CN105048509B - Station service electrical system equipped with DC frequency-changing device and DC frequency-changing motor - Google Patents

Abstract

The invention relates to a plant power system provided with a DC frequency converter and a DC frequency conversion motor. Specifically, the system includes an off-site AC power grid, an in-plant AC power grid, an in-plant DC power grid, an alternator or an alternator set, an AC transformer, an AC/DC converter or transformer, a DC frequency converter and a DC frequency conversion motor. Adopting the system can effectively realize the variable-speed operation of power plant equipment, and at the same time can significantly reduce the energy loss of the generating set, improve the overall efficiency of the generating set, simplify the generating set, and have the characteristics of controllable cost.

Description

Factory power system with DC frequency converter and DC variable frequency motor

technical field

The invention relates to power plant equipment, in particular to a plant power system provided with a DC frequency converter and a DC frequency conversion motor.

Background technique

In a large-capacity power plant, according to the change of the operating conditions of the unit, the electric pumps, fans or compressors in the power plant generally need to be operated at variable speeds to achieve the purpose of saving energy and improving economy. The existing plant power system realizes the variable speed operation of the equipment through the combination of AC frequency converter and AC variable frequency motor. Among them, the working principle of the AC drive is to convert the power frequency AC into DC first, and then convert the DC into variable frequency AC. This conversion process leads to a large energy loss in the AC drive, and the frequency conversion efficiency is only about 90%, which greatly improves the efficiency of the AC drive. Reduced system efficiency and power plant economics. In addition, due to the different speeds of power plant equipment, AC drives and equipment motors are usually configured one-to-one, and multiple sets of equipment need to be equipped with multiple AC drives, which makes the electrical system complex and cumbersome, and the corresponding investment cost and operation and maintenance The cost will also increase accordingly, and the reliability of the system operation will decrease, and the more the number of AC drives, the more energy loss will be brought, and the more serious the negative impact on the economics of the power plant will be. Therefore, it is necessary to reduce the number of AC drives used as much as possible to reduce the energy loss caused by the introduction of AC drives, to ensure the economy of the unit during variable load operation, and to simplify the electrical system and improve the reliability of the system. sex.

Specifically, Figure 1-2 is a schematic diagram of a system in the prior art that uses a combination of an AC frequency converter and an AC variable frequency motor to regulate the speed of equipment that requires variable speed operation in the plant power system, where the plant power system shown in Figure 1 In the system, the AC power generated by the generator set passes through the AC transformer, and part of it is sent to the AC grid outside the plant for external power supply, and the other part is directly connected to the AC grid inside the plant to provide power for the plant. For AC power frequency motors with larger power, the AC power in the factory can be directly used. However, for AC variable frequency motors, AC frequency converters are required to convert the AC power frequency in the factory into AC variable frequency power, and each equipment motor needs to be equipped with a set of AC frequency converters. Correspondingly, the investment cost of the AC drive is relatively high, and the electrical system is relatively complicated. At the same time, the connection of the AC drive will cause system energy loss and efficiency decline, which will have a negative impact on the economics of the power plant.

When some equipment in the power plant needs to operate at a lower voltage level, in order to meet the needs of some low-voltage operating equipment, an AC transformer is used to convert the high-voltage in-plant AC into low-voltage in-plant AC, as shown in Figure 2. The medium and low-voltage AC power grid in the factory in Figure 2 can directly supply power to AC power frequency motors, and can also drive AC variable frequency motors after frequency conversion by AC converters. Similar to Figure 1, in Figure 2, whether it is a high-voltage or low-voltage AC grid, when supplying power to an AC variable frequency motor, one-to-one configuration of AC inverters is required, which will cause energy loss during the power supply process and affect system efficiency. Moreover, the access of the AC frequency converter makes the electrical system complex and cumbersome, reduces the operation reliability, and greatly increases the investment and maintenance costs.

