CN108092261A - Combined floodgate mode selection method, device and the storage medium of cascade transformer - Google Patents

Abstract

The invention provides a method and device for selecting a closing mode of a cascaded transformer. The method includes: using a pre-established transformer closing operation mathematical model to determine the closing mode of two or more cascaded transformers when the input voltage is fixed. In the switching mode, the excitation inrush current value output by the primary transformer; according to the determined excitation inrush current value, a closing mode is selected from the closing modes of the two or more cascaded transformers. The present invention solves the problem in the related art that a large excitation inrush current is generated during the closing operation of various cascaded transformers, thereby affecting the stability of the system, and then achieves an optimal closing operation mode that reduces the closing excitation inrush current beneficial effect.

Description

Closing mode selection method, device and storage medium of cascaded transformer

technical field

The invention relates to a transformer closing technology, in particular to a method, device and storage medium for selecting a closing mode of a cascaded transformer.

Background technique

In order to improve the reliability of power supply to power users and reduce the impact of power supply failure on the normal life of users, emergency power supply will generally be provided for power users separately. When supplying power to power users, in case of mains power failure, the backup power supply will be used for emergency power supply, and the backup power supply must be used for emergency power supply. To start the emergency power supply system, the cascaded transformers in the system structure need to be closed. The cascaded transformer closing inrush current generated during this operation not only directly affects the closing operation scheme, but also the excessive excitation inrush current is likely to cause the transformer differential Malfunction of the protection will affect the stability of the system operation.

Since there are many ways to switch on and off the cascade transformer, different ways of switching on will produce different levels of transformer inrush current, so the size of the inrush current generated during the closing process of the cascade transformer cannot be accurately estimated. The inability to estimate the magnitude of the inrush current during the closing operation has great guiding significance for determining the best emergency power supply transformer closing input scheme, and will directly affect the selection of the closing operation scheme.

In the actual engineering field operation process, there are usually multiple transformer closing and input methods for the same emergency power supply system, and the inrush currents generated by different closing methods are also different, so it is necessary to adopt an appropriate method for different closing operations. The size of the inrush current is analyzed, and finally the closing scheme with the best effect is selected.

At present, the excitation inrush current generated by the no-load closing of a single transformer is usually weakened by the phase selection closing and closing technology and the phase selection opening and closing method; the excitation inrush current generated by the on-load closing of the transformer is simulated by building a nonlinear mathematical model analyze. However, in the operation of on-site engineering, it is often faced with the situation that multiple transformers are switched on. For multiple transformers connected in parallel, due to the influence of system impedance, the flux linkage interaction between parallel transformers weakens the magnetic flux. The number of transformers connected in parallel increases, and the closing inrush current of a single transformer decreases. The existing method cannot give the best emergency power supply closing scheme for a specific system structure, and does not have engineering practicability.

For the above-mentioned problems existing in the prior art, no effective solution has been proposed yet.

Contents of the invention

Embodiments of the present invention provide a method, device and storage medium for selecting a closing mode of a cascaded transformer, so as to at least solve the problem in the related art that a large excitation inrush current is generated during the closing operation of various cascaded transformers, which affects system stability The problem.

According to an embodiment of the present invention, a method for selecting a closing mode of a cascaded transformer is provided, including: using a pre-established mathematical model of transformer closing operation to determine the The excitation inrush value output by the first-stage transformer in the closing mode; select a closing mode from the closing modes of the two or more cascaded transformers according to the determined exciting inrush current value.

Optionally, the closing modes of the two or more cascaded transformers include the following at least two modes: two transformers cascaded no-load closing mode, two transformers cascaded on-load closing mode, secondary transformers with Load closing mode and secondary transformer no-load closing mode.

Optionally, when the closing mode of the cascaded transformer is the no-load closing mode of the two transformers cascaded, determine the excitation output by the primary transformer in the no-load closing mode of the two transformers cascaded The inrush value includes: within the first time after inputting the voltage for the cascaded transformer, using the mathematical model of the transformer closing operation to simulate the no-load closing of the two transformers cascaded to determine the excitation inrush current of the primary transformer; In the second time after inputting the voltage, use the mathematical model of the transformer closing operation to simulate a load with a predetermined resistance on the secondary transformer to determine the change state of the excitation inrush current of the primary transformer, wherein the The second time is greater than the first time.

Optionally, when the closing mode of the cascaded transformer is two transformers cascaded on-load closing mode, determine the excitation inrush current value output by the primary transformer in the two transformers cascaded on-load closing mode Including: within the first time after inputting the voltage for the cascaded transformer, using the mathematical model of the transformer closing operation to simulate the cascaded on-load closing of the two transformers to determine the excitation inrush current of the primary transformer; After the exciting inrush current of the primary transformer, the change state of the exciting inrush current of the primary transformer is recorded.

