Constant-current pre-charging circuit for improving power-on stability of single power grid of inverter

Abstract

The invention relates to the technical field of electronic circuits, discloses a constant-current pre-charging circuit for improving the starting stability of a single power grid of an inverter, and remarkably improves the starting stability and safety of a grid-connected and off-grid hybrid inverter. Compared with the prior art, when only the mains supply is used for supplying power, the system can still be stably started and operated, and the problems of potential safety hazards and shortened service life caused by direct rectification power supply of a bus capacitor are effectively avoided. Specifically, the constant-current pre-charging module pre-charges the bus capacitor before startup, so that the charging time is greatly shortened, meanwhile, the impact of large current on a power device at the moment of charging is avoided, and the service life of equipment is prolonged. The flyback auxiliary source module supplies power to the control module before the main circuit is closed, so that the control module scans the working condition before starting up in advance. If the bus short circuit is detected, starting is forbidden, and the equipment safety is further guaranteed. According to the scheme, the adaptability and reliability of the inverter under special working conditions are effectively improved, and a powerful guarantee is provided for safe and stable operation of equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic circuits, and particularly relates to a constant current pre-charge circuit for improving single-grid starting stability of an inverter. BACKGROUND

[0002] Under the current technical development background, as for the hybrid inverter, the PV end (photovoltaic end) adopts the pre-charge architecture, which has become a relatively common and common technical means and has been widely applied in the industry. However, there are still obvious deficiencies and shortcomings in the adaptability design for some special application scenarios and extreme conditions.

[0003] For example, when in such a special working condition, the PV end and the battery end cannot normally provide power supply, and cannot meet the basic power demand of the equipment start and operation. In this case, in order to ensure that the hybrid inverter can start normally and run stably, the power supply (power provided by the public grid) is often used to realize the starting process of the equipment. However, it is worth noting that, starting from the strict requirements of electrical safety specifications (safety regulations), when starting operation by using the power supply, the power supply and the internal circuit of the equipment must be reliably electrically isolated. This is to prevent various interference signals, overvoltage, overcurrent and other abnormal conditions in the power supply from damaging the internal circuit of the equipment, and to protect the safe operation of the equipment and the personal safety of the operator.

[0004] For the above-mentioned special working condition requirements, the technical solution adopted in the past is to directly connect the rectified DC to the bus after rectification, so as to realize the starting operation of the equipment. However, this traditional technical architecture exposes some serious problems in actual application. When the capacity of the bus capacitor is relatively large, the charging time of the bus capacitor will be too long at the moment of starting, because the bus capacitor needs to be charged. At the same time, according to the characteristics of capacitor charging, a large instantaneous current will be generated at the initial stage of charging, which will cause the power to increase sharply in a short time. Such excessive instantaneous power not only causes a great impact on the internal power devices of the equipment, affecting their service life and performance stability, but also may cause a series of electrical safety problems.

[0005] In addition, in another special case, when the bus is short-circuited, the previous technical architecture usually adopts the method of connecting a large number of resistors in series on the bus to alleviate the short-circuit current. However, this design method has obvious disadvantages. When the bus is short-circuited, although the series resistance can limit the size of the short-circuit current to a certain extent, because the short-circuit current may still be at a high level, it is easy to cause the series resistance to burn out due to overheating. Once the resistance is burned out, it not only cannot continue to limit the current, but also may cause more serious electrical faults, and even cause the entire equipment to be damaged.

[0006] In summary, the existing technology architecture directly provides power for the main circuit without accurately judging the special working conditions, which has many potential safety hazards. These safety hazards not only threaten the personal safety of the operator, but also have a serious negative impact on the service life of the on-off grid hybrid inverter, reducing the reliability and stability of the equipment.

[0007] Based on the above analysis of the problems existing in the prior art, in order to effectively solve these safety hazards and improve the adaptability and reliability of the on-off grid hybrid inverter under various special working conditions, and ensure the safe and stable operation of the equipment, it is urgent to comprehensively and deeply improve and optimize the existing technology.

[0008] The above information is given as background information only to assist with understanding the present disclosure and has not been determined or acknowledged as being available as prior art against the present disclosure. SUMMARY

[0009] The present application provides a constant current pre-charging circuit for improving the stability of single grid start-up of an inverter to solve the problems existing in the prior art.

[0010] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0011] A constant current pre-charging circuit for improving the stability of single grid start-up of an inverter, comprising a rectifier module, a flyback auxiliary source module, a control module and a constant current pre-charging module; wherein,

[0012] The rectifier module is connected with three-phase mains for rectifying the three-phase mains into direct current before starting;

[0013] The flyback auxiliary source module is connected between the rectifier module and the control module for reducing the voltage of the rectified direct current to supply power to the control module;

[0014] The constant current pre-charging module is connected between the rectifier module and the bus capacitor for pre-charging the bus capacitor with constant current before starting;

[0015] The control module is used to detect the circuit state of the bus before starting. If the bus is detected to be short-circuited, the main circuit between the three-phase mains and the bus is not closed, so that the inverter cannot start. If the bus is detected to be not short-circuited, the main circuit between the three-phase mains and the bus is closed, so that the inverter starts.

