An electrical fire protection and current limiting protection system with normalized rated current amplitude

Abstract

The present invention provides an electrical fire protection and current limiting protection system with normalized rated current amplitude, which relates to the field of electrical safety technology. The system uses hardware-based real-time adaptive normalization of rated current amplitude to convert the output voltage of current sensors at different rated currents into a standard sinusoidal signal, making the system independent of the rated current magnitude. 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. Short-circuit fault identification is achieved by directly comparing the instantaneous current values ​​at different times with the corresponding short-circuit threshold function values, and overload fault identification is determined by directly comparing the effective current value with the overload threshold function value. Through this design, the present invention can achieve fast and accurate short-circuit and overload protection, effectively reducing the risk of electrical fires and improving the reliability and efficiency of electrical safety protection. The system aims to address the problems of existing electrical fire protection devices with poor versatility for different rated currents, easy misjudgment, and long response time.

Description

Technical Field

[0001] The present 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] Due to their high incidence and destructive nature, electrical fires have become a major threat to modern social safety. According to statistics, electrical fires currently account for over one-third of all fires, and over two-thirds of major fires. This high proportion of electrical fires not only causes serious casualties but also substantial property damage. Short circuits and overloads are the two primary causes of electrical line failures. A short circuit can generate incandescent sparks and localized transient high temperatures, while prolonged overload can cause overheating. These high temperatures and sparks are significant contributors to electrical fires. Therefore, fire prevention and current limiting protection methods have become a key technology of concern in the electrical safety field.

[0003] To prevent these fires, various current-limiting protection technologies have been developed. These technologies typically employ current-limiting devices. Existing current-limiting devices primarily include short-circuit protectors (PCIs), which trip when the circuit current exceeds the short-circuit setting current and delay trip when the current exceeds the overload setting current. These devices quickly disconnect the circuit when the current exceeds the set value, preventing further damage. Since typical overcurrent protectors operate in the tens to hundreds of milliseconds, the circuit current can continue to rise to hundreds of times the rated current between the moment of the short circuit and when the circuit is fully disconnected. The sparks and high temperatures generated by such high currents can easily cause fires. To shorten the tripping time and reduce the likelihood of electrical fires, fire-preventing current-limiting protection methods for contactless switches are now available on the market. These methods utilize algorithms such as real-time current values ​​and the rate of change of current between two adjacent points. When the current detection value exceeds a preset threshold, the protector triggers protection.

[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. As a result, a protector with one rated current cannot be used for circuits with other rated currents, resulting in 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 suddenly changes due to the influence of load characteristics, the rate of change of the current 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 using the instantaneous current relative change rate method, the short-circuit current setting coefficient needs to be input on the keyboard and 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 0÷0, and the algorithm fails. When the sampling interval is very small, the numerator of the current relative change rate is an extremely small number close to 0, while 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 actual applications, or to malfunction in the case of non-sinusoidal waveforms or sudden current changes. 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 protection 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 protection 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 in parallel 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] 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 a 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 to obtain a delay of the voltage 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 of 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 1 is a module 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 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 This is a schematic representation of the short-circuit protection threshold value of the electrical fire protection and current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention;

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

[0023] Figure 5 This 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 This 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 This is a flow chart of the INT1 effective value detection interrupt service of the electrical fire protection and current limiting protection system with normalized rated current amplitude provided by an embodiment of the present invention;

[0026] Figure 8This is a flow chart of a short-circuit detection and 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. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended 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, 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, where 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 via the dip switch. One end of the first resistor R1 is electrically connected to the output end of the power frequency filter module, and 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.

[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 at 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 sinusoidal signal amplitude is greater than 1; when the instantaneous current is less than the rated current, the sinusoidal signal amplitude is less than 1. Simply put, the amplitude normalization network module 6 converts different rated currents into an output voltage of 1V, and can also convert it to a voltage of 0.5V depending on the specific application scenario, facilitating data collection.

[0037] Using nine resistors R i A DIP switch forms the feedback resistor for the first operational amplifier U1, connected across the inverting input and output terminals of the first operational amplifier U1. For rated currents between 6A and 63A, the output of the first operational amplifier U1 is always -1V. Specifically, current-limiting protection for circuits with different rated currents simply requires turning on the corresponding DIP switch. The algorithm and hardware remain independent of the rated current, ensuring the versatility of the current-limiting protection device.

[0038] Among them, the resistor R i The subscript "i" represents the rated current value, i = 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A. Therefore, when the rated current of the amplitude normalization network module 6 is 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, and 63A, respectively, the output of the first operational amplifier U1 is always -1V. Simply put, when the corresponding DIP switch of the first operational amplifier U1, which uses a fixed resistor (i.e., the first resistor R1) as the input resistor, is selected for different rated current levels, its output voltage is always -1V.

