CN112640283B - Inverter control method, power supply system for AC load, and refrigeration circuit - Google Patents
Inverter control method, power supply system for AC load, and refrigeration circuit Download PDFInfo
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- CN112640283B CN112640283B CN201980055943.5A CN201980055943A CN112640283B CN 112640283 B CN112640283 B CN 112640283B CN 201980055943 A CN201980055943 A CN 201980055943A CN 112640283 B CN112640283 B CN 112640283B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
Abstract
Suppressing heat generation of the inverter. The inverter supplies power to an ac load by applying an ac voltage converted from a dc voltage. When the voltage value (Vac) of the ac voltage converted into the dc voltage by the inverter is smaller than the first value (Vt1), the power can be reduced (steps S84, S85).
Description
Technical Field
The present invention relates to a technique for converting electric power.
Background
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 63-290193
Disclosure of Invention
Problems to be solved by the invention
The invention suppresses heat generation of a converter that outputs a voltage input to an inverter.
Means for solving the problems
The power supply system for an AC load according to the present invention includes: an inverter (4) that supplies electric power (Po) to an AC load (5) by applying a first AC voltage (V1) converted from a DC voltage (Vdc); an inverter (2) that converts a second alternating voltage (V2) into the direct voltage (Vdc); and a control circuit (6).
In the first aspect, the control circuit may cause the inverter to reduce the electric power when the voltage value (Vac) of the second ac voltage is smaller than a predetermined first value (Vt1) (S85).
And, if the voltage value (Vac) is the first value (Vt1) or more, the power is lowered (S85) based on a first condition (S83, S84) for lowering the power. If the voltage value is less than the first value, the power is reduced (S85) based on a second condition (S82, S84) for reducing the power, which is gentler than the first condition.
In a second aspect of the power supply system to an ac load according to the present invention, in the first aspect, if the voltage value (Vac) is smaller than the first value (Vt1) and a current (Iw) input to the inverter (4) or output to the ac load (5) is equal to or greater than a first upper limit value (I3), droop control is performed on the current (S85). The first upper limit value is monotonically non-decreasing with respect to a rise in the voltage value.
In the third aspect of the power supply system to the ac load according to the present invention, in the first or second aspect, if the voltage value (Vac) is smaller than the first value (Vt1) and the current value (Ii) of the input current to the inverter (2) is equal to or larger than a second upper limit value, droop control is performed on the input current (S85). The second upper limit value is monotonically non-decreasing with respect to a rise in the voltage value (Vac).
A fourth aspect of the power supply system to an ac load according to the present invention is the first, second, or third aspect wherein if the voltage value (Vac) is less than a predetermined second value (Vt2) lower than the first value (Vt1), the supply of the power (Po) to the ac load (5) is stopped (S73, S74).
In a fifth aspect of the power supply system for an ac load according to the present invention, in the second or third aspect, the ac load (5) is a motor. The droop control (S85) includes a control of reducing the rotation speed of the motor.
In a sixth aspect of the power supply system to an ac load according to the present disclosure, in the fifth aspect, the motor (5) is any one of a motor that drives a compressor (91) used in a refrigeration circuit (9), a motor that drives a fan used in an air conditioner, and a motor that drives a fan used in an air cleaner.
In a seventh aspect of the power supply system to an ac load according to the present invention, in the fifth aspect, the motor (5) is a motor that drives a compressor (91) included in a refrigeration circuit (9). The refrigeration circuit also has an expansion valve (93). The droop control (S85) includes control for increasing the opening degree of the expansion valve.
An eighth aspect of the power supply system to an ac load according to the present invention is the power supply system to an ac load according to any one of the first to seventh aspects, wherein when the voltage value (Vac) is smaller than the first value (Vt1), the power supplied to a dc load (93) driven by the dc voltage is reduced.
A refrigeration circuit (9) of the present invention has a compressor (91) driven by a motor (5) and an expansion valve (93). The motor (5) is the alternating-current load (5) to which power is supplied by the seventh aspect of the power supply system for an alternating-current load according to the present invention.
