WO2017158891A1 - 電力変換装置および電力システム - Google Patents
電力変換装置および電力システム Download PDFInfo
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- WO2017158891A1 WO2017158891A1 PCT/JP2016/078587 JP2016078587W WO2017158891A1 WO 2017158891 A1 WO2017158891 A1 WO 2017158891A1 JP 2016078587 W JP2016078587 W JP 2016078587W WO 2017158891 A1 WO2017158891 A1 WO 2017158891A1
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- power
- voltage
- power converter
- control unit
- direct current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0009—Devices or circuits for detecting current in a converter
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0096—Means for increasing hold-up time, i.e. the duration of time that a converter's output will remain within regulated limits following a loss of input power
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
Definitions
- the present invention relates to a power conversion apparatus that performs power conversion by being connected between a power generation system and a demand area system, and a power system that includes the power conversion apparatus, and more particularly has an operation relay function when a demand area system is disturbed. Is.
- High-voltage direct current (HVDC) power transmission systems are often used in systems where the transport distance of power is long.
- HVDC power transmission system power from a certain AC system is converted into high-voltage DC power by a power converter equipped with a forward converter and transmitted to a DC system bus such as a long-distance cable. Then, the DC power is converted again into AC power by a power conversion device equipped with an inverse converter, and transmitted to another AC system.
- a power generation system installed far away from an urban area which is a power demand area
- a demand area system is often linked to a demand area system via this HVDC power transmission system.
- facilities connected to the demand point system are operated according to the degree of disturbance even in the event of system disturbance such as an instantaneous voltage drop in the demand point system due to an accident in the demand point system. It is required to satisfy FRT (Fault Ride Through) requirements for continuous control.
- FRT fault Ride Through
- Non-Patent Document 1 when a voltage drop occurs in the demand area system, the control device of the inverse converter calculates the power that can be output to the demand area system, and the communication line The information is transmitted to the control device of the power converter equipped with the forward converter. And a power converter performs the protection operation which reduces the alternating voltage of the alternating current side terminal of a forward converter based on the information.
- the power adjustment device in the power generation system suppresses the output power of the power generation system according to a decrease in the AC voltage at the AC side terminal of the forward converter.
- the power conversion device suppresses the generated power of the power generation system in accordance with the power that can be supplied to the demand area system, and maintains the power balance of the entire power system including the power generation system.
- Patent Document 1 when the control device of the power conversion device including the forward converter detects that the DC voltage of the DC system bus has risen above the threshold, the AC voltage of the AC side terminal of the forward converter is detected. Protective action to reduce the Thus, the power conversion device suppresses the generated power of the power generation system in accordance with the power that can be supplied to the demand area system, and maintains the power balance of the entire power system including the power generation system.
- the control device for the reverse converter connected to the demand point system includes the forward converter with information on the power that can be output to the demand point system.
- a long-distance communication line for transmission to the control device of the power converter is required. Therefore, securing the space for installing the communication line and increasing costs are problematic.
- the control device of the power converter device including the forward converter protects by detecting that the DC voltage of the DC system bus exceeds the threshold value. The operation is being executed. In this case, if the rated DC voltage during normal operation of the power converter is close to the threshold value, the protective operation is frequently performed due to control fluctuation. Therefore, it is necessary to provide a sufficient design margin between the rated DC voltage value and the threshold value during normal operation of the power conversion device. Furthermore, this threshold value needs to be smaller than the overvoltage level of the converter and the withstand voltage of cables used for the DC system bus.
- the present invention has been made to solve the above-described problems, and protection control of the power converter can be started before reaching the threshold voltage abnormality of the DC bus without requiring a long-distance communication line,
- An object of the present invention is to provide a power conversion device and a power system capable of improving the degree of freedom in voltage design with respect to the voltage of the DC bus.
- a power converter according to the present invention is connected to a power generation system, converts AC power received from the power generation system into DC power, and transmits power via a DC bus, and control for controlling the power converter
- the control device includes a detection unit that detects a direct current of the direct current bus, and protective control that suppresses the amount of power received from the power generation system based on fluctuations in the direct current. And a protection control unit to be performed.
- the power system according to the present invention includes a power conversion device configured as described above, a reverse power converter that converts DC power from the power converter into AC power and transmits the AC power to a demand point system, and A control device for controlling the reverse power converter, the control device for the reverse power converter includes a DC voltage control unit that causes the DC voltage of the reverse power converter to follow a DC voltage command, and the reverse power converter.
- An AC current control unit that causes the AC current to follow the AC current command, and generates an output voltage command for the reverse power converter based on the output of the DC voltage control unit and the output of the AC current control unit. is there.
- the power conversion device and the power system of the present invention since protection control is performed to suppress the amount of power received from the power generation system based on the fluctuation of the DC current of the DC bus, before reaching the threshold abnormality of the voltage of the DC bus. Then, protection control of the power conversion device can be started. Therefore, the degree of freedom in voltage design with respect to the voltage of the DC bus can be improved, and a high-performance power conversion device and power system can be provided with space saving and low cost.
- FIG. 1 is a schematic configuration diagram showing configurations of a power conversion device 30 and a power system 100 according to Embodiment 1 of the present invention.
- the power system 100 of the present embodiment is connected between the power generation system 20 and the power generation system 20 and the demand area system 80, and the generated power of the power generation system 20 is supplied to the demand area system 80.
- An HVDC power transmission system 70 (hereinafter referred to as a power transmission system 70) is provided.
- the power transmission system 70 includes a power conversion device 30 that converts alternating current into direct current, a power conversion device 40 that converts direct current into alternating current, and a long-distance cable for transmitting the DC output power of the power conversion device 30 to the power conversion device 40. And a DC system bus 60 as a DC bus.
- the power generation system 20 includes at least one power generation system 21 connected to the power generation system bus 61.
- Each power generation system 21 includes at least one power generation device 22 and a power generation side power conversion device 23 for adjusting the voltage and current of the power generated by the power generation device 22.
- the power generation device 22 may be any type of power generation device. For example, when the power generation device 22 outputs AC power from a wind power generation facility or the like, the power generation side power conversion device 23 is between AC and AC. The power conversion is performed by Further, for example, when the power generation device 22 outputs DC power from a photovoltaic power generation facility or the like, the power generation side power conversion device 23 performs power conversion between direct current and alternating current.
- each power generation system 21 is configured to supply AC power to the power conversion device 30 via the power generation system bus 61.
- the configuration of the power generation system bus 61 may be any configuration such as a tree type, a star type, or a ring type, and the present invention is not limited by the configuration of the power generation system bus 61.
- the power converter 30 that receives AC power from the power generation system 20 includes a power converter 32 that is a main circuit, and a controller 31 that controls the power converter 32.
- the power converter 32 performs power conversion between a plurality of phases of alternating current, in this case, three-phase alternating current and direct current.
- the alternating current side terminal is connected to the power generation system bus 61 and the direct current side terminal is connected to the direct current system bus 60. It is connected. In this way, AC power received from the power generation system 20 is converted into DC power and transmitted to the DC system bus 60.
- the power conversion device 40 that receives DC power from the power conversion device 30 includes an inverse power converter 42 that is a main circuit, and a control device 41 that controls the inverse power converter 42. Similar to the power converter 32, the reverse power converter 42 performs power conversion between a plurality of phases of alternating current, in this case, three-phase alternating current and direct current.
- the DC side terminal of the reverse power converter 42 is connected to the DC system bus 60, and the AC side terminal is connected to the demand area system bus 62. In this way, the DC power received from the power converter 32 is converted into AC power and supplied to the demand site system 80 via the demand site system bus 62.
- FIG. 2 is a circuit configuration example of the power converter 32 and the inverse power converter 42 according to the first embodiment of the present invention.
- FIG. 3A and FIG. 3B are circuit configuration examples of the unit converter cell 5 constituting the power converter 32 and the inverse power converter 42 according to the first embodiment of the present invention, respectively.
- FIGS. 4A and 4B are circuit configuration examples of the unit converter cell 5 constituting the power converter 32 and the inverse power converter 42 according to Embodiment 1 of the present invention, respectively.
- a converter having a phase called a modular multilevel converter and having a plurality of unit converter cells 5 connected in series is used.
- the positive side arm 6p and the negative side arm 6n are connected in series, and the AC side terminal D1, which is the connection point, is connected to each phase AC line U, V, W.
- the leg circuit 7 is connected.
- Each of the positive side arm 6p and the negative side arm 6n of each leg circuit 7 includes one or more unit converter cells 5 connected in series. These phase leg circuits 7 are connected in parallel between the positive and negative DC buses.
- the left side in the figure is the AC side terminal D1
- the right side in the figure is the DC side terminal D2.
- the reverse power converter 42 shown in FIG. 1 has a DC side terminal E2 on the left side in the figure and an AC side terminal E1 on the right side in the figure. This is opposite to the left and right of the reverse power converter 42 shown in FIG. 2, but is shown in this way for convenience.
- An interconnection transformer 8 may be provided between the AC side terminal D1 of the power converter 32 and the power generation system 20, and an interconnection reactor (not shown) is used instead of the transformer 8. May be provided. Similarly, an interconnection transformer 8 may be provided between the AC side terminal E1 of the reverse power converter 42 and the demand area system 80, and an interconnection reactor is provided instead of the transformer 8. (Not shown) may be provided. Moreover, the reactor 2 for connection may be provided between the direct current side terminal D2 of the power converter 32 and the direct current system bus 60. Similarly, the direct current side terminal E2 of the reverse power converter 42 and the direct current system An interconnection reactor 2 may be provided between the bus 60 and the bus 60.
