An energy feedback efficiency optimization control method for a programmable alternating current source integrated test system

Abstract

The application discloses a programmable AC source load integrated test system energy feedback efficiency optimization control method, and relates to the technical field of energy feedback optimization. The programmable AC source load integrated test system energy feedback efficiency optimization control method collects AC side LCL filter network state data, power grid voltage phase angle and DC bus voltage, adaptively determines energy storage adjustment coefficients and generates guide current instructions, calculates mode switching induced energy after guiding to a low transient energy storage state, extracts switching induced harmonic free components when a criterion is met, constructs transient energy evaluation values and generates transient compensation control quantities, continuously reconstructs transient energy exchange paths, calculates DC bus excess energy and feedbacks, and dynamically restricts and smooths a transition starting power value according to residual induced resonance energy to transition to a target value. The application improves feedback efficiency when the energy feedback efficiency and the transient loss reduction rate meet the preset efficiency optimization target.

Description

Technical Field

[0001] This invention relates to the field of energy feedback optimization technology, specifically to an energy feedback efficiency optimization control method for a programmable AC source-carrier integrated test system. Background Technology

[0002] The programmable AC source-load integrated test system is a bidirectional converter device used for testing power electronic equipment. The system contains core components such as a grid-side converter, a DC bus, and an AC-side filter. In source mode, the system draws power from the grid and provides a settable AC power supply to the device under test after power conversion, simulating various grid operating conditions. In load mode, the system absorbs the AC power output from the device under test, simulating various load characteristics. The source mode and load mode can be flexibly switched through software programming to meet the rapid alternation requirements of power supply and load for different test sequences.

[0003] During the test, the electrical energy absorbed under load mode is usually fed back to the public grid through the grid-side converter to achieve energy recycling. As the core execution unit of energy feedback, the control performance of the grid-side converter directly determines the quality of the power fed back to the grid and the energy utilization efficiency. In order to improve the energy feedback efficiency, attention is usually paid to the waveform quality of the grid-connected current and the stable control of the DC bus voltage. The energy loss during the conversion and transmission process is reduced by optimizing the modulation and control strategy of the grid-side converter.

[0004] The limitations of the existing technology include at least the following problems: When the existing programmable AC source-carrier integrated test system performs rapid switching between source mode and carrier mode, the power flow direction of the grid-side converter is reversed almost instantaneously. The power balance state of the DC bus is subjected to step disturbances of large signals, which can easily cause the excitation AC side LCL filter to generate dynamic oscillations near its resonant frequency. The existing technology is designed with steady-state power feedback as the benchmark operating condition. Its parameter tuning and feedback structure are based on the tracking accuracy of the fundamental current and the gradual adjustment of the DC bus voltage. It does not set up corresponding energy coordination for transient events such as mode switching. When the power command changes drastically, the transient energy stored and resonant energy excited in the AC-side LCL filter is difficult to actively guide to the DC bus or grid side through control. Instead, it tends to gradually decay in the form of heat dissipation along the equivalent parasitic impedance of the filter elements and the conduction path of the power devices. In dynamic test sequences that require high-frequency mode switching, this portion of unrecoverable dissipated energy accompanies each switch and accumulates repeatedly over time, causing the average energy feedback efficiency of the system to decrease throughout the entire test cycle. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an energy feedback efficiency optimization control method for a programmable AC source-carrier integrated test system. This method solves the problems of insufficient transient energy coordination and difficulty in recovering oscillating energy caused by mode switching, which leads to reduced dynamic feedback efficiency.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an energy feedback efficiency optimization control method for a programmable AC source-carrier integrated test system, comprising the following steps: upon receiving a switching command between source mode and carrier mode, acquiring network status data of the AC-side LCL filter, as well as the grid voltage phase angle and DC bus voltage; based on the network status data, extracting the total electromagnetic energy and operating condition set, and adaptively determining the energy storage adjustment coefficient based on the operating condition set, and generating a guiding current command in conjunction with the total electromagnetic energy to guide the AC-side LCL filter to a low transient energy storage state; After the low transient energy storage state guidance is completed, the switching network state data after the switching command is collected to calculate the mode switching induced energy. When the mode switching induced energy meets the preset induced energy criterion, the switching network state data is subjected to free mode separation processing based on the grid voltage phase angle to extract the switching induced resonance free component; a transient energy evaluation value is constructed and, after adaptive parameter optimization processing, a transient compensation control quantity corresponding to the switching induced resonance free component is generated, and the transient energy exchange path is continuously reconstructed until the switching induced resonance free component meets the preset attenuation condition; The excess energy of the DC bus is calculated based on the DC bus voltage, and excess energy feedback processing is performed; the transition initiation power value and residual induced resonance energy are obtained, and the transition initiation power value is dynamically constrained and smoothed to transition the transition initiation power value to the target power value corresponding to the switching command; the energy feedback efficiency and transient loss reduction rate during the entire switching process are analyzed, and the energy feedback efficiency optimization control is completed when the preset efficiency optimization target is met.