An inverter control method of the present invention controls an inverter (4) that converts an input direct current voltage (Vdc) into a first alternating current voltage (V1) and supplies power to an alternating current load (5). The direct voltage (Vdc) is converted from a second alternating voltage (V2) by an inverter (2).
When the voltage value (Vac) of the second ac voltage is smaller than the predetermined first value (Vt1), the electric power can be supplied by reducing the electric power (S85) (S8).
If the voltage value (Vac) is above the first value (Vt1), the power is reduced (S85) based on a first condition (S83, S84) for reducing the power. If the voltage value is less than the first value, the power is reduced (S85) based on a second condition (S82, S84) for reducing the power, which is gentler than the first condition.
Drawings
Fig. 1 is a block diagram showing a configuration of an ac load driving system.
Fig. 2 is a flowchart showing the power-down operation of the control circuit and the operation associated therewith.
Fig. 3 is a graph showing the dependence on voltage value as a function of current droop.
Fig. 4 is a block diagram showing the configuration of the refrigeration circuit.
Detailed Description
Fig. 1 is a block diagram showing a configuration of an ac load driving system 100, and here, the ac load driving system 100 drives an ac load 5. As the ac load 5, any one of a single-phase ac load and a multi-phase ac load can be used. The ac load 5 is, for example, an ac motor. For example, the ac motor drives a compressor used in a refrigeration circuit. Alternatively, the ac motor drives a fan that blows air to a heat exchanger used in the refrigeration circuit, for example. Alternatively, the ac motor drives a fan for the air purifier, for example.
The ac load driving system 100 has an inverter 4. The inverter 4 converts the direct-current voltage Vdc input thereto into an alternating-current voltage V1, and applies an alternating-current voltage V1 to the alternating-current load 5. The inverter 4 supplies power Po for operating the ac load 5 (hereinafter referred to as "operating power") to the ac load 5. The number of phases of the ac voltage V1 corresponds to the number of phases of the ac load 5.
The ac load driving system 100 has an inverter 2. The inverter 2 converts the ac voltage V2 to output a dc voltage Vdc. The ac voltage V2 is output from, for example, a commercial power supply 1 as an ac power supply. An input current having a current value Ii is input to the inverter 2 from the commercial power supply 1. Power Ps is supplied from commercial power supply 1 to ac load drive system 100.
The inverter 2 is, for example, a diode bridge rectifier circuit, a boost inverter, a buck inverter, or a buck-boost inverter.
Fig. 1 shows a case where the ac load drive system 100 further includes a filter 7 between the commercial power source 1 and the input side of the inverter 2. In this case, ac voltage V2 is applied from commercial power supply 1 to inverter 2 via filter 7. The filter 7 is, for example, a low-pass filter of a choke input type. The current value Ii may be a value of a current flowing from the commercial power supply 1 to the filter 7. The voltage across the capacitor provided in the filter 7 can be understood as an alternating voltage V2.
The ac load driving system 100 is also shown in fig. 1 with a capacitor 3. The capacitor 3 supports a direct voltage Vdc. The inverter 2 charges the capacitor 3. The capacitor 3 is discharged to supply the power (hereinafter referred to as "input power") Pi input to the inverter 4 alone or together with the converter 2. The input power Pi is equal to the operating power Po if losses in the inverter 4 are neglected.
The ac load driving system 100 has a control circuit 6. The control circuit 6 controls the operation of the inverter 4. For example, the inverter 4 performs a switching operation to convert the dc voltage Vdc into the ac voltage V1. The inverter 4 includes, for example, a switching element that performs the switching operation.
The control circuit 6 generates a control signal G for controlling the switching operation and outputs the control signal G to the inverter 4. The ac voltage V1 varies depending on the switching operation of the inverter 4. The fluctuation of the ac voltage V1 fluctuates the operation power Po. The variation in the operating power Po varies the operation of the ac load 5.
Therefore, the control circuit 6 varies the operating power Po by the control of the inverter 4, and drives the ac load 5 in various operations. The description will be given taking as an example a case where the ac load 5 is a three-phase motor.
