Power conversion module and power supply system

Abstract

The application provides a power conversion module and a power supply system. The power conversion module comprises a power switch tube and a sampling control unit. The sampling control unit determines a bus reference voltage of a DC bus and a power supply reference voltage of a power supply module based on a maximum power point of the power supply module. The sampling control unit determines a bus reference duty cycle based on the bus reference voltage, determines a power supply reference duty cycle based on the power supply reference voltage, and determines a current limiting reference duty cycle based on a preset current limiting value of the power conversion module. The sampling control unit determines a given duty cycle of the power conversion module based on the bus reference duty cycle, the power supply reference duty cycle and the current limiting reference duty cycle, and controls the power switch tube to work based on the given duty cycle, so as to control the DC bus to have a target bus voltage and make the power conversion module operate at the maximum power point. In the application, the DC bus can be stabilized and the power conversion module can operate at the maximum power point, the system stability is improved, and the applicability is strong.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power supply, and particularly relates to a power conversion module and a power supply system. BACKGROUND

[0002] In a pure photovoltaic system or a photovoltaic system equipped with energy storage, when the photovoltaic system operates off-grid to supply power to a load, the energy storage battery or the photovoltaic unidirectional DC / DC conversion module will operate in a voltage source mode to provide a stable DC bus voltage for the photovoltaic system, so as to ensure that the DC / AC conversion module can normally operate to provide high-quality AC voltage to the load. When the energy storage battery is in an offline state (such as insufficient battery energy, shutdown, failure or no energy storage battery is configured), only the photovoltaic unidirectional DC / DC conversion module can provide the bus voltage. However, due to the unique characteristics of the photovoltaic curve, when the system operates to the left of the maximum power point, the bus will be out of control, which will cause the system to crash.

[0003] The present application relates to the technical field of power supply, and particularly relates to a power conversion module and a power supply system. SUMMARY

[0004] The present application provides a power conversion module and a power supply system, which can stabilize the DC bus and control the power conversion module to operate at the maximum power point, thereby improving the stability of the system and having strong applicability.

[0005] In a first aspect, the present application provides a power conversion module, which is suitable for a power supply system, the power supply system further comprising a power supply module and a DC bus, the power supply module being connectable to the DC bus in parallel through the power conversion module, the power conversion module comprising a power switch tube and a sampling control unit. The sampling control unit is configured to track a maximum power point of the power supply module, and determine a bus reference voltage of the DC bus and a power supply reference voltage of the power supply module based on the maximum power point of the power supply module, so that the bus reference voltage and the power supply reference voltage can be updated in real time based on the tracked maximum power point. The sampling control unit is further configured to determine a bus reference duty cycle based on the bus reference voltage, determine a power supply reference duty cycle based on the power supply reference voltage, and determine a current limiting reference duty cycle based on a preset current limiting value of the power conversion module. The sampling control unit is configured to determine a given duty cycle of the power conversion module based on the bus reference duty cycle, the power supply reference duty cycle and the current limiting reference duty cycle, and control the power switch tube to operate based on the given duty cycle, so as to control the DC bus to have a target bus voltage and control the power conversion module to operate at the maximum power point. In the present application, the off-grid mode and the grid-connected mode can be unified, and the complex mode switching is reduced. In addition, the given duty cycle of the power conversion module can be determined based on the bus reference duty cycle, the power supply reference duty cycle and the current limiting reference duty cycle, so as to achieve the dual purposes of stabilizing the bus voltage of the DC bus and tracking the maximum power point, improve the system stability, and have stronger applicability.

[0006] In combination with the first aspect, in a first possible implementation manner, the sampling control unit comprises a bus voltage loop, a power supply voltage loop and a current limiting loop, the power supply voltage loop being a voltage loop for maximum power point tracking control of the power supply module. The bus voltage loop is configured to determine the bus reference duty cycle based on the bus reference voltage of the DC bus. The power supply voltage loop is configured to determine the power supply reference duty cycle based on the power supply reference voltage of the power supply module. The current limiting loop is configured to determine the current limiting reference duty cycle based on the preset current limiting value of the power conversion module. In the power conversion module provided in the present application, the off-grid mode and the grid-connected mode can be unified, so that the bus voltage loop, the power supply voltage loop and the current limiting loop can be operated in parallel, and the complex mode switching is reduced. In addition, the bus reference duty cycle, the power supply reference duty cycle and the current limiting reference duty cycle can be directly determined through the bus voltage loop, the power supply voltage loop and the current limiting loop, the system has a fast response speed, and has stronger applicability.

