converter

Abstract

To propose a converter capable of suppressing deviation of voltage balance between units to a certain value or less when multiple units which are an insulation type DC / DC converter are connected in series.SOLUTION: In a converter 1A, multiple units are connected in series on an input-side, each of the units includes a voltage conversion circuit 2 and a control circuit 3. An error calculation unit 5 outputs, as an error value, a value obtained by subtracting an input-side average voltage value from a voltage value of a self-machine on the input side and adding the input-side offset value. An error amplification calculation unit 6 outputs, as a voltage balance control operation amount, a value obtained by performing amplification calculation on the error value when the value obtained by performing amplification calculation on the error value is equal to or less than zero, and outputs the voltage balance control operation amount having a value of zero when the value obtained by performing the amplification calculation on the error value is greater than zero. A control signal generation unit 7 is configured to generate a control signal based on a total operation amount obtained by adding a conventional control operation amount and the voltage balance control operation amount.SELECTED DRAWING: Figure 3B

Description

Technical Field

[0001] The present invention relates to a converter including a series connection on an input side or an output side when connecting a plurality of units, each of which is an isolated DC / DC converter, on the input side and the output side.

Background Art

[0002] There is a converter in which a plurality of units, each of which is an isolated DC / DC converter, are connected on the input side and the output side (see, for example, Patent Document 1). This converter can generate a high-voltage DC voltage by connecting the units in series, and can perform voltage conversion of a large current by connecting the units in parallel.

[0003] Each unit is provided with a control circuit that controls its own voltage conversion circuit, and the control circuit controls the voltage, current, and power of its own unit so as to operate at a target value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] <� By the way, even for units of the same design product, parts such as capacitors that make up the units have characteristic variations, so there will be differences in circuit constants for each unit. In addition, since each control circuit controls each unit individually, the operation of each unit may differ due to subtle deviations in the timing at which the control circuit controls its own unit and the calculation results in the control circuit. Therefore, when a plurality of units are connected in series, these factors may cause a difference in the voltage value of each unit, which may lead to a concentration of load on a specific unit and result in a failure of the unit.

[0006] In view of these points, the present invention aims to propose a converter that can suppress the voltage imbalance between units to a certain value or less when multiple isolated DC / DC converter units are connected in series. [Means for solving the problem]

[0007] One of the converters of the present invention is a plurality of units, each being an isolated DC / DC converter, connected in series on the input side, each of the plurality of units comprising a voltage conversion circuit that converts the input voltage and outputs it to the output side, and a control circuit that controls the voltage conversion circuit, each of the control circuits comprising a conventional control unit, an error calculation unit that outputs an error value, an error amplification calculation unit that outputs a voltage balance control operation variable based on a value amplified by the error value, and a control signal generation unit that generates a control signal for controlling the voltage conversion circuit, the conventional control unit is configured to output a conventional control operation variable for controlling the voltage conversion circuit with constant voltage control, constant current control, or constant power control. The error calculation unit is configured to output the error value by subtracting the input-side average voltage value, obtained by dividing the total voltage of the multiple units on the input side by the number of units, from the voltage value of the machine on the input side, and then adding a predetermined input-side offset value greater than 0. The error amplification calculation unit is configured to output the amplified value of the error value as the voltage balance control operation variable if the amplified value of the error value is 0 or less, and to output the voltage balance control operation variable whose value is 0 if the amplified value of the error value is greater than 0. The control signal generation unit is configured to generate the control signal based on a total operation variable obtained by adding the conventional control operation variable and the voltage balance control operation variable. [Effects of the Invention]

[0008] According to the converter of the present invention, when multiple units are connected in series, the voltage imbalance between the units can be kept below a certain value. [Brief explanation of the drawing]

[0009] [Figure 1A] This is a circuit diagram showing a first embodiment of the converter according to the present invention. [Figure 1B] This is a circuit diagram showing a second embodiment of the converter according to the present invention. [Figure 1C] This is a circuit diagram showing a third embodiment of the converter according to the present invention. [Figure 1D] This is a circuit diagram of a converter used as an example. [Figure 2] Figures 1A to 1D show the circuit diagrams for the k-th unit. [Figure 3A] This diagram shows a conventional block diagram of a control circuit. [Figure 3B] This figure shows a block diagram of one embodiment of the control circuit according to the present invention. [Figure 4] Figure 3B conceptually illustrates the relationship between the manipulated variable and time in the control circuit shown. [Figure 5A] This is a diagram relating to the error calculation unit in the first embodiment. [Figure 5B] This is a diagram relating to the error calculation unit in the second embodiment. [Figure 5C] This is a diagram relating to the error calculation unit in the third embodiment. [Figure 5D] This is a diagram of the error calculation unit in the example. [Figure 6A] This is a circuit diagram illustrating the effects of the converter according to the present invention in comparison with conventional converters. [Figure 6B] This figure shows the voltage change on the input side when the converter shown in Figure 6A is controlled using a conventional block diagram. [Figure 6C] This figure shows the voltage change on the output side when the converter shown in Figure 6A is controlled using a conventional block diagram. [Figure 7A] This figure shows the voltage change on the input side when the converter shown in Figure 6A is controlled according to the block diagram of the third embodiment. [Figure 7B]FIG. 6A is a diagram showing voltage changes on the output side when the converter shown in FIG. 6A is controlled by the block diagram of the third embodiment.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, an example of an embodiment in which a converter according to the present invention is embodied will be described with reference to the accompanying drawings.

