Power Electronic Interfaced Generation Research Articles

Adaptive Central Control Scheme and Investigation of Fault Current Contribution for Protection of Microgrid

Microgrids suffer from issues namely protection blinding, sympathetic tripping. Microgrids operate in which differs from the conventional power system. Micro-grids operate in grid-connected mode or islanded mode of operation. In islanded mode microgrids utilize distributed energy resources that are renewable such as solar, wind, along with energy storage systems. In both, the modes of the system undergo various challenges such as protection blinding, sympathetic tripping, or short circuit current in power electronic interfaced generation. This work focuses on the analysis of fault in both modes of operation as well as the issues that are specific to a microgrid. Hence adaptive settings of the relay are required to switch over under the different modes of operation. This work utilizes an adaptive central controller for MG protection. Hence the sensed data from the system is fed to the controller and managing the relay operation which is the IDMT relay. This work focuses on the relay setting and plug set for the relays under modes of operation. The detailed analysis is carried out in IEEE 13 bus system and adaptive relay setting calculation for adaptive centralized MG protection is carried out.

Probabilistic multi-stability operational boundaries in power systems with high penetration of power electronics

This paper presents a framework for defining multi-stability operational boundaries of power systems under varying penetration levels of power electronic interfaced generation and uncertain system’s loading. Boundaries are established considering the small-disturbance and large-disturbance rotor angle stability, as well as the frequency and voltage stability of the system. Estimating system’s operational boundary from multi-stability perspectives will provide invaluable information on how to best operate the system and how to mitigate certain condition that leads to instability especially in the current deregulated market and high penetration of power electronic interfaced generations. A singular stability assessment and its subsequent operational boundary may be valid only for a specific stability study and those may not be true for other types of stability. This paper illustrates the proposed framework in a modified New England Test System using a probabilistic approach. The impact of these varying loading conditions and renewable energy sources penetration levels are quantified on a per-stability-type basis and then aggregated into the multi-stability perspective. The established multi-stability operational boundary is heavily influenced by the frequency and large-signal disturbance rotor angle stability. A significant improvement in the system’s operational stability boundaries, particularly for voltage stability and small disturbance rotor angle stability, occur when the voltage source converter high voltage direct current’s ability to independently control active and reactive power via VDC-Q control is fully utilized.

Analysis and tuning methodology of FAPI controllers for maximising the share of grid‐connected wind generations

In this study, a novel methodology is proposed for sensitivity-based tuning and analysis of derivative-based fast active power injection (FAPI) controllers in type-4 wind turbine units integrated into a low-inertia power system. The FAPI controller is attached to a power electronic interfaced generation (PEIG) represented by a generic model of wind turbines type 4. It consists of a combination of droop and derivative controllers, which is dependent on the measurement of the frequency. The tuning methodology performs parametric sensitivity to search for the most suitable set of parameters of the attached FAPI that minimises the maximum frequency deviation in the containment period. The FAPI is adjusted to safeguard system stability when increasing the share of PEIG. Since the input signal of the FAPI is the measured frequency, the impact of different values and parameter settings of the phase-locked loop used for the FAPI controller is also investigated. Detailed validation with a full-scaled wind power converter is also provided with a real-time digital simulator testbed. Obtained simulation results using a three-area test system, identify the maximum achievable degree of increase in the share of wind power when a proper combination of wind park locations considering their suggested settings for inertia emulation.

Power-Angle Modulation Controller to Support Transient Stability of Power Systems Dominated by Power Electronic Interfaced Wind Generation

During the last few years, electric power systems have undergone a widespread shift from conventional fossil-based generation toward renewable energy-based generation. Variable speed wind generators utilizing full-scale power electronics converters are becoming the preferred technology among other types of renewable-based generation, due to the high flexibility to implement different control functions that can support the stabilization of electrical power systems. This paper presents a fundamental study on the enhancement of transient stability in electrical power systems with increasing high share (i.e., above 50%) of power electronic interfaced generation. The wind generator type IV is taken as a representative form of power electronic interfaced generation, and the goal is to investigate how to mitigate the magnitude of the first swing while enhancing the damping of rotor angle oscillations triggered by major electrical disturbances. To perform such mitigation, this paper proposes a power-angle modulation (PAM) controller to adjust the post-fault active power response of the wind generator type IV, after a large disturbance occurs in the system. Based on a small size system, the PAM concept is introduced. The study is performed upon time-domain simulations and analytical formulations of the power transfer equations. Additionally, the IEEE 9 BUS system and the test model of Great Britain’s system are used to further investigate the performance of the PAM controller in a multi-machine context, as well as to perform a comparative assessment of the effect of different fault locations, and the necessary wind generators that should be equipped with PAM controllers.

