JP2001255949A - Photovoltaic power generating inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve power using efficiency at the time of using plural solar battery assembly, and to realize stable power converting operation. SOLUTION: Photovoltaic cell strings 35, 36, and 37 are respectively provided with boosting chopper circuits 39a, 39b, and 39c a to constitute a DC power source circuit 22, and chopper control circuits 61a, 61b, and 61c respectively make switching controls of the boosting chopper circuits 39a, 39b, and 39c, so that the photovoltaic cell strings 35, 36, and 37 can be controlled for the maximum power point tracking. An inverter control circuit 60 calculates a reference power Po*, by adding a full output power Po of the cell strings 35, 36, and 37 and a power correction value ΔPo, based on an output voltage VCH, and adjusts an output power. A control power source circuit 28 operates the cell string, whose output voltage is the highest among the cell strings 35-37 as an input.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generation inverter device that performs a DC-AC power conversion operation by using a plurality of solar cell assemblies as inputs.

[0002]

2. Description of the Related Art FIG. 4 shows an electrical configuration of a photovoltaic power generation inverter device to which two solar cell strings (corresponding to a solar cell assembly) are connected. In FIG. 4, the photovoltaic power generation inverter apparatus 1 includes a voltage input circuit 2, a DC power supply circuit 3 configured as a boost chopper circuit, an inverter circuit 4 having a single-phase bridge configuration, a filter circuit 5, a breaker 6, and a control circuit 7. It is configured.

The voltage input circuit 2 includes diodes 10a, 1a, 1b, 1c, 1c, and 1c shown between the positive terminals of the solar cell strings 8a, 8b and the input power supply line 9p.
0b, and the solar cell strings 8a, 8b
Are connected to the input power supply line 9n.

Further, voltage detectors 11, 12, 13 and current detectors 14, 15 are provided. The input voltage VD from the solar cell strings 8a, 8b and the DC voltage VCH output from the DC power supply circuit 3, respectively. , AC voltage VAC,
The input current ID from the solar cell strings 8a and 8b and the alternating current IAC are detected.

[0005] The input voltage VD from the solar cell strings 8a and 8b is boosted by the DC power supply circuit 3 and then converted by the inverter circuit 4 into an AC voltage having a PWM waveform. , Can be connected to an AC power supply 16 indicating a power system via the breaker 6.

The control circuit 7 includes a DC power supply control circuit 17 for controlling the DC power supply circuit 3 and an inverter control circuit 18 for controlling the inverter circuit 4. The DC power supply control circuit 17 includes a solar cell string 8a,
The input power from 8b is calculated, and a reference input voltage VD * at which the input power is maximum is obtained. Then, after obtaining a reference input current ID * based on the difference between the reference input voltage VD * and the input voltage VD, the DC power supply circuit 3 further obtains a reference input current ID * based on the difference between the reference input current ID * and the input current ID. A gate signal F1 by PWM control is output to a switching element (not shown). The DC power supply control circuit 17 controls the output power of the DC power supply circuit 3 to be reduced when the DC voltage VCH becomes overvoltage.

On the other hand, the inverter control circuit 18 obtains a difference between the DC voltage VCH and the reference DC voltage VCH *, and generates a reference AC current IAC * based on the difference and the AC voltage VAC. Then, the inverter control circuit 18 outputs gate signals G1 to G4 by PWM control to each switching element (not shown) of the inverter circuit 4 based on the difference between the reference AC current IAC * and the AC current IAC. I do.

[0008]

The solar cell string 8a connected to the solar power generation inverter device 1 will now be described.
And 8b may have different configurations depending on the requirements such as the area and shape of the roof to be installed, the installation standard for electrical equipment, and the like.

FIGS. 5A and 5B show an example of output characteristics of the solar cell strings 8a and 8b, respectively.
In these figures, the output characteristics shown by solid lines are voltage-current characteristics, and the output characteristics shown by dashed lines are voltage-power characteristics. The solar cell string 8a, which is a solar cell assembly, is configured by connecting eight solar cell panels in series, and the solar cell string 8b is configured by connecting four identical solar cell panels in series. .

In this case, the combined output characteristics of the solar cell strings 8a and 8b viewed from the input power supply lines 9p and 9n are shown in FIG.
The result is as shown in FIG. That is, when the input voltage VD is equal to or lower than the open-circuit voltage Vbmax of the solar cell string 8b, the output voltage Va of the solar cell string 8a and the output voltage Vb of the solar cell string 8b are both equal to the input voltage VD. Solar cell string 8
The currents determined by the output characteristics a and 8b (FIGS. 5A and 5B) are combined and flow into the photovoltaic power inverter device 1.

On the other hand, when the input voltage VD exceeds the open-circuit voltage Vbmax of the solar cell string 8b, only the output voltage Va of the solar cell string 8a becomes equal to the input voltage VD. 8a
5 (a) flows into the photovoltaic power generation inverter device 1.

