Electricity from Sunlight, 2nd Edition

4Grid‐Connected PV Systems

4.1 Introduction

Photovoltaic (PV) systems are generally divided into two major categories: grid‐connected (also known as grid‐tied) systems that are interfaced to an electricity grid and stand‐alone systems that are self‐contained. Over the years it has been customary for books on PV to describe stand‐alone systems first, probably because they are seen as “pure PV.” Also we should remember that stand‐alone systems, including those launched into space and the solar home systems (SHSs) that supply electricity to individual families in developing countries, accounted for much of the PV industry in its early days. But since the 1990s the market has shifted decisively toward PV power plants and installations on buildings connected to an electricity grid. In 2000 grid‐connected PV had overtaken stand‐alone systems in global market share, and in 2016 more than 98% of solar cell production was being deployed in grid‐connected systems. In many ways such systems are simpler to design and describe than their stand‐alone cousins. For both these reasons our own story begins with grid‐connected PV.

Since most people have seen PV arrays mounted on the roofs of homes, this seems a good place to start. Figure 4.1 shows the elements of a domestic PV installation, typically with an array power between 3 and 8 kW_p, interfaced to the local electricity grid. The major advantage of this arrangement is that the output from the PV array is fed into the grid when not required ...