A sewage treatment plant in city A, the 10kV/0.4kV LV power distribution room, the capacity of the transformer is 800kVA. There are variable-frequency submersible axial flow pump, variable-frequency supernatant reflux pump, deodorization centrifugal fan (with soft starter), mixer and crane as the main loads. The transformer capacity is fluctuate between 15% to 80% frequently, the harmonic is concentrate at the 5th order and 7th order.

The former reactive power compensation installation is use capacitor+thyristor+reactive power controller, the compensation capacity is 300kvar, but under this compensation solution the devices are not running very well. When the reactive power compensation capacity change frequently, the former reactive power compensation installation could not provide the request reactive power by the loads. The consequence is the penalty of the electricity sector by the lower monthly average power factor. Meanwhile the bulged of the capacitor caused by the harmonic will make the capacitor lose its functioning. Considering the above circumstance, the user remove the capacitor compensation installation and replace to the rank mounted SVG modules and the MCCB and the relevant components.

The power factor was increased from 0.84 to 0.95 since the SVG has been implemented. The electricity rate change from penalty to award, the total electricity bill has decreased dramatically. The THDu decrease from 2.8% to 1.4%, the THDi decreased from 9.5% to 3.9%, the SVG reactive power solution is effectively suppress the harmonic current.