An active control method for suppressing secondary ripple of two-stage inverter DC side

Abstract

The application discloses an active control method for suppressing secondary ripples on the DC side of a two-stage inverter, and relates to the technical field of new energy power generation. The core characteristic parameters of the secondary ripples on the DC side are accurately and timely captured by a ripple detection module, a dynamic compensation current instruction with opposite phase and matched amplitude is generated by combining a compensation signal generation module, and the dynamic compensation current instruction is superimposed on a current inner loop reference signal through a front-stage DC-DC converter control module, so that the secondary ripples on the DC side are effectively offset, compared with a traditional passive filtering scheme, no additional bulky filtering elements are needed, the system size and cost are reduced, and a higher ripple suppression rate is achieved; a rear-stage inverter coordination module can dynamically respond to the front-stage compensation action, the spectral characteristics of a modulation wave are optimized, the total harmonic distortion rate of the output power on the AC side is ensured to be maintained at a low level, the front-stage module and the rear-stage module are cooperatively worked, and the ripple suppression effect and the power quality are considered.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation technology, specifically an active control method for suppressing secondary ripple on the DC side of a two-stage inverter. Background Technology

[0002] A two-stage inverter is a power electronic device that achieves high-efficiency energy conversion by cascading two inverters in series, primarily used in the field of new energy power generation. A two-stage inverter consists of a first-stage DC-AC inverter and a second-stage AC-AC inverter connected in series. The first stage boosts the input DC power (such as photovoltaic cell output) to a higher voltage, while the second stage converts the high-voltage DC power into AC power that meets grid requirements.

[0003] Existing technologies for suppressing secondary ripple on the DC side of two-stage inverters mainly include the following methods, along with their respective drawbacks:

[0004] Control strategy optimization (voltage outer loop + current inner loop): By optimizing the control loop (voltage outer loop + current inner loop) of the upstream DC / DC converter, secondary ripple can be effectively suppressed. However, this method has limitations, such as insufficient suppression capability for high-frequency ripple and the need for complex circuit design.

[0005] Filtering circuit design: LC resonant circuit: Ripple is eliminated by designing an LC circuit with a resonant frequency twice that of the output frequency, but the electrolytic capacitor has a limited lifespan and requires a large inductor and capacitor volume, which reduces system reliability and power density; Active filter: It can effectively filter out ripple, but requires an additional control system, which increases system complexity and is not conducive to integrated design.

[0006] Input capacitor and intermediate bus capacitor: Connecting a large electrolytic capacitor or intermediate bus capacitor in parallel in the circuit can reduce ripple. However, electrolytic capacitors are prone to aging, and filtering low-frequency ripple requires large-capacity components, affecting the system's compactness.

[0007] Parameter tuning and optimization: Ripple can be indirectly suppressed by adjusting inverter parameters (such as switching frequency and duty cycle). However, parameter selection needs to balance performance and stability, and the effect on high-frequency ripple suppression is limited.

[0008] In summary, existing technologies mainly rely on control optimization and filtering methods, but these suffer from problems such as increased component losses, larger size, and higher system complexity. A combination of methods and optimized circuit design are needed to improve the suppression effect. Therefore, this invention provides an active control method for suppressing secondary ripple on the DC side of a two-stage inverter. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides an active control method for suppressing secondary ripple on the DC side of a two-stage inverter, thereby solving the aforementioned problems.

[0010] To achieve the above objectives, the present invention provides the following technical solution: an active control method for suppressing secondary ripple on the DC side of a two-stage inverter. This active control method is based on an active control system, which includes: a ripple detection module, a compensation signal generation module, a front-stage DC-DC converter control module, and a back-stage inverter coordination module.

[0011] The ripple detection module is used to acquire DC-side bus voltage and current signals in real time.

[0012] The compensation signal generation module generates a compensation current command with opposite phase and matching amplitude to the secondary ripple based on the ripple parameters detected by the ripple detection module using a proportional resonance control algorithm.

[0013] The front-end DC-DC converter control module is used to superimpose the compensation current command onto the original current inner loop reference signal and adjust the switching duty cycle of the converter so that the front-end output current includes a component that cancels out the secondary ripple.

[0014] The back-stage inverter coordination module is used to dynamically optimize the harmonic components of the modulated wave based on the compensation actions of the front-stage inverter.

[0015] Preferably, the ripple detection module includes:

[0016] The signal acquisition unit uses high-precision Hall voltage sensors and Hall current sensors to acquire the raw voltage and current signals of the DC side bus in real time.

[0017] The signal preprocessing unit uses a second-order low-pass filter circuit and a digital filtering algorithm to denoise the acquired raw signal, eliminate high-frequency interference and measurement errors, and obtain smooth DC-side voltage and current signals.

