Comparison of Fuzzy and ANFIS Controllers for Asymmetrical 31-Level Cascaded Inverter With Super Imposed Carrier PWM Technique

ABSTRACT:

 The modified topology for an asymmetrical 31-level cascaded inverter is analyzed with less number of DC voltage sources, power diodes, and power electronic knobs. The Super Imposed Carrier Pulse Width Modulation (SIC-PWM) is proposed for a 31-level asymmetrical modified cascaded inverter topology to reduce the Total Harmonic Distortions (THD). The Fuzzy logic controller (FLC) and Adaptive Neuro-Fuzzy Inference System (ANFIS) are suggested for a 31-level asymmetrical modified cascaded inverter topology to control the root mean square (RMS) voltage. These controllers help in maintaining the output voltage constant even when there is a change in input voltage to the inverter. This study aims to compare Fuzzy logic and ANFIS controllers by applying them to the 31-level cascaded inverter. Using both the controllers the inverter is controlled and its performance is compared using a step response tool in MATLAB. The study of the proposed modified 31-level Asymmetrical cascaded inverter is carried out to evaluate the THD without and with Fuzzy logic and ANFIS controller. Using the step response tool, Settling Time, Overshoot, RMS Voltage values, Peak Time, Peak value, and Rise Time were evaluated and compared for Fuzzy and ANFIS controlled 31-level asymmetrical cascaded inverter. The THD value for without a controller is 4.97%, with the fuzzy logic controller is 4.15% and with ANFIS controller is 3.77%. In both MatLab and real-time simulation, total harmonic distortion (THD) is observed to be the almost same and is lower than 5% which is under IEEE standards. The performance of Fuzzy and ANFIS controlled 31-level asymmetrical cascaded inverter is evaluated and compared with the use of MATLAB/Simulink and the same is done with Real-Time simulation using OPAL-RT 5700.

 KEYWORDS:

1.      Asymmetrical cascaded inverter

2.      Super imposed carrier PWM technique

3.      Total harmonic distortion

4.      Adaptive neuro-fuzzy inference system (ANFIS)

5.      Fuzzy logic controller (FLC)

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Figure 1. The fundamental circuit diagram of symmetrical and asymmetrical cascaded inverter.

 EXPECTED SIMULATION RESULTS:

 

Figure 2. Load wide output voltage for 31-level modified asymmetrical inverter.

 

Figure 3. Output Current through load for 31-level modified asymmetrical inverter.

Figure 4. FFT Analysis for output voltage of 31-level modified asymmetrical inverter.

 

Figure 5. Reference and output RMS voltage for 31-level inverter with fuzzy.

Figure 6. Output voltage across load with Fuzzy logic controller.

Figure 7. FFT analysis for 31-level inverter with fuzzy.

Figure 8. Output voltage across load with ANFIS controller.

CONCLUSION:

The proposed modified 31-level Asymmetrical cascaded inverter with and without Fuzzy logic and ANFIS controller is presented in this paper, demonstrating a substantial change in THD percentages and RMS voltage control. The proposed modified 31-level Asymmetrical cascaded inverter with Fuzzy logic and ANFIS controller is designed in MATLAB/ SIMULINK and verified in Real-Time simulation using OPAL-RT 5700. By using Super Imposed Carrier Pulse Width Modulation (SIC-PWM) with and without the controller, the RMS output voltage is controlled and THD is decreased. The performance of step response parameter values is evaluated and compared for Fuzzy and ANFIS controlled 31-level Asymmetrical cascaded inverter. The dynamic conditions were also analyzed for different DC source voltages and variable resistive loads, the RMS output voltage is controlled and maintained constant (i.e., RMS value is 21.98V for Fuzzy and 22.21V for ANFIS). Using the analytical solution for a 31-level cascaded inverter, it has been identified that the THD value for without a controller is 4.97%, with the fuzzy logic controller is 4.15% and with ANFIS controller is 3.77%. As compared to the Fuzzy logic controller, the ANFIS controller gives better performance. i.e., the RMS Voltage is controlled and settled in less settling time.

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