No power outage device

Abstract

The uninterruptible power supply (100) receives power from the AC power source (1) and supplies power to the load (3) whose power consumption fluctuates periodically. The control device (20) has an input power limit value to limit the AC input power. When the AC power source (1) is healthy, the control device (20) controls the converter (10) so that the AC input power is equal to the input power limit value, and controls the bidirectional chopper (14) so ​​that the energy storage device (2) compensates for the difference between the input power limit value and the power consumption. The control device (20) periodically acquires the charge state of the energy storage device (2) at each discharge start timing of the energy storage device (2). At each discharge start timing, the control device (20) controls the input power limit value based on the acquired charge state so that the amount of power charged to the energy storage device (2) is equal to the amount of power discharged from the energy storage device.

Description

Technical Field

[0001] The present disclosure relates to an uninterruptible power supply device.

Background Art

[0002] For example, Japanese Patent Application Laid-Open No. 2015-61396 (Patent Document 1) discloses an uninterruptible power supply device having a power peak cut function. This uninterruptible power supply device includes a rectifier, a chopper, an inverter, and a controller. The rectifier rectifies the AC power received from the power system and supplies it to the inverter and the chopper. The inverter converts the input DC power into AC power and supplies it to the load. The chopper chops the DC power from the rectifier and supplies it to the battery during charging of the battery. The chopper chops the DC power from the battery and supplies it to the inverter during discharging of the battery.

[0003] In the above configuration, the controller has an assist mode in which the battery is discharged to assist power supply to the load, and a normal operation mode in which power supply to the load and charging of the battery are performed. The controller starts the assist mode in accordance with the time period when the power demand of the entire customer equipment reaches a peak, and reduces the power reception amount from the power system to a predetermined set value. At this time, the controller sequentially calculates the remaining dischargeable time of the battery, and ends the assist mode when the remaining dischargeable time reaches the lower limit value. Thereafter, in the time period when the power demand of the entire customer equipment decreases, the controller executes the normal operation mode to charge the battery.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The power consumption of loads connected to an uninterruptible power supply (UPS) may fluctuate periodically. For example, in data centers supporting AI (Artificial Intelligence) and IoT (Internet of Things) technologies, the power consumption of loads may fluctuate periodically due to the synchronous operation of multiple servers. In UPS systems applied to such loads, the input power required by the power grid will also fluctuate periodically in line with the periodic fluctuations in the load's power consumption. Therefore, there are concerns that increasing the load size could lead to instability in the power grid.

[0006] In the above-mentioned Patent Document 1, the system is configured to execute an assist mode for a certain period of time in accordance with the peak power demand of the entire customer's equipment when the load is operating at a constant power. However, when the power consumption of the load fluctuates periodically, it is necessary to repeatedly charge and discharge the battery in accordance with the periodic fluctuations in load power in order to assist in supplying power to the load. However, since the fluctuation patterns of load power consumption vary widely depending on the load, there is a concern that the battery may not be able to absorb the difference between the input power from the power grid and the power consumption of the load for loads with large fluctuations in power consumption. Therefore, there is a need for an uninterruptible power supply that can flexibly respond to various load fluctuation patterns.

[0007] This disclosure is made to solve the above-mentioned problems, and the purpose of this disclosure is to provide an uninterruptible power supply that can stabilize the power system by flexibly responding to fluctuations in the power consumption of the load. [Means for solving the problem]

[0008] An uninterruptible power supply (UPS) according to one aspect of this disclosure supplies power to a load whose power consumption fluctuates periodically. The UPS comprises a converter that converts AC input power supplied from an AC power source into DC power and supplies it to a DC line, an inverter that converts DC power received from the DC line into AC output power and supplies it to a load, a bidirectional chopper that exchanges DC power bidirectionally between the DC line and the energy storage device, and a control device that controls the UPS. The control device has an input power limit value for limiting the AC input power. When the AC power source is healthy, the control device controls the converter so that the AC input power is equal to the input power limit value. The control device controls the bidirectional chopper so that the energy storage device compensates for the difference between the input power limit value and the power consumption. The control device periodically acquires the charge state of the energy storage device at each discharge start timing of the energy storage device. At each discharge start timing, the control device controls the input power limit value based on the acquired charge state so that the amount of power charged to the energy storage device is equal to the amount of power discharged from the energy storage device. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide an uninterruptible power supply that can stabilize the power system by flexibly responding to fluctuations in the power consumption of the load. [Brief explanation of the drawing]

[0010] [Figure 1] This is a circuit block diagram showing the overall configuration of an uninterruptible power supply according to an embodiment of the present disclosure. [Figure 2] This is a block diagram showing an example of the hardware configuration of a control device. [Figure 3] This is a block diagram showing the main components of the control device. [Figure 4] This is a time chart showing an example of the operation of an uninterruptible power supply (UPS). [Figure 5] This block diagram shows the portion of the control circuit shown in Figure 3 that is related to the control of the converter. [Figure 6] This is a flowchart illustrating the processing in the input power control unit. [Figure 7] This block diagram shows the portion of the control circuit shown in Figure 3 that is related to the control of the bidirectional chopper. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will be described in detail below with reference to the drawings. In the following, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their descriptions will not be repeated in principle.

