Power conversion device

Abstract

To provide a power conversion device capable of reducing a ripple generated at a bulk capacitor.SOLUTION: A power conversion device 1 includes: an AC / DC converter circuit 10 connected to an AC power-supply 2; a bulk capacitor C1 connected to an output terminal of the AC / DC converter circuit 10 in parallel; a DC / DC converter circuit 20 having an input terminal connected to the bulk capacitor C1 in parallel and an output terminal connected to a battery 3; a DC / AC inverter circuit 30 having an input terminal connected to the bulk capacitor C1 in parallel and an output terminal connected to an AC power output part 4; and a control circuit 40. The control circuit 40 observes an AC voltage V1 of the AC power-supply 2, and controls an AC voltage V2 which is output from the DC / AC inverter circuit 30 according to the AC voltage V1 of the AC power-supply 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] Patent Document 1 describes a power conversion device that includes an AC / DC converter and a DC / DC converter connected via a DC capacitor as a bulk capacitor, and converts AC power from a commercial frequency AC power source and DC power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6026049 Summary of the Invention [Problem to be solved by the invention]

[0004] In the power conversion device of Patent Document 1, a large ripple at an extremely low frequency twice the commercial frequency is superimposed on the bulk capacitor, which in turn superimposes a large ripple at an extremely low frequency twice the commercial frequency on the output current of the DC / DC converter. As a result, excessive ripple occurs in the smoothing capacitor connected to the output of the DC / DC converter, and to avoid this, the capacitance of the smoothing capacitor must be increased, which requires an increase in the size of the device. Furthermore, a reactor is required on the output side of the DC / DC converter to smooth the output current of the DC / DC converter, which further requires an increase in the size of the device.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a power conversion device capable of reducing ripples occurring in a bulk capacitor. [Means for solving the problem]

[0006] A power conversion device according to one aspect of the present invention includes an AC / DC converter circuit connected to an AC power source, a bulk capacitor connected in parallel to an output terminal of the AC / DC converter circuit, a DC / DC converter circuit having an input terminal connected in parallel to the bulk capacitor and an output terminal connected to a battery, a DC / AC inverter circuit having an input terminal connected in parallel to the bulk capacitor and an output terminal connected to an AC power output unit, and a control circuit. The control circuit monitors the AC voltage of the AC power source and controls the AC voltage output by the DC / AC inverter circuit in accordance with the AC voltage of the AC power source. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a power conversion device that can reduce ripples occurring in a bulk capacitor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit diagram showing the configuration of a power conversion device according to a first embodiment. [Figure 2A] FIG. 2A is a waveform diagram when control for synchronizing phases is not performed in the power conversion device according to the first embodiment. [Figure 2B] FIG. 2B is a waveform diagram when control for synchronizing phases is performed in the power conversion device according to the first embodiment. [Figure 3] FIG. 3 is a time chart for explaining the operation of the power conversion device according to the second embodiment. [Figure 4A] FIG. 4A is a waveform diagram when control to shift a carrier signal is not performed in the power conversion device according to the second embodiment. [Figure 4B] FIG. 4B is a waveform diagram when control is performed to shift the carrier signal in the power conversion device according to the second embodiment. [Figure 5] FIG. 5 is a circuit diagram showing the configuration of a power conversion device according to the third embodiment. [Figure 6A]FIG. 6A is a waveform diagram when control for synchronizing the phases is not performed in the power conversion device according to the third embodiment. [Figure 6B] FIG. 6B is a waveform diagram when control for synchronizing the phases is performed in the power conversion device according to the third embodiment. [Figure 7] FIG. 7 is a time chart for explaining the operation of the power conversion device according to the fourth embodiment. [Figure 8A] FIG. 8A is a waveform diagram when control to shift the carrier signal is not performed in the power conversion device according to the fourth embodiment. [Figure 8B] FIG. 8B is a waveform diagram when control is performed to shift the carrier signal in the power conversion device according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A power conversion device according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and the description thereof will be omitted.

[0010] (First embodiment) The first embodiment will be described with reference to FIG. FIG. 1 is a circuit diagram showing the configuration of a power conversion device 1 according to a first embodiment. The power conversion device 1 can be used, for example, as an on-board charging device mounted on an electric vehicle or the like. For example, AC power with an effective value of 200 V and a frequency of 50 Hz (or 60 Hz) is input to the power conversion device 1 from an AC power source 2, which is a commercial power source. As a result, the power conversion device 1 charges a battery 3 with the DC power, and outputs AC power with an effective value of 100 V and a commercial frequency of 50 Hz (or 60 Hz) to an AC power output unit 4 as, for example, a household AC output to supply to an AC load. The battery 3 is, for example, a high-power battery that is a secondary battery such as a lithium-ion battery (LIB) mounted on an electric vehicle. The output voltage of the battery 3 is, for example, a DC voltage of about 300 to 400 V.

