Power interchange system

Abstract

To provide a power interchange system capable of interchanging DC power between power converters at high speed.SOLUTION: A power interchange system (100) includes a plurality of first DC systems (1A, 1B, and 2C) including power converters (1A, 1B, and 2C), first facility units (3A, 3B, and 1C) that perform at least one of consumption of DC power from the power converters (,, and) and supply of the DC power, and first control units (,, and) that control the power converters (,, and). 2C 1A 10C 10A 2B 1B 10B 2A 2C, the first DC systems (10A, 10B, 10C) are connected to each other via the DC system (50), and the first control units (2A, 2B, 2C) control the power converters (1A, 1B, 2C) in accordance with sharing characteristics that define sharing ratios of input / output currents of the power converters (,,) to a DC voltage of the DC system (50). 1A 1B 2C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power interchange system. [Background technology]

[0002] In factories and other places, various machines such as machine tools and robots are in operation. These machines store kinetic energy in their mechanical systems in addition to the energy used for their intended work. This stored energy is converted into heat electrically or mechanically when the mechanical system is braked, and the energy converted electrically is called regenerative power. The regenerative power is extracted as DC power via a motor drive circuit such as an inverter. To utilize this regenerative power, there is a DC system that connects a device that generates regenerative power with a device that consumes the regenerative power.

[0003] A DC system typically includes an AC / DC converter, which exchanges power bidirectionally between the AC system and the DC bus. Any regenerative power that cannot be absorbed by the equipment is output to the AC system via this AC / DC converter, preventing an increase in the DC bus voltage due to the regenerative power. However, conversion loss occurs when converting DC power to AC power. Furthermore, when load equipment is operating and there is no regenerative power in the DC bus, power must be supplied from the AC system to the DC bus, which also results in conversion loss in the AC / DC converter. To reduce such conversion loss, a power interchange system with the following configuration has been disclosed.

[0004] That is, a conventional power interchange system includes power lines that connect multiple power communities without going through a commercial power grid, power interchange equipment that is installed on the power lines and adjusts the power exchanged between the multiple power communities, a control device that controls the power interchange equipment, and a management device that manages the multiple power communities, and the control device is connected to the management device via a communication line and controls the power interchange equipment in response to control commands from the management device (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7121902 Summary of the Invention [Problem to be solved by the invention]

[0006] In the conventional power interchange system described above, multiple power communities are connected by power lines separate from the commercial power grid, and power is interchanged by controlling power interchange devices installed on the power lines, eliminating the need for reverse power flow to the commercial power grid. However, because the power interchange devices interchange power between DC systems in response to commands from a management device, their control response speed is slow, and there are cases where rapid power interchange is not possible. As a result, there are issues with the system being unable to quickly respond to short-term power fluctuations such as sudden load changes and regeneration. For example, there is a problem that excessive power may temporarily exist in the DC power system, causing the system to become unstable.

[0007] The present disclosure discloses a technology for solving the above-mentioned problems, and aims to provide a power interchange system that controls the interchange of power present in a DC power system between power converters at high speed at a set sharing rate, thereby ensuring stability. [Means for solving the problem]

[0008] The power interchange system of the present disclosure includes: a power converter for supplying DC power; a first DC transmission line that transmits DC power from the power converter; a first facility unit connected to the first DC transmission line and configured to at least one of consume DC power supplied from the first DC transmission line and supply DC power to the first DC transmission line; a first control unit that controls the power converter; and a plurality of first DC systems each having the first DC system and the first control unit. A power interchange system that interchanges DC power between each of the first DC systems via a DC system configured by connecting the first DC transmission lines of each of the first DC systems by a second DC transmission line, The first control unit of each of the first DC systems controlling the power converters in accordance with sharing characteristics that define the respective sharing rates of input and output currents of the power converters in the power interchange system; It is something. [Effects of the Invention]

[0009] According to the power interchange system of the present disclosure, the power present in the DC power system is quickly interchange-controlled between power converters at a set sharing rate, thereby providing a power interchange system with ensured stability. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a schematic configuration of a power interchange system according to a first embodiment. [Figure 2] 1 is a block diagram showing a schematic configuration of a regenerative load facility according to a first embodiment. [Figure 3] 1 is a block diagram showing a schematic configuration of an AC / DC converter and a converter control section according to a first embodiment. [Figure 4] 1 is a block diagram showing a schematic configuration of a DC / DC converter and a power storage device control unit according to a first embodiment. [Figure 5] FIG. 3 is a diagram for explaining the operation of the regenerative load equipment according to the first embodiment. [Figure 6] FIG. 4 is a diagram illustrating a drooping characteristic according to the first embodiment. [Figure 7] FIG. 4 is a diagram illustrating a drooping characteristic according to the first embodiment. [Figure 8] 5 is a diagram illustrating changes in output current of each of the AC / DC converter and the power storage device according to the first embodiment. FIG. [Figure 9]10 is a diagram illustrating a change in current sharing during a transient state when a low-pass filter is set for a DC voltage command value according to the first embodiment. FIG. [Figure 10] FIG. 10 is a block diagram showing a schematic configuration of a power interchange system according to a second embodiment. [Figure 11] FIG. 11 is a block diagram showing a schematic configuration of a power interchange system according to a third embodiment. [Figure 12] FIG. 11 is a block diagram showing a schematic configuration of a power interchange system according to a third embodiment. [Figure 13] FIG. 2 is a diagram illustrating a schematic configuration of hardware of a control device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiment 1 FIG. 1 is a block diagram showing a schematic configuration of a power interchange system 100 according to a first embodiment of the present disclosure. FIG. 2 is a block diagram showing a schematic configuration of the regenerative load facility F according to the first embodiment of the present disclosure. FIG. 3 is a block diagram showing a schematic configuration of AC / DC converters 1A and 1B and converter control units 2A and 2B according to the first embodiment of the present disclosure. FIG. 4 is a block diagram showing a schematic configuration of a DC / DC converter 2C and a power storage device control unit 3C according to the first embodiment of the present disclosure.

