JP2001286078A - Uninterruptible power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply stable power to an important load without any short interruption also when an upstream open mode occurs when a load is connected in parallel with a serial/parallel compensation instantaneous drop countermeasure system. SOLUTION: This uninterruptible power supply system is provided with a power supply 60, an important load 70 that does not allow instantaneous drop of power that is fed from the power system 60, and the series/parallel compensation instantaneous drop countermeasure system that consists of a parallel transformer 40 that is inserted in parallel with the power line that is provided between the power system 60 and the important load 70, a series transformer 50 that is connected in series with the power line, a parallel compensation converter 10 that is connected to the parallel transformer, a series compensation inverter 20 that is connected to the series transformer, and a power storage medium 30 that is connected between the parallel compensation converter and the series compensation inverter, and copes with instantaneous power drop and power failure. Also, the interruptible power supply system is provided with an input switch 80 for breaking between the power system 60 and the series/ parallel compensation instantaneous drop countermeasure system when detecting an open fault at a power system side or the overload or overcurrent of the parallel compensation converter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a parallel transformer or a parallel reactor connected to a power supply line in parallel, a series transformer connected in series to a power supply line, and a parallel compensation connected to the parallel transformer or the parallel reactor. A converter, a series compensation inverter connected to the series transformer, a power storage medium connected between the parallel compensation converter and the series compensation inverter, a parallel compensation converter control circuit for controlling the parallel compensation converter, A power supply system that uses a series-parallel compensation type instantaneous voltage sag countermeasure system that supplies a power to the important load from the power storage medium when the voltage of the power supply line drops when the power supply line voltage drops. And an uninterruptible power supply system.

[0002]

2. Description of the Related Art Conventionally, as a power supply system for supplying power without interruption to a load that does not allow instantaneous voltage drop of a power supply line,
There is a power supply system using an uninterruptible power supply system described in Japanese Patent Application No. 11-310524.

The configuration of a power supply system using a conventional series-parallel compensation type instantaneous voltage drop countermeasure system will be described with reference to FIG. The power supply system includes a load (important load) 70 that does not allow a sag, a power system 60 that supplies power to the important load, and a primary winding that is connected to a power supply line that supplies power from the power system to the important load. A parallel transformer or a parallel reactor 40 connected in parallel, a series transformer 50 having a primary winding connected in series to the power supply line, and a parallel compensation converter connected to a secondary winding or the parallel reactor of the parallel transformer 10, a series compensation inverter 20 connected to the secondary winding of the series transformer, a power storage medium 30 connected between the parallel compensation converter and the series compensation converter, and a voltage of the DC intermediate circuit. A DC intermediate circuit voltage detection circuit (VSDC) 35 that outputs a DC intermediate circuit voltage detection value EDC, and an output current (input voltage) of the parallel compensation converter ) And a parallel compensation converter output current detection circuit (CTC) 63 for detecting the load current and outputting a load current detection value IL.
And an input voltage detection circuit (P) that detects the input voltage of the series-parallel compensation type sag protection system and outputs an input voltage detection value Vi.
TI) 67, a parallel compensation converter control circuit 100 for controlling the parallel compensation converter, a series compensation inverter control circuit 200 for controlling the series compensation inverter,
An upstream open detection circuit 85 that detects a frequency drop or a voltage drop of the input voltage and outputs an input switch open signal; and disconnects the connection between the power system and the series-parallel compensation type instantaneous sag prevention system by the input switch open signal. An input switch 80 is provided.

In such a power supply system,
As a countermeasure against voltage sag or power failure occurring in the power system, the parallel compensation converter 10 is connected in parallel to a feeder (power supply line) of the important load 70 which is a power failure and voltage sag compensation target via a parallel transformer or a parallel reactor 40. , The series compensating inverter 20 is connected in series via a series transformer 50, and the power storage medium 30 is connected to a DC line (DC intermediate circuit) between the parallel compensating converter 10 and the series compensating inverter 20 to perform a series-parallel compensation method. Constructs a sag protection system.

In this system, the voltage applied to the important load 70 is changed to the rated voltage of the important load 70 by directly adding the output voltage of the series compensation inverter 20 to the voltage of the power supply line via the series transformer 50 as a compensation voltage. Compensated. That is, when the voltage of the power supply line is constantly lower than the rated voltage or when an instantaneous voltage drop occurs, the shortage is generated by the series compensation inverter 20 and the voltage is converted to the voltage of the power supply line via the series transformer 50. To maintain the rated voltage.

In such a system, when an open accident such as a complete power failure of the system, disconnection of the power system, or opening of the upstream circuit breaker occurs, the upstream open detecting circuit 85 is used to reduce the frequency of the input voltage or to reduce the voltage. After detecting the upstream opening accident due to the drop and opening the input switch 80, the control mode of the parallel compensation converter 10 is switched from the current control mode to the voltage control mode to establish a stable voltage from the parallel compensation converter 10, and the parallel compensation converter 10 → Series transformer 50 → Important load 70 → Parallel compensation converter 10
, A stable electric power is supplied to the important load 70.

In this system, the energy shortage in the power supply line is supplied from the power storage medium 30. That is, when the voltage of the power supply line is lower than the rated voltage, the power can be supplied from the power storage medium 30 via the series transformer 50 and the series compensation inverter 20 to maintain the rated voltage of the important load 70.

Further, when energy is exchanged with the power supply line in accordance with the voltage compensation operation of the series compensation inverter 20, the parallel compensation converter 10 supplies or regenerates the power and supplies the energy to the important load 70. It also operates as an active filter that compensates for reactive and unbalanced currents (negative-sequence currents) and harmonic currents.

Next, a control method of the parallel compensation converter 10 by the series-parallel compensation system instantaneous voltage reduction system will be described with reference to FIG. FIG. 10 is a diagram showing a specific configuration of the parallel compensation converter control circuit 100 in FIG.

