Power converters and outdoor units of air conditioners

Abstract

This power conversion device (1) comprises: a rectifier unit (130) that rectifies a first AC power supplied from a commercial power supply (110); a capacitor (210) that is connected to the output end of the rectifier unit (130); an inverter (310) that is connected to both ends of the capacitor (210), and that converts the power outputted from the rectifier unit (130) and the capacitor (210) to a second AC power and outputs that to a load having a motor (314); and a control unit (400) that, by controlling the operation of the inverter (310) so that the inverter (310) outputs to the load the second AC power including pulsations according to the pulsations of the power flowing from the rectifier unit (130) to the capacitor (210), performs capacitor load suppression control that suppresses the current flowing to the capacitor (310). The control unit (400) estimates the capacitor load of the capacitor (210) and determines whether to perform capacitor load suppression control on the basis of the estimated value of the capacitor load.

Description

Technical Field

[0001] The present disclosure relates to a power conversion device that rectifies AC power supplied from a commercial power source and then converts it into AC power for output, and an outdoor unit of an air conditioner equipped with the same. electric power

Background Art

[0002] Conventionally, in a power conversion device that rectifies AC power supplied from a commercial power source and then converts it into AC power for output, a smoothing capacitor is used to smooth the power rectified by a rectifying section that rectifies the AC current supplied from the commercial power source.

[0003] Patent Document 1 discloses a power conversion device that suppresses deterioration of a smoothing capacitor by suppressing a large current from flowing through the smoothing capacitor.

Prior Art Documents

Patent Documents

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the power conversion device disclosed in Patent Document 1, the current of the capacitor is suppressed by including a pulsation corresponding to the pulsation of the power flowing into the smoothing capacitor in the output from the inverter to a device having a motor. Therefore, in the power conversion device disclosed in Patent Document 1, the output of the inverter tends to increase, and the loss increases regardless of the magnitude of the capacitor load of the smoothing capacitor, resulting in a problem that the energy saving performance deteriorates.

[0006] This disclosure has been made in view of the above, and aims to provide a power conversion device that suppresses the degradation of smoothing capacitors and reduces the decline in energy-saving performance. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the power conversion device according to this disclosure comprises: a rectifier unit that rectifies a first AC power supplied from a commercial power source; a capacitor connected to the output terminal of the rectifier unit; an inverter connected to both ends of the capacitor, which converts the power output from the rectifier unit and the capacitor into a second AC power and outputs it to a load having a motor; and a control unit that controls the operation of the inverter to output a second AC power from the inverter to the load that includes pulsations corresponding to the pulsations of the power flowing from the rectifier unit to the capacitor, thereby suppressing the current flowing to the capacitor. The control unit estimates the capacitor load in the capacitor and decides whether or not to perform capacitor load suppression control based on the estimated value of the capacitor load. [Effects of the Invention]

[0008] The power conversion device described herein has the effect of suppressing the degradation of smoothing capacitors and preventing a decrease in energy-saving performance. [Brief explanation of the drawing]

[0009] [Figure 1] Diagram showing the configuration of the power conversion device according to Embodiment 1. [Figure 2] This figure shows examples of currents and capacitor voltages of the capacitors in the smoothing section when the control unit of the power converter according to Embodiment 1 smooths the current output from the rectifier section with the smoothing section, thereby keeping the current flowing through the inverter constant. [Figure 3] This figure shows examples of currents and capacitor voltages of the capacitors in the smoothing section when the control unit of the power converter according to Embodiment 1 controls the operation of the inverter to reduce the current flowing through the smoothing section. [Figure 4]Flowchart showing the operation of the control unit of the power converter according to Embodiment 1 [Figure 5] This figure shows an example of a hardware configuration that realizes the control unit included in the power conversion device according to Embodiment 1. [Figure 6] Diagram showing the configuration of the power converter according to Embodiment 2. [Figure 7] Diagram showing the configuration of the power converter according to Embodiment 3. [Figure 8] Diagram showing the operation of the power converter according to Embodiment 4. [Figure 9] Diagram showing the operation of the power converter according to Embodiment 5 [Figure 10] Diagram showing the operation of the power converter according to Embodiment 6. [Figure 11] This figure shows an example of the relationship between the capacitor current and the capacitor load suppression control amount of the power converter according to Embodiment 8. [Figure 12] Diagram showing the configuration of the outdoor unit of the air conditioner according to Embodiment 9. [Modes for carrying out the invention]

[0010] The power conversion device and the outdoor unit of the air conditioner according to the embodiment will be described in detail below with reference to the drawings.

[0011] Embodiment 1. Figure 1 shows the configuration of a power converter according to Embodiment 1. The power converter 1 is connected between the commercial power supply 110 and the compressor 315. The power converter 1 converts the first AC power of the power supply voltage Vs supplied from the commercial power supply 110 into a second AC power and supplies it to the compressor 315. The second AC power may have at least one of its amplitude and phase different from the first AC power, or both its amplitude and phase may be the same as the first AC power.

[0012] The power conversion device 1 includes a voltage and current detection unit 501, a reactor 120, a rectification unit 130, a voltage detection unit 502, a smoothing unit 200, an inverter 310, current detection units 313a and 313b, and a control unit 400. The compressor 315 is a device that serves as a load including a motor 314 for driving the compressor, which is supplied with power from the power conversion device 1. The motor 314 included in the compressor 315 and the power conversion device 1 constitute a motor drive device 2.

