POWER TRANSMISSION USING LOW FREQUENCY AC AS AN ALTERNATE TO CONVENTIONAL TRANSMISSION

Conventional transmission systems utilize either high voltage ac (HVAC), operating at 50 or 60 Hz, or high voltage dc (HVDC) to transfer bulk power efficiently and reliably. The HVAC system is designed to operate at a high voltage level to reduce losses and increase bulk power transfer. This method

Project Title

POWER TRANSMISSION USING LOW FREQUENCY AC AS AN ALTERNATE TO CONVENTIONAL TRANSMISSION

Project Area of Specialization

Electrical/Electronic Engineering

Project Summary

Conventional transmission systems utilize either high voltage ac (HVAC), operating at 50 or 60 Hz, or high voltage dc (HVDC) to transfer bulk power efficiently and reliably. The HVAC system is designed to operate at a high voltage level to reduce losses and increase bulk power transfer. This method is limited, however, by the constraints of installed transmission overhead lines, such as voltage level and power transfer capability. In contrast, the HVDC system can handle a large amount of power on the transmission line by utilizing dc current instead of ac. The HVDC system has no limitation in transmission line length for power transfer; however, it requires a high initial cost for converter stations and specialized protection systems. This system is also a point-to-point connection, and is therefore not flexible for a multi-terminal connection. 

Another solution for bulk power transmission is that it inherits advantages from both HVAC and HVDC systems is to use a low frequency ac (LFAC) transmission system.The primary advantage of LFAC is that by operating the system at a frequency lower than 50 or 60 Hz, the transmission line reactance can be significantly reduced, thus extending power capacity. This allows the LFAC system to inherit advantages of both HVAC and HVDC systems, such as multi-terminal connections, distance protection using alternating-current based circuit breakers, and improving power transfer capability close to that of an HVDC system.

Project Objectives

The goal of the work is to evaluate the superiority of a low frequency system and utilize it for bulk power transmission instead of using the HVAC and HVDC systems. We aim to investigate the transmission distance and operating frequency range that an LFAC system can be used for specific applications. The first objective is thus to examine the steady-state performance of the LFAC system under various operating frequencies. Specifically, the impacts of skin effect on the transmission line parameters are investigated to see if any line model corrections are needed. Additionally, power transfer capability and the relationship between voltage to real and reactive power are also inspected to evaluate the benefits of the LFAC system.

Project Implementation Method

We want to verify the benefits of low frequency operation over the conventional 60 Hz by the voltage profile along the line. Our final target is testing a multi-frequency power system operation, which consists of a 60 Hz and a low frequency system, on our test-bed facility. The test-bed is a complete model of a real world power system with the transmission level scaled at 208 V, and distribution level with loads scaled at 41.6V. A power converter system is also developing to integrate a low frequency system into the test-bed for further study and testing.

Benefits of the Project

Conventional transmission systems utilize either high voltage ac (HVAC), operating at 50 or 60 Hz, or high voltage dc (HVDC) to transfer bulk power efficiently and reliably. The HVAC system is designed to operate at a high voltage level to reduce losses and increase bulk power transfer. This method is limited, however, by the constraints of installed transmission overhead lines, such as voltage level and power transfer capability. In contrast, the HVDC system can handle a large amount of power on the transmission line by utilizing dc current instead of ac. The HVDC system has no limitation in transmission line length for power transfer; however, it requires a high initial cost for converter stations and specialized protection systems. This system is also a point-to-point connection, and is therefore not flexible for a multi-terminal connection.

Technical Details of Final Deliverable

As part of our work, we also plan to model low frequency power systems, and a switching model that includes a power converter for frequency conversion.

Our work also aims to build a hardware test-bed for a low frequency transmission. This system is to demonstrate a low operating frequency power system and to verify theoretical studies. A long transmission line model and an inverter is to be installed on this small-scaled test-bed to examine the benefits of an LFAC system such as voltage profiles at no-load and full-load conditions.

Final Deliverable of the Project

Hardware System

Core Industry

Energy

Other Industries

Core Technology

Others

Other Technologies

Sustainable Development Goals

Affordable and Clean Energy, Decent Work and Economic Growth

Required Resources

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