JPH08322269A - Controller for power converter - Google Patents

Abstract

PURPOSE: To suppress the wide fluctuation of a DC voltage by accurately detecting the electric energy flowing to a DC side through a power converter and precisely processing the electric energy in a normal state or even when such a disturbance occurs that an unbalanced voltage is generated on the AC side of the power converter or an unbalanced current flows to the AC side of the converter. CONSTITUTION: A controller for a power converter in which two converters 1 and 2 which convert a direct current or alternating current into an alternating current or direct current is provided with a current detecting means 5 which detects the AC-side current of the converter 1, voltage detecting means 9 which detects a pulsative voltage on the AC side of the converter 1, power detecting means 10 which detects the electric power flowing through the converter 1 from the current and voltage detected by the detecting means 5 and 9, and means which corrects commands to the converters 1 and 2 so that the same electric power as the detected electric power flowing through the converter 1 can flow through the converter 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a power converter, and more particularly to a control device for a power converter that suppresses voltage fluctuations in the DC parts of two power converters.

[0002]

2. Description of the Related Art Conventionally, a control device for a power converter that suppresses voltage fluctuations in the DC parts of two power converters has been described in JP-A-62-9414 and JP-A-3-245793. Known technology is known. The technology of the former publication detects active power flowing to the DC side through a converter, and suppresses DC voltage fluctuations by adding a compensation signal obtained from the active power detected here to the active current command from the voltage control circuit. In the technique of the latter publication, a current equivalent to the input average current of the inverter is obtained from the output current of the inverter, and a compensation signal obtained from this current value is added to the current command value of the converter to correct it. However, it is intended to suppress the DC voltage fluctuation.

[0003]

In the prior art, the technique of the former publication accurately detects the inflow power of the converter when the unbalanced current or unbalanced voltage occurs and the sine wave steady state is lost. It is difficult to do so, and there is a risk that the control will not be stable due to a detection error. In addition, because the detection of power is active power, when power repeatedly flows in and out instantaneously,
It is difficult to suppress voltage fluctuation due to a control delay or the like. Then, in order to suppress the overvoltage, the direct current voltage is compared with the set value, and when the switching element is operated according to the magnitude relationship, the switching frequency of the element changes, or due to the delay for processing after the voltage changes,
There is a problem that voltage fluctuation cannot be suppressed sufficiently. Further, the technique of the latter publication does not consider accurately detecting the power flowing into the converter when an unbalanced current or an unbalanced voltage occurs.

An object of the present invention is to accurately detect the amount of electric power flowing into the DC side through the converter, and to accurately, even under normal conditions and when an unbalanced state occurs on the AC side of the converter. An object of the present invention is to provide a controller for a power converter that is suitable for processing and suppressing fluctuations in DC voltage.

[0005]

In order to achieve the above object, current detecting means for detecting a current on the AC side of a converter,
Voltage detection means for detecting the voltage on the AC side, power detection means for detecting the passing power flowing through the converter from the current and voltage detected by the detecting means, and the same power as the detected passing power on the other side. Means are provided for modifying the command of the converter to flow through the converter. Further, a current detecting means for detecting an alternating current of the converter, a voltage estimating means for estimating a voltage of the alternating current using a gate signal for driving a semiconductor element of the converter and a detected direct current voltage, and the detecting means. The electric power detection means for detecting the passing electric power flowing through the converter from the current detected by the electric current and the voltage estimated by the estimating means, and the same electric power as the detected passing electric power is caused to flow through the other converter. Means are provided for modifying the command of the transducer. In addition, a current detection unit that detects an AC side current of a converter connected to the electric motor, a voltage detection unit that detects an AC side voltage, and a current and a voltage detected by the detection unit via the converter. A power detection unit that detects the passing power that flows and a unit that corrects the command of the converter so that the same power as the detected passing power flows through the other converter. In addition, it has two converters for converting direct current and alternating current, each of which is connected in parallel via a reactor.
A pair of power converters, a current detecting means for detecting an alternating current of each converter, a voltage detecting means for detecting a voltage on an alternating current side of an inductive element connected between an alternating current and a reactor, and A power detection unit that detects the passing power that flows through the two corresponding converters based on the current and the voltage that are detected by the detection unit, and a power that is the same as the detected passing power that flows through the other two converters. Thus, means for correcting the command of each converter is provided. Further, the passing electric power detected by the electric power detecting means is calculated by using the pulse-like changing voltage detected by the voltage detecting means or the pulse-like changing voltage estimated by the voltage estimating means and the three-phase current. Further, the power detection means is connected to the DC circuit of the power converter and processes the DC power, and the power detection means has the instantaneous inflow power flowing into one of the power converters exceeding the processing capability of the other power converter. Then, the instantaneous inflow power is processed by the power processing means. Alternatively, the difference between the instantaneous inflow power flowing into one of the power converters and the power that can be processed by the other power converter is detected, and power that exceeds the power that can be processed by the other power converter is processed by the power processing means. To do. Further, the power processing means has a direct current power self-extinguishing type semiconductor element, and is provided with means for changing the conduction ratio of the semiconductor element according to the amount of power exceeding the power that can be processed by the power converter. The amount of electric power is processed based on the conduction ratio.