- AC side terminal D1 (E1) which is a connection point of the positive side arm 6p and the negative side arm 6n to each phase AC line U, V, W in this way
- the positive side arm 6p and the negative side arm 6n may be connected in series and connected to each phase AC line U, V, W via a transformer.
- the unit converter cell 5a shown in FIG. 3A has a circuit configuration called a half-bridge configuration.
- a capacitor 3 is connected in parallel to a series body formed by connecting semiconductor switching elements 1p and 1n as two semiconductor elements in series. In this way, both terminals of the semiconductor switching element 1n or both terminals of the semiconductor switching element 1p are used as input / output terminals, and the voltage across the capacitor 3 and zero voltage are output by the switching operation of the semiconductor switching elements 1p and 1n.
- the unit converter cell 5b shown in FIG. 3B has a circuit configuration called a full bridge configuration.
- a serial body formed by connecting semiconductor switching elements 1p1 and 1n1 as two semiconductor elements in series and a serial body formed by connecting semiconductor switching elements 1p2 and 1n2 as two semiconductor elements in series are formed. Yes.
- the two series bodies and the capacitor 3 are connected in parallel.
- the midpoint between the semiconductor switching element 1p1 and the semiconductor switching element 1n1 and the midpoint between the semiconductor switching element 1p2 and the semiconductor switching element 1n2 are used as input / output terminals of the unit converter cell 5.
- the switching operation of the semiconductor switching elements 1p1, 1n1, 1p2, and 1n2 outputs a voltage across the capacitor 3, a reverse voltage of the voltage across the capacitor 3, and a zero voltage.
- a unit converter cell 5c shown in FIG. 4A has a circuit configuration in which the semiconductor switching element 1p2 of the unit converter cell 5b shown in FIG. 3B is replaced with a diode 9 as a semiconductor element.
- the voltage across the capacitor 3 and the zero voltage are output by the switching operation of the semiconductor switching elements 1p1 and 1n1.
- the reverse voltage of the voltage across the capacitor 3 is output only when the current passing through the unit converter cell 5c flows from the lower side to the upper side and the semiconductor switching elements 1p1, 1n2 are off.
- the unit converter cell 5d shown in FIG. 4B has a circuit configuration called a clamped double cell or a double clamp cell.
- the semiconductor switching elements 1p2, 1n2, the semiconductor switching element 1p3 as the semiconductor element, the capacitor 3b, and the diode 9a as the semiconductor element form a circuit having a configuration as shown in FIG.
- the connection point between the capacitor 3a and the semiconductor switching element 1p1, and the connection point between the semiconductor switching element 1p3 and the diode 9a are defined. Connecting. Further, the connection point between the capacitor 3a and the semiconductor switching element 1n1 is connected to the connection point between the semiconductor switching element 1p3 and the capacitor 3b via a diode 9b as a semiconductor element.
- the midpoint of the semiconductor switching element 1p1 and the semiconductor switching element 1n1, and the midpoint of the semiconductor switching element 1p2 and the semiconductor switching element 1n2 are used as input / output terminals of the unit converter cell 5d.
- a voltage across the capacitor 3a or the capacitor 3b By switching operation of the semiconductor switching elements 1p1, 1n1, 1p2, 1n2, and 1p3, a voltage across the capacitor 3a or the capacitor 3b, a reverse voltage of the voltage across both ends, and a zero voltage are output.
- the semiconductor switching elements 1p1, 1n2 are turned off, the sum of the voltage across the capacitor 3a and the voltage across the capacitor 3b is the reverse voltage. Output as.
- These semiconductor switching elements 1p, 1n, 1p1, 1n1, 1p2, 1n2, 1p3 are FWD (Freewheeling) as self-extinguishing type switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and GCTs (Gate Committed Turn-off) thyristors. (Diode) are connected in antiparallel.
- IGBTs Insulated Gate Bipolar Transistors
- GCTs Gate Committed Turn-off thyristors.
- Diode Diode
- any of the unit converter cells 5a, 5b, 5c, and 5d shown in FIGS. 3 and 4 may be used.
- FIG. 5 is a block diagram showing a configuration of control device 31 of power converter 32 according to the first embodiment of the present invention.
- FIG. 6 is a block diagram showing a configuration of the protection control unit 50 of the control device 31 shown in FIG.
- FIG. 7 is a block diagram showing the configuration of the control device 41 of the inverse power converter 42 according to the first embodiment of the present invention.
- the control device 31 includes a capacitor voltage control unit 36, an AC voltage control unit 33, a DC voltage control unit 34, a DC current control unit 35, a control output combining unit 37, and a DC current Idc.
- a direct current detection unit 38 as a detection unit for detecting the signal and a protection control unit 50. Details of each part will be described below.
- the direct current detection unit 38 detects the direct current Idc flowing through the direct current system bus 60 output from the power converter 32.
- the AC voltage control unit 33 performs control calculation so that the AC voltage Vac at the power receiving end (AC side terminal D1) of the power converter 32 follows the AC voltage command Vac * having a certain amplitude and frequency, and performs AC control.
- a command 33a is generated and output.
- the capacitor voltage control unit 36 performs a control calculation so that the voltage Vcap of each capacitor 3 in the power converter 32 follows the capacitor voltage command Vcap *, and generates a voltage balance control command 36a and a DC current command Idc *. Output.
- the capacitor voltage control unit 36 generates a DC current command Idc * for the DC current Idc to be output based on the voltage Vcap of the capacitor 3 in the power converter 32 that fluctuates due to received power and output power. ing.
- the direct current control unit 35 performs a control calculation so that the direct current Idc detected by the direct current detection unit 38 follows the direct current command Idc *, and generates and outputs a direct current control command 35a.
- the DC voltage control unit 34 generates and outputs a DC control command 34a based on a DC voltage command Vdc * that keeps the DC voltage at the DC side terminal D2 of the power converter 32 constant.
- the DC voltage at the DC side terminal D2 of the power converter 32 is adjusted by the DC control command 34a and the DC control command 35a.
- the DC voltage at the DC side terminal D2 is adjusted in consideration of a voltage drop when the DC current Idc flows through the DC system bus 60.
- the control output combining unit 37 combines the AC control command 33a, the DC control command 34a, the DC control command 35a, and the voltage balance control command 36a to generate an output voltage command 37a for controlling the power converter 32.
- a gate signal for controlling the unit converter cell 5 of each phase of the power converter 32 is generated by a gate signal generation circuit (not shown) such as a PWM circuit.
- the control device 31 allows the AC voltage Vac of the AC side terminal D1 to have a constant amplitude and a constant frequency according to the generated output voltage command 37a and based on the power received from the AC side terminal D1.
- the power converter 32 is controlled so as to adjust the direct current Idc output to D2.
- the protection control unit 50 of the control device 31 includes a determination unit 51 that detects a change in the DC current Idc of the DC system bus 60, an inverter 52, a delay unit 53 that is an on-delay timer, and a reset input.
- a flip-flop circuit 54 having a terminal R, a set input terminal S, and an output terminal Q, and a multiplier 55 are provided.
- the determination unit 51 detects that the direct current Idc has fluctuated beyond a predetermined range, the determination unit 51 outputs “1” as the determination information s1.
- the determination information s1 is input to the set input terminal S of the flip-flop circuit 54 and output, and then multiplied by a predetermined constant const by the multiplier 55 and output from the protection control unit 50 as correction information cor.
- This correction information cor is configured to subtract the AC voltage command Vac * input to the AC voltage control unit 33.
- the determination unit 51 detects that the fluctuation of the direct current Idc has returned to the predetermined range, it outputs “0” as the determination information s1.
- the determination information s1 is inverted by the inverter 52, delayed by a delay unit 53 for a predetermined period, and input to the reset input terminal R of the flip-flop circuit 54. In this way, the protection control unit 50 invalidates the correction information cor as “0” when a predetermined period has elapsed after detecting that the fluctuation of the direct current Idc has returned to the predetermined range.
- the determination unit 51 detects the fluctuation amount of the direct current Idc, for example, as a method of detecting the fluctuation exceeding the predetermined range of the direct current Idc.
- the determination unit 51 may detect the fluctuation of the direct current Idc that exceeds the current fluctuation range during normal operation. Further, for example, it is possible to detect the speed of fluctuation when the DC current Idc changes. In this case, there is a method of detecting a differential coefficient at the tangent line of the current waveform of the direct current Idc.
- the control device 41 includes a capacitor voltage control unit 46, an AC current control unit 49, a DC voltage control unit 44, and a control output synthesis unit 47.
- the DC voltage control unit 44 performs control calculation so that the DC voltage Vdc at the DC side terminal E2 of the reverse power converter 42 follows the DC voltage command Vdc * with a constant voltage, and generates a DC control command 44a. Output.
- the capacitor voltage control unit 46 performs a control calculation so that the voltage Vcapx of each capacitor 3 in the reverse power converter 42 follows the capacitor voltage command Vcapx *, and generates a voltage balance control command 46a and an AC current command Iac *. And output.
- the capacitor voltage control unit 46 generates an AC current command Iac * for the AC current Iac to be output based on the voltage Vcapx of the capacitor 3 in the inverse power converter 42 that varies due to the received power and the output power. is doing.
