CN104201955A - Ultra high voltage conversion transformer tap switch control method based on variable discourse domain fuzzy - Google Patents

Abstract

The invention discloses a method for controlling an ultra-high voltage converter transformer tap changer based on variable universe fuzzy, and belongs to the field of ultra-high voltage direct current transmission system control. The control method of the present invention is divided into three stages, the first stage is to fuzzify the input data, i.e. the trigger angle and its change amount; the second stage is to determine the domain of discussion of the trigger angle and its change amount; The output gear is obtained by inferring the trigger angle and its variation after the domain change; the invention realizes more precise control of the tap changer, and can make the control process faster when a valve group tap changer fails to be adjusted. Find the precise gear and improve the reliability of the UHV DC transmission system.

Description

A Control Method of UHV Converter Transformer Tap-Changer Based on Variable Discourse Fuzzy

technical field

The invention relates to the technical field of UHV direct current transmission system control, in particular to a method for controlling UHV converter tap-changers based on variable universe fuzzy.

Background technique

The HVDC transmission system is mainly composed of an AC system, a rectifier station, a long-distance transmission line, and an inverter station. The rectifier station rectifies the alternating current into direct current through the converter valve group, and the direct current is transmitted to the inverter station through the line, and then converted into alternating current by the inverter station valve group for use.

The rectifier side of the existing UHV DC transmission system is composed of two valve groups connected in series, and the voltage control of each valve group is realized through joint control of each valve group's respective firing angle and converter tap-changer. The way to increase the voltage of the valve group is to reduce the trigger angle and reduce the tap changer gear of the converter transformer. At the same time, in order to ensure the stable operation of the valve group and reduce the probability of commutation failure, the trigger angle of the valve group on the rectification side has an optimal operating range, which needs to be maintained between 12.5° and 17.5°. Coordinated cooperation keeps the firing angle within the optimum operating range while ensuring that the voltage is within the normal range.

There are two main control methods for converter tap-changers in UHVDC transmission systems: automatic fixed angle control and automatic constant voltage control. The automatic angle setting control includes the automatic angle setting control of the converter transformer on the rectification side. The control goal of the automatic angle setting control of the converter transformer on the rectification side is to ensure that the firing angle of the converter is within a given range by changing the position of the converter transformer tap. . The firing angle of the rectifier side is kept within the normal range of 12.5° to 17.5° by adjusting the tap position of the rectifier. On the rectifier side, when the trigger angle is lower than 12.5°, the converter tap changer control system issues a command to lower the tap; when the trigger angle is higher than 17.5°, it issues a command to raise the tap.

In the current automatic angle-fixed mode, the gear adjustment of the converter transformer tap-changer needs to be added and subtracted step by step after the angle is found to be beyond the limit. This adjustment occurs when the trigger angle of the valve group is serious In the case of exceeding the limit, it can only be adjusted step by step, the adjustment process is slow, and the intelligent control of the tap changer cannot be realized.

Contents of the invention

The purpose of the present invention is to make up for the defects of the current UHV converter tap-changer control method in the aspect of artificial intelligence, and to quickly adjust the tap control and improve the stability of the tap-changer control, and propose a method based on variable universe The fuzzy converter tap changer control method realizes the intelligent control of the tap changer, which can quickly find the tap position that can make the system run smoothly during the control process, and improves the robustness of the tap changer control system.

The purpose of the present invention is achieved through the following technical solutions:

A method for controlling a converter transformer tap-changer based on variable universe fuzzy, characterized in that the converter transformer tap-changer control method is realized by a converter transformer tap-changer control system, and the converter transformer tap-changer control system It is a dual-input-single-output system, using the tap control signal firing angle and its variation as two inputs of the fuzzy controller; the two inputs determine the output through the fuzzy reasoning of the variable universe fuzzy control system; it includes the following steps:

1) Determining the domain of trigger angle and its variation

The domain of discourse refers to the variation range of the input quantity; the expansion factor is used to change the size of the domain of discourse; the design of the expansion factor; as shown in formula (1‐1);

