Reverse power supply control method and system supporting mains disconnection

Abstract

The present application relates to reverse power supply control technical field, especially to a kind of reverse power supply control method and system supporting commercial power disconnection.The voltage amplitude and frequency of commercial power side are obtained, controllable impedance unit is configured between the output end of reverse power supply unit and load end, impedance value is adjusted according to commercial voltage amplitude, output power is determined, the difference between output power and load power is nonlinearly increased with the decrease of voltage amplitude;The phase error of output frequency and commercial frequency is determined, and second-order time derivative constraint is applied to it, the upper limit value of the constraint is inversely proportional to impedance value, and output voltage amplitude and frequency are adjusted synchronously according to output power and constraint, so as to maintain the continuity of load end voltage and phase difference convergence when commercial voltage amplitude decreases.

Description

Technical Field

[0001] This invention relates to the field of reverse power supply control technology, and in particular to a reverse power supply control method and system that supports mains power disconnection. Background Technology

[0002] The reverse power supply unit typically serves as a backup power source during mains power outages, its core task being to ensure an uninterrupted power supply to the load. The conventional approach is to keep the reverse power supply unit in hot standby mode when mains power is normal, continuously monitoring the voltage amplitude and frequency on the mains side. Once a mains power failure or exceeding permissible limits is detected, the power converter is activated, inverting the DC power stored in the energy storage element into AC power to supply power to the load. During this process, the control strategy generally employs a linear proportional-integral (PI) regulator, using a dual closed-loop structure of voltage outer loop and current inner loop to track the output voltage. Simultaneously, a phase-locked loop (PLL) is used to synchronously lock the mains phase, aiming to achieve phase consistency and amplitude matching at the moment of switching. System parameters are factory-set based on typical load conditions and remain fixed during operation. The direction and magnitude of power flow are passively determined by load demand, and the control quantity changes approximately linearly within a small signal disturbance range.

[0003] The shortcomings of conventional methods are as follows: When the mains power is disconnected, the bus voltage drops rapidly. Since the linear regulator's response to amplitude changes is based on a fixed error gain, its adjustment rate cannot keep up with the speed of the voltage drop. This results in significant transient dips or overshoots in the load-side voltage during switching. While power supply continuity is nominally maintained, the actual waveform quality degrades significantly, posing a potential threat to sensitive loads. Phase-locked loops (PLLs) have inherent capture and tracking delays during frequency jumps or phase abrupt changes. During dynamic processes, the phase error converges slowly according to a linear law. If the mains voltage amplitude drops rapidly, the phase alignment process may not be complete before entering full-load output mode. This causes a beat frequency phenomenon between the output frequency and the mains residual voltage frequency, resulting in periodic power oscillations and voltage fluctuations at the load end. In severe cases, this triggers overcurrent protection, causing reverse power supply failure. Linear control architectures based on fixed parameters cannot achieve a balance between transient response speed and steady-state regulation accuracy. Their adjustment capability is limited by a constant bandwidth, lacking adaptive capability in the face of wide-range mains voltage drop characteristics, becoming a major bottleneck restricting power supply reliability. Summary of the Invention

[0004] The present invention provides a reverse power supply control method and system that supports mains power disconnection, which can solve the problems in the prior art.

[0005] A first aspect of the present invention provides a reverse power supply control method for supporting mains power disconnection, comprising:

[0006] Obtain the voltage amplitude and frequency on the mains power side;

[0007] A controllable impedance unit is configured between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude on the mains side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, so that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude.

[0008] The output power of the reverse power supply unit is determined based on the power-law increasing relationship, and the difference between the output power and the load power increases nonlinearly as the voltage amplitude decreases.

[0009] The phase error between the output frequency of the reverse power supply unit and the frequency of the mains power side is determined, and a second-order time derivative constraint is applied to the phase error. The upper limit of the second-order time derivative constraint is inversely proportional to the impedance value. When the impedance value decreases, the convergence speed of the phase error increases.

[0010] The output voltage amplitude and output frequency of the reverse power supply unit are synchronously adjusted according to the output power and the second-order time derivative constraint, so as to maintain the continuous voltage at the load end and the convergence of the phase difference during the voltage amplitude decrease on the mains side.

[0011] A controllable impedance unit is configured between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude on the mains side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, so that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude, including:

[0012] The instantaneous sample value of the voltage amplitude on the mains power side is collected, and the instantaneous sample value is subjected to sliding window filtering to obtain the filtered value of the voltage amplitude;

[0013] Performing a time derivative operation on the filtered value yields the first-order time derivative of the voltage amplitude, which characterizes the instantaneous rate of change of the voltage amplitude.

[0014] When the first time derivative is negative, it is determined to be the voltage decrease phase; when the first time derivative is positive, it is determined to be the voltage increase phase.

[0015] During the voltage rise phase, the impedance value of the controllable impedance unit remains unchanged or is gradually increased according to a preset recovery rate, so that the reverse power supply unit gradually withdraws from power supply;

[0016] During the voltage drop phase, the power exponent of the power-law increasing relationship is dynamically adjusted based on the absolute value of the first-order time derivative. When the absolute value increases, the power exponent increases, so that the rate of change of the impedance value relative to the rate of change of the voltage amplitude increases as the decay rate of the voltage amplitude increases.

[0017] Substitute the filtered value into the adjusted power-law increasing function expression to calculate the target value of the impedance.

[0018] The method further includes:

[0019] The rate of change of the target impedance value is limited, and the minimum time interval required for the impedance value to change from the current value to the target value is calculated. When the minimum time interval is less than the preset minimum response time, the impedance value is adjusted according to the rate of change corresponding to the minimum response time. When the minimum time interval is greater than or equal to the minimum response time, the impedance value is directly adjusted to the target value to prevent the sudden change of the impedance value from causing a step change in the output power of the reverse power supply unit.

[0020] Based on the adjusted impedance value, the conduction state of the switching device or the duty cycle of the modulation signal in the controllable impedance unit is controlled to realize the physical representation of the impedance value. The conduction state of the switching device or the duty cycle and the impedance value satisfy a preset mapping relationship.

[0021] The output power of the reverse power supply unit is determined based on the power-law increasing relationship. The difference between the output power and the load power increases non-linearly as the voltage amplitude decreases, including:

[0022] The real-time load power and load power factor at the load terminal are obtained, and the load power factor is calculated by the phase difference between the voltage and current at the load terminal.

[0023] A second-order time derivative operation is performed on the voltage amplitude on the mains side to obtain the first-order time derivative and the second-order time derivative. The trajectory of the voltage amplitude change within a preset time period is predicted. Based on the trajectory and the power-law increasing relationship, the predicted value of the mains power transmitted from the mains side to the load side within the preset time period is calculated.

[0024] Calculate the predicted power deficit, which is equal to the difference between the real-time load power and the predicted mains power.

[0025] The power of the power-law increasing relationship is corrected based on the load power factor. When the load power factor decreases, the power factor is increased. The corrected power factor is then increased by 1 to obtain a non-linear growth power factor. The power deficit prediction value is then transformed using the non-linear growth power factor to obtain the target value of the output power. This results in the output power growth rate leading the voltage amplitude decrease rate as the load power factor decreases.

[0026] Based on the target output power value, adjust the inverter output voltage amplitude and output current amplitude of the reverse power supply unit so that the output power of the reverse power supply unit reaches the target value.

[0027] Predicting the trajectory of the voltage amplitude change within a preset time period includes:

[0028] The voltage amplitude is subjected to second-order time differentiation to obtain the first-order time derivative and the second-order time derivative. The absolute value of the second-order time derivative is calculated and compared with a preset acceleration threshold. When the absolute value is greater than the preset acceleration threshold, it is determined to be an abrupt drop and a short prediction window is used. When the absolute value is less than or equal to the preset acceleration threshold, it is determined to be a gradual drop and a long prediction window is used.

