JPH07322634A - Control method of inverter and inverter device - Google Patents

Abstract

PURPOSE:To eliminate the need for complicated control, and to control even the waveform distortion of output currents from an inverter at a small value by alternately inverting the positive and negative polarity of a PWM-modulated pulse train using a since wave signal and a carrier signal and exciting the primary side of a transformer by an obtained high-frequency AC signal. CONSTITUTION:A rectangular wave signal, which has the same frequency as a carrier signal formed from a rectangular-wave signal generator and in which the phase is shifted by a quarter period, and first to fourth pulse train signals are exclusively ORed by an XOR circuit, thus acquiring first 'to fourth' pulse train signals. These first 'to fourth' pulse train signals are output to a gate drive circuit 10, and the on-off of four switching elements Q1-Q4 constituting a high-frequency inverter bridge 4 is controlled. As a result of the on-off control, a high-frequency transformer 5 is excited by the same high frequency as the frequency of the carrier signal, in which the positive and negative polarity of a PWM-modulated pulse train are inverted alternately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention converts DC power generated by an independent DC power source such as a solar cell into AC power and supplies the power to a general AC load for home use, office work, or an existing commercial power system. The present invention relates to an inverter device that supplies

[0002]

2. Description of the Related Art A conventional inverter device includes an inverter bridge composed of several switching elements, a transformer for electrically insulating a DC power source from a commercial power system, a load, a low-pass filter, and It is composed of a control circuit for controlling on / off of a plurality of switching elements forming an inverter bridge, and a commercial frequency transformer or a high frequency transformer for downsizing the device is used as the transformer.

First, a conventional example of an inverter device using a commercial transformer will be described with reference to FIG. The DC power output from the solar cell 2 is input to the inverter 1, converted into AC power by the inverter bridge 32, and commercialized at the output end of the inverter 1 to insulate the solar cell 2 from the commercial grid 3. Commercial power system 3 via transformer 33
Is supplied to. In front of the inverter bridge 32, a DC capacitor 1 that suppresses fluctuations in input power to the inverter 1
2 and the DC input current detector 13 are connected.
Further, an AC filter 16 for removing harmonic components of an alternating current and an inverter output current detector 14 are connected to the latter stage of the inverter bridge 32, and an interconnection relay 15 is further provided to the latter stage of the AC filter 16 for commercial use. Connection and disconnection with the power system 3 are performed.

The control circuit 34 of the inverter 1 includes a gate drive circuit 35, a PWM modulation control section 36, and an error amplifier 3.
7, carrier wave signal generator 38, signal calculation processing unit 39,
It is composed of a sine wave signal storage unit 40, an A / D converter 41, and a D / A converter 42.

In the PWM modulation control section 36, a sine wave signal having the same frequency (50/60 Hz) as the voltage waveform of the commercial power system 3 described above and a high frequency wave (equation 10) synchronized with this sine wave signal.
a first pulse train signal obtained by comparison with a carrier signal of 1 kHz or more), and a second pulse train signal obtained by inverting the first pulse train signal.
Pulse train signal, a third pulse train signal obtained by comparing the inverted carrier signal obtained by inverting the carrier signal with the sine wave signal, and a fourth pulse train signal obtained by inverting the third pulse train signal. These pulse train signal waveforms are shown in FIG. In the figure, a high frequency of several tens of kHz is schematically shown, so that the frequency is low.

These first to fourth pulse train signals are input to the gate drive circuit 35, and on the basis of these signals, gate drive signals having the same frequency as the carrier signals for the four switching elements Q1 to Q4 forming the inverter bridge 32 are generated. Q1 to Q4 are generated and generated, and Q1 to Q4 are on / off controlled at the same frequency as the carrier signal. As a result, the output pulse train waveform Ei shown in FIG. 9 is output from the inverter bridge 32. Further, the output waveform Ei is subjected to the removal and smoothing of harmonic components by the AC filter 16 in the next stage, and becomes a 50/60 Hz sine wave AC output. The sine wave AC output is connected to the commercial power system 3 after being insulated between the input and the output by the commercial transformer 33. In this case, the commercial transformer 33 is 50 / 60Hz
It will be excited at the frequency of the sine wave AC output.

The A / D converter 41 converts the DC voltage signal VOUT, the DC current signal VIN, and the commercial power system voltage signal VOUT, which are analog signals from the solar cell 2, into a digital amount, and the signal calculation processing unit 39. Signal to. The signal calculation processing unit 39 is a maximum power point tracking calculation for matching the solar cell operating point with the maximum point on the solar cell output characteristic curve in order to maximize the output power from the solar cell 2, and the inverter 1 A process of reading a sine wave signal (50/60 Hz), which is a current command value for controlling, from the sine wave signal storage unit 40 in which a plurality of different amplitudes are stored in advance is performed. The sine wave signal storage unit 40 quantizes the sine wave signal having a plurality of different amplitude values proportional to the amplitude value of the rated output current waveform of the inverter 1 in units of half cycle or one cycle and at certain time intervals. Stored as a digital quantity. The D / A converter 42 converts the read sine wave signal into an analog signal and outputs it to the error amplifier 37. The error amplifier 37 is the inverter output current detector 1
The inverter output current signal IOUT from 4 and the sine wave signal are input, and a reference wave signal obtained by amplifying a comparison error between the two is output to the PWM modulation control unit 36.
The carrier signal generator 38 also outputs a carrier signal (20 kHz) synchronized with the sine wave signal to the PWM modulation controller 36. As a result, the output current of the inverter 1 changes following the sine wave signal that is the current command value. Here, when the output current of the inverter 1 is controlled by the sine wave signal, by setting it to the same phase and the same frequency (50/60 Hz) as the voltage of the commercial power system 3, the power is applied to the existing commercial power system 3. AC power with a rate of 1 can be supplied.

