Grid-connected phase synchronization device and method for energy storage converter

Abstract

The invention discloses a grid-connected phase synchronization device and method for an energy storage converter. A voltage division circuit of the device reduces and preprocesses the high voltage of a power grid, a voltage comparator module converts an analog signal into a digital level signal, a zero-cross detection comparator provides a phase reference, and an amplitude detection comparator judges the voltage grade; the control logic unit integrates the signal to generate a coding synchronization pulse; the output driving circuit enhances the signal driving capability and converts the level; the synchronizing signal transmission cable stably transmits pulses; and the PCS end detection circuit receives the analysis signal and controls the energy storage converter to adjust the phase and the amplitude. According to the method, synchronization is achieved through the processes of power grid voltage signal preprocessing and detection, synchronizing signal encoding, synchronizing signal transmission, PCS end decoding and phase synchronization. The phase synchronization precision is high, and the anti-interference capability and the reliability are high.

Description

Technical Field

[0001] This invention relates to the field of energy storage converters, and more specifically to a grid-connected phase synchronization device and method for an energy storage converter. Background Technology

[0002] As the energy conversion hub between the energy storage system and the power grid, the energy storage converter is responsible for bidirectional conversion between DC and AC power. Grid-connected phase synchronization is a prerequisite for ensuring the safe and stable connection of the energy storage converter to the power grid.

[0003] Currently, mainstream grid-connected phase synchronization schemes for energy storage converters generally employ the following process: real-time acquisition of grid voltage signals; calculation and analysis of the sampled data using digital signal processing algorithms to derive key synchronization parameters such as the frequency, phase, and amplitude of the grid voltage; transmission of the calculated synchronization parameters to the control unit of the energy storage converter via a dedicated communication bus; and adjustment of the inverter circuit's output characteristics by the control unit to achieve phase synchronization with the grid. The main problems with the above-mentioned existing technical solutions are:

[0004] (1) Slow response speed: From grid voltage sampling and parameter calculation to the transmission of synchronization parameters to the energy storage converter through the communication link, multiple links are required, and each link will generate time delay; especially when the communication link is unstable or the transmission is congested, the delay will be further aggravated, resulting in the synchronization process being delayed and unable to adapt to scenarios with high synchronization speed requirements such as distributed energy storage and microgrids.

[0005] (2) Limited synchronization accuracy: The sampling error of the analog-to-digital converter, the calculation delay of the digital signal processing algorithm, and the signal jitter during the communication process will be superimposed, resulting in deviations in the synchronization parameters finally transmitted to the energy storage converter, reducing the synchronization accuracy between the energy storage converter output and the power grid.

[0006] (3) High cost and complexity: The solution requires multiple high-precision analog-to-digital converters, high-speed data processors and dedicated communication interface modules, resulting in high hardware procurement costs. At the same time, the development of digital signal processing algorithms, the adaptation of communication protocol stacks and the debugging of software development are highly complex, which is not conducive to the large-scale promotion and application of the technology.

[0007] In summary, a new technical solution is needed to address the aforementioned problems in order to meet the practical requirements of efficient and reliable grid connection of energy storage systems. Summary of the Invention

[0008] To address the problems of slow response, low accuracy, high cost, poor reliability, and weak anti-interference capability in existing energy storage converter grid-connected phase synchronization technologies, this invention proposes an energy storage converter grid-connected phase synchronization technology solution that does not rely on communication protocols.

