Integrated high-capacity photovoltaic grid-connected converter power module

Abstract

The application relates to a kind of integrated large-capacity photovoltaic grid-connected converter power modules, characterized in that, including for converting grid-connected side DC voltage into three-level square wave inverter module, for energy transfer and electrical isolation transformer module, for converting square wave into DC voltage resonant module and for converting DC voltage into grid-connected side AC voltage MMC module;The DC side of the three-level inverter module is the DC grid-connected side of the power module, and the AC side is connected with the primary side of the transformer module;The secondary side of the transformer module is connected with the AC side of the resonant module, the DC side of the resonant module is connected with the DC side of the MMC module, and the AC side of the MMC module is the AC grid-connected side of the power module. To solve the problem of large-scale new energy grid-connected sending and consumption in the prior art.

Description

Technical Field

[0001] This invention relates to an integrated high-capacity photovoltaic grid-connected converter power module, belonging to the field of power electronics technology. Background Technology

[0002] Currently, large-scale centralized photovoltaic power plants with a capacity of hundreds of megawatts use the traditional photovoltaic inverter collection and boosting grid connection method. Due to the small capacity of a single inverter, the large number of inverters, and the decentralized layout, photovoltaic power plants suffer from poor equipment coordination, weak system support capacity caused by multi-stage boosting, complex inverter interactions, and difficulties in achieving coordinated active grid construction and black start capability. The coupling of a large number of inverters with long-distance cables leads to voltage over-limit and wide-frequency oscillation problems that restrict the power plant's transmission capacity, and high AC line losses affect the overall system efficiency.

[0003] With the development and maturation of power electronics and flexible DC technology, new grid-friendly photovoltaic (PV) grid-connected systems have become possible. These systems focus on improving the grid regulation performance of the PV power source itself, comprehensively enhancing the frequency regulation, peak shaving, voltage support, system inertia support, and oscillation damping capabilities of the PV power generation system, thus solving the challenges of large-scale renewable energy grid connection and consumption. A modular multilevel technology approach is adopted to construct a new PV grid-connected conversion technology, changing the distributed access scheme to a centralized access method, significantly reducing the number of grid-connected inverters, and constructing a new generation of grid-connected systems that easily achieve active grid support functions. For this purpose, large-capacity PV grid-connected converters are required. Summary of the Invention

[0004] The purpose of this invention is to provide an integrated, high-capacity photovoltaic grid-connected converter power module to solve the problem of large-scale grid connection and consumption of new energy in the existing technology.

[0005] To achieve the above objectives, the present invention includes:

[0006] The present invention discloses an integrated high-capacity photovoltaic grid-connected converter power module, characterized in that it comprises a three-level inverter module for converting grid-connected DC voltage into a three-level square wave, a transformer module for energy transfer and electrical isolation, a resonant module for converting the square wave into DC voltage, and an MMC module for converting DC voltage into grid-connected AC voltage; the DC side of the three-level inverter module serves as the DC grid-connected side of the power module, and the AC side is connected to the primary side of the transformer module; the secondary side of the transformer module is connected to the AC side of the resonant module, the DC side of the resonant module is connected to the DC side of the MMC module, and the AC side of the MMC module serves as the AC grid-connected side of the power module.

[0007] The module of this invention consists of a three-level module, a high-frequency module, a resonant module, and an MMC module. All switching transistors used in each module are half-bridge IGBT modules, and multiple switching transistors are connected in parallel to form a high-power, high-current switching transistor. It can be connected to an AC or DC power grid to achieve bidirectional energy flow in the system. Furthermore, it can be cascaded to convert the low-voltage, low-power energy at the photovoltaic port into medium-voltage, high-power energy in the bridge arm, forming a medium-voltage AC port or medium-voltage DC port that outputs a large capacity of photovoltaic power.

[0008] Furthermore, the three-level inverter module is a half-bridge three-level inverter module, which uses a half-bridge IGBT module as the switching transistor, and includes a circuit breaker for controlling the DC connection of the power module to the grid, a capacitor for providing energy support for the half-bridge three-level inverter module, and a resistor for providing an energy discharge channel for the half-bridge three-level inverter module.

[0009] Furthermore, the transformer module is a high-frequency transformer module, including a high-frequency transformer for energy transfer and electrical isolation and a filter inductor for storing and releasing the energy of the half-bridge three-level inverter module.

[0010] Furthermore, the resonant module is a resonant full-bridge module, including several switching transistors connected in parallel. The switching transistors are half-bridge IGBT modules. The capacitors used to provide energy support for the resonant full-bridge module and the resistors used to provide energy discharge channels for the resonant full-bridge module are also included.

[0011] Furthermore, the MMC module is an MMC full-bridge module, using a half-bridge IGBT module as the switching transistor, including a capacitor for providing energy support to the MMC full-bridge module, a resistor for providing an energy discharge channel to the MMC full-bridge module, and a bypass switch for controlling the connection and disconnection of the MMC full-bridge module; the switching transistor is a half-bridge IGBT module.

