JP2004140909A - Control method of parallel connection self-excited ac power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a parallel AC power supply system of a master-slave system in which an electric power is stably supplied to a load even if a master stops due to failure, etc. <P>SOLUTION: In this control method, an inverter 2a and a controller 9a, for example, operate as a voltage source (master) while inverters 2b and 2c and controllers 9b and 9c operate as a current source (slave). Here, a fluctuation tolerance range for a different frequency and voltage effective value is set for each current source, and if a frequency or voltage at a grid point exceeds the fluctuation tolerable range, the voltage source is judged to be defective. And a corresponding controller switches function so that a corresponding inverter operates as a voltage source, resulting in allowing a stable power to be supplied to a load. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control system for a self-excited AC power supply that converts a DC voltage into an AC voltage.
[0002]
[Prior art]
As a method of converting a DC voltage to an AC voltage, for example, there is a self-excited conversion method using voltage-type inverters 2a to 2c in which a diode 4 is connected in anti-parallel to a self-extinguishing type switching element 3, as shown in FIG. The inverter shown in the figure is connected to an AC voltage bus via AC reactors 5a to 5c and AC circuit breakers 6a to 6c, and supplies power to a load 8. The voltage-source inverter has a mode in which it operates as a voltage source at a rated voltage and a rated frequency, and a mode in which it operates as a current source that changes a voltage so that a current has a predetermined value. There is a system in which a plurality of voltage-source inverters are connected in parallel, one is operated as a voltage source, and the other is operated as a current source, which is called a master-slave system.
[0003]
As a control method for controlling each voltage source inverter in such a master-slave method, a control method shown in FIG. 8 is conventionally known (for example, see Non-Patent Document 1).
In FIG. 8, the master inverter is a master controller 41 (controller 9a if the master inverter is 2a), and the slave inverter is a slave controller 42 (the slave inverters are 2b... 2c). Then, they are controlled by the controllers 9b... 9c).
[0004]
The master controller 41 integrates the reference frequency 25 with the integrator 31, finds a sine function with the sine function unit 32, and multiplies the reference voltage effective value 30 by the gain with the gain calculator 43 to obtain the sine function. The function is further multiplied by a multiplier 33 to generate a voltage command. The deviation between the voltage command and the interconnection point voltage detected via the voltage detector 12 is input to a voltage regulator (AVR) 34, and the output thereof and the sum of the voltage command and a separately provided carrier 36 are output. The gate pulse is generated by the PWM (pulse width modulation) calculator 39 so that the voltage at the interconnection point becomes the rated voltage and the rated frequency.
[0005]
On the other hand, the slave control unit 42 calculates the deviation between the 1 / N value (37) of the load current obtained by the load current detector 7 and the divider 10 in FIG. 7 and the output current obtained by the current detectors 11b. Is input to a current controller (ACR) 38, and a gate pulse is generated by a PWM (pulse width modulation) calculator 39 using the sum of the output of the current controller 38 and the interconnection point voltage and a separately provided carrier 36.
Here, the switching between the master and the slave is performed by the changeover switch 35, but it is common sense to perform the switching by the manual or automatic switching signal 40 after the apparatus stops.
[0006]
[Non-patent document 1]
"Combination Voltage-Controlled and Current-Controlled and PW Bluetooth Inverters for UPS Parallel Operation" IEE Transaction on Power Electronics, Volume 10, Number 5, September 1995, pp. 547-557 ("Combination Voltage-Controlled"). and Current-Controlled PWM Inverters for UPS Parallel Operation "IEEE TRANSACTION ON POWER ELECTRONICS" VOL.10, NO.5, SEPTEMBER1995, p.547-557)
[0007]
[Problems to be solved by the invention]
However, in the above-described master-slave parallel AC power supply system, if the master stops due to a failure, the slave is stopped and all the circuit breakers (6a to 6c) are opened. Becomes completely 0, and power cannot be supplied until the next time the master is started.
Therefore, an object of the present invention is to stably supply power to a load even when a master stops.
[0008]
[Means for Solving the Problems]
In order to solve such a problem, in the invention of claim 1, a plurality of self-excited AC power supply devices for converting a DC voltage to an AC voltage are connected in parallel on the AC side, and one of the AC power supply devices is connected to a voltage source. In a parallel-connected self-excited AC power supply that operates each of the other AC power supplies as a current source,
The frequency variation allowable range and the voltage effective value variation allowable range at the interconnection point of each AC power supply device operating as a current source are different from each other, and the AC power supply device deviating from at least one of the ranges is operated as a voltage source. And
[0009]
According to the invention of claim 2, a plurality of self-excited AC power supplies for converting a DC voltage to an AC voltage are connected in parallel on the AC side, one of the AC power supplies is a voltage source, and the other AC power supply is a current source. In a parallel-connected self-excited AC power supply that operates as
The present invention is characterized in that the allowable range of the frequency variation at the interconnection point of each AC power supply device operating as a current source is different from each other, and the AC power supply device outside this range is operated as a voltage source.
