JP6549049B2 - Control device of power converter - Google Patents

Description

  The embodiment of the present invention relates to a control device of a power converter which controls a power converter which interconnects an AC system and a DC system.

  BACKGROUND ART In recent years, expectations for high voltage direct current transmission (hereinafter, HVDC) have been increasing as a means for realizing long distance power transmission and different grid interconnection. With HVDC, reduction of transmission loss and reduction of transmission line equipment cost can be realized. In particular, long distance power transmission is advantageous in cost over AC power transmission. For this reason, HVDC is rapidly spreading at home and abroad.

  The HVDC employs a power converter (hereinafter, referred to as a converter) for converting the power of the AC system into DC or converting the DC flowing through the DC system into AC. Conventionally, a separately excited converter to which a thyristor is applied has been used as a converter. However, recently, the application of a self-excitation type voltage converter has been actively studied. The self-excitation type voltage converter can reduce the dependency on the AC system as compared with the separately excited converter, and can reduce the installation area.

  In particular, a multilevel converter in which switching elements are multi-staged can be compatible with high voltage and sine wave of output voltage, and its practical use is in progress. Among them, Modular Multilevel Converter (hereinafter referred to as MMC) has attracted high attention. The MMC realizes a high breakdown voltage by connecting a chopper circuit including a switching element and a capacitor in multiple stages to each arm, and outputs an AC voltage close to a sine wave.

Patent No. 4673428

  The MMC as described above can control DC power and AC power separately. However, when using it as HVDC, it does not control the electric power by the side of alternating current correctly, but gives and controls the interchange power which comes from a host system as a direct-current power command. On the other hand, from the AC side, it is necessary to input the power necessary for the output from the DC side. Also, the AC side power is also used to control the voltage of the capacitor in the MMC. Therefore, the command value of the AC power is the sum of the interchange power and the power for controlling the capacitor voltage. This balances the power on the AC side and the DC side to prevent a sharp rise or drop in the capacitor voltage.

  However, at the time of black start, the voltage that determines the power output by the MMC will depend only on the load. The black start refers to starting up the AC system from the converter when the AC system does not have a power source such as a generator and is configured by only a load. For example, at the time of a power failure, it becomes a black start. Under normal conditions, as described above, by using the power on the AC side, it was possible to perform subtle control of the capacitor voltage. However, in the case of black start, the power on the AC side completely depends on the load. For this reason, the freedom to control the capacitor voltage is lost. While there is a constant command value on the DC side, on the AC side, the capacitor voltage can not be maintained considering that power is consumed by the load.

  An embodiment of the present invention aims to provide a control device of a power converter capable of maintaining a capacitor voltage even at the time of black start.

  In order to solve the above problems, the embodiment is a control device that controls a power converter that interconnects an AC system and a DC system, and a command for requesting a voltage required for a capacitor in the power converter AC voltage outputting a command value for requesting a required voltage to the AC side of the power converter based on a capacitor voltage control unit that outputs a value and a current command value to which a command value from the capacitor voltage control unit is added A command value for requesting a voltage necessary for circulating current in the power converter based on a control unit and a circulating current command value to which a DC current command value is added, the command output from the AC control unit The DC current command value added to the circulating current command value according to the circulating current control unit that outputs the command value added to the value, and the input of the black start command operating with no power supply of the AC system , Having a first switching unit for switching the command value from the capacitor voltage control unit

Power converter of the embodiment and a block diagram showing a power system to which this is applied A circuit diagram showing a converter used in the embodiment Block diagram showing the configuration of the control device Control block diagram showing capacitor voltage control unit Control block diagram showing AC control unit Control block diagram showing the circulating current control unit

First Embodiment
[Constitution]
The configuration of the present embodiment will be described with reference to the drawings.
[Power system]
The power system 100 to which the present embodiment is applied is a system for mutually converting direct current and alternating current and supplying power between the AC system AS1, the AC system AS2, and the DC system DS1 as shown in FIG. . AC system AS1 and AS2 are systems which supply AC power. Both of the AC system AS1 and the AC system AS2 can be on the power transmission side and the power reception side. As elements constituting the AC systems AS1 and AS2, there are a power supply, a load, an AC transmission line, and the like. For example, the AC systems AS1 and AS2 can be configured to include three-phase or single-phase 50 Hz or 60 Hz power supplies, loads, and AC transmission lines. The DC system DS1 is an electric power system that supplies DC power to the AC systems A1 and AS2.

