In this, artificial neural network controller is designed for LLC resonant converter for voltage regulation. The performance of the proposed converter with proportional-integral (PI) controller and ANN controller are analysed from the simulation results. A voltage mode control is provided to get regulated load voltage irrespective of the changes in supply. ANN controller is used for the voltage mode control and the efficiency of the proposed ANN controller is estimated and comparison is made with conventional PI controller. The simulation work is done with MATLAB/Simulink software.
In past, the conventional energy sources such as coal, gas, oil, etc, are utilized for power generation until the renewable sources are introduced for electrical power generation. Also, the regulations regarding emission of pollutants and impact on environmental pollution reduction caused the quick growth on these renewable sources. The Photovoltaic (PV) energy was utilized for charging the batteries in isolated areas and wind turbines also used in few occasions. These two energy sources are extended over other applications also and they both get combined to design hybrid system after the idea of grid connected system is introduced. Several new ideas regarding control circuits, design of converters, MPPT (Maximum Power Point Tracking), real and reactive power control and injection, etc, are proposed regarding the hybrid energy resources. The key issue in this is the availability of irradiation in solar and wind speed cannot be predetermined as it relied on the environmental conditions. The wind and solar energies are complement to each other and provides power almost all over the year is the main reason for choosing them for hybrid power generation. Hence these two can be used as main power sources and also it is possible to include an auxiliary power source such as battery, diesel plant, biogas, fuel cell, etc, as backup. As the power generation unit consists of multiple sources, it is more reliable than individual sources irrespective of the location of the power generation unit. It can be utilized in remote villages as the distribution of electrical energy from grid is near to impossible in those locations. A control strategy is important for the hybrid system in order to regulate the variables such as voltage, power, etc. As these renewable sources are volatile in nature voltage control is essential for the reliable power generation and distribution. Various renewable sources are interlinked using dc bus in which the voltage regulation is provided using controllers such as PI control (Proportional Integral), PID control (Proportional Integral Derivative), SM control (Sliding Mode Control), etc, in order to enhance the performance of the HRES.
In this paper, a dc-dc converter system with LLC converter is added to proposed system for providing voltage regulation for dc load. The resonant LLC converter is designed for dc-dc conversion and a comparison is made with conventional controller and proposed controller under varying load conditions. A simple voltage mode control loop is designed with PI and ANN controller and the performance of the proposed system is observed for these two controllers based on simulation results. A hardware prototype model was designed and both buck and boost operations are performed for the output voltage range of 4-20V with input voltage of 12V.
II. LLC CONVERTER
The proposed LLC converter is given in Fig 1 as follows:
In this, when Q1 is ON, the inductor get charged and the capacitor get discharged and provides energy to the primary winding of transformer. In secondary, the energy is utilized by the load with the help of diode rectifier. When Q2 is ON, the inductor starts discharging and provides energy to transformer primary and resonant capacitor. In this also, the load utilizes the energy induced in secondary with the help of diode rectifier.
A. Mode 1
This mode is started at the instant, switch Q2 is off. The ILr current starts to flow in opposite direction through the body diode of Q1. This will cause the secondary side diode D1 to conduct and Io starts to increase. The magnetizing inductance of the coupled inductor Lm is getting charged with input source voltage.
In this, a 12V dc voltage from regulated power supply of 12V, 1A is connected as source which provides energy to the inductor of the converter for boosting up the dc link voltage which is provided to the primary of coupled inductor which doubles the voltage across the secondary. The secondary is provided to the load via resonant capacitor and dc link capacitor. The secondary voltage is controlled by controlling the primary voltage which is done by controlling the pulse width of S1. A transformer is used to provide supply to the controller and driver circuit. The rectified voltage is provided to 12V regulator and arduino along with driver ics so that the arduino and driver circuit gets the Vcc supply. For buffer ic 5V regulator is used. The arduino generates pulses for converter switches. The pulses for switches S1-S4 are generated in arduino controller and provided with pins 2-5. The reference voltage is varied with the help of a variable resistor which is provided to the input pin A1. The pulses from pins 2 to 5 is provided to buffer ic which isolates the controller and driver circuit and also provides smooth pulses without disturbances. The output of buffer ic is provided to driver ic (individual ic for each switch) through resistance of 1000 ohm and the output of driver ic is provided to the switches.
