RU185666U1 - MULTI-PHASE VESSEL ELECTRIC MOVEMENT SYSTEM - Google Patents

Abstract

The utility model relates to the field of ship propulsion and can be used as part of the electric power systems of large vessels with AC power generators. The use of electric ships and the use of propeller steering columns with electric motors is a global trend, especially when developing marine vessels of newly designed series. There are main and auxiliary electric propulsion systems, which are distinguished by their power. The electric propulsion systems used for the main course of the vessel operate in a continuous mode and have power commensurate with the entire electric power system. Auxiliary (thrusters) electric propulsion systems have less power, but its absolute value can also be great. Known to their prior art electric propulsion systems have a number of disadvantages: intermediate conversion (power loss), low quality of voltages and currents (interference radiation, failures of automation systems), the presence of power transformers in the system (increase in the cost of the entire installation). Most electric propulsion systems incorporate a frequency converter with pulse-width modulation, therefore, different types of filters are used to smooth and filter currents and voltages - which leads to an increase in size and cost. The proposed system does not have the above disadvantages. Due to the use of a six-phase propeller motor powered by a two-channel direct frequency converter, the integration of an electric propulsion system and a ship's electric power source has been implemented, which has reduced the weight and cost of installation. Compared with the main prototype, the proposed electric propulsion system allows you to increase the number of phases of the propeller motor without increasing the number of semiconductor switches in the switch.

Description

The technical field to which the utility model belongs. The utility model relates to the field of ship propulsion and can be used in electric propulsion systems of ships with AC power.

The level of technology. A ship electric propulsion system is known from the prior art [RF patent for utility model No. 157368], which contains two three-phase voltage sources, two matching transformers, a two-channel frequency converter, a six-phase asynchronous rowing electric motor, and a disconnected jumper is introduced between the voltage sources, and each transformer has 6 secondary multiphase windings connected to the frequency converter. Each channel of the frequency converter has a three-phase output and is equipped with three sets of two series-connected reversible bridges. The mentioned sets of reversible bridges of each channel are connected to a star, forming a three-phase voltage system, and the outputs of the channels of the frequency converter through the switches are connected to the stator winding of a six-phase propeller motor.

The disadvantages of this solution include the use of transformers to match the output voltage levels of the channels of the direct frequency converter, which leads to a significant increase in the cost of the entire installation as a whole, as well as an increase in operational losses due to a decrease in the efficiency. The disadvantages include a significant number of power semiconductor switches, which leads to an increase in cost, and a decrease in the reliability of the entire system.

The ship electric propulsion system is also known from the prior art [RF patent for utility model No. 181202], comprising a source with two three-phase windings, two reversing semiconductor switches, a three-phase AC electric propeller. Reversible semiconductor switches are connected in series with three-phase supply windings, alternating with them. The beginning of the first of the three-phase windings is going to a common point (that is, the neutral of the winding), the second three-phase winding is open and connected in series in the circuit between the semiconductor switches. The output of the second semiconductor switch is connected to the motor.

The disadvantages of this solution include the use of a significant number of keys (transistors) in semiconductor switches, which leads to an increase in the cost of installation, and an increase in the cost of operation due to a decrease in reliability. The generated voltage allows you to power only a three-phase propeller motor, to obtain a six-phase voltage, two frequency conversion channels are necessary, which doubles the number of keys (transistors) in semiconductor switches and leads to a corresponding increase in size and cost.

This technical solution is the closest prototype in its technical essence.

Disclosure of a utility model. The first use of ship electric propulsion systems almost coincided with the appearance of electricity on ships. At the beginning of the 20th century, with the development of technology, the saturation of ships with electrical equipment increased, the power of ship's electric power sources (generators) increased, which gave rise to the development of electric propulsion systems. In the future, there was an improvement in the equipment and automation systems of ship electric power systems, accompanied by an increase in the number of consumers. The advent of nuclear power plants, for example, on icebreakers, has opened up new prospects for the development of ship electric propulsion systems.

