ACDC power supply and power supply control method

Abstract

To achieve voltage balance of each DC bus when power is unbalanced without using an additional balancing circuit or a multi-winding commercial transformer in an ACDC power supply.SOLUTION: An ACDC power supply includes an AC-DC converter ACDC, a primary side DC capacitor C1, an isolated DC-DC converter DCDC, and a secondary side DC capacitor C2. Each phase has m (m: an integer of 2 or more) cells, and includes a plurality of DC buses Vdc21, Vdc22 to which a plurality of secondary side DC capacitors C2 are connected in series or in parallel, and supplies the voltages of the plurality of DC buses Vdc21, Vdc22 to a load or power supply. When a power imbalance occurs due to the condition of the load or power supply, the ACDC power supply outputs a voltage while maintaining the voltage balance of the secondary side DC voltage and the primary side DC voltage of each cell.SELECTED DRAWING: Figure 1

Description

[Technical field]

[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 for use with AC input and multiple DC bus outputs, and to a technology for achieving balance between each DC voltage. [Background technology]

[0002] Non-Patent Document 1 introduces circuit methods and control methods for when the power of each DC bus is unbalanced. As a circuit method, a method is disclosed in which a balancing circuit is connected to achieve voltage balance of the DC buses when the power is unbalanced. In addition, a method is disclosed in which a multi-winding transformer of commercial frequency and a power converter are used to achieve voltage balance of each DC bus when the power is unbalanced without a balancing circuit.

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

[0004] Patent Document 1 discloses an SST method for generating two DC buses from a high voltage AC voltage. In addition, an isolated DC-DC converter is connected between the two DC buses to achieve voltage balance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2023-510035 [Patent Document 2] JP 2022-50739 A [Non-patent literature]

[0006] [Non-Patent Document 1] 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 [Non-Patent Document 2] 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 [Non-Patent Document 3] Yuki Kinoshita, Hitoshi Haga, "LLC Converter with Wide Voltage Gain for PEV Charger Using Six-Switch Bridge", IEEJ Transactions on Electrical Engineering, Vol. 140, No. 1, pp. 36-44 [Non-Patent Document 4] Jun Higa, Shunsuke Takuma, Keisuke Kusaka, Junichi Ito, "Development of a T-type Dual Active Bridge DC-DC Converter with Operation Mode Switching Method for a Wide Voltage Drive Range", IEEJ Transactions on Power Electronics, Vol. 139, No. 4, pp. 388-400 (2019) Summary of the Invention [Problem to be solved by the invention]

[0007] When there is a power imbalance among multiple DC buses, an imbalance occurs in the voltage of each DC bus. To deal with this, the withstand voltage of the DC bus and the withstand voltage required for the load connected to the DC bus also increase, which leads to an increase in cost 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 size and cost.

[0009] The method disclosed in Non-Patent Document 2 does not mention the balance of DC bus voltages when the power of each DC bus is unbalanced.

[0010] As described above, the challenge for an ACDC power supply is to achieve voltage balance of each DC bus when the power is unbalanced without using an additional balancing circuit or a commercial transformer with multiple windings. [Means for solving the problem]

[0011] The present invention has been devised in view of the above-mentioned problems in the related art. One aspect of the present invention is an AC / DC 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, a plurality of DC buses to which a plurality of the secondary side DC capacitors are connected in series or in parallel, and supplying the voltages of the plurality of DC buses to a load or a power source, characterized in that when a power imbalance occurs due to the condition of the load or the power source, the AC / DC 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 includes 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 a 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 obtained. a primary side DC voltage intra-phase balance control value is subtracted from the primary side DC voltage to generate a voltage command value for each phase, and a gate signal for the AC-DC converter is generated based on the voltage command value, and the 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, 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 a result of the current control.

[0013] In another aspect, the control unit of the AC-DC converter includes 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 a 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 a fixed coordinate system 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 comprises a primary-side DC voltage individual balance control unit which 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 which 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 which 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 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 DC voltage total value control value, and

[0014] In one embodiment, the primary side DC voltage average value control unit includes a first sum calculation unit that calculates a sum of the primary side DC voltages of all cells and outputs it as a primary side DC voltage all-cell sum; 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 sum 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 embodiment, the system current control unit includes a second subtractor that subtracts a system current active component from the system current active component command value, a second amplifier that amplifies an output of the second subtractor and outputs the result as the system voltage active component command value, a third subtractor that subtracts a system current reactive component from the system current reactive component command value, and a third amplifier that amplifies an output of the third subtractor and outputs the result as the system voltage reactive component command value.

