JP5787053B2 - Control device for three-phase V-connection converter - Google Patents

Description

  The present invention controls a PWM (pulse width modulation) converter, particularly a system in which a main circuit configuration is a V-connection and a three-level PWM converter and a PWM inverter, and suppresses DC voltage imbalance in any case. The present invention also relates to a PWM converter control device that enables stable control.

  There is a PWM converter / inverter system as a system for supplying an alternating voltage having an arbitrary amplitude and frequency to a load. In this system, an AC voltage from the system is converted into a DC voltage by a PWM converter, and the DC voltage is converted into a desired AC voltage by a PWM inverter. Such a system is an inverter for driving a motor or an uninterruptible power supply ( It is used in a wide range of fields such as UPS).

In recent years, it has become common to make the main circuit of a PWM converter / inverter into three levels from the viewpoint of reducing high frequency and loss.
FIG. 10 shows a general example of a three-phase full-bridge three-level inverter.
As shown in the figure, four semiconductor switches S1 to S4 corresponding to one are provided, and a direct current capacitor is connected in series to the direct current portion and divided into two.

  In FIG. 10, when S1 and S2 are turned on, positive voltage + ED1 (DC midpoint reference) is output, when S2 and S3 are turned on, 0 voltage is output, and when S3 and S4 are turned on, negative voltage -ED2 is output. To do. Thus, arbitrary voltage output is enabled by combining the three states. Further, there are merits such that the three levels make it possible to reduce the harmonics of the output voltage, to reduce switching loss, and to facilitate high voltage and large capacity.

  One of the problems of the three-level converter is suppression of voltage sharing imbalance (also simply referred to as DC voltage imbalance or DC imbalance) of the DC capacitor divided into two. That is, when ED1 and ED2 should be equal to each other, when S2 and S3 are turned on and 0 voltage is output, a current flows through the midpoint of the DC capacitor. This means that the potential at the DC midpoint changes, and imbalance occurs in ED1 and ED2. Such DC voltage imbalance becomes prominent depending on the type of load. Not only does the inverter not be able to output the voltage as commanded, but the voltage exceeding the withstand voltage is applied to the main circuit element, and the device is destroyed in the worst case. Problems arise. As described above, in the three-level converter, some measure for suppressing the DC voltage imbalance is essential.

Thus, for example, there is a method (first method) as shown in FIG.
Here, a sine wave having a frequency 6 times the output is added to the output phase voltage command of the inverter, and this is used as a true output phase voltage command to perform PWM comparison to generate a voltage. This is an operation of changing the time for outputting the zero voltage, and thereby the current flowing through the DC midpoint is changed to suppress the DC voltage imbalance. Since the amplitude of the sine wave of 6 times frequency is calculated by inputting the deviation between ED1 and ED2 to the PI controller 12, the amplitude of the sine wave can be obtained so that ED1 and ED2 are equal, and the DC voltage imbalance can be obtained. Can be suppressed. Although a sine wave is added to the output phase voltage command, the frequency of the sine wave is 6 times the output frequency, so this operation does not change the output line voltage of the inverter, and it affects the load. There is no.

FIG. 12 is an explanatory diagram for explaining the method (second method) disclosed in Patent Document 2. FIG.
Here, the correction amount Δe is calculated from the respective voltages Vd1 and Vd2 of the DC capacitors connected in series, and is added to the voltage command of each phase of the converter, thereby suppressing the DC voltage imbalance. Is. The DC voltage imbalance is suppressed by a principle similar to that shown in FIG. 11, and it can be said that it is realized by inverter control or converter control.
FIG. 13 is an explanatory diagram for explaining the method (third method) disclosed in Patent Document 3. FIG.
This is to suppress DC voltage imbalance by adding semiconductor switching elements DB1, DB2 and a reactor L1 to the main circuit and controlling on / off of the semiconductor switching elements DB1, DB2.