[0007] Furthermore, the operating condition set includes the current power level and grid impedance. The specific steps for extracting the total electromagnetic energy and the operating condition set are as follows: Based on the network status data and combined with the preset filter hardware parameters, extract the stored component set and sum them to obtain the total electromagnetic energy; Based on the network status data, calculate the active power before switching and compare it with the preset rated power to obtain the current power level; Based on the online impedance identification method, estimate the equivalent inductance of the grid from the network status data and compare it with the preset grid-side inductance value to obtain the grid impedance.

[0008] Furthermore, the specific steps for adaptively determining the energy storage regulation coefficient are as follows: Substitute the current power level into the preset power level regulation function to obtain the power regulation factor; substitute the grid impedance into the preset grid impedance regulation function to obtain the impedance regulation factor; and adjust the preset basic energy storage mapping coefficient based on the power regulation factor and the impedance regulation factor to obtain the energy storage regulation coefficient.

[0009] Further, the specific steps for generating the guiding current command are as follows: obtain the peak value of the grid phase voltage, and preset the guiding time window and the active current command value; calculate the guiding current increment based on the energy storage regulation coefficient, total electromagnetic energy, peak value of the grid phase voltage and the preset guiding time window; extract the guiding current command within the preset guiding time window based on the active current command value and the guiding current increment.

[0010] Further, the specific steps for extracting the free components of switching-induced resonance are as follows: Based on the switching network state data and combined with the grid voltage phase angle, a synchronous rotating coordinate transformation is performed to obtain the voltage and current components; based on the filter hardware parameters, the resonant frequency is calculated, and the fundamental cutoff frequency and maximum cutoff frequency are set. After frequency adjustment processing based on induced energy feedback, the cutoff frequency is determined; a low-pass filter with the cutoff frequency as a parameter is used to process the voltage and current components, and the discretization coefficient of the low-pass filter is calculated to separate the fundamental voltage component and the fundamental current component; based on the voltage component, current component, fundamental voltage component, and fundamental current component, the free components of switching-induced resonance are generated.

[0011] Furthermore, the specific steps for constructing the transient energy evaluation value are as follows: obtain the active power output from the grid-side converter to the grid in the low transient energy storage state, and integrate it to obtain the feedback energy increment; obtain the Joule heat loss, power conduction loss and power switching loss in the AC-side LCL filter, and sum them to obtain the transient energy loss; apply loss penalty processing to the feedback energy increment and transient energy loss to obtain the transient energy evaluation value.

[0012] Further, the specific steps for generating the transient compensation control quantity corresponding to the switching-induced resonance free component are as follows: Preset initial values ​​for the voltage compensation coefficient and current compensation coefficient, corresponding to the switching-induced resonance voltage free component and the switching-induced resonance current free component, respectively; determine the energy gain change based on the transient energy evaluation value; based on the energy gain change, update the voltage compensation coefficient and current compensation coefficient through a gain change gradient-driven update process to obtain the current voltage compensation coefficient and current current compensation coefficient; based on the current voltage compensation coefficient and current current compensation coefficient, compensate and synthesize the switching-induced resonance free component to obtain the transient compensation control quantity.

[0013] Furthermore, the specific steps for dynamic constraint power smoothing are as follows: obtain the resonant frequency of the AC-side LCL filter; determine the power trajectory constraint based on the resonant frequency and residual induced resonance energy; under the power trajectory constraint, perform smoothing trajectory generation processing on the transition initial power value to obtain the power transition trajectory, so that the transition initial power value transitions to the target power value corresponding to the switching command.

[0014] Furthermore, the specific steps for analyzing the energy feedback efficiency and transient loss reduction rate throughout the entire switching process are as follows: During the entire switching process, the active power output from the grid-side converter to the grid is obtained and integrated to obtain the total feedback energy; the total loss during the entire switching process is obtained and combined with the total feedback energy for efficiency evaluation to obtain the energy feedback efficiency; based on the total loss during the entire switching process and a preset benchmark loss value, the transient loss reduction rate is obtained through loss improvement evaluation.

[0015] Furthermore, the specific steps to determine whether the preset efficiency optimization target is met are as follows: record the switching duration of the entire switching process; compare the switching duration, energy feedback efficiency, and transient loss reduction rate with the corresponding preset threshold conditions; if the comparison results all meet the preset threshold conditions, then the preset efficiency optimization target is determined to be met.

[0016] The present invention has the following beneficial effects: (1) The energy feedback efficiency optimization control method of the programmable AC source-carrier integrated test system, after receiving the switching command, uses the energy storage adjustment coefficient and the total electromagnetic energy to generate the guiding current command, and pre-adjusts the AC side LCL filter to a low transient energy storage state, thereby reducing the amplitude of the oscillation energy that may be excited when the power direction reverses. When the power direction is switched and the mode switching induced energy exceeds the threshold, the switching induced resonance free component is extracted from the network state data after the switch through free mode separation processing, and the compensation coefficient is adaptively adjusted according to the change direction of the transient energy evaluation value to generate a transient compensation control quantity to continuously reconstruct the transient energy exchange path. The oscillation energy that would have been lost in the form of heat dissipation on the parasitic impedance is guided to the DC bus side, and this part of the energy is then sent back to the grid with a unit power factor through excess energy feedback processing, thereby reducing the energy loss during the mode switching process and improving the feedback efficiency of the system during high-frequency switching operation.