[0006]

In the present invention, the instantaneous passing power is detected from the AC side current of the converter and the AC side pulse changing voltage, so that the instantaneous passing power can be accurately measured even in the normal state and the three-phase unbalanced state. If the command of the converter control device of the other converter is corrected according to the detected value, the voltage fluctuation of the DC part can be effectively suppressed, and the capacity of the DC smoothing capacitor C can be reduced. can do. In addition, since the voltage on the AC side of the converter is estimated from the DC voltage detected as the pulse command, the instantaneous passing power can be accurately estimated without using a voltage detector that directly detects the AC voltage, and the size is small. It is possible to suppress the fluctuation of the DC voltage even in the system having no AC voltage detection means. In addition, the instantaneous passing power is detected from the AC side current and AC side voltage of the converter connected to the wire wound induction motor, and the excess inflow power is applied to the load before the DC voltage fluctuates according to the detected value. By treating it, it is possible to prevent the increase of DC voltage.Therefore, make sure that the withstand voltage of the switching elements used in the converter is as small as the DC voltage determined from the output voltage of the converter in the normal operating range. make use of,
The wound-rotor induction motor can be safely operated even when AC is unbalanced. Also, when a reactor for balancing the current is connected to the output end of the converter and the power converter is connected in parallel, the voltage is detected at the common position and the common voltage detection value is used. Since the instantaneous passing power of the converter is detected, it is possible to detect the instantaneous passing power of a plurality of converters connected in parallel with a small number of voltage detecting means and suppress the DC voltage fluctuation. Also, up to the maximum power that can be processed by the converter, the converter control unit controls the converter to output AC,
By processing the power that cannot be processed due to the converter specifications with a load, fluctuations in DC voltage can be suppressed even when the converter capacity is small, so the converter and DC smoothing capacitor can be downsized. it can. In addition, by controlling each converter based on the instantaneous passing power detected from the three-phase current and output voltage of each of the two converters, fluctuations in the DC voltage occur due to the control delay of the converter control device. Can be prevented, and the DC voltage can be further stabilized.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a control device for a power converter showing an embodiment of the present invention. In the present embodiment, the power converter is such that the DC portion of the converter 2 having the same configuration as the converter 1 including switching elements connected in a three-phase bridge is connected via the smoothing capacitor C, and AC 3 to AC 4 Or AC 4 to AC 3
To transfer power to. A magnetic coupling element T1 such as a transformer is provided between the converter 1 and the AC 3, and a magnetic coupling element T2 such as a transformer is provided between the converter 2 and the AC 4. Further, the control device includes a current detector 5 that detects three-phase currents Iu1, Iv1, and Iw1, a current detector 6 that detects three-phase currents Iu2, Iv2, and Iw2, and a gate drive signal 12 of the converter 1.
, A converter controller 7 for generating the gate drive signal 13 of the converter 2, a voltage detector 9 for detecting the output voltages Vu1, Vv1, Vw1 of the converter 1, and output voltages Vu1, Vv1. , Vw1 and three-phase current Iu
1, a power detection device 10 for detecting an instantaneous power from Iv1, Iw1, and a DC voltage control device 11 for detecting a voltage Ed across a DC smoothing capacitor C and generating a command to keep the voltage constant. Now, when the converters 1 and 2 are actuated by the gate drive signals 12 and 13, the three-phase current Iu is supplied from the alternating current 4 to the converter 2 via the magnetic coupling element T2.
2, Iv2, Iw2 flow in. The three-phase current is converted into a DC current Id by the converter 2, charges the DC smoothing capacitor C, and is supplied to the converter 1. The direct current Id is converted into three-phase currents Iu1, Iv1, and Iw1 by the converter 1, and is output to the alternating current 3 via the magnetic coupling element T1. At this time, the three-phase current Iu output from the converter 1
1, Iv1, Iw1 are detected by the current detector 5, and the converter control device 7 is used by using the error between the three-phase current and the current command.
The gate drive signal 12 is generated by the three-phase current I
Pulse width modulation control is performed so that u1, Iv1, and Iw1 are sinusoidal currents. The DC voltage controller 11 detects the voltage across the DC smoothing capacitor C, that is, the DC voltage Ed, operates so that this voltage becomes constant, and issues a command to the converter controller 8. Three-phase current Iu2 input to the converter 2,
Iv2 and Iw2 are detected by the current detector 6, and the converter control device 8 creates the gate drive signal 13 based on the three-phase current and the command from the DC voltage control device 11, and the three-phase currents Iu2 and Iv2. , Iw2 is controlled to be a sine wave current by pulse width modulation control. Here, the converter control devices 7 and 8 include an AC control for creating a pulse width modulation signal by proportional-plus-integral control using an error between the detected three-phase current and the three-phase AC current command, and the detected three-phase. The current is converted into coordinates by three-phase / two-phase conversion, converted into a direct current amount, and direct current control is used to generate a pulse width modulation signal by proportional integral control using an error from the direct current command. On the other hand, in the converter 1,
Output voltage Vu output from the converter 1 by the voltage detector 9
1, Vv1, Vw1 are detected, and the instantaneous power passing through the converter 1 is detected by the power detection device 10 using the three-phase currents Iu1, Iv1, Iw1 described above, and this is sent to the converter control device 8. Is converted into a value based on the command and output, and the command of the DC voltage control device 11 issued to the converter control device 8 is corrected. Here, in order to convert the detected power to the current command base used for the current control, for example, a method of dividing the power by the AC side voltage is applied.