In FIG. 5 (c), the combined voltage-power characteristic is shown by a dashed line. The input power to the photovoltaic power generation inverter device 1 is the
, And two maximum power points Mc and Md corresponding to the maximum power point Mb of the solar cell string 8b.

However, the photovoltaic power inverter 1 is connected to any of the maximum power points Mc (Vd = Vap), Md (Vd = Vb).
Even when driving in p), the solar cell string 8
The maximum power Pa that a can output and the solar cell string 8b
Power (Pa + Pb) with maximum power Pb that can be output
Only smaller power could be used, and the efficiency of using the power generated by the solar cell strings 8a and 8b was poor.

In order to cope with this, in the conventional photovoltaic power generation inverter device 1, the same number of photovoltaic panels are connected in series to use the photovoltaic strings 8a and 8b having the same output characteristics. The degree of freedom when installing in such places was limited. Further, even when the solar cell strings 8a and 8b having the same configuration are used, the amount of solar radiation of the solar cell strings 8a and 8b may be different due to a difference in the direction of the installation surface. In this case, a difference occurs between the output characteristics of the two, and it becomes impossible to operate both of the solar cell strings 8a and 8b at the maximum power point, resulting in a reduction in the efficiency of using the generated power.

Further, when a plurality of solar cell strings having various output characteristics are connected to the photovoltaic power generation inverter device 1, if a sudden change in the solar radiation state or a change in the interconnected power system occurs, the DC power supply Hunting may occur between the circuit 3 and the inverter circuit 4 to make the control unstable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an apparatus having a plurality of solar cell assemblies as inputs, even if the solar cell assemblies have different configurations and solar radiation states. An object of the present invention is to provide a photovoltaic power generation inverter device that can increase the efficiency of use of the power generated by a solar cell assembly and can perform a stable power conversion operation.

[0017]

In order to achieve the above object, a photovoltaic power generation inverter device according to the present invention comprises: a DC power supply circuit having a plurality of solar cell assemblies as inputs; A solar circuit comprising: an inverter circuit that converts the voltage into an output voltage; and a control unit that controls the DC power supply circuit and the inverter circuit so as to convert the power input from the solar cell assembly into AC output power of the inverter circuit. The photovoltaic inverter device includes voltage detection means for detecting an output voltage of the DC power supply circuit, and the DC power supply circuit is configured by a DC power conversion circuit individually provided for each of the solar cell assemblies. ,
The control unit controls each of the DC power conversion circuits so that the output power of each of the solar cell assemblies is maximized, and controls the voltage detected by the voltage detection unit and the total output power of the solar cell assembly. The inverter circuit is controlled based on the above (claim 1).

[0018] According to this configuration, the control means controls each solar cell assembly to follow the maximum power point using the DC power conversion circuit individually provided for each of the plurality of solar cell assemblies. Even when the configuration of the solar cell assemblies (for example, the number of series in the basic unit) and the solar radiation conditions at the installation location are different from each other, each solar battery aggregate has the maximum power that can be generated in the respective solar radiation conditions. Can be output. Thereby, the utilization efficiency of the generated power of each solar cell assembly can be increased.

Further, the control means performs cooperative control between the DC power supply circuit and the inverter circuit based on the total output power of the solar cell assembly, so that the DC power supply circuit controls the power input from the solar cell assembly and the inverter circuit. The power output to the load is balanced. This suppresses the occurrence of unstable phenomena such as hunting between the DC power supply circuit and the inverter circuit, even when, for example, the solar radiation condition changes suddenly or the load (such as the interconnected power system) fluctuates. Can be

Further, the control means controls the inverter circuit based on the output voltage of the DC power supply circuit detected by the voltage detection means, so that the output voltage of the DC power supply circuit is controlled to be constant, and the input power, output power and Is more balanced. Thus, even when the solar radiation state or the load fluctuates, the output voltage of the DC power supply circuit does not become overvoltage or undervoltage, and a more stable power conversion operation can be performed.

The control means detects a maximum power point at which the output power of the specific solar cell assembly is maximum, controls the DC power conversion circuit for the specific solar cell assembly, and controls the specific solar cell assembly. It is preferable to set the maximum power point of the other solar cell assembly based on the maximum power point of the battery assembly and control the DC power conversion circuit for the other solar cell assembly (claim 2).

The maximum power points of the respective solar cell assemblies have a relative relationship with each other based on a difference in configuration or a difference in the tendency of the solar radiation at the installation location. Therefore, if the maximum power point of a specific solar cell assembly is detected by the above configuration, the maximum power points of the other solar cell assemblies can be estimated based on the maximum power point. This makes it possible to reduce the processing of detecting the maximum power point that is complicated and requires a long processing time, thereby reducing the processing load on the control means and shortening the control cycle. As a result, the control system is further stabilized.