[0012] <Configuration of an uninterruptible power supply> Figure 1 is a circuit block diagram showing the overall configuration of an uninterruptible power supply (UPS) according to an embodiment of the present disclosure. As shown in Figure 1, the UPS 100 according to the present disclosure is connected between an AC power source 1 and a load 3. In reality, the UPS 100 receives three-phase AC power from the AC power source 1 and supplies three-phase AC power to the load 3, but for the sake of simplicity in the drawings and explanation, only a single-phase circuit is shown in Figure 1.

[0013] AC power source 1 is, for example, a power grid. Load 3 is driven by AC power Pout supplied from an uninterruptible power supply 100. The power consumption of load 3 (hereinafter also referred to as "load power") is assumed to fluctuate periodically. That is, AC power Pout fluctuates periodically in accordance with the load power.

[0014] The uninterruptible power supply (UPS) 100 includes an input terminal T1, a DC terminal T2, and an output terminal T3. The input terminal T1 receives AC power Pin at a predetermined frequency (e.g., commercial frequency) from an AC power source 1. The output terminal T3 is connected to a load 3. The DC terminal T2 is connected to a battery 2. The power storage device connected to the DC terminal T2 is not limited to a battery, but may be an electric double-layer capacitor.

[0015] The uninterruptible power supply 100 further includes a converter 10, a DC line 11, a capacitor 12, a bidirectional chopper 14, an inverter 16, switches S1 to S3, current detectors CD1 to CD3, an operating unit 18, and a control device 20.

[0016] The switch S1 is connected between the input terminal T1 and the AC node of the converter 10 and is controlled by the control device 20. When AC power is being normally supplied from the AC power supply 1 (when the AC power supply 1 is healthy), the switch S1 is turned on, and AC power is supplied from the AC power supply 1 to the converter 10 via the switch S1. When AC power is not being normally supplied from the AC power supply 1 (when the AC power supply 1 is abnormal), the switch S1 is turned off, and the connection between the AC power supply 1 and the converter 10 is interrupted.

[0017] The instantaneous value of the AC input voltage VI supplied from the AC power supply 1 is detected by the control device 20. The control device 20 determines whether the AC power supply 1 is healthy or abnormal based on the instantaneous value of the AC input voltage VI. The current detector CD1 detects the AC input current Ii flowing between the AC power supply 1 and the converter 10 and gives a signal Iif indicating the detected value to the control device 20.

[0018] The converter 10 is controlled by the control device 20 and, when the AC power supply 1 is healthy, converts the AC power from the AC power supply 1 into DC power and outputs it to the DC line 11. The converter 10 is a well-known one including a plurality of sets of semiconductor switching elements and diodes.

[0019] The capacitor 12 is connected to the DC line 11 and smoothes and stabilizes the DC voltage VD of the DC line 11. The instantaneous value of the DC voltage VD of the DC line 11 is detected by the control device 20.

[0020] When the AC power supply 1 is healthy, the control device 20 controls the converter 10 so that the AC power supplied from the AC power supply 1 becomes the input power limit value Pin*. The input power limit value Pin* is for limiting the AC power Pin (AC input power) supplied from the AC power supply 1 to the uninterruptible power supply device 100 to a constant value. The input power limit value Pin* will be described in detail later. When the AC power supply 1 is abnormal, the control device 20 stops the operation of the converter 10.

[0021] The DC line 11 is connected to the DC terminal T2 via the bidirectional chopper 14 and switch S2. Switch S2 is controlled by the control device 20. When the uninterruptible power supply 100 is in use, switch S2 is turned on. When the battery 2 or the bidirectional chopper 14 is being maintained, switch S2 is turned off.

[0022] The instantaneous value of the terminal voltage VB of battery 2 (hereinafter referred to as "battery voltage") is detected by the control device 20. The current detector CD2 detects the DC current IB (hereinafter referred to as "battery current") flowing between battery 2 and the bidirectional chopper 14, and provides the control device 20 with a signal IBf indicating the detected value.

