JP2000032764A - Inverter device, inverter controller and inverter system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely realize the compatibility of pull-in at the time of starting and the suppression of frequency fluctuation at the time of a regular operation, and to synchronously operate a plurality of inverters in parallel without adding a special signal line. SOLUTION: An output frequency characteristic against effective power which an effective power operation part 111 calculates is divided into that at the time of starting and that at the time of a regular operation in a starting time frequency setting part 12 and a regular operation time frequency setting part 113. A frequency switching part 114 changes over them by a starting signal Gst and they are used for the voltage control of inverters. Thus, the compatibility of pull-in at the time of starting and the suppression of frequency fluctuation at the time of the regular operation is realized. Thus, a plurality of inverters 1-1 and 2-1 can synchronously be operated without adding a special signal line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an inverter device,
The present invention relates to an inverter control device and an inverter system.

[0002]

2. Description of the Related Art Conventionally, only one inverter, such as an uninterruptible power supply or an auxiliary power supply for a vehicle, for supplying an AC voltage having a constant voltage and a constant frequency is connected to a load system to control an output voltage and a frequency. However, there is a demand that two or more units be connected in parallel and operated synchronously in order to increase the capacity of the device and provide redundancy in the event of a failure.

[0003]

However, in the conventional inverter control device, if an inverter provided with the inverter is connected in parallel as it is, the AC phase of the two is generally not synchronized, so that the phase shift occurs. As a result, the cross current between the inverters becomes excessive, and there is a problem that the operation cannot be continued due to the overcurrent protection and the loss increases.

Therefore, there is a method of synchronizing by exchanging instantaneous phase information between two inverters. This inverter system has a configuration as shown in FIG.
WM inverters 1-1 and 2-1 have wiring inductance 3
Connected in parallel by each inverter 1-
Outputs 1 and 2-1 are connected to loads 1-4 and 2-4. The three-phase output of each of the PWM inverters 1-1 and 2-1 has an LC for removing harmonics caused by PWM.
Filters 1-2 and 2-2 (filters composed of reactors and capacitors) are installed, and the output
Transformers 1-3 and 2-3 for electrically insulating the inverter input and the AC output are provided. And PWM
Inverter control device 1 for each of inverters 1-1 and 2-1
-10 and 2-10, each of which is provided with an active power calculator 10 for calculating the output active power of its own inverter.
1, an active power calculating unit 102 for calculating the output active power of the other inverter, a frequency setting unit 103 for setting and outputting an output frequency based on a difference between these active powers,
A voltage command setting unit 104 for setting an output voltage command for each phase with respect to the output frequency output from the frequency setting unit 103;
The voltage control unit 10 calculates the output voltage command based on the difference between the output voltage command output from the voltage command setting unit 104 and the output voltage detection value of the own inverter, and controls the inverter.
5 is comprised.

However, in such an inverter system, it is necessary to newly add a large number of signal lines for information transmission, and there is a problem that the cost is increased.

Therefore, a method has been proposed in which the output frequency is changed between a plurality of inverters connected in parallel according to the respective output active powers, thereby achieving phase synchronization without adding a new signal line. This is because if there is a phase difference between the two inverters, a cross flow of the active power component occurs from the leading phase to the lagging phase, so the output frequency decreases as the active power increases. By doing so, the phase of the other inverter whose phase is delayed can catch up and be synchronized.

However, according to this method, it is necessary to largely change the output frequency depending on the load condition in order to reliably pull in the synchronous condition even from a state where the phases are greatly separated at the time of starting. There is a problem that the performance as a power supply is not satisfied.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional technical problems, and sets output frequency characteristics with respect to active power separately for a start-up time and a steady-state operation.
Inverter device and inverter control device that, by switching between them to operate, achieve both synchronous pull-in during start-up and suppression of frequency fluctuation during steady-state operation, and enable parallel synchronous operation without adding a special signal line The purpose is to provide.

Further, the present invention achieves both synchronous pull-in during startup and suppression of frequency fluctuation during steady-state operation by simply interposing a simple signal transmission section between inverter control devices. An object of the present invention is to provide an inverter system that enables synchronous operation.

[0010]

According to a first aspect of the present invention, there is provided an inverter for supplying an AC output to a load, and a frequency setting unit for setting and outputting a frequency command for the AC output of the inverter. An inverter control section that calculates and outputs an AC output command according to a frequency command, wherein the frequency setting section calculates active power from an output voltage and an output current of the inverter, and Accordingly, at the time of startup, as the active power increases, the output frequency is output in accordance with the first active power-output frequency characteristic such that the output frequency becomes lower, and at the time of steady operation, the first active power-output frequency characteristic is output. The output frequency according to the second active power-output frequency characteristic has a characteristic that the change of the output frequency set value with respect to the change of the active power is smaller than that of the active power. It is characterized in that output.

In the inverter device according to the first aspect of the present invention, the output frequency characteristic with respect to the active power is set separately for the start-up and the steady-state operation, and the operation is performed by switching the two.
The synchronous synchronization at the time of starting and the suppression of the frequency fluctuation at the time of the steady operation can be compatible, and the parallel synchronous operation of a plurality of inverters can be performed without adding a special signal line.

