JP5194998B2 - Inverter device and air conditioner equipped with the same - Google Patents

Description

  The present invention relates to an inverter device that performs PWM control according to an instantaneous voltage vector output with a predetermined pulse width based on a voltage command vector, and particularly relates to control of an output voltage.

  2. Description of the Related Art Conventionally, as an inverter device that performs PWM (pulse width modulation) control, one that performs modulation control using an instantaneous space vector method that can reduce waveform distortion of an output voltage is known. In such an inverter device, three switching legs in which two switching elements are connected in series are connected in parallel, and eight instantaneouss corresponding to the on / off states of these six switching elements are connected. The voltage vector is output with a predetermined pulse width in accordance with the voltage command vector, and the switching element is operated.

Here, the instantaneous voltage vector V is determined by the following equation. In the following equation, S _x (x = u, v, w) indicates the switching state of each phase, and is 1 when the upper switching element of each switching leg is on, and the lower switching element is off When the state is defined as 0, these switching states are arranged in the order of the U-V-W phase and expressed as, for example, (100).

_{V = S u + S v e} j (2/3) π + S w e -j (2/3) π
That is, when a voltage command vector is given, the inverter device calculates a pulse width for outputting each instantaneous voltage vector, and operates the switching element according to the pulse width to output an output voltage having a waveform closer to a sine wave. be able to.

  Here, each of the instantaneous voltage vectors is divided into six basic output vectors that are out of phase with each other by π / 3 and equal in magnitude, and two zero vectors. Therefore, when each instantaneous voltage vector is drawn on the voltage vector plane, each instantaneous voltage vector points to the vertices of a regular hexagon, and the voltage vector diagram connecting these vertices becomes a regular hexagon, and this inner range However, it corresponds to the voltage range (output possible range) that the inverter device can output.

By the way, in the inverter device as described above, although the distortion of the waveform of the output voltage can be reduced as described above, the over-modulation region cannot be used in the instantaneous space vector method for outputting a sinusoidal voltage, and the output is an inverter. The maximum voltage that can be output by the device (at 6 STEP) is approximately 0.9, which is not a very efficient configuration. Therefore, for example, as disclosed in Patent Document 1, a configuration is considered in which PWM control can be performed by an instantaneous space vector method even in an overmodulation region by correcting the pulse width of the output voltage vector for each carrier period. It has been. Specifically, in Patent Document 1, the pulse width is corrected so that the total pulse width of the output instantaneous voltage vector falls within the carrier period for each carrier period. Thus, in the case of the configuration of Patent Document 1, the waveform of the voltage output from the inverter device in the overmodulation region is substantially rectangular (6 STEP) limited by the upper limit value determined by the DC voltage output from the DC power supply. ).
Japanese Patent No. 3821145

  However, as described above, for example, when the pulse width is corrected and the inverter device is driven in the overmodulation region, the maximum value of the instantaneous value of the output voltage is limited by the input voltage of the inverter device, The instantaneous value of the output voltage is greatly affected by fluctuations in the input voltage. For example, when pulsation occurs in the input voltage due to resonance in the apparatus, the instantaneous value of the output voltage in the interval also pulsates. In addition, when the input voltage suddenly increases when recovering from an instantaneous power failure or voltage drop, the instantaneous value of the output voltage within the interval also increases rapidly with the increase of the input voltage, which occurs in the inverter device. There is a risk that the components connected to the device and the load connected to the inverter device may be damaged by the overcurrent.

  On the other hand, a method of lowering the peak of the voltage command and reducing the amplitude of the output voltage as a whole can be considered, but in this method, the voltage range (output possible range) that the inverter device can output is considered. The output voltage needs to be considerably reduced, which causes a problem that the voltage utilization rate is greatly deteriorated.

  In the inverter device as described above, control is generally performed to correct the voltage command according to the input voltage so that the output voltage does not fluctuate due to fluctuations in the input voltage. In the interval in which the maximum value of the instantaneous value of the output voltage is limited by the input voltage, the instantaneous value of the output voltage and the instantaneous value of the voltage command do not match, so the conventional correction control as described above is performed in that interval. However, the effect of voltage correction cannot be obtained.

  The present invention has been made in view of such various points, and an object of the present invention is to provide an instantaneous value of an output voltage in an overmodulation region in an inverter device that performs PWM control using an instantaneous space vector method. It is to obtain a configuration capable of driving without being affected by the pulsation or fluctuation of the vehicle.

In order to achieve the above object, in the inverter device (1) according to the present invention, the AC voltage output possible range (S1) represented on the voltage vector plane is similar to the range and is within the range. Set the voltage output area (S2) to be equal to or less than the area, and perform PWM control based on the voltage vector in the voltage output area (S2) obtained by converting the voltage command vector (V ^* ) Therefore, the output voltage can be set within a range not affected by the pulsation or fluctuation of the input voltage (V _DC ).

Specifically, the first invention drives a plurality of switching elements (4a) connected to each other so that an input voltage (V _DC ) can be converted into a three-phase AC voltage, and the switching elements (4a). And a control means (10) for performing PWM control by outputting an instantaneous voltage vector (V0 to V7) with a predetermined pulse width based on the voltage command vector (V ^* ). .

The control means (10) has a voltage output region that is similar to the range and equal to or less than the area of the AC voltage output possible range (S1) represented on the voltage vector plane. A region setting unit (13) for setting (S2) and the voltage command vector (V ^* ) are converted into a voltage vector in the voltage output region (S2), and an instantaneous voltage vector (V0) is converted based on the voltage vector. Output limiter (14) for outputting ~ V7) with a desired pulse width.

With the above configuration, in the inverter device (1) that performs PWM control by the instantaneous space vector method, the region setting unit (13) is similar to the AC voltage output possible range (S1) on the voltage vector plane and Since the voltage output region (S2) that is equal to or smaller than the area of the range can be set, the output voltage of the inverter device (1) can be limited by the voltage output region (S2). Then, the voltage limiter (14) converts the voltage command vector (V ^* ) into a voltage vector in the voltage output region (S2) and outputs the instantaneous voltage vector (V0 to V7) with a desired pulse width. Thus, a three-phase AC voltage can be output in the voltage output region (S2) using the instantaneous space vector method.

