Performance Investigation of D-Q Model for PI and Fuzzy Controller Based UPFC

Optimization of system capacity electric power transmission systems requires a reliable power flow controller. The power flow controllers must be able to control the level of electrical voltage and active and reactive power flow without reducing the level of stability and security of the transmission system. Latest technology in the control of power flow is a Unified Power Flow Controller (UPFC). The entire transmission line parameters are impedance, voltage, and phase angle can be controlled simultaneously by the UPFC. The method used in the conventional algorithms based UPFC is still firmly with logic. These algorithms have difficulties to electric power transmission systems multimachine very dynamic, i.e. systems that are experiencing rapid changes in the electrical load from time to time. Therefore, in this study was developed based on neuro-fuzzy method is applied to the adaptive UPFC for adaptively controlling the power flow in electric power transmission systems multimachine very dynamic. In this study, three phase fault is applied to the multimachine system. The results are taken to be consideration of PI and neuro-fuzzy controllers. The PI and neuro-fuzzy controllers show nearly same results but there is a low overshoot occurred during the fault in the neuro-fuzzy controllers results. According to results that UPFC improves the system performance under the transient and the normal conditions. However, it can control the power flow in the transmission line, effectively.

Power flow control in double circuit transmission lines is crucial for maintaining system stability and ensuring optimal utilization of resources. This paper proposes a novel approach using a Five Level Unified Power Flow Controller (UPFC) with a Grey Wolf Optimizer (GWO) tuned Proportional-Integral (PI) controller. The Five Level UPFC acts as a flexible and efficient solution, facilitating the concurrent regulation of both active and reactive power flow in transmission lines. By applying the GWO algorithm, the aim is to improve the performance of the UPFC control system through the optimization of the PI controller's parameters. By imitating the natural hunting behaviour of grey wolves, the GWO algorithm achieves exceptional convergence and solution accuracy. The suggested control scheme is implemented and tested on a double circuit transmission line system. The system's effectiveness is evaluated under various operating conditions and compared against alternative control approaches. The findings establish the efficacy of the Five Level UPFC with a GWO-optimized PI controller in effectively regulating power flow and enhancing overall system stability. Furthermore, the proposed approach exhibits excellent robustness against parameter variations, load fluctuations, and system disturbances. The GWO optimization technique ensures optimal tuning of the PI controller, this leads to decreased power losses, enhanced voltage profile, and improved system reliability. Overall, the application of the Five Level UPFC with GWO-tuned PI controller provides an efficient and reliable solution for power flow control in double circuit transmission lines. The suggested method can make a substantial contribution to enhancing the operational efficiency of power systems, this enables the seamless integration of renewable energy sources and the progression of smart grid infrastructures. The circuit is simulated using the MATLAB/SIMULINK software. And the following results from the simulation are presented below

The independent control of active and reactive power flow in a transmission line is necessary for the transfer of bulk power along a desired path in the most economical way. A 'Sen' transformer (ST) uses transformer and tap changers that are traditionally used to build a voltage-regulating transformer (VRT) and a phase angle regulator (PAR). The ST regulates the voltage at a point in the transmission line as a VRT does. Additionally, the ST provides an independent and bidirectional active and reactive power (P and Q) flow control in the transmission line as a voltage-sourced converter (VSC)-based unified power flow controller (UPFC) does. Although both the ST and the PAR use a comparable number of components, the ST provides an area of controllability in the P-Q plane similar to a UPFC, while the PAR provides a linear P-Q characteristic. The technology of transformer and tap changer is proven to be reliable and cost-effective when compared with the emerging technology of VSC. The new ST is adequate to provide independent control of active and reactive power flow in most utility applications.

