REACTIVE POWER SUPPLY FROM PV INVERTERS IN DISTRIBUTION

REACTIVE POWER SUPPLY FROM PV INVERTERS IN DISTRIBUTION NETWORKS Mohamed Thamby Mohamed Naasir Department of Electrical and Telecommunication Engineering, Faculty of Engineering, South Eastern University of Sri Lanka

CONTENTS Introduction Solar PV System Self Regulations By Consumers Reactive Power Compensation Analysis Pros & Cons Feasibility In Sri Lanka References

INTRODUCTION With the reduction of prices, the solar PVs getting popular Feeding reactive power from generator plants is not effective due to increased line losses and inefficient use of generators We have the possibility of using solar inverters as a reactive power source to system during night peaks Also have the possibility of solving under voltage issue

SOLAR PV SYSTEM

DC AC • Inverter convert direct current (DC) from solar PV into alternative current (AC) • We are currently using unity power factor output but, to use it for reactive power feed in we have to switch the power factor to different levels.

REACTIVE POWER FEEDING METHODOLOGY Cos Ɵ = Power Factor Apparent Power (S) Ɵ Active Power (P) Power Triangle Reactive Power (Q)

LIMITATIONS IN REACTIVE POWER FEEDING This plot explains us, The Inverter performs relatively better in the power factor range of 0. 8 to 0. 85 But, can’t afford to reduce beyond 0. 77 as the increasing nature of Total harmonic distortions (THD) that lowers the power quality The variation of THD Vs power factor

REACTIVE POWER COMPENSATION It is much important that to ensure stability of the grid reactive power demand must be compensated During peaks we are having more reactive power requirement Available methods of compensating reactive power 1. Capacitor banks 2. Synchronous generators 3. Phase advancer 4. Using solar PV inverters

SELF REGULATION BY CONSUMERS • Most of the reactive power demand that comes from customers like factories • It is the best solution if we able feed in reactive power from their end. • Consider following scenario, q. Assume that they installed 60 k. W PV system with unity power ( Case – A) q. Assume that they installed 60 k. W PV system with 0. 95 leading power factor ( Case – B)

Lets compare two cases, • Case A • Case B • Solar system should therefore be designed to produce the maximum amount of savings across all of these areas. • For example, it maybe financially beneficial to reduce the amount of active power drawn from the grid at the expense of increased charges due to a poor power factor.

REACTIVE POWER FEED IN METHODS OF INVERTERS Fixed Power Factor Operation Multi Level Inverter With SCADA Control Capability Time Based Control

VOLTAGE REGULATION • The inductive coupling in the transmission network and resistive coupling in distribution network leads to different scenarios of voltage control • The enhancement of voltage regulation by using a power factor control method Power factor control of PV inverters

LOW VOLTAGE FEEDERS During late evening peaks more reactive power need & under-voltage issue rises while panels produce no energy. PV inverters can be used to feed reactive power to system like a STATCOM. Hence, reactive power to the grid can be obtained from solar inverters. By using customers’ inverter, utility’s Low Voltage (LV) system also can be improved.

OPERATION OF INVERTER DURING NIGHT • Inverter will be connected series to the grid. • It will feed pure reactive power. Inverter takes active power to charge capacitors Inverter supplies reactive power to grid

IMPROVING LINE EFFICIENCY

COST FACTORS FOR REACTIVE POWER FROM SOLAR INVERTERS

ADVANTAGES & DISADVANTAGES • Advantages • Disadvantages • Reduced Line Losses • Can eliminate the cost of generators to feed reactive power and capacitor banks • More economical benefits since consumer getting paid for reactive power • Increased Line Capacity • Consumer no need to rely on grid • Total Harmonic Distortion (THD) will be decreased • Micro grids can accommodate • Poor reliability • Additional thermal stress will be on inverters • Additional cost • Consumers needed to be well educated of system otherwise they don’t get attract • Life time of inverter will reduce

Feasibility in Sri Lanka • The following table contains commonly used inverters in Sri Lanka Inverter Brand Normal operation Power factor Available additional PF option SMA Sunny boy 1. 5, 2. 5 Unity 0. 8 ( lead/ lag) Growatt 7000 UE, 8000 UE, 9000 UE Unity 0. 8 ( lead/ lag) Good. WE 1000 -NS, 1500 -NS, 2000 -NS, 2500 -NS, 3000 -NS Unity 0. 9 ( lead/ lag) KACO blue planet 15. 0 TL 3, 20. 0 TL 3 Unity 0. 7 (lead/lag) Omniksol-m 248 micro inverter Unity Not supported Solis Unity Not supported JYINS Unity Not supported AP Systems YC 500 A micro inverters Unity Not supported Solar EDGE Unity Not supported ABB Unity 0. 8 (lead/ lag) • It clearly shows that we have difficulties to implement in operating different power factor to solve under voltage issue as some widely us. So It is needed that we need to introduce standards for inverters that includes reactive power producing capability which exists in several countries

CONCLUSIONS "As a customer premises equipment, solar inverters can be utilized for empowering the grid" relevant compensation should provide to consumers by considering the benefits and costs we can operate inverter within 0. 775 power factor range as further reduction increases the THD It is preferable to operate in 0. 85 power factor where results in superior Existing tariff methodology must be revised in terms of reactive power usage. As tariff only contains maximum demand charge to account reactive power usage which is inadequate we must properly address economic benefits for consumers to use their inverters by considering aforementioned cost and benefits This scheme would increase the overall economic efficiency of solar inverters.

REFERENCES Gandhi, O. , Rodriguez-Gallegos, C. D. , Gorla, N. B. Y. , Bieri, M. , Reindl, T. , & Srinivasan, D. (2019). Reactive Power Cost from PV Inverters Considering Inverter Lifetime Assessment. IEEE Transactions on Sustainable Energy, 10(2), 738– 747. Navoda, K. K. , & Rodrigo, A. S. (2017). Optimum Use of Solar Inverter by Feeding Reactive Power at the Night. Annual Sessions of IESL 439 - 446 Santos-Martin, D. , Lemon, S. , Watson, J. D. , Wood, A. R. , Miller, A. J. V. , & Watson, N. R. (2016). Impact of solar photovoltaics on the low-voltage distribution network in New Zealand. IET Generation, Transmission & Distribution, 10(1), 1– 9. Beach, T. , Kozinda, A. , & Rao, V. (2013). Latent Opportunities for Localized Reactive Power Compensation, “Cal x Clean and coalition Energy C 226” Kutkut, N. , & Solar, P. (2012). An AC PV Module with Reactive Power Capability: Need and Benefit. Braun, M. (2008). Reactive power supply by distributed generators. 2008 IEEE Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21 st Century, Braun, M. (2007). 22 nd European Photovoltaic Solar Energy Conference and Exhibition, September 2007, Milan, Italy. Soorya Bala Sangramaya (Battle for Solar Energy) (2019, July 30). Retrieved from //energy. gov. lk/index. php/en/soorya-bala- sangramaya

Thank You • Questions ?

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