CN110160296A - Screw parallel unit electric current dynamic control method - Google Patents
Screw parallel unit electric current dynamic control method Download PDFInfo
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- CN110160296A CN110160296A CN201910436114.3A CN201910436114A CN110160296A CN 110160296 A CN110160296 A CN 110160296A CN 201910436114 A CN201910436114 A CN 201910436114A CN 110160296 A CN110160296 A CN 110160296A
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- 238000000034 method Methods 0.000 title claims abstract description 63
- 238000005057 refrigeration Methods 0.000 claims abstract description 7
- 238000001704 evaporation Methods 0.000 claims abstract description 6
- 238000011068 loading method Methods 0.000 claims description 77
- 230000001105 regulatory effect Effects 0.000 claims description 68
- 238000009833 condensation Methods 0.000 claims description 8
- 230000005494 condensation Effects 0.000 claims description 8
- 230000006835 compression Effects 0.000 claims description 6
- 238000007906 compression Methods 0.000 claims description 6
- 238000002715 modification method Methods 0.000 claims description 6
- 230000008020 evaporation Effects 0.000 claims description 5
- 230000001276 controlling effect Effects 0.000 claims description 3
- 238000001816 cooling Methods 0.000 abstract description 2
- 230000005611 electricity Effects 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 3
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
- F25B49/022—Compressor control arrangements
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Air Conditioning Control Device (AREA)
- Control Of Positive-Displacement Pumps (AREA)
Abstract
Screw parallel unit electric current dynamic control method provided by the invention passes through the anticipation calculating and the floating of current protection parameter setting before compressor loads; control compressor adds unloading; to avoid breaker overcurrent protection caused by compressor loads and the shutdown of compressor to cause refrigeration output inadequate as far as possible; while guaranteeing that compressor cooling capacity as big as possible exports; protect compressor safety, and distribution system overcurrent protection caused by being avoided as far as possible because of compressor overcurrent.In the case where distribution system capacity is limited, this method can also be by reading total current/power meter measured value, and combines runing time section, and dynamic changes current protection value and evaporating pressure setting value, to realize the saving of the electricity charge.This method is arranged and combines Learning Control Method using anticipation control plus floating parameter, makes compressor before it overcurrent may occur, and is not loaded with or reduces energy output as far as possible to avoid the generation of compressor overcurrent.
Description
Technical Field
The invention relates to a current control method of a compressor unit, in particular to a dynamic control method of a screw parallel unit current.
Background
Under some industrial control bad use working conditions or under the condition that power distribution is limited, the screw rod parallel compressor unit needs to scientifically control the output of the compressor so as to avoid the overcurrent protection of a circuit breaker of the compressor or the overcurrent protection of the circuit breaker of the whole equipment main distribution box.
The compressor unit works under the working conditions of high evaporation pressure and high condensation pressure, and the compressor can overflow, so that a compressor breaker is frequently tripped, the work of a refrigeration system is influenced, and even the safety of goods is endangered.
The conventional compressor current protection method adopts circuit breaker tripping protection, cuts off power supply of a compressor when overcurrent occurs, and has the consequences that the compressor cannot be restarted if unattended on site, and a thermal relay which automatically resets can be frequently started and stopped to cause power grid fluctuation, and meanwhile, the installation space and the material cost of a thermal relay of a large screw compressor are also an extra burden.
Disclosure of Invention
In order to solve the problems, the invention provides a screw parallel unit current dynamic control method for controlling the loading and unloading of a compressor through the pre-judgment calculation before the loading of the compressor and the floating setting of current protection parameters, thereby avoiding the insufficient refrigeration output caused by the overcurrent protection of a circuit breaker and the halt of the compressor caused by the loading of the compressor as much as possible, protecting the safety of the compressor while ensuring the maximum cold output of the compressor, and avoiding the overcurrent protection of a power distribution system caused by the overcurrent of the compressor as much as possible, and the specific technical scheme is as follows:
the dynamic control method of the screw parallel unit current comprises a dynamic loading method of the screw parallel unit current, and the dynamic loading method of the screw parallel unit current comprises the following steps:
s100, starting a screw rod parallel unit;
s101, detecting whether the unit is in a loading interval, entering S102 if the unit is in the loading interval, keeping all compressors in a shutdown state if the unit is not in the loading interval, and detecting whether the unit is in the loading interval again after delaying;
s102, sending a starting signal to the Nth compressor;
s103, predicting the total current It1 after loading, entering S104 if the total current It1 after loading is predicted to be smaller than the total protection current Its, and entering S230 if the total current It1 after loading is predicted to be larger than the total protection current Its;
s104, starting an Nth compressor, and keeping two energy regulating valves arranged on the Nth compressor closed;
s105, detecting the actual total current Id1 of the loaded unit, entering S106 if the actual total current Id1 after loading is smaller than the total protection current Its, and entering S250 if the actual total current Id1 after loading is larger than the total protection current Its;
