Ensuring Power Quality and Stability in Industrial and Medium Voltage Public Grids

2018, IEEE

 ABSTRACT: Until recently, most of the power system equipment in industrial grids has been operating with deviations from the nominal voltage and frequency supplied by the utility. However, power electronics based equipment is vulnerable to such deviations and might get damaged in case of possible grid faults. This paper addresses this issue by proposing a stabilizing device that can be connected between the public grid and the industrial grid which provides not only power quality and security of supply during fault for the industrial grid but also ensuring the power quality for the public grid.


  1. Public grid
  2. Industrial grid
  3. Power quality
  4. Security of supply
  5. Grid stability




 Fig. 1. Device representation



 Fig. 2. Harmonic current injection and compensation


Fig. 3. Individual harmonic distortion voltage for different Sk’’

Fig. 4. THDu for different Sk’’

Fig. 5. Voltage behavior during load switching with and without Netz-Patron unit

Fig. 6. Voltage behavior during motor starting with and without Netz-Patron unit

Fig. 7. Voltage behavior during three phase fault with and without Netz-Patron unit


The paper presents the different functionalities of the Netz-Patron unit that is designed to provide different support functionalities like harmonic compensation and voltage support in case of disturbed grid operation. In order to analyze the effectiveness of the Netz-Patron unit, a simulation model has been developed within the DIgSILENT PowerFactory software environment. The different scenarios and their simulation results are shown in this paper and the behavior of different functionalities has been analyzed. A brief summary of the main findings is given in the following. A 900 kVA active filter has been considered to provide harmonic compensation from the AC/DC converter for Sk ’’ greater than 50 MVA.

In this paper, the study has been carried out by considering a class 2 type of load with injected harmonics of 10 minutes average value (long term). The harmonic values considered for the study are not measured values, but typical values observed in practice. Real laboratory tests are planned to be performed to check the harmonics injected by th

load before designing the Netz-Patron unit to provide harmonic compensation. The effectiveness of the voltage support function provided by the Netz-Patron unit in case of any disturbance registered at the PCC has also been analyzed in this paper.

Future work is planned to focus on a multimaster      concept which implies the analysis of the parallel operation of several Netz-Patron units connected at the PCC of different industrial grids or same industrial grid in the medium voltage network.


[1] EPRI PEAC Corporation, “C. E. Commission:, Power Quality Solutions for Industrial Customers,” August 2000.

[2] R.C.Dugan, M.F.McGranaghan, S.Santoso and H.W.Beaty, Electrical Power Systems Quality, second edition, McGraw- Hill, 2004.

[3] W. Reid, “Power Quality Issues – Standards and Guidelines,” in IEEE Transactions of Industry Applications Vol.32,No.3, 1996.

[4] DIN EN 61000-2-4: Electromagnetic compatibility (EMC) Part 2-4: Environment – Compatibility levels in industrial plants for low-frequency conducted disturbances, VDEVerlag GmbH, 2002-06.

[5] DIN EN 61000-4-11: Electromagnetic compatibility (EMC) Part 4-11: Environment – Testing and measurement techniques – Voltage dips, short interruptions and voltage variations immunity tests for equipment with input current less than 16 A per phase, February 2005.

MPPT Schemes for PV System under Normal and Partial Shading Condition: A Review


The photovoltaic system is one of the renewable energy device, which directly converts solar radiation into electricity. The I-V characteristics of PV system are nonlinear in nature and under variable Irradiance and temperature, PV system has a single operating point where the power output is maximum, known as Maximum Power Point (MPP) and the point varies on changes in atmospheric conditions and electrical load. Maximum Power Point Tracker (MPPT) is used to track MPP of solar PV system for maximum efficiency operation. The various MPPT techniques together with implementation are reported in literature. In order to choose the best technique based upon the requirements, comprehensive and comparative study should be available. The aim of this paper is to present a comprehensive review of various MPPT techniques for uniform insolation and partial shading conditions. Furthermore, the comparison of practically accepted and widely used techniques has been made based on features, such as control strategy, type of circuitry, number of control variables and cost. This review work provides a quick analysis and design help for PV systems.


