JPH05260665A - Parallel operation controller for ac output converter - Google Patents

Abstract

PURPOSE:To provide a parallel operation controller for balancing an allotted current at a high speed in a power source system in which a plurality of instantaneous control type AC output converters are connected in parallel and operated in parallel with a common load. CONSTITUTION:Outputs of converters are connected to simulated bus 9. A cross current DELTAI1 flowing between the converters is detected by the bus 9, Z x al) is obtained by a cross current limiting virtual impedance circuit 405, a signal V1* (=V*- ZXDELTAI1) obtained by subtracting this signal from a bus voltage command value V* by a subtracter 504 is used as a command value of an instantaneous voltage controller 403 to be so operated as to eliminate the cross current.

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 the 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 operated in parallel with a common load. Is.

[0002]

2. Description of the Related Art FIG. 15 is a block diagram showing a parallel operation system of conventional AC output converters shown in, for example, Japanese Examined Patent Publications Sho 53-36137 and Sho 56-13101.

In the figure, the No. 1 inverter unit 1 supplies electric power to the load 4 while operating in parallel through the No. 2 inverter unit 2 and the output busbar 3 having the same structure. The No. 1 inverter device 1 has an inverter body 100, a filter reactor 101, and the same capacitor 102 as main constituent elements, converts the power of a DC power supply 5 into AC, and is connected to an output bus bar 3 through an output switch 103a. Inverter device 1
And 2 operate in parallel, the 1st inverter device 1
Output current I ₁ from CT 200a detected signal I _1a
Similarly, the difference from the detection signal I _2a obtained from the No. 2 inverter device 2, that is, the signal ΔI ₁ corresponding to the cross current is obtained by the cross current detection circuit 151. Next, two orthogonal voltage vectors E _A and E _B are created from the phase shifter 150, and reactive power corresponding component ΔQ and active power corresponding component ΔP are obtained from the ΔI ₁ signal by the arithmetic circuits 152 and 153, respectively. In the inverter, based on the signals from the voltage setting circuit 7 and the voltage feedback circuit 300, the voltage control circuit 403 detects that the pulse width modulation circuit (hereinafter referred to as P
The pulse width modulation of the inverter main body 100 is performed via the WM circuit) 400 to control the internally generated voltage.

The reactive current corresponding component ΔQ is given to the voltage control circuit 403 as an auxiliary signal, and the inverter body 10
By adjusting the internally generated voltage of 0 by several percent, ΔQ
Works to make zero.

On the other hand, the active power corresponding component ΔP is the PLL
(Phase-locked loop) Amplifier 15 that constitutes the circuit
4, the phase of the internally generated voltage of the inverter main body 100 is controlled by finely adjusting the frequency of the reference oscillator 155, and ΔP is set to zero.

In this way, since the voltage and phase are controlled so that both ΔQ and ΔP are zero, cross current between the two inverters is eliminated, and stable load sharing is performed.

[0007]

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

The fourth problem is that the test adjustment in parallel operation is difficult, and the test adjustment cannot be performed unless the inverters are actually connected to the output busbar 3 and operated. The fifth problem is that since the output current of the inverter contains the harmonic components contained in the load current, the harmonics flow in the cross current detection circuit, resulting in a control error.

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 the shared currents at high speed and facilitates test adjustment. is there.

Another object of the present invention is to provide means that can be applied to parallel operation of not only inverters but also other instantaneous control type AC output converters.

[0011]

A parallel operation control device for an AC output converter according to the present invention connects an output of an instantaneous voltage control type converter in parallel to a simulated bus bar separated from a load, and connects the converters to each other. The cross current component of the current flowing in is obtained from the signal flowing in the simulated bus. In addition, the cross current component is separated into a component mainly due to the phase difference between the converters and a component mainly due to the output voltage difference to control the output voltage phase and average value of the converter.

Further, for each converter, a simulated converter driven by the same control signal as the drive control signal of the converter may be connected to the simulated busbar to detect the cross current.

Further, the above can be applied during parallel operation of one or a plurality of AC output converters and another power supply system. The instantaneous voltage control circuit may be equipped with a current minor loop to control the instantaneous value of the converter output current.

