post-damage (electrical) systems availability · in the example the top event “no electrical...

Post-damage (Electrical) Systems Availability

!Konstantinos Sfakianakis

MEng, PhD candidate !!

University of Strathclyde Department of Naval Architecture, Ocean and Marine Engineering

!Design for Safety

/ Probabilistic-based Design

• Introduction • Approach Adopted • Example • Case study (1) • Case study (2) • Concluding Remarks

Presentation Outline

Introduction

Containing Risk Today (Human Life)

SOLAS !!

Consensus-based, minimum standards of safety Targeting to reduce consequences

Historical risk, reflecting specific data sets !!!Compliance with Rules/Regulations

Introduction Passenger ships accidents

Introduction Accident Statistics

Introduction

• Ship systems design is addressed as one of the most dominant issues in shipping industry

• Systems reliability is considered as driving force during the systems design

Even though:

Introduction Up to now

• The strict international rules and regulations concerning systems safety

• The systems design simplicity based on past experience with lack of a systematic and structured approach

No room for innovations !

Introduction Up to now

In specific: • SOLAS ’90 and independent classification societies

imposing the systems components location, geometry and in some cases topology, to comply with their requirements in order to be accepted without the presence of any alternative design.

Reg. 41- Main source of electrical power and lighting systems !Par. 3. The main switchboard shall be placed relative to one main generating station … An environmental enclosure for the main switchboard, such as may be provided by a machinery control room situated within the main boundaries of the space, is not to be considered as separating the switchboard from the generators. !Par. 4. Where the total installed electrical power of the main generating sets is in excess of 3MW, the main busbars shall be subdivided into at least two parts which shall normally be removable links or other approved means;…

Introduction Example- SOLAS ‘90

Introduction Up to now – SOLAS ‘90

• The previous example highlights the deterministic approaches based on past experience that the ship systems are designed and reveals the need for increased designers flexibility adopting innovative design methodologies. !

• The absence of the nature of the accident lead to insufficient, in terms of safety, and possibly more expensive systems designs.

• New international regulations (SRtP) address the availability issues for more efficient and safe systems design. !

• Intend to ensure high systems reliability (not only in normal operation but also in emergencies) !

• Consider abandonment as the last safety barrier to be used when all means of saving the vessel failed !

• Impose capability by the vessel to sail to the nearest port post-casualty (3 hours operation)

Introduction New international regulations - Safe Return to Port (1)

Introduction IMO (SLF 47/48) Passenger Ship Safety

Introduction Example of Loss Scenario – Flooding / Collision

preventionmitigation

Introduction Systems Availability Analysis – SRtP Casualty Scenarios

• “A passenger ship shall be designed so that it’s safety-critical systems remain operational when the ship is subject to flooding of any single watertight compartment” (SOLAS II-1/8-1) !

• “Design criteria for (safety-critical) systems to remain operational after a fire casualty” (SOLAS II-2/22)

Introduction Safe Return to Port (2)

Casualty threshold, in the context of a fire, includes: • Loss of space of origin up to the nearest “A” class

boundaries, which may be a part of the space of origin, if the space of origin is protected by a fixed fire-extinguishing system; or

• Loss of the space of origin and adjacent spaces up to the nearest “A” class boundaries which are not part of the space of origin.

Introduction Safe Return to Port – Casualty Threshold

Introduction Systems Availability Analysis – SRtP Safety Critical Systems

Safe areas functional requirements: • The safe area(s) shall generally be an internal

spaces(s) • The safe areas shall provide all occupants with the

following basic services to ensure that the health of passengers and crew is maintained:

– Sanitation – Water – Food – Alternate space for medical care – Shelter from the weather – Means of preventing heat stress and hypothermia – Light – Ventilation

Introduction Safe Return to Port – Safe Areas

• Ventilation design shall reduce the risk of smoke and hot gases that could affect the use of the safe area(s) !

