Photovoltaic optimizer system capable of synchronously modulating energy and information

Abstract

The invention discloses an energy and information synchronous modulation photovoltaic optimizer system, which comprises photovoltaic modules, photovoltaic optimizers, a voltage regulator and a grid-connected inverter, and is characterized in that the output end of each photovoltaic module in the system is connected with a DC-DC photovoltaic optimizer, so that the maximum power tracking of the photovoltaic modules is realized; a plurality of photovoltaic assemblies are connected in series at the output end through a photovoltaic optimizer to form photovoltaic group strings, each group string is connected with a DC-DC voltage regulator, the output ends of different voltage regulators are connected in parallel to the direct current side of a grid-connected inverter, and stable and controllable direct current bus voltage is provided for the grid-connected inverter in a full working range; the photovoltaic optimizer and the voltage regulator communicate in an energy and information synchronous modulation mode. According to the invention, the maximum power tracking of each photovoltaic module is ensured, the voltage balance between the strings is realized through the voltage regulator, the power supply, wiring and layout of communication equipment do not need to be considered in the provided communication realization mode, the installation is simple, the expandability is strong, and the maintenance is convenient.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic power generation, and particularly relates to a photovoltaic optimizer system with synchronous modulation of energy and information. Background Art

[0002] Due to advantages such as zero pollution, flexible installation, and suitability for distributed deployment, photovoltaic power generation is gradually becoming an important direction for the global new energy transformation. According to the national power industry statistics data for 2024 released by the National Energy Administration, the cumulative installed power generation capacity in the country in 2024 was approximately 3.35 billion kilowatts, of which the installed capacity of solar power generation was approximately 890 million kilowatts, a year-on-year increase of 45.2%. A common photovoltaic system generally consists of multiple photovoltaic modules connected in series / parallel to form a photovoltaic array, which outputs a DC voltage of 400 - 800V, and then is connected to the grid for power generation by a grid-connected inverter.

[0003] In a photovoltaic power generation system, photovoltaic modules have strong non-linearity. Their operating points are related to the load, and there is a peak point, which is the maximum power point (MPP) of the photovoltaic module. However, the output characteristics of photovoltaic modules are related not only to the load but also to the external environment. For example, as the light intensity decreases and the temperature of the photovoltaic module increases, the maximum output power point of the photovoltaic module will decrease. In addition, the actual photovoltaic power generation system is also affected by factors such as the working environment, manufacturing process, hot spot effect, and battery aging, which may lead to a decrease in the overall working efficiency of the photovoltaic power generation system, and even damage to the photovoltaic module, causing accidents such as fires.

[0004] In response to the above problems, scholars at home and abroad have conducted a large number of studies. Currently, a relatively mature solution is to equip each photovoltaic module with a photovoltaic optimizer. By using the photovoltaic optimizer, the photovoltaic module can always operate at the maximum power point to achieve maximum power point tracking (MPPT), and then the output ends are connected in series. This solution can achieve MPPT for each photovoltaic module, which not only solves the problem of component-level power mismatch well but also can monitor the working status of each component, facilitating the maintenance, management, and protection of the photovoltaic system. Therefore, in addition to the MPPT function, the photovoltaic optimizer also needs to have a communication function to meet the information interaction requirements of the photovoltaic system.

[0005] The data communication of the PV optimizer can adopt wired or wireless communication methods. Wired communication includes independent wiring method or power line carrier communication method. The independent wiring communication method includes RS485, CAN bus communication, etc. Since the PV system has high requirements for line waterproofing, independent wiring not only increases the installation cost but also reduces the system reliability. Therefore, it is generally not adopted in practical applications. DC power line carrier communication (DC-PLC) is a better choice for the communication of the PV optimizer, which does not require additional wiring. The PV optimizer can also adopt wireless communication methods such as Wifi or Zigbee. Although this method avoids the wiring problem of wired communication, the installation method of the antenna and the network debugging of wireless communication are relatively complex, reducing the system reliability. In addition, the wireless communication circuit also increases the system cost.

