JP2019022408A - Three-level chopper and control circuit of the same - Google Patents

Abstract

To provide a three-level chopper and a control circuit of the chopper, capable of preventing an overheat of a switching element and continuing an operation while equalizing a voltage of two series capacitors.SOLUTION: A control circuit in a DC power supply system, comprises: a balance correction amount generation part 300 that generates a balance correction amount in accordance with a voltage of a capacitor of a three-level chopper of a main circuit; means of turning on/off switching elements Sand Son the basis of the balance correction amount; and a balance correction amount adjustment part 200A that adjusts the balance correction amount in accordance with the voltage of the capacitor and a temperature and a temperature threshold value of the switching elements Sand S. The adjustment part 200A holds the balance correction amount to both of the switching elements Sand Sto a predetermined threshold value in a period where one temperature is less than the threshold value, and holds the balance correction amount to the other one by setting the balance correction amount in accordance with one to 0 in the period where one temperature is equal to the threshold value or more.SELECTED DRAWING: Figure 1

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 a DC power supply voltage and converts it into a DC voltage having a neutral point by operation of a semiconductor switching element (hereinafter simply referred to as a switching element), and is constituted by a so-called three-level chopper. Yes.

The three-level chopper includes a DC power source 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. , S _4, and capacitors C ₁ and C ₂ connected in series with each other, and a load LD is connected to both ends of the series circuit of the capacitors C ₁ and C ₂ .
D _{1 to} D ₄ are free-wheeling diodes connected in reverse parallel to the switching elements S _{1 to} S ₄ , P is a positive terminal, N is a negative terminal, and M is the switching elements S ₁ and S ₂ . This is a series connection point (neutral point) of the capacitors C ₁ and C ₂ connected to the series connection point.

The operation of this circuit will be briefly described below.
First, when both switching elements S ₁ and S ₂ are turned on, energy is accumulated in 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 . Then, when turning on the switching element _{S 2} turns off the switching element _{S 1,} the capacitor _{C 1} is charged through the stored energy of the reactor _L 1, _{L 2} and wheel 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, since the output voltage V _pn can take three levels (V _dcp , V _dcn , and V _dcp + V _dcn ), it is called a three-level chopper.

In this type of three-level chopper, if the voltage of the two capacitors on the output side is biased due to a failure of the switching element or variations in circuit constants, the switching element or the capacitor may be destroyed by overvoltage. is there.
For this reason, in Patent Document 1, control is performed to equalize the voltages V _dcp and V _dcn using the control circuit of FIG.

FIG. 5 shows a control circuit for driving the switching elements 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 respectively equal to ½ of the DC voltage command value (output voltage command value) V _pn ^*. In operation, these outputs are applied to PWM circuits PWM _A and PWM _B having the same configuration via changeover switches SW ₁ and SW ₂ .

The PWM circuits PWM _A and PWM _{B each} include a comparator Cmp, timers TM ₁ and TM ₂ , logic circuits 11 to 15, falling detection circuits 16 and 17, and a DQ flip-flop 18. The switching signals 1 and ₂ for the input side switches SW ₁ and SW _{2 are} provided.
The pulse output determination circuit PJ uses the output signals S ₁ ′ to S ₄ ′ of the PWM circuits PWM _A and PWM _B as drive signals for the switching elements S _{1 to} S ₄ according to the magnitude relationship between the voltage detection values V _dcp and V _dcn. Select (gate signal) and output.

In the control circuit, as shown in FIGS. _6A and _6B , the ON times of the switching elements S ₁ and S ₂ are adjusted according to the magnitude relation between the voltage detection values V _dcp and V _dcn . Specifically, in order to increase the charge amount of the capacitor having the lower voltage, the on-time of the switching element connected in series with the capacitor is increased to increase / decrease the current I _{ch in} FIG. 4, and the voltage V _dcp , Control to equalize V _dcn is performed.
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 and maintain the voltages V _dcp and V _dcn at predetermined values.

JP 2013-5649 A (paragraphs [0015] to [0023], FIGS. 1 and 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 operating the device.
Accordingly, the problem to be solved by the present invention is to provide a three-level chopper and a control circuit for the three-level chopper that can stably operate while preventing overheating of the switching element while equalizing the voltage of the series capacitor on the output side. is there.

