WO2019049713A1

WO2019049713A1 - Power conversion device and method for controlling same

Info

Publication number: WO2019049713A1
Application number: PCT/JP2018/031665
Authority: WO
Inventors: 川添　裕成; 智道伊藤; 健太渡邊; 康博今津; 一瀬　雅哉
Original assignee: 株式会社日立製作所
Priority date: 2017-09-07
Filing date: 2018-08-28
Publication date: 2019-03-14
Also published as: JP6851291B2; JP2019047701A

Abstract

The purpose of the present invention is to make it possible to control cell voltage balance appropriately in a power conversion device. Accordingly, a power conversion device S1 is provided with: a plurality of arms (3) each of which includes a plurality of cells (2), each cell (2) having at least one capacitor and at least one switching element; a gate pulse signal output unit (108) which, on the basis of output currents (Iau, Iav, Iaw) from the arms 3, outputs a gate pulse signal which is a PWM modulated wave for controlling the switching elements; a harmonic current extraction unit (101) which extracts a harmonic current, included in the output currents (Iau, Iav, Iaw), of a harmonic component in a predetermined band including a modulation period of the PWM modulated wave; and a current control unit (102) which controls the gate pulse signal output unit (108) so as to suppress the extracted harmonic current.

Description

Power converter and control method thereof

The present invention relates to a power converter and a control method thereof.

In a power converter referred to as MMC (Modular Multilevel Converter), a plurality of single-phase converters (hereinafter referred to as cells) having capacitors individually are connected in series in each of the three-phase arms. . In MMC, in order to output a desired AC voltage to an AC system, it is preferable to balance capacitor voltages of the plurality of cells. For this reason, many MMCs are provided with a control function of adjusting the charge / discharge amount of the capacitor for each cell to balance the voltage of the DC section.

Here, as described in, for example, Patent Document 1 below, each energy storage element (capacitor) in the power converter even if the amount of power interchanged between the AC system and the power converter is small. There is known a technology for keeping balance of energy storage amount (voltage).

JP, 2016-197940, A

Incidentally, various external devices are also connected to the AC system to which the MMC is connected. Then, there are cases where these external devices generate a harmonic current having a period identical to or close to that of a PWM (Pulse Width Modulation) carrier in MMC. In the technique of Patent Document 1 described above, there is a problem that when this type of harmonic current flows into the MMC via the AC system, control for securing the voltage balance of the cell can not be appropriately executed.
This invention is made in view of the situation mentioned above, and it aims at providing the power converter which can control the voltage balance of a cell appropriately, and its control method.

In order to solve the above problems, a power converter according to the present invention comprises a plurality of arms, each having a plurality of cells, wherein one cell includes at least one capacitor and at least one switching element; A gate pulse signal output unit that outputs a gate pulse signal that is a PWM modulation wave for controlling the switching element based on the output current of each of the arms, and modulation of the PWM modulation wave included in the output current A harmonic current extraction unit that extracts a harmonic current that is a harmonic component in a predetermined band including a cycle; and a current control unit that controls the gate pulse signal output unit to suppress the extracted harmonic current , And is characterized by.

According to the present invention, the voltage balance of the cell can be properly controlled.

FIG. 1 is a block diagram showing an overall configuration of a power conversion device according to an embodiment of the present invention. It is a wave form diagram which shows an example of a PWM carrier wave. It is a block diagram of a harmonic current extraction part. FIG. 6 is a block diagram of a current control unit and a control on / off determination unit. It is operation | movement explanatory drawing of a converter output determination part. It is operation | movement explanatory drawing of a system | strain harmonic determination part. It is a block diagram of a coordinate conversion part. It is a wave form diagram of the capacitor voltage in one embodiment. It is a wave form diagram of the capacitor voltage in a comparative example.