Next, the operation of the power detection device 10 will be described with reference to FIGS. 2 and 3. FIG. 2 is an explanatory diagram of current and voltage waveforms detected by the current detector 5 and the voltage detector 9 according to the present embodiment, and FIG. 3 shows a detection result by the power detection method according to the present embodiment, as well as conventional power consumption. It is an explanatory view of passing electric power detection showing a detection result by a detection method. In this embodiment,
As shown in FIG. 2, at the output terminal of the converter 1, three-phase currents are detected in a sine wave shape and three-phase voltages are detected in a pulse shape. For each detected value, the current is Iu1, Iv1, Iw
1, and the voltages are Vu1, Vv1, and Vw1, the converter 1
The instantaneous electric power P passing through is expressed by (Equation 1) or (Equation 2).

[Equation 1]

[Equation 2] When the three-phase currents Iu1, Iv1, Iw1 of the converter 1 detected by the current detector 5 and the voltages Vu1, Vv1, Vw1 of the converter 1 detected by the voltage detector 9 are input to the power detection device 10, power is supplied. The detection device 10 calculates the instantaneous power P passing through the converter 1 according to (Equation 1) or (Equation 2), converts it into a command-based value for the converter control device 8, and outputs it. Here, in the power detection device 10, the voltage detected by the voltage detector 9 is a voltage that changes in a pulsed manner, the line-to-line voltage between the two phases is calculated from the detected pulsedly changed voltage, and this line-to-line voltage is calculated. The passing power passing through the converter 1 is detected using the voltage and the three-phase current detected by the current detector 5. The command of the DC voltage control device 11 is corrected by this value. In this embodiment, the voltage on the alternating current side and the current on the alternating current side are used to detect the electric power, but a current detector is installed on the direct current side of the converter 1 to detect the direct current Id and detect the detected direct current. The instantaneous passing electric power P can be detected by (Equation 3) using the voltage Ed.