[0009] The first objective of this invention is to provide a grid-connected phase synchronization device for an energy storage converter, comprising a voltage divider circuit, a voltage comparator module, a control logic unit, and an output drive circuit connected in sequence, and a synchronization signal transmission cable with one end connected to the output drive circuit and the other end connected to a PCS terminal detection circuit built into the energy storage converter. The voltage divider circuit is connected to the AC side of the power grid, performing voltage reduction, filtering, and overvoltage protection on the high voltage of the grid, and outputting a low-voltage analog signal. The voltage comparator module includes a zero-crossing detection comparator channel and an amplitude detection comparator channel. The zero-crossing detection comparator channel provides a zero-crossing trigger signal for the grid voltage, and the amplitude detection comparator channel determines the grid voltage amplitude level. The control logic unit integrates the digital level signals to generate an encoded synchronization pulse signal. The output drive circuit enhances the driving capability of the synchronization pulse signal and converts its level. The synchronization signal transmission cable transmits the enhanced synchronization pulse signal. The PCS terminal detection circuit receives and analyzes the synchronization pulse signal, controlling the energy storage converter to adjust the phase and amplitude of the inverter output, thereby achieving grid-connected phase synchronization.

[0010] Preferably, the voltage divider circuit uses a metal film resistor to form a voltage divider network, and incorporates a bidirectional transient suppression diode for overvoltage protection and an RC filter network composed of resistors and capacitors.

[0011] Preferably, the voltage comparator module uses a high-speed voltage comparator chip; the reference voltage of the zero-crossing detection comparator channel is set to the level corresponding to the AC zero point of the power grid and calibrated by a bias circuit; the reference voltage of the amplitude detection comparator channel is adjusted in multiple stages by a potentiometer to divide the power grid voltage amplitude into low, normal, and overvoltage levels, and outputs a high-level or low-level digital signal.

[0012] Preferably, the control logic unit adopts any of the following implementation methods: (1) a pure hardware logic gate circuit composed of AND gate, OR gate and delay circuit to realize the generation of synchronous pulse signal; (2) a microcontroller is used to collect the digital level signal output by the voltage comparator module through the digital IO port, configure the encoding rules and realize fault diagnosis and signal filtering functions.

[0013] Preferably, the output driving circuit adopts a totem pole driving structure composed of PNP transistors and NPN transistors, and has a built-in level conversion module, reverse protection diode and overcurrent protection resistor.

[0014] Preferably, the PCS terminal detection circuit includes a pull-up resistor, an optocoupler isolation circuit, a timer / counter module, and a microprocessor; the pull-up resistor is connected in series with the optocoupler isolation circuit, the timer / counter module is used to capture the rising and falling edges of the synchronization pulse, and the microprocessor is used to calculate the grid frequency, decode the amplitude level, and reset the inverter output phase of the energy storage converter to 0° and adjust the PWM modulation depth when the synchronization pulse rises; the grid frequency is calculated by dividing 1 by the time interval between two adjacent rising edges of the synchronization pulse.

[0015] The second objective of this invention is to provide a grid-connected phase synchronization method for energy storage converters, based on the aforementioned grid-connected phase synchronization device for energy storage converters, comprising the following steps:

[0016] S1: The AC voltage from the power grid is connected, and after being stepped down, filtered, and protected against overvoltage by a voltage divider circuit, a low-voltage analog signal is output. The low-voltage analog signal is input to a voltage comparator module, which obtains the zero-crossing trigger signal of the power grid voltage through the zero-crossing detection comparator channel and the amplitude level signal of the power grid voltage through the amplitude detection comparator channel, and outputs a digital level signal.

[0017] S2: The control logic unit receives the digital level signal, matches the correspondence between amplitude level and pulse width according to the preset encoding rules, and generates an encoded synchronization pulse signal of corresponding width when it receives the zero-crossing rising edge trigger signal.

[0018] S3: The output drive circuit performs level conversion and drive enhancement on the encoded synchronization pulse signal, and then transmits it to the PCS terminal detection circuit of the energy storage converter via the synchronization signal transmission cable.

[0019] S4: The PCS terminal detection circuit receives and isolates the synchronization pulse signal, and measures the pulse frequency and width through the timer counter module to analyze the grid frequency and amplitude level; based on the analysis results, at the rising edge of the synchronization pulse, the inverter output phase of the energy storage converter is reset to 0° and the PWM modulation depth is adjusted to synchronize the output of the energy storage converter with the grid.

