JP2014187742A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter device capable of removing the DC component of an AC output voltage with high accuracy.SOLUTION: An inverter device 1 includes a zero-cross signal generation unit (70, 71) for generating a zero-cross signal Sbased on the magnitude relation of an AC detection signal Sand a ground voltage, a half period time detection unit (72, 73) for determining a first half period time Twhen the AC detection signal Sis positive, and a second half period time Twhen the AC detection signal Sis negative, respectively, based on the zero-cross signal S, and a correction unit (74, 75, 76) for correcting an AC detection signal Sso that the first half period time Tand second half period time Tmatch. A control unit 5 controls a bridge circuit 2 so that an AC detection signal Safter corrected by the correction unit 7 matches a reference waveform signal S.

Description

  The present invention relates to an inverter device that supplies AC power to a general household load or the like in cooperation with a commercial system, and in particular, an inverter including a bridge circuit that converts DC power output from a solar battery, a storage battery, or the like into AC power. Relates to the device.

  The inverter device includes a bridge circuit unit that converts a DC input voltage into an AC output voltage, a filter unit that removes ripples included in the AC output voltage obtained by the conversion, and a control unit that includes a reference sine wave signal generation circuit. Consists of. In this inverter device, normally, the bridge circuit unit is feedback-controlled based on the error between the AC detection signal related to the voltage value of the AC output voltage and the reference sine wave signal generated by the reference sine wave signal generation circuit. Thereby, the inverter device can output a stable AC output voltage to the load even if the load fluctuates.

  By the way, in this inverter device, when a DC offset is superimposed in a system for detecting a voltage value of an AC output voltage, a DC component is included in the AC output voltage. There is a problem that household appliances as a load may be damaged by heating.

  As a conventional inverter device that takes measures against this problem, for example, the one described in Patent Document 1 is known. This conventional inverter device integrates the positive side area and negative side area of the AC output signal, and then feedback-controls the bridge circuit so that the difference between the two areas becomes zero. The direct current component is prevented from being included.

Japanese Patent No. 3249709

  However, the conventional inverter device requires current detection when calculating the area, but does not take into consideration that a DC offset is superimposed in this current detection system. That is, this inverter device has insufficient measures against DC offset superposition, and there is a possibility that a DC component is included in the AC output voltage as in other conventional inverter devices.

  This invention is made | formed in view of the said situation, The place made into the subject makes it a subject to provide the inverter apparatus which can remove the direct current | flow component of alternating current output voltage with high precision.

  In order to solve the above problems, an inverter device according to the present invention includes a converter that converts a DC input voltage input from the outside into an AC output voltage, and detects a voltage value of the AC output voltage and responds to the voltage value. An inverter device including a detection unit that generates an AC detection signal and a control unit that controls the conversion unit so that the AC detection signal matches the reference waveform signal. A zero-cross signal generation unit that generates a zero-cross signal based on the first half-cycle time that is a time when the AC detection signal is positive based on the zero-cross signal and a second half-cycle time that is a time when the AC detection signal is negative Each of the obtained half cycle time detection units further includes a correction processing unit that corrects the AC detection signal so that the first half cycle time and the second half cycle time coincide with each other. And controlling the conversion unit to the alternating-current detection signal corrected by the processing section matches the reference waveform signal.

  In this configuration, the first half-cycle time and the second half-cycle are based on a zero-cross signal indicating a magnitude relationship between an AC detection signal that may have a DC offset superimposed thereon and a ground voltage that is strong against the DC offset overlay. Time is detected, and the AC detection signal is corrected so that the first half-cycle time and the second half-cycle time coincide. That is, in this configuration, the difference between the first half-cycle time and the second half-cycle time reflects the amount of DC offset superimposed on the AC detection signal with high accuracy. Therefore, according to this configuration, the DC component of the AC output voltage can be removed with high accuracy by correcting the AC detection signal so that the first half cycle time and the second half cycle time coincide. Accordingly, it is possible to provide an inverter device capable of removing a DC component from an AC output voltage with a relatively simple configuration even if the AC detection signal (AC output voltage detection system) includes a DC component. it can.

  The correction performed by the correction processing unit of the inverter device includes, for example, (1) correction for adding a correction value (correction signal) corresponding to a time obtained by subtracting the second half cycle time from the first half cycle time to the AC detection signal. And (2) correction by subtracting a correction value (correction signal) corresponding to a time obtained by subtracting the first half-cycle time from the second half-cycle time from the AC detection signal.

