JP7774008B2 - Power Conversion Device - Google Patents

Description

This disclosure relates to a power conversion device.

JP 2008-234298 A (Patent Document 1) discloses a control device that controls a power converter that supplies three-phase AC power to an AC power system in accordance with a three-phase voltage command value. This control device includes a dq converter that converts the three-phase AC current into a d-axis current and a q-axis current based on a reference phase, a current controller that generates a d-axis voltage command value based on the deviation of the d-axis current from the d-axis current command value, and a current controller that generates a q-axis voltage command value based on the deviation of the q-axis current from the q-axis current command value. The control device is configured to generate a three-phase voltage command value by performing an inverse dq transformation on the d-axis voltage command value and the q-axis voltage command value in accordance with a corrected reference phase.

Japanese Patent Application Laid-Open No. 2008-234298

The control device described in Patent Document 1 is configured to generate three-phase voltage command values by performing control calculations to compensate for deviations in the d-axis current and q-axis current in the positive-phase coordinate system.

On the other hand, if a transient fluctuation in the system voltage of an AC power system causes the system voltage to enter a three-phase unbalanced state, a negative-phase component occurs in addition to a positive-phase component. Therefore, in order to handle three-phase unbalance, it is necessary to consider the negative-phase component in addition to the positive-phase component. However, in Patent Document 1, the system is configured to control only the positive-phase component of the power converter's output current, and therefore does not control the negative-phase component of the output current. As a result, there is a problem in that a steady-state deviation of the negative-phase component remains.

This disclosure has been made to solve these problems, and the purpose of this disclosure is to provide a power conversion device that can eliminate steady-state deviation in the output current of a power converter.

A power conversion device according to one aspect of the present disclosure includes a power converter that converts DC voltage into three-phase AC voltage and outputs the voltage to a three-phase AC power system or a three-phase AC load, a current detector that detects the output current of the power converter, and a control device that controls the power converter. The control device includes a current control unit that generates a three-phase AC voltage command value through feedback control to compensate for the deviation of the current detector's detection value from the AC current command value, and a PWM circuit that PWM-controls the power converter by generating a control signal for the power converter based on the three-phase AC voltage command value. The AC current command values include a positive-phase d-axis current command value, a positive-phase q-axis current command value, and a negative-phase d-axis current command value, and a negative-phase q-axis current command value. The current control unit includes means for generating a d-axis current command value by combining a positive-phase d-axis current command value and a negative-phase d-axis current command value, and for generating a q-axis current command value by combining a positive-phase q-axis current command value and a negative-phase q-axis current command value, means for performing proportional-integral control calculations on the deviation of the current detector's detection values from the d-axis current command value and the q-axis current command value, means for converting the deviation of the current detector's detection values into a negative-phase coordinate system, means for performing integral control calculations on the deviation of the current detector's detection values converted into the negative-phase coordinate system, and means for generating a three-phase AC voltage command value using the values calculated by the proportional-integral control calculations and the values calculated by the integral control calculations.

This disclosure provides a power conversion device that can eliminate steady-state deviation in the output current of a power converter.

1 is a circuit block diagram showing a configuration of a power conversion device according to a first embodiment; FIG. 2 is a circuit diagram showing a configuration example of the power converter shown in FIG. 1 . FIG. 10 is a circuit block diagram showing a configuration of a power conversion device according to a second embodiment. FIG. 10 is a circuit block diagram showing a configuration of a power conversion device according to a third embodiment. FIG. 1 is a circuit block diagram showing a configuration of a power conversion device according to a reference example.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that, below, identical or equivalent parts in the drawings will be designated by the same reference numerals, and their descriptions will generally not be repeated.

[First Embodiment]
1 is a circuit block diagram showing the configuration of a power conversion device according to embodiment 1. The power conversion device according to embodiment 1 is used, for example, as a reactive power compensator that compensates for reactive power in a three-phase AC power system 1. Alternatively, the power conversion device according to embodiment 1 is used as a power supply device that supplies power to a three-phase AC load (not shown).

As shown in FIG. 1, the power conversion device according to embodiment 1 includes a reactor 2, a power converter 3, a voltage detector 4, a current detector 5, and a control device 7. The three AC terminals of the power converter 3 are connected via the reactor 2 to a three-phase transmission line of a three-phase AC power system 1 having U, V, and W phases. Note that while in FIG. 1 the power converter 3 is connected to the three-phase AC power system 1 via the reactor 2, it may also be configured to be connected to the three-phase AC power system 1 via a three-phase transformer.

The DC terminals of the power converter 3 are connected to a power storage device that stores DC power, such as a battery or capacitor, or to a DC power source that generates DC power. Figure 2 is a circuit diagram showing an example configuration of the power converter 3 shown in Figure 1.

As shown in Figure 2, power converter 3 has self-extinguishing switching elements. In the example of Figure 2, IGBTs (Insulated Gate Bipolar Transistors) are used as the switching elements. Power converter 3 has IGBT elements Q1 to Q6 and diodes D1 to D6. The collectors of IGBT elements Q1, Q3, and Q5 are all connected to the DC positive bus PL, and their emitters are connected to AC terminals Tu, Tv, and Tw, respectively. The collectors of IGBT elements Q2, Q4, and Q6 are connected to AC terminals Tu, Tv, and Tw, respectively, and their emitters are connected to the DC negative bus NL. Diodes D1 to D6 are connected in anti-parallel to IGBT elements Q1 to Q6, respectively.

The IGBT elements Q1 to Q6 are controlled to be turned on and off by control signals (gate pulses) provided by the control device 7. In this embodiment, PWM (Pulse Width Modulation) control can be applied as the control method for the IGBT elements Q1 to Q6.

The power converter 3 converts DC power into three-phase AC power in accordance with gate pulses provided by the control device 7. The three-phase AC power generated by the power converter 3 is supplied to the three-phase AC power system 1 via the reactor 2.

Returning to Figure 1, the voltage detector 4 detects the three-phase AC voltage of the three-phase AC power system 1 and provides a signal indicating the detected value to the control device 7. The three-phase AC voltage has a U-phase voltage Vu, a V-phase voltage Vv, and a W-phase voltage Vw.

The current detector 5 detects the output current (three-phase AC current) of the three-phase AC power system 1 and provides a signal indicating the detected value to the control device 7. The output current of the three-phase AC power system 1 includes a U-phase current iu, a V-phase current iv, and a W-phase current iw.

The control device 7 includes a phase detector 9, a dq converter 10, a current control unit 8, adders 11 and 12, and an inverse dq converter 13.

The phase detector 9 generates a reference phase θ based on the output signal of the voltage detector 4 using a well-known PLL (Phase Locked Loop) circuit or DFT (Discrete Fourier Transform) circuit. The reference phase θ is the positive-sequence voltage phase of the system voltage of the three-phase AC power system 1.