A second aspect of the present invention provides a frequency setting section for setting and outputting a frequency command of an AC output of an inverter, a phase calculating section for calculating a voltage command phase for the frequency command output by the frequency setting section, A voltage command setting unit that sets and outputs an output voltage command of each AC phase with respect to a voltage command phase calculated by a phase calculation unit, an output voltage command of each AC phase output by the voltage command setting unit, and the inverter A voltage control unit that calculates an output voltage command of each AC phase of the inverter based on a difference between the inverter output voltage of each AC phase and gives the output voltage command to the inverter, further comprising: An active power calculation unit that calculates active power from the output voltage and output current of the active power calculation unit, according to the active power calculated by the active power calculation unit, as the active power increases, Active power set in advance so that the output frequency is set in accordance with the output frequency characteristics according to the output frequency characteristics, the starting frequency setting section, and the active power-output frequency characteristics of the starting frequency setting section. In comparison, a change in the output frequency set value with respect to a change in the active power has a characteristic that the active power-output frequency characteristic has a small characteristic. An output frequency to be output and an output frequency output from the steady-state operation frequency setting unit as inputs, and a frequency switching unit that outputs both as a frequency command of the inverter by switching both at startup and during steady operation. It has.

In the inverter control device according to the second aspect of the present invention, the output frequency characteristic with respect to the active power is set separately for the start-up time and the steady-state operation, and the two are switched to operate, so that the reliable synchronization at the start-up time is obtained. And the suppression of frequency fluctuations during steady-state operation, and enable the parallel synchronous operation of multiple inverters without adding a special signal line.

According to a third aspect of the present invention, in the inverter control device according to the second aspect, the steady-state operation frequency setting unit outputs the active power calculated by the active power calculation unit during the steady-state operation of the inverter. When the active power limit value determined by the current capacity is about to be exceeded, an adjustment is made to increase the amount of the output frequency to be reduced according to the active power, and the output active power of the inverter is reduced by the current of the inverter. It effectively suppresses frequency fluctuations while ensuring that it falls within the active power limit determined by the capacity.

According to a fourth aspect of the present invention, in the inverter control apparatus according to the second aspect of the present invention, the output voltage of the inverter is detected before the start of the inverter, and the detected output voltage amplitude is equal to or larger than a predetermined value. Includes a start-up phase matching unit that starts up the inverter after synchronizing a voltage phase command output from the phase calculation unit with a detected voltage phase value, in a state where another inverter is started up first. In the case of starting the own inverter, it is possible to cause a plurality of inverters to enter the parallel synchronous operation while suppressing transient fluctuation and overcurrent at the time of starting.

According to a fifth aspect of the present invention, in the inverter control device according to the second aspect of the present invention, the AC voltage output from the voltage command setting section is further changed according to a change rate of the reactive power calculated from the output voltage and the output current. An output voltage amplitude corrector for correcting an amplitude command value in a phase output voltage command is provided, and control stability of the inverter during transient is improved.

According to a sixth aspect of the present invention, in the inverter control device according to the second aspect of the present invention, furthermore, the frequency setting section for the steady operation is set so that the average frequency during the steady operation becomes a constant value regardless of the load of the load. Is provided with an output frequency characteristic adjustment unit for changing the active power-output frequency characteristic used by the control unit.

According to a seventh aspect of the present invention, in the inverter control apparatus according to the sixth aspect of the present invention, the output frequency characteristic adjusting section includes an active power used by the normal operation frequency setting section.
The output frequency characteristic is calculated as the active power of the
This is the same as the output frequency characteristic.

In the inverter control device according to the sixth and seventh aspects of the present invention, a plurality of inverters can be operated in parallel synchronously while maintaining a predetermined frequency regardless of the load during normal operation.

The inverter system according to the invention of claim 8 is:
A plurality of inverters having AC output sides connected in parallel, a plurality of inverter control devices connected to the respective inverters, and a transmission device for mutually transmitting an active power value between the inverter control devices, A frequency setting unit that sets and outputs a frequency command of an AC output of the inverter, a phase calculation unit that calculates a voltage command phase with respect to the frequency command output by the frequency setting unit, For the voltage command phase to be calculated,
A voltage command setting unit that sets and outputs an output voltage command of each AC phase, based on a difference between an output voltage command of each AC phase output from the voltage command setting unit and an output voltage of each AC phase of the inverter, A voltage control unit that calculates an inverter output voltage command for each phase of the AC of the inverter and gives the command to the inverter, and the frequency setting unit calculates active power from an output voltage and an output current of the inverter. An active power calculation unit, and according to the active power calculated by the active power calculation unit, as the active power increases, the output is performed according to an active power-output frequency characteristic that is set in advance so as to have a low output frequency. The start-time frequency setting unit that sets and outputs the frequency, the active power of the own inverter calculated by the active power calculation unit of the own device, and the transmission device transmit the active power. Estimate the lateral flow rate between the inverters based on the active power of each inverter calculated by the active power calculation unit of each of the other inverter control devices, and set the steady-state output frequency of the inverter using the lateral flow rate. The steady-state frequency setting unit to be output, the output frequency output from the start-up frequency setting unit, and the output frequency output from the steady-state frequency setting unit are input, and the start-up time and the steady-state operation A frequency switching unit that switches between the two and outputs the frequency command of the inverter.

In the inverter system according to the eighth aspect of the present invention, by simply interposing a simple signal transmission unit between the inverter control devices, it is possible to achieve a reliable synchronization at the time of starting each inverter and to suppress a frequency fluctuation at the time of steady operation. This enables parallel synchronous operation of a plurality of inverters.

