JP6625929B2 - Power conversion device and power conversion system - Google Patents

Description

  The present invention relates to a power conversion device and a power conversion system linked to an AC system via a transformer.

  In general, a power converter connected to an AC system is provided with a transformer between the AC system and the AC system from the viewpoint of stepping up / down of an AC voltage and securing electrical insulation. The power converter connected to such a transformer controls the DC voltage and DC current not to be output to the core of the transformer, thereby preventing magnetic saturation due to superimposition of the DC component on the magnetic flux density of the core. . In the present specification, the superposition of the DC component on the magnetic flux density of the transformer core will be referred to as DC magnetic field (DC magnetization).

  However, if there is an offset error in a detection value of a voltage detector VT (Voltage transformer) or a current detector CT (Current transformer), or a control unit that performs feedback control of the power conversion device, DC bias occurs.

  Excessive DC bias may cause magnetic saturation of the transformer core. When the core of the transformer is magnetically saturated due to the DC bias, the leakage magnetic flux that does not pass through the core of the transformer increases, so that the stray load loss of the side plate of the transformer tank, the tightening bolt, and the like increases. The stray load loss overheats the side plate of the tank, the tightening bolts, and the like, and may reduce the mechanical strength of the transformer. Further, when the iron core of the transformer is magnetically saturated due to the DC bias, the exciting inductance of the transformer decreases, and the exciting current increases. Since a part of the exciting current also flows to the power conversion device, the allowable current value of the power conversion device may be exceeded, and the device may be stopped by an overcurrent. Further, when the transformer core is saturated, the noise generated by the transformer also increases.

  As described above, if magnetic saturation occurs in the core of the transformer, various problems occur. Therefore, it is necessary to suppress DC bias and magnetic saturation of the transformer core by some means. As an example of the means that does not generate magnetic saturation, there is a means of assuming in advance the existence of an offset error such as the voltage detector VT and the current detector CT and using a transformer having an increased magnetic resistance. However, there is a problem in that the core cross-sectional area of the transformer must be increased in order to increase the magnetic field resistance.

  In view of the above-described problems, there is a need for a demagnetization suppression control unit that detects DC polarization and suppresses the detection by a power converter without using a transformer having an increased magnetic polarization tolerance. As such a bias suppression control means, for example, an AC current detector ACCT is installed on each of the primary side (AC system side) of the transformer and the secondary side (power conversion device side) of the transformer. 2. Description of the Related Art There is known a technique in which a DC bias state of an iron core of a transformer is detected based on a signal from an AC current detector ACCT, and the power converter controls the state. Such a technique is described in Patent Document 1, for example.

JP 2014-150598 A

  According to the above-described conventional technology, two currents, an excitation current and a load current, flowing on each of a primary side and a secondary side of a transformer are detected by an AC current detector ACCT, and an excitation current of the transformer is calculated from a difference current between the two detected currents. Of the AC component of the exciting current, and a deflected detection value which is the sum of the positive peak value and the negative peak value of the AC component of the exciting current is obtained. As described in Patent Document 1, a demagnetization correction value is generated by multiplying a demagnetization detection value obtained from a demagnetization detection unit by a demagnetization control gain, and based on the demagnetization correction value, an iron core of a transformer is used. In general, a method of controlling the power conversion device so as to suppress the DC bias is well known.

  Here, the demagnetization detection value and the demagnetization correction value have non-linear characteristics. This is due to the relationship between the magnetizing current and magnetic flux of the transformer.The peak value of the magnetic flux and magnetizing current of the transformer core has a non-linear relationship with the case where the magnetic flux is not magnetically saturated and the case where it is magnetically saturated. You can see from To cope with such non-linear characteristics, for example, a non-linear curve of the demagnetization detection value and the demagnetization correction value is linearly approximated to obtain a constant value of the demagnetization control gain, and the error due to the linear approximation is large. For the region, a method of applying a dead zone or the like can be considered. However, in the above-described method, since the demagnetization control gain is determined from the approximate waveform, there is a region where the gain is set low (or high) due to an error from the original nonlinear curve. There was a problem that performance deteriorated. In addition, since the dead zone is applied, there is a problem that the control range of the demagnetization suppression control is limited.

