A dc power spring topology and control method based on cascaded half-bridge

Abstract

The application discloses a kind of based on cascaded half-bridge DC power spring topology and control method, belong to the technical field of power electronics application, this topology is based on three-port converter DC converter topology, port I accesses new energy power supply, port II is parallel with critical load, port III is parallel with cascaded half-bridge energy storage module, then through a Flyback circuit and non-critical load parallel connection.This topology guarantees the power stability of critical load at the same time, using the charge-discharge mode of cascaded half-bridge energy storage module, consumes the power fluctuation that non-critical load cannot bear, realizes the effect of reducing non-critical load power fluctuation, clamps the outlet voltage of port III.The DC power spring topology and control method containing cascaded half-bridge and flyback converter of the application can be applied to photovoltaic power generation and distributed power grid and other scenes, suppress the influence of input side fluctuation on critical load, while facilitating independent monitoring and management of battery, so that the overall system can be long-term stable operation.

Description

Technical Field

[0001] This invention relates to a DC power spring topology and control method based on a cascaded half-bridge, belonging to the field of power electronics application technology. Background Technology

[0002] Against the backdrop of finite and unsustainable global fossil energy resources, my country has put forward the requirements of "carbon peaking" and "carbon neutrality," and the demand for new energy power generation is becoming increasingly strong both domestically and internationally. Although new energy power generation, mainly composed of photovoltaic and wind power, has the advantages of being clean and sustainable, its inherent instability and intermittency lead to problems such as voltage fluctuations, frequency deviations, and harmonic injection caused by the unstable output of new energy power generation in time and space, which seriously threaten the stable and safe operation of the power grid. To solve the above problems caused by instantaneous power imbalance, the integration of new energy through DC microgrids has become a research hotspot, and the concept of electric springs has emerged accordingly.

[0003] The core concept of electric power springs is to transfer power fluctuations from new energy sources to non-critical loads by controlling the internal energy storage system and converter, thereby stabilizing the power of critical loads. DC current springs are particularly suitable for such DC microgrid systems. However, traditional DC power springs rely on energy storage batteries, which are difficult to manage and have complex internal monitoring systems, making it impossible to guarantee long-term stable operation. Therefore, the research prospects for DC power springs that can be effectively applied to DC microgrids are very broad. Summary of the Invention

[0004] Objective: Building upon existing DC power spring topologies and their control methods, this invention proposes a DC power spring topology and its control method based on a cascaded half-bridge. In DC microgrid applications (such as rooftop photovoltaic systems), this method allows fluctuations in the input source to be shared by non-critical loads and energy storage modules, maintaining the stability of the voltage and power of critical loads. Simultaneously, it replaces the original large-capacity energy storage batteries with a cascaded half-bridge-based battery structure, enabling real-time monitoring of the battery status of each module and utilizing battery energy management to achieve long-term stable operation of the overall system.

[0005] Based on the above-mentioned DC power spring topology, this invention discloses a control method for the topology. This control method can drive the three active bridge converter, cascaded half-bridge module and Flyback circuit to work normally, so that the critical load voltage remains stable, and realize the "fragmentation" of the energy storage battery, which is beneficial for subsequent monitoring and energy management and improves the robustness of system operation.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The proposed DC-DC Electric Springs (DCES) topology and control based on cascaded half-bridges is characterized by the functional superposition of a Triple Active Bridge (TAB) converter, a Flyback circuit, and cascaded half-bridge modules to form a new DC-DC electric spring topology, and the adoption of a joint control strategy for each part. The TAB converter consists of a three-terminal transformer, transformer leakage inductance, H-bridges at each port, and filter capacitors. Port I is the input port connected to the new energy input; Port II is the critical load (CL) port and is connected to the critical load; Port III is connected to the cascaded half-bridge energy storage module and, through the Flyback circuit, to the non-critical load (NCL). The cascaded half-bridge module is composed of multiple cascaded half-bridge sub-modules, with each sub-module connected in parallel to a small-capacity energy storage battery for external power absorption, thus forming the energy storage module.

