Single-phase inverter active filtering method and device based on current slope control

Abstract

The embodiment of the invention discloses a single-phase inverter active filtering method and device based on current slope control, and the method comprises the steps: firstly, converting the voltage of a DC power supply through an L-type grid-connected single-phase bridge type inverter through a single-pole pulse width modulation technology, and generating a pulse width modulation wave output voltage; in the process of generating the pulse width modulation wave, a current slope change rule is generated by performing relation analysis on slope change factors influencing the output current. Afterwards, according to a current slope change rule, an active filtering single-phase inverter is utilized to compensate the voltage change at the two ends of the inductor, and control over the current slope in the direct current conversion process is guaranteed. According to the embodiment of the invention, the design of the filter inductor is optimized at the cost of increasing an additional bridge circuit, and the filter inductance value is reduced by 5-10 times. After the size of the filter is greatly reduced, it can be guaranteed that the harmonic suppression effect is not affected.

Description

Technical Field

[0001] The present disclosure relates to the technical field of active filter applications, and in particular to a single-phase inverter active filtering method and device based on current slope control. Background Art

[0002] In recent years, with the development of power electronics technology, the size and weight of filters have gradually become bottlenecks in high power density applications. Especially under high-frequency operation and compact design requirements, passive filters are often large in size and heavy in weight, making it difficult to meet the power density requirements of modern power electronic converters.

[0003] In order to meet this challenge, the existing technology has proposed four solutions. First, the concept of two-port active inductor, which minimizes the apparent power processing requirements by utilizing auxiliary circuits, thereby effectively reducing the energy storage requirements, volume and weight of the inductor. However, despite the significant theoretical advantages of this technology, the problems caused by high-frequency current harmonics have not been completely solved. Second, the two-port active inductor is further applied to the DC bus LC filter design of the three-phase diode bridge rectifier, achieving significant miniaturization and cost reduction of the filter. However, due to the use of a single-phase H-bridge as the basic unit, this solution requires a larger DC bus capacitor capacity when processing subharmonic power, which to some extent limits its application in high-efficiency, high-power density systems. Third, a two-port unified active inductor-capacitor topology structure eliminates the reliance on large-capacity DC capacitors by integrating active inductor and capacitor functions and modulation strategies in a single circuit. However, this solution also faces the problems of additional losses caused by high-frequency switching and increased system complexity. Fourth, a new type of matrix-coupled inductor filter uses matrix coupling technology to effectively reduce the volume while maintaining good high-frequency ripple attenuation performance. However, this technology's reliance on custom magnetic cores significantly increases manufacturing costs, making it face certain challenges in large-scale production.

[0004] Therefore, how to ensure the stability of high-frequency performance and system efficiency while further improving power density, reducing cost and complexity remains a key challenge in current research.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0006] The purpose of the present disclosure is to provide a single-phase inverter active filtering method and device based on current slope control, thereby overcoming one or more problems caused by limitations and defects of related technologies at least to a certain extent.

[0007] According to one aspect of the present disclosure, a single-phase inverter active filtering method based on current slope control is provided, comprising:

[0008] Using unipolar pulse width modulation technology, the voltage of the DC power supply is converted through an L-type grid-connected single-phase bridge inverter to generate a pulse width modulated wave output voltage;

[0009] In the process of generating the pulse width modulation wave output voltage, the current slope change law is generated by analyzing the relationship between the factors affecting the slope change of the output current;

[0010] According to the current slope variation law, an active filtering single-phase inverter is used to compensate for the voltage variation across the inductor, thereby ensuring the control of the current slope during the conversion process of the DC power supply.

[0011] In an exemplary embodiment of the present disclosure, the voltage of a DC power supply is converted by an L-type grid-connected single-phase bridge inverter, including:

[0012] Based on the standard of the power grid where the inverter is located, a control strategy is generated by setting the conduction state of the power switch in the L-type grid-connected single-phase bridge inverter;

[0013] According to the set control strategy, the input direct current is converted into alternating current;

[0014] By using the unipolar pulse width modulation technology, the high-frequency harmonics generated in the conversion process are suppressed by the filter in the L-type grid-connected single-phase bridge inverter to generate a pulse width modulation wave output voltage.

