Power supply system, power conversion device, and power conversion circuit

Abstract

To contribute to the improvement in conversion efficiency during power conversion and the improvement in responsiveness during load fluctuation.SOLUTION: A power supply system 11 applied to a housing 10 is configured to supply power, upon occurrence of power outage, to an electric apparatus 14 from an on-vehicle battery 31 on a vehicle 30. The power supply system 11 includes a power conversion device 40 that converts the power supplied from the on-vehicle battery 31 from a DC power to an AC power. The power conversion device 40 has a first converter and a second converter that are insulating-type DC-DC converters disposed to be parallel to each other relative to the electric apparatus 14. The first converter and the second converter are connected by wiring, and a first target current value that is a target current value in the first converter is transmitted from the first converter side to the second converter side. A second target current value that is a target current value in the second converter is set to be lower than the received first target current value on the basis of the first target current value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply system, and a power conversion device and a power conversion circuit applied to the power supply system. [Background technology]

[0002] For example, power supply systems having solar panels and household batteries are widely used as power supply systems applied to buildings such as houses. Some of these power supply systems are configured to supply power from the household battery to power loads (electrical appliances) in the house via a power conversion device (more specifically, a power conversion circuit) in the event of a power outage (see, for example, Patent Document 1).

[0003] Furthermore, in recent years, development of plug-in hybrid vehicles (so-called PHVs) and electric vehicles (so-called EVs) has progressed, and power supply systems applicable to buildings such as homes that can charge these vehicles have been proposed. In this type of power supply system, a technology has been studied that supplies power from an on-board battery to power loads (electrical appliances) in a home via a power conversion device when a power outage occurs while the on-board battery is connected to the power supply system (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-135125 [Patent Document 2] Japanese Patent Application Publication No. 2020-178419 Summary of the Invention [Problem to be solved by the invention]

[0005] Because the amount of power stored in a battery is limited, improving the conversion efficiency of a power conversion device is necessary to maintain the battery's power supply for as long as possible. In particular, given the uncertainty of when power supply from a main power source, such as a commercial power source, will resume, it is of great technical significance to maintain the battery's power supply for as long as possible to eliminate or shorten the period of power supply interruption. Furthermore, the power consumed by a power load (required power) is not necessarily constant and may fluctuate over time. Poor response to such fluctuations in required power (load fluctuations) can cause the power load to operate unstably. In other words, improving responsiveness to load fluctuations is necessary to stabilize the power load's operation. As described above, there is still room for improvement in the configuration of a power conversion device for converting power stored in a battery and supplying it to a power load.

[0006] The present invention has been made in view of the above-mentioned problems, and a main object of the present invention is to contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations. [Means for solving the problem]

[0007] The following describes means for solving the above problems.

[0008] First means: A power conversion device comprising a first DC-DC converter and a second DC-DC converter arranged in parallel with a power load, and converting power supplied from a battery to the power load from DC power to AC power by the DC-DC converters, a first target value, which is a target current value in the first DC-DC converter, is set based on a current voltage value and a target voltage value in the first DC-DC converter; the first DC-DC converter includes an output unit that outputs a command value that is either the first target value or a correlation value that is correlated with the first target value to the second DC-DC converter side; the second DC-DC converter has a setting unit that sets a second target value, which is a target current value in the second DC-DC converter, based on the command value; The setting unit is capable of setting the second target value to be lower than the first target value.

[0009] According to the configuration of this aspect, the target value of the second DC-DC converter is set based on the command value from the first DC-DC converter. This configuration can prevent output bias due to individual differences between the DC-DC converters. DC-DC converters have the characteristic that their conversion efficiency varies depending on the magnitude of their output. Given this characteristic, reducing the bias between the output of the first DC-DC converter and the output of the second DC-DC converter is preferable for improving the conversion efficiency of the entire conversion device.

[0010] On the other hand, in a configuration in which the target value of the second DC-DC converter is set based on a command value from the first DC-DC converter, a delay in the update period of the second DC-DC converter relative to the first DC-DC converter may cause the operation of the second DC-DC converter to lag behind the operation of the first DC-DC converter. Specifically, if the same target value is set for both DC-DC converters, when the output of the preceding first DC-DC converter reaches a steady state, the delay in the update period may cause the output of the first DC-DC converter to increase or decrease inversely to the output of the second DC-DC converter. In other words, the output from the power conversion device may oscillate, lengthening the time until the output stabilizes. This may hinder improved responsiveness to load fluctuations. In this regard, the configuration described in this aspect allows the second target value of the second DC-DC converter to be set lower than the first target value of the first DC-DC converter. If the second target value is deliberately set lower than the first target value, the increase in the output of the second DC-DC converter can be delayed relative to the increase in the output of the first DC-DC converter, thereby making it possible to suppress the above-mentioned vibrations.

[0011] For the above reasons, the configuration of the present invention can contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations.

[0012] Second means: A power supply system capable of supplying power from a battery to a power load when power supply from a commercial power source to the power load is interrupted, a first DC-DC converter and a second DC-DC converter that are arranged in parallel with the power load and convert power supplied from the battery to the power load from DC power to AC power; a first target value, which is a target current value in the first DC-DC converter, is set based on a current voltage value and a target voltage value in the first DC-DC converter; the first DC-DC converter includes an output unit that outputs a command value that is either the first target value or a correlation value that is correlated with the first target value to the second DC-DC converter side; the second DC-DC converter has a setting unit that sets a second target value, which is a target current value in the second DC-DC converter, based on the command value; The setting unit is capable of setting the second target value to be lower than the first target value.

[0013] The configuration of this aspect can contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations.

[0014] Third means: A power conversion circuit comprising a first DC-DC converter and a second DC-DC converter arranged in parallel with a power load, the DC-DC converters converting power supplied from a battery to the power load from DC power to AC power, a first target value, which is a target current value in the first DC-DC converter, is set based on a current voltage value and a target voltage value in the first DC-DC converter; the first DC-DC converter includes an output unit that outputs a command value that is either the first target value or a correlation value that is correlated with the first target value to the second DC-DC converter side; the second DC-DC converter has a setting unit that sets a second target value, which is a target current value in the second DC-DC converter, based on the command value; The setting unit is capable of setting the second target value to be lower than the first target value.

[0015] The configuration of this aspect can contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a block diagram illustrating a power supply system according to an embodiment. [Figure 2] FIG. 10 is a schematic diagram showing a first comparative example. [Figure 3] 10 is a timing chart illustrating the flow of power supply according to a first comparative example. [Figure 4] (a) is a schematic diagram showing the relationship between the conversion efficiency and output of each DC-DC converter, and (b) is a schematic diagram showing the relationship between the driving mode and conversion efficiency of an isolated converter. [Figure 5] FIG. 10 is a schematic diagram showing a second comparative example. [Figure 6] 10 is a timing chart illustrating the flow of power supply according to a second comparative example. [Figure 7] A schematic diagram showing the relationship between the two DC-DC converters that make up the isolated converter. [Figure 8] 4 is a timing chart illustrating the flow of power supply. [Figure 9] FIG. 2 is a schematic diagram showing the relationship between the driving mode and conversion efficiency of an isolated converter. [Figure 10] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. In this embodiment, the present invention is embodied in a residential power supply system (hereinafter referred to as a power supply system).

[0018] As shown in the block diagram of FIG. 1 , a power supply system 11 applied to a house 10 includes a distribution board 12, which is connected to a commercial power source (system power supply) 20 via a service line 13. In the commercial power source 20, 6600V AC power flowing through a distribution line is stepped down to 100V / 200V by a pole-mounted transformer installed on a utility pole, and the stepped-down power is supplied to the distribution board 12 via the service line 13. Electrical appliances 14 (corresponding to "power loads") such as lighting, air conditioners, and refrigerators are connected to the distribution board 12, and power from the commercial power source 20 is supplied to these electrical appliances 14 via the distribution board 12.

