Direct-current coupling inversion device for photovoltaic power station

Abstract

The invention relates to the technical field of photovoltaic power generation, and particularly discloses a direct-current coupling inversion device for a photovoltaic power station. The direct-current coupling inversion device comprises an alternating-current side transformer, an inverter, a photovoltaic module, a DCDC converter, a battery cluster, a current and voltage detection sub-control box, a box transformer measurement and control unit, a real-time controller, a current sensor, a voltage sensor, a circuit breaker and a contactor. According to the invention, peak regulation and frequency modulation of the photovoltaic power station can be realized under the condition of no AC side energy storage system configuration, so that the operation of the photovoltaic power station system is more stable and reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and more specifically, to a DC-coupled inverter device for a photovoltaic power station. Background Art

[0002] At present, with the adjustment of the energy structure and the promotion of low-carbon economy, the proportion of new energy power generation methods represented by photovoltaic power generation and wind power generation in the power system has increased significantly. However, the volatility and intermittency of new energy power generation pose a severe challenge to the stability of the power grid. For example, photovoltaic power generation is greatly affected by sunlight intensity and weather conditions, and the power generation power may fluctuate violently in a short period of time. Such power fluctuations not only affect the power supply quality of the photovoltaic power station itself, but also impact the frequency and voltage stability of the power grid. To address this issue, energy storage systems are widely used in current technologies to achieve the frequency modulation and peak shaving functions of photovoltaic power stations through centralized energy storage solutions, so as to smooth power fluctuations and improve power quality. However, centralized energy storage systems are usually deployed on the AC side of photovoltaic power stations, with complex control systems and low charge and discharge efficiencies. In addition, the energy storage structure with multiple battery clusters connected in parallel is prone to inter-cluster circulating current, which further shortens the service life of the batteries and increases the operation and maintenance costs. Summary of the Invention

[0003] To overcome the above-mentioned defects of the prior art, the present invention provides a DC-coupled inverter device for a photovoltaic power station, which reduces harmonics through an inverter, enables the photovoltaic modules and the battery cluster to work together, allows the transformer substation measurement and control to collect data of the AC-side transformer, and enables the real-time controller to coordinate the operation of each component. The photovoltaic power station can achieve system peak shaving and frequency modulation even without an AC-side energy storage system configuration. The DC-coupled inverter device uses single-battery-cluster charge and discharge management, further improving the system life and safety, reducing the operation and maintenance costs, so as to solve the problems raised in the above background art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A DC-coupled inverter device for a photovoltaic power station includes an AC-side transformer, an inverter, photovoltaic modules, a DCDC converter, a battery cluster, a current and voltage detection sub-control box, transformer substation measurement and control, a real-time controller, a current sensor, a voltage sensor, a circuit breaker, and a contactor; the DCDC converter is embedded with a digital signal processor and real-time monitors the input and output voltages and currents, and dynamically adjusts the duty cycle. The steps of dynamically adjusting the duty cycle are as follows:

[0006] Step S1, the relationship between the output voltage V out and the input voltage V in of the DCDC converter is expressed by the following formula: V out = D·V in, where D is the duty cycle;

[0007] Step S2, the duty cycle D satisfies where V ref is the preset target output voltage value, V load is the voltage value actually required by the load, and k is the gain factor used to convert the error signal into an appropriate duty cycle adjustment value;

[0008] Step S3, perform real-time error detection, and the calculation formula is: e = V ref -V out , where e is the error value; then perform error correction to adjust the duty cycle: D new = D prev +ΔD, where D new is the adjusted duty cycle, D prev is the duty cycle before adjustment, and ΔD is the correction value based on the error adjustment, satisfying ΔD = k·e.

[0009] As a further solution of the present invention, the AC-side transformer consists of a primary winding, a secondary winding, and an iron core. The AC-side transformer plays the role of harmonic filtering. One side is directly connected to the AC output terminal of the inverter group, and the other side communicates with the system dispatching interface through a short-distance connector or cable; the secondary winding adopts a phase-shifting design, and the two windings operate independently. The secondary windings are respectively connected to the corresponding inverter groups through circuit breakers to provide the required AC input for the inverters, forming two independent power supply circuits; the input side of the AC-side transformer is directly connected to the power grid, and the voltage level of the output side is adjusted by the inverter and then output to the power grid interface of the photovoltaic power station.