[0014]

In the present invention, the cross current between the converter and the power supply system is detected from the signal flowing through the simulated bus, and the output voltage of each converter is controlled so as to suppress this cross current.

[0015]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, No. 1 inverter device 1
Supplies electric power to the load 4 while operating in parallel through the output busbar 3 and the No. 2 inverter device 2 having the same configuration as shown in the figure. Reference numeral 5 is a DC power supply connected to the No. 1 inverter device 1, 6 is a DC power supply connected to the No. 2 inverter device 2, 8 is an output voltage reference circuit which gives an output voltage reference to each inverter, and 9 is each inverter This is a simulated bus with the output connected. In addition, although the same numbers are given to the functions corresponding to those in FIG. 15 described above, FIG. 15 shows an inverter device of the type that controls the average value of the output voltage, while FIG. Since it is an inverter device of the type that controls the average value, circuits with the same number do not necessarily have the same function.

Numbers after 100 are constituent elements of the inverter device. Numbers without subscripts and numbers with subscript a are constituent elements of No. 1 inverter device 1 and numbers with subscript b are No. 2 inverter. It is a component of the device 2.

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

Reference numeral 200a is the output current I ₁ of the No. 1 inverter device, and 201 is the output current I ₁ of the inverter main body 100.
_A1 and 203a are current sensors for detecting the currents flowing through the simulated bus bar 9, respectively. 202a is an isolation transformer that insulates the output of the inverter from the simulated busbar. Reference numeral 204a is a switch that opens and closes the simulated busbar in cooperation with the output switch 103a. Reference numeral 300 is a voltage sensor for detecting the voltage of the capacitor 102 (which is the output bus voltage during parallel operation).

Reference numeral 400 denotes a PWM circuit that determines 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 the voltage command signal for the fundamental wave to be output from the inverter main body 100 and the triangular wave carrier. It is a circuit. 40
Reference numeral 1 is an instantaneous current control circuit for controlling the output current I _A1 of the inverter body 100. 402 is the inverter main body 100
This is a limiter circuit that limits the output current command value of. 40
3 is an instantaneous voltage control circuit for controlling the voltage of the capacitor 102. Reference numeral 404 is 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
It is a virtual impedance circuit for limiting the cross current that inserts an impedance Z between the No. 2 inverter device 2 and the inverter device 2 and operates so as to limit the cross current.

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

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

Next, the operation will be described.

This inverter device is provided with a current minor loop. In the instantaneous current control circuit 401, the output current I _A1 of the inverter main body 100 fed back by the current sensor 201 is the current command I _A1 ^* from the limiter circuit 402 ^. The command value of the voltage to be applied to the reactor 101 is output so as to match with. Since the output bus 3 has a voltage from the capacitor 102 and the No. 2 inverter device 2, in order 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 the adder 500, and this signal is used as a voltage command for the triangular wave comparison type PW.
It is given to the M circuit 400.

The capacitor current reference generation circuit 404 generates a sine wave current reference which is 90 degrees out of phase with 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 the signal calculated by the subtractor 503 as the deviation between the voltage command V ₁ ^{* of} the capacitor 102 and the voltage of the capacitor 102 detected by the voltage detector 300, and reduces the deviation. The inverter main body 100 outputs a correction current signal to be output.

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

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

When the response and accuracy of the voltage control system of the No. 1 inverter device 1 and that of the No. 2 inverter device 2 are exactly the same, the cross current does not flow in the above control system configuration, but in reality, the accuracy and control of the components are controlled. Due to variations in gain and main circuit constants, stable parallel operation with little cross current is difficult if left unchanged. For example, the voltage sensors of the first inverter device 1 and the second inverter device 2 are -0.5% and +0.5, respectively.
If there is an error of%, the output voltage difference ΔV during islanding becomes 1%, and if the wiring impedance between the inverters is 1% or less, the cross current will flow 100% or more.

The present invention suppresses the cross current 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 device 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 device 2 also passes through the insulating transformer 202b and the switch 204b. Connected to the simulated bus bar 9. Now the switches 204a, b are on
If so, since the simulated bus 9 is a circuit obtained by removing the load 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 No. 1 inverter device: ΔI ₁ = I ₁ becomes -I _L / n) only. Therefore, the current sensor 203 detects only the cross current flowing between the converters.