  ADVANTAGE OF THE INVENTION According to this invention, the inverter apparatus which can remove the direct current | flow component of alternating current output voltage with high precision can be provided.

It is a circuit diagram of the inverter apparatus which concerns on this invention. It is a wave form diagram of each part of an inverter device concerning the present invention, and (A) is a wave form diagram in case a positive direct current component is included in an alternating current output voltage, and (B) is a negative direct current component in an alternating current output voltage. FIG. It is a circuit diagram of the inverter apparatus which concerns on the 1st modification of this invention. It is a circuit diagram of the inverter apparatus which concerns on the 2nd modification of this invention.

  Hereinafter, embodiments of an inverter device according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an inverter device according to an embodiment of the present invention. The inverter device 1 outputs an AC output voltage V _ac generated from a DC input voltage V _dc output from a solar cell, a storage battery, or the like toward a load (not shown) (for example, a general household load). As shown in the figure, the inverter device 1 according to the present embodiment includes a bridge circuit unit 2, a filter unit 3, a detection unit 4, a control unit 5, a drive unit 6, and a correction unit 7. Among these, the bridge circuit unit 2 and the filter unit 3 constitute the “conversion unit” of the present invention. The detection unit 4, the control unit 5, the drive unit 6, and the correction unit 7 constitute a control system that feedback-controls the bridge circuit unit 2 of the conversion unit according to the state of the AC output voltage _Vac .

First, in order to facilitate understanding of the present invention, when the correction unit 7 is not present, i.e., a case will be described in which the signal S ₅ to be described later is inputted as it is to the effective voltage calculation unit 52 and the like.

The bridge circuit unit 2 mainly includes four switching elements SW _{A to} SW _D. In this embodiment, MOSFETs that are turned on or off under the control of the drive unit 6 are used as the switching elements SW _{A to} SW _D. Instead, any switching element such as an IGBT is used. You can also When the switching elements SW _A and SW _D are turned on under the control of the drive unit 6 and the others are turned off, the AC output voltage V _ac becomes positive. On the other hand, when the switching elements SW _B and SW _C are turned on and the others are turned off, the AC output voltage V _ac becomes negative. In the present embodiment, the voltage value of the AC output voltage _Vac is adjusted by adjusting the time during which two of the switching elements SW _{A to} SW _D are in the ON state by the drive unit 6.

The filter unit 3 includes a capacitor C and two coils L. The filter unit 3 removes ripples included in the output voltage of the bridge circuit unit 2. As a result, an AC output voltage V _ac that does not include a ripple is obtained. The AC output voltage V _ac is, for example, AC 100V or AC 220V depending on the type of load. In the present invention, the voltage at the output terminal P when the output terminal N is used as a reference is the AC output voltage _Vac .

The detection unit 4 includes a voltage dividing resistor unit 40, a first differential amplifier unit 41, an insulation amplifier unit 42, a bias unit 43, and a second differential amplifier unit 44. The detection unit 4 detects the voltage value of the AC output voltage _Vac , and is finally adjusted to fall within the input allowable voltage range (0 [V] to D5 [V]) of the analog input terminal 51. generating a differential amplifier output signal S _4.

More specifically, the first differential amplifier unit 41 outputs the first differential amplifier output based on the difference (S ₁ −S ₂ ) between the divided signals S ₁ and S ₂ obtained by dividing by the voltage dividing resistor unit 40. The signal S ₃ is generated, and then the second differential amplifier unit 44 receives the first differential amplifier output signal S ₃ input through the isolation amplifier unit 42 and the bias voltage V _B generated by the bias unit 43 (this embodiment) in the _example, generates a V B = D5 [V] / 2) and the second differential amplifier output signal _{S 4} based on. The gain of the first differential amplifier 41, the gain and bias voltage V _B of the second differential amplifier unit 44, as a second differential amplifier output signal S ₄ falls within the allowable input voltage range of the analog input terminal 51 It has been adjusted.