[Power converter]
The power conversion device of the present embodiment is a device that interconnects the AC systems AS1 and AS2 and the DC system DS1. The power converter includes, as shown in FIG. 1, a converter 1A, a converter 1B, a control device 2A, and a control device 2B.

(converter)
Converters 1A and 1B link AC system AS1, DC system DS1, and AC system AS2 by mutually converting AC power and DC power.

  Converter 1A is connected between AC system AS1 and DC system DS1. The converter 1B is connected between the DC system DS1 and the AC system AS2. The converters 1A, 1B function as both a forward converter and an inverse converter. That is, the power conversion device 100 can bidirectionally exchange power between the AC system AS1 and the AC system AS2.

  The forward converter is a converter that converts AC power into DC power. The reverse converter is a converter that converts DC power into AC power. For example, in the case where the AC system AS1 functions as a power transmission side and the converter 1A functions as a forward converter, the converter 1A converts AC power from the AC system AS1 into DC power and supplies it to the DC system DS1. When the AC system AS2 functions as a power receiving side and the converter 1B functions as an inverse converter, the converter 1B converts DC power from the DC system DS1 into AC power and supplies the AC system AS2.

  As an example of such a converter 1A, 1B, the converter 1 which is an MMC will be described with reference to FIG. The MMC has legs 11 connected in parallel corresponding to the three phases. Each leg 11 has unit arms 12a and 12b connected in series on the positive side and the negative side.

  The unit arms 12a and 12b are configured by connecting chopper cells 13 in multiple stages in series. Hereinafter, the chopper cell 13 may be simply referred to as a cell. The chopper cell 13 is a unit converter having a switching element 13a, a diode 13b, and a capacitor 13c. The switching element 13a is a self-extinguishing type semiconductor element. For example, GTO, IGBT, IEGT or the like can be used as the switching element 13a. Two switching elements 13a are connected in series. Although not shown, a drive circuit and a power source for turning on and off the self arc-extinguishing element are connected to each switching element 13a.

  The diode 13 b is a free wheeling diode. Two diodes 13 b are connected in anti-parallel to the respective switching elements 13 a. The capacitor 13c is a voltage source that supplies the stored energy as a voltage. The capacitor 13c is connected in parallel to the two switching elements 13a connected in series. Although not illustrated, each capacitor 13 c is provided with a voltage sensor that measures the voltage of each.

  The positive and negative terminals of the legs 11 connected in parallel are the DC terminals 15 connected to the DC system DS1. The positive and negative unit arms 12 a and 12 b in each leg 11 are connected via a buffer reactor 14. The alternating current terminal 17 of each phase is drawn out from the middle point of the buffer reactor 14 on the positive side and the negative side via the transformer 16 and connected to the alternating current system AS1 or AS2.

  Furthermore, a total of six current sensors 18 are provided, one each, between the three-phase buffer reactor 14 and the unit arms 12a and 12b. These six current sensors 18 provide various measurement values described below. For example, when the measured values of the current sensors 18 are summed up, they become components of the circulating current flowing through the unit arms 12a and 12b. A direct current can be defined as the zero phase of this circulating current.

  That is, of the three-phase circulating current, the zero-phase component flowing in the three in-phase flows out to the DC side without circulating in the converter 1. More specifically, by converting the R phase, the S phase, and the T phase of the circulating current by αβ0, the α phase, the β phase, and the 0 phase that circulate inside the converter 1 are separated. The zero phase is a direct current component supplied to the outside.

  The unit arms 12a and 12b may each have N chopper cells 13 connected in series. The above is an example of N = 2, but it is sufficient if N ≧ 1. In addition, the circuit configuration may be such that the buffer reactor 14 is reduced by using the reactance component of the transformer 16.

  The above-described converters 1A and 1B operate in response to control signals generated by the control circuit according to command values from the control devices 2A and 2B, with the drive circuit turning on and off the switching elements 13a.

