JP3386295B2 - Interconnected power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] [0001] The present invention relates to a method for installing in a house.
In a photovoltaic power generation system, the DC output of
Interconnected power that is converted to electrical power and flows back to the distribution line
The present invention relates to a conversion device. [0002] 2. Description of the Related Art Conventionally, in solar power generation systems,
Supply DC power generated by solar cells to system distribution lines
The DC power of the solar cell
Is converted to electric power that is coordinated with the voltage and frequency of the system distribution line
And supply. FIG. 10 shows a conventional interconnected power converter 10.
System block representing the photovoltaic power generation system to which No. 1 is applied
FIG. Output electrode of solar cell 100 (+ and-)
P and N are connected to the input of the grid-type power converter 101.
The output of the interconnection type power converter 101 is connected to the interconnection protection device 1
System power distribution line fed from the system power supply 103
106. The interconnection protection device 102
Between the power converter 101 and the distribution line 106
It is set up for the purpose of coordination, and
Some are built into the conversion device 101. Here, a conventional interconnected power converter 101
Converts the DC power generated by the solar cell 100 into AC power
DC-AC conversion circuit 104 for conversion and this DC-AC
Transform the AC output of the conversion circuit 104 to mix with the system distribution line.
It consists of a commercial insulation transformer 105 to prevent touch.
You. This commercial insulation transformer 105 is a large heavy object,
Interconnected power conversion independent of DC-AC conversion circuit 104
It is built into the device 101. Interconnected power converter 10
The AC power obtained by the conversion by the
02, which is supplied with power from the system power supply 103
Power is supplied to the distribution line 106 by reverse power flow. [0005] Also, Japanese Unexamined Patent Application Publication No. 2-81107 discloses
As is being said, a large, heavy-duty commercial isolation transformer
105, high-frequency insulating transformer T_TwoTo use
Further, there has been known a device in which the size and weight of the device are reduced.
FIG. 11 shows this high-frequency insulating transformer T_TwoIs composed using
Grid-type power converter 111
It is a system block diagram used. This interconnected power conversion
The device 111 converts the DC output of the solar cell 100 from DC to DC.
Voltage conversion by the converter 112, and further DC-AC conversion
The power is converted into AC power by an
And convert it to power that is coordinated with the voltage and frequency on the side
It has become something. [0006] By the way, as described above,
Interconnection using large and heavy commercial insulation transformers
It is difficult to reduce the size and weight of the
Problem. On the other hand, Japanese Patent Laid-Open Publication No.
No. 7 discloses an interconnected power converter 111
Is effective in reducing the size and weight of the device,
00 to keep the output voltage constant,
Maximum output of solar cell 100 fluctuating with solar cell element temperature
Power cannot be taken out and the solar cell 100
It is not possible to effectively use the generated power
There was a problem. [0008] Further, during the interconnection operation with the system distribution line 106,
Connection protection device 102 is indispensable for protection coordination in
This is also an obstacle to miniaturization and cost reduction of equipment.
I was Further, for example, a single-phase two-wire 200 V output
Connect the interconnected power converter to a single-phase three-wire 200V / 100V
When connecting to 200V side of electric wire, interconnection type power converter
Switches connected between the power distribution system and
When the earth leakage breaker of the panel is released, the single-phase three-wire 200
To the load connected to the 100V side of the V / 100V distribution line,
Overvoltage is applied by the power from the interconnected power converter.
May be To protect the load from this overvoltage,
An overvoltage protection relay is provided at the output of the power converter
Needed to be The present invention has been made in view of such a problem.
Therefore, the device can be made compact and lightweight.
In addition, the maximum output power of the solar cell can be used effectively.
The load connected to the grid distribution line from overvoltage.
To provide an interconnected power converter that can be protected.
And the subject. [0011] Means for Solving the Problems To solve the above problems,
Therefore, the present invention has the following configuration. [0012]The present inventionInput the DC output of the solar cell
A DC-DC conversion circuit for DC-DC conversion;
DC for inputting the output of a DC conversion circuit and performing DC-AC conversion
-Comprising an AC conversion circuit and a control circuit,DC-DC
The conversion circuit inputs the output of the solar cell and converts it to high-frequency power.
A switching circuit for converting and outputting,
A high-frequency insulating transformer for receiving an output of the circuit;
A rectifier circuit for inputting and rectifying the output of the isolation transformer
The control circuit controls the DC output power of the solar cell.
