JP2010213365A - Inverter apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter apparatus which can improve its efficiency by reducing a switching loss a switching element. <P>SOLUTION: The inverter apparatus 13 PWM-converts a DC intermediate voltage generated by the power generation of a generator 12 by means of switching elements S1-S4 and forms it with AC reactors L1 and L2 thereby generating a regenerative current of sine waves, and interconnecting it with an AC commercial power source. The inverter apparatus 13 (MPU20, etc.) computes a DC voltage value, where an amount of voltage drop generated by a regenerative current Iinv by an AC reactor L2 and an amount of voltage drop by the switching elements S1-S4 are added to the maximum voltage Vac of the AC voltage of the AC commercial power source detected by a transformer 21 for meters, as its target DC intermediate voltage Vdc-ref, and controls the drive of the switching elements S1-S4 so that the DC intermediate voltage Vdc detected by a DC voltage detecting circuit 25 may accord with the target DC intermediate voltage Vdc-ref. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inverter device that converts DC power based on power generation from a power generation source into AC power and links it to an AC commercial power source.

  Conventionally, various inverter devices have been proposed. For example, the inverter device of Patent Document 1 obtains a DC intermediate voltage (Vdc) by AC-DC conversion of a voltage generated by a generator. Subsequently, the inverter device generates an AC regenerative current (Iinv) having a frequency that can be linked to an AC commercial power source by PWM conversion of the DC intermediate voltage by a switching element (MOSFET, IGBT, etc.) The regenerative current is shaped into a sine wave through an AC reactor, and this is connected to an AC commercial power supply of AC voltage (power supply voltage) (Vac).

  In this case, the DC intermediate voltage fluctuates within a certain voltage range depending on the regenerative current (that is, the power load of the AC commercial power supply) or the output (that is, the rotation speed) of the generator. For example, when the rotation speed of the generator is high, the DC intermediate voltage The intermediate voltage increases. Therefore, in the inverter device of Patent Document 2, it is also proposed to control the DC intermediate voltage to a constant voltage so that the DC intermediate voltage is not excessively adjusted and the waveform of the regenerative current is not distorted.

JP 2002-101560 A Japanese Patent No. 3950706

  By the way, in such a conventional inverter device, the AC voltage maximum value (Vac) of the AC commercial power supply, the voltage drop (VL) due to the AC reactor, and the voltage drop due to the switching element cannot be matched with the DC intermediate voltage (Vdc). Extra power is generated as a switching loss in the switching element, and the efficiency of the inverter device is inevitably reduced.

  The objective of this invention is providing the inverter apparatus which can reduce the switching loss of a switching element and can make it more efficient.

  In order to solve the above-mentioned problems, the invention described in claim 1 generates a sine wave regenerative current by converting a DC voltage generated by power generation of a power generation source by PWM using a switching element and shaping it by a reactor. In the inverter device linked to the AC commercial power supply, DC voltage detection means for detecting a DC voltage generated by power generation of the power generation source, power supply voltage detection means for detecting the AC voltage maximum value of the AC commercial power supply, Current detecting means for detecting a regenerative current linked to the AC commercial power supply, a voltage drop generated by the regenerative current due to the reactor to the detected AC voltage maximum value of the AC commercial power supply, and a voltage by the switching element A calculation means for calculating a DC voltage value obtained by adding the drop as a target DC voltage; and the detected DC voltage is the target DC voltage. And summarized in that a control means for driving and controlling the switching element to match the pressure.

  For example, the detected DC voltage is a voltage value obtained by adding the detected AC voltage maximum value of the AC commercial power supply, the voltage drop generated by the regenerative current (Iinv) by the reactor, and the voltage drop by the switching element. If it is larger by an arbitrary amount, a product of an arbitrary voltage value and the regenerative current is consumed by the switching element as a power loss. According to this configuration, the calculation means adds a voltage drop generated by the regenerative current (Iinv) due to the reactor and a voltage drop due to the switching element to the detected AC voltage maximum value of the AC commercial power supply. A DC voltage value is calculated as the target DC voltage. Therefore, the target DC voltage is controlled so that the extra voltage value is minimized, so that the amount consumed by the switching element can be minimized and efficiency can be improved.