The parallel compensation converter control circuit 100 includes a DC intermediate circuit voltage compensation current operation circuit 110, a load current compensation current operation circuit 120, a parallel compensation converter output current control operation circuit 130, and a parallel compensation converter output voltage command operation circuit. 140, a PWM control circuit 150, a carrier signal generation circuit 155, and a gate drive circuit 160
A current / voltage control mode switcher 170, an input voltage control operation circuit 180, an input voltage reference value setter 191,
An input frequency reference value setting device 193 and a time limit setting device 195 are provided.

DC intermediate circuit voltage compensation current operation circuit 110
Is the DC intermediate circuit voltage target value EDC ^*And DC intermediate circuit
To make the DC intermediate circuit voltage constant from the pressure detection value EDC
Active current to be output from necessary parallel compensation converter 10
(Hereinafter referred to as DC intermediate circuit voltage compensation effective current signal)
No.).

The load current compensation current calculation circuit 120 calculates a calculated value obtained by extracting an invalid component, a harmonic component, and a negative phase component of the load current flowing into the load from the load current detection value IL and the input voltage detection value Vi. The current necessary to cancel the reactive component, the harmonic component, and the negative phase component of the load current to be output by the parallel compensation converter 10 from the DC intermediate circuit voltage compensation effective current signal output from the circuit voltage compensation current calculation circuit 110. In addition, a current required to keep the DC intermediate circuit voltage constant (hereinafter, referred to as a current control mode parallel compensation converter output current target value signal) is calculated.

The parallel compensation converter output current control operation circuit 130 calculates a deviation between the current control mode parallel compensation converter output current target value signal or the voltage control mode parallel compensation converter output current target value signal and the parallel compensation converter output current detection value Ic. Is calculated (hereinafter, referred to as a parallel compensation converter output voltage change command signal) required to make the output zero equal to zero.

The parallel compensation converter output voltage command calculation circuit 140 calculates the output voltage command signal of the parallel compensation converter 10 from the parallel compensation converter output voltage change command signal and the input voltage detection value Vi.

The PWM control circuit 150 includes an output voltage command signal of the parallel compensation converter 10 and a carrier signal generation circuit 1
A comparison is made with the carrier signal from 55, and a switching signal of a switching element bridge constituting the parallel compensation converter 10 is output.

The gate drive circuit 160 supplies driving power to the switching element bridge based on the switching signal.

The current / voltage control mode switch 170 is a current control mode parallel compensation converter output current target value signal from the load current compensation current calculation circuit 120 or a voltage control mode parallel compensation converter described later from the input voltage control calculation circuit 180. One of the output current target value signals is selected based on the control mode selection signal from the upstream open detection circuit 85, and whether the parallel compensation converter 10 is operated in the current control mode or the voltage control mode is selected.

The input voltage control operation circuit 180 calculates the input voltage detection value Vi, the input voltage reference value Vi ^* from the input voltage reference value setting device 191, and the input frequency reference value ω 0 from the input frequency reference value setting device 193. , The time limit value T from the time limiter 195 is input, and the input voltage detection value Vi and its frequency at the moment when the start signal is received from the upstream open detection circuit 85, the input voltage reference value Vi ^* (for example, 95% of the rating) ,
From the input frequency reference value ω0 (for example, 50 Hz) and the time limit value T, the parallel compensation converter necessary for the input voltage to become the reference voltage and the reference frequency after the time limit value T from the input voltage and input frequency at the moment when the start signal is received. 10 calculates a current to be output (hereinafter referred to as a voltage control mode parallel compensation converter output current target value).

The input switch 80 is connected to the upstream open detection circuit 8.
When the input switch release signal is received from the input switch 5, the input switch release signal is detected, and the input switch release answer back signal is output.

The upstream open detection circuit 85 monitors the frequency or voltage of the input voltage, and outputs an input switch open signal to the input switch 80 when detecting a frequency drop or a voltage drop in the input voltage. Further, when the upstream open detection circuit 85 receives the input switch open answer back signal from the input switch 80, the upstream open detection circuit 85 outputs a control mode switching signal to the current / voltage control mode switch 170, and outputs an input voltage control operation circuit 180. Output a start signal.

By establishing a stable voltage from the parallel compensation converter 10, the parallel compensation converter 10 →
A current closed circuit of the series transformer 50 → important load 70 → parallel compensation converter 10 is formed, and stable power can be supplied to the important load 70.

With the above control operation, the upstream open detection circuit 85 detects an upstream open accident due to a drop in the frequency or voltage of the input voltage, opens the input switch 80, and switches the control mode of the parallel compensation converter 10 to the current. Switch from control mode to voltage control mode. The parallel compensation converter 10 outputs the current so that the input voltage and the frequency become the reference values after the time limit. As a result, the input voltage and the frequency can be controlled to the reference values. A stable voltage can be established from the parallel compensation converter 10 before the self-defense function of the compensation converter operates, and a current closed circuit of the parallel compensation converter 10 → the series transformer 50 → the important load 70 → the parallel compensation converter 10 is formed. Thus, stable power can be supplied to the important load 70.

The flow of current and power at the time of an upstream opening accident in the prior art series-parallel compensation system voltage sag countermeasure system will be described with reference to FIGS.

<When an upstream accident occurs> If the voltage of the power system is, for example, 95% of the rated voltage of the important load 70 before the occurrence of the upstream opening accident, the input voltage must be 95% of the rated voltage of the important load 70. From the series compensation inverter 20
Generates a voltage of 5% of the rated voltage of the important load 70 and superimposes it on the input voltage via the series transformer 50 to establish a voltage of 100% for the important load 70.

