JP7616322B1 - ACDC power supply and method for controlling ACDC power supply - Google Patents

Abstract

In an ACDC power supply, voltage balance of each DC bus is achieved when power is unbalanced without using an additional balancing circuit or a multi-winding commercial transformer.
[Solution] The 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 cells (m: an integer of 2 or more). The power supply has a plurality of DC buses _Vdc21 , _Vdc22 to which a plurality of secondary side DC capacitors C2 are connected in series or parallel. The voltages of the plurality of DC buses _Vdc21 , _Vdc22 are supplied to a load or a power supply. When a power imbalance occurs due to the condition of the load or power supply, a voltage is output while maintaining the voltage balance of the secondary side DC voltage and the primary side DC voltage of each cell.
[Selected Figure] Figure 1

Description

The present invention relates to a solid state transformer (SST) 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.

Non-Patent Document 1 introduces circuit methods and control methods for when there is a power imbalance in each DC bus. As a circuit method, a method is disclosed in which a voltage balance is achieved in the DC bus when there is a power imbalance by connecting a balancing circuit. In addition, a method is disclosed in which a voltage balance is achieved in the DC bus when there is a power imbalance without a balancing circuit by using a commercial frequency multi-winding transformer and a power converter.

In Non-Patent Document 2, the SST method is adopted, which uses a high-frequency multi-winding transformer in the circuit that generates multiple DC buses. In this method, by increasing the frequency of the multi-winding transformer, it is possible to make it smaller than a commercial frequency transformer.

Patent document 1 discloses an SST method for generating two DC buses from high voltage AC. In addition, an isolated DC-DC converter is connected between the two DC buses to achieve voltage balance.

Special Publication No. 2023-510035 JP 2022-50739 A

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 Hitoshi Haga, "LLC Converter for PEV Chargers with Wide Voltage Gain Using Six-Switch Bridge", Transactions on Electrical Engineering of Japan, Vol. 140, No. 1, pp. 36-44 Higa, Jun, Takuma, Shunsuke, Kusaka, Keisuke, 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 Electronics, Vol. 139, No. 4, pp. 388-400 (2019)

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 bus and the withstand voltage required for the load connected to the DC bus also increase, resulting in increased costs and size.

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

The method disclosed in Non-Patent Document 2 does not mention the balance of DC bus voltages when there is a power imbalance in each DC bus.

As described above, the challenge for ACDC power supplies is to achieve voltage balance for each DC bus when there is a power imbalance without using additional balancing circuits or commercial transformers with multiple windings.

The present invention was devised in view of the above-mentioned problems of the related art. One aspect of the present invention is an ACDC power supply that has 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 has a plurality of DC buses to which a plurality of the secondary side DC capacitors are connected in series or in parallel, and supplies the voltages of the plurality of DC buses to a load or power source, and is characterized in that when a power imbalance occurs due to the condition of the load or power source, the ACDC power supply outputs a voltage while maintaining the 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.

In one embodiment, 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 the primary DC voltage intra-phase average value of each phase and the primary 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 fixed coordinates and multiplying them by the primary DC voltage all-cell average value. The 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 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, and performs current control 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 generates a gate signal for the isolated DC-DC converter based on the result of the current control.

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 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, subtracting the primary DC voltage intra-phase balance control value from the result, and then applying a voltage command value to this voltage command value. The control unit of the isolated DC-DC converter is provided with a primary DC voltage individual balance control unit that generates a primary DC voltage individual balance control value based on the primary DC voltage, a secondary DC voltage balance control unit that generates a secondary DC voltage balance control value based on the secondary DC voltage, and a secondary DC voltage total value control unit that generates a secondary DC voltage total value control value based on the secondary DC voltage total value command value and the secondary DC voltage total value, and performs current control based on the primary DC voltage and a value obtained by subtracting the 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 generates a gate signal for the isolated DC-DC converter based on the result of the current control.

In one embodiment, the primary DC voltage average value control unit includes a first total value calculation unit that calculates the total value of the primary DC voltages of all cells and outputs it as a total primary DC voltage 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.