s106, detecting whether the unit is in a loading interval, if so, entering S107, and if not, entering S260;
s107, predicting the current Ib1 of the Nth compressor when one of the energy regulating valves of the Nth compressor is opened and is loaded to 66%, entering S108 if the predicted current Ib1 is smaller than the primary protection current Iset1, and entering S380 if the predicted current Ib1 is larger than the primary protection current Iset 1;
s108, predicting the total current It2 of the unit when one energy regulating valve of the Nth compressor is opened and loaded to 66%, entering S109 if the predicted total current It2 is smaller than the total protection current Its, keeping the output unchanged if the predicted total current It2 is larger than the total protection current Its, and predicting the total current It2 of the unit when one energy regulating valve of the Nth compressor is opened and loaded to 66% again after delaying T3;
s109, one energy regulating valve of the Nth compression is opened, and the other energy regulating valve is kept closed;
s110, detecting the actual current Ib2 of the Nth compressor when one of the energy regulating valves of the Nth compressor is opened and is loaded to 66%, entering S111 if the detected actual current Ib2 is smaller than the primary protection current Iset1, and entering S290 if the detected actual current Ib2 is larger than the primary protection current Iset 1;
s111, detecting an actual total current Id2 of the unit, entering S112 if the detected actual total current Id2 of the unit is smaller than the total protection current Its, and entering S310 if the detected actual total current Id2 of the unit is larger than the total protection current Its;
s112, detecting whether the unit is in a loading interval, if so, entering S113, and if not, entering S320;
s113, predicting the current Ic1 of the Nth compressor when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, entering S114 if the predicted current Ic1 is smaller than the secondary protection current Iset2, and entering S380 if the predicted current Ic1 is larger than the secondary protection current Iset 2;
s114, predicting the total current It3 of the unit when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, entering S115 if the predicted total current It3 is smaller than the total protection current Its, keeping the output unchanged if the predicted total current It3 is larger than the total protection current Its, and predicting the total current It3 of the unit when the two energy regulating valves of the Nth compressor are opened and loaded to 100% again after delaying T4;
s115, opening two energy regulating valves of the Nth compressor and the Nth compressor;
s116, detecting the actual current Ic2 of the Nth compressor when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, and entering S350 if the detected actual current Ic2 is greater than the secondary protection current Iset 2;
s117, detecting the actual current It4 of the unit when the two energy regulating valves of the Nth compressor are both opened and loaded to 100%, entering S118 if the detected actual current It4 of the unit is smaller than the total protection current Its, and entering S360 if the detected actual current It4 of the unit is larger than the total protection current Its;
s118, detecting whether the unit is in a loading interval, if so, entering S119, and if not, entering S370;
s119, detecting whether all the compressors of the unit are completely loaded, if all the compressors are completely loaded, entering S120, and if all the compressors are not completely loaded, entering S380;
s120, keeping the current situation of all the compressors;
wherein,
s230, keeping the output unchanged, and entering S231;
s231, after delaying T2, entering S103;
s250, the Nth compressor is closed after time delay, and then the process enters S251;
s251, recording the number of times of loading and unloading, and then entering S252;
s252, judging the number of times of overcurrent and unloading in unit time, entering S231 if the number of times of overcurrent and unloading in unit time is smaller than a set value, keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value, and giving a prompt;
s260, detecting whether the unit is in a holding interval, if so, entering S261, and if not, entering S262;
s261, keeping the existing output unchanged, and then entering S106;
s262, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
s290, keeping the Nth compressor in a starting state, closing two energy regulating valves of the Nth compressor, and then entering S380;
s310, keeping the Nth compressor in a starting state, closing two energy regulating valves of the Nth compressor, and then entering S311;
s311, recording the number of times of over-current unloading, and then entering S312;
s312, judging the number of times of overcurrent and unloading in unit time, entering S380 if the number of times of overcurrent and unloading in unit time is smaller than a set value, keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value, and giving a prompt;
s320, detecting whether the unit is in a holding interval, if so, entering S321, and if not, entering S322;
s321, keeping the existing output unchanged, and then entering S112;
s322, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
s350, the Nth compressor is kept in a starting state, one energy regulating valve of the Nth compressor is kept in an opening state, the other energy regulating valve of the Nth compressor is closed, and then the process enters S380;
s360, the Nth compressor keeps a starting state, two energy regulating valves of the Nth compressor are closed, and then the process enters S361;
s361, recording the number of times of over-current unloading, and then entering S362;
s362, judging the number of times of overcurrent and unloading in unit time, entering S380 if the number of times of overcurrent and unloading in unit time is smaller than a set value, and keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value and sending a prompt;
s370, detecting whether the unit is in a holding interval, if the unit is in the holding interval, entering S371, and if the unit is not in the holding interval, entering S372;
s371, keeping the existing output unchanged, and then entering S118;
s372, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
and S380, starting the (N + 1) th compressor.
