MODELING AND FPGA IMPLEMENTATION OF A PMSM

SPEED CONTROLLER

GINTU GEORGEROLL NUMBER : 7

VAES

GUIDED BY,Mr. ANOOP THOMAS

Introduction

A holistic approach to modeling and FPGAimplementation of digital controllers. The case study ofa permanent magnet synchronous motor (PMSM)speed controller is considered. The whole system ismodeled in the Matlab Simulink environment. Thecontroller is then translated to discrete time andremodelled using System Generator blocks, directlysynthesizable into FPGA hardware.

The algorithm is further refined and factorized to fitinto a low cost FPGA, without significantly increasingthe execution time. The resulting controller is thenintegrated together with sensor interfaces and analysistools and implemented into an FPGA device.

Aim

• Derive the control algorithm.

• Modeling motor and controller in Simulink Matlab

• Modeling the designed simulink model in Xilinx ise

• FPGA implementation

• Capture internal signals

FPGA

• A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturing

• The FPGA configuration is generally specified using a hardware description languages (HDL).

• FPGAs contain programmable logic components called "logic blocks", and a hierarchy of reconfigurable interconnects that allow the blocks to be "wired together"

• Nowadays, the whole complex digital system can reside into the FPGA, leading to the concept of system on a chip (SoC).

• The main advantage FPGAs offer is the possibility to implement algorithms directly into hardware, maintaining the parallelism of the algorithm in the implementation and thus minimizing the execution time.

Permanent Magnet Synchronous Motor (PMSM)

• The PMSM is a brushless machine with sinusoidal flux distribution, for which reason it is also known as a brushless AC (BLAC) machine.

• In a PMSM the stator voltage must be sinusoidal. The amplitude and frequency of the stator voltage must be related to the rotor speed, and the sinusoidal waveform must be in tune with the rotor position.

Modeling of a PMSM in SIMULINKThe PMSM is usually modeled in the rotor

synchronous rotating frame (q/d frame). A three phase PMSM is electrically described in the rotor synchronous rotating frame by the following equations (Park equations)

(Where Vq,Vd,iq,id are the stator voltage and current quadrature and direct components, Rs is the stator resistance Lqs,Lds are the stator quadrature and direct impedances, λm is the amplitude of the flux linkages established by the rotor permanent magnet, and ωe is the angular speed of the stator electromagnetic field. )

• The electromagnetic torque produced by the motor is given by:

(2)

• where P is the number of rotor magnetic poles. If the rotor is perfectly round, the quadrature and direct impedances are equal, and in this case the electromagnetic torque only depends on the quadrature stator current.

• The mechanical equation of the motor is:

(3)

• where J is the rotor moment of inertia, TL is the load torque, and F is the friction factor.

• As it can be observed in equation (4), the speed is controlled by controlling the electromagnetic torque. This, in turn, is controlled by controlling the quadrature current, as it is indicated by (2). The quadrature and direct currents are controlled by the quadrature and direct applied voltages, according to (1). It can be observed that cross-coupling appears between the two axes currents. This cross-coupling must be compensated in the controller.

The motor is fed by a three phase voltage source inverter (VSI). The VSI is controlled using space vector modulation (SVM) and the SVM algorithm is applied directly to the α/β voltage components.

• The PI controllers were discretized using the Tustin approximation, and are described in discrete time by the equation:

• Where KI is the integral gain ,Kp is the proportional gain, ε is the controller input, and u is the controller output.

• The a/b/c to q/d transform consists of two consecutive transforms, a/b/c to α/β and α/β to q/d:

The SVM algorithm was replaced at this stage of simulation by an α/β to a/b/c transformation and the three phase voltages were fed to the motor model by means of SimPowerSystems controlled voltage sources.

Simulation results

Ia,Ib,Ic CURRENTS

Id,Iq Currents

Torque of pmsm motor

Speed of pmsm motor

Conclusion

A novel holistic modeling of an FPGA speed controller for PMSM was presented, using

Matlab Simulink and System Generator. The approach presented allows the modeling of

the controller and the controlled system in the same environment, leading to a real time

FPGA implementation.

Future work

• The classical PWM method is used to generate the requested motor voltages. To

• improve the system performance in terms of torque ripple, power quality and better DC

• voltage utilization, space vector modulation can be employed. The speed is estimated by

• the measurement of the position. The speed estimation can be improved by the use of

• Kalman lters

THANKYOU