Power conversion devices, motor drive devices, and refrigeration cycle application equipment
By rectifying and boosting the voltage and controlling the operation of the inverter, the problems of smoothing capacitor degradation and device enlargement were solved, thus achieving miniaturization and cost optimization of the power conversion device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- MITSUBISHI ELECTRIC CORP
- Filing Date
- 2020-10-26
- Publication Date
- 2026-07-17
AI Technical Summary
In the prior art, the accelerated deterioration of smoothing capacitors and the increasing size of the devices lead to increased costs and larger equipment dimensions.
The AC power is rectified and boosted by the rectifier and boost unit, and the operation of the inverter is controlled by the control unit, which reduces the current flowing to the smoothing capacitor, reduces the capacitor's pulsating current and voltage ripple, and reduces the number of capacitors used and the size of the device.
It effectively suppresses the deterioration of smoothing capacitors, reduces the size and cost of the device, and at the same time reduces current and voltage ripple, improving the efficiency and reliability of the equipment.
Smart Images
Figure CN116458049B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to power conversion devices, motor drive devices, and refrigeration cycle application equipment for converting alternating current into desired power. Background Technology
[0002] Conventionally, there are power conversion devices that convert AC power supplied from an AC power source into desired AC power and supply it to loads such as air conditioners. For example, Patent Document 1 discloses a technology in which a power conversion device serving as a control device for an air conditioner uses a diode stack as a rectifier to rectify the AC power supplied from an AC power source, and then uses an inverter composed of multiple switching elements to convert the power smoothed by a smoothing capacitor into the desired AC power, and outputs it to the compressor motor serving as the load.
[0003] Existing technical documents
[0004] Patent documents
[0005] Patent Document 1: Japanese Patent Application Publication No. 7-71805 Summary of the Invention
[0006] The problem the invention aims to solve
[0007] However, according to the aforementioned prior art, the flow of a large current into the smoothing capacitor leads to an accelerated degradation of the smoothing capacitor over time. To address this problem, methods such as increasing the capacitance of the smoothing capacitor to suppress voltage ripple or using a smoothing capacitor with a high tolerance to ripple-induced degradation are considered. However, this increases the cost of the capacitor components and requires a larger device.
[0008] This disclosure was made in view of the above circumstances, and its purpose is to provide a power conversion device that can suppress the deterioration of the capacitor used for smoothing and suppress the enlargement of the device.
[0009] means for solving problems
[0010] To solve the above problems and achieve the objective, the power conversion device disclosed herein includes: a rectifier boost unit that rectifies and boosts the voltage of a first AC power supplied from a commercial power source; a capacitor connected to the output terminal of the rectifier boost unit; an inverter connected to both ends of the capacitor that converts the power output from the rectifier boost 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 rectifier boost unit and the operation of the inverter, such that the inverter outputs a second AC power to the load containing pulsations corresponding to the pulsations of the power flowing from the rectifier boost unit to the capacitor, thereby suppressing the current flowing to the capacitor.
[0011] The effects of the invention
[0012] The power conversion device disclosed herein has the effect of suppressing the deterioration of the capacitor used for smoothing and suppressing the enlargement of the device. Attached Figure Description
[0013] Figure 1 This is a diagram showing a structural example of the power conversion device according to Embodiment 1.
[0014] Figure 2 This is a diagram showing, as a comparative example, an example of the currents and the capacitor voltage of the smoothing unit's capacitor when the smoothing unit smooths the current output from the boost unit and keeps the current flowing to the inverter constant.
[0015] Figure 3 This diagram illustrates an example of the currents and capacitor voltages of the smoothing section's capacitors when the control unit of the power conversion device in Embodiment 1 controls the operation of the inverter to reduce the current flowing to the smoothing section.
[0016] Figure 4 This is a flowchart illustrating the operation of the control unit included in the power conversion device of Embodiment 1.
[0017] Figure 5 This is a diagram showing an example of the hardware structure of the control unit included in the power conversion device implementing Embodiment 1.
[0018] Figure 6 This is a diagram showing a structural example of the power conversion device according to Embodiment 2.
[0019] Figure 7 This is a diagram showing a structural example of the power conversion device according to Embodiment 3.
[0020] Figure 8 This is a diagram showing a structural example of the refrigeration cycle application device according to Embodiment 4. Detailed Implementation
[0021] Hereinafter, the power conversion device, motor drive device, and refrigeration cycle application equipment of the present disclosure will be described in detail based on the accompanying drawings.
