JP2016127679A - Power converter and control method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter, etc. that can greatly reduce the DC voltage variation of an inverter even in a general configuration that respective transformers are connected to one another in parallel.SOLUTION: In a power converter which has plural first power conversion circuits for converting AC power of plural phases from an AC power source to DC voltages, plural second power conversion circuits for converting the respective converted DC voltages to AC power of plural phases and outputting the AC power to a load circuit, and control means for controlling the plural first and second power conversion circuits, the control means performs feed-forward control on the plural first power conversion circuits based on load current flowing in the load circuit and a voltage instruction value of the load circuit so that the deviation of the respective DC voltages is reduced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power converter including a plurality of converters and a plurality of single-phase inverters, and controlling the plurality of converters based on load information to suppress fluctuations in DC voltage and a control method thereof.

  Patent Document 1 discloses a power conversion device for reducing fluctuations in a DC link voltage without increasing the capacity of a DC link capacitor of the power conversion device.

  In Patent Document 1, the power conversion device includes a converter that converts a three-phase AC voltage into a DC voltage of each phase of the three-phase AC load, and each of the phases of the three-phase AC load. And an inverter for converting into a single-phase AC voltage. The power converter includes a capacitor connected between a converter and an inverter, and the converter has a circuit including a plurality of switching elements connected in series for each phase of the power system. In this power converter, for each phase of the power system, a voltage for reducing fluctuations in DC voltage corresponding to each phase of the three-phase AC load between the converter and the inverter is output from the converter. Further, on / off control of the switching element corresponding to any phase of the power system in the converter is performed.

JP 2014-090581 A

  Patent Document 1 proposes a control law for reducing the DC voltage deviation of a single-phase inverter, but a transformer connected to the converter is configured such that three converter output end transformers are connected in series. There is a problem that it cannot be applied in a general configuration in which each transformer is connected in parallel.

  Moreover, it is necessary to switch a control law according to the positive / negative of electric power. Further, the feedback control is performed by detecting a change in the DC voltage itself, and a transient voltage fluctuation is unavoidable with respect to a sudden load fluctuation.

  Furthermore, in the configuration in which the system-side transformer of each converter corresponding to the single-phase inverter is parallel, it is inevitable that the load power shared by the single-phase inverter is vibrated by the three-phase AC load connected to the inverter. In order to suppress the DC voltage fluctuation, there is a problem that it is necessary to cope with the converter.

  An object of the present invention is to provide a power conversion device and a control method thereof that can significantly reduce the DC voltage deviation of an inverter even in a general configuration in which transformers are connected in parallel.

The power conversion device according to the first invention is:
A plurality of first power conversion circuits for converting each of a plurality of phases of AC power from an AC power source into a DC voltage;
A plurality of second power conversion circuits that convert each of the converted DC voltages into a plurality of phases of AC power and output the same to a load circuit;
A power conversion device comprising a control means for controlling the plurality of first and second power conversion circuits,
The control means performs feedforward control of the plurality of first power conversion circuits so that a deviation between the DC voltages is reduced based on a load current flowing through the load circuit and a voltage command value of the load circuit. It is characterized by.

  In the power converter, the control means has a load current flowing through the load circuit, a voltage command value of the load circuit, and a deviation of each of the DC voltages, each being twice the AC phase on the load circuit side, and Deviation of each DC voltage in the rotating coordinate system in which the phase power fluctuation of the load circuit is converted to DC by converting into load current, voltage command value and DC voltage deviation of a predetermined rotating coordinate system rotating in reverse phase The plurality of first power conversion circuits are feedforward controlled so as to be small.

The power converter according to the second invention is
A plurality of first power conversion circuits for converting each of a plurality of phases of AC power from an AC power source into a DC voltage;
A plurality of second power conversion circuits that convert each of the converted DC voltages into a plurality of phases of AC power and output the same to a load circuit;
A power conversion device comprising a control means for controlling the plurality of first and second power conversion circuits,
The control means performs feedforward control on the plurality of second power conversion circuits so that a deviation between the DC voltages is reduced based on a power supply current flowing from the AC power supply and a voltage command value of the AC power supply. It is characterized by.

  In the power converter, the control means is configured such that a power source current flowing through the AC power source, a voltage command value of the AC power source, and a deviation of each DC voltage are each twice the AC phase on the AC power source side, and The deviation of each DC voltage in the rotating coordinate system in which the phase power fluctuation of the AC power source is converted to DC by converting the load current, voltage command value and each DC voltage deviation of a predetermined rotating coordinate system rotating in reverse phase. The plurality of second power conversion circuits are feedforward controlled so as to be small.

  In the power conversion device, the control means may further feedback control the plurality of second power conversion circuits so that a difference between each DC voltage and a predetermined corresponding voltage deviation is reduced. Features.

  Further, in the power conversion device, the control means converts the DC voltages into deviations of DC voltages in a predetermined rotating coordinate system that is twice the AC phase and rotates in the opposite phase. A plurality of second power conversion circuits are feedback-controlled.

  Furthermore, the power conversion device further includes a smoothing circuit that is inserted between the first voltage-current conversion circuit and the second power conversion circuit and includes a plurality of capacitors.

  Still further, in the power conversion device, each of the first power conversion circuits is a converter, and each of the second power conversion circuits is a converter.

The control method of the power converter according to the third invention is:
A plurality of first power conversion circuits for converting each of a plurality of phases of AC power from an AC power source into a DC voltage;
A plurality of second power conversion circuits that convert each of the converted DC voltages into a plurality of phases of AC power and output the same to a load circuit;
A control method for a power conversion device comprising a control means for controlling the plurality of first and second power conversion circuits,
Control in which the control means performs feedforward control of the plurality of first power conversion circuits so that a deviation between the DC voltages is reduced based on a load current flowing through the load circuit and a voltage command value of the load circuit. Including steps.