In one embodiment, 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 the output of the second subtractor and outputs it 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 the output of the third subtractor and outputs it as the grid voltage reactive component command value.

In one embodiment, the primary DC voltage intra-phase balance control unit includes a second total value calculation unit that calculates the total value of the primary DC voltages in the phase and outputs it as a primary DC voltage intra-phase total value, an intra-phase average value 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 total value and the reciprocal of the number of cells in the phase, a fourth subtractor that calculates the 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 it as the primary DC voltage intra-phase balance control value.

In one embodiment, the primary DC voltage individual balance control unit includes a third sum calculation unit that calculates the sum of the primary DC voltages of the cells connected to each DC bus, a third average calculation unit that calculates the product of the output of the third sum calculation unit and the reciprocal of the number of cells connected to each DC bus to calculate the DC bus primary DC voltage average value of the cells connected to each DC bus, a band elimination filter that removes the 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 the 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.

In one aspect, the secondary DC voltage individual control unit includes a sixth subtractor that calculates the difference between the secondary DC voltage command value and the secondary DC voltage of each DC bus, 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.

In one aspect, the secondary DC voltage balance control unit includes an eighth subtractor that calculates the deviation between the 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.

In one embodiment, the secondary DC voltage total value control unit includes 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.

According to the present invention, in an ACDC power supply, it is possible to achieve voltage balance of each DC bus when there is a power imbalance without using an additional balancing circuit or a multi-winding commercial transformer.

FIG. 1 shows an SST main circuit configuration for generating multiple DC buses. FIG. 4 is a block diagram showing a control unit of the AC-DC converter. FIG. 2 is a block diagram showing a control unit of the isolated DC-DC converter according to the first embodiment. FIG. 11 is a block diagram showing a control unit of an isolated DC-DC converter according to a second embodiment.

Below, embodiments 1 and 2 of the ACDC power supply of the present invention will be described in detail with reference to Figures 1 to 4.

[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 those known in the art. The AC-DC converter ACDC and the isolated DC-DC converter DCDC are well known, so detailed description thereof will be omitted here.

Here, the AC-DC converter ACDC, the primary side DC capacitor C1, the isolated DC-DC converter DCDC, and the secondary side DC capacitor C2 constitute one cell. The number of cells per phase is m (m: an integer of 2 or more). Furthermore, three cells for three phases constitute one unit. The number of units is n (n: an integer of 2 or more).

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 _Vdc21 or one DC bus _Vdc22 . The DC bus _Vdc21 , _Vdc22 , or _Vdc21 + _Vdc22 is supplied to a load. Each cell (AC-DC converter ACDC, isolated DC-DC converter DCDC) includes a switching element. The voltage and current of each cell can be controlled by turning the switching element on and off.

The primary DC voltage of the kth unit connected to the xth secondary voltage _Vdc2x in the a-phase is denoted as _Vdc1axk (x=1, 2, k=number of units connected to each DC bus=1, 2, . . . n/2).

Figure 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 Figure 2 is common to this embodiment 1 and embodiment 2 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.

The following signals are input to this control unit.

Primary side DC voltage average value command value V _{dc1_ave_ref}
Three-phase system current values _iU , _iV , _iW
Three-phase system voltage values _Vu , _Vv , _Vw
Active component of grid current i _d on the rotating coordinate system, reactive component of grid current i _q
System current reactive component command value _{iq_ref}
Primary side DC voltage V _dc1axk
Primary DC voltages of each phase _Vdc1uxk , _{Vdc1vxk, Vdc1wxk}
Grid voltage active component command value V _{d_ref} , Grid voltage reactive component command value V _{q_ref}
A phase ωt synchronized with the three-phase system voltage values V _u , V _v , and V _w .

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.

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 becomes the primary DC voltage all-cell average value _{Vdc1_ave} .

The first subtractor 3 obtains a deviation between the primary side DC voltage average value command value _{Vdc1_ave_ref} and the primary side DC voltage all-cell average value _{Vdc1_ave} . The first amplifier (PI amplifier) 4 amplifies the output of the first subtractor 3 and outputs it as a system current active component command value _{id_ref} .