[0023] The bidirectional chopper 14 is controlled by the control device 20 and exchanges DC power between the DC line 11 and the battery 2. The bidirectional chopper 14 is a well-known type that includes multiple sets of semiconductor switching elements and diodes, and a reactor. The control device 20 controls the bidirectional chopper 14 so that the DC voltage VD of the DC line 11 becomes the reference DC voltage VDR. In Figure 1, Pchg represents the power supplied from the DC line 11 to the battery 2 via the bidirectional chopper 14, i.e., the charging power to the battery 2. Pdischg represents the power supplied from the battery 2 to the DC line 11 via the bidirectional chopper 14, i.e., the discharge power from the battery 2.

[0024] The DC line 11 is connected to the DC node of the inverter 16, and the AC node of the inverter 16 is connected to the output terminal T3 via switch S3. Switch S3 is controlled by the control device 20. When the uninterruptible power supply 100 is in use, switch S3 is turned on. During maintenance of the inverter 16, switch S3 is turned off.

[0025] The current detector CD3 detects the AC output current Io of the inverter 16 and provides a signal Iof indicating the detected value to the control device 20. The instantaneous value of the AC output voltage VO applied to the load 3 from the uninterruptible power supply 100 is detected by the control device 20.

[0026] The inverter 16 is controlled by the control device 20 and converts the DC power supplied from the converter 10 or bidirectional chopper 14 via the DC line 11 into AC power of a predetermined frequency (e.g., commercial frequency) and supplies it to the load 3. The inverter 16 is a well-known one that includes multiple sets of semiconductor switching elements and diodes.

[0027] When AC power supply 1 is functioning correctly, inverter 16 converts the DC power supplied from converter 10 and bidirectional chopper 14 into AC power and supplies it to load 3. When AC power supply 1 malfunctions, inverter 16 converts the DC power supplied from bidirectional chopper 14 into AC power and supplies it to load 3. At this time, control device 20 controls inverter 16 so that the AC output voltage VO becomes the reference AC voltage VOR.

[0028] The control unit 18 includes multiple buttons operated by the user of the uninterruptible power supply 100, a display that shows various information, and other components. By operating the control unit 18, the user can turn the power of the uninterruptible power supply 100 on and off, and set various information.

[0029] The control device 20 controls the entire uninterruptible power supply 100 based on the AC input voltage VI, AC output voltage VO, DC voltage VD, battery voltage VB, AC input current Ii, battery current IB, AC output current Io, signals from the operation unit 18, and the like.

[0030] (Example of hardware configuration of control device 20) Figure 2 is a block diagram showing an example of the hardware configuration of the control device 20. Typically, the control device 20 can be configured using a microcomputer with a predetermined program pre-stored in it.

[0031] As shown in Figure 2, the control unit 20 comprises a CPU (Central Processing Unit) 200, memory 202, and input / output (I / O) circuit 204. The CPU 200, memory 202, and I / O circuit 204 can exchange data with each other via bus 206. A program is stored in a portion of the memory 202, and the CPU 200 can execute this program to realize various functions described later. The I / O circuit 204 exchanges signals and data between the control unit 20 and external devices.

[0032] Alternatively, unlike the example in Figure 2, at least a portion of the control device 20 can be configured using circuits such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit). Furthermore, at least a portion of the control device 20 can also be configured using analog circuits.

[0033] (Functional configuration of the control device 20) Figure 3 is a block diagram showing the main components of the control device 20. As shown in Figure 3, the control device 20 comprises voltage detectors 30-33, an anomaly detector 34, and a control circuit 35, and controls the entire uninterruptible power supply 100. Each functional block shown in Figure 3 can be implemented by program, hardware, or a combination thereof.

[0034] The voltage detector 30 detects the instantaneous value of the AC input voltage VI supplied from the AC power supply 1 and outputs a signal VIf indicating the detected value to the control circuit 35.

[0035] The voltage detector 31 detects the instantaneous value of the AC output voltage VO applied to the load 3 and outputs a signal VOf indicating the detected value to the control circuit 35.

[0036] The voltage detector 32 detects the instantaneous value of the DC voltage VD on the DC line 11 and outputs a signal VDf indicating the detected value to the control circuit 35.

[0037] The voltage detector 33 detects the instantaneous value of the terminal voltage (battery voltage) VB of the battery 2 and outputs a signal VBf indicating the detected value to the control circuit 35.

[0038] The abnormality detector 34 detects whether an abnormality has occurred in the AC power supply 1 based on the output signal VIf of the voltage detector 30, and outputs an abnormality detection signal DET to the control circuit 35 indicating the detection result. If the AC power supply 1 is healthy, the abnormality detection signal DET is set to the deactivation level L. If an abnormality has occurred in the AC power supply 1, the abnormality detection signal DET is set to the activation level H.

[0039] For example, if the AC input voltage VI is within the normal range, the anomaly detector 34 determines that the AC power supply 1 is healthy and sets the anomaly detection signal DET to a low level. If the AC input voltage VI is outside the normal range, the anomaly detector 34 determines that an anomaly has occurred in the AC power supply 1 and sets the anomaly detection signal DET to a high level.

