Inter national J our nal of Electrical and Computer Engineering (IJECE) V ol. 11, No. 6, December 2021, pp. 4740 4750 ISSN: 2088-8708, DOI: 10.11591/ijece.v11i6.pp4740-4750 r 4740 P o wer system operation considering detailed modelling of the natural gas supply netw ork Ricardo Mor eno 1 , Diego Larrahondo 2 , Oscar Flor ez 3 1,2 Uni v ersidad Aut ´ onoma de Occidente, Cali, Colombia 3 Uni v ersidad Distrital Francisco Jos ´ e de Caldas, Colombia Article Inf o Article history: Recei v ed May 11, 2020 Re vised May 25, 2021 Accepted Jun 12, 2021 K eyw ords: Natural g as system Optimal po wer flo w Po wer systems Rene w able ener gy W ind po wer ABSTRA CT The ener gy transition from fossil-fuel generators to rene w able ener gies re presents a paramount challenge. This is mainly due to the uncertainty and unpredictability asso- ciated with rene w able re sources. A greater fle xibility is requested for po wer system op- eration to fulfill demand requirements considering security and economic restrictions. In particular , the use of g as-fired generators has increased to enhance system fle xibility in response to the inte gration of rene w able ener gy sources. This paper pro vides a com- prehensi v e formulation for modeling a natural g as supply netw ork to pro vide g as for thermal generators, considering the use of wind po wer sources for the operation of the electrical system o v er a 24-hour period. The results indicate the requirements of g as with dif ferent wind po wer le v el of inte gration. The model is e v aluated on a netw ork of 20 N G nodes and on a 24-b us IEEE R TS system with v arious operati v e settings during a 24-hour period. This is an open access article under the CC BY -SA license . Corresponding A uthor: Ricardo Moreno Ener gy and Mechanical Department Uni v ersidad Aut ´ onoma de Occidente Cali, Colombia Email: rmoreno@uao.edu.co, odflorez@udistrital.edu.co 1. INTR ODUCTION T w o crucial sectors for life no w adays are natural g as (NG) and electricity . Although these sectors follo wed dif ferent paths throughout the majority of the 20th century , in the last 25 years the y ha v e progressi v ely con v er ged. The usage of NG for electrici ty generation through g as-fired generation plants has enhanced the interdependence among g as and electric po wer sources [1]. Consequently , the g as and po wer systems ha v e become intertwined, leading to ne w challenges due to the comple xity in v olv ed in the issues that each poses to the other [2]. In terms of g as-fired po wer plants, limitations due to both g as supply contracts and access to the g as netw ork are unkno wn, generating ef fects and e xternalities in their operation. From the g as system perspecti v e, the demand for natural g as from residential and industrial areas is more predictable and less v olatile, compared to the natural g as consumption for electricity generation. F or these reasons, the g as system interconnected to the electrical system requires greater fle xibility . Ne v ertheless, fle xibility is e xpensi v e because it requires additional e xtraction and transmission capacities to pro vide the necessary operational mar gin [3]. Moreo v er , reducing greenhouse g as emissions is imperati v e for climate change mitig ation, leading to increased in v estments in reducing con v entional fossil fuel-based po wer generation [4]-[6]. Therefore, a massi v e ef fort has been made w orldwide to inte grate rene w able ener gy technologies [7]. This implementation J ournal homepage: http://ijece .iaescor e .com Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 4741 has lar gely been done through photo v oltaic and wind systems [8]. Despite this, the use of these resources can influence the electric po wer system operation due to certain characteristics of these resources such as uncertainty and v ariability [9]. Generating ne w requirements for dealing with disruptions, i.e. challenges in stability [10]. Therefore, ener gy systems require strate gies to impro v e their fle xibility and stability , and thus achie v e the inte gration of these intermittent resources and meeting the requirements of the demand [11], [12]. One