Power prediction control system and method of micro inverter

Abstract

The invention discloses a power prediction control system and method for a micro inverter. The power prediction control system comprises a main control unit and a consumption load unit, the main control unit comprises a sampling module and a control DSP, the consumption load unit comprises a load loop arranged at the output end of the transformer, a load R2 and a switch Q are arranged on the load loop, and the switch Q is connected with the control DSP through an isolation driving module. In an initial state, the relay KA is disconnected, and the switch Q is turned on; during sampling detection, a change ratio threshold value is set firstly, the change ratio of voltage and current of the primary side circuit module in rated time is detected, and when the change ratio is larger than the change ratio threshold value, the switch Q is closed, and the relay KA is closed; when the change ratio is smaller than the change ratio threshold value, the switch Q is turned on, and the relay KA is turned off. The load can consume output energy of the transformer when the relay is in an open-circuit state, the frequent switching condition of a traditional relay is improved, and the effective service life of the system is guaranteed and prolonged.

Description

Technical Field

[0001] The invention relates to a power prediction control system and method for a micro inverter, belonging to the technical field of power prediction and relay control of a micro inverter. Background Art

[0002] Micro single-stage inverter topology, the input voltage is a safe voltage, the system voltage is low, the operating voltage range is wide, and the light intensity is weak. The whole system is prone to frequent restarts and reconnections, which affects the life of the whole system. In particular, the frequent switching of mechanical relays in the system directly affects the electrical and mechanical life.

[0003] The micro inverter generally includes a secondary inverter bridge connected to the grid end. The secondary inverter bridge is connected to the primary circuit modules one by one through several parallel transformers. The primary circuit modules are connected to the PV end, and the secondary inverter bridge is connected to the EMC module at the grid end through the relay KA. The PV end will be affected by light and there will be a certain instability. At this time, supplying the grid end will cause system instability, and the relay KA will cause frequent switching. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the above-mentioned prior art. Aiming at the problem that the traditional micro-inverter frequently restarts the system and frequently switches the relay to be damaged under unstable light conditions, a power prediction control system and method for a micro-inverter are proposed.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A power prediction control system for a micro inverter, comprising a grid end with an EMC module, the EMC module being connected to a secondary inverter bridge via a relay KA, the secondary inverter bridge being connected in parallel to a plurality of transformers, any transformer being connected to a PV end via a primary circuit module, comprising a main control unit for collecting data of the primary circuit module for working state judgment and relay KA control, and a consumption load unit for consuming electric energy at the output end of the plurality of transformers; The main control unit includes a sampling module connected to any of the primary circuit modules, a control DSP connected to the sampling module, and the control DSP is connected to the relay KA phase drive control; The load consumption unit includes a first grounding branch and a second grounding branch, the first grounding branch is connected to the first end of any of the transformers, the second grounding branch is connected to the second end of any of the transformers, and a load R2 and a switch Q connected in series are provided on the first grounding branch or the second grounding branch, and the switch Q is connected to the control DSP through an isolation drive module.

[0006] Preferably, the main control unit includes an auxiliary power supply, and the auxiliary power supply is connected to the sampling module, the control DSP, and the isolation driving module for power supply respectively.

[0007] Preferably, the auxiliary power supply is connected to a power supply PV terminal.

[0008] Preferably, the switch Q is a MOS switch tube.

[0009] The present invention also proposes a control method for a power prediction control system of a micro inverter, comprising the following steps: In the initial state of S1, relay KA is disconnected, switch Q is turned on, and load R2 consumes the output energy of the transformer; S2 sampling detection, setting the change ratio threshold, the sampling module detects the change ratio of the voltage and current of the primary circuit module in real time within the rated time, and triggers the path signal when the change ratio is greater than the change ratio threshold; S3 relay path drive, after the control DSP receives the path signal, it closes the switch Q through the isolation drive module and closes the relay KA; S4 supplies detection, and the sampling module detects the change ratio of the voltage and current of the primary circuit module within the rated time in real time. When it is detected that the change ratio is less than the change ratio threshold, the circuit breaker signal is triggered. After receiving the circuit breaker signal, the control DSP opens the switch Q through the isolation drive module and disconnects the relay KA.

