JP3058928B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply used for a power supply of a computer and an inverter used for a battery power supply.

[0002]

2. Description of the Related Art FIG. 2 is a single-line diagram of a main circuit of a conventional inverter device and a control block diagram showing an example of a chopper circuit thereof. The AC is converted to DC by the forward converter 1, the required DC voltage is converted by the chopper circuit 2, the DC voltage is converted to the AC voltage by the inverter circuit 3, and the voltage is fixed to the load 7 via the inverter transformer 4. This is an inverter device having a main circuit configuration for supplying a voltage and a constant frequency AC voltage.

The output voltage of the inverter device detected by the instrument transformer 5 is input to the constant voltage control circuit 9 as a feedback signal, and the output voltage of the chopper circuit 2 is controlled to the set value of the chopper control reference 15. Pulse control circuit 12
, A gate signal is input to the chopper circuit 2. The capacitor current detection current transformer 16 is provided to input the charge / discharge current of the capacitor 17 on the output side of the chopper circuit 2 to the pulse control circuit 12 in an open loop, and to improve the transient characteristics of the pulse control circuit 12. Things.

The invar circuit 3 has a function of converting a DC voltage into an AC voltage having a predetermined frequency, and the AC output voltage is controlled by the chopper circuit 2. When the power on the load 7 side increases, the output of the chopper circuit 2 increases, and the load 7
The constant-voltage control circuit 9 is automatically closed-loop controlled so that the output of the chopper circuit 2 decreases when the power on the side decreases.

Here, when the fluctuation amount of the power on the load 7 side is small and the change speed is sufficiently slower than the control response of the constant voltage control circuit 9, the AC output voltage is controlled stably.
When the power consumption of the load 7 fluctuates sharply, the constant voltage control circuit 9 cannot respond according to the amount of load fluctuation, so that the output voltage of the chopper circuit 2 and the AC voltage of the load 7 become large. fluctuate. In order to improve the control response at the time of a sudden load change, the capacitor current detecting current transformer 16 is provided.

As the load 7 increases, the capacitor current also increases. Utilizing this principle, the capacitor current is input to the pulse control circuit 12 in an open loop to improve the control characteristics. However, the capacitor current flows in both positive and negative directions (charging direction and discharging direction) even during steady operation with little power fluctuation on the load 7 side. Disturbance occurs in the closed loop control system, and adverse effects occur in the closed loop control system. In particular, if the number of input of the capacitor current detection value to the chopper control system is increased, the chopper control system becomes unstable.

[0007]

As described above, in the inverter device having the configuration of the chopper circuit 2 and the inverter circuit 3, when the power consumption of the load 7 fluctuates rapidly, the control response of the chopper circuit 2 is sufficient. Without following, fluctuations in the output voltage of the load 7 and the chopper circuit 2 become large, and in the worst case, a serious failure may lead to an accidental stop of the device. SUMMARY OF THE INVENTION An object of the present invention is to provide an inverter device capable of stably operating even when a load fluctuates rapidly.

[0008]

In order to achieve the above object, the present invention comprises a chopper circuit for converting a DC voltage to a predetermined voltage, and an inverter circuit for converting the DC voltage of the chopper circuit to an AC. Inverter device that supplies AC power to

Detecting means for detecting the power or load impedance on the load side from the AC current and AC voltage on the inverter circuit side, and the detected value of the detecting means is used as a correction signal for a control system of the chopper circuit. And means for regenerating the power on the output side of the chopper circuit to the input side of the chopper circuit when the chopper circuit output overvoltage is detected.

[0010]

According to the present invention, when an output overvoltage of the chopper circuit is detected, the chopper circuit is regenerated to the input side of the chopper circuit, whereby the chopper circuit is operated almost instantaneously with an appropriate control amount in accordance with the power fluctuation of the load. You. Also, when the chopper output voltage and the AC output voltage of the inverter device become excessive, a gate pulse is applied to the elements of the chopper circuit before a severe failure stop, and the chopper output power is regenerated to the input side of the chopper circuit, and the overvoltage is generated. Works to suppress. Therefore, the operation can be stably continued even when the load suddenly changes.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to a single-line diagram of a main circuit in FIG. 1 and a block diagram of a chopper control circuit. 1 is a forward converter for converting a commercial AC voltage to a DC voltage, 2 is a chopper circuit for converting a voltage converted to DC by the forward converter 1 to a predetermined voltage, and 3 is a DC voltage obtained by the chopper circuit 2. Inverter circuit for converting into an AC of a predetermined frequency, 4 is an inverter transformer, 5 is an instrument transformer for detecting the output voltage of the inverter device, 6 is an instrument current transformer for detecting the output voltage of the inverter device, 7 is A load consumed by the customer, 8 is a regenerative GTO element for regenerating the chopper output voltage to the input side of the chopper circuit 2, 9 is a constant voltage control circuit for controlling the chopper circuit 2, 10 is an instrument transformer 5 and an instrument. An AC power detecting circuit for detecting load power from the current transformer 6; a fluctuation detecting circuit 11 for detecting AC fluctuation; a pulse control circuit 12 for controlling a pulse timing of the chopper circuit 2; The DC voltage detector for detecting the chopper output voltage, 14 regeneration control circuit for controlling the pulse timing of regenerating GTO element 8, 15 is a chopper control criteria for controlling the output voltage of the inverter to a constant value.

