JP2020025398A - Power unit - Google Patents

Abstract

To suppress noise generated in a voltage to be supplied to an AC power supply system by impedance of a transmission line.SOLUTION: A DC/AC converter 12 performs switching conversion on a current from a solar cell 2 from DC to AC and supplies the current through a transmission line 18 to a power supply system 6. The output current from the DC/AC converter 12 is detected, and a control section 20 supplies a control signal to the DC/AC converter 12 in such a manner that the output current becomes a predetermined reference current. In the control section 20, an effective value of a voltage detected by a detection circuit 34 for the output voltage of the DC/AC converter 12 is calculated by an effective value calculation section 36. A multiplication value of a reference sign wave, which is generated by a sine wave generator 32, corresponding to a voltage of the power supply system 6 and the effective value calculated by the effective value calculation section 36 is added to the control signal by an addition section 40, and the control signal is corrected.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply device, and more particularly, to a power supply device that performs DC-AC conversion.

  A DC-AC converter may be used for a power conditioner, for example. An example of a power conditioner is disclosed in Patent Document 1. In the technique of Patent Literature 1, DC from a DC power supply such as a solar cell is boosted or stepped down by a DC-DC converter, converted into AC by an inverter, and then output to an external commercial power supply system. In order to suppress the ripple component of the voltage supplied from the DC-DC converter to the inverter, an active filter is provided on the output side of the DC / DC converter, and the AC current is activated so that the output voltage of the DC / DC converter is stabilized. Supplied from filter. The output voltage of the DC / DC converter is detected, and feedback control is performed on the active filter so that the output voltage becomes the reference voltage.

JP-A-2017-220996

  In the power conditioner as described above, the ripple component of the intermediate voltage in the power conditioner can be suppressed. However, a transmission line is used to supply the output of the power conditioner to the commercial power system, and the transmission line has an impedance, and the impedance varies depending on the length of the transmission line. When the length of the transmission line is long and the impedance is large, switching noise generated by the inverter may occur in the voltage supplied to the commercial power supply system. This switching noise cannot be suppressed by an active filter whose intermediate voltage of the inverter is feedback-controlled.

  An object of the present invention is to provide a power supply device capable of suppressing noise generated in a voltage supplied to an external power supply system due to the impedance of a transmission line.

  The power supply device according to one embodiment of the present invention includes a DC power supply. As the DC power supply, for example, a DC generation unit such as a solar cell or an AC-DC conversion unit can be used. Switching means, for example, an inverter performs switching conversion of the direct current from the direct current power supply into an alternating current, and supplies the converted power to a power supply system via a transmission line. The control means detects an output current from the switching means and supplies a control signal to the switching means such that the output current becomes a predetermined reference current. The control means further includes means for detecting the output voltage of the switching means. The effective value calculating means calculates the effective value of the voltage detected by the detecting means. The reference sine wave generating means generates a reference sine wave corresponding to the voltage of the power supply system. The correction means corrects the control signal with a multiplied value of the effective value by the calculation means and the reference sine wave.

  In the power supply device configured as described above, even if the control signal is supplied to the switching means so that the output current matches the reference current, the control means performs feedback control so that the output current matches the reference current. As a result, noise occurs in the voltage supplied to the power supply system. For example, when the length of the transmission line is long, noise having a frequency corresponding to the switching frequency of the switching means is supplied to the power supply system. In order to remove the influence of the noise, the correction signal is corrected by the correction means so that the switching means is feedforward controlled based on a reference sine wave corresponding to the sine wave of the voltage of the power supply system. However, in order to match the magnitude of the value of the reference sine wave to the magnitude of the value of the output voltage, the output voltage of the switching means is detected by the voltage detection means, and based on this, the effective value of the output voltage of the switching means is determined. Is calculated by the effective value calculating means, the effective value is multiplied by the reference sine wave, the control signal for the switching means is corrected by the multiplied value, and the value obtained by multiplying the reference sine wave by the effective value is output by the switching means. The voltage corresponds to the output voltage from which noise has been removed.

  The reference sine wave generating means may generate the reference sine wave at a frequency synchronized with a voltage of the power supply system. With this configuration, even if the frequency of the voltage of the power supply system changes, a reference sine wave that follows the change can be obtained, so that the output voltage of the switching means corresponding to the frequency of the power supply system can be obtained. it can.

  As described above, according to the present invention, it is possible to attenuate the noise generated in the output voltage due to the influence of the length of the transmission line.

It is a block diagram of a power supply device of one embodiment of the present invention. FIG. 2 is a voltage waveform diagram of each part of the power supply device of FIG. 1.

  The power supply device 2 according to one embodiment of the present invention is a power conditioner that converts DC power, for example, DC from a solar cell 4 into AC and supplies the AC to an AC power system 6 as necessary. The direct current from the solar cell 4 is supplied to a boosting unit, for example, a DC-DC converter 10 via an input terminal 8, where it is boosted and supplied to a switching unit, for example, a DC-AC converter 12. As the DC-AC converter 12, for example, an inverter can be used. The DC-AC converter 12 switches the supplied step-up DC to a plurality of switching means (not shown), for example, IGBTs and MOSFETs, and converts the step-up AC to an AC whose frequency matches that of the AC power supply system 6. The power is supplied to the AC power supply system 6 via the open / close switch 14, the output terminal 16, and the transmission line 18. The open / close switch 14 is closed when the AC power is supplied from the power supply device 2 to the AC power supply system 6.

