Transactions Template JOURNAL OF ENGINEERING RESEARCH AND TECHNOLOGY, VOLUME 7, ISSUE 2, OCTOBER 2020 12 Investigation of Power Quality Indices in Jordan University of Science and Technology Grid-Tie Photovoltaic Plant MOHAMMED S. IBBINI and ABDULLAH H. ADAWI DOI: https://doi.org/10.33976/JERT.7.2/2020/2 Abstract—In this paper, the effects of the grid-tie photovoltaic plant (PV) are analyzed on the power factor and the voltage harmonic distortion in the power quality aspect of the distribution network. The conditions for the total harmonic distortion (THD) in the power grid related to the photovoltaic power station connected to the user side are also summarized. Based on MATLAB/SIMSCAPE software, one string of the photovoltaic system at the Jordan University of Science and Technology (JUST) was simulated and hence, compared its results with the real results of the system. Measurement and simulation results illustrate that the voltage harmonic distortions to the power grid do not exceed the recommended levels, but the photovoltaic system needs to have a capacitor bank to get a unity power factor. Index Terms—Power quality, Power factor, THD, Photovoltaic, PV Module, and MATLAB/SIMSCAPE. I INTRODUCTION Photovoltaic is considered a promising technology, and it has witnessed rapid growth in recent years, especially af- ter increasing the costs of fossil fuel. In the case of Jordan, shrinking resources and a reasonable energy crisis se- verely constrain economic prospects and industrial growth. Therefore, it is more urgent to increase the use of renewable energy. Despite the great benefits that can be obtained from con- necting the PV system with the power grid, new chal- lenges on the grid designing and protection can emerge. Power flow direction and power quality (harmonics and voltage fluctuation) at the user side are affected after the PV system connected to the distribution network [1]. The energy extracted from the PV panel depends on vari- ous factors such as temperature, irradiance, and climate conditions. However, the sun irradiation strongly affects the performance of the power system due to continuous changes in the amount of radiation falling and leading to voltage flickering and fluctuation. The larger the capacity of the PV power system connected to the electrical grid, the higher the dynamic power quality problems resulting from photovoltaic power generation like frequency varia- tion, voltage sag …etc [2, 3]. Power systems designed to function at the fundamental frequency, which is 50-Hz in Jordan, are prone to unsatis- factory operation and, at times, failure when subjected to voltages and currents that contain substantial harmonic frequency elements. Many problems can be caused by har- monics such as over-voltage, over-current, resonance, loss of transmission lines, and protection faults. Ensuring the voltage level and the power quality at the joint coupling point of the photovoltaic system is very important to achieve the best possible power system performance [4, 5]. In the Jordan University of Science and Technology (JUST) PV plant, SMA inverters are used due to the capa- bility of providing reactive power and voltage adjustment. In many PV plants, the reactive power could be adjusted by external types of equipment like reactive power com- pensation systems, but it is better to use inverters that can adjust reactive power values [6]. If an immediate change in voltage happens, then this leads to the cause of what is known as a voltage flicker. Despite the voltage flicker usually happened at the user side, it af- fects the sinusoidal voltage waveform of the power grid. In the case of grid-tie PV plants, continuous changes in the amount of solar radiation leading to voltage flickering. Such distortions can disturb the user’s equipment and cause the inrush current. Moreover, it affects the mecha- nism of the network impedance and leads to a sudden rise of voltage or sudden fall and hence, the causes of the volt- age flicker [7]. The voltage flicker limits are contained in the following documents [8]: (a) IEC/TR3 61000-3-7 (1996) “Assessment of emission limits for fluctuating loads in MV and HV power sys- tems.” (b) IEC 868 / Engineering Recommendations P28 (pg 17) “Limits on voltage flicker short term and long-term sever- ity values.” Harmonics are typically produced by the user’s apparatus generating waveforms that distort the fundamental 50 Hz wave. Such harmonic generation can damage user appa- ratus and can fail transmission network apparatus. The limits for harmonic distortion levels are given in the fol- lowing documents: https://doi.org/10.33976/JERT.7.2/2020/2 Mohammed S. Ibbini and Abdullah H. Adawi/ Investigation of Power Quality Indices in Jordan University of Science and Technology Grid -Tie Photovoltaic Plant (2020) 13 (a) BS EN 50160:2000 “Voltage characteristics of electric- ity supplied by public distribution systems.” (b) UK Engineering Recommendation G5/4, February 2001 “Planning levels for harmonic voltage distortion and the connection of non-linear equipment to transmission systems and distribution networks.” (c) IEC/TR3 61000-3-6 (1996) “Assessment of emission limits for distorting loads in MV and HV power systems.” All the requirements mentioned above and standards are essential for the power quality of the electrical