Therefore, since the maximum value of the instantaneous value of the output voltage of the inverter device (1) can be limited to an arbitrary voltage by the above-described configuration, for example, when operating in the overmodulation region, the input voltage (V _DC )) avoids the range of pulsation, and even if the input voltage (V _DC ) increases suddenly, the sudden increase in the instantaneous value of the output voltage is suppressed and overcurrent occurs in the inverter device (1). Can be prevented.

In the above configuration, the output limiting unit (14) is configured to convert the voltage command vector (V ^* ) to a voltage vector in the voltage output region (S2), so that the pulse width of the zero vector (V0, V7) It is preferable to be configured to adjust (second invention).

In this way, by adjusting the pulse width of the zero vector (V0, V7), the voltage command vector (V ^* ) within the voltage output area (S2) narrower than the possible output range (S1) on the voltage vector plane Therefore, the configuration of the first aspect of the present invention can be easily realized.

The region setting section (13) is preferably configured to set the voltage output region (S2) in accordance with the input voltage (V _DC ) (third invention). As a result, the voltage output region (S2) can be set in consideration of the input voltage (V _DC ). For example, when a pulsation occurs in the input voltage (V _DC ), the influence of the pulsation is reduced. The voltage output area (S2) can be set in such a range that it will not be affected, and even if the input voltage (V _DC ) increases rapidly, the instantaneous value of the output voltage will not increase rapidly. Can be set.

The region setting unit (13) is configured to set the voltage output region (S2) such that an increase amount per predetermined time of the maximum value of the instantaneous value of the AC voltage is equal to or less than a predetermined value. (4th invention) is preferable. By doing this, the increase amount per predetermined time of the maximum value of the instantaneous value of the AC voltage that is the output voltage can be suppressed to an increase amount that is less than the predetermined value so that no overcurrent is generated in the inverter device (1). . Further, the predetermined value, that the instantaneous value of the output voltage is set to increase in a range that is not affected by the pulsation of the input voltage (V _DC), not detect a pulsation of the input voltage (V _DC) However, the occurrence of pulsation of the instantaneous value of the output voltage can also be prevented. Therefore, an overcurrent is generated in the inverter device (1), the components in the inverter device (1) and the load connected to the inverter device (1) are damaged, or the instantaneous value of the output voltage pulsates. Can be prevented.

  Here, the predetermined time may be a unit time, or a control period or a carrier period.

The region setting section (33) includes a rapid increase detection means (31) for detecting a rapid increase state in which the amount of increase in the input voltage (V _DC ) per predetermined time is greater than a predetermined value (Vd). When the rapid increase detection means (31) detects a rapid increase state in which the input voltage (V _DC ) increase per predetermined time is larger than a predetermined value (Vd), the maximum value of the instantaneous value of the AC voltage is determined. It is preferable to set the voltage output region (S2) so that it is maintained or reduced as it is (fifth invention).

As described above, when the amount of increase in the input voltage (V _DC ) per predetermined time is in a sudden increase state larger than the predetermined value (Vd), the maximum value of the instantaneous value of the AC voltage as the output voltage is maintained or decreased as it is. In addition, since the voltage output region (S2) is set, it is possible to reliably prevent the instantaneous value of the output voltage from rapidly increasing, and to reliably prevent the occurrence of overcurrent in the inverter device (201). In addition, even when the input voltage (V _DC ) increases suddenly due to pulsation, the maximum value of the instantaneous value of the output voltage can be maintained or decreased as it is, so that operation can be reliably performed without being affected by pulsation. .

Here, the predetermined time may be a unit time, or a control period or a carrier period. The predetermined value may be a constant value or a value that changes according to the input voltage (V _DC ) or time.

  Moreover, it is preferable that the area setting unit (23) is configured to expand the voltage output area (S2) until it matches the output possible range (S1) (sixth invention).

  As a result, in a state where the input voltage is not rapidly increasing, the voltage output region (S2) can be expanded to increase the effective value of the output voltage as much as possible. Furthermore, since the voltage output region (S2) can be expanded until it matches the output possible range (S1), when the input voltage goes from the sudden increase state to the steady state, the output is limited wastefully. It can be prevented from continuing.

  The seventh invention is directed to an air conditioner. Specifically, the inverter device (1) according to any one of claims 1 to 6 is mounted, and the compressor motor (5) is driven by the three-phase AC voltage converted by the inverter device (1). (7th invention).

With this configuration, the inverter device (1) that drives the motor (5) of the compressor of the air conditioner can be configured not to be easily affected by the pulsation or sudden increase of the input voltage (V _DC ). Therefore, even when the inverter device (1) is operated in the overmodulation region, it is possible to obtain an air conditioner in which the instantaneous value of the output voltage hardly pulsates and the inverter device (1) hardly generates overcurrent. .

As described above, according to the inverter device (1) of the present invention, in the configuration in which the PWM control is performed by the instantaneous space vector method, the voltage output is similar to the voltage output possible range (S1) on the voltage vector plane. Set a voltage output area (S2) that is equal to or less than the area, convert the voltage command vector (V ^* ) to a voltage vector in this area (S2), and output an instantaneous voltage vector (V0 to V7) Therefore, it is possible to control the maximum value of the instantaneous value of the output voltage in the overmodulation range to an arbitrary value so that the instantaneous value of the output voltage is not affected by the pulsation or sudden increase of the input voltage (V _DC ). It becomes possible to do.

According to the second aspect of the invention, the pulse width of the zero vector (V0, V7) is adjusted so that the voltage command vector (V ^* ) is converted into a voltage vector in the voltage output region (S2). The configuration of the first invention can be realized with a simple configuration.

According to the third invention, the voltage output region (S2), since that is determined according to the input voltage (V _DC), in a range that is not affected by variation of the input voltage (V _DC) The output voltage can be limited, the instantaneous value of the output voltage can be prevented from pulsating, and the inverter device (1) can be more reliably protected.

  According to the fourth aspect of the invention, the voltage output region (S2) is set so that the increase amount per predetermined time of the maximum value of the instantaneous value of the AC voltage is less than or equal to the predetermined value. It is possible to reliably prevent occurrence of pulsation and sudden increase of instantaneous value.

