Auxiliary power supply system with controllable bus voltage and bus voltage control method thereof

Abstract

The invention relates to a station service power supply system with controllable bus voltage and a bus voltage control method thereof.The station service power supply system comprises a high-voltage bus, a step-up transformer, a generator, a high station transformer and a station service power bus, the high-voltage bus is connected with the high-voltage side of the step-up transformer through a high-voltage circuit breaker, and the low-voltage side of the step-up transformer is connected with the voltage input end of the high station transformer; the voltage output end of the generator is connected with the voltage input end of the high plant transformer through an outlet circuit breaker, the plant power bus is connected with a plant power load through a plant circuit breaker, and the voltage regulating device is arranged between the high plant transformer and the plant circuit breaker; wherein the voltage regulating device regulates and controls the output voltage of the voltage regulating device so as to regulate the voltage of the auxiliary power bus to be within an allowable voltage fluctuation range. Therefore, the fluctuation of the station service bus voltage can be reduced, and the stability of the station service bus voltage can be improved.

Description

Technical Field

[0001] The present invention relates to the field of auxiliary power supplies for industrial enterprises, and particularly to an auxiliary power supply system with controllable bus voltage and a method for controlling the bus voltage thereof. Background Art

[0002] Due to the limitation of its insulation capacity, the rated voltage of a large generator does not exceed 28 kV at most, and the working current is very large. Usually, it is connected to the high-voltage bus after being stepped up by a transformer. A large number of mechanical devices are provided as power sources for the boilers, steam turbines and their auxiliary equipment of the cogeneration units in refining enterprises. These power sources for power are called auxiliary power. Refer to Figure 1 As shown, in the existing auxiliary power supply system, a transformer (usually called the high-voltage auxiliary transformer 3) is generally provided in the auxiliary power branch circuit at the outlet of the generator 2 to solve the situation where the voltage at the generator outlet is inconsistent with the auxiliary power bus voltage, and to enable the auxiliary power to obtain the working power from the high-voltage bus. In addition, the auxiliary power generally also needs to obtain the standby power from other high-voltage power sources.

[0003] The design principle of the cogeneration unit in the refining enterprise is usually "determining electricity by steam". The stable operation of the cogeneration unit (especially the boiler) is the basis for the continuous and safe production of the refining enterprise. Therefore, the power supply reliability of the auxiliary power must be guaranteed. In order to improve the power supply reliability of the auxiliary power, an outlet circuit breaker is generally provided at the generator outlet to ensure that after the generator is shut down, the auxiliary power can obtain the working power from the high-voltage bus through the step-up transformer and the high-voltage auxiliary transformer, without having to switch to the standby power.

[0004] The existing cogeneration units in refining enterprises usually adopt the unit wiring of generator - step-up transformer - auxiliary power branch circuit - high-voltage auxiliary transformer - auxiliary power, and its typical auxiliary power supply system topology is as Figure 1 shown. The voltage ratio of the step-up transformer 1 and the high-voltage auxiliary transformer 3 is generally designed according to when the generator 2 is put into operation. The voltage on the low-voltage side of the step-up transformer is selected according to the rated voltage of the generator, and the voltage on the high-voltage side of the step-up transformer is usually selected at 110% of the nominal voltage of the high-voltage bus; the voltage on the high-voltage side of the high-voltage auxiliary transformer is selected according to the rated voltage of the generator, and the voltage on the low-voltage side of the high-voltage auxiliary transformer is usually selected at 105% of the nominal voltage of the auxiliary power bus; in this way, the electric power generated by the generator can be transmitted to the high-voltage bus through the step-up transformer, and at the same time, it is ensured that the auxiliary power bus voltage meets the standard requirements.

[0005] When the generator is taken out of service, the high-voltage busbar supplies power to the plant service power through the step-up transformer and the high-voltage auxiliary transformer and via the plant service busbar. The step-up transformer operates in the step-down mode. Since the value of the voltage on the high-voltage side of the step-up transformer is usually 110% of the nominal voltage of the high-voltage busbar, coupled with the voltage fluctuations of the high-voltage busbar, it will cause the voltage of the plant service busbar to drop, and even drop outside the range of the standard allowable voltage fluctuations. The fluctuating voltage of the plant service busbar will pose a hidden danger to the normal operation of the plant service load, and further pose a hidden danger to the stable operation of the cogeneration device of the refinery and petrochemical enterprise. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a plant service power supply system with controllable busbar voltage in view of the above-mentioned prior art. This plant service power supply system can adjust and control the voltage of the plant service busbar, reduce the voltage fluctuations of the plant service busbar, and improve the stability of the voltage of the plant service busbar.

[0007] The second technical problem to be solved by the present invention is to provide a method for controlling the busbar voltage of the above-mentioned plant service power supply system.

