JP7849596B2 - Voltage change detection device and power conversion device - Google Patents

Description

This invention relates to a voltage change detection device and a power conversion device for detecting phase changes in three-phase input voltages.

Power conversion devices are known that improve the power factor of an input power supply by performing switching operations corresponding to the phase of the input voltage. As an example of such a power conversion device, Patent Document 1 discloses a power conversion device comprising a PWM converter having a bridge circuit composed of multiple diodes, a switching element connected in parallel to the multiple diodes, and a smoothing capacitor connected to the output terminal of the bridge circuit.

In the power conversion device disclosed in Patent Document 1, the switching element performs a switching operation corresponding to the phase of the input voltage, thereby converting the waveform of the input current into a sine wave. This results in a power supply voltage with minimal waveform distortion.

Japanese Patent Publication No. 6550314

Incidentally, in the power conversion device described above, if the phase of the input voltage does not change significantly, the phase angle can be calculated from the input voltage, and a drive signal for switching the switching element can be generated.

However, in cases where power supply switching occurs, such as in aircraft power converters, the phase of the input voltage may change rapidly. This can result in a period during which the phase angle cannot be accurately calculated from the input voltage. During this period, a difference arises between the actual phase of the input voltage and the phase calculated from the input voltage, which may prevent the accurate generation of the drive signal.

In such cases, a current exceeding its rated current may flow through the switching element, potentially causing it to malfunction.

Therefore, in order to stop the operation of the switching element when the phase of the input voltage changes abruptly, there is a need for a device that can quickly detect when the phase change of the input voltage exceeds a predetermined phase change amount.

The objective of this invention is to realize a voltage change detection device capable of detecting when the phase change amount of a three-phase input voltage exceeds a predetermined phase change amount.

A voltage change detection device according to one embodiment of the present invention comprises: a conversion unit that converts the three-phase input voltage into d-axis voltage and q-axis voltage; a conversion value calculation unit that obtains a d-axis equivalent value and a q-axis equivalent value by normalizing the d-axis voltage and the q-axis voltage by dividing them, respectively, by the effective value of the input voltage; and a phase change detection unit that detects that the phase change amount of the three-phase input voltage is greater than or equal to a predetermined phase change amount when the d-axis equivalent value is greater than or equal to a d-axis threshold, or when the q-axis equivalent value is greater than or equal to a q-axis threshold (first configuration).

This allows for accurate detection of whether the phase change amount of the three-phase input voltage exceeds a predetermined phase change amount, based on changes in the d-axis equivalent value obtained from the d-axis voltage or changes in the q-axis equivalent value obtained from the q-axis voltage. Therefore, the above configuration allows for accurate detection of rapid phase changes in the input voltage.

In the first configuration described above, the phase change detection unit detects that the phase change amount of the three-phase input voltage is greater than or equal to a predetermined phase change amount when the d-axis converted value is greater than or equal to the d-axis threshold, and detects that the phase change amount of the three-phase input voltage is greater than or equal to a predetermined phase change amount when the q-axis converted value reaches the q-axis threshold before the timing when the d-axis converted value reaches the d-axis threshold (second configuration).

When the phase of the input voltage is changed, there exists a phase angle in which the d-axis equivalent value hardly changes during a predetermined period immediately following the phase change. Therefore, as in the configuration described above, by detecting that the phase change amount of the input voltage is greater than or equal to a predetermined phase change amount when the q-axis equivalent value reaches the q-axis threshold before the d-axis equivalent value reaches the d-axis threshold, rapid phase changes in the input voltage can be detected more quickly and accurately.

A power conversion device according to one embodiment of the present invention comprises a voltage change detection device with the first or second configuration described above, a switching circuit having a plurality of switching elements, and a drive control unit that converts a three-phase input voltage into a predetermined DC voltage by switching-driving the plurality of switching elements, and stops driving the switching elements when the voltage change detection device detects that the phase change amount of the three-phase input voltage is greater than or equal to a predetermined phase change amount (third configuration).