  In view of the above, an object of the present invention is to solve the above-described problems, and to provide a power conversion device and a power conversion system that do not degrade control performance by expanding a control range of demagnetization suppression control. It is in.

  In order to achieve the above object, the present invention includes a power converter connected to a transformer including a magnetic flux detector for detecting DC magnetic polarization, and a control device for controlling an output voltage of the power converter. A power converter, wherein the controller is configured to provide a current controller that obtains a target signal of an output voltage of the power converter from a current flowing through the power converter and a current target value, and to provide a current for generating a magnetic bias to the current controller. Magnetization generating means for shifting the output of the current controller, magnetizing suppression control means for obtaining a magnetizing correction voltage necessary for suppressing DC biasing in the transformer, and a target signal of the output voltage of the power converter Is provided with a bias correction voltage, and the output voltage of the power converter is controlled by the output voltage of the corrector.

  Further, according to the present invention, a power converter connected to a transformer including a magnetic polarization detector that detects DC magnetic polarization, and a power conversion device including a control device that controls an output voltage of the power converter, The control device includes a current controller that obtains a target signal of an output voltage of the power converter from a current flowing through the power converter and a current target value, and a biasing current that is supplied to the current controller to bias the output of the current controller. A demagnetization generating means for shifting, a demagnetization suppression control means for obtaining a demagnetization correction voltage necessary for controlling the DC demagnetization in the transformer, and correcting the target signal of the output voltage of the power converter with the demagnetization correction voltage A demagnetization suppression control means, the demagnetization suppression control means having a control gain as a ratio of the magnitude of the demagnetization detection voltage detected by the demagnetization detector corresponding to the magnitude of the demagnetization current supplied by the demagnetization generation means Storage means for respectively storing At the time of execution, from among the control gains stored in the storage means, the control gain at the time of the demagnetization generation current corresponding to the demagnetization detection voltage detected when executing the demagnetization suppression control is extracted. A variable control gain for multiplying the demagnetization detection voltage for detecting the control gain, so as to obtain the demagnetization correction voltage.

  According to the present invention, since the control gain of the demagnetization suppression control is automatically set according to the detected value of the demagnetization, the control range of the demagnetization suppression control can be expanded.

  Further, according to the embodiment of the present invention, since the control performance is not deteriorated by the linear approximation, the demagnetization suppression control can be performed accurately even in the low demagnetization detection region. In addition, in anticipation of the limitation of the control range due to the dead zone, there is no need to take measures such as increasing the biasing resistance of the transformer in advance, so that it is possible to reduce the cost and installation area by reducing the cross-sectional area of the core of the transformer. Become.

FIG. 1 is a diagram illustrating an overall configuration of a power conversion device 102 according to a first embodiment of the present invention. FIG. 7 is a diagram showing a relationship between a detected magnetic bias value and a magnetic bias compensation value. FIG. 2 is a diagram showing a configuration of a magnetization suppression control unit 110 according to the first embodiment of the present invention. FIG. 4 is a diagram showing a control gain change sequence of the magnetic bias suppression control means 110. FIG. 2 is a diagram illustrating an overall configuration of a power conversion device 102 according to a second embodiment of the present invention. FIG. 9 is a diagram illustrating a configuration of a magnetization suppression control unit 110 according to a second embodiment of the present invention. FIG. 9 is a diagram showing a control gain change of a magnetization suppression control unit 110 and a gain table reset sequence according to the second embodiment. FIG. 9 is a diagram illustrating a configuration of a magnetization suppression control unit 110 according to a third embodiment of the present invention. FIG. 9 is a diagram illustrating a configuration of a magnetization suppression control unit 110 according to a fourth embodiment of the present invention. FIG. 4 is a diagram showing a gain table generated in a storage device 302.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, an overall configuration of a power conversion device 102 according to a first embodiment of the present invention will be described with reference to FIG.

