阅读说明：本技术 电力转换装置 (Power conversion device ) 是由 池田和也 于 2019-07-16 设计创作，主要内容包括：电力转换装置是将交流电力转换为直流电力的电力转换装置,具备：整流部,包括晶闸管；电容器,设置于整流部的后级；以及控制部,控制晶闸管的导通,控制部通过在从达到交流电力的电压为零的过零点时起经过根据交流电力的规定频率而决定的规定时间后进行晶闸管的导通,来使电力供给至电容器,且控制部在每次进行晶闸管的导通时都将规定时间设定得更短,控制部以如下方式进行控制：在交流电力的频率从规定频率发生了变动的情况下,在根据规定频率决定的规定时间后不进行晶闸管的导通。(The power conversion device is a power conversion device that converts alternating-current power into direct-current power, and includes: a rectifying section including a thyristor; a capacitor provided at a subsequent stage of the rectifying unit; and a control unit that controls conduction of the thyristor, wherein the control unit supplies power to the capacitor by conducting the thyristor after a predetermined time determined in accordance with a predetermined frequency of the ac power has elapsed from a zero-crossing point at which a voltage of the ac power is zero, and the control unit sets the predetermined time to be shorter each time the thyristor is conducted, and the control unit controls: when the frequency of the ac power fluctuates from the predetermined frequency, the thyristor is not turned on after a predetermined time determined according to the predetermined frequency.)

1. A power conversion device that converts AC power to DC power, the power conversion device comprising:

a rectifying section including a thyristor;

a capacitor provided at a subsequent stage of the rectifying unit; and

a control section for controlling the conduction of the thyristor,

the control unit supplies power to the capacitor by conducting the thyristor after a predetermined time determined according to a predetermined frequency of the alternating-current power has elapsed from a zero-crossing point at which the voltage of the alternating-current power is zero, and sets the predetermined time to be shorter each time the thyristor is conducted,

the control unit performs control in the following manner: when the frequency of the ac power fluctuates from the predetermined frequency, the thyristor is not turned on after a predetermined time determined according to the predetermined frequency.

2. The power conversion apparatus according to claim 1,

the control unit detects a voltage waveform of the ac power during a period from when the zero-cross point is reached to when the predetermined time elapses, and determines whether or not the frequency of the ac power has fluctuated from the predetermined frequency.

3. The power conversion apparatus according to claim 2,

the control unit sets, based on the predetermined frequency, voltage ranges of voltage values for each predetermined timing within one cycle of the alternating-current power, and determines that the frequency of the alternating-current power has fluctuated from the predetermined frequency when the voltage value of the alternating-current power deviates from the voltage range set for the timing corresponding to the voltage value.

4. The power conversion apparatus according to claim 1,

the control unit does not turn on the thyristor for a predetermined period when the frequency of the ac power fluctuates from the predetermined frequency.

5. The power conversion apparatus according to claim 1,

a voltage detection unit for detecting a voltage value of the AC power,

the control unit determines the predetermined frequency based on a voltage value of the ac power.

6. The power conversion apparatus according to claim 1,

the power conversion device is an in-vehicle charger for charging an in-vehicle battery,

the power conversion device is provided with:

a power factor improving section having the capacitor; and

a DC/DC converter, which is a DC/DC converter, provided at a subsequent stage of the power factor correction unit,

the control unit operates the power factor correction unit and the DC/DC converter unit to charge the battery when the voltage of the capacitor reaches a predetermined voltage.

7. The power conversion apparatus according to any one of claims 1 to 6,

the rectifying portion is a rectifying circuit including the thyristor and a diode.

8. The power conversion apparatus according to claim 1,

the rectifying portion is a rectifying circuit including the thyristor and a switching element.

Technical Field

The present invention relates to a power conversion device.

Background

In a power conversion device that converts ac power into dc power, such as a charger, a capacitor for smoothing voltage is precharged by a thyristor. For example, patent document 1 discloses a configuration in which a thyristor is used as a rectifying element, and conduction of the thyristor is performed based on a difference between a voltage of ac power and a voltage charged in a capacitor.