[0010] The beneficial effects of the present invention are mainly reflected in: 1. The load can consume the transformer output energy when the relay is in the disconnected state, so that the sampling module can sample data to determine the switching signal to produce a reliable interval, eliminating the frequent switching of traditional relays, and the effective life of the system is guaranteed and extended.

[0011] 2. The system circuit is ingenious and easy to build and implement.

[0012] 3. It can realize power prediction and load energy consumption, which is particularly suitable for improving and solving the problem of frequent restart of the whole system under weak light conditions, and maintaining the reliability and stability of system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 It is a structural schematic diagram of a power prediction control system of a micro inverter of the present invention.

[0014] Figure 2 It is a flow chart of a control method of a power prediction control system of a micro inverter of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant inventions, rather than to limit the inventions. It should also be noted that, for ease of description, only the parts related to the relevant inventions are shown in the accompanying drawings. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0017] The present invention provides a power prediction control system for a micro inverter, such as Figure 1 As shown, it includes a grid end with an EMC module, the EMC module is connected to a secondary inverter bridge through a relay KA, the secondary inverter bridge is connected in parallel with several transformers, and any transformer is connected to a PV end through a primary circuit module. The above system structure belongs to the prior art of micro inverters and will not be described in detail here.

[0018] In the present invention, Figure 1 As shown, it includes a main control unit for collecting data of the primary circuit module to determine the working state and control the relay KA, and a consumption load unit for consuming electric energy at the output end of several transformers.

[0019] The main control unit comprises a sampling module connected to any primary circuit module, a control DSP connected to the sampling module, and the control DSP is connected to the relay KA for phase driving control.

[0020] The load consumption unit includes a first grounding branch and a second grounding branch. The first grounding branch is connected to the first end of any transformer, and the second grounding branch is connected to the second end of any transformer. A load R2 and a switch Q connected in series are arranged on the first grounding branch or the second grounding branch. The switch Q is connected to the control DSP through an isolation driving module.

[0021] Specific implementation process and principle description: First, the first end and the second end of the transformer are explained. The first end and the second end are distinguished according to the positive and negative poles, that is, the first grounding branch is connected to the positive end or the negative end of each transformer, and the second grounding branch is also connected in parallel. The method of connecting the output ends of the transformers in parallel belongs to the prior art and will not be repeated here.

[0022] In traditional systems, a sampling module is also used. The sampling module samples the primary circuit module and then controls the on-off of the relay KA through the control DSP. However, the secondary inverter bridge of the transformer is not sufficient to maintain a stable output of the entire system. Therefore, after the on-off control of the relay KA, the sampling of the primary circuit module will fluctuate, resulting in frequent switching of the relay KA, which affects the electrical and mechanical life.

[0023] In this case, an electrical circuit is formed by using the first grounding branch and the second grounding branch. The output energy consumption of the transformer can be realized through the load R2 on the electrical circuit, so that the sampling module can control the on-off control of the relay KA by the DSP after sampling more stably, eliminate the frequent switching, and improve the effective service life.

[0024] To explain in more detail, before relay KA is switched on, the output energy of the transformer is consumed. After the switch is controlled, it can maintain a relatively stable output. When the sampling module performs a circuit-breaking operation on relay KA after sampling, the output end of the transformer will be shut down, which is insufficient to maintain the stable output of the whole system. This affects the sampling data at the original end, and it is easy to meet the control requirements of the switch again. At this time, due to the existence of load R2, the consumption that is insufficient to maintain the stable output of the whole system can be achieved, so that the conditions for switching on again will not be frequently met, reducing the on and off frequency of relay KA.

[0025] In addition, the load circuit can be isolated from the control DSP through the isolation drive module to meet the isolation control requirements, and the isolation drive module can be used to realize the isolation drive of the control DSP to the switch Q.

[0026] In a specific embodiment, the main control unit includes an auxiliary power supply, which is connected to the sampling module, the control DSP, and the isolation drive module for power supply. The auxiliary power supply is connected to a power supply PV terminal.

[0027] Specifically, the auxiliary power supply is used to supply power to each electrical component, and the auxiliary power supply is stored through the power supply PV terminal.

[0028] In a specific embodiment, the switch Q is a MOS switch tube, which meets the requirements of the coordinated implementation of the isolation drive, and the MOS switch tube controls the on and off circuit safely, reliably and stably.

