Presence Of Unified Power Flow Controller Research Articles

Transient stability enhancement in renewable energy integrated multi-microgrids: A comprehensive and critical analysis

Multi-microgrids offer various benefits including the decreased overloading of a single microgrid, more options during faulty conditions, and more utilization of renewable energy resources. However, the implementation of a multi-microgrid brings the challenges such as power system complexity, interconnection issues, bidirectional power flow management, and power flow balancing. In the presence of these challenges, the power flow stability of the multi-microgrids is a challenging problem. In this context, this study evaluates a transient stability analysis model in multi-microgrids using solar photovoltaics, wind power, and a unified power flow controller (UPFC). UPFC offers a more robust power flow control strategy compared with other flexible alternating current transmission systems (FACTS) devices. First, a multi-microgrid structure consisting of the two microgrids was designed in DIgSILENT PowerFactory software. Second, the load flow calculation was performed in the absence and presence of UPFC, short circuit fault, and grid connection. Third, the electromagnetic transients (EMT) simulation was performed for all these situations. The results exhibited that the UPFC would offer significant power flow stability in the multi-microgrids. It was observed that the UPFC resulted in more transient stability in the microgrid where it was located. However, it improved the power flow quality at all the locations in the multi-microgrids. In addition, UPFC offered significant transient stability during the fault occurrence. The results offer various insights into power flow management in multi-microgrids.

Sensitivity analysis index to determine the optimal location of multi-objective UPFC for improvement of power quality parameters

Today, advanced technologies are used for the reliable operation of power systems. In order to access a reliable and practical function in the systems, it is necessary to use precise control systems with higher efficiency in the systems to minimize the problems of the distribution system. Devices that are made on the basis of power electronics have wide applications in power systems today. These devices, which are called FACTS devices, provide the possibility of improving energy transmission with the least investment cost, as well as quick control of power system problems. FACTS devices are placed in series, parallel or series-parallel transmission lines and control the operation of distribution systems in permanent states as well as the dynamic behavior of the system in transient states. FACTS devices are an effective method to solve the problems and limitations of lines. Transmission and replacement networks are used to create new lines in the network. From the point of view of power distribution control, FACTS controllers can be placed anywhere in the transmission line, but the elements are most effectively used when they are placed at the most critical point. Unified Power Flow Controller (UPFC) is one of the most important FACTS devices that can improve parameters. The quality of power used in the power system depends on the effect of this controller in improving the loss reduction, reducing the total harmonic distortion (THD), and removing the clogged lines to their proper location in the power system. This device is capable of all different effective parameters at a time. These parameters usually include voltage, impedance, and phase. This paper uses a new sensitivity analysis index to determine the optimal size and location of the UPFC to improve the power quality parameters of the distribution system. The proposed method is evaluated on the IEEE 14-bus network in the Simulink environment of MATLAB software. Finally, according to the simulation results and the results obtained from the base network, it is determined that using the proposed sensitivity analysis index in UPFC location, losses Network, total harmonic distortions (THD) and eclipses Network lines are much improved. The results indicate that the proposed method has provided a good answer to determine the optimal size and location of UPFC to improve power quality parameters. Using the results of the sensitivity analysis method, the best place to install UPFC in the power grid, mode number 6 between buses 2 and 11 is obtained. and The amount of network power losses after sensitivity analysis, compared to the base network Active losses of about 55% and reactive losses of about 11% deceased, Due to the circular structure of the network, the current passing through the lines is different depending on the amount of load in the bases near that line, and with the presence of UPFC, the network is optimized and the current passing through the lines is also reduced. 4) Percentage of total harmonic distortion (THD) mains voltage before the presence of UPFC is about 27.12%, which after installation in the 6th place with a maximum size has been reduced to about 11.11%.

