JPH06225537A - Control circuit of static power unit - Google Patents

Abstract

(57) [Summary] [Object] To provide a control circuit of a static power supply device that does not cause a difference in output voltage of each phase when three-phase AC is generated by using three sets of single-phase inverters. A static power supply device for outputting a three-phase alternating current is provided with three sets of voltage control circuits for controlling an output voltage, and one set of current control circuits for controlling a three-phase output current output from the static power supply device. By collectively controlling the output current of each phase using this one set of current control circuits, the difference in voltage between each phase can be minimized, and the obstacle to the load device can be reduced. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for a static power supply used for an uninterruptible power supply or the like.

[0002]

2. Description of the Related Art Conventionally, three sets of single-phase inverters are used to control a static power supply device that generates a three-phase alternating current.
A voltage control circuit and a current control circuit were provided in each of the single-phase inverters. Normally, the output voltage of the single-phase inverter is controlled by a voltage control circuit so that the deviation between the voltage actually output by the single-phase inverter and a preset value is zero, and the output current of the single-phase inverter is controlled by some factor. Is suppressed, the output voltage is controlled to be reduced by the current control circuit in order to suppress it.

[0003]

When the voltage control circuit and the current control circuit are provided in each of the single-phase inverters and the control is performed as described above, the following problems occur. When the output current of the single-phase inverter of a certain phase increases due to some factor and a difference occurs in the output current of each phase, the control by the voltage control circuit is switched to the control by the current control circuit. That is, the output voltage is controlled to be reduced by the current control circuit in order to suppress the increased current. However, since this control is individually performed for each phase, a difference also occurs in the output voltage of each single-phase inverter, which impairs the load.

The present invention has been made in view of the above-mentioned problems of the prior art, and when three sets of single-phase inverters are used to generate a three-phase alternating current, a static that does not cause a difference in the output voltage of each phase. A control circuit for a mold type power supply device is provided.

[0005]

In order to achieve the above object, a voltage detector for detecting an output voltage of the single-phase inverter and a deviation between a detection value of the voltage detector and a predetermined voltage set value are set. A voltage control circuit that calculates and outputs a control amount for controlling the output voltage of the single-phase inverter so as to be zero is provided for each of the three sets of single-phase inverters.

Further, a current detector is provided on the output side of the single-phase inverter to detect the output current of each of the three sets of single-phase inverters, and each detected value is led to a three-phase current detection value calculation circuit to generate a three-phase current. When the detected value is calculated and the three-phase current detected value exceeds a predetermined current set value, the three-phase current detected value is calculated from each control amount for controlling the output voltage of each of the single-phase inverters. Provide a voltage droop circuit before subtracting the value.

[0007]

The output current of each phase is controlled by controlling the output current of the static power supply unit by one current control circuit using the three-phase current detection value calculated based on the output current detection value of each phase. It is controlled collectively.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a connection configuration diagram of a static power supply device configured by using three sets of single-phase inverters and a control circuit that controls an output current and an output voltage of the static power supply device. In FIG. 1, 1 is a single-phase inverter, 2 is a voltage detector, 3 is a current detector, 4 is a transformer, 5 is a three-phase current detection value calculation circuit, 6
Is a voltage setting device, 7 is a current setting device, 8 is a voltage control circuit, 9
Is a voltage drooping circuit.

The static power supply device uses three sets of single-phase inverters 1 and generates three-phase AC power of A-phase, B-phase, and C-phase through a transformer 4. A voltage detector 2 and a current detector 3 are connected to the output side of the single-phase inverter 1,
The B-phase and C-phase voltage detection values V _A , V _B , and V _C and the current detection values V _IA , V _IB , and V _IC are detected, respectively. The detected voltage values V _A , V _B , and V _C are respectively guided to the voltage control circuit 8, and the control amounts A, B, and C are calculated so that the deviation from the set value V ₀ set by the voltage setter 6 is zero. To be done. At the same time, the current detection values V _IA , V _IB , V _IC are guided to the three-phase current detection value calculation circuit 5 to calculate the three-phase current detection value V _I.
When the phase current detection value V _I is smaller than the preset value V _I0 preset in the current setter 7, each of the A-phase, B-phase, and C-phase single-phase inverters is controlled based on the control amounts A, B, and C. It

