The 3Φ induction motor is a broadly used electric machine in industrial applications, which plays a vital role in industries because of having plenty of beneficial impacts like low cost and easiness but the problems like decrease in motor speed due to load, high consumption of current and high ripple occurrence of ripples have reduced its preferences. The ultimate objective of this study is to control change in motor speed due to load variations. An improved Trans Z Source Inverter (ΓZSI) with a clamping diode is employed to maintain constant input voltage, reduce ripples and voltage overshoot. To operate induction motor at rated speed, different controllers are used. The conventional Proportional-Integral (PI) controller suffers from high settling time and maximum peak overshoot. To overcome these limitations, Fractional Order Proportional Integral Derivative (FOPID) controller optimized by Gray Wolf Optimization (GWO) technique is employed to provide better performance by eliminating maximum peak overshoot problems. The proposed speed controller provides good dynamic response and controls the induction motor more effectively. The complete setup is implemented in MATLAB Simulation to verify the simulation results. The proposed approach provides optimal performance with high torque and speed along with less steady state error.

In many industrial applications and irrigation systems, three phase induction motors are most commonly used. For several applications, fundamental field oriented control is realized by means of simple, easy control and highly efficient conventional cascade PI control system. The adaptive controller is designed for induction motor drives with inaccurate model to control speed but it has a drawback of high complexity [

A new and robust control is introduced in [

In single-phase qZSI PV system, a novel control scheme is suggested to minimize the requirement of capacitance [

A speed controller aimed at indirect field concerned with the IM drives control using FLC is developed [

An improved ΓZSI with a clamping diode is employed in this proposed work. The main aim is to control speed that varies with load. To operate IM at rated speed, different controllers are used to control the voltage source inverter. With conventional PI controller, settling time increases and maximum peak overshoot occurs. To overcome these limitations, FOPID controller is employed with GWO technique to eliminate maximum peak overshoot problems.

The block representation of the entire work is presented in

3Φ AC supply is given to the diode bridge rectifier. In 3Ф induction motor, the speed decreases due to load and the ripples get injected. This ripples get increased with the increase in speed. Due to this oscillation, the produced back emf is increased and it affects the source voltage. In order to rectify source voltage problem, diode bridge rectifier is employed, which involves in converting AC to DC. The output of diode bridge rectifier is given to improved ΓZSI, which significantly enhances the low DC voltage and minimizes the ripples in input voltage. The output of ΓZSI is fed to 3Ф induction motor through 3Ф VSI. The improved ΓZSI operates in shoot through mode to prevent short circuit problem. The current when pass through the short circuit side gets charged immediately. Advantages of this inverter are constant input voltage, reduction of ripples and voltage overshoots due to an additional clamping diode and high output voltage.

Basic structure of the proposed inverter is depicted at

An improved ΓZSI boost Factor (B) is expressed as,

Here,

Characteristic of improved ΓZSI are given below,

In improved ΓZSI, input current is continuous and there is no need for any extra filter.

Unlike Trans-ZSI, tZSI and ΓZSI, it delivers startup inrush current suppression since there is no current flow at startup to the major circuit.

It has maximum voltage gain. An improved ΓZSI uses lesser shoot through duty cycle with similar input or output states, which in turn results in lesser voltage stress and improved power quality output.

Improved ΓZSI with clamping diodes circuit of mode 1 is depicted in

All switches of same legs are switched ON in shoot-through mode and network is similar to short circuit. In this mode, diodes

The circuit of improved ΓZSI in mode 2 is depicted in

It contains two zero modes as well as six active modes. Diodes

DC-link voltage ratio at bridge inverter is known as boost factor of inverter. A simplified circuits of improved ΓZSI inverter during mode 1 and mode 2 are depicted in

Apply KVL in shoot through mode,

Similarly, Apply Kirchhoff’s Voltage Law in non-shoot through mode,

Here, the input voltage is specified as

Substitute

Across

Substitute

Improved ΓZSI with clamping diode’s DC-link potential,

Thus, the Boost factor

The potential and torque equations, which characterize dynamic behavior at induction motor aid in explaining the differential equation at trouble-free way. In order to reduce difficulties in solving the equations, a change in variable is employed by neglecting time fluctuating inductances. The circuit diagram of induction motor is significantly highlighted in

Even though real parameters remain sinusoidal, it is beneficial for obtaining device variables like dc quantities. These are accomplished through requiring the reference frame that is same as that of sinusoidal variable at the same angular speed. Instead of calculating every particular reference frame, this is beneficial to maintain common conversion of arbitrary reference frame.

