WO2020054262A1

WO2020054262A1 - Inverter control method, system for supplying power to ac load, and refrigeration circuit

Info

Publication number: WO2020054262A1
Application number: PCT/JP2019/030849
Authority: WO
Inventors: 俊彰佐藤; 雄希中島
Original assignee: ダイキン工業株式会社
Priority date: 2018-09-14
Filing date: 2019-08-06
Publication date: 2020-03-19
Also published as: CN112640283B; JP6729650B2; CN112640283A; JP2020048242A; MY187349A; BR112021003200A2

Abstract

The present invention suppresses heat generation of a converter. According to the present invention, an inverter applies an AC voltage converted from a DC voltage, and supplies power to an AC load. The power can be reduced when the voltage value Vac of the AC voltage converted into the DC voltage by the converter is less than a first value Vt1 (steps S84, S85).

Description

Inverter control method, power supply system to AC load, refrigeration circuit

The present disclosure relates to a technology for converting power.

Patent Document 1 below discloses that when the voltage input to the inverter drops extremely, the operation of the inverter is stopped, thereby preventing malfunction of the inverter and destruction of components.

JP-A-63-290193

(4) The present disclosure suppresses heat generation of a converter that outputs a voltage input to an inverter.

The power supply system for an AC load according to the present disclosure includes an inverter (4) that applies a first AC voltage (V1) converted from a DC voltage (Vdc) and supplies power (Po) to an AC load (5). , A converter (2) for converting the second AC voltage (V2) into the DC voltage (Vdc), and a control circuit (6).

In the first aspect, when the voltage value (Vac) of the second AC voltage is lower than a predetermined first value (Vt1), the control circuit allows the inverter to reduce the power (S85).

A second aspect of the system for supplying power to an AC load according to the present disclosure is the first aspect, wherein the power is in the first condition if the voltage value (Vac) is equal to or more than the first value (Vt1). Under the conditions (S83, S84), if the voltage value is less than the first value, the power is reduced under the second condition (S82, S84) in which the power is less than the first condition, respectively ( S85) is performed.

A second aspect of the system for supplying power to an AC load according to the present disclosure is the first aspect, wherein the voltage value (Vac) is less than the first value (Vt1), and the inverter (4) If the current (Iw) input to the AC load (5) or output to the AC load (5) is equal to or more than the first upper limit (I3), the droop control (S85) for the current is performed. The first upper limit is monotonically non-decreasing with respect to the increase in the voltage value.

A third aspect of the system for supplying power to an AC load according to the present disclosure is the first aspect, wherein the voltage value (Vac) is less than the first value (Vt1) and the converter (2) If the current value (Ii) of the input current input to the input current is equal to or greater than the second upper limit, droop control (S85) for the input current is performed. The second upper limit is monotonically non-decreasing with respect to an increase in the voltage value (Vac).

A fourth aspect of the system for supplying power to an AC load according to the present disclosure is the first aspect, the second aspect, or the third aspect, wherein the voltage value (Vac) is the first value (Vt1). If it is lower than the second predetermined value (Vt2), the supply of the power (Po) to the AC load (5) is stopped (S73, S74).

A fifth aspect of the power supply system for an AC load according to the present disclosure is the second aspect or the third aspect, wherein the AC load (5) is a motor. The drooping control (S85) includes control for reducing the rotation speed of the motor.

A sixth aspect of the system for supplying power to an AC load according to the present disclosure is the fifth aspect, wherein the motor (5) drives a compressor (91) employed in a refrigeration circuit (9). Either a motor, a fan used in an air conditioner, or a motor that drives a fan used in an air purifier.

A seventh aspect of the system for supplying power to an AC load according to the present disclosure is the fifth aspect, wherein the motor (5) is a motor that drives a compressor (91) included in a refrigeration circuit (9). is there. The refrigeration circuit further includes an expansion valve (93). The drooping control (S85) includes control for increasing the opening of the expansion valve.

An eighth aspect of the power supply system for an AC load according to the present disclosure is any one of the first to seventh aspects, wherein the voltage value (Vac) is less than the first value (Vt1). If so, the power supplied to the DC load (93) driven by the DC voltage is reduced.

冷凍 The refrigeration circuit (9) of the present disclosure includes a compressor (91) driven by the motor (5) and an expansion valve (93). The motor (5) is the AC load (5) to which power is supplied by the seventh aspect of the system for supplying power to an AC load according to the present disclosure.

