JP2730383B2 - Parallel operation control device for AC output converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a means for controlling a current balance between converters in a power supply system in which a plurality of AC output converters such as inverters are connected in parallel and a common load is operated in parallel. .

[0002]

2. Description of the Related Art FIG. 15 is a block diagram showing a conventional parallel operation system of AC output converters disclosed in, for example, JP-B-53-36137 and JP-B-56-13101.

In FIG. 1, a No. 1 inverter 1 supplies power to a load 4 while operating in parallel with a No. 2 inverter 2 of the same configuration through an output bus 3. The first inverter device 1 includes an inverter body 100, a filter reactor 101, and a capacitor 102 as main components, converts the power of the DC power supply 5 into AC, and is connected to the output bus 3 through an output switch 103a. Inverter device 1
No. 1 inverter 1
From the output current I ₁ of the detection signal I _1a by the CT 200a
And a difference from the detection signal I _2a obtained from the second inverter device 2, that is, a signal ΔI ₁ corresponding to the cross current is obtained by the cross current detection circuit 151. Then from the phase shifter 150, creating two voltage vectors E _A and E _B orthogonal to obtain a reactive power corresponding component ΔQ and an active power corresponding component ΔP respectively by the arithmetic circuits 152 and 153 from the [Delta] I ₁ signal. The inverter controls the voltage control circuit 403 based on the signals of the voltage setting circuit 7 and the voltage feedback circuit 300, and controls the pulse width modulation circuit (hereinafter referred to as P).
The pulse width modulation of the inverter body 100 is performed via the WM circuit 400 to control the internally generated voltage.

[0004] reactive power corresponding component ΔQ described above auxiliary signal to be supplied to the voltage control circuit 403, the inverter 10
By adjusting the internally generated voltage of 0 to about several percent, ΔQ
Works to zero.

On the other hand, the above-mentioned active power corresponding component ΔP is a PLL
(Phase Locked Loop) Amplifier 15 Constituting Circuit
4, the frequency of the reference oscillator 155 is finely adjusted to control the phase of the internally generated voltage of the inverter body 100, and to operate so that ΔP becomes zero.

In this way, since the voltage and phase are controlled so that both ΔQ and ΔP become zero, there is no cross flow between the two inverters, and stable load sharing is performed.

[0007]

Since the conventional converter parallel operation system is configured as described above, there are the following five problems. The first problem is that it is difficult to improve the response speed of the control in order to balance the shared current by controlling the phase of the internally generated voltage of the inverter and the average value of the voltage. That is not possible. The second problem is that cross-flow control cannot be performed at high speed because a filter is required to detect and separate cross flow into effective and ineffective components. Therefore, there is a limit to the application to high-speed voltage control systems such as instantaneous waveform control that maintains the output of the inverter as a high-quality sine wave with little distortion. The third problem is that
It is difficult to operate the converter and other power sources in parallel, and it is especially difficult to control the cross current when trying to operate the converter and the power system in parallel.

The fourth problem is that it is difficult to perform test adjustment in parallel operation, and test adjustment cannot be performed unless each inverter is actually connected to the output bus 3 and operated. The fifth problem is that since the output current of the inverter contains harmonic components included in the load current, harmonics flow in the cross current detection circuit and control errors occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a parallel operation control device for an AC output converter that balances a shared current at a high speed and that can easily perform test adjustment. is there.

It is another object of the present invention to provide a means which can be universally applied not only to inverters but also to parallel operation of other instantaneous control type AC output converters.

[0011]

A parallel operation control device for an AC output converter according to the present invention uses the output of the converter as a load.
When connected in parallel to the simulated bus for separated parallel operation control
In both cases, the signal flowing through the simulated bus
Detects the cross current of the current flowing through the
Multiplication function to create a correction signal, and
By correcting the control signal of the voltage control circuit,
This is to suppress the cross current. Also strange
Simulation of converter output for parallel operation control separated from load
Connected in parallel to the bus,
The cross current of the current flowing between the converters is detected and this cross current is detected.
Create a first correction signal by multiplying the minute by a predetermined transfer function
At the same time, the cross current is mainly converted to a phase difference between the converters.
The first component and the voltage difference mainly between the converters
Detected as a second component caused by the
Changes the output voltage phase and average value of the converter
A second correction signal is generated, and the first and second correction signals are generated.
Correcting the control signal of the voltage control circuit with a signal
Thus, the above-mentioned cross flow component is suppressed.

Further, for each converter, drive control of the converter is performed.
Model for parallel operation control driven by the same control signal as the
A pseudo-transformer is provided and its output is separated from the above-mentioned load.
Connected in parallel to the simulated bus for train operation control and
Current flowing between the transducers from the signal flowing through the pseudo bus
Of the cross current, and multiply this cross current by a predetermined transfer function.
To generate a correction signal, and the voltage
By correcting the control signal of the control circuit,
This is to suppress it.

The above description can be applied to a case where one or more AC output converters are operated in parallel with another power supply system .

[0014]

[Action] In the present invention, it detects a cross current component between mutual converter and power supply system from a signal flowing in the simulated bus, the cross current component
Is multiplied by a predetermined transfer function.
By correcting the control signal of the voltage control circuit of the converter.
Suppress flow.