[0008] In some publicly available descriptions, DCES has three operating modes: battery balancing mode, battery discharging mode, and battery charging mode. When the input power of the renewable energy source fluctuates, if the fluctuation range is small, the cascaded half-bridge module is in an isolated state. The TAB converter distributes the input power of the renewable energy source to maintain the stability of the CL voltage at port II. The energy distributed to port III flows through the Flyback circuit and is consumed by the NCL, which is used to handle the power fluctuations of the renewable energy source. When the input power of the renewable energy source is significantly insufficient, DCES is in battery discharging mode. In this case, the power distribution by the TAB converter alone is insufficient to maintain the stability of the CL voltage. The cascaded half-bridge energy storage module at port III needs to discharge its output power and adjust the power consumed by the NCL to make up for the power difference. When the input power of the renewable energy source is severely excessive, DCES is in battery charging mode. The cascaded half-bridge energy storage module at port III needs to charge and absorb power and adjust the power consumed by the NCL to make up for the excessive power.

[0009] In some disclosures, the three active bridge converter module includes three single-phase full-bridge circuits: full-bridge circuit I, full-bridge circuit II, and full-bridge circuit III, with their DC-side ports being port I, port II, and port III, respectively.

[0010] In some disclosures, a cascaded half-bridge energy storage module is connected in parallel at port III of the three active bridge converter.

[0011] In some disclosures, a filter inductor is connected in series at port I of the three active bridge converter.

[0012] In some disclosures, the cascaded half-bridge energy storage module is composed of multiple cascaded sub-modules, with each sub-module using a half-bridge connection and containing a small-capacity battery connected in parallel with a filter capacitor.

[0013] In some disclosures, a filter capacitor is connected in parallel at port II of the three active bridge converter.

[0014] In some disclosures, a filter capacitor is connected in parallel at port III of the three active bridge converter.

[0015] In some disclosures, the topology of the three ports of the three active bridge converter module is a single-phase full-bridge circuit composed of four switching transistors connected in anti-parallel with diodes.

[0016] The control method for the aforementioned DC power spring topology based on a cascaded half-bridge refers to a three-dimensional decoupled overall control method for the DCES based on single-phase-shift control. The input current of port I, the output voltage of port II, and the branch current of the cascaded half-bridge module connected to port III are used as input variables. Through their respective PI regulators and decoupling networks, the phase shift angles of ports II and III relative to port I are obtained, thus yielding the trigger signals for the three ports and the duty cycle of the Flyback converter. In the cascaded half-bridge energy storage module section, carrier phase-shift control is selected to maintain the overall stability of the output DC voltage. Simultaneously, its operating state is determined based on the difference between the output voltage and the rated value: isolation is performed within a certain threshold, and battery charging and discharging are performed above a certain threshold, thereby achieving long-term stable operation of the overall system. One control cycle includes the following control steps:

[0017] (1) A three-dimensional decoupled overall control scheme based on SPS is adopted to obtain the control method of DC power spring, which realizes the decoupling between input quantities such as CL voltage, input power, and battery current and control quantities such as phase shift angle and Flyback circuit duty cycle.

[0018] (2) The trigger signals for each port are obtained through SPS. Port I is driven by a square wave with a duty cycle of 50%; the square wave driving port II is obtained by phase shifting the square wave driving port I, with the phase shift angle being... The square wave driving port III is obtained through the CL voltage control loop; the square wave driving port I is obtained by phase shifting the square wave driven by port I, and the phase shift angle is... It is obtained through the input power control loop.

[0019] (3) The current of the cascaded half-bridge module branch at port III is detected. The difference between the current and the given value is obtained by the PI controller to obtain the duty cycle of the Flyback converter. The Flyback converter trigger signal is obtained by the duty cycle modulation. The necessary voltage range and power quality of NCL are maintained by setting the upper and lower limits.

[0020] (4) Determine whether the voltage of the cascaded half-bridge energy storage module exceeds the predetermined fluctuation range. When the voltage fluctuation of the cascaded half-bridge energy storage module exceeds the upper limit of the threshold, each sub-module is in working state. At the same time, the difference between the module voltage and the rated value is obtained through the PI controller to obtain the modulation wave signal, and the carrier phase shift control is used to obtain the trigger signal of each sub-module. When the voltage fluctuation of the cascaded half-bridge energy storage module is lower than the upper limit of the threshold, each sub-module is in bypass state, and the cascaded half-bridge energy storage module is in isolation mode, with the non-critical load independently bearing the fluctuation of the input power.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention transfers input power fluctuations to non-critical loads and energy storage modules, thereby ensuring the stability of voltage and power at critical loads. In terms of device selection, compared to traditional microgrids that utilize large energy storage devices to absorb input power fluctuations, this invention significantly reduces the capacity requirements of the energy storage device because most of the fluctuations are transferred within the power springs, saving on initial procurement and subsequent maintenance costs.