[0022] Implementation method 1.
[0023] Figure 1This diagram illustrates a structural example of the power conversion device 1a according to Embodiment 1. The power conversion device 1a is connected to a commercial power supply 110 and a compressor 315. The power conversion device 1a converts a first AC power supply voltage Vs from the commercial power supply 110 into a second AC power supply with a desired amplitude and phase, and supplies it to the compressor 315. The power conversion device 1a includes a voltage and current detection unit 501, a rectifier unit 130, a reactor 120, a boost unit 600, a voltage detection unit 502, a smoothing unit 200, an inverter 310, current detection units 313a and 313b, and a control unit 400. Furthermore, in the power conversion device 1a, the rectifier unit 130, the reactor 120, and the boost unit 600 constitute a rectifier-boost unit 700. Additionally, the power conversion device 1a and the motor 314 included in the compressor 315 constitute a motor drive device 2a.
[0024] The voltage and current detection unit 501 detects the voltage and current values of the first AC power supply Vs from the commercial power supply 110, and outputs the detected voltage and current values to the control unit 400. The rectifier unit 130 has a bridge circuit composed of rectifier elements 131-134, which rectifies and outputs the first AC power supply Vs from the commercial power supply 110. The rectifier unit 130 performs full-wave rectification. The reactor 120 is connected between the rectifier unit 130 and the boost unit 600. The boost unit 600 has a switching element 611 and a rectifier element 621. Under the control of the control unit 400, the boost unit 600 switches the switching element 611 on and off, boosts the power output from the rectifier unit 130, and outputs the boosted power to the smoothing unit 200. In this embodiment, the boost unit 600 is controlled by the control unit 400 using full PAM (Pulse Amplitude Modulation) with the switching element 611 continuously switching. The power conversion device 1a controls the power factor of the commercial power supply 110 via the boost unit 600, making the capacitor voltage Vdc of the capacitor 210 in the smoothing unit 200 higher than the power supply voltage Vs. The rectifier-boost unit 700 rectifies the first AC power supplied from the commercial power supply 110 via the rectifier unit 130 and the boost unit 600, and boosts the voltage of the first AC power supplied from the commercial power supply 110. In this embodiment, the rectifier unit 130 and the boost unit 600 are connected in series in the rectifier-boost unit 700.
[0025] The voltage detection unit 502 detects the voltage value of the power boosted by the boost unit 600 and outputs the detected voltage value to the control unit 400. The smoothing unit 200 is connected to the output terminal of the boost unit 600 via the voltage detection unit 502. The smoothing unit 200 has a capacitor 210 as a smoothing element to smooth the power boosted by the boost unit 600. The capacitor 210 is, for example, an electrolytic capacitor or a film capacitor. The capacitor 210 has a capacitor that smooths the power rectified by the rectifier unit 130. Through smoothing, the voltage in the capacitor 210 is not the full-wave rectified waveform of the commercial power supply 110, but becomes a waveform with voltage ripple corresponding to the frequency of the commercial power supply 110 superimposed on the DC component, without large fluctuations. The frequency of this voltage ripple is twice the frequency of the power supply voltage Vs when the commercial power supply 110 is single-phase, and six times the frequency becomes the main component when the commercial power supply 110 is three-phase. When the power input from commercial power supply 110 remains constant compared to the power output from inverter 310, the amplitude of the voltage ripple is determined by the capacitance of capacitor 210. For example, the voltage ripple generated in capacitor 210 pulsates within a range where the maximum value is less than twice the minimum value.
[0026] The inverter 310 is connected to the two ends of the smoothing section 200, i.e., the capacitor 210. The inverter 310 has switching elements 311a-311f and freewheeling diodes 312a-312f. Under the control of the control unit 400, the inverter 310 switches the switching elements 311a-311f on and off, converting the power output from the rectifier boost section 700 and the smoothing section 200 into a second AC power with the desired amplitude and phase, and outputting it to the compressor 315. Current detection units 313a and 313b detect the current value of one phase of the three-phase current output from the inverter 310, and output the detected current value to the control unit 400. Furthermore, by obtaining the current values of two phases of the three-phase current output from the inverter 310, the control unit 400 can calculate the current value of the remaining phase output from the inverter 310. The compressor 315 is a load having a compressor drive motor 314. The motor 314 rotates according to the amplitude and phase of the second AC power supplied by the inverter 310, and performs a compression operation. For example, in the case where the compressor 315 is a hermetic compressor used in air conditioners, the load torque of the compressor 315 is mostly considered to be a constant torque load.
