paulo toledo - Academia.edu (original) (raw)
Papers by paulo toledo
Tunnelling and Underground Space Technology, 2005
The paper covers the fundamental aspects of integration of multiple HVDC links feeding power into... more The paper covers the fundamental aspects of integration of multiple HVDC links feeding power into different points in the same ac network area. Considering that the number of power systems that includes this type of application of HVDC is increasing, the performance needs to be studied in detail. There are a number of technical aspects related to multiple infeed configurations with HVDC transmission links. Focus on critical network conditions where the strength of the system is relatively low as compared to the amount of power that the HVDC transmission links are feeding into the system will be given in this paper. In those cases the phenomena of concern that might occur which could result in adverse interaction among the HVDC transmission links and the receiving ac network are discussed. The following basic issues are addressed in the paper: voltage and power stability; coordination of power or voltage modulation between different HVDC links for stabilization of the ac network; nee...
2003 IEEE Bologna Power Tech Conference Proceedings,
Power flow control is needed to feed power into cities for different reasons: to ensure optimum p... more Power flow control is needed to feed power into cities for different reasons: to ensure optimum power flow in the system, to recover from emergency conditions, to reduce reactive power flow, and to reduce loop flows when the system topology is built up with rings. There are also other reasons, for example, to limit the short-circuit currents, to improve the
The interaction of an HVDC converter with the connected power system is of complex nature. An acc... more The interaction of an HVDC converter with the connected power system is of complex nature. An accurate model of the converter is required to study these interactions. The use of analytical small-signal converter models provides useful insight and understanding of the interaction of the HVDC system and the connected system components.
Urban electrical power systems with steep demand increase need easily located solutions with shor... more Urban electrical power systems with steep demand increase need easily located solutions with short lead time from decision to transmission. While AC cable solutions can offer sufficient power ratings, the problems of load controllability and short circuit power increase with every added circuit. These problems may be countered with Voltage Source Converter (VSC) based technology using DC-cables for transmission, such as HVDC Light®. This technology offers up to 500 MW per station with small footprint, ideal for infeed to city centers. Fast implementation is possible thanks to modular pre-assembled design and extruded polymer underground cables. System benefits from the VSC technology, such as independent full active and reactive power control and no added short circuit power makes it easy to apply in a heavily loaded grid. From an environmental point of view, the dc-cable technology gives virtually no alternating magnetic field and no risk for oil leakage. Higher transmission capaci...
Urban electrical power systems with steep demand increase need easily located solutions with shor... more Urban electrical power systems with steep demand increase need easily located solutions with short lead time from decision to transmission. While AC cable solutions can offer sufficient power ratings, the problems of load controllability and short circuit power increase with every added circuit. These problems may be countered with Voltage Source Converter (VSC) based technology using DC-cables for transmission, such as HVDC Light®. This technology offers up to 500 MW per station with small footprint, ideal for infeed to city centers. Fast implementation is possible thanks to modular pre-assembled design and extruded polymer underground cables. System benefits from the VSC technology, such as independent full active and reactive power control and no added short circuit power makes it easy to apply in a heavily loaded grid. From an environmental point of view, the dc-cable technology gives virtually no alternating magnetic field and no risk for oil leakage. Higher transmission capaci...
Proceedings. International Conference on Power System Technology
This paper presents a study of SSTI related to VSC HVDC. The study was conducted with well establ... more This paper presents a study of SSTI related to VSC HVDC. The study was conducted with well established methods, which have been used in the design of SSDC and evaluation of SSTI in classic HVDC. Identical control systems for VSC HVDC as in the real plant are included in the study. The paper will show how the VSC and its control contribute to the electrical damping on subsynchronous oscillations. Different operation modes, load levels, control modes and AC network conditions have been considered in the study.