• Means of access to life-saving appliances shall be provided from each are identified or used as a safe area, taking into account that a main vertical zone may not be available for internal transit.

Introduction Safe Return to Port

SRtP afford design flexibility through the Alternative Design and Arrangements (AD&A) framework (SOLAS II-1/55) through the demonstration of equivalent designs.

Introduction Safe Return to Port (4) – Flexibility to designers

Approach Adopted

Introduction Up to now – Systems Reliability

Concerning the qualitative and quantitative systems reliability analysis, tools as:

• Fault Tree Analysis (FTA) • Failure Mode and Effects Analysis (FMEA) • Failure Mode, Effects and Criticality Analysis

(FMECA) • HiP-HOPS

• Driven by the absence of post-casualty systems performance in past regulations:

– Reliability analysis based on components failure description and their topology (FMEA/FMECA, FTA)

– Past operational experience

Approach AdoptedPractice Today

Independent to the ship environment!

Approach AdoptedPractice Today - Example

In the example the top event “no electrical power at motor 1” occurs if one of the following failure modes takes place (ordered from consumer to generator): !• Interruption (connection failure) in “cable1”, • Short circuit in “cable1”, • Short circuit in “switch1”, • “switch1” inadvertently open, • Short circuit in “switchboard1”, • Short circuit in “genSwitch1”, • “genSwitch1” inadvertently open.



The failure probability of all components within a time span t and for a failure rate λ is calculated using the cumulative exponential failure description: !!

!!

!The system failure probability is calculated to 2.5·10-9 for t = 24 hours

• The new regulations implicitly introduce concept of the absolute survivability, i.e. floatability combined with the survivability of the functions.

• Therefore, it is thought that the probabilistic approach used in the damage stability to evaluate safety of the ship (index-A) can be successfully used for systems availability assessment.

• The probabilistic, index-based, methodology not only allows meet the criteria but it additionally ensures consistency between survivability of vessel and onboard systems.

Approach AdoptedAdopting a performance-based approach

Approach AdoptedAdopting a performance-based approach

• Performance-based approach focused on the logical and topological modelling of the electrical distribution energy systems into the ship environment

• Systems quantitative performance assessment at emergencies under statistical flooding damages

• Mapping the functionality of each system to logical/dependency structures

• These structures comprises physical, functional and spatial distribution relations of each system

Approach AdoptedLogical and Topological Modelling

Approach AdoptedSystem dependency tree example of propulsion system

• Use of collision and grounding casualties • Damage scenarios are generated with use of NAPA

software • The probability of damage occurrence at each

compartment and at all possible combinations of compartments are called p-factors.

• The p-factors for all damage cases along with a list of compartments being damaged are passed as input for probabilistic assessment of systems availability.

Approach AdoptedDamage scenarios - Initiation of the systems and components failures at emergencies

• After the components placement within the vessel environment, with the parallel creation of dependency structures, the computational stage is following.

• All the system components and functions are subjected to individual damage scenarios, which are defined as a combination of probability of occurrence pi and a list of spaces (rooms) being affected.

• An average probability of system being unavailable given any considered damage scenario has happened is evaluated

Approach AdoptedAvailability Analysis

The element pi denotes probability of the i-th scenario and Fj stands for aggregated probability of j-th system being

unavailable. The normalising factor 1

1

n

iip

−

=

" #$ %& '∑ is used as p-factors should be sum up to one in case of all possible

damages are considered. However, for the case of SRtP compliance, only damages occurring in any single WT compartment are assessed and so the normalising factor equals the sum of the probability of damage occurrence in each specific WT compartment. Furthermore, the precise meaning of the components Fj of the vector F (probability of j-th system being unavailable) is an average probability of system being unavailable given any considered damage scenario has happened

Approach AdoptedAvailability Analysis

Example

Example

Apply the electric power system to the ship environment (with safety constraints)Example with the use of iSys software

•2 decks of a notional ship !

