[Virtual Presenter] Good morning everyone! I am very enthusiastic to tell you about the project we are about to talk about today. This project concentrates on finding a solution to reduce the adverse effects caused by the growing installment of rooftop photovoltaic systems on LV feeders. Let us go through the presentation to get more details about the project and what measures we can take to ensure its success.. 

Scene 1

MITIGATION OF NEGATIVE IMPACTS CAUSED BY ROOF TOP SOLAR PV PENETRATION ON LV FEEDERS

by H.M.P.K.A.Herath Reg. No. 509067399 Individual Project Type – B EEY6D95 Final Presentation

Department of Electrical & Computer Engineering Faculty of Engineering Technology The Open university of Sri Lanka

[Audio] I am presenting a project to you which is of great importance in understanding the serious repercussions of the increasing proliferation of rooftop solar photovoltaic systems on low-voltage feeders. Over the years, due to the advancement in power electronic devices and reduction in the cost of photovoltaic panels, the use of solar plants has grown exponentially and connected to the existing power infrastructure. I have collected some data which shows the growth in solar, wind, biomass, and mini hydro energy in Sri Lanka in the future. As you can see, solar energy in Sri Lanka has a very bright future. However, with the upsurge in renewable energy sources, there is also the possibility of adverse effects on the power grid. Therefore, this project seeks to identify techniques to contain the potential negative consequences of a high penetration of rooftop solar photovoltaic systems on low-voltage feeders.. 

Scene 2

Background of the project: The development of power electronic devices, decreasing prices of PV panels has promoted the use of solar plants and their connection to the existing Grid.

Growing nature of solar generation in the upcoming years in Sri Lanka.

• Solar (MW)
• Wind (MW)
Biomass (MW)
4500
Mini Hydro (MW) .Major Hydro
3500
1500
1000
0

[Audio] Our project focuses on mitigating the volts-rise caused by the penetration of rooftop solar PV systems on low voltage feeders. Volt-rise occurs when PV generation exceeds demand, resulting in the power flowing back to the LV grids, causing an increase in voltage at the point of common coupling. For this purpose, our project centers around identifying the problem and its potential solutions.. 

Scene 3

Problem Identification: Voltage Rise :  A  high PV inﬂux could cause  voltage rise  when the load is at its minimum and the PV generation is at its maximum during peak irradiance periods (noon time) . When PV generation exceeds demand, power  flows towards LV grids, resulting in a voltage rise at the point of common coupling (PCC ).

Voltage [pul
Nominal
Load
now
Voltage (pul
V
e (puJ
distance
Voltage tpuJ
Light
Load
distance
distance
Pos•€er now
distance

[Audio] This project explores the consequences of the fast expansion of rooftop solar photovoltaic (PV) systems on low voltage (LV) feeders. Our mission is to reduce such adverse effects, as well as to find methods to maximize the use of PV systems, addressing the increasing power demand of our nation. We are establishing and examining the potential difficulties that a high penetration of PV technology may bring to a distinct LV distribution feeder. Besides, we are employing different real and reactive power control approaches to counteract these adverse effects. Eventually, we will present the optimal mitigation technique to the power utility side, in order to better the power quality on all LV lines, for the advantage of the utility and the consumer.. 

Scene 4

Project Aim:   To mitigate the negative impacts of high level of solar PV penetration and increase the use of the solar PV resource to meet the increasing power demand in the country.   Objectives:   Determine and investigate the potential negative impacts of a high degree of PV penetration in a specific LV distribution feeder. Hence, employ real and reactive power control strategies to counteract the negative effects of high PV penetration on LV lines. 3.   Introduce the initiated optimum mitigation method to the power utility side in order to improve power quality  in LV lines for the utility's and consumers' benefit.

[Audio] The proposed system in this project is Real and Reactive Power Control techniques of Smart PV Inverters. Smart PV inverters are equipped with features like power factor control, leading and lagging power factor control, real and reactive power control, voltage and frequency control, allowing control of power output from the PV system and regulation of power flow in the grid. This project aims to take advantage of the features of Smart PV inverters in order to reduce the damaging effects of rooftop PV penetration on LV feeders.. 