According to a ninth aspect of the present invention, in the inverter system according to the eighth aspect of the present invention, the two inverters are connected in parallel, and the frequency setting section in the steady state operation of the inverter control device includes the inverters in the steady state operation. The steady-state frequency set value is set and output based on the active power-output frequency characteristic taking into account the active power difference of the inverter. Parallel synchronous operation of two inverters is possible.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a circuit configuration of the inverter system according to the first embodiment of the present invention. This first
In this embodiment, two PWM inverters 1-1, 2-
1 are connected in parallel by a wiring inductance 3, and the load 1-
4, 2-4 are connected. The three-phase outputs of the PWM inverters 1-1 and 2-1 are provided with LC filters 1-2 and 2-2 (filters composed of reactors and capacitors) for removing harmonics caused by PWM. At the output, transformers 1-3 and 2-3 for electrically insulating the inverter input and the AC output are installed. Here, each PWM inverter 1-1, 2-1
Output frequency is 60 Hz, and output voltage is 44
0V.

Inverter control devices 1-10 and 2-10 are provided for each of the PWM inverters 1-1 and 2-1 to control the inverters 1-1 and 2-1 individually. Since the inverter control device 1-10 and the inverter control device 2-10 have the same internal configuration, only the inverter control device 1-10 will be described below.

An inverter control device 1-10 for controlling the PWM inverter 1-1 includes a frequency setting unit 11, a phase calculation unit 12, a voltage command setting unit 13, and a voltage control unit 14. The frequency setting unit 11 includes an active power calculation unit 111, a startup frequency setting unit 112, a steady operation frequency setting unit 113, and a frequency switching unit 114.

The active power calculator 111 performs the following calculation and outputs the active power Pwr. First, the inverter 1-1
Three-phase output voltage detection values Vu, Vv, Vw and three-phase output current detection values
Using Iu, Iv, and Iw as inputs, the dq-axis voltage V is obtained by using the phase angle θ between the rectangular coordinate dq-axis rotating at 60 Hz and the fixed coordinate axis.
d, Vq and dq-axis currents Id, Iq are calculated by equation (1).

[0027]

(Equation 1) Then, the active power Pwr is calculated from the dq-axis voltage and the dq-axis current obtained by the equation (1) and is output by the following equation (2).

[0028]

Pwr = VdPId + Vq ・ Iq In the startup frequency setting unit 112, as shown in FIG. 2A, the active power Pwr output from the active power calculation unit 111
, And obtains and outputs the frequency setting value fo at the start-up by the calculation of the following equation (3).

[0029]

(Equation 3) Here, Pmax is the maximum value of the inverter output active power.

In the above equation (3), a frequency characteristic of ± 2 Hz is provided with a center frequency of 60 Hz.
The value can be increased or decreased by an arbitrary value according to the magnitude of the wiring inductance 3 between the two inverters 1-1 and 2-1.

In the frequency setting section 113 during normal operation,
As shown in (b), the active power calculation unit 111 receives the active power Pwr as an input, and calculates and outputs the steady-state frequency set value fc by the following equation (4).

[0032]

(Equation 4) In equation (4) as well, ± 60% is defined as the center frequency.
Although a frequency characteristic of 0.2 Hz is provided, the frequency may be increased or decreased by an arbitrary value smaller than ± 2 Hz, which is the frequency range set by the start-time frequency setting unit 112.

In the frequency switching unit 114, a start-up frequency setting value fo output from the start-up frequency setting unit 112, a steady-state frequency setting value fc output from the steady-state operation frequency setting unit 113, and a start-up command signal Gst , And obtains and outputs a new frequency set value ffin by the following calculation.

The start command signal Gst is [1] at the time of a start command, and is [0] otherwise. Thus, immediately after the start command signal Gst is changed from [0] to [1], the frequency switching unit 114 selects and outputs the start-time frequency set value fo as the frequency set value ffin.

At the time of activation: ffin = fo The activation command signal Gst is changed from [0] to [1], and after a lapse of a predetermined time, for example, 2 seconds, the frequency switching unit 1
Reference numeral 14 selects and outputs the steady-state frequency set value fc as the frequency set value finv.

An example in which the frequency switching unit 114 continuously switches the frequency will be described with reference to FIG. The post-startup time Tgst is obtained by calculating the elapsed time after setting the time when the start command signal Gst is changed from [0] to [1] to 0 (sec). The switching gain KGchg is obtained by the following equation 5 using the post-startup time Tgst. This equation shows a case where the switching is completed in 2 seconds after the activation.

[0037]

(Equation 5) Further, the frequency switching unit 114 performs the calculation of Expression 6, and outputs a frequency set value ffin.

[0038]

Finv = (1−KGchg) · fo + KGchg · fc The phase calculation unit 12 uses the frequency setting value ffin output from the frequency switching unit 114 to integrate the voltage command phase θinv by the following equation (7). Find and output.

[0039]

(Equation 7) Further, the voltage command setting unit 13 receives the voltage command phase θinv output from the phase calculation unit 12 and the start command signal Gst, and calculates the three-phase voltage command by the following equations (8) and (9).
Find and output VuRef, VvRef, VwRef.

First, the time at which the start command signal Gst is changed from [0] to [1] is set to 0 (sec), and the time Tgst after the start time obtained by calculating the elapsed time thereafter is calculated by the following equation (8). Find the command amplitude V1Ref.