Next, the case where a high frequency transformer is used will be described. An apparatus using a commercial transformer is disadvantageous in reducing the size and weight of the inverter because the weight and capacity of the commercial transformer are large. On the other hand, using a high frequency transformer can solve such a problem. In this case, it is necessary to excite the high frequency transformer with a high frequency voltage, and an example using the current instantaneous value control method considered for this purpose will be described below with reference to FIG.

The inverter 1 is inserted between the solar cell 2 and the existing commercial power system 3, converts DC power generated by the solar cell 2 into AC power of 50/60 Hz, and is connected to the commercial power system 3. And supply to the load. In the inverter 1, the input DC power is converted into high frequency AC by the current instantaneous value control in the high frequency inverter bridge 4 composed of switching elements Q1 to Q4, and is supplied to the primary side of the high frequency transformer 5. This high-frequency alternating current is rectified by the diode bridge 6 on the secondary side of the high-frequency transformer 5, and harmonics are removed and smoothed by a filter circuit including a DC reactor 7 and a capacitor connected in parallel. Further, the low-frequency inverter bridge 8 composed of switching elements S1 to S4 is converted into AC power of commercial frequency by folding control,
Electric power is supplied to the commercial power system 3 via the interconnection relay 15 and the AC filter 16.

The signal calculation processing unit 43 receives the voltage signal VIN of the solar cell 1 and the current signal II detected by the DC input current detector 3.
N, the primary side current (inverter output current) signal IT of the high frequency transformer 5 detected by the inverter output current detector 14 and the voltage signal VOUT of the commercial power system 3 are input, and the current command signal and the polarity determination signal are input. Is output. The hysteresis comparator 44 inputs the primary side current IT of the high frequency transformer 5 detected by the inverter output current detector 14 and the current command signal, and the primary side current of the high frequency transformer 5 has an upper limit value centered on the current command signal. And switching elements Q1, Q4, and Q composing the high-frequency inverter bridge 4 so as to repeatedly reciprocate within a certain width range having a lower limit value.
ON / OFF control of 2 and Q3 is performed alternately via the NOT circuit 45. That is, the current command signal (IRE
For F), the upper limit I + and the lower limit I− having a constant width ΔI are given to the hysteresis comparator 44 as set values. Then, the inverter output current detector 14 detects the high-frequency transformer 5 and the primary side current signal IT of FIG. 10, which is the actual value of the control amount, and inputs it to the hysteresis comparator 44 together with the current command signal. The current signal IT, which is the actual value of the controlled variable, is the upper limit set value I + (I +
= IREF + ΔI) is exceeded, the switching elements Q1 and Q4 of the high frequency inverter bridge 4 of FIG. 11 are turned off.
Then, through the NOT circuit 45, Q2 and Q3 are turned on so that the current gradient is in the decreasing direction, and the current signal IT in FIG. 11 decreases, and the lower limit setting value I- (I- = IREF-
When it is less than ΔI), Q1 and Q4 are turned on, Q3 and Q4 are turned off, and the current signal IT is controlled to increase. By performing such switching control, the actual value of the current signal IT transits between I + and I- so as to reciprocate at each switching. Here, when a sine wave signal having the same frequency as the commercial power system 3 and an arbitrary amplitude value is used as the current command signal (IREF), the current signal IT is the current command signal even if switching is performed at extremely high speed. Centered on ± △
It is possible to obtain a sinusoidal current waveform that is proportional to the amplitude value of the current command signal at the commercial frequency and changes so as to repeatedly reciprocate and follow the width of I. As described above, the current command signal (I
The magnitude of the high-frequency transformer 5, primary side current in the inverter 1, that is, the magnitude of the inverter output current can be controlled by the amplitude value of (REF).

The turn-back control circuit 46 receives the polarity determination signal and inputs the voltage signal VOUT of the commercial power system 3.
The switching elements S1, S4 and S2, S3 forming the low frequency inverter bridge 8 are alternately switched on / off in accordance with the polarity of. By this control, the DC power rectified in the full-wave rectification by the diode bridge 6 becomes a sine wave AC output in the subsequent stage of the low frequency inverter bridge 8.

[0012]

It is preferable to use a high frequency transformer in order to reduce the size and weight of the inverter device. This is because the high frequency transformer has a capacity ratio of about 1/30 and a weight ratio of about 1/20 as compared with a commercial transformer.

However, although the current instantaneous value control method used as a method for exciting a high frequency transformer with a high frequency voltage is excellent, it is difficult to optimize the setting of the upper limit value and the lower limit value of the hysteresis width in the control method. ，
If the set value is too large, the distortion becomes large, and if the set value is too small, the width of the pulse train signal obtained by comparing the current command value and the inverter output current becomes small,
The control system becomes unstable as compared with the PWM control in the case of the above low frequency transformer. In addition, when a more stable control system is sought, the control circuit becomes complicated.

