JPH07322626A - Pwm converter device - Google Patents

Abstract

PURPOSE:To eliminate the adverse effect of surge voltage on equipment connected to a same system by switching the reference signal of a current reference signal generator from the signal of a power supply phase detection circuit to the phase signal according to the operation by a microcomputer after detecting the loss of an input voltage. CONSTITUTION:When a power failure detection circuit 12 detects a power failure, the signal from a phase detection circuit 11 to a sinusoidal wave generator 4b is switched to a phase signal from a microcomputer 15 and a signal with the same phase as that of a power supply when no power failure occurs is given to the sinusoidal wave generator 4b. Then, an operation mode immediately before the power failure is judged according to the output of an operation mode detection circuit 14. In the case of power-running mode, a power converter 3 of a PWM converter is stopped. Then, after a specific amount of time passes, a stop command is outputted to an inverter device. When the operation mode immediately before power failure is in regeneration mode, the power converter 3 of the PWM converter is stopped after a specific amount of time and at the same time a stop command is outputted to the inverter device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PWM converter device having an improved power failure detection function.

[0002]

2. Description of the Related Art First, the principle structure of a PWM converter device will be described with reference to FIG. An input reactor 2 is connected to the alternating current from the alternating-current power supply 1, and electric power composed of switching elements 3a to 3f and switching elements 3a to 3f and rectifying elements 3g to 3l having reverse conduction characteristics in parallel via the input reactor 2. It is connected to the converter 3.
The switching elements 3a to 3f of the power converter 3 exchange the AC power supplied from the AC power supply 1 with a desired DC current by a PWM signal from the control circuit 4 described later, and set the voltage of the DC circuit by the voltage setting circuit 5. The control is performed so that the voltage value becomes the specified value. A smoothing capacitor 6 is connected between the poles of the power converter 3, and a voltage detection circuit 7 and a load are connected between the poles of the smoothing capacitor 6. This load is generally an inverter device 8 for exchanging DC power for AC, and the inverter device 8 controls the electric motor 9 at a variable speed.

Between the input reactor 2 and the power converter 3, there are provided a current detector 10 for detecting the current flowing through the power converter 3 and a phase detection circuit 11 for detecting the phase of the AC power supply 1.

The control circuit 4 described above will be described below with reference to FIG. The voltage controller 4a calculates the deviation between the DC voltage detected by the voltage detection circuit 7 and the DC voltage command set by the voltage setting circuit 5. Further, the output of the sine wave generator 4b that generates a sine wave signal synchronized with the power supply phase detected by the phase detection circuit 11 is the multiplier 4
At c, the output of the voltage controller 4a is multiplied to form a current command signal. The electric current signal and the electric current command signal detected by the electric current detector 10 are compared and calculated by the arithmetic unit 4d, and further the triangular wave generated by the triangular wave generator 4e and the comparator 4f.
Is compared and becomes a PWM signal, and the switching elements 3a to
It becomes a control signal of 3f.

In the powering mode in which the output power of the inverter device 8 flows to the electric motor 9, the DC voltage of the PWM converter becomes smaller than the DC voltage command set by the voltage setting circuit 5. On the contrary, when the electric motor 9 is in the regenerative mode, the electric power returns to the inverter device 8, and thus the PW
The DC voltage of the M converter becomes larger than the DC voltage command set by the voltage setting circuit 5. Therefore, the polarity of the output signal of the voltage controller 4a is inverted.
This means that the polarity of the current command during powering and regeneration is 180
It means that the input current is inverted as shown in FIG.
It is controlled so as to have the same phase as the power supply phase detected by the phase detection circuit 11 during power running, and have the opposite phase during regeneration.

[0006]

When the power supply voltage drops and a power failure occurs, the phase signal of the power supply is lost, the phase reference of the current command signal is lost, and stable current control cannot be achieved. Therefore, there is a risk of applying a voltage with an abnormal cycle to devices connected to the same system. Also, if the current control of the converter is stopped instantly after the occurrence of a power failure, the problem of voltage such as an abnormal cycle can be solved, but the current control and the stop of the inverter device frequently operate even for a momentary power failure. It becomes impossible to operate the system.

Further, when the power source is cut off in the regenerative mode, the power regenerated from the PWM converter device to the power source cannot be returned to the power source and is connected in parallel with the PWM converter device, that is, connected to the same system. Will be consumed by the existing equipment. The voltage applied to the device connected to the same system as the PWM converter device at this time is P which is the input terminal voltage of the PWM converter device.
The PWM voltage waveform has a value obtained by sharing the WM waveform with the impedance of the device connected to the input reactor 2 and the system, and adversely affects the device connected to the system. Further, since the control power source of the converter itself is also supplied by the regenerative power, the power failure cannot be detected even if the power source is interrupted, the regenerative operation is continued, and the PW is connected to the system equipment.
There is a risk of continuing to apply the M waveform voltage.