[0029] For abrupt drops, the weighting coefficient of the first-order time derivative is increased; for gradual drops, the weighting coefficient of the second-order time derivative is increased. The first-order and second-order time derivatives are weighted and combined according to the weighting coefficients to predict the trajectory of change.

[0030] In each sampling period, the predicted voltage value of the previous sampling period is compared with the actual voltage value of the current sampling period to calculate the prediction deviation rate. When the prediction deviation rate is positive, the weighting coefficient of the first-order time derivative in the current prediction is increased. When the prediction deviation rate is negative, the weighting coefficient of the first-order time derivative in the current prediction is decreased, so that the prediction error is fed back to the subsequent prediction process through the weighting coefficient adjustment.

[0031] Determine the phase error between the output frequency of the reverse power supply unit and the frequency of the mains power supply side, apply a second-order time derivative constraint to the phase error, the upper limit of the second-order time derivative constraint being inversely proportional to the impedance value, and accelerate the convergence speed of the phase error as the impedance value decreases, including:

[0032] The output voltage waveform of the sampled reverse power supply unit is compared with the voltage waveform of the mains power side, and the phase error is calculated by detecting the zero-crossing moments of the two voltage waveforms.

[0033] Obtain the current impedance value of the controllable impedance unit and the current output power of the reverse power supply unit. Calculate the instantaneous circulating current power based on the phase error, the current impedance value, and the current output power. The instantaneous circulating current power is directly proportional to the phase error and the current output power, and inversely proportional to the current impedance value.

[0034] Based on a preset maximum circulating current power threshold and an upper limit constraint value for the second-order time derivative of the phase error derived in reverse from the current impedance value and the current output power, the upper limit constraint value is inversely proportional to both the current impedance value and the current output power.

[0035] The phase error is subjected to a second-order time derivative operation to obtain a second-order time derivative, which is then limited to the upper limit constraint value. The output frequency adjustment of the reverse power supply unit is calculated based on the limited second-order time derivative, so that the phase error converges to zero with controlled acceleration and the instantaneous circulating power does not exceed the maximum circulating power threshold.

[0036] The output voltage amplitude and output frequency of the reverse power supply unit are synchronously adjusted according to the output power and the second-order time derivative constraint, maintaining continuous load-side voltage and convergent phase difference during the voltage amplitude decrease on the mains side, including:

[0037] The adjustment amount of the output voltage amplitude is calculated based on the target value of the output power, and the adjustment amount of the output frequency is calculated based on the second-order time derivative constraint.

[0038] Based on the adjustment amount of the output voltage amplitude and the adjustment amount of the output frequency, predict the voltage amplitude at the load end in the next sampling period, and calculate the voltage deviation between the predicted voltage amplitude and the actual voltage amplitude at the load end in the current sampling period;

[0039] When the absolute value of the voltage deviation is greater than a preset continuity threshold, the maximum allowable adjustment rate under the preset continuity threshold constraint is calculated, and the adjustment amount of the output voltage amplitude and the adjustment amount of the output frequency are synchronously scaled according to the maximum adjustment rate.

[0040] The inverter control signal of the reverse power supply unit is synchronously adjusted according to the limited adjustment amount, so that the change in the load-side voltage amplitude between adjacent sampling periods does not exceed the preset continuity threshold, thereby achieving a smooth transition of the load-side voltage.

[0041] A second aspect of the present invention provides a reverse power supply control system that supports mains power disconnection, comprising:

[0042] The mains power detection unit is used to obtain the voltage amplitude and frequency of the mains power side;

[0043] An impedance regulation unit is used to configure a controllable impedance unit between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude of the mains power side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, so that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude.

[0044] A power determination unit is used to determine the output power of the reverse power supply unit based on the power-law increasing relationship. The difference between the output power and the load power increases nonlinearly as the voltage amplitude decreases.

[0045] A phase constraint unit is used to determine the phase error between the output frequency of the reverse power supply unit and the frequency of the mains power side, and to apply a second-order time derivative constraint to the phase error. The upper limit of the second-order time derivative constraint is inversely proportional to the impedance value. When the impedance value decreases, the convergence speed of the phase error increases.

[0046] The output adjustment unit is used to synchronously adjust the output voltage amplitude and output frequency of the reverse power supply unit according to the output power and the second-order time derivative constraint, and to maintain the load voltage continuous and the phase difference converged during the voltage amplitude decrease on the mains side.

[0047] A third aspect of the present invention provides an electronic device, comprising:

[0048] processor;

[0049] Memory used to store processor-executable instructions;

[0050] The processor is configured to invoke instructions stored in the memory to execute the aforementioned method.

[0051] A fourth aspect of the present invention provides a computer-readable storage medium having stored thereon computer program instructions that, when executed by a processor, implement the aforementioned method.

[0052] The beneficial effects of this invention are:

[0053] In the initial stage of a mains voltage drop, the impedance value increases rapidly, effectively suppressing the instantaneous impact of the reverse power supply unit's output power and preventing a sharp drop in load voltage. As the voltage amplitude continues to decrease, the increase in impedance value causes the difference between the output power and the load power to expand non-linearly, forming a power compensation that matches the drop depth, extending the load support time, and reducing the disturbance of voltage drop to sensitive loads.

[0054] A second-order time derivative constraint is applied to the phase error. The upper limit of this constraint is inversely proportional to the impedance value; as the impedance value decreases, the phase error convergence speed increases. During dynamic adjustment, the phase difference can quickly converge to the allowable range, preventing out-of-synchronization oscillations between the reverse power supply unit and the load. The output voltage amplitude and output frequency are synchronously adjusted according to the output power and the second-order time derivative constraint. The load-side voltage remains continuous during the mains voltage drop, and the phase difference convergence process is smooth, achieving seamless switching of reverse power supply when the mains power is disconnected.

[0055] The aforementioned control method enables the reverse power supply system to adaptively adjust to voltage amplitude fluctuations. The power-law relationship between impedance and voltage reduces the difficulty of control parameter tuning and maintains stability under different voltage drop depths and rates of change. Second-order time derivative constraints improve the dynamic quality of phase tracking and suppress transient overcurrents and overvoltages caused by frequency abrupt changes. Load-side voltage continuity ensures uninterrupted power supply during switching, and phase difference convergence avoids loop-closing impacts. Overall, this improves the reliability and power quality of reverse power supply and extends equipment lifespan. Attached Figure Description

[0056] Figure 1 A flowchart illustrating the reverse power supply control method to support mains power disconnection;

[0057] Figure 2 Phase error convergence curve under second-order time derivative constraint. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below 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.

[0059] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0060] Figure 1 This is a flowchart illustrating a reverse power supply control method supporting mains power disconnection according to an embodiment of the present invention. The reverse power supply control method supporting mains power disconnection includes:

[0061] Obtain the voltage amplitude and frequency on the mains power side;

[0062] A controllable impedance unit is configured between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude on the mains side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, so that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude.

[0063] The output power of the reverse power supply unit is determined based on the power-law increasing relationship, and the difference between the output power and the load power increases nonlinearly as the voltage amplitude decreases.

[0064] The phase error between the output frequency of the reverse power supply unit and the frequency of the mains power side is determined, and a second-order time derivative constraint is applied to the phase error. The upper limit of the second-order time derivative constraint is inversely proportional to the impedance value. When the impedance value decreases, the convergence speed of the phase error increases.

[0065] The output voltage amplitude and output frequency of the reverse power supply unit are synchronously adjusted according to the output power and the second-order time derivative constraint, so as to maintain the continuous voltage at the load end and the convergence of the phase difference during the voltage amplitude decrease on the mains side.

[0066] In one optional implementation, a controllable impedance unit is configured between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude on the mains side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, such that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude. This includes:

[0067] The instantaneous sample value of the voltage amplitude on the mains power side is collected, and the instantaneous sample value is subjected to sliding window filtering to obtain the filtered value of the voltage amplitude;

[0068] Performing a time derivative operation on the filtered value yields the first-order time derivative of the voltage amplitude, which characterizes the instantaneous rate of change of the voltage amplitude.

