Integration of residential distributed generators and heat pumps into the low voltage grid from a voltage level perspective

Abstract

In context of combating climate change, carbon saving goals are defined on European level. One effect of this is the increased installation of photovoltaic, heat pump and combined heat and power systems on low voltage distribution grids. As the distribution grid was not designed to handle this quantity of distributed generators and large loads, there are undesirable influences. The voltage level is identified as the main issue in low voltage grids. From the point of view of a manufacturer of such devices the influence on possible connections to the low voltage grid and necessary measures are of interest. The characteristic voltage influence of combined-heat-and-power, heat pump and photovoltaic systems is evaluated. In order to quantify the influence, a 2020 penetration scenario of these devices is developed using market expectation data. It is shown that different grids show violations of the voltage limits according to EN 50160 and measures for voltage control are therefore necessary in order to integrate the anticipated number of appliances. A range of measures are evaluated regarding effectiveness, system operator and end-user economics, comfort and environmental influence. The measures are based on grid operator equipment or enduser appliances. Battery storage based measures are identified as effective but very expensive compared to other solutions. The most cost efficient measure is the installation of on-load tap-changers at the low voltage transformers. Demand side management of heat pumps can be effective under certain circumstances but end-user comfort is endangered here. Considering the total economics, demand side management is more expensive than the use of on-load tap changers. From a manufacturer perspective there are no additional requirements for end-user appliances identified for voltage control on low voltage grids. Connection restrictions and the grid planning process have to be reviewed in order to enable cost efficient integration of the anticipated number of appliances in 2020. The results are validated for increased generator penetrations in a ’maximum PV’ scenario.