Photovoltaic system bus voltage control method and apparatus

Abstract

A method for controlling the bus voltage of a photovoltaic system (100). The photovoltaic system (100) includes a DC / DC converter (104) and a DC / AC converter (106). The DC / DC converter (104), the DC / AC converter (106), and an energy storage battery (108) are connected via a bus. The DC / DC converter (104) is connected to a photovoltaic DC source and performs maximum power point tracking (MPPT) on the input power from the photovoltaic DC source. A load (110) connected to the DC / AC converter (106) has a load power. The energy storage battery (108) has a maximum charging power and a maximum discharging power. The method includes controlling the bus voltage in multiple discontinuous voltage ranges based on different results of a comparison between the photovoltaic maximum power and the load power, as well as the maximum charging power and the maximum discharging power. The multiple discontinuous voltage ranges correspond to different operating states of the inverter (120).

Description

[0001] This application is a divisional application. The original application has the application number 202080031294.8 and the original application date is October 29, 2020. The entire contents of the original application are incorporated herein by reference. Technical Field

[0002] This application relates to power electronics technology, specifically to a method and device for controlling the bus voltage of a photovoltaic system. Background Technology

[0003] New energy technologies such as photovoltaic (PV) power generation have experienced rapid development. PV power generation refers to the conversion of solar radiation energy into electrical energy using the photovoltaic effect of semiconductor materials, for example, by generating direct current (DC) under sunlight through PV modules. PV modules are the core component of a PV power generation system; they are formed by connecting several individual solar cells in series and parallel and then encapsulating them into a single module to convert solar energy into electrical energy. Multiple PV modules connected in series and parallel constitute a solar photovoltaic array.

[0004] In a photovoltaic (PV) power generation system, energy is supplied to the load by a solar photovoltaic array. Influenced by sunlight and environmental factors, the energy supplied by the solar PV array fluctuates. Maximum power point tracking (MPPT) technology can be used to track the output voltage and current to obtain the maximum PV power. On the other hand, when the energy supplied by the solar PV array is excessive, the excess energy can be stored or fed into the AC grid. When there is a lack of solar radiation or the energy supplied by the solar PV array is insufficient, energy storage devices supply energy to the system load. Therefore, PV power generation systems need to control the charging and discharging power of energy storage devices to match load changes.

[0005] In existing technologies, the charging and discharging power of energy storage devices is calculated based on the bus voltage, and the relationships between bus voltage and charging power, as well as between bus voltage and discharging power, are linear. To maximize charging and discharging efficiency, given the often large size of the inverter bus capacitor, the bus voltage needs to be gradually adjusted to a specified range. However, this results in a wide adjustment range and slow dynamic response, leading to low inverter conversion efficiency, reduced system returns, and hindering the rapid adjustment of the bus voltage to control charging and discharging power and match load changes. Summary of the Invention

[0006] The purpose of this application is to provide a bus voltage control method for a photovoltaic system. The photovoltaic system includes a DC / DC converter and a DC / AC converter, wherein the DC / DC converter, the DC / AC converter, and an energy storage battery are connected via a bus. The DC / DC converter is connected to a photovoltaic DC source and performs maximum power point tracking (MPPT) on the input power from the photovoltaic DC source. A load connected to the DC / AC converter has a load power, and the energy storage battery has a maximum charging power and a maximum discharging power. The method includes controlling the bus voltage within multiple discontinuous voltage ranges based on different results of a comparison between the photovoltaic maximum power and the load power, as well as the maximum charging power and the maximum discharging power. These discontinuous voltage ranges correspond to different operating states of the inverter. Thus, by controlling the bus voltage across multiple discontinuous voltage ranges, the inverter's operating state can be switched, which is beneficial for stability and flexibility. In addition, by controlling the bus voltage based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power, rapid power balance under load change scenarios is achieved, as well as rapid response to changes in the charging and discharging power of the energy storage battery. This helps to improve the inverter's conversion efficiency, narrow the inverter's operating range, and thus improve inverter efficiency and system profitability.

[0007] In a first aspect, embodiments of this application provide a bus voltage control method for a photovoltaic system. The photovoltaic system includes a DC / DC converter and a DC / AC converter, wherein the DC / DC converter, the DC / AC converter, and an energy storage battery are connected via a bus. The DC / DC converter is connected to a photovoltaic DC source and performs maximum power point tracking (MPPT) on the input power from the photovoltaic DC source. A load connected to the DC / AC converter has a load power, and the energy storage battery has a maximum charging power and a maximum discharging power. The method includes: controlling the bus voltage within multiple discontinuous voltage ranges based on different results of a comparison between the photovoltaic maximum power and the load power, as well as the maximum charging power and the maximum discharging power. These discontinuous voltage ranges correspond to different operating states of the inverter.

[0008] The technical solution described in the first aspect achieves the switching of inverter operating states by controlling the bus voltage across multiple discontinuous voltage ranges, which is beneficial for stability and flexibility. In addition, by controlling the bus voltage based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power, rapid power balance is achieved under load change scenarios, and rapid response to changes in the charging and discharging power of the energy storage battery is also achieved. This helps to improve inverter conversion efficiency, narrow the inverter operating range, and thus improve inverter efficiency and system benefits.

[0009] According to the first aspect, in one possible implementation, controlling the bus voltage across multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power, includes: controlling the bus voltage to operate in a first voltage range when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is greater than the maximum charging power, wherein the first voltage range corresponds to a reference value for the bus voltage on the BST side, wherein when the inverter operates in a state corresponding to the reference value for the bus voltage on the BST side, the energy storage battery is in a charging state and the charging power of the energy storage battery reaches the maximum charging power, and the photovoltaic output power of the photovoltaic DC source is less than the maximum photovoltaic power, wherein the photovoltaic output power of the photovoltaic DC source is equal to the sum of the load power and the maximum charging power.

[0010] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage within a specific voltage range.

[0011] According to the first aspect, in one possible implementation, controlling the bus voltage across multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power, includes: controlling the bus voltage to operate in a second voltage range when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, wherein the second voltage range corresponds to a reference value for the energy storage battery charging bus voltage, wherein when the inverter operates in a state corresponding to the reference value for the energy storage battery charging bus voltage, the energy storage battery is in a charging state and the charging power of the energy storage battery is less than the maximum charging power, and the photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, wherein the charging power of the energy storage battery is equal to the maximum photovoltaic power minus the load power.

[0012] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage within a specific voltage range.

[0013] According to the first aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is less than the maximum discharging power, the bus voltage is controlled to operate in a third voltage range, wherein the third voltage range corresponds to the INV-side bus voltage reference value. When the inverter operates in a state corresponding to the INV-side bus voltage reference value, the energy storage battery is in a discharging state and the discharge power of the energy storage battery reaches the maximum discharging power, the photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, and the load obtains compensation power from the AC grid, the compensation power being equal to the load power minus the maximum photovoltaic power plus the maximum discharging power.

[0014] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage within a specific voltage range.

[0015] According to the first aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharging power, the bus voltage is controlled to operate in a fourth voltage range, wherein the fourth voltage range corresponds to a reference value for the discharge bus voltage of the energy storage battery. When the inverter operates in a state corresponding to the reference value for the discharge bus voltage of the energy storage battery, the energy storage battery is in a discharging state and the discharge power of the energy storage battery is greater than the maximum discharge power. The photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, and the discharge power of the energy storage battery is equal to the maximum photovoltaic power minus the load power.

[0016] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage within a specific voltage range.

[0017] According to the first aspect, in one possible implementation, controlling the bus voltage across multiple discontinuous voltage ranges based on different results of a comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power, includes: controlling the bus voltage to operate in a first voltage range when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is greater than the maximum charging power, wherein the first voltage range corresponds to a reference value for the bus voltage on the BST side; and controlling the bus voltage to operate in a second voltage range when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, wherein the second voltage range corresponds to a reference value for the charging bus voltage of the energy storage battery. When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum discharge power, the bus voltage is controlled to operate in a third voltage range, where the third voltage range corresponds to the INV side bus voltage reference value. When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is greater than the maximum discharge power, the bus voltage is controlled to operate in a fourth voltage range, where the fourth voltage range corresponds to the energy storage battery discharge bus voltage reference value. The BST side bus voltage reference value is greater than the energy storage battery charging bus voltage reference value, the energy storage battery charging bus voltage reference value is greater than the energy storage battery discharge bus voltage reference value, and the energy storage battery discharge bus voltage reference value is greater than the INV side bus voltage reference value.

[0018] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage in different voltage ranges based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power.

[0019] According to the first aspect, in one possible implementation, a BST-side bus voltage loop control command is generated based on the bus voltage sample value of the inverter and the BST-side bus voltage reference value, for controlling the output power of the inverter to stabilize the bus voltage at the BST-side bus voltage reference value; an INV-side bus voltage loop control command is generated based on the bus voltage sample value and the INV-side bus voltage reference value, for controlling the output power of the inverter to stabilize the bus voltage at the INV-side bus voltage reference value; an energy storage battery charging bus voltage loop control command is generated based on the bus voltage sample value and the energy storage battery charging bus voltage reference value, for controlling the charging power of the energy storage battery to stabilize the bus voltage at the energy storage battery charging bus voltage reference value; and an energy storage battery discharging bus voltage loop control command is generated based on the bus voltage sample value and the energy storage battery discharging bus voltage reference value, for controlling the discharging power of the energy storage battery to stabilize the bus voltage at the energy storage battery discharging bus voltage reference value.

