JP6895067B2 - 3-level chopper and its control circuit - Google Patents

Description

The present invention relates to a technique for equalizing the voltages of two capacitors that share the output voltage of a three-level chopper.

FIG. 4 is a main circuit configuration diagram of the DC power supply system described in Patent Document 1.
This DC power supply system boosts the DC power supply voltage and converts it into a DC voltage having a neutral point by the operation of a semiconductor switching element (hereinafter, simply referred to as a switching element), and is composed of a so-called three-level chopper. There is.

This three-level chopper is a series circuit of a DC power supply BAT, a series circuit of switching elements S ₁ and S _{2 connected between the positive and negative electrodes via reactors L 1} and L _{2 , and a switching element S 3 at} both ends of the series circuit. , a capacitor _C 1, _{C 2} connected in series to each other through _{S 4,} respectively, across the load LD of the series circuit of the capacitor _C 1, _{C 2} are connected.
Note that D _{1 to} D ₄ are freewheeling diodes connected in antiparallel to switching elements S _{1 to} S ₄ , respectively, P is a positive terminal, N is a negative terminal, and M is a switching element S ₁ and S ₂ . It is a series connection point (neutral point) of _{capacitors C 1} and C _{2 connected to the series connection point.}

The operation of this circuit will be briefly described below.
First, when the switching elements S ₁ and S ₂ are turned on together, energy is stored in the _{reactors L 1} and L _2. Next, to turn off the switching element S ₂ remains turned on the switching element S _1, the capacitor C ₂ is charged via a switching element S ₁ and the freewheeling diode D ₄ by stored energy of the reactor L _1, L ₂ .. Next, when the switching element S ₁ is turned off and the switching element S ₂ is turned on, the capacitor C ₁ is charged by _{the stored energy of the reactors L 1} and L ₂ via the freewheeling diode D ₃ and the switching element S _2.

By repeating the above operation, the output voltage V _pn between the terminals P and N is boosted to a voltage higher than the DC power supply voltage V _bat. Here, the output voltage V _pn is called a three-level chopper because it can take three levels (V _dcp , V _dcn , and V _dcp + V _dcn).

In this type of 3-level chopper, if the voltages of the two capacitors on the output side are biased due to a failure of the switching element or a variation in the circuit constant, the switching element and the capacitor may be destroyed by the overvoltage. is there.
Therefore, in Patent Document 1, the control circuit of FIG. 5 is used to control the voltages V _dcp and V _dcn to be equal.

Figure 5 shows a control circuit for driving the switching element S ₁ to S _4.
In FIG. 5, the _{voltage regulators AVR 1} and AVR ₂ are set so that the voltages V _dcp and V _{dcn of the capacitors C 1} and C ₂ are equal to 1/2 of the DC voltage command value (output voltage command value) V _pn ^{*, respectively.} It operates, and these outputs are applied to _{the PWM circuits PWM A} and PWM _B having the same configuration via the _{changeover switches SW 1} and SW _2.

PWM circuits PWM _A and PWM _B include a comparator Cmp, timers TM ₁ , TM ₂ , logic circuits 11 to 15, fall detection circuits 16 and 17, and a DQ flip-flop 18, and the output of each of the DQ flip-flops 18 is It becomes the changeover signals 1 and ₂ for the changeover switches SW ₁ and SW 2 on the input side.
Pulse output determining circuit PJ, the voltage detection value _{V dcp,} depending on the magnitude of _{V dcn,} PWM circuit _PWM A, the drive signal of the output signal _{S 1} '~S _4' the switching element _S 1 to S ₄ of the PWM _B Select as (gate signal) and output.

In the control circuit, FIG. 6 (a), to adjust the (b), the voltage detection value _{V dcp,} the switching element _S 1 in accordance with the magnitude of _{V dcn, S 2} of the on-time. Specifically, to increase the amount of charge towards the capacitor voltage is low, to increase or decrease the current I _ch in FIG 4 lengthening the on time of the switching devices connected in series to the capacitor, the voltage V _dcp, Control is performed to equalize V- _dcn.
The switching elements S ₃ and S ₄ function to regenerate the energy of the capacitors C ₁ and C ₂ to the DC power supply side _{to maintain the voltages V dcp} and V _dcn at predetermined values.