A PLL (Phase Locked Loop) 5 receives the three-phase system voltage values _Vu , _Vv , and _Vw , and outputs a phase ωt synchronized with the system.

The first dq converter 6 receives the three-phase system voltage values _Vu , _Vv , _Vw and the phase ωt, performs dq conversion, and outputs values on the rotating coordinate system synchronized with the system (system voltage active component _Vd , system voltage reactive component _Vq ). The system voltage reactive component _Vq output by the first dq converter 6 is zero in the steady state if the PLL 5 is normal.

The second dq converter 7 inputs the three-phase system current values _iu , _iv , _iw and the phase ωt, performs dq conversion, and outputs values on the rotating coordinate system synchronized with the system (system current active component _id , system current reactive component _iq ).

The second subtractor 8 of the system current control unit 13 obtains the deviation between the system current active component command value i _{d_ref} , which is the output of the first amplifier 4, and the system current active component i _d , which is the output of the second dq converter 7. The third subtractor 9 obtains the deviation between the system current reactive component command value i _{q_ref} and the system current reactive component i _q, which is the output of the second dq converter 7. Here, the system current reactive component command value i _{q_ref} is adjusted in accordance with the power factor.

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 become a system voltage active component command value V _{d_ref} and a system voltage reactive component command value V _{q_ref} on the rotating coordinate system.

The primary side DC voltage intra-phase balance control unit 14 and gate generation (generation of on/off commands for switching elements) in Figure 2(b) are configured as follows.

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 phase 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 calculate the primary DC voltage intra-phase average value _{Vdc1a_ave} of each phase.

A fourth subtractor 17 calculates the deviation between the primary DC voltage in-phase average value _{Vdc1a_ave} of each phase and the primary DC voltage _Vdc1uxk of each cell in the phase. 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 sign of the system current value ( _iu ). The output of the first multiplier 19 becomes the primary DC voltage in-phase balance control value of each cell in each phase. The primary DC voltage in-phase balance control values are outputted for each phase m times (i.e., the number of cells).

The dq inverter 20 receives the system voltage active component command value _{Vd_ref} , the system voltage reactive component command value _{Vq_ref} , and the phase ωt on the rotating coordinate system, and converts the values on the rotating coordinate system synchronized with the system into values on the fixed coordinate system. The multipliers 21u, 21v, and 21w multiply the output of the dq inverter 20 by the primary side DC voltage all-cell average value _{Vdc1_ave} .

The fifth subtractors 22u, 22v, 22w calculate the difference between the outputs of the multipliers 21u, 21v, 21w and the primary side DC voltage balance control value of each phase and each cell. The outputs of the fifth subtractors 22u, 22v, 22w become the three-phase voltage command values _{Vu_ref1} ... _{Vu_refm} , _{Vv_ref1} ... _{Vv_refm} , _{Vw_ref1} ... _{Vw_refm} of the AC-DC converter ACDC in each phase and each cell.

The PWM controllers 23u, 23v, and 23w perform PWM processing based on the three-phase voltage command values _{Vu_ref1} ... _{Vu_refm} , _{Vv_ref1} ... _{Vv_refm} , _{Vw_ref1} ... _{Vw_refm} of the AC-DC converter ACDC, convert them into gate signals, and input them to the switching elements of each cell of the AC-DC converter ACDC.

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

The following signals are input to this control unit.

Secondary side DC voltage command values V _{dc21_ref} , V _{dc22_ref}
Primary side DC voltage V _dc1a1k of the cell connected to DC bus V _dc21 (or V _dc22 ).

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

The third sum calculation unit 26 of the primary DC voltage individual balance control unit 24 calculates the sum of the primary DC voltages of the cells connected to each DC bus _Vdc21 (or _Vdc22 ). In the present embodiment 1, the total number of cells is 3m, and there are two DC buses, so the sum is the primary DC voltages of 3m/2 cells. The third average 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 DC bus primary DC voltage average value _{Vdc11_ave,} which is the average value of the primary DC voltages of the cells connected to each DC bus _Vdc21 (or _Vdc22 ).