[0016] Further, the constant current pre-charging circuit for improving the starting stability of the inverter single grid includes a first rectifier element D1, a second rectifier element D2, a third rectifier element D3, a fourth rectifier element D4, a fifth rectifier element D5, a sixth rectifier element D6, a seventh rectifier element D7, an eighth rectifier element D8, and an inductor L1.

[0017] The reverse ends of the first rectifier element D1, the second rectifier element D2, the third rectifier element D3, and the fourth rectifier element D4 are connected in parallel and then connected to the first end of the inductor L1.

[0018] The forward ends of the fifth rectifier element D5, the sixth rectifier element D6, the seventh rectifier element D7, and the eighth rectifier element D8 are connected in parallel and then connected to the second end of the inductor L1.

[0019] The forward end of the first rectifier element D1 is connected to the reverse end of the fifth rectifier element D5.

[0020] The forward end of the second rectifier element D2 is connected to the reverse end of the sixth rectifier element D6.

[0021] The forward end of the third rectifier element D3 is connected to the reverse end of the seventh rectifier element D7.

[0022] The forward end of the fourth rectifier element D4 is connected to the reverse end of the eighth rectifier element D8.

[0023] The R phase of the three-phase power supply is connected between the forward end of the first rectifier element D1 and the reverse end of the fifth rectifier element D5.

[0024] The S phase of the three-phase power supply is connected between the forward end of the second rectifier element D2 and the reverse end of the sixth rectifier element D6.

[0025] The T phase of the three-phase power supply is connected between the forward end of the third rectifier element D3 and the reverse end of the seventh rectifier element D7.

[0026] The N phase of the three-phase power supply is connected between the forward end of the fourth rectifier element D4 and the reverse end of the eighth rectifier element D8.

[0027] The third end of the inductor L1 serves as a positive output terminal, and the fourth end of the inductor L1 serves as a negative output terminal.

[0028] The first end of the inductor L1 and the third end of the inductor L1 are the two ends of one coil of the inductor L1, and the second end of the inductor L1 and the fourth end of the inductor L1 are the two ends of another coil of the inductor L1.

[0029] Further, in the constant current pre-charging circuit for improving the single-grid starting stability of an inverter, the rectifying module further comprises a first capacitor C1.

[0030] One end of the first capacitor C1 is connected between one end of the first rectifying element D1, the second rectifying element D2, the third rectifying element D3 and the fourth rectifying element D4 in parallel and the inductor L1, and the other end of the first capacitor C1 is connected between one end of the fifth rectifying element D5, the sixth rectifying element D6, the seventh rectifying element D7 and the eighth rectifying element D8 in parallel and the inductor L1.

[0031] Further, in the constant current pre-charging circuit for improving the single-grid starting stability of an inverter, the rectifying module further comprises a second capacitor C2.

[0032] One end of the second capacitor C2 is connected to the third end of the inductor L1, and the other end of the second capacitor C2 is connected to the fourth end of the inductor L1.

[0033] Further, in the constant current pre-charging circuit for improving the single-grid starting stability of an inverter, the first rectifying element D1, the second rectifying element D2, the third rectifying element D3, the fourth rectifying element D4, the fifth rectifying element D5, the sixth rectifying element D6, the seventh rectifying element D7 and the eighth rectifying element D8 are all diodes.

[0034] Further, in the constant current pre-charging circuit for improving the single-grid starting stability of an inverter, the constant current pre-charging module comprises a first resistor R1, a second resistor R2, a third resistor R3, a first diode D9, a second diode D10, a third diode D11, a first switch Q1 and a second switch Q2.

[0035] One end of the first resistor R1 is connected to the rectifying module, and the other end is connected to the second end of the first switch Q1.

[0036] The third end of the first switch Q1 is connected to one end of the third resistor R3.

[0037] The other end of the third resistor R3 is connected to the forward end of the second diode D10.

[0038] The reverse end of the second diode D10 is connected to the forward end of the third diode D11.

[0039] The reverse end of the third diode D11 is connected to the bus capacitor.

[0040] One end of the second resistor R2 is connected between the first resistor R1 and the rectifying module, and the other end is connected to the second end of the second switch Q2.

[0041] The third terminal of the second switch Q2 is connected between the third resistor R3 and the second diode D10;

[0042] The first terminal of the first switch Q1 is connected between the second resistor R2 and the second terminal of the second switch Q2;

[0043] The first terminal of the second switch Q2 is connected between the third resistor R3 and the third terminal of the first switch Q1;

[0044] The forward terminal of the first diode D9 is connected between the third terminal of the first switch Q1 and the third resistor R3, and the reverse terminal of the first diode D9 is connected between the second resistor R2 and the second terminal of the second switch Q2.