[0013] The voltage and current detection unit 501 detects the voltage and current values ​​of the first AC power supplied from the commercial power supply 110 and outputs the detected voltage and current values ​​to the control unit 400. The voltage of the first AC power is the power supply voltage Vs. The reactor 120 is connected between the voltage and current detection unit 501 and the rectifier unit 130. The rectifier unit 130 has a bridge circuit composed of rectifier elements 131, 132, 133, and 134. The rectifier unit 130 rectifies the first AC power supplied from the commercial power supply 110 and outputs it. In the power converter 1 according to Embodiment 1, the rectifier unit 130 performs full-wave rectification. The voltage detection unit 502 detects the voltage value of the power rectified by the rectifier unit 130 and outputs the detected voltage value to the control unit 400. The smoothing unit 200 is connected to the output terminal of the rectifier unit 130 via the voltage detection unit 502. The smoothing section 200 has a capacitor 210, which is a smoothing element, and smooths the power rectified by the rectifier section 130. The capacitor 210 is, for example, an electrolytic capacitor or a film capacitor. The capacitor 210 has a capacitance that smooths the power rectified by the rectifier section 130, and the voltage generated in the capacitor 210 due to smoothing is not the full-wave rectified waveform shape of the commercial power supply 110, but a waveform shape in which a voltage ripple corresponding to the frequency of the commercial power supply 110 is superimposed on the DC component, and does not pulsate greatly. The frequency of this voltage ripple is twice the frequency of the power supply voltage Vs if the commercial power supply 110 is single-phase, and the frequency six times the frequency is the main component if the commercial power supply 110 is three-phase. If the power input from the commercial power supply 110 and the power output from the inverter 310 do not change, the amplitude of this voltage ripple is determined by the capacitance of the capacitor 210. For example, the voltage generated across capacitor 210 due to smoothing pulsates within a range such that the maximum voltage ripple generated across capacitor 210 is less than twice the minimum voltage ripple.

[0014] The inverter 310 is connected to both ends of the capacitor 210 provided in the smoothing section 200. The inverter 310 has switching elements 311a, 311b, 311c, 311d, 311e, 311f and freewheeling diodes 312a, 312b, 312c, 312d, 312e, 312f. The inverter 310 turns on and off the switching elements 311a, 311b, 311c, 311d, 311e, 311f under the control of the control section 400, converts the power output from the rectifying section 130 and the smoothing section 200 into second AC power, and then outputs it to the compressor 315. Each of the current detection sections 313a, 313b detects the current value of one phase of the three-phase current output from the inverter 310, and outputs the detected current value to the control section 400. Note that the control section 400 can calculate the remaining one-phase current value output from the inverter 310 by acquiring the current values of two phases of the three-phase current values output from the inverter 310. The motor 314 rotates according to the amplitude and phase of the second AC power supplied from the inverter 310 and performs a compression operation. For example, when the compressor 315 is a hermetic compressor used in an air conditioner or the like, the load torque of the compressor 315 can often be regarded as a constant torque load.

[0015] Note that in the power conversion device 1, the arrangement of each component shown in FIG. 1 is an example, and the arrangement of each component is not limited to the example shown in FIG. 1. For example, the reactor 120 may be arranged at the subsequent stage of the rectifying section 130. In the following description, the voltage-current detection section 501, the voltage detection section 502, and the current detection sections 313a, 313b may be collectively referred to as a detection section. Further, the voltage value and current value detected by the voltage-current detection section 501, the voltage value detected by the voltage detection section 502, and the current value detected by the current detection sections 313a, 313b may be referred to as detection values. element

[0016] The control unit 400 acquires the voltage and current values ​​of the first AC power from the voltage and current detection unit 501, the voltage value of the power rectified by the rectifier unit 130 from the voltage detection unit 502, and the current value of the second AC power having amplitude and phase converted by the inverter 310 from the current detection units 313a and 313b. The control unit 400 uses the detected values ​​detected by each detection unit to control the operation of the inverter 310, specifically the on / off switching of the switching elements 311a, 311b, 311c, 311d, 311e, and 311f of the inverter 310. In this embodiment, the control unit 400 controls the operation of the inverter 310 so that it outputs the second AC power, which includes pulsations corresponding to the pulsations of the power flowing from the rectifier unit 130 to the capacitor 210 of the smoothing unit 200, to the compressor 315, which is the load. The pulsation corresponding to the power pulsation flowing into the capacitor 210 of the smoothing unit 200 is, for example, a pulsation that fluctuates depending on the frequency of the power pulsation flowing into the capacitor 210 of the smoothing unit 200. As a result, the control unit 400 suppresses the current flowing into the capacitor 210 of the smoothing unit 200. Note that the control unit 400 does not need to use all the detection values ​​obtained from each detection unit, and may perform control using only some of the detection values.

[0017] It is known that there is a correlation between the capacitor load, which is the amount of charge transfer in capacitor 210, and the amount of voltage fluctuation applied to capacitor 210. Therefore, the control unit 400 detects the amount of voltage fluctuation applied to capacitor 210 by removing the DC component of the voltage across capacitor 210 and extracting the AC component, and estimates the capacitor load. The control unit 400 then calculates the estimated value of the capacitor load. to Based on this, a decision is made as to whether or not to implement capacitor load suppression control. Capacitor load suppression control will be described later.

