JP4670867B2 - Current-controlled power converter - Google Patents

Description

  The present invention relates to a current control type power converter.

  Conventionally, as a current control type power converter, there is one that detects a line current with one DC-side current sensor (see, for example, Japanese Patent Application Laid-Open No. 2004-282974 (Patent Document 1)).

  This current control type power conversion device has a phase in which a line current cannot be detected in principle, and it is necessary to provide a current sensor for detecting an instantaneous value of a three-phase current on the AC side in order to obtain a dq axis current by coordinate conversion. .

  In such a current control type power conversion device provided with a current sensor on the AC side, when a current including a DC component flows to the transformer on the system side when connected to the power system, the transformer is demagnetized. There is a problem of inviting. According to the Agency for Natural Resources and Energy's “Guidelines for Grid Connection Technology Requirements”, the DC level on the AC side must be about 1% or less of the rated AC current.

For this reason, it is necessary to provide a DCCT capable of detecting a DC component on the AC side for current control of the current control type power converter provided with a current sensor on the AC side, and output from such a DCCT Hall element. Since a low voltage signal to be generated must be amplified by an amplifier, it is necessary to use DCCT compensated with high accuracy with respect to amplitude, offset, and temperature drift, which increases the cost.
JP 2004-282974 A

  Accordingly, an object of the present invention is to provide a current control type power converter that can compensate for the amplitude, offset, and temperature drift of a current sensor used on the AC side with a simple configuration and can reduce the cost by using an inexpensive current sensor. There is.

In order to solve the above problems, a current control type power converter according to the present invention is
A converter that has six switching elements constituting a three-phase bridge circuit and converts a three-phase AC voltage into a DC voltage or converts a DC voltage into a three-phase AC voltage;
An AC side current detection unit that detects an AC side current of the conversion unit;
A DC side current detection unit for detecting a DC side current of the conversion unit;
Based on the AC side current detected by the AC side current detection unit and the DC side current detected by the DC side current detection unit, the conversion unit is controlled by pulse width modulation using a space vector modulation method. A control unit,
The control unit
Of the DC side current detected by the DC side current detection unit, a current corresponding to a current component of a predetermined phase of the AC side current, and the AC side current detected by the AC side current detection unit With the amplitude correction value obtained based on the current component of the predetermined phase, the amplitude error of the alternating current detected by the alternating current detector is corrected,
Of the DC-side current detected by the DC-side current detector, a DC-side offset component corresponding to a current component of a predetermined phase of the AC-side current and detected by the AC-side current detector Correcting an offset error of the AC side current detected by the AC side current detection unit by an offset correction value obtained based on an AC side offset component corresponding to a current of a predetermined phase of the AC side current. Features.

According to the current-controlled power conversion device having the above configuration, in the pulse width modulation by the space vector modulation method, in the predetermined phase section of the DC side current of the conversion unit detected by the DC side current detection unit, the conversion unit A current corresponding to a predetermined phase of the AC side current flows. In addition, the DC current detected by the DC current detector that normally uses a shunt resistor has less amplitude error, offset, and temperature drift, and is based on a current corresponding to a current component of a predetermined phase of the AC current. As a result, the amplitude error and the offset error can be corrected with respect to the current component of a predetermined phase of the AC side current detected by the AC side current detection unit. Therefore, the amplitude, offset, and temperature drift of the current sensor used on the AC side can be compensated with a simple configuration, and the cost can be reduced by using an inexpensive current sensor.

In the current control type power converter of one embodiment, the control unit performs at least one of the correction of the amplitude error of the AC side current and the correction of the offset error of the AC side current at the time of activation.

According to the embodiment, at the time of start-up, the control unit performs at least one of the amplitude error correction or the offset error correction of the AC side current detected by the AC side current detection unit. Amplitude and offset temperature drift can be eliminated.

In the current control type power converter of one embodiment, the control part performs at least one of correction of the amplitude error of the AC side current or correction of the offset error of the AC side current during operation.

According to the embodiment, during operation, the control unit performs at least one of the amplitude error correction or the offset error correction of the AC side current detected by the AC side current detection unit, thereby the AC side current. The temperature drift of the amplitude and offset can be eliminated.

  As is clear from the above, according to the current control type power converter of the present invention, it is possible to compensate for the amplitude, offset and temperature drift of the current sensor used on the AC side with a simple configuration. Can be reduced.

Further, according to the current control type power conversion device of one embodiment, at the time of start-up, by performing at least one of correction of the amplitude error of the AC side current or correction of the offset error of the AC side current, the AC current Variations in amplitude and offset of the side current detector can be eliminated.

