CN111288697B - Frequency conversion control method for refrigeration parallel unit - Google Patents
Frequency conversion control method for refrigeration parallel unit Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 67
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 41
- 238000005057 refrigeration Methods 0.000 title claims abstract description 18
- 238000011068 loading method Methods 0.000 claims abstract description 66
- 230000008020 evaporation Effects 0.000 claims description 10
- 238000001704 evaporation Methods 0.000 claims description 10
- 239000003507 refrigerant Substances 0.000 claims description 9
- 230000003247 decreasing effect Effects 0.000 claims description 8
- 229920006395 saturated elastomer Polymers 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 2
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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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Abstract
The invention relates to a frequency conversion control method of a refrigeration parallel unit, which comprises a frequency conversion loading method and a frequency conversion unloading method; the variable frequency loading method comprises the following steps: starting a first compressor, starting an Nth compressor when the compressor needs to be loaded, simultaneously reducing the output frequency of a frequency converter downwards, increasing the output frequency of the frequency converter after the Nth compressor is started, and starting the rest compressors in sequence according to the method if the unit still needs to be loaded with the compressor; the frequency conversion unloading method comprises the following steps: and when the unit needs to unload the compressors, closing the Nth compressor, simultaneously adjusting the output frequency of the frequency converter, after the Nth compressor is closed, adjusting the output frequency of the frequency converter downwards, if the unit still needs to unload the compressors, sequentially closing the rest compressors according to the method, and finally closing the first compressor. The frequency conversion control method of the refrigeration parallel unit only needs one frequency converter, is simple to control, can realize stepless refrigeration regulation, and has stable system operation and low cost.
Description
Technical Field
The invention relates to control of a refrigeration parallel unit, in particular to a frequency conversion control method of the refrigeration parallel unit.
Background
The common frequency conversion scheme of the parallel unit is that each compressor is provided with a frequency converter, and the energy-saving operation of the system is realized by dynamically adjusting the frequency converters. Although this method can save energy, the control is complicated, a plurality of inverters need to be controlled simultaneously, the number of control factors considered is large, the control logic is complicated, and the cost is high because each compressor is provided with an inverter.
Disclosure of Invention
In order to solve the problems, the invention provides a frequency conversion control method of a refrigeration parallel unit, which only needs one frequency converter, has simple control, stable operation and low cost, and the specific technical scheme is as follows:
the frequency conversion control method of the refrigeration parallel unit comprises at least two compressors and a frequency converter, wherein the compressors are arranged in parallel, the frequency converter is arranged on a first compressor, and the frequency conversion control method comprises a frequency conversion loading method and a frequency conversion unloading method; the variable frequency loading method comprises the following steps: the method comprises the steps that when the unit is started, the first compressor is started first, when the unit needs to load the compressor, the Nth compressor is started, the output frequency of the frequency converter is adjusted downwards, after the Nth compressor is started, the output frequency of the frequency converter is adjusted upwards, if the unit still needs to load the compressor, the (N + 1) th compressor is started, the output frequency of the frequency converter is adjusted downwards, after the (N + 1) th compressor is started, the output frequency of the frequency converter is adjusted upwards, and if the unit still needs to load the compressor, the rest compressors are started in sequence according to the method; the frequency conversion unloading method comprises the following steps: and when the unit needs to unload the compressors, closing the Nth compressor, simultaneously increasing the output frequency of the frequency converter, decreasing the output frequency of the frequency converter after the Nth compressor is closed, closing the (N + 1) th compressor if the unit still needs to unload the compressors, simultaneously increasing the output frequency of the frequency converter, decreasing the output frequency of the frequency converter after the (N + 1) th compressor is closed, sequentially closing the rest compressors according to the method if the unit still needs to unload the compressors, and finally closing the first compressor.
Further, in the variable frequency loading method, the output frequency of the frequency converter is adjusted downwards to the lowest output frequency when the compressor is started; in the frequency conversion unloading method, the output frequency of the frequency converter is adjusted upwards to the highest output frequency when the compressor is closed.
