This component models the load characteristics as a function of voltage magnitude and frequency, where the load real and reactive power our considered separately using the well known expressions:
And,
Where,
|
Equivalent load real power |
|
Rated real power per phase |
|
Load voltage |
|
Rated load voltage (RMS, L-G) |
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dP/dV Voltage index for real power |
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dP/dF Frequency index for real power |
|
Equivalent load reactive power |
|
Rated reactive power (+inductive) per phase |
|
dQ/dV Voltage index for reactive power |
|
dQ/dF Frequency index for reactive power |
NOTE: dQ, dP, dV and dF are in all per-unit quantities
If this component is used in single-phase mode, every half cycle (at the appropriate voltage zero), the shunt resistor is updated to reflect the non-linear load effect as a function of RMS voltage and frequency. Similarly, the shunt inductor or capacitor, in parallel to the load resistor, is updated every half cycle (at its voltage zero) to reflect its non-linear characteristic.
If used in a 3-phase, single-line mode, the RLC values of all phases are changed when the voltage of any one of the phases goes through a zero crossing. The load remains in constant impedance form until 10 cycles of the fundamental frequency is passed. The non-linear characteristic is effective within ±20% of the rated RMS voltage and ±DF% of the rated frequency (DF is defined as minimum of 10, 90/KPF and 90/KQF). Outside this range, the load reverts to constant impedance.
IMPORTANT NOTE: The initial values of R, L and C are computed based on the rated conditions supplied by the user. These values are kept constant until 10 cycles of the fundamental frequency has passed.
More: |
See Reference [3] for more details on static load models and typical values for NP, NQ, KPF and KQF. |
