EvseManager¶
Handwritten Documentation¶
The module EvseManager is a central module that manages one EVSE
(i.e. one connector to charge a car).
It may control multiple physical connectors if they are not usable at the same
time and share one connector id,
but one EvseManager always shows as one connector in OCPP for example. So in
general each connector should have a dedicated EvseManager module loaded.
The EvseManager contains the high level charging logic (Basic charging and HLC/SLAC interaction), collects all relevant data for the charging session (e.g. energy delivered during this charging session) and provides control over the charging port/session. For HLC it uses two helper protocol modules that it controls (SLAC and ISO15118).
Protocol modules such as OCPP or other APIs use EvseManagers to control the charging session and get all relevant data.
The following charge modes are supported:
AC charging: Basic Charging according to IEC61851/SAE J1772 and HLC according to ISO15118-2
DC charging: ISO15118-2 and DIN SPEC 70121
Additional features:
Autocharge support (PnC coming soon)
Seamlessly integrates into EVerest Energy Management
The lowest level IEC61851 state machine can be run on a dedicated microcontroller for improved electrical safety
Support for seperate AC and DC side metering in DC application
Typical connections¶
TODO: AC and DC module graphs and description
AC Configuration¶
DC Configuration¶
In DC applications, the EvseManager still has an AC side that behaves similar to a normal AC charger. The board_support module therefore still has to report AC capabilities which refer to the AC input of the AC/DC power supply. If an AC side RCD is used it also belongs to the board_support driver. An AC side power meter can be connected and it will be used for Energy management.
In addition, on the DC side the following hardware modules can be connected:
A DC powermeter: This will be used for billing purposes if present. If not connected, billing will fall back to the AC side power meter.
Isolation monitoring: This will be used to monitor isolation during CableCheck, PreCharge and CurrentDemand steps.
DC power supply: This is the AC/DC converter that actually charges the car.
Software over-voltage supervision is always active during DC charging. The configuration option
internal_over_voltage_duration_ms defines for how long the measured DC voltage
must exceed the negotiated limit before EvseManager raises MREC5OverVoltage.
Set it to 0 to trigger immediately once the threshold is crossed.
Software over-voltage supervision is always active during DC charging. The configuration option
internal_over_voltage_duration_ms defines for how long the measured DC voltage
must exceed the negotiated limit before EvseManager raises MREC5OverVoltage.
Set it to 0 to trigger immediately once the threshold is crossed.
Published variables¶
session_events¶
EvseManager publishes the session_events variable whenever an event happens. It does not publish its internal state but merely events that happen that can be used to drive an state machine within another module.
Example: Write a simple module that lights up an LED if the evse is reserved. This module requires an EvseManager and subscribes to the session_events variable. Internally it has only two states: Reserved (LED on), NotReserved (LED off).
The state machine transitions are driven by the two events from EvseManager: ReservationStart and ReservationEnd.
All other events are ignored in this module as they are not needed.
powermeter¶
EvseManager republishes the power meter struct that if it has a powermeter connected. This struct should be used for OCPP and display purposes. It comes from the power meter that can be used for billing (DC side on DC, AC side on AC). If no powermeter is connected EvseManager will never publish this variable.
Authentication¶
The Auth modules validates tokens and assignes tokens to EvseManagers, see Auth
documentation. It will call Authorize(id_tag, pnc) on EvseManager to
indicated that the EvseManager may start the charging session.
Auth module may revoke authorization (withdraw_authorization command) if
the charging session has not begun yet (typically due to timeout), but not once
charging has started.
Autocharge / PnC¶
Autocharge is fully supported, PnC support is coming soon and will use the same
logic. The car itself is a token provider that can provide an auth token to be
validated by the Auth system (see Auth documentation for more details).
EvseManager provides a token_provider interface for that purpose.
If external identification (EIM) is used in HLC (no PnC) then Autocharge is
enabled by connecting the token_provider interface to Auth module. When the
car sends its EVCCID in the HLC protocol it is converted to Autocharge format
and published as Auth token. It is based on the following specification:
To enable PnC the config option payment_enable_contract must be set to
true. If the car selects Contract instead of EIM PnC will be used instead of
Autocharge.
Reservation¶
Reservation handling logic is implemented in the Auth module. If the Auth module wants to reserve a specific EvseManager (or cancel the reservation) it needs to call the reserve/cancel_reservation commands. EvseManager does not check reservation id against the token id when it should start charging, this must be handled in Auth module. EvseManager only needs to know whether it is reserved or not to emit an ReservatonStart/ReservationEnd event to notify other modules such as OCPP and API or e.g. switch on a specific LED signal on the charging port.
Energy Management¶
EvseManager seamlessly intergrates into the EVerest Energy Management. For further details refer to the documentation of the EnergyManager module.
EvseManager has a grid facing Energy interface which the energy tree uses to provide energy for the charging sessions. New energy needs to be provided on regular intervals (with a timeout).
If the supplied energy limits time out, EvseManager will stop charging. This prevents e.g. overload conditions when the network connection drops between the energy tree and EvseManager.
EvseManager will send out its wishes at regular intervals: It sends a
requested energy schedule into the energy tree that is merged from hardware
capabilities (as reported by board_support module), EvseManager module
configuration settings
(max_current, three_phases) and external limts (via set_external_limits
command) e.g. set by OCPP module.