[0018] The ripple extraction unit, based on fast Fourier transform or second-order generalized integral phase-locked loop technology, extracts the amplitude, frequency and phase information of the secondary ripple from the preprocessed signal and transmits these parameters to the compensation signal generation unit in real time.

[0019] Preferably, the compensation signal generation module includes:

[0020] The parameter parsing unit is used to receive the secondary ripple amplitude, phase and frequency parameters transmitted by the ripple detection module, verify the validity of the parameters, and convert the parameters into the standard format required for algorithm operation through a normalization algorithm.

[0021] The algorithm operation unit, based on the proportional resonance control algorithm and combined with the normalized ripple parameters, calculates and generates a compensation current reference command that is opposite in phase and matches the amplitude of the secondary ripple.

[0022] The instruction output unit converts the calculated compensation current instruction into a signal format recognizable by the front-end DC-DC converter control module and sends it to the algorithm calculation unit in real time through a high-speed serial communication interface, ensuring the rapid transmission and execution of the compensation instruction, thereby achieving active cancellation of the secondary ripple on the DC side.

[0023] Preferably, the front-end DC-DC converter control module includes:

[0024] The instruction receiving unit is used to receive the compensation current instruction sent by the compensation signal generation module through the high-speed serial communication interface, and to use a cyclic redundancy check mechanism to verify the integrity and correctness of the instruction data, and to eliminate invalid or erroneous instructions.

[0025] The signal superposition unit linearly superimposes the compensation current command with the original current inner loop reference signal of the preceding DC-DC converter to generate a new current inner loop control reference signal, so that the output current of the preceding stage includes a compensation component to cancel the secondary ripple.

[0026] The duty cycle adjustment unit, based on the superimposed inner current reference signal, uses a pulse width modulation algorithm to calculate the duty cycle of the drive signal of the switching transistor, dynamically adjusts the switching state of the DC-DC converter, controls the inductor current to track the new reference signal, and achieves active cancellation of secondary ripple.

[0027] The feedback closed-loop unit collects the output current and bus voltage signals of the preceding DC-DC converter in real time, and uses a proportional-integral controller to perform closed-loop adjustment of the current tracking error, correcting the output of the duty cycle adjustment unit and improving the compensation accuracy.

[0028] Preferably, the downstream inverter coordination module includes:

[0029] The compensation action sensing unit is used to receive the compensation action status signal sent by the front-end DC-DC converter control module, perform CRC check and validity verification on the received signal, and filter out abnormal or invalid compensation status data.

[0030] The modulation wave optimization unit identifies additional harmonic components in the modulation wave based on the parameters of the compensation action sensing unit, dynamically optimizes the spectral characteristics of the modulation wave, and suppresses AC side harmonic distortion.

[0031] The monitoring unit uses high-precision AC voltage and current sensors to collect the three-phase voltage and current signals output by the inverter. It extracts key indicators such as total harmonic distortion, fundamental amplitude and phase through digital signal processing technology, and sets THD threshold and fundamental parameter abnormality threshold.

[0032] The coordination and control unit is used to integrate the state information of the compensation action sensing unit and the output quality data of the monitoring unit, establish a dynamic mapping relationship between the pre-stage compensation action and the post-stage modulation optimization, and dynamically correct the harmonic suppression strategy of the modulated wave.

[0033] Preferably, the active control system further includes a system monitoring and fault diagnosis module, used to monitor the operating status of each module of the system in real time and quickly locate and handle faults.

[0034] Preferably, the system monitoring and fault diagnosis module includes:

[0035] The status monitoring unit is connected to the ripple detection module and is used to obtain the sampling accuracy of the ripple detection module, the command response time of the compensation signal generation module, the switching frequency of the front-end DC-DC converter, and the core parameters of the output harmonics of the back-end inverter, forming a multi-dimensional operating status matrix.

[0036] The fault diagnosis unit, connected to the status monitoring unit, is used to receive the multi-dimensional operating status matrix output by the status monitoring unit and to perform quantitative analysis on the parameter deviation of each module using a diagnostic algorithm that integrates rule-based expert system and machine learning.

[0037] The alarm and log unit is connected to the fault diagnosis unit and is used to trigger different levels of alarms according to the severity of the fault when the fault diagnosis unit outputs the fault diagnosis result.

[0038] Preferably, the active control system further includes an energy management and mode switching module, which is used to dynamically adjust the system energy distribution strategy and operating mode according to the DC side bus status, AC side load demand and grid operating conditions, so as to ensure the ripple suppression effect while improving the overall system operating efficiency.

[0039] Preferably, the energy management and mode switching module includes:

[0040] The operating condition sensing unit is used to collect multi-dimensional operating condition data such as DC side bus voltage and current, AC side load power, grid voltage and frequency, etc., and to identify the current operating status of the system (such as grid-connected, off-grid, load change, etc.) through data fusion algorithms, providing a basis for energy distribution and mode switching.