of the technologies currently used, to balance intermittenc y and increase system fle xibility , is g as- fired thermal generators [13]. This is because the y ha v e technical requirements, such as shorter on/of f times, greater up and do wn ramps, lo wer emissions and higher financial performance in comparison with traditional coal-fired po wer plants [14]. Despite this, the fle xibility the y can b r ing to the system is limited a n d requires greater fle xibility of the g as system [3]. Consequently , this paper pro vides a comprehensi v e formulation for modeling a NG supply netw ork to pro vide g as for thermal generators, considering the use of wind po wer sources for the operation of the electrical system o v er a 24-hour period. Inte grated NG and electricity system’ s tar get functionality is to minimize the o v erall cost of the system, taking into account po wer generation costs, g as costs and losses in both systems. The resulting formulation pro vides optimum results re g arding all generators, g as consumption requirements and technical requirements of the g as-fired generators, all under v arious operating states and scenarios. This paper is structured in these sections: Section 2 presents the problem description and formul ation. In section 3, the electrical and g as systems and their parameters are outlined. Then, using the described systems, the formulation is tested. The results are analyzed and discussed at the end of this section. Some concluding remarks on this topic are gi v en in section 4. Electric po wer systems and g as systems ha v e been e xtensi v ely studied from dif ferent points of vie w . The first ha v e been analyzed, through the optimal ener gy flo w for the dispatch of the generation resources [15]- [17]. As a result, the formulation of the multi-period DC optimal po wer flo w (DCOPF) has been enhanced in order to incorporate rene w able ener gy generation’ s v ariability , considering f actors such as electricity demand and wind a v ailability uncertainty [18]-[21]. On the other hand, the g as system has been analyzed through dif ferent studies. In one of them, a detailed study of g as transmission w as made, implementing a simple x algorithm e xpansion [22]. Martin et al. [23], a fully intermix ed model w as applied for the g as netw ork optimization steady-state case. Pfetsch et al. [24] in v estig ate se v eral approaches in order to resolv e a main challenge in pipeline g as transmission, which is the nomination v alidation problem, through dif ferent algorithms based on linear and nonlinear mix ed-inte gral methods. The interdependence of electricity and NG systems has been e xtensi v ely studied. Zhang et al. [25], in order to simulate the coordinated stochastic model for the economic response of the hourly po wer system demand, along with the NG transport constraints, a Monte-Carlo simulati on w as applied. Operational perfor - mance of h ydrothermal systems and the NG netw ork in the short term w as studied at [26]. Because of the necessity of g as-fired po wer plants, the transport of NG through pipelines af fects po wer generation and trans- mission with respect to safety and economics, a situation that w as studied in [27]. And the reference [28] used the Ne wton-Raphson formulation to analyze inte grated electricity and NG systems. In addition, considerable research has been done on the coordination of natural g as and electr icity systems. Qadrdan et al. [29]-[31] in v estig ated ho w the increase in wind po wer plants impacts on the British g as netw ork. Sohrabi et al. [32], performed ste ady-state inte grated NG transmission netw ork and po wer system formulation, taking into account the mark et price of electricity on the basis of the information g ap decision theory . The impact of NG system on the short-term planning of the electricity system considering a considerable increase of rene w able ener gies is presented in [33]. An operational strate gy based on interv al optimization for inte grated g as and electricity systems is proposed in [34] to enhance system performance considering demand response and rene w able ener gy sources uncertainty . P ower system oper ation considering detailed modelling of the natur al gas supply network (Ricar do Mor eno) Evaluation Warning : The document was created with Spire.PDF for Python.
