Optimisation of the distribution of power from a photovoltaic generator between two pumps working in parallel

Abstract

In this work, a method for distributing the power generated in a photovoltaic pumping system equipped with two equal pumps, working in parallel is analysed.For this purpose, a system equipped with two pumping groups 0.75 kW each was investigated. Experimental tests at five different working frequencies (30 to 50 Hz), and at six pumping heads (18 to 48 m) were carried out.The main objective of this paper is to establish a strategy for the distribution of the generated power that maximises the flow rate from the set of two pumps. This distribution depends both on the available electric power and on the pumping head.The results show some differences between higher and lower pumping heads, but in both cases for lower power values, the strategy involves the operation of a single pump with the limitation that the power assigned to this pump cannot exceed the maximum value (Pmax). However, if the available power exceeds a certain value, referred to as Pe, it must then be distributed at 50% between the two pumps. Thus, there is no power distribution ratio other than 0 and 50% that maximises the flow rate, except that required to limit the power assigned to one of the pumps to Pmax.It was proven that the optimal distribution strategy for the available power depends on whether Pe > Pmax (for higher pumping heads) or Pe < Pmax (in case of lower heads). In practice, it is easy to determine which case applies using a simple pumping test.