Japanese Unexamined Patent Publication No. 2013-5649 (paragraphs [0015] to [0023], FIGS. 1, 3 to 5)

In the technique described in Patent Document 1, if _{the on-time of the switching elements S 1} and S ₂ becomes too long, the temperature of the element becomes higher than the design value, and as a result, a protective operation for preventing the switching element from being destroyed. May stop the operation of the device.
Therefore, the problem to be solved by the present invention is to provide a three-level chopper and its control circuit that can prevent overheating of the switching element and continue stable operation while equalizing the voltage of the series capacitor on the output side. is there.

In order to solve the above problem, the three-level chopper according to claim 1 is
The first and second switching elements are connected in series between the positive and negative sides of the DC power supply via a reactor, and the first and second diodes are connected to both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the respective capacitors, and the series connection points of the first and second switching elements and the series connection points of the first and second capacitors are connected to each other. A 3-level chopper in which a load is connected to both ends of the series circuit of the first and second capacitors.
A voltage command generator that generates a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value, and
A balance correction amount generation unit that generates a balance correction amount for equalizing the voltages of the first and second capacitors, and a balance correction amount generation unit.
A means for generating a drive signal for turning on / off the first and second switching elements based on the voltage command and the balance correction amount, and
A balance correction amount adjusting unit that adjusts the balance correction amount according to the voltage of the first and second capacitors, the temperature of the first and second switching elements, and the temperature threshold value is provided.
The balance correction amount adjusting unit is
During the period when the temperature of one of the first and second switching elements is less than the temperature threshold, the balance correction amount for both switching elements is kept at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the above period, the balance correction amount for the switching element is set to 0, and the balance correction amount for the other switching element is maintained at the predetermined value.

The three-level chopper according to claim 2 is
The first and second switching elements are connected in series between the positive and negative sides of the DC power supply via a reactor, and the first and second diodes are connected to both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the respective capacitors, and the series connection points of the first and second switching elements and the series connection points of the first and second capacitors are connected to each other. A 3-level chopper in which a load is connected to both ends of the series circuit of the first and second capacitors.
A voltage command generator that generates a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value, and
A balance correction amount generating unit that generates a balance correction amount for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
A means for generating a drive signal for turning on / off the first and second switching elements based on the voltage command and the balance correction amount, and
A balance correction amount adjusting unit that adjusts the balance correction amount according to the voltage of the first and second capacitors, the temperature of the first and second switching elements, and the temperature threshold value is provided.
The balance correction amount adjusting unit is
During the period when the temperature of one of the first and second switching elements is less than the temperature threshold, the balance correction amount for both switching elements is kept at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the above period, the balance correction amount for the switching element is gradually changed toward 0, and the balance correction amount for the other switching element is maintained at the predetermined value.

The three-level chopper according to claim 3 is the three-level chopper according to claim 1 or 2. In the balance correction amount adjusting unit, the absolute value of the voltage difference between the first and second capacitors is the voltage difference threshold. When it is less than, the balance correction amount for the first and second switching elements is set to 0.

The three-level chopper according to claim 4 is the three-level chopper according to any one of claims 1 to 3, wherein the voltage of the DC power supply is boosted and supplied to the load.

The three-level chopper according to claim 5 is the three-level chopper according to any one of claims 1 to 4, wherein a third switching element is connected to the first diode in antiparallel and the third level chopper is described. It is characterized in that a fourth switching element is connected to the diode of 2 in antiparallel.

The three-level chopper according to claim 6 is the three-level chopper according to claim 5, in which the third and fourth switching elements are turned on and the energy of the first and second capacitors is regenerated to the DC power supply. It is characterized by doing.

The control circuit of the three-level chopper according to claim 7 is
The first and second switching elements are connected in series between the positive and negative sides of the DC power supply via a reactor, and the first and second diodes are connected to both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the respective capacitors, and the series connection points of the first and second switching elements and the series connection points of the first and second capacitors are connected to each other. A 3-level chopper control circuit in which a load is connected to both ends of the series circuit of the first and second capacitors.
A voltage command generator that generates a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value, and
A balance correction amount generating unit that generates a balance correction amount for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
A means for generating a drive signal for turning on / off the first and second switching elements based on the voltage command and the balance correction amount, and
A balance correction amount adjusting unit that adjusts the balance correction amount according to the voltage of the first and second capacitors, the temperature of the first and second switching elements, and the temperature threshold value is provided.
The balance correction amount adjusting unit is
During the period when the temperature of one of the first and second switching elements is less than the temperature threshold, the balance correction amount for both switching elements is kept at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the above period, the balance correction amount for the switching element is set to 0, and the balance correction amount for the other switching element is maintained at the predetermined value.