[0008] The technical solution adopted by the present invention to solve the first technical problem is as follows: A plant service power supply system with controllable busbar voltage, including a high-voltage busbar, a step-up transformer, a generator, a high-voltage auxiliary transformer, and a plant service busbar. The high-voltage busbar is connected to the high-voltage side of the step-up transformer through a high-voltage circuit breaker. The low-voltage side of the step-up transformer is connected to the voltage input end of the high-voltage auxiliary transformer. And the voltage output end of the generator is connected to the voltage input end of the high-voltage auxiliary transformer through an outlet circuit breaker. The plant service busbar is connected to the plant service load through a plant service circuit breaker. It is characterized in that it further includes a voltage regulating device arranged between the high-voltage auxiliary transformer and the plant service circuit breaker; wherein, the voltage regulating device adjusts and controls its own output voltage to adjust the voltage of the plant service busbar within the allowable voltage fluctuation range.

[0009] As an implementation manner of the above voltage regulating device, improved, in the plant service power supply system with controllable busbar voltage, the voltage regulating device has:

[0010] A voltage regulating element formed by an inductor with multiple taps. The voltage regulating element has a high-voltage input end and a high-voltage output end; wherein, the high-voltage input end is connected to the voltage output end of the high-voltage auxiliary transformer, and the high-voltage output end is connected to the plant service circuit breaker;

[0011] Multiple bypass switches, each bypass switch corresponding to a tap of the voltage regulating element respectively, and each bypass switch being connected in parallel with the corresponding tap;

[0012] A voltage sampling terminal for collecting the output voltage when the voltage regulating device is working;

[0013] A current sampling terminal for collecting the working current when the voltage regulating device is working;

[0014] A controller is respectively connected to a current sampling terminal and a voltage sampling terminal for signal connection, and the controller controls the opening or closing of a bypass switch based on the received working current and output voltage.

[0015] As another implementation manner of the above voltage regulating device, improved, in the auxiliary power supply system with controllable bus voltage, the voltage regulating device has:

[0016] A voltage regulating component formed by connecting multiple inductors in series, the voltage regulating component has a high-voltage input terminal and a high-voltage output terminal; wherein, the high-voltage input terminal is connected to the voltage output terminal of the high-voltage auxiliary transformer, and the high-voltage output terminal is connected to the auxiliary breaker.

[0017] Multiple bypass switches, each bypass switch corresponds to one inductor of the voltage regulating component respectively, and each bypass switch is respectively connected in parallel with the corresponding inductor.

[0018] A voltage sampling terminal for collecting the output voltage when the voltage regulating device works.

[0019] A current sampling terminal for collecting the working current when the voltage regulating device works.

[0020] A controller is respectively connected to the current sampling terminal and the voltage sampling terminal for signal connection, and the controller controls the opening or closing of the bypass switch based on the received working current and output voltage.

[0021] Further improved, in the auxiliary power supply system with controllable bus voltage, the controller is a device with data processing and logic programming functions, and the bypass switch is a high-voltage contactor or a high-voltage breaker.

[0022] Furthermore, in the auxiliary power supply system with controllable bus voltage, the basic parameters of the high-voltage bus are: the nominal voltage is 110 kV, and the voltage fluctuation range is within 97% - 107% of the nominal voltage; the basic parameters of the step-up transformer are: the rated capacity is 120 MVA, the short-circuit loss is 303 kW, and the impedance voltage is 10.5%; the basic parameters of the generator are: the rated power is 100 MW, the rated voltage is 13.8 kV, and the power factor is 0.85; the basic parameters of the high-voltage auxiliary transformer are: the rated capacity is 16 MVA, the short-circuit loss is 65.8 kW, and the impedance voltage is 6.5%; the basic parameters of the auxiliary power bus are: the nominal voltage is 10 kV, the allowable voltage fluctuation range is within 95% - 105% of the nominal voltage, the calculated load is 8 MW, and the average power factor during operation is 0.8.

[0023] The technical solution adopted by the present invention to solve the second technical problem is: a bus voltage control method applied to the auxiliary power supply system, which is characterized by including the following steps:

[0024] Step 1, the voltage regulating device obtains its own real-time output voltage value; wherein, the voltage regulating device has at least one voltage regulating element;

[0025] Step 2, the voltage regulating device makes a judgment and processing based on the obtained real-time output voltage value:

[0026] When the real-time output voltage value is higher than the preset maximum voltage allowable value, it proceeds to Step 3; otherwise, it maintains the real-time output voltage value of the voltage regulating device and proceeds to Step 1;

[0027] Step 3, the voltage regulating device performs a step-down adjustment operation to make its real-time output voltage value lower than the preset maximum voltage allowable value, and proceeds to Step 1.

[0028] Improved, in the bus voltage control method of the auxiliary power supply system, when the voltage regulating device determines that its real-time output voltage value is higher than the preset maximum voltage allowable value and all voltage regulating elements have been put into operation, it performs an alarm prompt operation to give an alarm prompt to the operation and maintenance personnel, reminding the operator to perform manual intervention.