[0011] FIGS. 1A to 1C are diagrams showing converters 1A to 1C which are an example of an embodiment in which a converter according to the present invention is embodied. The converters 1A to 1C all include a first unit, a second unit, ···, an nth unit (n is an integer of 2 or more). The first unit to the nth unit in this specification are described as Unit_1 to Unit_n in the accompanying drawings. The first unit to the nth unit are all isolated DC / DC converters of the same specification, and hereinafter, the kth unit which is one of these units will be described. Note that FIG. 1D is a diagram showing the converter 1D of the reference example.

[0012] When connecting a plurality of units on the input side and the output side, the connection methods on the input side and the output side of the converters 1A to 1D are different from each other. In the converter 1A, the first unit to the nth unit are connected in series on the input side and in parallel on the output side. That is, the converter 1A is formed by connecting a plurality of isolated DC / DC converters in series on the input side and in parallel on the output side (Input Series Output Parallel, hereinafter referred to as ISOP connection).

[0013] The converter 1B of the second embodiment shown in FIG. 1B has the first unit to the nth unit connected in parallel on the input side and in series on the output side. That is, the converter 1B is formed by connecting a plurality of isolated DC / DC converters in parallel on the input side and in series on the output side (Input Parallel Output Series, hereinafter referred to as IPOS connection).

[0014] In the converter 1C of the third embodiment shown in FIG. 1C, the first unit to the nth unit are connected in series on the input side and also connected in series on the output side. That is, the converter 1C is formed by connecting a plurality of isolated DC / DC converters in series on the input side and in series on the output side (Input Series Output Series, hereinafter referred to as ISOS connection).

[0015] In the converter 1D of the reference example shown in FIG. 1D, the first unit to the nth unit are connected in parallel on the input side and also connected in parallel on the output side. That is, the converter 1D is formed by connecting a plurality of isolated DC / DC converters in parallel on the input side and in parallel on the output side (Input Parallel Output Parallel, hereinafter referred to as the so-called IPOP connection).

[0016] Here, the kth unit included in the converters 1A to 1D will be described while referring to FIG. 2. The kth unit, which is an isolated DC / DC converter, is composed of a capacitor C, a switching element (not shown), an isolation transformer (not shown), etc., and includes a voltage conversion circuit 2 that converts the voltage on the input side and outputs it to the output side, and a control circuit 3 that controls the voltage conversion circuit 2.

[0017] In explaining the control circuit 3 of this embodiment, first, the control circuit 30 when the kth unit is a conventional isolated DC / DC converter will be described while referring to FIG. 3A. The conventional control circuit 30 includes a conventional control unit 40 and a control signal generation unit 70. The conventional control unit 40 outputs a conventional control operation amount AVR1_k for controlling the voltage conversion circuit of its own device by using conventional constant voltage control, constant current control, or constant power control. The control signal generation unit 70 generates a control signal based on the input conventional control operation amount AVR1_k, and the control circuit 3 controls the voltage conversion circuit of its own device based on the control signal.

[0018] In contrast to the conventional control circuit 30, the control circuit 3 of this embodiment, as shown in Figure 3B, comprises a conventional control unit 4, an error calculation unit 5, an error amplification calculation unit 6, and a control signal generation unit 7. The conventional control unit 4 functions similarly to the conventional control unit 40 described above, and the control signal generation unit 7 functions similarly to the control signal generation unit 70. The error calculation unit 5 of the k-th unit is configured to output an error value SerErr_k according to the connection method of the first to n-th units.

[0019] Here, the control circuit 3 of converter 1A will be explained in detail with reference to Figures 1A, 3B, and 5A. The connection method of the first to nth units in converter 1A is an ISOP connection, where the input side is connected in series and the output side is connected in parallel. In the case of an ISOP connection, the error calculation unit 5 provided in the control circuit 3 of the kth unit subtracts the input side average voltage value Vin_ave, which is obtained by dividing the total voltage of the first to nth units on the input side (Vin_1 + Vin_2 + ... + Vin_n) by the number of units n, from the voltage value Vin_k of the unit on the series-connected input side, and then adds the input side offset value offset_in (a predetermined value greater than 0) to output the error value SerErr_k. That is, in the case of an ISOP connection, the error calculation unit 5 outputs the error value SerErr_k = Vin_k - Vin_ave + offset_in (see Figure 5A).

