Power Quality
The electric power quality service involves using storage to protect customer on-site loads downstream (from storage) against short-duration events that affect the quality of power delivered to the customer’s loads. Some manifestations of poor power quality include the following:
- Variations in voltage magnitude (e.g., short-term spikes or dips, longer term surges, or sags).
- Variations in the primary 60-hertz (Hz) frequency at which power is
- Low power factor (voltage and current excessively out of phase with each other).
- Harmonics (i.e., the presence of currents or voltages at frequencies other than the primary frequency).
- Interruptions in service, of any duration, ranging from a fraction of a second to several seconds.
Technical Considerations
Storage System Size Range: 100 kW – 10 MW
Target Discharge Duration Range: 10 seconds – 15 minutes
Minimum Cycles/Year: 10 – 200
Typically, the discharge duration required for the power quality use ranges from a few seconds to a few minutes. The on-site storage system monitors the utility power quality and discharges to smooth out the disturbance so that it is transparent to the load.
The upper plot in Figure 15 shows a voltage spike of 50 volts (V) and the lower plot shows storage absorbing the 50V-spike to maintain a constant 480V to the load. These anomalies in the electric supply to the customer, which can occur several times in quick succession due to events in the T&D network that supplies the customer, need to be corrected to protect sensitive processes and loads at the customer site.
