Electric fireproof current-limiting protection system with normalized rated current amplitude

Abstract

The invention provides an electrical fireproof current-limiting protection system with normalized rated current amplitude, and relates to the technical field of electrical safety. The system converts the output voltage of a current sensor under different rated currents into a standard sinusoidal signal through hardware real-time rated current amplitude self-adaptive normalization processing; the system is not changed depending on the rated current; compensating the time delay of the instantaneous current and the main loop by using the difference value between the instantaneous current zero-crossing point and the main loop voltage zero-crossing point; and the instantaneous current values at different moments are directly compared with the corresponding short circuit threshold function values to realize short circuit fault identification, and the effective current values are directly compared with the overload threshold function values to judge overload faults. Through the design, rapid and accurate short circuit and overload protection can be realized, the risk of electrical fire is effectively reduced, and the reliability and efficiency of electrical safety protection are improved. The invention aims to solve the problems of poor universality, easy misjudgment and long response time of the existing electrical fireproof protection device for different rated currents.

Description

Technical Field

[0001] The invention relates to the technical field of electrical safety, and in particular to an electrical fire prevention and current limiting protection system with normalized rated current amplitude. Background Art

[0002] Electrical fires have become one of the major threats to the safety of modern society due to their high incidence and destructiveness. According to statistics, electrical fires currently account for more than one-third of all fires, and in major fires, the proportion of electrical fires is as high as more than two-thirds; the high proportion of electrical fires has not only caused serious personal injuries and deaths, but also caused huge property losses. Among them, short circuit and overload are the two main causes of electrical line failures; when a short circuit occurs in the line, hot sparks and local instantaneous high temperatures may be generated, and long-term overload operation will cause the line to overheat; these high temperatures and sparks are important causes of electrical fires. Therefore, fire prevention and current limiting protection methods have become a key technology in the field of electrical safety.

[0003] At present, in order to prevent such fires, a variety of current limiting protection technologies have been developed. These technologies usually use current limiting protection devices. The existing current limiting protection devices are mainly short-circuit protectors, which perform disconnection protection when the circuit current exceeds the short-circuit setting current, and perform delayed disconnection protection when the current exceeds the overload setting current; they can quickly disconnect the circuit when the current exceeds the set value to prevent further damage. Since the action time of a general overcurrent protector is between tens and hundreds of milliseconds, from the moment of short circuit to the complete disconnection of the circuit, the loop current may continue to rise to hundreds of times the rated current. The electric sparks and high temperatures generated by such a large current are very likely to cause fires. In order to shorten the disconnection time and reduce the probability of electrical fires, fire-proof current limiting protection methods for contactless switches are currently available on the market. These methods use real-time current values, the rate of change of currents between two adjacent points, and other processing in the algorithm. When the current detection value exceeds the preset threshold, the protector will start the protection action.

[0004] Despite this, existing protection methods and devices still have some shortcomings. First, when the rated current is different, the instantaneous value and rate of change of the current will change accordingly, making the "threshold" for determining short circuit or overload a variable that changes with the rated current, resulting in a protector with one rated current that cannot be used for circuits with other rated currents, and poor versatility. Secondly, these methods are only applicable to standard sinusoidal current waveforms. When the current waveform deviates from the sinusoidal wave or the waveform changes suddenly due to the influence of load characteristics, the current change rate approaches infinity, far exceeding the short-circuit threshold, causing the protector to malfunction. In addition, due to the influence of the load or signal processing circuit, there may be a delay between the instantaneous current and the loop voltage, and the instantaneous current value at one moment is used to make an incorrect comparison with the threshold at another moment, causing misjudgment. Finally, when the instantaneous current relative change rate method is adopted, the short-circuit current setting coefficient needs to be input on the keyboard-display, and real-time detection cannot be achieved; when the load current has a flat shoulder, the current relative change rate also becomes an indeterminate form of 0÷0, and the algorithm fails; when the sampling interval is very small, the numerator of the current relative change rate is a very small number close to 0, and the denominator is a finite number, and the size of the quotient loses comparability.

[0005] Simply put, these protectors have limitations in response time and protection algorithms, which may cause them to fail to respond to short circuits or overloads in a timely manner in practical applications, or to malfunction in the case of non-sinusoidal waveforms or current mutations. Existing current limiting protection devices usually rely on the instantaneous value or rate of change of the current to determine whether a short circuit or overload has occurred. When faced with circuits with different rated currents, these methods need to adjust the settings of the protector to adapt to different current levels, which limits the versatility and flexibility of the protector. In addition, due to the influence of load characteristics or signal processing circuits, the current signal may have a phase difference with the voltage signal, causing the protector to have errors when comparing the current value and the threshold, increasing the risk of misjudgment. Therefore, it is necessary to develop a new electrical fire current limiting protection method and device with normalized rated current to solve the above problems.