[Control device]
Control devices 2A and 2B are connected to the converters 1A and 1B, respectively. Control devices 2A and 2B are devices that control the operation of converters 1A and 1B. In the description of the present embodiment, when the converters 1A and 1B are not distinguished from each other, the converter 1 is used. When the control devices 2A and 2B are not distinguished from each other, the control device 2 is used.

  As shown in FIG. 1 and FIG. 3, the control device 2 includes a capacitor voltage control unit 21, an alternating current control unit 22, a circulating current control unit 23, a first switching unit 24, a second switching unit 25, and a third switching. It has a section 26.

  The capacitor voltage control unit 21 outputs a command value for requesting a necessary voltage to the capacitor 13 c in the converter 1. AC control unit 22 outputs a command value for requesting a necessary voltage to the AC side of converter 1 based on the current command value to which the command value from capacitor voltage control unit 21 is added.

  The circulating current control unit 23 is a command value that requests a voltage necessary for the circulating current in the converter 1 based on the circulating current command value to which the DC current command value is added, and is output from the AC control unit 22 Command value to be added to the command value. The circulating current is a current circulating in each leg 11 mainly for the purpose of equalizing the capacitor voltage. The circulating current referred to here includes a component which stays without going out and a component which goes out on the DC side.

  The first switching unit 24 switches the direct current command value added to the circulating current command value to the command value from the capacitor voltage control unit 21 in response to the input of the black start command. The second switching unit 25 switches the power added to the command value from the capacitor voltage control unit 21 from DC power to AC power according to the input of the black start command. The third switching unit 26 switches the output of the command value from the AC control unit 22 to a predetermined command value of AC voltage.

  The details of each of the above-described units will be described below. The gain in each of the following parts is a control block that performs PID control with respect to the deviation and performs mutual conversion of the current command value and the voltage command value. In addition, various measured values input to the control device 2 are obtained by calculation from voltage values, current values, and values from the current sensor 18, the voltage sensor of the capacitor 13c, a sensor installed in the system, and the like. Further, the upper management system which determines various command values and the like and inputs them to the control device 2 is called a higher system. The calculation of the measured value or the calculation of the command value based on the measured value may be calculated outside the control device 2 or may be calculated by a calculation unit in the control device 2. That is, it is free to use a value calculated outside the host system or the like or a value calculated inside the control device 2.

(Capacitor voltage control unit)
As shown in FIG. 4, the capacitor voltage control unit 21 obtains a deviation between the capacitor voltage command value of each cell and the capacitor average voltage of all cells, and generates a current command value according to the deviation by PID control in the gain. . The capacitor voltage command value is input from the upper system. The capacitor average voltage is obtained by calculation based on the measurement value from the voltage sensor of the capacitor 13c.

  Under normal conditions, in order to include energy corresponding to the power to be output from the converter 1 to the DC side in the AC command value, the DC current value obtained by converting the power into the current command value from the capacitor voltage control unit 21 Add and feed forward. That is, the power supplied in the DC power transmission is the power which the converter 1 has in addition to the energy of the capacitor 13c. The current command value obtained by combining the interchanged power becomes the AC effective current command value described below (see FIGS. 3 and 5).

(AC controller)
As shown in FIG. 5, the AC control unit 22 divides and controls the active current and the reactive current. The effective current and the reactive current are considered to correspond to the d-axis component and the q-axis component when the three phases are subjected to dq conversion. That is, the AC control unit 22 takes a deviation between the AC effective current command value and the AC effective current, and generates a voltage command value corresponding to the deviation in the gain. The AC effective current is obtained from the measurement value from the current sensor 18.

  Further, the AC control unit 22 takes a deviation between the AC reactive current command value and the AC reactive current, and generates a voltage command value corresponding to the deviation in the gain. The AC reactive current command value is input from the upper system. The AC reactive current is obtained from the measurement value from the current sensor 18.

  Furthermore, in the AC control unit 22, each of the active component and the ineffective component is multiplied by ω L which is a kind of gain, and the active component and the ineffective component do not affect the other even if one is changed. To be

  As shown in FIG. 3, an AC voltage measurement value from the AC side system and a voltage command value from the circulating current control unit 23 are added to such a voltage command value from the AC control unit 22 as shown in FIG. It is output as a command value for 1.