[0029] A control method of a power prediction control system of a micro inverter of the present invention is described, which comprises the following steps: In the initial state, the relay KA is disconnected, the switch Q is turned on, and the load R2 consumes the output energy of the transformer; that is, the load circuit where the load R2 is located is in the open state, and the output energy of the transformer is continuously consumed.

[0030] Perform sampling detection and set the change ratio threshold. The sampling module detects the change ratio of the voltage and current of the primary circuit module within the rated time in real time. When it is detected that the change ratio is greater than the change ratio threshold, the path signal is triggered. The change ratio is used as a judgment condition to determine whether the system can meet the conditions for stable operation. When the conditions are met, the path signal is triggered.

[0031] Relay path drive, after controlling DSP to receive the path signal, close switch Q through the isolation drive module and close relay KA; at this time, relay KA is turned on to output stably to the EMC module.

[0032] Supply detection, the sampling module detects the change ratio of the voltage and current of the primary circuit module in real time within the rated time. When the change ratio is detected to be less than the change ratio threshold, the circuit breaker signal is triggered. After receiving the circuit breaker signal, the control DSP opens the switch Q through the isolation drive module and disconnects the relay KA. At this time, the output end of the transformer is insufficient to maintain the stable output of the entire system, and there is continuous power generation at the primary end. The sampling data of the primary side will be affected, causing the change ratio to fluctuate. Due to the energy consumption of the load R2, the influence on the sampling data of the primary side is eliminated, making the change ratio detection more reliable and stable, and there will be no frequent on and off control of the relay KA.

[0033] From the above description, it can be found that the load can consume the transformer output energy in the relay disconnected state, so that the sampling module samples data to determine the switching signal to produce a reliable interval, eliminate the frequent switching of traditional relays, and ensure and extend the effective life of the system. The system circuit is ingenious and easy to build and implement. It can realize power prediction and load energy consumption, and is particularly suitable for improving and solving the problem of frequent restart of the whole system under weak light conditions, maintaining the reliability and stability of system operation.

[0034] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or also includes elements inherent to such process, method, article, or apparatus / device.

[0035] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A power prediction control system for a micro inverter, comprising a grid end with an EMC module, the EMC module is connected to a secondary inverter bridge through a relay KA, the secondary inverter bridge is connected in parallel with a plurality of transformers, and any transformer is connected to a PV end through a primary circuit module, characterized in that: It includes a main control unit for collecting data of the primary circuit module to judge the working state and control the relay KA, and a consumption load unit for the output end power consumption of several transformers; The main control unit includes a sampling module connected to any of the primary circuit modules, a control DSP connected to the sampling module, and the control DSP is connected to the relay KA phase drive control; The load consumption unit includes a first grounding branch and a second grounding branch, the first grounding branch is connected to the first end of any of the transformers, the second grounding branch is connected to the second end of any of the transformers, and a load R2 and a switch Q connected in series are provided on the first grounding branch or the second grounding branch, and the switch Q is connected to the control DSP through an isolation drive module.

2. The power prediction control system of a micro inverter according to claim 1, characterized in that: The main control unit includes an auxiliary power supply, and the auxiliary power supply is connected to the sampling module, the control DSP, and the isolation driving module for power supply respectively.

3. The power prediction control system of a micro inverter according to claim 2, characterized in that: The auxiliary power supply is connected to a power supply PV terminal.

4. The power prediction control system of a micro inverter according to claim 1, characterized in that: The switch Q is a MOS switch tube.

5. A control method for a power prediction control system of a micro-inverter based on any one of claims 1 to 4, characterized in that The steps include: In the initial state of S1, relay KA is disconnected, switch Q is turned on, and load R2 consumes the output energy of the transformer; S2 sampling detection, setting the change ratio threshold, the sampling module detects the change ratio of the voltage and current of the primary circuit module in real time within the rated time, and triggers the path signal when the change ratio is greater than the change ratio threshold; S3 relay path drive, after the control DSP receives the path signal, it closes the switch Q through the isolation drive module and closes the relay KA; S4 supplies detection, and the sampling module detects the change ratio of the voltage and current of the primary circuit module within the rated time in real time. When it is detected that the change ratio is less than the change ratio threshold, the circuit breaker signal is triggered. After receiving the circuit breaker signal, the control DSP opens the switch Q through the isolation drive module and disconnects the relay KA.

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