JP4667771B2 - Inverter device - Google Patents

Description

  The present invention relates to an inverter device, and more particularly to an inverter device that automatically compensates a DC offset component of an AC output phase voltage.

  The inverter device performs voltage control so that the output voltage follows the output voltage command value of the inverter of each phase, for example, generates a gate signal of each phase by a triangular wave PWM method, and forms a semiconductor power element that forms each phase arm. A system is generally used in which switching is performed to output pulsed positive and negative square waves, and this is converted into a sine wave by an output filter composed of a reactor and a capacitor.

  In this conventional inverter device, the output voltage does not necessarily follow the voltage command value, and a direct current component appears in the output. As a result, a DC voltage containing a DC component is applied to the load, and there is a risk that electrical components such as a transformer of the load will burn out.

As a countermeasure, a DC current detector can be used to detect the DC component of the output, and the output voltage can be corrected according to the detected value. However, a high-precision DC current detector is expensive and the circuit is complicated. There was a problem of becoming. Therefore, paying attention to the gate signal of each phase of the inverter device, the difference between the effective value components of the positive and negative sides of the drive pulse by this gate signal is detected, and the pulse width of the drive pulse is corrected according to this detection signal (For example, refer to Patent Document 1).
JP 2002-272140 A (page 2-5, FIG. 1)

  Although the method disclosed in Patent Document 1 can be realized with a relatively simple circuit, since the output voltage of the inverter device is not directly detected, there is a possibility that a problem may occur in the detection accuracy. The cause is that the on / off operation of the semiconductor power elements forming each arm is not necessarily ideal, and there is a delay in switching on and off, and the delay in switching due to variations in the characteristics of the individual semiconductor power elements. This is because it is not uniform for each arm or each semiconductor power element.

  The present invention has been made in view of the above, and an object of the present invention is to provide an inverter having a relatively simple circuit configuration and a function of detecting and compensating for a DC component of a device output by a method having a small detection error. An object is to provide an apparatus.

In order to achieve the above object, an inverter device of the present invention comprises a bridge-connected semiconductor power element, converts DC power into AC power, and supplies power to a load via an output filter, and a voltage command. In response, a control unit for controlling the output voltage of the inverter circuit, phase voltage detection means for detecting an output phase voltage that is a rectangular wave before the output filter of the inverter circuit, and a positive of the output phase voltage that is a rectangular wave Conduction time detection means for detecting each of the conduction time on the side and the negative side with a photocoupler, the phase voltage detection means comprising a diode circuit for rectifying the output voltage of the inverter circuit, and the diode A capacitor for smoothing the output voltage of the circuit; and a plurality of serially connected components for each phase between the output of the inverter circuit and the input of the diode circuit A voltage dividing resistor, and at least one of the plurality of voltage dividing resistors is used as a phase voltage detecting voltage dividing resistor, and a phase voltage is detected by a voltage applied to the phase voltage detecting voltage dividing resistor. The control unit corrects the DC component of the voltage command in accordance with an integral value of a difference between the positive conduction time and the negative conduction time obtained by the conduction time detection unit. Yes.

  According to the present invention, it is possible to provide an inverter device having a function of detecting and compensating for a DC component of a device output by a method having a relatively simple circuit configuration and a small detection error.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit configuration diagram showing Embodiment 1 of an inverter device according to the present invention.

  The inverter circuit 1 converts a direct current obtained from a direct current power source into a three-phase alternating current and supplies power to the load 3 through the output filter 2. Here, the direct current fed to the inverter circuit 1 may be a storage battery as shown in the figure, but a direct current power source may be obtained from a commercial power source via a converter circuit. The inverter circuit 1 is normally configured by connecting semiconductor power elements in a bridge connection.

