Alternating current and direct current composite voltage withstand test control method and device for circuit breaker

Abstract

The invention relates to the technical field of electrical equipment tests, and particularly provides an AC-DC composite voltage withstand test control method and device for a circuit breaker, and the method comprises the steps: applying a test AC voltage to a power supply side of the circuit breaker, and measuring the actual AC voltage of the power supply side; applying test direct-current voltage to the load side of the circuit breaker, and measuring actual direct-current voltage of the load side; adjusting the test AC voltage through an AC PID control algorithm and a feedforward control algorithm based on the target AC voltage and the actual AC voltage; and based on the target direct-current voltage and the actual direct-current voltage, adjusting the test direct-current voltage through a direct-current PID control algorithm and a feedforward control algorithm. According to the method, a feed-forward-PID composite control algorithm is deeply fused, the feed-forward control algorithm can counteract power grid voltage disturbance, the PID control algorithm with an integral saturation resisting function can ensure that the voltage smoothly rises and falls without overshoot, extremely high precision is maintained in a steady-state stage, and the control precision and stability of the test are greatly improved through the combination.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of power equipment testing, in particular to a control method and device for AC-DC composite withstand voltage testing of a circuit breaker. BACKGROUND

[0002] A circuit breaker is one of the most important protection and control elements in a power system, and its insulation performance is crucial. Traditional circuit breaker withstand voltage tests, such as power frequency withstand voltage tests and lightning impulse tests, usually only apply a single type of test voltage to one side of the breaking point of the circuit breaker. However, in actual operation, the circuit breaker may be in a more complex working condition, i.e., one end bears the DC voltage of a capacitor bank after switching off, and the other end bears the power frequency voltage of the system. This working condition is also the most severe working condition for the capacitor bank. The existing single voltage test method cannot effectively simulate the scenario of the composite insulation stress field in which AC and DC voltages simultaneously act on both sides of the breaking point of the circuit breaker, resulting in a deviation between the test evaluation conditions and the actual operating conditions, and the insulation reliability of the circuit breaker under real complex working conditions cannot be comprehensively evaluated. Therefore, there is an urgent need for a test method that can simulate such complex working conditions to more comprehensively and strictly test the insulation performance of the circuit breaker. However, the existing test device control methods are mostly open-loop or simple closed-loop control, and when dealing with the complex control scenario of AC-DC voltage composite loading, which is multi-variable, strongly coupled and high-precision, there are pain points such as insufficient control precision, poor dynamic response and lack of coordination. SUMMARY

[0003] The purpose of the present application is to overcome the deficiencies in the prior art and provide a control method and device for AC-DC composite withstand voltage testing of a circuit breaker, which can simulate the extreme working condition of the presence of AC and DC voltages on both sides of the breaking point of the circuit breaker and improve the control precision and stability of the test.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0005] In a first aspect, the present application provides a control method for AC-DC composite withstand voltage testing of a circuit breaker, comprising:

[0006] applying a test AC voltage to the power supply side of the circuit breaker and measuring the actual AC voltage of the power supply side of the circuit breaker; and applying a test DC voltage to the load side of the circuit breaker and measuring the actual DC voltage of the load side of the circuit breaker;

[0007] based on a preset target AC voltage and the actual AC voltage, adjusting the test AC voltage through an AC PID control algorithm and a feedforward control algorithm;

[0008] based on a preset target DC voltage and the actual DC voltage, adjusting the test DC voltage through a DC PID control algorithm and a feedforward control algorithm;

[0009] wherein the target AC voltage and the target DC voltage are both ramp functions varying with time;

[0010] freezing the integral gain of the AC PID control algorithm and the integral gain of the DC PID control algorithm, and setting the test AC voltage and the test DC voltage to 0, when the actual AC voltage exceeds a preset AC overvoltage threshold, the actual DC voltage exceeds a preset DC overvoltage threshold, or a leakage current of a breaker break exceeds a preset overcurrent threshold.

[0011] Further, based on a preset target AC voltage and the actual AC voltage, the test AC voltage is adjusted by an AC PID control algorithm and a feedforward control algorithm, including:

[0012] calculating an AC voltage error between the target AC voltage and the actual AC voltage;

[0013] obtaining an adjusted AC voltage by the AC PID control algorithm based on the AC voltage error;

[0014] obtaining a feedforward compensation by the feedforward control algorithm based on a grid voltage;

[0015] superimposing the adjusted AC voltage and the feedforward compensation to obtain an adjusted test AC voltage.