[0006] In view of this, this application is filed. Summary of the invention

[0007] The present invention provides an electrical fire protection and current limiting protection system with normalized rated current amplitude, which can at least partially improve the above-mentioned problem.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] An electrical fire prevention and current limiting protection system with normalized rated current amplitude, comprising: a control component, a first zero-crossing detection component, an instantaneous current acquisition component, an amplitude normalization network module, a second zero-crossing detection circuit module, an effective value detection module, a power supply module, and an IGBT switch module, wherein the input end of the first zero-crossing detection component is connected in parallel to the electrical circuit of the load, the output end of the first zero-crossing detection component is electrically connected to the first external interrupt input end of the control component, the input end of the instantaneous current acquisition component is connected in series to the electrical circuit of the load, and the output end of the instantaneous current acquisition component is connected to the amplitude normalization network module. The input end of the normalization network module is electrically connected, the output end of the amplitude normalization network module is electrically connected to the input end of the second zero-crossing detection circuit module and the input end of the effective value detection module, the output end of the second zero-crossing detection circuit module is electrically connected to the second external interrupt input end (INT0) of the control component, the output end of the effective value detection module is electrically connected to the first digital-to-analog conversion input port (AD1) of the control component, the output end of the control component is electrically connected to the control end of the IGBT switch module, and the output end of the power supply module is electrically connected to the power supply end of the control component;

[0010] Wherein, the amplitude normalization network module is configured to convert the voltage signal output by the instantaneous current acquisition component under different rated currents into a standard sinusoidal signal, and the effective value detection module is configured to obtain the effective value of the induced voltage output by the instantaneous current acquisition component;

[0011] The control component is configured to implement the following steps by executing a computer program stored therein:

[0012] Obtain preset parameter information and perform initialization processing;

[0013] Acquire the first positive pulse signal sent by the first zero-crossing detection component, and perform delay detection processing or sampling processing according to the first positive pulse signal to detect the delay beat of the instantaneous current and the load main circuit;

[0014] Obtaining a second positive pulse signal sent by the second zero-crossing detection circuit module, performing calculation processing based on the second positive pulse signal, obtaining a delay of the voltage to be received by the instantaneous current acquisition component relative to the load main circuit voltage, and determining a delay beat size based on the delay;

[0015] According to the number of sampling points and the delay beat, the short-circuit threshold at the current moment is determined, and the short-circuit threshold is compared with the sampling value of the instantaneous current value at the current moment to generate a short-circuit fault judgment result;

[0016] Obtaining the effective value sent by the effective value detection module, comparing the effective value with the overload current threshold, and generating an overload judgment result;

[0017] When the short-circuit fault judgment result is a short-circuit fault, or the overload judgment result is an overload, the IGBT switch module is turned off to achieve short-circuit protection and overload protection.

[0018] In summary, the electrical fire protection and current limiting protection system with normalized rated current amplitude uses a normalized network module to normalize the amplitude of the rated current. When the rated current is between 0A and 63A, the output amplitude of the normalized network module is always equal to 1, so that the system does not depend on the rated current. At the same time, the difference between the instantaneous current zero-crossing point and the main circuit voltage zero-crossing point is used to compensate for the delay between the instantaneous current and the main circuit. The amplitude of the instantaneous current at different times is directly compared with the corresponding short-circuit threshold function value to realize short-circuit fault identification, and the effective current is directly compared with the overload threshold function to judge the overload fault. It effectively solves the problems of poor versatility, easy misjudgment, and long response time of electrical fire protection devices in the prior art for different rated currents. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a module schematic diagram of an electrical fire protection and current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention;

[0020] Figure 2 1 is a schematic diagram of a module of an amplitude normalization network module of an electrical fire protection and current limiting protection system for normalizing rated current amplitude provided by an embodiment of the present invention;

[0021] Figure 3 It is a schematic representation of the short-circuit protection threshold of the electrical fire protection current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention;

[0022] Figure 4 It is a schematic diagram showing the division of detection time within one half-wave of the electrical fire protection and current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention;

[0023] Figure 5 is an initialization flow chart of an electrical fire protection and current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention;

[0024] Figure 6 It is a flow chart of instantaneous current and main circuit voltage delay detection of an electrical fire protection current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention;

[0025] Figure 7 It is a flow chart of INT1 effective value detection interruption service of an electrical fire protection and current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention;

[0026] Figure 8It is a short-circuit detection interruption service flow chart of an electrical fire protection and current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] refer to Figure 1 As shown, the first embodiment of the present invention discloses an electrical fire protection and current limiting protection system with normalized rated current amplitude, which includes: a control component, a first zero-crossing detection component, an instantaneous current acquisition component, an amplitude normalization network module 6, a second zero-crossing detection circuit module 8, an effective value detection module 9, a power supply module 5, and an IGBT switch module 12, wherein the input end of the first zero-crossing detection component is connected in parallel to the electrical circuit of the load, the output end of the first zero-crossing detection component is electrically connected to the first external interrupt input end of the control component, the input end of the instantaneous current acquisition component is connected in series to the electrical circuit of the load, and the output end of the instantaneous current acquisition component is electrically connected to the first external interrupt input end of the control component. The output end is electrically connected to the input end of the amplitude normalization network module 6, the output end of the amplitude normalization network module 6 is electrically connected to the input end of the second zero-crossing detection circuit module 8 and the input end of the effective value detection module 9, the output end of the second zero-crossing detection circuit module 8 is electrically connected to the second external interrupt input end INT0 of the control component, the output end of the effective value detection module 9 is electrically connected to the first digital-to-analog conversion input port AD1 of the control component, the output end of the control component is electrically connected to the control end of the IGBT switch module 12, and the output end of the power supply module 5 is electrically connected to the power supply end of the control component;

[0029] Among them, the amplitude normalization network module 6 is configured to convert the voltage signal output by the instantaneous current acquisition component under different rated currents into a standard sinusoidal signal, and the effective value detection module 9 is configured to obtain the effective value of the induced voltage output by the instantaneous current acquisition component.