[0010] As a further solution of the present invention, the AC side and the DC side of the inverter are connected by copper bars or cables, and the DC input terminal of the inverter is connected to the DCDC converter through a DC bus. The inverter converts the direct current generated by the photovoltaic modules and the energy storage battery cluster into alternating current that meets the requirements of the power grid, and controls the output voltage and frequency through sine pulse width modulation technology to ensure the stability of the voltage and frequency of the output electric energy and reduce harmonic components.

[0011] As a further solution of the present invention, the photovoltaic modules are connected to the inverter through contactors or circuit breakers, and directly convert the energy of sunlight into direct current through the photovoltaic effect. The output power of the photovoltaic modules is dynamically adjusted with the changes in light intensity and temperature, and through the management of the real-time controller, it works in coordination with the battery cluster. The calculation formula for the dynamic adjustment is: where P pv is the actual output power of the photovoltaic module, P stc$P_{0}$ is the rated output power of the photovoltaic module under standard test conditions, $G$ is the current light intensity, and $G_{0}$ stc is the light intensity under standard test conditions, $T$ is the current operating temperature of the photovoltaic module, and $T_{0}$ stc is the operating temperature under standard test conditions. $\alpha$ is the temperature coefficient of the photovoltaic module, which represents the sensitivity of the module efficiency to temperature changes. When the light intensity $G$ increases, the scaling factor in the formula becomes larger, resulting in an increase in the actual output power $P$ pv of the photovoltaic module, which reflects that higher solar radiation leads to higher power generation capacity. When the temperature $T$ rises, since $\alpha$ is negative, the temperature correction factor $1 + \alpha\cdot(T - T_{0})$ stc in the formula decreases, thereby reducing the actual output power $P$ pv of the photovoltaic module, indicating that high temperature will have a negative impact on the performance of the module. The photovoltaic module is composed of a number of photovoltaic cells connected in series and in parallel. Each cell uses crystalline silicon material, and the photovoltaic cells are encapsulated in glass with high light transmittance and waterproof materials. Current and voltage signal sampling is performed on each photovoltaic module circuit.

[0012] As a further aspect of the present invention, the batteries in the battery cluster are lithium-ion batteries, which are responsible for storing the excess electrical energy of the photovoltaic module and releasing electrical energy when the photovoltaic power generation is insufficient. The battery cluster is connected to the inverter through a DCDC converter, and the battery cluster and the DCDC converter are connected through a contactor or a circuit breaker. The battery cluster feeds back the battery status, including the remaining capacity, operating temperature, and health status, to the real-time controller through a battery management system. The battery cluster receives the excess electrical energy output by the photovoltaic module through the DCDC converter and stores it as chemical energy. When the photovoltaic power generation is insufficient or the load demand increases, the battery cluster releases electrical energy to ensure stable system output.

[0013] As a further aspect of the present invention, the function of the current and voltage detection sub-control box is to collect the current and voltage signals of each circuit of the photovoltaic module, DCDC converter, battery cluster, and inverter in real time, and transmit the collected data to the real-time controller through a high-speed communication bus. The current and voltage detection sub-control box includes a signal processing unit, a communication module, and a control logic unit. The signal processing unit filters and amplifies the collected current and voltage signals through a signal conditioning circuit to eliminate high-frequency noise, and uses an analog-to-digital converter to convert the analog signals into digital signals. The communication module is equipped with a variety of communication interfaces, including CAN, RS485, and Ethernet, which support data transmission. The control logic unit is embedded with a microcontroller and can implement basic overcurrent and overvoltage fast-disconnection logic control.

[0014] As a further aspect of the present invention, the box-type substation measurement and control unit is used to collect the operation data of the AC-side transformer and transmit it to the real-time controller to assist in the operation monitoring and status management of the power station. The box-type substation measurement and control unit is connected to the primary and secondary sides of the AC-side transformer through voltage transformers and current transformers to collect electrical signals in real time. The box-type substation measurement and control unit is connected to the real-time controller through a communication interface, sends the collected operation data to the real-time controller, receives the instructions issued by the real-time controller, and maintains data interaction with the power station dispatching system through a remote communication module to achieve centralized management and remote monitoring of the power station.