α _angle = (sumANGLE/30/DomainANGLE) ^0.8

α _dangle = (sumdANGLE/30/DomaindANGLE) ^0.8 (1-1)

Among them, sumANGLE is the sum value of the firing angle angle of the first 30 cycles of the recorded current operation cycle, DomainANGLE is the domain value of the externally input converter trigger angle angle; sumdANGLE is the recorded value of the first 30 cycles of the current operation cycle The sum value of dangle, DomaindANGLE is the domain value of dangle, the variation of trigger angle of the converter input externally;

Before the domain of discourse changes, the basic domain of discourse of the trigger angle angle is [0,0.5244], corresponding to the change of the angle from 0° to 30°, the basic domain of discourse of the trigger angle change dangle is [-0.1311,0.1311], corresponding to The angle transformation of d is from -7.5° to 7.5°; after the domain of discourse changes, the discourse domain of trigger angle angle becomes [0,0.5244*α _angle ], and the discourse domain of d trigger angle change amount angle becomes [‐0.1311* α _dangle ,0.1311*α _dangle ]. Domain of discourse refers to the variation range of the input quantity;

2) Fuzzification of system variables.

In the designed UHV converter tap-changer fuzzy controller, the input variables are fuzzy processed according to the triangular membership function, and the membership function is a triangle, as shown in formula (1-2);

$\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{c}\frac{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; a</span>}}\\ \frac{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; b</span>}}\end{array}\right.\left(\begin{array}{ccccc}\mathrm{<span\; class="notranslate">\; a</span>}& \mathrm{<span\; class="notranslate">\; p</span>}& \mathrm{<span\; class="notranslate">\; x</span>}& \mathrm{<span\; class="notranslate">\; p</span>}& \mathrm{<span\; class="notranslate">\; b</span>}\end{array}\right)<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, x is the input quantity, a and b are the boundary values of fuzzy rules, is the degree of membership of a, is the membership value of b, μ(x) represents the membership function of the input x;

For the values of the fuzzy rules of angle, they are Negative Big (NBB), Negative Big (NBS), Negative Medium Big (NMB), Negative Medium Small (NMS), Negative Small Big (NSB), Negative Small (NBB), Zero (ZO), Plus Small (PSS), Plus Small Big (PSB), Plus Medium Small (PMS), Plus Medium Big (PMB), Plus Size (PBS), and Plus Big (PBB);

The discourse domain of trigger angle variation dangle is between [‐0.1311*α _dangle ,0.1311*α _dangle ], and there are 7 fuzzy rules for dangle, which are negative large (NB), negative medium (NM), and negative small (NS), Zero (ZO), Positive Small (PS), Positive Medium (PM) and Positive Big (PB);

3) The adjustment amount of the controller control gear is calculated by formula (1‐3):

Among them, ΔTAP is the gear adjustment value of the converter tap changer controller, α is the input trigger angle value, It is the adjustment amount of tap switch gear corresponding to the change amount of firing angle.

If the firing angle belongs to (0, 2.5°*α _angle ), and the variation of the firing angle belongs to (‐∞, -7.5°*α _angle ), the adjustment of the converter tap-changer is reduced by 6 gears, and its The gear calculation process is ΔTAP=(cos15°-cos2.5°)/0.0125-3=6

If the firing angle belongs to (2.5°*α _dangle , 7.5°*α _dangle ) and the variation of firing angle belongs to (‐∞, ‐7.5°*α _dangle ), the adjustment of the converter tap changer is reduced by 5 file, ΔTAP=(cos15°-cos5°)/0.0125-3=5.

The method of the invention makes up for the shortcoming of slow adjustment speed when the traditional converter transformer tap changer control is disturbed by faults, adds variable domain fuzzy control to the tap changer control system, and realizes optimal control of tap adjustment. The variable universe fuzzy control process is divided into three stages: the first stage is to fuzzify the input data; the second stage is to process the input data through the rule base and the variable universe fuzzy inference algorithm; the third stage is to defuzzify.