[0007] In combination with the first possible implementation manner of the first aspect, in a second possible implementation manner, the sampling control unit is configured to determine the minimum reference duty ratio among the bus reference duty ratio, the supply reference duty ratio and the current-limiting reference duty ratio as the given duty ratio of the power conversion module. When the minimum reference duty ratio is the bus reference duty ratio, the given duty ratio of the power conversion module is output by the bus voltage loop. It can be understood that, when the power conversion module is in grid-connected operation or off-grid load shedding, the bus voltage of the DC bus is controlled by the bus voltage loop, so that the bus voltage of the DC bus is stabilized, thereby stabilizing the bus voltage of the DC bus. When the minimum reference duty ratio is the supply reference duty ratio, the given duty ratio of the power conversion module is output by the supply voltage loop. It can be understood that, when the power conversion module is in off-grid operation, the decrease of the bus voltage will cause the bus voltage loop to fail in competition, and the given duty ratio of the power conversion module is output by the supply voltage loop, so that the bus voltage loop does not form positive feedback, thereby stabilizing the bus voltage of the DC bus, and improving the system stability. When the minimum reference duty ratio is the current-limiting reference duty ratio, the given duty ratio of the power conversion module is output by the current-limiting loop, so as to ensure that the system current does not overcurrent, and the applicability is stronger. In the power conversion module provided in the present application, the bus voltage loop, the supply voltage loop and the current-limiting loop can be used for loop competition to achieve the dual purposes of stabilizing the bus voltage of the DC bus and maximum power point tracking, thereby improving the system stability and applicability.

[0008] In combination with the second possible implementation manner of the first aspect, in a third possible implementation manner, when the sampling control unit determines the bus reference duty ratio or the current-limiting reference duty ratio as the given duty ratio of the power conversion module, the sampling control unit is further configured to control the power conversion module to operate at the maximum power point. It can be understood that, when the sampling control unit determines the bus reference duty ratio or the current-limiting reference duty ratio as the given duty ratio of the power conversion module, the sampling control unit can determine that the supply voltage loop fails in competition. In the power conversion module provided in the present application, when the supply voltage loop fails in competition, the power conversion module can be controlled to operate at the maximum power point, so that the system response speed is fast, and the applicability is stronger.

[0009] In combination with any one of the first possible implementation manner of the first aspect to the third possible implementation manner of the first aspect, in a fourth possible implementation manner, the bus voltage loop is a closed-loop controller, and the closed-loop controller is a proportional-integral controller without static error or other controller. The bus voltage loop is further configured to clear the integral input when the bus reference duty ratio is greater than the current given duty ratio of the power conversion module. In other words, when the bus reference duty ratio is greater than the current given duty ratio of the power conversion module, the bus voltage loop fails in competition and clears the integral input, so that the system response speed can be improved while having an anti-saturation effect, and the applicability is stronger.

[0010] In the fifth possible implementation manner of any one of the first to fourth possible implementation manners of the first aspect, the power supply voltage loop is a closed-loop controller, which is a proportional-integral controller without static error or other controller. The power supply voltage loop is further configured to clear an integral input when the power supply reference duty cycle is greater than the current given duty cycle of the power conversion module. In other words, when the power supply reference duty cycle is greater than the current given duty cycle of the power conversion module, the power supply voltage loop fails in the competition and clears the integral input, so that the system response speed can be improved while having an anti-saturation effect, and the applicability is stronger.

[0011] In the sixth possible implementation manner of any one of the first to fifth possible implementation manners of the first aspect, the current limiting loop is a closed-loop controller, which is a proportional-integral controller without static error or other controller. The current limiting loop is further configured to clear an integral input when the current limiting reference duty cycle is greater than the current given duty cycle of the power conversion module. In other words, when the current limiting reference duty cycle is greater than the current given duty cycle of the power conversion module, the current limiting loop fails in the competition and clears the integral input, so that the system response speed can be improved while having an anti-saturation effect, and the applicability is stronger.

[0012] In the sixth possible implementation manner of any one of the first to fifth possible implementation manners of the first aspect, the current limiting loop is a closed-loop controller, which is a proportional-integral controller without static error or other controller. The current limiting loop is further configured to clear an integral input when the current limiting reference duty cycle is greater than the current given duty cycle of the power conversion module. In other words, when the current limiting reference duty cycle is greater than the current given duty cycle of the power conversion module, the current limiting loop fails in the competition and clears the integral input, so that the system response speed can be improved while having an anti-saturation effect, and the applicability is stronger.