In this case, the voltage at the maximum power point detected for the specific solar cell assembly is Vp
[V], the number of series of the specific solar cell assembly is m
(M ≧ 1), and the number of series of other solar cell assemblies is n (n
≧ 1), the control means sets the voltage at the maximum power point of the other solar cell assembly to (n / m) × Vp
[V] (claim 3).

The voltage at the maximum power point of the solar cell assembly is substantially proportional to the number of series (series) of basic units (for example, solar cell panels of a certain standard) constituting the solar cell assembly when the solar radiation conditions and the like are the same. There are characteristics that change. Therefore, by using the above means, the maximum power point can be obtained only by simple proportional calculation without detecting the maximum power point for the other solar cell assemblies.

In each of the above cases, it is preferable to provide a control power supply circuit for generating a power supply voltage of the control means by using the one having the largest output voltage among the plurality of solar cell assemblies as an input. . According to this configuration, even when the output voltage of the solar cell assembly is low such as in the morning or evening or on a cloudy day, the control power supply circuit can secure a high input voltage and easily supply the control voltage to the control means. Therefore, the operable time of the photovoltaic power generation inverter device is extended, and the utilization efficiency of the generated power is further improved.

Further, the DC power supply circuit is preferably configured so that the DC power conversion circuit provided for each of the solar cell assemblies is housed in one housing. According to this configuration, the combination of the DC power supply circuit and the inverter circuit according to the number of solar cell assemblies to be connected becomes easy.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 1 showing the electrical configuration of the entire system, a photovoltaic power generation inverter device 21 includes a DC power supply circuit 22, a capacitor 23, an inverter circuit 24, a filter circuit 25, a breaker 26, a control circuit 27 as control means, It comprises a power supply circuit 28, voltage detectors 29 and 30, and a current detector 31. Although not shown, a switch for connecting the AC output of the photovoltaic power generation inverter device 21 to an AC power supply 32 which is a power system is provided.

The DC power supply circuit 22 has three input terminals (3
3a, 33b), (33c, 33d), (33e, 33
f) and a set of output terminals (34p, 34n). Each input terminal (33a, 33b), (33c, 33
d) and (33e, 33f) are connected to the positive and negative output terminals of the solar cell strings 35, 36, 37, respectively. The output terminals 34p and 34n are respectively a DC power supply line 38p connected to the positive input terminal of the inverter circuit 24 and a DC power supply line 38n connected to the negative input terminal.
It is connected to the.

The solar cell strings 35, 36, and 37 as a solar cell assembly constitute, for example, a solar cell array installed on the roof of a house, and have eight, six, and four solar cell panels, respectively. (Series). As will be described in detail later, due to such a difference in the number of series, the solar cell string 3
5, 36 and 37 have different output characteristics (FIG. 2).
reference).

The DC power supply circuit 22 is connected to each input terminal (33
a, 33b), (33c, 33d), (33e, 33)
f) and three boost chopper circuits 39a, 39b, 39c (corresponding to the DC power conversion circuit of the present invention) having the same circuit configuration and provided between the output terminals (34p, 34n) in one housing. It is constituted by being stored in. Thus, the modularized DC power supply circuit 22 with multiple inputs and one output can be replaced as appropriate according to the number of solar cell strings connected to the solar power generation inverter device 21. Among them, the boost chopper circuit 39
a is configured as follows.

That is, the input terminal 33a is connected to the reactor 4
0a and the diode 41a of the illustrated polarity are connected in series to the output terminal 34p, and the input terminal 33b is directly connected to the output terminal 34n. Input terminals 33a and 33b
, A capacitor 42a is connected,
A voltage detector 43a for detecting the output voltage VD1 of the solar cell string 35 is connected. The voltage detector 43a is configured by, for example, a voltage dividing circuit using a resistor.

The collector-emitter of the IGBT 44a is connected between the anode of the diode 41a and the output terminal 34n, and the input terminal 33b is connected to the IGBT 44a.
Between the emitter of 44a and the solar cell string 35
Is provided with a current detector 45a (for example, CT using a Hall element) for detecting the output current ID1.

Similarly, the boost chopper circuit 39b
A voltage detector 43b for detecting the output voltage VD2 of the solar cell string 36 and a current detector 45b for detecting the output current ID2 are provided. The boost chopper circuit 39c detects the output voltage VD3 of the solar cell string 37. And a current detector 45c for detecting the output current ID3.

Further, input terminals 33a, 33c, 33e
Are diodes 46a, 46b, 4
6c, an input terminal 33b connected to the positive input terminal of the control power supply circuit 28 and connected to the DC power supply line 38n;
33d and 33f are both connected to the negative input terminal of the control power supply circuit 28. The control power supply circuit 2
8 generates a power supply voltage necessary for operating the control circuit 27.