•The main switchboard supplying two loads is defined !

•The cable routing is defined !

•Application of flooding damage is under investigation

Example (explanation of iSys software)

• The diagram of the electrical components is presented in the next slide with their corresponding topologies !

• The Switchboard-Load1 are connected directly since they are placed in rooms one next to the other. However, the connection of Switchboard-Load2 is achieved through the cable routing of Load1 room. !

• Afterwards, we apply a damage to each room and the results show the damage effects in our systems.First, we apply to room of load2, after to the load1 and last at the switchboards room.

switchboard

load1

load2

load2

load1

switchboard

Example

• We can easily notice that when a damage applied to the room of Load1 (middle compartment), there isn’t supply to Load2. !

• By re-routing the distribution system and adding circuit-breakers for elimination of the damage, we can achieve the appropriate redundancy of power distribution.Having this in mind, the redundant energy routing is through the upper deck. !

• We are now add a ship function to supply power the load2 either through the initial path or through the new design.

New design of power distribution

Example - Results

As we see below, during the damage in the middle compartment, the initial cabling is damaged and eliminated by the circuit-breakers to both directions, as well as the Load2 is supplied through the new design path

Case Study(1)

SAFEDOR

Alternative design

Results Explanation

• Average probability of systems being unavailable given collision and flooding within a single WT-compartment. !

• Average probability of systems being unavailable given uncontrolled fired on a single deck within a single MVZ

Results

Case Study(2)

Case Study

• Compare a conventional with an alternative design of a RoPax ship electrical distribution systems considering: – Damage scenarios to any single WT compartment – All possible damage scenarios

• Damage propagation is not investigated • Rooms and spaces current usability is not taken under

consideration

System Sub-System Component Number of

sets (in use) Location Source

Propulsion

Ventilation

Engine Room Supply fan 2(1) Upper deck MSWBD

Auxiliary Room Supply fan 2(1) Upper deck MSWBD

Engine Room Exhaust fan 1(1) 4th deck MSWBD

Auxiliary Room Exhaust fan 1(1) 4th deck MSWBD

Air M/E Air Compressor 2(1) Engine Room SWBD_4

Fuel

ME FO Booster pump 2(2) Engine Room SWBD_3

DE FO Booster pump 2(2) Auxiliary

Room SWBD_1

DO Transfer pump 1(1) Auxiliary

Room SWBD_1

FO Transfer pump 1(1) Auxiliary

Room SWBD_1

DO Purifier 1(1) Auxiliary

Room SWBD_1

FO Purifier 2(2) Auxiliary

Room SWBD_1

Lubrication

LO pump 4(2) Engine Room SWBD_3,

SWBD_5

Reduction Gear LO pump 4(4) Engine Room SWBD_4,

SWBD_5

LO Purifier 2(2) Auxiliary

Room SWBD_2

DE LO Purifier 1(1) Auxiliary

Room SWBD_2

Cooling

ME LT FW cooling pump 2(2) Engine Room SWBD_5,

SWBD_6 ME FW cooling pump 2(2) Engine Room SWBD_3

ME HT FW cooling pump 2(2) Engine Room SWBD_3

SW cooling pump 3(2) Engine Room SWBD_3,

SWBD_6

DE LT FW cooling pump 2(2) Auxiliary

Room SWBD_2

CPP CPP Propeller pitch setting pump 4(4)