  The power converter 102 of the present invention is connected to the AC system 101. Note that the present invention is not limited to one of a single-phase AC system and a three-phase AC system, and the same effect can be obtained by applying to either power system. Although FIG. 1 shows a power conversion system such as a self-excited reactive power compensator (STATCOM) in which one power converter is connected to one power system, the present invention is applicable to such an application. There is no limitation. For example, a plurality of power converters are connected to a plurality of AC systems, such as a BTB (Back To Back) type power converter that exchanges power between AC power systems and a self-excited high-voltage DC power transmission system. In the power conversion system as described above, the same effects as those of the present invention can be obtained.

  The power converter 102 includes a transformer 103 and a self-excited power converter 104 (hereinafter simply referred to as a power converter) formed of a self-extinguishing element such as an IGBT (insulated-gate bipolar transistor) or an IGCT (integrated gate-committed thyristor). Converter), a current detector CT, a voltage detector VT, a bias detection unit 107 for detecting DC bias of a transformer, and control for controlling an output voltage command value Vrefu of a power converter. The device 108 and a PWM circuit 109 for generating a gate pulse gu for controlling the on / off of the self-extinguishing element are configured as main components. In FIG. 1, for example, a u-phase circuit configuration is shown as a single phase, and a symbol u indicating the u-phase is added to the end of each part symbol. Therefore, in the case of a three-phase configuration, the same equipment may be provided for each phase.

  The power converter 104 is, for example, a two-level, three-level, or multi-level power converter that includes at least one power storage element and a plurality of self-extinguishing elements.

  The current detector CT and the voltage detector VT detect the current Iu of the power converter 104 and the voltage Vs of the AC system 101, respectively, and input them to the control device 108, thereby performing feedback control of the power converter 104. . Although the current detector CT in FIG. 1 is installed on the power converter 104 side of the transformer 103 (hereinafter simply referred to as a secondary side), the current detector CT is located on the AC system 101 side of the transformer 103 (hereinafter simply referred to as a primary side). And the voltage detector VT may be installed on either the primary side or the secondary side of the transformer 103.

  The magnetism detecting means 107 detects the DC magnetism of the transformer 103 from the input signal obtained from the transformer 103. For example, as described in Patent Document 1, if the DC bias amount of the transformer can be estimated from an input signal, the bias detection unit 107 can obtain the same effect as that of the present invention using any bias detection unit. Can be.

  The control device 108 is a composite of a plurality of control systems. When roughly classified, the control device 108 causes a current control system which is an original control system for the power converter 104, and artificially generates a magnetic bias in the transformer 103. The system includes a bias generation system and a bias suppression control system for controlling the bias in the transformer 103.

  The current control system mainly includes a current control unit 112, and uses a current command value Irefu to be output from the power converter 104 and a voltage Vs obtained from the voltage detector VT to generate the power converter 104. A control signal is supplied to the PWM circuit 109 in order to control the current Iu flowing through the PWM circuit 109. PWM circuit 109 outputs a gate pulse gu for controlling on / off of the self-extinguishing element of power converter 104 according to output voltage command Vrefu given from control device 108.

  Note that the specific circuit configuration of the current control means 112 will be described. The voltage command value Vrefu0 is obtained by adding the voltage Vs to a value obtained by performing a proportional-integral operation in the adjustment circuit on the deviation between the current command value Irefu and the current feedback value Iu. It is what it was.

  The magnetic field generating system mainly includes magnetic field generating means 113. The magnetic field generating means 113 receives the DC current Idcu and the gain table generation / storage start signal Sgu and outputs the magnetic field generating current Iexdcu. I do. The demagnetization current Iexdcu is superimposed on the detection current Iu of the current detector CT, and the feedback signal of the current control means 112 is a corrected feedback signal Iu obtained by adding the demagnetization generation current Iexdcu from the original detection current Iu of the current detector CT. The power converter 104 has a function of intentionally generating a DC bias in the transformer 103 by being corrected to “′”. The DC bias generated in the transformer 103 in this case corresponds to the bias generation current Iexdcu created intentionally and mixed into the current control system. The power converter 104 intentionally generates a DC bias in the transformer 103 by superimposing the bias current Iexdcu on the detection current of the current detector CT.

