JPS6338944B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides power supply equipment in which two power sources are connected to a common bus to which loads are connected via switches, in which power is supplied from each power source to the load at an arbitrary ratio. The present invention relates to a load sharing control method for sharing the load.

Generally, power supply to important loads is performed by an uninterruptible power supply configured with a static inverter. However, even with such uninterruptible power supplies, there are times when it is necessary to stop operation of a part of the inverter for maintenance and inspection, but in this case it is not possible to maintain the power supply to the load at the rated level. It disappears. Therefore, in such a case, it is necessary to partially stop the operation of the uninterruptible power supply after sharing part of the load with another power source such as a commercial power source.

The applicant first stated that upon stopping the operation of the uninterruptible power supply,
Developed a load transfer control method for power supply equipment that transfers the load to a commercial power source, and filed a patent application (Japanese Patent Application Laid-Open No. 1989-1999).
Publication No. 23943). In other words, the load transfer control method proposed earlier transfers the voltage of the first power source to the second power source in a power supply facility in which two power sources are connected to a common bus to which loads are connected via switches, respectively. a first regulation loop to match the voltage of the
A second adjustment loop is provided to match the phase of the power supply with the phase of the second power supply, and when a load is transferred from either power supply to the other power supply, the action of both adjustment loops causes the power supply to match the phase of the second power supply. said one power supply by applying the other power supply to the common bus after matching the voltage and phase, and then giving auxiliary target values to the first and second regulation loops, respectively, in accordance with the output current of said one power supply. This feature is characterized in that the output current is narrowed down.
The load transfer control method configured in this way has no effect of transient fluctuations during load transfer (for example, inrush current) and has no effect on the load, and can perform extremely smooth load transfer. It has excellent advantages such as being able to perform without interruption.

However, since the load transfer control method proposed earlier transfers the entire load from one power source to the other, it is possible to have a stable and stable system by sharing part of the load with the other power source as described above. This was not satisfactory for continuous operation control.

Therefore, the inventor of the present invention has conducted various studies in order to obtain a load sharing control method that allows the load to be operated at an arbitrary power supply ratio using two power sources. When moving, the inverter's internal induced voltage is controlled under the action of the inverter's amplitude control loop system and phase control loop system so that the current of each inverter's output bus is detected and the difference current becomes zero. to match the amplitude and phase of both power supplies,
After that, after turning on the commercial power to the common bus, the currents of the inverter's output bus and the common bus are detected through the load sharing ratio setting device, and the inverter's amplitude control loop system and phase control are performed so that the difference current becomes zero. We found that by controlling the internal induced voltage of the inverter by giving auxiliary target values to each loop system, it is possible to share the load between the inverter and the commercial power supply at a predetermined ratio.

Therefore, an object of the present invention is to control the sharing of loads in an arbitrary ratio between the two power sources in a power supply facility in which two power sources are connected to a common bus line to which loads are connected via switches, respectively. The purpose of the present invention is to provide a load sharing control method that can

In order to achieve the above object, the present invention comprises a power supply facility in which two power sources are connected to a common bus to which loads are connected via switches, and the voltage of the first power source is transferred to the second power source. a first regulation loop that matches the voltage of the first power supply and a second regulation loop that matches the phase of the first power supply with the phase of the second power supply to transfer a load from either power supply to the other power supply; In this case, after matching the voltage and phase of both power supplies under the action of both regulation loops and applying the other power supply to the common bus, the voltage and phase of the one power supply is adjusted by giving an auxiliary target value to both regulation loops. In a load transfer control method for power supply equipment configured to narrow down the output current, a first power supply with opposite polarity is connected to the output bus of the first power supply.
A current transformer and a second current transformer are connected in series, a third current transformer is connected to a common bus, and one end of the output side of the second current transformer and the third current transformer is connected in common to obtain a reference potential. The output side of the second current transformer is short-circuited with a series circuit of the load sharing ratio setting device and the second relay, and the output side of the first current transformer is connected to the output side of the first current transformer. A current detector with a differential current detection terminal is provided,
The currents of the output bus of the first power supply and the common bus are respectively detected, and the voltages and phases of the two power supplies are matched under the action of both adjustment loops so that the difference current becomes zero, and the load sharing ratio of the two power supplies is adjusted. Accordingly, the currents of the output bus of the first power supply and the common bus are respectively detected, and an auxiliary target value is provided to both of the adjustment loops so that the difference current becomes zero.

In the load sharing control method described above, it is preferable that the first adjustment loop is an amplitude control loop system and the second adjustment loop is a phase control loop system.