[0020] In this way, corresponding loop control commands can be generated based on the bus voltage sampling value and each voltage reference value.

[0021] According to the first aspect, in one possible implementation, the BST side bus voltage loop control command, the INV side bus voltage loop control command, the energy storage battery charging bus voltage loop control command, and the energy storage battery discharging bus voltage loop control command all employ a PI controller.

[0022] Thus, using a PI controller can improve inverter conversion efficiency, narrow the inverter's operating range, and thereby increase inverter efficiency and system profitability.

[0023] According to the first aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: controlling the bus voltage to operate in a fifth voltage range when the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharging power, or when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power. The fifth voltage range corresponds to a reference value for the charging and discharging bus voltage of the energy storage battery. When the inverter operates in a state corresponding to the reference value for the charging and discharging bus voltage of the energy storage battery, the photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, where the maximum photovoltaic power minus the load power is less than the maximum charging power and greater than the maximum discharging power.

[0024] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage in different voltage ranges based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power.

[0025] According to the first aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is greater than the load power and the difference between the maximum photovoltaic power and the load power is greater than the maximum charging power, controlling the bus voltage to operate in a first voltage range, wherein the first voltage range corresponds to a reference value for the bus voltage on the BST side; and when the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum discharging power, controlling the bus voltage to operate in a... The third voltage range corresponds to the INV side bus voltage reference value. When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharge power, or when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, the bus voltage is controlled to operate in the fifth voltage range. The fifth voltage range corresponds to the energy storage battery charge / discharge bus voltage reference value. The BST side bus voltage reference value is greater than the energy storage battery charge / discharge bus voltage reference value, and the energy storage battery charge / discharge bus voltage reference value is greater than the INV side bus voltage reference value.

[0026] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage in different voltage ranges based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power.

[0027] According to the first aspect, in one possible implementation, a BST-side bus voltage loop control command is generated based on the bus voltage sampling value of the inverter and the BST-side bus voltage reference value, for controlling the output power of the inverter to stabilize the bus voltage at the BST-side bus voltage reference value; an INV-side bus voltage loop control command is generated based on the bus voltage sampling value and the INV-side bus voltage reference value, for controlling the output power of the inverter to stabilize the bus voltage at the INV-side bus voltage reference value; and an energy storage battery charge / discharge bus voltage loop control command is generated based on the bus voltage sampling value and the energy storage battery charge / discharge bus voltage reference value, for controlling the charge / discharge power of the energy storage battery to stabilize the bus voltage at the energy storage battery charge / discharge bus voltage reference value.

[0028] In this way, corresponding loop control commands can be generated based on the bus voltage sampling value and each voltage reference value.

[0029] According to the first aspect, in one possible implementation, the BST side bus voltage loop control command, the INV side bus voltage loop control command, and the energy storage battery charge / discharge bus voltage loop control command all employ a PI controller.

[0030] Thus, using a PI controller can improve inverter conversion efficiency, narrow the inverter's operating range, and thereby increase inverter efficiency and system profitability.

[0031] According to the first aspect, in one possible implementation, the maximum charging power and the maximum discharging power are preset.

[0032] In this way, by pre-setting the maximum charging power and maximum discharging power, the configuration can be adjusted as needed.

[0033] Secondly, embodiments of this application provide a photovoltaic system. The photovoltaic system includes: a DC / DC converter; a DC / AC converter, wherein the DC / DC converter, the DC / AC converter, and an energy storage battery are connected via a bus, the DC / DC converter is connected to a photovoltaic DC source and performs maximum power point tracking (MPPT) on the input power from the photovoltaic DC source, a load connected to the DC / AC converter has a load power, and the energy storage battery has a maximum charging power and a maximum discharging power; and a bus voltage controller. The bus voltage controller is used to: control the bus voltage within multiple discontinuous voltage ranges based on different results of a comparison between the photovoltaic maximum power and the load power, as well as the maximum charging power and the maximum discharging power, wherein the multiple discontinuous voltage ranges correspond to different operating states of the inverter.

[0034] The technical solution described in the second aspect achieves the switching of inverter operating states by controlling the bus voltage across multiple discontinuous voltage ranges, which is beneficial for stability and flexibility. In addition, by controlling the bus voltage based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power, rapid power balance is achieved under load change scenarios, and rapid response to changes in the charging and discharging power of the energy storage battery is also achieved. This helps to improve inverter conversion efficiency, narrow the inverter operating range, and thus improve inverter efficiency and system benefits.

[0035] According to the second aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is greater than the maximum charging power, the bus voltage is controlled to operate in a first voltage range, wherein the first voltage range corresponds to a reference value for the bus voltage on the BST side, wherein when the inverter operates in a state corresponding to the reference value for the bus voltage on the BST side, the energy storage battery is in a charging state and the charging power of the energy storage battery reaches the maximum charging power, and the photovoltaic output power of the photovoltaic DC source is less than the maximum photovoltaic power, wherein the photovoltaic output power of the photovoltaic DC source is equal to the sum of the load power and the maximum charging power.

[0036] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage within a specific voltage range.

[0037] According to the second aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, the bus voltage is controlled to operate in a second voltage range, wherein the second voltage range corresponds to a reference value for the energy storage battery charging bus voltage; wherein when the inverter operates in a state corresponding to the reference value for the energy storage battery charging bus voltage, the energy storage battery is in a charging state and the charging power of the energy storage battery is less than the maximum charging power, and the photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power; wherein the charging power of the energy storage battery is equal to the maximum photovoltaic power minus the load power.

[0038] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage within a specific voltage range.

[0039] According to the second aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is less than the maximum discharging power, the bus voltage is controlled to operate in a third voltage range, wherein the third voltage range corresponds to the INV-side bus voltage reference value. When the inverter operates in a state corresponding to the INV-side bus voltage reference value, the energy storage battery is in a discharging state and the discharging power of the energy storage battery reaches the maximum discharging power, the photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, and the load obtains compensation power from the AC grid, the compensation power being equal to the load power minus the maximum photovoltaic power plus the maximum discharging power.

[0040] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage within a specific voltage range.

[0041] According to the second aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharging power, the bus voltage is controlled to operate in a fourth voltage range, wherein the fourth voltage range corresponds to a reference value for the discharge bus voltage of the energy storage battery. When the inverter operates in a state corresponding to the reference value for the discharge bus voltage of the energy storage battery, the energy storage battery is in a discharging state and the discharge power of the energy storage battery is greater than the maximum discharge power. The photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, and the discharge power of the energy storage battery is equal to the maximum photovoltaic power minus the load power.

[0042] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage within a specific voltage range.

[0043] According to the second aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is greater than the maximum charging power, the bus voltage is controlled to operate in a first voltage range, where the first voltage range corresponds to a reference value for the BST-side bus voltage; when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, the bus voltage is controlled to operate in a second voltage range, where the second voltage range corresponds to a reference value for the energy storage battery charging bus voltage. When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum discharge power, the bus voltage is controlled to operate in a third voltage range, where the third voltage range corresponds to the INV side bus voltage reference value. When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is greater than the maximum discharge power, the bus voltage is controlled to operate in a fourth voltage range, where the fourth voltage range corresponds to the energy storage battery discharge bus voltage reference value. The BST side bus voltage reference value is greater than the energy storage battery charging bus voltage reference value, the energy storage battery charging bus voltage reference value is greater than the energy storage battery discharge bus voltage reference value, and the energy storage battery discharge bus voltage reference value is greater than the INV side bus voltage reference value.

[0044] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage in different voltage ranges based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power.

[0045] According to the second aspect, in one possible implementation, the bus voltage controller is further configured to: generate a BST-side bus voltage loop control command based on the bus voltage sample value of the inverter and the BST-side bus voltage reference value, for controlling the output power of the inverter to stabilize the bus voltage at the BST-side bus voltage reference value; generate an INV-side bus voltage loop control command based on the bus voltage sample value and the INV-side bus voltage reference value, for controlling the output power of the inverter to stabilize the bus voltage at the INV-side bus voltage reference value; generate an energy storage battery charging bus voltage loop control command based on the bus voltage sample value and the energy storage battery charging bus voltage reference value, for controlling the charging power of the energy storage battery to stabilize the bus voltage at the energy storage battery charging bus voltage reference value; and generate an energy storage battery discharging bus voltage loop control command based on the bus voltage sample value and the energy storage battery discharging bus voltage reference value, for controlling the discharging power of the energy storage battery to stabilize the bus voltage at the energy storage battery discharging bus voltage reference value.

[0046] In this way, corresponding loop control commands can be generated based on the bus voltage sampling value and each voltage reference value.

[0047] According to the second aspect, in one possible implementation, the BST side bus voltage loop control command, the INV side bus voltage loop control command, the energy storage battery charging bus voltage loop control command, and the energy storage battery discharging bus voltage loop control command all employ a PI controller.

[0048] Thus, using a PI controller can improve inverter conversion efficiency, narrow the inverter's operating range, and thereby increase inverter efficiency and system profitability.

[0049] According to the second aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: controlling the bus voltage to operate in a fifth voltage range when the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharging power, or when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power. The fifth voltage range corresponds to a reference value for the charging and discharging bus voltage of the energy storage battery. When the inverter operates in a state corresponding to the reference value for the charging and discharging bus voltage of the energy storage battery, the photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, where the maximum photovoltaic power minus the load power is less than the maximum charging power and greater than the maximum discharging power.