As shown in FIG. 11, when an open accident occurs on the upstream side, the parallel compensation converter 10
And supplies 95% of the power supplied to the important load 70. Series compensation inverter 2
0 establishes a voltage of 5% of the rated voltage of the critical load 70,
5% of the power supplied to the important load 70 is supplied.

The current of the important load 70 is supplied from the parallel compensation converter 10 to form a closed loop of the parallel compensation converter 10 → the series transformer 50 → the important load 70 → the parallel compensation converter 10. The output current Ii of the series compensation inverter 20 forms a closed loop via the secondary winding of the series transformer 50.

The power storage medium 30 supplies power Pes to the parallel compensation converter 10 and the series compensation inverter 20. This corresponds to exactly 100% of the power supplied to the important load 70.

Therefore, the voltage of the power storage medium 30 drops sharply. In order to keep the voltage of the DC intermediate circuit constant, the operation of the parallel compensation converter control circuit 100 causes the parallel compensation converter 10 to perform an operation of absorbing power from the power supply line. Therefore, the output voltage of the parallel compensation converter 10 decreases or the frequency is delayed.

Since the current and power flows are not significantly related to frequency, the following description will be disregarded with respect to frequency.

<When the input switch 80 is opened by detecting that the input voltage has dropped to 90%, for example, by the upstream open detection circuit 85> As shown in FIG.
When the upstream open detection circuit 85 detects that the input voltage has dropped to 90% of the rated voltage of the important load 70, an input switch open signal is output and the input switch 80 is opened. The parallel compensation converter 10 is switched from the current control mode to the voltage control mode by the above-described control mode switching operation before being stopped by the self-defense function due to the voltage drop. Since this time is instantaneous, the input voltage remains at 90% of the rated voltage of the important load 70.

Since the input voltage is 90% of the rated voltage of the important load 70, the series compensation inverter 20
A voltage of 10% of the rated voltage of 0 is generated and superimposed on the input voltage via the series transformer 50, so that the important load 70 establishes a voltage of 100% of the rated voltage.

The current of the important load 70 is supplied from the parallel compensation converter 10 to form a closed loop of the parallel compensation converter 10, the series transformer 50, the important load 70, and the parallel compensation converter 10. In addition, the series compensation inverter 2
The output current Ii of 0 forms a closed loop via the secondary winding of the series transformer 50.

Since the parallel compensation converter 10 has established a voltage of 90% of the rated voltage of the important load, it supplies 90% of the power supplied to the important load 70. Further, since the series compensation inverter 20 establishes a voltage of 10% of the rated voltage of the important load 70, the power supplied to the important load 70 is 1%.
0% is supplied.

The power storage medium 30 supplies the power Pes of the parallel compensation converter 10 and the series compensation inverter 20. This corresponds to exactly 100% of the power supplied to the important load 70. Therefore, although the voltage of the power storage medium 30 is still sharply reduced, since the parallel compensation converter 10 is switched to the voltage control mode, there is no further decrease in the input voltage or the frequency, and the parallel compensation is performed by the self-defense function. There is no danger that converter 10 will stop.

Thereafter, the input voltage is gradually increased with a time limit T to, for example, 95% of the reference by the above-described control operation.

<When the input voltage is controlled to a reference value, for example, 95% and the parallel compensation converter 10 is controlled> As shown in FIG.
Is the same as <at the time of occurrence of an upstream accident> shown in FIG.

As described above, according to the embodiment of the present invention, even when an open accident occurs upstream, the power for driving parallel compensation converter 10 and series compensation inverter 20 is stored in power storage medium 30. During this time, the parallel compensation converter 10 does not stop due to the self-protection function, and the power supply to the important load 70 can be maintained.

In a conventional circuit configuration using the series-parallel compensation system sag protection system, when a load is connected in parallel to the series-parallel compensation system sag protection system, complete power failure of the system and disconnection of the power system. If an open accident occurs such as the opening of the upstream circuit breaker, there is a problem that the operation of the important load is hindered, and the load may be damaged. That is,
The flow of current and power in the case where a load is connected in parallel to the series-parallel compensation type sag protection system and an open accident occurs on the upstream side will be described with reference to FIGS. 14 and 15.

Assuming that the voltage of the power system is, for example, 95% of the rated voltage of the important load 70 before an open accident occurs in the upstream of the series-parallel compensation system voltage sag countermeasure system, Since the voltage is 95%, the series compensation inverter 20 generates a voltage of 5% of the rated voltage of the important load 70, and superimposes it on the input voltage via the series transformer 50 so that the important load 70 has 100% of the rated voltage.
Has established voltage. It is assumed that a load 75 is connected to the power system 60 in parallel.

When an open-circuit accident occurs upstream, as shown in FIG. 14, the parallel compensation converter 10 becomes a current supply source for the important loads 70 and 75, and the parallel compensation converter 10 → the series transformer 50 → the important load. 70 → the closed loop of the parallel compensation converter 10 and the parallel compensation converter 10
→ Load 75 → A closed loop of the parallel compensation converter 10 is formed. Since the parallel compensation converter 10 has established a voltage of 95% of the rated voltage of the important load 70, the important load power P
Supply 95% of iL and load power PL. Since the series compensation inverter 20 has established a voltage of 5% of the rated voltage of the important load 70, it supplies 5% of the important load power PiL.

The output current Ii of the series compensation inverter 20
Form a closed loop via the secondary winding of the series transformer 50.

As described above, when an upstream opening accident occurs, the power storage medium 30 supplies the power storage medium power Pes to the parallel compensation converter 10 and the series compensation inverter 20. This is just the important load power PiL and load power PL
Is equivalent to the sum of

Generally, the load power PL is the important load power Pi
It is much larger than L. Since the supply source of the load power PL is the parallel compensation converter 10, the output current of the parallel compensation converter is considerably larger than the rated current of the important load 70. Usually, the parallel compensation converter 10 has a self-defense function for automatically stopping the operation in the case of overload or overcurrent.

