5. DE LAS PRÁCTICAS DE LABORATORIO Y ESCUELA AL GRUPO SOCIAL
5.3. Rousseau y la libertad, Skinner y el control de la conducta ¿A qué se refieren?
Fig. 8.14 presents the power output from the solar farm during a sunny day with measured harmonics, current THD, and the calculated TDD.
Figure 8.14 10 MW Solar Farm Output for a Sunny Day
Three arbitrary harmonic datasets are chosen: evening time, noon time, and the moment of the highest harmonic injection in that day, which are depicted in Fig. 8.15, Fig. 8.16 and Fig. 8.17, respectively. The corresponding simulation results are presented in Table 8.7, Table 8.8 and Table 8.9 for the evening, noon, and the high harmonics injection time, respectively. Note that the simulation results are obtained for worst network condition in Fig. 8.1.
It is observed from Fig. 8.14, Fig. 8.15, Fig. 8.16, and Fig. 8.17 that the pattern of harmonics is similar at different times, but the magnitude of harmonics varies with the power output level of the solar farm. Comparing Table 8.7, Table 8.8 and Table 8.9, the voltage THD as well as the voltage harmonics are seen to be higher for the case of high harmonic injection from the solar farm, as seen in Table 8.9.
Figure 8.15 Harmonics Dataset in the Evening of a Sunny Day
Table 8.7 Power, Voltage, Harmonics Distortion during the Evening of a Sunny Day
Quantities St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) 2.639+j6.789 5.33-j0.1482 5.33-j0.1501
Fundamental Phase Voltage, Vf (kV)
16.532 16.463 16.461
Fundamental Current, If (Amp) 145.56 108.08 108.08
Current TDD (%) - 1.3 1.3
Voltage THD (%) 0.356 0.927 0.919
Voltage Harmonic Distortion (kV) 0.0589 0.15263 0.15136
Table 8.8 Power, Voltage, and Harmonics Distortion at noon on a Sunny Day.
Quantities St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) -6.508+j6.471 9.983+j0.2518 9.981+j0.2455
Fundamental Phase Voltage, Vf (kV)
16.66 16.738 16.736
Fundamental Current, If (Amp) 184.46 199.12 199.12
Current TDD (%) - 1.175 1.175
Voltage THD (%) 0.32 0.864 0.857
Voltage Harmonic Distortion (kV) 0.05345 0.14467 0.14342
Figure 8.17 High Harmonics Dataset on a Sunny Day
Table 8.9 Power, Voltage, and Harmonics Distortion for High Harmonics Injection on a Sunny Day.
Quantities St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) 7.852+j6.756 2.712-j0.1716 2.712-0.1721
Fundamental Phase Voltage, Vf (kV)
16.65 16.513 16.512
Fundamental Current, If (Amp) 205.75 54.88 54.88
Current TDD (%) - 1.474 1.474
Voltage THD (%) 0.4085 1.0457 1.0372
Voltage Harmonic Distortion (kV) 0.06801 0.17269 0.17127
Further investigation is made for a cloudy day. Fig. 8.18 presents the power output from the solar farm during a cloudy day with measured harmonics, current THD, and the calculated TDD. Like the sunny day case, three arbitrary harmonic datasets are chosen: evening, noon, and the moment of highest harmonic injection in the day, which are
depicted in Fig. 8.19, Fig. 8.20 and Fig. 8.21, respectively. The corresponding harmonics simulation results are presented in Table 8.10, Table 8.11 and Table 8.12 for the evening, noon, and the high harmonics injection time, respectively. The same worst case network is used for this simulation study as well.
