load flow model of the philippine power system grid

Journal of Multidisciplinary Studies Vol. 6, Issue No. 2, pp. 91-113, December 2017 ISSN 2350-7020 (Print) ISSN 2362-9436 (Online) doi: http://dx.doi.org/10.7828/jmds.v6i2.1047

Load Flow Model of the Philippine Power System Grid

Philips B. Ocang

Department of Electrical Engineering, College of Engineering and Technology, Misamis University, H. T. Feliciano St., Ozamiz City 7200, Philippines

Corresponding author: Phillip Ocang, email: [email protected]

Abstract

Load flow is vital in the planning and operation of any power system grid. Load flow analysis determines primarily the magnitude and phase angle of voltage at each bus and the active and reactive power flowing in each transmission line. These data require numerous non-linear equations which often make power flow solution difficult. In an attempt to simplify the process of load flow analysis and generate data at real time, this study aims to develop a reduced load flow model of Philippine power system grid to fit into the maximum bus limit of Power World simulator software. Initially, the researcher reduced and simulated the Luzon, Visayas, and Mindanao power flow models. Comparison of system loss of the reduced models and the actual models determined the reliability of the former. F-test and student t-test at significance level α=0.05 validated the results for Luzon and Visayas models while %Error was used in the Mindanao model. The three reduced models were interconnected via High Voltage Direct Current to constitute the unified load flow model of the Philippine power system grid. Load flow simulation of the unified model showed bus under-voltage problem. However, reactive volt-ampere compensation scheme and de-energization corrected the three-voltage problem in Visayas and one voltage problem in Mindanao, respectively. Eventually, the unified model passed the Philippine Grid Code. This model can provide power system engineers ease of data generation, address problems or add installations when the Philippine power system grid will be finally unified for full deregulation. Keywords: bus, deregulation, model, simulator, voltage

91

P. B. OcangLoad Flow Model of the Philippine Power System GridJournal of Multidisciplinary StudiesVol. 6, Issue No. 2, pp. 91-113, December 2017ISSN 2350-7020 (Print)ISSN 2362-9436 (Online)doi: http://dx.doi.org/10.7828/jmds.v6i2.1047


The addition of participating entities in a deregulated environment added a new dimension to the task of maintaining a reliable electric system (Lai, 2001). Deregulation of the power system bid the participation of generating companies (GENCOS), transmission companies (TRANSCOS), distribution companies (DISCOS), retail energy service companies (RESCOS), and independent system operator (ISO) (Abhyankar & Kharparde, 2013). In the country, the National Grid Corporation of the Philippines (NGCP) is engaged in the operation and transmission of power and the implementation of the electricity trade in the market (NGCP, 2011). Wholesale Energy Spot Market (WESM), an ISO, operates in Luzon and Visayas grid (PEMC, 2012). Recently created Interim Mindanao Electricity Market (IMEM), also an ISO, operates in Mindanao grid (Cayon, 2013). Since these entities principally facilitate and coordinate the power delivery, control and operation, they require accurate and reliable information from the power flow studies for faster solution time (Abhyankar & Kharparde, 2013). In an attempt to simplify the process of power flow analysis and data generation, and facilitate interaction among participating entities in Philippines power system grid, this study aimed to develop a unified Philippines power system model that fits into Glover Sarma Power World Simulator software, open version 17. The software is an interactive power system simulator on a time frame ranging from several minutes to several days. It contains a highly effective power flow analysis package (Leite, 2010) along with a user-friendly environment whereby basic power system operations would be learned with maximum portability, minimum maintenance and excellent interactive capability (Overbye et al., 1995). Specifically, this study created and simulated reduced power system models of Luzon, Visayas, and Mindanao. Subsequently, the study compared the system loss of the three reduced models to the system loss of the actual models. The Wholesale Energy Spot Market provided the system loss data from the actual model for Luzon and