In this case, the difference current component obtained by the current detector is calculated into a parallel component and a perpendicular component to the common bus voltage, and the parallel component is used as the auxiliary target value of the amplitude control loop system, and the perpendicular component is used for phase control. It is preferable to use it as an auxiliary target value for a loop system.

Further, in the load sharing control method described above, the load sharing ratio setting device can be adjusted to any range from 1 to 100% using a variable resistor.

Next, an embodiment of the load sharing control method for power supply equipment according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the basic configuration of a circuit implementing the method of the present invention. That is, the first
In the figure, reference numeral 10 indicates an output bus connected to a first power source constituted by an inverter, and reference numeral 12 indicates an output bus connected to a second power source such as a commercial power source. These output buses 10 and 12 are connected to a common bus 18 via switches 14 and 16, respectively, and a load 20 is connected to this common bus 18.

The inverter constituting the first power supply is composed of a plurality of inverter sections depending on the number of phases thereof. However, in the embodiment of FIG.
indicates an individually configured inverter section. The inverter section 22 includes a conversion element 24 composed of a thyristor or the like, a voltage regulator 26 for maintaining the output voltage at a rated value, and a pulse distributor (ring counter) for forming control pulses for the exchange element 24. ) 28, a firing angle regulator 30, and a pulse amplifier 32.

In order to make it possible to match the output voltage of the inverter section 22 with the voltage of the second power supply (hereinafter referred to as the commercial power supply in this embodiment), another voltage regulator 34 is provided.
is provided, and the output end of this voltage regulator 34 is switched
It is connected to the input terminal a on the voltage regulator 26 side of the inverter section 22 via _S1 . The voltage regulator 34 receives the voltage value of the commercial power supply detected by the voltage detector 36 as a target value, and the inverter output power supply value detected by the voltage detector 38 as an actual value. On the other hand, in order to operate the inverter section 22 at the rated frequency with high precision, a crystal oscillator 40 is provided, and the output of the crystal oscillator 40 is transmitted to a waveform shaper 4.
After the waveform is shaped in step 2, the input terminal b on the pulse distributor 28 side of the inverter section ₂₂ is connected via the changeover switch S2.
Configure it to be installed in In addition, the inverter section 2
In order to make it possible to match the output frequency of the inverter section 22 with the frequency of the commercial power source, a voltage frequency converter 44 is connected via the changeover switch _S2 , and further to match the phase of the inverter section 22 with the phase of the commercial power source. A phase adjuster 46 is provided to input the output voltage of the phase adjuster 46 to the voltage-frequency converter 44. Note that the input end of the phase adjuster 46 is configured to be connected to the output end of either of the phase discriminators 50, 52 via the phase difference detector 48 and the changeover switch _S3 . In this case, the phase discriminator 50 includes the voltage detectors 36, 3
8, the detected voltages of both power supplies are guided to determine the phase between the two voltages, a phase difference detector 48 detects the phase difference, and a phase adjuster 46 performs an adjustment operation to match the phases. On the other hand, the phase discriminator 52
determines the phase between the output pulse from the crystal oscillator 40 and the output pulse from the voltage-frequency converter 44, detects the phase difference with the phase difference detector 48, and generates both output pulses with the phase adjuster 46. Make adjustments to match the time points. Thereby, a shock to the inverter section 22 due to switching of the changeover switch _S2 can be completely avoided.

The above configuration is a circuit configuration that is substantially common to a circuit that implements a conventional load transfer control method.

In the present invention, a current detector 54 and a calculator 56 are further provided. The current detector 54 includes a current transformer 58 that detects the current of the inverter output bus 10 and a current transformer 60 that detects the current of the common bus 18. Further, the calculator 56 forms an auxiliary input voltage for the voltage regulator 34 and the phase regulator 46 according to the output voltage of the current detector 54 .