[0018] Next, the operation of the control unit 400 provided in the power converter 1 will be described. In the power converter 1 according to Embodiment 1, the load generated by the inverter 310 and the compressor 315 can be considered a constant load, and the following explanation will be given assuming that a constant current load is connected to the smoothing unit 200 when viewed in terms of the current output from the smoothing unit 200. Here, as shown in Figure 1, the current flowing from the rectifier unit 130 is denoted as current I1, the current flowing to the inverter 310 is denoted as current I2, and the current flowing from the smoothing unit 200 is denoted as current I3. Current I2 is the sum of current I1 and current I3. Current I3 can be expressed as the difference between current I2 and current I1, i.e., current I2 - current I1. Current I3 has a positive discharge direction in the smoothing unit 200 and a negative charge direction in the smoothing unit 200. That is, current may flow into the smoothing unit 200, and current may flow out.

[0019] Figure 2 shows examples of currents and capacitor voltages of the capacitor in the smoothing unit when the control unit of the power converter according to Embodiment 1 smooths the current output from the rectifier unit in the smoothing unit, thereby keeping the current flowing through the inverter constant. In Figure 2, from top to bottom, the figures show current I1, current I2, current I3, and capacitor voltage Vdc. The capacitor voltage Vdc is the voltage of the capacitor 210 generated in response to current I3. The vertical axes for currents I1, I2, and I3 show the current values, and the vertical axis for capacitor voltage Vdc shows the voltage values. The horizontal axis for all figures shows time t. In reality, the carrier components of the inverter 310 are superimposed on currents I2 and I3, but these are omitted here. The same applies to subsequent figures. As shown in Figure 2, in the power converter 1, if the current I1 flowing from the rectifier unit 130 is sufficiently smoothed by the smoothing unit 200, the current I2 flowing through the inverter 310 will be a constant current value. However, a large current I3 flows through the capacitor 210 of the smoothing unit 200, which becomes a cause of degradation. Therefore, in this embodiment, in the power converter 1, the control unit 400 controls the current I2 flowing through the inverter 310, that is, controls the operation of the inverter 310, in order to reduce the current I3 flowing through the smoothing unit 200.

[0020] Figure 3 shows examples of currents and capacitor voltages of the capacitors in the smoothing section when the control unit of the power converter according to Embodiment 1 controls the operation of the inverter to reduce the current flowing to the smoothing section. In Figure 3, from top to bottom, the figures show current I1, current I2, current I3, and capacitor voltage Vdc. The capacitor voltage Vdc is the voltage of the capacitor 210 generated in response to current I3. The vertical axes for currents I1, I2, and I3 show the current values, and the vertical axis for capacitor voltage Vdc shows the voltage values. The horizontal axis for all shows time t. The control unit 400 of the power converter 1 controls the operation of the inverter 310 so that current I2 flows to the inverter 310 as shown in Figure 3, thereby reducing the frequency component of the current flowing from the rectifier section 130 to the smoothing section 200 and reducing the current I3 flowing to the smoothing section 200, compared to the example in Figure 2. Specifically, the control unit 400 controls the operation of the inverter 310 so that current I2, which includes a pulsating current with the frequency component of current I1 as its main component, flows to the inverter 310.

[0021] The frequency components of current I1 are determined by the frequency of the AC current supplied from the commercial power supply 110 and the configuration of the rectifier unit 130. Therefore, the control unit 400 can make the frequency components of the pulsating current superimposed on current I2 components that have predetermined amplitudes and phases. The frequency components of the pulsating current superimposed on current I2 have a waveform similar to the frequency components of current I1. As the control unit 400 brings the frequency components of the pulsating current superimposed on current I2 closer to the frequency components of current I1, it can reduce the current I3 flowing through the smoothing unit 200 and reduce the pulsating voltage generated at the capacitor voltage Vdc.

[0022] The control unit 400 controls the pulsation of the current flowing through the inverter 310 by controlling the operation of the inverter 310, which is equivalent to controlling the pulsation of the first AC power output from the inverter 310 to the compressor 315. The control unit 400 controls the operation of the inverter 310 so that the pulsation included in the second AC power output from the inverter 310 is smaller than the pulsation of the power output from the rectifier unit 130. The control unit 400 controls the amplitude and phase of the pulsation included in the second AC power output from the inverter 310 so that the voltage ripple of the capacitor voltage Vdc, i.e., the voltage ripple generated in the capacitor 210, is smaller than the voltage ripple generated in the capacitor 210 when the second AC power output from the inverter 310 does not include pulsation corresponding to the pulsation of the power flowing into the capacitor 210. Alternatively, the control unit 400 controls the amplitude and phase of the pulsation included in the second AC power output from the inverter 310 so that the current ripple flowing into and out of the capacitor 210 is smaller than the current ripple generated in the capacitor 210 when the second AC power output from the inverter 310 does not include pulsation corresponding to the pulsation of power flowing into the capacitor 210. The case when the second AC power output from the inverter 310 does not include pulsation corresponding to the pulsation of power flowing into the capacitor 210 is the control shown in Figure 2.