[0045] Furthermore, in the constant current pre-charging circuit for improving the single-grid start-up stability of the inverter, both the switching transistor Q1 and the switching transistor Q2 are transistors;

[0046] The first terminal of the switching transistor Q1 is the base, the second terminal is the collector, and the third terminal is the emitter;

[0047] The first terminal of the switching transistor Q2 is the base, the second terminal is the collector, and the third terminal is the emitter.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] This invention provides a constant current pre-charge circuit for improving the startup stability of inverters operating on a single grid. Through innovative circuit design, it significantly enhances the startup stability and safety of grid-connected hybrid inverters under special operating conditions. Compared with existing technologies, this invention can still achieve stable startup operation even with only mains power supply, effectively solving the safety hazards and shortened lifespan problems caused by direct rectification power supply to the bus capacitors. Specifically, by pre-charging the bus capacitors before startup using a constant current pre-charge module, not only is the charging time of the bus capacitors significantly reduced, but the impact on internal power devices caused by excessive instantaneous current during bus capacitor charging is also avoided, thereby extending the lifespan of the equipment and improving its performance stability. In addition, before closing the main circuit, the flyback auxiliary power module can first supply power to the control module, enabling it to scan and judge the operating conditions before startup. If a short circuit is detected on the bus, startup is prohibited, further enhancing the safety of the equipment. This series of improvements significantly enhances the adaptability and reliability of grid-connected hybrid inverters under special operating conditions, providing a strong guarantee for the safe and stable operation of the equipment.

[0050] The present invention has other features and advantages, which will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of a constant current pre-charge circuit for improving the startup stability of an inverter on a single grid, provided by an embodiment of the present invention.

[0053] Figure 2 This is a schematic diagram of the circuit principle of the rectifier module provided in an embodiment of the present invention;

[0054] Figure 3 This is a schematic diagram of the circuit principle of the constant current pre-charge module provided in an embodiment of the present invention.

[0055] Figure label:

[0056] 1. Rectifier module, 2. Flyback auxiliary power supply module, 3. Control module, 4. Constant current precharge module, 5. Three-phase mains power, 6. Bus capacitor. Detailed Implementation

[0057] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0058] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0059] Unless otherwise defined, the meanings of technical terms used in the present application are the same as commonly understood by one of ordinary skill in the art to which the present application belongs; the use of related terms in the present application is only for the purpose of describing specific embodiments, and is not intended to limit the present application.

[0060] In the description of the present application, the phrase "and / or" is a description of the logical relationship between objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally represents that the associated objects before and after are a "or" logical relationship.

[0061] In the present application, the terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, primary and secondary, or order relationship between the entities or operations.

[0062] In the present application, the "includes", "contains", "has" or other similar expressions used in the sentence are intended to cover non-exclusive inclusion, and these expressions do not exclude the presence of additional elements in the process, method or product including the described elements, so that the process, method or product including a series of elements can not only include those limited elements, but also include other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0063] In the present application, the expressions such as "greater than", "less than", "exceed" are understood as not including the number; the expressions such as "above", "below", "within" are understood as including the number. In addition, in the description of the embodiments of the present application, the meaning of "multiple" is more than two (including two), and similar expressions related to "multiple" are also understood in this way, for example, "multiple groups", "multiple times" and the like, unless otherwise explicitly limited.

[0064] In the description of the embodiments of the present application, the spatial-related expressions used, such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or the drawings, and are only for the convenience of describing the specific embodiments of the present application or for the reader to understand, and are not intended to indicate or imply that the indicated device or component must have a particular position, a particular orientation, or be constructed or operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0065] Unless otherwise clearly indicated or implied to the contrary by context, the word "mount", "connected", "connection", "fixed", "set", etc., used in the description of the embodiments of the present application, should be interpreted in a broad manner. For example, "connection" can be fixed connection, detachable connection, or integrated setting; it can be mechanical connection, electrical connection, or communication connection; it can be direct connection or indirect connection through an intermediate medium; it can be internal communication of two elements or interaction relationship between two elements. Those skilled in the art of the present application can understand the specific meaning of the above-mentioned words in the embodiments of the present application according to the specific circumstances.

[0066] Please refer to Figure 1 The embodiment of the present application provides a constant current pre-charging circuit for improving the single grid starting stability of an inverter. The circuit system structure is complete and the functions are coordinated. The circuit system is mainly composed of a rectifier module 1, a flyback auxiliary source module 2, a control module 3, and a constant current pre-charging module 4. The modules cooperate with each other and work closely to achieve the goal of improving the starting performance of the inverter.