  In the control method of the power converter, the control step includes a load current flowing through the load circuit, a voltage command value of the load circuit, and a deviation of each of the DC voltages, each being twice the AC phase on the load circuit side. The load current, voltage command value, and deviation of each DC voltage of a predetermined rotating coordinate system that rotates in the opposite phase are converted into deviations of each DC voltage, and each DC power in the rotating coordinate system in which the phase power fluctuation of the load circuit is converted to DC The plurality of first power conversion circuits are feedforward controlled so that a deviation in voltage is small.

The control method of the power converter according to the fourth invention is:
A plurality of first power conversion circuits for converting each of a plurality of phases of AC power from an AC power source into a DC voltage;
A plurality of second power conversion circuits that convert each of the converted DC voltages into a plurality of phases of AC power and output the same to a load circuit;
A control method for a power conversion device comprising a control means for controlling the plurality of first and second power conversion circuits,
Control in which the control means feeds forward-controls the plurality of second power conversion circuits so that a deviation between the DC voltages is reduced based on a power supply current flowing from the AC power supply and a voltage command value of the AC power supply. Including steps.

  In the control method of the power conversion device, the control step includes a power source current flowing through the AC power source, a voltage command value of the AC power source, and a deviation of each DC voltage at twice the AC phase on the AC power source side. In the rotating coordinate system in which the phase power fluctuation of the AC power source is converted to DC by converting the load current, the voltage command value and the deviation of each DC voltage in a predetermined rotating coordinate system that rotates in reverse phase. The plurality of second power conversion circuits are feedforward controlled so that a deviation in voltage is small.

  In the control method of the power converter, the control step further feedback-controls the plurality of second power converter circuits so that a difference between each DC voltage and a predetermined corresponding voltage deviation is reduced. It is characterized by doing.

  Furthermore, in the method for controlling the power converter, the control step converts each DC voltage into a deviation of each DC voltage in a predetermined rotating coordinate system that is twice the AC phase and rotates in the opposite phase. Thus, the plurality of second power conversion circuits are feedback-controlled.

  Therefore, according to the power conversion device or the like according to the present invention, the DC voltage deviation of the inverter can be greatly reduced even in a general configuration in which the transformers are connected in parallel.

It is a block diagram which shows the structural example of the power converter device which concerns on Embodiment 1. FIG. It is a circuit diagram which shows the structural example of the converter 5 of FIG. It is a circuit diagram which shows the structural example of the inverter 6 of FIG. It is a figure which shows the relationship between the electric power system side abc phase and the DQ axis | shaft of a rotation coordinate system in the power converter device of FIG. It is a figure which shows the relationship between the xyz phase of a three-phase alternating current load and the dq axis | shaft of a rotating coordinate system in the power converter device of FIG. FIG. 2 is a diagram illustrating a relationship between an xyz axis of a DC voltage side Q-axis component and a δγ axis of a rotating coordinate system in the power conversion device of FIG. 1. It is a block diagram which shows the structural example of the arithmetic control circuit 50 in the converter control part 10a of the control apparatus 10 of FIG. It is a block diagram which shows the structural example of the arithmetic control circuit 70 in the converter control part 10a of the control apparatus 10 of FIG. It is a block diagram which shows the structural example of the power converter device which concerns on Embodiment 2. FIG. It is a simulation result of the power converter device of FIG. 1, Comprising: It is a graph which shows the x phase high voltage | pressure side DC voltage and x phase low voltage | pressure side DC voltage without correction control. It is a simulation result of the power converter device of FIG. 1, Comprising: It is a graph which shows the x phase high voltage | pressure side DC voltage and x phase low voltage | pressure side DC voltage with correction | amendment control.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each following embodiment, the same code | symbol is attached | subjected about the same component.

Embodiment 1. FIG.
FIG. 1 is a block diagram illustrating a configuration example of the power conversion apparatus according to the first embodiment. 1 includes a circuit breaker 2, a three-phase transformer 3, voltage detectors 11 and 12, a triple three-phase transformer 4, current detectors 21 to 29, and a first power conversion circuit. Single-phase converters 5-1, 5-2, and 5-3 (generally referred to as individual converter 3), voltage detectors 31 to 36, and six electrolytic capacitors each. Smoothing circuit 9 comprising capacitors C _px , C _nx , C _py , C _ny , C _pz , and C _nz, and single-phase inverters 6-1, 6-2, 6-3 (second power conversion circuits) And the current detectors 41 to 43 and the control device 10 are provided. Here, the power converter converts the AC power from the power system 1 into a DC voltage by the converters 5-1, 5-2, and 5-3, and then converts the AC power by the inverters 6-1, 6-2, and 6-3. The motor 8 which is a synchronous rotating machine is driven by converting into voltage. Here, the motor 8 includes an angle sensor 8s that outputs an angle sensor signal. The control device 10 is composed of a controller such as a digital computer, for example, and controls the operation of each converter 5 based on the load current detected by the current detectors 41 to 43, and the control from the converter control unit 10a. An inverter control unit 10b that controls the operation of each inverter 6 based on the signal, and arithmetic control circuits 50 and 70 described later in detail with reference to FIGS. 7 and 8 are provided.

  In FIG. 1, the three-phase AC power in the circuit from the three-phase power system 1 to the converters 5-1, 5-2, and 5-3 has three phases of a phase, b phase, and c phase. Append “grid” to the subscript. Further, “C” is added to the suffixes of the voltage and capacitor names processed by the voltage detectors 31 to 36 and the smoothing circuit 9. Further, the three-phase AC power in the circuit from the inverters 6-1, 6-2, 6-3 to the motor 8 has three phases of x-phase, y-phase, and z-phase. gen ".