The band elimination filter (BEF) 28 removes the double system frequency component of the primary side DC voltage of each cell connected to the DC bus _Vdc21 (or DC bus _Vdc22 ). The fifth subtractor 29 obtains the difference between the DC bus primary side DC voltage average value _{Vdc11_ave} and the output of the band elimination filter 28 corresponding to each cell. The fifth amplifier (P amplifier) 30 amplifies the output of the fifth subtractor 29. The second multiplier 31 obtains the product of the output of the fifth amplifier 30 and the turns ratio _N1 / _N2 of the transformer of the AC-DC converter ACDC and the transformer of the isolated DC-DC converter DCDC. Here, _N1 is the number of turns of the transformer of the AC-DC converter ACDC, and _N2 is 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 number of outputs of the second multiplier 31 is 3m/2 for x=1 and x=2).

The sixth subtractor 32 of the secondary DC voltage individual control unit 25 obtains the difference between the secondary DC voltage command value _{Vdc21_ref} and the secondary DC voltage _Vdc21 (or the secondary DC voltage command value _{Vdc22_ref} and the secondary DC voltage _Vdc22 ). 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 secondary DC voltage individual control value.

The seventh subtractor 35 takes 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 for x=1 and x=2).

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). 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.

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.

[Explanation of Action and Operation]
In a configuration having multiple DC buses ( _Vdc21 , _Vdc22 ) as in the configuration of Fig. 1, two secondary DC outputs are connected in series, and a load or power source is connected to each DC bus ( _Vdc21 , _Vdc22 ) and the output ( _Vdc21 + _Vdc22 ) in which each DC terminal is connected in series. Therefore, a power imbalance occurs in each DC bus _Vdc21 , _Vdc22 . Therefore, when the power imbalance occurs in each DC bus, it is necessary to output a voltage while maintaining the voltage balance between the secondary DC voltage ( _Vdc21 , _Vdc22 ) which is the voltage of the DC bus and the primary DC voltage _Vdc1axk which is the voltage of the primary DC capacitor C1 of each cell.

The control of the AC-DC converter ACDC involves primary side DC voltage phase balance control and primary side DC voltage average value control.

2A, the all-cell primary DC voltage average value control unit 12 amplifies the deviation between the all-cell primary DC voltage average value _{Vdc1_ave} and the primary DC voltage average value command value _{Vdc1_ave_ref} by the first amplifier 4, and outputs the grid current active component command value _{id_ref} on the rotating coordinate system. In addition, the power factor of the grid current can be controlled by calculating the grid current reactive component command value _{iq_ref} on the rotating coordinate system from the power factor command value.

In the system current control unit 13, the second and third amplifiers 10 and 11 output a system voltage active component command value _{Vd_ref} and a system voltage reactive component command value _{Vq_ref} on the rotating coordinate system using the deviation between the system current active component command value _{Id_ref} and the system current reactive component command value _{iq_ref} and the system current active component _id and the system current reactive component _iq .

In Figure 2(b), primary side DC voltage intra-phase balance control is performed. Balance control is achieved by adjusting the ACDC voltage command value of each cell.

First, the deviation between the primary DC voltage in-phase average value _{Vdc1u_ave} and the primary DC voltage _Vdc1uxk of each cell in the phase 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 multiplied by the output of the fourth amplifier 18.

Next, the system voltage active component command value _{Vd_ref} on the rotating coordinate system, the system voltage reactive component command value _{Vq_ref,} and the phase difference ωt synchronized with the system voltage are converted to three-phase coordinates by the dq inverter 20. A three-phase voltage command value that does not take into account the imbalance in the primary DC voltage is calculated by multiplying the output of the dq inverter 20 and the primary DC voltage all-cell average value _{Vdc1_ave} .

The voltage command value for each phase is calculated by taking the difference between the primary DC voltage intra-phase balance control value of each cell of each phase and the three-phase voltage command value that does not take into account the imbalance of the primary 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.

In the control of the isolated DC-DC converter DCDC in FIG. 3, individual balance control of the primary side DC voltage and individual control of the secondary side DC voltage are performed for each DC bus (V _dc21 , V _dc22 ).

