1. Distributed Energy Engineering
(IKE1002)
Part5: PLC controls

2. Programmable Logic Controllers
Program is a integral part of the device
Application area – All technical devices and systems
Logic diagram represents the functionality unambigiously
Binary commands
Mathematical and number handling commands
The easiest way to make control programs
Easy to read and understand
Ability to apply needs some practise

3. Programmable Logic Controllers
Operating principle
How the program, memory and I/O work together
PLC-Commands
Binary commands
Math and number related commands
How to control inverters
Fieldbus interface
How to utilize control and status information of inverters
CPU
Input
Output
Input register
Output register
Memory

4. Characteristics of PLC
IO-connections
Inputs - Measure the status of the ”Outside World”
Outputs – Control the ”Outside World” to desired direction
The only multipurpose device designed to do this
Easy to program
Designed to describe logical relationships
Document your ideas – Voila, It is the program solution
Graphical representation – figures instead of text
Fast
Reaction time is faster than mechanical phenomens – Less than 10 ms
Optimized dedicated CPU’s for binary logical operations

5. Characteristics of PLC
Reliable
Designed to industrial environments
No moving parts
Long design history
Fast
Reaction time is faster than mechanical phenomens – Less than 10 ms
Optimized dedicated CPU’s for binary logical operations
Cheap
Prices start from 100 eur upwards
With this price you can substitute about 10 mechanical relays
Data logging
Has the knowledge of the measured data by the nature
Has the fieldbus communication interfaces by the nature
Collects and refines the data and sends it to PC-based databases

6. Typical application – Energy Generation

7. Operating principle of PLC
Input Register
Inputs are the binary measurements
At input card the are normally screw terminals
For every input screw there exists a memory bit in the PLC memory
A voltage at the screw reflects 0 or 1 status at the memorybit (True/False)
Ouput Register
Outputs are the binary controls
At ouput card the are also normally screw terminals
For every output screw there exists a memory bit in the PLC memory
Status 0 or 1 at the memorybit is reflected as a voltage at output screw.
Program
The program measures the state of the outside world with the inputs
Based on the inputs the program decides what actions should be taken
The program actuates the decisions with the control outputs

8. Operating principle of PLC
Program
Program consists several logical networks
Program is executed network by network
The networks are executed in the order they exists at the program
Each network ends to logical value True or False
Each network writes the logical value to memory location
Memory locations where writes takes place are Output register or help-memory (Merker)
The values which are compared at the logical networks are Input register, Output register or Help-memoryvalues
Program scan
Before the network execution starts the input register is updated – Voltage status at the input terminals are transferred to memory bit values
Then networks are executed
At the end the output register values are transferred to output terminal voltages
All outputs are effected at the same time – at the end of the program scan, not while networks are executed
Output registers are affected directly during the program scan

9. Binary commands AND OR ASSIGNMENT NEGATE
If all the inputs are 1 then the output is one
The number of the input terminals are not limited
If the AND-gate has only one input, it is the same as copy OR
If any of the inputs are one then the output is one
ASSIGNMENT
AND- and OR-GATES requires assignment command ”=”
It ends the network
It gives the the logical value of the network to a given memory bit.
NEGATE
Inverts the logical value
01 and 10

10. Binary commands SR RS S R S R Q No change 1 Set – Reset gate
Functionality is one bit memory
If Set-terminal is one then the memory bit is set to one
If Reset-terminal is one then the memory bit is reset to zero
If both in-terminals are zero tehn the memory bit is unaffected. It stays the same as at previous program scan
Reset has priority over Set. If both are one then the memory bit is zero RS
Same as SR, but Set overrides Reset S
Same as Set-terminal R
Same as Reset-terminal S R Q
No change 1

11. Binary commands Midline output - # P N Positive edge
If the input chanages 01 then the output is one
Functionality is:
Recognizes events
Gives a pulse, which has duration of one program cycle
Needs a help memory bit. Used to remember the input value at the previous program scan. This is not the edge. Do not use this memory anywhere else N
Negative edge
If the input chanages 10 then the output is one
Midline output - #
Copies the value of the specified location to the memory bit

