Jan. 2008

Data communication in renewable energy systems

George Wang

Jan. 2008

Grid Tie PV System

Jan. 2008

Jan. 2008

Small-scale wind turbine system

Jan. 2008

US Wind Power Capacity (MW)

1 vs. 5 year

Jan. 2008

Inverters

Jan. 2008

Communication ports on inverter

Jan. 2008

Setting up a connection

Jan. 2008

Data communication platform

Jan. 2008

Communication Gateway• Bridges the gap between a solar

inverter and a computer. • Includes built-in Wi-Fi and

Ethernet.• Can be configured to send

energy and alarm reports via email

• Embedded web page for configuring and upgrading inverter firmware

• The Gateway is sold at $650 list price.

Jan. 2008

Communication Gateway SpecsCommunication Physical layer 2, CAN

Communication protocol Xanbus™

Connectors 3 RJ-45 – 8 pins (2 Xanbus, 1 Ethernet)

Ethernet IEEE Std 802.3™-2005

Wireless 802.11.4b and 802.11.4g; WEP and WPA security

North America EMC FCC part 15B class B

Industry Canada ICES-003 class B

Safety Low Voltage Directive 2006/95/EC

EN60950-1:2001  

EMC EMC Directive 2004/108/EC

  EN55022 A2: 2003

  EN55024 A2: 2003

Telecom R&TTE Directive 1999/5/EC

  ETSI EN 301 489-1 ver. 1.6.1

  ETSI EN 301 489-17 ver. 1.2.1

 

Jan. 2008

Data Acquisition Server

• independent product from the inverter manufacturers

• provides “plug & play” connectivity for monitoring solar system performance.

• It is sold at $1,649 list price.

Jan. 2008

Data Acquisition Server

Jan. 2008

Data Acquisition Server Specs• Processor Main processor: ARM 9 ; I/O co-processor: ARM 7• Operating System Linux 2.6• Flash ROM 16 MB NOR Flash (expandable with USB memory device)• Memory 32 MB RAM• LED 8x pulse input, 4 modem activity, Modbus TX/RX, power status• Console 2 x 16 LCD character, two buttons• LAN 10/100, Auto crossover detection• Modem (phone) V.34 bis, 33,600 bps (Part number A8812-1)• Modem (cellular) GSM/GPRS Class10, 85 kbps (Part number A8812-GSM)• Protocols Modbus/RTU, Modbus/TCP, TCP/IP, PPP, HTTP/HTML, FTP,SNMP, SMTP• Power Supply 24 VDC, included• Serial Port RS-485 Modbus• Approvals CE; FCC Part 15, Class A• USB port USB memory expansion port• Power Requirement 110-120VAC• Interval recording User selectable 1-60 minutes. Default 15 minute interval.• Outputs 2x, Dry contact 30 VDC, 150 mA max• Inputs 8x, user selectable:

– 0-10 V - Min/Max/Ave/Instantaneous– 4-20 mA - Min/Max/Ave/Instantaneous– Pulse - Consumption, Rate– Resistance - Min/Max/Ave/Instantaneous– Runtime - Runtime, Status

Jan. 2008

Wireless Transceiver• Provide the wireless connectivity

among the monitoring devices. • Submeter commercial and industrial

facilities• Add Modbus devices to any network

without the need for costly communications wiring

• Connect up to 128 RS 485 Modbus devices to any Modbus network

• Use “Plug and play” connectivity for supported devices to the data acquisition server

• Unique “mesh” technology means optimized routing of communications

• Accepts standard pulse inputs or Modbus

• It is sold at $535 list price.

Jan. 2008

Wireless Transceiver

Jan. 2008

Modbus Protocol• Modbus is a serial communications protocol published by Modicon in 1979 for use with its

programmable logic controllers (PLCs). It has become a de facto standard communications protocol in industry, and is now the most commonly available means of connecting industrial electronic devices. The main reasons for the extensive use of Modbus over other communications protocols are:

– It is openly published and royalty-free – Relatively easy industrial network to deploy – It moves raw bits or words without placing many restrictions on vendors – Modbus allows for communication between many devices connected to the same

network, for example a system that measures temperature and humidity and communicates the results to a computer. Modbus is often used to connect a supervisory computer with a remote terminal unit (RTU) in supervisory control and data acquisition (SCADA) systems.

• Most Modbus devices communicate over a serial EIA-485 physical layer • Limitations

– The number of data types is limited to those understood by PLCs. Large binary objects are not supported.

– No standard way exists for a node to find the description of a data object, for example, to determine if a register value represents a temperature between 30 and 175 degrees.

– Since Modbus is a master/slave protocol, there is no way for a field device to "report by exception" (except over Ethernet TCP/IP, called open-mbus)- the master node must routinely poll each field device, and look for changes in the data. This consumes bandwidth and network time in applications where bandwidth may be expensive, such as over a low-bit-rate radio link.

– Modbus is restricted to addressing 247 devices on one data link, which limits the number of field devices that may be connected to a master station (once again Ethernet TCP/IP proving the exception).

– Modbus transmissions must be contiguous which limits the types of remote communications devices to those that can buffer data to avoid gaps in the transmission.

Jan. 2008

Monitoring Software