Documentation

Four-Quadrant Single-Phase Rectifier DC Drive

Implement single-phase dual-converter DC drive with circulating current

Library

Electric Drives/DC drives

Description

The Four-Quadrant Single-Phase Rectifier DC Drive (DC2) block represents a four-quadrant, single-phase, thyristor-based (or phase controlled) drive for DC motors. This drive features closed-loop speed control with two anti-paralleled single-phase thyristor rectifiers. The anti-parallel rectifiers operate in circulating current mode with the help of circulating current inductors. The speed control loop outputs the reference armature current of the machine. Using a PI current controller, the thyristor firing angles (for the two rectifiers) corresponding to the commanded armature current are derived. These firing angles are then used to obtain the required gate signals for the rectifiers through a thyristor bridge firing unit.

The main advantage of this drive, compared with other DC drives, is that it can operate in all four quadrants (forward motoring, reverse regeneration, reverse motoring, and forward regeneration). However, two anti-paralleled converters along with circulating current inductors are required, which increases the complexity of the drive system.

Note

In Simscape™ Power Systems™ software, the Four-Quadrant Single-Phase Rectifier DC Drive block is commonly called the DC2 motor drive.

The Four-Quadrant Single-Phase Rectifier DC Drive block uses these blocks from the Electric Drives/Fundamental Drive Blocks library:

  • Speed Controller (DC)

  • Regulation Switch

  • Current Controller

  • Bridge Firing Unit (DC)

Remarks

The machine is separately excited with a constant DC field voltage source. There is thus no field voltage control. By default, the field current is set to its steady-state value when a simulation is started.

The armature voltage is provided by two single-phase antiparallel-connected converters controlled by two PI regulators. The circulating current produced by the instantaneous voltage difference at the terminal of both converters is limited by inductors connected between these terminals. Armature current oscillations are reduced by a smoothing inductance connected in series with the armature circuit.

The average-value converter represents the average behavior of a single-phase rectifier for continuous armature current in a dual-converter topology. This model is thus not suitable for simulating DC drives under discontinuous armature current conditions. The converter outputs a continuous voltage value equal to the average-value of the real-life rectified voltage. The armature voltage, armature current, and electromagnetic torque ripples are thus not represented. The input currents have the frequency and amplitude of the fundamental current component of the real-life input currents.

The model is discrete. Good simulation results have been obtained with a 4-µs time step. The control system (speed and current controllers) samples data following a user-defined sample time in order to simulate a digital controller device. Keep in mind that this sampling time has to be a multiple of the simulation time step.

The average-value converter allows the use of bigger simulation time steps since it does not generate small time constants (due to the RC snubbers) inherent to the detailed converter. For a controller sampling time of 100-µs, good simulation results have been obtained for a simulation time step of 100 µs. This time step cannot be higher than the controller time step.

Parameters

General

Output bus mode

Select how the output variables are organized. If you select Multiple output buses (default), the block has three separate output buses for motor, converter, and controller variables. If you select Single output bus, all variables output on a single bus.

Model detail level

Select between the detailed and the average-value inverter. Default is Detailed.

Mechanical input

Select between the load torque, the motor speed and the mechanical rotational port as mechanical input. Default is Torque Tm.

If you select and apply a load torque, the output is the motor speed according to the following differential equation that describes the mechanical system dynamics:

Te=Jddtωr+Fωr+Tm

This mechanical system is included in the motor model.

If you select the motor speed as mechanical input, then you get the electromagnetic torque as output, allowing you to represent externally the mechanical system dynamics. The internal mechanical system is not used with this mechanical input selection and the inertia and viscous friction parameters are not displayed.

For the mechanical rotational port, the connection port S counts for the mechanical input and output. It allows a direct connection to the Simscape environment. The mechanical system of the motor is also included in the drive and is based on the same differential equation.

See Mechanical Coupling of Two Motor Drives.

Use signal names as labels

When you select this check box, the Motor, Conv, and Ctrl measurement outputs use the signal names to identify the bus labels. Select this option for applications that require bus signal labels to have only alphanumeric characters.

When this check box is cleared (default), the measurement output uses the signal definition to identify the bus labels. The labels contain nonalphanumeric characters that are incompatible with some Simulink® applications.

DC Machine Tab

The DC Machine tab displays the parameters of the DC Machine block of the Fundamental Blocks (powerlib) library.

Converters Tab

DC Bus and Excitation Circuit Section

Smoothing inductance

The smoothing inductance value (H). Default is 50e-3.

Field DC source

The DC motor field voltage value (V). Default is 150.

Circulating current inductors

The four circulating current inductors inductance value (H). Default is 0.

Converter Sections

The Converter 1 and Converter 2 sections of the Converter tab display the parameters of the Universal Bridge block of the Fundamental Blocks (powerlib) library. For more information on the Universal Bridge block parameters, refer to the Universal Bridge reference page.

RMS voltage

RMS voltage of the single-phase voltage source connected to the A+,A− terminals of the drive (V). This parameter is not used when using the detailed rectifier. Default is 460.