In view of the above, the present invention does not require complicated control in order to reduce the size and weight of the inverter device.
An object of the present invention is to provide a control method of an inverter device capable of controlling the waveform distortion of an inverter output current to be sufficiently small and an inverter device using this method.

[0015]

An inverter control method of the present invention is a method for controlling an inverter device for converting electric power generated from a DC power supply into AC and supplying the AC power to a load or an existing commercial power supply. Exciting the primary side of the transformer that inverts every other positive and negative polarities of the PWM-modulated pulse train by PWM control using the carrier signal and the carrier signal, and insulates the input and output with the high-frequency AC signal obtained by this Is characterized by.

As a method of inverting the positive and negative polarities of the PWM-modulated pulse train by the PWM control, the first pulse train signal is obtained by comparing the sine wave signal with the carrier signal. To obtain a second pulse train signal, generate an inverted carrier signal by inverting the carrier signal, and compare the inverted carrier signal with the sine wave signal to obtain a third pulse train signal, A fourth pulse train signal is obtained by inverting the third pulse train signal to generate a rectangular wave signal having the same frequency as the carrier signal and having a phase shift of 1/4 cycle. Each of the first to fourth pulse train signals is gated, and four pulse train signals obtained by the gate processing are used to control ON / OFF of four switching elements that form an inverter bridge. Cormorants method is good to use. Then, in the gate processing, it is preferable to perform an exclusive OR processing so that four kinds of pulse train signals are generated.
4 types of pulse train signals to form an inverter bridge
It is preferable that the high-frequency AC signal having the same frequency as the carrier frequency be obtained by inputting each of the switching elements to ON / OFF control of the switching elements. In this case, a sine wave signal of 50/60 to several hundreds of Hz and a carrier signal of several tens of kHz or more are preferably used, and the inverter device is provided with an inverter bridge consisting of four switching elements. .

Further, as a method of obtaining the four pulse train signals, a sine wave signal and a carrier signal are compared with each other, and if the sine wave signal exceeds the carrier signal, the first level is output, and if the sine wave signal is below the carrier signal, the second level is output. To generate a first pulse train signal, invert the first pulse train signal to generate a second pulse train signal, and compare the inverted carrier signal obtained by inverting the carrier signal with the sine wave signal to obtain an inverted carrier signal. A method of generating a third pulse train signal by outputting a first level when the signal exceeds the sine wave signal and a second level when the signal is below the sine wave signal, and inverting the third pulse train signal to generate a fourth pulse train signal Good to use. The first level and the second level mean so-called High or Low levels.

In the method of the present invention described above, preferably, the high-frequency alternating current excited on the secondary side of the transformer is rectified by a rectifier (AC / DC converter), so that continuous PWM modulation with one polarity is performed. It is better to convert to the pulse train output.

The inverter device that enables the inverter control method of the present invention includes a first power conversion unit for converting DC into AC, and a secondary voltage transformed by using the AC voltage as a primary voltage. A transformer, a second power conversion unit that connects two wires on the secondary side of the transformer to convert alternating current to direct current, and a reactor that is connected in series to each two wires output from the second power conversion unit, Further, a third power converter connected to the output of the reactor for converting direct current into alternating current, and a control circuit for controlling on / off of the switching elements forming the first power converter and the third power converter. And a control circuit configured to generate a sine wave signal that is an output target value of the inverter, and a PWM using the sine wave signal.
The means for generating a carrier signal for controlling, the means for generating a rectangular wave signal having the same frequency as the carrier signal and having a phase shifted by ¼ cycle, the sine wave method according to claim 2. First from the wave signal and the carrier signal
Means for gate-processing the rectangular wave signal to these signals after generating the fourth pulse-train signal from the above, and turning on / off of the switching element constituting the first power conversion unit with the pulse-train signal after the gate-processing. It is preferable to use an inverter device provided with means for performing off control. The first power converter converts a direct current input into a high frequency alternating current (tens of kHz).
It is preferable to use a high-frequency inverter bridge for converting into the above). As the transformer, a high-frequency transformer that insulates the input side and the output side of the high-frequency inverter bridge may be used, and the second power conversion unit may output the high-frequency transformer. A diode bridge for rectifying high-frequency alternating current at the end is preferable.

A low-frequency inverter bridge in which the rectified waveform is smoothed in the reactor to remove high-frequency components, and the third power converter is controlled by folding back at a low frequency (for example, 50/60 to several hundred Hz). It is better to configure with.

Further, with respect to the inverter device of the present invention, an intermediate tap is further provided on the secondary side of the transformer, and a wire from the intermediate tap is connected to a neutral wire of a low-voltage single-phase three-wire distribution line, The reactor is connected to the output two lines of the second power conversion unit, capacitors are connected vertically symmetrically between each of the two lines and the line from the intermediate tap, and the third line is connected.
It is more preferable that the two output lines of the power conversion unit are connected to each line other than the neutral line of the low voltage single-phase three-wire distribution line.

[0022]

According to the control method of the present invention, the required high-frequency AC signal can be obtained only by inverting every other PWM-modulated pulse train. And this inversion is, for example, 4
It can be obtained by driving the gates of the switching elements that form the inverter bridge with pulse train signals of various types.