However, if a problem occurs in which the voltage value of the ac power at the time of starting the conduction of the thyristor deviates from the assumed voltage value (hereinafter, referred to as "misconduction"), if the above-described difference is large, an excessive inrush current may occur, which may affect the circuit of the power conversion device and the like. Therefore, for example, patent document 2 discloses a configuration for preventing the above-described erroneous conduction by detecting a pulse-like voltage drop or a momentary voltage drop in the input voltage.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4337032

Patent document 2: japanese laid-open patent publication No. 8-275532

Disclosure of Invention

Problems to be solved by the invention

However, when the frequency of the ac power fluctuates, the voltage value of the ac power before and after the frequency fluctuation of the timing at which the thyristor is turned on may deviate from each other, and thus the above-described erroneous turn-on may easily occur. In the configuration described in patent document 2, since the variation in the frequency of the ac power is not taken into consideration, there is a certain limitation as a configuration for preventing the misconduction of the thyristor.

The invention aims to provide a power conversion device capable of preventing misconduction of a thyristor.

Means for solving the problems

The present invention provides a power conversion device that converts ac power into dc power, the power conversion device including:

a rectifying section including a thyristor;

a capacitor provided at a subsequent stage of the rectifying unit; and

a control section for controlling the conduction of the thyristor,

the control unit supplies power to the capacitor by conducting the thyristor after a predetermined time determined according to a predetermined frequency of the alternating-current power has elapsed from a zero-crossing point at which the voltage of the alternating-current power is zero, and sets the predetermined time to be shorter each time the thyristor is conducted,

the control unit performs control in the following manner: when the frequency of the ac power fluctuates from the predetermined frequency, the thyristor is not turned on after a predetermined time determined according to the predetermined frequency.

Effects of the invention

According to the invention, the misconduction of the thyristor can be prevented.

Drawings

Fig. 1 is a diagram showing a power conversion device according to an embodiment of the present invention.

Fig. 2 is a timing chart for explaining control of conduction of the thyristor.

Fig. 3 is a timing chart for explaining an example of the deviation of the turn-on timing of the thyristor.

Fig. 4A is a diagram for explaining a voltage range set for each predetermined timing.

Fig. 4B is a diagram for explaining an example of determination of frequency fluctuation of ac power.

Fig. 5 is a flowchart showing an operation example of the conduction control of the thyristor in the power conversion device.

Fig. 6 is a diagram showing a voltage waveform of ac power when a sudden voltage fluctuation occurs.

Fig. 7 is a diagram showing a power conversion device according to a modification.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a diagram showing a power conversion device 100 according to an embodiment of the present invention.

As shown in fig. 1, the power conversion device 100 is a charger that is connected to an external ac power supply 10 and converts ac power supplied from the external ac power supply 10 into dc power to charge a battery 20. The battery 20 is mounted on a vehicle such as an electric vehicle or a hybrid vehicle.

The power converter 100 includes a rectifier 110, a voltage detector 120, a power factor corrector 130, a DC/DC converter (DC/DC converter) 140, and a controller 150.

The rectifying section 110 has a bridge circuit including a first thyristor 111, a second thyristor 112, a first diode 113, and a second diode 114.

The anode of the first thyristor 111 is connected to the positive electrode of the external ac power supply 10, and the cathode of the first thyristor 111 is connected to the input wiring 130A of the power factor correction unit 130. The gate of the first thyristor 111 is connected to the control unit 150.

The anode of the second thyristor 112 is connected to the ground wiring 130B of the power factor correction unit 130, and the cathode of the second thyristor 112 is connected to the positive electrode of the external ac power supply 10. The gate of the second thyristor 112 is connected to the control unit 150.

The anode of the first diode 113 is connected to the cathode of the external ac power supply 10, and the cathode of the first diode 113 is connected to the input wiring 130A of the power factor correction unit 130.

The anode of the second diode 114 is connected to the ground wiring 130B of the power factor correction unit 130, and the cathode of the second diode 114 is connected to the cathode of the external ac power supply 10.

