Abstract: .Hardware realization of a Neural Network (NN), to a large extent depends on the efficient implementation of a single neuron. FPGA-based reconfigurable computing architectures are suitable for hardware implementation of neural networks. FPGA realization of ANNs with a large number of neurons is still a challenging task. This paper discusses the issues involved in implementation of a multi-input neuron with linear/nonlinear excitation functions using FPGA. Implementation method with resource/speed tradeoff is proposed to handle signed decimal numbers. The VHDL coding developed is tested using Xilinx XC V50hq240 Chip. To improve the speed of operation a lookup table method is used. The problems involved in using a lookup table (LUT) for a nonlinear function is discussed. The percentage saving in resource and the improvement in speed with an LUT for a neuron is reported. An attempt is also made to derive a generalized formula for a multi-input neuron that facilitates to estimate approximately the total resource requirement and speed achievable for a given multilayer neural network. This facilitates the designer to choose the FPGA capacity for a given application. Using the proposed method of implementation a neural network based application, namely, a Space vector modulator for a vector-controlled drive is presented
Abstract: In this paper a sliding-mode torque and flux control is
designed for encoderless synchronous reluctance motor drive. The
sliding-mode plus PI controllers are designed in the stator-flux field
oriented reference frame which is able to track the mentioned
reference signals with a minimum pulsations in the state condition. In
addition, with these controllers a fast dynamic response is also
achieved for the drive system. The proposed control scheme is robust
subject to parameters variation except to stator resistance. To solve
this problem a simple estimator is used for on-line detecting of this
parameter. Moreover, the rotor position and speed are estimated by
on-line obtaining of the stator-flux-space vector. The effectiveness
and capability of the proposed control approach is verified by both
the simulation and experimental results.
Abstract: In this paper the optimal control strategy for
Permanent Magnet Synchronous Motor (PMSM) based drive system
is presented. The designed full optimal control is available for speed
operating range up to base speed. The optimal voltage space-vector
assures input energy reduction and stator loss minimization,
maintaining the output energy in the same limits with the
conventional PMSM electrical drive. The optimal control with three
components is based on the energetically criteria and it is applicable
in numerical version, being a nonrecursive solution. The simulation
results confirm the increased efficiency of the optimal PMSM drive.
The properties of the optimal voltage space vector are shown.
Abstract: This paper presents a comparison between two Pulse
Width Modulation (PWM) algorithms applied to a three-level Neutral
Point Clamped (NPC) Voltage Source Inverter (VSI). The first
algorithm applied is the triangular-sinusoidal strategy; the second is
the Space Vector Pulse Width Modulation (SVPWM) strategy. In the
first part, we present a topology of three-level NCP VSI. After that,
we develop the two PWM strategies to control this converter. At the
end the experimental results are presented.
Abstract: In this paper, a direct torque control - space vector
modulation (DTC-SVM) scheme is presented for a six-phase speed
and voltage sensorless induction motor (IM) drive. The decoupled
torque and stator flux control is achieved based on IM stator flux field orientation. The rotor speed is detected by on-line estimating of
the rotor angular slip speed and stator vector flux speed. In addition, a simple method is introduced to estimate the stator resistance.
Moreover in this control scheme the voltage sensors are eliminated
and actual motor phase voltages are approximated by using PWM
inverter switching times and the dc link voltage. Finally, some simulation and experimental results are presented to verify the
effectiveness and capability of the proposed control scheme.
Abstract: This paper presents a speed sensorless direct torque
control scheme using space vector modulation (DTC-SVM) for
permanent magnet synchronous motor (PMSM) drive based a Model
Reference Adaptive System (MRAS) algorithm and stator resistance
estimator. The MRAS is utilized to estimate speed and stator
resistance and compensate the effects of parameter variation on stator
resistance, which makes flux and torque estimation more accurate
and insensitive to parameter variation. In other hand the use of SVM
method reduces the torque ripple while achieving a good dynamic
response. Simulation results are presented and show the effectiveness
of the proposed method.
Abstract: Direct Torque Control is a control technique in AC
drive systems to obtain high performance torque control. The
conventional DTC drive contains a pair of hysteresis comparators.
DTC drives utilizing hysteresis comparators suffer from high torque
ripple and variable switching frequency. The most common solution
to those problems is to use the space vector depends on the reference
torque and flux. In this Paper The space vector modulation technique
(SVPWM) is applied to 2 level inverter control in the proposed
DTC-based induction motor drive system, thereby dramatically
reducing the torque ripple. Then the controller based on space vector
modulation is designed to be applied in the control of Induction
Motor (IM) with a three-level Inverter. This type of Inverter has
several advantages over the standard two-level VSI, such as a greater
number of levels in the output voltage waveforms, Lower dV/dt, less
harmonic distortion in voltage and current waveforms and lower
switching frequencies. This paper proposes a general SVPWM
algorithm for three-level based on standard two-level SVPWM. The
proposed scheme is described clearly and simulation results are
reported to demonstrate its effectiveness. The entire control scheme is
implemented with Matlab/Simulink.