Further, the output frequency of the frequency converter is 20-70 Hz.
Further, the unit needs to load the compressor or the unit needs to unload the compressor, and the judgment is performed according to the current suction pressure and the set loading pressure and unloading pressure: the loading pressure is the corresponding refrigerant saturation temperature after the deviation of the set evaporation temperature; the unloading pressure is the corresponding refrigerant saturation temperature after the deviation of the set evaporation temperature is reduced; when the current suction pressure is higher than the set loading suction pressure, the unit is in a loading interval, and the loading interval is used for increasing the starting number of the compressors; when the current suction pressure is between the set loading suction pressure and the set unloading suction pressure, the unit is in a middle interval, and the middle interval is used for dynamically fine-tuning the frequency converter; and when the current suction pressure is smaller than the set unloading suction pressure, the unit is in an unloading interval, and the unloading interval is used for reducing the starting number of the compressors or closing the unit.
Further, the method also comprises the step of calculating the frequency modulation increasing amplitude, wherein the frequency modulation increasing amplitude is used for calculating the increasing speed of the current output frequency of the frequency converter to be adjusted to the highest output frequency within the set time when the compressor is loaded in the loading interval; v1 ═ (P0-P)/T1; where V1 is the frequency modulation increase amplitude; p0 is the set suction pressure; p is the current suction pressure; t1 is the set load time; the method also comprises the step of calculating the frequency modulation reduction amplitude, wherein the calculated frequency modulation reduction amplitude is used for calculating the reduction speed of the current output frequency of the frequency converter which is reduced to the lowest output frequency within the set time when the compressor is unloaded in an unloading interval; v2 ═ (P-P0)/T2; where V2 is the frequency modulation increase amplitude; p0 is the set suction pressure; p is the current suction pressure; t2 is the set unload time.
The frequency converter adjusting method is used for gradually reducing or increasing the output frequency of the frequency converter in an intermediate interval, the frequency converter adjusting method comprises reducing or increasing the output frequency once every interval, the frequency increased every time is A V1 or the frequency decreased every time is A V2, the time at one end of the interval is 3-7 seconds, the adjusting range of the frequency converter adjusting method is 25-65Hz, A is an adjusting coefficient, and A is 0.1.
Furthermore, the variable-frequency loading method sequentially loads the compressors according to the sequence of the accumulated running time of the compressors from small to large; the frequency conversion unloading method sequentially unloads the compressors according to the sequence of the accumulated running time of the compressors from large to small.
The nth compressor is the compressor with the shortest operation time in the variable frequency loading method and the compressor with the longest operation time in the variable frequency unloading method.
The cost is greatly reduced by adopting one frequency converter, and the frequency conversion of the frequency converter is matched with the starting or closing of other compressors, so that the stable operation of the refrigerating system is realized. And only one frequency converter needs to be controlled, so that the control is simple.
The running frequency of the first compressor is set to be 20-70Hz, the output frequency of the first compressor is reduced from 70Hz to 20Hz when the second compressor is started during variable frequency loading, and the output frequency of the second compressor is gradually loaded to 70Hz from 20Hz after the second compressor is started; then the Nth compressor is started, the frequency output of the first compressor is reduced from 70Hz to 20Hz, and the frequency of the first compressor is gradually increased from 20Hz to 70Hz after the Nth compressor is started. When unloading, on the contrary, when the frequency of the first compressor is 70Hz, one of the compressors without the frequency converter is closed, and when the frequency of the first compressor is reduced to 20Hz, the other compressors without the frequency converter are closed according to the method, and the compressors are closed one by one. The compressors are loaded or unloaded one by one, and the refrigerating output is unchanged during loading or unloading, so that stepless grading of the refrigerating output is realized, and the stable operation and the energy-saving effect of the system are ensured.
If the refrigeration parallel unit has three compressors, the parallel refrigeration unit can realize stepless refrigeration regulation within the range of 40-340 percent.