Further, according to the current control type power conversion device of one embodiment, during operation, by performing at least one of the correction of the amplitude error of the AC side current or the correction of the offset error of the AC side current, The temperature drift of the amplitude and offset of the AC side current detector can be eliminated.

  Hereinafter, the current control type power converter of the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 shows the configuration of a current-controlled power converter according to an embodiment of the present invention. This current control type power conversion device shows an example configured as an inverse converter in which a current flows from the DC side to the AC side, but as shown by a dotted line, a load R is connected instead of the DC power source E, It can also operate as a forward converter in which current flows from the AC side to the DC side.

The current controlled power converter, as shown in FIG. 1, the first AC terminals of the power module 3 as one example of the conversion unit output terminal of the R-phase of the three-phase AC power supply 10 via the reactor L _R connect, connected to the second AC terminals of the power module 3 to the output terminal of the S-phase of the three-phase AC power supply 10 via the reactor L _S, an output terminal of the T-phase of the three-phase AC power supply 10 to reactor L _T To the third AC side terminal of the power module 3. One end of a capacitor C is connected to the positive terminal of the power module 3, and the other end of the capacitor C is connected to the negative terminal via a shunt resistor 7. A DC power source E is connected to the capacitor C in parallel.

The current control type power converter includes a phase detector 4 that detects the phase of the R-phase voltage of the three-phase AC power supply 10, and an AC-side current detector that detects currents flowing through the reactor L _R and the reactor L _S , respectively. As an example, the current sensors 1 and 2, the amplifier 6 that amplifies a signal representing the current detected by the shunt resistor 7, the signal from the phase detector 4, the signal from the current sensors 1 and 2, and the amplifier 6 And a control circuit 5 that outputs a control signal to the power module 3 based on the above signal. The phase detector 4, the amplifier 6, and the control circuit 5 constitute a controller 11. The shunt resistor 7 and the amplifier 6 constitute a DC side current detector.

  The power module 3 constitutes a three-phase bridge circuit with six transistors Q1 to Q6 as examples of switching elements.

Ｔ₀：キャリア周期、ｋs：電圧制御率 The control circuit 5 controls the power module 3 by PWM modulation using a space vector modulation method that sequentially selects voltage vectors shown in FIG. Here, the time ratios of the voltage vectors τ4, τ6, τ0 are obtained by the following equations (1) to (3) based on the phase angle φ in the region of the six modes divided every 60 degrees.

T ₀ : carrier cycle, ks: voltage control rate

  Table 1 shows the voltage vector, DC current, line current component appearing on the DC side during reverse conversion, line current component appearing on the DC side during forward conversion, and output time of the voltage vector for each mode area. Is shown.

  For example, in the mode 1, the voltage vectors V4 and V6 are selected, and the R-phase upper arm (transistor Q1) is turned on in the voltage vector V4, so that the R-phase current flows through the shunt resistor 7 on the DC side and is inversely converted. Is detected as a positive voltage signal Ir, and forward conversion is detected as a negative voltage signal -Ir. In addition, since the T-phase lower arm (transistor Q6) is turned on in the voltage vector V6, the T-phase current flows through the shunt resistor 7 on the DC side, and is detected as a negative voltage signal -It in the reverse conversion, and in the forward conversion. Detected as a positive voltage signal It. In this way, by sampling the voltage signal generated in the shunt resistor 7 within the output time of the voltage vectors V4 and V6, the AC side line current can be detected.

  Sampling of the voltage signal generated in the shunt resistor 7 is performed by starting the A / D converter of the control circuit 5 by the trigger signal.

  FIG. 4 shows the detection timing in the two-phase modulation waveform, and FIG. 5 shows the detection timing in the three-phase modulation waveform.

  As shown in FIGS. 4 and 5, the PWM output is obtained by comparing the energization time obtained from the above equations (1) to (3) with a PWM counter, and the detectable period is from the output period of each voltage vector. It becomes an inclined part in the figure excluding the dead time. For this reason, using another A / D trigger counter synchronized with the PWM counter, the trigger signal for starting the A / D converter is generated in the middle of the detectable period by comparing with the value obtained by the equation in the figure Can be made.

  In FIG. 4, when the A / D trigger counter counts the middle τ0 / 2 of the output time τ0 of the voltage vector V0, the DC current i0 is sampled, and the A / D trigger counter counts the time (τ0 + τ4 / 2 + td / 2). When the DC current i1 is sampled and the A / D trigger counter counts time (τ0 + τ4 + τ6 / 2 + td / 2), the DC current i2 is sampled.