4742 r ISSN: 2088-8708 2. PR OBLEM FORMULA TION 2.1. Notation 2.1.1. Indices g Inde x of thermal units of generation. i; j Inde x of netw ork b uses connected by transmission branches. m; n Inde x of g as b uses connected by a line pipe. t Inde x of time periods (hour). 2.1.2. P arameters A i W ind turbine po wer connected to b us i (MW). w i;t A v ailable wind for the turbine connected to b us i at time t C m;n Constant of the g as line pipe connecting node m to n . L i;t Electric load in b us i at time t . b g Thermal unit fuel cost ratio. P max g , P min g Maximum/Minimum po wer generation limits for thermal units. P max ij Maximum po wer flo w limits of branch connecting b us i to j . x ij Reactance of branch connecting b us i to j . r ij Resistance of branch connecting b us i to j . Ef ficienc y of thermal units. k t Gas demand percentage at time t . R up g , R dow n g Ramp-up/do wn limits of thermal generation unit g (MW/h). S g max n , S g min n Maximum/Minimum g as supply limits at node n . S d n Gas demand in node n (Scm). P r max n , P r min n Maximum/Minimum g as pressure limits at node n . V O O L Load loss v alue ($/MWh). V W C W ind loss v alue ($/MWh). H Con v ersion v alue (MBtu/10 6 S cm ) : 2.1.3. V ariables P ij ;t Acti v e po wer flo w of branch connecting b us i to j at time t (MW). P g ;t Acti v e po wer produced by thermal unit g at time t (MW). P w i;t Acti v e po wer generated by wind turbine connected to b us i at time t (MW). P w c i;t Constrained wind turbine po wer connected to b us i at time t (MW). f m;n;t Gas flo w from node m to node n at time t (Scm). LS i;t Load shedding in b us i at time t (MW). P r n;t Gas pressure at node n time t (bar). S g n;t Gas supply in node n time t (Scm). S e n;t Gas demand in node n time t for generation of thermal units (Scm). E C 24-hour electrical operating costs ($). GC 24-hour g as operating costs ($). O F 24-hour T otal operating costs ($). i;t V oltage angle of b us i at time t (rad). 2.2. F ormulation This formulation is based on an optimization problem, designed to determine the lo west o v erall system operating cost, deri v ed from the production of electricity to meet demand o v er a 24-hour period, including all g as system costs as specified in (1). O F = E C + GC (1) The (2) sho ws the total cost of electricity generation for a 24-hour period. Through the sum of the cost of producing ener gy with g thermal units during a t time interv al, plus the costs associated with load loss, plus the costs associated with non-utilization of the maximum wind generation source a v ailable. Int J Elec & Comp Eng, V ol. 11, No. 6, December 2021 : 4740 4750 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 4743 E C = X g ;t b g P g + X i;t ( V O LL LS i;t + V W C P w c i;t ) (2) Dispatch model constraints are determined by the optimal po wer flo w equations. The DC optima l po wer flo w equilibrium is defined by (3). The amount of po wer flo wing in each line is determined by (4). The constraints on the maximum amount of po wer that can flo w through each line are gi v en by the (5). X g P g ;t + LS i;t + P w i;t L i;t = X j P ij ;t (3) P ij ;t = 1 X ij ( i;t j ;t ) (4) P max ij ;t P ij ;t P max ij ;t (5) On the other hand, the restrictions for thermal generation units are defined in (6), (7), and (8), where (6) corresponds to the operational range of thermal generators. The (7) and (8) specify the maximum limits of the ramp-up and ramp-do wn of thermal generators, i.e. the maximum v alue that can v ary the po wer of a generator in a one-hour interv al. P min g ;t P g ;t P max g ;t (6) P g ;t P g ;t 1 R up g (7) P g ;t 1 P g ;t R dow n g (8) The load shedding of b us i is restricted to the e xisting demand at time t as indicated in (9). 