Ac / DC power supply and method for controlling ac / DC power supply

Abstract

This AC / DC power supply comprises an AC / DC converter ACDC, a primary side DC capacitor C1, an insulated DC / DC converter DCDC, and a secondary side DC capacitor C2. The AC / DC power supply has m (m: an integer of 2 or more) cells per phase. The AC / DC power supply has a plurality of DC buses Vdc21, Vdc22 in which the plurality of secondary side DC capacitors C2 are connected in series or in parallel. The AC / DC power supply supplies the voltages of the plurality of DC buses Vdc21, Vdc22 to a load or a power supply. The AC / DC power supply outputs, during power unbalance occurring due to the states of the load or the power supply, a voltage while maintaining the voltage balance of a secondary side DC voltage and the primary side DC voltage of each cell. The AC / DC power supply achieves the voltage balance of each DC bus during the power unbalance without using an additional balance circuit or a commercial transformer with multiple windings.

Description

A-DC power supply and method for controlling an A-DC power supply

[0001] The present invention relates to an SST (Solid State Transformer) system in which multiple power converters (AC-DC converter + isolated DC-DC converter) are connected in series or parallel in applications with AC input and multiple DC bus outputs, and to a technology for achieving balance between each DC voltage.

[0002] Non-Patent Document 1 introduces circuit methods and control methods for when there is a power imbalance among the DC buses. The circuit method involves connecting a balancing circuit to achieve voltage balance among the DC buses when there is a power imbalance. The document also discloses a method for achieving voltage balance among the DC buses when there is a power imbalance without a balancing circuit by using a commercial frequency multi-winding transformer and a power converter.

[0003] Non-Patent Document 2 employs an SST system using a high-frequency multi-winding transformer in a circuit that generates multiple DC buses. In this system, the multi-winding transformer can be made smaller than a commercial frequency transformer by increasing its frequency.

[0004] Patent Document 1 discloses an SST system for generating two DC buses from a high voltage AC voltage, and also connects an isolated DC-DC converter between the two DC buses to achieve voltage balance.

[0005] JP 2023-510035 A JP 2022-50739 A

[0006] S. Rivera, R. Lizana F, S. Kouro, T. Dragicevic and B. Wu, "Bipolar DC Power Conversion: State-of-the-Art and Emerging Technologies," in IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 9, no. 2, pp. 1192-1204, April 2021. H. Kim, J. Baek, M. Kim, H. Yun, D. Jeong and J. Cho, "A 13.2kV ​​ / 150kVA Solid State Transformer for a Bipolar LVDC Distribution System," 2019 IEEE Third International Conference on DC Microgrids (ICDCM), Matsue, Japan, 2019, pp. 1-4. Yuki Kinoshita and Jin Haga, "A 6-Switch Bridge LLC Converter with Wide Voltage Gain for PEV Chargers," IEEJ Transactions on Power Electronics, Vol. 140, No. 1, p. 36-44. Higa, Shunsuke, Takuma, Keisuke, and Ito, Junichi, "Development of a T-type Dual Active Bridge DC-DC Converter with an Operation Mode Switching Method for a Wide Voltage Drive Range," IEEJ Transactions on Power Supply Design, Vol. 139, No. 4, pp. 388-400 (2019)

[0007] When there is a power imbalance among multiple DC buses, an imbalance occurs in the voltage of each DC bus. To address this, the withstand voltage of the DC buses and the withstand voltage required for the loads connected to the DC buses also increase, resulting in increased costs and size.

[0008] The methods disclosed in Non-Patent Document 1 and Patent Document 1 require a commercial multi-winding transformer or a balancing circuit, which increases the size and cost.

[0009] The method disclosed in Non-Patent Document 2 does not mention balancing of DC bus voltages when there is a power imbalance among the DC buses.

[0010] As described above, in an AC-DC power supply, it is necessary to achieve voltage balance among the DC buses when the power is unbalanced without using an additional balancing circuit or a multi-winding commercial transformer.

[0011] The present invention has been devised in view of the above-mentioned problems of the related art, and one aspect of the present invention is an ACDC power supply having m (m is an integer of 2 or more) cells per phase, each cell including an AC / DC converter, a primary-side DC capacitor connected to the DC side of the AC / DC converter, an isolated DC / DC converter having one DC side connected to the primary-side DC capacitor, and a secondary-side DC capacitor connected to the other DC side of the isolated DC / DC converter, and having a plurality of DC buses to which a plurality of the secondary-side DC capacitors are connected in series or in parallel, and supplying voltages of the plurality of DC buses to a load or a power source, wherein when a power imbalance occurs due to the condition of the load or the power source, the ACDC power supply outputs a voltage while maintaining a voltage balance between the secondary-side DC voltage which is the voltage of the DC bus and the primary-side DC voltage which is the voltage of the primary-side DC capacitor of each cell.

[0012] In one aspect, the control unit of the AC-DC converter comprises: a primary-side DC voltage average value control unit that generates a grid current active component command value based on a primary-side DC voltage average value command value and a primary-side DC voltage all-cell average value; a grid current control unit that generates a grid voltage active component command value and a grid voltage reactive component command value based on the grid current active component command value and the grid current reactive component command value; and a primary-side DC voltage intra-phase balance control unit that generates a primary-side DC voltage intra-phase balance control value based on the primary-side DC voltage intra-phase average value of each phase and the primary-side DC voltage of each cell, and a value obtained by converting the grid voltage active component command value and the grid voltage reactive component command value to values ​​on a fixed coordinate system and multiplying them by the primary-side DC voltage all-cell average value is calculated. a primary-side DC voltage individual balance control unit that generates a primary-side DC voltage individual balance control value based on the primary-side DC voltage, and a secondary-side DC voltage individual control unit that generates a secondary-side DC voltage individual control value based on the secondary-side DC voltage, and performs current control based on the primary-side DC voltage and a value obtained by subtracting the primary-side DC voltage individual balance control value from the secondary-side DC voltage individual control value, and generates a gate signal for the isolated DC-DC converter based on the result of the current control.