Divided signal _{S 1,} divided signal _{S 2,} first differential amplifier output signal _{S 3,} the second differential amplifier output signal _{S 4} and the signal _{S 5} to be described later are both a voltage value of the AC output voltage _{V ac} Will change accordingly. In the present invention, these five signals are collectively referred to as an “AC detection signal”. Note that the divided signal S ₁ obtained by dividing the voltage at the output terminal P changes in phase with the AC output voltage V _ac . On the other hand, divided voltage signal S ₁ obtained by dividing the voltage of the output terminal N varies the AC output voltage V _ac and opposite phase. The other AC detection signals S _{3 to} S ₅ change in phase with the AC output voltage V _ac .

The control part 5 consists of microcomputers, for example. As shown in FIG. 1, the control unit 5 has an AD converter 50 connected to an analog input terminal 51. AD converter 50 converts the second differential amplifier output signal (ac detection signal) S ₄ input through the analog input terminal 51 to the alternating-current detection signal S ₅ is a digital signal. If the correction unit 7 is absent, the alternating-current detection signal S ₅ is directly input to the effective voltage calculation unit 52 and the like.

The effective voltage calculation unit 52 calculates the effective voltage value of the AC output voltage V _ac on the basis of the alternating-current detection signal S _5. The PI calculator 54 generates an error signal between the calculated effective voltage value and an effective voltage instruction value (for example, 100 [V], 120 [V], 240 [V], etc.) stored in advance in the storage unit 53. performs PI control compensation based, it produces an effective voltage error signal S _7. The effective voltage error signal S ₇ is multiplied by the sine wave signal S _{8 of} 50 [Hz] or 60 [Hz] generated by the sine wave signal generation unit 55 to become the reference waveform signal S ₉ .

PI computing unit 56 performs PI control compensation based on the error signal between the reference waveform signal _{S 9} and the alternating-current detection signal _{S 5,} and generates a PWM control signal _{S PWM.} That is, the PI calculator 56 generates the PWM control signal S _PWM that can match the reference waveform signal S ₉ and the AC detection signal S ₅ . Thereafter, the PWM control signal S _PWM is converted into a plurality of PWM control signals S _{PWMA to} S _PWMD corresponding to the switching elements SW _{A to} SW _D of the bridge circuit unit 2 in the PWM signal generation unit 57.

Based on the PWM control signals S _{PWMA to} S _PWMD , the drive unit 6 applies a High level or Low level voltage to the control terminals (the gate terminals of the MOSFETs in this embodiment) of the switching elements SW _{A to} SW _D , Thereby, each of the switching elements SW _{A to} SW _D is turned on or off.

In the inverter device in which the correction unit 7 does not exist, when the detection unit 4 superimposes the DC offset on the AC detection signal S ₃ or S ₄ , the control unit 5 removes the DC offset of the AC output voltage V _ac that does not exist originally. Performs feedback control, and as a result, the AC output voltage _Vac includes a DC component. For example, a positive DC offset in the alternating-current detection signal S ₃ or S ₄ is superposed, the control unit 5 is attempted to lower the voltage value of the AC output voltage V _ac, the result, a negative direct current component in the AC output voltage V _ac It will be included. On the other hand, when a negative DC offset in the alternating-current detection signal S ₃ or S ₄ is superposed, the control unit 5 is attempt to raise the voltage value of the AC output voltage V _ac, the result, a positive DC component to the AC output voltage V _ac It will be included. The inverter device 1 solves this problem by including the correction unit 7.

  As shown in FIG. 1, the correction unit 7 includes a comparator unit 70, a photocoupler unit 71, a first half cycle time detection unit 72, a second half cycle time detection unit 73, a subtractor 74, a PI calculator 75, and correction processing. The adder 76 is used. Among these, the comparator unit 70 and the photocoupler unit 71 constitute a “zero cross signal generation unit” of the present invention, and the subtractor 74, the PI calculator 75, and the correction processing adder 76 include the “correction processing” of the present invention. Part ". As shown in the figure, the functions of the respective units 74, 75 and 76 constituting the first half cycle time detection unit 72, the second half cycle time detection unit 73 and the correction processing unit are realized by a microcomputer.

The comparator unit 70 compares the AC detection signal (divided signal) S ₁ that changes in phase with the AC output voltage V _ac and the ground voltage (0 [V]), and outputs a signal corresponding to the result. Specifically, if the alternating-current detection signal _{S 1} is higher than the ground voltage _{(S 1> 0 [V]} ), the comparator unit 70 outputs a signal of the High level (≒ P5 [V]). On the other hand, when the AC detection signal S ₁ is equal to or lower than the ground voltage (S ₁ ≦ 0 [V]), the comparator unit 70 outputs a low level (≈0 [V]) signal. The comparator unit 70 preferably has a hysteresis. When the comparator unit 70 has a hysteresis width of 2 × ΔV, the comparator unit 70 outputs a high level signal when the AC detection signal S ₁ rises and S ₁ > ΔV, while the AC detection signal S ₁ falls. When S ₁ ≦ −ΔV, a low level signal is output.