Engine Room SWBD_4, SWBD_6

Steering

Rudder Steering Gear 4(2) Steering Room MSWBD

Thruster Bow Thruster 1(1) Bow Thruster

Room MSWBD

Stern Thruster 1(1) Stern Thruster

Room MSWBD

Bilge & Ballast

Bilge, Fire & Ballast pump 2(1) Engine Room SWBD_4

E/R Fire & Bilge pump 1(1) Auxiliary

Room SWBD_2

Ballast pump 2(1) Auxiliary

Room SWBD_1, SWBD_2

Drencher 1(1) Engine Room MSWBD

Emergency

Auxiliary Room Supply fan 1 Upper deck EMSWBD

Engine Room Supply fan 1 Upper deck EMSWBD

M/E Air Compressor 1 Engine Room EMSWBD

Steering Gear 2 Steering Room EMSWBD

Bilge, Fire & Ballast pump 1 Engine Room EMSWBD

Passenger vessel WT arrangements

Case Study Conventional design

Case Study Alternative design

System Conventional Alternative Sub-systems Conventional Alternative

Propulsion 0.2 0.2

Ventilation 0.05 0.1Air 0.2 0.18Fuel 0.2 0.2

Lubrication 0.2 0.2Cooling 0.2 0.2

CPP 0.2 0.2

Steering 0.45 0.22Rudder 0.4 0.15Thruster 0.1 0.07

Bilge & Ballast 0.2 0.2

Emergency 0.85 0.2

Case Study Results

Average probability of systems being unavailable given collision and flooding within any single WT compartment.

System Conventional Alternative Sub-systems Conventional Alternative

Propulsion 0.27 0.27

Ventilation 0.16 0.32Air 0.26 0.2Fuel 0.26 0.26

Lubrication 0.26 0.26Cooling 0.26 0.26

CPP 0.26 0.26

Steering 0.54 0.27Rudder 0.42 0.11Thruster 0.18 0.15

Bilge & Ballast 0.26 0.26

Emergency 0.93 0.27

Average probability of systems being unavailable given collision and flooding considering all the damage scenarios

Concluding Remarks (1)

• Considering Safety as a design objective, more efficient in terms of costs, spaces and safety, electrical onboard distribution energy systems can be obtained

• The redundant components can be minimised and the option of redundant flow paths, usually close to the centre of the ship and in WT compartments far from the MSWBD through higher decks, is possible

• The size of the emergency source of power can be optimised

• Taken under consideration all possible damage scenarios during the assessment, more accurate design recommendations can be applied.

• Approval of Alternatives and Equivalents (IMO MSC/Circ. 1455)



• This work is a part of the holistic performance-based approach for the design of the electrical onboard energy systems aiming to the multi-objective optimisation in terms of energy efficiency, safety and cost.

!Design for Energy Efficiency

/ Dynamic Energy Modelling

• Introduction • Approach Adopted • Example – Cargo • Design of Power Generation (Capacity) • Power Management Systems (PMS) • PMS during Design – Example • PMS during Operation - Example • Multi-objective optimisation

Presentation Outline

Introduction

Legislation Environmental performance of ships

EEDI, EEOI, SEEMP

Environmental performance

Energy efficiency

Legislation Energy Efficiency Design Index (EEDI)

CO2 emissions [grams CO2]

Benefit to society [tonnes x nm]

• Design index applicable to new ships only • Aimed to stimulate more efficient ship

designs and technologies • Regulated through IMO as technical

means to control CO2 • New ships must meet a required efficiency

level (reference line)

Legislation Energy Efficiency Design Index (EEDI)

• MARPOL Annex VI, Chapter 4, “Regulations on Energy Efficiency for Ships”

• Enters into force 1st January 2013 • EEDI (new ships) • SEEMP (all ships) • Both will form part of the International

Energy Efficiency Certificate (IEEC) • EEOI: optional tool for operational

indexing

What do the regulations say? Goal-based legislation (performance standard)

• Ships > 400 GT (excluding ships with gas turbine, diesel-electric and hybrid propulsion): – Bulk carrier – Gas carrier – Tanker – Container ship – General cargo ship – Refrigerated cargo carrier – Combination carrier – Passenger ship1

– Ro-Ro ships1 (cargo, vehicle, – passenger)

