Advanced power management

August 15th, 2014, Published in Articles: EE Publishers, Articles: EngineerIT, Featured: EE Publishers

 

Jack Faett

Jack Faett

With integrated advanced power management control systems, companies can design and implement highly available backup power infrastructures for maximised uptime, reduced costs, and improved performance and efficiency, all of which drive the bottom line as well as customer satisfaction.

This article will explore the merits of integrating power synchronisation and measurement into the backup power monitoring and control system. Functionality required for grid synchronisation and measurement will be detailed. The benefits of integrating this functionality into the control system will be discussed.

In today’s “always on” society, facilities that support operations in data centres, healthcare, power and emergency response, are under intense pressure to maintain continuous system availability and at the same time increase energy efficiency to reduce costs.These modern demands require a renewed focus on the design of mission critical backup power control systems which play a key role in the ability to maintain continuous operations and increase efficiency. Integrating advanced power management strategies into backup power control systems enhance the ability to deliver on these metrics by enabling power grid synchronisation coupled with measurement of power consumption metrics.

Any advanced power management application strategy is only as good as the power monitoring data the solution can deliver. For best results, it is recommended that the following specification criteria be considered for effective management of the backup power infrastructure:

Specification Description
Power measurement configuration Single-phase or three-phaseThree-phase delta or three-phase WYE
 Electric meter ANSI C12 Class .2
Power factor resolution Measure up to 0,01 units of control
Frequency = ±0,01 Hz
Phase angle = ±0.1°
Note: Power factor penalties are utility-dependent, but typically imposed at 0,90. A power factor resolution of 0,01 provides 10 times the units of control for measurement and predictive decision making.
Integrated ANSI standard protective calculations:  System fault condition monitoring–equipment damage avoidance.

  • Under/over voltage
  • Reverse power
  • Voltage imbalance
  • Under/over frequency
  • Over current
  • Mismatched phase sequence/angle
Control system integration Backplane communications for full access to control system data and I/O

With the intelligence gained from the mission critical backup power infrastructure data specification, several key advanced power management strategies can be implemented to deliver best asset performance and reduced total cost of ownership.

Power grid synchronisation 

Critical facilities typically have multiple onsite backup power generators that need to be managed and synchronised in the event of a power outage of the main utility source.   For example, backup generator synchronisation to the grid may require that voltages difference should be less than 2%, frequency should match between the bus 0,5 Hz and phase shift between generators < 20. The genset controller or auto-synchroniser commands the engine to go faster or slower to change the frequency and also interact with the field voltage of the alternator that changes the voltage. When the frequency and phase angle values are within the synchronising bandwidth,the generator can be “switched” to the grid as the main power source.

Load sharing and/or load shedding

Measurement of reactive power metrics provides the ability to collect and analyse power consumption of the electrical power systems over time. This critically important data can be used to avoid peak demand charges and to shed loads during peak operating periods to increase efficiency and reduce costs. The functionality enables:

  • Synchronisation of multiple buses to split the load requirements based on the relative capacity of each of the backup power generators;
  • Speed control of each generator so the load does not deviate from the preset dead band;
  • Raise and/or reduce power load share adjust signals based on load share metrics and error conditions.

Power factor correction

Uninterruptible power supplies (UPS), generators and utilities all have power factor specifications. Utility companies generally impose power factor penalties when the consumer’s power factor is lagging or leading by as little as 0,1. Power factor correction canbe as simple as switching to additional circuit capacitance, such as capacitor banks.  It may, however, require significantly more coordination to minimise the operation of lightly loaded motors, such as cooling fans, which may require moving loads to other circuits.

Power quality monitoring

Advanced power management data collection can be used to drive a waveform capture function of the backup power electrical infrastructure.  Waveform captures can provide detailed fault condition views, harmonic power analysis and capture of transient voltages and currents to verify power quality and validate system configurations.