[0013] In another aspect, the control unit of the AC-DC converter comprises a primary DC voltage average value control unit that generates a grid current active component command value based on a primary DC voltage average value command value and a primary DC voltage all-cell average value; a grid current control unit that generates a grid voltage active component command value and a grid voltage reactive component command value based on the grid current active component command value and the grid current reactive component command value; and a primary DC voltage intra-phase balance control unit that generates a primary DC voltage intra-phase balance control value based on the primary DC voltage intra-phase average value of each phase and the primary DC voltage of each cell, and generates a voltage command value for each phase by converting the grid voltage active component command value and the grid voltage reactive component command value into values ​​on fixed coordinates and multiplying them by the primary DC voltage all-cell average value, and subtracting the primary DC voltage intra-phase balance control value from the resultant value, and generating a voltage command value for each phase. and a control unit of the isolated DC-DC converter includes a primary-side DC voltage individual balance control unit that generates a primary-side DC voltage individual balance control value based on the primary-side DC voltage, a secondary-side DC voltage balance control unit that generates a secondary-side DC voltage balance control value based on the secondary-side DC voltage, and a secondary-side DC voltage total value control unit that generates a secondary-side DC voltage total value control value based on a secondary-side DC voltage total value command value and the secondary-side DC voltage total value, and performs current control based on the primary-side DC voltage and a value obtained by subtracting a value obtained by adding the secondary-side DC voltage balance control value to the primary-side DC voltage individual balance control value from the secondary-side DC voltage total value control value, and

[0014] In one aspect, the primary-side DC voltage average value control unit includes a first total value calculation unit that calculates the total value of the primary-side DC voltages of all cells and outputs it as a primary-side DC voltage all-cell total value, an all-cell average value calculation unit that calculates the primary-side DC voltage all-cell average value from the product of the primary-side DC voltage all-cell total value and the reciprocal of the total number of cells, a first subtractor that calculates the deviation between the primary-side DC voltage average value command value and the primary-side DC voltage all-cell average value, and a first amplifier that amplifies the output of the first subtractor and outputs it as the system current active component command value.

[0015] In one aspect, the grid current control unit includes a second subtractor that subtracts the grid current active component from the grid current active component command value, a second amplifier that amplifies an output of the second subtractor and outputs the amplified output as the grid voltage active component command value, a third subtractor that subtracts the grid current reactive component from the grid current reactive component command value, and a third amplifier that amplifies an output of the third subtractor and outputs the amplified output as the grid voltage reactive component command value.

[0016] In one aspect, the primary DC voltage intra-phase balance control unit includes: a second sum calculation unit that calculates a sum of the primary DC voltages in a phase and outputs the sum as a primary DC voltage intra-phase sum; an intra-phase average calculation unit that calculates the primary DC voltage intra-phase average value of each phase from the product of the primary DC voltage intra-phase sum and the reciprocal of the number of cells in the phase; a fourth subtractor that calculates a deviation between the primary DC voltage intra-phase average value of each phase and the primary DC voltage of each cell in the phase; a fourth amplifier that amplifies the output of the fourth subtractor; and a first multiplier that multiplies the output of the fourth amplifier by the sign of the system current value of each phase and outputs the result as the primary DC voltage intra-phase balance control value.

[0017] In one aspect, the primary-side DC voltage individual balance control unit includes: a third sum calculation unit that calculates a sum of the primary-side DC voltages of the cells connected to each DC bus; a third average value calculation unit that calculates a product of an output of the third sum calculation unit and the reciprocal of the number of cells connected to each DC bus, and calculates an average DC bus primary-side DC voltage of the cells connected to each DC bus; a band elimination filter that removes double system frequency components of the primary-side DC voltage of the cells connected to each DC bus; a fifth subtractor that outputs the difference between the DC bus primary-side DC voltage average value and the output of the band elimination filter; a fifth amplifier that amplifies the output of the fifth subtractor; and a second multiplier that multiplies the output of the fifth amplifier by a turns ratio of a transformer of the AC-DC converter and a transformer of the isolated DC-DC converter, and outputs the result as the primary-side DC voltage individual balance control value.

[0018] In one aspect, the secondary-side DC voltage individual control unit includes a sixth subtractor that calculates a difference between the secondary-side DC voltage command value of each of the DC buses and the secondary-side DC voltage, a sixth amplifier that amplifies the output of the sixth subtractor, and a third multiplier that calculates the product of the output of the sixth amplifier and the reciprocal of the number of cells connected to the DC bus and outputs the product as the secondary-side DC voltage individual control value.

[0019] In one aspect, the secondary-side DC voltage balance control unit includes an eighth subtractor that calculates a deviation between the secondary-side DC voltage average value and the secondary-side DC voltage of each DC bus, and a seventh amplifier that amplifies the output of the eighth subtractor and outputs the amplified output as the secondary-side DC voltage balance control value.

