Final Report Summary - UNIFLEX-PM (Advanced Power Converters for Universal and Flexible Power Management in Future Electricity Networks)
The overall objective of UNIFLEX-PM project was to develop and experimentally verify new, innovative modular power conversion architectures for universal application in the future European electricity network. The project focussed on technology capable of addressing emerging problems and requirements in electricity networks, such as implementation of certain SmartGrids scenarios and deep penetration of distributed energy generation technologies.
UNIFLEX-PM was divided in interrelated work packages (WPs), which addressed the following issues:
1. emerging and future application requirements and priorities;
2. converter structures;
3. isolation modules;
4. control and grid interaction;
5. reliability and economics and
6. technology validation.
UNIFLEX-PM aimed to determine the performance requirements, electrical specifications and control requirements for innovative power electronic converters in order to address various demands and priorities of the electricity network. Functionalities included monitoring and control of all electricity characteristics. Potential applications of the system include active node and DG Interface, where the UNIFLEX-PM system can replace the classical iron based solutions representing an 'intelligent transformer'. In that way increased flexibility in the power management and control of the distribution network is obtained.
UNIFLEX-PM developed and validated through simulation alternative multi-cellular, modular and scalable converter concepts that could be employed. Optimised modulation strategies, such as selective harmonic elimination (SHE) were investigated and applied in order to control the power flow between cells of a multi-cellular structure. The potential increase in waveform quality at low device switching frequency was also examined.
Regarding isolation modules, UNIFLEX-PM considered two variants, based on either DC-DC or AC-DC (cycloconverter) isolation. The first module used a transformer operating between two voltage sources and the second had a voltage source converter at the primary side and a current source at the secondary side. Two different medium frequency transformers (MFT) were constructed for each module and employed for their testing, in order to compare their performance and define which to use in the technology validation phase. The selection of the option to be included in the technology validation platform was based on theoretical efficiency comparison, which resulted in the promotion of the DC-DC module.
The objective of the control and grid interaction investigation was to research overall control structures, so that the modular converters could achieve efficient manipulation and storage of energy along with coordinated control across the network. The control strategies investigated were based on a two-port structure of the UNIFLEX-PM system, while the rated parameters used in modelling resembled those included in the technology validation platform. Four alternative control structures were considered and their performance was critically analysed so that a selection could be made and promoted for use.
A reliability and economics study was carried out, which aimed to:
1. define and parameterise the reliability models for the analysed configurations taking into account conditions related to the operating environment.
2. perform a preliminary assessment of the impacts derived from the adoption of the proposed solution through a technical and economical comparison with a reference case. The example chosen was a high voltage direct current (HVDC) converter, having a four quadrant operation capability. The performed simulations took into account different working conditions, architectures, technologies and maintenance policies in order for the comparison to be reliable. The results proved that the two alternatives were comparable in terms of availability, thus the UNIFLEX-PM architecture could be successfully industrialised. More detailed analysis allowed for identification of the margin of improvement so that reliability could be increased with simultaneous ownership cost reduction.
The developed technology was validated through the construction and evaluation of a UNIFLEX-PM multi-cellular converter, which was commissioned in sections over six months. Different tests, related to all parameters influencing the platform performance were successfully carried out.
Among the major achievements of the UNIFLEX-PM project were that the designed converter proved to be suitable for application in a range of future distribution grid scenarios and that its commercial exploitation turned out as being feasible. Moreover, advanced reliability and availability modelling tools were developed, which could be applied to other network equipment. The acquisition of in-depth knowledge in power electronic systems for medium voltage network applications was also among the project exploitable results in terms of expanding future research and commercial prospects.
UNIFLEX-PM was divided in interrelated work packages (WPs), which addressed the following issues:
1. emerging and future application requirements and priorities;
2. converter structures;
3. isolation modules;
4. control and grid interaction;
5. reliability and economics and
6. technology validation.
UNIFLEX-PM aimed to determine the performance requirements, electrical specifications and control requirements for innovative power electronic converters in order to address various demands and priorities of the electricity network. Functionalities included monitoring and control of all electricity characteristics. Potential applications of the system include active node and DG Interface, where the UNIFLEX-PM system can replace the classical iron based solutions representing an 'intelligent transformer'. In that way increased flexibility in the power management and control of the distribution network is obtained.
UNIFLEX-PM developed and validated through simulation alternative multi-cellular, modular and scalable converter concepts that could be employed. Optimised modulation strategies, such as selective harmonic elimination (SHE) were investigated and applied in order to control the power flow between cells of a multi-cellular structure. The potential increase in waveform quality at low device switching frequency was also examined.
Regarding isolation modules, UNIFLEX-PM considered two variants, based on either DC-DC or AC-DC (cycloconverter) isolation. The first module used a transformer operating between two voltage sources and the second had a voltage source converter at the primary side and a current source at the secondary side. Two different medium frequency transformers (MFT) were constructed for each module and employed for their testing, in order to compare their performance and define which to use in the technology validation phase. The selection of the option to be included in the technology validation platform was based on theoretical efficiency comparison, which resulted in the promotion of the DC-DC module.
The objective of the control and grid interaction investigation was to research overall control structures, so that the modular converters could achieve efficient manipulation and storage of energy along with coordinated control across the network. The control strategies investigated were based on a two-port structure of the UNIFLEX-PM system, while the rated parameters used in modelling resembled those included in the technology validation platform. Four alternative control structures were considered and their performance was critically analysed so that a selection could be made and promoted for use.
A reliability and economics study was carried out, which aimed to:
1. define and parameterise the reliability models for the analysed configurations taking into account conditions related to the operating environment.
2. perform a preliminary assessment of the impacts derived from the adoption of the proposed solution through a technical and economical comparison with a reference case. The example chosen was a high voltage direct current (HVDC) converter, having a four quadrant operation capability. The performed simulations took into account different working conditions, architectures, technologies and maintenance policies in order for the comparison to be reliable. The results proved that the two alternatives were comparable in terms of availability, thus the UNIFLEX-PM architecture could be successfully industrialised. More detailed analysis allowed for identification of the margin of improvement so that reliability could be increased with simultaneous ownership cost reduction.
The developed technology was validated through the construction and evaluation of a UNIFLEX-PM multi-cellular converter, which was commissioned in sections over six months. Different tests, related to all parameters influencing the platform performance were successfully carried out.
Among the major achievements of the UNIFLEX-PM project were that the designed converter proved to be suitable for application in a range of future distribution grid scenarios and that its commercial exploitation turned out as being feasible. Moreover, advanced reliability and availability modelling tools were developed, which could be applied to other network equipment. The acquisition of in-depth knowledge in power electronic systems for medium voltage network applications was also among the project exploitable results in terms of expanding future research and commercial prospects.