JP2006129594A - Method and apparatus for controlling marine electric propulsion device - Google Patents

Abstract

Harmonics are suppressed even when a load operating state of a marine electric propulsion device changes.
A marine electric propulsion apparatus includes a plurality of generators 1 and a plurality of electric motors 2 connected via a plurality of power converters 3 to form one or more load systems. The control device for suppressing harmonics includes a detecting unit 5 that detects the number of load systems and the number of operating motors, and a setting unit 12 that sets a multiple of the carrier frequency of the power converter 3 that is a harmonic component to be suppressed. And the control means 6 which calculates | requires the phase difference of each power converter based on the said operation number and the multiple for every said load system, and controls the carrier phase of each power converter is provided.
[Selection] Figure 1

Description

  The present invention relates to a marine electric propulsion apparatus, and more particularly to a control method for suppressing harmonic current by optimizing a carrier phase of a power converter.

  A marine electric propulsion device includes a propulsion motor directly connected to a propeller shaft, a power converter that controls the propulsion motor, a reactor that reduces harmonic current generated from the power converter, a generator that supplies power to these, and Consists of switchboard.

  In a marine electric propulsion system, it is fundamental that all propulsion motors in operation are operated with the same output, and there is no operation in which each propulsion motor is operated with different outputs. The balance of the propulsion motor is controlled. The reactor is a general inductance component that is inserted to reduce harmonics generated from the power converter, and a transformer may be arranged depending on the ship.

  When two or more generators are operated, they are operated synchronously. Since the generator uses the point where it crosses 0v in one cycle of the output voltage as the synchronization reference point, if the output voltage of the generator contains harmonics, multiple reference points where 0V intersects will be generated. , Stable synchronous operation becomes difficult. It can also lead to generator burnout.

  FIG. 4 shows the output voltage of the generator and its zero cross point. (A) is a case where there is no harmonic, and the zero cross point is one point. (B) shows a case where there are harmonics, and there are a plurality of zero-cross points.

  As described above, each generator needs to be designed to withstand harmonics, and it is necessary to install filter equipment and the like on the generator side and the general load side. However, ships are required to reduce the number of filter equipment due to restrictions on the installation space in the ship, and new harmonic measures other than the filter equipment are required.

  In a rolling mill main drive system for steel, the system of which is similar to that of a marine electric propulsion device, the method described in Patent Document 1 is adopted as one of the measures for reducing the harmonic current flowing to the commercial power supply side. Here, the carrier phase of each power converter is controlled so that the harmonic currents cancel each other.

Japanese Patent No. 3236986

  The harmonic countermeasures by carrier phase control implemented in the rolling mill main drive system for steel are based on the assumption that the number of operating loads and the load system are constant. That is, the steel system receives commercial power and controls the rolling main machine (electric motor) with a power converter, the load system is always operated constantly, and the number of operating loads does not change. For this reason, if each power converter is operated with a constant carrier phase difference in the steel system, the harmonic currents in the system are reduced by canceling each other, so that the filter equipment can be reduced and reduced.

  However, in the case of a marine electric propulsion device, the load system and the number of operating loads change in a pattern. Therefore, if the power converter is operated with a constant carrier phase difference as in a steel system, the power changes every time the pattern changes. Harmonic current flows through the system, and the effect of reducing harmonics cannot be obtained.

  In view of the above prior art, an object of the present invention is to provide a control system for a marine electric propulsion apparatus that has an effect of suppressing harmonics even when the operation status of a load changes.

  In order to achieve the above object, the present invention provides a method for controlling a marine electric propulsion apparatus in which a plurality of power converters and motors are connected in the same load system, and detects the number of operating load systems and motors, The carrier phase difference of each power converter is obtained according to the harmonic component to be reduced set for each system and the number of operating units, and the carrier phase of each power converter is controlled.

  Further, the present invention is a control device for a marine electric propulsion device in which one or a plurality of generators and a plurality of electric motors are connected via a plurality of power converters to constitute one or more load systems, Detection means for detecting the number of load systems and the number of operating motors, setting means for setting a multiple of the carrier frequency of the power converter that is a harmonic to be suppressed, and the number of operating systems and the multiple for each load system A control means is provided for obtaining the phase difference of each power converter based on the above and controlling the carrier phase of each power converter.

  According to the marine electric propulsion apparatus of the present invention, since the carrier phase of each power converter can be optimally controlled according to the operating status of the number of motors operated and the load system, the harmonic current in the same load system is reduced. There is an effect that can be suppressed.

  If the present invention is adopted, the filter equipment can be reduced or reduced, so that it is possible to secure a space on the ship, and it is possible to expand the cabin and the cargo compartment, and the freedom of arrangement of the filter equipment itself is increased, and the degree of freedom of hull design is increased Widen. Moreover, the harmonic tolerance design of the generator and the synchronous operation are facilitated, and the stability of a general load on the same system is increased, so that a highly reliable electric propulsion device for ships can be obtained.