Further, according to the method of claim 2, the PW
Every other M-modulated pulse train, the positive and negative inverted high-frequency alternating current has the same frequency as the carrier signal. In this case, an inverted signal of a sine wave signal may be used instead of the inverted signal of the carrier signal, and the same result is obtained.

When the primary side of the transformer is controlled so that every other PWM-modulated pulse train is excited by positive and negative inverted AC, the secondary side of the transformer transforms the primary side voltage. A high-frequency alternating current with positive and negative inversions is output every other PWM-modulated pulse train. Therefore, by rectifying this high-frequency alternating current, it is converted into a PWM-modulated pulse train output that is continuous on one side.

On the other hand, according to the inverter device of the present invention,
As a result of adopting the inverter control method in which the primary side of the high frequency transformer is inverted by positive and negative every other PWM-modulated pulse train and is excited by the high frequency AC having the same frequency as the carrier frequency, the output waveform of the secondary side of the high frequency transformer is also PWM. Since every other modulated pulse train has a positive and negative inverted high-frequency AC waveform, the diode bridge provided after the high-frequency transformer rectifies the positive-negative inverted pulse train signal every other PWM modulation. To obtain a continuous PWM pulse train waveform on the positive side. Then, a DC reactor provided at the latter stage of the diode bridge smoothes and removes high frequency components, and a DC waveform similar to that obtained by full-wave rectifying the sine wave AC waveform having the same frequency as the sine wave signal can be obtained. Further, in the commercial frequency inverter bridge in the latter stage, a sine wave AC waveform can be obtained by performing a turn-back control in which every other DC waveform similar to the one obtained by full-wave rectifying the sine wave AC waveform is inverted.

Furthermore, by providing an intermediate tap on the secondary side of the high frequency transformer, the secondary side of the high frequency transformer can obtain three output lines with the intermediate tap and two other output lines. Further, two line voltages having the same potential are generated between the intermediate tap and the other two output lines, and a line voltage twice the line voltage is generated between the two lines other than the intermediate tap. To do. That is, a total of three line voltages can be obtained. The three line voltages are connected to the low-voltage single-phase three-wire distribution line of the commercial power system, but the three line voltages on the secondary side of the high frequency transformer are sinusoidal waveforms of the commercial power system. However, in the same manner as described above, every other PWM-modulated pulse train has a high-frequency AC waveform with positive and negative inversions. For this reason, the three line voltages are once rectified by the diode bridge in the above configuration, smoothed by a low-pass filter composed of a DC reactor and a capacitor, and a high-frequency component is removed from the DC voltage waveform (commercial frequency sine wave). Is a full-wave rectified waveform) and the commercial frequency sinusoidal AC waveform is obtained by folding control of the low-frequency inverter bridge.

With the above operation, the inverter device of the present invention can use the high frequency transformer instead of the commercial transformer, and can realize the reduction in size and weight.
A stable sine wave AC waveform can be obtained by a simple control method by simply adding gate processing typified by exclusive OR processing to conventional PWM control, and further three line voltages (for example, 100 VAC, 100 VAC). , 200
It is also possible to perform interconnection operation with a low-voltage single-phase three-wire distribution line of a commercial power system by using an output three-line having VAC).

[0028]

【Example】

Embodiment 1 Hereinafter, the first embodiment of the inverter device of the present invention will be described.
This will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a grid-connected photovoltaic power generation system including an inverter of the present invention.

Solar cell 2 (output 3.5 kW, open circuit voltage 2
The DC power output from a 70 V power supply) is converted into AC power having the same phase and frequency 50/60 Hz as the commercial power system 3 by the inverter 1 and supplied to the commercial power system 3.

The DC power input from the solar cell 2 to the inverter 1 is converted into high frequency AC in the high frequency inverter bridge 4 and supplied to the primary side of the high frequency transformer 5. In this embodiment, a high frequency transformer of 16 to 19 KHz is used, but for simplicity, a case of using a high frequency transformer of 19 KHz will be described below. The high frequency transformer 5 has a role of insulating the solar cell 2 side (primary side) from the commercial power system 3 side (secondary side), and the insulated high frequency alternating current is a diode bridge provided on the secondary side of the high frequency transformer 5. 6 is rectified. Then, a high-frequency component included in the rectified waveform is removed and smoothed by a filter circuit composed of the DC reactor 7 and a capacitor, and a full-wave rectified DC is obtained. In the low frequency inverter bridge 8,
DC of the full-wave rectified wave is low frequency (50 / 60Hz)
By controlling the loopback with, a low frequency sine wave AC can be obtained. The switching elements constituting the high frequency inverter bridge 4 and the low frequency inverter bridge 8 are on / off controlled by the control circuit 9 and the gate drive circuits 10 and 11. In addition, in front of the high-frequency inverter bridge 4, a DC capacitor 12 that suppresses fluctuations in input power to the inverter 1 and a DC input current detector 1
3, the inverter output current detector 14 is connected on the primary side or the secondary side of the high frequency transformer 5, and is connected to and disconnected from the commercial power system 3 side after the low frequency inverter bridge 8. Interconnection relay 15, and A
The C filter 16 is provided. In addition, although it is connected to the primary side in the figure, it may be connected to the secondary side.

