JP2022012104A - Dc power converter and control method of the same - Google Patents

Abstract

To suppress the imbalance of transmission power between legs in a DC power converter without increasing a DC component of a lateral current flowing between the legs.SOLUTION: In a DC power converter, multiple legs leg1, leg2 are connected in parallel. Within each leg leg1, leg2, multiple units 11 to 1 N are connected in multi-stage series. Each cell 2 has its own DC voltage 1 and cell 2. A phase shift angle δ between legs leg1, leg2 is controlled by a control unit of the DC power converter.SELECTED DRAWING: Figure 1

Description

The present invention relates to power transmission between legs of a DC power converter having a plurality of legs.

A DC power conversion device as shown in FIG. 1 has been conventionally known. In the DC power conversion device shown in FIG. 1, a unit unit (hereinafter referred to as a unit) in which a cell 2 is connected to a DC voltage 1 is used. Further, a unit leg (hereinafter referred to as a leg) is a unit in which a plurality (N units) of the units 11 to 1N are connected in series. By connecting the first leg 1 and the second leg 2 in parallel on the DC voltage 1 side, DC power is supplied to the DC load 3. In such a DC power conversion device, phase shift PWM control may be applied.

Assuming that the number of units in series is N, in the configuration using the full bridge type power conversion device shown in FIG. 1 (b), the triangular wave carriers are phase-shifted by π / N [rad] between the units in the leg for operation. Further, since the number of parallel legs is 2, the triangular wave carrier is phase-shifted by π / 2N [rad] between the legs for operation.

By this operation, the ripple frequency of the leg current is N times and the current ripple frequency flowing into the output capacitor 4 is 2N times as compared with the case where the triangular wave carrier is not phase-shifted. As a result, the current ripple flowing through the output capacitor 4 is reduced, and the voltage ripple of the output capacitor 4 is reduced.

Similarly, in the configuration using the half-bridge type power conversion device shown in FIG. 1 (c), the triangular wave carriers are phase-shifted by 2π / N [rad] between the units in the leg for operation. Further, since the number of parallel legs is 2, the triangular wave carriers are phase-shifted by π / N [rad] between the legs for operation.

Consider the case where an imbalance occurs in the transmission power between the legs in FIG. 1. Generally, by distributing the DC component of the leg current between the legs and positively flowing a DC cross current, the DC power is transmitted between the legs and the transmission power is balanced between the legs. In addition, even if heat generation or loss bias occurs, DC power is transmitted between the legs.

Japanese Unexamined Patent Publication No. 2019-68559 Patent No. 6552774

In the configuration of the DC power conversion device shown in FIG. 1, the imbalance of the transmission power between legs is suppressed by using the DC current. In the case of this method, the DC current flowing through the DC reactors L1 to L4 connected between the output capacitor 4 and the leg also increases, which may be affected by abnormal heat generation due to magnetic saturation and an increase in current ripple.

From the above, it is an issue in the DC power conversion device to suppress the imbalance of the transmission power between the legs without increasing the DC component of the cross flow flowing between the legs.

The present invention has been devised in view of the above-mentioned conventional problems, and one aspect thereof has a plurality of legs connected in parallel, a DC voltage and a cell, respectively, and is connected in series in multiple stages in each leg. It is a DC power conversion device including a plurality of units, and is characterized by including a control unit for controlling a phase shift angle between the legs.

Further, as one aspect thereof, the plurality of legs are characterized by having two legs, a first leg and a second leg.

Further, as one aspect thereof, the cell is a full bridge type power conversion device, and the control unit is a transmission power command value from the first leg to the second leg and from the first leg to the second leg. A subtractor that calculates the deviation from the transmission power detection value of the above, a multiplier that multiplies the deviation by -1, a PI control unit that performs PI control based on the deviation multiplied by -1, and the PI control unit. It is characterized by including an adder that adds π / 4 to the output of the first leg and outputs the phase delay angle command value of the second leg with respect to the first leg.

Further, as another aspect, the cell is a half-bridge type power conversion device, and the control unit is a transmission power command value from the first leg to the second leg and from the first leg to the second leg. A subtractor that calculates the deviation from the transmission power detection value of, a multiplier that multiplies the deviation by -1, a PI control unit that performs PI control based on the deviation multiplied by -1, and the PI control unit. It is characterized by including an adder that adds π / 2 to the output of the first leg and outputs the phase delay angle command value of the second leg with respect to the first leg.

According to the present invention, in the DC power conversion device, it is possible to suppress the imbalance of the transmission power between the legs without increasing the DC component of the cross current flowing between the legs.

