Keywords

1 Introduction

To preserve the earth for next generation, environmental friendly energy solution is required to overcome the demanding load and global warming. For that, we need more renewable-based technology that could provide sustainable and pollution-free technology. There are several benefits of the non-conventional technologies offer the potential of clean, less effect on the environment and abundant energy collected from self-renewing resources like sun and wind. In power electronics technology, renewable energy resources are now being use with energy storage systems and this type of integration of more than two technologies [1] are now in trend. Based on the consideration of low technological cost, several environmental benefits and their relative policies, so that penetration of hybrid renewable energy has grown rapidly in last two decades. Later on due to several technological advancements on distributed power generation has given the concept of microgrid, where more than one renewable resource integrate with other sources like the battery storage system could serve the demand power to the load [2]. So, these issues must be suppressed. BESSFootnote 1 works as an uninterruptible power backup energy source that is capable to provide a definite amount of power into the desired load, when the combined wind turbine system and solar photovoltaic system cannot meet the overall load demand under all conditions [3]. Our HRES-based proposed technique has designed to deliver continuous power into the load or utility grid. Sudden load-level fall causes several power quality issues such as harmonic distortion. Therefore, FFT-based analysis will be utilized for providing the power quality solution to entire grid system.

1.1 Issues and Recent Developments in the Hybrid-Based Grid System

Each conventional technology is in a several stage of research and development based on the many factors such as availability of different resources, cost, and their potential impact on the environment. There are several disadvantages of BESS such as battery cost as well as there is no guarantee to meet the certain load demands by BESS at all the times, especially when sufficient PV–wind generation to meet the desired load level at good environmental conditions. Conventional energy resources in the form of various renewable-based distributed generations and microgrid with artificial control techniques are emergent technology in the current electrical deregulated power system, because of the growing in power demand and decay in power generation by the fossil fuels for clean environmental aspects. To improve and maintain the power quality, new strategies for better reliability are required with the increasing number of renewable energy resources. The modern artificial-intelligence-based technological advancement has played a vital role such as wavelet-artificial-neural-network-based approach for the short-term day-ahead power production prediction from the base of irradiance and wind speed variation. These intelligence based approach offering the open doors for the grid independent system operator to preplan and management of power dispatch. Today’s population growth rate increasing day by day, which directly leading to the power demand. Several modern techniques of power generation have concerns with growth in power demand, while conservation of the environment stances is an emergent challenge.

2 Description of Proposed Hybrid-Based Grid Integration System

Saib and Gherbi [4] described the concept and principle of the hybrid system and its control. The wind turbine system with PMSG unit which converts wind power into electrical power [5] (generally converts AC into DC power with a rectifier bridge). The Solar PV-System with converter unit, Converts the PV-power into DC power and then both generation units coupled with MPPT system for maximize the power. Both the wind–PV powers fed into common DC link, which is coupled through VSC, where a battery backup system also attached. This BESS is installed to provide the required load power under deficit PV–wind power generation conditions (Fig. 1).

Fig. 1
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External layout of a grid system with several sources and their control configurations

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2.1 Modeling and System Specification of Proposed Methodology

The aim of this proposed methodology is to control the generation based on load demand [4] and energy storage for the load/utility system comes from the accumulated battery storage system or the hybrid renewable energy based system [6]. Microgrid loads can operate next to the other network or can switch to another utility grid to provide continuously electrical power; otherwise, the energy system of the microgrid can change to a reserve of accumulators, such as a battery source. Hill-climbing-based MPPT techniques provide the maximum amount of power [7, 8], under the variation of atmospheric conditions, which are variable in nature such as variations in solar irradiance (in W/m2) and wind speed (in m/s2). (Figure 2, Table 1)

Fig. 2
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Demonstration of a hybrid PV–wind-based renewable energy system with a battery backup source using MATLAB/Simulink toolbox [9]

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Table 1 Specification of several parameters associated with the hybrid grid system
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3 Design of Fuzzy Logic Controller for PWM Inverter Control

The FLC control technique for PWM-based inverter voltage control is capable of providing power balance to the microgrid. These three PV–wind-battery energy sources coupled to a fuzzy-logic-based inverter, which clamps the output voltages of the inverter at a desired level by comprising the inputs such as Errors (E) and Change of Error (COE). Description of fuzzy-based rule matrix with “if and then rule” referred in Table 2. In the proposed modes of operation, a fuzzy-logic-based control strategy regulates the gate pulse so, as to give the desired gate signal to operate the PWM-based inverter [8]. Symmetric rules of 49-rule base applied to the inverter pulse control using “MAMDANI” fuzzy interface method.