(Equation 3)

FIG. 3 shows the electric power passing through the converter 1 when a three-phase unbalanced state (for example, a one-phase ground fault) occurs on the AC3 side. Here, the horizontal axis represents time, and the vertical axis represents the time integrated value of the passing power when the direction in which the power passes from the DC side to the AC side is positive, and this differential value corresponds to the instantaneous passing power. In the figure, Pinv represents the time integrated value of the power that actually passed through the converter 1. P2p is a conversion when the three-phase current is converted into a direct current by a three-phase two-phase conversion, and the power is estimated based on this and a two-phase direct current voltage command which is an internal value of the converter control device 7. Shows the time integrated value of the power that has passed through the converter 1, and P3p is the time integrated value of the power that has passed through the converter 1 when the power is estimated based on the three-phase voltage command and the three-phase current detection value. Show. Further, Ppul indicates a time integrated value of the electric power that has passed through the converter 1 when estimated by (Equation 1) or (Equation 2) using a voltage that changes in a pulsed manner and a three-phase current. Both P2p and P3p are detected values by the conventional detection method, and as is clear from FIG. 3, when the time integrated value of the passing power is obtained by the detecting method of P2p and P3p, the actual passing shown as the Pinv inverter passing power is shown. Compared to the time integrated value of electric power, P3p
The time integrated value of the passing electric power by the detection method of No. a is decreased from the point a, and that by the detection method of P2p is greatly decreased. This is because in the detection method of P2p and P3p, a reactor is connected between the converter 1 and the magnetic coupling element T1,
Since the output voltage of the converter 1 is corrected to the sine wave voltage and the voltage is detected, a detection delay occurs, which means that the operation of the converter 1 is not accurately captured. Therefore, with the detection method using P2p and P3p, it is not possible to suppress voltage fluctuations in the DC portion that occur when a three-phase unbalanced state occurs on the AC3 side. On the other hand, Ppul is a detection value according to the present embodiment, and as is clear from FIG. 3, the time integrated value of the passing power obtained by the Ppul detection method is the time of the actual passing power shown as the Pinv inverter passing power. It is almost equal to the integrated value. This is because, in the present embodiment, the reactor is not connected between the converter 1 and the magnetic coupling element T1 and the output voltage that changes in a pulsed manner of the converter 1 is directly detected, so that there is no detection delay and therefore the converter 1 Will accurately capture the behavior of. Therefore, in the example power detection device 10 according to the present embodiment, the estimation of the passing power is extremely accurate and coincides with the actual passing power, and a correct detection value can be obtained even in a three-phase unbalanced state. As described above, in the present embodiment, the passing power can be detected very accurately even in the state where the three phases are unbalanced, so the command to the converter control device 8 of the converter 2 is corrected according to the detected value. By so doing, it is possible to effectively suppress voltage fluctuations in the DC portion and reduce the capacitance of the DC smoothing capacitor C. Further, in the present embodiment, the command of the converter 2 is corrected by using the instantaneous inflow power flowing into the converter 1, but the control device of the converter 1 and the converter 2 is completely targeted. When the power flows from the converter 1 side, the command of the converter 2 is corrected, and when the power flows from the converter 2 side, the command of the converter 1 is corrected. It is possible to keep the voltage of the DC portion constant regardless of which one of the AC 4 is in an unbalanced state. Note that, also in the embodiments described below, the control device of the converter 1 and the converter 2 is completely targeted for the configuration, and the voltage fluctuation of the DC part is suppressed even when either the AC 3 or the AC 4 is in an unbalanced state. It can be suppressed as in the present embodiment.

Next, FIG. 4 shows another embodiment of the present invention. 4, the same symbols as in FIG. 1 represent the same elements. The present embodiment is a configuration example in which the switching element is turned on or off, that is, the switching speed is sufficiently faster than the sine wave period of the current, and the voltage Vu1 on the AC side of the converter 1 is
Instead of detecting Vv1 and Vw1, the output voltages Vue, Vve, and Vwe are obtained using the three-phase switching states Pu, Pv, Pw and the DC voltage detection value Ed obtained from the pulse command of the switching element, that is, the gate drive signal 12.
The voltage estimation device 50 for estimating is used. When the switching speed is sufficiently higher than the operation cycle of the converter 1, the switching delay can be ignored, so that even if the electric power is detected using the pulse commands Pu, Pv, Pw of the switching element, the electric power is detected. Can be done accurately. By using the pulse command in this way, the voltage detector 9 is not required, and the control device can be downsized.

