CN110401194A - A gas-steam combined cycle distributed energy three-power fast switching system and method - Google Patents

Abstract

The present invention discloses a kind of fast cutting system of three power supply of Combined cycle gas-steam turbine distributed energy and method; including three units; every unit is respectively arranged with a high-voltage auxiliary bus and for providing the working power inlet wire of work incoming power; working power inlet wire is connected to main transformer low-pressure side through current-limiting reactor, and current-limiting reactor both ends are parallel with high speed current-limiting protection switch；It is connected respectively by different backup power source incoming switches between the high-voltage auxiliary bus of any two units, the connection between the high-voltage auxiliary bus between unit is controlled by the on-off of backup power source incoming switch；Make full use of Combined cycle gas-steam turbine distributed energy station-service electric load in interim distribution, the feature that unit number is more, capacity is small, working power is derived from main transformer low-pressure side, double spare power supply is derived from adjacent unit high-voltage auxiliary bus, it solves existing station service and cuts the problems such as investment in allocation plan is more, and land occupation is wide and generator rotor angle is big fastly.

Description

A gas-steam combined cycle distributed energy three-power fast switching system and method

technical field

The invention belongs to the electrical design field of a gas-steam combined cycle distributed energy power station, and specifically relates to a gas-steam combined cycle distributed energy three-power fast switching system and method.

Background technique

The "Code for Design of Large and Medium-Sized Thermal Power Plants" stipulates that for loads that will directly affect the safety of people or important equipment due to power failure, an automatic backup power supply must be installed. In the design of the conventional factory power fast switching system, the working power is usually taken from the high-voltage factory transformer of the unit, and the backup power is taken from the separately set start-up backup transformer. Toggle between switches. There are three switching methods: normal switching, abnormal switching and accident switching. This set of fast cut-off system requires a separate high-voltage plant transformer, start-up backup transformer and closed busbar. This kind of system occupies a large area; the investment is large; the power angle of the working power supply and the backup power supply is large, and the normal switching can only be selected in series switching mode; the backup power supply is an external power supply, and the cost is relatively high. The gas-steam combined cycle cooling, heating and power trigeneration system is a distributed energy system based on the concept of energy cascade utilization, which integrates refrigeration, heating (heating and hot water supply) and power generation. It has a small unit capacity , small footprint, large number of units, flexible layout, high efficiency, etc., is the main form of realization of distributed energy in my country. However, the traditional way of realizing fast switching system of plant power cannot meet the needs of distributed energy power plants.

Contents of the invention

In order to solve the problems existing in the prior art, the object of the present invention is to provide a gas-steam combined cycle distributed energy three-power fast switching system and method, which fully utilizes the staged distribution of the power load of the gas-steam combined cycle distributed energy plant , The number of units is large and the capacity is small. The working power supply is taken from the low-voltage side of the main transformer, and the dual backup power supply is taken from the high-voltage plant busbar of the adjacent units. Problems such as large power angle.

In order to achieve the above object, the technical solution adopted by the present invention is: a gas-steam combined cycle distributed energy three-power fast switching system, which is characterized in that it includes three units, and each unit is respectively equipped with a high-voltage plant busbar and for Provide the working power incoming line of the working incoming power supply, the working power incoming line is connected to the low-voltage side of the main transformer through the current-limiting reactor, and the high-speed current-limiting protection switch is connected in parallel at both ends of the current-limiting reactor; the high-voltage factory bus of any two units They are respectively connected through the incoming line switch of the standby power supply, and the connection between the high-voltage plant buses between the units is controlled by the on-off of the incoming line switch of the standby power supply; when the working incoming line switch of a certain unit is in the closing state, One of the backup power inlet switches between the high-voltage service busbar and the high-voltage factory-use busbars of the other two units is in the position, and the backup power inlet switch connected between the other two units is in the position.

When the system is running normally, the high-speed current-limiting protection switch is in the closed state, and the current-limiting reactor has no current passing through, which is realized as no loss, no voltage drop, and no leakage magnetic field; when a short-circuit fault occurs in the system, the high-speed current-limiting protection switch Quickly disconnect and put in a current-limiting reactor to achieve the effect of limiting short-circuit current.