[0011] The power conversion device 1 includes a power factor correction circuit 10, a bulk capacitor C1, a DC / DC converter circuit 20, a smoothing capacitor C2, a DC / AC inverter circuit 30, and a control circuit 40.

[0012] The power factor correction circuit 10 is capable of bidirectional conversion between AC power and DC power and is a circuit for correcting the power factor during power conversion. The power factor correction circuit 10 functions as an AC / DC converter circuit when converting AC power to DC power, and functions as a DC / AC inverter circuit when converting DC power to AC power. In the first embodiment, the power factor correction circuit 10 functions as an AC / DC converter circuit that converts AC power to DC power. The DC / DC converter circuit 20 is for performing voltage conversion of DC power and is capable of bidirectional operation. The DC / AC inverter circuit 30 converts DC power to AC power and outputs it to the AC power output unit 4.

[0013] The power factor correction circuit 10 has a first terminal as a pair of input terminals connected in parallel to an AC power supply 2, and a second terminal as a pair of output terminals connected in parallel to a bulk capacitor C1. The DC / DC converter circuit 20 has a first terminal as a pair of input terminals connected in parallel to the bulk capacitor C1, and is connected in parallel to a battery 3 via a smoothing capacitor C2 connected in parallel to a second terminal as a pair of output terminals. The DC / AC inverter circuit 30 has a first terminal as a pair of input terminals connected in parallel to the bulk capacitor C1, and a second terminal as a pair of output terminals connected in parallel to an AC power output unit 4. The control circuit 40 controls the power factor correction circuit 10, the DC / DC converter circuit 20, and the DC / AC inverter circuit 30.

[0014] The power factor correction circuit 10 is illustrated as an example of an existing power factor correction circuit using multiple switching elements, but is not limited to this and may be replaced with a power factor correction circuit of another configuration depending on the application. The power factor correction circuit 10 includes a full bridge circuit of semiconductor switching elements Q11-Q14, a reactor L11, and a reactor L12. A first main electrode of semiconductor switching element Q11 and a second main electrode of semiconductor switching element Q12 are connected in series. A first main electrode of semiconductor switching element Q13 and a second main electrode of semiconductor switching element Q14 are connected in series. The reactor L12 is connected between the connection point of semiconductor switching elements Q11 and Q12 and one electrode (e.g., anode) of the AC power source 2. The reactor L11 is connected between the connection point of semiconductor switching elements Q13 and Q14 and the other electrode (e.g., cathode) of the AC power source 2. The ends of the reactors L11 and L12 connected to the AC power source 2 form a pair of first terminals. The connection point between the first main electrodes of semiconductor switching elements Q12 and Q14 and the connection point between the second main electrodes of semiconductor switching elements Q11 and Q13 form a pair of second terminals, which are connected in parallel to bulk capacitor C1. Each of semiconductor switching elements Q11-Q14 has a reverse diode. The reverse diode may be a parasitic diode of semiconductor switching elements Q11-Q14. While N-channel IGBTs are used for semiconductor switching elements Q11-Q14, this is not limiting and power semiconductor elements such as N-channel MOSFETs may also be used. In addition, power factor correction circuit 10 is provided with AC voltage detection circuit 11 for detecting the frequency and phase of AC voltage V1 from AC power source 2.

[0015] The bulk capacitor C1 has a large capacitance of, for example, about 2000 μF, and serves to stabilize the voltage before the DC / DC converter circuit 20 in order to charge the battery 3 stably.

[0016] DC / DC converter circuit 20 is shown as an example of an existing LLC resonant DC / DC converter circuit using multiple switching elements, but is not limited to this and may be replaced with a DC / DC converter circuit of other configurations depending on the application. DC / DC converter circuit 20 includes a full-bridge circuit of semiconductor switching elements Q21-Q24, reactor L20, capacitor C21, high-frequency isolation transformer T1, capacitor C22, and a full-bridge circuit of semiconductor switching elements Q25-Q28. A first main electrode of semiconductor switching element Q21 is connected in series to a second main electrode of semiconductor switching element Q22. A first main electrode of semiconductor switching element Q23 is connected in series to a second main electrode of semiconductor switching element Q24. The junction of the first main electrodes of semiconductor switching elements Q22 and Q24 and the junction of the second main electrodes of semiconductor switching elements Q21 and Q23 form a pair of first terminals connected in parallel to bulk capacitor C1. A series circuit consisting of reactor L20, primary coil L21 of high-frequency isolation transformer T1, and capacitor C21 is connected between the junction of semiconductor switching elements Q21, Q22 and the junction of semiconductor switching elements Q23, Q24. A first main electrode of semiconductor switching element Q25 is connected in series with a second main electrode of semiconductor switching element Q26. A first main electrode of semiconductor switching element Q27 is connected in series with a second main electrode of semiconductor switching element Q28. A series circuit consisting of secondary coil L22 of high-frequency isolation transformer T1 and capacitor C22 is connected between the junction of semiconductor switching elements Q25, Q26 and the junction of semiconductor switching elements Q27, Q28. The junction of the first main electrodes of semiconductor switching elements Q26, Q28 and the junction of the second main electrodes of semiconductor switching elements Q25, Q27 form a pair of second terminals, which are connected in parallel to battery 3 via smoothing capacitor C2 connected in parallel. Each of semiconductor switching elements Q21-Q28 is equipped with a reverse diode. The reverse diodes may be parasitic diodes of semiconductor switching elements Q21-Q28. Although N-channel IGBTs are used for semiconductor switching elements Q21-Q28, this is not limiting and other power semiconductor elements such as N-channel MOSFETs can also be used.