[0016] Further, based on a preset target DC voltage and the actual DC voltage, the test DC voltage is adjusted by a DC PID control algorithm and a feedforward control algorithm, including:

[0017] calculating a DC voltage error between the target DC voltage and the actual DC voltage;

[0018] obtaining an adjusted DC voltage by the DC PID control algorithm based on the DC voltage error;

[0019] obtaining a feedforward compensation by the feedforward control algorithm based on a grid voltage;

[0020] superimposing the adjusted DC voltage and the feedforward compensation to obtain an adjusted test DC voltage.

[0021] Further, a calculation formula of the adjusted AC voltage is as follows:

[0022] ;

[0023] wherein, represents the adjusted AC voltage; represents a proportional gain of the AC PID control algorithm; Kp represents the proportional gain of the AC PID control algorithm; Kd represents the differential gain of the AC PID control algorithm; V(t) represents the AC voltage error at time t;

[0024] The calculation formula for obtaining the adjusted DC voltage is as follows:

[0025] ;

[0026] Kp represents the proportional gain of the AC PID control algorithm; V(t) represents the AC voltage error at time t; Kp represents the proportional gain of the AC PID control algorithm; Ki represents the integral gain of the AC PID control algorithm; Kd represents the differential gain of the AC PID control algorithm; V(t) represents the AC voltage error at time t;

[0027] Further, based on the grid voltage, a feedforward compensation amount is obtained through the feedforward control algorithm, including:

[0028] The grid voltage is collected as a disturbance input;

[0029] According to the deviation of the disturbance input and the rated disturbance value, the feedforward compensation amount is calculated through the feedforward control algorithm.

[0030] Further, the calculation formula of the feedforward compensation amount is as follows:

[0031] ;

[0032] Kp represents the proportional gain of the AC PID control algorithm; V(t) represents the AC voltage error at time t; Kp represents the proportional gain of the AC PID control algorithm; V(t) represents the AC voltage error at time t; V(t) represents the AC voltage error at time t;

[0033] In a second aspect, the application also provides a control device for AC-DC composite withstand voltage test of a circuit breaker, comprising: a central control unit, an AC control unit, a DC control unit, an AC high-voltage generating unit and a DC high-voltage generating unit;

[0034] The central control unit is configured to receive test parameters set by a test personnel, and to issue the test parameters to the AC control unit and the DC control unit according to a preset test procedure; wherein the test parameters include: target AC voltage, target DC voltage, voltage rising rate, AC overvoltage threshold, DC overvoltage threshold and overcurrent threshold;

[0035] The alternating current control unit is configured to receive instructions of the central control unit and to perform closed-loop control on the alternating current high-voltage generating unit.

[0036] The direct current control unit is configured to receive instructions of the central control unit and to perform closed-loop control on the direct current high-voltage generating unit.

[0037] The alternating current high-voltage generating unit is configured to receive instructions of the alternating current control unit, to apply a test alternating current voltage to the power supply side of the circuit breaker, to measure an actual alternating current voltage of the power supply side of the circuit breaker, and to feed back the actual alternating current voltage to the alternating current control unit.

[0038] The direct current high-voltage generating unit is configured to receive instructions of the direct current control unit, to apply a test direct current voltage to the load side of the circuit breaker, to measure an actual direct current voltage of the load side of the circuit breaker, and to feed back the actual direct current voltage to the direct current control unit.

[0039] Further, the alternating current high-voltage generating unit comprises an alternating current voltage regulator, a power frequency test transformer and an alternating current voltage divider connected in sequence.

[0040] The alternating current voltage regulator is in communication connection with the alternating current control unit; the power frequency test transformer is connected with the power supply side of the circuit breaker; and the alternating current voltage divider is in communication connection with the alternating current control unit.

[0041] The direct current high-voltage generating unit comprises a direct current voltage regulator, a direct current high-voltage generator and a direct current voltage divider connected in sequence.

[0042] The direct current voltage regulator is in communication connection with the direct current control unit; the direct current high-voltage generator is connected with the load side of the circuit breaker; and the direct current voltage divider is in communication connection with the direct current control unit.

[0043] Further, the alternating current control unit and the direct current control unit comprise an embedded microprocessor.

[0044] The embedded microprocessor stores an alternating current PID control algorithm model, a direct current PID control algorithm model and a feedforward control algorithm model.

[0045] Further, a protection unit interlocked with the central control unit is further included.

[0046] The protection unit is configured to monitor the actual direct current voltage, the actual alternating current voltage and the leakage current of the circuit breaker fracture; and to send a fault signal to the central control unit when the actual alternating current voltage exceeds the alternating current overvoltage threshold, the actual direct current voltage exceeds the direct current overvoltage threshold or the leakage current of the circuit breaker fracture exceeds the overcurrent threshold.