Calculate and maintain the maximum output power point of the solar cell.
By controlling the conduction time of the switching circuit,
The feature is to control the input impedance of the flow conversion circuit
It is an interconnection type power converter. [0013]In addition, the present invention provides a DC output of a solar cell.
A DC-DC conversion circuit for applying DC-DC conversion,
Input DC-DC conversion circuit output and perform DC-AC conversion
A DC-AC conversion circuit, and a control circuit.
The circuit is designed so that the output power of the solar cell is
The input of the DC-DC conversion circuit
The DC-DC conversion circuit by increasing impedance
Input should not exceed current and power tolerances.
An interconnected power converter is characterized in that: [0014]Here, the control circuit is configured to supply power to a system distribution line.
Detecting means for detecting the pressure or its frequency;
Based on the results detected by the
If the grid connection cannot be maintained, or
When a voltage is generated, the control circuit controls its operation.
Temporarily stop operation of one or more element circuits controlled
It is characterized by that. [0015] [0016]BookAccording to the interconnected power converter according to the invention
For example, DC-DC conversion, which becomes an output load when viewed from the solar cell side
If the input impedance of the circuit changes, the output of the solar cell
The output voltage of the solar cell changes according to its characteristic curve.
Change along. The control unit calculates the output power of the solar cell
DC-DC so that the output of the solar cell is at the maximum power.
Controls the input impedance of the conversion circuit. [0017]Also bookFor the interconnection type power converter according to the invention
According to the switching circuit, which is the output load of the solar cell,
By controlling the conduction time, this switching circuit
Is controlled. As a result, DC-DC conversion
Input impedance of the conversion circuit (load characteristics of the solar cell)
Controlled. [0018]Also bookFor the interconnection type power converter according to the invention
According to the control circuit, the output power of the solar cell is DC-DC
If the allowable input of the conversion circuit is exceeded,
The input of the circuit is the allowable input current and allowable
As long as the input power is not exceeded, the input
Increase impedance. This allows the output of the solar cell
The power point deviates from the high power area including the maximum power point,
The power input to the DC converter is limited. [0019]Also bookFor the interconnection type power converter according to the invention
According to the control circuit, the voltage of the system distribution line or its frequency
And temporarily stop the operation of the DC-DC conversion circuit, etc.
To protect the interconnected power converter. [0020] BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment will be described. FIG. 1 shows an interconnected power supply according to the embodiment.
The configuration of the photovoltaic power generation system provided with the force conversion device 1
It is a system block diagram showing. The interconnection type power converter 1 includes a solar cell 100
DC output generated by the above is converted to a single-phase two-wire 200V (V_ug)of
Converts to AC power and outputs the single-phase three-wire 200V / 1
Connected to 200V of 00V system distribution line 11 for interconnection operation
Is to do. The single-phase three-wire system distribution line 11
The power supplied from the power source 103 is
Power is supplied after being transformed to 00V and 200V. Sand
The neutral terminal N of the pole transformer 10 is grounded.
A voltage of 100 V (V) is applied between the characteristic point terminal N and the output terminal H.₁)But
Has been output. In addition, the neutral terminal N and the output terminal L
100V (V_Two) Is output, and the terminal H and the output terminal
200V (V_ug) Will be output
ing. The output terminal A of the interconnection type power converter 1
_OUTAnd B_OUTBetween the output of the interconnected power converter 1 and
And 200V (V_ug) Appears, and these output terminals A
_OUTAnd B_OUTIs a pole transformer 10 via a system distribution line 11
Are connected to the terminals H and L, which are 200V output terminals.
You. In this manner, the solar power generation system is incorporated.
The configuration of the connected interconnection type power converter 1 will be described below.
You. The interconnection type power converter 1 has an input relay 2, DC-DC
Conversion circuit 3, DC-AC conversion circuit 4 and interconnection relay 5
A main circuit (unsigned) composed of each element circuit,
Control circuit 6 for controlling the main circuit of
3 input current I_inAnd the output current of the DC-AC conversion circuit 4
I_outCurrent sensors 8 and 9 for detecting
And control by inputting part of the power output from the solar cell
And a control power supply 7 for generating operating power for the circuit 6.
ing. Hereinafter, the configuration will be described in more detail. First, the sun
A pair of input terminals A to which the output of the battery 100 is connected_INas well as
B_INAre connected to the input terminals 2a and 2b of the input relay 2.
