Perovskite photovoltaic module inversion system based on multi-level low electric leakage
By optimizing the voltage waveform through a nine-level multi-level inverter structure and a modulation controller, the leakage current and power quality issues of perovskite photovoltaic modules in power plant applications have been resolved, extending system life and improving power generation efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-14
AI Technical Summary
Existing perovskite photovoltaic modules suffer from problems such as excessive leakage current, insufficient power quality, short lifespan, and low power utilization in power plant applications, making it difficult to meet grid connection requirements, especially in high-power power plants.
The system employs a nine-stage multilevel inverter structure, which combines a multilevel inverter composed of switched capacitor units and flying capacitor units with a blocking switch module and a common ground module to achieve stable voltage output and leakage current suppression. The voltage waveform is optimized through a modulation controller module and a filtering module.
It significantly reduces system leakage current, extends system lifespan, improves power quality, increases power generation efficiency, reduces filter size, and reduces voltage stress on power devices.
Smart Images
Figure CN121863889A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of perovskite photovoltaic module grid connection technology, and specifically relates to a perovskite photovoltaic module inverter system based on multi-level low leakage current. Background Technology
[0002] While the application of perovskite photovoltaic (PV) modules in power plants is gradually expanding, the following problems arise in grid connection due to differences in their characteristics compared to traditional crystalline silicon modules: Severe leakage current issues: Transformerless topologies in large-area perovskite power plants are prone to parasitic capacitive coupling, leading to excessive leakage current and affecting safety and grid friendliness. Insufficient power quality: Traditional two-level inverters suffer from high output harmonics and strong electromagnetic interference, making it difficult to meet the power quality requirements of high-power power plants. Insufficient lifespan and system reliability of perovskite PV modules: High switching stress and voltage fluctuations accelerate the failure of perovskite PV modules and their encapsulation. Low power utilization: Centralized inverters struggle to achieve differentiated maximum power point tracking (MPPT) and health management for perovskite PV strings. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a perovskite photovoltaic module inverter system based on multi-level low leakage current. Through a nine-level multi-level inverter structure composed of switched capacitor (SC) units and flying capacitor (FC) units, the system leakage current is reduced, the system life is extended, and the system power generation is increased.
[0004] This invention is implemented as follows: It provides a perovskite photovoltaic module inverter system based on multi-level low-leakage current, comprising a perovskite photovoltaic string, a blocking switch module, a common ground module, a multi-level inverter module, a modulation controller module, a filter module, and a grid connection interface, connected sequentially by wires. Multiple perovskite photovoltaic strings are connected in parallel to the input of the blocking switch module. The blocking switch module is used to quickly disconnect the DC circuit when leakage current or abnormal operating conditions are detected. The common ground module provides a stable reference potential to the inverter system. Nine multi-level output components are sequentially connected in series within the multi-level inverter module. Each multi-level output component... The device consists of switched capacitor units and flying capacitor units connected in series. Each switched capacitor unit consists of two power divider switches and one voltage divider capacitor connected in series between the two power divider switches. Each flying capacitor unit consists of two power equalization switches and one flying capacitor connected in series between the two power divider switches. The modulation controller module includes a DSP controller, an FPGA controller, or an MCU controller. The modulation controller module communicates with the power divider switches and the power equalization switches to control their on / off states so that the output voltage is a sinusoidal waveform. The filtering module is used to suppress harmonics in the output voltage.
[0005] Furthermore, the blocking switch module includes a MOSFET switch or an IGBT switch.
[0006] Furthermore, the filtering module includes two inductor elements and one capacitor element.
[0007] Compared with existing technologies, the multi-level low-leakage perovskite photovoltaic module inverter system of the present invention includes a perovskite photovoltaic string, a blocking switch module, a common ground module, a multi-level inverter module, a modulation controller module, a filter module, and a grid connection interface, which are connected in sequence by wires. Within the multi-level inverter module, nine multi-level output components are arranged in series. Each multi-level output component consists of a series-connected switched capacitor unit and a flying capacitor unit. Each switched capacitor unit consists of two power divider switches and one voltage divider capacitor, and each flying capacitor unit consists of two power equalization switches and one flying capacitor. The modulation controller module communicates with the power divider switches and the power equalization switches to control their on / off states, ensuring a sinusoidal output voltage waveform. The filter module suppresses harmonics in the output voltage. This invention, through the nine-level multi-level inverter structure composed of switched capacitor units and flying capacitor units, reduces system leakage current, extends system lifespan, and increases system power generation. Attached Figure Description
[0008] Figure 1 This is a schematic diagram illustrating the structural principle of the present invention; Figure 2 for Figure 1 A schematic diagram of the principle of a multi-level inverter module; Figure 3 The waveform diagrams are shown for the output voltage of the perovskite photovoltaic module inverter system in Example 1 and Comparative Example 1. Figure 4 This is a schematic diagram of the system efficiency of the perovskite photovoltaic module inverter system in Example 1 after one year of operation; Figure 5 This is a schematic diagram illustrating the system efficiency of the perovskite photovoltaic module inverter system in Comparative Example 1 after one year of operation. Figure 6 This is a schematic diagram of the two-level inverter in Comparative Example 1.
