Multi-power-supply level inversion system suitable for energy storage network construction

Abstract

The invention discloses a multi-power-supply level inversion system suitable for an energy storage network construction type, and relates to the field of new energy power generation grid connection and power supply manufacturing, and the system comprises at least three dual-power-supply switching devices which are respectively corresponding to a plurality of DC input ends and are used for providing a DC voltage; the plurality of first-class switch units are communicated with the dual-power-supply switching device and are used for receiving the direct-current voltage, and different connection combination modes of the dual-power-supply switching device are obtained by controlling on and off of the first-class switch units; the plurality of second-type switch units are used for cutting off the dual-power switching device on the basis of the main power conversion module; and the control logic module is used for generating a conduction strategy of each switch unit in real time according to the target output voltage. By reducing the number of switching tubes and optimizing the switching time sequence, switching loss is reduced, the efficiency of the inverter is improved, a dual-power-supply automatic switching mechanism is added, and it is ensured that the standby power supply can be automatically switched when the power supply breaks down.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy power generation and grid connection and power supply manufacturing, and particularly relates to a multi-source high-fault-tolerant multi-level inverter system suitable for energy storage grid connection. BACKGROUND

[0002] At present, inverters are widely used in the field of new energy power generation and grid connection and power supply manufacturing, especially in energy storage systems and smart grids. Inverters undertake the task of converting direct current to alternating current. In practical applications, inverters need to adjust the output voltage efficiently and accurately to meet the needs of different grid loads.

[0003] Traditional inverter design uses pulse width modulation (PWM) technology to adjust the output voltage. However, to achieve high voltage accuracy, especially in energy storage systems or smart grid applications, multi-level inverters usually require a large number of switching devices to participate, resulting in complex systems, large switching losses, and low efficiency. Inverters also need to cope with changing grid loads, main power supply failures, and other variable operating conditions.

[0004] Current multi-level inverters use a large number of switching devices to achieve multi-level output, resulting in large system size, large switching losses, and low efficiency.

[0005] When some switching devices fail, the system takes a long time to recover to a stable state, affecting the stability of the system, especially when the power supply fails, additional adjustment networks are needed.

[0006] Due to the use of a large number of switching devices and complex control systems, recovery and control are difficult when a fault occurs, affecting the stability and reliability of the inverter.

[0007] The purpose of the present application is to solve the shortcomings of existing multi-level inverters in the application of energy storage systems and smart grids, and to propose a multi-source high-fault-tolerant multi-level inverter. By reducing the number of switching devices and optimizing the design, switching losses are reduced and system efficiency is improved. At the same time, fault-tolerant switching devices and power automatic switching mechanisms are added to ensure that the system can quickly recover when the power supply fails and maintain system stability. The inverter is particularly suitable for integration of energy storage systems and smart grids, and can ensure the continuity and efficiency of power supply. SUMMARY

[0008] In view of the above problems, the present application is proposed.

[0009] Therefore, the problem to be solved by the present application is that traditional inverter design uses pulse width modulation (PWM) technology to adjust the output voltage, however, to achieve high voltage accuracy, multi-level inverters usually require a large number of switching devices to participate, resulting in complex systems, large switching losses, and low efficiency. Inverters also need to cope with changing grid loads, main power supply failures, and other variable operating conditions.

[0010] To solve the above technical problems, the application provides the following technical scheme: a multi-power level inverter system suitable for energy storage network construction, comprising: a multi-power automatic switching module, containing at least three double-power switching devices corresponding to multiple DC input ends for providing DC voltage; a main power conversion module containing a plurality of first switching units connected to the double-power switching devices for receiving DC voltage; wherein different connection combinations of the double-power switching devices are obtained by controlling the opening and closing of the first switching units; an auxiliary level synthesis module containing a plurality of second switching units for isolating the double-power switching devices based on the main power conversion module; a control logic module for generating a conduction strategy of each switching unit in real time according to a target output voltage to realize step modulation of the output voltage; wherein the main power conversion module and the auxiliary level synthesis module cooperate to generate at least eleven levels of AC output.

