7 References
This section outlines information about the various features and functionalities included in the eSite Modular hardware and software.
7.1 Power Source Prioritization
The eSite Modular system uses the following power source priority:
Solar power
Grid power
Genset power
If solar or grid power is not available, the genset is automatically started when the batteries need to be charged. If grid becomes available during a genset charge cycle, the genset is stopped and the power source is switched to grid. Only one AC source can be active at a time.
If solar power is available at the same time as grid or genset power is available, solar power is always prioritized and maximized. Using the Green Power Influx feature, AC power sources can be inhibited, given that certain conditions are met, to fully utilize solar power when applicable.
7.2 Silicon Controlled Rectifier (SCR) with ATS functionality
The eSite Modular RE and RSE converter units convert input AC power via three rectifiers into -48 V DC. The maximum conversion capacity is 3.5 kW per rectifier, for a total of 10.5 kW per converter unit. The inputs from the AC sources are continuously measured to ensure that the most efficient AC source is used. The switching between the connected AC sources (gensets/grid) is automatic.
The eSite Modular patented Silicon Controlled Rectifier (SCR) functionality is designed to improve the performance of the system compared to a traditional Automatic Transfer Switch (ATS). Both an ATS and SCR allows for switching between two AC sources, but while the ATS is based on mechanical switching, the SCR uses power semiconductors.
One or two (optional) AC sources can be configured in the eSite Web interface. Possible AC source configurations are: No Source, AC Genset 1, AC Genset 2 and Grid.
7.3 System Mode
The eSite Modular system always operates in one of the 6 defined system modes: 'Auto', 'Auto Full Charge', 'Manual', 'Safe Mode' , 'UPS Mode 'and 'Registration Mode'.
Auto mode is the normal mode the system operates in. The eSite Modular system is working automatically with no user interference and controls all features and external command signals.
Auto Full Charge mode is activated when the batteries need to do a Full Charge cycle.
A Full Charge cycle is activated automatically by one of the following conditions being met :
One of the Load Voltage Disconnect (LVD) breakers has tripped.
The time interval between two Full Charge cycles has elapsed. This parameter can be changed in the local eSite Web settings .
The battery Energy throughput has reached its limit value. This parameter can be changed in the local eSite Web settings.
For further information, see section Full charge cycles
Manual mode is activated when a controlled AC source, typically a genset, is manually forced on or off. This can be done from the local eSite Web or remotely via eSite Tools.
In Manual mode, normal functionalities, including power prioritizing and automatic external commands, are overridden. Manual mode is exited when all AC source controls are set to Auto.
Safe mode is activated when the battery MCB is tripped or if the main controller cannot determine the correct state of the battery bank, i.e. one or both of the battery voltage or current sensors have failed.
When Safe mode is active, the set voltage levels and the maximum battery charge current are reduced to protect the system, and the genset is commanded to run continuously to ensure that the load is supported.'
UPS Mode can be selected by the user, e.g. under Genset settings, if uninterrupted AC power supply is required. In this mode, normal hybrid operation is disabled and the Genset is continuously commanded to run. If there are Dual Gensets installed, runtime is divided between the two gensets based on a configured time interval. Operation in this mode is mainly suitable for sites with poor-quality batteries.
In Registration mode, a connected unregistered Converter Unit has been detected by the system. On the eSite Web, the user is forced into the Site Commissioning guide to complete the registration. All communication to any rectifiers and solar converters is stopped until all connected Converter Units are registered and the system exits Registration mode.
7.4 Batteries
The eSite Modular system supports usage of two different types of battery chemistry: lead-acid batteries and lithium-ion (Li-ion) batteries. Several different brands, models and sizes of batteries have premade configurations available that will simplify site commissioning and operation. New premade configurations can be created upon request. The battery parameters are also possible to set individually through several interfaces (e.g. eSite Web, eSite Tools, SNMP) in order to support new battery types and to improve performance.
7.4.1 Lead-Acid Batteries
Traditionally, conventional lead-acid batteries have been the main choice for hybrid operation on remote sites. They are attractive for a wide variety of usages due to being of relatively low cost, having a long life-time and high reliability, but they also come with drawbacks including the need for temperature compensation and bulky storage, especially for high-capacity banks.
7.4.1.1 Voltage levels
Two different set voltage levels are used when charging lead-acid batteries: Boost voltage and Float voltage.
Boost voltage is higher than float voltage and is used to improve the charge performance. However, batteries kept at boost voltage for longer periods of time eventually take damage. Float voltage is lower and is used for long periods of continuous available AC power, for example when the grid is available for a long time.
7.4.1.2 Battery states
The following battery states are defined for lead-acid batteries. The states indicate at what stage in the charge cycle the battery bank is. The battery state information is available on eSite Web.