[0069] When the first time derivative is negative, it is determined to be the voltage decrease phase; when the first time derivative is positive, it is determined to be the voltage increase phase.

[0070] During the voltage rise phase, the impedance value of the controllable impedance unit remains unchanged or is gradually increased according to a preset recovery rate, so that the reverse power supply unit gradually withdraws from power supply;

[0071] During the voltage drop phase, the power exponent of the power-law increasing relationship is dynamically adjusted based on the absolute value of the first-order time derivative. When the absolute value increases, the power exponent increases, so that the rate of change of the impedance value relative to the rate of change of the voltage amplitude increases as the decay rate of the voltage amplitude increases.

[0072] Substitute the filtered value into the adjusted power-law increasing function expression to calculate the target value of the impedance.

[0073] For example, when acquiring mains voltage signals, the voltage waveform is typically converted from analog to digital at a fixed sampling period to obtain a discrete instantaneous sampling sequence. However, due to harmonic interference, switching noise, and high-frequency disturbances introduced by the measurement circuit in actual power grids, directly using the original sampled values ​​for subsequent calculations can cause jitter in impedance adjustment commands, affecting the stability of the controllable impedance unit. Therefore, a sliding window filter is applied to the instantaneous sampled values, selecting the average of several consecutive sampling points as the current voltage amplitude filter value. The length of the sliding window needs to strike a balance between filtering effect and response delay: a window that is too short will result in insufficient noise suppression, while a window that is too long will cause a significant lag in the response to rapid voltage drops. In engineering practice, the window length typically corresponds to the number of sampling points within half to one power frequency cycle to ensure that higher-order harmonic components are effectively filtered out while preserving the fundamental amplitude information.

[0074] By performing time differentiation on the filtered voltage amplitude sequence, the first-order time derivative of the voltage amplitude can be obtained. This derivative physically characterizes the instantaneous rate of change of the voltage amplitude at the current moment. In the discrete implementation, the first-order time derivative is approximated by dividing the difference between two adjacent filtered values ​​by the sampling time interval. When the first-order time derivative is negative, it indicates that the voltage amplitude is in a decreasing trend, and it is determined that the current phase is a voltage decrease phase; when the first-order time derivative is positive, it indicates that the voltage amplitude is rising, and it is determined that the current phase is a voltage increase phase; when the first-order time derivative is close to zero, a small threshold can be set as a dead zone to avoid frequent phase switching caused by small fluctuations in the steady segment.

[0075] During the voltage rise phase, the impedance value of the controllable impedance unit remains constant or gradually increases according to a preset recovery rate. Maintaining a constant impedance is suitable for the initial voltage recovery phase, when the reverse power supply unit still needs to maintain a certain power supply capacity to prevent the voltage from dropping again. Gradually increasing the impedance value is suitable for the phase where the voltage has stabilized and is approaching normal levels. By slowly increasing the impedance, the output power of the reverse power supply unit decreases smoothly, avoiding voltage fluctuations at the load end caused by sudden impedance changes. The recovery rate setting needs to consider the typical speed of mains power recovery. An excessively fast recovery rate may cause the reverse power supply unit to exit prematurely before the mains power is fully stable, while an excessively slow recovery rate will prolong the operating time of the reverse power supply unit and increase energy loss.

[0076] During the voltage drop phase, the exponent of the power-law relationship is no longer fixed, but dynamically adjusted based on the absolute value of the first-order time derivative. Let the filtered voltage amplitude be... The target impedance value of the controllable impedance unit is The power exponent is Then the functional expression for the power-law increasing relationship is: ,in This is the proportionality constant. When the absolute value of the first-order time derivative is small, it indicates that the voltage decreases slowly. Taking a smaller value (but still greater than 1) results in a relatively gradual change in impedance with voltage amplitude; when the absolute value of the first-order time derivative increases, it indicates that the voltage drop rate accelerates, and increasing the value further is appropriate. The value of makes the impedance value more sensitive to changes in voltage amplitude, and the rate of impedance decrease leading the rate of voltage decrease increases accordingly. The physical meaning of this dynamic adjustment mechanism is that the faster the voltage drops, the faster the reverse power supply unit needs to reduce the output impedance to increase the output power, thereby compensating for the power gap at the load end in a shorter time.

[0077] The mapping relationship between the first-order time derivative and the absolute value of the first-order time derivative can be achieved using piecewise linear functions or a lookup table. Let the first-order time derivative be... During the voltage drop phase Take its absolute value As a basis for adjustment. When When it is below a certain lower threshold, Take the baseline value (Usually set between 1.5 and 2); when When it exceeds a certain upper limit threshold, Take the maximum value (Usually not exceeding 4 to 5, to avoid excessive compression of the impedance value in the low voltage range leading to overcurrent); between the two thresholds, Follow The parameter increases linearly. This segmented processing method ensures the continuity of adjustment while avoiding parameter values ​​exceeding the hardware's allowable range in extreme cases.

[0078] Filter the voltage amplitude at the current moment. Substitute the adjusted power-law function The target impedance value of the controllable impedance unit can then be calculated. The target value is then sent as a control command to the drive circuit of the controllable impedance unit. The drive circuit adjusts the conduction state of internal switching devices or the connection amount of passive components according to the target value, so that the actual impedance tracks the target value. In practical engineering, the controllable impedance unit can be implemented by multiple sets of resistors or reactance components switched in stages via relays or power semiconductor devices. The impedance target value is quantized and mapped to the corresponding switching combination, thereby selecting the range closest to the target value from the discrete impedance ranges for operation.

[0079] proportionality coefficient The determination needs to be based on the system's rated parameters during calibration. This is done when the mains voltage is within the normal range. At this time, the controllable impedance unit should present a higher impedance to limit the output of the reverse power supply unit. Therefore, let... Thus we obtain When the mains voltage drops to the switching threshold In the following cases, the impedance value should be reduced to the minimum value that allows the reverse power supply unit to output full power. This constraint is used for verification. and Does the combination satisfy? If the requirements are not met, adjustments are necessary. or The value of is determined by the above calibration process, which ensures that the target impedance value remains within the hardware-achievable range throughout the entire voltage drop range, while also satisfying the power-law increasing relationship requirement that the impedance change rate leads the voltage amplitude change rate.

[0080] In an optional implementation, the method further includes:

[0081] The rate of change of the target impedance value is limited, and the minimum time interval required for the impedance value to change from the current value to the target value is calculated. When the minimum time interval is less than the preset minimum response time, the impedance value is adjusted according to the rate of change corresponding to the minimum response time. When the minimum time interval is greater than or equal to the minimum response time, the impedance value is directly adjusted to the target value to prevent the sudden change of the impedance value from causing a step change in the output power of the reverse power supply unit.

[0082] Based on the adjusted impedance value, the conduction state of the switching device or the duty cycle of the modulation signal in the controllable impedance unit is controlled to realize the physical representation of the impedance value. The conduction state of the switching device or the duty cycle and the impedance value satisfy a preset mapping relationship.

[0083] For example, in practical engineering implementations, the impedance value of a controllable impedance unit cannot follow the target value change indefinitely. If the impedance value changes abruptly, the output power of the reverse power supply unit will experience a step fluctuation in a very short time. This step change will excite the parasitic inductance and distributed capacitance in the circuit to oscillate, which in severe cases can lead to overcurrent protection activation or a temporary drop in output voltage, affecting the continuity of the load voltage. Therefore, it is necessary to impose a rate-of-change limit on the change process of the target impedance value, so that the actual adjustment process of the impedance value is subject to time-constrained control.

[0084] Let the actual impedance value of the controllable impedance unit at the current moment be... The target impedance value calculated from the power-law increasing relationship is The preset minimum response time is The maximum allowable rate of change of the controllable impedance unit is Calculate the minimum time interval required for the current value to change to the target value. Its expression is .when This indicates that if the impedance value is adjusted directly according to the maximum rate of change, the change will be too drastic. In this case, the actual rate of change is limited to [a certain value]. That is, in Complete within a time limit arrive A smooth transition; when When this occurs, it indicates that the difference between the target value and the current value is within the allowable rate of change and can be safely reached; the impedance value can then be directly adjusted to... No additional rate limit is required.

