High-Power L110 Hybrid / EV-only Regen Potential Issues?

[mdrobnak]

I was out on a walk and was thinking about what was said with respect to the interaction of the ICE speed vs MG1's regen and how if you were going to bypass the buck/boost converter, you may have to severely limit the Engine RPM in order to not grossly exceed the battery voltage. My thoughts then went to two possible options:

1. Determine which components needed to be upgraded to support more power across the buck / boost converter.

2. Run MG1 through the converter, and MG2 directly from battery.

If 2 were possible that seems like that would be the ideal case. But then thinking upon this further - doesn't that mean that MG2 will run into the exact same issue under regenerative braking as MG1 would be being driven by the engine? If so, doesn't that effectively mean that either regen couldn't be enabled above a certain RPM, or that it'll never work?

What am I missing, and if I'm not missing anything, how can this be made to work?

-Matt

[arber333]

I was out on a walk and was thinking about what was said with respect to the interaction of the ICE speed vs MG1's regen and how if you were going to bypass the buck/boost converter, you may have to severely limit the Engine RPM in order to not grossly exceed the battery voltage. My thoughts then went to two possible options:

1. Determine which components needed to be upgraded to support more power across the buck / boost converter.

2. Run MG1 through the converter, and MG2 directly from battery.

If 2 were possible that seems like that would be the ideal case. But then thinking upon this further - doesn't that mean that MG2 will run into the exact same issue under regenerative braking as MG1 would be being driven by the engine? If so, doesn't that effectively mean that either regen couldn't be enabled above a certain RPM, or that it'll never work?

What am I missing, and if I'm not missing anything, how can this be made to work?

-Matt

Hm... Wouldnt HV battey perform as RC load to MG1/2 in regen? I am speculating but when you use FW you are in effect boosting voltage across motor winding so field is allowed to rotate faster. If you then regen at higher RPM what you get back is slightly higher votlage and much higher amp load than normal.
Last week i was in a hurry to get home and i sped on our highway at 150km/h or so which is 10000rpm give or take. When i was on a downslope i set regen to max, released throttle and observed amps flowing.
Before continuing let me explain i set limit for max battery regen current conservatively at 100A which is enough to efficiently stop you - medium braking effect, nothing panic.

Now at 150km/h downhill i saw 170A flowing back!!! Way more than i set limit current at. But as speed reduced i saw it wind down towards 100A slowly. At 100km/h i only saw about 100A.

I expect if you boost(or provide higher voltage) back into the battery it will sink amps similarly like my crude AC autotransformer charger. If i set it to 400V rectified it can sink 60A into the battery directly, but as voltage equalizes you see current diminishing.

[celeron55]

Field weakening can allow a motor to run faster than what it could run as a simple generator. No idea if Toyota's motor control will do field weakening in a way that will support this, as the boost converter would enable them to entirely skip field weakening (and avoid losing power and efficiency due to it).

[mdrobnak]

I always forget about field weakening. But I'm going to assume that's not in play here, at least not in the MG1 situation, as it's being driven by the engine externally.

I guess the other issue is we don't have working regen (as of the last time I looked into this deeply) so the current behavior is unknown at the moment.

I'm trying to think this through before making a working vehicle into a nonworking one.

I guess it would be useful to see some real-world data from other setups.

-Matt