[0047] The AC / DC composite withstand voltage test control method and device for circuit breakers provided by this invention accurately reproduces the extreme operating condition where AC and DC voltages exist simultaneously on both sides of the circuit breaker break. This can more effectively expose potential insulation defects and achieve a more comprehensive and rigorous assessment of the circuit breaker's insulation performance. The control method of this invention deeply integrates a feedforward-PID composite control algorithm. The feedforward control algorithm can actively cancel grid voltage disturbances, while the PID control algorithm with anti-integral saturation function can ensure smooth voltage rise and fall without overshoot and maintain extremely high accuracy in the steady-state stage. This combination greatly improves the repeatability, reliability, and safety of the test. The method of this invention enhances the automation level of the test, reduces dependence on test personnel, and can simultaneously monitor multiple parameters such as leakage current and partial discharge, providing test personnel with more status information and improving work efficiency. Attached Figure Description

[0048] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other embodiments based on these drawings without creative effort.

[0049] Figure 1 This is a flowchart illustrating a method for controlling the AC / DC composite withstand voltage test of a circuit breaker according to an embodiment of the present invention.

[0050] Figure 2 This is a schematic diagram of the structure of an AC / DC composite withstand voltage test control device for a circuit breaker provided in an embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram of the process for conducting AC / DC composite withstand voltage tests on circuit breakers using the AC / DC composite withstand voltage test control device of this embodiment of the invention. Detailed Implementation

[0052] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0053] like Figure 1 As shown in the figure, this embodiment of the invention provides a method for controlling the AC / DC composite withstand voltage test of a circuit breaker. Figure 1The flowchart is a flowchart of the control method for the AC-DC composite withstand voltage test of the circuit breaker. The flowchart only shows the logical sequence of the method in the embodiment. In other possible embodiments of the present application, the steps shown or described can be completed in a sequence different from that shown on the premise that they do not conflict with each other. Figure 1 The steps shown or described can be completed in a sequence different from that shown on the premise that they do not conflict with each other.

[0054] Referring to Figure 1 The method of the embodiment of the present application specifically includes the following steps:

[0055] Step S101: applying a test AC voltage to the power supply side of the circuit breaker, measuring the actual AC voltage of the power supply side of the circuit breaker, and applying a test DC voltage to the load side of the circuit breaker, measuring the actual DC voltage of the load side of the circuit breaker;

[0056] Step S102: adjusting the test AC voltage through an AC PID control algorithm and a feedforward control algorithm based on a preset target AC voltage and the actual AC voltage;

[0057] Step S103: adjusting the test DC voltage through a DC PID control algorithm and a feedforward control algorithm based on a preset target DC voltage and the actual DC voltage.

[0058] Before the test starts, test parameters such as the target AC voltage, the target DC voltage, the voltage rise rate, the AC overvoltage threshold, the DC overvoltage threshold, and the overcurrent threshold are set according to the test requirements and the type of the circuit breaker.

[0059] The target AC voltage and the target DC voltage are ramp functions that change with time, representing an ideal state. At the initial moment of the test, the test AC voltage is equivalent to the target AC voltage, and the test DC voltage is equivalent to the target DC voltage. Subsequently, the test AC voltage is closed-loop controlled through the AC PID control algorithm, and the test DC voltage is closed-loop controlled through the DC PID control algorithm.

[0060] In addition, the initial proportional gain, integral gain, and differential gain of the AC PID control algorithm and the DC PID control algorithm are also set in advance.

[0061] The proportional gain Kp is the gain of amplifying the current error, which determines the reaction of the PID control algorithm to the current deviation. When Kp increases, the algorithm response will be faster, and the error can be reduced faster. However, when Kp is too large, the system will oscillate violently (the output voltage will fluctuate greatly above and below the target value), and even become unstable, like the water temperature regulation that reacts too aggressively and keeps turning the valve on and off. Therefore, a suitable Kp value can ensure a fast response speed during the voltage rise stage.

[0062] The integral gain Ki is the gain that amplifies the accumulated historical error, and it determines the PID control algorithm's responsiveness to how long the deviation has persisted. Increasing Ki allows for faster elimination of steady-state error (i.e., eventually stopping at a value close to but not quite reaching the target). However, excessively large Ki not only leads to significant integral accumulation in the initial response phase, causing severe overshoot, but also exacerbates system oscillations and prolongs the settling time. Ki is crucial for ensuring the voltage ultimately stabilizes accurately.