[0027] In addition, in the power conversion device 1a, Figure 1 The configurations of the structures shown are examples, and the configurations of the structures are not limited to... Figure 1The example shown. Depending on the configuration of the reactor 120, the rectifier boost unit 700 may not include the reactor 120. In the following description, the voltage and current detection units 501, 502, and 313a and 313b will sometimes be collectively referred to as detection units. Furthermore, the voltage and current values detected by the voltage and current detection unit 501, the voltage value detected by the voltage detection unit 502, and the current value detected by the current detection units 313a and 313b will sometimes be referred to as detection values.
[0028] The control unit 400 obtains the voltage and current values of the first AC power supply voltage Vs from the voltage and current detection unit 501, the voltage value of the power boosted by the boost unit 600 from the voltage detection unit 502, and the current value of the second AC power with the desired amplitude and phase converted by the inverter 310 from the current detection units 313a and 313b. The control unit 400 uses the detection values from each detection unit to control the operation of the boost unit 600 of the rectifier boost unit 700, specifically the switching of the switching elements 611 of the boost unit 600. Furthermore, the control unit 400 uses the detection values from each detection unit to control the operation of the inverter 310, specifically the switching of the switching elements 311a to 311f of the inverter 310. In this embodiment, the control unit 400 controls the operation of the rectifier boost unit 700. The control unit 400 controls the operation of the rectifier boost unit 700, performing power factor improvement control on the first AC power supplied from the commercial power supply 110 and average voltage control on the capacitor 210 of the smoothing unit 200. Furthermore, the control unit 400 controls the operation of the inverter 310, causing it to output a second AC power to the compressor 315, which is a load. This second AC power includes pulsations corresponding to the pulsations of the power flowing from the rectifier 130 to the capacitor 210 of the smoothing unit 200. The pulsations corresponding to the pulsations of the power flowing into the capacitor 210 of the smoothing unit 200 are, for example, pulsations that vary according to the frequency of the pulsations of the power flowing into the capacitor 210 of the smoothing unit 200. Thus, the control unit 400 suppresses the current flowing into the capacitor 210 of the smoothing unit 200. Additionally, the control unit 400 may use only a portion of the detection values obtained from each detection unit for control, rather than all of them.
[0029] Next, the operation of the control unit 400 provided in the power conversion device 1a will be explained. In this embodiment, the load generated by the inverter 310 and the compressor 315 in the power conversion device 1a can be considered as a fixed load. The following explanation assumes that the smoothing unit 200 is connected to a constant current load, taking into account the current output from the smoothing unit 200. Here, as... Figure 1As shown, let the current flowing from the boost unit 600 be current I1, the current flowing to the inverter 310 be current I2, and the current flowing from the smoothing unit 200 be current I3. Current I2 is the combined current 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. For current I3, let the discharge direction of the smoothing unit 200 be the positive direction, and the charging direction of the smoothing unit 200 be the negative direction. That is, sometimes current flows into the smoothing unit 200, and sometimes current flows out of the smoothing unit 200.
[0030] Figure 2 This diagram illustrates, as a comparative example, an example of currents I1 to I3 and the capacitor voltage Vdc of capacitor 210 in the smoothing unit 200 when the current output from the boost unit 600 is smoothed by the smoothing unit 200 and the current I2 flowing to the inverter 310 is fixed. From top to bottom, currents I1, I2, and I3, and the capacitor voltage Vdc of capacitor 210 corresponding to current I3 are shown. The vertical axis of currents I1, I2, and I3 represents the current value, and the vertical axis of capacitor voltage Vdc represents the voltage value. The horizontal axis represents time t. Furthermore, the carrier component of inverter 310 is actually superimposed on currents I2 and I3, but this is omitted here. The same applies thereafter. Figure 2 As shown, in the power conversion device 1a, assuming that the current I1 flowing from the boost unit 600 is sufficiently smoothed by the smoothing unit 200, the current I2 flowing to the inverter 310 becomes a fixed current value. However, a large current I3 flows to the capacitor 210 of the smoothing unit 200, which becomes the main cause of degradation. Therefore, in this embodiment, in the power conversion device 1a, the control unit 400 controls the current I2 flowing to the inverter 310, that is, controls the operation of the inverter 310, so as to reduce the current I3 flowing to the smoothing unit 200.