Compared with the prior art, the invention has the following beneficial effects:
the frequency conversion control method of the refrigeration parallel unit only needs one frequency converter, is simple to control, can realize stepless refrigeration regulation, and has stable system operation and low cost.
Drawings
FIG. 1 is a flow chart of a variable frequency loading method;
fig. 2 is a flow chart of a variable frequency offloading method.
Detailed Description
The invention will now be further described with reference to the accompanying drawings.
As shown in fig. 1 and fig. 2, a frequency conversion control method for a refrigeration parallel unit, the unit includes at least two compressors and one frequency converter, the compressors are arranged in parallel, the frequency converter is installed on a first compressor, and the frequency conversion control method includes a frequency conversion loading method and a frequency conversion unloading method;
the variable frequency loading method comprises the following steps:
starting a first compressor when a unit is started, starting an Nth compressor when the unit needs to load the compressor, simultaneously reducing the output frequency of a frequency converter downwards, increasing the output frequency of the frequency converter after the Nth compressor is started, starting an (N + 1) th compressor if the unit still needs to load the compressor, simultaneously reducing the output frequency of the frequency converter downwards, increasing the output frequency of the frequency converter after the (N + 1) th compressor is started, and sequentially starting the rest compressors according to the method if the unit still needs to load the compressor;
the frequency conversion unloading method comprises the following steps:
and when the unit needs to unload the compressors, closing the Nth compressor, simultaneously up-regulating the output frequency of the frequency converter, down-regulating the output frequency of the frequency converter after the Nth compressor is closed, closing the (N + 1) th compressor if the unit still needs to unload the compressors, simultaneously up-regulating the output frequency of the frequency converter, down-regulating the output frequency of the frequency converter after the (N + 1) th compressor is closed, sequentially closing the rest compressors according to the method if the unit still needs to unload the compressors, and finally closing the first compressor.
In the variable frequency loading method, the output frequency of the frequency converter is adjusted downwards to the lowest output frequency when the compressor is started;
in the frequency conversion unloading method, the output frequency of the frequency converter is up-regulated to the highest output frequency when the compressor is closed.
The output frequency of the frequency converter is 20-70 Hz.
The unit needs to load the compressor or the unit needs to unload the compressor, and the judgment is carried out according to the current suction pressure and the set loading pressure and unloading pressure: the loading pressure is the corresponding refrigerant saturation temperature after the deviation of the set evaporation temperature; the unloading pressure is the corresponding refrigerant saturation temperature after the deviation of the set evaporation temperature is reduced; when the current suction pressure is higher than the set loading suction pressure, the unit is in a loading interval, and the loading interval is used for increasing the starting number of the compressors; when the current suction pressure is between the set loading suction pressure and the set unloading suction pressure, the unit is in a middle interval, and the middle interval is used for dynamically fine-tuning the frequency converter; when the current suction pressure is smaller than the set unloading suction pressure, the unit is located in an unloading interval, and the unloading interval is used for reducing the starting number of the compressors or closing the unit.
The method also comprises the steps of calculating the frequency modulation increasing amplitude, wherein the frequency modulation increasing amplitude is used for calculating the increasing speed of the current output frequency of the frequency converter which is adjusted to the highest output frequency within the set time when the compressor is loaded in the loading interval;
V1＝(P0-P)/T1；
in the formula
V1 is the frequency modulation increase amplitude;
p0 is the set suction pressure;
p is the current suction pressure;
t1 is the set load time;
the method also comprises the steps of calculating the frequency modulation reduction amplitude, wherein the frequency modulation reduction amplitude is used for calculating the reduction speed of the current output frequency of the frequency converter which is reduced to the lowest output frequency within the set time when the compressor is unloaded in the unloading interval;
V2＝(P-P0)/T2；
in the formula
V2 is the frequency modulation increase amplitude;
p0 is the set suction pressure;
p is the current suction pressure;
t2 is the set unload time.