[0015] In an exemplary embodiment of the present disclosure, a relationship analysis is performed on factors affecting the slope change of the output current, including:

[0016] Based on Kirchhoff's voltage law, when the upper bridge arm is turned on, the period of the pulse width modulation wave output voltage is the positive half cycle;

[0017] Based on Kirchhoff's voltage law, when the lower bridge arm is turned on, the period of the pulse width modulation wave output voltage is the negative half cycle;

[0018] During the positive half cycle and the negative half cycle, two states of the inductor current in the filter are analyzed respectively to generate a current slope variation rule.

[0019] In an exemplary embodiment of the present disclosure, the current slope variation rule includes:

[0020] The current increases linearly, and the current slope is proportional to the difference between the input DC voltage and the grid voltage, and inversely proportional to the inductance value;

[0021] The current decreases linearly, and the current slope is proportional to the negative value of the grid voltage and inversely proportional to the inductance value.

[0022] In an exemplary embodiment of the present disclosure, an active filtering single-phase inverter includes:

[0023] The L-type filter in the L-type grid-connected single-phase bridge inverter is replaced with an active filter by connecting in series to generate an active filter single-phase inverter;

[0024] The trigger signal of the active filter is shared with the trigger signal of the single-phase bridge inverter;

[0025] The power supply of the active filter is provided by a voltage divider circuit.

[0026] In an exemplary embodiment of the present disclosure, the voltage variation across the inductor is compensated, including:

[0027] During the positive half cycle of the pulse width modulation wave output voltage, the active inductor of the active filter is charged by a voltage source and a compensation voltage based on the current linear increase law;

[0028] During the positive half cycle of the pulse width modulation wave output voltage, based on the current linear reduction law, the active inductor of the active filter is discharged through the voltage source and the compensation voltage;

[0029] Based on the charging and discharging behavior of the active inductor during the positive half cycle, compensation is provided for the voltage across the inductor, thereby ensuring the control of the current slope during the generation of the sinusoidal pulse width modulation wave output voltage.

[0030] In an exemplary embodiment of the present disclosure, the voltage variation across the inductor is compensated, including:

[0031] During the negative half cycle of the pulse width modulation wave output voltage, the active inductor of the active filter is charged by a voltage source and a compensation voltage based on the current linear increase law;

[0032] During the negative half cycle of the pulse width modulation wave output voltage, based on the current linear reduction law, the active inductor of the active filter is discharged through the voltage source and the compensation voltage;

[0033] Based on the charging and discharging behavior of the active inductor during the negative half cycle, compensation is provided for the voltage across the inductor to ensure control of the current slope during the generation of the negative sinusoidal pulse width modulation wave output voltage.

[0034] In one aspect of the present disclosure, a single-phase inverter active filter device based on current slope control is provided, comprising:

[0035] The single-phase bridge inverter module is used to convert the voltage of the DC power supply through an L-type grid-connected single-phase bridge inverter using unipolar pulse width modulation technology to generate a pulse width modulation wave output voltage;

[0036] A current slope analysis module, used to generate a current slope change rule by analyzing the relationship between factors affecting the slope change of the output current during the process of generating the pulse width modulation wave output voltage;

[0037] The active filtering single-phase inverter module is used to ensure the control of the current slope during the conversion process of the DC power supply by compensating the voltage change at both ends of the inductor according to the current slope change law using the active filtering single-phase inverter.

[0038] An active filtering method of a single-phase inverter based on current slope control in an exemplary embodiment of the present disclosure: First, using unipolar sinusoidal pulse width modulation technology, the voltage of the DC power supply is converted through an L-type grid-connected single-phase bridge inverter to generate a pulse width modulated wave output voltage. In the process of generating the pulse width modulated wave, the relationship between the factors affecting the slope change of the output current is analyzed to generate the current slope change law. Afterwards, according to the current slope change law, an active filtering single-phase inverter is used to compensate for the voltage change at both ends of the inductor to ensure the control of the current slope during the conversion of DC power. The embodiment of the present disclosure optimizes the design of the filter inductance at the cost of adding an additional bridge circuit, and reduces the filter inductance value by 5 to 10 times. It is achieved that the volume of the filter is greatly reduced while ensuring that the harmonic suppression effect is not affected.

[0039] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and other features and advantages of the present disclosure will become more apparent by describing in detail example embodiments thereof with reference to the attached drawings.