[0013] With reference to the second aspect, in a first possible implementation, in the light storage hybrid power supply scenario, the power supply module is a photovoltaic array, and the power conversion module is a DC / DC conversion module.

[0014] With reference to the second aspect, in a second possible implementation, in the wind storage hybrid power supply scenario, the power supply module is a generator, and the power conversion module is an AC / DC conversion module.

[0015] In the present application, the off-grid mode and the grid-connected mode can be unified, and the complex mode switching is reduced. In addition, the given duty ratio of the power conversion module can be determined through the bus reference duty ratio, the power supply reference duty ratio, and the current limiting reference duty ratio, so as to realize the dual purposes of stabilizing the bus voltage of the direct current bus and maximum power point tracking, improve the system stability, and have stronger applicability. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a schematic diagram of an application scenario of a power supply system provided by the present application;

[0017] Figure 2 is a schematic diagram of a structure of a power supply system provided by the present application;

[0018] Figure 3 is a schematic diagram of a structure of a power conversion module provided by the present application;

[0019] Figure 4 is a schematic diagram of a working process of a bus voltage loop provided by the present application;

[0020] Figure 5 is a schematic diagram of a working process of a power supply voltage loop provided by the present application;

[0021] Figure 6 is a schematic diagram of a working process of a current limiting loop provided by the present application;

[0022] Figure 7 is a schematic diagram of a working process of a power conversion module provided by the present application;

[0023] Figure 8 is a schematic diagram of a power conversion module improved by the present application. DETAILED DESCRIPTION

[0024] New energy (NE, also known as unconventional energy) plays a wide role in people's lives and work, one of which is converting new energy into electricity. New energy sources can include solar energy, geothermal energy, wind energy, ocean energy, biomass energy, or other new energy sources. The power supply system provided in this application can be a hybrid power supply system based on new energy power generation and different types of energy storage modules. New energy power generation can include solar power generation (such as solar photovoltaic power generation or solar thermal power generation), geothermal power generation, wind power generation, ocean energy power generation (such as wave power generation or tidal power generation), and biomass power generation. New energy power generation has the characteristics of no moving parts, no noise, no pollution, and high reliability, and has excellent application prospects in communication power supply systems in remote areas. The components in the different types of energy storage modules can include lithium-ion batteries, lead-acid batteries (or lead-acid storage batteries), and supercapacitors (also known as electrochemical capacitors), etc. This application does not specifically limit the specific types of components in the energy storage modules. The power supply system provided in this application can be applied to base station equipment in remote areas where there is no mains power or the mains power is poor, or various types of power generation equipment such as photovoltaic power generation equipment or wind power generation equipment, or other electrical equipment (such as power grid, household equipment or industrial and commercial electrical equipment). The specific application scenario can be determined, and no restrictions are imposed here.

[0025] The power supply system provided in this application may include a power supply module, an energy storage module, a DC / DC converter module (also referred to as a DC / DC converter), a DC bus, a DC / AC converter module (also referred to as a DC / AC converter), a grid-connected junction box, and a power conversion module. The power supply module is connected in parallel to the DC bus through the power conversion module, and the energy storage module is connected in parallel to the DC bus through the DC / DC converter module. One end of the DC / AC converter module is connected in parallel to the DC bus, and the other end of the DC / AC converter module is connected to an AC load or the AC power grid through the grid-connected junction box. The energy storage module may include at least one battery cluster, and the battery clusters are connected in parallel. The power conversion module can convert the electrical energy provided by the power supply module into DC electrical energy and output DC electrical energy to the DC / AC converter. The DC / DC converter module can convert the DC electrical energy provided by the energy storage module into a target DC electrical energy and output the target DC electrical energy to the DC / AC converter module. The DC / AC conversion module can convert the DC power input from the power conversion module and the target DC power input from the DC / DC conversion module into AC power, and then supply power to AC loads or the AC grid through the grid-connected junction box. The following will use the photovoltaic-storage hybrid power supply scenario as an example for explanation, and will not be elaborated further.

