AC power supply

Abstract

To provide an AC power supply device that can further reduce the impact of inrush current during load application on AC voltage output devices. [Solution] The AC power supply device A1 includes an AC voltage output device 6 that outputs an AC voltage, output terminals T1 and T2, and an inrush current supply circuit 3 connected between the AC voltage output device 6 and the four output terminals T1 and T2. The inrush current supply circuit 3 includes a capacitor C1 connected in parallel between the output terminals T3 and T4 of the AC voltage output device 6, and an inductor L1 connected in parallel to the capacitor C1.

Description

Technical Field

[0001] The present invention relates to an AC power supply device that outputs an AC voltage.

Background Art

[0002] An AC power supply device that supplies an AC voltage to an AC load is known. When a load is connected to the AC power supply device and the load is turned on, an excessive inrush current may flow through the load. Since the inrush current flows through the inverter circuit provided in the AC power supply device, it has a great influence on the inverter circuit. The inverter circuit may malfunction when an inrush current exceeding the rated current flows through it. Patent Document 1 discloses a method of estimating a load current based on the output current of an inverter and the output voltage of an LC filter, and controlling the output voltage of the inverter based on the estimated value of the load current. By controlling the output voltage of the inverter by this method, it is possible to reduce the inrush current at the time of load connection.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when reducing the inrush current by control, the control is not in time for the inrush current that flows instantaneously at the time of load connection, so the inrush current cannot be completely suppressed. Therefore, the inverter circuit is affected by the inrush current. The same applies when the AC power supply device includes an AC voltage output device other than the inverter circuit, and the AC voltage output device is affected by the inrush current at the time of load connection.

[0005] The present invention was conceived under the circumstances described above, and aims to provide an AC power supply device that can further reduce the impact of inrush current during load application on the AC voltage output device. [Means for solving the problem]

[0006] An AC power supply device provided by a first aspect of the present invention comprises an AC voltage output device that outputs an AC voltage, an output terminal, and an inrush current supply circuit connected between the AC voltage output device and the output terminal, wherein the inrush current supply circuit comprises a first element which is a capacitor connected in parallel between the output terminals of the AC voltage output device, and a second element which is an inductor connected in parallel to the first element.

[0007] In a preferred embodiment of the present invention, when the frequency of the fundamental wave is f and the capacitance of the first element is C, the inductance Lx of the second element is Lx = 1 / (4 × π) 2 ×f 2 ×C) That is the case.

[0008] In a preferred embodiment of the present invention, the frequency f is greater than 50 Hz and less than 60 Hz.

[0009] In a preferred embodiment of the present invention, the transformer further comprises a primary winding which is the second element and a secondary winding which is magnetically coupled to the primary winding.

[0010] In a preferred embodiment of the present invention, a switch is further provided to switch between conduction and non-conductivity between the AC voltage output device and the output terminal, and no circuits other than the inrush current supply circuit are connected between the AC voltage output device and the switch. [Effects of the Invention]

[0011] According to the present invention, the inrush current supply circuit includes a first element, which is a capacitor connected in parallel between the output terminals of the AC voltage output device. The first element supplies current to the load when the load is applied. This suppresses the current flowing to the AC voltage output device from the inrush current that flows to the load when the load is applied. Therefore, the AC power supply device according to the present invention can further reduce the impact of the inrush current when the load is applied on the AC voltage output device. [Brief explanation of the drawing]

[0012] [Figure 1] This is a block diagram showing the overall configuration of the AC power supply device according to the first embodiment. [Figure 2] This is a block diagram showing the overall configuration of the AC power supply device according to the second embodiment. [Figure 3] This is a block diagram showing the overall configuration of the AC power supply device according to the third embodiment. [Modes for carrying out the invention]

[0013] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0014] Figure 1 is a block diagram showing the overall configuration of the AC power supply A1 according to the first embodiment. The AC power supply A1 is a power supply that supplies AC voltage to a load 9 connected to output terminals T1 and T2. The load 9 is a power-consuming device that operates when supplied with AC voltage from the AC power supply A1. The load 9 includes, but is not limited to, a capacitor, a transformer, or an AC motor. When the load 9 is connected to the power supply and the application of AC voltage begins, an excessive inrush current may flow. The AC power supply A1 has a function to suppress the effect of this excessive inrush current on its internal circuits. The AC power supply A1 includes a battery 5, an inverter circuit 1, a control circuit 2, an inrush current supply circuit 3, and a switch 4.

[0015] The storage battery 5 is a secondary battery that can perform repeated charging and discharging, for example, a lithium-ion battery. Note that the storage battery 5 may be other secondary batteries such as nickel-metal hydride batteries, nickel-cadmium batteries, and lead-acid batteries. Note that the storage battery 5 may be a capacitor such as an electric double-layer capacitor instead of a secondary battery.