The control circuit 6 receives command data J, a voltage value Vac of the ac voltage V2, and a value of a current Iw flowing through the inverter 4 (hereinafter also referred to as "current value Iw"). The command data J is, for example, a command value regarding the rotational speed or torque of the motor 5. The value of the direct voltage Vdc may also be input to the control circuit 6.
The voltage value Vac is obtained by a known method using a known voltage sensor, and the current value Iw is obtained by a known method using a known current sensor. The current value Iw can be obtained by measuring the current input to the inverter 4.
The command data J is set, for example, in accordance with the cooling performance of a refrigeration circuit using the compressor when the motor 5 drives the compressor. This setting is a technique known as control for driving the compressor based on the temperature setting of the air conditioner, for example. For example, in order to improve the cooling performance, a command value for increasing the rotation speed of the compressor, for example, the rotation speed indicated by the command data J, can be used.
The control circuit 6 determines the operating power Po using the command data J, the voltage value Vac, and the current value Iw. For example, when the command data J is a command value regarding the rotational speed or the torque, an increase in the command value causes an increase in the operating power Po.
The control circuit 6 generates a control signal G so as to supply operating power Po from the inverter 4 to the ac load 5.
When the inverter 4 supplies operating power Po of a certain value, the current value Ii increases as the voltage value Vac decreases. This is because the input power Pi is proportional to the product of the voltage value Vac and the current value Ii when the power conversion efficiency of the converter 2 is considered to be constant, and is equal to the operating power Po when the loss in the inverter 4 is neglected. The rise in the current value Ii causes heat generation of the diode or the switching element constituting the inverter 2. The heat generation of the diode or the switching element causes a reduction in efficiency and a reduction in performance of the element. Therefore, it is desirable to suppress heat generation of the inverter 2.
In the present embodiment, as a technique for suppressing this heat generation, a method of controlling an inverter is proposed in which the inverter 4 is caused to perform an operation of reducing the operating power Po when the voltage value Vac is reduced. Specifically, for example, the control circuit 6 varies the control signal G so that the inverter 4 performs the above-described operation. This is to reduce the input power Pi and further the power Ps by reducing the operating power Po, and to alleviate or reduce the increase in the current value Ii.
This suppresses heat generation of the inverter 2. When the filter 7 is provided, heat generation in the coil provided in the filter 7 is also suppressed. In other words, heat generation on the commercial power supply 1 side including at least the inverter 2 in the ac load drive system 100 is suppressed.
When the voltage value Vac of the dc voltage Vdc is increased or decreased by increasing or decreasing the voltage value Vac in the inverter 2 as in a diode bridge rectifier circuit, the voltage value Vdc is decreased by decreasing the voltage value Vac. Therefore, the switching loss of the inverter 4 is reduced regardless of the reduction in the operating power Po, and the heat generation of the inverter 4 is suppressed. When the operating power Po is lowered, the current value Iw also decreases, and therefore heat generation of the inverter 4 is further suppressed. For example, according to the function of the converter 2, even when the voltage value of the dc voltage Vdc is not increased or decreased by the increase or decrease of the voltage value Vac, the heat generation of the inverter 4 can be suppressed when the operating power Po is decreased.
The operating power Po does not need to be always reduced with respect to the reduction in the voltage value Vac. Since heat generation of the switching element and the like can be allowed to a prescribed upper limit. For example, in the case of using a transistor as a switching element, the upper limit of such tolerance depends on a so-called allowable collector loss.
Therefore, as a technique proposed in the present embodiment, the following technique is listed: if the voltage value Vac is smaller than a predetermined threshold value (hereinafter, referred to as "first value Vt 1" for convenience of description), the operating power Po supplied from the inverter 4 to the ac load 5 is more likely to be reduced than when the voltage value Vac is equal to or greater than the predetermined threshold value.