[0026] Please see also Figure 1 , Figure 1This is a schematic diagram illustrating an application scenario of the power supply system provided in this application. In a photovoltaic-storage hybrid power supply scenario, the power supply module is a photovoltaic array, and the aforementioned power conversion module is a DC / DC conversion module (also referred to as a DC / DC converter). Figure 1 As shown, the power supply system (such as power supply system 1) may include photovoltaic power supply devices, an energy storage container, and a DC / AC converter. The photovoltaic power supply devices may include a photovoltaic array and a DC / DC converter. The photovoltaic array may consist of multiple photovoltaic modules connected in series and parallel; photovoltaic modules can also be called solar panels or photovoltaic panels. The energy storage container may include at least one battery cluster and a DC / DC converter, with each battery cluster connected in parallel. A battery cluster may consist of multiple battery groups connected in series. Each battery group may be a battery pack, which may consist of one or more battery cells (the voltage of which is typically between 2.5V and 4.2V) connected in series and parallel to form a minimum energy storage and management unit. After power supply system 1 is turned on, the photovoltaic array in the photovoltaic power supply devices can convert solar energy into electrical energy (i.e., DC power) and output electrical energy to the DC / DC converter. The DC / DC converter can convert the electrical energy input from the photovoltaic array into DC power and output DC power to the DC / AC converter, thus realizing the output of DC power from the photovoltaic power supply devices to the DC / AC converter. In the energy storage container, each battery cluster in at least one battery pack can output DC power to a DC / DC converter. The DC / DC converter can convert the DC power input from each battery cluster into target DC power and output the target DC power to a DC / AC converter, thus enabling the energy storage container to output the target DC power to the DC / AC converter. At this point, the DC / AC converter can convert the DC power input from the photovoltaic power supply devices and the target DC power input from the energy storage container into AC power and output AC power to the AC power grid (e.g., grid 2) or AC load (e.g., household appliance 3) to supply power to grid 2 or household appliance 3.

[0027] The following will combine Figures 2 to 8 This application provides an example illustration of the power supply system, power conversion module, and their working principle.

[0028] See Figure 2 , Figure 2 This is a schematic diagram of the power supply system provided in this application. (For example...) Figure 2As shown, the power supply system 1 may include a power supply module 10, a power conversion module 20, an energy storage module 30, a DC / DC conversion module 40, a DC bus 50, a DC / AC conversion module 60, and a grid-connected junction box 70. The power supply module 10 can be connected in parallel to the DC bus 50 via the power conversion module 20. The energy storage module 30 can be connected in parallel to the DC bus 50 via the DC / DC conversion module 40. One end of the DC / AC conversion module 60 is connected in parallel to the DC bus 50, and the other end of the DC / AC conversion module 60 is connected to an AC load or the AC power grid via the grid-connected junction box 70. The power conversion module 20 can be an AC / DC conversion module or a unidirectional DC / DC conversion module, and its circuit topology can be a bootstrap circuit (BST circuit, also known as a boost circuit). Therefore, the power conversion module can also be called a BST conversion module or a BST converter. The DC / DC conversion module 40 can be a bidirectional DC / DC conversion module. Optionally, the DC bus 50 may include a single bus capacitor or multiple bus capacitors connected in series, for example, such as... Figure 2 As shown, the DC bus 50 includes a bus capacitor C.

[0029] In some feasible implementations, in a photovoltaic-storage hybrid power supply scenario, the power supply module 10 can be a photovoltaic array, and the aforementioned power conversion module 20 can be a unidirectional DC / DC converter module. The photovoltaic array can convert solar energy into electrical energy (i.e., DC power) and output electrical energy to the unidirectional DC / DC converter module. This unidirectional DC / DC converter module can convert the electrical energy input to the photovoltaic array into DC power and output DC power to the DC / AC converter module 60. The energy storage module 30 can output DC power to the DC / DC converter module 40. The DC / DC converter module 40 can convert the DC power input to the energy storage module 30 into target DC power and output the target DC power to the DC / AC converter module 60. Further, the DC / AC converter module 60 can convert the DC power input to the unidirectional DC / DC converter module and the target DC power input to the DC / DC converter module 40 into AC power, and output AC power to the AC grid or AC load through the grid-connected junction box 70 to supply power to the AC grid or AC load.

[0030] In some feasible implementations, in a wind-storage hybrid power supply scenario, the power supply module 10 is a generator, and the power conversion module 20 is an AC / DC conversion module (also referred to as an AC / DC converter). The generator can convert wind energy into AC power and output AC power to the AC / DC conversion module. The AC / DC conversion module can convert the AC power input from the generator into DC power and output DC power to the DC / AC conversion module 60. The energy storage module 30 can output DC power to the DC / DC conversion module 40. The DC / DC conversion module 40 can convert the DC power input from the energy storage module 30 into a target DC power and output the target DC power to the DC / AC conversion module 60. Further, the DC / AC conversion module 60 can convert the DC power input from the AC / DC conversion module and the target DC power input from the DC / DC conversion module 40 into AC power, and output AC power to the AC grid or AC load through the grid-connected junction box 70 to supply power to the AC grid or AC load.