  On the other hand, in FIG. 5, when the A / D trigger counter counts the time τ0 / 4, the DC current i0 is sampled, and when the A / D trigger counter counts the time (τ0 / 2 + τ4 / 2 + td / 2), the DC current i1. When the A / D trigger counter counts time (τ0 / 2 + τ4 + τ6 / 2 + td / 2), the DC current i2 is sampled.

During the zero vector period in which the voltage vectors V0 and V7 are selected, no current flows through the shunt resistor 7 because it circulates between the three-phase AC power supply 10 and the power module 3, but here the shunt resistor 7 In order to first correct the offset level of the amplifier 6 that amplifies the above signal, sampling is performed in the same manner as other vectors, and correction is performed by the following equations (4) and (5).

  In the two-phase modulation waveform and the three-phase modulation waveform, vector patterns other than those shown in FIGS. 4 and 5 can be selected. However, the A / D of the control circuit 5 is based on the energization time of the above equations (1) to (3). The trigger timing for the converter may be set, and the offset detection may be performed at any timing of the voltage vectors V0 and V7.

  FIG. 3 shows the waveforms of line current, output time and direct current based on Table 1 and the above equations (1) to (3). Note that the output time t4 of the voltage vector V4 is minimum at a phase angle of 60 degrees, the output time t6 of the voltage vector V6 is 0 degrees, and the output time is minimum, and accompanying the mode transition from the output time t6 to t4 If a state in which the same vector is selected is used, a current for a period of 120 degrees can be detected.

  For example, for the voltage vector V6 that can detect the T phase in mode 1, the output time t6 is maximum at a phase angle of 60 degrees, and in the next mode 2, the output time is t4, so that the maximum output time is obtained at a phase angle of 0 degrees. Therefore, the current can be continuously detected through the two modes for a period of 120 degrees.

  The above operation is also apparent from the voltage vector diagram of FIG. 2, and the line current corresponding to each voltage vector can be detected for a period of ± 60 degrees around each vertex.

  FIG. 6 shows gain and offset detection waveforms.

The full wave rectified average value of the sine wave is expressed by the following equation (6) (A is a constant).

Since the current detected by the shunt resistor 7 on the DC side corresponds to the full-wave rectification waveform excluding the 120-degree period of the line current, the full-wave rectification average value A _avg is obtained by the following equation (7). Is done.

In the above equation (7), an average value of about 0.87 times is obtained as compared with the equation (6), and full-wave rectification at a level sufficient as a reference signal for amplitude correction of the current sensors 1 and 2 on the AC side. An average value A _{avg (DC)} can be secured.

In the period of 120 degrees of the above line current, the AC current sensors 1 and 2 are also sampled synchronously to obtain the full-wave rectified average value A _{avg (AC)} , and the amplitude is corrected by the following equation (8) A gain correction value ΔG as a value is obtained.

On the other hand, for the offset voltage, the half-wave rectified average values H _{avg +} and H _avg− for a 120-degree period for each half-wave are obtained on both the DC side and the AC side by the following equations (9) and (10). From the relationship of equation (11), an AC side current offset component V _{offset (AC)} and a DC side current offset component V _{offset (DC)} are obtained respectively (see FIG. 3).

On the AC side, since it is difficult to separate the offset of the detected current and the amplifier during operation, the AC side current offset component V _{offset (AC)} is removed from the signal, and the DC side current offset component V _{offset (DC )} Is added.

7A and 7B show the configuration of the control unit based on the current detection method described above. FIG. 7A shows a configuration of a current control type power converter provided with a control unit 11A in the case of reverse conversion in which current flows from the DC side to the AC side, and FIG. 7B shows in forward conversion in which current flows from the AC side to the DC side. The structure of the current control type power converter device provided with this control part 11B is shown. 7A and 7B, the same reference numerals are given to the same components as those of the current-controlled power converter shown in FIG. 1 (however, the reactors Lr, Ls, and Lt are omitted and denoted L). ). 7A and 7B, the amplifier 6 that amplifies the DC-side current I _dc detected by the shunt resistor 7 is omitted.