According to the fifth aspect of the present invention, when the amount of increase of the input voltage (V _DC ) per predetermined time is in a sudden increase state larger than the predetermined value, the maximum value of the instantaneous value of the AC voltage is maintained in the region as it is. Alternatively, since the voltage output region (S2) is set so as to decrease, the output voltage can be limited to a range that is not affected by the input voltage (V _DC ). The generation of overcurrent due to a sudden increase in the instantaneous voltage value can be reliably prevented.

  According to the sixth aspect of the invention, the voltage output region (S2) is expanded until it matches the output possible range (S1), so that it is possible to prevent the output from being restricted unnecessarily and more efficiently. Driving becomes possible.

Further, according to the air conditioner of the seventh invention, the three-phase AC voltage output from the inverter device (1) of any one of the first to sixth inventions is supplied to the motor (5) of the compressor. Since it is supplied, it is possible to easily obtain an air conditioner including the inverter device (1) that is not easily affected by the pulsation or rapid increase of the input voltage (V _DC ).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

Embodiment 1 of the Invention
Embodiment 1 of the present invention will be described below. As shown in FIG. 1, the inverter device (1) according to the present embodiment includes a capacitor circuit (3) and an inverter circuit (4), and the inverter circuit (4) has a DC voltage V as an input voltage. It is configured to receive _DC . The inverter device (1) is used, for example, for driving a compressor motor (5) (hereinafter also referred to as a motor) provided in a refrigerant circuit of an air conditioner. Here, the refrigerant circuit of the air conditioner is not particularly shown, but the compressor, the condenser, the expansion mechanism, and the evaporator are connected to form a closed circuit, and the refrigerant circulates to form a vapor compression refrigeration. It is configured to perform a cycle. By this refrigerant circuit, in the cooling operation, air cooled by the evaporator is supplied into the room, and in the heating operation, air heated by the condenser is supplied into the room.

  The capacitor circuit (3) includes a capacitor (3a) that constitutes a part of the DC power supply. This capacitor circuit (3) is for smoothing the voltage converted from alternating current to direct current by a converter circuit (not shown), thereby supplying a stable direct current voltage to the inverter circuit (4) side. It becomes possible.

  The inverter circuit (4) is connected in parallel to the capacitor circuit (2). The inverter circuit (4) includes a plurality of switching elements (4a) (for example, six in the case of a three-phase alternating current) that are bridge-connected. That is, the inverter circuit (4) includes three switching legs (6, 7, 8) formed by connecting two switching elements (4a, 4a) in series with each other, and each switching leg (6, 7, In 8), the midpoint between the switching element (4a) and the switching element (4a) is connected to each phase of the motor (5). The inverter circuit (4) is configured to convert the DC voltage into a three-phase AC voltage and supply it to the motor (5) by the on / off operation of these switching elements (4a). In the present embodiment, each of the switching elements (4a) is formed by connecting a transistor and a diode in antiparallel. However, the present invention is not limited to this, and any other configuration may be used as long as it can be switched. .

The inverter device (1) includes a PWM control unit (10) (control means) for drivingly controlling each switching element (4a) in the inverter circuit (4). The PWM control unit (10) is a signal for PWM control based on a DC voltage _VDC which is an input voltage of the inverter circuit (4) and a voltage command input to the PWM control unit (10). Is output, and the switching element (4a) is driven and controlled to control the output voltage of the inverter circuit (4).

Specifically, the PWM control unit (10) is configured to perform a so-called instantaneous space vector type modulation that outputs a PWM signal based on the DC voltage V _DC and a voltage command.

  The instantaneous space vector modulation method will be briefly described below. In this instantaneous space vector method, the pulse width of eight instantaneous voltage vectors indicating the driving state of each switching element (4a) constituting the inverter circuit (4) is calculated and output from the inverter circuit (4). A voltage pattern is obtained and modulated. FIG. 2 showing these instantaneous voltage vectors on the voltage vector plane (complex plane) is a so-called voltage vector diagram. In FIG. 2, V0 and V7 are the upper arm side (DC voltage) of the inverter circuit (4). All of the switching elements on the side connected to the high potential side) or all the switching elements on the lower arm side (side connected to the low potential side of the DC voltage) are in the ON state, and the inverter circuit (4) The output is in a short circuit state and becomes a zero vector. Further, since the remaining six instantaneous voltage vectors are different in phase by π / 3, the voltage vector diagram is a regular hexagon.

  Further, in FIG. 2, the numbers in parentheses of the instantaneous voltage vectors V0 to V7 indicate the switching elements (4a) of the switching legs (6, 7, 8) corresponding to the U phase, the V phase, and the W phase, respectively. The ON-OFF state is shown. Specifically, when the switching element (4a) on the upper arm side of each switching leg (6, 7, 8) is in the ON state and the switching element (4a) on the lower arm side is in the OFF state, 0 when the switching element (4a) is OFF and the switching element (4a) on the lower arm side is ON. For example, in the case of V2 (010), the switching element on the lower arm side of the U phase and the W phase is ON, and the switching element on the upper arm side of the V phase is ON.

In the voltage vector diagram as described above, when the voltage command vector V ^* is given, the pulse width of the instantaneous voltage vector to be output changes depending on the position of the vector V ^* on the voltage vector diagram. For example, in FIG. 2, when the voltage command vector V ^* is positioned at the position where the phase θ is 0 to π / 3, the PWM is set so that the instantaneous voltage vectors V0, V4, V6, and V7 are output. A signal is generated by the control unit (10). The pulse widths τa, τb, τc indicating the output period of the instantaneous voltage vector in the interval of every π / 3 of the phase θ are respectively expressed by the following equations.

τa = T · Ks · sin (π / 3−Φ0) (I)
τb = T · Ks · sin (Φ0) (II)
τc = T−τa−τb
= T · {1-Ks · sin (π / 3 + Φ0)} (III)
Here, Ks is a voltage control rate (= √2 × V ₁ / V _DC ), Φ 0 (0 ≦ Φ 0 <π / 3) is a phase angle, and V ₁ is an output voltage (fundamental wave voltage) of the inverter circuit (4). , _VDC respectively indicate DC voltages on the input side of the inverter circuit (4), and τa, τb, τc are 0 or more. Φ0 is obtained by dividing the phase θ into 6 sections every π / 3, and the remainder obtained by dividing θ by π / 3 is Φ0. The voltage command vector V ^* represents the output voltage of the inverter circuit (4) on the voltage vector plane, and is expressed by V ^* = √3 / 2 · Ks · e ^jθ (0 ≦ Ks). The

  Further, as can be seen from the above equations, the pulse widths τa, τb, τc are obtained so that the sum of them coincides with the carrier period T.

