Cooperation of Wide Area Control with Renewable Energy Sources for Robust Power Oscillation Damping

In this paper, a Wide Area Control (WAC) scheme cooperates with Renewable Energy Sources (RESs) to achieve a robust power oscillation damping. The WAC signals are synthesized by a two-level hierarchical controller which utilizes global measurements from all the installed synchronous generators to maximize the performance of the generators’ local controllers. In the proposed WAC scheme, the dynamic operation of RES is also taken into consideration for the implementation of WAC signals, in order to make the generators “aware” of the RES oscillations. Further, the local controller of the RES is modified in order to utilize the available reactive power for compensating any local voltage oscillations, leading that way to a controller which does not require any WAC signals. The performance of the proposed scheme has been tested and validated in the IEEE 9-bus test system where it is indicated that the proposed scheme improves the power system’s dynamic stability

Performance Enhancement of MAF based PLL with Phase Error Compensation in the Pre-Filtering Stage

The large scale integration of Renewable Energy Sources (RES) requires sophisticated control techniques for efficient power transfer under faults and/or off-nominal grid conditions. A RES is efficiently integrated to the grid via proper control of the Grid Side Converter (GSC) by accurately estimating the grid voltage phase angle. Moving Average Filter (MAF) based Phase Lock Loop (PLL) techniques provide reduced complexity, however, they present disadvantages under specific grid fault conditions. The most recent MAF based technique is the EPMAFPLL, which provides improved dynamic response and reduces the phase error under off-nominal grid frequencies. However, the EPMAFPLL presents high phase and frequency overshoot at the time of fault. Furthermore, inaccurate harmonic mitigation under off-nominal grid frequencies was not investigated in EPMAFPLL. A modified EPMAFPLL (EPMAFPLL Type 2) is proposed in this paper. The modified EPMAFPLL accurately compensates the offset errors under off-nominal grid frequencies, offers lower frequency overshoot and faster dynamics under faults. In addition, it provides accurate compensation of grid voltage harmonics under off-nominal grid frequencies

Three-phase phase-locked loop synchronization algorithms for grid-connected renewable energy systems:A review

The increasing penetration of distributed renewable energy sources (RES) requires appropriate control techniques in order to remain interconnected and contribute in a proper way to the overall grid stability, whenever disturbances occur. In addition, the disconnection of RES due to synchronization problems must be avoided as this may result in penalties and loss of energy generation to RES operators. The control of RES mainly depends on the synchronization algorithm, which should be fast and accurately detect the grid voltage status (e.g., phase, amplitude, and frequency). Typically, phase-locked loop (PLL) synchronization techniques are used for the grid voltage monitoring. The design and performance of PLL directly affect the dynamics of the RES grid side converter (GSC). This paper presents the characteristics, design guidelines and features of advanced state-of-the-art PLL-based synchronization algorithms under normal, abnormal and harmonically-distorted grid conditions. Experimental tests on the selected PLL methods under different grid conditions are presented, followed by a comparative benchmarking and selection guide. Finally, corresponding PLL tuning procedures are discussed.This work was supported by the supported by the Research Promotion Foundation (RPF) of Cyprus under Project KOINA/SOLAR-ERA.NET/1215/06

Real data from PMUs

Real data that are derived from two PMUs installed in different substations of a real system that includes timestamp, three phase voltage and current phasor measurements for two lines of the system, frequency measurements, and rate of change of frequency (ROCOF) measurements