The method of controlling the inverter according to the present disclosure is a method of controlling the inverter (4) that converts the input DC voltage (Vdc) into the first AC voltage (V1) and applies the converted voltage to the AC load (5). The DC voltage (Vdc) is obtained by converting the second AC voltage (V2) by the converter (2).

(4) When the voltage value (Vac) of the second AC voltage is less than a predetermined first value (Vt1), the power is reduced (S85) and the supply of the power is enabled (S8).

FIG. 2 is a block diagram illustrating a configuration of an AC load driving system. 4 is a flowchart illustrating a power reduction operation of a control circuit and an operation accompanying the power reduction operation. 5 is a graph illustrating the dependence of a function that becomes a current droop value on a voltage value. It is a block diagram which illustrates the structure of a refrigeration circuit.

FIG. 1 is a block diagram showing the configuration of the AC load driving system 100. Here, the AC load driving system 100 drives the AC load 5. As the AC load 5, either a single-phase AC load or a multi-phase AC load can be adopted. For example, the AC load 5 is an AC motor. For example, the AC motor drives a compressor used in a refrigeration circuit. Alternatively, for example, the AC motor drives a fan that blows air to a heat exchanger used in a refrigeration circuit. Alternatively, for example, the AC motor drives a fan used in an air purifier.

The AC load driving system 100 includes the inverter 4. The inverter 4 converts the DC voltage Vdc input thereto into an AC voltage V1 and applies the AC voltage V1 to the AC load 5. The inverter 4 supplies the AC load 5 with power (hereinafter referred to as “operating power”) Po for operating 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 includes the converter 2. Converter 2 converts AC voltage V2 and outputs DC voltage Vdc. The AC voltage V2 is output from, for example, a commercial power supply 1 that is an AC power supply. An input current having a current value Ii is input from the commercial power supply 1 to the converter 2. Electric power Ps is supplied from the commercial power supply 1 to the AC load driving system 100.

The converter 2 employs, for example, a diode bridge rectifier circuit, a step-up converter, a step-down converter, and a step-up / step-down converter.

FIG. 1 illustrates a case where the AC load driving system 100 further includes a filter 7 between the commercial power supply 1 and the input side of the converter 2. In this case, the AC voltage V2 is applied from the commercial power supply 1 to the converter 2 via the filter 7. For example, the filter 7 is a choke input type low-pass filter. As the current value Ii, the value of the current flowing from the commercial power supply 1 to the filter 7 may be adopted. The voltage across the capacitor of the filter 7 may be regarded as the AC voltage V2.

FIG. 1 illustrates a case where the AC load driving system 100 further includes a capacitor 3. Capacitor 3 supports DC voltage Vdc. Converter 2 charges capacitor 3. The capacitor 3 discharges and supplies power (hereinafter, referred to as “input power”) Pi to be input to the inverter 4 alone or together with the converter 2. If the loss in the inverter 4 is ignored, the input power Pi is equal to the operating power Po.

The AC load driving system 100 includes the 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 to an AC voltage V1. Inverter 4 includes a switching element that performs the above-described switching operation, for example.

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 fluctuates depending on the switching operation of the inverter 4. The fluctuation of the AC voltage V1 fluctuates the operating power Po. The fluctuation of the operating power Po fluctuates the operation of the AC load 5.

Therefore, the control circuit 6 varies the operating power Po through the control of the inverter 4 to drive the AC load 5 by various operations. The case where the AC load 5 is a three-phase motor will be described as an example.

(4) The command data J, the voltage value Vac of the AC voltage V2, and the value of the current Iw flowing through the inverter 4 (hereinafter also referred to as “current value Iw”) are input to the control circuit 6. The command data J is, for example, a command value for the rotation speed or rotation torque of the motor 5. The value of the DC voltage Vdc may 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 depending on, for example, the cooling performance of a refrigeration circuit using the compressor when the motor 5 drives the compressor. The setting is, for example, a technique known as control for driving a compressor based on a temperature setting in an air conditioner. For example, to increase the cooling performance, an increase in the rotational speed of the compressor can be adopted. For example, the instruction value of the rotational speed indicated by the instruction data J increases.

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 for a rotation speed or a rotation torque, an increase in the command value results in an increase in the operating power Po.

The control circuit 6 generates the control signal G so that the operating power Po is supplied from the inverter 4 to the AC load 5.

