Based on the transmission theory, the mechanism of the generation of the motor terminal over voltage caused by the long line transmission of PWM pulses in the PWM variable frequency driving system is studied. This p...Based on the transmission theory, the mechanism of the generation of the motor terminal over voltage caused by the long line transmission of PWM pulses in the PWM variable frequency driving system is studied. This paper focuses on the effects of the variant length and characteristic impedance of cables on the over voltage by large numbers of experiment results. In terms of the impedance matching method, a network fixed at motor terminal is designed to reduce the over voltage. The utility of this network is testified by the experiments.展开更多
The first completely localized DC back-to-back project for asynchronous interconnection between Northwest and Central China plays an important role in realizing national power grid interconnection, spurring indigenous...The first completely localized DC back-to-back project for asynchronous interconnection between Northwest and Central China plays an important role in realizing national power grid interconnection, spurring indigenous manufacturing industries and promoting DC transmission equipment. Insisting on the principle of autonomous innovation, this project was based on domestic forces in every aspect, from engineering organization, system design, equipment completion, engineering design, equipment manufacturing and procurement to construction and debugging. By passing through strict quality control, intermediate supervision and acceptance test and assessment, the project has been proved up to world advanced level.展开更多
In this paper a practical but sufficiently accurate method of calculating transient components in short circuit currents and voltages is proposed. It enables to find the roots of the chara...In this paper a practical but sufficiently accurate method of calculating transient components in short circuit currents and voltages is proposed. It enables to find the roots of the characteristic equation of high order without forming and solving it. This method is convenient to use especially in case of complicated expansionary power systems.展开更多
This paper gives an insight on the effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system＇s steady state and dynamic performance. The impact of dy...This paper gives an insight on the effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system＇s steady state and dynamic performance. The impact of dynamic load models on system stability is also studied. The steady-state and dynamic stability simulation results of a 39 bus system for constant line impedance （the traditional simulation practice） are compared to the results with estimated, but realistic, temperature varied line impedances using PSLF （positive sequence load flow） software. The modulated line impedances will affect the thermal loading levels and voltage profiles of buses under steady state response, while the dynamic results will show improved damping in electro-mechanical oscillations at generator buses.展开更多
In this article, a transmission line is represented by a cascade of n circuits using a single phase. It is analyzed what is the reasonable number of n circuits and the number of blocks composed by parallel resistor an...In this article, a transmission line is represented by a cascade of n circuits using a single phase. It is analyzed what is the reasonable number of n circuits and the number of blocks composed by parallel resistor and inductor in parallel for reduction of numerical oscillations. It is simulated the numerical routine with and without the effectof frequency in the longitudinal parameters. Initially, it is used to state variables and 7t circuits representing the transmission line composing a linear system which is solved by numerical routines based on the trapezoidal rule. The effect of frequency on the line is synthesized by resistors and inductors in parallel and this representation is analyzed in details. It is described as transmission lines and the frequency influence in these lines through the state variables.展开更多
文摘Based on the transmission theory, the mechanism of the generation of the motor terminal over voltage caused by the long line transmission of PWM pulses in the PWM variable frequency driving system is studied. This paper focuses on the effects of the variant length and characteristic impedance of cables on the over voltage by large numbers of experiment results. In terms of the impedance matching method, a network fixed at motor terminal is designed to reduce the over voltage. The utility of this network is testified by the experiments.
文摘The first completely localized DC back-to-back project for asynchronous interconnection between Northwest and Central China plays an important role in realizing national power grid interconnection, spurring indigenous manufacturing industries and promoting DC transmission equipment. Insisting on the principle of autonomous innovation, this project was based on domestic forces in every aspect, from engineering organization, system design, equipment completion, engineering design, equipment manufacturing and procurement to construction and debugging. By passing through strict quality control, intermediate supervision and acceptance test and assessment, the project has been proved up to world advanced level.
文摘In this paper a practical but sufficiently accurate method of calculating transient components in short circuit currents and voltages is proposed. It enables to find the roots of the characteristic equation of high order without forming and solving it. This method is convenient to use especially in case of complicated expansionary power systems.
文摘This paper gives an insight on the effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system＇s steady state and dynamic performance. The impact of dynamic load models on system stability is also studied. The steady-state and dynamic stability simulation results of a 39 bus system for constant line impedance （the traditional simulation practice） are compared to the results with estimated, but realistic, temperature varied line impedances using PSLF （positive sequence load flow） software. The modulated line impedances will affect the thermal loading levels and voltage profiles of buses under steady state response, while the dynamic results will show improved damping in electro-mechanical oscillations at generator buses.
文摘In this article, a transmission line is represented by a cascade of n circuits using a single phase. It is analyzed what is the reasonable number of n circuits and the number of blocks composed by parallel resistor and inductor in parallel for reduction of numerical oscillations. It is simulated the numerical routine with and without the effectof frequency in the longitudinal parameters. Initially, it is used to state variables and 7t circuits representing the transmission line composing a linear system which is solved by numerical routines based on the trapezoidal rule. The effect of frequency on the line is synthesized by resistors and inductors in parallel and this representation is analyzed in details. It is described as transmission lines and the frequency influence in these lines through the state variables.