[0019] A parking space for vehicle 30 is provided adjacent to house 10. Vehicle 30 is, for example, a plug-in hybrid vehicle (PHV) having an on-board battery 31 for driving, and a connection port to which a vehicle power supply cable 17 can be connected is provided on the side of vehicle 30. Power supply system 11 includes a power conversion device 40 installed in a location adjacent to the parking space, and power conversion device 40 is connected to vehicle 30 via vehicle power supply cable 17 and to distribution board 12 via wiring 18. In other words, vehicle 30 has an external power supply function, and a supply path for supplying power from commercial power source 20 to vehicle 30 is constructed by vehicle power supply cable 17, power conversion device 40, wiring 18, and distribution board 12.

[0020] The vehicle 30 is provided with a control unit 32 that monitors the state of charge (remaining capacity SOC) of the on-board battery 31, controls charging and discharging, and the like. The control unit 32 is capable of communicating with the power supply system 11 (e.g., power converter 40) of the house 10 via the vehicle power supply cable 17, and when the control unit 32 determines that the on-board battery 31 is not sufficiently charged, the control unit 32 outputs a request to start charging to the power supply system 11 (e.g., power converter 40). When the power supply system 11 receives this request to start charging, it supplies power from the commercial power source 20 to the vehicle 30 via the power converter 40.

[0021] The power conversion device 40 includes a board on which a connector to which the vehicle power supply cable 17 and wiring 18 are connected and a conversion circuit 41 are mounted, and a housing that houses the board. The conversion circuit 41 includes an inverter 51 that converts AC power from the commercial power source 20 into DC power, and an insulating converter 52 that separates the conversion circuit 41 into the house 10 side and the vehicle 30 side. The voltage of the on-board battery 31 is 300 V, which is higher than the voltage of the AC power supplied to the distribution board 12. The insulating converter 52 is a DC-DC converter with a boost function, and the DC power converted by the inverter 51 is boosted to 350 V by the insulating converter 52 before being supplied to the vehicle 30.

[0022] Furthermore, the power supply system 11 shown in this embodiment is capable of supplying power from the on-board battery 31 of the vehicle 30 to the house 10 when a power outage occurs at the house 10 due to a disaster or the like (i.e., when the power supply from the commercial power source 20 is stopped). Specifically, when the power supply system 11 detects a power outage, the power supply system 11 outputs a power supply request to the control unit 32 of the vehicle 30. When the control unit 32 receives this power supply request, it starts supplying power stored in the on-board battery 31 to the house 10. Note that it is also possible to configure the system to supply power from the on-board battery 31 of the vehicle 30 to the house 10 when the power supply from the commercial power source 20 is unstable (for example, insufficient) instead of or in addition to when the power supply from the commercial power source 20 is stopped due to a power outage or the like.

[0023] Incidentally, in FIG. 1, the flow of power when power is being supplied from commercial power source 20 is indicated by solid arrows, and the flow of power when power is not being supplied from commercial power source 20 (during a power outage) is indicated by dashed arrows.

[0024] Here, both the isolated converter 52 and the inverter 51 are so-called bidirectional, and when power is supplied from the vehicle 30 to the house 10, the DC power boosted by the isolated converter 52 is converted to AC power by the inverter 51 and then supplied to the electrical equipment 14 via the distribution board 12. In other words, it can be said that a supply path for supplying power from the vehicle 30 to the electrical equipment 14 is constructed by the vehicle power supply cable 17, the power conversion device 40, the wiring 18, and the distribution board 12. Incidentally, the isolated converter 52 can also be configured to have a boost converter used when supplying power from the commercial power source 20 to the on-board battery 31, and a boost converter used when supplying power from the on-board battery 31 to the electrical equipment 14, respectively.

[0025] The isolated converter 52 shown in this embodiment has multiple (two in this embodiment) DC-DC converters connected in parallel to the power load in order to improve power conversion efficiency under low load conditions. As will be described in detail later, when the power load is lower than a threshold, one DC-DC converter is driven, while when the power load is higher than the threshold, each DC-DC converter is driven. This configuration reduces power conversion loss in the transformer compared to simply using a large-capacity transformer. In other words, it is advantageous for improving conversion efficiency under low load conditions.

[0026] However, when DC-DC converters are arranged in parallel, non-negligible differences in benefits such as conversion efficiency can occur depending on the relationship between the DC-DC converters. Below, with reference to the comparative examples of Figures 2 to 6, issues that can arise when DC-DC converters are arranged in parallel will be described. For ease of explanation, the first comparative example shown in Figure 2 and other figures is distinguished by adding an "X" to the reference numerals, while the second comparative example shown in Figure 5 and other figures is distinguished by adding a "Y" to the reference numerals.

[0027] The isolated converter 52X shown in FIG. 2 includes a first converter 61X and a second converter 62X arranged in parallel. The first converter 61X determines a first target current value, which is a target current value for the first converter 61X, based on the difference between a target voltage (e.g., 350 V) corresponding to the first converter 61X and the current voltage of the first converter 61X. PI control is then performed so that the difference between the current current value of the first converter 61X and the first target current value becomes zero. Similarly to the first converter 61X, the second converter 62X determines a second target current value, which is a target current value for the second converter 62X, based on the difference between a target voltage (e.g., 350 V) corresponding to the second converter 62X and the current voltage of the second converter 62X. PI control is then performed so that the difference between the current current value of the second converter 62X and the second target current value becomes zero. The target voltage corresponding to the first converter 61X and the target voltage corresponding to the second converter 62X are the same.

[0028] The first converter 61X and the second converter 62X may have individual differences in the measurement results of various analog data, such as current voltage and current values, and in the time lag during measurement. Using these measurement results to perform feedback control can cause a bias (unbalance) between the outputs of the first converter 61X and the second converter 62X. For example, in the example shown in FIG. 3 , the power load increases at time ta1. The first converter 61X detects the increase in power load (a drop in voltage) at time ta2, immediately after the increase in power load at time ta1, and begins increasing its supply power. In contrast, the second converter 62X detects the increase in power load (a drop in voltage) at time ta3, which is later than time ta2, and begins increasing its supply power. In other words, due to the influence of the individual differences described above, the response delay DA1 of the first converter 61X is relatively small, while the response delay DA2 of the second converter 62X is relatively large. After the timing ta4 when the supply power is increased in response to the load fluctuation, the output of the first converter 61X and the output of the second converter 62X are both stable, but a large difference remains between the supply power (current value CX1) of the first converter 61X and the supply power (current value CX2) of the second converter 62X.

[0029] Generally, the conversion efficiency of a DC-DC converter varies depending on its output (power or current) (see, for example, Figure 4(a)). Specifically, when the output is lower or higher than a specific range, the conversion efficiency is lower than when the output is within the specific range. In other words, to efficiently operate a DC-DC converter, it is desirable to keep the output within the specific range. Figure 4(b) illustrates an example in which a switchover occurs from a state in which one DC-DC converter is being operated to a state in which two DC-DC converters are being operated because the required power exceeds a reference value (switching reference). When two DC-DC converters are being operated, the conversion efficiency is lower than when only one DC-DC converter is being operated. This phenomenon becomes more pronounced when the difference in output between the two DC-DC converters becomes large.

[0030] 3, when the first converter 61X and the second converter 62X, which are connected in parallel, are controlled independently, the load may be concentrated on one DC-DC converter (the first converter 61X in the example shown in FIG. 3), making it difficult to improve the conversion efficiency. In other words, it is difficult to improve both the responsiveness to load fluctuations and the conversion efficiency.

