The increasing penetration of variable-speed wind turbines in the electricity grid will result in a reduction of the number of connected conventional power plants. This will require changes in the way the grid frequency is controlled. In this letter, a method is proposed to let variable-speed wind turbines emulate inertia and support primary frequency control. The required power is obtained from the kinetic energy stored in the rotating mass of the turbine blades.

/pdf/wind-turbines-emulating-inertia-and-supporting-primary-13qg1bzk50.pdf

Wind turbines emulating inertia and supporting primary frequency control

This paper endeavors to present a comprehensive summary of the causes and effects of voltage unbalance and to discuss related standards, definitions, and mitigation techniques. Several causes of voltage unbalance on the power system and in industrial facilities are presented as well as the resulting adverse effects on the system and on equipment such as induction motors and power electronic converters and drives. Standards addressing voltage unbalance are discussed and clarified, and several mitigation techniques are suggested to correct voltage unbalance problems. This paper makes apparent the importance of identifying potential unbalance problems for the benefit of both the utility and customer.

Assessment of Voltage Unbalance

Power-grid networks must be synchronized in order to function. A condition for the stability of the synchronous state enables identification of network parameters that enhance spontaneous synchronization—heralding the possibility of smart grids that operate optimally in real-world systems.

Spontaneous synchrony in power-grid networks

The statistical tools of Complex Network Analysis are of useful to understand salient properties of complex systems, may these be natural or pertaining human engineered infrastructures. One of these that is receiving growing attention for its societal relevance is that of electricity distribution. In this paper, we present a survey of the most relevant scientific studies investigating the properties of different Power Grids infrastructures using Complex Network Analysis techniques and methodologies. We categorize and explore the most relevant literature works considering general topological properties, physical properties, and differences between the various graph-related indicators and reliability aspects. We also trace the evolution in such field of the approach of study during the years to see the improvement achieved in the analysis.

/pdf/the-power-grid-as-a-complex-network-a-survey-1ypu7fix7j.pdf

The Power Grid as a Complex Network: a Survey

Combined analysis of electricity and heat networks

1 Basic Concepts 2 Transformers 3 The Synchronous Machine 4 Series Impedance of Transmission Lines 5 Capacitance of Transmission Lines 6 Current and Voltage Relations on a Transmission Line 7 The Admittance Model and Network Calculations 8 The Impedance Model and Network Calculations 9 Power Flow Solutions 10 Symmetrical Faults 11 Symmetrical Components and Sequence Networks 12 Unsymmetrical Faults 13 Economic Operation of Power Systems 14 Zbus Methods in Contingency Analysis 15 State Estimation of Power Systems 16 Power System Stability

William D. Stevenson

Papers

Power System Analysis

Power systems analysis