[0017] The DC / AC inverter circuit 30 is illustrated as an example of an existing DC / AC inverter circuit using multiple switching elements, but is not limited to this and may be replaced with a DC / AC converter circuit of another configuration depending on the application. The DC / AC inverter circuit 30 includes a full-bridge circuit of semiconductor switching elements Q31-Q34, reactor L31, and reactor L32. The first main electrode of semiconductor switching element Q31 and the second main electrode of semiconductor switching element Q32 are connected in series. The first main electrode of semiconductor switching element Q33 and the second main electrode of semiconductor switching element Q34 are connected in series. The junction of the first main electrodes of semiconductor switching elements Q32 and Q34 and the junction of the second main electrodes of semiconductor switching elements Q31 and Q33 form a pair of first terminals connected in parallel to bulk capacitor C1. Reactor L32 is connected between the junction of semiconductor switching elements Q31 and Q32 and one electrode (e.g., the anode) of AC power output unit 4. Reactor L31 is connected between the connection point of semiconductor switching elements Q33, Q34 and the other electrode (e.g., cathode) of AC power output unit 4. The ends of reactor L31 and reactor L32 connected to AC power output unit 4 form a pair of second terminals. Semiconductor switching elements Q31-Q34 include reverse diodes. The reverse diodes may be parasitic diodes of semiconductor switching elements Q31-Q34. While N-channel IGBTs are used for semiconductor switching elements Q31-Q34, this is not limiting and other power semiconductor elements such as N-channel MOSFETs may also be used.

[0018] The control circuit 40 includes a first control unit 41, a second control unit 42, and a main control unit 43. The first control unit 41 controls the power factor correction circuit 10 and the DC / DC converter circuit 20. The first control unit 41 is connected to the control electrodes of the semiconductor switching elements Q11-Q14 of the power factor correction circuit 10 and the control electrodes of the semiconductor switching elements Q21-Q28 of the DC / DC converter circuit 20. The first control unit 41 outputs a pulse-width-modulated pulse voltage signal generated by the semiconductor switching elements Q11-Q14 and the semiconductor switching elements Q21-Q28 based on a high-frequency triangular carrier voltage signal, for example, several kHz to several hundred kHz. The second control unit 42 controls the DC / AC inverter circuit 30 and is connected to the AC voltage detection circuit 11 to monitor the AC voltage V1. The second control unit 42 is connected to the control electrodes of the semiconductor switching elements Q31-Q34 of the DC / AC inverter circuit 30 and is capable of monitoring, for example, the frequency and phase of the AC voltage V1 output from the AC power source 2, which is detected by the AC voltage detection circuit 11. Second control unit 42 applies pulse-width-modulated pulse voltage signals generated according to semiconductor switching elements Q31-Q34 to the control electrodes of each semiconductor element based on the same high-frequency triangular wave carrier voltage signal of, for example, several kHz to several hundred kHz as first control unit 41. Second control unit 42 can control AC voltage V2 output by DC / AC inverter circuit 30 according to AC voltage V1 output by AC power supply 2 detected by AC voltage detection circuit 11. Main control unit 43 can collectively control the carrier voltage signals of first control unit 41 and second control unit 42.

[0019] The power factor correction circuit 10, DC / DC converter circuit 20, and DC / AC inverter circuit 30 are existing circuits, and their basic operations are well known, so detailed explanation of the basic operations will be omitted.

[0020] In the circuit configuration shown in FIG. 1, an AC power supply 2 is connected to a pair of first terminals of a power factor correction circuit 10, and an AC voltage V1 having an effective value of 200 V and a frequency of 50 Hz (or 60 Hz) is input. This charges a battery 3 connected to a second terminal of a DC / DC converter circuit 20. An AC voltage V2 having an effective value of 100 V and a frequency of 50 Hz (or 60 Hz) is output to an AC power output unit 4 connected to a second terminal of a DC / AC inverter circuit 30, and supplied to an AC load connected to the AC power output unit 4. Under the control of a control circuit 40, an output current I1 of the power factor correction circuit 10 and an input current I2 of the DC / AC inverter circuit 30 are generated. A current Icap corresponding to the output current I1 and the input current I2, as well as a ripple voltage Vcap of 100 Hz (or 120 Hz), which is twice the frequency of the AC voltage V1 of the AC power supply 2, are generated in the bulk capacitor C1.

