JPH1084633A - Operation of solar power generation inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To most effectively utilize the electrical power generated by the solar power generation by preventing excessive phase leading operation at the time of controlling a linkage voltage and also prevent fluctuation of the power factor of the operation by the phase leading operation control when a plurality units of the inverters are operated simultaneously. SOLUTION: A linkage voltage based on the linkage operation of the power distribution line 5 is detected, the amount of phase shift to the phase leading operation of the power factor depending on the detected voltage is repeatedly obtained when the detected voltage rises exceeding the preset phase leading operation start voltage, the operation phase of the solar power generation inverter 1 is led depending on the amount of phase shift and the solar power generation inverter 1 is controlled to the phase leading operation in the power factor depending on the detected voltage when the detected voltage is higher than the phase leading operation start voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a photovoltaic power generation inverter that forms a so-called distributed power source, and more particularly, to a suppression of an increase in an interconnection voltage (interconnection point voltage).

[0002]

2. Description of the Related Art Conventionally, this type of solar power inverter 1 shown in FIG. 3 uses a current control system as a power conditioner for a solar cell 2 in order to utilize the generated power (active power) of the solar cell 2 as effectively as possible. The inverter unit 3 is connected so that the output current is controlled according to the amount of power generated by the solar cell 2.

[0003] The output side of the inverter unit 3 is connected to a system power supply 6 of a distribution system via a distribution line 5 indicated by a wiring impedance 4, and the solar power generation inverter 1 is connected to the system power supply 6 to operate. The output is supplied to the load 7 together with the system power supply 6.

Next, when the inverter unit 3 is of a voltage-type current control system, the inverter unit 3 is
It is controlled and operated as described below.

That is, the amount of power generated by the solar cell 2 is monitored and detected from the DC voltage and current on the input side of the inverter unit 3, and an amplitude control signal proportional to the amount of power generation is supplied from the voltage control circuit 9 to the multiplier 10. Is done.

The output current of the inverter unit 3 is detected by the current transformer 11, and an output current detection signal having a voltage corresponding to the output current is output from the current transformer 11.

Further, the voltage of the distribution line 5 based on the interconnection operation between the photovoltaic power generation inverter 1 and the system power supply 6, ie, the interconnection voltage, is detected by the transformer 12, and the voltage corresponding to the interconnection voltage of the transformer 12 is detected. The voltage detection signal is supplied to the synchronization detection circuit 13 and the effective voltage value calculation circuit 14.

[0008] Then, the synchronization detection circuit 13 forms a phase-based synchronization pulse synchronized with, for example, the zero-cross point of the interconnection voltage, and supplies this pulse to the phase shift circuit 15 for advanced phase operation.

Further, the effective voltage value calculation circuit 14 obtains the effective value of the interconnection voltage from the voltage detection signal, and supplies the detection signal of the effective value to the phase advance operation start determination circuit 16.

The determination circuit 16 is a voltage effective value calculation circuit 1
The change in interconnection voltage from fourth detection signals detected by monitoring, the interconnection voltage increases to a predetermined fast operation start voltage V _1, and generates a phase advance operation command, moves a phase advance operation of this command Phase circuit 1
5

During normal operation in which no phase-advance operation command is generated, the phase-advance operation phase-shift circuit 15 uses the sine wave signal of the phase of the interconnection voltage as a phase control signal based on the synchronization pulse of the synchronization detection circuit 13. And supplies this signal to the multiplier 10.

At this time, the multiplier 10 multiplies the amplitude control signal of the voltage control circuit 9 by the phase control signal of the phase-advancing phase shift circuit 15 and generates a sine wave that is phase-synchronized with the interconnection voltage of the amplitude of the amplitude control signal. A wave signal is formed and supplied to the subtractor 17.

The subtracter 17 calculates the difference between the output signal of the multiplier 10 and the output current detection signal of the current transformer 11 and corrects the output current of the inverter 3 according to the amount of power generated by the solar cell 2. An error signal is formed.

Further, the error signal of the subtracter 10 is supplied to a current control circuit 18, which forms a reference signal for output current control according to the error signal, and a frequency sufficiently higher than the reference signal and the system frequency. The PWM pulse creating unit 19 creates a PWM drive pulse according to the error signal based on the carrier signal.

When the inverter unit 3 is operated by the PWM drive pulse and the normal operation in which the phase advance operation command is not generated, the output current of the phase of the interconnection voltage corresponding to the power generation amount by the operation at the power factor of 1 is output by the inverter. Output from the unit 3.