[0012] Furthermore, the system includes a frame with a first compartment, a second compartment, a third compartment, and a fourth compartment arranged vertically; the first compartment is used to place a three-level inverter module; the second compartment is used to place a transformer module; the third compartment is used to place a resonant module; and the fourth compartment is used to place an MMC module.

[0013] By setting up four compartments for installing four modules in the vertical direction, the floor space occupied by the modules can be reduced, and the space utilization rate can be improved.

[0014] Furthermore, the first compartment, the second compartment, the third compartment, and the fourth compartment are arranged vertically within the frame from bottom to top.

[0015] Arranging the four compartments vertically in sequence avoids the need for adjacent modules to cross over other modules to connect, reducing the length of the connecting lines between modules, which is simple and cost-effective.

[0016] Furthermore, the three-level inverter module is interconnected with the transformer module, the transformer module with the resonant module, and the resonant module with the MMC module via copper busbars.

[0017] Furthermore, the upper end of the frame is provided with a water outlet pipe for heat dissipation, and the lower end is provided with a water inlet pipe for heat dissipation.

[0018] By setting an inlet pipe at the bottom of the frame and an outlet pipe at the top, water can be kept inside the module for a sufficient amount of time to carry away the heat inside the module and achieve the effect of heat dissipation.

[0019] Furthermore, the frame retains a large size setting in one of the width, height, and depth directions.

[0020] This invention retains a large dimension in only one of the three dimensions of the frame (width, height, and depth), thereby ensuring that the integrated power module has the smallest volume and the power density is maximized, thus meeting the compact and integrated land requirements of cities. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the integrated power module topology according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the integrated power module structure layout according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of an MMC topology composed of cascaded integrated power modules according to an embodiment of the present invention;

[0024] In the diagram: 1. DC port; 2. AC port; 3. AC port; 4. DC positive port; 5. DC negative port; P1. Half-bridge three-level module; P2. High-frequency transformer module; P3. Resonant full-bridge module; P4. MMC full-bridge module. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 As shown, the integrated power module consists of a half-bridge three-level module P1, a high-frequency transformer module P2, a resonant full-bridge module P3, and an MMC full-bridge module P4. The integrated power module is connected to the DC grid through the DC port of the half-bridge three-level module P1 and to the AC grid through the AC port of the MMC full-bridge module.

[0027] like Figure 1As shown, the half-bridge three-level module P1 uses a half-bridge IGBT module as the switching transistor, and consists of circuit breaker 1Q1, capacitors 1C1-1C2, resistors 1R1-1R2, and current sensors 1CT1-1CT2. It is used to convert the grid-connected DC voltage into a three-level square wave. The number of switching transistors is determined by the capacity of the half-bridge three-level module P1; the larger the current of the half-bridge three-level module P1, the larger the capacity and the more switching transistors are required. Circuit breaker 1Q1 controls the DC input of the power module. 1C1-1C2 are identical in model and specifications, providing energy support for the half-bridge three-level module P1. Resistors 1R1-1R2 are identical in model and specifications, providing an energy discharge path for the half-bridge three-level module P1. Current sensor 1CT1 measures the DC current, and current sensor 1CT2 measures the AC current.

[0028] like Figure 1 As shown, the high-frequency transformer module P2 includes a high-frequency transformer 2TR1 and a filter inductor 2L1. The filter inductor 2L1 is used to store and release the energy of the half-bridge three-level module P1, ensuring its continuous operating current and good waveform; the high-frequency transformer 2TR1 is used for energy transfer and electrical isolation.

[0029] like Figure 1 As shown, the resonant full-bridge module P3 uses a half-bridge IGBT module as the switching transistor, including capacitor 3C1, resistor 3R1, and current sensor 3CT1, to convert the square wave into DC voltage. The number of switching transistors is determined by the capacitance of the resonant full-bridge module P3; the larger the current of the resonant full-bridge module P3, the larger the capacitance and the more switching transistors are required. Capacitor 3C1 provides energy support for the resonant full-bridge module P3; resistor 3R1 provides an energy discharge path for the resonant full-bridge module P3; and current sensor 3CT1 is used to measure the DC-side current.

[0030] like Figure 1 As shown, the MMC full-bridge module P4 uses a half-bridge IGBT module as the switching transistor, including capacitor 4C1, resistor 4R1, and bypass switch 4K1, to convert DC voltage to grid-connected AC voltage. The number of switching transistors is determined by the capacitance of the MMC full-bridge module P4; the larger the current of the MMC full-bridge module, the larger the capacitance and the more switching transistors are required. Capacitor 4C1 provides energy support for the MMC full-bridge module; resistor 4R1 provides an energy discharge path for the MMC full-bridge module P4; and bypass switch 4K1 is used to control the connection and disconnection of the MMC full-bridge module P4.