(Circulating current control unit)
The zero (0) phase component of the circulating current control unit 23 takes a deviation between the direct current command value and the direct current as shown in FIG. 6, and generates a voltage command value according to the deviation in the gain. Furthermore, a DC voltage command value is added to this voltage command value. The direct current command value is a command value input from the upper system. A circulating current command value is added to the direct current command value as described later. The circulating current command value is a command value corresponding to zero phase obtained from the measured value by αβ 0 conversion as described later. The DC voltage command value is a command value input from the upper system. The output of the circulating current control unit 23 is added to the output of the AC control unit 22.

  Furthermore, the circulating current control unit 23 includes a limiter 23 a and a setting unit 23 b. The limiter 23a defines the fluctuation range of the circulating current command value. The setting unit 23 b sets the limiter value input from the upper system to the limiter 23 a.

  The setting unit 23b sets a limiter value in which the converter 1A on the side receiving the black start command out of the pair of converters 1A and 1B installed at both ends of the DC system DS1 serves as a current control terminal. The limiter value is set such that the power converter 1B of FIG.

  The limiter value for the current control end is a non-zero value, and the limiter value for the voltage control end is zero. If the limiter value is not zero, the input value has a fluctuation range, and its upper and lower limits are defined. When the limiter value is 0, the DC voltage command value is output as it is. The current control end and the voltage control end will be described later.

  The circulating current command value is a zero-phase component obtained by performing αβ 0 conversion based on the inter-phase balance control operation amount and the inter-PN balance control operation amount. The interphase balance control manipulated variable is a current value corresponding to a voltage for balancing three phase capacitor voltages. The inter-PN balance control operation amount is a current value corresponding to a voltage for balancing capacitor voltages in the positive and negative unit arms 12a and 12b. The inter-phase balance control operation amount and the inter-PN balance control operation amount are obtained by calculation from measured values from a voltage sensor of the capacitor 13c.

  The αβ0 conversion is a process of converting an α phase and a β phase into two phase components (three phase two phase conversion) and a zero phase component. The zero-phase component is added to the direct current command value as a circulating current command value. Although the α phase component and the β phase component may also be used for the calculation, they are not necessarily required to explain the principle of the present embodiment, and thus the description of the calculation is omitted.

(First switching unit)
The first switching unit 24 includes switches 24a and 24b. The switch 24 a switches the output destination of the current command value from the capacitor voltage control unit 21 from the AC control unit 22 to the circulating current control unit 23 based on the black start command from the host system. The switch 24 b switches the direct current command value input to the circulating current control unit 23 to the current command value from the capacitor voltage control unit 21 while switching the switch 24 a.

(Second switching unit)
The second switching unit 25 is a switch that switches power to be fed forward to the output from the capacitor voltage control unit 21 from DC power to AC power in response to the input of the black start command. The DC power is obtained from the measured value from the current sensor 18 and the DC voltage command value from the upper system. The DC voltage command value is the same as the DC voltage command value input to the circulating current control unit 23. The AC power is obtained from the measured value from the current sensor 18 and the command value of the AC voltage from the host system. Here, the power to be fed forward is a value obtained by converting the power into the dimension of the current.

(Third switching unit)
The third switching unit 26 includes switches 26a and 26b. The switch 26 a switches the output from the AC control unit 22 to 0 in response to the input of the black start command. The switch 26 b switches the AC voltage measurement value added to the command value to the converter 1 to a predetermined command value of AC voltage. That is, at the time of black start, since a system voltage can not be obtained by measurement, for example, a normal system voltage is used as a fixed AC voltage command value. The predetermined alternating voltage may be increased at a predetermined slope.

[Effect]
The operation of the present embodiment as described above will be described. In the following description, the converter 1A functions as a forward converter on the power transmission side, and the converter 1B functions as an inverse converter on the power reception side, and in particular, an example of controlling the converter 1A as a forward converter and Do. Also, during normal operation, converter 1A converts AC power from the power supply in AC system AS1 to DC power and supplies it to DC system DS1, converter 1B converts this DC power to AC power and AC system It is in the state of being supplied to AS2.

(Normal time)
Under normal conditions, the capacitor voltage control unit 21 obtains a voltage necessary as the current capacitor voltage from the average capacitor voltage of all cells and the deviation of the capacitor voltage command value of each cell, converts it into a current command value, and outputs it. . For example, the current command value is output so as to increase the voltage when the capacitor average voltage is lower than the capacitor voltage command value and lower the voltage when the capacitor average voltage is higher than the capacitor voltage command value.

