Solar Inverter Step-Up (ISU) Transformers
With the advent of renewable energy, the number of wind and solar farms has been on the rise, and economical benefits were originally found in the use of pad mount transformers to step up the voltage as produced by the solar inverters. The uniqueness of solar inverter step-up (ISU) transformers does not permit for standard off-the-shelf distribution transformers to be used in this application. This article looks at factors we have adopted to meet the requirements of this application and to improve robustness of solar ISU transformers.
Solar ISUs are gaining popularity in the field of green energy, and where economic benefits can be derived in the use of distribution pad mount transformers. There are also sufficient differences that would call for some level of customization. Some of these differences are based on the nature of solar farms and the inverter technology, and others would be based on how they are operated or their failure modes. These include:
- Location of solar farms – As a harvester of solar energy, solar farms are usually located in open areas sometimes with a maximum ambient temperature higher than 40°C, and maximum average daily temperatures over 30°C as per ANSI/IEEE standards.
This location is usually remote and the need for transmission at high voltages to grid connection points is also a requirement. To minimize the number of step-up operations, the voltage ratio on the solar ISU transformer is usually high and adds to design complexity.
- Inverter technology – The inverter is the only source of power for the ISU transformer, with sizing of the transformer based on the sizing of the inverter. Due to limitations in inverter technology, as well as increasing the inverter sizes and ratings, (though newer Inverter technologies now make it possible to design and manufacture higher rated Inverters) dual low-voltage windings are being provided on ISU transformers for the optimization of resources and maximizing efficiency. The coupling between low-voltage windings, and the coupling between each of the low-voltage windings and the high-voltage winding needs to be considered.
To ensure the reliability of our designed and manufactured solar ISU transformers, we employ certain considerations for solar ISU transformers applications, including but not limited to: