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8/13/2019 Battery Storage Unit for Residential Rooftop PV System to Compensate Impacts of Solar Variations
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Electrical and Electronics Engineering: An International Journal (ELELIJ) Vol 2, No 4, November 2013
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Battery Storage Unit for Residential Rooftop PV
System to Compensate Impacts of SolarVariations
Nasim Jabalameli and Mohammad A.S. Masoum
Department of Electrical and Computer Engineering, Curtin University, Perth, WA,
Australia
Abstract-Electric utilities are becoming concern about unexpected changes in output power ofresidential rooftop PV systems due to sudden changes in solar radiation and impacts of passing clouds.
This paper implements a battery storage energy management strategy (BS-EMS) for existing rooftop PVs
to support the household loads, compensate impacts of solar variations and passing clouds whileregulating the voltage at point of common coupling (PCC) and providing the grid with a constant output
power during daylight. Performance of BS-EMS is investigated through detailed simulations under
various grid, rooftop PV and environment conditions
Index Terms: Rooftop PV, battery storage, constant power and passing clouds
I. INTRODUCTION
Among various distributed generation (DG) technologies, PV systems are becoming very
popular and finding more applications particularly in residential networks due to the increasing
concern about environmental issues and adopted feed-in tariffs in many developing countries
such as Australia [1-3]. However, PV systems still have a payback time and as the electricityprice rises steadily; their cost efficiency becomes more attractive particularly for residential
applications such as rooftop photovoltaic generation systems (rooftop PVs). Consequently, it is
expected that contributions of PV power will be increasing particularly in industrial and
residential networks.
Currently, most PV generators are designed with maximum power point tracking abilities
without any energy storage options to justify their relatively high investment cost. The main task
of the PV converter is to extract the maximum possible energy from the sun and deliver it to the
power grid to increase the profit. However, due to the stochastic nature of the solar cell output
power, large developments of grid-connected PV systems involve large fluctuations of the
frequency, power and voltage in the grid.Utilities are beginning to notice these problems in
distribution networks utilizing large three-phase PV power plants and residential feeders withsmall single-phase rooftop PVs scattered along individual phases causing.
The unpredictable and stochastic nature of renewable energy sources such as wind and PV is a
serious issue that causes grid balance gradually difficult to attain [2, 4]. In this term, energy
storage (ES) units such as researchable batteries [4-6], ultra-capacitor and fuel cells [2-3] can be
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used to balance the lack of power or to store the extra power during the off-peak hours.
Anderson presents an economic energy management strategy based on time of use (TOU) rating
for grid-connected PV with battery storage (BS) system (BSS) for increasing cost efficiency [3].
Similarly, reference [7] investigates the design of an optimal charge\discharge algorithm for
distributed BS systems connected to PV systems that also considers cost analysis.Reference [6]
presents grid-connected distributed energy systems in combination with lithium-ion battery asthe storage element. Reference [8] explains how batteries interconnected to distributed systems
can be utilized to expand the energy production of conventional gridconnected PV power plants,
mostly under mismatching operating conditions. Apart from these works, Hector ei al. proposed
an energy management strategy (EMS) for largescale power plants operating with different ES
ratings [2]. On the other hand, some researches have considered applications of ES in isolatedPV systems. In this regard, [9] investigates the performance and energy supplies of different
types of battery technologies suitable for usage in isolated power systems. While, there are a few
literatures in terms of PV sources combined with ES [2], more research is required to evaluate
the application and capacity of BS in grid-connected PV systems particularly with consideration
of real-time weather and load conditions.
This paper recommends connection of BS system across terminals of existing rooftop PVs tocompensate impacts of load variations, solar radiation, passing clouds and short duration PV
outages. The goal is to inject constant net output power to the grid during daylight under various
environmental conditions while feeding the household loads and regulating the bus voltage at thepoint of common coupling (PCC). To do this, a battery storage energy management strategy
(BS-EMS) will be implemented to dynamically control the BS converter and obtain power
balance between rooftop PV, BS and the grid. Detailed simulations are performed in PSCAD
and analyzed to investigate BS-EMS ability in regulating output power and voltage and
compensating for impacts of solar variations, passing clouds and PV outages.
II. ROOFTOP PV AND BATTERY STORAGE SYSTEM
Distributed PV systems are gradually being accepted as one of the main alternatives to theconventional contaminating energy resources. These environmentally friendly renewable energy
systems are currently representing only a few percentage of the global electricity production.