[0017] (2) The energy feedback efficiency optimization control method of the programmable AC source-carrier integrated test system estimates the equivalent inductance of the power grid in real time through online impedance identification method, and calculates the active power level before switching. The real-time changing operating parameters are substituted into the power level adjustment function and the power grid impedance adjustment function to obtain the power adjustment factor and the impedance adjustment factor. Then, the basic energy storage mapping coefficient is adjusted so that the strength of the guiding current command always matches the real state of the current system, avoiding overcompensation or undercompensation under weak power grid or light load conditions. In the power smooth transition stage, the power trajectory constraint is determined according to the residual induced resonance energy and resonance frequency, so that when the residual energy is large, the upper limit of the rate of change is automatically tightened to prevent secondary oscillation, and when the residual energy is small, the constraint is appropriately relaxed to accelerate the transition speed, so as to ensure that the switching can be completed smoothly.

[0018] (3) The energy feedback efficiency optimization control method of the programmable AC source-carrier integrated test system takes energy feedback efficiency as the optimization target of transient compensation, drives the update of compensation coefficient based on the change direction of transient energy evaluation value, so that the compensation depth is always adjusted in the direction of improving feedback efficiency. When constructing transient energy evaluation value, the incremental feedback energy is combined with transient energy loss including Joule heat loss, power device conduction loss, and switching loss, and the weight of the two is balanced by loss penalty weight coefficient. When updating compensation coefficient, the gradient direction is determined according to the change of benefit, and the voltage compensation coefficient and current compensation coefficient are adjusted along the direction. Then, the adjusted coefficients are multiplied by the switching induced resonance free component and superimposed to obtain the transient compensation control quantity, so that the core index of feedback efficiency is always dynamically optimized during the mode switching process, thereby improving the accuracy of the compensation control response to energy recovery.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0020] Figure 1 This is a flowchart of an energy feedback efficiency optimization control method for a programmable AC source-carrier integrated test system according to the present invention.

[0021] Figure 2 This is a flowchart illustrating the specific steps involved in extracting the switching-induced resonance free component in the energy feedback efficiency optimization control method of a programmable AC source-carrier integrated test system according to the present invention.

[0022] Figure 3 This is a flowchart illustrating the specific steps involved in generating transient compensation control quantities in the energy feedback efficiency optimization control method of a programmable AC source-carrier integrated test system according to the present invention. Detailed Implementation

[0023] Please see Figure 1This invention provides a technical solution: an energy feedback efficiency optimization control method for a programmable AC source-carrier integrated test system, comprising the following steps: upon receiving a switching command between the source mode and the carrier mode of the source-carrier integrated test system (obtaining the target power value contained in the switching command). ;when If the value is positive, meaning the current switch is from load mode to source mode and energy needs to be fed back to the grid, the following steps are executed; when When the value is negative, the switch is performed directly in the normal manner without starting the following control. The network status data of the AC side LCL filter (instantaneous values ​​of three-phase voltage and three-phase current) as well as the grid voltage phase angle and DC bus voltage are collected. Based on network status data, the total electromagnetic energy currently stored in the AC-side LCL filter and the set of operating conditions (current power level and grid impedance) are extracted. The energy storage regulation coefficient is adaptively determined based on the set of operating conditions. Combined with the total electromagnetic energy, a guiding current command is generated to guide the AC-side LCL filter to a low transient energy storage state and record the baseline energy storage. After the low transient energy storage state is guided, the power direction is switched between the source mode and the load mode. The switching network state data after the switching command is collected. The mode switching induced energy is calculated in combination with the benchmark energy storage. When the mode switching induced energy meets the preset induced energy criterion, the switching network state data is processed by free mode separation based on the grid voltage phase angle to extract the switching induced resonance free component. A transient energy evaluation value is constructed and, after adaptive parameter optimization, a transient compensation control quantity corresponding to the switching-induced resonance free component is generated. The transient energy exchange path is continuously reconstructed to reduce net energy loss until the switching-induced resonance free component meets the preset attenuation condition and the transient compensation control quantity is stopped. After the transient compensation control is stopped, the excess energy of the DC bus is calculated based on the DC bus voltage, and excess energy feedback is performed (the excess energy of the DC bus is fed back to the grid with priority at the unity power factor). After the DC bus excess energy feedback is completed, the transition start power value (i.e. the current power after the transient compensation control is stopped) and the residual induced resonance energy are obtained. The transition start power value is dynamically constrained and smoothed to transition the transition start power value to the target power value corresponding to the switching command. The system analyzes the energy feedback efficiency and transient loss reduction rate throughout the switching process. When the preset efficiency optimization target is met, the energy feedback efficiency optimization control for this mode switch is completed.