[0050] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage in different voltage ranges based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power.

[0051] According to the second aspect, in one possible implementation, the bus voltage is controlled in multiple discontinuous voltage ranges based on different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power. This includes: when the maximum photovoltaic power is greater than the load power and the difference between the maximum photovoltaic power and the load power is greater than the maximum charging power, controlling the bus voltage to operate in a first voltage range, wherein the first voltage range corresponds to a reference value for the bus voltage on the BST side; and when the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum discharging power, controlling the bus voltage to operate in a... The third voltage range corresponds to the INV side bus voltage reference value. When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharge power, or when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, the bus voltage is controlled to operate in the fifth voltage range. The fifth voltage range corresponds to the energy storage battery charge / discharge bus voltage reference value. The BST side bus voltage reference value is greater than the energy storage battery charge / discharge bus voltage reference value, and the energy storage battery charge / discharge bus voltage reference value is greater than the INV side bus voltage reference value.

[0052] In this way, the inverter can be switched to the corresponding operating state by controlling the bus voltage in different voltage ranges based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power.

[0053] According to the second aspect, in one possible implementation, the bus voltage controller is further configured to: generate a BST-side bus voltage loop control command based on the bus voltage sample value of the inverter and the BST-side bus voltage reference value, for controlling the output power of the inverter to stabilize the bus voltage at the BST-side bus voltage reference value; generate an INV-side bus voltage loop control command based on the bus voltage sample value and the INV-side bus voltage reference value, for controlling the output power of the inverter to stabilize the bus voltage at the INV-side bus voltage reference value; and generate an energy storage battery charging / discharging bus voltage loop control command based on the bus voltage sample value and the energy storage battery charging / discharging bus voltage reference value, for controlling the charging / discharging power of the energy storage battery to stabilize the bus voltage at the energy storage battery charging / discharging bus voltage reference value.

[0054] In this way, corresponding loop control commands can be generated based on the bus voltage sampling value and each voltage reference value.

[0055] According to the second aspect, in one possible implementation, the BST side bus voltage loop control command, the INV side bus voltage loop control command, and the energy storage battery charge / discharge bus voltage loop control command all employ a PI controller.

[0056] Thus, using a PI controller can improve inverter conversion efficiency, narrow the inverter's operating range, and thereby increase inverter efficiency and system profitability.

[0057] According to the second aspect, in one possible implementation, the maximum charging power and the maximum discharging power are preset.

[0058] In this way, by pre-setting the maximum charging power and maximum discharging power, the configuration can be adjusted as needed. Attached Figure Description

[0059] To illustrate the technical solutions in the embodiments or background art of this application, the accompanying drawings used in the embodiments or background art of this application will be described below.

[0060] Figure 1 This is a structural block diagram of a photovoltaic power generation system including an inverter bus voltage controller, provided in an embodiment of this application.

[0061] Figure 2This is a flowchart illustrating the inverter bus voltage control method of the first implementation provided in this application embodiment.

[0062] Figure 3 The embodiments provided in this application are based on Figure 2 The diagram shows a method for controlling the inverter bus voltage.

[0063] Figure 4 This is a flowchart illustrating the inverter bus voltage control method according to the second implementation method provided in this application embodiment.

[0064] Figure 5 The embodiments provided in this application are based on Figure 4 The diagram shows a method for controlling the inverter bus voltage. Detailed Implementation

[0065] This application provides a method for controlling the bus voltage of a photovoltaic system. The photovoltaic system includes a DC / DC converter and a DC / AC converter, wherein the DC / DC converter, the DC / AC converter, and an energy storage battery are connected via a bus. The DC / DC converter is connected to a photovoltaic DC source and performs maximum power point tracking (MPPT) on the input power from the photovoltaic DC source. A load connected to the DC / AC converter has a load power, and the energy storage battery has a maximum charging power and a maximum discharging power. The method includes controlling the bus voltage within multiple discontinuous voltage ranges based on different results of a comparison between the photovoltaic maximum power and the load power, as well as the maximum charging power and the maximum discharging power. These discontinuous voltage ranges correspond to different operating states of the inverter. Thus, by controlling the bus voltage across multiple discontinuous voltage ranges, the inverter's operating state can be switched, which is beneficial for stability and flexibility. In addition, by controlling the bus voltage based on the different results of the comparison between the maximum photovoltaic power and the load power, as well as the maximum charging power and the maximum discharging power, rapid power balance under load change scenarios is achieved, as well as rapid response to changes in the charging and discharging power of the energy storage battery. This helps to improve the inverter's conversion efficiency, narrow the inverter's operating range, and thus improve inverter efficiency and system profitability.

[0066] The embodiments of this application can be used in the following application scenarios, including but not limited to photovoltaic inverters, photovoltaic power generation systems, and other application scenarios that require rapid load power balancing and rapid response of energy storage batteries.

[0067] The embodiments of this application can be adjusted and improved according to specific application environments, and no specific limitations are made here.

[0068] To enable those skilled in the art to better understand the present application, the embodiments of the present application will be described below with reference to the accompanying drawings.

[0069] Please see Figure 1 , Figure 1 This is a structural block diagram of a photovoltaic power generation system including an inverter bus voltage controller, provided in an embodiment of this application. Figure 1 As shown, the photovoltaic power generation system 100 includes a solar photovoltaic array 102, an inverter 120, an energy storage battery 108, a load 110, and an electricity meter 112. The solar photovoltaic array 102 is composed of multiple photovoltaic modules connected in series and parallel. Each photovoltaic module converts solar radiation energy into direct current (DC) based on the photovoltaic effect. The inverter 120 includes a DC / DC converter 104 and a DC / AC converter 106. The DC / DC converter 104 is located on the BST side of the inverter 120, corresponding to the DC-DC conversion section of the inverter 120, while the DC / AC converter 106 is located on the INV side of the inverter 120, corresponding to the DC-AC conversion section of the inverter 120. It should be understood that the DC / DC converter 104 and the DC / AC converter 106 can be integrated into one device or divided into multiple devices. This application does not limit the specific physical form of the DC / DC converter and DC / AC converter. That is, the inverter can be a single device containing at least one DC / DC converter and at least one DC / AC converter, or it can consist of multiple devices, with one DC / DC converter as one device and another DC / AC converter as another, where at least one DC / DC converter and at least one DC / AC converter together constitute the inverter. A specific embodiment of this application uses an inverter composed of a DC / DC converter and a DC / AC converter. These can be adjusted and improved according to actual circumstances, and this application does not impose specific limitations on them. In some embodiments, the DC / DC converter 104 can function entirely as a photovoltaic power optimizer, as a standalone optimizer product, connected between the photovoltaic DC source (including photovoltaic panels and photovoltaic arrays) and the inverter.

[0070] The DC input side of DC / DC converter 104 is connected to solar photovoltaic array 102, converting the DC power output from solar photovoltaic array 102 into suitable DC power to meet the operating requirements of DC / AC converter 106. Simultaneously, it executes a maximum power point tracking (MPPT) control strategy on the DC power provided by solar photovoltaic array 102 to obtain the maximum photovoltaic power of solar photovoltaic array 102, which is then output from the DC output side of DC / DC converter 104. The DC output side of DC / DC converter 104 is connected to the DC input side of DC / AC converter 106, which converts the received DC power into AC power and outputs it from its AC output side. The coupling point between the DC output side of DC / DC converter 104 and the DC input side of DC / AC converter 106 is the bus (hereinafter referred to as BUS). Energy storage battery 108, as an external energy storage device, can be connected to the bus of inverter 120, meaning that energy storage battery 108 can be connected between DC / DC converter 104 and DC / AC converter 106. Inverter 120 outputs electrical energy to load 110, which is then connected to the AC grid 114 via meter 112. Load 110 can be powered by inverter 120, AC grid 114, or both simultaneously. Meter 112 detects the power obtained from AC grid 114. When photovoltaic power generation system 100 is configured for zero-power grid connection, it indicates that photovoltaic power generation system 100 does not feed power back to AC grid 114, and the meter reading is greater than or equal to zero.

[0071] Please continue reading. Figure 1 The DC / DC converter 104, DC / AC converter 106, and energy storage battery 108 are coupled to the bus of the inverter 120. It should be understood that the DC bus refers to the positive and negative terminals connected between the DC / DC converter 104 and the DC / AC converter 106, the DC bus capacitor refers to the capacitor located between the DC buses, and the DC bus voltage refers to the voltage between the positive and negative terminals of the DC bus, that is, the voltage applied across the DC bus capacitor. Figure 1 The lines shown indicate the direction of electrical energy flow, and the labels are explained below: P PV This represents the photovoltaic output power, which is the actual output power of the solar photovoltaic array 102. PV_MPP (Not shown) represents the maximum photovoltaic power, which is the maximum power that the solar photovoltaic array 102 can output under the MPPT control strategy, and is also the maximum photovoltaic power obtained by the DC / DC converter 104 based on MPPT. BAT The charging and discharging power of the energy storage battery 108 can be uniformly represented by a value with positive and negative signs, where positive indicates charging and negative indicates discharging. P INVThis represents the output power of inverter 120, which is also the AC output power provided by DC / AC converter 106. LOAD This indicates the load power of load 110. P Meter The meter 112 indicates the power drawn from the AC grid, which can be uniformly represented by a positive or negative value, where a positive value indicates power drawn from the AC grid and a negative value indicates power fed back to the AC grid. The inverter 120 receives photovoltaic output power P from the solar photovoltaic array 102. PV and output power P INV When the photovoltaic power generation system 100 is configured for zero-power grid connection, the meter power P Meter If the value is greater than or equal to 0, no power is fed into the grid. This is based on the maximum photovoltaic power P. PV_MPP Load power P LOAD The comparison between the maximum charging power and the maximum discharging power of the energy storage battery 108 can be used to implement a loop competition strategy for power matching. The inverter 120 also includes a bus voltage controller 122 to implement the loop competition strategy. The bus voltage controller 122 can be integrated into the inverter 120 or configured separately. The bus voltage controller 122 is communicatively connected to the energy storage battery 108 to control its charging and discharging power, and also possesses the necessary hardware to acquire bus voltage sampling values. It should be understood that the bus voltage controller 122 has a basic structure of processor and memory to perform the required detection and control functions, and stores program code for the loop competition strategy, or has the circuitry and components required to implement the control functions. The specific structure and function of the bus voltage controller 122 can be set or improved according to specific application scenarios, and are not specifically limited here.

