JP6907855B2 - 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. 13 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 consists of a DC power supply BAT, a series circuit of switching elements S ₁ and S _{2 connected between the positive and negative circuits of the DC power supply BAT 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 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 V _dcp and V _{dcn of the capacitors C 1} and C ₂ on the output side are biased due to a failure of the switching element or a variation in the circuit constant, the switching element or the capacitor will be damaged. It may be destroyed by overvoltage.
Therefore, in Patent Document 1, the control circuit of FIG. 14 is used to control the voltages V _dcp and V _dcn to be equal.

Figure 14 shows a control circuit for driving the switching element _S 1 to S _4.
In FIG. 14, 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. 15 (a), the regulate 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 Figure 13 by increasing 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 element S 1} or S ₂ becomes too long in order to equalize the voltage, the temperature of the element becomes equal to or higher than the design value, and as a result, the switching element The protective operation to prevent destruction may work and the operation of the device may stop.
On the other hand, _{if the voltages of the capacitors C 1} and C ₂ are not equal, the current flowing through the chopper contains a large amount of ripple current, and the power system connected to this chopper via the inverter circuit and its connection load. There was a problem such as adversely affecting.

Therefore, the problem to be solved by the present invention is a three-level chopper capable of equalizing the voltage of the series capacitor on the output side, preventing overheating of the switching element, continuing stable operation, and suppressing the ripple current. The purpose is to provide the control circuit.

In order to solve the above problem, in the three-level chopper according to claim 1, 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 switching elements are connected in series. The first and second capacitors are connected in series to both ends of the series circuit of the switching element via the first and second diodes, respectively, and the series connection points of the first and second switching elements and the above. A three-level chopper in which a series connection point of the first and second capacitors is connected and a load is connected to both ends of the series circuit of the first and second capacitors.
A PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
To adjust the balance command value according to the input voltage and output voltage of the three-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the step-down operation of the three-level chopper. The balance command value adjustment unit that generates the balance command adjustment value, and
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
It is characterized by being equipped with.

In the three-level chopper according to claim 2, 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 both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the first and second diodes, respectively, and the series connection point of the first and second switching elements and the first and second capacitors. It is a three-level chopper that is connected to the series connection point of the above and a load is connected to both ends of the series circuit of the first and second capacitors.
A PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
To adjust the balance command value according to the input voltage and output voltage of the three-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the boosting operation of the three-level chopper. The balance command value adjustment unit that generates the balance command adjustment value, and
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
It is characterized by being equipped with.

In the three-level chopper according to claim 3, 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 both ends of the series circuit of the first and second switching elements. The first and second capacitors are connected in series via the first and second diodes, respectively, and the series connection point of the first and second switching elements and the first and second capacitors. It is a three-level chopper that is connected to the series connection point of the above and a load is connected to both ends of the series circuit of the first and second capacitors.
A PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
The balance command value is adjusted according to the input voltage and output voltage of the 3-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the step-up / step-down operation of the 3-level chopper. Balance command value adjustment unit that generates the balance command adjustment value for
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
It is characterized by being equipped with.

The three-level chopper according to claim 4 is the three-level chopper according to any one of claims 1 to 3.
The balance command value adjusting unit obtains a deviation between the product of the output voltage and the input / output voltage ratio and the input voltage, and adjusts the balance command value based on the product of this deviation and a predetermined gain. It is characterized by.

The three-level chopper according to claim 5 is the three-level chopper according to any one of claims 1 to 4.
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.

The three-level chopper according to claim 6 is the three-level chopper according to claim 5.
The third and fourth switching elements are turned on to regenerate the energy of the first and second capacitors to the DC power supply.

