Energy storage PCS device based on two-stage three-level inverter topological structure

Abstract

The utility model discloses an energy storage PCS device based on a two-stage three-level inverter topological structure. The energy storage PCS device comprises an energy storage battery, a dual active bridge converter, a three-level inverter, an SVPWM signal generator, an AC contactor and an AC filter. The energy storage battery, the dual active bridge converter, the three-level inverter, the SVPWM signal generator, the AC contactor and the AC filter are connected. According to the utility model, the output electric energy quality and the electromagnetic compatibility are improved, the three-level inverter adopts the diode clamping topology design, the harmonic content of the output current is obviously reduced, the electric energy quality is improved, the electromagnetic interference is effectively inhibited, the stability of equipment in the aspect of electromagnetic compatibility (EMC) is ensured, and the normal operation of peripheral equipment is prevented from being influenced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to power distribution equipment technical field, concretely relates to a kind of energy storage PCS device based on two-stage three-level inverter topological structure. BACKGROUND

[0002] With the continuous increase of new energy installed capacity, its generation instability and volatility bring challenges to the frequency and voltage stability of power grid. As an effective solution to the grid fluctuation of new energy, distributed energy storage technology has become an important means to maintain the stability of power grid. Distributed energy storage equipment generally takes energy storage converter (PCS) as the core, connects the DC side energy storage device to the AC power grid, and performs bidirectional conversion of electric energy. Compared with centralized energy storage, distributed energy storage device has the advantages of flexible deployment and plug-and-play, and can quickly respond to grid regulation demand, but there is still room for improvement in conversion efficiency, off / on-grid switching smoothness, etc.

[0003] Currently, the mainstream technology topology of energy storage converter includes two-level inverter and three-level inverter. Single-stage two-level structure is suitable for low-voltage applications. Due to the limitation of topological structure, the DC side energy storage medium voltage variation range is relatively narrow. This structure is suitable for some energy storage media with small change in terminal voltage with state of charge. Compared with two-level structure, three-level structure has more output levels, and the output waveform power quality and system efficiency are greatly improved. To broaden the DC side energy storage medium voltage variation range, a DC / DC conversion link is added before the three-level structure, forming a two-stage three-level structure PCS. SUMMARY

[0004] The utility model aims at solving the deficiency of prior art, and provides the following scheme:

[0005] An energy storage PCS device based on two-stage three-level inverter topological structure, comprising: an energy storage battery, a dual active bridge converter, a three-level inverter, an SVPWM signal generator, an AC contactor and an AC filter; the energy storage battery, the dual active bridge converter, the three-level inverter, the SVPWM signal generator, the AC contactor and the AC filter are connected.

[0006] Preferably, the energy storage battery is connected to the input end of the dual active bridge converter;

[0007] The DC high-voltage output end of the dual active bridge converter is connected to the three-level inverter;

[0008] The input end of the AC contactor is connected to the AC output end of the three-level inverter;

[0009] The input end of the AC filter is connected to the output end of the AC contactor;

[0010] The SVPWM signal generator is connected with the three-level inverter.

[0011] Preferably, the dual active bridge converter comprises 2 full-bridge circuits and 1 high-frequency isolation transformer; the full-bridge circuit on the high-voltage side and the full-bridge circuit on the low-voltage side are connected through the high-frequency isolation transformer.

[0012] Preferably, the full-bridge circuit on the high-voltage side and the full-bridge circuit on the low-voltage side adopt a symmetrical design.

[0013] Preferably, the three-level inverter is composed of a first capacitor, a second capacitor and a plurality of clamping diodes.

[0014] The three-level inverter adopts the structure of a diode clamping type inverter, and the first capacitor and the second capacitor are added on the DC side of each phase bridge arm, and 1 clamping diode is added on the AC side, thereby forming 3 levels.

[0015] Compared with the prior art, the utility model has the beneficial effects that:

[0016] (1) The utility model enhances the dynamic response capability of the system, the SVPWM control of the three-level inverter optimizes the output waveform, reduces the harmonic content, improves the bus voltage utilization rate, shortens the adjustment time of the system when responding to external load fluctuation, can quickly respond to the change of grid frequency and voltage at the same time, effectively meets the dynamic adjustment demand of new energy grid connection, and enhances the support capability to grid frequency and voltage;

[0017] (2) The utility model improves the output power quality and electromagnetic compatibility, the three-level inverter is designed through diode clamping topology, the harmonic content of output current is reduced significantly, the power quality is improved, electromagnetic interference is effectively inhibited simultaneously, the stability of equipment in electromagnetic compatibility (EMC) is guaranteed, and the normal operation of surrounding equipment is avoided;

[0018] (3) The utility model improves the safety and reliability of equipment, has overvoltage, overcurrent, short circuit and other protection functions, through the real-time monitoring and automatic protection mechanism of the control module, the safety of the device under various loads and external conditions is guaranteed, and the service life of equipment is prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical scheme of the utility model, the following briefly introduces the drawing needed to be used in the embodiment, and obviously, the drawing in the following description is only some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained according to these drawings without paying the creative labor.

