Analysis of Inverters with ANN Controllers for THD Minimization

This report provides a comprehensive overview of inverters and their applications, focusing on the use of Artificial Neural Network (ANN) controllers for Total Harmonic Distortion (THD) minimization. It begins with an introduction to inverters, their role in power conversion, and their widespread applications in various industries, including power generation and transmission. The report then delves into multilevel inverters, highlighting their advantages over conventional inverters, such as reduced harmonic distortion and lower switching losses. A specific focus is given to H-bridge inverters, their applications, and their limitations, which lead to the exploration of asymmetrical cascaded H-bridge inverters. The core of the report centers on the design of an ANN controller for THD reduction. The design utilizes a Genetic Algorithm (GA) to determine optimal switching angles, which are then used to train the ANN. This approach enables the ANN controller to effectively eliminate harmonics, as demonstrated in the context of a two-level three-phase inverter. The report references key publications and research papers that support the concepts and methodologies discussed.

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ANN Controllers
Student’s Name
Institutional Affiliation
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Introduction
An inverter can be generally defined as a device that transforms DC power into AC
power or DC power from one level to another (dc-dc conversion) (Rashid, 2010). However,
the term is used more specifically to define devices that convert dc to ac power. Despite the
fact that the inverters operate on dc power sources as the input, this dc power is sometimes
derived from ac supply, for example from the utility ac source (Rashid, 2010). This ac power
is first converted into dc power using rectifiers after which it is fed to the inverter.
The need for inverters and their application areas
Inverters are very useful devices and find applications in many electrical and
electronic applications. In the power generation industry, inverters are used in solar and wind
power generating stations to convert the direct current from storage batteries into alternating
voltage, for instance, for connection to the grid. They are also used in High Voltage DC
(HVDC) power transmission systems to convert the transmitted power back to ac.
Multilevel inverters
The rising use of high power, high voltage apparatus in many industrial applications has
led to the development of multilevel inverters. These are inverters that generate stepped
voltage waveforms using an array of power semiconductors in conjunction with capacitor
voltage sources (Colak, Kabalci, & Bayindir, 2011). The higher the number of steps (levels)
in a multilevel inverter, the more the steps in the output waveform. Multilevel inverters offer
several benefits over their conventional counterparts. These include,
i) They are capable of generating an output voltage with very low distortion and low
dv/dt stress

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ii) They can operate at lower switching frequencies hence have lower switching loss
and higher efficiency
H-bridge inverters
An H bridge inverter is a type of single phase inverter that allows the application of a
voltage across a load in either direction. Its basic implementation requires the use of four
controlled electronic switches such as IGBTs and MOSFETs that change states pairwisely
(Prayag & Bodkhe, 2017). They are commonly applied in robotic applications and other
applications that require the forward and backward operation of DC motors (Khoucha,
Lagoun, Kheloui, & Benbouzid, 2010).
Drawbacks of the H bridge inverter
The half-bridge inverter exhibits several disadvantages which makes it unsuitable for use
in certain applications. These drawbacks include,
i) For nonresistive loads, it is incapable of generating zero/null output voltage
intervals.
ii) The maximum peak output voltage pulse is 50 % that of the input dc voltage
iii) At the dc input stage, two electrolytic capacitors must be connected in series
which increases cost and the number of harmonics generated.
According to Prayag & Bodkhe (2017), most of the drawbacks associated with the h
bridge inverter can be overcome by using an asymmetrical cascaded multilevel h bridge
inverter which produces greater voltage levels as well as higher peak voltage using an
equal number of bridges.
ANN controller design

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Total Harmonic Distortion (THD) in converters can be reduced or eliminated by using
pulse width modulation (PWM) in combination with a technique known as Selective
Harmonic Elimination. In this design, the optimum switching angles are determined using
artificial neural networks (ANN) to solve a set of nonlinear equations. These angles are
then used to generate PWM signals. Genetic algorithm is used as the primary method for
generating the optimum switching angles which are then used to train the ANN. This
design produces an ANN controller which is capable of eliminating harmonics. Deniz,
Aydogmus, & Aydogmus (2016) used this design technique to successfully eliminate
low-order harmonics from a two-level three-phase inverter.

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References
Colak, I., Kabalci, E., & Bayindir, R. (2011). Review of multilevel voltage source
inverter topologies and control schemes. Energy Conversion and Management,
52(2), 1114-1128. doi:10.1016/j.enconman.2010.09.006
Deniz, E., Aydogmus, O., & Aydogmus, Z. (2016). Implementation of ANN-based
Selective Harmonic Elimination PWM using Hybrid Genetic Algorithm-based
optimization. Measurement, 85, 32-42. doi:10.1016/j.measurement.2016.02.012
Khoucha, F., Lagoun, S. M., Kheloui, A., & Benbouzid, M. E. (2010). Symmetrical and
asymmetrical H-bridge multilevel inverter for DTC induction motor drive
automotive applications. 2009 35th Annual Conference of IEEE Industrial
Electronics. doi:10.1109/iecon.2009.5414710
Prayag, A., & Bodkhe, S. (2017). Performance evaluation of Symmetrical and
Asymmetrical Cascaded H Bridge Multilevel Inverter Topology. International
Journal of Engineering Research and Applications, 07(07), 20-24.
doi:10.9790/9622-0707102024
Rashid, M. H. (2010). Power Electronics Handbook: Devices, Circuits, and Applications.
Amsterdam, Netherlands: Elsevier.