[0012] As shown in FIG. 1, the power interchange system 100 is configured by connecting a regenerative load system 10A as a first DC system, a regenerative load system 10B as a first DC system, and a power storage device 10C as a first DC system via a DC system 50.

[0013] The regenerative load system 10A includes an AC / DC converter 1A as a power converter, a converter control unit 2A as a first control unit that controls the AC / DC converter 1A, and a regenerative load equipment group 3A as a first equipment unit having multiple regenerative load equipment F. The AC / DC converter 1A and the regenerative load equipment group 3A are connected via a DC bus 51A serving as a first DC transmission line for transmitting DC power.

[0014] The AC / DC converter 1A is driven by a signal output from the converter control unit 2A, converts AC power from the AC system 90 into DC power, and supplies the converted DC power to the regenerative load equipment group 3A via the DC bus 51A. The converter control unit 2A performs constant voltage control so that the output voltage of the AC / DC converter 1A becomes a target value.

[0015] If the voltage range of AC system 90 differs from the input voltage range of AC / DC converter 1A of regenerative load system 10A, the voltage of AC system 90 is converted by transformer 91 and input to AC / DC converter 1A. A protection device 92 is installed between transformer 91 and AC / DC converter 1A to detect and cut off overcurrent, leakage current, etc.

[0016] The AC / DC converter 1A may also perform reverse conversion, converting DC power regenerated by the regenerative operation of the regenerative load equipment group 3A into AC power and outputting it to the AC system 90.

[0017] As shown in the schematic configuration diagram of FIG. 2, each of the regenerative load equipment F included in the regenerative load equipment group 3A includes an inverter unit F1, a rotating machine F2, and an inverter control unit F3. The inverter control unit F3 outputs a signal for controlling the operation of the rotating machine F2 to the inverter unit F1. The inverter unit F1 converts the received DC power into AC power for driving the rotating machine F2 and outputs the AC power. The rotating machine F2 is driven by AC power received from the inverter unit F1.

[0018] The regenerative load system 10B has a configuration similar to that of the regenerative load system 10A, and includes an AC / DC converter 1B as a power converter, a converter control unit 2B as a first control unit that controls the AC / DC converter 1B, and a regenerative load equipment group 3B as a first equipment unit having multiple regenerative load equipment F. The AC / DC converter 1B and the regenerative load equipment group 3B are connected via a DC bus 51B serving as a first DC transmission line for transmitting DC power.

[0019] The AC / DC converter 1B is driven by a signal output from the converter control unit 2B, converts AC power from the AC system 90 into DC power, and supplies the converted DC power to the regenerative load equipment group 3B via the DC bus 51B. The converter control section 2B performs constant voltage control so that the output voltage of the AC / DC converter 1B reaches a target value. When the voltage range of AC system 90 differs from the input voltage range of AC / DC converter 1B of regenerative load system 10B, the voltage of AC system 90 is converted by transformer 93 and input to AC / DC converter 1B. A protection device 94 is installed between transformer 93 and AC / DC converter 1B to detect and cut off overcurrent, leakage current, etc.

[0020] In addition, the AC / DC converter 1B may also perform reverse conversion by receiving DC power regenerated by the regenerative operation of the regenerative load equipment group 3B via the DC bus 51B, converting it into AC power, and outputting it to the AC system 90. Each of the regenerative load equipment F included in the regenerative load equipment group 3B has the same configuration as that shown in FIG. Hereinafter, when there is no need to distinguish between regenerative load systems 10A and 10B, they will be referred to as regenerative load system 10.

[0021] The power storage device 10C includes a power storage unit 1C as a first facility unit, a DC / DC converter 2C as a power converter, and a power storage device control unit 3C as a first control unit. The power storage unit 1C stores or supplies DC power via a DC / DC converter 2C. The power storage device control unit 3C outputs a signal for controlling the DC / DC converter 2C. The DC / DC converter 2C converts DC power based on the signal. The power storage unit 1C may be, for example, a storage battery such as a lithium ion battery or a lead storage battery, or a capacitor such as a lithium ion capacitor or a super capacitor.

[0022] The DC / DC converter 2C is driven by the above signal, and the power storage device control unit 3C has constant voltage control that keeps the output voltage of the DC / DC converter 2C at a target value, and constant power control that keeps the charge / discharge power of the DC / DC converter 2C at a target value, and is able to switch between the two types of control. The control switching may be performed based on an external command or based on the internal characteristics of the power storage device control unit 3C. The charge / discharge power command in the constant power control is determined based on information such as the charge / discharge capacity, remaining energy state, health state, and voltage of the DC bus 51 of the power storage unit 1C.