Load Flow Model of the Philippine Power System Grid P. B. Ocang

Introduction

In a power system, power flows from a generator to the load through different branches of the network. The flow of active and reactive power is known as load flow or power flow (Afolabi et al., 2015). Load flow is a fundamental tool for the analysis of any power system whereby results served as inputs in load forecasting, system planning, and operation (Zimmerman & Chiang, 1995; Musti & Ramkhelawan, 2012). Load flow studies ensure that electrical power transfer from generators to consumers through the grid system is stable, reliable, and economic (Murthy & Kumar, 2012). Load flow studies are conducted on a daily basis by system engineers with varying system configurations, load patterns, and generating conditions to understand the behavior of the system at different operating conditions (Musti & Ramkhelawan, 2012). Load flow analysis determines primarily the magnitude and phase angle of voltage at each bus as well as the active and reactive power flowing in each transmission line (Dharamjit, 2012). Generation of these data, requires numerous non-linear equations which often make computation of power flow solution difficult (Silva, 2000). Nonetheless, many tools and software packages are already available for power system studies which can be customized and generate end data at a real time (Musti & Ramkhelawan, 2012; Afolabi et al., 2015). Load flow analysis starts with the formulation of appropriate model in power system grid (Anderson, 2004). The quality of the studies and the efficiency of power system operation are closely associated with the accuracy of the power system models (Gartia et al., 2009). Model development requires detailed data about components such as generators, transformers, and transmission lines. Periodic system model validation is necessary to ensure that the power system models are accurate and up to date (NERC, 2010).

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Journal of Multidisciplinary StudiesVol. 6, Issue No. 2, pp. 91-113, December 2017ISSN 2350-7020 (Print)ISSN 2362-9436 (Online)doi: http://dx.doi.org/10.7828/jmds.v6i2.1047


The addition of participating entities in a deregulated environment added a new dimension to the task of maintaining a reliable electric system (Lai, 2001). Deregulation of the power system bid the participation of generating companies (GENCOS), transmission companies (TRANSCOS), distribution companies (DISCOS), retail energy service companies (RESCOS), and independent system operator (ISO) (Abhyankar & Kharparde, 2013). In the country, the National Grid Corporation of the Philippines (NGCP) is engaged in the operation and transmission of power and the implementation of the electricity trade in the market (NGCP, 2011). Wholesale Energy Spot Market (WESM), an ISO, operates in Luzon and Visayas grid (PEMC, 2012). Recently created Interim Mindanao Electricity Market (IMEM), also an ISO, operates in Mindanao grid (Cayon, 2013). Since these entities principally facilitate and coordinate the power delivery, control and operation, they require accurate and reliable information from the power flow studies for faster solution time (Abhyankar & Kharparde, 2013). In an attempt to simplify the process of power flow analysis and data generation, and facilitate interaction among participating entities in Philippines power system grid, this study aimed to develop a unified Philippines power system model that fits into Glover Sarma Power World Simulator software, open version 17. The software is an interactive power system simulator on a time frame ranging from several minutes to several days. It contains a highly effective power flow analysis package (Leite, 2010) along with a user-friendly environment whereby basic power system operations would be learned with maximum portability, minimum maintenance and excellent interactive capability (Overbye et al., 1995). Specifically, this study created and simulated reduced power system models of Luzon, Visayas, and Mindanao. Subsequently, the study compared the system loss of the three reduced models to the system loss of the actual models. The Wholesale Energy Spot Market provided the system loss data from the actual model for Luzon and

93

P. B. OcangLoad Flow Model of the Philippine Power System Grid


the cities or provinces where the equipment and devices were located (PEMC, 2013). The document also showed the transmission voltage (KV), Line capacity (MVA) and kind, (i.e. overhead or submerged) for Luzon and Visayas. For Mindanao, the thesis work of Sabelita (2012) was used as the source of the necessary data. It provided the generation, the load at buses and the transformer locations for thermal plants as well as the transmission voltage (KV), line capacity (MVA) and kind, (i.e. overhead or submerged).

The National Grid Corporation of the Philippines (NGCP) transmission line development plan, volume 2 part 1- final report, showed transmission line route for Luzon, Visayas, and Mindanao (NGCP, 2012). From this pictured route, line length approximation was undertaken using Google Earth Measures with +10% error due to terrain contour and piece-wise linear measurement. Philippine Electricity Market Corporation (2013) also provided the transmission location and capacity of Luzon and Visayas grid while the thesis of Sabelita (2012) for Mindanao.