[0006] According to the above analysis, considering reliability and cost performance, the best way for the PV optimizer to exchange data with the inverter is power line carrier communication. However, the traditional design method uses different circuits and methods to implement the two functions of power conversion and information transmission respectively. Therefore, there are still disadvantages such as complex system, more components, and high cost. In addition, the working frequency of power line carrier is generally high, and there are often crosstalk problems between carrier signals in different strings, and it is easily interfered by converters such as optimizers and inverters. If a lower working frequency is set, the device volume will increase. Summary of the Invention

[0007] In view of the above technical problems existing in the prior art, the present invention provides a PV optimizer system with synchronous modulation of energy and information, which can maximize the power of the PV array and realize information interaction in the system without additional communication equipment.

[0008] The present invention adopts the following technical solutions: A PV optimizer system with synchronous modulation of energy and information, including PV modules, PV optimizers, voltage regulators, and grid-connected inverters (as Figure 1 shown):

[0009] The output end of each PV module is connected to the PV optimizer. Multiple PV modules are connected in series at the output end through the PV optimizer to form a PV string. Each string is connected to a voltage regulator, and the output ends of different voltage regulators are connected in parallel to the DC side of the grid-connected inverter;

[0010] The PV optimizer and the voltage regulator adopt different synchronous modulation mechanisms of energy and information to achieve two-way communication;

[0011] The PV optimizer transmits data to the voltage regulator while achieving energy output through the following mechanism: The data to be sent is first converted into a frequency band signal through frequency band modulation. This frequency band signal is then superimposed onto the power control loop of the PV optimizer. After being amplified by the power control loop, the modulated data signal is superimposed on the DC output and transmitted to the voltage regulator through the DC line. After receiving the superimposed signal, the voltage regulator demodulates it to recover the original data;

[0012] The voltage regulator transmits data to the PV optimizer through the following mechanism: The data to be sent is first modulated onto the PWM carrier of the voltage regulator, compared with the output of the power control loop to generate a control signal, thereby generating a ripple signal containing the modulated data at the power input port of the voltage regulator. This ripple signal is transmitted to the PV optimizer through the DC line. After receiving the ripple signal, the PV optimizer demodulates it to extract the original data.

[0013] Furthermore, the PV optimizer includes a Buck-type DC-DC converter, a signal conditioning circuit, a digital controller, a drive circuit, and an external communication interface; where:

[0014] The Buck-type DC-DC converter is used to regulate the output power of the PV module to make the PV module operate at the maximum power point;

[0015] The signal conditioning circuit is used to collect the output current and output voltage of the PV module, as well as the current at the output port of the Buck-type DC-DC converter, and filter it to obtain the ripple current therein, and transmit the output current, output voltage, and ripple current of the PV module to the digital controller;

[0016] When the PV optimizer communicates, the digital controller modulates the data to be sent into a frequency band signal, superimposes it on the power control loop, and generates a control signal for the Buck-type DC-DC converter after comparing it with the switching carrier;

[0017] The drive circuit is used to amplify the control signal and then drive and control the Buck-type DC-DC converter;

[0018] The external communication interface is connected to the communication interface of the digital controller itself to realize the digital information interaction between the external device and the digital controller.

[0019] Furthermore, the modulation methods that can be adopted when the PV optimizer sends data include: ASK, FSK, PSK, QPSK, OFDM.

[0020] Furthermore, the voltage regulator includes a Boost-type DC-DC converter, a signal conditioning circuit, a digital controller, a drive circuit, and an external communication interface, where:

[0021] The Boost-type DC-DC converter is used to regulate the output voltage of the photovoltaic string.

[0022] The signal conditioning circuit is used to collect the output current and output voltage of the photovoltaic string, as well as the current at the input port of the Boost-type DC-DC converter, filter the ripple current therefrom, and transmit the output current, output voltage and ripple current of the photovoltaic string to the digital controller.