[0085] The physical significance of this rate-of-change limiting mechanism lies in the fact that in scenarios where the mains voltage amplitude decreases rapidly, the power-law increasing relationship will cause the target impedance value to decrease rapidly. If it follows without restriction, the output power of the reverse power supply unit will undergo a large jump within milliseconds. By introducing... Constraints stretch the power change process to a controllable time scale, so that the adjustment of output power matches the dynamic response of the load, avoiding voltage dips or overshoots caused by power steps. The value needs to be determined by combining the control bandwidth of the reverse power supply unit and the dynamic characteristics of the load. The typical value range is between several milliseconds and tens of milliseconds. The specific value is calibrated according to the power level and switching frequency of the actual system.

[0086] After the rate of change is limited, the adjusted impedance value needs to be physically realized by controlling the switching devices in the controllable impedance unit. The specific circuit configuration of the controllable impedance unit determines the mapping relationship between the impedance value and the control signal. In the scheme of using a switched capacitor array to realize controllable impedance, capacitors of different capacitances are connected in parallel or series through their corresponding switching devices. By controlling the on and off states of each switching device, different capacitor combinations are selected, thereby achieving the target impedance value in a discrete stepwise sense. At this time, the mapping relationship between the impedance value and the switching state is pre-stored in the form of a lookup table. The corresponding switching state code is directly indexed according to the adjusted impedance value to drive the operation of each switching device.

[0087] In a variable impedance unit controlled by pulse width modulation, the switching device switches at a fixed frequency, and the duty cycle is adjusted by regulating the ratio of the on-time to the switching period. The equivalent impedance value is adjusted using a Buck converter-based controllable impedance unit. For example, the equivalent impedance... Duty cycle Between satisfy ,in The reference impedance parameter is determined by the circuit topology and component parameters. Based on the adjusted impedance value... The required duty cycle can be obtained by inverse kinematics. The duty cycle value is written into the pulse width modulation register, which drives the switching devices to turn on and off according to the corresponding timing, thereby realizing the physical representation of the target impedance.

[0088] In actual control implementation, duty cycle The calculation results need to be subjected to saturation limiting to ensure that they always remain within the physically realizable range. Within this timeframe, abnormal control commands caused by calculation errors or boundary conditions are prevented. Simultaneously, the drive signals for the switching devices must undergo dead-time compensation to avoid short circuits caused by simultaneous conduction of the upper and lower bridge arms. The length of the dead time depends on the turn-off delay characteristics of the switching devices. It is typically configured during the drive circuit design phase based on parameters in the device datasheet, and the impact of the dead time on the equivalent duty cycle is corrected at the software level using a compensation algorithm to ensure that the deviation between the actual equivalent impedance value and the target value is within the allowable range.

[0089] For controllable impedance units constructed using contact-based or semi-controlled devices such as thyristors or relays, the switching of their conduction states is subject to inherent constraints on minimum on-time and minimum off-time. In such schemes, the rate-of-change limiting mechanism must also consider the minimum operating interval of the device, ensuring that the time interval between two adjacent state transitions is not less than the minimum value specified in the device datasheet, preventing overheating or contact sticking due to frequent switching. The control logic calculates... At this time, the minimum operating interval of the device needs to be compared with the preset value. A larger value is chosen as the actual constraint, thereby protecting the device while maintaining the smoothness of impedance adjustment.

[0090] The mapping relationship between the adjusted impedance value and the on-state or duty cycle of the switching device is established during the system initialization phase through a calibration process. During calibration, each target impedance value is set sequentially, the corresponding actual equivalent impedance is measured, and the correspondence between the control quantity and the measured impedance is recorded, forming a calibration table or fitting curve. During operation, the control quantity is calculated directly by looking up the table or substituting it into the fitting formula, avoiding impedance deviations caused by component parameter dispersion or temperature drift. For applications requiring high accuracy, the actual impedance value can be periodically estimated online during operation, and the deviation between the estimated result and the target value is fed back to the control quantity correction stage, forming a closed-loop correction and further improving impedance control accuracy.

[0091] In one optional implementation, the output power of the reverse power supply unit is determined based on the power-law increasing relationship, wherein the difference between the output power and the load power increases non-linearly as the voltage amplitude decreases, including:

[0092] The real-time load power and load power factor at the load terminal are obtained, and the load power factor is calculated by the phase difference between the voltage and current at the load terminal.

[0093] A second-order time derivative operation is performed on the voltage amplitude on the mains side to obtain the first-order time derivative and the second-order time derivative. The trajectory of the voltage amplitude change within a preset time period is predicted. Based on the trajectory and the power-law increasing relationship, the predicted value of the mains power transmitted from the mains side to the load side within the preset time period is calculated.

[0094] Calculate the predicted power deficit, which is equal to the difference between the real-time load power and the predicted mains power.

[0095] The power of the power-law increasing relationship is corrected based on the load power factor. When the load power factor decreases, the power factor is increased. The corrected power factor is then increased by 1 to obtain a non-linear growth power factor. The power deficit prediction value is then transformed using the non-linear growth power factor to obtain the target value of the output power. This results in the output power growth rate leading the voltage amplitude decrease rate as the load power factor decreases.

[0096] Based on the target output power value, adjust the inverter output voltage amplitude and output current amplitude of the reverse power supply unit so that the output power of the reverse power supply unit reaches the target value.

[0097] For example, when obtaining the real-time load power and load power factor at the load end, it is necessary to synchronously sample the voltage and current signals at the load end. The load power factor is obtained by calculating the phase difference between the voltage and current waveforms at the load end. Specifically, the sampled voltage and current signals are subjected to discrete Fourier transforms respectively, and the phase angle of the fundamental component is extracted. The difference between the two is the phase difference angle. Load power factor satisfy Real-time load power It is obtained by multiplying the effective value of voltage, the effective value of current, and the power factor, i.e. ,in This is the effective value of the load terminal voltage. This represents the effective value of the load current. In practical engineering, the load power factor fluctuates with changes in load type. The power factor is lower when the inductive load is heavy, and closer to 1 when the load is purely resistive. Therefore, it is necessary to track the power factor in real time rather than using a fixed value.

[0098] When performing second-order time derivative calculations on the mains voltage amplitude, the first-order time derivative of the voltage amplitude is calculated sequentially using the finite difference method based on a discrete-time series. With the second time derivative Let the amplitude of the mains voltage at the current moment be... The sampling time step is Then the first derivative is approximately: The second derivative is approximately: .based on and The second-order Taylor expansion is used to predict the future time period. The voltage amplitude change trajectory within is predicted, and the predicted value is... satisfy: ;in To predict the time offset, the predicted trajectory is substituted into a power-law increasing relationship to obtain the predicted impedance value of the controllable impedance unit in the future time period. Then, based on the equivalent circuit on the mains side, the predicted mains power transmitted from the mains to the load side is calculated. The predicted mains power reflects the actual power level that the mains side can provide to the load during a continuous decline in mains voltage, providing a basis for subsequent power deficit calculations.

[0099] Power deficit prediction Defined as the difference between real-time load power and the predicted mains power, i.e. When the mains voltage amplitude decreases, the predicted mains power decreases accordingly, while the load power remains relatively stable for a short period. Therefore, the predicted power deficit increases as the voltage amplitude decreases. This nonlinear increase stems from the power-law relationship's control over impedance: the impedance increases at a rate greater than 1 as the voltage amplitude decreases, causing the power transmitted from the mains side to the load to decrease at a superlinear rate. Consequently, the rate of increase in the power deficit outpaces the rate of decrease in the voltage amplitude.

