JP2016088289A - Direct current feeding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct current feeding system which can suppress generation of a circulation current with a small-sized configuration.SOLUTION: A direct current feeding system is equipped with: a first current detection part 16 which detects an inverter current flowing to a regenerative inverter 12; a second current detection part 6 which detects a rectifier current flowing to a rectifier 10; and a controller 14 for controlling the regenerative inverter 12. The controller 14 includes: a voltage control part 50 which so makes a voltage command as to be a preset fixed value, and so controls the regenerative inverter 12 that a cable voltage to be detected by a voltage detection part 54 is coincident with the voltage command; a circulation current detection part 40 which detects a circulation current flowing into the regenerative inverter 12 from the rectifier 10 on the basis of an inverter current and a rectifier current; and a correction part 42 which so corrects the voltage command that the circulation current detected by the circulation current detection part 40 becomes a set value.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a DC feeding system, and more particularly to control of a regenerative inverter that converts regenerative power of an electric vehicle into AC power and regenerates it to an AC power source.

  For example, as disclosed in Japanese Patent Application Laid-Open No. 2004-351952 (Patent Document 1), a DC power feeding system includes a power running power source that rectifies an AC input with a rectifier and supplies a power running current to an electric vehicle, and a constant voltage. Some inverters have a regenerative power source that converts a regenerative current from an electric vehicle into alternating current power and regenerates the alternating current input side by a controlled inverter device.

  In the above-mentioned Patent Document 1, as a constant voltage control method for the inverter device, there is a configuration in which the inverter device is controlled such that the voltage is set higher than the DC voltage fluctuation range of the rectifier and the feeder voltage keeps the set voltage. It is disclosed.

Japanese Patent Laid-Open No. 2004-319552

  In the DC feeding system as described above, if the potential difference between the output voltage of the rectifier and the set voltage of the inverter device is large, an excessive circulating current may flow between the rectifier and the inverter device. Since the circulating current causes a circuit loss, the running cost of the DC feeding system is increased. Therefore, in order to suppress an increase in circulating current when switching between power running and regeneration, it is necessary to prevent the output voltage of the rectifier from becoming higher than the set voltage of the inverter device.

  On the other hand, since the output voltage of the rectifier fluctuates in conjunction with the voltage fluctuation on the AC input side, the potential difference between the output voltage of the rectifier and the set voltage also fluctuates in response to the voltage fluctuation of the AC input. For this reason, the output voltage of the rectifier becomes higher than the set voltage, and an excessive circulating current may occur.

  As a countermeasure for suppressing the generation of circulating current during such voltage fluctuation, it has been conventionally studied to control an inverter device in consideration of voltage fluctuation on the AC input side. However, in order to detect an AC input voltage, it is necessary to install an instrument transformer for detecting an extra high voltage. Since such an instrument transformer is large, there is a problem in that the system becomes large. In particular, when the installation space of the system is limited, such as in an underground substation, the above problem becomes significant.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a DC feeding system capable of suppressing the generation of circulating current with a small configuration.

  According to an aspect of the present invention, a DC feeding system includes a rectifier that converts AC power received from an AC power source into DC power and supplies the electric vehicle via an electric wire, and regenerative power generated during regenerative operation of the electric vehicle. A regenerative inverter that converts AC to AC power, a first current detector that detects an inverter current flowing through the regenerative inverter, a second current detector that detects a rectifier current flowing through the rectifier, and a control for controlling the regenerative inverter And a control device. The control device controls the regenerative inverter so that the voltage detection unit that detects the voltage of the feeder and the voltage command has a preset fixed value and the feeder voltage detected by the voltage detection unit matches the voltage command. For detecting the circulating current flowing from the rectifier into the regenerative inverter based on the voltage control unit for the inverter, the inverter current detected by the first current detector and the rectifier current detected by the second current detector It includes a detection unit and a correction unit for correcting the voltage command at least when the electric vehicle is not loaded so that the circulating current detected by the circulating current detection unit becomes a set value.

  According to the present invention, a DC feeding system capable of suppressing the generation of circulating current can be constructed with a small configuration.

1 is an overall configuration diagram of a DC feeding system according to Embodiment 1 of the present invention. It is a circuit diagram of the regenerative inverter in FIG. It is a figure which shows the output characteristic of the feeder with respect to the load current in a DC feeding system. It is a figure explaining the control structure of the regenerative inverter in a prior art. 3 is a functional block diagram illustrating a configuration of a control device for a regenerative inverter according to Embodiment 1. FIG. FIG. 10 is a functional block diagram illustrating a configuration of a control device for a regenerative inverter according to a third embodiment. FIG. 10 is a circuit diagram illustrating a configuration of a correction amount calculation unit in a control device for a regenerative inverter according to a modification of the third embodiment. FIG. 10 is a functional block diagram illustrating a configuration of a control device for a regenerative inverter according to a fourth embodiment. FIG. 10 is a functional block diagram illustrating a configuration of a control device for a regenerative inverter according to a fifth embodiment. FIG. 3 is an overall configuration diagram of a DC feeding system according to a modification of the first embodiment. It is a circuit diagram of the regenerative inverter in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Embodiment 1]
(Overall configuration of DC feeding system)
1 is an overall configuration diagram of a DC feeding system according to Embodiment 1 of the present invention.

  Referring to FIG. 1, the DC feeding system according to the first embodiment converts three-phase AC power supplied from AC power supply 1 into DC power and supplies it to electric vehicle 5 via electric wire 3.

  The DC feeding system includes a rectifier 10, a rectifier transformer 20, a regenerative inverter 12, a regenerative inverter transformer 22, and a control device 14.