[0011] As a preferred scheme of the multi-power level inverter system suitable for energy storage network construction, the double-power switching device contains a main power source and a backup power source, and the backup power source is quickly put into use when the main power source fails.

[0012] As a preferred scheme of the multi-power level inverter system suitable for energy storage network construction, when the double-power switching device is working normally, the contactor of the main power source is closed, the current is connected to the external circuit through the main power source contactor, and the external circuit is powered through the normally open contact, at the same time, the contactor of the backup power source is opened, and the backup power source does not participate in power supply.

[0013] As a preferred scheme of the multi-power level inverter system suitable for energy storage network construction, when the main power source fails or is powered off, the contactor of the main power source is automatically opened, the system is switched to the backup power source for power supply through automatic control, the contactor of the backup power source is closed, the backup power source is connected to the system, and starts to supply power to the load. The backup power source ensures that the load continues to obtain stable power supply during the failure of the main power source, thereby avoiding power interruption of the load.

[0014] As a preferred scheme of the multi-power level inverter system suitable for energy storage network construction, after the main power source restores power supply, the contactor of the main power source is closed again, the power supply is automatically switched back to the main power source, and the contactor of the backup power source is opened, so that the backup power source exits the power supply link. In this process, the power switching mechanism ensures quick, smooth and uninterrupted switching process through automatic operation of the contactor, and ensures system stability and safety.

[0015] As a preferred scheme of the multi-power-level inverter system suitable for the energy storage network type, the first type of switch unit comprises a positive switch unit and a negative switch unit; the positive switch unit is connected to the output positive direction end of the dual-power switching device and is used for conducting a positive voltage; the negative switch unit is connected to the output reverse direction end of the dual-power switching device and is used for conducting a negative voltage; the number of the positive switch units is equal to the number of the negative switch units; the positive switch units and the negative switch units are symmetrically arranged.

[0016] As a preferred scheme of the multi-power-level inverter system suitable for the energy storage network type, the isolation of the dual-power switching device comprises that the second type of switch unit is used for conducting a branch, so that the dual-power switching device is isolated from the circulation circuit and cannot provide a direct-current voltage in the circulation circuit.

[0017] As a preferred scheme of the multi-power-level inverter system suitable for the energy storage network type, the dual-power switching device outputs a fixed direct-current voltage value, and the direct-current voltage values output by the dual-power switching devices are not required to be completely the same.

[0018] As a preferred scheme of the multi-power-level inverter system suitable for the energy storage network type, the step modulation of the output voltage comprises that when the positive switch unit is conducted, the dual-power switching device connected with the current positive switch unit outputs a positive direct-current voltage value; when the negative switch unit is conducted, the dual-power switching device connected with the current negative switch unit outputs a negative direct-current voltage value; and when the second type of switch unit is conducted, the dual-power switching device corresponding to the current second type of switch unit is isolated from the circulation circuit.

[0019] As a preferred scheme of the multi-power-level inverter system suitable for the energy storage network type, the generation of at least eleven levels of alternating current output comprises that by conducting different first type of switch units and second type of switch units, the direct-current voltage values output by the dual-power switching devices are superimposed positively and negatively and zero, so as to obtain different output voltage values to meet the demand of the target output voltage. Based on the switch combination corresponding to different levels, an approximate sine step voltage waveform is output, the harmonic content of the output voltage is significantly reduced, the power quality is improved, the filter design difficulty is reduced, and the whole machine volume is reduced.

[0020] The present application has the advantages that: the number of switch tubes is reduced and the switch timing is optimized, the switching loss is reduced, and the efficiency of the inverter is improved.

[0021] The application increases the dual power automatic switching mechanism, ensures automatic switching to the standby power supply when the power fails, and quickly restores the system power supply, especially suitable for intelligent power grids and energy storage systems with high requirements for power continuity and stability.

[0022] The application is particularly suitable for integration with energy storage systems and intelligent power grids, can quickly respond when the power grid or load changes, and ensures the stability and efficiency of power grid power supply. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 The structure diagram of a multi-source level inverter system suitable for energy storage network type in embodiment 1.

