Bidirectional 3 phase power meter for compensating reverse load flow and method for metering thereby

摘要

The present invention relates to a bidirectional 3 phase power meter for compensating reverse load flow and a method for metering thereby. According to the present invention, there is provided a bidirectional 3 phase power meter for compensating reverse load flow which allows calculating power receiving and power transmitting apparent power and power factor using the detected voltage/current and a method for metering thereby.

主权项

1. A bidirectional 3 phase power meter for compensating reverse load flow comprising:
a voltage/current detecting unit detecting a voltage per phase or current per phase; a bidirectional measuring unit measuring power receiving direction or power transmitting direction by calculating phase difference per phase using the voltage per phase or current per phase value and calculating neutral line current; an instantaneous power calculating unit calculating instantaneous power by using the voltage per phase or current per phase and the phase difference per phase; a reverse load flow determining unit determining occurrence of reverse load flow through the phase difference per phase and the neutral line current calculated from the bidirectional measuring unit; a reverse load flow calculating unit calculating reverse load flow power generated when the reverse load flow determining unit determines occurrence of reverse load flow; an actual power usage calculating unit calculating actual power usage by calculating instantaneous compensation power per phase and 3 phase instantaneous compensation power using the instantaneous power and the reverse load flow power; a power transmitting/receiving direction determining unit determining active power or reactive power of the actual power usage; a power meter value storing unit compensating the amount of active power and reactive power calculated from the power transmitting/receiving direction determining unit and accumulating and storing the result; and an apparent power/power factor calculating unit calculating apparent power and power factor using the active power and reactive power stored at the power meter value storing unit and the amount of accumulated power, wherein the reverse load flow determining unit further comprises: a negative-sequence selecting unit selecting a negative-sequence from a positive-sequence and a negative-sequence; a current intensity comparing unit comparing a negative-sequence intensity outputted from the negative-sequence selecting unit with a zero-sequence intensity; a plurality of voltage phase difference comparing units comparing phase difference of voltages per phase; a first AND gate comparing outputs of the voltage phase difference comparing units; and a second AND gate comparing outputs of the current intensity comparing unit and the first AND gate.