Further, when the working incoming line switch of a certain unit is in the closing state, one of the backup power incoming line switches between its high-voltage service busbar and the high-voltage service busbars of the other two units is in position.

Further, each unit is provided with a fast switching device. Among the three units, for the high-voltage factory bus of a certain unit, the high-voltage factory bus of the other two units is used as a backup power supply, and the quick-cut device realizes two Setting of a backup power priority.

Further, the low-voltage side of the main transformer is connected to the incoming line of the working power by pouring bus bars, and the incoming line of the standby power is connected by cables. The working power and the standby power come from the same substation and use the same wiring method.

Further, the high-voltage side of the current-limiting reactor is provided with an isolating switch for maintenance isolation, and the standby power incoming switch connected between the high-voltage factory busbars of any two units is also connected in series with an isolating knife switch.

The present invention also provides a gas-steam combined cycle distributed energy three-power fast switching method, including the following steps:

Step 1) Combining the start-up curve of the gas turbine and the output of the auxiliary system at different stages, the distribution of utility loads at different stages is comprehensively analyzed, including the distribution of utility loads of the gas-steam combined cycle unit at the high plate and the load stage of the unit ; Make full use of the characteristics that the plant load of the gas-steam combined cycle unit is distributed in stages, select the capacity of the working incoming line switch and the standby incoming line switch, and enter step 2 after determination;

Step 2) Set the voltage of the high-voltage power plant to be the same as the generator voltage and the voltage on the low-voltage side of the main transformer, and enter step 3) after confirmation;

Step 3) Install a reactor between the low-voltage side of the main transformer and the working incoming line, and proceed to step 4) after confirmation;

Step 4) Set up a dual backup power switching device between the electronic equipment, and set up a locking logic in the quick-cut closing circuit of the power inlet switch to prevent the same high-voltage factory power from the same unit from running on three units at the same time. After confirming, go to step 5) ;

Step 5) The dual backup power quick switching device selects the priority of the backup power, realizes the two-way switching between the working power and the first backup power or the two-way switching between the working power and the second backup power, and improves the secondary circuit of the quick switching system.

Further, the total plant load of each unit is counted to confirm the capacity of the working incoming line switch; the maximum plant load under different operating conditions is calculated to determine the capacity of the standby incoming line switch.

Further, the total factory load of each unit in step 1) is the sum of the capacity of all high-voltage motors and low-voltage factory transformers; the switching capacity of the working incoming line is based on the requirements of factory loads at different stages and there is a margin of not less than 10%. quantity.

Further, in step 2), the incoming power supply for medium and high voltage substation power is taken from the low voltage side of the main transformer, and the dual backup power supply is taken from the high voltage substation busbar of adjacent units.

Further, in step 3), calculate the short-circuit current at the low-voltage side of the main transformer through the system capacity, system impedance and impedance of the main transformer, use the node method to calculate the short-circuit current at the low-voltage side of the main transformer, and determine the current-limiting reactance according to the short-circuit current at the low-voltage side of the main transformer capacity of the device.

The plant power fast switching device mentioned in the present invention is used to realize the fast switching of plant power. The fast switching device is used to judge the current operating state, and performs different fast switching operations according to different commands. The simulation of the fast switching device collection Measure the voltage of the working power supply, the incoming line of the standby power supply and the busbar, the switching status of the incoming line switch of the working line and the incoming line switch of the standby power supply, the current of the incoming line of the working power supply line and the incoming line of the standby power supply, which are used to judge the operating state of the plant power system ; It is used to execute the instruction circuit of the opening and closing operation of the working incoming line switch and the standby incoming line switch. The large-capacity high-speed switch FSR is called a high-speed current-limiting protection switch. Breaking, large-capacity high-speed switch has the characteristics of short breaking time, strong breaking capacity, and low price.

Compared with the prior art, the present invention has the following beneficial technical effects: the working incoming line switch set according to the normal load has a larger margin, which can satisfy the simultaneous full-load operation of two sets of units, and does not need to set a high factory transformer and start-up It also eliminates the problem of where the power source of the start-up substation comes from, and only adds reactors and large-capacity switches, which not only reduces equipment investment, but also saves floor space.