(4) When the inverter 4 supplies a certain value of the operating power Po, if the voltage value Vac decreases, the current value Ii increases. 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 the input power Pi is equal to the operating power Po if the loss in the inverter 4 is ignored. An increase in the current value Ii causes heat generation of a diode or a switching element included in the converter 2. The heat generated by the diode or the switching element lowers the efficiency and lowers the performance of the element. Therefore, it is desired that the heat generation of converter 2 be suppressed.

In the present embodiment, as a technique for suppressing such heat generation, a method of controlling an inverter that causes the inverter 4 to perform an operation of reducing the operating power Po when the voltage value Vac decreases is proposed. Specifically, for example, the control circuit 6 changes the control signal G so that the inverter 4 performs the above operation. This is because the reduction in the operating power Po leads to a reduction in the input power Pi, and thus the power Ps, so that the increase in the current value Ii is reduced or reduced.

This suppresses the heat generation of converter 2. When the filter 7 is provided, heat generation in the coil of the filter 7 is also suppressed. In other words, in the AC load drive system 100, heat generation on at least the commercial power supply 1 including the converter 2 is suppressed.

(4) When the voltage value of the DC voltage Vdc is also increased / decreased by the increase / decrease of the voltage value Vac as in the case of the diode bridge rectifier circuit of the converter 2, the voltage value of the DC voltage Vdc is decreased by the decrease in the voltage value Vac. Therefore, the switching loss of the inverter is reduced irrespective of the reduction of the operating power Po, and the heat generation of the inverter 4 is suppressed. When the operating power Po is reduced, the current value Iw also decreases, so that the heat generation of the inverter 4 is further suppressed. For example, even when the voltage value of the DC voltage Vdc does not increase or decrease due to the increase or decrease of the voltage value Vac, the function of the converter 2 suppresses the heat generation of the inverter 4 when the operating power Po is reduced.

(4) It is not necessary to always reduce the operating power Po for a decrease in the voltage value Vac. This is because heat generation of the switching element and the like can be allowed up to a predetermined upper limit. For example, when a transistor is used as a switching element, such an allowable upper limit depends on so-called allowable collector loss.

Therefore, as a technique proposed in the present embodiment, if voltage value Vac is less than a predetermined threshold value (hereinafter, referred to as “first value Vt1” for convenience), voltage value Vac is equal to or greater than the predetermined threshold value. A technique for easily reducing the operating power Po supplied from the inverter 4 to the AC load 5 as compared with the conventional technique will be described.

This is an operation of reducing the operating power Po when the voltage value Vac is less than the first value Vt1 and when the voltage value Vac is equal to or more than the first value Vt1 (hereinafter also referred to as “power reducing operation”). Are performed under different conditions for supplying the operating power Po to the inverter 4. For example, the control circuit 6 generates a control signal G that causes 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 reduction operation of the control circuit 6 and the accompanying operation. In step S71, the operating power Po is set. The 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, not only the operating power Po is determined directly, but also the operating power Po may be determined indirectly by determining the operating state of the AC load 5 (for example, the rotational speed or torque of the motor load). .

(4) After step S71, in step S72, control for operating inverter 4 while maintaining operating power Po is performed. The control is a control for operating the inverter 4 while maintaining the operation power Po set in step S71, and is a process performed by a known technique.

(4) After step S72, in step S73, when the voltage value Vac drops abnormally, a comparison for stopping the driving of the AC load 5 is performed.

In step S73, for example, the voltage value Vac is compared with a predetermined second value Vt2. The second value Vt2 is smaller than the first value Vt1. If voltage value Vac is less than second value Vt2 (that is, if Vac ≧ Vt2 is denied), the process proceeds to step S74.

In step S74, the supply of the operating power Po from the inverter 4 to the AC load 5 is stopped. For example, when a diode bridge rectifier circuit is employed for converter 2, a decrease in voltage value Vac causes a decrease in DC voltage Vdc. Step S73 may include a process of protecting the DC voltage Vdc from a low voltage in such a case.

Here, the stop of the supply of the operating power Po is treated as a process different from the power reduction operation of supplying the operating power Po, although the process is reduced.

If the voltage value Vac is equal to or greater than the second value Vt2 in step S73 (that is, if Vac ≧ Vt2 is affirmative), the process proceeds to step S8. In step S8, control circuit 6 performs a power reduction operation. However, also in step S8, as described later, the operating power Po is not necessarily reduced. Specifically, step S8 includes a plurality of steps S81 to S85, and in step S84, the process may branch and exit from the middle of step S8.