The dq converter 10 performs a dq transformation (three-phase to two-phase transformation) on the three-phase AC voltages Vu, Vv, and Vw detected by the voltage detector 4 using a reference phase (positive-phase voltage phase) θ to calculate a d-axis voltage Vd (hereinafter also referred to as the "positive-phase d-axis voltage Vd") coordinate-transformed in the positive-phase rotation direction, and a q-axis voltage Vq (hereinafter also referred to as the "positive-phase q-axis voltage Vq") coordinate-transformed in the positive-phase rotation direction. The dq converter 10 is configured as a positive-phase dq vector coordinate system that is coordinate-transformed in a direction synchronized with the positive-phase voltage of the three-phase AC power system 1. Hereinafter, the positive-phase dq vector coordinate system will also be simply referred to as the "positive-phase coordinate system." The coordinate transformation from the fixed coordinate system to the positive-phase coordinate system is expressed by the following equation (1).

The current control unit 8 calculates a feedback control amount through control calculations to reduce the deviation of the detection value of the current detector 5 from the AC current command value. The AC current command value includes positive-phase current command values id* and iq* and negative-phase current command values idn* and iqn*. The positive-phase current command value is composed of a positive-phase d-axis current command value id* and a positive-phase q-axis current command value iq*. The negative-phase current command value is composed of a negative-phase d-axis current command value idn* and a negative-phase q-axis current command value iqn*.

The AC current command value is generated to maintain a constant system voltage in the three-phase AC power system 1 or to control the DC voltage input to the power converter 3 to a constant value. The AC current command value is generally generated by a host controller. When voltage control of the three-phase AC power system 1 is performed by a power conversion device, the system control system is the host controller.

The current control unit 8 includes adders 21, 22, 25-28, subtractors 23 and 24, first compensators CP11 and CP12, second compensators CP21 and CP22, third compensators CP31 and CP32, inverse dq converters 29 and 31, and a dq converter 30.

The inverse dq converter 29 performs an inverse dq transformation using the reference phase (positive-phase voltage phase) θ to transform the negative-phase current command values idn* and iqn* into the positive-phase coordinate system. The coordinate transformation from the negative-phase coordinate system to the positive-phase coordinate system is expressed by the following equation (2).

Adder 21 generates a d-axis current command value idpn* by adding the positive-phase d-axis current command value id* and the negative-phase d-axis current command value idn* using the following equation (3). Adder 22 generates a q-axis current command value iqpn* by adding the positive-phase q-axis current command value iq* and the negative-phase q-axis current command value iqn* using the following equation (4).

The dq converter 32 performs coordinate transformation (three-phase to two-phase transformation) on the three-phase AC currents iu, iv, and iw detected by the current detector 5 from a fixed coordinate system to a positive-phase coordinate system using equation (1), and calculates the positive-phase d-axis current id and the positive-phase q-axis current iq.

Subtractor 23 calculates the deviation Δid of the positive-phase d-axis current id from the d-axis current command value idpn* (hereinafter also referred to as the "positive-phase d-axis deviation Δid") (Δid = idpn* - id). Subtractor 24 calculates the deviation Δiq of the positive-phase q-axis current iq from the q-axis current command value iqpn* (hereinafter also referred to as the "positive-phase q-axis deviation Δiq") (Δiq = iqpn* - iq).

The first compensators CP11 and CP12 are compensators with proportional elements. The first compensators CP11 and CP12 perform proportional control calculations to reduce the positive-phase d-axis deviation Δid and the positive-phase q-axis deviation Δiq, and calculate the proportional control variables. Specifically, the first compensator CP11 calculates the proportional control variable Kp·Δid based on the positive-phase d-axis deviation Δid. The first compensator CP12 calculates the proportional control variable Kp·Δiq based on the positive-phase q-axis deviation Δiq. Kp is the proportional gain. The first compensators CP11 and CP12 correspond to an example of a "first compensator."

The second compensators CP21 and CP22 are compensators with integral elements. The second compensators CP21 and CP22 perform integral control calculations to reduce the positive-phase d-axis deviation Δid and the positive-phase q-axis deviation Δiq, and calculate integral control variables. The second compensator CP21 calculates the integral control variable Σ (Ki·Δid) based on the positive-phase d-axis deviation Δid. The second compensator CP22 calculates the integral control variable Σ (Ki·Δiq) based on the positive-phase q-axis deviation Δiq. Ki is the integral gain. The second compensators CP21 and CP22 may further include a filter (such as a moving average filter) for removing frequency components other than DC components. The second compensators CP21 and CP22 correspond to an example of a "second compensator."

Adder 25 generates the positive-phase d-axis voltage command value Vdp* required for feedback control to reduce the positive-phase d-axis deviation Δid by adding the proportional control variable Kp·Δid from the first compensator CP11 and the integral control variable Σ(Ki·Δid) from the second compensator CP21. Adder 28 generates the positive-phase q-axis voltage command value Vqp* required for feedback control to reduce the positive-phase q-axis deviation Δiq by adding the proportional control variable Kp·Δiq from the first compensator CP12 and the integral control variable Σ(Ki·Δiq) from the second compensator CP22.

The dq converter 30 performs a dq transformation using a negative-phase voltage phase (-θ) that rotates in the opposite direction to the reference phase (positive-phase voltage phase) θ, and calculates the d-axis deviation Δidn (hereinafter also referred to as the "negative-phase d-axis deviation Δidn") coordinate-transformed in the negative-phase rotation direction, and the q-axis deviation Δiqn (hereinafter also referred to as the "negative-phase q-axis deviation Δiqn") coordinate-transformed in the negative-phase rotation direction. The dq converter 30 is configured as a negative-phase dq vector coordinate system that is coordinate-transformed in a direction synchronized with the negative-phase voltage of the three-phase AC power system 1. Hereinafter, the negative-phase dq vector coordinate system will also be simply referred to as the "negative-phase coordinate system." The coordinate transformation from the positive-phase coordinate system to the negative-phase coordinate system is expressed by the following equation (5).

The third compensators CP31 and CP32 are compensators with integral elements. The third compensators CP31 and CP32 perform integral control calculations to reduce the negative-phase-sequence d-axis deviation Δidn and the negative-phase-sequence q-axis deviation Δiqn, and calculate integral control variables. Specifically, the third compensator CP31 calculates the integral control variable Σ (Ki·Δidn) based on the negative-phase-sequence d-axis deviation Δidn. The third compensator CP32 calculates the integral control variable Σ (Ki·Δiqn) based on the negative-phase-sequence q-axis deviation Δiqn. Ki is the integral gain. The third compensators CP31 and CP32 may further include a filter (such as a moving average filter) for removing frequency components other than DC components. The third compensators CP31 and CP32 correspond to an example of a "third compensator."