[0063] The differential gain Kd is the gain related to the rate of change of the error. When Kd increases, the PID control algorithm becomes more "predictive," suppressing overshoot, reducing oscillations, and increasing system stability (equivalent to increasing damping). However, excessively large Kd makes the system extremely sensitive to high-frequency noise in the feedback signal, causing severe fluctuations in the control output and thus reducing the system's response speed. Therefore, a suitable Kd value is crucial for achieving smooth voltage boost and preventing voltage overshoot.

[0064] A built-in PID parameter self-tuning algorithm can be activated when testing a new type of circuit breaker for the first time to automatically calculate the optimal PID parameters, thereby adapting to the capacitive load characteristics of different circuit breakers.

[0065] In this embodiment of the invention, an anti-integral saturation mechanism is added to both the AC PID control algorithm and the DC PID control algorithm. The anti-integral saturation mechanism is a combination of strategies and calculation methods designed to correct the behavior of the integral term in the standard PID control. This invention employs both conditional integration and inverse calculation methods.

[0066] The conditional integral method determines whether to perform integral operations based on whether the output of the PID control algorithm is saturated.

[0067] First, the PID control algorithm, as normal, calculates an ideal output value without amplitude limiting. The calculation formula is as follows:

[0068] ;

[0069] in, Indicates the current control cycle. express Control cycle error, express Error in the control cycle; This represents the cumulative value of the integral term from the previous control cycle; This represents the proportional gain of the PID control algorithm. This represents the derivative gain of the PID control algorithm. This indicates the sampling time of the control cycle.

[0070] The calculated ideal output The actual output is obtained by applying the limiter to the output of the integrator .

[0071] The reverse calculation method is as follows And Continue to calculate the saturation difference, and the formula for calculating the saturation difference is as follows:

[0072] ;

[0073] Quantify the degree and direction of saturation, and the direction of saturation can be judged by the positive and negative of the saturation interpolation .

[0074] When updating the integral term, not only the error term is added, but also the saturation difference term, and the integral term update formula is as follows:

[0075] ;

[0076] Indicates the updated integral term value in the current period; Indicates the anti-saturation feedback gain, which is usually set to , Is the anti-saturation time constant.

[0077] Is a negative feedback term, which acts on the integral term in the opposite direction when the output is saturated, preventing it from continuing to accumulate. When not saturated, , the correction term disappears, and the algorithm degenerates into a standard integral update.

[0078] In the boost stage, the anti-saturation mechanism can effectively prevent voltage overshoot and protect the circuit breaker from unnecessary overvoltage stress. After the emergency shutdown signal is issued, the integral terms of the two loops can be immediately frozen. In this way, when the set value is zero, the PID control algorithm can make a proper negative feedback control to smoothly reduce the voltage to zero, preparing for the next test. Without the anti-saturation algorithm, the integral term will accumulate wildly in the negative direction, which may cause the PID control algorithm to output a very large negative value, although the physical booster is only turned off to 0%, but it will cause problems when recovering.

[0079] The adjustment idea of the application for the test AC voltage and the test DC voltage is the same, no matter the DC voltage or the AC voltage, the establishment and change of the voltage cannot be completed instantaneously, when the target voltage instruction is issued, the actual voltage will have a short lag in rising. The task of the PID control algorithm of the application is to reduce the lag error as much as possible by calculating the error (target value-actual value) and outputting the control signal. However, the circuit breaker presents a complex capacitive and resistive load characteristic under high voltage, especially in the voltage rising process, the polarization of the insulation material and the possible micro leakage current will cause the dynamic change of the load, thereby affecting the stable tracking of the actual voltage. In addition, considering that the grid voltage fluctuates, it will directly cause the fluctuation of the output test voltage, thereby deviating from the target slope, therefore, the application compensates the influence of the grid fluctuation on the test voltage through the feedforward control algorithm.

[0080] Step S102 specifically comprises:

[0081] Step S1021: calculating the AC voltage error between the target AC voltage and the actual AC voltage;

[0082] Step S1022: based on the AC voltage error, obtaining the adjusted AC voltage through the AC PID control algorithm, the calculation formula is as follows:

[0083] ;

[0084] Among them, The adjusted AC voltage is represented by Kp, Ki and Kd. Kp represents the proportional gain of the AC PID control algorithm. Ki represents the integral gain of the AC PID control algorithm. Kd represents the differential gain of the AC PID control algorithm. The AC voltage error at t time is represented by e(t). The change rate of the AC voltage error, that is, the change speed of the error with time is represented by de(t) / dt.

