Direct-current and alternating-current circuit breaker and application method

Abstract

The invention relates to the field of power electronic technology and electrical protection, and discloses a direct-current and alternating-current circuit breaker and an application method, and the circuit breaker comprises a power conversion stage which is configured to convert input electric energy and output the electric energy to a load; the sensing unit is configured to collect voltage and current signals of an output load of the power conversion stage; the control unit is electrically connected with the power conversion stage and the sensing unit, and is configured to control the power conversion stage to generate and apply a composite voltage containing a fundamental wave voltage and an active detection voltage to a load; obtaining response current of the load to the composite voltage through a sensing unit; based on the response current, a real-time electrical characteristic of the load is determined. By controlling the power conversion stage to generate and apply the composite voltage containing the active detection voltage and calculating the broadband complex impedance spectrum of the load based on the response current, tiny electrical characteristic changes caused by degradation of internal elements of the load can be accurately recognized in an early stage, and therefore predictive recognition of potential faults is achieved.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology and electrical protection, specifically to a DC / AC circuit breaker and its application method. Background Technology

[0002] In power systems, circuit breakers, as fundamental and critical protective electrical devices, primarily function to rapidly interrupt current in the event of overcurrent, short circuit, or other faults, thereby protecting lines, load equipment, and personnel safety. Existing circuit breakers, whether traditional electromagnetic, thermomagnetic, or more advanced electronic types, largely rely on core protection logic based on monitoring the amplitude of the load current. Specifically, these circuit breakers use current transformers or Hall effect sensors to monitor the current flowing through the load in real time and compare its effective value with one or more preset fixed thresholds. Once the detected current exceeds the threshold, the circuit breaker trips, disconnecting the circuit.

[0003] However, the aforementioned traditional protection methods have limitations. Protection is only triggered when a fault has occurred or is about to occur, manifesting as a significant abnormal current overload or short circuit. For the gradual aging or early deterioration of internal load components, such as a slight decrease in the insulation performance of AC motor windings or the drying out or capacity decay of the electrolyte in the filter capacitors of a switching power supply, these initial physical changes do not immediately cause drastic changes in the power frequency current. Therefore, traditional circuit breakers are completely insensitive to such latent fault symptoms and cannot provide any form of early warning. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a DC-AC circuit breaker and its application method, which solves the problem that existing circuit breakers rely solely on limited power frequency information such as the fundamental current for judgment, making it impossible to obtain the broadband electrical characteristics of the load and thus difficult to predictively identify and protect against the progressive degradation of internal components of the load.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a DC / AC circuit breaker, comprising: A power conversion stage configured to convert input electrical energy and output it to the load; The sensing unit is configured to acquire voltage and current signals from the output load of the power conversion stage; The control unit, electrically connected to the power conversion stage and the sensing unit, is configured as follows: The control power conversion stage generates and applies a composite voltage, including the fundamental voltage and the active sensing voltage, to the load; The load's response current to the composite voltage is obtained through the sensing unit; Based on the response current, the real-time electrical characteristics of the load are determined; Real-time electrical characteristics are compared with pre-stored baseline electrical characteristics to calculate the health deviation. When the health deviation exceeds the preset circuit breaker threshold, the control power conversion stage performs a circuit breaker operation to cut off the power supply to the load.

[0006] The above technical solution involves controlling the power conversion stage to generate and apply a composite voltage including an actively sensed voltage, and determining the real-time electrical characteristics of the load based on the load's response current to this composite voltage. This enables the circuit breaker to acquire accurate electrical characteristics of the load over a wide frequency range, rather than relying solely on the current amplitude or fundamental frequency parameter at a single power frequency, as traditional technologies do.

[0007] Since the progressive degradation of internal components of a load often manifests primarily in subtle changes in its high-frequency impedance characteristics, the broadband electrical characteristics obtained in this invention are highly sensitive to these early signs of failure. By quantitatively comparing real-time electrical characteristics with benchmark characteristics representing the health status, this invention can identify potential fault risks earlier and more accurately, achieving predictive diagnosis of load health status.

