Wind-Diesel Hybrid System: Overview of the Requirements, Models and Software Tools Hussein Ibrahim, Ph.D.

Transcription

1 Numerical Modeling Wind-Diesel Hybrid System: Overview of the Requirements, Models and Software Tools Hussein Ibrahim, Ph.D. Electrical Power and Energy Conference (EPEC 2011 Winnipeg, Manitoba, Canada October 3-5, 2011

2 Outline General context Wind-Diesel-Systems Wind Energy/Power Penetration Classification of Wind-Diesel Systems Mode of Operation of Wind-Diesel Systems Numerical Models Numerical Models: Dynamic Models Software Tools Conclusions 2

3 Remote areas General context Forcommunitiesthatarenotorcannotbelinkedwiththenationalgrid (Nordic villages, islands,...) Towers and telecommunication relays, meteorological equipments, suppliers, chalets, agricultural and fish farming installations as well as for mines, scientific and military bases. Usually fuelled by diesel generators(associated problems) 3

4 Diesel Generators General context 1. Optimization required: energetic, economic and environmental 2. Minimal exploitation power limited to 30% of the nominal power because of the diesel generators wear low utilization factors. 3. Requires frequent visits and maintenance services 4. Highly depends on imported fuel and the transportation mode 5. Difficulty for on-time supply of fuel 6. High cost of exploitation Annual deficit of 133M$ (Quebec isolated grids) 7. Source of continuous emission of Greenhouse gases (140,000 tons per year: Canadian isolated grids) 4

5 Wind-Diesel Systems Utilization of wind energy provides reduction of fuel consumption, whereas the diesel genset assures the reliability of power supply. The diesel genset cannot be completely eliminated, because the wind turbine is not reliable power source and requires very large energy storage to assure the power at low wind conditions. In the most cases, the power of installed diesel gensets is much higher than the power of wind turbines. In peak, the wind turbines can cover evenmore than90% of demanded power, but in long term the fuel saving is10-15%. 5

6 Wind Energy/Power Penetration There are many different potential configurations for Wind Diesel power systems, one of the critical design factors is how much energy is coming from the wind called wind penetration. 1. Instantaneous Penetration = Wind Power Output (kw) Primary Electrical Load (kw) Voltage and frequency control Reactive power 2. Average Penetration = Wind Energy Produced (kwh) Primary Energy Demand (kwh) Total energy savings Loading on the diesel engines Spinning reserve losses/efficiencies 6

7 Classification of Wind-Diesel Systems Penetration class Low Medium High Operating characteristics Diesel runs full-time. Wind power reduces net load on diesel. All wind energy goes to primary load. No supervisory control system Diesel runs full-time. At high wind power levels, secondary loads dispatched to ensure sufficient diesel loading or wind generation is curtailed. Requires relatively simple control system. Diesel may be shut down during high wind availability. Auxiliary components required to regulate voltage and frequency.requires sophisticated control system. Instantaneo us penetration <50% 50%-100% 100%-400% 7

8 Mode of Operation of Wind-Diesel Systems High penetration wind-diesel system has three types of operating conditions: 1. Diesel Only (DO):the maximum power from the wind turbine generator (WTG) is always significantly less than the system load. In this case, the Diesel generators (DG) never stop operation and supply the active and reactive power demanded by the consumer load. 2. Wind Diesel (WD): the WTG power is frequently approximately the same as the consumer load and in addition to DG(s), WTG(s) also supply active power. 3. Wind Only (WO):the WTG power is often substantially greater than the system load and the Diesel generators are not running, sothatnofuelisconsumedinthismode. 8

9 Numerical Modeling: Requirements The wind-diesel models include: 1. modeling the diesel-generator set, 2. modeling the wind turbine, 3. modeling and operation of the system controllers, 4. parasitic losses, 5. modeling variations in system load 6. Modeling variations in wind speed(from both synoptic effects (longer term) and turbulence) Many factors influence the layout of a numerical model, and the main factors include: 1. The objectives of the simulations 2. Timescaleofthemodeling 3. Modeling principle(deterministic or probabilistic) 4. Representation of the technical& economic scenarios 5. System configurations, including dispersed vs. single system configurations Additional factors must be take into account as: Screening or optimization of possible system/grid configurations. Overall annual performance of selected configurations. Supervisory control including scheduling/dispatch of generating units. Grid modeling, stability or load flow. 9