Compared with the prior art, the present invention has the following advantages: the present invention realizes the intelligent and fast control of the rheological tap changer, and replaces the control system of the original tap changer when a tap changer failure of a certain valve group occurs. The step-by-step adjustment can realize the rapid adjustment of the switch of another valve group, which greatly improves the reliability of the direct current transmission system.

Description of drawings

Fig. 1 is a framework diagram of the fuzzy control of the discourse domain of the converter transformer tap changer of the present invention.

Figure 2 shows the changes in the domain of discourse of the input trigger angle angle.

Figure 3(a) The membership function of the input angle.

Figure 3(b) The membership function of the input dangle.

Figure 4 is a waveform diagram of the firing angle α on the rectifier side under the general control of the simulated tap changer.

Fig. 5 is a waveform diagram of the firing angle α on the rectification side under the fuzzy control of the variable universe of the simulated tap changer.

Figure 6 shows the low-end valve group on the rectification side in the general control mode of the simulated tap changer tap position.

Fig. 7 shows the low-end valve group on the rectification side under the fuzzy control mode of the tap changer in the simulation tap changer.

Detailed ways

In order to better understand the present invention, the present invention will be further described below in conjunction with the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example

This embodiment is realized by building a ±800kV UHV DC transmission model through the PSCAD/EMTDC software simulation platform and adding a variable universe fuzzy tap-changer controller.

The up and down gears of the existing converter tap changer controllers are adjusted according to one gear. No matter how large the deviation of the trigger angle of the rectification side is, the up and down gears can only be adjusted according to one gear, and each time the gear is adjusted It takes a certain amount of time (the action frequency of the tap-changer is calculated in seconds). After adding the fuzzy tap-changer controller in the debate domain, the change of the up and down gears is not limited to one gear. The fuzzy controller in the debate domain will The deviation of the firing angle on the commutation side determines the adjustment amount of the up/down gear.

In the UHV converter tap-changer fuzzy control system of the present invention, the trigger angle of the tap control signal and its variation are used as the input of the fuzzy controller, and the fuzzy controller calculated according to the angle and the variation of the angle is output to the tap-changer. Adjustment amount.

1) Determining the domain of trigger angle and its variation

The domain of discourse refers to the variation range of the input quantity. The expansion factor can change the size of the universe, and the variable universe fuzzy controller can achieve the purpose of optimizing the control effect by modifying the universe of input. There are many design rules for the expansion factor, and a commonly used proportional expansion factor is used here, as shown in formula (1‐1).

α _angle = (sumANGLE/30/DomainANGLE) ^0.8

α _dangle = (sumdANGLE/30/DomaindANGLE) ^0.8 (1-1)

Among them, sumANGLE is the sum value of the firing angle angle of the first 30 cycles of the recorded current operation cycle, DomainANGLE is the domain value of the externally input converter trigger angle angle; sumdANGLE is the recorded value of the first 30 cycles of the current operation cycle The sum value of dangle, DomaindANGLE is the domain value of dangle, the variation of trigger angle of the converter input externally;

As shown in Figure 2; before the domain of discourse changes, the basic domain of discourse of the trigger angle angle is [0,0.5244], corresponding to the change of the angle from 0° to 30°, the basic domain of discourse of the trigger angle change dangle is [‐ 0.1311,0.1311], the corresponding angle change is ‐7.5° to 7.5°; after the domain of discourse changes, the discourse domain of trigger angle angle becomes [0,0.5244*α _angle ], the domain of discourse of d trigger angle variation angle becomes [-0.1311*α _dangle ,0.1311*α _dangle ]. Domain of discourse refers to the variation range of the input quantity;

2) Fuzzification of system variables.

In the designed UHV converter tap-changer fuzzy controller, the input variable is fuzzy processed according to the triangular membership function, and the discourse domain of the trigger angle angle is [0,0.5244*α _angle ], corresponding to the angle change is 0° to 30°*α _angle , the domain of trigger angle change dangle is [‐0.1311*α _dangle ,0.1311*α _dangle ], and the corresponding angle change is from ‐7.5°*α _dangle to 7.5*α _dangle ° , and its membership function is triangular, as shown in formula (1‐2).