[0015]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the first inverter device 1
Supplies electric power to the load 4 while operating in parallel through the output bus 3 and the No. 2 inverter device 2 of the same configuration simplified in the figure. 5 is a DC power supply connected to the 1st inverter device 1, 6 is a DC power supply connected to the 2nd inverter device 2, 8 is an output voltage reference circuit that gives an output voltage reference to each inverter, and 9 is an output voltage reference circuit. Simulated bus with output connected. In addition, the same numbers are assigned to the functions corresponding to those in FIG. 15 described above. FIG. 15 shows an inverter device that controls the average value of the output voltage, whereas FIG. Since it is an inverter device that controls the average value, the same number is not necessarily the same function circuit.

Numbers 100 and thereafter are constituent elements of the inverter device. A number without a suffix and a number with a suffix a are components of the first inverter device 1, and a number with a suffix b is a second inverter device. It is a component of the device 2.

Reference numeral 100 denotes an inverter body, which is constituted by a self-extinguishing element such as a transistor or a MOSFET capable of high-frequency switching, for example, a three-phase bridge inverter as shown in FIG. Each arm of a single-phase bridge inverter has an output frequency (for example, 60
It switches at a high frequency of about 10 times to several hundred times of (Hz), and converts a DC voltage into a rectangular high-frequency AC voltage containing a sinusoidal fundamental wave. Numerals 101 and 102 denote a reactor and a capacitor constituting a low-pass filter, which removes harmonics from a rectangular high-frequency AC voltage generated by the inverter main body 100, obtains a sine wave output voltage, and outputs the sine wave output voltage through an output switch 103a. Connected to output bus 3.

Reference numeral 200a denotes the output current I ₁ of the _first inverter device, and 201 denotes the output current I of the inverter body 100.
_A1 and 203a are current sensors for detecting the current flowing through the simulated bus 9, respectively. 202a is an insulating transformer for insulating the inverter output from the simulated bus. A switch 204a opens and closes a simulated bus in conjunction with the output switch 103a. Reference numeral 300 denotes a voltage sensor that detects the voltage of the capacitor 102 (the output bus voltage during parallel operation).

Reference numeral 400 denotes a PWM circuit for determining the switching timing of the inverter main body 100. For example, a triangular wave comparison type PWM for switching the inverter main body 100 at the intersection of a voltage command signal for a fundamental wave to be output from the inverter main body 100 and a triangular wave carrier. It is a circuit. 40
1 is the instantaneous current control circuit for controlling the output current I _A1 of the inverter 100. 402 is the inverter body 100
This is a limiter circuit that limits the output current command value. 40
An instantaneous voltage control circuit 3 controls the voltage of the capacitor 102. Reference numeral 404 denotes a capacitor current reference generation circuit that outputs a current value to be passed through the capacitor 102 to generate a desired output voltage. 405 is the first inverter device 1
This is a cross-current limiting virtual impedance circuit for virtually inserting an impedance Z between the inverter device 2 and the second inverter device 2 so as to limit the cross current.

500, 501, 502, 503, 504
Is an adder / subtracter.

The No. 2 inverter 2 has the same configuration as the No. 1 inverter 1, and the output is connected in parallel with the No. 1 inverter 1 through the output bus 3 and the simulated bus 9. 103b is the No. 2 inverter 2 Output switch, 2
00b is a current sensor for detecting an output current I ₂ of the No. 2 inverter device 2, 203b is a current sensor for detecting current flowing in the simulated bus from No.2 inverter device, 204b is a switch for opening and closing a simulated bus.

Next, the operation will be described.

This inverter device is provided with a current minor loop. The instantaneous current control circuit 401 uses the current command I _A1 ^* from the limiter circuit 402 to output the output current I _A1 of the inverter body 100 fed back by the current sensor 201 ^. A command value of a voltage to be applied to reactor 101 is output so as to match. Since the output bus 3 has a voltage by the capacitor 102 and the No. 2 inverter device 2, to apply a desired voltage to the reactor 101,
The inverter body 100 needs to generate the sum of the voltage of the output bus 3 and the voltage to be applied to the reactor 101.
Therefore, the capacitor 102 detected by the voltage sensor 300
And the output of the current control circuit 401 are added by an adder 500, and this signal is used as a voltage command as a triangular wave comparison type PW
Give to the M circuit 400.

The capacitor current reference generating circuit 404 generates a sine wave current reference having a phase advanced by 90 degrees from the voltage command V ₁ ^* of the capacitor 102 according to the capacitance of the capacitor 102 as a current to flow through the capacitor. It will be described later that the voltage command V ₁ ^* of the capacitor 102 is obtained from the output of the subtractor 504. The instantaneous voltage control circuit 403 receives, as an input, a signal obtained by calculating the difference between the voltage command V ₁ ^{* of} the capacitor 102 and the voltage of the capacitor 102 detected by the voltage detector 300 by the subtractor 503, and reduces the difference. The inverter 100 outputs a correction current signal to be output.

Output current command value I of inverter body 100
_A1 ^* is an adder 5 that adds the output of the capacitor current reference generation circuit 404 and the instantaneous voltage control circuit 403 to the load current signal I _L1 ^* of the first inverter device 1 output by the current sensor 200.
02 is a signal whose result is calculated by the limiter circuit 402. Therefore, in a no-load state, the inverter body 100 establishes a no-load voltage by supplying a current to flow to the capacitor 102. In this case, the instantaneous voltage control circuit 403 corrects an excess or deficiency of the output of the capacitor current reference generation circuit 404 caused by an error in current control or an error between a design value of the capacitance of the capacitor 102 and an actual value. Next, when the load 4 is turned on, the load current signal I _L1 ^* is given as a command from the current sensor 200 to the current minor loop, and the inverter shares the load current. Here, the limiter circuit 402 limits the command value to the current control circuit 401 to be equal to or less than the current allowable value of the inverter body 100 so that the inverter body 100 does not supply an overcurrent such as an inrush current at the time of starting the load.