The frequency converter adjusting method is used for gradually reducing or increasing the output frequency of the frequency converter in the middle interval, the frequency converter adjusting method comprises the step of reducing or increasing the output frequency once every interval, the frequency increased each time is A V1 or the frequency reduced each time is A V2, the time at one end of the interval is 3-7 seconds, the adjusting range of the frequency converter adjusting method is 25-65Hz, A is an adjusting coefficient, and A is 0.1.
Sequentially loading according to the sequence of the accumulated running time of the compressor from small to large in the variable-frequency loading method;
in the frequency conversion unloading method, the unloading is performed in sequence according to the sequence of the accumulated running time of the compressor from large to small.
The nth compressor is the compressor with the shortest operation time in the variable frequency loading method and the compressor with the longest operation time in the variable frequency unloading method.
In order to guarantee the stable operation of the unit, reduce the frequent start and stop of the compressor, the operation of the unit needs to be subjected to state judgment, and the operation of the unit can be divided into three intervals: middle section, loading section and unloading section. The interval is judged according to the suction pressure of the unit, the middle interval is a range, the unit is in the loading interval when the current suction pressure is smaller than the minimum suction pressure in the middle interval, the unit is in the middle interval when the current suction pressure is in the middle interval, and the unit is in the unloading interval when the current suction pressure is larger than the maximum suction pressure in the middle interval. The judgment of the interval needs a set pressure, the set pressure refers to the set suction pressure, the set pressure can be set in a floating way according to time and seasons, namely, the set pressure is dynamically changed in different seasons and time, and therefore the running cost is saved. The set suction pressure Po is an intermediate value and the interval judgment requires a range, so that the range can be set to be ± 0.5bar, for example, 2bar is set, the maximum pressure is 2.5bar, the minimum pressure is 1.5bar, and the intermediate range is 1.5-2.5 bar.
Po is the gas pressure of the saturated refrigerant corresponding to the evaporation temperature set by the unit, and the evaporation temperature value set by the unit is usually obtained by subtracting the heat exchange temperature difference from the temperature set value of the refrigeration storage.
The controller needs to set the evaporation temperature of the unit and also needs to set the deviation of the evaporation temperature, and the deviation is generally symmetrical up and down; the lower limit of the loading area is the corresponding gas pressure of the saturated refrigerant after the temperature deviation of the saturation temperature set by the unit is increased, and the upper limit of the unloading area is the corresponding gas pressure of the saturated refrigerant after the temperature deviation of the saturation temperature set by the unit is decreased.
As shown in fig. 1, the frequency conversion loading method includes the following steps:
s100, starting a refrigeration parallel unit;
s101, detecting whether the unit is in a loading interval, namely detecting whether the suction pressure is greater than 2.5bar, if the unit is in the loading interval, entering S102, and if the unit is not in the loading interval, keeping all the compressors in a shutdown state;
s102, sending a starting signal to the first compressor and detecting the state of the first compressor, if the first compressor is started, entering S103, and if the first compressor is not started, entering S109;
s103, after the first compressor is started, gradually increasing the frequency of the frequency converter to 20Hz, and running for 1-2 minutes; after the operation is carried out for 1 minute, the working condition is stable and convenient to detect, and the time cannot be too short or too long;
s104, calculating the frequency modulation increase amplitude, and controlling the frequency converter according to the frequency modulation increase amplitude;
s105, detecting whether the unit is in a loading interval, if so, entering S105, and if not, entering S211;
s106, adjusting the frequency of the frequency converter every 5 seconds according to the frequency modulation increasing amplitude calculated in the S104; 5 seconds is a set frequency regulation period parameter, and a user can modify the frequency regulation period parameter on an operation interface;
