JP2017011933A - Power Conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a power conditioner so that an output waveform, from which DC components are removed, is obtained from the beginning of operation.SOLUTION: An output voltage sensor for detecting the output voltage of a power conversion unit is provided on the input side of a parallel-off unit. When paralleled off from the system, the power conversion unit is controlled in voltage control mode, and the correction data related to the differential voltage of the center voltage of the output voltage waveform from the power conversion unit and the center voltage of a system voltage waveform is stored. When the power conversion unit is connected in parallel with the system and control is started in the current control mode, zero-point correction of the output voltage waveform is performed based on the correction data by a power conditioner.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conditioner used in a power generation system such as a fuel cell power generation system or a solar power generation system.

  In various power generation systems connected to a commercial power system, a power conditioner for converting DC power generated by a power generation facility (power generation unit) such as a fuel cell or a solar cell into AC power linked to the system power It is used. Generally, a power conditioner boosts DC generated power output from a power generation facility by a booster circuit, and then outputs a DC voltage boosted by a PWM-controlled bridge inverter in a pulse form, which is output from an LC filter. By passing through a smoothing circuit, a sinusoidal waveform linked to the system power is output to the system.

  In such a power conditioner, it has been known from the past that the actual output voltage is offset from the system voltage due to variations in the delay time of the switching elements constituting the bridge inverter, and the DC component flows out. Has been. In order to remove the direct current component, for example, the techniques disclosed in the following Patent Documents 1 to 3 are configured to remove or suppress the direct current component included in the output of the inverter during the power generation operation.

Japanese Patent No. 3218160 JP 2006-280107 A JP 2000-184739

  However, in the above conventional technique, the DC component is detected and removed after the power generation operation is started, and the DC component output immediately after the power conditioner is parallel to the system cannot be removed.

  Therefore, an object of the present invention is to remove a DC component that is output immediately after the start of an operation in an interconnected operation or a self-sustained operation in a power conditioner.

  In order to achieve the above object, the present invention takes the following technical means.

  That is, the present invention includes a power converter that converts DC power into AC power that is linked to system power, a disconnector that switches whether the power converter is parallel or disconnected from the system, and the solution A system voltage detecting means for detecting a system voltage on the output side of the column device, and a control unit for controlling the operation of the power conversion unit and the disconnector, the control unit being an output of the power conversion unit In the power conditioner configured to be able to control the power conversion unit in any one of a voltage control mode for controlling a voltage and a current control mode for controlling an output current of the power conversion unit, the disconnector Output voltage detecting means for detecting the output voltage of the power converter on the input side of the power converter, and the controller controls the voltage of the power converter when the disconnector is operating Control by mode Correction data related to the DC component of the output voltage waveform of the power converter with respect to the system voltage waveform is stored, and when the power converter is operated in the current control mode in parallel with the system, the correction data Based on this, it is configured to correct the zero point of the output voltage waveform of the power converter (claim 1).

  According to the power conditioner of the present invention, by providing the output voltage detection means different from the system voltage detection means on the input side of the disconnector, the power converter is operated in the voltage control mode during disconnection. The actual output voltage can be detected. Further, instead of detecting the direct current component of the output during the interconnected operation, correction data relating to the direct current component of the output voltage waveform with respect to the system voltage waveform is stored in advance during the disconnection, and the interconnected system is based on the corrected data. Since power output from the power converter can be performed with an output voltage waveform that has been zero-corrected immediately after the start of operation, the DC component can be removed immediately after the start of the interconnected operation.