With this configuration, the inverter is protected against overcurrent by its own current minor loop, and also quickly follows the distortion or sudden change in load current so that the output voltage is always sinusoidal. Can keep on the waves. The feature of this method is that such control is performed every time the high frequency PWM of the inverter is switched,
The response is very fast. For example, when a switching frequency of 10 kHz is used, control is performed every 100 μsec. Therefore, a transient phenomenon such as a sudden change in load can be completed in about 10 times of 100 μsec, and excellent control performance can be obtained.

When the response and accuracy of the voltage control systems of the first inverter device 1 and the second inverter device 2 are exactly the same, no cross current flows in the above control system configuration. Due to variations in gain, main circuit constants, etc., stable parallel operation with little cross current is difficult if it is left as it is. For example, the voltage sensors of the first inverter device 1 and the second inverter device 2 are -0.5% and + 0.5%, respectively.
% Error, the output voltage difference ΔV during isolated operation is 1%. If the wiring impedance between the inverters is 1% or less, the cross current will flow 100% or more.

According to the present invention, the cross current is detected by detecting the cross current flowing between the inverters and configuring the control circuit so that the impedance exists only for the cross current as follows.

The output of the No. 1 inverter 1 is connected in parallel to the simulated bus 9 via the insulating transformer 202a and the switch 204a, and the output of the No. 2 inverter 2 is also connected via the insulating transformer 202b and the switch 204b. Connected to the simulation bus 9. Now switches 204a, b are on
In this case, since the simulated bus 9 is a circuit in which the load is removed from the equivalent circuit of the main circuit, the current flowing therethrough is a cross current component ΔI between the inverters (for example, for the first inverter device: ΔI ₁ = I ₁ −I _L / n) only. Therefore, the current sensor 203 detects only the cross current flowing between the converters.

The virtual impedance circuit 405 for limiting the cross current
Calculates a correction signal by calculating ΔI ₁ × Z (ΔI ₁ is a cross flow, and Z is a transfer function of a virtual impedance), and outputs the correction signal to the output voltage output from the output voltage reference circuit 8. subtracted from the command value V ^*, a voltage command of this capacitor 102 V ₁ ^*
And The voltage of the capacitor 102 instantaneously follows the voltage command V ₁ ^* by the above-described voltage control system.

Referring now to FIG. 3, it will be described that the inverter has an output impedance of Z only for the cross current and operates as a low-impedance voltage source for current components other than the cross current by the cross current limiting virtual impedance circuit 405. . FIG. 3 is a simplified block diagram of the instantaneous cross current controller of FIG. 1. In FIG. 3, 700a and 700b denote voltage command values V ₁ ^* and V ₂ ^{* of the} _first inverter device 1 and the second inverter device 2, respectively. The transfer function up to the output voltage is shown. Other numbers are already described in FIG. 1 described above, and the same functions are given the same numbers. Some symbols have already been used, but the following symbols are defined anew. V _B : Output bus voltage V ^* : Output voltage command value V ₁ ^* : No. 1 inverter capacitor voltage command value V ₂ ^* : No. 2 inverter capacitor voltage command value _IL : Load current I ₁ : No. 1 inverter output current I ₂ : No. 2 inverter output current ΔI ₁ : No. 1 inverter cross current (= I ₁ −I _L / 2) ΔI ₂ : No. 2 inverter cross current (= I ₂ −I _L / 2) G ₁ : Transmission of No. 1 inverter voltage control system Function G ₂ : Transfer function of No. 2 inverter voltage control system Z: Cross-current limiting virtual impedance value Using these symbols, a relational expression showing the effect of the cross-current limiting virtual impedance will be derived next.

From Kirchhoff's law, the following equation holds. I _L = I ₁ + I ₂ (1) From equation (1), ΔI ₁ and ΔI ₂ are as follows. ΔI ₁ = I ₁ −I _L / 2 = (I ₁ −I ₂ ) / 2 (2) ΔI ₂ = I ₂ −I _L / 2 = (I ₂ −I ₁ ) / 2 (3) ΔI ₂ = − ΔI ₁ (4) From FIGS. 3 and (4), V ₁ ^* and V ₂ ^* are as follows. V ₁ ^* = V ^* −Z × ΔI ₁ (5) V ₂ ^* = V ^* −Z × ΔI ₂ = V ^* + Z × ΔI ₁ (6) From the definitions of G ₁ and G ₂ , the following equation holds. V _B = V ₁ ^* × G ₁ (7) V _B = V ₂ ^* × G ₂ (8) From the equations (5) to (8), the following equation is established. V _B = V ^* × G ₁ −Z × ΔI ₁ × G ₁ (9) V _B = V ^* × G ₂ + Z × ΔI ₁ × G ₂ (10) From equation (9)-(10), ΔI ₁ is This gives the following equation.

(Equation 1)

When the equation (9) + (10) is obtained and divided by 2, the following equation is obtained.

(Equation 2)

From equation (11), it can be seen that the cross current can be suppressed by the virtual impedance value Z. That is, since the gain of G ₁ and G ₂ can be set to almost 1 at the output frequency by configuring the voltage control system by the instantaneous voltage control type as described above, the equation (11) becomes the following equation. .