This prevents excessive current from flowing through and causing failure of the switching elements in the switching circuit by stopping the drive of multiple switching elements when a rapid phase change in the three-phase input voltage is detected by the voltage change detection device.

A voltage change detection device according to one embodiment of the present invention detects that the phase change amount of the input voltage is greater than or equal to a predetermined phase change amount when the d-axis equivalent value obtained from the three-phase input voltage is greater than or equal to the d-axis threshold, or when the q-axis equivalent value obtained from the input voltage is greater than or equal to the q-axis threshold. This allows for accurate detection of rapid phase changes in the input voltage based on the change in the d-axis equivalent value or the change in the axis equivalent value.

Figure 1 is a functional block diagram showing the schematic configuration of a power conversion device according to an embodiment. Figure 2 is a functional block diagram showing the schematic configuration of the phase angle calculation unit. Figure 3 shows the relationship between an example of the input voltage when the phase of the input voltage of the power converter changes continuously, and an example of the phase angle obtained by the phase angle conversion unit. Figure 4 shows the relationship between an example of the input voltage when the phase of the input voltage of the power converter changes rapidly, and an example of the phase angle obtained by the phase angle conversion unit. Figure 5 shows an example of the change in the d-axis equivalent value when the phase of the input voltage is shifted. Figure 6 shows an example of the change in the q-axis equivalent value when the phase of the input voltage is shifted. Figure 7 is a flowchart showing the detection operation of the input voltage phase change by the power converter.

The embodiments of the present invention will be described in detail below with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated.

(Overall structure)
Figure 1 is a functional block diagram showing the schematic configuration of a power converter 1 equipped with a voltage change detection device 50 (see Figure 2) according to an embodiment of the present invention. The voltage change detection device 50 detects abrupt changes in the phase of the three-phase input voltages Vr, Vs, and Vt. In this embodiment, the voltage change detection device 50 is part of the phase angle calculation unit 23, which will be described later, in the power converter 1.

The power converter 1 outputs a DC voltage by driving multiple switching elements SW1 to SW6 that constitute the switching circuit 10 based on the three-phase input voltages Vr, Vs, Vt and input current supplied from the AC power supply 2.

The power conversion device 1 comprises a switching circuit 10 having multiple switching elements SW1 to SW6, and a control unit 20 that outputs PWM signals to the switching elements SW1 to SW6 of the switching circuit 10.

The switching circuit 10 has multiple switching elements SW1 to SW6 and diodes D1 to D6 connected in parallel to each of the switching elements SW1 to SW6. In this embodiment, the switching circuit 10 has six switching elements SW1 to SW6 and six diodes D1 to D6. The six switching elements SW1 to SW6 constitute a bridge circuit. The six switching elements SW1 to SW6 are electrically connected to the R phase, S phase, and T phase of the AC power supply 2.

The switching circuit 10 is electrically connected to the AC power supply 2 and the capacitor 3. Specifically, switching elements SW1 and SW2 are electrically connected to the R phase of the AC power supply 2. Switching elements SW3 and SW4 are electrically connected to the S phase of the AC power supply 2. Switching elements SW5 and SW6 are electrically connected to the T phase of the AC power supply 2. Switching elements SW1 to SW6 are electrically connected to the capacitor 3.

The control unit 20 includes a voltage control unit 21, a current control unit 22, a phase angle calculation unit 23, and a PWM signal generation unit 24.

The voltage control unit 21 generates a current command from the detected DC voltage of capacitor 3 and the output voltage command, and outputs it to the current control unit 22. In other words, the voltage control unit 21 generates the current command so that the DC voltage output of the power converter 1 approaches the output voltage command.

The current control unit 22 generates a command signal for the PWM signal generation unit 24 from the detected input current value of the power converter 1, the current command input from the voltage control unit 21, and the phase angle signal input from the phase angle calculation unit 23. The configuration of the current control unit 22 is the same as that of current control in conventional power converters. Therefore, a detailed explanation of the configuration of the current control unit 22 is omitted.