[0041] Figure 1 A flow chart of a single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown;

[0042] Figure 2 A schematic diagram of an L-type grid-connected single-phase bridge inverter topology structure of a single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown;

[0043] Figure 3A schematic diagram of a unipolar sinusoidal pulse width modulation waveform of a single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown;

[0044] Figure 4 An equivalent schematic diagram of a passive L-type filter topology structure of a single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown;

[0045] Figure 5 A schematic diagram of a current waveform when the inductance value is L in a single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown;

[0046] Figure 6 A single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown. Schematic diagram of current waveform when ;

[0047] Figure 7 An equivalent schematic diagram of a series active filter topology structure of a single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown;

[0048] Figure 8 A schematic diagram of a current waveform after adding a compensation voltage to a single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown;

[0049] Fig. 9 A schematic diagram of a topology structure of an active filtering single-phase inverter of a single-phase inverter active filtering method based on current slope control according to an exemplary embodiment of the present disclosure is shown;

[0050] Fig.10 A first schematic diagram of a working current path of an active filtering single-phase inverter according to an exemplary embodiment of the present disclosure is shown;

[0051] Fig.11 A second schematic diagram of a working current path of an active filtering single-phase inverter according to an exemplary embodiment of the present disclosure is shown;

[0052] Fig.12 A third schematic diagram of a working current path of an active filtering single-phase inverter according to an exemplary embodiment of the present disclosure is shown;

[0053] Fig.13 A fourth schematic diagram of a working current path of an active filtering single-phase inverter according to an exemplary embodiment of the present disclosure is shown;

[0054] Fig.14A schematic diagram of a simulated current waveform of a series active filter when L=0.2 mH according to an exemplary embodiment of the present disclosure is shown;

[0055] Fig.15 A schematic block diagram of a single-phase inverter active filter device based on current slope control according to an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0056] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0057] In addition, the described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, materials, devices, steps, etc. may be adopted. In other cases, known structures, methods and devices, implementations, materials or operations are not shown or described in detail to avoid blurring the various aspects of the present disclosure.

[0058] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or these functional entities or parts of functional entities may be implemented in one or more software hardened modules, or these functional entities may be implemented in different networks and / or processor devices and / or microcontroller devices.

[0059] In this exemplary embodiment, a single-phase inverter active filtering method based on current slope control is first provided; Figure 1 As shown in , the single-phase inverter active filtering method based on current slope control may include the following steps:

[0060] Step S110 , using unipolar sinusoidal pulse width modulation technology, converting the voltage of the DC power supply through an L-type grid-connected single-phase bridge inverter to generate a pulse width modulated wave output voltage.

[0061] Step S120, in the process of generating the pulse width modulation wave, by analyzing the relationship between the factors affecting the slope change of the output current, a current slope change rule is generated.

[0062] Step S130, according to the current slope variation rule, using an active filtering single-phase inverter, by compensating for the voltage variation across the inductor, thereby ensuring the control of the current slope during the direct current conversion process.

[0063] An active filtering control method for a single-phase inverter based on current slope control in an exemplary embodiment of the present disclosure is as follows: First, using unipolar sinusoidal pulse width modulation technology, the voltage of a DC power supply is converted through an L-type grid-connected single-phase bridge inverter to generate a pulse width modulated wave output voltage. In the process of generating a pulse width modulated wave, the relationship between the factors affecting the slope change of the output current is analyzed to generate a current slope change law. Afterwards, according to the current slope change law, an active filtering single-phase inverter is used to compensate for the voltage change at both ends of the inductor to ensure the control of the current slope during the conversion of DC power. The embodiment of the present disclosure optimizes the design of the filter inductance at the cost of adding an additional bridge circuit, and reduces the filter inductance value by 5 to 10 times. It is achieved that the volume of the filter is greatly reduced while ensuring that the harmonic suppression effect is not affected.

[0064] Next, a single-phase inverter active filtering method based on current slope control in this exemplary embodiment will be further described.

[0065] In the template configuration step S110, the unipolar pulse width modulation technology can be used to convert the voltage of the DC power supply through an L-type grid-connected single-phase bridge inverter to generate a pulse width modulation wave output voltage.

[0066] In the embodiment of this example, the L-type grid-connected single-phase bridge inverter is an inverter topology used to convert a DC power source (usually the output of a solar panel or a battery energy storage system) into an AC power that matches the grid. Through this type of inverter, DC power can be converted into AC power that meets the frequency and voltage requirements of the grid. In this process, an L-type filter is usually used to smooth the output AC current and reduce harmonics and current ripple.