[0072] Please continue reading. Figure 1Changes in load will cause changes in load power PLOAD, and changes in conditions such as sunlight will cause changes in photovoltaic output power PPV. Therefore, inverter 120 needs to control the charging and discharging power of energy storage battery 108 based on the power data of meter 112 to match these changes. Inverter 120 also includes bus voltage controller 122 for performing MPPT of solar photovoltaic array to obtain photovoltaic maximum input power PPV_MPP and output power PINV. Bus voltage controller 122 is also communicatively connected to energy storage battery 108 to control the charging and discharging power PBAT of energy storage battery 108. Bus voltage controller 122 acquires the bus voltage sample value of inverter 120 and performs loop contention strategy to determine the control of bus voltage and perform energy management accordingly. It should be understood that bus voltage controller 122 has a processor and memory architecture to perform the required detection and control functions, and stores program code for loop contention strategy, or has the circuitry and components required to implement control functions. The bus voltage controller 122 can acquire the bus voltage sample value and detect the output power PINV of the inverter 120 by means of appropriate existing technologies, which are not specifically limited here.

[0073] In some exemplary embodiments, the solar photovoltaic array 102 can be any DC source capable of obtaining maximum power according to the MPPT control strategy. These can be adjusted and improved according to the specific application environment, and are not specifically limited here.

[0074] In some exemplary embodiments, the DC / DC converter 104 achieves MPPT control of the DC input provided by the solar photovoltaic array 102 through a fixed voltage method, a perturbation-observation method, or an incremental conductance method, thereby obtaining the maximum photovoltaic power. In some exemplary embodiments, the DC-DC converter 104 can use pulse width modulation and may include necessary components such as control chips and inductors and capacitors, and can be a boost, buck, or buck-boost converter. These can be adjusted and improved according to specific application environments, and are not specifically limited here.

[0075] In some exemplary embodiments, the DC / AC converter 106 may be a single-phase inverter, a three-phase inverter, or other types of inverter circuits capable of converting direct current to alternating current. These can be adjusted and improved according to specific application environments, and are not specifically limited here.

[0076] Please see Figure 2 , Figure 2 This is a flowchart illustrating the inverter bus voltage control method of the first implementation provided in this application. Figure 2 As shown, the control method includes the following steps.

[0077] Step S200: Generate a BST-side bus voltage loop control command based on the inverter's bus voltage sampling value and the BST-side bus voltage reference value, which is used to control the inverter's output power so that the bus voltage is stabilized at the BST-side bus voltage reference value.

[0078] The inverter includes a DC / DC converter and a DC / AC converter. The DC input side of the DC / AC converter is connected to the solar photovoltaic array, and the coupling point between the DC output side and the DC input side of the DC / AC converter is the bus. The DC input side of the DC / AC converter, connected to the solar photovoltaic array, converts the DC power output from the array into suitable DC power to meet the operating requirements of the DC / AC converter. Simultaneously, it executes a maximum power point tracking (MPPT) control strategy on the DC power provided by the solar photovoltaic array to obtain the maximum photovoltaic power of the array. An energy storage battery, as an external energy storage device, can be connected to the inverter bus, meaning the battery can be connected between the DC / DC converter and the DC / AC converter. It should be understood that the solar photovoltaic array can be any DC source capable of obtaining maximum power according to the MPPT control strategy. These can be adjusted and improved according to the specific application environment, and no specific limitations are made here.

[0079] The generation of the BST side bus voltage loop control command can be in the form of a proportional-integral controller (PI) and according to the following formulas (1) and (2).

[0080] (1) (2) Where t represents time, UREF_BST represents the reference value of the bus voltage on the BST side, UBUS(t) represents the sampled value of the bus voltage, e(t) represents the difference between the reference value and the sampled value of the bus voltage on the BST side, PBST(t) represents the output power of the inverter under the control command of the BST side bus voltage loop, thereby stabilizing the bus voltage at the reference value UREF_BST on the BST side, Kp represents the proportional regulation coefficient, and Ki represents the integral regulation coefficient. It should be understood that stabilizing the bus voltage at the reference value on the BST side means that bus voltage fluctuations, jitter, ripple, or multiple different voltage values ​​are limited to a certain range. Each range has a measurable difference between its upper or lower limit and the lower or upper limits of other ranges, giving each range a clear definition and boundary. Bus voltage sampling can be performed by directly detecting the voltage, measuring it through a sampling resistor, or using other suitable techniques. Furthermore, by using a PI controller, the bus voltage can be stabilized at the reference value UREF_BST on the BST side, which helps improve inverter conversion efficiency, narrow the inverter operating range, and thus improve inverter efficiency and system profitability. It should be understood that the embodiments of this application do not limit the controller to a PI controller; other controllers can be used as needed.

[0081] Step S202: Generate an INV-side bus voltage loop control command based on the bus voltage sample value and the INV-side bus voltage reference value, which is used to control the output power of the inverter so that the bus voltage is stabilized at the INV-side bus voltage reference value.

[0082] Among them, the generation of the INV side bus voltage loop control command can be in the form of a PI controller, and according to the following formulas (3) and (4).

[0083] (3) (4) Where t represents time, UREF_INV represents the reference value of the INV-side bus voltage, UBUS(t) represents the sampled value of the bus voltage, e(t) represents the difference between the reference value and the sampled value of the INV-side bus voltage, PINV(t) represents the output power of the inverter under the loop control command of the INV-side bus voltage, thereby stabilizing the bus voltage at the reference value UREF_INV of the INV-side bus voltage, Kp represents the proportional regulation coefficient, and Ki represents the integral regulation coefficient. It should be understood that the bus voltage stabilizing at the reference value UREF_INV of the INV-side bus voltage means that the bus voltage fluctuation or ripple is less than a threshold, or that the average or effective value of the bus voltage remains constant to a certain extent. Sampling the bus voltage can be achieved by directly detecting the voltage, measuring it through a sampling resistor, or using other suitable techniques. Furthermore, by using a PI controller, the bus voltage can be stabilized at the reference value UREF_INV of the INV-side bus voltage, which is beneficial for improving inverter conversion efficiency, narrowing the inverter operating range, and thus improving inverter efficiency and system benefits. It should be understood that the embodiments of this application do not limit the controller to a PI controller, and other controllers may be used as needed.

[0084] Step S204: Generate a loop control command for the energy storage battery charging bus voltage based on the sampled bus voltage value and the reference value of the energy storage battery charging bus voltage, which is used to control the charging power of the energy storage battery so that the bus voltage is stabilized at the reference value of the energy storage battery charging bus voltage.

[0085] Among them, the generation of the energy storage battery charging bus voltage loop control command can be in the form of a PI controller, and according to the following formulas (5) and (6).

[0086] (5) (6) Where t represents time, UREF_CHARGE represents the reference value of the charging bus voltage of the energy storage battery, UBUS(t) represents the sampled value of the bus voltage, e(t) represents the difference between the reference value and the sampled value of the charging bus voltage of the energy storage battery, PBAT_CHARGE(t) represents the charging power of the energy storage battery under the loop control command of the charging bus voltage of the energy storage battery, thereby stabilizing the bus voltage at the reference value UREF_CHARGE of the charging bus voltage of the energy storage battery, Kp represents the proportional adjustment coefficient, and Ki represents the integral adjustment coefficient. It should be understood that the bus voltage stabilizing at the reference value UREF_CHARGE of the charging bus voltage of the energy storage battery means that the fluctuation or ripple of the bus voltage is less than the threshold, or that the average value or effective value of the bus voltage remains constant to a certain extent. The bus voltage can be sampled by directly detecting the voltage, measuring it through a sampling resistor, or through other suitable technical means. Furthermore, by using a PI controller, the bus voltage can be stabilized at the reference value UREF_CHARGE for the energy storage battery charging bus voltage, which helps improve inverter conversion efficiency, narrow the inverter operating range, and thus improve inverter efficiency and system profitability. It should be understood that the embodiments of this application do not limit the controller to a PI controller; other controllers can be used as needed.

[0087] Step S206: Generate a loop control command for the energy storage battery discharge bus voltage based on the sampled bus voltage value and the reference value of the energy storage battery discharge bus voltage, which is used to control the discharge power of the energy storage battery so that the bus voltage is stabilized at the reference value of the energy storage battery discharge bus voltage.