[0020] Preferably, in step S1: the voltage divider circuit converts the high voltage of the power grid into a low voltage analog signal, filters out high-frequency interference through an RC filter network, and clamps the surge voltage through a bidirectional transient suppression diode; the zero-crossing detection comparator channel outputs a rising edge or falling edge trigger signal, the amplitude detection comparator channel outputs a digital level signal corresponding to the low, normal, or overvoltage level, and the outputs of the zero-crossing detection comparator and the amplitude detection comparator are both transmitted to the control logic unit.

[0021] Preferably, in step S2: the preset encoding rule is: a 5ms wide high-level pulse corresponds to a normal amplitude level, a 2ms wide high-level pulse corresponds to a low amplitude level, and an 8ms wide high-level pulse corresponds to an overvoltage level; the generation of the encoding synchronization pulse signal is triggered by the rising edge of the zero-crossing detection comparator channel, and the high level continues for a set width before switching to a low level.

[0022] Preferably, in step S4: the PCS terminal detection circuit receives the synchronization pulse signal through a pull-up resistor and an optocoupler isolation circuit; the phase and amplitude adjustment period of the energy storage converter is less than or equal to 1 millisecond.

[0023] The present invention has the following beneficial effects:

[0024] (1) This invention adopts a pure physical layer signal transmission mechanism, which does not rely on communication protocols to transmit synchronization parameters, thus avoiding the time delay of multiple links such as grid voltage sampling, digital signal calculation, and communication link transmission in traditional schemes. By constructing an efficient signal processing link through high-speed voltage comparators and hardware logic gate circuits, and combined with the real-time parsing and phase reset design at the PCS end, it can quickly adapt to scenarios with high synchronization speed requirements such as distributed energy storage and microgrids.

[0025] (2) The device uses a voltage divider network composed of high-precision metal film resistors. The zero-crossing detection comparator is precisely biased and calibrated to generate a time trigger signal based on the AC zero point of the power grid. This avoids the cumulative effects of analog-to-digital converter sampling errors, digital signal processing calculation delays, and communication jitter in traditional schemes. At the same time, the PCS end uses a high-precision timer to capture the rising and falling edges of the synchronization pulse, achieving accurate analysis of the power grid frequency and amplitude, with very small phase synchronization errors.

[0026] (3) The core of the device of the present invention consists of a voltage divider circuit, a common voltage comparator, a low-cost logic gate circuit and a common shielded twisted pair cable. It does not require an additional communication module or a complex digital signal processing chip, thus reducing the hardware procurement cost. In terms of software development, it does not require adaptation to a complex communication protocol stack, but only simple logic control or basic parameter configuration, which reduces the difficulty of algorithm development and system debugging and is conducive to the large-scale promotion and application of the technology.

[0027] (4) The device integrates bidirectional transient suppression diodes and RC filter networks in the voltage divider circuit, which can quickly clamp grid surge voltage and filter out high-frequency interference noise; the PCS terminal achieves electrical isolation between the device and the converter through an isolation circuit, and the synchronization signal is transmitted using tinned copper wire shielded twisted pair cable, which effectively resists external electromagnetic interference. In addition, since it does not rely on the communication link, it avoids the risk of synchronization failure caused by communication congestion, signal instability or protocol incompatibility, and improves the overall reliability of the system.

[0028] In summary, this invention can be stably applied to various scenarios such as industrial energy storage stations, outdoor energy storage projects, and emergency power systems, and has strong adaptability. Attached Figure Description

[0029] Figure 1 This is a diagram illustrating the method steps of an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the phase synchronization principle in an embodiment of the present invention;

[0031] Figure 3 This is a circuit diagram of a phase synchronization device according to an embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] The grid-connected phase synchronization device for the energy storage converter in this embodiment adopts a pure physical layer transmission mechanism, independent of communication protocols. Through modular design, it achieves rapid acquisition, encoding, and transmission of grid frequency, phase, and amplitude information, providing accurate synchronization data for the energy storage converter. The device as a whole consists of a voltage divider circuit, a voltage comparator module, a control logic unit, an output drive circuit, a synchronization signal transmission cable, and a PCS terminal detection circuit, etc. Figure 2 and Figure 3 As shown, each part works in concert through a clearly defined signal link to ensure the efficient transmission and accurate parsing of the synchronization signal.