- the AC current control unit 49 performs a control calculation so that the AC current Iac output from the reverse power converter 42 follows the AC current command Iac *, and generates and outputs an AC control command 49a.
- the control output combining unit 47 combines the AC control command 49a, the DC control command 44a, and the voltage balance control command 46a to generate an output voltage command 47a for controlling the reverse power converter 42.
- a gate signal for controlling the unit converter cell 5 of each phase of the reverse power converter 42 is generated by a gate signal generation circuit (not shown), for example, a PWM circuit.
- the control device 41 outputs the output voltage command 47a to the AC side terminal E1 so that the DC voltage Vdc of the DC side terminal E2 becomes a constant voltage and based on the power received from the DC side terminal E2.
- the reverse power converter 42 is controlled so as to adjust the alternating current Iac.
- the determination unit 51 of the protection control unit 50 included in the power conversion device 30 detects a fluctuation of the DC current Idc that exceeds a predetermined range.
- the protection control unit 50 detects a decrease exceeding the predetermined range of the direct current Idc of the power converter 32 and outputs correction information cor as a correction amount.
- the output correction information cor subtracts the AC voltage command Vac * input to the AC voltage controller 33.
- the amplitude of the AC voltage Vac at the AC side terminal D1 of the power converter 32 decreases.
- the power converter 30 subtracts the AC voltage command Vac * from the correction information cor, thereby reducing the amplitude of the AC voltage Vac at the AC side terminal D1 of the power converter 32 and receiving power from the power generation system 20. Protection control to suppress the amount is performed.
- the power generation side power conversion device 23 of the power generation system 21 has an FRT function for a voltage drop of the connected power generation system bus 61. For this reason, when the AC voltage on the output side of the power generation side power conversion device 23 decreases in accordance with the decrease in the amplitude of the AC voltage at the AC side terminal D1 of the power conversion device 30 due to the protection control, this FRT function is activated and The device 23 performs continuous operation while suppressing the output power.
- the output power in the power generation system 20 is suppressed according to the decrease in the output power of the power conversion device 40 caused by the system disturbance in the demand place system 80. Thereby, the power supply to the demand place system 80 is continued in a state where the power balance in the power transmission system 70 and the power system 100 is maintained even when the system is disturbed.
- the protection control unit 50 invalidates the correction information cor after a predetermined period, and the protection control is thereby stopped. In this way, the suppression of the generated power in the power generation system 20 is released, and normal operation for supplying the power to be supplied in the normal state to the demand place system 80 is resumed.
- the power conversion device 30 connected to the power generation system 20 side is based on the fluctuation of the direct current Idc output from the power converter 32.
- Protective control that suppresses the amount of power received from the power generation system 20 by detecting a voltage abnormality or the like of another system connected to the output side of the converter 32 is performed. Therefore, it is not necessary to receive information for performing protection control from other electrical equipment, and protection control can be performed by the power converter 30 alone. Further, since no delay due to information transmission for performing protection control occurs, protection control can be started quickly from detection of a voltage abnormality in another system.
- the imbalance between the received power and the output power in the power converter 32 can be suppressed, and the power converter 32 can be stabilized immediately. Further, by detecting only the fluctuation of the direct current Idc exceeding the predetermined range, it is possible to prevent the fluctuation control of the direct current Idc within the rated range of the power converter 30 from being erroneously detected and performing protection control.
- the power converter 30 detects the DC current Idc that fluctuates before the output-side DC voltage reaches the threshold abnormality when the output-side system is abnormal, the voltage of the output-side DC voltage is detected. It is possible to detect voltage abnormalities in the system on the output side while maintaining within the rated operating range. Therefore, the design margin between the rated operating voltage of the power converter 32 and the overvoltage level of the power converter 32 can be reduced. Thereby, the high performance power converter 30 with few design restrictions can be provided.
- the power conversion device 30 when the power conversion device 30 is connected to a demand place system 80 such as an urban area through the DC power bus 60 and the power conversion apparatus 40 including the reverse power converter 42, an accident in the demand place system 80 is caused.
- the system disturbance can be detected by detecting the fluctuation of the direct current Idc. Even in this case, the system disturbance in the demand area system 80 can be detected while the voltage of the DC system bus 60 is kept within the rated operation range. Therefore, the design margin between the overvoltage level of power converter 32 and reverse power converter 42 and the withstand voltage of DC system bus 60 and the rated voltage during normal operation can be reduced. Thereby, the high performance power converter 30, the power transmission system 70, and the power system 100 with few design restrictions can be provided.
- the protection control unit 50 stops the protection control after a predetermined period has elapsed. By providing the predetermined period in this manner, frequent start and stop of unintended protection control can be suppressed, and the operations of the power conversion device 30, the power transmission system 70, and the power system 100 can be stabilized.
- the direct current Idc tends to decrease during the system disturbance, even when the fluctuation of the DC current Idc is used for detecting the system disturbance, the power converter 32, the reverse power converter 42, and the DC system bus 60 There is no need to increase the DC current resistance of the cables used.
- the direct current Idc which is information used by the protection control unit 50 of the power conversion device 30 to determine the system disturbance, is information used in the control when the power conversion device 30 is operating normally. Therefore, it is not necessary to newly provide a detector for detecting system disturbance.
- control device 31 suppresses the amount of power received from the power generation system 21 by reducing the amplitude of the AC voltage Vac of the AC side terminal D1 of the power converter 32a using the correction information cor. In this way, a communication line between the power conversion device 30 and the power generation system 21 is not required, and further space reduction and cost reduction can be achieved.
- FIG. 8 is a block diagram showing a configuration of a control device 31a having a configuration different from that of the control device 31 shown in FIG. Similar to the control device 31 described above, the protection control unit 50 outputs correction information cor when detecting a decrease in the direct current Idc of the power converter 32. The correction information cor is transmitted to each power generation system 21 provided in the power generation system 20.
- the power generation side power conversion device 23 of each power generation system 21 has an FRT function for protection control of the protection control unit 50. For this reason, when the correction information cor is received from the protection control unit 50, the FRT function operates to reduce the amplitude of the output power to suppress the output power and perform continuous operation. In this way, the power conversion device 30 suppresses the amount of power received from the power generation system 20 by transmitting the correction information cor to the power generation system 21. In this way, the control device 31a transmits the correction information cor to the power generation system 21, and the power generation system 21 can quickly start the suppression control of the output power together with the reception of the correction information cor. Thereby, the suppression control of generated electric power can be started quickly from the detection of the system disturbance in the demand place system 80, and the power balance of the power conversion device 30, the power transmission system 70, and the power system 100 can be stabilized quickly.
- FIG. 9 is a circuit configuration example of a power converter 32a and a reverse power converter 42a having configurations different from those of the power converter 32 and the reverse power converter 42 illustrated in FIG.
- each phase is constituted by a leg having a half-bridge configuration, a capacitor 3 c is provided between the DC buses, and a low-pass filter circuit 10 for suppressing harmonics is provided on the AC output side.
- (Reverse power converter 42a) is shown.
- the power converter 32 and the inverse power converter 42 used above are modular multi-level converters each having a plurality of unit converter cells 5 connected in series. You may use the power converter 32a of the structure called a converter, and the reverse power converter 42a.
- the power converters 32 and 32a having a plurality of phases and the inverse power converters 42 and 42a have been described. However, the power converters are not limited to a plurality of phases and may be a single phase.
- the power converter 32a and the inverse power converter 42a may be self-excited power converters composed of self-extinguishing type switching elements such as IGBTs and GCT thyristors as described above, and FIG. 2, FIG. 3, FIG.
- the circuit configuration shown in FIG. 9 does not limit the present invention.
- the power converters 32 and 32a used in the power conversion device 30 and the inverse power converters 42 and 42a used in the power conversion device 40 do not necessarily have the same circuit configuration.
- one converter is modular.
- the multi-level converter and the other converter may be a two-level converter.
- FIG. 10 is a block diagram illustrating a configuration example of the direct current control unit 35 in the control device 31 of the power conversion device 30 according to the first embodiment of the present invention.
- the DC current control unit 35 receives a deviation between the DC current command Idc * and the DC current Idc as an input, calculates a control amount 91, and outputs an output 91a of the DC current control unit 35 to a predetermined value.
- an output limiter 90 for limiting with a limit value.
- the DC voltage at the DC-side terminal D2 of the power conversion device 30 includes the DC control command 34a output from the DC voltage control unit 34 of the control device 31 and the DC control command output from the DC current control unit 35. 35a. Therefore, by providing the direct current control unit 35 with an output limiter 90 that restricts the output of the direct current control unit 35 with a predetermined limit value, the direct current voltage at the direct current side terminal D2 of the power conversion device 30 exceeds the desired voltage. It is possible to suppress the rise. Thereby, it can suppress reliably that the DC voltage in the direct current
- FIG. 11 is a block diagram showing a configuration of protection control unit 250 in control device 31 of power conversion device 30 according to the second embodiment of the present invention.
- the determination unit 251 of the protection control unit 250 of the present embodiment has a first threshold T1 that is set with respect to the deviation between the DC current Idc and the DC current command Idc * of the power converter 32.
- the determination unit 251 When determining that the deviation between the direct current Idc of the direct current system bus 60 and the direct current command Idc * exceeds the set first threshold value T1, the determination unit 251 outputs “1” as determination information s1. .