[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 seen 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 takes 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 is composed of R i =20 / I i (A)(kΩ) calculation.

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

[0042] Specifically, this embodiment discloses an electrical fire protection and current limiting system with normalized rated current amplitude. This system prevents electrical fires through precise control and rapid response. The control component, the brain of the entire system, receives signals from various modules, executes core algorithms based on these signals, determines circuit status, and ultimately controls the IGBT switching module to achieve protection. A first zero-crossing detection component, connected in parallel with the load electrical circuit, captures the zero-crossing point of the voltage signal and transmits the signal to the control component, providing a synchronization reference for current signal acquisition.

[0043] The instantaneous current acquisition component, connected in series with the load's electrical circuit, directly captures the instantaneous current flowing through the load and converts it into a voltage signal for subsequent processing. The amplitude normalization network module 6 receives these voltage signals and converts them into standard sinusoidal signals, enabling unified processing of signals at different rated currents, simplifying algorithm complexity and improving system adaptability.

[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 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 to provide a basis for overload judgment.

[0045] Precision rectifier circuit module 7 receives the output of 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, facilitating further processing and analysis by microprocessor 10. The rectified signal is more stable, reduces noise interference, and improves signal accuracy and reliability.

[0046] Finally, the power module 5 provides a stable power source for the entire system, ensuring reliable operation under all conditions. The IGBT switch module 12, acting as the system's actuator, rapidly operates according to the control component's instructions to disconnect or connect the circuit, providing short-circuit and overload protection.

[0047] In practical applications, when the system detects a short circuit or overload, 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 system's high adaptability and accuracy, makes the system of this invention 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 protection and 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 asynchrony 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, set the number of instantaneous current sampling points in one half-wave to N, calculate the sampling interval to dt, set the overload delay protection time limit, calculate the half-wave number corresponding to the overload delay protection time limit to M, the instantaneous current sampling start flag Flag = 0, the sampling sequence number n = 0, the delay beat k delay =0; at the same time, each interface, counter, etc. of the microprocessor are 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 a zero-crossing point of the voltage waveform of the load main circuit;

[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 the 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 system initialization is complete, it enters a standby state, awaiting a first positive pulse signal from the first zero-crossing detection component. The first zero-crossing detection circuit module is connected in parallel to the load's main circuit and monitors the zero-crossing point of the voltage waveform in real time. Upon detecting a zero-crossing point, 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 unit receives the first positive pulse signal, the system immediately starts counter T1 and begins using a half-cycle to detect the instantaneous current and the delay between the load and the main circuit. This step is crucial because it provides the system with an accurate time reference for the current signal relative to the voltage signal, which is crucial for subsequent short-circuit and overload detection. Next, when the control unit receives the second positive pulse signal, the system samples the instantaneous current according to the preset sampling time dt. After each sampling time dt, timer T2 triggers an interrupt to sample the instantaneous current, continuing until the end of the half-cycle. This continuous sampling process ensures that the system captures the complete current waveform, providing rich data support for accurate short-circuit and overload detection. Through this precise timing control and sampling strategy, the system achieves high-resolution monitoring of current changes in electrical circuits, enabling immediate detection of potential short-circuit and overload risks. This real-time monitoring and rapid response capability significantly improves the safety and reliability of electrical circuits and reduces the risk of fires caused by electrical faults.

[0058] Furthermore, the preset sampling time dt can be adjusted based on specific application scenarios to accommodate different monitoring requirements. For example, in high-current or high-power electrical systems, a shorter sampling time dt may be required to achieve a higher sampling frequency. The system design allows for this flexibility, enhancing its adaptability and versatility.

[0059] S3, 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 time delay of the voltage received by the instantaneous current acquisition component relative to the load main circuit voltage, and determining a delay beat size based on the time 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 stops counting and the value T1 of the counter T1 is read;

[0062] Calculate the voltage sensed by the current sensor according to the value T1, and the delay T relative to the load main circuit voltage delay , the calculation formula is T delay =T1×t1, where t1 is the counter counting period in μs;

[0063] According to the delay T delay Determine the delay beat kdelay 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 key time point in the voltage waveform. When the control component receives the first second positive pulse signal, the system immediately stops counting the counter T1 and reads the value of the 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 as follows: when the microprocessor detects that the first zero-crossing detection module outputs a positive pulse, it starts the counter T1. When the microprocessor detects that the second zero-crossing detection module outputs a positive pulse, it stops counting the counter T1 and reads the final value of the counter T1. The instantaneous current hysteresis time is equal to T delay =T1×counter counting period (μs), delay beat number k daly =T delay / 20μs is rounded to an integer, and the instantaneous current signal hysteresis time occupies one half-wave time after initialization, that is, 10ms.

