Rockwell Automation 2364F Regenerative DC Bus Supply Unit (RGU) - Manual (Page 36)

Publication 2364F-5.01– October 2003
1-20 Overview
How Does the RGU Control the DC
Bus Voltage? The voltage source converter block, shown in Figure 1.28, regulates
the DC bus voltage to a set value. This arrangement provides near
unity power factor, allows regeneration, and yields a low line current
distortion.
To maintain constant DC bus voltage, regardless of line voltage
fluctuation, the DC bus voltage regulator changes Iq (the active
current reference), causing an increase, decrease, or reversal in the
power flow from the line to the DC bus.
Iq regulates the amplitude of line current components in phase with
the line to neutral voltage (see Figures 1.13 and 1.15 for unity power
factor). Id (the reactive current reference) regulates reactive
component having a 90º angle with respect to the phase voltage (see
Figures 1.10 and 1.12 for lagging power factor, and Figures 1.16 and
1.18 for leading power factor). The polarity of Id will determine
lagging or leading power factor. The magnitude of Id will determine
how much leading or lagging current will flow.
The pulse-width modulator (PWM), which is between the current
regulators and power structure, provides the gating pulses to the
power structure IGBTs.
The line synchronization unit provides information about utility
voltage phase angles to maintain proper phase angles between the line
currents and line voltages.