An array-based study of increased system lifetime probability Carsten Nesgaard Technical University of Denmark in collaboration with 1
Outline • Power system description • Traditional redundancy vs. proposed redundancy concept • Advantages and disadvantages • Statistical representation of system survivability 2
Power system specifications • Unidirectional power flow • N + 2 redundancy • The power path of a converter is comprised of 5 blocks • Each converter uses a front switch 3
Redundancy in reliable power supplies 4
Alternative redundancy scheme 5
Configuration of converter 1 6
Efficiency enhancement 7
Advantages and disadvantages • Compared to a static system the ability to reconfigure itself increases the reliability of any system • The overall reliability of the proposed power system approaches that of a static N + 3 redundant system • Increased reliability with minimal increase in parameters such as volume and mass • Worst case reliability scenario equals that of the traditional static power system • Cost price increases considerably due to the large number of switches • Individual block failure rates increase 8
System configuration Nial: Nested interactive array language 9
NIAL - Nested Interactive Array Language Designed to allow easy construction and manipulation of data structures, thus enabling the user to create ultra fast – loop free – algorithms for control purposes. NIAL is developed by professor Mike Jenkins at Queen’s University in Canada. 10
Successive path finding Step 1 Step 2 Step 3 Traditional logic require multiple loops to find a feasible path. 11
Solution array Having calculated all switch positions the following array is established: +-----+-----+ |ooooo|ooooo|olooo| +-----+-----+ |loooo|olooo|ooooo| +-----+-----+ |ooloo|ooloo| +-----+-----+ |ooolo|ooolo| +-----+-----+ |ooool|ooool| +-----+-----+ Resulting matrix Switch configuration 12
Array theoretical implementation of step 1 AA: +--+--+ |lo|oo|oo|ol| +--+--+ |ol|ll|ll|lo| +--+--+--+--+ |ll|ll|ll|ll| +--+--+ Q: =((0 pick (cols AA) eachleft = ll) link o) oolllo Y: =Q sublist (reverse Res_1) +-----+-----+ |oo 1 oo|ooolo|ooool| +-----+-----+ index gets each first (Y eachleft sublist tell (first shape AA)) 2 3 4 Y (cart index 0) placeall AA All 4 lines of code can be combined and form a very fast algorithm for step 1. Modified AA: +-----+--+ |lo |oo|oo|ol| +-----+--+ |ol |ll|ll|lo| +-----+--+ |ooloo|ll|ll|ll| +-----+--+ |ooolo|ll|ll|ll| +-----+--+ |ooool|ll|ll|ll| +-----+--+ 13
Block failure rates Static power system failure rate: l Total = l Block Proposed power system failure rate: l Total = l Switch + l Block 14
Statistical assessment Power system survival probability: Proposed configuration Static configuration Minimizing individual converter failure rate does NOT imply maximum system survivability. 15
Survivability comparison Comparing the survival probability of the two configurations it can be seen that the proposed configuration is worse at total converter failure rates lower than: However, the total failure rate in a real world implementation will most often exceed the above boundary failure rate. 16
Mechanical analogy of the redundancy control 17
Mechanical analogy of the redundancy control 18
Conclusion An alternative approach in the design of reliable power systems has been presented. A redundancy control scheme using the array-based logic has been established and its capabilities in ensuring a maximum number of operational paths through the power system has been shown. The drawback of the proposed system configuration is the large number of switches. Finally, a statistical assessment of the increase in system survivability has been presented and compared to that of a traditional redundant power system. 19
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