JP2008206286A - Controller for ac-ac direct converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller which enables the drive of a motor without increasing an output current without generating low-frequency torque pulsation or noise, even in case that it outputs voltage 0.866 times as high as the power voltage. <P>SOLUTION: An AC-AC direct converter includes first absolute value limiting means 11u, 11v, 11w which limit first phase voltage command of each phase so that the instant absolute value may be a first reference value or under, a means 12 which calculates zero-phase components from these output, addition means 13u, 13v, 13w which calculate second phase voltage commands by adding the above zero phase components to the first phase voltage command, and a second absolute value limiting means 2 which calculates a third phase voltage command by limiting the second phase voltage command so that the instant absolute value may be a second reference value or under. It calculates the on-off command to the semiconductor switching element of the AC-AC direct converter, using a third phase voltage command. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an AC / AC direct converter that directly converts a polyphase AC voltage into an AC voltage having an arbitrary amplitude and frequency by a switching operation of a semiconductor switching element.

A matrix converter is well known as this type of AC / AC direct converter.
FIG. 7 is a diagram showing the main circuit configuration of the matrix converter. A plurality of semiconductor switching elements can be combined between the system connection terminals R, S, T and the output terminals U, V, W to allow current to flow bidirectionally. The bidirectional switches S _ru , R _su , S _tu , S _rv , S _sv , S _tv , S _rw , S _sw , S _tw are respectively connected.

There are various control methods for the matrix converter. Here, a system (virtual rectifier / virtual inverter system) including a virtual rectifier 100 and a virtual inverter 200 as shown in FIG. A method for creating an on / off command for a directional switch (a semiconductor switching element constituting a bidirectional switch) will be described as an example.
In FIG. 9, 300 is a DC intermediate capacitor, S _{1r to} S _6r are semiconductor switching elements constituting the virtual rectifier 100, and S _{1 to} S ₆ are semiconductor switching elements constituting the virtual inverter 200.

FIG. 8 is a block diagram showing the configuration of the control device of the virtual rectifier / virtual inverter system.
In FIG. 8, the virtual rectifier command calculation means 21 and the virtual inverter command calculation means 23 to which the output frequency command f ^* is input are respectively the same as the conventional rectifier / inverter, in the virtual rectifier shown in FIG. 100, current command _i ^r * of the virtual inverter _{^{200, i s *, i t}} * and the voltage command _{^{v u *, v v *,}} v computes ^{w *,} respectively. The switching pattern calculation means 22 and 24 calculate the switching pattern (on / off command) of each switching element constituting the virtual rectifier 100 and the virtual inverter 200 based on the above commands. The command synthesizing unit 25 synthesizes the on / off commands of the virtual rectifier 100 and the virtual inverter 200 calculated by the calculating units 22 and 24 to generate and output an on / off command for the bidirectional switch of the matrix converter.

For example, the state in which the switching elements S _1r and S ₂ in FIG. 9 are on is nothing but a state in which the R phase on the input side and the V phase on the output side are connected. This state corresponds to the bidirectional switch _Srv being on in the matrix converter shown in FIG.
8 is performed by the command synthesizing unit 25 in FIG. 8, the matrix converter ON / OFF command can be uniquely obtained from the switching pattern of the virtual rectifier 100 and the virtual inverter 200.

  The symbol shown in Formula 1 is the switching function of the bidirectional switch of FIG. 7 and the switching element of FIG. 9 with the same symbol, and is 1 when each bidirectional switch or switching element is on, and 0 when it is off. It becomes. According to this control method, since the conventional control of the rectifier / inverter can be applied as it is, it is very easy to realize. This type of technology is disclosed in Non-Patent Document 1 described later.

On the other hand, since the matrix converter directly switches the power supply voltage with a bidirectional switch and outputs the voltage, the range in which the voltage can be output by the PWM control is an envelope range of a six-phase alternating current. Therefore, the range of the output voltage command for obtaining a desired output voltage is 0.866 times the power supply voltage (phase voltage) at the maximum. This range is a range shown by hatching in FIG. 10, and is also referred to as a PWM possible range below.
When a voltage exceeding 0.866 times the power supply voltage is output (during operation in a so-called overmodulation region), distortion of the output voltage occurs as shown by a thick line in FIG. Due to this distortion, not only an odd multiple component of the output frequency but also a low frequency component peculiar to the matrix converter determined by the input / output frequency is generated.