[0031] Figure 3 This diagram illustrates an example where the control unit 400 of the power conversion device 1a in Embodiment 1 controls the operation of the inverter 310, thereby reducing the current I3 flowing to the smoothing section 200, and the capacitor voltage Vdc of the capacitor 210 in the smoothing section 200. From top to bottom, the diagram shows the currents I1, I2, and I3, and the capacitor voltage Vdc of the capacitor 210 generated corresponding to the current I3. The vertical axis for currents I1, I2, and I3 represents the current value, and the vertical axis for capacitor voltage Vdc represents the voltage value. The horizontal axis represents time t. The control unit 400 of the power conversion device 1a controls the operation of the inverter 310 to reduce the currents I1 to I3 and the capacitor voltage Vdc of the smoothing section 200. Figure 3 The current I2 shown flows to inverter 310, thus, with Figure 2Compared to the previous example, the frequency component of the current flowing from the boost section 600 to the smoothing section 200 can be reduced, thereby reducing the current I3 flowing to the smoothing section 200. Specifically, the control section 400 controls the operation of the inverter 310 so that a current I2 containing a pulsating current with the frequency component of the current I1 as the main component flows to the inverter 310.
[0032] The frequency component of current I1 is determined by the frequency of the AC current supplied from commercial power supply 110, the structure of rectifier 130, and the switching speed of switching element 611 in boost unit 600. Therefore, control unit 400 can set the frequency component of the pulsating current overlapping with current I2 to a component with a predetermined amplitude and phase. The frequency component of the pulsating current overlapping with current I2 becomes a similar waveform to the frequency component of current I1. By bringing the frequency component of the pulsating current overlapping with current I2 closer to the frequency component of current I1, control unit 400 can reduce the current I3 flowing to smoothing unit 200 and reduce the pulsating voltage generated in capacitor voltage Vdc.
[0033] The control unit 400 controls the pulsation of the current flowing to the inverter 310 by controlling the operation of the inverter 310, which is the same as controlling the pulsation of the second AC power output from the inverter 310 to the compressor 315. The control unit 400 controls the operation of the inverter 310 such that the pulsation contained in the second AC power output from the inverter 310 is less than the pulsation of the power output from the rectifier boost unit 700. The control unit 400 controls the amplitude and phase of the pulsation contained in the second AC power output from the inverter 310 such that the voltage ripple of the capacitor voltage Vdc, i.e., the voltage ripple generated in the capacitor 210, is less than the voltage ripple generated in the capacitor 210 when the second AC power output from the inverter 310 does not contain pulsations corresponding to the pulsation of the power flowing into the capacitor 210. When the second AC power output from the inverter 310 does not contain pulsations corresponding to the pulsation of the power flowing into the capacitor 210, it means... Figure 2 The controls shown.
[0034] Furthermore, the AC current supplied from the commercial power supply 110 is not particularly limited; it can be single-phase or three-phase. The control unit 400 determines the frequency component of the pulsating current overlapping with the current I2 based on the first AC power supplied from the commercial power supply 110. Specifically, when the first AC power supplied from the commercial power supply 110 is single-phase, the control unit 400 controls the pulsating waveform of the current I2 flowing to the inverter 310 to be a shape obtained by adding a DC component to a pulsating waveform whose main component is a frequency component that is twice the frequency of the first AC power. Alternatively, when the first AC power supplied from the commercial power supply 110 is three-phase, the control unit 400 controls the pulsating waveform of the current I2 flowing to the inverter 310 to be a shape obtained by adding a DC component to a pulsating waveform whose main component is a frequency component that is six times the frequency of the first AC power. The pulsating waveform can 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 also add at least one frequency component of the sine wave whose frequency is an integer multiple of the sine wave to the pulsating waveform with a predetermined amplitude. Furthermore, the pulsating waveform may be a rectangular wave or a triangular wave. In this case, the control unit 400 may also set the amplitude and phase of the pulsating waveform to predetermined values.
[0035] The control unit 400 can also use the voltage applied to the capacitor 210 or the current flowing to the capacitor 210 to calculate the amount of pulsation contained in the second AC power output from the inverter 310, and can also use the voltage or current of the first AC power supplied from the commercial power supply 110 to calculate the amount of pulsation contained in the second AC power output from the inverter 310.