[0009] The labels in each diagram are as follows: 1. Perovskite photovoltaic string; 2. Blocking switch module; 3. Common ground module; 4. Multilevel inverter module; 5. Modulation controller module; 6. Filter module; 7. AC grid; 8. Switched capacitor unit; 9. Flying capacitor unit; 10. Power divider switch; 11. Voltage divider capacitor; 12. Power balancing switch; 13. Flying capacitor. Detailed Implementation
[0010] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
[0011] Please refer to the following at the same time Figure 1 as well as Figure 2 As shown, a preferred embodiment of the perovskite photovoltaic module inverter system based on the present invention includes a perovskite photovoltaic string 1, a blocking switch module 2, a common ground module 3, a multilevel inverter module 4, a modulation controller module 5, a filter module 6, and a grid connection interface (not shown in the figure) connected in sequence by wires. The perovskite photovoltaic module inverter system is connected to the external AC power grid 7 through the grid connection interface to realize AC output.
[0012] Multiple perovskite photovoltaic strings 1 are connected in parallel to the output of the blocking switch module 2. The blocking switch module 2 is used to quickly disconnect the DC circuit when leakage current or abnormal operating conditions are detected, thereby preventing damage to the perovskite photovoltaic strings 1 and improving the safety of the inverter system operation. The common ground module 3 serves as the common ground terminal of the perovskite photovoltaic module inverter system, providing a stable reference potential for the inverter system and reducing leakage current caused by parasitic capacitive coupling.
[0013] Please refer to this again. Figure 2 As shown, a nine-stage multilevel output assembly is installed in series within the multilevel inverter module 4. Each stage of the multilevel output assembly consists of a switched capacitor unit 8 and a flying capacitor unit 9 connected in series. Each switched capacitor unit 8 consists of two power divider switches 10 and one voltage divider capacitor 11, with the voltage divider capacitor 11 connected in series between the two power divider switches 10. Each flying capacitor unit 9 consists of two power equalization switches 12 and one flying capacitor 13, with the flying capacitor 13 connected in series between the two power equalization switches 12.
[0014] The two power divider switches 10 of the switched capacitor unit 8 are connected in series with the two power equalizing switches 12 of the adjacent flying capacitor unit 9. The output of each switched capacitor unit 8 is connected to the input of the next flying capacitor unit 9. First, the first-stage switched capacitor unit 8 and the flying capacitor unit 9 form the first-stage level. Then, the second-stage switched capacitor unit 8 and the flying capacitor unit 9 are cascaded in sequence to form the second-stage level, until the second-stage switched capacitor unit 8 and the flying capacitor unit 9 form the eighth-stage level. As the input voltage is decomposed and superimposed stage by stage, nine levels of output are achieved.
[0015] The multilevel inverter module 4 includes eight switched capacitor units 8 and eight flying capacitor units 9, with each switched capacitor unit 8 and flying capacitor unit 9 connected in series alternately. The eight switched capacitor units 8 each include sixteen power divider switches 10, namely S1 and S2, S5 and S6, S9 and S10, S13 and S14, S17 and S18, S21 and S22, S25 and S26, S29 and S30, and eight voltage divider capacitors 11, namely Csc1 to Csc8. The eight flying capacitor units 9 each include sixteen power balancing switches 12, namely S3 and S4, S7 and S8, S11 and S12, S15 and S16, S19 and S20, S23 and S24, S27 and S28, S31 and S32, and eight flying capacitors 13, namely Cfc1 to Cfc8.
[0016] The modulation controller module 5 includes a DSP controller, an FPGA controller, or an MCU controller; in this embodiment, the modulation controller module 5 includes an MCU controller. The modulation controller module 5 communicates with the power divider switch 10 and the power equalization switch 12 to control their on / off states, outputting a sinusoidal voltage waveform. The filter module 6 is used to suppress harmonics in the output voltage.