0 LS i;t L i;t (9) The constraints for wind ge n e ration are defined in (10) and (11), where (10) corresponds to to the amount of a v ailable wind po wer not utilized. In (11) indicates the range of minimum and maximum po wer that a wind turbine can produce, taking into account the capacity v ariables and wind a v ailability . P w c i;t = w t A i P w i;t (10) 0 P w i;t w t A i (11) The (12) indicates the total cost to supply g as considering the purchase price of g as deli v ered at node n during an interv al of time t . GC = X n;t c n S g n;t H (12) The flo w conserv ation equation at node n , insures the g as balance at node n and is gi v en by the (13). X m f n;m;t = X m f m;n;t + S g n;t k t S d n S e n;t (13) No w , is up to consider the constraints on the g as transportation tubes. In this case, there’ s no dis tinction between passi v e and acti v e g as transportation tubes. F or the g as transportation tube, the relation between the flo w f m;n;t in the g as transport ation tube ( m; n ) and the pressures P r m;t and P r n;t is gi v en by the (14). P ower system oper ation considering detailed modelling of the natur al gas supply network (Ricar do Mor eno) Evaluation Warning : The document was created with Spire.PDF for Python.
4744 r ISSN: 2088-8708 Where C m;n is a v alue that v aries according to length, diameter and absolute roughness of the pipeline and g as composition. f 2 m;n;t = C 2 m;n ( P r 2 m;t P r 2 n;t ) (14) Alternately , the restrictions for g as units are defined in (15), and (16), where (15) corresponds to the limitations of g as inflo w at a supply node n . In the case of g as pressure restrictions, natural g as transportation companies must not recei v e natural g as at a higher pressure than that guaranteed by the supplier at the input point. On the contrary , the demand at each e xit point must be satisfied at a minimum pressure secured to the industrial user or the local distrib ution compan y , this is e xpressed in (16). S g min n S g n;t S g max n (15) P r min n P r n;t P r max n (16) Finally , g as-fired po wer plants connect the electricity and natural g as systems. Since g as fired po wer plants produce ener gy for the electric system as a supplier , and at the same time, the y consume natural g as, making it a requirement for the natural g as system. This is e xpressed in the (17). b g P g = S e n;t H 2 N (17) 3. RESUL TS AND DISCUSSION W ith the objecti v e of quantify the requirements of g as according to wind inte gration, a po wer system case is used to simulate operational conditions with a detailed modeli ng of the g as netw ork. In this section dif ferent scenarios are e v aluated, with a 24 hour period to consider the dispatching of generators. All simula- tions were completed by a personal computer (PC) using Ipopt R Solv er (3.12.10) under the JuMP 0.1 9.2 Julia platform [35]. 3.1. Case description: IEEE 24-b us and gas netw ork 20-stations This section presents the results and simulations on the g as needs in the ener gy transition considering the inte gration of wind ener gy . This is based on the g as netw ork linkage with electricity netw ork, sho wn in Figure 1. Also, considering dif ferent demand cases, wind a v ailability profiles, and installed wind capacities. The g as netw ork linkage with electricity netw ork, is composed for a modified IEEE 24-b us po wer system and the g as netw ork of Belgium, modified from [15], [22]. The data for thermal units are listed in T able 1, modify from [15]. In T able 2 the lines reactance, po wer line constraints and interconnections are sho wn, modify from [15]. NG system nodes’ technical and economic features are sho wn in T able 3, and the operational specifications of g as netw ork are pro vided in T able 4, modifying the information from [15], [22]. 