FB_MaximumDemandController

Function block for peak load optimization, which ensures that the set power limit is maintained by switching up to eight consumers on or off. The consumers can be switched off according to their power and priority in such a manner that the production process is not disturbed.

In order to distinguish the individual measurement cycles, a synchronization pulse is supplied by the electricity supply company. It indicates the start of a new measuring cycle and must be linked to the input bPeriodPulse. The actual power is recorded via the KL1501 counter terminal.

The function block works with a fixed measuring period of 15 minutes. If the synchronization pulse exceeds the 16 minute limit, the output bEmergencySignal is set.

All consumers are switched on at the start of each measuring period. In the event that the power limit (fAgreedPower) threatens to be exceeded within the measuring period, the consumers are switched off one after the other. If the danger of an excess load no longer exists, the consumers are switched on again.

Special items, such as minimum power-on time, minimum power-off time or maximum power-off time can be specified via an input variable. The priority of the individual consumers can similarly be determined. Consumers with a low priority will be switched off before consumers with a high priority.

VAR_INPUT

bStart              : BOOL;
fMeterConstant      : LREAL;
fAgreedPower        : LREAL;
bPeriodPulse        : BOOL;
arrLoadParameter    : ARRAY[1..8] OF ST_MDCLoadParameters;     

bStart: The function block is activated by a positive edge at this input.

fMeterConstant: Meter constant [pulses / kWh].

fAgreedPower: This is the agreed power limit which, as far as possible, should not be exceeded in the operational case [kW].

bPeriodPulse: Synchronization pulse sent by the electricity supply company (ESC). This pulse starts the measurement interval.

arrLoadParameter: Parameter structure of the respective consumer (see ST_MDCLoadParameters).

VAR_OUTPUT

arrLoad               : ARRAY[1..8] OF BOOL;
fAgreedEnergy         : LREAL;
fInstantaneousEnergy  : LREAL;
fActualEnergy         : LREAL;
tRemainingTime        : TIME;
fLastPeriodEnergy     : LREAL;
bEmergencySignal      : BOOL;
bError                : BOOL;
nErrorId              : UDINT;

arrLoad: This is an array of data type BOOL; consumers that are switched on are TRUE.

fAgreedEnergy: Agreed energy consumption [kWh].

fInstantaneousEnergy: Current energy consumption [kWh] over an integration period of 15s (internal measuring interval).

fActualEnergy: Energy consumed at the "presently" observed point in time of the measuring period.

tRemainingTime: Time remaining until the next measurement interval.

fLastPeriodEnergy: Rated power from the preceding measuring period [kWh].

bEmergencySignal: This output is set as soon as the specified energy is exceeded.

bError: This output is switched to TRUE as soon as an error occurs during the execution of a command.

nErrorId: Contains the error code.

VAR_IN_OUT

stInDataKL1501      : ST_MDCInDataKL1501;
stOutDataKL1501     : ST_MDCOutDataKL1501;

stInDataKL1501: Linked to KL1501 (see ST_MDCInDataKL1501).

stOutDataKL1501: Linked to KL1501 (see ST_MDCOutDataKL1502).

Example

VAR_GLOBAL
  arrLoadParameters      AT %MB100 : ARRAY[1..8] OF ST_MDCLoadParameters;

  (* KL1002 *)
  bPeriodPulse       AT %IX6.0 : BOOL;

  (* KL1501*)
  stInDataKL1501     AT %IB0 : ST_MDCInDataKL1501;
  stOutDataKL1501    AT %QB0 : ST_MDCOutDataKL1501;

  (* KL2404 *)
  bLoadOut1          AT %QX6.0 : BOOL;
  bLoadOut2          AT %QX6.1 : BOOL;
  bLoadOut3          AT %QX6.2 : BOOL;
  bLoadOut4          AT %QX6.3 : BOOL;

  (* KL2404 *)
  bLoadOut5          AT %QX6.4 : BOOL;
  bLoadOut6          AT %QX6.5 : BOOL;
  bLoadOut7          AT %QX6.6 : BOOL;
  bEmergencySignal       AT %QX6.7 : BOOL;
END_VAR

PROGRAM MAIN
VAR
  fbMaximumDemandController : FB_MaximumDemandController;
END_VAR

arrLoadParameters[1].bConnected := TRUE;
arrLoadParameters[1].nDegreeOfPriority := 1;
arrLoadParameters[1].tMINPowerOnTime := t#60s;
arrLoadParameters[1].tMINPowerOffTime := t#120s;
arrLoadParameters[1].tMAXPowerOffTime := t#600s;

arrLoadParameters[2].bConnected := TRUE;
arrLoadParameters[2].nDegreeOfPriority := 2;
arrLoadParameters[2].tMINPowerOnTime := t#60s;
arrLoadParameters[2].tMINPowerOffTime := t#120s;
arrLoadParameters[2].tMAXPowerOffTime := t#600s;

arrLoadParameters[3].bConnected := TRUE;
arrLoadParameters[3].nDegreeOfPriority := 3;
arrLoadParameters[3].tMINPowerOnTime := t#60s;
arrLoadParameters[3].tMINPowerOffTime := t#120s;
arrLoadParameters[3].tMAXPowerOffTime := t#300s;

arrLoadParameters[4].bConnected := TRUE;
arrLoadParameters[4].nDegreeOfPriority := 4;
arrLoadParameters[4].tMINPowerOnTime := t#20s;
arrLoadParameters[4].tMINPowerOffTime := t#30s;
arrLoadParameters[4].tMAXPowerOffTime := t#8m;

arrLoadParameters[5].bConnected := TRUE;
arrLoadParameters[5].nDegreeOfPriority := 5;
arrLoadParameters[5].tMINPowerOnTime := t#20s;
arrLoadParameters[5].tMINPowerOffTime := t#50s;
arrLoadParameters[5].tMAXPowerOffTime := t#20m;

arrLoadParameters[6].bConnected := TRUE;
arrLoadParameters[6].nDegreeOfPriority := 6;
arrLoadParameters[6].tMINPowerOnTime := t#30s;
arrLoadParameters[6].tMINPowerOffTime := t#1m;
arrLoadParameters[6].tMAXPowerOffTime := t#1m;

arrLoadParameters[7].bConnected := TRUE;
arrLoadParameters[7].nDegreeOfPriority := 7;
arrLoadParameters[7].tMINPowerOnTime := t#0s;
arrLoadParameters[7].tMINPowerOffTime := t#0s;
arrLoadParameters[7].tMAXPowerOffTime := t#1m;

arrLoadParameters[8].bConnected := FALSE;

fbMaximumDemandController(bStart := TRUE,
              fMeterConstant := 20000,
              fAgreedPower := 600,
              bPeriodPulse := bPeriodPulse,
              arrLoadParameters := arrLoadParameters,
              stInDataKL1501 := stInDataKL1501,
              stOutDataKL1501 := stOutDataKL1501);

bLoadOut1 := fbMaximumDemandController.arrLoad[1];
bLoadOut2 := fbMaximumDemandController.arrLoad[2];
bLoadOut3 := fbMaximumDemandController.arrLoad[3];
bLoadOut4 := fbMaximumDemandController.arrLoad[4];
bLoadOut5 := fbMaximumDemandController.arrLoad[5];
bLoadOut6 := fbMaximumDemandController.arrLoad[6];
bLoadOut7 := fbMaximumDemandController.arrLoad[7];
bEmergencySignal := fbMaximumDemandController.bEmergencySignal;

Requirements