The control circuit of the three-level chopper according to claim 8 is
The first and second switching elements are connected in series between the positive and negative sides of the DC power supply via a reactor, and the first and second diodes are connected to both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the respective capacitors, and the series connection points of the first and second switching elements and the series connection points of the first and second capacitors are connected to each other. A 3-level chopper control circuit in which a load is connected to both ends of the series circuit of the first and second capacitors.
A voltage command generator that generates a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value, and
A balance correction amount generating unit that generates a balance correction amount for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
A means for generating a drive signal for turning on / off the first and second switching elements based on the voltage command and the balance correction amount, and
A balance correction amount adjusting unit that adjusts the balance correction amount according to the voltage of the first and second capacitors, the temperature of the first and second switching elements, and the temperature threshold value is provided.
The balance correction amount adjusting unit is
During the period when the temperature of one of the first and second switching elements is less than the temperature threshold, the balance correction amount for both switching elements is kept at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the above period, the balance correction amount for the switching element is gradually changed toward 0, and the balance correction amount for the other switching element is maintained at the predetermined value.

According to the present invention, it is possible to continue stable operation of the apparatus by equalizing the voltage of the series capacitor while preventing destruction due to overheating without lengthening the on-time of the switching element more than necessary.

It is a block diagram of the control circuit which concerns on 1st Embodiment of this invention. It is a block diagram of the control circuit which concerns on 2nd Embodiment of this invention. It is a figure which shows the relationship between the temperature detection value of the switching element and the balance correction amount in each embodiment of this invention. It is a main circuit block diagram of the DC power supply system described in Patent Document 1. It is a block diagram of the control circuit described in Patent Document 1. It is a waveform diagram which shows the operation of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram of a control circuit according to a first embodiment of the present invention. The control circuit is for generating a driving signal of the switching element S ₁ to S ₄ as a target for three-level chopper of Figure 4 described above.

In FIG. 1, the PWM command generation unit 100 is based on the DC voltage command value V _pn ^{*, the} DC voltage detection value V _pn, and the DC current detection value (detection value of the current flowing in from the battery BAT in FIG. 4) _Ich. , Generates a PWM command (voltage command) for controlling the above V _pn to V _pn ^*.
This PWM command is added / subtracted by the addition / subtractors 101 and 102 to the balance correction amount which is the output of the low-pass filters 211 and 213, which will be described later, and is input to _{the PWM circuits PWM 1} and PWM _2. The PWM circuit _PWM 1, PWM _2, by comparing each with each command and the carrier 2 with the input switching element _S 1, _{S 3} of FIG. 4, and, the switching element _S 2, _{S 4} Generate a drive signal.

The balance correction amount adjusting unit 200A controls the balance correction amount to be added or subtracted to the PWM command to the output of the balance correction amount generation unit 300 or “0”. The configuration and function of the balance correction amount adjusting unit 200A will be described later.
The balance correction amount generation unit 300 generates a balance correction amount for equalizing the voltage detection values V _dcp and V _{dcn of the capacitors C 1} and C ₂ , and outputs the balance correction amount to the balance correction amount adjustment unit 200A.

Next, the balance correction amount adjusting unit 200A will be described in detail.
The balance correction amount adjusting unit 200A sets the voltage detection values V _dcp , V _{dcn of the capacitors C 1} and C ₂ , the temperature detection values T ₁ and T _{2 of} the switching elements S ₁ and S ₂ , and the temperature thresholds T _1t and T _2t . Based on this, it has a function of switching and outputting the balance correction amount or "0" output from the balance correction amount generation unit 300.

That is, the detected temperature value _{T 1} of the switching element _{S 1} and the temperature threshold value _{T 1t} are compared by the comparator 203, the output of which is inputted to the AND circuit 208. Further, the voltage detection values V _dcp and V _dcn are compared by the comparator 204, and the output thereof is input to the AND circuit 208 and input to the AND circuit 209 via the negative circuit 207.

_{Further, the difference between} the voltage detection values V dcp and V _dcn is obtained by the adder / subtractor 201, and the absolute value thereof is calculated by the absolute value calculator 202. The output of the absolute value calculator 202 and the voltage difference threshold value ΔV _t are compared by the comparator 205, and the output is input to the AND circuits 208 and 209.
Further, the detected temperature value _{T 2} of the switching element _{S 2} and the temperature threshold value _{T 2t} is compared by the comparator 206, the output of which is inputted to the AND circuit 209.

