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Power Delivery Systems: Transmission and Distribution
Published in J. Lawrence, P.E. Vogt, Electricity Pricing, 2017
Several FACTS controller types have been developed. These devices are installed in shunt, series, or combined shunt-series configurations. For instance, the Static Synchronous Compensator (STATCOM) is a shunt-connected VAR compensation apparatus, which provides for greater power transmission capability by means of controllable inductive or capacitive current independent of voltage. The Static Synchronous Series Compensator (SSSC) increases the voltage across the line impedance by injecting a controllable voltage in quadrature with and independent of the current. The Unified Power Flow Controller (UPFC) combines the STATCOM and the SSSC devices. The UPFC therefore provides a wide range of control to transmission line impedances, voltage levels, and bus voltage phase angles, and thus provides extensive control over real and reactive power flows.
High-Voltage Power Electronic Substations
Published in John D. McDonald, Electric Power Substations Engineering, 2017
Dietmar Retzmann, Asok Mukherjee
While SVC and STATCOM controllers are shunt devices, and TCSCs are series devices, the so-called unified power flow controller (UPFC) is a combination of both [20]. The UPFC uses a shunt-connected transformer and a transformer with series-connected line windings, both interconnected to a DC capacitor via related voltage-source-converter circuitry within the control building. A further development [21,54,64] involves similar shunt and series elements as the UPFC, and this can be reconfigured to meet changing system requirements. This configuration is called a convertible static compensator (CSC). Figure 5.36 depicts this CSC system at the 345 kV Marcy substation in New York state.
Unified Power Flow Controllers
Published in Timothy L. Skvarenina, The Power Electronics Handbook, 2018
Ali Feliachi, Azra Hasanovic, Karl Schoder
UPFC can be used for voltage support and for improvement of transient stability of the entire electric power through a supplementary control loop. The proposed supplementary control, based on fuzzy control, is effective in damping power oscillations. The controller requires only a local measurement—the tie-line power flow at the UPFC location. Simulation results have shown that controller exhibits good damping characteristics for different operating conditions and performs better than conventional controllers. The performance is illustrated with a two-area-four-generator test system. Simulation is performed using the MATLAB-based Power System Toolbox package, which is modified to incorporate the UPFC model.
Optimal location and sizing of UPFC for optimal power flow in a deregulated power system using a hybrid algorithm
Published in International Journal of Ambient Energy, 2022
Hareesh Sita, P. Umapathi Reddy, R. Kiranmayi
UPFC is a FACTS tool which manages the transmission line power flow by injecting active and reactive voltage components to the line in series. The presence of FACTS devices (Yu et al. 2018) gives a new prospect to controlling powers, which enhances the transmission line capacity. It increases the transient and dynamic stability, limits short-circuit currents and provides greater flexibility for the generation of active powers. Hence, making system more secure UPFC has the following advantages when compared with devices for a meshed network, an optimal location of the UPFC permits the power flow control which results in an increased system load ability. In contrast, beyond the limited number of devices, the load ability can’t be increased. In power system, the optimal location and capacity of FACTS is the combinatorial study (Ghadimi 2013). Several optimisation algorithms are proposed to the specific issues, such as simulated annealing, GAs and taboo search (Sarker and Goswami 2014; Dutta, Roy, and Nandi 2015). However, combination algorithms (hybrid algorithms) have proved several basic power system general problems and issues (Taher and Amooshahi 2012).
Design of an Improved Nonlinear H∞ Control for UPFC to Enhance Transient Stability of Power System
Published in Electric Power Components and Systems, 2018
Bangjun Lei, Xiang Wu, Shumin Fei
The unified power flow controller (UPFC), which consists of shunt and series three-phase voltage source converters (VSCs) sharing a back-to-back common DC-link, is one of the most versatile and complex FACTS devices [1]. The UPFC is able to simultaneously provide independently both shunt compensation to the sending-end bus to provide reactive support and series compensation to the transmission line to achieve active and reactive power flow control [1]–[10]. While the conventional power injection model of UPFC can provide effectively the required active and reactive powers for power system by using the UPFC active and reactive power injection as the control inputs into the power system, it neglects the internal dynamics of the UPFC. Comprehensive UPFC control should comprise three levels of control, as shown in Figure 1 [1]. The UPFC can effectively control power flow of power system. Therefore, design of UPFC's advanced controller has become a research hotspot [1]–[18].
Decoupling Controller Design and Controllable Regions Analysis for the Space Vector Modulated Matrix Converter-Unified Power Flow Controller in Transmission Systems
Published in Electric Power Components and Systems, 2018
Jianwei Zhang, David G. Dorrell, Li Li, Youguang Guo
Flexible alternating current transmission systems (FACTS) technologies are able to control power flow efficiently, enhance system reliability, mitigate congestion and increase transmission capacity. This can alleviate the problem of continuously increasing electricity demand and provide potential solutions to multi-objective problems in modern power industries [1], [2]. The unified power flow controller (UPFC) [3] uses power electronic technology to control transmission system parameters, such as voltage amplitude, phase angle and line equivalent impedance, simultaneously or selectively. It has been recognized as the most versatile one among FACTS devices [4], [5]. Unlike other FACTS devices, the UPFC can control active and reactive power, or adjust system parameters through injecting a series voltage with the desired amplitude and phase angle into the transmission line. The theoretical transmission capacity potential can be realized, thus increasing the practical capacity of existing systems with an essential stability level. The system stability can be enhanced by injecting or compensating required active and reactive power. The UPFC was designed to solve problems facing the power delivery industry, such as real-time control, dynamic compensation, and multifunctional flexibility [6]. Current active research on the UPFC mainly addresses new controller design [1], optimal location and size determination [7], [8], impacts on system devices [9], and new topology development such as transformer less UPFCs [10], [11], and matrix converter based unified power flow controllers (MC-UPFCs) [12]–[14]. The back-to-back converter is the core of the UPFC and its linear operating regions have been evaluated recently in Ref. [15]. The MC-UPFC is a promising technology and more efforts need to be dedicated to its development.