In microhydro plant, speed governer is not used because of its high cost. ELC is preferred. This ELC regulates speed, compensates reactive power and mitigates current harmonics.
It senses deviation in speed, then calculates power to be dumped(Pdump). Then, it senses load current and voltage from which p and q is calculated(pq theory). Then oscillating part of p (say p1) is found using digital filter. To compensates reactive power and mitigate current harmonics, p1 and q should be injected. To regulate speed, Pdump should be drawn. So, net power p1-Pdump is to be injected along with q. With this value, current to be injected is calculated. This reference current is fed to hysteresis band current controller which generates gate signal for inverter. Inverter injects the current.
Pdump drawn charges the capacitor C1 and C2. So, voltage across them increases. When sum of their voltage exceeds certain value (1025 V in this case), MOSFET switch S is turned on. So, capacitor is discharged to resistor. In this way, power is dumped in resistor.