[0023] 2. This invention combines a Flyback circuit with a three-phase active bridge converter, while avoiding direct connection between non-critical loads and the three-port transformer. By changing the duty cycle of the Flyback circuit, the voltage of the non-critical load is made to bear the fluctuation of the input power, thereby reducing the output voltage fluctuation of the three-port transformer and solving the problem that it is not easy to analyze the transmission power and zero-voltage switching conditions.

[0024] 3. This invention replaces the traditional large-capacity battery with a cascaded half-bridge energy storage module, breaking down the whole into smaller parts and independently controlling the smaller capacity batteries. This facilitates energy management and real-time monitoring of the system, improves the overall system's operational stability, and enables the DC power spring to operate safely for a long time.

[0025] 4. Compared with existing DC power spring topologies, this invention broadens the application range of DC power springs, improves the overall power level of the device, and has good practicality in engineering applications.

[0026] 5. The device of this invention adopts a modular design, which is convenient to assemble and move, and can independently monitor and maintain each module, making it suitable for home energy storage application scenarios. Attached Figure Description

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] Figure 1 This is a topology diagram of the DC power spring based on a cascaded half-bridge according to the present invention;

[0029] Figure 2 This is a topology diagram of the cascaded half-bridge energy storage module and its sub-modules of the present invention;

[0030] Figure 3 This is a block diagram of the three-dimensional decoupling phase-shifting control of the present invention;

[0031] Figure 4 This is a block diagram of the charging and discharging control of the cascaded half-bridge energy storage module of the present invention;

[0032] Figure 5 , Figure 6 This describes the operational effect of the topology of this invention under certain working conditions. Detailed Implementation

[0033] 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.

[0034] exist Figure 1 In the DC power spring topology diagram of this invention, 1.1 is the input-side photovoltaic array; 1.2, 1.5, and 1.6 are the full-bridge circuits I, II, and III inside the three active bridge DC converter; 1.3 is the filter inductor; 1.4 is the three-terminal transformer inside the three active bridge converter; 1.7, 1.8, and 1.11 are the filter capacitors for port II, port III, and the Flyback circuit; 1.9 and 1.10 are the non-critical load and critical load, respectively; and 1.12 is the cascaded half-bridge energy storage module. Figure 2 In the topology diagram of the cascaded half-bridge energy storage module of the present invention, 2.1 is a small-capacity energy storage battery; 2.2 is a filter capacitor; 2.3 is a half-bridge circuit; and 2.4 is a filter inductor.

[0035] like Figure 1 As shown, the DC current spring topology based on a cascaded half-bridge includes a three-active bridge converter, a flyback circuit, and a cascaded half-bridge energy storage module. The TAB converter consists of a three-terminal transformer, transformer leakage inductance, H-bridges at each port, and filter capacitors C2 and C3. All four switching transistors are anti-parallel diodes. Port I is the input port connected to the new energy input, passing through a filter inductor L1. Port II is the critical load port and is connected to the critical load R. CL Connected, port III is connected to the cascaded half-bridge energy storage module and connected to the non-critical load R via a Flyback circuit. NCL Connected, the Flyback circuit is connected to R NCLA filter capacitor C4 is connected in parallel. The cascaded half-bridge module is composed of multiple cascaded half-bridge sub-modules. Each sub-module consists of a half-bridge circuit with two switching transistors connected in anti-parallel to diodes and a filter capacitor. The capacitor is connected in parallel to a small-capacity battery to absorb external power, thus forming an energy storage module.