- the protection control unit 250 outputs the correction information cor that reduces the amplitude of the AC voltage command Vac *, and performs protection control that suppresses the amount of power received from the power generation system 20. Further, when the determination unit 251 detects that the deviation between the direct current command Idc * and the direct current Idc is equal to or less than the first threshold value T1, the determination unit 251 outputs “0” as the determination information s1. Then, when a predetermined period has elapsed since the detection, the protection control unit 250 invalidates the correction information cor as “0” and stops the protection control.
- the operation continuation function at the time of system disturbance of the demand place system 80 in the power conversion device 30 including the protection control unit 250 according to the second embodiment will be described.
- the protection control unit 250 detects the decrease in the DC current Idc when the deviation between the DC current Idc and the DC current command Idc * exceeds the first threshold value T1, and executes protection control.
- the AC power received by the power converter 32 is suppressed, and the power converter 32 adjusts the DC current command Idc * to decrease so as to output power corresponding to the received AC power.
- the deviation between the direct current Idc and the direct current command Idc * becomes equal to or less than the first threshold value T1, and after a predetermined period, the protection control is stopped and normal operation is resumed.
- the protection control is stopped and the normal operation is resumed after a predetermined period has elapsed since the execution of the protection control. I am doing so.
- the predetermined period may be determined in advance in consideration of a general period of system disturbance occurring in the demand area system 80. If the system disturbance in the demand place system
- strain 80 is removed after restarting normal operation, the power converter device 30, the power transmission system 70, and the electric power system 100 will continue normal operation as it is. If the system disturbance is not removed even after the power conversion device 30, the power transmission system 70, and the power system 100 resume normal operation, the protection control unit 250 re-detects the system disturbance and the protection control is performed again. .
- the power conversion device 30 of the present embodiment configured as described above, the same effects as those of the first embodiment can be obtained, and the power conversion device 30 is based on the fluctuation of the direct current Idc.
- the control control which detects the voltage abnormality of the other system linked to the output side of the power generation system and suppresses the amount of power received from the power generation system 20 is performed. Therefore, it is not necessary to receive information for performing protection control from other electrical equipment, and protection control can be performed by the power converter 30 alone.
- the power conversion device 30 can detect a voltage abnormality of the output side system while keeping the voltage of the output side DC voltage within the rated operation range. Thereby, the high performance power converter 30 with few design restrictions can be provided. Further, also in the power transmission system 70 and the power system 100 including the power conversion device 30 according to the present embodiment, space saving and cost reduction can be achieved and design constraints can be reduced.
- the determination unit 251 of the protection control unit 250 detects the fluctuation of the direct current Idc from the deviation between the direct current Idc and the direct current command Idc *.
- the DC current command Idc * is a command value generated so as to adjust the DC power output based on the AC power received by the power converter 32, and is not a fixed value. . Therefore, the determination unit 251 does not erroneously detect a change in the direct current Idc within the rated range during normal operation of the power conversion device 30, the power transmission system 70, and the power system 100 as a change due to system disturbance. Thus, the start of unintended protection control can be suppressed, and the operation of the power conversion device 30, the power transmission system 70, and the power system 100 can be further stabilized.
- FIG. 12 is a block diagram illustrating a configuration of a control device 331 that controls the power converter 32 according to the third embodiment of the present invention.
- FIG. 13 is a block diagram showing a configuration of DC current control unit 335 in control device 331 shown in FIG.
- FIG. 14 is a block diagram showing a configuration of the protection control unit 350a in the control device 331 shown in FIG.
- the direct current control unit 335 outputs an internal variable xIdc (details will be described below), and the output internal variable xIdc is output to the protection control unit 350a. It is configured to be input.
- the direct current control unit 335 includes a controller 91 that calculates an internal variable xIdc as a control amount by using a deviation between the direct current command Idc * and the direct current Idc as an input. The internal variable xIdc is adjusted by the controller 91 so as to reduce the deviation between the direct current command Idc * and the direct current Idc during normal operation of the power conversion device 30.
- a value obtained by multiplying the value of the internal variable xIdc output from the controller 91 by a predetermined limiter value by the output limiter 90 is the DC control command 335a.
- the determination unit 351a of the protection control unit 350a shown in FIG. 14 has a second threshold value xIdcth2 that indicates the adjustment range of the internal variable xIdc during normal operation of the power converter 32.
- “1” is output as determination information s1, thereby performing protection control.
- the determination unit 351a outputs “0” as determination information s1 when detecting that the input internal variable xIdc is equal to or less than the second threshold value xIdcth2, and protection control is performed when a predetermined period has elapsed from this detection. Is stopped.
- the operation continuation control function at the time of system disturbance of the demand place system 80 in the power conversion device 30 including the protection control unit 350a according to the third embodiment will be described.
- the DC current Idc flowing through the DC system bus 60 decreases.
- the controller 91 of the direct current controller 335 generates the internal variable xIdc so that the direct current Idc follows the direct current command Idc *.
- the protection control unit 350a detects that the internal variable xIdc exceeds the second threshold value xIdcth2, the protection control unit 350a performs protection control.
- the AC power received by the power converter 32 is suppressed, and the power converter 32 adjusts the DC current command Idc * to decrease so as to output DC power corresponding to the AC power received.
- the deviation between the direct current Idc and the direct current command Idc * is suppressed, the internal variable xIdc becomes equal to or smaller than the second threshold value xIdcth2, and the protection control is stopped after a predetermined period has elapsed.
- FIG. 15 is a block diagram illustrating a configuration of a protection control unit 350b having a configuration different from that of the protection control unit 350a illustrated in FIG.
- the determination unit 351b of the protection control unit 350b illustrated in FIG. 15 includes a second threshold value xIdcth2 and a lower limit threshold value xIdcth-low set to a value smaller than the second threshold value xIdcth2.
- the determination unit 351b detects that the input internal variable xIdc exceeds the second threshold value xIdcth2, the determination unit 351b outputs “1” as determination information s1, thereby performing protection control.
- the determination unit 351b outputs “0” as the determination information s1 when detecting that the input internal variable xIdc is equal to or lower than the lower limit threshold xIdcth ⁇ low, and protects when a predetermined period has elapsed from this detection. Control is stopped.
- FIG. 16 is a block diagram illustrating a configuration of a protection control unit 350c having a configuration different from the protection control units 350a and 350b illustrated in FIGS.
- the protection control unit 350c illustrated in FIG. 16 includes a correction amount adjustment unit 356 that adjusts the correction amount of the correction information cor according to the detected value of the direct current Idc.
- the correction amount adjustment unit 356 has three stages of correction values (1, 0.7, 0.4) corresponding to the value of the direct current Idc. In this way, the correction amount adjustment unit 356 corrects the output 54a from the flip-flop circuit 54 according to the value of the direct current Idc by the multiplier 55, and adjusts the correction amount of the correction information cor.
- the power conversion device 30 of the present embodiment configured as described above, the same effect as that of the first embodiment is achieved, and the power conversion device 30 is based on the internal variable xIdc for adjusting the direct current Idc.
- Protective control that suppresses the amount of power received from the power generation system 20 by detecting voltage abnormality of the system linked to the output side of the power converter 32 is performed.
- the internal variable xIdc is a value calculated in the control device 331 of the power conversion device 30, and it is not necessary to receive information for performing the protection control from other electrical equipment, and the power control device 30 alone performs the protection control. It can be carried out.
- the power conversion device 30 detects the voltage abnormality of the output side system using the internal variable xIdc based on the DC current Idc that fluctuates before the output side DC voltage reaches the threshold abnormality, It is possible to detect voltage abnormalities in the output side system while keeping the output side DC voltage within the rated operating range. Thereby, the high performance power converter 30 with few design restrictions can be provided. Further, also in the power transmission system 70 and the power system 100 including the power conversion device 30 according to the present embodiment, space saving and cost reduction can be achieved and design constraints can be reduced.
- the protection control units 350a, 350b, and 350c are configured to detect fluctuations in the internal variable xIdc based on fluctuations in the direct current Idc within the rated range during normal operation of the power conversion device 30, the power transmission system 70, and the power system 100. It is not a false detection of fluctuations caused by Therefore, the operation of the power conversion device 30, the power transmission system 70, and the power system 100 can be further stabilized.
- the hysteresis width is provided by using different threshold values (second threshold value xIdcth2, lower limit threshold value xIdcth-low) with respect to the threshold values used for determination of start and stop of protection control.
- second threshold value xIdcth2, lower limit threshold value xIdcth-low threshold values used for determination of start and stop of protection control.
- the start and stop of unintended protection control can be suppressed, and operation of power converter 30, power transmission system 70, and power system 100 can be stabilized more.
- the correction amount of the correction information cor can be adjusted according to the value of the direct current Idc, the amount of power received from the power generation system 20 can be adjusted according to the degree of system disturbance.
- 13 is provided with the output limiter 90 that limits the output of the controller 91.
- the DC current control unit 335 having a configuration in which the output limiter 90 is not provided may be used.
- FIG. 17 is a block diagram showing a configuration of a protection control unit 450a according to Embodiment 4 of the present invention.
- FIG. 18 is a block diagram illustrating a configuration of a protection control unit 450b having a configuration different from that of the protection control unit 450a illustrated in FIG.
- the protection control units 450a and 450b perform protection control when the relationship between the direct current Idc and the internal variable xIdc changes beyond a predetermined proportional relationship.