[0041]

(Equation 8) Here, [440] indicates the effective value of the line voltage command,
The calculation for making the voltage amplitude a steady value in 2 seconds is performed.

The voltage command setting unit 13 further uses the obtained voltage command amplitude V1ref and voltage command phase θinv to calculate
The three-phase voltage commands Vuref, Vvref, Vwref are obtained by the following equation (9).

[0043]

(Equation 9) Finally, in the voltage control unit 14, the three-phase output voltage commands Vuref, Vvref, Vwref output from the voltage command setting unit 13
And the three-phase output voltage detection values Vu, Vv, Vw, and the inverter output voltage commands Vuinv, Vvinv, Vw by the following equation (10).
Inv is calculated and output to the PWM inverter 1-1.

[0044]

(Equation 10) Here, Kd: differential gain, Kp: proportional gain, Ki: integral gain, and s: differential operator.

In PWM inverter 1-1, three-phase inverter output voltage command Vu provided from voltage control unit 14
It performs PWM control targeting inv, Vvinv, and Vwinv, and outputs three-phase power.

In the above embodiment, in particular, the voltage control unit 14 converts the three-phase voltage command and the three-phase voltage detection value into the rotating coordinate dq axis, and performs the differential proportional integral control on the dq axis. It may be.

As a result, in the inverter control device according to the first embodiment, the synchronous synchronization at the time of starting and the suppression of the frequency fluctuation at the time of the steady operation are compatible, and the parallel synchronous operation can be performed without adding a special signal line. It becomes possible.

In the first embodiment, the characteristic shown in FIG. 4 may be used instead of the characteristic shown in FIG. 2 adopted by the frequency setting unit 113 during normal operation. In this case, the steady-state operation frequency setting unit 113 receives the active power Pwr output from the active power calculation unit 111 as an input,
The steady-state frequency set value fc is determined and output according to the following equation (11).

[0049]

[Equation 11] Here, Pmax is the maximum value of the active power of the inverter output.

By employing such an arithmetic expression,
Frequency fluctuation can be suppressed more effectively during steady operation.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. In the second embodiment, the inverter control device 1-1 in the first embodiment shown in FIG.
0, 2-10 are configured as shown in FIG. Therefore, the other parts are common to the first embodiment shown in FIG. Also, the PWM inverter 2-1
Is common to the inverter control device 1-10 for the PWM inverter 1-1, and hence only the inverter control device 1-10 will be described below.

The inverter control device 1-10 according to the second embodiment includes a frequency setting unit 11-1, a phase calculation unit 1
2, a voltage command setting unit 13-1, a voltage control unit 14, a voltage establishment determination unit 15, a power supply phase detection unit 16, a phase synchronization unit 17, and a start-up determination unit 18.
Then, the frequency setting unit 11-1
1, a startup frequency setting unit 112, a steady operation frequency setting unit 113, and a frequency switching unit 114-1.

The active power calculating section 111, the starting frequency setting section 112, the steady-state frequency setting section 113, the phase calculating section 12, and the voltage control section 14 in the frequency setting section 11-1 are of the first embodiment. And the same arithmetic processing is performed.

The voltage establishment determining unit 15 which is a characteristic part of the second embodiment calculates the voltage amplitude by using the three-phase output voltage detection values Vu, Vv, Vw as inputs, and checks whether the voltage amplitude is equal to or more than a certain value. Determine whether Then, a voltage establishment signal FlgVfix is output according to the determination result.

The voltage amplitude V1 is obtained by the following equation (12).

[0056]

(Equation 12) Here, if the voltage amplitude V1 is, for example, 30% or more of the voltage command value 440V, it is determined that the voltage is established, and the voltage establishment signal FlgVfix is set to 1 and smaller than 30%. If it is a value, the voltage establishment signal FlgVfix = 0 is output.

[0057]

(Equation 13) In the power supply phase detector 16, the three-phase output voltage detection values Vu, Vv,
With Vw as an input, a voltage phase θv is obtained by calculation of the following Expressions 14 and 15, and output.

First, voltages Va and Vb on orthogonal fixed ab coordinates are obtained.

[0059]

[Equation 14] Using the ab-axis voltages Va and Vb, the voltage phase θv is obtained by the following equation 15 and output.

[0060]

(Equation 15) The phase synchronization unit 17 receives the voltage phase θv output from the power supply phase detection unit 16, the voltage command phase θinv output from the phase calculation unit 12, and the voltage establishment signal FlgVfix output from the voltage establishment determination unit 15. And the following equation (16), equation (1)
According to equation 7, the phase synchronization frequency fsyn and the phase synchronization completion signal Fl
Output gSYN.

[0061]

Fsyn = KpSYN (θv−θinv) where KpSYN is a phase synchronization proportional gain.

The absolute value | θ of the deviation between θv and θinv
If v−θinv | becomes, for example, 1% or less of 2π, it is determined that the synchronization is completed, and the phase synchronization completion signal FlgSYN is output.

[0063]

[Equation 17] In the activation possibility determination unit 18, the activation command signal Gst and the above-described phase synchronization completion signal FlgSYN output from the phase synchronization unit 17 are output.
And outputs a start enable signal FlgGst according to the following condition determination.