1.      Renewable Energy System

2.       Solar Photovoltaic

3.       Solar Power Conversion

4.       Maximum Power Point Tracking

5.       Partial Shading

6.      Global MPPT





 Fig. 1 Current feedback methodology for MPPT tracking



 Fig. 2 Irradiance pattern for the testing of MPPT controller

Fig. 3 Power output response for Voltage Fraction MPPT


Fig. 4 Power output response for the P&O and INC controller

Fig. 5 Power output response for Fuzzy Logic MPPT controller

Fig. 6 The P-V curve for the demonstration of Power slope technique algorithm

Fig. 7 The output power of PV array for the Power Curve Scanning technique

Fig. 8 The output power of PV array for the modified Power Slope Detection GMPPT technique


The prominent techniques of MPPT are discussed in this paper. It may be used as tutorial material on solar MPPT. Also, an attempt has been made to describe the important GMPPT techniques with sufficient details. A comprehensive comparative analysis has been contributed in this paper considering performance, cost, complexity of circuit and other parameters of MPPT. The results of this analysis will be helpful for proper selection of MPPT method. The generated power performance through few MPPT controllers has been illustrated with the help of simulation excercise. This also provides better understanding through numerical comparison. This review work has also presented a brief analysis and comparison of MPPT techniques for partial shading conditions. This paper may be useful for solar PV system manufacturer and solar inverter designer.


Abdourraziq, S., & El. Bachtiri Rachid (2014) A perturb and observe method using fuzzy logic control for PV pumping system. International Conference on Multimedia Computation and Systems, Marrakech, 1608-1612.

Adly, M., El-Sherif, H., & Ibrahim, M. (2011) Maximum Power Point Tracker for a PV cell using a fuzzy agent adapted by the Fractional open circuit voltage technique. IEEE International Conference on Fuzzy System, Taipei, 1918-1922.

Ahmad, J. (2010) A fractional open circuit voltage based maximum power point tracker for photovoltaic arrays. International Conference on Soft Technology and Engineering, San Juan, 247-250.

Ahmed, N.A., and Miyatake, M. (2008) A novel maximum power point tracking for photovoltaic applications under partially shaded insolation conditions. Electric Power System Research, 78, 777-784.

Altas, I.H., & Sharaf, A.M. (1996) A novel on-line MPP search algorithm for PV arrays. IEEE Transactions on Energy Conversions, 11 (4), 748-754.

Maximum Power Point Tracking Using Fuzzy Logic Controller under Partial Conditions

Scientific Research Publishing, Smart Grid and Renewable Energy, 2015.

Maximum Power Point  ABSTRACT: This study proposes a fuzzy system for tracking the maximum power point of a PV system for solar panel. The solar panel and maximum power point tracker have been modeled using MATLAB/Simulink. A simulation model consists of PV panel, boost converter, and maximum power point tack MPPT algorithm is developed. Three different conditions are simulated: 1) Uniform irradiation; 2) Sudden changing; 3) Partial shading. Results showed that fuzzy controller successfully find MPP for all different weather conditions studied. FLC has excellent ability to track MPP in less than 0.01 second when PV is subjected to sudden changes and partial shading in irradiation.


  • Fuzzy Logic Controller
  • Maximum Power Point
  • Photovoltaic System
  • Partial Shading




Figure 1. Schematic diagram of PV system with MPPT.



Figure 2. P-V characteristics at different irradiations.

Figure 3. P-V characteristics when partial shading from 1000 to 600 Watt/m2.

Figure 4. Output of fuzzy at1000 Watt/m2.

Figure 5. Output of fuzzy controller. (a) Full shading from 600 to 300 Watt/m2; (b) Full shading from 700 to 400 Watt/m2; (c) Full shading from 900 to 400 Watt/m2; (d) Increasing shading from 300 to 800 Watt/m2.

Figure 6. Comparison between fuzzy and P & O partial shading (partial shading 1000 to 800 Watt/m2).


 In this study, FLC has been developed to track the maximum power point of PV system. PV panel, boost converter with FLC connected to a resistive load has been simulated using Matlab/Simulink. Simulation results have been compared to nominal power values. The proposed system showed its ability to reach MMP under uniform irradiation, sudden changes of irradiation, and partial shading. Simulation results have shown that using FLC has great advantages over conventional methods. It is found that Fuzzy controller always finds the global MPP. It is found that fuzzy logic systems are easily implemented with minimal oscillations with fast convergence around the desired MP


 [1] Devabhaktuni, V., Alam, M., Reddy Depuru, S.S.S., Green II, R.C., Nims, D. and Near, C. (2013) Solar Energy: Trends and Enabling Technologies. Renewable and Sustainable Energy Reviews, 19, 555-556. http://dx.doi.org/10.1016/j.rser.2012.11.024

[2] Bataineh, K.M. and Dalalah, D. (2012) Optimal Configuration for Design of Stand-Alone PV System. Smart Grid and Renewable Energy, 3, 139-147. http://dx.doi.org/10.4236/sgre.2012.32020

[3] Bataineh, K. and Dalalah, D. (2013) Assessment of Wind Energy Potential for Selected Areas in Jordan. Journal of Renewable Energy, 59, 75-81.