[0040] The control circuit 35 controls the uninterruptible power supply 100 based on the output signals VIf, VOf, VDf, VBf from the voltage detectors 30 to 33, the output signals Iif, IBf, Iof from the current detectors CD1 to CD3, and the abnormality detection signal DET, etc.

[0041] Specifically, when AC power supply 1 is healthy (DET=L), the control circuit 35 controls the converter 10 so that the AC power supplied from AC power supply 1 is equal to the input power limit value Pin*. The control circuit 35 also controls the input power limit value Pin* based on the charge state of battery 2. Furthermore, the control circuit 35 controls the bidirectional chopper 14 so that the DC voltage VD of DC line 11 is equal to the reference DC voltage VDR. The control circuit 35 also controls the inverter 16 so that the AC output voltage VO is equal to the reference AC voltage VOR.

[0042] When the AC power supply 1 is abnormal (DET = H), the control circuit 35 turns off the switch S1, stops the operation of the converter 10, and controls the bidirectional chopper 14 so that the DC voltage VDB of the DC line 11 becomes the reference DC voltage VDR. Further, the control circuit 35 controls the inverter 16 so that the AC output voltage VO becomes the reference AC voltage VOR.

[0043] <Operation of the uninterruptible power supply device> Next, the operation of the uninterruptible power supply device 100 will be described.

[0044] FIG. 4 is a time chart showing an operation example of the uninterruptible power supply device 100. FIG. 4(A) shows the waveform of the output power Pout of the uninterruptible power supply device 100, and FIG. 4(B) shows the waveform of the input power Pin of the uninterruptible power supply device 100. FIG. 4(C) shows the waveform of the charge / discharge power of the battery 2, and FIG. 4(D) shows the waveform of the state of charge of the battery 2. In FIG. 4(D), the state of charge (SOC) is used as an index of the state of charge of the battery 2. The SOC represents, for example, the ratio of the current stored amount to the stored amount in the fully charged state, expressed as 0 to 100%. In FIG. 4(C), the discharge power Pdischg of the battery 2 is represented by a positive value, and the charge power Pch is represented by a negative value.

[0045] As shown in FIG. 4(A), the output power Pout of the uninterruptible power supply device 100 varies periodically in response to the variation of the load power. For example, the output power Pout varies periodically between the maximum power consumption P1 [W] and the minimum power consumption P2 [W]. Specifically, in each variation cycle, the output power Pout increases temporarily to the maximum power consumption P1 [W] and then maintains the minimum power consumption P2 [W].

[0046] On the other hand, as shown in FIG. 4(B), in each variation cycle of the load power, power Pin equal to the input power limit value Pin* is constantly input to the uninterruptible power supply device 100. In FIG. 4(B), Pin* = P3 [W] is set. The relationship P1 < P2 < P3 holds among P1 to P3.

[0047] By setting the input power limit value Pin* in this way, the uninterruptible power supply 100 can maintain a constant input power Pin even though the output power Pout fluctuates periodically. This makes it possible to stabilize the power system against fluctuations in load power.

[0048] On the other hand, a discrepancy arises between the power Pin supplied from AC power source 1 and the power Pout that should be output to load 3. In the example in Figure 4(A), the output power Pout fluctuates between P1[W] and P2[W]. Therefore, if the output power Pout is greater than the input power limit value Pin*, there will be insufficient power supply from AC power source 1, and if the output power Pout is less than the input power limit value Pin*, there will be an excess of power supply from AC power source 1.

[0049] Therefore, the uninterruptible power supply (UPS) 100 is configured to compensate for the difference between the input power limit value Pin* and the output power Pout by charging and discharging the battery 2. Specifically, if the output power Pout is greater than the input power limit value Pin*, the power equivalent to the deficit is compensated for by the discharge power Pdischg from the battery 2. Conversely, if the output power Pout is less than the input power limit value Pin*, the power equivalent to the surplus is used as the charging power Pchg to the battery 2.

[0050] The charging and discharging of the battery 2 is performed by a bidirectional chopper 14. Specifically, the bidirectional chopper 14 is configured to exchange DC power between the DC line 11 and the battery 2, which includes a feedback component whose value corresponds to the deviation ΔVDR = VDR - VD between the reference DC voltage VDR and the DC voltage VD detected by the voltage detector 32.