In FIG. 1, the power converter is divided into the following three group circuits, and “x”, “y”, and “z” are added to the subscripts of the symbols of the respective parameters.
(1) x group circuit: A circuit from the current detectors 21 to 23 to the current detector 41 through the converter 5-1, the voltage detectors 31 and 32, the capacitors C _px and C _nx , and the inverter 6-1.
(2) y group circuit: A circuit from the current detectors 24 to 26 to the current detector 42 through the converter 5-2, the voltage detectors 33 and 34, the capacitors C _py and C _ny , and the inverter 6-2.
(3) z group circuit: A circuit from the current detectors 27 to 29 to the current detector 43 through the converter 5-3, the voltage detectors 35 and 36, the capacitors _Cpz and _Cnz , and the inverter 6-3.

In FIG. 1, a voltage detector 11 detects and controls an AC voltage Vab between a phase and b phase of three-phase AC power input from a three-phase power system 1 via a circuit breaker 2 and a three-phase transformer 3. The controller 10 detects the AC voltage Vbc between the b-phase and the c-phase of the three-phase AC power output to the device 10 and input from the three-phase power system 1 through the circuit breaker 2 and the three-phase transformer 3. Output to. The triple three-phase transformer 4 divides the input voltage of the three-phase AC power into three, and the divided first three-phase AC voltage is supplied to the terminals T1 to T1 of the converter 5-1 through the current detectors 21 to 23. Output to T3, and output the divided second three-phase AC voltage to terminals T1 to T3 of converter 5-2 via current detectors 24 to 26, and output the divided third three-phase AC voltage as current. It outputs to the terminals T1 to T3 of the converter 5-3 via the detectors 21 to 23. Here, the current detector 21 detects the current i _gridxa and outputs it to the control device 10, the current detector 22 detects the current i _gridxb and outputs it to the control device 10, and the current detector 23 outputs the current i _gridxc . Detect and output to the control device 10. Further, the current detector 24 detects the current i _gridya and outputs it to the control device 10, the current detector 25 detects the current i _gridyb and outputs it to the control device 10, and the current detector 26 detects the current i _gridyc . And output to the control device 10. Furthermore, the current detector 27 detects the current i _gridza and outputs it to the control device 10, the current detector 28 detects the current i _gridzb and outputs it to the control device 10, and the current detector 29 detects the current i _gridzc . And output to the control device 10.

  FIG. 2 is a circuit diagram showing a configuration example of the converter 5 of FIG. In FIG. 2, the converter 5 includes a plurality of switching transistors and a plurality of backflow prevention protection diodes as is well known, and is input to terminals T1 to T3 based on a control signal from the converter control unit 10a. The three-phase AC voltage is converted into a predetermined DC voltage and output through terminals T4 to T6.

In FIG. 1, the DC voltage from terminals T4 and T5 of converter 5-1 is output to terminals T11 and T12 of inverter 6-1 via voltage detector 31 and capacitor C _px, and terminal T5 of converter 5-1. , T6 are output to terminals T12 and T13 of the inverter 6-1 through the voltage detector 32 and the capacitor _Cnx . Further, the DC voltage from the terminals T4 and T5 of the converter 5-2 is output to the terminals T11 and T12 of the inverter 6-2 via the voltage detector 32 and the capacitor _Cpy, and the terminals T5 and T6 of the converter 5-2. Is output to the terminals T12 and T13 of the inverter 6-2 through the voltage detector 34 and the capacitor _Cny . Further, the DC voltage from the terminals T4 and T5 of the converter 5-3 is output to the terminals T11 and T12 of the inverter 6-3 via the voltage detector 35 and the capacitor _Cpz, and the terminals T5 and T6 of the converter 5-3. Is output to the terminals T12 and T13 of the inverter 6-3 through the voltage detector 36 and the capacitor _Cnz .

The voltage detector 31 detects the voltage V _px of the DC voltage from the terminals T4 and T5 of the converter 5-1, and outputs it to the control device 10, and the voltage detector 32 outputs the DC voltage from the terminals T5 and T6 of the converter 5-1. The voltage −V _nx of the voltage is detected and output to the control device 10. The voltage detector 33 detects the voltage V _py of the DC voltage from the terminals T4 and T5 of the converter 5-2 and outputs it to the control device 10, and the voltage detector 34 is supplied from the terminals T5 and T6 of the converter 5-2. _Is detected and output to the control device 10. Further, the voltage detector 35 detects the DC voltage V _pz from the terminals T4 and T5 of the converter 5-3 and outputs it to the control device 10, and the voltage detector 36 is supplied from the terminals T5 and T6 of the converter 5-3. _Is detected and output to the control device 10.

  FIG. 3 is a circuit diagram showing a configuration example of the inverter 6 of FIG. In FIG. 3, the inverter 6 includes a plurality of switching transistors and a plurality of backflow prevention protection diodes as is well known, and is input to terminals T11 to T13 based on a control signal from the inverter control unit 10b. The DC voltage is switched to convert the power into a predetermined three-phase voltage and output through terminals T14 and T15.

In FIG. 1, terminals T <b> 15 of inverters 6-1, 6-2 and 6-3 are connected together to become a three-phase intermediate point 7. Here, the voltage of the three-phase intermediate point 7 is V ₀ . The x-phase AC voltage from the terminal T14 of the inverter 6-1 is output to the motor 8 via the current detector 41, and the y-phase AC voltage from the terminal T14 of the inverter 6-2 is output to the motor 8 via the current detector 42. The z-phase AC voltage from the terminal T14 of the inverter 6-3 is output to the motor 8 via the current detector 43. The current detector 41 detects the x-phase AC load current i _genx and outputs it to the control device 10, and the current detector 42 detects the y-phase AC load current i _geny and outputs it to the control device 10 for current detection. The device 43 detects the z-phase AC load current i _genz and outputs it to the control device 10. The inverters 6-1, 6-2 and 6-3 have a constant motor load power and a constant rotation speed of the motor 8 by the inverter control unit 10 b, and the average value of the three input DC voltage values is It is controlled to be constant.