[0031] Here, if a master-slave relationship is established between the two DC-DC converters and the master side controls the power supply to the slave side, it is possible to prevent the outputs of the two DC-DC converters from becoming unbalanced. For example, an isolated converter 52Y shown in Fig. 5 is similar to the isolated converter 52X in that it has a first converter 61Y and a second converter 62Y arranged in parallel with each other, the first converter 61Y determines a target current value for the first converter 61Y based on the difference between a target voltage (e.g., 350 V) corresponding to the first converter 61Y and the current voltage in the first converter 61Y, and performs PI control so that the difference between the current current value and the target current value in the first converter 61Y becomes zero. In contrast, the first converter 61Y and the second converter 62Y are connected by wiring, and the target current value of the first converter 61Y is input to the second converter 62Y, and the second converter 62Y performs PI control so that the difference between the target current value and the current current value of the second converter 62Y becomes 0, which is a difference that differs from the isolated converter 52X. That is, the isolated converter 52Y is configured such that a master-slave relationship is established in which the first converter 61Y is on the "master" side and the second converter 62Y is on the "slave" side, and the output of the second converter 62Y is adjusted using the same target current value as the first converter 61Y.

[0032] With this configuration, as shown in the timing chart of FIG. 6, the output of the first converter 61X and the output of the second converter 62Y can be made uniform. This solves the problem (decrease in conversion efficiency) that occurs when multiple DC-DC converters connected in parallel are used. However, simply taking such measures can result in the following problem. In a configuration in which the first converter 61Y and the second converter 62Y perform feedback control to periodically update the target current value, a time lag equivalent to the update cycle occurs between the timing at which the target current value independently calculated by the first converter 61Y is reflected in the feedback control of the first converter 61Y and the timing at which the target current value commanded from the first converter 61Y is reflected in the feedback control of the second converter 62Y. In other words, the operation of the second converter 62Y lags behind the operation of the first converter 61Y by the update cycle.

[0033] In the example shown in FIG. 6 , the first converter 61Y starts increasing its output power at time tb2, which is after time tb1 when a load fluctuation occurs. The second converter 62Y starts increasing its output power at time tb3, which is delayed by an update cycle from time tb2. Such delays occur repeatedly while the first converter 61Y and the second converter 62Y are being driven. At time tb4, the current value of the master first converter 61Y reaches the maximum target value TM corresponding to the load fluctuation. At the following time tb5, the current value of the slave second converter 62Y reaches the maximum target value TM corresponding to the load fluctuation. By achieving an increase in the supply power in response to the load fluctuation, the outputs from the first converter 61Y and the second converter 62Y should each stabilize. However, due to the delay of the update cycle and the setting of the same target current value, the following phenomenon occurs. Specifically, the output adjustments of the first converter 61Y and the second converter 62Y increase and decrease in opposite directions, resulting in unstable output (oscillation). Such an unstable output hinders improvement of the response to load fluctuations.

[0034] In other words, as shown in Figure 5, in a configuration in which the second converter 62Y operates based on commands from the first converter 61Y and both converters 61Y, 62Y are controlled with the same target current value, it is possible to improve conversion efficiency, but it becomes difficult to improve responsiveness to load fluctuations.

[0035] The isolated converter 52 shown in this embodiment is different in configuration from the isolated converters 52X and 52Y in that it is designed to improve both responsiveness to load fluctuations and conversion efficiency. The design of this embodiment will be described below with reference to the block diagram of FIG.

[0036] As already explained, the isolated converter 52 includes a first converter 61 and a second converter 62 arranged in parallel with the power load, and is configured to switch between drive modes such that the first converter 61 operates alone when the power load (required power or output) is lower than a threshold value that is a switching criterion, and both the first converter 61 and the second converter 62 operate when the power load is higher than the threshold value that is a switching criterion. The decision to switch between drive modes is made by the first converter 61. Note that the first converter 61 and the second converter 62 in this embodiment have the same target voltage (e.g., 350 V), conversion efficiency characteristics, control period (update period), etc.

[0037] The first converter 61 is provided with a voltage detection unit for detecting a current voltage value (hereinafter referred to as a current voltage value PV) in the first converter 61, and a determination unit 71 for determining a target current value (first target current value TC1) based on the current voltage value PV detected by the voltage detection unit and the target voltage value TV in the first converter 61. The first converter 61 is also provided with a current detection unit for detecting a current output of the first converter 61, specifically a current value (hereinafter referred to as a current current value PC1), a calculation unit 76 for calculating the difference between the current current value PC1 detected by the current detection unit and the first target current value TC1 determined by the determination unit 71, and a PI control unit 75 for receiving the difference calculated by the calculation unit 76 and performing feedback control (more specifically, PI control) to adjust the amount of current (amount of power) to be supplied based on the difference. That is, in the first converter 61, the supply power is adjusted so that the current current value PC1 matches the first target current value TC1. The feedback control in the first converter 61 is periodically executed, and the first target current value TC1 and the like are updated by each feedback control. This period (update period) is set in accordance with the detection cycle of the voltage detection unit and the current detection unit provided in the first converter 61.

[0038] The first converter 61 and the second converter 62 are connected by a wiring 63, and a first target current value TC1 is output to the second converter 62 via the wiring 63. The second converter 62 is provided with a current detection unit for detecting a current output of the first converter 61, specifically a current value (hereinafter referred to as a present current value PC2), and a calculation unit 81 for calculating a second target current value TC2, which is a target current value for the second converter 62, by adding the present current value PC2 detected by the current detection unit and the input first target current value TC1 at a predetermined ratio. In this embodiment, the predetermined ratio is 1:1, and is defined so that the second target current value TC2 = present current value PC2 × (½) + first target current value TC1 × (½).

[0039] The second converter 62 is also provided with a calculation unit 86 that calculates the difference between a present current value PC2 detected by the current detection unit and a second target current value TC2 calculated by the calculation unit 81, and a PI control unit 85 that receives the difference calculated by the calculation unit 86 and performs feedback control (more specifically, PI control) to adjust the amount of current (amount of power) to be supplied based on the input difference. That is, in the second converter 62, the supply power is adjusted so that the present current value PC2 matches the second target current value TC2. The feedback control in the second converter 62 is also performed in the same cycle as that of the first converter 61, and the second target current value TC2, etc. are updated by each feedback control.

[0040] That is, the isolated converter 52 shown in this embodiment is similar to the isolated converter 52Y described above in that the power supply by the slave second converter 62 is controlled based on a command value input from the master first converter 61. However, in this embodiment, the second target current value TC2 of the second converter 62 is set to be lower than the first target current value TC1, which is the command value. According to the above calculation formula, the second target current value TC2 is maintained in a relationship of second target current value TC2<first target current value TC1 at least during the period from when a load fluctuation (increase in required power) occurs until the second target current value TC2 becomes equal to the present current value PC2. Here, the flow of power supply from the vehicle battery 31 will be described with reference to the timing chart of FIG. 8. Note that FIG. 8 illustrates an example in which a load fluctuation occurs during power supply from the vehicle battery 31 to the house 10 (electrical appliances 14).

[0041] At time tc1 when power is being supplied from the in-vehicle battery 31 to the house 10, a load fluctuation occurs in a manner that the required power increases, for example, when some of the electrical appliances 14 (e.g., lights) are turned on. This causes a drop in the voltage at the isolated converter 52. At time tc2 after the load fluctuation occurs, the first converter 61 performs periodic processing to detect the voltage value at the first converter 61, and the first target current value TC1 is updated based on the dropped voltage value. Specifically, the first target current value TC1 is increased to increase the power to be supplied in accordance with the load fluctuation. The updated first target current value TC1 is then output to the second converter 62.