[0067] The rectifier module 1 is directly electrically connected with a three-phase power supply 5. In a specific stage before the starting of the inverter, the rectifier module 1 fully plays its core function of converting alternating current into direct current, and accurately and efficiently rectifies the alternating current provided by the three-phase power supply 5 into direct current that meets the requirements of the subsequent circuit, thereby providing basic power support for the stable operation of the entire circuit system.

[0068] The flyback auxiliary source module 2 is connected in series between the rectifier module 1 and the control module 3 in a clever circuit connection manner. It undertakes the important task of reasonably adjusting the voltage of the rectified direct current. Through specific circuit principles and parameter design, the voltage of the rectified direct current is reduced to a voltage range suitable for the normal operation of the control module 3, thereby stably and reliably supplying power to the control module 3, ensuring that the control module 3 can timely and accurately obtain the required power before starting, and laying a solid foundation for subsequent circuit state detection and control instruction output.

[0069] The constant current pre-charging module 4 is connected between the rectifier module 1 and a bus capacitor 6, and plays a crucial role at a critical moment before the starting of the inverter. It can accurately pre-charge the bus capacitor 6 according to the pre-set constant current parameters. Through this constant current pre-charging method, the bus capacitor 6 can be charged with a relatively stable and controllable current before starting, avoiding the problem of excessive current fluctuation in the traditional charging method, and creating favorable conditions for the stable starting of the inverter.

[0070] The control module 3 as the "wisdom brain" of the whole circuit system undertakes the key responsibility of comprehensively and carefully detecting the busbar circuit state before starting. It uses advanced detection technology and accurate algorithm to monitor and analyze the electrical parameters of the busbar in real time. If abnormal conditions such as short circuit of the busbar are found in the detection process, the control module 3 will quickly respond and ensure that the main circuit between the three-phase power supply 5 and the busbar is not closed through accurate control signals, thereby effectively preventing the inverter from starting under abnormal conditions and avoiding possible equipment damage and safety accidents; on the contrary, if the detection result shows that the busbar has no abnormal conditions such as short circuit, the control module 3 will timely issue a closing instruction to smoothly close the main circuit between the three-phase power supply 5 and the busbar, and then realize the normal starting of the inverter.

[0071] The embodiment of the present application has achieved remarkable results in improving the starting stability and safety of the hybrid inverter under special working conditions through a series of innovative circuit designs. Compared with the existing traditional technical solutions, the present application has outstanding advantages and excellent performance. In the specific scenario of only power supply, the circuit system designed by the present application can still ensure the stable and reliable starting operation of the inverter, effectively solving a series of problems caused by the direct rectification of the busbar capacitor 6 in the previous technology. Specifically, the direct rectification of the busbar capacitor in the traditional technology often leads to long charging time and excessive instantaneous current of the busbar capacitor during charging. However, the present application performs careful pre-charging operation on the busbar capacitor 6 before starting through the constant current pre-charging module 4, which not only greatly shortens the charging time of the busbar capacitor 6 and improves the charging efficiency, but also skillfully avoids the strong impact on the internal power devices caused by the excessive instantaneous current of the busbar capacitor 6 during charging. This effective protection of power devices significantly prolongs the service life of the equipment and improves the performance stability of the equipment during long-term operation, providing a solid guarantee for the reliable operation of the inverter.

[0072] In addition, before closing the main circuit, the flyback auxiliary power module 2 can supply power to the control module 3 in advance, so that the control module 3 has enough time and energy to comprehensively and carefully scan and judge the working condition before starting. This forward-looking working condition detection mechanism can discover potential safety hazards such as busbar short circuit in the first time and take measures to prohibit starting in time, further enhancing the safety of the equipment under complex working conditions. This series of carefully designed improvement measures complement each other, making the adaptability and reliability of the hybrid inverter under special working conditions have a qualitative leap and significant improvement, providing all-round and multi-level strong protection for the safe and stable operation of the equipment in various complex environments, and having broad application prospect and important practical value.

[0073] Please refer to Figure 2In an embodiment of the present embodiment, the rectifier module 1 is carefully designed and laid out with a rich composition of components working in synergy, specifically including a first rectifier element D1, a second rectifier element D2, a third rectifier element D3, a fourth rectifier element D4, a fifth rectifier element D5, a sixth rectifier element D6, a seventh rectifier element D7, an eighth rectifier element D8, and an inductor L1. These components are orderly combined according to specific circuit principles and connection methods to collectively undertake the important task of converting three-phase mains power into direct current.

[0074] From the perspective of circuit connection, the reverse ends of the first rectifier element D1, the second rectifier element D2, the third rectifier element D3, and the fourth rectifier element D4 adopt a parallel connection method. This parallel structure enables them to collectively withstand reverse voltage in the circuit, enhancing their resistance to reverse voltage.

