Converter device, air conditioner, and converter device control method and program

Abstract

To operate a converter circuit at an appropriate switching frequency in terms of both noise regulation and reactor temperature rise.SOLUTION: A converter device that converts a power from an AC power supply into a DC power through a converter circuit, comprises: a load determination unit that determines whether an operation state is low or high load operation on the basis of detection results of a current flowing in a load; a frequency decision unit that decides a switching frequency of the converter circuit depending on the operation state; and a region identification unit that identifies a regulation clear frequency region that satisfies noise regulation. The frequency decision unit, in a case where the operation state is high load operation, decides the switching frequency to be a frequency with the lowest reactor loss among frequencies belonging to the regulation clear frequency region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a converter device, an air conditioner, and a control method and program for a converter device. [Background technology]

[0002] Among converter devices used in air conditioners, etc., there is an interleaved type that uses an electromagnetic steel sheet reactor to reduce the size and weight of the boost chopper. In particular, when the reactor material is electromagnetic steel sheet, it is necessary to operate it at an appropriate switching frequency taking into account its frequency characteristics.

[0003] As a technology related to the present disclosure, Patent Document 1 discloses a converter device that is connected between an AC power supply and a load, converts AC power from the AC power supply into DC power and outputs the DC power, the converter device including: rectifying means that converts the AC power input from the AC power supply into DC power; smoothing means that is connected in parallel to the rectifying means on the DC output side of the rectifying means; two switching circuits that are provided in parallel with each other between the rectifying means and the smoothing means; and control means that controls the switching circuits. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-150622 Summary of the Invention [Problem to be solved by the invention]

[0005] The need to suppress temperature rises due to losses in the reactor of the converter circuit (hereinafter referred to as "reactor losses") requires the selection of an appropriate switching frequency, but at the same time, it is necessary to satisfy regulations based on electromagnetic interference (EMI) (hereinafter referred to as "noise regulations").From these perspectives, it is desirable to operate at an optimal switching frequency.

[0006] An object of the present disclosure is to provide a converter device, an air conditioner, and a control method and program for a converter device that can operate a converter circuit at an optimal switching frequency from the standpoints of both noise regulations and reactor temperature rise. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a converter device converts power from an AC power source into DC power through a converter circuit, and includes: a load determination unit that determines whether an operating state is low-load operation or high-load operation based on a detection result of a current flowing through a load; a frequency determination unit that determines a switching frequency of the converter circuit according to the operating state; and a range specification unit that specifies a regulation-compliant frequency range that satisfies noise regulations. When the operating state is high-load operation, the frequency determination unit determines the switching frequency to be a frequency that minimizes reactor loss among frequencies belonging to the regulation-compliant frequency range.

[0008] According to one aspect of the present disclosure, a control method for a converter device is a control method for a converter device that converts power from an AC power source into DC power through a converter circuit, the control method including the steps of: determining whether an operating state is low-load operation or high-load operation based on a detection result of a current flowing through a load; determining a switching frequency of the converter circuit according to the operating state; and specifying a regulation-clearing frequency range that satisfies noise regulations. In the step of determining the switching frequency, when the operating state is high-load operation, the switching frequency is determined to be a frequency that minimizes reactor loss among frequencies belonging to the regulation-clearing frequency range.

[0009] According to one aspect of the present disclosure, a program causes a computer of a converter device that converts power from an AC power source into DC power through a converter circuit to execute the following steps: determining whether an operating state is low-load operation or high-load operation based on a detection result of a current flowing through a load; determining a switching frequency of the converter circuit according to the operating state; and specifying a regulation-clearing frequency range that satisfies noise regulations. In the step of determining the switching frequency, when the operating state is high-load operation, the switching frequency is determined to be a frequency that minimizes reactor loss among frequencies belonging to the regulation-clearing frequency range. [Effects of the Invention]