The inverse dq converter 31 performs an inverse dq transformation using equation (2) to convert the integral control variables Σ(Ki·Δidn) and Σ(Ki·Δiqn), which are the values calculated by the third compensators CP31 and CP32, from the negative phase coordinate system to the positive phase coordinate system.

Adder 27 generates a d-axis voltage command value Vd* that includes both positive and negative sequence components by adding the integral control variable Σ (Ki·Δidn) from the inverse dq converter 31 to the positive-phase d-axis voltage command value Vdp* from adder 25. Adder 28 generates a q-axis voltage command value Vq* that includes both positive and negative sequence components by adding the integral control variable Σ (Ki·Δiqn) from the inverse dq converter 31 to the positive-phase q-axis voltage command value Vqp* from adder 26.

Adder 11 adds the d-axis voltage Vd from the dq converter 10 to the d-axis voltage command value Vd* from adder 27. Adder 12 adds the q-axis voltage Vq from the dq converter 10 to the q-axis voltage command value Vq* from adder 28.

The inverse dq transformer 13 performs an inverse dq transform (two-phase to three-phase transformation) on the d-axis voltage command value Vd* from the adder 11 and the q-axis voltage command value Vq* from the adder 12 to generate three-phase voltage command values (U-phase voltage command value Vu*, V-phase voltage command value Vv*, and W-phase voltage command value Vw*). The coordinate transformation (two-phase to three-phase transformation) from the normal phase coordinate system to the fixed coordinate system is expressed by the following equation (6). The three-phase AC voltage command values are provided to the PWM circuit 14.

The PWM circuit 14 generates gate pulses based on a comparison between the three-phase AC voltage command value and a carrier wave (e.g., a triangular wave). It is sufficient for the PWM circuit 14 to generate gate pulses so that the AC voltage of the power converter 3 contains a component proportional to the voltage command value. In addition to generating gate pulses using a carrier wave, other methods include generating gate pulses based on the three-phase AC voltage command values Vu*, Vv*, and Vw* by referencing a predetermined table, or generating gate pulses by performing arithmetic processing using the amplitude and phase of the three-phase AC voltage command values Vu*, Vv*, and Vw*. The power converter 3 supplies three-phase AC power to the three-phase AC power system 1 via the reactor 2 in accordance with the gate pulses.

In the power conversion device according to embodiment 1, the dq converter 32 corresponds to the "first coordinate converter," the inverse dq converter 29 corresponds to the "second coordinate converter," the dq converter 30 corresponds to the "third coordinate converter," the inverse dq converter 31 corresponds to the "fourth coordinate converter," and the inverse dq converter 13 corresponds to the "fifth coordinate converter." Adders 21 and 22 correspond to "adders."

Furthermore, the inverse dq converter 29 and adders 21 and 22 correspond to an embodiment of "means for generating a d-axis current command value and a q-axis current command value." The first compensators CP11 and CP12 and the second compensators CP21 and CP22 correspond to an embodiment of "means for performing proportional-integral control on the deviation of the current detector's detection value from the d-axis current command value and the q-axis current command value." The dq converter 30 corresponds to an embodiment of "means for converting the deviation of the current detector's detection value into a negative-phase coordinate system." The third compensators CP31 and CP32 correspond to an embodiment of "means for performing integral control calculation on the deviation of the current detector's detection value converted into the negative-phase coordinate system." Adders 25 to 28 correspond to an embodiment of "means for generating a three-phase AC voltage command value using the calculated value obtained by the proportional-integral control calculation and the calculated value obtained by the integral control calculation."

The following describes the effects of the power conversion device according to embodiment 1, comparing it with a power conversion device serving as a reference example (see Figure 5).

Figure 5 is a circuit block diagram showing the configuration of a power conversion device according to a reference example.

As shown in FIG. 5, the power conversion device according to the reference example includes a power converter 3, a voltage detector 4, a current detector 5, and a control device 7A. The power conversion device according to the reference example basically has the same configuration as the power conversion device according to embodiment 1 shown in FIG. 1, but differs from the power conversion device according to embodiment 1 in that it includes a control device 7A instead of the control device 7.

The control device 7A includes a phase detector 9, a dq converter 10, a current control unit 8A, adders 11 and 12, an inverse dq converter 13, and a PWM circuit 14.

The phase detector 9 generates a reference phase θ (positive voltage phase) based on the output signal of the voltage detector 4.

The dq converter 10 converts the three-phase AC voltages Vu, Vv, and Vw detected by the voltage detector 4 into a d-axis voltage Vd and a q-axis voltage Vq by dq transformation (three-phase to two-phase transformation) in the positive phase coordinate system using equation (1).

The current control unit 8A calculates a feedback control amount through control calculations to reduce the deviation of the detection value of the current detector 5 from the AC current command value. The AC current command value includes a positive-phase d-axis current command value id* and a positive-phase q-axis current command value iq*.

The current control unit 8A includes a dq converter 70, subtractors 71 and 72, proportional converters 73 and 76, integrators 74 and 77, and adders 75 and 78.

The dq converter 70 performs coordinate transformation (three-phase to two-phase transformation) from a fixed coordinate system to a positive-phase coordinate system using equation (1) on the three-phase AC currents iu, iv, and iw detected by the current detector 5, and calculates the positive-phase d-axis current id and the positive-phase q-axis current iq.

Subtractor 71 calculates the deviation of the positive-phase d-axis current id from the positive-phase d-axis current command value id* (positive-phase d-axis deviation) Δid. Subtractor 72 calculates the deviation of the positive-phase q-axis current iq from the positive-phase q-axis current command value iq* (positive-phase q-axis deviation) Δiq.

Proportional regulator 73 performs proportional control calculations on the positive phase d-axis deviation Δid to calculate the proportional control amount Kp·Δid. Proportional regulator 76 performs proportional control calculations on the positive phase q-axis deviation Δiq to calculate the proportional control amount Kp·Δiq. Note that Kp is the proportional gain.

Integrator 74 performs integral control calculations on the positive-phase d-axis deviation Δid to calculate the integral control amount Σ (Ki · Δid). Integrator 77 performs integral control calculations on the positive-phase q-axis deviation Δiq to calculate the integral control amount Σ (Ki · Δiq). Note that Ki is the integral gain.

Adder 75 adds the proportional control variable Kp·Δid from proportional unit 73 and the integral control variable Σ(Ki·Δid) from integrator 74 to generate the d-axis voltage command value Vd* required for feedback control to reduce the positive-phase d-axis deviation Δid. Adder 78 adds the proportional control variable Kp·Δiq from proportional unit 76 to the integral control variable Σ(Ki·Δiq) from integrator 77 to generate the q-axis voltage command value Vq* required for feedback control to reduce the positive-phase q-axis deviation Δiq.

Adder 11 adds the d-axis voltage Vd from the dq converter 10 to the d-axis voltage command value Vd* from adder 75. Adder 12 adds the q-axis voltage Vq from the dq converter 10 to the q-axis voltage command value Vq* from adder 78.