Table 1 shows the relationship between τa, τb, τc obtained from the above equations and the pulse width of each instantaneous voltage vector in the voltage vector diagram of FIG. Here, τn corresponds to the pulse width of the instantaneous voltage vector Vn, and τz in the table is a value corresponding to any one of τ0, τ7, and τ0 + τ7. For example, when the voltage command vector V ^* is located at the position shown in FIG. 2, the pulse width τ4 of V4 is τa, the pulse width τ6 of V6 is τb, and the pulse widths τ0 + τ7 of V0 and V7 are calculated from τc. Desired.

  Thereby, when the PWM signal is output by the PWM control unit (10) using the instantaneous space vector method, the switching element (4a) in the inverter circuit (4) is driven by the PWM signal, thereby The inverter circuit (4) converts the DC voltage into a sinusoidal three-phase AC voltage.

  However, in such instantaneous space vector PWM control, the voltage control rate Ks can only be set to a maximum of 1, so the output voltage of the inverter circuit (4) is limited at operating frequencies above the base frequency. There is a drawback that the efficiency of power conversion is not so good. In order to compensate for this, in the inverter device (1) according to the present embodiment, the PWM control unit (10) is provided with a correction control unit (12) that performs pulse width correction control as disclosed in, for example, Japanese Patent No. 3821145. I have.

  The correction control unit (12) is configured to output a low-distortion three-phase AC voltage from the inverter circuit (4) using an instantaneous space vector method even in an overmodulation region where the voltage control rate Ks is greater than 1. Has been. Specifically, when the voltage command is larger than the output possible range determined from the DC voltage, the sum of the pulse widths τa, τb, and τc exceeds the carrier period T, and therefore falls within the carrier period T. Thus, the pulse width of each τa, τb, τc is corrected. Thereby, a power conversion operation can be efficiently performed by the inverter circuit (4).

-Limitation of output voltage-
As described above, if the operation can be performed using the instantaneous space vector method even in the overmodulation region, the waveform of the instantaneous value of the voltage command in the overmodulation region does not match the waveform of the instantaneous value of the output voltage, The output voltage (instantaneous value) in the overmodulation region is limited by the DC voltage on the input side of the inverter circuit (4).

  Then, for example, when a pulsation occurs in the DC voltage on the input side due to resonance generated in the inverter device (1), the instantaneous value of the output voltage in the overmodulation region also pulsates.

  Similarly, when the DC voltage suddenly changes upon recovery from an instantaneous power failure or voltage drop, the instantaneous value of the output voltage in the overmodulation region increases rapidly. When the instantaneous value of the output voltage increases rapidly in this way, the current flowing through the inverter circuit (4) becomes an overcurrent state, and the components connected to the inverter circuit (4) and the load connected to the inverter circuit (4) May cause damage.

  On the other hand, in the present invention, an area setting unit (13) and an output limiting unit (14) for limiting the output of the inverter circuit (4) are provided in the PWM control unit (10). The region setting unit (13) and the output limiting unit (14) are configured to limit the output so as not to be affected by the pulsation or increase of the output voltage due to the DC voltage as described above.

  Specifically, in order to limit the voltage output range of the inverter circuit (4), the region setting unit (13) converts the voltage output region S2 on the voltage vector plane as shown in FIG. 4) is configured to be the same as or smaller than the output possible range S1, which is the output voltage range. That is, the region setting unit (13) is configured to set the output region of the output voltage to a region that is not affected by the pulsation of the DC voltage on the input side. In addition, the region setting unit (13) sets the voltage output region S2 so that the increase amount per predetermined time of the maximum value of the instantaneous value of the AC voltage that is the output voltage is equal to or less than a predetermined value where no overcurrent occurs. Configured to set. In the case of the present embodiment, as described later, the voltage output region S2 is automatically determined according to the change of the DC voltage.

  The output limiting unit (14) is configured to convert the voltage command vector into a voltage vector that falls within the voltage output region S2, and to output an instantaneous voltage vector with a desired pulse width based on the voltage vector. ing. Specifically, the output limiting unit (14) limits the sum of the pulse widths of the respective instantaneous voltage vectors V1 to V6 in the section of the carrier cycle T to be equal to or less than the limit value T ′ smaller than the carrier cycle T, Adjustment is made so that the minimum value of the pulse width of the zero vectors V0 and V7 is equal to or greater than TT ′. Therefore, the output limiting unit (15) calculates the pulse width using the following equation instead of the equations (I) to (III).

τa = T ′ · Ks · sin (π / 3−Φ0) (IV)
τb = T '· Ks · sin (Φ0) (V)
τc = T−τa−τb
= T−T ′ · Ks · sin (π / 3 + Φ0)} (VI)
Here, T ′ = Kt · T, and 0 <Kt ≦ 1. This Kt is obtained by the ratio of the maximum voltage value that can be output in the output possible range S1 and the maximum voltage value that can be output in the voltage output region S2, and Kt = (maximum voltage value that can be output in the voltage output region S2). / (Maximum voltage value that can be output in the output possible range S1). Further, τa, τb, and τa + τb are each not less than 0 and not more than T ′. When these τa, τb, and τa + τb do not satisfy the condition of 0 or more and T ′ or less, it is necessary to perform correction control of the pulse width so as to satisfy the condition by the correction control unit (12).

  In this way, when modulating by the instantaneous space vector method, the output voltage of the output voltage vector is shortened to limit the output voltage of the inverter circuit (4), thereby reducing the output voltage from the range affected by the DC voltage. Thus, the instantaneous value of the output voltage can be reduced, or a sudden increase in the instantaneous value of the output voltage can be suppressed, and the influence of the DC voltage can be reduced. As a result, it is possible to prevent the instantaneous value of the output voltage from pulsating due to the influence of the pulsation of the DC voltage, or the overcurrent from flowing through the inverter circuit (4) due to the sudden increase in the DC voltage.

  Next, a method for determining the voltage output region S2 by the region setting unit (13) will be described below.