[0015] As a further aspect of the present invention, the real-time controller is responsible for managing and coordinating the operation states of the components in the system. The real-time controller receives the real-time voltage and current data of the photovoltaic modules through the current and voltage detection sub-control box to control the operation states of the modules; and receives the state data of the battery cluster through the battery management system to control the charge and discharge process.

[0016] As a further aspect of the present invention, the current sensor collects the current values of each circuit in real time, including the output current of the photovoltaic modules, the charge and discharge current of the battery cluster, the input and output currents of the DCDC converter, and the DC-side current of the inverter. The voltage sensor measures the output voltage of the photovoltaic modules, the charge and discharge voltage of the battery cluster, the input and output voltages of the DCDC converter, and the DC input voltage and AC output voltage of the inverter in real time. When the circuit breaker detects faults such as overcurrent, overvoltage, or short circuit, it can quickly disconnect the circuit to protect downstream equipment from damage. The circuit breaker provides overload protection. When the load current in the circuit exceeds the rated value but does not reach the short-circuit level, the circuit breaker can cut off the circuit within a certain delay time to prevent equipment from being damaged due to overheating. At the same time, the circuit breaker can also provide short-circuit protection. When the circuit is short-circuited, the circuit breaker can cut off the faulty circuit within an extremely short time to avoid damage to other equipment in the circuit. The contactor realizes the dynamic connection and disconnection of the circuits between components such as photovoltaic modules, DCDC converters, and battery clusters to meet the requirements of different working modes. The contactor can be remotely operated through the instructions of the real-time controller to achieve automated management of the system and reduce manual intervention. During equipment maintenance or fault handling, the faulty components are isolated through the contactor to ensure safe operation.

[0017] As a further aspect of the present invention, a control method for a DC-coupled inverter device includes the following specific steps:

[0018] Step Z1, start the device system to ensure that all photovoltaic modules are put into operation, and the inverter, DCDC converter, and battery cluster are in a standby state. The dispatching system sends a demand power instruction to the real-time controller through communication. The content of the instruction includes the target power value required by the current power grid or load.

[0019] Step Z2, the real-time controller collects the current and voltage signals of all photovoltaic modules, and determines the instantaneous power of the photovoltaic modules according to the power calculation formula P = V × I, where P is the electric power instantaneously generated by the photovoltaic modules, V is the voltage across the photovoltaic modules, and I is the current output by the photovoltaic modules. Then, according to the required power instruction, the instantaneous power is compared with the required power to judge whether the photovoltaic power generation can meet the required power.

[0020] Step Z3, detect the battery state and judge whether the battery is fully charged. If the battery is not fully charged, the DC bus of the inverter charges the lithium battery pack through the DCDC converter, and the real-time controller continuously detects the battery power. When the power reaches the set full charge state, the charging stops automatically; if the battery is fully charged, the real-time controller decides whether to disconnect some photovoltaic modules by calculating and analyzing the current photovoltaic power generation situation and the required power, and controls the contactor to disconnect the single or multiple photovoltaic module circuits to reduce the power generation and avoid waste, while protecting the system stability.

[0021] Step Z4, when the photovoltaic instantaneous power is not enough to meet the required power, the real-time controller detects the remaining power of the battery pack. If the battery power is sufficient, the real-time controller instructs the DCDC converter to transfer the electric energy of the lithium battery pack to the DC bus of the inverter, and converts the battery electric energy into alternating current through the inverter to supplement the insufficient power generation of the photovoltaic modules and ensure that the system output power reaches the required power; if the power of the lithium battery pack is insufficient and the photovoltaic power generation cannot meet the required power, the real-time controller feeds back an alarm of insufficient power to the dispatching system, and the dispatching system adjusts the load demand or activates other backup power sources according to the feedback information.