The inverse dq converter 13 generates three-phase AC voltage command values (U-phase voltage command value Vu*, V-phase voltage command value Vv*, and W-phase voltage command value Vw*) by performing coordinate transformation (two-phase to three-phase transformation) from the normal phase coordinate system to the fixed coordinate system using equation (6) on the d-axis voltage command value Vd* from adder 11 and the q-axis voltage command value Vq* from adder 12. The three-phase AC voltage command values are provided to the PWM circuit 14.

The PWM circuit 14 generates gate pulses based on a comparison between the three-phase AC voltage command value and the carrier wave. The power converter 3 supplies three-phase AC power to the three-phase AC power system 1 via the reactor 2 in accordance with the gate pulses.

As shown in Figure 5, in the power conversion device according to the reference example, the control device 7A is configured to calculate the d-axis voltage command value Vd* and the q-axis voltage command value Vq* by control calculations to compensate for the d-axis deviation Δid and the q-axis deviation Δiq in the positive phase coordinate system, and to generate a three-phase AC voltage command value based on the d-axis voltage command value Vd* and the q-axis voltage command value Vq*.

On the other hand, transient fluctuations in the system voltage of the three-phase AC power system 1 can cause the system voltage to enter a three-phase unbalanced state. A three-phase balanced state is a state in which the amplitudes of the phase voltages are equal and the phases are shifted by 120°. In contrast, a three-phase unbalanced state is a state in which the amplitudes of the phase voltages are different and/or the phase shift between the phase voltages is not 120°.

When a three-phase unbalance occurs, negative-sequence and zero-sequence components occur in addition to the positive-sequence components. In other words, to handle a three-phase unbalance, it is necessary to consider the negative-sequence and zero-sequence components in addition to the positive-sequence components. However, because the power converter 3 is connected to the three-phase AC power system 1 via the reactor 2, the power converter 3 cannot output a zero-sequence current. Therefore, it is necessary to control the positive-sequence and negative-sequence components.

As described above, the power conversion device according to the reference example is configured to control only the positive-phase component of the output current of the power converter 3, and therefore does not control the negative-phase component of the output current. As a result, there is a problem in that a steady-state deviation of the negative-phase component remains.

In contrast, in the power conversion device according to embodiment 1, the control device 7 generates a current command value by combining the positive-phase current command values id*, iq* and the negative-phase current command values idn*, iqn*. It also converts the positive-phase d-axis deviation Δid and the positive-phase q-axis deviation Δiq relative to the current command value into the negative-phase d-axis deviation Δidn and the negative-phase q-axis deviation Δiqn, and performs integral control calculations to compensate for the negative-phase d-axis deviation Δidn and the negative-phase q-axis deviation Δiqn. This eliminates steady-state deviations relative to the negative-phase current command values idn*, iqn*. As a result, it is possible to obtain an output current from the power converter 3 that matches the current command value, even in a three-phase unbalanced state.

In addition, because the detected values (three-phase AC current) of the current detector 5 are used to calculate the feedback control amount without performing any calculations other than coordinate transformation on the detected values, high-speed control is possible without causing transient detection delays in the three-phase AC current. Furthermore, because there is no need to separate the detected values (three-phase AC current) of the current detector 5 into positive and negative phases, the calculation load on the control device 7 can be reduced.

[Embodiment 2]
FIG. 3 is a circuit block diagram showing the configuration of a power conversion device according to the second embodiment.

As shown in Figure 3, the power conversion device of embodiment 2 basically has the same configuration as the power conversion device of embodiment 1 shown in Figure 1, but the configuration of the control device 7 is different from that of the power conversion device of embodiment 1.

The control device 7 includes a phase detector 9, a current control unit 8, an adder 15, and a PWM circuit 14.

The phase detector 9 generates a reference phase θ (positive voltage phase) based on the output signal of the voltage detector 4.

The current control unit 8 calculates a feedback control amount through control calculations to reduce the deviation of the detection value of the current detector 5 from the AC current command value. The AC current command value includes positive-phase current command values id* and iq* and negative-phase current command values idn* and iqn*.

The inverse dq converter 29 converts the negative-phase current command values idn* and iqn* into the positive-phase coordinate system by performing an inverse dq transformation using equation (2).

Adder 21 generates the d-axis current command value idpn* by adding the positive-phase d-axis current command value id* and the negative-phase d-axis current command value idn* using equation (3). Adder 22 generates the q-axis current command value iqpn* by adding the positive-phase q-axis current command value iq* and the negative-phase q-axis current command value iqn* using equation (4).

The fixed coordinate converter 33 converts the d-axis current command value idpn* and the q-axis current command value iqpn* into three-phase current command values by converting them from the positive-phase coordinate system to the fixed coordinate system (two-phase to three-phase conversion) using equation (6). The three-phase AC current command values are output current command values of the power converter 3, and include a U-phase current command value iu*, a V-phase current command value iv*, and a W-phase current command value iw*.

Subtractor 34 calculates the deviation Δiu between the U-phase current command value iu* and the U-phase current iu detected by the current detector 5 (Δiu = iu* - iu). Subtractor 35 calculates the deviation Δiv between the V-phase current command value iv* and the V-phase current iv detected by the current detector 5 (Δiv = iv* - iv). Subtractor 35 calculates the deviation Δiw between the W-phase current command value iw* and the W-phase current iw detected by the current detector 5 (Δiw = iw* - iw).

The first compensators CP11 to CP13 have proportional elements and perform proportional control calculations to reduce the deviation of the three-phase AC current from the three-phase AC current command value, calculating the proportional control amount. Specifically, the first compensator CP11 calculates the proportional control amount Kp·Δiu based on the deviation Δiu. The first compensator CP12 calculates the proportional control amount Kp·Δiv based on the deviation Δiv. The first compensator CP13 calculates the proportional control amount Kp·Δiw based on the deviation Δiw. Note that Kp is the proportional gain.

The dq converter 39 converts the deviations Δiu, Δiv, and Δiw into a positive-phase d-axis deviation Δidp and a positive-phase q-axis deviation Δiqp by performing a dq transformation (three-phase to two-phase transformation) from the fixed coordinate system to the positive-phase coordinate system using equation (1).

The second compensators CP21 and CP22 have integral elements and calculate integral control variables through integral control calculations to reduce the positive-phase d-axis deviation Δidp and the positive-phase q-axis deviation Δiqp. Specifically, the second compensator CP21 performs integral control calculations on the positive-phase d-axis deviation Δidp to calculate the integral control variable Σ (Ki · Δidp). The second compensator CP22 performs integral control calculations on the positive-phase q-axis deviation Δiqp to calculate the integral control variable Σ (Ki · Δiqp). Ki is the integral gain. The second compensators CP21 and CP22 may further include a filter (such as a moving average filter) to remove components other than DC.

