System Acceptance Testing & Performance Evaluation of Battery Energy Storage Systems

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System Acceptance Testing & Performance Evaluation of Battery Energy Storage Systems Battery Energy Storage System Testing Quanta Technology offers field testing of Battery Energy Storage Systems

The portable test device can interface and exchange commands with BESS through analog signals or communicate with the BESS controller using Modbus or DNP3 protocols.

control and operation of Battery Energy Storage Systems (BESSs).

The built-in power/energy tracking capabilities and performance assessment tool allows the user to compare the generated set-points and expected power output of a BESS with the measured outputs, for

BESSTI simulates the expected control behavior of various applications of BESSs and generates setpoints or profiles to control and compare battery functionalities.

1 System Acceptance Testing & Performance Evaluation of Battery Energy Storage Systems Battery Energy Storage System Testing Quanta Technology offers field testing of Battery Energy Storage Systems (BESSs) by introducing a test device specifically developed for the purpose of test and evaluation of BESS controls and communication systems. The portable test device can interface and exchange commands with BESS through analog signals or communicate with the BESS controller using Modbus or DNP3 protocols. Test Device Overview The Battery Energy Storage Simulator and Tester Instrument (BESSTI ) is a portable Programmable Logic Controller (PLC) based automation and analysis tool for examination of the control and operation of Battery Energy Storage Systems (BESSs). BESSTI can be utilized in the laboratory environment and/or in the field to facilitate Factory Acceptance Tests (FATs), Site Acceptance Tests (SATs) and commissioning of BESSs. The built-in power/energy tracking capabilities and performance assessment tool allows the user to compare the generated set-points and expected power output of a BESS with the measured outputs, for any pre-specified control strategy. The device can be used for Testing or Simulation of advanced battery control features, such as Peak Shaving, Generation Smoothing, Ramp Rate Control, etc. BESSTI simulates the expected control behavior of various applications of BESSs and generates setpoints or profiles to control and compare battery functionalities. An optional Hardware-in-Loop (HIL) feature enables integration of the BESS into a real-time digital simulation environment, such as RTDS for precise evaluation with simulated grid. Key features of the unit and system specifications include: Generating P(ref) and Q(ref) for automated BESS control & dynamic testing BESS installation topology selection to incorporate DC or AC connected loads and contribution from on-site generation (e.g., solar PV production) Set-point generation for individual battery controls (e.g., Charge and Discharge set-points or ramp rate control) Set-point generation based on hybrid system controls (e.g., BESS + PV smoothing or load following and peak shaving) Communications with external signal generating schemes through communication ports (selectable DNP3 or Modbus protocol), pre-specified data files for off-line profiling, and analog input terminals (real-time profiling) Voltage and current measurements for trending and performance comparison (direct connection up to 480 V, 3-phase voltages and 5A currents, or through conventional CTs/PTs) Hardware Description BESSTI is designed as a rack mounted or portable device. The user can control the device and perform tests using a touch-screen HMI or access the device through VPN interface. Touch Screen Interface: A Human-to-Machine Interface (HMI) provides graphical user interface for operating the unit. Interactive touch-screen HMI pages enable the user to configure BESS topology and controls, run the tests and observe the expected versus actual trends, as well as a summary of the entire operation. PLC: The unit utilizes a reliable and precise industrial grade PLC to implement controls, automation processes and interface with the external devices. The PLC executes the BESS simulation algorithms, manages the HMI pages, and refreshes Inputs and Outputs. Input/Output Modules: Various input and output terminals on the unit provide physical digital and analog I/O connections for signals and data exchange with the unit. Specific Figure 1 BESSTI portable device

analog I/Os are utilized for low-level signal exchange (± 10V) and/or power quality grade measurement for connecting to unit to BESS or RTDS.

The setpoints for BESS can also be communicated through either port.

USB Port: This port functions as a way to receive various profiles and save the final result in a text file or CSV format.