  The present invention also provides a power conversion unit that converts DC power into AC power linked to system power, a disconnector that switches whether the power conversion unit is parallel or disconnected from the system, and the power A self-supporting relay connected in parallel to the disconnector with respect to the converter, a self-supporting load connecting unit connected to the power converter via the self-supporting relay, the power converter, the disconnector, and the A control unit that controls the operation of the self-supporting relay, the control unit disconnecting the disconnector and closing the self-supporting relay to operate the power converter by voltage control. In the power conditioner having a self-sustaining operation function of outputting power from the conversion unit to the self-supporting load connection unit, output voltage detection means for detecting the output voltage of the power conversion unit on the input side of the self-supporting relay The control unit operates the power conversion unit by voltage control when the disconnecting unit is operated to be disconnected and the independent relay is opened, and the output voltage waveform of the power conversion unit at this time The correction data relating to the direct current component is stored, and the zero point correction of the output voltage waveform is performed based on the correction data when the self-sustained operation is started. Claim 2).

  According to the power conditioner of the present invention, the output voltage detecting means is provided on the input side of the self-supporting relay, so that the power converter is actually operated by voltage control during disconnection and during the opening of the self-supporting relay. Output voltage can be detected. Further, instead of detecting the direct current component of the output during the self-sustained operation, correction data related to the direct current component of the output voltage waveform is stored in advance during the disconnection and during the opening of the self-supporting relay, and based on the correction data. Since power output from the power conversion unit can be performed with an output voltage waveform that has been zero-corrected immediately after the start of independent operation, the DC component can be removed immediately after the start of independent operation.

  As described above, according to the power conditioner of the first aspect of the present invention, by providing the output voltage detection means different from the system voltage detection means on the input side of the disconnector, The actual output voltage when the power converter is operated in the voltage control mode can be detected. Further, instead of detecting the direct current component of the output during the interconnected operation, correction data relating to the direct current component of the output voltage waveform with respect to the system voltage waveform is stored in advance during the disconnection, and the interconnected system is based on the corrected data. Since power output from the power converter can be performed with an output voltage waveform that has been zero-corrected immediately after the start of operation, the DC component can be removed immediately after the start of the interconnected operation.

  According to the power conditioner of claim 2 of the present invention, by providing the output voltage detection means on the input side of the self-supporting relay, the power conversion unit is controlled by voltage control during disconnection and during the opening of the self-supporting relay. The actual output voltage when operated can be detected. Further, instead of detecting the direct current component of the output during the self-sustained operation, correction data related to the direct current component of the output voltage waveform is stored in advance during the disconnection and during the opening of the self-supporting relay, and based on the correction data. Since power output from the power conversion unit can be performed with an output voltage waveform that has been zero-corrected immediately after the start of independent operation, the DC component can be removed immediately after the start of independent operation.

1 is a schematic circuit diagram of a power conditioner according to an embodiment of the present invention. It is an output voltage waveform diagram of the same inverter.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a power conditioner 1 according to an embodiment of the present invention. The power conditioner 1 according to the present embodiment converts the DC power output from the DC power supply unit 2 into AC power linked to the commercial power system 3 and outputs the AC power to the commercial power system 3. Converter 4 for boosting DC power input from power supply unit 2 to a predetermined voltage (eg, 320 V) corresponding to the maximum value of system voltage (280 V in the case of 200 V power system), and connecting DC power after boosting to system power Provided between the interconnected inverter 5 for converting to alternating current power, the DC link unit 6 comprising a DC link capacitor provided between the converter 4 and the inverter 5, and the output unit of the inverter 5 and the commercial power system 3. The disconnector 7 (protection relay for disconnection), the independent relay 8 connected in parallel with the disconnector 7 to the output of the inverter 5, and the output of the inverter 5 via the independent relay 8. A self-supporting outlet 9 (self-supporting load connection unit) connected to the control unit, a control unit 10 for controlling the operation of the converter 4, the inverter 5, the disconnector 7 and the self-supporting relay 8, and an input voltage smoothing capacitor 11. The converter 4 and the inverter 5 constitute a power converter that converts DC power into AC power linked to the commercial power system 3. Note that power output to the power system 3 may be any power supply power that is connected to the system power in, for example, a home or on-site lead-in wiring. There is no need to reverse flow.