[0021] The second control unit 42 controls the AC voltage V2 output by the DC / AC inverter circuit 30 in accordance with the AC voltage V1 output by the AC power supply 2 detected by the AC voltage detection circuit 11. More specifically, the second control unit 42 controls the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 so that it has a phase difference of 0 degrees or 180 degrees from the phase of the AC voltage V1 of the AC power supply 2. Furthermore, the frequency of the AC voltage V1 output by the AC power supply 2 is not strictly constant at 50 Hz (or 60 Hz) but has slight fluctuations. For this reason, the second control unit 42 may control the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 so that it has a phase difference of 0 degrees or 180 degrees from the phase of the AC voltage V1 of the AC power supply 2, and synchronize the frequency of the AC voltage V2 with the frequency of the AC voltage V1.

[0022] As a result, the peaks of the waveforms of the output current I1 of the power factor correction circuit 10 and the input current I2 of the DC / AC inverter circuit 30 are synchronized, and their peaks form a crest-and-trough relationship, thereby suppressing the ripple of the voltage Vcap generated in the bulk capacitor C1. As a result, the ripple of the voltage Vcap does not become larger than when the power factor correction circuit 10 and the DC / AC inverter circuit 30 are operating alone, and it is possible to avoid an increase in the size of the bulk capacitor C1.

[0023] Furthermore, in the past, the on-board charger function and the home AC output power supply function were separate functions, with the power factor correction circuit 10 for the on-board charger function and the DC / AC inverter circuit 30 for the home AC output power supply function connected in parallel between the bulk capacitor C1. This allows parts to be shared without significantly changing the specifications of the bulk capacitor C1, DC / DC converter circuit 20, smoothing capacitor C2, and battery 3.

[0024] Continuing to operate the second control unit 42 to control the AC voltage V2 output by the DC / AC inverter circuit 30 in accordance with the AC voltage V1 output by the AC power supply 2 detected by the AC voltage detection circuit 11 places a heavy load on the control circuit 40. Therefore, to reduce the load on the control circuit 40, the second control unit 42 may be controlled as follows. The second control unit 42 may detect the effective value of the current Icap flowing through the bulk capacitor C1. If the second control unit 42 determines that the effective value of the detected current Icap exceeds a predetermined threshold current, it may monitor the AC voltage V1 of the AC power supply 2 and control the AC voltage V2 output by the DC / AC inverter circuit 30 in accordance with the AC voltage V1 of the AC power supply 2. An increase in the current Icap flowing through the bulk capacitor C1 increases loss, i.e., heat generation, which affects the lifetime of the bulk capacitor C1. Therefore, the lifetime of the bulk capacitor C1 may be calculated experimentally in advance based on its size and usage, and an allowable threshold current may be set. Alternatively, the second control unit 42 may detect the voltage Vcap applied to the bulk capacitor C1. When the second control unit 42 determines that the detected voltage Vcap exceeds a predetermined threshold voltage, the second control unit 42 may monitor the AC voltage V1 of the AC power supply 2 and control the AC voltage V2 output by the DC / AC inverter circuit 30 in accordance with the AC voltage V1 of the AC power supply 2. This makes it possible to suppress ripples in the voltage Vcap, maintain the stability of the power conversion device 1, and reduce the impact on the life of the bulk capacitor C1. It is desirable to experimentally determine the predetermined threshold voltage in advance.

[0025] Next, the operation of the power conversion device 1 according to the first embodiment will be described with reference to FIGS. 2A and 2B, which show operational waveforms of the output current I1, input current I2, current Icap, and voltage Vcap in response to control by the control circuit 40. FIG. 2A shows waveforms when phase synchronization control is not performed in the power conversion device 1. FIG. 2B shows waveforms when phase synchronization control is performed in the power conversion device 1. In both FIGS. 2A and 2B, the power factor correction circuit 10 and the DC / AC inverter circuit 30 are operated by a pulse-width-modulated pulse voltage signal generated based on a 2-kHz carrier voltage signal. In both FIGS. 2A and 2B, the output power of the AC power source 2 is 6 kW, the output voltage V1 is 200 V (effective value) and the frequency is 50 Hz, and the output power of the DC / AC inverter circuit 30 is 1.5 kW, the output voltage V2 is 100 V (effective value) and the frequency is 50 Hz.

[0026] It is assumed that the second control unit 42 does not observe the AC voltage V1 of the AC power supply 2 detected by the AC voltage detection circuit 11, and controls the DC / AC inverter circuit 30 independently of the AC voltage V1 of the AC power supply 2. In this case, for example, it is assumed that the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 is different from the phase of the AC voltage V1 of the AC power supply 2 by 90 degrees. The operating waveforms of the output current I1, input current I2, current Icap, and voltage Vcap at this time are as shown in Figure 2A. As shown, the envelope of the output current I1 and the envelope of the input current I2 are waveforms that correspond to the case where the phase of the AC voltage V2 is 90 degrees different from the phase of the AC voltage V1. The waveform of the current Icap is the sum of the output current I1 and the input current I2. In addition, the waveform of the voltage Vcap is a ripple with an amplitude of about ±30V.