Furthermore, all the power used by the plant comes from self-generated electricity, which saves the price difference between purchased electricity and self-produced electricity.

Furthermore, the working power supply and the standby power supply come from the same substation, and the problem of large power angles between the working power supply and the standby power supply is solved due to the same wiring method.

Furthermore, this system adopts the fast switching mode of the factory power with dual backup power supplies, and has set up a special locking logic, which has high reliability and flexible operation.

Description of drawings

Fig. 1 is the schematic diagram of the plant power fast cut-off system containing starting and standby transformer in the prior art;

Figure 2 is the plant load distribution diagram of the gas-steam combined cycle distributed energy unit under different states;

Fig. 3 is a schematic diagram of the three-power fast switching system of the present invention;

Fig. 4 is a logical diagram of switching and locking of the three-power fast switching system of the present invention;

Fig. 5 is a flow chart of the three-power fast switching system and method of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

As shown in Figure 1, in the traditional system of fast power cut-off for factory power, it is necessary to set up a special high-voltage factory transformer to provide working incoming power, and set up a special start-up and standby transformer to provide start-up backup power. Become a booster station or take it from a dedicated line. Gas-steam combined cycle distributed energy projects usually have centralized equipment layout, a large number of units, and a small footprint; for gas-steam combined cycle distributed energy projects, the traditional factory power fast switching system has the following shortcomings: the fast switching system needs to be set up separately For high-voltage plant transformers, start-up and backup transformers, and closed busbars, the system occupies a large area and requires a large investment, regardless of whether the start-up and backup transformer power is taken from the booster station of the factory or a separate line. The power angle of the two power sources is large, and the normal switching can only be selected in series switching mode. During the switching process of plant power, there is a short-term power failure, which is not conducive to the stable operation of the unit; the backup power supply is an external power supply, which is expensive; and the starting and standby transformer power supply is purchased Electricity costs more.

As shown in Figure 2, the plant load of a typical gas-steam combined cycle distributed energy project is distributed in stages; the first load peak occurs during the ignition of the high plate, at about 60% speed; the other load peak occurs in parallel During the full load operation of the after-grid unit; the load peak is the largest during the ignition of the high plate. According to the design specification "Code for Design of Large and Medium-sized Thermal Power Plants" GB 50660-2011, the switch capacity of the working incoming line is designed considering the requirements of all plant loads and leaving a margin of more than 10%, so the capacity of the switch can simultaneously meet The factory load of the two units.

As shown in Figure 3, it is an embodiment of the present invention. The working incoming line switch is installed on the working power incoming line and connected between the high-voltage plant busbar and the current-limiting reactor. In this embodiment:

For Unit 1’s plant power quick-cut system: switch 9101 is the working incoming line switch, 9100 is the standby power supply first incoming line switch, and 9300 is the standby power secondary incoming line switch;

For the quick cut-off system of plant power of unit 2: switch 9201 is the working incoming line switch, 9200 is the standby power supply first incoming line switch, and 9100 is the standby power secondary incoming line switch;

For No. 3 unit plant power quick cut system: switch 9301 is the working incoming line switch, 9300 is the standby power supply first incoming line switch, 9200 is the standby power supply second incoming line switch;

Among them, 9100G, 9200G and 9300G are all isolation switches; 9101G, 9201G and 9301G isolation switches.

Gas-steam combined cycle distributed energy three-power fast switching system, the voltage level of the high-voltage utility power is the same as the generator outlet voltage and the voltage of the low-voltage side of the main transformer, the working power of the high-voltage utility power is taken from the low-voltage side of the main transformer, and the dual backup power is taken from the phase For the high-voltage service bus of the adjacent unit, a reactor is installed between the low-voltage side of the main transformer and the incoming line of the working power to limit the short-circuit current.