The primary DC voltage individual balance control unit 24 balances the primary DC voltages of the cells connected to the DC bus _Vdc21 (x=1) or the DC bus _Vdc22 (x=2). However, a voltage ripple of twice the system frequency occurs in the primary DC voltage of each phase. This voltage ripple can cause control instability if the gain of the P control is increased, so the voltage is passed through a band elimination filter (BEF) 28 that removes only the twice the system frequency.

The output of the fifth amplifier 30 becomes the current of the primary side DC capacitor C1, and is converted into the current of the secondary side DC capacitor C2 by multiplying the output of the fifth amplifier 30 by the transformer turns ratio _N1 / _N2 .

Next, the secondary DC voltage individual control unit 25 inputs the deviation between the secondary DC voltage command value _{Vdc21_ref} and the secondary DC voltage _Vdc21 to the sixth amplifier 33. The output of the sixth amplifier 33 is multiplied by the reciprocal of the number of cells connected to the DC bus, 3m/2, to convert it into the current _idc21 of the secondary DC capacitor C2 of each cell.

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 and used as a command value for the secondary DC capacitor current. The command value for the secondary DC capacitor current and the primary DC voltage connected to the DC bus _Vdc21 (x=1) are 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 the frequency command value is input to a PWM controller 37 to generate a gate signal for the isolated DC-DC converter DCDC.

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 the PI controller is converted to the 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 the duty command value.

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 equation between a current command value and a phase difference. Next, as an example of a PWM controller, as in patent document 2, a gate signal is generated that achieves the phase difference command value by comparing a sawtooth carrier with the phase difference command value.

[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 condition.

In addition, compared to Non-Patent Document 1 and Patent Document 1, this 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, making it possible to avoid increases in size and cost.

In addition, compared to Non-Patent Document 2, it is possible to reliably perform balance control of the DC voltage of each cell, which reduces the device's voltage resistance and avoids increases in size and cost.

With this embodiment 1, it is possible to simply increase the control blocks according to the number of series (x) in the DC bus, so software implementation is simple when changing the number of series in the DC bus.

[Embodiment 2]
The main circuit and the control unit of the AC-DC converter ACDC in the present embodiment 2 are similar to 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 DC voltage individual balance control unit 38, a secondary DC voltage balance control unit 39, and a secondary DC voltage total value control unit 40 (which may be a current control unit).

Compared to embodiment 1, this control unit inputs the following additional signals:

Secondary side DC voltage total value command value V _{dc2_ref}
Secondary side DC voltage total value _Vdc21 + _Vdc22
Secondary-side DC voltage average value _{Vdc2_ave} of secondary-side DC voltages _Vdc21 and _Vdc22 .

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 embodiment 1 (FIG. 3). In the control unit of the isolated DC-DC converter DCDC in FIG. 4, the following blocks are added and modified from those in embodiment 1.

The eighth subtractor 42 of the secondary DC voltage balance control unit 39 calculates the difference between the secondary DC voltage _Vdc21 (or _Vdc22 ) and the secondary DC voltage average value _{Vdc2_ave} . The seventh amplifier (P amplifier) 43 amplifies the output of the eighth subtractor 42. The output of the seventh amplifier 43 becomes the secondary DC voltage balance control value.

The first adder 44 takes the sum of 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).

The ninth subtractor 45 of the secondary DC voltage total value control unit 40 obtains the difference between the secondary DC voltage total value command value _{Vdc2_ref} and the secondary DC voltage total value _Vdc21 + _Vdc22 . 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 1/3n of the total number of cells in the three phases. 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 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.

[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 components in the first embodiment.

The secondary DC voltage total value control unit 40 controls the secondary DC voltage total value _Vdc21 + _Vdc22 . 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.

First, the deviation between the secondary DC voltage average value _{Vdc2_ave} of each secondary DC voltage _Vdc21 , _Vdc22 and each secondary DC voltage _Vdc21 , _Vdc22 is input to the seventh amplifier 43. Next, the output of the seventh amplifier 43 and the output of the primary 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.

