Voltage Recovery Characteristics Research Articles

An improved control method of fault ride-through for DPMWT-based wind farm considering coupling effect of HVDC transmission system

With the continuous increase of wind power penetration, a large number of wind farm have been constructed. The large-scale wind farm is usually transmitted through high voltage direct current(HVDC) transmission system. The reactive power output on the grid-side converter is utilized to support grid voltage, which is a common method of fault ride-through for direct-drive permanent magnet synchronous generator-based wind turbine (DPMWT). The power control capability of DPMWT-based wind farm(DPMWF) is affected by safety constraints and operating characteristics of the external system. However, the control strategy of DPMWF cannot yet take into account the coupling effect of HVDC and may be difficult to meet the voltage recovery requirements of the grid during the grid fault. Even the DPMWT may oscillate due to the over-threshold of the control setting value. Therefore, a power coupling model between DPMWF and rectifier station of HVDC transmission system is established, and an evaluation method for the power controllability of DPMWF under fault considering the coupling effect of HVDC transmission system is proposed. A calculation method of maximum reference value of reactive power control of DPMWF based on model predictive control is proposed taking into account the converter constraints of DPMWF and the influence of the external system. An improved control method of fault ride-through is further proposed, which takes into account the coupling effect of HVDC transmission system. The simulation shows that the proposed method can improve the voltage recovery characteristics under the grid fault, effectively guarantee the fault ride-through of DPMWF.

Improvement of system strength under high wind penetration: A techno-economic assessment using synchronous condenser and SVC

Variable speed wind turbine generators (WTGs) are replacing traditional fossil fuel based synchronous generators in the generation fleet as wind penetration increases. These variable speed WTGs are decoupled from the grid by power electronics inverters and usually generate less fault current compared to synchronous generators. As a result, system strength (indicates the fault recovery capability) at the point of common coupling (PCC) of wind power plants may reduce. A minimum value level of system strength is essential for wind power plants to properly identify and overcome a fault. To enhance system strength at wind PCC buses, supplementary devices such as synchronous condenser and Static VAR Compensator (SVC) can be deployed to have additional fault current. Since these devices are expensive, their optimal allocation considering economic feasibility is a major concern. In the existing literature, locations and ratings of the optimally allocated synchronous condenser are reported. However, this approach may cause oversizing of synchronous condensers. In addition, a SVC can be utilised instead of a synchronous condenser to enhance system strength. However, no detailed study is carried out yet to find the optimal size of SVCs. Evidently, both synchronous condenser and SVC can be installed to improve system strength. However, no comprehensive techno-economic assessment is performed for selecting an appropriate choice between them. To address these research gaps, this paper develops a framework to find the optimal sizes of synchronous condensers and SVCs by taking into account the long-term financial viability. Also, to ensure the maximum possible fault contribution, synchronous condensers/SVCs are connected directly to those wind PCC buses where system strength is below the acceptable limit. Afterwards, a detailed techno-economic assessment using synchronous condenser and SVC is performed in a wind dominated grid. In addition, post-fault voltage recovery characteristics with optimally sized synchronous condenser and SVC are explored. The developed methodology is applied to the IEEE 39 bus test system considering 45% wind power penetration scenario. Also, the performance of the proposed approach is compared to that of an existing technique. Finally, based on the technical and economic aspects, a better choice between synchronous condenser and SVC is recommended to improve system strength under high wind penetration.

Study on the characteristics of secondary arc current of UHV high compensation degree TCSC line under the fine-tuning mode

Abstract In the transmission line, the series compensation device is often used to improve the transmission capacity. However, when the fixed series capacitor (FSC) is used in high compensation series compensation device, the stability margin cannot meet the requirements. Therefore, thyristor controlled series compensator (TCSC) is often installed in transmission lines to improve the transmission capacity of the line and the stability of the system. For cost considerations, the hybrid compensation mode of FSC and TCSC is often adopted. However, when a single-phase grounding fault occurs in a transmission line with increased series compensation degree, the unreasonable distribution of FSC and TCSC will lead to the excessive amplitude of secondary arc current, which is not conducive to rapid arc extinguishing. To solve this problem, this paper is based on 1000 kV Changzhi-Nanyang-Jingmen UHV series compensation transmission system, using PSCAD simulation program to established UHV series compensation simulation model, The variation law of secondary arc current and recovery voltage during operation in fine tuning mode after adding TCSC to UHV transmission line is analyzed, and the effect of increasing series compensation degree on secondary arc current and recovery voltage characteristics is studied. And analyze the secondary arc current and recovery voltage when using different FSC and TCSC series compensation degree schemes, and get the most reasonable series compensation configuration scheme. The results show that TCSC compensation is more beneficial to arc extinguishing under the same series compensation. Compared with several series compensation schemes, it is found that with the increase of the proportion of TCSC, the amplitude of secondary arc current and recovery voltage vary greatly. Considering various factors, the scheme that is more conducive to accelerating arc extinguishing is chosen.