The inverse dq converter 40 converts the integral control variables from the second compensators CP21 and CP22 into integral control variables for three phases by performing an inverse dq transformation (two-phase to three-phase transformation) from the normal phase coordinate system to the fixed coordinate system using equation (6).

The adder 37 adds the proportional control variables for three phases, which are values calculated by the first compensators CP11 to CP13, and the integral control variable of the positive-phase component by the inverse dq converter 40, to generate the three-phase AC voltage command values Vup*, Vvp*, and Vwp* required for feedback control to reduce the current deviations Δiu, Δiv, and Δiw.

The dq converter 41 converts the deviations Δiu, Δiv, and Δiw into the negative-phase d-axis deviation Δidn and the negative-phase q-axis deviation Δiqn by performing a dq coordinate transformation (three-phase to two-phase transformation) from the fixed coordinate system to the negative-phase coordinate system. The coordinate transformation from the fixed coordinate system to the negative-phase coordinate system is expressed by the following equation (7).

The third compensators CP31 and CP32 have integral elements and calculate integral control variables through integral control calculations to reduce the negative-phase-sequence d-axis deviation Δidn and the negative-phase-sequence q-axis deviation Δiqn. Specifically, the third compensator CP31 performs integral control calculations on the negative-phase-sequence d-axis deviation Δidn to calculate the integral control variable Σ (Ki · Δidn). The third compensator CP32 performs integral control calculations on the negative-phase-sequence q-axis deviation Δiqn to calculate the integral control variable Σ (Ki · Δiqn). Ki is the integral gain. The third compensators CP31 and CP32 may further include a filter (such as a moving average filter) to remove components other than DC.

The inverse dq converter 42 converts the integral control variables from the third compensators CP31 and CP32 into integral control variables for three phases by performing an inverse dq transformation (two-phase to three-phase transformation) from the negative-phase coordinate system to the fixed coordinate system. The coordinate transformation from the negative-phase coordinate system to the fixed coordinate system is expressed by the following equation (8).

Adder 38 adds the three-phase AC voltage command values Vup*, Vvp*, and Vwp* of the positive-phase components from adder 37 to the integral control amount for three phases of the negative-phase components from the inverse dq converter 42 to generate the three-phase AC voltage command values (U-phase voltage command value Vu*, V-phase voltage command value Vv*, and W-phase voltage command value Vw*) required for feedback control to reduce the current deviations Δiu, Δiv, and Δiw of the positive-phase and negative-phase components.

Adder 15 adds the three-phase AC voltage detected by voltage detector 4 to the three-phase voltage command value from adder 38 to generate a three-phase voltage command value. The three-phase AC voltage command value is provided to PWM circuit 14.

The PWM circuit 14 generates gate pulses based on a comparison between the three-phase AC voltage command value and the carrier wave. It is sufficient for the PWM circuit 14 to generate gate pulses so that the AC voltage of the power converter 3 contains a component proportional to the voltage command value. In addition to generating gate pulses using a carrier wave, other methods include generating gate pulses corresponding to the three-phase AC voltage command values Vu*, Vv*, and Vw* by referencing a predetermined table, or generating gate pulses by performing arithmetic processing using the amplitude and phase of the three-phase AC voltage command values Vu*, Vv*, and Vw*. The power converter 3 supplies three-phase AC power to the three-phase AC power system 1 via the reactor 2 in accordance with the gate pulses.

In the power conversion device according to embodiment 2, the inverse dq converter 29 corresponds to the "first coordinate converter," the fixed coordinate converter 33 corresponds to the "second coordinate converter," the dq converter 39 corresponds to the "third coordinate converter," the inverse dq converter 40 corresponds to the "fourth coordinate converter," the dq converter 41 corresponds to the "fourth coordinate converter," and the inverse dq converter 42 corresponds to the "fifth coordinate converter." Adders 21 and 22 correspond to the "first adder," and adders 37 and 38 correspond to the "second adder."

Furthermore, the inverse dq converter 29 and adders 21 and 22 correspond to an embodiment of "means for generating a d-axis current command value and a q-axis current command value." The fixed coordinate converter 33, subtractors 34-36, first compensators CP11-CP13, dq converter 39, second compensators CP21 and CP22, and inverse converter 40 correspond to an embodiment of "means for performing proportional-integral control on the deviation of the current detector's detected values from the d-axis current command value and the q-axis current command value." The dq converter 41 corresponds to an embodiment of "means for converting the deviation of the current detector's detected values into a negative-phase coordinate system." The third compensators CP31 and CP32 correspond to an embodiment of "means for performing integral control calculation on the deviation of the current detector's detected values converted to the negative-phase coordinate system." Adders 37 and 38 correspond to an embodiment of "means for generating a three-phase AC voltage command value using the calculated value obtained by the proportional-integral control calculation and the calculated value obtained by the integral control calculation."

As described above, in the power conversion device according to the second embodiment, the control device 7 coordinate-transforms the current command values idpn* and iqqn*, which are obtained by combining the positive-phase current command values id* and iq* and the negative-phase current command values idn* and iqn*, into three-phase AC current command values iu*, iv*, and iw*. It also converts the deviations Δiu, Δiv, and Δiw of the three-phase AC currents iu, iv, and iw relative to the three-phase AC current command values iu*, iv*, and iw* into the negative-phase d-axis deviation Δidn and the negative-phase q-axis deviation Δiqn. The control device 7 is then configured to perform integral control calculations to compensate for the negative-phase d-axis deviation Δidn and the negative-phase q-axis deviation Δiqn. Therefore, similar to the power conversion device according to the first embodiment, the power conversion device according to the second embodiment can also eliminate steady-state deviations relative to the negative-phase current command values idn* and iqn*.

Furthermore, in the power conversion device according to embodiment 2, proportional control is performed on each of the deviations Δiu, Δiv, and Δiw of the three-phase AC currents iu, iv, and iw from the three-phase AC current command values iu*, iv*, and iw*. This allows each phase current to be controlled individually, making it possible to appropriately respond to disturbances occurring at each of the AC terminals Tu, Tv, and Tv of the power converter 3.

Furthermore, in the power conversion device according to embodiment 2, as in the power conversion device according to embodiment 1, the detected value (three-phase AC current) of the current detector 5 is used to calculate the feedback control amount without performing any calculations other than coordinate transformation on the detected value, thereby enabling high-speed control without causing any transient detection delay in the three-phase AC current.

Note that because the deviations Δiu, Δiv, and Δiw are AC quantities, the steady-state deviations cannot be eliminated by integral control, which integrates these deviations over time. Therefore, integral control is performed on the d-axis and q-axis deviations Δid and Δiq of the positive-phase-sequence components, and the d-axis deviations Δidn and q-axis deviations Δiqn of the negative-phase-sequence components.

Third Embodiment
FIG. 4 is a circuit block diagram showing the configuration of a power conversion device according to the third embodiment.