The photocoupler unit 71 includes a light emitting element that emits light only when the output signal of the comparator unit 70 is at a low level, and a light receiving element that detects light emission of the light emitting element. Light-receiving element of the photocoupler 71, Low level in synchronization with the light emission of the light emitting element (≒ 0 [V]) or outputs a zero-cross signal _{S 10} which becomes High level (≒ D5 [V]). Specifically, the alternating-current detection signal _{S 1} is higher than the ground voltage, when the output signal of the comparator 70 is High level, the zero-cross signal _{S 10} becomes High level. On the other hand, the alternating-current detection signal _{S 1} is lower than the ground voltage, when the output signal of the comparator 70 is at Low level, the zero-cross signal _{S 10} becomes Low level. The photocoupler unit 71 plays a role of insulating the output of the comparator unit 70.

The first half cycle time detection unit 72 detects the first half cycle time T ₁ that is the time from the rising edge to the falling edge of the zero-cross signal S ₁₀ , and outputs a signal corresponding to the detected first half cycle time T _1. Output. In addition, the second half cycle time detection unit 73 detects the second half cycle time T ₂ that is the time from the falling edge to the rising edge of the zero-cross signal S ₁₀ , and according to the detected second half cycle time T ₂ . Output a signal.

The PI calculator 75 outputs an error signal between the signal corresponding to the first half cycle time T ₁ output from the subtractor 74 and the signal corresponding to the second half cycle time T ₂ , that is, the expression “T ₁ -T _2”. It performs PI control compensation of the error signal corresponding to ΔT sought ", and outputs the corrected signal S ₁₁ related to the correction value. When the error signal corresponding to ΔT is x and predetermined positive constants are α and β, the correction signal S ₁₁ output from the PI calculator 75 is as shown in Expression (1). , Α and x, and the product of the cumulative addition of β and x. The constants α and β are determined by considering the response time of PI control compensation and robustness against disturbance.

S ₁₁ = α × x + β × Σx (1)

Correction adder 76 corrects the AC detection signal S ₅ by adding the correction signal S _11, and outputs an AC detection signal S _6. Then, a reference waveform signal S ₉ and the AC detection signal S _6, which is generated based on the alternating-current detection signal S ₆ is to match, the bridge circuit 2 is feedback-controlled.

Here, the effective voltage calculation unit 52, since the calculated effective voltage value after removing the DC component from the AC detection signal S ₅ as described above, it is possible to reduce the load of the microcomputer. That is, when a DC component is included in a signal (AC detection signal) that is a basis for calculating an effective voltage value, an operation with a relatively large load including an average value operation for removing the DC component is required. However, according to the present invention, the effective voltage value can be calculated without performing such calculation.

When the AC output voltage _Vac includes a positive DC component, the control system of the inverter device 1 according to the present embodiment performs the following operations of Step 1A to Step 6A, thereby performing the DC of the AC output voltage _Vac . The component is removed (see FIG. 2A).

(Step 1A) dividing resistor unit 40, forward direction Δe only divided voltage signal offset (the alternating-current detection signal) to a ground voltage (0 [V]) and outputs the S _1.
(Step 2A) photocoupler 71 is first half period time _{T 1} is output longer zero-cross signal _{S 10} signal than the second half period time _{T 2.}
(Step 3A) The subtracter 74 outputs an error signal corresponding to ΔT (= T ₁ −T ₂ ).
(Step 4A) PI calculator 75 outputs a positive correction signal _{S 11.}
(Step 5A) correction adder 76 adds a positive correction signal S ₁₁ to the alternating-current detection signal S _5, larger than the alternating-current detection signal S ₅ before correction an AC detection signal S ₆ after correction.
(Step 6A) The PI calculator 56 outputs a PWM control signal S _PWM that lowers the voltage value of the AC output voltage _Vac as compared with the prior art.

On the other hand, when the AC output voltage _Vac includes a negative DC component, the control system of the inverter device 1 according to the present embodiment performs the following operations of Step 1B to Step 6B, whereby the AC output voltage _Vac. Are removed (see FIG. 2B).

