SVPWM Generator (2-Level)

Generate pulses for SVPWM-controlled two-level converter

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Libraries:
Simscape / Electrical / Specialized Power Systems / Power Electronics / Power Electronics Control

Description

The SVPWM Generator (2-Level) block generates pulses for three-phase two-level DC/AC converters using the space-vector pulse width modulation (SVPWM) technique.

The converter switches are represented by the following equivalent circuit:

As shown in the following figure, the objective of the SVPWM technique is to approximate the reference voltage vector (U_ref) instantaneously by combining the switching states corresponding to the basic space vectors.

More precisely, for every PWM period, the reference vector U_ref is averaged by using its two adjacent space vectors (U₃ and U₄ in the figure) for a certain duration of time and a null vector (U₇ or U₈) for the rest of the period.

Vector	Q1	Q3	Q5
U1	1	0	0
U2	1	1	0
U3	0	1	0
U4	0	1	1
U5	0	0	1
U6	1	0	1
U7	0	0	0
U8	1	1	1

The block implements two symmetrical switching patterns [1]:

Pattern #1: With this pattern, known as Software-Determined, each PWM channel switches twice per every PWM period.

Pattern #2: With this pattern, known as Hardware-Determined, one PWM channel remains constant for the entire PWM period. Consequently, the number of switching times for this pattern is less than pattern #1. As a result, switching losses are reduced with Pattern #2.

Characteristics

Sample Time	Specified in the Sample Time parameter Continuous if Sample Time = 0
Scalar Expansion	No
Dimensionalized	No

Examples

The power_SVPWMGenerator2Level model uses two simple circuits to show how the SVPWM Generator (2-Level) works and to compare the two switching pattern options. Run the simulation and open the FFT Analysis tool of the Powergui block to see the harmonics and the THD value of the voltages produced by the two converters.

The model sample time is parameterized by the Ts variable set to a default value of 2e-6 s. Set Ts to 0 in the command window and change the Simulation type parameter of the Powergui block to Continuous to simulate the model in continuous mode.

Ports

Input

|U| — Magnitude of rotating reference vector

Magnitude of the rotating reference vector U_ref.

Dependencies

To enable this port, set Data type of input reference vector (Uref) to Magnitude-Angle (rad).

⦟U — Phase of rotating reference vector

Phase, in radians, of the rotating reference vector U_ref.

Dependencies

To enable this port, set Data type of input reference vector (Uref) to Magnitude-Angle (rad).

Uα — Alpha components of rotating reference vector

Alpha components of the rotating reference vector U_ref.

Dependencies

To enable this port, set Data type of input reference vector (Uref) to alpha-beta components.

Uβ — Beta components of rotating reference vector

Beta components of the rotating reference vector U_ref.

Dependencies

To enable this port, set Data type of input reference vector (Uref) to alpha-beta components.

Output

P — Pulse signals used to fire self-commutated devices

Six pulse signals to fire the self-commutated devices (Q1 to Q6) of a converter device.

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Data type of input reference vector (Uref) — Type of reference vector

Magnitude-Angle (rad) (default) | alpha-beta components | Internally generated

Specify the type of reference vector.

When set to Magnitude-Angle (rad) (default), the U_ref vector is specified by the following inputs:

|U| Magnitude of Uref (value between 0 and 1)

When set to alpha-beta components, the U_ref vector is specified by the Uα and Uβ inputs.

When set to Internally generated, the U_ref is no longer an input to the block. It is internally generated in order to control the converter output voltage as specified in the output voltage parameter.

Switching pattern — Switching pattern

Pattern #1 (default) | Pattern #2

When set to Pattern #1 (default), every device of the converter switches twice per every PWM period.

When set to Pattern #2, the status of one of the three arms stays constant (no switching) for the entire PWM period.

PWM frequency (Hz) — PWM frequency

2000 (default)

PWM frequency that determines the PWM period.

$$PWMperiod=1/PWMFrequency$$

Output voltage: [ Mag (0<m<1), Phase (degrees), Freq (Hz)] — Magnitude, phase, and frequency of output voltage

[0.8 -30 50] (default)

Magnitude, phase, and frequency of the output voltage of the two level converter controlled by the block. The magnitude of the fundamental component of the converter line-to-line output voltage is defined as

$$V_{LLrms}=m\times \frac{V_{dc}}{\sqrt{2}}$$

Dependencies

To enable this parameter, set Data type of input reference vector Uref to Internally generated.

Sample time — Sample time

0 (default)

Specify the sample time of the block, in seconds. Set to 0 to implement a continuous block.

References

[1] Yu, Z., Application Report SPRA524, Space-Vector PWM with TMS320C24x Using H/W & S/W Determined Switching Patterns, Texas Instruments, 1999.

Extended Capabilities

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

Version History

Introduced in R2013a