[0025] Figure 2 The module structure diagram of a multi-source level inverter system suitable for energy storage network type in embodiment 1.

[0026] Figure 3 The 0.5V dc Conduction strategy diagram of a multi-source level inverter system suitable for energy storage network type in embodiment 1.

[0027] Figure 4 The 1.0V dc Conduction strategy diagram of a multi-source level inverter system suitable for energy storage network type in embodiment 1.

[0028] Figure 5 The 1.5V dc Conduction strategy diagram of a multi-source level inverter system suitable for energy storage network type in embodiment 1.

[0029] Figure 6 The 2.0V dc Conduction strategy diagram of a multi-source level inverter system suitable for energy storage network type in embodiment 1.

[0030] Figure 7 The 2.5V dc Conduction strategy diagram of a multi-source level inverter system suitable for energy storage network type in embodiment 1.

[0031] Figure 8 The -0.5V dc Conduction strategy diagram of a multi-source level inverter system suitable for energy storage network type in embodiment 1.

[0032] Figure 9 -1.0V for a multi-source level inverter system suitable for energy storage network type in example 1 dc Conduction strategy diagram.

[0033] Figure 10 -1.5V for a multi-source level inverter system suitable for energy storage network type in example 1 dc Conduction strategy diagram.

[0034] Figure 11 -2.0V for a multi-source level inverter system suitable for energy storage network type in example 1 dc Conduction strategy diagram.

[0035] Figure 12 -2.5V for a multi-source level inverter system suitable for energy storage network type in example 1 dc Conduction strategy diagram.

[0036] Figure 13 0V for a multi-source level inverter system suitable for energy storage network type in example 1 dc Conduction strategy diagram.

[0037] Figure 14 Output voltage and current waveform diagram of an eleven-level inverter for a multi-source level inverter system suitable for energy storage network type in example 1.

[0038] Figure 15 Internal structure diagram of a dual power automatic switching device for a multi-source level inverter system suitable for energy storage network type in example 2.

[0039] Figure 16 Work flow diagram of a dual power automatic switching device for a multi-source level inverter system suitable for energy storage network type in example 2. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0041] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the scope of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0042] Example 1, refer to Figures 1-14This is the first embodiment of the present invention. This embodiment provides a multi-power level inverter system suitable for energy storage grid construction. This embodiment takes an eleven-level inverter as an example, which consists of fourteen switching transistors and three dual-power automatic switching devices, such as... Figure 1 As shown, it specifically includes: first switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, sixth switch S6, seventh switch S7, eighth switch S8, ninth switch S9, and tenth switch S1. 10 Eleventh switch S 11 12th switch S 12 13th switch S 13 Fourteenth switch S 14 The first dual-power automatic switching device V1, the second dual-power automatic switching device V2, and the third dual-power automatic switching device V3.

[0043] V1, V2, and V3 are controlled by a multi-power automatic switching module, corresponding to three DC input terminals, used to provide DC voltage.

[0044] S1, S4, S 10 and S 14 This is a positive voltage switching unit, connected to the positive output terminal of the dual power supply switching device, used to conduct positive voltage. For example, S1 and S4 conduct V1 to output positive voltage, and S4 and S... 10 When V2 is turned on, a positive voltage is output, and S 10 and S 14 Turn on V3 to output a positive voltage.

[0045] S2, S3, S9 and S 13 This is a negative voltage switching unit, connected to the reverse output terminal of the dual power supply switching device, used to conduct negative voltage. For example, S2 and S3 conduct V1 to output negative voltage, and S3 and S... 94 When V2 is turned on, a negative voltage is output, and S9 and S... 13 When V3 is turned on, a negative voltage is output.

[0046] As can be seen, the number of positive switch units must be equal to the number of negative switch units, and the positive switch units and negative switch units are arranged symmetrically.

[0047] Among them, the positive and negative switching units belong to the first type of switching units and are controlled by the main power conversion module. By controlling the opening and closing of the first type of switching units, different connection combinations of the dual power supply switching device can be obtained.