  The DC power supply unit 2 may be an appropriate one such as a fuel cell, a solar cell, or a storage battery.

  Although the converter 4 is illustrated as a step-up chopper in FIG. 1, it may be an isolated converter, or a circuit configuration that boosts the voltage in two stages by a step-up chopper and an insulating converter.

  The inverter 5 is a full-bridge voltage-type bridge inverter, and is configured by connecting a plurality of switching elements such as IGBTs and MOS-FETs in an H-bridge type and connecting a feedback diode to each switching element in parallel. On the output side, a smoothing circuit constituted by an LC filter is provided. In FIG. 1, a two-level inverter is exemplified as the inverter 5, but a three-level inverter can also be used.

  The control unit 10 controls each power conversion operation in the converter 4 and the inverter 5 and the opening / closing operation of the circuit breaker 7, and a display unit (not shown) including a liquid crystal display attached to the casing of the power conditioner 1. 3) display control, various abnormality detection controls in the power conditioner 1, and various controls such as integration of the amount of generated power and the amount of power consumption in the home. The control unit 10 typically includes a microprocessor as a central processing unit, and includes a drive circuit for generating and outputting a drive signal for each control target based on a control signal from the microcomputer for each control target. Yes.

  Further, the inverter 5 of the present embodiment detects an input current sensor 12 that detects an input current to the converter 4, an input voltage sensor 13 that detects an input voltage of the converter 4, a DC link voltage sensor 14, and an output current of the inverter 5. Output current sensor 15 (output current detection means), an output voltage sensor 16 (output voltage detection means) for detecting the output voltage of the inverter 5, and a system voltage sensor 17 (system voltage detection means) for detecting the system voltage. The detection signals of these sensors are input to the control unit 10 and used for the various controls described above. The output current sensor 15 and the output voltage sensor 16 are provided between the branch point to the circuit breaker 7 and the self-supporting relay 8 and the output part of the inverter 5 (the input side of the circuit breaker 7 and the self-supporting relay 8). The system voltage sensor 17 is provided on the output side (system side) of the circuit breaker 7. The detection signals of the output current sensor 15, the output voltage sensor 16, and the system voltage sensor 17 that detect the AC signal are sampled by the control unit 10 at a sufficiently fast cycle (for example, 1 millisecond), and the phase of each detection signal, The period and amplitude can be detected.

  The control unit 10 operates the converter 4 and the inverter 5 in a state where the independent relay 8 is opened and the disconnector 7 is operated in parallel at the time of the interconnection operation to the system 3. Is output. In particular, during the interconnected operation, the output current is controlled by so-called current mode control of the inverter 5 (current control of the voltage source inverter).

  The general current control of such a voltage source inverter will be described. The pulse waveform obtained by outputting the output voltage Vinv (t) of the bridge circuit section of the inverter 5, that is, the DC voltage of the DC link section 6 in a pulse shape by PWM control. The sine wave output voltage Vinv (t) equivalent to the voltage can be expressed by the following equation (1).

  Vinv (t) = Vuw (t) + (Zi + Zs) · Iout (t) ... Equation (1)

  Here, Vuw is the system voltage, Zi is the equivalent impedance of the LC filter (smoothing circuit) of the inverter 5, Zs is the system impedance, and Iout is the output current of the inverter 5. Vinv is a little larger than Vuw, and the phase is advanced, which causes Iout to be output. Hereinafter, Z = Zi + Zs.