  Here, assuming a case where the electric motor is driven by a matrix converter, particularly when the voltage rating of the electric motor is equal to the power supply voltage, the matrix converter needs to output a voltage exceeding 0.866 times the power supply voltage. is there. However, in such a case, the pulsation of the torque and the rotation unevenness occur due to the distortion of the output voltage described above, which causes noise generation and destruction of the electric motor. In particular, the effect of torque pulsation due to components below the input frequency is significant.

  As a control method for solving these problems, Non-Patent Document 2 and Patent Document 1 disclose a technique of operating without generating distortion by weakening the magnetic flux of the motor and suppressing the terminal voltage in the overmodulation region. Has been.

Shinichi Ito and five others, “Controlling Matrix Converter by Virtual AC / DC / AC Conversion System Using Carrier Comparison System”, IEEJ Transactions D, Vol. 124, No. 5, p.457-p.463 May 2004 issue Ikuya Sato et al., “Research on improvement of motor drive performance of matrix converter”, IEEJ Semiconductor Power Conversion Study Paper, SPC-04-75, 2004 Japanese Patent Laid-Open No. 5-260762 (paragraphs [0014] to [0020], FIG. 1 etc.)

  If the techniques disclosed in Non-Patent Document 2 and Patent Document 1 are used, the output voltage can be controlled in a sine wave form, so problems such as torque pulsation and noise can be solved. However, in these conventional techniques, the output voltage of the matrix converter is suppressed to 0.866 times or less of the power supply voltage and a sine wave voltage is output in the modulation region, so that the output current increases greatly. As a result, the loss of the motor may increase, leading to abnormal overheating and failure of the switching element, etc. In order to avoid these inconveniences, a motor with a large capacity is required and the system cost is increased. Cause it.

  Therefore, the problem to be solved by the present invention is that even when a voltage more than 0.866 times the power supply voltage is output, the motor can be driven without generating low-frequency torque pulsation or noise and without increasing the output current. It is in providing the control apparatus of the alternating current direct current converter which was made.

In order to solve the above-described problem, an invention according to claim 1 is an AC / AC direct converter that directly converts a multiphase AC voltage into an AC voltage having an arbitrary amplitude and frequency by a switching operation of a semiconductor switching element.
First absolute value limiting means for limiting the instantaneous absolute value to be equal to or less than the first reference value with respect to the first phase voltage command of each phase;
Means for calculating a zero-phase component from the output of the first absolute value limiting means;
Means for calculating the second phase voltage command by adding the zero phase component to the first phase voltage command;
Second absolute value limiting means for calculating a third phase voltage command by limiting the instantaneous absolute value of the second phase voltage command to be equal to or less than the second reference value;
An on / off command for the semiconductor switching element is calculated using a third phase voltage command.

  According to a second aspect of the present invention, in the control device described in the first aspect, the first reference value and the second reference value are set to 0.75 times the amplitude of the power supply phase voltage.

The invention according to claim 3 is the control device according to claim 1 or 2,
As the AC / AC direct converter, assuming a power converter comprising a virtual rectifier and a virtual inverter connected to the virtual rectifier via a DC intermediate circuit,
Means for calculating a switching pattern of the virtual inverter using the third phase voltage command;
Means for computing a switching pattern of the virtual rectifier;
And means for synthesizing both switching patterns of the virtual inverter and the virtual rectifier to calculate an on / off command of a semiconductor switching element constituting the AC / AC direct converter.