For the reactance and resistance per length of overhead transmission line and submerged transmission cables, this study referred to standard values of X and R corresponding to rated voltage of Li and Choudhury (2007). Moreover, the study used the transformer resistance and reactance to the standard transformer parameters in Stevenson (1984) and converted to 100 MVA base. Power world simulator modeling This study reduced the number of buses in Luzon, Visayas, and Mindanao power system grids into 16 buses, 12 buses, and 13 buses, respectively. The reduction of buses ensures to satisfy the student version Power World Simulator bus limit when the three major islands will be interconnected to form the unified Philippine power system grid.


Visayas, while Sabelita (2012) provided system loss data for Mindanao. F-test, Student’s t-test and % Error validated the comparison result.

The three reduced models constituted the reduced load flow model of the Philippine power system grid. Finally, the unified model was simulated and evaluated. The result of the study provides power system engineers ease of data generation, address problems or add installations when the Philippine power system grid will be finally unified for full deregulation. The unified model also creates additional work model for students and professionals in the field of electrical engineering to explore other power system analysis like power system reliability, fault studies, stability, and optimization.

Materials and Methods Data gathering

The study used public available data (Hutcheon & Bialek, 2013; Seack et al., 2014). Documents from 2014 WESM Market Prices and Schedules which contain Ex-post market prices and scheduled data for Luzon and Visayas grid were downloaded. Information obtained from this document included the delivery date, delivery hour, region, type (generation or load), participant, the scheduled energy (MW), and the Locational Marginal Price (LMP). The document also provided data for the calculation of the available energy and the load for a particular day and a particular hour. The list of existing power plants, taken from the Department of Energy [DOE], also provides the installed capacity of generator type (i.e. hydro, coal, geothermal, etc.) power plants of Luzon, Visayas, and Mindanao (DOE, 2012).

Another public data used in this study were from the Philippine Electricity Market Corporation (PEMC). The document provided the market network model of WESM for Luzon and Visayas. The models showed the actual location of buses, the generator generating capacity and node name, the load capacity and node name, the actual color-coded line capacity, the var compensators (condenser, reactor), substations and

94



the cities or provinces where the equipment and devices were located (PEMC, 2013). The document also showed the transmission voltage (KV), Line capacity (MVA) and kind, (i.e. overhead or submerged) for Luzon and Visayas. For Mindanao, the thesis work of Sabelita (2012) was used as the source of the necessary data. It provided the generation, the load at buses and the transformer locations for thermal plants as well as the transmission voltage (KV), line capacity (MVA) and kind, (i.e. overhead or submerged).

The National Grid Corporation of the Philippines (NGCP) transmission line development plan, volume 2 part 1- final report, showed transmission line route for Luzon, Visayas, and Mindanao (NGCP, 2012). From this pictured route, line length approximation was undertaken using Google Earth Measures with +10% error due to terrain contour and piece-wise linear measurement. Philippine Electricity Market Corporation (2013) also provided the transmission location and capacity of Luzon and Visayas grid while the thesis of Sabelita (2012) for Mindanao.

For the reactance and resistance per length of overhead transmission line and submerged transmission cables, this study referred to standard values of X and R corresponding to rated voltage of Li and Choudhury (2007). Moreover, the study used the transformer resistance and reactance to the standard transformer parameters in Stevenson (1984) and converted to 100 MVA base. Power world simulator modeling This study reduced the number of buses in Luzon, Visayas, and Mindanao power system grids into 16 buses, 12 buses, and 13 buses, respectively. The reduction of buses ensures to satisfy the student version Power World Simulator bus limit when the three major islands will be interconnected to form the unified Philippine power system grid.

95



Percent technical losses from the simulation were calculated using the formula below in order to evaluate. F-test was used to compare the variances of percent losses from developed and actual models for Luzon and Visayas. Subsequently the appropriate student’s t-test (Walpole et al., 1998) was used to determine the extent of the difference between the system losses of the two models. Percent error determined the accuracy of the Mindanao model. Minitab (trial version) facilitated the calculations.

Finally, the three reduced models of Luzon, Visayas, and Mindanao were interconnected to constitute the reduced load flow model of the Philippine power system grid. The unified model was simulated and evaluated using the standards of Philippine Grid Code. Results and Discussion

The component of a model in given power system varies significantly according to the purpose of the study (Anderson, 2004). In this study, compendium of data which included public documents (Seack et al., 2014) and results from prior studies to create reduced load flow models of Luzon, Visayas, and Mindanao power system were gathered and analyzed. Cano and Shaikh (2013) provided the characteristics of the power grids, total generation, reserve margins, transmission lines, and load profile of Luzon, Visayas and Mindanao power grids. Sabelita (2012) presented the actual generation data of the power plants and the actual load data of Mindanao.