Scene 5

Proposed System – Real & Reactive Power Control techniques of                                  Smart PV Inverters

[Audio] Rooftop solar photovoltaic systems are capable of regulating voltage levels on low voltage feeders through the utilization of a Volt/Var curve. In the event of the voltage exceeding the set upper bound, the system absorbs reactive power; whilst when the terminal voltage drops below the pre-set lower bound, it injects reactive power. This process helps the voltage levels on these feeders remain within the desirable range with increased consistency.. 

Scene 6

According to the Figure, if the terminal voltage drops below the pre-set lower bound (V3), the inverter injects reactive power to support the voltage at the connection point.  On the contrary, if the terminal voltage exceeds the pre-set upper bound (V4), the inverter absorbs reactive power to reduce the voltage at the connection point.

Reactive Power in Var
Absorbi ng
Injecting

[Audio] The slide is about mitigating the impact of rooftop solar PV systems on LV feeders. One way to do this is by using a Volt-Watt curve. This curve is used to curtail active power output when the voltage goes above or below the permissible voltage bounds. When the voltage exceeds the lower bound and varies between Vvw2 and Vvw3, the active power output is curtailed in accordance with the slope of the curve. Once the voltage reaches the upper voltage bound, the active power output is completely curtailed to ensure that the voltage remains within the permissible limits.. 

Scene 7

Active   Power curtailment – Volt/Watt Control

When the voltage exceeds the lower bound and varies between Vvw2 and Vvw3, the active power output is curtailed in accordance with the slope of the curve. Once the voltage reaches the upper voltage bound (Vvw3), the active power output is completely curtailed to maintain the voltage within the permissible voltage limits.

[Audio] We have chosen a low-voltage network with voltage problems caused by the installation of rooftop solar PV systems. To assess the effect of the penetration of PV systems, power flow simulations were done with OPENDSS. The aim is to identify an optimized solution to resolve the network issues by using advanced inverter control strategies.. 

Scene 8

M
Start
e e selecte
network
ea Ive power
control techniques
1. Fixed PF
2.Volt-var control
3.Volt-Watt control
Integrate the PV systems
the selected networ
Run time- series Three-Phase
power flow simulations
m act ssessment
Any Voltage
violation
Select the Control technique to
be anal ed
Implement and integrate the selected
control techni ue
Run time- series Three-Phase power
Evaluate the performance of the contro
Compare the performance of the control
technique with the impact
End

Selected a  LV network  with voltage issues The power flow simulations were performed at different levels of penetration to convey the voltage problems in the network using OPENDSS.  Hence, find a optimum mitigation method to alleviate those negative impacts using smart inverter control strategies.

Source Bus AZO 199 FEEDER 2 1 kV/400V FEEDER 1 (lx1P+2x3P) o c 1/2 c 4/2 Cl/l C4/1 (3P) P3 c CIO (3P) C3/A CYB C3,'C CYD GI Ci2 G5 (3P) H12 (2x3P) HIO (IP+3P) H4/'A (3P+1P) (2x3P) H5. 

Scene 9

Source Bus
AZO 199
FEEDER 2
1 kV/400V
FEEDER 1
(lx1P+2x3P)
o
c 1/2
c 4/2
Cl/l
C4/1
(3P)
P3
c
CIO
(3P)
C3/A
CYB
C3,'C
CYD
GI
Ci2
G5
(3P)
H12
(2x3P)
HIO
(IP+3P)
H4/'A
(3P+1P)
(2x3P)
H5

Single Line Diagram of Selected LV Network

[Audio] This slide presents data from a two-feeder-line network comprising 240 customers. It is equipped with a 11KV/415V transformer with a capacity of 160kVA, spanning a total of 1.5 km on the low-voltage (LV) network. The two feeder lines have different numbers of customers and different amounts of installed rooftop solar PV prosumers of 85.01 kWp. Cable types used for the installation include aluminium aerial bundle cables LV244, 3x50+1x16+N35 and 3x70+1x16+N35. This data is necessary to alleviate any potential negative impacts from the penetration of rooftop solar PV systems into the LV feeders.. 