According to the present invention, by correcting the output voltage command in consideration of the absolute value of each phase output voltage command, a sinusoidal voltage up to 0.866 times the power supply voltage, which is the theoretical limit of the AC / AC direct converter, can be obtained. Can be output. Further, by making the output voltage trapezoidal, it is possible to output a voltage of 0.866 times or more of the power supply voltage using only the modulation region. Since only the modulation region is used in this way, even when a voltage more than 0.866 times the power supply voltage is output, low frequency output distortion inherent to the AC / AC direct converter does not occur.
In particular, when electric motor driving is performed, not only low-frequency torque pulsation is not generated, but also a voltage more than 0.866 times the power supply voltage can be output, so that an increase in output current can also be suppressed. As a result, it is not necessary to use an electric motor that allows for a capacity, so that a power conversion system using an AC / AC direct converter can be realized at low cost.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 is a block diagram showing a configuration of a control device according to this embodiment, and is for controlling an AC / AC direct converter such as a matrix converter for driving an electric motor, as in the prior art.
In this embodiment, no matter how large a voltage command is input, the voltage is output using only the modulation region. Since only the modulation region is used in this way, a voltage that is at least 0.866 times the power supply voltage can be output without generating low-frequency output distortion as in the prior art.
In this embodiment, the method of controlling the matrix converter by the control assuming the virtual rectifier / virtual inverter system is described, but the present invention is also applicable to the case of using another method for controlling the matrix converter. is there.

In FIG. 1, the same components as those in FIG. 8 are denoted by the same reference numerals. The difference from FIG. 8 is that the voltage command correcting means 1 and the absolute value limiting means (second absolute value limiting means for convenience). 2).
The voltage command correcting means 1 is a three-phase voltage command (referred to as a first phase voltage command) v _u ^* , v _v ^* , v _w ^* calculated by the virtual inverter command calculating means 23, which will be described later in absolute value restriction After the operation, the zero-phase voltage component is obtained, and the zero-phase voltage component is corrected by adding the zero-phase voltage component to the original first phase voltage command v _u ^* , v _v ^* , v _w ^*. Outputs voltage commands v _u ^** , v _v ^** , and v _w ^** . Next, the second absolute value limiting means 2 limits the instantaneous absolute values of the second phase voltage commands v _u ^** , v _v ^** , and v _w ^** to be equal to or lower than the second reference value. The third phase voltage commands v _u ^*** , v _v ^*** , and v _w ^*** are generated.

Finally, the third phase voltage commands v _u ^*** , v _v ^*** , and v _w ^*** output from the second absolute value limiting means 2 are used as in the conventional case. The switching pattern computing means 24 computes the switching pattern of the virtual inverter 200, and the command synthesizing means 25 synthesizes the switching pattern with the switching pattern of the virtual rectifier 100 to turn on and off the bidirectional switch of the AC / AC direct converter. Is generated.

FIG. 2 is a block diagram showing the configuration of the voltage command correction means 1.
In the first absolute value limiting means 11u, 11v, and 11w provided in each phase, the instantaneous absolute values of the first phase voltage commands v _u ^* , v _v ^* , and v _w ^* are always the first. Processing is performed so that the reference value is 1 or less.

FIG. 3 is a waveform diagram showing the operation of the first absolute value limiting means 11u, 11v, 11w. When the peak value of the sine wave voltage command exceeds the first reference value A, the peak value of the voltage command is limited to be equal to the reference value A, and a trapezoidal wave shape lacking the peak portion of the sine wave as shown in FIG. Is output.
Such absolute value limiting means 11u, 11v, 11w can be easily realized by arithmetic processing such as a CPU.

Also, the zero-phase calculating means 12 in FIG. 2, three phases of the absolute value limiting means 11u, 11v, the output of 11w adds calculates a zero-phase component _{v 0.} Then, the addition means 13u, 13v, by 13w, as in Equation 2, the first phase voltage command _v ^u _*, ^v v _{*, v} is added ^{w *} to _{v 0,} respectively, the second phase voltage command v _{u ^{**, v} v} ^**, get the ^{v w **.}
[Equation 2]
^{_{v u ** = v u * +}} v 0
v _v ^** = v _v ^* + v _{0
^{v w ** = v w * +}} v 0

The second absolute value limiting means 2 in FIG. 1 performs processing for setting the instantaneous absolute values of the second phase voltage commands v _u ^** , v _v ^** , and v _w ^** to be equal to or less than the second reference value. The result is output as third phase voltage commands v _u ^*** , v _v ^*** , and v _w ^*** . The operation of the second absolute value limiting means 2 is exactly the same as the operation of the first absolute value limiting means 11u, 11v, 11w shown in FIG.
Finally, the switching pattern of the virtual inverter 200 is calculated using the third phase voltage commands v _u ^*** , v _v ^*** , and v _w ^*** that are the outputs of the absolute value limiting means 2. To do.

