DC/AC Converter ControlTorque and Flux Control

• Converter circuit

+ Motor

• Control design– Design sliding surface for torque and flux

– Lyapunov function

denote

S1

S4 S2

S5S3

S6

(U_m)

-(U_m)

ia

ic

ib

va

vb

vc

Motor

Torque and Flux Control (cont.)

– Calculate

where does not depend on control

and

Torque and Flux Control (cont.)

– Select control logic such that

tends to zero

ControlLogic

Torque & Flux Control (approach 2)

• Cascade Control– From torque and flux equations:

where

– Desired can be calculated– Sliding mode to provide desired current

Cascade Sliding Mode Control

• Idea: Utilize extra degree of freedom

• Sliding surface design L R

S1

S4 S2

S5S3

S6

(U_dc)

-(U_dc)

n

ia

ic

ib

va

vb

vc

Ea

Eb

Ec

Lyapunov Approach• Select control logic based on Lyapunov

function such that sliding mode is enforced

• Advantage: simple

ControlLogic

Decoupling Approach to Enforce Sliding Mode

• Idea: to decouple motions in

• Method: non-singular transformation:

• Advantage: allows frequency analysis performed for each surface individually

ControlLogic

Vn Control• Objective: optimality

by changing• Example: switching

frequency reduction

ont offt

Slidling Surface

SMPWM Simulation Results

• Current tracking and vn tracking

Experimental Setup

• Controller: TMS320F2812 DSP• Switching devices: 2MBI100NC-12 IGBT• 3 phase RL load• 50 V DC supply

DSP Board

Full Bridge Converter

PWM Signal

DC Voltage

Current Measurements

Load

The first waveforms show the current tracking (and ), the second ones show tracking as a sinusoidal function by the average value of (after filtering out a high frequency component of discontinuous function ).