!1 EEDI to be calculated but not yet subject to regulatory limits

Where do the regulations apply? Targeted ship types

Capacity [DWT or GT]Cut off limit

0%

Phase 0: 2013-2015

-10%

Phase 1: 2015-2020

-30%

Phase 3: 2025 +

-15% -20%

Phase 2: 2020-2025

EEDI – How will it be implemented?A 4-phase implementation approach

World Fleet (fuel-saving market)Share by EEDI-targeted ships

Ship TypeMedium

(500<GT<25000)Large

(25000<GT<60000)Very Large (GT>60000) Total

Bulk Carriers 3650 12% 3702 42% 1174 31% 8526 20%Gas Tankers 995 3% 192 2% 319 8% 1506 4%Oil and Chemical Tankers 6595 22% 2205 25% 1238 33% 10038 24%Container Ships 2417 8% 1663 19% 772 21% 4852 11%General Cargo Ships 12999 43% 228 3% 0 0% 13227 31%Passenger Ships 2554 8% 268 3% 130 3% 2952 7%Ro-‐Ro Cargo Ships 843 3% 559 6% 126 3% 1528 4%

Total 30053 100% 8817 100% 3759 100% 42629 100%

55% of the world market

World MarketEEDI targets

Approach Adopted

• Modelling the dynamics of energy flows within complex engineering systems as function of time

• Accurate assessment of life-cycle fuel costs and carbon “footprint” early in the design stage and during operation

• Design for energy efficiency and minimum environmental impact, alongside other design objectives

The Way Forward Dynamic Energy Modelling

• DEM integrates knowledge from component-level to ship-system level

• The performance of ship systems is assessed by time-domain simulation revealing the true energy performance of systems

• DEM takes into consideration inherent properties of systems in relation to environmental conditions and the operational profile of the ship.

Dynamic Energy ModellingConcept

Dynamic Energy ModellingFrom Static Balance to Time-Domain Simulations

Complex Systems

Dynamic Systems

Steady State Systems

Simple Systems

Response Function Methods • Based on first principles • Accommodate relatively complex systems • Reasonable for short time periods • System parameters linear & time invariant, hence results may be unrealistic

Static Balance Methods •Accommodate isolated systems •No mechanism for complex interactions • Safeguarding against worse-case scenarios

Numerical Simulation Methods • Founded on first principles • Accommodate design and operational complexity • Account for complex interactions • Energy flow instead of energy balance • Suitable for any design stage •No limit in time periods (seconds to life cycle)

Simple Dynamic Methods • Based on regression models of past / existing designs or simplified simulations • Can not accommodate innovative designs

Components Systems Global System/Ship

Sumi

Sum

Dynamic Energy ModellingEnergy Systems and Components

Dynamic Energy ModellingIntegration

Added Resistance

Engine Room Systems

Auxiliary Energy

Propeller

Frictional resistance/ Hull coatings

Advanced Surface technology

Wave Resistance

Superstructure Component

Prime Mover Component

Electric Power System

Time-domain simulation of power demand

Optimisation

• Global Efficiency!• Local Efficiency!• Operational Costs!• Life-cycle

Performance!• Other

Dynamic Energy ModellingMethodology

Dynamic Energy ModellingApproach Adopted

MECHANICAL ENERGY

DEM PLATFORM Integration /Simulation

Optimisation

LIFE-CYCLE ENERGY MANAGEMENT

•DESIGN •OPERATION •RETROFITTING

THERMAL ENERGY

CHEMICAL ENERGY

ELECTRIC ENERGY

Dynamic Energy Modelling Electric Power System - Objectives

• Scope – Electric power components

(generators, motors, transformers etc)

– Control strategies during operation • Objectives

– Dynamic modelling of shipboard electric power system

– Power Management System (PMS) to monitor and control the overall performance of the marine power system.

Dynamic Energy Modelling Electric Power System – Practice today

• The sizing of the diesel generators is based on static balance calculations ( i.e. electric load analysis)

• Based on the maximum values of these calculations, appropriate engines are selected from suitable database

• All auxiliary systems connected to the engines are sized based on their maximum power output!