This is a control method for supplying the operating power Po to the inverter 4 under different conditions when the voltage value Vac is smaller than the first value Vt1 and when the voltage value Vac is equal to or greater than the first value Vt1 (hereinafter, also referred to as "power reduction operation"), as an operation of the control circuit 6. For example, the control circuit 6 generates a control signal G for causing the inverter 4 to perform an operation of reducing the operating power Po and outputs the control signal G to the inverter 4.
Fig. 2 is a flowchart showing the power-down operation of the control circuit 6 and the operation associated therewith. In step S71, the operating power Po is set. This setting is a determination of the operating power Po based on the command data J, the voltage value Vac, and the current value Iw, and is a process performed by a known technique. In step S71, the operating power Po may be determined not only directly but also indirectly by determining the operating state of the ac load 5 (for example, the rotation speed or torque of the motor load).
After step S71, in step S72, control is performed to operate the inverter 4 while maintaining the operating power Po. This control is control for operating the inverter 4 while maintaining the operating power Po set in step S71, and is processing performed by a known technique.
After step S72, in step S73, when the voltage value Vac abnormally decreases, a comparison is made to stop the driving of the ac load 5.
In step S73, the voltage value Vac is compared with a predetermined second value Vt2, for example. The second value Vt2 is less than the first value Vt 1. If the voltage value Vac is less than the second value Vt2 (i.e., when Vac ≧ Vt2 is NO), the process advances to step S74.
In step S74, supply of operating power Po from inverter 4 to ac load 5 is stopped. For example, in the case where the inverter 2 employs a diode bridge rectifier circuit, a decrease in the voltage value Vac leads to a decrease in the dc voltage Vdc. Step S73 may include a process of low-voltage protection of the direct-current voltage Vdc in this case.
Here, the stop of the supply of the operating power Po is handled as a process different from the power lowering operation in which the supply of the operating power Po is performed although the operating power Po is lowered.
If the voltage value Vac is not less than the second value Vt2 in step S73 (i.e., if Vac ≧ Vt2 is affirmative), the process proceeds to step S8. In step S8, the control circuit 6 performs the power reduction operation. However, as will be described later, the operating power Po is not necessarily reduced in step S8. Specifically, step S8 includes a plurality of steps from step S81 to step S85, and the processing branches at step S84 and sometimes exits from the middle of step S8.
At the beginning of the process of step S8, a comparison of the first value Vt1 and the voltage value Vac is performed in step S81. As a result of this comparison, if the voltage value Vac is smaller than the first value Vt1 (i.e., Vac < Vt1 is affirmative), the process proceeds to step S82. If the voltage value Vac is greater than or equal to the first value Vt1 (i.e., if Vac < Vt1 is positive), the process advances to step S83.
For convenience of explanation, steps S84 and S85 will be explained before steps S82 and S83 are explained. In step S85, so-called droop control is performed on the current Iw, and before step S85, it is determined in step S84 whether droop control is necessary.
As an example of the droop control, a control in which the ac load 5 is a motor and the rotation speed thereof is reduced can be given. The reduction in the rotation speed of the motor is achieved by reducing the current Iw, and contributes to a direct reduction in the operating power Po.
Whether or not droop control is performed is determined by comparing the current output from the inverter 4 to the ac load 5 with the current droop value I3. This current is a current flowing through the inverter 4, and therefore can be measured as a current value Iw.
In step S84, when Iw ≧ I3 is affirmative, the process proceeds to step S85, and droop control is performed. Thereby, the current value Iw decreases. That is, in steps S84 and S85, the current droop value I3 functions as the upper limit value of the current value Iw.
When Iw ≧ I3 is NO in step S84 (i.e., Iw < I3), the process exits from step S8 and returns to step S72.
Steps S82, S83 are both processing for determining the current droop value I3. In step S82, the current droop value I3 is set by a function f (Vac) of the voltage value Vac. Here, the function f (Vac) is monotonous rather than decreasing with respect to the rise of the voltage value Vac. In step S83, the current droop value I3 is set to the prescribed value I31. For example, the predetermined value I31 is a value not related to the voltage value Vac.