In this paper, a new control scheme using recurrent fuzzy neural controllers is proposed for the series branch of the unified power flow controller (UPFC) to improve the dynamic performance of real‐time power flow control functions with the aim of reducing the inevitable interaction between the real and reactive power flow control parameters. To simplify the theoretical analysis of the coupled dynamics within the UPFC and the controlled power system, the three phase description of a two‐bus test power system embedded with a UPFC is transformed into d−q components based on a synchronously rotating reference frame. For control systems with inherent nonlinear coupling features, a feed‐forward control scheme based on fuzzy neural controllers is developed to realize the decoupling control objectives. Based on the simulation results, the proposed control scheme is able to overcome the drawbacks of the traditional power flow controllers designed on small disturbance linearizing methods. Comprehensive simulation results on the EMTDC/PSCAD and MATLAB programs are presented and discussed to verify the effectiveness of the proposed control scheme. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

The problem of low-frequency power swings is a matter of concern for power systems engineers in the operation and planning of power systems. Therefore, this paper is an investigation of the use of unified power flow controller (UPFC) that is suitably tuned to improve the damping of low frequency power oscillations present in Nigerian grid system. A large disturbance is initiated, during simulation in PSAT, in the network to induce nonlinear oscillations of the power system in order to ascertain the damping effect of UPFC. The dynamic responses of the system simulated show that the system is well damped and is stabilized at minimal time which confirms the robustness of the UPFC. Finally, a comparative study in a typical transient stability problem on IEEE 14-bus system using a UPFC model and the Nigerian high voltage interconnected system is used to illustrate the concepts presented in this paper. Key words: Power oscillation damping, power systems, unified power flow controller (UPFC), flexible AC transmission system (FACTS) devices, low frequency oscillation

The problem of low-frequency power swings is a matter of concern for power systems engineers in the operation and planning of power systems. Therefore, this paper is an investigation of the use of unified power flow controller (UPFC) that is suitably tuned to improve the damping of low frequency power oscillations present in Nigerian grid system. A large disturbance is initiated, during simulation in PSAT, in the network to induce nonlinear oscillations of the power system in order to ascertain the damping effect of UPFC. The dynamic responses of the system simulated show that the system is well damped and is stabilized at minimal time which confirms the robustness of the UPFC. Finally, a comparative study in a typical transient stability problem on IEEE 14-bus system using a UPFC model and the Nigerian high voltage interconnected system is used to illustrate the concepts presented in this paper. Key words: Power oscillation damping, power systems, unified power flow controller (UPFC), flexible AC transmission system (FACTS) devices, low frequency oscillation

This paper proposes a new real and reactive power coordination controller for a unified power flow controller (UPFC). The basic control for the UPFC is such that the series converter of the UPFC controls the transmission line real/reactive power flow and the shunt converter of the UPFC controls the UPFC bus voltage/shunt reactive power and the DC link capacitor voltage. In steady state, the real power demand of the series converter is supplied by the shunt converter of the UPFC. To avoid instability/loss of DC link capacitor voltage during transient conditions, a new real power coordination controller has been designed. The need for reactive power coordination controller for UPFC arises from the fact that excessive bus voltage (the bus to which the shunt converter is connected) excursions occur during reactive power transfers. A new reactive power coordination controller has been designed to limit excessive voltage excursions during reactive power transfers. PSCAD-EMTDC simulation results have been presented to show the improvement in the performance of the UPFC control with the proposed real power and reactive power coordination controller.

P– Q decoupled control schemes using fuzzy neural networks for the unified power flow controller

This paper presents a screening technique for greatly reducing the computation involved in determining the optimal location of a unified power flow controller (UPFC) in a power system. The first-order sensitivities of the generation cost with respect to UPFC control parameters are derived. This technique requires running only one optimal power flow (OPF) to obtain UPFC sensitivities for all possible transmission lines. To implement a sensitivity-based screening technique for guidance in optimally locating a single UPFC in a power system, we propose a new UPFC model, which consists of an ideal transformer with a complex turns ratio and a variable shunt admittance. In this model, the UPFC control variables do not depend explicitly on UPFC input and output currents and voltages. Accordingly, this model does not require adding extra buses for UPFC input and output terminals. IEEE five-, 14- and 30-bus systems were used to illustrate the technique