[0010] According to the above-described aspects, the converter circuit can be operated at an optimum switching frequency from the viewpoints of both noise regulation and reactor temperature rise. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing a circuit configuration of an air conditioner according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating a functional configuration of a converter control unit according to the first embodiment. [Figure 3]FIG. 4 is a diagram showing a processing flow of a converter control unit according to the first embodiment. [Figure 4] 3 is a diagram used to explain in detail the processing of a converter control unit according to the first embodiment. FIG. [Figure 5] 3 is a diagram used to explain in detail the processing of a converter control unit according to the first embodiment. FIG. [Figure 6] 3 is a diagram used to explain in detail the processing of a converter control unit according to the first embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] First Embodiment A converter device according to a first embodiment and an air conditioner including the converter device will be described below with reference to FIGS. 1 to 6. FIG.

[0013] (Air conditioner circuit configuration) FIG. 1 is a diagram showing the circuit configuration of an air conditioner according to the first embodiment. As shown in Fig. 1, the air conditioner 1 includes a converter device 2, a zero-cross detector 3, and a load 4. Here, the load 4 is actually an inverter device and a motor. The zero-cross detector 3 outputs a zero-cross signal that indicates the zero-cross points of the AC power of the AC power source P.

[0014] The converter device 2 converts AC power input from an AC power source P into DC power and outputs it to a load 4 (an inverter device and a motor). The converter device 2 includes a converter control unit 20, a rectifier circuit 21, a converter circuit 22, and a smoothing capacitor 23.

[0015] The converter control unit 20 is a processor such as an MPU (Micro Processing Unit), and operates according to a pre-prepared program. The converter control unit 20 drives the converter circuit 22 at a predetermined switching frequency based on a zero-cross signal. Furthermore, the converter control unit 20 according to this embodiment identifies the current operating state (high load operation or low load operation) by referring to the load current (motor current), and drives the converter circuit 22 at a switching frequency according to the operating state. Details of the processing executed by the converter control unit 20 according to this embodiment will be described later.

[0016] The converter circuit 22 according to this embodiment has an interleaved circuit configuration and includes reactors L1 and L2, switching elements T1 and T2, and diodes D1 and D2. Generally, in the interleaved configuration, the switching elements T1 and T2 are switched at different phases, thereby suppressing the superposition of harmonic components on the AC power supply P and achieving a higher power factor improvement effect.

[0017] (Functional configuration of converter control unit) FIG. 2 is a diagram illustrating a functional configuration of the converter control unit according to the first embodiment. The converter control unit 20 according to this embodiment operates in accordance with a program prepared in advance, and thereby functions as a load determining unit 201, a region specifying unit 202, and a frequency determining unit 203.

[0018] The load determining unit 201 determines whether the operating state of the air conditioner 1 is low-load operation or high-load operation based on the detection result of the current (load current) flowing through the load 4.

[0019] The region specifying unit 202 specifies a frequency region that satisfies noise regulations (hereinafter also referred to as a "regulation-clearing frequency region"). In particular, the region specifying unit 202 according to this embodiment specifies a regulation-clearing frequency region that corresponds to the magnitude of the load (the magnitude of the load current).

[0020] The frequency determination unit 203 determines the optimum switching frequency of the converter circuit 22 depending on the operating state of the air conditioner 1. In particular, when the operating state is low-load operation, the frequency determination unit 203 according to this embodiment determines the switching frequency of the converter circuit 22 to be the frequency at which the sum of reactor loss and switching loss is smallest. Furthermore, when the operating state is high-load operation, the frequency determination unit 203 determines the switching frequency of the converter circuit 22 to be the frequency at which the reactor loss is smallest among frequencies belonging to the regulation-compliant frequency range.

[0021] (Processing flow of the converter control unit) FIG. 3 is a diagram illustrating a processing flow of the converter control unit according to the first embodiment. 4 to 6 are diagrams used to explain in detail the processing of the converter control unit according to the first embodiment. The processing flow shown in FIG. 3 is repeatedly executed while the air conditioner 1 is in operation.