After the steps S82, S83 are performed, step S84 is performed. In this case, the processing in step S84 is to compare the current value Iw with a predetermined value I31. That is, steps S82, S83, S84, and S85 are a set of steps for performing droop control so that the current value Iw does not exceed the predetermined value I31.
Fig. 3 is a graph showing the correlation with respect to the voltage value Vac as a function f (Vac) of the current droop value I3. The method specifically comprises the following steps:
when Vac is not less than Vt1, f (Vac) is I31;
when Vac ≦ Vt2, f (Vac) ═ I32;
when Vt2 ≦ Vac ≦ Vt1,
f(Vac)＝I32+(Vac-Vt2)(I31-I32)/(Vt1-Vt2)。
the prescribed value I32 is smaller than the prescribed value I31 and is irrelevant to the voltage value Vac.
Of course, the function f (Vac) is exemplary, and the function f (Vac) may be non-linear with respect to the voltage value Vac when Vt2 Vac is less than Vt 1. For example, the function f (Vac) may be continuously changed or may be stepwise changed with respect to the change in the voltage value Vac.
In executing step S81, since the determination in step S73 is affirmative, Vt2 ≦ Vac holds. Therefore, in step S82, the current droop value I3 is set to a value that monotonically decreases with respect to a decrease in the voltage value Vac.
By adopting the thus set current droop value I3 and executing steps S84 and S85, in the droop control of the current Iw, the lower the voltage value Vac, the lower the current droop value I3 is set as the upper limit, and the current Iw is suppressed. Therefore, as the voltage value Vac decreases, the operating power Po decreases and the power Ps decreases. Therefore, even if the voltage value Vac decreases, the increase in the current value Ii is suppressed, and the heat generation of the inverter 2 is suppressed. The reduction of the operating power Po in steps S82, S84, and S85 is an example of the power reduction operation described above.
According to the descriptions of the steps S82, S83, S84, it can be shown as follows:
when the voltage value Vac is equal to or greater than the first value Vt1, the supply operation power Po is reduced under the first condition I3 — I31;
if the voltage value Vac is smaller than the first value Vt1, the supply operating power Po is reduced under the second condition I3 ═ f (Vac).
If Vac < Vt1, f (Vac) < I31, and therefore, the operating power Po is more easily reduced when the voltage value Vac is smaller than the first value Vt1 than when the voltage value Vac is equal to or greater than the first value Vt 1. In other words, the second condition for lowering the operating power Po is gentler than the first condition.
Although the second condition is less than the first condition, the operating power Po may not be reduced even if Vac < Vt 1. This is because, if the determination at step S84 is negative, the process does not proceed to step S85, and the droop control is not performed. Therefore, when Vac < Vt1, the control circuit 6 can reduce the power to the inverter 4.
If the determination at step S73 is negative, step S74 is executed, and the value of the function f (Vac) may not be set when Vac < Vt2, in view of stopping the supply of the operating power Po.
A second value Vt2 'smaller than the second value Vt2 of the determination function f (Vac) may be introduced, and the second value Vt2 compared with the voltage value Vac may be replaced with the second value Vt2' in step S73. In this case, the supply of the operating power Po is stopped when Vac < Vt2', and the current droop value I3 is controlled to have the predetermined value I32 as the upper limit when Vt2' is equal to or less than Vac < Vt 2.
The first value Vt1 'larger than the first value Vt1 of the determination function f (Vac) may be introduced, and the first value Vt1 compared with the voltage value Vac may be replaced with the first value Vt1' in step S81. In this case, when Vt1 ≦ Vac ≦ Vt1', the current droop value I3 takes the predetermined value I31 as the upper limit, and droop control is performed on the current Iw. That is, the function f (Vac) monotonically decreases with a decrease in the voltage value Vac, but there may be a region unrelated to the voltage value Vac (monotonically not decreasing with an increase in the voltage value Vac).
The decrease in the rotation speed of the motor exemplified as the droop control directly decreases the current Iw. The operation power Po is indirectly reduced through the reduction of the rotation speed or the torque of the motor by the phenomenon of causing the reduction of the rotation speed or the torque of the motor, which is also considered to be included in the droop control. Next, such control will be described.