[0023] The AC current supplied from the commercial power supply 110 is not particularly limited and may be single-phase or three-phase. The control unit 400 should determine the frequency components of the pulsating current superimposed on the current I2 according to the first AC power supplied from the commercial power supply 110. Specifically, the control unit 400 controls the pulsating waveform of the current I2 flowing through the inverter 310 to a shape in which a DC component is added to a pulsating waveform whose main component is a frequency component that is twice the frequency of the first AC power if the first AC power supplied from the commercial power supply 110 is single-phase, or a frequency component that is six times the frequency of the first AC power if the first AC power supplied from the commercial power supply 110 is three-phase. The pulsating waveform may be, for example, the shape of the absolute value of a sine wave, or the shape of a sine wave. In this case, the control unit 400 may add at least one frequency component from among the components that are integer multiples of the frequency of the sine wave to the pulsating waveform as a predetermined amplitude. The pulsating waveform may also be the shape of a square wave or a triangular wave. In this case, the control unit 400 may set the amplitude and phase of the pulsation waveform to predetermined values.

[0024] The control unit 400 may calculate the amount of pulsation in the second AC power output from the inverter 310 using the voltage applied to the capacitor 210 or the current flowing through the capacitor 210, or it may calculate the amount of pulsation in the second AC power output from the inverter 310 using the voltage or current of the first AC power supplied from the commercial power supply 110.

[0025] The operation of the control unit 400 will be explained using a flowchart. Figure 4 is a flowchart of the operation of the control unit of the power converter according to Embodiment 1. In step S1, the control unit 400 acquires detected values ​​from each detection unit of the power converter 1. In step S2, the control unit 400 estimates the capacitor load. In step S3, the control unit 400 determines whether or not it is necessary to suppress the capacitor load. If the control unit 400 determines that it is necessary to suppress the capacitor load, the answer in step S3 is Yes, and in step S4, the control unit 400 implements capacitor load suppression control. That is, when the control unit 400 outputs the second AC power from the inverter 310 to the load, it includes pulsation corresponding to the pulsation of power flowing into the capacitor 210. If capacitor load suppression control is already being implemented, the control unit 400 continues the capacitor load suppression control. On the other hand, if the control unit 400 determines that it is not necessary to suppress the capacitor load, the answer in step S3 is No, and in step S5, the control unit 400 does not implement capacitor load suppression control. In other words, when the control unit 400 outputs the second AC power from the inverter 310 to the load, it does not include pulsations corresponding to the pulsations of power flowing into the capacitor 210. If capacitor load suppression control is already not being performed, the control unit 400 will continue not to perform capacitor load suppression control.

[0026] Next, the hardware configuration of the control unit 400 of the power converter 1 will be described. Figure 5 is a diagram showing an example of the hardware configuration for realizing the control unit of the power converter according to Embodiment 1. The control unit 400 is realized by a processor 91 that performs various processes, a memory 92 which is the main memory, and a storage device 93 that stores information.

[0027] The processor 91 may be an arithmetic unit, microprocessor, microcomputer, CPU (Central Processing Unit), or DSP (Digital Signal Processor). The memory 92 may be a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). The storage device 93 stores a program for executing capacitor load suppression control processing. The processor 91 reads the program stored in the storage device 93 into the memory 92 and executes it. The functions of the control unit 400 are realized when the processor 91 reads the program stored in the storage device 93 into the memory 92 and executes it.

[0028] As described above, in the power converter 1 according to Embodiment 1, the control unit 400 controls the operation of the inverter 310 based on the detected values ​​obtained from each detection unit, and reduces the current I3 flowing through the smoothing unit 200 by superimposing a pulsation of a frequency component corresponding to the frequency component of the current I1 flowing from the rectifier unit 130 onto the current I2 flowing through the inverter 310. As a result, the power converter 1 can use a capacitor with a smaller ripple current capacity compared to the case where the control in Embodiment 1 is not performed, because the current I3 flowing through the smoothing unit 200 is reduced. In addition, the power converter 1 can reduce the capacitance of the mounted capacitor 210 compared to the case where the control in Embodiment 1 is not performed, because the pulsation voltage of the capacitor voltage Vdc is reduced. For example, if the power converter 1 is configured with multiple capacitors 210 to make up the smoothing unit 200, the number of capacitors 210 that make up the smoothing unit 200 can be reduced.

[0029] Furthermore, the control unit 400 estimates the capacitor load and decides whether or not to implement capacitor load suppression control based on the estimated value of the capacitor load. Therefore, if the degradation of the capacitor 210 when capacitor load suppression control is not performed is within an acceptable range, it is possible to prevent losses from occurring due to reducing the capacitor current in order to suppress the capacitor load.

[0030] Embodiment 2. Figure 6 shows the configuration of the power converter according to Embodiment 2. The power converter 1 according to Embodiment 2 differs from the power converter 1 according to Embodiment 1 in that it includes a first current detection unit 601 and a second current detection unit 602. The first current detection unit 601 is installed in the rectifier unit 130. That is, the first current detection unit 601 is installed on the commercial power supply 110 side of the capacitor 210. The second current detection unit 602 is installed in the inverter 31 0 It is installed such that the second current detection unit 602 is located on the compressor 315 side, which is the load, rather than on the capacitor 210 side. The control unit 400 calculates the current flowing through the capacitor 210 from the difference between the current value detected by the first current detection unit 601 and the current value detected by the second current detection unit 602, and estimates the capacitor load.

