1. Introduction

Nowadays, though there is an enormous degree of power production and energy conservation, there is a void which could be filled by familiarizing renewables into the power market. The major renewable energy sources include wind, solar, fuel cells, geo-thermal, tidal waves, and biofuel systems; by analyzing the pros and cons of all these sources, wind and solar energy

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seem to be economically accessible and less prone to pollution and thus becomes inevitable. Gearless construction with a total elimination of DC excitation system, compactness in yielding maximum power extraction, smooth grid interfacing, and ease in handling fault ride make PMSG the most sought appliance in wind power industry.

Since wind speed and wind power associated with wind force is not constant, the torque developed is not constant as well. Therefore, whenever PMSG is coupled with wind turbine, the output voltage generated varies in both frequency and magnitude. In order to synchronize load bus with grid of fixed frequency AC, the power output of PMSG is converted to DC and then inverted to 50 Hz AC. In addition, the change in DC-link voltage fluctuates in an uncontrolled manner, which has to be regulated by suitable modulation strategy applied to the inverter on grid side.

Considering these facts, a summary of the literature survey has been included to compare the research outcomes carried out so far on PMSG-based WECS. Various control strategies along with the modeling of PMSG were analyzed in order to control DC-link voltage, output power and pitch of the turbine in these articles elaborately [1–4]. Several maximum power point tracking (MPPT) algorithms were used to obtain the maximum power from the high-power turbines [5–9] with a simple and effective controller to ensure smooth control over voltage, frequency, and power output. The performance and analysis of an ultra-large wind turbine using validated models of mechanical and electrical systems of a wind turbine have been conducted under various conditions of step changes in wind speed generated by TurbSim [10]. A multipole PMSG model with maximum power point tracking (MPPT) mechanism was developed to extract maximum power in this paper [11]. Vector control and sliding mode control techniques were implemented to maximize the electromagnetic torque to regulate the DC bus voltage and concluded that PMSG was the best for wind power generation systems with good performance characteristics of speed, flux, and torque [12].

Various control algorithms were proposed and implemented to control the speed of PMSG with respect to wind speed in both generation and grid side to maintain the power flow [13–17]. PMSG performed well for step changes of load while implementing direct torque control (DTC)-based space-vector modulation, and the regulation of power factor was quiet good [18, 19]. Sensorless control strategies were compared with various modeling techniques, and simulation results were analyzed in these articles [20–23].

The two modulation techniques, namely sinusoidal pulse width modulation (SPWM) and space-vector pulse width modulation technique (SVPWM), are compared, and the resultant voltage space vector is found to be rotating consistently at synchronous speed with a magnitude 1.5 times greater than the peak value of the phase voltage [24]. The maximum power is obtained using the SVPWM modulation technique with the DC-link voltage kept at stable level to obtain decoupled control of active and reactive power. The DC voltage utilization ratio is around 71% of the DC-link voltage as compared to the conventional sinusoidal pulse width modulation which is found to be 61.2%. Space-vector PWM generates less harmonic distortion in the output voltage/current waveform in comparison with a sine PWM [25].

In this paper [26], the simulated results show that the proposed Fuzzy-PI controller is very effective in improving the transient stability of overall wind farm systems during temporary and permanent fault conditions. The main advantage of the proposed MPPT method in [27] is that there is no need of measuring wind velocity and generator speed. As such, the control algorithm is independent of turbine characteristics, achieving the fast dynamic responses with nonlinear fuzzy logic systems.

With the use of PI controller, the harmonic spectrum (THD) for load voltage and load current are found to be 1.31 and 37.92%, respectively. The harmonic spectrums for load voltage and load currents with fuzzy logic are 0.47 and 35.72%, respectively. Simulation results and harmonic spectrum obtained in [28] demonstrate that the fuzzy-based controller works very well and shows very good dynamic and steady-state performance. The research contributions of this technical article [29] deals with the development of single-ended primary-inductor converter (SEPIC)-based FLC-WECS which can maintain constant voltage at the output with minimized ripple content and improvement of dynamic response using fuzzy logic controller.

This paper [30] focuses on robust control based on T-S approach that allows tracking of rotational speed, stator current, and voltage references which correspond to the optimum power and therefore operate with the maximum power.

Here, this chapter discusses open-loop as well as closed-loop method with intelligent controller, and it is confirmed that sufficient revenue could be generated from it by implementing the same in real time with very little computation. The following sections dealt in detail about modeling of PMSG based WECS with its simulation, open-loop and closed-loop control with fuzzy logic technique and concluded with the note that the generated power exceeds load power, hence apart from meeting the load demands, it supplies the battery load in addition.