2008 Joint International Conference on Power System Technology and IEEE Power India Conference, 2008
There are serious concerns relating to a Multi-Infeed HVDC system when feeding a weak AC network.... more There are serious concerns relating to a Multi-Infeed HVDC system when feeding a weak AC network. Typical issues concerning multi-infeed configurations are: need for coordination of the recovery control, need for different DC modulation strategies to stabilize the system, possibility of voltage instability of the area receiving large amount of power from multiple HVDC links and the risk of mutual commutation failures. In contrast, if the area receiving electrical power from multiple HVDC transmission links is relatively strong due to the presence of large amount of generation units nearby there are still some questions that need to be investigated such as the issues underlining the operation of such a multi-infeed system, the proper design of the controls of the HVDC systems and the system dynamic performance under extreme contingencies. This paper investigates into an example of such a multi-infeed HVDC system. The authors have performed small signal analysis of the system to assess instability associated with the control modes. Electromechanical and voltage stability analysis were performed for harmful contingencies. Dynamic performance analysis was also carried out to analyze the interaction amongst various HVDC inverters during disturbances.
2005 IEEE/PES Transmission & Distribution Conference & Exposition: Asia and Pacific, 2005
The paper suggests an extension of the classical definition of Short Circuit Ratio and Effective ... more The paper suggests an extension of the classical definition of Short Circuit Ratio and Effective Short Circuit Ratio to multiple infeed of HVDC transmission configuration. With such new indexes, which consider the interaction between converter stations, it is possible to predict low frequency resonances, dynamic overvoltages and risk for voltage and power instability at low value of the index, similar to single infeed configuration. In this paper it is also discussed other relevant issues related to integration of multiple HVDC links when the strength of the system is relatively low compared to the amount of power delivered by the HVDC links.
It is well recognized that direct current and direct voltage offer special advantages for both la... more It is well recognized that direct current and direct voltage offer special advantages for both land and sea cable systems, both with regard to power transmission capability, losses, as well as possible transmission length due to no capacitive currents. As cable systems were used very early in large cities, one of the first applications considered for HVDC was to use it for city infeed and some schemes were also built. However, it turned out that the cost for the stations was too high and that the savings on the cable part were not high enough to justify the high costs of the converter stations, even considering other possible benefits of the HVDC techniques such as fast control of active power and almost no contribution to fault currents. During the 1990s new HVDC Voltage Source Converters, VSC, and new HVDC cables with solid insulation have been developed and the relative cost for the converters has been steadily decreasing. It was, therefore, found justifiable to reexamine the feasibility of using HVDC, especially based on the new VSC technique, for feeding electrical power to large cities. It was also decided, that the study should clarify the special requirements that had to be considered in the planning of city infeed systems as no good survey could be found. Because of this the study has been performed in close cooperation with a number of utilities responsible for the power supply of some medium sized and large cities. One such requirement, that also justified the study, was that it is expected that in the future more overhead lines in the cities or close to the cities have to be replaced by cables. Although the transmission and distribution of electrical power will be preferably made with conventional AC technique, but HVDC transmission would offer special advantages for long transmission cable, systems with especial requirements with regard to power flow control, systems with restrictions to short circuit currents, and other relevant issues related to city center infeed. The use of HVDC transmission to feed power into city centers will also be preferable when severe restrictions exist in the system that would require significant additional measures to mitigate using conventional AC technique. In those cases, the cost of these additional measures can be significant enough to justify the use of an alternative technique. Or, the implementation of those measures will make the system too complex to operate. In these cases, HVDC transmission would have advantages over the conventional AC solution, simplifying the operation of the system or resulting in a more economical solution.
The connection of a large wind farm to the electrical grid network is one of the main concerns of... more The connection of a large wind farm to the electrical grid network is one of the main concerns of the transmission system planners, especially when the strength of the system is relatively low compared to the amount of power delivered by the wind farm. The purpose of this paper is to make analysis of a configuration consisting of a Wind Farm based on conventional Fixed Speed Induction Generator. The generator is magnetized with fixed capaci- tor banks for unit power factor operation during steady state conditions. To increase the transient stability condi- tions of the generator a STATCOM is introduced in the system as an active voltage/var supporter. The paper quali- fies and quantifies the improved short-term voltage and rotor stability performance obtained when a STATCOM is introduced during different types of failure events in the connected power system.