The control unit 150 controls the conduction of the first thyristor 111 and the second thyristor 112. Specifically, the control unit 150 applies a voltage to the gates of the first thyristor 111 and the second thyristor 112, thereby adjusting the on states of the first thyristor 111 and the second thyristor 112. The rectifying unit 110 full-wave rectifies the ac power output from the external ac power supply 10 by conduction of the first thyristor 111 and the second thyristor 112, converts the ac power into dc power, and outputs the dc power to the power factor improving unit 130. The control of the rectifying unit 110 will be described later.

The voltage detection unit 120 is a voltage sensor that detects a voltage value of the ac power input to the rectification unit 110, and is provided at a stage preceding the rectification unit 110.

The power factor correction unit 130 is a power factor correction circuit for correcting the power factor of the dc power input from the rectifier unit 110. The power factor correction unit 130 includes a coil 131, a switching element 132, a diode 133, and a capacitor 134.

The coil 131 is provided on the input wiring 130A. One end of the coil 131 is connected to a cathode-side output terminal of the first thyristor 111 of the rectifying unit 110, and the other end of the coil 131 is connected to an anode of the diode 133.

The switching element 132 is a field effect transistor, and is provided between the input wiring 130A and the ground wiring 130B. Specifically, the drain of the switching element 132 is connected to the other end of the coil 131 and the anode of the diode 133 in the input wiring 130A, and the source of the switching element 132 is connected to the ground wiring 130B of the power factor improving unit 130. The gate of the switching element 132 is connected to the control unit 150.

The diode 133 is provided on the input wiring 130A. The anode of diode 133 is connected to the other end of coil 131, and the cathode of diode 133 is connected to DC/DC converter 140.

The capacitor 134 is disposed at a subsequent stage of the diode 133. Specifically, one end of the capacitor 134 is connected to the cathode of the diode 133, and the other end of the capacitor 134 is connected to the ground of the power factor correction unit 130. Thereby, the electric charge corresponding to the output of the power factor correction unit 130 is charged in the capacitor 134, and the dc power output from the power factor correction unit 130 is smoothed.

The DC/DC converter 140 is a circuit that converts the DC power output from the power factor corrector 130 into DC power that can be charged in the battery 20, and is connected to the subsequent stage of the power factor corrector 130. The control unit 150 controls a switching element, not shown, mounted on the DC/DC converter unit 140. Thereby, the DC power converted by the DC/DC converter 140 is output to the battery 20, and the battery 20 is charged.

The control Unit 150 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input/output circuit, which are not shown. The control unit 150 is configured to control the conduction of the first thyristor 111 and the second thyristor 112 in addition to the control of the power factor correction unit 130 and the DC/DC converter unit 140 based on a preset program. In the following description, the first thyristor 111 and the second thyristor 112 are simply referred to as "thyristors" unless they are distinguished from each other intentionally.

The control unit 150 controls the amount of dc power output from the rectifying unit 110 by controlling the conduction of the thyristor. Specifically, when precharging the voltage to the capacitor 134, the control unit 150 adjusts the timing of the thyristor conduction so that the voltage value increases stepwise in accordance with the voltage value of the capacitor 134.

The reason for this will be explained below.

In order to normally operate the power factor correction unit 130 of the power conversion device 100, it is necessary to precharge the voltage value of the capacitor 134 to a desired voltage value. However, in a case where the capacitor 134 is not sufficiently charged, a difference between the voltage value of the capacitor 134 and the voltage value of the alternating-current power may be excessively large. As a result, the surge current may be excessively large due to the difference, and may affect the peripheral circuit.

Therefore, the control unit 150 adjusts the on timing of the thyristor so that the voltage value of the capacitor 134 rises stepwise.

More specifically, the control unit 150 turns on one of the first thyristor 111 and the second thyristor 112 for a predetermined period of time after a predetermined time has elapsed from the time when the zero-crossing point at which the voltage value of the ac power output from the external ac power supply 10 becomes zero is reached. The first thyristor 111 is turned on when the voltage value of the ac power is a positive value. The second thyristor 112 is turned on when the voltage value of the ac power is negative.

The predetermined time is a time determined according to the predetermined frequency, and is, for example, a time shorter than a half cycle of the predetermined frequency. The predetermined frequency is a frequency of the ac power, and is, for example, a frequency determined by the control unit 150 based on the voltage value of the ac power detected by the voltage detection unit 120.