The multi-objective optimal allocation method of static var compensator based on transient voltage security control

Based on the detailed consideration of the dynamic characteristics of Static Var Compensator (SVC), the mathematical method for installing location and optimal capacity of SVC considering transient voltage security is proposed. Firstly, the trajectory sensitivity index is used to determine the key fault set and SVC candidate location. Then, transient voltage security constraint of the bus voltage is restored to 0.75pu within 1s and the bus voltage is restored to 0.9pu within 3s after remove fault, Finally, considering the transient voltage recovery characteristics and dynamic characteristics of SVC, the minimum of bus voltage deviation after fault removed and minimum of installtion capacity of SVC as objective function for hybrid optimal allocation model. The bus voltage and capacity of SVC are introduced as variables into the Crisscross Optimization Algorithm (CSO) for solving. The effectiveness of the proposed SVC installation location and capacity optimization method is verified by the time domain simulation of the IEEE39-bus system.

Network Security Assessments for Integrating Large-Scale Tidal Current and Ocean Wave Resources Into Future Electrical Grids

Marine energy, especially tidal current and ocean wave resources, bear immense potential for generating renewable power toward meeting global electricity needs. A number of conversion technologies have been successfully demonstrated worldwide and precommercial/commercial deployments are expected to appear in the near future. While electric power utilities foresee renewable technologies as a viable alternative to fossil fuels, marine energy technologies are generally excluded in their energy planning processes. Lack of technological preparedness and unavailability of device information are two major obstacles in that regard. This article provides an insight on how such novel schemes of power generation can be analyzed under conventional network planning exercises using generic information. The first study focuses on wave power integration along the coasts of Oregon, USA for the year 2019 and analyzes the Northwest electrical network. The second study considers both tidal current and ocean wave resources in South Korea for the years 2017 and 2022. The primary objective of these high-level grid scenario analysis is to identify the practical potential for longer term large-scale wave and/or tidal power generation, particularly focusing on the transmission networks. Steady-state (overloading and voltage deviations/collapses), time-domain (angular stability and dynamic voltage recovery characteristics), and small-signal (eigenvalue) stability analysis are carried out for these systems. Subsequent to establishing a number of study scenarios, N-1 contingencies and various suitable violation criteria are prepared, which are used in identifying the underlying network bottlenecks, especially within the coastal areas. Simplified generic dynamic models of tidal current and ocean wave devices are developed for the time-domain analysis. It is expected that similar studies, once conducted by the interested utilities, will equip them better toward considering marine energy in their future portfolios. In addition, device manufacturers and project developers will have greater confidence in the emerging marine energy market.

The operation of repetitive high-pressure spark gap switches

Two parallel experiments have been undertaken to investigate the mechanisms which govern the recovery of spark gap switches in repetitive applications. Measurement of the neutral gas density is accomplished using a laser Schlieren technique which enables spatial and temporal cooling of the gas to be observed. The rate of rise of voltage recovery is recorded using a double-pulse modulator system which determines the breakdown voltage of the gas at specific time intervals after breakdown by the first pulse. A continuous sweep voltage is applied to the switch in order to establish the influence of ions on the recovery characteristics. Results are presented for SF6/bin and air which show that voltage recovery is not solely governed by recovery of neutral gas density. There is a significant influence from the residual ion population created by the previous discharge. This influence is dominant for several hundred milliseconds after breakdown. The application of a suitable sweep voltage effectively minimizes the ion population, which results in significantly improved voltage recovery characteristics.

Experimental study of the voltage recovery characteristics of small air gaps

The electrical recovery characteristics of relatively small air gaps between 0.3 and 9 mm were determined using a two-pulse method. The first pulse was used to over-volt the gap and initiate the arc current. The second pulse was used to determine the recovery voltage of the gap. A plot of the recovery voltage with time was obtained by varying the time delay of the second pulse relative to the arc extinction time of the first arc, in the time range form 50 mu s to 100 ms. It is found that the recovery characteristics are independent of the electrode materials (Cu, Al , St) and the arc current in the range from 40 to 200 A. It is also found that the shorter gaps and the rod plane gaps recover their dielectric strength faster than the longer gaps and the sphere gaps, respectively. >

Control configurations for a synchronous machine with dual excitation†

Abstract This paper describes some digital computer studies of the influences of various control-loop parameters and configurations on the performance of a synchronous machine with two field windings. The basic excitation control is provided by angle and voltage regulators. The effects of using stabilizing transformers to obtain subsidiary feedback within the main control loops is examined. Derivative regulators, with additional feedback signals proportional to rotor velocity and acceleration, are used on both field windings. The rotor-angle transducer is also considered. Steady-state stability is investigated by means of regulation curves, and the Domain separation method is applied in the case of derivative regulators. Transient performance is assessed in terms of swing curves, which indicate stability, and also by voltage recovery characteristics. It is shown that both steady-state and transient stability can be significantly improved by derivative regulators on both axes, and that stabilizers can prev...