The output of the AND circuit 208 is added to the changeover switch 210 as a changeover signal 208S, and the output of the AND circuit 209 is added to the changeover switch 212 as a changeover signal 209S.
"0" is input to the input terminals T (True) of the changeover switches 210 and 212, respectively, and the balance correction amount generated by the balance correction amount generation unit 300 is input to the input terminal F (False), respectively. There is.

Here, the changeover switches 210 and 212 are connected to the input terminal T side when the logic of the changeover signals 208S and 209S is at the "H (High)" level, and are connected to the input terminal F side when the logic of the changeover signals 208S and 209S is at the "L (Low)" level. Connected to.
The outputs of the changeover switches 210 and 212 are input to the addition / subtractors 101 and 102 with reference numerals as shown through the first and second low-pass filters 211 and 213, respectively.

Next, the magnitude relation of the voltage detection values V _dcp and V _dcn of the capacitors C ₁ and C ₂ and the operation of the first embodiment according to the temperature detection values T ₁ and T ₂ of the switching elements S ₁ and S _{2 are performed.} , FIGS. 3 (a) and 3 (b) will be described.

₍₁₎ V _dcp> a _{V dcn, and,} if the absolute value of the difference between _{V dcp} and _{V dcn} is less than the voltage difference threshold [Delta] V _t In this case, the switching element applied voltage of the capacitor _{C 1} in FIG. 4 It is necessary to protect _{S 1} from the voltage V _dcp.

For that purpose, so as to increase the voltage V _dcn by increasing the charge amount of the capacitor C _2, the balance correction amount for lengthening the on time of the switching element S _1, the PWM command via the subtracter 101 it may be added, but in the present embodiment, as shown by the solid line in FIG. 3 (a), the zero balance correction amount when the temperature detection value T ₁ of the switching element S ₁ is equal to or greater than a threshold value T _1t.
Meanwhile, in order to suppress the increase of less to voltage V _dcp the charge amount of the capacitor C _1, as indicated by broken line in FIG. 3 (a), balance correction for shortening the ON time of the switching element S ₂ is a constant value regardless of the temperature of the switching element S _1.

In the circuit of FIG. 1, _{since the switching signal 208S output from the AND circuit 208 is “L” during the period when the temperature detection value T 1} does not exceed the threshold value T _1t , the balance correction amount is the input terminal F of the changeover switch 210 and the input terminal F of the changeover switch 210. It is input to the adder / subtractor 101 via the low-pass filter 211. When T ₁ becomes T _1t or more, the output of the comparator 203 becomes "H", and the outputs of the other comparators 204 and 205 are also "H", the switching signal 208S becomes "H" and the low pass is performed. The input of the filter 211 becomes 0, and the balance correction amount for _{the switching element S 1 also becomes 0.}

Incidentally, the balance adjustment operation to provide a balance correction amount of a predetermined value with respect to the switching element S _2, the switching signal output from the AND circuit 209 in the case of V _dcp> V _dcn becomes "L", the balance correction amount Is input to the adder / subtractor 102 via the input terminal F of the changeover switch 212 and the low-pass filter 213.

_{When the temperature of the switching element S 1} rises due to the above operation, it is possible to suppress an increase in the voltage V _{dcp of the capacitor C 1} by shortening only the on time of the switching element S _{2 without changing the on time. Therefore, it is possible to equalize the voltages V dcp} and V _dcn while reducing the loss of the switching element S ₁ and to continue the operation of the apparatus.

(2) When V _dcp <V _dcn and the absolute value of the difference _{between V dcp} and V _{dcn is smaller than the voltage difference threshold ΔV t In} this case, the switching element S _{2 to which the voltage of the capacitor C 2} is applied is used. It needs to be protected from the voltage V _dcn.

For that purpose, so as to increase the voltage V _dcp by increasing the charge amount of the capacitor C _1, the balance correction amount for lengthening the on time of the switching element S _2, the PWM command through the adder-subtractor 102 it may be added, but in the present embodiment, as indicated by broken line in FIG. 3 (b), the zero balance correction amount when the temperature detection value T ₂ of the switching element S ₂ is equal to or greater than a threshold value T _2t.
Meanwhile, in order to suppress the increase of less to voltage V _dcn the charge amount of the capacitor C _2, as shown by the solid line in FIG. 3 (b), balance correction for shortening the ON time of the switching element S ₁ is a constant value regardless of the temperature of the switching element S _2.