[0020] In one aspect, the secondary-side DC voltage total value control unit includes a ninth subtractor that calculates the difference between the secondary-side DC voltage total value command value and the secondary-side DC voltage total value of all DC buses, an eighth amplifier that amplifies the output of the ninth subtractor, and a fourth multiplier that calculates the product of the output of the eighth amplifier and the reciprocal of the total number of cells and outputs the product as the secondary-side DC voltage total value control value.

[0021] According to the present invention, in an AC-DC power supply, it is possible to achieve voltage balance among the DC buses when there is a power imbalance without using an additional balancing circuit or a multi-winding commercial transformer.

[0022] 1 is a block diagram showing a control unit of an isolated DC-DC converter according to a first embodiment of the present invention; FIG. 2 is a block diagram showing a control unit of an isolated DC-DC converter according to a second embodiment of the present invention;

[0023] First and second embodiments of the AC-DC power supply of the present invention will be described in detail below with reference to FIGS.

[0024] [Embodiment 1] Figure 1 shows the configuration of an SST main circuit that generates multiple DC buses. As shown in Figure 1, the SST includes an AC-DC converter ACDC connected to a high-voltage AC system, a primary-side DC capacitor C1 connected to the DC side of the AC-DC converter ACDC, an isolated DC-DC converter DCDC having one DC side connected to the primary-side DC capacitor C1, and a secondary-side DC capacitor C2 connected to the other DC side of the isolated DC-DC converter DCDC. The AC-DC converter ACDC and the isolated DC-DC converter DCDC may be appropriately selected from conventionally known converters. Since the AC-DC converter ACDC and the isolated DC-DC converter DCDC are well known, detailed description thereof will be omitted here.

[0025] Here, the AC-DC converter ACDC, primary side DC capacitor C1, isolated DC-DC converter DCDC, and secondary side DC capacitor C2 constitute one cell. The number of cells per phase is m (m: integer equal to or greater than 2). Three cells for three phases constitute one unit. The number of units is n (n: integer equal to or greater than 2).

[0026] In the first embodiment and the second embodiment described later, the secondary side DC capacitors C2 are connected in series or in parallel to form one DC bus V ｄｃ２１ or DC bus V ｄｃ２２ In addition, DC bus V ｄｃ２１ , or V ｄｃ２２ , or V ｄｃ２１ +V ｄｃ２２ Each cell (AC-DC converter ACDC, isolated DC-DC converter DCDC) is equipped with a switching element. The voltage and current of each cell can be controlled by turning the switching element on and off.

[0027] In addition, the xth secondary voltage V in the a phase ｄｃ２ｘ The primary DC voltage of the kth unit connected to ｄｃ１ａｘｋ (x=1, 2, k=number of units connected to each DC bus=1, 2 . . . n / 2).

[0028] Fig. 2 shows a block diagram of the control unit of the AC-DC converter ACDC. The control unit of the AC-DC converter ACDC shown in Fig. 2 is common to the first embodiment and the second embodiment described later. The control unit of the AC-DC converter ACDC includes a primary-side DC voltage average value control unit 12, a grid current control unit 13, and a primary-side DC voltage intra-phase balance control unit 14, and generates three-phase voltage command values.

[0029] The control unit receives the following signals:

[0030] Primary side DC voltage average command value V ｄｃ１＿ａｖｅ＿ｒｅｆ Three-phase system current value i Ｕ , i Ｖ , i Ｗ Three-phase system voltage value V ｕ , V ｖ , V ｗ Active component of the system current on the rotating coordinate system i ｄ , system current reactive component i ｑ System current reactive component command value i ｑ＿ｒｅｆ Primary side DC voltage V ｄｃ１ａｘｋ Primary DC voltage V of each phase ｄｃ１ｕｘｋ , V ｄｃ１ｖｘｋ、 V ｄｃ１ｗｘｋ System voltage active component command value V ｄ＿ｒｅｆ , system voltage reactive component command value V ｑ＿ｒｅｆ Three-phase system voltage value V ｕ , V ｖ , V ｗ Phase ωt synchronized to.

[0031] The primary side DC voltage average value control unit 12 and the system current control unit 13 shown in FIG. 2(a) are configured as follows.

[0032] The first total value calculation unit 1 of the primary DC voltage average value control unit 12 calculates the total value of the primary DC voltages of all cells (3m = 3 phases × m units per phase) as the total primary DC voltage cell value. The total cell average value calculation unit 2 calculates the product of the total primary DC voltage cell value and the reciprocal of the total number of cells (3m). The output of the total cell average value calculation unit 2 is the total primary DC voltage cell average value V ｄｃ１＿ａｖｅ This becomes:

[0033] The first subtractor 3 calculates the primary side DC voltage average value command value V ｄｃ１＿ａｖｅ＿ｒｅｆ and the primary side DC voltage all cell average value V ｄｃ１＿ａｖｅThe first amplifier (PI amplifier) ​​4 amplifies the output of the first subtractor 3 to obtain the system current active component command value i ｄ＿ｒｅｆ Output as

[0034] The PLL (Phase Locked Loop) 5 is a three-phase system voltage value V ｕ , V ｖ , V ｗ and outputs a phase ωt synchronized with the grid.

[0035] The first dq converter 6 converts the three-phase system voltage value V ｕ , V ｖ , V ｗ and phase ωt are input, and the value on the rotating coordinate system synchronized with the grid (the grid voltage active component V ｄ , system voltage reactive component V ｑ The system voltage reactive component V ｑ is zero in the steady state if the PLL 5 is normal.

