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. The schematic diagram of the boost rectifier is shown below.

The control goals for the three-phase boost rectifier are to draw sinusoidal current from the input supply, v_n, and to regulate the output voltage, V_dc. Current control is achieved using an inner current control loop that measures the phase current, I_n, and controls the inductor-neutral voltage, v_n1, 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.

In this model, both the power electronics and controllers are implemented using PLECS components and controllers. The space vector modulator is implemented as a custom PLECS C-Script block that has been optimized for speed.

Requirements

PLECS Blockset

 PLECS Blockset 3.1 or newer
 Matlab 7.0 (R14) or newer

PLECS Standalone

 PLECS Standalone 3.1 or newer

Download

The package file for PLECS Blockset plecs_svpwm.zip (346 KB) and for PLECS Standalone plecs_standalone_svpwm.zip (346 KB) contain the example model and the documentation in PDF format.