Fig. 4 is a block diagram showing the structure of the refrigeration circuit 9. The refrigeration circuit 9 includes a compressor 91, heat exchangers 92 and 94, and an expansion valve 93. A refrigerant, not shown, is compressed by the compressor 91, evaporated by the heat exchanger 92, expanded by the expansion valve 93, and condensed by the heat exchanger 94. The white arrows in the figure indicate the direction of refrigerant circulation.
The ac load 5 is a motor that drives a compressor 91 included in the refrigeration circuit 9. The expansion valve 93 is an electromagnetic valve, and its opening degree is adjusted by a control signal L generated by the control circuit 6. For example, the opening degree of the electromagnetic valve is determined by a stepping motor driven by a control signal L. For example, the operating power of the stepping motor can be obtained from the output of the inverter 2.
In step S85 (see fig. 2), the opening degree of the expansion valve 93 is increased in accordance with the control signal L. This reduces the mechanical load on the compressor 91, and therefore reduces the torque required to drive the motor 5 of the compressor 91, and reduces the current Iw. Therefore, it is considered that the droop control includes a process of increasing the opening degree of the expansion valve 93.
As described above, the control circuit 6 that generates the control signal L and/or the control signal G may be configured to include a microcomputer and a storage device. The microcomputer executes the steps of the respective processes (in other words, programs) described in the programs. For example, the steps of fig. 2 are executed by the microcomputer.
The storage device may be one or more of various storage devices such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a rewritable nonvolatile Memory (EPROM (Erasable Programmable ROM)). The storage device stores various information, data, and the like, and stores a program executed by a microcomputer, and in addition, provides a work area for executing the program. The microcomputer can be understood as functioning as various means corresponding to each processing step described in the program, or can be understood as realizing various functions corresponding to each processing step. The control circuit 6 is not limited to this, and a part or all of various steps executed by the control circuit 6, various units implemented, or various functions may be implemented by hardware.
As described above, in the present embodiment, a technique for controlling the inverter 4 that converts the input dc voltage Vdc into the ac voltage V1 and applies the ac voltage V1 to the ac load 5 is proposed. The dc voltage Vdc is converted from the ac voltage V2 by the inverter 2.
In the ac load driving system 100, when the voltage value Vac is smaller than the first value Vt1, the control circuit 6 can lower the operation power Po to the inverter 4. This reduces the operating power Po and further reduces the power Ps, thereby suppressing heat generation of the inverter 2. This technique can also be regarded as a method for controlling the inverter 4, and the inverter 4 can reduce the supply operating power Po when the voltage value Vac is smaller than the first value Vt 1.
When the voltage value Vac is equal to or higher than the first value Vt1, the operating power Po supplied from the inverter 4 to the ac load 5 is reduced (step S85) based on the first condition (steps S83 and S84), and the operating power Po is supplied. If the voltage value Vac is smaller than the first value Vt1, the operating power Po is lowered (step S85) based on the second condition (steps S82 and S84), and the operating power Po is supplied. The second condition is more moderate than the first condition.
For example, if the voltage value Vac is smaller than the first value Vt1 and the input current (current value Ii) to the inverter 4 or the current Iw to be output to the ac load 5 is equal to or greater than the current droop value I3, which is the upper limit value thereof, droop control is performed on the current (step S85). The current droop value I3 monotonically decreases with respect to the increase in the voltage value Vac. This reduces the operating power Po supplied from the inverter 4 to the ac load 5.
The current input to the converter 2 may also be droop-controlled. For example, if the voltage value Vac is smaller than the first value Vt1 and the current value Ii is equal to or larger than the upper limit value, droop control is performed for the current. For example, the upper limit value may be set to be monotonous rather than decreasing with respect to the increase of the voltage value Vac. Specifically, for example, a flowchart in which current value Iw is replaced with current value Ii in step S84 (see fig. 2) can be employed. The upper limit value can be set independently of the current droop value I3 described above.