However, there is a difference between the output voltages of the respective phases due to the influence of load fluctuations and disturbances, or the current of the phases increases, or the output current of each phase increases. In that case, the following control is performed. That is, the current detection values V _IA , V _IB , and V _IC obtained by detecting the output current of each single-phase inverter by the current detector 3 are guided to the 3-phase current detection value calculation circuit 5, and the 3-phase current detection value V is calculated.
_{When I} exceeds the set value V _I0 set by the current setter 7, the voltage drooping circuit 9 acts on the controlled variables A, B, C to reduce the output voltage of the single-phase inverter, and the controlled variable A ′. , B ′, C ′ are obtained, and each single-phase inverter 1 is controlled by the control amounts A ′, B ′, C ′. Then, the controlled variables A ', B', C'controlled to reduce the output voltage.
When the control is performed based on the above, the output voltage of the inverter is reduced in each phase and the output current is reduced.

Next, the configuration of the three-phase current detection value calculation circuit 5 for calculating the three-phase current detection value V _I will be described with reference to FIGS. 2 to 4. The three-phase current detection value calculation circuit 5 is configured by the circuit shown in FIG. 2 in the first embodiment. In FIG. 2, 11 is a three-phase full-wave rectifier, and 12 is a filter that holds the maximum value of the input waveform. Current detector 3
The detected values V _IA , V _IB , V _{IC according} to the above are guided to the three-phase full-wave rectifier 11 to perform three-phase full-wave rectification, and the maximum value V _{I1 of the} full-wave rectified waveform
To detect. The maximum value V _I1 of this full-wave rectified waveform is output to the voltage drooping circuit 9 as the three-phase current detection value V _I.

The second embodiment is composed of the circuit shown in FIG. In FIG. 3, 13 is a single-phase full-wave rectifier, and 14 is a filter that has three input terminals and that calculates the average sum of input waveforms. The detected values V _IA , V _IB , and V _IC by the current detector 3 are full-wave rectified by the single-phase full-wave rectifier 13, and each waveform is input to the filter 14, and the detected values V _IA ,
The sum V _I2 of the average values of V _IB and V _IC is obtained, and this V _I2 is output to the voltage drooping circuit 9 as the three-phase current detection value V _I.

In the third embodiment, the circuit shown in FIG.
It is composed by. In FIG. 4, 15 is a smooth frame.
The filter 16 is a diode. Similar to the second embodiment
The detected value V by the current detector 3_IA, V_IB, V_{I c}The single phase
Full-wave rectified by the full-wave rectifier 13, and the detected value V_IA，
V_IB, V_{I c}Smoothing filter 15 for each
Smoothed and led to the filter 12 via the diode 16.
Each detected value V_IA, V_IB, V _{I c}Calculate the average of. this
Largest value V of each average value_I33 phase current detection value V _I
Is output to the voltage drooping circuit 9.

The three-phase current detection value calculation circuit 5 described above calculates the three-phase current detection value V _I, and the current setter 7 is selected according to each circuit.
The current setting value V _I0 is set to the current setting value, and when the three-phase current detection value V _I exceeds the current setting value V _I0 , the control amount D is output.

[0015]

When three sets of single-phase inverters are used to generate a three-phase alternating current, the output voltage of the single-phase inverter is controlled by each voltage control circuit, and the output currents of all the phases are controlled by one current control. By controlling by the circuit,
The voltage difference between the phases can be suppressed to a minimum, and the obstacle to the load device can be reduced.