As shown in FIG. 2, the control circuit 9 includes an A / D converter 17, a signal calculation processing unit 18 for generating a sine wave signal (50/60 Hz) which is an output target value of the inverter 1, and the sine wave signal. Carrier signal (19 kHz) generator 19 for performing PWM control together with, rectangular wave signal generator 20 having the same frequency as the carrier signal and having a phase shifted by 1/4 cycle, inverting circuit 21, the sine wave A comparison circuit 22 for comparing a signal with a carrier signal, a NOT circuit 23,
XOR (exclusive OR) circuit 24, and four switching elements Q1 of the high frequency inverter bridge 4
A pulse train signal for turning on / off Q4 is output to the gate drive circuit 10 in FIG.

In the above structure, the high frequency inverter bridge 4 receives the direct current power from the solar cell 2 as a high frequency alternating current (19
and the input / output insulation is realized by using the high frequency transformer 5. On / off control in the high frequency inverter bridge 4 is performed as follows based on FIG.
First, the first pulse train signal obtained by comparing the sine wave signal (50/60 Hz), which is the output target value of the inverter 1 generated by the signal calculation processing unit 18, and the carrier signal (19 kHz), the first pulse train signal A second pulse train signal obtained by inverting the pulse train signal, a third pulse train signal obtained by comparing the inverted carrier signal obtained by inverting the carrier signal with the sine wave signal, and a fourth pulse train signal obtained by inverting the third pulse train signal. To obtain the pulse train signal of. Next, XOR is performed on each of the first to fourth pulse train signals and a rectangular wave signal generated from the rectangular wave signal generator 20 and having the same frequency as the carrier signal and a phase shift of 1/4 cycle.
Exclusive OR processing is performed by the circuit 24 to obtain the first to fourth pulse train signals. Then, the first to fourth 'pulse train signals are output to the gate drive circuit 10 shown in FIG. 1 to control ON / OFF of the four switching elements forming the high frequency inverter bridge 4. Here, a series of the pulse train signals (first to fourth, first 'to fourth')
Is shown in FIG. Signals below the carrier signal with respect to the sine wave signal in FIG. 3 should be represented by a high frequency of several tens to several hundreds of kHz, but they are simplified here schematically. As a result of this on / off control, the high frequency transformer 5 is excited at a high frequency (19 kHz) Ei which is the same as the frequency of the carrier signal in which every other PWM-modulated pulse train is inverted.

The output timing of the pulse train signal to the gate drive circuit 10 at this time is synchronized with the voltage signal Vout of the commercial power system 3. As a result, the inverter output current is controlled to be in phase with the commercial power system voltage.

As described above, the output waveform of the high-frequency transformer 5 is a high-frequency AC waveform in which every other PWM-modulated pulse train is inverted in positive and negative. 6
Rectifies every other pulse train signal with positive and negative inversion, and obtains a continuous PWM pulse train waveform on the positive side, as indicated by E0 in FIG. Then, a high-frequency component is removed by a filter circuit composed of a DC reactor 7 and a capacitor provided in the latter stage of the diode bridge 6 shown in FIG.
Smoothing is performed, and a DC waveform equivalent to a waveform obtained by full-wave rectifying a sine wave AC waveform having the same frequency as the sine wave signal is obtained. Further, in the low frequency inverter bridge 8 in the subsequent stage, folding control is performed to invert every other of the full-wave rectified sine wave AC waveforms to positive and negative, and a sine wave AC waveform is obtained.

Embodiment 2 In the embodiment shown in FIG. 4, in the control circuit 9, the carrier signal generator 19, the rectangular wave signal generator 20, the inverting circuit 21, the comparison circuit 22, the NOT circuit 23, and the XOR circuit shown in FIG. All of these means are processed in the signal calculation processing section 18 without using 24. That is, the control circuit 9 shown in FIG. 4 includes the A / D converter 17 and the signal calculation processing section 18.

Regarding the processing performed in the signal calculation processing section 18, since the PWM calculation is made up of a digital circuit, it is not processed in sequence but
By inputting necessary signals to the signal calculation processing unit 18, processing is collectively performed, and as a result, ON / OFF control of four switching elements of the high frequency inverter bridge 4 of FIG. 1 is performed. ~ The 4'th pulse train signal is obtained. In this embodiment, the signal calculation processing unit 18 includes the CPU 25, the memory (ROM 26, RAM 27),
It is composed of an I / O 28 and a timer 29. The operation in the signal calculation processing section 18 will be described based on this configuration with reference to FIG. Note that the carrier signal in FIG. 3 should actually be shown at a high frequency, but it is schematically simplified here.

In the signal calculation processing section 18, the sine wave signal (5
0/60 to several hundreds Hz and carrier signal (several tens to several hundreds of kHz)
z) (dashed-dotted line), when the sine wave signal exceeds the carrier signal, the first pulse train signal becomes High level, and when it falls below the carrier signal, it becomes Low level. A pulse train signal and an inverted carrier signal obtained by inverting the carrier signal (several tens to several hundreds of kHz)
z) (solid line) and the sine wave signal, if the inverted carrier signal exceeds the sine wave signal, the high level,
An operation is performed to generate a third pulse train signal that becomes Low level if it is lower and a fourth pulse train signal that is an inversion of the third pulse train signal. In the above, if it exceeds the above, Lo
It may be set to the w level, or to the High level if it is lower.

