Power supply device and control method for power supply device

Abstract

To provide a power source device and a control method for a power source device that are able to prevent current control and voltage control from interfering with each other when a short circuit or such accident occurs.SOLUTION: A power supply device includes an energy storage device, a DC-AC converter that converts a DC output of the energy storage device into an AC output, and a control unit (60) that controls the DC-AC converter. The control unit (60) includes: a voltage control block (81) that refers to a deviation of a value of voltage of the AC output from a normal value of the voltage to control the DC-AC converter so that the value of the voltage has the normal value; an input cut-off unit that, when a value of current of the AC output exceeds a first limit value, the deviation input to the voltage control block (81) is substantially set to 0; and a current control block (61) that, when the value of the current exceeds the first limit value, refers to a difference between the value of the current and a predetermined value greater than the first limit value to control the DC-AC converter so that the value of the current has the predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a power supply device and a method for controlling a power supply device. [Background technology]

[0002] Power supply devices equipped with an energy storage device such as a secondary battery are known for backing up and smoothing the power supply from a power generation system to a power grid, etc. Such power supply devices include a converter that converts DC power output from the energy storage device into AC power of a required voltage and frequency. When the power supply from the power generation system drops or stops, such power supply devices operate to supply the required AC power to the power grid or specific electrical equipment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 033299 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional power supply devices described above, for example, when a short circuit or momentary drop occurs in the power grid, the voltage value of the AC output of the converter drops and the current value of the AC output of the converter increases rapidly. Therefore, the converter is controlled by a combination of voltage control using the voltage value of the AC output and current control using the current value of the AC output.

[0005] However, in the conventional power supply device as described above, when a short circuit or the like occurs, there is a problem that the current control and the voltage control interfere with each other.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a power supply device and a control method for a power supply device that can suppress mutual interference between current control and voltage control when a short-circuit accident or the like occurs. [Means for solving the problem]

[0007] In order to solve the above problem, a power supply device according to one aspect of the present disclosure includes an energy storage device, a converter that converts a DC output of the energy storage device into an AC output, a current meter that measures the current of the AC output, a voltage meter that measures the voltage of the AC output, and a control unit that controls the converter, wherein the control unit has a voltage control block that controls the converter by referring to a deviation of the voltage value from a normal value of the voltage so that the voltage value becomes the normal value, an input cut-off unit that sets the deviation input to the voltage control block to substantially zero when the current value exceeds a first limit value, and a current control block that controls the converter by referring to a difference between the current value and a predetermined value that is greater than the first limit value so that the current value becomes the predetermined value when the current value exceeds the first limit value.

[0008] Furthermore, a control method for a power supply device according to one aspect of the present disclosure is a control method for a power supply device including an energy storage device, a converter that converts a DC output of the energy storage device into an AC output, and a control unit that controls the converter, and executes a first control that controls the converter by referring to a deviation of a voltage value of the AC output from a normal value of the voltage so that the voltage value becomes the normal value, and when a current value of the AC output exceeds a first limit value, executes a second control that forcibly sets the deviation in the first control to essentially zero, and by referring to the difference between the current value and a predetermined value that is greater than the first limit value, controls the converter so that the current value becomes the predetermined value. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, it is possible to provide a power supply device and a control method for a power supply device that can suppress mutual interference between current control and voltage control when a short-circuit accident or the like occurs. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram illustrating a power supply device according to an embodiment of the present disclosure and a power system to which the power supply device is applied; [Figure 2] FIG. 4 is a diagram illustrating a control logic of a control unit included in the power supply device. [Figure 3] 4 is a time chart showing signal waveforms of various parts of the power supply device. [Figure 4] FIG. 10 is a waveform diagram showing a specific example of an operating waveform in a power supply device of the comparative example. [Figure 5] 5A and 5B are waveform diagrams showing specific examples of operating waveforms in the power supply device. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Embodiment] Hereinafter, one embodiment of the present invention will be described in detail.