The output terminals 2c and 2d of the relay 2₀,
B₀To the input of the DC-DC converter 3.
Also, input terminal A_INAnd B_INIs connected to the input of the control power supply 7.
Subsequently, the output of the control power supply 7 is sent to the control circuit 6 for its operation.
Supplied as power supply. On the other hand, the DC-DC conversion circuit 3
Is output at connection point A₁And B₁DC-AC conversion circuit
The output of the DC-AC conversion circuit 4 is connected to the input of the
Connection point A_TwoAnd B_TwoInput terminal 5 of interconnection relay 5 via
a, 5b. And the connection relay 5
The power terminals 5c and 5d are connected to the output of the interconnection type power converter 1.
Terminal A which is a terminal_OUTAnd B_OUTConnected to each other. The input terminal A_INAnd terminal of input relay 2
2a between the DC-DC conversion circuit 3
Style I_inCurrent sensor 8 for detecting
The output of the DC-AC conversion circuit 4 (connection point A_TwoSide) and ream
DC-AC conversion between the input terminal 5a of the system relay 5
Current I output from circuit 4_outCurrent for detecting
A sensor 9 is provided. The currents detected by the current sensors 8 and 9 are as follows.
Current I_inAnd I_outGives information to the control circuit 6 as information.
Can be In addition, the control circuit 6 directly receives the signal from the solar cell 100.
Voltage V input to current-DC conversion circuit 3_in, DC-DC
Output voltage V of conversion circuit 3_COutput of the DC-AC conversion circuit 4
Force voltage V_outAnd an output terminal of the interconnection type power converter 1
A_OUT, B_OUTIs connected to the single-phase three-wire system distribution line 11
Voltage V₁, V_Two, V_ugIs given as information. And
Based on the information, the control circuit 6 sends the relay control signal.
No.SR₁And SR_TwoTo input relay 2 and interconnection relay
-5, the drive signal SC₁And SC_TwoDirectly
To the DC / DC conversion circuit 3 and the DC / AC conversion circuit 4.
You. Here, the control circuit 6 includes the following 5
It has two control functions. That is, first, the input relay 2
Secondly, the input input of the DC-DC conversion circuit 3
Third, the DC-AC conversion circuit 4
Output current I_outControl, 4th, disconnection controller of interconnection relay 5
Fifth, detect abnormalities in the voltage or frequency of the distribution line.
Stop the power conversion operation of the lever-type power conversion circuit 1
Function. These functions and the circuit configuration to achieve them
The details will be described later in the description of the operation. FIG. 2 shows the configuration of the DC-DC converter 3.
FIG. Connection point A₀, B₀Has a capacitor C₁
Through an input filter 30 composed of
Element Q₁~ Q_FourFull-bridge type switch composed of
The input of the switching circuit 31 is connected. This switchon
The output of the switching circuit 31 is a high-frequency insulating transformer T₁Entered in
You. This high-frequency insulating transformer T₁Is a rectifier D₁~ D_Four
Input to the full-bridge rectifier circuit 32 composed of
The output of the full-bridge rectifier circuit 32 is
Coil L₁And smoothing capacitor C_TwoOutput consisting of
Through the smoothing circuit 33, the connection point A₁And B₁Given to. FIG. 3 shows the configuration of the DC-AC conversion circuit 4.
FIG. Connection point A₁And B₁The switching
Element Q₁₁~ Q₁₄Full-bridge switch composed of
The input of the switching circuit 34 is connected to this full-bridge type switch.
The output of the switching circuit 34 is the coil L₁₁, L₁₂And con
Densa C₁₁Through an output filter 35 composed of
Connection point A_TwoAnd B_TwoGiven to. The switching element Q₁~ Q_FourAnd Q₁₁
~ Q₁₄Are, for example, bipolar transistors, field effect type
Using elements such as transistors and power transistors.
Is done. The interconnected power converter having the above-described structure.
Operation 1 will be described below. First, solar cell 1
00 is excited by sunlight and transfers DC power to its electrodes (+ and
-) Output to P and N. And this output power is
Terminal A_INAnd B_INInput to the interconnection type power converter 1 via
Is done. The input relay 2 is connected to a control circuit 6 by a control power supply 7.
The power supply output to the power supply is established and the control circuit 6 is activated.