  It should be noted that the magnetizing means 113 may be any as long as it finally shifts the output of the current control means 112. Therefore, in the embodiment of FIG. 1, the deviation is generated by adding the demagnetization generation current Iexdcu to the detection current Iu which is the feedback signal, but this is caused by the current command value Irefu which is the target signal of the current control means 112. The output of the current control means 112 can be similarly shifted by adding In short, what is necessary is just to shift the output Vrefu of the current control means 112.

  The demagnetization suppression control system mainly includes a demagnetization suppression control unit 110, and generates a demagnetization correction current Icomppu of a magnitude and a phase necessary for controlling the demagnetization, and generates the demagnetization correction voltage Vexdcu. After the conversion, a bias correction signal is given to the PWM circuit 109. More specifically, the demagnetization suppression control system includes: a demagnetization suppression control unit 110 for controlling the demagnetization of the transformer 103 from the demagnetization detection voltage Vmagu obtained by the demagnetization detection unit 107; And a voltage / current conversion unit 111 for converting the demagnetization correction current Icompu output from the means 110 into a demagnetization correction voltage Vexdcu. The specific circuit configuration of the magnetization suppression control unit 110 will be described later with reference to FIG.

  Next, with reference to FIG. 2, a relationship between the magnetization detection voltage Vmagu and the magnetization generation current Iexdcu will be described. In FIG. 2, the vertical axis represents the magnetization generation current Iexdcu, and the horizontal axis represents the magnetization detection voltage Vmagu. This figure shows the corresponding relationship with the observed magnetization detection voltage Vmagu when the magnetization generation current Iexdcu is intentionally varied and applied.

  The characteristics of FIG. 2 will be described in more detail. When the output from the demagnetization suppression control means 110 in FIG. 1 is zero and the current Iexdcu from the demagnetization generation means 113 is added to the current Iu obtained from the current detector CT, the current control means 112 Operates such that the power converter 104 outputs a voltage that causes the magnetic flux generation current Iexdcu to flow. When the magnetic flux generation current Iexdcu flows through the transformer 103, the magnetic flux is superimposed on the iron core of the transformer 103, so that the magnetic flux is DC-magnetized. This DC bias is detected by the bias detection unit 107 as a DC bias voltage Vmagu. As can be seen from FIG. 2, the DC bias voltage Vmagu and the bias current Iexdcu have non-linear characteristics. This is due to the excitation characteristics of the transformer 103, and the fact that the peak values of the magnetic flux of the transformer core and the excitation current are non-linear between non-magnetic saturation and magnetic saturation.

  If the nonlinear characteristic of FIG. 2 is simply expressed for each region, the gain when the magnitude of the DC bias voltage Vmagu is less than Vmagu1 is Kmagu1, and when the magnitude of the DC bias voltage Vmagu is greater than Vmagu1 and less than Vmagu2. Can be linearly approximated as Kmagu2 and the gain when the magnitude of the DC bias voltage Vmagu is equal to or greater than Vmagu2. Note that the gain Kmagu = Vmagu / Iexdcu.

  Next, with reference to FIG. 3, the configuration of the demagnetization suppression control unit 110 showing the first embodiment of the power converter 102 of the present invention will be described.

  The demagnetization suppression control means 110 cancels the demagnetization generation current Iexdcu by multiplying the demagnetization detection voltage Vmagu obtained from the demagnetization detection means 107 by the variable control gain 114 and the demagnetization suppression control start signal Sstu. To output the demagnetization correction current Icompu.

  The gain table generation / storage means 115 receives the demagnetization detection value Vmagu, the demagnetization generation current Iexdcu of the demagnetization generation means 113, and the gain table generation / storage start signal Sgu as inputs and performs variable control by the control gain Kmagu calculation means 301. The gain 114 is calculated, various parameters are stored in the storage device 302, and the control gain Kmagu is set to the variable control gain 114 by the control gain Kmagu setting means 303. In this case, the control gain Kmagu is a coefficient determined by linearly approximating the nonlinear characteristic of FIG. 2 for each region. The gain table generation / storage means 115 in FIG. 3 basically determines the approximation coefficient for each area in FIG.