By the way, as shown in FIG. 4A, the wiring impedance 4 can be generally equalized by a series circuit of a coil L and a resistor R.

Assuming that the system voltage and the output voltage of the inverter unit 3 (interconnection voltage) are Vs and Vinv, and the output current of the inverter unit 3 flowing through the distribution line 5 is Ia, the power generation amount of the solar cell 2 is zero. At this time, since the output current Ia becomes 0, the output voltage Vinv becomes equal to the system voltage Vs as shown by the voltage vector in FIG. 4B, and the interconnection voltage matches the system voltage Vs.

Next, when the solar cell 2 generates power and generates an output current Ia in the same phase as the system voltage Vs due to the operation at a power factor of 1, the output voltage Vinv becomes as shown in the voltage vector of FIG. The voltage drop V _R (=
Ia · R), the output of the inverter unit 3 corresponding to the amount of power generation is supplied to the load 7, and the power generated by the solar cell 2 is effectively used.

However, only when the output current having the same phase as the system voltage Vs is formed, particularly when the short-circuit capacity of the system power supply 6 is not so large as compared with the capacity of the photovoltaic power generation inverter 1 which is connected and operated. In addition, the load 7 and the like may be in an overvoltage applied state due to an increase in the interconnection voltage due to an increase in the amount of power generated by the solar cell 2.

In order to prevent the occurrence of the overvoltage application state, it is conceivable to limit the output current of the inverter unit 3 when the interconnection voltage rises to some extent. Effective utilization cannot be achieved.

On the other hand, if the interconnection voltage is suppressed by controlling the phase to be advanced instead of limiting the output current, the generation of the overvoltage is prevented by effectively utilizing the power generated by the solar cell. can do.

[0022] Therefore, when the conventional interconnection voltage rises fast operation starting voltage V ₁ of the said phase advance operation start determination circuit 16
, And supplies this command to the phase shift circuit 15 for phase advance operation.

The phase shift circuit 15 for advanced phase operation
The phase control signal is advanced from the phase of the synchronization pulse of the synchronization detection circuit 13.

At this time, the output signal of the multiplier 10 is advanced in phase from the system voltage in accordance with the phase control signal of the phase shift circuit 15 for advanced phase operation.

For this reason, based on the error signal between the output signal of the multiplier 10 and the output current detection signal of the current transformer 11, the inverter unit 3 is driven in the fast-phase operation deviating from the operation of the power factor 1, and the output current Is controlled to a phase advanced from the system voltage.

At this time, assuming that the leading phase of the output current is θ, as shown in FIG. 4D, the output current Ia flowing through the distribution line 5 has a component in phase with the system voltage Vs, Ia · co.
sθ, and the component of the phase leading 90 ° from the system voltage Vs becomes Ia · sinθ.

Therefore, the output voltage Vinv is determined by the system voltage Vs and the voltage drop V _{R of the} resistor R based on Ia · cos θ.
Than added voltage _{Vs + V R (= Vs +} Ia · cosθ) with phase advance component Ia · voltage drop of the coil L based on _{sinθ V L (= -ωL · Ia} · sinθ) decreases, interconnection voltage perform phase advancing operation is suppressed than the voltage Vs + V _R in the absence.

Incidentally, the deviation of the inverter unit 3 into the phase-advanced operation is determined by the power factor 0 from the viewpoint of preventing the inverter unit 3 from being overloaded, as shown in the guideline of the phase-advanced operation method for the distributed power source. .85 is the limit.

Conventionally, a predetermined leading phase operation start voltage V
_{When the} phase-advance operation is started at ₁ , the operation of the inverter unit 3 is continuously advanced until the phase-advance operation with a power factor of 0.85, unless the interconnection voltage falls below the phase-advance operation start voltage V1.

When the interconnection voltage falls below the phase-advance operation start voltage V ₁ by this control, the operation of the inverter unit 3 is gradually returned to the power factor of 1.0.

[0031]

Set the phase advance operation start voltages V ₁ as in the prior [0005], when the interconnection voltage rises to the phase advance operation start voltages V ₁ or more, continuously advancing operation phase to phase, continues to be phase-shifted in the phase advance direction unless reduced to the operation starting voltage V _1, there is a problem that can not be the most effective use of power generated by the solar battery 2.