[0023] When the digital controller communicates with the voltage regulator, it modulates the data to be sent onto the PWM carrier of the voltage regulator, switches to the modulated PWM carrier by the communication selection switch, compares the output of the power control loop with the modulated PWM carrier, generates the control signal of the Boost-type DC-DC converter, so as to generate a ripple signal containing the modulated data at the power input port of the voltage regulator, and this ripple signal is transmitted to the photovoltaic optimizer through the DC line.

[0024] The drive circuit is used to amplify the control signal and then drive and control the Boost-type DC-DC converter.

[0025] The external communication interface is connected to the communication interface of the digital controller itself to realize the digital information interaction between the external device and the digital controller.

[0026] Further, when the voltage regulator sends data, the modulation methods that the PWM carrier can adopt include FSK and PSK.

[0027] The present invention has the following beneficial technical effects:

[0028] (1) The present invention is equipped with a photovoltaic optimizer for each photovoltaic module, which can make each photovoltaic module work near the maximum power point. At the same time, the photovoltaic optimizer is used for information modulation to complete the communication with the inverter side, realizing the monitoring, control and protection of the photovoltaic module.

[0029] (2) The present invention uses the voltage regulator as the device for information interaction between the inverter side and the photovoltaic optimizer, without the need to add additional carrier modulation and injection devices, reducing the system cost and volume.

[0030] (3) The voltage regulator of the present invention can regulate the output voltage of the photovoltaic string in the full range, provide a stable DC bus voltage input for the grid-connected inverter, and at the same time use the voltage regulator for information modulation, converting the relatively large switching ripple noise into a carrier carrying information, effectively improving the reliability of communication.

[0031] (4) The present invention is simple in engineering installation, has strong scalability, does not need to consider the power supply, wiring and layout of the communication equipment, and is convenient for later maintenance. Description of the Drawings

[0032] Figure 1 Schematic diagram of the structure of the photovoltaic power generation system of the present invention;

[0033] Figure 2 Schematic diagram of the principle of the Buck-type DC-DC converter adopted by the photovoltaic optimizer of the present invention;

[0034] Figure 3 Schematic diagram of the principle of the Boost-type DC-DC converter adopted by the voltage regulator of the present invention;

[0035] Figure 4 Partial schematic diagram of the structure of the photovoltaic optimizer adopted by the present invention;

[0036] Figure 5 Partial schematic diagram of the structure of the voltage regulator adopted by the present invention. Detailed implementation manners

[0037] In order to describe the present invention more specifically, the technical solutions of the present invention will be described in detail below with reference to the drawings and specific implementation manners.

[0038] The photovoltaic power generation system of the present invention is a photovoltaic optimizer system with synchronous modulation of energy and information. As Figure 1 shown, it includes photovoltaic modules, a photovoltaic optimizer, a voltage regulator, and a grid-connected inverter. The output end of each photovoltaic module is connected to the photovoltaic optimizer. Multiple photovoltaic modules are connected in series at the output end through the photovoltaic optimizer to form a photovoltaic string. Each string is connected to the voltage regulator, and the output ends of different voltage regulators are connected in parallel to the DC side of the grid-connected inverter.

[0039] The photovoltaic optimizer and the voltage regulator adopt different mechanisms for synchronous modulation of energy and information to achieve two-way communication.

[0040] The photovoltaic optimizer adopts a Buck-type DC-DC converter, as Figure 2 shown. On the one hand, it adjusts the output voltage of the photovoltaic module through the MPPT control loop to make the photovoltaic module work at the maximum power point. On the other hand, information modulation is carried out in the control loop to send a digital information modulation carrier signal to the output port. This carrier signal is received by the voltage regulator on the inverter side. When the light intensity is strong, the optimizer works in the through mode to reduce losses. If there is a need for data transmission at this time, the optimizer is briefly adjusted to the duty cycle working mode, so as to send a digital information modulation carrier signal to the output port, and then continue to work in the through mode.