FACTS devices expands the range of options aimed at controlling power delivery along with increasing capacity of current and new lines. The UPFC(unified power flow controller) is a highly complex power electronic interface that could regulate a voltage bus(local) along with optimize power flow in an electric drive system at the same time. By connecting the UPFC at the transmitting and receiving ends, this paper shows how to manage actual as well as reactive(VAR) power flow across the transmission channels. Main aim is to figure out how to monitor and perform a UPFC that will be installed at the transmission line to control complex power flow. Complex power via the transmission line cannot managed if no UPFC is mounted. To test the UPFC's results, simulations are run in the Matlab/Simulink setting.

This paper presents the results of experimental study on the performance of a Unified Power Flow Controller (UPFC), one of the FACTS (Flexible AC Transmission Systems) controllers. A laboratory‐scale UPFC was manufactured and installed on a laboratory electric power system to investigate its multifunctional capabilities as a power flow controller. The UPFC consists of two 4.5‐kVA, 200‐V back‐to‐back voltage‐sourced converters, labeled “Converter 1” and “Converter 2,” operated from a common DC link provided by a DC storage capacitor of 380 V. It can provide independent control of both the real and reactive power flow in the line. Tests were performed to examine the capabilities of the UPFC, under one‐machine connected to an infinite‐bus system. Steady‐state responses under various kinds of operating conditions were measured and analyzed. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 8– 15, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20538

The successful application of the unified power flow controller (UPFC) provides a new control method for the secure and economic operation of power system. In order to make the full use of UPFC and improve the economic efficiency and static security of a power system, a preventive security-constrained power flow optimization method considering UPFC control modes is proposed in this paper. Firstly, an iterative method considering UPFC control modes is deduced for power flow calculation. Taking into account the influence of different UPFC control modes on the distribution of power flow after N-1 contingency, the optimization model is then constructed by setting a minimal system operation cost and a maximum static security margin as the objective. Based on this model, the particle swarm optimization (PSO) algorithm is utilized to optimize power system operating parameters and UPFC control modes simultaneously. Finally, a standard IEEE 30-bus system is utilized to demonstrate that the proposed method fully exploits the potential of static control of UPFC and significantly increases the economic efficiency and static security of the power system.

Reactive power compensation is a main problem in the control of electric power system. Reactive power from the source increases the transmission losses and reduces the power transmission ability of the transmission lines. In addition, reactive power must not be transmitted throughout the transmission line to a longer distance. Consequently, flexible ac transmission systems devices such as static compensator unified power‐flow controller (UPFC) and static volt‐ampere compensator are used to ease these harms. UPFC is the mainly adaptable and composite power electronic equipment that has emerged as the vital equipment for the control and optimisation of power flow in electrical power transmission system. In this study, a d–q model‐based UPFC is developed with proportional‐integral (PI) and PID controller. The above controllers are simulated using MATLAB and their performance is analysed. Outcome of the analysis shows the superiority of PID control over the PI control method. Also this study presents comparative evaluation (both controllers) of dynamic response when initial and final load disturbances.

New approach for optimal UPFC placement using hybrid immune algorithm in electric power systems

Interconnecting power transmission systems provide reliability of electric power supply. The security of the system is however questioned when a disturbance in any part of the interconnected system causes instability in the entire network. Unified Power Flow Controller (UPFC), which is a member of the flexible alternating current transmission system (FACTS) family, has the capability of controlling active and reactive power flow in a transmission line thereby improving the voltage stability of the system especially at the 500 kV configuration level. The performance of a 161-kV UPFC modelled in SimPowerSystems is tested on Ghana’s power transmission network. The optimal placement of the UPFC is done using fast voltage stability index (FVSI) and maximum loadability assessment (MLA). The results show that the device improved the connecting bus voltage from 0.88 p.u. to 0.98 p.u. Active power loss in the network was also reduced from 13.40 MW to 10.39 MW when the UPFC was in circuit. Keywords: Ghana, Stability, Transmission system and Unified Power Flow Controller (UPFC)