In the control circuit of the three-level chopper according to claim 7, 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 switching elements are connected in series. The first and second capacitors are connected in series at both ends of the circuit via the first and second diodes, respectively, and the series connection points of the first and second switching elements and the first and first capacitors are connected. A control circuit of a three-level chopper in which a series connection point of two capacitors is connected and a load is connected to both ends of the series circuit of the first and second capacitors.
A PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
To adjust the balance command value according to the input voltage and output voltage of the three-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the step-down operation of the three-level chopper. The balance command value adjustment unit that generates the balance command adjustment value, and
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
It is characterized by being equipped with.

In the control circuit of the three-level chopper according to claim 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 switching elements are connected in series. The first and second capacitors are connected in series at both ends of the circuit via the first and second diodes, respectively, and the series connection points of the first and second switching elements and the first and first capacitors are connected. A control circuit of a three-level chopper in which a series connection point of two capacitors is connected and a load is connected to both ends of the series circuit of the first and second capacitors.
A PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
To adjust the balance command value according to the input voltage and output voltage of the three-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the boosting operation of the three-level chopper. The balance command value adjustment unit that generates the balance command adjustment value, and
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
It is characterized by being equipped with.

In the control circuit of the three-level chopper according to claim 9, 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 switching elements are connected in series. The first and second capacitors are connected in series at both ends of the circuit via the first and second diodes, respectively, and the series connection points of the first and second switching elements and the first and first capacitors are connected. A control circuit of a three-level chopper in which a series connection point of two capacitors is connected and a load is connected to both ends of the series circuit of the first and second capacitors.
A PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
The balance command value is adjusted according to the input voltage and output voltage of the 3-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the step-up / step-down operation of the 3-level chopper. Balance command value adjustment unit that generates the balance command adjustment value for
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
It is characterized by being equipped with.

The control circuit of the three-level chopper according to claim 10 is
In the control circuit of the three-level chopper according to any one of claims 7 to 9.
The balance command value adjusting unit obtains a deviation between the product of the output voltage and the input / output voltage ratio and the input voltage, and adjusts the balance command value based on the product of this deviation and a predetermined gain. It is characterized by.

According to the present invention, it is not necessary to lengthen the on-time of the switching element more than necessary in order to equalize the voltage of the series capacitor on the output side in each of the step-down mode region and the step-up mode region of the three-level chopper. Therefore, overheating of the switching element can be prevented, and stable operation of the device can be continued without activating the protective operation.
In addition, it is possible to suppress the ripple component of the current flowing through the chopper and prevent adverse effects on the power system and its connection load.

It is a figure which shows the relationship between the input voltage of a chopper and the current ripple rate. It is a figure explaining the current path in the step-down mode of a chopper, and the operation of a switching element. It is a figure explaining the current path in the step-up mode of a chopper, and the operation of a switching element. It is a figure which shows the ripple current at the time of equalization and unevenness of the voltage of the output side capacitor of a chopper. It is a block diagram of the control circuit which concerns on 1st Embodiment of this invention. It is a figure which shows the relationship between the input voltage of a chopper and each signal of FIG. 5 in 1st Embodiment. It is a figure which shows the relationship between the input voltage, the current ripple rate and the balance command rate in 1st Embodiment. 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 input voltage of a chopper and each signal of FIG. 8 in 2nd Embodiment. It is a figure which shows the relationship between the input voltage, the current ripple rate, and the balance command rate in the 2nd Embodiment. It is a block diagram of the control circuit which concerns on 3rd Embodiment of this invention. It is a figure which shows the relationship between the input voltage and the current ripple rate in 3rd Embodiment. 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.
First, the principle of the present invention will be described. In the present invention, three-level chopper (hereinafter, simply referred to as a chopper) is defined by noting the ripple factor of the DC input current varies according to the imbalance of the capacitor C _1, C ₂ of the voltage on the output side. That is, for each of the step-down operation and the step-up operation of the chopper, the balance command value (balance command rate) for equalizing the voltages of _{the capacitors C 1} and C _{2 is adjusted according to the relationship between the input / output voltage of the chopper.} Accordingly, to equalize the voltage of the capacitor C _1, C ₂ to suppress the ripple current.