[0041] The energy distribution unit optimizes the power transmission ratio between the front-end DC-DC converter and the back-end inverter based on the operating condition perception results, minimizing system energy loss while meeting load requirements.

[0042] The mode switching unit predefines operating modes such as grid-connected, off-grid, and standby. When the operating conditions change, it triggers a smooth switching mechanism to synchronously adjust the front-end compensation signal and the back-end modulation wave parameters to ensure that the DC-side secondary ripple suppression effect is not affected during the switching process.

[0043] The mode verification unit collects key indicators such as DC-side ripple amplitude and AC-side total harmonic distortion rate after the mode switch is completed to verify whether the system performance after the switch meets the standards. If it does not meet the standards, it triggers a secondary adjustment to ensure operational stability.

[0044] An active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to any one of the preceding claims includes the following steps:

[0045] S1. Each functional module completes its initialization self-test in sequence, verifies the connectivity of hardware interfaces, the running status of software algorithms and the calibration accuracy of sensors, and enters the standby ready state after ensuring that there are no abnormalities.

[0046] S2. Start the signal acquisition unit and acquire the original voltage and current signals of the DC side bus in real time through the high-precision Hall voltage sensor and Hall current sensor. The high-frequency interference and measurement error are removed by the second-order low-pass filter circuit and digital filtering algorithm of the signal preprocessing unit to obtain smooth DC side voltage and current signals.

[0047] S3. The ripple extraction unit uses fast Fourier transform or second-order generalized integral phase-locked loop technology to extract the amplitude, phase and frequency parameters of the secondary ripple from the preprocessed signal, and transmits these parameters to the compensation signal generation module in real time to provide accurate input basis for the subsequent generation of compensation current command.

[0048] S4. The parameter parsing unit of the compensation signal generation module receives the secondary ripple amplitude, phase and frequency parameters transmitted in S3, verifies the validity of the parameters, removes abnormal data and converts the parameters into the standard format required for algorithm operation through a normalization algorithm.

[0049] S5. The algorithm operation unit is based on the proportional resonance control algorithm. It calculates and generates a compensation current reference command that is opposite in phase and matches the amplitude of the secondary ripple by combining the normalized ripple parameters. It also dynamically adjusts the gain coefficient of the PR controller according to the DC side load fluctuation through an adaptive gain adjustment mechanism to adapt to the ripple suppression requirements under different operating conditions.

[0050] S6. The instruction output unit converts the calculated compensation current instruction into a signal format recognizable by the front-end DC-DC converter control module, and sends it to the instruction receiving unit of the front-end DC-DC converter control module in real time through a high-speed serial communication interface to ensure the rapid transmission and execution of the compensation instruction.

[0051] Beneficial effects

[0052] Compared with the prior art, the present invention has the following advantages:

[0053] The ripple detection module accurately captures the core characteristic parameters of the DC-side secondary ripple in real time. Combined with the compensation signal generation module, it generates a dynamic compensation current command with opposite phase and matched amplitude. This command is then superimposed onto the current inner loop reference signal by the front-stage DC-DC converter control module, effectively canceling the DC-side secondary ripple fluctuations. Compared with traditional passive filtering schemes, no additional bulky filtering components are required, which reduces system size and cost while achieving a higher ripple suppression rate. The downstream inverter coordination module can dynamically respond to the upstream compensation action, optimize the spectral characteristics of the modulation wave, and ensure that the total harmonic distortion rate of the AC-side output power is maintained at a low level. This enables the upstream and downstream modules to work together, balancing ripple suppression effect and power quality. The energy management and mode switching module can dynamically adjust the energy distribution strategy and operating mode, and simultaneously optimize the upstream compensation signal and downstream modulation parameters to ensure stable ripple suppression effect under all operating conditions, expanding the applicable scenarios of the two-stage inverter. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the active control system modules in this invention;

[0055] Figure 2 This is a flowchart of the active control method in this invention. Detailed Implementation

[0056] 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.

[0057] Please see Figure 1-2 An active control method for suppressing secondary ripple on the DC side of a two-stage inverter is proposed. The active control method is based on an active control system, which includes: a ripple detection module, a compensation signal generation module, a front-stage DC-DC converter control module, and a back-stage inverter coordination module.

[0058] The ripple detection module is used to acquire DC-side bus voltage and current signals in real time, and extract the amplitude and phase information of the secondary ripple through Fourier transform or phase-locked loop technology. That is, under the action of the ripple detection module, the key characteristic parameters of the DC-side secondary ripple can be accurately obtained, and these parameters are transmitted to the compensation signal generation module in real time, providing a reliable reference for the subsequent generation of compensation current commands, thereby providing a stable data foundation for actively suppressing secondary ripple.