  First, a method for determining the voltage output region S2 when a DC voltage pulsation or rapid increase occurs will be described.

The maximum voltage value that can be output in the output possible range S1 is proportional to the DC voltage V _DC on the input side of the inverter circuit (4), and is one side of the hexagon shown by S1 in the voltage vector diagram shown in FIG. Corresponds to the length. On the other hand, the maximum voltage value that can be output in the voltage output region S2 is proportional to V _DC ′ obtained by the following equation, and the length of one side of the hexagon indicating the range of S2 in the voltage vector diagram shown in FIG. It corresponds to.

V _DC '= V _DC × (length of one side of S2) / (length of one side of S1)
Therefore, the voltage output region S2 is
(Length of one side of S2) = (Length of one side of S1) × V _DC '/ V _DC
Therefore, for example, when V _DC becomes large due to the pulsation or rapid increase of the DC voltage in the above equation, a narrow voltage output region S2 is set accordingly.

Since the relationship of Kt = V _DC '/ V _DC is established with the above-described Kt,
(Maximum voltage value that can be output in voltage output region S2) = (Maximum voltage value that can be output in output possible range S1) × Kt
It becomes.

  In addition, the region setting unit (13) changes the voltage output region S2 according to the flow shown in FIG. 4 according to the fluctuation of the DC voltage with respect to the voltage output region S2 set as described above.

That is, when the flow shown in FIG. 4 starts, first, in step SA1, the DC voltage V _DC ′ corresponding to the voltage output region S2 is increased with respect to the allowable output voltage for each control cycle. A new V _DC ′ is obtained by adding the increment dV (area change). In the subsequent step SA2, the magnitude relationship between the calculated V _DC 'and the DC voltage V _DC is compared. That is, in this step SA2, whether or not the voltage difference between V _DC 'and the DC voltage V _DC before one control cycle is smaller than the DC voltage increment dV, that is, whether the DC voltage V _DC has not increased rapidly. Judgment is made.

When it is determined in step SA2 that the DC voltage V _DC ′ corresponding to the voltage output region S2 is greater than the DC voltage V _DC corresponding to the output possible range S1 (in the case of YES), that is, the DC voltage V _DC Is smaller than the increment dV, and it is determined that the DC voltage V _DC is not increasing rapidly, in the subsequent step SA3, V _DC is substituted for the DC voltage V _DC ′, and the voltage output region S2 is set to the same range as the output possible range S1, and this flow is ended (END).

On the other hand, when it is determined in step SA2 that the DC voltage V _DC ′ is equal to or less than the value of the DC voltage V _DC (in the case of NO), that is, the voltage difference from the DC voltage V _DC is greater than or equal to the increment dV. If it is determined, this flow is terminated as it is (end). As described above, when the fluctuation of the DC voltage V _DC is equal to or greater than the allowable increment dV, that is, when the DC voltage V _DC increases rapidly, the increase amount of the V _DC ′ is limited to thereby reduce the narrow voltage as described above. In addition to setting the output region S2, the voltage output region S2 can be brought closer to the output possible range S1 by the allowable increment dV. Therefore, by repeating this operation, it is possible to gradually bring the voltage output region S2 closer to the output possible range S1 while suppressing a sudden increase in the instantaneous value of the output voltage.

  That is, by setting the voltage output region S2 by the flow as described above, the voltage output region S2 can be set to the same range as the output possible range S1 if the voltage fluctuation is within an allowable range. Thereby, it is not necessary to limit the output of the inverter circuit (4) for a minute voltage change or a steady change (hereinafter, this case is also referred to as a steady state).

Further, even when the DC voltage _VDC greatly varies and changes beyond the allowable range, the voltage output region S2 can be brought close to the output possible range S1 within the allowable range while suppressing the output voltage variation. it can.

Here, the allowable increment dV may be a constant value set in advance, or may be arbitrarily changed, for example, may be changed according to the DC voltage V _DC ′. As described above, when the increment dV is changed according to the DC voltage V _DC ′, V _DC ′ × α may be substituted for dV in FIG. By doing so, the voltage output region S2 can be expanded at a constant rate according to the DC voltage V _DC '. Also, 'if that is changed according to the DC voltage V _DC' the dV DC voltage V _DC expansion rate is too slow, the DC voltage V _DC 'is high at the time when the spread of the voltage output region S2 from a low state Therefore, an upper limit value and a lower limit value may be provided for the dV so as to prevent the enlargement speed when the voltage output region S2 is expanded from being too fast.

In the flow of FIG. 4 above, when the voltage difference between the DC voltages V _DC and V _DC 'is smaller than the allowable increment dV, V _DC is substituted for the _DC voltage V _DC ' and the voltage output Although the region S2 is set to the output possible range S1, this is not limited, and a flow for determining whether or not output restriction is performed is added to the flow of FIG. 4 and the output restriction control is performed for a predetermined time or more. If not, control for making the voltage output region S2 coincide with the output possible range S1 may be performed.

-Effect of Embodiment 1-
As described above, according to this embodiment, in the inverter device (1) configured to modulate the DC voltage (input voltage) into the three-phase AC voltage by the instantaneous space vector method, the voltage output region S2 in the voltage vector diagram is Since the output possible range S1 is narrowed, the output of the inverter circuit (4) can be limited to a predetermined voltage. Therefore, in the overmodulation region, even when the instantaneous value of the output voltage of the inverter circuit (4) is greatly influenced by the DC voltage on the input side, the output voltage is not affected by the pulsation of the _DC voltage _VDC. In addition to being able to set, when the DC voltage V _DC rapidly increases, it is possible to prevent the output voltage from rapidly increasing and overcurrent from flowing in the inverter circuit (4).

  In the voltage vector diagram, the voltage output region S2 limits the total of the pulse widths of the instantaneous voltage vectors other than the zero vector in the section of the carrier period T to T ′ which is smaller than the carrier period T, and the zero. It can be easily obtained by adjusting the minimum value of the pulse width of the vector to be equal to or greater than TT ′. Therefore, the above-described operational effects can be obtained only by changing a part of the relational expression used in the conventional instantaneous space vector modulation method (in this embodiment, the carrier period T is changed to T ′ shorter than that). The structure obtained can be realized. For example, the pulse width correction control as disclosed in the above-mentioned Japanese Patent No. 3821145 can be realized only by changing a part of the relational expression as necessary.