In order to reduce the number of AC frequency converters that need to be configured and simplify the electrical system, some power plants use variable-speed small steam turbines to drive generators to generate electricity, and uniformly use the variable-frequency AC power generated by variable-speed small machines to drive the motors of various equipment. However, since the speed adjustment of the small steam turbine is realized by throttling the inlet steam valve, the throttling adjustment must have throttling loss, which reduces the overall efficiency. In addition, although this factory power system can simplify the electrical system, under the same load condition, all equipment motors share the same power supply frequency, which means that it is impossible for all motors to run at the highest efficiency, and there must be some The operating efficiency of the electric motor is low, which reduces the overall efficiency of the plant power system. Therefore, the existing plant power system has key technical problems such as energy loss, low efficiency, complex electrical system, and high investment cost of frequency converters.

To sum up, there is an urgent need in this field to develop a new type of system that can reduce energy loss, improve efficiency, simplify the electrical system, and control the cost to realize variable speed operation of power plant equipment.

Contents of the invention

The purpose of the present invention is to provide a novel system capable of reducing energy loss, improving efficiency, simplifying the electrical system, and controlling the cost, which can realize variable-speed operation of power plant equipment.

The first aspect of the present invention provides a plant power system equipped with a DC frequency converter and a DC variable frequency motor, the system includes an external AC power grid, an in-plant AC power grid, an in-plant DC power grid and an alternator or an AC Generating sets, AC transformers, AC/DC converters or transformers, DC frequency converters and DC variable frequency motors, of which,

The alternator or alternator set is connected to the AC transformer, and the AC transformer transforms the AC power frequency output from the alternator or the alternator set and then transmits it to the off-site AC grid and The AC grid in the plant;

The AC/DC converter or transformer is connected to the AC grid in the plant, and the AC/DC converter or transformer converts the AC power frequency input from the AC grid in the plant into DC power and then inputs it into the plant DC grid;

The DC frequency converter is connected to the DC power grid in the plant, and the DC frequency converter converts the DC power input by the DC power grid in the plant into DC variable frequency power;

The DC frequency conversion motor is connected to the DC frequency converter, and the DC frequency conversion motor drives the DC frequency conversion motor.

In another preferred example, the AC transformer is three-phase or two-phase.

In another preferred example, one AC/DC converter or transformer is configured with one DC frequency converter, and one DC frequency converter can be configured with one or more DC variable frequency motors at the same time.

In another preferred example, the number of DC variable frequency motors configured in the system is 1-15, preferably 1-10, more preferably 1-8, most preferably 1-5 .

In another preferred example, the system further includes a direct current generator connected to the in-plant direct current grid for outputting direct current.

In another preferred example, the DC generators are shared.

In another preferred example, the "shared" means that the direct current output by the direct current generator is input into the in-plant DC grid for use by all equipment connected to the in-plant DC grid.

In another preferred example, the number of the DC generators is 1-15, preferably 1-10, more preferably 1-8, most preferably 1-5.

In another preferred example, a switch A is provided between the AC/DC converter or transformer and the DC grid in the plant; and/or

A switch B is provided between the direct current generator and the in-plant direct current grid.

In another preferred example, when the switch A is in the open state and the switch B is in the closed state, the DC power output by the DC generator is input into the DC power grid in the plant and then converted into DC variable frequency power by the DC converter to Drive the DC variable frequency motor.

In another preferred example, when both switch A and switch B are in the closed state, the DC power output by the DC generator is input into the DC power grid in the plant and then converted into DC variable frequency power by the DC converter to drive the The DC frequency conversion motor and/or the AC/DC converter or the transformer converts the AC power into the AC power grid in the plant.

In another preferred example, the system further includes an AC power frequency motor, and the AC power frequency motor is connected to the in-plant AC power grid.

In another preferred example, the number of AC power frequency motors is 1-15, preferably 1-10, more preferably 1-8, most preferably 1-5.

In another preferred example, the in-plant AC grid includes a high-voltage segment grid of the in-plant AC grid and a low-voltage segment grid of the in-plant AC grid; and/or

The in-plant DC power grid includes a high-voltage section of the in-plant DC power grid and a low-voltage section of the in-plant DC power grid.

In another preferred example, the power grid in the high-voltage section of the in-plant AC power grid and the power grid in the low-voltage section of the in-plant AC power grid are connected via an AC transformer.