In the circuit of FIG. 1, _{since the switching signal 209S output from the AND circuit 209 is “L” during the period when the temperature detection value T 2} does not exceed the threshold value T _2t , the balance correction amount is the input terminal F of the changeover switch 212 and the input terminal F of the changeover switch 212. It is input to the adder / subtractor 102 via the low-pass filter 213. When the temperature detection value T ₂ becomes the threshold value T _2t or more and the output of the comparator 206 becomes “H” and the outputs of the comparator 205 and the negative circuit 207 are also “H”, the switching signal 209S becomes “H”. It becomes "H", the input of the low-pass filter 213 becomes 0, and the balance correction amount for _{the switching element S 2 also becomes 0.}

In the balance adjustment operation of giving a constant balance correction amount to the switching element S ₁ , the output of the AND circuit 208 becomes “L” when _{V dcp} <V _{dcn, and the balance correction amount is the changeover switch 210.} It is realized by inputting to the addition / subtractor 101 via the input terminal F and the low-pass filter 211.

_{When the temperature of the switching element S 2} rises due to the above operation, it is possible to suppress an increase in the voltage V _{dcn of the capacitor C 2} by shortening only the on time of the switching element S _{1 without changing the on time.} .. _{Therefore, it is possible to equalize the voltages V dcp} and V _dcn while reducing the loss of the switching element S ₂ and to continue the operation of the apparatus.

(3) When the absolute value of the difference _{between V dcp} and V _{dcn is equal to or greater than the voltage difference threshold ΔV t In} this case, the capacitor or switching element on the overvoltage state may exceed the withstand voltage, so the switching element It is necessary to equalize the _{voltages V dcp} and V _dcn regardless of the temperature of.

When the absolute value of the difference _{between V dcp} and V _{dcn is ΔV t} or more, the output of the comparator 205 becomes “L”, and the switching signals 208S and 209S output from the AND circuits 208 and 209 also become “L”. Therefore, the changeover switches 210 and 212 are all switched to the input terminal F side, and the balance correction amount is input to the adder / subtractor 101 and 102 via the changeover switches 210 and 212 and the low-pass filters 211 and 213, respectively, so that the voltage V _Control to equalize dcp and V _dcn will be executed.

Next, the second embodiment of the present invention will be described. This second embodiment is obtained so as to gradually change the balance correction amount for one of the switching elements in accordance with the temperature of the switching element S _1, S _2.
FIG. 2 is a configuration diagram of a control circuit according to a second embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals and description thereof will be omitted. Hereinafter, parts different from FIG. 1 will be mainly described. ..

In the balance correction amount adjusting unit 200B shown in FIG. 2, the output signal of the comparator 204 is input to the AND circuit 214 and is input to the AND circuit 215 via the negative circuit 207. Further, the output signal of the comparator 205 is input to the AND circuits 214 and 215.

The difference between the switching element _{S 1} of the detected temperature value _{T 1} and the threshold _{T 1t} is calculated by subtracter 216, the difference and the gain _{G 1} is multiplied by the multiplier 217. The output of the multiplier 217 is applied to the input terminal T of the changeover switch 219 via the limiter 218 whose lower limit value is 0, and 0 is set to the other input terminal F. The output of the changeover switch 219 is input to the adder-subtracter 220 by the symbol shown with balance correction amount from the balance correction amount generating unit 300, and its output is added to the adder-subtracter 101 of the switching element S ₁ side.

Similarly, the difference between the detected temperature value T ₂ and the threshold T _2t of the switching element S ₂ is calculated by the subtractor 221, the difference and the gain G ₂ is multiplied by the multiplier 222. The output of the multiplier 222 is applied to the input terminal T of the changeover switch 224 via the limiter 223 whose lower limit value is 0, and 0 is set to the other input terminal F. The output of the switch 224, together with the balance correction amount from the balance correction amount generating unit 300 is input to the adder-subtracter 225 in the illustrated code, and its output is added to the adder 102 of the switching element S ₂ side.
The above-mentioned gain G _1, G ₂ are equal in magnitude, positive or negative are reversed.

Next, the magnitude relation of the voltage detection values V _dcp and V _dcn of the capacitors C ₁ and C ₂ and the operation of the second embodiment according to the temperature detection values T ₁ and T ₂ of the switching elements S ₁ and S _{2 are described.} This will be described with reference to FIGS. 3 (c) and 3 (d).