[0024] The specific steps for calculating energy induced by mode switching are as follows: After the power direction switching, obtain the instantaneous voltage and current values ​​of the AC-side LCL filter, and calculate based on the total electromagnetic energy. The calculation method for calculating real-time energy storage after power direction switching. ; Real-time energy storage Subtract benchmark energy storage , obtain mode switching induced energy : ; Mode switching induced energy A low-pass filter with a cutoff frequency of 10Hz is applied to obtain the filtered induced energy. ; Among them, the rated energy storage of the AC-side LCL filter Based on the effective value of the rated current of the inductor on the converter side RMS value of grid-side inductor rated current and the rated effective value of the filter capacitor calculate: ; RMS value of rated current of inductor on converter side RMS value of rated current of grid-side inductor and the rated effective value of the filter capacitor Determined by system design parameters; Preset induced energy threshold The preset induced energy threshold is taken as the rated energy storage of the AC-side LCL filter. 2% to 10%, and in this implementation example, the value is taken as 5% of the rated energy storage.

[0025] The preset induced energy criterion is: continuous The number of control cycles exceeds the preset induced energy threshold. In this implementation example If the preset induced energy criterion is met, it is determined that there is significant disturbance energy that is excited by mode switching and exceeds the low transient energy storage state benchmark, and the process enters the free mode separation processing step. When the preset induced energy criterion is not met, it indicates that the mode switching has not generated significant additional disturbance energy. The free mode separation process and transient compensation control quantity generation steps are skipped, and the process directly proceeds to the DC bus excess energy feedback process, whereby the residual induced resonance energy is processed. Set to zero.

[0026] The switching of the induced resonance free component satisfies the preset attenuation condition, namely: Calculate the instantaneous oscillation power of the switching-induced resonant free component. : ; Preset power attenuation threshold Take 0.2% to 1.0% of the system's rated power; in this implementation example, take 0.5%. Number of consecutive determination periods The number of control cycles corresponding to 5 to 20 fundamental frequency cycles is selected; in this implementation example, 10 fundamental frequency cycles are selected. when continuous Each control cycle is lower than When the compensation is stopped, the residual induced resonance energy is calculated using the free components of the resonant voltage and current obtained from the current control cycle. The value is then latched and the free mode separation process is turned off. The resonant current of the filter capacitor is calculated using the backward Euler method based on the resonant component of the filter capacitor voltage. Then the resonant component of the inductor current on the converter side is ; The instantaneous values ​​of the resonant voltage and resonant current in the three-phase stationary coordinate system are obtained by inverse synchronous rotating coordinate transformation of the switched induced resonant voltage and current components, and the residual induced resonant energy is calculated. : ; The summation is the sum of squares of the three phase components.

[0027] The excess energy of the DC bus is calculated based on the DC bus voltage, and the excess energy is then fed back. Specifically: Obtain the capacitance value of the DC bus (5000μF is used in this example) and the preset DC bus voltage reference value (700V is used in this implementation example); Based on the current DC bus voltage Calculate excess energy of DC bus : ; when At that time, set the excess energy regulation time window. (Use 2-5 fundamental frequency cycles) Calculate the additional active current. The active current command is forcibly set to Excess energy is preferentially fed back to the grid with a unity power factor until the DC bus voltage recovers to the preset DC bus voltage reference value. If the system remains within the preset error band for a preset time, the excess energy feedback is considered complete. After the excess energy feedback is completed, the current command will be restored to the target power transition. When the DC bus energy is not exceeded, the excess energy feedback step is skipped, and the process directly enters the power smoothing stage.

[0028] Specifically, the operating condition set includes the current power level and grid impedance. The specific steps for extracting the total electromagnetic energy currently stored in the AC-side LCL filter and the operating condition set (current power level and grid impedance) are as follows: Based on the instantaneous values ​​of three-phase voltage and three-phase current in the network status data, and combined with the preset filter hardware parameters (including the inductance values ​​of the converter-side inductor, the grid-side inductor, and the filter capacitor), the stored component sets (including the converter magnetic field energy storage of the converter-side inductor, the grid-side magnetic field energy storage of the grid-side inductor, and the electric field energy storage of the filter capacitor in the AC-side LCL filter) are extracted and summed to obtain the total electromagnetic energy, which is as follows: Extract the instantaneous three-phase voltage values ​​of the filter capacitor from the network status data. Instantaneous value of three-phase current of grid-side inductor The instantaneous value of the three-phase voltage through the filter capacitor and the capacitance value of the filter capacitor Calculate the filter capacitor current : ; in, The value of the filter capacitor ranges from 10μF to 100μF. In this example, the value is 50μF. In the digital implementation, the backward Euler method can be used for discretization. Based on the inductance value on the converter side and converter-side inductor current Calculate the magnetic field energy storage of the converter-side inductor : ; in, The value of the inductance on the converter side ranges from 0.5mH to 5mH, and is set to 2mH in this implementation example. , , This represents the instantaneous value of the three-phase inductor current on the converter side; Based on the inductance value of the grid side and grid-side inductor current Calculate the magnetic field energy storage of the grid-side inductor : ; in, The value is the inductance value on the grid side, ranging from 0.1mH to 1mH, and is set to 0.5mH in this embodiment. , , This represents the instantaneous value of the three-phase current in the grid-side inductor; Based on the capacitance value of the filter capacitor Instantaneous value of three-phase voltage with filter capacitor Calculate the electric field energy storage of the filter capacitor. : ; in, , , This represents the instantaneous value of the three-phase voltage across the filter capacitor. Storing energy in the magnetic field of the inductor on the converter side Magnetic field energy storage of grid-side inductors Electric field energy storage of filter capacitors Summing them up yields the total electromagnetic energy. : ; Based on the instantaneous values ​​of three-phase voltage and three-phase current in the network status data, the active power at the instant before switching is calculated and compared with the preset system rated power to obtain the current power level, specifically: Based on the instantaneous values ​​of three-phase voltage and three-phase current, the instantaneous three-phase power is calculated. The instantaneous three-phase power is then subjected to a low-pass filter with a cutoff frequency lower than the fundamental frequency. The filtered value is taken as the average active power instantaneously before switching. The cutoff frequency of the low-pass filter is taken as 1 / 5 of the fundamental frequency, and in this implementation example, it is taken as 10Hz for a 50Hz power grid. The absolute value of the average active power is compared with the system's rated power. The ratio of the normalized power level : ; in, The rated power of the system is determined by the system hardware design parameters, and its value ranges from 10kW to 500kW. In this implementation example, the value is 100kW. The equivalent inductance of the power grid is estimated from the instantaneous values ​​of three-phase voltage and three-phase current in the network state data using the online impedance identification method, and then compared with the preset grid-side inductance value to obtain the power grid impedance, which is as follows: Establish discrete voltage equations for the power grid side in a synchronous rotating coordinate system, using the equivalent inductance of the power grid. Using the voltage prediction error as the recursive objective and the recursive least squares method with a forgetting factor as the parameter to be estimated, the calculation is performed in real time. ; In a synchronously rotating coordinate system, the d-axis voltage equation of the grid side can be expressed as: ; in This represents the d-axis voltage on the grid side. , For the d-axis and q-axis currents on the grid side, This is the equivalent resistance on the grid side. The angular frequency of the power grid. The voltage across the d-axis at the common coupling point; After discretizing it, with The parameters to be estimated are identified online using the recursive least squares method with a forgetting factor. The forgetting factor ranges from 0.95 to 0.99, and is set to 0.98 in this implementation example.