[0048] S5, S6, S7, S8, S 11 and S 12The second type of switch unit is used for conducting branch, and isolates the dual power switching device from the circulation circuit, so that the dual power switching device cannot provide DC voltage in the circulation circuit.

[0049] The second type of switch unit is controlled by the auxiliary level synthesis module, and is used for isolating the dual power switching device on the basis of the main power conversion module, such as S5 and S6 for isolating V1, S7 and S8 for isolating V2, S 11 and S 12 for isolating V3.

[0050] As Figure 2 indicated, the control logic module is further included, which is used for generating the conduction strategy of each switch unit in real time according to the target output voltage, so as to realize the step modulation of the output voltage.

[0051] The main power conversion module and the auxiliary level synthesis module cooperate based on the conduction strategy to generate eleven kinds of AC output.

[0052] Specifically, the dual power switching device outputs a fixed DC voltage value, and the DC voltage values output by each dual power switching device do not require to be completely the same. In the embodiment, the first dual power automatic switching device V1, the second dual power automatic switching device V2 and the third dual power automatic switching device V3 satisfy the relationship: V1=V dc , V2=V dc , V1=0.5V dc , V dc represents a unit DC voltage.

[0053] If the target output voltage value is positive, such as when the microgrid is reconnected to the grid after offline operation, the output gradually synchronizes with the main grid by using the step output voltage. At this time, the inverter needs to gradually output from low level to target level, for example, from 0.5V dc →1.0V dc →1.5V dc →2.0V dc →2.5V dc , and the conduction strategy includes the following steps:

[0054] Initial grid connection preparation: the controller judges the initial state of grid connection, instructs the inverter to output 0.5V dc , and turns on the switches S1, S3, S 10 , S 14 , to output the minimum positive step voltage, as shown in Figure 3 .

[0055] Step-by-step voltage boost to 1.0V dc : With the progress of synchronization control, the voltage is boosted by one level, and the switches S1, S5, S6, S11 , S 12 , S 14 , S Figure 4 .

[0056] Boost voltage to 1.5V dc (Fit the rising section of the sine wave): The controller issues further instructions to adjust the control logic, turn on switches S1, S4, S7, S8, S 14 , S Figure 5 .

[0057] Continue to boost voltage to 2.0Vdc (close to the main network peak): Turn on switches S1, S4, S 10 , S 13 , S Figure 6 .

[0058] Output maximum level 2.5V dc (positive peak): completed in synchronization with the grid voltage waveform, turn on switches S1, S4, S 10 , S 14 , S Figure 7 .

[0059] In another optional embodiment, if the scenario is the voltage rapid compensation under the condition of inductive load mutation, that is, a group of large inductive loads (such as motors) are connected to the system, due to the inductive characteristics, the load instantaneous current fluctuates, in order to prevent the output voltage from falling, the inverter needs to be quickly adjusted to a high level for voltage support, and the specific implementation steps of the conduction strategy are as follows:

[0060] The system detects the voltage drop trend, the control system triggers the emergency voltage stabilization logic, and quickly boosts to 2.0V dc , turn on switches S1, S4, S 10 , S 13 .

[0061] If there is still a downward trend, further compensation to 2.5V dc , the control system instructs the inverter to adjust to the maximum positive level again, turn on switches S1, S4, S 10 , S 14 .

[0062] After the load current tends to be stable, the voltage drops to 1.5V dc , and the normal operation is restored, turn on switches S1, S4, S7, S8, S 14 .

[0063] When the load is completely stable, it is adjusted back to 1.0V dc ~ 0.5V dc interval to save energy, turn on switches according to the target, 0.5V dc → S1, S3, S10 , S 14 .

[0064] If the target output voltage value is negative, such as in an inductive load, the inverter needs to output a nearly sinusoidal wave voltage, and the negative half cycle stage needs to gradually output from 0 to -2.5V dc of each level. The specific implementation steps of the conduction strategy include:

[0065] Start entering the negative half cycle output -0.5V dc , the controller judges the voltage zero-crossing and starts the negative half cycle output, and turns on switches S2, S5, S6, S 11 , S 12 , S 13 , as shown in Figure 8 .