The first simulation of the Luzon model using Load and Generator rating of WESM on June 2, 2014, period 19 resulted in system loss that was considerably different from the actual WESM loss. Without pre-selected slack bus, the simulator automatically selected bus 11 (Tayabas EHV). The recorded line losses during simulations were evaluated in order to modify it. Since it was eminent from the


Three cluster areas constituted the Luzon model, namely: north, south, and central. The three cluster areas for Visayas include east, west, and central, while Mindanao into four areas: north, central, west, and south east.

An assigned area bus of the reduced model integrated considerable number of buses and the electrical equipment and devices. The loads in those area buses were sorted and made into a lumped load. Within each area, generating units with similar characteristics were clustered into equivalent power plants with a combined capacity and weighted average characteristics that represented all the units (Quelhas et al., 2007)

For a more robust transmission lines, 500 KV lines (i.e. Kadampat, Elijan, etc.) and 230 KV lines (i.e. Binga, Kalayaan, etc.) were prioritized for Luzon, and 230 KV lines (i.e. Tabango, Compostela, etc.) and 138 KV lines (i.e. Naga, Toledo,etc.) were prioritized for Visayas. Mindanao’s priority was its 138 KV lines but a 230 KV line traversing Abaga to Pulangi to Bunawan was included.

In modeling the unified Philippine power system grid, Luzon and Visayas were interconnected by a 380 KV HVDC (High Voltage Direct Current) line from Naga/Tayabas 230 KV bus to Ormoc, Leyte 230 bus. Visayas and Mindanao were also interconnected by HVDC cable from Anislagan to Tongonan, Leyte.

Load flow simulation In testing the accuracy of the reduced models of the Philippine major islands, the reduced Luzon and Visayas models were simulated in load flow mode using the generation (supply) and load (demand) scheduling given by WESM Market Price and Schedules (June, 2014) from June 2 to 7, 2014, period 19. Mindanao model was simulated using the actual generation and load data provided by Sabelita (2012). To ensure that the simulator will run at the specified scheduled generation, the AGC (Automatic Generation Control) was turned off.

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Percent technical losses from the simulation were calculated using the formula below in order to evaluate. F-test was used to compare the variances of percent losses from developed and actual models for Luzon and Visayas. Subsequently the appropriate student’s t-test (Walpole et al., 1998) was used to determine the extent of the difference between the system losses of the two models. Percent error determined the accuracy of the Mindanao model. Minitab (trial version) facilitated the calculations.

Finally, the three reduced models of Luzon, Visayas, and Mindanao were interconnected to constitute the reduced load flow model of the Philippine power system grid. The unified model was simulated and evaluated using the standards of Philippine Grid Code. Results and Discussion

The component of a model in given power system varies significantly according to the purpose of the study (Anderson, 2004). In this study, compendium of data which included public documents (Seack et al., 2014) and results from prior studies to create reduced load flow models of Luzon, Visayas, and Mindanao power system were gathered and analyzed. Cano and Shaikh (2013) provided the characteristics of the power grids, total generation, reserve margins, transmission lines, and load profile of Luzon, Visayas and Mindanao power grids. Sabelita (2012) presented the actual generation data of the power plants and the actual load data of Mindanao.

The first simulation of the Luzon model using Load and Generator rating of WESM on June 2, 2014, period 19 resulted in system loss that was considerably different from the actual WESM loss. Without pre-selected slack bus, the simulator automatically selected bus 11 (Tayabas EHV). The recorded line losses during simulations were evaluated in order to modify it. Since it was eminent from the

97



model the error of Google measures on transmission line lengths, double lines were added to those transmission lines with large power flow, specifically lines between bus 8 and 9, and bus 13 and 15. Reactive (var) compensation was attempted but was not pursued because of its negligible effect since the system had already an excellent implementation of the scheme. Simulation of the modified model yields satisfactory results (very close to the given WESM system loss). The developed model is the final reduced load flow model for Luzon grid.