[0031] In some feasible implementations, when the AC power grid fails or the power supply system 1 operates off-grid to supply power to the AC load, the DC / AC conversion module 60 needs to provide high-quality AC power to the AC load. At this time, the power conversion module 20 or the DC / DC conversion module 40 operates in voltage source mode to provide a stable bus voltage (i.e., DC bus voltage) to the DC / AC conversion module 60, thereby ensuring the normal operation of the DC / AC conversion module 60 to provide high-quality AC power to the AC load. Optionally, if the power supply system 1 does not have an energy storage module 30, the energy storage module 30 is insufficient, the energy storage module 30 is turned off, or the energy storage module 30 is faulty, it can be indicated that the energy storage module 30 is offline. At this time, the power conversion module 20 operates in voltage source mode to provide a stable bus voltage to the DC / AC conversion module 60. At the same time, in order to prevent the power supply system 1 from operating to the left of the maximum power point, which would cause the DC bus 50 to run out of control, the power conversion module 20 needs to operate at the maximum power point. Therefore, when the AC power grid fails, the power supply system 1 operates off-grid to supply power to the AC load, or the energy storage module 30 is offline, the power conversion module 20 needs to operate at its maximum power point and provide a stable bus voltage to the DC / AC conversion module 60.

[0032] Further, please see Figure 3 , Figure 3 This is a schematic diagram of the power conversion module provided in this application. Figure 3 As shown above Figure 2The power conversion module 20 shown may include a sampling control unit 201 and a power switch 202, which may be a bidirectional power switch. The sampling control unit 201 may include a bus voltage loop 2011, a supply voltage loop 2012, and a current limiting loop 2013. The supply voltage loop 2012 is a voltage loop used for maximum power point tracking (MPPT) control of the power supply module 10. In this application, the optimal operating point of the power supply module 10 (such as a photovoltaic array) can be referred to as the maximum power point. For ease of description, a photovoltaic array will be used as an example below. Since the maximum power point of a photovoltaic array mainly depends on its operating temperature and light intensity, and the maximum power point of the photovoltaic array differs under different operating temperatures and light intensities, the photovoltaic maximum power point can be tracked by the supply voltage loop 2012 to ensure that the photovoltaic array operates at its maximum power point as much as possible. In this application, one or more functional units or hardware devices with sampling and control logic functions in the power conversion module can be collectively referred to as the sampling control unit.

[0033] In some feasible implementations, the sampling control unit 201 can track the maximum power point of the power supply module 10 in real time and determine the bus reference voltage of the DC bus 50 and the power supply reference voltage of the power supply module 10 based on the maximum power point of the power supply module 10. The sampling control unit 201 can determine the bus reference duty cycle based on the bus reference voltage, the power supply reference duty cycle based on the power supply reference voltage, and the current limiting reference duty cycle based on the preset current limiting value of the power conversion module 20. The preset current limiting value here can be the maximum operating current value configured internally by the power conversion module 20, or the maximum operating current value set by the user according to the power conversion module 20. The specific value can be determined according to the actual application scenario and is not limited here. Further, the sampling control unit 201 can determine the given duty cycle of the power conversion module 20 based on the bus reference duty cycle, the power supply reference duty cycle, and the current limiting reference duty cycle, and control the power switch 202 to operate based on the given duty cycle, so as to control the DC bus 50 to have the target bus voltage (i.e., the voltage across the bus capacitor C) and make the power conversion module 20 operate at the maximum power point. This application refers to the actual duty cycle used to control the operation of the power conversion module as the given duty cycle. The target bus voltage here can be a bus voltage value within a preset bus voltage range, thereby achieving the purpose of stabilizing the bus voltage of the DC bus 50. At this time, the power conversion module 20 can provide a stable bus voltage to the DC / AC conversion module 60, enabling the DC / AC conversion module 60 to provide high-quality AC power to the AC load. Furthermore, when the power conversion module 20 operates at its maximum power point, the power supply system 1 can operate at its maximum power point, resulting in higher power supply efficiency and wider applicability.

[0034] In some feasible implementations, the sampling control unit 201 can acquire the current output voltage and / or current output current of the power supply module 10 in real time based on its sampling function, and process the current output voltage and / or current output current of the power supply module 10 through perturbation observation, incremental conductance, current scanning, or other methods to obtain the maximum power point of the power supply module 10. It is understood that the maximum power point of the power supply module 10 is different under different operating temperatures and / or light intensities. At this time, the bus reference voltage and power supply reference voltage will also change with the change in the maximum power point, thus the bus reference voltage and power supply reference voltage can be updated in real time by tracking the maximum power point. For example, when the maximum power point increases, the bus reference voltage and power supply reference voltage will also increase. Furthermore, the sampling control unit 201 can determine the bus reference voltage of the DC bus 50 and the power supply reference voltage of the power supply module 10 based on the real-time tracked maximum power point of the power supply module 10.