As shown in Figure 4, the power conversion device of embodiment 3 basically has the same configuration as the power conversion device of embodiment 1 shown in Figure 1, but the configuration of the control device 7 is different from that of the power conversion device of embodiment 1.

The control device 7 includes a phase detector 9, a current control unit 8, adders 11 and 12, an inverse dq converter 13, and a PWM circuit 14.

The phase detector 9 generates a reference phase θ (positive voltage phase) based on the output signal of the voltage detector 4.

The dq converter 10 converts the three-phase AC voltages Vu, Vv, and Vw detected by the voltage detector 4 into a positive-phase d-axis voltage Vd and a positive-phase q-axis voltage Vq through a dq coordinate transformation (three-phase to two-phase coordinate transformation) using a positive-phase coordinate system.

The current control unit 8 calculates a feedback control amount through control calculations to reduce the deviation of the detection value of the current detector 5 from the AC current command value. The AC current command value includes positive-phase current command values id* and iq* and negative-phase current command values idn* and iqn*.

The current control unit 8 includes adders 21, 22, 55, 56, 62-65, subtractors 23, 24, 58, 59, inverse dq converters 29, 57, filters 51-54, first compensators CP11, CP12, second compensators CP21, CP22, third compensators CP31, CP32, a dq converter 60, and an inverse dq converter 61.

The inverse dq converter 29 performs an inverse dq coordinate transformation using the reference phase (positive-phase voltage phase) θ, and converts the negative-phase current command values idn* and iqn* to the positive-phase coordinate system.

Adder 21 generates the d-axis current command value idpn* by adding the positive-phase d-axis current command value id* and the negative-phase d-axis current command value idn* using equation (3). Adder 22 generates the q-axis current command value iqpn* by adding the positive-phase q-axis current command value iq* and the negative-phase q-axis current command value iqn* using equation (4).

The dq converter 32 performs coordinate transformation (three-phase to two-phase transformation) on the three-phase AC currents iu, iv, and iw detected by the current detector 5 from a fixed coordinate system to a positive-phase coordinate system using equation (1), and calculates the positive-phase d-axis current id and the positive-phase q-axis current iq.

Subtractor 23 calculates the deviation of the positive-phase d-axis current id from the d-axis current command value idpn* (positive-phase d-axis deviation) Δid. Subtractor 24 calculates the deviation of the positive-phase q-axis current iq from the q-axis current command value iqpn* (positive-phase q-axis deviation) Δiq.

The first compensators CP11 and CP12 perform proportional control calculations to reduce the positive-phase d-axis deviation Δid and the positive-phase q-axis deviation Δiq, and calculate the proportional control amounts Kp·Δid and Kp·Δiq. Kp is the proportional gain.

Filter 51 removes high-frequency components above a predetermined frequency from the positive-phase d-axis current command value id*. Filter 52 removes high-frequency components above a predetermined frequency from the positive-phase q-axis current command value iq*. Filters 51 and 52 may be, for example, low-pass filters (LPFs) or rate-of-change limiters.

Filter 53 removes high-frequency components above a predetermined frequency from the negative-phase d-axis current command value idn*. Filter 54 removes high-frequency components above a predetermined frequency from the negative-phase q-axis current command value iqn*. Filters 53 and 54 may be, for example, an LPF or a rate-of-change limiter.

The inverse dq converter 57 performs an inverse dq coordinate transformation using the reference phase (positive-phase voltage phase) θ using equation (2) to transform the negative-phase current command values idn* and iqn* into the positive-phase coordinate system.

Adder 55 generates a d-axis current command value idpn* by adding the positive-phase d-axis current command value id* and the negative-phase d-axis current command value idn* using equation (3). Adder 56 generates a q-axis current command value iqpn* by adding the positive-phase q-axis current command value iq* and the negative-phase q-axis current command value iqn* using equation (4).

Subtractor 58 calculates the deviation of the positive-phase d-axis current id from the d-axis current command value idpn* (positive-phase d-axis deviation) Δid. Subtractor 59 calculates the deviation of the positive-phase q-axis current iq from the q-axis current command value iqpn* (positive-phase q-axis deviation) Δiq.

The second compensators CP21 and CP22 calculate integral control variables Σ(Ki·Δid) and Σ(Ki·Δiq) through integral control calculations to reduce the positive-phase d-axis deviation Δid and the positive-phase q-axis deviation Δiq. Ki is the integral gain. The second compensators CP21 and CP22 may further include a filter (such as a moving average filter) to remove components other than DC.

The dq converter 60 performs coordinate conversion from the positive-phase coordinate system to the negative-phase coordinate system using equation (5) to calculate the negative-phase d-axis deviation Δidn and the negative-phase q-axis deviation Δiqn.

The third compensators CP31 and CP32 perform integral control calculations to reduce the negative-phase-sequence d-axis deviation Δidn and the negative-phase-sequence q-axis deviation Δiqn, and calculate the integral control amount. Specifically, the third compensator CP31 performs integral control calculations on the negative-phase-sequence d-axis deviation Δidn and calculates the integral control amount Σ (Ki · Δidn). The third compensator CP32 performs integral control calculations on the negative-phase-sequence q-axis deviation Δiqn and calculates the integral control amount Σ (Ki · Δiqn). Ki is the integral gain.

The inverse dq converter 61 performs an inverse dq transformation using equation (2) to convert the integral control variables Σ(Ki·Δidn) and Σ(Ki·Δiqn), which are the values calculated by the third compensators CP31 and CP32, from the negative phase coordinate system to the positive phase coordinate system.

Adder 62 adds the positive-phase-sequence integral control variable Σ (Ki·Δid) from second compensator CP21 and the negative-phase-sequence integral control variable Σ (Ki·Δidn) from inverse dq converter 61. Adder 63 adds the positive-phase-sequence integral control variable Σ (Ki·Δiq) from second compensator CP22 and the negative-phase-sequence integral control variable Σ (Ki·Δiqn) from inverse dq converter 61.

Adder 64 adds the proportional control variable Kp·Δid from first compensator CP11 and the integral control variable Σ(Ki·Δid) + Σ(Ki·Δidn) from adder 62 to generate the d-axis voltage command value Vd* required for feedback control to reduce the positive-phase d-axis deviation Δid and the negative-phase d-axis deviation Δidn. Adder 65 adds the proportional control variable Kp·Δiq from first compensator CP12 and the integral control variable Σ(Ki·Δiq) + Σ(Ki·Δiqn) from adder 63 to generate the q-axis voltage command value Vq* required for feedback control to reduce the positive-phase q-axis deviation Δiq and the negative-phase q-axis deviation Δiqn.

Adder 11 adds the d-axis voltage Vd from the dq converter 10 to the d-axis voltage command value Vd* from adder 64. Adder 12 adds the q-axis voltage Vq from the dq converter 10 to the q-axis voltage command value Vq* from adder 65.