Scene 10

Transformer Details 11kV/415V Capacity 160kVA Dyn11 with a solidly earthed neutral point Geometrically located in middle of the network Total length of LV network 1.5 km Number of feeders Two feeders Total Number of customers 240 Feeder 1= 174 Single Phase = 129 Three Phase = 45 Feeder 2= 66 Single Phase = 56 Three Phase = 10 Rooftop Solar PV prosumers Total installed solar capacity  of 85.01 kWp Feeder 1= 70.01 Single Phase = 10.55 Three Phase = 59.46 Feeder 2= 15 Single Phase = 5 Three Phase = 10 Cables Aluminium Aerial Bundle Cable Code=(LVB244) 3x50+1x16+N35 3x70+1x16+N35

[Audio] Out of the five scenarios determined for this project, the voltage rise, voltage profile, power flow, and power loss in the feeder will be evaluated in order to assess the impact of each scenario on the LV feeders. These scenarios are defined by the level of penetration and capacity of solar customers, as well as cumulative solar capacity in kilowatts.. 

Scene 11

For this study, five scenarios were determined.   Voltage Rise ,  Voltage profile ,  Power flow  and  Power loss  in the selected feeder   will be investigated in these described scenarios

Scenario Penetration Level No of solar Customers Cumulative solar capacity(kWp) 1 0% 0 0 2 40%(Present situation) 17 70.01 3 60% 22 96 4 80%(CEB allowed  capacity) 27 128 5 100% (TF full capacity) 32 160

Solar Installed Capacity Under Various Scenarios

[Audio] We analysed the fluctuation of phase voltage at three points on Feeder 1 - the Feeder Head, the middle of the Feeder, and the Feeder End - throughout the day to gain an understanding of the effects of rooftop solar PV systems on low-voltage power supply lines, referred to as 'LV feeders'. The figure in front of us displays the voltage variation along the line under a situation where PV generation is at 0%, thought of as the standard condition.. 

Scene 12

Voltage variation along the feeder 1 at 0%  (No PV) Penetration level

The fluctuation of phase voltage along Feeder 1 were observed at the 'Feeder Head,' 'Middle of the feeder,' and 'Feeder End' at mentioned scenarios during a day. This figure depicts the voltage variation along the line at  ‘0%’  PV generation (Normal Condition)

230
229
228
S 227
226
225
224
223
Feeder Head
Feeder Mid
Feeder End
1.000
0.995
0.990
0.985
0.980
0.975
0.970
N.OO
•1•.00
.00
.00
Tme(hr
.00

[Audio] The figure indicates that when the solar penetration reaches 100%, an overvoltage condition occurs at the feeder end, beyond the upper voltage limit. Fortunately, we have the advantage that the transformer maximum capacity can handle a solar penetration of up to 100%, thus avoiding any more overvoltage conditions on the feeder. This project seeks to find ways to deal with the negative effects brought about by the mass installation of rooftop solar PV systems on low voltage feeders.. 

Scene 13

Voltage variation along the feeder 1 at 100% (TF capacity)

With 100% penetration, the figure  displays an over voltage condition  at ‘feeder end’(upper voltage  limit 1.06 p.u). Feeder 1 voltages do not exceed  any specified restrictions until  solar penetration reaches  the 100% penetration limit,  i.e. transformer maximum capacity.

245
1.06
240
1.04
235
1.02 a:
230
225
Feeder Head
Feeder Mid
Feeder End
Time(hr)
1.00
0.98

[Audio] We can observe from this slide that once rooftop solar PV systems are put in place, voltage is likely to be above the upper limit of 1.06 p.u. at the end of the feeder. Nevertheless, this won't occur everywhere along the feeder. This project focuses on diminishing the drawbacks that come from this circumstance.. 

Scene 14

When solar PV penetration reaches 100%, the voltages at the end of the feeder will exceed the upper norms (1.06 p.u). This will not take place at any other scenarios over the feeder distance.

Voltage profiles at different Penetration levels

1.08
1.06
1.04
1.02
1.00
0.98
0.96
0.94
at 0% Penetration
at 40% Penetration
at 60% Penetration
at 80% Penetration
at 100% Penetration
200
400
600
Distance (M)
800
1000
1200

[Audio] This project is a response to the issue of solar PV penetration on LV feeders. As the level of penetration increases, so does the risk of reverse power flow. We have observed a reverse power flow of 43kW at 100% of the solar PV penetration level. This project aims to reduce the risk of this reverse power flow and reduce the potential negative impacts it can cause.. 