As shown in Figure 4, when the same unit is connected to the substation power of three units at the same time, the working incoming line switch and the standby incoming line switch are easily overloaded. In addition, too many substation load connections are not conducive to the stable operation of the unit; therefore, setting The blocking logic prevents the utility power of a certain unit from carrying the utility load of three generating units at the same time. In this embodiment, the blocking logic is realized by DCS or hard wiring, as shown in Figure 4. The blocking logic, the first The set of quick switching system is composed of quick switching device, 9101 switch, 9100 switch and 9300 switch. There is no switching relationship between 9300 switches; the switching locking logic takes the first set as an example:

The closing conditions of the 9101 switch are: when the 9100 switch is opened and the 9300 switch is closed; the 9300 switch is opened and the 9100 switch is closed; the 9100 switch and the 9300 switch are both open. When the switches 9300 and 9300 are both closed, the quick-cut device closes the 9101 switch, causing the high-voltage service system of the first unit to run with the service power of the three units at the same time.

The closing condition of the 9100 switch is: both the 9200 and 9300 switches are in the open state, because if any one of the 9200 switch and the 9300 switch is in the closed position, after the 9100 switch is closed, it becomes the high-voltage factory-use system of the first unit Simultaneously with three units of factory power operation.

The closing conditions of the 9300 switch are as follows: both the 9100 and 9200 switches are in the open state, because if any one of the 9100 switch and the 9200 switch is in the closed position, after the 9300 switch is closed, it becomes the high-voltage plant of the first set of units. Use the system to operate with the factory power of three units at the same time.

In addition, the closing locking logic of the switch 9201 and the switch 9301 refers to the closing locking logic of the switch 9101.

The invention makes full use of the characteristics of small unit capacity, low voltage, large number of units and staged distribution of plant load in the gas-steam combined cycle distributed energy project. The working power supply and the backup power supply are respectively taken from the low-voltage side of the main transformer and the busbar of the adjacent unit, and there is no need to set up the start-up and backup transformers and the high-power plant transformer.

Specifically, as shown in Figure 5, a gas-steam combined cycle distributed energy three-power fast switching system and method, the implementation includes the following steps:

Step 1: Calculate the total plant load of each unit (the sum of the capacity of all high-voltage motors and low-voltage plant transformers), which is used to confirm the capacity of the working incoming line switch, and comprehensively analyze the output of the gas turbine start-up curve and auxiliary system at different stages Calculate the maximum plant load under different operating conditions to determine the capacity of the standby incoming line switch. As shown in Figure 2, the calculation and actual measurement of multiple gas-steam combined cycle power plants show that the highest load occurs during the ignition of the unit's high plate. The high plate load is the maximum plant load of the unit before the high plate ignition of the SFC dragged gas turbine to the grid, mainly including the SFC system load, water system, oil system and partial load of the waste heat boiler. Work change, water system change and complex building change are estimated at 25% of capacity. The SFC transformer is estimated according to 90% of the capacity, and the excitation transformer is considered according to the output of 30%. During the ignition of the high plate, start two circulating water pumps to meet the requirements of circulating water.

Step 2: Select the same voltage level of the high-voltage power plant as the outlet of the generator. The high-voltage commercial working power is taken from the low-voltage side of the main transformer, and the high-voltage commercial standby power supply 1 and power supply 2 are taken from the high-voltage commercial busbars of adjacent units. The low-voltage side of the main transformer is connected to the incoming line of the working power by pouring bus bars, the incoming line of the standby power is connected by cables, and an isolating switch is set for maintenance and isolation.

Step 3: Calculate the short-circuit current of the low-voltage side of the main transformer through the system capacity, system impedance and main transformer impedance, and determine the capacity of the reactor according to this current, and the reactor is used to limit the short-circuit current.

Step 4: For safety reasons, it is not allowed for the factory power supply of the three sets of units to be taken from the same busbar, so a special locking logic is designed, which can be realized by DCS or hard wiring.

Step 5: The fast switching device adopts the fast switching device with dual backup power supply. The device can select the priority of the backup power supply remotely or locally. There is no switching relationship between power supplies. Improve the secondary circuit of the quick-cut system.