The inverse dq converter 13 performs an inverse dq coordinate transformation (two-phase to three-phase transformation) on the d-axis voltage command value Vd* from the adder 11 and the q-axis voltage command value Vq* from the adder 12 in the positive phase coordinate system to generate three-phase voltage command values (U-phase voltage command value Vu*, V-phase voltage command value Vv*, and W-phase voltage command value Vw*). The three-phase AC voltage command values are provided to the PWM circuit 14.

The PWM circuit 14 generates gate pulses based on a comparison between the three-phase AC voltage command value and a carrier wave (e.g., a triangular wave). It is sufficient for the PWM circuit 14 to generate gate pulses so that the AC voltage of the power converter 3 contains a component proportional to the voltage command value. In addition to generating gate pulses using a carrier wave, other methods include generating gate pulses based on the three-phase AC voltage command values Vu*, Vv*, and Vw* by referencing a predetermined table, or generating gate pulses by performing arithmetic processing using the amplitude and phase of the three-phase AC voltage command values Vu*, Vv*, and Vw*. The power converter 3 supplies three-phase AC power to the three-phase AC power system 1 via the reactor 2 in accordance with the gate pulses.

In the power conversion device according to embodiment 3, the dq converter 32 corresponds to the "first coordinate converter," the inverse dq converter 29 corresponds to the "second coordinate converter," the inverse dq converter 57 corresponds to the "third coordinate converter," the dq converter 60 corresponds to the "fourth coordinate converter," the inverse dq converter 61 corresponds to the "fifth coordinate converter," and the inverse dq converter 13 corresponds to the "sixth coordinate converter." Adders 21 and 22 correspond to the "first adder," and adders 55 and 56 correspond to the "second adder."

Furthermore, the inverse dq converters 29 and 57, filters 51-54, and adders 21, 22, 55, and 56 correspond to an embodiment of "means for generating a d-axis current command value and a q-axis current command value." The first compensators CP11 and CP12 and the second compensators CP21 and CP22 correspond to an embodiment of "means for performing proportional-integral control on the deviation of the current detector's detection value from the d-axis current command value and the q-axis current command value." The dq converter 60 corresponds to an embodiment of "means for converting the deviation of the current detector's detection value into a negative-phase coordinate system." The third compensators CP31 and CP32 correspond to an embodiment of "means for performing integral control calculation on the deviation of the current detector's detection value converted into the negative-phase coordinate system." Adders 62-65 correspond to an embodiment of "means for generating a three-phase AC voltage command value using the calculated value obtained by the proportional-integral control calculation and the calculated value obtained by the integral control calculation."

As described above, in the power conversion device according to embodiment 3, similar to the power conversion device according to embodiment 1 described above, the control device 7 generates a current command value by combining the positive-phase current command values id*, iq* and the negative-phase current command values idn*, iqn*, converts the positive-phase d-axis deviation Δid and the positive-phase q-axis deviation Δiq relative to the current command value into the negative-phase d-axis deviation Δidn and the negative-phase q-axis deviation Δiqn, and performs integral control calculations to compensate for the negative-phase d-axis deviation Δidn and the negative-phase q-axis deviation Δiqn. This makes it possible to eliminate steady-state deviations for the negative-phase current command values idn*, iqn*.

Furthermore, in the power conversion device according to embodiment 3, the d-axis and q-axis deviations input to the second compensators CP21, CP22 and the third compensators CP31, CP32, which perform integral control calculations, are calculated based on the current command value from which high-frequency components have been removed using filters 51-54 and the detection value of the current detector 5. This suppresses interference between the integral control of the positive-phase sequence component and the integral control of the negative-phase sequence component. Specifically, assume that the positive-phase sequence current command values id* and iq* change stepwise (i.e., discontinuously). In this case, the d-axis current command value idpn* and the q-axis current command value iqpn* also change stepwise. In response, the negative-phase sequence d-axis deviation Δidn and the negative-phase sequence q-axis deviation Δiqn calculated by the dq converter 60 also change stepwise. When integral control calculations are performed on these stepwise changing current deviations Δidn and Δiqn, a transient response may occur in the integral control variable of the negative-phase sequence component. In other words, a change in the current command value of the positive-phase component can cause a transient response in the integral control of the negative-phase component.

Conversely, consider a case where the negative-phase sequence current command values idn* and iqn* change in steps (i.e., discontinuously). In this case, the d-axis current command value idpn* and the q-axis current command value iqpn* also change in steps, causing the positive-phase sequence d-axis deviation Δid and the positive-phase sequence q-axis deviation Δiq to also change in steps. Then, in the integral control calculation for these step-like changing current deviations Δid and Δiq, a transient response may occur in the integral control amount of the positive-phase sequence component. In other words, a change in the current command value of the negative-phase sequence component may cause a transient response in the integral control of the positive-phase sequence component.

In the power conversion device according to embodiment 3, filters 51 to 54 remove high-frequency components from the positive-phase current command values id*, iq* and the negative-phase current command values idn*, iqn*, thereby preventing a sudden change in the current command value of either the positive-phase or negative-phase component from affecting the integral control of the other. In other words, interference between the integral control of the positive-phase component and the integral control of the negative-phase component can be suppressed.

In the power conversion device according to embodiment 3, proportional control of the positive and negative phase components is performed by calculating the current deviations Δid and Δiq relative to the AC current command values idpn* and iqpn* without using a filter. This is because, unlike the integral control described above, proportional control requires a high-speed response proportional to the magnitude of the deviation in order to suppress fluctuations in the output current. By not using a filter for proportional control, it is possible to suppress current control interference between the positive and negative phase components while ensuring a high-speed response.

Furthermore, in the power conversion device according to embodiment 3, as in the power conversion device according to embodiment 1, the detected value (three-phase AC current) of the current detector 5 is used to calculate the feedback control amount without performing any calculations other than coordinate transformation on the detected value, thereby enabling high-speed control without causing any transient detection delay in the three-phase AC current.

It is intended from the outset that the configurations described in the above-mentioned embodiments and modified examples may be combined as appropriate, including combinations not mentioned in the specification, to the extent that no inconvenience or contradiction arises.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications that are equivalent in meaning to and within the scope of the claims.

1 Three-phase AC power system, 2 Reactor, 3 Power converter, 4 Voltage detector, 5 Current detector, 7, 7A Control device, 8, 8A Current control unit, 9 Phase detector, 10, 30, 32, 39, 41, 60 dq converter, 11, 12, 15, 21, 22, 25 to 28, 37, 38, 55, 56, 62 to 65, 75, 78 Adder, 13, 29, 31, 40, 42, 57, 61 Inverse dq converter, 14 PWM circuit, 23, 24, 34, 35, 58, 59 Subtractor, 33 Fixed coordinate converter, 51 to 54 Filter, 73, 76 Proportional converter, 74, 77 Integrator, CP11 to CP13 First compensator, CP21, CP22 Second compensator, CP31, CP32 Third compensator.