Optionally, when the closing mode of the cascaded transformer is the on-load closing mode of the secondary transformer, determining the excitation inrush current value output by the primary transformer in the on-load closing mode of the secondary transformer includes: In the first time after inputting the voltage for the cascaded transformer, use the mathematical model of the transformer closing operation to simulate the no-load closing of the primary transformer to determine the excitation inrush current of the primary transformer; the first time after inputting the voltage Within three hours, use the transformer closing operation mathematical model to simulate the on-load closing of the secondary transformer to determine the new excitation inrush current of the primary transformer, wherein the third time is greater than the first time; after determining the After the new excitation inrush current of the primary transformer, the change state of the excitation inrush current of the primary transformer is recorded.

Optionally, when the closing mode of the cascaded transformer is the no-load closing mode of the secondary transformer, determining the excitation inrush current value output by the primary transformer in the no-load closing mode of the secondary transformer includes: In the first time after the input voltage of the cascaded transformer, use the mathematical model of the transformer closing operation to simulate the no-load closing of the primary transformer to determine the excitation inrush current of the primary transformer; and in the third time after inputting the voltage Within, using the mathematical model of the transformer closing operation to simulate the no-load closing of the secondary transformer to determine the new excitation inrush current of the primary transformer, wherein the third time is greater than the first time; after inputting the voltage Within the second time period, use the mathematical model of the transformer closing operation to simulate a load with a predetermined resistance on the secondary transformer to determine the change state of the excitation inrush current of the primary transformer, wherein the second time is greater than the specified Describe the third time.

According to another embodiment of the present invention, a cascaded transformer switching-on mode selection device is provided, including: a determination module, which is used to use the pre-established mathematical model of transformer switching-on operation to determine whether the input voltage is fixed. The excitation inrush current value output by the primary transformer in the closing mode of the above cascaded transformer; the selection module is used to select one closing mode from the two or more cascaded transformer closing modes according to the determined exciting inrush current value gate mode.

Optionally, the closing modes of the two or more cascaded transformers include the following at least two modes: two transformers cascaded no-load closing mode, two transformers cascaded on-load closing mode, secondary transformers with Load closing mode and secondary transformer no-load closing mode.

According to still another embodiment of the present invention, a storage medium is further provided, the storage medium includes a stored program, wherein, when the program is running, the method described in any one of the above-mentioned methods is executed.

According to yet another embodiment of the present invention, an electronic device is also provided, including a memory, a processor, and a computer program stored in the memory and operable on the processor, wherein the processor uses the The computer program performs the method described in any one of the above.

Through the present invention, due to the pre-established mathematical model of the transformer closing operation, after using the backup power supply for power supply, in the case of a fixed input voltage, by comparing and analyzing the closing modes of more than two cascaded transformers, the output of the primary transformer is The changing state of the excitation inrush current value, and then select an optimal emergency power supply closing mode from the closing modes of more than two cascaded transformers. Therefore, it can solve the problem in the related art that a large excitation inrush current is generated during the closing operation of various cascaded transformers, which affects the stability of the system, and then achieves the beneficial effect of obtaining the optimal closing operation mode to reduce the closing excitation inrush current. Effect.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

Fig. 1 is a flow chart of a method for selecting a closing mode of a cascaded transformer according to an embodiment of the present invention;

Fig. 2 is a structural diagram of an emergency power supply system according to an embodiment of the present invention;

3 is a simulation model diagram of a cascaded transformer closing inrush current according to an embodiment of the present invention;

Fig. 4 is a schematic diagram of a no-load closing model of two transformers cascaded according to an embodiment of the present invention;

Fig. 5 is a T-shaped equivalent circuit diagram of two transformers cascaded with no-load closing provided according to an embodiment of the present invention;

FIG. 6 is a waveform diagram of a primary transformer inrush current in a two-transformer cascaded no-load closing model according to an embodiment of the present invention;

7 is a model diagram of a secondary transformer on-load closing circuit according to an embodiment of the present invention;

Fig. 8 is a waveform diagram of a primary transformer inrush current in a secondary transformer on-load closing model according to an embodiment of the present invention;

Fig. 9 is a waveform diagram of an inrush current in a primary transformer under the no-load closing mode of two transformers cascaded according to an embodiment of the present invention;

Fig. 10 is a waveform diagram of an inrush current in a primary transformer under the on-load closing mode of two transformers cascaded according to an embodiment of the present invention;

Fig. 11 is a waveform diagram of an inrush current in a primary transformer in the on-load closing mode of a secondary transformer according to an embodiment of the present invention;

Fig. 12 is a waveform diagram of an inrush current in a primary transformer under no-load closing mode of a secondary transformer according to an embodiment of the present invention;

Fig. 13 is a structural block diagram of a device for selecting a closing mode of a cascaded transformer according to an embodiment of the present invention.