Discharge: The discharge state is entered when current is drawn from the batteries and the voltage is decreasing.
Charge: Charging occurs when either the rectifiers or the solar converters are delivering constant charging current to the batteries.
Absorb: Absorb is a charging state where the charging voltage is limited by the rectifiers or solar converters. The charging voltage has an optional temperature compensation feature. When in the Absorb state the battery bank is charged at constant voltage.
Equalized: Equalized is an extended constant voltage charging mode to help eliminate soft sulfation in lead-acid batteries. The voltage level is adjustable.
Fully Charged: In the Fully Charged state, the batteries are considered to be fully charged. The battery bank will remain in this state until SOC has dropped 5 % since the fully charged state was entered.
7.4.1.2 Battery charge strategies
The eSite Modular system offers four battery charge strategies to optimize the use of the lead-acid battery bank used on site. Battery charge parameters can be viewed on eSite Web under the Battery menu.
Voltage control
The battery bank starts to charge at specified voltage levels. The charging stops when a specified voltage level is reached and the charge current falls below a specified value. The method does not take into account the state of charge.
Used with a basic battery bank. The use of batteries is not optimized. The life-time of the battery bank is relatively short.
Static state of charge (SSOC)
The batteries start and stop charging at predefined levels of the state of charge. The SOC values for starting and stopping charge cycles is dependent on battery configuration and can be changed in the local web pages.
Used with battery bank delivered with proper data. SSOC gives a good estimation of the battery life-time. This method is convenient for a very remote site where it takes a great effort to switch battery bank.
Partial state of charge (PSOC)
The batteries are charged up until the charging performance decreases, based on the charge acceptance of the battery. When the charge current has decreased below a specified threshold the normal charge cycle is finished. The SOC level when this occurs minus a SOC window, default 30 %, decides when the next charge cycle starts. SOC level when the normal charge cycle is finished depends on several factors.
Used with battery bank delivered with proper data. Partial state of charge saves fuel costs and is the most cost saving strategy. The life-time of the battery bank may be shorter than if the SSOC strategy is used. The batteries are charged with low current as it is fuel inefficient when the batteries have a poor charge acceptance. As the genset runs more efficiently at higher output power compared to when it is running at idle or has low output power, the frequency of genset maintenance is also lowered. Thus, PSOC is a fuel efficient option.
UPS mode
The system operates in UPS mode, where the batteries are not cycled and AC power is not turned off when the batteries are fully charged. The AC power can be either grid or genset.
7.4.1.3 Full charge cycles
A Full Charge cycle is a longer charge cycle that charges the batteries to the maximum available capacity. Periodic use of the Full Charge cycle is needed to maintain the health of the battery bank, balance battery banks/strings and to “recalibrate” the state of charge. A Full Charge cycle charges the batteries at boost voltage until the battery is in the Fully Charged state. A Full Charge cycle can be triggered manually, for example during site commissioning, or by one of these three threshold values:
Time interval
Energy throughput
Low voltage, used on Static SOC and Partial SOC charge strategies
An Extended Full Charge cycle is triggered when the battery voltage has fallen so low that both HP and LP LVD are activated. An extended full charge cycle prolongs the Full Charge cycle with an extra timer, default set to 18 hours. This is an effort to recover the battery bank from any damages caused by the low voltage. An Extended Full Charge cycle can also be triggered manually.
7.4.1.4 Charge Mode
The battery charge mode indicate what type of battery management that is currently active. The charge mode is independent of the selected charge strategy and gives information about whether the battery bank is subjected to normal charge cycling or if a scenario that overrides these settings is active, such as when a Full Charge cycle is triggered.
The active charge mode is presented under the Battery tab on eSite Web and in eSite Tools.
For handling of lead-acid batteries, one of the following charge modes is used.
Normal Charge: Standard hybrid operation is active. The battery bank is charged/discharged according to the selected charge strategy and its associated control parameters.
Full Charge: A Full Charge cycle has been triggered and is active.
Extended Full Charge: An Extended Full Charge cycle has been triggered and is active.
Safe Mode: The eSite Modular system is currently in Safe Mode and cannot determine the correct state of the battery bank. Maximum allowed charge current and set voltages are lowered to protect the system.
7.4.1.5 Temperature compensation
The temperature is of great importance regarding the health of lead-acid batteries. The temperature information is used to adjust the voltage level when the batteries are charged. At high temperatures, the batteries are charged at a lower voltage level and at low temperatures batteries are charged at a higher voltage level. This temperature compensation can be configured.
The battery temperature sensor is placed at the centre of the battery bank (see figure 7.1) and connected to the BTMP+ and - ports on the eSite RMC front.