[0022] Step Z5, the real-time controller continuously collects the operation status data of the photovoltaic modules, battery pack, DCDC converter and inverter, and the operation status data includes current, voltage, power and temperature, etc. In any abnormal situation (such as overload, overvoltage or equipment failure), the real-time controller immediately cuts off the faulty circuit, triggers the protection mechanism, and sends an alarm to the dispatching system.

[0023] Technical effects and advantages of a DC-coupled inverter device for a photovoltaic power station: In the present invention, the AC-side transformer undertakes the tasks of harmonic filtering and power supply, improving power quality and power supply stability. The inverter converts direct current into stable alternating current, reducing harmonics and ensuring that the electric energy meets the grid requirements. The photovoltaic modules dynamically adjust the output power according to light and temperature, and work in coordination with the battery cluster to improve energy utilization efficiency. The DCDC converter can flexibly adjust voltage and current, and stabilizes the output by dynamically adjusting the duty cycle. Its input filter and real-time monitoring function enhance the stability and reliability of the system. The battery cluster stores excess electric energy and releases it in a timely manner to ensure stable system output. The feedback function of the battery management system helps to grasp the battery status in real time. The current and voltage detection sub-control box collects data and transmits it, and has multiple communication interfaces and control logics, improving the system monitoring and control capabilities. The substation measurement and control realizes data acquisition and interaction of the AC-side transformer, facilitating centralized management and remote monitoring of the power station. The real-time controller effectively coordinates the operation of each component to ensure the high efficiency and stability of the system. The current sensor, voltage sensor and circuit breaker provide monitoring and protection, and the contactor realizes dynamic management of the circuit. The DC-coupled inverter device can flexibly regulate according to the power generation and demand conditions, ensure stable power supply of the system, and at the same time respond and protect in a timely manner in case of abnormalities, solving the problems existing in the AC side of the centralized energy storage system, improving the ability of the photovoltaic power station to cope with power fluctuations, increasing the charge and discharge efficiency of the system, extending the service life of the battery, reducing the operation and maintenance costs, and enhancing the stability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. is a schematic structural diagram of a DC-coupled inverter device for a photovoltaic power station according to the present invention.

[0025] Figure 2 FIG. is a flowchart of a control method for a DC-coupled inverter device according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] Embodiment 1

[0028] Refer to Figure 1Schematic structural diagram as shown. An embodiment of the present invention provides a DC-coupled inverter device for a photovoltaic power station, which includes an AC-side transformer, an inverter, photovoltaic modules, a DCDC converter, a battery cluster, a current and voltage detection sub-control box, a substation measurement and control unit, a real-time controller, a current sensor, a voltage sensor, a circuit breaker, and a contactor; the AC-side transformer consists of a primary winding, a secondary winding, and an iron core. The AC-side transformer plays a role in harmonic filtering. One side is directly connected to the AC output terminal of the inverter group, and the other side communicates with the system dispatching interface through a short-distance connector or cable; the secondary winding adopts a phase-shifting design, and the two windings operate independently. The secondary windings are respectively connected to the corresponding inverter groups through circuit breakers to provide the required AC input for the inverters, forming two independent power supply circuits; the input side of the AC-side transformer is directly connected to the power grid, and the voltage level of the output side is adjusted by the inverter and then output to the power grid interface of the photovoltaic power station.

[0029] Further, the AC side and the DC side of the inverter are connected by copper bars or cables, and the DC input terminal of the inverter is connected to the DCDC converter through a DC bus. The inverter converts the direct current generated by the photovoltaic modules and the energy storage battery cluster into alternating current that meets the requirements of the power grid, and controls the output voltage and frequency through sinusoidal pulse width modulation technology to ensure the stability of the voltage and frequency of the output electric energy and reduce harmonic components.