FIG. 2 shows a specific example of the configuration of the current detector 54 shown in FIG. That is, two current transformers CT ₁ and CT ₂ are connected to the inverter output bus 10, and the output sides of both current transformers CT ₁ and CT ₂ are connected in series with opposite polarities. On the other hand, common bus line 1
One current transformer CT ₃ is connected to 8. A load resistor R is connected to the output sides of these current transformers CT ₁ , CT ₂ , CT _3, respectively, and one end of the output side of current transformer CT ₂ and one end of the output side of current transformer CT ₃ are commonly connected. and placed at the reference potential point (OV), both current transformers CT ₂ ,
The other end of the output side of CT ₃ is configured to be connectable via relay Ry ₁ . Further, the output side of the current transformer CT ₂ is configured to be short-circuitable by a series circuit of a variable resistor Rv that sets a load sharing ratio and a relay Ry ₂ . Therefore, the output terminal A of the current detector 54 is led out from the other end of the output side of the current transformer _CT1 . Current transformer
CT ₁ and CT ₂ each generate an output voltage proportional to the inverter output current I〓 _R , and the current transformer CT ₃ generates a voltage proportional to the common bus current I〓 _L. As shown in the figure, when the relays Ry ₁ and Ry ₂ are in the open state, the output current △ appearing at the output terminal A of the current detector 54
I〓 is zero. When relay Ry ₁ is closed, the second
The circuit shown in the figure becomes an equivalent circuit as shown in FIG. 3, and an output current △I〓 proportional to the difference current between the inverter output current I〓 _R and the common bus current I〓 _L is obtained.
However, in the equivalent circuit shown in FIG. 3, the vector relationships among the terminals A, C, and O when relay Ry ₂ is in the open state are as shown in FIG. 4. In Figure 4, if I〓 _R = I〓 _L , then E〓 ₁ = I〓 ₂ Therefore △I〓 =
It becomes O. Further, in the equivalent circuit shown in FIG. 3, the vector relationships among the terminals A, C, and O when relay Ry ₂ is closed are as shown in FIG. 5. In this case, the voltage E〓 ₁ between terminals OC becomes E ₁ =R·R _V /R+2R _V (i〓 _R +i〓 _L ). If control such as △I〓→O is performed in this state, E〓 ₂ =E〓 ₁ as a result. That is, i〓 _R =
ki〓 _L , so I〓 _R = kI〓 _L (where k=R _V /R+R _V
). From the above, since the common bus current I〓 _L is constant,
Of this, 100k% is supplied with the inverter output current _I〓R , and the remaining 100(1-k)% is supplied with the commercial current _I〓C . In other words, load sharing control can be performed between the inverter power source and the commercial power source using the power supply ratio.

FIG. 6 shows an equivalent circuit of the arithmetic unit 56 shown in FIG. 1. From the equivalent circuit shown in FIG. 6, the following relational expression is established between the inverter internal induced voltage E〓 _i and the output common bus voltage (reference bus voltage) E〓 _O.

E〓 ₁ =V〓 _X +V〓 _R +E〓 _O =△I〓(X+R)+E〓
_O However, E〓 _O : Output common bus voltage △I〓: Difference current (amount equivalent to I〓 _R − I〓 _L ) E〓i: Inverter internal induced voltage caused by △I〓 V〓 _X : Inductance (X) voltage drop V〓 _R : Voltage drop due to resistance (R) Now, if we take the phase angle of the output common bus voltage E〓 _O and the difference current △I〓, the above relational expression is a vector relation. The result is as shown in FIG. Therefore _, in the vector diagram _shown in Figure 7, if we decompose the voltage drop due to inductance _V〓 The result is as shown in FIG.

That is, as is clear from Fig. 8, the difference current △
If we _decompose the voltage _{drop V〓} I〓(Xsin+Rcos) The perpendicular component is b〓=△I〓(Xcos−Rsin), and when the internal induced voltage of the inverter is the control target, the parallel component a〓 constitutes the control loop system of the amplitude control system. However, the orthogonal component b〓 constitutes the control loop system of the phase control system, and the internal induced voltage of the inverter can be rationally controlled.

Therefore, as described above, the computing unit 56 converts the difference current △I〓 component detected by the current detector 54 into a component a〓 parallel to the output common bus voltage E〓 _O and a component perpendicular to the output common bus voltage E〓 O.
b〓 is calculated, and the parallel component a〓 is given as an auxiliary target value to the voltage regulator 34 of the amplitude control loop system, and the orthogonal component b〓 is given as an auxiliary target value to the phase adjuster 46 of the phase control loop system. It is given as a target value, and the internal induced voltage of the inverter is controlled.

The partial configuration and operation of the embodiment shown in FIG. 1 have been explained above, and next, the overall operation of the load sharing control system according to the present invention will be explained.

When partially supplying commercial power from inverter power supply (1) Inverter power supply First, switch 14 is closed, and switch 16
It is assumed that the inverter is in an open state and the load 20 is supplied with power only from the inverter output bus 10. In this case, the switches S ₁ , S ₂ , and S ₃ are in the state shown in FIG. 1, and the relay of the current detector 54 is
Ry ₁ and Ry ₂ (see Figure 2) are also in the open state. The inverter section 22 is operated at a rated voltage by a built-in voltage regulator 26 and at a rated frequency by a crystal oscillator 40.