[0051] According to this, the battery 2 will be discharged and charged repeatedly in response to fluctuations in output power Pout. As shown in Figure 4(C), in each fluctuation cycle, during the period Tdischg when the output power Pout temporarily increases, power Pdischg equivalent to the difference between the maximum power consumption P1[W] and the input power limit P3[W], Pout-Pin*=P1-P3[W], is discharged from the battery 2. Also, during the period Tchg when the output power Pout is at the minimum power consumption P2[W], power Pchg equivalent to the difference between the minimum power consumption P2[W] and the input power limit P3[W], Pout-Pin*=P2-P3[W], is charged into the battery 2.

[0052] Here, if the amount of discharged power in period Tdischg and the amount of charged power in period Tchg can be made equal in each fluctuation cycle, the total amount of power input and output to battery 2 per fluctuation cycle will be 0, and the input power limit value Pin* can be set to the lowest constant value.

[0053] However, the load power fluctuation pattern (such as the magnitude and frequency of the load power fluctuation) varies greatly depending on the load 3. Therefore, if the input power limit value Pin* is fixed to a constant value, depending on the load 3, it may not be possible to make the total amount of power input and output to the battery 2 per fluctuation period zero. In such cases, it becomes difficult for the uninterruptible power supply 100 to compensate for the load power fluctuation by charging and discharging the battery 2, and as a result, the power stored in the battery 2 may become unusable when the AC power supply 1 malfunctions. Therefore, the uninterruptible power supply 100 is required to be able to flexibly respond to various load 3 fluctuation patterns.

[0054] To address these concerns, in this embodiment, when the AC power supply 1 is healthy, the control device 20 is configured to control the input power limit value Pin* based on the charge state of the battery 2. The method for controlling the input power limit value Pin* will be described below.

[0055] If, in each fluctuation cycle, the amount of discharged energy during period Tdischg is equal to the amount of charged energy during period Tchg, then, as shown in Figure 4(D), the State of Charge (SOC) at the timing of the switch from charging to discharging in each fluctuation cycle (corresponding to "Discharge Start Timing Tdischg" in the figure) will be a constant value.

[0056] Therefore, the control device 20 acquires the charge state of the battery 2 at each timing Tdischg when the discharge of the battery 2 begins, and controls the input power limit value Pin* so that the acquired charge state becomes a predetermined target charge state. For example, when acquiring the State of Charge (SOC) of the battery 2 as the charge state of the battery 2, the control device 20 controls the input power limit value Pin* so that the acquired SOC becomes the target SOC (hereinafter referred to as "SOC*").

[0057] Figure 5 is a block diagram showing the portion of the control circuit 35 shown in Figure 3 that is related to the control of the converter 10. As shown in Figure 5, the control circuit 35 consists of a timing detection unit 50, an SOC calculation unit 52, an input power control unit 54, a multiplier 56, a subtractor 58, a current control unit 60, and a PWM (Pulse Width Modulation) circuit 62.

[0058] The timing detection unit 50 detects the discharge start timing Tdischg of the battery 2 based on the battery current IB indicated by the output signal IBf of the current detector CD2. If the discharge current of the battery 2 is represented by a positive value and the charging current by a negative value, the timing detection unit 50 can detect the timing at which the polarity of the battery current IB switches from negative to positive as the discharge start timing Tdischg. The timing detection unit 50 notifies the SOC calculation unit 52 that the Nth (current) discharge start timing Tdischg(N) has arrived.

[0059] The SOC calculation unit 52 calculates the State of Charge (SOC) of battery 2 for each discharge start timing Tdischg. In the following description, the SOC of battery 2 calculated at the Nth (current) discharge start timing Tdischg(N) will be represented as SOC(N). In some cases, the SOC calculation unit 52 calculates SOC(N) based on the battery current IB detected by the current detector CD2 and / or the battery voltage VB detected by the voltage detector 33. Various known methods can be used to calculate the SOC of battery 2, such as a method using current value integration or a method using open circuit voltage (OCV) estimation. The SOC calculation unit 52 outputs a signal SOCf indicating the acquired SOC(N) to the input power control unit 54. The SOC calculation unit 52 corresponds to one embodiment of the "charge state acquisition unit" that acquires the charge state of battery 2.

[0060] In another scenario, the charge state acquisition unit may acquire the State of Charge (SOC) of the battery 2 by communicating with a Battery Management Unit (BMU) for monitoring the state of the battery 2. The BMU has sensors for detecting the terminal voltage of the battery 2, the current input and output to the battery 2, and the temperature of the battery, and is configured to calculate the SOC of the battery 2 based on the output of these sensors.

[0061] In another scenario, the charge state acquisition unit may acquire the charge state of the battery 2 based on the battery voltage VB detected by the voltage detector 33. For example, the charge state acquisition unit can acquire the charge state of the battery 2 based on the deviation between the battery voltage VB and a predetermined target battery voltage VB*.