[0085] The calculation formula is a decision algorithm, which calculates a "control command" based on the current error, so that the controlled object (test AC voltage) can quickly, smoothly and accurately reach and maintain the target value. It is composed of three independent parts, which represent the response strategies for current, past and future errors.

[0086] The first term is the proportional term, which is the immediate reaction to the "current" error, the output of which is proportional to the size of the current error, and the error The larger the error is, the larger the output of this term is.

[0087] The second term is the integral term, which corrects the cumulative effect of all the tiny errors in the past, and its output is proportional to the integral of the error over time (i.e. the cumulative sum of the error). From the start of the test to now, the error value at each moment is being accumulated, and the integral gain determines the degree of influence of this cumulative value on the output.

[0088] The third term is the derivative term, which can predict the trend of the error in the future and react in advance. Its output is proportional to the rate of change of the error (i.e. the speed of change of the error). Its core task is to "dampen" and "suppress overshoot", that is, if the voltage rises too fast, that is, the error between the actual value and the set value decreases rapidly, this term will output a large negative value to offset the positive value output by the proportional term and the integral term.

[0089] Step S1023: based on the grid voltage, obtaining a feedforward compensation amount through the feedforward control algorithm;

[0090] Step S1023 specifically includes:

[0091] collecting the grid voltage as a disturbance input ;

[0092] According to the deviation of the disturbance input and the pre-set rated disturbance value , the feedforward compensation amount is calculated through the feedforward control algorithm, and the calculation formula is as follows:

[0093] ;

[0094] Wherein, represents the feedforward compensation amount; represents the feedforward compensation gain; represents the disturbance input collected at t moment.

[0095] Step S1024: superimposing the adjustment alternating voltage and the feedforward compensation amount to obtain an adjusted test alternating voltage.

[0096] The method of the present application monitors the grid voltage in real time. When the grid voltage fluctuation is detected, the feedforward control algorithm will directly calculate the feedforward compensation amount in proportion without the PID control algorithm, and superimpose it on the output of the alternating PID control algorithm and the direct current PID control algorithm, so as to offset the influence of the grid fluctuation on the test voltage in advance.

[0097] On the other hand, step S103 specifically includes:

[0098] Step S1031: calculating the direct current voltage error between the target direct current voltage and the actual direct current voltage;

[0099] Step S1032: based on the DC voltage error, obtaining an adjusted DC voltage by the DC PID control algorithm, the calculation formula is as follows:

[0100]

[0101] Wherein, represents the adjusted DC voltage; represents the proportional gain of the DC PID control algorithm; represents the integral gain of the DC PID control algorithm; represents the differential gain of the DC PID control algorithm; represents the DC voltage error at t time.

[0102] Step S1033: based on the grid voltage, obtaining a feedforward compensation amount by the feedforward control algorithm;

[0103] The specific obtaining steps of the feedforward compensation amount refer to the above-mentioned step S1023, and will not be described here.

[0104] Step S1034: superimposing the adjusted DC voltage and the feedforward compensation amount to obtain an adjusted test DC voltage.

[0105] In addition, when the actual AC voltage exceeds the AC overvoltage threshold, the actual DC voltage exceeds the DC overvoltage threshold, or the leakage current of the breaker breakage exceeds the overcurrent threshold, the integral gain of the AC PID control algorithm and the integral gain of the DC PID control algorithm are frozen to prevent the accumulation of error values during the voltage reduction process, and the test AC voltage and test DC voltage are switched to 0 instantaneously. The AC PID control algorithm and the DC PID control algorithm drive the test AC voltage and the test DC voltage to quickly and smoothly return to zero according to the huge negative error, realize synchronous and undamped safe voltage reduction, and maximize the protection of the equipment.

[0106] On the other hand, as Figure 2 indicated, the embodiment of the present application also provides a kind of AC-DC composite withstand voltage test control device of circuit breaker, the device provided in the embodiment of the present application can realize the control method of AC-DC composite withstand voltage test of circuit breaker in the above-mentioned embodiment, Figure 3 It is shown that the AC-DC composite withstand voltage test of circuit breaker is carried out by the AC-DC composite withstand voltage test control device of circuit breaker of the embodiment of the present application.

[0107] Referring to Figure 2 , the device of the embodiment of the present application includes: central control unit, AC control unit, DC control unit, AC high voltage generating unit and DC high voltage generating unit;

[0108] ​The central control unit is configured to receive test parameters set by a test personnel, and to issue the test parameters to the AC control unit and the DC control unit according to a preset test procedure; wherein the test parameters include: a target AC voltage, a target DC voltage, a boosting rate, an AC overvoltage threshold, a DC overvoltage threshold, and an overcurrent threshold.