Note that the set_external_limits should not be used by multiple modules,
as the last one always wins. If you have multiple sources of exernal limits
that you want to combine, add extra EnergyNode modules in the chain and
feed in limits via those.
The combined schedule sent to the energy tree is the minimum of all energy limits.
After traversing the energy tree the EnergyManager will use this information to assign limits (and a schedule) for this EvseManager and will call enforce_limits on the energy interface. These values will then be used to configure PWM/DC power supplies to actually charge the car and must not be confused with the original wishes that were sent to the energy tree.
The EvseManager will never assign energy to itself, it always requests energy from the energy manager and only charges if the energy manager responds with an assignment.
Limits in the energy object can be specified in ampere (per phase) and/or watt. Currently watt limits are unsupported, but it should behave according to that logic:
If both are specified also both limits will be applied, whichever is lower. With DC charging, ampere limits apply to the AC side and watt limits apply to both AC and DC side.
Energy Management: 1ph/3ph switching¶
EVerest has support for switching between 1ph and 3ph configurations during AC charging (e.g. for solar charging when sometimes charging with less then 4.2kW (6A*230V*3ph) if desired).
Be warned: Some vehicles (such as first generation of Renault Zoe) may be permanently damaged when switching from 1ph to 3ph during charging. Use at your own risk!
To use this feature several things need to be enabled:
In EvseManager, adjust two config options to your needs:
switch_3ph1ph_delay_s,switch_3ph1ph_cp_stateIn the BSP driver, set
supports_changing_phases_during_chargingto true in the reported capabilities. If your bsp hardware detects e.g. the Zoe, you can set that flag to false and publish updated capabilities any time.BSP driver capabilities: Also make sure that minimum phases are set to one and maximum phases to 3
BSP driver: make sure the
ac_switch_three_phases_while_chargingcommand is correctly implementedEnergyManager: Adjust
switch_3ph1ph_while_charging_mode,switch_3ph1ph_max_nr_of_switches_per_session,switch_3ph1ph_switch_limit_stickyness,switch_3ph1ph_power_hysteresis_W,switch_3ph1ph_time_hysteresis_sconfig options to your needs
If all of this is properly set up, the EnergyManager will drive the 1ph/3ph switching. In order to do so, it needs an (external) limit to be set. There are two options: The external limit can be in Watt (not in Ampere), even though we are AC charging. This is the preferred option as it gives the freedom to the EnergyManager to decide when to switch. The limit can come from OCPP schedule or e.g. via an additional EnergyNode.
The second option is to set a limit in Ampere and set a limitation on the number of phases (e.g. min_phase=1, max_phase=1). This will enforce switching and can be used to decide the switching time externally. EnergyManager does not have the freedom to make the choice in this case.
Take care especially with the power(watt) and time based hysteresis settings. They should be adjusted to the actual use case to avoid relays wearing due too a lot of switching cycles. Consider also to limit the maximum number of switching cycles per charging session.
Error Handling¶
The control flow of this module can be influenced by the error implementation of its requirements. This section documents the side effects that can be caused by errors raised by a requirement.
This module subscribes to all errors of the following requirements:
evse_manager
evse_board_support
connector_lock
ac_rcd
isolation_monitor
power_supply_DC
powermeter (if the config option fail_on_powermeter_errors is set true)
A raised error can cause the EvseManager to stop the charging session and become inoperative. Charging is not possible until the error is cleared. If no charging session is currently running, it will prevent sessions from being started. If a charging session is currently running and an error is raised this will interrupt the charging session.
Almost all errors that are reported from the requirements of this module cause the EvseManager to become Inoperative until the error is cleared. The following sections provide an overview of the errors that do not cause the EvseManager to become Inoperative.
evse_manager¶
evse_manager/Inoperative
evse_manager/MREC11CableCheckFault
evse_board_support¶
evse_board_support/MREC3HighTemperature
evse_board_support/MREC18CableOverTempDerate
evse_board_support/VendorWarning
connector_lock¶
connector_lock/VendorWarning
ac_rcd¶
ac_rcd/VendorWarning
isolation_monitor¶
isolation_monitor/VendorWarning
power_supply_DC¶
power_supply_DC/VendorWarning
powermeter¶
Powermeter errors cause the EvseManager to become Inoperative, if fail_on_powermeter_errors is configured to true. If it is configured to false, errors from the powermeter will not cause the EvseManager to become Inoperative.
powermeter/CommunicationFault
When a charging session is stopped because of an error, the EvseManager differentiates between Emergency Shutdowns and Error Shutdowns. The severity of the error influences the type of the shudown. Emergency shutdowns are caused by errors with Severity::High and error shutdowns are caused by errors with Severity::Medium or Severity::Low.
In case of an Emergency Shutdown the EvseManager will immediately:
Signal PWM state F if HLC is not active
Turn off the PWM
Turn off the DC power supply in case of DC
Signal to open the contactor
In case of an Error Shutdown the EvseManager will:
Signal PWM state F if HLC is not active
Keep the PWM on if HLC is active
Turn off the DC power supply in case of DC
Signal to open the contactor
Report the error via HLC to the EV (if HLC active)