Detailed ways

Hereinafter, the present invention will be described in detail with reference to the drawings and examples. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

It should be noted that the terms "first" and "second" in the description and claims of the present invention and the above drawings are used to distinguish similar objects, but not necessarily used to describe a specific sequence or sequence.

At present, the closing operations of cascaded transformers in the start-up process of the emergency power supply system mainly include transformer cascading no-load closing, secondary transformer on-load closing, transformer cascading on-load closing, and two transformers and load closing step by step. Waiting for several kinds, but these kinds of operations will bring about the problem of excessive closing excitation inrush current. A single transformer will generate a large excitation inrush current when it is closed with no load, which may easily cause the malfunction of the transformer differential protection device and affect the stability of the system operation; when the transformer is in a supersaturated state, it will also cause abnormal Large excitation inrush current is not suitable for engineering site operation.

Fig. 1 is a flow chart of a method for selecting a closing mode of a cascaded transformer according to an embodiment of the present invention. As shown in Fig. 1, the process includes the following steps:

Step S102, using the pre-established transformer closing operation mathematical model to determine the inrush current value output by the primary transformer in the closing mode of more than two cascaded transformers under the condition of a fixed input voltage;

Step S104, selecting a closing mode from more than two closing modes of the cascaded transformer according to the determined excitation inrush current value.

Through the above steps, due to the mathematical model of transformer closing operation established in advance, after using the backup power supply, in the case of a fixed input voltage, by comparing and analyzing the closing methods of more than two cascaded transformers, the output of the primary transformer is The changing state of the excitation inrush current value, and then select an optimal emergency power supply closing mode from the closing modes of more than two cascaded transformers. Therefore, it can solve the problem in the related art that a large excitation inrush current is generated during the closing operation of various cascaded transformers, which affects the stability of the system, and then achieves the beneficial effect of obtaining the optimal closing operation mode to reduce the closing excitation inrush current. Effect.

A further description will be made below in conjunction with a system model for a diesel generator set as an emergency power supply to provide electric energy to the load through a two-stage transformer.

The emergency power supply system consists of two diesel generator sets as emergency power supply. When the mains fails to supply power to users normally, the emergency power supply is put into use. FIG. 2 is a structural diagram of an emergency power supply system provided according to an embodiment of the present invention. As shown in Figure 2, the generated electric energy is raised to the 10kV mains voltage level through the 0.4/10kV transformer, and then stepped down by the 10/0.4kV transformer to supply the system structure diagram for emergency load use.

FIG. 3 is a simulation model diagram of a cascaded transformer closing inrush current. As shown in Figure 3, Generator1 and Generator2 in the figure are diesel generator modules, including excitation subsystem and speed regulation subsystem. The diesel generator set with a rated power of 500kVA generates 400V and 50Hz electric energy, which is raised to 10kV through a 0.4/10kV transformer Mains electricity is stepped down by 10/0.4kV transformer to supply urgent load. Breaker1, Breaker2 and Breaker3 are three three-phase circuit breakers that control the on-off of subsequent circuits. The transformer parameters are as follows:

P ₀ =1450W, P _k =6300W, i ₀ =1.4%, S _N =630KVA

The saturation characteristic is set to:

In an optional embodiment, the closing modes of more than two cascaded transformers include the following at least two modes: two transformers cascaded no-load closing mode, two transformers cascaded on-load closing mode, and two transformers cascaded on-load closing mode. The on-load closing mode of the primary transformer and the no-load closing mode of the secondary transformer. In this embodiment, after setting up various closing modes of cascaded transformers in the emergency power supply system, the no-load closing mode of two transformers cascaded and the on-load closing mode of two transformers cascaded are compared from the perspective of theory and simulation. The magnitude of the excitation inrush current generated by the first-stage transformer in the four closing operation modes, the on-load closing mode of the secondary transformer and the no-load closing mode of the secondary transformer, finally determines the optimal closing operation of the cascaded transformer Way.