  Next, with reference to FIG. 4, a control gain change sequence of the magnetization suppression control unit 110 of the present invention will be described. FIG. 4 shows, from the top, the gain table generation / storage start signal Sgu, the magnetization generation current Iexdcu, the magnetization detection voltage Vmagu, and the magnetization suppression control start signal Sstu. The horizontal axis in FIG. 4 indicates time t.

  In order for the bias control device 110 to suppress the DC bias of the transformer 103, it is necessary to calculate the control gain Kmagu of each region from the nonlinear characteristics of the bias detection voltage Vmagu and the bias current Iexdcu. . Therefore, first, at time t1, generation of a gain table relating to Kmagu is started. The storage device 302 stores the gain table in a period from time t1 to time t2, and in a period from the gain table generation end time t2 to the output start time t3 of the demagnetization suppression control unit 110, the demagnetization suppression is performed. The control unit 110 does not output the bias correction current Icompu.

  Although not shown in FIGS. 3 and 4, the gain table generation / storage start signal Sgu is also given to the magnetization generating means 113 at the same time, and the function of the magnetization generating means 113 causes the magnetization generation current Iexdcu to be reduced. As shown in FIG. 4, the sequential increase control results in a change in the bias voltage Vmagu. The demagnetization suppression control means 110 detects the demagnetization generation current Iexdcu and the demagnetization detection voltage Vmagu that have been changed in response to the result of the above control, and obtains the ratio as a control gain Kmagu.

  In FIG. 4, when the gain table generation / storage start signal Sgu changes from off to on, the storage device 302 changes the demagnetization detection voltage Vmagu, the demagnetization generation current Iexdcu, and the control gain Kmag obtained from the control gain Kmagu calculating means 301. Remember. Thereafter, when the bias generation current Iexdcu of the bias generation unit 113 is gradually changed, some change occurs in the bias detection voltage Vmagu. The control gain Kmag in that region can be determined from the slopes of the two magnetization generation currents Iexdcu and the two magnetization detection voltages Vmagu. The storage device 302 stores the Kmagu, Vmagu, and Icompu.

As a specific example, for example, Kmag2 in FIG. 3 is determined by Expression (1).
[Equation 1]
Kmagu2 = (Iexdcu2-Iexdcu1) / (Vmagu2-Vmagu1) (1)
In the equation (1), Kmagu2 is determined by calling Vmagu2 and Icompu2 detected by the control gain Kmagu calculating means 301 and the previous values Vmagu1 and Icompu1 stored in the storage device 302.

  Then, Vmagu2 and Icompu2 detected by the control gain Kmagu calculating means 301 are stored in the storage device 302 in the same manner as Kmagu2, and are used when determining the control gain Kmag for the next period. By repeating such means in a period from time t1 to time t2, the storage device 302 operates to generate a gain table as shown in FIG.

  Note that the magnetizing generation current Iexdcu does not exceed the magnetizing tolerance of the transformer when the gain table is generated, for example, by determining an upper limit in advance so as not to exceed the magnetizing tolerance (DC current withstanding) of the transformer. Other means may be provided. Further, the operation sequence in FIG. 4 is not limited to one of the operation and the stop of the power converter 104, and a gain table generation period may be provided regardless of the operation state.

  After the gain table as shown in FIG. 10 is generated, at time t2, the gain table generation / storage start signal Sgu is changed from ON to OFF, and the output of the magnetization generation current Iexdcu is stopped. Then, at time t3, the optimum control gain Kmagu is selected from the gain table stored in the storage device 302 on the basis of the detected demagnetization detection voltage Vmagu, and the control gain Kmagu setting means 303 sets the variable control gain 114. . Further, by changing the start signal Sstu of the demagnetization suppression control from off to on, the demagnetization correction current Icompu is output from the demagnetization suppression control means. With the above-described configuration, it is possible to automatically calculate the control gain Kmagu according to the demagnetization detection voltage Vmagu and to automatically adjust the demagnetization suppression control gain Kmagu.

  According to the first embodiment, since the variable control gain 114 of the demagnetization suppression control unit 110 can be automatically adjusted according to the detected demagnetization value Vmag, the control range of the demagnetization suppression control unit 110 can be expanded. Further, since the control performance is not deteriorated, the demagnetization suppression control can be applied with high accuracy even in the low demagnetization detection region. In addition, in anticipation of the limitation of the control range due to the dead zone, there is no need to take measures such as increasing the biasing resistance of the transformer in advance, so that it is possible to reduce the cost and installation area by reducing the cross-sectional area of the core of the transformer. Become.