Japanese Patent Application Laid-Open No. 07-079574 Japanese Patent Laid-Open No. 06-233537 JP 2002-199738 A

By the way, it is known that when the main circuit configuration of the converter is V-connected, the number of semiconductor switching elements is 2/3 as compared with the three-phase full-bridge configuration, and the cost and switching loss are reduced. . Therefore, it is conceivable that the main circuit configuration is a three-level system with V-connection, but in this case as well, some measure to suppress the DC voltage imbalance is necessary.
Here, the first method described above is to add an external circuit in order to suppress DC voltage imbalance, and can be applied even if the main circuit configuration is a V connection. However, the size, loss, and cost of the external circuit to be added cannot be ignored, and there is a problem that hinders high efficiency and low cost of the system.

  The second method described above can suppress the DC voltage imbalance without changing the output line voltage of the inverter by adding the same compensation amount to the inverter phase voltage command. However, when the main circuit configuration is V-connection, only two phases can be controlled. If this method is applied, the voltage between the output lines of the inverter is changed, and a desired voltage cannot be supplied to the load, which is adversely affected. Therefore, it cannot be applied.

  From the above viewpoint, it is desirable to suppress DC voltage imbalance by converter control as in the third method described above. However, if this method is applied to a three-phase V-connection converter, the circuit has a special circuit configuration in which one phase of the three-phase V-connection converter is directly connected to the DC midpoint, and the potential at the DC midpoint is Since there is a characteristic that pulsates at the output frequency of the converter, there is no conventional example that discloses a technique for suppressing DC voltage imbalance by converter control.

  Accordingly, an object of the present invention is to provide a control device for suppressing DC voltage imbalance in a three-level converter / inverter device having a three-phase V-connection main circuit configuration.

In order to solve such a problem, the invention according to claim 1 converts the three-phase AC voltage into a DC voltage having an arbitrary magnitude by controlling on / off of the semiconductor switching elements for two phases. The input voltage of the connection type three level converter is detected, the input current amplitude command is calculated, the input current command is calculated from the input current amplitude command and the input voltage, and the input current is matched with the input current command. In a control device for a three-phase V-connection type three-level converter that performs control in response to obtaining a voltage command,

The voltage between the DC positive potential point and the DC midpoint and the voltage between the DC negative potential point and the DC midpoint of the output of the three-phase V-connection type three-level converter are detected, and the deviation between the detected values is changed to this deviation. An extraction means for removing the included ripple and extracting the DC amount of the deviation and an arithmetic means for calculating a correction amount for the phase voltage command from the extracted amount are provided, and the correction amount is added to the phase voltage command. Then, control is performed.

According to the second aspect of the present invention, the input voltage of the three-phase V-connection type three-level converter that converts the three-phase AC voltage into a DC voltage of an arbitrary magnitude by controlling on / off of the semiconductor switching elements for two phases. In addition to detection, an input current amplitude command is calculated, an input current command is calculated from the input current amplitude command and the input voltage, and control is performed by obtaining a voltage command that matches the input current with the input current command. In a control device for a three-phase V-connection type three-level converter,
The voltage between the DC positive potential point and the DC midpoint and the voltage between the DC negative potential point and the DC midpoint of the output of the three-phase V-connection type three-level converter are detected, and the deviation between the detected values is changed to this deviation. Extraction means for removing the included ripple and extracting the DC amount of the deviation, and calculation means for calculating a correction amount for the phase input current command from the extracted amount are provided, and the correction amount is used as the phase input current command. Control is performed by adding to the above.

In the first or second aspect of the present invention, a device capable of moving average processing is used as the extraction means, and the output of the three-phase V-connection type three-level converter is subjected to moving average processing between a DC positive potential point and a DC midpoint. And the voltage deviation between the DC negative potential point and the DC middle point can be output as a DC amount of the deviation by removing the ripple included in the deviation (invention of claim 3), or A low-pass filter is used as the extracting means, and the voltage between the DC positive potential point and the DC midpoint of the output of the three-phase V-connection type three-level converter obtained through this low-pass filter, and between the DC negative potential point and the DC midpoint. The voltage deviation can be output as a DC amount of the deviation by removing the ripple included in the deviation (invention of claim 4).

