JP2013027114A - Ship driving device and method of protecting braking resistor for ship driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ship driving device which can accurately protect a braking resistor with a relatively simple circuit configuration, and a method of protecting the braking resistor for the device.SOLUTION: A ship driving device comprises: a converter 2 that converts AC voltage fed from a generator into DC; a DC capacitor 3 that smooths output voltage of the converter 2; an inverter 4 that converts the converter output into AC voltage and drives an AC motor 5; a series circuit of a braking resistor 7 and a semiconductor switch 6, which is connected in parallel to the output of the converter 2 so as to absorb regenerative power at the time of braking of the AC motor 5; a temperature detector 8 that detects temperature of the braking resistor 7; and a current detector 9 that detects current flowing through the braking resistor 7. The device obtains an overheat protection output for protecting the braking resistor 7 when the magnitude of current that is detected by the current detector 9 for a predetermined first monitoring time exceeds a predetermined first threshold value or the temperature that is detected by the temperature detector 8 exceeds a predetermined threshold value.

Description

  The present invention relates to a marine drive device including a braking resistor and a method for protecting the braking resistor for the device.

  In a marine drive device that performs electric propulsion, it is necessary to apply a braking torque to the motor during deceleration. In order to apply the braking torque, a method of converting the inertial energy transmitted from the propeller to the electric motor into electric energy by an inverter and regenerating it to the power supply system can be considered. However, when the motor capacity is relatively large with respect to the power capacity of the marine generator, there is a problem that large power fluctuations occur due to the regenerated power. For this reason, the regenerative electric power given from the electric motor is generally consumed by a braking resistor provided on the input side of the inverter.

  Thus, the capacity of the braking resistor provided exclusively for regenerative power absorption may be smaller than the capacity of the drive device, but it is necessary to perform overheat protection if an excessive current flows due to a failure of the braking circuit, etc. is there.

  Although it is conceivable that overheating protection of the braking resistor is performed at the temperature detected by the resistance temperature detector, it is necessary to insulate the braking resistor from the resistance temperature detector. Therefore, the spatial distance becomes large, and a delay in response time becomes a problem. For this reason, a proposal has been made to estimate and calculate the temperature of the braking resistor from the regenerative power during deceleration without directly detecting the temperature (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 10-225158 (page 3-4, FIG. 1)

  Although the method disclosed in Patent Document 1 is possible in principle, there is a problem that the temperature estimation calculation becomes complicated. The present invention has been made in view of the above, and provides a marine drive device capable of accurately protecting a braking resistor with a relatively simple circuit configuration and a method for protecting the braking resistor for the device. Objective.

In order to achieve the above object, a marine drive device and a braking resistor protection method according to the present invention include a converter that converts an AC voltage supplied from a generator into a DC voltage, and a smooth output voltage of the converter. A DC capacitor, an inverter for driving the AC motor by converting the output of the converter into an AC voltage, and a braking resistor connected in parallel to the output of the converter to absorb regenerative power during braking of the AC motor A series circuit of a device and a semiconductor switch,
In a marine drive device comprising a temperature detector for detecting a temperature of the braking resistor and a current detector for detecting a current flowing through the braking resistor, the current detector at a predetermined first monitoring time is provided. An overheat protection output for protecting the braking resistor is obtained when the magnitude of the detected current exceeds a predetermined first threshold value or the detected temperature of the temperature detector exceeds a predetermined threshold value. It is characterized by that.

  According to the present invention, it is possible to provide a marine drive device capable of accurately protecting a braking resistor with a relatively simple circuit configuration and a method for protecting the braking resistor for the device.

The circuit block diagram of the ship drive device which concerns on Example 1 of this invention. Explanatory drawing of the braking resistor protection operation | movement of the ship drive device which concerns on Example 1 of this invention. The block block diagram of the braking resistor protection circuit of the ship drive device which concerns on Example 2 of this invention.