Preferably, the method further comprises a screw parallel unit current dynamic unloading method, and the screw parallel unit current dynamic unloading method comprises the following steps:
s500, completing the loading of all compressors with the starting signals of the unit;
s501, detecting whether the unit is in an unloading interval, entering S502 if the unit is in the unloading interval, keeping all the compressors in the existing state if the unit is not in the unloading interval, and detecting whether the unit is in the unloading interval again after delaying;
s502, detecting the state of the Nth compressor, entering S503 if the Nth compressor is in a starting state and the running time of the Nth compressor is longest, and entering S610 if the Nth compressor is in the starting state and the running time of the Nth compressor is not the longest;
s503, the Nth compressor keeps a starting state, one energy regulating valve of the Nth compressor is closed, and the other energy regulating valve keeps an opening state;
s504, detecting whether the unit is in an unloading interval, if so, entering S505, and if not, entering S620;
s505, the Nth compressor keeps a starting state, and two energy regulating valves of the Nth compressor are closed;
s506, detecting whether the unit is in an unloading interval, if so, entering S507, and if not, entering S630;
s507, closing the Nth compressor and the two energy regulating valves for the Nth compression;
s508, detecting whether all the compressors of the unit are completely unloaded, if all the compressors of the unit are completely unloaded, entering S509, and if all the compressors of the unit are not completely unloaded, entering S650;
s509, keeping the current status of the compressor, and entering S101;
wherein
S610, unloading the (N + 1) th compressor, and then entering S502;
s620, detecting whether the unit is in a holding interval, if so, entering S504, and if not, entering S621;
s621, detecting whether the unit is in a loading interval or not, and entering S113 if the unit is in the loading interval;
s630, detecting whether the unit is in a holding interval, if so, entering S506, and if not, entering S631;
s631, detecting whether the unit is in a loading interval or not, and entering S107 if the unit is in the loading interval;
and S650, unloading the (N + 1) th compressor.
Preferably, in S262, if the unit is in the unloading interval, the process proceeds to S506;
if the unit is in the unloading interval in the step S322, entering step S504;
if the unit is in the unloading interval in the step S372, the step S502 is entered;
after all the compressors in S120 are maintained as they are, the process proceeds to S501.
Preferably, the first and second liquid crystal materials are,
the loading section, the holding section and the unloading section all use set suction pressure as judgment reference;
the loading interval is as follows: p > P0+ P1;
the holding interval is: p is more than P0 and P1, and P is 0-P1;
the unloading interval is as follows: p is less than P0-P1;
in the formula
P is actually detected suction pressure;
p0 is the set suction pressure;
p1 is the set intake pressure deviation, which is within the range of ± P1.
Preferably, the time delay T2, the time delay T3 and the time delay T4 are not less than 5 minutes.
Preferably, the set value of the number of times of the overflowing unloading is 6.
Preferably, the first and second liquid crystal materials are,
further comprising a total protection current modification method, said total protection current modification method comprising the steps of:
s401, after the screw parallel unit is started in S100, detecting the current of all compressors, the suction pressure, the exhaust pressure, the condensation pressure, the suction temperature and the exhaust temperature of a refrigeration system;
s402, reading the total power of an external power distribution main ammeter, and reading the current real-time;
and S403, judging whether the current time Is in a low-load time period, if the current time Is in the low-load time period and the total load margin Is2 Is greater than 1.2 times of the total protection current Its, modifying the total protection current Its, and if the current time Is not in the low-load time period, entering S402.
Preferably, the step S102 further includes determining whether the nth compressor has the shortest running time and is not started, entering step S103 if the nth compressor has the shortest running time and is not started, and sending a starting signal to the (N + 1) th compressor if the nth compressor has the shortest running time and is not started, and then entering step S102.
Preferably, the step S104 further includes correcting the current prediction fitting coefficient according to the detected actual current Id1, and then predicting the current value Ib1 loaded to the next stage according to the corrected current prediction fitting coefficient and the system parameter;
s109 further comprises correcting a current prediction fitting coefficient according to the detected actual current Ib2, and predicting a current value Ic1 loaded to the next stage according to the corrected current prediction fitting coefficient and system parameters;
the step S115 further includes correcting the current prediction fitting coefficient according to the detected actual current Ic2, and then predicting the current when the next compressor is loaded to 33% according to the corrected current prediction fitting coefficient and the system parameters.
Preferably, the formula of the total current after the prediction loading of S103, S107 and S115 is as follows:
Z＝p1+p2*X+p3*Y+p4*X2+p5*X*Y+p6*Y2+p7*X3+p8*Y*X2+p9*X*Y2+p10*Y3；
in the formula,
z is the predicted current;
x is the evaporation temperature;
y is the condensation temperature;
p 1-p 9 are fitting coefficients of the compressor.