In an optional embodiment, when the closing mode of the cascaded transformer is two transformers cascaded no-load closing mode, determine the excitation inrush current output by the primary transformer in the two transformers cascaded no-load closing mode The values include: in the first time after the voltage is input to the cascaded transformer, use the mathematical model of transformer closing operation to simulate the no-load closing of two transformers cascaded to determine the excitation inrush current of the primary transformer; in the second time after the input voltage Within a certain period of time, the mathematical model of transformer closing operation is used to simulate a load with a predetermined resistance on the secondary transformer to determine the change state of the excitation inrush current of the primary transformer, wherein the second time is greater than the first time. In the embodiment of the present invention, when two transformers are cascaded in no-load closing mode, after the standby power supply supplies power to the mathematical model of the transformer closing operation, the excitation inrush waveform generated by the primary transformer is first simulated, and when the excitation inrush value reaches a certain After the peak value, put in a load with a predetermined resistance to increase the power, so that it gradually decays to the normal current.

In this embodiment, two single-phase transformers of the same type are used as the cascaded no-load closing model. By establishing a mathematical model for the two transformers cascaded and no-load closing, the theoretical analysis is equivalent to obtaining the voltage equation, and from the simulation Angle simulated and analyzed the excitation inrush current of transformer cascaded no-load closing.

The following will further describe the no-load closing operation of two transformers cascaded in combination with specific embodiments.

Fig. 4 is a schematic diagram of a no-load closing model of two transformers cascaded according to an embodiment of the present invention. As shown in Figure 4, two single-phase transformers of the same type are cascaded and no-load closing model. The transient process of the transformer cascading no-load closing in Figure 4 can be studied with the T-type equivalent circuit of the transformer. The embodiment provides a T-type equivalent circuit diagram of two transformers cascaded with no-load switching on.

The physical meanings of the physical quantities in Figure 5 are as follows: u ₁₁ , u ₁₂ : primary and secondary side voltages of the primary transformer; u ₂₁ , u ₂₂ : primary and secondary side voltages of the secondary transformer; i ₁₁ , i ₁₂ : primary and secondary side voltages of the primary transformer Secondary side current; i ₂₁ , i ₂₂ : primary and secondary side current of secondary transformer; R ₁₁ , R ₁₂ : primary and secondary side leakage resistance of primary transformer; R ₂₁ , R ₂₂ : primary and secondary side leakage of secondary transformer Resistance; Ψ _m1 , Ψ _m2 : primary and secondary transformer main flux linkage; Ψ _σ11 , Ψ _σ12 : primary and secondary side leakage flux linkage of primary transformer; Ψ _σ21 , Ψ _σ22 primary and secondary side leakage flux linkage of secondary transformer. Write the voltage equation for loop 1 and loop 2, from Kirchhoff's voltage law,

For the linear branch, Ψ=Li, for the excitation branch inductance is related to the saturation degree of the magnetic flux, record L _m1 ＝f ₁ (Ψ _m1 ), L _m2 ＝f ₂ (Ψ _m1 ), get Ψ _m1 ＝f ₁ ( Ψ _m1 )(i ₁₁ -i ₁₂ ), Ψ _m2 ＝f ₂ (Ψ _m2 )i ₁₂ , the flux linkage is eliminated:

The mathematical model of transformer cascaded no-load closing is finally equivalent to two voltage equations. Due to the influence of iron core saturation, the excitation inductance of the two transformers is different and is a function of flux linkage. The two differential equations are variable coefficient differential equations. The differential equation method is difficult to solve the result, and the differential equation is transformed into an algebraic equation by Laplace transform:

Further get:

Bring into formula (3) to eliminate i ₁₂ (s) to get:

where A=f ₁ (Ψ _m1 )[f ₂ (Ψ _m2 )+2L ₁₂ ]

B＝2R ₁₂ +(R ₁₁ +R ₁₁ )[f ₁ (Ψ _m1 )+f ₂ (Ψ _m2 )+2L ₁₂ ]

When the cascaded transformer is switched on at the moment, in the case of severe saturation of the magnetic flux, the excitation inductance is very small, and the two poles of the characteristic equation are located in the left half plane of the complex plane, and the corresponding inverse Laplace transform results are two The superposition of attenuation components makes the excitation inrush current generated by the primary transformer very large at the moment of switching on.

FIG. 6 shows the inrush current waveform diagram of the primary transformer in the two-transformer cascaded no-load closing model provided by the embodiment of the present invention. In this embodiment, in the excitation inrush simulation model of no-load closing of cascaded transformers, the no-load closing mode of two transformers cascaded is simulated. The no-load closing simulation process of two transformers cascaded is as follows: Breaker1 closes at the 7th second after the simulation starts, Breaker2 remains closed, and Breaker3 closes at the 9th second, and no-load closing simulation is performed for the two cascaded transformers , The inrush waveform of the first-stage transformer is shown in Figure 6 when measuring 7-9 seconds. It can be seen from the simulation results that the no-load closing of the two transformers cascaded makes the total peak value of the inrush current generated by the on-load closing of the primary transformer reach 2702A, which is three times the rated current.