[0012] <Configuration of power system 100 to which power supply device 1 is applied> FIG. 1 is a diagram showing a power supply device 1 according to an embodiment. FIG. 1 shows the entirety of a power system 100 to which the power supply device 1 is applied. The power supply device 1 is a device that is equipped with an energy storage device 10 and can store power. Alternating current power (AC output) output by the power supply device 1 is supplied to a plurality of feeders 90.

[0013] Each feeder 90 is composed of a breaker 91 and a load 92. In each feeder 90, when a short circuit occurs within the feeder 90, the breaker 91 detects that an overcurrent has continued for a predetermined period of time and trips, thereby disconnecting the feeder 90 from the power grid 100.

[0014] Although not shown in FIG. 1, the power grid 100 may also include a power generation system that uses natural energy, such as a solar power generation system or a wind power generation system, arranged in parallel with the power supply device 1. Alternatively, a power generation system that uses fuel, such as a diesel generator or a cogeneration system, may also be arranged in parallel with the power supply device 1. The power supply device 1 can be used as a backup for the output of at least one of these power generation systems. In that sense, the power supply device 1 is also an uninterruptible power supply (UPS).

[0015] A specific example of the power system 100 is an isolated power system on a remote island or in a mountainous region. If a power generation system using natural energy is used in such a power system, applying the power supply device 1 equipped with the energy storage device 10 can smooth the power supply using natural energy. Alternatively, if a power generation system using fuel is used in such a power system 100, the power supply device 1 can also be used as a backup power source in case of a failure of the power generation system.

[0016] However, specific examples of the power system 100 are not limited to isolated power systems on remote islands or in mountainous areas, but may also be power systems within factories that use natural energy-based power generation systems or other power generation systems. Even in the case of a power system within a factory, the effects and functions of the disclosed examples of the present invention are similarly achieved.

[0017] The power supply device 1 according to the embodiment operates to continue supplying power to the power system 100 without stopping operation as much as possible even when a short circuit occurs in the feeder 90 while supplying power to the power system 100. In the following description, for ease of understanding, it is described as if only the power supply device 1 is supplying power to the power system 100. However, as long as the power supply device 1 is supplying power to the power system 100, the operation of the power supply device 1 is the same even if it is operated in parallel with another power generation system.

[0018] <Configuration of power supply unit 1> As shown in FIG. 1, the power supply device 1 includes an energy storage device 10, a DC-AC converter 20 (converter), a filter 30, a current meter 40, a voltage meter 50, and a control unit 60.

[0019] The energy storage device 10 is a device that stores input power as energy and outputs the stored energy as direct current power (DC output) as needed. The energy storage device 10 may be a device equipped with a secondary battery such as a lithium ion battery, a NaS (sodium-sulfur) battery, a redox flow battery, or a lead-acid battery.

[0020] However, the energy storage device 10 is not limited to a device equipped with a secondary battery. Any unit having a function of storing electrical energy, such as a capacitor, a superconducting power storage unit, a flywheel-type power storage unit, or a compressed air-type power storage unit, can be used as the energy storage device 10. Note that the concept of the energy storage device 10 being a device that outputs DC power also includes cases where power is first output internally as AC power and then converted to DC power using a rectifier circuit, converter, or the like.

[0021] The DC-AC converter 20 is a device that converts the direct current power (DC output) output by the energy storage device 10 into alternating current power (AC output). The DC-AC converter 20 converts the direct current power into alternating current power of the required voltage and frequency to be used by the power grid 100 via a filter 30 using PWM (Pulse Width Modulation) in accordance with an output command from the control unit 60. The filter 30 is a filter that removes harmonics contained in the output of the DC-AC converter 20. The current meter 40 and the voltage meter 50 respectively measure the current and voltage of the alternating current power (AC output) output by the power supply device 1 and transmit the information to the control unit 60.

[0022] <Configuration of control unit 60> Next, the configuration and operation of the control unit 60 will be specifically described with reference to Figures 2 and 3. Figure 2 is a diagram showing the control logic of the control unit 60 included in the power supply device 1. Figure 3 is a time chart showing signal waveforms of each part of the power supply device 1.