最初 At the beginning of the process in step S8, in step S81, the first value Vt1 is compared with the voltage value Vac. As a result of the comparison, if the voltage value Vac is less than the first value Vt1 (that is, if Vac <Vt1 is affirmative), the process proceeds to step S82. If voltage value Vac is equal to or greater than first value Vt1 (that is, if Vac <Vt1 is denied), the process proceeds to step S83.

ステップ For convenience of description, steps S84 and S85 will be described before describing steps S82 and S83. In step S85, so-called droop control is performed on the current Iw. In step S84, it is determined whether droop control is necessary prior to step S85.

As an example of the drooping control, there is a control in which the AC load 5 is a motor and the rotation speed is reduced. The rotation speed of the motor is reduced by reducing the current Iw, and contributes to a direct reduction in the operating power Po.

Whether or not to perform the droop control is determined by comparing the current output from the inverter 4 to the AC load 5 with the current droop value I3. Since the current is a current flowing through the inverter 4, it can be measured as a current value Iw.

ＩIf Iw ≧ I3 is affirmed in step S84, the process proceeds to step S85, where the drooping control is performed. As a result, the current value Iw decreases. That is, in steps S84 and S85, the current droop value I3 functions as the upper limit of the current value Iw.

とき If Iw ≧ I3 is denied in step S84 (that is, if Iw <I3), the process exits from step S8 and returns to step S72.

Steps S82 and S83 are processes 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 monotonic and non-decreasing with respect to an increase in the voltage value Vac. In step S83, the current droop value I3 is set to a predetermined value I31. For example, a value that does not depend on the voltage value Vac is adopted as the predetermined value I31.

After step S82 and S83 are executed, step S84 is executed. The process in step S84 in this case is a comparison between the current value Iw and the 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 illustrating the dependence of the function f (Vac), which becomes the current droop value I3, on the voltage value Vac. In particular:
When Vac ≧ Vt1, f (Vac) = I31;
When Vac ≦ Vt2, f (Vac) = I32;
When Vt2 ≦ Vac ≦ Vt1,
f (Vac) = I32 + (Vac−Vt2) (I31−I32) / (Vt1−Vt2);
It is. The predetermined value I32 is smaller than the predetermined value I31 and does not depend on the voltage value Vac.

{Of course, the above function f (Vac) is an example, and when Vt2 ≦ Vac ≦ Vt1, the function f (Vac) may be nonlinear with respect to the voltage value Vac. For example, the function f (Vac) may change continuously or stepwise in response to a change in the voltage value Vac.

ときには When Step S81 is executed, Vt2 ≦ Vac is satisfied because the determination in Step S73 is affirmative. Therefore, in step S82, the current droop value I3 is set to a value that monotonously decreases with a decrease in the voltage value Vac.

By adopting the current droop value I3 set in this way, by executing steps S84 and S85, in the droop control of the current Iw, the lower the voltage value Vac is, the lower the current droop value I3 becomes, and the current Iw becomes the upper limit. Suppress. Therefore, the operating power Po and, consequently, the power Ps decrease as the voltage value Vac decreases. Therefore, even if voltage value Vac decreases, increase in current value Ii is suppressed, and heat generation of converter 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.

From the description of steps S82, S83 and S84, the following can be said:
If the voltage value Vac is equal to or greater than the first value Vt1, the operating power Po is reduced and supplied under the first condition of I3 = I31;
If the voltage value Vac is less than the first value Vt1, the operating power Po is reduced and supplied under the second condition of I3 = f (Vac).

If Vac <Vt1, f (Vac) <I31, so that the operating power is lower when the voltage value Vac is less than the first value Vt1 than when the voltage value Vac is equal to or more than the first value Vt1. Po is easily reduced. In other words, the second condition for reducing the operating power Po is more relaxed than the first condition.

２The second condition is relaxed than the first condition, but if Vac <Vt1, the operating power Po is not necessarily reduced. If the determination in step S84 is a negative result, the process does not proceed to step S85 and the droop control is not performed. Therefore, when Vac <Vt1, it can be said that the control circuit 6 enables the inverter 4 to reduce the power.

If the determination in step S73 is negative, step S74 is executed, and in view of stopping the supply of the operating power Po, when Vac <Vt2, the value of the function f (Vac) need not be set. Is also good.