A Method for Studying Circuit Transient Recovery Voltage Characteristics of Electric Power Systems [includes discussion

A Method for Studying Circuit Transient Recovery Voltage Characteristics of Electric Power Systems [includes discussion

Transient Fault Current and Voltage Recovery Characteristics of Distribution Systems [includes discussion

Transient Fault Current and Voltage Recovery Characteristics of Distribution Systems [includes discussion

The Geometry of Arc InterruptionߞII Current-Zero Phenomena

During the microsecond period in which an interrupter is performing the act of changing from a conductor to an insulator (termed interruption) the current, voltage, and arc resistance undergo variations which materially affect the performance characteristics of the interrupter. The nature of these variations depends upon the medium of interruption design features of the interrupter, and the constants of the current and recovery-voltage circuits. Modern power interrupters employing air present variations in the current-zero region of an entirely different type from that observed in the fluid interrupters. A knowledge of the nature and cause of these variations is becoming of more importance from a design performance and application viewpoint. The rapidly varying resistances within the interrupter during the process of interruption have always presented obstacles to the analyst. In reapproaching this problem on the basis of an orderly, yet practical, variation of circuit current in the region of current zero and allowing the parameter of resistance to become secondary, the problem reduces to one of linear constants and can be solved by standard methods. This paper presents such a treatment. It is generalized in such a way as to include all practical types of current-zero phenomena generally encountered. Recovery-voltage characteristics are literally fabricated from "standard building blocks" of which relatively few are required. The method is flexible enough to be applied to any assumed current variation in the region of current zero. The analysis is presented in terms of the accepted nomenclature of circuit theory. The operational attack is employed.

Transient recovery-voltage characteristics of electric-power systems

Transient recovery-voltage characteristics of electric-power systems

Transient recovery-voltage characteristics of electric-power systems

THE existence of transient recovery-voltage phenomena in connection with the interruption of short circuits by circuit breakers has been recognized for a number of years, and from time to time measurements and calculations have been made on actual field circuits. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2,5</sup> However, while these more or less isolated and scattered instances have provided some valuable information, they have not afforded a comprehensive picture of transient-recovery voltage conditions existing in the field.

Power-System Voltage-Recovery Characteristics

WITH the increased use of protector tubes, a thorough knowledge of the recovery voltages to which they may be subjected has become highly desirable. The current range over which a tube can be expected to function successfully is necessarily dependent on the voltage recovery characteristics of the system in which the tube is applied. Since many systems have a large range of fault currents for the different fault and system conditions, it is essential that the corresponding voltage recovery characteristics be carefully considered. This paper presents the results of an investigation to determine and evaluate the importance of the factors which influence the voltage recovery characteristics of power systems. A very large number of tests were made on a specially designed miniature equivalent circuit representing a transmission line, connected apparatus, and the fault-clearing device. In that a miniature system was used, this investigation is similar to that made by Messrs. Evans and Monteith and presented in two recent papers.1,2 The results presented in this paper represent refinements and extensions to the understanding of the phenomena which will be of interest to both designers and users of protector tubes or other fault-clearing devices. Factors which have not been evaluated previously are shown to influence the phenomena considerably.

Recovery-voltage characteristics of typical transmission systems and relation to protector-tube application

THE SUCCESSFUL operation of an are-interrupting device requires that the insulation recovery-voltage characteristics of the device be higher than the recovery-voltage characteristics of the system. A broad understanding of the recovery-voltage problem from the application point of view, requires a knowledge of the effects caused by the range of systems, by the different types of faults and the different fault conditions encountered in practice. With this object in mind an investigation was undertaken to provide a general picture of the recovery-voltage characteristics of transmission systems.

Recovery-Voltage Characteristics or Typical Transmission Systems and Relation to Protector-Tube Application

1. This paper presents a general picture of the recovery-voltage characteristics of transmission systems obtained from the study of nine selected systems subjected to the varying factors encountered in practical operation. The a-c calculating-board method has been of major importance in carrying out this investigation. 2. The recovery-voltage characteristics of systems subjected to faults which are cleared without a line-sectionalizing operation are much less severe than that for the clearing of the last circuit breaker on a bus. This difference is so marked that advantage should be taken of it, in the design of certain pieces of apparatus. 3. The method of analysis and the data presented should be of value in the application of certain pieces of apparatus and in the preparation of test codes for specific devices. 4. This general analysis is of immediate interest in connection with the application of protector tubes, and operating experience with this device supports the analysis. Erosion of the protector tubes due to operation is such that the insulation-recovery characteristics are not changed at an impractical rate.

System recovery voltage determination by analytical and A-C calculating board methods

THE PERFORMANCE of current interrupting devices on systems is dependent not only on the characteristics of the device itself but also on the characteristics of the system. The voltage rating of the system and the connections at the time of fault have considerable influence on the recovery voltage and in turn on the application of the interrupting device. For example, the last oil circuit breaker to open must be capable of interrupting current under extreme system recovery conditions, while a deion protector tube always has at least the line section on which it is applied, connected at the time of clearing. This means that in considering broadly the current interruption problem it is necessary to have a knowledge of voltage recovery characteristics for a large number of system conditions. Tests can be made for particular system conditions, but this is expensive and it is difficult to obtain data for all possible combinations of faults and system connections. A general analysis taking into account all the factors makes calculations practically impossible, and on account of the complexity, the human factor cannot be overlooked.