[0023] The output command output by the control unit 60 to the DC-AC converter 20 is the instantaneous value of the output voltage instructed by the control unit 60. The instantaneous value Vsin(ωt) is the product of the phase component sin(ωt) and the amplitude component V. The phase command representing the phase component sin(ωt) is calculated by a phase calculation 902 function block based on the frequency command (corresponding to ω).

[0024] The amplitude component V is calculated as an amplitude command. Since the amplitude is non-negative, a limiter 901 is provided to limit signals below 0 in the calculation of the amplitude command. The output command is generated by multiplying the amplitude command and the phase command in a multiplier 903.

[0025] In the control unit 60 of this embodiment, during normal times when no short circuit fault or momentary voltage drop (of about several hundred milliseconds) has occurred in any of the feeders 90, for example, during the period up to time T1 in Fig. 3 (the period indicated as "voltage control"), a voltage control mode is executed as a first control by the voltage control block 81 for the DC-AC converter 20. Furthermore, when a short circuit fault or the like has occurred in any of the feeders 90, for example, during the period from time T1 to time T2 in Fig. 3 (the period indicated as "current control"), a current control mode is executed as a second control by the current control block 61 for the DC-AC converter 20.

[0026] The voltage control block 81 is a functional block that is normally included in a control unit that controls the output of a DC-AC converter. The voltage control block 81 is provided with a voltage controller 802, to which a difference (voltage deviation) between a normal value (generally a rated voltage) of a voltage reference amplitude value as a voltage command is input.

[0027] The voltage controller 802 is a functional block that performs, for example, general PI control. The voltage controller 802 calculates its output based on the voltage deviation and the integration of the voltage deviation from the past. If the voltage deviation and the integration of the voltage deviation are zero, the voltage controller 802 continues to calculate a constant value as its output. If the voltage deviation and the integration of the voltage deviation are other than zero, the voltage controller 802 calculates its output so that the voltage deviation approaches zero. In this way, the control unit 60 feedback-controls the DC-AC converter 20 during normal times (up to time T1 in FIG. 3 ) so that the measured voltage value becomes the normal value.

[0028] In the above description, a functional block that performs general PI control is used for the voltage controller 802. However, the voltage controller 802 of this embodiment is not limited to any particular type as long as it can perform feedback control. For example, a functional block that performs other control such as general P control or differential control can also be used for the voltage controller 802.

[0029] Furthermore, voltage control block 81 includes multiplier 801 that multiplies the voltage deviation between the voltage measurement value (AC output voltage value) from voltage meter 50 and the normal value by the output of inverter circuit 703. The operation of inverter circuit 703 will be described later. During the normal operation, for example, as shown in the period up to time T1 in FIG. 3 , a signal of 1 (High level) is input from inverter circuit 703 to multiplier 801 of voltage control block 81. As a result, during the normal operation, in voltage control block 81, the voltage deviation is not set to 0 but is input to voltage controller 802, and feedback control of DC-AC converter 20 is performed.

[0030] 2, the control unit 60 is configured to add the normal value as the output of the voltage control block 81 and input the result to the DC-AC converter 20. However, since the normal value (rated voltage) is a constant value, as a result, the DC-AC converter 20 is feedback-controlled by the voltage deviation during normal operation.

[0031] Next, other functional blocks of the control unit 60 will be described. A current control block 61 is provided with a current controller 602, which receives as input the difference (current deviation) between the current output upper limit set value and the current measurement value as a current command. Here, in the control unit 60, the current output upper limit set value is a value determined as follows. Note that the current output upper limit set value L1 is indicated by a dotted line in the converter current chart of FIG. 3.

[0032] In normal operation when the measured current value is smaller than the first limit value, the first limit value is set as the current output upper limit setting value, which is set to a current value that will not damage the DC-AC converter 20 even if such a current is continuously output.

[0033] If a short circuit occurs in any of the feeders 90, a fault current flows, causing a sudden increase in the current output by the DC-AC converter 20. This causes the measured current value to exceed the first limit value. When the measured current value exceeds the first limit value, the control unit 60 increases the current output upper limit setting value calculated by the current control block 61 to the second limit value.