First, FIG. 1 shows the relationship between _{the input voltage and the current ripple rate (ΔI / I dc} ) in the step-down mode region and the step-up mode region of the chopper. Here, the DC input current _{I dc} chopper is the same as the _{I ch} in FIG 13, the output voltage _{V o} is the same as the _{V pn} in FIG.
The chopper step-down mode refers to a mode in which the input voltage V _in > (output voltage V _o / 2), and the chopper boost mode refers to a mode in which the input voltage V _in <(output voltage V _o / 2). To tell.
In the step-down mode region and the step-up mode region of FIG. 1, the relationship between the input / output voltage when the current ripple rate is maximized can be obtained as follows (in conclusion, in the step-down mode of the chopper, the input voltage V when _in is (√3 + 3) / 6 times the output voltage _{V o,} in boost mode chopper, when the input voltage _{V in} is 1/3 times the output voltage _{V o,} each current ripple factor becomes maximum ).

FIG. 2 is a diagram for explaining the relationship between the input / output voltage when the current ripple rate is maximized in the step-down mode of the chopper. 2 (a) is, when turning off the switching element _{S 2} by turning on the switching element _{S 1,} FIG. 2 (b), the path of the input current _{I dc} when the off the switching element _S 1, _{S 2} ( The arrow) is shown. _{Incidentally, C in} the smoothing _{capacitor, V in} is the input voltage of the chopper.

また、電流リップル率（ΔＩ／Ｉ_ｄｃ）は数式２となる。この数式２において、ＬはリアクトルＬ_１，Ｌ_２のインダクタンス、Ｐは入力電力である。

As shown in FIG. 2 (c), when the switching elements S ₁ and S ₂ switch alternately in the period T = 1 / f _sw (f _sw : switching frequency), the on-time of the _{switching element S 1 is calculated by Equation 1.} Represented by.

Further, the current ripple rate (ΔI / I _dc ) is given by Equation 2. In this formula 2, L is the inductance of the reactor _L 1, _{L 2,} P is the input power.

Input voltage V _in when the current ripple ratio (ΔI / I _dc) is maximum is the value when the value obtained by differentiating Equation 2 by V _in becomes zero, can be represented by Equation 3.

The on FIG. 3, the chopper boosting mode is a diagram for explaining a relationship between the input and output voltage when the current ripple ratio becomes maximum, FIG. 3 (a) the switching element S _1, S ₂ 3 (b) shows the path (arrow) of _{the input current I dc} when the switching element S ₂ is turned off while the _{switching element S 1 is turned on.} In FIG. 3C, ton _S12 is the time for turning on both the switching elements S ₁ and S _2.

また、電流リップル率（ΔＩ／Ｉ_ｄｃ）は数式５となる。

Here, the on-time switching element S ₁ is represented by Equation 4.

Further, the current ripple rate (ΔI / I _dc ) is given by Equation 5.

Input voltage V _in when the current ripple ratio (ΔI / I _dc) is maximum is the value when the value obtained by differentiating the equation 5 by V _in becomes zero, can be represented by Equation 6.

4 (a) shows the ripple current ΔI of the voltage of the capacitor _C 1, _{C 2} is included in the input current _{I dc} when a uniform, FIG. 4 (b), the voltage of the capacitor _C 1, _{C 2} The ripple current ΔI when it is not uniform is shown. From these FIGS. 4 (a) and 4 (b), it can be seen that _{when the voltages of the capacitors C 1} and C ₂ are unbalanced, the ripple current ΔI and thus the current ripple rate (ΔI / I _{dc) become large.}

Next, FIG. 5 is a configuration diagram of a control circuit according to the first embodiment of the present invention.
The first embodiment, when operating the chopper in buck mode region (see FIG. 1) generates a drive signal of the switching element S ₁ to S ₄ in order to equalize the voltage of the capacitor C _1, C ₂ It is a thing.