As shown in FIG. 7A, the control unit 11A of the current control type power conversion device that performs reverse conversion in which current flows from the DC side to the AC side includes an adder / subtracter 20 that subtracts the active power command value p * and the active power p, Based on the power controller 21 that proportionally integrates the output from the adder / subtractor 20 and outputs the active current command value Iq *, and the active current command value Iq * and the reactive current command value Id * = 0 from the power controller 21. A non-interference current control unit 22 that outputs a voltage command value Vi *; a space vector modulation unit 23 that outputs a PWM control signal to the power module 3 based on the voltage command value Vi * from the non-interference current control unit 22; based on the timing signal from the spatial vector modulation part 23, the AC side of the current sensor DCCT current I _r detected by the (1,2 in Fig. 1), the minimum pulse width limiting part 24 for limiting the calibration process I _s Minimum pulse width limiter 24 A control signal al, and the current I _dc of the detected direct current side by the shunt resistor 7, the current I _r from the current sensor DCCT, based on the I _s, the gain correction value ΔG and the AC side current offset component V _{offset (AC )} And the DC side current offset component V _{offset (DC)} , and the AC side for subtracting the AC side current offset component V _{offset (AC)} from the current calibration unit 25 from the currents I _r and I _s , respectively. A subtractor 26 as an example of a current offset correction unit, a multiplier 27 as an example of an AC side current amplitude correction unit that multiplies the output of the subtractor 26 by a gain correction value ΔG from the current calibration unit 25, and a multiplier 27. And an adder 28 as an example of an AC side current offset addition unit that adds the DC side current offset component V _{offset (DC)} from the current calibration unit 25, and the corrected currents I _r and I from the adder 28. two phase based on _s A coordinate converter 29 that outputs the effective current Id and the reactive current Id to the non-interference current control unit 22 by three-phase conversion.

The current calibrating unit 25 uses the DC side current detected by the shunt resistor 7 in the third switching state as an offset component, and offsets the DC side current in the first and second switching states. An offset correction unit 25a for correction, and a current component corresponding to a current component (currents I _r , I _s ) of a predetermined phase of the AC side current among the DC side currents whose offset is corrected by the offset correction unit 25a; , current component of a predetermined phase of the ac side current (current I _r, I _s) based on the current content of a predetermined phase of the ac side current (current I _r, I _s) for correcting the amplitude of the An amplitude correction value calculation unit 25b for calculating a gain correction value ΔG as an amplitude correction value, and a current component of a predetermined phase of the AC side current among the DC side currents whose offset is corrected by the offset correction unit 25a ( Current I _r , I _s ) based on the current corresponding to the DC side current offset component V _{offset (DC),} and a current component of a predetermined phase of the AC side current (current I _r , And an AC-side current offset component calculation unit 25d for calculating an _AC- side current offset component V _{offset (AC)} based on I _s ).

On the other hand, as illustrated in FIG. 7B, the control unit 11B of the current control type power conversion device that performs forward conversion in which current flows from the AC side to the DC side includes the control unit 11A adder / subtractor 20 and the power controller 21 illustrated in FIG. Instead, an adder / subtractor 30 that subtracts the voltage command value V _dc * and the voltage value V _dc and a voltage controller 31 that proportionally integrates the output from the adder / subtractor 30 and outputs an effective current command value Iq * are provided. Yes.

At the detection timing of the current-controlled power converter shown in FIGS. 7A and 7B, the voltage vector output time is shortened at both ends of the 120-degree section due to the voltage control rate, carrier frequency, and dead time, and cannot be detected. There is a case. Thus, the minimum pulse width limiting part 24 is provided as a block to be limited by the minimum pulse width, when the output time of the voltage vector becomes shorter than the minimum pulse width, and stops the correction of the current I _r, I _s.

  According to the current control type power converter having the above configuration, the amplitude, offset, and temperature drift of the AC current sensors 1 and 2 can be compensated with a simple configuration, and the cost can be reduced by using an inexpensive current sensor. .

  In the current control type power converter that controls the power module 3 by pulse width modulation using a space vector modulation method that selects six different voltage vectors every 60 degrees, in the first and second switching states The DC side current detected by the shunt resistor 7 and the amplifier 6 has a current corresponding to a current component of a predetermined phase of the AC side current. It is possible to correct the offset and amplitude of the AC current detected by the current sensors 1 and 2 by using the current corresponding to the current of a predetermined phase of the AC current in the DC current. Become.

Further, after correcting the offset of the current in the predetermined phase of the AC side current using the _AC side current offset component V _{offset (AC)} , the amplitude correction value ΔG is used to calculate the current in the predetermined phase of the AC side current. certain current I _r, corrects the amplitude of I _s, the current I _r which amplitude is corrected by adding the dc side current offset component V _{offset (DC)} to I _s, is difficult current offset of the separation of the amplifier current I _r of the detected AC side by sensors 1 and 2, the amplitude of I _s, the offset can be corrected.

