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Static synchronous series compensator (SSSC) based on the cascaded H-bridge multilevel converter is used as the power flow controller by injecting controllable sinusoidal voltage into the high voltage AC transmission lines. After analyzing the basic working principle of the cascaded H-bridge multilevel SSSC, a hierarchical control strategy with multiple control loops is proposed in this paper. At...
Single Wire Earth Return (SWER) system with long transmission line is introduced as one method for low cost remote electrification. Long transmission line and load growth can makes voltage regulation a concern. Distribution STATic COMpensator (DSTATCOM) as a voltage support equipment in SWER system with ability of injecting or absorbing reactive power is proposed. In this paper the placement of DSTATCOM...
The performance of a distance protection scheme along with related supervisory elements is investigated when a shunt connected static synchronous compensator (STATCOM) is tapped to the midpoint of a transmission line. The paper examines responses for different fault types and locations while the STATCOM absorbs reactive power and is being controlled by two different control schemes. An emtp-type model...
Power Swing Blocker (PSB) is a complementary part in distance relay that detects power swing in the transmission line to prevent unintended operation of distance relay. Unified Power Flow Controller (UPFC) is used in a transmission line to control active and reactive power. The UPFC operation during power swing influences the performance of PSBs in different ways. In this paper, two methods (the center...
Sen Transformer (ST) emulates an impedance in series with the transmission line and, in turn, allows the active and reactive power flows to change independently, meaning as desired. Traditionally, power flow control has been attempted with the use of a phase angle regulator (PAR), which can only regulate the phase angle of the line voltage and, in turn, allows the active and reactive power flows to...
This paper extends the analysis of low frequency AC (LFAC) transmission systems and investigates short-circuit fault characteristics and distance protection considerations. Due to operation at a low frequency, transmission line reactance is reduced and thus the power system transfer capability is increased significantly. The transmission line impedance reduction, however, creates a drawback in LFAC...
Travelling waves for real and complex reference impedance are reviewed. New power waves are defined and their behavior on a lossy transmission line are examined.
As discussed throughout this paper, the employment of load encroachment and OOS blinders make it difficult to ensure that the relay will operate for symmetrical faults when these two functions are enabled and still comply with the standard. The use of current differential relays solves this issue when these type of relays are available. The relay engineer can also decide to disable the OOS function...
A SMART Power Flow Controller (SPFC) enhances the controllability in an electric power grid by using functional requirements and cost-effective solutions. Utilities that are looking for ways to enhance the controllability in their power grid by voltage regulation, phase angle regulation, line impedance regulation, fault-current limitation, and much more can benefit from using a SPFC, the heart of...
This paper investigates some aspects of reactive power and voltage control. In general, load tap changers, local shunt compensation and reactive power generation help to enhance the system voltage level. In some cases, however, these actions deteriorate the system, leading to a voltage instability scenario. To diagnose the problem and prevent voltage collapse, this paper supports the idea that relationships...
Distance relay may maloperate during power swing condition which can arise due to variation of heavy load and switching of adjacent loaded line. Hence, it is necessary to discriminate the fault condition and power swing condition in case of line protection. During fault on transmission line the reactive power & voltage will change drastically compare to power swing condition. This paper demonstrates...
Low short circuit capacity and high grid impedance are the main electrical characteristics of weak grid, and there are some stability and power quality problems with a large number of PV power generation systems incorporated into weak grid. The increasing penetration of PV power generation easily lead to voltage rise at the end of grid, and it affects the ability of weak grid to accept PV power capacity...
Voltage-controlled inverters are grid-friendly and can cope with the high penetration caused by connecting a lot of distributed generations. In low voltage power systems This paper proposes a simple and precise PQ control strategy based on improved voltage-controlled inverters with inner output impedance. The PLL part is replaced by second order generalized integrator method and it performs well when...
This paper proposes a virtual series impedance emulation control strategy for current controlled remote PV or wind farms, in order to enhance the power transfer capability of the transmission line. This approach can be regarded as integrating the functions of the FACTS devices, such as series capacitors, into the grid-side converters of PV or wind farms, by utilizing the reactive power capability...
This paper analyzes the distance relay performance during power swing conditions for an uncompensated and compensated transmission line with a unified power-flow controller (UPFC). UPFC can control voltage and power flow of the transmission line independently; hence, it has an impact on the apparent impedance seen by the distance relay. To analyze the case, the apparent impedance seen by the distance...
The reactive power is the major drawback of the AC electric grids. This paper proposes a performance index, “Q/loss”, based on the energy loss share of the MVAR flows. If computed with powers, the performance index is time-dependent and characterizes one grid operating regime. Calculated on energy basis, it stamps the quality of the MVAR control over a period of time. As outlined by simulations conducted...
In the fast development of the power system, the cost of the transmission lines plays a vital role in the network company. Because of the various practical constraints, the transmission lines are often only utilized for a fraction of it individual limits. To improve the economical aspects one possibility would be to add to the value of transmission lines by transport large amount of energy through...
This Paper proposes a new algorithm for estimating the zero sequence impedance of a live transmission line by means of Phasor Measurement Units (PMU). In this algorithm the line impedance matrix is calculated and its sequence impedance matrix calculates by means of symmetrical components matrix. A case study contains a 230kv single circuit un-transposed transmission line was simulated and results...
Power flow control, in an existing long transmission line, plays a vital role in Power System area. This paper employs the shunt connected compensation (STATCOM) based FACTS device for the control of voltage and the power flow in long distance transmission line. The proposed device is used in different locations such as sending end of the transmission line, middle and receiving end of the transmission...
The half-wavelength AC transmission technology is attracting more and more attentions home and abroad by its unique economic and technological advantages. The paper starts by describing the history and research status of the half-wavelength AC transmission technology, and then sums up the basic transmission characteristics of the technology. This paper carries out a detailed analysis about several...
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