7.4.1.6 Charge Current limit
The eSite Modular system continuously ensures that the battery max charge current is not exceeded. This threshold value for current limitation is configurable. The battery charge current is measured with a dedicated pre-installed LEM current sensor inside the battery cabinet. A positive current indicates that the batteries are being charged. A negative current indicates that the batteries are being discharged.
7.4.2 Lithium-ion batteries
An increasingly popular alternative to lead-acid batteries for powering remote sites together with the eSite Modular system is Li-ion batteries.
Due to their superior power density and sophisticated module designs, including the possibility of external communication, Li-ion batteries make for effective storage solutions of high capacity, combined with intelligent monitoring and managing, albeit at a slightly higher cost and a higher sensitivity to overcharging/overdischarging.
All commercial Li-ion battery modules relevant for this application are equipped with internal electronic protection, cell balancing circuits and supervision/alarm circuits.
The eSite Modular system is capable of managing a Li-ion battery bank of up to 16 installed BMUs connected in parallel. If a communication cable is mounted between the battery bank and the eSite RMC, all alarms and important data (e.g. Voltage, SOC, Current) from the modules are logged, presented on the local eSite Web and sent to eSite Tools. For operation without communication, or when communication is lost, this data is either measured or calculated by dedicated estimation algorithms based upon the available information about the battery type and the size of the battery bank.
The eSite RMC ensures that charging voltage levels and maximum current stays within the limits according to the battery specifications. Maximum charge current is automatically adjusted depending on how many modules are connected or if any battery fuses are tripped.
Li-ion batteries from the following manufacturers are currently integrated with the eSite Modular system. Contact eSite Power Systems for information regarding models and version.
LG Chem
Sacred Sun
SAFT
Shoto
Vision
Polarium (previously Incell)
See the Appendix for more information on installation and configuration of Li-ion batteries.
7.4.2.1 Voltage levels
When charging Li-ion batteries, a configurable set voltage level is used. For long periods of operation with available AC power, the set voltage is ramped down to a lower level to preserve the health of the battery bank.
These voltage levels are individual for each power source and may be preconfigured upon delivery. Normally, they are provided by the battery manufacturer.
7.4.2.2 Battery states
The following battery states are defined for Li-ion batteries. The battery state information is presented on eSite Web and in eSite Tools. For Li-ion configurations, all BMUs connected in parallel will be considered as one battery bank.
Precharge: Precharge is the initial state of the battery state algorithm. In Precharge, the system takes necessary precautions to stop inrush currents from going into the battery bank by slowly ramping up the system voltage from a low starting point until the battery voltage is matched. When current is detected going in or out of the battery bank, the Precharge state is exited.
Discharge: The discharge state is entered when current is drawn from the batteries and the voltage is decreasing.
Charge: The Charge state indicates that either the rectifiers or the solar converters deliver sufficient current to charge the batteries.
Fully Charged: In the Fully Charged state, the batteries have met the manufacturer specifications for being considered fully charged and will not accept further charging. This state is exited when the SOC has decreased by 1 % since the Fully Charged state was entered.
Equilibrium State During equilibrium, no current flows in or out of the battery. This state is exited as soon as current going in or out of the battery bank is detected.
7.4.2.3 Li-ion battery charge strategies
The eSite Modular system currently offers two charge strategies to optimize the use of a Li-ion battery bank on site: Voltage Control (VC) and Static SOC (SSOC). Battery charge parameters can be viewed on eSite Web under the Battery menu.
The Voltage Control strategy works very similarly to the corresponding lead-acid strategy, see section Lead-acid batteries. Operation will be based on the overall measured battery voltage. This strategy is well suited for site setups with no battery communication or when SOC shall not be considered.
The Static SOC strategy starts and stops charging based on configured Start SOC and Stop SOC levels. This is arguably the best adapted strategy for Li-ion battery banks with active communication to the eSite Modular system. The strategy offers several options to control the cycling based on the reported BMU data that are configurable via the Static SOC Control Options parameter. The options are:
Average SOC - A charge cycle will start and stop when the average calculated SOC of the battery bank reaches the start/stop thresholds.
Protective SSOC - Start/stop on Min/Max BMU SOC value. A charge cycle will start when the minimum reported BMU SOC value reaches the Start SOC threshold and stop when the maximum reported BMU SOC value reaches the Stop SOC threshold. This behaviour will prevent overcharging and overdischarging of any single BMU in the bank.
Balancing SSOC - Start/stop on Min/Min SOC value. A charge cycle will start when the minimum reported BMU SOC value reaches the Start SOC threshold and stop when the minimum reported BMU SOC value reaches the Stop SOC threshold. This behaviour will ensure that all BMUs are charged up to the desired SOC.
