## 1 Introduction  
Grid-connected photovoltaic (PV) systems have acquired quite a good proportion of usage among different renewable energy sources. Every year, the amount of grid-feeding PV systems in use is increasing. As a result, it is becoming highly required that the grid-connected PV systems operate optimally to perform stable grid operation and meet user demand. One of the primary models for grid-connected solar PV is single-stage model that uses only a single converter. Such converters either can be voltage source or current source inverters. The control of the converters requires inner current control loops and an outer voltage control loop. The reference of the outer voltage control loop can be found by maximum power point tracking (MPPT) technique, and the output of the voltage control loop can be used a reference for the inner current control loop. These controllers require tuning of their respective parameters for optimal operation of the system. Development of different controllers for optimal operation of grid-connected distributed generation or PV systems has been widely described in different literature. [PERSON] et al. [1] proposed a grasshopper optimization algorithm-based optimal power flow controller for a grid-connected Distributed Generation (DG) system. The authors only tuned the outer control loop while keeping fixed internal loop values, which makes the system difficult to tune when the values of internal loop gain parameters are unknown. [PERSON] et al. [2] proposed a reactive power control and adaptive predictive current control strategy, where the Reactive Power controller (RPC) generates the reactive current usinga PI controller. [PERSON] et al. [3] proposed a three-level neutral point clamped inverter instead of a two-level Voltage Source Inverter (VSI) with voltage-oriented control strategy using proportional resonant (PR) controller. A fictitious reference iterative tuning method using particle swarm optimization for tuning a DC link voltage controller was proposed in [4]. In [5] authors discussed single-stage topology with a current source inverter (CSI) with MPPT and double tuned resonant filter. They also proposed series addition of a small DC link inductor with double-tuned resonant filter to eliminate harmonics. The authors used proportional resonant controller for voltage and current control loop. [PERSON] et al. [6] proposed sliding mode control to force the output voltage of the PV and grid power factor to follow a certain trajectory reference. This requires rigorous calculation for determination of control law. [PERSON] et al. presented a precise phasor model and employed an active power loop cascaded with an inner reactive power loop [7]. Few works also proposed methodologies to work under fault conditions. DC link voltage control of a grid-connected PV system with enhanced fault ride through capability enhancement was proposed by [PERSON] et al. [8]. The proposed control scheme includes control without MPPT which activates when DC link voltage exceeds the nominal value. In [9], [PERSON] et al. proposed a three-phase grid-connected PV system working with MPPT and non-MPPT mode to work under grid fault mode. Recently, [PERSON] et al. [10] designed a proportional resonant controller with resonant harmonic compensator for a grid-connected photovoltaic system. The authors have also proposed a switch-type fault current limiter for fault ride through a capability which can work under asymmetrical faults also. Although different methodologies have been proposed by different authors, almost all of them have considered the controllers with internal gain parameters; these works have rarely discussed any systematic approach for tuning of those parameters irrespective of the controller type, which is one of the most important issues while designing a successful controller.