  The primary side of the rectifier transformer 20 is connected to the power transmission line 2 via the circuit breaker CB, and the secondary side is connected to the rectifier 10. The rectifier transformer 20 uses a three-phase AC special high voltage (for example, three-phase AC 77 kV, hereinafter referred to as “system voltage”) received from the transmission line 2 and is suitable for feeding (in the case of 1500 V DC, three Step down to a phase AC of 1200V).

  The rectifier 10 is composed of, for example, a diode rectifier. The rectifier 10 rectifies the three-phase AC power received from the rectifier transformer 20 into DC power. The DC power is supplied to the electric vehicle 5 through the feeder 3 as indicated by the dotted arrow in FIG. The rail 4 is used as a current return path for the rectifier 10. A plurality of rectifiers are connected to the feeder 3 and the rail 4. FIG. 1 illustrates one rectifier 10.

  The regenerative inverter 12 is a device for converting regenerative power generated during regeneration of the electric vehicle 5 into AC power. The AC side of the regenerative inverter 12 is connected to the power transmission line 2 via the regenerative inverter transformer 22 and the circuit breaker CB.

  The regenerative inverter 12 is composed of, for example, a separately excited converter. FIG. 2 is a circuit diagram of the regenerative inverter 12 in FIG. Referring to FIG. 2, regenerative inverter 12 is a 12-pulse rectifier, and includes switching elements Q1 to Q12 made of thyristors. Each of switching elements Q1-Q12 performs a switching operation in accordance with a drive signal (gate pulse signal) from control device 14.

  The regenerative inverter transformer 22 converts the AC voltage output from the regenerative inverter 12 into a system voltage and regenerates it to the transmission line 2 side. Thereby, as indicated by the solid line arrow in FIG. 1, the regenerative electric power generated when the electric vehicle 5 is regenerated can be regenerated to the transmission line 2, so that stable braking operation and effective use of electric power are realized.

  The control device 14 is typically configured mainly by a CPU (Central Processing Unit), a memory area such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and an input / output interface. And the control apparatus 14 performs control of the regenerative inverter 12, when CPU reads the program previously stored in ROM etc. to RAM, and performs it.

(Control structure of regenerative inverter)
Next, the control structure of the regenerative inverter 12 will be described in detail.

  As shown in FIG. 1, the regenerative inverter 12 and the rectifier 10 are connected in parallel between the feeder 3 and the rail 4. Therefore, switching between power supply by the rectifier 10 during power running of the electric vehicle 5 and regeneration by the regenerative inverter 12 during regeneration of the electric vehicle 5 can be performed automatically and continuously smoothly without using a switch or the like. it can.

  A control pattern of the regenerative inverter 12 will be described with reference to FIG. FIG. 3 is a diagram showing the output characteristics of the feeder 3 with respect to the load current (the running current of the electric vehicle 5) in the DC feeder system. In FIG. 3, the horizontal axis indicates the load current Id, and the vertical axis indicates the feeder voltage Ed that is the voltage between the feeder 3 and the rail 4. The polarity of the load current Id is positive on the power running side and negative on the regeneration side.

  Referring to FIG. 3, region I indicates a forward conversion region (powering region) in which rectifier 10 operates. The feeder voltage Ed corresponds to the output voltage of the rectifier 10. In the region I, as the load current (powering current) increases, the wire voltage Ed decreases due to the influence of the internal impedance of the rectifier 10 and the like.

  Region III indicates an inverse conversion region (regeneration region) in which the regenerative inverter 12 operates. The feeder voltage Ed corresponds to the DC side voltage (output voltage) of the regenerative inverter 12. In region III, as the load current (regenerative current) increases, the wire voltage Ed increases due to the influence of the internal impedance of the regenerative inverter 12 and the like. The control device 14 controls the ignition phase of the thyristor in the regenerative inverter 12 using a control structure described later.

  A region IV indicates a region where the regenerative inverter 12 operates at a constant voltage. When the electric wire voltage Ed rises and exceeds the predetermined voltage Edi as the regenerative current increases, the regenerative operation in the regenerative inverter 12 is controlled so that the electric wire voltage Ed does not exceed the predetermined voltage Edi. The predetermined voltage Edi is set to the rated voltage of the regenerative inverter 12, for example.

  Region II is a transition region where the operation of the regenerative inverter 12 and the operation of the rectifier 10 are switched. In the following description, the output voltage Edr0 of the rectifier 10 when the load current Id is near zero is referred to as “rectifier no-load voltage”, and the DC side voltage Edi0 of the regenerative inverter 12 when no load is applied. Also referred to as “inverter no-load voltage”.

  In region II, when the rectifier no-load voltage Edr0 becomes higher than the inverter no-load voltage Edi0, an excessive circulating current flows from the rectifier 10 toward the regenerative inverter 12. Since this unnecessary circulating current flows, a circuit loss occurs, resulting in an increase in the running cost of the DC feeding system. Therefore, in order to suppress an increase in circulating current, it is necessary to control the regenerative inverter 12 so that the inverter no-load voltage Edi0 is higher than the rectifier no-load voltage Edr0, as shown in FIG.

  First, the control structure of the regenerative inverter in the prior art will be described with reference to FIG. FIG. 4 shows a functional block diagram of a control device for regenerative inverter 12 in the prior art.

  Referring to FIG. 4, the control structure of regenerative inverter 12 in the prior art includes a voltage command generation circuit 30, a voltage control unit (VC) 50, a gate pulse generation unit (GPG) 52, and a voltage detection unit (VS). 54.

  The voltage command generation circuit 30 generates a voltage command for instructing a DC voltage to be output by the regenerative inverter 14 based on the three-phase AC extra high voltage (system voltage) received from the AC power supply 1. Specifically, the voltage command generation circuit 30 includes an instrument transformer (PT: Potential Transformer) 32 and a rectifier 34. The instrument transformer 32 detects a system voltage. The instrument transformer 32 converts the detected system voltage into a voltage suitable for processing in the voltage control unit 50. The rectifier 32 generates a voltage command by rectifying the AC voltage received from the instrument transformer 32 into a DC voltage. The voltage command generation circuit 30 outputs the generated voltage command to the voltage control unit 50.