Later, signal SR output from control circuit 6₁Control
(The first function of the control circuit 6). Input
When the laser 2 is turned on, the output of the solar cell 100 is set to a relay
The signal is input to the DC-DC conversion circuit 3 through the DC-DC converter 2. The solar power input to the DC-DC conversion circuit 3
The output of the pond 100 is fully bridged through the input filter 30.
The signal is input to the switching circuit 31. Full bridge
Switching element Q forming the switching circuit 31
₁, Q_FourAnd Q_Two, Q_ThreeThe two pairs of switching elements are described later.
Signal S₁₄, S_{twenty three}To control the conduction alternately
To generate high-frequency power. This high frequency power is high frequency
Wave isolation transformer T₁, And excites it. Soshi
And high-frequency insulation transformer T₁From transformed high frequency power
Is output, and this output is full-wave rectified by the rectifier circuit 32.
And further converted to DC power again through the output smoothing circuit 33.
Is done. Here, a full-bridge type switching circuit
31 switching frequencies above the audible frequency band
Switch around in one cycle, around kilohertz
Element Q₁~ Q_FourOf the conduction time (= duty ratio)
When changed, the current flowing through the switching circuit 31
The amount can be varied. That is, the solar cell 10
From the 0 side, the input impedance of the DC-DC conversion circuit 3
The result is that the dance changes. Based on this, next, DC-DC conversion
The operation in which the circuit 3 tracks and inputs the maximum output power of the solar cell
The work will be described. FIG. 4 shows the output voltage-current of the solar cell
Characteristic curve (I) and input voltage of DC-DC converter 3
FIG. 3 is a diagram in which current characteristics (II) are superimposed. DC-DC
The slope of the straight line representing the input voltage-current characteristic (II) of the conversion circuit 3
Represents the input impedance of the DC-DC conversion circuit 3.
Therefore, in the following description, the DC-DC conversion circuit 3
Input voltage-current characteristics (II)
I will say. Output voltage-current characteristics represented by the curve in FIG.
The output of the solar cell 100 having (I) is represented by a straight line in FIG.
DC with input impedance characteristic (II) expressed
When the input of the DC conversion circuit 3 is connected,
Output power (that is, input power of the DC-DC conversion circuit 3)
Are the voltage and current determined at the intersection P of these two characteristic lines.
Is the power obtained from the product of In other words, DC-DC
To change the input impedance of the current conversion circuit 3
Input from the solar cell 100 to the interconnection type power conversion circuit 1
Power can be controlled. The maximum output of the solar cell of the DC-DC converter 3
The power tracking function focuses on this point.
100 output voltage and current (i.e., DC-DC conversion circuit
3 input voltage V_inAnd current I_in) Is monitored from time to time.
The product of the output voltage and the output current of the positive battery 100 is maximized.
Thus, the control circuit 6 controls the input impedance of the DC-DC conversion circuit 3.
Controlling the dance (the second function of the control circuit 6)
is there. Here, the second control function of the control circuit 6 is described.
Control of the input impedance of the DC-DC converter 3
Will be described. FIG. 5 shows the input incorporated in the control circuit 6.
It is a circuit block diagram of an impedance control unit, and
FIG. 6 is a diagram showing the MP constituting this input impedance control unit.
It is a flowchart showing the operation of U21. The output of the solar cell 100, that is, DC-DC conversion
Input voltage V of conversion circuit 3_inAnd current I_inIs an A / D converter
Is converted into a digital quantity by the data
Is entered. Input voltage V input to MPU 21_inas well as
Current I_inAre stored in variables V and I, respectively (step
Steps S12a and S12b). The MPU 21
Calculate the product of numbers V and I to calculate power P_Two(Step S
13), previous power calculation result P₁And size comparison
Step S14). In the initial state, the last power
Variable P to store force calculation result₁Contains zero
(Step S11), and a control voltage signal S described later.
_tThe initial input impedance of the DC-DC converter 3
Zero is stored so that the
S11). As a result of the comparison, the power P calculated this time is_Twoof
If it is larger (step S14, Yes), control
Voltage signal S_tIs slightly increased (step S15a).
Conversely, the power P calculated this time is_TwoIs smaller
Is (Step S14, No), the control voltage signal S_tThe minute
It is decreased (step S15b). Then, the variable for storing the result of the previous power operation is stored.