<Configuration of Embodiment>
FIG. 1 is a block diagram showing an entire configuration of a power conversion device S1 according to an embodiment of the present invention.
Power conversion device S1 is connected between three-phase AC system 5 and power conversion device S2. The power conversion device S1 includes a power converter 1, a transformer 4, a current sensor 7, a voltage sensor 8, a positive electrode terminal 10P, a negative electrode terminal 10N, and a control device 100. The power converter 1 has

arms

3 u, 3 v, 3 w corresponding to three phases of U phase, V phase and W phase. These may be generically referred to as "arm 3".

The arm 3 u includes M cells 2 u-1 to 2 u-M connected in series. These cells are provided with capacitors (not labeled), and the terminal voltages of these capacitors are output as capacitor voltages Vcu1 to VcuM. Similarly, arm 3v has M cells 2v-1 to 2v-M connected in series, and these cells output capacitor voltages Vcv1 to VcvM. Similarly, arm 3w has M cells 2w-1 to 2w-M connected in series, and these cells output capacitor voltages Vcw1 to VcwM.

These cells 2u-1 to 2u-M, 2v-1 to 2v-M, and 2w-1 to 2w-M may be collectively referred to as "cell 2". Further, the capacitor voltages Vcu1 to VcuM, Vcv1 to VcvM, and Vcw1 to VcwM may be collectively referred to as "capacitor voltage Vc". For example, a chopper circuit or a full bridge circuit can be applied to the cell 2. The cell 2 includes, for example, switching elements such as IGBTs (Insulated Gate Bipolar Transistors), and the control device 100 supplies gate pulse signals for on / off controlling the switching elements. The gate pulse signal is obtained by PWM (Pulse Width Modulation) modulation of a voltage command value.

The current sensor 7 detects arm currents Iau, Iav, Iaw (output currents) flowing through the

arms

3u, 3v, 3w. Further, voltage sensor 8 detects system voltages Vu, Vv, Vw of AC system 5. The transformer 4 has a primary winding 4a and a secondary winding 4b. A winding structure of delta or star connection is applied to the primary winding 4a, and a winding structure of zigzag connection is applied to the secondary winding 4b. One end of the three-phase arm 3 described above is connected to the positive electrode terminal 10P, and the other end is connected to each phase of the secondary winding 4b via the current sensor 7. The neutral point of the secondary winding 4b is connected to the negative electrode terminal 10N.

An external device 50 is connected to the AC system 5. The external device 50 leaks a harmonic current having a period equal to or close to the PWM modulation period to the power conversion device S1 via the AC system 5. That is, among the harmonic components included in the arm currents Iau, Iav and Iaw, the harmonic current corresponds to a component of a predetermined band which is the same as or close to the PWM modulation period. The external device 50 is, for example, a rectifier load or a thyristor-type power converter. When this harmonic current flows into the power conversion device S1, the balance of the capacitor voltage Vc in each cell 2 is affected.

The power conversion device S2 is configured in the same manner as the power conversion device S1, and is connected to the positive electrode terminal 10P and the negative electrode terminal 10N, and is also connected to another AC system 15. The AC system 15 is independent of voltage, frequency, and phase with respect to the AC system 5. And power conversion device S1, S2 performs mutual conversion of alternating current and direct current, respectively. With this configuration, AC networks 5 and 15 can mutually exchange power via power conversion devices S1 and S2.

The control device 100 includes hardware as a general computer, such as a central processing unit (CPU), a digital signal processor (DSP), a random access memory (RAM), and a read only memory (ROM). , A control program executed by the CPU, a microprogram executed by the DSP, various data, and the like are stored. In FIG. 1, the inside of the control device 100 shows functions implemented by a control program and a microprogram as blocks.

In the control device 100, the harmonic current extraction unit 101 extracts harmonic currents included in the arm currents Iau, Iav, Iaw detected by the current sensor 7. Here, the harmonic current refers to a component of a predetermined band that is the same as or similar to the PWM modulation period among the arm currents Iau, Iav, and Iaw. The current control unit 102 suppresses the harmonic current extracted by the harmonic current extraction unit 101. The details will be described later.