The PWM signal generation unit 24 uses the command signal generated by the current control unit 22 to generate PWM signals for driving the switching elements SW1 to SW6. The generated PWM signals are input to the switching elements SW1 to SW6. The configuration of the PWM signal generation unit 24 is the same as that of conventional power conversion devices that generate PWM signals. Therefore, a detailed explanation of the configuration of the PWM signal generation unit 24 is omitted.

Furthermore, the PWM signal generation unit 24 generates a PWM signal to stop the driving of switching elements SW1 to SW6 when a drive stop signal is input from the phase change detection unit 36 to stop the switching operation of switching elements SW1 to SW6.

The current control unit 22 and the PWM signal generation unit 24 convert the three-phase input voltages Vr, Vs, and Vt into predetermined DC voltages by switching and driving a plurality of switching elements SW1 to SW6. Furthermore, when the voltage change detection device 50 (described later) detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount, the driving of the switching elements SW1 to SW6 is stopped. Therefore, the current control unit 22 and the PWM signal generation unit 24 constitute the drive control unit 40 of the present invention.

The phase angle calculation unit 23 calculates the phase angle θ from the detected input voltage of the power converter 1. The phase angle θ calculated by the phase angle calculation unit 23 is input to the current control unit 22. Furthermore, the phase angle calculation unit 23 detects whether the phase of the input voltages Vr, Vs, and Vt has changed abruptly, based on the detected input voltages Vr, Vs, and Vt of the power converter 1. Figure 2 is a functional block diagram showing the schematic configuration of the phase angle calculation unit 23.

As shown in Figure 2, the phase angle calculation unit 23 includes a three-phase to two-phase conversion unit 31, an effective value calculation unit 32, a converted value calculation unit 33, a PI control unit 34, a phase angle conversion unit 35, and a phase change detection unit 36. The three-phase to two-phase conversion unit 31, the effective value calculation unit 32, the converted value calculation unit 33, and the phase change detection unit 36 constitute the voltage change detection device 50 of the present invention. That is, the phase angle calculation unit 23 of this embodiment includes the voltage change detection device 50.

The three-phase to two-phase conversion unit 31 converts the three-phase input voltages Vr, Vs, and Vt of the power converter 1 into a d-axis voltage Vd and a q-axis voltage Vq. The three-phase to two-phase conversion unit 31 has the same configuration as conventional units. Therefore, a detailed explanation of the three-phase to two-phase conversion unit 31 is omitted.

The RMS value calculation unit 32 calculates the RMS value Vpp using the three-phase input voltages Vr, Vs, and Vt of the power converter 1. Specifically, the RMS value calculation unit 32 calculates the RMS value Vpp by calculating the square root of the sum of the squares of the three-phase input voltages Vr, Vs, and Vt.

The conversion value calculation unit 33 uses the d-axis voltage Vd and q-axis voltage Vq output from the 3-phase 2-phase conversion unit 31, and the RMS value Vpp output from the RMS value calculation unit 32, to determine the d-axis converted value Vd/Vpp and the q-axis converted value Vq/Vpp. Specifically, the conversion value calculation unit 33 calculates the d-axis converted value Vd/Vpp by dividing the d-axis voltage Vd by the RMS value Vpp. The conversion value calculation unit 33 calculates the q-axis converted value Vq/Vpp by dividing the q-axis voltage Vq by the RMS value Vpp. The conversion value calculation unit 33 outputs the d-axis converted value Vd/Vpp and the q-axis converted value Vq/Vpp.

The PI control unit 34 performs PI control using the d-axis converted value Vd/Vpp and the q-axis converted value Vq/Vpp output from the converted value calculation unit 33. The PI control unit 34 performs PI processing on the d-axis converted value Vd/Vpp to determine the frequency Freq of the input voltage used when generating the command signal in the current control unit 22. Although not described in detail, the PI control unit 34 includes a differentiator and an integrator.