Number P₁Power P calculated this time_TwoUpdate to
(Step S16) Next, the input voltage V to be monitored_inPassing
And current I_inWait for input. The D / A converter 22 has a power P_TwoAnd P₁of
The control voltage signal S updated based on the magnitude comparison result_tTo
Converted to analog quantity and applied to one input of comparator 24
Output. The other input of the comparator 24 is
The triangular wave signal from the angular wave signal generation circuit 23 is used as a reference signal.
Given. Then, the comparator 24 calculates the reference signal
And the control voltage signal S converted to an analog quantity_tAnd compare
Clock signal which is a PWM (Pulse Width Modulation) wave
Generate a number. The pulse distributor 25 converts this clock signal
Input the clock signal S₁₄And S_{twenty three}Generate this
Clock signal S₁₄And S_{twenty three}Is the control voltage signal S_tThe size of
The duty ratio has a duty ratio corresponding to the duty ratio. And
Clock signal S₁₄Is the switching element Q₁And Q_FourContinuity
And the clock signal S_{twenty three}Is the switching element Q_TwoPassing
And Q_ThreeIs controlled. The pulse distributor 25 outputs a clock signal.
S₁₄And S_{twenty three}When generating the signal
Switching ratio is the same,₁, Q_FourAnd Q
_Two, Q_ThreeDo not conduct at the same time
So that the clock signal S₁₄And S_{twenty three}Constant phase difference between
Is provided. In the case of the present embodiment, the clock signal S₁₄,
S_{twenty three}When each clock is high level (H)
Switching element Q₁~ Q_FourConducts
So, the duty ratio is the ratio of the high level period of the signal.
If it is expressed, the clock signal S₁₄And S
_{twenty three}Increase of the duty ratio of the DC-DC conversion circuit 3
This results in a reduction in force impedance. As described above, in the initial state,
-The input impedance of the DC conversion circuit 3 becomes infinite
It is set as follows. Also, as understood from FIG.
In this initial state, the DC-DC conversion circuit 3
The current flowing into the solar cell 100 is zero.
The power input to the flow conversion circuit 3 is also zero. this thing
Therefore, immediately after the control circuit 6 operates, the DC-DC conversion circuit
The input impedance of path 3 gradually decreases from infinity
Is controlled as follows. As this input impedance decreases,
Thus, the output power of the solar cell 100, that is, DC-DC conversion
The power input to the circuit 3 increases and the maximum output of the solar cell
Power point P_maxTo reach. Further, the input input of the DC-DC conversion circuit 3
The impedance is controlled to decrease, but the solar cell
Large output power point P_maxIs passed, the output of the solar cell 100
Starts decreasing, the control circuit 6 outputs the control voltage signal S_tTo
The power input to the DC-DC conversion circuit 3 is slightly increased.
Positive battery maximum output power point P_maxDC-DC to stay in
The input impedance of the conversion circuit 3 is controlled. The DC-DC output from the control circuit 6 as described above
The input impedance control operation of the
The solar cell maximum output power tracking function is realized. In addition,
The DC conversion circuit 3 is provided with a solar cell maximum output power point tracking function.
In addition, the solar cell 100 side and the system distribution line 11 side are insulated.
It also has functions. Here, the power input from the solar cell 100
When the power exceeds the allowable input of the interconnection type power converter 1
The operation will be described. FIG. 9 shows an interconnected power converter 1
Power range that can be input to the
When the input power exceeds the input power range.
In the diagram to explain the maximum output power point tracking function of the positive battery
is there. From the solar cell 100 to the interconnection type power converter 1
Is input to the interconnection type power converter 1.
The circuit rated input power (IV)
Is forbidden. In addition, interconnection type power converter
Due to the restrictions on the operation of the circuit that composes
Device 1 has a constant input voltage range. Furthermore, from FIG.
As will be understood, the output current of the solar cell 100 is rated
Positive battery short-circuit current I_SThe solar cell will not exceed
The output power of 100 is the rated short-circuit current I_SDetermined by
It does not exceed the power (III). The above three constraints
The input power range of the interconnection type power converter 1 (the shaded area in FIG. 9)
Area) is defined. Therefore, the output of the solar cell 100
When the power-voltage characteristic (V) is within this range
In addition, it is possible to track the maximum output point of the solar cell. Also,
The maximum output point of the solar cell as the temperature of the solar cell increases
Characteristic curve (VI) is within this range even if the
Within the range, the solar cell along this characteristic curve (VI)
Tracking of a large output point becomes possible. However, the characteristic curve (VII) shown in FIG.