[0041] The photovoltaic optimizer of the present invention further includes a signal conditioning circuit, a digital controller, a drive circuit, and an external communication interface. The schematic diagram of its principle is as Figure 4As shown in the figure, the signal conditioning circuit is used to collect the output current and output voltage of the photovoltaic module, as well as the current at the output port of the Buck DC-DC converter, filter it to obtain the ripple current therein, and then transmit the output current, output voltage and ripple current of the photovoltaic module to the digital controller; when the photovoltaic optimizer does not communicate, the digital controller compares the output of the power control loop with the switching carrier wave to generate the control signal of the Buck DC-DC converter. When the photovoltaic optimizer communicates, the digital information to be sent is modulated into a band signal, which is superimposed on the power control loop and compared with the switching carrier wave to generate the control signal of the Buck DC-DC converter; the drive circuit is used to amplify the control signal and drive and control the Buck DC-DC converter; the external communication interface is connected to the digital controller through the digital controller's own communication interfaces such as USART, I2C, SPI and CAN to realize the digital information interaction between the external device and the digital controller.

[0042] The digital controller of the photovoltaic optimizer according to the present invention includes the following hardware or software functional modules: a signal sampling and processing module, which performs AD sampling on the output current, output voltage and ripple current of the photovoltaic module, calculates the power of the photovoltaic module, and performs Fourier transform on the collected ripple current to obtain its frequency information; a maximum power tracking module, which is used to determine the control amount of power adjustment according to the output power by using the maximum power tracking algorithm; a communication carrier modulation module, which, when the photovoltaic optimizer communicates externally, modulates the digital information to be sent into a sine disturbance signal, and the modulation methods include ASK, FSK, PSK, QPSK, OFDM, etc., and superimposes it on the control amount of power adjustment to obtain a modulated wave signal; a control signal generation module, which is used to compare the modulated wave signal with the switching carrier wave signal to generate the control signal of the Buck DC-DC converter.

[0043] The voltage regulator according to the present invention uses a Boost DC-DC converter, as Figure 3 shown. In addition, it also includes a signal conditioning circuit, a digital controller, a drive circuit and an external communication interface, and its schematic diagram is as Figure 5As shown, the signal conditioning circuit is used to collect the output current and output voltage of the photovoltaic string, as well as the current at the input port of the Boost-type DC-DC converter, filter it to obtain the ripple current therein, and then transmit the output current, output voltage and ripple current of the photovoltaic string to the digital controller; when the voltage regulator does not communicate, the digital controller compares the output of the power control loop with the PWM carrier wave to generate the control signal of the Boost-type DC-DC converter. When the voltage regulator communicates, the digital information to be sent is modulated onto the PWM carrier wave of the voltage regulator, switched to the modulated PWM carrier wave by the communication selection switch, and then the output of the power control loop is compared with the modulated PWM carrier wave. When the amplitude is higher than the modulated PWM carrier wave, a high level is output, otherwise a low level is output, generating the control signal of the Boost-type DC-DC converter, so as to generate a ripple signal containing modulated data at the power input port of the voltage regulator. This ripple signal is transmitted to the photovoltaic optimizer through the DC line. After receiving the ripple signal, the photovoltaic optimizer demodulates it to extract the original data; the drive circuit is used to amplify the control signal and drive and control the Boost-type DC-DC converter; the external communication interface is connected to the digital controller through the digital controller's own communication interfaces such as USART, I2C, SPI and CAN to realize the digital information interaction between the external device and the digital controller.

[0044] The digital controller of the voltage regulator described in the present invention includes the following hardware or software function modules: a signal sampling and processing module, which performs AD sampling on the output current, output voltage and ripple current of the photovoltaic string, calculates the power of the photovoltaic string, and performs Fourier transform on the collected ripple current to obtain its frequency information; a communication carrier modulation module, which, when the voltage regulator communicates with the photovoltaic optimizer, modulates the digital information to be sent into a switching carrier signal carrying the digital information and is selected and output by the communication selection switch. The modulation methods include FSK and PSK, etc.; a voltage regulator control signal generation module, which is used to compare the modulation wave signal of the voltage regulator with the switching carrier signal to generate the control signal of the Boost-type DC-DC converter.