[0020] The error amplification calculation unit 6 of the k-th unit amplifies the error value SerErr_k and outputs the voltage balance control manipulated variable AVR2_k. If the amplified value of the error value SerErr_k is 0 or less, the error amplification calculation unit 6 outputs the amplified value as the voltage balance control manipulated variable AVR2_k. If the amplified value of the error value SerErr_k is greater than 0, it outputs a voltage balance control manipulated variable AVR2_k with a value of 0. In other words, the voltage balance control manipulated variable AVR2_k is limited to a value of 0 or less. In this embodiment, the amplification calculation of the error value SerErr_k by the error amplification calculation unit 6 is performed by PI control or PID control.

[0021] The conventional control unit 4 of the k-th unit outputs a conventional control operation variable AVR1_k for controlling the machine's voltage conversion circuit 2 using constant voltage control, constant current control, or constant power control.

[0022] The control signal generation unit 7 of the k-th unit receives a total manipulated variable AVR_k (AVR_k = AVR1_k + AVR2_k), which is the sum of the conventional manipulated variable AVR1_k and the voltage balancing manipulated variable AVR2_k. The control signal generation unit 7 of the k-th unit then generates a control signal based on the total manipulated variable AVR_k, and the control circuit 3 controls the machine's voltage conversion circuit 2 based on this control signal, as shown in Figure 2.

[0023] Here, the advantages of the converter 1A equipped with the control circuit 3 of this embodiment will be explained in comparison with a conventional converter composed of multiple units equipped with control circuits 30. In a converter in which multiple units are connected in series, a state in which the voltage balance between units is maintained can be said to be a state in which the average voltage value obtained by dividing the total voltage of the multiple units on the series-connected side by the number of units is approximately equal to the voltage value of each unit on the series-connected side. On the other hand, the timing at which the control circuits control their own units and the calculation results of the control circuits differ slightly from unit to unit, so the average voltage value is constantly changing. For this reason, in a conventional converter, if all control circuits 30 attempt to control the voltage value of their own units using the average voltage value as the target value, the voltage of each unit will continue to change and influence each other, making it unstable, and therefore the voltage balance between units may be disrupted.

[0024] In contrast, the error calculation unit 5 of the control circuit 3 of this embodiment outputs the error value SerErr_k as, as described above, the voltage value of the machine at the input side Vin_k - the average voltage value at the input side Vin_ave + the offset value at the input side offset_in. Here, the voltage balance control manipulated variable AVR2_k, which is the value obtained by the error amplification calculation unit 6 amplified from the error value SerErr_k, is limited to a value of 0 or less, as described above. That is, if the voltage value of the machine at the input side Vin_k is greater than the value of the average voltage value at the input side Vin_ave - the offset value at the input side offset_in, the voltage balance control manipulated variable AVR2_k becomes 0, and in this case the total manipulated variable AVR_k input to the control signal generation unit 7 becomes equal to the conventional control manipulated variable AVR1_k. In other words, among the first to nth units, those units whose own voltage value Vin_k on the input side is greater than the value of Vin_ave-offset_in are controlled by constant voltage control, constant current control, or constant power control based on the conventional control operation variable AVR1_k, as in the conventional method.

[0025] On the other hand, if the voltage value Vin_k of the machine at the input side is less than or equal to the value of Vin_ave-offset_in, the voltage balance control manipulated variable AVR2_k becomes the value obtained by amplified calculation of the error value SerErr_k. In this case, the total manipulated variable AVR_k = AVR1_k + AVR2_k is input to the control signal generation unit 7. Now, referring to Figure 4, the relationship between the total manipulated variable AVR_k, the conventional control manipulated variable AVR1_k, and the voltage balance control manipulated variable AVR2_k will be explained. Figure 4 is a conceptual diagram showing the relationship between each manipulated variable and time for the total manipulated variable AVR_k, the conventional control manipulated variable AVR1_k, and the voltage balance control manipulated variable AVR2_k. As mentioned above, the voltage balance control manipulated variable AVR2_k is limited to 0 or less. Therefore, as shown in Figure 4, the total manipulated variable AVR_k is smaller than the conventional control manipulated variable AVR1_k by the amount of the voltage balance control manipulated variable AVR2_k. In other words, among the first to nth units, units whose input voltage value Vin_k is less than or equal to the value of Vin_ave-offset_in will have their output suppressed more than before and will be controlled to aim for the value of Vin_ave-offset_in. That is, the first to nth units will have different operation and target values ​​depending on whether their input voltage value Vin_k is greater than the value of Vin_ave-offset_in or less than or equal to the value of Vin_ave-offset_in. This makes them less likely to influence each other and stabilizes the control, thus keeping the voltage balance bias between units below a certain value. The input offset value offset_in defines the allowable voltage deviation from the input average voltage value Vin_ave. A smaller value reduces the voltage balance bias between units, but if it is too small, it becomes difficult to maintain the voltage balance, so it is set appropriately according to the allowable voltage balance bias.