[0059] The compensation signal generation module generates a compensation current command with opposite phase and matching amplitude to the secondary ripple based on the ripple parameters detected by the ripple detection module and using a proportional resonance control algorithm. That is, under the action of the compensation signal generation module, a reverse compensation current command that precisely matches the characteristics of the secondary ripple can be generated, and the command is sent to the front-end DC-DC converter control module in real time.

[0060] The front-stage DC-DC converter control module is used to superimpose the compensation current command onto the original current inner loop reference signal and adjust the switching duty cycle of the converter so that the front-stage output current includes a component that cancels out the secondary ripple. In other words, under the action of the front-stage DC-DC converter control module, the output current of the front-stage DC-DC converter can be precisely adjusted to include a compensation component with the same amplitude but opposite phase to the DC-side secondary ripple, effectively canceling the secondary ripple fluctuations of the DC-side bus, while ensuring the stable operation of the front-stage converter, providing a smooth DC input for the subsequent inverter, and thus improving the power quality and operational reliability of the entire two-stage inverter system.

[0061] The post-stage inverter coordination module is used to dynamically optimize the harmonic components of the modulation wave based on the compensation action of the pre-stage inverter, ensuring that the AC output quality is not affected. In other words, under the action of the post-stage inverter coordination module, the modulation strategy of the inverter can be dynamically adjusted according to the DC voltage state after the pre-stage compensation, ensuring that the waveform quality of the output power of the post-stage inverter is not affected during the ripple suppression process, realizing the coordinated work of the pre-stage and post-stage modules, and jointly ensuring the efficient and stable operation of the system.

[0062] Specifically, the ripple detection module includes:

[0063] The signal acquisition unit uses high-precision Hall voltage and Hall current sensors to acquire the raw voltage and current signals of the DC bus in real time, ensuring that the signal sampling frequency meets the real-time requirements of ripple detection.

[0064] The signal preprocessing unit uses a second-order low-pass filter circuit and a digital filtering algorithm to denoise the acquired raw signal, eliminate high-frequency interference and measurement errors, and obtain smooth DC-side voltage and current signals.

[0065] The ripple extraction unit, based on fast Fourier transform or second-order generalized integral phase-locked loop technology, extracts the amplitude, frequency and phase information of the secondary ripple from the preprocessed signal and transmits these parameters to the compensation signal generation unit in real time, providing an accurate basis for the generation of subsequent compensation commands.

[0066] With the effective cooperation of the signal acquisition unit, signal preprocessing unit, and ripple extraction unit, the ripple detection module can accurately and in real time capture the core characteristic parameters such as amplitude, phase, and frequency of the DC-side secondary ripple, ensuring the accuracy and timeliness of these parameters. This provides data support for the subsequent generation of reverse compensation current commands by the compensation signal generation module, thereby ensuring the effectiveness and stability of the entire active control system in suppressing secondary ripple.

[0067] Specifically, the compensation signal generation module includes:

[0068] The parameter parsing unit is used to receive the secondary ripple amplitude, phase and frequency parameters transmitted by the ripple detection module, verify the validity of the parameters, and convert the parameters into the standard format required for algorithm operation through a normalization algorithm to ensure the accuracy and consistency of the input data.

[0069] The algorithm operation unit, based on the proportional resonance control algorithm and combined with the normalized ripple parameters, calculates and generates a compensation current reference command that is opposite in phase and matches the amplitude of the secondary ripple. At the same time, an adaptive gain adjustment mechanism is introduced to dynamically adjust the gain coefficient of the PR controller according to the DC side load fluctuation to adapt to the ripple suppression requirements under different operating conditions.

[0070] The instruction output unit converts the calculated compensation current instruction into a signal format recognizable by the front-end DC-DC converter control module and sends it to the algorithm calculation unit in real time through a high-speed serial communication interface, ensuring the rapid transmission and execution of the compensation instruction, thereby achieving active cancellation of secondary ripple on the DC side.

[0071] With the effective cooperation of the parameter analysis unit, algorithm operation unit, and instruction output unit, the compensation signal generation module can accurately generate a reverse compensation current instruction that perfectly matches the secondary ripple characteristics of the DC side. The generated reverse compensation current instruction can not only dynamically adjust the gain according to load fluctuations to adapt to different operating conditions, but also quickly transmit it to the front-end DC-DC converter control module to ensure the real-time performance and accuracy of the compensation action.

[0072] Specifically, the front-end DC-DC converter control module includes:

[0073] The instruction receiving unit is used to receive the compensation current instruction sent by the compensation signal generation module through the high-speed serial communication interface. It adopts a cyclic redundancy check mechanism to verify the integrity and correctness of the instruction data, eliminate invalid or erroneous instructions, and ensure the reliability of instruction reception.