  In the present invention, it is possible to provide an inverter device capable of reducing the switching loss of the switching element and making it more efficient.

1 is a configuration block diagram showing a grid interconnection system to which the present invention is applied. The flowchart which shows the control aspect of the embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 is a configuration block diagram showing a grid interconnection system to which the inverter device according to the present embodiment is applied. As shown in the figure, the system includes a gas engine 11 and a generator 12 including a three-phase AC machine that is drivingly connected to the gas engine 11. This generator 12 has a rotor that is rotationally driven by the gas engine 11 and one terminal is commonly connected at a neutral point O, so-called Y-connected U-phase coil 12a, V-phase coil 12b, and W-phase coil. It has a stator with 12c. The other terminals of these coils 12 a to 12 c are connected to the inverter device 13.

  That is, the inverter device 13 includes a converter circuit 14 having six transistors Q1 to Q6 made of, for example, N-channel MOSFETs, and the other terminal of the U-phase coil 12a is connected to a connection point Nu between the transistors Q1 and Q2, and V The other terminal of phase coil 12b is connected to node Nv of transistors Q3 and Q4, and the other terminal of W phase coil 12c is connected to node Nw of transistors Q5 and Q6. The drains of the transistors Q1, Q3, and Q5 are connected to the positive terminal N1, and the sources of the transistors Q2, Q4, and Q6 are connected to the negative terminal N2. The gates of the transistors Q1 to Q6 are connected to the converter gate 15. In the converter circuit 14, the gates of the transistors Q1 to Q6 are individually turned on / off by the converter gate 15 to convert the AC power generated by the generator 12 into DC power, and the positive terminal N1 and the negative terminal N2 A DC intermediate voltage (Vdc) is output between them. The positive terminal N1 and the negative terminal N2 are connected to both terminals of a smoothing polar capacitor C, respectively.

  The inverter device 13 includes an inverter circuit 16 connected to the positive terminal N1 and the negative terminal N2. The inverter circuit 16 has four switching elements S1 to S4 made of, for example, N-channel MOSFETs, and the drains of the switching elements S1 and S3 are connected to the positive terminal N1 and the sources of the switching elements S2 and S4. Is connected to the negative terminal N2. The connection point N3 of the switching elements S1 and S2 is connected to one terminal of the AC reactor L1, and the connection point N4 of the switching elements S3 and S4 is connected to one terminal of the AC reactor L2. Further, the gates of the switching elements S <b> 1 to S <b> 4 are connected to the inverter gate 17. The inverter circuit 16 converts the DC intermediate voltage (DC power) between the positive terminal N1 and the negative terminal N2 into AC power by individually turning on and off the gates of the switching elements S1 to S4 by the inverter gate 17. Then, alternating current regenerative currents (Iinv) having opposite phases to each other are output to the alternating current reactors L1 and L2.

  The AC reactors L1 and L2 are for shaping the regenerative current (Iinv) output from the inverter circuit 16 into a sine wave. Each other terminal is connected to a relay 19 via a common-mode noise reduction filter 18. The switches 19a and 19b are respectively connected. The relay 19 is connected to an AC commercial power source having an AC voltage (Va) of 200 V, for example. That is, the switches 19a and 19b are respectively connected to a U-phase electric wire U and a V-phase electric wire V of an AC commercial power source connected to an internal (for example, home) power load (not shown), and the inverter device 13 and the AC Switch between conduction and non-conduction (interconnection / non-interconnection) between commercial power sources. The neutral phase electric wire N of the AC commercial power supply is grounded.

  Here, the U-phase electric wire U, the V-phase electric wire V, and the neutral phase electric wire N are connected to the primary side of the instrument transformer 21, and both output terminals on the secondary side of the instrument transformer 21 are amplifiers 22. Are connected to the non-inverting input terminal and the inverting input terminal, respectively. The output terminal of the amplifier 22 is connected to an A / D converter of an MPU (Micro Processor Unit) 20. The amplifier 22 rectifies and amplifies a voltage having a magnitude corresponding to the AC voltage (Va) between the U-phase electric wire U and the V-phase electric wire V generated in the instrument transformer 21, and the amplified voltage is supplied to the MPU 20. Output to the A / D converter. Thereby, MPU20 detects the present alternating voltage maximum value Vac supplied to internal electric power load.