[0036] The second dq converter 7 converts the three-phase system current value i ｕ , i ｖ , i ｗ and phase ωt are input, and the value on the rotating coordinate system synchronized with the grid (the grid current active component i ｄ , system current reactive component i ｑ ) is output.

[0037] The second subtractor 8 of the system current control unit 13 subtracts the system current active component command value i ｄ＿ｒｅｆ and the system current active component i which is the output of the second dq converter 7. ｄ The third subtractor 9 calculates the deviation of the system current reactive component command value i ｑ＿ｒｅｆ and the system current reactive component i which is the output of the second dq converter 7. ｑ Here, the deviation of the system current reactive component command value i ｑ＿ｒｅｆ is adjusted to the power factor.

[0038] The second and third amplifiers (PI amplifiers) 10 and 11 amplify the outputs of the second and third subtractors 8 and 9. The outputs of the second and third amplifiers 10 and 11 are converted into the system voltage active component command value V ｄ＿ｒｅｆ , system voltage reactive component command value V ｑ＿ｒｅｆThis becomes:

[0039] The primary side DC voltage intra-phase balance control unit 14 and gate generation (generation of ON / OFF commands for switching elements) in FIG. 2B are configured as follows.

[0040] The second sum calculation unit 15 of the primary DC voltage intra-phase balance control unit 14 calculates the sum of the primary DC voltages in the phases and outputs it as the primary DC voltage intra-phase sum. The intra-phase average calculation unit 16 calculates the product of the primary DC voltage intra-phase sum and the reciprocal of the number of cells m in the phase to obtain the primary DC voltage intra-phase average V ｄｃ１ａ＿ａｖｅ Calculate.

[0041] The fourth subtractor 17 calculates the average value V of the primary DC voltage in each phase. ｄｃ１ａ＿ａｖｅ and the primary DC voltage V of each cell in the phase ｄｃ１ｕｘｋ A fourth amplifier (PI amplifier) ​​18 amplifies the output of the fourth subtractor 17. A first multiplier 19 multiplies the output of the fourth amplifier 18 by the system current value (i ｕ The output of the first multiplier 19 becomes the primary side DC voltage intra-phase balance control value of each phase and each cell. The primary side DC voltage intra-phase balance control values ​​are outputted in m numbers for each phase (i.e., the number of cells).

[0042] The dq inverse converter 20 calculates the system voltage active component command value V ｄ＿ｒｅｆ , system voltage reactive component command value V ｑ＿ｒｅｆ and phase ωt, and converts the value on the rotating coordinate system synchronized with the grid into a value on the fixed coordinate system. ｄｃ１＿ａｖｅ Multiply by this.

[0043] The fifth subtractors 22u, 22v, and 22w calculate the difference between the outputs of the multipliers 21u, 21v, and 21w and the primary side DC voltage balance control value of each cell in each phase. ｕ＿ｒｅｆ１ …V ｕ＿ｒｅｆｍ , V ｖ＿ｒｅｆ１ …V ｖ＿ｒｅｆｍ , V ｗ＿ｒｅｆ１ …V ｗ＿ｒｅｆｍ This becomes:

[0044] The PWM controllers 23u, 23v, and 23w control the three-phase voltage command value V ｕ＿ｒｅｆ１ …V ｕ＿ｒｅｆｍ , V ｖ＿ｒｅｆ１ …V ｖ＿ｒｅｆｍ , V ｗ＿ｒｅｆ１ …V ｗ＿ｒｅｆｍ Based on this, PWM processing is performed to convert it into a gate signal, which is then input to the switching element of each cell of the AC-DC converter ACDC.

[0045] 3 shows a block diagram of a control unit of the isolated DC-DC converter DCDC in embodiment 1. The control unit of the isolated DC-DC converter DCDC in embodiment 1 includes a primary-side DC voltage individual balance control unit 24 and a secondary-side DC voltage individual control unit 25.

[0046] The control unit receives the following signals:

[0047] Secondary DC voltage command value V ｄｃ２１＿ｒｅｆ , V ｄｃ２２＿ｒｅｆ DC bus V ｄｃ２１ (or V ｄｃ２２ ) the primary DC voltage V of the cell connected ｄｃ１ａ１ｋ .

[0048] The control unit of the isolated DC-DC converter DCDC in FIG. 3 is configured as follows.

[0049] The third sum calculation unit 26 of the primary side DC voltage individual balance control unit 24 calculates the sum of the voltages of each DC bus V ｄｃ２１ (or V ｄｃ２２ In the first embodiment, the total number of cells is 3m and there are two DC buses, so the total value is the total value of the primary DC voltages of 3m / 2 cells. The third average value calculation unit 27 calculates the product of the output of the third total value calculation unit 26 and the reciprocal (2 / 3m) of the number of cells connected to each DC bus, and calculates the total value of the primary DC voltages of each DC bus V ｄｃ２１ (or V ｄｃ２２ ) The DC bus primary DC voltage average value V ｄｃ１１＿ａｖｅ Calculate.