According to the invention of claim 5, the input of a three-phase V-connection type three-level converter that converts a three-phase AC voltage into a DC voltage of an arbitrary magnitude by controlling on / off of the semiconductor switching elements for two phases. Detects the voltage, calculates the input current amplitude command, calculates the input current command from the input current amplitude command and the input voltage, and obtains and controls the voltage command that matches the input current with the input current command. In the control device for a three-phase V-connection type three-level converter, the voltage between the DC positive potential point and the DC midpoint and the voltage between the DC negative potential point and the DC midpoint of the output of the three-phase V-connection type three-level converter input current amplitude command correction means of deviation ripple component contained in the deviation is removed from the extracted DC amount of the deviation, it corrects the input current amplitude command based on the DC amount and the extracted Characterized by providing.
In the fifth aspect of the invention, the input current amplitude command correcting means converts the deviation between the voltage between the DC positive potential point and the DC midpoint of the converter and the voltage between the DC negative potential point and the DC midpoint. An amplitude correction basic amount calculating means for calculating the input current amplitude correction basic amount based on the extracted DC amount, and the polarity of the input voltage are discriminated by removing the included ripple and extracting the deviation DC amount. And a polarity discriminating means for correcting the amplitude of the input current in accordance with the polarity of the input voltage (invention of claim 6).

  According to the present invention, in a three-level converter / inverter device having a three-phase V-connection main circuit configuration, it is possible to suppress DC voltage imbalance without adding an external circuit in particular, and a low-cost and highly reliable control device Can be provided.

The block diagram which shows the 3 level PWM converter * inverter apparatus of 3 phase V connection. The block diagram which shows the structure of the converter control apparatus of FIG. The block diagram which shows the specific example of the input current control means of FIG. The block diagram which shows the specific example of the correction amount calculating means of FIG. The block diagram which shows another example of the converter control apparatus of FIG. Explanatory drawing for demonstrating operation | movement of this invention. The block which shows another example of the converter control apparatus of FIG. 7 is a block diagram showing a specific example of the input current amplitude command correction means. The block diagram which shows the specific example of the amplitude correction value calculating means of FIG. The circuit diagram which shows the general example of the three-level inverter of a three-phase full bridge. The block diagram which shows a 1st prior art example. The block diagram which shows a 2nd prior art example. The block diagram which shows a 3rd prior art example.

FIG. 1 is a block diagram showing a three-level V-connected three-level PWM converter / inverter device to which the present invention is applied. SI is an input system, CN is a converter, and IN is an inverter.
As shown in FIG. 1, the three-phase V-connected three-level converters CN and IN have semiconductor switching elements for only two of the three phases, and the remaining one phase is directly connected to the middle point of the capacitor. It has a structure. In addition, this is an example in which a reverse blocking IGBT (insulated gate bipolar transistor) is used as the semiconductor switching element.

FIG. 2 shows an example of the converter control device in FIG.
First, the input current amplitude command value calculating means 1 calculates the input current amplitude command value of the converter CN shown in FIG. 1 from the deviation between the DC voltage command value and the detected value. The input current amplitude command value calculation means 1 is generally configured by P (proportional) control and PI (proportional / integral) control. Next, the separately detected input line voltage is converted into a phase voltage by the line voltage-phase voltage conversion means 2. The input current amplitude command value obtained by the input current amplitude command value calculation means 1 is multiplied by the input phase voltage obtained by the line voltage-phase voltage conversion means 2 to obtain an instantaneous value of the input current command.

  The instantaneous value of the input current command is input to the input current control means 4A and 4B, and an output voltage command value of the converter is obtained so that the input current becomes as the command value. The correction amount calculated by the correction amount calculation means 5 is added to the output voltage command value of the converter to obtain a final voltage command value. The modulation signal creating means 7 creates a modulation signal for a three-level converter from the final voltage command value. This modulation signal is compared in magnitude with a triangular wave carrier, and a pulse command to be given to the semiconductor switching element (IGBT) is created.