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

In this second embodiment, there is only one secondary DC voltage control unit, regardless of the number of serial cells connected to the DC bus. Therefore, since voltage control and current control can be switched during operation, it can also be applied to large-capacity battery charging/discharging devices that require constant voltage charging (voltage control) and constant current charging (current control).

The present invention has been described in detail above only with respect to the specific examples described. However, it will be clear to those skilled in the art that various modifications and alterations are possible within the scope of the technical concept of the present invention, and it goes without saying that such modifications and alterations fall within the scope of the claims.

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

Claims (11)

An ACDC power supply comprising 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 a 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 which supplies voltages of the plurality of DC buses to a load or a power source,
When a power imbalance occurs due to the condition of the load or the power source, a voltage is output while maintaining a voltage balance between a secondary side DC voltage, which is the voltage of the DC bus, and a primary side DC voltage, which is the voltage of the primary side DC capacitor of each cell;
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 the primary-side DC voltage average value command value and the primary-side DC voltage all-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 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,
converting the system voltage active component command value and the system voltage reactive component command value into values on a fixed coordinate system, multiplying the converted value by the primary side DC voltage all-cell average value, subtracting the primary side DC voltage intra-phase balance control value from the resulting value to generate a voltage command value for each phase, and generating a gate signal for the AC-DC converter based on the 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;
a secondary DC voltage individual control unit that generates a secondary DC voltage individual control value based on the secondary DC voltage;
Equipped with
An ACDC power supply characterized in that current control is performed based on a 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 of the isolated DC-DC converter is generated based on a result of the current control. An ACDC power supply comprising 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 a 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 which supplies voltages of the plurality of DC buses to a load or a power source,
When a power imbalance occurs due to the condition of the load or the power source, a voltage is output while maintaining a voltage balance between a secondary side DC voltage, which is the voltage of the DC bus, and a primary side DC voltage, which is the voltage of the primary side DC capacitor of each cell;
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 the primary-side DC voltage average value command value and the primary-side DC voltage all-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 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,
converting the system voltage active component command value and the system voltage reactive component command value into values on a fixed coordinate system, multiplying the converted value by the primary side DC voltage all-cell average value, subtracting the primary side DC voltage intra-phase balance control value from the resulting value to generate a voltage command value for each phase, and generating a gate signal for the AC-DC converter based on the 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;
a secondary DC voltage balance control unit that generates a secondary DC voltage balance control value based on a secondary DC voltage;
a secondary DC voltage total value control unit that generates a secondary DC voltage total value control value based on the secondary DC voltage total value command value and the secondary DC voltage total value;
Equipped with
an ACDC power supply performing 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 generating a gate signal for the isolated DC-DC converter based on a result of the current control. The primary side DC voltage average value control unit is
a first sum calculation unit that calculates a sum of the primary DC voltages of all the cells and outputs the sum as a primary 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 value and the reciprocal of the total number of cells;
A first subtractor that calculates a deviation between the primary side DC voltage average command value and the primary side DC voltage all-cell average value;
a first amplifier that amplifies an output of the first subtractor and outputs the amplified output as the grid current active component command value;
3. The ACDC power supply according to claim 1, further comprising : The system 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 system voltage active component command value;
a third subtractor that subtracts a grid current reactive component from the grid current reactive component command value;
a third amplifier that amplifies an output of the third subtractor and outputs the amplified output as the system voltage reactive component command value;
3. The ACDC power supply according to claim 1, further comprising : The primary side 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 in-phase sum;
an in-phase average value calculation unit that calculates an in-phase average value of the primary DC voltage of each phase from the product of the in-phase total value of the primary DC voltage and the reciprocal of the number of cells in the phase; and a fourth subtractor that calculates a deviation between the in-phase average value of the primary DC voltage 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;
a first multiplier that multiplies an output of the fourth amplifier by a sign of a system current value of each phase and outputs the result as the primary side DC voltage intra-phase balance control value;
3. The ACDC power supply according to claim 1, further comprising : 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 a 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 a double system frequency component of the primary side DC voltage of the cell connected to each DC bus;
a fifth subtractor that outputs a difference between the DC bus primary side DC voltage average value and the output of the band elimination filter;
a fifth amplifier that amplifies an output of the fifth subtractor;
a second multiplier that multiplies an 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;
3. The ACDC power supply according to claim 1, further comprising : The secondary side DC voltage individual control unit includes:
a sixth subtractor that calculates a difference between the secondary DC voltage command value and the secondary DC voltage of each of the DC buses;
a sixth amplifier that amplifies an output of the sixth subtractor;
a third multiplier that multiplies an output of the sixth amplifier by the reciprocal of the number of cells connected to the DC bus, and outputs the multiplied value as the secondary-side DC voltage individual control value;
2. The ACDC power supply of claim 1, comprising : The secondary side DC voltage balance control unit includes:
an eighth subtractor that calculates a deviation between the average secondary DC voltage and the secondary DC voltage of each DC bus;
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;
3. The ACDC power supply of claim 2, further comprising: The secondary DC voltage total value control unit is
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 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 the product as the secondary side DC voltage total value control value;
3. The ACDC power supply of claim 2, further comprising: A method for controlling an ACDC power supply comprising: m (m: an integer of 2 or more) cells per phase, each cell including an AC/DC converter, a primary side DC capacitor connected to a 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 a voltage of the plurality of DC buses is supplied to a load or a power source, the method comprising:
The control unit outputs a voltage while maintaining a voltage balance between a secondary side DC voltage, which is the voltage of the DC bus, and a primary side DC voltage, which is the voltage of the primary side DC capacitor of each cell, when a power imbalance occurs due to a state of the load or the power source;
The control unit of the AC/DC converter includes:
A primary-side DC voltage average value control unit generates a grid current active component command value based on the primary-side DC voltage average value command value and the primary-side DC voltage all-cell average value,
a system current control unit 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 DC voltage intra-phase balance control unit 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,
converting the system voltage active component command value and the system voltage reactive component command value into values on a fixed coordinate system, multiplying the converted value by the primary side DC voltage all-cell average value, subtracting the primary side DC voltage intra-phase balance control value from the resulting value to generate a voltage command value for each phase, and generating a gate signal for the AC-DC converter based on the voltage command value;
The control unit of the isolated DC-DC converter includes:
a primary-side DC voltage individual balance control unit generating a primary-side DC voltage individual balance control value based on the primary-side DC voltage;
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;
A method for controlling an ACDC power supply, comprising: performing current control based on a 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 generating a gate signal for the isolated DC-DC converter based on a result of the current control . A method for controlling an ACDC power supply comprising: m (m: an integer of 2 or more) cells per phase, each cell including an AC/DC converter, a primary side DC capacitor connected to a 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 a voltage of the plurality of DC buses is supplied to a load or a power source, the method comprising:
The control unit outputs a voltage while maintaining a voltage balance between a secondary side DC voltage, which is the voltage of the DC bus, and a primary side DC voltage, which is the voltage of the primary side DC capacitor of each cell, when a power imbalance occurs due to a state of the load or the power source;
The control unit of the AC/DC converter includes:
A primary-side DC voltage average value control unit generates a grid current active component command value based on the primary-side DC voltage average value command value and the primary-side DC voltage all-cell average value,
a system current control unit 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 DC voltage intra-phase balance control unit 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,
converting the system voltage active component command value and the system voltage reactive component command value into values on a fixed coordinate system, multiplying the converted value by the primary side DC voltage all-cell average value, subtracting the primary side DC voltage intra-phase balance control value from the resulting value to generate a voltage command value for each phase, and generating a gate signal for the AC-DC converter based on the voltage command value;
The control unit of the isolated DC-DC converter includes:
a primary-side DC voltage individual balance control unit generating a primary-side DC voltage individual balance control value based on the primary-side DC voltage;
a secondary DC voltage balance control unit that generates a secondary DC voltage balance control value based on the secondary DC voltage;
a secondary DC voltage total value control unit that generates a secondary DC voltage total value control value based on the secondary DC voltage total value command value and the secondary DC voltage total value;
a control method for an ACDC power supply, characterized in that current control is performed 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 generating a gate signal for the isolated DC-DC converter based on a result of the current control.

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