Energy Storage

NPPT performs a variety of services relating to the planning, specification, control, protection, testing and performance analysis of energy storage plants, including:

  • Design, implementation, and laboratory and field testing of BESS controllers
  • EMT or HIL simulation studies in support of planning, design, and operations, to facilitate
    • Selection of inverters, measurement path devices, and controllers
    • Design of controls to meet performance objectives
    • Protection system design and specification, including AC and DC-side arc flash
    • Understanding of expected system behavior during events, such as faults, load switching, or on-to-off-grid transitions.
  • Power system studies and BESS interconnection engineering
  • Design, execution and interpretation of tests and commissioning, in the laboratory or in the field
  • Measurement and simulation-based analysis and diagnosis of performance issues in fielded systems
  • Event, failure, and root-cause analysis

NPPT provides these services with an exceptional level of skill, professionalism, responsiveness, and creative but practical thinking. If you have a need that does not appear on this list, please contact us to discuss it.

Example projects


A brief listing of a few relevant recent projects includes the following.

Development of controls for a battery-energy storage system (BESS) for PV plant output smoothing. Specific duties:
  • Construction and validation of a detailed transient model of the BESS, PV plant, and circuit with loads
  • Development of a controller to cause the system to meet performance objectives, and testing of that controller via simulation
  • Provision of documentation and collaboration to facilitate inverter manufacturer’s implementation of the control algorithm in the fielded system
  • Specification and interpretation of tests of the BESS and controller
  • Ongoing performance evaluation and issue resolution for the BESS
Engineering of a battery-inverter system for frequency support on a small island grid.This was a roughly 5 MW diesel-based island grid in which PV penetration levels are becoming high (on an instantaneous power basis, sometimes as high as 90%). One constraint was that the BESS needed to perform its frequency regulation function without being connected to the existing generator plants’ control or measurement systems. Specific duties:
  • Assistance with inverter specification and selection
  • Construction and validation of a detailed transient model of the BESS, generator plant, PV plants, and the entire island grid with loads (including motor load)
  • Design of all controls for the battery-inverter system
  • Implementation of the controls in collaboration with the manufacturer andmanufacturer’s third party
  • Specification of the measurement path devices for the BESS
  • Complete system protection and underfrequency load shedding reviews
  • Design and interpretation of system tests
  • Ongoing performance assessment and measurement interpretation
Protection coordination and arc-flash study for a low-inertia system containing BESS, PV and rotating The key considerations were to ensure that reasonable protection coordination was maintained when only inverter-based sources were present, and to assess the true arc-flash risk in a case in which the fault current is highly dynamic. Specific duties:
  • Construction and validation of a detailed transient model of the BESS and all system components
  • Use of the model to determine fault currents
  • Specification of protection equipment and all settings
  • Determination of arc flash PPE ratings for all critical points on the system