[0074] The signal superposition unit linearly superimposes the compensation current command with the original current inner loop reference signal of the preceding DC-DC converter to generate a new current inner loop control reference signal, so that the output current of the preceding stage includes a compensation component to cancel the secondary ripple.

[0075] The duty cycle adjustment unit, based on the superimposed inner current reference signal, uses a pulse width modulation algorithm to calculate the duty cycle of the drive signal of the switching transistor, dynamically adjusts the switching state of the DC-DC converter, controls the inductor current to track the new reference signal, and achieves active cancellation of secondary ripple.

[0076] The feedback closed-loop unit collects the output current and bus voltage signals of the preceding DC-DC converter in real time, and uses a proportional-integral controller to perform closed-loop adjustment of the current tracking error, correcting the output of the duty cycle adjustment unit and improving the compensation accuracy.

[0077] With the effective cooperation of the command receiving unit, signal superposition unit, duty cycle adjustment unit and feedback closed loop unit, the front-end DC-DC converter control module can accurately track the superimposed current inner loop reference signal, so that the output current of the front-end DC-DC converter contains a compensation component with the same amplitude and opposite phase as the secondary ripple on the DC side, effectively offsetting the secondary ripple fluctuation of the DC side bus.

[0078] Specifically, the downstream inverter coordination module includes:

[0079] The compensation action sensing unit is used to receive the compensation action status signal (such as compensation current amplitude and phase change information) sent by the front-end DC-DC converter control module, perform CRC check and validity verification on the received signal, filter out abnormal or invalid compensation status data, and provide accurate input basis for subsequent modulation wave optimization.

[0080] The modulation wave optimization unit, based on the parameters of the compensation action sensing unit, identifies additional harmonic components in the modulation wave, dynamically optimizes the spectral characteristics of the modulation wave, and suppresses AC side harmonic distortion.

[0081] The monitoring unit uses high-precision AC voltage and current sensors to collect the three-phase voltage and current signals output by the inverter. It extracts key indicators such as total harmonic distortion (THD), fundamental amplitude, and phase through digital signal processing technology, and sets THD thresholds and fundamental parameter abnormality thresholds. When the monitored indicators exceed the range, it provides real-time feedback to the modulation wave optimization unit and triggers adjustments. At the same time, the monitoring data is uploaded to the system monitoring platform, allowing maintenance personnel to monitor the output status in real time.

[0082] The coordination and control unit is used to integrate the status information of the compensation action sensing unit and the output quality data of the monitoring unit, establish a dynamic mapping relationship between the pre-stage compensation action and the post-stage modulation optimization, and dynamically correct the harmonic suppression strategy of the modulated wave.

[0083] With the effective cooperation of the compensation action sensing unit, modulation wave optimization unit, monitoring unit and coordination control unit, the downstream inverter coordination module can dynamically respond to the compensation action of the upstream stage, accurately optimize the spectrum characteristics of the modulation wave, effectively suppress the additional harmonics that may be introduced by the upstream compensation on the AC side, and ensure that the total harmonic distortion (THD) of the output three-phase voltage and current is maintained at a low level, so as to meet the strict requirements of the power grid or load for power quality.

[0084] Specifically, the active control system also includes a system monitoring and fault diagnosis module, which is used to monitor the operating status of each module of the system in real time and quickly locate and handle faults.

[0085] Specifically, the system monitoring and fault diagnosis module includes:

[0086] The status monitoring unit, connected to the ripple detection module, is used to obtain the sampling accuracy of the ripple detection module, the command response time of the compensation signal generation module, the switching frequency of the front-end DC-DC converter, and the core parameters of the output harmonics of the back-end inverter, forming a multi-dimensional operating status matrix.

[0087] The fault diagnosis unit, connected to the condition monitoring unit, is used to receive the multi-dimensional operating status matrix output by the condition monitoring unit. It employs a diagnostic algorithm that combines rule-based expert systems and machine learning to quantitatively analyze the parameter deviation of each module.

[0088] The alarm and log unit is connected to the fault diagnosis unit and is used to trigger different levels of alarms according to the severity of the fault when the fault diagnosis unit outputs the fault diagnosis results.

[0089] Through the effective coordination of the status monitoring unit, fault diagnosis unit, and alarm and log unit, the operating status of each module of the system can be tracked in real time, accurately identifying fault types such as abnormal sampling of the ripple detection module, instruction delay of the compensation signal generation module, switching frequency drift of the front-end DC-DC converter, or excessive harmonics in the output of the back-end inverter. At the same time, the time, location, cause, and handling process of the fault are fully recorded, forming a traceable operation log, providing data support for system maintenance and optimization, and further improving the reliability and maintainability of the entire active control system.