FIG. 3 shows a specific example of the input current control means in FIG.
A subtractor 11 obtains a deviation between the U-phase input current command and the detected value, and a multiplier 14 multiplies the deviation by a proportional gain to calculate a correction amount. Instead of these calculations, the input current deviation may be obtained by a PI controller (regulator). Next, the subtractor 12 obtains a difference between the U-phase input voltage and the V-phase input voltage, and the subtractor 13 subtracts the correction amount from the difference to obtain a U-phase voltage command value. This correction amount works when the detected input current value deviates from the command value, and this allows the input current to be controlled in a sinusoidal shape with a power factor of 1. Furthermore, if active power corresponding to the state of the DC voltage is supplied, the DC voltage can be controlled according to the command value. The above is the case of the U phase, but the case of the W phase is obtained in the same manner.

  The above is the basic control principle of the three-level V-connection three-level converter. In the present invention, a common correction amount for suppressing DC voltage imbalance is added to the phase voltage command of each phase of the converter. In other words, in a three-level V-connected three-level PWM converter / inverter device, if the inverter is controlled to suppress DC voltage imbalance, it is necessary to manipulate the output line voltage of the inverter, and the load is in accordance with the command value. Therefore, the DC voltage imbalance is suppressed by converter control.

FIG. 4 shows a specific example of the correction amount calculation means in FIG.
The subtractor 51 calculates a deviation between the upper detection value ED1 and the lower detection value ED2 of the DC voltage divided into two by the capacitors C4 and C5 at the output of the converter CN shown in FIG. Ripple included in the deviation is removed, and the DC amount of the deviation is extracted. This DC amount is supplied to the PI controller 53, and a correction amount (such that the deviation between the DC intermediate voltage upper detection value ED1 and the DC intermediate voltage lower detection value ED2 becomes 0, that is, eliminates the DC voltage imbalance. Compensation amount) is obtained as an output of the PI controller 53. By adding this correction amount to the voltage command of each phase, the converter controls the DC intermediate voltage according to the command value, and operates so as to eliminate the DC voltage imbalance.

The direct current amount extraction means 52 provided in the correction amount calculation means 5 is newly added to correspond to a V-connection converter and can be said to be a feature of the present invention. That is, as described with reference to FIG. 1, the V-connected converter has a structure in which only one of the three phases is directly connected to the direct current midpoint.
Since the input current is controlled so as to be a sine wave having the same phase as the phase voltage of each input phase, during operation, the DC current passes through a phase (V phase in FIG. 1) directly connected to the DC midpoint. A current having the same frequency as the input frequency flows through the point. This indicates that during operation, the DC midpoint potential constantly pulsates at the same cycle as the input frequency. For this reason, the DC intermediate voltage upper detection value ED1 and the DC intermediate voltage lower detection value ED2 and the respective deviations of the waveforms include ripples of the input frequency. This phenomenon is remarkably caused by the structure in which only one of the three phases is directly connected to the DC midpoint.

  On the other hand, in the case of a three-phase full-bridge three-level converter, since there are switching arms in all three phases, the direct current midpoint and the input voltage are not directly connected. Since all the current to the DC midpoint flows through the intermediate phase switching elements of each phase, the current to the DC midpoint has a frequency that is six times the input frequency. Therefore, the potential of the DC midpoint pulsates at a frequency six times the input frequency, but the impedance of the DC capacitor decreases as the frequency becomes higher, and there is no phase directly connected to the DC midpoint. In comparison, since the amplitude of the current flowing through the DC midpoint is also small, the potential pulsation at the DC midpoint of the three-phase full-bridge three-level converter is sufficiently smaller than that of the V-connection converter. Thus, in the DC voltage unbalance suppression control in the V-connection converter, means for compensating for the influence of the DC midpoint potential fluctuation of the input frequency is essential, and this is the reason why the DC amount extraction means 52 is provided in FIG. It is.