[0022] First, the load determination unit 201 of the converter control unit 20 acquires the load current detection result detected in the load 4 (step S01), and determines whether the current operating state is high-load operation or low-load operation (step S02). The determination process in step S02 may be, for example, a determination based on a comparison between the load current detection result and a predetermined threshold value. "High-load operation" in the operating state of the air conditioner 1 refers to, for example, operation performed immediately after starting operation to rapidly bring the current temperature close to the set temperature. Also, "low-load operation" in the operating state of the air conditioner 1 refers to, for example, operation performed after the current temperature has reached the set temperature and to maintain that state.

[0023] When the operating state of the air conditioner 1 is low-load operation (step S02; low-load operation), the frequency determination unit 203 of the converter control unit 20 determines the switching frequency to be the frequency at which the sum of the reactor loss and the switching loss is minimum (step S03).

[0024] The process of step S03 will now be described in detail with reference to FIG. Figure 4 is a graph showing the relationship between the reactor loss (left vertical axis) generated in reactors L1 and L2 and the switching frequency (horizontal axis), and the relationship between the switching loss (left vertical axis) generated in switching elements T1 and T2 and the switching frequency (horizontal axis).The graph in Figure 4 also shows the relationship between the sum of the reactor loss and the switching loss (right vertical axis) and the switching frequency (horizontal axis).

[0025] As shown in Figure 4, switching losses generally increase as the switching frequency increases. On the other hand, reactor losses tend to decrease as the switching frequency increases, but reach a minimum value at a certain frequency and then begin to increase.

[0026] Low-load operation accounts for the majority of the operating time of the air conditioner 1, so it is desirable to keep power consumption as low as possible. On the other hand, because the load is low (the current is small), it is less subject to restrictions due to noise regulations. Therefore, in order to meet the above needs, a frequency that minimizes power consumption during low-load operation, that is, a switching frequency (frequency f1 shown in FIG. 4) that minimizes the sum of reactor loss and switching loss, is selected.

[0027] Returning to FIG. 3, if the operating state of the air conditioner 1 is high-load operation (step S02; high-load operation), the region identification unit 202 of the converter control unit 20 then identifies a frequency region that clears noise regulations (regulation-clearing frequency region) (step S04).

[0028] Then, the frequency determination unit 203 determines the switching frequency to be the frequency at which the reactor loss is minimum among the frequencies belonging to the regulation-compliant frequency range identified in step S04 (step S05).

[0029] The processing in steps S04 and S05 will now be described in detail with reference to FIGS. Similar to Figure 4, Figures 5 and 6 show the relationship between reactor loss (left vertical axis) and switching frequency (horizontal axis), the relationship between switching loss (left vertical axis) and switching frequency (horizontal axis), and the relationship between the sum of reactor loss and switching loss (right vertical axis) and switching frequency (horizontal axis).

[0030] High-load operation usually lasts only for a short time immediately after the air conditioner 1 is started, so there is relatively little need for low power consumption. However, because the air conditioner 1 is operated at a high load (a large current flows), temperature rise in the reactor elements (reactors L1 and L2) can become a problem. In order to suppress the temperature rise in the reactor elements, it is necessary to suppress reactor loss as much as possible. Therefore, the frequency determination unit 203 selects a frequency from the perspective of minimizing reactor loss rather than minimizing overall power consumption.

[0031] Furthermore, during high-load operation, restrictions based on noise regulations may be imposed. That is, during high-load operation, restrictions (upper limits) are imposed on the settable switching frequency in order to satisfy noise regulations. These restrictions become stricter as the load increases. Therefore, the region identification unit 202 first obtains the magnitude of the current load (magnitude of the load current) and identifies a regulation-compliant frequency region corresponding to that load (step S04 in FIG. 3).

