An improved hybrid unified power flow controller (IHUPFC) is developed in this paper to control the power flow and increase the utilization rate of the existing transmission lines. The IHUPFC is ...composed of an improved "Sen" transformer (IST) and a small capacity unified power flow controller (UPFC). After a detailed introduction of the structure and voltage regulation performance of the IST, this paper derives the capacity relationship between the IST and the UPFC. Then, this paper introduces the technology of the IHUPFC in power flow regulation and transmission capability improvement. Besides, the advantages of the IHUPFC in performance and structure are analyzed. The IST has simpler structure and larger power flow control area than a "Sen" transformer, and the IHUPFC provides a continuous active and reactive power flow control. Simulation and experiment studies are used to verify the practicability and superiority of the IHUPFC.
Power-flow control ability of meshed high-voltage direct-current grids can be improved by inserting a dc power-flow controller into the grids. Based on the study of existing dc power-flow ...controllers, this paper proposes a novel interline dc power-flow controller (IDCPFC) which has the benefit of fewer active switching devices, simpler control, little side effect on meshed grids, no external power source needed, and wide application occasions. The performance of the IDCPFC is validated by simulation and experimental tests. The results show that the proposed IDCPFC can achieve stable power-flow control in different conditions.
This paper focuses on the modelling and control of an interline current flow controller (CFC) for meshed HVDC grids. The operation states of the CFC are presented, and an average model is derived. ...The average model is used to perform steady-state analysis on a 3-terminal meshed grid, showing the current change capabilities and the benefits on the operation area. The converter control is designed using a linearized model. The system performance of the CFC is tested by means of simulation in a 3-terminal grid and in a 5-terminal grid.
Composite DC Power Flow Controller Zhong, Xu; Zhu, Miao; Chi, Yongning ...
IEEE transactions on power electronics,
2020-April, 2020-4-00, Letnik:
35, Številka:
4
Journal Article
Recenzirano
The utilization of a dc power flow controller in multiterminal HVDC (MTDC) can increase the control dimension of dc power flow, by which both the active power distribution capability and coordination ...control performance can be enhanced in MTDC. In this article, a novel concept of "composite dc power flow controller (CDCPFC)" has been proposed, and the general construction principles of technical frame have been given for function description. A specific CDCPFC topology has been implemented, which is featured with a straightforward dc-dc power conversion path via a transformerless structure. The operation principle, circuit characteristics, and control strategy of the proposed CDCPFC are analyzed in detail. Both simulation and experimental results proved that the proposed topology could realize power flow control function of two individual lines under various conditions with a good application prospect.
The existence of a generalized interline power-flow controller (GIPFC) in the transmission lines changes the voltage and current signals which are measured with the protection relays of power system ...dynamically. In this paper, the effects of the GIPFC on the measured impedance by the loss of excitation (LOE) relay of the synchronous generator are first investigated by analytical and computational methods for different operating modes of the power system. The results indicate that the presence of GIPFC causes a substantial delay on the operation of the LOE relay. It is also shown that when partial LOE occurs, the GIPFC causes to the LOE relay under-reaching. Consequently, to readjust the relay in the presence of the GIPFC, a new modified LOE protection algorithm on the basis of synchronized phasor measurements received from phasor measurement units is presented. The most important advantage of this modified algorithm is that it is a general algorithm which considers all voltage-source-converter-based flexible ac transmission systems controllers. Regarding the simulations results, it is concluded that using the modified algorithm for the LOE relay can sufficiently decrease the delay and prevent the relay from under-reaching. The impacts of the unified power-flow controller and interline power-flow controller on the LOE relay are also demonstrated.
In recent years, due to the reduction of non-renewable resources and increasing environmental pollution, exploiting of renewable energy sources is a good solution. Wind turbines and fuel cells are ...appropriate sources of renewable energy. On the other hand, FACTS devices are used to maximize the power injection capability to supply electricity demand and minimizing voltage deviation, power losses and operational cost of power system. Generalized Unified Power Flow Controller (GUPFC) and Interline Power Flow Controller (IPFC) are two kinds of the best FACTS devices. GUPFC can adjust the voltage and the power flow in the connected transmission lines synchronically. IPFC is capable of minimizing voltage drops and reactive power of line, enhancing the system stability against the dynamic disturbance, and load ability of the system. In this paper, with the aim of minimizing the cost function and improving the performance of system wind farm and fuel cell are integrated with power system in the presence of GUPFC and IPFC via power injection model. Then, using a new algorithm integrated with the Newton-Raphson method, the best place for installing IPFC and GUPFC is funded. This algorithm is improved squirrel search which is inspired by nature. On the other hand, the optimum range of parameter (value and angle of injected voltage) is determined with the aim of achieving the best performance of system. Ultimately, the proposed method has been applied in IEEE 57 Bus system in the presence of wind turbine, fuell cell and DG to test the effect of M-FACTS. The result confirms that the new method improved voltage profile, minimized the operational cost and power losses of system. Final, it is concluded that the performance of GUPFC is better than the IPPFC.