[0088] Among them, the generation of the energy storage battery discharge bus voltage loop control command can be in the form of a PI controller, and according to the following formulas (7) and (8).

[0089] (7) (8) Where t represents time, UREF_DISCHARGE represents the reference value of the energy storage battery discharge bus voltage, UBUS(t) represents the sampled value of the bus voltage, e(t) represents the difference between the reference value and the sampled value of the energy storage battery discharge bus voltage, PBAT_DISCHARGE(t) represents the discharge power of the energy storage battery under the loop control command of the energy storage battery discharge bus voltage, thereby stabilizing the bus voltage at the reference value UREF_DISCHARGE, Kp represents the proportional adjustment coefficient, and Ki represents the integral adjustment coefficient. It should be understood that the bus voltage stabilizing at the reference value UREF_DISCHARGE means that the bus voltage fluctuation or ripple is less than a threshold, or that the average or effective value of the bus voltage remains constant to a certain extent. The bus voltage can be sampled by directly detecting the voltage, measuring it through a sampling resistor, or using other suitable technical means. Furthermore, by using a PI controller, the bus voltage can be stabilized at the reference value UREF_DISCHARGE for the energy storage battery discharge bus voltage, which helps improve inverter conversion efficiency, narrow the inverter operating range, and thus improve inverter efficiency and system profitability. It should be understood that the embodiments of this application do not limit the controller to a PI controller; other controllers can be used as needed.

[0090] Step S208: Based on the comparison results between the maximum photovoltaic power, load power, maximum charging power and maximum discharging power of the energy storage battery, select to execute the BST side bus voltage loop control command, the INV side bus voltage loop control command, the energy storage battery charging bus voltage loop control command, or the energy storage battery discharging bus voltage loop control command.

[0091] The energy storage battery has a maximum charging power, representing the maximum charging power of the energy storage battery when it is charging, and a maximum discharging power, representing the maximum discharging power of the energy storage battery when it is discharging. The maximum charging power and the maximum discharging power are preset, for example, based on the application scenario of the inverter, or based on the design limits or factory settings of the energy storage battery. The loop competition strategy in step S208 can be implemented by the inverter's controller or control circuit. The aforementioned loop control commands can also be generated by this controller. Thus, the control of the bus voltage is determined by the result of the loop competition, and corresponding energy management is implemented, such as controlling the inverter's output power or the charging and discharging power of the energy storage battery based on the loop competition result. Furthermore, the load power change caused by sudden load changes is taken into account, thus enabling rapid power balance under sudden load changes. Meanwhile, compared to the response speed limited by the bus voltage itself and the bus capacitor, the loop competition strategy directly controls the relevant power and stabilizes the bus voltage at the reference voltage value through the loop competition result. This enables a rapid response to changes in the charging and discharging power of the energy storage battery, which helps to improve the inverter conversion efficiency, narrow the inverter operating range, and thus improve inverter efficiency and system benefits.

[0092] Specifically, in step S208, the loop competition strategy can be expressed as making a series of judgments based on the maximum photovoltaic power, load power, maximum charging power, and maximum discharging power to select the loop control command to be executed: When the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is greater than the maximum charging power of the energy storage battery, the BST side bus voltage loop control command is executed. When the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power of the energy storage battery, the energy storage battery charging bus voltage loop control command is executed. When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is less than the maximum discharge power of the energy storage battery, the INV side bus voltage loop control command is executed. When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharge power of the energy storage battery, the energy storage battery discharge bus voltage loop control command is executed.

[0093] In step S208, when the BST side bus voltage loop control command is executed, the energy storage battery is in a charging state and the charging power of the energy storage battery reaches the maximum charging power. The photovoltaic output power is less than the maximum photovoltaic power, wherein the photovoltaic output power is equal to the sum of the load power and the maximum charging power of the energy storage battery. Combining steps S200 and S208, the photovoltaic output power is calculated according to the following formulas (9) and (10).

[0094] (9) (10) Where PLOAD represents load power, PBAT_CHARGE_MAX represents maximum charging power, PPV_MPP represents maximum photovoltaic power, and PPV represents photovoltaic output power under the BST side bus voltage loop control command. Thus, when the maximum photovoltaic power still has surplus after meeting the load power supply and maximum battery charging power requirements, and the system requires zero-power grid connection (i.e., excess energy is not allowed to be fed into the AC grid), the DC source output power can be less than the maximum photovoltaic power, only meeting the load power supply and maximum battery charging power requirements, thereby achieving rapid power balance and improving system efficiency.

[0095] In step S208, when the INV-side bus voltage loop control command is executed, the energy storage battery is in a discharging state and the discharge power of the energy storage battery reaches the maximum discharge power, the photovoltaic output power reaches the maximum photovoltaic power, and the inverter obtains compensation power from the power grid connected to the inverter. The compensation power is equal to the load power minus the maximum photovoltaic power plus the maximum discharge power. Combining steps S202 and S208, the compensation power is calculated according to the following formulas (11) and (12).

[0096] (11) (12) Where PMeter represents the compensation power, PLOAD represents the load power, PPV_MPP represents the maximum photovoltaic power, PPV represents the photovoltaic output power, and PBAT_DISCHARGE_MAX represents the maximum discharge power. Thus, when the sum of the maximum photovoltaic power and the maximum discharge power of the energy storage battery still does not meet the load's power supply requirements, the compensation power is provided by the AC grid. In this case, the DC source provides the maximum photovoltaic power, the energy storage battery discharges at its maximum discharge power, and obtains the corresponding compensation power from the AC grid, thereby meeting the load power requirements and achieving rapid power balance and improved system efficiency.

[0097] In step S208, when the energy storage battery charging bus voltage loop control command is selected to be executed, the energy storage battery is in a charging state and the charging power of the energy storage battery is less than the maximum charging power. The photovoltaic output power reaches the maximum photovoltaic power, and the charging power is equal to the maximum photovoltaic power minus the load power. Combining steps S204 and S208, the charging power is calculated according to the following formulas (13) and (14).

[0098] (13) (14) Here, PBAT_CHARGE represents charging power, PPV represents photovoltaic output power, PLOAD represents load power, and PPV_MPP represents maximum photovoltaic power. Thus, after the maximum photovoltaic power meets the load's power requirements, the remaining power is used to charge the energy storage battery. By controlling the charging power of the energy storage battery to prioritize meeting the load's power needs, rapid power balancing and improved system efficiency can be achieved.

[0099] In step S208, when the energy storage battery discharge bus voltage loop control command is selected to be executed, the energy storage battery is in a discharge state and the discharge power of the energy storage battery is greater than the maximum discharge power, the photovoltaic output power reaches the maximum photovoltaic power, and the discharge power is equal to the maximum photovoltaic power minus the load power. Combining steps S206 and S208, the discharge power is calculated according to the following formulas (15) and (16).

[0100] (15) (16) Here, PBAT_DISCHARGE represents the discharge power, PPV represents the photovoltaic output power, PLOAD represents the load power, and PPV_MPP represents the maximum photovoltaic power. Thus, when the maximum photovoltaic power cannot meet the load power requirements, the compensation power is provided by the discharge of the energy storage battery. By controlling the discharge power of the energy storage battery to prioritize meeting the load power needs, rapid power balance and improved system efficiency can be achieved.

[0101] It should be understood that the order of steps S200, S202, S204, and S206 can be adjusted or rearranged. This application embodiment does not limit the order of these four steps; steps S200 to S206 can be performed simultaneously and can be rearranged in any order. This application embodiment and its appendix... Figure 2 Steps S200 to S206 are described one by one for the sake of convenience only.

[0102] Please see Figure 3 , Figure 3 The embodiments provided in this application are based on Figure 2 The diagram illustrates the method for controlling the inverter bus voltage. (See attached diagram.) Figure 3 As shown, the Y-axis represents the charging and discharging power of the energy storage battery. The positive direction, i.e., the upper half of the Y-axis, represents the charging power, while the negative direction, i.e., the lower half of the Y-axis, represents the discharging power. The maximum charging and discharging power is 3kW / -3kW. The X-axis represents the corresponding bus voltage and various voltage reference values. Specifically, the BST side bus voltage reference value is marked as F, corresponding to 430V, also known as the first voltage range; the energy storage battery charging bus voltage reference value is marked as C, corresponding to 410V, also known as the second voltage range; the energy storage battery discharging bus voltage reference value is marked as D, corresponding to 390V, also known as the third voltage range; and the INV side bus voltage reference value is marked as G, corresponding to 370V, also known as the fourth voltage range. The voltage range is simplified to a single voltage value, with a 20V difference between each value, giving each range a clear definition and boundary. Additionally, the median voltage is marked as E, corresponding to 400V. Figure 3 As shown, the reference value of the BST side bus voltage is greater than the reference value of the energy storage battery charging bus voltage, the reference value of the energy storage battery charging bus voltage is greater than the reference value of the energy storage battery discharging bus voltage, and the reference value of the energy storage battery discharging bus voltage is greater than the reference value of the INV side bus voltage. Thus, combined with... Figure 2 and Figure 3 By setting the values ​​of each voltage reference, we can obtain... Figure 3 The diagram shows the relationship between the bus voltage and the charging / discharging power. Thus, the energy storage battery has a stable charging power between C and F, and a stable discharging power between G and D. Furthermore, by directly controlling the relevant power and stabilizing the bus voltage at the reference voltage value, a rapid response to changes in the charging / discharging power of the energy storage battery is achieved. This helps improve the inverter's conversion efficiency, narrows the inverter's operating range, and ultimately increases inverter efficiency and system profitability.