The phase angle conversion unit 35 converts the frequency Freq generated by the PI control unit 34 into the phase angle θ of the input voltage used when generating the command signal in the current control unit 22. The phase angle θ generated by the phase angle conversion unit 35 is used by the three-phase to two-phase conversion unit 31 to convert the three-phase input voltages Vr, Vs, and Vt to the d-axis voltage Vd and the q-axis voltage Vq.

Figure 3 shows the relationship between an example of the input voltage of the power converter 1 when the phase of the input voltage changes continuously, and an example of the phase angle θ obtained by the phase angle conversion unit 35. As shown in Figure 3, as the input voltage of the power converter 1 changes, the phase angle θ obtained by the phase angle conversion unit 35 also gradually changes in accordance with the input voltage.

Incidentally, when the phase of the input voltage of the power converter 1 changes rapidly, the phase angle obtained from the input voltage by the phase angle conversion unit 35 also changes rapidly. Figure 4 is a diagram showing the relationship between an example of the input voltage when the phase of the input voltage of the power converter 1 changes rapidly, and an example of the phase angle θ obtained by the phase angle conversion unit 35. As shown in Figure 4, when the phase of the input voltage of the power converter 1 changes rapidly, the phase angle θ obtained by the phase angle conversion unit 35 also changes rapidly.

As shown in Figure 4, when the phase angle θ changes rapidly, the calculated phase angle θ changes as shown by the thick dashed line in Figure 4 due to a delay in calculation in the phase angle calculation unit 23. If the calculated phase angle θ deviates from the actual phase angle in this way, the PWM signal input to the switching elements SW1 to SW6 cannot be generated correctly. Therefore, a current exceeding their rated current may flow through the switching elements SW1 to SW6, potentially damaging them.

The abrupt change in phase angle θ shown in Figure 4 occurs, for example, when switching AC power source 2 to another power source. Examples of power converters that can switch power sources in this way include aircraft power converters. The power converter of this embodiment may also be used in power converters other than aircraft power converters.

The phase change detection unit 36 detects when the phase of the three-phase input voltages Vr, Vs, and Vt of the power converter 1 changes abruptly. Specifically, the phase change detection unit 36 detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount, i.e., that the phase of the three-phase input voltages Vr, Vs, and Vt has changed abruptly, when the d-axis converted value Vd/Vpp obtained by the converted value calculation unit 33 is greater than or equal to the d-axis threshold, or when the q-axis converted value Vq/Vpp is greater than or equal to the q-axis threshold.

The phase change detection unit 36, upon detecting a rapid change in the phase of the three-phase input voltages Vr, Vs, and Vt, generates and outputs a drive stop signal to the PWM signal generation unit 24, which stops the switching operation of the switching elements SW1 to SW6. This drive stop signal causes the PWM signal generation unit 24 to generate a PWM signal that stops the switching operation of the switching elements SW1 to SW6.

The d-axis threshold is set to a d-axis equivalent value Vd/Vpp such that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is equal to or greater than a predetermined phase change amount. For example, the d-axis threshold is set to a d-axis equivalent value Vd/Vpp such that the predetermined phase change amount is 10 degrees. However, the d-axis threshold may be set to a d-axis equivalent value Vd/Vpp such that the predetermined phase change amount is a value other than 10 degrees.

The q-axis threshold is set to a q-axis equivalent value Vq/Vpp such that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount. The q-axis equivalent value Vq/Vpp represents a smaller phase change amount for the three-phase input voltages Vr, Vs, and Vt compared to the d-axis equivalent value Vd/Vpp. Therefore, the q-axis threshold is set to a q-axis equivalent value Vq/Vpp such that the predetermined phase change amount is greater than that of the d-axis threshold (for example, 30 degrees). Alternatively, the q-axis threshold may be set to a q-axis equivalent value Vq/Vpp such that the predetermined phase change amount is the same as or smaller than the predetermined phase change amount for the d-axis threshold.