System security enhancement using hybrid HUA‐GPC approach under transmission line(s) and/or generator(s) outage conditions

AbstractIn this manuscript, a hybrid HUA‐GPC strategy with unified power flow controller (UPFC) is proposed to enhance that security of power system under the condition of transmission and/or generator failure. The proposed hybrid strategy is joint implementation of Human urbanization algorithm (HUA) and Giza Pyramids Construction (GPC) and commonly named as HUA‐GPC approach. GPC approach is utilized to develop that search behavior of HUA. The main aim of the proposal is the operation and control of electrical system is to satisfy the demand continuously in the absence of failures. A new severity function is created with transmission line loads and bus voltage magnitude deviations. The proposed function and generation fuel cost are evaluated in contingency conditions of transmission line (s) and/or generator (s). System safety in contingency conditions is evaluated with optimal power flow issue. To improve system safety in contingency conditions in the presence of UPFC, it is essential to recognize an optimal position to install this device. To recognize an optimal UPFC position, in this proposal, a HUA‐GPC technique depending on line overload sensitivity index (LOSI) is evolved. The LOSI is assessed for every transmission lines in contingencies. An energy injection model based on UPFC voltage source, incorporation process and optimal location recognition approach depending on line overload sensitivity indices is proposed. The constraints are the constraints of equality and inequality. The proposed approach is then performed on the MATLAB/Simulink work platform and the efficiency is compared with existing strategies. The quality of the solution for the proposed system is analyzed in terms of best aptitude, worst aptitude, mean aptitude, SD, coefficient of variation and the error of best is 1110936.01, 1097382.12, 1107656.56, 1051.98, 0.075, and 0.82.

Effect of unified power flow controller installation in dual feed induction generator (DFIG) wind turbines

Abstract In recent years, the use of wind energy to generate electricity in the world has been accelerating and growing. Wind farms are unstable when dynamic voltage fluctuations occur, especially sudden and sudden changes in load, and show oscillating performance at their output. In this paper, the Unified Power Flow Controller (UPFC) has been simulated and studied by Matlab software to improve the dynamic stability and transient behavior of the wind power plant in the event of sudden load changes. The simulation results show that by controlling the UPFC series inverter, voltage fluctuations in the PCC bus are prevented and the UPFC parallel inverter injects power after changing the load for faster recovery and stability of the PCC bus voltage and thus the stability of the wind farm. The UPFC can control the active and reactive power at the transmission line, and in fact, controls the output of the wind turbine with the generator from both sides to the fluctuations caused by sudden load changes that play a role such as sudden disturbances and oscillating errors. Also, the presence of UPFC in the system reduces power fluctuations.

Detection of Partial Loss of Excitation Faults in Generator in the Presence of UPFC

Loss of excitation (LOE) occurs in synchronous generators and can harm the generator and have severe implications on the overall power system. LOE was detected with the help of mho-negative offset conventionally that has very low detection speed and misinterprets other conditions such as a stable power swing (SPS) or partial LOE as LOE itself. Such cases of misinterpretation have severe outcomes such as causing blackouts. On top of it, with additional devices in transmission system such as flexible alternating current transmission system (FACTS) devices in particular an unified power flow controller (UPFC), the system impedances vary slightly which is the basis of conventional LOE relays, and therefore ultimately hinders its performance. Here, the system is simulated in MATLAB and Simulink and some useful features are extracted and analyzed. Based on the extracted features an artificial intelligence-based scheme is proposed to differentiate complete LOE, partial LOE (PLOE), SPS and normal conditions. Performance and validity of proposed scheme are highlighted, and results are obtained to show the usefulness of the scheme proposed. Also, the speed of detection and reliability of the proposed scheme are presented keeping in mind the system performances with and without the presence of FACTS devices.

Comparison of Transient Stability Response for MMPS using UPFC with PI and Fuzzy Logic Controller

The increasing pressure on the power system increases the complexity that is becoming a concern for the stability of the power system and mainly for transitory stability. To operate the system in the event of faults, Flexible AC Transmission System (FACTS) devices are used that provide opportunities to control power and vibrations damping. This paper deals with the two control strategies of the Unified Power Flow Controller (UPFC) to damping the system oscillations stability. The stability of the Multi-Machine Power System (MMPS) was analysed with the presence of UPFC. The first strategy is the traditional PI controller (PI-C) with UPFC, and the second strategy is the proposed Fuzzy Logic controller (FL-C) proposed for UPFC device along with PI controller. The MATLAB R2014a was used in all simulations. Based on the results, FL-C for UPFC device along with the PI controller has proven its superiority by has enhanced response to the system, thus minimized in the transitions overshoot and undershoot, and has lower ripple compared to traditional PI-C, both with and without UPFC.