[0036] Depending on the fluctuations in the input power of the renewable energy source, the DCES operates in different modes. When the fluctuation range of the renewable energy input power is small, the cascaded half-bridge energy storage module does not operate. The fluctuating energy flows through the TAB converter and is consumed by the NCL in the Flyback circuit. The NCL is used to handle the power fluctuations of the renewable energy source, thereby maintaining the stability of the CL voltage at port II. When the fluctuation of the renewable energy input power is large, the power consumption by non-critical loads alone is insufficient to maintain the stability of the CL voltage. The cascaded half-bridge energy storage module at port III needs to charge and discharge to absorb power and adjust the power consumption of the NCL to compensate for or offset this power fluctuation, thereby maintaining the stability of the CL power and voltage. This allows the Flyback circuit and non-critical loads to form an equivalent variable load, making the "spring" concept of this topology clearer in the system. At the same time, it also effectively reduces the frequency of battery charging and discharging, extending battery life.

[0037] It should be noted that the three active bridge converter module includes three single-phase full-bridge circuits: full-bridge circuit I, full-bridge circuit II, and full-bridge circuit III, with their DC-side ports being port I, port II, and port III, respectively.

[0038] It should be noted that a cascaded half-bridge energy storage module is connected in parallel at port III of the three active bridge converter.

[0039] It should be noted that a filter inductor is connected in series at port I of the three active bridge converter.

[0040] It should be noted that the cascaded half-bridge energy storage module is composed of multiple cascaded sub-modules. The sub-modules adopt a half-bridge connection method, and a small-capacity battery is connected in parallel with a filter capacitor.

[0041] It should be noted that a filter capacitor is connected in parallel at port II of the three active bridge converter.

[0042] It should be noted that a filter capacitor is connected in parallel at port III of the three active bridge converter.

[0043] It should be noted that the topology of the three ports of the three active bridge converter module is a single-phase full-bridge circuit composed of four switching transistors connected in anti-parallel with diodes.

[0044] The control method for the aforementioned DC power spring topology based on a cascaded half-bridge refers to a three-dimensional decoupled overall control method for the DCES based on single-phase-shift control. The input current of port I, the output voltage of port II, and the branch current of the cascaded half-bridge module connected to port III are used as input variables. Through their respective PI regulators and decoupling networks, the phase shift angles of ports II and III relative to port I are obtained, thus yielding the trigger signals for the three ports and the duty cycle of the Flyback converter. In the cascaded half-bridge energy storage module section, carrier phase-shift control is selected to maintain the overall stability of the output DC voltage. Simultaneously, its operating state is determined based on the difference between the output voltage and the rated value: isolation is performed within a certain threshold, and battery charging and discharging are performed above a certain threshold, thereby achieving long-term stable operation of the overall system. One control cycle includes the following control steps:

[0045] (1) A three-dimensional decoupling overall control scheme based on SPS is adopted to obtain a control method for a DC power spring topology containing a cascaded half-bridge and a flyback converter, thereby realizing the decoupling between input quantities such as CL voltage, input power, and battery current and control quantities such as phase shift angle and Flyback circuit duty cycle.

[0046] (2) The trigger signals for each port are obtained through SPS. Port I is driven by a square wave with a duty cycle of 50%; the square wave driving port II is obtained by phase shifting the square wave driving port I, with the phase shift angle being... The square wave driving port III is obtained through the CL voltage control loop; the square wave driving port I is obtained by phase shifting the square wave driven by port I, and the phase shift angle is... It is obtained through the input power control loop.

[0047] (3) The current of the cascaded half-bridge module branch at port III is detected. The difference between the current and the given value is obtained by the PI controller to obtain the duty cycle of the Flyback converter. The Flyback converter trigger signal is obtained by the duty cycle modulation. The necessary voltage range and power quality of NCL are maintained by setting the upper and lower limits.

[0048] (4) Determine whether the voltage of the cascaded half-bridge energy storage module exceeds the predetermined fluctuation range. When the voltage fluctuation of the cascaded half-bridge energy storage module exceeds the upper limit of the threshold, each sub-module is in working state. At the same time, the difference between the module voltage and the rated value is obtained through the PI controller to obtain the modulation wave signal, and the carrier phase shift control is used to obtain the trigger signal of each sub-module. When the voltage fluctuation of the cascaded half-bridge energy storage module is lower than the upper limit of the threshold, each sub-module is in bypass state, and the cascaded half-bridge energy storage module is in isolation mode, with the non-critical load independently bearing the fluctuation of the input power.