Next, FIG. 5 shows another embodiment of the present invention. This embodiment is a block diagram of a converter control apparatus according to the embodiment of FIG. 1, and the same reference numerals as those in FIG. 1 represent the same parts. In the present embodiment, the amount of electric power that the converter 2 can process is smaller than the instantaneous electric power that flows in through the converter 1 when the voltage is unbalanced, and the voltage fluctuation cannot be suppressed only by controlling the converter 2. The configuration is shown. Therefore, in this embodiment, the load 21 provided in the DC portion and the switching element SW1 connected in series to the load 21 are provided, and the overvoltage suppression control device 2 is provided.
2 is provided. Here, although a resistance is generally used for the load 21, an element that stores electric power or an element that consumes electric power, such as a battery or an electric motor, may be used. Further, the overvoltage suppression control device 22 converts the input electric energy into a conduction ratio of the switching element SW1 and outputs a pulse width modulation signal having this conduction ratio. When a momentary electric power larger than the electric power that can be processed by the converter 2 flows in through the converter 1, the electric power passing through the converter 1 is detected by the electric power detection device 20 in the same manner as in FIG. The power detection device 20 is
The detected electric power that can be processed by the converter 2 is output as the command correction amount of the converter control device 8, and the electric power larger than this is output to the overvoltage processing control device 22. A pulse width modulation signal is output from the overvoltage processing control device 22, the switching element SW1 is turned on at regular intervals, and power is discharged to the load 21. Here, as the magnitude of power that can be processed by the converter 2, a preset constant value can be used. In this embodiment, the converter 2 is controlled by the converter controller 8 up to the maximum power that the converter 2 can process.
From the AC to the AC 4 and the load 21 processes the electric power that cannot be processed due to the specifications of the converter 2, and the fluctuation of the DC voltage can be suppressed even when the capacity of the converter 2 is small. The device 2 and the DC smoothing capacitor C can be downsized. Further, the voltage estimator 50 of FIG. 4 may be used instead of the voltage detector 9 of the present embodiment to function similarly.

Next, FIG. 6 shows another embodiment of the present invention. The present embodiment is a configuration diagram of a converter control device according to the embodiment of FIG. 5, and the same reference numerals as those in FIG. 5 represent the same parts. In this embodiment, the output voltages Vu1 and Vv on the converter 1 side are
1, a voltage detector 30 for detecting Vw1 and a voltage detector 31 for detecting output voltages Vu2, Vv2, Vw2 on the converter 2 side are provided, and these voltage detection values and a current I of the converter 1 are provided.
u1, Iv1, Iw1 and currents Iu2, Iv of the converter 2
2, Iw2 is input to the power detection device 32. Now, in the power detection device 32, the output voltages Vu1, Vv1 on the converter 1 side,
Vw1 and currents Iu1, Iv1, Iw1 and output voltages Vu2, Vv2, Vw2 on the converter 2 side and currents Iu2, Iv
2, when Iw2 is input, the power detection device 32 detects the instantaneous passing power P1 of the converter 1 and the passing power P2 of the converter 2 from (Equation 1) or (Equation 2) from these currents and voltages, respectively. Then, the command to the converter control device 8 is corrected according to the magnitude of P1, and the differential power dP = P1−
The conduction ratio of the switching element SW1 is determined according to the size of P2, a pulse width modulation signal having this conduction ratio is output, the switching element SW1 is turned on at regular intervals, and the load 21 receives a difference power dP. To release. In the present embodiment, it is possible to prevent the fluctuation of the DC voltage due to the influence of the control delay of the converter control device 8 and to further stabilize the DC voltage.