[0075] At the same time, the forward ends of the fifth rectifier element D5, the sixth rectifier element D6, the seventh rectifier element D7, and the eighth rectifier element D8 also adopt a parallel connection form. The output end after parallel connection is connected to the second end of the inductor L1, forming a complete rectifier circuit architecture with the reverse end parallel part, laying the foundation for the rectification process of three-phase mains power.

[0076] In terms of connection between rectifier elements, the forward end of the first rectifier element D1 is precisely connected to the reverse end of the fifth rectifier element D5. This connection ensures that under a specific potential relationship, the current can flow according to the predetermined path, achieving the rectification function. Similarly, the forward end of the second rectifier element D2 is connected to the reverse end of the sixth rectifier element D6, the forward end of the third rectifier element D3 is connected to the reverse end of the seventh rectifier element D7, and the forward end of the fourth rectifier element D4 is connected to the reverse end of the eighth rectifier element D8. These precise connection relationships collectively form a complex and orderly rectifier circuit network, enabling efficient rectification conversion between different rectifier element pairs for each phase of three-phase mains power.

[0077] For the connection of the three-phase power supply 5 and the rectifier module, there is a clear and detailed correspondence. The R phase of the three-phase power supply 5 is accurately connected between the positive end of the first rectifier element D1 and the negative end of the fifth rectifier element D5, which allows the AC power of the R phase to enter the specific rectifier element pair for rectification. The S phase of the three-phase power supply 5 is connected between the positive end of the second rectifier element D2 and the negative end of the sixth rectifier element D6, and the T phase is connected between the positive end of the third rectifier element D3 and the negative end of the seventh rectifier element D7. In addition, the N phase of the three-phase power supply 5 is connected between the positive end of the fourth rectifier element D4 and the negative end of the eighth rectifier element D8. Through these precise phase connections, each phase of the three-phase power supply can enter the corresponding rectifier element pair, realizing comprehensive rectification conversion.

[0078] In the output design of the rectifier module, the third end of the inductor L1 is set as the output positive terminal, and the fourth end of the inductor L1 is set as the output negative terminal. Such output design provides stable DC power input for the subsequent circuit.

[0079] It is particularly worth mentioning that the inductor L1 plays a crucial role in isolating the entire circuit. It can effectively electrically isolate the input side from the output side of the DC circuit, preventing interference signals from the input side from being transmitted to the output side, while also preventing the output side of the DC circuit from affecting the input side. This isolation not only improves the anti-interference ability of the circuit, but also ensures the safety and stability of the circuit, providing strong support for the normal operation of the entire inverter system.

[0080] In one embodiment of the present embodiment, the first rectifier element D1, the second rectifier element D2, the third rectifier element D3, the fourth rectifier element D4, the fifth rectifier element D5, the sixth rectifier element D6, the seventh rectifier element D7, and the eighth rectifier element D8 are all selected as diodes, which have clear unidirectional conduction characteristics.

[0081] Diodes are a basic and key semiconductor device, and their core feature is to allow current to flow only in one specific direction, while under the action of reverse voltage, they exhibit high impedance and almost prevent current flow. In the rectifier module 1 involved in the present embodiment, the selection of diodes as rectifier elements is a deliberate and important choice.

[0082] From the perspective of rectification function implementation, when the three-phase mains 5 is connected to the rectifier module 1, since the voltage and current of the three-phase mains are periodic AC signals following the sine law, their directions will change constantly over time. The unidirectional conduction characteristic of diodes makes the diode connected to the positive pole of the power supply conduct in the positive half cycle of the AC power, and the current can flow smoothly; while in the negative half cycle, the diode is in the off state, preventing the current from flowing in the opposite direction. By reasonably arranging and connecting the eight diodes, the AC power of the three-phase mains can be ingeniously converted into pulsating DC power with a single direction and varying size, providing the subsequent circuit with a DC power input that meets the requirements, which is the basic link to realize the stable operation of the inverter.

[0083] From the perspective of circuit stability and reliability, diodes have many advantages such as simple structure, stable performance, and low cost. In the rectifier module 1 of the present embodiment, a large number of diodes are used as rectifier elements, which helps to simplify the circuit structure and reduce the complexity and cost of circuit design. At the same time, diodes have been developed and proven through long-term practice, and their performance parameters are stable and reliable, allowing them to maintain good working conditions under different working environments and load conditions, effectively reducing abnormal situations caused by component failures, thereby improving the stability and reliability of the entire rectifier module and even the entire inverter system.

[0084] In addition, diodes also have a certain protection effect in the circuit. For example, when transient overvoltage or reverse voltage occurs in the circuit, the unidirectional conduction characteristic of diodes can prevent excessive current from flowing in the opposite direction into other components, avoiding damage to other sensitive components in the circuit, further enhancing the anti-interference ability and safety of the circuit.