- the protection controller 450a has a proportionality constant K that represents a proportional relationship between the direct current Idc and the internal variable xIdc during normal operation.
- the determination unit 451a has a third threshold value xIdcth3 set for the error of the proportional relationship during normal operation of the power converter 32.
- the determination unit 451a detects that the deviation between K ⁇ Idc and the internal variable xIdc is equal to or smaller than the third threshold value xIdcth3, the determination unit 451a outputs “0” as the determination information s1, and a predetermined period from this detection is output. Protection control is stopped when it passes.
- the determination unit 451b of the protection control unit 450b detects that the value obtained by dividing the internal variable xIdc by the direct current Idc exceeds the set fourth threshold value xIdcth4, the determination unit 451b outputs “1” as the determination information s1.
- the protection control units 450a and 450b start and stop the protection control by using the proportional relationship between the direct current Idc and the internal variable xIdc.
- FIG. 19 is a block diagram showing a configuration of protection control unit 450c in the control device for power converter 32 according to the fourth embodiment of the present invention.
- the determination unit 451c of the protection control unit 450c outputs “1” as the determination information s1.
- the determination unit 457 detects that the deviation between K ⁇ Idc and xIdc exceeds the third threshold value xIdcth3, the determination unit 457 outputs “0” as the determination information s2.
- the determination information s1 is input to the set input terminal S of the flip-flop circuit 54, and after being inverted by the inverter 11, is also input to one terminal of the AND circuit 12.
- the determination information s2 is input to the other terminal of the AND circuit 12.
- the output of the AND circuit 12 is delayed for a predetermined period by the delay unit 53 and input to the reset input terminal R of the flip-flop circuit 54.
- the determination unit 451c When the determination unit 451c detects that the deviation between the direct current Idc and the direct current command Idc * is equal to or less than the first threshold value T1 by executing the protection control, the determination unit 451c outputs “0” as the determination information s1. Further, when the determination unit 457 detects that the deviation between K ⁇ Idc and xIdc is equal to or less than the third threshold value xIdcth3, the determination unit 457 outputs “1” as the determination information s2.
- the output of the AND circuit 12 is delayed by a delay unit 53 for a predetermined period and input to the reset input terminal R of the flip-flop circuit 54. Thus, when a predetermined period has elapsed from this detection by the determination unit 451c and the determination unit 457, the protection control unit 450c invalidates the correction information cor to “0” and stops the protection control.
- the power conversion device 30 of the present embodiment configured as described above, the same effect as that of the first embodiment is achieved, and the power conversion device 30 has a proportional relationship of the internal variable xIdc for adjusting the direct current Idc. Based on this, a voltage abnormality or the like of the system linked to the output side of the power converter 32 is detected, and protection control for suppressing the amount of power received from the power generation system 20 is performed.
- the internal variable xIdc is a value calculated in the control device 331 of the power conversion device 30, and it is not necessary to receive information for performing the protection control from other electrical equipment, and the power control device 30 alone performs the protection control. It can be carried out.
- the power conversion device 30 detects a voltage abnormality of the output side system using the proportional relationship of the internal variable xIdc based on the DC current Idc that fluctuates before the output side DC voltage reaches the threshold abnormality. Therefore, it is possible to detect a voltage abnormality in the output side system while keeping the DC voltage on the output side within the rated operating range. Thereby, the high performance power converter 30 with few design restrictions can be provided. Further, also in the power transmission system 70 and the power system 100 including the power conversion device 30 according to the present embodiment, space saving and cost reduction can be achieved and design constraints can be reduced.
- the protection control units 450a, 450b, and 450c are configured to change the proportional relationship of the internal variable xIdc according to the variation of the direct current Idc within the rated range during normal operation of the power conversion device 30, the power transmission system 70, and the power system 100. It does not falsely detect fluctuations caused by disturbance. Therefore, the operation of the power conversion device 30 and the power transmission systems 70 and 100 can be further stabilized.
- first threshold value T1 and the third threshold value xIdcth3 which are a plurality of threshold values, in each determination of start and stop of protection control, it is possible to detect a system disturbance with high reliability and suppress false detection. can do.
- first threshold value T1 and third threshold value xIdcth3 two different threshold values
- unintended start and stop of protection control are suppressed. Thereby, operation
- the protection control unit 450c uses two conditions: a deviation between the DC current Idc and the DC current command Idc * and a deviation between K ⁇ Idc and xIdc in order to detect a voltage abnormality in the output-side system.
- the present invention is not limited to the combination of these two conditions.
- a combination of two conditions of a value obtained by dividing the internal variable xIdc by the direct current Idc and a deviation between the direct current Idc and the direct current command Idc * may be used, and the combination can be appropriately selected.
- FIG. 20 is a block diagram showing a configuration of protection control unit 550 according to Embodiment 5 of the present invention.
- FIG. 21 is a block diagram showing a configuration of control device 541 of reverse power converter 42 according to the fifth embodiment of the present invention.
- the protection control unit 450a shown in FIG. 17 of the fourth embodiment. Therefore, when the determination unit 451a detects that the deviation between K ⁇ Idc and xIdc is equal to or less than the set third threshold value xIdcth3, the correction information cor is immediately invalidated without elapse of a predetermined period. Thus, the protection control is stopped.
- the control device 541 of the reverse power converter 42 shown in FIG. 21 is configured by adding a DC current adjustment unit 551 as an adjustment unit and a DC current control unit 545 to the control device 41 shown in the first embodiment. It has become.
- the direct current adjustment unit 551 is configured to detect that a system disturbance has occurred in the demand place system 80 based on a change in the voltage Vcapx of the capacitor 3 in the reverse power converter 42. Then, when the DC current adjustment unit 551 detects that the system disturbance has occurred, the DC voltage command Vdc * and the DC current command Idc * so as to suppress the DC current Idc flowing into the reverse power converter 42. Correct. Further, the direct current adjustment unit 551 detects the convergence of the system disturbance in the demand place system 80 based on the convergence of the fluctuation of the voltage Vcapx of the capacitor 3 in the reverse power converter 42. Thus, when the DC current adjustment unit 551 detects the convergence of the system disturbance, the DC current adjustment unit 551 stops the correction of the DC voltage command Vdc * and the DC current command Idc *.
- the DC current control unit 545 performs a control calculation so that the DC current Idc flowing into the reverse power converter 42 follows the corrected DC current command Idc *, and generates and outputs a DC control command 545a.
- the direct current control unit 545 is configured to operate only when the direct current adjustment unit 551 detects a system disturbance in the demand area system 80.
- the DC voltage control unit 44 performs a control calculation so that the DC voltage Vdc input to the reverse power converter 42 at the DC side terminal E2 follows the corrected DC voltage command Vdc *, and outputs the DC control command 44a. Generate and output.
- the DC current Idc is suppressed by the DC control command 44a and the DC control command 545a generated using the corrected DC voltage command Vdc * and the DC current Idc *.
- the operation continuation control function when the demand place system 80 is disturbed in the power conversion device 30 according to the fifth embodiment will be described.
- the DC current adjustment unit 551 of the power converter 40 connected to the demand area system 80 side detects this system disturbance. Then, the direct current adjustment unit 551 corrects the direct current voltage command Vdc * and the direct current command Idc * so as to suppress the direct current Idc flowing into the reverse power converter 42. Thereby, the direct current Idc is suppressed.
- the direct current Idc and the internal variable xIdc are in a proportional relationship, but the power conversion device 40 performs control to suppress the direct current Idc in this way. If this is the case, this proportional relationship will collapse.
- the determination unit 451a of the protection control unit 550 of the power conversion device 30 has a deviation between K ⁇ Idc and xIdc exceeding the set third threshold value xIdcth3, similarly to the determination unit 451a of the fourth embodiment. When this is detected, “1” is output as determination information s1, and protection control is performed.
- the correction of the DC voltage command Vdc * and the DC current command Idc * by the DC current adjustment unit 551 of the power conversion device 40 is continued while the system disturbance occurs in the demand point system 80, and the convergence of the system disturbance is detected. Is stopped.
- the determination unit 451a of the power conversion device 30 has a deviation between K ⁇ Idc and the internal variable xIdc. It is detected that the set threshold value is less than or equal to the third threshold value xIdcth3, and the protection control is immediately stopped.
- the power conversion device 30 of the present embodiment configured as described above, the same effect as that of the first embodiment is achieved, and the power conversion device 30 has a proportional relationship of the internal variable xIdc for adjusting the direct current Idc. Based on this, a voltage abnormality or the like of the system linked to the output side of the power converter 32 is detected, and protection control for suppressing the amount of power received from the power generation system 20 is performed.
- the internal variable xIdc is a value calculated in the control device 331 of the power conversion device 30, and it is not necessary to receive information for performing the protection control from other electrical equipment, and the power control device 30 alone performs the protection control. It can be carried out.
- the power conversion device 30 detects the voltage abnormality of the output side system using the proportional relationship of the internal variable xIdc based on the DC current Idc that fluctuates before the output side DC voltage reaches the threshold abnormality. Therefore, it is possible to detect a voltage abnormality in the output side system while keeping the voltage of the output side DC voltage within the rated operating range. Thereby, the high performance power converter 30 with few design restrictions can be provided. Further, also in the power transmission system 70 and the power system 100 including the power conversion device 30 according to the present embodiment, space saving and cost reduction can be achieved and design constraints can be reduced.
