Air conditioning compressor drive control device

Abstract

This disclosure provides a drive control device for a compressor of an air conditioning system that can meet power supply harmonic standards. [Solution] A drive control device for a compressor in an air conditioning system, comprising: a three-phase bridge circuit that rectifies a three-phase AC voltage from a three-phase commercial power supply; an LC filter circuit that smooths the output of the three-phase bridge circuit; an inverter circuit that receives power from the LC filter circuit and supplies drive power to the drive motor of a compressor located in an air conditioning system; and a control device that controls the inverter circuit, wherein the cutoff frequency FC of the LC filter circuit satisfies the following equation (A). α × FA ≤ FC ≤ FU (A) Here, frequency FA is the frequency of the three-phase commercial power supply, and coefficient α is 14 or greater. The upper limit value FU is the frequency at which the LC filter circuit cuts out the 6th harmonic of the fundamental frequency of the compressor's drive motor by a first-degree margin or more.

Description

Technical Field

[0001] The present disclosure relates to a drive control device for a compressor of an air conditioner.

Background Art

[0002] Patent Document 1 discloses a configuration for supplying power to a motor mounted on a compressor of an air conditioner. Further, in Patent Document 1, it is proposed to regulate the cut-off frequency of an LC filter circuit based on a carrier frequency.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a drive control device for a compressor of an air conditioner that can satisfy power supply harmonic standards.

Means for Solving the Problems

[0005] The drive control device for a compressor of an air conditioner in the present disclosure includes a three-phase bridge circuit that rectifies a three-phase AC voltage from a three-phase commercial power supply, an LC filter circuit that smoothes the output of the three-phase bridge circuit, an inverter circuit that is supplied with power from the LC filter circuit and supplies drive power to a drive motor of a compressor disposed in the air conditioner, and a control device that controls the inverter circuit, and the cut-off frequency FC of the LC filter circuit satisfies the following formula (A), which is a drive control device for a compressor of an air conditioner. α × FA ≤ FC ≤ FU (A) Here, frequency FA is the frequency of the three-phase commercial power supply, and coefficient α is 14 or greater. The upper limit value FU is the frequency at which the LC filter circuit cuts out the 6th harmonic of the fundamental frequency of the compressor's drive motor by 1 percentage (75%) or more.

[0006] Furthermore, the compressor drive control device for an air conditioning system according to this disclosure comprises a three-phase rectifier circuit that rectifies a three-phase AC voltage from a three-phase commercial power supply, an LC filter circuit that smooths the output of the three-phase rectifier circuit, an inverter circuit that receives power from the LC filter circuit and supplies drive power to the drive motor of a compressor located in the air conditioning system, and a control device that controls the inverter circuit, wherein the cutoff frequency of the LC filter circuit is 700 Hz or higher and 935 Hz or lower. [Effects of the Invention]

[0007] The drive control device for the compressor of the air conditioning system of this disclosure can meet the power supply harmonic standards. [Brief explanation of the drawing]

[0008] [Figure 1] Diagram showing the overall configuration of the air conditioning system in Embodiment 1. [Figure 2] This figure shows the configuration of the compressor drive control device in Embodiment 1. [Figure 3] A graph showing an example of power supply harmonics in the drive control device in Embodiment 1. [Figure 4] A graph showing an example of power supply harmonics in a conventional drive control device. [Modes for carrying out the invention]

[0009] (Knowledge and other information that formed the basis of this disclosure)

[0010] At the time the present inventors conceived of this disclosure, it was known from Patent Document 1, etc., that the cutoff frequency of an LC filter circuit could be regulated based on the carrier frequency. However, the inventors found that regulating the cutoff frequency of an LC filter circuit based on the carrier frequency may not meet the power supply harmonic standards specified in IEC (International Electrotechnical Commission) 61000-3-12.

[0011] Furthermore, the inventors have found that the above-mentioned power supply harmonic standard can be met by defining the cutoff frequency of the LC filter circuit based on the power supply frequency. They have also found that by defining the cutoff frequency of the LC filter circuit based on the fundamental frequency of the compressor's drive motor, the pulsation of the 6th harmonic of the fundamental frequency of the compressor's drive motor can be suppressed from affecting the above-mentioned power supply harmonic standard.

[0012] Therefore, this disclosure provides a drive control device for a compressor of an air conditioning system that can meet power supply harmonic standards.

[0013] The embodiments will be described in detail below with reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. The attached drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0014] The drive control device 2 for the compressor 11 of the air conditioning system 1 in Embodiment 1 will be described below with reference to Figures 1-4.

[0015] (Embodiment 1) [1-1. Structure] [1-1-1. Configuration of the air conditioning system] First, referring to FIG. 1, the overall configuration of the air conditioner 1 in Embodiment 1 will be described. FIG. 1 is a diagram showing the overall configuration of the air conditioner 1 in Embodiment 1. As shown in FIG. 1, the air conditioner 1 includes a compressor 11, a hydrothermal heat exchanger condenser 12, an expansion valve 13, and an evaporator 14. The compressor 11, the hydrothermal heat exchanger condenser 12, the expansion valve 13, and the evaporator 14 are sequentially connected by a refrigerant pipe 15.

