Power Electronics for Renewable Energy Technologies
Most renewable energy harvesting technologies present their energy output as electricity. Wind, wave and tidal technologies convert the kinetic energy of natural air or water movement into electrical energy via rotating generators. Solar panels use the photo-voltaic effect to produce electricity directly from sunlight. Biomass and hydrogen technologies can be used to produce electricity - either directly or via generators. Whichever renewable energy harvesting technology is used, however, the electrical output will almost certainly be in a form which is unsuitable for use by the energy user. The most convenient form of electricity for the consumer is the familiar 220V, 50Hz AC used extensively in domestic, commercial and industrial environments. Solar panels, for example, produce a DC output which requires an inverter for conversion to AC. Similarly, generators associated with other renewable energy technologies, may output DC or AC power. Even if the output is AC it will need to be conditioned to correspond with voltage, frequency and phase supply standards. Power electronics for renewable energy technologies, then, is concerned with extracting electrical power from the energy harvesting system and converting it, with optimum efficiency, into a usable form. System sizes range from micro-generation of a few Kilowatts for individual domestic use, to full-scale power generation installations which may be many Megawatts.
Of course, there are many other power electronics issues which must be addressed when considering the whole renewable energy installation. Renewable energy systems may be either grid-connected or stand-alone.
Grid-connected systems allow any generated power which is not used locally to be sent to the national network. Additionally, the network can be used as a backup when the renewable energy system is not producing electricity. Grid-connected systems must meet stringent power quality requirements imposed by the national network operators.
Stand-alone systems may not be subject to the same stringent power quality requirements, but have other engineering challenges to be addressed. With no permanent network to rely on, the stand-alone system must have its own back-up power source to maintain local supply when the renewable energy source is not generating. Usually this back-up takes the form of batteries which are charged when excess energy is produced.
Whether grid-connected or stand-alone, there are many common requirements in power electronics systems. The electronics must ensure that the maximum power is extracted from the energy harvester. As the operating point for maximum power varies with operating conditions (light intensity, tidal activity, etc), the electronics continuously checks for optimum operation. Also, the switching between renewable generation and back-up, whether grid or battery, and the decision-making and control associated with it, is a power electronics function. Related to this are the protection protocols associated with under/over voltage, over current and other fault conditions for which the electronic system is continuously monitoring.
Most importantly, the power electronics system must convert the electrical power as efficiently as possible. Any inefficiency is not only a loss of useful power, but that power also will manifest itself as heat within the electronic converter. Excess heat is damaging to electronic components and can be difficult to get rid of. Electronic power converters with efficiencies >> 95% are realisable and engineers continuously strive for ever more efficient conversion techniques.
WEST course
The modules on power electronics for renewable energy technologies which have been developed by the WEST project, are designed to provide the professional engineer with the knowledge to understand modern techniques and to integrate power electronics within a renewable energy system. The course material will benefit both electronic system designers, who require an in-depth knowledge of power electronics for future system design, and non-electronic engineers who wish to upgrade their knowledge in order to more efficiently integrate power electronics into their own specialised sphere of expertise. The course content has been developed after consultation with industrial and commercial companies in the renewable energy sector, and reflects the real training needs which have been identified in this growing market. The course material includes :-Power conversion techniques
- AC >DC
- DC > AC
- DC > DC
- PWM switching techniques
- Protection strategies
- PFC and harmonic control
Power electronics interfacing to energy harvesting systems
- Maximising the power output from renewable energy sources
- Control techniques
- Conversion efficiency
Power device circuit models
- Electro-thermal modelling techniques
- Compact model analysis
Power integrated circuit technology
- Semiconductor technology for power electronic devices
- Isolation strategies
- Power integration techniques
Reliability
- Concepts of reliability
- Enhancing reliability – techniques for both manufacturer and user
- Accelerated life processing
- Hi-Rel manufacturing – a case study
Project
- A power electronic project intended to illustrate the design, simulation, construction and evaluation process for the production of a power converter.
- Techniques covered in the course content will be utilised for the successful completion of the project.
Power Point Presentations
- System Strategies Workshop
- Building Integration Workshop
- Reliability Issues Workshop
Further Information
Stephen BatcupCourseware Developer
Electronics Systems Design Centre
School of Engineering
Swansea University
Singleton Park
Swansea
SA2 8PP
Tel : (01792) 295690
Fax : (01792) 295676
Email: s.g.batcup@swan.ac.uk