[0103] In some exemplary embodiments, the maximum charging and discharging power can be other values, such as 4kW / -4kW or 5kW / -5kW. These can be adjusted and improved according to the specific application environment, and are not specifically limited here.

[0104] In some exemplary embodiments, the voltage reference values ​​may be other values. These can be adjusted and improved according to the specific application environment, and are not specifically limited here.

[0105] Figure 4 This is a flowchart illustrating the inverter bus voltage control method according to the second implementation of this application. Figure 4As shown, the control method includes the following steps.

[0106] Step S400: Generate a BST-side bus voltage loop control command based on the bus voltage sampling value of the inverter and the BST-side bus voltage reference value, which is used to control the output power of the inverter so that the bus voltage is stabilized at the BST-side bus voltage reference value.

[0107] The inverter includes a DC / DC converter and a DC / AC converter. The DC input side of the DC / AC converter is connected to the solar photovoltaic array. The coupling point between the DC output side and the DC input side of the DC / AC converter is the bus, and the bus voltage is referred to as the bus voltage or bus voltage sample value. The DC input side of the DC / AC converter is connected to the solar photovoltaic array, converting the DC power output from the solar photovoltaic array into suitable DC power to meet the operating requirements of the DC / AC converter. Simultaneously, it executes a maximum power point tracking (MPPT) control strategy on the DC power provided by the solar photovoltaic array to obtain the maximum photovoltaic power of the array. An energy storage battery, as an external energy storage device, can be connected to the inverter bus, meaning the energy storage battery can be connected between the DC / DC converter and the DC / AC converter. It should be understood that the solar photovoltaic array can be any DC source capable of obtaining maximum power according to the MPPT control strategy. These can be adjusted and improved according to the specific application environment, and no specific limitations are made here.

[0108] For the generation of the BST side bus voltage loop control command, please refer to step S200, which will not be repeated here.

[0109] Step S402: Generate an INV-side bus voltage loop control command based on the bus voltage sample value and the INV-side bus voltage reference value, which is used to control the output power of the inverter so that the bus voltage is stabilized at the INV-side bus voltage reference value.

[0110] For the generation of the INV side bus voltage loop control command, please refer to step S202, which will not be repeated here.

[0111] Step S404: Generate a loop control command for the charging and discharging bus voltage of the energy storage battery based on the sampled bus voltage value and the reference value of the charging and discharging bus voltage of the energy storage battery. This command is used to control the charging and discharging power of the energy storage battery so that the bus voltage is stabilized at the reference value of the charging and discharging bus voltage of the energy storage battery.

[0112] Among them, the generation of the energy storage battery charging and discharging bus voltage loop control command can be in the form of a PI controller, and according to the following formulas (17) and (18).

[0113] (17) (18) Where t represents time, U REF_BAT U represents the reference value of the charging and discharging bus voltage of the energy storage battery, or the reference value of the bus voltage on the energy storage battery side. BUS (t) represents the sampled value of the bus voltage, e(t) represents the difference between the reference value of the charging and discharging bus voltage of the energy storage battery and the sampled value of the bus voltage, and P BAT (t) represents the charging and discharging power of the energy storage battery under the loop control command of the energy storage battery charging and discharging bus voltage, thereby stabilizing the bus voltage at the reference value U of the energy storage battery charging and discharging bus voltage. REF_BAT K p K represents the proportional adjustment coefficient. i This represents the integral adjustment coefficient. It should be understood that the bus voltage is stabilized at the reference value U of the energy storage battery charging / discharging bus voltage. REF_BAT This refers to the bus voltage fluctuation or ripple being less than a threshold, or the average or effective value of the bus voltage remaining relatively constant. Sampling the bus voltage can be achieved through direct voltage detection, measurement using a sampling resistor, or other suitable techniques. Furthermore, a PI controller can stabilize the bus voltage at the energy storage battery charging / discharging bus voltage reference value U. REF_BAT This is beneficial for improving inverter conversion efficiency, narrowing the inverter's operating range, and thus improving inverter efficiency and system profitability. It should be understood that the embodiments of this application do not limit the controller to a PI controller; other controllers can be used as needed.

[0114] Step S406: Based on the comparison results between the maximum photovoltaic power, load power, maximum charging power and maximum discharging power of the energy storage battery, select to execute the BST side bus voltage loop control command, the INV side bus voltage loop control command, or the energy storage battery charging and discharging bus voltage loop control command.

[0115] The energy storage battery has a maximum charging power, representing the maximum charging power of the energy storage battery when it is charging, and a maximum discharging power, representing the maximum discharging power of the energy storage battery when it is discharging. The maximum charging power and the maximum discharging power are preset, for example, based on the application scenario of the inverter, or based on the design limits or factory settings of the energy storage battery. The loop competition strategy in step S406 can be implemented by the inverter's controller or control circuit. The aforementioned loop control commands can also be generated by this controller. Thus, the control of the bus voltage is determined by the result of the loop competition, and corresponding energy management is implemented, such as controlling the inverter's output power or the charging and discharging power of the energy storage battery based on the loop competition result. Furthermore, the load power change caused by sudden load fluctuations is taken into account, thus enabling rapid power balance under sudden load fluctuation scenarios. Meanwhile, compared to the response speed limited by the bus voltage itself and the bus capacitor, the loop competition strategy directly controls the relevant power and stabilizes the bus voltage near the reference voltage value through the loop competition result. This enables a rapid response to changes in the charging and discharging power of the energy storage battery, which is beneficial to improving the inverter conversion efficiency, narrowing the inverter operating range, and thus improving inverter efficiency and system benefits.

[0116] Specifically, in step S406, the loop competition strategy can be expressed as making a series of judgments based on the maximum photovoltaic power, load power, maximum charging power, and maximum discharging power to select the loop control command to be executed: When the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is greater than the maximum charging power of the energy storage battery, the BST side bus voltage loop control command is executed. When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is less than the maximum discharge power of the energy storage battery, the INV side bus voltage loop control command is executed. When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharge power of the energy storage battery, or when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power of the energy storage battery, the energy storage battery charging and discharging bus voltage loop control command is executed.

[0117] In step S406, when the BST side bus voltage loop control command is selected to be executed, the details are similar to those in step S208 and will not be repeated here. In step S406, when the INV side bus voltage loop control command is selected to be executed, the details are similar to those in step S208 and will not be repeated here.

[0118] In step S406, when the energy storage battery charge / discharge bus voltage loop control command is executed, the DC source provides the maximum photovoltaic power. The maximum photovoltaic power minus the load power is less than the maximum charging power of the energy storage battery, but greater than the maximum discharging power of the energy storage battery. Combining steps S404 and S406, the charging / discharging power of the energy storage battery is the actual output power of the DC source, which is between the photovoltaic output power and the load power, and is determined by the actual situation as either charging or discharging. Under the energy storage battery charge / discharge bus voltage loop control command, the bus voltage stabilizes at the energy storage battery charge / discharge bus voltage reference value U. REF_BAT The DC source operates at the maximum power of the photovoltaic system.

[0119] It should be understood that the order of steps S400, S402, and S404 can be adjusted or rearranged. This application embodiment does not limit the order of these three steps; steps S400 to S404 can be performed simultaneously and can be rearranged in any order. This application embodiment and its appendix... Figure 4 Steps S400 to S404 are described one by one for the sake of convenience only.

[0120] Figure 5 The embodiments provided in this application are based on Figure 4 The diagram illustrates the method for controlling the inverter bus voltage. (See attached diagram.) Figure 5 As shown, the Y-axis represents the charging and discharging power of the energy storage battery. The positive direction, i.e., the upper half of the Y-axis, represents the charging power, while the negative direction, i.e., the lower half of the Y-axis, represents the discharging power. The maximum charging and discharging power is 3kW / -3kW. The X-axis represents the corresponding bus voltage and various voltage reference values ​​according to the first configuration. Specifically, the BST side bus voltage reference value is marked as F, corresponding to 430V, also known as the fifth voltage range; the energy storage battery side voltage reference value is marked as E, corresponding to 400V, also known as the sixth voltage range; and the INV side bus voltage reference value is marked as G, corresponding to 370V, also known as the seventh voltage range. Figure 5 The configuration shown indicates that the BST-side bus voltage reference value is greater than the energy storage battery-side voltage reference value, and the energy storage battery-side voltage reference value is greater than the INV-side bus voltage reference value. Thus, combined with... Figure 4 and Figure 5 By setting the values ​​of each voltage reference, we can obtain... Figure 5The diagram shows the relationship between bus voltage and charging / discharging power. Furthermore, by directly controlling the relevant power and stabilizing the bus voltage near the reference voltage value, it is beneficial to improve inverter conversion efficiency, narrow the inverter operating range, and thus improve inverter efficiency and system profitability.

[0121] In some exemplary embodiments, the maximum charging and discharging power can be other values, such as 4kW / -4kW or 5kW / -5kW. These can be adjusted and improved according to the specific application environment, and are not specifically limited here.

[0122] In some exemplary embodiments, the voltage reference values ​​may be other values. These can be adjusted and improved according to the specific application environment, and are not specifically limited here.

