Power Quality Improvement Using GUPFC

Transcription

1 Power Quality Improvement Using GUPFC D.Rajesh Reddy Assistant.Professor / EEE Narayana Engineering College, Gudur Andhra Pradesh Dr.R.Veera Sudarasana Reddy Principal Narayana Engineering College, Gudur Andhra Pradesh Abstract The power quality issue will take new dimension due to power system restructuring and shifting trend towards distributed generation. Huge loss in terms of time and money has made power quality problems a major anxiety for modern industries with non-linear loads in electrical power system. Power quality consists of a large number of disturbances such as voltage sags, swells, harmonics, notch, flicker, etc. Power quality problems can be mitigated by many methods but most appropriate solution to mitigate these problems is FACTS devices. In this paper a brief survey of FACTS devices are presented which are used to mitigate power quality problems. Keyword s GUPFC, Restructuring, Distributed Generation, Sag, Swell, Harmonics, Notch, Flicker, PCC, FACTS devices. INTRODUCTION A power quality issue is an issue that is becoming increasingly important to electricity consumers at all levels of usage. PQ related issues are of most distress because of the extensive use of electronic equipment. In arrears to this, various PQ issues arises like voltage sag or dip, very short and long interruptions, voltage spike, voltage swells, harmonic distortion, voltage fluctuation, noise, voltage unbalance and altered our power system. Power quality problems have been attracting the eye of researches for decade. The presence of voltage disturbances at the point of common coupling (PCC) results in malfunction of sensitive industrial instrumentality, that turn out grid part failures, such as transformers, and economical losses. FACTS devices are the possible answer to shield sensitive loads against the most significant voltage disturbances, voltage harmonics, imbalance and sags [1]. Definition of power quality may vary from person to person because we cannot define what power quality we only define what good is or bad power quality is as we can see that two identical devices or pieces of equipment might react differently to the same power quality parameters due to differences in their manufacturing or component tolerance [2]. According to institute of Electrical and Electronic Engineers (IEEE) Standard power quality is defined as a, the concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment. The focus of this survey is on the use of FACTS devices in mitigation of PQ problems. FACTS DEVICES A. Introduction Studies of power quality phenomena have emerged as a main subject in recent years due to renewed interest in improving the excellence of the generation of power. As sensitive electronic equipment continues to proliferate, the studies of power quality have been further emphasized [1]. There are two main ways for improving power quality: a. The cost-free improving power quality. b. Not cost-free improving power quality. The cost-free means for improving power quality include actions like: 1. Using of tap changing transformers. 2. Operation of conventional compensating devices for example capacitor bank 3. Control by FACTS devices Flexible AC Transmission Systems (FACTS) forms a new domain in power system control engineering, using power electronic devices and circuits and the more recent existing technologies in automatic control. The two main objectives of FACTS are: a) To increase the capability of transmission capacity of lines. b) Control power flow over designated transmission, electronically and statically, without need of operator s actions and without need of mechanical manipulations or conventional breakers switching. B. Main Sources, Causes and Effects Of Electrical Power Quality Problems Power Quality is Any power problem manifested in voltage, current, or frequency deviations that result in failure or disoperation of customer equipments. Power systems, ideally, should provide their customers with an uninterrupted flow of energy at smooth sinusoidal voltage at the contracted magnitude level and frequency [3-4]. Some of the primary sources of distortion can be identified as below: , IJIRAE- All Rights Reserved Page -41

2 Non Linear Loads Power Electronic Devices IT and Office Equipments Arcing Devices Load Switching C. Mitigation Echniques Using Facts Devices The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags and swells. The control for DVR based on dqo algorithm was discussed in [5]. Rosli Omar et. al [5] have described the problem of voltage sags and swells and its severe impact on nonlinear loads or sensitive loads. The proposed control scheme was simple to design. Simulation results carried out by Mat lab / Simulink verify the performance of the proposed method. S. Sadaiappan et. al [6] have used a series compensator (SC) to improve power quality was an isolated power system investigated. The role of the compensator is not only to mitigate the effects of voltage sag, but also to reduce the harmonic distortion due to the presence of nonlinear loads in the network. In this proposed method, a series compensator was proposed, a method of harmonic compensation is described, and a method to mitigate voltage sag was investigated by S. Sadaiappan [6]. Chong Han et al. [7] have proposed a method in which an electrical arc furnace (EAF) is a major flicker source that causes major power quality problems. In this proposed method, flicker mitigation techniques by using a CMC-based STATCOM was presented and verified through a transient network analyzer (TNA) system. The required STATCOM capacity was first studied through a generalized steady-state analysis. Second, the STATCOM control strategy for flicker mitigation is introduced, and simulation results are given. Finally, a TNA system of the STATCOM and an EAF system are designed and implemented. This paper deals with new technique of the simulation and analysis of Generalized Unified Power Flow Controller (GUPFC) or multi-line Unified Power Flow Controller (UPFC) which is the novel concept for controlling the bus voltage and power flows of more than one line or even a sub-network. In this paper Generalized Unified Power Flow Controller (GUPFC) has been analyzed for both open loop and close loop configuration. GUPFC Introduction of Generalized Unified Power Flow Controller (GUPFC) An innovative approach of utilization of complex FACTS controllers providing a multifunctional power flow management device was proposed in [8] and [9]. There are several possibilities of operating configurations by combing two or more converter blocks with flexibility. Among them, there is a novel operating configuration, namely the Generalized Unified Power Flow Controller (GUPFC) which is significantly extended to control power flows of multilines or a sub-network rather than control power flow of single line by a Unified Power Flow Controller (UPFC) or Static Synchronous Series Compensator (SSSC) [11]. A fundamental model of the GUPFC consisting of one shunt converter and two series converters which can be increase if needed as shown in fig.1. and variable magnitude and phase angle. One approach involves multi-connected,. A MATHEMATICAL MODEL OF THE GUPFC A. The Equivalent Circuit of the GUPFC The GUPFC with combing three or more converters working together extends the concepts of voltage and power flow control beyond what is achievable with the known two-converter UPFC FACTS controller [7], [8]. Fig. 1. Operational principle of the GUPFC with three converters , IJIRAE- All Rights Reserved Page -42