Compared with the prior art, the invention has the following beneficial effects:
the dynamic control method for the current of the screw parallel unit controls the loading and unloading of the compressor through the pre-judgment calculation before the loading of the compressor and the floating setting of the current protection parameters, thereby avoiding the over-current protection of a circuit breaker caused by the loading of the compressor and the insufficient refrigeration output caused by the halt of the compressor as much as possible, protecting the safety of the compressor while ensuring the maximum cold output of the compressor, and avoiding the over-current protection of a power distribution system caused by the over-current of the compressor as much as possible.
In the case of limited capacity of the power distribution system, the method can also realize the saving of the electricity fee by reading the measured value of the total current/power meter and dynamically changing the current protection value and the evaporation pressure set value in combination with the operation time period.
The method uses the pre-judgment control and floating parameter setting and combines a self-learning control method, so that the compressor is not loaded or the energy output is reduced as far as possible before the overflow of the compressor is possible, and the overflow of the compressor is avoided.
Drawings
FIG. 1 is a flow chart 1 of a dynamic current loading method for a screw parallel unit;
FIG. 2 is a flow chart 2 of a method for dynamically loading current to a screw parallel unit;
FIG. 3 is a flow chart of a method for dynamically unloading the current of the screw parallel unit.
Detailed Description
The invention will now be further described with reference to the accompanying drawings.
As shown in fig. 1 and fig. 2, the method for dynamically controlling the current of the screw parallel unit includes a method for dynamically loading the current of the screw parallel unit, where the method for dynamically loading the current of the screw parallel unit includes the following steps:
s100, starting a screw rod parallel unit;
s101, detecting whether the unit is in a loading interval, entering S102 if the unit is in the loading interval, keeping all compressors in a shutdown state if the unit is not in the loading interval, and detecting whether the unit is in the loading interval again after delaying;
s102, sending a starting signal to the Nth compressor;
s103, predicting the total current It1 after loading, entering S104 if the total current It1 after loading is predicted to be smaller than the total protection current Its, and entering S230 if the total current It1 after loading is predicted to be larger than the total protection current Its;
s104, starting an Nth compressor, and simultaneously keeping two energy regulating valves arranged on the Nth compressor closed, wherein the refrigerating output is 33%;
s105, detecting the actual total current Id1 of the loaded unit, entering S106 if the actual total current Id1 after loading is smaller than the total protection current Its, and entering S250 if the actual total current Id1 after loading is larger than the total protection current Its;
s106, detecting whether the unit is in a loading interval, if so, entering S107, and if not, entering S260;
s107, predicting the current Ib1 of the Nth compressor when one of the energy regulating valves of the Nth compressor is opened and is loaded to 66%, entering S108 if the predicted current Ib1 is smaller than the primary protection current Iset1, and entering S380 if the predicted current Ib1 is larger than the primary protection current Iset 1;
s108, predicting the total current It2 of the unit when one energy regulating valve of the Nth compressor is opened and loaded to 66%, entering S109 if the predicted total current It2 is smaller than the total protection current Its, keeping the output unchanged if the predicted total current It2 is larger than the total protection current Its, and predicting the total current It2 of the unit when one energy regulating valve of the Nth compressor is opened and loaded to 66% again after delaying T3;
s109, one energy regulating valve of the Nth compression is opened, the other energy regulating valve is kept closed, and the refrigerating capacity is output by 66%;
s110, detecting the actual current Ib2 of the Nth compressor when one of the energy regulating valves of the Nth compressor is opened and is loaded to 66%, entering S111 if the detected actual current Ib2 is smaller than the primary protection current Iset1, and entering S290 if the detected actual current Ib2 is larger than the primary protection current Iset 1;
s111, detecting an actual total current Id2 of the unit, entering S112 if the detected actual total current Id2 of the unit is smaller than the total protection current Its, and entering S310 if the detected actual total current Id2 of the unit is larger than the total protection current Its;
s112, detecting whether the unit is in a loading interval, if so, entering S113, and if not, entering S320;
s113, predicting the current Ic1 of the Nth compressor when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, entering S114 if the predicted current Ic1 is smaller than the secondary protection current Iset2, and entering S380 if the predicted current Ic1 is larger than the secondary protection current Iset 2;
s114, predicting the total current It3 of the unit when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, entering S115 if the predicted total current It3 is smaller than the total protection current Its, keeping the output unchanged if the predicted total current It3 is larger than the total protection current Its, and predicting the total current It3 of the unit when the two energy regulating valves of the Nth compressor are opened and loaded to 100% again after delaying T4;
s115, opening two energy regulating valves of the Nth compressor, and keeping the Nth compressor on;