In order to solve the above problem, a three-level chopper according to claim 1 is:
The first and second switching elements are connected in series between the positive and negative electrodes 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 each, and the series connection point of the first and second switching elements and the series connection point of the first and second capacitors are connected, A three-level chopper in which a load is connected to both ends of a series circuit of first and second capacitors,
A voltage command generator for generating a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value;
A balance correction amount generator for generating a balance correction amount for equalizing the voltages of the first and second capacitors;
Means for generating a drive signal for turning on and off the first and second switching elements based on the voltage command and the balance correction amount;
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,
The balance correction amount adjustment unit
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 the switching elements is maintained 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.

A three-level chopper according to claim 2
The first and second switching elements are connected in series between the positive and negative electrodes 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 each, and the series connection point of the first and second switching elements and the series connection point of the first and second capacitors are connected, A three-level chopper in which a load is connected to both ends of a series circuit of first and second capacitors,
A voltage command generator for generating a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value;
A balance correction amount generator for generating a balance correction amount for equalizing the voltages of the first and second capacitors in accordance with the voltages of the first and second capacitors;
Means for generating a drive signal for turning on and off the first and second switching elements based on the voltage command and the balance correction amount;
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,
The balance correction amount adjustment unit
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 the switching elements is maintained at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the period described above, 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.

  A three-level chopper according to a third aspect is the three-level chopper according to the first or second aspect, wherein the balance correction amount adjusting unit is configured such that an absolute value of a voltage difference between the first and second capacitors is a voltage difference threshold value. The balance correction amount for the first and second switching elements is set to 0 when the value is less than 0.

  A three-level chopper according to a fourth aspect is the three-level chopper according to any one of the first to third aspects, wherein the voltage of the DC power supply is boosted and supplied to the load.

  A three-level chopper according to a fifth aspect is the three-level chopper according to any one of the first to fourth aspects, wherein a third switching element is connected in antiparallel to the first diode, and The fourth switching element is connected in antiparallel to the two diodes.

  A three-level chopper according to a sixth aspect is the three-level chopper according to the fifth aspect, wherein the third and fourth switching elements are turned on to regenerate the energy of the first and second capacitors to the DC power source. 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 electrodes 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 each, and the series connection point of the first and second switching elements and the series connection point of the first and second capacitors are connected to each other. A control circuit of a three-level chopper in which a load is connected to both ends of a series circuit of first and second capacitors,
A voltage command generator for generating a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value;
A balance correction amount generator for generating a balance correction amount for equalizing the voltages of the first and second capacitors in accordance with the voltages of the first and second capacitors;
Means for generating a drive signal for turning on and off the first and second switching elements based on the voltage command and the balance correction amount;
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,
The balance correction amount adjustment unit
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 the switching elements is maintained 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 electrodes 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 each, and the series connection point of the first and second switching elements and the series connection point of the first and second capacitors are connected to each other. A control circuit of a three-level chopper in which a load is connected to both ends of a series circuit of first and second capacitors,
A voltage command generator for generating a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value;
A balance correction amount generator for generating a balance correction amount for equalizing the voltages of the first and second capacitors in accordance with the voltages of the first and second capacitors;
Means for generating a drive signal for turning on and off the first and second switching elements based on the voltage command and the balance correction amount;
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,
The balance correction amount adjustment unit
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 the switching elements is maintained at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the period described above, 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, the on-time of the switching element is not increased more than necessary, and the stable operation of the apparatus can be continued by equalizing the series capacitor voltage while preventing destruction due to overheating.

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 balance correction amount in each embodiment of this invention. 2 is a main circuit configuration diagram of a DC power supply system described in Patent Document 1. FIG. 2 is a configuration diagram of a control circuit described in Patent Document 1. FIG. It is a wave form diagram which shows the operation | movement of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a control circuit according to the first embodiment of the present invention. This control circuit generates drive signals for the switching elements S _{1 to} S _{4 for} the above-described three-level chopper of FIG.

In FIG. 1, the PWM command generation unit 100 is based on a DC voltage command value V _pn ^{*, a} DC voltage detection value V _pn, and a DC current detection value (a detection value of a current flowing from the battery BAT in FIG. 4) I _ch. Then, a PWM command (voltage command) for controlling V _pn to V _pn ^* is generated.
This PWM command is added / subtracted by the adder / subtracters 101 and 102 with balance correction amounts which are outputs of low pass filters 211 and 213, which will be described later, and input to the PWM circuits PWM ₁ and PWM ₂ . In the PWM circuits PWM ₁ and PWM ₂ , the input commands are compared with the carriers 1 and 2, respectively, so that the switching elements S ₁ and S ₃ and the switching elements S ₂ and S ₄ in FIG. 4 are compared. A drive signal is generated.

