JP3032953B2 - Uninterruptible power supply current detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an effective uninterruptible power supply current detector for detecting and controlling the current of an uninterruptible power supply (hereinafter referred to as UPS) having a built-in converter or inverter. Things.

[0002]

2. Description of the Related Art Conventionally, a UPS current detector is implemented by a circuit as shown in FIG. In the UPS, the commercial input power 1 is received, and the received commercial power is converted into a DC voltage by the input filter 27 and the converter 8. The DC converted voltage is converted again into an AC voltage by the inverter 19 and the output filter 28. At this time, the current flowing through the switching elements 4 and 5 of the converter 8 is detected, and the converter controller 30 protects the switching elements 4 and 5 of the converter 8 and detects the current flowing through the switching elements 13 and 14 of the inverter 19. The switching elements 13 and 14 of the inverter 19 are protected by the inverter controller 32.

Hereinafter, detection of the current of the converter 8 will be described. Converter 8 is a half-bridge type converter. In the converter 8 including the switching element 4 and the switching element 5 and the flywheel diodes 6 and 7 connected in series, the anode of the switching element 4 is connected to the anode of the capacitor 11, and the cathode of the switching element 5 is connected to the cathode of the capacitor 12. Connected. The input power supply 1, the input filter 27, and the input current converter (hereinafter referred to as CT) 31 are connected between a connection point between the capacitors 11 and 12, and a connection point between the switching elements 4 and 5. The converter 8 obtains the PWM waveform shown in FIG. 2B accompanying the comparison between the reference oscillation and the sine wave shown in FIG.
By controlling the pulse width with the WM waveform, the energy stored in the reactor 3 of the filter 27 is transmitted to the capacitors 11 and 12 for each pulse, and the input AC voltage is converted to a DC voltage. At this time, PWM control is performed at a switching frequency of several tens of kHz so that the input current becomes a sine wave. Therefore, the input current includes a converter current close to a sine wave having the same commercial frequency as the input voltage as shown in FIG. Flows. Similarly, a current having a commercial frequency shown in FIG. On the other hand, a delay current due to the reactor 3 of the input filter 27 flows through the flywheel diode 6 when the switching element 4 is off, and a delay current due to the reactor 3 of the input filter 27 flows through the flywheel diode 7 when the switching element 5 is off.

Next, detection of the current of the inverter 19 will be described. The inverter 19 is a half-bridge type inverter, in which the switching elements 13 and 14 are connected in series, and uses a DC voltage divided by the capacitors 11 and 12 as an input voltage. CT3
3. The output filter 28 and the load 20 are connected between the connection point of the capacitors 11 and 12 and the connection point of the switching elements 13 and 14. When the switching element 13 is on, current flows from the switching element 13 to the capacitors 11 and 12 through the CT 33, the output filter 28 and the load 20. When the switching element 14 is on, the switching element 1 is passed through the capacitor 11 and the capacitor 12 through the CT 33, the output filter 28 and the load 20.
4, a positive and negative voltage is applied to the filter 28 and the load 20. The repetition of the positive and negative voltages is based on the reference oscillation shown in FIG.
By switching at z and modulating the pulse width at the commercial frequency of 50 Hz or 60 Hz by the PWM waveform shown in FIG. 2B, a voltage of a predetermined frequency is obtained at the output. Further, an output filter 28 including the reactor 18 and the capacitor 17 reduces high frequency current ripple due to switching. At this time, similarly to the inverter output, an inverter current having a commercial frequency of 50 Hz or 60 Hz shown in FIG. On the other hand, when the switching element 13 is off, a delay current due to the reactor 18 of the output filter 28 flows through the flywheel diode 15, and when the switching element 14 is off, a delay current due to the reactor 18 of the output filter 28 flows through the flywheel diode 16.

[0005]

In the conventional UPS current detector, the input current of the commercial frequency of 50 Hz or 60 Hz on the converter 8 side is passed through the CT 31 and the current of the switching elements 4 and 5 of the converter 8 is detected. When an excessive current flows, the driving signals of the switching elements 4 and 5 are stopped to protect the switching elements 4 and 5. Further, on the inverter 19 side, 50
Hz or 60 Hz commercial frequency current is passed through the CT 33 to perform current detection. When an excessive current flows, the drive signals for the switching elements 13 and 14 are stopped to protect the switching elements 13 and 14. 50 Hz regardless of whether the current is detected on the converter 8 side or the inverter 19 side
Alternatively, when a commercial frequency of 60 Hz is passed through the CT, the magnetic flux density of the CT becomes larger than the magnetic flux density when passing a high-frequency current of several tens of kHz, and it is necessary to increase the core of the CT. Becomes larger.
That is, when the current of the switching element is detected at a commercial frequency of 50 Hz or 60 Hz, there is a problem that the current detection CT becomes large.