The DC voltage of the series circuit of each two capacitors of the smoothing circuit 9 in FIG. 1 is defined as follows.
(1) x-phase DC voltage v _{Cx of} a series circuit of capacitors C _px and C _nx ;
(2) y-phase DC voltage v _{Cy of} a series circuit of capacitors C _py and C _ny ;
(3) z-phase DC voltage v _{Cz of} a series circuit of capacitors C _pz and C _nz ;
(4) The average value v _{Coverage of the} DC voltages v _Cx , v _Cy , and v _Cz .

  Next, the relationship between the stationary coordinate system (abc axis, xyz axis) and the rotational coordinate system (DQ axis, dq axis, δγ axis) will be described below with reference to FIGS.

  A transformation matrix A (θ) from a stationary coordinate system to a rotating coordinate system used in the present embodiment is expressed by the following equation.

FIG. 4 is a diagram showing the relationship between the power system side abc phase and the DQ axis of the rotating coordinate system in the power conversion apparatus of FIG. In FIG. 4, θ _grid is a system voltage phase [rad], which is defined by a D-axis phase angle with respect to the a-axis, and is based on the detected values of the AC voltages Vab and Vbc of the power system 1. Calculate by circuit. The D axis rotates at an angular velocity ω _grid .

FIG. 5 is a diagram showing the relationship between the xyz phase of the three-phase AC load and the dq axis of the rotating coordinate system in the power conversion device of FIG. In FIG. 5, θ _gen is the motor magnetic pole phase [rad], which is the d-axis phase angle with respect to the x-axis, and the rotor magnetic pole phase when the three-phase AC load is the motor 8 (rotary machine). And an angle sensor signal from the angle sensor 8s such as a resolver or an encoder, or an estimator based on a current voltage. The d axis rotates at an angular velocity ω _gen .

FIG. 6 is a diagram showing the relationship between the xyz axis of the DC voltage (power system) side Q-axis component and the δγ axis of the rotating coordinate system in the power conversion apparatus of FIG. 1. In FIG. 6, the δ axis is defined by being rotated by −2θ _gen from the x axis, and the γ axis is rotated by 2ω _gen . Here, since there are three converters 5-1, 5-2 and 5-3 for x phase, y phase and z phase, there are also three Q axis components: xQ, yQ and zQ. Note that these are mapped to δγ coordinates.

Here, the DQ conversion is expressed by the following equation using a conversion matrix A (θ _grid ).

Further, the dq conversion is expressed by the following equation using the conversion matrix A (θ _gen ).

Further, the δγ conversion is expressed by the following equation using the conversion matrix A (−2θ _gen ).

Furthermore, a converter output power command value P ^* _grid [W] that is generated by the control device 10 and is to be output from the converters 5-1, 5-2, and 5-3 is defined. Represents an electric power (command) to be output, and is determined by an output command value, DC voltage control, and the like. In this embodiment, the use and purpose are not limited.

The alternating current input to the converter 5-1 of the x group circuit is as follows.
(1) i _gridxa : a-phase current detected by the current detector 21;
(2) i _gridxb : b-phase current detected by the current detector 22;
(3) i _gridxc : c-phase current detected by the current detector 23.

The alternating current input to the converter 5-2 of the y group circuit is as follows.
(1) i _gridya : a-phase current detected by the current detector 24;
(2) i _gridyb : b-phase current detected by the current detector 25;
(3) i _gridyc : c-phase current detected by the current detector 26.

The alternating current input to the converter 5-2 of the z group circuit is as follows.
(1) i _gridza : a-phase current detected by the current detector 27;
(2) i _gridzb : b-phase current detected by the current detector 28;
(3) i _gridzc : c-phase current detected by the current detector 29.

The DQO axis current of the converter 5-1 of the x group circuit is expressed by the following equation using a conversion matrix A (θ _grid ).

The DQO axis current of the converter 5-2 of the y group circuit is expressed by the following equation using the conversion matrix A (θ _grid ).

The DQO axis current of the z-group circuit converter 5-3 is expressed by the following equation using the conversion matrix A (θ _grid ).

The δγε-Q axis current i _grid δγεQ in the rotating coordinate system of the converters 5-1, 5-2, and 5-3 is expressed by the following equation using the conversion matrix A (−2θ _gen ).

  The DC voltage deviation output from converters 5-1, 5-2, 5-3 is expressed by the following equation.

  The δγε axis DC voltage deviation in the rotating coordinate system is expressed by the following equation.

Next, the three-phase AC load information output from the inverters 6-1, 6-2, 6-3 to the motor 8 is as follows.
(1) v ^* _genx : a command value for the x-phase load voltage of the three-phase AC load, and a command value for the output voltage from the inverter 6-1.
(2) v ^* _geny : the command value of the y-phase load voltage of the three-phase AC load, and the command value of the output voltage from the inverter 6-2.
(3) v ^* _genz : a command value for the z-phase load voltage of the three-phase AC load, and a command value for the output voltage from the inverter 6-3.
(4) i _genx : x-phase load current of the three-phase AC load detected by the current detector 41.
(5) _igeny : the y-phase load current of the three-phase AC load detected by the current detector 42.
(6) i _genz : z-phase load current of the three-phase AC load detected by the current detector 43.