Currently, the global trend is the use of alternating current electric propulsion systems - both on ships and on civilian vessels, such as atomic icebreakers. The change in the speed of the propeller motor in alternating current electric motor systems is realized by regulating the frequency of the static frequency converters included in the propulsion system. Electric propulsion systems with DC motors have slightly larger dimensions along the length, and less resource due to the brush apparatus on the collector. The latter makes it difficult to create particularly powerful DC propeller drives, especially in submersible design.

The most common type are pulse width modulated (PWM) frequency converters. A higher switching frequency of semiconductor switches than classical converters causes increased heating and reduces the durability of the modules, and the current break during switching requires protective snubber circuits to suppress switching emissions [1]. One of the ways to improve PWM quality is the use of multilevel converters, in which one way or another, the separation of the supply voltage into several levels is achieved, which allows you to approximate the shape of the output voltage to a sinusoid and improve its harmonic composition [1, 2, 3]. For this, high-voltage capacitors of large capacity are used, which leads to a deterioration in the dimensions of the converter and a decrease in its reliability. Increasing the switching frequency of semiconductor switches leads to a deterioration in electromagnetic compatibility.

Thus, the main technical problem of modern marine converting technology can be recognized as the process of switching current, and as a consequence of it - the presence of switching surges and a low degree of sinusoidal shape of the output voltage.

As a rule, in the static converters used on ships for rowing installations, transformers are mainly used for matching the supply voltage with the voltage at the converter output [2]. In powerful static frequency converters, most often, a DC link is used, obtained by rectifying an alternating voltage of the network, and a power transformer is used for galvanic isolation and voltage matching.

There is also a class of converters of alternating voltage of one frequency to alternating voltage of another frequency [1, 2]. Such frequency conversion devices without an intermediate DC link are called direct-coupled converters (direct frequency converters, or NPFs).

The basis of any LFN is a reversible switch (three-phase bridge) connected to an AC voltage source and load [1, 2]. A three-phase electric drive with direct frequency conversion is shown in figure 1, and is formed by connecting the outputs of three reversible bridges (which are known from the prior art and are described in detail in the educational literature on converter technology). Shown in figure 1, the drive circuit with the converter LPC has a large number of semiconductor switches, and increased cost due to the need to use power transformers for galvanic isolation of each phase.

Direct conversion can be described as the case of piecewise sinusoidal modulation of the output voltage, since the output voltage is formed from fragments of a sinusoid with a frequency of the supply network [4, 5]. Moreover, at the output of the converter, it is possible at any time to obtain fragments of both a decreasing and increasing front of the sinusoid, which is explained by a symmetrical shift in voltage between the phases of the supply network.

There are several algorithms for generating the output voltage of the NPF, shown in figure 2 and figure 3. The option shown in figure 2 has large harmonic distortion, and is used mainly in converters with thyristors. The figure 3 shows the formation of the output voltage, consisting of similar fragments of the supply voltage, so that the ascending front consists of ascending fragments, and the descending front of the descending fragments. This provides the best quality output voltage.

The prior art method of frequency conversion [6], so that the output voltage is formed from the sum of the inverse fragments of the two voltage channels, resulting in a smoothed sinusoidal function, as shown in figure 4. This option is characterized by the best approximation of the shape of the output voltage of the Converter to a sinusoidal , and allows you to implement natural switching current. The implementation of the algorithm is possible using semiconductor switches with fully controllable keys (for example, IGBT transistors).

As a result of summing the voltages of two series-connected reversible bridges, a smooth output function is formed without gaps, and the switching of the valves occurs at the moments of equality of the EMF, which corresponds to natural switching without breaking the current curve.

Such a conversion requires a large number of semiconductor switches, as shown in Figure 5. Figure 6 shows a circuit diagram of one phase of a two-channel direct frequency converter [8]. To supply a three-phase output load in such a circuit, a switch with 72 semiconductor switches is required. A similar two-channel direct frequency conversion is described in [6].