Then, the control unit 150 sets the predetermined time to be short every time one of the first thyristor 111 and the second thyristor 112 is turned on. The control of the conduction of the thyristor will be described in detail with reference to fig. 2.

As shown in fig. 2, after the output of the ac power is started, the conduction of the thyristor is started at a time TT1 after a predetermined time (predetermined time of the 1 st conduction) has elapsed from a time T1 at which the zero-cross point is reached. Since the voltage value of the ac power from time T1 to time T2 is positive, the first thyristor 111 is turned on at time TT 1. Note that the voltage value of the capacitor 134 at this time is zero. The time T2 is a time when a time corresponding to a half cycle of the ac power has elapsed from the time T1.

The predetermined time of the 1 st conduction is a time in which the angle of the phase of the ac power corresponds to an angle from 0 ° (corresponding to a point corresponding to time T1) to an angle slightly smaller than 180 ° (corresponding to time T2) (time TT 1). The predetermined time of the 1 st conduction is appropriately set by an experiment or the like, and is a time at which a rush current generated due to a voltage value equal to a voltage value of the ac power when the predetermined time elapses is a value to such an extent that the rush current does not affect the peripheral circuit.

When the 1 st conduction is started, a current (hereinafter referred to as "precharge current") based on a difference between the voltage value of the ac power at the start of the 1 st conduction and the voltage value of the capacitor 134 flows, and the capacitor 134 is charged with a charge corresponding to the precharge current. Thereby, the voltage value of the capacitor 134 rises to a voltage value corresponding to the electric charge. During the period from time TT1 to time T2, the voltage of the ac power decreases, and the voltage value of the capacitor 134 does not increase beyond the voltage value corresponding to the charge corresponding to the precharge current, so the first thyristor 111 automatically stops and the precharge current also stops.

Note that the control unit 150 applies a voltage to the gate of the first thyristor 111 for a certain period (a period from the time TT1 to a time immediately after the time T2 elapses) (see the gate voltage of the first thyristor in fig. 2).

After the ac power reaches the zero-crossing point at time T2, the conduction of the thyristor is started at time TT2 after a predetermined time (predetermined time of the 2 nd conduction) has elapsed from time T2. Since the voltage value of the ac power from the time T2 to the time T3 is a negative value, the second thyristor 112 is turned on at the time TT 2. The time T3 is a time when the same time as the half cycle of the ac power has elapsed since the time T2.

The predetermined time of the 2 nd turn-on is shorter than the 1 st predetermined time. The 2 nd predetermined time is appropriately set by an experiment or the like, and is a time at which an inrush current caused by a voltage value equivalent to a difference between the voltage value of the ac power and the voltage value of the capacitor 134 when the predetermined time elapses is a value to such an extent that the inrush current does not affect the peripheral circuits.

When the 2 nd conduction is started, a precharge current based on a difference between the voltage value of the ac power at the start of the 2 nd conduction and the voltage value of the capacitor 134 flows, and the capacitor 134 is charged with a charge corresponding to the precharge current. Thereby, the voltage value of the capacitor 134 rises to a voltage value corresponding to the electric charge. During the period from the time TT2 to the time T3, the voltage of the ac power decreases, and the voltage value of the capacitor 134 does not increase beyond the voltage value corresponding to the charge corresponding to the precharge current, so that the second thyristor 112 automatically stops and the precharge current also stops.

By repeating the conduction of the thyristor in this manner, the voltage value of the capacitor 134 gradually rises. Then, in the nth (n is an arbitrary natural number) conduction, the conduction is performed at time TTn when a predetermined time has elapsed from time Tn of the zero-crossing point, and the voltage value of the capacitor 134 reaches a desired value.

Thereafter, a voltage is always applied to the gate of the first thyristor 111 and the gate of the second thyristor 112, and the power factor improvement unit 130 and the DC/DC conversion unit 140 start operating.

Further, the control unit 150 performs control as follows: when the frequency of the ac power fluctuates from a predetermined frequency, the thyristor is not turned on after a predetermined time has elapsed from the time when the zero-cross point is reached.