[0034] The second limit value is a value larger than the first limit value and is selected from values ​​equal to or lower than the short-term overload level of the DC-AC converter 20. The second limit value is set from a current value that will cause the breaker 91 of the feeder 90 in which a short circuit fault has occurred to trip if an overcurrent continues for a certain period of time in the breaker 91. A specific value of the second limit value that is appropriate is approximately 1.5 to 2 times the first limit value.

[0035] It is preferable that the control unit 60 gradually changes the current output upper limit setting value from the first limit value to the second limit value, in order to stably control the output voltage of the power supply device 1 in accordance with the change in the current upper limit value.

[0036] Furthermore, if the breaker 91 of the feeder 90 where the short-circuit fault occurs trips, the feeder 90 is disconnected. This is because the second limit value is set to a value that causes tripping when an overcurrent (fault current) continues for a certain period of time in the breaker 91 of the feeder 90 where the short-circuit fault occurred.

[0037] When the location where the short-circuit fault occurred is disconnected from the power grid 100, the outflow of the fault current stops, and the current output by the DC-AC converter 20 suddenly decreases and returns to a value smaller than the first limit value. When the measured current value falls below the first limit value, the control unit 60 sets the first limit value as the current output upper limit setting value. In other words, the setting of the current output upper limit setting value returns to normal.

[0038] The current control block 61 includes an effective value calculation 601 functional block to which the current measurement value (value of the AC output current) from the current measuring instrument 40 is input, a current controller 602 to which the difference (current deviation) between the current output upper limit setting value and the current measurement value (if the current measurement value is an instantaneous value, a value proportional to the effective value of the current waveform calculated by the effective value calculation 601 functional block) is input, and a limiter 603 connected to the current controller 602.

[0039] The current controller 602 is, for example, a functional block that performs general PI control. If the current deviation and the integral of the current deviation are 0, the current controller 602 continues to calculate 0 as the output. If the current deviation and the integral of the current deviation are other than 0, the current controller 602 calculates the output so that the current deviation approaches 0.

[0040] In the above description, a functional block that performs general PI control is used for the current controller 602. However, the current controller 602 of this embodiment is not limited to any particular type as long as it can perform feedback control. For example, a functional block that performs other control such as general P control or differential control can also be used for the current controller 602.

[0041] The output of the current controller 602 is calculated as a current suppression command (i.e., the output of the current control block 61) as it is through the limiter 603 if it is negative. Otherwise, the current suppression command is 0 due to the action of the limiter 603, and the output of the current controller 602 is not reflected.

[0042] Furthermore, the control unit 60 is equipped with a suppression detector 701 to which the output of the current control block 61 is input, a delay circuit 702 to which the output of the suppression detector 701 is input, and an inversion circuit 703 to which the output of the delay circuit 702 is input, and is configured so that the output of the inversion circuit 703 is input to the multiplier 801 of the voltage control block 81.

[0043] The suppression detector 701 is a functional block that outputs a signal of 1 (High level) when the current suppression command is a negative value, i.e., when the output of the current controller 602 is output without being cut by the limiter 603, and outputs a signal of 0 (Low level) otherwise. The delay circuit 702 is a functional block that, when the input signal is inverted from 0 to 1, inverts the signal from 0 to 1 with a predetermined delay time (for example, 10 ms) and outputs the signal.

[0044] At other times, the delay circuit 702 outputs the input signal as is. The inversion circuit 703 is a functional block that inverts the input 1 (high level) signal and 0 (low level) signal and outputs them. The suppression detector 701, delay circuit 702, inversion circuit 703, and multiplier 801 constitute the input blocking unit.

[0045] <Power supply unit 1 operation> Next, we will explain the operation of the power supply device 1. As described above, during the period up to time T1 in Fig. 3, the DC-AC converter 20 is feedback controlled by the voltage control block 81. At this time, the current output upper limit setting value L1 is the first limit value, and the measured current value is equal to or less than the first limit value, so a positive current deviation is input to the current controller 602.

