JPS6338945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides power supply equipment in which two power supplies are connected to a common bus to which loads are connected via switches, in which power supply from one power supply to the load is switched from one power supply to the other power supply. The present invention relates to a load transfer control method that switches power supply from

Generally, power supply to important loads is performed by an uninterruptible power supply configured with a static inverter. However, even in such an uninterruptible power supply, it may be necessary to stop the operation for maintenance inspection, etc., but in this case, it may not be possible to stop the power supply to the load. Therefore, in such a case, it is necessary to move the load to another power source such as a commercial power source before stopping the operation of the uninterruptible 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
and a second adjustment loop that matches the phase of the second power supply with 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, the load transfer control method proposed earlier controls the internal induced voltage of the inverter so that the common bus voltage matches the commercial voltage in both amplitude and phase, for example, when transferring the load from the inverter side to the commercial power source side. Since the configuration of the current detector for this purpose has become complicated, manufacturing costs have increased and problems have arisen in terms of performance and reliability.

Therefore, as a result of various studies to overcome the problems of the conventional load transfer control method described above, the inventor of the present invention discovered that, for example, when transferring a load from an inverter to a commercial power source, the inverter output bus and common bus Each current is detected by a single current transformer, and the internal induced voltage of the inverter is controlled under the action of the inverter's amplitude control loop system and phase control loop system so that the difference current becomes zero. Match the amplitude and phase, then turn on the commercial power to the common bus, and then detect the inverter's output bus and common bus currents to make sure the inverter's common bus current is zero (when moving from the commercial power to the inverter, By controlling the internal induced voltage of the inverter by giving auxiliary target values to the amplitude control loop system and phase control loop system of the inverter respectively so that the output bus current and common bus current become equal, the commercial power supply ( We also found that it is possible to easily and appropriately control load transfer from commercial power sources to inverters.

Therefore, it is an object of the present invention to provide a power supply system in which two power sources are connected to a common bus to which loads are connected via switches, and to provide a simple structure and a stable structure, especially for the current detector. An object of the present invention is to provide a load transfer control method that can perform load transfer with high reliability.

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 current transformer is connected to the output bus of the first power supply,
A second current transformer is connected to the common bus, one end of the output side of the first current transformer and the second current transformer is commonly connected to provide a reference potential point, and the other end is connected via a relay, A current detector having a differential current detection terminal derived from the output side of the first current transformer is provided to detect the currents of the output bus of the first power supply and the common bus, respectively, and adjust the voltage between the two so that the difference current becomes zero. Matching the voltage and phase of both power supplies under the action of a regulating loop, detecting the currents of the output bus of the first power supply and the common bus so that the output bus current of the first power supply becomes zero or equal to the common bus current. It is characterized in that an auxiliary target value is provided to both said regulation loops.

In the load transfer 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.

Next, embodiments of the load transfer control system for power supply equipment according to the present invention will be described in detail 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 conversion 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 . To this voltage regulator 34, the voltage value of the commercial power supply detected by the voltage detector 36 is introduced as a target value, and the inverter output voltage value detected by the voltage detector 38 is introduced 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 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 furthermore, the phase of the inverter section 22 can be matched with the phase of the commercial power source. A phase adjuster 46 for matching is provided, and the output voltage of the phase adjuster 46 is configured to be input 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 is 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 computing unit 56 is connected to the current detector 5
4 forms the auxiliary input voltage for the voltage regulator 34 and the phase regulator 46.

