Optimal Control Of Centrifugal Water Pump Driven By A High Speed Wind Turbine

Abstract

Agriculture is the main livelihood of the majority of the population of Sri Lanka and as such ours is defined as an agro based or agricultural economy. In this respect contribution of the farmers of the north and the east is immense and continue to receive attention of legislators and planners. As a result the largest ever irrigation scheme Mahaweli became a reality. However even in spite of a development project of that magnitude people of the Dry Zone still continue to face hardships due to lack of adequate supply of water for cultivation during the South – West Monsoon (“Yala” Season). It is high time we focussed our attention on a viable system to supplement existing irrigation systems in the dry zone. In this backdrop a wind based Lift Irrigation system is suggested due to high wind potential in this season. It is essential to develop a system which requires low maintenance, is less labour intensive and highly productive. The study was focussed on developing a wind based electric water pumping system in order to replace the existing multi bladed wind water pump which has high failure rate. In the new system the water pump and the wind turbine are not required to be located at the same place and wind turbine can be installed in a good wind site. As a solution, high speed wind turbine driven electric centrifugal pumping system was developed. This system works using Maximum Power Point Tracking (MPPT) base optimal controller to harvest the maximum power from the available wind without using a battery backup. This system was a wind sensor less application method and wind estimator was developed to have wind estimation for the controller by using PMG output voltage (Ve) and PMG output power (Pe) at a given instance. DC motor driven centrifugal pump voltage was controlled to have maximum available power using a Buck Boost controller. PI controller was used to provide the duty ratio for PWM generator that uses for the Buck Boost controlling. Maximum power point base optimum voltage finder provides the MPPT commands to the system to drive in maximum power points relevant to each and every wind speeds. Centrifugal pump model for the variable speeds were developed in experimental base method and capacity of the pump is 1Hp with maximum flow rate of 2.3 l/s for the system. The NACA 4415 two bladed wind rotor was used with permanent magnet generator. It was modelled and simulated using MATLAB Simulink 7.9 and simulated the performance of wind turbine generator and electrical centrifugal pump by optimal controlling (Maximum Power Point Tracking). Dynamic simulation was done for 1s wind data for one hour and steady state analysis was done for analyze the maximum performance. Performance comparisons of the newly developed system as against multi bladed water pump system developed by NERD Centre, at Higurakgoda site, had been carried out and benefits were identified. It is established that the new system is capable of irrigating as much as twice the area than the existing one.