The calculation method will be described with respect to the first pulse train signal generation method. First, the intersection of the sine wave signal and the carrier signal (dashed line) is obtained. The time between each intersection corresponds to the pulse width, which is the on-time or off-time of the pulse train signal. Next, this pulse width is calculated for one cycle of the sine wave signal (it may be calculated for half cycle). In the CPU 25 of FIG. 4, the pulse width is replaced by the timer count of the timer 29. And
A series of timer count sequences corresponding to the pulse width calculated for one cycle of the sine wave signal is temporarily stored in the RAM 27. When the synchronization signal generated from the voltage signal Vout of the commercial power system 3 is input to the signal calculation processing unit 18 through the I / O 28, the timer count sequence temporarily stored is RA.
The data is sequentially read from M27 and set in the timer 29. When a timer interrupt occurs, the timer 29 is down-counted by the timer count set. At the same time, bit 1 corresponding to the high level of the pulse signal or bit 0 corresponding to the low level is output to the I / O 28. By doing so, the high level or the low level is maintained until the down count reaches 0, that is, until the next timer interrupt occurs, and the gate drive circuit of FIG. By outputting to 10, a pulse signal having one pulse width is generated.

The above operation is executed by the CPU 25 by reading out the command operation in the ROM 26. And these are R
When it is performed for all the timer counts temporarily stored in the AM 27, the first pulse train signal for one cycle of the sine wave signal is generated, and the gate drive circuit 10 of FIG.
Will be output to. The second to fourth pulse train signals are similarly generated and output. In the gate drive circuit 10, on / off control of the four switching elements forming the high frequency inverter bridge 4 is performed, and as a result, the high frequency transformer is PWM.
Every other modulated pulse train is positive and negative, and the same high frequency as the carrier signal frequency (several tens to several hundreds of kHz).
z) Excited by Ei. When the control circuit 9 is configured by a digital circuit in this way, simplification of the control circuit is realized.

Third Embodiment An inverter device according to the third embodiment will be described with reference to FIG. The inverter 1 of the present invention is inserted between the solar cell 2 and the existing commercial power system 3, converts DC power generated by the solar cell 2 into AC power of 50/60 Hz, and connects it to the commercial power system 3. The system is supplied to the load and the reverse flow of electric power is performed to the commercial power system 3. Here, the names of each line of the single-phase three-wire type distribution line of the commercial power system 3 are neutral line o line, u line, and v line, respectively, as shown in FIG.

Explaining the configuration of the inverter 1 of the present invention, the input capacitor 4 is provided in order to suppress a sudden change in the input voltage of the inverter 1 due to a solar cell output fluctuation due to a solar radiation fluctuation. In addition, the DC power input to the inverter 1 is guided to the high frequency inverter bridge 4 composed of switching elements Q1 to Q4, and the power is converted from DC to AC. Further, the output of the high frequency inverter bridge 4 is supplied to the primary side of the high frequency transformer 5 and electrically insulated here. An intermediate tap is provided on the secondary side of the high frequency transformer 5, and the wire from this intermediate tap is connected to the neutral wire o wire of the single-phase three-wire distribution line of the commercial power system through the interconnection relay 15. . Further, the other two wires on the secondary side of the high frequency transformer 5 are input to the AC input terminal of the diode bridge 6 and converted into electric power from AC to DC. The two wires from the DC output terminal of the diode bridge 6 are vertically symmetrically connected to DC reactors 7a and 7b and capacitors 30a and 30b inserted between the two wires and the neutral wire. After that, it is input to the low-frequency inverter bridge 8 composed of switching elements S1 to S4, and is converted from direct current to alternating current again. The output 2 lines of the low-frequency inverter bridge 8 are of the single-phase 3-wire type of the commercial power system 3 via the interconnection relay 15 and the filter circuits 31a and 31b arranged vertically symmetrically with the neutral line. It is configured to be connected to each of two wires other than the neutral wire o wire, u wire, and v wire of the distribution line.

Next, the operation of the inverter of the present invention will be described. First, in the high frequency inverter bridge 4, the four IGBT elements (Q1 to Q4) that compose the same are provided.
By generating a gate drive signal of the sine wave signal (50/60 Hz) and a high frequency carrier signal (19 kHz), the primary side of the high frequency transformer 5 has a sine wave PW.
It is excited by a pulse train signal that has been M-modulated. At this time, a high-frequency alternating current (1
At the time of exciting at 9 kHz), in this embodiment, the pulse train signal subjected to the PWM modulation is excited by a pulse train as shown in FIG. Although it is schematically shown in the figure for the sake of clarity, the frequency of this pulse train has the same frequency as the frequency of the high frequency carrier signal. As described above, as a control method for exciting the high frequency transformer 5 with the high frequency alternating current, the gate drive signal of the IGBT element forming the high frequency inverter bridge 4 is set in the same manner as in the first or second embodiment. To generate.

As described above, high frequency alternating current (19 kHz)
z) is supplied to the primary side of the high frequency transformer 5, and the high frequency alternating current transformed into a voltage according to the turns ratio of the transformer is output to the secondary side of the high frequency transformer 5. Here, the high frequency transformer 5 has a function of electrically insulating the commercial power system 3 from the solar cell 2 and a function of transforming an output voltage with respect to an input voltage at a transformation ratio according to a turns ratio. Further, by the intermediate tap provided on the secondary side of the high frequency transformer 5, from the secondary side of the transformer, between the intermediate tap and the transformer output 2 line, between the intermediate tap and the upper line of the transformer output, and the intermediate, respectively. Three line voltages are generated between the tap and the lower line of the transformer output, between the upper line of the transformer output and between the lower line of the transformer output. These high frequency transformers 5
The three line voltage waveforms on the secondary side are also high-frequency alternating current in which every other PWM-modulated pulse train similar to that on the primary side shown in FIG.