[0023] These AC / DC converter 1A, AC / DC converter 1B, and DC / DC converter 2C are connected via a DC system 50 formed by connecting DC buses 51A, 51B, and 51C, which serve as first DC transmission paths, respectively, with a DC power line 52, which serves as a second DC transmission path.

[0024] The power interchange system 100 of this embodiment also includes a management control unit 30 as a second control unit. The management control unit 30 communicates with the converter control unit 2A of the regenerative load system 10A, the converter control unit 2B of the regenerative load system 10B, and the storage device control unit 3C of the storage device 10C, and is able to acquire information, set control characteristics, etc. The management control unit 30 is constructed using, for example, a programmable logic controller, a personal computer, an LCD (Liquid Crystal Display), etc., and may also have an interface that allows the user to directly input numerical values.

[0025] In the present embodiment, the regenerative load system includes two regenerative load systems, 10A and 10B, and one power storage device, 10C, but the present invention is not limited to this. There may be a plurality of power storage devices, three or more regenerative load systems, or one regenerative load system and one load facility. A load (not shown) may also be connected to the DC system 50.

[0026] Next, the AC / DC converter 1A (1B) and the converter control unit 2A (2B) will be described with reference to Fig. 3. The AC / DC converter 1A and the AC / DC converter 1B, and the converter control unit 2A and the converter control unit 2B have the same configuration except for differences that will be described later. The AC / DC converter 1A (1B) includes a sensor unit 1A1 that detects the voltage and current of the AC system 90, a sensor unit 1A2 that detects the voltage and current of the DC system 50, and a power conversion unit 1A3 that converts between DC power and AC power. Converter control section 2A (2B) includes voltage control section 2A1 and current control section 2A2.

[0027] The voltage control unit 2A1 generates an AC current command value Iac_ref based on the voltage of the DC system 50 measured by the sensor unit 1A2 and the DC voltage command value Vdc_ref. The current control unit 2A2 outputs an operation command to the power conversion unit 1A3 based on the AC side current measured by the sensor unit 1A1 and the AC current command value Iac_ref.

[0028] Here, the DC voltage command value Vdc_ref may be held as a constant internally by the converter control unit 2A, may be received as a command value from the outside, or may be generated by the converter control unit 2A. The DC voltage command value Vdc_ref may be input to the voltage control unit 2A1 via a command value filter for suppressing abrupt changes in the DC voltage command value Vdc_ref, or a limiter for setting the upper and lower limits of the DC voltage command value Vdc_ref. Similarly, a command value filter and a limiter may be set for the AC current command value Iac_ref. In this way, the AC / DC converter 1A controls the voltage of the DC system 50 based on the DC voltage command value Vdc_ref, and therefore, it can be said that the AC / DC converter 1A operates as a constant voltage source.

[0029] Next, the DC / DC converter 2C will be described with reference to FIG. DC / DC converter 2C includes sensor unit 2C1 that detects the voltage and current of power storage unit 1C, sensor unit 2C2 that detects the voltage and current of DC system 50, and power conversion unit 2C3 that performs voltage conversion of DC power. The power storage device control unit 3C includes a voltage control unit 3C1, a charge / discharge power control unit 3C2, and a current control unit 3C3.

[0030] Voltage control unit 3C1 generates a current command value Ibat_ref for power storage unit 1C based on the voltage of DC system 50 measured by sensor unit 2C2 and a DC voltage command value Vdc_ref2. Charge / discharge power control unit 3C2 generates a current command value Ibat_ref based on charge / discharge power command value P_ref for power storage unit 1C and the voltage and current of power storage unit 1C measured by sensor unit 2C1.

[0031] Current control unit 3C3 issues an operation command to power conversion unit 2C3 based on the current of power storage unit 1C measured by sensor unit 2C1 and a current command value Ibat_ref. It is necessary to ensure that either voltage control unit 3C1 or charge / discharge power control unit 3C2 is enabled so that the current command value Ibat_ref does not conflict with each other in current control unit 3C3.

[0032] As in the case of the AC / DC converter 1A (1B), the DC voltage command value Vdc_ref2 may be held internally as a constant by the power storage device control unit 3C, may be received externally as a command value, or may be generated by the power storage device control unit 3C. Similarly, when the charge / discharge power command value P_ref is received as a command value from the outside, it may be generated by the power storage device control unit 3C. Furthermore, a command value filter and a limiter may be set for the DC voltage command value Vdc_ref2, the current command value Ibat_ref, and the charge / discharge power command value P_ref.

[0033] The operation of the regenerative load equipment F in the regenerative load system 10 will be described with reference to FIG. FIG. 5 is a diagram for explaining the operation of the regenerative load facility F according to the first embodiment of the present disclosure. The operating states of the regenerative load equipment F are divided into three states: a powering state in which it consumes electricity and performs mechanical work; a regenerative state in which electricity is generated from mechanical energy; and a stopped state.

[0034] The following description will be given taking as an example a case where two regenerative loads, F-1 and F-2, are operating as regenerative load equipment F. For simplicity of explanation, the power consumed and generated by regenerative load equipment F during powering and regenerative operation is assumed to be the same.