[0016] In the air conditioner 1, the compressor 11, the hydrothermal heat exchanger condenser 12, the expansion valve 13, the evaporator 14, and the refrigerant pipe 15 constitute a refrigeration cycle. The air conditioner 1 circulates the refrigerant compressed by the compressor 11 through the refrigerant pipe 15 between the compressor 11 and the expansion valve 13 to heat the room in which the water pipe 121 is arranged.

[0017] In Embodiment 1, the case where the air conditioner 1 uses a flammable refrigerant as the refrigerant is exemplified. The flammable refrigerant is, for example, R290. Note that the flammable refrigerant may also be R32. Further, the refrigerant is not limited to a flammable refrigerant and may be a non-flammable refrigerant.

[0018] The evaporator 14 is connected to the suction side of the compressor 11. In the evaporator 14, heat exchange (heat absorption) occurs between the air and the refrigerant flowing through the evaporator 14. The refrigerant in a low-temperature and low-pressure vapor state is supplied from the evaporator 14 to the compressor 11 through the refrigerant pipe 15.

[0019] The compressor 11 compresses the refrigerant in a low-temperature and low-pressure vapor state to generate a refrigerant in a high-temperature and high-pressure vapor state, and outputs it toward the hydrothermal heat exchanger condenser 12 through the refrigerant pipe 15.

[0020] In the hydrothermal exchange condenser 12, heat exchange (heat release) takes place between the water flowing through the water pipe 121 and the refrigerant flowing through the hydrothermal exchange condenser 12. The water pipe 121 supplies water that has flowed out of the room to be heated to the hydrothermal exchange condenser 12. Then, in the hydrothermal exchange condenser 12, heat from the refrigerant is released to the water flowing through the water pipe 121, causing the water temperature to rise. The hot water generated by the heat exchange with the refrigerant is supplied to the room to be heated via the water pipe 121.

[0021] High-temperature, high-pressure liquid refrigerant is supplied from the hydrothermal exchange condenser 12 to the expansion valve 13. In the expansion valve 13, the refrigerant expands, and low-temperature, low-pressure liquid refrigerant is supplied to the evaporator 14. In the evaporator 14, the refrigerant is vaporized, causing it to absorb heat from the outside air. The refrigerant then becomes a low-temperature, low-pressure vapor, which is supplied to the compressor 11 via the refrigerant piping 15. In Figure 1, the air conditioning unit 1 was shown to provide heating for a room with water piping 121. However, by reversing the heat absorption and heat dissipation in Figure 1 (for example, reversing the direction of refrigerant flow), the air conditioning unit 1 can also provide cooling for a room with water piping 121.

[0022] [1-1-2. Configuration of the compressor drive control device] Next, the configuration of the drive control device 2 for the compressor 11 will be described with reference to Figure 2. Figure 2 is a diagram showing the configuration of the drive control device 2 for the compressor 11 in Embodiment 1. As shown in Figure 2, the drive control device 2 comprises a three-phase rectifier circuit 22, an LC filter circuit 23, an inverter circuit 24, a drive motor 25, a gate drive circuit 3, and a control device 4. Furthermore, at least a portion of the drive control device 2 is placed inside a sealed box (not shown) to prevent it from becoming an ignition source even if flammable refrigerant leaks. The sealed box is formed in a box shape from a non-combustible material (e.g., aluminum, iron, etc.). The sealed box forms a sealed space inside. In Embodiment 1, at least the capacitor 232 constituting the LC filter circuit 23 of the drive control device 2 is placed inside a sealed box. The inside of a sealed box corresponds to an example of a "sealed space."

[0023] The three-phase rectifier circuit 22 is supplied with three-phase AC power from the three-phase commercial power supply 21. The three-phase AC power has a frequency FA of, for example, "50Hz" and a voltage of "400V". The three-phase rectifier circuit 22 is composed of six diodes. The three-phase rectifier circuit 22 includes diodes 221, 222, 223, 224, 225, and 226. The three-phase rectifier circuit 22 is composed of what is known as a "three-phase diode bridge".

[0024] Diode 221 and diode 224 are connected in series, and a first-phase voltage V1 from the three-phase commercial power supply 21 is applied between diode 221 and diode 224. Diode 222 and diode 225 are connected in series, and a second-phase voltage V2 from the three-phase commercial power supply 21 is applied between diode 222 and diode 225. Diode 223 and diode 226 are connected in series, and a third-phase voltage V3 from the three-phase commercial power supply 21 is applied between diode 223 and diode 226. The first phase voltage V1, the second phase voltage V2, and the third phase voltage V3 are out of phase by 120 degrees from each other.