[0031] The power converter 1 according to Embodiment 2 estimates the capacitor load based on the current flowing through the capacitor 210, which is calculated based on the difference between the current value detected by the first current detection unit 601 and the current value detected by the second current detection unit 602. Therefore, compared to the power converter 1 according to Embodiment 1, the capacitor load can be estimated more accurately. Consequently, the power converter 1 according to Embodiment 2 can more accurately determine whether or not it is necessary to implement capacitor load suppression control, thereby suppressing the deterioration of the capacitor 210.

[0032] Furthermore, since the first current detection unit 601 and the second current detection unit 602 are generally installed in the power converter 1 for the purposes of motor control and control and protection of the boost circuit, estimating the capacitor load using the first current detection unit 601 and the second current detection unit 602, which are installed for motor control and control and protection of the boost circuit, eliminates the need to add a new first current detection unit 601 and second current detection unit 602 for the purpose of estimating the capacitor load.

[0033] Embodiment 3. Figure 7 shows the configuration of the power converter according to Embodiment 3. The power converter 1 according to Embodiment 3 differs from the power converter 1 according to Embodiment 2 in that it includes a first voltage detection circuit 701 and a second voltage detection circuit 702. The first voltage detection circuit 701 is installed between the reactor 120 and the rectifier 130. That is, the first voltage detection circuit 701 is installed on the commercial power supply 110 side of the capacitor 210. The second voltage detection circuit 702 is installed between the smoothing unit 200 and the inverter 310. That is, the second voltage detection circuit 702 is installed on the compressor 315 side, which is the load, from the capacitor 210.

[0034] The control unit 400 calculates a first power value from the current value detected by the first current detection unit 601 and the voltage value detected by the first voltage detection circuit 701. Therefore, the first current detection unit 601 and the first voltage detection circuit 701 form a first power detection unit 801. The control unit 400 also calculates a second power value from the current value detected by the second current detection unit 602 and the voltage value detected by the second voltage detection circuit 702. Therefore, the second current detection unit 602 and the second voltage detection circuit 702 form a second power detection unit 802. formation The first power detection unit 801 is installed on the commercial power supply 110 side of the capacitor 210, and the second power detection unit 802 is installed on the compressor 315 side, which is the load, side of the capacitor 210.

[0035] The control unit 400 calculates the power consumption in the capacitor 210 based on the first power value and the second power value, and estimates the capacitor load.

[0036] The power converter 1 according to Embodiment 3 calculates the power consumption of the capacitor 210 and estimates the capacitor load based on a first power value calculated from the current value detected by the first current detection unit 601 and the voltage value detected by the first voltage detection circuit 701, and a second power value calculated from the current value detected by the second current detection unit 602 and the voltage value detected by the second voltage detection circuit 702. Therefore, compared to the power converter 1 according to Embodiment 2, the capacitor load can be estimated more accurately.

[0037] Embodiment 4. The circuit configuration of the power converter 1 according to Embodiment 4 is the same as that of the power converter 1 according to Embodiment 1. In Embodiment 4, the compressor 315, which is a load equipped with a motor 314 that receives power from the power converter 1, is applied to the outdoor unit of an air conditioner and compresses the refrigerant flowing through the refrigerant circuit. In Embodiment 4, the air conditioner equipped with the compressor 315 is operated in one of several operating modes with different power consumption. The power converter 1 according to Embodiment 4 switches whether or not to perform capacitor load suppression control according to the operating mode of the air conditioner. Here, it is assumed that the air conditioner is operated in either a normal operating mode or an energy-saving operating mode, and the control unit 400 performs capacitor load suppression control when the operating mode of the air conditioner is the normal operating mode, and does not perform capacitor load suppression control when the operating mode of the air conditioner is the energy-saving operating mode.

[0038] Figure 8 shows the operation of the power converter according to Embodiment 4. In Figure 8, the mode switching signal is a signal that switches the operating mode of the air conditioner, with a high level corresponding to the normal operating mode and a low level corresponding to the energy-saving operating mode. At time t10, the mode switching signal is at a high level, and the air conditioner is operating in the normal operating mode. Therefore, at time t10, the control unit 400 is performing capacitor load suppression control. At time t11, the control unit 400 changes the mode switching signal from a high level to a low level, causing the air conditioner to switch from the normal operating mode to the energy-saving operating mode. Therefore, at time t11, the control unit 400 does not perform capacitor load suppression control. By the control unit 400 not performing capacitor load suppression control, the amount of capacitor load suppression control begins to decrease at time t11. As the amount of capacitor load suppression control decreases, the capacitor load increases, but the loss of the motor 314 is improved, so the input power of the capacitor 210 decreases. At time t12, the control unit 400 changes the mode switching signal from a low level to a high level, causing the air conditioner to switch from energy-saving operation mode to normal operation mode. As a result, at time t12, the control unit 400 starts capacitor load suppression control, and the capacitor load suppression control amount begins to increase. As the capacitor load suppression control amount increases, the capacitor load decreases, and the input power to the capacitor 210 increases. The amount of work done by the motor 314 on the refrigerant circuit of the air conditioner does not change with respect to the capacitor load suppression control amount, so the air conditioning capacity of the air conditioner remains constant regardless of the capacitor load suppression control amount.

[0039] The power converter 1 according to Embodiment 4 switches whether or not to perform capacitor suppression control according to the operating mode of the air conditioner. Therefore, if the input power to the capacitor 210 is small and the capacitor load can be kept low without performing capacitor load suppression control, the capacitor load suppression control is not performed, thereby reducing losses in the motor 314 and improving energy saving performance.