3 International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: Fig. 2. The equivalent circuit of the GUPFC The simplest GUPFC consists of three converters, one connected in shunt and the other two in series with two transmission lines in a substation [12]. It can control total five power system quantities such as a bus voltage and independent active and reactive power flows of two lines.in the steady state operation, the main objective of the GUPFC is to control voltage and power flow. The equivalent circuit of the GUPFC consisting of one controllable shunt injected voltage source and two controllable series injected voltage sources is shown in Fig. 2. Such a GUPFC, which is shown in Fig. 1, is used to show the basic operation principle for the sake of simplicity. However, the mathematical derivation is applicable to a GUPFC with an arbitrary number of series converters. From fig.2.real power can be exchanged among these shunt and series converters via the common DC link. The sum of the real power exchange should be zero if we neglect the losses of the converter circuits. For the GUPFC shown in Figs. 1 and 2, it has total 5 degrees of control freedom, that means it can control five power system quantities such as one bus voltage, and 4 active and reactive power flows of two lines. It can be seen that with more series converters included within the GUPFC, more degrees of control freedom can be introduced and hence more control objectives can be achieved. in Fig. 2 are shunt and series transformer impedances. The controllable injected voltage sources shown in Fig. 2 are defined as, (1.1) (1.2) Where n=i,j B. Power Flow Equations of the GUPFC According to the equivalent circuit of the GUPFC shown in Fig. 2, the power flow equations can be derived: (2.1) , IJIRAE- All Rights Reserved Page -43

4 International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: (2.2) (2.3) (2.4) (2.5) (2.6) (2.7) (2.8) where. NUMERICAL EXAMPLES A. Test Systems Test cases in this paper are carried out on the IEEE 30 bus system. The IEEE 30 bus system has 6 generators, 4 OLTC transformers and 37 transmission lines. The IEEE 118 bus system has 18 controllable active power generation, 54 controllable reactive power generation, 9 OLTC transformers, 177 transmission lines. For all cases in this paper, the convergence tolerances are 5.0e-4 for complementary gap and 1.0 e-4 (0.01 MW/Mvar) for maximal absolute bus power mismatch, respectively. B. The IEEE 30 Bus System Results In order to show the power flow control capability of the non-linear interior point OPF algorithm proposed, four cases based on the IEEE 30 bus system are carried out. In the discussion thereafter, the control settings of active and reactive power flow are referred to,, which are at the sending end of a line. Active power flow and reactive power flow at the sending end of a line are referred to, ( or ) since the sending end of a line is connected to bus ( or ). Case 1): This is a base case without GUPFC. Case 2): This is similar to case 1 expect that there is a GUPFC installed for control of voltage of bus 12 active and reactive power flow of line and line the control setting of the bus voltage is 1.0 p.u.the control settings for active and reactive power flow of line and line are 25 MW+j5 Mvar and 10MW +j2mvar respectively. Case 3): It is similar to the case 2 except that second GUPFC is further installed for control of voltage at bus 10 and control of active and reactive power flow of line and line The control setting of voltage at bus 10 is 1.0 p.u. The control settings of active and reactive power flow are 10 MW 6 Mvar and 12 MW 4 Mvar for line and line 10 22, respectively. The active power flow set-ting of line is about 60% of the corresponding base case active power flow. While the active power flows setting of line is about 160% of the base case active power flow. Case 4): This is similar to the case 3 except that third GUPFC is further installed for control of voltage at bus 6 and control of active and reactive power flow of line 6 2 and line 6 8. The control setting of voltage at bus 6 is 1.0 p.u. The control settings of active and reactive power flow are 60 MW 4 Mvar, and 10 MW 4 Mvar for line 6 2 and line 6 8, respectively , IJIRAE- All Rights Reserved Page -44