[0025] The three-phase rectifier circuit 22 full-wave rectifies the three-phase AC voltage from the three-phase commercial power supply 21 and outputs it to the LC filter circuit 23. The LC filter circuit 23 includes a reactor 231 and a capacitor 232. The reactor 231 is positioned between the three-phase rectifier circuit 22 and the inverter circuit 24, and is arranged in series with the three-phase rectifier circuit 22 and the inverter circuit 24. The reactor 231 has an inductance L.

[0026] Capacitor 232 is positioned between the three-phase rectifier circuit 22 and the inverter circuit 24, and is arranged in parallel with the three-phase rectifier circuit 22 and the inverter circuit 24. That is, one end of capacitor 232 is connected to the positive output terminal of the three-phase rectifier circuit 22 via reactor 231, and the other end of capacitor 232 is connected to the negative output terminal of the three-phase rectifier circuit 22. Capacitor 232 has capacitance C. Capacitor 232 is also composed of, for example, a film capacitor.

[0027] The LC filter circuit 23 functions as a low-pass filter. The cutoff frequency FC of the LC filter circuit 23 can be calculated using the following equation (1). Note that the cutoff frequency FC of the LC filter circuit 23 coincides with the resonant frequency of the LC filter circuit 23. FC = 1 / (2 × π × (L × C)) 1 / 2 ) (1)

[0028] The cutoff frequency FC satisfies equation (2) below. α × FA ≤ FC ≤ FU (2) Here, frequency FA is the frequency of the three-phase commercial power supply 21, and coefficient α is 14 or greater. The upper limit value FU is the frequency at which the LC filter circuit 23 cuts the 6th harmonic of the fundamental frequency FM of the drive motor 25 of the compressor 11 by a first ratio RT1 or more. If the frequency FA is, for example, "50 Hz" and the coefficient α is "14", then (α × FA) is "700 Hz".

[0029] The upper limit FU is defined by the following equation (2). FU=6×FM / ((1 / (1-RT1)-1) 1 / 2 ) (2) The first ratio RT1 is, for example, 75%, and the fundamental frequency FM is, for example, "270Hz". In this case, the upper limit FU is, for example, "935Hz". As described above, when the frequency FA, ​​coefficient α, first ratio RT1, and fundamental frequency FM are set, equation (1) above is expressed as equation (3) below. 700Hz ≤ FC ≤ 935Hz (3)

[0030] As shown in equation (1) above, since the cutoff frequency FC of the LC filter circuit 23 is set to be higher than the frequency of the 14th harmonic of the three-phase commercial power supply 21, it is possible to avoid increasing the harmonic currents corresponding to low-order harmonics such as the 5th, 7th, 11th, and 13th harmonics, which have large harmonic currents due to resonance of the LC filter circuit 23, and thus it becomes possible to satisfy the power supply harmonic standard specified in IEC61000-3-12. Furthermore, as shown in equation (1) above, the upper limit FU is the frequency at which the LC filter circuit 23 cuts 75% or more of the 6th harmonic of the fundamental frequency FM of the drive motor 25 of the compressor 11. Therefore, the influence of the pulsation of the 6th harmonic of the fundamental frequency FM of the drive motor 25 on the voltage input from the 3-phase rectifier circuit 22 to the LC filter circuit 23 can be reduced. Consequently, it becomes possible to satisfy the power supply harmonic standard specified in IEC61000-3-12.

[0031] The capacitance C of capacitor 232 is 100μF or less. In Embodiment 1, the capacitor 232 is configured by connecting, for example, three film capacitors in parallel. The capacitance of each film capacitor is, for example, "11.5 μF". In this case, the capacitance C of the capacitor 232 is "34.5 μF". In this case, the inductance L of the reactor 231 that satisfies equation (1) above is 0.83 mH or more and 1.50 mH or less.

[0032] Furthermore, the reactor 231 exhibits a decrease in inductance L at the rated current of, for example, 10% or less. The rated current is, for example, 40A. Furthermore, the decrease in inductance L at the rated current may be 7% or less. The smaller the decrease in inductance L at the rated current, the more effectively the change in the attenuation performance of the LC filter circuit 23 can be suppressed when the load on the compressor 11's drive motor 25 is high.

[0033] The inverter circuit 24 has six IGBTs (Insulated Gate Bipolar Transistors). A so-called reverse-connected diode is connected between the collector terminal and the emitter terminal of each of the six IGBTs. The inverter circuit 24 includes IGBT241, IGBT242, IGBT243, IGBT244, IGBT245, and IGBT246.

[0034] IGBT241 and IGBT244 are connected in series, and power is supplied between IGBT241 and IGBT244 to, for example, the U-phase of the drive motor 25. IGBT242 and IGBT245 are connected in series, and power is supplied between IGBT242 and IGBT245 to, for example, the V-phase of the drive motor 25. IGBT243 and IGBT246 are connected in series, and power is supplied between IGBT243 and IGBT246 to, for example, the W-phase of the drive motor 25.

