Small Scale Renewable Energy Sources and Energy Saving: 6-17 th July 2009 Monitoring & Control of Small-scale Renewable Energy Sources Dr G A Taylor Brunel Institute of Power Systems Brunel University, London, UK E-mail: gareth.taylor@brunel.ac.uk Web: www.brunel.ac.uk/~eesrgat
Monitoring & Control of Small-scale Renewable Energy Sources Overview Introduction to Monitoring & Control of Electricity Networks SCADA & Distribution Management Systems Overview of SCADA systems PV SSEG Case Study
Uncertainty in Power Networks Load levels change (UK Winter Peak 60 GW) Load pattern changes (Lighting up times) Unusual events Equipment failure Equipment faults (storms, floods) Uncertainty always exists in power system operation and control
Networks & Guiding Principles Sustainability Affordability Market Driven Security of Supply
Network Operation & Control Cycle Power Network Observation Power Network Implementation Operational Network Analysis Decision making process
SCADA - DMS What is SCADA - DMS? SCADA - DMS (Supervisory Control and Data Acquisition - Distribution Management System) supervises, controls, optimizes and manages distribution networks SCADA - DMS enable utilities to collect, store and analyze data from hundreds of data points in distribution networks, perform network modelling, simulate power operation, pinpoint faults and pre-empt outages
SCADA - DMS Enables integrated power network management & control Traditionally requires centralised operation & control Provides economies of scale Enables resource sharing (ie plant margin) Provides improved system security Distribution Management System (DMS) Requirements Dedicated networked hardware and software systems Large-scale data processing and storage capability Fast reaction times for operational control State Estimation System Optimisation Procedures
Introduction to SCADA SCADA - Supervisory Control And Data Acquisition A SCADA system is an automated process that Gathers data from a network of meters, sensors and instruments located at remote sites Transmits and displays gathered data at a central site for either control or monitoring purposes Control centre is traditionally a central or master site Gathered data is usually viewed on one or more SCADA host computers located at the control centre A typical SCADA system can monitor and control hundreds to hundreds of thousands of I/O points
Introduction to SCADA Typical Power System SCADA application: Monitor voltage levels at various substations and when the voltage level exceeds a preset limit, activate a system of transformer tapping to compensate (EDF Energy 132/33 kv Substation, West Weybridge) Common analogue signals that SCADA systems monitor and control are voltages, currents, power flows etc Typical digital signals to monitor and control are transformer tap positions, circuit breakers, relays etc.
SCADA There is typically another layer of equipment between remote sensors and instruments and the control centre This intermediate equipment exists on the remote sites and connects to the sensors and field instruments Sensors typically have digital and/or analogue I/O
SCADA Data Communications Sensor signals are not usually in a form that can be easily communicated over long distances Intermediate equipment is used to digitize and then packetize the sensor signals Signals can then be digitally transmitted via industry standard communication protocols to a control centre
SCADA Typical equipment that handle the data communication are RTU (Remote Terminal Unit) Data Logger Such devices employ industry standard data communication protocols to transmit sensor and instrument data Modbus Profibus AB-DF1 DNP3.0 Traditional physical layer interface standards are RS-232 RS-485 (longer distances & higher speeds) Bel 202 modem
SCADA SCADA Host The SCADA Host is usually an industrial PC running sophisticated SCADA HMI (Human Machine Interface) software The software is used to poll the remote sites and store the collected data in a centralized database (eg SQL, Oracle etc) Logic can be configured in the SCADA Host software which then automatically monitors and controls plant or equipment
SCADA SCADA Host The control may be automatic or initiated by operator commands Data acquisition is initially accomplished by an RTU scanning the field instrument inputs connected to the RTU This data is usually collected at a polling rate configured by the system operator
SCADA SCADA Host The polling rate is determined by: Number of remote sites Amount of data at each site Maximum bandwidth of communication channel Minimum required display and control time
SCADA After data has been acquired at the SCADA Host HMI software will scan the acquired data usually at a slower rate Data is then processed to detect preset alarm conditions If an alarm is present: An alarm message will flash on the operator screen and is added to an alarm list The operator must then acknowledge this alarm
SCADA There are 3 common types of data collected by SCADA: Analog - used for trending (voltage or frequency) Digital (on/off) - used for alarming (circuit breaker) Pulse (eg revolutions of some kind of meter) - accumulated or counted
SCADA Primary operator interface is a set of graphical screens that show a representation of the system and equipment being monitored Real-time data is displayed numerically or graphically as changing bars, circles, lines or other shapes over a static background As the acquired data changes in real-time, the bar, circle, line or other representative shape is updated For instance, an analogue level increase may be displayed as a lengthening of the representative vertical bar or a breaker graphic may look open to represent that it is open
SCADA A typical HMI will have a nested tree structure of many such screens, usually with the many overview screen on the first page with the most relevant data displayed There are then links that go to other pages Users can usually easily configure Type of I/O point Communication protocol driver Polling rate Alarm thresholds and notifications Trend process data Visibility and layout of User and Operator screens
PV SSEG CASE STUDY
PV SSEG CASE STUDY Sunny Portal Daily Information Reports for PV SSEG
PV SSEG CASE STUDY Sunny Portal Daily Information Reports for PV SSEG 24/06/09 Daily Production: 5 kwh Daily Power (max.): 1.32 kw Daily Revenue: 2.34 Daily CO2 Reduction: 3.5 kg 02/07/09 Daily Production: 4 kwh Daily Power (max.): 1.29 kw Daily Revenue: 1.87 Daily CO2 Reduction: 2.8 kg
PV SSEG CASE STUDY Sunny Portal Daily Information Reports for PV SSEG 24/06/2009 02/07/2009
PV SSEG CASE STUDY Sunny Portal Monthly Information Reports for PV SSEG 03/09 Monthly Production: 27 kwh Monthly Power (max.): 1.32 kw Monthly CO2 Reduction: 18.9 kg 05/09 Monthly Production: 102 kwh Monthly Power (max.): 1.33 kw Monthly CO2 Reduction: 71.4 kg
References 1. Shahidehpour & Wang, Communications & Control in Electric Power Systems, Wiley, 2003 2. G. M. Masters, Renewable and Efficient Electric Power Systems, Wiley, 2004 3. SMA Technology: http://www.sma.de/en/products/wind-energy-inverters/ (Last accessed July 2009) 4. F. K. Paterakis, Monitoring and Control of Small-scale Embedded Generation, MSc Thesis, Sustainable Electrical Power, Brunel University, Sep. 2008 5. S. Chowdhury, P. Day and G. A. Taylor, Supervisory Data Acquisition and Performance Analysis of a PV Array Installation with Data Logger IEEE PES General Meeting, Pittsburgh, USA, August 2007 6. P. Day, Wide-Area monitoring of small-scale embedded generation, Final Year Project, Electronic & Electrical Engineering, Brunel University, Mar. 2009.