The three-phase current detection value calculation circuit calculates the three-phase current detection value by using a circuit for full-wave rectifying the three-phase current and calculating the maximum value, and the three-phase current detection value is predetermined. When the set value is exceeded, the output voltage of each phase is reduced based on the three-phase current detection value, so that the inrush current to the transformer or the like can be limited. Similarly, a circuit for obtaining the sum of average values of single-phase inverter output currents is used in the three-phase current detection value calculation circuit to calculate the three-phase current detection value, and the three-phase current detection value exceeds a preset value. In this case, by decreasing the output voltage of each phase based on the detected value of the three-phase current, even if the capacity of the load is temporarily increased, the increase in current can be suppressed.

Furthermore, the three-phase current detection value is calculated by using a three-phase current detection value calculation circuit and a circuit that calculates the maximum value of the average values of the single-phase inverter output currents. If the preset value is exceeded, the 3
By reducing the output voltage of each phase based on the detected value of the phase current, it is possible to supply power stably even to an unbalanced load.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit according to the present invention.

FIG. 2 is a configuration diagram of a three-phase current detection value calculation circuit according to the first invention.

FIG. 3 is a configuration diagram of a three-phase current detection value calculation circuit according to a second invention.

FIG. 4 is a configuration diagram of a three-phase current detection value calculation circuit according to a third invention.

[Explanation of symbols]

 1 Single-Phase Inverter 2 Voltage Detector 3 Current Detector 4 Transformer 5 3-Phase Current Detection Value Calculation Circuit 6 Voltage Setting Device 7 Current Setting Device 8 Voltage Control Circuit 9 Voltage Drooping Circuit 11 3-Phase Full Wave Rectifier 12 Filter 13 Single Phase All Wave rectifier 14 Filter 15 Smoothing filter 16 Diode

Claims (4)

[Claims] 1. A control circuit for controlling an output voltage of a static power supply device for generating three-phase AC power by using three sets of single-phase inverters for converting DC power into single-phase AC power, the output of the single-phase inverter. A voltage detector that detects a voltage, and calculates and outputs a control amount for controlling the output voltage of the single-phase inverter so that the deviation between the detection value of the voltage detector and a preset voltage setting value becomes zero. A voltage control circuit for each of the three sets of single-phase inverters, and a current detector provided on the output side of the single-phase inverter for detecting the output current of each of the three sets of single-phase inverters; A three-phase current detection value calculation circuit for calculating a three-phase current detection value from the value, and when the three-phase current detection value exceeds a predetermined current setting value, the three-phase current detection value calculation circuit is connected to the three-phase current detection value calculation circuit, The control circuit of the static power supply apparatus characterized in that a voltage droop circuit to subtract a value based on the three-phase current detection values from the respective control amount output from the pressure control circuit. 2. The control circuit for a static power supply device according to claim 1, wherein the three-phase current detection value calculation circuit outputs the output current detection value of each phase detected by the current detector as a three-phase full wave. A control circuit for a static power supply device, comprising: leading to a rectifier for full-wave rectification, and comparing the maximum value of the output of the three-phase full-wave rectifier as a three-phase current detection value with the current setting value. 3. The control circuit for a static power supply device according to claim 1, wherein the three-phase current detection value calculation circuit outputs the output current detection value of each phase detected by the current detector as a single phase. Conducting full-wave rectification by leading to a full-wave rectifier, obtaining an average value of output current of each phase from the output of the single-phase full-wave rectifier, and comparing the sum of the average values with the current setting value as a three-phase current detection value. A control circuit for a static power supply device characterized by: 4. The control circuit for a static power supply device according to claim 1, wherein the three-phase current detection value calculation circuit outputs the output current detection value of each phase detected by the current detector as a single phase. Conducting full-wave rectification by leading to a full-wave rectifier, obtaining the average value of the output current of each phase from the output of the single-phase full-wave rectifier, and the largest value among the average values as the three-phase current detection value and the current setting value. A control circuit of a static power supply device characterized by comparison.