(Equation 3)

Assuming that the output voltage difference between the individual inverter devices in the case of the isolated operation is ΔV, the equation (13) becomes the following equation.

(Equation 4) For example, when ΔV is 1%, if Z is selected to be 50%, the cross current is ΔV / (2 × Z) = 1% / 100% = 1%.

Next, the second term on the right side of the equation (12) becomes the following equation by substituting the equation (13).

(Equation 5)

Since ΔV is as small as about 1%, (ΔV) ²
≒ 0. Therefore, equation (12) has only the first term on the right-hand side, and is given by the following equation.

(Equation 6) (16) from the equation, bus voltage V _B of the parallel operation becomes the output voltage average value of the individual inverter during isolated operation, there is no influence of the virtual impedance value Z.

Z may be any transfer function as long as it has an appropriate impedance value for limiting the cross current at the output frequency. For example, if this circuit is a proportional circuit, Z is a resistor; if it is a differential circuit, Z is a reactor; if it is an integrating circuit, Z is a capacitor;
If it is a combination circuit of integration and differentiation, Z operates as a combination circuit of resistor, capacitor and reactor.
In addition, Z can stably limit the cross current even in a circuit including a non-linear element such as an asymmetrical limiter as long as it has an appropriate impedance value for limiting the cross current at the output frequency.

In the above description, for the sake of simplicity, the description has been made ignoring that the current and the voltage are vector quantities. However, the same relationship holds even with vector quantities.

Next, a method for performing test adjustment by connecting only the simulated buses in parallel before the main circuits are operated in parallel will be described. During normal parallel operation, the switch 204 is opened and closed in conjunction with the output switch 103, so that parallel control is performed only when the inverter is actually operating in parallel. However, only the switch 204 is kept with the output switch 103 off. When turned on, the parallel operation control can be adjusted while the inverter is disconnected from the output bus 3. Therefore, sufficient adjustments can be made in advance even when the devices are operated in parallel for the first time. You can also adjust the inverter.

Although the control method of FIG. 1 described above is an example of a single-phase inverter, it can be applied to a three-phase inverter by providing a similar control circuit for each phase or for two phases.

In the above description, two inverters having the same capacity have been described for simplicity. However, the present invention can be applied to parallel operation of n converters having different capacities. In this case, all converters should be configured to share the load in proportion to the capacity.

Embodiment 2 FIG. Next, an example of controlling the average value by separating the cross flow into two components will be described with reference to FIG.

If the No. 1 and No. 2 inverters are operated in parallel only by the virtual impedance Z as in the first embodiment, as described above, the voltage difference ΔV between them and the difference ΔI = ΔV / (2 × Z). Since this cross-flow active power component is reversibly converted by the inverter, for example, when two inverters are operating in parallel with no load, the DC power of one inverter is changed to the DC power of the other inverter. Active power will flow. If the DC power supplies 5 and 6 cannot regenerate power, such as a thyristor rectifier, the DC voltage rises due to the inflow of the active power, which may cause an overvoltage.

In FIG. 4, each device has an individual voltage reference generation circuit, and in order to suppress such inflow of active power and to operate stably in parallel without DC overvoltage, a cross current Δ
I ₁ is separated into two components ΔI _1P and ΔI _1Q and controlled.

From equation (14), the cross flow ΔI ₁ is

(Equation 7) . FIG. 5 shows a vector diagram in the case where the absolute values of V ₁ ^* and V ₂ ^* coincide and V ₂ ^* lags behind V ₁ ^* by the phase angle θ. Here, if the resistance component of the virtual impedance Z is R and the reactance component is X, Z = R + j
The impedance angle α can be expressed as α = argZ = tan ⁻¹ (X / R) (17) According to this vector diagram, the cross flow vectors ΔI ₁ and ΔI ₂ do not have a component parallel to the virtual voltage vector Er delayed by α from the bus voltage vector V _B, and have another virtual voltage advanced by 90 ° from the virtual voltage vector. Vector E
It has only components parallel to x.

FIG. 6 shows that there is no phase difference between V ₁ ^* and V ₂ ^* ,
A vector diagram is shown for a case where the absolute value of ₂ ^* is smaller than the absolute value of V ₁ ^* . From this vector diagram, the crossflow vector Δ
I ₁ and ΔI ₂ have only components parallel to the virtual voltage vector Er delayed by α from the bus voltage vector V _B, and do not have components parallel to Ex.

From FIGS. 5 and 6, among the cross current components ΔI ₁ and ΔI ₂ , those components caused by the phase difference between V ₁ ^* and V ₂ ^* are perpendicular to the virtual voltage vector Er of these cross current vectors. It can be seen that the component is a component (a component parallel to the virtual voltage vector Ex). In other words, of the cross current components ΔI ₁ and ΔI ₂ , the component caused by the phase difference between the two voltage command values V ₁ ^* and V ₂ ^* has the load bus voltage vector V _B of 90 °.
It is equal to the ineffective component of each cross current component ΔI ₁ , ΔI _{2 based on} the voltage Ex obtained by advancing the phase by −α.

Similarly, each of the cross flow components ΔI ₁ and ΔI ₁
Of I ₂ , components resulting from the voltage absolute value difference between both voltage command values V ₁ ^* and V ₂ ^* are the cross current components ΔI ₁ , ΔI _{2 of} these cross current vectors based on virtual voltage vector Er.
You can see that it is equal to the effective component of.