  If the case where no DC amount extraction means is provided is considered, the DC imbalance correction amount includes ripples of the input frequency component. By the way, considering the operation of the V-connection converter, the ripple of the input frequency component of the DC voltage always occurs and cannot be compensated for. Therefore, even if the DC imbalance correction amount is calculated while including the ripple component, not only the ripple components of the DC intermediate voltage upper detection value ED1 and the DC intermediate voltage lower detection value ED2 can be compensated, but also the voltage command of the converter. Includes ripples of the input frequency component, which may adversely affect the stable operation of the converter. On the other hand, the three-phase full-bridge three-level converter has little influence on the control performance because the potential fluctuation itself at the DC midpoint is small even without the DC amount extracting means.

  As described above, in the present invention, the DC amount extracting means is provided in the correction amount calculating means, and the DC imbalance correction is performed after removing the ripple components of the DC intermediate voltage upper detection value ED1 and the DC intermediate voltage lower detection value ED2. The amount is calculated. Since the DC imbalance correction amount is a DC amount, adding the correction amount to the converter voltage command does not adversely affect the stability of the converter control. The ripple contained in the DC intermediate voltage upper detection value ED1 and the DC intermediate voltage lower detection value ED2 cannot be compensated, but the average value of both can be controlled so as to always match, and steady DC imbalance can be suppressed. is there.

Further, as a specific method for realizing the direct current amount extraction means, for example, moving average processing can be considered.
If the detected values are sampled and averaged during a period that is an integral multiple of the input voltage period, the ripple of the input frequency component can be completely removed. As the sampling period for calculating the average value, it is considered that 2 or 3 times the input period is appropriate. This is because if the sampling period is too short, the ripple removal effect is reduced when the input frequency is changed, and if the sampling period is too long, control responsiveness is deteriorated.

Furthermore, it is conceivable to use a low-pass filter for the DC amount extraction.
In this case, the cut-off frequency may be about 1/5 to 1/10 of the input frequency. The smaller the cut-off frequency, the higher the ripple removal effect, but there is a risk that control will become unstable due to a delay.
In general, the moving average process can exhibit a large ripple removing effect without deteriorating control responsiveness and stability. However, since a large memory area for storing the sample values is required for calculating the average value, the calculation load of the CPU becomes larger than that of the low-pass filter. Therefore, it may be determined in consideration of required control performance, CPU performance, and the like.

Here, the reason why the DC voltage imbalance can be suppressed by the correction amount calculated by the correction amount calculation means of FIG.
The DC imbalance correction amount is a DC amount determined according to a deviation between the upper detection value ED1 and the lower detection value ED2 of the DC intermediate voltage. When the DC imbalance correction amount is added to the voltage command of the converter, a DC amount is generated in the converter output voltage, and thus a DC amount is also generated in the input current.
The fact that a DC amount is also generated in the input current changes the total amount of current flowing to the DC midpoint during one cycle, which means that the potential at the DC midpoint changes. Therefore, by adding the DC amount to the output voltage of the converter, the potential at the DC midpoint can be manipulated to control the DC voltage imbalance. Thus, the correction amount calculation means 5 plays a role of automatically adjusting the correction amount to be added to the converter voltage command so that there is no steady imbalance in the DC voltage.

FIG. 2 shows an example in which the present invention is applied to the converter control based on the instantaneous value of the phase voltage. However, there are various types of converter control such as coordinate conversion and control calculation.
However, since the present invention simply adds the correction amount to the finally calculated converter voltage command, it can be applied regardless of the converter control method.