[0100] Based on load power factor When correcting the exponent of a power-law increasing relationship, the correction rule is: when When decreasing, the power factor is increased to enhance the lead of the output power of the reverse power supply unit. Let the basic power factor of the power-law increasing relationship be... Corrected power satisfy: ;in To correct the gain coefficient, the value is calibrated according to the load characteristics, and is usually selected between 2 and 5. The lower, The larger the power, the more corrected the power. The larger the value, the more aggressive the power lead compensation strategy is needed when the inductive load is heavy. The corrected power factor... Adding 1 yields a non-linear growth exponent. It is used to perform a power transformation on the predicted power deficit value and output the target power value. satisfy: ;in For dimensionless normalization coefficients, ensure The dimensions of the power are consistent with those of the power, and its value is determined by the typical range of the system's rated power and power deficit. The power transformation makes the growth of the target output power value relative to the power deficit exhibit superlinear characteristics. That is, when the power deficit is small, the increase in output power is limited, while when the power deficit expands rapidly, the output power follows at a higher rate, thereby achieving timely compensation for load power in scenarios where the mains voltage drops rapidly.

[0101] When adjusting the inverter output voltage and current amplitudes of the reverse power supply unit according to the output power target value, the inverter's control loop uses... As the outer loop power setpoint. The outer loop power controller will With the actual output power of the inverter The deviation is fed into the proportional-integral regulator, and the output current amplitude setpoint is... Inner loop current controller tracking Precise control of the output current amplitude is achieved by adjusting the modulation amplitude of the inverter. Simultaneously, the inverter output voltage amplitude... Closed-loop regulation is performed based on the difference between the measured load voltage and the setpoint to ensure that the load voltage remains within the allowable range as the mains voltage drops. The two control loops work together to converge the actual output power of the reverse power supply unit to the target value. This enables dynamic compensation for load power deficit.

[0102] Under conditions of low load power factor, inductive loads absorb a large amount of reactive power, requiring the inverter to provide reactive power support to the load while simultaneously supplying active power. In this case, the corrected power factor... With a larger output power target, the inverter becomes more sensitive to power deficits, leading to a higher output current amplitude setpoint. This allows for the rapid establishment of sufficient output power reserves in the early stages of a mains voltage drop, preventing load-side voltage drops from exceeding permissible limits due to power compensation lag. The entire power control process, from real-time acquisition of the load power factor, second-order differential prediction of the voltage amplitude, calculation of power deficit, power correction and transformation, to the execution of the inverter's dual-loop control, forms a complete closed-loop power management chain, ensuring the continuity and stability of power supply to the load during mains power outage transitions.

[0103] In one optional implementation, predicting the trajectory of the voltage amplitude change over a future preset time period includes:

[0104] The voltage amplitude is subjected to second-order time differentiation to obtain the first-order time derivative and the second-order time derivative. The absolute value of the second-order time derivative is calculated and compared with a preset acceleration threshold. When the absolute value is greater than the preset acceleration threshold, it is determined to be an abrupt drop and a short prediction window is used. When the absolute value is less than or equal to the preset acceleration threshold, it is determined to be a gradual drop and a long prediction window is used.

[0105] For abrupt drops, the weighting coefficient of the first-order time derivative is increased; for gradual drops, the weighting coefficient of the second-order time derivative is increased. The first-order and second-order time derivatives are weighted and combined according to the weighting coefficients to predict the trajectory of change.

[0106] In each sampling period, the predicted voltage value of the previous sampling period is compared with the actual voltage value of the current sampling period to calculate the prediction deviation rate. When the prediction deviation rate is positive, the weighting coefficient of the first-order time derivative in the current prediction is increased. When the prediction deviation rate is negative, the weighting coefficient of the first-order time derivative in the current prediction is decreased, so that the prediction error is fed back to the subsequent prediction process through the weighting coefficient adjustment.

[0107] For example, when performing a second-order time derivative operation on the mains voltage amplitude, it is necessary to calculate the first-order and second-order time derivatives of the voltage amplitude sequentially within a continuous sampling period. Let the mains voltage amplitude at the current sampling moment be... The voltage amplitude at the previous sampling time was The sampling time step is Then the first time derivative It is obtained by dividing the difference between adjacent sampled values ​​by the sampling step size, i.e. Second-order time derivative This is obtained by dividing the difference between adjacent first derivatives by the sampling step size, i.e. To suppress the interference of sampling noise on the differential operation, a low-pass filter is applied to the original voltage sampling sequence before performing the above differential calculation. The filter cutoff frequency is determined based on several harmonic components of the mains frequency to ensure that the filtered voltage sequence is smooth and retains the drop trend information.

[0108] The second time derivative was calculated. Then, take its absolute value. and with preset acceleration threshold Comparison. When When the voltage drop is determined to be a sudden drop, this type of drop is usually caused by a short-circuit fault, a sudden connection of a large-capacity load, or the operation of grid-side protection. The voltage amplitude changes drastically in a very short time, and the absolute value of the second derivative is significantly larger. When this occurs, it is determined to be a gradual voltage drop. This type of drop is usually caused by a slow increase in load, a gradual increase in line impedance, or a slow decrease in generator output. The voltage amplitude decreases continuously at a relatively gentle rate, and the absolute value of the second derivative is small. Preset acceleration threshold. The value needs to be calibrated during the commissioning phase in combination with the actual power grid characteristics and load type. The typical value range corresponds to the acceleration level corresponding to the voltage amplitude changing by 5% to 10% of the rated amplitude within one power frequency cycle.

[0109] For abrupt drops, a short prediction window is used. The prediction window is typically set to 1 to 3 power frequency cycles to ensure that the prediction results can quickly track rapid voltage changes and avoid interference from historical data on the current trend due to an excessively long prediction window. For gradual voltage drops, a longer prediction window is used. The prediction time is typically set to 5 to 10 power frequency cycles. By utilizing the voltage change trend over a longer period, the prediction accuracy is improved, and the impact of short-term noise on the prediction results is reduced. The prediction window is switched immediately when the drop type determination result changes, without any delay, to ensure timely response.

[0110] In the weighted portfolio prediction phase, for abrupt drops, the weighting coefficient of the first-order time derivative is increased. Reduce the weighting coefficient of the second time derivative This ensures that the prediction result is primarily determined by the current voltage change rate, thereby quickly capturing the immediate trend of voltage dips. For gradual voltage dips, the weighting coefficient of the second-order time derivative is increased. Reduce the weighting coefficient of the first-order time derivative This allows the prediction results to fully utilize the acceleration information of voltage changes, improving the prediction accuracy for slow drop processes. Future moments voltage amplitude prediction Calculated using the following formula: ;

[0111] in To predict the time offset, and Satisfy normalization constraints The specific values ​​for both are dynamically adjusted based on the drop type determination result. For abrupt drop types, the typical values ​​are... The typical value for a gradual drop is... The above values ​​can be further optimized based on the characteristics of the power grid in actual engineering projects.

[0112] In each sampling period, the predicted voltage value from the previous sampling period for the current moment is used. The voltage value actually measured during the current sampling period Compare the results and calculate the prediction bias rate. Its definition is: ;

[0113] when If this occurs, it indicates that the predicted value of the previous cycle was higher than the actual value, meaning the prediction was too optimistic and underestimated the rate of voltage drop. In this case, the weighting coefficient of the first-order time derivative in the current prediction should be increased. This makes the prediction results more sensitive to the actual rate of voltage drop. When When this occurs, it indicates that the predicted value of the previous cycle was lower than the actual value, meaning the prediction was too pessimistic and overestimated the rate of voltage drop. In this case, the weighting coefficient of the first-order time derivative in the current prediction should be reduced. The weighting coefficient of the second time derivative is increased accordingly. This makes the prediction results rely more on acceleration information to correct the tendency of overtracking. The adjustment amount of the weight coefficients is proportional to the absolute value of the prediction bias rate, and the adjustment step size is... Determined by the following formula: ;in The gain coefficient is adjusted for weighting, and its value typically ranges from 0.05 to 0.2. A value that is too large... This can cause the weighting coefficients to oscillate; if they are too small, the feedback adjustment effect will be insignificant. The adjusted weighting coefficients need to undergo saturation limiting to ensure... and All remain within the preset upper and lower limits, while maintaining normalization constraints.

