JP4147449B2 - Power regeneration converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a converter device that converts AC power into DC current, and particularly to a power regeneration converter that regenerates DC power to AC power.
[0002]
[Prior art]
A conventional power regeneration converter is as shown in FIG. 3 (Japanese Patent Laid-Open No. 11-289794). In FIG. 3, the power regeneration converter unit 10 is disposed between a three-phase commercial power source and the inverter unit 40. The power regeneration converter unit 10 includes a power running / regeneration determination unit 11 for determining the motor operating state, a power supply voltage phase detection unit 32 for detecting the phase of the power supply voltage, a switching control unit 33, and an instantaneous overcurrent limiting circuit 34. , AC reactor 35 and current detector 36 arranged on the commercial power line, switching element 37 by an element such as IGBT, smoothing capacitor 38 connected to the output side of switching element 37 and the input side of inverter unit 40, switching element It comprises a voltage detector 39 for detecting the voltage of the smoothing capacitor 38 on the 37 side.
In addition, the switching element 37 and the inverter part 40 are shown with one element for convenience.
[0003]
When the operation state of the load is monitored by the power running / regeneration determination unit 11 and is determined to be in the regenerative operation state, the switching control unit 33 uses the detection result from the power supply voltage phase detection unit 32 to generate the highest voltage among the three phases. Determine the largest phase and the smallest voltage phase. Based on this determination result, the switching control unit 33 outputs a switching signal that turns on the upper arm switching element 37 having the maximum voltage and the lower arm switching element 37 having the minimum voltage. On the other hand, the switching control part 33 turns off all the switching elements 37, when it determines with a power running state. By switching the switching element 37 based on such a switching signal, the regenerative power is returned to the commercial power source via the AC reactor 35. In the instantaneous overcurrent limiting circuit 34, when the current value detected by the current detector 36 exceeds a preset threshold level, the switching signal is cut off, so that an overcurrent due to a cause such as power supply voltage fluctuation is reduced. To prevent.
[0004]
The power regeneration converter 10 according to the present embodiment is characterized by a power running / regeneration determination unit 11 for determining an operation state. In other words, the power running / regeneration determination unit 11 adds not only the conventional DC voltage information but also the input current information to the determination condition of the operation state.
In addition to the hysteresis comparator 12 (second hysteresis comparator) for performing determination based on voltage and the one-shot trigger circuit 13 connected to the output side, the power running / regeneration determination unit 11 performs determination based on input current. As means, it has a three-phase to two-phase coordinate conversion unit 14, a low-pass filter 15, and a hysteresis comparator 16 (first hysteresis comparator), and further takes the sum of the output of the one-shot trigger circuit 13 and the output of the hysteresis comparator 16. An OR gate 17 is provided.
[0005]
Below, the driving | running state determination operation | movement in the power running / regeneration determination part 11 is demonstrated. The three-phase to two-phase coordinate conversion unit 14 performs coordinate conversion of the current value detected by the current detector 36 into a two-axis rotational coordinate system synchronized with the power supply phase detected by the power supply voltage phase detection unit 32. A current value Id having a component in phase with the power supply voltage phase is calculated. The current value Id corresponds to an effective current, and assuming that the commercial power supply voltage is substantially constant, the effective power can be estimated from this value. However, since the input current includes a higher harmonic current and the detected value fluctuates greatly, stabilization is achieved by removing the influence of the higher harmonic current with the low-pass filter 15. The hysteresis comparator 16 monitors the polarity of the current value Id, and when the current value Id becomes smaller than the minus threshold level, it is determined as a regenerative state. As can be understood from the above points, in this embodiment, the current value detected by the current detector 36 and the power supply phase detected by the power supply voltage phase detector 32 are used as input current information.
On the other hand, the determination from the DC voltage information is performed by monitoring the difference between the DC voltage and the voltage peak value of the commercial power supply with the hysteresis comparator 12 as in the conventional type. Here, once the regenerative operation is started by adding the one-shot trigger circuit 13, the regenerative operation is continued for a set time or longer so that a time until the determination on the input current information side is stabilized can be secured. ing. In other words, a time until the output from the low-pass filter 15 is stabilized can be secured.
The determination result obtained from the input current information and the determination result obtained from the DC voltage information are logically ORed by the OR gate 17 to obtain a final determination. In this determination, if either one is determined to be in the regenerative state, the final determination is also in the regenerative state.
[0006]
[Problems to be solved by the invention]
However, in the prior art, the overcurrent detection unit is composed of a simple hysteresis comparator, and it is necessary to make the overcurrent detection level the same during regeneration and during electric drive. For this reason, since the overcurrent withstand capability of the switching element 37 in the power regeneration converter unit and the overcurrent withstand capability of the freewheeling diode provided for each switching element 37 need to be the same, the switching element 37 has an excessive overcurrent more than necessary. Tolerance was necessary and it was uneconomical.