The capacitor 23 is connected between the DC power supply line 38p and the DC power supply line 38n, and a voltage detector 29 (the present invention) for detecting the DC voltage VCH output from the DC power supply circuit 22. Are connected). The voltage detector 29 is constituted by, for example, a voltage dividing circuit using a resistor.

The inverter circuit 24 comprises four switching elements, for example, IGBTs 47 to 50 and four return diodes 51 to 54, as a well-known single-phase bridge circuit. The output lines 55 and 56 are connected to the reactor 5
7 through a filter circuit 25 including a capacitor 58 and a breaker 26, an electric power system, that is, an AC power supply 32.
It is connected so that interconnection is possible.

Between the output terminals of the filter circuit 25, a voltage detector 30 composed of, for example, a PT (instrument transformer) or a differential amplifier is provided. This voltage detector 30
Detects the AC voltage output from the photovoltaic power generation inverter device 21 (the voltage of the AC power supply 32 at the time of system interconnection) and outputs it to the control circuit 27 as the AC voltage VAC. Further, the output line 56 is provided with a current detector 31 using, for example, a Hall element. The current detector 31 detects the AC current IAC output from the inverter circuit 24 and outputs the AC current IAC to the control circuit 27.

The control circuit 27 is mainly composed of a microcomputer and includes a DC power supply control circuit 59 for controlling the DC power supply circuit 22 and an inverter control circuit 60 for controlling the inverter circuit 24. Then, the control circuit 27 outputs the detected output voltages VD1, VD2, VD3, the output currents ID1, ID2, ID3, the DC voltage VCH, and the AC voltage VA.
C, an alternating current IAC is input. Among them, the DC power supply control circuit 59 is configured as follows.

That is, the DC power supply control circuit 59 is composed of chopper control circuits 61a, 61b, 61c for controlling the boost chopper circuits 39a, 39b, 39c, respectively, and an overvoltage prevention circuit 61d for preventing an overvoltage of the DC voltage VCH. ing. Chopper control circuits 61a, 61b, 6
Since 1c has the same configuration, the chopper control circuit 61a will be described here.

The power detection circuit 62a calculates the output power P1 of the solar cell string 35 by multiplying the output voltage VD1 of the solar cell string 35 by a reference current ID1 * (described later), and calculates the maximum power point detection circuit. 63a.

The maximum power point detection circuit 63a performs maximum power point tracking control (MPPT control: Maximum Power Point Trackin
When performing g), this is a circuit for obtaining a reference voltage VD1 * at which the solar cell string 35 outputs the maximum power, and the current reference voltage VD1 * is varied within a range of predetermined minute voltages -ΔV * and + ΔV *. Based on the change in the output power P1 of the solar cell string 35 at this time, the reference voltage VD1 * is adjusted to a value (VD1mp in FIG. 2) which is the maximum power point.

The subtraction circuit 64a is connected to the solar cell string 3
5, the controller 65a performs, for example, a proportional operation and an integral operation (hereinafter, referred to as PI operation) on the voltage deviation as a result of the subtraction, thereby obtaining a solar cell string. The reference current ID1 * with respect to 35 is output. A subtraction circuit 66a after the controller 65a subtracts the output current ID1 of the solar cell string 35 from the reference current ID1 *, and the controller 67a
For example, a PI operation is performed on the current deviation as a result of the subtraction to generate a modulation signal for the PWM circuit 68a.

The PWM circuit 68a includes the chopper control circuit 6
A triangular wave signal from a carrier signal generation circuit (not shown) provided in common with 1a, 61b, 61c and controller 6
There is provided a comparator (not shown) for comparing with the modulation signal output from 7a. The square-wave drive signal S1 obtained from the comparator is supplied to the gate of the IGBT 44a via a drive circuit (not shown). In this case, as the level of the modulation signal output from the controller 67a increases, the duty ratio of the drive signal S1 increases, and the ratio of the ON time of the IGBT 44a increases.

The chopper control circuits 61b, 61c
Calculates and outputs the output powers P2 and P3 of the photovoltaic strings 36 and 37, respectively.
Drive signals S2 and S3 are supplied to the gates of b and 44c.

The overvoltage protection circuit 61d includes a subtraction circuit 69,
It comprises a controller 70 and a limit circuit 71. The subtraction circuit 69 subtracts a preset limit voltage VCHL * from the DC voltage VCH, and the result of the subtraction is amplified by the controller 70 and then input to the limit circuit 71. The limit circuit 71 determines, based on the amplification result, that VCHL * <
When VCH is reached, each of the chopper control circuits 61a, 61
b, 61c are provided with limit signals for limiting the reference currents ID1 *, ID2 *, ID3 * (controllers 65b, 65c and reference currents ID2 *, ID3). * See Figure 3).