Next, FIG. 7 shows another embodiment of the present invention. This embodiment is a block diagram of a converter control apparatus according to the embodiment of FIG. 6, and the same reference numerals as those in FIG. 6 represent the same parts. In this embodiment, the converters 1 and 2 are both the same AC 4
0, and on the converter 1 side, is connected to an alternating current 40 via a winding-type induction motor 41. In this embodiment, assuming that the output frequency fs of the converter 1 is the frequency f1 of the alternating current 40, the wire wound induction motor 41 rotates at the frequency fr corresponding to the difference. Here, if the frequency f1 is changed, the rotation speed of the wire wound induction motor 41 is changed. Winding type induction motor 4
1, the frequency ratio fs / f1 of the voltage applied to the stator side
Since a voltage proportional to is output to the rotor side as an induced voltage, when fs is smaller than f1, the AC voltage to be output by the converter 1 may be small. In this case, the voltage across the smoothing capacitor C is Will also be small. However, when the alternating current 40 is in an unbalanced state, a high frequency component is placed on the rotor currents Iu1, Iv1, and Iw1 and the induced voltage rapidly increases. In such a situation, the AC output voltage of the converter 1 becomes insufficient. , Very large electric power flows into the smoothing capacitor C via the converter 1.
In the present embodiment, with the same configuration as shown in FIG. 6, in such a situation, the load of the difference power between the power flowing in through the converter 1 and the power processed through the converter 2 is loaded. It is discharged to No. 21 and processed before the DC voltage fluctuates. In the present embodiment, the excess inflow power is processed by the load 21 before the fluctuation of the DC voltage to prevent the increase of the DC voltage. Therefore, the withstand voltage of the switching elements and the like used in the converter 1 and the converter 2 is set in the normal operation range. Converter 1
Even if the magnitude of the DC voltage is determined from the output voltage of, the safe operation can be performed when the AC 40 is unbalanced.

Next, FIG. 8 shows another embodiment of the present invention. The present embodiment is a configuration diagram of a converter control device according to the embodiment of FIG. 1, and the same reference numerals as those in FIG. 1 or 7 represent the same parts. In the present embodiment, the electric power that flows in when the alternating current 40 is unbalanced is the same as that described in FIG.
Since the AC output voltage is insufficient to flow through the winding type induction motor 41, only the instantaneous electric power passing through the converter 1 is detected. In this embodiment, since the AC side voltage of the converter 2 is not detected, the system can be downsized. Further, the same function can be achieved by using the voltage estimator 50 of FIG. 4 instead of the voltage detector 9 of the present embodiment. Further, by using the overvoltage suppressing control device 22 of FIG. 5 together with the present embodiment, the fluctuation of the DC voltage can be suppressed even when the capacity of the converter 2 is small, and the winding type induction can be safely performed even when the AC is unbalanced. The electric motor 41 can be operated. Further, in this embodiment, as shown in FIG. 6, the voltage detector 3 is provided on the converter 2 side.
1 is provided and the voltage and current on the converter 2 side are input to the power detector 32, the same function is exhibited.

Next, FIG. 9 shows another embodiment of the present invention. This embodiment is a block diagram of a converter control apparatus according to the embodiment of FIG. 1, and the same reference numerals as those in FIG. 1 represent the same parts. In this embodiment, the reactor Lu is connected to the AC side of the converter 1.
1, Lv1 and Lw1 are connected. In addition, a reactor Lu2, Lv2, Lw2 is provided on the AC side of the converter 51 which is different from the above.
Connect. And the converter 1 and the converter 2 are connected in parallel by connecting the AC side of these reactors in parallel. The currents flowing in the respective converters 1 and 52 are added and flow into the magnetic coupling element T1. In this case, reactors Lu1, Lv1, Lw1 and Lu2, L
v2 and Lw2 balance the currents flowing through the converter 1 and the converter 51. The magnetic coupling element T1 may be the transformer as in the present embodiment, or may be the above-mentioned wire wound induction motor 41. In this embodiment, the converter 51
And a current control device 5 having exactly the same configuration as the current control device 52.
3 is provided. The current controller 52 is the current detector 5, the converter controller 7, and the power detector 10 described in FIG.
Consists of The voltage detector 9 detects a common voltage on the alternating-current side of both reactors, and since the voltage has a common value in the converter 1 and the converter 51, it is input to both the current control device 52 and the current control device 53. Used as. Current control device 53
Inputs the three-phase current of the converter 51 and the common voltage detected by the voltage detector 9, and performs exactly the same operation as the current control device 52 described in FIG. In the present embodiment, when the converters are connected in parallel, by detecting the voltage at a common position, it is not necessary to provide a voltage detector for each converter individually, and the system can be downsized. In this example,
In the case where the direct current of the converter 51 is completely independent of the direct current of the converter 1, the configuration may be such that the correction of the command of the other one converter is made independently, and when the common direct current is used. For that, the sum of the instantaneous passing powers detected by each may be used to correct the command of the other converter. Further, also in the embodiments shown in FIGS. 4 to 8, when the converters are connected in parallel, the common voltage can be similarly used. In addition, the overvoltage suppression control device 22 of FIG. 5 is also used in this embodiment, and the voltage detector 31 is provided on the converter 2 side in this embodiment as shown in FIG. Even if input to the power detector 32, the same function is exhibited.