Options 2 and 3 require active communication with the battery bank. In setups with no communication or if communication is lost, the SSOC strategy will be based on the calculated average SOC value for the entire battery bank regardless of the selected option.
Voltage control
The battery bank starts to charge at specified voltage levels. The charging stops when a specified voltage level is reached and the charge current falls below a specified value. The method does not take into account the state of charge.
Used in applications where no communication is available or when the state of charge is not of interest. The use of batteries is not optimized.
Static state of charge
The batteries start and stop charging at predefined SOC levels. The SOC level values for starting and stopping charge cycles are configurable and can be changed in the local eSite Web pages.
Used with battery bank delivered with proper data. Static SOC gives a good estimation of battery life-time. Use of batteries is optimized with data from the internal BMS of the batteries.
7.4.2.4 Synchronize step
For battery banks with apparent propagating unbalance during charge cycles, a synchronization step at the end of each charge cycle can be enabled, where the BMUs are allowed to synchronize internally under a period of no or very low charge current. This final balancing touch is best performed while charging at the top of the charge cycle when internal voltage differences in the bank are more apparent and internal cell resistances are minimized. The charge current limit and the duration of this period are both configurable.
7.4.2.5 Balancing Full Charge
As a complement to regular charge cycles in hybrid operation for Li-ion batteries, optional full charge cycles, here labelled Balancing Full Charge cycles, are supported by the eSite Modular system. They are slightly different from the Full Charge cycles used for lead-acid batteries, where maintained charge current for long periods of time is necessary for ensuring good battery performance. Li-ion batteries are less sensitive to damage from partially charging the battery bank than lead-acid batteries, and do not have the same need to repeatedly be fully charged. Indeed, it can be argued that fully charging Li-ion batteries to a large extent should be avoided in order to not risk overcharging the batteries, which may cause damage. However, for a newly installed or a severely unbalanced battery bank, it might be necessary to perform a full charge cycle to reach the very top of the battery voltage/SOC characteristic and achieve appropriate balance within the bank.
Balancing Full Charge cycles are available, and will work in the same way, for both the Li-ion VC and SSoC strategies. For the SSoC strategy, a configurable safety voltage level has been introduced that will trigger a Balancing Full Charge cycle in any faulty scenario where the SOC cannot be reported or calculated correctly. This voltage level should be set to a higher value than the LP load LVD voltage level as a precaution to prevent LVD.
A Balancing Full Charge cycle can also be triggered manually via a command from the eSite Web Battery tab.
If desired, periodic Balancing Full Charge cycles may be enabled. When enabled, Balancing Full Charge cycles will be triggered automatically based on intervals of either accumulated energy throughput from the battery bank or number of completed regular charge cycles, whichever occurs first. Both interval parameters are configurable.
A Balancing Full Charge cycle is completed when the battery voltage has exceeded the BMS Fully charged voltage level and the charge current has fallen below the battery cut-off level specified by the manufacturer. Upon completion, the periodic intervals for energy throughput and number or cycles are both reset.
7.4.2.6 Charge Mode
The active charge mode is presented under the Battery tab on eSite Web and in eSite Tools.
For handling of Li-ion batteries, one of the following charge modes is used.
Ramp Up: The battery bank is in the Precharge state and the system is slowly ramping up the voltage to avoid initial inrush currents.
Normal Charge: Normal hybrid operation is active. The battery bank is charged/discharged according to the selected charge strategy.
Synchronize: Synchronization of the BMUs in the battery bank is active. The battery bank is forced into the Equilibrium state and is not charged/discharged.
Balancing Full Charge: The battery bank is currently being charged in a Balancing Full Charge cycle. The system will be in Auto Full Charge mode.
Safe Mode: The eSite Modular system is currently in Safe Mode and cannot determine the correct state of the battery bank. Maximum allowed charge current and set voltages are lowered to protect the system.
7.4.2.7 Hybrid Shifting
The purpose of Hybrid Shifting (HS) is to increase solar production efficiency on hybrid sites during the day by having a lower battery bank SOC in the morning and thus have more solar energy captured in the batteries. The simple concept of hybrid shifting is to split a day into 2 periods where the DG stop voltage differs.
Note
Hybrid Shifting function is only available for lithium-ion batteries configured to run in the 'Voltage Control' charge strategy.
Example:
03:00-09:00
54.0 V
09:00-02:59
56.5 V
The HS configurable parameters can be set via local Web, eSite Tools and SNMP. See the Battery section for details how to configure the feature.
7.4.2.8 Peak Load Shifting
The purpose of Peak Load Shifting (PLS) is to maximize the solar energy for on-grid sites where the grid is available and stable. The idea behind the feature is to power the site load and charge the Li-ion battery bank with solar power as much as possible during daytime. The functionality steps in order to achieve this are as follows:
During the night, the grid will be used to power the load and keep the battery bank at Vmax, normally at float voltage.
