Project Sponsors:ADVANCED POWER & ENERGY PROGRAM

www.apep.uci.edu

GOALS

1. Characterize the dynamic behavior of an advanced nanogrid comprised of solar PV, battery energy

storage system, and electric vehicle charging.

2. Assess the impact of the nanogrid on the connected primary microgrid circuit power quality.

3. Determine preferred battery dispatch strategies.

RESULTS

Four different BESS control modes were tested: (1) Peak-load-shifting (PLS), (2) Minimize Peak

Period Impact (MPPI), (3) Cap-demand, and (4) PV-capture (Fig.2).

A power quality survey combined with a harmonic load flow model allowed total harmonic

distortions (THD) to be calculated (Fig.3).

All voltage THD remained below the 5% threshold (IEEE 519 -1992). Transformers T1 and T2

delta/wye grounding scheme trapped 3rd harmonics. Harmonic cancellation also occurred due to the

effect of 20 EVs charging simultaneously.

OVERVIEW

Microgrids with distributed assets including renewable energy sources and Zero Emission Vehicles

(ZEV) are emerging to play a key role in offsetting greenhouse gas emissions and fossil fuel reliance.

Given this trend, it is expected that the integration of these new components will affect the power quality,

stability, integrity, and also reliability of the power distribution system.

As part of the Irvine Smart Grid Demonstration (ISGD) project, a unique distributed energy

resource has been deployed in a primary circuit of University of California, Irvine (UCI) Microgrid. On the

roof of a parking structure, 48kW of PV panels are installed to power 20 monitored EV chargers. The

system is integrated with a 100kW/100kWh battery energy storage system (BESS) (Fig.1).

Figure 1 – The Car Shade System

An Integrated PV/Battery for EV Charging in a Microgrid Topology

RESULTS (continued)

October, 2015

U.S. Department of Energy

Southern California Edison

Figure 2 – BESS modes daily dynamics

Figure 3 –Car Shade nanogrid voltage THD

0.92 %

1.51 %

3.08 %

1.47 %

1.54 %

1.52 %

PCC

Peak Load Shifting Minimize Peak Period ImpactMinimize Peak Period Impact

CAP demand – 20 kW PV Capture

A steady state load flow model calculated daily voltage profiles under different BESS operation

modes. Preferred modes have voltage profiles above 95% p.u. within the nanogrid. CAP 20 mode

showed such low voltages (Fig.4)

Table 1 ranks BESS dispatch modes in under-voltage occurrences, ability to increase PV contribution

to EV charging, and ability to zero-net charging demand.

Figure 4 – CAP demand 20 KW voltage profile

Table 1 – BESS modes ranking per category

PERSONNEL

Graduate Student: Laura Novoa

Principal Investigators: J. Brouwer, G.S Samuelsen

Advanced Power and Energy Program

University of California, Irvine

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