[0114] Through the aforementioned prediction error rate feedback mechanism, the prediction error is quantified and converted into an adjustment amount for the weight coefficients in each sampling period, which is then fed back to the subsequent prediction process, forming a closed-loop adaptive prediction structure. This mechanism enables the prediction model to automatically correct the weight allocation when the voltage drop characteristics change, without manual intervention. This maintains high prediction accuracy even during the transition between abrupt and gradual voltage drops, providing accurate voltage change trajectory data for subsequent output power adjustment and phase error control of the reverse power supply unit.

[0115] In one optional implementation, the phase error between the output frequency of the reverse power supply unit and the frequency of the mains power side is determined, and a second-order time derivative constraint is applied to the phase error. The upper limit of the second-order time derivative constraint is inversely proportional to the impedance value. When the impedance value decreases, the convergence speed of the phase error increases, including:

[0116] The output voltage waveform of the sampled reverse power supply unit is compared with the voltage waveform of the mains power side, and the phase error is calculated by detecting the zero-crossing moments of the two voltage waveforms.

[0117] Obtain the current impedance value of the controllable impedance unit and the current output power of the reverse power supply unit. Calculate the instantaneous circulating current power based on the phase error, the current impedance value, and the current output power. The instantaneous circulating current power is directly proportional to the phase error and the current output power, and inversely proportional to the current impedance value.

[0118] Based on a preset maximum circulating current power threshold and an upper limit constraint value for the second-order time derivative of the phase error derived in reverse from the current impedance value and the current output power, the upper limit constraint value is inversely proportional to both the current impedance value and the current output power.

[0119] The phase error is subjected to a second-order time derivative operation to obtain a second-order time derivative, which is then limited to the upper limit constraint value. The output frequency adjustment of the reverse power supply unit is calculated based on the limited second-order time derivative, so that the phase error converges to zero with controlled acceleration and the instantaneous circulating power does not exceed the maximum circulating power threshold.

[0120] Combination Figure 2 The convergence curve of the phase error under the second-order time derivative constraint is used to illustrate this. This figure is a screenshot from within the system, showing the convergence process of the phase error between the output frequency of the reverse power supply unit and the frequency on the mains side under the second-order time derivative constraint during the mains voltage drop. The horizontal axis represents the time series (t-3 to t+1), and the vertical axis represents the phase error value (unit: rad). The curve shows that the phase error starts at 0.12 rad, converges to 0.023 rad after three control cycles, and is predicted to further converge to 0.008 rad in the next cycle, verifying the technical effect of "phase error converging to zero with controlled acceleration". The frequency adjustment amount of +0.12 Hz is calculated based on the upper limit constraint of the second derivative, ensuring that the instantaneous circulating current power does not exceed the preset threshold during the convergence process.

[0121] When sampling the output voltage waveform of the reverse power supply unit and the voltage waveform of the mains side, zero-crossing detection circuits need to be configured on both signal acquisition channels. The zero-crossing detection circuits monitor the voltage waveform in real time, recording the timestamp when the waveform changes from a negative value across the zero axis to a positive value, thus obtaining the zero-crossing time of the reverse power supply unit's output voltage. Zero crossing time of the mains voltage Phase error Defined as the difference between two zero-crossing moments and the mains voltage period. The ratio is then multiplied by ,Right now To suppress noise interference, a moving average is applied to the zero-crossing time differences over multiple consecutive periods, and the most recent value is taken. The average value of each period is used as an estimate of the current phase error, where The frequency fluctuation range of the mains power is pre-set, usually taking 3 to 5 cycles.

[0122] Obtain the current impedance value of the controllable impedance unit. Current output power of the reverse power supply unit Then, calculate the instantaneous circulating power. The circulating current power reflects the ineffective power exchange between the reverse power supply unit and the mains power due to phase asynchrony. Its magnitude is directly proportional to the sine of the phase error and the current output power, and inversely proportional to the current impedance. When the phase error is small... Therefore, the instantaneous circulating power can be approximately expressed as ,in The dimensional normalization coefficient is used to ensure that the units on both sides of the equation are consistent. This expression shows that, under the same phase error conditions, the smaller the impedance value, the greater the circulating current power. This is consistent with the operating state of the controllable impedance unit as the impedance decreases during the mains voltage drop. Therefore, it is necessary to suppress the growth of circulating current power by accelerating the convergence of phase error.

[0123] Based on the preset maximum circulating current power threshold Combined with the current impedance value With current output power Inversely derive the upper limit constraint value of the second-order time derivative of the phase error. The derivation is based on the following logic: if the phase error is expressed as a second derivative... Convergence occurs when the maximum value of the phase error during the convergence process is affected by the initial error. This is determined in conjunction with the convergence acceleration. To ensure that the circulating power never exceeds [a certain value] throughout the entire convergence process. It is necessary to Apply constraints. Substituting the circulating power constraint condition, we obtain... ,in These are the tuning coefficients related to the control cycle and initial error. This expression directly reflects the relationship between the upper limit constraint value and... Proportional to, and They are inversely proportional. When the mains voltage drops, it causes... When decreasing, The reduction in this rate means that the phase error is allowed to converge at a greater acceleration, thereby accelerating the synchronization speed under conditions of reduced impedance and increased circulating current risk.

[0124] For phase error The discrete difference method is used when performing second-order time differential operations. Let the control period be... The phase error at the current moment is The previous moment was The moment before that was Then the first difference Second-order difference Calculations yielded Then, compare it with the upper limit constraint value. Comparison: If Then Cut off to ;like Then cut off to Otherwise, the original value remains unchanged. The truncation operation ensures that the convergence acceleration of the phase error is always within a controlled range, avoiding distortion of the output voltage waveform caused by excessive frequency adjustment.

[0125] Based on the restricted second-order time derivative Calculate the output frequency adjustment of the reverse power supply unit. The frequency adjustment is related to both the first and second derivatives of the phase error: the first derivative reflects the current trend of phase error change, and the second derivative reflects the convergence acceleration. The output frequency adjustment is expressed as... ,in These are the proportional, derivative, and second-order derivative gain coefficients, respectively, which are tuned offline based on the system's damping characteristics and response speed requirements. Reference output frequency superimposed on the reverse power supply unit The actual output frequency command is obtained from the above. The command is then sent to the inverter's pulse width modulation module to drive the output voltage waveform to track the mains frequency in real time.

[0126] As the amplitude of the mains voltage continues to decrease... It decreases as the power-law increasing relationship reverses. As the voltage decreases synchronously, the response bandwidth of frequency regulation increases accordingly. This adaptive mechanism makes the convergence speed of phase error positively correlated with the risk of mains power disconnection: the lower the mains voltage and the higher the risk of disconnection, the faster the phase error converges, and the sooner the reverse power supply unit completes frequency synchronization with the mains, laying the foundation for a seamless switch to islanded power supply mode. Meanwhile, due to... Because of its existence, the rate of change of the frequency regulation is always constrained, and the instantaneous circulating power will not exceed [a certain limit]. This protects the power devices of the reverse power supply unit from overcurrent surges. The entire phase error control process completes a full sampling, calculation, and adjustment closed loop in each control cycle, ensuring that the phase continuity of the load-side voltage is maintained throughout the entire process of mains voltage drop.

[0127] In one optional implementation, the output voltage amplitude and output frequency of the reverse power supply unit are synchronously adjusted according to the output power and the second-order time derivative constraint, maintaining continuous load-side voltage and convergent phase difference during the voltage amplitude decrease on the mains side, including:

[0128] The adjustment amount of the output voltage amplitude is calculated based on the target value of the output power, and the adjustment amount of the output frequency is calculated based on the second-order time derivative constraint.