Scene 15

A  reverse power flow of around  43kW  at day time, which is higher than the daytime average demand load, has been seen at 100% of the solar PV penetration level .

Active Power flow at the LV Transformer for different PV penetration levels

at 0% Penetration
60
at 40% Penetration(Present Network)
at 60% Penetration
at 80% Penetration
at 100% Penetration
20
-20
Time (h)

[Audio] "It is now well established that the integration of rooftop solar PV systems on LV feeders can have a significant impact on the power loss. Our project has shown that active and reactive power loss are seen to be reduced up to 80% of the penetration level. However, beyond that power loss increase compared to no solar PV. This means that there are limits to how much rooftop solar PV can be integrated onto LV feeders without undue negative impacts on power loss. The implications of this are important for the design of our power grid in the future.”. 

Scene 16

Active & Reactive power loss are seen to be reduced with the integration of solar PV up to 80% of the penetration level. Further increase in solar PV up to 100% has resulted in a higher power loss compared with scenario 1 (0% - No PV)

2.5
at 0% Penetration
at 40% Penetration(Present Network)
at 60% Penetration
at 80% Penetration
at 100% Penetration
> 1.5
1.0
0.0
Tme (h)

Active & Reactive Power loss at the LV Transformer for different PV penetration levels

[Audio] Focus of Slide 17 is on the smart inverter technology which assists in managing the rooftop solar PV system. The smart inverter acts as a bridge between the PV panel and the grid. It takes into consideration various inputs like power factor, irradiance, temperature, voltage, and power efficiency, along with measuring voltage, active power, reactive power, and apparent power. This assists in keeping the quality and safety of the grid intact, while simultaneously improving the efficiency of the solar PV system.. 

Scene 17

Smart Inverter
Control
Inputs
Power Factor
Irradiance
Temperature
Voltage
Power
Efficiencv
Inverter
Measurements
Voltage
Active Power
Reactive Power
Apparent Power
Grid
PV Panel

Block Diagram of OpenDSS PV system model with smart inverter controls

Parameter Settings of smart PV Inverters. 

Scene 18

[Audio] We employed three control techniques for the project to reduce voltage threshold breaks that were observed when a great amount of rooftop solar PV systems were connected to a low voltage (LV) feeder. By implementing these techniques, we were able to increase active power generation and prevent overvoltage issues. Simulation results revealed the three control techniques were effective in preventing voltage limit violations, enabling us to fend off the problem of overvoltage created by the integration of rooftop solar PV systems on LV feeders.. 

Scene 19

245.0
242.5
240.0
3 237.5
235.0
232.5
230.0
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225.0
at No Control(100% Loading)
at Fixed PF
at Volt/Var VV2(with Dead Band)
at Volt/Var VVI(W/O Dead band)
at VoltWatt
1.06
1.04
a:
1.02
1.00
0.98
1.00
.00
.00
Tme(hr)
.00

Alleviating Voltage rise  using different control techniques

The upper voltage limit violations observed in  100%  penetration  were successfully alleviated after using the control techniques of solar PV inverters.  According to the simulation results, the three techniques were capable of preventing overvoltage problems while providing the maximum active power generation.

[Audio] The figure shows that when the transformer capacity for rooftop solar PV systems reaches 100%, a voltage violation occurs. However, if smart inverter control strategies are employed, this can reduce the overvoltage to an acceptable level.. 

Scene 20

This figure depicts that the voltage violation occurs with  100% PV  loading (i.e., transformer maximum capacity) at the end of the feeder as opposed to a  "No PV"  situation.  It also demonstrates that the use of smart inverter control strategies completely reduces the overvoltage to the permissible limit.

Voltage Profiles at different mitigation strategies

[Audio] This slide's figure demonstrates that the Volt-Watt control technique can significantly cut the active power of a rooftop solar PV system to 48.84%, in comparison to a 25.85% active power reduction that the Fixed PF technique produces, with a maximum power production of 43 kW. This project attempts to minimize the adverse impacts that this system can have on low voltage feeders.. 