[0016] In one embodiment, 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 an 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 embodiment, the primary DC voltage individual balance control unit includes a third sum calculation unit that calculates a sum of the primary DC voltages of the cells connected to each DC bus, a third average 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 a DC bus primary DC voltage average value of the cells connected to each DC bus, a band elimination filter that removes a system frequency double component of the primary DC voltage of the cells connected to each DC bus, a fifth subtractor that outputs the difference between the DC bus primary 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 the transformer of the AC-DC converter and the transformer of the isolated DC-DC converter and outputs the result as the primary 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 a secondary-side DC voltage command value and a secondary-side DC voltage of each of the DC buses, a sixth amplifier that amplifies an output of the sixth subtractor, and a third multiplier that calculates a product of an output of the sixth amplifier and a reciprocal of a 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 DC voltage balance control unit includes 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 an output of the eighth subtractor and outputs the amplified output as the secondary DC voltage balance control value.

[0020] In one embodiment, the secondary DC voltage total value control unit includes a ninth subtractor that calculates a 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 an output of the ninth subtractor, and a fourth multiplier that calculates a 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. Effect of the Invention

[0021] According to the present invention, in an ACDC power supply, it is possible to achieve voltage balance of each DC bus when power is unbalanced without using an additional balancing circuit or a commercial transformer with multiple windings. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 shows the configuration of an SST main circuit that generates multiple DC buses. [Diagram 2] FIG. 4 is a block diagram showing a control unit of the AC-DC converter. [Diagram 3] FIG. 2 is a block diagram showing a control unit of the isolated DC-DC converter according to the first embodiment. [Figure 4] FIG. 11 is a block diagram showing a control unit of an isolated DC-DC converter according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] First and second embodiments of the ACDC power supply according to the present invention will now be described in detail with reference to FIGS.

[0024] [Embodiment 1] FIG. 1 shows the configuration of an SST main circuit that generates multiple DC buses. As shown in FIG. 1, the SST has 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 with 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. The AC-DC converter ACDC and the isolated DC-DC converter DCDC are well known, so 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 2 or greater). Also, three cells for three phases constitute one unit. The number of units is n (n: integer 2 or greater).

[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 Also, DC bus V dc21 , or V dc22 , or V dc21 +V dc22 The load is supplied with power from the power supply. 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 phase a dc2xThe 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] A block diagram of the control unit of the AC-DC converter ACDC is shown in Fig. 2. 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 system current control unit 13, and a primary side DC voltage intra-phase balance control unit 14, and generates a three-phase voltage command value.

[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 System current active component i on rotating coordinate system d , system current reactive component i q System current reactive component command value i q_ref Primary side DC voltage V dc1axk Primary side 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 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 primary DC voltage all-cell total value. The all-cell average value calculation unit 2 calculates the product of the primary DC voltage all-cell total value and the reciprocal of the total number of cells (3m). The output of the all-cell average value calculation unit 2 is the primary DC voltage all-cell average value V dc1_ave It becomes.

[0033] The first subtractor 3 subtracts the primary side DC voltage average command value V dc1_ave_ref and the primary side DC voltage all cell average value V dc1_ave The 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 The output is as follows:

[0034] 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 (system 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 PLL5 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 in the rotating coordinate system synchronized with the grid (the grid current active component i d , system current reactive component i q )

[0037] The second subtractor 8 of the system current control unit 13 subtracts the system current active component command value id_ref and the system current active component i 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 according 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_ref It 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. 2(b) 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 in the phase m to obtain the primary DC voltage intra-phase average V dc1a_ave Calculate.

[0041] The fourth subtractor 17 calculates the primary side DC voltage intra-phase average value V dc1a_ave and the primary DC voltage V of each cell in the phase dc1uxk The fourth amplifier (PI amplifier) ​​18 amplifies the output of the fourth subtractor 17. The 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 units of m for each phase (i.e., the number of cells).