Claims (3)

a power converter that converts a DC voltage into a three-phase AC voltage and outputs the voltage to a three-phase AC power system or a three-phase AC load;
a current detector for detecting an output current of the power converter;
a control device for controlling the power converter,
The control device
a current control unit that generates a three-phase AC voltage command value by feedback control for compensating for a deviation of a detection value of the current detector from an AC current command value;
a PWM circuit that generates a control signal for the power converter based on the three-phase AC voltage command value, thereby PWM-controlling the power converter;
the AC current command values include a positive-phase d-axis current command value, a positive-phase q-axis current command value, and a negative-phase d-axis current command value, and a negative-phase q-axis current command value,
The current control unit
means for generating a d-axis current command value by combining the positive-phase d-axis current command value and the negative-phase d-axis current command value, and for generating a q-axis current command value by combining the positive-phase q-axis current command value and the negative-phase q-axis current command value;
means for performing proportional-integral control calculations on deviations of the detected values of the current detectors from the d-axis current command value and the q-axis current command value;
means for converting the deviation of the detected value of the current detector into a reverse phase coordinate system;
means for performing integral control calculations on the deviation of the detected value of the current detector transformed into the reverse phase coordinate system;
a means for generating the three-phase AC voltage command value using a calculated value obtained by the proportional-integral control calculation and a calculated value obtained by the integral control calculation,
The current control unit
a first coordinate converter that converts the output current detected by the current detector into a positive-phase d-axis current and a positive-phase q-axis current;
a second coordinate converter that converts the negative-phase d-axis current command value and the negative-phase q-axis current command value into a positive-phase coordinate system;
a first adder that generates a first d-axis current command value by adding the positive-phase d-axis current command value and the negative-phase d-axis current command value obtained by the second coordinate converter, and that generates a first q-axis current command value by adding the positive-phase q-axis current command value and the negative-phase q-axis current command value obtained by the second coordinate converter;
a first compensator that performs proportional control calculations on a deviation of the positive-phase d-axis current from the first d-axis current command value and a deviation of the positive-phase q-axis current from the first q-axis current command value;
a first filter that attenuates high-frequency components of the positive-phase d-axis current command value and the positive-phase q-axis current command value;
a second filter that attenuates high-frequency components of the negative-phase d-axis current command value and the negative-phase q-axis current command value;
a third coordinate converter that converts the negative-phase-sequence d-axis current command value and the negative-phase-sequence q-axis current command value that have passed through the second filter into the positive-phase coordinate system;
a second adder that generates a second d-axis current command value by adding the positive-phase d-axis current command value that has passed through the first filter and the negative-phase d-axis current command value obtained by the third coordinate converter, and that generates a second q-axis current command value by adding the positive-phase q-axis current command value that has passed through the first filter and the negative-phase q-axis current command value obtained by the third coordinate converter;
a second compensator that performs integral control calculations on a deviation of the positive-phase d-axis current from the second d-axis current command value and a deviation of the positive-phase q-axis current from the second q-axis current command value;
a fourth coordinate converter that converts a deviation of the positive-phase d-axis current from the second d-axis current command value and a deviation of the positive-phase q-axis current from the second q-axis current command value into the negative-phase coordinate system;
a third compensator that performs integral control calculations on the deviation of the positive-phase d-axis current and the deviation of the positive-phase q-axis current transformed into the negative-phase coordinate system;
a fifth coordinate converter that converts a value calculated by the third compensator into the positive phase coordinate system;
a sixth coordinate converter that generates the three-phase AC voltage command value by performing two-phase to three-phase conversion on a sum of a value calculated by the first compensator, a value calculated by the second compensator , and a value calculated by the fifth coordinate converter. a power converter that converts a DC voltage into a three-phase AC voltage and outputs the voltage to a three-phase AC power system or a three-phase AC load;
a current detector for detecting an output current of the power converter;
a control device for controlling the power converter,
The control device
a current control unit that generates a three-phase AC voltage command value by feedback control for compensating for a deviation of a detection value of the current detector from an AC current command value;
a PWM circuit that generates a control signal for the power converter based on the three-phase AC voltage command value, thereby PWM-controlling the power converter;
the AC current command values include a positive-phase d-axis current command value, a positive-phase q-axis current command value, and a negative-phase d-axis current command value, and a negative-phase q-axis current command value,
The current control unit
means for generating a d-axis current command value by combining the positive-phase d-axis current command value and the negative-phase d-axis current command value, and for generating a q-axis current command value by combining the positive-phase q-axis current command value and the negative-phase q-axis current command value;
means for performing proportional-integral control calculations on deviations of the detected values of the current detectors from the d-axis current command value and the q-axis current command value;
means for converting the deviation of the detected value of the current detector into a reverse phase coordinate system;
means for performing integral control calculations on the deviation of the detected value of the current detector transformed into the reverse phase coordinate system;
means for generating the three-phase AC voltage command value using a calculated value obtained by the proportional-integral control calculation and a calculated value obtained by the integral control calculation;
The current control unit
a first coordinate converter that converts the negative-phase d-axis current command value and the negative-phase q-axis current command value into a positive-phase coordinate system;
a first adder that generates the d-axis current command value by adding the positive-phase d-axis current command value and the negative-phase d-axis current command value obtained by the first coordinate converter, and that generates the q-axis current command value by adding the positive-phase q-axis current command value and the negative-phase q-axis current command value obtained by the first coordinate converter;
a second coordinate converter that converts the d-axis current command value and the q-axis current command value into three-phase AC current command values;
a first compensator that performs proportional control calculation on a deviation of the output current detected by the current detector from the three-phase AC current command value;
a third coordinate converter that converts a deviation of the output current detected by the current detector from the three-phase AC current command value into a deviation of a positive-phase d-axis current and a deviation of a positive-phase q-axis current;
a second compensator that performs integral control calculations on the deviation of the positive-phase d-axis current and the deviation of the positive-phase q-axis current;
a fourth coordinate converter that converts a calculated value by the second compensator from two phases to three phases;
a fifth coordinate converter that converts a deviation of the output current detected by the current detector from the three-phase AC current command value into a deviation of a negative-phase d-axis current and a deviation of a negative-phase q-axis current;
a third compensator that performs integral control calculations on the deviation of the negative-phase-sequence d-axis current and the deviation of the negative-phase-sequence q-axis current;
a sixth coordinate converter for converting a calculated value by the third compensator from two phases to three phases;
a second adder that generates the three-phase AC voltage command value by adding together a value calculated by the first compensator, a value calculated by the fourth coordinate converter, and a value calculated by the sixth coordinate converter. 3. The power conversion device according to claim 1 , wherein at least one of the second compensator and the third compensator has a filter characteristic that attenuates components other than DC in addition to an integral control characteristic.