At a predetermined and configurable time (PLS_start_time), the rectifiers are inhibited and the battery bank will power the load until the battery bank voltage has reached an adjustable voltage set point (PLS_Voltage).
Grid will maintain the battery bank at the PLS_Voltage level if solar power is not sufficient to carry the customer load.
If grid becomes unavailable and the battery bank reaches the DG start voltage, the genset will start. At this point, PLS functionality will be suspended and Hybrid Shifting will take over until the battery bank reaches the genset stop voltage and the genset is shut off again.
At a configurable time (PLS_end_time), the grid should be used to charge the battery bank at full power up to the Vmax float voltage level.
Note
The Peak Load Shifting function is only available for lithium-ion batteries.
The configuration parameters can be set via the local eSite Web, eSite Tools and SNMP. See the the Battery settings section for details how to configure the feature.
Note
Note that the Hybrid Shifting and the Peak Load Shifting parameters must be configured separately.
7.5 Genset
This section describes the management of a connected AC Genset by the eSite Modular system.
Read
Always follow the genset manufacturer's instructions during work with the genset.
The eSite RMC automatically starts and stops the genset when requested by the selected battery charge strategy, voltage level or set time. The genset start signal is controlled by a relay that is closed when the system requires the genset to start. The output relay can be configurable via the local web.
The eSite RMC determines the genset power request and controls the genset power output to ensure that the genset is not overloaded.
7.5.1 Genset modes
Ready. Genset is ready to start, waiting for a charge request.
Start request. Genset is requested to start. It stays in this mode until eSite sense voltage.
Warm up. Warming up genset without any power request.
Ramp up. The requested power is linearly ramping up.
Running. Genset is providing power.
Ramp down. Genset is ramping down.
Cooldown. Genset is running in idle without any power output.
Off state. Waiting for the genset to turn off. The state is active until the genset has stopped or 5 min has passed.
The times for the genset warm up, ramp up/down and cooldown stages can be configured.
Note
Always configure the genset according to the genset manufacturer recommendations. This extends the genset lifetime.
7.5.2 Genset Communication
Apart from the start/stop signal cable, there are a number of ways of sending useful information from a genset to the eSite Modular system.
Digital Inputs. The eSite RMC has 6 available configurable inputs to be used for genset signal relays, 3 inputs for genset 1 and 3 inputs for genset 2. Each relay is triggered when an internal Genset alarm is activated, which will in turn activate an alarm in th eSite Modular system. The input relays can be configured as normally open, normally closed or not used.
Modbus. The eSite RMC supports communication with genset panels to read signals and alarms directly from a genset AMF panel. The supported protocol for this communication is Modbus-RTU. Configuration for different genset panels can be customized on site or a premade configuration set can be created upon request. The data and alarms that are retrieved from the genset panel are stored and logged, both locally and remotely, every 10 minutes.
Note
AMF panel communication over RS485 (Modbus-RTU) can not be used if the RS485 port is already used for Modbus communication with a different Baudrate.
7.5.3 Dual Genset
The eSite Modular system supports operation with two connected gensets. Only one genset at a time can deliver power to the system. In regular hybrid operation, the system alternates the charge cycles between the two gensets. If one genset fails during operation, the other genset is immediately commanded to start.
For example:
Genset 1 fails during a charge cycle.
The start command to genset 1 stops. Genset 2 is commanded to start and completes the charge cycle.
Next charge cycle starts with genset 1. If genset 1 does not start, genset 2 will be commanded to start.
7.5.4 Genset Runtime and Service
The eSite Modular system keeps track of the total genset runtime and the remaining time (hours) until genset service is required. The service interval and when the alarm is triggered can be configured. Total runtime can be reset manually.
7.5.5 Estimated Time to Genset Start
When the Static SOC or the Partial SOC charge strategy is selected, the eSite Modular system estimates the time until the genset starts next time. The estimation is based on the discharge current and the low SOC threshold level where the charge cycle starts.
7.6 Night Silence
Caution
The Night Silence function prevents the genset from running at night. This can have a negative impact on battery health and site performance and void the battery warranties.
The Night Silence feature enabled the user to define a time period where genset operation is not desired and where the system prevents the genset from running. This is applicable mainly during the night for sites where the area around the site is populated.
The Night Silence period start and stop times can be configured. The system is able to pre-charge the battery bank to ensure that it is sufficiently charged when the Night Silence period starts. The Night Silence period can be configured to end at the configured stop time only or, if desired, by an emergency battery condition, i.e. a reached voltage or SOC level, whichever occurs first. Outside of the Night Silence period, the configured charge strategy will be used as usual.