In this embodiment, the distributed energy project uses three sets of one-to-one gas-steam combined cycle units to realize the combined supply of cooling, heating and electricity, which is a typical gas-steam combined cycle distributed energy project. Based on the consideration of economy and convenience, the factory area is 550 meters long and 80 meters wide, which puts forward new requirements for the design of the factory power quick cut system. The gas generator has a capacity of 51MW, a voltage of 10.5kV, and a GCB at the outlet of the generator. Based on the consideration of economy and practicability, the level of high-voltage factory power is set to 10.5kV, which is the same as the generator outlet voltage and the low-voltage side voltage of the main transformer. According to the factory load statistics table, the total factory load of a single unit is 11920kW, and the working incoming line switch is selected according to a 10% margin, and the capacity is 721A; according to the above principles, the maximum load is 7340kW, and according to the 10% margin Quantity selection interconnection switches 9100 and 9300 with a capacity of 444A.

As shown in Figure 3, the high-voltage commercial power supply is taken from the low-voltage side of the main transformer, and the high-voltage commercial standby power supply 1 and power supply 2 are taken from the high-voltage commercial busbars of adjacent units. The low-voltage side of the main transformer is connected to the incoming line of the working power by pouring bus bars, the incoming line of the standby power is connected by cables, and an isolating switch is set for maintenance and isolation.

A reactor is installed in parallel with a large-capacity switch between the low-voltage side of the main transformer and the working incoming line to limit the short-circuit current. Based on the system capacity of 100MVA as the benchmark, the system impedance Z1=0.0349, Z2=0.0349, Z3=0.0508, the capacity of the main transformer is 100000kVA, Ud=13.88%, and the short-circuit current of the low-voltage side of the main transformer is calculated by the node method. Design Manual: Electrical Primary Part" Select the model of the reactor, select the reactor as 0.303Ω, and the reactance rate is 5%. The whole plant is equipped with three sets of quick-cutting devices, and each set of quick-cutting devices realizes the power switching of the unit.

Each system consists of working power supply, backup power supply 1 and backup power supply 2. Each set of quick switch device is provided with a conversion handle to select the priority of the backup power supply, and the priority of the backup power supply can also be selected in the DCS. When the backup power supply is selected as the main one, it is a two-way switch between the working power supply and the backup power supply. Selecting the backup power supply 2 refers to the two-way switching between the working power supply and the backup power supply 2, and there is no switching relationship between the backup power supply 1 and the backup power supply 2. As shown in Figure 3, for the No. 1 unit on the far left in the figure, the working power is taken from the low-voltage side of the main transformer 1, the backup power source is the high-voltage bus section of the No. Bus section The bus is the 10kV III section. The first set of quick-cutting device is composed of switches 9101, 9100 and 9300. The bus voltage is taken from the voltage transformer 91PT, the working incoming line voltage is taken from the voltage transformer 9101PT, and the spare incoming line-voltage is taken from the The voltage transformer 92PT connected to the 10kV Section II busbar, the second voltage of the spare incoming line is taken from the voltage transformer 93PT connected to the 10kV Section III busbar;

When the standby power supply is selected as the main one, it refers to the switching between switches 9101 and 9100;

When the backup power supply 2 is selected as the main one, it refers to switching between switches 9101 and 9300.

Taking the above-mentioned distributed gas-steam combined cycle distributed energy project as an example, the plant power fast switching system designed by this method saved the cost of three high-power plant transformers in the whole plant (about 720,000 yuan for a single 12500KVA transformer), It saves the cost of a start-up transformer (a single 25000KVA transformer is about 1.05 million yuan), a 110kV GIS interval (400,000 yuan), and the additional cost is three sets of reactors and large-capacity switches (reactor 20,000 + large-capacity switch 200,000 yuan) ), saving a total of about 2.95 million. In addition, the construction land for three high-level factory substations, the start-up substation and one GIS interval was saved, effectively alleviating the land shortage. All the power used by the plant comes from self-generated power, which saves the price difference between purchased power and self-produced power. The working power supply and the backup power supply come from the same substation, and the problem of large power angle between the working power supply and the backup power supply is solved due to the same wiring method. Furthermore, this system adopts the double backup power supply fast switching method of plant power, and sets up a special blocking logic, which improves the reliability of plant power and the flexibility of operation.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still belong to the technical aspects of the present invention. within the scope of protection of the scheme.