Further, as described above, correction of automatically narrowing the voltage output region S2 in the voltage vector diagram in accordance with a change in the DC voltage V _DC on the input side is facilitated by correcting the relational expression used for modulation. It can be carried out. Further, after the voltage output region S2 is set according to the DC voltage, the voltage difference between the _DC voltages V _DC and V _DC 'is compared with an allowable increment dV, and the voltage output region is determined according to the result. Since S2 is corrected, the output restriction by the voltage output region S2 is relaxed according to the voltage difference between the DC voltages V _DC and V _DC 'while suppressing the sudden increase and pulsation of the instantaneous value of the output voltage. Can do.

<< Embodiment 2 of the Invention >>
Next, an inverter device (101) according to Embodiment 2 of the present invention will be described below. Since this inverter device (101) differs from the first embodiment only in part of the configuration and control contents, the same parts are denoted by the same reference numerals and only different parts will be described below.

  Specifically, as shown in FIG. 5, the PWM control unit (20) of the inverter device (101) includes the same correction control unit (12) and output limiting unit (14) as those of the first embodiment. The counter unit (21) and the increment setting unit (22) are provided.

As will be described later, the counter unit (21) is configured to count the number of times when the DC voltages V _DC and V _DC ′ are continuously determined to be in a steady state. In the inverter device (101) according to the present embodiment, the increment dV of the DC voltage is set by the increment setting unit (22) according to the number of counts by the counter unit (21).

The increment setting section (22) is provided in the area setting section (23) having substantially the same configuration as the area setting section (13) of the first embodiment, and an allowable increment of the DC voltage V _DC ′. The dV is set according to the count number of the counter unit (21). That is, as will be described in detail later, the increment setting unit (22) can set different increments dV1 and dV2 depending on whether the DC voltages V _DC and V _DC ′ are in a steady state or in a case other than the steady state. It is configured.

Next, operation | movement of the inverter apparatus (101) which concerns on this embodiment is demonstrated below using FIG. Note that the setting of the voltage output region S2 when the DC voltage V _DC increases rapidly (such as the relationship between the output possible range S1 and the voltage output region S2) is the same as in the first embodiment. Only the operation when changing the above will be described.

As shown in FIG. 6, in the second embodiment, unlike the first embodiment, whether or not the change of the DC voltages V _DC and V _DC ′ is within the allowable increment dV, that is, the DC voltages V _DC and V _DC . The value of dV is changed depending on whether the change of _DC ′ is steady or non-steady.

That is, when the flow of FIG. 6 starts, as in FIG. 4 of the first embodiment, in step SB1, an increment dV that is allowable for each control cycle is added to the DC voltage V _DC ′. The DC voltage V _DC ′ when increased is obtained.

Then, in the subsequent step SB2, the magnitude relationship between the calculated V _DC 'and the DC voltage V _DC is compared. In step SB2, as in the first embodiment, whether or not the voltage difference between the DC voltages V _DC and V _DC 'is smaller than the allowable DC voltage increment dV, that is, the change in the DC voltage V _DC increases rapidly. It is judged whether it is not in the state.

When it is determined in step SB2 that the DC voltage V _DC ′ corresponding to the voltage output region S2 is larger than the DC voltage V _DC corresponding to the output possible range S1 (in the case of YES), that is, the DC voltage V _DC Is smaller than the increment dV, and it is determined that the change in the DC voltage V _DC is not a sudden increase (in a steady state), in the subsequent step SB3, V _DC is substituted for the DC voltage V _DC '. Then, the voltage output region S2 is set to the same range as the output possible range S1.

  In step SB4, it is determined whether or not the number of counters is equal to or greater than N−1. If it is equal to or greater than N−1 (in the case of YES), the increment dV is set to dV1 in the subsequent step SB5. Thereafter, this flow is ended (END).

On the other hand, when it is determined in step SB2 that the DC voltage V _DC ′ is equal to or less than the value of the DC voltage V _DC (in the case of NO), that is, it is determined that the fluctuation of the DC voltage V _DC is not less than the increment dV. In this case, since a sudden increase in the DC voltage V _DC is detected, the process proceeds to step SB7, the counter is reset to 0, and then the increment dV is set to dV2 in step SB8, and this flow ends. (End).

If it is determined in step SB4 that the number of counters is not greater than or equal to N-1 (NO), the process proceeds to step SB6, 1 is added to the count, and the increment dV is added in step SB8. Is set to dV2, and this flow is ended (END). That is, even if the DC voltage _VDC is in a steady state (even in the case of YES in step SB2), until it is determined in step SB4 that the number of counters is N-1 or more (YES), that is, in the above step. The increment dV2 set when the DC voltage V _DC is in a rapidly increasing state is applied until it is determined to be YES more than N times in SB2.

In the above flow, when dV1> dV2 and the DC voltage _VDC is in a steady state, a relatively large increment dV1 is allowed, whereas when the DC voltage is rapidly increasing, it is relatively small. Only increments up to dV2 are allowed. Further, the number N of YES detections in step SB2 is preferably set to a plurality of times so as not to be erroneously detected, but may be one. In this way, when the increment is switched by one detection, steps SB4, SB6 and SB7 can be omitted in the flow of FIG.

  Furthermore, in the above flow, when the number of times YES is detected in step SB2 is greater than or equal to N, the increment is switched from dV2 to dV1, but this is not restrictive, that is, according to the number of counters, that is, the elapsed time. The increment may be gradually changed from dV2 to dV1 in accordance with. In this case, in the flow of FIG. 6, “dV ← dV2” may be changed to “dV ← dV2 + (dV1−dV2) × cnt / N” in step SB8.

-Effect of Embodiment 2-
As described above, according to this embodiment, when the DC voltage V _DC is suddenly increased, the allowable increment dV is smaller than that in the steady state, so that the sudden increase in the output voltage of the inverter circuit (4) can be reliably prevented. Thus, the occurrence of overcurrent in the inverter circuit (4) can be reliably prevented.