The final reduced model was simulated again using WESM data at randomly selected time intervals in order to validate, without manipulating further or changing or adding any physical attributes of the model except the load data and generation schedule corresponding to the selected periods. The percent technical loss of the final reduced model was computed and compared to the actual data provided by WESM (Table 1). The percent system technical loss was then computed.

The actual generation column for WESM is the difference between the scheduled generation (i.e.7896.1 MW) and the HVDC flow schedule from Luzon to Visayas (i.e. 27.38 MW) for the same day and period. Most data are almost the same except the data in 6/6/2014. Although F-test showed that variances of Luzon reduced model and the actual model significantly differ, the corresponding t-test on system loss showed no significant difference at α = 0.05. The calculated t-calculated value (-1.29) is lesser than the t-critical value (2.571). Thus, the two models are approximately the same.

Similar study was also conducted in Europe by Hutcheon and Bialek (2013). The study updated previous load flow model using power world load flow simulation. The updated model was validated using the published Winter Scenario and Monthly Statistics reports taken on 16/12/2009 at 11:00 am as the reference day. Once the generation and demand data were entered into the model, generations in individual power stations were manipulated, within their generation limits, to obtain as close as possible cross-border flows to those observed in practice (Hutcheon & Bialek, 2013).

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loss

com

para

tive

resu

lts.

Sour

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Pow

er w

orld

sim

ulat

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WES

M

Peri

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19

Gen

. (M

W)

Load

(M

W)

Loss

(M

W)

Loss

(%

) G

ener

atio

n (M

W)

Load

(M

W)

Loss

(M

W)

Loss

(%

)

6/2/

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78

67.2

2 77

32.5

13

4.72

1.

712

7896

.1-2

7.38

= 78

68.7

2 77

32.5

13

6.22

1.

731

6/3/

2014

77

61.6

8 76

29.6

13

2.08

1.

702

7787

.7-2

4.06

= 77

63.6

4 76

29.6

13

4.04

1.

727

6/4/

2014

77

41.6

8 76

00

141.

68

1.83

77

46.2

- 4.8

6=

7741

.34

7600

14

1.34

1.

826

6/5/

2014

76

01.9

4 74

66.4

13

5.54

1.

783

7695

.1 –

84.8

6=

7610

.24

7466

.4

143.

84

1.89

6/6/

2014

74

23.6

7 72

93.2

13

0.47

1.

757

7556

.7 -8

7.98

= 74

68.7

2 72

93.2

17

5.52

2.

35

6/7/

2014

71

86.5

2 70

63.5

12

3.02

1.

712

7280

.8 –

91.

62=

7189

.18

7063

.5

125.

68

1.74

8

Ave

rage

1.

749

1.

879

99



The reduced load flow of Visayas model was tested using the June 2, 2014, period 19 data. First system loss simulation result was considerably far from the given WESM system loss. It was modified to approximate the actual WESM system technical loss by employing double lines from bus 24 to 25 and bus 25 and 26. The result was the final model. Simulation of the final Visayas model was again conducted at different time intervals to gather system loss data (Table 2). No slack bus was pre-selected, the simulator automatically selected bus 17 (Leyte 230 kv).

The simulation of reduced load flow Visayas model showed that the load is the same as the WESM data. The actual generation column for WESM is the sum of the scheduled generation (i.e.7896.1 MW) and the HVDC flow schedule from Luzon to Visayas (i.e. 27.38 MW) for the same day and period. Most of the system loss values are equal except for the 6/6/2014. F-test showed no significant difference on variances of the two models. Similarly, the corresponding t-test on system loss showed no significant difference at α = 0.05. The calculated t-value = 1.19, is lesser than the critical value t (table) = 2.365. Thus, reduced load flow model of Visayas and the actual load flow model are approximately the same.

Since there was no WESM data for Mindanao, the reduced Mindanao model was tested using the load and generator status given in Sabelita’s model (Sabelita, 2012). The latter is composed of 37 buses, 8 transformers, 17 generators, and 51 transmission lines while the reduced model in this study used only 13 buses, 17 generators, 2 transformers, and 24 transmission lines. Power loss of the two models was determined and compared (Table 3). The two figures are almost the same. Percent error validated the reduced Mindanao model considering the system loss of Sabelita’s model (Sabelita, 2012) as the accepted value. The percent error (%Error = 0.129) is very small, thus the two values are almost the same.