  A current value converted from DC power is fed forward to this current command value, and is input to the AC side control unit 22 as an AC effective current command value. That is, the active power on the AC side is determined by the sum of the control current of the capacitor 13c and the energy on the DC side which is the interchange power.

  The AC control unit 22 outputs an AC voltage command value corresponding to the active current and the reactive current required for the converter 1 based on the AC active current command value and the AC reactive current command value. An AC voltage measurement value obtained from the system is added to this AC voltage command value, and further, a voltage command value from a circulating current control unit 23 described later is added, and is output as a voltage command value to the converter 1. That is, the voltage required for the capacitor 13c and the command value for requesting the voltage required for the circulating current are added to the system voltage to obtain a voltage command value.

  The circulating current control unit 23 obtains a necessary voltage command value from the deviation between the DC current command value to which the circulating current command value is added as described above and the measured DC current, and further, the DC voltage from the host system Output a voltage command value that combines the command values.

  Here, the converters 1A and 1B used for the power transmission end and the power reception end in HDVC are either a voltage control end determining a voltage or a current control end determining a current. Normally, the power transmission end is a voltage control end, and performs control of constant voltage. The power receiving end is a current control end, and the voltage is variable to control the current. Thus, the power receiving end can freely move the voltage by generating a command value that can obtain the current to be flowed within a certain range. The operating point of such two converters 1A and 1B of the voltage control end and the current control end is an intersection of a constant voltage of the voltage control end and a fluctuating voltage of the current control end. This is because the operating point can not be determined if either voltage is free to fluctuate.

  For example, as described above, it is assumed that the converter 1A is a forward converter at the power transmission end and the converter 1B is an inverse converter at the power reception end. The setting unit 23b of the control device 2A at the power transmission end sets 0 in the limiter 23a. Therefore, the DC voltage command value is output as it is, so the voltage becomes constant. Thereby, converter 1A functions as a voltage control end which fixes a voltage.

  On the other hand, the setting unit 23b of the control device 2B at the power receiving end sets the limiter 23a to a non-zero value. For this reason, the DC voltage command value has an allowable fluctuation range. The converter 1B functions as a current control terminal that changes the current as the DC voltage command value changes in the range of fluctuation depending on the situation.

  The control circuit of the converter 1A generates a control signal of the switching element 13a based on the AC voltage command value output as described above, and the drive circuit turns each switching element 13a on and off. Output is controlled.

(At black start)
At the time of black start, a black start command is input from the upper system. Then, the switch 24 a of the first switching unit 24 disconnects the output destination of the capacitor voltage control unit 21 from the AC control unit 22. At the same time, the switch 24 b switches the direct current voltage command value input to the direct current side circulating current control unit 23 to the command value of the capacitor voltage control unit 21.

  Under normal conditions, since there is a system voltage, as described above, power can be generated and output from the system voltage and the current output from the converter 1A. However, at the time of black start, there is no AC power supply, and the current depends only on the load.

  Therefore, by switching the output destination of the capacitor voltage control unit 21, the command value added to the circulating current command value is set as the current command value of the capacitor voltage control unit 21. That is, the voltage required by the capacitor 13c is not included in the alternating current effective current command value on the alternating current side and requested from the alternating current control unit 22, but is included in the circulating current command value on the direct current side to calculate the circulating current control unit. Change from 23 to request.

  Further, in response to the black start command, the second switching unit 25 switches the current value added to the current command value output from the capacitor voltage control unit 21 to the current value converted from the AC power. That is, at the time of black start, since the command value is controlled on the DC side, AC power is added in advance to feed forward this time.

  The AC voltage in this AC power is a fixed voltage command value described later. This voltage command value is a value added to the voltage command value instead of the AC voltage measurement value from the system. The alternating current in this alternating current power is a measured value from the current sensor 18.

  Further, in response to the black start command, the switch 26a of the third switching unit 26 switches the output side of the AC control unit 22 to 0 in order to turn off the alternating current control. At the same time, the switch 26b switches so as to output a fixed AC voltage command value from the AC voltage measurement value from the grid.