[0008] Preferably, the control unit is configured to determine the real-time electrical characteristics of the load as follows: Separate the active response current induced by the active probe voltage from the response current; Based on the active detection voltage and active response current, the broadband complex impedance spectrum of the load is calculated and used as part of the real-time electrical characteristics.

[0009] Preferably, the reference electrical characteristics are established through a calibration phase, and the reference electrical characteristics include: Passive electrical characteristics determined when only the fundamental voltage is applied; The defined active electrical characteristics of the broadband complex impedance spectrum included when the composite voltage is applied.

[0010] Preferably, the active detection voltage is a preset broadband signal, which is selected from a linear frequency modulated signal or a pseudo-random binary sequence signal.

[0011] Preferably, the health deviation is obtained by calculating the weighted distance between the feature vectors corresponding to the real-time electrical features and the reference electrical features.

[0012] Preferably, the control unit is further configured to: Compare the degree of health deviation to at least two incremental thresholds; Based on the comparison results, at least one of the following actions, either a warning or a power intervention, is performed before the circuit breaker operation is executed.

[0013] Preferably, the control unit is further configured to execute a hybrid modulation strategy when converting DC input electrical energy to generate AC output.

[0014] Preferably, the control unit is further configured to: Based on the broadband complex impedance spectrum determined according to the response current of the load, one or more control parameters of the hybrid modulation strategy are dynamically adjusted.

[0015] Preferably, the power conversion stage includes semiconductor switching devices based on silicon carbide or gallium nitride materials.

[0016] A method for applying a DC / AC circuit breaker includes the following steps: a. Control the power conversion stage to generate and apply a composite voltage containing the fundamental voltage and the active sensing voltage to the load; b. Collect the load's response current to the composite voltage; c. Determine the real-time electrical characteristics of the load based on the response current; d. Compare the real-time electrical characteristics with the pre-stored baseline electrical characteristics to calculate the health deviation. e. When the health deviation exceeds the preset circuit breaker threshold, the control power conversion stage performs a circuit breaker operation to cut off the power supply to the load.

[0017] This invention provides a DC / AC circuit breaker and its application method. It has the following beneficial effects: 1. This invention obtains accurate electrical characteristics of the load over a wide frequency range by controlling the power conversion stage to generate and apply a composite voltage including an active probe voltage, and calculating the broadband complex impedance spectrum of the load based on the response current. Compared with traditional techniques that rely solely on fundamental current analysis, this method can identify subtle changes in electrical characteristics caused by the degradation of internal components of the load earlier and more accurately, thereby achieving predictive identification of potential faults.

[0018] 2. This invention compares the calculated real-time electrical characteristics with baseline electrical characteristics to obtain a quantified "health deviation." Based on the comparison results of this deviation with multi-level thresholds, an early warning or power intervention can be performed before the final circuit breaker operation. This hierarchical response mechanism changes the traditional circuit breaker's only "on" or "off" state, enabling the system to take corresponding measures at different stages of fault development, avoiding unnecessary power outages, and providing a basis for equipment maintenance decisions.

[0019] 3. This invention uses the broadband complex impedance spectrum of the load obtained through active detection to dynamically adjust the control parameters of the hybrid modulation strategy of the power conversion stage. This directly links load diagnostic information with the power conversion control process, enabling the control of the conversion stage to adapt to the actual impedance characteristics of the load in real time. This achieves predictive protection while optimizing the efficiency of the conversion process and the quality of the output waveform, realizing synergistic effects between protection and conversion functions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the DC / AC circuit breaker architecture of the present invention; Figure 2 This is a schematic diagram of the logic judgment of the present invention; Figure 3 This is a schematic diagram of the application method steps of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see the appendix Figure 1 -Appendix Figure 3 The DC-AC circuit breaker includes a power conversion stage, a sensing unit, and a control unit. The control unit is electrically connected to both the power conversion stage and the sensing unit to transmit control signals and receive data signals.

[0023] The power conversion stage has its input connected to a DC power supply and its output connected to a load. This power conversion stage is configured to receive control commands from a control unit, convert the input DC power, and output AC voltage to the load.