5 TABLE I - TEST RESULTS OF THE IEEE 30 BUS SYSTEM C. CASE-1 CASE-2 CASE-3 CASE-4 THE NO OF GUPFC THE TOTAL NO OF CONTROL OBJECTIVE BY GUPFC THE TOTAL NO OF CONTROLLABLE OF ACTIVE AND REACTIVE POWER FLOW BY GUPFC - 2 P Flow 2 Q Flow 4P Flow 2 Q Flow 6 P flow 2 Q Flow THE TOTAL NUMBER OF BUS VOLTAGES BY GUPFC THE NO OF ITERATIONS Discussion of the Results From these results on the IEEE 30 bus system it can be seen: 1) Numerical results demonstrate the feasibility as well as the effectiveness of the GUPFC model established and the OPF method proposed. 2) The OPF with GUPFC can find a solution in reasonable iterations. The number of iterations for an OPF solution with the GUPFC devices is comparable with that of a base case OPF solution, which can be found in Tables I and II. It should be pointed out here that initialization of the GUPFC variables based on the analytical solutions de-rived in this paper is very helpful to improve the convergence characteristics of the OPF. 3) The GUPFC is a quite flexible and powerful FACTS con-troller. It can control bus voltage and active and reactive power flows of several lines simultaneously. It may be in-stalled in some central substations to manage power flows of multilines or a group of lines and provide voltage sup-port as well. 4) By using the GUPFC devices, the transfer capability of transmission lines can be increased significantly. Furthermore, by using the multi-line management capability of the GUPFC, active power flows on lines can not only be increased, but also be decreased with respect to operating and market transaction requirements in an open access environment. In the cases 3) and 4) above, such scenarios are simulated. Therefore, the GUPFC can be used to in-crease transfer capability and relieve congestion as well in power systems. CONCLUSIONS In this paper, we have reviewed the mitigation techniques using FACTS devices of various PQ issues like voltage sag or dip, very short and long interruptions, voltage spike, voltage swells etc. Power system and its equipment is badly affected to this PQ issues like breakdown of information technology equipment or may be stoppage of all equipment, circuit breakers trip without being overloaded, automated systems stop for no apparent reason, electronic systems work in one location but not in another location. A mathematical model of the Generalized Unified Power Flow Controller (GUPFC), which is suitable for power flow and optimal power flow study, is established. The model with one shunt converter and two or more series converters. Most of the research highlight on product innovation and cost reduction. But few of them focuses on studying the PQ related issues are of most distress because of the extensive use of electronic equipments. Here I have intended to propose a proper change in perspective of PQ. Numerical results based on the IEEE 30 bus system with various GUPFC devices demonstrate the feasibility as well as the effectiveness of the GUPFC and the OPF method proposed. It is obvious that the implementation principles of the GUPFC proposed can also be used in modelling other members of the Convertible Static Compensator (CSC) family in power Systems. REFERENCES: [1]. R. K. Rojin A Review of Power Quality Problems and Solutions in Electrical Power System, International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, Vol. 2, No. 11, pp , 2013 [2]. Hingorani N.G., Introducing custom power, IEEE Spectrum, Vol. 32, No. 6, pp , [3]. Rosli Omar and Nasrudin Abd Rahim, Modeling and Simulation for Voltage Sags/Swells Mitigation Using Dynamic Voltage Restorer (DVR), in preceding of Australasian Universities Power Engineering Conference, Sydney, NSW, pp. 1-5, [4]. S. Sadaiappan, P. Renuga and D. Kavitha Modeling and Simulation of Series Compensator to Mitigate Power Quality Problems, International Journal of Engineering Science and Technology, Vol. 2, No. 12, pp , 2010 [5]. S. Sadaiappan, P. Renuga and D. Kavitha Modeling and Simulation of Series Compensator to Mitigate Power Quality Problems, International Journal of Engineering Science and Technology, Vol. 2, No. 12, pp , , IJIRAE- All Rights Reserved Page -45

6 [6]. Chong Han, Zhanoning Yang, Bin Chen, Alex Q. Huang, Bin Zhang, Michael R. Ingram and Abdel-Aty Edris Evaluation of Cascade-Multilevel-Converter- Based STATCOM for Arc Furnace Flicker Mitigation, IEEE Transactions On Industry Applications, Vol. 43, No. 2, March/April [7]. B. Fardanesh, M. Henderson, B. Shperling, S. Zelingher, L. Gyugyi, C. Schauder, B. Lam, J. Moundford, R. Adapa, and A. Edris, Convertible static compensator: Application to the New York transmission system, in CIGRE , Paris, France, Sept [8]. L. Gyugyi, K.K. Sen, and C.D.Schauder, The interline power flow controller: A new approach to power flow management in transmission systems, IEEE Trans. Power Delivery, vol. 14, no. 3, pp , July [9]. L. Gyugyi, C.D. Shauder, S.L. Williams, T. R. Rietman, D. R. Torg-erson, and A. Edris, The unified power flow controller: A new approach to power transmission control, IEEE Trans. Power Delivery, vol. 10, no. 2, pp , Apr [10]. L. Gyugyi, C.D. Shauder, and K.K.Sen, Static synchronous series compensator: A solid-state approach to the series compensation of trans-mission lines, IEEE Trans. Power Delivery, vol. 12, no. 1, pp , Jan , IJIRAE- All Rights Reserved Page -46