[0032] For example, when the load is relatively light, the upper limit frequency fmax increases, resulting in a wider frequency range that satisfies the regulations, as shown in Figure 5. On the other hand, when the load is relatively heavy, the upper limit frequency fmax decreases, resulting in a narrower frequency range that satisfies the regulations, as shown in Figure 6.

[0033] Furthermore, in order to minimize the temperature rise of the reactor element (that is, to minimize the reactor loss), the frequency determination unit 203 selects the frequency that will minimize the reactor loss within the regulation-compliant frequency range (step S05 in FIG. 3).

[0034] 5, the frequency at which the reactor loss is smallest within the regulation-compliant frequency range is frequency f2, at which the reactor loss is at its minimum value. Therefore, frequency determiner 203 determines the switching frequency to be frequency f2. 6, the upper limit frequency fmax is smaller than the frequency f2. Therefore, the frequency f2' at which the reactor loss is smallest in the regulation-compliant frequency range coincides with the upper limit frequency fmax. Therefore, the frequency determiner 203 determines the switching frequency to be frequency f2' (= fmax).

[0035] In the above-described processing, for example, an information table showing the relationship between the magnitude of the load and the upper limit frequency fmax may be prepared in advance, and the region identification unit 202 may refer to this information table to uniquely identify the upper limit frequency fmax (regulation-clear frequency region) corresponding to the magnitude of the load.

[0036] Returning to FIG. 3, the frequency determining unit 203 drives the converter circuit 22 at the switching frequency determined in step S03 or step S05 (step S06).

[0037] (Action and effect) As described above, the converter device 2 (frequency determination unit 203) according to the first embodiment is characterized in that, when the operating state is high-load operation, the switching frequency of the converter circuit 22 is determined to be the frequency that minimizes reactor loss among the frequencies that belong to the regulation-clear frequency range. By doing so, the converter circuit 22 can be driven at a frequency that can most effectively suppress the temperature rise of the reactor element within the given constraints, with the highest priority being given to satisfying noise regulations.

[0038] Furthermore, the converter device 2 (area specifying unit 202) according to the first embodiment specifies the regulation-clearing frequency range according to the magnitude of the load, and therefore can specify the widest regulation-clearing frequency range for each magnitude of the load.

[0039] Furthermore, when the operating state is low load operation, the converter device 2 (frequency determination unit 203) according to the first embodiment determines the switching frequency of the converter circuit 22 to be the frequency at which the sum of the reactor loss and the switching loss is smallest. In this way, power consumption during low load operation can be reduced.

[0040] <Other embodiments> In the first embodiment, the region identification unit 202 is described as identifying a regulation-compliant frequency range depending on the magnitude of the load, but this is not limited to the above in other embodiments. For example, the region identification unit 202 according to other embodiments may identify a regulation-compliant frequency range that is uniformly determined regardless of the magnitude of the load.

[0041] In the above-described embodiment, the various processing steps of the converter device 2 are stored in the form of a program on a computer-readable recording medium, and the computer reads and executes this program to perform the various processing steps. The computer-readable recording medium may include a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc. Alternatively, the computer program may be distributed to a computer via a communication line, and the computer that receives the program may execute the program.

[0042] The program may be a program for realizing some of the above-mentioned functions, or may be a so-called differential file (differential program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0043] As described above, several embodiments according to the present disclosure have been described, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as defined in the claims, as well as in the scope and spirit of the invention.

[0044] <Additional Notes> The converter device, the air conditioner, and the converter device control method and program described in each embodiment can be understood, for example, as follows.

[0045] (1) In a first aspect, the converter device 2 is a converter device that converts power from an AC power source P into DC power through a converter circuit 22, and includes a load determination unit 201 that determines whether the operating state is low-load operation or high-load operation based on a detection result of a current flowing through a load 4, a frequency determination unit 203 that determines a switching frequency of the converter circuit 22 depending on the operating state, and a range identification unit 202 that identifies a regulation-clearing frequency range, which is a frequency range that satisfies noise regulations. When the operating state is high-load operation, the frequency determination unit 203 determines the switching frequency to be a frequency that minimizes reactor loss among frequencies belonging to the regulation-clearing frequency range.