Returning to FIG. 4, the description will be continued. A converter 411 converts the cross current ΔI ₁ detected by the current sensor 203 into two orthogonal components ΔI _1P and ΔI _1Q (DC signals). These converters include a synchronous rectifier circuit or a multiplier and a smoothing filter. Is performed. The component ΔI _1P is the current ΔI ₁
Is the effective component based on the voltage Er of the current, and ΔI _1Q is the current Δ
It is a reactive component relative to the voltage Er of I _1.

ΔI _1P is set by the adder / subtractor 506 by the setting unit 40.
9 is subtracted from the voltage command value from the control unit 9 and input to the average voltage control circuit 408 as a reference voltage. On the other hand, the output voltage of the inverter device is determined by the voltage detector 300 and the average value circuit 410.
Through the adder / subtracter 5 as a feedback voltage of an average value
05 is subtracted from the reference voltage.

[0052] [Delta] I _1Q is directed to the input end of the phase adjustment device 412. Phase signal output from the phase adjuster 412 adjusts the output phase of the oscillator 414 by shifting <br/> phase 413,
A sine wave signal sinωt which is a phase reference of the output voltage is created.

The multiplier 407 includes an average voltage control circuit 40
The absolute value of the output voltage reference output from 8 | V ^* | and the sine wave signal sin .omega.t output from the phase shifter 413 is input, the output voltage command value ^{V * = | V * | ·} sinωt is outputted . This signal V ^* is input to the subtractor 504.

As described above, the signal for controlling the output voltage phase is corrected by the component ΔI _1Q caused by the phase difference between the inverters of the cross current ΔI ₁ , and the voltage is controlled by the component ΔI _1P caused by the voltage absolute value difference. The control is performed so as to reduce the cross current by correcting the signal to be generated . This control may be performed relatively slowly as long as the crossflow does not become harmful.

Embodiment 3 FIG. Next, an example in which a simulated inverter that simulates an inverter is used to detect a cross current will be described with reference to FIG. In the figure, reference numeral 206 denotes the inverter body 1
00 is a simulated inverter driven by a common PWM circuit 400, the output of which is connected to the simulated bus 9 via an insulating transformer 202 and a switch 204. Although not shown, a filter equivalent to the reactor 101 and the capacitor 102 is connected to the simulated inverter output. The insulation amplifier 205 is connected to the DC input of the simulated inverter 206.
The purpose of the present invention is to insulate the DC power supplies 5 and 6 from the DC power supplies 5 and 6 and obtain a DC voltage proportional to the DC power supply voltage. The simulated inverter 206 may be as small as several tens VA even if the capacity of the inverter main body 100 is several tens kVA or more, and its output voltage is arbitrarily selected depending on the output voltage of the insulating amplifier and the insulating transformer 202. be able to.

By connecting in this way, the circuit of the simulated bus 9 constitutes an equivalent circuit excluding the load 4 from the main circuit performing the parallel operation. Therefore, only the cross current ΔI can be detected by the current sensor 203.
Performs the same operation as 2. In this embodiment, a simulated inverter independent of the inverter body is used, so that even if the actual output voltage is distorted by a harmonic component included in the load current, the cross current control is not affected.
The independence between parallel converters can be improved. The insulation amplifier 205 may be a DC / DC converter or the like, as long as it can input a DC voltage and output a DC voltage of an appropriate level proportional thereto, and does not need to be insulated.

Embodiment 4 FIG. Next, a description will be given of an embodiment in which the load current reference to be shared per inverter calculated by dividing the load current by the number of parallel units is given to the current minor loop to share the load current with reference to FIG. In the figure, reference numeral 406 denotes a current detection circuit for detecting a load current value to be shared by the first inverter device 1.

FIG. 9 is a block diagram showing details of the current detection circuit 406. 406t is an adder, and 406u is an amplifying circuit having a gain of 1 / n, where n is the number of paralleled inverter devices. Adder output current I ₁ of the No. 1 inverter device 1 and adding the No.2 inverter device 2 of the output current I ₂ in search of the load current I _L at 406t, enter this signal to the amplifier circuit 406U, the load current I _L is the number of parallel units n
(In this case, n = 2), and calculates a value I _L / n, and calculates a load current value I _L1 to be shared by the first inverter device 1.
Output as ^* .

The load current sharing command value I _L1 ^* output from the current detection circuit 406 is added by the adder 502 to the outputs of the capacitor current reference generation circuit 404 and the instantaneous voltage control circuit 403, and the result is sent to the limiter circuit. The limited signal is given to the instantaneous current control circuit 401 as the output current command value I _A1 ^* of the inverter. When the load 4 is turned on, a command value (I _L1 ^* ) is given from the current detection circuit 406 to the current minor loop so as to share one half of the load current I _L , and each inverter reduces the load current by 1 / It is controlled so that it is shared by two. In this embodiment, since the load current sharing control is mostly performed by the load current command, the cross current control by the virtual impedance circuit 405 can be performed in a small amount, so that the cross current control can be performed with higher accuracy.