  The voltage detector 54 detects the voltage (feeder voltage) between the feeder 3 and the rail 4 and outputs the detected value to the voltage controller 50.

  The voltage control unit 50 controls the output voltage of the regenerative inverter 12 in accordance with the voltage command instructed from the voltage command generation circuit 30. Specifically, the voltage control unit 50 executes feedback control for increasing or decreasing the feeder voltage based on the comparison between the feeder voltage detected by the voltage detector 54 and the voltage command. The voltage control unit 50 amplifies the deviation of the feeder voltage with respect to the voltage command, thereby generating a thyristor firing phase command in the regenerative inverter 12 according to the deviation.

  The gate pulse generator 52 generates a gate pulse signal to be given to the thyristor based on the firing phase command instructed from the voltage controller 50. Each thyristor of regenerative inverter 12 receives a gate pulse signal from gate pulse generator 52 at its gate. By turning on the plurality of thyristors at a predetermined timing, DC power can be converted into AC power.

  In addition, when the feeder voltage exceeds a predetermined voltage Edi due to an increase in the regenerative current, the regenerative inverter 12 enters a constant voltage operation region (region IV in FIG. 3). Thereby, the raise of feeder voltage is suppressed and the regeneration invalidity of the electric vehicle 5 is prevented.

  When the control structure of the regenerative inverter 12 is configured as shown in FIG. 4, when the system voltage fluctuates, the voltage command also changes accordingly. And the voltage control part 50 controls feeder voltage so that the change of a voltage command may be followed. Therefore, in the transition region (region II in FIG. 3) where the power running and the regeneration are switched, the inverter no-load voltage Edi0 changes in conjunction with the change in the system voltage. On the other hand, since the output voltage of the rectifier 10 changes in conjunction with the change of the system voltage, the rectifier no-load voltage Edr0 also changes. That is, when the system voltage changes, both the inverter no-load voltage Edi0 and the rectifier no-load voltage Edr0 change in conjunction with the change in the system voltage. As a result, the rectifier no-load voltage Edr0 is suppressed from becoming higher than the inverter no-load voltage Edi0 due to the fluctuation of the system voltage. Thereby, it is possible to avoid an increase in circulating current even when the system voltage fluctuates.

  However, in the control structure of the conventional regenerative inverter 12 shown in FIG. 4, since a voltage command is generated based on the system voltage, a dedicated instrument transformer for detecting the system voltage (the instrument transformer of FIG. 4). It is necessary to install a device 32). Since the system voltage is as high as three-phase AC 77 kV, the physique of the instrument transformer 32 (particularly, the physique of the insulator covering the input / output terminals of the transformer) becomes large. Therefore, there is a problem that it is difficult to realize a control structure when the installation space of the system is limited, such as in an underground substation. Moreover, in order to detect a system voltage, since the expensive instrument transformer was needed, there existed a subject that a system raised the cost.

  Therefore, in the control structure of the regenerative inverter 12 according to the first embodiment, when the electric vehicle 5 is not loaded, the voltage command is set to a predetermined fixed value, and the regenerative inverter 12 is set so that the feeder voltage matches the voltage command. Adopt a control method. This eliminates the need for installing the instrument transformer 32 shown in FIG. Further, in the above configuration, the circulating current flowing from the rectifier 10 to the regenerative inverter 12 is detected, and a voltage command is issued so that the detected value of the circulating current matches the set target value (or also referred to as “set value”). to correct.

  FIG. 5 is a functional block diagram showing the configuration of the control device 14 of the regenerative inverter 12 according to the first embodiment. Note that each functional block described in FIG. 5 can be realized by the control device 14 executing software processing according to a preset program. Alternatively, it is possible to configure a circuit (hardware) corresponding to the functional block in the control device 14.

  Referring to FIG. 5, control device 14 includes current transformers (CT: Current Transformers) 6 and 16, rectifiers 8 and 18, a circulating current detector (CD) 40, a voltage detector, and a voltage detector. A command correction unit 42, a voltage control unit (VC) 50, a gate pulse generation unit (GPG) 52, and a voltage detection unit (VS) 54 are included.

  The control device 14 according to the first embodiment has a circulating current detection unit 40 and a voltage command correction unit 42 instead of the voltage command generation circuit 30 as compared with the conventional control structure shown in FIG. . The control device 14 has the voltage command Vref as a preset fixed value. The voltage command Vref is set to a voltage (for example, DC 1600 V) higher than the output voltage (for example, DC 1500 V) of the rectifier 10. The control device 14 is configured to correct the voltage command Vref so that the circulating current Ic matches the set value Ith.

  The instrument current transformer 6 (second current detector) detects a current (hereinafter referred to as “rectifier current”) Ir flowing in the rectifier 10. The rectifier 8 rectifies the rectifier current Ir detected by the instrument current transformer 6 and outputs the rectifier current Ir to the circulating current detector 40. The instrument current transformer 16 (first current detector) detects a current (hereinafter referred to as “inverter current”) Ii flowing through the regenerative inverter 12. The rectifier 18 rectifies the inverter current Ii detected by the instrument current transformer 16 and outputs it to the circulating current detector 40.