[0006]

According to a first aspect of the present invention, a UPS current detector receives a commercial AC input, and an AC input in which a first switching element and a second switching element are connected in series through an input filter. A converter for converting a voltage to a DC voltage, two series-connected capacitors connected in series for smoothing the output of the converter, and a third switching element and a fourth switching element connected in series to the two series capacitors. An inverter for converting the DC voltage to an AC voltage, and an output filter circuit for converting the output of the inverter to a sine wave, wherein an anode side of a first switching element of the converter and a second A first current path and a second current path for leading a current to the two series capacitors are connected to a first current of the same iron core. Those having features for detecting a current on the output side of the converter through exchanger (CT).

A UPS current detector according to a second aspect of the present invention receives a commercial AC input, and converts an AC input voltage in which a first switching element and a second switching element are connected in series to a DC voltage through an input filter. A converter, two series capacitors connected in series for smoothing the output of the converter, and the DC voltage in which a third switching element and a fourth switching element are connected in series to the two series capacitors. And an output filter circuit for converting the output of the inverter into a sine wave. In the uninterruptible power supply, the anode side of the third switching element of the inverter and the fourth A third electric path and a fourth electric path for conducting a current to the cathode side of the switching element are connected to each other through a second current converter having the same iron core. Those having features to detect the current at the input of the converter.

[0008]

According to the first aspect, a commercial AC voltage is received,
The first and second switching elements are modulated at a reference frequency synchronized with the frequency of an input power supply through an input filter connected to a connection point connecting the first and second switching elements of the converter in series. P
By the WM control, a substantially sine-wave current synchronized with the input voltage is applied to the input, and the two series capacitors are charged to convert the AC input voltage into a DC voltage. In this state,
Current flowing in the first circuit connecting the anode of the first switching element and the anode of the two series capacitors and the current flowing in the second circuit connecting the cathode of the second switching element and the cathode of the two series capacitors Varies with the frequency at which the first and second switching elements are switched. The current of the converter is detected at the switching frequency of the switching element by penetrating the first electric circuit and the second electric circuit through a first current converter (CT) having the same iron core.

According to the second invention, when the third switching element in the inverter is on, the third switching element is turned on.
Current flows from the switching element to the two series capacitors through the second current converter, the output filter, and the load, and when the fourth switching element is on, the second current converter Since current flows to the fourth switching element through the output filter, negative and positive voltages are applied to the output filter and the load. By switching the repetition of the positive and negative voltages at several tens of kHz and modulating the pulse width of the ratio of the positive and negative voltages at a predetermined frequency, a voltage of a predetermined frequency is obtained at the output. In this state, a third current is guided from the two series capacitors to the anode side of the third switching element and the cathode side of the fourth switching element of the inverter.
And the fourth circuit are connected to a second current converter (C
By passing through T), the current of the inverter is detected at the switching frequency of the third and fourth switching elements.

[0010]

FIG. 1 shows an embodiment of the present invention. In the UPS, a commercial input voltage is received, and the received commercial voltage is converted into a DC voltage by the input filter 27 and the converter 8. The voltage converted to DC is applied to inverter 19 and output filter 27.
Is again converted into an AC voltage. At this time, the currents of the switching elements 4 and 5 of the converter 8 are detected, and when an excessive current flows through the converter 8, the converter controller 21
Thus, the drive signals of the switching elements 4 and 5 are stopped to protect the switching elements 4 and 5 of the converter 8. Further, the current of the switching element of the inverter 19 is detected, and when an excessive current flows to the inverter 19, the drive signal of the switching elements 13 and 14 is stopped by the inverter controller 22 to switch the switching element 1 of the inverter 19.
Protect 3 and 14.

Hereinafter, the current detection of the converter 8 will be described. Converter 8 is a half-bridge type converter. In the converter 8 including the switching element 4 and the switching element 5 and the flywheel diodes 6 and 7 connected in series, the anode of the switching element 4 is connected to the anode of the capacitor 11, and the cathode of the switching element 5 is connected to the cathode of the capacitor 12. Connected. The input power supply 1 and the input filter 27 are composed of the capacitor 11 and the capacitor 1
2 and a connection point between the switching elements 4 and 5. The electric circuit 23 penetrates the electric circuit 23 in the forward direction through the CT 9 and the electric circuit 2
Reference numeral 4 penetrates in the negative direction to detect the current of the converter. The converter 8 obtains a PWM waveform shown in FIG. 2B accompanying the comparison between the reference oscillation shown in FIG. 2A and the sine wave to the switching elements 4 and 5, and obtains the PWM waveform.
By controlling the pulse width with the M waveform, the energy stored in the reactor 3 is transmitted to the capacitors 11 and 12 for each pulse to convert the input AC voltage into a DC voltage. At this time, PWM control synchronized with the input voltage is performed by switching the switching elements 4 and 5 by several tens of kHz so that the input current becomes a sine wave, so that the input current includes the input voltage as shown in FIG. A current close to a sine wave of the same commercial frequency flows. The converter current shown in FIG. 2D flows through CT9. This current is applied to switching elements 4 and 5
Is a high-frequency current having a switching frequency of several tens of kHz. On the other hand, when the switching element 4 is turned off, a delay current due to the reactor 3 of the input filter 27 flows through the flywheel diode 6 and the flywheel diode 7
, A delay current due to the reactor 3 of the input filter 27 flows when the switching element 5 is turned off.