[0035] In some feasible implementations, the bus voltage loop 2011 can determine the bus reference duty cycle based on the bus reference voltage of the DC bus 50. The bus reference duty cycle can be understood as a drive signal extracted by the bus voltage loop 2011 from the bus reference voltage, which is proportional to the bus reference voltage. For example, this drive signal can be a pulse width modulation (PWM) signal for a switch, which can be simply referred to as a PWM signal. For instance, a 1 in the PWM signal can represent the switch being on, and a 0 in the PWM signal can represent the switch being off. The bus voltage loop 2011 can be a closed-loop controller (also called a negative feedback controller). This closed-loop controller can be a proportional-integral controller (PI controller) with no steady-state error or other controllers. Here, the PI controller is a linear controller. Please refer to [further details omitted]. Figure 4 , Figure 4 This is a schematic diagram of the working process of the bus voltage loop provided in this application. For example... Figure 4 As shown, when the bus reference duty cycle is greater than the current given duty cycle of the power conversion module 20, the bus voltage loop 2011 can perform integral input zeroing, thereby improving the system response speed while having anti-saturation effect and making it more versatile. Conversely, when the bus reference duty cycle is less than or equal to the current given duty cycle of the power conversion module 20, the bus voltage loop 2011 can compete with the supply voltage loop 2012 and the current limiting loop 2013 for the given duty cycle of the power conversion module 20.

[0036] In some feasible implementations, the power supply voltage loop 2012 can determine the power supply reference duty cycle based on the power supply reference voltage of the power supply module 10. Here, the power supply reference duty cycle can be understood as a drive signal, such as a PWM signal, extracted by the power supply voltage loop 2012 from the power supply reference voltage and proportional to it. The power supply voltage loop 2012 can be a closed-loop controller, which is a zero-steady-state-error proportional-integral controller (i.e., a PI controller) or other controllers. Please refer to [further details omitted]. Figure 5 , Figure 5 This is a schematic diagram of the power supply voltage loop provided in this application. For example... Figure 5 As shown, when the power supply reference duty cycle is greater than the current given duty cycle of the power conversion module 20, the power supply voltage loop 2012 can perform integral input zeroing, thereby improving the system response speed while having anti-saturation effect and making it more versatile. Conversely, when the power supply reference duty cycle is less than or equal to the current given duty cycle of the power conversion module 20, the power supply voltage loop 2012 can compete with the bus voltage loop 2011 and the current limiting loop 2013 for the given duty cycle of the power conversion module 20.

[0037] In some feasible implementations, the current limiting loop 2013 can determine the current limiting reference duty cycle based on the preset current limiting value of the power conversion module 20. This current limiting reference duty cycle can be understood as a drive signal, such as a PWM signal, extracted by the current limiting loop 2013 from the preset current limiting value and proportional to it. The current limiting loop 2013 can be a closed-loop controller, which is a proportional-integral controller (PI controller) with zero steady-state error or other controllers. Please refer to [further details omitted]. Figure 6 , Figure 6 This is a schematic diagram of the working process of the current limiting ring provided in this application. Figure 6 As shown, when the current-limiting reference duty cycle is greater than the current given duty cycle of the power conversion module 20, the current-limiting loop 2013 can perform integral input zeroing, thereby improving the system's response speed while having anti-saturation effect, and controlling the current of the power conversion module within a safe range, making it more versatile. Conversely, when the current-limiting reference duty cycle is less than or equal to the current given duty cycle of the power conversion module 20, the current-limiting loop 2013 can compete with the bus voltage loop 2011 and the supply voltage loop 2012 for the given duty cycle of the power conversion module 20.

[0038] In some feasible implementations, the sampling control unit 201 can determine the minimum reference duty cycle from the bus reference duty cycle, the power supply reference duty cycle, and the current limiting reference duty cycle, and set this minimum reference duty cycle as the given duty cycle of the power conversion module 20. When the minimum reference duty cycle is the bus reference duty cycle, the given duty cycle of the power conversion module 20 is output by the bus voltage loop 2011. The bus voltage loop 2011 successfully competes, while the power supply voltage loop 2012 and the current limiting loop 2013 fail to compete. At this time, the sampling control unit 201 can control the power conversion module 20 to operate at the maximum power point. It can be understood that during grid-connected operation or off-grid load shedding, the bus voltage loop 2011 controls the DC bus 50, which can limit the rise of the DC bus voltage 50, thereby stabilizing the DC bus voltage 50.