[0046] Then, the current controller 602 outputs a positive signal to increase the output of the DC-AC converter 20, but the output is set to 0 by the action of the limiter 603, and the current suppression command becomes 0. Therefore, the current control block 61 does not contribute to the control of the DC-AC converter 20. Also, the suppression detector 701, which does not detect the output of the current controller 602, outputs a signal of 0 (low level), and a signal of 1 (high level) is output to the multiplier 801 via the inverting circuit 703, as described above.

[0047] When a short circuit occurs and the value of the AC output current exceeds the first limit value at time T1, the current deviation suddenly turns negative, the output of the current controller 602 becomes negative, and a current suppression command is output. The current suppression command is added to the amplitude command, and the output of the DC-AC converter 20 is rapidly suppressed. In this way, the value of the AC output current (measured current value) is rapidly suppressed.

[0048] Furthermore, the input cutoff unit forcibly sets the voltage deviation input to the voltage control block 81 to substantially zero in the following manner. Then, the voltage control block 81 does not substantially contribute to the control of the DC-AC converter 20.

[0049] The current suppression command from the current controller 602 is also output to the suppression detector 701. Then, the suppression detector 701 outputs a signal of 1 (High level) to a delay circuit 702 in accordance with the output (current suppression command) of the current control block 61. The delay circuit 702 outputs the signal received from the suppression detector 701 to an inversion circuit 703. The inversion circuit 703 inverts the level of the signal received from the suppression detector 701 via the delay circuit 702, and outputs the inverted signal to a multiplier 801 in the voltage control block 81.

[0050] 3, at time T1, the output from suppression detector 701 to delay circuit 702 is switched from low to high, and the output from inverter circuit 703 to multiplier 801 is switched from high to low. As a result, at time T1, the input cutoff unit including suppression detector 701, delay circuit 702, inverter circuit 703, and multiplier 801 forces the voltage deviation input to voltage control block 81 to be essentially zero.

[0051] In this way, after time T1, the DC-AC converter 20 is feedback-controlled by the current control block 61. That is, the control unit 60 controls the DC-AC converter 20 in the current control mode (second control mode). As described above, the control unit 60 gradually increases the current output upper limit setting value up to the second limit value, so the value of the AC output current (measured current value) gradually increases up to the second limit value and then becomes constant.

[0052] At time T2 in Fig. 3, when feeder 90, which generated the current itself, is disconnected as described above, the current output by DC-AC converter 20 suddenly decreases to a value smaller than the first limit value, as shown in the converter current in Fig. 3. Then, the current deviation suddenly turns positive, the output of current controller 602 becomes 0, and the current suppression command also becomes 0 due to the action of limiter 603. As a result, from time T2 onwards, current control block 61 no longer contributes to the control of DC-AC converter 20.

[0053] 3, at time T2, the output from suppression detector 701 to delay circuit 702 is switched from a signal of 1 (high level) to a signal of 0 (low level). Also, due to the function of delay circuit 702, at time T3, which is the delay period after time T2 in FIG. 3, the output from inverter circuit 703 to multiplier 801 is switched from a signal of 0 (low level) to a signal of 1 (high level).

[0054] That is, during the delay period between time points T2 and T3, the signal from the suppression detector 701 to the inverting circuit 703 is delayed by the delay circuit 702. Therefore, during this delay period, neither the current control block 61 nor the voltage control block 81 contributes to the control of the DC-AC converter 20, and open-loop control based on the voltage reference amplitude value (rated voltage value) is performed.

[0055] After that, from time T3 onwards, the signal from the inverting circuit 703 to the multiplier 801 is set to a signal of 1 (high level), so that the voltage control block 81 starts to control the DC-AC converter 20.

[0056] That is, in this embodiment, when the value of the current of the AC output exceeds the first limit value and then drops below the first limit value, the control unit 60 stops control of the DC-AC converter 20 by the current control block 61, and then, after a predetermined delay time has elapsed, causes the input cutoff unit to cancel the cutoff of the input of the voltage deviation to the voltage control block 81. Then, the control unit 60 causes the voltage control block 81 to perform feedback control.