Incidentally, as shown in Figure 5, the d-axis equivalent value Vd/Vpp changes more slowly when the phases of the three-phase input voltages Vr, Vs, and Vt are shifted by 180 degrees compared to cases where the phase shift is not 180 degrees. On the other hand, as shown in Figure 6, the q-axis equivalent value Vq/Vpp changes more quickly and by a larger amount when the phases of the three-phase input voltages Vr, Vs, and Vt are shifted by 180 degrees compared to cases where the phase shift is not 180 degrees.

Therefore, when the phase shift is 180 degrees, the phase change detection unit 36 uses the q-axis equivalent value Vq/Vpp and the q-axis threshold to detect whether the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount.

In other words, the phase change detection unit 36 detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount when the d-axis equivalent value Vd/Vpp is greater than or equal to the d-axis threshold, and detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount when the q-axis equivalent value Vq/Vpp reaches the q-axis threshold before the timing when the d-axis equivalent value Vd/Vpp reaches the d-axis threshold.

As a result, the phase change detection unit 36 can quickly and accurately detect whether the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount.

(Detection of phase change in input voltage)
Next, the detection operation of the input voltage phase change by the power converter 1 having the above configuration will be explained using Figure 7. Figure 7 is a flowchart showing the detection operation of the input voltage phase change by the power converter 1.

As shown in Figure 7, in step S1, the phase angle calculation unit 23 first acquires the three-phase input voltages Vr, Vs, and Vt from the AC power supply 2. In the subsequent step S2, the three-phase to two-phase conversion unit 31 of the phase angle calculation unit 23 converts the three-phase input voltages Vr, Vs, and Vt into the d-axis voltage Vd and the q-axis voltage Vq.

Subsequently, in step S3, the conversion value calculation unit 33 normalizes the d-axis voltage Vd and q-axis voltage Vq obtained by the 3-phase 2-phase conversion unit 31 by dividing them by the effective value Vpp obtained by the effective value calculation unit 32. This allows the conversion value calculation unit 33 to obtain the d-axis converted value Vd/Vpp and the q-axis converted value Vq/Vpp.

In step S4, the phase change detection unit 36 uses the d-axis converted value Vd/Vpp and the q-axis converted value Vq/Vpp obtained by the converted value calculation unit 33 to detect whether the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount. Specifically, the phase change detection unit 36 determines that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount if the d-axis converted value Vd/Vpp is greater than or equal to the d-axis threshold, or if the q-axis converted value Vq/Vpp is greater than or equal to the q-axis threshold.

At this time, the phase change detection unit 36 detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount when the d-axis equivalent value Vd/Vpp is greater than or equal to the d-axis threshold, and detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount when the q-axis equivalent value Vq/Vpp reaches the q-axis threshold before the timing when the d-axis equivalent value Vd/Vpp reaches the d-axis threshold.

If the determination in step S4 is YES, the process proceeds to step S5, where the power converter 1 stops the switching operation of switching elements SW1 to SW6.

Specifically, if the phase change detection unit 36 determines YES in step S4, it generates and outputs a drive stop signal to the PWM signal generation unit 24 to stop the switching operation of the switching elements SW1 to SW6. Upon receiving the drive stop signal, the PWM signal generation unit 24 generates a PWM signal that stops the switching operation of the switching elements SW1 to SW6. This allows the power converter 1 to stop the operation of the switching elements SW1 to SW6.

On the other hand, if the determination in step S4 is NO, this flow terminates (END). That is, if the determination in step S4 is NO, the power converter 1 continues to drive the switching elements SW1 to SW6.