[0035] In time interval t1, regenerative load equipment F-1 performs powering operation for a period ta from the start time of interval t1, and regenerative load equipment F-2 starts regenerative operation from a stopped state until the period ta has elapsed since regenerative load equipment F-1 started powering operation, and ends regenerative operation at the end time of time interval t1. In this case, there is a time when the powering operation of regenerative load equipment F-1 and the regenerative operation of regenerative load equipment F-2 overlap, and the power generated by regenerative load equipment F-2 can be consumed by regenerative load equipment F-1. Therefore, the difference in power between the regenerative power and the power consumption consumed by powering exists in DC system 50. During the time when the powering operation of regenerative load equipment F-1 and the regenerative operation of regenerative load equipment F-2 do not overlap, each power exists in DC system 50.

[0036] Next, in time section t2, the regenerative load equipment F-1 and the regenerative load equipment F-2 each perform power running at the same timing. In this case, the power running powers of the respective equipments overlap, resulting in a power running peak power being present in the DC system 50. In the case of a single regenerative load system, the power running peak power is normally supplied from the AC system 90 to the DC bus 51A (51B) via the AC / DC converter 1A (1B). When the regenerative operation timing of the regenerative load equipment F-1 and the regenerative load equipment F-2 coincides, the regenerative peak power is output to the DC bus 51A (51B), and the AC / DC converter 1A (1B) flows power back to the AC system 90.

[0037] In this way, when the regenerative load equipment F-1 and the regenerative load equipment F-2 are operating, it is necessary to consider that the AC / DC converter 1A (1B), and the transformer 91 (93) and protective device 92 (94) installed in the AC system 90 will handle the powering peak power and the regenerative peak power. The powering peak power and the regenerative peak power occur when the regenerative load equipment F-1 and F-2 operate in the same manner at the same time, and therefore occur infrequently. Therefore, by constructing a power interchange system 100 as shown in this embodiment and interchangeing power between a plurality of regenerative load systems 10A and 10B and a power storage device 10C, the maximum input / output power of the AC / DC converters 1A and 1B in the regenerative load systems can be reduced.

[0038] For example, in the power sharing system 100, when the forward current rating of the AC / DC converter 1A is IA, the forward current rating of the AC / DC converter 1B is IB, and the discharge current rating of the energy storage device 10C is IC, and IC < IB < IA, consider changing the current limit value of the AC / DC converter 1B and the energy storage device 10C to their rated current values and changing the current limit value of the AC / DC converter 1A to IA2 which is smaller than IA. At this time, the AC / DC converter 1A can limit the output current by providing a current limit limiter for current limiting at the input of the current control unit 2A2 of the converter control unit 2A. By limiting the output current, it is possible to prevent the enlargement of the transformer 91 and the protection device 92 connected to the AC / DC converter 1A.

[0039] In the power sharing system, when each device of the AC / DC converter 1A, the AC / DC converter 1B, and the energy storage device 10C operates as a constant voltage source, if there is an error in the output voltage, a current will flow between the devices in the DC system 50, causing useless losses in the system. This current is called a cross current. Therefore, when connecting a device that operates as a constant voltage source to the DC system 50, the droop characteristic is set for each device to suppress the cross current. The droop characteristic is a characteristic with the DC voltage command value on the vertical axis and the forward (discharge) current on the horizontal axis, and the relationship between the DC voltage command value and the current is expressed by the following formula.

[0040] DC voltage command value = reference voltage value - slope × current

[0041] Thus, the droop characteristic is such that the input and output currents of the AC / DC converter 1A, the AC / DC converter 1B, and the energy storage device 10C, which are power converters, droop with a change rate set with respect to the DC voltage command value of the DC system 50. In this way, for example, when the input and output current of a certain power converter increases, it is controlled so that the DC voltage command value decreases according to the droop characteristic. As a result, the input and output currents of other power converters increase, and the sharing ratio of the input and output currents of each power converter is controlled. The reference voltage value in the drooping characteristic is a reference voltage for DC system 50 and is set to, for example, 340 V. The gradient, which is the rate of change of current, is a parameter that determines the increase or decrease in the DC voltage command value in response to an increase or decrease in current, and by setting the gradient, it is possible to arbitrarily set the share rates of the output currents of AC / DC converter 1A, AC / DC converter 1B, and DC / DC converter 2C.

[0042] FIG. 6 is a diagram illustrating drooping characteristics for setting a share rate for each device such as AC / DC converter 1A, AC / DC converter 1B, and DC / DC converter 2C. Management control unit 30 sets drooping characteristics as sharing characteristics for converter control unit 2A, converter control unit 2B, and power storage device control unit 3C, respectively.

[0043] Converter control unit 2A, converter control unit 4B, and power storage device control unit 3C generate a DC voltage command value Vdc_ref from the drooping characteristics based on the output current. The smaller the slope of the drooping characteristic, the larger the output current at a certain DC system voltage. Therefore, by adjusting the magnitude relationship between the slope αa of the drooping characteristic set in AC / DC converter 1A, the slope αb of the drooping characteristic set in AC / DC converter 1B, and the slope αc of the drooping characteristic set in power storage device 10C, it is possible to control the output priority and interchange power quickly.

[0044] By setting the relationship of the magnitude of the gradients as αc<αa<αb, the output of power storage device 10C is given the highest priority until power storage device 10C reaches current limit value IC. When the current in DC system 50 increases, the output of AC / DC converter 1A is given priority until the output current of AC / DC converter 1A reaches current limit value IA2, and ultimately the output current of AC / DC converter 1B is given priority and becomes the highest.