3.2. Results The system performance w as e v aluated on the basis of an increase in wind po wer generation capac- ity , starting with a case without wind po wer installed (i.e. 0 MW), then a case with an installed capacity of 500 MW and a case of 1000 MW . The analysis highlights the changes in g as requirements for po wer generation during a 24-hour period due to wind a v ailability . The g as requirements according to wind po wer generation o v er a 24-hour period are sho wn in Figure 2. It can be seen that t he g as requirements in the case without wind po wer a v ailable ha v e a similar performance in all the simulations. Con v ersely , when ha ving an installed wind po wer (i.e. 500 MW), the g as requirements present a greater v ariability , which gro ws when f acing dif ferent wind patterns as the installed wind po wer increases (i.e. 1000 MW). As instal led wind po wer increases, in some cases, peak g as requirements also rise. These peaks may be more noticeable in cases with high v ariability in the wind profile, lik e the one presented in Figure 2(b). At hour 11 in the case with 0 MW of installed wind capacity , there is a requirement of g as 41130 Scm, in the cases of 500 MW and 1000 MW of installed wind capacity , the g as requirements increase by 100% and 315% respecti v ely . Also in Figure 2(b), it can be seen that when there is a decrease in the g as requirement, the decrease is more considerable, as the installed wind capacity increases, as can be seen in the 16th hour . Int J Elec & Comp Eng, V ol. 11, No. 6, December 2021 : 4740 4750 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 4745 Figure 1. Gas netw ork linkage with electricity netw ork T able 1. Thermal generation data for the 24-b us test system Gen Bus P min g (MW) P max g (MW) Mar ginal Cost (MW) R up g (MW/h) R dow n g (MW/h) 1 18 100 400 5.47 17 17 2 21 100 400 5.49 17 17 3 1 30.4 152 23.32 84 84 4 2 30.4 152 23.32 84 84 5 15 54.25 155 16 21 21 6 16 54.25 155 10.52 21 21 7 23 108.5 310 10.52 21 21 8 23 140 350 10.89 28 28 9 7 75 350 20.7 49 49 10 13 206.85 591 20.93 21 21 11 15 12 60 26.11 7 7 12 22 0 300 30 100 100 T able 2. Branch data for the 24-b us test system From T o X ij (p.u) Rating (MV A) From T o X ij (p.u) Rating (MV A) 1 2 0.0139 175 11 13 0.0476 500 1 3 0.2112 175 11 14 0.0418 500 1 5 0.0845 175 12 13 0.0476 500 2 4 0.1267 175 12 23 0.0966 500 2 6 0.192 175 13 23 0.0865 500 3 9 0.119 175 14 16 0.0389 500 3 24 0.0839 400 15 16 0.0173 500 4 9 0.1037 175 15 21 0.0245 1000 5 10 0.0883 175 15 24 0.0519 500 6 10 0.0605 175 16 17 0.0259 500 7 8 0.0614 175 16 19 0.0231 500 8 9 0.1651 175 17 18 0.0144 500 8 10 0.1651 175 17 22 0.1053 500 9 11 0.0839 400 18 21 0.013 1000 9 12 0.0839 400 19 20 0.0198 1000 10 11 0.0839 400 20 23 0.0108 1000 10 12 0.0839 400 21 22 0.0678 500 P ower system oper ation considering detailed modelling of the natur al gas supply network (Ricar do Mor eno) Evaluation Warning : The document was created with Spire.PDF for Python.
4746 r ISSN: 2088-8708 T able 3. T echnical and economical characteristics of g as nodes Gas Node S g min n (Scm) S g max n (Scm) S d n (Scm) P r min n (Scm) P r max n (Scm) C n (USD/MBTU) Anderlues 0 1.20 0.00 0.00 66.2 0.00 Antwerpen 0 0.00 4.03 1.25 80.0 0.00 Arlon 0 0.00 0.22 0.00 66.2 0.00 Berneau 0 0.00 0.00 0.00 66.2 0.00 Blare gnies 0 0.00 15.62 2.08 66.2 0.00 Brugge 0 0.00 3.92 1.25 80.0 0.00 Dudzele 0 8.40 0.00 0.00 77.0 2.28 Gent 0 0.00 5.26 1.25 80.0 0.00 Lie ge 0 0.00 6.39 1.25 66.2 0.00 Loenhout 0 4.80 0.00 0.00 77.0 2.28 Mons 0 0.00 6.85 0.00 66.2 0.00 Namur 0 0.00 2.12 0.00 66.2 0.00 Petange 0 0.00 1.92 1.04 66.2 0.00 Peronnes 0 0.96 0.00 0.00 66.2 1.68 Sinsin 0 0.00 0.00 0.00 63.0 0.00 V oeren 0 22.01 0.00 2.08 66.2 1.68 W anze 0 0.00 0.00 0.00 66.2 0.00 W arland 0 0.00 0.00 0.00 66.2 0.00 Zeebrugge 0 11.59 0.00 0.00 77.0 2.28 Arlon 0 0.00 0.00 0.00 80.0 0.00 T able 4. T echnical characteristics of g as netw ork From T o Acti v e C 2 m;n From T o Acti v e C 2 m;n Zeebrugge Dudzele 0 9.07027 Berneau Lie ge 0 0.02701 Zeebrugge Dudzele 0 9.07027 Lie ge W arnand 0 1.45124 Dudzele Brugge 0 6.04685 Lie ge W arnand 0 0.02161 Dudzele Brugge 0 6.04685 W arnand Namur 0 0.86384 Brugge Zomer gem 0 1.39543 Namur Anderlues 0 0.90703 Loenhout Antperwen 0 0.10025 Anderlues Peronnes 0 7.25622 Antperwen Gent 0 0.14865 Peronnes Mons 0 3.62811 Gent Zomer gem 0 0.22689 Mons Blare gnies 0 1.45124 Zomer gem Peronnes 0 0.65965 W arnand W anze 0 0.05144 V oeren Berneau 1 7.25622 W anze Sinsin 1 0.00642 V oeren Berneau 1 0.10803 Sinsin Arlon 0 0.00170 Berneau Lie ge 0 1.81405 Arlon Petange 0 0.02782 Similar to peak g as requirements, as wind capacity increases, so can o v erall g as consumption in a 24-hour period. This can be seen in Figure 2(d), in which g as