s107, detecting whether the output frequency of the frequency converter is greater than the maximum output frequency of 70Hz, if not, entering S108, and if so, entering S104;
s108, detecting whether the unit is in a loading interval, if so, entering S109, and if not, entering S221;
s109, sending a starting signal to the Nth compressor and detecting the state of the Nth compressor, if the Nth compressor is started, entering S110, and if the Nth compressor is not started, entering S112;
s110, starting an Nth compressor, switching the frequency of the frequency converter to the lowest output frequency of 20Hz when the Nth compressor is started, and then entering S111;
s111, adjusting the output frequency of the frequency converter to enable the refrigerating capacity output by the refrigerating unit to be matched with the refrigerating requirement, detecting whether the unit is in a loading interval, if so, entering S112, and if not, entering S231;
s112, detecting the states of all compressors with starting signals, if the compressors with the starting signals are all loaded with full load, entering S113, and if the compressors with the starting signals are not loaded with full load, entering S102;
s113, ending the loading process;
wherein,
s211, detecting whether the unit is in the middle interval or not, if the unit is in the middle interval, entering S212, and if the unit is not in the middle interval, entering S213;
s212, adjusting the frequency converter, multiplying the frequency modulation calculated in the S104 by an adjustment coefficient of 0.1, adjusting the frequency once every 5 seconds, wherein the adjustment range is 25-65Hz, detecting the frequency of the frequency converter, and entering S105 if the frequency is more than 65 Hz; the adjusting coefficient is used for reducing the adjusting amplitude and fine adjusting the frequency, and the purpose of fine adjusting is to adjust the current pressure to operate in the middle region and approach to the central position in the middle region; when the frequency adjusting range reaches 25-65Hz, if the rising or falling trend of the pressure can not be changed, the pressure is led to enter a loading or unloading area to transfer to an loading and unloading control process;
s213, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
s221, detecting whether the unit is in the middle interval, if so, entering S222, and if not, entering S223;
s222, keeping the existing output unchanged, and entering S108;
s223, detecting whether the unit is in an unloading interval or not, and entering an unloading process if the unit is in the unloading interval;
s231, detecting whether the unit is in the middle interval or not, if so, entering S232, and if not, entering S233;
s232, keeping the existing output unchanged, and entering S111;
and S233, detecting whether the unit is in an unloading interval, and entering an unloading process if the unit is in the unloading interval.
As shown in fig. 2, the frequency conversion unloading method includes the following steps:
s300, all the compressors with the starting signals are loaded, namely all the compressors with the starting signals of the unit are in a starting state;
s301, detecting whether the unit is in an unloading interval, if so, entering S302, and if not, entering S411;
s302, detecting the state of the first compressor (namely detecting the state of the frequency converter), entering S303 if the first compressor is in a starting state and the output frequency of the first compressor is 70Hz at the maximum, and entering S307 if the first compressor is in the starting state and the output frequency of the first compressor is 25-65 Hz;
s303, calculating the frequency modulation reduction amplitude, and controlling the frequency converter according to the frequency modulation reduction amplitude;
s304, detecting whether the unit is in an unloading interval, if so, entering S305, and if not, entering S421;
s305, adjusting the frequency of the frequency converter every 5 seconds according to the frequency modulation reduction amplitude calculated in the S302;
s306, detecting whether the output frequency of the frequency converter is less than the minimum output frequency of 20Hz, if so, entering S307, and if so, entering S303;
s307, sending a shutdown signal to the Nth compressor and detecting the state of the Nth compressor, if the Nth compressor is not closed, entering S308, and if the Nth compressor is closed, entering S310;
s308, closing the Nth compressor;
s309, detecting whether the unit is in an unloading interval, if so, entering S310, and if not, entering S441;
s310, detecting the states of all the other compressors except the first compressor, if all the other compressors are closed, entering S311, and if all the other compressors are not stopped, entering S451;