[0010]
According to the third aspect of the present invention, a plurality of self-excited AC power supplies for converting a DC voltage to an AC voltage are connected in parallel on the AC side, and one of the AC power supplies is a voltage source and the other AC power supply is a current source. In a parallel-connected self-excited AC power supply that operates as
The present invention is characterized in that the permissible ranges of voltage effective value fluctuation at the interconnection point of each AC power supply device operating as a current source are different from each other, and an AC power supply device outside this range is operated as a voltage source.
[0011]
According to the first or second aspect of the present invention, the allowable range of the frequency variation of the current source which is first switched to the voltage source can be minimized (the invention of claim 4), or the current source is switched to the voltage source. Can be gradually returned from the frequency at the time of switching to the prescribed frequency (the invention of claim 6).
According to the first or third aspect of the present invention, the allowable range of the effective voltage variation of the current source which is first switched to the voltage source can be minimized (the invention of claim 5), or the current source can be used as the voltage source. In the case of switching, it is possible to gradually return from the voltage effective value at the time of switching to a prescribed voltage effective value (the invention of claim 7).
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
In a voltage source inverter that operates as a current source, the deviation between the current command 37 and the output current is input to the current regulator 38 as in the conventional case, and the sum of the output and the interconnection point voltage is selected. The changeover switch 35 is operated so that the PWM operation is performed between the changeover switch 35 and the carrier 36.
[0013]
In such a configuration, in order to detect that the master has stopped, the interconnection point voltage is input to a phase locked loop circuit (PLL: phase locked loop circuit) 20, and the output frequency and the allowable frequency value 21 are output. In addition to the comparison by the comparator 22, the output of the effective value calculator 26 and the voltage effective value allowable value 27 are compared by the comparator 28.
[0014]
As shown in detail in FIG. 2, for example, the PLL circuit 20 obtains a phase difference between the reference signal 45 and a signal obtained by integrating the current frequency value 48 by the integrator 51 with the phase comparator 49, and outputs the output to the controller 50. After the input, the current value 48 is obtained by adding the reference frequency 47 to the current frequency 48.
On the other hand, as shown in FIG. 3, for example, the effective value calculator 26 inputs the detected voltage value 55 to the square calculator 58, inputs the output thereof to the square root calculator 59, obtains the effective value, and further calculates the effective value. The signal is input to a hold circuit 60 and is held by a hold signal 56.
[0015]
The outputs of the comparators 22 and 28 are input to the OR circuit 23. When at least one of the frequency and the effective voltage value exceeds the allowable range, the switch 35 is switched to operate as a voltage source. At this time, the controller hold signal 46 of the PLL circuit 20 and the hold signal 56 of the hold circuit 60 are output.
[0016]
The deviation between the held current frequency and the reference frequency 25 is input to a ramp function generator (HLR) 24, the sum of the output and the reference frequency 25 is integrated by an integrator 31, and a sine function unit 32 is used. To find the sine function. The deviation between the held voltage effective value and the reference voltage effective value 30 is input to the HLR 29, and the sum of the output and the reference voltage effective value 30 is used as an amplitude value by the gain calculator 43. A voltage command is generated by multiplying the sine function from S32. The deviation between the voltage command and the interconnection point voltage is input to a voltage regulator 34, and a gate pulse is generated by a PWM calculator 39 using the sum of the output and the voltage command and a separately provided carrier 36. . FIG. 4 shows the input / output characteristics of the HLRs 24 and 29. That is, the held current frequency or effective value of voltage is controlled so as to gradually return to the reference frequency or effective value of reference voltage from each value at the time of switching.
[0017]
The operation of the voltage-source inverter that normally operates as a slave has been described above. At this time, the allowable variation range of the frequency and the effective value of the voltage is made different for each voltage-source inverter. Therefore, when the switching from the current source to the voltage source is performed only in the frequency variation range as shown in FIG. 5, the frequency variation range is set for each voltage source inverter, and as shown in FIG. Is performed only in the effective range of the voltage effective value, the effective range of the voltage effective value is changed for each voltage source inverter, and the starting priority of a plurality of current sources is determined based on the allowable range. , The allowable range of the current source to be switched is made the narrowest, and the allowable range is sequentially expanded. 5 and FIG. 6 are the same as those in FIG.