[0049] Simulation results are shown below:

[0050] The following operating conditions are set: input disturbances cause the cascaded half-bridge module to start working and enter the charging and discharging state. The power and voltage fluctuations of the critical load are shared by the non-critical load and the energy storage module.

[0051] Under this operating condition, the DCES cannot guarantee the power stability of the CL simply by transferring the large fluctuations in the primary-side photovoltaic cell input power to the NCL; the battery also needs to charge or discharge to cope with the primary-side input power fluctuations. In this simulation, the input light intensity of the primary-side photovoltaic cell is set to change from 1000 W / m² at 1s and 2s. 2 Change to 800W / m 2 Reduce it to 600W / m 2 The simulated waveform is as follows Figure 5 , 6 As shown in the figure, under battery charging or discharging conditions, the control method proposed in this paper can realize the basic functions of DCES and ensure the stability of CL power.

[0052] When the input light intensity of the photovoltaic cell is 800W / m 2 At that time, the NCL voltage V2 was 44V and the CL voltage V3 was 120V; when the light intensity increased to 1000W / m 2 At that time, the NCL voltage V2 rises to 57V, while the CL voltage V3 remains unchanged at 120V; when the light intensity drops to 600W / m 2 At this time, the NCL voltage V2 drops to 21V, while the CL voltage V3 remains unchanged at 120V. Therefore, under the condition of large fluctuations in the input power of the primary photovoltaic cells, the battery needs to perform charging and discharging operations. The control method proposed in this paper can realize the basic functions of the parallel DCES, as well as the charging and discharging control of the cascaded half-bridge module, to ensure the stability of the CL voltage.

[0053] The simulation waveforms show that the voltage of the critical load remained stable at 120V, unaffected by changes in the photovoltaic input. Simultaneously, the input current of the photovoltaic module also remained at 3A, demonstrating that the topology's functionality has been fully validated.

[0054] The above method is only a relatively reasonable implementation of the invention. The scope of protection of the present invention is not limited to the above implementation method. Any equivalent modifications or changes made by those skilled in the art based on the content disclosed in the present invention should be included in the scope of protection of the claims.

[0055] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A DC power spring topology based on a cascaded half-bridge, characterized in that: The system includes a three-phase active bridge converter, a flyback circuit, and a cascaded half-bridge energy storage module. The three-phase active bridge converter consists of a three-terminal transformer, full-bridge circuit I, full-bridge circuit II, full-bridge circuit III, and a filter capacitor. The DC-side ports of full-bridge circuit I, full-bridge circuit II, and full-bridge circuit III are port I, port II, and port III, respectively. Port I is the input port connected to the new energy input, port II is the critical load port connected to the critical load, and port III is connected to the cascaded half-bridge energy storage module and connected to non-critical loads through the flyback circuit. The flyback circuit includes a switch, a transformer, and a diode, providing insulation between the input and output stages. The cascaded half-bridge energy storage module is composed of multiple cascaded half-bridge sub-modules. Each half-bridge sub-module is connected in parallel to a small-capacity energy storage battery to absorb external power, thus forming the energy storage module.

2. The DC power spring topology based on cascaded half-bridge as described in claim 1 has three operating modes: battery balancing mode, battery discharging mode, and battery charging mode. When the input power of the new energy source fluctuates, if the fluctuation range is small, the cascaded half-bridge energy storage module is in an isolated state, and the three active bridge converters distribute the input power of the new energy source to maintain the stability of the critical load voltage at port II. The energy distributed to port III flows through the Flyback circuit and is consumed by non-critical loads, using non-critical loads to bear the power fluctuations of the new energy source. When the input power of the new energy source is significantly insufficient, the DC power spring topology is in battery discharging mode. At this time, the power distribution by the three active bridge converters alone is insufficient to maintain the stability of the critical load voltage. The cascaded half-bridge energy storage module at port III needs to discharge its output power and adjust the power consumed by non-critical loads to make up for the power difference. When the input power of the new energy source is severely overflowing, the DC power spring topology is in battery charging mode. The cascaded half-bridge energy storage module at port III needs to charge and absorb power and adjust the power consumed by non-critical loads to make up for the overflow power.