As shown in fig. 3, the frequency of the ac power output from the external ac power supply 10 may vary. The solid line in fig. 3 shows an example in which the frequency of the ac power in the second cycle (the frequency after time T3) is smaller than the frequency of the ac power in the first cycle (the frequency from time T1 to time T3). The broken line in fig. 3 shows an example in which the frequency of the ac power in the second cycle does not vary from the frequency of the ac power in the first cycle.

For example, when the frequency of the ac power fluctuates so that the frequency of the ac power in the second cycle is smaller than the frequency of the ac power in the first cycle, the 3 rd conduction is performed based on the predetermined time of the 3 rd conduction set according to the predetermined time of the conduction in the first cycle (the 1 st conduction and the 2 nd conduction). That is, the conduction of the first thyristor 111 is started at a time TT3 when a predetermined time of 3 rd conduction has elapsed from a time T3 which is a zero-crossing point of the ac power of the second cycle.

Therefore, if the frequency of the ac power fluctuates, there is a problem that a large difference D occurs between the voltage value at the time TT3, which is the time when the conduction starts when the frequency of the ac power does not fluctuate (see the broken line), and the voltage value at the time TT3 when the frequency of the ac power fluctuates (see the solid line) (hereinafter, referred to as "false conduction"). If the difference D becomes large due to erroneous conduction, the difference between the voltage value of the capacitor 134 and the voltage value of the ac power at the start of conduction may become excessively large, and the inrush current may become excessively large.

However, in the present embodiment, the control unit 150 performs control as follows: when the frequency of the ac power fluctuates from the predetermined frequency, the thyristor is not turned on after a predetermined time. So at time TT3, the thyristor does not conduct. As a result, the generation of a rush current due to the fluctuation of the frequency of the ac power can be prevented. Furthermore, the following example is shown in fig. 3: since the voltage value of the ac power related to the 3 rd conduction is positive, the first thyristor 111 is not turned on at time TT 3.

Specifically, the control unit 150 detects the voltage waveform of the ac power until a predetermined time elapses after the zero-crossing point is reached, and thereby determines whether or not the frequency of the ac power has fluctuated from the predetermined frequency.

More specifically, the control unit 150 sets a plurality of voltage ranges of voltage values for each predetermined timing in one cycle of the ac power, based on the predetermined frequency. The plurality of voltage values are, for example, voltage values in a cycle before the current time point of the ac power, and are stored in a storage unit, not shown. The predetermined timing is a timing determined according to the frequency of the ac power, and is, for example, a timing every 1 ms.

For example, the voltage values of the voltage waveforms after time T3 in fig. 3 are voltage waveforms having a voltage value corresponding to one cycle from time T1 to time T3. The voltage value of the voltage waveform from time T1 to time T3 is detected by voltage detector 120 at a predetermined timing, and stored in a storage unit or the like at a predetermined timing. The voltage waveform to be compared may be a voltage waveform of one cycle before time T1.

Then, the control unit 150 reads the voltage value corresponding to each timing from the storage unit, and sets the voltage range of the voltage value.

Specifically, as shown in fig. 4A, the control unit 150 sets a voltage range of the voltage value of the ac power for each predetermined timing during a predetermined time period. In fig. 4A, the following example is shown: voltage ranges v1, v2, v3, v4, v5, v6, v7, v8, v9, and v10 are set for times m1, m2, m3, m4, m5, m6, m7, m8, m9, and m 10.

When the voltage value of the ac power does not deviate from the voltage range set for the timing corresponding to the voltage value, the control unit 150 determines that the frequency of the ac power does not fluctuate from the predetermined frequency. When the voltage value of the ac power deviates from the voltage range set for the timing corresponding to the voltage value, the control unit 150 determines that the frequency of the ac power has fluctuated from the predetermined frequency.

For example, in the example shown in fig. 4B, since the voltage of the ac power at time m1 (see the solid line) is within the voltage range v1 set according to the voltage of the ac power in the previous cycle (see the broken line), controller 150 determines that the frequency of the ac power does not fluctuate from the predetermined frequency at time m 1.

On the other hand, for example, since the voltage of the ac power at the time m3 is out of the voltage range v3 set according to the voltage of the ac power in the previous cycle, the controller 150 determines that the frequency of the ac power has fluctuated from the predetermined frequency at the time m 3.