[0016] The inverter circuit 1 is a bidirectional power conversion circuit that converts DC power and AC power. The input / output terminals on the DC side of the inverter circuit 1 are connected to the storage battery 5, and the DC voltage discharged from the storage battery 5 is converted into an AC voltage and output. Also, the inverter circuit 1 can convert the AC voltage input from the input / output terminals on the AC side into a DC voltage to charge the storage battery 5. The input / output terminals on the AC side of the inverter circuit 1 are connected to the switch 4. The inverter circuit 1 charges and discharges the connected storage battery 5 according to a command from the control circuit 2. Note that the specific internal configuration of the inverter circuit 1 is not limited. As an example of the inverter circuit 1, a single-phase full-bridge type inverter having four switching elements can be mentioned.

[0017] The control circuit 2 is realized by, for example, a microcomputer or the like, and controls the inverter circuit 1. The control circuit 2 outputs a drive signal to the inverter circuit 1 to cause the inverter circuit 1 to perform a power conversion operation and charge and discharge the storage battery 5 connected to the inverter circuit 1. The specific control method of the control circuit 2 is not limited. As an example of the control method of the control circuit 2, constant voltage control by PWM control can be mentioned.

[0018] Hereinafter, the combination of the storage battery 5, the inverter circuit 1, and the control circuit 2 may be described as an AC voltage output device 6. The AC voltage output device 6 is a configuration that exhibits the function of outputting an AC voltage of the AC power supply device A1. Hereinafter, the input / output terminals on the AC side of the inverter circuit 1 may be described as the output terminals T3 and T4 of the AC voltage output device 6.

[0019] Switch 4 is a switch that switches between conduction and non - conduction of the output terminals T3, T4 of the AC voltage output device 6 and the output terminals T1, T2 of the AC power supply device A1. In this embodiment, switch 4 includes a switch that switches between conduction and non - conduction of output terminal T3 and output terminal T1, and a switch that switches between conduction and non - conduction of output terminal T4 and output terminal T2. When switch 4 is off (non - conducting), even if a load 9 is connected to the output terminals T1, T2 of the AC power supply device A1, the AC voltage output by the AC voltage output device 6 is not supplied to the load 9. On the other hand, when switch 4 is turned on (conducting), load connection occurs, and the AC voltage output by the AC voltage output device 6 is supplied to the load 9 connected to the output terminals T1, T2 of the AC power supply device A1. Note that switch 4 is not always necessary, and the AC power supply device A1 may not include switch 4. In this case, when a load 9 is connected to the output terminals T1, T2, load connection occurs.

[0020] The inrush current supply circuit 3 is a circuit for suppressing the influence on the inverter circuit 1 caused by an excessive inrush current at the time of load connection. The inrush current supply circuit 3 is connected between the output terminals T3, T4 of the AC voltage output device 6 and the switch 4. The inrush current supply circuit 3 includes a capacitor C1 and a reactor L1.

[0021] Capacitor C1 is a capacitor, one end of which is directly connected to the output terminal T3 of the AC voltage output device 6, and the other end of which is directly connected to the output terminal T4 of the AC voltage output device 6. That is, capacitor C1 is connected in parallel between the output terminals T3 and T4 of the AC voltage output device 6. Capacitor C1 supplies current to the load 9 at the time of load connection. Thereby, among the inrush current flowing through the load 9 at the time of load connection, the current flowing through the inverter circuit 1 is suppressed. The capacitance of capacitor C1 is designed to have a capacitance such that the voltage does not drop even with that inrush current, based on the magnitude of the inrush current at the time of load connection. Note that even if capacitor C1 cannot supply all of the inrush current, it can suppress the current flowing through the inverter circuit 1. Therefore, the capacitance of capacitor C1 may be designed considering the size and price of the capacitor.

[0022] Reactor L1 is an inductor, with one end connected to one end of capacitor C1 and the other end connected to the other end of capacitor C1. In other words, reactor L1 is connected in parallel with capacitor C1. Reactor L1 is provided to cancel out the fundamental wave current flowing through capacitor C1 so that the fundamental wave current output by the AC voltage output device 6 does not circulate between output terminal T3 and output terminal T4 during steady state. The fundamental wave current flowing through capacitor C1 leads the voltage by 90° in phase. On the other hand, the fundamental wave current flowing through reactor L1 lags the voltage by 90° in phase. As a result, the fundamental wave current flowing through capacitor C1 is canceled out by the fundamental wave current flowing through reactor L1. The inductance Lx of reactor L1 is designed so that the impedance ZL of reactor L1 and the impedance ZC of capacitor C1 are equal at the fundamental wave current frequency f.