grid, and there are always taken into account to ensure the energy quality of the Jordanian power system [9]. II PV SYSTEM MODELING The whole model of the PV system is built by MATLAB/SIMSACPE simulation software. The injection current, which comes from the photovoltaic generation system to the grid, could be transferred into essential com- ponents. The frequency of the inverter is the same as the power grid frequency, and its capacity is related to the out- put power of the PV system [10-12]. PV systems are like any other electrical power generation system, with only different components and hence, differ- ent physical properties. Although a PV array produces power when exposed to sunlight, several other compo- nents are required to conduct correctly, control, convert, distribute, and store the energy produced by the array. De- pending on the functional and operational requirements of the system, the specific components required may include significant entities such as DC-AC power inverter, battery bank, etc. The essential element of a PV module is called a PV cell. In SIMSCAPE workspace, a PV cell block can be used to precisely simulate the behavior of a real PV cell. More than one PV cell block can be used to make a PV module out of series and parallel connected cells. The module will have one input, irradiance in W/m2, and two voltage po- larity outputs, +V and –V. The whole PV system, which consists of PV modules, MPPT controller, DC-DC con- verter and utility can be easily modeled using SIMSCAPE, as shown in Figure 1. The adopted PV Cell specifications are as shown in Table1 below Fig. 1. MATLAB /SIMSCAPE model of the photovoltaic system. TABLE 1 The PV Cell Specifications Number of PV module 220 Number of PV module in series 22 Open circuit voltage 38.6V Short circuit current 9.03A Voltage at MPP 31.4V Current at MPP 8.44A Maximum power 265W Number of inverters 1 Inverter power 60000W III CASE ANALYSIS At the JUST PV plant, one string is simulated in MATLAB/SIMSCAPE environment. Two hundred and twenty PV modules are connected, every 22 PV modules connected in series with total voltage about 850VDC, these PV panels are combined in a DC combiner box. DC combiner box is directly connected to an SMA 60KW grid-tie inverter. The following figures show the practical characteristics of the system during 2018, where the figures show the feasibility of installing such projects in Jordan. In Figure 2, which shows the amount of solar radiation during the year, it is clear that the majority of the year has a very high level of solar radiation, which significantly in- creases the efficiency of the system and reduces the cost of project recovery. Mohammed S. Ibbini and Abdullah H. Adawi/ Investigation of Power Quality Indices in Jordan University of Science and Technology Grid -Tie Photovoltaic Plant (2020) 14 Fig. 2. Irradiation in JUST PV plant during the year 2018 The following tables show the differences between simulation and actual results in the same operating conditions. The proposed simulation performance is tested under two conditions, the first condition at 1000W/m2solar radiation and temperature of 17.94 Co, the second condition at 615W/m2so- lar radiation, and temperature of 16.86 Co. According to the following results, it’s evident that the simulation results are very close to the real readings of the photovoltaic system at the same operating conditions. TABLE 2 Differences between simulation results and actual results at 1000 W/m2, 17.94 Co Real system results Simulation results Irradiance 1000 W/m2 1000 W/m2 Temperature 17.94 Co 17.94 Co Maximum DC Power 50.04 KW 58.30 KW Maximum DC Voltage 619.4 V 690.8 V Active Power 47.69 KW 58.30 KW Power Factor 0.93 1 Maximum AC current L1 74.7 A 84.49 A Maximum AC current L2 74.8 A 84.49 A Maximum AC current L3 74.6 A 84.49 A Maximum AC voltage L1 242.95 V 230 V Maximum AC voltage L2 240.57 V 230 V Maximum AC voltage L3 240.23 V 230 V TABLE 3 Differences between simulation results and actual results at 615 W/m2, 16.86 Co Real sys- tem results Simulation results Irradiance 615 W/m2 615 W/m2 Temperature 16.86 Co 16.86 Co Maximum DC Power 30.95 KW 36.80 KW Maximum DC Voltage 640.8 V 400 V Active Power 30.47 KW 36.80 KW Power Factor 0.92 1 Maximum AC current L1 46.5 A 53.30 A Maximum AC current L2 46.6 A 53.30 A Maximum AC current L3 46.5 A 53.30 A Maximum AC voltage L1 239.04 V 230 V Maximum AC voltage L2 236.74 V 230 V Maximum AC voltage L3 236.17 V 230 V These values in the tables show the differences between the real values of the solar system and the simulation val- ues when modeling the solar system through a MATLAB/SIMSCAPE program. Many values, such as the value of solar radiation and temperature are assumed to be constant. However, these values are constantly changing, resulting in differences between actual values and simula- tion values. Another reason may strongly affect the differ- ence in readings between actual and simulated values, which is partial shading. In the case of partial shading, the actual power values of the PV system less than the simu- lation values. The simulation programs cannot consider the impact of all operating conditions, but it is clear that its results are very close to the actual values and this indi- cates the strength of the simulation program. THD in the output voltage is illustrated in Figure 3. Mohammed S. Ibbini and Abdullah H. Adawi/ Investigation of Power Quality Indices in Jordan University of Science and Technology Grid -Tie Photovoltaic Plant (2020) 15 Fig. 3. THD in the output voltage. It’s evident from the previous figure that the THD over a whole year was very few and within the recommended levels in international standards rules. On the other hand, the simu- lation result illustrates that the THD=0.02, MATLAB/SIM- SCAPE software, provides an FFT command window. This command window is used to make many analysis features like THD. The terms of calculation and assessment of the reactive power of the grid-tie PV systems are [13]: 1) The voltage levels of the electrical grid must remain stable and within normal range with PV power generation. 