s116, detecting the actual current Ic2 of the Nth compressor when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, and entering S350 if the detected actual current Ic2 is greater than the secondary protection current Iset 2;
s117, detecting the actual current It4 of the unit when the two energy regulating valves of the Nth compressor are both opened and loaded to 100%, entering S118 if the detected actual current It4 of the unit is smaller than the total protection current Its, and entering S360 if the detected actual current It4 of the unit is larger than the total protection current Its;
s118, detecting whether the unit is in a loading interval, if so, entering S119, and if not, entering S370;
s119, detecting whether all the compressors of the unit are completely loaded, if all the compressors are completely loaded, entering S120, and if all the compressors are not completely loaded, entering S380;
s120, keeping the current situation of all the compressors;
wherein,
s230, keeping the output unchanged, and entering S231;
s231, after delaying T2, entering S103;
s250, the Nth compressor is closed after time delay, the two electromagnetic valves are kept closed, the refrigerating output is 0, and then the process enters S251;
s251, recording the number of times of loading and unloading, and then entering S252;
s252, judging the number of times of overcurrent and unloading in unit time, entering S231 if the number of times of overcurrent and unloading in unit time is smaller than a set value, keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value, and giving a prompt;
s260, detecting whether the unit is in a holding interval, if so, entering S261, and if not, entering S262;
s261, keeping the existing output unchanged, and then entering S106;
s262, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
s290, keeping the Nth compressor in a starting state, closing two energy regulating valves of the Nth compressor, enabling the refrigerating output to be 33%, and then entering S380;
s310, keeping the Nth compressor in a starting state, closing two energy regulating valves of the Nth compressor, and then entering S311;
s311, recording the number of times of over-current unloading, and then entering S312;
s312, judging the number of times of overcurrent and unloading in unit time, entering S380 if the number of times of overcurrent and unloading in unit time is smaller than a set value, keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value, and giving a prompt;
s320, detecting whether the unit is in a holding interval, if so, entering S321, and if not, entering S322;
s321, keeping the existing output unchanged, and then entering S112;
s322, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
s350, the Nth compressor is kept in a starting state, one energy regulating valve of the Nth compressor is kept in an opening state, the other energy regulating valve of the Nth compressor is closed, and then the process enters S380;
s360, the Nth compressor keeps a starting state, two energy regulating valves of the Nth compressor are closed, and then the process enters S361;
s361, recording the number of times of over-current unloading, and then entering S362;
s362, judging the number of times of overcurrent and unloading in unit time, entering S380 if the number of times of overcurrent and unloading in unit time is smaller than a set value, and keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value and sending a prompt;
s370, detecting whether the unit is in a holding interval, if the unit is in the holding interval, entering S371, and if the unit is not in the holding interval, entering S372;
s371, keeping the existing output unchanged, and then entering S118;
s372, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
and S380, starting the (N + 1) th compressor.
As shown in fig. 3, the method further includes a screw parallel unit current dynamic unloading method, where the screw parallel unit current dynamic unloading method includes the following steps:
s500, completing the loading of all compressors with the starting signals of the unit;
s501, detecting whether the unit is in an unloading interval, entering S502 if the unit is in the unloading interval, keeping all the compressors in the existing state if the unit is not in the unloading interval, and detecting whether the unit is in the unloading interval again after delaying;
s502, detecting the state of the Nth compressor, entering S503 if the Nth compressor is in a starting state and the running time of the Nth compressor is longest, and entering S610 if the Nth compressor is in the starting state and the running time of the Nth compressor is not the longest;
s503, the Nth compressor keeps a starting state, one energy regulating valve of the Nth compressor is closed, and the other energy regulating valve keeps an opening state;
s504, detecting whether the unit is in an unloading interval, if so, entering S505, and if not, entering S620;
s505, the Nth compressor keeps a starting state, and two energy regulating valves of the Nth compressor are closed;
s506, detecting whether the unit is in an unloading interval, if so, entering S507, and if not, entering S630;
s507, closing the Nth compressor and the two energy regulating valves for the Nth compression;
s508, detecting whether all the compressors of the unit are completely unloaded, if all the compressors of the unit are completely unloaded, entering S509, and if all the compressors of the unit are not completely unloaded, entering S650;
s509, keeping the current status of the compressor, and entering S101;
wherein
S610, unloading the (N + 1) th compressor, and then entering S502;
s620, detecting whether the unit is in a holding interval, if so, entering S504, and if not, entering S621;
s621, detecting whether the unit is in a loading interval or not, and entering S113 if the unit is in the loading interval;
s630, detecting whether the unit is in a holding interval, if so, entering S506, and if not, entering S631;
s631, detecting whether the unit is in a loading interval or not, and entering S107 if the unit is in the loading interval;
and S650, unloading the (N + 1) th compressor.