Figure 8.18 10 MW Solar Farm Output for a Cloudy Day
Table 8.10 Power, Voltage, Harmonics Distortion during the Evening on Cloudy Day
Quantiites St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) 11.97+j6.582 0.6519-j0.05674 0.6519-j0.05681
Fundamental Phase Voltage, Vf (kV)
16.599 16.416 16.416
Fundamental Current, If (Amp) 272.777 13.28 13.28
Current TDD (%) - 0.736 0.736
Voltage THD (%) 0.208 0.524 0.518
Voltage Harmonic Distortion (kV) 0.0346 0.086 0.085
Figure 8.20 Harmonics Dataset around noon on a Cloudy Day
Table 8.11 Power, Voltage, and Harmonics Distortion at noon on a Cloudy Day
Quantities St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) 5.785+j6.751 3.739-j0.1689 3.738-j0.1699
Fundamental Phase Voltage, Vf (kV)
16.491 16.379 16.378
Fundamental Current, If (Amp) 178.31 76.24 76.24
Current TDD (%) - 1.446 1.446
Voltage THD (%) 0.391 0.983 0.977
Figure 8.21 High Harmonics Dataset on a Cloudy Day
Table 8.12 Power, Voltage, and Harmonics Distortion for High Harmonics Current Injection on a Cloudy Day
Quantities St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) 7.175+j6.753 3.031-j0.18 3.031-j0.1807
Fundamental Phase Voltage, Vf (kV)
16.66 16.53 16.53
Fundamental Current, If (Amp) 195.8 61.28 61.28
Current TDD (%) - 1.506 1.506
Voltage THD (%) 0.4063 1.028 1.022
Voltage Harmonic Distortion (kV) 0.0677 0.17 0.169
From Fig. 8.18, Fig. 8.19, Fig. 8.20 and Fig. 8.21 it is seen that the harmonics data pattern is similar at different times. However, similar to the sunny day case, the magnitude of harmonics varies with the power output level of the solar farm. Comparing Table 8.10, Table 8.11 and Table 8.12, it is seen that the voltage THD becomes higher for the case of high harmonic injection from the solar farm for the worst condition of network, as in Table 8.9.
However, on both the sunny and cloudy days, the above studies show that the maximum voltage harmonics distortion occurs for the case of maximum harmonic injection level from the solar farm on that particular day.
Fig. 8.22 presents the harmonics spectrum for highest harmonics injection by the solar farm over the period of one month. Table 8.13, Table 8.14, and Table 8.15 present the simulation results at 1SCL, 1/3rd SCL, and 4SCL of the source on the selected network condition of Fig 8.1, respectively. The voltage distortions along with the power and voltage quantities for this highest level of harmonics injection by the solar farm are compiled in these tables.
Figure 8.22 Harmonics Spectrum for Highest Harmonics Current Injection Over the Whole Period.
Table 8.13 Simulated Power, Voltage, and Harmonics Corresponds to Highest Harmonics Injection by the Solar Farm at 1SCL
Quantities St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) 7.305+j6.77 2.98-j0.1796 2.98-j0.1802
Fundamental Phase Voltage, Vf (kV)
16.657 16.5266 16.526
Fundamental Current, If (Amp) 197.824 60.24 60.24
Current TDD (%) - 1.567 1.567
Voltage THD (%) 0.429 1.094 1.085
Table 8.14 Simulated Power, Voltage, and Harmonics Corresponds to Highest Harmonics Injection by the Solar Farm at 1/3rd SCL
Quantities St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) 7.297+j6.572 2.981-j0.08409 2.981-j0.08469
Fundamental Phase Voltage, Vf (kV)
15.662 15.498 15.497
Fundamental Current, If (Amp) 222.693 60.24 60.24
Current TDD (%) - 1.567 1.567
Voltage THD (%) 0.4867 1.129 1.119
Voltage Harmonic Distortion (kV) 0.076 0.175 0.173
Table 8.15 Simulated Power, Voltage, and Harmonics Corresponds to Highest Harmonics Injection by the Solar Farm at 4SCL
Quantities St. Andrew SS Sarnia Solar farm SS2 Sarnia Solar farm SS5
Power, P+jQ (MVA) 7.297+j6.572 2.981-j08409 2.981-j0.08469
Fundamental Phase Voltage, Vf (kV)
16.637 16.515 16.515
Fundamental Current, If (Amp) 195.45 60.24 60.24
Current TDD (%) - 1.567 1.567
Voltage THD (%) 0.395 1.097 1.087
Voltage Harmonic Distortion (kV) 0.066 0.181 0.1796
By comparing Table 8.13, Table 8.14 and Table 8.15, it is demonstrated that the distortion in voltage increases with the decrease in short circuit level of the source on the selected worst network condition (with the frequency response presented in Fig. 8.1).