A second value Vt2 ′ smaller than the second value Vt2 that determines the function f (Vac) may be introduced, and the second value Vt2 compared with the voltage value Vac in step S73 may be replaced with the second value Vt2 ′. . In this case, when Vac <Vt2 ', the supply of the operating power Po is stopped, and when Vt2'≤Vac≤Vt2, the current droop value I3 takes a predetermined value I32, and the droop control of the current Iw is performed with this value as an upper limit.

A first value Vt1 ′ larger than the first value Vt1 that determines the function f (Vac) may be introduced, and the first value Vt1 compared with the voltage value Vac in step S81 may be replaced with the first value Vt1 ′. . In this case, when Vt1 ≦ Vac ≦ Vt1 ′, the current drooping value I3 takes a predetermined value I31, and the drooping control for the current Iw is performed with this as an upper limit. In other words, although the function f (Vac) monotonously decreases as the voltage value Vac decreases, there may be a region that does not depend on the voltage value Vac (the function f (Vac) does not decrease monotonically as the voltage value Vac increases). .

の Reduction of the rotation speed of the motor exemplified as the droop control directly reduces the current Iw. Considering that the operation power Po is indirectly reduced through the reduction of the rotation speed or the rotation torque of the motor by causing an event that causes the reduction of the rotation speed or the rotation torque of the motor, is also included in the droop control. Can be. Hereinafter, such control will be described.

FIG. 4 is a block diagram illustrating the configuration 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 arrow in the figure indicates the direction in which the refrigerant circulates.

The AC load 5 is a motor that drives a compressor 91 provided in the refrigeration circuit 9. The expansion valve 93 is an electromagnetic valve, and its opening is adjusted by a control signal L generated by the control circuit 6. For example, the opening of the solenoid 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 converter 2.

では In step S85 (see FIG. 2), the opening of the expansion valve 93 is increased by the control signal L. As a result, the mechanical load on the compressor 91 is reduced, so that the rotational torque required for the motor 5 that drives the compressor 91 is reduced, and the current Iw is reduced. Therefore, the process of increasing the opening of the expansion valve 93 can be included in the droop control.

The control circuit 6 that generates the control signal L and / or the control signal G as described above can be configured to include a microcomputer and a storage device. The microcomputer executes the steps (in other words, procedures) of each processing described in the program. For example, each step in FIG. 2 is executed by the microcomputer.

The storage device can be configured by one or more of various storage devices such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a rewritable nonvolatile memory (such as an EPROM (Erasable Programmable ROM)). . The storage device stores various information, data, and the like, stores a program executed by the microcomputer, and 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. In addition, the control circuit 6 is not limited thereto, and various procedures executed by the control circuit 6 or some or all of the realized means or functions may be partially or entirely realized 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 converted voltage to the AC load 5 has been proposed. DC voltage Vdc is obtained by converter 2 converting AC voltage V2.

In the AC load driving system 100, when the voltage value Vac is less than the first value Vt1, the control circuit 6 allows the inverter 4 to reduce the operating power Po. As a result, the operating power Po and eventually the power Ps are reduced, and the heat generation of the converter 2 is suppressed. Such a technique can be viewed as a control method of the inverter 4 that enables the operating power Po to be reduced and supplied when the voltage value Vac is less than the first value Vt1.

If the voltage value Vac is equal to or greater than the first value Vt1, the operating power Po supplied from the inverter 4 to the AC load 5 is reduced (step S85) under the first condition (steps S83 and S84) to reduce the operating power Po. Supply. If the voltage value Vac is less than the first value Vt1, the operating power Po is reduced (step S85) under the second condition (steps S82 and S84) to supply the operating power Po. The second condition is more relaxed than the first condition.

For example, when the voltage value Vac is less than the first value, and the input current (current value Ii) input to the inverter 4 or the current Iw output to the AC load 5 is equal to or more than the upper limit current droop value I3. If there is, the droop control for the current is performed (step S85). As the voltage value Vac increases, the current droop value I3 is monotonic and non-decreasing. As a result, the operating power Po supplied from the inverter 4 to the AC load 5 is reduced.

