Udc 3500

[yaldrim]

Hi,

I want to control drum level of boiler with UDC 3500 using three element control.

I wonder how can I make my own control equation in controller.
I want to implement following equation.

SP of Secondary Loop= (OP(Primary Loop) + Steam Flow(%))-50%

Any help in this regard is appreciated and if someone has better equation, please let me know.

Regards,

 

[danw]

See the attached app note on 3 element boiler control.

The diagram appears to use 3 analog inputs, the dual loop cascade option and the math option's feedforward summer.

 

[yaldrim]

Thanks

 

[danw]

Note the rules in the 2nd to last post in this thread. For practical purposes the 3500 and 6300 are the same architecture.

http://www.eng-tips.com/viewthread.cfm?qid=205091

 

[strigoi]

Dear danw,

I have configured UDC3500 with the following configurations;

Input 1: Drum Level (0-100)
Input 2: Feed water Flow (0-30)
Input 3: Steam Flow (0-30)

ALGORITHMS
Cont Alg: PID A
PIDLOOPS: CASCADE
Cont2Alg: PID A
Timer: Disable
IN ALG 1: F FWRD
ALG 1 INA: Input 3
ALG 1 INB: LP2OUT
ALG 1 INC: NONE

CONTROL
PV Source: Input 1
PID Sets: 1 Only
LSP's : 1 Only
SP Track: NONE
PWR Mode: Manual
SP Hi Limit: 30
SP Lo Limit: 0
Action: Reverse
Out Rate: Disable
Out Hi Lim: 100
Out Lo Lim: 0

CONTROL 2
PV 2 SRC: Input 2
Link LPS: Disable
PID Sets: 1 Only
LSP's : 1 Only
RSP SRC: NONE
SP Track: NONE
PWR Mode: Manaul
SP Hi Lim: 100
SP Lo Lim: 0
Action: Reverse
Out Rate: Disable

After Putting all above configurations, result is not as it should be.
I get;

Loop 2 Out Loop 1 RSP
48.3 14.5
47.5 14.25
75.5 22.6

always with a same ration i.e. 3.3, no matter what is the value of steam flow (Input 3) is. I think Input 3 has no effect in anyway on this configuration.
According to my understanding, RSP of Loop 1 should change as Steam flow (Input 3) changes.
Please guide what am i missing here.

Best Regards,
Irfan Ali

 

[danw]

Without checking any settings other than PV sources, I can see that you have mixed up the loops.

Pay very close attention in the graphic which PV feeds which loop. You have to play by Honeywell's rules - how Honeywell defines cascade control to get the UDC to work.

Wrong PV for the wrong loop number.

Here's another summary:

Loop 1 needs a remote SP (RSP in Honeywell terminology), the output from loop 2.

 

[strigoi]

Dear Danw,

Thanks for your response.
I have got your point, Input 2 (Feed Water Flow) should be PV of Loop 1 and input 1 (Drum Level) should be PV of Loop 2.

But here is another problem;
How will I configure Input 3 (Steam Flow) with Loop 2 (Primary Loop)?

One More thing;
when I configure PIDs in CASCADE, the option of "RSP SRC" vanishes in "CONTROL" setting, but when I put Loop 1's SP at RSP, it gives me a value which auto changes as output of Loop 2 changes, it means these are auto configured, there is no need to set "RSP SRC" for Loop 1 in CASCADE. but input 3 (Steam Flow) is showing no effect on it, even when input 3 is 0, RSP of Loop 1 remains the same.
Please suggest what should I do now?

Best Regards,
Irfan Ali

 

[danw]

Under ALGORITHM group, note that the Feedforward sums with Loop 2's output.

Try this:
IN ALG 1 = NONE
IN ALG 2 = F FWR 2
ALG2 INA = INPUT 3 (if Input 3 is still Steam Flow)
ALG2 INB = NONE
ALG2 INC = NONE

Input 3 bias is where you subtract 50% (of whatever it is spanned) in order to get a bipolar value. The span of Input 3 reflects the 'gain' that it applies to loop 2's output.