[0123] The specific embodiments provided in this application can be implemented using any one or a combination of hardware, software, firmware, or solid-state logic circuits, and can be combined with signal processing, control, and / or dedicated circuitry. The devices or apparatuses provided in the specific embodiments of this application may include one or more processors (e.g., microprocessors, controllers, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), etc.) that process various computer-executable instructions to control the operation of the devices or apparatuses. The devices or apparatuses provided in the specific embodiments of this application may include a system bus or data transmission system that couples various components together. The system bus may include any one or a combination of different bus architectures, such as a memory bus or memory controller, a peripheral bus, a universal serial bus, and / or a processor or local bus utilizing any of a variety of bus architectures. The devices or apparatuses provided in the specific embodiments of this application may be provided separately, as part of a system, or as part of other devices or apparatuses.

[0124] The specific embodiments provided in this application may include computer-readable storage media or combinations thereof, such as one or more storage devices capable of providing non-transitory data storage. The computer-readable storage medium / storage device may be configured to store data, programs, and / or instructions that, when executed by a processor of the device or apparatus provided in the specific embodiments of this application, cause the device or apparatus to perform relevant operations. The computer-readable storage medium / storage device may include one or more of the following features: volatile, non-volatile, dynamic, static, readable / writable, read-only, random access, sequential access, location addressable, file addressable, and content addressable. In one or more exemplary embodiments, the computer-readable storage medium / storage device may be integrated into the device or apparatus provided in the specific embodiments of this application or belong to a common system. Computer-readable storage media / storage devices may include optical storage devices, semiconductor storage devices and / or magnetic storage devices, etc., and may also include random access memory (RAM), flash memory, read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, removable disks, recordable and / or rewritable optical discs (CD), digital versatile optical discs (DVD), mass storage media devices or any other suitable form of storage media.

[0125] The above are implementation methods of the embodiments of this application. It should be noted that the steps in the methods described in the specific embodiments of this application can be adjusted, merged, and deleted according to actual needs. In the above embodiments, the descriptions of each embodiment have their own emphasis. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. It is understood that the structures shown in the embodiments of this application and the accompanying drawings do not constitute a specific limitation on the relevant device or system. In other embodiments of this application, the relevant device or system may include more or fewer components than in the specific embodiments and accompanying drawings, or combine some components, or split some components, or have different component arrangements. Those skilled in the art will understand that various modifications or changes can be made to the arrangement, operation, and details of the methods and devices described in the specific embodiments without departing from the spirit and scope of the specific embodiments of this application; several improvements and refinements can also be made without departing from the principle of the embodiments of this application, and these improvements and refinements are also considered to be within the protection scope of this application.

Claims

1. A method for controlling the bus voltage of a photovoltaic system, the photovoltaic system comprising a DC / DC converter and a DC / AC converter, wherein, The DC / DC converter, the DC / AC converter, and the energy storage battery are connected via a bus. The DC / DC converter is connected to a photovoltaic DC source and performs maximum power point tracking (MPPT) on the input power from the photovoltaic DC source. The load connected to the DC / AC converter has a load power, and the energy storage battery has a maximum charging power and a maximum discharging power. The method is characterized by comprising: When the maximum photovoltaic power is greater than the load power, and the difference between the maximum photovoltaic power and the load power is greater than the maximum charging power, the bus voltage is controlled to operate in the first voltage range. When the maximum photovoltaic power is less than the load power, and the difference between the maximum photovoltaic power and the load power is greater than the maximum discharge power, the bus voltage is controlled to operate in the fourth voltage range; the first voltage range and the fourth voltage range are different and correspond to different operating states of the inverter.

2. The method according to claim 1, characterized in that, The first voltage range corresponds to the reference value of the bus voltage on the BST side. When the inverter is operating in a state corresponding to the reference value of the BST side bus voltage, the energy storage battery is in a charging state and the charging power of the energy storage battery reaches the maximum charging power. The photovoltaic output power of the photovoltaic DC source is less than the maximum photovoltaic power. The photovoltaic output power of the photovoltaic DC source is equal to the sum of the load power and the maximum charging power.

3. The method according to claim 1, characterized in that, The method further includes: When the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, the bus voltage is controlled to operate in the second voltage range. The first voltage range, the second voltage range, and the fourth voltage range are different voltage ranges and correspond to different operating states of the inverter. The second voltage range corresponds to the reference value of the charging bus voltage of the energy storage battery. When the inverter operates in a state corresponding to the reference value of the charging bus voltage of the energy storage battery, the energy storage battery is in a charging state and the charging power of the energy storage battery is less than the maximum charging power. The photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power. The charging power of the energy storage battery is equal to the maximum photovoltaic power minus the load power.

4. The method according to claim 1, characterized in that, The method further includes: When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is less than the maximum discharge power, the bus voltage is controlled to operate in the third voltage range. The first voltage range, the third voltage range and the fourth voltage range are different voltage ranges and correspond to different operating states of the inverter. The third voltage range corresponds to the INV side bus voltage reference value. When the inverter is operating in a state corresponding to the reference value of the INV side bus voltage, the energy storage battery is in a discharge state and the discharge power of the energy storage battery reaches the maximum discharge power. The photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power. The load obtains compensation power from the AC grid. The compensation power is equal to the load power minus the maximum photovoltaic power plus the maximum discharge power.

5. The method according to claim 1, characterized in that, The fourth voltage range corresponds to the reference value of the discharge bus voltage of the energy storage battery. Specifically, when the inverter operates in a state corresponding to the reference value of the discharge bus voltage of the energy storage battery, the energy storage battery is in a discharge state and the discharge power of the energy storage battery is greater than the maximum discharge power. The photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, and the discharge power of the energy storage battery is equal to the maximum photovoltaic power minus the load power.

6. The method according to claim 1, characterized in that, The method further includes: When the maximum photovoltaic power is greater than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum charging power, the bus voltage is controlled to operate in a second voltage range, wherein the second voltage range corresponds to the reference value of the energy storage battery charging bus voltage. When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum discharge power, the bus voltage is controlled to operate in the third voltage range, wherein the third voltage range corresponds to the INV side bus voltage reference value. The first voltage range, the second voltage range, the third voltage range, and the fourth voltage range are different voltage ranges and correspond to different operating states of the inverter; The first voltage range corresponds to the reference value of the bus voltage on the BST side, and the fourth voltage range corresponds to the reference value of the discharge bus voltage of the energy storage battery. Wherein, the reference value of the BST side bus voltage is greater than the reference value of the energy storage battery charging bus voltage, the reference value of the energy storage battery charging bus voltage is greater than the reference value of the energy storage battery discharging bus voltage, and the reference value of the energy storage battery discharging bus voltage is greater than the reference value of the INV side bus voltage.

7. The method according to claim 6, characterized in that, The method further includes: Based on the bus voltage sampling value of the inverter and the reference value of the BST side bus voltage, a BST side bus voltage loop control command is generated to control the output power of the inverter so that the bus voltage is stabilized at the reference value of the BST side bus voltage. Based on the bus voltage sample value and the INV side bus voltage reference value, an INV side bus voltage loop control command is generated to control the output power of the inverter so that the bus voltage is stabilized at the INV side bus voltage reference value. Based on the bus voltage sampling value and the energy storage battery charging bus voltage reference value, a loop control command for the energy storage battery charging bus voltage is generated to control the charging power of the energy storage battery so that the bus voltage is stabilized at the energy storage battery charging bus voltage reference value. Based on the sampled bus voltage value and the reference value of the energy storage battery discharge bus voltage, a loop control command for the energy storage battery discharge bus voltage is generated to control the discharge power of the energy storage battery so that the bus voltage is stabilized at the reference value of the energy storage battery discharge bus voltage.

8. The method according to claim 7, characterized in that, The BST side bus voltage loop control command, the INV side bus voltage loop control command, the energy storage battery charging bus voltage loop control command, and the energy storage battery discharging bus voltage loop control command all use a PI controller.

9. The method according to claim 1, characterized in that, The method further includes: When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is greater than the maximum discharge power, or when the maximum photovoltaic power is greater than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum charging power, the bus voltage is controlled to operate in the fifth voltage range. The fifth voltage range corresponds to the reference value of the charging and discharging bus voltage of the energy storage battery. The first voltage range and the fifth voltage range are different voltage ranges and correspond to different operating states of the inverter. Specifically, when the inverter operates in a state corresponding to the reference value of the charging and discharging bus voltage of the energy storage battery, the photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power. The maximum photovoltaic power minus the load power is less than the maximum charging power but greater than the maximum discharging power.

10. The method according to claim 1, characterized in that, The method further includes: When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum discharge power, the bus voltage is controlled to operate in the third voltage range, wherein the third voltage range corresponds to the INV side bus voltage reference value. When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharge power, or when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, the bus voltage is controlled to operate in the fifth voltage range. Wherein, the first voltage range corresponds to the reference value of the bus voltage on the BST side, and the fifth voltage range corresponds to the reference value of the charging and discharging bus voltage of the energy storage battery. The first voltage range, the third voltage range, and the fifth voltage range are different voltage ranges and correspond to different operating states of the inverter. The reference value of the BST side bus voltage is greater than the reference value of the energy storage battery charging and discharging bus voltage, and the reference value of the energy storage battery charging and discharging bus voltage is greater than the reference value of the INV side bus voltage.