- the protection control unit 550 causes the fluctuation of the proportional relationship of the internal variable xIdc according to the fluctuation of the direct current Idc within the rated range during normal operation of the power conversion device 30, the power transmission system 70, and the power system 100 due to the system disturbance. It is not a false detection of fluctuation. Therefore, the operation of the power conversion device 30, the power transmission system 70, and the power system 100 can be further stabilized.
- the power conversion device 40 connected to the demand area system 80 detects the system disturbance in the demand area system 80 and suppresses the direct current Idc, the DC current Idc is earlier than the natural decrease. Thus, the direct current Idc can be reduced. Therefore, from the detection of the system disturbance by the power converter 40, the protection control by the power converter 30 can be started quickly. Thereby, the power converter 40 can be stably operated by quickly suppressing an unbalanced state between the DC power received by the power converter 40 and the AC power to be output.
- the period required until the system disturbance of the demand place system 80 converges is determined in advance, and the protection control is stopped after the period.
- power conversion device 40 detects the convergence of the system disturbance of demand place system 80 and suppresses DC current Idc only while the system disturbance occurs. Therefore, the above-described predetermined period becomes unnecessary, and the time required from the detection of the convergence of the system disturbance to the restart of normal operation can be shortened.
- the DC current adjustment unit 551 of the power converter 40 detects the system disturbance based on the fluctuation of the voltage Vacx of the capacitor 3 in the reverse power converter 42.
- the DC current adjustment unit 551 may detect a system disturbance based on information on the AC voltage of the AC side terminal E1 of the reverse power converter 42. Further, for example, it may be detected based on both information of the voltage fluctuation of the capacitor 3 and the AC voltage of the AC side terminal E1.
- the protection control unit 550 of the fifth embodiment has a configuration in which the inverter 52, the delay unit 53, and the flip-flop circuit 54 are excluded from the protection control unit 450a illustrated in FIG. 17 of the fourth embodiment.
- a protection control unit having a configuration excluding the above-described circuit may be used for the protection control units 350a, 350b, 350c, 450b, and 450c shown in FIGS. 14, 15, 16, 18, 19, and 20.
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Abstract
Description
さらにこの閾値は、変換器の過電圧レベルおよび直流系統母線に用いるケーブルなどの絶縁耐圧より小さくする必要がある。よって、変換器の過電圧レベルおよびケーブルの絶縁耐圧と、正常運転時の定格電圧との間の設計余裕を通常よりも多く取る必要がある。そのため、設計制約が大きくなり、電力変換装置および電力システムの設計が困難になるという問題点があった。
また、本発明に係る電力システムは、上記のように構成された電力変換装置と、前記電力変換器からの直流電力を交流電力に変換して需要地系統に送電する逆電力変換器と、前記逆電力変換器を制御する制御装置とを備え、前記逆電力変換器の制御装置は、前記逆電力変換器の直流電圧を直流電圧指令に追従させる直流電圧制御部と、前記逆電力変換器の交流電流を交流電流指令に追従させる交流電流制御部とを備え、前記直流電圧制御部の出力および前記交流電流制御部の出力に基づいて、前記逆電力変換器の出力電圧指令を生成するものである。
以下、本発明の実施の形態1による電力変換装置および電力システムについて図を用いて説明する。
図1は、本発明の実施の形態1による電力変換装置30および電力システム100の構成を示す概略構成図である。
図1に示すように、本実施の形態の電力システム100は、発電系統20と、発電系統20と需要地系統80との間に接続されて、発電系統20の発電電力を需要地系統80に供給するHVDC送電システム70(以下送電システム70と称す)とを備える。送電システム70は、交流を直流に変換する電力変換装置30と、直流を交流に変換する電力変換装置40と、電力変換装置30の直流出力電力を電力変換装置40に送電するための長距離ケーブルなどの直流母線としての直流系統母線60とを備える。
こうして各発電システム21は、発電系統母線61を介して電力変換装置30に対して交流電力を供給するように構成されている。
発電系統母線61の構成は、ツリー型、スター型、リング型など、いずれの構成でもよく、発電系統母線61の構成により本発明が限定されることはない。
図3(a)、図3(b)はそれぞれ、本発明の実施の形態1による電力変換器32および逆電力変換器42を構成する単位変換器セル5の回路構成例である。
図4(a)、図4(b)はそれぞれ、本発明の実施の形態1による電力変換器32および逆電力変換器42を構成する単位変換器セル5の回路構成例である。
電力変換器32、逆電力変換器42の各相は、正側アーム6pと負側アーム6nとが直列接続され、その接続点である交流側端子D1が各相交流線U、V、Wに接続されるレグ回路7で構成される。各レグ回路7の正側アーム6p、負側アーム6nのそれぞれは、1以上の単位変換器セル5を直列接続して備える。そして、これら各相のレグ回路7が、正負の直流母線間に並列接続されている。
なお、図1に示す電力変換器32は、図中左側が交流側端子D1であり、図中右側が直流側端子D2である。これは図2に示す電力変換器32の左右と対応している。
一方、図1に示す逆電力変換器42は、図中左側が直流側端子E2であり、図中右側が交流側端子E1である。これは図2に示す逆電力変換器42の左右と逆となっているが、便宜上このように図示している。
また、電力変換器32の直流側端子D2と直流系統母線60との間には連系用のリアクトル2が設けられても良く、同様に、逆電力変換器42の直流側端子E2と直流系統母線60との間には連系用リアクトル2が設けられても良い。
なお、このように正側アーム6pと負側アーム6nとの接続点である交流側端子D1(E1)を各相交流線U、V、Wに接続する構成に限定するものではなく、例えば、正側アーム6pと負側アーム6nとが直列接続され、トランスを介して各相交流線U、V、Wに接続される構成でもよい。
図3(a)に示す単位変換器セル5aは、ハーフブリッジ構成と呼ばれる回路構成である。2つの半導体素子としての半導体スイッチング素子1p、1nを直列接続して形成した直列体に、コンデンサ3が並列接続された構成となっている。
こうして、半導体スイッチング素子1nの両端子、もしくは半導体スイッチング素子1pの両端子を入出力端子とし、半導体スイッチング素子1p、1nのスイッチング動作によりコンデンサ3の両端電圧、および零電圧を出力する。
半導体スイッチング素子1p1と半導体スイッチング素子1n1との中点と、半導体スイッチング素子1p2と半導体スイッチング素子1n2との中点とを単位変換器セル5の入出力端子とする。そして、半導体スイッチング素子1p1、1n1、1p2、1n2のスイッチング動作によりコンデンサ3の両端電圧、コンデンサ3の両端電圧の逆電圧、および零電圧を出力する。
電力変換器32、逆電力変換器42を構成する単位変換器セル5は、図3、図4に示したどの単位変換器セル5a、5b、5c、5dを用いてもよい。