[0090] Specifically, the active control system also includes an energy management and mode switching module, which is used to dynamically adjust the system's energy distribution strategy and operating mode according to the DC-side bus status, AC-side load demand and grid operating conditions, so as to ensure ripple suppression while improving the overall system operating efficiency.

[0091] Specifically, the energy management and mode switching module includes:

[0092] The operating condition sensing unit is used to collect multi-dimensional operating condition data such as DC side bus voltage and current, AC side load power, grid voltage and frequency, etc., and to identify the current operating status of the system (such as grid-connected, off-grid, load change, etc.) through data fusion algorithms, providing a basis for energy distribution and mode switching.

[0093] The energy distribution unit optimizes the power transmission ratio between the front-end DC-DC converter and the back-end inverter based on the operating condition perception results, minimizing system energy loss while meeting load requirements.

[0094] The mode switching unit predefines operating modes such as grid-connected, off-grid, and standby. When the operating conditions change, it triggers a smooth switching mechanism to synchronously adjust the front-end compensation signal and the back-end modulation wave parameters to ensure that the DC-side secondary ripple suppression effect is not affected during the switching process.

[0095] The mode verification unit collects key indicators such as DC-side ripple amplitude and AC-side total harmonic distortion rate after the mode switch is completed to verify whether the system performance after the switch meets the standards. If it does not meet the standards, it triggers a secondary adjustment to ensure operational stability.

[0096] Through the effective cooperation of the operating condition sensing unit, energy distribution unit, mode switching unit, and mode verification unit, it can accurately adapt to various operating conditions such as grid connection, off-grid, and load surges. It dynamically optimizes the power transmission ratio between the front-end DC-DC converter and the back-end inverter to minimize system energy loss, achieves efficient operation and stable output of the system under all operating conditions, further expands the applicable scenarios of the two-stage inverter, and improves its reliability and economy in complex power environments.

[0097] Working principle:

[0098] The ripple detection module uses a high-precision Hall sensor to acquire the raw signals of DC-side bus voltage and current. After noise reduction by the preprocessing unit, the amplitude, phase, and frequency characteristic parameters of the secondary ripple are extracted using Fast Fourier Transform or second-order generalized integral phase-locked loop technology. The compensation signal generation module receives these parameters, performs analytical verification, and uses a proportional-resonant control algorithm to generate a compensation current command with opposite phase and matching amplitude to the secondary ripple. This command is then transmitted to the front-stage DC-DC converter control module via a high-speed serial communication interface. The front-stage DC-DC converter control module superimposes the compensation command with the original current inner loop reference signal and adjusts the duty cycle accordingly. The unit dynamically adjusts the switching transistor drive signal to ensure that the output current includes a compensation component to offset secondary ripple, effectively smoothing the DC-side bus voltage. The downstream inverter coordination module senses the upstream compensation action and dynamically corrects the modulation strategy through the modulation wave optimization unit to suppress additional harmonics on the AC side. The monitoring unit provides real-time feedback on output indicators to ensure power quality. The system monitoring and fault diagnosis module monitors the operating status of each module throughout the process, uses a fusion algorithm to quickly locate faults and trigger alarms. The energy management and mode switching module dynamically adjusts energy distribution and operating mode based on the operating condition sensing results, minimizing system energy consumption while ensuring ripple suppression.

[0099] An active control method for suppressing DC-side secondary ripple in a two-stage inverter according to any one of the above claims includes the following steps:

[0100] S1. Each functional module (ripple detection module, compensation signal generation module, front-end DC-DC converter control module, back-end inverter coordination module, etc.) completes initialization self-test in sequence to verify hardware interface connectivity, software algorithm running status and sensor calibration accuracy. After ensuring there are no abnormalities, it enters standby ready state.

[0101] S2. Start the signal acquisition unit, which collects the original voltage and current signals of the DC bus in real time through high-precision Hall voltage and Hall current sensors. The signal preprocessing unit removes high-frequency interference and measurement errors through a second-order low-pass filter circuit and digital filtering algorithm to obtain smooth DC side voltage and current signals.

[0102] S3. The ripple extraction unit uses fast Fourier transform or second-order generalized integral phase-locked loop technology to extract the amplitude, phase and frequency parameters of the secondary ripple from the preprocessed signal, and transmits these parameters to the compensation signal generation module in real time to provide accurate input basis for the subsequent generation of compensation current command.

[0103] S4. The parameter parsing unit of the compensation signal generation module receives the secondary ripple amplitude, phase and frequency parameters transmitted in S3, verifies the validity of the parameters, removes abnormal data and converts the parameters into the standard format required for algorithm operation through a normalization algorithm.