[0050] The band reject filter (BEF) 28 is connected to the DC bus V ｄｃ２１ (or DC bus V ｄｃ２２The fifth subtractor 29 removes the double system frequency component of the primary side DC voltage of each cell connected to the DC bus. ｄｃ１１＿ａｖｅ and the output of the band-elimination filter 28 corresponding to each cell. A fifth amplifier (P amplifier) ​​30 amplifies the output of the fifth subtractor 29. A second multiplier 31 multiplies the output of the fifth amplifier 30 by the turns ratio N of the transformer of the AC-DC converter ACDC and the transformer of the isolated DC-DC converter DCDC. １ / N ２ Find the product of N １ : Number of turns of AC-DC converter transformer, N ２ : The number of turns of the transformer of the isolated DC-DC converter DCDC. The output of the second multiplier 31 becomes the primary side DC voltage individual balance control value (when x=1 and x=2, the output of the second multiplier 31 is 3m / 2).

[0051] The sixth subtractor 32 of the secondary DC voltage individual control unit 25 calculates the secondary DC voltage command value V ｄｃ２１＿ｒｅｆ and the secondary DC voltage V ｄｃ２１ (or secondary side DC voltage command value V ｄｃ２２＿ｒｅｆ and the secondary DC voltage V ｄｃ２２ ) is taken as the difference between the sixth amplifier (PI amplifier) ​​33 and the sixth subtractor 32. The sixth amplifier (PI amplifier) ​​33 amplifies the output of the sixth subtractor 32. The third multiplier 34 obtains the product of the output of the sixth amplifier 33 and the reciprocal (2 / 3m) of the number of cells connected to each DC bus. The output of the third multiplier 34 becomes the individual secondary-side DC voltage control value.

[0052] The seventh subtractor 35 calculates the difference between the secondary DC voltage individual control value and the primary DC voltage individual balance control value (the seventh subtractor 35 outputs 3m / 2 when x=1 and x=2).

[0053] The current control unit 36 ​​receives the output of the seventh subtractor 35 and the primary side DC voltage (3m / 2 for x=1 and x=2). The DAB (Dual Active Bridge) converter outputs a phase difference command value, and the LLC converter outputs a frequency command value.

[0054] The PWM controller 37 performs PWM processing based on the output of the current control unit 36, converts it into a gate signal, and inputs it to the switching element of the isolated DC / DC converter DCDC of each cell.

[0055] [Explanation of Action and Operation] As shown in the configuration of FIG. ｄｃ２１ , V ｄｃ２２ ), two secondary side DC outputs are connected in series, and each DC bus (V ｄｃ２１ , V ｄｃ２２ ) and the output (V ｄｃ２１ +V ｄｃ２２ ) is connected to a load or a power supply. ｄｃ２１ , V ｄｃ２２ Therefore, when there is a power imbalance between the DC buses, the secondary DC voltage (V ｄｃ２１ , V ｄｃ２２ ) and the primary DC voltage V, which is the voltage of the primary DC capacitor C1 of each cell. ｄｃ１ａｘｋ Therefore, it is necessary to output voltage while maintaining the voltage balance.

[0056] In the control of the AC-DC converter ACDC, primary side DC voltage intra-phase balance control and primary side DC voltage average value control are performed.

[0057] First, the primary side DC voltage average value control unit 12 for all cells shown in FIG. 2(a) calculates the primary side DC voltage average value V ｄｃ１＿ａｖｅ and the primary side DC voltage average command value V ｄｃ１＿ａｖｅ＿ｒｅｆ The deviation from the reference value i is amplified by the first amplifier 4, and the reference value i is calculated as the system current active component command value on the rotating coordinate system. ｄ＿ｒｅｆ In addition, the system current reactive component command value i ｑ＿ｒｅｆ It is also possible to control the power factor of the grid current by calculating from the power factor command value.

[0058] The system current control unit 13 calculates the system current active component command value I ｄ＿ｒｅｆ , system current reactive component command value i ｑ＿ｒｅｆ and the system current active component i ｄ , system current reactive component i ｑ The second and third amplifiers 10 and 11 use the deviation of ｄ＿ｒｅｆ , system voltage reactive component command value V ｑ＿ｒｅｆ Output.

[0059] In Fig. 2(b), the primary side DC voltage intra-phase balance control is performed by adjusting the ACDC voltage command value of each cell.

[0060] First, the average value of the primary side DC voltage in the phase V ｄｃ１ｕ＿ａｖｅ and the primary DC voltage V of each cell in the phase ｄｃ１ｕｘｋ The deviation from this is amplified by the fourth amplifier 18. However, since the sign of the cell voltage command value that achieves voltage balance changes depending on the direction of the grid current on the three-phase coordinate system, the sign of the grid current is taken using the sign block and multiplied by the output of the fourth amplifier 18.

[0061] Next, the system voltage active component command value V on the rotating coordinate system ｄ＿ｒｅｆ , system voltage reactive component command value V ｑ＿ｒｅｆ The phase difference ωt synchronized with the system voltage is converted into three-phase coordinates by the dq inverter 20. The output of the dq inverter 20 and the primary side DC voltage all-cell average value V ｄｃ１＿ａｖｅ By taking the product of these, a three-phase voltage command value is calculated that does not take into account the imbalance in the primary side DC voltage.

[0062] The voltage command value for each phase is calculated by taking the difference between the primary side DC voltage intra-phase balance control value of each cell in each phase and the three-phase voltage command value that does not take into account the primary side DC voltage imbalance. Finally, each voltage command value is processed by the PWM controllers 23u, 23v, and 23w, such as by comparing it with a triangular wave carrier signal, to generate a gate signal for the AC-DC converter ACDC.

[0063] In the control of the isolated DC-DC converter DCDC shown in FIG. ｄｃ２１ , V ｄｃ２２ ) for each inverter, the primary DC voltage is individually balanced and the secondary DC voltage is individually controlled.