Next, the configuration of the inverter control circuit 60 will be described. The generated power calculation circuit 72 outputs the output power P1 of the solar cell strings 35, 36, 37 output from the chopper control circuits 61a, 61b, 61c, respectively.
By adding P2 and P3, the total output power Po of the solar cell strings 35, 36 and 37 is obtained.

A subtraction circuit 73 subtracts a preset reference voltage VCH * from the DC voltage VCH, and a controller 74 performs a PI operation on the voltage deviation as a result of the subtraction to obtain a correction power ΔPo. It has become. Then, the addition circuit 75 adds the output power Po calculated by the generated power calculation circuit 72 and the correction power ΔPo obtained from the controller 74, and adds the reference power to be output from the photovoltaic power generation inverter device 21. Po * is required.

The voltage value detection circuit 76 rectifies and smoothes the AC voltage VAC stepped down by the voltage detector 30, and outputs the AC voltage (the AC power supply 32 of Effective voltage VAC (rms)
Is to be obtained. In addition, the power factor adjustment circuit 77
It is provided for performing advanced phase reactive power control. When the AC voltage VAC (rms) becomes a predetermined value, for example, 107 V or more, the power factor which is originally adjusted to 1 is set to the leading power factor. Has become. The dividing circuit 78 divides the reference power Po * output from the adding circuit 75 by the effective value VAC (rms) and the power factor to obtain a reference AC current IAC * described later.
(Effective value).

The sine wave generating circuit 79 detects the zero cross point of the AC voltage VAC, and generates the same frequency as the 50 Hz (or 60 Hz) of the AC power supply 32 based on the sine wave data stored in the memory in advance. Waveform generating circuit for generating a sinusoidal waveform (not shown)
It is comprised including. Then, a sine wave signal synchronized with the detected zero-cross point and advanced in phase corresponding to the power factor given from the power factor adjustment circuit 72 is generated.

The multiplying circuit 80 generates a reference AC current IAC * for the inverter circuit 24 by multiplying the output of the dividing circuit 78 by the sine wave signal output from the sine wave generating circuit 79. ing. The subtracting circuit 81 calculates an AC current I from the reference AC current IAC *.
The controller 82 is configured to subtract AC and perform, for example, a PI operation on the current deviation that is the result of the subtraction to generate a modulation signal for the PWM circuit 83.

The PWM circuit 83 includes a carrier signal generating circuit for generating a triangular wave signal having a predetermined frequency, and a comparator for comparing the generated triangular wave signal with the modulation signal output from the controller 82 (both in FIG. (Not shown). In this case, a triangular wave signal generated by the controller 67a may be used.

Based on the result of the comparison, square wave drive signals G1 and G2 and drive signals G3 and G4 having inverted waveforms with respect to the drive signals G1 and G2 are generated, and these drive signals G1 to G4 are shown in FIG. The gates of the IGBTs 47 to 50 are supplied to the gates of the IGBTs 47 to 50 via a drive circuit which is not used. In this case, the higher the level of the modulation signal output from the controller 82, the higher the AC voltage output from the inverter circuit 24.

Next, the operation of this embodiment at the time of system interconnection will be described. For example, a solar cell installed on a roof of a house is called a solar cell array, and generally includes a plurality of solar cell strings (in this embodiment, solar cell strings 35,
36, 37). These solar cell strings are configured by connecting solar cell panels formed by combining a plurality of solar cell modules in a series (series).

In this case, the area and shape of the roof to be installed,
Depending on requirements such as installation standards (for example, voltage regulation) as electrical equipment, the number of series of solar cell panels constituting each solar cell string may be different from each other.

FIG. 2 shows the output characteristics of the solar cell strings 35, 36, and 37 at the same temperature and the same solar radiation. The output characteristics shown by the solid line are the voltage-current characteristics, and the output characteristics shown by the dashed line. Are voltage-power characteristics. That is, 8S (indicating that the number of series is 8), 6
S, 4S solar cell strings 35, 36, 37 have open voltages of VD1max, VD2max, VD3max, respectively, and have maximum power points M1 (voltage VD1mp), M2 (VD2mp),
The maximum power is output at M3 (VD3mp).

In order to extract the maximum power from each of the solar cell strings 35, 36, 37 having different output characteristics, the chopper control circuits 61a, 61b, 61
c is a step-up chopper circuit 39a, 39b, 39c, respectively.
Are controlled independently. These chopper control circuits 61a,
Since the control operations of 61b and 61c are the same, the control operation of the chopper control circuit 61a will be described below.