8.8 Conclusion
In this chapter, a detailed harmonics impact study is performed for a 20 MW solar farm on the distribution network of Bluewater Power. The network is modeled with actual network data. Load flow studies are conducted to validate the network model built in CYME and EMTDC/PSCAD with actual SCADA measurements with PV systems. Network resonance studies for different network conditions are performed for the feeder 18M14, which connects the large-scale solar farms by using EMTDC/PSCAD. The measured harmonic data obtained from the solar farm is analyzed and utilized to demonstrate the impact on the network harmonic distortion for different short circuit levels.
The following conclusions are made:
2. The large substation capacitor (20 MVAr or 40 MVAr) causes resonance around the 3rd harmonics.
3. The load capacitor 1.2 MVAr causes network resonance around the 25th harmonics.
4. Presence of load on the feeder reduces the magnitude of network resonant impedances.
5. The solar farm typically injects high 5th, 7th,11th, and 13th harmonics. 6. A small number of ambient harmonics are observed in the network.
7. Network resonance at 3rd harmonics does not cause any substantial increase in voltage THD on the feeders.
8. The highest voltage distortion is observed for the case with no capacitor connected, and with high harmonics injection from the solar farm. Even in this case the voltage THD is seen to be 1.13%, which is much lower than the 5% level specified by the IEEE standard 519.
9. Thus, based on the studies conducted, it is inferred that the large solar farm of 20 MW may not cause any substantial voltage distortion on the feeder 18M14 during steady state operating conditions.
This study has been conducted with a huge set of data provided by Bluewater Power Corp., Hydro One Inc., and with the cooperation of Enbridge Inc. and First Solar, who are all sincerely acknowledged.
Chapter 9
9
Conclusion
9.1 Introduction
This thesis presents four novel applications of PV solar farms for providing various benefits to electric power systems in addition to generating real power from solar insolation. A conventional grid connected Photovoltaic (PV) solar farm utilizes an inverter for converting the DC power output from PV arrays into AC power to be supplied to the grid. During the night, the entire PV solar system remains completely idle and is also only partially utilized during the day, especially in the early morning and late evening hours. This thesis presents new technologies for a complete utilization of the inverter of a PV solar system, both during day and night time. These technologies transform the PV solar system inverter into a Static Synchronous Compensator (STATCOM) which is a major device in the family of Flexible AC Transmission Systems (FACTS). This novel technology is termed as PV-STATCOM.
A STATCOM is a dynamic reactive power compensator which provides very rapid voltage regulation and damping at the point of connection with the grid. It is known in power systems operation that a capacitor increases voltage and an inductor decreases voltage at the terminal when it is controlled. The STATCOM functions as a variable inductor (consuming reactive power) and as a variable capacitor (injecting reactive power), and thus, performs very rapid voltage control. In a similar manner, the PV system transformed into a PV-STATCOM performs voltage control or damping control by using the entire PV inverter capacity during the night, and the remaining capacity of the PV inverter after real power generation during the day.
In this thesis, novel control of PV-STATCOMs is proposed to perform loss reduction in a distribution network, to prevent the instability of a critical induction motor load, and to increase the power transfer limit of a long transmission line. These new applications of PV solar farms can help to improve the performance of power systems significantly. They can also potentially bring new sources of revenue for PV solar farms by providing
these benefits, in addition to those earned from the sale of real power. Moreover, a new technique for short circuit current management is presented for conventional PV solar farms that will potentially solve the problem which has caused several solar farms to be denied connectivity in Ontario. This thesis also presents a generalized PV solar system model in the EMTDC/PSCAD software environment. Another major study performed in this thesis is the harmonics impact of the largest PV solar farm in Canada, in the distribution utility network of Bluewater Power (BWP), located in Sarnia, Ontario.