Location

This example model can be found in the software under the category "FACTS & HVDC" with the file name "STATCOM.ecf".

Description

This demo example gives the application of a STATCOM in the power transmission network for reactive power control and voltage regulation.

In this demo, a 66 kV, 300 MVAR STATCOM is used on a three-bus, 500 kV transmission system. The STATCOM is composed of a three-level neutral point clamped (NPC) converter and it is connected to the Point of Common Coupling (PCC) through a 66/500 kV transformer. The STATCOM is designed to have a power rating of around 300 MVA and a rated DC link voltage set-point at 160 kV. The carrier frequency of the converter is 1650 Hz.

Simulation and Results

The STATCOM is designed to operate in two control modes and each mode shows two different cases as explained below.

(1) AC voltage regulation with and without droop: converter supplies enough reactive power to maintain voltage at PCC at 1.0 pu (without droop) or at voltage as specified by droop (with droop)

(2) Reactive power control: the converter supplies the reactive power as demanded.

Case 1: Voltage regulation: without droop

In this mode the voltage at the PCC is maintained at 1.0 pu. The source (grid) voltage at PCC is initially 1.0 pu and STATCOM supplies 0 MVAR. When the source voltage from 1 to 0.97 pu, at 1.0 sec, STATCOM injects reactive power to maintain it at reference voltage of 1.0 pu. Alternatively, when the source voltage was changed from 0.97 to 1.045 pu at 1.5 sec, the STATCOM absorbs reactive power.

To set the operating mode without droop, set mode of operation to "Voltage regulation" and droop value to zero as shown below image

Case 2: Voltage regulation: with droop

A droop of 2% is considered in this example which is a standard droop for practical systems. The source (grid) voltage at PCC is initially 1.0 pu and STATCOM supplies 0 MVAR. When the source voltage from 1 to 0.97 pu, at 1.0 sec, STATCOM injects reactive power inline with its droop characteristics to maintain and increases the voltage to a level as determined by the droop. It can be observed that the voltage is not exactly 1 pu but less, which is expected. Alternatively, when the source voltage was changed from 0.97 to 1.045 pu at 1.5 sec, the STATCOM absorbs reactive power.

To set the operating mode "with droop", set mode of operation to "Voltage regulation" and droop value to 0.02 as shown in below image

Case 3: Reactive power control model: Q generating mode

In this mode, the Q reference is set as 0.6 pu. STATCOM is generating the reactive power as requested by user.

To set the operating mode for reactive power generation, set mode of operation to "Q regulation" and droop value to “0” and Q ref value to 0.6 as shown below image

Case 4: Reactive power control model: Q absorbing mode

In this mode, the Q reference provided is set as -0.4 pu. STATCOM is generating the reactive power as requested by user.

To set the operating mode for reactive power absorption, set mode of operation to "Q regulation" and droop value to “0” and Q ref value to -0.4 as shown below image

References

G. Hingorani, L. Gyugyi, “Understanding FACTS; Concepts and Technology of Flexible AC Transmission Systems,” IEEE^®Press book, 2000.

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