  Second Embodiment With reference to FIG. 5, an overall configuration of a power conversion device 102 according to a second embodiment of the present invention will be described. However, description of the same or corresponding parts as those in the first embodiment will be omitted, and only different parts will be described.

  The difference from the first embodiment is the internal configuration of the demagnetization suppression control unit 110. The demagnetization suppression control unit 110 in FIG. 5 includes a variable control gain 114 and a gain table generation / storage / reset unit 503. ing.

  The configuration of FIG. 5 differs from the configuration of FIG. 1 in the gain table generation / storage / reset unit 503. Here, the demagnetization detection value Vmagu and the demagnetization generation current Iexdcu of the demagnetization generation unit 113 are shown. The control gain Kmagu is set to the variable control gain 502 by inputting the gain table generation / storage start signal Sgu and the gain table reset signal SuReset having a function of resetting the gain table of the storage device 602.

  Next, with reference to FIG. 6, a description will be given of a demagnetization suppression control unit 110 according to a second embodiment of the power converter 102 of the present invention.

  The demagnetization suppression control means 110 according to the second embodiment multiplies the demagnetization detection voltage Vmagu obtained from the demagnetization detection means 107 by the variable control gain 114 and the demagnetization suppression control start signal Sstu to generate the demagnetization. A demagnetization correction current Icompu for canceling the current is output.

  The gain table generation / storage / reset means 503 includes a control gain Kmagu calculation / reset means 601 for calculating the variable control gain 114, a storage device 602 for storing various parameters, and a control gain Kmagu for the variable control gain 114. And control gain Kmagu setting means 603. In the second embodiment, a gain table reset signal SuReset for resetting the gain table of the storage device 602 is added as an input signal of the control gain Kmagu calculation / reset unit 601.

  Next, with reference to FIG. 7, a description will be given of a control gain change of the demagnetization suppression control unit 110 and a gain table reset sequence according to the second embodiment of the power converter 102 according to the present invention. In the period from t1 to t3, the operation is the same as that in FIG.

  In FIG. 7, when an on-pulse is output to the gain table reset signal SuReset at time t4, the gain table of the storage device 602 is reset, and at time t5 after the reset signal SuReset is detected to be on, the gain table generation / storage starts. By turning on the signal Sgu and re-outputting the demagnetization generation current Iexdcu of the demagnetization generation means 113, the gain table is stored again. After the generation of the gain table ends at time t6 and Sgu is turned off, at time t7 the demagnetization suppression control is restarted by turning on the start signal Sstu of the demagnetization suppression control. The on-pulse of the gain table reset signal SuReset is not particularly limited as long as the gain table of the storage device 602 can be reset. For example, the on-pulse may be operated by receiving an input from an external signal. An operation of outputting an on-pulse may be performed.

  According to the second embodiment, the gain table is periodically reset / restored by the gain table reset signal SuReset, so that the temperature drift of the amplifier inside the demagnetization detecting means 207 and the offset due to the aging deterioration of the detecting device. Can be changed.

  Referring to FIG. 8, a description will be given of a magnetization suppression control unit 110 according to a third embodiment of the power converter 102 of the present invention. However, description of the same or corresponding parts as those in the first embodiment will be omitted, and only different parts will be described.

  FIG. 8 shows a configuration of the demagnetization suppression control unit 110 when the power system 101, the transformer 103, and the power converter 104 of FIG. 1 are configured by three-phase AC. The demagnetization suppression control means 110 controls the demagnetization detection voltages Vmagu, Vmagv, Vmagw of each phase obtained from the demagnetization detection means 107, the variable control gains 114u, 114v, 114w of each phase, and the demagnetization suppression control of each phase. Are multiplied by the start signals Sstu, Sstv, Sstw to output the demagnetization correction currents Icompu, Icompv, Icompw given to each phase in order to cancel the demagnetization current.