$\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{c}\frac{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; a</span>}}\\ \frac{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; b</span>}}\end{array}\right.\left(\begin{array}{ccccc}\mathrm{<span\; class="notranslate">\; a</span>}& \mathrm{<span\; class="notranslate">\; p</span>}& \mathrm{<span\; class="notranslate">\; x</span>}& \mathrm{<span\; class="notranslate">\; p</span>}& \mathrm{<span\; class="notranslate">\; b</span>}\end{array}\right)<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, x is the input quantity, a and b are the boundary values of fuzzy rules, is the degree of membership of a, is the membership value of b, and μ(x) represents the membership function of the input x.

For the values of the fuzzy rules of angle, they are Negative Big (NBB), Negative Big (NBS), Negative Medium Big (NMB), Negative Medium Small (NMS), Negative Small Big (NSB), Negative Small (NBB), Zero (ZO), Positive Small (PSS), Positive Small Big (PSB), Positive Medium Small (PMS), Positive Medium Big (PMB), Positive Big (PBS) and Positive Big (PBB); the domain of these rules is divided according to the system The characteristics and debugging experience are divided. The domain of triggering angle rules adopted by the UHV converter tap-changer fuzzy controller in this model is shown in Figure 3(a).

The discourse domain of the firing angle change dangle of UHV converter tap-changer fuzzy controller is between [-0.1311*α _dangle ,0.1311*α _dangle ], and there are 7 fuzzy rules for dangle, which are respectively negative large (NB), Negative Medium (NM), Negative Small (NS), Zero (ZO), Positive Small (PS), Positive Medium (PM) and Positive Big (PB); used in UHV converter tap-changer fuzzy controller The universe of the dangle rule of the trigger angle variation is shown in Figure 3(b).

3) The analog controller of the present invention adopts the form of if-then-else. The two input firing angles angle and the firing angle change amount angle have been fuzzified previously. Then control rules are needed to describe the logic of the entire control.

This controller is realized through fuzzy control 13×7 rule table 1, and the gear adjustment amount in the rule table is calculated by formula (1‐3):

Among them, ΔTAP is the gear adjustment value of the converter tap changer controller, α is the input trigger angle value, It is the adjustment amount of the tap changer corresponding to the trigger angle variation; in the table, NB (negative large), NM (negative middle), NS (negative small), ZO (zero), PS (positive small), PM (positive middle ), PB (Zhengda) correspond to down 3 gears, down 2 gears, down 1 gear, unchanged, up 1 gear, up 2 gears, and up 3 gears respectively.

Table 1 Control rules table of variable universe fuzzy controller

NB N M NS ZO P.S. PM PB NBB -6 -5 -4 -3 -2 -1 -1 NBS -6 -5 -4 -3 -2 -1 -1 NMB -5 -4 -3 -2 -1 -1 -1 NMS -5 -4 -3 -2 -1 -1 -1 NSB -4 -3 -2 -1 -1 -1 -1 NSS 0 0 0 0 0 0 0 ZO 0 0 0 0 0 0 0 PSS 0 0 0 0 0 0 0 PSB 1 1 1 1 2 3 4 PMS 1 1 1 2 3 4 5

PMB 1 1 2 3 4 5 6 PBS 2 3 4 5 6 7 8 PBB 3 4 5 6 7 8 9

For the first rule: if the input firing angle angle is negative large (NBB), and the input firing angle variation dangle is negative large (NB), then the TCC adjustment value output thisAction is negative large large (NBBB), because the firing angle becomes smaller , in order to make the DC line voltage reach a given value, the controller adjusts the TCC command to make the tap ratio of the converter transformer smaller, that is, lower the tap position. In fuzzy language it can be described as:

if angle is NBB, dangle is NB then

this action is NBBB

The first rule corresponds to the first row and the first column in the rule table, which means that if the trigger angle belongs to (0, 2.5°*α _angle ), and the variation of the trigger angle belongs to (‐∞,‐ 7.5°*α _angle ), then the adjustment of the converter tap-changer is down 6 gears, and the gear calculation process is ΔTAP=(cos15°-cos2.5°)/0.0125-3=6