[0067] like Figure 2-Figure 3 As shown in the figure, the L-type grid-connected single-phase bridge inverter first modulates the input DC voltage and generates an AC waveform using PWM (pulse width modulation) technology. In the specific example, this step is achieved by switching the switch tube ( Figure 2 This is achieved by setting a control strategy to modulate the on and off of these switch tubes (for example, insulated gate bipolar transistors or metal oxide semiconductor field effect transistors) so that the output voltage of the inverter is close to a sine waveform.

[0068] During the modulation process, the inverter generates an SPWM (sinusoidal pulse width modulation) signal by quickly switching the switch tube. The frequency of this signal is much higher than the grid frequency, usually between several kilohertz and tens of kilohertz, which ensures that the output of the inverter is a signal close to a sine wave. However, the output signal of the inverter often contains high-frequency harmonics, so the signal needs to be smoothed through an L-type filter (composed of an inductor and a capacitor). The function of the inductor L is to limit the rate of change of the current (that is, to reduce the ripple of the current), while the capacitor C is used to filter out the high-frequency components, thereby obtaining an AC output that is closer to an ideal sine wave.

[0069] Finally, after modulation and filtering, the pulse width modulated output voltage of the inverter (it needs to be ensured that the amplitude and phase of the inverter output voltage are synchronized with the grid) matches the grid voltage and frequency, completing the integration into the grid.

[0070] In the template configuration step S120, in the process of generating the pulse width modulation wave, the current slope change rule can be generated by performing a relationship analysis on the factors affecting the slope change of the output current.

[0071] During the PHC (positive half cycle) in this exemplary embodiment, the upper bridge arm is turned on ( Figure 2 S1 in the figure), the change of inductor current can be described by Kirchhoff's voltage law (KVL) into two states:

[0072] When switches S1 and S4 are turned on, the slope of the inductor current With the input DC voltage V dc , Grid voltage V during switching g And the inductance value L is related to:

[0073]

[0074] From equation (1), it can be seen that in the current linear increase law, the current slope is proportional to the difference between the input DC voltage and the grid voltage during the switching period, and inversely proportional to the inductance value. Among them, when the switching frequency is much greater than the grid frequency, the grid voltage is regarded as a constant.

[0075] When switches S2 and S3 are turned on, the slope of the inductor current Only with the grid voltage V during switching g , inductance value L is related to:

[0076]

[0077] From formula (2), we can see that the current decreases linearly, and the current slope is proportional to the negative value of the grid voltage and inversely proportional to the inductance value. Among them, when the switching frequency is much greater than the grid frequency, the grid voltage is regarded as a constant.

[0078] Similarly, during the NHC (negative half cycle) in the embodiment of this example, the lower bridge arm is turned on ( Figure 2 The change of inductor current can also be described by Kirchhoff's voltage law (KVL) into the above two states.

[0079] Therefore, the current slope variation law can be analyzed as follows Figure 4-Figure 6 As shown, the current slope of the inductor current is (i.e. current ripple) is determined by the input DC voltage V dc , Grid voltage V during switching g And the inductance value L. If the size of the inductor is reduced by n times (that is, the filter inductance value is reduced by n times), the current slope will also increase by n times accordingly, thereby introducing a large number of harmonics.

[0080] In the template configuration step S130, the current slope can be controlled during the direct current conversion process by using an active filtering single-phase inverter to compensate for the voltage change across the inductor according to the current slope change rule.

[0081] In the embodiment of this example, the problem of the current slope variation in S120 is to be solved, that is, to minimize the inductor current ripple while maintaining a small inductance value. Then a feasible method is to modify or compensate the voltage across the inductor. Figure 7-Figure 8 As shown in the figure, when the filter inductance L is reduced to the original value When the voltage at both ends of the inductor is reduced to and This ensures that the current slope after reducing the inductance value is consistent with the original current slope.

[0082] To achieve this goal, Fig. 9 As shown in Figure 1, a series active filter is introduced to compensate the voltage across the inductor, thereby replacing the original large L-type filter with a smaller active filter. Unlike traditional passive filters (such as filters composed of inductors, capacitors, and resistors), active filters can provide gain or compensation to actively adjust the frequency response of the signal. They are often used to suppress noise at specific frequencies, filter out unwanted signals, or improve signal quality.

[0083] However, its disadvantage is also obvious that it needs an external power supply to power it so that the active components can adjust the current and voltage. Therefore, in a specific example, in order to simplify the driving circuit, the power supply of the active filter is provided by a voltage divider circuit, and its trigger signal is shared with the trigger signal of the single-phase bridge inverter.