[0017] Under the control of phase-shift sinusoidal pulse width modulation (SPWM) or space vector pulse width modulation (SVPWM) issued by the MCU controller of modulation controller module 5, each power voltage divider switch 10 and power equalization switch 12 are turned on and off according to a predetermined timing sequence, and the DC voltage is switched step by step and synthesized into a stepped waveform at the output terminal. Since the voltage of the voltage divider capacitor 11 and the flying capacitor 13 can achieve self-balancing during the modulation process, the entire inverter system can ensure stable output level without the need for additional equalization circuit.
[0018] The blocking switch module 2 includes a MOSFET switch or an IGBT switch; in this embodiment, the blocking switch module 2 includes a MOSFET switch. The blocking switch module 2 is connected in series on the DC main link to quickly cut off abnormal current and suppress leakage. The perovskite photovoltaic module inverter system monitors the leakage current in real time. When the leakage current exceeds a set threshold, it triggers the blocking switch module 2 to isolate the system and protect its safety.
[0019] The filter module 6 includes two inductors and one capacitor. The inductors on the multi-level inverter module 4 side have a capacitance of 0.7~1.5mH, while the inductors on the external AC power grid 7 side have a capacitance of 0.3~0.8mH. The capacitor has a capacitance of 10~30µF. The filter module 6 is suitable for 50 / 60Hz power grids, with a switching frequency of 8~16kHz, and a harmonic control target of THD ≤ 3%.
[0020] The working principle of the multi-level, low-leakage perovskite photovoltaic module inverter system of this invention is as follows: DC power from multiple perovskite photovoltaic strings 1 is collected and input to the DC bus (600~1500V). A blocking switch module 2 is connected in series at the positive terminal of the DC bus, and the negative terminal is connected to the system's common ground module 3 to provide a stable reference potential and suppress parasitic coupling leakage current from the perovskite photovoltaic modules to ground. The multi-level inverter module 4 is composed of cascaded switching capacitor units 8 and flying capacitor units 9 connected in alternating series. Each switching capacitor unit 8 consists of two power divider switches 10 and one voltage divider capacitor 11 for voltage grading; each flying capacitor unit 9 consists of two power balancing switches 12 and one flying capacitor 13 for cross-level voltage balancing. A nine-level stepped voltage output is achieved through eight cascaded stages, and capacitor voltage self-balancing is achieved during modulation. The modulation controller module 5 samples and estimates signals such as bus voltage, phase current, capacitor voltage, temperature, and leakage current. Based on phase-shift SPWM or SVPWM combined with MPC and self-balancing algorithms, it calculates the switching commands for each power divider switch 10 and power equalization switch 12. These commands are then sent to the gate drive boards of each power divider switch 10 and power equalization switch 12 via fiber optic or isolated communication, enabling them to turn on or off according to a predetermined timing sequence, thus achieving multi-level synthesis of DC voltage. The modulation controller module 5 also sends action or interlocking commands to the blocking switch module 2 and the common ground module 3 to achieve leakage current over-limit, rapid fault isolation, and safety interlocking control. The multi-level stepped wave output by the modulation controller module 5 is filtered by the filtering module 6 (including the multi-level inverter module-side inductor L1, filter capacitor Cf, and grid-side inductor L2), effectively suppressing harmonics and resulting in an output voltage close to a sine wave. This voltage is then fed into the external AC grid 7 via the grid interface.
[0021] The multi-level low-leakage perovskite photovoltaic module inverter system of the present invention realizes efficient and smooth conversion of DC to AC. While significantly reducing leakage current, it improves power quality, reduces filter size, and reduces voltage stress on power devices, thereby extending the life of the inverter system and the perovskite photovoltaic string 1.
[0022] The present invention, based on a multi-level, low-leakage perovskite photovoltaic module inverter system, is further illustrated below through specific embodiments.
[0023] Example 1
[0024] This invention relates to a first embodiment of a multi-level, low-leakage perovskite photovoltaic module inverter system, comprising four perovskite photovoltaic strings 1, a blocking switch module 2, a common ground module 3, a multi-level inverter module 4, a modulation controller module 5, a filter module 6, and a grid connection interface. The perovskite photovoltaic module inverter system is connected to an external AC power grid 7 via the grid connection interface. The output AC power is connected to a 0.4kV external AC power grid 7. The four perovskite photovoltaic strings 1 are connected in parallel with their respective blocking switch modules 2. DC fuses and surge protectors (SPDs) are installed on the DC bus after the four perovskite photovoltaic strings 1 converge to provide protection. A nine-level multi-level output component is installed in series within the multi-level inverter module 4. The switched capacitor unit 8 and the flying capacitor unit 9 of the nine-level multi-level output component are alternately connected in series to achieve nine output levels.