[0045] In this way, the DC voltage command value is controlled according to the input / output current of the power converter in accordance with the drooping characteristic as a sharing characteristic that defines the sharing rate of the input / output current of each power converter with respect to the DC voltage of DC system 50, and the sharing rate of the input / output current of each power converter is adjusted. By arbitrarily setting the output sharing priority, it is possible to prioritize the utilization of the power storage device 10C, for example, to reduce the forward current power from the AC grid 90 and the reverse current power to the AC grid 90, and thereby reduce energy consumption and loss.

[0046] Furthermore, as will be described below, by inputting the conversion loss characteristics of AC / DC converter 1A, AC / DC converter 1B, and DC / DC converter 2C into management control unit 30, it is possible to set the sharing priority in detail so as to minimize losses in the entire power interchange system. FIG. 7 is a diagram illustrating another example of setting the drooping characteristics for setting the sharing priorities of AC / DC converter 1A, AC / DC converter 1B, and power storage device 10C as the first DC system. As shown in Fig. 7, several thresholds TH1 and TH2 are set for the forward (discharging) current or reverse (charging) current, and the slope of the drooping characteristic is finely set to change at each threshold TH1 and TH2, allowing for control of power interchange. In other words, in the set drooping characteristic, the slope, which is the rate of change, is adjusted for each set current range (-IA2 to TH1, TH1 to TH2, TH2 to IA2).

[0047] The magnitude of the gradient αc set for the power storage device 10C may be changed depending on the remaining energy state, which is the remaining capacity of the power storage unit 1C, and the health state. For example, when the remaining energy of the power storage unit 1C is low, the gradient αc can be increased to lower the output priority and reduce the energy consumption of the power storage unit 1C.

[0048] FIG. 8 is a diagram illustrating changes in the output current of each of AC / DC converter 1A, AC / DC converter 1B, and DC / DC converter 2C over time when a sharing rate is set for the output current of each power converter using the above-described drooping characteristics. This is an example of a case where the power running power from regenerative load equipment F increases in the order of time intervals t3, t4, and t5, and the total current value output from AC / DC converter 1A, AC / DC converter 1B, and DC / DC converter 2C to the DC system increases.

[0049] In time section t3, in response to the increase in current required by DC system 50, power storage device 10C, AC / DC converter 1A, and AC / DC converter 1B output a large amount of current in the order of abrupt load changes, AC / DC converter 1A, and AC / DC converter 1B during transient periods such as regeneration, and during steady state conditions. Next, in time interval t4, the output current of power storage device 10C is fixed at limit value IC, and the outputs of AC / DC converters 1A and 1B increase. At this time, the output of AC / DC converter 1A operates so as to exceed IC midway through time interval t4 and reach its maximum. Next, in time section t5, the output current of AC / DC converter 1A is fixed at limit value IA2, and the output of AC / DC converter 1B increases to operate so as to maximize the output ratio.

[0050] The priority of power sharing during transient periods can be controlled more precisely by applying a low-pass filter L to the DC voltage command value Vdc_ref generated as the output of the drooping characteristic within each of the converter control unit 2A, converter control unit 2B, and storage device control unit 3C, and setting the filter characteristics of each low-pass filter L separately.

[0051] FIG. 9 is a diagram illustrating a change in current sharing during a transient state when the low-pass filter is set. As an example, assume that αa, αb, and αc have the same slope, a first-order low-pass filter is used as the low-pass filter, and the cutoff frequencies of the low-pass filters decrease in the order of power storage device 10C, AC / DC converter 1A, and AC / DC converter 1B. At this time, the smaller the cutoff frequency of a device, the more gradual the change in the DC voltage command value, so that the device responds quickly during a transient state and can be given a higher priority in sharing.

[0052] So far, we have used the forward current (discharging) direction as an example to explain this, but the same operation applies to the reverse current (charging) direction. By changing the slope depending on the direction of the current, it is possible to change the device that has priority for output in the forward current (discharging) direction and the reverse current (charging) direction.

[0053] The power interchange system of this embodiment configured as described above has the following features: a power converter for supplying DC power; a first DC transmission line that transmits DC power from the power converter; a first facility unit connected to the first DC transmission line and configured to at least one of consume DC power supplied from the first DC transmission line and supply DC power to the first DC transmission line; a first control unit that controls the power converter; and a plurality of first DC systems each having the first DC system and the first control unit. A power interchange system that interchanges DC power between each of the first DC systems via a DC system configured by connecting the first DC transmission lines of each of the first DC systems by a second DC transmission line, The first control unit of each of the first DC systems controlling the power converters in accordance with sharing characteristics that define the respective sharing rates of input and output currents of the power converters in the power interchange system; It is something.

[0054] This allows for rapid interchange control of power consumption during short-term power fluctuations such as sudden load changes or regeneration, at the respective power converter's set contribution rate, thereby stabilizing the system and enabling effective energy utilization. Therefore, there is no need to temporarily charge the power generated within the DC system into a storage battery, and each DC system does not need to have its own storage battery, allowing the system to be made smaller. Generally, the larger the capacity of a circuit breaker or transformer, the larger and more expensive it is, and there is no proportional relationship between the increase in price and size and the increase in capacity. Therefore, the above share rates and limit values ​​should be set taking into consideration the relationship between the capacity of each power converter and the price of the corresponding transformer and circuit breaker.