Thus, the power input to the interconnection type power converter 1
If the force exceeds the allowable range, the control circuit 6
Increases the input impedance of the DC-DC conversion circuit 3.
Let the maximum output power point P of the solar cell_maxStop tracking
And the input power point is A_aFrom A_bMove to This result
As a result, the input from the solar cell 100 to the DC-DC conversion circuit 3
Power is limited and the grid-type power converter 1
Protected from destruction by power. Next, the DC output voltage of the DC-DC
Pressure V_COf DC-AC conversion circuit 4 for inputting
explain. DC output voltage V of DC-DC conversion circuit 3
_CIs the connection point A₁And B₁DC-AC conversion circuit 4 via
Input to the full-bridge switching circuit 34
It is converted to flowing power. This AC power is further
Unnecessary frequency components are removed by the filter 35, and the connection point A_TwoPassing
And B_TwoIs output via. Here, the output voltage of the DC-DC conversion circuit 3
V_CIs obtained by the following equation (1), and the output characteristic of the solar cell 100 is
Area from the open-circuit voltage side to around the maximum output point
Shows almost constant voltage characteristics. [0053] V_C= V_IN× D × N2 / N1 (1) However, D: Duty ratio N1: high frequency insulation transformer T₁Number of primary windings N2: High-frequency insulation transformer T₁Number of secondary windings Thus, in this region, the switch
S for controlling the conduction of the switching circuit 31₁₄And S_{twenty three}Due
Input voltage V with respect to the increase in the tee ratio D_inIs only slightly reduced
It is. Therefore, the output of the DC-DC conversion circuit 3 has no load.
(That is, the output is open), the output voltage V_CIs high frequency
Edge transformer T₁Will increase in accordance with the transformation ratio. However, the input input of the DC-AC conversion circuit 4
The impedance is used as the output load of the DC-DC conversion circuit 3.
And the output voltage V of the DC-DC conversion circuit 3_CIs preset
Voltage V_CONSTControl circuit 6 does not exceed
The output current I of the AC conversion circuit 4_outControl. Sand
That is, the DC-AC conversion circuit 4 outputs the input current to the output current.
I_outThe control circuit 6 controls the amount released as
And the voltage V_COperates to maintain a constant voltage. This
Current I of the control circuit 6_outThe control function is a control circuit described later
6 is a third control function. Here, the voltage V_CONSTIs DC-AC conversion
Make sure that the output voltage of circuit 4 is coordinated with the voltage on the interconnection line
It is a value that is designed and determined. Thus, the voltage V_C
Is controlled as a result, the output power of the interconnection type power conversion circuit 1 is
Voltage can be kept constant, and the voltage and
Can be coordinated. Here, the third control function of the control circuit 6 is described.
Current I_outThe control function will be described. DC-AC conversion
Current I from circuit 4_outThe adjustment of the amount of current emitted as
The switches constituting the full-bridge switching circuit 34
Ching element Q₁₁~ Q₁₄The conduction time of the
Control is realized. FIG. 7 shows the current I incorporated in the control circuit 6.
_outFIG. 8 is a circuit block diagram of the control unit.
I_outA flow chart showing the operation of the MPU 51 constituting the control unit.
It is a chart. This output current I_outOperation to control
Input impedance in the DC-DC converter 3
It is the same as the control principle. This will be described below. Control circuit 6
Output power of the DC-DC conversion circuit 3 input as information
Pressure V_CIs converted into a digital quantity by the A / D converter 50.
The data is then input to the MPU 51. Input to MPU51
Voltage V_CIs the variable VC_Two(Step
Step S22). The MPU 51 uses the variable VC_TwoContent and
Fixed voltage V_min(Step S2)
3). This voltage V_minIs the voltage V_CAt the lowest possible voltage
Yes, voltage V_CIs V_CONSTNot to exceed
Can be As a result of the comparison, the variable VC_TwoThe contents of
Set voltage V_minIs determined not to exceed
(Step S23, No), control voltage signal S_aHas zero
Reset (step S24), then monitored
Voltage V_CWait for input. Also, the variable VC_TwoIs V_minYo
Is larger (step S23, Yes),
And the variable VC_TwoIs the previous voltage V_CMonitor value is stored
Variable VC₁Are compared with each other (step S25).