[0027] FIG. 2B shows the operational waveforms when the second control unit 42 controls the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 to be 0 degrees out of phase with the AC voltage V1 of the AC power supply 2 and synchronizes the frequency of the AC voltage V2 with the frequency of the AC voltage V1. As shown, the peaks of the waveforms of the output current I1 and the input current I2 are synchronized, with their peaks forming a crest-and-trough relationship. In this case, the waveform of the voltage Vcap has an amplitude of approximately ±10 V, indicating that the ripple of the voltage Vcap generated in the bulk capacitor C1 is suppressed. The same operation is achieved when the second control unit 42 controls the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 to be 180 degrees out of phase with the AC voltage V1 of the AC power supply 2.

[0028] (Second embodiment) Next, a second embodiment will be described with reference to FIGS. 3, 4A, and 4B.

[0029] In the first embodiment, the carrier voltage signals that operate the power factor correction circuit 10 and the DC / AC inverter circuit 30 have a phase difference of 0 degrees. In contrast, the second embodiment differs in that the carrier voltage signals that operate the power factor correction circuit 10 and the DC / AC inverter circuit 30 have a phase difference of 180 degrees. Since the other configurations are the same between the first and second embodiments, a description thereof will be omitted.

[0030] 3, in the second embodiment, main control unit 43 controls the phase difference between the phase of the carrier signal of first control unit 41 and the phase of the carrier signal of second control unit 42 to be 180 degrees. As a result, the phase difference between the pulse voltage signals applied to the control electrodes (gates) of semiconductor switching elements Q11-Q14 of power factor correction circuit 10 and semiconductor switching elements Q31-Q34 of DC / AC inverter circuit 30 also becomes 180 degrees.

[0031] At this time, the peaks of the output current I1 of the power factor correction circuit 10, which operates based on a pulse-width-modulated pulse voltage signal, and the peaks of the input current I2 of the DC / AC inverter circuit 30 are synchronized, resulting in a peak-to-peak relationship between the two currents, and the output current I1 and the input current I2 are canceled out. As a result, the ripple corresponding to the pulse-width-modulated pulse voltage signal is suppressed in the voltage Vcap generated in the bulk capacitor C1. As a result, it is possible to avoid increasing the size of the bulk capacitor C1.

[0032] More specifically, Fig. 4A corresponds to Fig. 2B and shows the operating waveforms when the main control unit 43 controls the phase difference between the carrier signal of the first control unit 41 and the carrier signal of the second control unit 42 to be 0 degrees. In both Figs. 4A and 4B, the output power of the AC power source 2 is 6 kW, the output voltage V1 is 200 V effective, and the frequency is 50 Hz. The output power of the DC / AC inverter circuit 30 is 1.5 kW, the output voltage V2 is 100 V effective, and the frequency is 50 Hz. Fig. 4B shows the operating waveforms when the main control unit 43 controls the phase difference between the carrier signal of the first control unit 41 and the carrier signal of the second control unit 42 to be 180 degrees, as compared to Fig. 4A. Thus, the voltage Vcap when the phase difference between the carrier signals of the first control unit 41 and the second control unit 42 is 180 degrees has smaller ripples corresponding to the pulse-width-modulated pulse voltage signal, and the ripple is suppressed, compared to the voltage Vcap when the phase difference between the carrier signals of the first control unit 41 and the second control unit 42 is 180 degrees, as shown in Fig. 4B.

[0033] (Third embodiment) Next, a third embodiment will be described with reference to Fig. 5. In the third embodiment, a power conversion device 1 supplies AC power to an AC load 2 connected to a first terminal of a power factor correction circuit 10 and an AC power output unit 4 connected to the second terminal of the DC / DC converter circuit 20, via a battery 3 connected to a second terminal of the DC / DC converter circuit 20. The power factor correction circuit 10 operates as a DC / AC inverter circuit that converts DC power into AC power. The basic circuit configuration in Fig. 5 is the same as that in Fig. 1, so a detailed description will be omitted.

[0034] In the circuit configuration shown in Fig. 5, a battery 3 is connected to a pair of second terminals of a DC / DC converter circuit 20, and a DC voltage Vdc is input thereto. Then, an AC voltage V1 having an effective value of 100 V and a frequency of 50 Hz (or 60 Hz) is output to a first terminal of a power factor correction circuit 10, and supplied to an AC load 2 connected to the first terminal of the power factor correction circuit 10. An AC voltage detection circuit 11 detects the AC voltage V1 output to the first terminal of the power factor correction circuit 10. Furthermore, an AC voltage V2 having an effective value of 100 V and a frequency of 50 Hz (or 60 Hz) is output to an AC power output unit 4 connected to a second terminal of the DC / AC inverter circuit 30, and supplied to an AC load connected to the AC power output unit 4. At this time, an input current I1 of the power factor correction circuit 10 and an input current I2 of the DC / AC inverter circuit 30 are generated in accordance with the control of a control circuit 40. In addition, a current Icap according to the input current I1 and the input current I2 and a ripple voltage Vcap of 100 Hz (or 120 Hz), which is twice the frequency of the AC voltage V1 of the AC power supply 2, are generated in the bulk capacitor C1.