When Gst = 1 and FlgSYN = 1: FlgGst = 1 In cases other than the above: FlgGst = 0 The frequency switching unit 114-1 in the frequency setting unit 11-1
Here, the start-time frequency setting value fo output from the start-time frequency setting unit 112, the steady-state frequency setting value fc output from the steady-state frequency setting unit 113, and the phase synchronization frequency fsyn output from the phase synchronization unit 17 , A voltage establishment signal FlgVfix output from the voltage establishment determination unit 15 and a start enable signal FlgGst output from the start enable determination unit 18, and a frequency setting value ffin is determined and output by the following condition determination.

(1) Immediately after FlgVst = 0 and FlgGst is switched from [0] to [1], ffin = fo (2) FlgVfix = 0 and FlgGst is switched from [0] to [1] and 2 After elapse of more than one second, ffinv = fc (3) FlgVfix = 1, when FlgGst = 0, ffin = fsyn (4) FlgVfix = 1, FlgGst = 1, ffin = fc Voltage command setting unit 13− In FIG. 1, the voltage command phase θinv output from the phase calculation unit 12 that performs the same calculation as in the first embodiment, the start enable signal FlgGst output from the start enable determination unit 18, and the voltage establishment determination unit 15 The output voltage establishment signal FlgVfix and the voltage amplitude V1 are input, and the three-phase voltage command values Vuref, Vvref, Vwref are obtained by the following conditional branches and calculations.
Is output.

First, when FlgVfix = 0, the start enable signal F
Time when lgGst is changed from [0] to [1] is 0 (sec)
As the post-startup time Tgst calculated from the elapsed time
Is used to determine the voltage command amplitude V1ref.

[0067]

(Equation 18) Also, when FlgVfix = 1, the time at which the start enable signal FlgGst is changed from [0] to [1] is set to 0 (sec), and the post-start time Tgst obtained by calculating the elapsed time thereafter,
Using the voltage amplitude V1 when Tgst = 0, the voltage amplitude command V1
Find ref.

[0068]

[Equation 19] In the calculations of Expressions 18 and 19, [440] indicates the effective value of the line voltage command, and the calculation is performed when the voltage amplitude is set to a steady value in 2 seconds.

The voltage command setting unit 13-1 further uses the above-mentioned voltage command amplitude V1ref and voltage command phase θinv to calculate the three-phase voltage command Vref according to the following equation (20), as in the first embodiment. , Vvref, Vwref.

[0070]

(Equation 20) Then, as in the case of the first embodiment, the voltage control unit 14 uses the three-phase voltage commands Vuref, Vvref, Vwref and the three-phase voltage detection values Vu, Vv, Vw according to Equation 10 described above. Inverter output voltage commands Vuinv, Vvinv, Vwinv are calculated and output to PWM inverter 1-1. In the PWM inverter 1-1, the PWM which targets the three-phase voltage commands Vuinv, Vvinv, Vwinv given from the voltage control unit 14 is used.
Performs control and outputs three-phase power.

In the second embodiment, by using the inverter control device 1-10 having the above-described configuration, even when another inverter is activated first, it is possible to suppress transient fluctuation and overcurrent at the time of activation. , Can enter parallel synchronous operation.

Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment is different from the inverter control device 1-1 in the first embodiment shown in FIG.
0, 2-10 are configured as shown in FIG. Therefore, the other parts are common to the first embodiment shown in FIG. Also, the PWM inverter 2-1
Is common to the inverter control device 1-10 for the PWM inverter 1-1, and hence only the inverter control device 1-10 will be described below.

The inverter control device 1-10 according to the third embodiment comprises a frequency setting unit 11, a phase calculation unit 12, a voltage command setting unit 13-2, a voltage control unit 14, and a reactive power change rate calculation unit 19. Have been. The internal configuration of the frequency setting unit 11 is the same as that of the first embodiment shown in FIG.

The feature of the third embodiment is that a reactive power change rate calculating section 19 is provided, and a voltage command setting section 13-2 is provided.
Performs the calculation described later. Note that the portions denoted by the same reference numerals as those in the first embodiment shown in FIG. 1 are the same.

The reactive power rate-of-change calculating section 19, which is a characteristic part of the third embodiment, includes three-phase AC output voltage detection values Vu, Vv, Vw of the PWM inverter 1-1 and three-phase output voltages of the PWM inverter 1-1. Using the phase output AC current detection values Iu, Iv, and Iw as inputs, the dq-axis voltage is obtained by using the phase angle θ of the rectangular coordinate dq-axis rotating at 60 Hz with the fixed coordinate axis according to the following equation (21).
Calculate Vd, Vq and dq-axis currents Id, Iq.

[0076]

(Equation 21) Further, the reactive power Q is obtained from the dq-axis voltage and the dq-axis current obtained by Expression 21 by the following expression.

[0077]

[Mathematical formula-see original document] Q = Vq * Id-Vd * Iq Finally, the time change rate [Delta] Q of the reactive power Q is obtained and output.

[0078]

(Equation 23) Voltage command setting unit 13 which is a feature of the third embodiment.
In −2, the voltage command phase θinv output from the phase calculation unit 12, the start command signal Gst, and the reactive power change rate calculation unit 1
9, the three-phase voltage command Vure is calculated by the following equations (24) and (25) using the reactive power change rate ΔQ output from
f, Vvref, and Vwref are obtained and output.

First, the time when the start command signal Gst is changed from [0] to [1] is set to 0 (sec), and the voltage command amplitude V1ref is calculated using the post-start time Tgst obtained by calculating the elapsed time thereafter. Ask.