The figure which shows the circuit composition example of the DC power conversion apparatus. The figure which shows the change example of the power transmission between legs by the change of the phase shift angle δ between legs when the full bridge type power conversion apparatus is applied to a cell. The figure which shows the relationship example of the 1st leg average output power and a phase shift angle. The control block diagram of the phase shift angle δ in Embodiment 1. FIG. The figure which shows the change example of the power transmission between legs by the change of the phase shift angle δ between legs when a half-bridge type power conversion apparatus is applied to a cell. The figure which shows the relationship example of the 1st leg average output power and a phase shift angle. The control block diagram of the phase shift angle δ in Embodiment 2. FIG.

Hereinafter, embodiments 1 and 2 of the DC power conversion device according to the present invention will be described in detail with reference to FIGS. 1 to 7.

In this specification, the DC power conversion device having the circuit configuration shown in FIG. 1 will be described as an example. As shown in FIG. 1, the DC power converter comprises a plurality of legs connected in parallel. In FIG. 1, the plurality of legs are two first leg legs 1 and a second leg leg 2. The first leg 1 includes first units 11 to N units connected in series in multiple stages. Similarly, in the second leg 2, N units are connected in series in multiple stages.

Each unit has a DC voltage 1 and a cell 2 connected to the DC voltage 1. The DC voltage 1 may be, for example, one in which an input capacitor is connected to a DC power supply. The cell terminals on the side not connected to the DC voltage 1 are connected in series in multiple stages.

Next, cell 2 will be described. The cell has a configuration to which the full-bridge type power conversion device of FIG. 1 (b) is applied and a configuration to which the half-bridge type power conversion device of FIG. 1 (c) is applied.

In the cell to which the full bridge type power conversion device of FIG. 1B is applied, the first and second semiconductor switching elements S1 and S2 are connected in series between one terminal of the DC voltage 1 and the other terminal. Further, the third and fourth semiconductor switching elements S3 and S4 are connected in series between one terminal of the DC voltage 1 and the other terminal. The connection points of the first and second semiconductor switching elements S1 and S2 are one cell terminal, and the connection points of the third and fourth semiconductor switching elements S3 and S4 are the other cell terminals.

In the cell to which the half-bridge type power conversion device of FIG. 1C is applied, the first and second semiconductor switching elements S1 and S2 are connected in series between one terminal of the DC voltage 1 and the other terminal. The connection points of the first and second semiconductor switching elements S1 and S2 are one cell terminal, and the connection points of the DC voltage 1 and the second semiconductor switching element S2 are the other cell terminals.

One cell terminal of the first unit 11 is connected to one end of the DC reactor L1, and the other cell terminal of the first unit 11 is connected to one cell terminal of the second unit 12. The second unit 12 to the Nth unit 1N are also connected by cell terminals in the same manner. The other cell terminal of the Nth unit 1N is connected to one end of the DC reactor L2.

The second leg 2 is also connected in the same manner, and is connected to one end of the DC reactors L3 and L4. A DC load 3 is connected to the other ends of the DC reactors L1 to L4 via an output capacitor 4.

In the first embodiment, the configuration in which the full-bridge type power conversion device of FIG. 1 (b) is applied as the cell 2 is targeted, and in the second embodiment, the half-bridge type power conversion device of FIG. 1 (c) is applied as the cell 2. Is targeted.

In the present invention, by controlling the phase shift angle between the legs, the cross current of an integral multiple of the carrier frequency is controlled, and the DC power is transmitted between the legs without flowing the DC cross current. Therefore, thereafter, the output waveform of the voltage V2 of the second leg 2 is a waveform obtained by delaying the output waveform of the voltage V1 of the first leg 1 by the phase shift angle between the legs.

Further, for the sake of simplicity, the number of units connected in series in the leg will be set to 2 from now on.

[Embodiment 1]
In the first embodiment, a case where a full bridge type power conversion device is applied to the cell 2 will be described.

The angular frequency of the triangular wave carrier is ω [rad / s], and the phase shift angle between the units in the leg of the triangular wave carrier is π / 2 [rad]. When a full-bridge type power conversion device is applied to the cell 2, the unit output voltages Vunit11 and Vunit12 of the first leg 1 have a rectangular wave shape having a frequency twice the triangular wave carrier frequency as a fundamental wave. Therefore, the unit output voltages Vunit11 and Vunit12 are represented by the equations (1) and (2). However, an is a _Fourier coefficient and the DC load voltage is Vout.

Therefore, the voltage V1 of the first leg 1, which is the sum of the unit currents, is given by the equation (3).

The voltage V2 of the second leg 2 has a waveform obtained by shifting the voltage V1 of the first leg 1 by the delay time due to the phase shift. When the phase shift angle is δ, the delay time is δ / ω, and the voltage V2 of the second leg 2 is given by the equation (4).