Control on / off determination unit 103 determines whether to execute control of current control unit 102 based on arm currents Iau, Iav, Iaw and grid voltages Vu, Vv, Vw, that is, suppresses harmonic current It is determined whether to do. The coordinate conversion unit 104 converts the output of the current control unit 102 into a three-phase harmonic voltage command. The fundamental wave current control unit 106 outputs a fundamental wave voltage command for controlling the current component of the fundamental wave (for example, 50 Hz or 60 Hz). The adder 105 adds the harmonic voltage command output from the coordinate conversion unit 104 and the fundamental voltage command output from the fundamental current control unit 106, and the result is output to the PWM modulator 108 (gate pulse signal output Supply to

The voltage balance control unit 107 has a control function to receive capacitor voltages Vcu1 to VcuM, Vcv1 to VcvM, and Vcw1 to VcwM of the respective cells 2 and to balance capacitor voltages of the

arms

3u, 3v, 3w and the respective cells 2. For a specific voltage balance control method, for example, “Technical trend of the Institute of Electrical Engineers of Japan No. 1374“ Technological trend of a new type self-commutated direct-current converter for power system ”-mainly on modular multi-level converter (MMC)- The methods described in pp. 14, 15, 28) may be used. The capacitor voltage calculated by the voltage balance control unit 107 is also supplied to the fundamental wave current control unit 106. The PWM modulation unit 108 generates a gate pulse signal for driving each cell 2 based on the output signal of the adder 105, the output signal of the voltage balance control unit 107, and the PWM carrier wave CR.

FIG. 2 is a waveform diagram showing an example of the PWM carrier wave CR. The period of the PWM carrier CR is called a carrier period Tc, and the period of the fundamental wave is called a fundamental wave period Tf. In the illustrated example, the fundamental frequency is 50 Hz, and the fundamental period Tf is 20 ms. Also, the carrier frequency is 250 Hz, and the carrier period Tc is 4 ms.

FIG. 3 is a block diagram of the harmonic current extraction unit 101. As shown in FIG. The harmonic current extraction unit 101 includes a three-phase / two-phase conversion unit 101A, a dq conversion unit 101B, and a moving average unit 101C. The three-phase / two-phase conversion unit 101A converts the three-phase arm currents Iau, Iav, Iaw into two-phase currents Iα, Iβ based on the following equation (1).

Here, assuming rotational coordinates that rotate at the same frequency as the carrier frequency fn (250 Hz in the above example) of the PWM carrier CR, axes orthogonal to this rotational coordinate are called dq axes (that is, d axes and q axes). The dq conversion unit 101B converts the two-phase currents Iα and Iβ into currents Idn and Iqn on the dq axis based on the following equation (2). As a result, a component having the same frequency as the carrier frequency fn of the PWM carrier CR is converted into a direct current amount in the currents Idn and Iqn. Here, t is time.

The moving average unit 101C extracts harmonic currents Idhm and Iqhm in a predetermined band that is the same as or similar to the PWM carrier CR from the currents Idn and Iqn on the dq axis based on the following equations (3) and (4). Execute arithmetic processing. In the following formulas (3) and (4), N is a moving average score. The moving average number N may be set to about a value obtained by dividing the sampling frequency at which the currents Idn and Iqn are sampled by the fundamental frequency. For example, assuming that the sampling frequency of the currents Idn and Iqn is 5 kHz and the fundamental wave frequency is 50 Hz, the moving average number N may be set to about 100 (= 5 kHz / 50 Hz). Also, Idn (1) to Idn (N-1) are values of the current Idn in the past by 1 to (N-1) sampling periods, and Iqn (1) to Iqn (N-1) are 1 to N-1) The value of the current Iqn in the past by the sampling period,

FIG. 4 is a block diagram of the current control unit 102 and the control on / off determination unit 103.
The current control unit 102 includes

subtractors

102D and 102E, a d-axis current controller 102A, and a q-axis current controller 102B. The subtractor 102D subtracts the harmonic current Idhm from the harmonic current command Idhmr. Further, the subtractor 102E subtracts the harmonic current Iqhm from the harmonic current command Iqhmr.

