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Battery Energy Storage System (BESS)

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Battery energy storage System (BESS) is a technology that enables power system operators and utilities to store energy for later use. A BESS is an electrochemical device connected to a DC-AC inverter that interfaces with an AC network. The battery can charge (i.e., consume energy) from the grid and then later discharge the stored energy to provide power to the grid when needed.

The diagram below illustrates the basic concept of the BESS. It is comprised of a battery used for energy storage, a smoothing capacitor across its outputs, and a Voltage-Source Converter (VSC) that provides the required DC/AC conversion for connecting the DC battery outputs with an external AC bus.

Mask and Parameters

Controller Tab

Controller subsection

Name

Unit

Description

Name

Unit

Description

Prioritiy

 

The user is able to define whether the controller should prioritize active or reactive power via the usage of this parameter.
Active power given preference if the total power is more than the converter rating.
Reactive power given preference

Nominal power Pn

VA

Nominal power of the converter in VA. Default is 60000.

Nominal frequency fn

Hz

This parameter allows the user to specify the nominal frequency in hertz. Default is 50.

Q regulator gain Kp

 

This parameter allows the user to specify the reactive regulator gain Kp. Default is 1.

Q regulator gain Ki

 

This parameter allows the user to specify the reactive regulator gain Ki. Default is 25.

P regulator gain Kp

 

This parameter allows the user to specify the active regulator gain Kp. Default is 1.

P regulator gain Ki

 

This parameter allows the user to specify the active regulator gain Ki. Default is 25.

Current regulator gain Kp

 

This parameter allows the user to specify the current regulator gain Kp. Default is 1.

Current regulator gain Ki

 

This parameter allows the user to specify the current regulator gain Ki. Default is 50.

Islanded mode voltage regulator gain Kp

 

This parameter allows the user to specify the islanded mode voltage regulator gain Kp. Default is 3.

Islanded mode voltage regulator gain Ki

 

This parameter allows the user to specify the islanded mode voltage regulator gain Ki. Default is 40.

DC voltage regulator enable

 

This parameter allows the user to specify the DC voltage regulator enable. Default is unchecked.

DC link voltage regulator Kp

 

This parameter allows the user to specify the DC link voltage regulator Kp. Default is 1.

DC link voltage regulator Ki

 

This parameter allows the user to specify the DC link voltage regulator Ki. Default is 50.

Current limit

 

This parameter allows the user to specify the current limit. Default is 1.2.

Sample time

s

This parameter allows the user to specify the block sample time in seconds. Default is 50e-6.

Proportional gain

 

This parameter enables the user to select the proportional gain for the PI controller in PV mode and grid-connected mode. Default is 1.

Integral gain

 

This parameter enables the user to select the integral gain for the PI controller in PV mode and grid-connected mode. Default is 5.

Upper limit

 

This parameter enables the user to select the upper limit for the PI controller in PV mode and grid-connected mode. Default is 1.

Lower limit

 

This parameter enables the user to select the lower limit for the PI controller in PV mode and grid-connected mode. Default is -1.

Antiwinup gain

 

This parameter enables the user to select the antiwinup gain for the PI controller in PV mode and grid-connected mode. Default is 1.

Measurement Filters subsection

Name

Unit

Description

Name

Unit

Description

Filter type

 

Specify the type of filter for voltage measurements: Lowpass (default), Highpass, Bandpass , or Bandstop (notch).

Nominal frequency fn

Hz

Specify the natural frequency of the filter for voltage measurements, in hertz. This value must be a scalar or a vector. Default is 1000.

Damping ratio Zeta (Q = 1/(2*Zeta))

 

Specify the damping ratio of the filter. The damping ratio is typically a value between 0 and 1. Default is 0.707.

Filter type

 

Specify the type of filter for current measurements: Lowpass (default), Highpass, Bandpass , or Bandstop (notch).

Nominal frequency fn

Hz

Specify the natural frequency of the filter for current measurements, in hertz. This value must be a scalar or a vector. Default is 1000.

