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The IUP Journal of Electrical and Electronics Engineering:
Stability Analysis of Grid Connected PV System
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Power generated can be used effectively by interconnecting the grid with Photovoltaic (PV) generation as no storage is required. In this paper, a small signal state space model of a grid connected PV inverter with L filter is presented. Direct and quadrature axis inductor currents, input DC capacitor voltages and PV system voltage are considered as state variables. d-q components of duty cycle and grid voltage are taken as input vectors and the state variables are considered as output vectors. Transfer function of the PV system is deduced from its small signal state space model. Bode plots are plotted for variations in voltage of the PV system (Vp), power (P), inductance (L) and transconductance (K), thereby stability of the overall system is analyzed using MATLAB programming. The control system is implemented with fuzzy controller in MATLAB Simulink. The inverter generates balanced currents with Total Harmonic Distortion (THD) less than 4%.

 
 

Renewable energy resources are an interesting alternative to nonrenewable energy sources because they can be used on a large-scale without polluting the environment. Photovoltaic (PV) power generation is a concept of converting solar energy into direct current electricity using semiconductor materials. A PV system includes a solar panel which consists of a number of solar cells which are used to generate the required solar power. These renewable energies can be used efficiently with power electronic converters. When power converters are placed in the system, harmonics are generated due to the switching process and cause disturbances in the grid. So to avoid disturbance in grid, harmonics in grid current are reduced using filters like L, LCL and LC to make the Total Harmonic Distortion (THD) of the grid current within the acceptable limit (Figueres et al., 2007 and 2009; and Fazeli et al., 2014). However, the usage of these filters may lead to stability problems; it is analyzed using small-signal modeling of the system and verified for what range of parameter changes the system remains stable.

 
 
 

Photovoltaic (PV) system, Small-signal modeling , Fuzzy Logic Controller (FLC), Total Harmonic Distortion (THD)