Virtual impedance circuit 405 for limiting cross current
Calculates ΔI ₁ × Z (ΔI ₁ is a cross current, Z is a virtual impedance transfer function), subtracts this signal from the output voltage command value V ^* output from the output voltage reference circuit 8, and this is subtracted from the capacitor. The voltage command V ₁ ^{* of} 102 is set. The voltage of the capacitor 102 is set to the voltage command V ₁ ^* by the voltage control system described above ^.
Instantly follows.

Here, it will be described with reference to FIG. 3 that the cross current limiting virtual impedance circuit 405 causes the inverter to have an output impedance of Z only with respect to the cross current and operate as a low impedance voltage source for current components other than the cross current. ． FIG. 3 is a simplified block diagram of the instantaneous cross current control unit of FIG. 1. In the figure, 700a and 700b are derived from the 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. The other numbers have already been described in FIG. 1 above, and the same functions are given the same numbers. Some symbols have already been used, but the following symbols will be defined again. 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 : No. 1 inverter voltage control system transmission Function G ₂ : No. 2 inverter voltage control system transfer function Z: Cross-current limiting virtual impedance value Using these symbols, the relational expression showing the effect of cross-current limiting virtual impedance is next derived.

From Kirchhoff's law, the following equation holds. I _L = I ₁ + I ₂ (1) From the formula (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 formula (9)-(10), ΔI ₁ The formula is as follows.

[Equation 1]

When the equations (9) + (10) are 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 can be made almost 1 at the output frequency by constructing the voltage control system of G ₁ and G ₂ by the above-mentioned instantaneous voltage control type, the formula (11) becomes the following formula. ．

[Equation 3]

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

[Equation 4] For example, if ΔV is 1% and Z = 50% is selected, the cross current becomes ΔV / (2 × Z) = 1% / 100% = 1%.

Next, the second term on the right side of the equation (12) becomes the following equation when the equation (13) is substituted.

[Equation 5]

Since ΔV is as small as about 1%, (ΔV) ²
It can be thought of as ≈0. Therefore, Eq. (12) has only the first term on the right side, and becomes the following equation.

[Equation 6] From Eq. (16), the bus voltage V _B during parallel operation is the average output voltage of the individual inverter devices during independent operation, and the virtual impedance value Z has no effect.

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 differentiating circuit, Z is a reactor, and 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 resistance, capacitor and reactor.
In addition, Z is a circuit that includes nonlinear elements such as positive and negative non-symmetrical limiters, but can stably limit the cross current as long as it has an appropriate impedance value for limiting the cross current at the output frequency.

In the above description, for simplification, the current and the voltage are vector quantities, but the same relationship holds even for 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. In normal parallel operation, the switch 204 is opened and closed in conjunction with the output switch 103 to perform parallel control only when the inverter is actually in parallel operation. However, the output switch 103 is kept off and only the switch 204 is operated. When turned on, parallel operation control can be adjusted with the inverter disconnected from the output bus 3. Therefore, even when the devices are operated in parallel for the first time, sufficient adjustment can be performed in advance, and, for example, when the device is inspected, the No. 1 inverter device supplies power to the load 4 without affecting the load. You can also adjust the inverter.

The control method of FIG. 1 described above is an example of a single-phase inverter, but 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 simplification, but the 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.

Example 2. Next, an example in which the lateral flow is separated into two components and the average value is controlled will be described with reference to FIG.

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

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

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

[Equation 7] Is. FIG. 5 shows a vector diagram when the absolute values of V ₁ ^* and V ₂ ^* match and V ₂ ^* lags V ₁ ^* by a phase angle θ. Here, when the resistance component of the virtual impedance Z is R and the reactance component is X, Z = R + j
It can be expressed as X, and its impedance angle α is α = argZ = tan ^-1 (X / R) (17). From this vector diagram, the cross current 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 another virtual voltage advanced by 90 ° from this virtual voltage vector. Vector E
It has only the component parallel to x.