Further, as shown in FIG. 5, # 1, # 2,
.., #N solar power generation inverters 1
If connected to drive at the same time, unlike the phase advance operation start voltages V ₁ due to variations in circuit characteristics or the like for each inverter 1, when the interconnection voltage rises, the lowest phase advance operation start voltages V ₁ inverter 1 , For example, the inverter 1 of # 1 first shifts to the advanced phase operation.

When the # 1 inverter 1 is controlled in the phase-advance operation, a voltage suppression effect appears by this control, and
Only the inverter 1 of 1 is operated in the leading phase at a power factor of 0.85,
The other inverters # 2,..., #N continue to be operated in the normal operation with a power factor of 1 without being operated in the leading phase.

That is, when a plurality of the photovoltaic power generation inverters 2 are used, some of the inverters 1 are easily operated in the phase-advanced operation and others are not so, and the operating power factor among the inverters 1 varies, and all the inverters 1 are operated. There is a problem that the inverter 1 cannot be operated under the same power factor condition. For example, if one inverter 1 is provided in each house, in an extreme case, only one specific inverter 1 always has a power factor of 0.8.
5, the inverter 1 of each of the remaining doors has a power factor of 1.
In normal operation.

The present invention prevents excessive phase advance operation when suppressing the interconnection voltage so as to make the most effective use of the photovoltaic power, and to reduce the power consumption when a plurality of inverters are operated simultaneously. It is an object of the present invention to suppress the variation of the driving power factor due to the early phase operation.

[0036]

In order to solve the above-mentioned problems, in a method for operating a photovoltaic power generation inverter according to the present invention, an interconnection voltage based on interconnection operation of a distribution line is detected, and the detected voltage is set. When the voltage rises above the phase-advanced operation start voltage, the phase shift amount of the power factor according to the detected voltage to the phase-advanced operation is repeatedly obtained, and the operation phase of the photovoltaic power generation inverter is advanced according to the phase shift amount. When the detected voltage is equal to or higher than the early phase operation start voltage, the photovoltaic power generation inverter is controlled to the early phase operation with a power factor corresponding to the detected voltage.

Therefore, when the interconnection voltage becomes equal to or higher than the phase start operation voltage, the photovoltaic power generation inverter continuously shifts the operation phase in the phase advance direction until the interconnection voltage decreases to the set voltage as in the related art. Rather than being phase-shifted, the operation is controlled to a phase-advance operation with a phase-advance amount corresponding to the detected interconnection voltage.

Therefore, the amount of phase advance of the operation of the photovoltaic power generation inverter changes following the interconnection voltage, so that appropriate phase advance operation without excess or deficiency can be performed, and the power generated by the solar cell is used most effectively. .

In addition, when a plurality of photovoltaic power generation inverters are operated at the same time, and when the interconnection voltage becomes equal to or higher than the phase operation start voltage, each of the inverters is controlled to the phase advance operation of the phase amount corresponding to the interconnection voltage. At this time, even if there is a slight variation in the phase start operation voltage between the inverters, a situation does not occur in which only one inverter is controlled to the phase advance operation, and the inverters are almost equally advanced. The vehicle is driven, and variations in the driving power factor are suppressed.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the configuration of a photovoltaic power inverter 1, and the same reference numerals as those in FIG. 3 denote the same or corresponding components.

The inverter 1 of FIG. 1 is different from that of FIG. 3 in that a phase advance amount setting function circuit 20 is provided instead of the phase advance operation start determination circuit 16 of FIG. Of the output signal of the function circuit 20 based on the output signal of the synchronous detection circuit 1
The point is that a phase shift control signal in which the synchronization pulse No. 3 is shifted in the leading direction is formed, and this signal is supplied to the multiplier 10.

Next, the phase advance amount setting function circuit 20 will be invented. This function circuit 20 is a voltage effective value calculation circuit 1
4 based on the detection voltage of the transformer 12 via, when interconnection voltage distribution line 5 operation start voltages V ₁ or more advanced phase, the phase advance operation limit voltage V ₂ of the interconnection voltage power factor 0.85 In order to linearly vary the advanced operation amount of the inverter unit 3 in accordance with the interconnection voltage until it rises to, the circuit is formed, for example, by a function circuit of the linear characteristic of interconnection voltage-advance amount of FIG. .