To obtain a three-phase output voltage, three pairs of serially connected reversible three-phase bridges are used, each bridge receiving power from a separate three-phase secondary winding of the power transformer, each phase of the output voltage is obtained by connecting two bridges in series - as shown in figure 6. The sets of reversing bridges are connected according to the scheme "star", forming a three-phase system of voltages.

The disadvantage is considerable bulkiness, obviously a large number of semiconductor switches, and the use of high-power power transformers, which increases the cost of the system. For implementation, 144 semiconductor switches (IGBTs) are required in the case of a six-phase electric motor. Such a system is technically feasible, but is cumbersome.

In the electromotor system selected for the main prototype [7], a semiconductor switch is used, shown in figure 7. As can be seen from the circuit diagram, such a semiconductor switch allows you to convert a three-phase input voltage to a three-phase output voltage. The advantage of such an electromotive system is in reducing the number of semiconductor switches (IGBTs).

The figure 8 shows a diagram of an electric propulsion system selected for the main prototype. Here, the electric propulsion system is powered by the generator windings, and semiconductor switches are combined with it. In this case, the converter and the ship's electric power source (generator) form an inextricably linked electric propulsion system, with integrated direct frequency conversion.

The main advantage of the main prototype is the reduction in the number of semiconductor switches, which by switching the switches and windings in series is reduced to 36 IGBT transistors for the case of a three-phase electric motor.

The decrease in the number of semiconductor switches is due to the following. In the previously known solution [8], three-phase reversible switches (bridges) were used, each of which forms a single-phase voltage. The voltages of the switches included in series are summed, forming the output voltage of one phase. Obtaining a three-phase system in this case requires the inclusion of three pairs of switches according to the star scheme. This is the reason for such a large number of keys (72 transistors for a three-phase output and 144 transistors for a six-phase output).

In the solution depicted in FIG. 8, the switching of the voltage of the phase windings is performed, which eliminates the intermediate conversion into a single-phase voltage. The figure 9 shows a functional diagram of an electric propulsion system with such a switch. Here, the ship's source (generator) has two three-phase windings, the first of which closes to a common point by the beginning of its phase windings, and connects to the input of the first reversing semiconductor switch with the ends of the mentioned windings. The second three-phase winding is open without a common point, the beginning of its phase windings are connected to the output of the first reversing semiconductor switch, and the ends of the phase windings are connected to the input of the second reversing switch. The output of the second reversing switch is connected to an AC motor.

This solution is the main prototype. A twofold reduction in the number of semiconductor switches is a significant advantage; at the same time, the task of reducing weight and dimensions is solved, and as a result, the cost of the entire installation, as well as improving reliability.

The disadvantages include the presence of an open three-phase winding, the use of which to power the ship's AC network is impossible. Another disadvantage is the need for two conversion channels to power a six-phase electric motor.

The listed drawbacks are deprived of the electric motor system depicted in figure 10, which makes it possible to power a six-phase electric motor when using only two semiconductor switches. The proposed solution uses the connection of two three-phase windings on the generator into a common neutral for them, which allows you to implement a symmetrical conversion circuit to power a six-phase motor.

The summation of the outputs of the semiconductor switches in this case occurs on the multiphase winding of the motor, all six phases of which are connected by a common neutral.

The neutrals of the generator and engine shown in figure 10 of the electric system can be combined through a circuit breaker. In this case, it is possible to continue the movement of the vessel while feeding the three phases of the electric motor in the single-channel conversion mode, which will be accompanied by a decrease in the allowable power.

The figure 11 shows a functional diagram of the electric power system of the vessel with the inventive multiphase electric propulsion system. Due to the symmetry of the three-phase generator windings, it is possible to power the main switchboards from any of the mentioned windings.

The inventive utility model is a new solution having the following fundamental differences from the prototype.

- the possibility of backup is provided, in the event of a failure of the semiconductor switch or the control system of one of the channels for converting the neutral frequency of the generator and the engine are combined;

- the electric propulsion system is integrated with the ship’s source of electricity (generator), while in contrast to the prototype, both three-phase windings of the source are connected to a star with a neutral and can be used to power ship consumers;

- A six-phase motor is used, and six connecting lines between the motor and the switches.