  Thus, Vinv can be expressed as the sum of the voltage component Vuw and the current component Z · Iout. Vuw is a constant term determined by the system voltage. Therefore, it is understood that Iout can be controlled by Vinv. In the current control mode, feedback control (PI control or PID control) is performed based on the output current value Iout detected by the output current sensor 15 to cause the output current Iout to follow the target output current waveform Iout-target (t). . More specifically, the target output voltage waveform Vinv-target (t) is determined with reference to equation (1) so that the output current Iout follows the target output current waveform Iout-target, and the target output voltage waveform Vinv-target is set to the target output voltage waveform Vinv-target. Based on the output voltage Vinv of the bridge circuit portion of the inverter 5 according to the target output voltage waveform Vinv-target by generating a PWM pulse signal for driving the inverter 5 based on this and outputting it to each switching element constituting the inverter 5 And

  However, in the above-described general current control, variation in response delay time of each switching element constituting the inverter 5 is not considered, and the output voltage Vinv does not match the target output voltage waveform Vinv-target. As a result, as shown in FIG. 2, the amplitude and the center voltage of the output voltage Vout of the inverter 5 are shifted from the system voltage Vuw, and a DC component is output toward the system 3.

  Thus, in the present embodiment, the control unit 10 is configured to perform output voltage correction control described below.

  First, when a predetermined interconnection operation start condition is satisfied, the control unit 10 operates the converter 4 while the disconnector 7 is disconnected, and operates the inverter 5 in the voltage control mode. In the voltage control mode, by generating a PWM pulse signal for driving the inverter 5 based on the target output voltage waveform Vinv-target (t) generated by the control unit 10 and outputting the PWM pulse signal to each switching element constituting the inverter 5, It is assumed that the output voltage Vinv (t) of the bridge circuit unit of the inverter 5 follows the target output voltage waveform Vinv-target (t). Further, the target output voltage waveform Vinv-target (t) is feedback-controlled so that the output voltage value Vout of the inverter 5 detected by the output voltage sensor 16 matches the system voltage Vuw detected by the system voltage sensor 17. At this time, since the output current Iout is 0, the impedance Z can be ignored.

  For example, the reference waveform of Vinv-target (t) is A · sin (ωt) + Vo, and the target output voltage waveform is Vinv-target (t) = V in consideration of amplitude correction data α and DC component correction data β. When expressed as (A + α) · sin (ωt) + (Vo + β), the correction data α and β are adjusted by feedback control so that Vout = Vuw. Such adjustment control of the correction data α and β may be continuously performed until it is stabilized to some extent, or may be ended in a predetermined time.

  When the adjustment processing of the correction data α and β is completed, the correction data α and β are stored in a storage means such as a non-volatile memory or a RAM, and then the operation of the converter 4 and the inverter 5 is temporarily stopped to turn off the circuit breaker 7. The parallel operation is started by resuming the operations of the converter 4 and the inverter 5 in parallel operation. During the interconnected operation, the inverter 5 operates by the above-described current control, but is controlled using the following equation (2) instead of the above equation (1).

  Vinv-target (t) = {(A + α) · sin (ωt + γ) + (Vo + β)} + Z · Iout (t) (2)

  Note that γ is a phase correction parameter for synchronizing the phase with the system voltage waveform detected by the system voltage sensor 17.

  In the first term of the above formula (2), the amplitude and the center voltage of the output voltage Vout of the inverter 5 are made to coincide with the system voltage Vuw when the output current is 0 by the above adjustment process, and the interconnection operation is started. Since Iout≈0 at the beginning, the output voltage waveform Vout of the inverter 5 can be matched with the system voltage waveform Vuw from the beginning of the interconnection operation by obtaining the Vinv-target waveform based on the equation (2). Thus, it is possible to correct the zero point of the output voltage waveform of the inverter 5 at the beginning of the interconnection operation and to avoid the output of the DC component.

  Note that the current control of the inverter 5 based on the above formula (2) can be continued during the interconnecting operation, and the DC current output suppression control during the other interconnecting operation is performed while the interconnecting operation is performed. It is also possible to replace the first term of the above formula (2) with the system voltage detection value Vuw during the system operation control.