  An embodiment of the present invention will be described. The motors of the marine propulsion system are all due to reasons such as the balance of the ship, and basically all motors with the same rating are used. One or two or more propeller shafts are connected to each propeller shaft. Sometimes it becomes. Decide the number of generators and propulsion motors to be operated according to the speed of the ship, and select those systems using the switchboard to propel the ship.

  FIG. 3 shows a load system diagram of the marine electric propulsion apparatus. (A) is a load system diagram at the time of entry / exit. Since the speed is slow when entering and leaving the port, only one generator (G3) is operated, and power is supplied to the three propulsion motors (M2, M3, M5) and the general load on the ship. (B) is a load system diagram at the time of cruising, and is composed of load systems 1 and 2, and since the speed increases, five generators (G2-G6) and four propulsion motors (M2-M5) Driving.

  In the load system 1, two generators are operated synchronously in the system to supply power to the two propulsion motors. In the load system 2, three generators are operated synchronously in the system to supply power to the two propulsion motors and the general load. Further, at full speed, all the switches in FIG. 3B are turned on, and six generators including G1 are operated synchronously to supply power to all the motors (M1-M6). These load operation numbers and load systems are changed in a pattern according to the operation status.

  In a marine electric propulsion system, the propulsion load (motor) and the general load in the ship (radio, radar, etc.) are on the same system, so harmonics generated from the power converter may adversely affect the general load. Yes, measures against harmonics are essential. For this reason, in an apparatus with multiple power converters (switching power supplies using semiconductor elements) in the same load system, the number of load operations and the operation status of the load system are constantly monitored by detectors that detect switch open / close and current. Monitor. And according to this operation state, the carrier phase of each power converter is optimally controlled, and the harmonic current in the same system is suppressed (cancelled).

  FIG. 1 is a configuration diagram of a marine power propulsion apparatus according to an embodiment of the present invention. The marine power propulsion apparatus includes a plurality of generators 1, a plurality of propulsion loads (electric motors: n = 1 to m) 2, and a plurality of power converters 3 (n = 1 to m). In addition, each reactor on a system | strain is a reactor for a harmonic countermeasure generally installed. In addition, a power supply monitoring panel 4 having a circuit breaker for connecting the generator 1 to the load, a circuit breaker for connecting the generators and the power converter 3, a detector 5 for detecting the load state, A power converter monitoring control panel 6 for controlling the phase of the converter 3 is provided.

  From the load operation information (electric power) from each detector 5 and the power operation information (voltage, current, circuit breaker on / off) from the power monitoring panel 4, the power converter monitoring control panel 6 determines the number of load systems and the motor. Detect the number of operating units. Furthermore, the integer multiple of the carrier frequency of the power converter 3 set by the setting device of the power converter monitoring control panel 6, that is, the multiple of the target harmonic to be suppressed is grasped. The power converter monitoring control panel 6 controls each power converter 3 in operation with each phase difference calculated based on these, and suppresses (cancels) the harmonic current.

  Here, the harmonics to be suppressed will be described. The power converter operated at the carrier frequency fc and the power supply frequency fe has the highest harmonic in the component (2fc ± fe) near twice the carrier frequency fc. These are characteristics corresponding to a PWM power converter, and if this component can be significantly reduced, harmonic current can be suppressed.

For example, when two power converters (A, B) are operating on the same load system, if the carriers (etA, etB) of the converter of the power converter are defined by equations 1 and 2, respectively, The harmonics (etkA, etkB) of K times the contained carrier can be expressed by equations 3 and 4.
etA = (2 / π) sin ⁻¹ {sin (2πfct + ΦA)} (1)
etB = (2 / π) sin ⁻¹ {sin (2πfct + ΦB)} (2)
Here, ΦA and ΦB are carrier phases of the power converters (converters A and B).
etkA = Hksink (2πfct + ΦA) (3)
etkB = Hksink (2πfct + ΦB) (4)
Therefore, in order for the components of k times the carrier frequency to cancel each other, the phase difference between the two (ΦA, ΦB) only needs to be π / k as shown in Equations 5 and 6.
k (ΦA−ΦB) = π (5)
(ΦA−ΦB) = π / k (6)
Here, π = 2π / T (T: number of operating power converters). In other words, at the time of entering and leaving the port shown in FIG. 3A, since three power converters are operating in the same system, 60 degrees and 4 times higher harmonics are required to cancel out the double harmonics of the carrier. In order to cancel out, a phase difference of 30 degrees may be added.