As shown in FIG. 15, when an overload or an overcurrent occurs, the parallel compensation converter 10 is stopped by its self-defense function. When the parallel compensation converter 10 stops, the series compensation inverter 20 generates a voltage of about 100% of the rated voltage of the important load 70 in order to establish the rated voltage of the important load 70.

The series compensation inverter 20 and the important load 70
And the load 75 form a series circuit. Therefore,
The voltage of the important load 70 is a voltage obtained by dividing the voltage of the series compensation inverter 20 by the impedance of the important load 70 and the impedance of the load 75.
Even if the voltage is about 100% of the rated voltage of 0, the voltage of the important load 70 becomes lower than the rated voltage, and the operation of the important load 70 is hindered. Further, as shown in FIG. 15, the voltage and current of the load 75 are reversed from the normal directions, and the load 75 may be damaged.

[0046]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a system in which a load 7
5 is connected, stable power is supplied to the important load 70 even when the upstream open mode occurs, and the load 7
It is an object of the present invention to provide an uninterruptible power supply system that does not damage the power supply system 5.

[0047]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a power system and a load (important) that is supplied from the power system and does not allow an instantaneous voltage drop (hereinafter referred to as an instantaneous voltage drop) of the power system. Load), a parallel transformer or a parallel reactor inserted in parallel to a power supply line provided between the power system and the important load, and a series transformer connected in series to the power supply line and connected to the parallel transformer or the parallel reactor. A parallel compensation converter, a series compensation inverter connected to the series transformer, and a power storage medium connected between the parallel compensation converter and the series compensation inverter. A series-parallel compensation type sag protection system, and an open circuit on the power system side between the series-parallel compensation system sag response system and the power system. Or said to constitute a uninterruptible power supply system provided with a switch which disconnects the power system and the serial-parallel compensation method sag measures system when it detects an overload or overcurrent of parallel compensation converter.

According to the present invention, in the above-described uninterruptible power supply system, the output current of the parallel compensation converter is limited to less than the overcurrent tolerance or the overload tolerance of the parallel compensation converter after detecting the overload or overcurrent of the parallel compensation converter. I made it.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an uninterruptible power supply system according to the present invention will be described below with reference to the drawings.

The present invention solves the above problem by limiting the current of the parallel compensation converter 10. The configuration of the present invention will be described with reference to the drawings.

The series-parallel compensation type instantaneous sag countermeasure system according to the present invention is different from the conventional uninterruptible power supply system shown in FIG. 9 in that the current limit signal is input to the upstream open detection circuit 85 and the parallel compensation converter control circuit 100 To output a current limit signal, and when an overcurrent or an overload of the parallel compensation converter 10 is detected, the output current of the parallel compensation converter is limited instantaneously. It is characterized in that an input switch 80 that performs a breaking operation is provided.

<First Embodiment> FIG. 1 is a block diagram showing a configuration of a power supply system using an uninterruptible power supply system according to the present invention. The configuration is the same as the configuration of the power supply system using the conventional uninterruptible power supply system described with reference to FIG. 9, and a current limit signal is input to the upstream open detection circuit 85 and a current limit signal is output from the parallel compensation converter control circuit 100. The point that we tried to do, and
Except for the point that the load 75 is connected in parallel with the uninterruptible power supply system, the detailed description is omitted since it is the same.

The configuration of the parallel compensation converter control circuit 100 used in the present invention will be described with reference to FIG.

The configuration of the parallel compensation converter control circuit 100 includes a PWM control circuit 150 and a gate drive circuit 160
, A limit current setter 157, a parallel compensation converter output current detection value Ic is input to the limit circuit 156, and a current limit signal is output from the limit circuit 156. Other than that, the configuration is the same as that of the conventional parallel compensation converter control circuit 100 described with reference to FIG.

DC intermediate circuit voltage compensation current calculation circuit 11
0, load current compensation current calculation circuit 120, parallel compensation converter output current control calculation circuit 130, parallel compensation converter output voltage command calculation circuit 140, carrier signal generation circuit 155, current / voltage control mode switcher 170, input voltage control calculation circuit The configuration and operation of the input switch 180 and the input switch 80 are the same as those of the prior art described with reference to FIG.

The PWM control circuit 150 includes an output voltage command signal of the parallel compensation converter 10 and the carrier signal generation circuit 1
A comparison is made with the carrier signal from 55 and a switching signal is output to the limit circuit 156.

The limit circuit 156 is a PWM control circuit 1
50 switching signal and limit current setting device 1
A switching processing signal is output to the gate drive circuit 160 based on the limit current set value IcL from the output signal 57 and the parallel compensation converter output current detection value Ic based on the control flowchart shown in FIG.
Output current limit signal to

The PWM control circuit 150 includes an output voltage command signal of the parallel compensation converter 10 and the carrier signal generation circuit 1
A comparison is made with the carrier signal from 55 and a switching signal is output to the limit circuit 156.

The limit circuit 156 is a PWM control circuit 1
50 switching signal and limit current setting device 1
A switching processing signal is output to the gate drive circuit 160 based on the limit current set value IcL from the output signal 57 and the parallel compensation converter output current detection value Ic based on the control flowchart shown in FIG. Output.

As shown in FIG. 3, the limit circuit 156
Compares the limit current setting value IcL from the limit current setter 157 with the parallel compensation converter output current detection value Ic (S1), and when the parallel compensation converter output current detection value Ic is less than the limit current setting value IcL (No). , The switching signal is output as it is as the switching processing signal (S4). In step S1, if the parallel compensation converter output current detection value Ic is equal to or larger than the limit current set value IcL (Yes), a current limit signal is output (S2).
At the same time, the switching processing signal is turned off for a predetermined time (S3), and then the switching signal is output as it is as the switching processing signal (S4), and the process returns to the start and repeats the same operation.