[0057] In the power supply device 1 and control method thereof of this embodiment configured as described above, the control unit 60 has a voltage control block 81 that references the voltage deviation of the AC output voltage from its normal value and controls the DC-AC converter 20 so that the voltage value becomes the normal value. When the AC output current value exceeds a first limit value, the control unit 60 sets the voltage deviation input to the voltage control block 81 to substantially zero, and references the difference between the current value and a predetermined value greater than the first limit value and controls the DC-AC converter 20 so that the current value becomes the predetermined value. This makes it possible to avoid mutual interference between current control and voltage control in the event of a short-circuit accident or the like in this embodiment.

[0058] Furthermore, in this embodiment, when the value of the current of the AC output exceeds a first limit value and then falls below the first limit value, the control unit 60 stops control of the DC-AC converter 20 by the current control block 61 and cancels the cut-off of the input of the voltage deviation to the voltage control block 81 by the input cut-off unit. As a result, in this embodiment, after recovery from a short-circuit fault or the like, it is possible to switch from a current control mode by the current control block 61 for the DC-AC converter 20 to a voltage control mode by the voltage control block 81 for the DC-AC converter 20, and to appropriately switch the control mode for the DC-AC converter 20.

[0059] In this embodiment, the control unit 60 adds the output of the current control block 61 and the normal value (voltage amplitude reference value) as the output of the voltage control block 81. As a result, in this embodiment, the control unit 60 performs feedforward control using the normal value, and after recovery from a short-circuit accident or the like, the AC output voltage can be restored quickly.

[0060] In addition to the above description, the control unit 60 may omit the execution of feedforward control using the normal value as the output of the voltage control block 81, without adding the normal value to the output of the current control block 61. When the execution of feedforward control is omitted in this way, the control unit 60 in the power supply device 1 controls the output voltage (measured voltage value) to gradually return to normal when a short-circuit fault or the like is restored. This effectively prevents the occurrence of a transient overcurrent (biased magnetizing inrush current) in the transformer in the power system 100 that could damage the DC-AC converter 20 of the power supply device 1, for example, when the output voltage (measured voltage value) increases suddenly.

[0061] <Operation when capacitive load is applied> In this embodiment, when the value of the AC output current exceeds the first limit value, the voltage control mode is stopped and the control mode is switched to the current control mode. Therefore, the control unit 60 of this embodiment can suppress overcurrent (inrush current) and the occurrence of overvoltage or voltage drop (instantaneous voltage drop) by executing the current control mode even when, for example, a capacitor or a transformer is turned on as the load 92 in any of the feeders 90, which causes overvoltage or voltage drop.

[0062] As a comparative example, Fig. 4 shows the operation of a power supply device equipped with a control unit having only functions equivalent to voltage control block 81 of embodiment 1, which is a control unit configuration for controlling a general DC-AC converter, when a capacitive load is applied. In the comparative example, when a capacitive load such as a capacitor is applied at time T14, the AC output current value of DC-AC converter 20 rises to about twice the rated current, as shown in the converter current chart in Fig. 4. In addition, in this comparative example, the effective load voltage also rises to about 1.4 times the rated voltage.

[0063] In contrast, in the power supply device 1 of this embodiment, when a capacitive load such as a capacitor is applied at time T4 as shown in Fig. 5, the increase in the AC output current value of the DC-AC converter 20 can be suppressed to about 1.5 times the rated current, as shown in the converter current chart. Furthermore, in this embodiment, the increase in the effective load voltage can also be suppressed to about 1.08 times the rated voltage.

[0064] In the above embodiment, a configuration has been described in which delay circuit 702 is provided in the input cutoff unit to delay the release of cutoff of the voltage deviation input to voltage control block 81 by the input cutoff unit after control of DC-AC converter 20 by current control block 61 is stopped. However, this embodiment is not limited to this, and a configuration may be used in which the release of cutoff of the voltage deviation input to voltage control block 81 is not delayed.