The balance correction amount adjustment unit 200A controls the balance correction amount to be added to or subtracted from 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 adjustment unit 200A will be described later.
The balance correction amount generation unit 300 generates a balance correction amount for making the voltage detection values V _dcp and V _dcn of the capacitors C ₁ and C ₂ equal, and outputs the balance correction amount to the balance correction amount adjustment unit 200A.

Next, the balance correction amount adjustment unit 200A will be described in detail.
The balance correction amount adjusting unit 200A adjusts the voltage detection values V _dcp and 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 threshold values 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. Also, the voltage detection values V _dcp and V _dcn are compared by the comparator 204, and the output is input to the AND circuit 208 and also 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 applied to the changeover switch 210 as a changeover signal 208S, and the output of the AND circuit 209 is applied 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). Yes.

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 “H (High)” level, and when the logic of the changeover signals 208S and 209S is “L (Low)” level. Connected to.
The outputs of the changeover switches 210 and 212 are input to the adder / subtractors 101 and 102 with the signs shown through the first and second low-pass filters 211 and 213, respectively.

Next, the operation of the first embodiment according to the magnitude relationship between the voltage detection values V _dcp and V _dcn of the capacitors C ₁ and C ₂ and the temperature detection values T ₁ and T ₂ of the switching elements S ₁ and S ₂ will be described. This will be described with reference to FIGS. 3 (a) and 3 (b).

(1) 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 to which the voltage of the capacitor C ₁ in FIG. 4 is applied S ₁ needs to be protected from the voltage V _dcp .

For this purpose, a balance correction amount for increasing the on-time of the switching element S ₁ is set to the PWM command via the adder / subtractor 101 so as to increase the charge amount of the capacitor C ₂ and increase the voltage V _dcn. 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 in which the temperature detection value T ₁ does not exceed the threshold value T _1t , the balance correction amount is the input terminal F and the switching switch 210. The signal is input to the adder / subtractor 101 via the low-pass filter 211. Further, when T ₁ becomes equal to or greater than T _1t and 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 balance correction for the switching element S ₁ input of the filter 211 is equal to zero is also zero.

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.

The above operation, when the temperature of the switching element S ₁ is increased, it is possible to suppress the increase in the voltage V _dcp of the capacitor C ₁ by shortening the ON time only the switching element S ₂ without changing the on-time. For this reason, 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 It is necessary to protect against the voltage V _dcn .

For this purpose, a balance correction amount for increasing the on-time of the switching element S ₂ is added to the PWM command via the adder / subtractor 102 so as to increase the voltage V _dcp by increasing the charge amount of the capacitor C ₁ . 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 in which 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 signal is input to the adder / subtractor 102 via the low-pass filter 213. Further, the detected temperature value _{T 2} is greater than or equal to a threshold value _{T 2t} output of the comparator 206 becomes "H", when the output of the comparator 205 and the NOT circuit 207 is also "H", the switching signal 209S is " H ", becomes zero the balance correction amount for the switching element S ₂ input becomes zero in the low-pass filter 213.

In the balance adjustment operation for giving a constant balance correction amount to the switching element S ₁ , when V _dcp <V _dcn , the output of the AND circuit 208 becomes “L”, and the balance correction amount is This is realized by being input to the adder / subtractor 101 via the input terminal F and the low-pass filter 211.

The above operation, when the temperature of the switching element S ₂ is high, can suppress an increase of the voltage V _dcn of the capacitor C ₂ by shortening the on time only the switching element S ₁ without changing the on-time . For this reason, 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 greater than or equal to the voltage difference threshold ΔV _{t In} this case, the capacitor or switching element in the overvoltage state may exceed the withstand voltage. It is necessary to equalize the voltages V _dcp and V _dcn regardless of the temperature.

When the absolute value of the difference between V _dcp and V _dcn is greater than or equal to ΔV _t , the output of the comparator 205 is “L”, and the switching signals 208S and 209S output from the AND circuits 208 and 209 are also “L”. Accordingly, both the changeover switches 210 and 212 are switched to the input terminal F side, and the balance correction amount is input to the adder / subtracters 101 and 102 via the changeover switches 210 and 212 and the low-pass filters 211 and 213, respectively. _dcp, so that the control to equalize the _{V dcn} is executed.

Next, a second embodiment of the present invention will be described. In the second embodiment, the balance correction amount for one switching element is gradually changed according to the temperature of the switching elements S ₁ and S ₂ .
FIG. 2 is a configuration diagram of a control circuit according to the second embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. Hereinafter, parts different from those in FIG. .