[0024] The preferred power conversion stage employs a circuit structure based on a full-bridge inverter or half-bridge inverter topology. To generate a composite voltage containing high-frequency components, the power switching devices in the power conversion stage can utilize third-generation semiconductor devices, such as silicon carbide-based metal-oxide-semiconductor field-effect transistors (MOSFETs) or gallium nitride high-electron-mobility transistors (GaN transistors). These devices offer higher switching frequencies and lower switching losses, providing a hardware foundation for generating a fundamental voltage superimposed with a high-frequency active-probe voltage.

[0025] The sensing unit is located on the output circuit of the power conversion stage and is used to synchronously acquire the instantaneous voltage and instantaneous current signals output from the power conversion stage to the load.

[0026] The sensing unit preferably includes a current sensor and a voltage sensor. The current sensor may be a high-bandwidth Hall effect sensor or a high-precision shunt resistor connected in series with the output circuit, and the voltage sensor may be a voltage sampling circuit based on a resistor divider network and a high common-mode rejection ratio isolation amplifier.

[0027] The sensing unit converts the acquired analog signals into digital signals and sends them to the control unit for processing. To ensure the analysis of composite signals containing high-frequency active probe voltages, the analog-to-digital converter in the sensing unit has a resolution of at least 16 bits and a sampling rate in the megahertz range to guarantee sufficient dynamic range and Nyquist sampling margin.

[0028] The control unit is the physical entity that executes the method of the present invention. The control unit is preferably implemented by a digital signal processor, a microcontroller, or a field-programmable gate array. The control unit includes a processor core for executing the algorithm, flash memory for storing program code and reference electrical characteristics, and random access memory for temporarily storing real-time data.

[0029] The control unit sends control signals to the drive circuit of the power conversion stage via its internal pulse width modulation signal generator to precisely control the on and off of each switching device, thereby synthesizing the required voltage waveform at the output. Simultaneously, the control unit receives voltage and current data from the sensing unit and performs a series of operations based on this data, including determining electrical characteristics, calculating health deviations, and making protection decisions.

[0030] The core technical principles of the DC-AC circuit breaker in this embodiment of the invention will be described in detail below. This method mainly includes three core stages: the establishment of reference electrical characteristics, real-time monitoring and hierarchical predictive protection, and coordinated high-efficiency conversion control.

[0031] When a DC-AC circuit breaker is first connected to a specific load in a healthy state, or when triggered by an external command, the control unit performs a one-time calibration procedure to establish its unique reference electrical characteristics for that load. This process includes two steps: passive feature extraction and active feature extraction.

[0032] First, passive feature extraction is performed, and the control unit controls the power conversion stage to output only the standard fundamental voltage v to the load. base (t). The fundamental voltage is a pure sine wave, which can be expressed as: v base (t)=V pk sin(ω0t); Among them, V pk The preset peak voltage and ω0 represent the preset fundamental angular frequency. During this period, the sensing unit synchronously acquires the output current of one or more complete cycles, i.e., the passive response current i. passive(t). The control unit collects i passive Perform a discrete Fourier transform on (t) to obtain its complex coefficients I at each harmonic frequency. passive,k .

[0033] Based on these coefficients, a set of passive electrical characteristics is calculated, which includes at least the fundamental current RMS value I. rms,1 Power factor (PF) and total harmonic distortion (THD) i and the normalized amplitude H of the predetermined 3rd, 5th, and 7th harmonics. amp,k With phase difference H ph,k .

[0034] Next, active feature extraction is performed, and the control unit controls the power conversion stage to generate and apply a composite voltage v to the load. out (t), this voltage is determined by the fundamental voltage v base (t) and active detection voltage v probe (t) is formed by linear superposition. Active detection voltage v probe (t) is designed as a wideband swept-frequency signal, such as a linear frequency modulated signal (Chirp signal), and its mathematical expression can be: Among them, A p To detect the signal amplitude, its value is much smaller than the fundamental peak value V. pk ;f start The sweep start frequency is set to 100Hz, and K is the sweep rate, which is set to T. sweep = Scan from 100Hz to 5kHz within 20 seconds.