FIG. 6 shows that there is no phase difference between V ₁ ^* and V ₂ ^*
A vector diagram for the case where the absolute value of ₂ ^* is smaller than the absolute value of V ₁ ^* is shown. From this vector diagram, the cross current vector Δ
I ₁ and ΔI ₂ have only a component parallel to the virtual voltage vector Er delayed by α from the bus voltage vector V _B , and have no component parallel to Ex.

From FIG. 5 and FIG. 6, the components due to the phase difference between V ₁ ^* and V ₂ ^* among the cross current components ΔI ₁ and ΔI ₂ are perpendicular to the virtual voltage vector Er of these cross current vectors. It can be seen that it is a component (a component parallel to the virtual voltage vector Ex). That is, of the cross current components ΔI ₁ and ΔI ₂ , the component caused by the phase difference between the voltage command values V ₁ ^* and V ₂ ^* is the load bus voltage vector V _B of 90 °.
It is equal to the reactive component of each of the cross current components ΔI ₁ and ΔI ₂ with reference to the voltage Ex obtained by advancing the phase by −α.

Similarly, each of the cross current components ΔI ₁ and ΔI
The components of I ₂ caused by the voltage absolute value difference between the voltage command values V ₁ ^* and V ₂ ^* are the cross current components ΔI ₁ and ΔI _{2 of} these cross current vectors with reference to the virtual voltage vector Er.
It turns out to be equal to the effective part of.

Returning to FIG. 4, the explanation will be continued. Reference numeral 411 is a converter for converting the cross current ΔI ₁ detected by the current sensor 203 into two quadrature components ΔI _1P and ΔI _1Q (DC signal). These converters are composed of a synchronous rectification circuit or a multiplier and a smoothing filter. Be done. The component ΔI _1P is the current ΔI ₁
Is the effective component with reference to the voltage Er of ΔI _1Q is the current Δ
It is a reactive component based on the voltage Er of I ₁ .

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

ΔI _1Q is guided to the input terminal of the phase adjuster 412. The phase signal output from the phase adjuster 412 adjusts the output phase of the oscillator 414 by the phase shifter 413,
Create a sinusoidal signal sinωt that serves as the phase reference for the output voltage.

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

As described above, the output voltage phase is controlled 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. Control so that the cross current is reduced. It should be noted that this control may be controlled relatively slowly within the range where the cross flow is not harmful.

Example 3. Next, an example of using a simulated inverter that simulates an inverter for detecting cross current will be described based on Fig. 7. In the figure, reference numeral 206 designates the inverter body 1
00 is a simulated inverter that is driven by a PWM circuit 400 that is common with 00, and its output is connected to the simulated bus bar 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 isolation amplifier 205 is connected to the DC input of the simulated inverter 206.
It is intended to insulate from the DC power supplies 5 and 6 of the main circuit by 05 and to obtain a DC voltage proportional to the voltage of the DC power supply. The simulated inverter 206 may be as small as several tens of VA even if the capacity of the inverter main body 100 is several tens of kVA or more, and its output voltage is arbitrarily selected by the output voltage of the isolation amplifier and the isolation transformer 202. be able to.

By connecting in this way, the circuit of the simulated bus bar 9 constitutes an equivalent circuit excluding the load 4 from the main circuit which operates in parallel. Therefore, the current sensor 203 can detect only the cross current ΔI.
Performs the same operation as 2. In this embodiment, since a simulated inverter independent of the inverter body is used, even if the actual output voltage is distorted by the harmonic component contained in the load current, the cross current control is not affected, and
The independence between parallel converters can be further increased. Note that the isolation 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 it does not need to be insulated.

Example 4. Next, an embodiment in which the load current reference, which is calculated by dividing the load current by the number of parallel units and which is shared by each inverter, is given to the current minor loop to share the load current will be described with reference to FIG. In the figure, 406 is a current detection circuit for detecting a load current value to be shared by the No. 1 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 amplifier circuit having a gain of 1 / n, where n is the number of parallel 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 in parallel number n
(In this case, n = 2) A value I _L / n is calculated and the load current value I _L1 to be shared by the No. 1 inverter device 1 is calculated.
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 signal thus limited 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 to the current minor loop from the current detection circuit 406 so as to share 1/2 of the load current I _L , and each inverter reduces the load current to 1 /. It is controlled so that it is divided into two. In this embodiment, since the sharing control of the load current is mostly performed by the load current command, the cross current control by the virtual impedance circuit 405 is sufficient in a few minutes, so that the cross current control can be performed more accurately.