2 analog I/Os are utilized for low-level signal exchange (± 10V) and/or power quality grade measurement for connecting to unit to BESS or RTDS. Communication Ports (Ethernet & Serial RS485): Communications ports are used to exchange data (e.g., price signals) and commands with external devices. The setpoints for BESS can also be communicated through either port. Typical data communication includes PI Historian information, off-line profiles, or real-time control signals from third party devices. USB Port: This port functions as a way to receive various profiles and save the final result in a text file or CSV format. Automation & Controls The unit configuration and system testing are performed through various HMI pages. Configuration One of the unique features of BESSTI is the ability to perform simulation and testing for various BESS installation topologies. Through the configuration page, the user can select the desired topology for BESS by touching the connection points (squares). Multiple prespecified configurations can be selected by users. In general, a BESS, PV system and associated load can be all connected in parallel with the grid or incorporating a hybrid arrangement of internal and parallel connections. Uncommon configurations can be added through firmware upgrade, if required. Figure 2 Overall connection diagram and hardware interfaces Figure 3 HMI page for system configuration Whenever they are selected, a check mark symbol will appear on connection points and the box color will change to red. There are also two options available for set-points, as well as pricing signal. The set-point can be received through the analog inputs or through the communications. A pricing signal can also be provided, either from a look-up table or through the communications. A check mark symbol will identify the selected sources of data exchange.

Battery Control Modes BESSTI supports different battery control modes commonly utilized in major grid applications, including Charge & Discharge, Peak Shaving, Ramp Rate Limiting and PV Smoothing.

The set-points can be sent to BESS through analog signals and/or via communications. The charging level will always be negative and discharge level defined as a positive value.

3 Battery Control Modes BESSTI supports different battery control modes commonly utilized in major grid applications, including Charge & Discharge, Peak Shaving, Ramp Rate Limiting and PV Smoothing. Charge & Discharge Set-Points: This mode provides pre-specified charge and discharge set-points, as well as reactive power reference points. The set-points can be sent to BESS through analog signals and/or via communications. The charging level will always be negative and discharge level defined as a positive value. Similarly, reactive power injection into the system (or lagging power factor) is considered positive. Leading power factor or reactive power absorption will be positive. Charge & Discharge Profile: Figure 4 Battery control modes A series of charge and discharge set-points and corresponding durations can be pre-programmed and executed through look-up tables and scheduler internal to the unit. An internal GPS time-synchronized clock coordinates the scheduler operation and proper time of transition from one set-point to another. Peak Shaving Control: In this mode, the unit uses pre-specified Lower Limit Threshold (LLT) and Upper Limit Threshold (ULT) values to compare the input signal associated with either a Circuit Load Profile (CLP) or a Circuit Generation Profile (CGP) to automatically determine the set-point and duration for charge and/or discharge of a BESS. In the case of CLP, if the profile transitions above ULT, a discharge set-point will be calculated and sent to BESS to reduce collective load seen by the grid. Similarly, anytime CLP goes below LLT, a charge setpoint will be determined and Figure 5 Charge/discharge control panel communicated to BESS. In the case of CGP, the set-point representation will have the opposite effect. Generation profile above ULP triggers a charge signal, and vice versa.

The unit contribution will be limited by the maximum practical ramp rate (user specified) and/or saturation of the charge/discharge set-points.

