Wide-area damping controller (WADC) requires communication networks to transmit remote signals. The usage of communication networks will introduce time delays into the control loop of the WADC. Ignoring this time delay would deteriorate the damping performance provided by the WADC or even cause the whole system instability. This paper employs networked predictive control (NPC) to design a WADC for the generator exciter to enhance the damping of interarea oscillations in a large-scale power system. The NPC incorporates with a generalized predictive control (GPC) to generate optimal control predictions, and a network delay compensator to detect and compensate both constant and random delays. Moreover, model identification is used to obtain an equivalent reduced-order model of the large-scale power system and deal with the model uncertainties and variation of operating conditions. Case studies are based on the New England 10-machine 39-bus system. Effectiveness of the proposed WADC is verified by simulation studies and compared with a conventional WADC and a GPC-based WADC without delay compensation.

Wide-Area Damping Controller for Power System Interarea Oscillations: A Networked Predictive Control Approach

Due to increasing level of power converter-based component and consequently the lack of inertia, automatic generation control (AGC) of interconnected systems is experiencing different challenges. To cope with this challenging issue, a derivative control-based virtual inertia for simulating the dynamic effects of inertia emulations by HVDC (high-voltage direct current) interconnected systems is introduced and reflected in the multi-area AGC system. Derivative control technique is used for higher level applications of inertia emulation. The virtual inertia will add an additional degree of freedom to the system dynamics which makes a considerable improvement on first overshoot responses in addition to damping characteristics of HVDC links. Complete trajectory sensitivities are used to analyse the effects of virtual inertia and derivative control gains on the system stability. The effectiveness of the proposed concept on dynamic improvements is tested through Matlab simulation of two-area test system for different contingencies.

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Analysis of derivative control based virtual inertia in multi-area high-voltage direct current interconnected power systems

Voltage-source converter-high-voltage direct current (VSC-HVDC) systems have become an attractive option for integrating remote and far-from-shore renewable energy resources to main AC grids. The desire for greater power transfer capability and the difficulty in securing right-of-way for new AC lines in many countries is also resulting in the increased use of embedded VSC-HVDC systems operating in parallel with existing AC lines. It has been stated that the control and operation of VSC-HVDC systems are of particular concern for weak grids with fewer large synchronous generation units (a highly probable case for many grids in future). If the anticipated proliferation of VSC-HVDC links continues, several aspects of system stability will be significantly impacted. This study presents an overview of the effects of VSC-HVDC control and operation on power system stability. The structure, control, control tuning, and modelling of VSC-HVDC is briefly summarised to provide context for subsequent discussion of the system dynamics. An extensive critical review of the previous research into mixed AC-DC systems incorporating VSC-HVDC is then provided including voltage stability, small and large-disturbance angle stability, high-frequency interaction, and frequency stability. Finally, recommendations are presented to guide critical future research.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-gtd.2017.1140

Stability and control of mixed AC–DC systems with VSC-HVDC: a review

This paper examines the feasibility of coordinating variable-speed wind farms with other power system devices, such as flexible ac transmission systems and synchronous generators, to damp low-frequency oscillations. For this purpose, an observer-based state-feedback approach is used to build a power oscillation damping (POD) controller, implemented through coordinated actions of multiple control devices, and able to manage several measurement channels. The wide-area POD controller also presents a time-delay compensation stage to mitigate adverse effects of latency involved in wide-area communication systems. Several practical issues are discussed and analyzed, such as measurement and control selection, model-order reduction, transmission time-delay compensation, impact of the POD control on wind farms, and robustness aspects. The control performance is evaluated and compared with other control schemes using eigenvalue analyses and nonlinear time-domain simulations over a wide range of operating conditions, for example, severe system faults, N - 1 outage contingencies, load/generation shedding, and line tripping.

Power Oscillation Damping Improvement by Adding Multiple Wind Farms to Wide-Area Coordinating Controls

Inter-area low frequency electromagnetic oscillation (LFEO) in inter-connected power systems is one of the major barriers to improve the dynamic performance of power systems, since they could either limit the amount of power transfer on the tie-lines or endanger the dynamic stability of the power systems. With the high penetration of wind and photovoltaic (PV) power plants in power systems, LFEO is becoming a problem worth more attention in renewable energy age and must be better solved in order to accept more wind and PV power in power systems. Wide-area damping control (WADC) has gained popularity in suppression of inter-area LFEO recently. Many control strategies have been developed on WADC design. This paper aims to provide a general review on practical issues, typical WADC off-line and adaptive design methods and engineering cases regarding WADC implementations. These practical issues include design flow, mode analysis, choice of actuator and feedback signal, system identification and the effect of time delay. In terms of designing WADC controllers, both offline and adaptive methods have been reviewed and compared. Finally, WADC engineering cases all around the world are summarized.

A review on wide-area damping control to restrain inter-area low frequency oscillation for large-scale power systems with increasing renewable generation

The paper presents a supplementary VSC-HVDC Power Oscillation Damping (POD) controller based on wide area measurement signals (WAMS). The controller is designed as Multi Input Single Output (MISO) using a Modal Linear Quadratic Gaussian (MLQG) methodology in order to target critical inter-area electromechanical modes. The approach has been tested on a large (16 machine, 68 bus) test network incorporating parallel HVDC/AC transmission and has shown improved damping compared to a traditional Power System Stabilizer (PSS) based controller structure utilizing local signals. The design process has incorporated the effects of wide area signal transmission delays. Variation in these signal delays and the complete loss of signals has been also investigated to establish the robustness of the WAMS based controller and its sensitivity to loss of signals. Extension of the controller to incorporate reactive power modulation has been investigated, as has variation in available active power modulation capacity. The proposed controller performance has been assessed through small and large disturbance analysis.

Abddulaziz M. Almutairi

Papers

Damping of inter-area oscillations in mixed AC/DC networks using WAMS based supplementary controller