[0029] Further improved, in this invention, the bus voltage control method of the auxiliary power supply system further includes:

[0030] Step S2, the voltage regulating device makes a judgment and processing based on the obtained real-time output voltage value:

[0031] When the real-time output voltage value is lower than the preset minimum voltage allowable value, it proceeds to Step S3; otherwise, it maintains the real-time output voltage value of the voltage regulating device and proceeds to Step 1;

[0032] Step S3, the voltage regulating device performs a step-up adjustment operation to make its real-time output voltage value higher than the preset minimum voltage allowable value, and proceeds to Step 1.

[0033] Furthermore, in the bus voltage control method of the auxiliary power supply system, the process of the voltage regulating device performing the step-up adjustment operation is as follows:

[0034] Step a1, when the voltage regulating device determines that the real-time output voltage value it obtains is lower than the preset minimum voltage allowable value and there is a voltage regulating element in the input state, the voltage regulating device withdraws a group of voltage regulating elements; otherwise, it performs an alarm prompt operation;

[0035] Step a2, the voltage regulating device obtains the real-time output voltage value after withdrawing a group of voltage regulating elements;

[0036] Step a3, the voltage regulating device makes a judgment and processing based on the real-time output voltage value after the voltage regulating element is withdrawn:

[0037] When the real-time output voltage value is lower than the preset minimum allowable voltage value after the voltage regulating element is withdrawn and there is a voltage regulating element in the on state, the voltage regulating device withdraws another group of voltage regulating elements and transfers to step a4; otherwise, an alarm prompt operation is performed;

[0038] Step a4, repeat steps a2 to a3 until all the voltage regulating elements of the voltage regulating device are withdrawn.

[0039] Further improvement, in the bus voltage control method of the auxiliary power supply system, when the real-time output voltage value obtained by the voltage regulating device is between the preset minimum allowable voltage value and the maximum allowable voltage value and there is a voltage regulating element in the on state, the voltage regulating device pre-calculates the voltage sum value of the real-time output voltage value after withdrawal and the voltage adjustment amount of a single group of voltage regulating elements; and when the voltage regulating device determines that the obtained voltage sum value is lower than the preset maximum allowable voltage value, the voltage regulating device withdraws another group of voltage regulating elements.

[0040] Compared with the prior art, the advantages of the present invention are as follows: The auxiliary power supply system of the present invention is based on the topological structure formed by the existing high-voltage bus, step-up transformer, generator, high-voltage auxiliary transformer, auxiliary power bus, outlet circuit breaker, and auxiliary circuit breaker. A voltage regulating device is provided between the high-voltage auxiliary transformer and the auxiliary circuit breaker. The voltage regulating device adjusts and controls its own output voltage to adjust the voltage of the auxiliary power bus within the allowable voltage fluctuation range. In this way, the voltage fluctuation of the auxiliary power bus can be reduced, and the stability of the voltage of the auxiliary power bus can be improved. Description of the Drawings

[0041] Figure 1 Schematic diagram of the existing auxiliary power supply system;

[0042] Figure 2 Schematic diagram of the auxiliary power supply system with controllable bus voltage in the embodiment of the present invention;

[0043] Figure 3 Schematic diagram of the main component connections when the first voltage regulating device in the embodiment of the present invention adopts the first method;

[0044] Figure 4 Schematic diagram of the main component connections when the second voltage regulating device in the embodiment of the present invention adopts the first method;

[0045] Figure 5 Schematic diagram of the main component connections when the first voltage regulating device in the embodiment of the present invention adopts the second method;

[0046] Figure 6 Schematic diagram of the main component connections when the second voltage regulating device in the embodiment of the present invention adopts the second method;

[0047] Figure 7 ForFigure 2 Schematic diagram of the method flow for controlling the bus voltage of the shown station service power supply system. Specific implementation mode

[0048] The present invention will be further described in detail below in conjunction with the embodiments of the attached drawings.

[0049] This embodiment provides a station service power supply system with controllable bus voltage. Specifically, it can adjust and control the voltage of the station service bus, reduce the voltage fluctuation of the station service bus, and improve the stability of the voltage of the station service bus. See Figure 2 and 3 As shown, the station service power supply system with controllable bus voltage in this embodiment includes a high-voltage bus L1, a step-up transformer 1, a generator 2, a high-voltage station transformer 3, and a station service bus L2. The high-voltage bus L1 is connected to the high-voltage side of the step-up transformer 1 through a high-voltage circuit breaker 4. The low-voltage side of the step-up transformer 1 is connected to the voltage input end of the high-voltage station transformer 3. And the voltage output end of the generator 2 is connected to the voltage input end of the high-voltage station transformer 3 through an outlet circuit breaker 5. The station service bus L2 is connected to a station service load 7 through a station service circuit breaker 6. A voltage regulating device 8 is provided between the high-voltage station transformer 3 and the station service circuit breaker 6. Among them, the voltage regulating device 8 adjusts and controls its own output voltage to adjust the voltage of the station service bus L2 within the allowable voltage fluctuation range.