FIG. 5 shows another embodiment of the present invention.
Here, the feature is that the correction amount by the correction amount calculation means 5 is added to the phase current command of each phase, and the others are the same as in FIG. The phase current command to which the DC imbalance correction amount is added is input to the input current control means 4A and 4B, and the DC imbalance correction amount is added to the sinusoidal phase current command, resulting in a current according to the new phase current command. Such a converter voltage command is obtained.
That is, the example of FIG. 5 is different from the case of FIG. 2 in the position where the correction amount is added, but is the same in that it controls the DC amount superimposed on the input current. Therefore, according to the same principle as in FIG. 2, the DC intermediate voltage can be controlled in accordance with the command value, and the DC voltage imbalance can be suppressed. 5 can be applied as it is to the correction amount calculation means 5 in FIG.

Generally, the voltage range that can be output by the power converter is determined by the magnitude of the DC voltage. Therefore, when a voltage command that is equal to or higher than the upper limit voltage that can be output by the power converter is provided, the power converter cannot output a voltage that is in accordance with the command value, and the control performance deteriorates, for example, the output voltage is distorted.
In FIG. 2 and FIG. 5, the correction amount is added to the converter phase voltage command or the phase current command, but as a result, both generate a DC amount in the output voltage of the converter. Therefore, depending on the magnitude of the correction amount, as shown in FIG. 6, there may be a case where the addition of the correction amount exceeds the voltage range in which the voltage command can be output (see the dotted line in FIG. 6).

  In such a case, not only the DC voltage imbalance cannot be suppressed, but also the control performance of the converter is remarkably deteriorated such that the DC voltage cannot be controlled according to the command value and a large distortion occurs in the input current. For example, when a half-wave rectification load is connected to the inverter output, a DC imbalance occurs. However, as the half-wave rectification load increases, the DC voltage imbalance correction amount increases and the above-described phenomenon tends to occur. Therefore, in the methods of FIGS. 2 and 5, there is an upper limit in the range in which the DC voltage imbalance can be suppressed, and it may be impossible to apply depending on the type and size of the load.

FIG. 7 shows an example that can cope with such a case.
This is the same as that shown in FIG. 5 in that the current command is corrected so as to compensate the DC imbalance, but the input current amplitude command value correcting means 8 for correcting the current command for each phase is used. It is different in the way. Also, the correction amount calculation algorithm is different.
FIG. 8 shows a specific example of the input current amplitude command value correcting means. Although only one phase is shown in the figure, it goes without saying that the other phases are configured in the same manner.

In FIG. 8, the input current amplitude command value of each phase is output by adding or subtracting the correction amount calculated by the amplitude correction value calculation unit 81 to the input current amplitude command value output from the calculation unit 1.
What is characteristic here is that the amplitude correction value calculation means 81 outputs different amplitude correction amounts depending on the polarity of the input phase voltage detection value. That is, in FIG. 2 and FIG. 5, the input current amplitude command value correcting means is not provided, and an instantaneous phase current command is created by multiplying the input current amplitude command value as it is by the phase voltage detection value. As a result, the phase current command becomes a sine wave with positive and negative symmetry synchronized with the input voltage, and the DC intermediate voltage can be controlled in accordance with the command value, and the input power factor of the converter can be controlled in a sine wave.

  On the other hand, in FIG. 8, the correction amount added to the input current amplitude command value is changed according to the polarity of the input phase voltage detection value, that is, the polarity of the instantaneous phase current command. Therefore, the phase current command has a sinusoidal waveform synchronized with the input voltage, but a positive and negative asymmetric sine wave. The fact that the input current becomes asymmetrical between positive and negative indicates that the sum of the current flowing into and out of the DC midpoint per input cycle changes, and by appropriately changing the positive and negative amplitudes of the input current command It becomes possible to control so as to suppress the DC imbalance.

FIG. 9 shows a specific example of the amplitude correction value calculation means 81 that outputs different amplitude correction amounts depending on the polarity of the input phase voltage detection value so as to suppress the DC voltage imbalance.
First, the deviation between the upper detection value ED1 and the lower detection value ED2 of the DC intermediate voltage divided into two is input to the DC amount extraction means 84, and the ripple component of the input frequency included in the DC voltage detection value is extracted. Similar to FIGS. 2 and 5, this is a configuration necessary to support the V-connection converter.