The cross current Icil circulating between the legs flows when the difference V1-V2 of the leg voltage is applied to the DC reactor L. Therefore, the cross current Icil is expressed by the equation (3). However, k is a coefficient.

The output power P ₁₁ of the first unit 11 of the first leg 1 by the cross current Icil is given by the equation (6).

Here, since the average power is 0 except for the product of the same frequency components due to the orthogonality of the trigonometric function, the average output power P ₁₁ ￣ of the first unit 11 can be transformed into the equation (7).

Further, the average output power P ₁₁ ￣ can be transformed as in Eq. (8) by removing the AC component.

Similarly, the average output power P ₁₂ ￣ of the second unit 12 of the first leg 1 by the cross current Icil is given by the equation (9).

Further, the average output power _P12 ￣ can be transformed as in Eq. (10) by removing the AC component.

The average output power P ₂₁ ￣ of the first unit 21 of the second leg 2 by the cross current Icil is given by the equation (11).

Further, the average output power P21 ￣ can be transformed as in Eq. ₍ 12) by removing the AC component.

The average output power P ₂₂ ￣ of the second unit 22 of the second leg 2 by the cross current Icir is given by the equation (13).

Further, the average output power P ₂₂ ￣ can be transformed as in Eq. (14) by removing the AC component.

From the above, the average output powers of the units in the legs are the same, and the sign is inverted between the legs. That is, power transmission between legs is possible by controlling the phase shift angle δ between the legs. FIG. 2 shows an example of a change in the average output power of the legs due to a phase shift between the legs.

When the normal phase shift angle δ = π / 4, the average output power becomes 0, and DC power transmission due to cross current does not occur. Here, consider a case where the phase shift angle δ between the legs is shifted from δ = π / 4. Since the term of n = 2 is dominant for the series part appearing in the equation of each average output power, it can be approximated as in equation (15).

Further, FIG. 3 shows an example of the relationship between the phase shift angle δ between the legs and the average output power. As shown in FIG. 3, in the vicinity of the phase shift angle δ = π / 4, when the phase shift angle δ is increased, the average output power of the first leg 1 decreases monotonically. Therefore, by using the control unit as shown in FIG. 4, the transmission power between the legs can be controlled.

As shown in FIG. 4, the control unit includes a subtractor 5, a multiplier 6, a PI control unit 7, and an adder 8. The subtractor 5 calculates the deviation by subtracting the transmission power detection value of the first leg 1 → the second leg 2 from the transmission power command value of the first leg 1 → the second leg 2. The multiplier 6 multiplies this deviation by -1. The PI control unit 7 performs PI control based on the deviation multiplied by -1. The adder 8 adds π / 4 to the output of the PI control unit 7. The output of the adder 8 becomes the phase delay angle command value δ [rad] of the second leg 2 with respect to the first leg leg 1.

As shown above, according to the first embodiment, DC power transmission between legs is performed without increasing the DC component of the cross current flowing between the legs. As a result, it is possible to suppress abnormal heat generation and an increase in current ripple due to magnetic saturation of the DC reactor, which may occur when the DC component of the cross current increases.

[Embodiment 2]
In the second embodiment, a case where a half-bridge type power conversion device is applied to the cell will be described.

The angular frequency of the triangular wave carrier is ω [rad / s], and the phase shift angle between the units in the leg of the triangular wave carrier is π [rad]. When a half-bridge type power conversion device is applied, the unit output voltages Vunit11 and Vunit12 of the first leg 1 have a rectangular wave shape having a triangular carrier frequency as a fundamental wave. Therefore, the unit output voltages Vunit11 and Vunit12 are represented by the equations (16) and (17). However, an is a _Fourier coefficient and the DC load voltage is Vout.

Therefore, the voltage V1 of the first leg 1, which is the sum of the unit currents, is given by the equation (18).

The voltage V2 of the second leg 2 has a waveform obtained by shifting the voltage V1 of the first leg 1 by the delay time due to the phase shift. When the phase shift angle is δ, the delay time is δ / ω, and the voltage V2 of the second leg 2 is given by the equation (19).

The cross current Icil circulating between the legs flows when the difference V1-V2 of the leg voltage is applied to the DC reactor L. Therefore, the cross current Icil is expressed by the equation (20). However, k is a coefficient.

The output power P ₁₁ of the first unit 11 of the first leg Leg 1 by the cross current Icil is given by the equation (21).

Here, since the average power is 0 except for the product of the same frequency components due to the orthogonality of the trigonometric function, the average output power P ₁₁ ￣ of the first unit 11 can be transformed into the equation (22).