However, their applications in residential and industrial networks are rapidly growing since the
peaks of most industrial and some residential loads coincide with the maximum output periods
of PV modules. Fig. 1 shows typical configuration of a house with linear loads and rooftop PV
connected to the power grid at PCC.
Fig. 1. Typical house with grid-connected rooftop PV and BS.
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One of the main limitations of rooftop PVs is the dependency of their output power to
environmental factors such as sun radiation, panel temperature, passing clouds and shading, as
well as loading level (operating point on their nonlinear v-i characteristics). This dependency may
result in sudden output power variations particularly during windy days with passing clouds
partially shading solar panels. A possible solution is including a shunt-connected BS system atPCC to ensure constant output power production to grid during daylight. This configuration
allows the consumer to store the excess generated solar energy in BS during offpeak hours and
return it back to the grid at appropriate times. It can also offer other advantages including such as:
Mitigating the stochastic nature of solar power. Taking advantage of solar feed-in tariffs to make profit by selling/purchasing electricity
to/from grid.
Injecting reactive power to improve power quality and support grid during transientdisturbances
Fig. 2 shows typical (measured) household daily load curves and daily summer and winter
rooftop PV generations in Perth, WA, Australia. According to these figures, there is about 50%reduction in PV output power during winter that can dramatically change the amount of power
delivered to the grid. Furthermore, there are considerable variations in PV output power due topassing clouds during winter and summer. A BS system can overcome these limitations and
provide constant power to the grid despite the unpredictable weather conditions. The storage
control algorithm should also consider household load characteristics as their type, duration and
levels will change depending on the season, temperature, social activities, standard working
hours, etc.
Fig. 2. Household load curve, constant daily output power to grid (PGridref),
typical rooftop PV generation for typical summer (a) and typical
winter (b) days in Perth, WA [10].
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III. BATTERY STORAGE ENERGY MANAGEMENT
STRATEGY(BS-EMS) FOR CONSTANT OUTPUT POWER
PRODUCTION
An EMS in conjunction with a BS system will be implemented to support the rooftop PV (Fig. 1)in providing constant power production during different periods throughout the day. Constant
output PV power will be produced by dynamically controlling the BS converter under various
operating conditions based on the following power balance equation:
where t = t,2t,...24 hours and t =15min is the time interval. PGrid-ref, PPV, PBS and PL are
the instantaneous constant output, PV, battery and load power, respectively(Fig. 2). Note that
PGrid-ref can be changed at each time intervalt and the power production patters can have up to
24x4=96 different durations Ppattern={p1 , p2, ..., p96}.However, in this paper a single constantoutput power level is considered during daylight (06:00h-18:00h).
BS system will be dynamically controlled based on the following charge and discharge
characteristics:
where EBS, c and d are the energy, charging and discharging efficiencies of BS system,
respectively.
The PV, load and BS energy profiles during the 24 hour period can be calculated as follows:
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where PPV,kt,max, PL,kt,max and PBS,kt,max are the maximum power of PV, load and BS
during period kt, respectively.
IV. FLOW CHART OF THE PROPOSED BS-EMS
Fig. 3 shows flowchart of the implemented BS-EMS that will dynamically control the battery
charge/discharge process according to Eqs. 1-3. At each time interval (t =15min), BS-EMS will
upgrade the status of rooftop PV based on solar radiation, feed the household loads and based on
the weather condition (sunny, cloudy) decides to either charge or discharge the battery. This
process will continue for 24 hours until the final time interval is reached.
Fig. 3. Flowchart of the proposed BS-EMS for battery charge/ discharge management to attain constant
output power to grid.
In order to protect the battery and increase its lifetime,BS-EMS will dynamically control battery
state-of-charge(SOC) within designated minimum and maximum levels of SOCmin and
SOCmax, respectively. The battery SOC can be defined from the perspective of energy as follows[11]:
SOC = Wremain/Winitial(7)
where Wremain and Winitial are the remaining and initial power of the battery, respectively. In
practice, determination of SOC is more complex and can be estimated based on discharge test,
ampere hour measurement, open circuit voltage, constant current voltage, internal resistance,
linear model, neural networks, Kalman filter etc. [11].
BS-EMS will also try to increase profit by using the excess stored energy to supply household
loads during peak load hours when the price of electricity is high (e.g., 19:00-24:00) and buy
cheap electricity from the grid during offpeak hours (00:00-7:00) to recharge the battery for thenext day. This can be done by considering the battery capacity(BCAP) and selecting a relatively
small value for PGrid-ref during peak load hours and a relatively large value during off-peak load
hours as shown in Fig. 2.