[0031] like Figure 2 As shown, the integrated power module is arranged in a frame with four layers, each layer housing one type of module. Figure 2The left side is the front view, and the right side is the rear view. From top to bottom, the frame consists of the MMC full-bridge module P4, the resonant full-bridge module P3, the high-frequency transformer module P2, and the half-bridge three-level module P1. These four modules are connected by copper busbars. The integrated power module uses water cooling for heat dissipation. Water inlet and outlet pipes are located at the top and bottom of the frame, with the inlet pipe at the bottom and the outlet pipe at the top. The water cooling systems of the four modules are connected in series. The half-bridge three-level module P1 has a DC port 1, and the MMC full-bridge module P4 has an AC port 2.

[0032] like Figure 2 As shown, the integrated power module adopts a 4-layer layout structure, with only one direction retaining a large size in the width, height and depth directions. This ensures that the integrated power module has the smallest volume and the maximum power density, thereby meeting the compact and integrated space requirements of cities.

[0033] like Figure 3 As shown, the single bridge arm uses an integrated power module cascaded configuration, including AC port 3, DC positive port 4, and DC negative port 5, to convert the low-voltage, low-power electricity from the photovoltaic port into medium-voltage, high-power electricity from the bridge arm. Then, by utilizing the three-phase six-bridge arm topology, a medium-voltage AC port or a medium-voltage DC port can be formed to output a large capacity of photovoltaic power.

[0034] In this example, the integrated power module can be flexibly connected to the AC or DC power grid. Its compact layout and high integration make it easy to form a large-capacity new photovoltaic grid-connected converter, thereby solving the problem of transmission and consumption brought about by large-scale new energy grid connection.

Claims

1. An integrated high-capacity photovoltaic grid-connected converter power module, characterized in that, It includes a three-level inverter module for converting grid-connected DC voltage into a three-level square wave, a transformer module for energy transfer and electrical isolation, a resonant module for converting the square wave into DC voltage, and an MMC module for converting DC voltage into grid-connected AC voltage. The DC side of the three-level inverter module serves as the DC grid-connected side of the power module, and the AC side is connected to the primary side of the transformer module. The secondary side of the transformer module is connected to the AC side of the resonant module. The DC side of the resonant module is connected to the DC side of the MMC module, and the AC side of the MMC module serves as the AC grid-connected side of the power module.

2. The integrated large-capacity photovoltaic grid-connected converter power module according to claim 1, characterized in that, The three-level inverter module is a half-bridge three-level inverter module, which uses a half-bridge IGBT module as the switching transistor. It includes a circuit breaker for controlling the DC connection of the power module to the grid, a capacitor for providing energy support for the half-bridge three-level inverter module, and a resistor for providing an energy discharge channel for the half-bridge three-level inverter module.

3. The integrated large-capacity photovoltaic grid-connected converter power module according to claim 2, characterized in that, The transformer module is a high-frequency transformer module, which includes a high-frequency transformer for energy transfer and electrical isolation and a filter inductor for storing and releasing the energy of the half-bridge three-level inverter module.

4. The integrated high-capacity photovoltaic grid-connected converter power module according to claim 3, characterized in that, The resonant module is a resonant full-bridge module, which includes several switching transistors connected in parallel. The switching transistors are half-bridge IGBT modules, a capacitor for providing energy support for the resonant full-bridge module, and a resistor for providing an energy discharge channel for the resonant full-bridge module.

5. The integrated high-capacity photovoltaic grid-connected converter power module according to claim 4, characterized in that, The MMC module is an MMC full-bridge module, using a half-bridge IGBT module as the switching transistor, including a capacitor for providing energy support to the MMC full-bridge module, a resistor for providing an energy discharge channel to the MMC full-bridge module, and a bypass switch for controlling the connection and disconnection of the MMC full-bridge module; the switching transistor is a half-bridge IGBT module.

6. The integrated high-capacity photovoltaic grid-connected converter power module according to claim 1, characterized in that, The frame includes a first compartment, a second compartment, a third compartment, and a fourth compartment arranged vertically; the first compartment is used to place a three-level inverter module; the second compartment is used to place a transformer module; the third compartment is used to place a resonant module; and the fourth compartment is used to place an MMC module.

7. The integrated large-capacity photovoltaic grid-connected converter power module according to claim 6, characterized in that, The first compartment, the second compartment, the third compartment, and the fourth compartment are arranged vertically within the frame from bottom to top.

8. The integrated large-capacity photovoltaic grid-connected converter power module according to claim 7, characterized in that, The three-level inverter module is interconnected with the transformer module, the transformer module with the resonant module, and the resonant module with the MMC module via copper busbars.

9. The integrated large-capacity photovoltaic grid-connected converter power module according to claim 8, characterized in that, The upper end of the frame is provided with a water outlet pipe for heat dissipation, and the lower end is provided with a water inlet pipe for heat dissipation.

10. The integrated large-capacity photovoltaic grid-connected converter power module according to claim 9, characterized in that, The frame retains a large size in one of the width, height, and depth directions.

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