[0050] In this embodiment, the above voltage regulating device 8 has two implementation methods. Specifically:

[0051] As the first implementation method of the above voltage regulating device, see Figure 3 As shown, the voltage regulating device 8 of this embodiment has:

[0052] A voltage regulating element 81, formed by an inductor L with multiple taps. The voltage regulating element 81 has a high-voltage input end 81a and a high-voltage output end 81b. The high-voltage input end 81a is connected to the voltage output end of the high-voltage station transformer 3, and the high-voltage output end 81b is connected to the station service circuit breaker 6;

[0053] Multiple bypass switches 82, each bypass switch 82 corresponding to a tap of the voltage regulating element 81 respectively, and each bypass switch is connected in parallel with the corresponding tap; for example, the bypass switch adopts a high-voltage contactor or a high-voltage circuit breaker as required;

[0054] A voltage sampling terminal 83, which collects the output voltage when the voltage regulating device is working;

[0055] A current sampling terminal 84, which collects the working current when the voltage regulating device is working;

[0056] A controller 85 is respectively connected to a voltage sampling terminal 83 and a current sampling terminal 84 for signal connection, and this controller 85 controls the opening or closing of a bypass switch 82 based on the received working current and output voltage. Herein, the controller is a device with data processing and logic programming functions.

[0057] As a second implementation manner of the above voltage regulating device, refer to Figure 4 As shown, the voltage regulating device 8 may also have:

[0058] A voltage regulating element 81 formed by connecting a plurality of inductors L in series. This voltage regulating element 81 has a high-voltage input terminal 81a and a high-voltage output terminal 81b; the high-voltage input terminal 81a is connected to the voltage output terminal of the high-voltage plant transformer 3, and the high-voltage output terminal 81b is connected to the plant breaker 6;

[0059] A plurality of bypass switches 82, each bypass switch 82 respectively corresponds to an inductor L of the voltage regulating element 81, and each bypass switch is respectively connected in parallel with the corresponding inductor; for example, the bypass switch adopts a high-voltage contactor or a high-voltage circuit breaker as required;

[0060] A voltage sampling terminal 83 for collecting the output voltage when the voltage regulating device is working;

[0061] A current sampling terminal 84 for collecting the working current when the voltage regulating device is working;

[0062] A controller 85 is respectively connected to a voltage sampling terminal 83 and a current sampling terminal 84 for signal connection, and this controller 85 controls the opening or closing of a bypass switch 82 based on the received working current and output voltage. Herein, the controller is a device with data processing and logic programming functions.

[0063] Regarding another connection manner between the voltage regulating element and the bypass switch in the first voltage regulating device, refer to Figure 5 As shown, regarding another connection manner between the voltage regulating element and the bypass switch in the second voltage regulating device, refer to Figure 6 As shown, it will not be elaborated here.

[0064] Regarding the plant power supply system of this embodiment, the basic parameter conditions of each device inside are as follows:

[0065] The basic parameters of the high-voltage bus L1 are: the nominal voltage is 110 kV, and the voltage fluctuation range is within 97% - 107% of the nominal voltage;

[0066] The basic parameters of the step-up transformer 1 are: the rated capacity is 120 MVA, the short-circuit loss is 303 kW, and the impedance voltage is 10.5%;

[0067] The basic parameters of the generator 2 are: the rated power is 100 MW, the rated voltage is 13.8 kV, and the power factor is 0.85;

[0068] The basic parameters of the high-voltage auxiliary transformer 3 are as follows: the rated capacity is 16 MVA, the short-circuit loss is 65.8 kW, and the impedance voltage is 6.5%;

[0069] The basic parameters of the auxiliary power bus L2 are as follows: the nominal voltage is 10 kV, the allowable range of voltage fluctuation is within 95% - 105% of the nominal voltage, the calculated load is 8 MW, and the average power factor during operation is 0.8.

[0070] This embodiment provides a bus voltage control method applied to the above-mentioned auxiliary power supply system. Specifically, refer to Figure 7 As shown, the bus voltage control method of the auxiliary power supply system in this embodiment includes the following steps:

[0071] Step 1, the voltage regulating device obtains its own real-time output voltage value; wherein, the voltage regulating device has at least one voltage regulating element;

[0072] Step 2, the voltage regulating device makes a judgment and processing according to the obtained real-time output voltage value:

[0073] When the real-time output voltage value is higher than the preset maximum allowable voltage value, go to Step 3; otherwise, maintain the real-time output voltage value of the voltage regulating device and go to Step 1;

[0074] Step 3, the voltage regulating device performs a step-down adjustment operation to make its real-time output voltage value lower than the preset maximum allowable voltage value, and then go to Step 1. Here, the step-down adjustment operation refers to opening the bypass switch.

[0075] During the execution process, once the voltage regulating device determines that its real-time output voltage value is higher than the preset maximum allowable voltage value and all voltage regulating elements have been put into operation, an alarm prompt operation is executed to give an alarm prompt to the operation and maintenance personnel, reminding the operator to perform manual intervention.

[0076] In addition, after the voltage regulating device obtains its real-time output voltage value, the bus voltage control method of the auxiliary power supply system in this embodiment further includes:

[0077] Step S2, the voltage regulating device makes a judgment and processing according to the obtained real-time output voltage value:

[0078] When the real-time output voltage value is lower than the preset minimum allowable voltage value, go to Step S3; otherwise, maintain the real-time output voltage value of the voltage regulating device and go to Step 1;

[0079] Step S3, the voltage regulating device performs a step-up adjustment operation to make its real-time output voltage value higher than the preset minimum allowable voltage value, and then go to Step 1. Here, the step-up adjustment operation is to close the bypass switch.