100


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flow

syst

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ss c

ompa

rativ

e re

sults

. So

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Po

wer

wor

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mul

atio

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ESM

Peri

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19

Gen

erat

ion

(MW

) Lo

ad

(MW

) Lo

ss

(MW

) Lo

ss

(%)

Gen

erat

ion

(MW

) Lo

ad

(MW

) Lo

ss

(MW

) Lo

ss

(%)

6/2/

2014

15

10.2

9 14

65.2

45

.10

2.98

6 14

83.7

+27.

38=

1511

.08

1465

.2

45.8

8 3.

036

6/3/

2014

15

36.2

9 14

94.5

41

.69

2.71

4 15

13.9

+24

.06=

15

37.9

6 14

94.5

43

.46

2.82

6

6/4/

2014

15

36.4

1 14

89.3

47

.11

3.06

6 15

32 +

4.8

6 =

1536

.86

1489

.3

47.5

6 3.

095

6/5/

2014

15

45.8

7 14

88.2

57

.67

3.73

14

55.3

+84

.86

= 15

40.1

6 14

88.2

51

.96

3.37

6/6/

2014

14

97.9

4 14

43.6

54

.34

3.62

13

73.4

+ 8

7.98

= 14

61.3

8 14

43.6

17

.78

1.21

6

6/7/

2014

14

31.7

4 13

83.8

47

.94

3.34

13

39.5

+ 91

.62=

14

31.1

2 13

83.8

47

.32

3.30

6

Ave

rage

3.

243

Ave

rage

2.

808

101



Table 4. First simulation: Philippine model bus record.


Table 3. Mindanao load flow results. Power world simulation Sabelita’s data

Generation (MW)

Load (MW)

Loss (MW)

Loss (%)

Generation (MW)

Load (MW)

Loss (MW)

Loss (%)

1196.82 1178.9.45 18.55 1.549 1197.42 1178.9 18.52 1.547

The three validated reduced models of Luzon, Visayas, and Mindanao were interconnected to create a unified reduced load flow model of the power system grid of the Philippines. The unified model was simulated and evaluated. When load flow simulation runs when all generators are on line and on their rated capacity, the slack bus absorbs power. This process occurs because the total generation of all available generators in the Philippines greatly exceeds the Philippine demand (load). Thus, to avoid overgeneration, the unified Philippine Grid Model was simulated using a specific WESM generation and load scheduling on June 2, 2014 period 19 for Visayas and Luzon and the actual data in Sabelita (2012) for Mindanao.

In the first simulation setting, the HVDC flow from Luzon to Visayas was set to the WESM actual HVDC flow on the same period of 27.3 MW, and the Visayas to Mindanao HVDC flow was randomly set to 100 MW. Simulation of the unified model showed that three of Visayas buses, bus 19 (Tabango), bus 20 (Daan Bantayan), bus 21 (Compostela), and bus 39 (Anislagan/Nasipit) of Mindanao which received the HVDC connection from Visayas did not pass the Philippine Grid Code specification for bus per unit (p.u.) voltages (Table 4).

This circumstance inevitably occurs in the future if the Mindanao grid will be finally connected to Luzon and Visayas interconnected grid to form the unified Philippine power system grid. Luzon to Visayas HVDC line lost transmitting power, 27.4-27.3 equal to 0.01 MW and the Visayas to Mindanao HVDC also lost 1.6 MW.

102



Table 4. First simulation: Philippine model bus record.

103



Table 5. Second and final simulation result: Bus records.


To address the undesirable conditions on bus voltages, more simulations were conducted and the results were analyzed. Consequently, var (volt ampere reactive) compensation scheme and de-energization of the existing 200 MVAR reactor of bus 19 (Tabango) and the 250 MVAR reactor of bus 20 (Daan Bantayan) raised up the voltages of Visayas buses. The VAR compensation is defined as the management of reactive power to improve the performance of ac power systems (Pal et al., 2013). In a similar situation, Aswani and Sakthivel (2014) used a capacitor bank to address under voltage and over voltage problems during power flow analysis of a 110/11kV substation under Kerala State University board. The Reduction of HVDC power flow to 50 MW raised the voltage of the Mindanao bus to acceptable values specified by the Philippine Grid Code, Art. 3.2.3.3 and 3.2.3.4 (Philippine Grid Code, 2001) (Table 5).