[0104] S5. The algorithm operation unit is based on the proportional resonance control algorithm. It calculates and generates a compensation current reference command that is opposite in phase and matches the amplitude of the secondary ripple by combining the normalized ripple parameters. It also dynamically adjusts the gain coefficient of the PR controller according to the DC side load fluctuation through the adaptive gain adjustment mechanism to adapt to the ripple suppression requirements under different operating conditions.

[0105] S6. The instruction output unit converts the calculated compensation current instruction into a signal format recognizable by the front-end DC-DC converter control module, and sends it to the instruction receiving unit of the front-end DC-DC converter control module in real time through a high-speed serial communication interface, ensuring the rapid transmission and execution of the compensation instruction.

[0106] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0107] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0108] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An active control method for suppressing secondary ripple on the DC side of a two-stage inverter, the active control method being implemented based on an active control system, characterized in that, The active control system includes: a ripple detection module, a compensation signal generation module, a front-end DC-DC converter control module, and a back-end inverter coordination module; wherein... The ripple detection module is used to acquire DC-side bus voltage and current signals in real time. The compensation signal generation module generates a compensation current command with opposite phase and matching amplitude to the secondary ripple based on the ripple parameters detected by the ripple detection module using a proportional resonance control algorithm. The front-end DC-DC converter control module is used to superimpose the compensation current command onto the original current inner loop reference signal and adjust the switching duty cycle of the converter so that the front-end output current includes a component that cancels out the secondary ripple. The back-stage inverter coordination module is used to dynamically optimize the harmonic components of the modulated wave based on the compensation actions of the front-stage inverter.

2. The active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to claim 1, characterized in that, The ripple detection module includes: The signal acquisition unit uses high-precision Hall voltage sensors and Hall current sensors to acquire the raw voltage and current signals of the DC side bus in real time. The signal preprocessing unit uses a second-order low-pass filter circuit and a digital filtering algorithm to denoise the acquired raw signal, eliminate high-frequency interference and measurement errors, and obtain smooth DC-side voltage and current signals. The ripple extraction unit, based on fast Fourier transform or second-order generalized integral phase-locked loop technology, extracts the amplitude, frequency and phase information of the secondary ripple from the preprocessed signal and transmits these parameters to the compensation signal generation unit in real time.

3. The active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to claim 1, characterized in that, The compensation signal generation module includes: The parameter parsing unit is used to receive the secondary ripple amplitude, phase and frequency parameters transmitted by the ripple detection module, verify the validity of the parameters, and convert the parameters into the standard format required for algorithm operation through a normalization algorithm. The algorithm operation unit, based on the proportional resonance control algorithm and combined with the normalized ripple parameters, calculates and generates a compensation current reference command that is opposite in phase and matches the amplitude of the secondary ripple. The instruction output unit converts the calculated compensation current instruction into a signal format recognizable by the front-end DC-DC converter control module and sends it to the algorithm calculation unit in real time through a high-speed serial communication interface, ensuring the rapid transmission and execution of the compensation instruction, thereby achieving active cancellation of the secondary ripple on the DC side.

4. The active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to claim 1, characterized in that, The front-end DC-DC converter control module includes: The instruction receiving unit is used to receive the compensation current instruction sent by the compensation signal generation module through the high-speed serial communication interface, and to use a cyclic redundancy check mechanism to verify the integrity and correctness of the instruction data, and to eliminate invalid or erroneous instructions. The signal superposition unit linearly superimposes the compensation current command with the original current inner loop reference signal of the preceding DC-DC converter to generate a new current inner loop control reference signal, so that the output current of the preceding stage includes a compensation component to cancel the secondary ripple. The duty cycle adjustment unit, based on the superimposed inner current reference signal, uses a pulse width modulation algorithm to calculate the duty cycle of the drive signal of the switching transistor, dynamically adjusts the switching state of the DC-DC converter, controls the inductor current to track the new reference signal, and achieves active cancellation of secondary ripple. The feedback closed-loop unit collects the output current and bus voltage signals of the preceding DC-DC converter in real time, and uses a proportional-integral controller to perform closed-loop adjustment of the current tracking error, correcting the output of the duty cycle adjustment unit and improving the compensation accuracy.

5. The active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to claim 1, characterized in that, The downstream inverter coordination module includes: The compensation action sensing unit is used to receive the compensation action status signal sent by the front-end DC-DC converter control module, perform CRC check and validity verification on the received signal, and filter out abnormal or invalid compensation status data. The modulation wave optimization unit identifies additional harmonic components in the modulation wave based on the parameters of the compensation action sensing unit, dynamically optimizes the spectral characteristics of the modulation wave, and suppresses AC side harmonic distortion. The monitoring unit uses high-precision AC voltage and current sensors to collect the three-phase voltage and current signals output by the inverter. It extracts key indicators such as total harmonic distortion, fundamental amplitude and phase through digital signal processing technology, and sets THD threshold and fundamental parameter abnormality threshold. The coordination and control unit is used to integrate the state information of the compensation action sensing unit and the output quality data of the monitoring unit, establish a dynamic mapping relationship between the pre-stage compensation action and the post-stage modulation optimization, and dynamically correct the harmonic suppression strategy of the modulated wave.