[0030] Preferably, the control component includes a microprocessor 10 and a core algorithm module 11, wherein the core algorithm module 11 is configured in a storage register of the microprocessor 10;

[0031] The first zero-crossing detection component includes a voltage conversion circuit 1 and a first zero-crossing detection circuit module 2, wherein the input end of the voltage conversion circuit 1 is connected in parallel to the electrical circuit of the load, the output end of the voltage conversion circuit 1 is electrically connected to the input end of the first zero-crossing detection circuit module 2, and the output end of the first zero-crossing detection circuit module 2 is electrically connected to the first external interrupt input end INT1 of the microprocessor 10, wherein the voltage conversion circuit 1 is configured to sense the voltage signal of the load main circuit, and the first zero-crossing detection circuit module 2 is configured to detect the zero-crossing point of the voltage waveform of the load main circuit.

[0032] Preferably, the instantaneous current acquisition component includes a current sensor 3 and a power frequency filter module 4, the input end of the current sensor 3 is connected in series to the electrical circuit of the load, the output end of the current sensor 3 is electrically connected to the input end of the power frequency filter module 4, and the output end of the power frequency filter module 4 is electrically connected to the input end of the amplitude normalization network module 6, wherein the current sensor 3 is configured to sense the instantaneous current I of the load main circuit instant , and the instantaneous current I instant Converted into voltage signal U in The power frequency filter module 4 is configured to extract the instantaneous current I instant The power frequency component in the conversion formula is: U in =I instant ×S, S is the sensitivity of the current sensor 3.

[0033] See also Figure 2 Preferably, the amplitude normalization network module 6 includes a resistor network, a first operational amplifier U1, and a second operational amplifier U2, the input end of the resistor network is electrically connected to the output end of the power frequency filter module 4, the first end of the resistor network is electrically connected to the negative electrode of the first operational amplifier U1, the second end of the resistor network is electrically connected to the output end of the first operational amplifier U1, the output end of the first operational amplifier U1 is electrically connected to the negative electrode of the second operational amplifier U2, the output end of the second operational amplifier U2 is electrically connected to the input end of the second zero-crossing detection circuit module, the positive electrode of the first operational amplifier U1 and the positive electrode of the second operational amplifier U2 are grounded, wherein the resistor network is the feedback resistor of the first operational amplifier U1.

[0034] Preferably, the resistor network includes a first resistor R1, a dip switch, nine resistors, a second resistor R2, and a third resistor R3, the nine resistors are connected in parallel through the dip switch, one end of the first resistor R1 is electrically connected to the output end of the power frequency filter module, the other end of the first resistor R1 is electrically connected to the negative electrode of the first operational amplifier U1, the output end of the first operational amplifier U1 is electrically connected to the negative electrode of the second operational amplifier U2 through the second resistor R2, and the other end of the second resistor R2 is electrically connected to the output end of the second operational amplifier U2 through the third resistor R3;

[0035] The dip switch is configured to set a rated current. When the rated current corresponds to the level of any one of the nine resistors, the output voltage of the first operational amplifier U1 is -1V, and the output voltage of the second operational amplifier U2 is 1V or 0.5V.

[0036] In this embodiment, the amplitude normalization network module 6 is used to convert the output voltage of the current sensor under different rated currents into a standard sinusoidal signal with an amplitude constant equal to 1. When the instantaneous current is greater than the rated current, the amplitude of the sinusoidal signal is greater than 1, and when the instantaneous current is less than the rated current, the amplitude of the sinusoidal signal is less than 1. In short, the amplitude normalization network module 6 converts different rated currents into an output voltage of 1V, and can also be converted into a voltage of 0.5V according to specific application scenarios, which facilitates data collection.

[0037] Using nine resistors R i The first operational amplifier U1 is composed of a feedback resistor and a dip switch, and the feedback resistor is connected across the inverting input terminal and the output terminal of the first operational amplifier U1; for a rated current of 6A to 63A, the output of the first operational amplifier U1 is always equal to -1V. Specifically, the current limiting protection of circuits with different rated currents only needs to turn on the corresponding dip switch, and the algorithm and hardware are independent of the rated current, thereby ensuring the versatility of the current limiting protection device.

[0038] Among them, the resistor R i The subscript represents the rated current value, i = 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A; it can be seen that when the rated current of the amplitude normalization network module 6 is 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A, the output of the first operational amplifier U1 is always equal to -1V. In simple terms, the first operational amplifier U1 with a fixed resistor, that is, the first resistor R1 as the input resistor, has an output voltage equal to -1V when the corresponding dip switch is selected for different rated current levels.

[0039] The second operational amplifier U2 is an inverter amplifier. The output of the second operational amplifier U2 can be configured to be constant at 1V or 0.5V according to the specific application scenario. Specifically, when the second resistor R2 is equal to 1kΩ and 2kΩ respectively, the output voltage U of the second operational amplifier U2 is out Equal to 1V and 0.5V to adapt to different application scenarios.

[0040] Taking the rated current I = 20A and the current sensor sensitivity S = 50mV / A as an example, it can be known that the sensor output voltage U in =50mV / A×20A=1000mV, the output voltage of the first operational amplifier U1 is U md =U in ×R20 / R1=1000mV×1kΩ / 1kΩ=-1V; where each feedback resistor R i =20 / I i (kΩ), i is 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A. Output terminal U out =-1×R3 / R2=0.5V, the input resistance R2 of the second operational amplifier U2 is determined by different application scenarios. When R2=1kΩ, the output terminal U out =-1×1kΩ / 2kΩ=0.5V, when R2=2kΩ, the output terminal U out =-1×2kΩ / 2kΩ=1V. Each feedback resistor consists of R i =20 / I i (A)(kΩ) calculation.