  In the balance correction amount adjustment unit 200 </ b> B illustrated in FIG. 2, the output signal of the comparator 204 is input to the AND circuit 214 and also input to the AND circuit 215 via the negative circuit 207. The output signal of the comparator 205 is input to 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 a 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 selector 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.
Note that the gains G ₁ and G ₂ have the same magnitude and the opposite signs.

Next, the operation of the second embodiment according to the magnitude relationship between the voltage detection values V _dcp and V _dcn of the capacitors C ₁ and C ₂ and the temperature detection values T ₁ and T ₂ of the switching elements S ₁ and S _{2 is} as follows. 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 It is necessary to protect from the voltage V _dcp .

For this purpose, a balance correction amount for increasing the on-time of the switching element S ₁ is set to the PWM command via the adder / subtractor 101 so as to increase the charge amount of the capacitor C ₂ and increase the voltage V _dcn. 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 linearly decreasing the balance correction amount as the temperature detection value T ₁ is higher than the foregoing period, eventually to zero.
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 in which 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 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 equal to or greater than the threshold value T _1t , the temperature deviation increases according to the increase, and the multiplication result of the gain G ₁ by the multiplier 217 also increases, so that the limiter 218 and the changeover switch 219 are set. The amount of adjustment input to the adder / subtracter 220 through the output gradually increases. Thereby, the balance correction amount output from the adder / subtracter 220 and input to the adder / subtractor 101 changes as shown by a solid line in FIG.

The balance adjustment operation for giving a constant balance correction amount to the switching element S ₂ is performed when the switch signal 215S output from the AND circuit 215 becomes “L” when V _dcp > V _{dcn and} the switch 224 is switched. Since 0 is input to, the balance correction amount is directly input to the adder / subtractor 102 via the adder / subtractor 225.

The above operation, by shortening the on time only the switching element S ₂ without changing the on-time of the switching element S _1, it is possible to suppress the increase in the voltage V _dcp. For this reason, 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 It is necessary to protect against the voltage V _dcn .

For this purpose, a balance correction amount for increasing the on-time of the switching element S ₂ is added to the PWM command via the adder / subtractor 102 so as to increase the voltage V _dcp by increasing the charge amount of the capacitor C ₁ . it 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 or more periods linearly increased (decreased in negative direction) the balance correction amount as the temperature detection value T ₂ increases, eventually to zero.
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 in which 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 0. The changeover switch 224 is switched to the input terminal T side by a 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, if the temperature detection value T ₂ is equal to or greater than the threshold T _2t, the temperature deviation increases with the rise, so also increases the multiplication result between the gain G ₂ by multiplier 222, a limiter 222 and the changeover switch 224 Thus, the adjustment amount input to the adder / subtractor 225 also gradually increases. As a result, the balance correction amount output from the adder / subtractor 225 and input to the adder / subtractor 102 changes as indicated by a broken line in FIG.

Note that in the balance adjustment operation for giving a constant balance correction amount to the switching element S ₁ , the switching signal 214 S output from the AND circuit 214 becomes “L” when V _dcp <V _dcn , and the changeover switch 219. Since 0 is input to, the balance correction amount is input to the adder / subtractor 101 via the adder / subtractor 220 as it is.

The above operation, by shortening the on time only the switching element S ₁ without changing the on-time of the switching element S _2, it is possible to suppress the increase in the voltage V _dcn. For this reason, 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 greater than or equal to the voltage difference threshold ΔV _{t In} this case, the capacitor or switching element in the overvoltage state may exceed the withstand voltage. It is necessary to equalize the voltages V _dcp and V _dcn regardless of the temperature.

When the absolute value of the difference between V _dcp and V _dcn is equal to or greater than ΔV _t , the output of the comparator 205 is “L”, and the switching signals 214S and 215S output from the AND circuits 214 and 215 are also “L”. Accordingly, the changeover switches 210 and 212 are both switched to the input terminal F side, and the adjustment amount input to the adders / subtracters 220 and 225 becomes zero.
Thus, by balancing the amount of which is directly input to the adder-subtracter 101 via the selector switch 210, 212, is controlled to equalize the voltage _{V dcp,} the _{V dcn} is executed.

As described above, in the first embodiment and the second embodiment, the on-time of the switching elements S ₂ and S ₁ for charging the capacitors C ₁ and C ₂ on the output side is increased as in the prior art. Since the voltage equalization method is not used, the switching element is not likely to be overheated beyond the design value, and the switching elements are prevented from being destroyed and the voltages V _dcp and V _dcn of the capacitors C ₁ and C ₂ are equalized. 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 three-level chopper that does not have

In the first embodiment and the second embodiment, the switching condition of the balance correction amount is 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 ₂ 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 flowing current, the flowing time, and the ambient temperature of the switching element.