2) The reactive power exchange between PV generation and grid on the point of common coupling is zero. As mentioned previously, the inverters used in the PV power system are of type SMA; this type can compensate for the re- active power values. Moreover, it is allowing the power factor values to stay within the normal range. The following picture illustrates the power factor values during 2018. Fig. 4. Power factor values in 2018. It’s evident from the previous figure that the power factor of the grid-tie photoelectric system is equal to 0.9 at most times and this is considered very well. To access a unity power factor using MATLAB/SIMSCAPE software. The values in Tables 2 and 3 are taken into account. Moreo- ver, the power factor correction is: 𝑘𝑉𝐴𝑟 = 𝑃𝑜𝑤𝑒𝑟 (𝐾𝑊)(𝑇𝑎𝑛 (∅𝐴 − ∅𝐵 )), Where, ∅𝐴 = 𝑐𝑜𝑠 −1 ( 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑝𝑜𝑤𝑒𝑟 𝑓𝑎𝑐𝑡𝑜𝑟 ) ∅𝐵 = 𝑐𝑜𝑠 −1 ( 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑝𝑜𝑤𝑒𝑟 𝑓𝑎𝑐𝑡𝑜𝑟 ) According to Table 3, ∅𝐴 = 𝑐𝑜𝑠 −1(0.92), and the re- quired power factor is 1. However, the active power is 30.47KW, so regarding the previous equation, the capac- itor bank should be added with a capacity of 20kVAR per string. The following figure illustrates the value of the power factor after the addition of the capacitor bank. Fig. 5. Power factor simulation result after the addition of compensator. V CONCLUSION In this paper, the impact of the grid-tie photovoltaic power system in JUST and the power quality in the distribution network was analyzed and studied. The power quality problems resulting from connecting the photovoltaic power plant to the electrical grid were summarized, and quality standards and requirements for maintaining power quality were mentioned. Based on the MATLAB/SIMSCAPE simulation software, this paper simulates the THD and power factor in the case of Jordan University of science and technology grid-tie photovoltaic plant. The result illustrated that 1) The THD caused by grid-tie photovoltaic plant inject- ing into the grid satisfies standards requirements. 2) 20KVAR capacitor bank capability per string should be added to the photovoltaic system to obtain a unity power factor. It is also recommended to study the effect of voltage fluc- tuation, voltage flickering, and other factors that impact the quality of electrical power. Mohammed S. 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[11] M. S. Ibbini, A. H. Adawi, “Analysis and Design of a Maximum Power Point Tracker for a Stand-Alone Photo Voltaic System Using Simscape”, International Journal of Advanced Trends in Computer Science and Engineer- ing, vol. 8, no. 1, January – February 2019. [12] M. S. Ibbini, A. H. Adawi, “A SIMSCAPE Based Design of a Dual Maximum Power Point Tracker of a Stand- Alone Photovoltaic System.” International Journal of Electrical and Computer Engineering (IJECE), vol. 10, no. 3, June 2020. [13] C. M. De Brito, P. Van Rhyn, and S. Africa, “The Use of Power Quality Standards to Establish an Equivalent Transformer Capability Under Harmonic Loading,” 2016. Mohammed Salameh Ibbini received his Ph. D in electrical engi- neering from the University of Illinois at Urbana-Champaign, his M. SC. in electrical engineering from the University of Coloradoat Boulder and his B. Sc. in Electronics from the ENSEEC in France. He is currently Professor of electrical and biomedical engineering at Jordan University of Science & Technology. He is currently the vice president of Jordan University of Science and Technology and had held different administrative and academic positions. Mohammed Ibbini has been professor of EE and BME at JUST since 2005, au- thoring and co-authoring over 70 articles and attending a huge num- ber of international conferences. Professor Ibbini taught different courses in linear and nonlinear control, biomedical instrumentation, signal and systems and machines. His research interest includes but not limited to nonlinear control, renewable energy, feedback lineari- zation, ultrasound and microwave cancer therapy, diabetes and bridging the gap between the university output and the work market needs. Prof. Ibbini is a strong advocate of hands-on, real life exam- ples, project based learning, learning by doing and innovation in En- gineering. Abdullah Hamed Adawi is born in Saudia Arabia In 1990, I ob- tained a bachelor degree in Electrical Power Engineering in 2012 from Albalqaa Applied University. I received my Master in 2019 in the field of Power and Control Engineering from Jordan University of Science and Technology. .