The present invention has been made in view of the above problems, and the object of the present invention is to determine the overcurrent tolerance of the switching element 37 in the power regeneration converter unit from the overcurrent tolerance of the freewheeling diode provided for each switching element 37. Is to make it smaller.
[0007]
[Means for Solving the Problems]
In order to solve the above problem, the present invention is a separate power regeneration converter (10) connected between a commercial power source and an inverter unit (40), and is provided on the input side of the inverter unit (40). Voltage detection means (39) for detecting DC voltage and outputting DC voltage information, current detection means (36) for detecting current on the commercial power supply side, and phase detection on the commercial power supply side A power supply voltage phase detection means (32); a switching control unit ( 33 ) for generating a switching pattern of the switching element (37) from information of the power supply voltage phase detection means (32); the current detection means (36); Power running / regeneration for estimating the output current information from the switching pattern and determining the operation state of the power running operation or the regenerative operation based on the output current information and the DC voltage information A constant means (11), the power regenerative converter (10) having a,
Each phase current (IR, IS, IT) , each inverted output of each phase current ( IR , IS , IT ) via the inverting amplifier (8-1), and OCLVL (8-) which is an overcurrent detection level 2) and the respective logic signals resulting from the comparison, taking the gate signal (PR synchronized with the power supply voltage phase, PS, PT, NR, NS, an aND between NT) by the aND gate (8-4) over An overcurrent detection protection means (60) for selecting a current determination result and changing an overcurrent detection level by power running / regeneration is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the present invention. The same names as described in the prior art are denoted by the same reference numerals as much as possible, and redundant description is omitted. In the figure, reference numeral 60 denotes overcurrent detection means which is a feature of the present invention. The overcurrent detection means 60 receives the input current detection value and the switch information, and outputs an overcurrent detection signal to the switching control unit 33. The detection direction of the current detector 36 is the positive direction from the switching element 37 to the AC reactor 35.
Next, the overcurrent detection protection means 60 for estimating the output current will be described with reference to FIG. In the figure, 8-1 is an inverting amplifier, 8-2 is an overcurrent detection level, 8-3 is a comparator, 8-4 is an AND gate, 8-5 is an OR gate, and 8-6 is a latch circuit. Reference numeral 8-7 denotes a changeover switch. 2 (a) and 2 (b) both have a circuit configuration that works only when regenerating or shorting between phases. The gate signals PR, PS, PT, NR, NS, NT are signals output from the switching control unit 33 and synchronized with the power supply voltage phase.
Next, the operation of FIGS. 2A and 2B will be described. In the circuit (a), each of the IR, IS, IT and inverted output via the inverting amplifier 8-1 is obtained by ANDing the logic signal resulting from comparing the overcurrent detection level OCLVL8-2 with the gate signal. In this method, the true overcurrent (OC) determination result is selected. In (b), the current detection value selected at the gate signal level from each of IR, IS, IT and the inverted output via the inverting amplifier 8-1 is excessively detected. Compared with the current detection level OCLVL, an overcurrent (OC) determination result is derived, and the same output result is obtained for both (a) and (b).
[0009]
【The invention's effect】
In the present invention, it is possible to change the overcurrent detection level at the time of electric drive and at the time of regeneration, so that the overcurrent tolerance of the switching element 37 in the power regeneration converter unit is more than the overcurrent tolerance of the freewheeling diode provided for each switching element 37. Can also be reduced. Therefore, a switching element and a diode can be appropriately selected, and an economical design is possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing an embodiment of the present invention. FIG. 3 is a block diagram showing a conventional embodiment.
DESCRIPTION OF SYMBOLS 10 Power regeneration converter 11 Power running / regeneration determination part 12 Hysteresis comparator 13 One shot trigger circuit 15 Low pass filter 16 Hysteresis comparator 17 OR gate 32 Power supply voltage phase detection part 33 Switching control part 34 Instantaneous overcurrent limiting circuit 35 AC reactor 36 Current detector 37 Switching element 38 Smoothing capacitor 39 Voltage detector 40 Inverter unit 50 Output current estimation unit 60 Overcurrent detection protection means 8-1 Inverting amplifier 8-2 Overcurrent detection level 8-3 Comparator 8-4 AND gate 8-5 OR gate 8 -6 Latch circuit 8-7 selector switch

Claims (1)

A separate power regeneration converter (10) connected between a commercial power source and an inverter unit (40), and detects DC voltage on the input side of the inverter unit (40) and outputs DC voltage information Voltage detection means (39) for detecting, current detection means (36) for detecting the current on the commercial power supply side, power supply voltage phase detection means (32) for detecting the phase on the commercial power supply side, A switching control unit ( 33 ) for generating a switching pattern of the switching element (37) from the information of the power supply voltage phase detection unit (32), the output current information is estimated by the current detection unit (36) and the switching pattern, Power running / regeneration determining means (11) for determining an operation state of power running or regenerative operation based on the output current information and the DC voltage information. In the converter (10),
Each phase current (IR, IS, IT) , each inverted output of each phase current ( IR , IS , IT ) via the inverting amplifier (8-1), and OCLVL (8-) which is an overcurrent detection level 2) and the respective logic signals resulting from the comparison, taking the gate signal (PR synchronized with the power supply voltage phase, PS, PT, NR, NS, an aND between NT) by the aND gate (8-4) over A power regeneration converter comprising overcurrent detection protection means (60) for selecting an electric current determination result and changing an overcurrent detection level by power running / regeneration.

Images