[0035] I. Voltage Divider Circuit. This is the front-end input processing module of the device. Its core function is to safely step down the high voltage of the power grid and preprocess the signal, providing a stable and reliable input signal for subsequent circuits.

[0036] The circuit employs a high-precision metal film resistor network to form a voltage divider, with resistor accuracy controlled within ±1% to ensure long-term stability of the voltage division ratio. The input terminal is directly connected to the AC side of the mains, adaptable to both 220V and 380V common mains voltages. It converts high voltage to a low-voltage analog signal of 0-5V at a fixed ratio, meeting the input voltage requirements of subsequent circuits while ensuring safe equipment operation.

[0037] The circuit incorporates overvoltage protection components and an RC filter network. The overvoltage protection component uses a bidirectional transient voltage suppressor diode, which quickly clamps the voltage when a surge voltage occurs in the power grid, preventing damage to subsequent circuits due to overvoltage. The RC filter network, composed of precision resistors and capacitors, effectively filters out high-frequency interference noise in the power grid voltage, outputting a smooth and stable low-voltage analog signal. The circuit has a compact structure, no complex semiconductor components, low power consumption, and high reliability, making it suitable for various power grid environments such as industrial plants and outdoor energy storage stations.

[0038] II. Voltage Comparator Module. This is a signal conversion module responsible for converting the analog voltage signal output from the voltage divider circuit into a digital level signal, providing a foundation for subsequent encoding. The module contains two independently operating comparator channels, both using high-speed voltage comparator chips, such as the LMV7219, with a response time of no more than ten nanoseconds, ensuring the timeliness and accuracy of signal conversion.

[0039] The reference voltage of the zero-crossing detection comparator channel is set to the level corresponding to the AC zero point of the mains power grid and is calibrated through a precise bias circuit. When the mains voltage, after voltage division, crosses from negative to positive zero, the comparator output level jumps from low to high, generating a rising edge trigger signal. When the voltage crosses from positive to negative zero, the output level jumps from high to low, generating a falling edge signal. This channel monitors the zero-crossing point of the mains voltage in real time throughout the entire process, providing a precise time reference for phase synchronization.

[0040] The reference voltage of the amplitude detection comparator channel is adjustable in multiple levels via potentiometers to adapt to amplitude detection requirements at different grid voltage levels. This channel acquires the peak value of the grid voltage after voltage division in real time and compares it with a preset reference threshold to determine the grid voltage amplitude level. Common levels are divided into three categories: low, normal, and overvoltage. The normal level corresponds to 90-110% of the grid's rated voltage, the low level is below 90% of the rated voltage, and the overvoltage level is above 110% of the rated voltage, providing a clear basis for subsequent amplitude encoding. Both channels output standard digital high and low levels, with a high level of 5 volts and a low level of 0 volts, exhibiting strong electromagnetic interference resistance and allowing direct connection to subsequent control logic units.

[0041] III. Control Logic Unit. This is the device's signal processing module, responsible for integrating the output signals of the two comparator channels to generate coded synchronization pulse signals. This unit supports two implementation methods, which can be flexibly selected according to the application scenario. Both have modular design features, ensuring the device's versatility and economy.

[0042] The first method uses pure hardware logic gates, consisting of AND gates, OR gates, and delay circuits. It requires no software programming and is extremely low-cost. The hardware logic is directly activated by the trigger signal of the zero-crossing detection comparator and simultaneously receives the level signal from the amplitude detection comparator, generating a pulse signal of corresponding width according to preset rules. Specifically, when the rising edge signal of the zero-crossing detection is received, the AND gate is triggered and conducts. Combined with the delay signal corresponding to the amplitude level, a fixed-width high-level pulse is output through the OR gate. There is no software delay throughout the process, resulting in a fast response speed; the delay time from signal reception to pulse generation does not exceed fifty nanoseconds.