[0036] Furthermore, when the control unit 400 controls the inverter 310 to output a second AC power containing a frequency component different from the frequency component of the first AC power supplied from the commercial power supply 110 to the compressor 315, the frequency component contained in the second AC power output from the inverter 310 to the compressor 315 may be superimposed on the drive signal used to turn the switching element 611 of the boost unit 600 on and off. That is, the control unit 400 controls the operation of the rectifier-boost unit 700, specifically the operation of the switching element 611 of the boost unit 600, so that the power output from the rectifier-boost unit 700 includes a frequency variation component. When the first AC power supplied from the commercial power supply 110 is single-phase, this frequency variation component is a frequency component other than twice the frequency of the first AC power in the power pulsation of the second AC power output from the inverter 310 to the compressor 315; or when the first AC power supplied from the commercial power supply 110 is three-phase, this frequency variation component is a frequency component other than six times the frequency of the first AC power in the power pulsation of the second AC power output from the inverter 310 to the compressor 315. The control unit 400 can control the frequency variation component using command values for the commercial power supply 110, or it can control the frequency variation component to be a component that is not an integer multiple up to the 40th order of the frequency of the first AC power supplied from the commercial power supply 110, or to a predetermined value, such as a desired specification value or lower.
[0037] The operation of the control unit 400 is explained using a flowchart. Figure 4 This is a flowchart illustrating the operation of the control unit 400 included in the power conversion device 1a according to Embodiment 1. The control unit 400 obtains detection values from each detection unit of the power conversion device 1a (step S1). Based on the obtained detection values, the control unit 400 controls the operation of the inverter 310, thereby reducing the current I3 flowing to the smoothing unit 200 (step S2). Based on the obtained detection values, the control unit 400 controls the operation of the boost unit 600, thereby performing power factor improvement control of the commercial power supply 110 and average voltage control of the capacitor voltage Vdc of the capacitor 210 of the smoothing unit 200 (step S3).
[0038] Next, the hardware structure of the control unit 400 of the power conversion device 1a will be described. Figure 5 This figure shows an example of the hardware structure of the control unit 400 included in the power conversion device 1a implementing Embodiment 1. The control unit 400 is implemented by a processor 91 and a memory 92.
[0039] Processor 91 is a CPU (also known as a Central Processing Unit, Central Processing Device, Processing Device, Arithmetic Device, Microprocessor, Microcomputer, Processor, DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). Memory 92 can exemplify non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (Electrically Erasable Programmable ROM). However, memory 92 is not limited to these and can also be a magnetic disk, optical disk, high-density disk, mini-disk, or DVD (Digital Versatile Disc).
[0040] As explained above, according to this embodiment, in the power conversion device 1a, the control unit 400 controls the operation of the inverter 310 based on the detection values obtained from each detection unit. It superimposes the 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 to the inverter 310, thereby reducing the current I3 flowing to the smoothing unit 200. As a result, in the power conversion device 1a, by reducing the current I3 flowing to the smoothing unit 200, a capacitor with a small ripple current tolerance can be used compared to the case without the control of this embodiment. Furthermore, in the power conversion device 1a, by reducing the pulsating voltage of the capacitor voltage Vdc, the capacitance of the mounted capacitor 210 can be reduced compared to the case without the control of this embodiment. For example, in the case where the smoothing unit 200 is composed of multiple capacitors 210, the power conversion device 1a can reduce the number of capacitors 210 constituting the smoothing unit 200.
[0041] Furthermore, the power conversion device 1a controls the operation of the inverter 310 so that the pulsation in the second AC power is less than the pulsation of the power output from the rectifier boost unit 700. This suppresses the excessive pulsation component that overlaps with the current I2 flowing to the inverter 310. The overlap of pulsation components increases the effective value of the current flowing through the inverter 310, motor 314, etc., compared to the non-overlapping state. However, by suppressing the excessive overlap of pulsation components, a system that suppresses the current capacity of the inverter 310, the increase in inverter 310 losses, and the increase in motor 314 losses can be provided.
[0042] Furthermore, by performing the control described in this embodiment, the power conversion device 1a can suppress the vibration of the compressor 315 caused by the pulsation of the current I2.
[0043] Furthermore, the power conversion device 1a performs a voltage boosting operation via the boost unit 600, which increases the capacitor voltage Vdc of the capacitor 210, thereby expanding the output voltage range of the inverter 310. In the power conversion device 1a, the control unit 400 reduces the pulsation of the current I3 and the capacitor voltage Vdc caused by the pulsating frequency component in the second AC power output from the inverter 310 by superimposing it onto the drive signal for the switching element 611 of the boost unit 600.