If the unit is in the unloading interval in the step S262, the step S506 is entered;
if the unit is in the unloading interval in the step S322, entering step S504;
if the unit is in the unloading interval in the step S372, the step S502 is entered;
after all the compressors in S120 are maintained as they are, the process proceeds to S501.
The loading section, the holding section and the unloading section all use set suction pressure as judgment reference;
the loading interval is as follows: p > P0+ P1;
the holding interval is: p is more than P0 and P1, and P is 0-P1;
the unloading interval is as follows: p is less than P0-P1;
in the formula
P is actually detected suction pressure;
p0 is the set suction pressure;
p1 is the set intake pressure deviation, which is within the range of ± P1.
And the time delay T2, the time delay T3 and the time delay T4 are not less than 5 minutes.
The set value of the overflowing unloading times is 6, and the unit time is 1 hour. The compressor is protected, and excessive frequent starting of the compressor is avoided.
Further comprising a total protection current modification method, said total protection current modification method comprising the steps of:
s401, after the screw parallel unit is started in S100, detecting the current of all compressors, the suction pressure, the exhaust pressure, the condensation pressure, the suction temperature and the exhaust temperature of a refrigeration system;
s402, reading the total power of an external power distribution main ammeter, and reading the current real-time;
and S403, judging whether the current time Is in a low-load time period, if the current time Is in the low-load time period and the total load margin Is2 Is greater than 1.2 times of the total protection current Its, modifying the total protection current Its, and if the current time Is not in the low-load time period, entering S402. Providing an output of cooling capacity during off-peak periods.
The step S102 further includes determining whether the nth compressor has the shortest running time and is not started, entering step S103 if the nth compressor has the shortest running time and is not started, and sending a start signal to the (N + 1) th compressor if the nth compressor has the shortest running time and is not started, and then entering step S102. The balanced operation of the compressor is ensured.
S104, correcting a current prediction fitting coefficient according to the detected actual current Id1, and predicting a current value Ib1 loaded to the next stage according to the corrected current prediction fitting coefficient and system parameters;
s109 further comprises correcting a current prediction fitting coefficient according to the detected actual current Ib2, and predicting a current value Ic1 loaded to the next stage according to the corrected current prediction fitting coefficient and system parameters;
the step S115 further includes correcting the current prediction fitting coefficient according to the detected actual current Ic2, and then predicting the current when the next compressor is loaded to 33% according to the corrected current prediction fitting coefficient and the system parameters.
The formula of the total current after the prediction loading of S103, S107 and S115 is as follows:
Z＝p1+p2*X+p3*Y+p4*X2+p5*X*Y+p6*Y2+p7*X3+p8*Y*X2+p9*X*Y2+p10*Y3；
in the formula,
z is the predicted current;
x is the evaporation temperature, namely the temperature corresponding to the suction pressure;
y is the condensation temperature and the temperature corresponding to the condensation pressure;
the p 1-p 9 are fitting coefficients of the compressor and are provided by a compressor manufacturer.
Different compressors and refrigerants have different fitting coefficients
And predicting the current of the compressor at different energy levels according to the proportion of the refrigerating output energy level. If the energy regulating valve is opened at 33%, the prediction current is predicted according to 33%, and the percentage is modified according to the actually detected current with different energy levels.
The energy regulating valve is an electromagnetic valve.
Claims (10)
1. The method for dynamically controlling the current of the screw parallel unit is characterized by comprising a method for dynamically loading the current of the screw parallel unit, wherein the method for dynamically loading the current of the screw parallel unit comprises the following steps:
s100, starting a screw rod parallel unit;
s101, detecting whether the unit is in a loading interval, entering S102 if the unit is in the loading interval, keeping all compressors in a shutdown state if the unit is not in the loading interval, and detecting whether the unit is in the loading interval again after delaying;
s102, sending a starting signal to the Nth compressor;
s103, predicting the total current It1 after loading, entering S104 if the total current It1 after loading is predicted to be smaller than the total protection current Its, and entering S230 if the total current It1 after loading is predicted to be larger than the total protection current Its;
s104, starting an Nth compressor, and keeping two energy regulating valves arranged on the Nth compressor closed;
s105, detecting the actual total current Id1 of the loaded unit, entering S106 if the actual total current Id1 after loading is smaller than the total protection current Its, and entering S250 if the actual total current Id1 after loading is larger than the total protection current Its;
s106, detecting whether the unit is in a loading interval, if so, entering S107, and if not, entering S260;
s107, predicting the current Ib1 of the Nth compressor when one of the energy regulating valves of the Nth compressor is opened and is loaded to 66%, entering S108 if the predicted current Ib1 is smaller than the primary protection current Iset1, and entering S380 if the predicted current Ib1 is larger than the primary protection current Iset 1;