[0080]

(Equation 24) Here, [440] is the effective value of the line voltage command value, and the calculation is performed when the voltage amplitude is set to a steady value in 2 seconds. Note that Kq is a proportional gain.

The voltage command setting unit 13-2 further uses the voltage command amplitude V1ref and the voltage command phase θinv to
The three-phase voltage commands Vuref, Vvref, Vwref are given by the following equation (25).
Ask for.

[0082]

(Equation 25) The voltage control unit 14 performs the same calculation as in the first embodiment on the three-phase voltage commands Vuref, Vvref, Vwref calculated by the voltage command calculation unit 13-2 in this manner, and performs the inverter voltage commands Vuinv, Vvinv, Vwinv. And obtain the PWM inverter 1-
Output to 1. In the PWM inverter 1-1, the three-phase voltage commands Vuinv, Vvinv,
Performs PWM control targeting Vwinv and outputs three-phase power.

In the third embodiment, the control stability of the inverters 1-1 and 2-1 during the transition period can be improved, and the inverters 1-1 and 2-1 can be operated in parallel and synchronously.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. The feature of the fourth embodiment is that the frequency setting unit 11 in the first embodiment shown in FIG. 1 is replaced by a frequency setting unit 11-2 having an internal configuration shown in FIG.
In that Other configurations are the same as those of the first embodiment shown in FIG.

The frequency setting section 11-2 includes an active power calculation section 111, a startup frequency setting section 112, a steady operation frequency setting section 113-1, a frequency switching section 114, and a new element, the average effective It comprises a power calculation unit 115.

The average active power calculation unit 115 receives the active power Pwr output from the active power calculation unit 111 that performs the same calculation as in the first embodiment, and calculates the average active power PwrAve by the following equation (26). Find and output.

[0087]

(Equation 26) Here, T is a filter time constant.

The frequency setting unit 113-1 during normal operation
Is the active power Pwr output from the active power calculation unit 111
And the average active power PwrAve output from the average active power calculation unit 115, and calculates the steady-state frequency set value fc by the following equation (27).

[0089]

[Equation 27] By employing the inverter control device 1-10 including the frequency setting unit 11-2 having such a configuration, in the fourth embodiment, as shown in FIGS. 8A and 8B, the load is reduced. Regardless of this, it is possible to perform the parallel synchronous operation at a fixed frequency of 60 Hz during the steady operation.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. The feature of the fifth embodiment is that in a system in which two PWM inverters 1-1 and 2-1 are operated in parallel and synchronously, active powers Pwr1 and Pw are mutually used.
r2 is transmitted to the other party by the transmission device 4, and the frequency setting unit 1 of each of the inverter control devices 1-10 and 2-10.
1-3. As in the other embodiments, inverter control devices 1-10 and 2-10 have the same configuration.
0 will be described.

The inverter control apparatus 1-10 according to the fifth embodiment is different from the inverter control apparatus 2-10 in that the frequency setting section 113-2 in the steady operation in the frequency setting section 11-3 is the frequency setting section of the inverter control apparatus 2-10. The active power Pwr2 calculated by the active power calculator 111 of the own device is taken from the active power calculator 111 of 11-3 through the transmission device 4 and used together with the active power Pwr1 of the own device.
Is transmitted to the other party's inverter control device 2-10 through the transmission device 4. The transmission speed of the transmission device 4 may be a relatively low transmission speed of, for example, about 100 msec.

In the frequency setting section 11-3 of the inverter control device 1-10, the active power calculation section 111 calculates and outputs the active power Pwr1 of the PWM inverter 1-1 as in the first embodiment. The startup frequency setting unit 112 calculates and outputs the startup frequency setting value fo, as in the first embodiment.

The frequency setting unit 113-2 for steady operation, which is a characteristic part of the present invention, includes the active power Pwr1 output from the active power calculation unit 111 on the own device side and the counterpart inverter transmitted from the transmission device 4. The active power Pwr2 is input from the control device 2-10, and the steady-state frequency set value fc is obtained and output by the following equations (28) and (29).

First, the estimated value of the cross flow active power ΔP is obtained by the following equation (28).

[0095]

[Equation 28] In a system in which three or more units perform parallel synchronous operation, the average value of the second unit on the right side in Equation 28 is changed to the average value.

Subsequently, the steady-state frequency set value fc is obtained by the following equation 29 using the estimated cross-flow active power value ΔP (see FIG. 10).

[0097]

(Equation 29) When the steady-state frequency set value fc is obtained in this manner, the subsequent arithmetic processing of the frequency switching unit 114, and all arithmetic processing of the phase arithmetic unit 12, the voltage command setting unit 13, and the voltage control unit 14,
This is the same as in the first embodiment.

According to the fifth embodiment, a plurality of inverters can be operated in parallel and synchronously at a fixed frequency of 60 Hz during a steady operation, regardless of the load of the load, in consideration of the active power of the other party. .

Next, a sixth embodiment of the present invention will be described with reference to FIG.
Description will be made based on 1 and 12. In the sixth embodiment,
The fifth embodiment shown in FIG. 9 is different from the fifth embodiment in that the frequency setting unit 11-3 is changed to the frequency setting unit 11-4 having the configuration shown in FIG. Other configurations are the same as those of the fifth embodiment in FIG.