  When circulating current detector 40 receives rectifier current Ir from rectifier 8 and inverter current Ii from rectifier 18, circulating current detector 40 detects circulating current Ic based on rectifier current Ir and inverter current Ii. Specifically, when the rectifier current Ir and the inverter current Ii are equal (Ir = Ii), the circulating current detection unit 40 determines that the electric vehicle 5 is in a no-load state. In this case, the circulating current detector 40 detects the inverter current Ii (or rectifier current Ir) as the circulating current Ic (Ic = Ii = Ir). The circulating current detection unit 40 may be configured to detect the load current Id by a current detection unit (not shown) and determine whether or not the electric vehicle 5 is in a no-load state based on the detected value of the load current Id. .

  Voltage command correction unit 42 includes switches SW1 and SW2, a correction amount setting unit 44, and an addition unit 45. The switch SW1 is connected between the rectifier 8 and the input terminal T1 of the correction amount setting unit 44. The switch SW2 is connected between the rectifier 18 and the input terminal T1 of the correction amount setting unit 44. For the switches SW1 and SW2, for example, any switch that can be turned on / off, such as an electromagnetic relay or a semiconductor relay, is applied. Each of switches SW1 and SW2 is turned on / off in response to a control signal from circulating current detection unit 40.

  Circulating current detection unit 40 turns on switch SW2 (or switch SW1) when it is determined that electric vehicle 5 is in the no-load state. When the switch SW2 is turned on, the inverter current Ii output from the rectifier 18 is input to the input terminal T1 of the correction amount setting unit 44 as the circulating current Ic. On the other hand, when the switch SW1 is turned on, the rectifier current Ir output from the rectifier 8 is input to the input terminal T1 of the correction amount setting unit 44 as the circulating current Ic.

  When receiving the circulating current Ic at the input terminal T1, the correction amount setting unit 44 sets the correction amount ΔV of the voltage command Vref based on a deviation from the circulating current Ic with respect to the set value Ith. Specifically, the correction amount setting unit 44 includes resistance elements R1 and R2, an operational amplifier OP1, and a capacitive element C1. The resistance elements R1 and R2 are connected between the input terminal T1 and the inverting input terminal (− terminal) of the operational amplifier OP1. The circulating current Ic is input to the inverting input terminal of the operational amplifier OP1 through the resistance element R1, and the set value Ith of the circulating current Ic is input through the resistance element R2. The set value Ith corresponds to the target value of the circulating current Ic, and is set to about 6% of the rated value of the circulating current Ic, for example. The ground voltage is input to the non-inverting input terminal (+ terminal) of the operational amplifier OP1.

  A capacitive element C1 is connected between the inverting input terminal and the output terminal of the operational amplifier OP1. That is, the operational amplifier OP1 and the capacitive element C1 constitute an integrating circuit. When the deviation of the circulating current Ic with respect to the set value Ith is expressed as the input current Iin, the output voltage Vout of the integrating circuit is expressed by Expression (1). Here, the capacitance value of the capacitive element C1 is C.

Vout = 1 / C∫Iindt (1)
The output voltage Vout of the integrating circuit is given to the adding unit 45 as a correction amount ΔV with respect to the voltage command Vref. Adder 45 adds voltage command Vref (fixed value) and correction amount ΔV set by correction amount setting unit 44 to generate voltage command Vref #.

  The voltage command Vref # corrected by the voltage command correction unit 42 is input to the voltage control unit 50. The voltage control unit 50 executes feedback control for increasing or decreasing the feeder voltage based on a comparison between the feeder voltage detected by the voltage detector 54 and the corrected voltage command Vref #.

  According to the control structure of the regenerative inverter 12 shown in FIG. 5, when the rectifier no-load voltage Edr0 rises in conjunction with the rise of the system voltage and becomes greater than the inverter no-load voltage Edi0, the set value The correction amount ΔV for the voltage command Vref, which is set based on the increase of the circulating current Ic with respect to Ith, increases. As a result, the voltage command Vref # also rises in conjunction with the rise of the system voltage, and the feeder voltage is controlled by the voltage control unit 50 so as to follow the rise of the voltage command Vref #. Therefore, in the transition region (region II in FIG. 3) where the power running and the regeneration are switched, the inverter no-load voltage Edi0 rises in conjunction with the rise of the system voltage.

  Thus, when the system voltage rises, both the inverter no-load voltage Edi0 and the rectifier no-load voltage Edr0 rise in conjunction with the rise of the system voltage, so that the rectifier no-load voltage Edr0 becomes the inverter due to the rise of the system voltage. It can be prevented that the voltage becomes larger than the no-load voltage Edi0. As a result, it is possible to suppress the circulating current Ic from increasing even when the system voltage fluctuates.

  As described above, according to the first embodiment of the present invention, in the configuration in which the voltage command is set to a preset fixed value and the regenerative inverter is controlled so that the feeder voltage matches the voltage command, By correcting the voltage command so that the detected value matches the set value, compared to the conventional control structure (FIG. 4), an increase in circulating current is suppressed without causing an increase in system size and cost. be able to.

[Embodiment 2]
In the first embodiment described above, the control structure of the regenerative inverter 12 for suppressing an increase in circulating current in the no-load state of the electric vehicle 5 has been described. However, according to the control structure described above, In addition, an increase in circulating current can be suppressed even during regeneration. In the second embodiment, a control structure of regenerative inverter 12 during powering and regeneration will be described.

  In the control structure shown in FIG. 5, when circulating current detector 40 receives rectifier current Ir from rectifier 8 and receives inverter current Ii from rectifier 18, it compares rectifier current Ir and inverter current Ii. When the rectifier current Ir is larger than the inverter current Ii (Ir> Ii), the circulating current detection unit 40 determines that the electric vehicle 5 is in powering. In this case, the circulating current detector 40 detects the inverter current Ii having the smaller current value as the circulating current Ic (Ic = Ii).