When the power supply voltage is lost due to the power supply voltage drop during the operation of the PWM converter device described above, the current control is continued for a period of about the momentary power failure compensation time of the inverter device, and the stable system operation is performed. (EN) Provided is a PWM converter device which eliminates the adverse effect of surge voltage on devices connected to the same system by instantaneously stopping current control at the time of interruption (opening).

[0009]

A PWM converter device of the present invention comprises a power failure detection circuit for detecting loss of input voltage,
Equipped with an input voltage waveform detection circuit that measures the input voltage waveform and an operation mode detection circuit that detects the power flow direction (powering or regeneration) of the PWM converter. When a loss of input voltage is detected, the current reference signal generator reference The signal is switched from the signal of the power supply phase detection circuit to the phase signal calculated by the microcomputer, and the current control phase is the same as before the power failure. Further, it is characterized in that the method of controlling the switching elements of the PWM converter and the method of controlling the operation command to the inverter device are switched according to the waveform state of the power supply voltage and the operation status when a power failure occurs.

[0010]

[Operation] When the loss of the input voltage is detected, the current control phase is the same as that before the power failure by switching the reference signal of the current reference signal generator from the signal of the power supply phase detection circuit to the phase signal calculated by the microcomputer. Prevents application of abnormal cycle voltage to equipment connected to the grid. When a power failure is detected during power running, control of the switching elements of the PWM converter is stopped instantaneously to prevent inrush current at power recovery, and an operation command is continuously output to the inverter device, which is then output to the DC circuit. Continue running the motor with the charged energy. Further, when a power failure is detected during the regenerative operation, the regenerative operation is continued by controlling the switching elements of the PWM converter and continuously outputting the operation command to the inverter device.

During operation, if the input voltage waveform detection circuit includes a frequency component proportional to the switching frequency of the PWM converter itself, it is determined that the power supply line has been cut off, and the PWM converter and the inverter device are operated. It is stopped instantaneously to avoid applying the PWM voltage to equipment connected to the same system as the PWM converter device.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram relating to the present invention, and the same functions as those of the related art and portions which are not necessary for the explanation regarding the present invention are omitted.

As a configuration, a power failure detection circuit 12 for detecting a power failure of the AC power supply 1 and an input voltage waveform for detecting a voltage waveform of the AC power supply 2 are provided at the same location as the phase detection circuit 11 for detecting the phase of the AC power supply 1. The detection circuit 13 and the operation mode detection circuit 14 for detecting the operation mode from the output of the voltage controller 4a of the control circuit 4 are added to the conventional one.

The detection signal of each control circuit will be described below. First, FIG. 2A shows a power supply voltage waveform, which normally has a sine wave waveform of 50 or 60 Hz as shown in the period t1. FIG. 2B shows the output of the power failure detection circuit 12 during the period t1.
Since the power supply voltage is generated at, the level 1 is output. FIG. 3C shows the output of the input voltage waveform detection circuit 13,
It is a signal having the same frequency component as the frequency of the power supply whose level changes according to the polarity of the power supply voltage (a).

Next, when a power failure occurs at time t2, the output (b) of the power failure detection circuit 12 becomes a level 0 output, and the output (c) of the input voltage waveform detection circuit 13 also stops according to the waveform of the power supply. Further, when the power supply is cut off (opened) during the regenerative mode, the PWM converter becomes the power supply of the system and the voltage waveform applied to the system, that is, the power supply voltage waveform (a) is at time t3, although it depends on the impedance of the system. As shown, the PWM voltage waveform is switched by the PWM converter. At this time, the output of the power failure detection circuit 12 is level 1 because the power supply voltage is generated.
Is output. Further, the output of the input voltage waveform detection circuit 13 generates a signal similar to the power supply voltage (a). The operation mode detection circuit 14 is a circuit that detects a power running when the value of the DC voltage is smaller than the setting value of the voltage setting circuit 5 and a regenerative mode when the value is large.

The combination of the output signal states of the detection circuits described above is processed by the microcomputer 15 as shown in FIG. FIG. 3 is a flow chart of a control program for the PWM converter, which shows that when the power converter is started after being turned on, the initialization process is first executed, and then the general control and the process are repeatedly executed. The contents of general control and processing will be omitted, and only the portions relevant to the present invention will be described below.

In the judgment processing (E), if the output of the input voltage waveform detection circuit 13 includes the PWM switching frequency component, the processing jumps to the processing A, and the current control of the PWM converter is stopped, that is, the power converter 3 is stopped. . In addition, a stop command is output to the inverter device 8 to stop the operation instantaneously. This process is executed when the output of the input voltage waveform detection circuit 13 includes a PWM switching frequency component, that is, when the power supply is cut off (opened) during the regenerative mode.

In the judgment process (F), when the power failure detection circuit 12 detects a power failure, the process B is jumped to. In the process B, first, the signal from the phase detection circuit 11 to the sine wave generator 4b is switched to the phase signal from the microcomputer 15, and the same signal as the phase of the power supply when no power failure occurs in the sine wave generator 4b. give.