[0029] The equivalent inductance of the power grid With grid-side inductance value The ratio of the two values ​​is used as the influence factor of grid impedance. : .

[0030] Specifically, the steps for adaptively determining the energy storage regulation coefficient are as follows: Substituting the current power level into the preset power level adjustment function yields the power adjustment factor, which is as follows: ; in, The preset power adjustment curvature parameter has a value range of 0.1 to 0.5, and in this implementation example, the value is 0.2. Substituting the grid impedance into the preset grid impedance adjustment function yields the impedance adjustment factor, which is as follows: ; in, The preset impedance adjustment coefficient has a value range of 0.1 to 0.3, and in this implementation example, it is set to 0.2. Based on the power regulation factor and impedance regulation factor, the preset basic energy storage mapping coefficient is adjusted to obtain the energy storage regulation coefficient, which is as follows: ; in, The basic energy storage mapping coefficient is taken as the calibration value under rated operating conditions, with a value range of 0.3 to 0.7. In this implementation example, the value is taken as 0.5.

[0031] The specific steps for generating the pilot current command are as follows: Obtain the peak value of the grid phase voltage at the current moment. It also presets the guidance time window and the current active current command value of the grid-side converter current control loop (before the guidance time window) (the active current command value is the active current setpoint received by the current control loop), that is: The peak value of the grid phase voltage is determined by the grid voltage phase angle output by the phase-locked loop and the instantaneous value of the three-phase voltage in the network status data; Preset boot time window The value ranges from 1 to 2 fundamental frequency cycles. For a 50Hz power grid, The value range is from 20ms to 40ms, and in this implementation example, the value is 30ms. Based on energy storage regulation coefficient Total electromagnetic energy Peak phase voltage of the power grid and preset boot time window Calculate the incremental guiding current. : ; In the preset boot time window Internally, based on the active current command value With the increase of the guiding current Extract the pilot current command, that is: ; in, The active current command value is the instant before the switch, with the power sent to the grid as the positive direction; Always positive superposition, since the direction of power output to the grid is positive, regardless of Positive and negative, plus positive Both of these factors increase the net output power or decrease the net absorbed power, thereby reducing the energy storage of the AC-side LCL filter.

[0032] Meanwhile, the center frequency is the resonant frequency of the AC-side LCL filter. Quality Factor Extract the resonant component of the filter capacitor voltage from bandpass filters of 3 to 8, and multiply this resonant component by a preset damping coefficient. Then superimposed on the reactive current command To accelerate the decay of reactive oscillations, a preset damping coefficient is used. The value ranges from 0.05 to 0.3. In this implementation example... Take 5. Take 0.15.

[0033] And monitor the total electromagnetic energy in real time. When the rate of change of total electromagnetic energy enters a sustained low-value plateau period, i.e., the absolute value of the rate of change of total electromagnetic energy is less than or equal to a preset rate of change threshold, and the total electromagnetic energy has dropped to below a preset proportion of the initial energy storage value, it is determined that the AC-side LCL filter has entered a low-transient energy storage state, and the energy storage value at this time is recorded as the baseline energy storage. ; The initial energy storage value is the total electromagnetic energy at the moment the guiding step begins. If within the preset boot time window If the above criteria are not met by the end of the process, the guidance will be forcibly terminated, and the current energy storage value will be used as the baseline energy storage. And then proceed to the next step.