[4] Bataineh, K.M. and Hamzeh, A. (2014) Efficient Maximum Power Point Tracking Algorithm for PV Application under Rapid Changing Weather Condition. ISRN Renewable Energy, 2014, Article ID: 673840. http://dx.doi.org/10.1155/2014/673840

[5] International Energy Agency (2010) Trends in Photovoltaic Applications. Survey Report of Selected IEA Countries between 1992 and 2009. http://www.ieapvps.org/products/download/Trends-in Photovoltaic_2010.pdf

Maximum Power Point

Electric power system Projects in asokatechnologies

An electric power system is a network of electrical components deployed to supply, transfer, and use electric power. An example of an electric power systems is the grid that provides power to an extended area. An electric power system can be broadly divided into the generators that supply the power, the transmission system that carries the power from the generating centres to the load centres, and the distribution system that feeds the power to nearby homes and industries. Smaller power systems are also found in industry, hospitals, commercial buildings and homes. The majority of these systems rely upon three-phase AC power—the standard for large-scale power transmission and distribution across the modern world. Specialised power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail systems, ocean liners and automobiles.

Dynamic voltage restorer employing multilevel cascaded H-bridge inverter

IET Power Electronics, 2016

ABSTRACT: This study presents design and analysis of a dynamic voltage restorer (DVR) which employs a cascaded multilevel inverter with capacitors as energy sources. The multilevel inverter enables the DVR to connect directly to the medium voltage networks, hence, eliminating the series injection transformer. Using zero energy compensation method, the DVR does not need active energy storage systems, such as batteries. Since the energy storage system only includes capacitors, the control system will face some additional challenges compared with other DVR systems. Controlling the voltage of capacitors around a reference voltage and keeping the balance between them, in standby and compensation period, is one of them. A control scheme is presented in this study that overcomes the challenges. Additionally, a fast three-phase estimation method is employed to minimize the delay of DVR and to mitigate the voltage sags as fast as possible. Performance of the control scheme and estimation method is assessed using several simulations in MATLAB / SIMULINK environments.


  1. Multilevel inverter
  2. cascaded H-bridge inverter
  3. Dynamic Voltage Restorer



 Multilevel inverter

 Fig. 1 DVR strcuctures  a) Conventional DVR b) CHB-based DVR


Fig. 2 Three-phase voltage sag a) Network voltage b) Injected voltage by the DVR c) Load-side voltage

 Fig. 3 Unbalanced voltage sag (a 20% voltage sag on phase A) a) Source voltage b) Injected voltage by the DVR c) Load-side voltage

Fig. 4 Voltages of the DC link capacitors

Fig. 5 Three-phase 20% voltage sag with voltage harmonics a) Network voltage b) Injected voltage by the DVR c) Load-side voltage



This paper presented design and performance assessment of a DVR based on the voltage sag data collected from MWPI. Using a multilevel converter, the proposed DVR was capable of direct connection to the medium voltage-level network without a series injection transformer. In addition, development of zero active power compensation technique helps to achieve voltage restoration goal just by the capacitors as energy storages. Due to internal losses of H-bridge cells and probable inaccuracies in measurements, voltage of DC link capacitors may become unequal, which prevents proper operation of the converter. A voltage control scheme, comprised of three separate controllers, was proposed in this paper for keeping voltage balance among the DC link capacitors within nominal range. A fast estimation method was also employed for calculation of phase and magnitude terms in an unbalanced three-phase system. This estimation method is able to recognise voltage sags in approximately half a cycle. Several simulations were performed in PSCAD/EMTDC environment to verify the performance of CHB-based DVR. Additionally, a laboratory-scale prototype of the proposed DVR was built and tested. Results of the experimental test also confirmed validity of the proposed control system.