[0084] In the embodiment of this example, the working principle of the L-type single-phase bridge inverter with a series active filter can be described by the following two half cycles.

[0085] Positive half cycle (PHC), such as Figure 10-11 As shown, S1 and S5 remain turned on, and S4, S8 and S3, S7 are turned on and off in a complementary manner to generate a positive SPWM output voltage.

[0086] There are two operating modes:

[0087] Mode 1, S1, S5 are on, S4, S8 are on. Active inductor The inductor current is charged by the voltage source and the compensation voltage, and the current flows through switches S1 and S4 and diodes D5 and D8 (freewheeling diodes of switches S5 and S8, respectively). The inductor current increases linearly, and the compensation voltage provided by the active filter is The variation law of current slope can be described as

[0088] Mode 2, S1, S5 are on, S3, S7 are on. Active inductor The inductor current is discharged through the voltage source and the compensation voltage, and the current flows through switches S1 and S7 and diodes D3 and D5 (respectively the freewheeling diodes of switches S3 and S5). The inductor current decreases linearly, and the compensation voltage provided by the active filter is The variation law of current slope can be described as

[0089] Negative half cycle (NHC), such as Figure 12-13 As shown, S2 and S6 remain turned on, and S3, S7 and S4, S8 are turned on and off in a complementary manner to generate a negative SPWM output voltage. The two operating modes included are the same as the two operating modes of the positive half cycle.

[0090] During the whole process, the current direction of the active filter is opposite to that of the main circuit, and the current slope of the active inductor is consistent with that of the traditional passive inductor filter (L-type filter).

[0091] In a specific example, in order to verify the performance of the proposed topology, a single-phase bridge inverter system was simulated in MATLAB / SIMULINK simulation software. The simulation compared the performance of the L-type single-phase bridge inverter with a series active filter and the traditional L-type single-phase bridge inverter.

[0092] In the passive L-type filter topology, when the filter inductance is set to 1.2mH, the current waveform quality is high, the ripple is minimal, and the total harmonic distortion (THD) is 5.36%. However, under the same operating conditions, reducing the filter inductance value in the passive L-type filter topology to 0.2mH significantly increases the current ripple, causing the total harmonic distortion (THD) to rise sharply to 31.0%. In contrast, the proposed series active filter topology uses only 0.2mH of filter inductance, which is 1 / 6 of the inductance value in the passive L-type filter topology, to achieve comparable performance, with only a slight increase in total harmonic distortion (THD) to 5.45%. Fig.14 shown.

[0093] The simulation results show that the proposed series active filter topology can still effectively suppress harmonics despite the significant reduction in filter inductance, demonstrating excellent harmonic suppression capabilities, which verifies the effectiveness of the design. This feature not only significantly reduces the size and cost of the filter, but also achieves the best balance between performance and cost-effectiveness.

[0094] It should be noted that, although the steps of the method in the present disclosure are described in a specific order in the drawings, this does not require or imply that the steps must be performed in this specific order, or that all the steps shown must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps, etc.

[0095] In addition, in this exemplary embodiment, a single-phase inverter active filter device based on current slope control is also provided. Fig.15 As shown, the single-phase inverter active filter device 400 based on current slope control may include: a single-phase bridge inverter module 410, a current slope analysis module 420 and an active filter single-phase inverter module 430. Among them:

[0096] The single-phase bridge inverter module 410 is used to convert the voltage of the DC power supply through an L-type grid-connected single-phase bridge inverter using a unipolar pulse width modulation technology to generate a pulse width modulation wave output voltage;

[0097] The current slope analysis module 420 is used to generate a current slope change rule by analyzing the relationship between factors affecting the slope change of the output current during the process of generating the pulse width modulation wave;

[0098] The active filtering single-phase inverter module 430 is used to control the current slope during the direct current conversion process by compensating for the voltage change across the inductor using the active filtering single-phase inverter according to the current slope change rule.

[0099] The specific details of each of the above-mentioned single-phase inverter active filter device modules based on current slope control have been described in detail in the corresponding single-phase inverter active filter method based on current slope control, so they will not be repeated here.

[0100] It should be noted that, although several modules or units of a single-phase inverter active filter device 400 based on current slope control are mentioned in the above detailed description, this division is not mandatory. In fact, according to the embodiment of the present disclosure, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided into multiple modules or units for embodiment.