[0041] Preferably, it also includes a precision rectification circuit module 7, the output end of the amplitude normalization network module 6 is electrically connected to the input end of the precision rectification circuit module 7, and the output end of the precision rectification circuit module 7 is electrically connected to the second digital-to-analog conversion input port AD0 of the microprocessor 10, wherein the precision rectification circuit module 7 is configured to rectify the output voltage of the amplitude normalization network module 6 into a half-wave rectification signal with a period of 0.01s.

[0042] Specifically, in this embodiment, an electrical fire prevention and current limiting protection system with normalized rated current amplitude is disclosed, which prevents electrical fires through precise control and rapid response. Among them, the control component is the brain of the entire system, responsible for receiving signals from each module, executing the core algorithm based on these signals, judging the circuit state, and finally controlling the IGBT switch module to achieve protection. The first zero-crossing detection component is connected in parallel to the load electrical circuit, used to capture the zero-crossing point of the voltage signal, and transmit the signal to the control component to provide a synchronization reference for the acquisition of the current signal.

[0043] The instantaneous current acquisition component is connected in series in the load electrical circuit to directly collect the instantaneous current passing through the load and convert it into a voltage signal output for subsequent module processing. The amplitude normalization network module 6 receives these voltage signals and converts them into standard sinusoidal signals, realizing unified processing of signals under different rated currents, simplifying the algorithm complexity and improving the adaptability of the system.

[0044] The second zero-crossing detection circuit module 8 and the effective value detection module 9 both receive the output of the amplitude normalization network module 6. The second zero-crossing detection circuit module 8 is used to detect the zero-crossing point of the voltage signal and provide the control component with the phase difference information between the current signal and the voltage signal, while the effective value detection module 9 is used to obtain the effective value of the current signal and provide a basis for overload judgment.

[0045] The precision rectifier circuit module 7 receives the output of the amplitude normalization network module 6 and rectifies it into a half-wave rectified signal with a period of 0.01 seconds. This step is crucial because it converts the continuous sinusoidal signal into a discrete digital signal, which is convenient for further processing and analysis by the microprocessor 10. The rectified signal is more stable, reduces noise interference, and improves the accuracy and reliability of the signal.

[0046] Finally, the power module 5 provides a stable power supply for the entire system, ensuring that the system can operate reliably under various conditions. The IGBT switch module 12, as the actuator of the system, acts quickly according to the instructions of the control component to cut off or connect the circuit to achieve short circuit and overload protection.

[0047] In practical applications, when the system detects a short circuit or overload condition, the control component immediately sends a signal to the IGBT switch module 12, causing it to disconnect the circuit in a very short time, thereby preventing the occurrence of electrical fires. This rapid response capability, combined with the high adaptability and accuracy of the system, makes the system have significant practical value and broad application prospects in the field of electrical safety.

[0048] See also Figure 3 , Figure 4 Specifically, in this embodiment, the electrical fire-proof current limiting protection system with normalized rated current amplitude performs hardware real-time amplitude adaptive normalization on different rated current amplitudes, and uses the product of a unit sinusoidal signal and a short-circuit setting coefficient to establish a short-circuit threshold function and a threshold table to solve the universality of the protector for different rated currents; directly compares the corresponding value of the amplitude normalized instantaneous current with the short-circuit threshold function to avoid false operation of the protector under non-sinusoidal current conditions; compensates for the lag time between the instantaneous current and the signal processing circuit and the main circuit voltage to solve the problem of asynchronism between the instantaneous current detection value and the threshold function time, and avoids misjudgment caused by delay.

[0049] The control component is configured to implement the following steps by executing a computer program stored therein:

[0050] S1, obtain preset parameter information and perform initialization processing;

[0051] In this embodiment, the initialization steps are as follows: Figure 5 As shown, the number of instantaneous current sampling points in one half-wave is set to N, the sampling interval is calculated to be dt, the overload delay protection time limit is set, the half-wave number corresponding to the overload delay protection time limit is calculated to be M, the instantaneous current sampling start flag Flag = 0, the sampling sequence number n = 0, and the delay beat k delay =0; at the same time, each interface, counter, etc. of the microprocessor is initialized.

[0052] See also Figure 6 , S2, obtaining the first positive pulse signal sent by the first zero-crossing detection component, and performing delay detection processing or sampling processing according to the first positive pulse signal to detect the delay beat of the instantaneous current and the load main circuit;

[0053] Specifically, step S2 includes: obtaining a first positive pulse signal sent by the first zero-crossing detection component, wherein the first zero-crossing detection circuit module sends a positive pulse signal to the control component when detecting that the voltage waveform of the load main circuit crosses the zero point;

[0054] When the first positive pulse signal is received, the counter T1 is started and the instantaneous current I is detected using a half-wave time. instant Delay beat k with load main circuit delay ;

[0055] When the second first positive pulse signal is received, sampling is performed according to the preset sampling time dt to collect the instantaneous current I instant , where each time a sampling time dt passes, the control timer T2 triggers the terminal once and samples the instantaneous current I instant , until the end of one half-wave, the sampling time dt = 20μs.

[0056] In this embodiment, after the system is initialized, it enters a standby state and waits for the first positive pulse signal sent by the first zero-crossing detection component. The first zero-crossing detection circuit module is connected in parallel to the load main circuit, and its responsibility is to monitor the zero-crossing point of the voltage waveform in real time. Once the zero-crossing point is detected, the module sends a positive pulse signal to the control component, marking the beginning of a new cycle of the voltage waveform.