[0062] In another scenario, the charge state acquisition unit may acquire the charge state of battery 2 based on the battery current IB detected by the current detector CD2. One method of charging the battery is to perform constant current charging, which charges the battery with a constant current until the battery voltage reaches a predetermined voltage, and then perform constant voltage charging, which charges the battery while maintaining a constant battery voltage. In this method, the battery current gradually decreases during constant voltage charging. The charge state acquisition unit can acquire the charge state of battery 2 based on the deviation between the battery current IB detected by the current detector CD2 and a predetermined target battery current IB*.

[0063] The input power control unit 54 controls the input power limit value Pin* based on the SOC(N) at the Nth discharge start timing Tdischg, which is calculated by the SOC calculation unit 52, and the target charge level SOC*.

[0064] The target charge level (SOC)* can be set to any value by the user of the uninterruptible power supply (UPS) 100 using the control unit 18. In certain situations, the SOC* is set to be equal to or greater than the SOC (hereinafter also referred to as "SOC for power outage compensation") necessary to ensure the UPS 100's function as a backup power source in the event of an abnormality in the AC power supply 1 (power outage compensation function). This SOC for power outage compensation can be calculated based on the rated current and compensation time of the UPS 100, assuming that the load 3 is at its rated load when an abnormality occurs in the AC power supply 1.

[0065] The input power control unit 54 compares SOC(N) and SOC*. It also compares SOC(N-1) and SOC(N). SOC(N-1) is the State of Charge (SOC) of battery 2 calculated at the N-1th (previous) discharge start timing Tdischg(N-1). Based on these comparison results, the input power control unit 54 controls the input power limit value Pin*. Figure 6 is a flowchart illustrating the processing in the input power control unit 54. The flowchart in Figure 6 is repeatedly executed by the control device 20 when the AC power supply 1 is healthy.

[0066] As shown in Figure 6, in step 10 (hereinafter simply referred to as "S"), the input power control unit 54 determines whether the Nth (current) discharge start timing Tdischg(N) has arrived based on the signal from the timing detection unit 50. In S10, each time the polarity of the battery current IB detected by the current detector CD2 switches from negative to positive, it is determined that the discharge start timing Tdischg has arrived.

[0067] If it is determined that the Nth discharge start timing Tdischg(N) has arrived (when S10 is determined to be YES), in S20 the input power control unit 54 obtains the SOC(N) of the battery 2 at the Nth discharge start timing Tdischg(N) based on the output signals of the current detector CD2 and / or the voltage detector 33.

[0068] Next, the input power control unit 54 performs the processes from S30 to S90 to determine the input power limit value Pin*(N) at the Nth discharge start timing Tdischg(N) based on the acquired SOC(N).

[0069] In detail, first in S30, the input power control unit 54 calculates the deviation ΔSOC = SOC* - SOC(N) between the target charge level SOC* and SOC(N). Then, the input power control unit 54 compares the magnitude (absolute value) of the deviation ΔSOC with a predetermined threshold Sth.

[0070] If the magnitude of the deviation ΔSOC is smaller than the threshold Sth (when S30 is judged as YES), the input power control unit 54 determines Pin*(N) to be equal to Pin*(N-1) in S40. Pin*(N-1) is the input power limit value Pin* determined at the N-1th (previous) discharge start timing Tdischg(N-1).

[0071] On the other hand, if the magnitude of the deviation ΔSOC is greater than or equal to the threshold Sth (when NO is determined in S30), the input power control unit 54 compares SOC(N) and SOC* in S50. If SOC(N) is smaller than SOC* (when YES is determined in S50), the input power control unit 54 further compares SOC(N) and SOC(N-1) in S60. In other words, the input power control unit 54 grasps the trend of change in SOC by comparing SOC(N) at the discharge start timing Tdischg(N) of the Nth time (this time) with SOC(N-1) at the discharge start timing Tdischg(N-1) of the N-1 time (previous time).

[0072] If SOC(N) is greater than SOC(N-1) (when S60 is determined to be YES), the input power control unit 54 determines Pin*(N) to be equal to Pin*(N-1) in S40.

[0073] On the other hand, if SOC(N) is less than or equal to SOC(N-1) in S60 (when NO is determined in S60), the input power control unit 54 increases Pin*(N) by a predetermined amount A compared to Pin*(N-1) in S70. The predetermined amount A at this time is set to an appropriate value that is smaller than the load power.

[0074] Returning to S50, if SOC(N) is greater than or equal to SOC* (when S50 is judged as NO), the input power control unit 54 compares SOC(N) and SOC(N-1) in S80. If SOC(N) is less than SOC(N-1) (when S80 is judged as YES), the input power control unit 54 determines Pin*(N) to be equal to Pin*(N-1) in S40.