[0080] As for the boosting adjustment work performed by the voltage regulating device here, it includes the following steps a1 to a4:

[0081] In step a1, when the voltage regulating device determines that the acquired real-time output voltage value is lower than the preset minimum allowable voltage value and there are voltage regulating elements in the on state, the voltage regulating device withdraws a group of voltage regulating elements; otherwise, it performs an alarm prompt operation;

[0082] In step a2, the voltage regulating device acquires the real-time output voltage value after withdrawing a group of voltage regulating elements; that is, after performing step a1, at this time, the voltage regulating device acquires its current real-time output voltage value again (i.e., the real-time output voltage value after the voltage regulating elements are withdrawn);

[0083] In step a3, the voltage regulating device makes a judgment and processing based on the real-time output voltage value after the voltage regulating elements are withdrawn:

[0084] When the real-time output voltage value after the voltage regulating elements are withdrawn is lower than the preset minimum allowable voltage value and there are voltage regulating elements in the on state, the voltage regulating device withdraws another group of voltage regulating elements and proceeds to step a4; otherwise, it performs an alarm prompt operation to give an alarm prompt to the operation and maintenance personnel and remind the operator to perform manual intervention;

[0085] In step a4, steps a2 to a3 are repeatedly executed until all the voltage regulating elements of the voltage regulating device are withdrawn.

[0086] In addition, when the real-time output voltage value after withdrawal acquired by the voltage regulating device is between the preset minimum allowable voltage value and the maximum allowable voltage value and there are voltage regulating elements in the on state, the voltage regulating device pre-calculates the voltage sum value of the real-time output voltage value after withdrawal and the voltage adjustment amount of a single group of voltage regulating elements; and when the voltage sum value obtained by the voltage regulating device is determined to be lower than the preset maximum allowable voltage value, the voltage regulating device withdraws another group of voltage regulating elements.

[0087] Specifically, this embodiment further explains the calculation method of the voltage fluctuation of the auxiliary power bus during the engineering design stage as follows:

[0088] (1) When the generator is put into operation and the auxiliary power bus supplies the calculated load, the voltage fluctuation calculation formula of the auxiliary power bus is:

[0089] ΔU 厂 =ΔU 发 +ΔU 高分 +ΔU 高降 +ΔU 高低 +ΔU 调 ≤ΔU 标 ;

[0090] Among them, ΔU 厂 represents the voltage deviation of the auxiliary power bus, and ΔU 发Represents the voltage deviation at the generator outlet, ΔU 高分 Represents the voltage deviation caused by the voltage ratio and tap position of the high-voltage auxiliary transformer, ΔU 高降 Represents the internal voltage drop of the high-voltage auxiliary transformer, ΔU 高低 Represents the voltage deviation caused by the voltage value taken at the low-voltage side of the high-voltage auxiliary transformer, ΔU 调 Represents the voltage drop caused by the voltage regulating device, ΔU 标 Represents the standard allowable voltage deviation of the auxiliary power bus. The values of the above-mentioned ΔU are all expressed as percentages;

[0091] (2) When the generator is out of operation, the high-voltage bus is operating at the highest or lowest voltage, and the auxiliary power bus is carrying the calculated load, the voltage fluctuation calculation formula for the auxiliary power bus is:

[0092] ΔU 厂 = ΔU 高母 + ΔU 升分 + ΔU 升降 + ΔU 高分 + ΔU 高降 + ΔU 高低 + ΔU 调 ≤ ΔU 标 ;

[0093] Among them, ΔU 厂 Represents the voltage deviation of the auxiliary power bus, ΔU 高母 Represents the voltage deviation of the high-voltage bus, ΔU 升分 Represents the voltage deviation caused by the voltage ratio and tap position of the step-up transformer, ΔU 升降 Represents the internal voltage drop of the step-up transformer, ΔU 高分 Represents the voltage deviation caused by the voltage ratio and tap position of the high-voltage auxiliary transformer, ΔU 高降 Represents the internal voltage drop of the high-voltage auxiliary transformer, ΔU 高低 Represents the voltage deviation caused by the voltage value taken at the low-voltage side of the high-voltage auxiliary transformer, ΔU 调 Represents the voltage drop caused by the voltage regulating device, ΔU 标 Represents the standard allowable voltage deviation of the auxiliary power bus. The values of the above-mentioned ΔU are all expressed as percentages.

[0094] (3) The calculation formula for the internal voltage drop of the transformer is as follows:

[0095] ΔU T =(P × U a + Q × U r ) / S rT ;

[0096] U a =(100 × ΔP T ) / S rT ,

[0097] Among them, ΔU T represents the internal voltage drop of the transformer (%), S rT represents the rated capacity of the transformer (kVA), U a represents the active component of the impedance voltage of the transformer (%), U r represents the reactive component of the impedance voltage of the transformer (%), U T represents the impedance voltage of the transformer (%), ΔP T represents the short-circuit loss of the transformer (kW), P represents the active power of the three-phase load (kW), and Q represents the reactive power of the three-phase load (kVar).

