CN109245580B - Multi-level inverter with energy storage system and control method thereof - Google Patents
Multi-level inverter with energy storage system and control method thereof Download PDFInfo
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- CN109245580B CN109245580B CN201811105204.6A CN201811105204A CN109245580B CN 109245580 B CN109245580 B CN 109245580B CN 201811105204 A CN201811105204 A CN 201811105204A CN 109245580 B CN109245580 B CN 109245580B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
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- Engineering & Computer Science (AREA)
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- Inverter Devices (AREA)
Abstract
The invention discloses a multi-level inverter with an energy storage system, which comprises a plurality of sub-topology circuits connected in series, wherein each sub-topology circuit comprises a low-voltage battery and an H-bridge circuit, the H-bridge circuits are connected to two ends of the low-voltage battery, the middle point of a bridge arm of the H-bridge circuit is the output end of the sub-topology circuit, and the sub-topology circuits are sequentially connected in series through the output ends of the sub-topology circuits. Only one switch is used as a high-frequency switch each time, so that the system loss is reduced, and higher conversion efficiency is realized; the sub-topologies work in turn, so that the average time of the whole topology work is actually reduced, namely the service life of the system topology is greatly prolonged.
Description
Technical Field
The invention relates to the field of photovoltaic inverters, in particular to a multi-level inverter with an energy storage system and a control method.
Background
In the conventional energy storage inverter system, a DC 48V battery is used for energy storage, so that AC (230Vac/50or 60Hz) can be output. The traditional boosting re-inversion structure has more energy conversion rings, and uses high-voltage devices and high-frequency switches more, so that the system efficiency is lower and the cost is higher.
Disclosure of Invention
The invention aims to provide a multi-level inverter with an energy storage system, which can realize the inversion function by effectively combining simple sub-topologies, realize higher system efficiency and realize automatic energy balance among battery modules.
The invention adopts the following technical scheme:
the multi-level inverter with the energy storage system comprises a plurality of sub-topology circuits connected in series, wherein each sub-topology circuit comprises a low-voltage battery and an H-bridge circuit, the H-bridge circuits are connected to two ends of the low-voltage battery, the middle point of a bridge arm of each H-bridge circuit is the output end of each sub-topology circuit, and the sub-topology circuits are sequentially connected in series through the output ends of the sub-topology circuits.
The H-bridge circuit is an H4 bridge circuit.
The H-bridge circuit comprises S1, S2, S3 and S4 which are MOSFET power devices.
The voltage of the low-voltage battery is 48V.
Eight sub-topology circuits are provided.
The low voltage battery may be a dc power supply.
In the starting process, S3 and S4 in each sub-topology are both in an on state, S3 in any sub-topology is changed into an off state from the on state, S1 is subjected to frequency conversion switching according to a sinusoidal modulation mode, the duty ratio D is gradually changed from 0 to 1, S1 is always conducted and keeps the conducting state unchanged until the duty ratio D is equal to 1, in the process, the switching states in other sub-topology circuits are unchanged, S1 and S2 are disconnected, S3 and S4 are turned on, and the topology output is gradually increased from 0V to 48V.
Keeping the state of the first topology circuit unchanged, repeating the action of the first sub-topology circuit by the second topology circuit, namely changing the S3 of the second sub-topology circuit from an on state to an off state, changing the frequency of the switches by the S1 of the second topology according to a sinusoidal modulation mode, gradually changing the duty ratio D from 0 to 1, and gradually increasing the system topology output from 48V to 96V when the duty ratio D is equal to 1.
The sub-topology circuits repeat the above process.
And each sub-topology circuit is sequentially and one by one reduced from the duty ratio D equal to 1 to the duty ratio D equal to 0, and finally the alternating current output voltage is returned to be 0V.