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

BAT: DC power supply S _{1 to} S ₄ : switching elements D _{1 to} D ₄ : freewheeling diodes L ₁ and L ₂ : reactors C ₁ and C ₂ : capacitor LD: load P: positive terminal N: negative terminal M: medium Sexual points PWM ₁ , PWM ₂ : PWM circuit 100: PWM command generators 101 and 102: adders / subtractors 200 A and 200 B: balance correction amount adjusters 201, 216, 220, 221 and 225: adders / subtractors 202: absolute value calculator 203 ˜206: Comparator 207: Negative circuit 208, 209, 214, 215: AND circuit 208S, 209S, 214S, 215S: Switching signal 210, 212, 219, 224: Changeover switch 211, 213: Low pass filter 217, 222: Multiplier 218, 223: Limiter 300: Balance correction amount generation unit

Claims (8)

The first and second switching elements are connected in series between the positive and negative electrodes 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 each, and the series connection point of the first and second switching elements and the series connection point of the first and second capacitors are connected, A three-level chopper in which a load is connected to both ends of a series circuit of first and second capacitors,
A voltage command generator for generating a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value;
A balance correction amount generator for generating a balance correction amount for equalizing the voltages of the first and second capacitors;
Means for generating a drive signal for turning on and off the first and second switching elements based on the voltage command and the balance correction amount;
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,
The balance correction amount adjustment unit
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 the switching elements is maintained at a predetermined value, and the temperature of the one switching element is the temperature threshold. The three-level chopper 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 during the above period. The first and second switching elements are connected in series between the positive and negative electrodes 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 each, and the series connection point of the first and second switching elements and the series connection point of the first and second capacitors are connected, A three-level chopper in which a load is connected to both ends of a series circuit of first and second capacitors,
A voltage command generator for generating a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value;
A balance correction amount generator for generating a balance correction amount for equalizing the voltages of the first and second capacitors in accordance with the voltages of the first and second capacitors;
Means for generating a drive signal for turning on and off the first and second switching elements based on the voltage command and the balance correction amount;
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,
The balance correction amount adjustment unit
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 the switching elements is maintained at a predetermined value, and the temperature of the one switching element is the temperature threshold. During the period described above, 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 adjustment unit
A three-level chopper, wherein a balance correction amount for the first and second switching elements is set to 0 when an absolute value of a voltage difference between the first and second capacitors is less than a voltage difference threshold value. In the three-level chopper according to any one of claims 1 to 3,
A three-level chopper, wherein the voltage of the DC power supply is boosted and supplied to the load. In the 3 level chopper described in any one of Claims 1-4,
3. A three-level chopper, wherein a third switching element is connected in antiparallel to the first diode, and a fourth switching element is connected in antiparallel to the second diode. The three-level chopper according to claim 5,
A three-level chopper, wherein the third and fourth switching elements are turned on to regenerate the energy of the first and second capacitors to the DC power source. The first and second switching elements are connected in series between the positive and negative electrodes 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 each, and the series connection point of the first and second switching elements and the series connection point of the first and second capacitors are connected to each other. A control circuit of a three-level chopper in which a load is connected to both ends of a series circuit of first and second capacitors,
A voltage command generator for generating a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value;
A balance correction amount generator for generating a balance correction amount for equalizing the voltages of the first and second capacitors in accordance with the voltages of the first and second capacitors;
Means for generating a drive signal for turning on and off the first and second switching elements based on the voltage command and the balance correction amount;
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,
The balance correction amount adjustment unit
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 the switching elements is maintained 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 first and second switching elements are connected in series between the positive and negative electrodes 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 each, and the series connection point of the first and second switching elements and the series connection point of the first and second capacitors are connected to each other. A control circuit of a three-level chopper in which a load is connected to both ends of a series circuit of first and second capacitors,
A voltage command generator for generating a voltage command for matching the voltage of the first capacitor and the voltage of the second capacitor to a predetermined value;
A balance correction amount generator for generating a balance correction amount for equalizing the voltages of the first and second capacitors in accordance with the voltages of the first and second capacitors;
Means for generating a drive signal for turning on and off the first and second switching elements based on the voltage command and the balance correction amount;
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,
The balance correction amount adjustment unit
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 the switching elements is maintained 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.

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