The gate pulses for the converter switches (S1, S3, S2 and S4 respectively) are provided below in Fig 14:
In this paper, a LLC converter is designed with ann based voltage mode control loop and compared with conventional PI controller. The performance of the converters are noted in terms of efficiency and ripple voltages. The LLC converter is more efficient and provides less voltage ripples than that of other converters under study. The PI controller is replaced with ANN controller in voltage mode control loop of LLC converter. This leads to further increase in efficiency and reduction in load voltage ripples. A hardware prototype model is developed for 10W and load voltage is designed for the range of 4V to 20V with input voltage of 12V. Here in boost mode, 98% of load regulation is achieved at full load conditions.
 S. Chen et al., \"Research on Topology of the High Step-Up Boost Converter With Coupled Inductor\", IEEE Trans. Power Electron, vol. 34, no. 11, pp. 10733-10745, Nov. 2019.
 S. Singirikonda and Y. P. Obulesu, \"A novel approach using adaptive Neuro Fuzzy based droop control Standalone microgrid in presences of multiple sources\", Int. J. Renew. Energy Dev., vol. 9, no. 1, pp. 43-51, 2020.
 A. Murali, R. S. Wahab, C. S. R. Gade, C. Annamalai and U. Subramaniam, \"Assessing finite control set model predictive speed controlled PMSM performance for deployment in electric vehicles\", World Electric Veh. J., vol. 12, no. 1, pp. 41, 2021.
 S. Singirikonda and Y. P. Obulesu, \"Active cell voltage balancing of Electric vehicle batteries by using an optimized switched capacitor strategy\", J. Energy Storage, vol. 38, no. 102521, pp. 102521, 2021.
 S. Bairabathina and S. Balamurugan, \"Review on non-isolated multi-input step-up converters for grid-independent hybrid electric vehicles\", Int. J. Hydrogen Energy, vol. 45, no. 41, pp. 21687-21713, 2020.
 S. Singirikonda and Y. P. Obulesu, \"Battery modelling and state of charge estimation methods for Energy Management in Electric Vehicle-A review\", IOP Conf. Ser. Mater. Sci. Eng., vol. 937, pp. 012046, 2020.
 G. K. Kumar, Elangovan and G. Arunkumar, \"Multiple input interleaved boost converter for non-conventional energy applications\", 2019 Innovations in Power and Advanced Computing Technologies (i-PACT), 2019.
 S. Singirikonda and Y. P. Obulesu, \"Advanced SOC and SOH estimation methods for EV batteries-A review\" in Advances in Automation Signal Processing Instrumentation and Control, Singapore:Springer Singapore, pp. 1963-1977, 2021.
 G. Kiran Kumar, E. Parimalasundar, D. Elangovan, P. Sanjeevikumar, F. Lannuzzo and J. B. Holm-Nielsen, \"Fault investigation in cascaded H-bridge multilevel inverter through Fast Fourier Transform and artificial neural network approach\", Energies, vol. 13, no. 6, pp. 1299, 2020.
 G. V. Brahmendra Kumar and K. Palanisamy, \"A Review on Microgrids with Distributed Energy Resources\", 2019 Innovations in Power and Advanced Computing Technologies (i-PACT), pp. 1-6, 2019.
 G.V.B. Kumar and K Palanisamy, \"A Review of Energy Storage Participation for Ancillary Services in a Microgrid Environment\", Inventions, vol. 5, no. 4, pp. 1-36, 2020.
 G.V.B Kumar, P. Kaliannan, S. Padmanaban, J.B. Holm-Nielsen and F. Blaabjerg, \"Effective Management System for Solar PV Using Real-Time Data with Hybrid Energy Storage System\", Applied Sciences, vol. 10, no. 3, pp. 1-15, 2020.