[0046] (2) In a second mode, when the operating state is low load operation, the frequency determination unit 203 determines the switching frequency to be the frequency at which the sum of the reactor loss and the switching loss is smallest.

[0047] (3) In the third aspect, the region specifying unit 202 specifies the regulation-compliant frequency region according to the magnitude of the load.

[0048] (4) In a fourth aspect, the air conditioner 1 includes the converter device 2 described above.

[0049] (5) In a fifth aspect, a control method for a converter device 2 is a control method for a converter device that converts power from an AC power source into DC power through a converter circuit, and includes the steps of: determining whether the operating state is low-load operation or high-load operation based on a detection result of a current flowing through a load; determining a switching frequency of the converter circuit according to the operating state; and specifying a regulation-clearing frequency range, which is a frequency range that satisfies noise regulations. In the step of determining the switching frequency, when the operating state is high-load operation, the switching frequency is determined to be a frequency that minimizes reactor loss among frequencies belonging to the regulation-clearing frequency range.

[0050] (6) In a sixth aspect, the program causes a computer of a converter device that converts power from an AC power source into DC power through a converter circuit to execute the following steps: determining whether the operating state is low-load operation or high-load operation based on a detection result of a current flowing through a load; determining a switching frequency of the converter circuit according to the operating state; and specifying a regulation-clearing frequency range, which is a frequency range that satisfies noise regulations; and in the step of determining the switching frequency, when the operating state is high-load operation, determining the switching frequency to be a frequency that minimizes reactor loss among frequencies belonging to the regulation-clearing frequency range. [Explanation of symbols]

[0051] 1. Air conditioner 2 Converter device 20 Converter control section 21 Rectifier circuit 22 Converter circuit 23 Smoothing capacitor 3 Zero-cross detection section 4. Load P AC power supply

Claims

1. A converter device that converts power from an AC power source into DC power through a converter circuit, a load determination unit that determines whether the operating state is low load operation or high load operation based on a detection result of a current flowing through the load; a frequency determination unit that determines a switching frequency of the converter circuit in accordance with the operating state; an area specifying unit that specifies a regulation-clearing frequency area that satisfies noise regulations; Equipped with the frequency determination unit determines, when the operating state is high-load operation, the switching frequency to a frequency that minimizes reactor loss among frequencies that belong to the regulation-clear frequency range. Converter device.

2. the frequency determination unit determines the switching frequency to a frequency that minimizes a sum of the reactor loss and the switching loss when the operating state is a low-load operation. The converter device according to claim 1 .

3. the region specifying unit specifies the regulation-compliant frequency region according to the magnitude of the load. The converter device according to claim 1 or 2.

4. The converter device according to any one of claims 1 to 3. An air conditioner equipped with:

5. A control method for a converter device that converts power from an AC power source into DC power through a converter circuit, comprising: determining whether the operating state is low load operation or high load operation based on the detection result of the current flowing through the load; determining a switching frequency of the converter circuit in accordance with the operating state; A step of identifying a regulation-clearing frequency range that satisfies noise regulations; and In the step of determining the switching frequency, when the operating state is a high-load operation, the switching frequency is determined to be a frequency that minimizes reactor loss among frequencies that belong to the regulation-clear frequency range. A method for controlling a converter device.

6. The computer of the converter device converts power from an AC power source into DC power through a converter circuit. determining whether the operating state is low load operation or high load operation based on the detection result of the current flowing through the load; determining a switching frequency of the converter circuit in accordance with the operating state; A step of identifying a regulation-clearing frequency range that satisfies noise regulations; Execute In the step of determining the switching frequency, when the operating state is a high-load operation, the switching frequency is determined to be a frequency that minimizes reactor loss among frequencies that belong to the regulation-clear frequency range. program.

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