s311, adjusting the output frequency of the frequency converter to be at least 20Hz, and closing the first compressor after the first compressor operates for 5 min;
s312, the unloading process is finished;
wherein,
s411, detecting whether the unit is in the middle interval, if the unit is in the middle interval, entering S412, and if the unit is not in the middle interval, entering S413;
s412, the existing output is kept unchanged, and the process enters S301;
s413, detecting whether the unit is in a loading interval or not, and if the unit is in the loading interval, entering S414;
s414, keeping the existing output unchanged, and entering S301;
s421, detecting whether the unit is in the middle interval, if so, entering S422, and if not, entering S423;
s422, adjusting the frequency converter, multiplying the frequency modulation calculated in the S303 by an adjustment coefficient of 0.1, adjusting the frequency once every 5 seconds, wherein the adjustment range is 25-65Hz, detecting the frequency of the frequency converter, and entering S304 if the frequency is less than 25 Hz; if the frequency is adjusted to 25-65Hz, if the descending or ascending trend is still unchanged, the frequency converter is not adjusted any more, and when the pressure is shifted to an unloading or loading interval, the frequency conversion is shifted to the conventional loading and unloading adjustment of unloading from 25Hz to 20Hz or loading from 65Hz to 70 Hz;
s423, detecting whether the unit is in the loading interval, and entering S106 if the unit is in the loading interval;
s431, detecting whether the unit is in the middle interval, if so, entering S432, and if not, entering S433;
s432, keeping the existing output unchanged, and entering S309;
s433, detecting whether the unit is in a loading interval or not, and entering S109 if the unit is in the loading interval;
s441, the N-1 compressor is closed, and then the process goes to S442;
s442, the first compressor 1 is operated at the highest frequency of 70Hz, and then the process proceeds to S302.
The first compressor of the parallel refrigerating unit carries out frequency conversion output through installing a frequency converter, the operating frequency range is 20-70Hz, and the corresponding refrigerating capacity of the compressor is 40% → 140% of the refrigerating capacity output of other power frequency compressors. The first compressor, equipped with a frequency converter, is first switched on and the last is switched off when the unit is in operation. After the first compressor is started, the speed of the frequency converter for increasing and decreasing the frequency is adjusted according to the suction pressure of the unit, the interval where the suction pressure is located and the decreasing rate of the suction pressure.
When the first compressor is loaded to 70Hz and then correspondingly outputs the refrigerating capacity of 140%, if the unit still has the loading requirement, namely is in the frequency conversion loading interval, the next compressor with the shortest running time is started according to the sequence of the running total time, the frequency of the first compressor is synchronously switched to 20Hz after the next compressor is started, at the moment, the total output refrigerating capacity is 140%, namely the refrigerating capacity output by the first compressor is 40%, the refrigerating capacity output by the compressor without the frequency converter is 100%, the sum of the refrigerating capacity output by the compressor without the frequency converter is 140%, namely the refrigerating capacity output when a new compressor is started is consistent with the refrigerating capacity before the compressor is not started, so that the smooth output of the refrigerating capacity is ensured, then the output frequency of the frequency converter is gradually increased, the adjustment is simple, and only one frequency converter is needed. As the pressure continues to rise, the frequency of the first compressor continues to be adjusted in accordance with the previous adjustment logic.
When unloading, the first compressor with the frequency conversion is unloaded to the lowest operation frequency of 20Hz, then the compressor with long operation time is unloaded firstly according to the accumulated operation time sequence, when the power frequency compressor with the longest operation time is unloaded, the frequency of the first compressor with the frequency conversion is synchronously switched to 70Hz, and then the next compressor is unloaded after the frequency of the frequency conversion compressor is adjusted to the lowest operation frequency of 20Hz according to the suction pressure.