FIG. 2 shows a specific example of the configuration of the current detector 54 shown in FIG. That is, single current transformers CT ₁ and CT ₂ are connected to the inverter output bus 10 and the common bus 18, respectively, and these current transformers
A load resistor R is connected to the output side of CT ₁ and CT ₂ , respectively, and one end of the output side of both current transformers CT ₁ and CT ₂ is commonly connected to derive a reference potential point 0, and both current transformers
The other ends of the output sides of CT ₁ and CT ₂ are configured to be connectable via a relay Ry, and an output terminal A is led out to the other end of the output side of the current transformer CT ₁ . The current transformer CT ₁ generates an output voltage proportional to the inverter output current I〓 _R , and the current transformer CT ₂ generates a voltage proportional to the common bus current I〓 _L. As shown in the figure, when the relay Ry is in the open state, the output current ΔI〓 appearing at the output terminal A of the current detector 54 becomes a current proportional to the inverter output current _I〓R . Therefore, the equivalent circuit in this case is as shown in FIG. However, the vector relationships between the terminals A, O, and A' in the equivalent circuit shown in FIG. 3 are as shown in FIG. 4. In FIG. 4, if ΔI = 0, -E = ₂ = 0 and I = _R = 0. Therefore, from the relationship I〓 _L = I〓 _R + I〓 _C , if I〓 _R = 0, then I〓 _L = I〓 _C (commercial power supply). Further, in the circuit shown in FIG. 2, an equivalent circuit when relay Ry is closed is as shown in FIG. 5. In this case, the vector relationship between terminals A and O is as shown in FIG. That is, in FIG. 6, ΔI =
If it is 0, ΔI〓=E〓 ₁ −E〓 ₂ = 0, and E〓 ₁ =E〓
It becomes ₂ . Therefore, from the relationship I〓 _L = I〓 _R + I〓 _C , I〓 _L = I
〓 _R (inverter power supply).

Based on the above relationship, the load can be moved from inverter power supply to commercial power supply and from commercial power supply to inverter power supply by controlling the opening and closing of relay Ry and narrowing down so that the output current of current detector 54 is always zero. Can be done.

FIG. 7 shows an equivalent circuit of the arithmetic unit 56 shown in FIG. 1. From the equivalent circuit shown in Figure 7,
The following relational expression holds between the inverter internal induced voltage E〓 _i and the output common bus voltage (reference bus voltage) E〓 ₀ .

_{E〓 i = V〓 _ _ _ _} E〓 _i : Induced voltage inside the inverter due to ΔI〓 V〓 _X : Voltage drop due to inductance (X) V〓 _R : Voltage drop due to resistance (R) Now, the output common bus voltage _E〓 If the phase angle of the differential current ΔI is taken as the phase angle, the above relational expression becomes a vector relation as shown in FIG. Therefore, in the vector diagram shown in Figure 8, if we decompose the voltage drop due to inductance V〓 _X and the voltage drop due to resistance V〓 _R into a component parallel to the output common bus voltage _E〓 , as shown in FIG.

In other words, as is clear from Fig. 9, _the voltage _{drop V〓} When broken down into A control loop system with complete amplitude control is constructed, and the orthogonal component b〓 is a control loop system of a 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 ΔI〓 component detected by the current detector 54 into the component a〓 parallel to the output common bus voltage E〓 ₀ and the component perpendicular to
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. given as a value,
The internal induced voltage of the inverter is controlled.

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

Load transfer from inverter power supply to commercial 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 (see Figure 2) is also in an 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.

From this state, when the load should be transferred 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 causes the switch to
S ₁ is closed 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 switch is closed.
S ₂ and S ₃ are switched to the opposite state as shown, and 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, the relay Ry (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〓 _C = 0)
is carried out [see Figures 5 and 6]. When the common bus voltage E〓 ₀ (equal to the inverter output voltage at this time) completely matches the standby commercial voltage in amplitude and phase, preparations for load transfer are completed.

(2) Commercial power supply The switch 16 is turned on when 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 turned on, the common bus voltage E〓 ₀ and the commercial voltage match in amplitude and phase, so no inrush current occurs immediately after the switch 16 is turned on. Therefore,
In this case, due to 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 source side.

When a predetermined period of time has elapsed since the generation of the closing command for the switch 16, a load transfer control command signal is issued, which opens the relay Ry (Fig. 2) in the current detector 54, and ΔI〓=
-E〓 ₂ , which corresponds to I〓 _R, is detected (see Figures 3 and 4). The difference current ΔI〓 detected by the current detector 54 in this way is calculated by the calculator 5
At step 6, the inverter internal induced voltage is controlled so that ΔI〓→0 in both amplitude and phase through loops to each control system (see FIGS. 7 to 9).

In this case, in order for ΔI〓→0 to become −E〓→
0, I〓 _R →0, that is, the target value of the control is inverter output current I〓 _R =0. Therefore, I〓 _L (constant)
= I〓 _C + I〓 _R , so I〓 _R = 0, that is, I〓 _L = I〓 _C , and the voltage induced inside the inverter is set so that the load 20 is supplied with 100% power from the commercial power supply side and not supplied from the inverter. controlled.