  Moreover, as shown in Table 1, two adjacent 120 degree sections adjacent to each other among the DC side currents detected by the DC side current detection units (6, 7) in the first and second switching states. Current corresponding to the current of the predetermined phase of the AC side current of the predetermined 120 degree section, the current of the DC side current associated with the predetermined 120 degree section and the current of the AC side current An amplitude correction value can be easily calculated by obtaining an average value of currents of a predetermined phase. In addition, each offset component can be easily calculated for the current component of the DC side current and the current component of the predetermined phase of the AC side current associated with each other in the predetermined 120-degree section.

  Further, at the time of start-up, the amplitude of the AC side current is corrected by the multiplier 27 which is the AC side current amplitude correcting unit, and the subtracter 26 which is the AC side current offset correcting unit and the adder 28 which is the AC side current offset adding unit. Thus, by correcting the offset of the AC side current, variations in the amplitude and offset of the AC side current can be eliminated. Note that at the time of startup, only one of the correction of the amplitude of the alternating current and the correction of the offset of the alternating current may be performed.

  Further, during operation, the amplitude of the AC side current is corrected by the multiplier 27 serving as the AC side current amplitude correcting unit, and the subtracter 26 serving as the AC side current offset correcting unit and the adder serving as the AC side current offset adding unit. By correcting the offset of the AC side current by 28, the temperature drift of the amplitude of the AC side current and the offset can be eliminated. During operation, only one of the correction of the amplitude of the alternating current and the correction of the offset of the alternating current may be performed.

FIG. 1 is a diagram showing a configuration of a current control type power converter according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the space vector modulation method of the current control type power converter. FIG. 3 is a diagram showing waveforms at various parts of the current-controlled power converter. FIG. 4 is a diagram showing the detection timing in the two-phase modulation waveform. FIG. 5 is a diagram showing the detection timing in the three-phase modulation waveform. FIG. 6 is a diagram showing gain and offset detection waveforms. FIG. 7A is a diagram illustrating a configuration of a current-controlled power conversion device in the case of reverse conversion. FIG. 7B is a diagram illustrating a configuration of a current-controlled power conversion device in the case of forward conversion.

DESCRIPTION OF SYMBOLS 1, 2, DCCT ... Current sensor 3 ... Power module 4 ... Phase detection part 5 ... Control circuit 6 ... Amplifier 7 ... Shunt resistance 10 ... Three-phase alternating current power supply 11 ... Control part 20 ... Adder / Subtractor 21 ... Power controller 22 ... Non Interference current control unit 23 ... space vector modulation unit 24 ... minimum pulse width limiting unit 25 ... current calibration unit 25a ... offset correction unit 25b ... amplitude correction value calculation unit 25c ... DC side current offset component calculation unit 25d ... AC side current offset component Arithmetic unit 26 ... subtractor 27 ... multiplier 28 ... adder 29 ... coordinate converter 30 ... adder / subtractor 31 ... voltage controller C ... capacitor L, L _R , L _S , L _T ... reactor Q1-Q6 ... transistor

Claims (3)

A conversion unit (3) having six switching elements constituting a three-phase bridge circuit and converting a three-phase AC voltage into a DC voltage or converting a DC voltage into a three-phase AC voltage;
An AC current detector (1, 2) for detecting an AC current of the converter (3);
A DC side current detector (6, 7) for detecting a DC side current of the converter (3);
Based on the AC side current detected by the AC side current detection unit (1, 2) and the DC side current detected by the DC side current detection unit (6, 7), the conversion unit (3) is A control unit (11, 11A, 11B) controlled by pulse width modulation using a space vector modulation method,
The control unit (11, 11A, 11B)
Of the DC-side current detected by the DC-side current detector (6, 7), a current corresponding to a current component of a predetermined phase of the AC-side current, and the AC-side current detector (1, 2). the amplitude correction value obtained on the basis of the current component of a predetermined phase of the detected the ac side current by), the detected the ac side current by the ac side current detection unit (1, 2) the amplitude error While correcting
Of the DC side current detected by the DC side current detector (6, 7), a DC side offset component corresponding to a current component of a predetermined phase of the AC side current, and the AC side current detection By the offset correction value obtained based on the AC side offset component for the current of the predetermined phase of the AC side current detected by the unit (1, 2), the AC side current detection unit (1, 2) A current control type power conversion device, wherein an offset error of the detected AC side current is corrected . The current control type power converter according to claim 1,
The controller (11, 11A, 11B) performs at least one of correction of the amplitude error of the AC side current or correction of the offset error of the AC side current at the time of start-up. . In the current control type power converter according to claim 1 or 2,
The controller (11, 11A, 11B) performs at least one of correction of an amplitude error of the AC side current and correction of an offset error of the AC side current during operation. apparatus.

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