PM Synchronous Motor Drive

Implement Permanent Magnet Synchronous Motor (PMSM) vector control drive

Library

Electric Drives/AC drives

Description

The PM Synchronous Motor Drive (AC6) block represents a classical vector control drive for permanent synchronous motors. This drive features a closed-loop speed control based on the vector control method. The speed control loop outputs the reference electromagnetic torque of the machine. The reference direct and quadrature (dq) components of the stator current corresponding to the commanded torque are derived based on vector control strategy. The reference dq components of the stator current are then used to obtain the required gate signals for the inverter through a hysteresis-band current controller.

The main advantage of this drive compared to scalar-controlled drives, is its fast dynamic response. The inherent coupling effect between the torque and flux in the machine is managed through decoupling (stator flux orientation) control, which allows the torque and flux to be controlled independently. However, due to its computation complexity, the implementation of this drive requires fast computing processors or DSPs.

Note

In Simscape™ Power Systems™ software, the PM Synchronous Motor Drive block is commonly called the AC6 motor drive.

The PM Synchronous Motor Drive block uses these blocks from the Electric Drives / Fundamental Drive Blocks library:

• Speed Controller (AC)

• Vector Controller (PMSM)

• DC Bus

• Inverter (Three-Phase)

Remarks

The model is discrete. Good simulation results have been obtained with a 2 µs time step. To simulate a digital controller device, the control system has two different sampling times:

• Speed controller sampling time

• Vector controller sampling time

The speed controller sampling time has to be a multiple of the vector controller sampling time. The latter sampling time has to be a multiple of the simulation time step. The average-value inverter 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 vector controller sampling time of 75 µs, good simulation results have been obtained for a simulation time step of 75 µs. The simulation time step can, of course, not be higher than the vector controller time step.

The stator current direct component id* is set to zero inside the vector controller block because the rotor flux is supplied by the permanent magnets.

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:

$$T_e=J\frac{d}{dt}{\omega }_r+F{\omega }_r+T_m$$

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.

Permanent Magnet Synchronous Machine Tab

The Permanent Magnet Synchronous Machine tab displays the parameters of the Permanent Magnet Synchronous Machine block of the Fundamental Blocks (powerlib) library.

Converters and DC Bus Tab

Rectifier Section

The Rectifier section of the Converters and DC Bus tab displays the parameters of the Universal Bridge block of the Fundamental Blocks (powerlib) library. For more information on the Universal Bridge parameters, refer to the Universal Bridge reference page.

DC Bus Section

Capacitance

The DC bus capacitance (F). Default is 2000e-6.

Braking Chopper Section

Resistance

The braking chopper resistance used to avoid bus over-voltage during motor deceleration or when the load torque tends to accelerate the motor (ohms). Default is 8.

Chopper frequency

The braking chopper frequency (Hz). Default is 4000.

Activation voltage

The dynamic braking is activated when the bus voltage reaches the upper limit of the hysteresis band. The following figure illustrates the braking chopper hysteresis logic. Default is 320.

Shutdown voltage

The dynamic braking is shut down when the bus voltage reaches the lower limit of the hysteresis band. Default is 310. The chopper hysteresis logic is shown in the following figure.

Inverter Section

The Inverter section of the Converters and DC Bus tab displays the parameters of the Universal Bridge block of the Fundamental Blocks (powerlib) library. For more information on the Universal Bridge parameters, refer to the Universal Bridge reference page.

The average-value inverter uses the following parameters.

Source frequency

The frequency of the three-phase voltage source (Hz). Default is 60.

On-state resistance

The on-state resistance of the inverter devices (ohms). Default is 1e-3.

Controller Tab

Regulation type

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

Modulation type

Select hysteresis or space vector modulation. The default modulation type is Hysteresis.

Schematic

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

Speed Controller Section

Speed ramps — Acceleration

The maximum change of speed allowed during motor acceleration (rpm/s). An excessively large positive value can cause DC bus under-voltage. This parameter is used in speed regulation mode only. Default is 1000.

Speed ramps — Deceleration

The maximum change of speed allowed during motor deceleration (rpm/s). An excessively large negative value can cause DC bus overvoltage. This parameter is used in speed regulation mode only. Default is -1000.

Speed cutoff frequency

The speed measurement first-order low-pass filter cutoff frequency (Hz). This parameter is used in speed regulation mode only. Default is 100.

Speed controller sampling time

The speed controller sampling time (s). The sampling time must be a multiple of the simulation time step. Default is 7*20e-6.

PI regulator — Proportional gain

The speed controller proportional gain. This parameter is used in speed regulation mode only. Default is 5.

PI regulator — Integral gain

The speed controller integral gain. This parameter is used in speed regulation mode only. Default is 100.

Torque output limits — Negative

The maximum negative demanded torque applied to the motor by the current controller (N.m). Default is -17.8.

Torque output limits — Positive

The maximum positive demanded torque applied to the motor by the current controller (N.m). Default is 17.8.

Vector Controller Section

Sampling time

The vector controller sampling time (s). The sampling time must be a multiple of the simulation time step. Default is 20e-6.

Current controller hysteresis band

The current hysteresis bandwidth. Default is 0.1. This value is the total bandwidth distributed symmetrically around the current set point (A). The following figure illustrates a case where the current set point is Is^* and the current hysteresis bandwidth is set to dx.

This parameter is not used when using the average-value inverter.

Note

This bandwidth can be exceeded because a fixed-step simulation is used. A rate transition block is needed to transfer data between different sampling rates. This block causes a delay in the gate signals, so the current may exceed the hysteresis band.

Maximum switching frequency

The maximum inverter switching frequency (Hz). Default is 20e3. This parameter is not used when using the average-value inverter.

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).

A, B, C

The three phase terminals of the motor drive.

Wm or Te

The mechanical output: motor speed (Wm) or electromagnetic torque (Te).

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. This vector allows you to observe the motor's variables using the Bus Selector block.

Conv

The three-phase converters measurement vector. This vector contains:

• The DC bus voltage

• The rectifier output current

• The inverter input current

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

Ctrl

The controller measurement vector. This vector contains:

• The torque reference

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

• 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 3 hp drive parameter set. The specifications of the 3 hp drive are shown in the following table.

3 HP Drive Specifications

Drive Input Voltage
	Amplitude	220 V
	Frequency	60 Hz
Motor Nominal Values
	Power	3 hp
	Speed	1800
	Voltage	300

Examples

The ac6_example example illustrates an AC6 motor drive simulation with standard load condition.

References

[1] Bose, B. K. Modern Power Electronics and AC Drives. Upper Saddle River, NJ: Prentice-Hall, 2002.

[2] Krause, P. C. Analysis of Electric Machinery. New York: McGraw-Hill, 1986.

Introduced in R2006a

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