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V. IMPLEMENTATION OF BS-EMS
BS-EMS is implemented using PSCAD software package.Fig. 4 shows the developed model of
grid-connected rooftop PV, household linear load and BS system which are dynamically
controlled over a 24 hour period by the BSEMS algorithm of Fig. 3. PSCAD is selected due to its
robustness in transient analysis and relative ease in defining custom nonlinear models. For
calculation of voltage reference (Vref), the following load flow equations are used:
where PBS and QBS are the active and reactive output power of the BS; V1 and V2 are the
capacitor and PCC voltages while 1 and 2 are the corresponding voltage phase angle.
The aim of BS converter control is to generate switching function (U) that can take +1 or -1values depending on the status of the (IGBT) switches [12]. A state space approach is used to
implement the converter control. The input state vector is:
where x, y and uc are input state vector, output state vector and the continuous time version of the
switching function U, respectively; while A and B are state matrix and input matrix, respectively.
In this paper, a hysteresis band approach is used to turn on/off the (IGBT) switches. The inverterswitching logic is:
where h is a small positive constant that defines the hysteresis band.
VI. SIMULATION RESULTS AND ANALYSES
The grid-connected rooftop PV system of Fig. 1 is simulated and controlled with the proposedBS-EMS of Fig. 3 using PSCAD software package (Fig. 4). PV rating is 1.59kW, SOCmin=0.20,
SOCmax=0.80, selected constant output power(PGrid-ref) during summer and winter are 0.50kW
and 0.13kW, respectively. Detailed simulations are performed for the five case studies of Table 1
and presented in Figs. 5-10 and Tables 2-4.
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Fig. 4. Generated PSCAD system model to implement proposed BS-EMS and perform simulations.
Case 1: Performance under Normal Operating Conditions
Fig. 5 shows detailed simulation for a typical cloudy summer day in Perth, WA with BS capacity
and PGrid-ref of 6kWh and 0.5kW, respectively. As expected, BS-EMS has successfully
managed to take advantage of the BS to deliver constant power to the grid from 0600h to 1800h
while also supporting the household loads after daylight until 1930h.The grid is feeding
household load and charging BS during early morning off-peak hours when the price of
electricity is cheap. Examination of the battery energy profile indicates that when necessary, thestores energy will be released to the grid to achieve constant output power (0600h-1030h
and1600h-1800h) while the excess solar power during high sun radiation hours (1200h-1500h)
are used to recharge the battery.
Case 2: Impact of Battery Capacity
To explore the impacts of battery capacity on performance of BS-EMS, simulations are
performed for typical sunny and cloudy days in both summer and winter with different battery
sizes (Table 2, Figs. 6-7). Performance of BS-EMS is significantly influenced by the battery
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rating. According to Table 2, the practical and moderate battery rating to fully support the grid
within the daylight in both summer and winter seasons while also providing partial support to the
household loads after 1800h is 6kWh.
To explore the impacts of battery capacity on performance of BS-EMS, simulations are
performed for typical sunny and cloudy days in both summer and winter with different batterysizes (Table 2, Figs. 6-7).
Fig. 5. Case 1: A typical cloudy summer day in Perth, WA (battery=6kWh,PGrid-ref=0.5kW).
Performance of BS-EMS is significantly influenced by the battery rating. According to Table 2,
the practical and moderate battery rating to fully support the grid within the daylight in both
summer and winter seasons while also providing partial support to the household loads after
1800h is 6kWh.
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Fig. 6. Case 2: A typical sunny summer day with a large battery capacity of 8kWh (PGrid-ref=0.50kW).
Fig. 7. Case 2: A typical cloudy winter day with a small battery of 2kWh(PGrid-ref=0.13kW).
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As expected, it will not be possible to support the grid with constant output power if the battery is
too small (Table 2:rows 4-5, 12-14). On the other hand, it will not be beneficial to select a large
battery rating. The only benefit in increasing the battery size beyond the moderate practical rating
(6kWh) is to increase the duration of load support in the evenings. However, as demonstrated in
Table 2 (rows 8-9 and 16-17), the duration of load support is mainly determined by the amount of
available solar energy. For example, changing the battery size from 6kWh to 7kWh will onlyextend the load support period by 15min while a further increase to 8kWh will not have any
impact.
Fig. 6 shows system operation in a typical sunny summer day with a large BS of 8kWh (Table 2:
row 9, columns 1-3) while Fig. 8 presents operation in cloudy winter with a small BS of 2kWh(Table 2: row 12, columns 4-5).