  The input voltage of the load 3 is detected by the voltage detector 5 for each phase and fed back to the inverter control circuit 4. In the inverter control circuit 4, the feedback voltage and the voltage command for each phase are compared by the comparator 41, and the difference is given to the PWM controller 43 via the voltage amplifier 42. The PWM controller 43 compares the output of the voltage amplifier 42 with the output of the carrier generation circuit 44, thereby obtaining a drive pulse for each phase, and supplying this drive pulse to the gate of the semiconductor power element of each arm of the inverter circuit 1. To do.

  A phase voltage dividing circuit 6 is connected to the output of the inverter circuit 1, and an instantaneous voltage of each phase is detected by the phase voltage dividing circuit 6. That is, the output of the inverter circuit 1 is supplied to the diode converter circuit 64 via the voltage dividing resistor 61, the voltage dividing resistor 62, and the voltage dividing resistor 63 for each phase. The output of the diode converter circuit 64 is connected to a series circuit of an electrolytic capacitor 65A and an electrolytic capacitor 65B whose midpoint is grounded. Resistors 66A and 66B are connected in parallel to the electrolytic capacitor 65A and the electrolytic capacitor 65B, respectively.

  The voltage across the voltage dividing resistor 62 is applied to the positive / negative arm on time detection circuit 7. In the positive / negative arm on-time detection circuit 7, the voltage across the voltage dividing resistor 62 is a photocoupler composed of a positive side photodiode 71A and a positive side phototransistor 72A, a negative side photodiode 71B, and a negative side phototransistor 72B. Are connected in parallel to the photodiode side of the photocoupler. With this configuration, the positive side phototransistor 72A outputs 1 during the on-time of the positive side arm of the target phase of the inverter circuit 1, and the negative side phototransistor 72B is the target of the inverter circuit 1. 1 is output during the on-time of the negative arm of the phase.

  The outputs of the positive side phototransistor 72A and the negative side phototransistor 72B, that is, the output of the positive / negative arm on time detection circuit 7 are supplied to the on time difference calculation circuit 8. The comparator 81 in the on-time difference calculation circuit 8 receives the positive and negative outputs of the positive / negative arm on-time detection circuit 7, extracts the difference between the positive on-time and the negative on-time of the target phase, and integrates it. To the vessel 82. The output integrated by the integrator 82 is given to the comparator 41 of the inverter control circuit 4 as an offset correction signal.

  The operation of the inverter device of the present invention in the above circuit configuration will be described below.

  For example, a case is assumed in which the balance between the upper and lower arm conduction times of the semiconductor power element directly connected to the R-phase output of the inverter circuit 1 is lost and a DC offset is applied to the R-phase voltage. In this case, the R phase voltage is divided from the voltage dividing resistor 62 corresponding to the R phase of the phase voltage dividing circuit 6, and the positive and negative arm on-times of the R phase voltage are detected by the photodiodes 71A and 71B, respectively. When there is a DC offset, a difference occurs between the positive arm on time and the negative arm on time. The integrator 82 integrates this on-time difference, and outputs a positive value when the R-phase output phase voltage has an offset in the positive direction, and outputs a negative value when it is in the negative direction. By subtracting this integral value from the R-phase voltage command value of the inverter control circuit 4, R-phase output phase voltage offset compensation is performed.

  The above is a description of the R phase, but the same applies when there is a DC offset in the S and T phases.

  FIG. 2 is a circuit configuration diagram showing Embodiment 2 of the inverter device according to the present invention.

About each part of this Example 2, the same part as each part of the inverter apparatus which concerns on Example 1 of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The second embodiment is different from the first embodiment in that a phase voltage dividing circuit 6A is configured by forming a series circuit of a voltage dividing resistor 62A and a voltage dividing resistor 62B for voltage detection, and a photodiode. the shunt regulator 73A in series 71A, the shunt regulator 73B is provided in series with the photodiode 71B, connecting the midpoint of the divider resistor 62A and the voltage dividing resistor 62B above the reference terminal of each of the shunt regulator, the voltage dividing resistors Positive / negative arm on time detection so that shunt regulator 73A is turned on when the voltage across 62A exceeds a predetermined value, and shunt regulator 73BA is turned on when the voltage across voltage dividing resistor 62B exceeds a predetermined value. The circuit 7A is configured.