Night Silence mode can be used for both off- and on-grid sites. For on-grid sites, pre-charge of the battery bank is usually not required. If the grid fails during the silent period the configuration determines when the genset is allowed to start.
When the Night Silence feature is inactive or disabled, charge cycles are performed without interference. The Night Silence feature is disabled by default.
7.6.1 Night Silence Pre-charge
The Night Silence pre-charge function charges the battery bank to a state where its autonomy time is enough to complete the Night Silence period. The function calculates the required number of ampere-hours (Ah) required for battery autonomy time based on the present site load and the duration of the silence period.
The following formula is the estimate of the preceding charge time in hours where Autonomy Ampere Hours is the needed energy required by the batteries for the duration of the Night Silence period. Safety margin is a configured threshold for the energy level that battery bank should be at in the end of the period. Present battery capacity is the capacity of the battery dynamically calculated, and the max charge current is the max allowed charge current.
7.6.2 Night Silence Active
For Night Silence to accurately shut off the genset at the configured time the site utilizes Network Time Protocol (NTP) time synchronization or is synchronized from eSite Tools. A local time zone must be configured at each site.
During an active Night Silence period, the genset is not commanded to start. The tenant receives power as long as the Low Voltage Disconnect is not triggered. The configurations are usually set for the period to be aborted before this happens. Manual start of the genset during the period overrides the Night Silence functionality and will start the genset.
7.6.3 Night Silence Aborted
The Night Silence period can be ended before the stop time is reached to allow the genset to start for several reasons .
7.6.3.1 Stop on charge request
If the stop on charge request configuration is ON, Night Silence is stopped when a charge request is triggered by the charge strategy. This configuration is usually used when the pre-charge cycle is desired to prepare the batteries for the night but standard charge strategy still is used.
A charge request always starts the genset if grid or solar is not available. A full charge cycle triggered by time or energy is postponed until the end of the Night Silence period. A full charge cycle not triggered by time or energy aborts the Night Silence period regardless if it was triggered during or before the Night Silence period.
7.6.3.2 Do not stop on charge request
If stop on charge request is OFF, the Night Silence period is aborted by the battery bank reaching a configured voltage level or a SOC level, whichever occurs first. A deeper discharge than intended by the charge strategy can be achieved to prolong the Night Silence period. The values can be set below the Low Voltage Disconnect threshold.
7.7 Solar
The eSite Modular system supports DC/DC conversion of solar array power through the RSE and SE converter units. The RSE unit is equipped with three (3) internal solar converters for a maximum capacity of 6.6 kW converted solar power and the SE unit is equipped with six (6) internal solar converters for a maximum of 13.2 kW converted solar power. The internal solar converters require no configuration and use individual maximum power point tracking (MPPT) algorithms to maximize the harvested solar power continuously.
Note
The total of solar array current output never exceeds 20 A per solar converter. Additional panels are not harmful to the eSite Modular system, but might not be utilized optimally.
7.7.1 Solar Management
The internal solar converters are designed for use with mono-crystalline and polycrystalline solar panels with 72 cells and 6 inch wafers. An optimal solar array is easily configured with these types of panels. It is also possible to use panels with other number of cells.
Caution
Do not connect solar panels with built-in electronics to an eSite Modular system. Contact eSite Power Systems for further information regarding this.
Caution
The open circuit voltage of each string of solar panels must never exceed 140 V.
Warning
If a solar array is incorrectly connected, for example with reversed polarity, an alarm is triggered and a relay disconnects the solar array to protect the eSite Modular system.
7.7.2 Green Power Influx
The Green Power Influx (GPI) component maximizes solar energy harvesting in relation to other power sources. When sufficient solar power is available, GPI becomes active and power drawn from the genset(s) and grid is inhibited.
Activation of the GPI functionality depends on the following conditions:
Green Power mode must be enabled.
Solar Power is sufficient.
Battery state of charge (SOC) is sufficient.
Batteries are in Normal charge mode and voltage is above limit.
System voltage is above limit.
Specified time interval (if applied).
Solar power is sufficient when it holds a configurable percentage of the load. To avoid frequent start and stop of the genset in case the solar power fluctuates, a delay timer for entering and exiting GPI is used to make sure that the solar power is sufficient and stable. This delay timer can be configured.
To ensure that the backup time is sufficient in case of a genset or grid failure, the battery bank must be above certain SOC and voltage threshold levels before GPI is activated. These thresholds are configurable, see Solar section for details how to configure the feature.
The GPI function is always in one of the following states:
Disabled. GPI is disabled (default)
Inactive. GPI is enabled by the user, but the solar power is insufficient or the eSite Modular system is currently in Safe mode.