[0026] As described above, the control circuit 3 of converter 1A limits the voltage balance control variable AVR2_k, which is calculated by amplifying the error value SerErr_k = Vin_k - Vin_ave + offset_in, to be 0 or less. This controls the output of units whose own voltage value Vin_k at the input side is lower than the value of Vin_ave - offset_in, thereby maintaining voltage balance. In other words, units whose own voltage value Vin_k at the input side is lower than the value of Vin_ave - offset_in are consuming a lot of power and their voltage is low. By controlling the output to be suppressed as described above, the power consumption of the unit is reduced and the voltage can be increased.

[0027] The amplification calculation of the error value SerErr_k by the error amplification calculation unit 6 is performed by PI control or PID control as described above. If the amplification calculation of the error value SerErr_k is performed by P control or PD control, steady-state errors in the control will remain, making it difficult to maintain the voltage balance between units. If the P gain or D gain is set large to suppress the effect of steady-state errors, it will affect the overall control of converter 1A. On the other hand, with PI control or PID control, steady-state errors can be eliminated, so the voltage balance between units can be maintained without affecting the overall control of converter 1A.

[0028] Next, the control circuit 3 of converter 1B will be explained in detail with reference to Figures 1B, 3B, and 5B. The connection method of the first to nth units in converter 1B is an IPOS connection, where the input side is connected in parallel and the output side is connected in series. In the case of an IPOS connection, the error calculation unit 5 provided in the control circuit 3 of the kth unit outputs an error value SerErr_k by subtracting the voltage value of the unit itself on the output side from the output side voltage value Vout_ave, which is obtained by dividing the total voltage of the first to nth units on the output side (Vout_1 + Vout_2 + ... + Vout_n) by the number of units n, and then adding the output side offset value offset_out (a predetermined value greater than 0). That is, in the case of an IPOS connection, the error calculation unit 5 outputs the error value SerErr_k = Vout_ave - Vout_k + offset_out (see Figure 5B).

[0029] The error amplification calculation unit 6 of the k-th unit in converter 1B also amplifies the error value SerErr_k using PI control or PID control and outputs the voltage balance control manipulated variable AVR2_k. In this case, if the amplified value of the error value SerErr_k is 0 or less, the amplified value is output as the voltage balance control manipulated variable AVR2_k, and if the amplified value of the error value SerErr_k is greater than 0, the voltage balance control manipulated variable AVR2_k with a value of 0 is output. In other words, the voltage balance control manipulated variable AVR2_k in converter 1B is also limited to a value of 0 or less.

[0030] The conventional control unit 4 of the k-th unit in converter 1B also outputs a conventional control variable AVR1_k for controlling the machine's voltage conversion circuit 2 with constant voltage control, constant current control, or constant power control. The control signal generation unit 7 generates a control signal based on the total control variable AVR_k (AVR_k = AVR1_k + AVR2_k), and the control circuit 3 controls the machine's voltage conversion circuit 2 based on this control signal, as shown in Figure 2.

[0031] As described above, the error calculation unit 5 in such a converter 1B outputs the error value SerErr_k as the output-side average voltage value Vout_ave - the voltage value of the machine at the output side Vout_k + the output-side offset value offset_out. In this embodiment as well, the voltage balance control manipulated variable AVR2_k, which is the value obtained by the error amplification calculation unit 6 amplified from the error value SerErr_k, is limited to a value of 0 or less. That is, if the voltage value of the machine at the output side Vout_k is smaller than the value of the output-side average voltage value Vout_ave + the output-side offset value offset_out, the voltage balance control manipulated variable AVR2_k becomes 0, and in this case the total manipulated variable AVR_k input to the control signal generation unit 7 becomes equal to the conventional control manipulated variable AVR1_k. In other words, among the first to nth units, those units whose output voltage value Vout_k is less than the value of Vout_ave + offset_out are controlled by constant voltage, constant current, or constant power based on the conventional control variable AVR1_k, as in the past.

[0032] On the other hand, if the voltage value Vout_k of the unit at the output side is greater than or equal to the value of Vout_ave + offset_out, the voltage balance control manipulated variable AVR2_k becomes the value obtained by amplified calculation of the error value SerErr_k. In this case, the total manipulated variable AVR_k = AVR1_k + AVR2_k is input to the control signal generation unit 7. As mentioned above, the voltage balance control manipulated variable AVR2_k is limited to 0 or less. Therefore, the total manipulated variable AVR_k is smaller than the conventional control manipulated variable AVR1_k by the amount of the voltage balance control manipulated variable AVR2_k. In other words, among the first to nth units, the unit in which the voltage value Vout_k of the unit at the output side is greater than or equal to the value of Vout_ave + offset_out will have its output suppressed more than before and will be controlled to aim for the value of Vout_ave + offset_out.