  Circulating current detector 40 turns on switch SW2 when it is determined that electric vehicle 5 is in powering. When the switch SW2 is turned on, the inverter current Ii output from the rectifier 18 is input to the input terminal T1 of the correction amount setting unit 44 as the circulating current Ic. Therefore, the correction amount setting unit 44 sets the correction amount ΔV for the voltage command Vref based on the deviation between the circulating current Ic (inverter current Ii) and the set value Ith. Then, the output voltage of regenerative inverter 12 is controlled in accordance with voltage command Vref # corrected using set correction amount ΔV.

  When the circulating current increases during power running of the electric vehicle 5, a current in which the circulating current is superimposed on the load current (powering current) flows through the rectifier 10, and the rectifier 10 may be overloaded. According to the second embodiment, since the circulating current is suppressed to the set value Ith even during powering of the electric vehicle 5, the rectifier 10 can be prevented from reaching an overload state.

  On the other hand, when the inverter current Ii is larger than the rectifier current Ir (Ii> Ir), the circulating current detection unit 40 determines that the electric vehicle 5 is in regeneration. In this case, the circulating current detector 40 detects the rectifier current Ir having a smaller current value as the circulating current Ic (Ic = Ir).

  Circulating current detection unit 40 turns on switch SW1 when it is determined that electric vehicle 5 is in regeneration. When the switch SW1 is turned on, the rectifier current Ir output from the rectifier 8 is input to the input terminal T1 of the correction amount setting unit 44 as the circulating current Ic. Therefore, the correction amount setting unit 44 sets the correction amount ΔV for the voltage command Vref based on the deviation between the circulating current Ic (rectifier current Ir) and the set value Ith. Then, the output voltage of regenerative inverter 12 is controlled in accordance with voltage command Vref # corrected using set correction amount ΔV.

  If the circulating current increases during regeneration of the electric vehicle, a current in which the circulating current is superimposed on the load current (regenerative current) flows through the regenerative inverter 12, and the regenerative inverter 12 may be overloaded. According to the second embodiment, since the circulating current is suppressed to the set value Ith even during regeneration of the electric vehicle 5, it is possible to prevent the regenerative inverter 12 from reaching an overload state.

[Embodiment 3]
In the first and second embodiments, the configuration in which the correction amount ΔV with respect to the voltage command Vref is set according to the deviation between the circulating current Ic and the set value Ith has been described. Then, since the voltage command Vref # of the regenerative inverter 12 is varied, when the system voltage fluctuates severely because the power system is unstable, the voltage command Vref # also varies drastically with time.

  However, when the system voltage drops below the rated voltage, the voltage command Vref # is corrected to a voltage lower than the voltage command Vref because the circulating current Ic shows a value sufficiently smaller than the set value Ith. May be. In such a case, if the system voltage rapidly increases after decreasing, it becomes difficult to immediately increase the voltage command Vref # following the system voltage. As a result, as the system voltage increases, the output voltage of the rectifier 10 greatly exceeds the output voltage of the regenerative inverter 12, and the circulating current Ic may be increased.

  In the third embodiment, a control structure capable of suppressing an increase in circulating current Ic even when the fluctuation of the system voltage is severe will be described. Note that the DC feeding system according to Embodiment 3 has the same configuration as the DC feeding system of FIG. 1 except for the control device 14A, and therefore illustration and description thereof are omitted.

  FIG. 6 is a functional block diagram showing the configuration of the control device 14A for the regenerative inverter 12 according to the third embodiment. Referring to FIG. 6, control device 14 </ b> A according to the third embodiment includes voltage command correction unit 42 </ b> A instead of voltage command correction unit 42, as compared with control device 14 according to the first embodiment shown in FIG. 5. It is provided.

  Voltage command correction unit 42A includes switches SW1 and SW2, a correction amount setting unit 44A, and an addition unit 45. The correction amount setting unit 44A is obtained by further adding a limiter circuit 46 as compared with the correction amount setting unit 44 shown in FIG.

  The limiter circuit 46 is connected between the output terminal of the integrating circuit composed of the operational amplifier OP1 and the capacitive element C1 and the adder 45. The limiter circuit 46 limits the correction amount ΔV output from the integration circuit so as not to exceed the upper limit value and the lower limit value. Specifically, limiter circuit 46 sets the upper limit value to + 5% of voltage command Vref (for example, DC 1600 V) and sets the lower limit value to 0% of voltage command Vref, for example. Each of the upper limit value and the lower limit value is set according to the fluctuation range (for example, within ± 5%) of the normal system voltage. The correction amount ΔV limited within a certain range by the limiter circuit 46 is added to the voltage command Vref in the adding unit 45, thereby generating a voltage command Vref #.

  As described above, by limiting the correction amount ΔV within a certain range using the limiter circuit 46, the voltage command Vref # varies within the certain range in accordance with the fluctuation of the system voltage. According to this, when the system voltage drops below the rated voltage, the voltage command Vref # is restricted so as not to fall below the lower limit value. The followability of # can be improved. As a result, it is possible to prevent the output voltage of the rectifier 10 from greatly exceeding the output voltage of the regenerative inverter 12, and thus it is possible to suppress an increase in the circulating current Ic when the system voltage rapidly increases.

  In the control structure shown in FIG. 6, the configuration in which the correction amount ΔV with respect to the voltage command Vref is limited to a certain range by the limiter circuit 46 has been described. However, when the circulating current Ic is out of the predetermined setting range, Even if the correction amount ΔV is fixed to a constant value regardless of the magnitude of the current Ic, the same effects as in FIG. 6 can be obtained.

  FIG. 7 is a circuit diagram showing a configuration of a modification of correction amount setting unit 44A in control device 14A of regenerative inverter 12 according to the third embodiment. Referring to FIG. 7, the correction amount setting unit 44A according to the present modification includes comparators CP1 and CP2, amplifiers AP1 and AP2, current sources 60 and 61, voltage sources 62 and 63, and switches SW4 and SW5. The resistor elements R1 and R3, the operational amplifier OP1, and the capacitor element C1 are included.