  The control unit, for example, the control unit 20 controls the DC-AC converter 12 so that the DC-AC converter 12 outputs an alternating current with a predetermined current value. Therefore, a current transformer 22 is provided on the output side of the DC-AC converter 12, shunts the output current of the DC-AC converter 12, and outputs the shunted output current value to a current detection unit, for example, a current detection unit. Detected by the detector 24 and supplied to the control unit 20.

  In the control unit 20, a difference between the output from the current detector 24 and a predetermined reference current is calculated by the deviation detector 26 and supplied to a control unit, for example, a feedback control unit, specifically, a PI control unit 28. . The PI control unit 28 performs a proportional operation and an integral operation based on the deviation from the deviation detector 25, generates an operation signal, and supplies the operation signal to a control signal generation unit, for example, a PWM signal generation unit 30. The PWM signal generator 30 generates a PWM (pulse wide modulation) signal to be supplied to the DC-AC converter 12 based on the operation signal. The switching means in the DC-AC converter 12 switches based on the PWM signal, and converts the supplied direct current into an alternating current having a value equal to the reference current.

  The impedance changes depending on the length of the transmission line 18 between the output terminal 16 and the AC power supply system 6, and when the length of the transmission line 18 is long and the impedance is large, the impedance is changed by the influence. As shown in FIG. 2A, noise, for example, large switching noise may be generated in the supplied AC voltage. The switching noise is generated by switching in the DC / AC converter 12, but when the impedance of the transmission line 18 is large, the magnitude becomes large and cannot be ignored.

  In order to improve this point, the control unit 20 has a feedforward control unit 31 added. For feedforward control, reference sine wave generating means, for example, a sine wave generator 32 is provided. The sine wave generator 32 generates a sine wave having the same waveform as the AC voltage waveform of the AC power supply system 6 as shown in FIG. Is synchronized with the voltage waveform of FIG. Thus, even if the AC voltage waveform of the AC power supply system fluctuates, the reference sine wave follows the fluctuation. The operation signal from the PI control unit 28 is corrected by the feedforward control unit 31 so as to suppress the switching noise based on the reference sine wave waveform, and is supplied to the PWM signal generation unit 30.

  However, the sine wave of the sine wave generator 32 does not represent the magnitude of the AC voltage of the DC / AC converter 12. Therefore, the AC voltage of the DC / AC converter 12 is detected by voltage detecting means, for example, a voltage detector 34. Based on the detected value, the effective value of the AC voltage of the DC / AC converter 12 is calculated by the effective value calculating means of the feedforward control unit 31, for example, the effective value calculating unit 36. The calculated effective value is multiplied by a reference sine wave in multiplication means of the feedforward control unit 31, for example, a multiplication unit 38, and a multiplication representing a sine wave having the same value as the reference sine wave as shown in FIG. A value is created, and this is added to the operation signal by the correction means of the feedforward control unit 31, for example, the addition unit 40, and the added value is supplied to the PWM signal generation unit 30. As a result, the operation signal is corrected. That is, even when the feedforward control is performed and the length of the transmission line 18 is long, the influence of noise of the AC voltage supplied to the AC power supply system 6 can be suppressed. Further, even when the length of the transmission line 18 varies depending on the installation location of the power supply device 2 and the magnitude of the noise varies depending on the installation location, the influence of the noise can be suppressed.

  Although the above description has been made in an analog manner, in practice, the current and voltage of the DC / AC converter 12 are sampled at a sampling frequency twice or more the frequency of the noise, and a digitalized signal is used. Control is performed digitally at each sampling cycle. In this case, the reference sine wave generated by the sine wave generator 12 is also a digital signal having the same sampling frequency.

  In the above embodiment, the solar cell 4 was used as the DC power supply. However, the present invention is not limited to this. For example, a fuel cell power generator can be used. -The DC converter can be used as a DC power supply. In the above embodiment, the DC / DC converter 10 is used. However, if the value of the voltage supplied from the DC power supply corresponds to the voltage required by the DC / AC converter 12, The / DC converter 10 is unnecessary. In the above embodiment, the PI control unit 28 is used. However, the present invention is not limited to this, and other control units, such as a PID control unit and a PD control unit, may be used as long as the control unit performs feedback control. You can also. In the above embodiment, the reference sine wave of the sine wave generator 32 is used in synchronization with the voltage of the AC power supply system 6. However, when the voltage of the AC power supply system 6 is stable and the change is small, It is not necessary to synchronize with the voltage of the AC power supply system 6.

2 Power supply 4 Solar cell (DC power supply)
6 AC power system 12 DC / AC converter 18 Transmission line 20 Control unit (control means)
Reference Signs List 22 current detector 28 PI control unit 32 sine wave generator (reference sine wave generator)
34 voltage detector (voltage detection means)
36 Effective value calculation unit (effective value calculation means)
38 Multiplication unit

Claims (2)

DC power supply,
Switching means for switching and converting DC from the DC power supply to AC, and supplying the DC power to a power supply system via a transmission line,
Control means for detecting an output current from the switching means, and supplying a control signal to the switching means such that the output current becomes a predetermined reference current,
And the control means further comprises:
Output voltage detection means for the switching means, and calculation means for calculating the effective value of the voltage detected by the detection means,
Means for generating a reference sine wave corresponding to the voltage of the power supply system;
Correction means for correcting the control signal with a multiplied value of the effective value and the reference sine wave by the calculation means,
Power supply having.   2. The power supply device according to claim 1, wherein the reference sine wave generating means generates the reference sine wave having a frequency synchronized with a voltage of the power supply system.

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