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

  Hereinafter, a marine drive device according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a circuit configuration diagram of a marine drive device according to a first embodiment of the present invention. FIG. 1A is an overall circuit configuration diagram, and FIG. 1B is a block configuration diagram of a braking resistor protection circuit. Indicates. As shown in FIG. 1A, two three-phase AC voltages having different phases obtained from an AC power source of a marine generator through an input transformer 1 are respectively supplied to a positive side converter 2P and a negative side converter 2N. Supplied. The DC output of the positive converter is applied to the smoothing DC capacitor 3P, and the DC output of the negative converter is applied to the smoothing DC capacitor 3N. The negative terminal of the DC capacitor 3P and the positive terminal of the DC capacitor 3N are mutually connected. It is connected. In this way, a three-level DC voltage of a positive potential P, a negative potential N, and a neutral point potential C is obtained, and this three-level DC voltage is applied to the three-level inverter 4. The three-level inverter 4 converts the three-level DC voltage into a three-level AC voltage and drives the AC motor 5.

  Here, the three-level inverter 4 configures a series connection body by connecting four switching elements per phase in series, and obtains an AC output from the midpoint thereof. Both ends of these series connection bodies are connected to positive and negative DC potentials, and the intermediate points of the switching elements on the positive side and the negative side and intermediate switching elements are clamped to neutral point potentials via diodes, respectively. ing. The switching element of the three-level inverter 4 is on / off controlled by a command from a control circuit (not shown). Usually, the control circuit is given a speed reference, outputs a current reference so that the deviation from the feedback speed becomes zero, and based on the voltage reference such that the deviation between the current reference and the feedback current becomes zero. On / off control is performed.

  Between the positive potential P and the neutral point potential C, a series circuit of a semiconductor switch 6P and a braking resistor 7P is connected. Similarly, a series circuit of a semiconductor switch 6N and a braking resistor 7N is connected between the neutral point potential C and the negative potential N. The surface temperatures of the braking resistors 7P and 7N are detected by the temperature detecting elements 8P and 8N, respectively, and are given to the braking resistor protection circuit 20. Further, currents flowing through the braking resistors 7P and 7N are detected by the current detectors 9P and 9N, respectively, and are supplied to the braking resistor protection circuit 20. Flywheel diodes 10P and 10N are connected in parallel with the braking resistors 7P and 7N, respectively. The braking resistors 7P and 7N consume regenerative power when the AC motor 5 is decelerated and braked. In general, regenerative electric power generated by the braking operation of the ship is generated for a short time on the order of several minutes, so that the braking resistors 7P and 7N are selected for a short-time rating. The braking current is controlled by ON / OFF control of the semiconductor switches 6P and 6N. A braking control circuit (not shown) gives a gate control pulse to the semiconductor switches 6P and 6N, but it is normal to control the PWM modulation rate so that the DC voltage increased by the regenerative power does not exceed a predetermined value.

  The internal configuration of the braking resistor protection circuit 20 will be described below with reference to FIG. The braking currents detected by the current detectors 9P and 9N are given to the RMS calculators 21P and 21N, respectively. The RMS calculators 21P and 21N calculate the effective value (RMS value) of the braking current during the predetermined monitoring time T1, and give the calculation results to the comparison circuits 23P and 23N, respectively. In the comparison circuits 23P and 23N, the set current value (threshold value) preset by the set current setter 22 is compared with the RMS value, respectively, and when the RMS value exceeds the set current value, the logic signal 1 is respectively output. Output to the OR circuit 24. The output of the OR circuit 24 becomes one input of the OR circuit 29.

  The temperature information detected by the temperature detection elements 8P and 8N is given to the temperature detection circuits 25P and 25N, respectively. In the temperature detection circuits 25P and 25N, each detection temperature is obtained by performing a predetermined calculation, and the result is given to the comparison circuits 27P and 27N, respectively. Accordingly, the temperature detector is configured by the combination of the temperature detection element 8P and the temperature detection circuit 25P, and the temperature detection element 8N and the temperature detection circuit 25N. In the comparison circuits 27P and 27N, the set temperature (threshold value) preset by the set temperature setter 22 is compared with the detected temperature, and when the detected temperature exceeds the set temperature, the logic signal 1 is output. To the OR circuit 28. The output of the OR circuit 28 becomes the other input of the OR circuit 29, and the output of the OR circuit 29 becomes the overheat protection signal of the protection circuit 20. When this overheat protection signal is output, for example, the operation of the three-level inverter is stopped, or the semiconductor switches 6P and 6N are gate-blocked.