(1a) When V _dcp > V _dcn and the absolute value of the difference _{between V dcp} and V _{dcn is smaller than the voltage difference threshold ΔV t In} this case, the switching element S _{1 to which the voltage of the capacitor C 1} is applied is used. It needs to be protected from the voltage V _dcp.

For that purpose, so as to increase the voltage V _dcn by increasing the charge amount of the capacitor C _2, the balance correction amount for lengthening the on time of the switching element S _1, the PWM command via the subtracter 101 it may be added, in the present embodiment, as shown by the solid line in FIG. 3 (c), the detected temperature value T ₁ is the threshold T _1t smaller than the period of the switching element S ₁ is a constant balance correction amount, the threshold value T _1t In the above period, the balance correction amount is linearly reduced as the _{temperature detection value T 1 becomes higher, and finally becomes 0.}
Meanwhile, in order to suppress the increase of less to voltage V _dcp the charge amount of the capacitor C _1, as indicated by broken line in FIG. 3 (c), balance correction for shortening the ON time of the switching element S ₂ is a constant value regardless of the temperature of the switching element S _1.

In the circuit of FIG. 2, since _{the output of the limiter 218 is limited to 0 during the period when the temperature detection value T 1} is smaller than the threshold value T _{1t, the} signal input to the adder / subtractor 220 via the input terminal T of the changeover switch 219 is It is 0. Here, the changeover switch 219 is switched to the input terminal T side by the changeover signal 214S output from the AND circuit 214.
Therefore, the balance correction amount generated by the balance correction amount generation unit 300 is input to the adder / subtractor 101 without being adjusted.

However, when the temperature detection value T ₁ becomes the threshold value T _1t or more, the temperature deviation increases according to the increase, _{and the multiplication result with the gain G 1} by the multiplier 217 also increases. Therefore, the limiter 218 and the changeover switch 219 are used. The amount of adjustment input to the adder / subtractor 220 via the adder / subtractor 220 also gradually increases. As a result, the balance correction amount output from the addition / subtractor 220 and input to the addition / subtractor 101 changes as shown by the solid line in FIG. 3C.

The switching element _S balance adjustment operation provide a constant balance correction for the _2, V _{dcp> V} selector switch 224 switching signal 215S is set to "L" output from the AND circuit 215 in the case of _dcn Since 0 is input to, the balance correction amount is directly input to the addition / subtractor 102 via the addition / subtractor 225.

By the above operation, _{the increase in the voltage V dcp} can be suppressed by shortening only the on-time _{of the switching element S 2} without changing the on-time _{of the switching element S 1. Therefore, it is possible to equalize the voltages V dcp} and V _dcn while reducing the loss of the switching element S ₁ and to continue the operation of the apparatus.

(2a) When V _dcp <V _dcn and the absolute value of the difference _{between V dcp} and V _{dcn is smaller than the voltage difference threshold ΔV t In} this case, the switching element S _{2 to which the voltage of the capacitor C 2} is applied is used. It needs to be protected from the voltage V _dcn.

For that purpose, so as to increase the voltage V _dcp by increasing the charge amount of the capacitor C _1, the balance correction amount for lengthening the on time of the switching element S _2, the PWM command through the adder-subtractor 102 may be added, in the present embodiment, as indicated by broken line in FIG. 3 (d), the detected temperature value T ₂ the threshold T _2t is smaller than the period of the switching element S ₂ is a constant balance correction amount, the threshold value T _2t In the above period, the balance correction amount is linearly increased (decreased in the negative direction) as the _{temperature detection value T 2 becomes higher, and finally becomes 0.}
Meanwhile, in order to suppress the increase of less to voltage V _dcn the charge amount of the capacitor C _2, balance correction for shortening the ON time of the switching element S _1, regardless of the temperature of the switching element S ₂ Set to a constant value.

In the circuit of FIG. 2, since _{the output of the limiter 223 is limited to 0 during the period when the temperature detection value T 2} is smaller than the threshold value T _{2t, the} signal input to the adder / subtractor 225 via the input terminal T of the changeover switch 224 is It is 0. The changeover switch 224 is switched to the input terminal T side by the changeover signal 215S output from the AND circuit 215.
Therefore, the balance correction amount generated by the balance correction amount generation unit 300 is input to the adder / subtractor 102 without being adjusted.

However, when the temperature detection value T ₂ becomes the threshold value T _2t or more, the temperature deviation increases according to the increase, _{and the multiplication result with the gain G 2} by the multiplier 222 also increases. Therefore, the limiter 222 and the changeover switch 224 are used. The adjustment amount input to the addition / subtractor 225 via the addition / subtractor 225 also gradually increases. As a result, the balance correction amount output from the addition / subtractor 225 and input to the addition / subtractor 102 changes as shown by the broken line in FIG. 3 (d).