When the frequency of the ac power fluctuates from the predetermined frequency, the control unit 150 does not perform control to turn on the thyristor for a predetermined period (for example, 3 periods). Then, after a predetermined period, the control unit 150 restarts controlling the conduction of the thyristor.

By doing so, when the frequency of the ac power fluctuates, the control of the conduction of the thyristor can be restarted after waiting for the predetermined period to elapse and the frequency of the ac power to return to normal.

The predetermined period may be varied according to the amount of variation in the frequency of the ac power. For example, the predetermined period may be set to be longer as the amount of fluctuation of the frequency of the ac power is larger. This can ensure a long time for the frequency of the ac power to return to normal.

When the control of the conduction of the thyristor is resumed, the voltage value of the capacitor 134 may fluctuate due to discharge or the like. Therefore, the control unit 150 may restart the control of the conduction of the thyristor after the predetermined time set in accordance with the voltage value of the capacitor 134.

This makes it possible to control the conduction of the thyristor in consideration of the variation in the voltage value of the capacitor 134 after the conduction of the thyristor is restarted. The voltage value of the capacitor 134 may be detected by a voltage detection unit, not shown.

In fig. 4A and the like, the voltage ranges at the respective times are set to the same range, but may be set to different ranges depending on the time. For example, if the voltage range is set so as to be narrower as the time point at which the conduction of the thyristor is started approaches, it is possible to prevent an excessive current from flowing at the time of erroneous conduction, and it is possible to improve the accuracy of the control of the conduction of the thyristor.

An operation example of the conduction control of the thyristors in the power conversion device 100 configured as described above will be described. Fig. 5 is a flowchart showing an operation example of the on control of the thyristors in the power conversion apparatus 100. The processing in fig. 5 is executed, for example, (1) after the ac power input to the external ac power supply 10 of the power conversion device 100 is started, (2) after the thyristor starts to be turned on, and (3) after an on/off counter described later is set. In addition, the process in fig. 5 is repeated until the voltage value of the capacitor 134 reaches a desired value.

As shown in fig. 5, the control unit 150 determines whether or not the voltage of the ac power reaches a zero-crossing point (step S101). If the voltage of the ac power does not reach the zero-crossing point as a result of the determination (no in step S101), the process of step S101 is repeated.

On the other hand, when the voltage of the ac power reaches the zero-crossing point (yes in step S101), the control unit 150 determines whether or not the on/off counter is 0 (step S102). The conduction stop counter is a counter set in accordance with a predetermined cycle when the thyristor is not turned on in step S112 to be described later.

If the on stop counter is not 0 as a result of the determination (no at step S102), control unit 150 decrements the on stop counter (step S103). After step S103, the present control ends.

On the other hand, when the on/off counter is 0 (yes at step S102), the control unit 150 stores the voltage value of the ac power in the previous cycle in a storage unit (not shown) or the like (step S104).

Next, the control unit 150 sets a predetermined time period according to the number of times of conduction (step S105). The control unit 150 calculates a predicted voltage value of the ac power at the present time (step S106). Then, the control unit 150 calculates the upper limit value and the lower limit value of the predicted voltage value (step S107). Then, the control unit 150 acquires an actual measurement value of the voltage of the ac power at the present time (step S108).

Next, the control unit 150 determines whether or not the actual measurement value is within the range between the upper limit value and the lower limit value (step S109). As a result of the determination, when the actual measurement value is within the range between the upper limit value and the lower limit value (yes in step S109), the control unit 150 determines whether or not a predetermined time has elapsed from the time point at which the zero-cross point is reached in step S101 (step S110).

If the predetermined time has not elapsed as a result of the determination (no at step S110), the process returns to step S106. On the other hand, when the predetermined time has elapsed (yes in step S110), the control unit 150 starts the conduction of the thyristor (step S111).

Returning to the determination of step S109, when the actual measurement value is not within the range between the upper limit value and the lower limit value (no in step S109), the control unit 150 sets the conduction stop counter to a predetermined value (for example, 3) without conducting the thyristor (step S112). After step S111 or step S112, the present control ends.