  In this case, the gain table generation / storage means 115 may be installed in each of the demagnetization suppression control means 110u, 110v, and 110w of each phase. I decided to do it. The control gain Kmagu is set to the variable control gain 114 by using the magnetization detection voltages Vmagu, Vmagv, Vmagw of each phase, the magnetization generation current Iexdcu of the magnetization generation unit 113, and the gain table generation / storage start signal Sgu as inputs. . Note that the gain table reset signal SuReset described in the second embodiment may be added to the input of the gain table generation / storage unit 115.

  When the excitation characteristics of the transformer 103 are substantially the same for each phase, the demagnetization detection voltage of each phase and the characteristics of the demagnetization current are almost the same. Therefore, the gain table generation / storage means 115 generates a gain table from the DC bias voltage Vmagu of any one of the three phases and the characteristics of the bias generation current Iexdcu, and generates a gain table according to the gain table. The effect of the present invention can also be obtained by changing the variable control gains Kmagu, Kmagv, and Kmagw.

  According to the third embodiment, a gain table is generated from the characteristics of the DC bias voltage Vmagu of any one of the three phases and the bias current Iexdcu. Can be shortened.

  The present invention intentionally causes the transformer to be DC-magnetized to generate the gain table. Therefore, the gain table generation period (magnetization generation period) is shortened, thereby reducing the DC magnetization generated in the transformer 103. The resulting stress such as loss and vibration can be reduced.

  Referring to FIG. 9, a description will be given of a demagnetization suppression control unit 901 according to a fourth embodiment of the power converter 102 of the present invention. However, description of the same or corresponding parts as those in the first embodiment will be omitted, and only different parts will be described.

  The demagnetization suppression control means 901 switches between the two demagnetization suppression control means using a variable gain, the demagnetization suppression control means 903 using a fixed gain consisting of a fixed control gain 907, and the above-mentioned two demagnetization suppression control means. It comprises a switch 908.

  The demagnetization suppression control unit 110 to which the variable gain is applied is the same as that of the first embodiment, and includes a variable control gain 114 and a gain table generation / storage unit 115. The demagnetization suppression control unit 903 to which the fixed gain is applied includes a dead zone 906 and a fixed control gain 907. Note that the gain table reset signal SuReset described in the second embodiment may be added to the input of the gain table generation / storage unit 905. The switch 908 switches the demagnetization suppression control means with a signal from the switching signal Sswu.

  According to the fourth embodiment, the two demagnetization suppression control units 110 and 903 can be switched. Therefore, when a failure due to a write error in the storage device due to aging or write restriction is detected, the backup demagnetization is controlled. It is possible to operate such as operating the magnetization suppression control means 903 to which a fixed gain is applied as the suppression control means.

  Therefore, it is possible to prevent the DC bias from expanding during the control suspension period due to the failure of the bias control device.

101: AC system 102: Power converter 103: Transformer 104: Self-excited power converter CT: Current detector VT: Voltage detector 107: Deflection detecting means 108: Control device 109: PWM circuit 110: Depolarization suppression control Means 111: Voltage / current conversion means 112: Current control means 113: Magnetization generation means 114: Variable control gain 115: Gain table generation / storage means 301: Magnetization suppression control gain calculation means 302: Storage device 303: Magnetization suppression Control gain setting means 503: gain table generation / storage / reset means 601: demagnetization suppression control gain calculation / reset means 602: storage device 603: demagnetization suppression control gain setting means 901: demagnetization suppression control means 903: fixed gain Applied demagnetization suppression control means 906: dead zone 907: fixed demagnetization suppression control gain 908: switching means

Claims (14)