  Then, the direct current amount obtained by the direct current amount extraction means 84 is input to the PI controller 85, and the amplitude correction value base amount is calculated. On the other hand, the polarity discriminating means 86 is a means for obtaining the polarity information of the input signal, and outputs “1” when the input signal is 0 or more and “−1” when it is negative. Here, an input phase voltage detection value is input as an input signal. As a result, the input current amplitude correction value is obtained by multiplying the amplitude correction value base amount by the polarity information.

As described above, in FIG. 9, the polarity of the amplitude correction value is changed according to the polarity of the input phase voltage detection value. This means that the positive amplitude and the negative amplitude of the input phase current command are individually operated, and as a result, a positive and negative asymmetric sinusoidal input phase current command can be obtained. At the same time, the amplitude correction value base amount is automatically changed according to the DC imbalance state, so that it can be controlled to have no DC imbalance.
In FIG. 9, the positive amplitude and the negative amplitude of the input phase current command are individually operated. However, the amplitude is corrected only when the input phase current command is positive. Even if the correction is not performed, the same effect can be obtained.

Here, the advantages of what is shown in FIG. 7 over those shown in FIGS. 2 and 5 will be described. Before that, the control principle of the PWM converter will be described first.
If the case where the output voltage of the PWM converter is equal to the voltage at the input voltage detection point is considered, the potential difference between both ends of the filter reactor in FIG. 1 is 0, so no current flows through the filter reactor. This indicates that there is no power supply to the direct current section. If the direct current voltage is in accordance with the command value, the converter only needs to output the same voltage as the input voltage.

For example, when the DC voltage decreases, for example, when the load on the inverter increases rapidly, the converter is controlled so that a current having the same phase as the input voltage flows, and active power is supplied from the input to the DC unit. At this time, the voltage command of the converter can be expressed by the following equation (1).
vcnv = vin−Ldi / dt (1)
Here, vcnv is an output voltage command of the converter, vin is an input voltage, L is an inductance value of the filter reactor, and i is an input current.

  From the above equation (1), when the converter supplies active power to the DC section, it is sufficient to output a sine wave whose phase and amplitude are changed with respect to the input voltage. In general, the filter reactor is designed so that the% impedance is about 5% to 10%. Therefore, considering from the equation (1), even if the input current, that is, the active power supplied to the DC unit, changes, the voltage output from the converter hardly changes. Therefore, it is safe to assume that the converter always outputs a voltage having the same amplitude as the input voltage and controls the effective power supplied to the DC unit by controlling the phase difference from the input voltage.

  The invention of FIG. 7 suppresses DC imbalance by appropriately adjusting the amplitude of the input current. That is, by changing the phase of the output voltage of the converter with respect to the input voltage as described above, the DC voltage is controlled as instructed and the DC imbalance is suppressed. That is, no DC amount is generated in the voltage command of the converter, and it is not necessary to change the amplitude of the converter output voltage. As a result, the voltage range that can be output by the converter is not limited, and the invention of FIG. 7 can be applied to any load.

  On the other hand, since the correction amount to the current command is switched according to the polarity of the current command, the configuration for calculating the correction amount is complicated. Therefore, when it is desired to reduce the calculation load of the CPU, it is desirable to select a method according to the situation, such as using the inventions of FIGS.

DESCRIPTION OF SYMBOLS 1 ... Input current amplitude command value calculating device, 2 ... Line voltage-phase voltage converting means, 3A, 3B, 14, 87 ... Multiplier, 4A, 4B ... Input current control means, 5 ... Correction amount calculating means, 52, 84 ... DC amount extracting means, 53, 85 ... PI controller, 6A, 6B, 61A, 61B ... adder, 7 ... modulation signal generating means, 8 ... input current amplitude command value correcting means, 81 ... amplitude correction value calculating means 11, 12, 13, 51, 82, 83 ... subtractor, C1, C2, C3 ... capacitor, SI ... input system, CN ... converter, IN ... inverter.

