage above 320 to 360Vac while using a direct transformer-less inversion. This was the starting point for Power-One to develop a novel circuit topology designed to specifically address the demanding needs of utility-scale applications. Since autumn 2011, the first products using the company's proprietary inverter concept have been commercially available: Power-One's new AURORA ULTRA central inverters with an output power of up to 1.5MW.
The aim of the patented technology was to remove the existing limitations of direct conversion architectures, thus allowing a voltage conversion at 690Vac - which is the industrial standard. At the same time, Power-One wanted to maintain or further improve the conversion efficiency over the widest possible input range. In addition, the new inverter system should ensure an easy maintenance, standardize spare parts and offer a compact outdoor construction to meet the requirements of large solar parks even better.