Unique experience in implementing POD — low-frequency vibration damping system

2023 At the beginning of 2023, the specialists of Eknis-Engineering LLC, together with Liaoning Rongxin Xingye Electric Power Technology Co., Ltd. (RXPE), implemented the first low-frequency power damping (LFO) system in Ukraine in the IPS of Ukraine. The mathematical form of the function and the study of power grids for its adjustment were developed and agreed upon together with the specialists of DTEK Renewables LLC.

This is currently a unique experience, the first project implemented in Ukraine to introduce the POD (Power oscillation damping) function through the use of reactive power compensation devices - STATCOM (static synchronous compensator).

At the same time, STATCOM is a part of FACTS systems (Flexible AC Transmission System), which are being implemented worldwide to maintain the stability of power systems, their reliability and improve the quality of electricity, prevent the development of system and inter-system accidents.

In total, the development, testing and implementation of the POD controller took about three months, and during the tests, the system demonstrated its ability to reduce the NFC in accordance with a given mathematical model. The STATCOM devices used allow to influence fluctuations in the high-voltage network by changing the reactive power with an amplitude of 64 MVAr.

Dynamic response of POD to power fluctuations

The transfer function of the POD model used is as follows:

 The input active power signal (Pline) affects the output reactive current signal (IQ) according to an algorithm consisting of:

- a delay link;

- a link of advance;

- anti-alias filter;

- integration link;

- saturation link.

Appearance of the transfer function of the POD algorithm

The function is flexible and has the ability to quickly adjust its parameters, so it can be used to dampen various types of noise, including

Irregular NPCs - caused by continuously occurring electromechanical transients due to the variability of the load and active power generation.

Torsional IPC - have a frequency of 0.2 to 2 Hz and arise as a result of mechanical vibrations of masses located on the generator shaft.

Local LFOs - have a frequency range of 0.7 to 4 Hz and are caused by a change in the operating mode of one or more generators at one power plant when the load in the power system changes

Intersystem LFOs - have a frequency range of 0.1 to 0.7 Hz and are caused by changes in the operating mode of power plants in the power system when the load changes

Other NFCs - for example, caused by incorrect settings of the control systems of reclosers, ARS, and other devices. The frequency range may vary.

NPCs in the infra-low frequency range. The occurrence of which is associated with the non-manoeuvrable operation of TPPs when the load in the grid changes, the fluctuation is more than 5 minutes.

These fluctuations can occur simultaneously or overlap.

Within the framework of the implemented project, the capacity of the LFO damping system was limited by the existing capacity of STATCOM devices that were previously installed at the power plant and performed the function of reactive power compensation and voltage fluctuation reduction.

Conclusions for future projects - STATCOM devices can be effectively used to implement the POD function using the above algorithm as a basic one. However, the settings of the controller's control system, the algorithm used, the type of device, and its power should be selected based on the analysis of existing and predicted low-frequency fluctuations of a particular power system node, taking into account possible operating modes.

The implementation of the POD function has become a unique experience for our company, and it also allows us to improve the integration of the Ukrainian power system into ENTSO-E, and in general, to increase the stability and resilience of the IPS of Ukraine.

We are proud of the results and are grateful to DTEK Renewables' specialists, the plant's operational staff and management, and the RXPE plant employees who made this joint achievement possible.