A SURVEY OF SYSTEMS TO INTEGRATE DISTRIBUTED ENERGY RESOURCES AND ENERGY STORAGE ON THE UTILITY GRID Joseph A. Carr, Juan Carlos Balda, H. Alan Mantooth National Center for Reliable Electric Power Transmission University of Arkansas

Simple Direct Grid Connection

PEI For Doubly Fed Induction Generator

Voltage Step-Up  Most DER’s Requires boost or step-up transformers  Transformers provide isolation required by the National Electric Code

Multiple Connections  DER’s require arrays of individual modules  Array limited to weakest module

Separate Grid Connections  Advantages  Optimize each PEI to the DER  Each PEI is simple  Disadvantages  Grid Power Line Use  Increased power electronics

Microgrid Connections  Consolidate DERs on single bus  3 types:  Line Frequency  DC Bus  High Frequency AC

Line Frequency Microgrid

DC Microgrid

High Frequency AC Microgrid

Multiport Converters  Common Bus like Microgrids  No Direct Local Load Connection  Regulation of Bus not needed  Converters do not have to match bus specifications

Standalone Multiport

Modular Multiport

High Frequency Multiport

Modular HF Multiport

Summary