If the uniformity among 3Φ and 2Φ machine is known, it is possible to obtain dynamic model of induction motor. The similarities depend on quantity of magneto motive force created in 2Φ as well as 3Φ windings with uniform current magnitudes. Consider every 3Φ winding as well as 2Φ windings that have

where,

Interconnection between

In direct and Quadrature axes, the above equation is expressed as,

By using forthcoming transformation the prompt value of stator as well as rotor currents are computed and it is expressed as,

The currents are find by substituting the value of flux linkage,

Torque plus speed in rotor are expressed like,

The sum of proportion and integration coefficient is known as PI controller. The schematic representation of PI is depicted in

At the same control error, proportion coefficient is greater and output power is low. To control proportional integral controller, position integration time is set to zero and proportion time is set to maximum. It attains periodic oscillation of device by gradually lowering the proportionality coefficient. The value received from proportionality coefficient is twice greater than optimal value of integration time. Problems faced by IM with PI controllers are increase in settling time and occurrence of maximum peak overshoot and also takes lot of time to stabilize the speed that aids the working of machine.

On comparing with integer order controller, FOPID controller gives enhanced performance. The block’s schematic representation for FOPID controller is presented in

As a part of control system, it uses fractional order integration. By using fractional calculus, it improves and generalizes well established system and control strategies. Due to their additional degrees of freedom, the fractional order controller is selected. The controller order of fractional satisfies the criterions like sensitivity, specification, removing steady state error.

When comparing fractional order PID controller with conventional PI controller, it gives better performance with good dynamic response.

The generalization of non-integer order of fractional PID controller is expressed as,

Here, the control signal is signified as

To tune proportional integral controller, the gray wolf optimizer is used. This novel population established algorithm is developed through aging. This technique imitates the social hierarchy as well as hunting performance of grey wolves. In GWO algorithm, four kinds of groups namely

A number of parameters are needed in this algorithm in order to be set are,

Initialize

Search the search agent’s amount.

Amount of iterations found is maximum.

Number of positions chosen as searching the neighborhood and the criteria for stopping.

One of the major steps for grey wolf hunting is given below,

Tracking, chasing as well as impending prey.

Pursuing, encircling as well as distressing prey till that ceases to move.

Violence against prey.

Almost appropriate solution is considered as alpha

where,

So far, the first three finest solutions has been attained and update other search agents to change their locations according to location of finest hunt agents. Thus the given expressions projected is regarded as follows,

Update current GW position is expressed as,

From this, we know that

A source voltage waveform of improved ΓZSI is depicted in ^{o} with respect to one another. It has the power to boost up input voltage in a wider range.

An input potential of improved ΓZSI waveform is depicted in

An output potential of improved ΓZSI waveform is depicted in

An

Speed waveform of IM with proportional integral controller is depicted in

Waveform for Induction motor instant response through FOPID controller is depicted in

The waveform of IM speed using GWO-FOPID is depicted in

The proposed method contains 3

FPGA controller is employed to operate motor at a constant speed and also 3

Input voltage of improved ΓZSI is depicted at

Output potential of the improved ΓZSI is depicted in

Output voltage of 3Ф VSI is depicted in

The VSI output potential with filter is depicted

Speed waveform with PI, FOPID and GWO-PI is illustrated in

After analysis of time domain, peak signal amplitude needed by motor is reduced from

The torque variable with PI controller, FOPID and GWO-FOPID are listed out in

Controllers | Speed = 1390 RPM | Torque = 2.1 Nm | ||||||
---|---|---|---|---|---|---|---|---|

PI | 1.52 | 1.6 | 1.7 | 1.8 | 1.33 | 1.44 | 1.71 | 1.2 |

FOPID | 1.53 | 1.56 | 1.61 | 1.6 | 1.16 | 0.96 | 1.24 | 0.92 |

GWO-FOPID | 0.53 | 0.72 | 0.8 | 0.9 | 0.42 | 0.57 | 0.63 | 0.8 |

Motor speed efficiency comparison of PI, FOPID and GWO-FOPID is depicted in

The performance of the GWO-PI controller in terms of raise time, peak time, settling time and steady state error is analogized with other existing controllers as highlighted in

An improved ΓZSI with a clamping diode is proposed in this work. To operate the induction motor at rated speed, different controllers are used to control the voltage source inverter. With conventional PI controller, settling time increases and maximum peak overshoot occurs. Additionally, fractional order PID controller and GWO technique that employed in enhancing its enactment of speed control of IM. Fractional order PID control is employed to enhance the performance of PI controller and also provide good speed response as well as steady state error. Moreover, Gray wolf optimization technique is used to optimize maximum peak overshoot problems in PI controller. In accordance with the comparative analysis of motor performance under optimal torque and speed values, it is validated that the speed response of rise time, settling time and peak time have been improved upto 50%, 44% and 36%. The improvement in reduction of steady state speed error and torque error are 40% and 20%. The whole performance is executed in MATLAB simulation.