1 Description
- 1.1 Active power control
- 1.2 Reactive Power Control
- 1.3 Current limit logic
- 1.4 Battery state of charge
2 Mask and Parameter
- 2.1 General Parameters
- 2.2 Voltage-dependent Limits
- 2.3 Initial Values
3 Inputs, Outputs and Signal Available for Monitoring
- 3.1 Inputs
- 3.2 Outputs
4 Acknowledgements
5 Reference

Description

The Renewable Energy Electrical Controller – Type C (REEC_C) is a WECC standard dynamic model for the purpose of modeling battery energy storage systems (BESS). This model removes some of the complexity around the switching logic for current injection during a fault, as much of this was developed in REEC_A. It also includes a simple model for the charging and discharging of the battery to allow for modeling the state of charge (SOC) of the battery.

It regulates current, voltage, and reactive power using measurements at the Point of Measurement (POM), while tracking voltage and reactive power objectives defined at the Point of Interconnection (POI). The block model mainly contains four parts:

Active current controls, which generate the active current command Ipcmd
Reactive current controls, which generate the reactive current command Iqcmd
The converter current limit logic, which limits the active and reactive current to within the ratings of the converter
State of charge (SOC) of the battery, which impacts the limits of active current command Ipcmd

Active power control

See modeling detail developed in REEC_A. The active power path cannot be modulated by speed and so this model cannot be used with the WTGT_A or WTGT_B models. In essence, it should not be used for modeling WTGs. [1]

Reactive Power Control

See modeling detail developed in REEC_A. It does not have the parameters and functionality of the REEC_A model associated with the state-transitions around the reactive current injection path. The reactive current injection path is always active, unless the gain is set to zero, or the deadband made extremely wide. [1]

Current limit logic

See modeling detail developed in REEC_A. The minimum active current (Ipmin) is equal to –Ipmax; that is, the model allows power to be both generated and absorbed, and therefore can be used to model energy storage. [1]

Battery state of charge

REEC_C contains an additional path with a simple representation for a battery charging/discharging mechanism. Thus, the model is primarily intended for use in modeling BESS.

Mask and Parameter

General Parameters

REEC_C diagram

Voltage, Q and PF Control

Parameter	Unit	Description	Variable = {Possible Values}

Parameter	Unit	Description	Variable = {Possible Values}
VFlag		Voltage control flag	1 if Q control 0 if voltage control
PfFlag		Power factor flag	1 if power factor control 0 if Q control (which can be controlled by an external signal)
Tp	s	Active power Pe filter time constant
Vmax	pu	Voltage regulator upper output limit
Vmin	pu	Voltage regulator lower output limit
Vref1	pu	User-defined reference bias. Can be set externally or remain fixed
Qmax	pu	Maximum reactive power limit
Qmin	pu	Minimum reactive power limit
QFlag		Reactive power control flag	1 if voltage or Q control 0 if constant pf or Q control
Kqp	-	Proportional gain of Q regulator. Typically, zero when using voltage-based control.
Kqi	1/s	Integral gain of Q regulator
Kvp	-	Voltage regulator P gain
Kvi	1/s	Voltage regulator I gain
Kqv	-	Voltage error to reactive current gain. If zero, no dynamic Iq response to voltage deviation.
Tiq	s	Time constant for Iq control response

Reactive Current Injection During Voltage Dips

Parameter	Unit	Description

Parameter	Unit	Description
Vdip	pu	Low voltage threshold for reactive current injection. Below this, the inverter starts injecting Iq for voltage support.
Vup	pu	High voltage threshold for reactive current injections. If Vup > 99, Iq injection is reduced or disabled.
dbd1	pu	Lower bound of voltage error deadband
dbd2	pu	Upper bound of voltage error deadband
Trv	s	Voltage measurement filter time constant
Iqhl	pu	Maximum limit of reactive current injection
Iqll	pu	Minimum limit of reactive current injection

Active Power Control

Parameter	Unit	Description

Parameter	Unit	Description
Pmax	pu	Maximum active power limit
Pmin	pu	Minimum active power limit. Can be above zero in storage modes.
Tpord	s	Power reference filter time constant
dPmax	pu/s	Max power ramp-up rate
dPmin	pu/s	Max power ramp-down rate

Current Limit Logic

Parameter	Unit	Description	Variable = {Possible Values}

Parameter	Unit	Description	Variable = {Possible Values}
Imax	pu	Maximum converter current limit (P and Q combined)
PqFlag		P/Q priority flag for current limit	0 for Q priority 1 for P priority

Battery state of charge Control

Parameter	Unit	Description

Parameter	Unit	Description
SOCmax	pu	Maximum allowable SOC
SOCmin	pu	Minimum allowable SOC
T	s	Battery discharge duration. Only relevant in storage mode.

Voltage-dependent Limits

The VDL1 and VDL2 characteristics are defined by 4 pairs of Vq-Iq points (pu voltage versus reactive current) and Vp-Ip points (pu voltage versus active current).

Name	Unit	Description

Name	Unit	Description
Vq1	pu	VDL1 (Voltage Dependent Limit 1): Voltage Point1
Vq2	pu	VDL1: Voltage Point2
Vq3	pu	VDL1: Voltage Point3
Vq4	pu	VDL1: Voltage Point4
Iq1	pu	VDL1: Iqmax(Maximum reactive current) Point1
Iq2	pu	VDL1: Iqmax Point2
Iq3	pu	VDL1: Iqmax Point3
Iq4	pu	VDL1: Iqmax Point4
Vp1	pu	VDL2(Voltage Dependent Limit 2): Voltage Point1
Vp2	pu	VDL2: Voltage Point2
Vp3	pu	VDL2: Voltage Point3
Vp4	pu	VDL2: Voltage Point4
Ip1	pu	VDL2: Ipmax(Maximum active current) Point1
Ip2	pu	VDL2: Ipmax Point2
Ip3	pu	VDL2: Ipmax Point3
Ip4	pu	VDL2: Ipmax Point4

Initial Values

Name	Unit	Description

Name	Unit	Description
Vref0	pu	Voltage reference
Pref0	pu	Active power reference
Qref0	pu	Reactive power reference
SOC_init	pu	Initial state of charge (typically 50%)

Inputs, Outputs and Signal Available for Monitoring

Inputs

Name	Unit	Description

Name	Unit	Description
Vt	pu	Terminal voltage measured at the POC
pfaref	rad	Power factor angle reference
Pe	pu	Active power measured at the POC
Qext	pu	Reactive power reference, initialized from the load flow solution or supplied by an external plant controller model
Qgen	pu	Reactive power measured at the POC
Pref	pu	Active power reference, initialized from the load flow solution or supplied by an external plant controller model
Paux	pu	Auxiliary input signal
Pgen	pu	Plant active power output

Outputs

Name	Unit	Description

Name	Unit	Description
Iqcmd	pu	Reactive current command
Ipcmd	pu	Active current command

Acknowledgements

The development of the REEC_C block in the Smart Inverter Control Library is a contribution of CanmetENERGY at Natural Resource Canada.

Reference

[1] Model User Guide for Generic Renewable Energy System Models, EPRI, October 2023.