[0035] Each of the IGBTs, IGBT241, IGBT242, IGBT243, IGBT244, IGBT245, and IGBT246, is switched ON / OFF by the gate drive circuit 3, which drives the drive motor 25. The gate drive circuit 3 outputs gate control signals for each of the IGBT241-IGBT246 and supplies a three-phase AC voltage to the drive motor 25 by switching the ON / OFF state of each of the IGBT241-IGBT246. The drive motor 25 drives the compressor 11.

[0036] A voltage sensor circuit 26 is positioned between the LC filter circuit 23 and the inverter circuit 24. The voltage sensor circuit 26 detects the voltage input from the LC filter circuit 23 to the inverter circuit 24. Furthermore, a current sensor 271 is placed in the wiring connected between IGBT241 and IGBT244 to the U-phase of the drive motor 25 to detect the current supplied to the U-phase of the drive motor 25. Also, a current sensor 272 is placed in the wiring connected between IGBT242 and IGBT245 to the V-phase of the drive motor 25 to detect the current supplied to the V-phase of the drive motor 25. Furthermore, a current sensor 273 is placed in the wiring connected between IGBT243 and IGBT246 to the W-phase of the drive motor 25 to detect the current supplied to the W-phase of the drive motor 25. Current sensors 271, 272, and 273 may sometimes be referred to as current sensor 27.

[0037] The drive motor 25 has, for example, 6 poles. If the fundamental rotational speed NR of the drive motor 25 is, for example, 90 rps, then the fundamental frequency FM of the drive motor 25 is 270 Hz. In this case, the 6th harmonic of the fundamental frequency FM is 1620 Hz. The LC filter circuit 23 cuts the 6th harmonic of the fundamental frequency FM of the drive motor 25 of the compressor 11 by a first percentage RT1 or more. The first percentage RT1 is, for example, 75%. In this case, the upper limit FU shown in equation (2) above is 940 Hz.

[0038] The control device 4 receives the voltage DV detected by the voltage sensor circuit 26 and the currents DJ1-DJ3 detected by the current sensors 271-273, respectively. The control device 4 controls the operation of the gate drive circuit 3 based on the voltage DV and the currents DJ1-DJ3. The control device 4 controls the operation of the gate drive circuit 3, for example, by so-called "sensorless vector control". In "sensorless vector control", the control device 4 estimates the phase θ of the drive motor 25.

[0039] The control device 4 includes a processor 41 and a memory 42. Processor 41 is a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Memory 42 is a memory that stores programs and data. Memory 42 stores the control program 421.

[0040] Memory 42 has a non-volatile storage area. Alternatively, memory 42 may also have a volatile storage area and constitute the work area of ​​the processor 41. Memory 42 can be composed of, for example, ROM (Read Only Memory) or RAM (Random Access Memory). The processor 41 functions as a current control unit 411 by reading and executing the control program 421.

[0041] The current control unit 411, via the gate drive circuit 3, causes the inverter circuit 24 to control the current flowing to the drive motor 25. The current control unit 411 controls the inverter circuit 24 using PWM (Pulse Width Modulation) via the gate drive circuit 3.

[0042] The current control unit 411 performs current control of the inverter circuit 24 using PI control (proportional-integral control). The current control unit 411 provides feedback control of the current flowing from the inverter circuit 24 to the drive motor 25 based on currents DJ1-DJ3, for example. The current control unit 411 provides PI control of the current control of the inverter circuit 24 based on currents DJ1-DJ3, for example.

[0043] The cutoff frequency FCM of the PI control performed by the current control unit 411 is the frequency at which the 6th harmonic of the fundamental frequency FM of the drive motor 25 is cut off by a second harmonic RT2 or higher. The relationship between the PI control cutoff frequency FCM and the second harmonic RT2 is given by the following equation (4). FCM = 6 × FM / ((1 / (1 - RT2)) 2 -1) 1 / 2 ) (4) The second ratio RT2 is, for example, 75%, and the fundamental frequency FM is, for example, "270Hz". In this case, the cutoff frequency FCM is "420Hz".

[0044] Furthermore, the current control unit 411 acquires the voltage DV. In the following description, the process of acquiring the voltage DV will be referred to as "DC voltage detection". The current control unit 411 is set so that the sampling period TS for DC voltage detection is set to sample a predetermined number of NS or more in one period of the 6th harmonic of the three-phase commercial power supply 21. One period of the 6th harmonic of the three-phase commercial power supply 21 is, for example, "(1 / 300) seconds". The predetermined number of NS is, for example, "10". The current control unit 411 sets the averaging time TA in the DC voltage detection averaging process to be greater than or equal to a predetermined period NT of the 6th harmonic of the 3-phase commercial power supply 21. The predetermined period NT is, for example, "5 periods". The predetermined period NT of the 6th harmonic of the 3-phase commercial power supply 21 is, for example, "(5 / 300) seconds". In this case, the number of currents DJ1-DJ3 that are subject to the DC voltage detection averaging process is "50".