Table 2 49-rule base of input error and input change of error
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A pulse generator is employed to provide the desired gating pulses for IGBT-based inverter as shown in Fig. 3. The FLC control procedure for VSC-based voltage controller is capable of providing balance power conversion to the microgrid. This type of inverter introduces the unusual harmonics, which further feed into the load/utility grid [10].

Fig. 3
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Subsystem simulink model of IGBT-based inverter control using FLC

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In the proposed modes of operation, FLC-based control strategy regulates the gate pulses of 4 kHz. Therefore it provides the desired 6 gate signals to operate the PWM based inverter. Figure 4a, b, respectively, represents that how the output variables are dependent corresponding to the membership function, using fuzzy logic controller for our proposed methodology. Seven-term fuzzy sets are provided earlier with trapezoidal and triangular shapes of the desired output variables, i.e., for alpha output levels are as; NLmf, NMmf, NSmf, Zmf, PSmf, PMmf, and PLmf.

Fig. 4
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a Three-dimensional surface viewer b membership function of desired Output ‘α’

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4 Simulation Result of Proposed Hybrid System

There are several operational modes, which includes grid operation with or without the use of battery in such a manner provide continuous power to the 4 kw load. Short-term solar irradiance amplitudes [1000 850 0 500] in W/m2 are varying corresponding to the time [0, 2, 3 and 5] in s. While the wind speed are varying [5 12 9 0] in m/s2 with respect to the time variation [0, 5, 3 and 4] in s (Fig. 5).

Fig. 5
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Characteristics of load power corresponding to generation power (PWind–PV-Battery)

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If the PV–wind generation have sufficient power to maintain the load demand, then the battery energy system is in charging state (0–3 s), else battery is in discharging mode (3.1–6 s) (Table 3).

Table 3 Operational analysis of several parameters associated with the hybrid grid system
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For maintaining the desired load demand and minimum penalties, it is essential to balance real and reactive power level in the grid system. Due to inductive nature of the load, it causes the reactive power injection, reduction of real power (or useful power), and reduction of overall fundamental power values in the power lines. Therefore, the usage of these quantities must be suppressed which is essential for grid operation under better power quality consideration.

Generally, harmonics are presented and passed through the power line but these limits must be within the definite range, these values are directly affects the overall power quality in such a manner that reactive power and real power must be preceded.

These quantities further relates with the THD [11, 12] using fast Fourier transformation analysis [13]. The THD analysis based on the standard code (according to IEEE-519, necessitates limit is up to 5% for total harmonic distortion [14]) within the definite limit is shown in Table 4.

Table 4 Overall power quality analysis of proposed grid system using FFT
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5 Conclusion

The simulation study shown that PV system and wind energy system with an emergency battery backup system is sufficiently capable to provide the continuous power for maintain the utility/load level. The overall dynamic performance of the wind–PV-battery-based hybrid grid system is achieved using fuzzy-based controller. Our simulation study achieved using fuzzy-logic-based PWM inverter with LC filter, and we can also employ the C-type filter for harmonics reduction effectively. THD analyzed using FFT toolbox to examine the harmonic behavior. The simulation results of HRES-based proposed methodology shown the overall performance and reliability of the generation units to feed the continuous power into the load. The renewable-based wind energy system and solar PV system used as significant energy sources operating with or without use of BESS to get the continuous power to the load. Our proposed methodology maintained the growth of distributed power generation in remote places such as rural areas at reasonable costs.