[0030] Further, the photovoltaic modules are connected to the inverter through contactors or circuit breakers, and directly convert the energy of sunlight into direct current through the photovoltaic effect. The output power of the photovoltaic modules is dynamically adjusted according to the changes in light intensity and temperature. Through the management of the real-time controller, it works in coordination with the battery cluster. The calculation formula for the dynamic adjustment is: where, P pv is the actual output power of the photovoltaic module, P stc is the rated output power of the photovoltaic module under standard test conditions, G is the current light intensity, G stc is the light intensity under standard test conditions, T is the current working temperature of the photovoltaic module, T stc is the working temperature under standard test conditions, and α is the temperature coefficient of the photovoltaic module, indicating the sensitivity of the module efficiency to temperature changes. When the light intensity G increases, the scaling factor in the formula becomes larger, resulting in an increase in the actual output power P pv of the photovoltaic module, which reflects that higher solar radiation leads to higher power generation capacity; when the temperature T rises, since α is negative, the temperature correction factor 1 + α·(T - T stc ) in the formula decreases, thereby reducing the actual output power P pv, indicating that high temperature will have a negative impact on the performance of the components. The photovoltaic module is composed of a number of photovoltaic cells connected in series and in parallel. Each cell uses crystalline silicon material, and the photovoltaic cells are encapsulated in glass with high light transmittance and waterproof material. Current and voltage signal sampling is performed on each photovoltaic module circuit.

[0031] Further, the DCDC converter is connected to the battery cluster through a contactor or a circuit breaker, and current and voltage signal sampling is performed on each DCDC input circuit. The DCDC converter receives the DC input from the photovoltaic module or the battery cluster, reduces voltage fluctuations and current spikes through an input filter, uses high-frequency power switching devices, and combines pulse width modulation technology to achieve flexible adjustment of voltage and current. The DCDC converter is embedded with a digital signal processor and real-time monitors the input and output voltages and currents, and dynamically adjusts the duty cycle. The steps for dynamically adjusting the duty cycle are as follows:

[0032] Step S1, the relationship between the output voltage V out and the input voltage V in of the DCDC converter is expressed by the following formula: V out = D·V in , where D is the duty cycle.

[0033] Step S2, the duty cycle D satisfies where V ref is the preset target output voltage value, V load is the voltage value actually required by the load, and k is the gain factor used to convert the error signal into an appropriate duty cycle adjustment value.

[0034] Step S3, perform real-time error detection, and the calculation formula is: e = V ref - V out , e is the error value; then perform error correction and adjust the duty cycle: D new = D prev + ΔD, where D new is the adjusted duty cycle, D prev is the duty cycle before adjustment, and ΔD is the correction value based on the error adjustment, satisfying ΔD = k·e.

[0035] Further, the batteries in the battery cluster are lithium-ion batteries, which are responsible for storing the excess electrical energy of the photovoltaic modules and releasing electrical energy when the photovoltaic power generation is insufficient. The battery cluster is connected to the inverter through a DCDC converter, and the battery cluster and the DCDC converter are connected through a contactor or a circuit breaker. The battery cluster feeds back the battery status to the real-time controller through the battery management system, including the remaining capacity, operating temperature, and health status. The battery cluster receives the excess electrical energy output by the photovoltaic modules through the DCDC converter and stores it as chemical energy. When the photovoltaic power generation is insufficient or the load demand increases, the battery cluster releases electrical energy to ensure stable system output.

[0036] Further, the function of the current and voltage detection sub-control box is to collect the current and voltage signals of each circuit of the photovoltaic modules, DCDC converter, battery cluster, and inverter in real time, and transmit the collected data to the real-time controller through a high-speed communication bus. The current and voltage detection sub-control box includes a signal processing unit, a communication module, and a control logic unit. The signal processing unit filters and amplifies the collected current and voltage signals through a signal conditioning circuit to eliminate high-frequency noise, and uses an analog-to-digital converter to convert the analog signals into digital signals; the communication module is equipped with a variety of communication interfaces, and the communication interfaces include CAN, RS485, and Ethernet, supporting data transmission; the control logic unit is embedded with a microcontroller, which can implement basic overcurrent and overvoltage fast-disconnection logic control.

[0037] Further, the box-type transformer measurement and control is used to collect the operation data of the AC-side transformer and transmit it to the real-time controller to assist in the operation monitoring and status management of the power station. The box-type transformer measurement and control is connected to the primary and secondary sides of the AC-side transformer through voltage transformers and current transformers to collect electrical signals in real time. The box-type transformer measurement and control is connected to the real-time controller through a communication interface, sends the collected operation data to the real-time controller, receives the instructions issued by the real-time controller, and maintains data interaction with the power station dispatching system through a remote communication module to achieve centralized management and remote monitoring of the power station.