[0033] Thus, in converter 1B, the first to nth units operate and have different target values ​​depending on whether the unit's output voltage value Vout_k is less than the value of Vout_ave + offset_out or whether the unit's output voltage value Vout_k is greater than or equal to the value of Vout_ave + offset_out. This makes them less susceptible to mutual influence and stabilizes control, thus keeping the voltage balance between units below a certain value. The output offset value offset_out defines the allowable voltage deviation from the average output voltage value Vout_ave. A smaller value reduces the voltage balance between units, but if it is too small, it becomes difficult to maintain voltage balance, so it is set appropriately according to the allowable voltage balance deviation.

[0034] As described above, the control circuit 3 of converter 1B limits the voltage balance control variable AVR2_k, which is calculated by amplifying the error value SerErr_k = Vout_ave - Vout_k + offset_out, to be 0 or less. This controls the output of units where the voltage value Vout_k at the output side exceeds the value of Vout_ave + offset_out, thereby suppressing the output and maintaining voltage balance. In other words, units where the voltage value Vout_k at the output side exceeds the value of Vout_ave + offset_out are outputting a lot of power and the output voltage is rising. By controlling the output to be suppressed as described above, the output voltage can be lowered.

[0035] Next, the control circuit 3 of converter 1C will be described in detail with reference to Figures 1C, 3B, and 5C. The connection method of the first to nth units in converter 1C is an ISOS connection, where the input side is connected in series and the output side is connected in series. In the case of an ISOS connection, the error calculation unit 5 provided in the control circuit 3 of the kth unit calculates the input side error value SerErr_IS_k (SerErr_IS_k = Vin_k - Vin_ave + offset_in) by subtracting the input side average voltage value Vin_ave, which is obtained by dividing the total voltage of the first to nth units on the series-connected input side (Vin_1 + Vin_2 + ... + Vin_n) by the number of units n, from the voltage value Vin_k of the unit on the series-connected input side, and further adding the input side offset value offset_in (a predetermined value greater than 0), and also calculates the input side error value SerErr_IS_k (SerErr_IS_k = Vin_k - Vin_ave + offset_in), and also the output The output-side error value SerErr_OS_k (SerErr_OS_k = Vout_ave - Vout_k + offset_out) is calculated by subtracting the voltage value Vout_k of the machine on the series-connected output side from the output-side average voltage value Vout_ave, obtained by dividing the total voltage of the 1st to nth units on the force side (Vout_1 + Vout_2 + ... + Vout_n) by the number of units n, and then adding the output-side offset value offset_out (a predetermined value greater than 0). The lower of the input-side error value and the output-side error value is output as the error value SerErr_k (see Figure 5C). Note that the input-side offset value offset_in is set to a value smaller than the output-side offset value offset_out.

[0036] The error amplification calculation unit 6 of the k-th unit in converter 1C also amplifies the error value SerErr_k using PI control or PID control and outputs the voltage balance control manipulated variable AVR2_k. In this case, if the amplified value of the error value SerErr_k is 0 or less, the amplified value is output as the voltage balance control manipulated variable AVR2_k, and if the amplified value of the error value SerErr_k is greater than 0, the voltage balance control manipulated variable AVR2_k with a value of 0 is output. In other words, the voltage balance control manipulated variable AVR2_k in converter 1C is also limited to a value of 0 or less.

[0037] The conventional control unit 4 of the k-th unit in converter 1C also outputs a conventional control variable AVR1_k for controlling the machine's voltage conversion circuit 2 with constant voltage control, constant current control, or constant power control. The control signal generation unit 7 generates a control signal based on the total control variable AVR_k (AVR_k = AVR1_k + AVR2_k), and the control circuit 3 controls the machine's voltage conversion circuit 2 based on this control signal, as shown in Figure 2.

[0038] In converter 1C configured in this way, the first to nth units are connected in series on the input and output sides. Therefore, the voltage balance between the units must be considered on both the input and output sides. The lower the value of the input error value SerErr_IS_k and the output error value SerErr_OS_k, the larger the voltage difference between the units, and thus the higher the priority of control required to maintain voltage balance. Therefore, in this embodiment, the lower of the input error value SerErr_IS_k and the output error value SerErr_OS_k is output as the error value SerErr_k. Also, normally, when the voltage balance between the units on the input side is maintained, the voltage difference on the output side automatically converges to a certain range. Therefore, in this embodiment, the input offset value offset_in is set to a smaller value than the output offset value offset_out, and the input error value SerErr_IS_k is preferentially selected as the error value SerErr_k. When the error calculation unit 5 outputs the input-side error value as the error value SerErr_k, the bias in the voltage balance between the units can be kept below a certain value, similar to the converter 1A described above. Similarly, when the output-side error value SerErr_OS_k is output as the error value SerErr_k, the bias in the voltage balance between the units can be kept below a certain value, similar to the converter 1B described above.