Damping ratio Zeta (Q = 1/(2*Zeta))

 

Specify the damping ratio of the filter for current measurements. The damping ratio is typically a value between 0 and 1. Default is 0.707.

Battery and DC link Tab

Battery parameters subsection

Name

Unit

Description

Name

Unit

Description

Type

 

Specify the battery model: Lithium-Ion (default), Lead-Acid, Nickel-Cadmium, Nickel-Metal-Hydride.

Nominal voltage

V

Specify the nominal voltage, Vnom, of the battery, in V. Default is 1200.

Rated capacity

Ah

Specify the rated capacity, Qrated, of the battery, in Ah. The rated capacity is the minimum effective capacity of the battery. Default is 166.67.

Initial state-of-charge

%

Specify of the state-of-charge (SOC) of the battery, expressed as a percentage of the maximum potential charge, at the beginning of simulation. An SOC of 100% indicates a fully charged battery and 0% indicates an empty battery. Default is 60.

Battery response time

s

Specify the response time of the battery, in s, at 95% of the final value. This value represents the voltage dynamics and can be observed when a current step is applied. Default is 0.5.

Discharge parameters subsection

 

Name

Unit

Description

Name

Unit

Description

Determined from the nominal parameters of the battery

 

Select to have the block determine the parameters in the Discharge settings based on the values specified for the parameters in the Parameters settings: on (default), off. Dependencies: Selecting this parameter disables the parameters in the Discharge settings.

Maximum capacity

Ah

Maximum theoretical capacity, Q, when a discontinuity occurs in the battery voltage, in Ah. This value is generally equal to 105% of the rated capacity. Dependencies: To enable this parameter, in the Parameters settings, set Use a preset battery to no.

Cut-off Voltage

V

Maximum theoretical capacity, Q, when a discontinuity occurs in the battery voltage, in Ah. This value is generally equal to 105% of the rated capacity. Dependencies: To enable this parameter, in the Parameters settings, set Use a preset battery to no.

Fully charged voltage

V

Fully charged voltage, Vfull, for a given discharge current. The fully charged voltage is not the no-load voltage. Dependencies: To enable this parameter, in the Parameters settings, set Use a preset battery to no.

Nominal discharge current

A

Nominal discharge current, in A, for which the discharge curve is measured. Dependencies: To enable this parameter, in the Parameters settings, set Use a preset battery to no.

Internal resistance

Ohms

Internal resistance of the battery, in ohms. When a preset model is used, a generic value is loaded that corresponds to 1% of the nominal power (nominal voltage multiplied by the battery rated capacity). The resistance is constant during the charge and the discharge cycles and does not vary with the amplitude of the current. Dependencies: To enable this parameter, in the Parameters settings, set Use a preset battery to no.

Capacity

Ah

Amp-hour capacity at nominal voltage. Capacity, Qnom, extracted from the battery until the voltage drops under the nominal voltage. Dependencies: To enable this parameter, in the Parameters settings, set Use a preset battery to no.

Exponential zone

[Voltage (V),
Capacity (Ah)]

Voltage, Vexp, and the capacity, Qexp, that correspond to the end of the exponential zone. The voltage should be between Vnom and Vfull. The capacity should be between 0 and Qnom. Dependencies: To enable this parameter, in the Parameters settings, set Use a preset battery to no.

DC link parameters subsection

 

Name

Unit

Description

 

Name

Unit

Description

Capacitance

F

The shunt capacitance, in farads (F). Default is 0.0120.

Set the initial capacitor voltage

 

If selected, the initial capacitor voltage is defined by the Capacitor initial voltage parameter. If cleared, the software calculates the initial capacitor voltage in order to start the simulation in steady-state. Default is selected.

Capacitor initial voltage

V

The initial capacitor voltage used at the start of the simulation. The Capacitor initial voltage parameter is not visible and has no effect on the block if the Set the initial capacitor voltage parameter is not selected.