[0075] On the other hand, if SOC(N) is greater than or equal to SOC(N-1) in S80 (when NO is determined in S80), the input power control unit 54 reduces Pin*(N) by a predetermined amount A from Pin*(N-1) in S90. This predetermined amount A may be the same as or different from the predetermined amount A in S70.

[0076] According to the process shown in Figure 6, Pin*(N) is determined to be equal to Pin*(N-1) in the following cases: (1) when the magnitude of the deviation between SOC(N) and SOC* is less than the threshold Sth; (2) when SOC(N) is less than SOC* but SOC(N) is greater than SOC(N-1) (i.e., when SOC is increasing); and (3) when SOC(N) is greater than SOC* but SOC(N) is less than SOC(N-1) (i.e., when SOC is decreasing).

[0077] Furthermore, (4) if SOC(N) is less than SOC* and SOC(N) is less than or equal to SOC(N-1) (i.e., SOC is decreasing), then Pin*(N) increases by a predetermined amount A from Pin*(N-1). (5) if SOC(N) is greater than or equal to SOC* and SOC(N) is greater than or equal to SOC(N-1) (i.e., SOC is increasing), then Pin*(N) decreases by a predetermined amount A from Pin*(N-1).

[0078] In this way, even when the load power fluctuation pattern (such as fluctuation range and fluctuation period) is unknown or when the fluctuation pattern changes depending on the operating state of load 3, the input power limit value Pin* can be controlled so that the sum of the discharged power amount of battery 2 and the charged power amount of battery 2 within the period defined by two adjacent discharge start timings (corresponding to the load power fluctuation period) is 0, based on the State of Charge (SOC) of battery 2 acquired for each discharge start timing Tdischg. By variably controlling the input power limit value Pin* in response to load power fluctuations in this way, it becomes possible to flexibly respond to load power fluctuations and achieve input power leveling.

[0079] Although not shown in the diagram, when acquiring the battery voltage VB as the charge state of battery 2, the input power control unit 54 is configured to control the input power limit value Pin* so that the acquired battery voltage VB becomes the target battery voltage VB*. Similarly, when acquiring the battery current IB as the charge state of battery 2, the input power control unit 54 is configured to control the input power limit value Pin* so that the acquired battery current IB becomes the target battery current IB*.

[0080] Returning to Figure 5, the input power limit value Pin* determined by the input power control unit 54 is provided to the multiplier 56. The multiplier 56 generates a current command value Ii* by dividing the input power limit value Pin* by the AC input voltage VI detected by the voltage detector 30. This generates a current command value Ii* that is in phase with the AC input voltage VI supplied from the AC power supply 1.

[0081] The subtractor 58 calculates the difference ΔIi = Ii* - Ii between the current command value Ii* and the AC input current Ii indicated by the output signal Iif of the current detector CD1.

[0082] The current control unit 60 generates a voltage command value VI* such that the deviation ΔIi becomes 0. The current control unit 60 generates the voltage command value VI* by, for example, proportional control or proportional-integral control of the deviation ΔIi.

[0083] The PWM circuit 62 controls the converter 10 based on a sinusoidal voltage command value VI* when the abnormality detection signal DET from the abnormality detector 34 is at a low level (when the AC power supply 1 is healthy). The PWM circuit 62 also stops the operation of the converter 10 when the abnormality detection signal DET is at a high level (when the AC power supply 1 is abnormal).

[0084] Figure 7 is a block diagram showing the portion of the control circuit 35 shown in Figure 3 that is related to the control of the bidirectional chopper 14. As shown in Figure 7, the control circuit 35 consists of subtractors 40, 44, a voltage control unit 42, a current control unit 46, and a PWM circuit 48.

[0085] The subtractor 40 calculates the difference ΔVD = VDR - VD between the reference DC voltage VDR and the DC voltage VD detected by the voltage detector 32.

[0086] The voltage control unit 42 determines a current command value IB* corresponding to the deviation ΔVD based on the battery voltage VB detected by the voltage detector 33. The voltage control unit 42 determines the current command value IB* by, for example, performing a proportional or proportional-integral operation on the deviation ΔVD.

[0087] The subtractor 44 calculates the difference ΔIB = IB* - IB between the current command value IB* generated by the voltage control unit 42 and the battery current IB indicated by the output signal IBf of the current detector CD2.

[0088] The current control unit 46 generates a voltage command value VD* based on the deviation ΔIB. The current control unit 46 determines the voltage command value VD* by, for example, performing a proportional or proportional-integral operation on the deviation ΔIB. The PWM circuit 48 controls the bidirectional chopper 14 based on the voltage command value VD*. The bidirectional chopper 14 exchanges DC power between the DC line 11 and the battery 2, with a value corresponding to the deviation ΔVD between the reference DC voltage VDR and the DC voltage VD.