In another preferred example, the AC transformer converts the high-voltage AC power-frequency power of the high-voltage section of the in-plant AC power grid into low-voltage AC power-frequency power before inputting it into the low-voltage section of the in-plant AC power grid.

In another preferred example, the AC/DC converter or transformer is connected to the low-voltage section grid of the in-plant AC grid, and the AC/DC converter or transformer is connected to the low-voltage section grid of the in-plant AC grid. The low-voltage AC power frequency power is converted into low-voltage DC power and then input to the low-voltage section of the DC power grid in the factory.

In another preferred example, the DC inverter is connected to the low-voltage section of the DC power grid in the factory, and the DC inverter converts the low-voltage DC power input by the low-voltage section of the DC grid in the factory into low-voltage DC frequency conversion Electricity.

In another preferred example, the DC frequency conversion motor is connected to the DC frequency converter, and the DC frequency conversion motor is driven by the low voltage DC frequency conversion motor.

In another preferred example, the system further includes an AC power frequency motor connected to the low-voltage section of the AC grid in the plant.

In another preferred example, the system further includes an AC frequency converter and an AC variable frequency motor, wherein,

The AC frequency converter is connected to the AC power grid in the plant, and the AC frequency converter converts the AC power frequency input from the AC power grid in the plant into AC variable frequency power;

The AC frequency conversion motor is connected to the AC frequency converter, and the AC frequency conversion motor drives the AC frequency conversion motor.

In another preferred example, the AC frequency converter and the AC variable frequency motor are configured one-to-one.

In another preferred example, the number of the AC inverter and the AC variable frequency motor is the same, and the number is 1-15, preferably 1-10, more preferably 1-8 , optimally 1-5 units.

In another preferred example, the alternator set is a large-capacity generator set.

In another preferred example, the capacity of the alternator set is ≥300MW, preferably ≥600MW, more preferably ≥900MW, most preferably ≥1000MW.

The second aspect of the present invention provides a method for regulating the speed of the utility power system described in the first aspect of the present invention, using a DC frequency converter and a DC variable frequency motor for speed regulation.

It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described in the following (such as embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, we will not repeat them here.

Description of drawings

Fig. 1-2 is a schematic diagram of a system in the prior art that uses a combination of an AC frequency converter and an AC variable frequency motor to regulate the speed of equipment that requires variable speed operation in the plant power system.

Fig. 3 is a schematic diagram of a utility power system provided with a DC frequency converter and a DC frequency conversion motor in Embodiment 1 of the present invention.

Fig. 4 is a schematic diagram of a utility power system provided with a DC frequency converter and a DC frequency conversion motor in Embodiment 2 of the present invention.

Fig. 5 is a schematic diagram of a utility power system provided with a DC frequency converter and a DC frequency conversion motor in Embodiment 3 of the present invention.

Fig. 6 is a schematic diagram of a utility power system provided with a DC frequency converter and a DC frequency conversion motor in Embodiment 4 of the present invention.

Fig. 7 is a schematic diagram of a utility power system provided with a DC frequency converter and a DC frequency conversion motor in Embodiment 5 of the present invention.

Detailed ways

After long-term and in-depth research, the inventor unexpectedly found that the combination of DC frequency converter and DC frequency conversion motor can effectively realize the variable speed operation of the equipment, and at the same time, the power plant with DC frequency converter and DC frequency conversion motor can be used. The system can significantly reduce the energy loss of the generating set, improve the overall efficiency of the generating set, simplify the generating set, and have the characteristics of controllable cost. Based on the above findings, the inventors have accomplished the present invention.

the term

As used herein, the term "frequency conversion" refers to changing the frequency. Specifically, the technology of controlling the operating speed of rotating equipment by changing the power supply frequency is called frequency conversion technology. The core of frequency conversion technology is the frequency converter, which can realize the adjustment of the motor running speed by controlling the change of the power supply frequency. Frequency converters include DC drives and AC drives.

As used herein, the term "alternator" refers to a generator that generates electricity that is alternating current, usually at a fixed frequency of 50 Hz or 60 Hz.

As used herein, the term "AC transformer" refers to a device that steps up or down the voltage of alternating current.