Meshed dc grids help improve the current network's configuration, flexible power management, and reliable power supply. However, the existing power converters implemented in dc grids do not have ...enough controllability in adjusting each feeder's power, leading to transmission congestion, overloads, and high-power loss issues. The DC power flow controller (DCPFC) is prominent in addressing problems with better system performance. This paper proposes an embedded DCPFC (eDCPFC) with full-bridge modular multilevel converter (FB-MMC) topology. The eDCPFC is directly integrated into a host MMC. The device's energy is balanced through the coordinated control of the eDCPFC and the host MMC without using isolation transformers or external power supplies. The working principle and the corresponding control strategies of the FB-MMC type eDCPFC and its host MMC are elaborated. Experimental results conducted in a scaled-down prototype validate the feasibility and effectiveness of the proposed topology and control schemes under typical working conditions.
The concept of the magnetic amplifier, a common electromagnetic device in electronic applications in the past, has seldom been used in power systems. The magnetic amplifier-based power-flow ...controller (MAPFC), an innovative low-cost device that adopts the idea of the magnetic amplifier for power-flow control applications, is introduced in this paper. The uniqueness of MAPFC is in the use of the magnetization of the ferromagnetic core, shared by an ac and a dc winding, as the medium to control the ac winding reactance inserted in series with the transmission line to be controlled. Large power flow in the line can be regulated by the small dc input to the dc winding. A project on the R&D of an MAPFC has been funded by the U.S. Department of Energy (DOE) and conducted by the Oak Ridge National Laboratory (ORNL), the University of Tennessee-Knoxville, and Waukesha Electric Systems, Inc. since early 2012. Findings from the project are presented along with some results obtained in a laboratory environment.
Flexible ac transmission system (FACTS) controllers offers innovative approaches for enhanced control of power utilities and have the potential to solve some of the grid's most pressing issues, ...specifically when used with smart grids. Furthermore, increasing smartening of distribution networks with micro grids, storage devices, and cognitive loads has made operating distribution feeders more challenging. Power electronics-based controllers and FACTS-based controller for distribution networks can both be used to successfully address these constraints. The paper proposes a reasonably priced FACTS controller that exhibits performance characteristics resembling those of reconfigurable Unified Power Flow Controller (UPFC). To mitigate the impacts of voltage sag, a hybrid power flow controller (HPFC) finds a spot between the sending and receiving terminals. This research work embraced with the comparison of four bus systems employing UPFC and HPFC. The model consists of four bus system which consists of a single generator bus using PV and a battery. The cost of making and selling solar panels today has decreased significantly from the past few decades, achieving energy price parity. The theoretical maximum efficiency that a single junction solar cell can display is known as the Shockley-Queisser limit. To increase the performance of solar cells, research is now being done to determine the best replacement materials and technologies. Increased efficiency and quick manufacturing have resulted from the research of the light spectrum and varied levels of semiconductor material absorption, unique coating, use of nanotechnology, and usage of organic polymers. The Simulation is done for 4 bus system using UPFC and HPFC with respect to the real and reactive power and the load bus voltage. The constructed model is utilised towards to show how well the controller works in resolving issues with distribution networks such as voltage sags brought on by feeder faults and power flow fluctuations carried on by fluctuating renewable generation for four bus system by comparing with UPFC.
Railway power flow controller (RPFC), as a promising technical route for railway power regulation, its rating determinization and the related flexible power regulation perplex designers and hinder ...large-scale applications, especially when the regenerative braking energy (RBE) is non-negligible. In this paper, a general power factors full-dimensionally hunted power distribution strategy (PFFDH-PDS), applicable for both off-line design & real-time control, is proposed. Two key methods are developed: 1) Full-dimensionally hunting the power factors (PFs) under the developed mathematic framework, from which the global optimal compensating power and RPFC's rating can be worked out; 2) Precisely partitioning two-phase loads on their PF-P and PF-PF distributing panels; in both methods, RBE is considered. By adopting PFFDH-PDS, RPFC's rating can be reduced by almost 60% compared to the conventional method, while the system has satisfactory grid-connection compatibility. Finally, the effectiveness and performance of the proposal are verified & conducted by real-measured data.
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