EPE Association: EPE 1993 - 17 - Lecture Session L6b: SYSTEM ENGINEERING: HARMONICS, EMC, RFI

EPE 1993 - 17 - Lecture Session L6b: SYSTEM ENGINEERING: HARMONICS, EMC, RFI
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 17 - Lecture Session L6b: SYSTEM ENGINEERING: HARMONICS, EMC, RFI

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   LOW FREQUENCY AND RADIO FREQUENCY ELECTROMAGNETIC COMPABILITY FOR RAPID TRANSIT RAILWAYS
By J. Allan; W. S. Chan; Z. Y. Shao; B. Mellitt [View]
[Download]

Abstract: This paper begins by explaining how EMC with signalling equipment first became identified as a major issue for rapid transit railway traction engineers when variable frequency chopper power electronic controllers were introduced due to adverse interaction with signalling systems. It explains the nature of the problem and the early steps taken to solve it by traction engineers, principally fixed frequency operation. Evolution of the signalling equipment in relation to this problem is explained together with design rules that still need to be applied to chopper traction drives even with modern signalling equipment. The introduction of inverter drives has created a similar situation to that for the early chopper drives. The paper shows this time, the EMC factor bas been solved despite the variation in frequency of operation inherent in a variable frequency variable voltage inverter drive. Finally, the paper introduces the new EMC problems being faced with radio frequency equipment and the inadequacy of existing European standards.

   REDUCTION OF TRANSFORMER RATED POWER AND LINE CURRENT HARMONICS IN A PRIMARY SWITCHED CONVERTER SYSTEM FOR TRACTION APPLICATIONS
By S. Östlund [View]
[Download]

Abstract: The transformer of traction vehicles fed from a 15 kV, 162/3 Hz AC supply has due to the low frequency a substantial weight. By using a primary switched converter system the transformer frequency can be increased and a reduction of the weight is possible. For a fixed frequency the transformer weight is determined mainly by its rated power. The rated power has to be about twice the transmitted power which limits the weight reduction. If the four-quadrant converter of the primary switched system is used for modulation of the line current, the transformer has to operate at a varying frequency. In the paper it is shown that the transformer rated power then can be reduced by approximately 40 % compared to constant frequency. The current modulation principle requires a fairly high operating frequency of the four-quadrant converter. Current modulation has with regard to line current harmonics been compared with a principle for harmonic reduction based on a division of the primary converter into several converters connected in series. The system then operates with a sinusoidally varying transformer voltage ratio thus increasing the number of possible line current derivatives. Computer simulations of a 4 MW system show that a division into six primary converters reduces the psofometric distortion current by more than 50 %.

   A HIGH POWER VOLTAGE SOURCE RECTIFIER WITH SINUSOIDAL INPUTS
By X. Pierre; J. P. Cambronne; J.L. Thomas [View]
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Abstract: To obtain a high-power DC current source, the SCR bridge is frequently used. The reactive power consumption, the line current absorption with high harmonic distortion combined with important filters, and a slow dynamic response are the main disadvantages of the previous actuator. An alternative approach is to use a 6 GTO structure associated with a three-phase line LC filter. A current control loop combined with the PWM space vector modulation synthesis assume an optimal input-output dynamic performance and a high line-current spectrum quality. Simulation results are discussed and demonstrate the effectiveness of the entire system behaviour.

   INTERFERENCE lMMUNITY TESTS OF AN HVDC VALVE SECTION CONSISTING OF TWO THYRISTOR LEVELS
By J. P. Ballad; J. K. Chester; R. C. Riley; N. Y. A. Shammas [View]
[Download]

Abstract: The constituent thyristor valves of High Voltage Direct Current (HVDC) convertor bridges are commonly installed as four-high stacks, presenting the possibility of electric and magnetic coupling into the thyristor gate electronics units in one valve occurring as a result of current and voltage transient in an adjacent valve. These electronic units perform the essential functions of firing, protection and monitoring of the thyristor levels. For reliable long term operation of the convertor bridges, these functions should not be corrupted. In general, immunity to Electromagnetic Interference (EMI) is demonstrated during the application of type tests on a complete thyristor valve or on valve sections (modules) as described in IEC700. However, during design and development testing and, in particular, when the interactions between adjacent valves must be investigated, special tests on reduced scale test objects are often required. The paper describes three onerous tests designed to represent the most severe levels of coupling expected in practice. The tests were applied to a standard fully equipped valve section comprising two series connected 100 mm diameter thyristors to demonstrate its immunity to such interference.