[0064] In the primary side DC voltage individual balance control unit 24, the DC bus V ｄｃ２１ (x=1) or DC bus V ｄｃ２２ The primary DC voltages of the cells connected (x=2) are balanced. However, a voltage ripple of twice the grid frequency occurs in the primary DC voltage of each phase. Since this voltage ripple can cause control instability when the gain of the P control is increased, the voltage is passed through a band elimination filter (BEF) 28, which removes only the twice the grid frequency component.

[0065] The output of the fifth amplifier 30 is the current of the primary side DC capacitor C1, so the output of the fifth amplifier 30 and the transformer turn ratio N １ / N ２ By taking the product of this and this, it is converted into the current of the secondary side DC capacitor C2.

[0066] Next, the secondary DC voltage individual control unit 25 calculates the secondary DC voltage command value V ｄｃ２１＿ｒｅｆ and the secondary DC voltage V ｄｃ２１ The deviation between the output of the sixth amplifier 33 and the current i of the secondary side DC capacitor C2 of each cell is calculated by multiplying the output of the sixth amplifier 33 by the reciprocal of the number of cells connected to the DC bus, 3m / 2. ｄｃ２１ Convert to.

[0067] The difference between the output of the secondary DC voltage individual control unit 25 and the output of the primary DC voltage individual balance control unit 24 is taken as a command value for the secondary DC capacitor current. ｄｃ２１ The primary-side DC voltage connected to (x=1) is input to a current control unit 36. The current control unit 36 ​​outputs a phase difference command value for the DAB converter and a frequency command value for the LLC converter. Finally, the phase difference command value or frequency command value is input to a PWM controller 37, which generates a gate signal for the isolated DC-DC converter DCDC.

[0068] Non-Patent Document 3 discloses an example of a current control section and PWM controller for an LLC converter. In the current control of Non-Patent Document 3, the output value of a PI controller is converted to a desired frequency value by a VCO (voltage controlled oscillator), and this frequency value is input to a carrier generator to generate a triangular wave carrier with the desired frequency. The PWM controller generates a gate signal by comparing the triangular wave carrier with a duty command value.

[0069] Non-Patent Document 4 discloses an example of a current control unit that uses a DAB converter. A phase difference command value is calculated from a current command value using a relational expression between the current command value and the phase difference. Next, as an example of a PWM controller, Patent Document 2 discloses a gate signal that compares a sawtooth wave carrier with the phase difference command value to achieve the phase difference command value.

[0070] [Effects] According to the first embodiment, in an SST system that inputs high voltage AC and outputs multiple DC buses, it is possible to achieve a balance between the primary side DC voltage and each secondary side DC voltage of each cell when a power imbalance occurs in each DC bus due to the load or power supply conditions.

[0071] Furthermore, compared to Non-Patent Document 1 and Patent Document 1, the present embodiment 1 does not require a commercial transformer and does not require an additional balancing circuit when a power imbalance occurs in each DC bus, thereby making it possible to avoid increases in size, cost, and size.

[0072] Furthermore, compared to Non-Patent Document 2, the balance control of the DC voltage of each cell can be reliably performed, so the withstand voltage of the device can be suppressed and increases in size and cost can be avoided.

[0073] According to the first embodiment, since it is possible to deal with the change in the number of series (x) in the DC bus simply by increasing the number of control blocks, software implementation for changing the number of series in the DC bus is simple.

[0074] [Embodiment 2] The main circuit and the control unit of the AC-DC converter ACDC in embodiment 2 are the same as those in embodiment 1. Fig. 4 shows a block diagram of the control unit of the isolated DC-DC converter DCDC in embodiment 2. The control unit of the isolated DC-DC converter DCDC in embodiment 2 includes a primary-side DC voltage individual balance control unit 38, a secondary-side DC voltage balance control unit 39, and a secondary-side DC voltage total value control unit 40 (which may be a current control unit).

[0075] In comparison with the first embodiment, the present control unit additionally receives the following signals.

[0076] Secondary side DC voltage total value command value V ｄｃ２＿ｒｅｆ Secondary side DC voltage total value V ｄｃ２１ +V ｄｃ２２ Secondary DC voltage V ｄｃ２１ and V ｄｃ２２ Secondary side DC voltage average value V ｄｃ２＿ａｖｅ .

[0077] The primary-side DC voltage individual balance control unit 38 in Fig. 4 is similar to the primary-side DC voltage individual balance control unit 24 in the first embodiment (Fig. 3). In the control unit of the isolated DC-DC converter DCDC in Fig. 4, the following blocks are added or changed compared to the first embodiment.

[0078] The eighth subtractor 42 of the secondary DC voltage balance control unit 39 subtracts the secondary DC voltage V ｄｃ２１ (or V ｄｃ２２ ) and the average secondary DC voltage V ｄｃ２＿ａｖｅ A seventh amplifier (P amplifier) ​​43 amplifies the output of the eighth subtractor 42. The output of the seventh amplifier 43 becomes the secondary-side DC voltage balance control value.

[0079] The first adder 44 sums the output of the seventh amplifier 43 (secondary DC voltage balance control value) and the output of the primary DC voltage individual balance control unit 38 (primary DC voltage individual balance control value).