(4) The drooping control for the current input to the converter 2 may be performed. For example, if the voltage value Vac is less than the first value and the current value Ii is equal to or more than the upper limit, the droop control for the current is performed. For example, the upper limit can be set to be monotonic and non-decreasing with respect to an increase in the voltage value Vac. Specifically, for example, a flowchart in which the current value Iw is replaced with the 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 less 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 is a motor, and the drooping control may include control for reducing the rotation speed of the motor 5. This leads to a direct reduction of the operating power Po.

モータ As an example of the motor 5, a motor for driving a compressor 91 provided in the refrigeration circuit 9 can be given. For example, the motor 5 drives a compressor 91 provided in the refrigeration circuit 9 including the expansion valve 93. The refrigeration circuit 9 includes a compressor 91 driven by the motor 5 to which the operating power Po is supplied by the AC load driving system 100, and an expansion valve 93. The drooping control may include control for increasing the opening of the expansion valve 93. This leads to an indirect reduction of the operating power Po.

The motor 5 can be employed as a motor for driving a fan employed in an air conditioner or a fan employed in an air purifier.

(4) When a DC load driven by the DC voltage Vdc is provided, control for reducing power supplied to the DC load may be performed. In this case, the input power Pi is the sum of the operating power Po and the power consumed by the DC power, and the reduction of the DC power contributes to the reduction of the power Ps. Such 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 whose operating power is supplied as DC power from the capacitor 3, the operation of the expansion valve 93 is performed when the voltage value Vac is less than the first value Vt1. You may stop.

交流 The AC load drive system 100 including the converter 2, the inverter 4, and the control circuit 6 for performing the power reduction operation can be said to be a power supply system to the AC load 5.

Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. The various embodiments and modifications described above can be combined with one another.

Claims

An inverter (4) for applying a first AC voltage (V1) converted from a DC voltage (Vdc) and supplying electric power (Po) to an AC load (5);
A converter (2) for converting a second AC voltage (V2) into the DC voltage (Vdc);
When the voltage value (Vac) of the second AC voltage is less than a predetermined first value (Vt1), the inverter includes a control circuit (6) that enables the power to be reduced (S85). Power supply system.
If the voltage value (Vac) is equal to or greater than the first value (Vt1), the power is reduced (S85) under the first condition (S83, S84),
2. The alternating current according to claim 1, wherein if the voltage value is less than the first value, the power is reduced (S85) under a second condition (S82, S84) that is less than the first condition. 3. A power supply system for a load (100).
The voltage value (Vac) is less than the first value (Vt1), and the current (Iw) input to the inverter (4) or output to the AC load (5) is a first upper limit value ( If I3) or more, the droop control (S85) for the current is performed,
3. The power supply system for an AC load according to claim 1, wherein the first upper limit is monotonically non-decreasing with respect to the increase in the voltage value. 4.
If the voltage value (Vac) is less than the first value (Vt1) and the current value (Ii) of the input current input to the converter (2) is equal to or more than a second upper limit value, Is performed (S85).
The power supply system for an AC load according to any one of claims 1 to 3, wherein the second upper limit is monotonically non-decreasing with respect to an increase in the voltage value (Vac).
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), the power supply system to an AC load according to any one of claims 1 to 4.
The AC load (5) is a motor,
The power supply system for an AC load according to claim 3 or 4, wherein the drooping control (S85) includes control for reducing a rotation speed of the motor.
The motor (5) is any one of a motor for driving a compressor (91) used in the refrigeration circuit (9), a fan used for an air conditioner, and a motor for driving a fan used for an air purifier. The power supply system for an AC load according to claim 6, wherein
The motor (5) is a motor that drives a compressor (91) included in the refrigeration circuit (9),
The refrigeration circuit further includes an expansion valve (93);
The power supply system for an AC load according to claim 6, wherein the drooping control (S85) includes control for increasing an opening degree of the expansion valve.
The power supply to the DC load (93) driven by the DC voltage is reduced if the voltage value (Vac) is less than the first value (Vt1). A power supply system for an AC load according to one aspect.
A compressor (91) driven by the motor (5), the AC load (5) being powered by the AC load power supply system of claim 8,
A refrigeration circuit (9) including an expansion valve (93).
A method of converting an input DC voltage (Vdc) into a first AC voltage (V1) to control an inverter (4) that supplies power to an AC load (5),
The DC voltage (Vdc) is obtained by converting the second AC voltage (V2) by the converter (2);
When the voltage value (Vac) of the second AC voltage is less than a predetermined first value (Vt1), the power is reduced (S85) to enable the supply of the power (S8), and the inverter control method.