図6は、図5に示す制御装置31の保護制御部50の構成を示すブロック図である。
図7は、本発明の実施の形態1による逆電力変換器42の制御装置41の構成を示すブロック図である。
図5に示すように、制御装置31は、コンデンサ電圧制御部36と、交流電圧制御部33と、直流電圧制御部34と、直流電流制御部35と、制御出力合成部37と、直流電流Idcを検出する検出部としての直流電流検出部38と、保護制御部50とを備える。以下、各部の詳細について説明する。
交流電圧制御部33は、電力変換器32の受電端(交流側端子D1)の交流電圧Vacを、一定の振幅および周波数を有する交流電圧指令Vac*に追従させるように制御演算を行い、交流制御指令33aを生成して出力する。
直流電圧制御部34は、電力変換器32の直流側端子D2における直流電圧を一定にする直流電圧指令Vdc*に基づいて直流制御指令34aを生成して出力する。この直流制御指令34aと直流制御指令35aとで、電力変換器32の直流側端子D2における直流電圧が調整される。この直流側端子D2における直流電圧は、直流電流Idcが直流系統母線60を流れた際の電圧降下が考慮されて調整されている。
こうして、制御装置31は、生成した出力電圧指令37aにより、交流側端子D1の交流電圧Vacが一定振幅、一定周波数となるように、かつ、交流側端子D1から受電した電力に基づいて直流側端子D2に出力する直流電流Idcを調整するように、電力変換器32を制御する。
判定部51は、直流電流Idcが所定の範囲を超えて変動したことを検知すると、「1」を判定情報s1として出力する。この判定情報s1はフリップフロップ回路54のセット入力端子Sに入力されて出力された後に乗算器55により所定の定数constが乗算され、補正情報corとして保護制御部50から出力される。この補正情報corが、交流電圧制御部33に入力される交流電圧指令Vac*を減算する構成となっている。
図7に示すように、制御装置41は、コンデンサ電圧制御部46と、交流電流制御部49と、直流電圧制御部44と、制御出力合成部47とを備える。
直流電圧制御部44は、逆電力変換器42の直流側端子E2における直流電圧Vdcを、電圧が一定の直流電圧指令Vdc*に追従させるように制御演算を行い、直流制御指令44aを生成して出力する。
交流電流制御部49は、逆電力変換器42から出力する交流電流Iacを、交流電流指令Iac*に追従させるように制御演算を行い、交流制御指令49aを生成して出力する。
こうして、制御装置41は、生成した出力電圧指令47aにより、直流側端子E2の直流電圧Vdcが一定電圧となるように、かつ、直流側端子E2から受電した電力に基づいて交流側端子E1に出力する交流電流Iacを調整するように、逆電力変換器42を制御する。
需要地系統80において系統擾乱が発生すると、逆電力変換器42の交流側端子E1における交流電圧が低下し、逆電力変換器42が需要地系統80に出力できる交流電力が低下する。その結果、逆電力変換器42に流入する直流電力が低下するため、直流電流Idcが低下する。
このように、電力変換装置30は、補正情報corにより交流電圧指令Vac*を減算することで、電力変換器32の交流側端子D1における交流電圧Vacの振幅を低下させて発電系統20からの受電量を抑制する保護制御を行う。
また、所定の範囲を超える直流電流Idcの変動のみを検知することで、電力変換装置30の定格範囲内の直流電流Idcの変動を誤検知して保護制御を行うことを防止することができる。
また、直流電流Idcの変動が所定の範囲内に復帰すると、保護制御部50は予め定められた期間の経過後に保護制御を停止する。このように予め定めた期間を設けることで、意図しない保護制御の頻繁な開始、停止を抑止し、電力変換装置30、送電システム70、電力システム100の動作を安定化させることができる。
また、電力変換装置30の保護制御部50が系統擾乱の判定に用いる情報である直流電流Idcは、電力変換装置30が正常運転時の制御においても用いる情報である。そのため、系統擾乱を検知するための検知器を新たに設ける必要がない。
前述した制御装置31と同様に、保護制御部50は、電力変換器32の直流電流Idcの低下を検知すると補正情報corを出力する。この補正情報corは、発電系統20が備える各発電システム21に対して送信される。
こうして制御装置31aは、補正情報corを発電システム21に送信し、発電システム21は、補正情報corの受信と共に迅速に出力電力の抑制制御を開始することができる。これにより、需要地系統80における系統擾乱の検知から迅速に発電電力の抑制制御を開始でき、電力変換装置30、送電システム70、電力システム100の電力バランスを早急に安定化させることができる。
上記で用いた電力変換器32、逆電力変換器42は、単位変換器セル5を複数直列に接続した各相を備えたモジュラーマルチレベル変換器を示したが、図9に示すような2レベル変換器と呼ばれる構成の電力変換器32a、逆電力変換器42aを用いるものでもよい。
以上、複数相構成の電力変換器32、32a、逆電力変換器42、42aを用いて説明したが、複数相に限定するものではなく単相構成でもよい。
また、電力変換装置30に用いられる電力変換器32、32aと、電力変換装置40に用いられる逆電力変換器42、42aは必ずしも同じ回路構成である必要はなく、例えば、一方の変換器がモジュラーマルチレベル変換器、もう一方の変換器が2レベル変換器といった構成でも良い。
図10は、本発明の実施の形態1による電力変換装置30の制御装置31における直流電流制御部35の構成例を示すブロック図である。
図10に示すように、直流電流制御部35は、直流電流指令Idc*と直流電流Idcとの偏差を入力として制御量を演算する制御器91と、直流電流制御部35の出力91aを所定の制限値で制限する出力リミッタ90とを備える。
以下、本発明の実施の形態2を、上記実施の形態1と異なる箇所を中心に図を用いて説明する。上記実施の形態1と同様の部分は同一符号を付して説明を省略する。
図11は、本発明の実施の形態2による電力変換装置30の制御装置31における保護制御部250の構成を示すブロック図である。
本実施の形態の保護制御部250の判定部251は、電力変換器32の直流電流Idcと直流電流指令Idc*との偏差に対して設定された第1閾値T1を有する。そして、判定部251は、直流系統母線60の直流電流Idcと直流電流指令Idc*との偏差が、設定された第1閾値T1を超えたことを検知すると「1」を判定情報s1として出力する。そして実施の形態1と同様に、保護制御部250は交流電圧指令Vac*の振幅を低下させる補正情報corを出力して、発電系統20からの受電量を抑制する保護制御を行う。
また、判定部251は、直流電流指令Idc*と直流電流Idcとの偏差が第1閾値T1以下となったことを検知すると「0」を判定情報s1として出力する。そして保護制御部250は、この検知から予め定められた期間を経過すると、補正情報corを「0」として無効にし、保護制御を停止する。
需要地系統80において系統擾乱が発生すると、実施の形態1にて述べたように直流系統母線60を流れる直流電流Idcが低下する。保護制御部250は、この直流電流Idcの低下を、直流電流Idcと直流電流指令Idc*との偏差が第1閾値T1を超えたことにより検知して保護制御を実行する。保護制御の実行により電力変換器32が受電する交流電力が抑制され、電力変換器32は受電する交流電力に応じた電力を出力するように、直流電流指令Idc*を減少させるように調整する。こうして直流電流Idcと直流電流指令Idc*との偏差が第1閾値T1以下となり、予め定められた期間が経過した後に保護制御が停止されて正常運転が再開される。
正常運転を再開してから、需要地系統80における系統擾乱が除去されていれば、電力変換装置30、送電システム70、電力システム100は、そのまま正常運転を継続する。電力変換装置30、送電システム70、電力システム100が正常運転を再開してからも系統擾乱が除去されていない場合は、保護制御部250が系統擾乱を再検知して、保護制御が再度行われる。
以下、本発明の実施の形態3を、上記実施の形態1と異なる箇所を中心に図を用いて説明する。上記実施の形態1と同様の部分は同一符号を付して説明を省略する。
図12は、本発明の実施の形態3による電力変換器32を制御する制御装置331の構成を示すブロック図である。
図13は、図12に示す制御装置331における直流電流制御部335の構成を示すブロック図である。
図14は、図12に示す制御装置331における保護制御部350aの構成を示すブロック図である。
図13に示すように、直流電流制御部335は、直流電流指令Idc*と直流電流Idcとの偏差を入力として、制御量としての内部変数xIdcを演算する制御器91を備える。内部変数xIdcは、電力変換装置30の正常運転時において、直流電流指令Idc*と直流電流Idcとの偏差を小さくするように制御器91により調整されるものである。制御器91から出力された内部変数xIdcの値に、出力リミッタ90により所定のリミッタ値を乗算して制限した値が直流制御指令335aとなる。このように出力リミッタ90を設けることで、電力変換器32から出力する直流電圧を定格運転範囲内に留めることができる。なお、制御器91には、PI制御器等が用いられる。
そして判定部351aは、入力された内部変数xIdcが設定された第2閾値xIdcth2を超えたことを検知すると「1」を判定情報s1として出力し、これにより保護制御が行われる。また、判定部351aは、入力された内部変数xIdcが第2閾値xIdcth2以下となったことを検知すると「0」を判定情報s1として出力し、この検知から予め定められた期間を経過すると保護制御が停止される。
需要地系統80において系統擾乱が発生すると、前述したように、直流系統母線60を流れる直流電流Idcが低下する。直流電流制御部335の制御器91は、前述したように、直流電流Idcが直流電流指令Idc*に追従するように内部変数xIdcを生成する。保護制御部350aは、内部変数xIdcが、第2閾値xIdcth2を超えたことを検知すると、保護制御を行う。この保護制御により電力変換器32が受電する交流電力が抑制され、電力変換器32は受電する交流電力に応じた直流電力を出力するように、直流電流指令Idc*を減少させるように調整する。こうして、直流電流Idcと直流電流指令Idc*との偏差が抑制され、内部変数xIdcは第2閾値xIdcth2以下となり、予め定められた期間が経過した後に保護制御が停止される。
図15に示す保護制御部350bの判定部351bは、第2閾値xIdcth2と、この第2閾値xIdcth2より小さい値に設定された下限閾値xIdcth-lowとを有する。
そして、判定部351bは、入力された内部変数xIdcが第2閾値xIdcth2を超えたことを検知すると「1」を判定情報s1として出力し、これにより保護制御が行われる。また、判定部351bは、入力された内部変数xIdcが下限閾値xIdcth-low以下となったことを検知すると「0」を判定情報s1として出力し、この検知から予め定められた期間を経過すると保護制御が停止される。