11. The method according to claim 10, characterized in that, The method further includes: Based on the bus voltage sampling value of the inverter and the reference value of the BST side bus voltage, a BST side bus voltage loop control command is generated to control the output power of the inverter so that the bus voltage is stabilized at the reference value of the BST side bus voltage. Based on the bus voltage sample value and the INV side bus voltage reference value, an INV side bus voltage loop control command is generated to control the output power of the inverter so that the bus voltage is stabilized at the INV side bus voltage reference value. Based on the sampled bus voltage value and the reference value of the charging and discharging bus voltage of the energy storage battery, a loop control command for the charging and discharging bus voltage of the energy storage battery is generated to control the charging and discharging power of the energy storage battery so that the bus voltage is stabilized at the reference value of the charging and discharging bus voltage of the energy storage battery.

12. The method according to claim 11, characterized in that, The BST side bus voltage loop control command, the INV side bus voltage loop control command, and the energy storage battery charging and discharging bus voltage loop control command all use a PI controller.

13. The method according to any one of claims 1-12, characterized in that, The maximum charging power and the maximum discharging power are preset.

14. A photovoltaic system, characterized in that, The photovoltaic system includes: DC / DC converter; A DC / AC converter, wherein the DC / DC converter, the DC / AC converter, and the energy storage battery are connected via a bus; the DC / DC converter is connected to a photovoltaic DC source and performs maximum power point tracking (MPPT) on the input power from the photovoltaic DC source; the load connected to the DC / AC converter has a load power; and the energy storage battery has a maximum charging power and a maximum discharging power. Bus voltage controller, wherein the bus voltage controller is used for: When the maximum photovoltaic power is greater than the load power, and the difference between the maximum photovoltaic power and the load power is greater than the maximum charging power, the bus voltage is controlled to operate in the first voltage range. When the maximum photovoltaic power is less than the load power, and the difference between the maximum photovoltaic power and the load power is greater than the maximum discharge power, the bus voltage is controlled to operate in the fourth voltage range; the first voltage range and the fourth voltage range are different and correspond to different operating states of the inverter.

15. The photovoltaic system according to claim 14, characterized in that, The first voltage range corresponds to the reference value of the bus voltage on the BST side. When the inverter is operating in a state corresponding to the reference value of the BST side bus voltage, the energy storage battery is in a charging state and the charging power of the energy storage battery reaches the maximum charging power. The photovoltaic output power of the photovoltaic DC source is less than the maximum photovoltaic power. The photovoltaic output power of the photovoltaic DC source is equal to the sum of the load power and the maximum charging power.

16. The photovoltaic system according to claim 14, characterized in that, The bus voltage controller is also used for: When the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, the bus voltage is controlled to operate in the second voltage range. The first voltage range, the second voltage range, and the fourth voltage range are different voltage ranges and correspond to different operating states of the inverter. The second voltage range corresponds to the reference value of the charging bus voltage of the energy storage battery. When the inverter operates in a state corresponding to the reference value of the charging bus voltage of the energy storage battery, the energy storage battery is in a charging state and the charging power of the energy storage battery is less than the maximum charging power. The photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power. The charging power of the energy storage battery is equal to the maximum photovoltaic power minus the load power.

17. The photovoltaic system according to claim 14, characterized in that, The bus voltage controller is also used for: When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is less than the maximum discharge power, the bus voltage is controlled to operate in the third voltage range. The first voltage range, the third voltage range and the fourth voltage range are different voltage ranges and correspond to different operating states of the inverter. The third voltage range corresponds to the INV side bus voltage reference value. When the inverter is operating in a state corresponding to the reference value of the INV side bus voltage, the energy storage battery is in a discharge state and the discharge power of the energy storage battery reaches the maximum discharge power. The photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power. The load obtains compensation power from the AC grid. The compensation power is equal to the load power minus the maximum photovoltaic power plus the maximum discharge power.

18. The photovoltaic system according to claim 14, characterized in that, The fourth voltage range corresponds to the reference value of the discharge bus voltage of the energy storage battery. Specifically, when the inverter operates in a state corresponding to the reference value of the discharge bus voltage of the energy storage battery, the energy storage battery is in a discharge state and the discharge power of the energy storage battery is greater than the maximum discharge power. The photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power, and the discharge power of the energy storage battery is equal to the maximum photovoltaic power minus the load power.

19. The photovoltaic system according to claim 14, characterized in that, The bus voltage controller is also used for: When the maximum photovoltaic power is greater than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum charging power, the bus voltage is controlled to operate in a second voltage range, wherein the second voltage range corresponds to the reference value of the energy storage battery charging bus voltage. When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum discharge power, the bus voltage is controlled to operate in the third voltage range, wherein the third voltage range corresponds to the reference value of the bus voltage on the INV side. The first voltage range, the second voltage range, the third voltage range, and the fourth voltage range are different voltage ranges and correspond to different operating states of the inverter; the first voltage range corresponds to the BST side bus voltage reference value, and the fourth voltage range corresponds to the energy storage battery discharge bus voltage reference value. Wherein, the reference value of the BST side bus voltage is greater than the reference value of the energy storage battery charging bus voltage, the reference value of the energy storage battery charging bus voltage is greater than the reference value of the energy storage battery discharging bus voltage, and the reference value of the energy storage battery discharging bus voltage is greater than the reference value of the INV side bus voltage.

20. The photovoltaic system according to claim 19, characterized in that, The bus voltage controller is also used for: Based on the bus voltage sampling value of the inverter and the reference value of the BST side bus voltage, a BST side bus voltage loop control command is generated to control the output power of the inverter so that the bus voltage is stabilized at the reference value of the BST side bus voltage. Based on the bus voltage sample value and the INV side bus voltage reference value, an INV side bus voltage loop control command is generated to control the output power of the inverter so that the bus voltage is stabilized at the INV side bus voltage reference value. Based on the bus voltage sampling value and the energy storage battery charging bus voltage reference value, a loop control command for the energy storage battery charging bus voltage is generated to control the charging power of the energy storage battery so that the bus voltage is stabilized at the energy storage battery charging bus voltage reference value. Based on the sampled bus voltage value and the reference value of the energy storage battery discharge bus voltage, a loop control command for the energy storage battery discharge bus voltage is generated to control the discharge power of the energy storage battery so that the bus voltage is stabilized at the reference value of the energy storage battery discharge bus voltage.

21. The photovoltaic system according to claim 20, characterized in that, The BST side bus voltage loop control command, the INV side bus voltage loop control command, the energy storage battery charging bus voltage loop control command, and the energy storage battery discharging bus voltage loop control command all use a PI controller.

22. The photovoltaic system according to claim 14, characterized in that, The bus voltage controller is also used for: When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is greater than the maximum discharge power, or when the maximum photovoltaic power is greater than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum charging power, the bus voltage is controlled to operate in the fifth voltage range. The fifth voltage range corresponds to the reference value of the charging and discharging bus voltage of the energy storage battery. The first voltage range and the fifth voltage range are different voltage ranges and correspond to different operating states of the inverter. Specifically, when the inverter operates in a state corresponding to the reference value of the charging and discharging bus voltage of the energy storage battery, the photovoltaic output power provided by the photovoltaic DC source reaches the maximum photovoltaic power. The maximum photovoltaic power minus the load power is less than the maximum charging power but greater than the maximum discharging power.

23. The photovoltaic system according to claim 14, characterized in that, The bus voltage controller is also used for: When the maximum photovoltaic power is less than the load power and the difference between the maximum photovoltaic power and the load power is less than the maximum discharge power, the bus voltage is controlled to operate in the third voltage range, wherein the third voltage range corresponds to the INV side bus voltage reference value. When the maximum photovoltaic power is less than the load power and the maximum photovoltaic power minus the load power is greater than the maximum discharge power, or when the maximum photovoltaic power is greater than the load power and the maximum photovoltaic power minus the load power is less than the maximum charging power, the bus voltage is controlled to operate in the fifth voltage range. Wherein, the first voltage range corresponds to the reference value of the bus voltage on the BST side, and the fifth voltage range corresponds to the reference value of the charging and discharging bus voltage of the energy storage battery. The first voltage range, the third voltage range, and the fifth voltage range are different voltage ranges and correspond to different operating states of the inverter. The reference value of the BST side bus voltage is greater than the reference value of the energy storage battery charging and discharging bus voltage, and the reference value of the energy storage battery charging and discharging bus voltage is greater than the reference value of the INV side bus voltage.

24. The photovoltaic system according to claim 23, characterized in that, The bus voltage controller is also used for: Based on the bus voltage sampling value of the inverter and the reference value of the BST side bus voltage, a BST side bus voltage loop control command is generated to control the output power of the inverter so that the bus voltage is stabilized at the reference value of the BST side bus voltage. Based on the bus voltage sample value and the INV side bus voltage reference value, an INV side bus voltage loop control command is generated to control the output power of the inverter so that the bus voltage is stabilized at the INV side bus voltage reference value. Based on the sampled bus voltage value and the reference value of the charging and discharging bus voltage of the energy storage battery, a loop control command for the charging and discharging bus voltage of the energy storage battery is generated to control the charging and discharging power of the energy storage battery so that the bus voltage is stabilized at the reference value of the charging and discharging bus voltage of the energy storage battery.

25. The photovoltaic system according to claim 24, characterized in that, The BST side bus voltage loop control command, the INV side bus voltage loop control command, and the energy storage battery charging and discharging bus voltage loop control command all use a PI controller.

26. The photovoltaic system according to any one of claims 14-25, characterized in that, The maximum charging power and the maximum discharging power are preset.

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