It is needless to say that the value of the limit current set value IcL is less than the overload tolerance or the overcurrent tolerance of the parallel compensation converter. The gate drive circuit 160
The driving power is supplied to the switching element bridge based on the switching processing signal from the limit circuit 156.

The upstream open detection circuit 85 detects a decrease in the input voltage (for example, 90% of the rated voltage) or a decrease in the input frequency (for example, 49.5 Hz (rated at 50 Hz)) from the detected input voltage Vi, or This is the same as the prior art except that an input switch open signal is output to the input switch 80 when the current limit signal is received.

The control method according to the first embodiment will be described below.

When an open accident occurs on the upstream side, the output current of the parallel compensation converter 10 increases for the reason described with reference to FIGS. 14 and 15, and the parallel compensation converter output current detection value Ic becomes the limit current set value IcL ( For example, when the current exceeds the rated current of the important load 70), the limit circuit 156 outputs a current limit signal to the upstream open detection circuit 85. The upstream open detection circuit 85 receives the current limit signal and outputs an input switch open signal to the input switch 80.

The input switch 80 which has received the input switch open signal is opened, and the load 75 and the power system 60 are opened.
And the series / parallel compensation system for instantaneous voltage sag countermeasures are separated, and it is detected that the system has been reliably opened, and an input switch open answerback signal is output.

Until the input switch 80 is opened, the output current of the parallel compensation converter is effectively limited to about the limit current setting IcL or less by the function of the limit circuit 156, and the parallel compensation converter 10 is stopped by its self defense function. There is no fear of doing.

Upon receiving the input switch open answerback signal, the upstream open detection circuit 85 outputs a control mode switching signal to the current / voltage control mode switch 170,
A start signal is output to input voltage control operation circuit 180. Instead of outputting the control mode switching signal and the start signal after receiving the input switch open answerback signal from the input switch 80, after outputting the input switch open signal, a sufficient time for the input switch 80 to open is provided. After this time, a control mode switching signal and a start signal may be output.

Upon receiving the control mode switching signal, current / voltage control mode switch 170 switches the control mode of parallel compensation converter 10 from the current control mode to the voltage control mode instantaneously.

Input voltage control operation circuit 18 which receives a start signal
0 is the input voltage detection value V at the moment the start signal is received.
i and the input frequency at the moment of receiving the start-up signal, and the input voltage reference value Vi ^* (for example, 95% of the rating), the input frequency reference value ω0 (for example, 50 Hz), and the time value T, and the input voltage after the time period is used. A voltage control mode parallel compensation converter output current target value to be output by the parallel compensation converter 10 necessary for setting the reference voltage Vi ^* and the reference frequency ω0 is calculated.

By the operation after the parallel compensation converter output current control operation circuit 130, the current output from the parallel compensation converter 10 is controlled to the voltage control mode parallel compensation converter output current target value.

With the above control operation, when an open accident on the upstream side occurs, the function of the limit circuit 156 limits the parallel compensation converter 10 to less than the overload tolerance or less than the overcurrent tolerance, and continues the operation of the parallel compensation converter 10. Thus, the parallel compensation converter 10 is prevented from being stopped due to overload or overcurrent. Further, when an opening accident on the upstream side occurs, the input switch 80 is opened, and the current of the parallel compensation converter 10 is output so that the input voltage and the frequency become the reference values after the time limit. As a result, the input voltage and the frequency are reduced. Since it can be controlled to the reference value, it is possible to form a current closed circuit of the parallel compensation converter 10 → the series transformer 50 → the important load 70 → the parallel compensation converter 10 and supply stable power to the important load 70.

The load 7 connected in parallel to the power supply system
The direction of the voltage and current of 5 is the same as the normal direction,
Load damage can be prevented.

<Second Embodiment> A second embodiment of the present invention will be described below.

The configuration of the power supply system using the uninterruptible power supply system according to the second embodiment of the present invention is the same as the configuration of the power supply system of the first embodiment shown in FIG. Detailed explanation is omitted.

Referring to FIG. 4, the configuration of parallel compensation converter control circuit 100 used in this embodiment will be described.

The configuration of the parallel compensation converter control circuit 100 is the same as that of the first embodiment shown in FIG. 2 except that the limit current setter 157 is replaced with a first limit current setter 158 and a second limit current setter 159. Since the configuration is the same as that of the parallel compensation converter control circuit 100 of the embodiment, detailed description is omitted.

DC intermediate circuit voltage compensation current calculation circuit 11
0, load current compensation current calculation circuit 120, parallel compensation converter output current control calculation circuit 130, parallel compensation converter output voltage command calculation circuit 140, carrier signal generation circuit 155, current / voltage control mode switcher 170, input voltage control calculation circuit The configuration and operation of the input switch 180 and the input switch 80 are the same as those of the prior art described with reference to FIG.

The PWM control circuit 150 includes an output voltage command signal of the parallel compensation converter 10 and a carrier signal generation circuit 1
A comparison is made with the carrier signal from 55 and a switching signal is output to the limit circuit 156.

The limit circuit 156 is a PWM control circuit 1
50, a first limit current set value IcL1 from the first limit current setter 158,
Based on the second limit current set value IcL2 from the second limit current setter 159 and the parallel compensation converter output current detection value Ic, a switching processing signal is output to the gate drive circuit 160 based on the control flowchart shown in FIG. A current limit signal is output to the open detection circuit 85.