[0042] In the second converter 62, when it is time to execute periodic processing, the second target current value TC2 is updated based on the input first target current value TC1 and the current current value PC2. Specifically, the second target current value TC2 is increased to increase the power supply in accordance with load fluctuations.

[0043] However, because the calculation of the second target current value TC2 takes into account the present current value PC2, the second target current value TC2 is kept lower than the first target current value TC1. As a result, the period (from timing tc2 to timing tc4) until the present current value PC2 of the second converter 62 reaches the first target current value TC1 (steady-state value SC) when it becomes steady is longer than the period (from timing tc3 to timing tc5) until the present current value PC1 of the first converter 61 reaches the first target current value TC1 (steady-state value SC) when it becomes steady. In other words, the rate of increase of the second target current value TC2 is lower than the rate of increase of the first target current value TC1. As a result, even if a command to increase the supplied power is received by the second converter 62 after timing tc4 when the present current value PC1 of the first converter 61 becomes equal to the steady-state value SC, the oscillation shown in FIG. 6 is suppressed.

[0044] In particular, the difference between the timing tc4 at which the present current value PC1 of the first converter 61 becomes equal to the steady-state value SC and the timing tc5 at which the present current value PC2 of the second converter 62 becomes equal to the steady-state value SC is longer than the update period, and after the power supply in the first converter 61 becomes stable, the present current value PC2 of the second converter 62 reaches the second target current value TC2, i.e., the first target current value TC1. Then, the present current value PC2 of the second converter 62 approaches the steady-state value SC without increasing at an excessively high rate, making it less likely that the power supplied by the second converter 62 will become excessive and exceed the steady-state value SC (overshoot).

[0045] According to the embodiment described above in detail, the following excellent effects can be expected.

[0046] The power conversion device 40 (insulated converter 52) shown in this embodiment has a first converter 61 and a second converter 62 that are connected in parallel to the power load, and using these multiple converters 61, 62 in combination can contribute to improving power conversion efficiency at low loads.

[0047] Here, the second target current value TC2, which is the target value for the second converter 62 on the slave side, is set based on the first target current value TC1, which is the command value from the first converter 61 on the master side. This configuration can prevent output imbalances due to individual differences between the converters 61 and 62. As shown in FIG. 4 , DC-DC converters have a characteristic in that their conversion efficiency varies depending on the magnitude of their outputs. In light of this characteristic, reducing the imbalance between the outputs of the first converter 61 and the second converter 62 is preferable for improving the conversion efficiency of the entire power conversion device 40 (isolated converter 52). In particular, when the power load (required power) exceeds a threshold value that serves as a switching criterion, power conversion is performed by each of the first converter 61 and the second converter 62. However, even when multiple converters 61 and 62 are used in combination, this contributes to realizing a configuration that is unlikely to deviate from the specific range of high conversion efficiency. This is advantageous in preventing the conversion efficiency in the drive mode in which both converters 61, 62 are driven from becoming lower than the conversion efficiency in the drive mode in which only one converter (first converter 61) is driven, as shown in FIG. 9.

[0048] In a configuration in which the second target current value TC2, which is the target value of the second converter 62, is set based on the first target current value TC1, which is the command value from the first converter 61, a delay in the update period of the second converter 62 relative to the first converter 61 may cause the operation of the second converter 62 to lag behind the operation of the first converter 61. Specifically, if the same target value (target current value) is set for both converters 61, 62, when the output of the preceding master-side first converter 61 reaches a steady state, a situation may occur in which the increase and decrease in the output of the first converter 61 and the second converter 62 are opposite to each other due to the delay in the update period. In other words, the output from the power conversion device 40 may oscillate, lengthening the time until the output stabilizes. This may hinder improved responsiveness to load fluctuations. In this regard, according to the configuration described in this embodiment, the second target current value TC2 of the slave-side second converter 62 is set to be lower than the first target current value TC1 of the master-side first converter 61. Specifically, the second target current value TC2 is set to be lower than the first target current value TC1 at least until the present current value PC2 of the second converter 62 on the slave side reaches the second target current value TC2. In other words, the rate of increase in the power supplied by the second converter 62 is set to be lower than the rate of increase in the power supplied by the first converter 61. By delaying the increase in the output of the second converter 62 relative to the increase in the output of the first converter 61 in this way, it is possible to prevent the behavior (increase / decrease) of the first converter 61 and the second converter 62 during output adjustment from becoming opposite due to a delay in the update period. This is preferable in terms of preventing the supplied power from becoming unstable (oscillation) and improving responsiveness during load fluctuations.

[0049] For the above reasons, the configuration shown in this embodiment can contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations.

[0050] In particular, in this embodiment, the second target current value TC2, which is a target value for the second converter 62, is set based on the first target current value TC1, which is a command value from the first converter 61, and the current current value PC2 in the second converter 62. More specifically, the second target current value TC2 is set to be lower than the first target current value TC1 by adding the first target current value TC1 and the current current value PC2 in the second converter 62 at a predetermined ratio (specifically, 1:1). This configuration makes it possible to appropriately suppress sudden fluctuations in the output of the second converter 62. This is preferable in terms of suppressing excessive supply and suppressing the occurrence of vibrations due to excessive supply when supplying power to compensate for load fluctuations.

[0051] A configuration in which a command value is output from the first converter 61 to the second converter 62 and the second target current value TC2 is set based on the command value is preferable in terms of improving the conversion efficiency while improving the ability to follow load fluctuations. However, a complex configuration (e.g., circuit) related to setting the second target current value TC2 may hinder efforts to improve the operational stability and durability of the DC-DC converter. In this regard, as shown in this embodiment, keeping the predetermined ratio constant regardless of the present current value PC2 in the second converter 62 is preferable in terms of simplifying the configuration for setting the second target current value TC2 as much as possible and improving the operational stability and durability of the power conversion device 40.

[0052] <Other embodiments> The present invention is not limited to the above-described embodiments, and may be implemented as follows: Each of the following configurations may be applied individually to the above-described embodiments, or a part or all of the configurations may be combined and applied to the above-described embodiments.

[0053] (1) In the above embodiment, the first converter 61 (corresponding to the "first DC-DC converter") on the master side and the second converter 62 (corresponding to the "second DC-DC converter") on the slave side are connected by a wiring 63, and the first target current value TC1, which is the target current value on the master side, is input to the second converter 62 via the wiring 63. As long as the first target current value TC1 can be input to the second converter 62 on the slave side, any specific configuration for this input is possible. For example, this does not exclude a configuration in which a communication unit is provided that enables wireless communication between the first converter 61 on the master side and the second converter 62 on the slave side, and the first target current value TC1 is input to the second converter 62 via this wireless communication.

[0054] (2) In the above embodiment, when the first converter 61 and the second converter 62 are driven to follow load fluctuations, priority is given to driving the first converter 61 so that the present current value PC1 of the first converter 61 first reaches the first target current value TC1 (steady-state value SC) at which the first converter 61 becomes steady, and then the second converter 62 is driven so that the present current value PC2 of the second converter 62 subsequently reaches the second target current value TC2 (steady-state value SC) at which the second converter 62 becomes steady. However, it is not always necessary to match the output of the first converter 61 with the output of the second converter 62. For example, it is also possible to configure a configuration in which a first steady-state value (a value at which the current value is constant) that is the first target current value targeted on the first converter 61 side and a second steady-state value (a value at which the current value is constant) that is the second target current value targeted on the second converter 62 side are set separately, and a difference between the two steady-state values ​​is provided so that the second steady-state value is lower than the first steady-state value.