  That is, at the time of black start, since there is no voltage in the system, it is not possible to control the current by inputting an AC voltage measurement value from the system. The current is determined by the voltage generated by the converter 1A and the impedance of the load resistance and the inductance. Therefore, the command value from the AC control unit 22 is switched to a fixed AC voltage command value. For example, when it is desired to bring out the alternating current 100V, the command value of the alternating current 100V is given. Note that, from the time of switching, the AC voltage may be gradually increased at a predetermined inclination to be a command value of a desired value.

  Furthermore, when the AC system AS1 is in black start, the setting of the limiter value is changed. For example, when the AC system AS1 loses power and the converter 1A at the power transmission end performs black start, in the control device 2A that receives the black start command, the setting unit 23b sets a non-zero value as the limiter value from the upper system. Set Thus, unlike in normal times, the converter 1A functions as a current control end that changes the current.

  On the other hand, in the control device 2B of the converter 1B at the power receiving end, the setting unit 23b sets 0 as the limiter value from the upper system. Thereby, unlike normal times, the converter 1B functions as a voltage control end that fixes a voltage.

  By the switching operation described above, circulating current control unit 23 determines the necessary voltage command from the deviation between the DC current command value obtained by adding the circulating current command value to the command value from capacitor voltage control unit 21 and the measured DC current. A value is determined, and further, a voltage command value obtained by combining a DC voltage command value from a host system is output.

  What added fixed AC voltage command value to this voltage command value is output as a voltage command value to converter 1A. Based on such an AC voltage command value, the control circuit in converter 1A generates a control signal for switching element 13a, and the drive circuit turns each switching element 13a on and off to control the output of converter 1A. Ru.

[effect]
The present embodiment as described above is the control device 2 that controls the converter 1 that interconnects the AC system AS1 and AS2 and the DC system DS1, and a command that requests the required voltage to the capacitor 13c in the converter 1 AC that outputs a command value for requesting a required voltage to the AC side of the converter 1 based on the capacitor voltage control unit 21 that outputs a value and the current command value to which the command value from the capacitor voltage control unit 21 is added A command value for requesting a voltage necessary for the circulating current in the converter 1 based on the control unit 22 and the circulating current command value to which the DC current command value is added, the command output from the AC control unit 22 And a circulating current control unit for outputting a command value to be added to the value.

  Then, according to the present embodiment, the DC current command value added to the circulating current command value according to the input of the black start command operated in the absence of the power supply of the AC system AS1, the command value from the capacitor voltage control unit 21. And a first switching unit 24 for switching to the

  Therefore, at the time of black start, the capacitor voltage can be maintained by switching from the control on the alternating current side to the control on the direct current side.

  Further, in the present embodiment, in order to obtain the power output from the converter 1, the power added to the command value from the capacitor voltage control unit 21 is switched from DC power to AC power according to the input of the black start command. A second switching unit 25 is provided.

  Therefore, it is possible to request the circulating current control unit 23 including the AC power to be obtained by the converter 1 in the command value from the capacitor voltage control unit 21.

  The present embodiment also includes a third switching unit 26 that switches the output of the command value from the AC control unit 22 to a command value of a predetermined AC voltage.

  For this reason, as a substitute for the grid voltage which can not be obtained for black start, it is possible to obtain a predetermined AC voltage and continue the operation.

  In addition, by increasing the predetermined alternating voltage with a predetermined slope, the soft start can be performed with a slope at the time of black start, and the rush current can be prevented.

The circulating current control unit 23 includes a limiter 23a that defines the fluctuation range of the circulating current command value.
The limiter 23a includes a setting unit 23b that sets a limiter value. The setting unit 23b then sets a limiter value that sets the converter 1A on the side receiving the black start command among the pair of converters 1A and 1B installed at both ends of the DC system DS1 as the current control end. The limiter value is set such that the other converter 1B is a voltage control end.

  In a situation where there is no power supply of the AC system AS1, it is not possible to freely supply the power required on the power receiving end side. Therefore, by setting the power receiving end side as the voltage control end and the power transmission end side as the current control end, the current can be controlled on the power transmission end side where the black start has been achieved. Moreover, switching between the voltage control end and the current control end can be performed only with the information on the DC side.