Gastrointestinal Endoscopy, 2005
The paper suggests an extension of the classical definition of short circuit ratio and effective ... more The paper suggests an extension of the classical definition of short circuit ratio and effective short circuit ratio to multiple infeed of HVDC transmission configuration. With such new indexes, which consider the interaction between converter stations, it is possible to predict low frequency resonances, dynamic overvoltages and risk for voltage and power instability at low value of the index, similar
Tunnelling and Underground Space Technology, 2005
The paper covers the fundamental aspects of integration of multiple HVDC links feeding power into... more The paper covers the fundamental aspects of integration of multiple HVDC links feeding power into different points in the same ac network area. Considering that the number of power systems that includes this type of application of HVDC is increasing, the performance needs to be studied in detail. There are a number of technical aspects related to multiple infeed configurations with HVDC transmission links. Focus on critical network conditions where the strength of the system is relatively low as compared to the amount of power that the HVDC transmission links are feeding into the system will be given in this paper. In those cases the phenomena of concern that might occur which could result in adverse interaction among the HVDC transmission links and the receiving ac network are discussed. The following basic issues are addressed in the paper: voltage and power stability; coordination of power or voltage modulation between different HVDC links for stabilization of the ac network; nee...
2003 IEEE Bologna Power Tech Conference Proceedings,
Power flow control is needed to feed power into cities for different reasons: to ensure optimum p... more Power flow control is needed to feed power into cities for different reasons: to ensure optimum power flow in the system, to recover from emergency conditions, to reduce reactive power flow, and to reduce loop flows when the system topology is built up with rings. There are also other reasons, for example, to limit the short-circuit currents, to improve the
The interaction of an HVDC converter with the connected power system is of complex nature. An acc... more The interaction of an HVDC converter with the connected power system is of complex nature. An accurate model of the converter is required to study these interactions. The use of analytical small-signal converter models provides useful insight and understanding of the interaction of the HVDC system and the connected system components.
Urban electrical power systems with steep demand increase need easily located solutions with shor... more Urban electrical power systems with steep demand increase need easily located solutions with short lead time from decision to transmission. While AC cable solutions can offer sufficient power ratings, the problems of load controllability and short circuit power increase with every added circuit. These problems may be countered with Voltage Source Converter (VSC) based technology using DC-cables for transmission, such as HVDC Light®. This technology offers up to 500 MW per station with small footprint, ideal for infeed to city centers. Fast implementation is possible thanks to modular pre-assembled design and extruded polymer underground cables. System benefits from the VSC technology, such as independent full active and reactive power control and no added short circuit power makes it easy to apply in a heavily loaded grid. From an environmental point of view, the dc-cable technology gives virtually no alternating magnetic field and no risk for oil leakage. Higher transmission capaci...
Urban electrical power systems with steep demand increase need easily located solutions with shor... more Urban electrical power systems with steep demand increase need easily located solutions with short lead time from decision to transmission. While AC cable solutions can offer sufficient power ratings, the problems of load controllability and short circuit power increase with every added circuit. These problems may be countered with Voltage Source Converter (VSC) based technology using DC-cables for transmission, such as HVDC Light®. This technology offers up to 500 MW per station with small footprint, ideal for infeed to city centers. Fast implementation is possible thanks to modular pre-assembled design and extruded polymer underground cables. System benefits from the VSC technology, such as independent full active and reactive power control and no added short circuit power makes it easy to apply in a heavily loaded grid. From an environmental point of view, the dc-cable technology gives virtually no alternating magnetic field and no risk for oil leakage. Higher transmission capaci...
Proceedings. International Conference on Power System Technology
This paper presents a study of SSTI related to VSC HVDC. The study was conducted with well establ... more This paper presents a study of SSTI related to VSC HVDC. The study was conducted with well established methods, which have been used in the design of SSDC and evaluation of SSTI in classic HVDC. Identical control systems for VSC HVDC as in the real plant are included in the study. The paper will show how the VSC and its control contribute to the electrical damping on subsynchronous oscillations. Different operation modes, load levels, control modes and AC network conditions have been considered in the study.