The chopper control circuit 61a performs the maximum power point tracking control for the solar cell string 35, so that the maximum power that can be generated at the temperature and the amount of solar radiation at that time is taken out of the solar cell string 35. Control. Solar cell string 35
As shown in FIG. 2, the output power P1 has a maximum (power P1mp) at a specific output voltage VD1mp, and has a characteristic of decreasing when the output voltage VD1 deviates from this voltage VD1mp. When the temperature or the amount of solar radiation changes, the power P1mp at the maximum power point changes, and the output voltage VD1mp at the maximum power also slightly changes.

Therefore, the maximum power point detecting circuit 63a changes the current reference voltage VD1 * by a predetermined minute voltage -ΔV *, + ΔV * during the system interconnection operation, and based on the change of the output power P1 at that time. To obtain the reference voltage VD1 * at which the maximum power is output.

The thus obtained reference voltage VD1 * (=
VD1mp), the output voltage V of the solar cell string 35
Consider the case where D1 has decreased. Solar cell string 35
Has an output characteristic in which the output current ID1 monotonously decreases as the output voltage VD1 increases (see FIG. 2). Therefore, the controller 65a operates to lower the reference current ID1 * of the solar cell string 35. I do. As a result, P
The modulation signal output to the WM circuit 68a decreases, and the ON time of the IGBT 44a in the boost chopper circuit 39a decreases. As a result, the output current ID1 of the solar cell string 35 decreases, and accordingly, the output voltage VD1 increases and is controlled to match the reference voltage VD1 *.

On the other hand, the inverter control circuit 60 converts the power substantially equal to the total DC power input from the photovoltaic strings 35, 36, 37 into an AC power so as to balance the input and output of the power of the photovoltaic power generation inverter device 21. The inverter circuit 24 is controlled so as to output to the power system.

As described above, the chopper control circuit 61
a, 61b, and 61c calculate the output powers P1, P2, and P3 of the photovoltaic strings 35, 36, and 37 in executing the maximum power point tracking control. , P2, and P3 are added to calculate the total output power P of the solar cell strings 35, 36, and 37.
Ask for o.

Further, in order to prevent the occurrence of imbalance in input / output power due to a calculation error, the efficiency of the photovoltaic power generation inverter device 21, disturbance, etc., the output voltage VCH and the reference voltage A power correction value ΔPo based on the difference from VCH * is added. For example, when the output voltage VCH is higher than the reference voltage VCH *, the power correction value ΔPo becomes positive, and the inverter control circuit 60
Controls the output power from the inverter circuit 24 to be increased by increasing the reference power Po *, so as to suppress an increase in the output voltage VCH.

When the power factor of the output of the inverter circuit 24 is cos φ, the inverter control circuit 60 calculates a reference AC current IAC * for the inverter circuit 24 according to the following equation (1). IAC * = Po * / (VAC · cosφ) (1)

(VAC · cos φ) in equation (1)
The division is performed by a voltage value detection circuit 76, a power factor adjustment circuit 77, and a division circuit 78, respectively, and a sine wave generation circuit 79 and a multiplication circuit 80 generate a reference AC current IAC * having a sine waveform. .

Since the division circuit 78 performs the division by the AC voltage VAC which is the voltage of the power system in accordance with the equation (1), even if the AC voltage VAC decreases due to a disturbance such as connection of a power load, the reference AC is immediately applied. The current IAC * increases, and a decrease in the output power of the inverter circuit 24 can be suppressed. The inverter circuit 24 outputs a current equal to the reference AC current IAC * to the system by PWM control based on the difference between the reference AC current IAC * and the AC current IAC.

As described above, the photovoltaic power generation inverter device 21 individually boosts the chopper circuits 39a, 39 for the solar cell strings 35, 36, 37, respectively.
b, 39c and chopper control circuits 61a, 61b, 6
1c, unlike the photovoltaic power generation inverter device 1 of the conventional configuration, the solar cell strings 35, 36, 37
Can be controlled independently of each other.

Under such a configuration, the chopper control circuit 6
1a, 61b, 61c are the solar cell strings 35, 3
Since the maximum power point tracking control is executed for each of the solar cell strings 6, 37, the photovoltaic power inverter device 21 outputs the respective solar cell strings 35, 36, 3
7, the maximum power that can be generated at each time can be taken out, and all the connected solar cell strings 3
The power use efficiency of 5, 36, and 37 can be increased.

As a result, it is not necessary to make the output characteristics of the plurality of solar cell strings constituting the solar cell array uniform in order to enhance the power use efficiency, and each solar cell string can be provided in accordance with the area and shape of the roof to be installed. The number of series can be appropriately selected. This increases the degree of freedom in designing and constructing the solar power inverter 21 and the solar cell array.

Further, even when the amount of solar radiation to each of the solar cell strings 35, 36, 37 is different due to a difference in the direction of the roof installation surface, etc., each of the solar cell strings 3
Since the maximum power can be extracted from 5, 36, and 37, the power use efficiency is further improved.