In an optional embodiment, when the closing mode of the cascaded transformer is two transformers cascaded on-load closing mode, determine the excitation inrush current output by the primary transformer in the two transformers cascaded on-load closing mode The values include: within the first time after the voltage is input to the cascaded transformer, use the mathematical model of transformer closing operation to simulate the on-load closing of two transformers cascaded to determine the excitation inrush current of the primary transformer; After the inrush, record the changing state of the excitation inrush current of the primary transformer. In this embodiment, when two transformers cascade on-load closing operation mode is selected, after the backup power supply supplies power to the mathematical model of the transformer closing operation, first simulate the excitation inrush current of the primary transformer to reach a peak value, and then gradually decay to normal Working current.

In an optional embodiment, when the closing mode of the cascaded transformer is the on-load closing mode of the secondary transformer, determining the excitation inrush current value output by the primary transformer in the on-load closing mode of the secondary transformer includes: In the first time after the input voltage for the cascaded transformer, use the mathematical model of transformer closing operation to simulate the no-load closing of the primary transformer, and determine the excitation inrush current of the primary transformer; in the third time after inputting the voltage, use the transformer closing operation The mathematical model of gate operation simulates the on-load closing of the secondary transformer, and determines the new excitation inrush current of the primary transformer, wherein the third time is greater than the first time; after determining the new excitation inrush current of the primary transformer, record the current of the primary transformer The changing state of the magnetizing inrush current. In this embodiment, when the on-load closing operation mode of the secondary transformer is selected, after the backup power supply supplies power to the mathematical model of the transformer closing operation, the no-load closing of the primary transformer is first simulated, and after the excitation inrush current reaches a peak value, the secondary transformer is switched on. When the primary transformer is switched on and loaded, the inrush current of the secondary transformer will be superimposed on the inrush current of the primary transformer to reach a total inrush current value, and then gradually decay to the normal operating current.

In the following, a further analysis will be made on the on-load closing model of the secondary transformer in combination with a specific embodiment.

Fig. 7 is a model diagram of a secondary transformer cascaded on-load switching circuit according to an embodiment of the present invention. The mathematical model of transformer switching on with load can be studied by using the transformer equivalent circuit. The circuit model is shown in Figure 7. The primary side of the transformer is a sinusoidal voltage source. In the figure, i ₀ is the excitation current, _RL is the load resistance, and other physical quantities The meaning of is the same as that in the mathematical model of two transformer cascaded no-load closing in the previous section.

According to Kirchhoff's voltage law and electromagnetic induction law:

For the linear branch, Ψ=Li, for the excitation branch inductance is related to the saturation degree of the magnetic flux, write Ψ _m ＝f ₂ (Ψ _m )i ₀ , and eliminate the flux linkage:

After Laplace transform, we get:

Eliminate the intermediate variables to get:

Among them, A ₁ =f ₂ (Ψ _m2 )L ₂₁ +L ₂₁ L ₂₂ +f ₂ (Ψ _m2 )L ₂₂

B ₁ ＝f ₂ (Ψ _m2 )R ₂₁ +R ₂₁ L ₂₂ +(R ₂₂ +R _L )L ₂₁ +f ₂ (Ψ _m2 )(R ₂₂ +R _L )

At the moment when the transformer is switched on with load, the iron core is in an unsaturated state, and the excitation inductance is relatively large. The two real roots of the characteristic equation are located in the left half plane of the complex plane, and their sizes are different. They are the superposition of two attenuated DC components. The reactance is large, the current mainly flows through the primary and secondary side windings, and the inrush current is small; when the iron core is saturated, the working point of the flux linkage shifts to the saturation point, the excitation inductance becomes very small, and the root of the characteristic equation is on the negative real axis The double pole of , the waveform first increases to the maximum and then gradually decreases.

Fig. 8 is the excitation inrush current waveform of the primary transformer in the on-load closing model of the secondary transformer provided by the embodiment of the present invention. In the transformer closing inrush current simulation model shown in Figure 8, the on-load closing simulation process of the secondary transformer is as follows: As shown in Figure 2, Breaker3 remains closed, and the primary transformer closes at the 7th second, and the 8th second When the secondary transformer is closed with a load of 300kW, the inrush current waveform of the primary transformer is measured for 8 to 10 seconds, as shown in Figure 8. In Fig. 8, due to the on-load input of the secondary transformer at the 8th second, its inrush current is superimposed on the primary transformer so that the total peak value of the inrush current is 1692A, and then gradually decays to the normal operating current.