[0085] Please refer to Figure 2 In one embodiment of the present embodiment, the rectifier module 1 further adds a first capacitor C1 and a second capacitor C2 based on the original component configuration, and the addition of these two capacitors plays a key role in improving the performance of the rectifier module.

[0086] From the specific details of the circuit connection, the first capacitor C1 is connected in a specific way. One end is accurately connected between the connection point formed by the parallel connection of the reverse ends of the first to fourth rectifier elements D1-D4 and the first end of the inductor L1; at the same time, the other end of the first capacitor C1 is reliably connected between the connection point formed by the parallel connection of the forward ends of the fifth to eighth rectifier elements D5-D8 and the second end of the inductor L1. Through such a connection mode, the first capacitor C1 is connected across the two key parts of the rectifier module, playing an important role in filtering and stabilizing the voltage in the circuit. During the rectification process, the conversion of alternating current to direct current will produce certain voltage fluctuations and ripples, and the first capacitor C1 can absorb and smooth these unstable electrical signals, making the voltage output to the inductor L1 more stable and providing a better power input for the subsequent circuit.

[0087] The second capacitor C2 also plays an indispensable role in the circuit. One end is tightly connected to the third end of the inductor L1, which is the positive output terminal, and the other end is connected to the fourth end of the inductor L1, which is the negative output terminal. This direct connection across the positive and negative output terminals allows the second capacitor C2 to further filter the direct current output by the rectifier module. During the output of direct current by the inductor L1, some small alternating components or voltage fluctuations may remain, and the second capacitor C2 can quickly charge and discharge these interference signals to suppress the output voltage fluctuations within a very small range, thereby providing a more pure and stable direct current power for the subsequent circuit, effectively improving the power quality of the entire inverter system and ensuring stable operation and performance of the system.

[0088] In summary, the first capacitor C1 and the second capacitor C2 are connected to the rectifier module 1 through their unique connection methods, working together to optimize the electrical signals after rectification and significantly improve the filtering effect and stability of the output voltage of the rectifier module.

[0089] Please refer to Figure 3 In one embodiment of the present embodiment, the constant current precharge module 4 has a precise and reasonable circuit architecture, which is specifically composed of the first resistor R1, the second resistor R2, the third resistor R3, the first diode D9, the second diode D10, the third diode D11, the first switch Q1, and the second switch Q2, and other elements. These elements work together through a rigorous and orderly connection method to realize the function of constant current precharge, providing key support for the stable start and reliable operation of the entire circuit system.

[0090] From the specific details of the circuit connection, the first resistor R1 plays an important role in current limiting and signal transmission in the circuit. One end is reliably connected with the rectifier module 1 to receive the rectified electrical signal output by the rectifier module; the other end is precisely connected with the second end of the first switch tube Q1 to deliver the signal to the first switch tube, providing a basis for subsequent circuit control.

[0091] The first switch tube Q1 as a key control element in the circuit, its third end is stably connected with one end of the third resistor R3. This connection method makes the on-off state of the first switch tube directly affect the current on-off of the branch where the third resistor is located, thereby playing a core role in the current control of the entire constant current pre-charging module.

[0092] The other end of the third resistor R3 is tightly connected with the forward end of the second diode D10. The second diode D10 plays a role of one-way conduction here, which can ensure that the current can only pass in a specific direction, preventing the current from flowing in the opposite direction and causing damage to the circuit elements, while also helping to rectify and stabilize the current.

[0093] The reverse end of the second diode D10 is reliably connected with the forward end of the third diode D11, and the reverse end of the third diode D11 is connected with the bus capacitor 6. This series connection method makes the two diodes work together to further rectify and filter the current, ensuring that the current input to the bus capacitor is more stable and pure, providing good electrical conditions for the charging process of the bus capacitor.

[0094] The second resistor R2 also plays an indispensable role in the circuit. One end is connected to the connection point between the first resistor R1 and the rectifier module 1, which can monitor the voltage and current changes at this location in real time; the other end is precisely connected with the second end of the second switch tube Q2, delivering the monitored signal to the second switch tube, providing a basis for the control of the second switch tube.

[0095] The third end of the second switch tube Q2 is connected to the connection point between the third resistor R3 and the second diode D10, and through the change of its on-off state, it can flexibly control the current of the branch where the third resistor and the second diode are located, and cooperate with the first switch tube to achieve accurate control of the constant current pre-charging module.

[0096] The first end of the first switch tube Q1 is connected to the connection point between the second resistor R2 and the second end of the second switch tube Q2. This connection method enables the first switch tube to obtain feedback signals from the second resistor and the second switch tube, so as to adjust its on-off state according to the actual situation of the circuit, achieving precise regulation of the current.

[0097] The first end of the second switch tube Q2 is connected to a connection point between the third resistor R3 and the third end of the first switch tube Q1, further enhancing the signal interaction and control synergy between the two switch tubes, ensuring that the entire constant current pre-charging module can quickly and accurately respond to input signals and circuit states.