Scene 21

As illustrates in the figure there is a substantial active power reduction was noted in  Volt-Watt  control compared with other control techniques. A  48.84%  &  25.85%  active power reduction was reported in  Volt-Watt  and  Fixed PF  techniques respectively from the maximum power generation of  43kW .

Variation of Active Power Generation in different control techniques at the LV Transformer secondary

[Audio] This project seeks to reduce the adverse effects of rooftop solar PV systems on low voltage feeders. Simulation results show that Volt-Var control is the most effective in managing reactive power absorption, reaching a maximum of 31kVAr. In contrast, Volt-Watt control did not provide any assistance to the system.. 

Scene 22

As depicted in the figure there is a significant reactive power absorption can be observed with  Volt-Var  controls compared to other techniques. According to the simulation results the maximum RPA of  31kVAr  was reported in  Volt/var   VV1(without dead band).  But  Volt-Watt  control has not provided any reactive power support to the system.

Variation of Reactive Power Absorption in different control techniques at the LV Transformer secondary

[Audio] Penetration of rooftop solar PV systems on Low Voltage feeders can cause marked effects on Power loss, as evident in the figures. It is discernible that two Volt-Var strategies have significantly more Active and Reactive loss than the other control scenarios. This is a consequence of reactive power passing over a long distance with low X/R ratio, resulting in the reactive power absorption taking place far from the distribution transformer.. 

Scene 23

3.0
2.0
at No Control(100% Loading)
at Fixed PF
at volt/Var WI(W/O Dead band)
at Volt/Var VV2(with Dead Band)
at VoltWatt
1.0
0.5
0.0
Tme (h)

Active Power Losses (kW) in different control techniques

As illustrated in the figures there is a significant increase in Active and Reactive losses at two different  Volt-Var  strategies compared to other control scenarios. This took place due to the fact that the reactive power passed over a long distance  (with low X/R ratio)  as the reactive power absorption occurred further away from the distribution transformer.

[Audio] The figures showed that the Volt-Watt control technique was the most successful in lowering both active and reactive power losses in comparison to other scenarios. It was the only method that not only achieved a reduction in active power, but also eliminated the absorption of reactive power - a crucial factor in preventing the LV feeders from suffering the detrimental effects of rooftop solar PV systems.. 

Scene 24

2.0
at No Control(100% Loading)
at Fixed PF
at Volt/Var VVI(W/O Dead band)
at Volt/Var VV2(with Dead Band)
at VoltWatt
c 1.5
1.0
0.5
0.0
Time (h)

Reactive Power Losses ( kVAr ) in different control techniques

As demonstrated in the figures, the  optimum  control technique with less active and reactive loss would be the  Volt-Watt  control technique compared to other scenarios. This was confirmed by the fact that there was no reactive power absorption and just active power reduction in the network with the  Volt-Watt  strategy.

Simulated results for the comparative analysis using control techniques of solar PV inverters. 

Scene 25

Simulated results for the comparative analysis using control techniques of solar PV inverters

Comparison Of Control Strategies Integrated in Smart PV Inverters

[Audio] The slide includes a chart outlining the measurements taken to analyze the impact of rooftop solar PV systems on low voltage feeders. It shows active power and reactive power in kilowatts and kilovolt amps respectively. Additionally, it shows fixed power factor, Volt/Var VV1, Volt/Var VV2, and Volt/Watt. This data was collected to investigate the possible effect of incorporating such systems into a power network.. 

Scene 26

Active Power (kW) Fixed PF Volt/Var VV1 Volt/Var VV2 Volt/Watt 9.26 13.33 13.36 5.6760000000000002 Reactive Power (kVAr) Fixed PF Volt/Var VV1 Volt/Var VV2 Volt/Watt 6.9980000000000002 15.069000000000001 6.2450000000000001 3.702 Network Loss (kW) Fixed PF Volt/Var VV1 Volt/Var VV2 Volt/Watt 0.56100000000000005 1.2410000000000001 0.96399999999999997 0.318

[Audio] This slide focuses on the effects of the penetration of rooftop solar PV systems on low voltage feeders. Although a voltage rise can be caused by solar PV, Watt and Var control may not be necessary due to the limited voltage rise. Watt control is more effective when using low X/R Conductors. We will further examine the feeder segmentation which includes the front segment, the middle segment, and the end segment featuring PV and the PV Substation.. 