 

[danw]

I don't think the Feed Forward is linked to a loop, so it could be either FFWD 1 or FFWD 2.

My syntax was wrong:
IN ALG 1 = NONE
IN ALG 2 = F FWR 2
ALG2 INA = INPUT 3 (if Input 3 is still Steam Flow)
ALG2 INB = NONE
ALG2 INC = NONE

FFWD needs both the ALGx INA and the ALGxINB factors:
IN ALG 1 = NONE
IN ALG 2 = F FWR 2
ALG2 INA = INPUT 3 (if Input 3 is still Steam Flow)
ALG2 INB = LP2OUT
ALG2 INC = NONE

 

[danw]

Nope, I'm wrong, according to the manual Loop 1 uses FFWD1

 

[danw]

The UDC I used has Firmware V 3505C.
I could not get it to run proportional only on either loop 1 or loop 3 with the input allocation you had.

I changed the PV Source to the same input as the loop number and it seems to work, so that's
Input 1, feedwater flow for Loop 1
Input 2, Drum level for Loop 2
Input 3, Steam Flow as the feedforward variable

Note that
Loop 1 uses a Remote Setpoint, so SP Track = RSP for Loop 1
Loop 2 uses a local setpoint (LSP)

The active setpoint appears with a solid green square to the left of the SP or RSP ID in the bottom display

ALGORITHMS
CONT ALG: PID A
PIDLOOPS: CASCADE
CONT2ALG: PID A
Timer: Disable
IN ALG 1: NONE
IN ALG 2: F FWR2
ALG 2 INA: INPUT 3
ALG 2 INB: LP2OUT
ALG 2 INC: NONE

OUTALG
OUT ALG: CURRENT

INPUT 1 (Feedwater Flow)
IN1 TYPE: 4-20MA
XMITTER1: LINEAR
IN1 HIGH 30.00
IN1 LOW: 0.00
RATIO 1: 1.000
BIAS IN1: 0.0
FILTER 1: 1

INPUT 2 (Drum Level)
IN2 TYPE: 4-20MA
XMITTER2: LINEAR
IN2 HIGH 100.00
IN2 LOW: 0.00
RATIO 2: 1.000
BIAS IN2: 0.0
FILTER 2: 1

INPUT 3 (Steam Flow)
IN3 TYPE: 4-20MA
XMITTER3: LINEAR
IN3 HIGH 30.00
IN3 LOW: 0.00
RATIO 3: 1.000
BIAS IN3: -15.0
FILTER 3: 1

CONTROL (loop 1)
PV Source: Input 1
PID Sets: 1 Only
LSP's : 1 Only
AUTOBIAS: DISABLE
SP Track: RSP
PWR Mode: A RSP (start up in Automatic mode, Remote SP)
SP Hi Limit: 30
SP Lo Limit: 0
Action: Reverse
Out Rate: Disable
Out Hi Lim: 100
Out Lo Lim: 0

CONTROL 2
PV 2 SRC: Input 2
Link LPS: Disable
PID Sets: 1 Only
LSP's : 1 Only
RSP SRC: NONE
SP Track: NONE (changed from RSP)
PWR Mode: A LSP
SP Hi Lim: 100
SP Lo Lim: 0
Action: Reverse
Out Rate: Disable
Out HiLIM: 100
Out LoLIM: 0

When I configure the tuning constants for PB = 100, Rate = 0, Reset = 0.02RPM, both loop 1 and loop 2 outputs drive in the correct directions.

Loop 1's RSP tracks Input 3 (Steam flow) - up when it goes up, down when it goes down
Loop 1's RSP inversely tracks Input 2 (drum level) - down when In2 goes up, up when In2 goes down

Loop 1's output reacts correctly to an increasing In1 PV (feedwater flow); (output decreases on increasing flowrate)


Loop 2's output reacts correctly to an increasing In2 PV (drum level); (output decreases on increasing drum level)

Loop 2's output increases when In 3 (steam flow) increases
Loop 2's output decreases when In 3 (steam flow) decreases