[0101] In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to an exemplary embodiment of the present invention, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0102] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary technical means in the art that are not disclosed in the present disclosure. The specification and examples are to be considered as exemplary only, and the true scope and spirit of the present disclosure are indicated by the claims.

[0103] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A single-phase inverter active filter control method based on current slope control, characterized in that: include: Using unipolar pulse width modulation technology, the voltage of the DC power supply is converted through an L-type grid-connected single-phase bridge inverter to generate a pulse width modulated wave output voltage; In the process of generating the pulse width modulation wave output voltage, the current slope change law is generated by analyzing the relationship between the factors affecting the slope change of the output current; According to the current slope variation law, an active filtering single-phase inverter is used to compensate for the voltage variation across the inductor, thereby ensuring the control of the current slope during the conversion process of the DC power supply.

2. The method according to claim 1, characterized in that: The voltage of the DC power supply is converted by an L-type grid-connected single-phase bridge inverter, including: Based on the standard of the power grid where the inverter is located, a control strategy is generated by setting the conduction state of the power switch in the L-type grid-connected single-phase bridge inverter; According to the set control strategy, the input direct current is converted into alternating current; By using the unipolar pulse width modulation technology, the high-frequency harmonics generated in the conversion process are suppressed by the filter in the L-type grid-connected single-phase bridge inverter to generate a pulse width modulation wave output voltage.

3. The method according to claim 2, characterized in that By analyzing the relationship between the factors that affect the slope change of the output current, including: Based on Kirchhoff's voltage law, when the upper bridge arm is turned on, the period of the pulse width modulation wave output voltage is the positive half cycle; Based on Kirchhoff's voltage law, when the lower bridge arm is turned on, the period of the pulse width modulation wave output voltage is the negative half cycle; During the positive half cycle and the negative half cycle, two states of the inductor current in the filter are analyzed respectively to generate a current slope variation rule.

4. The method according to claim 3, characterized in that The current slope variation law includes: The current increases linearly, and the current slope is proportional to the difference between the input DC voltage and the grid voltage, and inversely proportional to the inductance value; The current decreases linearly, and the current slope is proportional to the negative value of the grid voltage and inversely proportional to the inductance value.

5. The method according to claim 1, characterized in that Active filter single-phase inverter, including: The L-type filter in the L-type grid-connected single-phase bridge inverter is replaced with an active filter by connecting in series to generate an active filter single-phase inverter; The trigger signal of the active filter is shared with the trigger signal of the single-phase bridge inverter; The power supply of the active filter is provided by a voltage divider circuit.

6. The method according to claim 4, characterized in that By compensating for the voltage change across the inductor, including: During the positive half cycle of the pulse width modulation wave output voltage, the active inductor of the active filter is charged by a voltage source and a compensation voltage based on the current linear increase law; During the positive half cycle of the pulse width modulation wave output voltage, based on the current linear reduction law, the active inductor of the active filter is discharged through the voltage source and the compensation voltage; Based on the charging and discharging behavior of the active inductor during the positive half cycle, compensation is provided for the voltage across the inductor, thereby ensuring the control of the current slope during the generation of the sinusoidal pulse width modulation wave output voltage.

7. The method according to claim 4, characterized in that By compensating for the voltage change across the inductor, including: During the negative half cycle of the pulse width modulation wave output voltage, the active inductor of the active filter is charged by a voltage source and a compensation voltage based on the current linear increase law; During the negative half cycle of the pulse width modulation wave output voltage, based on the current linear reduction law, the active inductor of the active filter is discharged through the voltage source and the compensation voltage; Based on the charging and discharging behavior of the active inductor during the negative half cycle, compensation is provided for the voltage across the inductor to ensure control of the current slope during the generation of the negative sinusoidal pulse width modulation wave output voltage.

8. A single-phase inverter active filter control device based on current slope control, characterized in that: include: The single-phase bridge inverter module is used to convert the voltage of the DC power supply through an L-type grid-connected single-phase bridge inverter using unipolar pulse width modulation technology to generate a pulse width modulation wave output voltage; A current slope analysis module, used to generate a current slope change rule by analyzing the relationship between factors affecting the slope change of the output current during the process of generating the pulse width modulation wave output voltage; The active filtering single-phase inverter module is used to ensure the control of the current slope during the conversion process of the DC power supply by compensating the voltage change at both ends of the inductor according to the current slope change law using the active filtering single-phase inverter.

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