HARMONY - Harmonic identification, mitigation and control in power electronics based power systems
HARMONY - Harmonic identification, mitigation and control in power electronics based power systems
HARMONY stands for "Harmonic Identification, mitigation and control in Power Electronics based Power Systems". It is leaded by Aalborg University and the Principal Investigator is Professor, Frede Blaabjerg at the Department of Energy Technology
The global electrical energy consumption is still rising and there is a steady demand to increase the power capacity and the power transmission capabilities.
It is expected that it has to be doubled within 20 years. The importance of electricity in the overall energy budget will also increase. Today 40 % of the global energy consumption is processed through electricity and it is forecasted that in 2040, this may be up to 70 %.
The production, distribution and use of electrical energy should be as efficient as possible by cheap and advanced technology. Two major technologies will play important roles to solve the future challenges.
Two major technologies
- One is to change the electrical power production sources from the conventional, fossil based sources to renewable energy power resources.
- The second is to use high efficient and sustainable power electronics technology in power generation, power transmission/distribution and end-user application. Power electronics is also a key component in all kind of future transportation systems.
The energy supply is dominated by large fossil power plant units with a typical power capability of 300 MW to 1000 MW per unit and the size of the units enable rational operation and cheap energy production. Large units enable low service cost, efficient logistics and strong controllability. This strategy has worked with success and ensured reliable supply of electricity and heat - however the consequence of the last 20-40 years development of renewable power sources and the overall goal to save energy have led to a new situation.
Grid architetures
We are now building power electronics based power system in the future with its obvious advantages of controllability, sustainability and improved efficiency but it also brings new challenges. One of the important challenges is that the renewable power generation is interfaced through high switching frequency power electronics which cause harmonics generation into the power system and may make influence on other devices or even trigger resonances. Also the load side has a power electronics interface typically done by a diode-rectifier and a passive filter, which is cost-effective but increases the harmonic load currents generated in the system, and again it can trigger the other units connected to the system and trigger resonances in the grid it-self. Figure 1 below illustrates a small distribution system with its different power sources and loads including an illustration of the different harmonics being generated.
"Is it possible to establish a reliable power system which has a dominant amount of power electronics based sources and loads by means of analysis tools and control?"
The goal is to obtain “Harmony” between renewable energy sources, the power system and the loads in order to keep stability in all aspects seen from a harmonic point of view which is an urgent need due to the fast growth of power electronic based generators and loads.
Europe is leading the implementation of renewable energy systems as well as the European energy efficiency program results in a significant amount of power electronics interfaced loads. Germany is e.g. the leader in photo-voltaic and Denmark is the leader in the relative amount of installed wind power compared to the total installed power.
Being able in advance to develop tools and methods which solve critical issues in the implementation of the above programs will be of benefit for the industry, the power system operators and the society. It is planned that the results and tools will be available on a website for HARMONY.
In order to successfully run the project a number of research approaches need to be taken like harmonic analysis methods, modeling of the power system components, filter design, system analysis and mitigation methods to avoid harmonic problems.
Harmonic analysis in power systems
Harmonics are present in many ways in a power system. In order to carefully map harmonic sources, harmonic sinks and identify harmonic resonance risks, it is important to perform harmonic analysis of the different active and passive components in the power systems.
More wide-band modeling of power system devices
Models which describe the power system components (power lines, cables, transformers, capacitors, switch-gears) at the fundamental frequency exist to a large extend. However, for frequencies away from this still major challenges exist. Cable and line models are strongly frequency dependent and it is necessary to model those components in order to master the control of the harmonics in the power system.
Filter design of power electronics based systems
The overall goal of filter design is to reduce cost and increase efficiency to ensure a competitive product. Design tools to optimize those parameters may be based on step-by-step procedures, which are the most attractive seen from a designer point of view.
System modeling and analysis of power electronics based power system
The complexity of a power electronics based power system is high. Hence, it is necessary to develop system models in the simulation tools, which can assist to do analysis and help to identify problems in a given power system. The tools can be based Matlab/Simulink, but also more power system oriented tools like PSCAD or Digsilent.
Harmonic mitigation methods
In the case that serious stability problems are foreseen in a power system with a large amount of power electronic systems (generation, load), methods to reduce the harmonic risk are necessary.
The project will run for 5 years and is organized into 3 task areas.
Task 1 - Modeling of power electronics based power systems
The different apparatus in power electronics based power system will be moded taking into account a wide-band behavior.
Task 2 - Harmonic analysis and mitigation
Devloping tools for analysis of harmonics being present in a power system as well as proposing methods to reduce the harmonics in a proper way to keep stability.
Task 3 - Stability and system assessment
Using the knowledge of the previous two tasks to improve the harmonic reliability of small-scale and larger-scale power systems. The methods need also to be evaluated on an experimental platform.
Manpower
HARMONY will fund 4 Ph.D. students and 5 Post Docs (2 Year each). The Principal Investigator will overall be in charge of the project being responsible to achieve goals/milestones and he will supervise some of the Ph.D. students and Post Docs. Collaborators will provide guidance to the Ph.D. students and contribute with related activities, which they have in their own research portfolio.
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