[0055] Embodiment 2 The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. FIG. 10 is a block diagram showing a schematic configuration of a power interchange system 200 according to the second embodiment of the present disclosure. In addition to the configuration of embodiment 1, this embodiment 2 deals with a configuration that has an operation permission unit 40 as a second control unit that receives an operation request signal R requesting the start of operation of multiple regenerative load equipment F, and generates and outputs an inverter control signal S as a drive signal.

[0056] The operation of the second embodiment will be described in terms of differences from the first embodiment. When receiving the operation request signal R, the operation permission unit 40 calculates the peak power of the running power or regenerative power that will be generated until the regenerative load equipment F completes operation as requested. The calculated generated peak power is compared with a threshold value that indicates the total power that can be processed by the AC / DC converter 1A, the AC / DC converter 1B, and the power storage device 10C.

[0057] If the generated peak power is less than or equal to the processable power, the inverter control signal S for driving the regenerative load equipment F as requested is output to the regenerative load equipment group 3A and the regenerative load equipment group 3B. If the peak power generation is greater than the processable power, the operation permission unit 40 reduces the number of regenerative load equipment F to be operated so that the peak power generation is less than or equal to the processable power, and repeatedly calculates the peak power generation to determine a combination of inverter control signals S for the regenerative load equipment F to be operated. At this time, the combination of inverter control signals S is determined to comply with a predetermined rule, such as that regenerative load equipment F-1 and regenerative load equipment F-2 must always operate simultaneously. After a certain time has elapsed, the operation permission unit 40 outputs an inverter control signal S to the regenerative load equipment F that has not been operating, thereby suppressing the peak power.

[0058] According to the second embodiment, in a power interchange system equipped with an operation permission unit, the operation permission unit 40 calculates the peak power generated by operation based on an operation request signal, and if the generated peak power exceeds the power that can be processed by the system, the power peak is suppressed by shifting the operation timing of some regenerative load equipment so that the generated peak power is equal to or less than the power that can be processed. This prevents peak power, which occurs when multiple regenerative load facilities are instructed to operate in powered mode simultaneously, from exceeding the power that can be accommodated within the power interchange system, thereby stabilizing the system.

[0059] Embodiment 3 The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. FIG. 11 is a block diagram showing a schematic configuration of a power interchange system 300 according to the third embodiment of the present disclosure. In the first embodiment, the DC voltages in the regenerative load systems and power storage devices are the same value, but in the third embodiment, a case will be described in which regenerative load systems with different DC voltages are connected. The regenerative load system 10D includes an AC / DC converter 1D as a power converter, a converter control unit 2D as a first control unit that controls the AC / DC converter 1D, and a regenerative load equipment group 3D as a first equipment unit having multiple regenerative load equipment F. In FIG. 11, for simplicity of illustration, some of the configurations shown in the first embodiment are omitted.

[0060] In order to accommodate cases where the DC voltage on the regenerative load systems 10A and 10B side is different from the DC voltage of the DC bus 51D in the regenerative load system 10D, the DC buses 51A and 51B of the regenerative load systems 10A and 10B and the DC bus 51D of the regenerative load system 10D are provided on a DC power line 52D and connected via a voltage converter 360 that increases or decreases the voltage between the primary side and the secondary side.

[0061] The voltage converter 360 is configured as a DC / DC converter capable of bidirectional power conversion, and may also have an insulating function. The DC power line 52D and the DC bus 51D are treated as a DC system 50D because they are at the same voltage.

[0062] First, a case will be described in which the AC / DC converter 1D in the regenerative load system 10D can control the voltage of the DC bus 51D in the same way as in the first embodiment. At this time, the voltage converter 360 controls the voltage of either the DC system 50 or the DC system 50D so that it becomes a target voltage. For example, when the voltage converter 360 controls the voltage of the DC system 50D to be constant, the target voltage of the voltage converter 360, i.e., the DC voltage command value Vdc_ref given to the converter control unit 2D, is changed in accordance with changes in the voltage of the DC system 50. That is, when the voltage of the DC system 50 increases, the DC voltage command value Vdc_ref is also increased, and when the voltage of the DC system 50 decreases, the DC voltage command value Vdc_ref is also decreased, so that the ratio between the voltage of the DC system 50 and the voltage at the DC voltage command value Vdc_ref of the DC system 50D is always constant.

[0063] Here, the voltage converter 360 needs to have a sufficiently fast control response compared to the AC / DC converters 1A, 1B and DC / DC converter 2C included in the power interchange system. Management control unit 30 acquires information about the input voltage and output voltage of voltage converter 360, and converts the drooping characteristics to be set in converter control unit 2D according to the voltage ratio. For example, if the voltage of DC system 50 is 340V and the voltage of DC system 50D is 680V, ​​the drooping characteristics set for the 340V system are provided for converter control unit 2D with the voltage on the vertical axis of the drooping characteristics doubled and the current on the horizontal axis halved.

[0064] Note that if the drooping characteristics, converter control units, and power storage device control units are all controlled using PU values, the above conversion is not necessary. In this way, by operating voltage converter 360 at high speed so that the ratio of input and output voltages is always constant, AC / DC converter 1D in regenerative load system 10D, which has a different DC voltage, can be treated in the same way as other AC / DC converters, and power interchange can be controlled. In this configuration, a rectifier capable of controlling the voltage of the DC bus 51D can also be used as the AC / DC converter 1D.