In this state, when part of the load should be shared from the inverter power source to the commercial power source, a commercial power supply command is first issued, and this command generates a commercial synchronization command signal. This command signal closes the switch S ₁ , and the voltage regulator 34 starts adjusting the output voltage of the inverter section 22 to match the commercial voltage, and at the same time, the changeover switches S ₂ and S ₃ are placed in the opposite state as shown in the figure. Then, an adjustment operation is started to match the phase of the output voltage of the inverter section 22 with the phase of the commercial power supply voltage. Furthermore, relay Ry ₁ (Fig. 2) in the current detector 54 is closed by the commercial synchronization command signal, and differential current balance control (I〓 _R = I〓 _L , that is, △I〓
=O) is performed [see Figures 3 and 4].
When the common bus voltage E〓 _O (equal to the inverter output voltage at this time) completely matches the standby commercial voltage in both amplitude and phase, preparations for load sharing are completed.

(2) Load sharing by commercial power supply The switch 16 is turned on after a predetermined period of time, for example 10 seconds, has elapsed after the generation of the commercial synchronization command signal. Immediately before the switch 16 is closed, the common bus voltage E〓 _O and the commercial voltage match in amplitude and phase, so no inrush current occurs immediately after the switch 16 is closed. Therefore, in this case, due to the differential current balance control by the current detector 54, power is supplied to the load 20 100% from the inverter, and no power is supplied from the commercial power supply side.

When a predetermined period of time has elapsed since the generation of the closing command for the switch 16, a load sharing control command signal is issued, which closes the relay Ry ₂ (Fig. 2) in the current detector 54, and △I〓 =E〓 ₂
-E〓 A difference current of ₁ is detected (see Figure 5). The difference current △I〓 detected by the current detector 54 in this way is determined by the amplitude and the amplitude by the calculator 56.
The inverter's internal induced voltage is controlled by each control system loop so that the phase becomes △I〓→O [see FIGS. 6 to 8].

In this case, for △I〓→O, E〓 ₂ = E〓 ₁
That is, I〓 _R =kI〓 _L (k=R _V /R+R _V ), and the inverter output current I〓 _R becomes 100k% of the common bus current I〓 _L. Therefore, I〓 _L (constant) = I〓 _C +
Since I〓 _R , I〓 _P = kI〓 _L , that is, I〓 _C = (1-k)I
〓 _L
Therefore, for a load of 20, the load is 100 from the commercial power supply side.
(1-k)% power is supplied from the inverter.
The inverter internal induced voltage is controlled so that 100k% power is supplied.

After confirming that partial load sharing is completed, inverter power supply and commercial power supply are continuously performed at the above ratio. Note that the load sharing ratio can be freely changed by changing the resistance value R _V .

When performing inverter power supply from inverter power supply and some commercial power supply (1) Load sharing by commercial power supply First, an inverter power supply command is issued.
In this state, the switches 14 and 16 remain closed, the switches S ₁ , S ₂ , and S ₃ are in the opposite state to the state shown in FIG _{. 2} (see Figure 2) is also closed,
The inverter and commercial power supply each perform load sharing control. Then, when the output common bus voltage _E〓O during partial commercial power supply completely matches the voltage of the standby inverter in both amplitude and phase, preparation for load transfer is completed.

(2) Inverter power supply After the load transfer preparation is completed, the load sharing control command is reset, which causes the relay Ry ₂ (Fig. 2) in the current detector 54 to open. As a result, the current detector 54 starts differential current balance control, and the arithmetic unit 56 calculates I〓 _R =kI〓 _L , I〓 _C
The inverter internal induced voltage is controlled so that the state of =(1-k) _I〓L becomes _I〓R → _I〓L ( _I〓C →O) [see FIGS. 3 to 8].

In this way, until now for a load of 20,
Previously, 100(1-k)% of power was supplied from the commercial power supply side and 100k% of power was supplied from the inverter side, but the inverter internal induced voltage is controlled until power is supplied from the inverter side and power is no longer supplied from the commercial power supply side. After confirming the completion of load transfer, switch 16
By shutting off the power supply, the power supply switches to 100% inverter power supply.

Thereafter, the commercial synchronization command signal is reset after a predetermined period of time has elapsed, and this causes the current detector 5 to
The relay Ry ₁ (Fig. 2) of No. 4 is opened, and the switch S ₁ is also opened. After a predetermined time period, the changeover switches S ₂ and S ₃ are also switched to the state shown in FIG. 1. As a result, although the inverter output bus voltage has until now been synchronized with the commercial bus voltage in both amplitude and phase, the amplitude is controlled by the voltage regulator 26 inside the inverter, and the phase is synchronized with the crystal oscillator 40.