[0065] That is, in the above embodiment, as shown in Fig. 3, the open-loop control is executed after the current control mode, and then the voltage control mode is executed. However, a configuration in which the delay circuit 702 is not installed and the execution of the open-loop control is omitted may be adopted. However, performing the open-loop control in the control unit 60 is preferable because it can reliably prevent chattering between the operation of the current control block 61 and the operation of the voltage control block 81, and it can easily stabilize the AC output after recovery from a short-circuit fault or the like.

[0066] Specifically, the control unit 60 performs open-loop control to prevent the fluctuation in the load voltage from being input into the voltage measurement value, causing the voltage controller 802 to fluctuate and output an overcurrent again.This is because chattering can be reliably prevented by resuming feedback control after the load voltage and the voltage measurement value have stabilized (i.e., after the vibration has subsided).

[0067] In the above description of the embodiment, the control of each phase is described as being performed by collective control without any particular distinction between phases. In this case, the control unit may perform control by adopting the minimum voltage value among the phases and the maximum current value among the phases as the voltage measurement value and the current measurement value. Alternatively, the three-phase instantaneous effective value (the root mean square of the instantaneous voltage value of each phase) may be adopted as the current measurement value. However, the control unit may also control each phase separately. In this case, the current upper limit value may be determined collectively or for each phase.

[0068] Furthermore, in the above description of the embodiment, the voltage command and the frequency command are treated as constant values, particularly rated values, and are not treated as variable values. This corresponds to the case where the power system 100 is operated under so-called constant voltage constant frequency (CFC) operation. However, when the power supply device 1 is operated in conjunction with a power generation system such as a diesel generator, whose voltage and frequency vary depending on the load state, the voltage command and the frequency command may be adjusted in response to such variations.

[0069] [Software implementation example] Each functional block of the power supply device 1 (particularly the control unit 60) may be realized by a logic circuit (hardware) formed on an integrated circuit (IC chip) or the like, or may be realized by software.

[0070] In the latter case, the power supply device 1 includes a computer that executes instructions of a program, which is software that realizes each function. This computer includes, for example, at least one processor (control device) and at least one computer-readable recording medium that stores the program. The object of the present invention is achieved by having the processor in the computer read and execute the program from the recording medium. The processor can be, for example, a CPU (Central Processing Unit).

[0071] The recording medium may be a "non-transitory tangible medium," such as a ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, or a programmable logic circuit. The computer may further include a RAM (Random Access Memory) for expanding the program. The program may be supplied to the computer via any transmission medium capable of transmitting the program (such as a communications network or broadcast waves). One aspect of the present invention may also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

[0072] 〔summary〕 In order to solve the above problem, a power supply device according to one aspect of the present disclosure includes an energy storage device, a converter that converts a DC output of the energy storage device into an AC output, a current meter that measures the current of the AC output, a voltage meter that measures the voltage of the AC output, and a control unit that controls the converter, wherein the control unit has a voltage control block that controls the converter by referring to a deviation of the voltage value from a normal value of the voltage so that the voltage value becomes the normal value, an input cut-off unit that sets the deviation input to the voltage control block to substantially zero when the current value exceeds a first limit value, and a current control block that controls the converter by referring to a difference between the current value and a predetermined value that is greater than the first limit value so that the current value becomes the predetermined value when the current value exceeds the first limit value.

[0073] According to the above configuration, it is possible to provide a power supply device that can prevent mutual interference between current control and voltage control when a short circuit or other accident occurs.

[0074] In the power supply device according to the above aspect, when the value of the current exceeds the first limit value and then drops below the first limit value, the control unit may stop control of the converter by the current control block and cancel the blocking of the input of the deviation to the voltage control block by the input blocking unit.

[0075] According to the above configuration, after recovery from a short circuit accident or the like, it is possible to switch from a current control mode by a current control block for the converter to a voltage control mode by a voltage control block for the converter, and the control mode for the converter can be switched appropriately.