Stopped. Solar power is sufficient, but the battery voltage or SoC is too low.
Idle. The solar power has not reached the selected load percent activation level (Load Percent operational mode), or current time is outside the selected time interval (Time Interval operational mode).
Active. All conditions are fulfilled, genset(s) and grid are inhibited and the solar power is fully utilized.
Green Power Influx has two (2) operational modes to choose from when activated: Load Percent mode and Time Interval mode.
7.7.2.1 Load Percent Mode
Load Percent mode is the default operational mode for GPI. This mode is suitable for all AC source configurations and when active, it inhibits both grid and genset from running.
In Load Percent operational mode, GPI is activated and the AC sources are switched off at a predetermined percentage of Solar power with respect to the customer load. AC power remains inhibited as long as the Solar power is sufficient. When the Solar power drops to a certain percentage level of the customer load, GPI is deactivated and AC power is allowed again to continue charging of the batteries (see figure 7.2).
For the example above, the Solar Load activation threshold is set to 80 % of the customer load and the deactivation threshold is set to 70 % of the customer load.
If the Grid is the primary AC source, the GPI component switches off and reengages the grid at predetermined percentage levels of solar power with respect to the customer load. An example of this scenario is given in figure 7.3.
7.7.2.2 Time Interval Mode
In Time Interval mode, specified times are set to enable/disable the AC source(s) according to when the Solar power is expected to be sufficient to support the customer load. The start/stop times of this function are configurable.
The Time Interval operational mode is mainly intended for use on sites with reliable grid connections and high solar output during daytime. When the purpose is to disable the genset from running in a specified time interval, it is recommended to use the Night Silence function instead.
Thus, in a typical application scenario for an on-grid site with good grid quality, the customer can choose a disable time where the grid is disabled and an enable time for the site to re-enable the grid. An example of such a scenario is given figure (7.4).
7.8 Grid control
Grid control is the collection of functions that monitors and manages the power extraction of a connected grid. The system is designed for a three-phase grid connection, but is also capable of handling single phase connections.
Each rectifier measures its AC phase voltage and frequency independently. If one phase is invalid, any other rectifiers connected to valid phases continue to operate at full performance. A phase is valid inside these ranges:
Voltage active range 85 – 300 Hz.
Frequency active range 45 – 65 Hz.
Outside of these ranges, the phase is considered invalid and the rectifier is disabled.
The performance of the rectifiers is monitored and presented as Grid status:
Invalid. All rectifiers are disabled due to insufficient phase voltage and/or frequency. Grid is not available.
Inhibited. Grid is available on at least one phase, but all rectifiers are inhibited from running and no power from grid is extracted. This state is entered when GPI is active or when the genset is prioritized to run, e.g. with an active Exercise Run request or when the genset is forced on.
Partial. One or two phases are valid, the rectifiers are active and running. Grid is partially available.
Ok. All three phases are valid, the rectifiers are active and running. Grid is available.
Power extraction from grid is limited by the size of the grid fuse. This value can be configured to ensure the fuse is not tripped and overloaded.
7.9 UPS mode
As an alternative to regular hybrid operation, the eSite Modular system can be set into an 'uninterruptible power supply' (UPS) mode, where AC power is being utilized constantly. The main purpose of the UPS mode is to always keep the site on-line and the batteries fully charged. This application is mainly intended for use on sites with poor-quality batteries that cannot be relied upon to carry the customer load for any length of time. The battery bank will always be in the Charge state regardless of SOC and charge current, and will normally be kept at the float voltage level. Periodic or singular Full Charge cycles at boost voltage level can be activated via settings.
For site setups with one AC source, i.e. a single genset or grid only, activation of this feature simply means that the available AC source will always be commanded to deliver power to the site.
As in normal hybrid operation, DC solar power may be utilized at all times in conjunction with the AC source(s). However, the Green Power Influx and Genset Night Silence features are not compatible with UPS AC mode and shall be disabled.
For grid/genset site configurations, AC power from either grid or genset may be utilized in UPS AC mode, with grid having higher priority than the genset. If one AC source fails, the second source is immediately commanded to start delivering power to the site.
For dual genset site configurations, equal runtime of the two gensets is achieved by regularly switching between the gensets based on a timer. Both gensets are requested to run before switching source to ensure minimum downtime. If one genset fails while running, an alarm is triggered and a start request to the second genset is commanded. The time to detect malfunction and activate the alarm is configurable with the "Genset start alarm delay time" parameter. See section Genset settings for more information.