Maximum power during operation

Size and number of diesel generators

Dynamic Energy Modelling Electric Power System – What we do

• Integrate all electric components into an electric power system (manufacturers data and first-principles models)

• Identification of dominant parameters affecting the process • Create knowledge intensive models (KIMs) to capture all the essential

information at component level • Integrate the electric power system into the ship system model

Dynamic Energy Modelling Electric Power System – Link with other systems

• The electric power system is linked with (almost) all other energy systems onboard ships

• For any changes in the power demand at the boundaries of the system (on/off of motors, lighting, etc) the system balances at a different operating state

Interaction with Diesel Engine Module

Interaction with Environment

Interaction with other energy systems

Interaction with other energy systems

Example !

Cargo ship

Example

• On-board electric power system of two bulk carriers. Example

Cargo bulk carrier ship 85,400 GT !• Diesel Generator x3 : 750kVA ( 600kW) • Induction motors : 0.5 – 300 kW • Transformers: 15kVA , 90kVA • Lighting : 15kVA, 100kVA • Minor equipment: 35 kW

It is investigating at sea going and as a result only one Diesel Generator is in function. The numbers next to the components are the number of components that are in function at the on-board measurements.

Three%phaseInduction1Motor

Three%phase1Induction1Motor

Lighting

Three%phase1Synchronous1Generator

Three%phase1Transformer

Fan

Minor1Equipment

Pump

Diesel1Engine

BUS1

x40

x12

MCTC

MCTC

MCTC

MCTC

Diagram

Results (Active & Reactive Power)

My results On-board measurements

Results (Power Factor)

My results On-board measurements

Design of Power Generation (Capacity)

Design of Power Generation Capacity - Empirical formulae

• Empirical formulae can be used successfully to obtain a first estimation if the electric power demand in the pre-design stage, if the formulas are based on a sufficient number of ships with the same mission statement and comparable size. However, for the detailed design of the ship and electrical systems one of the next methods is indispensable to get a more reliable result. !• When empirical formulae are at hand, they can be used to determine the

electric power demand or installed electric power by using, for instance, the main dimensions of the ship such as deadweight size or installed propulsion power. A common formulae is the one below that uses the installed propulsion power to determine the electric power demand as sea for a conventional cargo vessel without special equipment such as cargo refrigeration system or bow thruster. As a rule of thumb, the electric load when manoeuvring is 130% of the electric load at sea, and the load in power is 30 % to 40%.

!!• The use of empirical formulas might be successful

provided that the ships are comparable in size and mission.

0.7100 0.55*( )EL MCRP P= +

Empirical formulae

• The most widely method for determining the electric power demand is the so-called electric load analysis or electric load balance. The balance sheet lists all electric power consumers, highlighting the nominal properties of all the electric consumers.(predefined_ operational conditions of the ship). In addition, estimating a load factor and a simultaneity factor for all consumers at each operating state, the capacity of the generated power, in turn the size of the power generation units, can be approximated.

• However, the estimation of the load and simultaneity factors is the most difficult part of the electric load analysis. The load factor indicates the relative (%) load of the machinery and thus specifies how much electric power is absorbed in an actual situation. A steering gear pump, for example, will only occasionally be fully loaded, so a typical load factor for a steering gear pump is 0.1. The simultaneity factor accounts for pieces of machinery that are not operated continuously but intermittently. The simultaneity factor indicates the relative (%) mean operational time of the machinery. It is often possible to make a good estimation of this factor by comparing the machine capacity and the average capacity demand. Both factors vary between 0 and 1. Usually, no distinction is made between the load factor and the simultaneity factor, and the two factors are combined into one service factor. This does, not provide a clear insight into the actual load demand.

Electric Load Analysis


• To this end, both factors are often estimated too high, in order to minimise the risk of designing a plant with a generator capacity that is too small. This results in an overestimation of the electric power demand, and consequently the chosen generator capacity is too large. The drawbacks out of this estimations are the high initial investment, the operation of the diesel generator sets away from their optimum point increasing the fuel consumption and the pollutants and finally the increase of the maintenance costs.

