Space Vector Control of a Three Phase Boost Rectifier
Space vector control is a popular technique used in the control of motor drives
or three-phase rectifiers since it offers reduced switching losses and better
utilization of the dc bus compared to conventional PWM control. This example
model demonstrates space vector control of a three-phase boost-type rectifier
using PLECS.
Control
The control goals for the three-phase boost rectifier are to draw sinusoidal
current from the input supply, vn, and to regulate the output
voltage, Vdc. Current control is achieved using an inner current
control loop that measures the phase current, In, and controls
the inductor-neutral voltage, vn1, to force the phase current to
track its reference value. The current reference is provided by outer control
loops that implement dc voltage and power factor control.
With space vector control, the inductor-neutral voltage is controlled as a
vector quantity in the αβ or dq domains. In this
example, control is performed in the dq domain. The advantage of
dq control is that ac quantities become dc quantities in the dq
domain. Thus no tracking error exists when using a PI controller to regulate
the ac input current.
The reference ac voltage vector is generated by time-averaging the available
switching vectors. Two popular modulation strategies have been implemented in
the space vector modulator: an optimal modulation strategy that minimizes the
switching losses and a symmetrical modulation strategy that minimizes the THD.
A deadtime component has also been included to simulate the effect of switching
delay when changing the switch state of a rectifier leg.