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This paper demonstrates that the direction of a fault in an HVDC grid can be determined by comparing the rate of change of voltage (ROCOV) values at either side of the di/dt limiting inductors at the line terminals. For bi-pole HVDC grids with a metallic return and single earthing point, it is shown that directional information can be preserved by adding a small inductor in series with return conductor at each converter stations. Utilizing the estimated direction of the fault, a more secure ROCOV based transmission line and bus protection schemes are developed, relying on only local measurements. Through detailed time domain simulations, |dv/dt| characteristic under different fault conditions are analysed and the performance of the proposed fault detection schemes are evaluated for a test grid consisting of both cables and overhead lines. The ability to detect very low to significantly high resistance faults and the robustness of proposed scheme under changing grid configurations and operating conditions are demonstrated. [ABSTRACT FROM AUTHOR]

A new impedance based fault location algorithm is proposed for a generic multi-terminal transmission network consisting of a main line and tapped branches with no direct measurements available at the intermediate tapping nodes. The core of the algorithm is a threshold free faulted branch search algorithm that systematically compares the multiple estimates of voltages for the tapping nodes, computed using synchrophasor measurements at the terminals. Once the faulted branch is identified, multi-terminal fault location problem is reduced into a two-terminal fault location problem to determine the exact location of fault within the branch. The proposed algorithm is simple and does not involve resource intensive mathematical operations such as matrix inversion. The proposed algorithm was implemented as a module in an in-house developed real-time synchrophasor application software program, and its performance was evaluated using a test setup consisting of a real-time simulator, an actual synchrophasor network, and a phasor data concentrator. The tests showed that the proposed algorithm is capable of correctly determining the faulted branch, except for few faults that are very close to tapping nodes. When the algorithm is used with practical synchrophasor measurements, the fault location error was within a typical tower span for most cases. [ABSTRACT FROM AUTHOR]

• A novel hybridization scheme using both stochastic and deterministic techniques. • Achieves an optimum operational trajectory under forecast uncertainties. • Simplified and computationally efficient problem formulation. • Reduced dependence on frequently updated forecasts. • Proof-of-concept is depicted on a remote off-grid PV-Diesel-Battery power system. With the precipitated integration of intermittent renewable sources, operation optimization employed with uncertainty management strategies is imperative to ensure a reliable, cost-effective, and secure energy supply for the remote off-grid power systems. This paper presents a two-stage operation optimization process embedded in a model predictive control framework. The first stage decision variables are derived in a deterministic optimization framework to achieve minimum operational costs and emissions. The second stage uses a stochastic optimization framework to refine the first stage decision variables to achieve a feasible operation considering several candidate scenarios in a computationally inexpensive manner. Several measures are integrated to the proposed framework in order to address the operational requirements pertaining to remote off-grid power systems. The effectiveness of the proposed framework is demonstrated through numerical experiments for an isolated remote power system in Northern Canada for both summer and winter seasons. Quality of the obtained results as well as the computation efficiency of the overall framework has been verified compared to the existing energy management techniques. The overall result confirms the applicability of the proposed method in achieving a cost-effective and environmentally friendly operational trajectory while effectively accounting for the underlying uncertainties with a reduced computational burden. [ABSTRACT FROM AUTHOR]

• A three-level hierarchical controller is proposed in a centralized architecture. • Both logical and quantitatively optimized power system operation is ensured. • Improved situational awareness through simulation-based operation evaluation. • Proof-of-concept is shown on a remote off-grid PV-Diesel-Battery power system. Integration of locally available renewable energy sources and energy storage have proven to be a cost-effective and eco-friendly retrofit for the primarily diesel-based remote off-grid power systems. However, in the presence of multiple sources and energy storage, the energy management and power management mechanisms must be properly designed to enhance their envisioned benefits while assuring stability, availability, and security of power supply. This paper presents a hierarchical controller equipped with both energy management and power management strategies to obtain an optimum and stable system operation subjecting remote off-grid power systems. An operation evaluation framework is deployed to assess the applicability of the derived optimum operational routines as well as to verify the competence of the low-level controls. Results are demonstrated for a remote off-grid PV-Diesel-Battery power system under different diurnal and seasonal variations. Results revealed the competence of incorporated power management strategies as well as the use of proposed operation evaluation mechanism in identifying certain risks associated with optimum operational routines derived through energy management systems. The overall study confirmed that a coordinated control and operation evaluation platform is required to achieve a logical and quantitatively optimized operational trajectory. [ABSTRACT FROM AUTHOR]

• Demand Response (DR) is combined with operational optimization in a novel framework. • Probabilistic fuzzy theory is used to incorporate uncertainty to DR modelling. • Benefits are maximized for both the utility and the consumers. • Proof of concept is demonstrated on a remote off-grid PV-Diesel-Battery power system. With the anticipated future price reductions in renewable technologies, hybrid renewable energy systems have emerged as a feasible retrofit to the primarily diesel-based remote off-grid power systems. However, in the presence of many supply/storage systems along with high penetration of intermittent renewable energy, energy management becomes a decisive step to achieve a stable and reliable power system operation. The intended benefits can be further maximized when the energy management framework is unified with demand response strategies. This paper presents a novel demand response integrated day-ahead energy management framework subjecting remote off-grid power systems. Several measures are taken to enhance the consumer acceptance and practical implementation of the demand response platform. Responsiveness of the customers to price-based incentives is estimated using a probabilistic fuzzy inference system to accurately model the stochastic human nature. Results are demonstrated for an isolated remote community in Northern Canada for both summer and winter seasons. The results confirm the applicability of the proposed method in achieving the intended objectives of day-ahead energy management. [ABSTRACT FROM AUTHOR]

A new type of sensor is proposed to detect high frequency transients in currents and their initial polarities. The proposed sensing system replaces both high frequency signal sampling and processing by a simple detection coil wound on a ferrite core and an analogue electronic circuit. It is verified through laboratory experiments that transient occurrence, occurrence time, and initial transient polarity can be determined accurately. A detailed model of the sensor, including the dynamic hysteresis characteristics of the ferrite core, is developed and implemented on an electromagnetic transient simulation software, and verified through experimental measurements. Application of the developed model to simulate a transient current polarity comparison based protection scheme is demonstrated. The versatility of the proposed sensor compared to common digital signal processing based approaches, namely discrete wavelet transform and mathematical morphology, is highlighted using experimental waveforms. [ABSTRACT FROM AUTHOR]