Claims (1)
1. The frequency conversion control method of the refrigeration parallel unit is characterized in that the unit comprises at least two compressors and a frequency converter, the compressors are arranged in parallel, the frequency converter is arranged on a first compressor, and the frequency conversion control method comprises a frequency conversion loading method and a frequency conversion unloading method;
the variable frequency loading method comprises the following steps:
the method comprises the steps that when the unit is started, the first compressor is started first, when the unit needs to load the compressor, the Nth compressor is started, the output frequency of the frequency converter is adjusted downwards, after the Nth compressor is started, the output frequency of the frequency converter is adjusted upwards, if the unit still needs to load the compressor, the (N + 1) th compressor is started, the output frequency of the frequency converter is adjusted downwards, after the (N + 1) th compressor is started, the output frequency of the frequency converter is adjusted upwards, and if the unit still needs to load the compressor, the rest compressors are started in sequence according to the method;
the frequency conversion unloading method comprises the following steps:
when the unit needs to unload the compressors, closing an Nth compressor, simultaneously increasing the output frequency of the frequency converter, decreasing the output frequency of the frequency converter after the Nth compressor is closed, closing an (N + 1) th compressor if the unit still needs to unload the compressors, simultaneously increasing the output frequency of the frequency converter, decreasing the output frequency of the frequency converter after the (N + 1) th compressor is closed, sequentially closing the rest compressors according to the method if the unit still needs to unload the compressors, and finally closing the first compressor;
in the variable-frequency loading method, the output frequency of the frequency converter is adjusted downwards to the lowest output frequency when the compressor is started; in the frequency conversion unloading method, the output frequency of the frequency converter is adjusted upwards to the highest output frequency when the compressor is closed;
the output frequency of the frequency converter is 20-70 Hz;
the unit needs to load the compressor or the unit needs to unload the compressor, and the judgment is carried out according to the current suction pressure and the set loading pressure and unloading pressure:
the loading pressure is the corresponding refrigerant saturation temperature after the deviation of the set evaporation temperature;
the unloading pressure is the corresponding refrigerant saturation temperature after the deviation of the set evaporation temperature is reduced;
when the current suction pressure is higher than the set loading suction pressure, the unit is in a loading interval, and the loading interval is used for increasing the starting number of the compressors;
when the current suction pressure is between the set loading suction pressure and the set unloading suction pressure, the unit is in a middle interval, and the middle interval is used for dynamically fine-tuning the frequency converter;
when the current suction pressure is smaller than the set unloading suction pressure, the unit is in an unloading interval, and the unloading interval is used for reducing the starting number of the compressors or closing the unit;
the method further comprises the step of calculating the frequency modulation increasing amplitude, wherein the calculated frequency modulation increasing amplitude is used for calculating the increasing speed of the current output frequency of the frequency converter which is adjusted to the highest output frequency within the set time when the compressor is loaded in the loading interval;
V1＝(P0-P)/T1；
in the formula
V1 is the frequency modulation increase amplitude;
p0 is the set suction pressure;
p is the current suction pressure;
t1 is the set load time;
the method also comprises the step of calculating the frequency modulation reduction amplitude, wherein the calculated frequency modulation reduction amplitude is used for calculating the reduction speed of the current output frequency of the frequency converter which is reduced to the lowest output frequency within the set time when the compressor is unloaded in an unloading interval;
V2＝(P-P0)/T2；
in the formula
V2 is the frequency modulation increase amplitude;
p0 is the set suction pressure;
p is the current suction pressure;
t2 is the set unload time;
the frequency converter adjusting method is used for gradually reducing or increasing the output frequency of the frequency converter in an intermediate interval, the frequency converter adjusting method comprises the steps of reducing or increasing the output frequency once every interval, the frequency increased every time is A V1 or the frequency reduced every time is A V2, the time at one end of the interval is 3-7 seconds, the adjusting range of the frequency converter adjusting method is 25-65Hz, A is an adjusting coefficient, and A is 0.1;
the variable-frequency loading method comprises the steps of sequentially loading the compressors according to the sequence of the accumulated running time of the compressors from small to large;
the frequency conversion unloading method sequentially unloads the compressors according to the sequence of the accumulated running time of the compressors from large to small.
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| CN113028571B (en) * | 2021-04-07 | 2022-04-22 | 广东友电新能源科技有限公司 | Compressor control method and device of machine room air conditioner, air conditioner and medium |
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