consumption for the case of 500 MW of installed wind capacity is higher in almost e v ery hour o v er the case without wind capacity . As well as the g as require- ments are greater according with the increase in wind po wer capacity . Ne v ertheless, there may be cases in which increasing the wind capacity generates a decrease in g as consumption in a fe w hours, as sho wn in Figure 2(c). This is wh y g as consumption w as e v aluated for a period of 192 hours, equi v alent to 8 days, for dif ferent installed wind capacity , starting from 0 MW to 1100 MW , in periods of 100 MW , as sho wn in Figure 3. These results depend directly on the technical and economic requirements of the thermal generators, present in T able 1, and the economic requirements of the g as, present in T able 3. This is because, in this case, the cost of natural g as used for po wer generation is higher than the a v erage cost of thermal generators that are not g as-fired. This generates that when solving the optimal flo w of po wer and the economic dispatch, it looks for to use in a minimum w ay the g as, and t herefore the g as-fired generators. Ho we v er , due to the technical limitations of some thermal generators, in particular their reduced rate of po wer change per hour , it is necessary to use g as-fired thermals, to supply the v ariations present in the po wer system. V ariations in the po wer system as mentioned abo v e increase when implementing wind systems. This is due to the f act that in the search to use wind ener gy in totality , there are some fluctuations in the po wer generation of the el ectrical system, which must be controlled by the other generation plants, in order to ha v e an optimal po wer flo w . These fluctuations in po wer generation gro w proportionally as the installed wind capacity increases. Gi v en the limited ramps of coal-fired po wer plants, v ariations must be controlled by g as-fired po wer Int J Elec & Comp Eng, V ol. 11, No. 6, December 2021 : 4740 4750 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 4747 plants, which leads to increased g as consumption. And a s the fluctuati o ns gro w , due to the increase in installed wind capacity , so does g as consumption, as sho wn in Figure 3. Figure 2. Hourly g as requirements for installed wind po wer capacities within a 24-hour period Figure 3. T otal g as requirements for installed wind po wer capacities P ower system oper ation considering detailed modelling of the natur al gas supply network (Ricar do Mor eno) Evaluation Warning : The document was created with Spire.PDF for Python.
4748 r ISSN: 2088-8708 As mentioned abo v e, one of the points to consider were the technical requirements of the g as fired thermal generators, specifically in this case the up and do wn ramps. These ramps become critical to an inter - mittent rene w able ener gy source, such as wind po wer . In cases s uch as t his one, the ramps of the coal-fired generators are v ery limited, lea ving the task of controlling the intermittent to the g as-fired generators. Ho we v er , the ramps of the g as generators, ha v e their restrictions, and the v alue of these is intrinsic to the generator , which means that the limits designed for the generator cannot be e xceeded or changed [13]. Therefore, when including wind po wer generation, the limits of up and do wn ramps must be kno wn, especially those of the g as fired po wer plants. That is wh y the ramps were determined both up and do wn, for a period of 192 hours, for three cases of installed wind capacity (0 MW , 500 MW and 1000 MW), as sho wn in Figure 4. The ramps were calculated by the hourly dif ference of the po wer generated by all the g as fired thermal generators, i.e. the v alues of the ramps are not from a single generator , on the contrary the y are the sum of the ramps required from all the g as fired generators, at the same instant of time. In Figure 4, it can be seen ho w the gro wth in installed wind capacity leads to an increase in the technical requirements of g as fired boilers, in this case the ramps. Note that the gro wth is in the absolute v alue of the ramps, ie is gi v en both in the up and do wn