| Abstract: not available |
| Abstract: The conventional proportional-integral type control system loops of the current and extinction angle controllers at High Voltage Dc Converter are replaced with Fuzzy Logic based controls. The two approaches are compared using simulations on an electromagnetic transients simulation program. A method to further refine the Fuzzy Logic formulation to yield the most optimum response is presented. The results show that the Fuzzy Logic based approach can provide, at the minimum, a marginal improvement over the P-I based controller. |
| Abstract: not available |
| Abstract: Power quality is a field
of growing interest; among other because in recent years power electronic
components of increasing capacity have been introduced in power systems.
Use of power electronic components is of current interest in wind/diesel
systems. In such systems a converter can be used in combination with a battery
storage bank to compensate for the power fluctuations due to the stochastic
nature of the wind. The power quality aspect in such systems should be treated
with the same care as in power systems in general. In this paper we propose a model of a wind/diesel system, including wind turbine with a generator, diesel generator set, forced commutated converter and consumer load. This model is used for simulation studies, with emphasis on transient analysis and dynamic control. The models of the converter and its controls are of main concern here. Therefore this paper focuses mainly on these models and their usage in order to enhance the power quality in wind/diesel systems. |
| Abstract: not available |
| Abstract: This paper discusses the use of an RTDS real time simulator for testing the Grid Master Power Controller (GMPC) of the Cahora Bassa HVDC upgrade. The GNPC uses coordinated HVDC and optional braking resistor control technologies to ensure stable operation. The physical design of the dynamic braking resistor is described as well as the GMPC setup SIMADYN D and RTDS. For the real-time simulation, detailed models of the complex HVAC and HVDC systems are represented in RTDS. The verification of the simulator setup is done by comparison with site recordings, EMTDC, PSS/E and NETOMAC study results. The GMPC performance is verifiedby different types of AC and DC faults. Results of the tests are presented. |
| Abstract: This paper presents the
first high power verification of ABB's Capacitor Commutated Converter (CCC)
concept. The high power tests were performed in a 6-pulse back-to-back test
plant. The purpose of the CCC-tests was to gather experience of the concept with the plant run at high power and with components manufactured in the same manner as for commercial plants. The test results presented include steady state operation, valve short circuit and AC ground faults. The CCC tests in the high power test circuit have also verified the results obtained from calculations and computer simulations. The high power tests have confirmed that the CCC is a safe and robust converter alternative. |
| Abstract: This paper presents a novel control startergy for reduction of second harmonic oscillations on the DC side of an HVDC link. The paper presents an analytical model for harmonic transfer through AC-DC converters and gives causes of the 100Hz gamma oscillations. Based on this analytical model and discrete HVDC system model, a new control stratergy is developed and new controller designed. The controller was tested on the New Zealand HVDC system PSCAD/EMTDC model. The results from simulations show that the controller can noticeably reduce 100Hz gamma oscillationswith very little negative effect on the connected AC system. The controller shows good robustness when tested against various disturbances of the inverter AC system. The paper also discusses the possibility of controlling the AC voltage unbalance using the presented controller. The controller implementation requirements are analysed in the last section. |
| Abstract: At present passive filters are installed at the converter substations of the Cahora Bassa HVDC line. Pending the evaluation of these filters on the recommisioned line, active filtering may be necessary at Apolloa inverter station to reduce the induced telephone interference. This paper investigates the different active filter topologies that could be useful in this regard. The active filters are analysed and suitable control algorithms are developed for a simplified circuit. Simulations are conducted on EMTDC with the objective of comparing these filters with one another. Useful results are obtained that will form the foundation of more detailed simulations and practical verification. |
| Abstract: In the paper, the harmonic generation of the SVC and STATCOM systems is analysed. At the beginning, short characteristics of the SVC and STATCOM system is given. Then, method of performing the analysis of harmonics for SVC and STATCOM systems is described. The SVC and STATCOM systems have been modelled using PSCAD/EMTDC system. During simulation process voltage distortion factors for each of the tested systems have been calculated. Different parameters and conditions of operation of simulated systems have been taken into account. At the end of the paper, comparison of SVC and STATCOM systems from viewpoint of harmonic generation is presented. |
| Abstract: not available |
| Abstract: This paper describes a double circuit line protection relay which has all 6 line currents and voltages available for processing. This allows several alterations to the standard 3-phase distance package which enhance the performance of the protection system. Results are presented for the relay fed with simulated waveforms from a Playback Simulator. The system used in the simulations is modelled on a 69kV parallel line in the Winnipeg Hydro network. |
| Abstract: When analysing electromagnetic transients in localized parts of large power systems, it is common practice to represent the bulk of the AC system as a simple equivalent circuit. To obtain accurate transient results, it is necessary that the equivalent circuit mimic the frequency dependence of the system it is replacing. Present methods of designing such a frequency dependence are either not very accurate, require some skill to set-up, or employ difficult non-linear optimization. This paper describes an automatic and robust procedure for finding single-port frequency dependent equivalents using s-domain rational functions. The rational function is found directly in the least squares sense using Singular Value Decomposition (SVD), and can be employed directly in transient studies. |
