EPE Association: EPE 1987 - 29 - Lecture Session 5.2: HVDC AND HARMONICS

EPE 1987 - 29 - Lecture Session 5.2: HVDC AND HARMONICS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1987 - Conference > EPE 1987 - 29 - Lecture Session 5.2: HVDC AND HARMONICS

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   IMPROVING THE STABILITY OF HVDC TRANSMISSION TO WEAK NETWORKS
By H.-J. Knaak; A. Venne [View]
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Abstract: High Voltage Direct Current (HVDC) systems are used to transport electric energy over large distances or to exchange energy between asynchronous networks. HVDC equipment of modern design is able to work with relatively weak ac systems having a low resonance frequency. The line-commutating thyristor converters of an HVDC system produce characteristic harmonics and possibly, depending on several circumstances, non-characteristic harmonics. This can lead to harmonic instability, if the resonance frequency of the network is close to one of these harmonics. The instability mechanism for the second harmonic is explained and a method is presented, which is able to avoid second harmonic instability by means of control actions. For this purpose, the power frequency component of the direct current is detected by a special filtering system with dc output signals. This new approach allows the use of a PI controller to create a stabilizing signal, which is used to modulate the delay angle of the rectifier side. During field tests on a back-to-back tie, the stabilizing effect of this measure was demonstrated successfully.

   THE PROPAGATION OF HARMONIC CURRENTS GENERATED BY INVERTER-FED LOCOMOTIVES IN THE DISTRIBUTED OVERHEAD SUPPLY SYSTEM
By Joachim Holtz; Heinz-Jürgen Klein [View]
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Abstract: Modern PWM converter-fed locomotives generate current harmonics which give rise to travelling waves in the overhead supply system. The waves are partially reflected at the feeding substations, causing parallel and series resonances at various discrete frequencies. An investigation based on the wave propagation approach demonstrates the influence of the track topography and the varying position of locomotives within the track. The distribution of harmonic currents in the overhead supply system is evaluated and discussed. It is shown that these currents are much higher in certain locations of the railway track than the harmonic current injected by a locomotive.

EPE 1987 - 29 - Lecture Session 5.2: HVDC AND HARMONICS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1987 - Conference > EPE 1987 - 29 - Lecture Session 5.2: HVDC AND HARMONICS
	[return to parent folder]

	IMPROVING THE STABILITY OF HVDC TRANSMISSION TO WEAK NETWORKS By H.-J. Knaak; A. Venne	[View] [Download]
Abstract: High Voltage Direct Current (HVDC) systems are used to transport electric energy over large distances or to exchange energy between asynchronous networks. HVDC equipment of modern design is able to work with relatively weak ac systems having a low resonance frequency. The line-commutating thyristor converters of an HVDC system produce characteristic harmonics and possibly, depending on several circumstances, non-characteristic harmonics. This can lead to harmonic instability, if the resonance frequency of the network is close to one of these harmonics. The instability mechanism for the second harmonic is explained and a method is presented, which is able to avoid second harmonic instability by means of control actions. For this purpose, the power frequency component of the direct current is detected by a special filtering system with dc output signals. This new approach allows the use of a PI controller to create a stabilizing signal, which is used to modulate the delay angle of the rectifier side. During field tests on a back-to-back tie, the stabilizing effect of this measure was demonstrated successfully.

	THE PROPAGATION OF HARMONIC CURRENTS GENERATED BY INVERTER-FED LOCOMOTIVES IN THE DISTRIBUTED OVERHEAD SUPPLY SYSTEM By Joachim Holtz; Heinz-Jürgen Klein	[View] [Download]
Abstract: Modern PWM converter-fed locomotives generate current harmonics which give rise to travelling waves in the overhead supply system. The waves are partially reflected at the feeding substations, causing parallel and series resonances at various discrete frequencies. An investigation based on the wave propagation approach demonstrates the influence of the track topography and the varying position of locomotives within the track. The distribution of harmonic currents in the overhead supply system is evaluated and discussed. It is shown that these currents are much higher in certain locations of the railway track than the harmonic current injected by a locomotive.