The microcomputer 15 constantly reads the signal from the phase detector 11 and grasps the power supply phase. Next, in the determination process (d), the output of the operation mode detection circuit 14 is used to determine how the operation mode was immediately before the power failure.
If it is the power mode, the power converter 3 of the PWM converter is stopped. Next, after a lapse of time Ta, a stop command is output to the inverter device 8. If the operation mode immediately before the power failure is the regenerative mode, the power converter 3 of the PWM converter is stopped after the time Ta has elapsed after the power failure is detected, and a stop command is also output to the inverter device 8.

(Other Embodiments) In the present invention, in the case of a power failure due to a power source voltage drop, the operation command for the power converter and the inverter apparatus of the PWM converter apparatus after the power failure is switched according to the operation mode before the power failure. . Also,
The feature is that the abnormal voltage is not applied to the system by detecting the interruption of the power supply and stopping the operation of the power converter of the PWM converter device instantaneously, thereby detecting the power failure, detecting the operation mode and input voltage. The details of the waveform detection circuit are not limited to the circuits described in the embodiment section.

[0021]

Even if the power is cut off (opened) during the operation in the regenerative mode, the output of the input voltage waveform detection circuit can detect the cutoff of the power and the PWM converter operation can be stopped instantaneously. PW for the power supply system
The application of the M switching voltage can be prevented.

Further, at the time of power failure in the power line mode, P
By stopping the operation of the WM converter immediately after detecting a power failure, it is possible to prevent the inrush current to the switching element of the power conversion device at the time of power recovery, improve the reliability of the device, and keep the inverter device operating. By continuously outputting the operation command, the electric motor is operated for a certain period of time by the energy accumulated in the smoothing capacitor of the DC main circuit. In addition, even if the phase signal of the power supply disappears, the phase signal is output by the microcomputer against the power failure in the regenerative mode. Therefore, the voltage of the abnormal cycle is not applied to the power supply system to which the PWM converter is connected, and the PWM The regenerative operation can be continued while the converter control power is established. In other words, even if a power failure occurs, the system will not stop instantaneously, but operation will continue for a certain period of time, and reliable PWM
A converter device can be provided.

[Brief description of drawings]

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

FIG. 2 is an output waveform of the control circuit of the present invention,

FIG. 3 is a flowchart of a control program of the present invention,

FIG. 4 is a basic circuit block diagram of a PWM converter device,

FIG. 5 is a control circuit block diagram of a conventional PWM converter device;

FIG. 6 is a diagram showing a relationship between an input voltage and an input current of the PWM converter device.

[Explanation of symbols]

1 ... AC power supply, 2 ... Reactor, 3 ... Power converter,
4 ... Control circuit, 5 ... Voltage setting circuit, 6 ... Smoothing capacitor, 7 ... Voltage detector, 8 ... Inverter device,
9 ... Electric motor, 10 ... Current detector, 11 ... Phase detection circuit, 12 ... Power failure detection circuit, 13 ... Input voltage waveform detection circuit, 14 ... Operation mode detection circuit, 15
… Microcomputer.

Claims (4)

[Claims] 1. A phase detection circuit for detecting a phase of an input voltage by connecting an AC power source to a power converter composed of a switching element via an input reactor, an input current detection circuit for detecting an input current, and a switching element. It is equipped with a DC voltage detection circuit and a DC voltage setting circuit that detect the detection voltage of the DC voltage output from the power converter.The DC voltage is controlled to a constant value by controlling the switching timing of the switching element, and the input current By synchronizing the phase with the power supply voltage phase, the input power factor can be made approximately 1, and the DC power can be converted to an arbitrary frequency and voltage, and the power can be supplied to the inverter device that controls the AC motor at a variable speed and the inverter device can be used. In the PWM converter device that outputs the operation command to the power supply, the power failure detection circuit that detects the loss of the input voltage and the waveform of the input voltage An input voltage waveform detection circuit for measuring the input voltage waveform detection circuit and an operation mode detection circuit for detecting power running or regeneration of the power of the PWM converter, depending on the output of the input voltage waveform detection circuit and the state of the operation mode detection circuit at the time of a power failure. A PWM converter device characterized by changing stop control of the PWM converter. 2. The PWM converter device according to claim 1, wherein when the power failure detection circuit detects a power failure and the power is in a powering mode, the control of the switching element of the PWM converter is instantaneously stopped to change the variable frequency to the electric motor. And a variable voltage is supplied and the operation command to the inverter device is continuously output for a predetermined period, and when the power is in the regenerative mode, the control of the switching element of the PWM converter and the operation command to the inverter device are continuously output for a certain period. A PWM converter device characterized by: 3. The PWM converter device according to claim 1, wherein when the power is in a regenerative mode and the output of the input voltage waveform detection circuit includes a frequency component proportional to the control frequency of the switching element of the PWM converter itself. Is a PWM converter device characterized by instantaneously stopping the control of the PWM converter and the operation command to the inverter device. 4. The PWM converter device according to claim 1, wherein when a power failure is detected, the reference signal of the current reference signal generator is switched from the signal of the power supply phase detection circuit to a phase signal calculated by a microcomputer. P
WM converter device.