  In the distribution board, current sensors 23 and 24 are installed which are arranged on the U-phase electric wire U and the V-phase electric wire V and are respectively connected to the A / D conversion unit of the MPU 20. Current sensors 23 and 24 output voltages of magnitudes corresponding to alternating currents (Ir, Is) flowing through U-phase electric wire U and V-phase electric wire V to the A / D converter of MPU 20, respectively. Thereby, MPU20 detects the present alternating current Ir and Is supplied to internal electric power load.

  Further, a DC voltage detection circuit (for example, a resistor) 25 is connected in parallel with the polar capacitor C to the positive terminal N1 and the negative terminal N2, and an isolation amplifier 26 is connected to the DC voltage detection circuit 25. The A / D converter of the MPU 20 is connected via The DC voltage detection circuit 25 outputs a DC voltage having a magnitude corresponding to the DC intermediate voltage (Vdc) between the positive terminal N1 and the negative terminal N2 to the A / D converter of the MPU 20 via the isolation amplifier 26. Thereby, the MPU 20 detects the current DC intermediate voltage Vdc between the positive terminal N1 and the negative terminal N2.

  Further, a current sensor 27 including a current transformer is provided between the connection point N4 and the AC reactor L2. The current sensor 27 is connected to the A / D converter of the MPU 20 and outputs a voltage having a magnitude corresponding to the AC current (Iinv) flowing through the AC reactor L2 to the A / D converter of the MPU 20. Thereby, MPU20 detects the present regenerative current Iinv which flows into AC reactor L2.

  Furthermore, current sensors 28 and 29 each including a current transformer are disposed between the connection point Nu and the U-phase coil 12a, and between the connection point Nw and the W-phase coil 12c. These current sensors 28 and 29 are individually connected to the A / D conversion unit of the MPU 20, and a voltage having a magnitude corresponding to the alternating current (Iu, Iw) flowing through the U-phase coil 12 a or the W-phase coil 12 c is supplied to the MPU 20. To the A / D converter. Thereby, MPU20 detects the present generator output currents Iu and Iw which flow into U phase coil 12a or W phase coil 12c.

  The output terminal of the amplifier 22 is connected to a PLL (Phase Locked Loop) circuit 31. The PLL circuit 31 generates an output signal synchronized with an AC voltage (that is, an AC commercial power supply) supplied to an internal power load, and is connected to an output control unit 32. This output control unit 32 is connected to the isolation amplifier 26, and inputs a DC voltage correlated with the current DC intermediate voltage Vdc between the positive terminal N1 and the negative terminal N2. The output control unit 32 is connected to the D / A conversion unit of the MPU 20 and inputs a DC voltage correlated with the target DC intermediate voltage Vdc_ref calculated according to the following procedure.

  Then, the output control unit 32 generates an output control signal corresponding to the magnitude relationship between the DC voltages correlated to the DC intermediate voltage Vdc and the target DC intermediate voltage Vdc_ref and the output signal of the PLL circuit 31, and the inverter gate 17 to output. Thus, the inverter gate 17 synchronizes with the AC commercial power supply and generates a sine wave regenerative current (Iinv) that is increased or decreased so that the DC intermediate voltages Vdc and Vdc_ref coincide with each other. The gates S1 to S4 are driven on / off.

  Here, how the MPU 20 calculates the DC intermediate voltage Vdc_ref will be described. First, when the DC intermediate voltage (Vdc) between the positive terminal N1 and the negative terminal N2 is PWM-converted by the switching elements S1 to S4 (inverter circuit 16), a voltage drop generated in each of the switching elements S1 to S4 is represented by Vs. The voltage drop generated when the regenerative current Iinv flows through the AC reactor (L2) is represented by VL. In this case, the drop voltage Vs is expressed by the following expressions (1) and (2).

Vs = Vdc−VL−√2Vac−Von (1)
However,
VL = j × ω × L × Iinv (2)
(L: inductance of AC reactor, ω: angular velocity of frequency of AC commercial power)
Von is an on-voltage of the switching elements S1 to S4, and is a constant value (for example, 1.8 to 2.5 V) determined by the structure.

