ABB AC160Industrial Networks Connecting Controllers via OPC

[5].

2.2.1 OPC Data Acces

OPC DA is organized in the hierarchical structure server, group and item. Items correspond to variables and can be read and written. Furthermore, a quality and time stamp is provided with each of them. When reading items, the value usually comes from the OPC server’s cache, which is updated periodically with the values of the device (or bus, component). However, it is usually possible to force a read directly from the device. Clients organize their items in groups, which for example share the same access method and update rate. Each OPC server has an unique name, some vendors even offer the operation of multiple servers for the same device. OPC DA provides different methods to access items, first of all synchronous and asynchronous read and write operations. More important to us, there is also a subscription mechanism, which is commonly used by modern clients in order to reduce communication. That is, the client group subscribes to the server which then “pushes” values towards the client only if they changed respectively exceed a pre-defined dead-band. The client can force an update of all these values by issuing a refresh call, which corresponds to an asynchronous read for all items of a group [6].

2.3 Programmable Logic Controllers

This section informs about the two controllers involved and about the controller that has to be replaced. Please notice that we use the term controller equivalent to programmable logic controller (PLC) throughout our Master’s Thesis.

2.3.1 Advant Controller 160 (AC160)

The AC160 series was launched in 1997 to meet high speed requirements in turbine control. To this day its outstanding performance is needed for fast closed loop control (CLC). For our work, we were provided with a rack RF616 for the physical mounting of the controller parts. The rack also delivers power to each device and includes the BIOB Backplane Input/Output Bus which, among other tasks, processes the communication between the processor module and the communication interface. The tests in this Master’s Thesis were done with processor modules of the type PM665 (containing a Motorola MPC8240 processor) and the AF100 communication interface CI631, both supporting redundancy [7]. To program the processor module, its built-in EIA-232 interface was connected to the engineering PC.

2.3.2 Advant Controller 450 (AC450)

AC450 is the controller to be replaced by the new generation. Its processor module is built up around a Motorola 68040 microprocessor running at 25 MHz [8]. While its performance is quite limited, AC450 also lacks of modern communication interfaces and standards like Ethernet, which become more and more important.

2.3.3 Control IT AC800M

Control IT AC800M is the most current controller series used within all of ABB, introduced in 2001 [9]. It strikes with its small outline and offers modern communication interfaces. For our tests we were provided with a processor module PM864A which contains a Motorola MPC862 microprocessor running at 96 MHz [10]. In addition to two EIA-232 interfaces, the processor module of AC800M offers two built-in 10 Mbit/s standard Ethernet ports, used for instance to connect to the engineering computer. The communication interface CI854A is a sophisticated device to establish PROFIBUS communication. The device even offers an own web interface which

allows e.g. the surveillance of the cycle time. The device is directly coupled to the processor module via the Communication Extension Bus (CEX) [11]. At this point of time, CI854A can only act as a PROFIBUS master, but not as slave. As a consequence, communication partners must be slaves.

2.4 Bus and Network Communication

This section describes the different communication approaches used in our system

2.4.1 Advant Fieldbus 100 (AF100)

AF100 is a high performance fieldbus system with time synchronization and the most popular fieldbus used within ABB, 

common to almost all platforms. Although the name Advant Fieldbus 100 is ABB proprietary, it complies to IEC standard

 61375-3 as well as US-standard IEEE 1473 and is widely used in railways under the name of MVB. AF100 works over tw

isted pair, coaxial and optical media at a rate of 1.5 Mbit/s. For our system we made use of the first method only. Bus ma

ster responsibility is shared by all communication interfaces with administrator

Diplomarbeit ABB Schweiz AG

Power Systems / Power Generation

Industrielle Netzwerke Leistung – Verfügbarkeit – Zuverlässigkeit

Es sollen die bestehenden Strukturen von industriellen Netzwerken und Bussystemen für die Kraftwerksautomation basierend auf dem ABB Leitsystem 800xA analysiert werden. Dabei sollen verschiedene Fragestellungen in den Bereichen Verfügbarkeit, Leistung und Sicherheit bearbeitet werden.

Das ABB Control-System welches zur Steuerung von Hochleistungs-Gasturbinen eingesetzt wird, soll mit den neuesten Technologien punkto offener Schnittstellen, Anbindung an TCP/IP Netzwerke und Unterstützung von Device Management Tools etc. ausgerüstet werden. Hierzu soll der bestehende „Kopf-Rechner“ Advant Controller 450 durch einen Controller der neuesten Generation, einen AC800 M Controller ersetzt werden.