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Re: New transportation bills signed into law? Regen
Author: Clem
Date: 09-29-2024 - 19:39
Of course. I don't have detailed engineering drawings of the Caltrain traction power configuration, but I do have a copy of the RFP for their Traction Power Supply System, which stated as a requirement:
A power quality study by rolling stock consultant LTK, also included in the RFP package, contains the following:
LRVs are a very different animal, using low voltage DC traction. Modern 25 kV AC power control electronics can regenerate a clean sinusoidal waveform (with negligible harmonics) that can be fed right back through the traction transformers into one phase of the 115 kV grid if no local load exists to absorb it.
The single-phase unbalanced loading (actually, two phases at each of the two substations, since the corridor is electrically subdivided into four sections) is already accounted for in all their traction power load flow analysis, including contingency cases where 3/4 of the corridor hangs off one phase of one 115 kV feed. I imagine the imbalance from regeneration is not very remarkable compared to that.
Caltrain is also pursuing a net metering arrangement, as part of their energy procurement strategy, to reduce their energy costs by offsetting the amount fed back into the grid.
I checked the EMU RFP docs and you are correct, there are indeed brake resistors but they are rarely used (such as when no overhead power is connected, or when line voltage > 29 kV, the limit for regeneration).
Quote:The TPSS control and protection devices shall be configured to allow regenerative braking to permit power flow back into the utility grid, while also protecting against feeding faults on the utility 115kV incoming lines with regenerative braking energy.
A power quality study by rolling stock consultant LTK, also included in the RFP package, contains the following:
Quote:The regenerated power is consumed as follows:
• First, the regenerated power supplies the auxiliary equipment on-board of the train.
• When the auxiliary equipment power demand is satisfied, any excess regenerated power is fed through the train pantograph into the overhead power distribution system and is available for consumption by other rolling stock operating in the same section of the system.
• In the event that there is no rolling stock in the section, or the other trains do not require additional power, the excess power is fed back into the power utility system.
LRVs are a very different animal, using low voltage DC traction. Modern 25 kV AC power control electronics can regenerate a clean sinusoidal waveform (with negligible harmonics) that can be fed right back through the traction transformers into one phase of the 115 kV grid if no local load exists to absorb it.
The single-phase unbalanced loading (actually, two phases at each of the two substations, since the corridor is electrically subdivided into four sections) is already accounted for in all their traction power load flow analysis, including contingency cases where 3/4 of the corridor hangs off one phase of one 115 kV feed. I imagine the imbalance from regeneration is not very remarkable compared to that.
Caltrain is also pursuing a net metering arrangement, as part of their energy procurement strategy, to reduce their energy costs by offsetting the amount fed back into the grid.
I checked the EMU RFP docs and you are correct, there are indeed brake resistors but they are rarely used (such as when no overhead power is connected, or when line voltage > 29 kV, the limit for regeneration).