As used herein, the terms "AC/DC converter or transformer", "AC/DC converter" and "inverter" are used interchangeably to refer to a device that converts alternating current to direct current, or converts direct current to alternating current For the equipment, the voltage before and after conversion can be increased, decreased or unchanged.

As used herein, the term "DC converter" refers to a device that takes in a direct current and outputs an alternating current of variable frequency.

As used herein, the term "DC variable frequency motor" refers to a motor with a variable rotational frequency associated with a DC frequency converter.

As used herein, the term "dynamo" refers to a generator that generates electricity that is direct current.

As used herein, the term "AC power frequency motor" refers to a motor with a constant input frequency of alternating current and a constant operating speed.

As used herein, the term "alternating current drive" refers to a device that inputs alternating current of constant frequency and outputs alternating current of variable frequency.

As used herein, the term "AC variable frequency motor" refers to a motor with variable rotational frequency associated with an AC frequency converter.

Plant power system

The invention provides a plant power system equipped with a DC frequency converter and a DC variable frequency motor, the system includes an AC power grid outside the plant, an AC power grid in the plant, a DC power grid in the plant, an AC generator or an AC generator set, and an AC transformer , AC/DC commutation or transformer, DC frequency converter and DC variable frequency motor, among which,

The alternator or alternator set is connected to the AC transformer, and the AC transformer transforms the AC power frequency output from the alternator or the alternator set and then transmits it to the off-site AC grid and The AC grid in the plant;

The AC/DC converter or transformer is connected to the AC grid in the plant, and the AC/DC converter or transformer converts the AC power frequency input from the AC grid in the plant into DC power and then inputs it into the plant DC grid;

The DC frequency converter is connected to the DC power grid in the plant, and the DC frequency converter converts the DC power input by the DC power grid in the plant into DC variable frequency power;

The DC frequency conversion motor is connected to the DC frequency converter, and the DC frequency conversion motor drives the DC frequency conversion motor.

In another preferred example, the AC transformer is three-phase or two-phase.

In the present invention, one AC/DC converter or transformer is configured with one DC frequency converter, and one DC frequency converter can be configured with one or more DC variable frequency motors at the same time.

In another preferred example, the number of DC variable frequency motors configured in the system is 1-15, preferably 1-10, more preferably 1-8, most preferably 1-5 .

In the present invention, the system further includes a direct current generator, and the direct current generator is connected to the in-plant direct current grid for outputting direct current.

In another preferred example, the DC generators are shared.

In another preferred example, the "shared" means that the direct current output by the direct current generator is input into the in-plant DC grid for use by all equipment connected to the in-plant DC grid.

In another preferred example, the number of the DC generators is 1-15, preferably 1-10, more preferably 1-8, most preferably 1-5.

In the present invention, a switch A is provided between the AC/DC converter or transformer and the in-plant DC grid; and/or

A switch B is provided between the direct current generator and the in-plant direct current grid.

In the present invention, when the switch A is in the open state and the switch B is in the closed state, the direct current output by the direct current generator is input into the direct current grid in the factory and then converted into direct current variable frequency power by the direct current converter to drive the The DC variable frequency motor.

In another preferred example, when both switch A and switch B are in the closed state, the DC power output by the DC generator is input into the DC power grid in the plant and then converted into DC variable frequency power by the DC converter to drive the The DC frequency conversion motor and/or the AC/DC converter or the transformer converts the AC power into the AC power grid in the plant.

In the present invention, the system further includes an AC power frequency motor, and the AC power frequency motor is connected to the AC grid in the plant.

In another preferred example, the number of AC power frequency motors is 1-15, preferably 1-10, more preferably 1-8, most preferably 1-5.

In the present invention, the in-plant AC power grid includes the high-voltage section power grid of the in-plant AC power grid and the low-voltage section power grid of the in-plant AC power grid; and/or

The in-plant DC power grid includes a high-voltage section of the in-plant DC power grid and a low-voltage section of the in-plant DC power grid.

In another preferred example, the power grid in the high-voltage section of the in-plant AC power grid and the power grid in the low-voltage section of the in-plant AC power grid are connected via an AC transformer.