Example 5. 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 bar 9, 406
Is a current detection circuit that detects the load current shared by the inverter device 1. Only the current corresponding to the cross current ΔI flows through the simulation bus 9 by the simulation inverter 206, and this signal is detected by the current sensor 203 and the cross current is controlled.
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.

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

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 are controlled in parallel by the simulated bus 9. is there. It should be noted that the inside of the inverter 1 is represented in a simplified manner in parts that are substantially the same as in FIGS. The subscript s indicates the component on the output bus side.

103s is a switch on the AC power system side, 20
2s is a current sensor that detects the current Is of the AC power supply system 10, 415 is a current sharing circuit that determines the current shared by the inverter device 1, 415t is an adder, and 415u is the current sharing ratio β (0 ≦ 0 for the inverter device. This is an amplifier circuit with a gain β that determines β ≤ 1).

In the current sharing circuit 415, the inverter device 1
Output current I ₁ 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 amplifier circuit 415u to multiply the load current I _L by the inverter device 1. Output as _L1 ^* . Inverter device 1
Is the current sharing circuit 415 as in the embodiment of FIG.
It operates so as 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, and if it is continuously changed by a command from the outside, the sharing of the load current between the inverter device and the AC power system can be gradually changed. It can also be done.

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

Example 7. Next, an example in which parallel operation control by a simulated inverter is applied to a system in which a converter and another power supply system are operated 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 are operated in parallel by the parallel bus bar 3 while supplying electric power to the load 4. The simulated inverter 406a that simulates the inverter body is the transformer 202.
a is connected to the simulated bus 9 via the switch 204a, and the AC power supply system is the same as the insulation transformer 202s.
And the switch 204s to the simulated bus 9.

Also in this embodiment, the cross current ΔI ₁ between the inverter device and the AC power supply system is the same as in the third and fourth embodiments.
Is controlled to be substantially 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 minor loop command value the current value that should flow to the parallel capacitor 102 of the output filter of the inverter. 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 No. 1 inverter device 1 matches the output voltage reference V ₁ ^*, and as a result, generates a signal that replaces the capacitor current reference signal, the control of the sine wave inverter This is because the system operates without any problems. In this case, the deviation in the voltage control decreases when the amplification rate of the voltage control circuit 403 is sufficiently large.

Further, in the above description, the case where the control circuit is of the instantaneous voltage control type having the current minor loop has been described. However, the voltage control capable of controlling the output voltage at high speed without the current minor loop is described. If it is a system, it is possible to stably operate the AC output converters in parallel by adding a virtual impedance circuit for limiting the cross current.

Example 8. In the above description, the case where the present invention is applied to the parallel operation of the inverters has been described, but other converters may be used. For example, a high frequency inverter and a cycloconverter are combined as shown in FIG. The same principle can be applied to converters capable of instantaneous voltage control, such as high-frequency link converters that convert to low-frequency sine waves. In this case, the simulated converter is a converter that simulates the main circuit.

In the converter shown in FIG. 13, the transistor Q
By switching from 1 to Q4, a secondary wave of the transformer TR is obtained as shown in Fig. 14 (a). Then make a sawtooth wave that is synchronized with the switching of the inverter as shown in FIG. (B), the same as the intersection of the output voltage command signal indicated by the line X ₁ -X ₂ of FIG. (C) in FIG. Ask for. Based on the polarity of this signal and the voltage RS of the inverter, by selecting the switch of the cycloconverter as shown in FIG. 13E, the voltage corresponding to the signals X ₁ -X ₂ as shown in FIG. Can be obtained during UN.

As is clear from the above description, the circuit of FIG. 13 can obtain the single-phase PWM voltage equivalent to that of FIG. In the case of 3-phase output, the transformer TR of FIG.
It is also possible to use a three-phase high-frequency link converter that uses three sets of secondary side circuits.

