Equivalent circuit of photovoltaic generator using Newton-Raphson algorithm

摘要

Purpose - The purpose of this paper is to develop a linearized equivalent electrical circuit of a photovoltaic generator. This circuit is appropriate to confront problems such as numerical instability, increased computational time and nonlinearon-canonical form of system equations that arise when a photovoltaic system is modelled, either with differential equations or with equivalent resistive circuits that are generated by electromagnetic transient software packages for power systems studies. Design/methodology/approach - The proposed technique is based on nonlinear and well-tested ipv ~ vpv equations which are however used in an alternative mathematical manner. The application of the Newton-Raphson algorithm on the ipv - vpv equations leads to uncoupling of the ifiv and vpv quantities in each time step of a digital simulation. This uncoupling is represented by a linearized equivalent electrical circuit. Findings - The application of nodal analysis equivalent resistive circuits using the proposed equivalent photovoltaic generator circuit leads to a system model based on linear algebraic equations. This is in opposition to the nonlinear models that normally result when a nonlinear ipv - vpv equation is used. In addition, using the proposed scheme, the regular systematic methods of circuit analysis are fully capable of deriving the differential equations of a photovoltaic system in standard form, thus avoiding the time-consuming solution process of nonlinear models. Originality/value - In this paper, a new method of using the ipv - vpv characteristic equations is proposed which remarkably simplifies photovoltaic systems modeling. Moreover, a very important practical application is that by using this methodology one can develop a photovoltaic generator element in electromagnetic transient programs for power systems analysis, of great value to power engineers who are involved in photovoltaic systems modeling.