Embodiment 5 FIG. Next, an example of giving a load current command shared by the inverter to a circuit using the simulated inverter of the third embodiment will be described with reference to FIG. In the figure, 2
06 is a simulated inverter connected to the simulated bus 9, 406
Is a current detection circuit for detecting a load current shared by the inverter device 1. Only the current corresponding to the cross current ΔI flows through the simulated bus 9 by the simulated inverter 206, and this signal is detected by the current sensor 203 to control the cross current.
On the other hand, the load current sharing command value I _L1 ^* detected from the respective inverter currents I ₁ and I ₂ by the current detection circuit 406 is given to the current minor loop.

Embodiment 6 FIG. Next, an example in which the present invention is applied to a system in which a converter and another power supply system are operated in parallel is shown in FIG.
This is explained by

FIG. 11 is a block diagram showing a configuration in which the inverter device 1 and the AC power supply system 10 supply electric power to the load 4 while operating in parallel via the output bus 3, and perform parallel control by the simulated bus 9. is there. Note that, inside the inverter 1, portions substantially similar to those shown in FIGS. 1, 3 or 4 are simplified. The subscript s indicates a component on the output bus side.

[0063] 103s is the AC power system side switch, 20
0s is a current sensor for detecting the current Is of the AC power supply system 10, 415 is a current sharing circuit for determining the current shared by the inverter device 1, 415t is an adder, 415u is the current sharing ratio β (0 ≦ This is an amplifier circuit having a gain β that determines β ≦ 1).

In the current sharing circuit 415, the inverter device 1
The output current I ₁ of the AC power supply system 10 and the current Is of the AC power supply system 10 are added by an adder 415t to obtain a load current I _L , and this signal is multiplied by β by an amplification circuit 415u to load current I to be shared by the inverter device 1. Output as _L1 ^* . Inverter device 1
Is a current sharing circuit 415 as in the embodiment of FIG.
It operates to supply the command value I _L1 ^* output by. β
Can be determined from the ratio of the capacity of the inverter device to the capacity of the load. If it is continuously changed by an external command, the load current sharing between the inverter device and the AC power supply system will gradually shift. It can also be done.

In this embodiment, as in the first embodiment,
The cross current ΔI ₁ between the inverter device and the AC power supply system is
It is controlled to substantially zero by controlling with the virtual impedance Z.

Embodiment 7 FIG. Next, an example in which parallel operation control by a simulated inverter is applied to a system that operates a converter and another power supply system in parallel will be described with reference to FIG.

In FIG. 12, as in FIG. 11, the inverter device 1 and the AC power supply system 10 operate in parallel by the parallel bus 3 while supplying power to the load 4. The simulated inverter 406a that simulates the inverter main body is connected to the transformer 202.
a, and connected to the simulated bus 9 via the switch 204a, and the AC power supply system
And the switch 204s are connected to the simulation bus 9.

In this embodiment, as in the third and fourth embodiments, the cross current ΔI ₁ between the inverter device and the AC power supply system is used.
Is controlled substantially to zero by the virtual impedance Z and the control of ΔI _1P and ΔI _1Q .

In the embodiment described above, the controllability is improved by giving the current value to be passed through the parallel capacitor 102 of the output filter of the inverter to the command value of the current minor loop. The current reference generation circuit 404 may be omitted. This is because the voltage control circuit 403 operates so that the output voltage of the first inverter device 1 matches the output voltage reference V ₁ ^*, and as a result, generates a signal replacing the capacitor current reference signal. This is because the system operates without any problems. In this case, the deviation in the voltage control decreases as the amplification rate of the voltage control circuit 403 is sufficiently large.

In the above description, the case where the configuration of the control circuit is the instantaneous voltage control type having the current minor loop has been described. However, the voltage control which can control the output voltage at high speed without the current minor loop is provided. If the system is used, the AC output converter can be stably operated in parallel by adding a virtual impedance circuit for limiting cross current.

Embodiment 8 FIG. In the above description has described the case where the present invention is used in parallel operation of the inverter, it may be other transducers, for example as shown in FIG. 13, a combination of high-frequency inverter and cycloconverter, high frequency square wave even lower from DC The same principle can be applied to a converter capable of instantaneous voltage control such as a high-frequency link type converter for converting to a frequency sine wave. In this case, the simulation converter is a converter simulating the main circuit.

In the converter shown in FIG.
Obtaining a rectangular wave as shown in 2 following FIG 14 (a) of the transformer TR by switching Q ₄ from _1. Next, as shown in FIG. 3B, a sawtooth wave synchronized with the switching of the inverter is generated, and the intersection of the sawtooth wave and the output voltage command signal indicated by the line X ₁ -X ₂ in FIG. Ask for. Based on this signal and the polarity of the inverter voltage RS, the switch of the cycloconverter is selected as shown in FIG.
The voltage corresponding to the signals X ₁ -X ₂ as shown in FIG.
You can get in between.

As is clear from the above description, the circuit of FIG. 13 can obtain a single-phase PWM voltage equivalent to that of FIG. In the case of three-phase output, the transformer TR of FIG.
Alternatively, a three-phase high-frequency link converter using three sets of secondary side circuits may be used.

In the above description, the orthogonal component of cross flow ΔI _1P ,
Although ΔI _1Q is detected separately from the cross current ΔI ₁ , the output current I ₁ and the load current I _L1 ^* to be shared are each represented by the quadrature component I _L1 ^.
_1P , I _1Q and I _L1 ^* _P , I _L1 ^* _Q may be separated, and the orthogonal component of the cross current may be detected from the following equation. ΔI _1P = I _1P −I _L1 ^* _P ΔI _1Q = I _1Q −I _L1 ^* _Q

FIGS. 1, 4, 7, 8, 10, and 1
1, the principle shown in FIG. 12 can be realized by a discrete circuit using an analog operational amplifier or the like, or can be realized by software processing under digital control by a microprocessor or digital signal processor.