Next, detection of the current of the inverter 19 will be described. The inverter 19 is a half-bridge type inverter, in which the switching element 13 and the switching element 14 are connected in series, and uses an input voltage divided by the capacitors 11 and 12. The CT 33, the output filter 28 and the load 20 are connected between a connection point between the capacitors 11 and 12 and a connection point between the switching elements 13 and 14. The electric circuit 25 passes through the CT 10 in the positive direction, and the electric circuit 26 penetrates in the negative direction to detect the current of the inverter. When the switching element 13 is on, CT10
From the switching element 13, the output filter 28 and the load 2
Current flows into the capacitors 11 and 12 through 0. When the switching element 14 is on, the output filter 28 and the load 2
Since current flows through the switching element 14 and the CT 10 through 0, positive and negative voltages are applied to the filter 24 and the load. The repetition of the positive and negative voltages is performed by switching the reference oscillation shown in FIG. 2A at several tens of kHz, and changing the ratio of the positive and negative voltages to 50 Hz or 60 Hz by the PWM waveform shown in FIG. By modulating the pulse width at the commercial frequency, a voltage of a predetermined frequency can be obtained at the output. Further, an output filter 28 including the reactor 18 and the capacitor 17 reduces high frequency current ripple due to switching. At this time, the current flowing through the CT 10 is a high-frequency current of several tens kHz shown in FIG. On the other hand, a delay current due to the reactor 18 of the input filter 28 flows through the flywheel diode 15 when the switching element 13 is off, and a delay current due to the reactor 18 of the input filter 28 flows through the flywheel diode 16 when the switching element 14 is off.

[0013]

As described above, the UPS is used for protecting the switching element.
In the current detection of the converter 8 and the inverter 19,
In the UPS current detector of the first invention, a CT 9 is provided on the output side of the converter 8 for detecting the current of the converter 8, thereby detecting the current of the converter 8 at a high frequency of several tens of kHz. The detector detects the inverter current at a high frequency of several tens kHz by providing CT10 on the input side of the inverter for detecting the current on the inverter 19 side. By detecting the current of the converter and the inverter on the high frequency side, the current converter for current detection (C
The CT can be reduced in size by lowering the magnetic flux density of the iron core of T).

[Brief description of the drawings]

FIG. 1 is a connection diagram of an embodiment of the present invention.

FIG. 2 is an operation waveform of the uninterruptible power supply.

FIG. 3 is a connection diagram of an embodiment of the prior art.

[Explanation of symbols]

 Reference Signs List 1 power supply 2 capacitor 3 reactor 4, 5 switching element 6, 7 diode 8 converter 9, 10 current converter (CT) 11, 12 capacitor 13, 14 switching element 15, 16 diode 17 capacitor 18 reactor 19 inverter 21 converter controller 22 Inverter controller 23, 24, 25, 26 Electric circuit 27 Input filter 28 Output filter 30 Converter controller 31 Current converter (CT) 32 Inverter controller 33 Current converter (CT)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02J 9/06 504

Claims (2)

(57) [Claims] A converter for receiving a commercial AC input, converting an AC input voltage in which a first switching element and a second switching element are connected in series through an input filter into a DC voltage, and smoothing an output of the converter. An inverter for converting the DC voltage into an AC voltage, in which a third switching element and a fourth switching element are connected in series to the two series capacitors; An uninterruptible power supply having an output filter circuit for converting an output into a sine wave, wherein an electric current is led from the anode side of the first switching element and the cathode side of the second switching element of the converter to the two series capacitors. The first circuit and the second circuit are passed through a first current converter having the same iron core, and current is detected at the output side of the converter. An uninterruptible power supply current detector. 2. A converter for receiving a commercial AC input, converting an AC input voltage in which a first switching element and a second switching element are connected in series to a DC voltage through an input filter, and smoothing an output of the converter. An inverter for converting the DC voltage into an AC voltage, in which a third switching element and a fourth switching element are connected in series to the two series capacitors; An uninterruptible power supply having an output filter circuit for converting an output into a sine wave, wherein a current is guided from the two series capacitors to an anode side of a third switching element and a cathode side of a fourth switching element of the inverter. Current is detected at the input side of the inverter through a third current path and a fourth current path through a second current converter having the same iron core. A current detector for an uninterruptible power supply.