[0098] (4) The calculation formula for the total inductance value of the voltage regulating element is as follows:

[0099]

[0100] Among them, L represents the total inductance value of the voltage regulating element (mH), U n represents the rated voltage of the voltage regulating device (kV), ΔU l represents the total voltage drop of the voltage regulating device during load operation (%), f represents the power grid frequency (Hz), represents the load power factor angle, I e represents the calculated current of the voltage regulating device during load operation (kA). Among them, the main parameters of the voltage regulating device, including the rated voltage, rated current, total voltage regulation range, rated total inductance value, and grouping, need to be determined in advance.

[0101] Through the above calculation of the voltage fluctuation of the auxiliary power bus, the total voltage regulation range of the voltage regulating device 8, the voltage regulation range of each group of voltage regulating elements, and the total number of groups of voltage regulating elements can be obtained, and from this, the total inductance value of all voltage regulating elements and the inductance value of each group of voltage regulating elements can be calculated.

[0102] First, for the auxiliary power supply system of this embodiment, the basic parameter conditions of each device inside are as follows:

[0103] The basic parameters of the high-voltage bus L1 are: the nominal voltage is 110 kV, and the voltage fluctuation range is within 97% - 107% of the nominal voltage;

[0104] The basic parameters of the step-up transformer 1 are: the rated capacity is 120 MVA, the short-circuit loss is 303 kW, the impedance voltage is 10.5%, the voltage ratio is 121 ± 2 × 2.5% / 13.8 kV, and the tap is operating at the -1 position;

[0105] The basic parameters of the generator 2 are: the rated power is 100 MW, the rated voltage is 13.8 kV, and the power factor is 0.85;

[0106] The basic parameters of the high-voltage auxiliary transformer 3 are as follows: rated capacity is 16 MVA, short-circuit loss is 65.8 kW, impedance voltage is 6.5%, voltage ratio is 13.8 ± 2×2.5% / 10.5 kV, and the tap is operating at the -2 position;

[0107] The basic parameters of the plant service bus L2 are as follows: nominal voltage is 10 kV, the allowable range of voltage fluctuation is within 95% - 105% of the nominal voltage, the calculated load is 8 MW, and the average power factor during operation is 0.8.

[0108] (1) Determination of the voltage regulation range of the voltage regulation device in the engineering design stage

[0109] (1.1) When the generator is put into operation and the plant service bus is carrying the calculated load:

[0110] A. If the generator operates at the rated voltage, then ΔU 发 = 0.

[0111] B. From the tap position of the high-voltage auxiliary transformer, ΔU 高分 = +5 can be calculated.

[0112] C. From formula (3) ΔU T = (P×U a + Q×U r ) / S rT ; U a = (100×ΔP T ) / S rT , the ΔU when the high-voltage auxiliary transformer is carrying the calculated load of the plant service bus can be calculated 高降 = -2.6.

[0113] D. From the selection of the voltage on the low-voltage side of the high-voltage auxiliary transformer, ΔU 高低 = +5 can be calculated.

[0114] When the voltage regulation device 8 is not considered, ΔU 厂 = ΔU 发 + ΔU 高分 + ΔU 高降 + ΔU 高低 = 0 + 5 - 2.6 + 5 = 7.4. The voltage fluctuation of the plant service bus L2 has exceeded the upper limit allowed by the standard. At this time, if the voltage regulation device is put into operation with a voltage adjustment of -5%, then ΔU 厂 = ΔU 发 + ΔU 高分 + ΔU 高降 + ΔU 高低 + ΔU 调 = 0 + 5 - 2.6 + 5 - 5 = +2.4, making the voltage fluctuation of the plant service bus within the range allowed by the standard.

[0115] (1.2) When the generator is out of service, the high-voltage bus is operating at the lowest voltage, and the auxiliary power bus is carrying the calculated load:

[0116] A. ΔU can be calculated from the operating voltage of the high-voltage bus 高母 = -3.

[0117] B. ΔU can be calculated from the tap position of the step-up transformer 升分 = -7.3.

[0118] C. From formula (3) ΔU T = (P × U a + Q × U r ) / S rT ; U a = (100 × ΔP T ) / S rT , ΔU when the step-up transformer is carrying the calculated load of the auxiliary power bus can be calculated 升降 = -0.5.

[0119] D. ΔU can be calculated from the tap position of the high-voltage auxiliary transformer 高分 = +5.

[0120] E. From formula (3) ΔU T = (P × U a + Q × U r ) / S rT ; U a = (100 × ΔP T ) / S rT , ΔU when the high-voltage auxiliary transformer is carrying the calculated load of the auxiliary power bus can be calculated 高降 = -2.6.

[0121] F. ΔU can be calculated from the selection of the voltage on the low-voltage side of the high-voltage auxiliary transformer 高低 = +5.