As a result of the comparison, the variable VC_TwoIs determined to be larger
(Step S25, Yes), the control voltage signal S_aIs fine
It is slightly increased (step 26a). Conversely, judge as small
Then, it is slightly reduced (step S26b). A variable for storing the previous monitoring result
VC₁Variable that stores the result of monitoring the contents of_Two
(Step S27), and then monitored
Voltage V_CWait for the information input. In the initial state, the last monitor
Voltage V_CVC that stores the information of₁Contains zero
(Step S21), and the control voltage signal S
_aMeans that the input impedance of the DC-AC conversion circuit 4 is infinite
Zero is set to be large (step S2
1). The D / A converter 52 has a voltage VC₁And V
C_TwoControl voltage signal updated based on the comparison result
S_aIs converted to an analog quantity and given to the mixer 58. On the other hand, the reference sine wave signal generation circuit 54
Output voltage V of current-AC conversion circuit 4_outEnter as information
Then, a reference sine wave signal is generated. This reference sine wave signal
Control voltage signal S converted to analog quantity_aIs a mixer 5
8 and the output current of the DC-AC conversion circuit 4
I_outOne of the error amplifiers 55 using the information of
Is given to the input. In this way, the error amplifier 55
The output signal obtained is the output power of the interconnected power converter 1.
The flow waveform is generated so as to be a sine wave.
You. The comparator 56 includes a triangular wave signal generation circuit 5
3 to the output signal of the error amplifier 55.
Pulse width modulation (PMW) wave
A pulse signal is generated by the pulse distributor 57.
Input the clock signal and the clock signal S₁₁₄And S_{one two Three}Raw
To achieve. The signal S thus generated₁₁₄And S_{one two Three}
Is the control voltage signal S_aDuty ratio according to the size of
Will do. Then, the control voltage signal S_aResponds to
As a result, the conduction time of the switching circuit 34 is controlled, and the output
Current I_outIncreases or decreases. These clock signals S₁₁₄And S
_{one two Three}Of the switching circuit 34 by the switching
Since the circuit is the same as the circuit 31, the description is omitted. The clock signal S₁₁₄And S_{one two Three}Frequency
The number indicates that the power output from the interconnected power converter 1 is
To have a frequency component that cooperates with the system distribution line 11
Determined. As described above, the control circuit 6 applies the voltage V_CIncrease or decrease
To monitor the current I_outTo adjust. As a result, DC-
The AC conversion circuit 4 has a voltage V_CIs the voltage V_minAnd voltage V_CONST
Operates so as to be kept at a substantially constant voltage between
Thereby, the DC-AC conversion circuit 4 is connected to the system distribution line 11.
Output voltage V in coordination with the side voltage_outKeeping the interconnection
Output current I via relay 5_outTo the system distribution line 11
Pay. Here, the interconnection relay 5 is connected to the system distribution line 11.
Voltage and frequency are normal and DC-AC
After the output of the conversion circuit 4 is established,
(The fourth control function of the control circuit 6). As described above, power was generated by the solar cell 100.
For DC output, the power, voltage and frequency of the
Is converted to a regulated AC voltage, and output terminal A_OUT, B_OUTTo
Will appear. Next, the interconnection type power converter 1 is connected.
Of operation when operation cannot be performed in coordination with power distribution lines
(Fifth function of control circuit 6) will be described. First
In addition, the system voltage and frequency of the system
A case where the value deviates will be described. In this case, control
The circuit 6 releases the interconnection relay 5 and performs DC-DC conversion.
Switching circuit of conversion circuit 3 and DC-AC conversion circuit 4
Stop the switching operation of 31 and 34, and
The converter 1 is disconnected from the system distribution line 11 and operation is stopped.
Control so that Second, for example, the power converter 1 and the system power distribution
Circuit breakers connected to line 11 are released.
The following describes the case where In this case, the distribution line 11
V₁, V_TwoLoad between each 100V line becomes unbalanced
Overvoltage is applied to the load connected to this 100V line.
Be added. To protect the load due to this overvoltage, the control circuit
Road 6 is the voltage of the distribution line with respect to the neutral line of the system distribution line 11
(V₁, V_TwoMonitor) and this monitor voltage is a certain
When the value exceeds the value, the control circuit 6 releases the interconnection relay 5.
Release the grid-connected power converter 1 to the system distribution line 1
1 and the DC-DC converter 3 and the DC-AC converter.