Further, the average output power P ₁₁ ￣ can be transformed as in Eq. (23) by removing the AC component.

Similarly, the average output power P ₁₂ ￣ of the second unit 12 of the first leg 1 by the cross current Icil is given by the equation (24).

Further, the average output power _P12 ￣ can be transformed as in Eq. (25) by removing the AC component.

The average output power P ₂₁ ￣ of the first unit 21 of the second leg 2 by the cross current Icil is given by the equation (26).

Further, the average output power P21 ￣ can be transformed as in Eq. ₍ 27) by removing the AC component.

The average output power P ₂₂ ￣ of the second unit 22 of the second leg 2 by the cross current Icil is given by the equation (28).

Further, the average output power P ₂₂ ￣ can be transformed as in Eq. (29) by removing the AC component.

From the above, the average output powers of the units in the legs are the same, and the sign is inverted between the legs. That is, power transmission between legs is possible by controlling the phase shift angle δ between the legs. FIG. 5 shows an example of a change in the average output power of the legs due to a phase shift between the legs.

When the normal phase shift angle δ = π / 2, the average output power becomes 0, and DC power transmission due to cross current does not occur. Here, consider a case where the phase shift angle δ between the legs is shifted from δ = π / 2. Since the term of n = 2 is dominant for the series part appearing in the equation of each average output power, it can be approximated as in equation (30).

Further, FIG. 6 shows an example of the relationship between the phase shift angle δ between the legs and the average output power. As shown in FIG. 6, in the vicinity of the phase shift angle δ = π / 2, when the phase shift angle δ is increased, the average output power of the first leg 1 decreases monotonically. Therefore, by using the control unit as shown in FIG. 7, the transmission power between the legs can be controlled.

The control unit of FIG. 7 includes a subtractor 5, a multiplier 6, a PI control unit 7, and an adder 9. The subtractor 5, the multiplier 6, and the PI control unit 7 are the same as those in FIG. The adder 9 adds π / 2 to the output of the PI control unit 7. The output of the adder 9 becomes the phase delay angle command value δ [rad] of the second leg 2 with respect to the first leg leg 1.

As shown above, according to the second embodiment, DC power transmission between legs is performed without increasing the DC component of the cross current flowing between the legs. As a result, it is possible to suppress abnormal heat generation and an increase in current ripple due to magnetic saturation of the DC reactors L1 to L4, which may occur when the DC component of the cross current increases.

Although the above description has been made in detail only for the specific examples described in the present invention, it is obvious to those skilled in the art that various modifications and modifications are possible within the scope of the technical idea of the present invention. It goes without saying that such modifications and modifications fall within the scope of the claims.

1 ... DC voltage 2 ... Cell 3 ... DC load 4 ... Output capacitor 5 ... Subtractor 6 ... Multiplier 7 ... PI control unit 8, 9 ... Adder 11 to 1N ..., 21 to 2N ... 1st to Nth unit leg1 , Leg2 ... 1st and 2nd legs L1 to L4 ... DC reactor S1 to S4 ... 1st to 4th semiconductor switching elements

Claims (5)

With multiple legs connected in parallel,
Multiple units each having a DC voltage and a cell and connected in series in multiple stages within each leg,
It is a DC power converter equipped with
A DC power conversion device including a control unit that controls a phase shift angle between the legs. The DC power conversion device according to claim 1, wherein the plurality of legs are two, a first leg and a second leg. The cell is a full-bridge type power converter.
The control unit
A subtractor that calculates the deviation between the transmission power command value from the first leg to the second leg and the transmission power detection value from the first leg to the second leg.
A multiplier that multiplies the deviation by -1 and
A PI control unit that performs PI control based on the deviation multiplied by -1
An adder that adds π / 4 to the output of the PI control unit and outputs the phase delay angle command value of the second leg with respect to the first leg.
2. The DC power conversion device according to claim 2, wherein the DC power conversion device is provided. The cell is a half-bridge type power converter.
The control unit
A subtractor that calculates the deviation between the transmission power command value from the first leg to the second leg and the transmission power detection value from the first leg to the second leg.
A multiplier that multiplies the deviation by -1 and
A PI control unit that performs PI control based on the deviation multiplied by -1
An adder that adds π / 2 to the output of the PI control unit and outputs the phase delay angle command value of the second leg with respect to the first leg.
2. The DC power conversion device according to claim 2, wherein the DC power conversion device is provided. With multiple legs connected in parallel,
Multiple units each having a DC voltage and a cell and connected in series in multiple stages within each leg,
It is a control method of a DC power converter equipped with
A control method for a DC power conversion device, which comprises controlling a phase shift angle between the legs in a control unit.

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