In the above description, the cross flow orthogonal component 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 respectively quadrature components I.
_{It is also possible} to separate into _1P , I _1Q and I _L1 ^* _P , I _L1 ^* _Q and detect the orthogonal component of the cross current from the following equation. ΔI _1P = I _1P −I _L1 ^* _P ΔI _1Q = I _1Q −I _L1 ^* _Q

1, FIG. 4, FIG. 7, FIG. 8, FIG.
To implement the principle shown in Fig. 1 and Fig. 12, it is possible to use a discrete circuit that uses an analog operation amplifier or the like, or it can be implemented by software processing by digital control by a microprocessor or digital signal processor.

[0076]

As described above, according to the invention of claim 1, in the instantaneous voltage control circuit for controlling the instantaneous value of the output voltage, the cross current component of the current flowing between the converters detected by the simulated bus is detected. Providing a corresponding signal has the effect of quickly suppressing 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.

Further, according to the invention of claim 2, by adding the average value control in which the cross current is separated into two components, in addition to the effect of the invention of claim 1, conversion is performed by the cross flow of active power. It is possible to avoid a rise in the DC side voltage of the reactor, and more stable parallel operation can be achieved.

According to the third aspect of the present invention, the influence of the load current can be avoided by connecting the simulated converter, which is independent of the converter main body of the main circuit, to the simulated busbar to detect the cross current. , In addition, the independence between the converters can be increased.

Further, according to the invention of claim 4, in addition to the effect of the invention of claim 3, it is possible to prevent the converter DC side voltage from rising due to the cross current of the active power, so that it is more stable. The parallel operation can be performed.

Further, according to the inventions according to claims 5 to 8, in the case of a system in which the converter and another power supply system are connected to a common bus, each of the above-mentioned claims 1 to 4 is applied.
It has the same effect as the invention according to.

According to the invention of claim 9, 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 sharing can be controlled more accurately by giving the load current command value to be shared to the current minor loop.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment 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.

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

FIG. 5 is a vector diagram illustrating a second embodiment of the present invention.

FIG. 6 is a vector diagram illustrating a second embodiment 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.

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 Embodiment 6 of the present invention.

FIG. 12 is a block diagram showing Embodiment 7 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 operation explanatory diagram of the converter of Embodiment 8 of the present invention.

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

[Explanation of symbols]

 1 No. 1 inverter device 2 No. 2 inverter device 3 Output bus bar 4 Load 5, 6 DC power supply 8 Output voltage reference circuit 9 Simulated bus bar 10 AC power system 202 Insulation transformer 205 Insulation amplifier 206 Simulated inverter 403 Instantaneous voltage control circuit 405 Cross current limitation Virtual impedance circuit for use 406 Current detection circuit 408 Average value 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 (10)