[0025] The multilevel inverter module 4 includes eight switched capacitor units 8 and eight flying capacitor units 9, with each switched capacitor unit 8 and flying capacitor unit 9 alternately connected in series. The modulation controller module 5 sends a phase-shift SPWM signal, triggering the switching devices of each SC unit and FC unit step by step. The eight groups of SC units and FC units work together to achieve voltage self-balancing, ultimately forming a nine-step voltage waveform. The output voltage ranges from -300V to +300V, divided into nine steps: -300, -225, -150, -75, 0, +75, +150, +225, +300V, gradually approaching a sine wave. A near-sinusoidal AC voltage is synthesized at the three-phase output terminals. (See also...) Figure 3 The nine-level output voltage waveform shown is close to an ideal sine wave. During grid-connected operation, the MPC control algorithm adjusts the switching duty cycle in real time to ensure that THD ≤ 3% and leakage current is less than 300mA.
[0026] After the perovskite photovoltaic module inverter system has been running for one year, the detected system efficiency will be summarized as follows: Figure 4 The diagram shows the system efficiency. Figure 4 It can be observed that the system efficiency ranged from 95.7% to 98.4% over a year of operation, with relatively small fluctuations.
[0027] Comparative Example 1 This comparative perovskite photovoltaic module inverter system uses an existing centralized two-level inverter, and its schematic diagram is shown below. Figure 6As shown. The main circuit of the inverter uses a full-bridge two-level inverter composed of four power switches S1 and S3, S2 and S4. The switching devices directly "switch" the DC power to an AC square wave, which is then smoothed by a filter. The modulation method is mostly sinusoidal pulse width modulation. Due to the small number of levels, the output waveform is close to a square wave, with high harmonic content, requiring a large LCL filter. The two-level inverter outputs only two levels, +300V and -300V, which are rectangular waves. See also... Figure 3 The two-level output waveform is shown.
[0028] After the perovskite photovoltaic module inverter system has been running for one year, the detected system efficiency will be summarized as follows: Figure 5 The diagram shows the system efficiency. Figure 5 It can be observed that the system efficiency ranged from 91.3% to 94.8% over a year of operation, showing significant fluctuations.
[0029] pass Figure 4 and Figure 5 The comparison reveals that the system efficiency of Example 1 is not only higher than that of Comparative Example 1, but also exhibits less fluctuation.
[0030] Therefore, the multi-level, low-leakage perovskite photovoltaic module inverter system of this invention has the following characteristics: 1. Design of a combination of switched capacitor (SC) unit and flying capacitor (FC) unit: Through the capacitor voltage self-balancing mechanism, nine-level output can be achieved without adding too many switching devices.
[0031] 2. Transformerless direct grid connection: By setting up the blocking switch module 2 and the common ground module 3, leakage current is effectively suppressed, avoiding the safety hazards caused by parasitic capacitance in traditional transformerless inverters.
[0032] 3. Voltage balancing and low loss: By using multi-level output, the total voltage is distributed across multiple capacitors and switching devices, which reduces the voltage stress on individual switches and reduces system switching losses.
[0033] 4. Improved waveform quality: The output voltage waveform is close to sinusoidal, the harmonic content is significantly reduced, the filter size is reduced, and the overall efficiency is improved.
[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A perovskite photovoltaic module inverter system based on multi-level low leakage current, characterized in that, The system includes perovskite photovoltaic strings, a blocking switch module, a common ground module, a multilevel inverter module, a modulation controller module, a filter module, and a grid connection interface, all connected sequentially by wires. Multiple perovskite photovoltaic strings are connected in parallel at the input of the blocking switch module, which quickly cuts off the DC circuit when leakage current or abnormal operating conditions are detected. The common ground module provides a stable reference potential for the inverter system. The multilevel inverter module contains nine multilevel output components connected in series. Each multilevel output component consists of interconnected switched capacitor units and flying capacitor units. Each switched capacitor unit consists of two power divider switches and one voltage divider capacitor connected in series between the two power divider switches. Each flying capacitor unit consists of two power equalization switches and one flying capacitor connected in series between the two power equalization switches. The modulation controller module includes a DSP controller, an FPGA controller, or an MCU controller. The modulation controller module communicates with the power divider switches and the power equalization switches to control their on / off states, ensuring a sinusoidal output voltage waveform. The filter module is used to suppress harmonics in the inverter system's output voltage.
2. The perovskite photovoltaic module inverter system based on multi-level low leakage current as described in claim 1, characterized in that, The blocking switch module includes a MOSFET switch or an IGBT switch.
3. The perovskite photovoltaic module inverter system based on multi-level low leakage current as described in claim 1, characterized in that, The filtering module includes two inductors and one capacitor.