[0065] Next, we will explain the case where the AC / DC converter is composed of a diode rectifier that cannot control the voltage of the DC bus. FIG. 12 is a block diagram showing a schematic configuration of a power interchange system 300A according to the third embodiment of the present disclosure. The regenerative load system 10E as a 1R DC system includes a diode rectifier 1E that rectifies AC to DC, a DC bus 51E as a 1R DC transmission line that transmits DC power from the diode rectifier 1E, and a regenerative load equipment group 3E as a 1R equipment unit that is connected to the DC bus 51E and consumes DC power or supplies DC power to the DC bus 51E.

[0066] The diode rectifier 1E converts AC power from the AC system 90 into DC power and outputs it to a DC bus 51E in the regenerative load system 10E. The DC voltage to be output depends on the voltage of the AC system 90 and cannot be changed arbitrarily. To cooperate with the diode rectifier 1E, the voltage converter 360 controls the voltage of the DC system 50D to a constant value, and the target voltage is set to be slightly higher by a set voltage value than the maximum voltage generated by the diode rectifier 1E. As a result, when there is a power shortage in the DC system 50D, the voltage converter 360 can supply power from the DC system 50, and when there is an excess of power in the DC system 50D due to regenerative power, the voltage converter 360 can operate to output power from the DC system 50D to the DC system 50.

[0067] When using a rectifier that cannot perform reverse power operation, the regenerative load system 10E normally operates a regenerative consumption resistor to consume the regenerative power when the voltage of the DC bus 51E rises due to regenerative power and exceeds a threshold value, and consumes the regenerative power as thermal energy. By controlling the voltage of the DC system 50D, i.e., the voltage of the DC bus 51E, with the voltage converter 360, it becomes possible to utilize the regenerative power in the DC system 50D instead of discarding it as thermal energy.

[0068] When diode rectifier 1E is used, voltage converter 360 and regenerative load system 10E can be regarded as one large regenerative load facility connected to DC system 50, as viewed from the power interchange system. Therefore, AC / DC converter 1A of regenerative load system 10A, AC / DC converter 1B of regenerative load system 10B, and power storage device 10C can interchange power based on sharing priority by operating in accordance with drooping characteristics set in the same way as in the first embodiment.

[0069] FIG. 13 is a diagram showing the hardware configuration of a control device 80 that serves as converter control units 2A, 2B, and 2D, power storage device control unit 3C, management control unit 30, and operation permission unit 40. 13, an example of hardware of the control device 80 is shown, which includes a processor 81 and a storage device 82. The storage device 82 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory, both of which are not shown. Also, an auxiliary storage device such as a hard disk may be provided instead of flash memory. Processor 81 executes a program input from storage device 82. In this case, the program is input from the auxiliary storage device to processor 81 via a volatile storage device. Processor 81 may output data such as calculation results to a volatile storage device of storage device 82, or may store the data in the auxiliary storage device via the volatile storage device.

[0070] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not exemplified are conceivable within the scope of the technology disclosed in this specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment.

[0071] Various aspects of the present disclosure are summarized below as appendices.

[0072] (Appendix 1) a power converter for supplying DC power; a first DC transmission line that transmits DC power from the power converter; a first facility unit connected to the first DC transmission line and configured to at least one of consume DC power supplied from the first DC transmission line and supply DC power to the first DC transmission line; a first control unit that controls the power converter; and a plurality of first DC systems each having the first DC system and the first control unit. A power interchange system that interchanges DC power between each of the first DC systems via a DC system configured by connecting the first DC transmission lines of each of the first DC systems by a second DC transmission line, The first control unit of each of the first DC systems controlling the power converters in accordance with sharing characteristics that define the respective sharing rates of input and output currents of the power converters in the power interchange system; Power interchange system. Power interchange system. (Appendix 2) The shared characteristics are: a drooping characteristic in which the input / output current of the power converter of the first DC system droops with a set change rate relative to a DC voltage command value of the DC system is set for each of the first control units, The rate of change in the sharing characteristic of each of the first control units is set based on the sharing rate of each of the power converters. 1. An electric power interchange system as described in Appendix 1. (Appendix 3) The rate of change in the sharing characteristic is adjusted for each set input / output current range. Attachment 2: An electric power interchange system. (Appendix 4) a low-pass filter that receives the DC voltage command value as an input for each of the first control units; The cutoff frequency of each of the low-pass filters is adjusted based on the contribution ratio. 1. An electric power interchange system according to claim 2 or 3. (Appendix 5) the first DC systems having different DC voltage command values ​​are connected to each other via a voltage converter that is provided on the second DC transmission line and that increases or decreases a voltage between a primary side and a secondary side, the voltage converter controls the voltage of the second DC transmission line so that a voltage ratio between the primary side and the secondary side is constant; The sharing characteristics of each of the first control units are set according to the voltage ratio. 5. An electric power interchange system according to any one of appendices 2 to 4. (Appendix 6) a second control unit that receives a request signal to drive each of the first equipment units and outputs a drive signal to drive each of the first equipment units in response to the request signal; The second control unit is calculating a peak power value in the DC system due to DC power consumption in each of the first equipment units or DC power supply to the first DC transmission line based on each of the received request signals; When the power peak value exceeds a set threshold, the output timing of each of the drive signals is adjusted so that the power peak value does not exceed the threshold. Attachment 5: An electric power interchange system. (Appendix 7) the first DC system includes a power storage unit serving as the first equipment unit that outputs stored power as DC power, and a DC / DC converter serving as the power converter that converts a voltage of the DC power from the power storage unit into a voltage of the DC system; The second control unit is detecting a remaining capacity of the power storage unit, and adjusting the rate of change in the sharing characteristic of the first control unit of each of the first DC systems in accordance with the remaining capacity, thereby adjusting the sharing rate of the input / output current of each of the power converters; Attachment 6: An electric power interchange system. (Appendix 8) a rectifier that rectifies AC to DC; a first R DC transmission line that transmits DC power from the rectifier; a first R DC system including a first R facility unit connected to the first R DC transmission line and consuming DC power supplied from the first R DC transmission line or supplying DC power to the first R DC transmission line; the first DC transmission line of the first DC system and the first R DC transmission line of the first R DC system are connected by the second DC transmission line via a voltage converter that is provided on the second DC transmission line and that increases or decreases a voltage between a primary side and a secondary side, thereby constituting the DC system; the voltage converter controls the voltage of the second DC transmission line on the first R DC system side to a target voltage value that is higher than the output voltage of the rectifier by a set value. 8. An electric power interchange system according to any one of appendices 1 to 7. [Explanation of symbols]