  The operational amplifier OP1 and the capacitive element C1 constitute an integrating circuit. A resistance element R1 and a resistance element R3 are connected in series between the inverting input terminal (− terminal) of the operational amplifier OP1 and the ground terminal. The non-inverting input terminal (+ terminal) of the operational amplifier OP1 is connected to the ground terminal.

  A voltage source 62 and a voltage source 63 are connected in parallel to a connection point between the resistance element R1 and the resistance element R3. The voltage source 62 outputs a positive constant voltage V1 (for example, + 1V). The voltage source 63 outputs a negative constant voltage −V1 (for example, −1V).

  A switch SW4 is connected between the voltage source 62 and the connection point. The switch SW4 is turned on / off in response to a control signal input from the comparator OP1 via the amplifier AP1. A switch SW5 is connected between the voltage source 63 and the connection point. The switch SW5 is turned on / off in response to a control signal input from the comparator CP2 via the amplifier AP2.

  In the comparator CP1, the circulating current Ic is input to the non-inverting input terminal (+ terminal), and the constant current I1 is input from the current source 60 to the inverting input terminal (− terminal). The comparator CP1 compares the circulating current Ic and the current I1, and outputs a comparison result. The current I1 is set to a current value higher than the set value Ith. When set value Ith is set to about 10% of the rated value of circulating current Ic, for example, current I1 is set to about 10% of the rated value of circulating current Ic, for example. When the circulating current Ic exceeds the current I1, the output signal of the comparator CP1 becomes H (logic high) level. When the switch SW4 is turned on in response to the H level control signal from the comparator CP1, a positive constant voltage V1 (+1 V) is applied to the connection point between the resistance element R1 and the resistance element R3.

  In the comparator CP2, the constant current I2 is input from the current source 61 to the non-inverting input terminal (+ terminal), and the circulating current Ic is input to the inverting input terminal (− terminal). The comparator CP2 compares the circulating current Ic and the current I2, and outputs a comparison result. The current I2 is set to a current value lower than the set value Ith. When set value Ith is set to about 10% of the rated value of circulating current Ic, for example, current I2 is set to about 2% of the rated value of circulating current Ic, for example. When the circulating current Ic is smaller than the current I2, the output signal of the comparator CP2 becomes H level. When the switch SW5 is turned on in response to the H level control signal from the comparator CP2, a negative constant voltage −V1 (−1V) is applied to the connection point between the resistance element R1 and the resistance element R3.

  The integration circuit integrates the current flowing through the resistance element R1 according to the voltage input to the connection point, and outputs the integration value. The integrated value is added to the voltage command Vref in the adding unit 45 (FIG. 6) as a correction amount ΔV for the voltage command Vref.

  With the above configuration, when the circulating current Ic is larger than the current value I1, the correction amount setting unit 44A sets a positive constant value as the correction amount ΔV, while the circulating current Ic is the current When it is smaller than the value I2, a negative constant value is set as the correction amount ΔV. That is, since the positive correction amount ΔV and the negative correction amount ΔV are each fixed to a constant value, the voltage command Vref # varies within a certain range according to the variation of the system voltage. Therefore, when the system voltage drops below the rated voltage, the voltage command Vref # is restricted so as not to fall below the lower limit value. Therefore, even if the system voltage rises rapidly thereafter, the voltage command Vref # follows. Can increase the sex. As a result, increase in circulating current Ic due to the output voltage of rectifier 10 greatly exceeding the output voltage of regenerative inverter 12 can be suppressed.

[Embodiment 4]
FIG. 8 is a functional block diagram showing the configuration of the control device 14B of the regenerative inverter 12 according to the fourth embodiment. Note that the DC feeding system according to Embodiment 4 has the same configuration as the DC feeding system of FIG. 1 except for the control device 14B, and therefore illustration and description thereof are omitted.

  Referring to FIG. 8, control device 14B according to the fourth embodiment has a voltage command correction unit 42B, instead of voltage command correction unit 42, as compared with control device 14 according to the first embodiment shown in FIG. An instrument transformer 24 and a rectifier 25 are provided.

  Voltage command correction unit 42B includes switches SW1 and SW2, a correction amount setting unit 44, an addition unit 45, a comparator CP3, and a switch SW3. The voltage command correction unit 42B is obtained by further adding a comparator CP3 and a switch SW3 as compared with the voltage command correction unit 42 shown in FIG.

  The instrument transformer 24 detects the voltage on the secondary side of the rectifier transformer 20. The instrument transformer 24 converts the detected secondary voltage into a voltage suitable for processing in the voltage command correction unit 42B. The rectifier 25 rectifies the AC voltage received from the instrument transformer 24 into a DC voltage and inputs it to the non-inverting input terminal (+ terminal) of the comparator CP3. The threshold voltage Vth is input to the inverting input terminal (− terminal) of the comparator CP3. The threshold voltage Vth is set to the secondary voltage of the rectifier transformer 20 when the system voltage is equal to the rated voltage, for example.

  The comparator CP3 compares the voltage on the secondary side of the rectifier transformer 20 with the threshold voltage Vth. When the voltage on the secondary side of the rectifier transformer 20 is greater than the threshold voltage Vth, that is, when the system voltage is greater than the rated voltage, the output signal of the comparator CP3 becomes H level. On the other hand, when the voltage on the secondary side of the rectifier transformer 20 is equal to or lower than the threshold voltage Vth, that is, when the system voltage is equal to or lower than the rated voltage, the output signal of the comparator CP3 becomes L level.

  The switch SW3 is connected between the correction amount setting unit 44 and the addition unit 45. The switch SW3 is turned on in response to the H level control signal from the comparator CP3 and turned off in response to the L level control signal.