[0039] Here, the specific effects of converter 1C will be explained illustratively, in comparison with a conventional converter composed of multiple units equipped with the conventional control circuit 30 described above. Figure 6A shows a converter in which the first unit and the second unit are connected via ISOS. When each of the first and second units is equipped with the conventional control circuit 30 shown in Figure 3A, when each of the control circuits 30 operates, for example as shown in Figure 6B, even if the total input voltage value Vin remains constant, the input voltage value Vin_1 on the input side of the first unit increases over time, and the input voltage value Vin_2 on the input side of the second unit decreases over time, causing an imbalance in the voltage between the two. At this time, on the output side of the first unit, the output voltage value Vout_1 is maintained at a predetermined value because the input voltage value Vin_1 is high, while on the output side of the second unit, although it can initially output at a predetermined voltage value, the output voltage value Vout_2 decreases when it exceeds the boosting capability of the unit itself, and as a result, the total output voltage value Vout may decrease.

[0040] In contrast, if the first and second units shown in Figure 6A are equipped with the control circuit 3 shown in Figure 3B, this converter can operate each control circuit 3 as described for converter 1C, for example as shown in Figure 7A, to keep the input voltage value Vin_1 of the first unit and the input voltage value Vin_2 of the second unit within a range below a certain value relative to the average input voltage value Vin_ave over time, and to keep the output voltage value Vout_1 of the first unit and the output voltage value Vout_2 of the second unit within a range below a certain value relative to the average output voltage value Vout_ave over time, as shown in Figure 7B.

[0041] Next, the control circuit 3 of the example converter 1D will be described in detail with reference to Figures 1D, 3B, and 5D. The connection method of the first to nth units in converter 1D is an IPOP connection, where the input side is connected in parallel and the output side is also connected in parallel. In the case of an IPOP connection, the error calculation unit 5 provided in the control circuit 3 of the kth unit outputs an error value SerErr_k (SerErr_k=0) whose value is 0 (see Figure 5D).

[0042] The error amplification calculation unit 6 of the kth unit in converter 1D also amplifies the error value SerErr_k by PI control or PID control and outputs the voltage balance control manipulated variable AVR2_k. Since the error value SerErr_k = 0, the voltage balance control manipulated variable AVR2_k in converter 1D has a value of 0. The conventional control unit 4 then outputs the conventional control manipulated variable AVR1_k for controlling the machine's voltage conversion circuit 2 with constant voltage control, constant current control, or constant power control. The control signal generation unit 7 generates a control signal based on the total manipulated variable AVR_k (AVR_k = AVR1_k + AVR2_k), and the control circuit 3 controls the machine's voltage conversion circuit 2 based on this control signal, as shown in Figure 2. Here, the voltage balance control manipulated variable AVR2_k is 0, so the total manipulated variable AVR_k input to the control signal generation unit 7 is equal to the conventional control manipulated variable AVR1_k. Here, when multiple units are connected in parallel on the input and output sides, the voltage values ​​of each unit automatically balance. That is, the conventional control circuit 30 shown in Figure 3A can be used for the kth unit used in converter 1D, but as described above, by outputting an error value SerErr_k from the error calculation unit 5 that has a value of 0, it is possible to use the same unit as the unit used in converters 1A to 1C, thus eliminating the need to prepare a unit with a different specification, which is advantageous in terms of cost, etc.

[0043] The k-th unit used in the converters 1A to 1D described above is not limited to a unidirectional DC / DC converter in which the voltage conversion circuit 2 operates to convert the input voltage and output it to the output side. It may also be a bidirectional DC / DC converter equipped with a voltage conversion circuit 2 that is capable of converting the input voltage and outputting it to the output side, and also capable of converting the output voltage and outputting it to the input side. When the k-th unit is a bidirectional DC / DC converter, it operates as described above when converting the input voltage and outputting it to the output side, and when converting the output voltage and outputting it to the input side, the above description is applied with the input and output sides reversed. That is, when the k-th unit in converter 1A shown in Figure 1A is a bidirectional DC / DC converter, when converter 1A converts the input voltage shown in Figure 1A and outputs it to the output side shown in Figure 1A, it operates as if the input side were connected in series and the output side in parallel as described above, and when converter 1A converts the output voltage shown in Figure 1A and outputs it to the input side shown in Figure 1A, it operates as if the input side were connected in parallel and the output side in series as described above. Furthermore, it is also possible to use one of the first to nth units described above as a standalone isolated DC / DC converter. In this case, the error value SerErr_k output from the error calculation unit 5, as in converter 1D, should be set to 0.

