Power quality issues related to power flow control in systems with renewable energy micro sources

The paper is focused on power flow control in energy systems with grid-on renewable energy sources employing time-proportional controlled and phase angle controlled resistive loads (like boilers) to balance energy produced by the sources. The system operational properties are described and major mechanisms affecting power and voltage quality are identified. Contributions of the pulse-width regulated loads to voltage flicker, system harmonics and to high frequency conducted disturbances in audio range (2-250 kHz) are studied on a test system realized in a small laboratory measure. Finally, on the basis of experimental results, limiting power of regulated resistive loads from point of view of flicker and harmonic current emissions is estimated.