Table 2. Impact of battery capacity on performance of BS-EMS.
Case 3: Impact of Passing Clouds
To examine the ability of BS-EMS in delivering constant output power in the presence of passing
clouds, simulations are repeated for typical sunny winter and sunny summer days with passing
cloud periods of 30 minutes, one hour and two hours (Table 3). Fig. 8 illustrates the impact ofhaving passing cloud for duration of one hour (12:00h-13:00h) during a typical sunny summer
day. Clearly, the proposed BS-EMS has successfully taken advantage of the energy stored in the
6kWh battery to keep the output power constant at PGrid-ref=0.5kW for the requested 12
hours(0600h-1800h). Note that BS-EMS has also managed to continue feeding the household
load until 19:15h when the battery reaches its minimum SOC.
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Table 3. Impact of passing clouds
[
Fig. 8. Case 3: A typical sunny summer day considering passing cloud with duration of one hour
(battery=6kWh, PGrid-ref=0.50kW).
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Case 4: Grid Support During PV Outage
Table 4 summaries the ability of BS-EMS in providing constant output power with no PV power
that will depend on the duration of PV outage and the battery rating. As expected, it will be
possible to support the grid with constant output power during PV outages for longer periods asthe size of battery is increased. On the other hand, it will not be advantageous to select a very
large battery rating.The only benefit in increasing the battery size beyond the moderate practical
rating (6kWh) is to increase the duration of load support in the evenings. However, as
demonstrated in Table 4 (rows 10 and 12), the duration of grid support is mainly determined bythe amount of available BS energy.For example, changing the battery size from 6kWh to 7kWh
will only extend the grid support period by 33min from 12:00h-14:37h (with the battery size of
6kWh) to 12:00h-15:20h (with the battery size of 7KWh). Simulations results for a typical sunny
winter day considering PV outage at 1200h are shown in Figs. 10 and 11 for battery ratings of
6kWh and 7kWh, respectively.
Table 4. Grid support during PV outage
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Fig. 9. Case 4: Grid support with PV outage starting at 1200h on a typical sunny winter day (PGrid-
ref=0.13kW) with battery rating of 6kWh. BSEMS supports the gird for 2 hours and 37 minutes.
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Fig. 10. Case 4: Grid support with PV outage starting at 1200h on a typical sunny winter day (PGrid-
ref=0.13kW) with battery rating of 7kWh. BSEMS supports the gird for 3 hours and 10 minutes.
VII. CONCLUSION
This paper investigates inclusion of battery storage across an existing rooftop PV system to
deliver constant output power (PGrid-ref) to the grid during daylight hours while feeding
household loads and regulating voltage at PCC. The system operation is supervised by a batterystorage energy management strategy (BS-EMS) based on the power balance between rooftop PV,
BS and grid by dynamic control of BS converter while a PI controller is also implemented to
reduce voltage variations at PCC. Detailed simulations are performed to demonstrate BS-EMS
ability in regulating output power and voltage considering solar variations, passing clouds and
short duration PV outages.
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The main conclusions are:
BS-EMS can effectively control BS system to deliver constant output power PGrid-ref tothe grid during daylight.PV owners would like to have high PGrid-ref to increase their
profits by selling more electricity to the grid.
However, the maximum possible value of PGrid-ref will significantly depend on theamount of available daily PV power (that will considerably decrease during winter andcloudy days) and to some extent the rating of the battery.
For a moderate increase in the battery rating, BS-EMS can also support the householdloads during the evening peak load hours to further increase the profit. However,the
duration of load support is mainly determined by the amount of available solar energy not
the size of the battery (Tables II-III).
With large PGrid-ref values and/or small battery capacities, BS-EMS will not workproperly for the entire day as the battery will quickly reach SOCmin.
With small PGrid-ref values and/or large battery capacities,BS-EMS will work properly;however, the available battery capacity may not be fully utilized.
BS-EMS can also maintain constant output power during periods of passing clouds andshort term PV outages
REFERENCES
[1] P.G. Barbosa, L.G.B. Rolim, E.H. Watanabe and R.Hanitsch, Control strategy for grid-connected
DC-AC converters with load power factor correction, IEE Proc.Gener., Transm., Distrib., vol. 145,pp. 487-491, 1998.
[2] H. Beltran, E. Bilbao, E. Belenguer, I. Etxeberria-Otadui and P. Rodriguez, Evaluation of Storage
Energy Requirements for Constant Production in PV Power Plants, IEEE Trans.Industrial
Electronics, vol. 60, pp. 1225-1234, 2013.