| Abstract: Fixed time-step programs based on the trapezoidal algorithm present a challenge to the modelling of power-electronic devices. This is du to the fact that all switchings are constrained to occur at multiples of the basic simulation time-step. Interpolation of the switching instant is one answer to this challenge. The paper presents the impact of using interpolation on the simulation of HVDC and FACTS devices, in particular on the removal of firing angle jitter as well as on the elimination of spurious non-characteristic harmonics. It is also shown that a considerable accuracy improvement can be obtained with interpolation applied to the control system components only. |
| Abstract: The open systems approach provides hooks to a software package that makes it readily interfacable to other software packages. THE PSCAD/EMTDC electromagnetic transients simulation program through its FORTRAN interface allows for the introduction of such hooks. Similarly MATLAB also allows communication with other packages. Using these features a MATLAB interface to PSCAD/EMTDC was developed, which is accessible using PSCAD's graphical user interface (GUI). In addition to the description of the interface, a typical simulation example of a Fuzzy-Logic based controller for an ac-dc controlled rectifier is presented. |
| Abstract: This paper presents improvements to an existing multi-limb transformer model by applying normalized core concept. It shows that multi-limb transformers can be accurately modeled without having to specify actual core dimensions and winding turns number. This paper includes re-formulation of the unified magnetic equivalent circuit (UMEC) model to demonstrate the application of normalized core concept. The modified UMEC model in PSCAD/EMTDC is validated using experimental and field test data. |
| Abstract: In this paper, a specially designed air-core transformer, to be employed in a small power tapping scheme from HVDC transmission systems, is studied. First, the transformer is analyzed by classical electromagnetic theory. Next, a small prototype transformer is built and studied in the laboratory. Experimental results, confirm the validity and accuracy of the proposed method for calculating the self- and mutual-inductances of the transformer. The results of the digital simulation of the transformer by the EMTDC/PSCAD software package, too, are in good agreement with the lab observations. |
| Abstract: A control system for the control of HVDC, SVC and other FACTS devices can be developed, tested and debugged using an electromagnetic transients simulation program. The paper presents a procedure for the direct conversion of the developed emtp-type model into the control language for a real world implementation. The procedure is validated by comparing the simulated emtp-type output with that from the real-world control system automatically derived from this code. The procedure has been implemented on the PSCAD/EMTDC emtp-type program and produces control software that can be loaded on to the SIMADYN-D control system. The benefits of this capability are to achieve faster design of complex controls with greater accuracy and reduced engineering costs. |
| Abstract: This paper investigates electromechanical transients as a result of bus-transfer of an induction motor load from a main (preferred) supply to an auxiliary (alternate) supply. The bus-transfer is carried out by two sets of three-phase thyristor switches and is referred to as fast bus-transfer when compared with transfer process by means of mechanical switches. The Electromagnetic Transients Program for DC Systems (EMTDC) is used for investigation of transients associated with fast bus transfer. The studies conclude that fast bus-transfer by means of semiconductor switches can be properly adopted to limit transients and consequently prevent load interruption and possible damage to induction motor shaft system. |
| Abstract: Pre-strike will occur when the dielectric withstand voltage is exceeded by the voltage between the closing contacts. The result of this phenomenon is that there is a tendency for the pre-strike to occur over the rising and peak voltage across the contacts rather than when the voltage is falling or is a minimum in magnitude. This phenomenon can impact the probability distribution of overvoltages for transmission line energizations, a possible key factor in transmission line design. |
| Abstract: This paper describes a new playback simulator test set which incorporates a powerful emtp software program. Details are given of the main features of the test set. |
| Abstract: The paper describes a procedure for interfacing the computational engine of the powerful MATLAB program with an electromagnetic transients program. The interface is easily established using conversation pipes on the Unix platforms. Such pipies are available in both MATLAB and the host emtp-type program used. For ease of use, the interface incorporated into the host emtp-type Graphical User Interface (GUI). This allows entry of MATLAB commands merely by clicking on the appropriate GUI icon in the host program. In addition to description of the interface, atypical simulation example of an artificial neural network based controller for an ac-dc controoled rectifier is presented. |
| Abstract: This paper presents the use of an RTDS simulator for real-time testing of Static Var Compensators (SVC). SVCs are the fastest devices within the family of FACTS (Flexible AC Transmission Systems), which contribute substantially to improved voltage quality in power systems. In principle, they are shunt compensation devices which employ powerful thyristor valves for controllability. However, the SVC's high speed control can only be applied effectively if the type and size of the power components as well as the control and protection schemes are well matched to the specific network parameters and requirements. Hence, design verification by computer and real-time simulation is imperative to successful commissioning. |