As shown in FIG. 5, the limit circuit 156
Compares the first limit current set value IcL1 from the first limit current setter 158 with the parallel compensation converter output current detection value Ic (S11), and compares the parallel compensation converter output current detection value Ic with the first limit current. If the value is less than the set value IcL1 (No), the switching signal is output as it is as the switching processing signal (S15), and the parallel compensation converter output current detection value Ic becomes the first limit current set value Ic.
If it is equal to or greater than L1 (Yes), a current limit signal is output (S12), and the switching processing signal is turned off.
F (S13), and then the second limit current setting device 1
The second limit current set value IcL2 from 59 is compared with the parallel compensation converter output current detection value Ic (S14), and when the parallel compensation converter output current detection value Ic is equal to or greater than the second limit current set value IcL2 (Yes). Continuously turns off the switching signal (S13). If the parallel compensation converter output current detection value Ic is less than the second limit current setting value IcL2 (No), the switching signal is output as it is as a switching processing signal (S15), and the process returns to the start and repeats the same operation.

The values of the first limit current set value IcL1 and the second limit current set value IcL2 are less than the overload withstand capability or less than the overcurrent withstand capability of the parallel compensation converter, and the first limit current set value It goes without saying that IcL1 is larger than the second limit current set value IcL2.

The gate drive circuit 160 supplies drive power to the switching element bridge based on the switching processing signal from the limit circuit 156.

The upstream open detection circuit 85 detects a drop in the input voltage (for example, 90% of the rated voltage) or a drop in the input frequency (for example, 49.5 Hz (rated at 50 Hz)) from the detected input voltage Vi, or When a current limit signal is received, an input switch open signal is output to the input switch 80. Other than this, it is the same as the prior art.

A control method according to the second embodiment will be described below.

When an open accident occurs on the upstream side, the output current of the parallel compensation converter 10 increases for the reason described in FIGS. 14 and 15, and the parallel compensation converter output current detection value Ic becomes the first limit current. When the current value exceeds a set value IcL1 (for example, 120% of the rated current of the important load 70), the limit circuit 156 outputs a current limit signal to the upstream open detection circuit 85.

The upstream open detection circuit 85 receives the current limit signal and outputs an input switch open signal to the input switch 80.

The input switch 80 that has received the input switch open signal opens the load 75 and the power system 60
And the series / parallel compensation system for instantaneous voltage sag countermeasures are separated, and it is detected that the system has been reliably opened, and an input switch open answerback signal is output.

Until the input switch 80 is opened, the output current of the parallel compensation converter is effectively limited to about the first limit current set value IcL1 or less by the function of the limit circuit 156. There is no danger of stopping by the defense function.

Upon receiving the input switch open answerback signal, the upstream open detection circuit 85 outputs a control mode switching signal to the current / voltage control mode switch 170,
A start signal is output to input voltage control operation circuit 180. Instead of outputting the control mode switching signal and the start signal after receiving the input switch open answerback signal from the input switch 80, after outputting the input switch open signal, a sufficient time for the input switch 80 to open is provided. After this time, a control mode switching signal and a start signal may be output.

The current / voltage control mode switch 170 having received the control mode switching signal switches the control mode of the parallel compensation converter 10 from the current control mode to the voltage control mode instantaneously.

Input voltage control operation circuit 18 receiving a start signal
0 is the input voltage detection value V at the moment the start signal is received.
i and the input frequency at the moment of receiving the start-up signal, and the input voltage reference value Vi ^* (for example, 95% of the rating), the input frequency reference value ω0 (for example, 50 Hz), and the time value T, and the input voltage after the time period is used. A voltage control mode parallel compensation converter output current target value to be output by the parallel compensation converter 10 necessary for setting the reference voltage Vi ^* and the reference frequency ω0 is calculated.

By the operation after the parallel compensation converter output current control operation circuit 130, the current output from the parallel compensation converter 10 is controlled to the voltage control mode parallel compensation converter output current target value.

With the above control operation, when an open circuit accident on the upstream side occurs, the output of the parallel compensation converter 10 is limited to less than the overload tolerance or less than the overcurrent tolerance by the function of the limit circuit 156 to operate the parallel compensation converter. The operation is continued to prevent the parallel compensation converter 10 from stopping due to overload or overcurrent, and the input switch 80 is opened to output the current of the parallel compensation converter 10 so that the input voltage and the frequency become the reference values after the time limit. ,as a result,
Since the input voltage and frequency can be controlled to the reference values, a current closed circuit of the parallel compensation converter 10 → the series transformer 50 → the important load 70 → the parallel compensation converter 10 is formed, and stable power is supplied to the important load 70. be able to.

The directions of the voltage and current of the load are the same as those in the normal direction, so that damage to the load can be prevented.

The flow of current and power in the uninterruptible power supply system of the first embodiment and the second embodiment at the time of an upstream opening accident will be described with reference to FIGS.

<When an upstream accident occurs> Prior to the occurrence of an upstream opening accident, a critical load 70 is connected in parallel to the series-parallel compensation system
It is assumed that a load 75 having a capacity 10 times that of the load 75 is connected. If the voltage of the power system 60 is, for example, 95% of the rated voltage of the important load 70, the input voltage becomes
Is 95% of the rated voltage of the important load 70, the series compensation inverter 20 generates a voltage of 5% of the rated voltage of the important load 70, % Voltage is established.

As shown in FIG. 6, when an open accident occurs upstream, the parallel compensation converter 10 becomes a current supply source to the important loads 70 and 75, and the parallel compensation converter 10 → the series transformer 50 → the important load. 70 → the closed loop of the parallel compensation converter 10 and the parallel compensation converter 10 → the load 75 → the closed loop of the parallel compensation converter 10 are formed. Although the parallel compensation converter 10 may be overloaded or overcurrent for the reason described in FIGS. 14 and 15, the output current Ic of the parallel compensation converter 10 is reduced by the function of the limit circuit 156 in the first embodiment. In the embodiment, about the limit current set value IcL (for example, 120% of the rated current of the important load 70), and in the second embodiment, the first limit current set value IcL1 (for example, the important load 70).
Is about 120% of the rated current of the parallel compensation converter 10, so that the output current Ic of the parallel compensation converter 10
0, which is about 120% of the rated current, and the parallel compensation converter 10 is not likely to trip due to overload or overcurrent.