[0042] The dq inverse converter 20 converts the system voltage active component command value V d_ref , system voltage reactive component command value V q_refand phase ωt are input, and the value on the rotating coordinate system synchronized with the grid is converted to a value on the fixed coordinate system. The multipliers 21u, 21v, and 21w convert the output of the dq inverter 20 and the primary side DC voltage all-cell average value V dc1_ave Multiply it 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 of each phase. The outputs of the fifth subtractors 22u, 22v, and 22w are used to calculate the three-phase voltage command value V u_ref1 …V u_refm ,V v_ref1 …V v_refm ,V w_ref1 …V w_refm It 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 and input it to the switching elements 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 the present embodiment 1. The control unit of the isolated DC-DC converter DCDC in the present 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 to dc1a1k .

[0048] The control unit of the isolated DC-DC converter DCDC in Figure 3 is composed of the following:

[0049] The third sum value calculation unit 26 of the primary side DC voltage individual balance control unit 24 calculates the sum of each DC bus V dc21 (or V dc22 In the present embodiment 1, since the total number of cells is 3m and there are two DC buses, the total value is the total value of the primary side DC voltages of 3m / 2 cells. The third average value calculation unit 27 calculates the product of the output of the third sum 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 side DC voltages of each DC bus V dc21 (or V dc22 ) is the average value of the primary DC voltages of the cells connected to the DC bus. dc11_ave Calculate.

[0050] The band-elimination filter (BEF) 28 is connected to the DC bus V dc21 (or DC bus V dc22 The 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 1 / N 2 where 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 (the output of the second multiplier 31 is 3m / 2 at x=1 and x=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 the secondary DC voltage command value V dc22_ref and the secondary DC voltage V dc22) is taken as the difference. A sixth amplifier (PI amplifier) ​​33 amplifies the output of the sixth subtractor 32. A 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 DC voltage control value.

[0052] The seventh subtractor 35 obtains the difference between the secondary DC voltage individual control value and the primary DC voltage individual balance control value (the output of the seventh subtractor 35 is 3m / 2 at x=1 and x=2, respectively).

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

[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 Figure 1, multiple DC buses (V dc21 , V dc22 ), the secondary DC output is connected in series, and each DC bus (V dc21 , V dc22 ) and the output with each DC terminal connected in series (V dc21 +V dc22 ) is connected to a load or power supply. Therefore, each DC bus V dc21 ,V dc22 Therefore, when there is a power imbalance in each DC bus, the secondary DC voltage (V dc21 , V dc22 ) and the primary DC voltage V, which is the voltage across the primary DC capacitor C1 of each cell. dc1axk It is necessary to output a voltage while maintaining the voltage balance between the two.

[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 all-cell average value V dc1_ave and the primary side DC voltage average command value V dc1_ave_ref The deviation from the target value is amplified by the first amplifier 4, and the system current active component command value i d_ref 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] In the system current control unit 13, 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. Balance control is achieved by adjusting the ACDC voltage command value of each cell.

[0060] First, the average value of the primary DC voltage in each 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 positive / negative 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 by the sign block and the product is taken of the output of the fourth amplifier 18.

[0061] Next, the system voltage active component command value V d_ref , system voltage reactive component command value V q_ref The phase difference ωt synchronized with the system voltage is converted to 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 Vdc1_ave By taking the product of these, the three-phase voltage command value is calculated without taking into account the imbalance in the primary 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 of each phase and the three-phase voltage command value that does not consider the imbalance of the primary side DC voltage. 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 in Figure 3, the DC bus (V dc21 , V dc22 ) for each circuit, the primary DC voltage balance control and the secondary DC voltage control are performed individually.

[0064] In the primary side DC voltage individual balance control section 24, the DC bus V dc21 (x=1) or DC bus V dc22 The primary DC voltages of the cells connected to (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 that 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 turns ratio N 1 / N 2 By multiplying this by this, it is converted into the current of the secondary side DC capacitor C2.

[0066] Next, the secondary DC voltage individual control unit 25 determines 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 number of cells connected to the DC bus, 3m / 2, is input to the sixth amplifier 33. The current i 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 the command value of the secondary DC capacitor current. dc21 The primary side DC voltage connected to (x=1) is input to the 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 the frequency command value is input to the 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 of an LLC converter. In the current control of Non-Patent Document 3, the output value of the 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 a 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 section using a DAB converter. A phase difference command value is calculated from a current command value using a relational expression between a current command value and a phase difference. Next, as an example of a PWM controller, a gate signal is generated that achieves the phase difference command value by comparing a sawtooth carrier with the phase difference command value as in Patent Document 2.