[0040] Embodiment 5. The circuit configuration of the power converter 1 according to Embodiment 5 is the same as that of the power converter 1 according to Embodiment 1. The power converter 1 according to Embodiment 5 starts capacitor load suppression control when the capacitor load exceeds a preset upper limit threshold of the capacitor load, and stops capacitor load suppression control when the capacitor load falls below a preset lower limit threshold of the capacitor load.

[0041] Figure 9 shows the operation of the power converter according to Embodiment 5. In Embodiment 5, after the capacitor load exceeds the upper limit threshold of the capacitor load and the power converter 1 starts capacitor load suppression control, it increases or decreases the amount of capacitor load suppression control in accordance with the increase or decrease in input power or capacitor load until the capacitor load falls below the lower limit threshold of the capacitor load. At time t20, the control unit 400 is performing capacitor load suppression control. At time t21, the control unit 400 reduces the air conditioning capacity of the air conditioner. As a result, the input power of the capacitor 210 decreases, and the capacitor load also decreases. At time t22, the capacitor load falls below the lower limit threshold of the capacitor load. As a result, the control unit 400 stops performing capacitor load suppression control. As a result of not performing capacitor load suppression control, the capacitor load increases. At times t23 and t24, the capacitor load does not exceed the upper limit threshold of the capacitor load, so the control unit 400 continues not performing capacitor load suppression control. At time t25, the capacitor load exceeds the upper limit threshold of the capacitor load. Therefore, the control unit 400 implements capacitor load suppression control, and the amount of capacitor load suppression control begins to increase. As the amount of capacitor load suppression control increases, the capacitor load decreases, and the input power of the capacitor 210 increases. At times t26 and t27, the capacitor load is not below the lower limit threshold of the capacitor load, so the control unit 400 continues to implement capacitor load suppression control.

[0042] The power converter 1 according to Embodiment 5 can switch to an operation that prioritizes performance over capacitor load suppression when the capacitor load is low, thereby improving energy efficiency.

[0043] In Embodiments 1 to 5, the system switches between whether or not to implement capacitor load suppression control. However, a threshold value for the target capacitor load may be set in advance, and the capacitor load suppression control amount may be continuously changed according to the difference between the target threshold value and the capacitor load. Rather than simply deciding whether or not to include the pulsation amount output from the inverter 310 to the load, the system can operate the air conditioner while balancing its lifespan and air conditioning performance by continuously adjusting the pulsation amount included in the output from the inverter 310.

[0044] Embodiment 6. The circuit configuration of the power converter 1 according to Embodiment 6 is the same as that of the power converter 1 according to Embodiment 1. Figure 10 is a diagram showing the operation of the power converter according to Embodiment 6. In order to keep the capacitor load below the target load, the power converter 1 according to Embodiment 6 stops the control to suppress the capacitor load when the control amount of the control to suppress the capacitor load required falls below a predetermined capacitor load suppression control threshold, and restarts the output of the control to suppress the capacitor load when the estimated value of the capacitor load exceeds the predetermined capacitor load threshold.

[0045] At time t30, the control unit 400 is performing capacitor load suppression control, and the capacitor load is maintained at the target load amount. At time t31, the control unit 400 begins to reduce the air conditioning capacity of the air conditioner. Therefore, from time t31, the capacitor load suppression control amount also decreases in line with the decrease in air conditioning capacity. At time t32, the capacitor load suppression control amount falls below a predetermined capacitor load suppression control threshold. Therefore, the control unit 400 stops the capacitor load suppression control. Consequently, at time t32, the capacitor load suppression control amount decreases to 0. As the capacitor load suppression control amount decreases, the capacitor load increases, but the input power to the capacitor 210 decreases because the loss of the motor 314 is improved. At times t33 and t34, the capacitor load does not exceed the predetermined capacitor load threshold, so the control unit 400 continues to stop the capacitor load suppression control. At time t35, the capacitor load exceeds a predetermined capacitor load threshold, so the control unit 400 restarts capacitor load suppression control, and the capacitor load suppression control amount increases. As the capacitor load suppression control amount increases, the capacitor load decreases to the target load amount, and the input power of the capacitor 210 increases. At time t36, the capacitor load suppression control amount is not below the predetermined capacitor load suppression control amount threshold, so the control unit 400 continues capacitor load suppression control.

[0046] The power converter 1 according to Embodiment 6 controls the capacitor load so that it does not exceed a predetermined capacitor load threshold, and when it falls below a certain value, it allows the capacitor load to deteriorate to a certain value, thereby improving energy efficiency in operating conditions with a low capacitor load by setting the control amount to the minimum necessary.

[0047] Embodiment 7. The circuit configuration of the power converter 1 according to Embodiment 7 is the same as that of the power converter 1 according to Embodiment 1. The power converter 1 according to Embodiment 7 continuously changes the capacitor load suppression control amount so that the lifespan of the capacitor 210 estimated from the capacitor load does not fall below a preset period.

[0048] It is known that the lifespan of a capacitor follows Arrhenius's law. Therefore, the lifespan of a capacitor can generally be determined from a constant determined by the capacitor's specifications, as well as the ambient temperature of the capacitor, the voltage applied to the capacitor, and the capacitor current due to the heat generated by the capacitor. The ambient temperature of capacitor 210 can be determined, for example, by adding the temperature difference between the ambient temperature of capacitor 210 and the ambient temperature of the ambient air temperature confirmed in a prior evaluation, etc., based on the ambient air temperature detected by the air conditioner. The voltage applied to capacitor 210 can be determined from the value detected by the voltage detection unit 502. The amount of capacitor current can be determined from the fluctuation amount of the capacitor applied voltage, or from the difference between the grid power supply current and the motor current.