[0038] Further, the real-time controller is responsible for managing and coordinating the operation status of the components in the system. The real-time controller receives the real-time voltage and current data of the photovoltaic modules through the current and voltage detection sub-control box and controls the operation status of the components; it receives the status data of the battery cluster through the battery management system and controls the charging and discharging process.

[0039] Furthermore, the current sensor collects the current values of each circuit in real time, including the output current of the photovoltaic module, the charge and discharge current of the battery cluster, the input and output currents of the DCDC converter, and the DC-side current of the inverter. The voltage sensor measures the output voltage of the photovoltaic module, the charge and discharge voltage of the battery cluster, the input and output voltages of the DCDC converter, and the DC input voltage and AC output voltage of the inverter in real time. When the circuit breaker detects faults such as overcurrent, overvoltage, or short circuit, it can quickly disconnect the circuit to protect downstream equipment from damage. The circuit breaker provides overload protection. When the load current in the circuit exceeds the rated value but does not reach the short-circuit level, the circuit breaker can cut off the circuit within a certain delay time to prevent equipment from being damaged due to overheating. At the same time, the circuit breaker can also provide short-circuit protection. When the circuit is short-circuited, the circuit breaker can cut off the faulty circuit within an extremely short time to avoid damage to other equipment in the circuit. The contactor realizes the dynamic connection and disconnection of the circuits among components such as photovoltaic modules, DCDC converters, and battery clusters to meet the requirements of different working modes. The contactor can be remotely operated through the instructions of the real-time controller to achieve automatic system management and reduce manual intervention. During equipment maintenance or fault handling, the faulty components are isolated through the contactor to ensure safe operation.

[0040] In this embodiment, referring to Figure 2 the flowchart shown, a control method for a DC-coupled inverter device includes the following specific steps:

[0041] Step Z1, start the device system to ensure that all photovoltaic modules are put into operation, and the inverter, DCDC converter, and battery cluster are in a standby state. The dispatching system sends a demand power instruction to the real-time controller through a communication method, and the content of the instruction includes the target power value required by the current power grid or load.

[0042] Step Z2, the real-time controller collects the current and voltage signals of all photovoltaic modules, and determines the instantaneous power of the photovoltaic modules through the power calculation formula P = V×i, where P is the electric power instantaneously generated by the photovoltaic module, V is the voltage across the photovoltaic module, and I is the current output by the photovoltaic module. According to the demand power instruction, the instantaneous power is compared with the demand power to determine whether the photovoltaic power generation can meet the demand power.

[0043] Step Z3, detect the battery state to judge whether the battery is fully charged. If the battery is not fully charged, the DC bus of the inverter charges the lithium battery pack through the DCDC converter. The real-time controller continuously detects the battery charge. When the charge reaches the set full charge state, the charging is automatically stopped; if the battery is fully charged, the real-time controller decides whether to disconnect some photovoltaic modules by calculating and analyzing the current photovoltaic power generation situation and the demand power, and controls the contactor to disconnect a single or multiple photovoltaic module circuits to reduce the power generation and avoid waste, while protecting the system stability.

[0044] Step Z4: When the photovoltaic instantaneous power is insufficient to meet the demand power, the real-time controller detects the remaining power of the battery pack. If the battery is fully charged, the real-time controller instructs the DCDC converter to deliver the electrical energy of the lithium battery pack to the DC bus of the inverter, and the battery electrical energy is converted into alternating current through the inverter to supplement the insufficient power generation of the photovoltaic modules, ensuring that the system output power reaches the demand power; if the power of the lithium battery pack is insufficient and the photovoltaic power generation cannot meet the demand power, the real-time controller feeds back an insufficient power alarm to the dispatching system, and the dispatching system adjusts the load demand or activates other standby power sources according to the feedback information.

