High Levels Of Renewable Penetration Research Articles

Affine Arithmetic-based DC Power Flow for Automatic Contingency Selection with Consideration of Load and Generation Uncertainties

Power systems operate under uncertainties from variations of loads and generation with time. Power flow in a power system becomes increasingly uncertain, especially when renewable energy, such as wind and photovoltaic generation, is integrated. In this article, a DC power flow approach based on affine arithmetic is proposed to quantify risks due to uncertainties. The proposed method has been applied to the automatic contingency selection under uncertainties. Numerical studies on IEEE test systems (30, 57, and 118 buses) have proved that the DC power flow approach based on affine arithmetic is a fast and reliable method for power system planning and operation when considering uncertainty. Test cases have shown that the proposed method is as fast as the conventional DC power flow while it is much more efficient than the Monte Carlo method. Thus, the DC power flow approach based on affine arithmetic serves as a new and effective decision support tool for planners and operators to cope with high levels of renewable energy penetration, electric vehicle load integration, and other uncertain scenarios.

Implementation and Control of a Residential Electrothermal Microgrid Based on Renewable Energies, a Hybrid Storage System and Demand Side Management

This paper proposes an energy management strategy for a residential electrothermal microgrid, based on renewable energy sources. While grid connected, it makes use of a hybrid electrothermal storage system, formed by a battery and a hot water tank along with an electrical water heater as a controllable load, which make possible the energy management within the microgrid. The microgrid emulates the operation of a single family home with domestic hot water (DHW) consumption, a heating, ventilation and air conditioning (HVAC) system as well as the typical electric loads. An energy management strategy has been designed which optimizes the power exchanged with the grid profile in terms of peaks and fluctuations, in applications with high penetration levels of renewables. The proposed energy management strategy has been evaluated and validated experimentally in a full scale residential microgrid built in our Renewable Energy Laboratory, by means of continuous operation under real conditions. The results show that the combination of electric and thermal storage systems with controllable loads is a promising technology that could maximize the penetration level of renewable energies in the electric system.

Metrics for evaluating the impacts of intermittent renewable generation on utility load-balancing

This study has developed metrics to evaluate the impact of intermittent renewable generation on the electric load demand that must be balanced by dispatchable generation resources, allowing examination of the general impacts of accommodating high renewable penetration levels. The metrics focus on the sizing, utilization and coordination of load balancing resources to meet the load demand in time. Insights gained from increasing the renewable penetration level in California as an example indicated the following. The balancing generator fleet displayed low capacity factors at high penetration levels. At penetration levels above 45% with no uninterruptable base load, surplus generation occurred and increased exponentially. The occurrence of daily maximum and minimum load points became increasingly unpredictable, rendering fixed time-of-use electricity pricing inappropriate. Capacities of peaker and base load generator type increased and decreased respectively. Net load variability decreased on the 24-h timescale and increased on all shorter timescales, implying changes in the temporal dispatch of balancing generators. The use of energy management strategies such as energy storage was found to be necessary in order to accommodate high renewable penetration levels with minimal impact. The simple metrics allowed identification of key areas to be addressed in order to accommodate high renewable penetrations.