Comparison of Transient Stability Response for MMPS using UPFC with PI and Fuzzy Logic Controller

The increasing pressure on the power system increases the complexity that is becoming a concern for the stability of the power system and mainly for transitory stability. To operate the system in the event of faults, Flexible AC Transmission System (FACTS) devices are used that provide opportunities to control power and vibrations damping. This paper deals with the two control strategies of the Unified Power Flow Controller (UPFC) to damping the system oscillations stability. The stability of the Multi-Machine Power System (MMPS) was analysed with the presence of UPFC. The first strategy is the traditional PI controller (PI-C) with UPFC, and the second strategy is the proposed Fuzzy Logic controller (FL-C) proposed for UPFC device along with PI controller. The MATLAB R2014a was used in all simulations. Based on the results, FL-C for UPFC device along with the PI controller has proven its superiority by has enhanced response to the system, thus minimized in the transitions overshoot and undershoot, and has lower ripple compared to traditional PI-C, both with and without UPFC.

Upfc Compensated Transmission Line Fault Location Based on Travelling Wave Theory and Wavelet Modulus Maxima

Location of fault in a transmission line which includes flexible AC transmission system (FACTS) devices is a difficult task. This paper comprises of unified power flow controller (UPFC). The implementation control technique for UPFC devices set up dynamic problems in power system that must be reflecting on issues related to power system protection. The occurrence of a fault in the fault loop containing a UPFC affects transient and steady-state parameters of voltage and current in the power system. In this paper the identification of fault section before or after UPFC for a transmission line with wavelet fuzzy logic system discriminator. Wavelet technique extracts features, and the faulty location is found when the normalized features are fed to the fuzzy logic system. As soon as the fault section is located, the control shifts to that and is analyzed basing on the representation of the traveling wave theory through wavelet modulus maxima. This criterion detects the faulty section with respect to FACTS device very accuratelyin terms of distance from relay point. The above-said method is simulated for various fault situations and locations with wide changes in the conditions of operation in the presence of UPFC.

Adaptive algorithm for transmission line protection in the presence of UPFC

The presence of flexible ac transmission system (FACTS) controllers in transmission lines causes mal-operation of distance relays. The series-shunt FACTS devices have larger influence on the performance of the relays compare to the other FACTS controllers. Furthermore, high-resistance fault is another factor that relay become under-reach and cannot correctly identify the fault. In this paper, a method is provided based on synchrophasors to eliminate the effects of unified power-flow controller (UPFC) and fault resistance on the distance relay. In the presented method, the data of voltage and current signals of buses will be sent to system protection center (SPC). In SPC, an algorithm is provided based on active power calculation in buses which is able to eliminate the effects of both mentioned factors. The main advantage of the proposed method, in addition to the simplicity of the algorithm, is the ability to operate in all types of faults and in high-resistance faults. Furthermore, a technique is presented in this paper to calculate UPFC data. A comparison has been performed between this technique and another method where UPFC data is directly transmitted to SPC by communication channel. In modeling of UPFC, detail model is used based on 48-pulses voltage source converters.

Effects of Unified Power Flow Controller (UPFC) on Distance Relay Tripping Characteristics in the North-Central Nigerian 330kv Network

This paper investigates the effects of UPFC on Distance Relay tripping characteristics in Nigerian 330kV (North-Central) Network. Its operation is based on impedance measurement at the relaying point. However, the system performance is often impeded by certain operational or structural factors such as load angle, the voltage magnitude ratio at the line ends, pre-fault line loading and short circuit levels at the line ends. The Unified Power Flow controllers (UPFC) incorporated into the Nigerian 330kV (North-Central) Network was modelled in the environment of Power System Computer Aided Design (PSCAD) and kept within the protected zone of the relay to increase the Apparent Resistance causing the relay to malfunction. Therefore, it is deduced by simulation analysis that the presence of UPFC in a faulted transmission line loop, protected by distance relay greatly affects the trip boundaries of the distance relay by setting it to either an over reaching or an under reaching state. Hence, the tripping characteristics of distance relay with UPFC located at various points with respect to a fault on a transmission line culminated in three scenarios whose results were presented and discussed in this paper. http://dx.doi.org/10.4314/njt.v34i4.18