Power Management Systems (PMS)


The PMS is very important during all the ship stages: design, retrofitting and operation. •At the design stage PMS as an optimiser can be useful for the sizing and the number of the power generation units that has to be online at each operating stage based on the fuel consumption. •During operation the PMS can be helpful for fuel optimisation, disturbance rejection and in the maintenance of the equipment of generation, conversion, distribution and consumption through the actions of: load sharing and unit commitment, load shedding and the quality of power that it supplies. •At the retrofitting the re-configuration of the existing control system in conjunction with the appropriate location of monitoring and data collection points, can be obtained through the PMS improving so the energy efficiency as the marine power systems reliability

A sophisticated ship power management system usually provides the following main functions: • Diesel generator (DG) start, stop control • Auto-synchronizing of generators and breaker control • Load depend start, stop • Unit commitment - Load sharing • Load increase control • Blackout monitoring • Load shedding • Shaft generator (SG) load transfer


PMS during Design - Example

PMS during Design - Example

• Number of installed units is selected, Ng=4; • wr,gi = Pr,gi/Prg is manually pre-selected and listed in the table; • Total installed power Prg = 7 000 kW.

PMS during Operation - Example

Optimisation constraints (1)

The optimization of the operation of the ship power system is imposed to several constraints and limitations which are briefly described next. There are several technical constraints to be applied in order to ensure system safe operation as well as physical rules to be followed. !•Power balance constraint. It assures balance between generation and consumption as well as frequency stability. •High loading constraint. Generator should not be loaded above a certain power level for more than a specific time interval as thermal and mechanical losses are increased and blackout prevention capability is limited. •Low load constraint (technical minimum). The engine should not be loaded below a certain value specified by the engine manufacturer in order to reduce the maintenance costs and possible damage.

Optimisation constraints (2)

• GHG emissions constraint. EEOI should be monitored online and limited below a certain upper limit.

• Ramp rate constraint. High rate of change of generator loading must be avoided in order to eliminate mechanical stress and damages.

• Blackout prevention constraint. It defines the maximum allowable continuous loading of the generators where the system is blackout-proof.

• Generator start/stop constraint. Frequent start/stop of the generator results in increased maintenance cost and fuel consumption. It is a secondary priority constraint, and it can be applied by imposing a time window between successive start/stop of the generator.

Operation

Multi-Objective Optimisation

From ‘Spiral Design’ to Multi-Objective Design

D

Objective = max Area(D)

Constraints Design parameter

Design space

Two-objectives problem

Three-objectives problem Four-objectives problem...

Multi-Objective Design Optimisation Basic Principles – Definitions

• Two-Objectives Problem: maximise areas of two circles within a rectangle

• Strategies: • Sequential: subdivide problem into phases – maximise

first, then second • Holistic optimisation: maximise both simultaneously

Multi-Objective Design Optimisation Optimisation Strategies

!max

!max

max!max

max

Alternative 1 Alternative 2

Phase 1:

Phase 2:

• Number of overall alternatives is strongly limited • Design space exploration is inherently limited

Multi-Objective Design Optimisation Optimisation Strategies (Sequential / Stepwise)

maxmax

max max

!max

max!max

maxmax

max

max !max

• Number of overall alternatives is limited only by computational resources (unlimited!)

• Design space is well explored – maximum effect!

Multi-Objective Design Optimisation Optimisation Strategies (Holistic)

!!!!!!!!!!!! Design Space

Key Design ParameterCommon Key Design Parameters - reason for conflict

Obj – Design Objective/Goal

Multi-Objective Optimisation Multiple Conflicting Objectives (KPIs)

Thank you !

[email protected]

post-damage (electrical) systems availability · in the example the top event “no electrical...

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