[0080] The ninth subtractor 45 of the secondary DC voltage total value control unit 40 calculates the secondary DC voltage total value command value V ｄｃ２＿ｒｅｆ and the total secondary DC voltage V ｄｃ２１ +V ｄｃ２２ The difference between this and the eighth amplifier (PI amplifier) ​​46 is taken. The eighth amplifier (PI amplifier) ​​46 amplifies the output of the ninth subtractor 45. The fourth multiplier 47 multiplies the output of the eighth amplifier 46 by 1 / 3n, the reciprocal of the total number of three-phase cells. The output of the fourth multiplier 47 becomes the secondary DC voltage total value control value. The seventh subtractor 35 subtracts the value obtained by adding the secondary DC voltage balance control value and the primary DC voltage individual balance control value from the secondary DC voltage total value control value. The rest is the same as in embodiment 1.

[0081] [Explanation of Function and Operation] In the second embodiment, as shown in FIG. 4, a secondary DC voltage balance control unit 39 and a secondary DC voltage total value control unit 40 are added to the first embodiment.

[0082] The secondary DC voltage total value control unit 40 calculates the secondary DC voltage total value V ｄｃ２１ +V ｄｃ２２The output of the secondary DC voltage total value control unit 40 is input to the current control and gate generation blocks (both x=1 and x=2). However, since the secondary DC voltages cannot be balanced, secondary DC voltage balance control is applied.

[0083] First, each secondary DC voltage V ｄｃ２１ , V ｄｃ２２ Secondary side DC voltage average value V ｄｃ２＿ａｖｅ and each secondary DC voltage V ｄｃ２１ , V ｄｃ２２ The deviation between the x value and the x value is input to the seventh amplifier 43. Next, the output of the seventh amplifier 43 and the output of the primary-side DC voltage individual balance control unit 38 are summed and input to the current control unit 36 ​​corresponding to the x value. The current control unit 36 ​​and subsequent units are the same as in the first embodiment.

[0084] [Effects] According to the second embodiment, the same effects as those of the first embodiment are achieved.

[0085] In this second embodiment, the secondary side DC voltage control is one unit regardless of the number of series cells connected to the DC bus. Therefore, voltage control and current control can be switched during operation, and this can be applied to a large-capacity battery charge / discharge device that requires constant voltage charging (voltage control) and constant current charging (current control).

[0086] Although the present invention has been described in detail above only with respect to the specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the technical concept of the present invention, and it is natural that such modifications and variations fall within the scope of the claims.

[0087] 12... Primary side DC voltage average value control unit 13... System current control unit 14... Primary side DC voltage intra-phase balance control unit 24, 38... Primary side DC voltage individual balance control unit 25... Secondary side DC voltage individual control unit 39... Secondary side DC voltage balance control unit 40... Secondary side DC voltage total value control unit

Claims

1. An ACDC power supply having m (m: an integer of 2 or more) cells per phase, each cell comprising an AC-DC converter, a primary-side DC capacitor connected to the DC side of the AC-DC converter, an isolated DC-DC converter having one DC side connected to the primary-side DC capacitor, and a secondary-side DC capacitor connected to the other DC side of the isolated DC-DC converter, and having a plurality of DC buses to which a plurality of the secondary-side DC capacitors are connected in series or in parallel, and supplying voltages of a plurality of the DC buses to a load or power source, wherein when a power imbalance occurs due to the condition of the load or power source, the ACDC power supply outputs a voltage while maintaining a voltage balance between the secondary-side DC voltage, which is the voltage of the DC bus, and the primary-side DC voltage, which is the voltage of the primary-side DC capacitor of each cell.

2. The control unit of the AC-DC converter comprises: a primary DC voltage average value control unit which generates a grid current active component command value based on a primary DC voltage average value command value and a primary DC voltage all-cell average value; a grid current control unit which generates a grid voltage active component command value and a grid voltage reactive component command value based on the grid current active component command value and the grid current reactive component command value; and a primary DC voltage intra-phase balance control unit which generates a primary DC voltage intra-phase balance control value based on the primary DC voltage intra-phase average value of each phase and the primary DC voltage of each cell, wherein the grid voltage active component command value and the grid voltage reactive component command value are converted into values ​​on fixed coordinates, and multiplied by the primary DC voltage all-cell average value, from which the primary DC voltage intra-phase balance control value is subtracted to generate a voltage command value for each phase, and a gate signal for the AC-DC converter is generated based on this voltage command value; and the control unit of the isolated DC-DC converter comprises: a primary DC voltage individual balance control unit which generates a primary DC voltage individual balance control value based on the primary DC voltage; a secondary DC voltage individual control unit that generates a secondary DC voltage individual control value based on a secondary DC voltage, wherein current control is performed based on the primary DC voltage and a value obtained by subtracting the primary DC voltage individual balance control value from the secondary DC voltage individual control value, and a gate signal of the isolated DC-DC converter is generated based on a result of the current control.