1 Chapman, D.: ‘The cost of poor power quality’ (European Copper Institute, Copper Development Association, 2001), March

2 Radmehr, M., Farhangi, S., Nasiri, A.: ‘Effects of power quality distortions on electrical drives and transformer life in paper industries’, IEEE Ind. Appl. Mag., 2007, 13, (5), pp. 38–48

3 Lamoree, J., Mueller, D., Vinett, P.: ‘Voltage sag analysis case studies’, IEEE Trans. Ind. Appl., 1994, 30, (4), pp. 1083–1089

4 Bollen, M.H.J.: ‘Understanding power quality problems: voltage sags and interruptions’ (New York, Saranarce University of Technology, 2000)

5 Ghosh, A., Ledwich, G.: ‘Power quality enhancement using custom power devices’ (Berlin, Kluwer Academic Publications, 2002)

Design and Evaluation of a Mini-Size SMES Magnet for Hybrid Energy Storage Application in a kW-Class Dynamic Voltage Restorer

IEEE Transactions on Applied Superconductivity, 2017


This paper presents the design and evaluation of a mini-size GdBCO magnet for hybrid energy storage (HES) application in a kW-class dynamic voltage restorer (DVR). The HES-based DVR concept integrates with one fast-response highpower superconducting magnetic energy storage (SMES) unit and one low-cost high-capacity battery energy storage (BES) unit. Structural design, fabrication process and finite-elementmodeling (FEM) simulation of a 3.25 mH/240 A SMES magnet wound by state-of-the-art GdBCO tapes in SuNAM are presented. To avoid the internal soldering junctions and enhance the critical current of the magnet simultaneously, an improved continuous disk winding (CDW) method is proposed by introducing different gaps between adjacent single-pancake coil layers inside the magnet. About 4.41% increment in critical current and about 3.42% increment in energy storage capacity are demonstrated compared to a conventional CDW method. By integrating a 40 V/100 Ah valve-regulated lead-acid (VRLA) battery, the SMES magnet is applied to form a laboratory HES device for designing the kW-class DVR. For protecting a 380 V/5 kW sensitive load from 50% voltage sag, the SMES unit in the HES based scheme is demonstrated to avoid an initial discharge time delay of about 2.5 ms and a rushing discharging current of about 149.15 A in the sole BES based scheme, and the BES unit  is more economically feasible than the sole SMES based scheme for extending the compensation time duration.


  1. Superconducting magnetic energy storage (SMES)
  2. SMES magnet design, hybrid energy storage (HES)
  3. Battery energy storage (BES)
  4. Continuous disk winding (CDW)
  5. Dynamic voltage restorer (DVR)
  6. Voltage sag compensation



Fig. 1. Circuit topology of the HES-based DVR.



 Fig. 2. Transient voltage curves: (a) Load voltage before compensation; (b) Compensation voltage from the DVR; (c) Load voltage after compensation.

Fig. 3. Transient voltage curves: (a) Load voltage before compensation; (b) Compensation voltage from the DVR; (c) Load voltage after compensation.


The structural design, fabrication process and FEM simulation of a 3.25 mH/240 A SMES magnet wound by state-of-the-art GdBCO tapes have been presented in this paper. The FEM simulation results have proved the performance enhancements in both the critical current and energy storage capacity by using the improved CDW scheme. Such a mini-size SMES magnet having relatively high power and low energy storage capacity is further applied to combine with a 40 V/100 Ah VRLA battery for developing a laboratory HES device in a kW-class DVR. In a 5 Kw sensitive load applications case, voltage sag compensation characteristics of three different DVR schemes by using a sole SMES system, a sole BES system and a SMES-BES-based HES device have been discussed and compared. With the fast-response high-power SMES, the maximum output current from the BES system is reduced from about 149.15 A in the BES-based DVR to 62.5 A in the HES-based DVR, and the drawback from the initial discharge time delay caused by the inevitable energy conversion process is offset by integrating the SMES system. With the low-cost high-capacity BES, practical compensation time duration is extended from about 32 ms in the SMES-based DVR to a longer duration determined by the BES capacity. Therefore, the proposed HES concept integrated with fast-response high-power SMES unit and low-cost high-capacity BES unit can be well expected to apply in practical large-scale DVR developments and other similar SMES applications.


[1] Mohd. H. Ali, B. Wu, and R. A. Dougal, “An overview of SMES applications in power and energy systems,” IEEE Trans. Sustainable Energy, vol. 1, no. 1, pp. 38-47, 2010.

[2] X. Y. Chen et al., “Integrated SMES technology for modern power system and future smart grid,” IEEE Trans. Appl. Supercond., vol. 24, no. 5, Oct. 2014, Art. ID 3801605.

[3] IEEE Std 1159-2009, IEEE Recommended Practice for Monitoring Electric Power Quality, 2009.

[4] X. H. Jiang et al., “A 150 kVA/0.3 MJ SMES voltage sag compensation system,” IEEE Trans. Appl. Supercond., vol. 15, no. 2, pp. 1903-1906, Jun. 2005.