[0043] The second approach uses a low-cost microcontroller, such as the STM32F103 series, which is suitable for scenarios requiring flexible adjustment of encoding rules. The microcontroller acquires the output signals of the two comparators through digital I / O ports and has a built-in simple program to analyze the signals. Different amplitude levels of pulse width can be configured via software, and extended functions such as fault diagnosis and signal filtering can also be implemented.

[0044] IV. Output Driver Circuit. This circuit enhances the synchronization pulse signal generated by the control logic unit, ensuring the stability and integrity of the signal during long-distance transmission.

[0045] The core of the circuit uses high-speed power transistors in conjunction with a totem-pole drive structure. This totem-pole drive structure consists of PNP and NPN transistors, commonly the S8550 and S8050 models. This structure can boost the driving capability of pulse signals to over 500 mA, meeting the requirements of long-distance cable transmission and preventing signal attenuation and distortion due to insufficient driving capability.

[0046] The circuit incorporates a level conversion module, using a level conversion chip such as the 74HC245 to convert the 3.3V or 5V output from the control logic unit to a standard 12V industrial level, enhancing signal anti-interference capabilities. It is also equipped with a reverse protection diode and an overcurrent protection resistor. The reverse protection diode can be a 1N4007, and the overcurrent protection resistor is 10 ohms, preventing damage to the device due to external circuit malfunctions. The output uses standard Phoenix terminal blocks for direct connection to the synchronization signal transmission cable, simplifying wiring and adapting to complex installation environments.

[0047] 5. Synchronization signal transmission cable. This is the physical transmission carrier of the synchronization signal, and its function is to stably transmit the pulse signal enhanced by the output drive circuit to the PCS detection circuit.

[0048] The cable uses ordinary shielded twisted-pair cable with a tinned copper wire shielding layer, which effectively resists external electromagnetic interference and ensures signal transmission quality. The characteristic impedance of the cable is controlled at 120 ohms to reduce signal reflection and ensure distortion-free transmission of pulse signals.

[0049] One end of the cable connects to the output drive circuit via a Phoenix terminal block, while the other end remains suspended, not connected to any load or equipment, serving solely as a transmission channel for pulse signals. This design avoids the influence of the load on the signal, ensuring signal purity. The cable can be laid alongside the power cables of the energy storage system or laid independently, requiring minimal additional installation space and reducing wiring complexity. The cable length supports stable transmission up to 50 meters, meeting the installation requirements of distributed energy storage, microgrids, and other scenarios. The cable sheath is made of flame-retardant PVC material, possessing excellent high-temperature resistance and aging resistance, with an operating temperature range of -40°C to 80°C, suitable for long-term use in outdoor or industrial environments.

[0050] VI. PCS Terminal Detection Circuit. The PCS terminal detection circuit is integrated inside the energy storage converter. It is responsible for receiving and parsing the synchronization signal, providing a precise control basis for the phase synchronization of the energy storage converter. The circuit mainly consists of pull-up resistors, optocoupler isolation circuits, timer / counter modules, and control units. These parts work together to achieve signal reception, isolation, parsing, and control command output.

[0051] The pull-up resistor is a 10kΩ precision metal film resistor, connected in series with the input of the optocoupler isolation circuit to ensure signal level stability and avoid signal misinterpretation due to level drift. The optocoupler isolation circuit uses a high-speed optocoupler chip with a transmission delay of no more than 50 nanoseconds, achieving electrical isolation between the device and the PCS to avoid mutual interference and enhance the circuit's electromagnetic interference immunity.

[0052] The timer / counter module employs a 16-bit high-precision timer integrated within the PCS control chip. This module accurately measures the pulse frequency and width of the synchronization signal by capturing its rising and falling edges, providing fundamental data for power grid parameter calculations.