  When the voltage on the secondary side of the rectifier transformer 20 is larger than the threshold voltage Vth (when the system voltage is larger than the rated voltage), the switch SW3 is turned on in response to the control signal at the H level, thereby correcting the amount of correction. The correction amount ΔV set by the setting unit 44 is input to the adding unit 45. The addition unit 45 adds the correction amount ΔV to the voltage command Vref, thereby generating a voltage command Vref #.

  On the other hand, when the voltage on the secondary side of the rectifier transformer 20 is lower than the threshold voltage Vth (when the system voltage is lower than the rated voltage), the switch SW3 is turned off in response to the L level control signal. Thus, the correction amount ΔV set by the correction amount setting unit 44 is not input to the addition unit 45. Therefore, voltage command Vref is not corrected, and voltage command Vref # is equal to voltage command Vref.

  According to the control structure of the regenerative inverter 12 shown in FIG. 8, the secondary side voltage of the rectifier transformer 20 and the threshold voltage Vth are compared, and whether or not the voltage command Vref is corrected according to the comparison result. Can be switched. When the voltage on the secondary side of rectifier transformer 20 is greater than threshold voltage Vth, that is, when the system voltage is greater than a threshold (for example, rated voltage), voltage command Vref is corrected. On the other hand, the voltage command Vref is not corrected when the system voltage drops below a threshold value (rated voltage). Thereby, the output voltage of the regenerative inverter 12 is substantially limited so as not to fall below the voltage command Vref. Therefore, even if the system voltage suddenly increases after the system voltage drops below the threshold value, the followability of voltage command Vref # can be improved. As a result, it is possible to prevent the output voltage of the rectifier 10 from greatly exceeding the output voltage of the regenerative inverter 12, and thus it is possible to suppress an increase in the circulating current Ic when the system voltage rapidly increases.

[Embodiment 5]
FIG. 9 is a functional block diagram showing a configuration of control device 14C of regenerative inverter 12 according to the fifth embodiment. Note that the DC feeding system according to the fifth embodiment has the same configuration as the DC feeding system of FIG. 1 except for the control device 14C, and therefore its illustration and description are omitted.

  Referring to FIG. 9, control device 14 </ b> C according to the fifth embodiment replaces voltage command correction unit 42 with voltage command correction unit 42 </ b> C as compared with control device 14 according to the first embodiment shown in FIG. It is provided.

  The voltage command correction unit 42C includes switches SW1 and SW2, a correction amount setting unit 44, an addition unit 45, a determination unit 47, and a switch SW3. Compared with the voltage command correction unit 42BC and the voltage command correction unit 42 shown in FIG. 5, a determination unit 47 and a switch SW3 are further added.

  Determination unit 47 receives rectifier current Ir from rectifier 8 and receives inverter current Ii from rectifier 18. The determination unit 47 calculates a load current (powering current or regenerative current) based on the rectifier current Ir and the inverter current Ii. Specifically, when the rectifier current Ir is larger than the inverter current Ii, since the inverter current Ii corresponds to the circulating current Ic, the power running current can be obtained by subtracting the inverter current Ii from the rectifier current Ir. it can. On the other hand, when the inverter current Ii is larger than the rectifier current Ir, since the rectifier current Ir corresponds to the circulating current Ic, the regenerative current can be obtained by subtracting the rectifier current Ir from the inverter current Ii.

  When the load current is calculated, the determination unit 47 compares the load current with a preset current range, and controls on / off of the switch SW3 based on the comparison result. Specifically, the current range is set to have an upper limit value in the power running region (region I in FIG. 3) and a lower limit value in the regeneration region (region III in FIG. 3). When the load current Id is within the current range, the determination unit 47 outputs an H level control signal. On the other hand, when the load current Id is not within the current range, an L level control signal is output.

  The switch SW3 is connected between the correction amount setting unit 44 and the addition unit 45. The switch SW3 is turned on in response to an H level control signal from the determination unit 47, and is turned off in response to an L level control signal.

  In the configuration shown in FIG. 9, when the load current is within a preset current range, the switch SW <b> 3 is turned on in response to the H level control signal from the determination unit 47. As a result, the correction amount ΔV set by the correction amount setting unit 44 is input to the addition unit 45. The addition unit 45 adds the correction amount ΔV to the voltage command Vref, thereby generating a voltage command Vref #.

  On the other hand, when the load current Id is not within the current range, the switch SW3 is turned off in response to the L level control signal from the determination unit 47. Thus, the correction amount ΔV set by the correction amount setting unit 44 is not input to the adding unit 45. Therefore, voltage command Vref is not corrected, and voltage command Vref # is equal to voltage command Vref. That is, the determination unit 47 is configured to compare the load current Id with the current range and determine whether or not to correct the voltage command Vref according to the comparison result.

  Here, when the electric vehicle 5 transits from regeneration to power running when the system voltage exceeds the rated voltage, the circulating current Ic increases in the vicinity of the transition region (region II in FIG. 3) where the regeneration and power running are switched. However, the circulating current Ic decreases as the absolute value of the regenerative current or powering current increases. This is because the feeder voltage decreases as the power running current increases and increases as the regenerative current increases.

  In the control structure of the regenerative inverter 12 shown in FIG. 9, the current range is set corresponding to the region of the load current Id when the increase in the circulating current Ic becomes significant. When the load current Id is within this current range, the voltage command Vref is corrected.

  For example, during regeneration of electric vehicle 5, voltage command Vref # may be corrected to a voltage lower than voltage command Vref due to circulating current Ic showing a value sufficiently smaller than set value Ith. In such a case, when the electric vehicle 5 switches from regeneration to power running, the circulating current Ic increases, but it is difficult to immediately increase the voltage command Vref # to a voltage higher than the voltage command Vref. Thus, even when the circulating current Ic is sufficiently smaller than the set value Ith, by correcting the voltage command Vref, the electric vehicle 5 is switched from regeneration to power running (or when power running is switched to regeneration). However, there is a possibility that the circulating current Ic is increased.