Here, both harmonic current commands Idhmr and Iqhmr should be zero. The d-axis current controller 102A performs integral control or proportional integral control of the output signal of the subtractor 102D to bring the harmonic current Idhm closer to the harmonic current command Idhmr (for example, zero). (Command signal) is output. Similarly, the q-axis current controller 102B performs integration control or proportional integration control on the output signal of the subtractor 102E to bring the harmonic current Iqhm close to the harmonic current command Iqhmr (eg, zero). The voltage command Vqhmr (command signal) is output.

Further, the control on / off determination unit 103 includes an effective current extraction unit 103A, a harmonic voltage extraction unit 103B, a system harmonic determination unit 103D, and an AND circuit 103E (on / off state setting unit). There is. As described above, the control on / off determination unit 103 is supplied with the detection results of the arm currents Iau, Iav and Iaw from the current sensor 7 and the detection results of the system voltages Vu, Vv and Vw from the voltage sensor 8. Ru. The effective current extraction unit 103A calculates the effective current Iact output from the power converter 1 based on the following equation (5).

Further, based on system voltages Vu, Vv and Vw, harmonic voltage extraction unit 103B uses the equations (6) to (10) described below to determine harmonics within a predetermined band identical to or close to PWM carrier CR. The amplitude value Vhm of the voltage is extracted. Formulas (6) to (10) will be sequentially described below. The harmonic voltage extraction unit 103B first converts the system voltages Vu, Vv, and Vw into two-phase voltages Vα and Vβ based on the following equation (6).

Next, the harmonic voltage extraction unit 103B converts the voltages Vα and Vβ into the voltages Vdn and Vqn on the dq axis based on the following equation (7). As a result, a component having the same frequency as the carrier frequency fn of the PWM carrier CR is converted into a direct current amount at the voltages Vdn and Vqn. Here, t is time.

Next, based on the following equations (8) and (9), the harmonic voltage extraction unit 103B determines from the voltages Vdn and Vqn on the dq axis the harmonic voltage Vdhm in a predetermined band that is the same as or similar to that of the PWM carrier CR. , Vqhm are executed. In the following formulas (8) and (9), N is a moving average score. Further, Vdn (1) to Vdn (N-1) are voltages Vdn that are one sampling period to (N-1) sampling periods earlier. The same applies to Vqn (1) to Vqn (N-1). Assuming that the sampling frequency for sampling the voltages Vdn and Vqn is 5 kHz and the frequency of the fundamental wave is 50 Hz as in the moving average unit 101C described above, the moving average number N should be set to about 100 (= 5 kHz / 50 Hz). .

Next, the harmonic voltage extraction unit 103B calculates the amplitude value Vhm based on the following equation (10). The amplitude value Vhm is an amplitude value of a harmonic voltage in a predetermined band which is the same as or similar to that of the PWM carrier CR.

Further, converter output determination unit 103C receives effective current Iact from effective current extraction unit 103A, and outputs determination flag signal Scnt1 for turning on / off the function of current control unit 102. Further, the system harmonic determination unit 103D receives the amplitude value Vhm of the harmonic voltage from the harmonic voltage extraction unit 103B, and outputs a determination flag signal Scnt2 for turning on / off the function of the current control unit 102.

In the determination flag signals Scnt1 and Scnt2, the on state is “1” and the off state is “0”. The details of the determination methods of the converter output determination unit 103C and the system harmonics determination unit 103D will be described later. The AND circuit 103E outputs an AND operation result of the determination flag signals Scnt1 and Scnt2 as a determination flag signal Scnt. That is, the determination flag signal Scnt is "1" (on state) when the determination flag signals Scnt1 and Scnt2 are both "1", and is "0" (off state) otherwise.

The functions of the d-axis current controller 102A and the q-axis current controller 102B in the current control unit 102 are turned off when the determination flag signal Scnt becomes "0". More specifically, the d-axis current controller 102A and the q-axis current controller 102B bring the d-axis and q-axis harmonic voltage commands Vdhmr and Vqhmr close to zero at a constant rate of change, and eventually the d-axis and q The axial harmonic voltage commands Vdhmr and Vqhmr are reset to zero.