[0045] Thus, since the sampling period TS for DC voltage detection and the averaging time TA in the DC voltage detection averaging process are appropriately defined, the current control unit 411 can properly perform DC voltage detection. Furthermore, since the cutoff frequency FCM of the PI control performed by the current control unit 411 is appropriately set, the influence of the 6th harmonic pulsation of the fundamental frequency FM of the drive motor 25 on the current input from the 3-phase rectifier circuit 22 to the LC filter circuit 23 can be reduced. Therefore, it becomes possible to satisfy the power supply harmonic standard specified in IEC61000-3-12.

[0046] [1-1-3. Specific Examples of Effects] Next, with reference to Figures 3 and 4, specific examples of the effects of the drive control device 2 in Embodiment 1 will be described. Figure 3 is a graph showing an example of power supply harmonics of the drive control device 2 in Embodiment 1. Figure 4 is a graph showing an example of power supply harmonics of a conventional drive control device.

[0047] The horizontal axis in Figures 3 and 4 represents the harmonic order. The harmonic order indicates the higher frequency order of the three-phase commercial power supply 21. The vertical axis represents the harmonic current (%). The harmonic current indicates the percentage of the current corresponding to each harmonic order. Graph G2 shown in Figures 3 and 4 respectively represents the power supply harmonic standard specified in IEC 61000-3-12. Graph G1 shown in Figure 3 and graph G3 shown in Figure 4 are simulation results. The simulation will simulate the operation of the three-phase rectifier circuit 22, the LC filter circuit 23, the inverter circuit 24, the drive motor 25, the gate drive circuit 3, and the control device 4 shown in Figure 2.

[0048] The simulation conditions for graph G1 shown in Figure 3 and the simulation conditions for graph G3 shown in Figure 4 differ in the following respects. The simulation conditions in graph G1 shown in Figure 3 correspond to the configuration of the drive control device 2 described with reference to Figure 2. For example, the capacitance C of the capacitor 232 constituting the LC filter circuit 23 is "34.5 μF", and the cutoff frequency FC of the LC filter circuit 23 is "800 Hz". The simulation conditions for graph G3 shown in Figure 4 differ from those for graph G1 shown in Figure 3, in that the cutoff frequency FC of the LC filter circuit is "550Hz". Furthermore, in the simulation conditions for graph G3 shown in Figure 4, the capacitance C of capacitor 232 is "34.5μF".

[0049] As shown in graph G3 of Figure 4, the 11th harmonic harmonic current of the three-phase commercial power supply 21 does not meet the power supply harmonic standard specified in IEC61000-3-12. In contrast, as shown in graph G1 of Figure 4, the harmonic currents of all harmonics of the three-phase commercial power supply 21 satisfy the power supply harmonic standard specified in IEC61000-3-12.

[0050] As explained with reference to Figure 3, by appropriately setting the cutoff frequency FC of the LC filter circuit 23, the power supply harmonic standard specified in IEC61000-3-12 can be met.

[0051] [1-3. Effects, etc.] As described above, in Embodiment 1, the drive control device 2 for the compressor 11 of the air conditioner 1 comprises a three-phase rectifier circuit 22 that rectifies the three-phase AC voltage from the three-phase commercial power supply 21, an LC filter circuit 23 that smooths the output of the three-phase rectifier circuit 22, an inverter circuit 24 that receives power from the LC filter circuit 23 and supplies drive power to the drive motor 25 of the compressor 11 located in the air conditioner 1, and a control device 4 that controls the inverter circuit 24, and the cutoff frequency FC of the LC filter circuit 23 satisfies the following equation (A). α × FA ≤ FC ≤ FU (A) Here, frequency FA is the frequency of the three-phase commercial power supply 21, and coefficient α is 14 or greater. Upper limit FU is the frequency at which the LC filter circuit 23 cuts the 6th harmonic of the fundamental frequency FM of the drive motor 25 of the compressor 11 by a first ratio RT1 (for example, 75%) or more.

[0052] According to the above configuration, the cutoff frequency FC of the LC filter circuit 23 satisfies equation (A). That is, since the cutoff frequency FC is greater than or equal to (α × FA), it is possible to satisfy the power supply harmonic standard specified in IEC61000-3-12. Furthermore, since the cutoff frequency FC is less than or equal to the upper limit value FU, the influence of the 6th harmonic pulsation of the fundamental frequency FM of the drive motor 25 on the current input from the 3-phase rectifier circuit 22 to the LC filter circuit 23 can be reduced. Therefore, it is possible to satisfy the power supply harmonic standard specified in IEC61000-3-12.

[0053] In the drive control device 2 described above, the control device 4 performs current control of the inverter circuit 24 by PI control, the cutoff frequency FD in PI control is a frequency that cuts the 6th harmonic of the fundamental frequency FM of the drive motor 25 by a second percentage RT2 (e.g., 75%) or more, the averaging time TA in the averaging process of DC voltage detection is set to be a predetermined period NT (e.g., 5 periods) or more of the 6th harmonic of the 3-phase commercial power supply 21, and the sampling period TS for DC voltage detection is set to sample a predetermined number NS (e.g., 10) or more in one period of the 6th harmonic of the 3-phase commercial power supply 21.