[0044] Implementation method 2.
[0045] In Embodiment 2, a power conversion device will be described that has a rectifier-boost unit with a circuit structure different from that of the rectifier-boost unit 700 of the power conversion device 1a in Embodiment 1.
[0046] Figure 6 This is a diagram showing a structural example of the power conversion device 1b according to Embodiment 2. The power conversion device 1b is relative to... Figure 1 In the power conversion device 1a of Embodiment 1 shown, the rectifier-boost unit 700 is replaced with a rectifier-boost unit 701. Furthermore, the motor drive unit 2b is composed of the power conversion device 1b and the motor 314 included in the compressor 315. The rectifier-boost unit 701 has switching elements 611-614 and rectifier elements 621-624 connected in parallel with one of the switching elements 611-614. Under the control of the control unit 400, the rectifier-boost unit 701 turns the switching elements 611-614 on and off, rectifies and boosts the first AC power output from the commercial power supply 110, and outputs the boosted power to the smoothing unit 200. In this embodiment, the rectifier-boost unit 701 is controlled by the control unit 400 using full PAM (Power Actuation and Modulation) with the switching elements 611-614 continuously switching. The power conversion device 1b performs power factor improvement control on the commercial power supply 110 through the rectifier boost unit 701, so that the capacitor voltage Vdc of the capacitor 210 of the smoothing unit 200 becomes a voltage higher than the power supply voltage Vs.
[0047] The control unit 400 obtains the voltage and current values of the first AC power supply voltage Vs from the voltage and current detection unit 501, the voltage value of the power boosted by the rectifier boost unit 701 from the voltage detection unit 502, and the current value of the second AC power with the desired amplitude and phase converted by the inverter 310 from the current detection units 313a and 313b. The control unit 400 uses the detection values detected by each detection unit to control the operation of the inverter 310, specifically the switching elements 311a to 311f of the inverter 310. Furthermore, the control unit 400 uses the detection values detected by each detection unit to control the operation of the rectifier boost unit 701, specifically the switching elements 611 to 614 of the rectifier boost unit 701. By controlling the operation of the rectifier boost unit 701 and the inverter 310, the control unit 400 achieves the same effects as described in Embodiment 1.
[0048] Other operations in the power conversion device 1b are the same as those in the power conversion device 1a of Embodiment 1. In this case, the power conversion device 1b can also achieve the same effect as the power conversion device 1a of Embodiment 1.
[0049] Implementation method 3.
[0050] In Embodiment 3, a power conversion device will be described that has a rectifier-boost unit with a circuit structure different from that of the rectifier-boost unit 700 of the power conversion device 1a in Embodiment 1 and the rectifier-boost unit 701 of the power conversion device 1b in Embodiment 2.
[0051] Figure 7 This is a diagram showing a structural example of the power conversion device 1c according to Embodiment 3. The power conversion device 1c is relative to... Figure 1In the power conversion device 1a of Embodiment 1 shown, the rectifier-boost unit 700 is replaced by a rectifier-boost unit 702. Furthermore, the motor drive unit 2c is composed of the power conversion device 1c and the motor 314 included in the compressor 315. The rectifier-boost unit 702 includes a reactor 120, a rectifier 130, and a boost unit 601. In Embodiment 1, the boost unit 600 is connected in series with the rectifier 130 inside the power conversion device 1a, which is the downstream stage of the rectifier 130. However, in Embodiment 3, the boost unit 601 is connected in parallel with the rectifier 130 inside the power conversion device 1c. The boost unit 601 includes rectifier elements 621-624 and a switching element 611. The boost unit 601, under the control of the control unit 400, turns the switching element 611 on and off to boost the first AC power output from the commercial power supply 110, and outputs the boosted power to the rectifier 130. In this embodiment, the boost unit 601 of the rectifier boost unit 702 is controlled by the control unit 400 through a simple switch that performs one or more switching operations of the switching element 611 within half a cycle of the frequency of the first AC power supplied from the commercial power supply 110. The power conversion device 1c performs power factor improvement control of the commercial power supply 110 through the boost unit 601, so that the capacitor voltage Vdc of the capacitor 210 of the smoothing unit 200 becomes a voltage higher than the power supply voltage Vs.