[0129] Based on the adjustment amount of the output voltage amplitude and the adjustment amount of the output frequency, predict the voltage amplitude at the load end in the next sampling period, and calculate the voltage deviation between the predicted voltage amplitude and the actual voltage amplitude at the load end in the current sampling period;

[0130] When the absolute value of the voltage deviation is greater than a preset continuity threshold, the maximum allowable adjustment rate under the preset continuity threshold constraint is calculated, and the adjustment amount of the output voltage amplitude and the adjustment amount of the output frequency are synchronously scaled according to the maximum adjustment rate.

[0131] The inverter control signal of the reverse power supply unit is synchronously adjusted according to the limited adjustment amount, so that the change in the load-side voltage amplitude between adjacent sampling periods does not exceed the preset continuity threshold, thereby achieving a smooth transition of the load-side voltage.

[0132] For example, when the output voltage amplitude and output frequency of the reverse power supply unit need to be adjusted synchronously, the core challenge lies in constraining the rate of change of the two adjustment quantities to prevent discontinuous jumps in the load-side voltage between adjacent sampling periods. The calculation of the adjustment quantities is carried out in two parallel paths: the adjustment quantity of the output voltage amplitude is derived from the output power target value, and the adjustment quantity of the output frequency is derived from the second-order time derivative constraint of the phase error. Both need to undergo unified continuity verification and synchronous scaling processing before entering the inverter control signal.

[0133] The calculation of the output voltage amplitude adjustment is based on the power balance relationship. Let the target output power of the reverse power supply unit be [value missing]. The current output voltage amplitude of the inverter is The equivalent impedance of the load is Then the target voltage amplitude satisfy Thus we obtain Voltage amplitude adjustment amount Defined as the difference between the target voltage amplitude and the current output voltage amplitude, i.e. In actual engineering, It can be estimated in real time by the ratio of the effective value of the load terminal voltage to the effective value of the current during the current sampling period, so as to adapt to the scenario of dynamic load changes.

[0134] The calculation of the output frequency adjustment depends on the second-order time derivative constraint of the phase error. Let the current phase error be... Its first time derivative is The upper limit of the second-order time derivative constraint is In each control cycle Internal frequency adjustment amount It is calculated by applying a composite control law of proportional-derivative-second-derivative to the phase error. As the impedance value of the controllable impedance unit increases as it decreases, the allowable range of frequency adjustment expands accordingly, and the convergence speed of the phase error accelerates. This mechanism ensures that the frequency tracking response remains coordinated with the impedance adjustment process during the rapid decrease phase of the mains voltage amplitude.

[0135] In obtaining voltage amplitude adjustment amount With frequency adjustment Next, it is necessary to predict the voltage amplitude at the load end in the next sampling period to determine whether the adjustment meets the continuity constraint. Let the actual voltage amplitude at the load end in the current sampling period be... The predicted voltage amplitude is ,but ,in Frequency adjustment amount The resulting voltage amplitude coupling change can be estimated through linearization of the inverter's small-signal model. Voltage deviation Defined as the absolute value of the difference between the predicted voltage amplitude and the current actual voltage amplitude, i.e. .

[0136] Let the preset continuity threshold be... ,when At this time, the adjustment amount does not need to be scaled and is directly sent to the inverter control signal generation stage. At this time, it is necessary to calculate the maximum allowable adjustment rate under the continuity threshold constraint. Its expression is ,satisfy At this point, proportional scaling is applied simultaneously to both the voltage amplitude adjustment and the frequency adjustment, and the scaled adjustment values ​​are respectively... and The key to synchronized scaling is that both adjustment values ​​use the same scaling factor. This maintains the relative proportional relationship between the output voltage amplitude change and the output frequency change, avoiding the introduction of additional phase error or power fluctuation due to inconsistent scaling between the two.

[0137] The scaled adjustment is sent to the inverter control signal generation stage. The output voltage amplitude command is generated by... The output frequency command is given by Given, among which The inverter's pulse width modulation module generates a drive signal in real time based on the amplitude and frequency commands mentioned above, driving the power switching transistors to output AC voltage according to the target voltage amplitude and target frequency. Because the change in the load-side voltage amplitude within each control cycle is strictly limited to... Within this range, the voltage waveform between adjacent sampling periods achieves a smooth transition in amplitude, eliminating voltage abrupt changes caused by excessive adjustment.

[0138] As the mains voltage amplitude continues to decrease, the aforementioned synchronous adjustment mechanism is executed cyclically within each control cycle. As the mains voltage amplitude decreases, the impedance value of the controllable impedance unit decreases according to a power-law relationship, the output power target value of the reverse power supply unit increases accordingly, and the voltage amplitude adjustment... Gradually increase. At the same time, the upper limit of the second-order time derivative constraint of the phase error... The frequency adjustment increases as the impedance value decreases. The allowable range of variation is expanded, and the phase error convergence is accelerated. Continuity threshold The voltage remains constant throughout the transition process, ensuring that the change in the load-side voltage amplitude is always constrained in each control cycle. This enables a continuous and smooth transition of the load-side voltage and rapid convergence of the phase difference during the voltage drop phase before the mains power is disconnected.

[0139] When the mains voltage amplitude drops to near zero, the impedance value of the controllable impedance unit has dropped to near its minimum value, and the reverse power supply unit bears the full load power. At this time, the target output power value and the load power tend to be consistent, and the voltage amplitude adjustment... Approaching zero, frequency adjustment amount The phase error has also converged to near zero because it has fallen within the allowable range. The continuity check result satisfies... Scaling factor Approaching 1, the adjustment amount can be directly output without scaling. The load-side voltage maintains continuous amplitude and convergent phase difference throughout the entire mains power disconnection transition process, completing a smooth switch from mains power supply to reverse power supply.

[0140] A second aspect of the present invention provides a reverse power supply control system that supports mains power disconnection, comprising:

[0141] The mains power detection unit is used to obtain the voltage amplitude and frequency of the mains power side;

[0142] An impedance regulation unit is used to configure a controllable impedance unit between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude of the mains power side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, so that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude.

[0143] A power determination unit is used to determine the output power of the reverse power supply unit based on the power-law increasing relationship. The difference between the output power and the load power increases nonlinearly as the voltage amplitude decreases.

[0144] A phase constraint unit is used to determine the phase error between the output frequency of the reverse power supply unit and the frequency of the mains power side, and to apply a second-order time derivative constraint to the phase error. The upper limit of the second-order time derivative constraint is inversely proportional to the impedance value. When the impedance value decreases, the convergence speed of the phase error increases.

[0145] The output adjustment unit is used to synchronously adjust the output voltage amplitude and output frequency of the reverse power supply unit according to the output power and the second-order time derivative constraint, and to maintain the load voltage continuous and the phase difference converged during the voltage amplitude decrease on the mains side.

[0146] A third aspect of the present invention provides an electronic device, comprising:

[0147] processor;

[0148] Memory used to store processor-executable instructions;

[0149] The processor is configured to invoke instructions stored in the memory to execute the aforementioned method.

[0150] A fourth aspect of the present invention provides a computer-readable storage medium having stored thereon computer program instructions that, when executed by a processor, implement the aforementioned method.

Claims

1. A reverse power supply control method supporting mains power disconnection, characterized in that, include: Obtain the voltage amplitude and frequency on the mains power side; A controllable impedance unit is configured between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude on the mains side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, so that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude. The output power of the reverse power supply unit is determined based on the power-law increasing relationship, and the difference between the output power and the load power increases nonlinearly as the voltage amplitude decreases. The phase error between the output frequency of the reverse power supply unit and the frequency of the mains power side is determined, and a second-order time derivative constraint is applied to the phase error. The upper limit of the second-order time derivative constraint is inversely proportional to the impedance value. When the impedance value decreases, the convergence speed of the phase error increases. The output voltage amplitude and output frequency of the reverse power supply unit are synchronously adjusted according to the output power and the second-order time derivative constraint, so as to maintain the continuous voltage at the load end and the convergence of the phase difference during the voltage amplitude decrease on the mains side.