[0023] The impedance ZC of capacitor C1 is calculated by equation (1) below, where C is the capacitance of capacitor C1. The impedance ZL of reactor L1 is calculated by equation (2) below. From equations (1) and (2) below, by setting ZC = ZL, the inductance Lx of reactor L1 is calculated by equation (3) below. In Japan, the fundamental frequency f is set to 50Hz or 60Hz. ZC = 1 / (2 × π × f × C) ... (1) ZL = 2 × π × f × Lx ··· (2) Lx = 1 / (4 × π) 2 ×f 2 ×C)··· (3)

[0024] Next, the operation and effects of the AC power supply A1 according to this embodiment will be described.

[0025] According to this embodiment, the inrush current supply circuit 3 includes a capacitor C1 connected in parallel to the output terminals T3 and T4 of the AC voltage output device 6. The capacitor C1 supplies current to the load 9 when the load is turned on. This suppresses the current flowing through the inverter circuit 1 (switching element) of the inrush current that flows through the load 9 when the load is turned on. Therefore, the AC power supply A1 can further reduce the impact of the inrush current when the load is turned on on the inverter circuit 1. As a result, the AC power supply A1 can suppress failure of the inverter circuit 1. In addition, since the AC power supply A1 does not significantly affect the inverter circuit 1 even when an excessive inrush current flows, there are no restrictions on the loads that can be connected.

[0026] Furthermore, according to this embodiment, the inrush current supply circuit 3 includes a reactor L1 connected in parallel with the capacitor C1. The reactor L1 cancels out the fundamental wave current flowing through the capacitor C1 during steady-state operation. Therefore, the AC power supply A1 can suppress the circulation of the fundamental wave current through the inrush current supply circuit 3 during steady-state operation. As a result, the current flowing through the switching elements of the inverter circuit 1 can be suppressed, and the AC power supply A1 can reduce losses in the inverter circuit 1 and improve efficiency compared to a case where the inrush current supply circuit 3 does not include the reactor L1. In addition, by suppressing heat generation due to the reduction in losses, the AC power supply A1 can simplify the cooling mechanism of the inverter circuit 1. Furthermore, the AC power supply A1 can use components with low rated current as components such as the switching elements of the inverter circuit 1.

[0027] Furthermore, according to this embodiment, the inductance Lx of the reactor L1 is designed to the value calculated based on (3) above. This allows the fundamental wave current flowing through the reactor L1 to appropriately cancel out the fundamental wave current flowing through the capacitor C1 during steady-state operation.

[0028] Furthermore, according to this embodiment, the AC power supply A1 is simply a conventional AC power supply with the inrush current supply circuit 3 added. Therefore, the present invention makes it possible to counter inrush current in any AC power supply.

[0029] In this embodiment, the case in which the inductance Lx of reactor L1 is designed to the value calculated by equation (3) above so that the fundamental wave current flowing through reactor L1 completely cancels out the fundamental wave current flowing through capacitor C1 has been described, but it is not limited to this. Reactor L1 only needs to be able to cancel out at least a portion of the fundamental wave current flowing through capacitor C1. Also, in this embodiment, the case in which the inductance Lx of reactor L1 is designed with the fundamental wave frequency f set to 50Hz or 60Hz depending on the region in which the AC power supply A1 is used has been described, but it is not limited to this. The AC power supply A1 may be designed with the fundamental wave frequency f set to a value greater than 50Hz and less than 60Hz, for example 55Hz, so that it can be used in any region of Japan, and the inductance Lx is designed accordingly.

[0030] Furthermore, although this embodiment describes the case where the battery 5 is connected to the DC side of the inverter circuit 1, it is not limited to this. The DC side of the inverter circuit 1 may also output a DC power supply that outputs a DC voltage. Examples of such DC power supplies include solar cells and fuel cells. In this case, the inverter circuit 1 may also be a unidirectional inverter that converts DC power to AC power for output.

[0031] Figure 2 is a block diagram showing the overall configuration of the AC power supply A2 according to the second embodiment. In Figure 2, elements that are the same as or similar to those in the AC power supply A1 according to the first embodiment are denoted by the same reference numerals, and redundant explanations are omitted. The AC power supply A2 according to this embodiment differs from the AC power supply A1 according to the first embodiment in that it includes a transformer, and the primary winding of the transformer functions as an inductor instead of a reactor L1.