[5] S. Nagaya et al., “Field test results of the 5 MVA SMES system for bridging instantaneous voltage dips,” IEEE Trans. Appl. Supercond., vol. 16, no. 2, pp. 632-635, Jun. 2006.

An Interline Dynamic Voltage Restoring and Displacement Factor Controlling Device (IVDFC)

IEEE, 2013

ABSTRACT: An interline dynamic voltage restorer (IDVR) is invariably employed in distribution systems to mitigate voltage sag/swell problems. An IDVR merely consists of several dynamic voltage restorers (DVRs) sharing a common dc link connecting independent feeders to secure electric power to critical loads. While one of the DVRs compensates for the local voltage sag in its feeder, the other DVRs replenish the common dc-link voltage. For normal voltage levels, the DVRs should be bypassed. Instead of bypassing the DVRs in normal conditions, this paper proposes operating the DVRs, if needed, to improve the displacement factor (DF) of one of the involved feeders. DF improvement can be achieved via active and reactive power exchange (PQ sharing) between different feeders. To successfully apply this concept, several constraints are addressed throughout the paper. Simulation and experimental results elucidate and substantiate the proposed concept.


  1. Displacement factor improvement
  2. Interline dynamic voltage restorer (IDVR)
  3. Interline dynamic voltage restoring and displacement factor controlling (IVDFC)
  4. PQ sharing mode



 Fig. 1. Principle of IVDFC system operation during normal conditions (PQ sharing mode).



Fig. 2. Per-phase PQ sharing mode simulation results: (a)–(c) for first case and (d)–(f) for the second case.

Fig. 3. Per-phase simulation results for voltage sag condition at: (a) feeder 1 and (b) feeder 2.

Fig. 4. Per-phase experimental and corresponding simulation results for DF improvement case: (a) and (b) receiving feeder; (c) and (d) sourcing feeder (time/div= 10 ms/div).

Fig. 5 Per-phase experimental results and corresponding simulation results for voltage sag case: (a) and (b) at feeder 1 and (c) and (d) at feeder 2 (time/div = 10 ms/div).

Fig. 6 Per-phase experimental results and corresponding simulation results for voltage swell case at: (a) and (b) feeder 1 and (c) and (d) at feeder 2 (time/div = 10 ms/div).


This paper proposes a new operational mode for the IDVR to improve the DF of different feeders under normal operation. In this mode, theDFof one of the feeders is improved via active and reactive power exchange (PQ sharing) between feeders through the common dc link.

The same system can also be used under abnormal conditions for voltage sag/swell mitigation. The main conclusions of this work can be summarized as follows:

1) Under PQ sharing mode, the injected voltage in any feeder does not affect its load voltage/current magnitude, however, it affects the DFs of both sourcing and receiving feeders. The DF of the sourcing feeder increases while the DF of the receiving feeder decreases.

2) When applying the proposed concept, some constraints should be satisfied to maintain the DF of both sourcing and receiving feeders within acceptable limits imposed by the utility companies. These operational constraints have been identified and considered.

3) The proposed mode is highly beneficial if the active power rating of the receiving feeder is higher than the sourcing feeder. In this case, the DF of the sourcing feeder will have a notable improvement with only a slight variation in DF of the receiving feeder.

The proposed concept has been supported with simulation and experimental results.


[1] S. A. Qureshi and N. Aslam, “Efficient power factor improvement technique and energy conservation of power system,” Int. Conf. Energy Manage. Power Del., vol. 2, pp. 749–752, Nov. 21–23, 1995.

[2] J. J. Grainger and S. H. Lee, “Optimum size and location of shunt capacitors for reduction of losses on distribution feeders,” IEEE Trans. Power App. Syst., vol. PAS-100, no. 3, pp. 1105–1118, Mar. 1981.

[3] S. M. Kannan, P. Renuga, and A. R. Grace, “Application of fuzzy logic and particle swarm optimization for reactive power compensation of radial distribution systems,” J. Electr. Syst., 6-3, vol. 6, no. 3, pp. 407–425, 2010.

[4] L. Ramesh, S. P. Chowdhury, S. Chowdhury, A. A. Natarajan, and C. T. Gaunt, “Minimization of power loss in distribution networks by different techniques,” Int. J. Electr. Power Energy Syst. Eng., vol. 3, no. 9, pp. 521–527, 2009.

[5] T. P.Wagner, A. Y. Chikhani, and R. Hackam, “Feeder reconfiguration for loss reduction: An application of distribution automation,” IEEE Trans. Power Del., vol. 6, no. 4, pp. 1922–1933, Oct. 1991.