Grid forming control scheme for power systems with up to 100% power electronic interfaced generation: a case study on Great Britain test system

The penetration of power electronic interfaced generation (PEIG) is expected to reach up to 65% in some parts of the European power system by 2030 (at least during some hours of the year). Under such grid conditions, system security challenges are observed with frequency stability, voltage stability and undamped converter control interactions being among the most important issues. This study presents a short-term voltage stability assessment of the Great Britain synchronous area under EMT modelling assumptions. The study provides a mapping of system stability and identifies the critical penetration level of PEIG that instabilities are observed. In addition, an application of a grid forming control scheme (namely the enhanced direct power control) is proposed as a mitigation option which is applied here on full-converter interfaced wind power plants (type-4). The simulation results reveal that the application of the grid forming control to a part of the total wind power generation fleet can mitigate the instabilities observed, while enabling the system operation with 100% PEIG.

FAPI Controller for Frequency Support in Low-Inertia Power Systems

This paper presents different forms of Fast Active Power Injection (FAPI) control schemes for the analysis and development of different mitigation measures to address the frequency stability problem due to the growth of the penetration level of the Power Electronic Interfaced Generation (PEIG) in sustainable interconnected energy systems. Among the studied FAPI control schemes, two different approaches in the form of a derivative-based control and a virtual synchronous power (VSP) based control for wind turbine applications are also proposed. All schemes are attached to the PEIG represented by a generic model of wind turbines type 4. The derivative-based FAPI control is applied as an extension of the droop based control scheme, which is dependent on the measurement of the network frequency. By contrast, the proposed VSP-based FAPI is fed by the measurement of the active power deviation. Additionally, unlike existing approaches for virtual synchronous machines, which are characterized by high-order transfer functions, the proposed VSP-based FAPI is defined by a second-order transfer function, which can contribute to fast mitigation of the system primary frequency deviations during containment period. The Great Britain (GB) test system, for the Gone-Green planning scenario for the year 2030 (GG2030), is used to evaluate the effects of the proposed FAPI controllers on the dynamics of the system frequency within the frequency containment period. Thanks to proposed FAPI controllers, it is possible to reach up to 70% for the share of wind power generation without violating the threshold limits for frequency stability. For verification purposes, a full-scale wind turbine facilitated with each FAPI controller is tested in EMT real-time simulation environment.

A Key Performance Indicator to Assess the Frequency Stability of Wind Generation Dominated Power System

High penetration of power electronic interfaced generation, like wind power, has an essential impact on the inertia of the interconnected power system. It can pose a significant threat to the frequency stability. This paper introduces the notion of the key performance indicator (KPI) and illustrates its application on large scale power systems, including Fast Frequency Response (FFR) and a high share of wind power, to measure the possible distance to the frequency stability limit. The proposed KPI estimates the change of frequency performance (e,g., ROCOF, NADIR) in the frequency containment period. The effect of FFR is analyzed by introducing a droop based controller for wind power plants. The FFR controller responds to a drop in grid frequency with a temporary increase of the wind active power. The proposed KPI maps a change in key system variables (e.g., system kinetic energy, aggregated generation output) onto the change of frequency performance. A comprehensive analysis using DIgSILENT, Matlab, and Python is performed for GB reduced size system. According to the obtained results, the FFR capability of wind generator leads to improvements of NADIR especially in cases with high penetration levels of wind power. The proposed KPI is a valuable tool for the frequency stability assessment in power system planning studies. It can be determined based on off-line simulations, and it can assist the system operators for frequency stability assessment in intra-day operational planning.

A Virtual Power Plant with a Power Electronic Based Controller

More and more distributed generation (DG) units, including renewable energy based and power electronic interfaced generation units, are being integrated into distribution systems, consequently, conventional passive distribution networks are becoming active networks. An active network may be managed as a Virtual Power Plant (VPP), which has the possibility of sending power into a higher level grid like a generator. However, a VPP may have stochastic and non-ideal characteristics, for instance, power fluctuation, unbalance, non-linearity, harmonic distortions and lack of controllability due to the features of the connected load and renewable power sources. This paper studies the performance improvement of a VPP by using a Virtual Power Plant controller (VPPC). The VPPC is constructed by a power electronic voltage source converter (VSC) and an energy storage device, which can make a VPP to present good controllability of active power and reactive power, and can mitigate the unbalance and harmonics associated with the VPP. Furthermore, in dynamic situations, the VPPC can help to stabilize the VPP and support the grid. Simulation results are presented to demonstrate the effectiveness of the VPPC.