[0032] The AC power supply A2 according to the second embodiment includes a transformer 31 instead of a reactor L1. The transformer 31 is positioned to electrically isolate the load 9 from the inverter circuit 1. The transformer 31 includes a primary winding 311 and a secondary winding 312. One end of the primary winding 311 is connected to one end of capacitor C1, and the other end is connected to the other end of capacitor C1. In other words, the primary winding 311 is connected in parallel to capacitor C1. The primary winding 311 functions as an inductor in place of reactor L1. The inductance Lx of the primary winding 311 is calculated by equation (3) above, similar to the reactor L1 according to the first embodiment. The secondary winding 312 is magnetically coupled to the primary winding 311 and is connected to output terminals T1 and T2 via a switch 4.

[0033] In this embodiment as well, the inrush current supply circuit 3 includes a capacitor C1 connected in parallel to the output terminals T3 and T4 of the AC voltage output device 6. Therefore, the AC power supply A2 can further reduce the impact of the inrush current on the inverter circuit 1 when the load is applied. Furthermore, according to this embodiment, the inrush current supply circuit 3 includes a primary winding 311 connected in parallel to the capacitor C1. Therefore, the AC power supply A2 can suppress the circulation of the fundamental wave current through the inrush current supply circuit 3 during steady-state operation. Moreover, the AC power supply A2 can achieve the same effects as the AC power supply A1 by having a configuration common to the AC power supply A1. Furthermore, according to this embodiment, the primary winding 311 of the transformer 31, which is arranged to electrically isolate the load 9 and the inverter circuit 1, functions as an inductor instead of the reactor L1. Therefore, the AC power supply A2 does not need to separately provide the reactor L1.

[0034] Figure 3 is a block diagram showing the overall configuration of the AC power supply A3 according to the third embodiment. In Figure 3, elements that are the same as or similar to those in the AC power supply A1 according to the first embodiment are denoted by the same reference numerals, and redundant explanations are omitted. The AC power supply A3 according to this embodiment differs from the AC power supply A1 according to the first embodiment in that it is equipped with a diesel generator 7 instead of an AC voltage output device 6.

[0035] The AC power supply A3 according to the third embodiment includes a diesel generator 7 instead of an AC voltage output device 6. The diesel generator 7 outputs an AC voltage.

[0036] In this embodiment as well, the inrush current supply circuit 3 includes a capacitor C1 connected in parallel to the output terminals T3 and T4 of the diesel generator 7. Therefore, the AC power supply A3 can further reduce the impact of inrush current on the diesel generator 7 when a load is applied. In this embodiment as well, the inrush current supply circuit 3 includes a reactor L1 connected in parallel to the capacitor C1. Therefore, the AC power supply A3 can suppress the circulation of fundamental wave current through the inrush current supply circuit 3 during steady-state operation. Furthermore, the AC power supply A3 can achieve the same effects as the AC power supply A1 by having a configuration common to the AC power supply A1.

[0037] Furthermore, the AC power supply unit A3 may be equipped with another generator capable of outputting AC voltage instead of the diesel generator 7. As can be seen from this embodiment, the configuration of the AC voltage output device 6 (diesel generator 7) is not limited and any device that outputs AC voltage is acceptable.

[0038] The AC power supply device according to the present invention is not limited to the embodiments described above. The specific configuration of each part of the AC power supply device according to the present invention can be modified in various ways. [Explanation of Symbols]

[0039] A1, A2, A3: AC power supply unit, 3: Inrush current supply circuit, T1, T2: Output terminals, C1: Capacitor, L1: Reactor, 31: Transformer, 311: Primary winding, 312: Secondary winding, 4: Switch, 6: AC voltage output unit

Claims

1. AC voltage output device that outputs AC voltage, Output terminals, An inrush current supply circuit connected between the AC voltage output device and the output terminal, Equipped with, The inrush current supply circuit is, A first element, which is a capacitor, is connected in parallel between the output terminals of the AC voltage output device. A second element, which is an inductor connected in parallel to the first element, It is equipped with AC power supply.

2. When the frequency of the fundamental wave is f and the capacitance of the first element is C, The inductance Lx of the second element is Lx=1 / (4×π ２ ×f ２ ×C) That is, The AC power supply device according to claim 1.

3. The aforementioned frequency f is greater than 50 Hz and less than 60 Hz. The AC power supply device according to claim 2.

4. The transformer further comprises a primary winding, which is the second element, and a secondary winding that is magnetically coupled to the primary winding. An AC power supply device according to any one of claims 1 to 3.

5. The AC voltage output device and the output terminal are further equipped with a switch to switch between conductivity and non-conductivity, No circuits other than the inrush current supply circuit are connected between the AC voltage output device and the switch. The AC power supply device according to claim 1.

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