[0016]

As described above, according to the present invention,
Instantaneous passing power is detected from the current on the AC side of the converter and the voltage that changes in a pulsed manner on the AC side, so it is possible to accurately detect the instantaneous passing power even in the normal state and the three-phase unbalanced state. If the command of the converter control device of the other converter is corrected in accordance with the above, it is possible to effectively suppress the voltage fluctuation of the DC portion and reduce the capacity of the DC smoothing capacitor C. In addition, since the voltage on the AC side of the converter is estimated from the DC voltage detected as the pulse command, the instantaneous passing power can be accurately estimated without using a voltage detector that directly detects the AC voltage, and the size is small. It is possible to suppress the fluctuation of the DC voltage even in the system having no AC voltage detection means. In addition, the instantaneous passing power is detected from the AC side current and AC side voltage of the converter connected to the wire wound induction motor, and the excess inflow power is applied to the load before the DC voltage fluctuates according to the detected value. By treating it, it is possible to prevent the increase of DC voltage.Therefore, make sure that the withstand voltage of the switching elements used in the converter is as small as the DC voltage determined from the output voltage of the converter in the normal operating range. By using this, there is an effect of safely operating the wire wound induction motor even when AC is unbalanced. Also, when a reactor for balancing the current is connected to the output end of the converter and the power converter is connected in parallel, the voltage is detected at the common position and the common voltage detection value is used. Since the instantaneous passing power of the converter is detected, it is possible to detect the instantaneous passing power of a plurality of converters connected in parallel with a small number of voltage detecting means and suppress the DC voltage fluctuation. Also, up to the maximum power that can be processed by the converter, the converter outputs AC to the converter under the control of the converter controller, and the power that cannot be processed due to the converter specifications is processed by the load, so the capacity of the converter is small. Even in such a case, the fluctuation of the DC voltage can be suppressed, so that the converter and the DC smoothing capacitor can be miniaturized. In addition, by controlling each converter based on the instantaneous passing power detected from the three-phase current and output voltage of each of the two converters, fluctuations in the DC voltage occur due to the control delay of the converter control device. Can be prevented, and the DC voltage can be further stabilized.

[Brief description of drawings]

FIG. 1 is a controller for a power converter showing an embodiment of the present invention.

FIG. 2 is a waveform explanatory diagram according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of passing power detection according to an embodiment of the present invention.

FIG. 4 is another embodiment of the present invention.

FIG. 5 is another embodiment of the present invention.

FIG. 6 is another embodiment of the present invention.

FIG. 7 is another embodiment of the present invention.

FIG. 8 is another embodiment of the present invention.

FIG. 9 is another embodiment of the present invention.