[0045] Step Z5: The real-time controller continuously collects the operation status data of the photovoltaic modules, battery pack, DCDC converter and inverter. The operation status data includes current, voltage, power, temperature, etc. In any abnormal situation (such as overload, overvoltage or equipment failure), the real-time controller immediately cuts off the faulty circuit, triggers the protection mechanism, and sends an alarm to the dispatching system.

[0046] In the present invention, the AC-side transformer undertakes the tasks of harmonic filtering and power supply, improving the power quality and power supply stability. The inverter converts direct current into stable alternating current, reducing harmonics and ensuring that the electrical energy meets the grid requirements. The photovoltaic modules dynamically adjust the output power according to light and temperature, and cooperate with the battery cluster to improve the energy utilization efficiency. The DCDC converter can flexibly adjust the voltage and current, and stabilize the output by dynamically adjusting the duty cycle. Its input filter and real-time monitoring function enhance the stability and reliability of the system. The battery cluster stores excess electrical energy and releases it in due time to ensure the stable output of the system. The feedback function of the battery management system helps to grasp the battery status in real time. The current and voltage detection sub-control box collects data and transmits it, with a variety of communication interfaces and control logics, improving the system monitoring and control capabilities. The substation measurement and control realizes the data acquisition and interaction of the AC-side transformer, facilitating the centralized management and remote monitoring of the power station. The real-time controller effectively coordinates the operation of each component to ensure the high efficiency and stability of the system. The current sensor, voltage sensor and circuit breaker provide monitoring and protection, and the contactor realizes the dynamic management of the circuit. The DC-coupled inverter device can flexibly regulate according to the power generation and demand conditions, ensuring stable power supply of the system. At the same time, it responds promptly to protection in case of abnormalities, solves the problems existing in the AC side of the centralized energy storage system, improves the ability of the photovoltaic power station to cope with power fluctuations, increases the charge and discharge efficiency of the system, extends the battery service life, reduces the operation and maintenance cost, and enhances the grid stability.

[0047] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in this application, and all should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

[0048] Finally, the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A DC-coupled inverter device for a photovoltaic power station, characterized in that, It includes an AC-side transformer, an inverter, photovoltaic modules, a DCDC converter, a battery cluster, a current and voltage detection sub-control box, a substation transformer measurement and control device, a real-time controller, current sensors, voltage sensors, circuit breakers, and contactors; the DCDC converter monitors voltage data and current data in real time and dynamically adjusts the duty cycle. The steps for dynamically adjusting the duty cycle are as follows: Step S1, the relationship between the output voltage V of the DCDC converter out and the input voltage V in is expressed by the following formula: V out = D·V in , where D is the duty cycle; Step S2, the duty cycle D satisfies where V ref is the preset target output voltage value, V load is the voltage value actually required by the load, and k is the gain factor used to convert the error signal into an appropriate duty cycle adjustment value; Step S3, perform real-time error detection. The calculation formula is: e = V ref - V out , where e is the error value; then perform error correction and adjust the duty cycle: D new = D prev + ΔD, where D new is the adjusted duty cycle, D prev is the duty cycle before adjustment, and ΔD is the correction value based on error adjustment, satisfying ΔD = k·e.

2. The DC-coupled inverter device for a photovoltaic power station according to claim 1, wherein The output power of the photovoltaic module is dynamically adjusted according to the changes in light intensity and temperature, and works in coordination with the battery cluster through the management of the real-time controller. The calculation formula for the dynamic adjustment is as follows: Where, P pv is the actual output power of the photovoltaic module, P stc is the rated output power of the photovoltaic module under standard test conditions, G is the current light intensity, G stc is the light intensity under standard test conditions, T is the current operating temperature of the photovoltaic module, T stc is the operating temperature under standard test conditions, and α is the temperature coefficient of the photovoltaic module, representing the sensitivity of the module efficiency to temperature changes.

3. A DC-coupled inverter device for a photovoltaic power station according to claim 1, characterized in that, The AC-side transformer consists of a primary winding, a secondary winding, and an iron core. The primary side of the AC-side transformer is connected to the inverter AC output on the DC side through the output terminal of the inverter. The secondary winding adopts a phase-shifting design, and the two windings operate independently. The secondary windings are respectively connected to the corresponding inverter groups through circuit breakers.

