JP2823345B2 - Power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an instantaneous value PW used for an uninterruptible power supply or the like.
The present invention relates to a power supply device in which a plurality of M control power converters are connected in parallel.

(Prior art) Conventionally, as an uninterruptible power supply, an inverter apparatus that supplies uninterruptible power by inputting DC power of a storage battery even during a commercial power outage has been widely used. In many cases, a system is used in which a plurality of inverter devices serving as backup units are operated in parallel.

On the other hand, many loads of uninterruptible power supplies such as computers are non-linear loads such as capacitor input type rectifiers.Non-linear loads have been generated as a measure to reduce output voltage waveform distortion due to harmonic current. Instantaneous value PW
M-control inverters are starting to be used.

Instantaneous value PWM control inverter, Toshiba Review Vol. 42, No. 11, P
P877-880 (1987) and the like are well-known, and a specific configuration example is shown in FIG.

In the figure, 1 is a DC power supply (this corresponds to a DC voltage obtained from a rectifier or a storage battery that converts AC into DC, not shown), and 2 is a high-speed switching element such as a MOS-FET or IGBT. Inverters 3 and 4 are filter reactors and filter capacitors forming an AC filter for improving the output waveform of the inverter 2 to a sine wave, 11 is an oscillator serving as an output frequency reference of the inverter 2, and 12 is synchronized with the oscillator 11. A sine wave reference generator that generates a sine wave voltage reference, 13 is a voltage controller that compares the output voltage of the AC filter with the output of the sine wave reference generator 12 and issues a voltage control command, and 14 is a voltage controller A PWM control circuit for sending out the ignition pattern of the switching elements constituting the inverter 2 so that the output voltage waveform of the device becomes a sine wave based on the output. A gate amplifier circuit for amplifying.

According to the configuration as shown in FIG. 2, even if the load is a load such as a capacitor input type rectifier that generates a harmonic current, the output voltage waveform of the AC filter matches the sine wave reference 12. The ignition control pattern is controlled by the PWM control circuit 15 (equivalently, control is performed so as to generate a reverse-phase harmonic current that cancels the harmonic current generated by the load) so that the output voltage waveform is not distorted. I have to.

With regard to this type of uninterruptible power supply using instantaneous value control PWM inverters, it is desired that high reliability is achieved by a parallel operation system of a plurality of devices with one backup device. FIG. 3 shows an example of a configuration using the same concept as the parallel operation system of the power failure power supply devices. 3, the same reference numerals as those in FIG. 2 indicate the same functions as those in FIG. 6 is a CT (current transformer), 7 is a circuit breaker for parallel injection and disconnection, 15 is an output current deviation which detects a deviation (ΔI) between the output current detected by the CT 6 and the output current of another unit. The detectors 16 and 17 use the output current deviation (ΔI) and the output voltage to determine the active power deviation (Δ
P), an active power deviation detector that detects and amplifies the reactive power deviation (ΔQ), a reactive power deviation detector, and 18 is an oscillator that changes the frequency (phase) of an output pulse according to the output of the active power deviation detector 16 And 19 are voltage controllers which compare the output voltage of the AC filter with the output of the sine wave reference generator 12 and issue a voltage control command in accordance with the output of the reactive power deviation detector 17.

The configuration of the uninterruptible power supply 5A of the first unit and the uninterruptible power supply 5B of the second unit are exactly the same, and 8 is a parallel output common bus.

In other words, in order to operate a plurality of inverter devices in parallel, it is necessary that the output frequency / phase and output voltage of each device are the same. With the configuration as shown in FIG. 3, the output frequency / phase and output voltage of each inverter are corrected and controlled in accordance with the active power deviation and the reactive power deviation between the devices, thereby correcting the imbalance.

(Problems to be Solved by the Invention) However, in the instantaneous value PWM control inverter as described above, originally, the control to instantaneously match the output voltage to the sine wave reference, that is, the internal impedance of the device is equivalent to “ If the output voltage detection point is set to the parallel output common bus of each device as in the configuration example of FIG. 3, interference of the control system of each device is likely to occur and each device is loaded. In principle, it is difficult to select the gain of the control system so as to operate stably while taking good allotment.

In other words, in contrast to the instantaneous value PWM control that controls the internal impedance of the device to “zero”, the load sharing correction control makes the internal impedance of the device equivalent, and both are contradictory. In the case of value control, a system that satisfies both can be constructed, but in the case of instantaneous value control, it is extremely difficult.

The present invention has been made in view of the above points, and enables parallel operation of a plurality of instantaneous value PWM control power converters that output a sine wave AC voltage, which was conventionally difficult, and
It is an object of the present invention to provide a power supply device in which power converters of high performance by instantaneous value PWM control are connected in parallel.

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention relates to a power supply device in which a plurality of instantaneous value PWM control power converters for outputting a sine wave AC voltage are connected in parallel. A parallel connection reactor having a predetermined impedance connected in series between the AC output side of the power converter and the common connection point, and a connection point between the instantaneous value PWM control power converter output and the parallel connection reactor. Voltage detection means for detecting the output voltage of the instantaneous value PWM control power converter; current detection means for detecting the output current of the instantaneous value PWM control power converter;
Current deviation detecting means for determining a deviation of the output current of the M control power converter; active power deviation detecting means for detecting an active power deviation based on an output of the voltage detecting means and an output of the current deviation detecting means; Sine wave reference generating means for changing the frequency according to the output of the active power deviation detecting means, and reactive power deviation detecting means for detecting a reactive power deviation based on the output of the voltage detecting means and the output of the current deviation detecting means And a voltage control means for comparing the output of the voltage detection means with the output of the sine wave reference generation means and outputting a voltage control command according to the output of the reactive power deviation detection means.