[0034] The preset rate of change threshold is set according to the rated power of the system. In this implementation example, the value is 0.1% of the rated power (for example, when the rated power is 100kW, the threshold is 100W); the preset ratio ranges from 30% to 50%, and in this implementation example, the value is 40%.

[0035] Specifically, such as Figure 2 As shown, the specific steps for extracting the switching-induced resonance free component are as follows: Based on the instantaneous value of the three-phase filter capacitor voltage in the switching network state data , , Instantaneous value of inductor current on the three-phase grid side , , By combining the grid voltage phase angle with synchronous rotating coordinate transformation, the voltage components in the synchronous rotating coordinate system are obtained. , and current components , Specifically, it is as follows: Grid voltage phase angle For the transformation angle: The current transformation methods are the same; Based on the filter hardware parameters, the (LCL) resonant frequency is calculated, and the fundamental cutoff frequency and maximum cutoff frequency are set. After frequency adjustment processing based on induced energy feedback, the cutoff frequency is determined, specifically as follows: Calculate the resonant frequency of the AC-side LCL filter: ; in, The equivalent inductance of the power grid obtained through online impedance identification; by Based on the cutoff frequency, The maximum cutoff frequency; In the first control cycle before entering the free mode separation processing step, the filtered induced energy calculated in the current cycle is... Assign to As an initial value, starting from the second control cycle, the filtered induced energy from the previous control cycle is obtained. Calculate the cutoff adjustment coefficient Then the cutoff frequency of the current control cycle is: ; in, An upper limit is set on the adjustment coefficient to ensure that the cutoff frequency does not exceed [the limit]. ; A second-order Butterworth low-pass filter with cutoff frequency as the parameter is used to process the voltage and current components. The discretization coefficients of the second-order Butterworth low-pass filter are calculated to separate the fundamental voltage and current components. Specifically: Will Convert to analog angular frequency Pre-distortion after bilinear transformation Substituting the second-order Butterworth prototype into the input, we obtain the discrete domain transfer function, and update the discretization coefficients in each control cycle. Will , and , The fundamental voltage component is obtained through a filter. , and fundamental current component , ; Based on the voltage component, current component, fundamental voltage component, and fundamental current component, a switching-induced resonance free component is generated, specifically as follows: ; .

[0036] Specifically, the steps for constructing transient energy evaluation values ​​are as follows: Acquire the active power output from the grid-side converter to the grid during the low transient energy storage state, and during the duration of the transient compensation process. Integrating within the range yields the actual increase in the energy fed back to the grid, specifically: ; in, The moment when the transient compensation control quantity is first applied. The current moment; The Joule heat loss generated by the equivalent series resistance of the inductor and the equivalent series resistance of the capacitor in the AC-side LCL filter during the current transient process, as well as the power conduction loss and power switching loss of the power devices during the current transient process, are obtained and summed to obtain the transient energy loss during the current transient process. Specifically: Based on the equivalent series resistance of the converter-side inductance , grid-side inductance equivalent series resistance and the equivalent series resistance of the filter capacitor Calculate the Joule heat loss generated during the transient compensation process. : ; Obtaining the power device conduction loss during transient compensation and switching losses ; On-state losses according to Estimate, of which For the on-state resistance of the power device, This is the current effective value; Switching losses according to Estimate; in , These represent the energy loss during a single power-on and power-off cycle. For switching frequency, This is the current DC bus voltage. This is the reference voltage from the device datasheet. The voltage correction index is provided in the power device datasheet, and the parameters are for the duration of the transient compensation process. Integrate internally to obtain the corresponding energy loss; Summing the three values ​​yields the transient energy loss. ; The incremental feedback energy and transient energy loss are penalized to obtain the transient energy evaluation value, which is as follows: ; in, The preset loss penalty weight coefficient ranges from 1.0 to 2.0, and is set to 1.5 in this implementation example.

[0037] like Figure 3 As shown, the specific steps for generating the transient compensation control quantity corresponding to the switching induced resonance free component are as follows: Preset voltage compensation coefficient and current compensation coefficient The initial values ​​correspond to the free components of the switching-induced resonant voltage and the switching-induced resonant current, respectively. In this embodiment, , ; Based on the transient energy evaluation value, the change in energy gain is determined, specifically as follows: Calculate the difference between the transient energy evaluation value of the current control period and the previous control period. ; Based on the change in energy gain, the voltage compensation coefficient and current compensation coefficient are updated using a gradient-driven process to obtain the current voltage compensation coefficient and current current compensation coefficient, which are as follows: Evaluation value based on transient energy To optimize the objective, the step size is updated along the positive gradient direction. The gradient direction index is calculated. ,in Let be the sign function. If the gradient direction index is positive, then update along the original direction; if it is negative, then update in the opposite direction. The update formula is: ; ; in , , The preset step size coefficient has a value range of 0.01 to 0.1, and is set to 0.05 in this implementation example; Based on the current voltage compensation coefficient and the current current compensation coefficient, the switching-induced resonance free component is compensated and synthesized to obtain the transient compensation control quantity (i.e., the d-axis and q-axis transient compensation control quantity). , Specifically: ; ; It should be noted that the transient compensation control quantity is superimposed on the modulated wave voltage output by the PI regulator of the current control loop, and after inverse dq transformation and space vector pulse width modulation, a switching signal is generated to continuously reconstruct the transient energy exchange path.