[0053] The control unit, as the core processing module, employs a high-performance microprocessor to receive measurement data from the timer and counter in real time. It calculates the grid frequency using pulse frequency, specifically by dividing one second by the time interval between two adjacent rising edges of pulses. It decodes the grid voltage amplitude using pulse width modulation and matches the corresponding amplitude level according to preset encoding rules. Upon each rising edge of the synchronization signal, the control unit forcibly resets the phase of the energy storage converter's inverter output to 0°, achieving precise phase alignment. Simultaneously, it adjusts the PWM modulation depth based on the decoded amplitude information to ensure that the energy storage converter's output voltage amplitude matches the grid, with the entire synchronization adjustment cycle not exceeding one millisecond.

[0054] In this embodiment, the various parts of the grid-connected phase synchronization device for the energy storage converter cooperate with each other to achieve fast and high-precision phase synchronization.

[0055] Example 2

[0056] The energy storage converter grid-connected phase synchronization method in this embodiment is based on the device in Embodiment 1. Through a complete process of detection, encoding, transmission, decoding, and synchronization, it can achieve rapid and accurate synchronization between the energy storage converter and the power grid without relying on communication protocols, ensuring the efficiency and reliability of the synchronization process. Figure 1 As shown, the method includes the following steps:

[0057] S1. Power Grid Voltage Signal Preprocessing and Detection. This step involves safely converting the power grid voltage and detecting key features to provide an accurate signal foundation for subsequent encoding. The specific operations are as follows:

[0058] S11 Mains Voltage Divider Processing. The AC mains voltage is connected to a voltage divider circuit, and a high-precision resistor divider network steps down the voltage by a fixed ratio, converting the high voltage into a low-voltage analog signal of 0-5V. During this process, an RC filter network filters out high-frequency interference noise, and overvoltage protection components clamp surge voltage, ensuring a smooth, stable, and safe output low-voltage signal that meets the input requirements of subsequent comparator modules.

[0059] S12 Zero-crossing and amplitude characteristic detection. Two channels of the low-voltage signal synchronous input voltage comparator module. The zero-crossing detection comparator monitors voltage changes in real time, and outputs a corresponding rising or falling edge trigger signal when the voltage crosses zero. The amplitude detection comparator compares the voltage peak value with a preset reference threshold to determine whether the amplitude is low, normal, or overvoltage. The detection results of the two channels are output to the control logic unit in digital high and low level form.

[0060] S2 Synchronization Signal Encoding. This step, based on the detection results of S1, digitally encodes the power grid phase and amplitude information to generate a synchronization pulse signal with specific characteristics. The specific operation is as follows:

[0061] S21 Encoding Rule Matching. The control logic unit receives the zero-crossing detection trigger signal and the amplitude level signal, and matches them according to the preset encoding rule. The encoding rule is set so that different amplitude levels correspond to pulse signals of different widths: normal amplitude level corresponds to a 5ms wide high-level pulse, low amplitude level corresponds to a 2ms wide high-level pulse, and overvoltage level corresponds to an 8ms wide high-level pulse. This rule can be flexibly adjusted through hardware logic or microcontroller program.

[0062] S22 Synchronization Pulse Generation. Each time a rising edge trigger signal from the zero-crossing detection comparator is received, the control logic unit immediately initiates the pulse generation process. According to the matched encoding rules, a high-level signal of corresponding width is output. After the high-level duration reaches the set width, it automatically switches to a low level, forming a complete synchronization pulse signal. The pulse signal contains the grid phase triggered by the zero-crossing point, as well as the amplitude information obtained from pulse width decoding.

[0063] S3 Synchronization Signal Transmission. This step is responsible for transmitting the encoded synchronization pulse signal to the energy storage converter, ensuring that the signal is not distorted or delayed during transmission.

[0064] The output drive circuit receives the synchronous pulse signal generated by the control logic unit and converts it to a 12V standard industrial level through a level conversion module, while enhancing the signal driving capability. The enhanced pulse signal is transmitted through a synchronous signal transmission cable. The cable uses shielded twisted-pair cable to reduce electromagnetic interference. One end is connected to the output drive circuit, and the other end is left floating. The signal is transmitted stably in the cable in the form of digital pulses, without relying on any communication protocol, thus avoiding communication delays and failure risks.