[0076]

As described above, according to the first aspect of the present invention, the instantaneous voltage control circuit for controlling the instantaneous value of the output voltage includes the cross current of the current flowing between the converters detected by the simulated bus. By giving the corresponding signal, it is possible to quickly suppress the cross current with a simple circuit configuration. In addition, the parallel operation can be adjusted without connecting the main circuit, which has the effect of facilitating test adjustment.

According to the second aspect of the present invention, by adding the average value control in which the cross current is separated into two components, in addition to the effect of the first aspect, conversion by the cross current of the active power is performed. It is possible to prevent the DC voltage on the DC side from rising, and to achieve more stable parallel operation.

According to the third aspect of the invention, the influence of the load current can be avoided by connecting the simulated converter independent of the converter main body of the main circuit to the simulated bus and detecting the cross current. In addition, the independence between converters can be increased.

According to the fourth aspect of the present invention, in addition to the effect of the third aspect of the present invention, it is possible to prevent the DC voltage of the converter from increasing due to the cross flow of the active power, thereby achieving a more stable operation. Parallel operation.

Further, according to the invention according to claims 5 to 8, in a system in which the converter and another power supply system are connected to a common bus, the above-described claims 1 to 4 are respectively applied.
The same effects as the invention according to

According to the ninth aspect of the present invention, the current minor loop makes it possible to obtain a device that is resistant to overcurrent and has higher accuracy.

According to the tenth aspect of the present invention, the load current command value to be shared is given to the current minor loop, so that the load current sharing can be controlled more accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing Embodiment 1 of the present invention.

FIG. 2 is a circuit diagram showing an example of a converter used in the present invention.

FIG. 3 is a simplified block diagram of FIG. 1;

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a vector diagram illustrating Embodiment 2 of the present invention.

FIG. 6 is a vector diagram illustrating Embodiment 2 of the present invention.

FIG. 7 is a block diagram showing a third embodiment of the present invention.

FIG. 8 is a block diagram showing a fourth embodiment of the present invention.

FIG. 9 is a block diagram of the current detection circuit of FIG.

FIG. 10 is a block diagram showing a fifth embodiment of the present invention.

FIG. 11 is a block diagram showing a sixth embodiment of the present invention.

FIG. 12 is a block diagram showing a seventh embodiment of the present invention.

FIG. 13 is a circuit diagram showing a converter according to an eighth embodiment of the present invention.

FIG. 14 is an explanatory diagram of an operation of the converter according to the eighth embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration of a conventional system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1 inverter apparatus 2 2 inverter apparatus 3 Output bus 4 Load 5, 6 DC power supply 8 Output voltage reference circuit 9 Simulated bus 10 AC power supply system 202 Insulation transformer 205 Insulation amplifier 206 Simulated inverter 403 Instantaneous voltage control circuit 405 Cross current restriction Virtual impedance circuit 406 current detection circuit 408 average voltage control circuit 411 converter for separating cross current 412 phase adjuster 413 phase shifter 414,417 oscillator 415 current sharing circuit 416 PLL circuit

Claims (8)