12. Timers Common featues of the timers
WHEN TIMING STARTS THE TIME VALUE IS READ INTO TIMER AND IT GOES DOWNWARDS TO ZERO. THE OUTPUT CHANGES WHEN ZERO IS REACHED
T DESIGNATES THAT MEMORY AREA "T" IS USED; YOU HAVE TIMERS T0-T127
"T0" AND Q - MEANS THE SAME THING
S MEANS START; START TRIGGERS FROM RISING EDGE (NOT STATIC VALUE ONLY)
TV MEANS TIMER VALUE; GIVE TIME FORMAT "MANTRA" S5T#; THEN DESRIED TIME
R MENAS RESET; STOPS TIMING; RESETS TIME VALUE TO ZERO; OVERRIDES S
BI MEANS BINARY FORMAT; GIVES ACTUAL TIME OUT IN INTEGER; REQUIRES TWO BYTES
BCD MEANS BCD-FORMAT;GIVES ACTUAL TIME OUT IN BCD-FORMAT; REQUIRES TWO BYTES
RESLUTION OF TIME CHANGES AUTOMATICALLY ACCORDING TIME VALUE IN TV

13. Timers ON-DELAY TIMER WITH MEMORY ON-DELAY TIMER OFF-DELAY TIMER
DELAY BETWEEN INPUT AND OUTPUT
"ON" MEANS DELAY STARTS WHEN INPUT GOES ON
OFF-DELAY TIMER
"OFF" MEANS DELAY STARTS WHEN INPUT GOES OFF
ON-DELAY TIMER WITH MEMORY
S-INPUT MEMORIZES THAT IT HAS BEEN ONE
THIS TYPE ALLWAYS NEEDS RESET-INPUT AS WELL

14. COUNTERS Count Up and Down
S sets the counter value to the value specified at PV
PV is given as a counter format designated as C#
R resets the counter value to zero
CU – Rising edge at CU increments the counter value by one
CD – Rising edge at CD decrements the counter value by one
C DESIGNATES THAT MEMORY AREA “C" IS USED; YOU HAVE COUNTERS C0-C127
CV – Counter value in integer format
CV_BCD – Counter value in BCD-format
Q – Boolean Output of the counter – Zero if the counter value is zero, otherwise one. The boolean output can be addressed as Cx (C1) as well.
There exists counters as well with only count up or count down terminals

15. DATATYPES Boolean Byte Word DoubleWord
One memory bit represents true or false (1 or 0)
Example M1.0
Byte
Byte is 8 consecutive bits
Example MB 1
Word
Word is two consecutive bytes
Example MW 1
Word also means a positive number without decimals
DoubleWord
DoubleWord is two consecutive words
Example MD 1

16. DATATYPES Integer DoubleInteger Real
Integer means number without decimals, positive and negative
Integer occupies a word
MW100
DoubleInteger
DoubleInteger is same as Integer, but occupies two words – a doubleword
MD100
Real
Real means number with decimals
Integer occupies a doubleword
The number has allways to be written and read at the same datatype

17. DATACONVERSIONS From Integer to Real From Real to Integer
MW100 – Integer; MD102 – Double Word; MD106 - Real
From Real to Integer
Mw100 – Integer; MD102 – Double Word; MD106 - Real

18. Mathematical functions
Each datatype has own mathematical commands
Addition, Subtract, Division and Multiplication
Integer, Doubleinteger and Real
Example- function of a line – Y=k*x+b in real numbers

19. Comparators Each datatype has it’s own comparator command set
Equal; Not Equal; Grater Than; Less Than; Greater or Equal; Less than or Equal;
Integer, Doubleinteger and Real
Example- GT and GE commands

20. Symbol table
At symbol table you can give descriptive names to memory addresses

21. Datablock Datablock is a user definable help-memory area
Each datga can be reached by name or by address

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