Since the output voltage of the parallel compensation converter 10 establishes a voltage of about 2% of the rated voltage of the important load 70 in order to limit the output current of the parallel compensation converter 10, 2% of the important load power PiL is established. Supply about power.
The load 75 is supplied with about 0.4% of the power of the important load 70 (about 0.04% of the power of the load 75).

The series compensation inverter 20 is connected to the important load 70
Since the voltage of about 98% of the rated voltage is established, about 98% of the important load power PiL is supplied. The output current Ii of the series compensation inverter 20 forms a closed loop via the secondary winding of the series transformer 50.

The voltage and current of the important load 70 maintain their rated values, and the rated power of the important load 70 is supplied stably. On the other hand, about 2% of the rated voltage is established in the load 75, and the current of the load 75 is 20% of the rated current of the important load 70.
% (About 2% of the current of the load 75).
Is about 0.4% of the power of the important load 70 (load 75
About 0.04% of the power of Further, the voltage and current of the load 75 are in the normal direction, and there is no possibility of damaging the load.

Power storage medium 30 supplies power Pes to parallel compensation converter 10 and series compensation inverter 20. This is just the sum of the power supplied to the important load 70 and the power supplied to the load 75, and corresponds to about 100.4% of the rated power of the important load 70.

<When Input Switch 80 is Opened> FIG.
As shown in (5), when a current limit signal is output from the limit circuit 156 and the upstream detection circuit 85 receives this signal, an input switch open signal is output from the upstream detection circuit 85 and the input switch 80 is opened. The parallel compensation converter 10 is switched from the current control mode to the voltage control mode by a control mode switching operation as in the related art.
Since this time is instantaneous, the input voltage remains at about 2% of the rated voltage of the important load.

Since the input voltage is about 2% of the rated voltage of the important load 70, the series compensation inverter 20 generates a voltage of about 98% of the rated voltage of the important load 70, and outputs the input voltage via the series transformer 50. And the important load 70
Establish a voltage of 100% of the rated voltage.

The current of the important load 70 is supplied from the parallel compensation converter 10 to form a closed loop of the parallel compensation converter 10, the series transformer 50, the important load 70, and the parallel compensation converter 10. The current of this closed loop is
Since the supply of the current to the load 5 is interrupted by the input switch 80, the current becomes 100% of the rated current of the important load 70. The output current Ii of the series compensation inverter 20 forms a closed loop via the secondary winding of the series transformer 50.

The parallel compensating converter 10 has established a voltage of about 2% of the rated voltage of the important load.
About 2% of the power supplied to Since the series compensation inverter 20 has established a voltage of about 98% of the rated voltage of the important load, it supplies about 98% of the power supplied to the important load 70. The voltage and current of the important load 70 maintain their rated values, and the rated power of the important load 70 is supplied stably. On the other hand, power is not supplied to the load 75 because the input switch 80 is open.

Power storage medium 30 supplies electric power Pes of parallel compensation converter 10 and series compensation inverter 20. This corresponds to exactly 100% of the power supplied to the important load 70. Accordingly, although the voltage of the power storage medium 30 is still sharply reduced, the parallel compensation converter 10 is switched to the voltage control mode. There is no fear of stopping.

Thereafter, as described with reference to FIGS. 11 to 13, the input voltage gradually increases with a time limit T to, for example, 95% of the reference, as in the prior art.

<When the input voltage is controlled to a reference value, for example, 95%, and the parallel compensation converter 10 is controlled> As shown in FIG. Except that a load 75 having a capacity 10 times that of the important load 70 is connected in parallel, as shown in FIG. 13 <when the input voltage is controlled to a reference value, for example, 95%, the parallel compensation converter 10 is controlled> Is the same as

As described above, according to the embodiment of the present invention, when an opening accident on the upstream side occurs, the function of limit circuit 156 limits the parallel compensation converter 10 to less than the overload tolerance or less than the overcurrent tolerance. By continuing the operation of the parallel compensation converter 10 to prevent the parallel compensation converter 10 from stopping due to overload or overcurrent, the input switch 80 is opened so that the input voltage and the frequency become the reference values after the time limit. Since the current of the parallel compensation converter 10 is output and the input voltage and the frequency can be controlled to the reference values, the parallel compensation converter 10 → the series transformer 50 → the important load 70 → the current closed circuit of the parallel compensation converter 10 The critical load 70
Stable power can be supplied.

Further, the directions of the voltage and the current of the load 75 are the same as the normal directions, so that the damage of the load 75 can be prevented.

[0111]

According to the present invention, when a load is connected in parallel to the series-parallel compensation type voltage sag countermeasure system, an upstream opening accident (complete power outage of the system, disconnection of the power system, opening of the upstream circuit breaker, etc.) occurs. Even so, the function of the limit circuit 156 limits the output current of the parallel compensation converter 10 to less than the overload tolerance or less than the overcurrent tolerance, so that the parallel compensation converter 10 is continuously operated to overload or overcurrent the parallel compensation converter 10. Can be prevented from being stopped.

Further, it is possible to open the input switch 80 and output the current of the parallel compensation converter 10 so that the input voltage and the frequency become the reference values after the time limit. As a result, the input voltage and the frequency are controlled to the reference values. Since it is possible, the parallel compensation converter 10 → the series transformer 50 → the important load 7
By forming a current closed circuit of the 0 → parallel compensation converter 10, stable power can be supplied to the important load 70.