Further, the control circuit 27 performs cooperative control between the DC power supply circuit 22 and the inverter circuit 24 in order to balance the input / output power of the photovoltaic power generation inverter device 21. That is, the inverter control circuit 60 controls the solar cell string 3 input from the DC power supply control circuit 59.
Since feedforward control is performed using the output powers P1, P2, and P3 of 5, 36, and 37, the response speed of the control system is increased. As a result, the amount of solar radiation changes and the total output power P
Even if o changes suddenly, the DC voltage VCH is maintained at a value close to the reference voltage VCH *, and the reference current ID1 * is less likely to be limited by the overvoltage prevention circuit 61d, so that the stable maximum power point tracking control is always performed. Done.

Further, since the inverter control circuit 60 performs feedback control so that the output voltage VCH matches the reference voltage VCH *, even if there is an error in power calculation, disturbance, or the like, the solar cell strings 35, 36, 37 And the output power of the inverter circuit 24 can always be balanced, and more accurate and stable maximum power point tracking control can be performed.

Further, the control power supply circuit 28 is operated by the diodes 46a, 46b, 46c to control the solar cell strings 35, 36, 37 in which the maximum power point tracking control is performed.
Out of which the solar cell string outputting the highest voltage is operated. Therefore, even when the output voltage of the solar cell strings 35, 36, and 37 is entirely reduced, such as in the morning and evening or on cloudy days, the control power supply circuit 28 secures a high input voltage and controls the control circuit 27. The control voltage can be continuously supplied. Thereby, the operable time of the photovoltaic power generation inverter device 21 is extended, and the utilization efficiency of the generated power is further improved.

Since the DC power supply circuit 22 is modularized into a multi-input, one-output configuration in which the step-up chopper circuits 39a, 39b, 39c are housed in one housing, the DC power supply circuit 22 can be easily adapted to the number of solar cell strings. And the configuration of the solar power inverter 21 can be easily changed.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. This embodiment is a modification of the DC power supply control circuits 61b and 61c in the first embodiment described above. That is, the DC power supply control circuit 84
3, the chopper control circuit 85 that controls the solar cell string 36 to follow the maximum power point by the boost chopper circuit 39b includes a maximum power point calculation circuit 86 instead of the power detector and the maximum power point detection circuit. It has.

The maximum power point calculation circuit 86 has a reference voltage VD1 * (the voltage VD1 shown in FIG. 2) when the DC power supply control circuit 61a controls the solar cell string 35 to follow the maximum power point.
mp) with respect to the series number a of the solar cell string 35
(= 8) and the series number b (=
6) is multiplied by the ratio (b / a) to obtain the reference voltage VD2 *.

Similarly, the chopper control circuit 87 that controls the solar cell string 37 to follow the maximum power point by the boost chopper circuit 39c includes a maximum power point calculation circuit 88 instead of the power detector and the maximum power point detection circuit. I have. The maximum power point calculation circuit 87 calculates the reference voltage VD1 * (voltage VD1m
p) is the number of series a of the solar cell string 35
(= 8) and the series number c of the solar cell string 37 (=
4) is multiplied by the ratio (c / a) to obtain a reference voltage VD3 *.

In the case of the solar cell strings 35, 36 and 37 using the same solar cell panel and different series numbers, as shown in FIG. 2, the open-circuit voltages VD1max, VD2max,
The ratio of VD3max is almost equal to the ratio of the series numbers a, b, c. At the same time, the maximum power points M1, M2, M3
The ratio of the voltages VD1mp, VD2mp, and VD3mp at the time is also substantially equal to the ratio of the series numbers a, b, and c.

Therefore, if the maximum power point M1 is detected for a specific solar cell string 35 to obtain the voltage VD1mp,
For the other solar cell strings 36 and 37, the maximum power points M2 and M3 can be almost accurately estimated by simple multiplication processing by the maximum power point calculation circuits 86 and 88.

With the above configuration, the processing for detecting the maximum power point requiring complicated processing can be reduced, so that the processing load on the DC power supply control circuit 84 can be reduced and the control cycle can be shortened. This enables a more stable power conversion operation.

The present invention is not limited to the embodiment described above and shown in the drawings, but can be extended or modified as follows. The number of solar cell strings constituting the solar cell array is not limited to three, but may be two or four or more. Also, in the first embodiment, each solar cell string may be configured using different types of solar cell panels.

The DC power supply circuit 22 includes the boost chopper circuit 3
Not only 9a, 39b, 39c but also a step-down chopper circuit,
A configuration using a step-up / step-down chopper circuit using a transformer (for example, a high-frequency transformer) may be used. When the AC power supply 32 has three phases, the inverter control circuit 60
After the three-phase power is divided into active power and reactive power and controlled as a DC component, three-phase PWM control may be performed.