Performance comparison of LOE protection of synchronous generator in the presence of UPFC

Generator loss of excitation (LOE) protection is a principal protection of power system which operate based on impedance measurement. This relay calculates impedance by measuring voltage and current at the generator terminal. On the other hand, the presence of unified power flow controller (UPFC) in transmission lines changes measured voltage and current signals during loss of excitation. In this paper, the impact of UPFC on the performance of LOE protection has been analytically investigated. Afterwards, using modeling results, it has been attained that the presence of UPFC leads to the drastic delay on the performance of LOE relay. This delay results to the overloading and damaging of armature winding of generator. It is also shown that in partial LOE presence of UPFC causes under-reach of the relay. Finally, the phasor measurement units (PMUs) based method has been proposed to reduce the effect of UPFC on the LOE protection. The results indicate that using this new method, the delay of LOE relay has been reduced. In the surveys conducted, various conditions of the power system have been considered.

Optimal power flow by BAT search algorithm for generation reallocation with unified power flow controller

Abstract Optimal power flow with generation reallocation is a suitable method for better utilization of the existing system. In recent years, Flexible AC Transmission System (FACTS) devices, have led to the development of controllers that provide controllability and flexibility for power transmission. Out of the FACTS devices unified power flow controller (UPFC) is a versatile device, capable of controlling the power system parameters like voltage magnitude, phase angle and line impedance individually or simultaneously. The main aim of this paper is to minimize real power losses in a power system using BAT search algorithm without and with the presence of UPFC. Minimization of real power losses is done by considering the power generated by generator buses, voltage magnitudes at generator buses and reactive power injection from reactive power compensators. The proposed BAT algorithm based Optimal Power Flow (OPF) has been tested on a 5 bus test system and modified IEEE 30 bus system without and with UPFC. The results of the system with and without UPFC are compared in terms of active power losses in the transmission line using BAT algorithm. The obtained results are also compared with Genetic algorithm (GA).

Synchrophasor Assisted Adaptive Reach Setting of Distance Relays in Presence of UPFC

The operation of Flexible AC Transmission System Controllers (FACTS) in the power transmission system pose a challenge to the distance relaying scheme. This paper suggests an adaptive scheme for estimating the trip boundaries of a distance relay in presence of a Unified Power Flow Controller (UPFC), utilizing a Generalized Regression Neural Network (GRNN). Initially, the impact of the UPFC on the relay's trip boundary is studied for its automatic power flow control mode as well as bypass mode of operation. The GRNN has been trained off-line with the data generated from a detailed performance analysis of the power system for various faults considering the effects of the UPFC, fault resistance, and system loading conditions on the trip boundaries. This work has also proposed a strategy that computes the control parameters of the UPFC on-line, namely, series voltage and reactive current injections, utilizing the synchronized phasor measurements from Phasor Measurement Units (PMUs). Pre-fault system states, including the control parameters of the UPFC and the apparent impedance measured by the relay unit have been utilized by the GRNN for predicting the trip boundaries of the relay. The proposed scheme has considered Single Line-to-Ground (SLG), Double Line-to-Ground (LLG) and Three Phase-to-Ground (LLLG) faults and the effectiveness of the scheme has been tested on 39-bus New England system and also on a 17-bus system, a reduced equivalent of practical Northern Regional Power Grid (NRPG) system in India.

A simple method of solving the controlled load flow problem of a power system in the presence of UPFC

The unified power flow controller (UPFC) has the capability of controlling the steady state power flow of a particular branch in a transmission network. This paper proposes a simple method of solving the controlled load flow problem of a power system in the presence of UPFC. First, a new static model of the UPFC is proposed to control the power flow. Some standard load flow programs are then carefully modified to incorporate the effects of the proposed UPFC model without practically changing the basic computational algorithm of the program. During the iteration process, the computed bus voltages are used to modify the control parameters of the UPFC in such a way that the functionally dependent line power flow can be kept at the desired or specified value. The effectiveness of the proposed method is then demonstrated on a power system by solving a number of controlled load flow problems. It has been found that the proposed method is very efficient and reliable.