[0122] When the voltage regulating device is not considered, ΔU 厂 = ΔU 高母 + ΔU 升分 + ΔU 升降 + ΔU 高分 + ΔU 高降 + ΔU 高低 = -3 - 7.3 - 0.5 + 5 - 2.6 + 5 = -3.4, and the voltage fluctuation of the auxiliary power bus is within the standard allowable range. At this time, the voltage regulating device does not need to be put into operation.

[0123] (1.3) When the generator is out of service, the high-voltage bus is operating at the highest voltage, and the auxiliary power bus is carrying the calculated load:

[0124] A. The ΔU can be calculated from the operating voltage of the high-voltage busbar 高母 = +7.

[0125] B. The ΔU can be calculated from the tap position of the step-up transformer 升分 = -7.3.

[0126] C. From formula (3) ΔU T = (P × U a + Q × U r ) / S rT ; U a = (100 × ΔP T ) / S rT , the ΔU when the step-up transformer supplies the calculated load of the auxiliary power busbar can be calculated 升降 = -0.5.

[0127] D. The ΔU can be calculated from the tap position of the high-voltage auxiliary transformer 高分 = +5.

[0128] E. From formula (3) ΔU T = (P × U a + Q × U r ) / S rT ; U a = (100 × ΔP T ) / S rT , the ΔU when the high-voltage auxiliary transformer supplies the calculated load of the auxiliary power busbar can be calculated 高降 = -2.6.

[0129] F. The ΔU can be calculated from the selection of the voltage on the low-voltage side of the high-voltage auxiliary transformer 高低 = +5.

[0130] When the voltage regulating device is not considered, ΔU 厂 = ΔU 高母 + ΔU 升分 + ΔU 升降 + ΔU 高分 + ΔU 高降 + ΔU 高低 = +7 - 7.3 - 0.5 + 5 - 2.6 + 5 = +6.6. The voltage fluctuation of the auxiliary power busbar has exceeded the upper limit allowed by the standard. At this time, when the voltage regulating device is put into operation according to a voltage adjustment of -2.5%, then ΔU 厂 = ΔU 高母 + ΔU 升分 + ΔU 升降 + ΔU 高分 + ΔU 高降 + ΔU 高低 + ΔU 调= +7 - 7.3 - 0.5 + 5 - 2.6 + 5 - 2.5 = +4.1, so that the voltage fluctuation of the auxiliary power bus is within the range allowed by the standard.

[0131] Although the preferred embodiments of the present invention have been described in detail above, it should be clearly understood that various changes and modifications can be made to the present invention by those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. The auxiliary power supply system with controllable bus voltage includes a high-voltage bus (L1), a step-up transformer (1), a generator (2), a high-voltage auxiliary transformer (3), and an auxiliary power bus (L2). The high-voltage bus (L1) is connected to the high-voltage side of the step-up transformer (1) through a high-voltage circuit breaker (4). The low-voltage side of the step-up transformer (1) is connected to the voltage input terminal of the high-voltage auxiliary transformer (3). And the voltage output terminal of the generator (2) is connected to the voltage input terminal of the high-voltage auxiliary transformer (3) through an outlet circuit breaker (5). The auxiliary power bus (L2) is connected to the auxiliary power load (7) through an auxiliary circuit breaker (6), and it is characterized in that, It further includes a voltage regulating device (8) disposed between the high-voltage auxiliary transformer (3) and the auxiliary power circuit breaker (6); wherein, the voltage regulating device (8) adjusts and controls its own output voltage to adjust the voltage of the auxiliary power bus (L2) within the allowable voltage fluctuation range.

2. The auxiliary power supply system with controllable bus voltage according to claim 1, wherein, The voltage regulating device (8) has: A voltage regulating element (81) formed by an inductor (L) with multiple taps, the voltage regulating element (81) having a high-voltage input terminal (81a) and a high-voltage output terminal (81b); wherein, the high-voltage input terminal (81a) is connected to the voltage output terminal of the high-voltage auxiliary transformer (3), and the high-voltage output terminal (81b) is connected to the auxiliary power circuit breaker (6); Multiple bypass switches (82), each bypass switch (82) corresponding to one tap of the voltage regulating element (81), and each bypass switch being connected in parallel with the corresponding tap; A voltage sampling terminal (83) for collecting the output voltage when the voltage regulating device is operating; A current sampling terminal (84) for collecting the operating current when the voltage regulating device is operating; A controller (85) signal-connected to the voltage sampling terminal (83) and the current sampling terminal (84) respectively, and the controller (85) controls the opening or closing of the bypass switch (82) based on the received operating current and output voltage.