In addition, the switching of the increment dV to dV1 is performed only when the steady state of the DC voltage _VDC is continuously detected a plurality of times, so that erroneous detection can be reliably prevented and steady state can be prevented. Incremental increase dV2 is applied even in the state, the output of the inverter circuit (4) can be suppressed to the safe side, and the occurrence of overcurrent in the inverter circuit (4) can be more reliably prevented Can do.

Furthermore, by setting different increment dV in the steady state and the abnormal state of the DC voltage V _DC as described above, in the steady state of the DC voltage V _DC, an inverter circuit (4) to the extent that an overcurrent does not occur The pulsation of the instantaneous value of the output voltage can be set to an allowable increment dV, and thereby the effective value of the output voltage can be made as large as possible within a possible range. On the other hand, in the abnormal state in which the DC voltage V _DC increases rapidly, as described above, the increment dV can be made smaller than that in the steady state to reliably prevent the occurrence of overcurrent in the inverter circuit (4). Therefore, with the above-described configuration, it is possible to obtain the inverter device (101) capable of outputting a three-phase AC voltage having as large an effective value as possible while reliably preventing the occurrence of overcurrent in the inverter circuit (4).

<< Embodiment 3 of the Invention >>
Next, an inverter device (201) according to Embodiment 3 of the present invention will be described below. Since this inverter device (201) differs from the first embodiment only in part of the configuration and control contents, the same parts are denoted by the same reference numerals and only different parts will be described below.

  Specifically, as shown in FIG. 7, the PWM control unit (10) of the inverter device (201) includes the same correction control unit (12) and output limiting unit (14) as those of the first embodiment. , A rapid increase determination unit (31) (rapid increase detection means) and an increment setting unit (32) are provided.

The rapid increase determination unit (31) _compares the change between the current DC voltage V _DC and the DC voltage V _{DC_OLD} one control cycle before with a threshold value Vd (predetermined value), and determines whether or not the _DC voltage V _DC increases rapidly. Incremental dV is set by the increment determination unit (32) according to the determination result.

The increment setting section (32) is provided in the area setting section (33) having substantially the same configuration as the area setting section (13) of the first embodiment, and the determination result of the rapid increase determination section (31) In other words, the increment dV of the DC voltage V _DC ′ corresponding to the voltage output region S2 is set depending on whether the DC voltage V _DC is in a steady state or a sudden increase state. As described above, this increment dV is used when changing the voltage output region S2.

Next, operation | movement of the inverter apparatus (201) which concerns on this embodiment is demonstrated below using FIG. The setting of the voltage output region S2 when the DC voltage V _DC increases rapidly is the same as in the first embodiment, and the change of the voltage output region S2 is the same as in the first and second embodiments. Only the setting operation of the increment dV of the DC voltage V _DC will be described.

As shown in FIG. 8, in the third embodiment, unlike the second embodiment, first, it is determined whether or not the change in the DC voltage V _DC is rapidly increased, and the allowable increment is changed according to the determination result.

That is, when the flow of FIG. 8 is started, first, in step SC1, is the difference between the current DC voltage V _DC and the DC voltage V _{DC_OLD} one control cycle before larger than the threshold value Vd for determining rapid increase? Determine if. If it is determined in step SC1 that the difference from the DC voltage V _{DC_OLD} one control cycle before is greater than the threshold value Vd, that is, if it is determined that the DC voltage V _DC is rapidly increasing (in the case of YES). Proceeding to step SC2, the increment dV is set to dV0. On the other hand, if it is determined in step SC1 that the difference from the DC voltage V _{DC_OLD} one control cycle before is not greater than the threshold value Vd, that is, if the DC voltage V _DC is determined to be in a steady state (in the case of NO) In step SC3, the increment dV is set to dV1.

After setting the increment dV as described above, the current DC voltage V _DC is substituted into the DC voltage V _{DC_OLD} one control cycle before in step SC4, and this flow is ended (END).

Here, in the above flow, dV0 is zero or a negative value, and dV1 is a positive value. In this way, when the DC voltage V _DC increases rapidly, the voltage output region S2 can be maintained or reduced as it is by setting the increment dV to zero or a negative value, and the output voltage of the inverter circuit (4) can be increased rapidly. It can prevent more reliably.

  Note that the flow of FIG. 8 may be performed before the flow of FIGS. 4 and 6 of the first and second embodiments. However, when the flow of FIG. 8 is performed before the flow of FIG. 6, it is necessary to delete step SC3 (dV setting) of the flow of FIG.

-Effect of Embodiment 3-
As described above, according to this embodiment, when the sudden increase in the DC voltage V _DC is determined, the instantaneous value of the output voltage of the inverter circuit (4) is rapidly increased by setting the increment dV to zero or a negative value. Therefore, it is possible to reliably prevent the occurrence of overcurrent in the inverter circuit (4).

-Modification 1 of Embodiment 3
As shown in FIG. 9, the first modification differs from the third embodiment in that the increment dV is changed only immediately after the rapid increase of the DC voltage V _DC . In this modification, in order to realize the following operation, in addition to the configuration of FIG. 7 of the third embodiment, the PWM control unit (30) includes a counter unit (21) as in the second embodiment. It is necessary to provide.

When the flow of FIG. 9 starts, first, in step SD1, it is determined whether or not the difference from the DC voltage V _{DC_OLD} one control cycle before is greater than a threshold value Vd for determining a rapid increase, and if not greater than the threshold value Vd. When it is determined (in the case of NO), that is, when it is determined that the DC voltage is in a steady state, dV1 is substituted for the increment dV and the count is set to 0 in step SD5.

On the other hand, if it is determined in step SD1 that the difference from the DC voltage V _{DC_OLD} one control cycle before is greater than the threshold value Vd, that is, if the DC voltage V _DC is determined to be in a rapidly _increasing state (in the case of YES). Determines whether the count is zero. If the count is determined to be zero in this step SD2 (in the case of YES), since the DC voltage _VDC has just increased from the steady state to the sudden increase state, dV0 is substituted for the increment dV and the count is set to 1 ( Step SD3). If it is determined in step SD2 that the count is not zero (in the case of NO), although the DC voltage V _{DC is in} a rapidly increasing state, it is not immediately after changing from the steady state to the rapidly increasing state. Substitute dV1 for dV.

After setting the increment dV in this way, the current DC voltage V _DC is substituted into the DC voltage V _{DC_OLD} one control cycle before in step SD6.