In an optional embodiment, when the closing mode of the cascaded transformer is the no-load closing mode of the secondary transformer, determining the excitation inrush current value output by the primary transformer in the no-load closing mode of the secondary transformer includes: In the first time after the input voltage for the cascaded transformer, use the mathematical model of transformer closing operation to simulate the no-load closing of the primary transformer, and determine the excitation inrush current of the primary transformer; in the third time after inputting the voltage, use the transformer closing operation The mathematical model of gate operation simulates the no-load closing of the secondary transformer, and determines the new excitation inrush current of the primary transformer, wherein the third time is greater than the first time; in the second time after the voltage is input, the mathematical model of transformer closing operation is used Simulating a load with a predetermined resistance on the secondary transformer to determine the change state of the excitation inrush current of the primary transformer, wherein the second time is greater than the third time. In this embodiment, when the no-load closing operation mode of the secondary transformer is selected, after the backup power supply supplies power to the mathematical model of the transformer closing operation, the excitation inrush current waveform when the primary transformer is closed at no-load is first simulated, and when the primary transformer After the excitation inrush current reaches a peak value, the secondary transformer is put into no-load closing, and the excitation inrush current will be superimposed on the primary transformer to obtain the total excitation inrush current value, and then a pure resistive load is used to increase the power and gradually attenuate it. is the normal current.

In order to find the closing operation mode that causes the cascaded transformers to produce the least excitation inrush current, in the present invention, the no-load closing mode of two transformers cascaded, the on-load closing mode of two transformers cascaded, and the on-load closing mode of the secondary transformer And the no-load closing mode of the secondary transformer is simulated and analyzed respectively, and the waveforms of the excitation inrush current generated in the primary transformer under the four kinds of cascaded transformer closing modes are measured and shown in Figures 9-12.

The inrush current waveform of the primary transformer when the two transformers are cascaded and closed with no load is shown in Figure 9. In the 7th second of the simulation, the two transformers are cascaded and closed with no load, making the primary transformer inrush current reach 2224A. At the 9th second, The input of 300kW pure resistance load makes the power increase, and then gradually decays to the normal working current.

Figure 10 shows the inrush current waveform of the primary transformer when the two transformers are cascaded and closed on load. In the 7th second of the simulation, the two transformers are cascaded and closed on load, making the inrush current of the primary transformer reach 3065A, and then gradually decay to normal Working current.

The inrush current waveform of the primary transformer when the secondary transformer is switched on with load is shown in Figure 11. In the 7th second of the simulation, the primary transformer is switched on without load, and the inrush current reaches 1796A. The inrush current is superimposed on the primary transformer to increase the total inrush current to 1418A, and then gradually decays to the normal operating current.

The inrush current waveform of the primary transformer when the secondary transformer is switched on with no load is shown in Figure 12. In the 7th second of the simulation, the primary transformer is switched on with no load, and the inrush current reaches 1796A. The inrush current is superimposed on the primary transformer to increase the total inrush current to 1418A. At 9 seconds, a 300kW pure resistive load is input to increase the power, and then gradually decays to the normal operating current.

According to the above simulation analysis results, the following conclusions can be drawn:

① Transformer no-load closing will generate a large inrush current. In actual operation, transformer cascaded no-load closing will produce a more serious inrush current than a single transformer no-load closing.

②The primary transformer is put into operation and enters a stable operating state. At this time, the secondary transformer is closed with a load, and the inrush current generated is larger than that of a single transformer with no load.

③ The inrush current generated when the primary transformer is closed with the secondary transformer and the load is the largest among all closing methods.

Therefore, it is suggested that in the actual operation of the site, the first-level transformer can be put into operation, and then the second-level transformer is put into operation, and then the load is turned on, so as to reduce the inrush current generated during the transformer closing process.

Through the description of the above embodiments, the present invention is aimed at the emergency power supply system through two cascaded transformers, the two transformers cascaded no-load closing mode, the two transformers cascaded on-load closing mode, and the secondary transformer on-load closing mode. The analysis of the magnitude of the inrush current in the primary transformer in the four closing methods of the closing mode and the no-load closing of the secondary transformer finally worked out the best transformer closing scheme.

In this embodiment, a device for selecting a closing mode of a cascaded transformer is also provided. The device is used to implement the above embodiments and preferred implementation modes, and those that have already been described will not be repeated. As used below, the term "module" may be a combination of software and/or hardware that realizes a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementations in hardware, or a combination of software and hardware are also possible and contemplated.

Fig. 13 is a structural block diagram of a cascaded transformer closing mode selection device according to an embodiment of the present invention. As shown in Fig. 13, the device includes: a determination module 132, which is used to determine the In the case of a fixed input voltage, the inrush current value output by the primary transformer in the closing mode of more than two cascaded transformers; the selection module 134 is used to select from two or more cascaded transformers according to the determined inrush current value Select a closing mode from the closing mode.