[0065] S4 PCS terminal decoding and phase synchronization. This step is the execution stage of the synchronization process. The energy storage converter achieves precise synchronization with the grid by parsing the synchronization signal. The specific operation is as follows:

[0066] S41 Synchronization Signal Reception and Isolation. The PCS-side detection circuit receives the synchronization pulse signal transmitted via cable through a pull-up resistor and an optocoupler isolation circuit. The optocoupler isolation circuit provides electrical isolation, preventing external signals from interfering with the internal circuitry of the PCS, and simultaneously converts the pulse signal into a digital level signal recognizable by the PCS control unit, ensuring accurate signal reception.

[0067] S42 Signal Decoding and Parameter Calculation. The timer / counter module performs high-precision measurement of the received pulse signal and calculates the grid frequency by measuring the time interval between the rising edges of two adjacent pulses. By measuring the high-level duration of a single pulse and combining it with preset encoding rules, the grid voltage amplitude level is decoded. The measurement data is transmitted to the PCS control unit in real time, where the control unit processes the data in real time to ensure the timeliness of parameter calculation.

[0068] S43 Phase and Amplitude Synchronization Adjustment. The PCS control unit initiates the synchronization adjustment process based on the decoded grid frequency and amplitude information. At each rising edge of the synchronization pulse, the phase of its own inverter output is forcibly reset to 0°, achieving precise alignment with the grid phase. Simultaneously, the PWM modulation depth is adjusted according to the amplitude level to match the output voltage amplitude of the energy storage converter with the grid voltage. The entire adjustment process continues, ensuring that the energy storage converter remains synchronized with the grid at all times, meeting grid connection requirements.

[0069] The grid-connected phase synchronization method for energy storage converters in this embodiment achieves fast response, high accuracy, low cost, and good reliability through the above steps.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A grid-connected phase synchronization device for an energy storage converter, characterized in that, The system includes a voltage divider circuit, a voltage comparator module, a control logic unit, and an output drive circuit, all connected in sequence. A synchronization signal transmission cable connects one end to the output drive circuit and the other end to the PCS terminal detection circuit built into the energy storage converter. The voltage divider circuit is connected to the AC side of the power grid, performing voltage reduction, filtering, and overvoltage protection on the high voltage of the grid, and outputting a low-voltage analog signal. The voltage comparator module includes a zero-crossing detection comparator channel and an amplitude detection comparator channel. The zero-crossing detection comparator channel provides a zero-crossing trigger signal for the grid voltage, and the amplitude detection comparator channel determines the grid voltage amplitude level. The control logic unit integrates the digital level signals to generate an encoded synchronization pulse signal. The output drive circuit is used to enhance the driving capability of the synchronization pulse signal and convert its level; the synchronization signal transmission cable is used to transmit the enhanced synchronization pulse signal. The PCS terminal detection circuit is used to receive and analyze the synchronization pulse signal, control the energy storage converter to adjust the phase and amplitude of the inverter output, and achieve grid-connected phase synchronization.

2. The energy storage converter grid-connected phase synchronization device according to claim 1, characterized in that, The voltage divider circuit uses a metal film resistor to form a voltage divider network, and incorporates a bidirectional transient suppression diode for overvoltage protection and an RC filter network composed of resistors and capacitors.

3. The energy storage converter grid-connected phase synchronization device according to claim 1, characterized in that, The voltage comparator module uses a high-speed voltage comparator chip; the reference voltage of the zero-crossing detection comparator channel is set to the level corresponding to the AC zero point of the power grid and is calibrated by a bias circuit; the reference voltage of the amplitude detection comparator channel is adjusted in multiple stages by a potentiometer to divide the power grid voltage amplitude into low, normal, and overvoltage levels, and outputs a high-level or low-level digital signal.