According to the present embodiment configured as described above, since the thyristor is not turned on when the frequency of the ac power fluctuates, it is possible to prevent the thyristor from being turned on by mistake, and it is possible to suppress the occurrence of an excessive rush current caused by the misturning on.

Even when the voltage of the ac power fluctuates suddenly without fluctuation of the frequency of the ac power as shown in fig. 6, the voltage value of the ac power deviates from the voltage range at the timing of the voltage fluctuation. In the example shown in fig. 6, an example is shown in which the voltage value of the ac power deviates from the voltage range v 2. As described above, if the voltage value of the ac power deviates from the voltage range, the voltage value may deviate from the voltage value assumed to be used for conduction, and false conduction may occur.

However, in the present embodiment, even in such a case, since the voltage fluctuation of the ac power can be detected, it is possible to prevent the occurrence of the erroneous conduction due to the voltage fluctuation of the ac power.

In the above embodiment, the rectifying unit 110 including the thyristor is provided at the front stage of the power factor correction unit 130, but the present invention is not limited thereto. For example, as shown in fig. 7, a rectifying unit 135 including a thyristor may be provided in the power factor correction unit 130.

The power converter 100 shown in fig. 7 includes a voltage detection unit 120, a power factor improvement unit 130, a DC/DC conversion unit 140, and a control unit 150. The voltage detection unit 120 and the DC/DC conversion unit 140 have the same configuration as that shown in fig. 1.

The power factor correction unit 130 includes a coil 131, a capacitor 134, and a rectifier 135. One end of coil 131 is connected to the positive electrode of external ac power supply 10, and the other end of coil 131 is connected to rectifying unit 135. One end of the capacitor 134 is connected to the output wiring 130C of the power factor correction unit 130, and the other end of the capacitor 134 is connected to the ground wiring 130D of the power factor correction unit 130.

The rectifying section 135 has a bridge circuit including a first thyristor 135A, a second thyristor 135B, a first switching element 135C, and a second switching element 135D.

The anode of the first thyristor 135A is connected to the other end of the coil 131, and the cathode of the first thyristor 135A is connected to the output wiring 130C of the power factor correction unit 130. The gate of the first thyristor 135A is connected to the control unit 150.

The anode of the second thyristor 135B is connected to the ground wiring 130D of the power factor correction unit 130, and the cathode of the second thyristor 135B is connected to the other end of the coil 131. The gate of the second thyristor 135B is connected to the control unit 150.

The source of the first switching element 135C is connected to the negative electrode of the external ac power supply 10, and the drain of the first switching element 135C is connected to the output wiring 130C of the power factor correction unit 130. The gate of the first switching element 135C is connected to the control unit 150.

The source of the second switching element 135D is connected to the ground wiring 130D of the power factor correction unit 130, and the drain of the second switching element 135D is connected to the negative electrode of the external ac power supply 10. The gate of the second switching element 135D is connected to the control unit 150.

The first thyristor 135A, the second thyristor 135B, the first switching element 135C, and the second switching element 135D are controlled by the control unit 150 according to whether the voltage value of the ac power is positive or negative. Thus, the power factor correction unit 130 converts the ac power into dc power and corrects the power factor of the dc power.

Even with such a configuration, when the capacitor 134 is precharged, the conduction of the thyristor can be controlled in the same manner as in the above-described embodiment, thereby preventing erroneous conduction of the thyristor.

In the above embodiment, the control is performed as follows: when the alternating-current power fluctuates from a predetermined frequency, the thyristor is not turned on for a predetermined period from the zero-crossing point. However, the present invention is not limited thereto. Since the timing at which the voltage value becomes the voltage value at which conduction should be started is deviated when the ac power fluctuates from the predetermined frequency, for example, the thyristor may be turned on at the estimated start timing after the start timing of conduction is estimated in accordance with the frequency after the fluctuation. If this is done, when the ac power fluctuates from the predetermined frequency, the thyristor is not turned on when the predetermined time set when the ac power is the zero-crossing point has elapsed, but is turned on at the estimated start time. This eliminates the period during which the operation of the power conversion device 100 is stopped, and improves the operation efficiency.