[Other embodiments]
The present embodiment is not limited to the above aspect.
(1) In the above aspect, the predetermined AC voltage command value switched by the third switching unit 26 at the time of black start is set as the fixed AC voltage command value. However, a slope gain unit may be provided which applies a slope gain to this predetermined AC voltage command value. The slope gain is a process of correcting the voltage command value in accordance with the current flowing. That is, the command value of the predetermined AC voltage is corrected by the voltage calculated by AC current × slope gain measured by the current sensor 18.

  If the AC voltage command value is simply a fixed value, the power changes depending on the load, and if the load is heavy, a large current may flow more than necessary. Therefore, according to the current measured by the current sensor 18, the slope gain is used to adjust the AC voltage command value in which the current is suppressed. By applying the gain and impedance of the application to reduce the excess current from the voltage command value, the current can be suppressed even when the load is heavy.

(2) The control device 2 can be realized by controlling a computer including a CPU with a predetermined program. The program in this case realizes the processing of each part as described above by physically utilizing the hardware of the computer. The range of processing by hardware and the range of processing by software including a program are not limited to a specific mode. The control devices 2A and 2B can also be configured as a system realized by a common computer. The control block diagrams of FIGS. 4 to 6 are also examples, and any configuration that can realize the function of each part of the control device 2 described above may be used.

  Although not illustrated, the control device 2 includes a storage unit that stores information necessary for the processing of each unit, such as measured values and command values. A storage area can also be regarded as a storage area of information that is input from the outside and temporarily stored, and information that is exchanged by absorbing differences in processing timing between the respective units.

  For example, the processing unit that performs the αβ0 conversion in the block diagram of FIG. 3 may be an αβ0 conversion unit provided inside the control device 2 or an operation unit that performs the αβ0 conversion processing outside. The result calculated and input externally is temporarily stored in the storage unit and is input to the circulating current control unit 23.

(3) While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and the gist of the invention.

1, 1A, 1B Converter 2, 2A, 2B Control Device 11 Leg 12a, 12b Unit Arm 13 Chopper Cell 13a Switching Element 13b Diode 13c Capacitor 14 Buffer Reactor 15 DC Terminal 16 Transformer 17 AC Terminal 18 Current Sensor 21 Capacitor Voltage Control Section 22 alternating current control unit 23 circulating current control unit 23a limiter 23b setting unit 24 first switching unit 24a, 24b, 25a, 25b switch 25 second switching unit 26 third switching unit 100 power system AS1, AS2 alternating current system DS1 direct current system

Claims (6)

A control device that controls a power converter that interconnects an AC system and a DC system,
A capacitor voltage control unit that outputs a command value that requests a voltage required for a capacitor in the power converter;
An AC control unit that outputs a command value for requesting a required voltage to the AC side of the power converter based on a current command value to which a command value from the capacitor voltage control unit is added;
A command value for requesting a voltage necessary for a circulating current in the power converter based on a circulating current command value to which a DC current command value is added, the command value being added to the command value output from the AC control unit A circulating current control unit that outputs a command value
A first switch that switches the DC current command value added to the circulating current command value to a command value from the capacitor voltage control unit in response to an input of a black start command operating in a state where there is no power supply in the AC system. Department,
A control device of a power converter characterized by having.   In order to obtain the power output by the power converter, the second switching unit is configured to switch the power added to the command value from the capacitor voltage control unit from DC power to AC power according to the input of the black start command. The control device of a power converter according to claim 1, characterized in that it comprises:   The control device of the power converter according to claim 1 or 2, further comprising a third switching unit configured to switch an output of the command value from the AC control unit to a command value of a predetermined AC voltage.   The controller for a power converter according to claim 3, wherein the predetermined alternating voltage is increased at a predetermined slope.   The control device of the power converter according to claim 3 or 4, wherein the command value of the predetermined alternating current voltage is corrected by a voltage obtained by multiplying an alternating current by a slope gain. The circulating current control unit
A limiter that defines a fluctuation range of the circulating current command value;
And a setting unit that sets a limiter value in the limiter.
The setting unit sets a limiter value in which the power converter on the side receiving the black start command out of the pair of power converters installed at both ends of the DC system is a current control terminal, and the other power converter The control device of the power converter according to any one of claims 1 to 5, wherein a limiter value is set such that the voltage control terminal is a voltage control terminal.

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