BESS is a compact solution, equipped with all the components to provide a ready to use, flexible and modular energy storage system.

 

System

  • LiFePO4 Storage and BMS
  • Bidirectional Converter and Converter Controller
  • Master Controller (MC)
  • Filters and Transformer

 

BESS Grid Services

  • Limitation of overvoltage caused by RES power injection
  • Energy time shift
  • Peak shaving and load leveling
  • Reactive power regulation
  • Primary frequency regulation
  • Secondary and tertiary frequency regulation
  • Current harmonic compensation
  • Low Voltage Fault Ride Through (LVFRT)
  • Black start
  • Power Quality
  • Compliance with Grid Codes

 

BESS Specification

 

Scales from 600 kW – up to MVA range

  • Modular units from 600 kW – 1500 kW
  • On-grid and off-grid operation
  • Manages multiple renewable sources, storage system and loads
  • Distributed Energy Generation
  • Grid services
  • Renewable Integration
  • Mobile and stationary applications
  • Compensation of fluctuations in the generation and consumption of electricity
  • Grid stabilisation
  • Allows to level power generation, shaving peaks
  • The system can modulate active and reactive power
  • Microprocessor-based
  • Uninterruptible power supply
  • Fully reliable configuration and validation of any power plant

There are several technical and economical reasons to have a time shift of energy.

Energy vs Power performance of BESS

The battery energy storage size has to be chosen in terms both of power and energy. The BESS is capable to provide a time shift of energy, so that it accumulates a certain amount of energy in the battery during a time interval, and it returns it, or part of it, in a subsequent time.

There are several technical and economical reasons to have a time shift of energy.

In an isolated power system the BESS can accumulate energy when there is a surplus of generation, to return it when there is a shortage. Thus the BESS can compensate for the unbalances between the generation and the load profiles.

Since generation from renewable energies depends on seasonality, the BES contributes to counteract it too. The BESS can absorb energy from the grid in low cost times and dispatch it during high cost times. The load energy consumption is shifted in time (load shifting) and concentrated in the low cost periods.

The energy size of BESS (kWh of stored energy) is determined by the desired amount of energy to be time shifted, and it is related to the requested duration or autonomy.

The nominal power of BESS (kW) is determined by the output power of the bi-directional DC/AC converter which connects the BESS to the grid (or mini grid) and by the maximum current which can be extracted by the battery during discharge. This is also related to the capacity of battery (Ah) and to its admissible rate of charge and discharge.
The designer will select the requested BESS power according to the rate of battery charge and discharge and to the requirements of micro grid stability.

BESS can provide grid support through grid services.

Energy Services

  • Energy Time shift
  • Peak shaving/Load leveling
  • Restart of Power System
  • Tertiary Reserve

Power Services

  • Primary Regulation
  • Secondary Regulation
  • Voltage Support
  • Frequency regulation

 

Microgrid – Intelligent power supply

Microgrids are outstandingly suitable to cover the rapid increase in electricity consumption. It‘s not necessary to build new large power plants. Thus overloaded existing electricity transmission lines can be avoided.

The microgrid solution is able to connect and disconnect the mains very quickly. In the event of a mains failure, important facilities are provided with a safe, clean interruption-free power supply. The microgrid can absorb energy from the grid in low cost times and dispatch it during high cost times.

 

System

LiFePO4 Battery Storage

  • High specific power energy density, long life
  • Long cycle life, maintenance free
  • Most safe lithium battery
  • Flexible extension
  • Battery Management Sytem (BMS)
  • Protection due to overcharging, over discharging, overtemperature
  • Cell balancing at all times

Bidirectional Converter and Converter controller

The battery system is connected through a DC/AC bidirectional converter.

The Bidirectional Converter is equipped with a control logic algorithm and it can operate in different modes:

Grid following – The converter acts as a current generator when it is connected to a grid

Grid forming – The converter acts as a voltage generator. This mode is used in islanded operation and the converter creates the Power Balance node in a multi-source mini grid.

Grid supporting – The converter acts as a voltage generator with the frequency and the voltage amplitude dependent on the active and reactive power (Droop control). This operation mode is used to connect several source in parallel on a mini grid.

 

Filters and Transformer

The BESS system is connected to the grid through an interface stage, which includes filters and power transformer.

The transformer provides insulation between DC and AC systems, adapts the inverter output voltage to the grid voltage (LV and MV grid), creates the neutral point and compensates the load unbalances during off grid operation.

The filter reduces voltage and current harmonics injected into the grid. It consists of an LCL filter to cut the harmonics due to switching frequencies and of a high frequency EMI filter.

The purpose is to maintain a low harmonic distortion, typically :
Current THD < 3% in grid connected operation
Voltage THD < 3% in islanded operation

Master Controller

  • defines and implements the BESS control logic algorithm
  • defines the set points of the inverter controller
  • communicates with the BMS to manage the battery status

 

BESS can operate in two modalities:
Autonomous control:
The MCreceives measurements from the system and the BMS and decides autonomously the control strategy.

External control:
The MC receives the control strategy from an external controller and implements it depending on the battery status.

DGS-Monitor

to monitor PV and wind power plants through Ethernet or Internet
(GSM, EDGE, UMTS, HSDPA).

Production data are stored locally or can be transferred to a server to
detect and solve plant problems immediately.

 

BESS/C-BESS cabinets

Electrical connections

  • DC side: PV, battery system
  • AC side: Main grid or micro grid, wind/generator, user load

BESS/C-BESS cabinets include:

  • DC/AC power converter
  • Digital control of power converter
  • LCL and EMI filters
  • Output power transformer
  • Master Controller
  • Protections and switchgear
  • Measurement points
  • Forced air cooling
  • Touch screen display
  • External battery cabinet
  • Customization of C-BESS cabinets upon request

C-BESS Containers

The electrical equipment of C-BESSs are suitable for indoor operation.
In case of lack of proper rooms to install the equipment, a solution in 20’ or 40’ container can be provided upon request.

Containers are thermally insulated, furnished with doors for access of personnel, divided in spaces for separate installation of batteries and other electrical equipment.

They are normally air ventilated.

  • Air conditioning is available upon request
  • Lighting, sockets, aux power supply, fire fighting system are normally provided