FIG. 5 is an operation explanatory diagram of the converter output determination unit 103C. The horizontal axis in FIG. 5 is the effective current Iact, and the vertical axis is the determination flag signal Scnt1. In the figure, IactnL (first threshold), IactnH, IactpL (second threshold), IactpH are thresholds for determining on / off of the determination flag signal Scnt1, and the thresholds IactnL and IactnH are negative values, the threshold IactpL, IactpH is a positive value. That is, when the effective current Iact changes from a value less than the threshold IactnL to a value equal to or more than the threshold IactnL, the determination flag signal Scnt1 changes from "0" (off state) to "1" (on state).

When the effective current Iact changes from a value equal to or greater than the threshold IactnH to a value smaller than the threshold IactnH, the determination flag signal Scnt1 changes from “1” (on state) to “0” (off state). Further, when the effective current Iact changes from a value exceeding the threshold IactpL to a value less than the threshold IactpL, the determination flag signal Scnt1 changes from “0” (off state) to “1” (on state). When the effective current Iact changes from a value equal to or less than the threshold value IactpH to a value exceeding the threshold value IactpH, the determination flag signal Scnt1 changes from "1" (on state) to "0" (off state).

In other words, the determination flag signal Scnt1 is "0" (off state) when the absolute value of the effective current Iact is relatively large, and is "1" (on state) when the effective current Iact is relatively small. . This is because, if the absolute value of the effective current Iact is large, even if some harmonic current flows from the external device 50 (see FIG. 1) through the AC system 5 to the power converter 1, the capacitor voltage Vc It is because it is thought that the influence given is small. However, as shown in FIG. 5, by providing the determination condition with a hysteresis characteristic, frequent on / off determination fluctuations near the threshold are prevented.

FIG. 6 is an operation explanatory diagram of the system harmonics determination unit 103D. The horizontal axis of FIG. 6 is the amplitude value Vhm of the harmonic voltage, and the vertical axis is the determination flag signal Scnt2. VhmL and VhmH in the figure are thresholds for determining on / off of the determination flag signal Scnt2. That is, when the amplitude value Vhm changes from a value greater than or equal to the threshold value VhmL to a value smaller than the threshold value VhmL, the determination flag signal Scnt2 changes from “1” (on state) to “0” (off state). In addition, when the amplitude value Vhm changes from a value less than the threshold value VhmH (third threshold value) to a value greater than or equal to the threshold value VhmH, the determination flag signal Scnt2 changes from “0” (off state) to “1” (on state). .

In other words, the determination flag signal Scnt2 is “1” (on state) when the amplitude value Vhm of the harmonic voltage is relatively large, and is “0” (off state) when the amplitude value Vhm is relatively small. Become. This is because, when the amplitude value Vhm of the harmonic voltage is small, the harmonic current flowing from the external device 50 (see FIG. 1) into the power converter 1 via the AC system 5 is small, and the influence on the capacitor voltage Vc Is also considered small. Then, similar to the converter output determination unit 103C described above, the system harmonic determination unit 103D also applies the hysteresis characteristics to the determination conditions to prevent frequent on / off determination fluctuations near the threshold value. .

FIG. 7 is a block diagram of the coordinate conversion unit 104. As shown in FIG. The coordinate conversion unit 104 includes an inverse dq conversion unit 104A, a phase compensation unit 104B, and a two-phase three-phase conversion unit 104C. The inverse dq conversion unit 104A converts the d-axis and q-axis harmonic voltage commands Vdhmr and Vqhmr into two-phase (α-phase and β-phase) harmonic voltage commands Vαhmr and Vβhmr based on the following equation (11) . In equation (11), fn is the carrier frequency of the PWM carrier CR and t is time.

The phase compensation unit 104B is a block that compensates for the delay in the moving average unit 101C (see FIG. 3) described above. That is, phase compensation section 104B outputs harmonic voltage commands Vαhmr1 and Vβhmr1 obtained by advancing the phases of harmonic voltage commands Vαhmr and Vβhmr by the phase angle θ based on the following equation (12).

