The purpose of modern power systems is to supply electric energy while satisfying the potentially conflicting requirements of an economical solution with high reliability which offers the best environmental protection. This article discusses international views on the subject of future supply systems.
Electricity utilities and operators need to be aware of the impact of future technologies and make preparations to enable them to adapt to a changing environment where the involvement of the customer in the operation, reliability and use of the grid, will continue to increase. Electricity utilities and operators need to be aware of the impact of future technologies and make preparations to enable them to adapt to a changing environment where the involvement of the customer in the operation, reliability and use of the grid, will continue to increase.
Cigré, the Council on Large Electric Systems, which was founded in 1921, is an international non-profit association for promoting collaboration with experts from all around the world by sharing knowledge and joining forces to improve electric power systems.
Regarding the electricity supply systems of the future, Cigré has identified the following challenges:
With respect to the first two points, in order to operate an electricity supply grid reliably, there is a need for the full component of services to be provided by generators. This list as well as the ability of different generation (resources) to provide these services is shown in Fig. 1.
In Fig. 1, zero indicates no ability to contribute to a reliability function, and five indicates full capability. In order to operate the grid, resources with capability of at least four should ideally be constantly available.
With the increased deployment of inverter based resources, the synchronous resources are required to contribute a higher level of ancillary service than originally anticipated. This often comes at a cost to the synchronous resource either in terms of life of plant or cost of operation. These costs need to be recovered (e.g. by an ancillary service market) to ensure continued supply of these services.
Non-synchronous ancillary service can be provided via flywheels (inertia) but these are limited in the service provision and duration. Batteries provide more potential services and show promise for larger deployment in future.
In costing the resource it is important to include full cost of supply including additional ancillary service support if required. This will ensure maximum possible penetration of inverter based resources (if cost effective) with the ability to operate the grid reliably. In meeting the challenges listed above, it is necessary to focus on ten areas of technology which are covered in the following sections.
With the advent of distributed renewable generation, it was initially assumed that bulk transmission would not be required. This has proved not to be the case as the location of renewable resources are often in areas remote from the load.
There are two likely models that will coexist in future:
The role of transmission will become much more diverse covering bulk transmission, balancing resources across wider synchronous areas and providing a very different set of services to those it was originally developed for. Transmission has to evolve, and evolve quickly.
Ten issues of consideration to transform to the modern grid
The following ten points have been identified by Cigré as being necessary to take into account when moving to the modern grid. It is suggested that these points be considered in research, investment and development of standards by operators and utilities when moving to incorporate all types of resources in the modern grid. It is critical that all ten areas are addressed simultaneously. If one is omitted it will affect the purpose as described in the introduction.
Active distribution networks
This includes massive rollout of smart meters, determining network architectures as well as micro-grid and remote area connections.
Massive exchange of information
With the installation of large amounts of smart meters as well as smart generation and inverters, there will be large amounts of data available. It is important that this information is converted into usable information and does not lead to lower productivity. Data recovery and cyber security as well as management of big data is key.
Integration of HVDC power electronics
With the advent of large scale inverter base resources (many hundreds of thousands), there is a need to understand the integration of power electronics into the system as well as the impact “dumb” inverters may have on the waveform.
Massive installation of storage
In order to provide ancillary service and continuous source of energy massive storage is required for frequency, voltage control and reduction of peaks.
System operations and control
The ability to control the system with large scale inverter resources requires different measurement parameters (displays of inertia and rate of change of frequency (ROCOF) levels in control rooms) as well as different analysis models and operator skills.
This includes wide area schemes, ability to deal with low fault levels, rapid and reliable ROCOF protection as well as home energy management and electric vehicle integration.
New concepts in planning
Includes risk based planning, understanding full cost and capabilities of new technologies, integration of micro-grids and integration of HVDC grids and AC networks.
New tools for technical performance
This includes advanced numerical techniques and numerical methods for the solution of multiphase load-flow problems, and time domain simulation. Analysis of dynamic behaviour, islanding and power quality effects is also required as well as models simulating HVDC grid, converter stations, and FACTS (flexible AC transmission system) devices.
It should be noted that FACTS also applies to distribution voltages, but that the simplified tools used in the design of LV networks are no longer applicable. It is necessary to perform dynamic studies on LV networks with inverter based resources, which will drastically increase the workload of planners unless the correct tools, training and systems are in place.
Increased use of existing corridors
Includes uprating of lines, use of high temperature conductors, conversion of AC lines to DC and development of new insulated AC and DC submarine and underground cables.
The production consumer or prosumer needs to be aware of different products, ability to sell services into the grid as well as receive different services from the grid. Community involvement is critical for rollout of any new home based generation, storage, appliance control or smart metering device.
In the planning phase:
Community involvement in the construction and operation phases:
Utilities and operators need to be aware of the impact of future technologies and make preparations in each of the ten areas mentioned above.
Contact Rob Stephen, Cigré, Tel 031 563-0063, firstname.lastname@example.org
Source: EE plublishers