In the above-described embodiment, the control is performed so that the conduction of the thyristor is not performed when the voltage value of the ac power deviates from the voltage range at the timing corresponding to the voltage value. For example, the control may be performed such that the thyristor is not turned on when the voltage value of the ac power deviates from the voltage range a predetermined number of times.

The control unit 150 may determine whether or not to turn on the thyristor based on a specific timing within a predetermined time. For example, when the voltage value of the ac power deviates from the voltage range set for the timing at which the thyristor is not turned on at a timing relatively close to the timing at which the conduction starts, such as a timing closer to the timing at which the conduction starts than the timing at which the peak of the ac power is reached, the control unit 150 may determine that the thyristor is not turned on. The reason for this is considered to be that, when the voltage value of the ac power deviates from the assumed voltage range near the timing of the start of conduction, there is a high possibility that the voltage value of the ac power does not return to the assumed voltage range at the timing of the start of conduction.

In the above embodiment, the predetermined timing is set so that the voltage value of the ac power can be compared in a total of 10 voltage ranges v1 to v10 within the predetermined time period in fig. 4A, but the present invention is not limited to this. For example, the predetermined timing may be set so that the voltage value of the ac power can be compared using more than 10 voltage ranges or less than 10 voltage ranges.

The predetermined timing may be different depending on the situation. For example, as the voltage value of the capacitor 134 is smaller, the difference between the voltage value and the voltage value of the ac power at the time of occurrence of the erroneous conduction is likely to become larger, so that the surge current is likely to become excessively large, and it is necessary to accurately control the thyristor.

In this case, the control unit 150 sets the predetermined timing so that the number of timings of comparing the voltage ranges is large. Specifically, the control unit 150 sets the predetermined timing so that the number of timings for comparing the voltage ranges increases as the voltage value of the capacitor 134 decreases.

By doing so, it is easy to detect the frequency variation (voltage variation) more finely when the voltage value of the capacitor 134 is small, so the accuracy of preventing the misconduction of the thyristor can be further improved.

In the above-described embodiment, the voltage ranges of the voltage values at the predetermined timings in one cycle of the ac power are set, respectively, but the present invention is not limited to this, and the voltage ranges may be set only for the voltage values at the one timing in the one cycle.

In the above-described embodiment, the predetermined frequency of the ac power is determined based on the detection result of the voltage detection unit 120, but the present invention is not limited to this. For example, the predetermined frequency of the ac power may be determined by the power conversion device 100 communicating with one of the power supplies (the external ac power supply 10 or the like) to acquire information of the predetermined frequency. The predetermined frequency of the ac power may be determined by the power conversion device 100 communicating with a GPS (Global Positioning System) or the like to acquire information on the frequency of the ac power of the external ac power supply 10 as information on the current position.

In the above embodiment, the voltage range is calculated and set at each timing after the ac power reaches the zero cross point, but the present invention is not limited to this. For example, the voltage range may be set with reference to a table associated with a predetermined frequency and amplitude (maximum voltage value) of the ac power.

In the above embodiment, the rectifying unit 110, the power factor improving unit 130, and the DC/DC converting unit 140 are controlled by the control unit 150 having one CPU, but the present invention is not limited to this. For example, the rectifying unit 110, the power factor improving unit 130, and the DC/DC converter unit 140 may be controlled by a plurality of CPUs.

The above embodiments are merely examples of embodying the present invention, and the technical scope of the present invention should not be limited by these embodiments. That is, the present invention can be implemented in various forms without departing from the gist or main features thereof.

The disclosures of the description, drawings and abstract contained in japanese patent application laid-open application No. 2018-151085, filed on 8/10 in 2018, are incorporated in their entirety into the present application.

Industrial applicability

The power conversion device of the present invention is useful as a power conversion device capable of preventing misconduction of a thyristor.

Description of the reference numerals

10 external alternating current power supply

20 cell

100 power conversion device

110 rectifying part

111 first thyristor

112 second thyristor

113 first diode

114 second diode

120 voltage detection unit

130 power factor improving part

131 coil

132 switching element

133 diode

134 capacitor

140 DC/DC converter (DC/DC converter)

150 control part