Similarly, during the cruise of FIG. 3 (b), since two motors are operating in the load system 1, 90 degrees and 4 times higher harmonics are canceled to cancel twice the harmonics of the carrier. May have a phase difference of 45 degrees. In addition, since the load system 2 is operated by three electric motors, a phase difference of 30 degrees may be added to cancel a harmonic of 60 degrees and a quadruple harmonic of 60 degrees in order to cancel the harmonics of twice the carrier. In general, the phase difference Φ can be expressed by Equation 7.
Φ = 2π / TK (7)
When shifting from the port entry / exit of FIG. 3 (a) to the load system at the time of cruise of FIG. 3 (b), the generators G2, G4 to G6 to be newly operated are first synchronously operated according to G3, and synchronized. When the operation is complete, turn on each generator. Next, the circuit breakers VCB4 and VCB5 are opened, and the newly driven propulsion motor M4 is once separated from the system and started. At this time, since the motor M5 that has been operated is operated independently, the cancellation of harmonics is not performed, so the VCB6 is also opened simultaneously with the VCB4 (VCB5), and power is supplied to the general load through G6. Finally, when the propulsion motors M4 and M5 have the same output, VCB5 and VCB6 are turned on. At this time, the propulsion motors M4 and M5 are operated with a phase difference based on Equation 7.

  Note that the reason why the load system is divided into two during cruise is because the load is separated from the starboard propulsion load and the port propulsion load at the VCB4. When a ship changes course urgently, it may change the output of the starboard and port propellers at the same time as well as maneuvering by rudder. If starboard and port are operated with the same output, there is no problem even if VCB4 is inserted and one load system is used.

  According to the present embodiment, the number of operating loads and the load system are monitored by a detector or the like, and the carrier phase of each power converter is obtained by the above equation 7 and controlled according to these operating states. Thereby, even if the number of load operations and the load system change, the harmonic currents in the same system cancel each other and are reduced.

  FIG. 2 is a functional block diagram showing the configuration of the power converter monitoring control panel of FIG. Moreover, the arrow in a figure has shown the flow of control in a power converter control panel.

  The arithmetic unit 11 of the power converter monitoring control panel 6 determines the current number of load systems from the circuit breaker on / off signal, the generator output voltage, and the distribution board system current signal, which are operation information from the power supply monitoring panel 4. The number of the driving motor for each load system is determined. Moreover, the load operation number T in each load system is calculated from the power signal which is the load operation information of the detector 5 (n = 1 to m).

  The arithmetic device 13 calculates the reference phase Φ from the reduced harmonic order k (usually k = 2) set by the setting device 12 and the load operation number T. For example, when the number of operating units T = 3 and the reduced harmonic order k = 2, the reference phase Φ = π / 3 = 30 degrees.

  The arithmetic unit 14 calculates phases (Φ1 to ΦT) obtained by multiplying the calculated reference phase Φ by an integer from 0 to (T−1). For example, the reference load phase Φ1 = 0 and the second load phase Φ2 = 30 degrees, and the third load phase Φ3 = 60 degrees.

  By controlling each power converter 3 in operation with a carrier frequency obtained by adding this carrier phase (Φ1 to ΦT) to the carrier frequency e (t) oscillated from the reference carrier oscillator 15, the harmonic current is reduced. Can be suppressed.

The system block diagram concerning one Example of this invention. The block diagram which shows the control function and control procedure of FIG. The load system figure of the electric propulsion apparatus for ships. Explanatory drawing which shows the reference point (zero crossing point) in generator synchronous operation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Generator, 2 ... Load (electric motor), 3 ... Power converter, 4 ... Power supply monitoring board, 5 ... Detector, 6 ... Power converter monitoring control board, 11, 13, 14 ... Arithmetic unit, 12 ... Setting 15, reference carrier oscillator.

Claims (4)

In the control method of a marine electric propulsion device in which a plurality of power converters and electric motors are connected in the same load system,
The number of operating load systems and motors is detected from the state of power and circuit breakers, and the carrier phase difference of each power converter is determined according to the harmonic component to be reduced and the number of operating units set for each load system, A control method for a marine electric propulsion device, characterized by controlling a carrier phase of each power converter.   2. The method of controlling a marine electric propulsion device according to claim 1, wherein the harmonic component to be reduced is an integer multiple of a carrier frequency. 1 or a plurality of generators and a plurality of electric motors are connected via a plurality of power converters, and constitutes one or more load systems,
Detection means for detecting the number of load systems and the number of operating motors, setting means for setting a multiple of the carrier frequency of the power converter, which is a harmonic component to be suppressed, the number of operating systems for each load system, and the above A control device for a marine electric propulsion device, characterized in that a control means for obtaining a phase difference of each power converter based on a multiple and controlling a carrier phase of each power converter is provided. 4. The control device for a marine electric propulsion device according to claim 3, wherein the control means determines the number T of operation and a multiple K and obtains the phase difference Φ by Φ = 2π / TK.

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