Dynamic digital control schemes for three-phase UPS inverters

[摘要] ENGLISH ABSTRACT:This thesis presents the design and implementation of a voltage controller for anUninterruptible Power Supply (UPS) Inverter. The inverter is capable of producing anearly sinusoidal output voltage waveform, thereby keeping the Total HarmonicDistortion (THD) to a minimum.Digital controllers introduce a time delay in the control law that causes systeminstability. Various control techniques, which includes Pade approximations andsystem augmentation, are investigated to eliminate the effect of the time delay. Thesecontrollers employ classical control as well as modem control techniques. Theselection of the various control parameters is verified by mathematical equations. Aload-disturbance compensation scheme, implementing feed-forward and gainscheduling, is also developed to improve voltage distortion when varying loads, suchas non-linear loads, are connected to the system. It is shown that the constructedpulse-width modulated (PWM) control scheme can achieve fast dynamic response aswell as a low THD.

[发布机构] Stellenbosch University