s108, predicting the total current It2 of the unit when one energy regulating valve of the Nth compressor is opened and loaded to 66%, entering S109 if the predicted total current It2 is smaller than the total protection current Its, keeping the output unchanged if the predicted total current It2 is larger than the total protection current Its, and predicting the total current It2 of the unit when one energy regulating valve of the Nth compressor is opened and loaded to 66% again after delaying T3;
s109, one energy regulating valve of the Nth compression is opened, and the other energy regulating valve is kept closed;
s110, detecting the actual current Ib2 of the Nth compressor when one of the energy regulating valves of the Nth compressor is opened and is loaded to 66%, entering S111 if the detected actual current Ib2 is smaller than the primary protection current Iset1, and entering S290 if the detected actual current Ib2 is larger than the primary protection current Iset 1;
s111, detecting an actual total current Id2 of the unit, entering S112 if the detected actual total current Id2 of the unit is smaller than the total protection current Its, and entering S310 if the detected actual total current Id2 of the unit is larger than the total protection current Its;
s112, detecting whether the unit is in a loading interval, if so, entering S113, and if not, entering S320;
s113, predicting the current Ic1 of the Nth compressor when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, entering S114 if the predicted current Ic1 is smaller than the secondary protection current Iset2, and entering S380 if the predicted current Ic1 is larger than the secondary protection current Iset 2;
s114, predicting the total current It3 of the unit when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, entering S115 if the predicted total current It3 is smaller than the total protection current Its, keeping the output unchanged if the predicted total current It3 is larger than the total protection current Its, and predicting the total current It3 of the unit when the two energy regulating valves of the Nth compressor are opened and loaded to 100% again after delaying T4;
s115, opening two energy regulating valves of the Nth compressor and the Nth compressor;
s116, detecting the actual current Ic2 of the Nth compressor when the two energy regulating valves of the Nth compressor are opened and loaded to 100%, and entering S350 if the detected actual current Ic2 is greater than the secondary protection current Iset 2;
s117, detecting the actual current It4 of the unit when the two energy regulating valves of the Nth compressor are both opened and loaded to 100%, entering S118 if the detected actual current It4 of the unit is smaller than the total protection current Its, and entering S360 if the detected actual current It4 of the unit is larger than the total protection current Its;
s118, detecting whether the unit is in a loading interval, if so, entering S119, and if not, entering S370;
s119, detecting whether all the compressors of the unit are completely loaded, if all the compressors are completely loaded, S120, and if all the compressors are not completely loaded, entering S380;
s120, keeping the current situation of all the compressors;
wherein,
s230, keeping the output unchanged, and entering S231;
s231, after delaying T2, entering S103;
s250, the Nth compressor is closed after time delay, and then the process enters S251;
s251, recording the number of times of loading and unloading, and then entering S252;
s252, judging the number of times of overcurrent and unloading in unit time, entering S231 if the number of times of overcurrent and unloading in unit time is smaller than a set value, keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value, and giving a prompt;
s260, detecting whether the unit is in a holding interval, if so, entering S261, and if not, entering S262;
s261, keeping the existing output unchanged, and then entering S106;
s262, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
s290, keeping the Nth compressor in a starting state, closing two energy regulating valves of the Nth compressor, and then entering S380;
s310, keeping the Nth compressor in a starting state, closing two energy regulating valves of the Nth compressor, and then entering S311;
s311, recording the number of times of over-current unloading, and then entering S312;
s312, judging the number of times of overcurrent and unloading in unit time, entering S380 if the number of times of overcurrent and unloading in unit time is smaller than a set value, keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value, and giving a prompt;
s320, detecting whether the unit is in a holding interval, if so, entering S321, and if not, entering S322;
s321, keeping the existing output unchanged, and then entering S112;
s322, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
s350, the Nth compressor is kept in a starting state, one energy regulating valve of the Nth compressor is kept in an opening state, the other energy regulating valve of the Nth compressor is closed, and then the process enters S380;
s360, the Nth compressor keeps a starting state, two energy regulating valves of the Nth compressor are closed, and then the process enters S361;
s361, recording the number of times of over-current unloading, and then entering S362;
s362, judging the number of times of overcurrent and unloading in unit time, entering S380 if the number of times of overcurrent and unloading in unit time is smaller than a set value, and keeping the output unchanged if the number of times of overcurrent and unloading in unit time is larger than the set value and sending a prompt;
s370, detecting whether the unit is in a holding interval, if the unit is in the holding interval, entering S371, and if the unit is not in the holding interval, entering S372;
s371, keeping the existing output unchanged, and then entering S118;
s372, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
and S380, starting the (N + 1) th compressor.