The invention has the advantages that: only one switch is used as a high-frequency switch each time, so that the system loss is reduced, and higher conversion efficiency is realized; the low-voltage power device is adopted, the device selection range is wider, the price is lower, the system cost is reduced, the input is the energy storage battery, in the discharging process, the sub-topology battery voltage is higher, the discharging time is longer, and the sub-topology battery voltage is lower, the discharging time is shorter. Therefore, the energy balance among the battery systems is indirectly achieved; the bidirectional operation can be realized, namely the alternating current output end is connected with equipment such as a power grid, the battery can be reversely charged, the bidirectional operation is formed by a plurality of sub-topologies, and the sub-topologies work in turn, so that the average time of the work of the whole topology is actually reduced, namely the service life of the system topology is greatly prolonged.
Drawings
The invention is described in detail below with reference to examples and figures, in which:
FIG. 1 is a circuit schematic of a sub-topology circuit of the present invention.
Fig. 2 is a circuit diagram of embodiment 1 of the present invention.
Fig. 3 is a circuit diagram of embodiment 2 of the present invention.
Detailed Description
The following further illustrates embodiments of the invention:
the invention provides a novel inverter topology framework with an energy storage system, the topology framework is based on a sub-topology circuit series framework, a plurality of sub-topology circuits work coordinately through a unique modulation and control mode, devices in each sub-topology circuit only bear voltage at two ends of a low-voltage battery, only one power device in each sub-topology circuit has high-frequency switching action at each stage, and system loss is greatly reduced. Because the power device only bears low voltage and low current, the power device has larger selection range and lower cost.
A multi-level inverter with an energy storage system comprises a plurality of sub-topology circuits which are connected in series, as shown in figure 1, each sub-topology circuit comprises a low-voltage battery and an H-bridge circuit, the H-bridge circuits are connected to two ends of the low-voltage battery, the middle point of a bridge arm of each H-bridge circuit is the output end of the corresponding sub-topology circuit, the sub-topology circuits are sequentially connected in series through the output ends of the corresponding sub-topology circuits, the H-bridge circuit in the multi-level inverter is an H4 bridge circuit or other types of H-bridge circuits, the H-bridge circuits comprise S1, S2, S3 and S4 which are MOSFET power devices, and the voltage of the low-voltage battery is 48V.
A multi-level inverter with an energy storage system is shown in a topology of fig. 2, the system is formed by connecting 8 subsystems, and alternating current output of 230VAC 50/60Hz is generated under a certain modulation and control strategy. A control method of a multilevel inverter with an energy storage system is characterized in that initially when S3 and S4 are both turned on in each sub-topology, the alternating-current output voltage of the system is 0V. During the positive half cycle of the operation of the inverter, in any sub-topology, S3 is changed from an on state to an off state, S1 performs frequency conversion switching according to a sinusoidal modulation mode, the duty ratio D is gradually changed from 0 to 1, and S1 is always conducted and keeps the on state unchanged until the duty ratio D is equal to 1. In the process, the switch states in other sub-topologies are unchanged, S1, S2 is disconnected, S3 and S4 are switched on. The system topology output will gradually rise from 0V to 48V. Keeping the state of the first topology unchanged, the second topology repeats the action of the first topology, namely S3 of the second topology is changed into an off state from an on state, S1 of the second topology switches frequency according to a sinusoidal modulation mode, the duty ratio D is gradually changed from 0 to 1, and when the duty ratio D is equal to 1, the output of the system topology is gradually increased from 48V to 96V. And so on in this way until a peak voltage of 325V or so of sinusoidal alternating 230VAC is reached. And then the sub-topologies are sequentially reduced from the duty ratio D-1 to the duty ratio D-0 one by one, and finally the AC output voltage is returned to 0V.
Similarly, the inverter operates in the negative half cycle, the S4 is switched from the on state to the off state, the S2 is switched in a frequency conversion mode according to a sine modulation mode, the operation process is consistent with the positive half cycle principle, the operation of the inverter in the negative half cycle is completed, and the alternating current output voltage is finally returned to be 0V.