[0035] When applying composite voltage v out At the same time (t), the sensing unit collects the total response current i ωut (t). The control unit controls the current collected total response current i out (t) Subtract the passive response current i stored in the previous step passive (t), thus separating the active response current i induced by the active probe voltage in the time domain. active (t):i active (t)=i out (t)-i passive (t); To improve the robustness of active response current separation, the control unit preferably employs correlation-based signal processing technology. The total response current i collected is then analyzed in detail. o ut(t) and a frequency orthogonal to the fundamental voltage v b The reference signal of asc(t) is correlated to directly extract the correlation with the active detection voltage v. probe(t)-related components to maximize the suppression of interference caused by fundamental wave response drift.

[0036] The control unit then performs Fourier transform on the separated v probe (t) and i active (t) to obtain the complex representations V probe (jω) and I active (jω) in the frequency domain. By calculating the ratio of the two, the broadband complex impedance spectrum of the load within the detection frequency band is obtained where R(ω) is the resistance spectrum and X(ω) is the reactance spectrum. This set of complex impedance spectra constitutes the core of the active electrical characteristics. Finally, the control unit combines the above passive electrical characteristics with the active electrical characteristics (for example, the impedance modulus values and phase angles at multiple specific frequency points extracted from Z(jω)) to form a high-dimensional reference feature vector H base , and stores it in the non-volatile memory.

[0037] During the normal operation of the load, the control unit periodically repeats the above feature extraction process to obtain the real-time electrical characteristic vector H current .

[0038] The control unit quantifies the health deviation degree Δ current of the load by calculating the weighted distance between the real-time feature vector H base and the reference feature vector H H : where W is a diagonal weight matrix, and the weight coefficients in the matrix are set according to prior knowledge. For example, larger weight values are assigned to the frequency points sensitive to load degradation or the characteristic parameters of specific harmonics. The weight coefficients in the diagonal weight matrix W are determined by one of the following methods: A. Through offline experiments on a large number of similar loads at different aging stages, statistically analyze the sensitivity and change rate of each electrical characteristic parameter with respect to the health state, and assign high weights to the highly sensitive characteristics; B. By establishing a finite element simulation model of the load, simulating a specific physical aging process, and analyzing its projection on the electrical characteristic vector, thereby quantifying the importance of each characteristic and setting the corresponding weights.

[0039] The control unit compares the calculated health deviation degree Δ H with the preset three-level thresholds: warning threshold T1, intervention threshold T2, and open circuit threshold T3, and compares them according to T1 < T2 < T3, and executes hierarchical responses: If Δ H ≤ T1, it is judged that the load is in a healthy state; if T1 < Δ HIf the time interval is less than or equal to T2, execute the warning operation. If T2 < Δ H ≤T3, perform power intervention operations, such as actively reducing the output voltage amplitude; If Δ H >T3, immediately control the power conversion stage to perform a circuit breaker operation.

[0040] The values ​​of the warning threshold T1, intervention threshold T2, and circuit breaker threshold T3 are not arbitrarily set. These optimized thresholds are based on the health deviation Δ calculated from a large sample load over the entire life cycle. H The value is determined through statistical distribution analysis. For example, T1 can be set as Δ for a healthy sample. H The upper bound of the 95% confidence interval of the distribution, while T3 can be set as the known fault sample Δ H The lower bound of the 99% confidence interval of the distribution is used to ensure the statistical significance of the decision.

[0041] While performing the aforementioned monitoring and protection tasks, the control unit optimizes the switching process of the power conversion stage. The control unit preferably employs a hybrid modulation strategy: Within one power frequency cycle, when the normalized amplitude of the fundamental reference voltage is greater than a preset switching threshold V th At this time, the system uses unipolar SPWM modulation to reduce switching losses.

[0042] When the normalized magnitude is less than or equal to V th When this occurs, the system switches to bipolar SPWM modulation or introduces a common-mode clamping state to suppress common-mode voltage fluctuations in the region.

[0043] Furthermore, the control unit adaptively optimizes the transformation control using diagnostic information, with dead time compensation being the preferred method. The control unit can directly utilize the broadband complex impedance spectrum Z(jω) calculated in real time.