[0109] The AC control unit is configured to receive instructions of the central control unit, and to perform closed-loop control on the AC high-voltage generating unit.

[0110] The DC control unit is configured to receive instructions of the central control unit, and to perform closed-loop control on the DC high-voltage generating unit.

[0111] The AC high-voltage generating unit is configured to receive instructions of the AC control unit, to apply a test AC voltage to a power supply side of a circuit breaker, to measure an actual AC voltage of the power supply side of the circuit breaker, and to feed back the actual AC voltage to the AC control unit.

[0112] The DC high-voltage generating unit is configured to receive instructions of the DC control unit, to apply a test DC voltage to a load side of a circuit breaker, to measure an actual DC voltage of the load side of the circuit breaker, and to feed back the actual DC voltage to the DC control unit.

[0113] The central control unit of the embodiment of the application includes a main controller CPU and a man-machine interactive interface. The main controller CPU is the operation and control core of the central control unit, responsible for performing logical judgment, numerical calculation and coordinating the entire test device. It issues instructions according to a preset test procedure, coordinates the AC control unit and the DC control unit to act synchronously or in sequence, and is responsible for issuing test parameters set by a test personnel through the man-machine interactive interface, such as a target AC voltage, a target DC voltage, a boosting rate, an AC overvoltage threshold, a DC overvoltage threshold, and an overcurrent threshold, to the AC control unit and the DC control unit; at the same time, it receives real-time actual AC voltage and actual DC voltage data from the AC control unit and the DC control unit, and receives state information such as leakage current from the protection unit.

[0114] The man-machine interactive interface provides a graphical or form input interface for a test personnel to set all test parameters, and to display key state information of the test device in real time and intuitively. When an abnormality occurs, the man-machine interactive interface will issue an alarm information to the operator in an eye-catching way. Historical test data and fault logs are recorded and can be queried for subsequent analysis and report generation.

[0115] The AC high-voltage generating unit comprises an AC voltage regulator, a power frequency test transformer and an AC voltage divider connected in sequence; the AC voltage regulator is in communication connection with the AC control unit, the power frequency test transformer is connected to the power supply side of the circuit breaker, and the AC voltage divider is in communication connection with the AC control unit.

[0116] Specifically, the AC voltage regulator adjusts its output voltage according to the control signal output by the AC control unit, thereby controlling the input voltage of the power frequency test transformer; the power frequency test transformer is used to step up the low voltage output by the AC voltage regulator to the required test AC voltage and apply it to the power supply side of the circuit breaker; the AC voltage divider is used to measure the actual AC voltage of the power supply side of the circuit breaker in real time and feed it back to the AC control unit, thereby constituting a closed-loop control.

[0117] The DC high-voltage generating unit comprises a DC voltage regulator, a DC high-voltage generator and a DC voltage divider connected in sequence; the DC voltage regulator is in communication connection with the DC control unit, the DC high-voltage generator is connected to the load side of the circuit breaker, and the DC voltage divider is in communication connection with the DC control unit.

[0118] Specifically, the DC voltage regulator adjusts its output voltage according to the control signal output by the DC control unit, thereby controlling the input voltage of the DC high-voltage generator; the DC high-voltage generator is used to convert the low voltage output by the DC voltage regulator into the required test DC voltage and apply it to the load side of the circuit breaker; the DC voltage divider is used to measure the actual DC voltage of the load side of the circuit breaker in real time and feed it back to the DC control unit, thereby constituting a closed-loop control.

[0119] In the embodiment of the application, the core of the AC control unit and the DC control unit is an embedded microprocessor, and the embedded microprocessor stores an AC PID control algorithm model, a DC PID control algorithm model and a feedforward control algorithm model.

[0120] The AC high-voltage generating unit, the DC high-voltage generating unit and the circuit breaker itself in the test device of the application cannot complete the establishment and change of voltage instantaneously. After the target voltage instruction of the control unit is issued, the actual voltage of the high-voltage generating unit will have a short lag. The device of the application calculates the error between the target value and the actual value by the control algorithm model and outputs a control signal to reduce the lag error as much as possible. In addition, considering that the grid voltage fluctuates, if the grid voltage itself fluctuates (for example, ±10%), it will directly cause the test voltage output to fluctuate, thereby deviating from the target slope. Therefore, the device of the application compensates the influence of grid fluctuation on the test voltage by the feedforward control algorithm model.