7.10 Load Control
The eSite Modular system is equipped with dual Load Disconnect breakers that are controlled automatically. This makes it possible to divide the customer load into two parts of different priority, a low priority (LP) part and a high priority (HP) part. In any faulty scenario where the system, due to a major malfunction such as the genset not being able to start, is unable to properly support the load and charge the battery bank, the system is eventually protected by tripping the breakers, disconnecting the load.
In such a scenario, the LP customer load may be selected to disconnect before the HP load. The HP load is generally intended to be of smaller size than the LP load. Check the data sheet for default limitations of the HP and LP loads.
This functionality is designed to keep the site online for as long as possible in faulty scenarios and to protect the health of the batteries.
7.10.1 Low Voltage Disconnect (LVD)
The customer load is disconnected if incoming power is unavailable and the battery voltage falls below a configurable voltage threshold for a specified time (also configurable).
By disconnecting the customer load at low voltage levels, the battery bank is prevented from completely discharging. However, the delay timer makes it possible to handle sudden voltage drops upon engaging loads, i.e. if a load is engaged and the voltage drops below the defined threshold.
All LVD parameters are configurable on the eSite Web, see the Load disconnect settings.
7.10.1.1 LP Load LVD
When the system voltage falls below the threshold for LP load disconnect, the LP load will be disconnected after the LP load disconnect timer has expired . An alarm for LP load LVD will be triggered.
When incoming power is available again, the battery voltage recovers to the LP load reconnect volt threshold and the total delivered current exceeds the LP load reconnect current threshold (default 20 A), the load will be reconnected after a short LP load reconnect time .
For a quick recovery with a rapid increase to high voltage levels, the LP load may also be reconnected when the battery voltage exceeds the LP load fast reconnect level threshold without any delay.
7.10.1.2 HP Load LVD
HP load LVD functionality is disabled by default, but can be enabled with the HP load LVD enable setting. When this functionality is enabled, separate LVD settings (also configurable) for the HP load will be used.
If HP load LVD is disabled, the HP load will be disconnected and reconnected with the same settings as for the LP load LVD.
If HP load functionality is enabled and the HP load gets disconnected before the LP load, e.g. in case of a rapid voltage decrease, this will also trigger an LP load disconnect. Typically, the HP LVD has a lower voltage disconnect level but a shorter disconnect time. This will prevent the LP load from continuing to discharge the batteries.
7.10.2 Multi-tenant Monitoring
The eSite Modular system supports monitoring of up to ten (10) tenants separately. The total consumed load, including both HP and LP loads, is measured and logged. Auxiliary equipment on site is not included.
The sensors shall be connected via CAN, see detailed info in the Operations manual.
7.11 Cabinet Cooling
The eSite Modular system has a feature where it is possible to control, i.e. turn on/off, an external cooling device connected to a digital output port. The feature consists of turning this device on/off with a relay as a function of temperature.
The function can be used to control the temperature in the battery cabinet to further extend the battery lifetime in areas where appropriate battery temperature is not guaranteed by the site environmental conditions.
The Ambient temperature sensor and the Battery temperature sensors are required by the function. If one of them are invalid, the function will be in "Fallback" mode and the output will be ON.
The Digital output relay shall be configured to one of the standard output relays on the I/O board. See Configuration
The function can be set to operate in two different modes: Delta Ambient mode, which is based on the temperature difference between the battery and ambient temperatures, and Battery Temperature mode, which uses absolute temperature levels to start/stop cooling.
All Cabinet Cooling configurations can be made in the local eSite Web pages, see the Cabinet Cooling settings.
7.12 Fuel Monitoring
The Fuel Monitoring functionality gives the customer detailed information about the fuel level, consumption and abnormal events. Volume level, consumed, filled and lost volume is tracked and logged. Using fuel monitoring makes it easier to plan when to refill fuel.
A fuel monitoring sensor is connected to an Analogue In 0–10 V port and receives power from the 24 V output. All of the Analogue In 1-4 ports are available for configuration of fuel sensors. Two fuel sensors can be connected at the same time in order to monitor two separate tanks. By default, the fuel sensor for tank 1 is configured on Analogue In 1 and the fuel sensor for tank 2 is configured on Analogue In 2.
Filled and lost volume is calculated when a volume change has been detected. A volume change is triggered when the volume changes rapidly. This is configured as a percentage of the total tank volume / time span. Default is 4 % / 30 min.
The thresholds for low and very low fuel level alarms are configurable. A 'Sensor out of range' alarm is triggered when the voltage output of the sensor is outside its configured range.
7.13 Communication interfaces
7.13.1 SNMP
eSite Modular provides support for SNMP communication. A complete MIB with all signals specified can be requested from eSite Power Systems.
7.13.2 CAN
eSite Modular supports communication via the CAN protocol and can be used with e.g. Li-ion batteries or external LEM current sensors.
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