[0055] (3) In the above embodiment, the present current value PC2 of the second converter 62 reaches the steady-state value SC after a predetermined period longer than the update cycles of the first converter 61 and the second converter 62 (specifically, a period five times the update cycle) has elapsed since the present current value PC1 of the first converter 61 reached the steady-state value SC. The length of the predetermined period may be arbitrary as long as it is possible to suppress vibrations caused by deviations in the update cycles (see FIG. 6). For example, the predetermined period may be four or six times the update cycle. However, in order to suppress vibrations caused by deviations in the update cycles (see FIG. 6), it is preferable that the predetermined period be at least twice the update cycle.

[0056] (4) In the above embodiment, the first target current value TC1, which is a target value in the first converter 61, is input to the second converter 62, and the second converter 62 calculates the second target current value TC2 by adding the first target current value TC1 and the current current value PC2 in the second converter 62 together at a predetermined ratio, thereby generating a difference so that the second target current value TC2 is lower than the first target current value TC1. Any specific configuration may be used to generate a difference between the two target current values ​​TC1 and TC2 so that the second target current value TC2 is lower than the first target current value TC1. For example, as shown in the schematic diagram of Figure 10, in the second converter 62A, an adjustment unit 65A may be provided upstream of the PI control unit 85, specifically upstream of the calculation unit 86 that calculates the difference between the current current value PC2 and the second target current value TC2, to adjust the target current value by multiplying the first target current value TC1 by a coefficient α that is smaller than 1 to calculate the second target current value TC2, thereby creating a difference between the two target current values ​​TC1 and TC2 so that the second target current value TC2 is lower than the first target current value TC1.

[0057] 10 does not necessarily have to be provided in the second converter 62. It may be provided in the first converter 61 or separately from the first converter 61 and the second converter 62. In such a configuration, a correlation value correlated with the first target current value TC1 is calculated, and this correlation value is input to the second converter 62 as a command value for control. Then, the second converter 62 calculates a value (difference) to be input to the PI control unit 85 based on this command value. Note that, as described below, it is preferable to provide the adjustment unit 65A in the second converter 62, especially when adjusting the second target current value TC2 in consideration of the present current value PC2 in the second converter 62. This is because it reduces the load on the first converter 61 on the master side and contributes to improving the performance of the isolated converter 52.

[0058] The coefficient α in the adjustment unit 65A may be a fixed value (e.g., 0.98), or may be a variable value that is linked to an increase or decrease in the present current value PC2 in the second converter 62 (e.g., a variable value that gradually changes to approach 1 as the actual current value increases, in linkage with the increase). Incidentally, when the coefficient α is a variable value, it may be configured so that its value eventually becomes 1, i.e., so that the target current values ​​TC1 and TC2 eventually match, as shown in the above modification example (2), or it may be configured so that the value of the variable value eventually becomes a specific value smaller than 1, i.e., so that the second target current value TC2 remains smaller than the first target current value TC1.

[0059] In addition, when using the above-mentioned adjustment unit 65A or the like to keep the output of the second converter 62 on the slave side smaller than the output of the first converter 61 on the master side, it is also possible to change the degree of adjustment in accordance with the passage of time, instead of changing the degree of adjustment in accordance with an increase in the present current value PC2 on the slave side.

[0060] (5) In the above embodiment, two converters 61, 62 are arranged in parallel with the power load. However, the number of DC-DC converters arranged in parallel with the power load is not limited to two. For example, it may be three, four, or five or more. Even in such a case, it is preferable to configure one DC-DC converter as the master converter and the other DC-DC converters as slave converters, and input a target current value or a correlation value correlated to the target current value (for example, a value obtained by multiplying the master target current value by a coefficient and reducing it) as a command value to each slave converter.

[0061] (6) In the above embodiment, when setting the slave-side target current value, the actual current value on the slave side × ½ and the target current value on the master side × ½ are added together, i.e., the actual current value on the slave side and the target current value on the master side are added together in a ratio of 1:1. However, this is not limited to this, and it is also possible to add more weight to one side when adding the two together (weighting configuration). Specifically, to increase the weighting of the current current value PC2 on the slave side, for example, the current current value PC2 on the slave side × ½ and the first target current value TC1 on the master side may be added together, or the current current value PC2 on the slave side × 3 / 5 and the first target current value TC1 × 2 / 5 on the master side may be added together. Furthermore, when increasing the weighting of the first target current value TC1, which is the target current value on the master side, it is possible to configure the slave side to add together the current current value PC2×1 / 3 and the master side's first target current value TC1×2 / 3, or to configure the slave side to add together the current current value PC2×2 / 5 and the master side's first target current value TC1×3 / 5.

[0062] (7) In the above embodiment, the second target current value TC2 in the second converter 62 is adjusted. However, in order to realize a configuration that suppresses the output of the slave-side second converter 62 (a configuration that makes the output change more gradual than that of the first converter 61), it is also possible to adjust the difference calculated by the calculation unit 86, i.e., the input value to the PI control unit 85. In this case, the difference (input value) corresponds to the "second target value" shown in the following group of characteristics.

[0063] For example, by using the difference calculated by the calculation unit 86 from the first target current value TC1 and the current current value PC2 on the slave side as a provisional target value, and performing gain adjustment by multiplying the provisional target value by a coefficient α (a number smaller than 1), it is possible to make the input value to the PI control unit 85 smaller than the input value input to the PI control unit 75 of the first converter 61.

[0064] (8) In the above embodiment, the second target current value TC2, which is the target current value of the slave-side second converter 62, is adjusted to be lower than the first target current value TC1, which is the target current value of the master-side first converter 61, thereby suppressing sudden fluctuations in the output of the second converter 62. However, this may be modified to suppress sudden fluctuations in the output of the first converter 61 by adjusting the first target current value TC1, which is the target current value of the master-side first converter 61, to be lower than the second target current value TC2, which is the target current value of the slave-side second converter 62. Furthermore, a change unit may be provided that changes which of the master-side and slave-side converters 61, 62 to suppress its output, thereby reducing imbalances in the workload of the converters 61, 62 over a long period of time.

[0065] (9) In the above embodiment, when the power supply from the commercial power source 20 is interrupted due to a power outage or the like, power is supplied from the onboard battery 31 (corresponding to the "battery") mounted on the vehicle 30 to the electrical device 14 (corresponding to the "power load"), and the power from the onboard battery 31 is converted from DC power to AC power by the power conversion device 40. Alternatively or additionally, when the power supply from the commercial power source 20 is interrupted due to a power outage or the like, power can be supplied to the electrical device 14 (corresponding to the "power load") from a household battery charged by a solar panel or the like, and the power from the household battery can be converted from DC power to AC power by a component equivalent to the power conversion device 40. Incidentally, in the above embodiment, the commercial power source 20 is the AC current supply source, but this is not limited thereto. For example, an AC generator (corresponding to the "predetermined power source") such as a household AC generator can also be used as the AC power supply source. When constructing a power supply system in which power is supplied to the electrical appliance 14 from an in-vehicle battery 31 or a household battery when the power supply from the AC generator is stopped, it is advisable to apply a configuration equivalent to the power conversion device 40 shown in the above embodiment.

[0066] (10) In the above embodiment, the power conversion device 40 is applied to the residential power supply system 11, but this is not limiting. For example, a configuration equivalent to the power conversion device 40 may be applied to a power supply system capable of supplying power from a battery to a factory, laboratory equipment, medical equipment, server room, etc.

[0067] <Inventions extracted from the above embodiments> The following describes the features of the inventions extracted from the above embodiments, while indicating, as necessary, their effects, etc. Note that, for ease of understanding, the corresponding configurations in the above embodiments are indicated in parentheses as appropriate, but the invention is not limited to the specific configurations indicated in parentheses.