[Explanation of symbols]

 1, 2, 51 Power converter 5, 6 Current detector 3, 4, 40 AC 9, 30, 31 Voltage detector 10, 20, 32 Power detection device 7, 8 Converter control device 22 Overvoltage suppression control device 11 DC Voltage control device 41 Winding type induction motor 50 Voltage estimation device T Magnetic coupling element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Seito 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Mitsuyuki, 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi Ltd. Hitachi Research Laboratory

Claims (9)

[Claims] 1. A two-converter for converting direct current and alternating current is connected, a capacitive element in a direct current circuit connecting the two converters, a means for detecting the direct current voltage, and a predetermined value for the direct current voltage. In the control device of the power converter, which comprises the voltage control means for creating the command of at least one converter so as to do, and the converter control means for creating the pulse width modulation signal of the converter based on this command, Current detecting means for detecting an alternating current, voltage detecting means for detecting an alternating voltage, and power detecting means for detecting a passing electric power flowing through the converter from the current and the voltage detected by the detecting means. A control device for a power converter, which is provided with means for correcting a command of the converter so that the same electric power as the detected passing electric power flows through the other converter. 2. A two-converter for converting a direct current and an alternating current is connected, and a direct current part connecting the two converters has a capacitive element, a means for detecting the direct current voltage, and a predetermined value for the direct current voltage. In the controller of the power converter, the voltage control means for creating a command for at least one converter and the converter control means for creating a pulse width modulation signal for the power converter based on the command Current detecting means for detecting the AC side current, voltage estimating means for estimating the AC side voltage using the gate signal and the DC voltage detection value for driving the semiconductor element of the converter, and the current detected by the detecting means. And an electric power detection means for detecting the passing electric power flowing through the converter from the voltage estimated by the estimating means, and an instruction for the converter to flow the same electric power as the detected passing electric power through the other one converter. Fix A control device for a power converter, which is provided with a correcting means. 3. A capacitive element, means for detecting a DC voltage, and a DC voltage having a predetermined value are connected to a DC circuit connecting the two converters for converting DC and AC. In the control device for the power converter, which includes the voltage control means for creating the command of at least one converter so as to do, and the converter control means for creating the pulse width modulation signal of the power converter based on this command, Current detecting means for detecting the AC side current of the connected converter, voltage detecting means for detecting the AC side voltage, and passing power flowing through the converter from the current and voltage detected by the detecting means. An electric motor control device comprising: a power detection unit for detecting and a unit for correcting a command of a converter so that the same power as the detected passing power is caused to flow through the other converter. 4. Two sets of power converters having two converters for converting direct current and alternating current, each of which is connected in parallel via a reactor, each of which has a capacity in a direct current circuit in which two converters are connected. Element, a means for detecting a DC voltage, a voltage control means for creating a command for at least one of the power converters so that the DC voltage has a predetermined value, and a pulse width for the power converter based on this command. In a control device for a power converter, which comprises a converter control means for generating a modulated signal,
Current detecting means for detecting the AC side current of each converter, voltage detecting means for detecting the AC side voltage of the inductive element connected between the AC and the reactor, and the current and voltage detected by the detecting means Electric power detection means for detecting the passing electric power flowing through each of the two converters, and a command for each converter so that the same electric power as the detected passing electric power flows through each of the other two converters. A control device for a power converter, which is provided with a correcting means. 5. The voltage detected by the voltage detecting means according to claim 1 or 3, and the passing power detected by the power detecting means is the detected pulse changing voltage. And a three-phase current for use in the calculation. 6. The voltage estimated by the voltage estimating means according to claim 2, and the passing electric power detected by the electric power detecting means is three-phase with the estimated pulse changing voltage. A control device for a power converter, characterized in that calculation is performed using current. 7. The electric power processing unit according to claim 1, further comprising a power processing unit that is connected to a DC circuit and processes DC power, and the power detection unit is an instantaneous inflow power flowing into one of the power converters. When the power exceeds the processing capacity of the other power converter, the controller for the power converter is characterized in that the instantaneous inflow power is processed by the power processing means. 8. The power detection means according to any one of claims 1, 3, 4, 5, or 6, further comprising a power processing means connected to a DC circuit and processing DC power. , A difference between the instantaneous inflow power flowing into one power converter and the power that can be processed by the other power converter is detected, and the power processing means processes the power that exceeds the power that can be processed by the other power converter. A power converter control device characterized by the above. 9. The power processing means according to claim 7 or claim 8, wherein the power processing means has a direct current power self-extinguishing type semiconductor element, and the duty factor of the semiconductor element exceeds the power that can be processed by the power converter. The control device for a converter, which is provided with a means for changing the electric power according to the electric power, and processes the electric energy based on the flow rate.