2008 Joint International Conference on Power System Technology and IEEE Power India Conference, 2008
There are serious concerns relating to a Multi-Infeed HVDC system when feeding a weak AC network.... more There are serious concerns relating to a Multi-Infeed HVDC system when feeding a weak AC network. Typical issues concerning multi-infeed configurations are: need for coordination of the recovery control, need for different DC modulation strategies to stabilize the system, possibility of voltage instability of the area receiving large amount of power from multiple HVDC links and the risk of mutual commutation failures. In contrast, if the area receiving electrical power from multiple HVDC transmission links is relatively strong due to the presence of large amount of generation units nearby there are still some questions that need to be investigated such as the issues underlining the operation of such a multi-infeed system, the proper design of the controls of the HVDC systems and the system dynamic performance under extreme contingencies. This paper investigates into an example of such a multi-infeed HVDC system. The authors have performed small signal analysis of the system to assess instability associated with the control modes. Electromechanical and voltage stability analysis were performed for harmful contingencies. Dynamic performance analysis was also carried out to analyze the interaction amongst various HVDC inverters during disturbances.
2005 IEEE/PES Transmission & Distribution Conference & Exposition: Asia and Pacific, 2005
The paper suggests an extension of the classical definition of Short Circuit Ratio and Effective ... more The paper suggests an extension of the classical definition of Short Circuit Ratio and Effective Short Circuit Ratio to multiple infeed of HVDC transmission configuration. With such new indexes, which consider the interaction between converter stations, it is possible to predict low frequency resonances, dynamic overvoltages and risk for voltage and power instability at low value of the index, similar to single infeed configuration. In this paper it is also discussed other relevant issues related to integration of multiple HVDC links when the strength of the system is relatively low compared to the amount of power delivered by the HVDC links.
It is well recognized that direct current and direct voltage offer special advantages for both la... more It is well recognized that direct current and direct voltage offer special advantages for both land and sea cable systems, both with regard to power transmission capability, losses, as well as possible transmission length due to no capacitive currents. As cable systems were used very early in large cities, one of the first applications considered for HVDC was to use it for city infeed and some schemes were also built. However, it turned out that the cost for the stations was too high and that the savings on the cable part were not high enough to justify the high costs of the converter stations, even considering other possible benefits of the HVDC techniques such as fast control of active power and almost no contribution to fault currents. During the 1990s new HVDC Voltage Source Converters, VSC, and new HVDC cables with solid insulation have been developed and the relative cost for the converters has been steadily decreasing. It was, therefore, found justifiable to reexamine the feasibility of using HVDC, especially based on the new VSC technique, for feeding electrical power to large cities. It was also decided, that the study should clarify the special requirements that had to be considered in the planning of city infeed systems as no good survey could be found. Because of this the study has been performed in close cooperation with a number of utilities responsible for the power supply of some medium sized and large cities. One such requirement, that also justified the study, was that it is expected that in the future more overhead lines in the cities or close to the cities have to be replaced by cables. Although the transmission and distribution of electrical power will be preferably made with conventional AC technique, but HVDC transmission would offer special advantages for long transmission cable, systems with especial requirements with regard to power flow control, systems with restrictions to short circuit currents, and other relevant issues related to city center infeed. The use of HVDC transmission to feed power into city centers will also be preferable when severe restrictions exist in the system that would require significant additional measures to mitigate using conventional AC technique. In those cases, the cost of these additional measures can be significant enough to justify the use of an alternative technique. Or, the implementation of those measures will make the system too complex to operate. In these cases, HVDC transmission would have advantages over the conventional AC solution, simplifying the operation of the system or resulting in a more economical solution.
The connection of a large wind farm to the electrical grid network is one of the main concerns of... more The connection of a large wind farm to the electrical grid network is one of the main concerns of the transmission system planners, especially when the strength of the system is relatively low compared to the amount of power delivered by the wind farm. The purpose of this paper is to make analysis of a configuration consisting of a Wind Farm based on conventional Fixed Speed Induction Generator. The generator is magnetized with fixed capaci- tor banks for unit power factor operation during steady state conditions. To increase the transient stability condi- tions of the generator a STATCOM is introduced in the system as an active voltage/var supporter. The paper quali- fies and quantifies the improved short-term voltage and rotor stability performance obtained when a STATCOM is introduced during different types of failure events in the connected power system.
Gastrointestinal Endoscopy, 2005
The paper suggests an extension of the classical definition of short circuit ratio and effective ... more The paper suggests an extension of the classical definition of short circuit ratio and effective short circuit ratio to multiple infeed of HVDC transmission configuration. With such new indexes, which consider the interaction between converter stations, it is possible to predict low frequency resonances, dynamic overvoltages and risk for voltage and power instability at low value of the index, similar