6. The active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to claim 1, characterized in that, The active control system also includes a system monitoring and fault diagnosis module, which is used to monitor the operating status of each module of the system in real time and quickly locate and handle faults.

7. The active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to claim 6, characterized in that, The system monitoring and fault diagnosis module includes: The status monitoring unit is connected to the ripple detection module and is used to obtain the sampling accuracy of the ripple detection module, the command response time of the compensation signal generation module, the switching frequency of the front-end DC-DC converter, and the core parameters of the output harmonics of the back-end inverter, forming a multi-dimensional operating status matrix. The fault diagnosis unit, connected to the status monitoring unit, is used to receive the multi-dimensional operating status matrix output by the status monitoring unit and to perform quantitative analysis on the parameter deviation of each module using a diagnostic algorithm that integrates rule-based expert system and machine learning. The alarm and log unit is connected to the fault diagnosis unit and is used to trigger different levels of alarms according to the severity of the fault when the fault diagnosis unit outputs the fault diagnosis result.

8. The active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to claim 1, characterized in that, The active control system also includes an energy management and mode switching module, which is used to dynamically adjust the system's energy distribution strategy and operating mode according to the DC-side bus status, AC-side load demand and grid operating conditions, so as to ensure ripple suppression effect while improving the overall system operating efficiency.

9. The active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to claim 8, characterized in that, The energy management and mode switching module includes: The operating condition sensing unit is used to collect multi-dimensional operating condition data such as DC side bus voltage and current, AC side load power, grid voltage and frequency, etc., and to identify the current operating status of the system (such as grid-connected, off-grid, load change, etc.) through data fusion algorithms, providing a basis for energy distribution and mode switching. The energy distribution unit optimizes the power transmission ratio between the front-end DC-DC converter and the back-end inverter based on the operating condition perception results, minimizing system energy loss while meeting load requirements. The mode switching unit predefines operating modes such as grid-connected, off-grid, and standby. When the operating conditions change, it triggers a smooth switching mechanism to synchronously adjust the front-end compensation signal and the back-end modulation wave parameters to ensure that the DC-side secondary ripple suppression effect is not affected during the switching process. The mode verification unit collects key indicators such as DC-side ripple amplitude and AC-side total harmonic distortion rate after the mode switch is completed to verify whether the system performance after the switch meets the standards. If it does not meet the standards, it triggers a secondary adjustment to ensure operational stability.

10. An active control method for suppressing secondary ripple on the DC side of a two-stage inverter according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Each functional module completes its initialization self-test in sequence, verifies the connectivity of hardware interfaces, the running status of software algorithms and the calibration accuracy of sensors, and enters the standby ready state after ensuring that there are no abnormalities. S2. Start the signal acquisition unit and acquire the original voltage and current signals of the DC side bus in real time through the high-precision Hall voltage sensor and Hall current sensor. The high-frequency interference and measurement error are removed by the second-order low-pass filter circuit and digital filtering algorithm of the signal preprocessing unit to obtain smooth DC side voltage and current signals. S3. The ripple extraction unit uses fast Fourier transform or second-order generalized integral phase-locked loop technology to extract the amplitude, phase and frequency parameters of the secondary ripple from the preprocessed signal, and transmits these parameters to the compensation signal generation module in real time to provide accurate input basis for the subsequent generation of compensation current command. S4. The parameter parsing unit of the compensation signal generation module receives the secondary ripple amplitude, phase and frequency parameters transmitted in S3, verifies the validity of the parameters, removes abnormal data and converts the parameters into the standard format required for algorithm operation through a normalization algorithm. S5. The algorithm operation unit is based on the proportional resonance control algorithm. It calculates and generates a compensation current reference command that is opposite in phase and matches the amplitude of the secondary ripple by combining the normalized ripple parameters. It also dynamically adjusts the gain coefficient of the PR controller according to the DC side load fluctuation through an adaptive gain adjustment mechanism to adapt to the ripple suppression requirements under different operating conditions. S6. The instruction output unit converts the calculated compensation current instruction into a signal format recognizable by the front-end DC-DC converter control module, and sends it to the instruction receiving unit of the front-end DC-DC converter control module in real time through a high-speed serial communication interface to ensure the rapid transmission and execution of the compensation instruction.

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