In another preferred example, the AC transformer converts the high-voltage AC power-frequency power of the high-voltage section of the in-plant AC power grid into low-voltage AC power-frequency power before inputting it into the low-voltage section of the in-plant AC power grid.

In another preferred example, the AC/DC converter or transformer is connected to the low-voltage section grid of the in-plant AC grid, and the AC/DC converter or transformer is connected to the low-voltage section grid of the in-plant AC grid. The low-voltage AC power frequency power is converted into low-voltage DC power and then input to the low-voltage section of the DC power grid in the factory.

In another preferred example, the DC inverter is connected to the low-voltage section of the DC power grid in the factory, and the DC inverter converts the low-voltage DC power input by the low-voltage section of the DC grid in the factory into low-voltage DC frequency conversion Electricity.

In another preferred example, the DC frequency conversion motor is connected to the DC frequency converter, and the DC frequency conversion motor is driven by the low voltage DC frequency conversion motor.

In another preferred example, the system further includes an AC power frequency motor connected to the low-voltage section of the AC grid in the plant.

In the present invention, the system further includes an AC frequency converter and an AC variable frequency motor, wherein,

The AC frequency converter is connected to the AC power grid in the plant, and the AC frequency converter converts the AC power frequency input from the AC power grid in the plant into AC variable frequency power;

The AC frequency conversion motor is connected to the AC frequency converter, and the AC frequency conversion motor drives the AC frequency conversion motor.

In another preferred example, the AC frequency converter and the AC variable frequency motor are configured one-to-one.

In another preferred example, the number of the AC inverter and the AC variable frequency motor is the same, and the number is 1-15, preferably 1-10, more preferably 1-8 , optimally 1-5 units.

In the present invention, the alternator set is a large-capacity generator set.

In another preferred example, the capacity of the alternator set is ≥300MW, preferably ≥600MW, more preferably ≥900MW, most preferably ≥1000MW.

The utility power system mainly consists of the following parts:

1) AC generators, AC transformers, DC generators;

2) AC/DC converter or transformer, used to convert the AC power in the factory into DC power in the factory;

3) DC frequency converter, used to convert the DC power in the factory into DC frequency conversion power;

4) AC frequency converter, used to convert the AC power frequency in the factory into AC variable frequency power;

5) DC variable frequency motors, AC power frequency motors, and AC variable frequency motors for power plant equipment.

Usually, the working process of the AC drive is to convert the alternating current with a constant frequency into a direct current, and then convert the direct current into an alternating current with a variable frequency. The energy needs to be converted twice, and there are two energy losses; while the DC drive is once That is to convert direct current into variable frequency alternating current, there is only one energy loss, so using "DC inverter and DC variable frequency motor" instead of "AC inverter and AC variable frequency motor" can effectively save energy.

The utility power system of the present invention is equipped with DC frequency conversion motors for equipment such as electric pumps, fans or compressors that need to be operated at variable speeds, and is equipped with public converters, DC frequency converters and/or small steam turbines without throttling losses. The generator supplies power to each DC variable frequency motor, which can meet the variable speed operation requirements of each equipment. Compared with AC frequency conversion technology, this technology can not only reduce the energy loss in the process of frequency conversion, achieve the purpose of energy saving, but also increase the power sales income of the power plant, and the electrical system is relatively simple and reliable, and the investment cost and maintenance cost of electrical equipment are also lower. can be reduced. In addition, the small steam turbine has no throttling loss and has high overall efficiency, which makes the electrical system more efficient, which in turn can significantly reduce the final equipment investment cost.

method

The invention also provides a method for regulating the speed of the utility power system, using a DC frequency converter and a DC frequency conversion motor for speed regulation.

Compared with the prior art, the present invention has the following main advantages:

(1) It can efficiently realize variable speed operation of power plant equipment;

(2) It can significantly simplify the electrical system, reduce equipment maintenance costs, improve system operation reliability, and reduce investment costs;

(3) It can effectively avoid energy loss in the process of AC frequency conversion;

(4) There is no throttling loss, which can obviously improve the overall efficiency of the system;

(5) It has energy saving, environmental protection and high economic benefits.