[0039] In some feasible implementations, when the minimum reference duty cycle is the same as the power supply reference duty cycle, the given duty cycle of the power conversion module 20 is output by the power supply voltage loop 2012. At this time, the power supply voltage loop 2012 successfully competes for the duty cycle, while the bus voltage loop 2011 and the current limiting loop 2013 fail to compete. It can be understood that when the bus voltage drops off-grid, the bus voltage loop 2011 will fail to compete. In this case, the power supply voltage loop 2012 will output the given duty cycle of the power conversion module 20 to continue tracking the maximum power point of the power supply module 10, preventing the bus voltage loop 2011 from forming positive feedback. This stabilizes the bus voltage of the DC bus 50, thereby improving system stability.

[0040] In some feasible implementations, when the minimum reference duty cycle is the current-limiting reference duty cycle, the given duty cycle of the power conversion module 20 is output by the current-limiting loop 2013. The current-limiting loop 2013 succeeds in the competition, while the bus voltage loop 2011 and the supply voltage loop 2012 fail. At this point, the sampling control unit 201 can control the power conversion module 20 to operate at its maximum power point. It can be understood that when both the bus reference duty cycle and the supply voltage reference duty cycle are greater than the current-limiting reference duty cycle, to ensure that the system current does not exceed the current-limiting reference duty cycle, the sampling control unit 201 can control the current-limiting loop 2013 to output the given duty cycle of the power conversion module 20, thus offering greater applicability. Therefore, when the sampling control unit 201 determines the bus reference duty cycle or the current-limiting reference duty cycle as the given duty cycle of the power conversion module 20, it can control the power conversion module 20 to operate at its maximum power point. In other words, when the power supply voltage loop 2012 fails to compete, the sampling control unit 201 can control the power conversion module 20 to operate at the maximum power point.

[0041] Please see Figure 7 , Figure 7 This is a schematic diagram of the working process of the power conversion module provided in this application. For example... Figure 7As shown, the bus voltage loop 2011 can be based on the bus reference voltage (which can be represented as U). bus_ref Determine the reference duty cycle of the busbar (e.g., it can be expressed as D). bus_ref The power supply voltage loop 2012 can be based on the power supply reference voltage (e.g., it can be represented as U). pv_ref Determine the power supply reference duty cycle (e.g., it can be expressed as D). pv_ref The current limiting loop 2013 can be based on a preset current limiting value (e.g., it can be represented as I). limit Determine the current limiting reference duty cycle (e.g., it can be expressed as D). i_ref At this point, the sampling control unit 201 can adjust the bus reference duty cycle D. bus_ref Power supply reference duty cycle D pv_ref and the current limiting reference duty cycle D i_ref The minimum duty cycle in the process is determined as the given duty cycle of the power conversion module 20 (which can be expressed as D). ref ), and based on a given duty cycle D ref Control the operation of power switch 202.

[0042] In some feasible implementations, the power switch 202 can be an insulated-gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a diode made of silicon semiconductor material (Si), or third-generation wide-bandgap semiconductor material (silicon carbide (SiC), gallium nitride (GaN), diamond, zinc oxide (ZnO), or other materials. The specific choice depends on the actual application scenario and is not limited here. Please refer to [further details omitted]. Figure 8 , Figure 8 This is a circuit diagram of the power conversion module improved in this application. Figure 8As shown, the power conversion module 20 may include a filter inductor L, a diode D, and a power switch 202, which includes a switch S (which is an IGBT). One end of the filter inductor L is connected to the power supply module 10, and the other end is connected to one end of the diode D and the collector of the switch S. The emitter of the switch S is connected to the power supply module 10 and one end of the bus capacitor C. The base of the switch S can be connected to the sampling control unit 201, and the other end of the bus capacitor C is connected to the other end of the diode D. Here, the bus capacitor C can be understood as the output capacitor of the power conversion module 20. After determining the given duty cycle of the power conversion module 20, the sampling control unit 201 can control the switch S to operate based on the given duty cycle to stabilize the bus voltage of the DC bus 50 and ensure that the power conversion module 20 operates at its maximum power point. At this time, the power conversion module 20 can provide a stable bus voltage to the DC / AC conversion module 60, so that the DC / AC conversion module 60 can provide high-quality AC power to the AC load. When the power conversion module 20 is operating at the maximum power point, the power supply system 1 can operate at the maximum power point, resulting in higher power supply efficiency and stronger applicability.