| Abstract: This paper presents the use of an RTDS simulator for the testing of a Grid Master Power Controller (GMPC) implemented in a commercial project for the Cahora Bassa HVDC upgrade. Three AC systems are connected by the 1500 km bipolar HVDC and a relatively weak 330/400 kV AC link. The GMPC uses coordinated HVDC and braking resistor control technologies for the stabilization of the system during and after transients. A GPS (Global positioning system) satellite signal provides long distance angle measurement facilities. The real-time simulation requires detailed models of the complex HVAC and HVDC systems. The verification of the simulator setup is done by comparison with site recordings, EMTDC, PSS/E and NETOMAC study results. The GMPC performance is verified by different types of AC and DC faults. Results of the tests are presented. |
| Abstract: This paper discusses software that has been developed for the Real-Time Digital Simulator (RTDS) which permits users to assemble control and protection systems by graphically interconnecting basic function blocks. Operation of the new software with the existing power system simulation capabilities of the RTDS are discussed. |
| Abstract: This paper compares relay test results for a number of different testing methods ranging form full secondary level testing with an RTDS to off-line tests with a relay model. |
| Abstract: In this paper, the dual wound synchronous machine is studied from the circuit point of view. The dqo transformation is applied to the general equations of the machine and power and torque formulae are developed. Equivalent circuits are proposed to represent the transient and the steady state behavior of the machine. Finally, a digital model, developed to simulate the machine in conjunction with the EMTDC/PSCAD program, is introduced. |
| Abstract: In this paper, a specially designed air-core transformer, to be employed in a small power tapping scheme from HVDC transmission systems, is studied. First, the transformer is analyzed by classical electromagnetic theory. Next, a small prototype transformer is built and studied in the laboratory. Experimental results, confirm the validity and accuracy of the proposed method for calculating the self- and mutual-inductances of the transformer. The results of the digital simulation of the transformer by the EMTDC/PSCAD software package, too, are in good agreement with the lab observations. |
| Abstract: This paper addresses the protection issue of six-phase transmission systems which have emerged as a result of the search for compact and efficient transmission systems. Performance of the ground, line and the directional impedance algorithms of a digital distance relay on a six-phase transmission line under various short circuit fault conditions is reported. The distance relay algorithm assumes the availability of all six currents for processing and therefore the ground impedance algorithm is different to that of a standard three-phase distance package. The results presented are based on off-line fault studies on a hypothetical six-phase transmission line model. |
| Abstract: When the secondaries of CT's are connected in parallel to a spill circuit with non-zero impedance then the CT simulations are coupled by the common voltage across this spill circuit. This paper considers the case of 2 CT's feeding a high impedance spill circuit and gives comparison of the simulation results with test results. |
| Abstract: This paper describes a development of transformer core models for power and instrument transformers based on Jiles-Atherton algorithm. The models exhibit all of the main features of hysteresis such as the initial magnetization curve, saturation of magnetization, coercivity, remanence and hysteresis loss. |
| Abstract: When an EHV transmission line is energized by the closing of a circuit breaker, there are a number of well known parameters which effect the transient overvoltages on the line. These include the impact of pole closing span, use of closing resistors and point-on-wave closing. These factors are investigated along with the little studied effect of contact closing pre-strike included. Probability distribution of overvoltages for transmission line energizations are the means for comparing the various effects. |
| Abstract: not available |
| Abstract: A software model of a digital relay is added to an off-line emtp (EMTDC) and is then subjected to the same waveforms as the actual relay. Its performance is measured against the performance of the actual relay and the accuracy of the model is assessed. |
| Abstract: not available |
| Abstract: not available |
| Abstract: not available |
| Abstract: This paper presents a summary of guidelines for modeling power electronics in various power engineering applications. This document is designed for use by power engineers who need to simulate power electronic devices and sub-systems with digital computer programs. The guideline emphasizes the basic issues that are critical for successfully modeling power electronics devices and the interface between power electronics and the utility or industrial system. The modeling considerations addressed in this guideline are generic for all power electronics modeling independent of the computational tool. However, for the purposes of illustration, the simulation examples presented are based on the EMTP or EMTP type of programs. The procedures used to implement power electronics models in these examples are valuable for using other digital simulation tools. |
| Abstract: not available |
| Abstract: not available |
| Abstract: In this paper, a specially designed air-core transformer, to be employed in a small power tapping scheme from HVDC transmission systems, is studied. First, the transformer is analyzed by classical electromagnetic theory. Next, a small prototype transformer is built and studied in the laboratory. Experimental results, confirm the validity and accuracy of the proposed method for calculating the self- and mutual-inductances of the transformer. The results of the digital simulation of the transformer by the PSCAD/EMTDC software package, too, are in good agreement with the lab observations. Next, the transformer is incorporated into the proposed tapping scheme and the system performance is digitally analyzed. It is concluded that with this transformer, a load of 600 kW can be successfully tapped from the HVDC system. Finally, the field effects of the transformer is studied. |
| Abstract: not available |