[0054] According to this, the averaging time TA in the DC voltage detection averaging process is set to be equal to or greater than a predetermined period NT (e.g., 5 periods) of the 6th harmonic of the 3-phase commercial power supply 21, and the sampling period TS for DC voltage detection is set to sample a predetermined number NS (e.g., 10) or more in one period of the 6th harmonic of the 3-phase commercial power supply 21, so that the average voltage in the DC voltage detection averaging process can be calculated appropriately. Furthermore, the control device 4 performs current control of the inverter circuit 24 by PI control, and the cutoff frequency FD in the PI control is a frequency that cuts the 6th harmonic of the fundamental frequency FM of the drive motor 25 by a second percentage (e.g., 75%) or more, so that the influence of the pulsation of the 6th harmonic of the fundamental frequency FM of the drive motor 25 on the current input from the 3-phase rectifier circuit 22 to the LC filter circuit 23 can be reduced. Therefore, the power supply harmonic standard specified in IEC61000-3-12 can be satisfied.

[0055] In the above-described drive control device 2, the capacitor 232 constituting the LC filter circuit 23 is a film capacitor, and the capacitance C of the capacitor 232 is 100 μF or less.

[0056] According to this, since the capacitance C of capacitor 232 is 100 μF or less, capacitor 232 can be easily constructed by connecting multiple film capacitors in parallel. Furthermore, because capacitor 232 is made of film capacitors, the temperature rise of capacitor 232 can be suppressed, and the lifespan of capacitor 232 can be extended.

[0057] In the drive control device 2 described above, the number of poles of the drive motor 25 is set to 6 or more.

[0058] According to this, the number of poles of the drive motor 25 is set to 6 or more, so an LC filter circuit 23 that satisfies the above equation (A) can be easily realized.

[0059] In the above-described drive control device 2, at least a part of the drive control device 2 is provided in a sealed space formed by, for example, a sealed box, and the sealed space contains a capacitor 232 that constitutes an LC filter circuit 23, the capacitor 232 is made of a film capacitor, and the refrigerant of the air conditioner 1 is a flammable refrigerant.

[0060] According to this, since the refrigerant in the air conditioning unit 1 is a flammable refrigerant, there is a risk of fire if there is an ignition source when the refrigerant leaks. Therefore, by placing at least a part of the drive control device 2 in a sealed space, it is possible to suppress the drive control device 2 from becoming an ignition source in the event of a refrigerant leak. In addition, by configuring the capacitor 232 in the sealed space as a film capacitor, it is possible to suppress the temperature rise in the sealed space.

[0061] In Embodiment 1, the drive control device 2 for the compressor 11 of the air conditioning system 1 includes a three-phase rectifier circuit 22 that rectifies a three-phase AC voltage from a three-phase commercial power supply 21, an LC filter circuit 23 that smooths the output of the three-phase rectifier circuit 22, an inverter circuit 24 that receives power from the LC filter circuit 23 and supplies drive power to the drive motor 25 of the compressor 11 located in the air conditioning system 1, and a control device 4 that controls the inverter circuit 24, wherein the cutoff frequency FC of the LC filter circuit 23 is 700Hz or higher and 935Hz or lower.

[0062] According to the above configuration, the cutoff frequency FC of the LC filter circuit 23 is 700 Hz or higher and 935 Hz or lower. Therefore, it can satisfy the power supply harmonic standard specified in IEC 61000-3-12.

[0063] (Other embodiments) As described above, the above embodiments have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these embodiments and can be applied to embodiments that have been modified, replaced, added, or omitted. Therefore, other embodiments will be described below as examples.

[0064] In the above embodiment, a case was described in which the air conditioning system 1 heats the water flowing through the water pipe 121, but the embodiment is not limited to this. The air conditioning system 1 may also include an outdoor unit and an indoor unit, and the indoor unit may heat and cool the air in the space to be air-conditioned. In this case, the compressor 11 is located in the outdoor unit.

[0065] In the above embodiment, the case where the coefficient α is "14" was described, but the embodiment is not limited to this. The coefficient α can be "14" or greater. Furthermore, although the above embodiment described the case where the first percentage RT1 is "75%", the embodiment is not limited to this. The first percentage RT1 may be "80%" or "70%".

[0066] In the above embodiment, the case where the second proportion RT2 is "75%" was described, but the embodiment is not limited to this. The second proportion RT2 may be "80%" or "70%". Furthermore, although the above embodiment described the case where the predetermined period NT is "5 periods", the embodiment is not limited to this. The predetermined period NT may be "3 periods" or "7 periods". Furthermore, although the above embodiment described the case where the predetermined number of NS is "10," the embodiment is not limited to this. The predetermined number of NS may be "8" or "15."