[0082]

As is apparent from the above description, according to the first aspect of the present invention, a DC power supply circuit having a plurality of solar cell assemblies as inputs is provided with a DC power supply circuit provided separately for each solar cell assembly. It consists of a conversion circuit and controls so that each solar cell assembly has the maximum power.Even if the configuration and solar radiation of each solar cell assembly are different, each solar cell assembly can generate the maximum power. Can be output, and the use efficiency of the generated power is increased. Further, since the control means controls the inverter circuit based on the total output power of the solar cell assembly and the output voltage of the DC power supply circuit, the input / output power is easily balanced and a stable power conversion operation is performed.

According to the second and third aspects of the present invention, the control means detects a maximum power point for a specific solar cell assembly and sets the maximum power points of the other solar cell assemblies based on the maximum power point. Therefore, the processing load on the control means is reduced, the control cycle is shortened, and the control system can be further stabilized.

According to the fourth aspect of the present invention, since the control power supply circuit for generating the power supply voltage of the control means by using the one having the largest output voltage among the plurality of solar cell assemblies as an input is provided, The operable time is longer than before, and the utilization efficiency of the generated power is further improved.

According to the fifth aspect of the present invention, the DC power supply circuit is formed by accommodating the DC power conversion circuit provided for each solar cell assembly in a single housing. The combination of the DC power supply circuit and the inverter circuit according to the above becomes easy.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram of a photovoltaic power generation inverter device according to a first embodiment of the present invention.

FIG. 2 is an output characteristic diagram of a solar cell string.

FIG. 3 is a block diagram of a DC power supply control circuit showing a second embodiment of the present invention.

FIG. 4 is a diagram corresponding to FIG. 1 showing a conventional configuration.

5A and 5B are output characteristic diagrams of a solar cell string, and FIG. 5C is a combined output characteristic diagram of the solar cell string viewed from an input unit of the solar power inverter device.

[Explanation of symbols]

21 is a photovoltaic power generation inverter device, 22 is a DC power supply circuit, 24 is an inverter circuit, 27 is a control circuit (control means), 28 is a control power supply circuit, 29 is a voltage detector (voltage detection means), 35, 36, 37 is a solar cell string (solar cell assembly), and 39a, 39b, and 39c are boost chopper circuits (DC power conversion circuits).

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tsuyoshi Yonemoto 2121 Nagoya, Asahi-machi, Mie-gun, Mie Prefecture F-term in Toshiba Mie Plant (reference) 5G066 HA30 HB06 5H007 AA02 BB07 CB04 CB05 CC03 CC12 DA03 DA05 DA06 DB01 DB05 DC02 DC04 DC05 EA02 5H420 BB03 BB12 CC03 CC09 DD03 DD09 EA11 EA40 EA43 EA48 EA49 EB09 EB16 FF03 FF04 FF09 FF22 FF24 FF25 FF26

Claims (5)

[Claims] 1. A DC power supply circuit having a plurality of solar cell assemblies as inputs, an inverter circuit converting an output voltage of the DC power supply circuit into an AC voltage and outputting the AC voltage, and an electric power input from the solar cell assemblies. A photovoltaic power generation inverter device comprising: a control unit for controlling the DC power supply circuit and the inverter circuit so as to convert the output power to the AC output power of the inverter circuit; and a voltage detection unit for detecting an output voltage of the DC power supply circuit The DC power supply circuit is configured by a DC power conversion circuit individually provided for each of the solar cell assemblies, and the control unit controls the output power of each of the solar cell assemblies to be maximum. While controlling each of the DC power conversion circuits, based on the voltage detected by the voltage detection means and the total output power of the solar cell assembly, A photovoltaic power generation inverter device that controls an inverter circuit. 2. The control means detects a maximum power point at which the output power of a specific solar cell assembly becomes maximum, controls a DC power conversion circuit for the specific solar cell assembly, and controls the DC power conversion circuit for the specific solar cell assembly. The DC power conversion circuit for the other solar cell assembly is controlled by setting the maximum power point of another solar cell assembly based on the maximum power point of the solar cell assembly. Solar power inverter device. 3. The voltage of the maximum power point detected for the specific solar cell assembly is Vp [V], the series number of the specific solar cell assembly is m (m ≧ 1), and the other solar cell assemblies When the series number of the body is n (n ≧ 1), the control means sets the voltage at the maximum power point for the other solar cell assembly to (n / m) × Vp [V]. 3. The photovoltaic power generation inverter device according to claim 2, wherein: 4. A control power supply circuit for generating a power supply voltage of said control means by using a solar cell assembly having a maximum output voltage as an input among said plurality of solar cell assemblies. The photovoltaic power generation inverter device according to any one of the above. 5. The DC power supply circuit according to claim 1, wherein the DC power conversion circuit provided for each of the solar cell assemblies is housed in one housing. 5. The photovoltaic power generation inverter device according to any one of items 4 to 4.