[0044] By querying Z(jω) at the power conversion stage switching frequency ω sw The reactance component X(ω) at the point sw By observing the symbol, one can predict whether the load is locally inductive or capacitive at the switching frequency.

[0045] Based on this judgment, the control unit adjusts the compensation width of the PWM pulse in advance without waiting for the actual occurrence of the current zero crossing point, thereby achieving rapid adaptation to different and changing load characteristics and improving the quality of the output voltage waveform.

[0046] This application example illustrates the use of the DC / AC circuit breaker described in this invention in a specific industrial scenario. In this scenario, the DC / AC circuit breaker is used to power an AC induction motor that drives an exhaust system.

[0047] During initial system deployment, an AC induction motor is connected to the output of a DC-AC circuit breaker. After installation, the system operator sends a "Perform Calibration" command to the control unit via the host computer software. Upon receiving the command, the control unit begins the process of establishing reference electrical characteristics.

[0048] First, the power conversion stage outputs a stable, pure sinusoidal fundamental voltage to the motor. The sensing unit collects the response current under this condition, and the control unit calculates and stores a series of passive electrical characteristics of the motor, such as the power factor and current harmonic distribution.

[0049] Subsequently, the control unit controls the power conversion stage to superimpose a linear frequency modulated signal with a preset amplitude on the fundamental voltage, preferably sweeping from 100Hz to 5kHz. The sensing unit collects the total response current under the composite voltage, and the control unit separates the active response current from the total response current and calculates the broadband complex impedance spectrum Z of the motor in a healthy state. busc (jω).

[0050] Finally, the control unit combines the aforementioned passive and active features, with Z being the preferred option here. basc The magnitude and phase angle of (jω) at multiple predetermined frequency points are integrated into a high-dimensional reference eigenvector H. base This information is stored in internal non-volatile memory. Simultaneously, based on historical data for this motor model, warning threshold T1, intervention threshold T2, and circuit breaker threshold T3 are set.

[0051] In the months following the motor's commissioning, the control unit automatically executed a real-time monitoring process at set intervals, which involved repeating the feature extraction process to obtain the real-time feature vector H. current And calculate the health deviation Δ H .

[0052] Since the motor is in good condition, Δ H The circuit remained below the warning threshold T1. After about a year of operation, due to the presence of moisture and thermal stress in the environment, the insulating varnish of the motor windings began to deteriorate slightly, resulting in a small but continuous increase in the inter-turn equivalent capacitance of the windings.

[0053] This physical change cannot be detected by traditional overcurrent protection or fundamental frequency analysis. However, in the next periodic monitoring of this invention, the real-time broadband complex impedance spectrum Z calculated by the control unit... current (jω), in its high-frequency range (e.g., above 2kHz) and the reference spectrum Z base Compared to (jω), it exhibits a identifiable difference.

[0054] This difference leads to the calculated health deviation Δ HThe warning threshold T1 was exceeded for the first time, but it remained below the intervention threshold T2. The control unit then sent a warning message to the central monitoring system via its industrial bus interface, containing information on the early deterioration trend of the A-phase winding insulation and the current Δ... H At this time, the circuit breaker did not interrupt the power supply to the motor, and the ventilation system continued to operate normally.

[0055] Upon receiving the warning, maintenance personnel planned to inspect the motor during the next maintenance cycle. During this period, the motor continued to run, further exacerbating the deterioration of its winding insulation. Several weeks later, during a monitoring session, the control unit calculated a health deviation Δ... H The voltage increased further, exceeding the intervention threshold T2. The control unit determined that the motor condition had significantly deteriorated. At this point, an automatic power intervention operation was executed: the effective value of the fundamental voltage output by the power conversion stage was proactively reduced by 5%. This measure reduced the motor's operating voltage and temperature rise while ensuring the basic functions of the exhaust system, thus delaying the occurrence of complete insulation breakdown. Simultaneously, the system issued a higher-level alarm requiring immediate maintenance.

[0056] Throughout the entire operation of the motor, including all stages from healthy to deteriorating, the control unit continuously utilizes the real-time calculated broadband complex impedance spectrum Z. current (jω) is used to collaboratively optimize the power conversion process.