  The operation of the braking resistor protection circuit 20 configured as described above will be described below with reference to FIG. FIG. 2 is an explanatory diagram of the braking resistor protection operation created on the basis of simulation. The vertical axis shows time (s) and the horizontal axis shows current (%) on a logarithmic scale. The “resistance temperature upper limit” indicated by a solid line indicates the time to reach the temperature to be protected when a certain current is passed through the braking resistor. Therefore, it is necessary to perform the protection operation before the time for reaching the upper temperature limit. “Temperature monitoring” indicated by a broken line indicates a time during which a temperature detected by the temperature detecting element reaches the above temperature upper limit when a certain current is passed through the braking resistor. This “temperature monitoring” crosses the “resistance upper temperature limit” at point A. This is because it is possible to protect the braking resistor by the temperature detector at an abnormal current below the current at point A, but when an abnormal current above the current at point A flows, Indicates that the instrument cannot be protected.

  On the other hand, “current monitoring 5-minute RMS” indicated by a one-dot chain line indicates a time until the protection level is reached when the effective value of the current is measured with the monitoring time T1 = 5 minutes. Here, the protection level is set to a current value at which the temperature of the braking resistor becomes the “temperature upper limit of resistance” when the current is 100% or more and a predetermined duration has elapsed. The point B in FIG. 2 corresponds to this position. As is apparent from FIG. 2, when the braking current exceeds the current at point B, the “current monitoring 5 minutes RMS” reaches the protection level in the duration less than the solid line “resistance temperature upper limit”. Can be protected. Conversely, when the braking current is less than the current at point B, the braking resistor cannot be protected.

  As described above, if protection is performed under the OR condition of “temperature monitoring” and “current monitoring 5 minutes RMS” in the figure, the protection level of “current monitoring 5 minutes RMS” protects the braking resistor due to the detection delay of the temperature detection element. Since the area that cannot be used is complemented, reliable protection can be performed. Although the actual braking current is not constant, the fluctuation within the time range for calculating the effective value is included in the RMS current. Therefore, if the monitoring time is selected according to the thermal time constant of the braking resistor, the RMS current is as shown in the figure. In general, the temperature of the braking resistor can be simulated. The lower the protection level is, the safer it is, but it is preferable that as many braking operations as possible are possible from the operational side of the ship. For this purpose, the protection level needs to be as close as possible to the curve of “temperature rise of resistance”.

  As shown by a two-dot chain line in FIG. 2, when “current monitoring 20 minutes RMS” is applied with the monitoring time T2 = 20 minutes, the protection level in the high current region can be increased. However, in this case, the protection time in the high current region exceeds the “resistance temperature upper limit”. Therefore, in the example of FIG. 2, an intermediate value between “current monitoring 5 minutes RMS” and “current monitoring 20 minutes RMS” should be selected in order to obtain a protection level as close as possible to the curve of “temperature rise of resistance”. I understand.

  FIG. 3 is a block diagram of the braking resistor protection circuit of the marine drive device according to the second embodiment of the present invention. In the second embodiment, the same components as those in the block configuration diagram of the braking resistor protection circuit according to the first embodiment of the present invention shown in FIG. The second embodiment is different from the first embodiment in that the RMS calculators 31P and 31N having monitoring times different from those of the RMS calculators 21P and 21N are provided, and protection by two monitoring times is added to the temperature protection. It is.

  The braking currents detected by the current detectors 9P and 9N are supplied to the RMS calculators 21P and 21N, and are also supplied to the RMS calculators 31P and 31N in parallel. In the RMS calculators 31P and 31N, the effective value (RMS value) of the braking current during the predetermined monitoring time T2 is calculated and the calculation results are given to the comparison circuits 33P and 33N, respectively. In the comparison circuits 33P and 33N, the set current value preset by the set current setting unit 22 is compared with the RMS value, respectively, and when the RMS value exceeds the set current value, the logic signal 1 is output. This is given to the OR circuit 34. The output of the OR circuit 34 becomes the third input of the OR circuit 29A.

  As shown in FIG. 2, when protection is performed with the RMS current while changing the monitoring time, protection levels having different characteristics can be obtained. Therefore, when protection using RMS currents with different monitoring times as in the second embodiment is used in combination, it may be possible to perform finer protection from the low current region to the high current region.

  Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, in the first embodiment, the example using the three-level inverter 4 has been described. However, the inverter may be two-level. In this case, there are only one type of converter, DC capacitor, semiconductor switch, braking resistor, etc., and only one type of RMS computing unit for the braking resistor protection circuit.

  In the embodiment, the example of performing the RMS calculation of the current has been described. However, it is not always necessary to perform the RMS calculation, and the magnitude of the current during the monitoring time may be obtained. Here, the magnitude of the current means an average value of absolute values, an average value of squares, and the like.

  In the second embodiment, the set current value that is the comparison target protection level of the RMS calculators 31P and 31N is set to the value set by the set current setter 22. However, the set current setter is provided separately, and a different set current is set. It is good as a value.

  Further, the overheat protection output of the braking resistor protection circuit may be configured in two stages so that an alarm is given in the first stage and a gate block of a three-level inverter or semiconductor switch is given in the next stage. In this case, the temperature or current threshold may be set in two stages, or in the configuration of the second embodiment, only the set current for any monitoring time may be set in two stages.

  Furthermore, in the second embodiment, an example in which protection by RMS current of two types of monitoring times is used in combination has been described, but three or more types may be combined.

DESCRIPTION OF SYMBOLS 1 Input transformer 2P Positive side converter 2N Negative side converter 3P, 3N DC capacitor 4 3 level inverter 5 AC motor 6P, 6N Semiconductor switch 7P, 7N Braking resistor 8P, 8N Temperature detection element 9P, 9N Current detector 10P, 10N Flywheel diode 20 Braking resistor protection circuit 21P, 21N RMS calculator 22 Current setting device 23P, 23N Comparator 24, 25, 25A OR circuit 25P, 25N Temperature detection circuit 26 Temperature setting device 27P, 27N Comparator 28 OR circuit 29 29A OR circuit 31P, 31N RMS calculator 2
33P, 33N Comparator 34 OR circuit

Claims (5)

A converter that converts AC voltage fed from the generator into DC,
A DC capacitor that smoothes the output voltage of this converter;
An inverter that drives the AC motor by converting the output of the converter into an AC voltage;
A series circuit of a braking resistor and a semiconductor switch connected in parallel to the output of the converter to absorb regenerative power during braking of the AC motor;
A temperature detector for detecting the temperature of the braking resistor;
A current detector for detecting a current flowing through the braking resistor;
A braking resistor protection circuit that receives the detected temperature of the temperature detector and the detected current of the current detector as input and outputs an overheat protection output of the braking resistor;
The braking resistor protection circuit is
The overheat protection output is obtained when the magnitude of the detected current at a predetermined first monitoring time exceeds a predetermined first threshold or when the detected temperature exceeds a predetermined threshold. A marine drive device. The inverter is a three-level inverter;
Each of the converter, the DC capacitor, the series circuit, the braking resistor, the temperature detector, and the current detector is composed of two on the positive side and the negative side,
The braking resistor protection circuit is
The overheat protection output is obtained when the magnitude of the detected current of the positive current detector or the negative current detector in a predetermined first monitoring time exceeds a predetermined first threshold. The ship drive device according to claim 1, wherein: The braking resistor protection circuit is
2. The marine drive device according to claim 1, wherein the overheat protection output is obtained when the magnitude of the detection current in a predetermined second monitoring time exceeds a predetermined second threshold value. .   4. The marine drive device according to claim 1, wherein the magnitude of the detected current is an RMS value (effective value). A converter that converts AC voltage fed from the generator into DC,
A DC capacitor that smoothes the output voltage of this converter;
An inverter that drives the AC motor by converting the output of the converter into an AC voltage;
A series circuit of a braking resistor and a semiconductor switch connected in parallel to the output of the converter to absorb regenerative power during braking of the AC motor;
A temperature detector for detecting the temperature of the braking resistor;
In a marine drive device comprising a current detector for detecting a current flowing through the braking resistor,
The braking resistor when the magnitude of the detection current of the current detector in a predetermined first monitoring time exceeds a predetermined first threshold or when the detected temperature of the temperature detector exceeds a predetermined threshold A protection method for a braking resistor for a marine drive device, characterized in that an overheating protection output for protecting the vehicle is obtained.

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