Harmonic distortion of voltage and current waveforms are introduced into power systems from non-linear loads. Distorted waveforms can lead to excessive neutral currents, increased temperature and are a cause of premature equipment failure.

Visualisation, control and analytics

Utilising the data collected from the advanced power management solution, effective mission critical facility support strategies can be implemented. Continuous operation and performance improvements of all backup power systems are only as good as the run-time data collected for analysis. Coupling the advanced power management data with key software applications providesfacility managers and operations personnel with the ability to make informed decisions based on actionable data.

  • Critical alarm response management software empowers operators to make better decisions by providing information and guidance with the exact responses needed to address critical alarms within the backup power system.
  • Work process management software allows HMI/SCADA users to provide operators with specific instructions and the precise information they need to make the correct decisions in critical situations or switchover scenarios.
  • Advanced analyticssoftware provides insight into the likely causes of events or issues, perform “what if” scenario analysis, and identify opportunities for continuous improvements and preventing future problems.

For example, analytics can provide insight into metrics such as power usage effectiveness (PUE) to better understand the relationships between the factors that impact the metric, providing a means to take action on the extracted knowledge.

Conventional control systems

Advanced power management can be accomplished in conventional control systems with the right up-front system design, development and startup commissioning to ensure that all components operate seamlessly. Implementing these advanced power management strategies in a conventional control system does, however, have some drawbacks:

  • In addition to the control system, for each grid in the backup power electrical infrastructure a variety of synchroscopes, meters, switches, lamps and relays are required to provide the necessary control components. These additional components resultin a more complex system architecture and potential for single points of failure.
  • External scopes required to perform wave form capture and display are typically not integrated with the conventional control system.
  • Multiple programming environments which may be required to configure, control and maintain the control, network and metering systems increases the risk of human error during normal operation and/or problem resolution.
  • Application code must be developed in the backup power control system to collect, interpret and calculate the appropriate data values for executing the various advanced power management functions required to perform generator synchronistion and load sharing. Optionally, these functions could be implemented via manual input with visual indicators and pushbuttons.
  • Collecting, interpreting and contextualising power and generator parameters from the external devices for use in the control systems advanced power management functions creates potential for data accuracy and execution latency issues during run time.
  • Detailed work instructions for day-to-day operation, maintenance and failover for operations, engineering and maintenance personnel will be required.
  • Historical data will have to be memory mapped, collected and stored into a separate data base system for offline analysis.

Integrated advanced power management

Architecting a control solution that integrates advanced power management into the backplane of the control system provides the most flexibility in design and implementation of backup power electrical systems. Advanced technology control solutions that provide multi-function power synchronisation and measurement interfaces are ideal for equipment manufacturers and system integrators providing paralleling switchgear and generator sets for use in mission critical facilities.

A single control solution with integrated advanced power management delivers all functionality to manage the entire backup power infrastructure:

  • Automatic start/stop of generators
  • Engine status monitoring, frequency/voltage control and fault reporting
  • Automatic generator paralleling (synchronising)
  • Power quality monitoring and fault reporting
  • Measurement of power consumption metrics
  • Load shedding and load sharing
  • Waveform capture of all backup power grids
  • Data logging andreporting

In the end, having to design, develop, integrate startup and maintain a single control system for the entire backup power infrastructure provides the best possible performance with the lowest total cost of ownership:

  • Use of external manual devices can be reduced or eliminated
  • Wave form capture displayed directly on the control system HMI
  • One programming environment for the control system, HMI, power synchronisation and measurement interfaces
  • All power parameters are collected and calculated by the integrated advanced power management interfaces
  • All data is available in real time to the control via backplane communications, eliminating latency and integrity issues
  • Historical data will be available from one control system for visualisation, control and analytics
  • Taking the solution a step further, implementing highly available redundant control solution architectures with integrated advanced power management would help ensure continuous operation of the backup power infrastructure in a mission critical facility.

Contact Robert Sparg, GE Intelligent Platforms, Tel 011 653-8897, robert.sparg@ge.com

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