Peak Shaving with Battery Energy Storage System

This example shows how to model a battery energy storage system (BESS) controller and a battery management system (BMS) with all the necessary functions for the peak shaving. The peak shaving and BESS operation follow the IEEE Std 1547-2018 and IEEE 2030.2.1-2019 standards.

Introduction

In this example, an average converter, an output filter, and associated control model the BESS. The BESS can operate in grid-forming control and it receives setpoint from the operator control room for power dispatch. The BESS also receives the power flow measurements from point of common coupling (PCC) and changes control mode for peak shaving.

Description of BESS Controller

The BESS controller receives commands and setpoint from the control room operator as well as various measurements and status from different sources and loads connected to the feeder. The BESS in this model comprises these functions:

1. Reference frequency generation

2. Reference voltage generation

3. Receive setpoint and command from operator

4. Change control mode. According to the power flow measurement at PCC, the BESS starts peak shaving or enables to charging mode

Implementation of Photovoltaic (PV) Model

The model represents a three-phase grid-connected photovoltaic (PV) system that injects power with unity power factor (UPF) without using an intermediate DC-DC converter. The transformer-less configuration simulates leakage currents. To track the maximum power point (MPP), the example uses these maximum power point tracking (MPPT) techniques:

• Incremental conductance

• Perturbation and observation

Build Model for BESS Peak Shaving

Model Overview

Open the model sscv_peak_shaving.slx.

mdl = "sscv_peak_shaving";
open_system(mdl)

The Substation subsystem connects the BESS and the feeder to the main grid. This subsystem comprises a connecting breaker, disconnectors, and transformers to connect the main grid to the BESS and the outgoing feeder. The substation also contains the BESS controller and the BMS.

Building Components for Peak Shaving with BESS

This example comprises these main components:

1. Substation

2. BESS System

3. Battery Management System (BMS)

4. Battery Module

5. Operator Control Room

Substation

The Substation subsystem connects the BESS and the feeder to the main grid by using a connecting breaker, disconnectors, and transformers. The substation also contains the BESS controller and the BMS.

BESS System

The BESS system comprises:

1. Grid side converter, filter, measurement, and control

2. Battery management system (BMS)

3. Battery module

The BESS converter connects the battery modules to the grid and controls the power flow through the converter. The BESS controller implements the peak shaving function.

The power measurement at PCC detects high loading of the main grid at the substation and activates the peak shaving function. The peak shaving function limits the power from the main grid to the maximum rated power while the BESS system provides the rest of the power requirement.

Battery Management System (BMS)

The BMS receives the request from the grid-side converter on power requirement. The BMS also monitors the state-of-charge (SOC) of the battery module. In this example, the BMS disconnects the battery if the SOC is above the high SOC threshold and the battery is discharging. Similarly the BMS disconnects the battery if the SOC is below the low SOC threshold and the battery is charging. Once the battery opens from the DC side, the AC-side breaker also opens within one cycle.

Battery Module

The battery module is connected to the DC side of the BESS converter. Two battery packs are connected in series and grounded at the midpoint. The DC breakers can disconnect the battery module.

Operator Control Room

The Operator Control Room subsystem sends all the setpoints and commands. It also plots the measured quantities and the system performance analysis.

Define Parameters & Run Simulations

Initialize the BESS, grid, and PV parameters. At the MATLAB Command Window, enter:

run("sscv_peak_shaving_BESS_data.mlx");

Initialize Battery Parameters

The battery module in this example is generated by using the objects and functions in the Battery Pack Model Builder. For more information on how to build a battery pack, see the Build Simple Model of Battery Pack in MATLAB and Simscape example.

run("sscv_peak_shaving_param.m");
Ns=1500/25;
Np=round(150*1000/(59*Ns*25));
load('sscv_peak_shaving_data.mat')

Run Simulation

Simulate the model.

run("sscv_peak_shaving");

Plot Simulation Results

These plots show:

1. Voltage and current of BESS.

2. Active and reactive power output of BESS, PV, load, and main grid.

3. Voltage, current, and power consumption of loads.

4. Status, discharge, charge, and SOC of BESS.

This plot shows the three-phase voltage and current output of the BESS, as well as the grid current during peak shaving and BESS disconnection.

run('sscv_peak_shaving_plot_BESS_VI.m')

The plot shows the measured values around the start of peak shaving around 3.0 s and the BESS disconnection at 4.97 s. A stable voltage and current output from BESS verifies a good peak shaving. The disconnection of BESS happens due to low SOC.

This plot shows the active and reactive power of BESS, PV, main grid, and loads.

run('sscv_peak_shaving_plot_PQ.m')

The stable active and reactive power output verifies the efficacy of the peak shaving method.

This plot shows the voltage and current at the loads.

run('sscv_peak_shaving_plot_Load_VI.m')

The load voltage and load current remain steady during peak shaving and BESS disconnection.

This plot shows the charge, discharge, BESS status, and SOC of the BESS.

run('sscv_peak_shaving_plot_BMS_SoC.m')

The discharge status during peak shaving and the disconnection of the BESS due to low SOC matches with

the results from the AC-side output. This also validates the BMS functions for BESS SOC monitoring.

Evaluate System Performance

These plots show the results of the system performance and the impact of the peak shaving function.

These performance indices include:

1. Active Power Delivery and BESS Sizing.

2. IEEE 1547 -2018: Category II - Inverters Sourced with Energy Storage Mapping.

3. IEEE 2030.2.1-2019 Guide for Design, Operation, and Maintenance of Battery Energy Mapping.

4. Impact of peak shaving function time delay

This plot shows the loss in active power delivery with variation in BESS sizes. The grid capacity and

load variation are constant.

This plot shows the indices for the BESS system implemented in this model following the IEEE 1547 -2018: Category II - Inverters Sourced with Energy Storage standard.

This plot shows the indices for the BESS system operation and maintenance implemented in this model following the IEEE 2030.2.1-2019 Guide for Design, Operation, and Maintenance of Battery.

This plot shows the impact of peak shaving function time delay after grid power crosses the threshold.

The time delay of the peak shaving function has more impact on the overshoots of the active power from the grid and the BESS.

There are no significant impact on the load voltage and total harmonic distortion (THD) values.