Further, the dq-axis voltage command value [V] of the inverters 6-1, 6-2 and 6-3 is expressed by the following equation using the conversion matrix A (θ _gen ). The command values v ^* _genx , v ^* _geny , and v ^* _genz are generated by the converter control unit 10a.

Furthermore, the dq-axis current of the three-phase AC load of inverters 6-1, 6-2, and 6-3 is expressed by the following equation using conversion matrix A (θ _gen ). The load current values _i.sub.genx , _i.sub.geny , and _i.sub.genz are detected by current detectors 41, 42, and 43, respectively.

  FIG. 7 is a block diagram illustrating a configuration example of the arithmetic control circuit 50 in the converter control unit 10a of the control device 10 of FIG. In FIG. 7, an arithmetic control circuit 50 is a circuit for controlling the DC voltage deviation of the δγε coordinate, and includes multipliers 51 to 59, a subtractor 61, an adder 62, dividers 63 to 65, and an addition. And 66, 67.

In FIG. 50, a multiplier 51 multiplies the motor load d-axis voltage command value v ^* _gend calculated by Expression (9) by the motor load d-axis current _igend calculated by Expression (10). The result value is output to the subtractor 61. The multiplier 52 multiplies the motor load d-axis current _igend by the motor load q-axis voltage command value v ^* _genq calculated by the equation (9) and outputs the multiplication result value to the adder 62. Furthermore, the multiplier 53 multiplies the motor load q-axis voltage command value v ^* _genq by the motor load q-axis current i _genq calculated by Expression (10) and outputs the multiplication result value to the subtractor 61. Furthermore, the multiplier 54 multiplies the motor load d-axis voltage command value v ^* _gennd by the motor load q-axis current i _genq and outputs the multiplication result value to the adder 62.

の乗算係数を有する乗算器５５を介して除算器６３に出力する。加算器６２は、乗算器６２からの乗算結果値と、乗算器５４からの乗算結果値とを加算して加算結果値を、

の乗算係数を有する乗算器５７を介して除算器６５に出力する。乗算器５６は、コンバータ出力電力指令値Ｐ^＊ _ｇｒｉｄに

の乗算係数を乗算して乗算結果値を除算器６４に出力する。なお、上記コンバータ出力電力指令値Ｐ^＊ _ｇｒｉｄを増減することで、電力変換装置が三相交流負荷に対して与える電力を変化させることができる。 The subtractor 61 subtracts the multiplication result value from the multiplier 53 from the multiplication result value from the multiplier 51 to obtain a subtraction result value.

Is output to the divider 63 via the multiplier 55 having a multiplication coefficient of. The adder 62 adds the multiplication result value from the multiplier 62 and the multiplication result value from the multiplier 54 to obtain an addition result value,

To a divider 65 via a multiplier 57 having a multiplication coefficient of The multiplier 56 sets the converter output power command value P ^* _grid .

And the multiplication result value is output to the divider 64. In addition, the electric power which a power converter device provides with respect to a three-phase alternating current load can be changed by increasing / decreasing the said converter output electric power command value P ^* _grid .

The divider 63 divides the multiplication result value from the multiplier 55 by the average value v _Coverage of the DC voltages v _Cx , v _Cy , and v _Cz and inputs the result to the inverters 6-1, 6-2, and 6-3. The division result value corresponding to the direct current i _{grid δQ} in the rotating coordinate system (δγε coordinate system) is output to the adder 66. The divider 64 divides the division result value from the multiplier 56 by the average value v _Coverage and _outputs the division result value as the ε-Q axis current command value i _{grid εQ} . The divider 65 divides the multiplication result value from the multiplier 57 by the average value v _Coverage , and the direct current of the rotating coordinate system (δγε coordinate system) input to the inverters 6-1, 6-2 and 6-3. The division result value corresponding to the current i _{grid γQ} is output to the adder 67. The multiplier 58 multiplies the δ-axis DC voltage deviation e _Cδ calculated by the equation (7) by a predetermined control coefficient K _VE for the deviation control, and outputs the division result value to the adder 67. The multiplier 59 multiplies the δ-axis DC voltage deviation e _Cγ calculated by Expression (7) by a predetermined control coefficient K _VE for the deviation control, and outputs the division result value to the adder 66. The adder 66 adds the division result value from the divider 63 and the multiplication result value from the multiplier 59 and outputs the addition result value as a δ-Q axis current command value i ^* _gridδQ . The adder 67 adds the division result value from the divider 65 and the multiplication result value from the multiplier 58 and outputs the addition result value as the γ-Q axis current command value i ^* _{grid γQ} .

In the arithmetic control circuit 50 of FIG. 7 configured as described above, feedback control of DC voltage for reducing the mutual deviation of the DC voltages V _cx , V _cy , V _cz (δ-γ axis DC voltage of FIG. 2). In addition to the path circuit having the deviations e _Cδ and e _Cγ as inputs, the load current and voltage command value of the motor load are used to be applied to each DC section of the inverters 6-1, 6-2 and 6-3. The load current is calculated, and feedforward control is performed to provide compensation so that the deviation of the DC voltage output from the converters 5-1, 5-2, 5-3 becomes small. However, the present invention is not limited to this, and the adders 66 and 67 may not be provided, and only the latter feedforward control may be performed.

FIG. 8 is a block diagram illustrating a configuration example of the arithmetic control circuit 70 in the converter control unit 10a of the control device 10 of FIG. The arithmetic control circuit 70 in FIG. 8 includes PI (Proportional Integral) control circuits 71, 72, 73 and subtractors 74, 75, 76, and is a circuit that performs current control on the δγε-Q axis. three command value _{ⁱ *} ^gridδQ outputted from the control circuit _50, ⁱ _* gridεQ, and _{ⁱ *} ^gridγQ, corresponding to each, based current _{i GridderutaQ} calculated by equation _{(6), i} gridεQ, in the _{i GridganmaQ} The voltage command values v ^* _gridδQ , v ^* _gridεQ , v ^* _gridγQ of the rotating coordinate system are calculated by PI control. The specific calculation is as follows.