[0049] The power converter 1 according to Embodiment 7 does not perform capacitor load suppression control when it is estimated that the lifespan of the capacitor 210 will not fall below a preset period, and only performs capacitor load suppression control when it is estimated that the lifespan of the capacitor 210 will fall below a preset period. Therefore, when it is predicted that the lifespan of the capacitor 210 will not fall below a preset period, the power converter 1 allows the lifespan of the capacitor 210 to be shortened to the preset period and does not perform capacitor load suppression control, thereby suppressing the decrease in energy efficiency caused by performing capacitor load suppression control. As a result, the power converter 1 according to Embodiment 7 can ensure that the lifespan of the capacitor 210 is longer than the preset period while suppressing the decrease in energy efficiency.

[0050] Embodiment 8. The circuit configuration of the power converter 1 according to Embodiment 8 is the same as that of the power converter 1 according to Embodiment 2. In the power converter 1 according to Embodiment 8, the control unit 400 decomposes the capacitor current into frequency components and changes the control amount of the capacitor load suppression control so that the square root of the sum of the squares of each of the frequency components that are twice the power supply voltage Vs, or integer multiples of the power supply voltage Vs, does not exceed a predetermined constant value. Furthermore, if the square root of the sum of the squares of each of the frequency components that are twice the power supply voltage Vs, or integer multiples of the power supply voltage Vs, is less than or equal to a predetermined constant value, the control unit 400 allows the square root of the sum of the squares of each of the frequency components that are twice the power supply voltage Vs, or integer multiples of the power supply voltage Vs, to increase up to a predetermined constant value, and sets the capacitor load suppression control amount to the minimum necessary amount.

[0051] If the current flowing through capacitor 210 is a ripple current containing multiple frequency components, then the ripple current I R It is calculated by the following formula (1). In the following formula (1), I R This is the RMS value [Ams] of the ripple current at a specified frequency, and I X1 From I XN This is the effective value [Ams] of the ripple current at each frequency, from K1 to K N This is the frequency correction coefficient for each frequency. Since the frequency correction coefficient for each of the above frequency components differs for each capacitor component applied as capacitor 210, the control unit 400 stores information about the component specifications of the capacitor component to be applied as capacitor 210 in advance.

[0052]

number

[0053] Figure 11 shows an example of the relationship between the capacitor current and the capacitor load suppression control amount of the power converter according to Embodiment 8. The control unit 400 decomposes the capacitor current into a frequency component at twice the power supply voltage Vs and an integer multiple of the frequency component at twice the power supply voltage Vs using bandpass filters 401 and 402. The integer multiple of the frequency component at twice the power supply voltage Vs is, for example, a frequency component at four times the power supply voltage Vs. Then, the control unit 400 divides the frequency component at twice the power supply voltage Vs by a frequency correction coefficient using a divider 403, and divides the integer multiple of the frequency component at twice the power supply voltage Vs by a frequency correction coefficient using a divider 404. Then, the control unit 400 divides the frequency component at twice the power supply voltage Vs, which has been divided by the frequency correction coefficient, and the frequency correction coefficient The adder 405 calculates the square root of the sum of the squares of the components of the power supply voltage Vs divided by the frequency component that is an integer multiple of twice the power supply voltage Vs. The control unit 400 then uses the subtractor 406 to calculate the difference between the sum calculated by the adder 405 and a preset threshold, and changes the capacitor load suppression control amount based on the result of the subtractor 406. Note that the sum calculated by the adder 405 used in the processing of the subtractor 406 is an average value over a preset time rather than an instantaneous value, which helps to suppress frequent changes in the capacitor load suppression control amount.

[0054] The power converter 1 according to Embodiment 8 varies the control amount based on the magnitude of the square root of the sum of the squares of the frequency components at twice the power supply voltage Vs, or the frequency components at twice the power supply voltage Vs and their integer multiples, which are among the multiple frequency components included in the capacitor current. This prevents a sharp increase in the control amount required to keep the capacitor current from exceeding a certain value, which would otherwise impair energy efficiency, when the total capacitor load increases due to other frequency components that are not efficiently suppressed by control.

[0055] In the above explanation, the capacitor current was decomposed into a frequency component at twice the power supply voltage Vs and a component that is an integer multiple of the frequency component at twice the power supply voltage Vs. However, the capacitor current may also be decomposed into frequency components that are integer multiples of the power supply voltage Vs. Alternatively, the capacitor current may be decomposed into frequency components that are integer multiples of the power supply voltage Vs and a frequency component of the rotational speed of the compressor 315, or into frequency components that are integer multiples of the power supply voltage Vs and a frequency component that is twice the control cycle of the inverter 310 or converter. or at least one of the frequency components of the rotational speed of the compressor 315 and twice the frequency component of the control cycle of the inverter 310 or converter. Tsuni It is okay to disassemble it.

[0056] Embodiment 9. Figure 12 shows the configuration of the outdoor unit of the air conditioner according to Embodiment 9. The outdoor unit 900 of the air conditioner according to Embodiment 9 is equipped with a power conversion device 1 according to any of Embodiments 1 to 8.