The three line voltages are rectified by the diode bridge 6 at the next stage, and are the DC voltage of the PWM train of pulse trains which are continuous on the positive side as shown in A, B and C of FIG. It becomes the line voltage, the second line voltage, and the third line voltage. Further, the DC reactors 7a and 7b provided in series with the two output lines of the diode bridge 6, respectively.
And a capacitor 30 vertically symmetrically provided between the output 2 line and the output line from the intermediate tap of the high frequency transformer 5.
By passing through the low-pass filter composed of a and 30b, the first line voltage, the second line voltage, and the third line voltage are as shown in A ′, B ′, and C ′ of FIG. The high-frequency ripple component is removed and smoothed from the DC voltage waveforms of A, B, and C, and a DC voltage waveform similar to that obtained by full-wave rectifying the low-frequency sine wave is obtained.

Between the first line voltage and the second line voltage of the low pass filter output indicated by A'and B ', and between the other two lines except the line connected to the intermediate tap of the high frequency transformer 5. Between the third line voltage, which is the line voltage, C ′ in FIG.
As shown in, there is a relation of the first line voltage + the second line voltage = the third line voltage. Where the middle tap of the transformer is 2
At the midpoint of the secondary winding, the first line voltage and the second line voltage are equal, and the third line voltage has a voltage value that is twice the first line voltage or the second line voltage. It will be. Further, in the present embodiment, the current waveform flowing through the low-pass filter output two lines other than the one line connected to the center tap has the same phase as the voltage waveform as shown in FIG.

Furthermore, the two lines (other than the one line connected to the intermediate tap) that make up the third line voltage are input to the low frequency inverter bridge 8 in the next stage. Here, the four IGBT elements (S1
~ S4) gate terminals S1, S4 at commercial frequency
And S2 and S3 are alternately turned on and off. That is, in synchronism with the valleys (0 V point) of the voltage values of the line voltages shown in FIG. 7, when S1 and S4 are on, S2 and S3 are turned off, so that on and off are alternately controlled. As a result, the voltage and current waveforms shown in FIG. 7 are symmetrically inverted in the vertical direction with one crest of each sine wave in the full-wave rectified form. Is converted into a commercial frequency sine wave AC waveform. Further, through the interconnection relay 15, smoothed by the AC filter circuits 31a and 31b vertically symmetrically arranged between the neutral line and the two output lines of the low-frequency inverter bridge 8 to remove the harmonic component. The waveform-shaped commercial frequency AC voltage waveform and current waveform can be obtained.

Here, the voltage between the output line from the AC filter circuit 31a and the one line to which the intermediate tap is connected is the first line voltage, and the voltage between the output line from the AC filter circuit 31b and the intermediate tap is connected. If the voltage between the first line and the second line voltage is the second line voltage and the voltage between the two lines output from the AC filter circuits 31a and 31b is the third line voltage, A ", B" in FIG.
C "is the first line voltage waveform, the second line voltage waveform,
And a third line voltage waveform.

Here, similarly to the above, the third line voltage has a voltage value that is twice the first line voltage or the second line voltage. 1
Line voltage, 2nd line voltage is 100V, 3rd line voltage is 2
The transformation ratio of the high-frequency transformer 5 is set to be 00 V (since the rated input voltage is 200 VDC in this embodiment, the transformer turns ratio is 1: 2.2 to 2.7, and the transformer intermediate tap is the middle point of the secondary winding. By designing the above, the present inverter 1 uses the high-frequency transformer 5 to realize a compact and lightweight device, and at the same time, as the output of the inverter 1,
It has three lines, u line, o line, and v line including neutral line, and each line voltage has a line voltage that can be connected to the single-phase three-wire type distribution line of commercial power system 3. Therefore, the grid connection with the single-phase 3-wire type distribution line of the commercial power system 3 is also possible.

In addition to the method of providing an intermediate tap on the secondary side of the high frequency transformer 5, two secondary side windings are prepared and the winding start and winding end of each winding are connected to replace the above intermediate tap. It is also possible to do so.

The above-mentioned high frequency transformer 5 is provided with an intermediate tap, and this is connected to the neutral line of the commercial power system 3. The main circuit configuration of the inverter 1 and the high frequency transformer 5 are provided with every other PWM-modulated pulse train. By using the inverter control method of exciting with a positive and negative inverted high frequency alternating current, as shown in the present embodiment, connection by the same electric method as that of the single-phase three-wire type distribution line, which has been impossible in the past, can be achieved. An inverter device having a possible high frequency transformer can be realized.

[0051]

As described above, according to the present invention, a high frequency transformer having a capacity ratio of about 1/30 and a weight ratio of about 1/20 can be used instead of the commercial transformer. The inverter can be made smaller and lighter than the method used.

Furthermore, a sine wave AC waveform with sufficiently small distortion similar to the waveform output by the conventional PWM control can be obtained by a simple structure such as adding gate processing of exclusive OR processing to the conventional PWM control. Obtainable.