[0121] The calculation processes of the AC PID control algorithm model, the DC PID control algorithm model and the feedforward control algorithm model are similar to those in the AC / DC composite withstand voltage test control method of the circuit breaker, and will not be described here.

[0122] The device further comprises a protection unit interlocked with the central control unit, configured to monitor the actual DC voltage, the actual AC voltage and the leakage current of the circuit breaker break; and send a fault signal to the main controller CPU and the human-computer interaction interface when the actual AC voltage exceeds the AC overvoltage threshold, the actual DC voltage exceeds the DC overvoltage threshold or the leakage current of the circuit breaker break exceeds the overcurrent threshold.

[0123] After the human-computer interaction interface receives the fault signal, it will send an alarm information to the test operator in a conspicuous way. After the main controller CPU receives the fault signal, it will immediately execute an emergency shutdown program, send an emergency shutdown instruction to the AC control unit and the DC control unit to force them to stop the current PID control operation; freeze the integral term of the AC PID control algorithm and the DC PID control algorithm to prevent integral saturation caused by sudden change of the set value; set the set value of the test AC voltage and the test DC voltage to zero instantaneously, start the synchronous voltage reduction process; control the AC voltage regulator and the DC voltage regulator to zero output, cut off the high-voltage power supply; record the fault type, occurrence time and related voltage and current data and store them into the historical database; after the test operator confirms and resets, the device can enter the standby state and prepare for the next test.

[0124] It should be noted that the term "comprising" and its variants used in the embodiments of the present application are open and inclusive, i.e., "including but not limited to". The term "based on" is "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modification of "one" and "multiple" mentioned in the embodiments of the present application is illustrative and not restrictive, and those skilled in the art should understand that unless otherwise explicitly stated in the context, it should be understood as "one or more".

[0125] The various steps described in the method embodiments provided by the embodiments of the present application can be executed in different orders and / or in parallel. In addition, the method embodiments can include additional steps and / or omit the execution of the steps shown. The protection scope of the present application is not limited in this respect.

[0126] The word "implementation" in this description refers to the fact that the specific features, structures, or characteristics described in connection with an implementation can be included in at least one implementation of the invention. The occurrence of the phrase in various locations and repetitions of the phrase throughout the specification does not necessarily all refer to the same implementation, nor does it necessarily mean that other implementations are mutually exclusive or alternative. Each implementation described in this specification is described in a related manner, and the same or similar parts of each implementation refer to each other. In particular, for device, apparatus, system implementations, since they are basically similar to method implementations, the description is relatively simple, and the relevant parts refer to the part of the method implementation description.

[0127] The above-described implementations only express several implementation manners of the present invention, and the description is relatively specific and detailed, but it cannot be understood as a limitation on the protection scope. It should be noted that, for ordinary skilled persons in the art, under the premise of not departing from the inventive concept, a number of modifications and improvements can be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A control method of AC-DC combined withstand voltage test of a circuit breaker, characterized by, The method comprises: applying a test AC voltage to the power side of the circuit breaker and measuring an actual AC voltage of the power side of the circuit breaker; and applying a test DC voltage to the load side of the circuit breaker and measuring an actual DC voltage of the load side of the circuit breaker; adjusting the test AC voltage based on a preset target AC voltage and the actual AC voltage by an AC PID control algorithm and a feedforward control algorithm; adjusting the test DC voltage based on a preset target DC voltage and the actual DC voltage by a DC PID control algorithm and a feedforward control algorithm; wherein the target AC voltage and the target DC voltage are both ramp functions varying with time; when the actual AC voltage exceeds a preset AC overvoltage threshold, the actual DC voltage exceeds a preset DC overvoltage threshold, or a leakage current of a breaking gap of the circuit breaker exceeds a preset overcurrent threshold, freezing integral gains of the AC PID control algorithm and the DC PID control algorithm, and setting the test AC voltage and the test DC voltage to 0.

2. The control method of the AC-DC combined withstand voltage test of a circuit breaker according to claim 1, characterized by, The adjusting of the test AC voltage based on the preset target AC voltage and the actual AC voltage by the AC PID control algorithm and the feedforward control algorithm comprises: calculating an AC voltage error between the target AC voltage and the actual AC voltage; obtaining an adjusted AC voltage based on the AC voltage error by the AC PID control algorithm; obtaining a feedforward compensation based on a grid voltage by the feedforward control algorithm; superimposing the adjusted AC voltage and the feedforward compensation to obtain an adjusted test AC voltage.