In an optional embodiment, the closing modes of more than two cascaded transformers include the following at least two modes: two transformers cascaded no-load closing mode, two transformers cascaded on-load closing mode, and two transformers cascaded on-load closing mode. The on-load closing mode of the primary transformer and the no-load closing mode of the secondary transformer.

In an optional embodiment, the selection module 134 includes:

When the closing mode of the cascaded transformer is the no-load closing mode of two transformers cascaded, the excitation inrush value output by the first-stage transformer in the no-load closing mode of the two transformers cascaded includes: In the first time after the voltage is applied, use the mathematical model of transformer closing operation to simulate the no-load closing of two transformers cascaded to determine the excitation inrush current of the primary transformer; The model simulation puts a load of predetermined resistance on the secondary transformer to determine the change state of the excitation inrush current of the primary transformer, wherein the second time is greater than the first time.

When the closing mode of the cascaded transformer is two transformers cascaded on-load closing mode, the excitation inrush value output by the first-stage transformer in the cascaded on-load closing mode of two transformers includes: In the first time after voltage, use the mathematical model of transformer closing operation to simulate two transformers cascaded on-load closing, and determine the excitation inrush current of the primary transformer; after determining the excitation inrush current of the primary transformer, record the excitation inrush current of the primary transformer The changing state of the current.

When the closing mode of the cascaded transformer is the on-load closing mode of the secondary transformer, the determination of the excitation inrush current value output by the primary transformer in the on-load closing mode of the secondary transformer includes: For a period of time, use the mathematical model of the transformer closing operation to simulate the no-load closing of the primary transformer to determine the excitation inrush current of the primary transformer; within the third time after the input voltage, use the mathematical model of the transformer closing operation to simulate the secondary transformer. The load is closed to determine the new excitation inrush current of the primary transformer, wherein the third time is greater than the first time; after the new excitation inrush current of the primary transformer is determined, the change state of the excitation inrush current of the primary transformer is recorded.

When the closing mode of the cascaded transformer is the no-load closing mode of the secondary transformer, the determination of the excitation inrush current value output by the primary transformer in the no-load closing mode of the secondary transformer includes: Within a period of time, use the mathematical model of transformer closing operation to simulate the no-load closing of the primary transformer to determine the excitation inrush current of the primary transformer; within the third time after inputting the voltage, use the mathematical model of transformer closing operation to simulate the no-load switching of the secondary transformer. Load closing, to determine the new excitation inrush current of the primary transformer, wherein, the third time is greater than the first time; in the second time after the input voltage, use the mathematical model of the transformer closing operation to simulate the predetermined resistance on the secondary transformer The value of the load determines the change state of the excitation inrush current of the primary transformer, wherein the second time is greater than the third time.

It should be noted that the above-mentioned modules can be realized by software or hardware. For the latter, it can be realized by the following methods, but not limited to this: the above-mentioned modules are all located in the same processor; or, the above-mentioned modules can be combined in any combination The forms of are located in different processors.

An embodiment of the present invention also provides a storage medium, the storage medium includes a stored program, wherein the above-mentioned program executes the method described in any one of the above-mentioned methods when running.

Optionally, in this embodiment, the above-mentioned storage medium may include but not limited to: U disk, read-only memory (Read-Only Memory, ROM for short), random access memory (Random Access Memory, RAM for short), Various media that can store program codes such as removable hard disks, magnetic disks, or optical disks.

According to yet another embodiment of the present invention, there is also provided an electronic device, including a memory, a processor, and a computer program stored in the memory and operable on the processor, wherein the processor executes any of the above items through the computer program Methods.

Obviously, those skilled in the art should understand that each module or each step of the above-mentioned present invention can be realized by a general-purpose computing device, and they can be concentrated on a single computing device, or distributed in a network formed by multiple computing devices Alternatively, they may be implemented in program code executable by a computing device so that they may be stored in a storage device to be executed by a computing device, and in some cases in an order different from that shown here The steps shown or described are carried out, or they are separately fabricated into individual integrated circuit modules, or multiple modules or steps among them are fabricated into a single integrated circuit module for implementation. As such, the present invention is not limited to any specific combination of hardware and software.