[0043] In this application, off-grid mode and grid-connected mode can be unified, thereby allowing the bus voltage loop, power supply voltage loop and current limiting loop to operate in parallel, reducing complex mode switching; in addition, the dual purpose of stabilizing the DC bus voltage and maximum power point tracking can be achieved through loop competition, which improves system stability, increases system response speed, and enhances applicability.

[0044] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A power conversion module, characterized in that, The power conversion module is suitable for a power supply system, which also includes a power supply module and a DC bus. The power supply module is connected in parallel to the DC bus through the power conversion module. The power conversion module includes a power switching transistor and a sampling control unit. The sampling control unit is used to track the maximum power point of the power supply module, and determine the bus reference voltage of the DC bus and the power supply reference voltage of the power supply module based on the maximum power point of the power supply module; The sampling control unit is also used to determine the bus reference duty cycle based on the bus reference voltage, determine the power supply reference duty cycle based on the power supply reference voltage, and determine the current limiting reference duty cycle based on the preset current limiting value of the power conversion module; wherein, the preset current limiting value is the maximum operating current value of the power conversion module. The sampling control unit is also used to determine the minimum reference duty cycle among the bus reference duty cycle, the power supply reference duty cycle, and the current limiting reference duty cycle as the given duty cycle of the power conversion module, and control the power switch to operate based on the given duty cycle, so as to control the DC bus to have the target bus voltage and make the power conversion module operate at the maximum power point.

2. The power conversion module according to claim 1, characterized in that, The sampling control unit includes a bus voltage loop, a power supply voltage loop, and a current limiting loop. The power supply voltage loop is a voltage loop used for maximum power point tracking control of the power supply module. The bus voltage loop is used to determine the bus reference duty cycle based on the bus reference voltage of the DC bus. The power supply voltage loop is used to determine the power supply reference duty cycle based on the power supply reference voltage of the power supply module; The current limiting loop is used to determine the current limiting reference duty cycle based on the preset current limiting value of the power conversion module.

3. The power conversion module according to claim 2, characterized in that, When the minimum reference duty cycle is the same as the bus reference duty cycle, the given duty cycle of the power conversion module is output by the bus voltage loop; when the minimum reference duty cycle is the same as the power supply reference duty cycle, the given duty cycle of the power conversion module is output by the power supply voltage loop; when the minimum reference duty cycle is the same as the current limiting reference duty cycle, the given duty cycle of the power conversion module is output by the current limiting loop.

4. The power conversion module according to claim 3, characterized in that, The sampling control unit is also used to control the power conversion module to operate at the maximum power point when the bus reference duty cycle or the current limiting reference duty cycle is determined as the given duty cycle of the power conversion module.

5. The power conversion module according to any one of claims 2-4, characterized in that, The bus voltage loop is a closed-loop controller, and the closed-loop controller is a proportional-integral controller with zero steady-state error; The bus voltage loop is also used to clear the integral input when the bus reference duty cycle is greater than the current given duty cycle of the power conversion module.

6. The power conversion module according to any one of claims 2-4, characterized in that, The power supply voltage loop is a closed-loop controller, and the closed-loop controller is a proportional-integral controller with zero steady-state error; The power supply voltage loop is also used to clear the integral input when the power supply reference duty cycle is greater than the current given duty cycle of the power conversion module.

7. The power conversion module according to any one of claims 2-4, characterized in that, The current limiting loop is a closed-loop controller, and the closed-loop controller is a proportional-integral controller with zero steady-state error; The current limiting loop is also used to clear the integral input when the current limiting reference duty cycle is greater than the current given duty cycle of the power conversion module.

8. A power supply system, characterized in that, The power supply system includes a power supply module, an energy storage module, a DC / DC converter module, a DC bus, a DC / AC converter module, a grid-connected junction box, and a power conversion module as described in any one of claims 1-7. The power supply module is connected in parallel to the DC bus through the power conversion module, the energy storage module is connected in parallel to the DC bus through the DC / DC converter module, one end of the DC / AC converter module is connected in parallel to the DC bus, and the other end of the DC / AC converter module is connected to an AC load or an AC power grid through the grid-connected junction box.

9. The power supply system according to claim 8, characterized in that, When the power supply module is a photovoltaic array, the power conversion module is a DC / DC conversion module.

10. The power supply system according to claim 8, characterized in that, When the power supply module is a generator, the power conversion module is an AC / DC conversion module.

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