Based on the above, the voltage change detection device 50 according to this embodiment includes: a three-phase to two-phase conversion unit 31 that converts three-phase input voltages Vr, Vs, and Vt into d-axis voltage Vd and q-axis voltage Vq; a conversion value calculation unit 33 that obtains d-axis equivalent values Vd/Vpp and q-axis equivalent values Vq/Vpp by normalizing the d-axis voltage Vd and q-axis voltage Vq by dividing them by the effective values Vpp of the input voltages Vr, Vs, and Vt, respectively; and a phase change detection unit 36 that detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount when the d-axis equivalent value Vd/Vpp is greater than or equal to a d-axis threshold, or when the q-axis equivalent value Vq/Vpp is greater than or equal to a q-axis threshold.

This allows for accurate detection of whether the phase change amount of the three-phase input voltages Vr, Vs, and Vt exceeds a predetermined phase change amount, based on the change in the d-axis equivalent value Vd/Vpp obtained from the d-axis voltage Vd, or the change in the q-axis equivalent value Vq/Vpp obtained from the q-axis voltage Vq. Therefore, the above configuration enables accurate detection of rapid phase changes in the input voltages Vr, Vs, and Vt.

Furthermore, in this embodiment, the voltage change detection device 50 detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount when the d-axis equivalent value Vd/Vpp is greater than or equal to the d-axis threshold, and detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount when the q-axis equivalent value Vq/Vpp reaches the q-axis threshold before the timing when the d-axis equivalent value Vd/Vpp reaches the d-axis threshold.

When the phases of the input voltages Vr, Vs, and Vt are changed, there exists a phase angle such that the d-axis equivalent value Vd/Vpp hardly changes during a predetermined period immediately following the phase change. Therefore, as in the configuration described above, if the q-axis equivalent value Vq/Vpp reaches or exceeds the q-axis threshold before the d-axis equivalent value Vd/Vpp reaches the d-axis threshold, detecting that the phase change amount of the input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount allows for more rapid and accurate detection of rapid phase changes in the input voltages Vr, Vs, and Vt.

The power conversion device 1 according to this embodiment includes a voltage change detection device 50, a switching circuit 10 having a plurality of switching elements SW1 to SW6, and a drive control unit 40 that converts the three-phase input voltages Vr, Vs, and Vt into a predetermined DC voltage by switching-driving the plurality of switching elements SW1 to SW6, and stops driving the plurality of switching elements SW1 to SW6 when the voltage change detection device 50 detects that the phase change amount of the three-phase input voltages Vr, Vs, and Vt is greater than or equal to a predetermined phase change amount.

This prevents excessive current from flowing through the switching elements SW1 to SW6 of the switching circuit 10 and causing them to malfunction when the voltage change detection device 50 detects a sudden phase change in the three-phase input voltage.

(Other embodiments)
Although embodiments of the present invention have been described above, the embodiments described above are merely examples for carrying out the present invention. Therefore, the invention is not limited to the embodiments described above, and it is possible to carry out the invention by appropriately modifying the embodiments described above without departing from the spirit of the invention.

In the above embodiment, the voltage change detection device 50 detects a rapid phase change in the three-phase input voltages Vr, Vs, and Vt when the d-axis equivalent value Vd/Vpp is greater than or equal to the d-axis threshold, or when the q-axis equivalent value Vq/Vpp is greater than or equal to the q-axis threshold. However, the voltage change detection device may also detect a rapid phase change in the three-phase input voltages Vr, Vs, and Vt when the d-axis equivalent value Vd/Vpp is greater than or equal to the d-axis threshold.

Furthermore, the voltage change detection device may detect a rapid frequency change in the three-phase input voltages Vr, Vs, and Vt when the d-axis equivalent value Vd/Vpp is equal to or greater than the d-axis threshold, or when the q-axis equivalent value Vq/Vpp is equal to or greater than the q-axis threshold. That is, even when the frequencies of the three-phase input voltages Vr, Vs, and Vt change rapidly, the d-axis equivalent value Vd/Vpp will be equal to or greater than the d-axis threshold, or the q-axis equivalent value Vq/Vpp will be equal to or greater than the q-axis threshold, as described in the above embodiment.