Through the selection method of cascaded transformer closing mode provided by the present invention, the thinking is clear, the mathematical model is effectively combined with the actual situation, and finally the purpose of effectively reducing the inrush current in the transformer is achieved, and it is close to the field operation situation, and has the advantages of Strong practical guiding significance and practical application value.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the principle of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. a kind of combined floodgate mode selection method of cascade transformer, which is characterized in that including：

Using pre-establish Transformer Close operation mathematical model determine it is fixed in input voltage, it is two or more The excitation surge current value exported in the combined floodgate mode of cascade transformer by stage transformer；

A kind of combined floodgate side is selected from the combined floodgate mode of described two above cascade transformers according to definite excitation surge current value Formula.

2. the according to the method described in claim 1, it is characterized in that, combined floodgate mode bag of described two above cascade transformers Include following at least two mode：Two transformers cascade idle-loaded switching-on mode, and two transformer stages join switch in load mode, two level Transformer switch in load mode and secondary transformer idle-loaded switching-on mode.

3. according to the method described in claim 2, it is characterized in that, when the combined floodgate mode of the cascade transformer is described two When transformer cascades idle-loaded switching-on mode, determine to be exported by stage transformer in two transformers cascade idle-loaded switching-on mode Excitation surge current value include：

Within for the first time after the cascade transformer input voltage, imitated using Transformer Close operation mathematical model Very described two transformers cascade idle-loaded switching-on determines the excitation surge current of stage transformer；

Within the second time after inputting the voltage, mathematical model simulation is operated in two level transformation using the Transformer Close The load of predetermined resistance value is put on device, determines the variable condition of the excitation surge current of the stage transformer, wherein, when described second Between be more than the first time.

4. according to the method described in claim 2, it is characterized in that, when the combined floodgate mode of the cascade transformer is two transformations When device cascades switch in load mode, encouraging by stage transformer output in two transformer stages connection switch in load mode is determined Magnetic value of shoving includes：

Within for the first time after the cascade transformer input voltage, imitated using Transformer Close operation mathematical model Very described two transformer stages connection switch in load determines the excitation surge current of stage transformer；

After the excitation surge current of the stage transformer is determined, the variation shape of the excitation surge current of the stage transformer is recorded State.

5. according to the method described in claim 2, it is characterized in that, when the combined floodgate mode of the cascade transformer is the two level During transformer switch in load mode, the excitation for determining to be exported by stage transformer in the secondary transformer switch in load mode is gushed Flow valuve includes：

Within for the first time after the cascade transformer input voltage, imitated using Transformer Close operation mathematical model True stage transformer idle-loaded switching-on determines the excitation surge current of stage transformer；

Within the 3rd time after inputting the voltage, mathematical model simulation secondary transformer is operated using the Transformer Close Switch in load determines the new excitation surge current of stage transformer, wherein, the 3rd time is more than the first time；

After the new excitation surge current of the stage transformer is determined, the variation of the excitation surge current of the stage transformer is recorded State.

6. according to the method described in claim 2, it is characterized in that, when the combined floodgate mode of the cascade transformer is two level transformation During device idle-loaded switching-on mode, the excitation surge current value exported in the secondary transformer idle-loaded switching-on mode by stage transformer is determined Including：

Within for the first time after the cascade transformer input voltage, imitated using Transformer Close operation mathematical model True stage transformer idle-loaded switching-on determines the excitation surge current of stage transformer；

Within the 3rd time after inputting the voltage, mathematical model simulation secondary transformer is operated using the Transformer Close Idle-loaded switching-on determines the new excitation surge current of stage transformer, wherein, the 3rd time is more than the first time；

Within the second time after inputting the voltage, mathematical model simulation is operated in two level transformation using the Transformer Close The load of predetermined resistance value is put on device, determines the variable condition of the excitation surge current of the stage transformer, wherein, when described second Between be more than the 3rd time.

7. a kind of combined floodgate mode selection device of cascade transformer, which is characterized in that including：

Determining module, for being determined using the Transformer Close operation mathematical model pre-established in the fixed situation of input voltage Under, by the excitation surge current value of stage transformer output in the combined floodgate mode of two or more cascade transformers；

Selecting module, for being selected according to definite excitation surge current value from the combined floodgate mode of described two above cascade transformers Select a kind of combined floodgate mode.

8. device according to claim 7, which is characterized in that the combined floodgate mode bag of described two above cascade transformers Include following at least two mode：Two transformers cascade idle-loaded switching-on mode, and two transformer stages join switch in load mode, two level Transformer switch in load mode and secondary transformer idle-loaded switching-on mode.

9. a kind of storage medium, which is characterized in that the storage medium includes the program of storage, wherein, when described program is run Method any one of perform claim requirement 1 to 6.

10. a kind of electronic device, including memory, processor and it is stored on the memory and can transports on the processor Capable computer program, which is characterized in that the processor performs the claims 1 to 6 by the computer program Method described in one.