PWM Generator

Generate pulse width modulated signal or waveform

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Libraries:
Simscape / Electrical / Control / Pulse Width Modulation

Description

The PWM Generator block implements a PWM generator. The pulse width modulation technique controls power transfer from one electrical component to another by quickly switching between full power transfer and no power transfer.

Working Principle

The PWM generator block outputs either 1 when the duty cycle is greater than the carrier counter value, or 0 otherwise. You can set the period of each cycle by specifying the timer period Tper. You can change the initial output, or phase, of the PWM output by specifying one of three types of carrier counters:

• Up counter — The PWM output signal initializes at the start of the on cycle. This graphic shows the carrier counter signal and the corresponding PWM output.

  

• Down counter — The PWM output signal initializes at the start of the off cycle. This graphic shows the carrier counter signal and the corresponding PWM output.

  

• Up-down counter — The PWM output signal initializes halfway through the on cycle. This graphic shows the carrier counter signal and the corresponding PWM output.

  

Examples

DC Motor Control

A cascade speed-control structure for a DC motor. A PWM controlled four-quadrant Chopper is used to feed the DC motor. The Control subsystem includes the outer speed-control loop, the inner current-control loop, and the PWM generation. The total simulation time (t) is 4 seconds. At t = 1.5 seconds, the load torque increases. At t = 2.5 seconds, the reference speed is changed from 1000 rpm to 2000 rpm.

• Open Model

HESM Torque Control

Control the torque in a hybrid excitation synchronous machine (HESM) based electrical-traction drive. Permanent magnets and an excitation winding excite the HESM. A high-voltage battery feeds the SM through a controlled three-phase converter for the stator windings and through a controlled four quadrant chopper for the rotor winding. An ideal angular velocity source provides the load. The Control subsystem uses an open-loop approach to control the torque and a closed-loop approach to control the current. At each sample instant, the torque request is converted to relevant current references. The current control is PI-based. The simulation uses several torque steps in both the motor and generator modes. The Visualization subsystem contains scopes that allow you to see the simulation results.

• Open Model

HESM Velocity Control

Control the rotor angular velocity in a hybrid excitation synchronous machine (HESM) based electrical-traction drive. Permanent magnets and an excitation winding excite the HESM. A high-voltage battery feeds the HESM through a controlled three-phase converter for the stator windings and through a controlled four quadrant chopper for the rotor winding. An ideal torque source provides the load. The Control subsystem includes a multi-rate PI-based cascade control structure. The control structure has an outer angular-velocity-control loop and three inner current-control loops. The Visualization subsystem contains scopes that allow you to see the simulation results.

• Open Model

SM Torque Control

Control the torque in a synchronous machine (SM) based electrical-traction drive. A high-voltage battery feeds the SM through a controlled three-phase converter for the stator windings and a controlled four quadrant chopper for the rotor winding. An ideal angular velocity source provides the load. The Control subsystem uses an open-loop approach to control the torque and a closed-loop approach to control the current. At each sample instant, the torque request is converted to relevant current references. The current control is PI-based. The simulation uses several torque steps in both motor and generator modes. The task scheduling is implemented as a Stateflow® state machine. The Visualization subsystem contains scopes that allow you to see the simulation results.

• Open Model

SM Velocity Control

Control the rotor angular velocity in a synchronous machine (SM) based electrical-traction drive. A high-voltage battery feeds the SM through a controlled three-phase converter for the stator windings and a controlled four quadrant chopper for the rotor winding. An ideal torque source provides the load. The Control subsystem includes a multi-rate PI-based cascade control structure which has an outer angular-velocity-control loop and three inner current-control loops. The task scheduling in the Control subsystem is implemented as a Stateflow® state machine. The Visualization subsystem contains scopes that allow you to see the simulation results.

• Open Model

Ports

Input

DC — Duty cycle

scalar

Duty cycle in the range [0,1].

Data Types: single | double

Output

PWM — PWM signal

scalar

Pulse width modulation signal.

Data Types: single | double

Parameters

Carrier counter — Carrier counter strategy

Up (default) | Down | Up-Down

Use the carrier counter strategy to change the initial behavior of the PWM output:

• Up counter — PWM output begins at the start of the on state.

• Down counter — PWM output begins at the start of the off state.

• Up-down counter — PWM output begins in the middle of the on state.

Timer period (s) — PWM period

0.001 (default) | positive number

PWM timer period.

If you set Carrier counter to Up counter or Down counter, the Timer period (s) parameter is specified as $$\frac{1}{f_{sw}}$$, where $$f_{sw}$$ is the switching frequency. If you set Carrier counter to Up-down counter, the Timer period (s) parameter is specified as $$\frac{1}{2f_{sw}}$$.

Phase delay (s) — Phase delay

0 (default) | nonnegative number

Phase delay, in seconds. Add a phase delay to change the initial state of the counter.

Sample time — Block sample time

5e-5 (default) | positive number

Sample time for the block. For continuous-time simulation, set to zero. For discrete-time simulation, to ensure adequate resolution in the generated signal, specify a positive value that is less than or equal to Tper/10, where T_per is the Timer period (s).

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2017b