In the balance adjustment operation of giving a constant balance correction amount to the switching element S _{1 , when V dcp} <V _dcn , the switching signal 214S output from the AND circuit 214 becomes “L” and the switching switch 219. Since 0 is input to, the balance correction amount is directly input to the addition / subtractor 101 via the addition / subtractor 220.

By the above operation, it is possible to suppress an increase _{in the voltage V dcn} by shortening only the on-time _{of the switching element S 1} without changing the on-time _{of the switching element S 2. Therefore, it is possible to equalize the voltages V dcp} and V _dcn while reducing the loss of the switching element S ₂ and to continue the operation of the apparatus.

(3a) When the absolute value of the difference _{between V dcp} and V _{dcn is equal to or greater than the voltage difference threshold ΔV t In} this case, the capacitor or switching element on the overvoltage state may exceed the withstand voltage, so the switching element It is necessary to equalize the _{voltages V dcp} and V _dcn regardless of the temperature of.

When the absolute value of the difference _{between V dcp} and V _{dcn is ΔV t} or more, the output of the comparator 205 becomes “L”, and the switching signals 214S and 215S output from the AND circuits 214 and 215 also become “L”. Therefore, the changeover switches 210 and 212 are all switched to the input terminal F side, and the adjustment amount input to the addition / subtractors 220 and 225 becomes 0.
Therefore, the balance adjustment amount is directly input to the addition / subtractors 101 and 102 via the changeover switches 210 and 212, respectively, so that the control for equalizing the _{voltages V dcp} and V _{dcn is executed.}

As described above, the first embodiment, in the second embodiment, by increasing the switching element S _2, S ₁ on time for charging the prior art as in the output side capacitor C _1, C _2, respectively Since it does not depend on the method of equalizing the voltage, there is no risk that the switching element will be overheated beyond the design value, the destruction of the switching element will be prevented, and the voltages V _dcp and V _{dcn of the capacitors C 1 and C 2} will be equalized. The stable operation of the device can be continued.

Incidentally, it is possible to regenerate by turning on the switching element _S 3, _{S 4} in FIG. 4 the energy of the capacitor _C 1, _{C 2} to the DC power source BAT, the present invention, the switching element _S 3, _{S 4} It can also be applied to a 3-level chopper that does not have.

Further, in the first embodiment and the second embodiment, the switching conditions of the balance correction amount are determined using the temperature detection values T ₁ and T _{2 of the switching elements S 1} and S _{2 , but the switching elements S 1} and S are used. ₂ instead of the detected temperature value T _1, T _2, may be used estimated temperature of each switching element. The temperature of the switching element can be estimated using, for example, the applied voltage, the current, the flow time, and the ambient temperature of the switching element.

The three-level chopper according to the present invention can be used, for example, in an uninterruptible power supply, a photovoltaic power generation system, or the like.

BAT: DC power supply S _{1 to} S ₄ : Switching elements D _{1 to} D ₄ : Refluxing diode L ₁ , L ₂ : Reactor C ₁ , C ₂ : Condenser LD: Load P: Positive terminal N: Negative terminal M: Medium Sex points PWM ₁ , PWM ₂ : PWM circuit 100: PWM command generator 101, 102: Addition / subtractor 200A, 200B: Balance correction amount adjustment unit 2011, 216, 220, 221, 225: Addition / subtractor 202: Absolute value calculator 203 ~ 206: Comparator 207: Negative circuit 208, 209, 214, 215: AND circuit 208S, 209S, 214S, 215S: Changeover signal 210, 212, 219, 224: Changeover switch 211, 213: Low-pass filter 217, 222: Multiplier 218, 223: Limiter 300: Balance correction amount generator

Claims (8)