Resistance

Ohms

The shunt branch resistance, in ohms (Ω). Default is 1e12.

Voltage Source Converter Tab

Two-level converter subsection

Name

Unit

Description

Name

Unit

Description

Model type

 

Average model (Uref-controlled) is the only type of converter model.

Diode on-state resistance

Ohms

Internal resistance of the diodes, in ohms. The default value is 1e-3.

Diode snubber resistance

Ohms

The snubber resistance, in ohms. Set the snubber resistance to inf to eliminate the snubbers. The default value is 1000.

Diode snubber capacitance

F

The snubber capacitance in farads. Set the snubber capacitance to 0 to eliminate the snubbers. The default value is 1e-6.

Diode forward voltage

V

Forward voltage, in volts, across the diode when it is conducting. The default value is 1e-3.

Current source snubber resistance

Ohms

The snubber resistance across the two current sources, in ohms. Set the snubber resistance to inf to eliminate the snubbers. The default value is inf.

Rated voltage

V

The rated voltage of the BESS (Battery Energy Storage System).

Series RL branch subsection

Name

Unit

Description

Name

Unit

Description

Branch type

 

Series RL branch.

Resistance R

Ohms

The series branch resistances (chocke resistance), in ohms (Ω). Default is 0.01.

Inductance L

H

The series branch inductances (chocke inductance), in henries (H). Default is 0.0041.

Measurements Tab

 

Name

Unit

Description

Name

Unit

Description

Time contant

s

Low pass filter time constant for power measurements, in seconds. Default value is 0.05.

Cut-off frequency

Hz

Low pass filter cut-off frequency for voltage and current measurements, in hertz. Default is 10.

Nominal power of network

W

Nominal power of network, in watts. Default is 12e3.

Time constant for power measurement filter

 

Power measurement filter time constant for signal conditioning, in seconds. Default value is 0.05.

Time constant for voltage measurement filter

 

Voltage measurement filter time constant for signal conditioning, in seconds. Default value is 0.1.

Inputs, Outputs, and Signals Available for Monitoring

Inputs

Name

Unit

Description

Name

Unit

Description

P ref

pu

Specify the active power reference of the Battery Energy Storage System.

Q ref

pu

Specify the reactive power reference of the Battery Energy Storage System.

V ref

pu

Specify the voltage reference of the Battery Energy Storage System.

GC Mode

 

Specify the status of the Battery Energy Storage System whether it is in grid connected mode (1) or grid forming mode (0).

BESS mode

 

Specify the mode of Battery Energy Storage System.

status

 

Whether or not connected to the microgrid (1: connected, 0: disconnected).

Outputs

Name

Unit

Description

Name

Unit

Description

Measurements

kW, kVAr, kV, A, pu

With this port, the user can view the model's power measurements for six signals:

  1. Vrms Local (kV): the rms voltage of the BESS, in kvolt. To have it in pu, it must be deviated by the BESS nominal voltage.

  2. Irms Local (A): the rms current of the BESS , in amper. To have it in pu, it must be devied by the nominal current of BESS.

  3. Q Reserve (pu): the reactive power reserved from a BESS in per unit (pu) refers to the amount of reactive power that the BESS can provide to the micro grid when there is a demand for it.

  4. Battery Meas: Battery measurement comprises three signals obtained from the battery, which include:

    1. SOC (%): the battery's state of charge expressed as a percentage

    2. Current (A): the battery's current measured in amperes

    3. Voltage (V): the battery's voltage measured in volts.

  5. Vbess: the voltage of the BESS, in volt. To have it in pu, it must be deviated by the BESS nominal voltage.

  6. Ibess: the current of the BESS , in amper. To have it in pu, it must be devied by the BESS nominal current.

  7. P (kW): the active power of the BESS in kW.

  8. Q (kW): the reactive power of BESS in kVAR.

A

 

The actual circuit connection of BESS, Phase A.

B

 

The actual circuit connection of BESS, Phase B.

C

 

The actual circuit connection of BESS, Phase C.

 

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