[0073] 1A AC / DC converter (power converter), 1B AC / DC converter (power converter), 1C Power storage unit (first equipment unit), 1D AC / DC converter (power converter), 2A converter control section (first control section), 2B converter control section (first control section), 2C DC / DC converter (power converter), 2D converter control unit (first control unit), 3A, 3B regenerative load equipment group (first equipment part), 3C power storage device control part (first control part), 10A, 10B, 10D Regenerative load system (first DC system), 10E regenerative load system (1st R DC system), 10C storage device (first DC system), 1E diode rectifier, 30 management control unit (second control unit), 40 operation permission unit (second control unit), 51A, 51B, 51C, 51D, 51E DC bus (1st DC transmission line), 52 DC power line (second DC transmission line), 100, 200, 300, 300A power interchange system.

Claims

1. a power converter for supplying DC power; a first DC transmission line that transmits DC power from the power converter; a first facility unit connected to the first DC transmission line and configured to at least one of consume DC power supplied from the first DC transmission line and supply DC power to the first DC transmission line; a first control unit that controls the power converter; and a power interchange system that interchanges DC power between each of the first DC systems via a DC system configured by connecting the first DC transmission lines of each of the first DC systems by a second DC transmission line, The first control unit of each of the first DC systems controlling the power converters in accordance with sharing characteristics that define the respective sharing rates of input and output currents of the power converters in the power interchange system; Power interchange system.

2. The shared characteristics are: a drooping characteristic in which the input / output current of the power converter of the first DC system droops at a set change rate with respect to a DC voltage command value of the DC system is set for each of the first control units, the rate of change in the sharing characteristic of each of the first control units is set based on the sharing rate of each of the power converters. The power interchange system according to claim 1 .

3. The rate of change in the sharing characteristic is adjusted for each set input / output current range. The power interchange system according to claim 2 .

4. a low-pass filter receiving the DC voltage command value as an input for each of the first control units; The cutoff frequency of each of the low-pass filters is adjusted based on the contribution ratio. The power interchange system according to claim 3 .

5. the first DC systems having different DC voltage command values ​​are connected to each other via a voltage converter that is provided on the second DC transmission line and that increases or decreases a voltage between a primary side and a secondary side, the voltage converter controls the voltage of the second DC transmission line so that a voltage ratio between the primary side and the secondary side is constant; The sharing characteristics of each of the first control units are set according to the voltage ratio. The power interchange system according to claim 4.

6. a second control unit that receives a request signal for driving each of the first equipment units and outputs a drive signal for driving each of the first equipment units in response to the request signal; The second control unit is calculating a peak power value in the DC system due to DC power consumption in each of the first equipment units or DC power supply to the first DC transmission line based on each of the received request signals; When the power peak value exceeds a set threshold, the output timing of each of the drive signals is adjusted so that the power peak value does not exceed the threshold. The power interchange system according to claim 5 .

7. the first DC system includes a power storage unit serving as the first equipment unit that outputs stored power as DC power, and a DC / DC converter serving as the power converter that converts a voltage of the DC power from the power storage unit into a voltage of the DC system; The second control unit is detecting a remaining capacity of the power storage unit, and adjusting the rate of change in the sharing characteristic of the first control unit of each of the first DC systems in accordance with the remaining capacity, thereby adjusting the sharing rate of the input / output current of each of the power converters; The power interchange system according to claim 6.

8. a rectifier that rectifies AC to DC; a first R DC transmission line that transmits DC power from the rectifier; a first R DC system including a first R facility unit connected to the first R DC transmission line and consuming DC power supplied from the first R DC transmission line or supplying DC power to the first R DC transmission line, the first DC transmission line of the first DC system and the first R DC transmission line of the first R DC system are connected by the second DC transmission line via a voltage converter that is provided on the second DC transmission line and that increases or decreases a voltage between a primary side and a secondary side, thereby constituting the DC system; the voltage converter controls the voltage of the second DC transmission line on the first R DC system side to a target voltage value that is higher than the output voltage of the rectifier by a set value. The power interchange system according to any one of claims 1 to 7.

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