  For example, the voltage dividing resistor 62A is a voltage dividing resistor that bears a voltage of 2.5 V or more with respect to a predetermined output voltage in the R phase positive direction, and the voltage dividing resistor 62B is set to 2. with respect to the predetermined output voltage in the R phase negative direction. Assuming that the voltage dividing resistor carrying a voltage of 5V or more is used, the shunt regulator 73A has a current flowing from the cathode electrode to the anode electrode when the voltage across the voltage dividing resistor 62A is 2.5V or more, and the shunt regulator 73B is a voltage dividing resistor. When the voltage at both ends of 62B becomes 2.5 V or more, a current flows from the cathode electrode to the anode electrode. As a result, a current flows through the photodiode 71A or the photodiode 71B, and the R-phase positive side arm-on time or the R-phase negative side arm-on time can be detected.

  In this way, if the positive / negative arm on time detection circuit 7A is configured to operate at a voltage higher than a predetermined voltage level, the positive / negative time of the output phase voltage with higher noise resistance and less variation can be recognized. Therefore, more reliable output phase voltage offset compensation can be realized.

The circuit block diagram which shows Example 1 of the inverter apparatus which concerns on this invention. The circuit block diagram which shows Example 2 of the inverter apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter 2 Output filter 3 Load 4 Inverter control circuit 41 Comparator 42 Voltage amplifier 43 PWM controller 44 Carrier generation circuit 5 Voltage detector 6 Phase voltage dividing circuit 61, 62, 62A, 62B, 63 Voltage dividing resistor 64 Diode converter Circuits 65A, 65B Electrolytic capacitors 66A, 66B Resistor 7 Positive / negative arm on time detection circuits 71A, 71B Photodiodes 72A, 72B Phototransistors 73A, 73B Shunt regulator 8 On time difference calculation circuit 81 Comparator 82 Integrator

Claims (3)

An inverter circuit that is configured by bridge-connected semiconductor power elements, converts DC power to AC power, and supplies power to a load via an output filter;
A control unit that controls the output voltage of the inverter circuit in response to a voltage command;
Phase voltage detection means for detecting an output phase voltage in the form of a rectangular wave before the output filter of the inverter circuit;
A conduction time detecting means for detecting each of the conduction times on the positive side and the negative side of the output phase voltage in the form of a rectangular wave by insulating with a photocoupler;
The phase voltage detecting means includes
A diode circuit for rectifying the output voltage of the inverter circuit;
A capacitor for smoothing the output voltage of the diode circuit;
A plurality of voltage dividing resistors connected in series for each phase between the output of the inverter circuit and the input of the diode circuit,
At least one voltage dividing resistor of the plurality of voltage dividing resistors is used as a phase voltage detecting voltage dividing resistor, and the phase voltage is detected by a voltage applied to the phase voltage detecting voltage dividing resistor.
The controller is
An inverter device, wherein a DC component of the voltage command is corrected according to an integrated value of a difference between a positive side conduction time and a negative side conduction time obtained by the conduction time detection means. The conduction time detecting means includes
Two photocouplers are connected in antiparallel to the voltage dividing resistor for phase voltage detection,
2. The inverter device according to claim 1, wherein the conduction times on the positive side and the negative side of the semiconductor power element are detected from the outputs of the two photocouplers. The conduction time detecting means includes
A series circuit of two shunt regulators connected to the voltage dividing resistor for phase voltage detection and a photocoupler for detecting conduction time;
A midpoint of the phase voltage detecting voltage dividing resistor is connected to a reference terminal of the two shunt regulators;
3. The inverter device according to claim 2, wherein the photocoupler detects insulation of the conduction signal of the shunt regulator when the voltage of the reference terminal becomes equal to or higher than a predetermined value.

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