  Here, as in the third embodiment, the dV0 is zero or a negative value, and the dV1 is a positive value.

As described above, the output of the inverter circuit (4) when the DC voltage V _DC rapidly increases by setting dV to zero or a negative value only immediately after the DC voltage V _DC changes from the steady state to the rapid increase state. A sudden increase in voltage can be prevented. Thereafter, by setting dV to a positive value, the voltage output region S2 in the voltage vector diagram can be gradually brought closer to the output possible range S1, and unnecessary output restriction can be reduced.

-Modification 2 of Embodiment 3
As shown in FIG. 10, the third modification is different from the third embodiment in that the increment dV is gradually increased after the rapid increase of the DC voltage V _DC is finished.

Specifically, when the flow of FIG. 10 starts, first, at step SE1, it is determined whether or not the difference from the DC voltage V _{DC_OLD} one control cycle before is larger than a threshold value Vd for determining a rapid increase. When it is determined that it is greater than Vd (in the case of YES), that is, when it is determined that the DC voltage is in a rapidly increasing state, dV0 is substituted for increment dV in the subsequent step SE2.

On the other hand, if it is determined in step SE1 that the difference from the DC voltage V _{DC_OLD} one control cycle before is not greater than the threshold value Vd, that is, if the DC voltage V _DC is determined to be in a steady state (in the case of NO) In step SE3, ddV is added to the increment dV. In step SE4, it is determined whether or not the increment dV is larger than dV1, and if it is determined to be large (in the case of YES), dV1 is substituted into the increment dV in the subsequent step SE5.

After the increment dV is set in steps SE2 and SE5 and when it is determined in step SE4 that dV is not greater than dV1 (in the case of NO), the process proceeds to step SE6, and one control cycle before Substitute current DC voltage V _DC for DC voltage V _{DC_OLD} .

Thus, when the DC voltage V _DC is in a steady state, the voltage output region S2 in the voltage vector diagram is rapidly expanded by gradually increasing dV, and the output limitation of the inverter circuit (4) is relaxed. Thereby, unnecessary output restrictions can be eliminated as much as possible.

<< Other Embodiments >>
About each said embodiment, it is good also as the following structures.

In each of the above embodiments, each of the above-described configurations is applied to the inverter circuit (4) that converts the DC voltage _VDC as the input voltage into a three-phase AC voltage. The present invention may be applied to a circuit that directly converts AC voltage to AC voltage, such as a converter. In this case, for example, in each of the above embodiments, the input side DC voltage is set to the maximum voltage of the input voltage of the AC power supply or the like, so that it can be applied to the matrix converter as described above. .

  As described above, the present invention is particularly useful for an inverter device that performs PWM control using an instantaneous space vector method, for example.

FIG. 1 is a diagram illustrating a schematic configuration of the inverter device according to the first embodiment. FIG. 2 is an example of a voltage vector diagram used in the instantaneous space vector method. FIG. 3 is a diagram showing an output possible range S1 and a voltage output region S2 on the voltage vector plane. FIG. 4 is a flow showing the changing operation of the voltage output region S2. FIG. 5 is a diagram corresponding to FIG. 1 of the inverter device according to the second embodiment. FIG. 6 is a flowchart showing the changing operation of the voltage output region S2 according to the second embodiment. FIG. 7 is a view corresponding to FIG. 1 of the inverter device according to the third embodiment. FIG. 8 is a flowchart showing an operation of changing the increment dV. FIG. 9 is a flowchart showing an operation of changing the increment dV according to the first modification of the third embodiment. FIG. 10 is a flowchart showing an operation of changing the increment dV according to the second modification of the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 101, 201 Inverter apparatus 3 Capacitor circuit 4 Inverter circuit 4a Switching element 5 Electric motor 10, 20, 30 PWM control part (control means)
12 Correction control unit 13, 23, 33 Area setting unit 14 Output limiting unit 21 Counter unit 22, 32 Increment setting unit 31 Rapid increase determination unit (rapid increase detection means)

Claims (7)

Based on the voltage command vector (V ^* ) by driving a plurality of switching elements (4a) connected to each other so that the input voltage (V _DC ) can be converted into a three-phase AC voltage, and the switching element (4a). Control means (10) for performing PWM control by outputting instantaneous voltage vectors (V0 to V7) with a predetermined pulse width, and an inverter device comprising:
The control means (10)
A region setting unit that sets a voltage output region (S2) that is similar to the range and equal to or less than the area of the range, with respect to the AC voltage output possible range (S1) represented on the voltage vector plane. 13)
An output limiting unit that converts the voltage command vector (V ^* ) into a voltage vector in the voltage output region (S2) and outputs an instantaneous voltage vector (V0 to V7) with a desired pulse width based on the voltage vector (14) and an inverter device. In claim 1,
The output limiting unit (14) is configured to adjust the pulse width of the zero vector (V0, V7) so as to convert the voltage command vector (V ^* ) into a voltage vector in the voltage output region (S2). An inverter device characterized by being made. In claim 1 or 2,
The said area setting part (13) is comprised so that the said voltage output area (S2) may be set according to the said input voltage ( _VDC ), The inverter apparatus characterized by the above-mentioned. In claim 3,
The region setting unit (13) is configured to set the voltage output region (S2) such that an increase amount per predetermined time of the maximum value of the instantaneous value of the AC voltage is equal to or less than a predetermined value. A featured inverter device. In claim 3,
Rapid increase detection means (31) for detecting a rapid increase state in which the input voltage (V _DC ) increase per predetermined time is larger than a predetermined value (Vd);
The region setting unit (33) is configured to detect the rapid increase state when the rapid increase detection means (31) detects a rapid increase state in which the increase amount per predetermined time of the input voltage (V _DC ) is larger than a predetermined value (Vd). An inverter device characterized in that the voltage output region (S2) is set so as to maintain or decrease the maximum instantaneous value of the AC voltage as it is. In any one of Claims 1 to 5,
The said area setting part (23) is comprised so that the said voltage output area (S2) may be expanded until it corresponds to the said output possible range (S1).   The inverter device (1) according to any one of claims 1 to 6 is mounted, and the compressor motor (5) is driven by a three-phase AC voltage converted by the inverter device (1). An air conditioner characterized by comprising:

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