[0043] When the interconnection voltage in normal operation of the power factor 1 is raised to the phase advance operation start voltages V ₁ or more, phase advance amount setting function circuit 20, to the operating power factor corresponding to the detected interconnection voltage Is repeatedly determined and determined, and an output signal of the phase advance is supplied to the phase shift circuit 15 for phase advance operation.

[0044] Incidentally, when the interconnection voltage rises phase advance operation limit voltage V ₂ or more, because no driving power factor less than 0.85, to hold the phase advance amount constant amount of power factor 0.85 .

Then, the phase-advancing operation phase-shift circuit 15 supplies the multiplier 10 with a phase-shift control signal corresponding to the phase-advance amount of the output signal of the phase-advance-amount setting function circuit 20, and outputs the output current of the inverter unit 3. Operates the inverter unit 3 so that the phase of the inverter unit 3 is advanced from the interconnection voltage by the advance amount of the output signal of the function circuit 20 for setting the amount of advance.

In this case, the operation of the inverter unit 3 is not continuously advanced until the interconnection voltage falls below the phase-advance operation start voltage V ₁ as in the prior art, but is advanced according to the current interconnection voltage. Since the inverter unit 3 is operated with the phase amount, excessive phase advance operation does not occur, and the generated power of the solar cell 2 can be used most effectively.

As shown in FIG. 6, when a plurality of such solar power generation inverters 1 are operated simultaneously,
Even if there is some variation in the phase advance operation start voltage V ₁ of the,
When interconnection voltage is respective start voltages V ₁ or more, the operation of substantially equal phase advancing amount each inverter 1 according to the interconnection voltages, respectively.

For this reason, as in the prior art, for example, one inverter 1 is operated in a phase-advanced manner at a power factor of 0.85, and the remaining inverters 1 are normally operated at a power factor of 1 so that a deviation occurs in the operation. Instead, each of the inverters 1 is operated in a phase-advanced manner with substantially the same power factor, and the variation in the operating power factor among the inverters 1 is suppressed.

The function characteristics of the function circuit 20 for setting the phase advance amount are not limited to the ramp characteristics shown in FIG. 2, but may be, for example, a staircase wave shape, a quadratic function shape, or the like.

The same effect can of course be obtained even if the control signal of the inverter section 3 is a current signal.

Further, it is needless to say that the present invention can be applied to the case where the limitation of the deviation amount to the phase advance operation is different from the power factor of 0.85 and the case where there is no limitation of the phase advance amount.

[0052]

The present invention has the following effects. When the interconnection voltage of the distribution line 5 becomes equal to or higher than the phase start operation voltage, the photovoltaic inverter 1 is controlled to the phase advance operation of the phase advance amount corresponding to the detected interconnection voltage. The phase advance amount of the first operation changes according to the interconnection voltage, so that an appropriate phase advance operation can be performed, and the power generated by the solar cell can be used most effectively.

In addition, a plurality of solar power generation inverters 1
Are operated at the same time, when the interconnection voltage becomes equal to or higher than the phase-advance operation start voltage, each of the inverters 1 is controlled to the phase-advance operation of the phase-advance amount corresponding to the interconnection voltage. Even if there is some variation in the operation start voltage, a situation in which only one inverter 1 is controlled to the phase advance operation does not occur. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block connection diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a relationship between an interconnection voltage and a phase advance amount in FIG. 1;

FIG. 3 is a block connection diagram of a conventional example.

4A is an equivalent circuit diagram of a part of FIG. 3, and FIGS.
FIG. 4D is a vector diagram for explaining the operation in FIG. 3.

FIG. 5 is a block connection diagram when a plurality of solar power generation inverters are used at the same time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photovoltaic inverter 2 Solar cell 3 Inverter part 5 Distribution line 6 System power supply 7 Load 8 Control part 20 Function circuit for phase advance setting

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H02P 7/63 302 H02P 7/63 302B

Claims (1)

[Claims] 1. A method of operating a photovoltaic power generation inverter connected to a distribution line and connected to a system power supply and controlled to an output current according to a power generation amount, the method comprising: The system voltage is detected, and when the detected voltage rises above the set phase start operation start voltage, the phase shift amount to the phase advance operation of the power factor according to the detected voltage is repeatedly obtained, and according to the phase shift amount. Leading the operation phase of the photovoltaic power generation inverter to a phase leading operation with a power factor corresponding to the detection voltage when the detected voltage is equal to or higher than the phase start operation start voltage. A method of operating a photovoltaic power inverter, comprising the steps of: