JP2003116222A - Self-sustaining control method for distributed power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent voltage unbalancing of a three-phase AC output of an inverter by power supply to a single-phase load without using a Scott connection transformer or the like in a distributed power supply device for a photovoltaic power plant or the like. SOLUTION: When the distributed power supply device is disconnected from a system and operated by self-sustaining to supply the AC output to the load, a detected voltage of the AC output is converted into a two-phase voltage by three/two phase conversion and an effective value of the two-phase voltage for every phase is computed. Respective voltage errors of the two-phase voltage are obtained from a gap between a voltage command value of the AC output and the effective value of the two-phase voltage respectively, two-phase control errors of constant voltage control based on the respective voltage errors of the two-phase voltage are obtained, and the respective two-phase control errors are added to the voltage command value to determine the respective control command values for the two-phase voltage and to form three-phase control command values of the constant voltage control for the inverter by the two/ three-phase conversion of the control command values of the two-phase voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an independent operation control method for a distributed power supply such as a photovoltaic power generator.

[0002]

2. Description of the Related Art In general, a distributed power supply device formed by a so-called private power generation device such as a photovoltaic power generation device is formed as shown in a block diagram of FIG.

FIG. 5 shows a schematic configuration of a photovoltaic power generator, in which a DC output of a solar cell 1 as a DC power supply is supplied via a blocking diode 2 and an input side capacitor 3 composed of an electrolytic capacitor. It is supplied to the AC inverter 4.

[0004] Normally, the inverter 4 is connected and controlled by a drive control unit 5 to control the FET,
Each power semiconductor switch 6 such as an IGBT is switched to convert the DC output into a three-phase AC having a system frequency synchronized with the AC power supply 7.

[0005] Each power semiconductor switch 6 is connected in reverse parallel with a diode 8 for a discharge path.

Then, the three-phase AC power of the inverter 4 based on the above-mentioned interconnection operation control is supplied to the three-phase AC reactors 9, 3
Power is supplied to each load (not shown) of the system bus 13 through the AC filter of the phase filter capacitor 10 and the first and second interconnection switches 11 and 12 of the electromagnetic contact type.

Next, when a power failure occurs in the system due to a disaster or the like, a switch control unit (not shown) opens switches 11 and 12 mainly for the purpose of preventing electric shock on the system side, and the photovoltaic power generator Is disconnected from the system, and the operation of the inverter 4 is temporarily stopped by the drive control unit 5.

Thereafter, the photovoltaic power generator shifts to a self-sustaining operation by manual or automatic operation switching, and the drive control unit 5 controls the self-sustaining operation of the inverter 4. At this time, the switch control unit controls the electromagnetic contactor type. Is closed.

Under the independent operation control of the drive control unit 5, the inverter 4 outputs the three-phase AC output of the system fundamental wave frequency, which is constant-voltage controlled to the system rated voltage, via the switch 14, and the self-contained power supply bus 15 in the premises. Power to the load.

During the interconnection operation and the self-sustaining operation, the voltage and the current inside and outside the power generator are monitored and detected, and the inverter 4 is operated.
In order to control the operation of the motor, as shown in the single-line diagram of FIG. 6 showing a part of the detailed connection of FIG.
It has a D conversion circuit 5a, a digital operation circuit 5b composed of a microcomputer, and a drive pulse output circuit 5c.

A DC voltage (battery voltage) on the input side of the inverter 4 is detected by a voltage detector 16, and an AC current (inverter current) of each phase on the output side of the inverter 4 is detected.
A two-phase or three-phase AC voltage (inverter voltage) is detected by the current detector 17 and the voltage detector 18, and a system voltage of each phase of the bus 13 is detected by the voltage detector 19.

The voltage detection signals of the detectors 16, 18, and 19 and the current detection signal of the detector 17 are converted into digital data by an A / D conversion circuit 5a and supplied to an arithmetic circuit 5b. Note that the voltage detection signal of the detector 19 is also supplied to the switch control unit.

Next, the arithmetic circuit 5b executes the set operation control program with reference to the input detection voltage and detection current data, and supplies a three-phase drive control signal to the output circuit 5c.

Further, the output circuit 5c forms three-phase drive pulses according to the applied drive control signal, and supplies these pulses to the inverter 4 to switch the semiconductor switch 6 of each phase.

When the system is normal, the output circuit 5c forms three-phase drive pulses synchronized with the system by the interconnection operation control of the arithmetic circuit 5b, and the inverter 4 is synchronized with the system by these drive pulses. Connected operation.

On the other hand, when a system power failure occurs due to a disaster or the like, the switches 11 and 12 are opened to disconnect the photovoltaic power generator from the system, and the arithmetic circuit 5b stops outputting the drive control signal and the inverter 4 Operation stops.

Thereafter, when the operation shifts to the self-sustaining operation, the arithmetic circuit 5b conventionally executes the self-sustaining operation control shown in FIG.

[0018] Then, the sum of 3-phase 3-axis U of the AC output of the inverter 4, V, when the phases of W, at step A ₁ in FIG. 7, the detected three-phase voltage V _u, V _v, V _w Under the condition that (vector sum) becomes 0, the detection voltages V _u , V _w of the U-phase and the W-phase of the detector 18 are changed to three axes U, V, W, respectively.
The following equation 1 converts the phase voltage into a two-phase voltage of two axes α and β.
Is converted into two-phase voltages V _a and V _b (vector values) of the axes α and β by the three-phase / two-phase conversion of the following equation.

[0019]

(Equation 1)

Furthermore, in step A _2, the voltage V _a,
An effective value V _{ab · rms} of the AC output (inverter output voltage) of the inverter 4 represented by V _b is obtained from a three-phase collective effective value calculation of the following equation (2).

[0021]

(Equation 2)

[0022] Next, in step A _3, the effective value V
As _{ab · rms} is the output voltage command value V _AC inverter 4 performs P (proportional) I (integral) control operation based on the effective value V _{ab · rms.}

Specifically, first, from the calculation of the following equation (3), the three-phase voltage error Δ
_Find VAC.

[0024]

[Equation 3]

Then, the proportional control voltage V _P and the integral control voltage V _I for the three-phase batch PI control of the AC output of the inverter 4 are obtained from the calculation of the following equation (2). Note that P _G ,
_IG is a set proportional constant and integral constant.

[0026]

(Equation 4)

Further, the voltages V _P and V _I are added and synthesized by the calculation of the following equation (5) to obtain a control error (voltage control gain) V _PI for the three phases of the inverter 4.

[0028]

(Equation 5)

[0029] Then, by adding the control error V _PI to the output voltage command value V _AC in step A _4, 2-phase voltage shown in two equations in the number of the next 6 V _a, the same control command value V _b (amplitude control value)
Va _{· ref} and _{Vb · ref} are determined.

[0030]

(Equation 6)

Next, the control command values Va _{· ref} , V
Control command value Va _{· REF} , V obtained by adding phase information θ to _{b · ref
Find b REF} .

[0032]

(Equation 7)

Furthermore, in step A _5, the command value V
_{a · REF} and _{Vb · REF} are subjected to two-phase / three-phase conversion shown in the following equation (8) to obtain a three-phase control command value (control signal) V for constant voltage control.
_{u · REF} , Vv _{· REF} and _{Vw · REF} are obtained, and the three-phase control command value V
supplies a drive control signal _{u · REF} ~V w _{· REF} to the output circuit 5c.

[0034]

(Equation 8)

The control command value V is output from the output circuit 5c.
A three-phase drive pulse having a pulse width corresponding to _{u · REF to} Vw _{· REF} is formed, and the semiconductor switch 6 of each phase of the inverter 4 is switched by these drive pulses.
A constant voltage control to the command value V _AC voltage to the voltage of the three-phase AC output.

[0036]

In the conventional distributed power supply of this type, the voltage of the AC output of the inverter 4 during the self-sustaining operation is calculated based on the three-phase collective effective value calculation of the equation (2). By the three-phase collective control, control is performed so that the output voltage command value _{VAC has} a constant voltage (constant amplitude) for the entire three phases.

For this reason, the third inverter 4 in the self-sustaining operation
When a single-phase load as well as a three-phase load is directly connected to the self-contained power supply bus 15 to which a phase output is supplied, the voltage of the phase to which the single-phase load is connected even if the entire three phases are controlled to a constant voltage. The voltage of the phase to which the single-phase load is not connected rises, and the voltage imbalance of each phase occurs, and depending on the capacity and the number of single-phase loads, a significant voltage imbalance between phases occurs.

Then, in order to prevent this voltage imbalance,
It is conceivable that a single-phase load is equally distributed and connected to each phase, and each phase equally shares the single-phase load. However, it is practically difficult to realize such a load distribution.

Therefore, conventionally, as shown in FIG. 5, a Scott connection transformer 20 is provided on the self-contained power supply bus 15 and a single-phase load 21 is connected to the secondary side of the transformer 20 so that the single-phase load is reduced. Even if it is connected, the load becomes a three-phase balanced load when viewed from the inverter 4 side (power supply side). In addition, 22 in the figure indicates a three-phase load of the bus 15.

Therefore, conventionally, when performing independent operation control of this type of distributed power supply device, a complicated and expensive Scott is used in order to prevent three-phase imbalance of the voltage of the AC output of the inverter 4 by connecting a single-phase load. There is a problem that requires the connection transformer 20.

According to the present invention, in a distributed power supply of this type, the three-phase voltage imbalance of the AC output of the inverter due to the power supply to the single-phase load does not occur without using the Scott connection transformer 20 or the like. That is the task.

[0042]

In order to solve the above-mentioned problems, a self-sustaining operation control method according to the present invention comprises a distributed power supply device for converting a DC power supply such as a solar cell into a three-phase AC output by an inverter. It is disconnected from the system and operates in a self-sustaining operation, and when a constant voltage control is applied to the three-phase AC output of the inverter 3 to supply power to the load, the detected voltage of the AC output is converted to a two-phase voltage by three-phase / two-phase conversion Then, an effective value of each phase of the two-phase voltage is calculated, and a voltage error of each of the two-phase voltages is obtained from a difference between a voltage command value of the AC output and each of the effective values of the two-phase voltages.
A two-phase control error of the constant voltage control based on each voltage error of the phase voltage is obtained, and each of the two-phase control errors is added to the voltage command value to determine a control command value of each of the two-phase voltages.
A three-phase control command value for constant voltage control of the inverter is formed by two-phase / three-phase conversion of the control command value of the phase voltage.

Therefore, during autonomous operation, the inverter 3
On the basis of the two-phase voltage obtained by the three-phase / two-phase conversion of the three-phase AC output, the effective value of the AC output of the inverter is determined by the three-phase / two-phase conversion instead of the three-phase batch operation of the equation (2). Is calculated for each phase of the two-phase voltage.

Further, a voltage error for each phase is determined from a difference between the voltage command value of the AC output of the inverter and the effective value for each phase of the two-phase voltage, and based on these voltage errors,
A control error of the constant voltage control of the inverter is determined individually for each phase of the two-phase voltage, and a control command value is determined.

The control command values of the AC output of the inverter are individually obtained for each phase by two-phase / three-phase conversion of these control command values, and the independent operation of the inverter is controlled based on these control command values. Is done.

Then, on the basis of the control error of the two-phase voltage of the constant voltage control, the voltage of each phase of the inverter is individually suppressed and controlled to follow each fluctuation, and the voltage of each phase of the AC output of the inverter is reduced. , And is controlled to a constant command voltage.

Therefore, the three-phase AC output of the inverter during the self-sustained operation is controlled at a constant voltage for all three phases.
Constant voltage control is also performed for each phase, and voltage imbalance between phases based on power supply to a single-phase load is prevented without using a Scott connection transformer.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. This embodiment is applied to the independent operation control of the photovoltaic power generator of FIG. In FIG. 2, the same reference numerals as those in FIG. 5 denote the same or corresponding elements, and the difference between the photovoltaic power generator of FIG. 2 and the conventional apparatus of FIG. The point is that the three-phase load 22 and the single-phase load 21 are directly connected without providing the 20.

Further, at the time of self-sustaining operation, the drive control unit 5 shown in FIG.
In the digital computing circuit 5b shown in a point to perform autonomous operation control of Step B ₁ .about.B ₅ in FIG.

[0050] When the system in disaster shifts to autonomous operation by a power failure, in step B _1, Step A of FIG. 7
₁ from the calculation of a manner of the number 1 wherein the same manner as, and converts the detected voltage V _u of the three phases, the V _w 2-phase voltages V _a, the V _b.

Next, in step B _{2, 2} axis α, β
Voltage V _a, instead of obtaining the effective value V _{ab · rms} three phase batch of V _b, the voltage V _a, V _b each effective value V _{a · rms,} V
_{b · rms} is obtained by digital arithmetic of individual root mean squares.

Next, in step B _3, the effective value V
_{a · rms,} as V b _{· rms} is the output voltage command value V _AC inverter 11, respectively, perform effective value V _{a · rms,} individual PI control calculation of V b _{· rms.}

At this time, first, voltage errors ΔV _a and ΔV _b between the command value _VAC and the effective values Va _{· rms} and _{Vb · rms} are calculated from the following two equations (9).

[0054]

(Equation 9)

Further, from the calculation of the following two equations of Expression 10,
Two-phase voltage V of AC output of inverter 4 _a, V_bOne for each
PI control proportional control voltage V_ap, V_bpAsk for. What
Contact, P in the formula_GIs a set proportionality constant.

[0056]

(Equation 10)

Further, from the calculation of the following two equations of Expression 11,
2-phase voltage V _a of the AC output of the inverter 4, V _b integral control of the PI control for each voltage V _aI, seek V _bI.
Note that it is integral constant I _G is the set of in the formula.

[0058]

[Equation 11]

Then, the two control voltages V _ap , V a
_bp and the number 11 of the two equations of the control voltage V _aI, adds the V _bI for each phase, two-phase voltages V _a, based on the PI control of V _b, 2 Number 12
The control errors (voltage control gains) V _apI and V _bpI for each phase in the equation are _obtained .

[0060]

(Equation 12)

Next, in step B _4, the output voltage command value V _AC to control error V _API, adds each V _BPI, 2-phase voltage V _a shown in two equations in the number of the next 13, the V _b individual The control command values (amplitude control values) Va _{· ref} ′ and _{Vb · ref} ′ are obtained and determined.

[0062]

(Equation 13)

Then, the control command value V is obtained from the calculation of the following two equations (14) similar to the two equations (7) based on the phase information θ.
_The control command values Va _{· REF} ′ and _{Vb · REF} ′ are obtained by adding the phase information θ to each of _{a · ref} ′ and _{Vb · ref} ′.

[0064]

[Equation 14]

Further, the control command values Va _{· REF} ′ and _{Vb · REF} ′
Then, two-phase / three-phase conversion of the following equation (15) similar to the equation (8) is performed, and the three-phase control command of the constant voltage control corresponding to the conventional command values Vu _{· REF to} Vw _{· REF} is performed. Value V _{u · REF} ', V _{v · REF} ', V
_{w ・ REF} ' And the three-phase control command value V _{u · REF} 〜
_Vw.REF 'is supplied to the output circuit 5c.

[0066]

[Equation 15]

The command value V is output from the output circuit 5c.
A three-phase drive pulse having a pulse width corresponding to _{u · REF} ′ to Vw _{· REF} ′ is formed, and the semiconductor switch 6 of each phase of the inverter 4 is switched.

[0068] At this time, the voltage of the AC output of the inverter 4 is not only the whole 3-phase is the constant voltage control with the voltage of the command value V _AC, is clear from the comparison between the numerical formula 6 and the number 13 formula as such, while the conventional two-phase voltages V _a is a three-phase collective control, V _b control command value V _{a · ref} of the V b _{· ref} are the same,
2-phase voltage V _a in the present embodiment, the control command value V _{a · ref} of V _b ',
V b _{· ref} 'is 2-phase voltage V _a due to the voltage error of each of the 3-phase phase control error V _{a pI} of V _b, since different depending V _BPI, constant voltage as each phase voltage is also balanced Controlled.

Therefore, the single-phase load 2
1 can be connected directly to the inverter 4 based on the load imbalance.
The three-phase imbalance of the AC output is automatically prevented, and the conventional Scott-connected transformer 20 can be omitted to provide stable load power supply during self-sustaining operation.

Note that the AC output of the inverter 4 is
When a 200 V three-phase load and a 100 V single-phase load are connected to the self-supporting power supply bus 15 at 0 V, as shown in FIG. The primary side of the single-phase 200 V / 100 V conversion single-phase transformer 23 may be connected to these two phases, and the secondary side output may be supplied to the single-phase load 21 ′.

Further, the AC output of the inverter 4 is
0V, all the loads connected to the independent power supply bus 15 are 100
In the case of a single-phase load of V, as shown in FIG. 4, for example, two phases of V and W of the independent power supply bus 15 may be directly connected to each single-phase load 21 ′.

The present invention can be similarly applied to a case where the DC power supply is another power supply such as a storage battery or a fuel cell.

[0073]

The present invention has the following effects. In the case of self-sustained operation when the system goes out of power due to a disaster, the inverter 4
Of the inverter AC output based on the two-phase voltage obtained by the three-phase / two-phase conversion of the three-phase AC output, It can be obtained by calculation for each phase.

Further, based on the two-phase voltage error of the difference between the voltage command value of the AC output of the inverter 4 and the effective value of each of the two-phase voltages, each of the two-phase voltages is individually The control error of the constant voltage control of the inverter 4 can be obtained, and both control errors change variously according to the deviation of the AC output of the inverter 4 from the voltage command value of each phase voltage.

Then, based on the two control errors, a control command value for each phase of the two-phase voltage is determined.
By the phase / 3-phase conversion, control command values of the AC output of the inverter 4 are individually obtained for each phase, and the independent operation of the inverter 4 is controlled based on these control command values.

Then, on the basis of the control error of each phase of the two-phase voltage, the voltage of each phase of the AC output of the inverter 4 is individually subjected to the constant voltage control following the respective fluctuations.
Since the AC output of the inverter 4 is constant-voltage controlled to the voltage of the control command value, the AC output of the inverter 4 is not only constant-voltage controlled as a whole of three phases but also constant-voltage controlled for each phase.

Therefore, during the self-sustained operation, voltage imbalance based on power supply to the single-phase load of the three-phase AC output of the inverter 4 can be prevented simply and inexpensively without using a Scott connection transformer or the like.

[Brief description of the drawings]

FIG. 1 is a flowchart of an independent operation control according to one embodiment of the present invention.

FIG. 2 is a block connection diagram of the photovoltaic power generator performing the self-sustaining operation control of FIG.

FIG. 3 shows a three-phase load of 200 V and one
It is a connection diagram at the time of connecting with a single phase load of 00V.

FIG. 4 is a connection diagram when only a single-phase load of 100 V is connected to the self-contained power supply bus of FIG. 2;

FIG. 5 is a block connection diagram of a conventional solar power generation device.

FIG. 6 is a single-line diagram showing a detailed configuration of a part of FIG. 5;

FIG. 7 is a flowchart of the self-sustained operation control of FIG. 6;

[Explanation of symbols]

1 solar cell 4 Inverter

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 5G066 GA01 GB02                 5H007 AA07 AA17 BB07 CA01 CB04                       CB05 CC03 CC23 DA03 DA06                       DB02 DB07 DB12 DC04 DC05                 5H420 BB12 CC03 DD04 EA11 EA45                       EB25 EB39 FF03 FF11 FF22                       FF23 FF25

Claims (1)

[Claims] 1. A distributed power supply device for converting a DC power supply such as a solar cell into a three-phase AC output by an inverter is separated from a system, operates in an independent operation, and supplies a constant-voltage control of the AC output to a load. In this case, the detected voltage of the AC output is converted into a two-phase voltage by a three-phase / two-phase conversion, an effective value of each phase of the two-phase voltage is calculated, and the voltage command value of the AC output and the two-phase voltage are calculated. A voltage error of each of the two-phase voltages is obtained from a difference between each of the effective values of the voltages, and a control error of the two phases of the constant voltage control is obtained based on each of the voltage errors of the two-phase voltages. The control command value of each of the two-phase voltages is determined by adding the respective control errors of the phases, and the three-phase control command of the constant voltage control of the inverter is performed by performing two-phase / 3-phase conversion of the control command value of the two-phase voltage. Forming a value An independent operation control method for a distributed power supply.