Subtractor 74 outputs the subtraction result value by subtracting the current _{i GridderutaQ} from the command value _{ⁱ *} ^gridδQ the PI control circuit 71, the PI control circuit 71 such that the subtraction result value is substantially 0 [delta]-Q A shaft voltage command value v ^* _gridδQ is generated and output. Further, the subtracter 75 subtracts the current _{i GridipushironQ} from the command value _{ⁱ *} ^gridεQ outputs the subtraction result value to the PI control circuit 72, the PI control circuit 72 such that the subtraction result value is substantially 0 epsilon _-Generate and output Q-axis voltage command value v ^* _gridεQ . Furthermore, the subtracter 76 outputs a subtraction result value by subtracting the current _{i GridganmaQ} from the command value _{ⁱ *} ^gridγQ the PI control circuit 73, the PI control circuit 73 such that the subtraction result value is substantially 0 gamma _-Generate and output Q-axis voltage command value v ^* _gridγQ .

Converter control unit 10a includes three voltage command value _{^v *} ^gridδQ obtained by the arithmetic and control circuit 70 of FIG. _{^{8, v * gridεQ, v *}} gridγQ the voltage command value for the converter control using the following equation _{^v *} ^gridxQ , V ^* _gridyQ , v ^* _gridzQ .

Further, converter control unit 10a calculates a three-phase voltage command value using the following equation using voltage command values v ^* _gridxQ , v ^* _gridyQ , v ^* _gridzQ calculated by equation (11).

Here, 0 _{3 × 3} is a 3 × 3 zero matrix. It should be _noted that the D-axis voltage command values v ^* _gridxD , v ^* _gridyD , and v ^* _grizD of each xyz group circuit are the maximum values of the input currents to the converters 5-1, 5-2, and 5-3 of each xyz group circuit. Is preferably a voltage command value calculated so as to minimize the D-axis current, but the D-axis current may simply be set to 0A. Then, converter control unit 10a controls each switching transistor of converters 5-1, 5-2, and 5-3 using the three-phase voltage command value calculated by Expression (12).

  In addition, since the Q-axis currents of the converters 5-1, 5-2, and 5-3 of the xyz group circuits are not equal, the current may concentrate on some converters. Therefore, the D-axis current is distributed so as to correct the imbalance of the current effective value.

  A procedure for calculating a D-axis voltage command value that minimizes the maximum value of the alternating current input to converters 5-1, 5-2, and 5-3 will be described below.

(Step S1) First, in order to compare the current command value effective amount between the xyz group circuits, the Q axis current command value on the δγε coordinate is converted into xyz using the next Q axis current command value δγε inverse conversion formula. _Are converted into current command values i ^* _gridxQ , i ^* _gridyQ , i ^* _gridzQ .

を大小比較し、大きいものから降順で並べて

とする。以下、本項における添え字の１〜３はそれぞれ同様にｘ，ｙ，ｚと対応する。 (Step S2) Next, each absolute value of the current command values i ^* _gridxQ , i ^* _gridyQ , i ^* _gridzQ of the xyz group circuit

Compare the size and arrange them in descending order from the largest

And Hereinafter, subscripts 1 to 3 in this section correspond to x, y, and z, respectively.

(Step S3) Next, the conditions are determined in the order of case 1, case 2, and case 3 according to the following case classification, and the following corresponding processes are performed when the conditions are satisfied.

の場合、Ｑ軸電流絶対値が最小の相に全てのＤ軸電流を負担させる以下の演算を行って電流指令値ｉ^＊ _１Ｄ，ｉ^＊ _２Ｄ，ｉ^＊ _３Ｄを演算する。 (Case 1)

In the case of, current command values i ^* _1D , i ^* _2D , and i ^* _3D are calculated by performing the following calculation in which all D-axis currents are borne by the phase having the smallest Q-axis current absolute value.

の場合、下記の２つのＤ軸電流を負担させる以下の演算を行って電流指令値ｉ^＊ _１Ｄ，ｉ^＊ _２Ｄ，ｉ^＊ _３Ｄを演算する。 (Case 2)

In the case of, current command values i ^* _1D , i ^* _2D , and i ^* _3D are calculated by performing the following calculation that bears the following two D-axis currents.

の場合、３つすべてのＤ軸電流を負担させる以下の演算を行って電流指令値ｉ^＊ _１Ｄ，ｉ^＊ _２Ｄ，ｉ^＊ _３Ｄを演算する。 (Case 3)

In the case of, current command values i ^* _1D , i ^* _2D , and i ^* _3D are calculated by performing the following calculation that bears all three D-axis currents.

(Step S4) The calculated current command values i ^* _1D , i ^* _1D and i ^* _1D are respectively substituted into the corresponding current command values i ^* _gridxD , i ^* _gridxD and i ^* _gridxD to _obtain the D-axis current command value and To do. The above is the setting process of the D-axis current command values i ^* _gridxD , i ^* _gridxD , and i ^* _gridxD in Expression (12).

Further, the zero-phase voltage command values v ^* _gridx0 , v ^* _gridx0 , and v ^* _gridx0 in the equation (12) represent the AC three-phase voltage command values of the xyz group circuits obtained by the three-phase voltage command value calculation. Are given as the three-phase voltage command values of the converters 5-1, 5-2 and 5-3 of each group circuit. Thereby, the pulsation of the DC voltage due to the three-phase AC load can be compensated, and the pulsation of the DC voltage can be greatly suppressed.

In FIG. 7, adders 66 and 67 are feedback values for a feedforward value (division result value of dividers 63 and 65) of a rotation coordinate system command value determined by a load (load current). By adding a multiplication result value obtained by multiplying the shaft DC voltage deviation e _Cδ and the γ-axis DC voltage deviation e _Cγ by the proportional multiplication coefficient K _VE , it is possible to perform control for further suppressing the DC voltage deviation.

According to the above-described embodiment, the DC voltage feedback control (the δ-γ axis DC voltage deviations e _Cδ and e _Cγ in FIG. 2 are input) that reduces the deviation between the DC voltages V _cx , V _cy , and V _cz . The load current applied to each DC part of the inverters 6-1, 6-2 and 6-3 using the load current and voltage command value of the motor load, and the converter 5- Feedforward control is performed to provide compensation so that the deviation of the DC voltage output from 1,5-2,5-3 is reduced.

  Also, the effective current (Q-axis current) and DC voltage deviation of the rotating coordinate system are converted into γδε coordinates that rotate twice the load-side AC phase and in the opposite phase ([rad]) according to equations (3) and (4). Conversion is performed so that the deviation of the DC voltage is reduced on the coordinates where the phase power fluctuation of the load circuit is converted to DC.

  Furthermore, by mapping from a stationary coordinate system to a rotating coordinate system that rotates in the opposite direction at twice the speed of the current or voltage phase, voltage fluctuations that appear periodically can be grasped as a DC amount, and converter 5-1 , 5-2, and 5-3 can be compensated for fluctuations exceeding the response of the closed loop control.

By suppressing the voltage fluctuations of the capacitors C _px , C _nx , C _py , C _ny , C _pz , and C _nz of the smoothing circuit 9, the amount of current flowing through the capacitor and thus the amount of heat generation can be reduced, thereby extending the life of the capacitor. Can be obtained. Further, by suppressing capacitor _{C px, C nx, C py} , C ny, C pz, a change in the voltage of _{C nz,} capacitor _{C px, C nx, C py} , C ny, C pz, C nz corruption The risk of doing so can be reduced. Furthermore, by reducing the voltage change (overvoltage) and inflow current of the capacitors C _px , C _nx , C _py , C _ny , C _pz , and C _nz , it is possible to withstand operation under more severe conditions.

  In the above embodiment, the motor 8 is used as a load circuit. However, the present invention is not limited to this, and other various circuits may be used as a load.

Embodiment 2. FIG.
FIG. 9 is a block diagram illustrating a configuration example of the power conversion apparatus according to the second embodiment. The power converter according to Embodiment 2 differs from the power converter of FIG. 1 in the following points.
(1) The motor 8 is replaced with a power generator 8A.
(2) The inverters 6-1, 6-2, and 6-3 are operated as a converter that converts the three-phase AC voltage into a DC voltage. Therefore, the inverter control unit 10b becomes a converter control unit.
(3) Operate converters 5-1, 5-2, and 5-3 as inverters that convert DC voltage into three-phase AC voltage. Therefore, the converter control unit 10a becomes an inverter control unit.
(4) The power system 1 is on the load side and is connected to a load circuit (not shown).

In the power conversion device of FIG. 9, since the circuit from the circuit breaker 2 to the current detectors 41 to 43 is a bidirectional reversible circuit, the generator 8A is the power source, the power system 1 is the load side, and the current detector supply current _i genx detected in 41 to _43, i _GENy, based on _{i Genz,} to control the converter 5-1, 5-2, 5-3 using various formulas disclosed in embodiment 1 Thus, it can be operated in the same manner as in the first embodiment except that the power source and the load are switched. Note that the second embodiment also has a unique effect similar to that of the first embodiment.

  In the above embodiment, the generator 8A is used as a three-phase AC power supply. However, the present invention is not limited to this, and other various AC power supplies may be used.

Modified example.
In the above embodiment, although the power converter device of three-phase alternating current power is demonstrated, this invention is not limited to this, You may comprise the power converter device of multiple phase alternating current power. In this case, the triple three-phase transformer 4 is a multi-phase multi-phase transformer.

  The inventors performed simulation using the power conversion device of FIG. 1 to obtain the simulation results of FIGS. 10A and 10B.

  FIG. 10A is a graph showing the simulation result of the power conversion device of FIG. 1 and showing the x-phase high-voltage side DC voltage and the x-phase low-voltage side DC voltage without correction control. FIG. 10B is a graph showing the simulation result of the power conversion device of FIG. 1 and showing the x-phase high-voltage side DC voltage and the x-phase low-voltage side DC voltage with correction control. As is apparent from FIGS. 10A and 10B, when the compensation according to the embodiment is not performed, the DC voltage oscillates by about ± 40 [V], but by performing the compensation according to the embodiment, ± 20 [V] Decrease to a degree.

  As described above in detail, according to the power conversion device and the like according to the present invention, the DC voltage deviation of the inverter can be significantly reduced even in a general configuration in which the transformers are connected in parallel.

1 ... Power system,
2 ... circuit breaker,
3 ... Three-phase transformer,
4. Mie three-phase transformer,
5,5-1,5-2,5-3 ... converter,
6, 6-1, 6-2, 6-3 ... inverter,
6A ... Motor side inverter circuit,
6B ... Y connection side inverter circuit,
7 ... Three-phase midpoint,
8 ... motor,
8A ... Synchronous generator,
8s ... Angle sensor,
9: Smoothing circuit,
10 ... Control device,
10a: converter control unit,
10b: inverter control unit,
11, 12 ... Voltage detector,
21-29 ... current detector,
31-36 ... Voltage detector,
41-43 ... current detectors,
50, 70 ... arithmetic control circuit,
51-59 ... multiplier,
61 ... Subtractor,
62 ... adder,
63 to 65: divider,
66, 67 ... adder,
71-73 ... PI control circuit,
74-76 ... subtractor,
C _px , C _nx , C _py , C _ny , C _pz , C _nz ... capacitors,
T1 to T6, T11 to T15 ... terminals.