[0067] In the above embodiment, the case where the drive motor 25 has 6 poles was described, but the embodiment is not limited to this. The drive motor 25 may have 6 or more poles. For example, the drive motor 25 may have 8 poles or 10 poles.

[0068] In the above embodiment, the case in which the capacitor 232 constituting the LC filter circuit 23 of the drive control device 2 is arranged inside a sealed box is described, but the embodiment is not limited to this. For example, in addition to the capacitor 232, components other than the capacitor 232 may be arranged inside the sealed box. Furthermore, in order to prevent heat from accumulating inside the sealed box, the system may be configured to release the heat from inside the sealed box to the outside using a Peltier element, a fan, or the like.

[0069] Furthermore, while the above embodiment describes a case in which a part of the drive control device 2 is arranged inside a sealed box, the embodiment is not limited to this. For example, if the amount of flammable refrigerant sealed inside is small and safety measures are not required, or if the LC filter circuit 23 etc. is installed at a location sufficiently far from where leakage of flammable refrigerant is expected, a part of the drive control device 2 may be arranged inside, for example, a box that is not airtight. Note that a part of the drive control device 2 includes a capacitor 232 that constitutes the LC filter circuit 23.

[0070] The processor 41 may consist of a single processor or multiple processors. The processor 41 may also be hardware programmed to implement the corresponding functional unit. That is, the processor 41 may consist of, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0071] Since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the scope of the claims or equivalents thereof.

[0072] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0073] (Technology 1) A compressor drive control device for an air conditioning system, comprising: a three-phase rectifier circuit for rectifying a three-phase AC voltage from a three-phase commercial power supply; an LC filter circuit for smoothing the output of the three-phase rectifier circuit; an inverter circuit that receives power from the LC filter circuit and supplies drive power to a drive motor of a compressor located in an air conditioning system; and a control device for controlling the inverter circuit, wherein the cutoff frequency FC of the LC filter circuit satisfies the following equation (A). α × FA ≤ FC ≤ FU (A) Here, frequency FA is the frequency of the three-phase commercial power supply, and coefficient α is 14 or greater. The upper limit value FU is the frequency at which the LC filter circuit cuts out the 6th harmonic of the fundamental frequency of the compressor's drive motor by a first-degree margin or more.

[0074] With this configuration, the cutoff frequency FC of the LC filter circuit satisfies equation (A). That is, since the cutoff frequency FC is greater than or equal to (α × FA), it is possible to satisfy the power supply harmonic standard specified in IEC61000-3-12. Furthermore, since the cutoff frequency FC is less than or equal to the upper limit value FU, the influence of the 6th harmonic pulsation of the fundamental frequency of the drive motor on the current input from the 3-phase rectifier circuit to the LC filter circuit can be reduced. Therefore, it is possible to satisfy the power supply harmonic standard specified in IEC61000-3-12.

[0075] (Technology 2) The control device for the compressor of an air conditioning system according to Technical 1, wherein the control device performs current control of the inverter circuit by PI control, the cutoff frequency in the PI control is a frequency that cuts the 6th harmonic of the fundamental frequency of the drive motor by a 2% or greater ratio, the averaging time in the averaging process of DC voltage detection is set to be equal to or greater than a predetermined period of the 6th harmonic of the three-phase commercial power supply, and the sampling period for DC voltage detection is set to sample a predetermined number or more in one period of the 6th harmonic of the three-phase commercial power supply.

[0076] With this configuration, the averaging time in the DC voltage detection averaging process is set to be longer than a predetermined period of the 6th harmonic of the three-phase commercial power supply, and the sampling period for the DC voltage detection is set to sample a predetermined number of values ​​or more in one period of the 6th harmonic of the three-phase commercial power supply, so that the average voltage in the DC voltage detection averaging process can be calculated appropriately. Furthermore, the control device performs current control of the inverter circuit by PI control, and the cutoff frequency FD in the PI control is a frequency that cuts the 6th harmonic of the fundamental frequency of the drive motor by a second percentage or more, so that the influence of the pulsation of the 6th harmonic of the fundamental frequency of the drive motor on the current input from the three-phase rectifier circuit to the LC filter circuit can be reduced. Therefore, the power supply harmonic standard specified in IEC61000-3-12 can be satisfied.

[0077] (Technology 3) The drive control device for the compressor of an air conditioning system according to Technology 1 or Technology 2, wherein the capacitor constituting the LC filter circuit is a film capacitor, and the capacitance of the capacitor is 100 μF or less.

[0078] With this configuration, since the capacitance of the capacitor is 100 μF or less, the capacitor can be easily constructed by connecting multiple film capacitors in parallel. Furthermore, because the capacitor is made of film capacitors, the temperature rise of the capacitor can be suppressed, and the lifespan of the capacitor can be extended.

[0079] (Technology 4) The drive control device for a compressor of an air conditioning system according to any one of the three technologies described above, wherein the number of poles of the drive motor is set to 6 or more.