3. The control method of the AC-DC combined withstand voltage test of a circuit breaker according to claim 2, characterized by, The adjusting of the test DC voltage based on the preset target DC voltage and the actual DC voltage by the DC PID control algorithm and the feedforward control algorithm comprises: calculating a DC voltage error between the target DC voltage and the actual DC voltage; obtaining an adjusted DC voltage based on the DC voltage error by the DC PID control algorithm; obtaining a feedforward compensation based on a grid voltage by the feedforward control algorithm; superimposing the adjusted DC voltage and the feedforward compensation to obtain an adjusted test DC voltage.

4. The control method of the AC-DC combined withstand voltage test of a circuit breaker according to claim 3, characterized by, The calculation formula of the adjusted AC voltage is as follows: ； wherein, represents an adjusted AC voltage; represents a proportional gain of the AC PID control algorithm; represents an integral gain of the AC PID control algorithm; represents a differential gain of the AC PID control algorithm; represents an AC voltage error at time t; The calculation formula of the adjusted DC voltage is as follows: ； wherein, represents an adjusted direct current voltage; represents a proportional gain of a direct current PID control algorithm; represents an integral gain of a direct current PID control algorithm; represents a differential gain of a direct current PID control algorithm; represents a direct current voltage error at time t.

5. The control method of the AC-DC combined withstand voltage test of a circuit breaker according to claim 2 or 3, characterized by, The obtaining of the feedforward compensation based on the grid voltage by the feedforward control algorithm comprises: collecting the grid voltage as a disturbance input; calculating the feedforward compensation based on a deviation between the disturbance input and a rated disturbance value by the feedforward control algorithm.

6. The control method of the AC-DC combined withstand voltage test of a circuit breaker according to claim 5, characterized by, The calculation formula of the feedforward compensation is as follows: ； wherein, represents a feedforward compensation amount; represents a feedforward compensation gain; represents a disturbance input collected at time t; represents a rated disturbance value.

7. A control device for AC-DC combined withstand voltage test of a circuit breaker, characterized by comprising: The method comprises: a central control unit, an AC control unit, a DC control unit, an AC high-voltage generating unit, and a DC high-voltage generating unit; the central control unit is configured to receive test parameters set by a test personnel, and to issue the test parameters to the AC control unit and the DC control unit according to a preset test procedure; wherein the test parameters comprise a target AC voltage, a target DC voltage, a voltage-rising rate, an AC overvoltage threshold, a DC overvoltage threshold, and an overcurrent threshold. The AC control unit is configured to receive instructions from the central control unit and to perform closed-loop control on the AC high-voltage generating unit. The DC control unit is configured to receive instructions from the central control unit and to perform closed-loop control on the DC high-voltage generating unit. The AC high-voltage generating unit is configured to receive instructions from the AC control unit, to apply a test AC voltage to the power side of the circuit breaker, to measure the actual AC voltage of the power side of the circuit breaker, and to feed back the actual AC voltage to the AC control unit. The DC high-voltage generating unit is configured to receive instructions from the DC control unit, to apply a test DC voltage to the load side of the circuit breaker, to measure the actual DC voltage of the load side of the circuit breaker, and to feed back the actual DC voltage to the DC control unit.

8. The control device for AC-DC combined withstand voltage test of circuit breaker according to claim 7, wherein, The AC high-voltage generating unit comprises an AC voltage regulator, a power-frequency test transformer, and an AC voltage divider connected in sequence. The AC voltage regulator is in communication connection with the AC control unit; the power-frequency test transformer is connected to the power side of the circuit breaker; and the AC voltage divider is in communication connection with the AC control unit. The DC high-voltage generating unit comprises a DC voltage regulator, a DC high-voltage generator, and a DC voltage divider connected in sequence. The DC voltage regulator is in communication connection with the DC control unit; the DC high-voltage generator is connected to the load side of the circuit breaker; and the DC voltage divider is in communication connection with the DC control unit.

9. The control device for AC-DC combined withstand voltage test of circuit breaker according to claim 7, wherein, The AC control unit and the DC control unit comprise embedded microprocessors. The embedded microprocessors store an AC PID control algorithm model, a DC PID control algorithm model, and a feedforward control algorithm model.

10. The control device for AC-DC combined withstand voltage test of circuit breaker according to claim 7, wherein, A protection unit is further provided in interlock with the central control unit. The protection unit is configured to monitor the actual DC voltage, the actual AC voltage, and the leakage current of the circuit breaker; and to send a fault signal to the central control unit when the actual AC voltage exceeds the AC overvoltage threshold, the actual DC voltage exceeds the DC overvoltage threshold, or the leakage current of the circuit breaker exceeds the overcurrent threshold.

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