[0057] When the control component receives the first first positive pulse signal, the system immediately starts the counter T1 and begins to use a half-wave time to detect the delay beat of the instantaneous current and the load main circuit. This step is crucial because it provides the system with an accurate time reference of the current signal relative to the voltage signal, which is crucial for the subsequent short circuit and overload judgment. Next, when the control component receives the second first positive pulse signal, the system performs sampling processing according to the preset sampling time dt to collect the instantaneous current. Every time a sampling time dt passes, the control timer T2 triggers an interrupt and samples the instantaneous current once until the end of a half-wave time. This continuous sampling process ensures that the system can capture the complete waveform of the current signal and provides rich data support for the accurate judgment of short circuit and overload. Through this precise timing control and sampling strategy, the system can achieve high-resolution monitoring of current changes in electrical circuits, thereby detecting potential short circuit and overload risks at the first time. This real-time monitoring and rapid response capabilities significantly improve the safety and reliability of electrical circuits and reduce the risk of fire caused by electrical faults.

[0058] In addition, the preset sampling time dt can be adjusted according to the specific application scenario to meet different monitoring needs. For example, in high-current or high-power electrical systems, a shorter sampling time dt may be required to achieve a higher sampling frequency, and the system design allows this flexibility, enhancing the adaptability and versatility of the system.

[0059] S3, obtaining the second positive pulse signal sent by the second zero-crossing detection circuit module, performing calculation processing according to the second positive pulse signal, obtaining the delay of the voltage to be received by the instantaneous current acquisition component relative to the load main circuit voltage, and determining the delay beat size according to the delay;

[0060] Specifically, step S3 includes: obtaining a second positive pulse signal sent by the second zero-crossing detection circuit module, wherein the second zero-crossing detection circuit module sends a second positive pulse signal to the control component when detecting the zero-crossing point of the voltage waveform output by the amplitude normalization network module;

[0061] When the first second positive pulse signal is received, the counter T1 is stopped and the value T of the counter T1 is read. 1 ;

[0062] According to the value T 1 Calculate the voltage sensed by the current sensor, relative to the delay T of the load main circuit voltage delay , the calculation formula is T delay =T 1 ×t1, where t1 is the counter counting period in μs;

[0063] According to the delay T delay Determine the delay beat k delay The size of The integer part of .

[0064] Specifically, in this embodiment, after completing initialization and the first zero-crossing detection, the system continues to run and waits for the second positive pulse signal sent by the second zero-crossing detection circuit module. The second zero-crossing detection circuit module is responsible for monitoring the zero-crossing point of the voltage waveform output by the amplitude normalization network module. Once the zero-crossing point is detected, the module sends a second positive pulse signal to the control component, which marks a critical time point of the voltage waveform. When the control component receives the first second positive pulse signal, the system immediately terminates the counting of counter T1 and reads the value of counter T1. This value is the number of cycles recorded by the internal counter of the system since the first zero-crossing detection, which reflects the time interval from the voltage zero-crossing point to the current zero-crossing point.

[0065] In simple terms, the calculation process of the instantaneous current signal hysteresis time is mainly as follows: when the microprocessor detects that the first zero-crossing detection module outputs a positive pulse, the counter T1 is started, and when the microprocessor detects that the second zero-crossing detection module outputs a positive pulse, the counter T1 is stopped and the final value of the counter T1 is read. The instantaneous current hysteresis time is equal to T delay =T1×counter counting cycle (μs), delay beat number k daly =T delay / 20μs is rounded to an integer. The instantaneous current signal hysteresis time occupies one half-wave time after initialization, that is, 10ms.

[0066] Please refer to the figure, S4, according to the number of sampling points and the delay beat, determine the short-circuit threshold at the current moment, and compare the short-circuit threshold with the sampling value of the instantaneous current value at the current moment to generate a short-circuit fault judgment result;

[0067] Specifically, step S4 includes: according to the sampling sequence number n and the delay beat k delay , determine the short-circuit threshold I at the current moment short (n) = I Instant (n+k delay ), I Instant (i) represents the sampling value of the i-th instantaneous current value, i=1,...,n;

[0068] The short-circuit threshold I short (n) and the sampling value of the i-th instantaneous current value I Instant (i) performing comparison and generating a short circuit fault judgment result;

[0069] Among them, the sampling value of the i-th instantaneous current value is I Instant(i) Greater than the short-circuit threshold I short (n), the short-circuit fault judgment result is a short-circuit fault.

[0070] Specifically, in this embodiment, after completing initialization, zero-crossing detection and delay calculation, the system enters the key steps of current sampling and short-circuit judgment. In step S4, the system first calculates the current sampling and short-circuit judgment according to the sampling sequence number n and the delay beat k. delay , determine the short-circuit threshold at the current moment. This threshold is calculated based on the preset short-circuit protection algorithm and delay correction, ensuring that at any given moment, the system can know the maximum allowable value of the safe current at that moment. Subsequently, the system samples the instantaneous current value at each sampling point and compares it with the corresponding short-circuit threshold. This process involves comparing the sampled value of the i-th instantaneous current value with the short-circuit threshold, where i ranges from 1 to n. Each comparison is an assessment of the safety status of the electrical line, and the result of any comparison may trigger a short-circuit protection action. If the sampled value of the i-th instantaneous current value is greater than the corresponding short-circuit threshold, the system will generate a short-circuit fault judgment result and determine it as a short-circuit fault. This judgment result will directly cause the system to perform a short-circuit protection action, such as triggering the IGBT switch module to quickly disconnect the circuit to prevent the short-circuit fault from causing more serious damage.