  In the present embodiment, the correction data α and β are further used to prevent the direct current component from being output to the self-supporting load connected to the self-supporting outlet 9 at the beginning of the self-sustaining operation. That is, the power conditioner 1 of the present embodiment has a self-sustaining operation function of outputting power to the self-sustained outlet 9 by manually operating a self-sustaining operation switch (not shown). When the autonomous operation switch is set to the autonomous operation, the control unit 10 starts the autonomous operation control. When the independent operation control is started, the control unit 10 operates the converter 4 in a state where the disconnector 7 is disconnected and the independent relay 8 is opened as in the case of the start of the interconnected operation control and the inverter 10 5 is operated in the voltage control mode, and the correction data α and β are adjusted by the same method. When the adjustment process is completed, the correction data α and β are stored in a storage means such as a non-volatile memory or RAM, and then the operation of the converter 4 and the inverter 5 is temporarily stopped to close the self-supporting relay 8. Independent operation output is started by resuming the operation of the inverter 5. During this self-sustained operation, the inverter 5 operates in the voltage control mode, the target voltage Vinv-target (t) in the voltage control is obtained by the following expression (3), and the output voltage Vout of the inverter 5 matches the Vinv-target. Feedback control.

  Vinv-target (t) = (A + α) · sin (ωt + γ) + (Vo + β) (3)

  Even in such a self-sustained operation control, the output voltage waveform at the beginning of the control is already in the zero point corrected state, so that waveform distortion and direct current component at the beginning of the self-sustained operation can be reduced.

  The present invention is not limited to the above-described embodiment, and the design can be changed as appropriate. For example, in the above embodiment, the DC component of the output is removed by correcting the waveform of Vinv-target. However, any control target that contributes to the adjustment of the DC component may be corrected, for example, in PWM control It is also possible to correct the zero point of the output voltage by directly correcting the pulse width.

1 Power conditioner 2 DC power supply 3 Line 5 Inverter (Power converter)
7 Disconnector 8 Self-supporting relay 9 Self-supporting load connection unit 10 Control unit 15 Output current sensor 16 Output voltage sensor 17 System voltage sensor

Claims (2)

On the output side of the disconnector, a power converter that converts DC power into AC power that is linked to the grid power, a disconnector that switches whether the power converter is parallel or disconnected from the system, and A voltage control unit for controlling a voltage output from the power conversion unit, the system voltage detection unit for detecting a system voltage; and a control unit for controlling the operation of the power conversion unit and the disconnector. In a power conditioner configured to be able to control the power conversion unit in one of the control modes of the mode and the current control mode for controlling the output current of the power conversion unit,
Further comprising output voltage detection means for detecting the output voltage of the power converter on the input side of the circuit breaker,
The control unit controls the power conversion unit in the voltage control mode when the disconnecting operation of the disconnector is performed, and a DC component of the output voltage waveform of the power conversion unit with respect to the system voltage waveform at this time Correction data is stored, and when the power conversion unit is operated in the current control mode in parallel with the system, zero correction of the output voltage waveform of the power conversion unit is performed based on the correction data. A power conditioner characterized by being constructed. A power converter that converts DC power into AC power that is linked to system power, a disconnector that switches whether the power converter is paralleled or disconnected from the system, and the power converter A self-supporting relay connected in parallel with the disconnector, a self-supporting load connecting unit connected to the power conversion unit via the self-supporting relay, and controlling the operations of the power conversion unit, the disconnector and the self-supporting relay A control unit that performs a disconnection operation of the disconnector and closes the self-supporting relay so that the power converter is operated by voltage control from the power conversion unit. In a power conditioner having a self-sustaining operation function that outputs power to the connection part,
Further comprising output voltage detection means for detecting the output voltage of the power converter on the input side of the self-supporting relay;
The control unit operates the power conversion unit by voltage control when the disconnection operation is performed and the independent relay is opened, and a direct current of the output voltage waveform of the power conversion unit at this time is operated. A power conditioner configured to store correction data relating to components and perform zero point correction of an output voltage waveform based on the correction data when the self-sustaining operation is started.

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