Claims (6)

By controlling on / off of the semiconductor switching elements for two phases, the input voltage of a three-phase V-connection type three-level converter that converts a three-phase AC voltage into a DC voltage of an arbitrary magnitude is detected, and the input current amplitude A three-phase V-connection type three-level control that calculates a command, calculates an input current command from the input current amplitude command and the input voltage, and obtains a voltage command that matches the input current with the input current command. In the control device of the converter,
The voltage between the DC positive potential point and the DC midpoint and the voltage between the DC negative potential point and the DC midpoint of the output of the three-phase V-connection type three-level converter are detected, and the deviation between the detected values is changed to this deviation. An extraction means for removing the included ripple and extracting the DC amount of the deviation and an arithmetic means for calculating a correction amount for the phase voltage command from the extracted amount are provided, and the correction amount is added to the phase voltage command. And a control device for a three-phase V-connection type three-level converter. By controlling on / off of the semiconductor switching elements for two phases, the input voltage of a three-phase V-connection type three-level converter that converts a three-phase AC voltage into a DC voltage of an arbitrary magnitude is detected, and the input current amplitude A three-phase V-connection type three-level control that calculates a command, calculates an input current command from the input current amplitude command and the input voltage, and obtains a voltage command that matches the input current with the input current command. In the control device of the converter,
The voltage between the DC positive potential point and the DC midpoint and the voltage between the DC negative potential point and the DC midpoint of the output of the three-phase V-connection type three-level converter are detected, and the deviation between the detected values is changed to this deviation. Extraction means for removing the included ripple and extracting the DC amount of the deviation, and calculation means for calculating a correction amount for the phase input current command from the extracted amount are provided, and the correction amount is used as the phase input current command. And a control device for a three-phase V-connection type three-level converter. Using the device capable of moving average processing as the extracting means, the voltage between the DC positive potential point and the DC midpoint and the DC negative potential point and DC midpoint of the output of the three-phase V-connection type three-level converter subjected to the moving average processing 3. The control device for a three-phase V-connection type three-level converter according to claim 1, wherein the deviation of the voltage between them is output as a DC amount of the deviation by removing a ripple included in the deviation. . A low-pass filter is used as the extraction means, and the voltage between the DC positive potential point and the DC midpoint of the output of the three-phase V-connection type three-level converter obtained through this low-pass filter, and between the DC negative potential point and the DC midpoint. 3. The control device for a three-phase V-connection type three-level converter according to claim 1, wherein the voltage deviation is output as a direct current amount of the deviation by removing a ripple included in the deviation . By controlling on / off of the semiconductor switching elements for two phases, the input voltage of a three-phase V-connection type three-level converter that converts a three-phase AC voltage into a DC voltage of an arbitrary magnitude is detected, and the input current amplitude A three-phase V-connection type three-level control that calculates a command, calculates an input current command from the input current amplitude command and the input voltage, and obtains a voltage command that matches the input current with the input current command. In the control device of the converter,
The ripple included in this deviation is removed from the deviation of the voltage between the DC positive potential point and the DC middle point and the voltage between the DC negative potential point and the DC middle point of the output of the three-phase V-connection type three-level converter. A control device for a three-phase V-connection type three-level converter, characterized in that input current amplitude command correction means is provided for extracting a DC amount of deviation and correcting the input current amplitude command based on the extracted DC amount . The input current amplitude command correcting means adjusts this deviation from the deviation of the voltage between the DC positive potential point and the DC middle point and the voltage between the DC negative potential point and the DC middle point of the output of the three-phase V-connection type three-level converter. An amplitude correction basic amount calculating means for calculating the input current amplitude correction basic amount based on the extracted DC amount, and the polarity of the input voltage are discriminated by removing the included ripple and extracting the deviation DC amount. 6. The control device for a three-phase V-connection type three-level converter according to claim 5, further comprising a polarity discriminating means for performing amplitude correction of the input current according to the polarity of the input voltage.

Images