Further, the directions of the voltage and the current of the load 75 are the same as the normal directions, so that the damage of the load 75 can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an uninterruptible power supply system using a series-parallel compensation system voltage sag prevention system according to the present invention.

FIG. 2 is a block diagram showing a configuration of a parallel compensation converter control circuit of the uninterruptible power supply system using the series-parallel compensation system voltage sag countermeasure system according to the first embodiment;

FIG. 3 is a control flowchart of a limit circuit according to the first embodiment.

FIG. 4 is a block diagram showing a configuration of a parallel compensation converter control circuit of an uninterruptible power supply system using a series-parallel compensation system momentary voltage reduction system according to a second embodiment;

FIG. 5 is a control flowchart of a limit circuit according to a second embodiment.

FIG. 6 is a diagram for explaining the flow of current and power when an upstream opening accident occurs when a load is connected in parallel to an uninterruptible power supply system using the series-parallel compensation system voltage sag countermeasure system according to the present invention.

FIG. 7 shows the current and power when the input switch is opened at the time of an upstream opening accident when a load is connected in parallel to an uninterruptible power supply system using the series-parallel compensation type instantaneous sag prevention system according to the present invention. The figure explaining a flow.

FIG. 8 shows a case where a load is connected in parallel to an uninterruptible power supply system using the series-parallel compensation system voltage sag countermeasure system according to the present invention; FIG. 6 is a diagram for explaining current and power flows when the parallel compensation converter is controlled so as to be as follows.

FIG. 9 is a block diagram showing a configuration of an uninterruptible power supply system using a conventional series-parallel compensation system voltage sag countermeasure system.

FIG. 10 is a block diagram showing a configuration of a parallel compensation converter control circuit of the uninterruptible power supply system of FIG. 9;

FIG. 11 is a view for explaining the flow of current and power when an upstream opening accident occurs in an uninterruptible power supply system using a conventional series-parallel compensation system voltage sag protection system.

FIG. 12 shows that the input switch is opened by detecting that the input voltage has dropped to 90% by the upstream opening detection circuit when an upstream opening accident has occurred in the uninterruptible power supply system using the conventional series-parallel compensation type instantaneous voltage reduction measure system. FIG. 4 is a diagram illustrating current and power flows at the time.

FIG. 13: In an uninterruptible power supply system using a conventional series-parallel compensation type instantaneous voltage sag countermeasure system, the parallel compensation converter is controlled so that the upstream switch is opened and the input voltage becomes 95% (reference value). FIG. 4 is a diagram illustrating current and power flows at the time.

FIG. 14 is a diagram illustrating the flow of current and power when an upstream opening accident occurs when a load is connected in parallel to an uninterruptible power supply system using a conventional series-parallel compensation type instantaneous voltage reduction system.

FIG. 15 shows that a parallel compensation converter is stopped by a self-defense function due to an upstream opening accident when a load is connected in parallel to an uninterruptible power supply system using a conventional series-parallel compensation type instantaneous voltage reduction system. FIG. 4 is a diagram illustrating current and power flows at the time.

[Explanation of symbols]

 10: Parallel compensation converter 20: Series compensation inverter 30: Power storage medium 35: DC intermediate circuit voltage detection circuit 40: Parallel transformer or parallel reactor 50: Series transformer 60: Power system 70: Important load 75: Load 80: Input switch 85 : Upstream open detection circuit 100: Parallel compensation converter control circuit 110: DC intermediate circuit voltage compensation current calculation circuit 120: Load current compensation current calculation circuit 130: Parallel compensation converter output current control calculation circuit 140: Parallel compensation converter output voltage command calculation circuit 150: PWM control circuit 155: Carrier signal generation circuit 156: Limit circuit 157: Limit current setting device 158: First limit current setting device 159: Second limit current setting device 160: Gate drive circuit 170: Current / voltage control Mode switch 1 0: input voltage control calculation circuit 191: Input voltage reference value setting unit 193: input frequency reference value setting unit 195: timing setting unit 200: series compensation inverter control circuit

Continued on the front page F term (reference) 5G015 FA02 FA05 FA16 GA07 HA04 HA15 JA10 JA23 JA24 JA32 JA34 JA35 JA51 5H007 AA04 AA05 AA07 BB05 BB07 CA00 CB05 CC03 CC32 DA03 DA05 DA06 DB02 DC02 DC05 EA02 FA02 GA01 GA06 GA09

Claims (3)

[Claims] An electric power system, a load that is supplied from the electric power system and does not allow an instantaneous voltage drop (hereinafter referred to as an “instantaneous voltage drop”) of the electric power system, and a power supply line provided between the electric power system and the load. , A parallel transformer or a parallel reactor and a series transformer connected in series with a power supply line, a converter connected to the parallel transformer or the parallel reactor (hereinafter referred to as a parallel compensation converter), and an inverter connected to the series transformer ( A series-parallel compensation type instantaneous voltage drop countermeasure system (hereinafter referred to as a series-compensated inverter) comprising a parallel-compensated converter, a power storage medium connected between the series-compensated inverter, and an instantaneous voltage drop and power failure of a power system ( Hereinafter, referred to as a series-parallel compensation system sag suppression system). An input switch for shutting off the power system and the series-parallel compensation system momentary voltage sag countermeasure system when an open accident on the power system side or an overload or an overcurrent of the parallel compensation converter is detected between the power systems. Uninterruptible power supply system provided. 2. The circuit according to claim 1, wherein when an overload or an overcurrent of the parallel compensation converter is detected, an output current of the parallel compensation converter is limited to less than an overcurrent tolerance or an overload tolerance of the parallel compensation converter. Blackout power system. 3. The uninterruptible power supply system according to claim 1, wherein a load is connected in parallel to the series-parallel compensation type instantaneous sag countermeasure system.