With the above configuration, by appropriately setting the first and second reference values, a sinusoidal voltage having a commanded amplitude can be output up to 0.866 times the power supply voltage. When an output voltage of 0.866 times or more of the power supply voltage is required, a trapezoidal voltage command is output using only the modulation region (shaded portion in FIG. 10). In this case, although the amplitude of the output voltage is limited, the output voltage can be increased with respect to a sine wave command having the same amplitude by making the waveform of the voltage command trapezoidal.
Further, since only the modulation region is used as the voltage command, there is no inherent low frequency output distortion that would be a problem in the prior art. Furthermore, although voltages having different shapes such as a sine wave and a trapezoidal wave are output according to the voltage command, a special sequence for switching is not necessary, and the implementation is easy.

Next, the effect of the present invention will be described from simulation results. 4 to 6 are simulation waveforms when the magnitude of the phase voltage command is changed, and all of the first phase voltage command v ^* , the zero-phase divided voltage v ₀ , the second and third phases from the top. Voltage commands v ^** , v ^*** , and line voltage _vuv are shown.
However, the first and second reference values applied to the absolute value limiting means 11u, 11v, 11w, and 12 are both 0.75 times the amplitude of the power supply phase voltage. Further, the peak value of the power supply phase voltage is expressed as 1.0 pu.

FIG. 4 shows a simulation waveform when the first phase voltage command v ^* having an amplitude 0.6 times the power supply phase voltage is given. In this case, since v _u ^* , v _v ^* , and v _w ^* do not exceed the first and second reference values, v ₀ output from the zero-phase component calculating means 12 in FIG. As a result, the following Equation 3 is established.
[Equation 3]
v _u ^*** = v _u ^*
v _v ^*** = v _v ^*
v _w ^*** = v _w ^*
As described above, when the first phase voltage command having an amplitude not more than 0.75 times the power supply phase voltage is given, the third phase voltage command and the first phase voltage command are equal. A sine wave voltage according to the first phase voltage command can be output.

FIG. 5 shows a simulation waveform when a first phase voltage command having an amplitude 0.8 times the power supply phase voltage is given. In this case, since the absolute value limiting means 11u, 11v, and 11w operate, the second phase voltage commands v _u ^** , v _v ^** , v _w ^**, and the third phase voltage commands v _u ^** , v _v ^*** and v _w ^*** are not sinusoidal but trapezoidal. In this case, instead of fixing the voltage command of the phase where the absolute value of the amplitude is maximum to the first reference value, by correcting the other two phases with the zero-phase divided voltage v ₀ , The operation of keeping the voltage in a sine wave shape as the command value is performed. As a result, the output line voltage coincides with the line voltage command calculated from the first phase voltage command, and a voltage according to the command value can be output. Based on the above principle, a sinusoidal voltage up to 0.866 times the power supply voltage, which is the theoretical limit, can be output according to the command value.

FIG. 6 shows a simulation waveform when a first phase voltage command having an amplitude 0.95 times the power supply phase voltage is given. In this case, since the voltage command exceeds the theoretical limit of the voltage that can be output from the AC / AC direct converter, even if an operation for adding the zero-phase voltage v ₀ to each phase voltage command is performed, a sinusoidal voltage command Cannot be output, and inherent low-frequency distortion occurs.
However, in such a case, in the present embodiment, the second absolute value limiting unit 2 in FIG. 1 operates, and the instantaneous absolute values of the second phase voltage commands v _u ^** , v _v ^** , v _w ^** Always limit the value below the second reference value. As a result, no matter what value is input as the first phase voltage command, the peak value of the third phase voltage command v _u ^*** , v _v ^*** , v _w ^*** is the second phase voltage command. Since it is limited to the reference value or less, v _u ^*** , v _v ^*** , and v _w ^*** have a trapezoidal waveform, and the actual output voltage also has a trapezoidal waveform.