The two-phase / three-phase conversion unit 104C converts the harmonic voltage commands Vαhmr1 and Vβhmr1 into three-phase harmonic voltage commands Vuhmr, Vvhmr and Vwhmr, based on the following equation (13).

<Operation of Embodiment>
FIG. 8 is a waveform diagram of the capacitor voltage in the present embodiment, in which the horizontal axis represents time and the vertical axis represents voltage level. The waveform Vcu in FIG. 8 is obtained by superposing the waveforms of the capacitor voltages Vcu1 to VcuM. Similarly, the waveform Vcv is a superposition of the waveforms of the capacitor voltages Vcv1 to VcvM. Similarly, the waveform Vcw is obtained by superposing the waveforms of the capacitor voltages Vcw1 to VcwM. In the illustrated example, the number M of series connection of the cells 2 is “21”.

Each waveform shown in FIG. 8 is a waveform when a harmonic current having the same cycle as that of the PWM carrier CR (see FIG. 2) flows from the alternating current system 5 into the power conversion device S1. As a result, although the waveforms of the respective capacitor voltages Vcu1 to VcuM, Vcv1 to VcvM, and Vcw1 to VcwM are unbalanced, the variations of these waveforms remain at relatively low levels.

Comparative Example
Next, in order to clarify the effect of the present embodiment, the configuration of the comparative example will be described. The overall configuration of this comparative example is similar to that of the above embodiment (see FIG. 1), but the function of the current control unit 102 is always in the off state, which is different from the above embodiment.
FIG. 9 is a waveform diagram of a capacitor voltage in the present comparative example. The waveforms Vcu, Vcv and Vcw in FIG. 9 are waveforms obtained by superposing the waveforms of the capacitor voltages Vcu1 to VcuM, Vcv1 to VcvM, and Vcw1 to VcwM, as in the case of FIG. It can be seen that the waveform in FIG. 9 has larger variations in waveforms of the capacitor voltages Vcu1 to VcuM, Vcv1 to VcvM, and Vcw1 to VcwM, as compared with FIG.

<Effect of the embodiment>
As described above, the power conversion device (S1) of the present embodiment includes the harmonic current, which is a harmonic component within a predetermined band including the modulation period of the PWM modulation wave, included in the output current (Iau, Iav, Iaw). It has a harmonic current extraction part (101) to extract, and a current control part (102) which controls a gate pulse signal output part (108) so that the extracted harmonic current may be suppressed.
As a result, the harmonic current affecting the voltage balance of the cell (2) can be reduced, and the variation of the capacitor voltage waveform can be reduced as compared with the comparative example. In other words, it is possible to control the voltage balance of the cell appropriately.

More specifically, the current control unit (102) controls the gate pulse signal output unit (108) so that the extracted harmonic current approaches zero.
Thereby, the variation in the waveform of the capacitor voltage can be further reduced.

Further, in the power conversion device (S1) of the present embodiment, the active current extracting unit (103A) for extracting the effective current (Iact) included in the output current (Iau, Iav, Iaw) and the predetermined AC voltage A harmonic voltage extraction unit (103B) that extracts a harmonic voltage (Vhm) that is a harmonic component within a predetermined band including the modulation period of the modulation wave, and a magnitude of an effective current (Iact) or a harmonic voltage (Vhm) And an on / off state setting unit (103E) for setting the on / off state of the function of the current control unit (102).
Thereby, the on / off state of the function of the current control unit (102) can be set based on the magnitude of the effective current (Iact) or the harmonic voltage (Vhm).

More specifically, the on / off state setting unit (103E) is equal to or higher than a predetermined first threshold (IactnL) in which the effective current (Iact) is a negative value, and the effective current (Iact) is a positive value. If it is less than or equal to a predetermined second threshold (IactpL) and the harmonic voltage (Vhm) is greater than or equal to a predetermined third threshold (VhmH), the function of the current control unit (102) is turned on.
Thereby, the function of the current control unit (102) can be turned on when the absolute value of the effective current (Iact) is relatively small and the harmonic voltage (Vhm) is relatively large.

