WHAT IS ELC?
Electronic Load Controller (ELC) is a controller used in small hydro power generation to control the frequency of generator by diverting excess power to dummy/ballast load, thus the speed, frequency and voltage of generator will be controlled at certain set point. Power diversion to dummy load is done electronically through thyristor as electronic switch which controlled by ELC main board.
Unlike flow controller which regulate the flow entering turbine, load controller (ELC) is regulating the electric load to make sure that GENERATED POWER IS THE SAME WITH CONSUMED POWER BY MAIN LOAD+BALLAST LOAD. for micro hydro power scheme <200 kW, especially for rural electrification, flow control is rather too expensive and too complicated since its uses tricky hydraulic system with PLC, besides the price are very expensive. Electronic load controller offer the solution to solve the limitation of flow controller and offering state of the art controller as appropriate technology. Thanks to microcontroller technology to allow high accuracy and simpler electronic circuit with broader capability.
ELC Protel Multi Energy use microcontroller chip and thus based on digital technology where all the controller parameter is set from the software. It is ensure the high performance, accuracy and steady operation of the controller. No need of trimmer or potentiometer setting to adjust the control parameter during commissioning of the plant like analog based ELC.
ELC works based on frequency signal, microcontroller will continuously measure and calculate the generated AC signal every half cycle (10 ms) 00 times per second and will trigger the Thyristor at certain angle according to measured error. It will continuously adjust the triggering angle until set point is reached (50 Hz). Frequency will be keep at set point (50/60 Hz) with accuracy 0.1-0.2 Hz. Recovery time required takes ±2 seconds, which means in case of load change/disturbance the frequency will be back to set point at around 2 seconds. Controller response can be adjusted through provided dip switch on main board, it is possible to make slow, medium and fast response controller according to plant and load characteristics, but in most cases default setting are appropriate for most plant set up.
Ballast load or dummy load are basically resistive load (resistance) used to dump the excess power. We use tubular air heater resitance, industrial standard type to ensure long life expectancy and maintenance free. Water heated resistance can be used as well on special request. Since the voltage and current applied on the ballast load are not pure sine wave, the normal electrical appliances are not recommended to be used as dummy load. The capacity of dummy load should have at least 120% of rated turbine capacity to ensure the safe and smooth operation of the plant.
1. ELC Type : Digital system with microcontroller
2. Control method : Phase angle control with PI algorithm, two steps.
3. Switching method : Double Thyristor (SCR), 3 or 6 units
4. Power : 1 – 500 kW
5. Voltage : 220/380 V, 230/400 Volt
6. Phase : 1 and 3 Phase
7. Frequency : 50 / 60 Hz
8. Freq. accuracy : <0.2 Hz
9. Freq. sensing : every 10 ms or 100 times/s at 50 Hz
10. Recovery time : ±3 seconds
11. Standard protection
12. Standard metering (analog)
13. Ballast load : Tubular air heater
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