2. The screw parallel unit current dynamic control method according to claim 1,
the method also comprises a dynamic unloading method of the screw parallel unit current, and the dynamic unloading method of the screw parallel unit current comprises the following steps:
s500, completing the loading of all compressors with the starting signals of the unit;
s501, detecting whether the unit is in an unloading interval, entering S502 if the unit is in the unloading interval, keeping all the compressors in the existing state if the unit is not in the unloading interval, and detecting whether the unit is in the unloading interval again after delaying;
s502, detecting the state of the Nth compressor, entering S503 if the Nth compressor is in a starting state and the running time of the Nth compressor is longest, and entering S610 if the Nth compressor is in the starting state and the running time of the Nth compressor is not the longest;
s503, the Nth compressor keeps a starting state, one energy regulating valve of the Nth compressor is closed, and the other energy regulating valve keeps an opening state;
s504, detecting whether the unit is in an unloading interval, if so, entering S505, and if not, entering S620;
s505, the Nth compressor keeps a starting state, and two energy regulating valves of the Nth compressor are closed;
s506, detecting whether the unit is in an unloading interval, if so, entering S507, and if not, entering S630;
s507, closing the Nth compressor and the two energy regulating valves for the Nth compression;
s508, detecting whether all the compressors of the unit are completely unloaded, if all the compressors of the unit are completely unloaded, entering S509, and if all the compressors of the unit are not completely unloaded, entering S650;
s509, keeping the current status of the compressor, and entering S101;
wherein
S610, unloading the (N + 1) th compressor, and then entering S502;
s620, detecting whether the unit is in a holding interval, if so, entering S504, and if not, entering S621;
s621, detecting whether the unit is in a loading interval or not, and entering S113 if the unit is in the loading interval;
s630, detecting whether the unit is in a holding interval, if so, entering S506, and if not, entering S631;
s631, detecting whether the unit is in a loading interval or not, and entering S107 if the unit is in the loading interval;
and S650, unloading the (N + 1) th compressor.
3. The screw parallel unit current dynamic control method according to claim 2,
if the unit is in the unloading interval in the step S262, the step S506 is entered;
if the unit is in the unloading interval in the step S322, entering step S504;
if the unit is in the unloading interval in the step S372, the step S502 is entered;
after all the compressors in S120 are maintained as they are, the process proceeds to S501.
4. The screw parallel unit current dynamic control method according to claim 1,
the loading section, the holding section and the unloading section all use set suction pressure as judgment reference;
the loading interval is as follows: p > P0+ P1;
the holding interval is: p is more than P0 and P1, and P is 0-P1;
the unloading interval is as follows: p is less than P0-P1;
in the formula
P is actually detected suction pressure;
p0 is the set suction pressure;
p1 is the set intake pressure deviation, which is within the range of ± P1.
5. The screw parallel unit current dynamic control method according to claim 1,
and the time delay T2, the time delay T3 and the time delay T4 are not less than 5 minutes.
6. The screw parallel unit current dynamic control method according to claim 1,
the set value of the overflowing unloading times is 6, and the unit time is 1 hour.
7. The screw parallel unit current dynamic control method according to claim 1,
further comprising a total protection current modification method, said total protection current modification method comprising the steps of:
s401, after the screw parallel unit is started in S100, detecting the current of all compressors, the suction pressure, the exhaust pressure, the condensation pressure, the suction temperature and the exhaust temperature of a refrigeration system;
s402, reading the total power of an external power distribution main ammeter, and reading the current real-time;
and S403, judging whether the current time Is in a low-load time period, if the current time Is in the low-load time period and the total load margin Is2 Is greater than 1.2 times of the total protection current Its, modifying the total protection current Its, and if the current time Is not in the low-load time period, entering S402.
8. The screw parallel unit current dynamic control method according to claim 1,
the step S102 further includes determining whether the nth compressor has the shortest running time and is not started, entering step S103 if the nth compressor has the shortest running time and is not started, and sending a start signal to the (N + 1) th compressor if the nth compressor has the shortest running time and is not started, and then entering step S102.
9. The screw parallel unit current dynamic control method according to claim 1,
s104, correcting a current prediction fitting coefficient according to the detected actual current Id1, and predicting a current value Ib1 loaded to the next stage according to the corrected current prediction fitting coefficient and system parameters;
s109 further comprises correcting a current prediction fitting coefficient according to the detected actual current Ib2, and predicting a current value Ic1 loaded to the next stage according to the corrected current prediction fitting coefficient and system parameters;
the step S115 further includes correcting the current prediction fitting coefficient according to the detected actual current Ic2, and then predicting the current when the next compressor is loaded to 33% according to the corrected current prediction fitting coefficient and the system parameters.
10. The screw parallel unit current dynamic control method according to claim 1,
the formula of the total current after the prediction loading of S103, S107 and S115 is as follows:
Z＝p1+p2*X+p3*Y+p4*X2+p5*X*Y+p6*Y2+p7*X3+p8*Y*X2+p9*X*Y2+p10*Y3；
in the formula,
z is the predicted current;
x is the evaporation temperature;
y is the condensation temperature;
p 1-p 9 are fitting coefficients of the compressor.
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