Abstract: Recent developments in Soft computing techniques,
power electronic switches and low-cost computational hardware have
made it possible to design and implement sophisticated control
strategies for sensorless speed control of AC motor drives. Such an
attempt has been made in this work, for Sensorless Speed Control of
Induction Motor (IM) by means of Direct Torque Fuzzy Control
(DTFC), PI-type fuzzy speed regulator and MRAS speed estimator
strategy, which is absolutely nonlinear in its nature. Direct torque
control is known to produce quick and robust response in AC drive
system. However, during steady state, torque, flux and current ripple
occurs. So, the performance of conventional DTC with PI speed
regulator can be improved by implementing fuzzy logic techniques.
Certain important issues in design including the space vector
modulated (SVM) 3-ะค voltage source inverter, DTFC design,
generation of reference torque using PI-type fuzzy speed regulator
and sensor less speed estimator have been resolved. The proposed
scheme is validated through extensive numerical simulations on
MATLAB. The simulated results indicate the sensor less speed
control of IM with DTFC and PI-type fuzzy speed regulator provides
satisfactory high dynamic and static performance compare to
conventional DTC with PI speed regulator.
Abstract: This paper presents design and implements the
T-DOF PI controller design for a speed control of induction motor.
The voltage source inverter type space vector pulse width modulation
technique is used the drive system. This scheme leads to be able to
adjust the speed of the motor by control the frequency and amplitude
of the input voltage. The ratio of input stator voltage to frequency
should be kept constant. The T-DOF PI controller design by root
locus technique is also introduced to the system for regulates and
tracking speed response. The experimental results in testing the 120
watt induction motor from no-load condition to rated condition show
the effectiveness of the proposed control scheme.
Abstract: Space Vector Modulation (SVM) is an optimum Pulse Width Modulation (PWM) technique for an inverter used in a variable frequency drive applications. It is computationally rigorous and hence limits the inverter switching frequency. Increase in switching frequency can be achieved using Neural Network (NN) based SVM, implemented on application specific chips. This paper proposes a neural network based SVM technique for a Voltage Source Inverter (VSI). The network proposed is independent of switching frequency. Different architectures are investigated keeping the total number of neurons constant. The performance of the inverter is compared for various switching frequencies for different architectures of NN based SVM. From the results obtained, the network with minimum resource and appropriate word length is identified. The bit precision required for this application is identified. The network with 8-bit precision is implemented in the IC XCV 400 and the results are presented. The performance of NN based general purpose SVM with higher bit precision is discussed.
Abstract: Multi-level voltage source inverters offer several
advantages such as; derivation of a refined output voltage with
reduced total harmonic distortion (THD), reduction of voltage ratings
of the power semiconductor switching devices and also the reduced
electro-magnetic-interference problems etc. In this paper, new
carrier-overlapped phase-disposition or sub-harmonic sinusoidal
pulse width modulation (CO-PD-SPWM) and also the carrieroverlapped
phase-disposition space vector modulation (CO-PDSVPWM)
schemes for a six-level diode-clamped inverter topology
are proposed. The principle of the proposed PWM schemes is similar
to the conventional PD-PWM with a little deviation from it in the
sense that the triangular carriers are all overlapped. The overlapping
of the triangular carriers on one hand results in an increased number
of switchings, on the other hand this facilitates an improved spectral
performance of the output voltage. It is demonstrated through
simulation studies that the six-level diode-clamped inverter with the
use of CO-PD-SPWM and CO-PD-SVPWM proposed in this paper is
capable of generating multiple levels in its output voltage. The
advantages of the proposed PWM schemes can be derived to benefit,
especially at lower modulation indices of the inverter and hence this
aspect of the proposed PWM schemes can be well exploited in high
power applications requiring low speeds of operation of the drive.
Abstract: Pulse width modulation (PWM) techniques have been
the subject of intensive research for different industrial and power
sector applications. A large variety of methods, different in concept
and performance, have been newly developed and described. This
paper analyzes the comparative merits of Sinusoidal Pulse Width
Modulation (SPWM) and Space Vector Pulse Width Modulation
(SVPWM) techniques and the suitability of these techniques in a
Shunt Active Filter (SAF). The objective is to select the scheme that
offers effective utilization of DC bus voltage and also harmonic
reduction at the input side. The effectiveness of the PWM techniques
is tested in the SAF configuration with a non linear load. The
performance of the SAF with the SPWM and (SVPWM) techniques
are compared with respect to the THD in source current. The study
reveals that in the context of closed loop SAF control with the
SVPWM technique there is only a minor improvement in THD. The
utilization of the DC bus with SVPWM is also not significant
compared to that with SPWM because of the non sinusoidal
modulating signal from the controller in SAF configuration.
Abstract: Space Vector Pulse Width Modulation SVPWM is
one of the most used techniques to generate sinusoidal voltage and
current due to its facility and efficiency with low harmonics
distortion. This algorithm is specially used in power electronic
applications. This paper describes simulation algorithm of SVPWM
& SPWM using MatLab/simulink environment. It also implements a
closed loop three phases DC-AC converter controlling its outputs
voltages amplitude and frequency using MatLab. Also comparison
between SVPWM & SPWM results is given.