[0018]
【The invention's effect】
According to the present invention, in a voltage-source inverter connected in parallel in a master-slave manner, it is possible to stably supply power to a load even when the master stops, and to perform operation without voltage phase jump and amplitude jump. Can continue.
[Brief description of the drawings]
1 is a configuration diagram showing a first embodiment of the present invention; FIG. 2 is a block diagram showing a detailed example of a PLL circuit of FIG. 1; FIG. 3 is a detailed example of a voltage effective value calculation circuit of FIG. 1; FIG. 4 is a diagram illustrating the characteristics of a ramp function generator (HLR) in FIG. 1; FIG. 5 is a configuration diagram illustrating a second embodiment of the present invention; FIG. 6 is a third embodiment of the present invention; FIG. 7 is a configuration diagram showing a conventional master-slave system. FIG. 8 is a detailed configuration diagram showing a master controller and a slave controller in FIG. 7.
1a-1c DC power supply, 2a-2c voltage source inverter, 3 self-extinguishing element, 4 diode, 5a-5c AC reactor, 6a-6c AC breaker, 7 load current detector, 8 ... Load, 9a to 9c: controller, 10: divider, 11a to 11c: output current detector, 12a to 12c: voltage detector, 20: PLL (phase locked loop circuit: phase locked loop), 21: allowable frequency value , 22: frequency comparator, 23: logical OR calculator, 24, 29 ... ramp function generator (HLR), 25, 47 ... reference frequency, 26 ... voltage effective value calculator, 27 ... voltage effective value allowable value, 28 ... voltage effective value comparator, 30 ... reference voltage effective value, 31, 51 ... integrator, 32 ... sine wave function generator, 33 ... multiplier, 34 ... voltage regulator (AVR), 35 ... switcher, 36 ... Carrier, 37 Output current command, 38: current controller (ACR), 39: PWM calculator, 40: switching signal, 41: master controller, 42: slave controller, 43: gain calculator, 45: synchronization reference signal, 46: Arithmetic unit hold signal, 48: current frequency value, 49: phase comparator, 50: controller, 55: voltage detection value, 56: hold signal, 57: voltage amplitude value, 58: square operator, 59: square root operator , 60 ... hold circuit.

Claims (7)

A plurality of self-excited AC power supplies for converting a DC voltage to an AC voltage are connected in parallel on the AC side, and one of the AC power supplies is operated as a voltage source and the other AC power supply is operated as a current source. In the excited AC power supply,
The allowable range of frequency fluctuation and the allowable range of voltage effective value fluctuation at the interconnection point of each AC power supply device operating as a current source are different from each other, and the AC power supply device deviating from at least one of the ranges is operated as a voltage source. The control method of the self-excited AC power supply connected in parallel. A plurality of self-excited AC power supplies for converting a DC voltage to an AC voltage are connected in parallel on the AC side, and one of the AC power supplies is operated as a voltage source and the other AC power supply is operated as a current source. In the excited AC power supply,
A parallel-connected self-excited AC power supply characterized in that the allowable range of frequency variation at the interconnection point of each AC power supply that operates as a current source is different from each other, and an AC power supply that deviates from this range is operated as a voltage source. Control method. A plurality of self-excited AC power supplies for converting a DC voltage to an AC voltage are connected in parallel on the AC side, and one of the AC power supplies is operated as a voltage source and the other AC power supply is operated as a current source. In the excited AC power supply,
A parallel-connected self-excited AC characterized in that the permissible ranges of effective voltage fluctuations at the interconnection point of each AC power supply device operating as a current source are different from each other, and an AC power supply device outside this range is operated as a voltage source. Power supply control method. 3. The control method for a parallel-connected self-excited AC power supply device according to claim 1, wherein an allowable range of frequency fluctuation of a current source which is switched to a voltage source first is narrowed. 4. The control method for a parallel-connected self-excited AC power supply device according to claim 1, wherein an allowable range of voltage effective value fluctuation of a current source which is first switched to a voltage source is narrowed. 3. The control method for a parallel-connected self-excited AC power supply device according to claim 1, wherein when the current source is switched to a voltage source, the frequency is gradually returned from a frequency at the time of switching to a specified frequency. . 4. The parallel-connected self-excited AC power supply according to claim 1, wherein when the current source is switched to a voltage source, the voltage effective value at the time of switching is gradually returned to a prescribed voltage effective value. 5. Device control method.

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