Today we see many solar plants connected to the power grid, and there will be more and more in near future. All experienced power system engineers, and operators see that it is a must for these solar plants to have sophisticated control system to achieve coordination and integrity between them and other traditional power plants exist in the grid. This smart control system can be done only through solar inverters which represent the brain of the solar power plant.
Why We are needing sophisticated control system?
When connecting solar power plants to the electrical grid, there will be two main technical issues arise, and can be solved via the solar inverter as following;
Power Flow:
The normal power grid is designed, so that the electrical power flow will be in the direction from generation to transmission then to distribution feeders, so the protection system is designed to protect the grid that way. But with the solar plants added to the grid, the power flow will be reversed, it can flow from distribution to transmission or from distribution to other distribution networks, and this will conflict with the grid protection coordination scheme. Only the solar inverter can prevent this from occurring by limiting generated power.
Terminal Voltage:
In order for the solar plants to inject its power to the grid, it should generate output terminal voltage which is a bit little more than the grid nominal voltage, and as a result of many numbers of solar plants will be connected to the grid, voltage level will increase.
In order to prevent voltage, increase from damaging any components/loads in the grid, the inverter can change generated reactive power to regulate the grid voltage level. So generally, the solar inverter can regulate and stabilize the grid voltage via controlling the generated reactive power.
Will the solar inverter actually be capable of solving grid issues? And what are Utilities concerns?
The answer is yes, the inverter industry has been developed in both soft ware and hardware, the solar inverters become having many modern features to solve such issues like power factor control and many others, but honestly there still some some issues that concern utilities like the following:
1. As we discussed above, the solar inverter may need to increase generated reactive power and limit active power generation, but this feature is still Not existing in some of solar inverters at the market.
2. In order for the solar inverter to integrate with the power grid, its operating profile may be changed, as it may work for more hours per day at its full capacity and this of sure will make it hotter and reduce its life span.
Solar Inverter standards:
Still Not all requirements from the solar inverter are defined in the standards, so we are of sure in a bad need of unified standards for all solar inverter taking into consideration grid problems, this will solve the issues efficiently, the solar inverter price will be reduced and all operators will be able to use same interface for the sophisticated control system referred above.