[0052] The control unit 400 obtains the voltage and current values of the first AC power supply voltage Vs 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 with the desired amplitude and phase converted by the inverter 310 from the current detection units 313a and 313b. The control unit 400 uses the detection values detected by each detection unit to control the operation of the inverter 310, specifically the switching on / off of the switching elements 311a to 311f of the inverter 310. Furthermore, the control unit 400 uses the detection values detected by each detection unit to control the operation of the boost unit 601, specifically the switching on / off of the switching element 611 of the boost unit 601. The control unit 400 controls the operation of the boost unit 601 and the inverter 310 to achieve the same effect as described in Embodiment 1.
[0053] Other operations in the power conversion device 1c are the same as those in the power conversion device 1a of Embodiment 1. In this case, the power conversion device 1c can also achieve the same effect as the power conversion device 1a of Embodiment 1. Furthermore, compared with the power conversion device 1a of Embodiment 1 and the power conversion device 1b of Embodiment 2, the power conversion device 1c suppresses the number of switching operations, thus reducing losses and achieving low noise. In addition, the rectifier section 130 and the boost section 601 of the power conversion device 1c are connected in parallel, so the boost section 601 does not switch when the switching element 611 is not required, thereby reducing the number of current-carrying elements and achieving low losses.
[0054] Implementation method 4.
[0055] Figure 8 This is a diagram illustrating a structural example of the refrigeration cycle application device 900 according to Embodiment 4. The refrigeration cycle application device 900 of Embodiment 4 includes the power conversion device 1a described in Embodiment 1. Alternatively, instead of power conversion device 1a, the refrigeration cycle application device 900 may include power conversion device 1b described in Embodiment 2, or power conversion device 1c described in Embodiment 3. The refrigeration cycle application device 900 of Embodiment 4 can be applied to products with refrigeration cycles, such as air conditioners, cold storage rooms, freezers, and heat pump water heaters. Furthermore, in... Figure 8 In the text, structural elements that have the same function as in Embodiment 1 are labeled with the same reference numerals as in Embodiment 1.
[0056] In the refrigeration cycle application equipment 900, a compressor 315 with a built-in motor 314, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, as described in Embodiment 1, are installed via refrigerant piping 912.
[0057] Inside the compressor 315, there is a compression mechanism 904 for compressing refrigerant and a motor 314 for actuating the compression mechanism 904.
[0058] The refrigeration cycle application equipment 900 can operate in heating or cooling mode by switching the four-way valve 902. The compressor 904 is driven by a motor 314 that is controlled to have a variable speed.
[0059] During heating operation, as shown by the solid arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, then returns to the compression mechanism 904 through the four-way valve 902, indoor heat exchanger 906, expansion valve 908, outdoor heat exchanger 910, and the four-way valve 902.
[0060] During refrigeration operation, as shown by the dashed arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, then returns to the compression mechanism 904 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.
[0061] During heating operation, the indoor heat exchanger 906 acts as a condenser, releasing heat, while the outdoor heat exchanger 910 acts as an evaporator, absorbing heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser, releasing heat, while the indoor heat exchanger 906 acts as an evaporator, absorbing heat. The expansion valve 908 depressurizes the refrigerant, causing it to expand.
[0062] The structure shown in the above embodiments is an example, and it can also be combined with other known technologies, and the embodiments can be combined with each other. Some parts of the structure can also be omitted or changed without departing from the spirit.
[0063] Explanation of reference numerals in the attached figures
[0064] 1a, 1b, 1c power conversion devices; 2a, 2b, 2c motor drive devices; 110 commercial power supply; 120 reactor; 130 rectifier section; 131-134, 621-624 rectifier elements; 200 smoothing section; 210 capacitor; 310 inverter; 311a-311f, 611-614 switching elements; 312a-312f freewheeling diodes; 313a, 313b current detection sections; 314 motor; 315 compressor; 400 control section; 501 voltage and current detection section; 502 voltage detection section; 600, 601 boost section; 700, 701, 702 rectifier boost section; 900 refrigeration cycle application equipment; 902 four-way valve; 904 compression mechanism; 906 indoor heat exchanger; 908 expansion valve; 910 outdoor heat exchanger; 912 refrigerant piping.