The outline of the operation of the first embodiment is as follows.
That is, in the buck mode, when a V _{in =} V _o By balancing command value (balance command ratio) and 0 to continue the operation of the prevent by device bias the heat of the switching element.
_Also, the time of V in = _V from the state of _o with a decrease of _{V in} gradually increasing the balance command value, _V in = current ripple factor becomes maximum {(√3 + 3) / 6 } V o By maximizing the balance command value (balance command rate is 100%), the ripple current is reduced and the connected equipment of the power system is protected.
_{Moreover, V in = {(√3 +} 3) / 6} V from the time of _o with a decrease of _{V in} gradually reducing the balance command _value, V in _{= V} o / 0 balance command value 2 time points ( By setting the balance command rate to 0%), the heat bias of the switching element is prevented and the operation of the device is continued.

In the control circuit of Figure 5 according to the first embodiment, PWM command generation unit 101, based on the DC voltage command value V _o ^* and the DC voltage detected value V _o of the chopper DC current detection value I _dc, the V the _o generating a PWM command for controlling the _V ^{o *} (the voltage command).
This PWM command is added / subtracted from the balance command value output from the upper / lower limit limiter 211 of the balance command value adjusting unit 200A described later by the addition / subtractors 103 and 104, and is input to the PWM circuits 105 and 106 (PWM1, PWM2). NS. The PWM circuit 105, by comparing the input command value and the carrier 1 respectively, switching element _S 1, _{S 3} of FIG. 13, and the switching element _S 2, the drive signal for the _{S 4} To generate.

The balance command value generation unit 102 is a balance command value from the DC voltage upper detection value (voltage detection value of the capacitor C _{1 in} FIG. 13) _VC1 and the DC voltage lower detection value (voltage detection value of the _{capacitor C 2 ) VC2.} Is generated, and this balance command value is input to the balance command value adjusting unit 200A.

Next, the configuration of the balance command value adjusting unit 200A will be described.
First, the input voltage _{V in} of the chopper is input to the adder-subtracter 204 via the low-pass filter 201. Further, the output voltage V _o of the chopper is input to a multiplier 203 through a low-pass filter 202, the multiplication result of a constant {(√3 + 3) / 6 } is input to the adder-subtracter 204.
The output a of the adder / subtractor 204 is input to the comparator 205 for discriminating between positive and negative, and the comparison result with "0000 hex (hex is a hexadecimal number)" is added to the changeover switch 206.

Further, the output a of the adder / subtractor 204 is input to the input terminals T and F of the changeover switch 206 via the gains 1 and 2, respectively. Here, gain 1 _is a coefficient becomes "1000hex" when a _V in ₌ V o / 2, a gain of 2 _is a coefficient which is a "1000hex" when a _V in = V _o. The input terminal T of the changeover switch 206 indicates "True", and F indicates "False".
The comparator 205 outputs a signal for selecting the input terminal T side of the changeover switch 206 when the input a is negative.

The output of the changeover switch 206 becomes an absolute value signal b by the absolute value calculation circuit 207 and is input to the adder / subtractor 208. The addition / subtractor 208 detects a deviation c between “1000 hex” and the absolute value signal b, and this deviation c is input to the multipliers 209 and 210.
The multipliers 209 and 210 multiply the deviation c by the upper limit limiter value and the lower limit limiter value, respectively, and output these multiplication results as the upper limit limiter value and the lower limit limiter value of the upper and lower limit limiters 211. The upper / lower limit limiter 211 processes the balance command value input from the balance command value generation unit 102 for upper / lower limits, and outputs the output signal d to the addition / subtractors 103 and 104.

Figure 6 is a diagram showing the relationship between each signal a~d in the input voltage V _in and 5 of the chopper. The operation of the control circuit of Figure 5, the balance command value d which is finally output from the balance command value adjusting section 200A _is zero when _{V in = V o / 2,} V in = V o, V in = { maximum at (√3 + 3) / 6} V o ( balance command rate 100%) becomes.