The first and second switching elements are connected in series between the positive and negative sides of the DC power supply via a reactor, and the first and second diodes are connected to both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the respective capacitors, and the series connection points of the first and second switching elements and the series connection points of the first and second capacitors are connected to each other. A 3-level chopper in which a load is connected to both ends of the series circuit of the first and second capacitors.
A voltage command generator that generates a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value, and
A balance correction amount generation unit that generates a balance correction amount for equalizing the voltages of the first and second capacitors, and a balance correction amount generation unit.
A means for generating a drive signal for turning on / off the first and second switching elements based on the voltage command and the balance correction amount, and
A balance correction amount adjusting unit that adjusts the balance correction amount according to the voltage of the first and second capacitors, the temperature of the first and second switching elements, and the temperature threshold value is provided.
The balance correction amount adjusting unit is
During the period when the temperature of one of the first and second switching elements is less than the temperature threshold, the balance correction amount for both switching elements is kept at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the above period, the three-level chopper is characterized in that the balance correction amount for the switching element is set to 0 and the balance correction amount for the other switching element is maintained at the predetermined value. The first and second switching elements are connected in series between the positive and negative sides of the DC power supply via a reactor, and the first and second diodes are connected to both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the respective capacitors, and the series connection points of the first and second switching elements and the series connection points of the first and second capacitors are connected to each other. A 3-level chopper in which a load is connected to both ends of the series circuit of the first and second capacitors.
A voltage command generator that generates a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value, and
A balance correction amount generating unit that generates a balance correction amount for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
A means for generating a drive signal for turning on / off the first and second switching elements based on the voltage command and the balance correction amount, and
A balance correction amount adjusting unit that adjusts the balance correction amount according to the voltage of the first and second capacitors, the temperature of the first and second switching elements, and the temperature threshold value is provided.
The balance correction amount adjusting unit is
During the period when the temperature of one of the first and second switching elements is less than the temperature threshold, the balance correction amount for both switching elements is kept at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the above period, the three-level chopper is characterized in that the balance correction amount for the switching element is gradually changed toward 0 and the balance correction amount for the other switching element is maintained at the predetermined value. In the three-level chopper according to claim 1 or 2.
The balance correction amount adjusting unit is
A three-level chopper characterized in that the balance correction amount for the first and second switching elements is set to 0 when the absolute value of the voltage difference of the first and second capacitors is less than the voltage difference threshold value. In the three-level chopper according to any one of claims 1 to 3.
A three-level chopper characterized in that the voltage of the DC power supply is boosted and supplied to the load. In the three-level chopper according to any one of claims 1 to 4.
A three-level chopper characterized in that a third switching element is connected to the first diode in antiparallel and a fourth switching element is connected to the second diode in antiparallel. In the three-level chopper according to claim 5.
A three-level chopper characterized in that the third and fourth switching elements are turned on and the energy of the first and second capacitors is regenerated to the DC power supply. The first and second switching elements are connected in series between the positive and negative sides of the DC power supply via a reactor, and the first and second diodes are connected to both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the respective capacitors, and the series connection points of the first and second switching elements and the series connection points of the first and second capacitors are connected to each other. A 3-level chopper control circuit in which a load is connected to both ends of the series circuit of the first and second capacitors.
A voltage command generator that generates a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value, and
A balance correction amount generating unit that generates a balance correction amount for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
A means for generating a drive signal for turning on / off the first and second switching elements based on the voltage command and the balance correction amount, and
A balance correction amount adjusting unit that adjusts the balance correction amount according to the voltage of the first and second capacitors, the temperature of the first and second switching elements, and the temperature threshold value is provided.
The balance correction amount adjusting unit is
During the period when the temperature of one of the first and second switching elements is less than the temperature threshold, the balance correction amount for both switching elements is kept at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the above period, the control circuit of the three-level chopper is characterized in that the balance correction amount for the switching element is set to 0 and the balance correction amount for the other switching element is kept at the predetermined value. The first and second switching elements are connected in series between the positive and negative sides of the DC power supply via a reactor, and the first and second diodes are connected to both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the respective capacitors, and the series connection points of the first and second switching elements and the series connection points of the first and second capacitors are connected to each other. A 3-level chopper control circuit in which a load is connected to both ends of the series circuit of the first and second capacitors.
A voltage command generator that generates a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value, and
A balance correction amount generating unit that generates a balance correction amount for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
A means for generating a drive signal for turning on / off the first and second switching elements based on the voltage command and the balance correction amount, and
A balance correction amount adjusting unit that adjusts the balance correction amount according to the voltage of the first and second capacitors, the temperature of the first and second switching elements, and the temperature threshold value is provided.
The balance correction amount adjusting unit is
During the period when the temperature of one of the first and second switching elements is less than the temperature threshold, the balance correction amount for both switching elements is kept at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the above period, the control circuit of the three-level chopper is characterized in that the balance correction amount for the switching element is gradually changed toward 0 and the balance correction amount for the other switching element is maintained at the predetermined value.

Images