And loss Ps in switching element S1-S4 is represented by the following Formula (3).
Ps = (Vs + Von) × Iinv
+ 2 × (element switching loss due to tail current) (3)
Therefore, except for the element switching loss due to the tail current of the two items on the right side of Equation (3), Ps is minimized when Vs is made zero. In this embodiment, the target DC intermediate voltage Vdc_ref is expressed by the following equation: It is determined by (4).

Vdc_ref = VL + √2Vac + Von (4)
The output control unit 32 drives and controls the inverter gate 17 to increase or decrease the regenerative current Iinv so that the current DC intermediate voltage Vdc matches the target DC intermediate voltage Vdc_ref. For example, when the current DC intermediate voltage Vdc is smaller than the target DC intermediate voltage Vdc_ref, the inverter gate 17 is set so that the regenerative current Iinv decreases so as to reduce the DC intermediate voltage Vdc_ref from the equations (2) and (4). Drive control.

  The current sensors 28 and 29 are connected to both input terminals of an AC / DC converter 33 composed of, for example, a rectifier circuit, and compare a DC voltage obtained by rectifying an AC voltage corresponding to a difference between generator output currents (Iu, Iw). Output to the inverting input terminal of the unit 34. On the other hand, the non-inverting input terminal of the comparator 34 is connected to the D / A converter of the MPU 20 and inputs a DC voltage correlated with the target generator output current Ige_ref set by the MPU 20. The generator output current Ige_ref is a calculated value obtained by the MPU 20 according to a map based on the current receiving end power Pw (power supplied to the internal power load) calculated according to the following equation (5).

Pw = Vac × (Ir + Is) / 2 (5)
The output terminal of the comparator 34 is connected to the PWM converter 35, and the comparator 34 has a magnitude relationship between the DC voltage output from the AC / DC converter 33 and the DC voltage correlated with the generator output current Ige_ref. An output signal having a corresponding level is generated and output to the PWM converter 35.

  The PWM converter 35 generates an output control signal corresponding to the level of the output signal from the comparator 34 and outputs the output control signal to the converter gate 15. As a result, the converter gate 15 drives the gates of the transistors Q1 to Q6 of the converter circuit 14 so as to generate a generator output current (Iu, Iw) that matches the generator output current Ige_ref. Prior to this, the MPU 20 transmits a control command to the control device of the gas engine 11 via appropriate communication means. Thereby, the rotational speed of the gas engine 11 is controlled so that the required generator output current (Iu, Iw) can be generated.

  In addition, when the rotational speed of the gas engine 11 is rotationally driven in this manner, a required generator output current is generated in the generator 12 and is converted into DC power in the converter circuit 14, and the positive terminal N1 and As described above, the DC intermediate voltage (Vdc) is generated between the negative terminal N2. Note that the DC intermediate voltage is boosted to about 360 V to 380 V, for example, so as to be larger than the peak value of the AC voltage before conversion when converting into DC power in the converter circuit 14.

  Next, the control mode of the grid interconnection system by the MPU 20 and the like, particularly the control mode of the regenerative current Iinv of the inverter device 13 (inverter circuit 16) will be described in general with reference to the flowchart of FIG.

  First, when the power of the grid interconnection system is turned on (S1), the gas engine 11 is started (S2). When the gas engine 11 is started, power generation is started in the generator 12 that is rotationally driven by the gas engine 11. When starting the gas engine 11, the generator 12 can be driven as an electric motor (starting motor) by the inverter device 13, or a dedicated starting motor can be driven to rotate the rotating shaft of the gas engine 11. That's fine.

  Subsequently, the current power receiving end power Pw is calculated according to the above-described equation (5) (S3). Then, the output power of the target inverter device 13 is set to the receiving end power Pw. Accordingly, a rotational speed of the gas engine 11 is generated so that a required generator output current (Iu, Iw) can be generated by transmitting a control command to the control device of the gas engine 11 via an appropriate communication means. Is controlled.