If the voltage value Vac is smaller than the second value Vt2 lower than the first value Vt1, the supply of the operating power Po to the ac load 5 may be stopped.
For example, the ac load 5 may be a motor, and the droop control includes control for reducing the rotation speed of the motor 5. This results in a direct decrease in the action power Po.
An example of the motor 5 is a motor that drives a compressor 91 provided in the refrigeration circuit 9. For example, the motor 5 drives a compressor 91 provided in the refrigeration circuit 9 having an expansion valve 93. The refrigeration circuit 9 includes a compressor 91 and an expansion valve 93 driven by the motor 5 to which the ac load drive system 100 supplies operating power Po. The droop control may include control for increasing the opening degree of the expansion valve 93. This results in an indirect decrease in the action power Po.
The motor 5 can also be used as a motor for driving a fan used in an air conditioner and a fan used in an air cleaner.
When a dc load driven by the dc voltage Vdc is provided, control for reducing the power supplied to the dc load can be performed. In this case, the input power Pi is the sum of the operating power Po and the power consumed by the dc load, and the reduction of the dc power contributes to the reduction of the power Ps. This control can be performed independently of the control of the inverter 4.
For example, in the refrigeration circuit 9, when the expansion valve 93 is a dc load to which the operating power is supplied as dc power from the capacitor 3, the operation of the expansion valve 93 may be stopped when the voltage value Vac is smaller than the first value Vt 1.
The ac load drive system 100 having the converter 2, the inverter 4, and the control circuit 6 performing the power-lowering operation can be said to be a power supply system that supplies power to the ac load 5.
While the embodiments have been described above, it should be understood that various changes in form and details may be made therein without departing from the spirit and scope of the claims. The various embodiments and modifications described above may be combined with each other.
Claims (9)
1. A power supply system for an AC load, comprising:
an inverter (4) that supplies electric power (Po) to an AC load (5) by applying a first AC voltage (V1) converted from a DC voltage (Vdc);
an inverter (2) that converts a second alternating voltage (V2) into the direct voltage (Vdc); and
a control circuit (6) that can cause the inverter to reduce the electric power (S85) when the voltage value (Vac) of the second AC voltage is less than a predetermined first value (Vt1),
if the voltage value (Vac) is equal to or greater than the first value (Vt1), the power is reduced (S85) based on a first condition (S83, S84) for reducing the power, the first condition (S83, S84) being a condition that a current droop value (I3) acting as an upper limit value of a current (Iw) input to the inverter (4) or output to the AC load (5) in droop control (S84) for the current (Iw) takes a first predetermined value (I31),
reducing (S85) the power based on a second condition (S82, S84) for reducing the power, which is less than the first condition, if the voltage value is less than the first value, the second condition (S82, S84) being a condition that the current droop value (I3) takes a second prescribed value f (Vac),
The first prescribed value (I31) is greater than the second prescribed value f (Vac),
performing the droop control (S85) if the voltage value (Vac) is less than the first value (Vt1), is equal to or greater than a predetermined 2 nd value (Vt2) lower than the first value (Vt1), and the current (Iw) input to the inverter (4) or output to the AC load (5) is equal to or greater than the current droop value (I3),
the current droop value (I3) is monotonically non-decreasing with respect to the rise in the voltage value (Vac) and with the exception of a monotonic change.
2. The power supply system for an alternating-current load according to claim 1, wherein,
performing droop control (S85) for the input current if the voltage value (Vac) is less than the first value (Vt1) and is above the 2 nd value (Vt2) and a current value (Ii) of the input current input to the inverter (2) is above a second upper limit value,
the second upper limit value is monotonically non-decreasing with respect to a rise in the voltage value (Vac).
3. The power supply system for an alternating-current load according to claim 1, wherein,
if the voltage value (Vac) is less than a second predetermined value (Vt2) lower than the first value (Vt1), the supply of the electric power (Po) to the AC load (5) is stopped (S73, S74).
4. The power supply system for an alternating-current load according to claim 1,
the alternating current load (5) is an electric motor,
the droop control (S85) includes a control of reducing the rotation speed of the motor.
