Xantrex Technology PV-30208 - Manual (Page 17)

PV-30208 Photovoltaic Inverter
Operation and Maintenance Manual
Copyright 2003, Xantrex Technology
DOCUMENT: 151315 4-2
SECTION 4
OPERATION
OPERATION FEATURES
Automatic Phase Sequence Detection
During system power-up, the PV-30208 detects the phase rotation of the three-phase utility voltage as
seen at the inverter output terminals. The control software then determines the proper switching se-
quence for the output power stage. It is not necessary to maintain a particular phase sequence conven-
tion between the inverter and the utility point of interconnection.
Fixed Unity Power Factor Operation
The Xantrex PV series grid tied PV inverters maintain unity power factor during operation. The control
software constantly senses utility voltage, and constructs the output current waveform to match the
utility voltage. The PV line of inverters are not capable of operation without the presence of normal
utility voltage, nor are they capable of varying the output power factor off unity.
Variable Minimum DC Input Voltage Level
The minimum DC input voltage limit for the PV-30208 is a function of the utility AC line voltage. The
PV-30208 control software periodically changes the minimum allowable DC input voltage based upon
the actual line voltage during operation.
For monopolar PV array configurations: Minimum DC voltage will vary between 282 and 320Vdc for
line voltage fluctuations between factory set minimum and maximum line voltage limits. For example:
At the factory set high line voltage limit of 220.5, the minimum required DC input voltage is approxi-
mately 320Vdc. At the factory set low line voltage limit of 196Vac, the minimum required DC input
voltage is approximately 282Vdc. At nominal 208Vac, the minimum DC input voltage is 300Vdc.
For bipolar array configurations: Minimum DC voltage will vary between approximately 340 and
380Vdc.
Utility Voltage/Frequency Fault Automatic Reset
In the event of a utility voltage or frequency excursion outside of preset limits, the PV-30208 will stop
operation and annunciate a fault at the operator interface. Once the utility voltage has stabilized within
acceptable limits for a period of at least five minutes, the PV-30208 will automatically clear the fault
and resume normal operation. Voltage and frequency fault setpoints are detailed later in this section.
Active Island Detection
Much concern has been given to the possibility of an inverter causing a ‘utility island’ condition during
a utility power outage. An island condition is defined as grid tied inverter maintaining operation and
supporting a load that has been isolated from the utility power source. This requires the load to be
closely balanced to the output power of the inverter as well having a resonant frequency close to 60Hz.
Needless to say, this is a extremely remote possibility. To insure this condition does not occur, the PV-
30208 control software contains an active phase-shift-loop algorithm, which destabilizes a balanced
load, which may otherwise be capable of maintaining inverter operation in the absence of utility volt-
age. This feature has been extensively tested and proven to exceed the safety requirements of UL-1741
and IEEE-929-2000.