[0071] In this embodiment, the short-circuit current setting coefficient K is set short =6, dt = 20μs, N = 0.01÷dt = 500. Specifically, the short-circuit threshold function I short The value of (n) is determined by the following sine function, I(n) = K short ×|sin[π(n+k delay ) / N]|, where K short is the short-circuit setting coefficient, n is the sampling point number of a half-wave, n=0,1,2,……N-1, N is the number of sampling points on a half-wave, N=0.01÷dt=0.01÷(20×10-6)=500. Among them, when there is no delay: I short (n)=I(n), when there is a delay: I short (n) = I (n + k delay )

[0072] The short-circuit threshold function I short (n) is converted into two short-circuit threshold table sequences I(n) connected end to end. short (n), I short (n) = I (n + k delay ), at this time, n=0,1,2,……,N-1,N,N+1,N+2,……2N-2,2N-1, I short The second half of (n) is used to delay k delay ≠0 is the scenario.

[0073] See also Figure 7 , S5, obtaining the effective value sent by the effective value detection module, comparing the effective value with the overload current threshold, and generating an overload judgment result;

[0074] Specifically, step S5 includes: obtaining the effective value I sent by the effective value detection module once at the previous sampling time dt of each half-wave. e ;

[0075] For effective value I e and overload current threshold I overload Make a comparison and generate an overload judgment result;

[0076] Among them, when the effective value I e Greater than the overload current threshold I overload , and the half-wave number of the continuous overload is greater than the half-wave number M corresponding to the preset protection time limit, the overload judgment result is overload;

[0077] The overload current threshold I overload The calculation formula is: overload =K overload , K overload is the overload current setting factor.

[0078] In this embodiment, the system obtains the effective value sent by the effective value detection module at the previous sampling time dt of each half-wave. This effective value is obtained by processing and calculating the instantaneous current signal, reflecting the average power level of the current during the time period. Next, the effective value is compared with the preset overload current threshold. The overload current threshold is pre-set according to system parameters and safety standards, and is used to determine whether the electrical circuit is in an overload state. The formula of the overload current threshold ensures that the overload current threshold takes into account both the rated carrying capacity of the line and the safety degree. If the effective value is greater than the overload current threshold, and the number of half-waves of continuous overload is greater than the number of half-waves M corresponding to the preset protection time limit, the system will generate an overload judgment result and determine it as overload. This judgment result will directly cause the system to perform an overload protection action, such as triggering the IGBT switch module to disconnect the circuit to prevent the overload fault from causing more serious damage.

[0079] Specifically, let the short-circuit current setting coefficient K overload =1.2, overload delay protection time limit T max = 6s, equivalent to the number of half cycles of duration M = 6 ÷ 0.01 = 600. Overload threshold function, the output value of the effective current detection module is sampled once at the beginning of each current half-wave, the overload current threshold I overloadCalculated by the following overload function: I overload =K overload ; and the continuous overload time is greater than the overload delay protection time limit T max , or T max The corresponding half-wave number is M. Further, the microprocessor determines whether it is short-circuited or overloaded according to the core algorithm module. If the effective value I e Greater than the overload threshold I overload If the continuous half-wave number is greater than M, it is judged as overload, and the microprocessor turns off the IGBT to achieve overload protection; if the instantaneous current I Instant (n) is greater than the short-circuit threshold value. The corresponding value of the function is greater than the short-circuit threshold value I short (n) 1 time, it is judged as a short circuit, and the microprocessor immediately turns off the IGBT to achieve short-circuit protection.

[0080] S6, when the short-circuit fault judgment result is a short-circuit fault, or the overload judgment result is an overload, turning off the IGBT switch module to achieve short-circuit protection and overload protection.

[0081] Specifically, in this embodiment, the logic steps of the electrical fire protection current limiting protection system with normalized rated current amplitude are as follows: the microprocessor has a built-in short-circuit threshold table, an overload threshold, and the number of half cycles of uninterrupted overload duration M. The short-circuit threshold table I(n) is equal to the short-circuit current setting coefficient K short Multiply by the sampling value of the unit sine function |sin(πn / N)| at the integer n=0~2N-1, the overload threshold is equal to the overload current setting coefficient K overload And the half-cycle number corresponding to the uninterrupted duration of overload is M. Among them, the current sensor sensitivity rated current I = 20A, S = 50mV / A, R2 = 1kΩ, the dip switch 6 is connected, R20 = 1kΩ, then the normalized circuit output voltage Sampling interval dt = 20 μs, K short =6, K overload =1.2, T max =6s, M = 6÷0.01 = 600. Short circuit threshold table I short (n) = I (n + k delay ),like Figure 3 As shown. Overload current threshold K overload =1.2, and the continuous overload exceeds M=600 half waves.

[0082] The microprocessor uses the principle of time division to complete delay detection, overload detection and short circuit detection. After the system is reset, a half-wave microprocessor uses the query method to detect the delay k of the instantaneous current and the main circuit voltage. delay, and set the microprocessor in interrupt mode; starting from the second half-wave starting point, divide the time point into 20μs, and perform an overload detection at the 0th point of each half-wave to obtain the effective value I e , the 1st point to the N-2nd point detect the instantaneous current I N-3 times in sequence Instant (n), wait for the N-1th time. Figure 4 shown.

[0083] When the microprocessor 11 waits for a positive pulse to appear on the INT1 pin, it starts counting counter T1 and starts the 20μs timer T2. When the microprocessor 11 waits for a positive pulse to appear on the INT0 pin, it stops counter T1 and reads the final value T of T1. delay , measure the delay k between instantaneous current and main circuit voltage delay =T delay / 20μs to take the integer. The microprocessor 11 operates the IGBB according to the detection result: when the effective current value I e >I overload When the overload lasts for more than M half-waves, it is judged as overload, and the microprocessor turns off the IGBB switch through the driver to achieve overload delay protection; the instantaneous current I Instant (n), check the value I in the short-circuit threshold table short (n) = I (n + k delay ), when I Instant (n)>I short (n), it is judged as a short circuit, and the microprocessor turns off the IGBB switch through the driver to achieve short circuit protection.