<Modification example>
The present invention is not limited to the embodiments described above, and various modifications are possible. The embodiments described above are illustrated to facilitate understanding of the present invention, and are not necessarily limited to those having all the described configurations. Moreover, another configuration may be added to the configuration of the above embodiment, and a part of the configuration may be replaced with another configuration. Further, control lines and information lines shown in the drawing indicate those which are considered to be necessary for explanation, and not all the control lines and information lines necessary on the product are shown. In practice, almost all configurations may be considered to be mutually connected. Possible modifications to the above embodiment are, for example, as follows.

(1) The hardware of the control device 100 in the above embodiment can be realized by a general computer, so the control device 100 in FIG. 1 and programs etc. for realizing the functions shown in FIGS. 3, 4 and 7 are stored. It may be stored in a medium or distributed via a transmission line.

(2) The control apparatus 100 in FIG. 1 and the functions shown in FIGS. 3, 4 and 7 have been described as software processing using a program in the above embodiment, but some or all of them may be ASICs The processing may be replaced by hardware processing using (Application Specific Integrated Circuit; IC for specific application) or FPGA (field-programmable gate array) or the like.

S1 Power converter Iact Active current Iau, Iav, Iaw Arm current (output current)
Vdhmr d-axis harmonic voltage command (command signal)
Vqhmr q axis harmonic voltage command (command signal)
2, 2u-1 to 2u-M, 2v-1 to 2v-M, 2w-1 to 2w-

M Cell

3, 3u, 3v, 3w Arm 1 Power converter 100 Control device 101 Harmonic current extraction unit 102 Current control Unit 103 control on / off determination unit 103A active current extraction unit 103B harmonic voltage extraction unit 103E AND circuit (on / off state setting unit)
108 PWM modulation unit (gate pulse signal output unit)

Claims

A plurality of arms, each having a plurality of cells, one of said cells having at least one capacitor and at least one switching element;
A gate pulse signal output unit that outputs a gate pulse signal that is a PWM modulation wave for controlling the switching element based on the output current of each of the arms;
A harmonic current extraction unit for extracting a harmonic current which is a harmonic component within a predetermined band including the modulation period of the PWM modulation wave, which is included in the output current;
A current control unit that controls the gate pulse signal output unit so as to suppress the extracted harmonic current;
A power converter characterized by having.
The power conversion device according to claim 1, wherein the current control unit controls the gate pulse signal output unit such that the extracted harmonic current approaches zero.
An active current extraction unit that extracts an active current included in the output current;
A harmonic voltage extraction unit for extracting a harmonic voltage which is a harmonic component within a predetermined band including a modulation period of the PWM modulation wave from a predetermined AC voltage;
An on / off state setting unit that sets an on / off state of the function of the current control unit based on the magnitude of the active current or the harmonic voltage;
The power converter according to claim 2, further comprising:
The on / off state setting unit is configured such that the effective current is equal to or more than a predetermined first threshold that is a negative value, and the effective current is equal to or less than a predetermined second threshold that is a positive value. The power conversion device according to claim 3, wherein the function of the current control unit is turned on if the voltage is equal to or higher than a predetermined third threshold.
A plurality of arms, each having a plurality of cells, one of said cells having at least one capacitor and at least one switching element;
A gate pulse signal output unit that outputs a gate pulse signal that is a PWM modulation wave for controlling the switching element based on the output current of each of the arms;
A harmonic current extraction unit for extracting a harmonic current which is a harmonic component within a predetermined band including the modulation period of the PWM modulation wave, which is included in the output current;
A current control unit that controls the gate pulse signal output unit so as to suppress the extracted harmonic current;
A control method of a power converter for controlling a power converter having:
The effective current included in the output current is equal to or higher than a predetermined first threshold which is a negative value, and the effective current is equal to or lower than a predetermined second threshold which is a positive value, and at a predetermined alternating voltage. A power converter characterized in that the function of the current control unit is turned on when a harmonic voltage which is a harmonic component in a predetermined band including a modulation period of a modulation wave is equal to or more than a predetermined third threshold. Control method.