(Operation) In the power supply unit with this configuration, the instantaneous value PWM control loop of each device is separated by setting the voltage detection point for instantaneous value PWM control to the stage before the reactor from the parallel output common bus. Since it is possible (the reactor exists outside the instantaneous value PWM control loop), the problem of the interference of the control system of each device is solved and the optimal gain can be selected.

Also, for the parallel load sharing control by correcting the active power deviation and the reactive power deviation, the optimal control gain can be selected based on the impedance of the reactor, and the parallel operation of the instantaneous value PWM control power converter can be realized.

Embodiment An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the same parts as those in FIG. 3 are denoted by the same reference numerals and their description is omitted.
A parallel interconnection reactor 21 is provided between an AC filter and a parallel output common bus 8. Although the output voltage detection point for the instantaneous value PWM control is the parallel output common bus 8 in FIG. 3, the output voltage detection point is located before the parallel interconnection reactor 21 (AC filter output).

The configuration of the uninterruptible power supply 6A of the first unit and the uninterruptible power supply 6B of the second unit are completely the same.

Next, the operation of the power supply device configured as described above will be described.

Since the output voltage detection points of each device are separated by the parallel interconnection reactor 21, the instantaneous value PWM control loop of each device can be controlled independently without mutual interference, and the optimal control gain is selected. it can.

Further, assuming that the impedance of the parallel interconnection reactor 21 is X, the internal impedance of each device is controlled to “zero” by the instantaneous value PWM control, so that the output current deviation ΔI caused by the voltage difference ΔV between the outputs of each device. _Q is ΔI _Q
(= I ₁ −I ₂ ) = ΔV / 2X. Since ΔQ detected by the reactive power deviation detector 17 is proportional to ΔI _Q , the load sharing control loop based on the reactive power deviation correction of the reactive power deviation detector 17 to the voltage controller 19 from the above relationship. If the optimum gain is selected, stable operation can be achieved.

On the other hand, the output current deviation ΔI _P caused by the phase difference ΔQ between each device output is ΔI _P (= I ₁ −I ₂ ) = 2sin (ΔQ / 2) / 2X
In expressed, similarly to the above, [Delta] P detected by the active power deviation detector 16 than proportional to [Delta] I _P, the load sharing control loop according to the active power deviation correction active power deviation detector 16 to the oscillator 18 best A stable operation can be achieved by selecting an appropriate gain.

The impedance X of the parallel interconnection reactor 21 is
It is determined based on parameters such as the range of the voltage difference and phase difference between the outputs of each device, which causes the load sharing imbalance, and the allowable value of the load sharing imbalance. The voltage drop for a high power factor load such as a load is slight, and there is no practical problem.

Thus, in the present embodiment, the parallel interconnection reactor
The instantaneous value PW for stable parallel operation by separating the instantaneous value PWM control loop of each device by providing the instantaneous value PWM control inverter device output and the parallel output common bus
The control gain of the M control and the control gain of the parallel load sharing control can be optimized.

Although the embodiment of FIG. 1 describes a parallel operation system of the instantaneous value PWM control inverter device, the present invention is not limited to the inverter and may be another type of instantaneous value PWM control power converter.

Further, in the embodiment of FIG. 1, two parallel operation systems are used, but it is a matter of course that the same effect can be obtained even with three or more parallel operation systems.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform parallel operation of a plurality of instantaneous value PWM control power converters that output a sine wave AC voltage. A power supply device in which devices are connected in parallel can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing a configuration example of an instantaneous value PWM control inverter device, and FIG. 3 is a conventional parallel control circuit of an average value control inverter. FIG. 3 is a block diagram showing an example of a parallel operation system of the instantaneous value PWM control inverter device. DESCRIPTION OF SYMBOLS 1 ... DC power supply 2 ... Inverter 3 ... Filter reactor 4 ... Filter capacitor 6 ... CT, 7 ... Breaker, 8 ... Parallel output common bus, 10 ... Gate amplifier circuit, 12 … Sine wave reference generator, 14… PWM control circuit, 15… Output current deviation detector, 16… Active power deviation detector, 17… Reactive power deviation detector, 18 …… Oscillator, 21 …… Parallel interconnection reactor.

Claims (1)

(57) [Claims] 1. A power supply device in which a plurality of instantaneous value PWM control power converters for outputting a sine wave AC voltage are connected in parallel, wherein a series connection is provided between an AC output side of the instantaneous value PWM control power converter and a common connection point. The connected parallel interconnection reactor having a predetermined impedance and the instantaneous value PWM control from the connection point between the instantaneous value PWM control power converter output and the parallel interconnection reactor.
Voltage detection means for detecting the output voltage of the control power converter,
Current detection means for detecting the output current of the instantaneous value PWM control power converter; current deviation detection means for determining the deviation of the output current of each instantaneous value PWM control power converter; output of the voltage detection means and the current deviation An active power deviation detecting means for detecting an active power deviation based on an output of the detecting means, a sine wave reference generating means for changing a frequency according to an output of the active power deviation detecting means, and an output of the voltage detecting means. A reactive power deviation detecting means for detecting a reactive power deviation based on an output of the current deviation detecting means, and comparing the output of the voltage detecting means with the output of the sine wave reference generating means and the reactive power deviation detecting means And a voltage control means for outputting a voltage control command according to the output of the power supply.