[0098] The forward end of the first diode D9 is connected to a connection point between the third end of the first switch tube Q1 and the third resistor R3, and its reverse end is connected to a connection point between the second resistor R2 and the second end of the second switch tube Q2. The first diode D9 plays a role in protecting the circuit and stabilizing the voltage here, which can prevent the occurrence of excessive reverse voltage in the circuit from damaging the switch tube and other elements, while also helping to maintain the stability of the voltage in the circuit, ensuring that the constant current pre-charging module can operate reliably under various working conditions.

[0099] In summary, each element in the constant current pre-charging module 4 forms a complete and stable circuit system through the above complex and orderly connection method. They cooperate and influence each other, and together realize the constant current pre-charging function of the bus capacitor.

[0100] In one embodiment of the present embodiment, the type and pin definition of the switch tube Q1 and the switch tube Q2 are clearly and meticulously set. Specifically, the switch tube Q1 and the switch tube Q2 are both selected as triodes. As a semiconductor device with current amplification function and widely used in electronic circuits, triodes can provide strong support for specific control functions of the entire circuit system due to their unique electrical characteristics.

[0101] For the switch tube Q1, the pin definition follows specific circuit design requirements. Among them, the first end is specifically designated as the base (b). As a key control pin of the triode, the base plays a crucial role in the circuit. By applying appropriate electrical signals to the base, the on and off states of the triode can be accurately controlled, thereby realizing the regulation of the current between the collector and the emitter. The second end is defined as the collector (c), which is the main output end of the current in the triode, and its current size is controlled by the base current. In the circuit, it is usually connected to the load or other elements to realize functions such as signal amplification or switch control. The third end is the emitter (e), which is the input end of the current in the triode. It, together with the base and the collector, forms the current path of the triode, and the current change of the emitter can reflect the working state of the triode.

[0102] Similarly, the pin definition of the switch tube Q2 echoes that of the switch tube Q1. Its first end is also the base (b), similar to the base of the switch tube Q1, the base of the switch tube Q2 also undertakes the important task of controlling the conduction and cutoff of the triode, and adjusts the current between the collector and the emitter by receiving external control signals. The second end is the collector (c), which is the current output end, and cooperates with other parts in the circuit to realize specific circuit functions. The third end is the emitter (e), which cooperates with the base and the collector to complete the basic current amplification or switching action of the triode.

[0103] The explicit setting of the type and pin definition of the switch tubes Q1 and Q2 provides a clear basis for the design, analysis and debugging of subsequent circuits. In actual circuit applications, engineers can accurately design control circuits based on these characteristics of the triode, control the current between the collector and the emitter by reasonably adjusting the base current, and thus accurately control the entire circuit system. For example, in the constant current precharge module, by accurately controlling the base current of the switch tubes Q1 and Q2, the current flowing through the related resistors and diodes can be adjusted, and thus the constant current precharge of the bus capacitor can be realized, ensuring that the power electronic equipment can operate stably and reliably during the starting process. At the same time, the explicit pin definition also helps to avoid pin connection errors during circuit board layout and welding, improving the reliability and stability of the circuit.

[0104] Although the terms control module, rectifier module, etc. are used more in this application, the possibility of using other terms is not excluded. The use of these terms is only to facilitate the description and explanation of the essence of the invention; any additional limitation is contrary to the spirit of the invention.

[0105] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of this application, it does not limit the patent protection scope of this application. Any equivalent structure or equivalent process substitution or modification based on the essential concept of this application, using the content described in the specification and drawings, and directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, etc., are all included in the patent protection scope of this application.

Claims

1. A constant current pre-charge circuit for improving the start-up stability of an inverter on a single grid, characterized in that, It includes a rectifier module (1), a flyback auxiliary power supply module (2), a control module (3), and a constant current precharge module (4); among which, The rectifier module (1) is connected to the three-phase mains power (5) and is used to rectify the three-phase mains power (5) into DC power before power-on. The flyback auxiliary power module (2) is connected between the rectifier module (1) and the control module (3) to reduce the voltage of the rectified DC power to power the control module (3); The constant current pre-charge module (4) is connected between the rectifier module (1) and the bus capacitor (6) and is used to pre-charge the bus capacitor (6) with constant current before power-on. The control module (3) is used to detect the circuit status of the bus before power-on. If a short circuit is detected in the bus, the main circuit between the three-phase mains power (5) and the bus will not be closed, so that the inverter cannot be powered on. If no short circuit is detected in the bus, the main circuit between the three-phase mains power (5) and the bus will be closed, so that the inverter can be powered on.