  According to the fifth embodiment, the correction of the voltage command Vref is performed within the load current region where the increase of the circulating current Ic becomes significant, while the correction of the voltage command Vref is not performed outside the region. Therefore, when the electric vehicle 5 switches between regeneration and power running, it can suppress that the circulating current Ic increases.

  In the DC feeding system according to the first to fifth embodiments described above, the configuration using the separately excited converter as the regenerative inverter has been described. However, the regenerative inverter according to the present invention can be applied to the configuration using the self-excited converter as the regenerative inverter. It is possible to apply an inverter control structure. FIG. 10 is an overall configuration diagram of a DC feeding system according to a modification of the first embodiment.

  Referring to FIG. 10, the DC feeding system according to the modification of the first embodiment includes rectifier 10, rectifier transformer 20, regenerative inverter 70, regenerative inverter transformer 26, and control device 72. Prepare.

  The regenerative inverter 70 is a device for converting regenerative power generated during regeneration of the electric vehicle 5 into AC power. The AC side of the regenerative inverter 70 is connected to the power transmission line 2 via the regenerative inverter transformer 26 and the circuit breaker CB.

  The regenerative inverter 70 is composed of a self-excited converter. FIG. 11 is a circuit diagram of regenerative inverter 70 in FIG. Referring to FIG. 11, regenerative inverter 70 includes switching elements Q11-Q16 and diodes D11-D16. Switching elements Q11 to Q16 are, for example, thyristors, but are not limited to this as long as they are self-extinguishing type switching elements. Diodes D11-D16 are connected in antiparallel to switching elements Q11-Q16, respectively. Each of switching elements Q11 to Q16 is supplied with a gate pulse signal from control device 72. Switching elements Q11 to Q16 perform a switching operation based on the gate pulse signal, convert the regenerative power generated when the electric vehicle 5 is regenerated into AC power, and regenerate it on the transmission line 2 side.

  In the DC feeding system shown in FIG. 10, any of the control devices 14 and 14A to 14C according to the first to fifth embodiments described above can be applied to the control device 72 of the regenerative inverter 70.

  The embodiment disclosed this time is an exemplification, and is not limited to the above contents. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 AC power supply, 2 transmission line, 3 feeder, 4 rail, 5 electric vehicle, 6,16 Current transformer for instrument, 8, 10, 18, 34 Rectifier, 12, 70 Regenerative inverter, 14, 14A, 14B, 14C , 72 control device, 20 rectifier transformer, 22, 26 regenerative inverter transformer, 30 voltage command generation circuit, 32 instrument transformer, 40 circulating current detection unit, 42 voltage command correction unit, 44 correction amount setting unit, 45 addition unit, 46 limiter circuit, 47 determination unit, 50 voltage control unit, 52 gate pulse signal generation unit, 54 voltage detection unit, 60, 61 current source, 62, 63 voltage source, C1 capacitive element, OP1 operational amplifier, CP1 CP3 comparator, AP1, AP2 amplifier, R1-R3 resistance element, SW1-SW4 switch.

Claims (6)

A rectifier that converts AC power received from an AC power source into DC power and supplies the electric vehicle via an electric wire;
A regenerative inverter that converts regenerative power generated during regenerative operation of the electric vehicle into AC power;
A first current detector for detecting an inverter current flowing through the regenerative inverter;
A second current detector for detecting a rectifier current flowing through the rectifier;
A control device for controlling the regenerative inverter;
The controller is
A voltage detector for detecting the voltage of the feeder line;
A voltage control unit for controlling the regenerative inverter so that the voltage command is a preset fixed value and the feeder voltage detected by the voltage detection unit matches the voltage command;
Circulating current detection for detecting a circulating current flowing from the rectifier to the regenerative inverter based on the inverter current detected by the first current detector and the rectifier current detected by the second current detector. And
A DC feeding system including a correction unit for correcting the voltage command at least when the electric vehicle is not loaded so that the circulating current detected by the circulating current detection unit becomes a set value.   The correction unit determines a correction amount of the voltage command based on a deviation between the circulating current detected by the circulating current detection unit and the set value when the electric vehicle is unloaded and when the electric vehicle is loaded. The DC feeding system according to claim 1, further comprising a correction amount setting unit for setting.   The DC feeding system according to claim 2, wherein the correction unit further includes a limiter circuit for limiting an upper limit value and a lower limit value of the correction amount of the voltage command set by the correction amount setting unit.   The correction unit has a current range in which a current value larger than the set value is an upper limit value and a current value smaller than the set value is a lower limit value, and the circulation detected by the circulating current detection unit When the current is larger than the upper limit value, the correction amount of the voltage command is set to a positive constant voltage, while when the circulating current detected by the circulating current detection unit is smaller than the lower limit value, The DC feeding system according to claim 1, further comprising a correction amount setting unit for setting the correction amount of the voltage command to a negative constant voltage.   The correction unit detects a power running current and a regenerative current of the electric vehicle based on the inverter current detected by the first current detection unit and the rectifier current detected by the second current detection unit. The DC feeding system according to claim 1, further comprising a determination unit configured to determine whether to correct the voltage command based on the detected power running current or the magnitude of the regenerative current. The correction unit is
A comparator for comparing the system voltage received from the AC power supply with a threshold voltage;
A switch for switching whether to correct the voltage command according to the comparison result of the comparator,
The DC feeding system according to claim 1, wherein the switch is configured to correct the voltage command when the system voltage is larger than the threshold voltage.

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