Claims (14)

A plurality of first power conversion circuits for converting each of a plurality of phases of AC power from an AC power source into a DC voltage;
A plurality of second power conversion circuits that convert each of the converted DC voltages into a plurality of phases of AC power and output the same to a load circuit;
A power conversion device comprising a control means for controlling the plurality of first and second power conversion circuits,
The control means performs feedforward control of the plurality of first power conversion circuits so that a deviation between the DC voltages is reduced based on a load current flowing through the load circuit and a voltage command value of the load circuit. The power converter characterized by this.   The control means is configured to rotate a load current flowing through the load circuit, a voltage command value of the load circuit, and a deviation of each of the DC voltages, each of which is twice the AC phase on the load circuit side and rotates in a reverse phase. Are converted into deviations of the load current, voltage command value and each DC voltage of the rotating coordinate system, and the DC power deviation is reduced in the rotating coordinate system in which the phase power fluctuation of the load circuit is converted to DC. The power converter according to claim 1, wherein feedforward control is performed on the plurality of first power converter circuits. A plurality of first power conversion circuits for converting each of a plurality of phases of AC power from an AC power source into a DC voltage;
A plurality of second power conversion circuits that convert each of the converted DC voltages into a plurality of phases of AC power and output the same to a load circuit;
A power conversion device comprising a control means for controlling the plurality of first and second power conversion circuits,
The control means performs feedforward control on the plurality of second power conversion circuits so that a deviation between the DC voltages is reduced based on a power supply current flowing from the AC power supply and a voltage command value of the AC power supply. The power converter characterized by this.   The control means is configured to rotate the power source current flowing through the AC power source, the voltage command value of the AC power source, and the deviation of each DC voltage to be twice the AC phase on the AC power source side and in reverse phase. Is converted into a deviation of each DC voltage in the rotating coordinate system in which the phase power fluctuation of the AC power source is converted into a direct current. The power converter according to claim 3, wherein the plurality of second power converter circuits are feedforward controlled.   5. The control means according to claim 1, further comprising feedback control of the plurality of second power conversion circuits so that a difference between each of the DC voltages and a predetermined corresponding voltage deviation is reduced. The power converter device as described in any one of these.   The control means converts each DC voltage into a deviation of each DC voltage in a predetermined rotating coordinate system that is twice the AC phase and rotates in the opposite phase, and the plurality of second power conversion circuits. The power conversion device according to claim 5, wherein feedback control is performed.   7. The method according to claim 1, further comprising a smoothing circuit inserted between the first voltage-current conversion circuit and the second power conversion circuit and including a plurality of capacitors. The power converter described in one.   Each said 1st power converter circuit is a converter, Each said 2nd power converter circuit is a converter, The power converter device as described in any one of Claims 1-7 characterized by the above-mentioned. A plurality of first power conversion circuits for converting each of a plurality of phases of AC power from an AC power source into a DC voltage;
A plurality of second power conversion circuits that convert each of the converted DC voltages into a plurality of phases of AC power and output the same to a load circuit;
A control method for a power conversion device comprising a control means for controlling the plurality of first and second power conversion circuits,
Control in which the control means performs feedforward control of the plurality of first power conversion circuits so that a deviation between the DC voltages is reduced based on a load current flowing through the load circuit and a voltage command value of the load circuit. A method for controlling a power conversion apparatus, comprising: a step.   In the control step, a load current flowing through the load circuit, a voltage command value of the load circuit, and a deviation of each of the DC voltages are each set to be two times the AC phase on the load circuit side and rotating in a reverse phase. Are converted into deviations of the load current, voltage command value and each DC voltage of the rotating coordinate system, and the DC power deviation is reduced in the rotating coordinate system in which the phase power fluctuation of the load circuit is converted to DC. The method for controlling the power conversion apparatus according to claim 9, wherein feedforward control is performed on the plurality of first power conversion circuits. A plurality of first power conversion circuits for converting each of a plurality of phases of AC power from an AC power source into a DC voltage;
A plurality of second power conversion circuits that convert each of the converted DC voltages into a plurality of phases of AC power and output the same to a load circuit;
A control method for a power conversion device comprising a control means for controlling the plurality of first and second power conversion circuits,
Control in which the control means feeds forward-controls the plurality of second power conversion circuits so that a deviation between the DC voltages is reduced based on a power supply current flowing from the AC power supply and a voltage command value of the AC power supply. A method for controlling a power conversion apparatus, comprising: a step.   In the control step, a power supply current flowing through the AC power supply, a voltage command value of the AC power supply, and a deviation of each of the DC voltages are each set to be twice the AC phase on the AC power supply side and rotating in a reverse phase. Is converted into a deviation of each DC voltage in the rotating coordinate system in which the phase power fluctuation of the AC power source is converted into a direct current. The method for controlling the power conversion device according to claim 11, wherein the plurality of second power conversion circuits are feedforward controlled.   The control step further includes feedback-controlling the plurality of second power conversion circuits so that a difference between each DC voltage and a predetermined corresponding voltage deviation is reduced. The control method of the power converter device as described in any one of these.   The control step converts each DC voltage into a deviation of each DC voltage in a predetermined rotating coordinate system that is twice the AC phase and rotates in the opposite phase, and the plurality of second power conversion circuits. 14. The method of controlling a power converter according to claim 13, wherein feedback control is performed.

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