[0068] The following features relate to the background art of "Power supply systems having solar panels and household batteries are widespread as power supply systems applied to buildings such as homes. Some of these power supply systems are configured to supply power from the household battery to power loads (electrical devices) in the home via a power conversion device (more specifically, a power conversion circuit) in the event of a power outage (see, for example, Patent Document 1: JP 2012-135125 A). Furthermore, in recent years, the development of plug-in hybrid vehicles (so-called PHVs) and electric vehicles (so-called EVs) has progressed, and power supply systems applied to buildings such as homes that are capable of charging these vehicles have been proposed. Regarding this type of power supply system, a technology is being considered for supplying power from the on-board battery to the power loads (electrical devices) in the home via a power conversion device in the event of a power outage or the like while the on-board battery is connected to the power supply system (see, for example, Patent Document 2: JP 2020-178419 A)." "Here, since the power stored in a battery is limited, in order to continue the power supply from the battery for as long as possible, it is necessary to improve the conversion efficiency of the power conversion device. In particular, if it is assumed that the timing when power supply from a main power source such as a commercial power source will resume can be uncertain, there is great technical significance in continuing the power supply from the battery for as long as possible and eliminating or shortening the period when the power supply is interrupted. Furthermore, the power consumed by the power load (required power) is not necessarily constant, but can fluctuate over time, etc. Then, poor response to such fluctuations in required power (load fluctuations) can be a factor in destabilizing the operation of the power load. In other words, in order to stabilize the operation of the power load, it is necessary to improve responsiveness to load fluctuations. As described above in detail, there is still room for improvement in the configuration of the power conversion device when it comes to converting the power stored in the battery and supplying it to the power load."

[0069] Feature 1: A power conversion device (power conversion device 40) including a first DC-DC converter (first converter 61) and a second DC-DC converter (second converter 62) arranged in parallel with a power load (electrical device 14), and converting power supplied from a battery (vehicle battery 31) to the power load from DC power to AC power using the DC-DC converters, a first target value (for example, a first target current value TC1) that is a target current value in the first DC-DC converter is set based on a current voltage value (current voltage value PV) and a target voltage value (target voltage value TV) in the first DC-DC converter; the first DC-DC converter includes an output unit (a function of outputting the first target current value TC1 or the like via a wiring 63 in the first converter 61) that outputs a command value that is either the first target value or a correlation value correlated to the first target value (for example, a value calculated by multiplying the first target current value TC1 by a coefficient) to the second DC-DC converter side; the second DC-DC converter has a setting unit (e.g., calculation units 81, 86, adjustment unit 65A, etc.) that sets a second target value (e.g., second target current value TC2) that is a target current value in the second DC-DC converter based on the command value, The power conversion device is configured such that the setting unit can set the second target value to be lower than the first target value.

[0070] According to this characteristic, the target value of the second DC-DC converter is set based on the command value from the first DC-DC converter. This configuration can prevent output imbalances caused by individual differences between the DC-DC converters. DC-DC converters have the characteristic that their conversion efficiency varies depending on the magnitude of their output. Given this characteristic, reducing the imbalance between the output of the first DC-DC converter and the output of the second DC-DC converter is preferable for improving the conversion efficiency of the entire conversion device.

[0071] On the other hand, in a configuration in which the target value of the second DC-DC converter is set based on a command value from the first DC-DC converter, a delay in the update period of the second DC-DC converter relative to the first DC-DC converter may cause the operation of the second DC-DC converter to lag behind the operation of the first DC-DC converter. Specifically, if the same target value is set for both DC-DC converters, when the output of the preceding first DC-DC converter reaches a steady state, the delay in the update period may cause the output of the first DC-DC converter to increase or decrease inversely to the output of the second DC-DC converter. In other words, the output from the power conversion device may oscillate, lengthening the time until the output stabilizes. This may hinder improved responsiveness to load fluctuations. In this regard, according to this characteristic configuration, the second target value of the second DC-DC converter can be set to be lower than the first target value of the first DC-DC converter. If the second target value is deliberately set lower than the first target value, the increase in the output of the second DC-DC converter can be delayed relative to the increase in the output of the first DC-DC converter, thereby making it possible to suppress the above-mentioned vibrations.

[0072] For the above reasons, the configuration shown in this characteristic can contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations.

[0073] It should be noted that the description in this feature that "the second DC-DC converter has a setting unit (e.g., calculation units 81, 86, adjustment unit 65A, etc.) that sets a second target value (e.g., second target current value TC2) that is a target current value in the second DC-DC converter based on the command value, and the setting unit is capable of setting the second target value to be lower than the first target value" can also be modified to "the second DC-DC converter has a setting unit (e.g., calculation units 81, 86, adjustment unit 65A, etc.) that is capable of setting a second target value (e.g., second target current value TC2) that is a target current value in the second DC-DC converter to be lower than the first target value based on the command value" or "the second DC-DC converter has an adjustment unit (e.g., calculation units 81, 86, adjustment unit 65A, etc.) that is capable of adjusting the second target value (e.g., second target current value TC2) that is a target current value in the second DC-DC converter based on the command value to be lower than the first target value".

[0074] Incidentally, the configuration shown in this feature may be referred to as "a power conversion device (power conversion device 40) including a first DC-DC converter (first converter 61) and a second DC-DC converter (second converter 62) arranged in parallel with a power load (electrical device 14), and converting power supplied from a battery (vehicle battery 31) to the power load from DC power to AC power by the DC-DC converters, wherein the first DC-DC converter converts a first target value (for example, a first target current value TC1) that is a target current value in the first DC-DC converter or a correlation value (for example, a first target current value TC2) that is correlated with the first target value. the second DC-DC converter has a setting unit (e.g., calculation units 81, 86, adjustment unit 65A, etc.) that sets a second target value (e.g., second target current value TC2) that is a target current value in the second DC-DC converter based on the command value, and the setting unit is capable of setting the second target value to be lower than the first target value.The present invention also provides a power conversion device (power conversion device 40) that is applied to a power supply system (power supply system 11) that can supply power from a battery (vehicle battery 31) when the power supply from a main power source (commercial power source 20) to a power load (electrical equipment 14) is interrupted or when the power supplied from the commercial power source is insufficient, the power conversion device (power conversion device 40) includes a first DC-DC converter (first converter 61) and a second DC-DC converter (second converter 62) that are arranged in parallel with the power load, and converts the power supplied from the battery to the power load from DC power to AC power using the DC-DC converters, and a target voltage value (target voltage value TV) for the first DC-DC converter is set based on a current voltage value (current voltage value PV) in the first DC-DC converter. a first target value (e.g., first target current value TC1) which is a target current value is set, the first DC-DC converter has an output unit (a function of outputting the first target current value TC1 or the like via wiring 63 in the first converter 61) which outputs a command value which is either the first target value or a correlation value correlated to the first target value (e.g., a value calculated by multiplying the first target current value TC1 by a coefficient) to the second DC-DC converter side, the second DC-DC converter has a setting unit (e.g., calculation units 81, 86, adjustment unit 65A, etc.) which sets a second target value (e.g., second target current value TC2) which is a target current value in the second DC-DC converter based on the command value, and the setting unit is capable of setting the second target value to be lower than the first target value.

[0075] Feature 2: The power conversion device according to Feature 1, wherein when a load fluctuation occurs in which the required power of the power load increases and the supply power is changed to follow the load fluctuation, the second target value is set to be lower than the first target value, thereby adjusting the period required for increasing the supply power by the second DC-DC converter by a predetermined amount in response to the load fluctuation to be longer than the period required for increasing the supply power by the first DC-DC converter by the predetermined amount in response to the load fluctuation.

[0076] As shown in this feature, if the time required to increase the output of the second DC-DC converter by a predetermined amount in response to load fluctuations is longer than the time required to increase the output of the first DC-DC converter by a predetermined amount, it is possible to prevent the behavior (increase / decrease) of the first DC-DC converter and the second DC-DC converter from becoming opposite during output adjustment due to the delay in the update cycle shown in Feature 1. This is preferable in terms of preventing the supplied power from becoming unstable (oscillation) and improving responsiveness during load fluctuations.