[0045] It should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made without creative efforts shall be included in the protection scope of the present invention.

Claims

1. A photovoltaic optimizer system with synchronous modulation of energy and information, comprising a photovoltaic module, a photovoltaic optimizer, a voltage regulator and a grid-connected inverter, characterized in that: The output end of each PV module is connected to a PV optimizer. Multiple PV modules are connected in series at the output end through the PV optimizer to form a PV string. Each string is connected to a voltage regulator. The output ends of different voltage regulators are connected in parallel to the DC side of the grid-connected inverter. The PV optimizer transmits data to the voltage regulator while achieving energy output through the following mechanism: the data to be sent is converted into a frequency band signal through frequency band modulation, superimposed on the power control loop of the PV optimizer, and after amplification by the power control loop, the modulated data signal is superimposed on the DC output and transmitted to the voltage regulator through the DC line, and the voltage regulator demodulates the superimposed signal after receiving it; The voltage regulator transmits data to the PV optimizer through the following mechanism: the data to be sent is modulated onto the PWM carrier of the voltage regulator, compared with the output of the power control loop, and a control signal is generated, thereby generating a ripple signal containing the modulated data at the power input port of the voltage regulator. The ripple signal is transmitted to the PV optimizer through the DC line, and the PV optimizer demodulates the ripple signal after receiving it.

2. The photovoltaic optimizer system according to claim 1, characterized in that: The photovoltaic optimizer includes a Buck type DC-DC converter, a signal conditioning circuit, a digital controller, a drive circuit and an external communication interface; wherein: The Buck type DC-DC converter is used to adjust the output power of the photovoltaic module so that the photovoltaic module operates at the maximum power point; The signal conditioning circuit is used to collect the output current and output voltage of the photovoltaic module and the current of the output port of the Buck type DC-DC converter, and filter them to obtain the ripple current therein, and transmit the output current, output voltage and ripple current of the photovoltaic module to the digital controller; When the PV optimizer communicates, the digital controller modulates the data to be sent into a frequency band signal, superimposes it on the power control loop, and generates a control signal for the Buck type DC-DC converter after comparing it with the switch carrier; The driving circuit is used to drive and control a Buck type DC-DC converter after amplifying the control signal; The external communication interface is connected to the communication interface of the digital controller itself to realize digital information interaction between the external device and the digital controller.

3. The photovoltaic optimizer system according to claim 1, characterized in that: The modulation methods used by the photovoltaic optimizer to send data include: ASK, FSK, PSK, QPSK, and OFDM.

4. The photovoltaic optimizer system according to claim 1, characterized in that: The voltage regulator includes a Boost type DC-DC converter, a signal conditioning circuit, a digital controller, a drive circuit and an external communication interface, wherein: The Boost type DC-DC converter is used to adjust the output voltage of the photovoltaic string; The signal conditioning circuit is used to collect the output current and output voltage of the photovoltaic string and the current of the input port of the Boost type DC-DC converter, and filter them to obtain the ripple current therein, and transmit the output current, output voltage and ripple current of the photovoltaic string to the digital controller; When the voltage regulator communicates, the digital controller modulates the data to be sent onto the PWM carrier of the voltage regulator, switches to the modulated PWM carrier by the communication selection switch, compares the output of the power control loop with the modulated PWM carrier, generates a control signal of the Boost type DC-DC converter, thereby generating a ripple signal containing the modulated data at the power input port of the voltage regulator, and the ripple signal is transmitted to the photovoltaic optimizer through the DC line; The driving circuit is used to drive and control the Boost type DC-DC converter after amplifying the control signal; The external communication interface is connected to the communication interface of the digital controller itself to realize digital information interaction between the external device and the digital controller.

5. The photovoltaic optimizer system according to claim 1, characterized in that: When the voltage regulator sends data, the modulation methods used by the PWM carrier include: FSK and PSK.

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