Scene 27

PV VAr and Watt control may not be needed due minimal voltage rise caused by solar PVs Watt control is most effective with low X/R Conductors Front Segment Middle Segment End Segment PV PV Substation

Effectiveness of control strategies along Feeder segments

Feeder segments where Volt-Var and Volt-Watt control modes are effective

[Audio] Presenting the results of a detailed study of an urban Low Voltage (LV) distribution network, it was discovered that high penetration of solar PV can lead to various problems - such as voltage rise, reverse power flow, and power losses - when analyzed through OPENDSS and PYTHON software. Three power control strategies of solar PV inverters to tackle the overvoltage issue were presented and evaluated, with Volt-Watt control being found to be the most optimal technique for LV feeders with low X/R ratio in order to provide efficient voltage control and maximize the PV hosting capacity, while having minimal impact on customers.. 

Scene 28

A detailed study was conducted on a typical urban LV distribution network to analyze and review the negative impacts by using some simulation  software  like OPENDSS and PYTHON.  Results from the impact assessment showed that under high penetration of solar PV there are some negative impacts such as  voltage rise, reverse power flow, and power losses  looming to disturb the general power quality standards set by the CEB. After the impact assessment on LV feeders, three real and reactive power control strategies of solar PV inverters, namely the  Fixed power factor, Volt–Var, and Volt–Watt  controls, were presented and evaluated to alleviate overvoltage issues due to high PV influx in LV distribution networks.  So, based on the research,  Volt-Watt  control is the  optimum technique for the LV distribution feeders (with low X/R ratio)  to  provide efficient voltage control with minimal impact on  customers  and to increase PV hosting capacity.

[Audio] This project examines ways to reduce the effects of introducing rooftop solar PV systems to low-voltage power networks. We will analyse research in Indonesia, Sri Lanka and Saudi Arabia, as well as consider the potential of the Sri Lankan “Battle of Solar Programme”. Additionally, we will investigate the concept of smart inverters and volt/var control. We will also examine OpenDSS and the time series video tutorials, as well as the OpenDSS manual provided by EPRI. This project is a significant step in reducing the effect of high penetration of rooftop solar PV systems on low voltage feeders.. 

Scene 29

Mitigation of overvoltage due to high penetration of solar photovoltaics using smart inverters volt/var control  Article in Indonesian Journal of Electrical Engineering and Computer Science · April 2020.   Analysis of Rooftop Solar Impacts on Distribution Networks by D.W. Almeida, A.H.M.S.M.S.  Abeysinghe  and J.B.  Ekanayake  ,Ceylon Journal of Science 48(2) 2019: 103-112, Potentials in the Sri Lankan “Battle of Solar Programme” and the Roof top initiative Solar Power Generation Developments And Investment Opportunities In Sri Lanka by W.K.H.WEGAPITIYA,LAUGFS HOLDINGS LIMITED. Voltage Impact of Roof-Top Solar Photo-Voltaic Systems on Low Voltage Network and Measures of Mitigation by K.G.R.F.Comester,D.D.K.G.Sandasiri,G.A.I.Mihindukulasooriya,K.P.J.G  Premathilake ,  Ruwani  .P.  Wijesinghe  published at CEB R&D Journal June 2020 Mitigation of voltage rise due to high solar PV penetration in Saudi distribution network by  ThamerAlquthami,R.Sreerama  Kumar and Abdullah  AlShaikh OpenDSS Time series video tutorials from https://www.youtube.com/watch?v=DAbzXVuaPZk    OpenDSS manual – March2018 by EPRI

[Audio] We have come to the end of this presentation and I'd like to remind you of the importance of this project. The aim of this project is to reduce the negative impacts caused by the penetration of rooftop solar PV systems on LV feeders. Solar power is a renewable energy source that should be embraced; however, we need to ensure that potential risks are mitigated. Your attention is greatly appreciated. Thank you.. 

