Development of variable voltage variable frequency drive system for induction motor speed control

2.2.4 Improving the Dynamic Response of Scalar Control of Induction Machine 
Drive using Phase Angle Control 
A novel structure for improving the Dynamic Response of Scalar Control of Induction 
Machine Drive is using Phase Angle Control presented in this paper [17]. The problem 
discussed in this paper is where the Scalar technique has poor transient response limits 
when applied in high performance motor drive application while fast toque response 
is required. The purpose of this paper is to validate the improvements in the dynamic 
performances when phase angle control operates. Method used in this paper is to 
implement the Proportional Integral (PI) controller, Lookup table, Pulse width 
modulation (PWM), and Phase angle controller in MATLAB/Simulink. The result 
shows that torque reaches instantaneously to new steady state value when phase is 
controlled.
In addition, the phase angle controller has a two fast current loop that 
controls the stator voltage phase more quickly. This causes the improvement of 
dynamics performances of Scalar control which is the objective is successfully 
achieved. Figure 2.4 shows the block diagram closed loop control of the proposed 
method. 

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Figure 2.4: Block diagram showing the closed loop control of the proposed method 
[17] 
2.2.5 Hardware implementation of Simplified VVVF Inverter for Induction 
Motor Based on Space Vector Modulation (SVM) 
Paper [18] proposed a simplified variable voltage variable frequency (VVVF) inverter 
based on Space Vector Modulation (SVM) to control speed of three phase induction 
motor. The problem discussed in this paper is where the Sinusoidal pulse width 
modulation (SPWM) technique has a high Total harmonic distortion (THD). The 
purpose is to reduce THD value using the SVM method. The method implementation 
of VVVF is based on SVM technique that consists of LOOKUP table, Clarke 
transformation, magnitude or angle calculation, and duty cycle calculation. The VVVF 
inverter using dsPIC33F5128M C202. By using VVVF topology sinusoidal waves are 
controlled by magnitude and frequency variable. The experimental result validates that 
the SVM method is effective and efficient to control the speed and reduce THD. This 
is because by using SVM, the speed of the rotor is started to change continuously 
because of the change in the duty cycle generated by the modulation of the SWM 
technique. Figure 2.5 shows the hardware design for VVVF based on the SVM 
method. 

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Figure 2.5: Block Hardware Design for VVVF Based on SVM Implementation [18]