After confirming the completion of the load transfer, the switch 14 is shut off and the inverter power supply is switched to commercial power supply.

Load transfer from commercial power supply to inverter power supply (1) Commercial power supply First, an inverter power supply command is issued.
In this state, the switch 14 remains open, the switches S ₁ , S ₂ , and S ₃ are in the opposite state to that shown in FIG. ) is also open. Then, the output common bus voltage E〓 ₀ in the commercial power line is
Preparation for load transfer is completed when the amplitude and phase completely match the voltage of the standby inverter.

(2) Inverter power supply After the load transfer preparation is completed, the switch 14 is turned on. At this time, the current detector 54 and the arithmetic unit 56 control the load transfer to the commercial power supply side, so under the condition of I〓 _L = I〓 _C + I〓 _R , I〓 _R = 0 (that is, ∆I〓 = -E 〓 ₂ = 0), that is, the inverter internal induced voltage is controlled so that I 〓 _L = I 〓 _C , and the load 20 is supplied with 100% power from the commercial power supply side.
Power is not supplied from the inverter side.

When a predetermined period of time has passed after the switch 14 is turned on, the load transfer control command is reset, and this causes the relay Ry (second
) is closed. As a result, the current detector 5
4, differential current balance control is started, and the arithmetic unit 56
, from the relationship I〓 _L = I〓 _C + I〓 _R , I〓 _L = I〓 _C (
I〓 _R
The internal induced voltage of the inverter is controlled so that I〓 _R →I〓 _L (I〓 _C →0) from the state of I〓 R →I〓 L (I〓 C →0) [see FIGS. 5 to 9].

In this way, the load was previously supplied with 100% power from the commercial power source, but the inverter's internal induced voltage is controlled until the load is supplied with power from the inverter and is no longer supplied from the commercial power source. After the load transfer is completed, the switch 16 is shut off to switch 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
4 (Fig. 2) is opened, and switch _S1 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 or commercial power supply is performed to a common bus to which a load is connected, differential current balance control and calculation using a current detector having a simple configuration can be performed. By controlling the induced voltage inside the inverter,
Load transfer can be performed smoothly and stably. In particular, load transfer is performed without interruption.

Furthermore, since load transfer control is performed gradually with the commercial bus voltage and inverter bus voltage completely matched in both amplitude and phase, there is no effect of transient fluctuations during load transfer and no effect on the load. Therefore, the present invention can sufficiently improve reliability even when applied to 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 the drawing]

Fig. 1 is a block wiring diagram showing an embodiment of the load transfer 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. Figure 4 is a vector diagram showing the relationship between the equivalent circuits shown in Figure 3, Figure 5 is an equivalent circuit diagram when relay Ry of the current detector shown in Figure 2 is closed, Figure 6 is an equivalent circuit diagram of The figure is a vector diagram showing the relationship of the equivalent circuit shown in Fig. 5, Fig. 7 is an equivalent circuit diagram of the arithmetic unit shown in Fig. 1, and Figs. 8 and 9 are vector diagrams showing the relationship of the equivalent circuit shown in Fig. 7. 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 ... Transformer. Ryuki, Ry…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 power supply equipment, a first current transformer is connected to the output bus of the first power supply,
A second current transformer is connected to the common bus, one end of the output side of the first current transformer and the second current transformer is commonly connected to provide a reference potential point, and the other end is connected via a relay, A current detector having a differential current detection terminal derived from the output side of the first current transformer is provided to detect the currents of the output bus of the first power supply and the common bus, respectively, and adjust the voltage between the two so that the difference current becomes zero. Matching the voltage and phase of both power supplies under the action of a regulating loop, detecting the currents of the output bus of the first power supply and the common bus so that the output bus current of the first power supply becomes zero or equal to the common bus current. A load transfer control method for power supply equipment, characterized in that an auxiliary target value is given to both of the adjustment loops. 2. A load transfer control method for power supply equipment according to claim 1, in which the first adjustment loop consists of an amplitude control loop system, and the second adjustment loop consists of a phase control loop system. 3. In the load transfer 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 converted into an amplitude control loop system. A load transfer control method for power supply equipment that consists of using the orthogonal component as the auxiliary target value of the phase control loop system.