When Lighter Loads Cause Turbine Efficiency to Tumble
Mitsubishi Power, Ltd.
Industry: Electric Power Generation

When Lighter Loads Cause Turbine Efficiency to Tumble

A Fully-Automated Solution to Control Inlet Guide Vane (IGV) and Eliminate Overshoot Worries

BACKGROUND

Due to significant market penetration by renewable energy resources, a utility company has been forced to turn down the load on their gas turbines which compromised the fuel economy of the power plant because of lower thermal efficiency. They decided to address this issue to improve their finances.

THE PROBLEM
Manual adjustment is not the solution

An internal review found that IGV safe operation guidelines had margin for improvement which would increase the exhaust gas temperature and hence, the overall thermal efficiency.

One of the engineers who conducted the review recalls: “I realized that it would be difficult to adjust the IGV properly on our own—even careful tweaking did not result in any improvement in efficiency. In the interest of safety and reliability, the maximum exhaust temperature of a gas turbine is limited, to ensure several parameters do not exceed the design specifications. When a turbine changes load or receives sudden frequency response, these parameters become unstable, making it difficult to perform IGV adjustment without jeopardizing the safety of the turbines”

The plant management thought about asking the OEM but they have been worried about the possible costs attached to new equipment and controls. There were also questions about the future fuel cost savings which were hard to anticipate due to uncertain nature of the markets.

While the team explored potential solutions, none of the options they reviewed was a “game changer” and they were desperate to come up with a solid solution.

THE PROBLEM
While engineers at the power plant wanted to adjust the IGV to improve the combined cycle thermal efficiency, this was difficult to achieve because the adjustment might affect not only the performance but also reliability and operational flexibility of the plant.
In the past, the engineer heard from gas turbine OEM’s engineer that adjustment without careful consideration causes some control parameters to approach operation limits and worsen the frequency response forcing gas turbine users to perform urgent adjustments. As a result, the engineers realized that this should be achieved with support from gas turbine specialists.

Mitsubishi Power, as one of the core subsidiaries of Mitsubishi Heavy Industries group, offers generation technologies and solutions.

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