A power converter connected to a transformer including a magnetic polarization detector that detects DC magnetic polarization, and a power conversion device including a control device that controls an output voltage of the power converter,
A current controller that obtains a target signal of an output voltage of the power converter from a current flowing through the power converter and a current target value; and Magnetizing means for shifting the output of the transformer, magnetizing suppression control means for obtaining a magnetizing correction voltage necessary for controlling the DC magnetism in the transformer, and a target signal of the output voltage of the power converter. And a correcting means for correcting the output voltage of the power converter with the biasing correction voltage, and controlling the output voltage of the power converter by the output voltage of the correcting means. The power converter according to claim 1,
The power conversion method according to claim 1, wherein the demagnetization suppression control means obtains the demagnetization correction voltage from a ratio of a demagnetization generation current given by the demagnetization generation means to a demagnetization detection voltage detected by the demagnetization detector. apparatus. The power converter according to claim 1 or 2, wherein:
The current controller may obtain a target signal of an output voltage of the power converter by adding a voltage of the transformer to a signal obtained from a difference between a current flowing in the power converter and a current target value. Power converter. The power converter according to any one of claims 1 to 3, wherein
The transformer and the power converter are three-phase equipment, and the current controller, the demagnetization generating means, the demagnetization suppression control means, and the correction means in the control device are provided for each phase. A power conversion device, wherein the power conversion device is provided in a power conversion device. A power converter connected to a transformer including a magnetic polarization detector that detects DC magnetic polarization, and a power conversion device including a control device that controls an output voltage of the power converter,
A current controller that obtains a target signal of an output voltage of the power converter from a current flowing through the power converter and a current target value; and Magnetizing means for shifting the output of the transformer, magnetizing suppression control means for obtaining a magnetizing correction voltage necessary for controlling the DC magnetism in the transformer, and a target signal of the output voltage of the power converter. And correction means for correcting the magnetic field with the bias correction voltage,
The demagnetization suppression control means stores a control gain as a ratio of the magnitude of the demagnetization detection voltage detected by the demagnetization detector corresponding to the magnitude of the demagnetization generation current given by the demagnetization generation means. A storage unit configured to execute the demagnetization suppression control, and determine, from among the control gains stored in the storage unit, a demagnetization generation current corresponding to the demagnetization detection voltage detected when the demagnetization suppression control is executed. A variable control gain for extracting the control gain at the time of (1) and multiplying the demagnetization detection voltage for detecting the control gain, thereby obtaining the demagnetization correction voltage. The power converter according to claim 5,
The storage means of the magnetic field generation means and the magnetic field suppression control means are time-aligned so that the storage means obtains the magnetic field detection voltage when the magnetic field generation means supplies the magnetic field generation current. A power converter. The power converter according to claim 5 or 6, wherein:
The power conversion device according to claim 1, wherein the variable control gain of the bias control unit is multiplied by the control gain extracted from the storage unit when the bias detector detects DC bias. The power converter according to any one of claims 5 to 7, wherein:
A power converter, comprising: means for erasing a storage value of the storage means by a reset signal. It is a power converter of Claim 8, Comprising:
After detecting that the reset signal has been output, the demagnetization generating means gives the demagnetization generation current, and the storage means is time-set so as to obtain the demagnetization detection voltage, and the control gain Is recalculated and stored in the storage means. The power converter according to any one of claims 5 to 9, wherein
The transformer and the power converter are three-phase equipment, and the current controller in the control device, the demagnetization generation unit, the demagnetization suppression control unit, and the correction unit are provided for each phase. Is provided,
The power converter, wherein the storage unit in the bias control unit is provided in common for three phases. The power converter according to any one of claims 5 to 10, wherein
In addition to the demagnetization suppression control means, a fixed gain demagnetization suppression control means for obtaining the demagnetization correction voltage via a constant control gain and a dead band with respect to the demagnetization detection voltage detected by the A power converter comprising: a switch for selecting one of an output of the demagnetization suppression control means and an output of the fixed gain demagnetization suppression control means. A power conversion system comprising the power conversion device according to any one of claims 1 to 11,
A power conversion system, wherein at least one of the power converters operates as a self-excited reactive power compensator that is connected to at least one AC system via at least one transformer. A power conversion system comprising the power conversion device according to any one of claims 1 to 11,
At least two of the power converters are interconnected with at least two AC systems via at least two transformers, and operate as power converters that exchange power between the at least two AC systems. Conversion system. A power conversion system comprising the power conversion device according to any one of claims 1 to 11,
As a self-excited DC power transmission system interconnected with at least two AC systems via at least two transformers, and at least two power converters are connected via bus bars, cables or overhead power transmission lines to exchange power. A power conversion system characterized by operating.

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