Scene 30




MITIGATION OF NEGATIVE IMPACTS CAUSED BY ROOF TOP SOLAR PV PENETRATION ON LV FEEDERS
     


Scene 0

I am presenting a project to you which is of great importance in understanding the serious repercussions of the increasing proliferation of rooftop solar photovoltaic systems on low-voltage feeders

Over the years, due to the advancement in power electronic devices and reduction in the cost of photovoltaic panels, the use of solar plants has grown exponentially and connected to the existing power infrastructure

I have collected some data which shows the growth in solar, wind, biomass, and mini hydro energy in Sri Lanka in the future

As you can see, solar energy in Sri Lanka has a very bright future

However, with the upsurge in renewable energy sources, there is also the possibility of adverse effects on the power grid

Therefore, this project seeks to identify techniques to contain the potential negative consequences of a high penetration of rooftop solar photovoltaic systems on low-voltage feeders.

avatar

Our project focuses on mitigating the volts-rise caused by the penetration of rooftop solar PV systems on low voltage feeders

Volt-rise occurs when PV generation exceeds demand, resulting in the power flowing back to the LV grids, causing an increase in voltage at the point of common coupling

For this purpose, our project centers around identifying the problem and its potential solutions.

This project explores the consequences of the fast expansion of rooftop solar photovoltaic (PV) systems on low voltage (LV) feeders

Our mission is to reduce such adverse effects, as well as to find methods to maximize the use of PV systems, addressing the increasing power demand of our nation

We are establishing and examining the potential difficulties that a high penetration of PV technology may bring to a distinct LV distribution feeder

Besides, we are employing different real and reactive power control approaches to counteract these adverse effects

Eventually, we will present the optimal mitigation technique to the power utility side, in order to better the power quality on all LV lines, for the advantage of the utility and the consumer.

The proposed system in this project is Real and Reactive Power Control techniques of Smart PV Inverters

Smart PV inverters are equipped with features like power factor control, leading and lagging power factor control, real and reactive power control, voltage and frequency control, allowing control of power output from the PV system and regulation of power flow in the grid

This project aims to take advantage of the features of Smart PV inverters in order to reduce the damaging effects of rooftop PV penetration on LV feeders.

Rooftop solar photovoltaic systems are capable of regulating voltage levels on low voltage feeders through the utilization of a Volt/Var curve

In the event of the voltage exceeding the set upper bound, the system absorbs reactive power

whilst when the terminal voltage drops below the pre-set lower bound, it injects reactive power

This process helps the voltage levels on these feeders remain within the desirable range with increased consistency.

The slide is about mitigating the impact of rooftop solar PV systems on LV feeders

One way to do this is by using a Volt-Watt curve

This curve is used to curtail active power output when the voltage goes above or below the permissible voltage bounds

When the voltage exceeds the lower bound and varies between Vvw2 and Vvw3, the active power output is curtailed in accordance with the slope of the curve

Once the voltage reaches the upper voltage bound, the active power output is completely curtailed to ensure that the voltage remains within the permissible limits.

We have chosen a low-voltage network with voltage problems caused by the installation of rooftop solar PV systems

To assess the effect of the penetration of PV systems, power flow simulations were done with OPENDSS

The aim is to identify an optimized solution to resolve the network issues by using advanced inverter control strategies.

This slide presents data from a two-feeder-line network comprising 240 customers

It is equipped with a 11KV/415V transformer with a capacity of 160kVA, spanning a total of 1.5 km on the low-voltage (LV) network

The two feeder lines have different numbers of customers and different amounts of installed rooftop solar PV prosumers of 85.01 kWp

Cable types used for the installation include aluminium aerial bundle cables LV244, 3x50+1x16+N35 and 3x70+1x16+N35

This data is necessary to alleviate any potential negative impacts from the penetration of rooftop solar PV systems into the LV feeders.

Out of the five scenarios determined for this project, the voltage rise, voltage profile, power flow, and power loss in the feeder will be evaluated in order to assess the impact of each scenario on the LV feeders

These scenarios are defined by the level of penetration and capacity of solar customers, as well as cumulative solar capacity in kilowatts.