The frequency setting section 11-4 includes an active power calculation section 111, a startup frequency setting section 112, a steady operation frequency setting section 113-3, a frequency switching section 114, and a characteristic portion of the present embodiment. Average active power difference calculation unit 116
It is composed of

The average active power difference calculation unit 116 receives the active power Pwr1 from the active power calculation unit 111 that performs the same calculation as in the first embodiment, and performs the same operation as in the fifth embodiment shown in FIG. The active power Pwr2 from the other inverter control device 2-10 is input by the same transmission device 4, and the average active power difference ΔPwr is calculated and output from Expression 30.

[0102]

[Equation 30] Here, T is a first-order lag time constant.

In the normal operation frequency setting section 113-3,
The average active power difference ΔPwr calculated by the average active power difference calculation unit 116 is input, the active power Pwr1 from the active power calculation unit 111 is input, and the steady-state frequency setting value fc is calculated by the following equation (31). Is output.

[0104]

(Equation 31) Here, k is a proportional gain.

When the steady-state frequency set value fc is obtained in this way, the subsequent calculation processing of the frequency switching unit 114 and the calculation processing of the phase calculation unit 12, the voltage command setting unit 13, and the voltage control unit 14 are all performed by the first processing. This is the same as the fifth and fifth embodiments.

According to the sixth embodiment, the two inverters 1-1 and 1-10 are controlled while the imbalance of the active power caused by the individual difference between the two inverter controllers 1-10 and 2-10 is suppressed. 2-1 can be operated in parallel and synchronously.

[0107]

As described above, according to the inverter device of the first aspect of the present invention, the output frequency characteristics with respect to the active power are set separately for start-up and steady-state operation, and the operation is performed by switching both. The synchronous synchronization at the time of starting and the suppression of the frequency fluctuation at the time of the steady operation can be compatible, and the parallel synchronous operation of a plurality of inverters can be performed without adding a special signal line.

According to the inverter control device of the second aspect of the present invention, the output frequency characteristics with respect to the active power are set separately for the start-up and the steady-state operation, and the two are switched to operate. Synchronous pull-in and suppression of frequency fluctuation during steady operation are compatible, and parallel synchronous operation of a plurality of inverters is possible without adding a special signal line.

According to the inverter control device of the third aspect of the present invention, in addition to the effect of the second aspect of the invention, the frequency of the output active power of the inverter is reliably kept within the active power limit determined by the current capacity of the inverter. Fluctuations can be effectively suppressed.

According to the inverter control apparatus of the fourth aspect, in addition to the effect of the second aspect, when the own inverter is started in a state where another inverter is started first, a transient at the time of the start is performed. While suppressing fluctuations and overcurrent,
Multiple inverters can enter parallel synchronous operation.

According to the inverter control apparatus of the fifth aspect, in addition to the effect of the second aspect, the output of the voltage command setting section is changed according to the change rate of the reactive power calculated from the output voltage and the output current. Since the output voltage amplitude corrector for correcting the amplitude command value in the output voltage command of each AC phase is provided, it is possible to improve the control stability of the inverter during transition.

According to the inverter control device of the invention of claims 6 and 7, in addition to the effect of the invention of claim 2, a plurality of inverters are each maintained at a predetermined frequency during normal operation irrespective of the load lightness. Parallel synchronous operation.

According to the inverter system of the eighth aspect of the present invention, by simply interposing a simple signal transmission unit between the inverter control devices, it is possible to reliably introduce synchronization at the time of starting each inverter and to suppress frequency fluctuation at the time of steady operation. And a plurality of inverters can be operated in parallel and synchronously.

According to the inverter system of the ninth aspect, in addition to the effect of the eighth aspect, the number of inverters is two.
Connected in parallel with each other, and the steady-state frequency setting unit of the inverter control device sets the steady-state frequency set value based on the active power-output frequency characteristic taking into account the difference in active power between the inverters during the steady operation. Output
Parallel synchronous operation of two inverters is possible while suppressing imbalance of active power due to individual differences between the inverters.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a graph showing an operation of a frequency setting unit in the embodiment.

FIG. 3 is a timing chart showing an operation of a frequency switching unit in the embodiment.

FIG. 4 is a graph showing another example of the frequency setting process according to the first embodiment.

FIG. 5 is a block diagram showing a configuration according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a frequency setting unit according to a fourth embodiment of the present invention.

FIG. 8 is a graph showing a setting operation of a frequency at the time of steady operation in the embodiment.

FIG. 9 is a block diagram showing a configuration according to a fifth embodiment of the present invention.

FIG. 10 is a graph showing a frequency setting operation in the embodiment.

FIG. 11 is a block diagram illustrating a configuration of a frequency setting unit according to a sixth embodiment of the present invention.

FIG. 12 is a graph showing a setting operation of a frequency at the time of steady operation in the embodiment.

FIG. 13 is a block diagram showing a configuration of a conventional example.

