The Need for and Approaches to Power Quality Monitoring
There has been a noticeable increase in the amount of power quality monitoring taking place in electric power systems in recent years. Monitoring of voltages and currents gives the system operator information about the performance of their system, both for the system as a whole and for individual locations and customers. There is also pressure from customers and regulatory authorities to provide information on the actual power quality level. Developments in enabling technology (monitoring equipment, communication technology, data storage and processing) have made it possible to monitor on a large scale and to record virtually any parameter of interest. The change in types of loads connected to the network and proliferation of non-conventional, power electronic interface connected, generators as well as the envisaged further increase in non-conventional types of loads/storage (e.g., electric vehicles) puts additional pressure on system operators to monitor and document various aspects of system performance. While many system operators are installing monitoring equipment and while more and more manufacturers have monitors available, there is a lack of knowledge and agreement on a number of aspects of the monitoring process and in particular on processing the recorded data. Users of the data, be it system operators or their customers, are increasingly requesting useful information rather than just large amounts of data to be provided by installed monitors and supporting software. This lecture summarises current industrial practice in power quality monitoring based on international survey of PQ monitoring around the world and indicates major future trends and directions in Power Quality monitoring and reporting results of monitoring. The lecture is broadly based on results and conclusions of the work of CIGRE/CIRED JWG C4.112 “Guidelines for Power Quality monitoring – measurement locations, processing and presentation of data” Biography of the presenter
Modelling and Impact of Distributed Generation on System Dynamics
The power systems at present are principally characterised with large and ever increasing presence of variable and intermittent converter connected renewable energy sources (RES). This will be even more the case with future power systems. They will be further characterised by blurred boundaries between transmission and distribution system, by mix of wide range of electricity generating technologies (conventional hydro, thermal, nuclear and power electronic interfaced stochastic and intermittent renewable generation), responsive and highly flexible, typically power electronics interfaced, demand and storage with significant temporal and spatial uncertainty, proliferation of power electronics (HVDC, FACTS devices and new types of load devices) and significantly higher reliance on the use of measurement data including global (Wide Area Monitoring) signals for system identification, characterization and control and Information and Communication Technology embedded within the power system network and its components. The integration of variable renewable generation, converter connected generation in particular, leads to conventional synchronous generators being displaced, hence the total inertia of the system will be reduced. This in turn affects system dynamic performance by: i) Changing the flows on major tie-lines, which may in turn affect damping of inter-area modes and transient stability margins; ii) Displacing large synchronous generators, which may in turn affect the mode shape, modal frequency, and damping of electromechanical modes of rotor oscillations; iii) Influencing/affecting the damping torque of nearby synchronous generators, similar to the manner in which flexible ac transmission (FACTS) devices influence damping (reflected in changes in the damping of modes that involve those synchronous generators); iv) Displacing synchronous generators that have crucial power system stabilizers. In order to successfully control such complex system its parts and components and to ensure its stability and security at acceptable cost, the system modelling and analysis need to cater for significantly increased uncertainties, both in terms of model uncertainties and operational uncertainties, and for efficient knowledge extraction from large amount of data coming from different types of local and wide area distributed data acquisition devices and monitors. This presentation focuses on new appriach to modelling of RES to meet the above challenges, the impact of RES on system dynamics and gives and discusses the examples of probabilistic stability studies of power systems with RES.
Towards Resilient Net-Zero Power Systems
Due to the evident climate change and environmental pressures the future power/energy systems will have to operate, sooner rather than later, in a net-zero environment, i.e., any carbon emissions created will have to be balanced ( cancelled out) by taking the same amount of carbon out of the atmosphere, so that the amount of carbon emissions added to the etmosphere should not be more than the amount taken away. This will manifest in: by mix, at least during the trsnsition period, of wide range of electricity generating technologies including conventional hydro, reducing but still present thermal, possibly increasing nuclear and even higher and accelerated connection of power electronic interfaced stochastic and intermittent renewable generation; blurred boundaries between transmission and distribution system; responsive and highly flexible, typically power electronics interfaced, demand and storage trechnologied with significant temporal and spatial uncertainty; proliferation of power electronics (HVDC, FACTS devices and new types of load devices); significantly higher reliance on the use of legacy and measurement data including global (Wide Area Monitoring) signals for system identification, characterization and control and Information and Communication Technology embedded within the power system network and its components; and ever increasing emphasis on considering the “whole system”, not only comprising different energy vectors, but also ICT, traffic, water and social systems, to ensure energy supply security and efficiency. The key characteristics of such a complex system, if only a few are to be picked, would certainly be prolifereation of power electronic devices in different shapes and forms and for different purposes, increased uncertainites in system operation and parameters and much largerer reliance on the use of measurement and other data collected. This will increase controllability and observability of the system but may as a trade off result in different/unexpected dynamic behaviour of the system and possibly, under some circumstances, deterioration of some aspects of its performance.
This presentation first briefly introduces some of the key characteristics of future net-zero power systems, then identifies the key challenges associated with ensuring resilience (the ability to withstand low-frequency high-impact incidents efficiently while ensuring the least possible interruption in the supply of electricity) of such systems and finally discusses examples of the latest research results in the areas of probabilistic stability studies of uncertain systems, data analytics, risk assessment and complex system analysis, which all are essential constituent parts of comprehensive assessment of power system resilience.
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