Next, the operation of the inverter device configured as described above will be described. The inverter circuit 3 has a function of generating an AC voltage having a predetermined frequency, and the chopper circuit 2 has a function of controlling the AC output voltage of the inverter device to be constant. With these two main functions, the inverter device is operated at a constant frequency and a constant voltage. The chopper circuit 2 is operated by a constant voltage control circuit 9 under negative feedback control.

Here, when the power consumption of the load 7 suddenly decreases, the power detected by the detected load power detection circuit 10 decreases, and the fluctuation detection circuit 11 supplies the fluctuation detection circuit 11 with the fluctuation of the load power. A detection value occurs. By inputting this detection value to the chopper control system in an open loop, the pulse control circuit 12 of the chopper circuit 2 acts to rapidly reduce the output of the chopper, and outputs the chopper output corresponding to the electric energy on the load side. It works as follows. For this reason, the DC voltage on the output side of the chopper and the output voltage of the inverter device are kept substantially constant, and an overvoltage is not generated.

When the power consumption on the load side suddenly increases, a detection of the fluctuation in the load power increase is output to the fluctuation detection circuit 11, and the output of the chopper circuit 2 is instantaneously increased, and the output of the chopper circuit is increased. It acts to suppress a decrease in the device output voltage. In a steady state in which the fluctuation of the load 7 is small, the output of the fluctuation detecting circuit 11 becomes almost "0", and the operation is performed by the negative feedback control system.

It is effective to use active power on the AC side to improve the transient response characteristics of the chopper control circuit. The reason is that the chopper circuit 2 is a DC-to-DC converter circuit for increasing or decreasing the DC voltage, which means that the active power shifts from the input to the output of the chopper circuit 2. In contrast, the AC circuit has active power and reactive power. Even if the load current increases in the inverter device, if the increase is due to the reactive power, the control amount of the chopper circuit 2 hardly increases and the constant control of the output voltage is maintained.

If the output voltage of the chopper detected by the DC voltage detector 13 shown in FIG. 1 rises above a predetermined allowable range, the regenerative control circuit 14 controls the gate turn-off thyristor 8.
, And acts to regenerate electric power to the input side of the chopper circuit 2. The signal of the regenerative circuit operation is also input to the pulse control circuit 12, and this signal acts so that the output of the chopper circuit 2 decreases. By these operations, the chopper output voltage is operated within the allowable range of the predetermined value, and the output voltage of the inverter device can be operated at a stable and constant voltage even when the load 7 fluctuates rapidly.

According to the embodiment of the present invention described above, even if the load 7 on the output side of the inverter device fluctuates suddenly, the output voltage can be stably operated within a predetermined allowable range, and Transient control performance of the device is improved, and failure stop of the device can be prevented.

In the embodiment shown in FIG. 1, the detection of the power of the load 7 by the load power detection circuit 10 has been described.
The same effect can be obtained by detecting the impedance of The same applies to the case where the power of the inverter circuit 3 is detected instead of the power / impedance detection on the load 7 side.

Although the embodiment in which the gate turn-off thyristor 8 is used in the regenerative control circuit 14 for chopper output power in FIG. 1 has been described, it goes without saying that a power semiconductor element such as a transistor can be used. Nor.

[0020]

According to the present invention, it is possible to provide an inverter device capable of stably operating even when the load suddenly changes.

[Brief description of the drawings]

FIG. 1 is a single-line diagram of a main circuit of an inverter device according to the present invention and a control block diagram of a chopper circuit.

FIG. 2 is a single-line diagram of a main circuit of a conventional inverter device and a control block diagram of a chopper circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Forward converter, 2 ... Chopper circuit, 3 ... Inverter circuit, 4 ... Inverter transformer, 5 ... Instrument transformer, 6 ... Instrument current transformer, 7 ... Load, 8 ... GTO element for chopper output power regeneration (Gate turn-off thyristor), 9: constant voltage control circuit, 10: AC power detection circuit, 11: fluctuation detection circuit, 12: pulse control circuit of chopper circuit 2, 1
3 DC voltage detector, 14 Regenerative control circuit, 15 Chopper control reference, 16 Current transformer for capacitor current detection.

Claims (1)

(57) [Claims] 1. An inverter device comprising a chopper circuit for converting a DC voltage into a predetermined voltage and an inverter circuit for converting a DC voltage of the chopper circuit into an AC, and supplying AC power to a load. Detection means for detecting the load-side power or load impedance from the AC current and the AC voltage of the chopper circuit, means for using the detection value of the detection means as a correction signal for the control system of the chopper circuit, and output of the chopper circuit. Means for regenerating power on the output side of the chopper circuit to the input side of the chopper circuit when an overvoltage is detected.