図16に示す保護制御部350cは、検出した直流電流Idcの値に応じて補正情報corの補正量を調整する補正量調整部356を有する。本実施の形態では、補正量調整部356は、直流電流Idcの値に応じた3段階の補正値(1、 0.7, 0.4)を有している。こうして、補正量調整部356は、フリップフロップ回路54からの出力54aを、乗算器55により直流電流Idcの値に応じて補正して、補正情報corの補正量を調整する。
また、直流電流Idcの値に応じて補正情報corの補正量を調整できるため、系統擾乱の度合いに応じて発電系統20からの受電量を調整することができる。
なお、図13に示す直流電流制御部335には、制御器91の出力を制限する出力リミッタ90を設けたが、この出力リミッタ90を設けない構成の直流電流制御部335でもよい。
以下、本発明の実施の形態4を、上記実施の形態1、2、3と異なる箇所を中心に図を用いて説明する。上記実施の形態1、2、3と同様の部分は同一符号を付して説明を省略する。
実施の形態1の図5に示した制御装置31の保護制御部50の変形例を示す。
図17は、本発明の実施の形態4による保護制御部450aの構成を示すブロック図である。
図18は、図17に示す保護制御部450aとは異なる構成の保護制御部450bの構成を示すブロック図である。
通常、電力変換装置30が正常運転をしている場合は、直流電流Idcと内部変数xIdcとは比例関係にあるが、需要地系統80において系統擾乱が発生し、直流電流Idcが低下している場合はこの比例関係が崩れる。本実施の形態の保護制御部450a、450bは、直流電流Idcと内部変数xIdcとの関係が、所定の比例関係を超えて変動した場合に、保護制御を行うものである。
保護制御部450aは、正常運転時の直流電流Idcと内部変数xIdcとの比例関係を表す比例定数Kを有する。また、判定部451aは、電力変換器32の正常運転時の前記比例関係の誤差に対して設定された第3閾値xIdcth3を有する。
そして、判定部451aは、K×IdcとxIdcとの偏差が第3閾値xIdcth3を超えたことを検知すると「1」を判定情報s1として出力し、これにより保護制御が行われる。また、判定部451aは、K×Idcと内部変数xIdcとの偏差が第3閾値xIdcth3以下となったことを検知すると「0」を判定情報s1として出力し、この検知から予め定められた期間を経過すると保護制御が停止される。
保護制御部450bの判定部451bは、内部変数xIdcを直流電流Idcで除算した値が、設定された第4閾値xIdcth4を超えたことを検知すると「1」を判定情報s1として出力し、内部変数xIdcを直流電流Idcで除算した値が第4閾値xIdcth4以下となったことを検知すると「0」を判定情報s1として出力する。
このように、上記保護制御部450a、450bは、直流電流Idcと内部変数xIdcとの比例関係を用いて、保護制御の開始、停止を行うものである。
図19は、本発明の実施の形態4による電力変換器32の制御装置における保護制御部450cの構成を示すブロック図である。
保護制御部450cの判定部451cは、直流電流Idcと直流電流指令Idc*との偏差が第1閾値T1を超えたことを検知すると「1」を判定情報s1として出力する。また、判定部457は、K×IdcとxIdcとの偏差が第3閾値xIdcth3を超えたことを検知すると「0」を判定情報s2として出力する。この判定情報s1は、フリップフロップ回路54のセット入力端子Sに入力されると共に、インバータ11により反転された後にAND回路12の一方の端子にも入力される。また、判定情報s2は、AND回路12の他方の端子に入力される。AND回路12の出力は、遅延器53により予め定められた期間遅延されて、フリップフロップ回路54のリセット入力端子Rに入力される。こうして、保護制御部450cは、直流電流Idcと直流電流指令Idc*との偏差が第1閾値T1を超え、且つ、K×IdcとxIdcとの偏差が第3閾値xIdcth3を超えたことを検知すると、補正情報corを出力して発電系統20からの受電量を抑制する保護制御を行う。
以下、本発明の実施の形態5を、上記実施の形態1、2、3、4と異なる箇所を中心に図を用いて説明する。上記実施の形態1、2、3、4と同様の部分は同一符号を付して説明を省略する。
実施の形態1の図5に示した制御装置31の保護制御部50の変形例を示す。
図20は、本発明の実施の形態5による保護制御部550の構成を示すブロック図である。
図21は、本発明の実施の形態5による逆電力変換器42の制御装置541の構成を示すブロック図である。
また、直流電流調整部551は、需要地系統80における系統擾乱の収束を、逆電力変換器42内のコンデンサ3の電圧Vcapxの変動の収束に基づいて検知する。こうして、直流電流調整部551は、系統擾乱の収束を検知すると、直流電圧指令Vdc*および直流電流指令Idc*の補正を停止する。
直流電圧制御部44は、逆電力変換器42に入力される、直流側端子E2における直流電圧Vdcを、補正後の直流電圧指令Vdc*に追従させるように制御演算を行い、直流制御指令44aを生成して出力する。こうして、補正後の直流電圧指令Vdc*と直流電流Idc*とを用いて生成された直流制御指令44aと直流制御指令545aとにより、直流電流Idcが抑制される。
需要地系統80において系統擾乱が生じると、需要地系統80側に接続される電力変換装置40の直流電流調整部551がこの系統擾乱を検知する。そして直流電流調整部551は、逆電力変換器42内に流入する直流電流Idcを抑制するように、直流電圧指令Vdc*および直流電流指令Idc*を補正する。これにより直流電流Idcが抑制される。
Claims (19)
- 発電系統に接続され、前記発電系統から受電する交流電力を直流電力に変換し、直流母線を介して送電する電力変換器と、該電力変換器を制御する制御装置とを備えた電力変換装置において、
前記制御装置は、前記直流母線の直流電流を検出する検出部と、この直流電流の変動に基づいて、前記発電系統からの受電量を抑制する保護制御を行う保護制御部とを備えた、
電力変換装置。 - 前記制御装置は、前記電力変換器の受電端の交流電圧を、周波数および振幅が一定の交流電圧指令に追従させる交流電圧制御部と、前記直流電流を直流電流指令に追従させる直流電流制御部とを備え、前記交流電圧制御部の出力および前記直流電流制御部の出力に基づいて、前記電力変換器の出力電圧指令を生成する、
請求項1に記載の電力変換装置。 - 前記保護制御部は、前記直流電流と前記直流電流指令との偏差が、設定された第1閾値を超えた場合に、前記保護制御を行う、
請求項2に記載の電力変換装置。 - 前記直流電流制御部は、前記直流電流指令と前記直流電流との偏差を入力として制御量を演算する制御器を備え、
前記保護制御部は、前記制御量が設定された第2閾値を超えた場合に、前記保護制御を行う、
請求項2に記載の電力変換装置。 - 前記直流電流制御部は、前記直流電流指令と前記直流電流との偏差を入力として制御量を演算する制御器を備え、
前記保護制御部は、前記直流電流と前記制御量との関係が、所定の比例関係を超えて変動した場合に、前記保護制御を行う、
請求項2に記載の電力変換装置。 - 前記保護制御部は、前記保護制御において、前記交流電圧指令の振幅を低下させて、前記発電系統からの受電量を抑制する、
請求項2から請求項5のいずれか1項に記載の電力変換装置。 - 前記直流電流制御部は、該直流電流制御部の出力を所定の制限値で制限する出力リミッタを備えた、
請求項2から請求項6のいずれか1項に記載の電力変換装置。 - 前記電力変換器は、それぞれ正側アームと負側アームとが直列接続され、各相交流線に接続される複数のレグ回路を正負の直流母線間に並列接続して備え、
前記各レグ回路の前記正側アーム、前記負側アームのそれぞれは、互いに直列接続された複数の半導体素子の直列体と、この直列体に並列接続されたコンデンサとから成る単位変換器セルを複数直列接続して備えるものであり、
前記制御装置は、前記各単位変換器セル内の前記コンデンサの電圧を、コンデンサ電圧指令に追従させるように前記直流電流指令を生成する、
請求項2から請求項7のいずれか1項に記載の電力変換装置。 - 前記保護制御部は、前記直流電流の前記変動の復帰に応じて、前記保護制御を停止する、
請求項1または請求項2に記載の電力変換装置。 - 前記保護制御部は、
前記直流電流指令と前記直流電流との偏差、前記直流電流指令と前記直流電流との偏差を入力として演算される制御量、前記直流電流と前記制御量との比例関係、のいずれかがそれぞれに設定された範囲内となった場合に、前記保護制御を停止する、
請求項2に記載の電力変換装置。 - 前記保護制御部は、前記保護制御の停止を、前記直流電流の前記変動の復帰から設定された期間を経過した後に行う、
請求項9に記載の電力変換装置。 - 前記保護制御部は、前記保護制御の停止を、前記制御量、前記直流電流と前記制御量との比例関係、のいずれかのそれぞれに設定された範囲内への復帰から設定された期間を経過した後に行う、
請求項10に記載の電力変換装置。 - 前記電力変換器からの送電電力は、直流電力を交流電力に変換する逆電力変換器を介して需要地系統に供給される、
請求項1から請求項12のいずれか1項に記載の電力変換装置。 - 請求項13に記載の前記電力変換装置と、前記逆電力変換器と、前記逆電力変換器を制御する制御装置とを備え、
前記逆電力変換器の制御装置は、
前記逆電力変換器の直流電圧を直流電圧指令に追従させる直流電圧制御部と、前記逆電力変換器の交流電流を交流電流指令に追従させる交流電流制御部とを備え、前記直流電圧制御部の出力および前記交流電流制御部の出力に基づいて、前記逆電力変換器の出力電圧指令を生成する、
電力システム。 - 前記逆電力変換器の制御装置は、前記直流電流を調整する調整部を備えた、
請求項14に記載の電力システム。 - 前記調整部は、前記逆電力変換器の出力側の交流電圧の変動に基づいて、前記直流電流を調整する、
請求項15に記載の電力システム。 - 前記逆電力変換器は、
互いに直列接続された複数の半導体素子の直列体と、この直列体に並列接続されたコンデンサとを有する変換器を少なくとも1つ備え、
前記調整部は、
前記逆電力変換器内の前記コンデンサの電圧変動に基づいて、前記直流電流を調整する、
請求項15または請求項16に記載の電力システム。 - 少なくとも1つの発電装置と、該発電装置の発電電力を調整する発電側電力変換装置とを有する前記発電系統を備え、
前記発電側電力変換装置は、
前記保護制御部による前記保護制御に応じて、前記発電装置の発電電力の調整を行う、
請求項14から請求項17のいずれか1項に記載の電力システム。 - 前記発電側電力変換装置は、出力側の交流電圧が低下した際に、前記発電装置の発電電力の調整を行う、
請求項18に記載の電力システム。
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