Claims (10)

1. A gas-steam combined cycle distributed energy three-power fast switching system is characterized in that it includes three units, each unit is respectively provided with a high-voltage plant busbar and a working power supply line for providing a working power supply, The incoming line of the working power is connected to the low-voltage side of the main transformer through a current-limiting reactor, and a high-speed current-limiting protection switch is connected in parallel at both ends of the current-limiting reactor; the high-voltage factory busbars of any two units are respectively connected through a backup power supply incoming line switch, The connection between the high-voltage plant busbars between the units is controlled by the on-off of the backup power incoming switch. 2. A gas-steam combined cycle distributed energy three-power fast switching system according to claim 1, characterized in that, when the working incoming line switch of a certain unit is in the closing state, its high-voltage plant busbar is connected to another One of the backup power incoming switch between the high-voltage service busbars of the two units is in position. 3. A gas-steam combined cycle distributed energy three-power fast switching system according to claim 1, characterized in that, each unit is respectively provided with a fast switching device, among the three units, for the high pressure of a certain unit As for the factory busbar, the high-voltage factory busbars of the other two units are used as the backup power supply, and the priority setting of the two backup power supplies is realized through the quick switching device. 4. A gas-steam combined cycle distributed energy three-power fast switching system according to claim 1, characterized in that the low-voltage side of the main transformer is connected to the incoming line of the working power by a pouring busbar, and the incoming line of the standby power is connected by a cable. The working power and backup power come from the same substation and use the same wiring method. 5. A gas-steam combined cycle distributed energy three-power fast switching system according to claim 1, characterized in that, the high-voltage side of the current-limiting reactor is provided with an isolating switch for maintenance and isolation, and any two units The standby power incoming line switch connected between the high-voltage factory busbars is also connected in series with an isolating knife switch. 6. A gas-steam combined cycle distributed energy three-power fast switching method, characterized in that it comprises the following steps: Step 1) Combining the start-up curve of the gas turbine and the output of the auxiliary system at different stages, the distribution of utility loads at different stages is comprehensively analyzed, including the distribution of utility loads of the gas-steam combined cycle unit at the high plate and the load stage of the unit ; Make full use of the characteristics that the plant load of the gas-steam combined cycle unit is distributed in stages, select the capacity of the working incoming line switch and the standby incoming line switch, and enter step 2 after determination; Step 2) Set the voltage of the high-voltage power plant to be the same as the generator voltage and the voltage on the low-voltage side of the main transformer, and enter step 3) after confirmation; Step 3) Install a reactor between the low-voltage side of the main transformer and the working incoming line, and proceed to step 4) after confirmation; Step 4) Set up a dual backup power switching device between the electronic equipment, and set up a locking logic in the quick-cut closing circuit of the power inlet switch to prevent the same high-voltage factory power from the same unit from running on three units at the same time. After confirming, go to step 5) ; Step 5) The dual backup power quick switching device selects the priority of the backup power, realizes the two-way switching between the working power and the first backup power or the two-way switching between the working power and the second backup power, and improves the secondary circuit of the quick switching system. 7. A kind of gas-steam combined cycle distributed energy three power supply fast switching method according to claim 6, is characterized in that, counts the factory total load of each set of units, and is used to confirm the capacity of the working incoming line switch; the calculation is different The highest plant load under operating conditions is used to determine the capacity of the standby incoming switch. 8. A gas-steam combined cycle distributed energy three-power fast switching method according to claim 6, characterized in that the total plant load of each set of units in step 1) is between all high-voltage motors and low-voltage plant variable capacity And; the switching capacity of the working incoming line is based on the requirements of factory loads in different stages and a margin of not less than 10% is left. 9. A gas-steam combined cycle distributed energy three-power fast switching method according to claim 6, characterized in that, in step 2) the incoming power supply of the medium and high-voltage power plant is taken from the low-voltage side of the main transformer, and the double backup power supply is taken from the main transformer low-voltage side. From the high-voltage service bus of adjacent units. 10. A gas-steam combined cycle distributed energy three-power fast switching method according to claim 6, characterized in that, in step 3), the short circuit on the low-voltage side of the main transformer is calculated through the system capacity, system impedance and the impedance of the main transformer Current, the node method is used to calculate the short-circuit current of the low-voltage side of the main transformer, and the capacity of the current-limiting reactor is determined according to the short-circuit current of the low-voltage side of the main transformer.