[0044] (Note) This specification discloses, in one aspect, the following technologies:

[0045] (Technology 1) This is a converter (1A) in which multiple units, each being an isolated DC / DC converter, are connected in series on the input side. Each of the multiple units comprises a voltage conversion circuit (2) that converts the input voltage and outputs it to the output side, and a control circuit (3) that controls the voltage conversion circuit (2). Each of the aforementioned control circuits (3) comprises a conventional control unit (4), an error calculation unit (5) that outputs an error value (SerErr_k), an error amplification calculation unit (6) that outputs a voltage balance control manipulated variable (AVR2_k) based on a value amplified by the error value (SerErr_k), and a control signal generation unit (7) that generates a control signal to control the voltage conversion circuit (2). The conventional control unit (4) is configured to output a conventional control variable (AVR1_k) for controlling the voltage conversion circuit (2) with constant voltage control, constant current control, or constant power control. The error calculation unit (5) is configured to output the error value (SerErr_k) by subtracting the input-side average voltage value (Vin_ave), which is obtained by dividing the total voltage of the multiple units on the input side by the number of units, from the voltage value (Vin_k) of the machine on the input side, and then adding a predetermined input-side offset value (offset_in) that is greater than 0. The error amplification calculation unit (6) is configured to output the amplified value of the error value (SerErr_k) as the voltage balance control manipulated variable (AVR2_k) if the amplified value is 0 or less, and to output the voltage balance control manipulated variable (AVR2_k) with a value of 0 if the amplified value of the error value (SerErr_k) is greater than 0. The converter (1A) is configured to generate the control signal based on a total manipulated variable (AVR_k) obtained by adding the conventional manipulated variable (AVR1_k) and the voltage balance manipulated variable (AVR2_k).

[0046] (Technology 2) A converter (1B) in which multiple units, each being an isolated DC / DC converter, are connected in series on the output side, Each of the multiple units comprises a voltage conversion circuit (2) that converts the input voltage and outputs it to the output side, and a control circuit (3) that controls the voltage conversion circuit (2). Each of the aforementioned control circuits (3) comprises a conventional control unit (4), an error calculation unit (5) that outputs an error value (SerErr_k), an error amplification calculation unit (6) that outputs a voltage balance control manipulated variable (AVR2_k) based on a value amplified by the error value (SerErr_k), and a control signal generation unit (7) that generates a control signal to control the voltage conversion circuit (2). The conventional control unit (4) is configured to output a conventional control variable (AVR1_k) for controlling the voltage conversion circuit (2) with constant voltage control, constant current control, or constant power control. The error calculation unit (5) is configured to output the error value (SerErr_k) by subtracting the voltage value of the unit itself on the output side (Vout_k) from the output-side average voltage value (Vout_ave), which is obtained by dividing the total voltage of the multiple units on the output side by the number of units, and then adding a predetermined output-side offset value (offset_out) that is greater than 0. The error amplification calculation unit (6) is configured to output the amplified value of the error value (SerErr_k) as the voltage balance control manipulated variable (AVR2_k) if the amplified value is 0 or less, and to output the voltage balance control manipulated variable (AVR2_k) with a value of 0 if the amplified value of the error value (SerErr_k) is greater than 0. The converter (1B) is configured to generate the control signal based on a total manipulated variable (AVR_k) obtained by adding the conventional manipulated variable (AVR1_k) and the voltage balance control manipulated variable (AVR2_k).

[0047] (Technology 3) A converter (1C) in which multiple units, each being an isolated DC / DC converter, are connected in series on both the input and output sides, Each of the multiple units comprises a voltage conversion circuit (2) that converts the input voltage and outputs it to the output side, and a control circuit (3) that controls the voltage conversion circuit (2). Each of the aforementioned control circuits (3) comprises a conventional control unit (4), an error calculation unit (5) that outputs an error value (SerErr_k), an error amplification calculation unit (6) that outputs a voltage balance control manipulated variable (AVR2_k) based on a value amplified by the error value (SerErr_k), and a control signal generation unit (7) that generates a control signal to control the voltage conversion circuit (2). The conventional control unit (4) is configured to output a conventional control variable (AVR1_k) for controlling the voltage conversion circuit (2) with constant voltage control, constant current control, or constant power control. The error calculation unit (5) is configured to output the lower of the input error value (SerErr_IS_k) and the output error value (SerErr_OS_k) when it subtracts the input-side average voltage value (Vin_ave), which is obtained by dividing the total voltage of the multiple units on the input side by the number of units, from the voltage value (Vin_k) of the unit itself on the input side, and then adds a predetermined input-side offset value (offset_in) that is greater than 0. The error amplification calculation unit (6) is configured to output the amplified value of the error value (SerErr_k) as the voltage balance control manipulated variable (AVR2_k) if the amplified value is 0 or less, and to output the voltage balance control manipulated variable (AVR2_k) with a value of 0 if the amplified value of the error value (SerErr_k) is greater than 0. The control signal generation unit (7) is configured to generate the control signal based on a total manipulated variable (AVR_k) obtained by adding the conventional manipulated variable (AVR1_k) and the voltage balance control manipulated variable (AVR2_k), and is a converter (1C).

[0048] The technologies described above (1-3) make it possible to keep the voltage imbalance between units below a certain value when multiple units are connected in series.

[0049] (Technology 4) The unit is an isolated bidirectional DC / DC converter (1A to 1C) as described in any one of the technologies 1 to 3, wherein the voltage conversion circuit is capable of converting the voltage on the input side and outputting it to the output side, and is also capable of converting the voltage on the output side and outputting it to the input side.