2. The constant current pre-charge circuit for improving the single-grid start-up stability of an inverter according to claim 1, characterized in that, The rectifier module (1) includes a first rectifier element D1, a second rectifier element D2, a third rectifier element D3, a fourth rectifier element D4, a fifth rectifier element D5, a sixth rectifier element D6, a seventh rectifier element D7, an eighth rectifier element D8, and an inductor L1; The reverse terminals of the first rectifier element D1, the second rectifier element D2, the third rectifier element D3, and the fourth rectifier element D4 are connected in parallel and then connected to the first terminal of the inductor L1. The positive terminals of the fifth rectifier element D5, the sixth rectifier element D6, the seventh rectifier element D7, and the eighth rectifier element D8 are connected in parallel and then connected to the second terminal of the inductor L1. The positive end of the first rectifier element D1 is connected to the negative end of the fifth rectifier element D5; The positive terminal of the second rectifier element D2 is connected to the negative terminal of the sixth rectifier element D6; The positive end of the third rectifier element D3 is connected to the negative end of the seventh rectifier element D7. The positive end of the fourth rectifier element D4 is connected to the negative end of the eighth rectifier element D8. The R phase of the three-phase mains power (5) is connected between the positive end of the first rectifier element D1 and the reverse end of the fifth rectifier element D5. The S phase of the three-phase mains power (5) is connected between the positive end of the second rectifier element D2 and the reverse end of the sixth rectifier element D6; The T phase of the three-phase mains power (5) is connected between the positive end of the third rectifier element D3 and the reverse end of the seventh rectifier element D7. The N phase of the three-phase mains power (5) is connected between the positive end of the fourth rectifier element D4 and the reverse end of the eighth rectifier element D8. The third terminal of the inductor L1 serves as the positive output terminal, and the fourth terminal of the inductor L1 serves as the negative output terminal. The first end and the third end of the inductor L1 are the two ends of one coil of the inductor L1, respectively; the second end and the fourth end of the inductor L1 are the two ends of the other coil of the inductor L1, respectively.

3. The constant current pre-charge circuit for improving the single-grid start-up stability of the inverter according to claim 2, characterized in that, The rectifier module (1) also includes a first capacitor C1; One end of the first capacitor C1 is connected between the first rectifier element D1, the second rectifier element D2, the third rectifier element D3, and the fourth rectifier element D4 in parallel and the inductor L1. The other end of the first capacitor C1 is connected between the fifth rectifier element D5, the sixth rectifier element D6, the seventh rectifier element D7, and the eighth rectifier element D8 in parallel and the inductor L1.

4. The constant current pre-charge circuit for improving the single-grid start-up stability of the inverter according to claim 3, characterized in that, The rectifier module (1) also includes a second capacitor C2; One end of the second capacitor C2 is connected to the third terminal of the inductor L1, and the other end of the second capacitor C2 is connected to the fourth terminal of the inductor L1.

5. The constant current pre-charge circuit for improving the start-up stability of an inverter on a single grid, as described in claim 2, is characterized in that... The first rectifier element D1, the second rectifier element D2, the third rectifier element D3, the fourth rectifier element D4, the fifth rectifier element D5, the sixth rectifier element D6, the seventh rectifier element D7, and the eighth rectifier element D8 are all diodes.

6. The constant current pre-charge circuit for improving the single-grid start-up stability of an inverter according to claim 1, characterized in that, The constant current precharge module (4) includes a first resistor R1, a second resistor R2, a third resistor R3, a first diode D9, a second diode D10, a third diode D11, a first switch Q1, and a second switch Q2; One end of the first resistor R1 is connected to the rectifier module (1), and the other end is connected to the second end of the first switch Q1; The third terminal of the first switch Q1 is connected to one end of the third resistor R3; The other end of the third resistor R3 is connected to the positive terminal of the second diode D10; The reverse terminal of the second diode D10 is connected to the forward terminal of the third diode D11; The reverse terminal of the third diode D11 is connected to the bus capacitor (6); One end of the second resistor R2 is connected between the first resistor R1 and the rectifier module (1), and the other end is connected to the second end of the second switch Q2; The third terminal of the second switch Q2 is connected between the third resistor R3 and the second diode D10; The first terminal of the first switch Q1 is connected between the second resistor R2 and the second terminal of the second switch Q2; The first terminal of the second switch Q2 is connected between the third resistor R3 and the third terminal of the first switch Q1; The forward terminal of the first diode D9 is connected between the third terminal of the first switch Q1 and the third resistor R3, and the reverse terminal of the first diode D9 is connected between the second resistor R2 and the second terminal of the second switch Q2.

7. The constant current pre-charge circuit for improving the single-grid start-up stability of an inverter according to claim 6, characterized in that, Both the switching transistors Q1 and Q2 are bipolar transistors; The first terminal of the switching transistor Q1 is the base, the second terminal is the collector, and the third terminal is the emitter; The first terminal of the switching transistor Q2 is the base, the second terminal is the collector, and the third terminal is the emitter.

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