[0038] Specifically, the steps for performing dynamic constraint power smoothing are as follows: Obtain the resonant frequency (i.e., LCL resonant frequency) of the AC-side LCL filter. Based on the resonant frequency and the residual induced resonant energy (which is zero if no transient compensation has been performed previously), the power trajectory constraints are determined as follows: After the excess energy feedback is completed, the current actual power value is obtained as the transition starting power value. Combined with residual induced resonance energy The resonant frequency of the AC-side LCL filter Determine the maximum allowable rate of power change (as a power trajectory constraint): ; in, One fundamental frequency period is taken, which is 20ms for a 50Hz power grid; This is the resonance sensitivity coefficient, with a value ranging from 1.0 to 3.0; in this implementation example, it is set to 2.0. The normalized energy reference value is taken as the rated energy storage value of the AC-side LCL filter. 10%; Under power trajectory constraints, the initial transition power value is smoothed to generate a trajectory, resulting in a continuous third-order S-curve power transition trajectory with jerk. This transitions the initial power value to the target power value corresponding to the switching command, with a transition duration of [duration missing]. By working backward from the constraints, the inverse relationship is: ,in The preset smoothing coefficient ranges from 0.5 to 0.9, and is set to 0.75 in this implementation example; The power transition trajectory is as follows: ; The corresponding active current command is The reactive power instruction is zero, and any residual excess energy is fed back synchronously.

[0039] Specifically, the steps for analyzing the energy feedback efficiency and transient loss reduction rate throughout the entire switching process are as follows: Throughout the entire switching process, from receiving the switching command to the transition from the initial power value to the target power value, the active power output from the grid-side converter to the grid is acquired, and the positive value is integrated to obtain the total feedback energy. Specifically, it is as follows: ; And obtain the total loss during the entire switching process. (Including the integral of the equivalent series resistance loss of the AC-side LCL filter, the on-state loss of the power device, and the switching loss over the entire process), combined with the total feedback energy, an efficiency evaluation is performed to obtain the energy feedback efficiency, which is as follows: Will return total energy Total loss throughout the process Efficiency evaluation is performed to obtain the energy feedback efficiency. : ; Based on the total loss during the entire switching process, and after loss improvement evaluation processing compared with a preset baseline loss value, the transient loss reduction rate is obtained, which is as follows: Obtain the preset reference loss value , is the average loss value of the entire process calibrated by historical test data when transient coordination control is not enabled under the same switching conditions; If historical data is insufficient, the open-loop switching simulation loss value or the first round measured loss value under the same operating conditions without transient coordinated control shall be used as the initial benchmark. Calculate the transient loss reduction rate : .

[0040] The specific steps to determine whether the preset efficiency optimization target is met are as follows: Record the duration of the entire handover process. (That is, the total time from receiving the handover command to the completion of the power transition); The switching duration, energy feedback efficiency, and transient loss reduction rate are compared with corresponding preset threshold conditions, specifically: Will With the preset maximum allowable transition time In comparison, in this implementation example The value is set to 200ms. This value can be adjusted according to the actual dynamic response of the system. When the total transition time is exceeded, the constraint can be met by shortening the guiding window or increasing the excess energy feedback power. Will Compared with the preset efficiency threshold In comparison, in this implementation example Take 85%; Will Compared with the preset loss reduction rate threshold In comparison, in this implementation example Take 50%; If all comparison results meet the preset threshold conditions, then the preset efficiency optimization target is satisfied, which is as follows: When all three conditions meet the threshold conditions, it is determined that the preset efficiency optimization target is met, the control of the grid-side converter is returned to the steady-state current regulator, the transient coordinator status is cleared and it goes into sleep mode. It should be noted that if any condition is not met, the current record will be... , and This data is used as historical optimization data, and the loss penalty weighting coefficient is adjusted based on efficiency deviation. : ; in The preset adjustment gain ranges from 0.1 to 0.5; in this implementation example, it is set to 0.3. The updated loss penalty weighting coefficient is then applied. Stored in non-volatile memory for use when constructing transient energy evaluation values ​​for the next mode switch.

[0041] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0042] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for optimizing the energy feedback efficiency control of a programmable AC source-carrier integrated test system, characterized in that, Includes the following steps: Upon receiving a switching command between source mode and load mode, the network status data of the AC-side LCL filter, as well as the grid voltage phase angle and DC bus voltage, are collected. Based on network status data, the total electromagnetic energy and operating condition set are extracted, and the energy storage regulation coefficient is adaptively determined based on the operating condition set. Combined with the total electromagnetic energy, a guiding current command is generated to guide the AC side LCL filter to a low transient energy storage state. After the low transient energy storage state guidance is completed, the switching network state data after the switching command is collected to calculate the mode switching induced energy. When the mode switching induced energy meets the preset induced energy criterion, the switching network state data is processed by free mode separation based on the grid voltage phase angle to extract the switching induced resonance free component. A transient energy evaluation value is constructed and, after adaptive parameter optimization, a transient compensation control quantity corresponding to the switching-induced resonance free component is generated. The transient energy exchange path is continuously reconstructed until the switching-induced resonance free component meets the preset attenuation condition. Calculate the excess energy of the DC bus based on the DC bus voltage, and perform excess energy feedback processing; The transition initiation power value and residual induced resonance energy are obtained, and the transition initiation power value is dynamically constrained and smoothed to transition to the target power value corresponding to the switching command. The system analyzes the energy feedback efficiency and transient loss reduction rate throughout the switching process, and completes energy feedback efficiency optimization control when the preset efficiency optimization target is met.

2. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 1, characterized in that, The operating condition set includes the current power level and grid impedance. The specific steps for extracting the total electromagnetic energy and the operating condition set are as follows: Based on network status data and in conjunction with preset filter hardware parameters, the stored component sets are extracted and summed to obtain the total electromagnetic energy. Based on network status data, the active power before the switchover is calculated and compared with the preset rated power to obtain the current power level; The equivalent inductance of the power grid is estimated from the network state data based on the online impedance identification method, and then compared with the preset grid-side inductance value to obtain the power grid impedance.

3. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 2, characterized in that, The specific steps for adaptively determining the energy storage regulation coefficient are as follows: Substitute the current power level into the preset power level adjustment function to obtain the power adjustment factor; Substitute the grid impedance into the preset grid impedance adjustment function to obtain the impedance adjustment factor; Based on the power regulation factor and impedance regulation factor, the preset basic energy storage mapping coefficient is adjusted to obtain the energy storage regulation coefficient.

4. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 3, characterized in that, The specific steps for generating the pilot current command are as follows: Obtain the peak value of the grid phase voltage and preset the pilot time window and active current command value; Based on the energy storage regulation coefficient, total electromagnetic energy, peak phase voltage of the grid, and preset guidance time window, the incremental guidance current is calculated. Within the preset guidance time window, the guidance current command is extracted based on the active current command value and the guidance current increment.

5. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 1, characterized in that, The specific steps for extracting the switching-induced resonance free component are as follows: Based on the switching network state data and combined with the grid voltage phase angle, synchronous rotating coordinate transformation is performed to obtain the voltage and current components. Based on the filter hardware parameters, the resonant frequency is calculated, and the basic cutoff frequency and maximum cutoff frequency are set. After frequency adjustment processing based on induced energy feedback, the cutoff frequency is determined. A low-pass filter with cutoff frequency as a parameter is used to process the voltage and current components. The discretization coefficients of the low-pass filter are calculated to separate the fundamental voltage and current components. Based on the voltage component, current component, fundamental voltage component, and fundamental current component, a switching-induced resonance free component is generated.

6. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 1, characterized in that, The specific steps for constructing transient energy evaluation values ​​are as follows: The active power output from the grid-side converter to the grid in the low transient energy storage state is obtained and integrated to obtain the feedback energy increment; Obtain the Joule heat loss, power on-state loss, and power switching loss in the AC-side LCL filter, and sum them to obtain the transient energy loss; The incremental feedback energy and transient energy loss are processed by loss penalty to obtain the transient energy evaluation value.

7. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 6, characterized in that, The specific steps for generating and switching the transient compensation control quantity corresponding to the induced resonance free component are as follows: The initial values ​​of the preset voltage compensation coefficient and current compensation coefficient correspond to the switching induced resonance voltage free component and the switching induced resonance current free component, respectively; Based on the transient energy evaluation value, determine the change in energy gain; Based on the change in energy gain, the voltage compensation coefficient and current compensation coefficient are updated by gradient-driven processing of the change in gain to obtain the current voltage compensation coefficient and current current compensation coefficient. Based on the current voltage compensation coefficient and the current current compensation coefficient, the switching-induced resonance free component is compensated and synthesized to obtain the transient compensation control quantity.

8. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 1, characterized in that, The specific steps for performing dynamic constraint power smoothing are as follows: Obtain the resonant frequency of the AC-side LCL filter; Based on the resonant frequency and residual induced resonant energy, power trajectory constraints are determined. Under power trajectory constraints, the transition start power value is processed by smooth trajectory generation to obtain the power transition trajectory, so that the transition start power value transitions to the target power value corresponding to the switching command.

9. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 1, characterized in that, The specific steps for analyzing the energy feedback efficiency and transient loss reduction rate throughout the entire switching process are as follows: Throughout the entire switching process, the active power output from the grid-side converter to the grid is obtained and integrated to obtain the total feedback energy. It also obtains the total loss during the entire switching process, and performs efficiency evaluation processing in combination with the total feedback energy to obtain the energy feedback efficiency; Based on the total loss during the entire switching process, and after loss improvement evaluation processing with a preset baseline loss value, the transient loss reduction rate is obtained.

10. The energy feedback efficiency optimization control method for the programmable AC source-carrier integrated test system according to claim 9, characterized in that, The specific steps to determine whether the preset efficiency optimization target is met are as follows: Record the duration of the entire handover process; The switching duration, energy feedback efficiency, and transient loss reduction rate are compared with the corresponding preset threshold conditions. If all comparison results meet the preset threshold conditions, then the preset efficiency optimization target is satisfied.

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