10 Numerical Models Depending on the simulation time, two broad categories of hybrid systems models can be identified: logistic models and dynamic models. Logistic models are used to represent long-term operations of wind power hybrid systems. Thus, they assume that the short-term dynamics is stable (study state models) and they can be divided into two subgroups: probabilistic models and time-series models. Probabilistic modeling, based on probability distributions such as load duration curves or wind speed probability curves, can work directly with the outputs of typical utility statistics and WAsP analyses. Time Scale Time-scale 1(TS1) Time-scale 2(TS2) Time-scale3(TS3) Time-scale 4(TS4) Characteristics Logistic analysis of power flows and seasonal/annual energy production. Days, weeks, months, seasons or one year at time steps 10 minutes to one hour. Dispatch analysis of supervisory control, including diesel dispatch. Typically afewminutesto1hourattimestepsof0.1to1sec. Dynamic analysis of machine dynamics, power quality or grid stability. Typically around 1 minute at time steps around 0.01 sec. Transient analysis of electrical transients due to switching, or certain power quality measures. Typically a few seconds at time step < sec. 10

11 Numerical Models: Dynamic Models Type of model Quasi-steady-state models Dynamic mechanical model Dynamic mechanical, steady-state electrical model Dynamic mechanical and electrical model Characteristics These types of models may be used for wind and wind/hybrid systems with relatively large amounts of storage capacity or combined with a dynamic model for use with low or no storage systems. They are particularly useful for economic analysis. This type of model is based on the mechanical equations of motion andpowerbalances.ithasbeenusedtogetafirstapproximationof thedynamic behaviorofasystemandto findsuchlongterm effects as the start-stop behavior of the diesel engine component. This type of model is based on the mechanical equations of motion and the steady-state equations of the electrical components of the system. It can give a first approximation of the electrical behavior of the system. This type of model is based on the dynamic equations of motion of the mechanical and electrical components of the system. It is intended to investigate the electrical stability of the system (millisecond scale) and mechanical vibrations. 11

12 Software Tools Typeof tools Prefeasibility tools Sizing tools Simulation tools Openarchitecture tools Characteristics A prefeasibility tool automates the calculations that an engineer wouldnormallydobyhand. Ithelpstodeterminewhetherawind power system makes sense for a specified application, both in terms of the energy provided and the life-cycle cost of the energy. The sizing tool performs dimensioning of the system: given an energy requirement, it determines the optimal size of each of the different components of the system. With simulation tools, the user must specify the nature and size of each component. The tool then provides a detailed analysis of the behavior of the system. In open architecture tools: the software consists of a selection of routines, describing the components, and platform for linking these routines together. The user is at liberty to modify the routines or add wholly new routines Available Tools RETScreen FATE2-P HOMER HYBRID DESIGNER PROLOAD Proprietary tools HYBRID2 WINSYS SIMENERG INSEL HOGA SOMES RAPSIM SOLSIM Matlab/Simulink TRNSYS

13 Conclusions A realistic representation of wind-diesel system and control strategy in the modeling is essential for a reliable prediction of system performance. Several techniques can be applied to facilitate flexible modeling of system configuration/connectivity, while flexible modeling of supervisory control strategy appears to be even more challenging. For dispersed systems, the electric grid becomes part of the system. Deterministic load flow analysis is well established, but probabilistic load flow modeling is more in line with the stochastic nature of wind and loads in isolated systems, and the associated probabilistic power quality measures. Actual grid stability analysis requires real dynamic electromechanical models, and such analysis is frequently outside the scope of isolated system analysis. Finally, the design and simulation tools that have been developed over the past few years have been briefly described, highlighting the fact thatsomeofthemcanbedownloadedandusedfreeofcost. 13

14 Thank you for your attention Questions? 14

15 Merci! Hussein IBRAHIM, Ph.D. 51 chemin de la mine G0E 1W0, Murdochville, QC Tél: # EOLIENS