4. The energy storage converter grid-connected phase synchronization device according to claim 1, characterized in that, The control logic unit adopts any of the following implementation methods: (1) a pure hardware logic gate circuit composed of AND gate, OR gate and delay circuit to realize the generation of synchronous pulse signal; (2) a microcontroller is used to collect the digital level signal output by the voltage comparator module through the digital IO port, configure the encoding rules and realize the fault diagnosis and signal filtering functions.

5. The energy storage converter grid-connected phase synchronization device according to claim 1, characterized in that, The output drive circuit adopts a totem pole drive structure composed of PNP transistors and NPN transistors, and has a built-in level conversion module, reverse protection diode and overcurrent protection resistor.

6. The energy storage converter grid-connected phase synchronization device according to claim 1, characterized in that, The PCS terminal detection circuit includes a pull-up resistor, an optocoupler isolation circuit, a timer / counter module, and a microprocessor. The pull-up resistor is connected in series with the optocoupler isolation circuit. The timer / counter module is used to capture the rising and falling edges of the synchronization pulse. The microprocessor is used to calculate the grid frequency, decode the amplitude level, and reset the inverter output phase of the energy storage converter to 0° and adjust the PWM modulation depth when the synchronization pulse rises. The grid frequency is calculated by dividing 1 by the time interval between two adjacent rising edges of the synchronization pulse.

7. A method for grid-connected phase synchronization of an energy storage converter, implemented based on the device described in any one of claims 1-6, characterized in that, Includes the following steps: S1: The AC voltage from the power grid is connected, and after being stepped down, filtered, and protected against overvoltage by a voltage divider circuit, a low-voltage analog signal is output. The low-voltage analog signal is input to a voltage comparator module, which obtains the zero-crossing trigger signal of the power grid voltage through the zero-crossing detection comparator channel and the amplitude level signal of the power grid voltage through the amplitude detection comparator channel, and outputs a digital level signal. S2: The control logic unit receives the digital level signal, matches the correspondence between amplitude level and pulse width according to the preset encoding rules, and generates an encoded synchronization pulse signal of corresponding width when it receives the zero-crossing rising edge trigger signal. S3: The output drive circuit performs level conversion and drive enhancement on the encoded synchronization pulse signal, and then transmits it to the PCS terminal detection circuit of the energy storage converter via the synchronization signal transmission cable. S4: The PCS terminal detection circuit receives and isolates the synchronization pulse signal, and measures the pulse frequency and width through the timer counter module to analyze the grid frequency and amplitude level; based on the analysis results, at the rising edge of the synchronization pulse, the inverter output phase of the energy storage converter is reset to 0° and the PWM modulation depth is adjusted to synchronize the output of the energy storage converter with the grid.

8. The grid-connected phase synchronization method for energy storage converters according to claim 7, characterized in that, In step S1: the voltage divider circuit converts the high voltage of the power grid into a low voltage analog signal, filters out high-frequency interference through an RC filter network, and clamps the surge voltage through a bidirectional transient suppression diode; the zero-crossing detection comparator channel outputs a rising edge or falling edge trigger signal, and the amplitude detection comparator channel outputs a digital level signal corresponding to the low, normal, or overvoltage level; the outputs of the zero-crossing detection comparator and the amplitude detection comparator are both transmitted to the control logic unit.

9. The grid-connected phase synchronization method for energy storage converters according to claim 7, characterized in that, In step S2: the preset encoding rule is: normal amplitude level corresponds to a 5ms wide high-level pulse, low amplitude level corresponds to a 2ms wide high-level pulse, and overvoltage level corresponds to an 8ms wide high-level pulse; the generation of the encoding synchronization pulse signal is triggered by the rising edge of the zero-crossing detection comparator channel, and the high level continues for a set width before switching to a low level.

10. The grid-connected phase synchronization method for energy storage converters according to claim 7, characterized in that, In step S4: the PCS terminal detection circuit receives the synchronization pulse signal through a pull-up resistor and an optocoupler isolation circuit; the phase and amplitude adjustment period of the energy storage converter is less than or equal to 1 millisecond.

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