Wind-Diesel System: Mechanical Modeling Based on Power Flow Models Hussein Ibrahim, Ph.D. Electrical Power and Energy Conference (EPEC 2011

Transcription

1 No-Storage Wind-Diesel System: Mechanical Modeling Based on Power Flow Models Hussein Ibrahim, Ph.D. Electrical Power and Energy Conference (EPEC 2011 Winnipeg, Manitoba, Canada October 3-5, 2011

2 Outline General context Wind Energy/Power Penetration Classification of Wind-Diesel Systems Different Structures of Hybrid Wind-Diesel Systems No-Storage Wind-Diesel Systems System Overview and Technical Requirements System Modeling Power Flow Modeling Versus Operating Modes Conclusions 2

3 General Context The use of diesel engines to supply power to rural communities has provided light and energy services to places where previously there has only been darkness. During the past few years, wind energy is increasingly used to reduce diesel fuel consumption (specially at low load), providing economic, environmental, social, and security benefits. Wind-diesel are designed to use as much as possible wind power in order to lower diesel consumption. The challenge is to keep the power quality and stability of the system besides the variability of the wind power generation and diesel operational constraints. 3

4 General context In a typical wind-diesel hybrid system, due to the random fluctuation of wind speed, the power generation from wind fluctuates and often mismatches with the load demand. In such situation, the diesel generator has to supply the power for a short period of time and it acts as a cushion to take care of variation in wind speedandwouldalwaysmaintainanaveragepowerequaltothesetpoint. Another serious problem faced by the isolated power generation is the frequency deviation following sudden changes in load, generation and random wind power input. The problems regarding the control of the hybrid wind-diesel system are more complex compared to grid-connected wind power systems. The main problem is the major discrepancy between the stochastic and strongly fluctuating power from the wind and the extremely exigent control demands regarding the electrical energy parameters. Introduce of some storage medium into the system to 'buffer' the excess wind energy until it is needed Or improve the control system of wind-diesel to be function without storage 4

5 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 5

6 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% 6

7 Different Structures of Hybrid Wind-Diesel Systems 1. Wind-Diesel System without energy storage 2. Wind-Diesel System with short-term energy storage(flywheel) 3. Wind-Diesel System with long-term energy storage (batteries, hydrogen, etc.), with or without photovoltaic sources, etc. The main criteria in choosing HWDS structure are: 1. satisfying the technical performance by respecting quality demands of electrical energy parameters 2. improving the economical performance by increasing the fuel savings and minimizing the electrical energy production costs in autonomous systems. This involves a small price of investment and a highest average of wind energy penetration rate. 7

8 No-Storage Wind-Diesel Systems The wind power is less than the demand load (negative load scenario). The diesel generator(s) regulates the system frequency. The wind power exceeds the demand load, but the diesel engine(s) is still operating. The diesel(s) and the dump load work in parallel to regulate the system frequency and to maintain a minimum load on the diesel(s). The wind power frequency sufficiently exceeds the demand load to allow all the diesel engines to be shut down. The dump load is now solely responsible for regulating the system frequency. 8

9 System Overview and Technical Requirements 9

10 Genset ɺ θ = ω ω cl d sg ( J J ) ɺ ω ( B B ) + = Γ + ω Γ d fc d m d fc d cl ( J J ) ɺ ω ( B B ) fw sg sg cl fw sg d sg With: + = Γ + ω Γ Γ = K θ + B ɺ θ cl cl cl cl cl N Γ = Γ + Γ sin ( kω t) m mm k d k = 1 Γ = P ω = ( η mɺ p ) ω mm m d i f ci d η = a + bλ + cλ P 2 i a _ f a _ f = η mɺ p m i f ci τ d mɺ = [ e s (1 + τ s)] mɺ f c in System Modeling 10

11 Wind Turbine Modeling ɺ ec wt asg gb θ = ω ( ω n ) System Modeling J ɺ ω = Γ B ω Γ wt wt wt wt wt ec ɺ 2 2 ( Jasg + J gb n ) ωasg = ( Γec n) ( Basg + Bgb n ) ωasg Γasg Γ = K θ + B ɺ θ ec ec ec ec ec With: Pwt Γ wt = = ω wt 0.5 ρ A C ( λ) v 3 wt p w ω wt λ ( ω R ) = wt b vw C p 21 λ 116 i = β 5 e λ λi λi = 3 λ β β

12 Power Flow Modeling Versus Operating Modes The electrical nominal power of diesel generator chosen for the study is about 50 kw. The parameters of the fuel supply and combustion subsystem are based on the engine model 3054T Caterpillar. The parameters of wind turbine chosen here corresponds to a horizontal axis type (AEP 15/55, asynchronous generator-squirrel cage) with nominal power about 55 kw. This wind turbine is proper to a realistic and appropriate application of a wind-diesel hybrid system. 12

13 Power Flow Modeling Versus Operating Modes Diesel Production with wind speed and electrical load Wind speed [m/s] Wind production [kw] Electrical load [kw] Diesel production [kw] Parallel functioning of wind turbine and diesel generator without dump load white Functioning of diesel generator below 30% of its nominal output power Green Diesel generator is stopped and dump load is activated Blue Output power of diesel generator is not sufficient to supply the electrical load Red 13

14 Power Flow Modeling Versus Operating Modes Dump load power with wind speed and electrical load Wind speed [m/s] Wind production [kw] Electrical load [kw] Power absorbed by the dump load [kw] Dump load is not activated Wind energy production is limited to allow to the diesel generator to supply 30% of its nominal output power Diesel generator is stopped, dump load is activated and wind turbine operates at full capacity Operation case where a possible storage unit could be activated to provide a supplementary power and ensure the balance between production/demand white Green Blue Red 14

15 Conclusions This study focuses on the mechanical modeling of no-storage winddiesel hybrid system based on the power flow models. The flexible models (two mass) of wind turbine and diesel generator are presented. Also, the different operation modes of NSWDHS are presented in function to wind speed and electrical load. The obtained results show the effect of wind power regarding to reducing the rate of power supplied by the diesel generator. The power flow model allows identifying the ranges of the simultaneous operation of wind turbine and genset in function of the wind speed. The obtained results(for case study) show that the supervision system of wind-diesel must ensure a smooth transition between the following electrical load ranges[30-50],[40-60],[50-60],[50-70] and[60-70] kw corresponding to the ranges of wind speed [4-9], [6-9], [6-11], [8-11] and[8-25] m/s, respectively. 15

16 Thank you for your attention Questions? 16

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