[0070] [effect] 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 DC voltage and each secondary DC voltage of each cell when a power imbalance occurs in each DC bus due to the load or power supply conditions.

[0071] Moreover, compared with 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 an increase in size and cost.

[0072] Furthermore, compared to Non-Patent Document 2, the DC voltage balance control of each cell can be reliably performed, so that 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 in the DC bus by simply increasing the number of control blocks in accordance with the number of series (x) in the DC bus, software implementation for changing the number of series in the DC bus is easy.

[0074] [Embodiment 2] The main circuit and the control unit of the AC-DC converter ACDC in the present embodiment 2 are the same as those in the embodiment 1. Fig. 4 shows a block diagram of the control unit of the isolated DC-DC converter DCDC in the present embodiment 2. The control unit of the isolated DC-DC converter DCDC in the present 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 as input.

[0076] Secondary DC voltage total command value V dc2_ref Secondary side DC voltage total value V dc21 +V dc22 Secondary DC voltage V dc21 and V dc22 The average secondary DC voltage 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 and changed from those in the first embodiment.

[0078] The eighth subtractor 42 of the secondary DC voltage balance control unit 39 calculates the secondary DC voltage V dc21 (or V dc22 ) and the average secondary DC voltage V dc2_aveA 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 section 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 and calculates the difference between the two. 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 the reciprocal of the total number of three-phase cells, 1 / 3n. The output of the fourth multiplier 47 becomes the secondary DC voltage total value control value. The seventh subtractor 35 subtracts 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. The rest is the same as in the first embodiment.

[0081] [Explanation of Action 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] In the secondary DC voltage total value control unit 40, the secondary DC voltage total value V dc21 +V dc22 The 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, the secondary DC voltage V dc21 , V dc22 The average secondary DC voltage V dc2_ave and each secondary DC voltage V dc21 , V dc22The deviation from 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] [effect] According to the second embodiment, the same effects as those of the first embodiment are achieved.

[0085] In this embodiment 2, the secondary side DC voltage control is one regardless of the number of serial cells connected to the DC bus. Therefore, since the voltage control and the current control can be switched during operation, it can also 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. [Explanation of symbols]

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

Claims

1. An AC-DC power supply comprising, per unit cell, m (where m is an integer of 2 or more) cells each 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; a plurality of DC buses in which a plurality of the secondary-side DC capacitors are connected in series or in parallel; and a means for supplying the voltage of the plurality of DC buses to a load or a power source, wherein when a power imbalance occurs due to the status of the load or the power source, the voltage is output while maintaining the voltage balance of 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 includes a primary-side DC voltage average value control unit that generates a line current active component command value based on a primary-side DC voltage average value command value and a primary-side DC voltage average value of all cells; a line current control unit that generates a line voltage active component command value and a line voltage reactive component command value based on the line current active component command value and a line current reactive component command value; a primary-side DC voltage in-phase balance control unit that generates a primary-side DC voltage in-phase balance control value based on the in-phase average value of the primary-side DC voltage of each phase and the primary-side DC voltage of each cell, and generates a voltage command value for each phase by converting the line voltage active component command value and the line voltage reactive component command value into values on a fixed coordinate, multiplying the result by the primary-side DC voltage average value of all cells, and subtracting the primary-side DC voltage in-phase balance control value, and generates a gate signal for the AC-DC converter based on this voltage command value. The 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; 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. The AC-DC power supply according to claim 1, wherein current control is performed based on the value obtained by subtracting the primary-side DC voltage individual balance control value from the secondary-side DC voltage individual control value and the primary-side DC voltage, and a gate signal for the isolated DC-DC converter is generated based on the result of the current control.