4. A DC-coupled inverter device for a photovoltaic power station according to claim 1, characterized in that, The AC side and the DC side of the inverter are connected by copper bars or cables. The DC input terminal of the inverter is connected to the DCDC converter through the DC bus, converting DC power into AC power that meets the requirements of the power grid, reducing harmonic components, and controlling the output voltage and frequency through sinusoidal pulse width modulation technology.

5. A DC-coupled inverter device for a photovoltaic power station according to claim 1, characterized in that, The DCDC converter is connected to the battery cluster through a contactor or a circuit breaker. Each group of DCDC input circuits samples current and voltage signals, receives DC input, reduces voltage fluctuations and current spikes through an input filter, adjusts voltage and current using high-frequency power switching devices combined with pulse width modulation technology, and embeds a digital signal processor to monitor voltage and current in real time.

6. The DC-coupled inverter device for a photovoltaic power station according to claim 1, characterized in that, The battery cluster uses lithium-ion batteries and feeds back the battery status to the real-time controller through a battery management system, including remaining capacity, operating temperature, and health status, stores excess electrical energy, and releases it when the photovoltaic power generation is insufficient.

7. A DC-coupled inverter device for a photovoltaic power station according to claim 1, characterized in that, The current and voltage detection sub-control box collects current and voltage signals of each circuit in real time, filters and amplifies them through a signal conditioning circuit, converts them into digital signals through an analog-to-digital converter, and transmits the digital signals to the real-time controller through a communication interface.

8. A DC-coupled inverter device for a photovoltaic power station according to claim 1, characterized in that, The substation transformer measurement and control device collects operation data and transmits it to the real-time controller, and interacts with the real-time controller through a communication interface; the substation transformer measurement and control device maintains data interaction with the power station dispatching system to achieve centralized management and remote monitoring of the power station.

9. A control method for a DC-coupled inverter device used in a photovoltaic power station, characterized in that, Applied to a DC-coupled inverter device for a photovoltaic power station according to any one of claims 1-8, it includes the following steps: Step Z1, start the device system to ensure that all photovoltaic modules are put into operation, and the inverter, DCDC converter, and battery cluster are in a standby state. The dispatching system sends a demand power instruction to the real-time controller through communication. The content of the instruction includes the target power value required by the current power grid or load. Step Z2, the real-time controller collects the current and voltage signals of all photovoltaic modules, and determines the instantaneous power of the photovoltaic modules through the power calculation formula P = V × I, where P is the electric power instantaneously generated by the photovoltaic modules, V is the voltage across the photovoltaic modules, and I is the current output by the photovoltaic modules. Compare the instantaneous power with the demand power according to the demand power instruction. Step Z3: Detect the battery status and judge the battery power status. If the battery is not fully charged, the DC bus of the inverter charges the lithium battery pack through the DCDC converter. The real-time controller continuously detects the battery power. When the power reaches the set full charge state, the charging stops automatically. If the battery is fully charged, the real-time controller calculates and analyzes the current photovoltaic power generation situation and the required power, and disconnects the photovoltaic module circuit by controlling the contactor to reduce the power generation power, avoid waste, and protect the system stability at the same time. Step Z4: When the instantaneous photovoltaic power is not enough to meet the required power, the real-time controller detects the remaining power of the battery pack. If the battery power is sufficient, the real-time controller commands the DCDC converter to transfer the electrical energy of the lithium battery pack to the DC bus of the inverter, and converts the battery electrical energy into alternating current through the inverter to supplement the insufficient power generation of the photovoltaic module and ensure that the system output power reaches the required power. If the power of the lithium battery pack is insufficient and the photovoltaic power generation cannot meet the required power, the real-time controller feeds back an alarm of insufficient power to the dispatching system, and the dispatching system adjusts the load demand or enables other standby power sources according to the feedback information. Step Z5: The real-time controller continuously collects the operation status data of the photovoltaic module, the battery pack, the DCDC converter and the inverter. The operation status data includes current, voltage, power and temperature. In any abnormal situation, the real-time controller immediately cuts off the faulty circuit, triggers the protection mechanism, and sends an alarm to the dispatching system.

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