ramps. In the case where there is no wind po wer generation, the critical v alues of the up and do wn ramps are 332 MW/h and 159 MW/h respecti v ely . F or t h e case of 500 MW of installed wind capacity , the critical v alues of the up and do wn ramps are 1.3 and 2 times higher than the cas e of 0 MW res pecti v ely . And for the case of 1000 MW of installed wind capacity , the critical v alues of the up and do wn ramps are 2.1 and 3.3 times higher than the initial case respecti v ely . Whereas the v alues of the up and do wn ramps of a g as fired thermal generator tend to be the same, only the peak v alues of the ramps can be tak en. Hence, for the implementation of 500 MW of wind po wer generation, the critical v alues of the ramps are increased by 26%. Under normal conditions, the ramps required by thermal generators do not reach their limits, thus it is not necessary to mak e major changes to the system to achie v e these tar get ramps. Nonetheless, in the case of implementing 1000 MW of wind po wer generation, the critical v alues of the ramps are increased by 108% with respect to the initial case. Therefore, it is necessary to double the number of ram p s that are currently a v ailable, which generates the need for the implementation of another thermal g as generator , with certain technical requirements, to achie v e these tar get ramps. Figure 4. Gas netw ork linkage with electricity netw ork 4. CONCLUSION Global ener gy sources are being transitioned by reducing the consumption of fossil fuels and replacing them with rene w able resources, in an ef fort to reduce greenhouse g as emissions. In contrast, it is necessary to incorporate natural g as into the ener gy tra nsition discourse in order to meet the operational, economic, political and social needs of the countries. In this paper , a detailed model of an economic dispatch for a 24-b us electric system interconnected with a 20 node natural g as netw ork, that in v olv es wind ener gy w as presented under se v eral operational settings for a 24-hour time frame. It w as demonstrated that the planning process Int J Elec & Comp Eng, V ol. 11, No. 6, December 2021 : 4740 4750 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 4749 required between the NG infrastructure and the po wer system can be achie v ed through the mathematical model presented. Due to the uncertainty and unpredictability as sociated with rene w able resources and the limited te ch- nical characteristics of coal-fired generators, then the g as will play a role in the ener gy transition. This leads to a greater need for g as and g as-fired generators, re g ardless of the f act that the cost of generating ener gy from these is higher t h a n for coal-fired ones. The fle xibility of both the po wer and g as systems is vital for the imple- mentation of rene w able ener gy sources. Furthermore, this fle xibility is limited and costly . Consequently , the e xcessi v e increase in the use of rene w able ener gies can cause the system to reach its operational limits, with- out achie ving optimal resul ts, and it is necessary to mak e technical changes in the system. Examples of these changes include the implementation of ne w g as-fired po wer plants, ne w transmission lines, greater a v ailability of g as, and ne w g as transportation tubes. A CKNO WLEDGEMENT The authors gratefully ackno wledge the support of the Uni v ersidad Aut ´ onoma de Occidente in Cal i, Colombia. REFERENCES [1] H. Chuan, L. T ianqi, W . Lei, and M. Shahidehpour , “Rob ust coordination of interdependent electricity and natural g as systems in day-ahead scheduling for f acilit ating v olatile rene w able generations via po wer -to-g as technology , Journal of Modern Po wer Systems and Clean Ener gy , v ol. 5, no. 3, pp. 375–388, 2017, doi: 10.1007/s40565-017-0278-z. [2] T . Li, M. Eremia, and M. Shahidehpour , “Interdependenc y of natural g as netw ork and po wer system sec urity , IEEE T ransactions on Po wer Systems, v ol. 23, no. 4, pp. 1817–1824, 2008, doi: 10.1109/TPWRS.2008.2004739. [3] A. Street, L. A. Barroso, R. Chabar , A. T . M endes, and M. V . 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