Of the switching circuits 31 and 34 of the
By stopping the switching operation, the
Is controlled to stop the operation. Thus, the control times
The path 6 has a fifth control function,
The frequency is monitored, and the operation of the interconnected power converter 1 is stopped.
It has a control function to stop. [0072] 【The invention's effect】The present inventionIn the interconnection type power converter of
The output of the solar cell is input to the DC-DC conversion circuit,
The input impedance of the DC-DC converter is
Controlled so that the maximum output power is input
Converts DC output of solar cells into AC power efficiently
And the solar cell output can be used effectively.
Wear. Also,The present inventionOf power converters connected to
Use a high-frequency insulation transformer instead of a commercial insulation transformer.
Therefore, the size and weight of the device can be significantly reduced. Further,The present inventionOf power converters
If overpower is input from the solar cell,
Increase the input impedance of the force transducer.
Therefore, limit the power input to the grid-type power converter.
To prevent equipment destruction due to overpower input.
Can be Further,The present inventionInterconnected power converter
Cannot maintain interconnection operation in coordination with grid distribution lines.
Control or if an overvoltage occurs in the system distribution line,
Since the control circuit controls the operation of the device to stop,
There is no need to provide system protection devices and overvoltage protection relays.
Device can be made smaller, lighter, and lower in cost.
You.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system block diagram showing a configuration of a photovoltaic power generation system to which the present invention is applied. FIG. 2 is a circuit diagram illustrating a configuration of a DC-DC conversion circuit. FIG. 3 is a circuit diagram illustrating a configuration of a DC-AC conversion circuit. FIG. 4 is a diagram in which an output voltage-current characteristic curve (I) of a solar cell and an input voltage-current characteristic (II) of a DC-DC converter are superimposed. FIG. 5 is a circuit block diagram of an input impedance control unit in the control circuit. FIG. 6 is a flowchart showing the operation of the MPU 21. FIG. 7 is a circuit block diagram of a voltage V _C control unit in the control circuit. FIG. 8 is a flowchart showing the operation of the MPU 51. FIG. 9 is a diagram for explaining an inputtable power range and a solar cell maximum output power point tracking function of the interconnected power converter. FIG. 10 is a system block diagram illustrating a photovoltaic power generation system to which a conventional interconnected power conversion device is applied. FIG. 11 is a system block diagram illustrating a photovoltaic power generation system to which a conventional interconnected power converter configured using a high-frequency insulating transformer is applied. [Description of Signs] 1 interconnection type power converter 2 input relay 3 DC-DC converter 4 DC-AC converter 5 interconnection relay 6 control circuit 7 control power supply 8, 9 current sensor 10 pole transformer 11 single phase Three-wire system distribution line 30 Input filters 31, 34 Full-bridge switching circuit 32 Full-bridge rectifier circuit 33 Output smoothing circuit 35 Output filter 103 System power supplies C _{1 to} C ₂ , C ₁₁ Capacitors D _{1 to} D ₄ Rectifier L ₁ , L _11, L ₁₂ coil _{Q 1 ~Q 4, Q 11 ~Q} 14 switching elements T _1, T ₂ RF isolation transformer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI H02M 7/48 H02M 7/48 R (58) Investigated field (Int.Cl. ⁷ , DB name) G05F 1/67 H02H 3 / 20 H02J 3/46 H02M 3/28 H02M 7/48

Claims (1)

(1) A DC-DC conversion circuit for inputting a DC output of a solar cell and performing DC-DC conversion, and a DC-AC input receiving an output of the DC-DC conversion circuit. A DC-AC conversion circuit for converting, and a control circuit, wherein the DC-DC conversion circuit receives the output of the solar cell, converts the output to high-frequency power and outputs the high-frequency power, and receives the output of the switching circuit. A high-frequency insulating transformer, and a rectifier circuit for inputting and rectifying the output of the high-frequency insulating transformer, wherein the control circuit calculates the power of the DC output of the solar cell, and sets a maximum output power point of the solar cell. Controlling the conduction time of the switching circuit to control the input impedance of the DC-DC conversion circuit so that the output power of the solar cell exceeds the allowable input of the DC-DC conversion circuit,
An interconnected power converter, wherein an input impedance of the DC-DC converter is increased so that an input of the DC-DC converter does not exceed an allowable range of current and power.