As is clear from the embodiments described above, according to the present invention, when inverter power supply and commercial power supply are performed to a common bus to which a load is connected, differential current balance control by a current detector and inverter internal induction by a calculator are performed. By voltage control, the load sharing ratio can be freely and smoothly changed from 0 to 100%. In particular, load sharing and transfer is performed without interruption.

Furthermore, since load sharing control is performed gradually with the commercial bus voltage and inverter bus voltage matched in both amplitude and phase, there is no effect of transient fluctuations during load sharing and no effect on the load. Therefore, the present invention can sufficiently improve reliability even when applied to partial load transfer between systems in a large-capacity system.

Although the preferred embodiments of the present invention have been described above, the method of the present invention is not limited to inverters, and can be applied to various control targets such as rotating machines, in which the controlled variable has an amplitude and a phase. Of course, various other design changes can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

Fig. 1 is a block wiring diagram showing an embodiment of the load sharing control method according to the present invention, Fig. 2 is a circuit diagram of the current detector shown in Fig. 1, and Fig. 3 is a circuit diagram of the current detector shown in Fig. 2. Figures 4 and 5 are vector diagrams showing the relationship between the equivalent circuits shown in Figure 3, Figure 6 is an equivalent circuit diagram of the arithmetic unit shown in Figure 1, and Figures 7 and 8. 7 is a vector diagram showing the relationship of the equivalent circuit shown in FIG. 6. FIG. DESCRIPTION OF SYMBOLS 10...Commercial output bus, 12...Inverter output bus, 14...Switch, 16...Switch, 18...Common bus, 20...Load, 22...Inverter section, 24...Conversion element, 26...Voltage regulator, 28...Pulse Distributor, 30... Firing angle regulator, 32... Pulse amplifier,
34... Voltage regulator, 36... Voltage detector, 38... Voltage detector, 40... Crystal oscillator, 42... Waveform shaper, 44... Voltage-frequency converter, 46... Phase adjuster, 48... Phase difference detector, 50... Phase discriminator, 5
2... Phase discriminator, 54... Current detector, 56... Arithmetic unit, 58... Current transformer, 60... Current transformer, S ₁ ... Switch, S ₂ , S ₃ ... Changeover switch, CT ₁ , CT ₂ , CT ₃ ...
Current transformer, Ry ₁ , Ry ₂ ...Relay.

Claims (1)

[Claims] 1. Consists of power supply equipment in which two power sources are connected to a common bus to which loads are connected via switches, and a second power source that matches the voltage of the first power source with the voltage of the second power source. A first adjustment loop and a second adjustment loop that matches the phase of the first power supply with the phase of the second power supply are provided, and when moving a load from either one of the power supplies to the other power supply, After matching the voltage and phase of both power supplies under the action of a regulation loop and applying the other power supply to a common bus, the output current of the one power supply is narrowed down by giving an auxiliary target value to both regulation loops. In the load transfer control method of the power supply equipment, the output bus of the first power supply is connected to the first
A current transformer and a second current transformer are connected in series, a third current transformer is connected to a common bus, and one end of the output side of the second current transformer and the third current transformer is connected in common to obtain a reference potential. The output side of the second current transformer is short-circuited with a series circuit of the load sharing ratio setting device and the second relay, and the output side of the first current transformer is connected to the output side of the first current transformer. A current detector with a differential current detection terminal is provided,
The currents of the output bus of the first power supply and the common bus are respectively detected, and the voltages and phases of the two power supplies are matched under the action of both adjustment loops so that the difference current becomes zero, and the load sharing ratio of the two power supplies is adjusted. A load sharing control method for power supply equipment, characterized in that the currents of the output bus of the first power supply and the common bus are respectively detected in response to the current, and an auxiliary target value is given to both adjustment loops so that the difference current between the two becomes zero. 2. A load sharing control system for power supply equipment according to claim 1, in which the first adjustment loop is comprised of an amplitude control loop system, and the second adjustment loop is comprised of a phase control loop system. 3. In the load sharing control method described in claim 1, the difference current component obtained by the current detector is calculated into a component parallel to the common bus voltage and a component perpendicular to the common bus voltage, and the parallel component is used in the amplitude control loop system. A load sharing control method for power supply equipment that consists of using the orthogonal component as the auxiliary target value of the phase control loop system. 4. A load sharing control method for power supply equipment, in which the load sharing ratio setter is configured with a variable resistor, in the load sharing control method according to claim 1.