[Description of Signs] 1-1, 2-1 PWM inverter 1-2, 2-2 LC filter 1-3, 2-3 Transformer 1-4, 2-4 Load 3 Connected reactance 4 Transmission device 11, 11- 1, 11-2, 11-3, 11-4 Frequency setting unit 12 Phase calculation unit 13, 13-1, 13-2 Voltage command setting unit 14 Voltage control unit 15 Voltage establishment determination unit 16 Power supply phase detection unit 17 Phase synchronization Unit 18 Startable determination unit 19 Reactive power change rate calculation unit 111 Active power calculation unit 112 Frequency setting unit at start-up 113, 113-1, 113-2 Frequency setting unit at steady operation 114, 114-1 Frequency switching unit 115 Average effective Power calculator 116 Average active power difference calculator

Claims (9)

[Claims] An inverter that supplies an AC output to a load, and a frequency setting unit that sets and outputs a frequency command of the AC output of the inverter, and calculates an AC output command according to the frequency command The frequency setting unit calculates active power from an output voltage and an output current of the inverter, and the active power increases at the time of startup according to the active power. And outputs an output frequency in accordance with a first active power-output frequency characteristic such that the output frequency becomes low. In a steady state operation, the output frequency with respect to a change in active power is compared with the first active power-output frequency characteristic. Outputting an output frequency in accordance with a second active power-output frequency characteristic having a characteristic that a change in a set value is small. Converter equipment. 2. A frequency setting unit for setting and outputting a frequency command of an AC output of an inverter; a phase calculation unit for calculating a voltage command phase for the frequency command output by the frequency setting unit; and a calculation by the phase calculation unit. A voltage command setting unit that sets and outputs an output voltage command of each AC phase, and an output voltage command of each AC phase output by the voltage command setting unit and the AC voltage of the inverter. A voltage control unit that calculates an inverter output voltage command for each phase of AC of the inverter based on a difference between the output voltage and gives the command to the inverter, wherein the frequency setting unit includes an output voltage and an output current of the inverter. An active power calculation unit that calculates the active power from the following. According to the active power calculated by the active power calculation unit, the output frequency becomes lower as the active power increases. A start-up frequency setting unit for setting and outputting an output frequency according to a preset active power-output frequency characteristic, and an active power-output frequency characteristic of the start-up frequency setting unit, A steady-state frequency setting unit that sets and outputs an output frequency according to an active power-output frequency characteristic having a small change in an output frequency set value with respect to a change, and an output frequency output from the start-up frequency setting unit. ,
An inverter control device having, as an input, an output frequency output from the steady-state operation frequency setting unit, and a frequency switching unit that switches between the start-up operation and the steady-state operation and outputs the same as a frequency command of the inverter. . 3. The inverter control device according to claim 2, wherein the steady-state operation frequency setting unit determines that the active power calculated by the active power calculation unit is determined by the inverter current capacity during the steady operation of the inverter. When the power limit value is about to be exceeded, an adjustment is made to increase the amount of output frequency to be reduced according to the active power. 4. The inverter control device according to claim 2, wherein an output voltage of the inverter is detected before the inverter is started, and when the detected output voltage amplitude is equal to or more than a predetermined value, the phase calculation unit is controlled. An inverter control device comprising: a start-time phase matching unit that starts the inverter after synchronizing a voltage phase command output from the inverter with a detected voltage phase value. 5. The inverter control device according to claim 2, wherein an amplitude of an output voltage command of each AC phase output from the voltage command setting unit is output in accordance with a change rate of the reactive power calculated from the output voltage and the output current. An inverter control device comprising an output voltage amplitude correction unit for correcting a command value. 6. The inverter control apparatus according to claim 2, wherein the steady-state frequency setting section uses an active power-output so that an average frequency during a steady operation becomes a constant value regardless of the load of the load. An inverter control device comprising an output frequency characteristic adjusting unit for changing a frequency characteristic. 7. The inverter control device according to claim 6, wherein the output frequency characteristic adjusting unit sets the active power-output frequency characteristic used by the steady operation frequency setting unit to the active power of the startup frequency setting unit. An inverter control device characterized by having the same output frequency characteristics. 8. A plurality of inverters having AC output sides connected in parallel, a plurality of inverter control devices connected to each of the inverters, and a transmission device for mutually transmitting an active power value between the inverter control devices. A frequency setting unit that sets and outputs a frequency command of an AC output of an inverter; and a phase calculation unit that calculates a voltage command phase with respect to the frequency command output by the frequency setting unit. For a voltage command phase calculated by the phase calculation unit, a voltage command setting unit that sets and outputs an output voltage command of each AC phase, and an output voltage command of each AC phase output by the voltage command setting unit. Voltage control for calculating the inverter output voltage command of each AC phase of the inverter based on the difference between the output voltage of each phase of the inverter and the output voltage of the inverter. The frequency setting unit comprises: an active power calculating unit that calculates active power from an output voltage and an output current of the inverter; and the active power calculated by the active power calculating unit is: As the frequency increases, the output frequency is set and output in accordance with the active power-output frequency characteristic set in advance so that the output frequency becomes lower. The lateral flow between the inverters is estimated based on the active power of its own inverter and the active power of each inverter calculated by the active power calculation unit of each of the other inverter control devices sent by the transmission device. A steady-state operation frequency setting section that sets and outputs a steady-state output frequency of the inverter using the inverter, and is output from the start-up frequency setting section. And power frequency,
An inverter system comprising: a frequency switching unit which receives an output frequency output from the frequency setting unit at the time of steady operation as input, switches between the two at the time of startup and at the time of steady operation, and outputs the frequency command of the inverter. 9. The inverter system according to claim 8, wherein the two inverters are connected in parallel, and the frequency setting unit in a normal operation of the inverter control device includes:
An inverter system wherein a steady-state frequency set value is set and output based on active power-output frequency characteristics taking into account the difference in active power between the inverters during steady operation.