[0035] The second control unit 42 controls the AC voltage V2 output by the DC / AC inverter circuit 30 in accordance with the AC voltage V1 output by the power factor correction circuit 10 detected by the AC voltage detection circuit 11. More specifically, the second control unit 42 controls the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 so that it has a phase difference of 90 degrees or 270 degrees from the phase of the AC voltage V2 output by the power factor correction circuit 10. Furthermore, the frequency of the AC voltage V1 output by the power factor correction circuit 10 is not strictly constant at 50 Hz (or 60 Hz) and may have slight fluctuations. For this reason, the second control unit 42 may control the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 so that it has a phase difference of 90 degrees or 270 degrees from the phase of the AC voltage V2 output by the power factor correction circuit 10, and synchronize the frequency of the AC voltage V2 with the frequency of the AC voltage V1.

[0036] As a result, the phases of the peaks of the waveforms of the input current I1 of the power factor correction circuit 10 and the input current I2 of the DC / AC inverter circuit 30 are out of phase by 90 degrees or 270 degrees, and the peaks of each are shifted, thereby suppressing the ripple of the voltage Vcap of the bulk capacitor C1. As a result, the ripple of the voltage Vcap does not become larger than when the power factor correction circuit 10 and the DC / AC inverter circuit 30 are operating alone, and it is possible to avoid an increase in the size of the bulk capacitor C1.

[0037] Furthermore, in the past, the on-board charger function and the home AC output power supply function were separate functions, with the power factor correction circuit 10 of the on-board charger function and the DC / AC inverter circuit 30 of the home AC output power supply function connected in parallel between the bulk capacitor C1. This allows parts to be shared without significantly changing the specifications of the bulk capacitor C1, DC / DC converter circuit 20, smoothing capacitor C2, and battery 3.

[0038] Continuing to operate the second control unit 42 to control the AC voltage V2 output by the DC / AC inverter circuit 30 in accordance with the AC voltage V1 output by the power factor correction circuit 10 detected by the AC voltage detection circuit 11 places a heavy load on the control circuit 40. Therefore, to reduce the load on the control circuit 40, the second control unit 42 may be controlled as follows: The second control unit 42 may detect the effective value of the current Icap flowing through the bulk capacitor C1. Then, when the second control unit 42 determines that the effective value of the detected current Icap exceeds a predetermined threshold current, it may monitor the AC voltage V1 output by the power factor correction circuit 10 and control the AC voltage V2 output by the DC / AC inverter circuit 30 in accordance with the AC voltage V1. An increase in the current Icap flowing through the bulk capacitor C1 increases loss, i.e., heat generation, which affects the lifetime of the bulk capacitor C1. Therefore, the lifetime of the bulk capacitor C1 may be calculated experimentally in advance based on its size and usage, and an allowable threshold current may be set. Alternatively, the second control unit 42 may detect the voltage Vcap applied to the bulk capacitor C1. Then, when the second control unit 42 determines that the detected voltage Vcap exceeds a predetermined threshold voltage, the second control unit 42 may observe the AC voltage V1 output from the power factor correction circuit 10 and control the AC voltage V2 output from the DC / AC inverter circuit 30 in accordance with the AC voltage V1. This makes it possible to suppress ripples in the voltage Vcap, maintain the stability of the power conversion device 1, and reduce the impact on the life of the bulk capacitor C1. It is desirable to experimentally determine the predetermined threshold voltage in advance.

[0039] Next, the operation of the power conversion device 1 according to the third embodiment will be described with reference to FIGS. 6A and 6B, which show operational waveforms of the input current I1, the input current I2, the current Icap, and the voltage Vcap in response to control by the control circuit 40. FIG. 6A shows waveforms when phase synchronization control is not performed in the power conversion device 1. FIG. 6B shows waveforms when phase synchronization control is performed in the power conversion device 1. In both FIGS. 6A and 6B, the power factor correction circuit 10 and the DC / AC inverter circuit 30 are operated by pulse-width-modulated pulse voltage signals generated based on a 2-kHz carrier voltage signal. In both FIGS. 6A and 6B, the output power of the power factor correction circuit 10 is 3 kW, the output voltage V1 is 100 V (effective value), and the frequency is 50 Hz, and the output power of the DC / AC inverter circuit 30 is 1.5 kW, the output voltage V2 is 100 V (effective value), and the frequency is 50 Hz.