The equipment used for VAR compensation scheme to correct voltage problem of Visayas already existed on the island while HVDC power flow control was used to correct the Mindanao voltage problems. It is a noteworthy consideration that all simulation manipulations to correct the bus voltages problems utilized equipment that existed in the grid. The second simulation set HVDC power flow settings to 27.3 MW from Luzon to Visayas and 50 MW from Visayas to Mindanao. The manipulations on reactive var compensation scheme raised the voltages of the said buses, but decreased the system loss of all the major islands and thereby reducing the Philippine grid system loss.

104



Table 5. Second and final simulation result: Bus records.

105



Per cent power losses of Luzon, Visayas, and Mindanao of the unified model and that obtained from the reduced individual models are comparable (Table 6). The calculated and the simulation system loss of the unified Philippine model also showed almost identical results. Even the power system loss of the unified model only differs slightly from the average loss of the three major islands. The aggregation process and the reduced power station count justified slight differences observed (Seack et al., 2014).

The unified Model of the Philippine grid consisted of 110 generators, 41buses, 24 transformers, 1 HVDC cable connecting Leyte and Naga, 1 HVDC cable connecting Leyte and Anislagan, four submarine cables, and 84 overhead transmission lines (Figure 1). Wong et al. (1995) also developed a unified model to support network fault, reliability, and performance analysis. Except for system (technical) loss, this unified model of the Philippine power system grid possessed the comparable physical parameters as the actual model. System losses are generally the losses of transmission lines and transformers. A perfect identical behavior of the unified model with that of the actual model is less expected because of the utilization of public available data (Seack et al., 2014).

106


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107



Conclusion and Recommendations

Public documents and information from prior studies generated a reduced load flow models of the three islands, Luzon, Visayas, and Mindanao. The three reduced models possessed comparable physical parameters to the actual models. In addition, statistical result revealed that there is no significant difference between the system losses of the three reduced models and the actual model. Subsequently, the three reduced models were interconnected through HVDC cables to produce a unified model of Philippine power system grid. The VAR compensation scheme and de-energization were used to address under voltages issues of the unified model. With the specified manipulations, the unified model passed the Philippine Grid Code which can represent the actual model of the Philippine power system grid.

The unified model institutes power system analysis like optimization, fault studies, stabilities, and reliability in a more convenient way. It also provides a platform for improving power generation and transmission by introducing new equipment into the system. Further, scrutiny on the simulation results of the unified model will provide power system engineers more information for future use or full implementation of the Philippine power system grid.

Literature cited Abhyankar, A. R., & Khaparde, S. A. (2013). Introduction to

deregulation in power industry. Report by Indian Institute of Technology, Mumbai.

Afolabi, O. A., Ali, W. H., Cofie, P., Fuller, J., Obiomon, P., &

Kolawole, E. S. (2015). Analysis of the load flow problem in power system planning studies. Energy and Power Engineering, 7(10), 509. doi: http://dx.doi.org/10.4236/epe.2015.710048


Figure 1. Screen shot of the simulator’s unified Philippine model.

108



Conclusion and Recommendations

Public documents and information from prior studies generated a reduced load flow models of the three islands, Luzon, Visayas, and Mindanao. The three reduced models possessed comparable physical parameters to the actual models. In addition, statistical result revealed that there is no significant difference between the system losses of the three reduced models and the actual model. Subsequently, the three reduced models were interconnected through HVDC cables to produce a unified model of Philippine power system grid. The VAR compensation scheme and de-energization were used to address under voltages issues of the unified model. With the specified manipulations, the unified model passed the Philippine Grid Code which can represent the actual model of the Philippine power system grid.

The unified model institutes power system analysis like optimization, fault studies, stabilities, and reliability in a more convenient way. It also provides a platform for improving power generation and transmission by introducing new equipment into the system. Further, scrutiny on the simulation results of the unified model will provide power system engineers more information for future use or full implementation of the Philippine power system grid.

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deregulation in power industry. Report by Indian Institute of Technology, Mumbai.

Afolabi, O. A., Ali, W. H., Cofie, P., Fuller, J., Obiomon, P., &

Kolawole, E. S. (2015). Analysis of the load flow problem in power system planning studies. Energy and Power Engineering, 7(10), 509. doi: http://dx.doi.org/10.4236/epe.2015.710048

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113