Claims
1. A power conversion device comprising: The rectifier boost unit rectifies the first AC power supplied from the commercial power source and boosts the voltage of the first AC power. A capacitor connected to the output terminal of the rectifier boost section; An inverter, connected to both ends of the capacitor, converts the power output from the rectifier boost unit and the capacitor into a second AC power and outputs it to a load with a motor. A voltage and current detection unit is disposed between the commercial power supply and the rectifier boost unit to detect the voltage and current values of the first AC power supplied from the commercial power supply. A voltage detection unit is disposed between the rectifier and the capacitor to detect the voltage value of the power rectified and boosted by the rectifier and the capacitor. A current detection unit is disposed between the inverter and the load to detect the current value of the second AC power output from the inverter; as well as The control unit is configured to obtain the voltage and current values of the first AC power from the voltage and current detection unit as detection values, obtain the voltage value of the power rectified and boosted by the rectifier and boost unit from the voltage detection unit as a detection value, and obtain the current value of the second AC power from the current detection unit as a detection value. Based on the detection values, the control unit controls the operation of the rectifier and boost unit, and controls the operation of the inverter only based on the detection values, so that a current with a pulsating current superimposed on the frequency component of the current flowing from the rectifier and boost unit flows to the inverter, and outputs the second AC power containing pulsations corresponding to the pulsations of the power flowing from the rectifier and boost unit to the capacitor from the inverter to the load, and suppresses the current flowing to the capacitor.
2. The power conversion device according to claim 1, wherein, The control unit controls the operation of the rectifier boost unit, performs power factor improvement control on the first AC power supplied from the commercial power supply, and controls the average voltage of the capacitor.
3. The power conversion device according to claim 1 or 2, wherein, The control unit controls the operation of the inverter so that the pulsation in the second AC power output from the inverter is less than the pulsation in the power output from the rectifier boost unit.
4. The power conversion device according to any one of claims 1 to 3, wherein, The control unit controls the amplitude and phase of the pulsations contained in the second AC power output from the inverter, such that the voltage ripple generated in the capacitor is less than the voltage ripple generated in the capacitor when the second AC power output from the inverter does not contain pulsations corresponding to the pulsations of the power flowing into the capacitor.
5. The power conversion device according to any one of claims 1 to 4, wherein, The control unit controls the amplitude and phase of the pulsations contained in the second AC power output from the inverter, such that the current ripple flowing into and out of the capacitor is less than the current ripple generated in the capacitor when the second AC power output from the inverter does not contain pulsations corresponding to the pulsations of the power flowing into the capacitor.
6. The power conversion device according to any one of claims 1 to 5, wherein, The rectifier boost section includes: The rectifier section has multiple rectifier elements; and The boost unit includes a rectifier element and a switching element that is controlled to be turned on and off by the control unit. The rectifier section is connected in series or in parallel with the boost section.
7. The power conversion device according to any one of claims 1 to 5, wherein, The rectifier boost section includes: Multiple switching elements are controlled to be switched on and off by the control unit; and Multiple rectifier elements are connected in parallel with one of the multiple switching elements.
8. The power conversion device according to any one of claims 1 to 7, wherein, The control unit also controls the operation of the rectifier boost unit, so that the power output from the rectifier boost unit includes a frequency component with the following variation frequency component: when the first AC power is single-phase, the variation frequency component is a frequency component other than twice the frequency of the first AC power in the pulsation of the second AC power output from the inverter; or when the first AC power is three-phase, the variation frequency component is a frequency component other than six times the frequency of the first AC power in the pulsation of the second AC power output from the inverter.
9. The power conversion device according to claim 8, wherein, The control unit uses command values for the commercial power supply to control the variable frequency components.
10. The power conversion device according to claim 8, wherein, The control unit controls the variable frequency component to be a component that is not an integer multiple of the 40th order of the frequency of the first AC power, or to be below a predetermined value.
11. The power conversion device according to any one of claims 1 to 10, wherein, The capacitor is an electrolytic capacitor or a film capacitor.
12. The power conversion device according to any one of claims 1 to 11, wherein, The maximum value of the voltage ripple generated in the capacitor is less than twice the minimum value.
13. The power conversion device according to any one of claims 1 to 12, wherein, The rectifier boost section performs full-wave rectification, and the voltage generated in the capacitor is not the full-wave rectified waveform of the commercial power supply.
14. A motor drive device, wherein, The motor drive device includes the power conversion device according to any one of claims 1 to 13.
15. A refrigeration cycle application device, wherein, The refrigeration cycle application equipment includes the power conversion device according to any one of claims 1 to 13.