2. The method according to claim 1, characterized in that, A controllable impedance unit is configured between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude on the mains side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, so that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude, including: The instantaneous sample value of the voltage amplitude on the mains power side is collected, and the instantaneous sample value is subjected to sliding window filtering to obtain the filtered value of the voltage amplitude; Performing a time derivative operation on the filtered value yields the first-order time derivative of the voltage amplitude, which characterizes the instantaneous rate of change of the voltage amplitude. When the first time derivative is negative, it is determined to be the voltage decrease phase; when the first time derivative is positive, it is determined to be the voltage increase phase. During the voltage rise phase, the impedance value of the controllable impedance unit remains unchanged or is gradually increased according to a preset recovery rate, so that the reverse power supply unit gradually withdraws from power supply; During the voltage drop phase, the power exponent of the power-law increasing relationship is dynamically adjusted based on the absolute value of the first-order time derivative. When the absolute value increases, the power exponent increases, so that the rate of change of the impedance value relative to the rate of change of the voltage amplitude increases as the decay rate of the voltage amplitude increases. Substitute the filtered value into the adjusted power-law increasing function expression to calculate the target value of the impedance.

3. The method according to claim 2, characterized in that, The method further includes: The rate of change of the target impedance value is limited, and the minimum time interval required for the impedance value to change from the current value to the target value is calculated. When the minimum time interval is less than the preset minimum response time, the impedance value is adjusted according to the rate of change corresponding to the minimum response time. When the minimum time interval is greater than or equal to the minimum response time, the impedance value is directly adjusted to the target value. Based on the adjusted impedance value, the conduction state of the switching device or the duty cycle of the modulation signal in the controllable impedance unit is controlled to realize the physical representation of the impedance value. The conduction state of the switching device or the duty cycle and the impedance value satisfy a preset mapping relationship.

4. The method according to claim 1, characterized in that, The output power of the reverse power supply unit is determined based on the power-law increasing relationship. The difference between the output power and the load power increases non-linearly as the voltage amplitude decreases, including: The real-time load power and load power factor at the load terminal are obtained, and the load power factor is calculated by the phase difference between the voltage and current at the load terminal. A second-order time derivative operation is performed on the voltage amplitude on the mains side to obtain the first-order time derivative and the second-order time derivative. The trajectory of the voltage amplitude change within a preset time period is predicted. Based on the trajectory and the power-law increasing relationship, the predicted value of the mains power transmitted from the mains side to the load side within the preset time period is calculated. Calculate the predicted power deficit, which is equal to the difference between the real-time load power and the predicted mains power. The power of the power-law increasing relationship is corrected based on the load power factor. When the load power factor decreases, the power is increased. The corrected power is then incremented by 1 to obtain a non-linear growth power. The power deficit prediction value is then transformed using the non-linear growth power to obtain the target value of the output power. Based on the target output power value, adjust the inverter output voltage amplitude and output current amplitude of the reverse power supply unit so that the output power of the reverse power supply unit reaches the target value.

5. The method according to claim 4, characterized in that... Predicting the trajectory of the voltage amplitude change within a preset time period includes: The voltage amplitude is subjected to second-order time differentiation to obtain the first-order time derivative and the second-order time derivative. The absolute value of the second-order time derivative is calculated and compared with a preset acceleration threshold. When the absolute value is greater than the preset acceleration threshold, it is determined to be an abrupt drop and a short prediction window is used. When the absolute value is less than or equal to the preset acceleration threshold, it is determined to be a gradual drop and a long prediction window is used. For abrupt drops, the weighting coefficient of the first-order time derivative is increased; for gradual drops, the weighting coefficient of the second-order time derivative is increased. The first-order and second-order time derivatives are weighted and combined according to the weighting coefficients to predict the trajectory of change. In each sampling period, the predicted voltage value of the previous sampling period is compared with the actual voltage value of the current sampling period to calculate the prediction deviation rate. When the prediction deviation rate is positive, the weighting coefficient of the first-order time derivative in the current prediction is increased; when the prediction deviation rate is negative, the weighting coefficient of the first-order time derivative in the current prediction is decreased.

6. The method according to claim 1, characterized in that, Determine the phase error between the output frequency of the reverse power supply unit and the frequency of the mains power supply side, apply a second-order time derivative constraint to the phase error, the upper limit of the second-order time derivative constraint being inversely proportional to the impedance value, and accelerate the convergence speed of the phase error as the impedance value decreases, including: The output voltage waveform of the sampled reverse power supply unit is compared with the voltage waveform of the mains power side, and the phase error is calculated by detecting the zero-crossing moments of the two voltage waveforms. Obtain the current impedance value of the controllable impedance unit and the current output power of the reverse power supply unit. Calculate the instantaneous circulating current power based on the phase error, the current impedance value, and the current output power. The instantaneous circulating current power is directly proportional to the phase error and the current output power, and inversely proportional to the current impedance value. Based on a preset maximum circulating current power threshold and an upper limit constraint value for the second-order time derivative of the phase error derived in reverse from the current impedance value and the current output power, the upper limit constraint value is inversely proportional to both the current impedance value and the current output power. The phase error is subjected to a second-order time derivative operation to obtain a second-order time derivative, which is then limited to the upper limit constraint value. The output frequency adjustment of the reverse power supply unit is calculated based on the limited second-order time derivative, so that the phase error converges to zero with controlled acceleration and the instantaneous circulating power does not exceed the maximum circulating power threshold.

7. The method according to claim 1, characterized in that... The output voltage amplitude and frequency of the reverse power supply unit are synchronously adjusted according to the output power and the second-order time derivative constraint, maintaining continuous load-side voltage and convergent phase difference during the voltage amplitude decrease on the mains side, including: The adjustment amount of the output voltage amplitude is calculated based on the target value of the output power, and the adjustment amount of the output frequency is calculated based on the second-order time derivative constraint. Based on the adjustment amount of the output voltage amplitude and the adjustment amount of the output frequency, predict the voltage amplitude at the load end in the next sampling period, and calculate the voltage deviation between the predicted voltage amplitude and the actual voltage amplitude at the load end in the current sampling period; When the absolute value of the voltage deviation is greater than a preset continuity threshold, the maximum allowable adjustment rate under the preset continuity threshold constraint is calculated, and the adjustment amount of the output voltage amplitude and the adjustment amount of the output frequency are synchronously scaled according to the maximum adjustment rate. The inverter control signal of the reverse power supply unit is synchronously adjusted according to the limited adjustment amount, so that the change in the load-side voltage amplitude between adjacent sampling periods does not exceed the preset continuity threshold.

8. A reverse power supply control system supporting mains power disconnection, used to implement the method as described in any one of claims 1-7, characterized in that, include: The mains power detection unit is used to obtain the voltage amplitude and frequency of the mains power side; An impedance regulation unit is used to configure a controllable impedance unit between the output terminal of the reverse power supply unit and the load terminal. The impedance value of the controllable impedance unit is adjusted according to the voltage amplitude of the mains power side. The impedance value and the voltage amplitude satisfy a power-law increasing relationship with a power greater than 1, so that the rate of change of the impedance value is faster than the rate of change of the voltage amplitude. A power determination unit is used to determine the output power of the reverse power supply unit based on the power-law increasing relationship. The difference between the output power and the load power increases nonlinearly as the voltage amplitude decreases. A phase constraint unit is used to determine the phase error between the output frequency of the reverse power supply unit and the frequency of the mains power side, and to apply a second-order time derivative constraint to the phase error. The upper limit of the second-order time derivative constraint is inversely proportional to the impedance value. When the impedance value decreases, the convergence speed of the phase error increases. The output adjustment unit is used to synchronously adjust the output voltage amplitude and output frequency of the reverse power supply unit according to the output power and the second-order time derivative constraint, and to maintain the load voltage continuous and the phase difference converged during the voltage amplitude decrease on the mains side.

9. An electronic device, characterized in that, include: processor; Memory used to store processor-executable instructions; The processor is configured to invoke instructions stored in the memory to execute the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having computer program instructions stored thereon, characterized in that, When the computer program instructions are executed by the processor, they implement the method described in any one of claims 1 to 7.

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