[0089] When the AC power supply 1 malfunctions, the converter 10 stops operating, and the bidirectional chopper 14 is controlled to exclusively supply DC power from the battery 2 to the DC line 11. In this case, the control circuit 35 also controls the bidirectional chopper 14 so that the DC voltage VD becomes the reference DC voltage VDR. Therefore, during the period when the AC power supply 1 malfunctions, the state of charge (SOC) of the battery 2 gradually decreases from the target charge level (SOC*). However, when the AC power supply 1 is restored, the input power limit value Pin* is controlled according to the process shown in Figure 6 so that the SOC acquired at each discharge start timing Tdischg approaches SOC*, thereby allowing the SOC of the battery 2 to recover while suppressing fluctuations in the input power Pin from the AC power supply 1.

[0090] <Effects and Effects> As described above, the uninterruptible power supply 100 according to this embodiment is provided with an input power limit value Pin*, which allows the input power from the AC power supply 1 to be leveled out in response to fluctuations in load power.

[0091] Furthermore, in this embodiment, the input power limit value Pin* is appropriately controlled based on the charge state of the energy storage device acquired at each discharge start timing Tdischg, so that the charge state of the energy storage device, which compensates for the difference between the output power Pout of the uninterruptible power supply 100 and the input power limit value Pin*, maintains the target charge state. As a result, even when the fluctuation pattern of the load power (such as the fluctuation range and fluctuation period) is unknown or when the fluctuation pattern changes depending on the operating state of the load, the input power limit value Pin* can be controlled to the minimum input power that can maintain the charge state of the energy storage device. Therefore, the uninterruptible power supply 100 can flexibly respond to fluctuations in load power while leveling the input power from the AC power source 1.

[0092] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. This disclosure is indicated by the claims rather than the foregoing description and is intended to include all modifications in the meaning and scope of the claims equivalents. [Explanation of symbols]

[0093] 1 AC power supply, 2 Battery, 3 Load, 10 Converter, 11 DC line, 12 Capacitor, 14 Bidirectional chopper, 16 Inverter, 18 Operating unit, 20 Control unit, 30-33 Voltage detector, 34 Anomaly detector, 35 Control circuit, 40, 44, 58 Subtractor, 42 Voltage control unit, 46, 60 Current control unit, 48, 62 PWM circuit, 50 Timing detection unit, 52 SOC calculation unit, 54 Input power control unit, 56 Multiplier, 100 Uninterruptible power supply, 200 CPU, 202 Memory, 204 I / O circuit, 206 Bus, CD1-CD3 Current detector, S1-S3 Switch, T1 Input terminal, T2 DC terminal, T3 Output terminal.

Claims

1. An uninterruptible power supply that supplies power to a load whose power consumption fluctuates periodically, A converter that converts AC input power supplied from an AC power source into DC power and supplies it to a DC line, An inverter that converts the DC power received from the DC line into AC output power and supplies it to the load, A bidirectional chopper that transmits and receives DC power bidirectionally between the DC line and the energy storage device, The system includes a control device for controlling the aforementioned uninterruptible power supply, The control device has an input power limit value for limiting the AC input power, When the AC power supply is functioning properly, the control device will: The converter is controlled so that the AC input power becomes equal to the input power limit value. The bidirectional chopper is controlled so that the energy storage device compensates for the difference between the input power limit and the power consumption. At each discharge start timing of the energy storage device, the charge state of the energy storage device is periodically acquired. An uninterruptible power supply that controls the input power limit value so that the amount of power charged to the energy storage device and the amount of power discharged from the energy storage device are equal, based on the acquired charge state at each discharge start timing.

2. The uninterruptible power supply according to claim 1, wherein the control device controls the input power limit value based on the acquired charge state, the target charge state of the energy storage device, and the charge state at the previous discharge start timing, for each discharge start timing.

3. The control device, at each discharge start timing, If the acquired charge state is higher than the target charge state and higher than the previous charge state, the input power limit value is reduced by a predetermined amount. If the acquired charge state is lower than the target charge state and lower than the previous charge state, the input power limit value is increased by a predetermined amount. The uninterruptible power supply according to claim 2, wherein the acquired charge state is higher than the target charge state and lower than the previous charge state, the acquired charge state is equal to the target charge state, or the acquired charge state is lower than the target charge state and higher than the previous charge state, the input power limit value is maintained.

4. The uninterruptible power supply according to any one of claims 1 to 3, wherein, when the AC power supply is functioning properly, the control device controls the bidirectional chopper so that the DC voltage of the DC line becomes the reference DC voltage.

5. In the event of an abnormality in the AC power supply, the control device shall The operation of the aforementioned converter is stopped, The uninterruptible power supply according to claim 4, wherein the bidirectional chopper is controlled so that the DC voltage of the DC line becomes the reference DC voltage.

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