The second rule corresponds to the first row and the second column in the rule table, which means that if the trigger angle belongs to (2.5°*α _dangle , 7.5°*α _dangle ) and the variation of the trigger angle belongs to (‐ ∞, -7.5°*α _dangle ), then the adjustment of the converter tap-changer is to reduce by 5 gears, ΔTAP=(cos15°-cos5°)/0.0125-3=5, and the calculation of other rules is similar.

Fuzzy controller parameter setting

The appearance of the fuzzy controller of the UHV converter tap-changer in the PSCAD custom module environment is shown in Figure 4. The input angle is the trigger angle α detected in real time, the input tccin is the converter tap changer gear signal, and the output tccout is the new converter converter tap changer gear signal calculated by the fuzzy controller.

The variables domainangle and domaindangle located in the upper area of the picture and the domainchange in the lower area of the picture are the external variables of the fuzzy controller. The domainangle is an external parameter that controls the change of the domain value of the angle in real time. External parameters that control the output variable change. The adjustment of these external parameters can control the control effect of the fuzzy controller in real time and can be corrected online.

The present invention is realized based on the variable domain fuzzy controller. The whole control method is divided into three stages. The first stage is to fuzzify the input data, that is, the trigger angle and its transformation amount; the second stage is to determine the domain of discussion of the trigger angle and its change amount, and the output gear; the third stage is to pass The rule base and the fuzzy inference algorithm process the trigger angle and its variation after the domain of discourse changes to obtain the output gear; the fourth stage is to defuzzify the output gear. Its control flow is shown in accompanying drawing 1, specifically comprises the following steps:

Step 1. Determine the control target, that is, when the converter tap-changer fails, the control system can quickly adjust to the correct converter tap-changer position, so that the firing angle of the rectifier side is kept between 12.5° and 17.5° run smoothly.

Step 2. The converter tap-changer control system is designed as a dual-input-single-output system. The input of the system is to collect the real-time operation data of the converter to be controlled at the beginning of a control cycle. The first input of the control system is is α, representing the firing angle, and the second input is the variation of the firing angle between two control cycles. These two inputs determine the output through the fuzzy reasoning of the variable domain fuzzy control system, and the output of the control system is Gear input for rheological taps.

Step 3. Use trigonometric functions to fuzzify the firing angle α and its variation

Step 4: Determine the firing angle, the variation of the firing angle, and the discourse domain of the output gear according to the change of α of the firing angle.

Step 5. Determine the variable universe fuzzy control rules according to the basic working principle of the converter transformer tap changer control system.

Step 6. The determined variable universe fuzzy is actually a multiple fuzzy conditional statement, which can be expressed in matrix form.

Step 7. The output control quantity of the fuzzy controller is obtained from the input quantity and the fuzzy relationship after the domain of discourse change according to the reasoning synthesis rule.

Step 8. Return to Step 1 when the next control cycle comes.

Through the variable universe fuzzy control, when a fault occurs and the firing angle of the rectifier side is severely exceeded, the gear position of the converter tap-changer can be adjusted quickly.

Simulation

The simulated working condition is bipolar unlocking 5000MW, and the gear position of the high-end valve group converter transformer tap on the rectification side cannot be adjusted due to a fault, and is fixed at gear 5.

It can be seen from the operation waveform diagrams in Figures 4 and 5 that the gear position of the high-end valve group on the rectifier side and the converter transformer tap cannot be adjusted due to a fault, and the operating condition is stable when it is fixed at gear 5, and the bipolar voltage reaches ±800kV respectively , the DC current is stable, the firing angle of the rectification side is about 14.75°, the arc extinguishing angle of the inverter side is about 19.7°, and the high-end valve group converter tap position of the rectification side is at gear 5.