Further, it is possible to realize a high frequency insulation type inverter device which can be connected in the same electric system as the single-phase three-wire distribution line of the commercial power system.

[Brief description of drawings]

FIG. 1 is a block diagram of an inverter device according to a first embodiment.

FIG. 2 is a block diagram of a control circuit according to the first embodiment.

FIG. 3 is a diagram illustrating generation of a pulse train signal by exclusive OR processing of a pulse train signal and a rectangular wave signal according to the first embodiment.

FIG. 4 is a block diagram of a control circuit according to a second embodiment.

FIG. 5 is a block diagram of an inverter device according to a third embodiment.

FIG. 6 is a diagram illustrating waveforms at various parts of the third embodiment.

FIG. 7 is a diagram illustrating a waveform of each part of the third embodiment.

FIG. 8 is a block diagram of a conventional inverter device.

FIG. 9 is a diagram illustrating generation of a pulse train signal by comparing a conventional sine wave signal and a carrier signal.

FIG. 10 is a block diagram of a conventional inverter device.

FIG. 11 is a diagram illustrating a waveform of a conventional example.

[Explanation of symbols]

1 Inverter 2 Solar Cell 3 Commercial Power System 4 High Frequency Inverter Bridge 5 High Frequency Transformer 6 Diode Bridge 7 DC Reactor 8 Low Frequency Inverter Bridge 9 Control Circuit 10 Gate Drive Circuit 11 Gate Drive Circuit 12 DC Capacitor 13 DC Input Current Detector 14 Inverter Output Current detector 15 Interconnection relay 16 AC filter 17 A / D converter 18 Signal calculation processing unit 19 Carrier signal generator 20 Rectangular wave signal generator 21 Inversion circuit 22 Comparison circuit 23 NOT circuit 24 XOR circuit 25 CPU 26 ROM 27 RAM 28 I / O 29 Timer 30 Capacitor 31 Filter Circuit 32 Inverter Bridge 33 Commercial Transformer 34 Control Circuit 35 Gate Drive Circuit 36 PWM Modulation Generator 37 Error Amplifier 38 Carry Signal generator 39 the signal processing unit 40 a sine wave signal storage unit 41 A / D converter 42 D / A converter 43 the signal processing unit 44 the hysteresis comparator 45 NOT circuit 46 folded control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Fujii 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation

Claims (4)

[Claims] 1. A method of controlling an inverter device, which converts electric power generated from a DC power supply into an AC power and supplies the AC power to a load or an existing commercial power supply, which is PWM modulation by PWM control using a sine wave signal and a carrier signal. An inverter control method characterized by inverting every positive and negative polarities of the generated pulse train and exciting the primary side of the transformer that performs insulation between the input and output by the high-frequency AC signal obtained by this. 2. In the PWM control, a sine wave signal is compared with a carrier signal, and if the sine wave signal exceeds the carrier signal, a first level is output, and if a sine wave signal is below the carrier signal, a second level is output to output a first pulse train signal. To generate a second pulse train signal by inverting the first pulse train signal, compare the inverted carrier signal obtained by inverting the carrier signal with the sine wave signal, and the inverted carrier signal exceeds the sine wave signal. If it is lower than the first level, and if it is lower than the second level, the third level is output.
Pulse train signal is generated, the third pulse train signal is inverted to generate a fourth pulse train signal, and on the other hand, a rectangular wave signal having the same frequency as the carrier signal and a phase shift of 1/4 cycle is generated. Then, the rectangular wave signal and each of the first to fourth pulse train signals are subjected to exclusive OR processing to generate four types of pulse train signals, and the four types of pulse train signals form an inverter bridge. 2. The inverter control method according to claim 1, wherein the high frequency AC signal having the same frequency as the carrier frequency is obtained by inputting each of the switching elements to ON / OFF control of the switching elements. 3. A first power conversion unit for converting direct current into alternating current, a transformer for obtaining a secondary voltage transformed by using this alternating current voltage as a primary voltage, and two wires on the secondary side of the transformer are connected. A second power converter for converting alternating current into direct current, a reactor connected in series to each two lines of the output of the second power converter, and further connected to the output of the reactor for converting direct current to alternating current And a control circuit that controls ON / OFF of the switching elements that form the first power conversion unit and the third power conversion unit, and the control circuit includes an output target value of the inverter. A means for generating a sine wave signal, a means for generating a carrier signal for performing PWM control using the sine wave signal, and the same frequency as the carrier signal, but with a phase shift of 1/4 cycle Means for generating a square wave signal 3. A means for generating the first to fourth pulse train signals from the sine wave signal and the carrier signal by the method according to claim 2 and then gating the rectangular wave signal to these signals, and the gate processing. An inverter device comprising: a means for performing on / off control of a switching element that constitutes the first power conversion unit with a subsequent pulse train signal. 4. The intermediate side tap is further provided on the secondary side of the transformer, the line from the intermediate tap is connected to the neutral line of the low voltage single-phase three-wire distribution line, and the reactor is the first line. 2 is connected to the output 2 line of the power conversion unit.
Capacitors are connected symmetrically between each line and the line from the intermediate tap, and the two output lines of the third power conversion unit are each line other than the neutral line of the low voltage single-phase three-wire distribution line. The inverter device according to claim 3, being connected to the inverter device.