3. The auxiliary power supply system with controllable bus voltage according to claim 1, characterized in that The voltage regulating device (8) has: A voltage regulating element (81) formed by multiple inductors (L) connected in series, the voltage regulating element (81) having a high-voltage input terminal (81a) and a high-voltage output terminal (81b); wherein, the high-voltage input terminal (81a) is connected to the voltage output terminal of the high-voltage auxiliary transformer (3), and the high-voltage output terminal (81b) is connected to the auxiliary power circuit breaker (6); Multiple bypass switches (82), each bypass switch (82) corresponding to one inductor (L) of the voltage regulating element (81), and each bypass switch being connected in parallel with the corresponding inductor; A voltage sampling terminal (83) for collecting the output voltage when the voltage regulating device is operating; A current sampling terminal (84) for collecting the operating current when the voltage regulating device is operating; A controller (85) signal-connected to the voltage sampling terminal (83) and the current sampling terminal (84) respectively, and the controller (85) controls the opening or closing of the bypass switch (82) based on the received operating current and output voltage.

4. The auxiliary power supply system with controllable bus voltage according to claim 2 or 3, characterized in that The controller is a device with data processing and logic programming functions, and the bypass switch is a high-voltage contactor or a high-voltage circuit breaker.

5. The auxiliary power supply system with controllable bus voltage according to claim 1, characterized in that, The basic parameters of the high-voltage busbar (L1) are as follows: the nominal voltage is 110 kV, and the voltage fluctuation range is within 97% - 107% of the nominal voltage; the basic parameters of the step-up transformer (1) are: the rated capacity is 120 MVA, the short-circuit loss is 303 kW, and the impedance voltage is 10.5%; the basic parameters of the generator (2) are: the rated power is 100 MW, the rated voltage is 13.8 kV, and the power factor is 0.85; the basic parameters of the high-voltage auxiliary transformer (3) are: the rated capacity is 16 MVA, the short-circuit loss is 65.8 kW, and the impedance voltage is 6.5%; the basic parameters of the auxiliary power busbar (L2) are: the nominal voltage is 10 kV, the allowable voltage fluctuation range is within 95% - 105% of the nominal voltage, the calculated load is 8 MW, and the average power factor during operation is 0.

8.

6. The bus voltage control method applied to the plant power supply system according to any one of claims 2 to 4, characterized in that, It includes the following steps: Step 1, the voltage regulating device obtains its own real-time output voltage value; among them, the voltage regulating device has at least one voltage regulating element; Step 2, the voltage regulating device makes a judgment and processing according to the obtained real-time output voltage value: When the real-time output voltage value is higher than the preset maximum allowable voltage value, it goes to Step 3; otherwise, it maintains the real-time output voltage value of the voltage regulating device and goes to Step 1; Step 3, the voltage regulating device performs a step-down adjustment operation to make its real-time output voltage value lower than the preset maximum allowable voltage value, and goes to Step 1.

7. The bus voltage control method of the plant power supply system according to claim 6, characterized in that, It also includes: When the voltage regulating device judges that its real-time output voltage value is higher than the preset maximum allowable voltage value and all voltage regulating elements have been put into operation, it performs an alarm prompt operation to give an alarm prompt to the operation and maintenance personnel, reminding the operator to perform manual intervention.

8. The bus voltage control method of the plant power supply system according to claim 6 or 7, characterized in that, It also includes: Step S2, the voltage regulating device makes a judgment and processing according to the obtained real-time output voltage value: When the real-time output voltage value is lower than the preset minimum allowable voltage value, it goes to Step S3; otherwise, it maintains the real-time output voltage value of the voltage regulating device and goes to Step 1; Step S3, the voltage regulating device performs a step-up adjustment operation to make its real-time output voltage value higher than the preset minimum allowable voltage value, and goes to Step 1.

9. The bus voltage control method of the auxiliary power system according to claim 8, characterized in that, The process of the voltage regulating device performing the step-up adjustment operation is as follows: Step a1, when the voltage regulating device judges that the real-time output voltage value it obtains is lower than the preset minimum allowable voltage value and there is a voltage regulating element in the input state, the voltage regulating device withdraws a group of voltage regulating elements; otherwise, it performs an alarm prompt operation; Step a2, the voltage regulating device obtains the real-time output voltage value after withdrawing a group of voltage regulating elements; Step a3, the voltage regulating device makes a judgment and processing according to the real-time output voltage value after the voltage regulating element is withdrawn: When the real-time output voltage value after the voltage regulating element is withdrawn is lower than the preset minimum allowable voltage value and there is a voltage regulating element in the input state, the voltage regulating device withdraws another group of voltage regulating elements and goes to Step a4; otherwise, it performs an alarm prompt operation; Step a4, repeatedly execute Steps a2 - a3 until all the voltage regulating elements of the voltage regulating device are withdrawn.

10. The method for controlling the bus voltage of the auxiliary power supply system according to claim 9, wherein It also includes: When the real-time output voltage value obtained by the voltage regulating device after withdrawal is between the preset minimum allowable voltage value and the maximum allowable voltage value and there is a voltage regulating element in the input state, the voltage regulating device pre-calculates the voltage sum value of the real-time output voltage value after withdrawal and the voltage adjustment amount of a single group of voltage regulating elements; and when the voltage regulating device determines that the obtained voltage sum value is lower than the preset maximum allowable voltage value, the voltage regulating device withdraws another group of voltage regulating elements.

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