Next, FIG. 7 is a diagram showing the relationship between the input voltage, the current ripple rate, and the balance command rate in the design example based on the first embodiment. Here, the maximum value of the current ripple rate 20 [%], the output voltage _{V o} of the chopper and 1100 [V]. Therefore, the input voltage _{V in} when the current ripple ratio is _maximized, the _{V in = {(√3 + 3} ) / 6} V o ≒ 868 [V].

As is clear from the outline of the above-mentioned operation, at the time points (1) and (3) in FIG. 7, since the current ripple rate is small, the ripple current due to the voltage unevenness of the _{capacitors C 1} and C _{2 is hardly a problem.} .. Thus, settings to avoid bias in the switching element S _1, S ₂ of the on-time balance command value output from the balance command value adjustment unit 200A of FIG. 5 as 0 (the balance command of 0%), the thermal balance of the elements Keep.
Since the current ripple rate is large at the time point (2) in FIG. 7, the ripple current due to the voltage unevenness of the _{capacitors C 1} and C _{2 is large.} Therefore, the balance command value output from the balance command value adjusting unit 200A is set to the maximum value (balance command rate is 100%) to suppress the ripple current and protect the connected equipment of the power system.

As described above, by gradually changing the balance command value in the range of (1) to 7 (2) - (3) in accordance with the current ripple rate, the switching element S ₁ of the step-down mode _chopper, S ₂ Overheat protection and suppression of ripple current become possible.

Next, FIG. 8 is a block diagram of the control circuit according to the second embodiment of the present invention.
This second embodiment, when operating the chopper in boost mode region (see FIG. 1) generates a drive signal of the switching element S ₁ to S ₄ in order to equalize the voltage of the capacitor C _1, C ₂ It is a thing.

The outline of the operation of the second embodiment is as follows.
That is, in the boost mode, by balancing command value (balance command ratio) and 0 when a _{V in =} V o / _2, to continue the operation of the prevent by device bias the heat of the switching element.
_Also, depending from the state of V in _{= V} o / 2 in the reduction of _{V in} gradually increasing the balance command value, balance command value at the time of _V in _{= V} o / 3 that current ripple ratio becomes maximum By maximizing (balance command rate is 100%), the ripple current is reduced and the connected equipment of the power system is protected.
_Moreover, gradually decreasing the balance command value with a decrease of _{V in} from the time of V in _{= V} o / _3, the balance command value at the time of _{V in} = 0 to 0 (balance command 0%) As a result, the heat bias of the switching element is prevented and the operation of the device is continued.

_{If one} of the voltages of the capacitors C 1 and C ₂ becomes an overvoltage and the other becomes an undervoltage regardless of the step-down mode or the step-up mode, the balance command value is maximized regardless of the magnitude of the input voltage. , The operation of the device can be continued.

The difference between the control circuit of FIG. 8 and FIG. 5 according to the second embodiment is that the constant input to the multiplier 203 in the balance command value adjusting unit 200B is 1 / instead of (√3 + 3) / 6 of FIG. The point is that the gain is 3 and the gain on the input side of the changeover switch 206 is the gains 3 and 4. Here, gain 3 _is a coefficient becomes "1000hex" when a _{V in} = 0, gain 4 _is a coefficient which is a "1000hex" when a _V in ₌ V o / 2.

Figure 9 is a diagram showing the relationship between each signal a~d in the input voltage V _in and 8 of the chopper. The operation of the control circuit of Figure 8, the balance command value d which is finally output from the balance command value adjusting section 200B _{is, V in = 0, V in} = V o / 0 next when _{2, V} in = V _o When it is / 3, it becomes the maximum value (balance command rate is 100%).