[0080] With this configuration, the number of poles of the drive motor is set to 6 or more, so an LC filter circuit that satisfies the above equation (A) can be easily realized.

[0081] (Technology 5) A drive control device for a compressor of an air conditioner according to Technology 1 or Technology 2, wherein at least a part of the drive control device is provided in a sealed space, the sealed space includes a capacitor constituting the LC filter circuit, the capacitor is a film capacitor, and the refrigerant of the air conditioner is a flammable refrigerant.

[0082] In this configuration, since the refrigerant in the air conditioning system is a flammable refrigerant, there is a risk of fire if there is an ignition source when the refrigerant leaks. Therefore, by placing a part of the drive control device in a sealed space, it is possible to suppress the drive control device from becoming an ignition source in the event of a refrigerant leak. In addition, by using a film capacitor for the capacitor in the sealed space, the temperature rise in the sealed space can be suppressed.

[0083] (Technology 6) A drive control device for a compressor in an air conditioning system, comprising: a three-phase rectifier circuit for rectifying a three-phase AC voltage from a three-phase commercial power supply; an LC filter circuit for smoothing the output of the three-phase rectifier circuit; an inverter circuit that receives power from the LC filter circuit and supplies drive power to a drive motor of a compressor located in an air conditioning system; and a control device for controlling the inverter circuit, wherein the cutoff frequency of the LC filter circuit is 700 Hz or higher and 935 Hz or lower.

[0084] This configuration achieves the same effect as the compressor drive control device of the air conditioning system in Technology 1. [Industrial applicability]

[0085] This disclosure is applicable to applications that meet power supply harmonic standards. [Explanation of Symbols]

[0086] 1. Air conditioning system 11 Compressor 12 Hydrothermal exchange condenser 121 Water Piping 13 Expansion valve 14 Evaporator 15 Refrigerant piping 2. Drive control device 22 3-phase rectifier circuit 23 LC filter circuit 231 Reactor 232 Capacitors 24 Inverter Circuit 25 Drive motor 26 Voltage Sensor Circuit 27, 271, 272, 273 Current Sensors 3 Gate drive circuit 4. Control device 41 processors 411 Current Control Unit 42 memory 421 Control Program FA frequency (frequency of 3-phase commercial power supply) FC cutoff frequency (cutoff frequency of LC filter circuit) FD cutoff frequency (cutoff frequency in PI control) FM fundamental frequency FU upper limit RT1 1st proportion RT2 2nd proportion TA average time TS sampling period α coefficient

Claims

1. A three-phase rectifier circuit that rectifies the three-phase AC voltage from a three-phase commercial power supply, An LC filter circuit for smoothing the output of the three-phase rectifier circuit, An inverter circuit receives power from the LC filter circuit and supplies driving power to the drive motor of the compressor located in the air conditioning system, A control device for controlling the inverter circuit, Equipped with, The cutoff frequency FC of the LC filter circuit satisfies the following equation (A): A drive control device for the compressor of an air conditioning system. α×FA≦FC≦FU (A) Here, frequency FA is the frequency of the three-phase commercial power supply, and coefficient α is 14 or greater. The upper limit value FU is the frequency at which the LC filter circuit cuts out the 6th harmonic of the fundamental frequency of the compressor's drive motor by a first-degree margin or more.

2. The control device is The current control of the inverter circuit is performed by PI control, and the cutoff frequency in the PI control is a frequency that cuts off the 6th harmonic of the fundamental frequency of the drive motor by a ratio of 2 or more. The averaging time in the DC voltage detection averaging process is set to be longer than or equal to a predetermined period of the sixth harmonic of the three-phase commercial power supply. The sampling period for the DC voltage detection is set so that a predetermined number or more are sampled in one period of the sixth harmonic of the three-phase commercial power supply. A drive control device for the compressor of an air conditioning system according to claim 1.

3. The capacitors constituting the LC filter circuit are made of film capacitors. The capacitance of the aforementioned capacitor is 100 μF or less. A drive control device for a compressor of an air conditioning system according to claim 1 or claim 2.

4. The number of poles of the aforementioned drive motor is set to six or more. A drive control device for a compressor of an air conditioning system according to claim 1 or claim 2.

5. At least a part of the drive control device is provided in a sealed space, The sealed space contains capacitors that constitute the LC filter circuit. The capacitor is composed of a film capacitor. The refrigerant in the aforementioned air conditioning system is a flammable refrigerant. A drive control device for a compressor of an air conditioning system according to claim 1 or claim 2.

6. A three-phase rectifier circuit that rectifies the three-phase AC voltage from a three-phase commercial power supply, An LC filter circuit for smoothing the output of the three-phase rectifier circuit, An inverter circuit receives power from the LC filter circuit and supplies driving power to the drive motor of the compressor located in the air conditioning system, A control device for controlling the inverter circuit, Equipped with, The cutoff frequency of the LC filter circuit is 700 Hz or higher and 935 Hz or lower. A drive control device for the compressor of an air conditioning system.

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