[0077] Feature 3: The power conversion device according to Feature 1 or Feature 2, wherein when a load fluctuation occurs in which the required power of the power load increases and the supply power is changed to follow the load fluctuation, the second target value is set lower than the first target value for at least a predetermined period of time, thereby suppressing the rate of increase in the power supply by the second DC-DC converter to be lower than the rate of increase in the power supply by the first DC-DC converter.

[0078] According to the configuration of this feature, the rate of increase in the power supply in the second DC-DC converter is reduced by keeping the second target value lower than the first target value for at least a predetermined period. This configuration can prevent the behavior (increase / decrease) of the first DC-DC converter and the second DC-DC converter during output adjustment from becoming opposite due to the delay in the update period described in Feature 1. This is preferable in terms of preventing the power supply from becoming unstable (oscillation) and improving responsiveness during load fluctuations.

[0079] Feature 4: The power conversion device according to any one of Features 1 to 3, wherein the second target value, which is a target current value in the second DC-DC converter, is set based on the command value and a current current value in the second DC-DC converter.

[0080] As shown by this feature, if the second target value is set based on the current value of the second DC-DC converter (the slave converter), sudden fluctuations in the output of the second DC-DC converter can be suppressed. This is preferable for suppressing excessive supply and suppressing the occurrence of oscillations due to excessive supply when supplying power to compensate for load fluctuations.

[0081] Feature 5: The output unit is configured to output the first target value as the command value to the second DC-DC converter side; The power conversion device according to any one of Features 1 to 4, wherein the second target value is set to be lower than the first target value obtained by adding the first target value and a current current value in the second DC-DC converter at a predetermined ratio (for example, 1:1).

[0082] As shown by this feature, if the second target value is set based on the current current value of the second DC-DC converter (the slave converter), sudden fluctuations in the output of the second DC-DC converter can be suppressed. This is preferable for suppressing excessive power supply when supplying power in accordance with load fluctuations, i.e., for suppressing the occurrence of vibrations due to excessive supply. Furthermore, a configuration in which the command value (first target value) and the current current value of the second DC-DC converter are added at a predetermined ratio is preferable for accurately and easily realizing a configuration in which the second target value is lower than the first target value.

[0083] Feature 6: The power conversion device according to Feature 5, wherein the predetermined ratio is configured to be constant regardless of the current value in the second DC-DC converter.

[0084] A configuration in which a command value is output from the first DC-DC converter to the second DC-DC converter and the second target value is set based on the command value is preferable for improving the ability to follow load fluctuations and improving conversion efficiency. However, a complex configuration (e.g., circuit) for setting the second target value may hinder efforts to improve the operational stability and durability of the DC-DC converter. In this regard, keeping the predetermined ratio constant, as shown in this feature, is preferable for simplifying the configuration for setting the second target value as much as possible and improving the operational stability and durability of the power conversion device.

[0085] Feature 7. The power conversion device according to Feature 5, further comprising: means for changing the predetermined ratio such that the ratio of the current value in the second DC-DC converter increases when the current value in the second DC-DC converter increases.

[0086] According to this feature, the increase in the output of the second DC-DC converter is kept small as the output of the second DC-DC converter increases. This configuration effectively suppresses oscillations caused by the output of the second DC-DC converter. For example, the proportion of the current value may increase as the current value of the second DC-DC converter increases, or the proportion of the current value may increase over time.

[0087] Feature 8. The output unit is configured to output the first target value as the command value to the second DC-DC converter side; The power conversion device according to any one of Features 1 to 3, wherein the setting unit sets the second target value to be lower than the first target value by multiplying the first target value by a predetermined coefficient.

[0088] As shown in this feature, if the second target value is set lower than the first target value by multiplying the first target value by a predetermined coefficient, the relationship of first target value > second target value shown in feature 1 etc. can be easily realized. Also, the processing load on the first DC-DC converter on the master side can be reduced, contributing to an improvement in the performance of the entire power conversion device.

[0089] Feature 9: The power conversion device according to any one of Features 1 to 3, wherein the output unit is configured to output, as the command value to the second DC-DC converter, the correlation value, which is a value calculated by multiplying the first target value by a predetermined coefficient so that the correlation value is lower than the first target value.

[0090] According to this feature, the configuration for setting the second target value in the second DC-DC converter on the slave side can be simplified, which is advantageous in increasing the number of second DC-DC converters on the slave side.

[0091] Feature 10: A power conversion device (power conversion device 40) including a first DC-DC converter (first converter 61) and a second DC-DC converter (second converter 62) arranged in parallel with a power load (electrical device 14), and converting power supplied from a battery (vehicle battery 31) to the power load from DC power to AC power by the DC-DC converters, the first DC-DC converter includes an output unit (a function of outputting the first target current value TC1 or the like via a wiring 63 in the first converter 61) that outputs a command value to the second DC-DC converter, the command value being either a first target value (e.g., a first target current value TC1) that is a target current value in the first DC-DC converter or a correlation value that is correlated with the first target value (e.g., a value calculated by multiplying the first target current value TC1 by a coefficient); The second DC-DC converter has a setting unit (e.g., calculation unit 81, 86, adjustment unit 65A, etc.) that sets a second target value (e.g., second target current value TC2), which is a target current value in the second DC-DC converter, based on the command value, and is a power conversion device that can be set so that the second target value is different from the first target value.

[0092] This configuration can contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations.

[0093] Feature 11 (Power Supply System): A power supply system (power supply system 11) that can supply power from a battery (vehicle battery 31) when the power supply from a commercial power source (commercial power source 20) to a power load (electrical device 14) is interrupted or when the power supplied from the commercial power source is insufficient, a first DC-DC converter (first converter 61) and a second DC-DC converter (second converter) that are arranged in parallel with the power load and convert power supplied from the battery (vehicle battery 31) to the power load from DC power to AC power; a first target value (for example, a first target current value TC1) that is a target current value in the first DC-DC converter is set based on a current voltage value (current voltage value PV) and a target voltage value (target voltage value TV) in the first DC-DC converter; the first DC-DC converter includes an output unit (a function of outputting the first target current value TC1 or the like via a wiring 63 in the first converter 61) that outputs a command value that is either the first target value or a correlation value correlated to the first target value (for example, a value calculated by multiplying the first target current value TC1 by a coefficient) to the second DC-DC converter side; the second DC-DC converter has a setting unit (e.g., calculation units 81, 86, adjustment unit 65A, etc.) that sets a second target value (e.g., second target current value TC2) that is a target current value in the second DC-DC converter based on the command value, The setting unit is capable of setting the second target value to be lower than the first target value.

[0094] According to this characteristic, the target value of the second DC-DC converter is set based on the command value from the first DC-DC converter. This configuration can prevent output imbalances caused by individual differences between the DC-DC converters. DC-DC converters have the characteristic that their conversion efficiency varies depending on the magnitude of their output. Given this characteristic, reducing the imbalance between the output of the first DC-DC converter and the output of the second DC-DC converter is preferable for improving the conversion efficiency of the entire conversion device.

[0095] On the other hand, in a configuration in which the target value of the second DC-DC converter is set based on a command value from the first DC-DC converter, a delay in the update period of the second DC-DC converter relative to the first DC-DC converter may cause the operation of the second DC-DC converter to lag behind the operation of the first DC-DC converter. Specifically, if the same target value is set for both DC-DC converters, when the output of the preceding first DC-DC converter reaches a steady state, the delay in the update period may cause the output of the first DC-DC converter to increase or decrease inversely to the output of the second DC-DC converter. In other words, the output from the power conversion device may oscillate, lengthening the time until the output stabilizes. This may hinder improved responsiveness to load fluctuations. In this regard, according to this characteristic configuration, the second target value of the second DC-DC converter can be set to be lower than the first target value of the first DC-DC converter. If the second target value is deliberately set lower than the first target value, the increase in the output of the second DC-DC converter can be delayed relative to the increase in the output of the first DC-DC converter, thereby making it possible to suppress the above-mentioned vibrations.