[0040] Assume that the second control unit 42 does not monitor the AC voltage V1 output by the power factor correction circuit 10, detected by the AC voltage detection circuit 11, and controls the DC / AC inverter circuit 30 independently of the AC voltage V1. In this case, for example, assume that the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 is 0 degrees out of phase with the AC voltage V1 output by the power factor correction circuit 10. The operating waveforms of the input current I1, the input current I2, the current Icap, and the voltage Vcap at this time are as shown in FIG. 6A. As such, the envelope of the input current I1 and the envelope of the input current I2 correspond to the case where the phase of the AC voltage V2 is 0 degrees out of phase with the AC voltage V1. The waveform of the current Icap is the output current I1 and the input current I2. Furthermore, the waveform of the voltage Vcap exhibits a ripple with an amplitude of approximately ±40V.

[0041] FIG. 6B shows the waveforms of the operation when the second control unit 42 controls the AC voltage V2 output by the DC / AC inverter circuit 30 and the AC voltage V1 output by the power factor correction circuit 10 so that the phases of the AC voltage V2 and the AC voltage V1 are shifted by 90 degrees and synchronized with each other. As shown, the peaks of the waveforms of the input currents I1 and I2 are shifted by 90 degrees, and the peaks of the input currents I1 and I2 are shifted relative to each other. In this case, the amplitude of the voltage Vcap waveform is approximately ±15 V, indicating that the ripple of the voltage Vcap generated in the bulk capacitor C1 is suppressed. The same operation is achieved when the second control unit 42 controls the phase of the AC voltage V2 output by the DC / AC inverter circuit 30 so that the phase of the AC voltage V1 output by the power factor correction circuit 10 is shifted by 270 degrees.

[0042] (Fourth embodiment) Next, a fourth embodiment will be described with reference to FIGS. 7, 8A, and 8B.

[0043] In the fourth embodiment, the carrier voltage signals that operate the power factor correction circuit 10 and the DC / AC inverter circuit 30 have a phase difference of 0 degrees. In contrast, the fourth embodiment differs in that the carrier voltage signals that operate the power factor correction circuit 10 and the DC / AC inverter circuit 30 have a phase difference of 180 degrees. The other configurations are the same between the third and fourth embodiments, so a description thereof will be omitted.

[0044] 7, in the fourth embodiment, main control unit 43 controls the phase difference between the phase of the carrier signal of first control unit 41 and the phase of the carrier signal of second control unit 42 to be 180 degrees. As a result, the phase difference between the pulse voltage signals applied to the control electrodes (gates) of semiconductor switching elements Q11-Q14 of power factor correction circuit 10 and semiconductor switching elements Q31-Q34 of DC / AC inverter circuit 30 also becomes 180 degrees.

[0045] At this time, the peaks of the input current I1 of the power factor correction circuit 10, which operates based on a pulse-width-modulated pulse voltage signal, and the peaks of the input current I2 of the DC / AC inverter circuit 30 are synchronized, resulting in a peak-to-peak relationship between the input currents I1 and I2, which cancel each other out. This suppresses ripples in the voltage Vcap generated across the bulk capacitor C1 that correspond to the pulse-width-modulated pulse voltage signal. As a result, it is possible to avoid increasing the size of the bulk capacitor C1.

[0046] More specifically, Fig. 8A corresponds to Fig. 6A and shows the operating waveforms when the main control unit 43 controls the phase difference between the carrier signal of the first control unit 41 and the carrier signal of the second control unit 42 to be 0 degrees when the phase difference between the AC voltages V1 and V2 is 0 degrees. Both Figs. 8A and 8B show the case where the output power of the power factor correction circuit 10 is 3 kW, the output voltage V1 has an effective value of 100 V, and a frequency of 50 Hz, and the output power of the DC / AC inverter circuit 30 is 1.5 kW, the output voltage has an effective value of 100 V, and a frequency of 50 Hz. Fig. 8B shows the operating waveforms when the main control unit 43 controls the phase difference between the carrier signal of the first control unit 41 and the carrier signal of the second control unit 42 to be 180 degrees, as compared to Fig. 8A. As described above, the voltage Vcap when the phase difference of the carrier signals is 180 degrees as shown in FIG. 8B has smaller ripples corresponding to the pulse width modulated pulse voltage signal than the voltage Vcap when the phase difference of the carrier signals is 0 degrees as shown in FIG. 8A, and the ripples are suppressed.