(57) [Claims] 1. In a parallel converter system in which outputs of a plurality of AC output converters are connected to a common bus, and a parallel operation is performed while sharing a load current, each of the converters has an output voltage.
An instantaneous voltage control type converter having a voltage control circuit for controlling the instantaneous value of the output voltage by inputting the deviation between the voltage reference and its own output voltage feedback signal, and outputting the output of each of the converters Parallel connection to a simulated bus for parallel operation control separated from the above load
In addition, a cross current component of the current flowing between the converters is detected from the signal flowing through the simulated bus, and the cross current component is detected.
A correction signal is created by multiplying a constant transfer function.
To correct the control signal of the voltage control circuit.
More, the parallel operation control apparatus for an AC output transducer, characterized in that the so that to suppress the cross current component. 2. In a parallel converter system in which the outputs of a plurality of AC output converters are connected to a common bus and the parallel operation is performed while sharing the load current, each of the converters has an output voltage.
An instantaneous voltage control type converter having a voltage control circuit for controlling the instantaneous value of the output voltage by inputting the deviation between the voltage reference and its own output voltage feedback signal, and outputting the output of each of the converters The load is connected in parallel to a simulated bus for parallel operation control separated from the load, and a signal flowing through the simulated bus is used to connect between the converters.
Detects the cross current of the flowing current and transmits the predetermined transmission to this cross current.
The first correction signal is created by multiplying the function
A first component attributable to the phase difference between the flow amount largely the converter, the primarily due to a voltage difference between the transducer 2
Detecting formation minutes to the second correction signal for changing the average value and the output voltage phase of said transducer by the detection signal of these
And the above first and second correction signals
By correcting the control signal of the voltage control circuit, the parallel operation control apparatus for an AC output transducer, characterized in that the so that to suppress the lateral <br/> flow fraction. 3. In a parallel converter system in which the outputs of a plurality of AC output converters are connected to a common bus and operated in parallel while sharing the load current, each of the converters has an output voltage.
An instantaneous voltage control type converter having a voltage control circuit for controlling the instantaneous value of the output voltage by inputting a deviation between the voltage reference and its own output voltage feedback signal. A simulated converter for parallel operation control driven by the same control signal as the drive control signal of the device is provided, and its output is connected in parallel to a simulated bus for parallel operation control separated from the load ,
A cross current component of the current flowing between the converters is detected from a signal flowing through the simulated bus, and a predetermined transfer function is added to the cross current component.
To generate a correction signal, and the correction signal
By correcting the control signal of the voltage control circuit,
Parallel operation controller for an AC output transducer, characterized in that the so that to suppress the flow amount. 4. In a parallel converter system in which the outputs of a plurality of AC output converters are connected to a common bus, and the parallel operation is performed while sharing the load current, each of the converters has an output voltage.
An instantaneous voltage control type converter having a voltage control circuit for controlling the instantaneous value of the output voltage by inputting a deviation between the voltage reference and its own output voltage feedback signal. A simulated converter for parallel operation control driven by the same control signal as the drive control signal of the device is provided, and its output is connected in parallel to a simulated bus for parallel operation control separated from the load, and the simulated bus Of the current flowing between the converters
Detect the cross flow component and multiply this cross flow component by a predetermined transfer function.
Thereby generating a first correction signal, a first component attributable to the phase difference between primarily the transducer the cross current component, the second deposition minutes to be mainly due to the voltage difference between the transducers detecting, by the detection signal of these to create a second correction signal for changing the average value and the output voltage phase of said transducer,
The voltage control circuit according to the first and second correction signals
By correcting the control signal, the parallel operation control apparatus for an AC output transducer, characterized in that the <br/> so that to suppress the cross current component. 5. A parallel converter system in which the output of one or a plurality of AC output converters and another power supply system are connected to a common bus, and operate in parallel while sharing load current.
Above Symbol strange exchanger, the output voltage reference and the self of the output voltage feedback signal
Voltage control that controls the instantaneous value of the output voltage by inputting the deviation from
And instantaneous voltage control type converter having a control circuit, and an output and the power supply system of the converter connected in parallel to a simulated bus for parallel operation control separated from the above load, the from the signal flowing in the simulated bus The cross current of the current flowing between the converter and the power supply system is detected, and this cross current is multiplied by a predetermined transfer function.
The correction signal is created by the
By correcting the control signal of the control circuit,
Parallel operation controller for an AC output transducer, characterized in that the so that to suppress. 6. A parallel converter system in which the output of one or a plurality of AC output converters and another power supply system are connected to a common bus, and operate in parallel while sharing load current.
Above Symbol strange exchanger, the output voltage reference and the self of the output voltage feedback signal
Voltage control that controls the instantaneous value of the output voltage by inputting the deviation from
And instantaneous voltage control type converter having a control circuit, and an output and the power supply system of the converter connected in parallel to a simulated bus for parallel operation control separated from the above load, the from the signal flowing in the simulated bus The electricity flowing between the converter and the power system
The cross flow component of the flow is detected, and this cross flow component is multiplied by a predetermined transfer function.
Flip with creating the first correction signal, a first component and, mainly voltage between each other said transducer and power supply system due to the phase difference between each other mainly the transducer and power supply system of the cross current component and detected minutes the second growth due to the difference, this
Based on these detection signals, a second correction signal for changing the output voltage phase and the average value of the converter is created, and the first and second correction signals are generated.
And a control signal of the voltage control circuit according to the second correction signal.
By correcting the, to so that to suppress the cross current component
A parallel operation control device for an AC output converter. 7. A parallel converter system in which the output of one or a plurality of AC output converters and another power supply system are connected to a common bus, and operate in parallel while sharing load current,
Above Symbol strange exchanger, the output voltage reference and the self of the output voltage feedback signal
Voltage control that controls the instantaneous value of the output voltage by inputting the deviation from
An instantaneous voltage control type converter having a control circuit, a simulated converter for parallel operation control driven by the same control signal as the drive control signal of the converter provided for each converter, and its output and the power supply And a parallel connection to a simulated bus for parallel operation control, which is separated from the load , detects a cross current of a current flowing between the converter and the power supply system from a signal flowing through the simulated bus, and detects the cross current. Multiplied by a predetermined transfer function
A positive signal is created, and the voltage control circuit is
By correcting the road control signal, the above-mentioned cross flow component is suppressed.
Parallel operation controller for an AC output transducer, characterized in that the to so that. 8. A parallel converter system in which the output of one or more AC output converters and another power supply system are connected to a common bus and operate in parallel while sharing load current,
Above Symbol strange exchanger, the output voltage reference and the self of the output voltage feedback signal
Voltage control that controls the instantaneous value of the output voltage by inputting the deviation from
An instantaneous voltage control type converter having a control circuit, a simulated converter for parallel operation control driven by the same control signal as the drive control signal of the converter provided for each converter, and its output and the power supply a system connected in parallel with the simulated bus for parallel operation control which is separate from the above load, next to the current flowing between the converter and the power supply system each other from a signal flowing in the simulated bus
The flow component is detected and the cross flow component is multiplied by a predetermined transfer function.
Together to create a first correction signal, a first component attributable to the phase difference between each other mainly the transducer and power supply system of the horizontal flow component, mainly due to the voltage difference between each other of the transducers and power supply system second and detected minutes formed to, the detection signal of these to create a second correction signal for changing the average value and the output voltage phase of said transducer, said first and second
The control signal of the voltage control circuit is corrected by the correction signal of
By parallel operation control apparatus for an AC output transducer, characterized in that the so that to suppress the cross current component.