[Claims] 1. In a parallel converter system in which outputs of a plurality of AC output converters are connected to a common busbar and are operated in parallel while sharing a load current, each of the converters has an instantaneous value of its output voltage. An instantaneous voltage control type converter for controlling
The output of each of the converters is connected in parallel to a simulated busbar for parallel operation control that is separated from the load, a signal flowing through the simulated busbar is detected, and the detected signal causes a flow between the converters. A parallel operation control device for an AC output converter, characterized in that the output voltage of the converter is controlled so that the cross current of the current is suppressed. 2. In a parallel converter system in which outputs of a plurality of AC output converters are connected to a common busbar and are operated in parallel while sharing a load current, each of the converters has an instantaneous value of its output voltage. An instantaneous voltage control type converter for controlling
The output of each of the converters is connected in parallel to a simulated bus for parallel operation control, which is separated from the load, and a signal flowing through the simulated bus is detected, and the output of the instantaneous voltage control circuit is detected by this detection signal. While changing, the detection signal is detected as a first component mainly due to a phase difference between the converters and a second component mainly due to a voltage difference between the converters, and the detection signal Altering the output voltage phase and the average value of the converter, the output voltage of the converter is controlled so that the cross current of the current flowing between the converters is suppressed. Controller for parallel operation of reactors. 3. In a parallel converter system in which outputs of a plurality of AC output converters are connected to a common busbar and are operated in parallel while sharing a load current, each of the converters has an instantaneous value of its output voltage. An instantaneous voltage control type converter for controlling
For each of the converters, a simulated converter for parallel operation control driven by the same control signal as the drive control signal of the converter is provided, and its output is separated from the load to simulate bus for parallel operation control. Is connected in parallel with each other, detects a signal flowing through the simulated bus, and controls the output voltage of the converter by the detection signal so that the cross current of the current flowing between the converters is suppressed. AC output converter parallel operation control device. 4. In a parallel converter system in which outputs of a plurality of AC output converters are connected to a common busbar and are operated in parallel while sharing a load current, each of the converters has an instantaneous value of its output voltage. An instantaneous voltage control type converter for controlling
For each of the converters, a simulated converter for parallel operation control driven by the same control signal as the drive control signal of the converter is provided, and its output is separated from the load to simulate bus for parallel operation control. Is connected in parallel to the first bus, the signal flowing through the simulated bus is detected, the output of the instantaneous voltage control circuit is changed by this detection signal, and the detection signal is mainly caused by the phase difference between the converters. Component and a second component mainly caused by the voltage difference between the converters, and by changing the output voltage phase and average value of the converters by this detection signal A parallel operation control device for an AC output converter, characterized in that the output voltage of the converter is controlled so that the cross current of the flowing current is suppressed. 5. A parallel converter system in which the output of one or a plurality of AC output converters and a separate power supply system are connected to a common bus bar, and which operates in parallel while sharing a load current,
Each of the converters is an instantaneous voltage control type converter that controls the instantaneous value of its output voltage, and the output of each converter and the power supply system are simulated for parallel operation control separated from the load. Connected in parallel to the busbar, detect the signal flowing in the simulated busbar, and control the output voltage of the converter by the detection signal so that the crossflow of the current flowing between the converter and the power supply system is suppressed. A parallel operation control device for an AC output converter, characterized in that 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 line and which operates in parallel while sharing a load current,
Each of the converters is an instantaneous voltage control type converter that controls the instantaneous value of its output voltage, and the output of each converter and the power supply system are simulated for parallel operation control separated from the load. It is connected in parallel to the bus bar, the signal flowing in the simulated bus bar is detected, the output of the instantaneous voltage control circuit is changed by this detection signal, and the detection signal is mainly used as a phase difference between the converter and the power supply system. Is detected as the first component and the second component mainly due to the voltage difference between the converter and the power supply system, and the detection signal determines the output voltage phase and average value of the converter. A parallel operation control of an AC output converter, characterized in that the output voltage of the converter is controlled so that the cross current of the current flowing between the converter and the power supply system is suppressed by changing the output voltage. Location. 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 line and which operates in parallel while sharing a load current,
Each of the above converters is an instantaneous voltage control type converter that controls the instantaneous value of its output voltage, and for parallel operation control driven by the same control signal as the drive control signal of the converter for each converter. Is provided, and the output and the power supply system are connected in parallel to a simulated bus bar for parallel operation control separated from the load, and a signal flowing through the simulated bus bar is detected,
A parallel operation control device for an AC output converter, characterized in that the output voltage of the converter is controlled so that the cross current of the current flowing between the converter and the power supply system is suppressed by the detection signal. 8. 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 bar, and which operates in parallel while sharing a load current,
Each of the above converters is an instantaneous voltage control type converter that controls the instantaneous value of its output voltage, and for parallel operation control driven by the same control signal as the drive control signal of the converter for each converter. Is provided, and the output and the power supply system are connected in parallel to a simulated bus bar for parallel operation control separated from the load, and a signal flowing through the simulated bus bar is detected,
The output of the instantaneous voltage control circuit is changed by the detection signal, and the detection signal is used as a first component mainly due to the phase difference between the converter and the power supply system and mainly between the converter and the power supply system. Is detected as the second component resulting from the voltage difference between the two, and the output voltage phase of the converter and the average value are changed by this detection signal to detect the current flowing between the converter and the power supply system. A parallel operation control device for an AC output converter, characterized in that the output voltage of the converter is controlled so that a cross current is suppressed. 9. The parallel operation of the AC output converters according to claim 1, wherein the instantaneous voltage control circuit has a current minor loop for controlling the instantaneous value of the output current of the converter. Control device. 10. The load current value to be shared is given as a command of the current minor loop.
Parallel operation control device for the described AC output converter.