In the invention, only one switch is used as a high-frequency switch in the topology, thereby reducing the system loss and realizing higher conversion efficiency; this patent topology adopts low-voltage power device, and the device selection range is wider, and the price is lower to reduced system cost, topology input be energy storage battery, at the discharge process, sub-topology battery voltage is higher, then discharge time is longer, and sub-topology battery voltage is lower, then discharge time is shorter. Thereby indirectly achieving the balance of energy among the battery systems. The topology can run in two directions, namely the alternating current output end is connected with equipment such as a power grid and the like, and the battery can be charged reversely. The system is composed of a plurality of sub-topologies, and each sub-topology works in turn, so that the average working time of the whole topology is actually reduced, namely the service life of the system topology is greatly prolonged.
As shown in fig. 3, an embodiment of the topology can be implemented in which one of the cells is replaced by an independent 48V dc source. The output of 230VAC and 50/60Hz can be realized only by 6 48V energy storage batteries, and the sub-topologies with the batteries adopt power frequency switches, namely, the output current is positive half cycle, when a certain sub-topology works, S1 in the sub-topology is always conducted, and the switches in the H bridge connected with the isolated 48V direct current power supply are switched on and off at high frequency according to a sine modulation mode to output sine waves. The scheme is beneficial to reducing electromagnetic interference, and the reduction of the number of switches needing high-frequency control is beneficial to the design of a control system.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (1)
1. A control method of a multi-level inverter with an energy storage system is disclosed, wherein the multi-level inverter comprises a plurality of sub-topology circuits which are connected in series, each sub-topology circuit comprises a low-voltage battery and an H-bridge circuit, the H-bridge circuits are connected to two ends of the low-voltage battery, the middle point of a bridge arm of each H-bridge circuit is the output end of the corresponding sub-topology circuit, and the sub-topology circuits are sequentially connected in series through the output ends of the sub-topology circuits; each sub-topology circuit H-bridge circuit comprises a switch S1, a switch S2, a switch S3 and a switch S4, wherein the switch S1 and the switch S3 are sequentially connected between the positive electrode and the negative electrode of the low-voltage battery in series, the switch S2 and the switch S4 are sequentially connected between the positive electrode and the negative electrode of the low-voltage battery in series, and the connection point of the switch S1 and the switch S3 and the connection point of the switch S2 and the switch S4 respectively form two output ends of the sub-topology circuit; it is characterized in that the preparation method is characterized in that,
starting a switch S3 and a switch S4 in each sub-topology circuit to be in an on state, selecting any one of the sub-topology circuits as a first sub-topology circuit, operating the multi-level inverter for a positive half cycle, converting the switch S3 in the first sub-topology circuit from the on state to the off state, performing frequency conversion on the switch S1 according to a sinusoidal modulation mode, gradually increasing the duty ratio D from 0 to 1, keeping the switch S1 in an on state when the duty ratio D is 1, keeping the switch S1 in the on state in other sub-topology circuits, namely, turning off the switch S1 and the switch S2, switching on the switch S3 and the switch S4, gradually increasing the output of the multi-level inverter from 0V to 48V, keeping the state of the first sub-topology circuit unchanged, and repeating the action of the first sub-topology circuit by a second sub-topology circuit, namely, converting the switch S3 of the second sub-topology circuit from the on state to the off state, the switch S1 of the second sub-topology circuit is switched in a frequency conversion mode according to a sine modulation mode, the duty ratio D is gradually changed from 0 to 1, when the duty ratio D is 1, the output of the multi-level inverter is gradually increased from 48V to 96V, and the like, the rest sub-topology circuits sequentially repeat the process until the output of the multi-level inverter reaches the peak voltage 325V of the sine alternating current 230VAC, then the sub-topology circuits are sequentially decreased from the duty ratio D to 1 to the duty ratio D to 0 one by one, and the output of the multi-level inverter finally returns to the alternating current output voltage of 0V; during the negative half cycle of the operation of the multi-level inverter, the switch S4 is switched from the on state to the off state, the switch S2 is switched in a frequency conversion mode according to a sine modulation mode, and the operation process is consistent with the positive half cycle principle.
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CN201811105204.6A CN109245580B (en) | 2018-09-21 | 2018-09-21 | Multi-level inverter with energy storage system and control method thereof |
PCT/CN2019/076074 WO2020057057A1 (en) | 2018-09-21 | 2019-07-19 | Multilevel inverter having energy storage system and control method thereof |
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