Comparing the simulation waveforms without using variable universe fuzzy control under the same conditions, it can be seen from Figures 6 and 7 that without using variable universe fuzzy controller, it takes about 5 seconds for the firing angle of the rectifier side to reach 14°, and the control effect is faster and better when the variable domain fuzzy controller is used.

Claims (3)

1. A method for controlling a converter tap-changer based on the fuzzy domain of variable universe, characterized in that the converter tap-changer control method is realized by a converter tap-changer control system, and the converter tap-changer The control system is a dual-input-single-output system, and the trigger angle of the tap control signal and its variation are used as the two inputs of the fuzzy controller; the two inputs determine the output through the fuzzy reasoning of the variable universe fuzzy control system; including the following steps: 1) Determining the domain of trigger angle and its variation The domain of discourse refers to the variation range of the input quantity; the expansion factor is used to change the size of the domain of discourse; the design of the expansion factor; as shown in formula (1‐1); α _angle = (sumANGLE/30/DomainANGLE) ^0.8 α _dangle = (sumdANGLE/30/DomaindANGLE) ^0.8 (1-1) Among them, sumANGLE is the sum value of the firing angle angle of the first 30 cycles of the recorded current operation cycle, DomainANGLE is the domain value of the externally input converter trigger angle angle; sumdANGLE is the recorded value of the first 30 cycles of the current operation cycle The sum value of dangle, DomaindANGLE is the domain value of dangle, the variation of trigger angle of the converter input externally; Before the domain of discourse changes, the basic domain of discourse of the trigger angle angle is [0,0.5244], corresponding to the change of the angle from 0° to 30°, the basic domain of discourse of the trigger angle change dangle is [-0.1311,0.1311], corresponding to The angle transformation of d is from -7.5° to 7.5°; after the domain of discourse changes, the discourse domain of trigger angle angle becomes [0,0.5244*α _angle ], and the discourse domain of d trigger angle change amount angle becomes [‐0.1311* α _dangle ,0.1311*α _dangle ]. Domain of discourse refers to the variation range of the input quantity; 2) Fuzzification of system variables. the In the designed UHV converter tap-changer fuzzy controller, the input variables are fuzzy processed according to the triangular membership function, and the membership function is a triangle, as shown in formula (1-2); In the formula, x is the input quantity, a and b are the boundary values of fuzzy rules, is the degree of membership of a, is the membership value of b, μ(x) represents the membership function of the input x; For the values of the fuzzy rules of angle, they are Negative Big (NBB), Negative Big (NBS), Negative Medium Big (NMB), Negative Medium Small (NMS), Negative Small Big (NSB), Negative Small (NBB), Zero (ZO), Plus Small (PSS), Plus Small (PSB), Plus Medium Small (PMS), Plus Medium Big (PMB), Plus Size (PBS) and Plus Big (PBB); The discourse domain of trigger angle variation dangle is between [‐0.1311*α _dangle ,0.1311*α _dangle ], and there are 7 fuzzy rules for dangle, which are negative large (NB), negative medium (NM), and negative small (NS), Zero (ZO), Positive Small (PS), Positive Medium (PM) and Positive Big (PB); 3) The adjustment amount of the gear controlled by the controller is calculated by formula (1‐3): Among them, ΔTAP is the gear adjustment value of the converter tap changer controller, α is the input trigger angle value, It is the adjustment amount of tap switch gear corresponding to the change amount of firing angle. 2. The variable universe fuzzy converter tap changer control method according to claim 1, characterized in that, if the firing angle belongs to (0, 2.5°*α _angle ), and the variation of the firing angle belongs to (‐∞,‐7.5°*α _angle ), then the adjustment of the converter tap changer is down 6 gears, and the gear calculation process is ΔTAP＝(cos15°‐cos2.5°)/0.0125‐3＝6. 3. The variable universe fuzzy converter tap changer control method according to claim 1, wherein if the firing angle belongs to (2.5°*α _dangle , 7.5°*α _dangle ) and the change of firing angle ΔTAP=(cos15°-cos5°) _/0.0125-3=5 .