[0076] In the power supply device according to the above aspect, the control unit may cancel the blocking of the input of the deviation to the voltage control block by the input blocking unit after a predetermined delay time has elapsed since the control of the converter by the current control block has stopped.

[0077] According to the above configuration, open-loop control is performed in the control unit, which reliably prevents chattering between the operation of the current control block and the operation of the voltage control block, and makes it easy to stabilize the AC output after recovery from a short-circuit accident or the like.

[0078] In the power supply device according to the aforementioned aspect, the control unit may add together the output of the voltage control block, the output of the current control block, and the normal value, and input the result to the converter.

[0079] According to the above configuration, the control unit performs feedforward control using the normal value, and after recovery from a short circuit or the like, the AC output voltage can be restored quickly.

[0080] Furthermore, a control method for a power supply device according to one aspect of the present disclosure is a control method for a power supply device including an energy storage device, a converter that converts a DC output of the energy storage device into an AC output, and a control unit that controls the converter, and executes a first control that controls the converter by referring to a deviation of a voltage value of the AC output from a normal value of the voltage so that the voltage value becomes the normal value, and when a current value of the AC output exceeds a first limit value, executes a second control that forcibly sets the deviation in the first control to essentially zero, and by referring to the difference between the current value and a predetermined value that is greater than the first limit value, controls the converter so that the current value becomes the predetermined value.

[0081] According to the above configuration, it is possible to provide a control method for a power supply device that can prevent mutual interference between current control and voltage control when a short circuit or other accident occurs.

[0082] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0083] 1 Power supply 10 Energy storage device 20 DC-AC converter (converter) 40 Current Meter 50 Voltage measuring instrument 60 Control Unit 61 Current Control Block 81 Voltage Control Block 701 Suppression detector (input cutoff section) 702 Delay circuit (input cutoff section) 703 Inverting circuit (input cutoff section) 801 Multiplier (input cutoff section)

Claims

1. an energy storage device; a converter that converts the DC output of the energy storage device into an AC output; a current meter for measuring the current of the AC output; a voltage meter for measuring the voltage of the AC output; a control unit that controls the converter, The control unit a voltage control block that controls the converter based on a deviation of the voltage value from a normal voltage value so that the voltage value becomes the normal voltage value; an input cutoff unit that, when the value of the current exceeds a first limit value, forcibly inputs a value substantially equal to 0 as the deviation value to the voltage control block; a current control block that, when the value of the current exceeds the first limit value, controls the converter by referring to a difference between the value of the current and a predetermined value that is greater than the first limit value, so that the value of the current becomes the predetermined value; When the value of the current exceeds the first limit value, control of the converter switches from control by the voltage control block to control by the current control block.

2. The control unit When the value of the current exceeds the first limit value and then falls below the first limit value, 2. The power supply device according to claim 1, wherein the control of the converter by the current control block is stopped, and the input cutoff unit cancels the cutoff of the input of the deviation to the voltage control block by forcibly inputting substantially zero as the deviation value.

3. The control unit 3. The power supply device according to claim 2, wherein the input cutoff unit cancels the cutoff of the input of the deviation to the voltage control block after a predetermined delay time has elapsed since the control of the converter by the current control block was stopped.

4. The control unit 4. The power supply device according to claim 1, wherein an output of said voltage control block, an output of said current control block, and said normal value are added together and input to said converter.

5. an energy storage device; a converter that converts the DC output of the energy storage device into an AC output; a control unit that controls the converter, executes a first control that controls the converter by referring to a deviation of a voltage value of the AC output from a normal value of the voltage so that the voltage value becomes the normal value; When the value of the current of the AC output exceeds a first limit value, The value of the deviation in the first control is forcibly set to substantially 0, and performing a second control to control the converter by referring to a difference between the value of the current and a predetermined value that is greater than the first limit value, so that the value of the current becomes the predetermined value. A control method for a power supply device, wherein control of the converter is switched from control that causes the voltage value to be the normal value to control that causes the current value to be the predetermined value.

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