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. For the experimental methods without specific conditions indicated in the following examples, usually follow the conventional conditions or the conditions suggested by the manufacturer. Percentages and parts are by weight unless otherwise indicated.

Unless otherwise defined, all professional and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. In addition, any methods and materials similar or equivalent to those described can be applied to the method of the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only.

Example 1

The electricity generated by the AC generator set is transformed by the AC transformer and then sent to the AC power grid outside the factory and inside the factory. The AC power grid in the factory supplies power to the motors of various equipment in the factory. Among them, the AC power frequency motor with higher power can directly use the power frequency AC power provided by the AC power grid in the factory. The DC variable frequency motor needs the help of AC/DC converter or transformer and DC frequency converter. First, the AC/DC converter converts the plant's AC power to the plant's DC power. Secondly, the DC frequency converter converts the DC power in the factory into DC frequency conversion power, which is used to drive the DC frequency conversion motor.

In this system, both the AC/DC converter and the DC frequency converter are public equipment, and multiple DC variable frequency motors can be connected at the same time, without the need for one-to-one separate configuration. Because of this, the entire electrical system can be greatly simplified, the investment cost of the frequency converter is reduced accordingly, and the operation reliability of the entire system is also improved, and the maintenance cost of the electrical system is relatively low. In addition, due to the relatively simplified electrical system, the energy loss caused by converters and frequency converters will be greatly reduced, so the system economy will be significantly higher than the power system of AC frequency conversion plants, which meets the energy-saving requirements of power plants and improves Proceeds from electricity sales of power plants.

Example 2

The basic principle of the solution shown in Figure 4 is the same as that of Figure 3, except that for equipment motors operating under low-voltage conditions, AC transformers are added as needed to provide low-voltage factory AC power. Low-voltage in-factory AC power can supply power to AC power-frequency motors, and can also be converted into low-voltage in-factory DC power through AC/DC converters, and then supplied to DC variable-frequency motors after frequency conversion by DC converters. Similar to Fig. 3, the converters and DC frequency converters on the high and low voltage sides in Fig. 4 are common, and can drive multiple DC variable frequency motors at the same time.

Compared with Figure 2, the electrical system shown in Figure 4 is significantly simplified, the system energy loss is also greatly reduced, and the power supply economy is significantly improved.

Example 3

The basic principle of the scheme shown in Figure 5 is the same as that of Figure 3. The difference is that the AC frequency conversion motor is still retained in Figure 5, and this part of the motor still uses the AC frequency conversion system, that is, the AC frequency conversion system in the factory is still converted by the AC frequency converter. The frequency power is converted into AC frequency conversion power, and the AC frequency conversion power is used to drive the AC frequency conversion motor.

This plant power system scheme integrates the AC frequency conversion plant power system and the DC frequency conversion plant power system, which provides energy-saving space for the existing AC frequency conversion plant power system. For the built AC variable frequency plant power system, it is possible to retain part of the AC variable frequency motor to reduce the cost of transformation, and to improve the efficiency and economy of the plant power system to meet the requirements of energy saving.

Example 4

The basic principle of the scheme shown in Fig. 6 is the same as that in Fig. 5, except that a DC generator is added in Fig. 6 . Part or all of the direct current can be provided by means of a direct current generator.

Compared with the technology of throttling and speed-regulating small steam turbines to drive variable frequency generators to provide variable frequency power, the small steam turbines of DC generators have no throttling loss and have higher overall efficiency.

Example 5

The basic principle of the scheme shown in Figure 7 is the same as that in Figure 6, except that the DC power generated by the DC generator in Figure 7 can not only be used for the DC grid in the plant, but also can be returned to the AC grid in the plant through the AC/DC converter .

The scheme in Figure 7 makes the power consumption rate of the plant lower and the electricity sales benefit more.