Frequency

Frequency of the single-phase voltage source connected to the A+,A− terminals of the drive (Hz). This parameter is not used when using the detailed rectifier. Default is 60.

Source inductance

Source inductance of the single-phase voltage source connected to the A+,A− terminals of the drive (H). This parameter is not used when using the detailed rectifier. Default is 0.1e-3.

Phase angle

Phase angle of the single-phase voltage source connected to the A+,A− terminals of the drive (deg.). This parameter is not used when using the detailed rectifier. Default is 0.

Controller Tab

Regulation type

This pop-up menu allows you to choose between speed and torque regulation. Default is Speed regulation.

Sampling time (s)

The controller (speed and current) sampling time (s). The sampling time has to be a multiple of the simulation time step. Default is 20e-6.

Schematic

When you click this button, a diagram illustrating the speed and current controllers schematics appears.

Controller — Speed Controller Subtab

Nominal speed

The nominal speed value of the DC motor (rpm). This value is used to convert motor speed from rpm to pu (per unit). Default is 1750.

Initial speed reference

The initial speed reference value (rpm). This value allows the user to start a simulation with a speed reference other than 0 rpm. Default is 0.

Low-pass filter cutoff frequency

Cutoff frequency of the low-pass filter used to filter the motor speed measurement (Hz). Default is 40.

Proportional gain

The proportional gain of the PI speed controller. Default is 10.

Integral gain

The integral gain of the PI speed controller. Default is 50.

Acceleration

The maximum change of speed allowed during motor acceleration (rpm/s). Too great a value can cause armature over-current. Default is 1000.

Deceleration

The maximum change of speed allowed during motor deceleration (rpm/s). Too great a value can cause armature over-current. Default is -1000.

Controller — Current Controller Subtab

Low-pass filter cutoff frequency

Cutoff frequency of the low-pass filter used to filter the armature current measurement (Hz). Default is 500.

Symmetrical reference limit

Symmetrical current reference (pu) limit around 0 pu. 1.5 pu is a common value. Default is 1.5.

Power and Voltage nominal values

The DC motor nominal power (W) and voltage (V) values. These values are used to convert armature current from amperes to pu (per unit). Default for Power is 5*746. Default for Voltage is 440.

Proportional gain

The proportional gain of the PI current controller. Default is 2.

Integral gain

The integral gain of the PI current controller. Default is 200.

Controller — Bridge Firing Unit Subtab

Alpha min

Minimum firing angle value (deg.). 20 degrees is a common value. Default is 20.

Alpha max

Maximum firing angle value (deg.). 160 degrees is a common value. Default is 160.

Frequency of synchronization voltages

Frequency of the synchronization voltages used by the discrete synchronized pulse generator block (Hz). This frequency is equal to the line frequency of the single-phase power line. This parameter is not used when using the average-value converter. Default is 60.

Pulse width

The width of the pulses applied to the thyristor gates (deg.). This parameter is not used when using the average-value converter. Default is 10.

Block Inputs and Outputs

SP

The speed or torque set point. The speed set point can be a step function, but the speed change rate will follow the acceleration / deceleration ramps. If the load torque and the speed have opposite signs, the accelerating torque will be the sum of the electromagnetic and load torques.

Tm or Wm

The mechanical input: load torque (Tm) or motor speed (Wm). For the mechanical rotational port (S), this input is deleted.

A+, A-

The single-phase electric connections. The applied voltage must be adequate for the motor size.

Wm, Te or S

The mechanical output: motor speed (Wm), electromagnetic torque (Te) or mechanical rotational port (S).

When the Output bus mode parameter is set to Multiple output buses, the block has the following three output buses:

Motor

The motor measurement vector. It is composed of two elements:

  • The armature voltage

  • The DC motor measurement vector (containing the speed, armature current, field current, and electromagnetic torque values). Note that the speed signal is converted from rad/s to rpm before output.

Conv

The single-phase converter measurement vector. This vector includes

  • The output voltage of converter 1

  • The output voltage of converter 2

  • The output current of converter 1

  • The output current of converter 2

Note that all current and voltage values of the detailed bridges can be visualized with the Multimeter block.

Ctrl

The controller measurement vector. This vector contains:

  • The armature current reference

  • The firing angle computed by the current controller

  • The speed or torque error (difference between the speed reference ramp and actual speed or between the torque reference and actual torque)

  • The speed reference ramp or torque reference

When the Output bus mode parameter is set to Single output bus, the block groups the Motor, Conv, and Ctrl outputs into a single bus output.

Model Specifications

The library contains a 5-hp drive parameter set. The specifications of the 5-hp drive are shown in the following table.

5 HP Drive Specifications

Drive Input Voltage

 

Amplitude

320 V

 

Frequency

60 Hz

Motor Nominal Values

 

Power

5 hp

 

Speed

1750 rpm

 

Voltage

240 V

Examples

The dc2_example example illustrates the single-phase dual-converter drive used with the 5-hp drive parameter set during speed regulation.

References

[1] Sen, P.C., Thyristor DC Drives, J.Wiley and Sons, 1981.

Introduced in R2006a

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