[0050] This technology, when used in electric vehicles, for example, enables power supply from the battery to the motor and power recovery from the regenerative braking system back to the battery. Furthermore, because it can both boost and buck voltage, it offers advantages such as reduced installation space.

[0051] Although one embodiment of the present invention has been described above, the present invention is not limited to such specific embodiments, and unless otherwise specifically limited in the above description, various modifications and changes are possible within the scope of the spirit of the present invention as described in the claims. For example, the configuration of the above-described embodiment can be added or deleted as appropriate, and the configuration of one embodiment can be provided in other embodiments. Furthermore, the effects in the above-described embodiment are merely illustrative of the effects that may result from the present invention. In other words, the effects of the present invention are not limited to the above-described effects, and additional effects may also be produced in addition to the above-described effects. [Explanation of Symbols]

[0052] 1A~1C: Converter 2: Voltage conversion circuit 3: Control circuit 4: Conventional control unit 5:Error calculation section 6: Error amplification calculation unit 7: Control signal generation unit

Claims

1. This converter consists of multiple units, each being an isolated DC / DC converter, connected in series at the input side. Each of the plurality of units comprises a voltage conversion circuit that converts the input voltage and outputs it to the output side, and a control circuit that controls the voltage conversion circuit. Each of the aforementioned control circuits comprises a conventional control unit, an error calculation unit that outputs an error value, an error amplification calculation unit that outputs a voltage balance control operation variable based on a value amplified by the error value, and a control signal generation unit that generates a control signal for controlling the voltage conversion circuit. The conventional control unit is configured to output a conventional control operation variable for controlling the voltage conversion circuit with constant voltage control, constant current control, or constant power control. The error calculation unit is configured to output the error value by subtracting the average input voltage value, obtained by dividing the total voltage of the multiple units on the input side by the number of units, from the voltage value of the machine on the input side, and then adding a predetermined input offset value greater than 0. The error amplification calculation unit is configured to output the amplified value as the voltage balance control operation variable if the amplified value of the error value is 0 or less, and to output the voltage balance control operation variable that becomes 0 if the amplified value of the error value is greater than 0. The converter is configured such that the control signal generation unit generates the control signal based on a total manipulated amount obtained by adding the conventional manipulated amount and the voltage balance manipulated amount.

2. This converter consists of multiple units, each being an isolated DC / DC converter, connected in series on the output side. Each of the plurality of units comprises a voltage conversion circuit that converts the input voltage and outputs it to the output side, and a control circuit that controls the voltage conversion circuit. Each of the aforementioned control circuits comprises a conventional control unit, an error calculation unit that outputs an error value, an error amplification calculation unit that outputs a voltage balance control operation variable based on a value amplified by the error value, and a control signal generation unit that generates a control signal for controlling the voltage conversion circuit. The conventional control unit is configured to output a conventional control operation variable for controlling the voltage conversion circuit with constant voltage control, constant current control, or constant power control. The error calculation unit is configured to output the error value by subtracting the voltage value of the machine itself on the output side from the average output voltage value obtained by dividing the total voltage of the multiple units on the output side by the number of units, and further adding a predetermined output offset value greater than 0. The error amplification calculation unit is configured to output the amplified value as the voltage balance control operation variable if the amplified value of the error value is 0 or less, and to output the voltage balance control operation variable that becomes 0 if the amplified value of the error value is greater than 0. The converter is configured such that the control signal generation unit generates the control signal based on a total manipulated amount obtained by adding the conventional manipulated amount and the voltage balance manipulated amount.

3. A converter comprising multiple units, each being an isolated DC / DC converter, connected in series on both the input and output sides, Each of the plurality of units comprises a voltage conversion circuit that converts the input voltage and outputs it to the output side, and a control circuit that controls the voltage conversion circuit. Each of the aforementioned control circuits comprises a conventional control unit, an error calculation unit that outputs an error value, an error amplification calculation unit that outputs a voltage balance control operation variable based on a value amplified by the error value, and a control signal generation unit that generates a control signal for controlling the voltage conversion circuit. The conventional control unit is configured to output a conventional control operation variable for controlling the voltage conversion circuit with constant voltage control, constant current control, or constant power control. The error calculation unit is configured to output the lower of the input error value between the input error value and the output error value, which is the lower of the input error value and the lower of the two output error values. The error amplification calculation unit is configured to output the amplified value as the voltage balance control operation variable if the amplified value of the error value is 0 or less, and to output the voltage balance control operation variable that becomes 0 if the amplified value of the error value is greater than 0. The converter is configured such that the control signal generation unit generates the control signal based on a total manipulated amount obtained by adding the conventional manipulated amount and the voltage balance manipulated amount.

4. The converter according to any one of claims 1 to 3, wherein the unit is an isolated bidirectional DC / DC converter in which the voltage conversion circuit is capable of converting the voltage on the input side to a voltage and outputting it to the output side, and is capable of converting the voltage on the output side to a voltage and outputting it to the input side.

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