[0047] Although the embodiments of the present invention have been described above, the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure. [Explanation of symbols]

[0048] 1 Power conversion device 2 AC power supply (AC load) 3 Battery 4 AC power output section 10 Power factor correction circuit 11 AC voltage detection circuit 20 DC / DC converter circuit 30 DC / AC inverter circuit 40 Control circuit 41 First Control Section 42 Second Control Section 43 Main control unit C1 bulk capacitor C2 smoothing capacitor

Claims

1. an AC / DC converter circuit that converts AC power from an AC power source into DC power; a bulk capacitor connected in parallel to an output terminal of the AC / DC converter circuit; a DC / DC converter circuit having an input terminal connected in parallel to the bulk capacitor and an output terminal connected in parallel to a battery, the DC / DC converter circuit performing voltage conversion of DC power; a DC / AC inverter circuit having an input terminal connected in parallel to the bulk capacitor and an output terminal connected in parallel to an AC power output section, for converting DC power into AC power; a control circuit for controlling the AC / DC converter circuit, the DC / DC converter circuit, and the DC / AC inverter circuit; Equipped with the control circuit monitors the AC voltage of the AC power supply and controls the AC voltage output by the DC / AC inverter circuit in accordance with the AC voltage of the AC power supply; Power conversion device.

2. 2. The power conversion device according to claim 1, wherein the control circuit detects an effective value of the current flowing through the bulk capacitor, and when it determines that the detected effective value of the current exceeds a predetermined threshold current, observes the AC voltage of the AC power supply and controls the AC voltage output by the DC / AC inverter circuit in accordance with the AC voltage of the AC power supply.

3. 2. The power conversion device according to claim 1, wherein the control circuit detects a voltage applied to the bulk capacitor, and when it determines that the detected voltage exceeds a predetermined threshold voltage, observes an AC voltage of the AC power supply and controls the AC voltage output by the DC / AC inverter circuit in accordance with the AC voltage of the AC power supply.

4. The control circuit controls the phase of the AC voltage output by the DC / AC inverter circuit so that the phase difference between the AC voltage of the AC power supply is 0 degrees or 180 degrees. The power conversion device according to any one of claims 1 to 3.

5. The control circuit controls the phase of the AC voltage output by the DC / AC inverter circuit to have a phase difference of 0 degrees or 180 degrees from the phase of the AC voltage of the AC power supply, and controls the frequency of the AC voltage output by the DC / AC inverter circuit to be synchronized with the frequency of the AC voltage of the AC power supply. The power conversion device according to any one of claims 1 to 3.

6. The control circuit controls the phase of a carrier voltage signal for operating the DC / AC inverter circuit so that it has a phase difference of 180 degrees from the phase of a carrier voltage signal for operating the AC / DC converter circuit. The power conversion device according to any one of claims 1 to 3.

7. a bulk capacitor; a DC / DC converter circuit having an input terminal connected in parallel to a battery and an output terminal connected in parallel to the bulk capacitor, the DC / DC converter circuit converting a voltage of DC power; a first DC / AC inverter circuit having an input terminal connected in parallel to the bulk capacitor and an output terminal connected to an AC load, the first DC / AC inverter circuit converting DC power into AC power; a second DC / AC inverter circuit having an input terminal connected in parallel to the bulk capacitor and an output terminal connected to an AC power output section, the second DC / AC inverter circuit converting DC power into AC power; a control circuit for controlling the DC / DC converter circuit, the first DC / AC inverter circuit, and the second DC / AC inverter circuit; Equipped with the control circuit monitors the AC voltage output by the first DC / AC inverter circuit and controls the AC voltage output by the second DC / AC inverter circuit in accordance with the AC voltage output by the first DC / AC inverter circuit. Power conversion device.

8. 8. The power conversion device according to claim 7, wherein the control circuit detects an effective value of the current flowing through the bulk capacitor, and when it determines that the detected effective value of the current exceeds a predetermined threshold current, observes the AC voltage output by the first DC / AC inverter circuit, and controls the AC voltage output by the second DC / AC inverter circuit in accordance with the AC voltage output by the first DC / AC inverter circuit.

9. 8. The power conversion device according to claim 7, wherein the control circuit detects a voltage applied to the bulk capacitor, and when it determines that the detected voltage exceeds a predetermined threshold voltage, observes an AC voltage output by the first DC / AC inverter circuit, and controls an AC voltage output by the second DC / AC inverter circuit in accordance with the AC voltage output by the first DC / AC inverter circuit.

10. The control circuit controls the phase of the AC voltage output by the second DC / AC inverter circuit to have a phase difference of 90 degrees or 270 degrees with respect to the phase of the AC voltage output by the first DC / AC inverter circuit. The power conversion device according to any one of claims 7 to 9.

11. The power conversion device according to any one of claims 7 to 9, wherein the control circuit controls the phase of the AC voltage output by the second DC / AC inverter circuit to have a phase difference of 90 degrees or 270 degrees from the phase of the AC voltage output by the first DC / AC inverter circuit, and controls the frequency of the AC voltage output by the second DC / AC inverter circuit to be synchronized with the frequency of the AC voltage output by the first DC / AC inverter circuit.

12. The control circuit controls the phase of the carrier voltage signal for operating the second DC / AC inverter circuit so that it has a phase difference of 180 degrees with the phase of the carrier voltage signal for operating the first DC / AC inverter circuit. The power conversion device according to any one of claims 7 to 9.

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