[0066] Down to -1.0V dc (negative medium-low level), the control logic switches the conduction combination, and turns on switches S2, S3, S 10 , S 13 , as shown in Figure 9 .

[0067] Further down to -1.5V dc (negative intermediate level), turn on switches S2, S5, S6, S9, S 13 , as shown in Figure 10 .

[0068] Continue to drop to -2.0V dc (negative high level), turn on switches S2, S3, S7, S8, S 13 , as shown in Figure 11 .

[0069] Reach the maximum negative voltage -2.5V dc (negative peak value), turn on switches S2, S3, S9, S 13 , as shown in Figure 12 .

[0070] In another alternative embodiment, if the scenario is that after the main power supply of the power grid fails, the system enters island operation and stably outputs negative power, that is, when the main power supply of the power grid fails, the standby power supply is connected, and the inverter continues to supply power to the independent load. The system needs to stably output positive and negative alternating voltage, and the following is the implementation details of the negative voltage stage. The specific implementation steps of the conduction strategy include:

[0071] Detecting power grid outage, standby power supply automatically switching online, dual power supply switching module detecting power grid interruption, triggering S13 conduction as negative direction main path fixer.

[0072] Start island operation mode: initialize output -1.0Vdc , turn on switch S2, S3, S 10 , S 13 , as the island initial negative voltage support.

[0073] Output negative step up to -1.5V dc , turn on switch S2, S5, S6, S9, S 13 .

[0074] Compensation to -2.0V when high power load occurs dc / -2.5V dc , -2.0V dc → S2, S3, S7, S8, S 13 ; -2.5V dc → S2, S3, S9, S 13 , the controller dynamically judges the load impedance, and automatically selects the corresponding level.

[0075] After the load drops, gradually fall to -0.5V dc and maintain stable power supply, turn on switch S2, S5, S6, S 11 , S 12 , S 13 .

[0076] In another alternative embodiment, the output voltage needs to be kept at 0V for a short time before the end of the positive half cycle voltage or the beginning of the negative half cycle voltage of the inverter output dc , to realize complete sine wave zero crossing control and reduce cross distortion. At the same time, this process is also used for dynamic dead zone interpolation to avoid current jump when switching adjacent levels, turn on S2, S4, S7, S8, S13, so that V dc output is zero, as shown in Figure 13 .

[0077] Further, when implementing the turn-on strategy, the approximate output voltage waveform of the present application is shown in Figure 14 , assuming that the load is inductive, the load current i o slightly lags behind the output voltage V0.

[0078] Embodiment 2, refer to Figure 15 and Figure 16 , the second embodiment of the present application, which is different from the first embodiment: a multi-source level inverter system suitable for energy storage network type further comprises, the novel inverter topology disclosed in this embodiment, the double power automatic switching device will quickly put the standby power into use when the main power breaks down, so that the system continues to maintain stable operation, as shown in Figure 15 is the internal structure diagram of the double power automatic switching device, including the main power and the standby power.

[0079] Specifically, the working process of the dual power automatic switching device is as shown in the following table Figure 16 As shown in the following table, in the power switching control system of the present application, when the main power supply is in normal working state, the contactor of the main power supply (main contactor) is closed, the current is connected to the external circuit through the main power supply contactor, and the external circuit is powered through the normally open contact. At the same time, the contactor of the standby power supply (standby contactor) is open, and the standby power supply does not participate in power supply. At this time, the main power supply is responsible for power supply work, ensuring the continuous operation of the load.

[0080] When the main power supply fails or is powered off, the contactor of the main power supply is automatically opened, and the system is switched to the standby power supply for power supply through automatic control. The contactor of the standby power supply is closed, the standby power supply is connected to the system, and the standby power supply starts to supply power to the load. The standby power supply ensures that the load continues to obtain stable power supply during the failure of the main power supply, thereby avoiding power interruption of the load.