[0084] In summary, the electrical fire protection current limiting protection system with normalized rated current amplitude adopts a voltage conversion circuit to detect the first zero-crossing point of the AC voltage, and adopts a current sensor to detect the instantaneous current. The instantaneous current is converted into voltage through the internal circuit of the sensor, and the voltage is input into the standardization module after passing through the power frequency filter. The output end of the standardization module is respectively connected to the input end of the precision rectifier circuit module, the second zero-crossing detection circuit module and the effective value detection module. The standardization module performs standardization processing on the instantaneous current, establishes a short-circuit current threshold function by multiplying the unit sine signal by the short-circuit current setting coefficient, and uses the overload setting coefficient as the overload threshold; the second zero-crossing detection module obtains the second zero-crossing point, obtains the delay of the instantaneous current relative to the main circuit voltage through the time difference between the first and second zero-crossing points, and corrects the threshold function value according to the delay; if the instantaneous current exceeds the short-circuit threshold function value, it is judged as a short circuit, and if the instantaneous current effective value is greater than the effective current threshold and the duration exceeds the overload delay disconnection time, it is judged as an overload, which overcomes the shortcomings of the existing protection method. The detection time of the short-circuit fault can reach 80μs.

[0085] In general, the design of this system takes into account the diversity and complexity of electrical circuits. Through the flexibility of preset parameters and the adaptability of algorithms, the system can adapt to different electrical circuit conditions and load changes. This flexibility and adaptability not only improves the safety and reliability of the system, but also enhances the versatility and practicality of the system. In addition, this system, with its advanced technology, precise monitoring and rapid response, provides an efficient and reliable solution for the field of electrical safety. This system can not only reduce electrical fire accidents and protect the safety of personnel and property, but also improve the operating efficiency and stability of electrical circuits. It has important practical value and broad market application prospects.

[0086] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An electrical fire protection and current limiting protection system with normalized rated current amplitude, characterized in that: include: A control component, a first zero-crossing detection component, an instantaneous current acquisition component, an amplitude normalization network module, a second zero-crossing detection circuit module, an effective value detection module, a power supply module, and an IGBT switch module, wherein the input end of the first zero-crossing detection component is connected in parallel to the electrical circuit of the load, the output end of the first zero-crossing detection component is electrically connected to the first external interrupt input end of the control component, the input end of the instantaneous current acquisition component is connected in series to the electrical circuit of the load, the output end of the instantaneous current acquisition component is electrically connected to the input end of the amplitude normalization network module, the output end of the amplitude normalization network module is electrically connected to the input end of the second zero-crossing detection circuit module and the input end of the effective value detection module, the output end of the second zero-crossing detection circuit module is electrically connected to the second external interrupt input end (INT0) of the control component, the output end of the effective value detection module is electrically connected to the first digital-to-analog conversion input port (AD1) of the control component, the output end of the control component is electrically connected to the control end of the IGBT switch module, and the output end of the power supply module is electrically connected to the power supply end of the control component; Wherein, the amplitude normalization network module is configured to convert the voltage signal output by the instantaneous current acquisition component under different rated currents into a standard sinusoidal signal, and the effective value detection module is configured to obtain the effective value of the induced voltage output by the instantaneous current acquisition component; The control component is configured to implement the following steps by executing a computer program stored therein: Obtain preset parameter information and perform initialization processing; Acquire the first positive pulse signal sent by the first zero-crossing detection component, and perform delay detection processing or sampling processing according to the first positive pulse signal to detect the delay beat of the instantaneous current and the load main circuit; Obtaining a second positive pulse signal sent by the second zero-crossing detection circuit module, performing calculation processing based on the second positive pulse signal, obtaining a delay of the voltage to be received by the instantaneous current acquisition component relative to the load main circuit voltage, and determining a delay beat size based on the delay; According to the number of sampling points and the delay beat, the short-circuit threshold at the current moment is determined, and the short-circuit threshold is compared with the sampling value of the instantaneous current value at the current moment to generate a short-circuit fault judgment result; Obtaining the effective value sent by the effective value detection module, comparing the effective value with the overload current threshold, and generating an overload judgment result; When the short-circuit fault judgment result is a short-circuit fault, or the overload judgment result is an overload, the IGBT switch module is turned off to achieve short-circuit protection and overload protection.

2. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 1, characterized in that: The control component includes a microprocessor and a core algorithm module, wherein the core algorithm module is configured in a storage register of the microprocessor; The first zero-crossing detection component includes a voltage conversion circuit and a first zero-crossing detection circuit module, the input end of the voltage conversion circuit is connected in parallel to the electrical circuit of the load, the output end of the voltage conversion circuit is electrically connected to the input end of the first zero-crossing detection circuit module, and the output end of the first zero-crossing detection circuit module is electrically connected to the first external interrupt input end (INT1) of the microprocessor, wherein the voltage conversion circuit is configured to sense the voltage signal of the load main circuit, and the first zero-crossing detection circuit module is configured to detect the zero-crossing point of the voltage waveform of the load main circuit.

3. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 2, characterized in that: The instantaneous current acquisition component includes a current sensor and an industrial frequency filter module, wherein the input end of the current sensor is connected in series to the electrical circuit of the load, the output end of the current sensor is electrically connected to the input end of the industrial frequency filter module, and the output end of the industrial frequency filter module is electrically connected to the input end of the amplitude normalization network module, wherein the current sensor is configured to sense the instantaneous current I of the load main circuit instant , and the instantaneous current I instant Converted into voltage signal U in , the power frequency filter module is configured to extract the instantaneous current I instant The power frequency component in the conversion formula is: U in =I instant ×S, S is the sensitivity of the current sensor.

4. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 3, characterized in that: The amplitude normalization network module comprises a resistor network, a first operational amplifier (U1), and a second operational amplifier (U2); the input end of the resistor network is electrically connected to the output end of the power frequency filter module; the first end of the resistor network is electrically connected to the negative electrode of the first operational amplifier (U1); the second end of the resistor network is electrically connected to the output end of the first operational amplifier (U1); the output end of the first operational amplifier (U1) is electrically connected to the negative electrode of the second operational amplifier (U2); the output end of the second operational amplifier (U2) is electrically connected to the input end of the second zero-crossing detection circuit module; the positive electrode of the first operational amplifier (U1) and the positive electrode of the second operational amplifier (U2) are grounded; wherein the resistor network is a feedback resistor of the first operational amplifier (U1).

5. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 4, characterized in that: The resistor network comprises a first resistor (R1), a dip switch, nine resistors, a second resistor (R2), and a third resistor (R3); the nine resistors are connected in parallel via the dip switch; one end of the first resistor (R1) is electrically connected to the output end of the power frequency filter module; the other end of the first resistor (R1) is electrically connected to the negative electrode of the first operational amplifier (U1); the output end of the first operational amplifier (U1) is electrically connected to the negative electrode of the second operational amplifier (U2) via the second resistor (R2); and the other end of the second resistor (R2) is electrically connected to the output end of the second operational amplifier (U2) via the third resistor (R3); The dip switch is configured to set a rated current. When the rated current corresponds to the level of any one of the nine resistors, the output voltage of the first operational amplifier (U1) is -1V, and the output voltage of the second operational amplifier (U2) is 1V or 0.5V.

6. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 2, characterized in that: It also includes a precision rectification circuit module, wherein the output end of the amplitude normalization network module is electrically connected to the input end of the precision rectification circuit module, and the output end of the precision rectification circuit module is electrically connected to the second digital-to-analog conversion input port (AD0) of the microprocessor, wherein the precision rectification circuit module is configured to rectify the output voltage of the amplitude normalization network module into a half-wave rectification signal with a period of 0.01s.

7. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 3, characterized in that: The first positive pulse signal sent by the first zero-crossing detection component is obtained, and a delay detection process or a sampling process is performed according to the first positive pulse signal to detect the delay beat of the instantaneous current and the load main circuit, specifically: Acquire a first positive pulse signal sent by the first zero-crossing detection component, wherein the first zero-crossing detection circuit module sends a positive pulse signal to the control component when detecting a zero-crossing point of the voltage waveform of the load main circuit; When the first positive pulse signal is received, the counter (T1) is started and the instantaneous current I is detected using a half-wave time. instant Delay beat k with load main circuit delay ; When the second first positive pulse signal is received, sampling is performed according to the preset sampling time dt to collect the instantaneous current I instant , where every time a sampling time dt passes, the control timer (T2) triggers the terminal once and samples the instantaneous current I instant , until the end of one half-wave, the sampling time dt = 20μs.

8. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 7, characterized in that: The second positive pulse signal sent by the second zero-crossing detection circuit module is obtained, and calculation and processing are performed according to the second positive pulse signal to obtain the delay of the voltage to be received by the instantaneous current acquisition component relative to the load main circuit voltage, and the size of the delay beat is determined according to the delay, specifically: Acquire a second positive pulse signal sent by the second zero-crossing detection circuit module, wherein the second zero-crossing detection circuit module sends a second positive pulse signal to the control component when detecting the zero-crossing point of the voltage waveform output by the amplitude normalization network module; When the first second positive pulse signal is received, the counter (T1) stops counting and reads the value T1 of the counter (T1); The voltage sensed by the current sensor is calculated based on the value T1, and the delay T relative to the load main circuit voltage is calculated based on the value T1. delay , the calculation formula is T delay =T1×t1, where t1 is the counter counting period in μs; According to the delay T delay Determine the delay beat k delay The size of The integer part of .

9. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 8, characterized in that: According to the number of sampling points and the delay beat, the short-circuit threshold at the current moment is determined, and the short-circuit threshold is compared with the instantaneous current to generate the short-circuit fault judgment result, which is as follows: According to the sampling sequence number n and the delay beat k delay , determine the short-circuit threshold I at the current moment short (n) = I Instant (n+k delay ), I Instant (i) represents the sampling value of the i-th instantaneous current value, i=1,...,n; The short-circuit threshold I short (n) and the sampling value of the i-th instantaneous current value I Instant (i) performing comparison and generating a short circuit fault judgment result; Among them, the sampling value of the i-th instantaneous current value is I Instant (i) Greater than the short-circuit threshold I short (n), the short-circuit fault judgment result is a short-circuit fault.

10. The electrical fire protection and current limiting protection system with normalized rated current amplitude according to claim 9, characterized in that: The effective value sent by the effective value detection module is obtained, the effective value is compared with the overload current threshold, and an overload judgment result is generated, specifically: At the previous sampling time dt of each half-wave, the effective value I sent by the effective value detection module is obtained once. e ; For effective value I e and overload current threshold I overload Make a comparison and generate an overload judgment result; Among them, when the effective value I e Greater than the overload current threshold I overload , and the half-wave number of the continuous overload is greater than the half-wave number M corresponding to the preset protection time limit, the overload judgment result is overload; The overload current threshold I overload The calculation formula is: overload =K overload , K overload is the overload current setting factor.

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