Next, FIG. 10 is a diagram showing the relationship between the input voltage, the current ripple rate, and the balance command rate in the design example based on the second embodiment. Like the first embodiment, the maximum value of the current ripple rate 20 [%], the output voltage _{V o} of the chopper and 1100 [V]. Therefore, the input voltage _{V in} when the current ripple ratio is _maximized, and _{V in = V o / 3 ≒} 367 [V].

As is clear from the summary of the above-described operation, in FIG. 10 (4), at (6), since the current ripple rate is low, the ripple current due to the voltage unequal of capacitors C _1, C ₂ rarely a problem .. Thus, settings to avoid bias in the switching element S _1, S ₂ of the on-time balance command value output from the balance command value adjusting section 200B of FIG. 8 as 0 (the balance command of 0%), the thermal balance of the elements Keep.
Since the current ripple rate is large at the time point (5) in FIG. 10, the ripple current due to the voltage unevenness of the _{capacitors C 1} and C _{2 is large.} Therefore, the balance command value output from the balance command value adjusting unit 200B is set to the maximum value (balance command rate is 100%) to suppress the ripple current and protect the connected equipment of the power system.

As described above, by gradually changing the balance command value in the range of 10 according to the current ripple rate (4) - (5) - (6), the switching element S ₁ of the step-up mode of the _chopper, S ₂ Overheat protection and suppression of ripple current become possible.

Further, FIG. 11 is a configuration diagram of a control circuit according to a third embodiment of the present invention.
In the third embodiment, (buck mode region in FIG. 1, when selectively using the boost mode region) When operating the chopper as a temperature-down chopper, the capacitor C _1, the switching element in order to equalize the voltage of C ₂ It generates drive signals of _{S 1 to} S _4.

In FIG. 11, the parts other than the balance command value adjusting unit 200C are the same as those in FIGS. 5 and 8, and the balance command value adjusting unit 200C is the main part of the balance command value adjusting unit 200A in FIG. 5 and the balance in FIG. It corresponds to a combination with the main part of the command value adjusting part 200B.
In balance command value adjustment unit 200C, the step-down mode by comparing the _{V in} and _V o / 2 by the comparator 230, to determine the boost mode, the changeover switch 229 as long as the step-down mode _{(V in> V o / 2} ) On the terminal T side, if the boost mode (V _in <V _o / 2), the changeover switch 229 is switched to the terminal F side.

In the boost mode side in the balance command value adjusting unit 200C, 221,222 is a low-pass filter, 223 is a multiplier, 224,228 is an adder / subtractor, 225 is a comparator, 226 is a changeover switch, and 227 is an absolute value calculator. be. Further, the gain 5 is an appropriate coefficient for correcting the balance command value to match the current ripple rate.

FIG. 12 is a diagram showing the relationship between the input voltage and the current ripple in the design example based on the third embodiment. Since the relationship between the input voltage and the balance command rate is the same as in FIGS. 7 and 10, the illustration is omitted.
First, as in the second embodiment, the maximum value of the current ripple rate 20 [%], and the output voltage V _o of the chopper and 1100 [V], the input voltage V _in when the current ripple ratio becomes maximum Is Vin ≈ 868 [V] _{in the} step-down mode and Vin ≈ 367 [V] _{in the step-up mode.}

At the time points (1), (3), (4), and (6) in FIG. 12, since the current ripple rate is small, the ripple current due to the voltage unevenness of the _{capacitors C 1} and C _{2 is hardly a problem.} Thus, settings to avoid bias in the switching element S _1, S ₂ of the on-time balance command value output from the balance command value adjustment unit 200C of FIG. 11 0 (balance command of 0%), the thermal balance of the elements Keep.
Since the current ripple rate is large at the time point (2) in the step-down mode region of FIG. 12, the ripple current due to the voltage unevenness of the _{capacitors C 1} and C _{2 is large.} Therefore, the balance command value output from the balance command value adjusting unit 200C is set to the maximum value (balance command rate is 100%) to suppress the ripple current and protect the connected equipment of the power system.
Further, at the time point (5) in the step-up mode region, the balance command value may be set according to the current ripple rate.