According to the present embodiment, the peak value of the output voltage is limited. However, since the effective value can be increased with respect to a sine wave having the same peak value, a voltage more than 0.866 times the power supply voltage is output. can do. Further, since the operation in the overmodulation region is not performed, the voltage distortion that generates the low frequency torque pulsation of the motor does not occur.
As described above, it is possible to output a voltage of 0.866 times or more of the power supply voltage from the AC / AC direct converter without generating the inherent low-frequency distortion that occurs in the overmodulation region.

4 to 6, the first and second reference values are set to 0.75 times the amplitude of the power supply phase voltage, but the first and second reference values are set to the power supply phase voltage. The same effect can be obtained even if the amplitude is less than 0.75 times the amplitude.
However, when the first and second reference values are set to 0.75 times the amplitude of the power supply phase voltage, the voltage utilization factor (= output voltage / input voltage) is the highest, and the power supply voltage that is the theoretical limit of the direct converter is A sine wave output is possible up to 0.866 times, and in this case, the effect of the present invention is maximized.
If the first and second reference values are less than 0.75 times the amplitude of the power supply phase voltage, the range in which the sine wave output is possible becomes narrow, so the output current increases when the motor is driven as a load. Even in such a case, the present invention does not use an overmodulation region, and an inherent low-frequency distortion component does not occur, so there is no possibility of low-frequency torque pulsation.

It is a block diagram of a control device showing an embodiment of the present invention. It is a block diagram of the voltage command correction | amendment means in FIG. It is a wave form diagram which shows operation | movement of the 1st absolute value limiting means in FIG. It is a wave form diagram which shows the simulation result by embodiment of this invention. It is a simulation waveform diagram which shows the simulation result by embodiment of this invention. It is a simulation waveform diagram which shows the simulation result by embodiment of this invention. It is a main circuit block diagram of a matrix converter. It is a block diagram which shows the prior art of the control apparatus of a virtual rectifier / virtual inverter system. It is a block diagram of a virtual rectifier / virtual inverter system. It is an output voltage waveform figure at the time of the overmodulation of a matrix converter.

Explanation of symbols

1: Voltage command correcting means 2: Absolute value limiting means (second absolute value limiting means)
11u, 11v, 11w: Absolute value limiting means (first absolute value limiting means)
12: Zero-phase component calculating means 13u, 13v, 13w: Adding means 21: Virtual rectifier command calculating means 22: Switching pattern calculating means 23: Virtual inverter command calculating means 24: Switching pattern calculating means 25: Command combining means

Claims (3)

In the AC / AC direct converter that directly converts multi-phase AC voltage to AC voltage of arbitrary amplitude and frequency by switching operation of the semiconductor switching element,
First absolute value limiting means for limiting the instantaneous absolute value to be equal to or less than the first reference value with respect to the first phase voltage command of each phase;
Means for calculating a zero-phase component from the output of the first absolute value limiting means;
Means for calculating the second phase voltage command by adding the zero phase component to the first phase voltage command;
Second absolute value limiting means for calculating a third phase voltage command by limiting the instantaneous absolute value of the second phase voltage command to be equal to or less than the second reference value;
A control device for an AC / AC direct converter, wherein an on / off command of the semiconductor switching element is calculated using a third phase voltage command. The control device according to claim 1,
A control apparatus for an AC / AC direct converter, wherein the first reference value and the second reference value are set to 0.75 times the amplitude of the power supply phase voltage. In the control device according to claim 1 or 2,
As the AC / AC direct converter, assuming a power converter comprising a virtual rectifier and a virtual inverter connected to the virtual rectifier via a DC intermediate circuit,
Means for calculating a switching pattern of the virtual inverter using the third phase voltage command;
Means for computing a switching pattern of the virtual rectifier;
Means for synthesizing both switching patterns of the virtual inverter and the virtual rectifier to calculate an on / off command of a semiconductor switching element constituting the AC / AC direct converter;
An AC / AC direct converter control device comprising:

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