(Step 1B) The voltage dividing resistor section 40 outputs a divided voltage signal (AC detection signal) S ₁ that is offset by Δe in the negative direction with respect to the ground voltage (0 [V]).
(Step 2B) photocoupler 71 is first half period time _{T 1} is output a short zero-crossing signal _{S 10} signal than the second half period time _{T 2.}
(Step 3B) The subtracter 74 outputs an error signal corresponding to ΔT (= T ₁ −T ₂ ).
(Step 4B) PI calculator 75 outputs a negative correction signal _{S 11.}
(Step 5B) correction adder 76 adds a negative correction signal S ₁₁ to the alternating-current detection signal S _5, smaller than the alternating-current detection signal S ₅ before correction an AC detection signal S ₆ after correction.
(Step 6B) The PI calculator 56 outputs a PWM control signal S _PWM that increases the voltage value of the AC output voltage V _ac as compared with the prior art.

Thus, in the inverter device 1 according to the present embodiment, the DC component of the AC output voltage _Vac is removed.

  As mentioned above, although one Embodiment of the inverter apparatus which concerns on this invention has been described, the structure of this invention is not limited to this embodiment.

For example, as in the inverter device 1 'according to a first modification shown in FIG. 3, based on the error signal corresponding to ΔT ₍₌ T 2 -T ₁₎ to produce a correction signal _{S 11,} the correction signal _{S 11} it may be corrected for the alternating-current detection signal S ₅ by subtracting. In this case, exactly the same effect can be obtained. The inverter device 1 ′ includes a correction unit 7 ′ instead of the correction unit 7. The correction unit 7 ′ includes a point where the positions of the first half cycle time detection unit 72 and the second half cycle time detection unit 73 are switched, and a correction processing subtracter 76 ′ instead of the correction processing adder 76. This is different from the correction unit 7.

Also, generating a zero-cross signal S ₁₀ based on the inverter device 1 "as shown in, the alternating-current detection signal (divided signal) S ₂ that varies the AC output voltage V _ac and reverse-phase according to the second modification shown in FIG. 4 May be.

The configuration for generating a reference waveform signal S _9, and configuration for matching the AC detection signal S ₆ of the corrected and reference waveform signal S ₉ can be appropriately changed.

1, 1 ′, 1 ″ Inverter device 2 Bridge circuit unit 3 Filter unit 4 Detection unit 40 Voltage dividing resistor unit 41 First differential amplifier unit 42 Insulation amplifier unit 43 Bias unit 44 Second differential amplifier unit 5 Control unit 50 AD Converter 51 Analog input terminal 52 Effective voltage calculation unit 53 Storage unit 54 PI operation unit 55 Sine wave signal generation unit 56 PI operation unit 57 PWM signal generation unit 6 Drive unit 7, 7 'Correction unit 70 Comparator unit 71 Photocoupler unit 72 First half cycle time detector 73 Second half cycle time detector 74 Subtractor 75 PI calculator 76 Correction process adder 76 ′ Correction process subtractor

Claims (2)

A converter that converts a DC input voltage input from the outside into an AC output voltage, a detection unit that detects a voltage value of the AC output voltage and generates an AC detection signal corresponding to the voltage value, and the AC detection signal And a control unit that controls the conversion unit so as to match a reference waveform signal,
A zero-cross signal generator that generates a zero-cross signal based on the magnitude relationship between the AC detection signal and the ground voltage; and
A half-cycle time detection unit for obtaining a first half-cycle time that is a time when the AC detection signal is positive and a second half-cycle time that is a time when the AC detection signal is negative based on the zero-cross signal;
A correction processing unit that corrects the AC detection signal so that the first half-cycle time and the second half-cycle time coincide;
The said control part controls the said conversion part so that the alternating current detection signal after correction | amendment by the said correction | amendment process part may correspond to the said reference | standard waveform signal, The inverter apparatus characterized by the above-mentioned. The correction processing unit (1) corrects the AC detection signal by adding a correction value corresponding to a time obtained by subtracting the second half cycle time from the first half cycle time to the AC detection signal, Or (2) correcting the AC detection signal by subtracting a correction value corresponding to a time obtained by subtracting the first half cycle time from the second half cycle time from the AC detection signal. The inverter device according to Item 1.

Images