In general, the present invention aims at the technical problems of the existing utility power system, by configuring DC variable-frequency motors for equipment requiring variable-speed operation, and adding a public AC/DC converter and DC generator to provide DC power, and then Power is supplied to each DC variable frequency motor by means of a common DC frequency converter. This technical solution not only simplifies the electrical system, improves system reliability, and reduces the investment cost of electrical equipment, but more importantly, this solution avoids energy loss during AC frequency conversion. Compared with the technology of throttling and speed-regulating small steam turbines to drive variable frequency generators to provide variable frequency power, the small steam turbines of DC generators have no throttling loss and have higher overall efficiency. The invention has obvious energy-saving benefits, and has strong competitiveness in terms of improving the economic efficiency of power plants and the income from electricity sales.

Theoretical analysis shows that if a 1000MW ultra-supercritical generating set adopts the present invention, the annual electricity saving is about 30 million kwh, and the direct economic benefit reaches more than 12 million yuan.

All documents mentioned in this application are incorporated by reference in this application as if each were individually incorporated by reference. In addition, it should be understood that after reading the above teaching content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Reference signs:

1: Alternator

2: AC Transformer

3: AC/DC converter or transformer

4: DC inverter

5: DC variable frequency motor (multiple)

6: DC generator (multiple)

7: AC power frequency motor (multiple)

8: AC frequency converter (multiple units)

9: AC variable frequency motor (multiple)

Claims (7)

1. a kind of station service electrical system equipped with DC frequency-changing device and DC frequency-changing motor, which is characterized in that the system comprises AC network outside factory, AC network in factory, DC grid and alternating current generator or alternating current generating sets in factory, AC transformer, Friendship/straight the change of current or transformer, DC frequency-changing device and DC frequency-changing motor, wherein

The alternating current generator or alternating current generating sets are connect with the AC transformer, and the AC transformer is by the friendship AC network and described is delivered to outside the factory after stream generator or the AC power frequency electricity transformation of alternating current generating sets output respectively AC network in factory；

The friendship/straight change of current or transformer are connect with AC network in the factory, and the friendship/straight change of current or transformer will be described The AC power frequency electricity that AC network inputs in factory inputs DC grid in the factory after being converted to direct current；

The DC frequency-changing device is connect with DC grid in the factory, and the DC frequency-changing device is defeated by DC grid in the factory The direct current entered is converted to DC frequency-changing electricity；

The DC frequency-changing motor is connect with the DC frequency-changing device, and DC frequency-changing electricity described in the DC frequency-changing electric drive Motivation；

Also, the system also includes dc generator, the dc generator is connect with DC grid in the factory, for defeated Go out direct current；

In the friendship/straight change of current or transformer and the factory switch A is equipped between DC grid；And/or

Switch B is equipped in the dc generator and the factory between DC grid；

When switch A be off and switch B in the closure state, the DC supply input institute of dc generator output It states in factory and is converted to DC frequency-changing electricity through the DC frequency-changing device to drive the DC frequency-changing motor after DC grid.

2. the system as claimed in claim 1, which is characterized in that described in a friendship/straight change of current or transformer configuration one DC frequency-changing device, and a DC frequency-changing device can configure one or more DC frequency-changing motor simultaneously.

3. the system as claimed in claim 1, which is characterized in that the system also includes AC power frequency motor, and the friendship Stream power frequency motor is connect with AC network in the factory.

4. the system as claimed in claim 1, which is characterized in that AC network includes AC network high pressure section in factory in the factory AC network low pressure stage power grid in power grid and factory；And/or

DC grid includes DC grid low pressure stage power grid in DC grid high pressure section power grid and factory in factory in the factory.

5. the system as claimed in claim 1, which is characterized in that the system also includes AC converter and AC frequency conversion are electronic Machine, wherein

The AC converter is connect with AC network in the factory, and the AC converter is defeated by AC network in the factory The AC power frequency electricity entered is converted to alternating-current variable frequency power；

The ac variable-frequency electric motor is connect with the AC converter, and alternating-current variable frequency power described in the AC frequency conversion electric drive Motivation.

6. the system as claimed in claim 1, which is characterized in that the alternating current generating sets are heavy-duty generator groups.

7. a kind of method carrying out speed governing to station service electrical system described in claim 1, which is characterized in that using DC frequency-changing device and DC frequency-changing motor carries out speed governing.