3. The control unit of the AC-DC converter ​ A primary-side DC voltage average value control unit that generates a system current active component command value based on a primary-side DC voltage average value command value and a primary-side DC voltage full-cell average value; A system current control unit that generates a system voltage active component command value and a system voltage reactive component command value based on the system current active component command value and the system current reactive component command value; A primary-side DC voltage in-phase balance control unit that generates a primary-side DC voltage in-phase balance control value based on the primary-side DC voltage in-phase average value of each phase and the primary-side DC voltage of each cell, and is provided with: The system voltage active component command value and the system voltage reactive component command value are converted into values on a fixed coordinate, and the primary-side DC voltage in-phase balance control value is subtracted from the value obtained by multiplying the primary-side DC voltage full-cell average value to generate a voltage command value for each phase, and a gate signal of the AC-DC converter is generated based on this voltage command value. The control unit of the isolated DC-DC converter is 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; 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 a secondary-side DC voltage total value; Comprising Based on the value obtained by subtracting the 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 the primary-side DC voltage, current control is performed, and a gate signal of the isolated DC-DC converter is generated based on the result of the current control. The AC-DC power supply according to claim 1, characterized in that.

4. The primary-side DC voltage average value control unit is A first total value calculation unit that calculates the total value of the primary-side DC voltage of all cells and outputs it as the primary-side DC voltage full-cell total value; A full-cell average value calculation unit that calculates the primary-side DC voltage full-cell average value from the product of the primary-side DC voltage full-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 full-cell average value; A first amplifier that amplifies the output of the first subtractor and outputs it as the system current active component command value; The AC-DC power supply according to claim 2 or 3, characterized in that it is provided with.

5. The system current control unit is 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 subtracter and outputs it as the system voltage active component command value; A third subtracter that subtracts the system current reactive component from the system current reactive component command value; A third amplifier that amplifies the output of the third subtracter and outputs it as the system voltage reactive component command value; The AC-DC power supply according to claim 2 or 3, characterized by comprising the above.

6. The primary-side DC voltage in-phase balance control unit: A second total value calculation unit that calculates the total value of the primary-side DC voltage in the phase and outputs it as the primary-side DC voltage in-phase total value; An in-phase average value calculation unit that calculates the primary-side DC voltage in-phase average value of each phase from the product of the primary-side DC voltage in-phase total value and the reciprocal of the number of cells in the phase; A fourth subtracter that calculates the deviation between the primary-side DC voltage in-phase average value of each phase and the primary-side DC voltage of each cell in the phase; A fourth amplifier that amplifies the output of the fourth subtracter; A first multiplier that multiplies the output of the fourth amplifier by the sign of the system current value of each phase and outputs it as the primary-side DC voltage in-phase balance control value; The AC-DC power supply according to claim 2 or 3, characterized by comprising the above.

7. The primary-side DC voltage individual balance control unit: A third total value calculation unit that calculates the total value of the primary-side DC voltage of the cells connected to each DC bus; A third average value calculation unit that obtains the product of the output of the third total value calculation unit and the reciprocal of the number of cells connected to each DC bus, and calculates the DC bus primary-side DC voltage average value of the cells connected to each DC bus; A band rejection filter that removes the twice power frequency component of the primary-side DC voltage of the cells connected to each DC bus; A fifth subtracter that outputs the difference between the DC bus primary-side DC voltage average value and the output of the band rejection filter; A fifth amplifier that amplifies the output of the fifth subtracter; A second multiplier that multiplies the output of the fifth amplifier by the turns ratio of the transformer of the AC-DC converter and the transformer of the isolated DC-DC converter and outputs it as the primary-side DC voltage individual balance control value; The AC-DC power supply according to claim 2 or 3, characterized by comprising the above.

8. The secondary-side DC voltage individual control unit: A sixth subtracter that calculates the difference between the secondary-side DC voltage command value of each DC bus and the secondary-side DC voltage; A sixth amplifier that amplifies the output of the sixth subtracter; A third multiplier that obtains the product of the output of the sixth amplifier and the reciprocal of the number of cells connected to the DC bus, and outputs it as the secondary-side DC voltage individual control value; The AC-DC power supply according to claim 2, characterized by comprising the above.

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

10. 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, 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 it as the secondary-side DC voltage total value control value, The AC-DC power supply according to claim 3, characterized in that it comprises the above.

11. An AC-DC power supply control method, comprising m (m: an integer of 2 or more) cells per unit, 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 in which a plurality of the secondary-side DC capacitors are connected in series or in parallel, and supplying the voltages of the plurality of DC buses to a load or a power supply, When there is a power imbalance generated due to the situation of the load or the power supply, the control unit outputs a voltage while maintaining the voltage balance of 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. The control method of the AC-DC power supply is characterized by the above.

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