[3] A. Aichhorn, M. Greenleaf, H. Li and J. Zheng, A cost effective battery sizing strategy based on a
detailed battery lifetime model and an economic energy management strategy, Power and Energy
Society General Meeting, 2012 IEEE, 2012, pp. 1-8.
[4] H. Fakham, L. Di and B. Francois, Power Control Design of a Battery Charger in a Hybrid Active
PV Generator for Load-Following Applications, IEEE Trans. Industrial Electronics, vol. 58, pp. 85-
94, 2011.
[5] H. Beltran, M. Swierczynski, A. Luna, G. Vazquez and E.Belenguer, Photovoltaic plants generation
improvement using Li-ion batteries as energy buffer, IEEE International Symposium on Industrial
Electronics (ISIE), pp. 2063-2069,2011.[6] Q. Hao, Z. Jianhui, L. Jih-Sheng and Y. Wensong, A highefficiency grid-tie battery energy storage
System, IEEE Trans. Power Electronics, vol. 26, pp. 886-896, 2011.
[7] J. H. Teng, S. W. Luan, D. J. Lee and Y. Q. Huang, Optimal charging/discharging scheduling of
battery storage systems for distribution systems interconnected with sizeable PV generation systems,
IEEE Trans. Power Systems, vol. PP,pp. 1-1, 2012.
8/13/2019 Battery Storage Unit for Residential Rooftop PV System to Compensate Impacts of Solar Variations
16/16
Electrical and Electronics Engineering: An International Journal (ELELIJ) Vol 2, No 4, November 2013
70
[8] R. Carbone, Grid-connected photovoltaic systems with energy storage, International Conference on
Clean Electrical Power, pp. 760-767, 2009.
[9] M. Lafoz, L. Garcia-Tabares and M. Blanco, Energy management in solar photovoltaic plants based
on ESS,13th Conference on Power Electronics and Motion Control, EPEPEMC,pp. 2481-2486,
2008.
[10] http://www.perthsolarcity.com.au/holdingpage/[11] W. Marwali, Q. Yan, Research on state of charge estimation of batteries used in electric vehicle,
Asia-Pacific Power and Energy Engineering Conference (APPEEC), pp. 1-4, 2011.
[12] A. Ghosh, "Performance study of two different compensating devices in a custom power park,"
Generation, Transmission and Distribution, IEE Proceedings-, vol. 152, pp. 521-528,2005.
[13] M. Sechilariu, B. Wang, and F. Locment, Building integrated photovoltaic system with energy
storage and smart grid communication, IEEE Trans.Industrial Electronics, vol. 60, pp. 1607-1618,
2013.
[14] S.Y. Derakhshandeh, A.S. Masoum, S. Deilami, M.A.S.Masoum and M. E. H. Golshan,
Coordination of generation scheduling with PEVs charging in industrial microgrids,IEEE Trans. on
Power Systems, vol. 28, pp. 3451-3461,2013.
[15] J. Traube, F. Lu, D. Maksimovic, J. Mossoba, M. Kromer, P.Faill, S. Katz, B. Borowy, S. Nichols,
and L. Casey,Mitigation of solar irradiance intermittency in photovoltaic power systems with
integrated electric-vehicle charging functionality, IEEE Trans. Power Electronics, vol. 28, pp.3058-
3067, 2013.
[16] H. Beltran, E. Prez, N. Aparicio, and P. Rodrguez, Daily solar energy estimation for minimizing
energy storage requirements in PV power plants, IEEE Trans. Sustainable Energy, vol. 4, pp. 474-
481, 2013.
[17] E. Prez, H. Beltran, N. Aparicio, and P. Rodrguez, Predictive power control for PV plants with
energy storage, IEEE Trans. Sustainable Energy, vol. 4, pp. 482-490, 2013.
AUTHORS
Nasim Jabalameli received her B.S. degree in Electrical Engineering from Islamic Azad University,
Tehran, Iran in 2005. She is presently working towards the MS degree at Curtin University, Perth,
Australia. Her research interests include distribution systems, smart grids and renewableenergy.
Mohammad A. S. Masoum(S88M91SM05) received his B.S., M.S. and Ph.D. degrees in Electricaland Computer Engineering in 1983, 1985, and 1991, respectively, from the University of
Colorado,USA.Currently, he is a Professor at the Electrical and Computer Engineering Department, Curtin
University, Australia. He is the co-author of Power Quality in Power Systems and Electrical Machines
(Elsevier) and Power Conversion of Renewable Energy Systems (Springer).