5. The power supply system for an alternating-current load according to claim 4, wherein,
the motor (5) is any one of a motor for driving a compressor (91) used in the refrigeration circuit (9), a fan used in an air conditioner, and a fan used in an air cleaner.
6. The power supply system for an alternating-current load according to claim 4, wherein,
the motor (5) is a motor for driving a compressor (91) provided in the refrigeration circuit (9),
the refrigeration circuit also has an expansion valve (93),
the droop control (S85) includes control for increasing the opening degree of the expansion valve.
7. The power supply system for an alternating-current load according to claim 1,
-if said voltage value (Vac) is lower than said first value (Vt1), reducing the power supplied to a dc load (93) driven by said dc voltage.
8. Refrigeration circuit (9), the refrigeration circuit (9) having:
a compressor (91) driven by the motor (5) as the alternating-current load (5) supplied with electric power by the electric power supply system for alternating-current loads according to claim 6; and
An expansion valve (93).
9. A method for controlling an inverter, which controls an inverter (4) that converts an input direct-current voltage (Vdc) into a first alternating-current voltage (V1) and supplies power to an alternating-current load (5),
the direct voltage (Vdc) is converted from a second alternating voltage (V2) by an inverter (2),
when the voltage value (Vac) of the second AC voltage is less than a predetermined first value (Vt1), the electric power can be supplied by reducing the electric power (S85) (S8),
if the voltage value (Vac) is equal to or greater than the first value (Vt1), the power is reduced (S85) based on a first condition (S83, S84) for reducing the power, the first condition (S83, S84) being a condition that a current droop value (I3) acting as an upper limit value of a current (Iw) input to the inverter (4) or output to the AC load (5) in droop control (S84) for the current (Iw) takes a first predetermined value (I31),
reducing (S85) the power based on a second condition (S82, S84) for reducing the power, which is less than the first condition, if the voltage value is less than the first value, the second condition (S82, S84) being a condition that the current droop value (I3) takes a second prescribed value f (Vac),
The first prescribed value (I31) is greater than the second prescribed value f (Vac),
performing the droop control (S85) if the voltage value (Vac) is less than the first value (Vt1), is equal to or greater than a predetermined 2 nd value (Vt2) lower than the first value (Vt1), and the current (Iw) input to the inverter (4) or output to the AC load (5) is equal to or greater than the current droop value (I3),
the current droop value (I3) is monotonically non-decreasing with respect to the rise in the voltage value (Vac) and with the exception of a monotonic change.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2018-172046 | 2018-09-14 | ||
| JP2018172046A JP6729650B2 (en) | 2018-09-14 | 2018-09-14 | Inverter control method, AC load power supply system, refrigeration circuit |
| PCT/JP2019/030849 WO2020054262A1 (en) | 2018-09-14 | 2019-08-06 | Inverter control method, system for supplying power to ac load, and refrigeration circuit |
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| CN112640283A CN112640283A (en) | 2021-04-09 |
| CN112640283B true CN112640283B (en) | 2022-06-10 |
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| CN (1) | CN112640283B (en) |
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| US8900169B2 (en) | 2013-03-15 | 2014-12-02 | Tbi Innovations, Llc | Methods and devices to reduce the likelihood of injury from concussive or blast forces |
| EA201891055A1 (en) | 2015-11-16 | 2018-11-30 | Кью30 Спортс Сайенс, Ллк | DEVICES FOR PROTECTION AGAINST TRAUMATIC DAMAGE OF THE BRAIN |
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- 2019-08-06 BR BR112021003200-2A patent/BR112021003200A2/en active Search and Examination
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Also Published As
| Publication number | Publication date |
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| CN112640283A (en) | 2021-04-09 |
| JP2020048242A (en) | 2020-03-26 |
| MY187349A (en) | 2021-09-22 |
| BR112021003200A2 (en) | 2021-05-11 |
| JP6729650B2 (en) | 2020-07-22 |
| WO2020054262A1 (en) | 2020-03-19 |
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