As described above, for each of the step-down mode region and the step-up mode region, the range of (1) to (2) to (3) or (4) to (5) to (6) in FIG. 12 depending on the current ripple rate. in by gradually changing the balance command value, allowing the switching element S _1, the overheat protection of S ₂ and ripple current suppression.

Incidentally, it is possible to regenerate by turning on the switching element _S 3, _{S 4} in FIG. 13 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.

The three-level chopper according to the present invention can be used, for example, in an uninterruptible power supply, a photovoltaic power generation system, a power conversion device for vehicles such as railroad vehicles and electric vehicles in which the input voltage fluctuates greatly.

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 : Capacitor C _in : Smoothing capacitor LD: Load P: Positive terminal N: Negative Side terminal M: Neutral point 101: PWM command generation unit 102: Balance command value generation unit 103, 104, 204, 208, 224,228: Addition / subtractor 105, 106: PWM circuit 200A, 200B, 200C: Balance command value adjustment Part 201, 202, 221, 222: Low-pass filter 203, 209, 210, 223: Multiplier 205, 225, 230: Compacitor 206, 226, 229: Changeover switch 207, 227: Absolute value calculator 211: Upper and lower limit limiter

Claims (10)

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 PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
To adjust the balance command value according to the input voltage and output voltage of the three-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the step-down operation of the three-level chopper. The balance command value adjustment unit that generates the balance command adjustment value, and
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
A 3-level chopper featuring. 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 PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
To adjust the balance command value according to the input voltage and output voltage of the three-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the boosting operation of the three-level chopper. The balance command value adjustment unit that generates the balance command adjustment value, and
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
A 3-level chopper featuring. 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 PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
The balance command value is adjusted according to the input voltage and output voltage of the 3-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the step-up / step-down operation of the 3-level chopper. Balance command value adjustment unit that generates the balance command adjustment value for
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
A 3-level chopper featuring. In the three-level chopper according to any one of claims 1 to 3.
The balance command value adjusting unit
A three-level chopper characterized in that a deviation between the product of the output voltage and the input / output voltage ratio and the input voltage is obtained, and the balance command value is adjusted based on the product of the deviation and a predetermined gain. 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 PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
To adjust the balance command value according to the input voltage and output voltage of the three-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the step-down operation of the three-level chopper. The balance command value adjustment unit that generates the balance command adjustment value, and
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
A control circuit for a 3-level chopper, which is characterized by being equipped with. 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 PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
To adjust the balance command value according to the input voltage and output voltage of the three-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the boosting operation of the three-level chopper. The balance command value adjustment unit that generates the balance command adjustment value, and
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
A control circuit for a 3-level chopper, which is characterized by being equipped with. 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 PWM command generator that generates a PWM command value for matching the voltage across the series circuit of the first and second capacitors to the command value, and a PWM command generator.
A balance command value generator that generates a balance command value for equalizing the voltages of the first and second capacitors according to the voltage of the first and second capacitors.
The balance command value is adjusted according to the input voltage and output voltage of the 3-level chopper and the input / output voltage ratio at which the ripple rate of the current flowing through the chopper is maximized during the step-up / step-down operation of the 3-level chopper. Balance command value adjustment unit that generates the balance command adjustment value for
A means for generating a drive signal for turning on / off the first and second switching elements based on the PWM command value and the balance command adjustment value, and
A control circuit for a 3-level chopper, which is characterized by being equipped with. In the control circuit of the three-level chopper according to any one of claims 7 to 9.
The balance command value adjusting unit
A three-level chopper characterized in that a deviation between the product of the output voltage and the input / output voltage ratio and the input voltage is obtained, and the balance command value is adjusted based on the product of this deviation and a predetermined gain. Control circuit.

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