We analysed the fluctuation of phase voltage at three points on Feeder 1 - the Feeder Head, the middle of the Feeder, and the Feeder End - throughout the day to gain an understanding of the effects of rooftop solar PV systems on low-voltage power supply lines, referred to as 'LV feeders'

The figure in front of us displays the voltage variation along the line under a situation where PV generation is at 0%, thought of as the standard condition.

The figure indicates that when the solar penetration reaches 100%, an overvoltage condition occurs at the feeder end, beyond the upper voltage limit

Fortunately, we have the advantage that the transformer maximum capacity can handle a solar penetration of up to 100%, thus avoiding any more overvoltage conditions on the feeder

This project seeks to find ways to deal with the negative effects brought about by the mass installation of rooftop solar PV systems on low voltage feeders.

We can observe from this slide that once rooftop solar PV systems are put in place, voltage is likely to be above the upper limit of 1.06 p.u

Nevertheless, this won't occur everywhere along the feeder

This project focuses on diminishing the drawbacks that come from this circumstance.

This project is a response to the issue of solar PV penetration on LV feeders

As the level of penetration increases, so does the risk of reverse power flow

We have observed a reverse power flow of 43kW at 100% of the solar PV penetration level

This project aims to reduce the risk of this reverse power flow and reduce the potential negative impacts it can cause.

"It is now well established that the integration of rooftop solar PV systems on LV feeders can have a significant impact on the power loss

Our project has shown that active and reactive power loss are seen to be reduced up to 80% of the penetration level

However, beyond that power loss increase compared to no solar PV

This means that there are limits to how much rooftop solar PV can be integrated onto LV feeders without undue negative impacts on power loss

The implications of this are important for the design of our power grid in the future.”

Focus of Slide 17 is on the smart inverter technology which assists in managing the rooftop solar PV system

The smart inverter acts as a bridge between the PV panel and the grid

It takes into consideration various inputs like power factor, irradiance, temperature, voltage, and power efficiency, along with measuring voltage, active power, reactive power, and apparent power

This assists in keeping the quality and safety of the grid intact, while simultaneously improving the efficiency of the solar PV system.

We employed three control techniques for the project to reduce voltage threshold breaks that were observed when a great amount of rooftop solar PV systems were connected to a low voltage (LV) feeder

By implementing these techniques, we were able to increase active power generation and prevent overvoltage issues

Simulation results revealed the three control techniques were effective in preventing voltage limit violations, enabling us to fend off the problem of overvoltage created by the integration of rooftop solar PV systems on LV feeders.

The figure shows that when the transformer capacity for rooftop solar PV systems reaches 100%, a voltage violation occurs

However, if smart inverter control strategies are employed, this can reduce the overvoltage to an acceptable level.

This slide's figure demonstrates that the Volt-Watt control technique can significantly cut the active power of a rooftop solar PV system to 48.84%, in comparison to a 25.85% active power reduction that the Fixed PF technique produces, with a maximum power production of 43 kW

This project attempts to minimize the adverse impacts that this system can have on low voltage feeders.

This project seeks to reduce the adverse effects of rooftop solar PV systems on low voltage feeders

Simulation results show that Volt-Var control is the most effective in managing reactive power absorption, reaching a maximum of 31kVAr

In contrast, Volt-Watt control did not provide any assistance to the system.

Penetration of rooftop solar PV systems on Low Voltage feeders can cause marked effects on Power loss, as evident in the figures

It is discernible that two Volt-Var strategies have significantly more Active and Reactive loss than the other control scenarios

This is a consequence of reactive power passing over a long distance with low X/R ratio, resulting in the reactive power absorption taking place far from the distribution transformer.

The figures showed that the Volt-Watt control technique was the most successful in lowering both active and reactive power losses in comparison to other scenarios

It was the only method that not only achieved a reduction in active power, but also eliminated the absorption of reactive power - a crucial factor in preventing the LV feeders from suffering the detrimental effects of rooftop solar PV systems.

The slide includes a chart outlining the measurements taken to analyze the impact of rooftop solar PV systems on low voltage feeders

It shows active power and reactive power in kilowatts and kilovolt amps respectively

Additionally, it shows fixed power factor, Volt/Var VV1, Volt/Var VV2, and Volt/Watt

This data was collected to investigate the possible effect of incorporating such systems into a power network.