EPE 1993 - 17 - Lecture Session L6b: SYSTEM ENGINEERING: HARMONICS, EMC, RFI
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 17 - Lecture Session L6b: SYSTEM ENGINEERING: HARMONICS, EMC, RFI
	[return to parent folder]

	LOW FREQUENCY AND RADIO FREQUENCY ELECTROMAGNETIC COMPABILITY FOR RAPID TRANSIT RAILWAYS By J. Allan; W. S. Chan; Z. Y. Shao; B. Mellitt	[View] [Download]
Abstract: This paper begins by explaining how EMC with signalling equipment first became identified as a major issue for rapid transit railway traction engineers when variable frequency chopper power electronic controllers were introduced due to adverse interaction with signalling systems. It explains the nature of the problem and the early steps taken to solve it by traction engineers, principally fixed frequency operation. Evolution of the signalling equipment in relation to this problem is explained together with design rules that still need to be applied to chopper traction drives even with modern signalling equipment. The introduction of inverter drives has created a similar situation to that for the early chopper drives. The paper shows this time, the EMC factor bas been solved despite the variation in frequency of operation inherent in a variable frequency variable voltage inverter drive. Finally, the paper introduces the new EMC problems being faced with radio frequency equipment and the inadequacy of existing European standards.

	REDUCTION OF TRANSFORMER RATED POWER AND LINE CURRENT HARMONICS IN A PRIMARY SWITCHED CONVERTER SYSTEM FOR TRACTION APPLICATIONS By S. Östlund	[View] [Download]
Abstract: The transformer of traction vehicles fed from a 15 kV, 162/3 Hz AC supply has due to the low frequency a substantial weight. By using a primary switched converter system the transformer frequency can be increased and a reduction of the weight is possible. For a fixed frequency the transformer weight is determined mainly by its rated power. The rated power has to be about twice the transmitted power which limits the weight reduction. If the four-quadrant converter of the primary switched system is used for modulation of the line current, the transformer has to operate at a varying frequency. In the paper it is shown that the transformer rated power then can be reduced by approximately 40 % compared to constant frequency. The current modulation principle requires a fairly high operating frequency of the four-quadrant converter. Current modulation has with regard to line current harmonics been compared with a principle for harmonic reduction based on a division of the primary converter into several converters connected in series. The system then operates with a sinusoidally varying transformer voltage ratio thus increasing the number of possible line current derivatives. Computer simulations of a 4 MW system show that a division into six primary converters reduces the psofometric distortion current by more than 50 %.

	A HIGH POWER VOLTAGE SOURCE RECTIFIER WITH SINUSOIDAL INPUTS By X. Pierre; J. P. Cambronne; J.L. Thomas	[View] [Download]
Abstract: To obtain a high-power DC current source, the SCR bridge is frequently used. The reactive power consumption, the line current absorption with high harmonic distortion combined with important filters, and a slow dynamic response are the main disadvantages of the previous actuator. An alternative approach is to use a 6 GTO structure associated with a three-phase line LC filter. A current control loop combined with the PWM space vector modulation synthesis assume an optimal input-output dynamic performance and a high line-current spectrum quality. Simulation results are discussed and demonstrate the effectiveness of the entire system behaviour.

	INTERFERENCE lMMUNITY TESTS OF AN HVDC VALVE SECTION CONSISTING OF TWO THYRISTOR LEVELS By J. P. Ballad; J. K. Chester; R. C. Riley; N. Y. A. Shammas	[View] [Download]
Abstract: The constituent thyristor valves of High Voltage Direct Current (HVDC) convertor bridges are commonly installed as four-high stacks, presenting the possibility of electric and magnetic coupling into the thyristor gate electronics units in one valve occurring as a result of current and voltage transient in an adjacent valve. These electronic units perform the essential functions of firing, protection and monitoring of the thyristor levels. For reliable long term operation of the convertor bridges, these functions should not be corrupted. In general, immunity to Electromagnetic Interference (EMI) is demonstrated during the application of type tests on a complete thyristor valve or on valve sections (modules) as described in IEC700. However, during design and development testing and, in particular, when the interactions between adjacent valves must be investigated, special tests on reduced scale test objects are often required. The paper describes three onerous tests designed to represent the most severe levels of coupling expected in practice. The tests were applied to a standard fully equipped valve section comprising two series connected 100 mm diameter thyristors to demonstrate its immunity to such interference.