4 Figure 7 Ramp rate limiting example Figure 6 Charge & discharge profile testing Figure 8 Example of control signal generation for PV Ramp Rate Limiting: This control will utilize the same CLP or CGP signals to limit ramp rate of the selected profile for any transition between two consecutive variations. Ramp rate is calculated and applied per second. The unit contribution will be limited by the maximum practical ramp rate (user specified) and/or saturation of the charge/discharge set-points. Figure 7 represents an output example using the BESSTI Ramp Rate Limiting control model. PV Smoothing: This mode provides one of the advanced controls for hybrid integration of BESS + PV systems. Using an input signal representing PV radiation profile or site measurement (through analog inputs and/or communications), the unit will apply a smoothing algorithm to calculate BESS set-points based on 5-minute or 15-minute averages and expected state of the charges. Figure 8 represents an output example using the BESSTI PV Smoothing model. Price Calculation BESSTI has the capability to receive and utilize various price signals for operation and control of a BESS. Three commonly utilized pricing schemes are implemented, and they are selectable through an HMI page (Figure 9). Day Ahead Price Profile: Mainly utilized in dispatch scenarios Real-Time Profile: Used for ancillary service market representation and aggregation Time of Day Profile: Used for specific applications such as arbitrage and system relief such as peak/off-peak discharge and charge control Battery Type Database As different types of batteries show different charging and discharging behavior, the BESSTI is designed to incorporate appropriate battery characteristics through settings. A user will be able to identify a battery type from a library of pre-specified types or define a custom battery. Examples of pre-defined batteries and customization page for specifying a new battery are given below (Figure 10).

The Initial State of Charge (SOC), Start Time and Duration (hh:mm) should be entered by the user.

These items can also be modified by user, if needed. According to this information, the simulation algorithm calculates the set-point, and estimates SOC.

5 Figure 9 Pricing profile Figure 10 Battery type database Performing a Test or Simulation Figure 11 shows the execution page, when Charge & Discharge mode for a Nickelcadmium battery is selected. The green box shows the main battery parameters. A user needs to enter some parameters manually and some parameters are populated from selected modes, configuration and battery type. The Initial State of Charge (SOC), Start Time and Duration (hh:mm) should be entered by the user. The battery characteristic including Battery Capacity, Charging Efficiency, Max SOC, Min SOC and Battery Standby Loss are taken from the battery type. These items can also be modified by user, if needed. According to this information, the simulation algorithm calculates the set-point, and estimates SOC. Figure 12 shows a schematic of the main Figure 11 Running simulation decision making matrix that is used in the performance evaluation algorithm to analyze the effect of various BESS applications on battery performance and characteristics. Three types of signals and parameters are used in the algorithm, namely: a) Input variables that describe the locally measured quantities, such as PV generation profile and load, control and communicated action signals to derive applications, such as frequency regulation signal from ISO or emergency demand response level, and real-time price signals including RMCP and LMP b) Constant parameters, such as battery size, PV unit size and battery efficiency, and system constraints, such as minimum and maximum SOC limits for frequency regulation and PV smoothing, daily solar radiation duration, limits of arbitrage charge or discharge, etc.

6 c) Output variables describing the outcome of analysis, such as SOC profile and number of cycle charges, estimated total battery charge and discharge (accumulated) and associated revenues per application for the duration of study PV Profile (System) Arbitrage Demand (On/Off) Frequency Regulation (ISO) LMP Cost ($/MWh) RMCP Price ($/MWh) Battery Power Size (20-30kW) Battery Energy Size (1-3 Hours) PV Size (20kW) Battery Critical Minimum SOC (10%) SOC Lower Limit (Provides 15 min of Freq. Reg.) SOC Upper Limit (95%) Initial Battery Capacity (30%) PV Smoothing Limit (6kW 12kW) LMP Average Price ($0.04 / kwh) Solar Radiation Time ( 6am 8pm) Mandatory Arb. Charge SOC limit (50% - 90%) Mandatory Arb. Charge Time (3am - 6am) Decision Matrix Variable Signal Constants & Constraints Variable Output SOC (%) (Profile) Charge Meter ($) (Cost) Discharge Meter ($) (Revenue) Frequency Reg. Meter ($) (Revenue) Arbitrage Charge Meter ($) (Cost) Arbitrage Discharge Meter ($) (Revenue) Number of Cycles Charged (DCC, SCC, ECC) Battery Charge/Discharge Efficiency (85%) Figure 12 Design making matrix (input/output signals) For more information regarding Quanta Technology's Energy Storage Testing Services and BESSTI automation and analysis tool, please contact Farid Katiraei at (647) or fkatiraei@quanta-technology.com. This material is intended strictly as general information about Quanta Technology, LLC and does not constitute the basis of any design advice or contract. Copyright 2015

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