Generate pulses for PWM-controlled three-level converter - Simulink - 万博1manbetx,s manbetx 845,万博尤文图斯

Description

ThePWM Generator (3-Level)block generates pulses for carrier-based pulse-width modulation (PWM) converters using three-level topology. The block can control switching devices (FETs, GTOs, or IGBTs) of three different converter types: single-phase half-bridge (one arm), single-phase full-bridge (two arms), or three-phase bridge (three arms).

The reference signal (Uref input), also called the modulating signal, is naturally sampled and compared with two symmetrical level-shifted triangle carriers.

The following figure shows how the pulses are generated for a single-phase, half-bridge three-level converter.

The converter arm can have three states: +1, 0, or −1. When the reference signal is greater than the positive carrier, the state of the arm is +1; when the reference signal is smaller than the negative carrier, the state of the arm is −1.

Otherwise, the state is 0. Based on the current state of the arm, the appropriate pulses are generated.

State	第一季度	第二季	第三季	第四季度
1	1	1	0	0
0	0	1	1	0
−1	0	0	1	1

One reference signal is required to generate the four pulses of an arm. For a single-phase full-bridge converter, a second reference signal is required to generate the four pulses of the second arm. This signal is internally generated by phase-shifting the original reference signal by 180 degrees. For a three-phase bridge, three reference signals are required to generate the 12 pulses.

The reference signal also can be internally generated by the PWM generator. In this case, specify a modulation index, voltage output frequency, and phase.

Parameters

Generator type

Specify the number of pulses to generate. The number of pulses generated by the block is proportional to the number of bridge arms to control.

SelectSingle-phase half-bridge (4 pulses)to fire the self-commutated devices of a single-phase half-bridge converter. Pulses (1, 2) fire the upper devices and pulses (3, 4) fire the lower devices.

SelectSingle-phase full-bridge (8 pulses)to fire the self-commutated devices of a single-phase full-bridge converter. Eight pulses are then generated. Pulses (1, 2) and (5, 6) fire the upper devices of the first and second arms. Pulses (3, 4) and (7, 8) fire the lower devices of the first and second arms.

SelectThree-phase bridge (12 pulses)(default) to fire the self-commutated devices of a three-phase bridge converter. Pulses (1, 2), (5, 6), and (9, 10) fire the upper devices of the first, second, and third arms. Pulses (3, 4), (7, 8), and (11, 12) fire the lower devices of the three arms.

Mode of operation

When set toUnsynchronized(default), the frequency of the unsynchronized carrier signal is determined by theCarrier frequencyparameter.

When set toSynchronized, the carrier signal is synchronized to an external reference signal (input wt), and the carrier frequency is determined by theSwitching ratioparameter.

Carrier frequency (Hz)

Specify to determine the frequency, in hertz, of the two triangular carrier signals. Default is27*60. TheCarrier frequencyparameter is visible only when theMode of operationparameter is set toUnsynchronized.

Switching ratio (carrier frequency/output frequency)

Determines the frequency (F_c) of the two triangular carrier signals.

$F_{c} = S w i t c h i n g R a t i o \times O u t p u t V o l t a g e F r e q u e n c y$

Default is27. TheSwitching ratioparameter is visible only when theMode of operationparameter is set toSynchronized.

Internal generation of modulating signal (s)

When this check box is selected, the block generates the reference signal. Default is cleared.

The parameter is visible only when theMode of operationparameter is set toUnsynchronized.

Modulation index

Specify the modulation index to control the amplitude of the fundamental component of the output voltage of the converter. Default is0.8. The modulation index must be greater than0,低于或等于1. The parameter is visible only when theInternal generation of modulating signal (s)check box is selected.

Output voltage frequency (Hz)

Specify the output voltage frequency to control the fundamental component frequency of the output voltage of the converter. Default is60. The parameter is visible only when theInternal generation of modulating signal (s)check box is selected.

Output voltage phase (degrees)

This parameter controls the phase of the fundamental component of the output voltage of the converter. Default is0. The parameter is visible only when theInternal generation of modulating signal (s)check box is selected.

Sample time

Specify the sample time of the block, in seconds. Default is0. Set to0to implement a continuous block.

Inputs and Outputs

Uref

The vectorized reference signal used to generate the output pulses. The input is visible only when theInternal generation of modulating signal (s)is not selected. Connect this input to:

A single-phase sinusoidal signal when the block controls a single-phase half- or full-bridge converter
A three-phase sinusoidal signal when the PWM Generator block controls a three-phase bridge converter

对于线性操作这一块,magnitude of Uref must be between −1 and +1.

P

The output contains the 4, 8, or 12 pulses used to fire the self-commutated devices (MOSFETs, GTOs, or IGBTs) of a one-, two- or three-arm three-level converter.

Characteristics

Sample Time	Specified in theSample Timeparameter Continuous ifSample Time= 0
Scalar Expansion	No
Dimensionalized	No

Examples

Thepower_PWMGenerator3Levelmodel uses a simple circuit to show how the PWM Generator (3-Level) operates. Run the simulation and use the FFT Analysis tool of the Powergui block to see the harmonics and the THD value of the voltages produced by the three-phase three-level converter.

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

PWM Generator (3-Level)

Library

Description

Parameters

Inputs and Outputs

Characteristics

Examples

Version History