[0057] Specifically according to Z current (jω) is the reactance value at the switching frequency point. The dead time compensation value of PWM modulation is dynamically adjusted to adapt to the changes in load impedance characteristics caused by insulation degradation, thereby continuously ensuring the low distortion rate of the inverter output waveform.

[0058] Ultimately, before maintenance personnel arrived on site, a sudden voltage surge accelerated the insulation collapse, causing an unstable micro-arc to form between the turns. In the following second of monitoring, the control unit detected a drastic nonlinear jump in the impedance spectrum and calculated Δ... H The circuit breaker momentarily exceeded the tripping threshold T3. The control unit immediately performed a tripping operation, and all switching devices in the power conversion stage were simultaneously turned off. Before a deterministic inter-turn short circuit occurred and triggered a huge overcurrent, the power supply to the motor was cut off, thus protecting the motor from burnout and preventing the circuit breaker itself from being damaged by the short-circuit current.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A DC / AC circuit breaker, characterized in that, include: A power conversion stage configured to convert input electrical energy and output it to the load; The sensing unit is configured to acquire voltage and current signals from the output load of the power conversion stage; The control unit, electrically connected to the power conversion stage and the sensing unit, is configured as follows: The control power conversion stage generates and applies a composite voltage, including the fundamental voltage and the active sensing voltage, to the load; The load's response current to the composite voltage is obtained through the sensing unit; Based on the response current, the real-time electrical characteristics of the load are determined; Real-time electrical characteristics are compared with pre-stored baseline electrical characteristics to calculate the health deviation. When the health deviation exceeds the preset circuit breaker threshold, the control power conversion stage performs a circuit breaker operation to cut off the power supply to the load.

2. The DC / AC circuit breaker according to claim 1, characterized in that: The control unit is configured to determine the real-time electrical characteristics of the load as follows: Separate the active response current induced by the active probe voltage from the response current; Based on the active detection voltage and active response current, the broadband complex impedance spectrum of the load is calculated and used as part of the real-time electrical characteristics.

3. A DC / AC circuit breaker according to claim 2, characterized in that: The reference electrical characteristics are established through a calibration phase, and the reference electrical characteristics include: Passive electrical characteristics determined when only the fundamental voltage is applied; The defined active electrical characteristics of the broadband complex impedance spectrum included when the composite voltage is applied.

4. A DC / AC circuit breaker according to claim 1, characterized in that: The active detection voltage is a preset broadband signal, which is selected from a linear frequency modulated signal or a pseudo-random binary sequence signal.

5. A DC / AC circuit breaker according to claim 1, characterized in that: The health deviation is obtained by calculating the weighted distance between the feature vectors corresponding to the real-time electrical features and the baseline electrical features.

6. A DC / AC circuit breaker according to claim 5, characterized in that: The control unit is also configured to: Compare the degree of health deviation to at least two incremental thresholds; Based on the comparison results, at least one of the following actions, either a warning or a power intervention, is performed before the circuit breaker operation is executed.

7. A DC / AC circuit breaker according to claim 1, characterized in that: The control unit is also configured to execute a hybrid modulation strategy when converting DC input electrical energy to generate AC output.

8. A DC / AC circuit breaker according to claim 2, characterized in that: The control unit is also configured to: Based on the broadband complex impedance spectrum determined according to the response current of the load, one or more control parameters of the hybrid modulation strategy are dynamically adjusted.

9. A DC / AC circuit breaker according to claim 1, characterized in that: The power conversion stage includes semiconductor switching devices based on silicon carbide or gallium nitride materials.

10. A method for applying a DC / AC circuit breaker, wherein the DC / AC circuit breaker according to any one of claims 1-9 is characterized in that, Includes the following steps: a. Control the power conversion stage to generate and apply a composite voltage containing the fundamental voltage and the active sensing voltage to the load; b. Collect the load's response current to the composite voltage; c. Determine the real-time electrical characteristics of the load based on the response current; d. Compare the real-time electrical characteristics with the pre-stored baseline electrical characteristics to calculate the health deviation. e. When the health deviation exceeds the preset circuit breaker threshold, the control power conversion stage performs a circuit breaker operation to cut off the power supply to the load.

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