Thus, the set of essential features of the solution leads to a new technical result - improving the reliability of the work due to redundancy, increasing the efficiency of using electrical equipment of the electric power system, due to the possibility of supplying ship consumers from the generator windings.

A brief description of the drawings.

The figure 1 shows a schematic diagram of an electric drive with direct frequency conversion. Here 1 is an electric motor, 2 is a semiconductor switch, 5 is a three-phase power transformer.

The figure 2 shows a graph of the output voltage of the direct frequency conversion according to the algorithm with reverse edges.

The figure 3 shows a graph of the output voltage of the direct frequency conversion according to the algorithm with straight edges.

The figure 4 shows a graph of the output voltage of a two-channel direct frequency conversion with summing the voltage of the algorithms with forward and reverse edges.

The figure 5 shows a schematic diagram of an electric propulsion system with two-channel direct frequency conversion, input transformers and a three-phase propeller motor. Here 1 is an electric motor, 2 is a semiconductor switch, 5 is a three-phase power transformer.

The figure 6 shows a schematic diagram of one phase of a two-channel direct converter with transformers at the input. Here 2 is a semiconductor switch, 5 is a three-phase power transformer.

The figure 7 shows a schematic diagram of a three-phase reversible semiconductor switch.

Figure 8 shows a schematic diagram of an electric propulsion system with integrated dual-channel direct frequency conversion. Here 1 is an electric motor, 2 is a semiconductor switch, 4 is a three-phase winding of a generator.

The figure 9 shows a functional diagram of an electric propulsion system with integrated dual-channel direct frequency conversion. Here 1 is an electric motor, 2 is a semiconductor switch, 3 is a ship generator, 4 is a three-phase winding of the generator.

The figure 10 shows a schematic diagram of a multiphase ship electric propulsion system by two-channel direct frequency conversion. Here 1 is an electric motor, 2 is a semiconductor switch, 3 is a generator.

The figure 11 shows a functional diagram of a single electric power system of a vessel with a multiphase electric propulsion system. Here 1 is an electric motor, 2 is a semiconductor switch, 3 is a generator, 6 is a main switchboard.

List of used literature.

1. Zinoviev G.S. Power Electronics - M .: Yurayt, 2012.667 s.

2. Dmitriev B.F., Ryabenky V.M., Cherevko A.I., Music M.M. Marine semiconductor converters: a textbook. - Arkhangelsk: Publishing House of NArFU, 2015 .-- 556 p.

3. Novikov G.V. Frequency control of induction motors. - M.: Publishing House of MSTU. N.E. Bauman, 2016 .-- 498 p.

4. Proshin I.A. Asynchronous electric drive with a low-fan direct frequency converter // dissertation. - Penza: Publishing House of the Penza Polytechnic Institute, 1983. - 274 p.

5. Proshin I.A. Management in systems with direct converters of electric energy // thesis. - Penza: Publishing House of Penza State University, 2003. - 432 p.

6. Evseev R.I., Ivlev M.L., Koptyaev E.N., Khomyak V.A., Cherevko A.I. The method of frequency conversion // RF patent for the invention No. 2639048

7. Koptyaev E.N., Popkov E.N. Ship electric propulsion system // RF patent for utility model No. 181202

8. Koptyaev E.N. Two-channel direct frequency converter // Electricity. 2018. No3. from. 33-37

Claims (1)

Rowing electric installation of a vessel, containing a voltage source with two three-phase windings, two three-phase reversing semiconductor switches connected in series with taps of three-phase windings, an alternating current electric propulsion motor, and characterized in that both of these three-phase windings are star-shaped and have a common neutral , the rowing electric motor is made with a six-phase winding according to the "star" scheme, the phases of which are connected to the outputs of the reversible semiconductor switches, and between y neutrals engine and three-phase windings of the voltage source is installed jumper, equipped with a circuit breaker.

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