[0066] Please refer to FIG. S4 , based on the number of sampling points and the delay beat, the short-circuit threshold value at the current moment is determined, and the short-circuit threshold value is compared 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 determination result;

[0069] Among them, the sampling value of the i-th instantaneous current value 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 sequence number n and the delay beat k. delay , determine the short-circuit threshold at the current moment. This threshold is calculated based on a preset short-circuit protection algorithm and delay correction, ensuring that at any given moment, the system knows the maximum allowable safe current value at that moment. The system then 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 circuit, 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 execute 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 comparison and generate 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 coefficient.

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

[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 overload Calculated 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 function corresponding value is greater than the short-circuit threshold 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 and 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 the sampling value of the unit sine function |sin(πn / N)| at the integer n=0~2N-1, and the overload threshold is equal to the overload current setting coefficient K overload The overload duration corresponds to the number of half cycles M. Among them, the current sensor sensitivity rated current I = 20A, S = 50mV / A, R2 = 1kΩ, the dip switch pin 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 value 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 the delay detection, overload detection and short circuit detection. After the system is reset, the 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, point 1 to point N-2 detect N-3 times of instantaneous current I 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 the counter T1 and starts the 20μs timer T2. The microprocessor 11 waits for a positive pulse to appear on the INT0 pin to terminate the 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 rounded to an 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 IGBT switch through the driver to achieve short circuit protection.

[0084] In summary, the described electrical fire protection and current limiting protection system with normalized rated current amplitude uses a voltage conversion circuit to detect the first zero-crossing point of the AC voltage and a current sensor to detect the instantaneous current. The instantaneous current is converted into a voltage by the sensor's internal circuitry. The voltage then passes through a power frequency filter and is input to a standardization module. The output of the standardization module is connected to the inputs of a precision rectifier circuit module, a second zero-crossing detection circuit module, and an effective value detection module. The standardization module normalizes the instantaneous current by multiplying a unit sinusoidal signal by a short-circuit current setting coefficient to establish a short-circuit current threshold function, using the overload setting coefficient as the overload threshold. The second zero-crossing detection module obtains the second zero-crossing point and uses the time difference between the first and second zero-crossing points to determine the delay of the instantaneous current relative to the main circuit voltage. The threshold function value is then corrected based on this delay. If the instantaneous current exceeds the short-circuit threshold function value, a short circuit is detected. If the instantaneous current effective value is greater than the effective current threshold and lasts longer than the overload delay tripping time, an overload is detected. This overcomes the shortcomings of existing protection methods and can detect short-circuit faults within 80μs.

[0085] Overall, the system's design takes into account the diversity and complexity of electrical circuits. Through the flexibility of pre-set parameters and the adaptability of algorithms, the system can adapt to varying electrical circuit conditions and load variations. This flexibility and adaptability not only improves the system's safety and reliability, but also enhances its versatility and practicality. Furthermore, with its advanced technology, precise monitoring, and rapid response, this system provides an efficient and reliable solution for the electrical safety field. This system not only reduces electrical fire incidents and protects personnel and property, but also improves the operational efficiency and stability of electrical circuits, possessing significant practical value and broad market application prospects.

[0086] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles 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; 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 a 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 to obtain a delay of the voltage 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 a power frequency filter module. 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 power frequency filter module, and the output end of the power frequency filter module is electrically connected to the input end of the amplitude normalization network module. 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 serves as 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 rectifier circuit module, the output end of the amplitude normalization network module is electrically connected to the input end of the precision rectifier circuit module, and the output end of the precision rectifier circuit module is electrically connected to the second digital-to-analog conversion input port (AD0) of the microprocessor, wherein the precision rectifier circuit module is configured to rectify the output voltage of the amplitude normalization network module into a half-wave rectified 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: 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 instantaneous current and the delay beat of 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 the 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: Obtain the second positive pulse signal sent by the second zero-crossing detection circuit module, and perform calculation processing based on 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 determine the size of the delay beat based on 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 a 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 the value T1 of the counter (T1) is read; Calculate the voltage sensed by the current sensor according to the value T1, and the delay T relative to the load main circuit voltage 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 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 determination result; Among them, the sampling value of the i-th instantaneous current value 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: Obtain the effective value sent by the effective value detection module, compare the effective value with the overload current threshold, and generate an overload judgment result, 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 comparison and generate 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 coefficient.

Images