3. The DC power spring topology based on cascaded half-bridge according to claim 1, characterized in that: The full-bridge circuit I, full-bridge circuit II, and full-bridge circuit III are all single-phase full-bridge circuits.

4. The DC power spring topology based on cascaded half-bridge according to claim 1, characterized in that: A cascaded half-bridge energy storage module is connected in parallel at port III of the three active bridge converter.

5. The DC power spring topology based on cascaded half-bridge according to claim 1, characterized in that: A filter inductor is connected in series at port I of the three active bridge converter.

6. The DC power spring topology based on cascaded half-bridge according to claim 1, characterized in that: The cascaded half-bridge energy storage module is composed of multiple cascaded sub-modules. The sub-modules adopt a half-bridge connection method, and a small-capacity battery is connected in parallel with a filter capacitor.

7. The DC power spring topology based on cascaded half-bridge according to claim 1, characterized in that: A filter capacitor is connected in parallel at port II of the three active bridge converter.

8. The DC power spring topology based on cascaded half-bridge according to claim 1, characterized in that: A filter capacitor is connected in parallel at port III of the three active bridge converter.

9. The DC power spring topology based on cascaded half-bridge according to claim 1, characterized in that: The topology of each of the three ports of the three active bridge converter module is a single-phase full-bridge circuit consisting of four switching transistors connected in anti-parallel with diodes.

10. A control method based on a cascaded half-bridge DC power spring topology as described in claim 1, characterized in that, The method includes a three-dimensional decoupling overall control method for DC power spring topology selection based on single phase shift control. The input current of port I, the output voltage of port II, and the branch current of the cascaded half-bridge energy storage module connected to port III are used as input variables. The input variables are PI-regulated and decoupled to obtain the phase shift angle of port II and port III relative to port I, thereby obtaining the trigger signals of port I, port II and port III and the duty cycle of the Flyback circuit. In the cascaded half-bridge energy storage module section, carrier phase-shift control is used to maintain the stability of the output DC voltage of port III, and the operating state of the cascaded half-bridge energy storage module is determined based on the difference between the output DC voltage of port III and its rated value. When the difference is within a predetermined fluctuation range, the cascaded half-bridge energy storage module is in an isolated state; when the difference exceeds the predetermined fluctuation range, the cascaded half-bridge energy storage module is in a charging or discharging state, thereby achieving long-term stable operation of the overall system. Specifically, the steps include the following: (1) A three-dimensional decoupled overall control scheme based on SPS control is adopted to obtain a control method for DC power spring topology containing cascaded half-bridge and flyback converter, which realizes the decoupling between key load voltage, input power, battery current, phase shift angle and Flyback circuit duty cycle; the SPS control is a single phase shift control, which realizes power transmission by controlling the external phase shift angle of port II relative to port I and the external phase shift angle of port III relative to port I; (2) The trigger signals for ports I, II, and III are obtained through SPS; port I is driven by a square wave with a duty cycle of 50%; the square wave driving port II is obtained by phase shifting the square wave driving port I, with the phase shift angle being... Obtained through the critical load voltage control loop; The square wave driving port III is obtained by phase shifting the square wave driving port I, with the phase shift angle being... Obtained through the input power control loop; (3) The branch current of the cascaded half-bridge energy storage module at port III is detected. The difference between the current setpoint and the current is obtained by the PI controller to obtain the duty cycle of the Flyback circuit. The Flyback circuit trigger signal is obtained by the duty cycle modulation. The voltage range and power quality of non-critical loads are maintained by setting the upper and lower limits. (4) Determine whether the voltage of the cascaded half-bridge energy storage module exceeds the predetermined fluctuation range. When the voltage fluctuation of the cascaded half-bridge energy storage module exceeds the upper limit of the threshold, each half-bridge sub-module of the cascaded half-bridge energy storage module is in working state. At the same time, the difference between the module voltage and the rated value is obtained through the PI controller to obtain the modulation wave signal, and the carrier phase shift control is used to obtain the trigger signal of each half-bridge sub-module. When the voltage fluctuation of the cascaded half-bridge energy storage module is lower than the upper limit of the threshold, each half-bridge sub-module is in bypass state, and the cascaded half-bridge energy storage module is in isolation mode, with non-critical loads independently bearing the fluctuation of input power.

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