[0096] For the above reasons, the configuration shown in this characteristic can contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations.

[0097] It is also possible to state this feature as "a power supply system including the power conversion device according to any one of Features 1 to 9."

[0098] Incidentally, the description in this feature that "a power supply system (power supply system 11) capable of supplying power from a battery (vehicle battery 31) when the power supply from a commercial power source (commercial power source 20) to a power load (electrical equipment 14) is interrupted or when the power supplied from the commercial power source is insufficient" can be changed to "a power supply system (power supply system 11) capable of supplying power from a battery (vehicle battery 31) when the power supply from a specified power source (commercial power source 20) to a power load (electrical equipment 14) is interrupted or when the power supplied from the specified power source is insufficient."

[0099] Feature 12 (Power supply system): The power supply system described in Feature 110, wherein the setting unit is configured to adjust the second target value to be lower than the first target value for at least a predetermined period of time when increasing the power supply to the power load in accordance with load fluctuations in the power load.

[0100] As shown in this feature, if the output of the second DC-DC converter is suppressed at least until a predetermined period of time has elapsed, it is possible to suitably suppress the vibrations described in Feature 1. Note that the predetermined period of time preferably includes the period from when a load fluctuation occurs until the output of the first DC-DC converter becomes stable.

[0101] Feature 13 (Power Conversion Circuit): A power conversion circuit (conversion circuit 41) including a first DC-DC converter (first converter 61) and a second DC-DC converter (second converter 62) arranged in parallel with a power load (electrical device 14), and converting power supplied from a battery (vehicle battery 31) to the power load from DC power to AC power using the DC-DC converters; a first target value (for example, a first target current value TC1) that is a target current value in the first DC-DC converter is set based on a current voltage value (current voltage value PV) and a target voltage value (target voltage value TV) in the first DC-DC converter; the first DC-DC converter includes an output unit (a function of outputting the first target current value TC1 or the like via a wiring 63 in the first converter 61) that outputs a command value that is either the first target value or a correlation value correlated to the first target value (for example, a value calculated by multiplying the first target current value TC1 by a coefficient) to the second DC-DC converter side; the second DC-DC converter has a setting unit (e.g., calculation units 81, 86, adjustment unit 65A, etc.) that sets a second target value (e.g., second target current value TC2) that is a target current value in the second DC-DC converter based on the command value, The setting unit is capable of setting the second target value to be lower than the first target value.

[0102] According to this characteristic, the target value of the second DC-DC converter is set based on the command value from the first DC-DC converter. This configuration can prevent output imbalances caused by individual differences between the DC-DC converters. DC-DC converters have the characteristic that their conversion efficiency varies depending on the magnitude of their output. Given this characteristic, reducing the imbalance between the output of the first DC-DC converter and the output of the second DC-DC converter is preferable for improving the conversion efficiency of the entire conversion device.

[0103] On the other hand, in a configuration in which the target value of the second DC-DC converter is set based on a command value from the first DC-DC converter, a delay in the update period of the second DC-DC converter relative to the first DC-DC converter may cause the operation of the second DC-DC converter to lag behind the operation of the first DC-DC converter. Specifically, if the same target value is set for both DC-DC converters, when the output of the preceding first DC-DC converter reaches a steady state, the delay in the update period may cause the output of the first DC-DC converter to increase or decrease inversely to the output of the second DC-DC converter. In other words, the output from the power conversion device may oscillate, lengthening the time until the output stabilizes. This may hinder improved responsiveness to load fluctuations. In this regard, according to this characteristic configuration, the second target value of the second DC-DC converter can be set to be lower than the first target value of the first DC-DC converter. If the second target value is deliberately set lower than the first target value, the increase in the output of the second DC-DC converter can be delayed relative to the increase in the output of the first DC-DC converter, thereby making it possible to suppress the above-mentioned vibrations.

[0104] For the above reasons, the configuration shown in this characteristic can contribute to improving the conversion efficiency during power conversion and improving the responsiveness during load fluctuations. [Explanation of symbols]

[0105] 10...building, 11...power supply system, 14...electrical equipment (power load), 20...commercial power supply, 30...vehicle, 31...on-board battery (battery), 32...control unit, 40...power conversion device, 41...conversion circuit, 51...inverter, 52...isolated converter, 61...first converter (first DC-DC converter), 62...second converter (second DC-DC converter), 63...wiring, 65A...adjustment unit, 75...PI control unit, 76...calculation unit, 81...calculation unit, 85...PI control unit, 86...calculation unit, PC1...present current value, PC2...present current value, PV...present voltage value, SC...steady-state value, TC1...first target current value, TC2...second target current value, TV...target voltage value.

Claims

1. A power conversion device comprising a first DC-DC converter and a second DC-DC converter arranged in parallel with a power load, the DC-DC converters converting power supplied from a battery to the power load from DC power to AC power, a first target value, which is a target current value in the first DC-DC converter, is set based on a current voltage value and a target voltage value in the first DC-DC converter; the first DC-DC converter includes an output unit that outputs a command value that is either the first target value or a correlation value that is correlated with the first target value to the second DC-DC converter side; the second DC-DC converter has a setting unit that sets a second target value, which is a target current value in the second DC-DC converter, based on the command value; The setting unit is capable of setting the second target value to be lower than the first target value.

2. 2. The power conversion device according to claim 1, wherein when a load fluctuation occurs in which the required power of the power load increases and the supply power is changed to follow the load fluctuation, the second target value is made lower than the first target value for at least a predetermined period of time, thereby suppressing the rate of increase in power supplied by the second DC-DC converter to be lower than the rate of increase in power supplied by the first DC-DC converter.

3. 3. The power conversion device according to claim 1, wherein the second target value, which is a target current value in the second DC-DC converter, is set based on the command value and a current current value in the second DC-DC converter.

4. the output unit is configured to output the first target value as the command value to the second DC-DC converter side, 3. The power conversion device according to claim 1, wherein the second target value is set to be lower than the first target value obtained by adding the first target value and a current value in the second DC-DC converter at a predetermined ratio.

5. A power supply system capable of supplying power from a battery to a power load when power supply from a commercial power source to the power load is interrupted, a first DC-DC converter and a second DC-DC converter arranged in parallel with the power load and configured to convert power supplied from the battery to the power load from DC power to AC power; a first target value, which is a target current value in the first DC-DC converter, is set based on a current voltage value and a target voltage value in the first DC-DC converter; the first DC-DC converter includes an output unit that outputs a command value that is either the first target value or a correlation value that is correlated with the first target value to the second DC-DC converter side; the second DC-DC converter has a setting unit that sets a second target value, which is a target current value in the second DC-DC converter, based on the command value; The setting unit is capable of setting the second target value to be lower than the first target value.

6. A power conversion circuit comprising a first DC-DC converter and a second DC-DC converter arranged in parallel with a power load, the DC-DC converters converting power supplied from a battery to the power load from DC power to AC power, a first target value, which is a target current value in the first DC-DC converter, is set based on a current voltage value and a target voltage value in the first DC-DC converter; the first DC-DC converter includes an output unit that outputs a command value that is either the first target value or a correlation value that is correlated with the first target value to the second DC-DC converter side; the second DC-DC converter has a setting unit that sets a second target value, which is a target current value in the second DC-DC converter, based on the command value; The setting unit is capable of setting the second target value to be lower than the first target value.

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