In the above embodiment, the power converter 1 stops the switching operation of the multiple switching elements SW1 to SW6 when a rapid phase change in the three-phase input voltages Vr, Vs, and Vt is detected by the voltage change detection device 50. However, the voltage change detection device may also output the detection result of a rapid phase change in the input voltage to devices other than the power converter that are affected by rapid phase changes in the input voltage.

For example, if a rapid phase change in the three-phase input voltage is detected by a voltage change detection device, the control system gain (e.g., proportional gain, integral gain, etc.) may be corrected according to the phase change. This allows for a faster control response in the control system when a rapid phase change occurs in the input voltage. Specifically, the time it takes for Vd/Vpp (shown in Figure 5) and Vq/Vpp (shown in Figure 6) to converge can be shortened. Therefore, the time during which the input voltage and the PWM signal are out of sync can be reduced. Incidentally, when the input voltage and the PWM signal are out of sync, the current flowing through the switching element increases at a predetermined gradient. Therefore, by converging Vd/Vpp and Vq/Vpp before the current flowing through the switching element reaches a level that would damage the switching element, the output from the device can be continued without stopping the switching element.

Furthermore, for example, when a phase change is detected by a voltage change detection device, the amount of phase change is estimated, and the frequency Freq and phase angle θ in Figure 2 are corrected (for example, the frequency Freq and phase angle θ are set to predetermined values according to the amount of phase change). This allows the frequency Freq and phase angle θ within the control to be quickly adjusted to changes in the input voltage. As a result, the output from the device can be continued without stopping the switching elements.

In the above embodiment, the voltage change detection device 50 is composed of a part of the phase angle calculation unit 23 of the power conversion device 1. However, the voltage change detection device may be provided as a separate device from the power conversion device. Furthermore, the voltage change detection device may be provided in a device other than the power conversion device.

This invention can be used in a voltage change detection device that detects changes in three-phase input voltage.

1 Power conversion device 2 AC power supply 3 Capacitor 10 Switching circuit 20 Control unit 21 Voltage control unit 22 Current control unit 23 Phase angle calculation unit 24 PWM signal generation unit 31 3-phase 2-phase conversion unit (conversion unit)
32 Effective value calculation unit 33 Conversion value calculation unit 34 PI control unit 35 Phase angle conversion unit 36 Phase change detection unit 40 Drive control unit 50 Voltage change detection device SW1 to SW6 Switching elements Vr, Vs, Vt Input voltage

Claims (2)

A voltage change detection device for detecting changes in three-phase input voltage,
A conversion unit that converts the three-phase input voltage into d-axis voltage and q-axis voltage,
A conversion value calculation unit that obtains a d-axis converted value and a q-axis converted value by normalizing the d-axis voltage and the q-axis voltage by dividing them by the effective value of the input voltage, respectively.
A phase change detection unit detects that the phase change amount of the three-phase input voltage is greater than or equal to a predetermined phase change amount when the d-axis converted value is greater than or equal to the d-axis threshold, or when the q-axis converted value is greater than or equal to the q-axis threshold.
It has ,
The phase change detection unit detects that the amount of phase change in the three-phase input voltage is greater than or equal to a predetermined phase change amount when the d-axis converted value is greater than or equal to the d-axis threshold, and detects that the amount of phase change in the three-phase input voltage is greater than or equal to a predetermined phase change amount when the q-axis converted value reaches greater than or equal to the q-axis threshold before the timing when the d-axis converted value reaches greater than or equal to the d-axis threshold.
Voltage change detection device . A voltage change detection device according to claim 1 ,
A switching circuit having multiple switching elements,
A drive control unit that drives the plurality of switching elements to convert the three-phase input voltage into a predetermined DC voltage, and stops driving the plurality of switching elements when the voltage change detection device detects that the amount of phase change in the three-phase input voltage is greater than or equal to a predetermined phase change,
Having,
Power converter.