  Next, the target generator output current Ige_ref calculated by the map based on the current power receiving end power Pw is set, and the target DC intermediate voltage Vdc_ref calculated by the above-described equation (4) is set ( S6). As a result, the converter circuit 14 is driven and controlled to generate a generator output current having the generator output current Ige_ref, and the DC intermediate voltage (Vdc) between the positive terminal N1 and the negative terminal N2 is boosted (S7). .

  Subsequently, it is determined whether or not the current DC intermediate voltage Vdc is smaller than the target DC intermediate voltage Vdc_ref (S8). When it is determined that the DC intermediate voltage Vdc is smaller than the DC intermediate voltage Vdc_ref, the regenerative current Iinv is decreased so as to reduce the DC intermediate voltage Vdc_ref, as is apparent from the above formulas (2) and (4). (S9). When the DC intermediate voltage Vdc is determined to be equal to or higher than the DC intermediate voltage Vdc_ref, the regenerative current Iinv is increased to increase the DC intermediate voltage Vdc_ref (S9). Such increase / decrease correction of the regenerative current Iinv is performed by drive control of the inverter circuit 16. When the increase / decrease correction of the regenerative current Iinv according to the magnitude relationship between the DC intermediate voltages Vdc and Vdc_ref is performed in S9 or S10, the process returns to S3 and the same processing is repeated.

As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) In the present embodiment, the detected AC voltage maximum value Vac (√2 Vac) of the AC commercial power supply corresponds to the voltage drop VL generated by the regenerative current Iinv by the AC reactor L2 (, L1) and the switching elements S1 to S4 A DC voltage value obtained by adding the voltage drop (ON voltage Von) is calculated as the target DC voltage Vdc_ref. Therefore, since the target DC voltage Vdc_ref is controlled so that the voltage value (Vs) of an extra arbitrary amount is minimized, the amount consumed by the switching elements S1 to S4 can be minimized, and efficiency can be improved. Can do.

In addition, you may change the said embodiment as follows.
In the embodiment, the transistors Q1 to Q6 and the switching elements S1 to S4 may be IGBTs or the like.

  In the embodiment, the current sensor 27 may be provided between the connection point N3 and the AC reactor L1 instead of or in addition to the connection point N4 and the AC reactor L2.

In the embodiment, the inverter device 13 may be linked to a three-phase AC commercial power source.
In the above embodiment, the generated power of the power generation source is direct current power such as a solar cell or a fuel cell, or direct current power obtained by converting alternating current power such as a wind power generator or a gas turbine generator via a converter. Also good.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
In the inverter device according to claim 1,
When the target DC voltage is represented by Vdc_ref, the detected AC voltage maximum value of the AC commercial power supply is Vac, the detected regenerative current is represented by Iinv, and the ON voltage (voltage drop) of the switching element is represented by Von. The calculation means is
Vdc_ref = VL + √2Vac + Von
However,
VL = j × ω × L × Iinv
(L: inductance, ω: angular velocity of AC commercial power supply frequency)
The target DC voltage is calculated based on the inverter device.

  L1, L2 ... AC reactor (reactor), S1 to S4 ... switching element, 11 ... gas engine (power generation source), 12 ... generator (power generation source), 14 ... converter circuit (power generation source), 13 ... inverter Device: 16 ... Inverter circuit, 20 ... MPU (calculation means, control means), 21 ... Instrument transformer (power supply voltage detection means), 25 ... DC voltage detection circuit (DC voltage detection means), 27 ... Current sensor (current) Detection means), 31... PLL circuit (control means), 32... Output control section (control means), 17... Inverter gate (control means).

Claims (1)

In the inverter device linked to the AC commercial power source, the DC voltage generated by the power generation of the power generation source is PWM-converted by the switching element and is formed by the reactor to generate a sine wave regenerative current.
DC voltage detecting means for detecting a DC voltage generated by power generation of the power generation source;
Power supply voltage detection means for detecting the AC voltage maximum value of the AC commercial power supply;
Current detection means for detecting a regenerative current linked to the AC commercial power supply;
Calculating means for calculating a DC voltage value obtained by adding a voltage drop generated by the regenerative current due to the reactor and a voltage drop caused by the switching element as a target DC voltage, to the detected AC voltage maximum value of the AC commercial power supply; ,
An inverter device comprising: control means for driving and controlling the switching element so that the detected DC voltage matches the target DC voltage.

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