[0057] The outdoor unit 900 of the air conditioner includes a compressor 315 incorporating the motor 314 shown in Embodiments 1 to 8, and a four-way valve 902. , room The external heat exchanger 910 is attached via refrigerant piping 912.

[0058] Inside the compressor 315 are a compression mechanism 904 for compressing the refrigerant and a motor 314 for operating the compression mechanism 904.

[0059] The outdoor unit 900 can operate in heating or cooling mode by switching the four-way valve 902. The compression mechanism 904 is driven by a motor 314 that is controlled by variable speed control.

[0060] During heating operation, as indicated by the solid arrows, the refrigerant is pressurized by the compression mechanism 904 and sent out, then returns to the compression mechanism 904 after passing through the four-way valve 902, indoor heat exchanger 906, expansion valve 908, outdoor heat exchanger 910 and the four-way valve 902.

[0061] During cooling operation, as indicated by the dashed arrows, the refrigerant is pressurized by the compression mechanism 904 and sent out, then returns to the compression mechanism 904 after passing through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902.

[0062] During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant and causes it to expand.

[0063] The configurations shown in the above embodiments are merely examples of the content, and can be combined with other known technologies. It is also possible to omit or modify parts of the configuration without departing from the gist of the invention. [Explanation of Symbols]

[0064] 1 Power converter, 2 Motor drive unit, 91 Processor, 92 Memory, 93 Storage device, 110 Commercial power supply, 120 Reactor, 130 Rectifier section, 131, 132, 133, 134 Rectifier element, 200 Smoothing section, 210 Capacitor, 310 Inverter, 311a, 311b, 311c, 311d, 311e, 311f Switching element, 312a, 312b, 312c, 312d, 312e, 312f Freewheeling diode, 313a, 313b Current detection section, 314 Motor, 315 Compressor, 400 Control section, 401, 402 Bandpass filter, 403, 404 Divider, 405 Adder, 406 Subtractor, 501 Voltage / current detection section, 502 Voltage detection unit, 601; First current detection unit, 602; Second current detection unit, 701; First voltage detection circuit, 702; Second voltage detection circuit, 801; First power detection unit, 802; Second power detection unit, 900; Outdoor unit, 902; Four-way valve, 904; Compression mechanism, 906; Indoor heat exchanger, 908; Expansion valve, 910; Outdoor heat exchanger, 912; Refrigerant piping.

Claims

1. A rectifier unit that rectifies the first AC power supplied from the commercial power source, A capacitor connected to the output terminal of the rectifier section, An inverter connected to both ends of the capacitor converts the power output from the rectifier and the capacitor into a second AC power and outputs it to a load having a motor, A control unit performs capacitor load suppression control to suppress the current flowing to the capacitor by controlling the operation of the inverter to output the second AC power, which includes pulsations corresponding to the pulsations of the power flowing from the rectifier into the capacitor, to the load from the inverter, and Equipped with, The control unit estimates the capacitor load in the capacitor, determines whether or not to perform the capacitor load suppression control based on the estimated value of the capacitor load, decomposes the capacitor current into frequency components, and performs the capacitor load suppression control if the magnitude of the square root of the sum of the squares of at least twice the power supply voltage frequency, or integer multiples of the power supply voltage frequency, is greater than or equal to a predetermined constant value, and stops the capacitor load suppression control if the magnitude of the square root of the sum of the squares of at least twice the power supply voltage frequency, or integer multiples of the power supply voltage frequency, is less than a predetermined constant value.

2. The power conversion device according to claim 1, further comprising means for detecting the voltage across the capacitor.

3. The system comprises a first current detection unit installed on the commercial power supply side of the capacitor, and a second current detection unit installed on the load side of the capacitor. The power conversion device according to claim 1, wherein the control unit estimates the capacitor load based on the detected value of the first current detection unit and the detected value of the second current detection unit.

4. The control unit, The power conversion device according to claim 1, which switches whether or not to perform the capacitor load suppression control according to the operating mode of the load.

5. The power conversion device according to claim 1, wherein the control unit starts the capacitor load suppression control when the capacitor load exceeds a preset upper limit threshold for the capacitor load, and stops the capacitor load suppression control when the capacitor load falls below a preset lower limit threshold for the capacitor load.

6. The power conversion device according to claim 1, wherein the control unit continuously adjusts the amount of pulsation corresponding to the pulsation of power flowing into the capacitor in the capacitor load suppression control.

7. The control unit starts the capacitor load suppression control when the capacitor load exceeds a preset capacitor load threshold, and stops the capacitor load suppression control when the amount of capacitor load suppression control by the capacitor load suppression control falls below a preset capacitor load suppression amount threshold. The power conversion device according to claim 1, wherein the capacitor load suppression control continuously adjusts the minimum necessary amount of pulsation corresponding to the pulsation of power flowing into the capacitor so that the estimated value of the capacitor load is less than or equal to a predetermined target load amount.

8. The power conversion device according to claim 1, wherein the control unit continuously adjusts the minimum necessary amount of pulsation in response to the pulsation of power flowing into the capacitor in the capacitor load suppression control, such that the lifespan of the capacitor estimated from the capacitor load is longer than a predetermined period.

9. An outdoor unit of an air conditioner equipped with a power conversion device according to any one of claims 1 to 8.

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