[0081] After the main power supply resumes power supply, the contactor of the main power supply is closed again, the power supply is automatically switched back to the main power supply, and the contactor of the standby power supply is opened, and the standby power supply exits the power supply link. In this process, the power switching mechanism ensures that the switching process is fast, smooth and uninterrupted through the automatic operation of the contactor, ensuring the stability and safety of the system.

[0082] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A multi-source level inverter system suitable for energy storage network configuration, characterized in that: The utility model relates to a multi -power automatic switching module, including at least three double power supply switching devices correspond to multiple DC input end for providing DC voltage, A main power conversion module includes a plurality of first switching units, the first switching units are connected to the double power supply switching devices for receiving DC voltage, Wherein, through the control of the first switching unit's opening and closing, the different connection combination mode of double power supply switching device is obtained, An auxiliary level synthesis module includes a plurality of second switching units for isolating double power supply switching device on the basis of main power conversion module, A control logic module is used to generate the conduction strategy of each switching unit according to the target output voltage, realizing the step modulation of output voltage, Wherein, the main power conversion module and the auxiliary level synthesis module cooperate to generate at least eleven levels of AC output. The double power supply switching device includes a main power supply and a backup power supply, when the main power supply breaks down, the backup power supply is quickly put into use.

2. A multi-level inverter system for energy storage grid forming application as claimed in claim 1, wherein: When the double power supply switching device works normally, the contactor of the main power supply is closed, the current passes through the main power supply contactor to access the external circuit, and the normally open contact supplies power to the external circuit, at the same time, the contactor of the backup power supply is opened, and the backup power supply does not participate in power supply.

3. A multi-level inverter system for energy storage grid forming network as claimed in claim 2, wherein: When the main power supply fails or is powered off, the contactor of the main power supply is automatically opened, the system is switched to the backup power supply for power supply through automatic control, the contactor of the backup power supply is closed, the backup power supply accesses the system and starts to supply power to the load.

4. A multi-level inverter system for energy storage grid forming application as claimed in claim 3, wherein: After the main power supply resumes power supply, the contactor of the main power supply is closed again, the power supply is automatically switched back to the main power supply, and the contactor of the backup power supply is opened immediately, so that the backup power supply exits the power supply link.

5. A multi-level inverter system for energy storage grid forming application as claimed in claim 4, wherein: The first switching unit includes a positive switching unit and a negative switching unit; 6. A multi-level inverter system for energy storage grid forming network as claimed in claim 5 wherein: The positive switching unit is connected to the output positive direction end of the double power supply switching device for conducting positive voltage; The negative switching unit is connected to the output reverse direction end of the double power supply switching device for conducting negative voltage; The number of positive switching units is equal to the number of negative switching units; The positive switching unit and the negative switching unit are symmetrically arranged. The isolation of the double power supply switching device includes that the second switching unit is used for conducting branch, isolating the double power supply switching device from the circulating circuit, so that the double power supply switching device cannot provide DC voltage in the circulating circuit.

7. A multi-power-level inverter system suitable for energy storage grid construction as described in claim 6, characterized in that: The double power supply switching device outputs a fixed DC voltage value, and the DC voltage values output between each double power supply switching device do not require to be completely the same.

8. A multi-power-level inverter system suitable for energy storage grid construction as described in claim 7, characterized in that: The step modulation of output voltage includes that when the positive switching unit is conducted, the double power supply switching device connected with the current positive switching unit outputs a positive DC voltage value; 9. A multi-power-level inverter system suitable for energy storage grid construction as described in claim 8, characterized in that: When the negative switching unit is conducted, the double power supply switching device connected with the current negative switching unit outputs a negative DC voltage value; When the second switching unit is conducted, the double power supply switching device corresponding to the current second switching unit is isolated from the circulating circuit. ​ 10. A multi-power-level inverter system suitable for energy storage grid construction as described in claim 9, characterized in that: The generation of the at least eleven levels of AC output includes positive and negative superposition and zero superposition of the DC voltage value output by the dual power switching device by turning on different first and second switching units, so as to obtain different output voltage values to meet the demand of the target output voltage.

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