3. The control unit of the AC-DC converter comprises: a primary DC voltage average value control unit which generates a grid current active component command value based on a primary DC voltage average value command value and a primary DC voltage all-cell average value; a grid current control unit which generates a grid voltage active component command value and a grid voltage reactive component command value based on the grid current active component command value and the grid current reactive component command value; and a primary DC voltage intra-phase balance control unit which generates a primary DC voltage intra-phase balance control value based on the primary DC voltage intra-phase average value of each phase and the primary DC voltage of each cell, wherein the grid voltage active component command value and the grid voltage reactive component command value are converted into values ​​on fixed coordinates, and multiplied by the primary DC voltage all-cell average value, from which the primary DC voltage intra-phase balance control value is subtracted to generate a voltage command value for each phase, and a gate signal for the AC-DC converter is generated based on this voltage command value; and the control unit of the isolated DC-DC converter comprises: a primary DC voltage individual balance control unit which generates a primary DC voltage individual balance control value based on the primary DC voltage; 2. The ACDC power supply according to claim 1, comprising: a secondary DC voltage balance control unit that generates a secondary DC voltage balance control value based on a secondary DC voltage; and a secondary DC voltage total value control unit that generates a secondary DC voltage total value control value based on a secondary DC voltage total value command value and the secondary DC voltage total value, wherein current control is performed based on the primary DC voltage and a value obtained by subtracting a value obtained by adding the secondary DC voltage balance control value to the primary DC voltage individual balance control value from the secondary DC voltage total value control value, and 4. The ACDC power supply as claimed in claim 2 or 3, characterized in that the primary DC voltage average value control unit comprises: a first total value calculation unit that calculates a total value of the primary DC voltages of all cells and outputs the total value as a primary DC voltage all-cell total value; an all-cell average value calculation unit that calculates the primary DC voltage all-cell average value from the product of the primary DC voltage all-cell total value and the reciprocal of the total number of cells; a first subtractor that calculates the deviation between the primary DC voltage average value command value and the primary DC voltage all-cell average value; and a first amplifier that amplifies the output of the first subtractor and outputs it as the system current active component command value.

5. An ACDC power supply as claimed in claim 2 or 3, characterized in that the system current control unit comprises: a second subtractor that subtracts the system current active component from the system current active component command value; a second amplifier that amplifies the output of the second subtractor and outputs it as the system voltage active component command value; a third subtractor that subtracts the system current reactive component from the system current reactive component command value; and a third amplifier that amplifies the output of the third subtractor and outputs it as the system voltage reactive component command value.

6. The ACDC power supply according to claim 2 or 3, characterized in that the primary DC voltage intra-phase balance control unit comprises: a second sum calculation unit which calculates a sum of the primary DC voltages in a phase and outputs the sum as a primary DC voltage intra-phase sum; an in-phase average value calculation unit which calculates the primary DC voltage intra-phase average value of each phase from the product of the primary DC voltage intra-phase sum and the reciprocal of the number of cells in the phase; a fourth subtractor which calculates a deviation between the primary DC voltage intra-phase average value of each phase and the primary DC voltage of each cell in the phase; a fourth amplifier which amplifies the output of the fourth subtractor; and a first multiplier which multiplies the output of the fourth amplifier by the sign of the system current value of each phase and outputs the result as the primary DC voltage intra-phase balance control value.

7. The ACDC power supply according to claim 2 or 3, characterized in that the primary side DC voltage individual balance control unit comprises: a third sum value calculation unit that calculates a sum value of the primary side DC voltage of cells connected to each DC bus; a third average value calculation unit that calculates a product of an output of the third sum value calculation unit and the reciprocal of the number of cells connected to each DC bus, and calculates a DC bus primary side DC voltage average value of the cells connected to each DC bus; a band elimination filter that removes twice the system frequency component of the primary side DC voltage of the cells connected to each DC bus; a fifth subtractor that outputs the difference between the DC bus primary side DC voltage average value and the output of the band elimination filter; a fifth amplifier that amplifies the output of the fifth subtractor; and a second multiplier that multiplies the output of the fifth amplifier by a turns ratio of a transformer of the AC-DC converter and a transformer of the isolated DC-DC converter, and outputs the result as the primary side DC voltage individual balance control value.

8. The ACDC power supply according to claim 2, characterized in that the secondary DC voltage individual control unit comprises: a sixth subtractor that calculates the difference between the secondary DC voltage command value and the secondary DC voltage of each of the DC buses; a sixth amplifier that amplifies the output of the sixth subtractor; and a third multiplier that calculates the product of the output of the sixth amplifier and the reciprocal of the number of cells connected to the DC bus and outputs the product as the secondary DC voltage individual control value.

9. The ACDC power supply according to claim 3, characterized in that the secondary DC voltage balance control unit comprises: an eighth subtractor that calculates a deviation between an average secondary DC voltage and the secondary DC voltage of each DC bus; and a seventh amplifier that amplifies the output of the eighth subtractor and outputs it as the secondary DC voltage balance control value.

10. The ACDC power supply according to claim 3, characterized in that the secondary DC voltage total value control unit comprises: a ninth subtractor that calculates the difference between the secondary DC voltage total value command value and the secondary DC voltage total value of all DC buses; an eighth amplifier that amplifies the output of the ninth subtractor; and a fourth multiplier that calculates the product of the output of the eighth amplifier and the reciprocal of the total number of cells and outputs the product as the secondary DC voltage total value control value.

11. A control method for an ACDC power supply having m (m: an integer of 2 or more) cells per phase, each cell comprising an AC-DC converter, a primary-side DC capacitor connected to the DC side of the AC-DC converter, an isolated DC-DC converter having one DC side connected to the primary-side DC capacitor, and a secondary-side DC capacitor connected to the other DC side of the isolated DC-DC converter, a plurality of DC buses to which a plurality of the secondary-side DC capacitors are connected in series or in parallel, and supplying voltages of a plurality of the DC buses to a load or a power source, wherein the control unit outputs a voltage while maintaining a voltage balance between the secondary-side DC voltage, which is the voltage of the DC bus, and the primary-side DC voltage, which is the voltage of the primary-side DC capacitor of each cell, when a power imbalance occurs due to the condition of the load or the power source.

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