[0020] Figure 1 The circuit connection schematic diagram of the utility model;

[0021] Figure 2 The internal circuit topology diagram of the dual active bridge converter of the utility model;

[0022] Figure 3 The internal circuit topology diagram of the three-level inverter of the utility model. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the utility model will be described clearly and completely below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0024] In order to make the above-mentioned purposes, features and advantages of the utility model more apparent, obvious and easy to understand, the utility model will be further described in detail below with reference to the drawings and specific embodiments.

[0025] In the embodiment, as shown in the figure, Figure 1 A kind of energy storage PCS device based on double-stage three-level inverter topology structure, including: energy storage battery, dual active bridge converter, three-level inverter, SVPWM signal generator, AC contactor and AC filter.

[0026] Energy storage battery, dual active bridge converter, three-level inverter, SVPWM signal generator, AC contactor and AC filter are connected. Specifically, energy storage battery is connected with the input end of dual active bridge converter;The DC high voltage output end of dual active bridge converter is connected with three-level inverter;The input end of AC contactor is connected with the AC output end of three-level inverter;The input end of AC filter is connected with the output end of AC contactor;SVPWM signal generator is connected with three-level inverter.

[0027] In the embodiment, the energy storage battery is directly connected to the input end of the dual active bridge converter, responsible for providing a direct current power supply; the input end of the three-level inverter is connected to the high-voltage direct current output end of the dual active bridge converter, and is connected to the output end of the alternating current side through the LCL filter and the EMI filter inside the three-level inverter; the SVPWM signal generator directly controls the switching state of the three-level inverter to realize space vector pulse width modulation (SVPWM) control; the input end of the alternating current contactor is connected to the alternating current output end of the three-level inverter; and the input end of the alternating current filter is connected to the output end of the alternating current contactor. Among them, the alternating current contactor is used to support the seamless switching of the energy storage device between the grid-connected mode and the off-grid mode, enhancing the flexibility and reliability of the system. The alternating current filter filters out the high-frequency harmonics of the inverter output, improves the voltage and current waveform quality, improves the power quality and suppresses electromagnetic interference, and ensures the stable operation of the system. The technical parameters of the energy storage PCS device are shown in Table 1.

[0028] Table 1

[0029]

[0030] The dual active bridge converter includes 2 full-bridge circuits and 1 high-frequency isolation transformer; the high-voltage side full-bridge circuit and the low-voltage side full-bridge circuit are connected through the high-frequency isolation transformer. The high-voltage side full-bridge circuit and the low-voltage side full-bridge circuit are symmetrically designed.

[0031] In the embodiment, as shown in Figure 2 , it is the internal circuit topology diagram of the dual active bridge converter. The dual active bridge converter (DAB) is formed by 2 full-bridge circuits and 1 high-frequency isolation transformer. The high-voltage side full-bridge circuit and the low-voltage side full-bridge circuit are symmetrically structured, and the high-frequency isolation transformer connects the high-voltage side and the low-voltage side to realize electrical isolation. In the embodiment, the high-frequency isolation transformer is a three-phase isolation type power frequency transformer, which has electrical isolation characteristics and is safer. The dual active bridge converter realizes bidirectional transmission of energy through fewer passive devices. The two full-bridge circuits generate two alternating square wave voltages on both sides of the transformer. By adjusting the phase difference of the alternating square wave voltages on both sides of the transformer, the output voltage and output power can be controlled.

[0032] The three-level inverter is composed of a first capacitor, a second capacitor and a plurality of clamping diodes; the three-level inverter adopts the structure of a diode clamping type inverter, and a first capacitor and a second capacitor are added on the direct current side of each phase bridge arm, and a clamping diode is added on the alternating current side, thereby forming three levels.

[0033] In the embodiment, as shown in Figure 3As shown, it is a three-level inverter topology diagram, the three-level inverter adopts the structure of diode clamped inverter, and the diode clamped inverter is also called neutral point clamped inverter; based on the two-level diode clamped inverter, the first capacitor and the second capacitor are added on the DC side, the number of switching tubes of each phase bridge arm is changed from two of two-level to four, and clamping diodes are added on each phase bridge arm, so that a level is added on the basis of the positive and negative two levels to become three levels, the sine degree of the output voltage waveform is improved, and the waveform quality is improved to a certain extent. The clamping diode provides a current path when the switching tube is turned on to prevent the capacitor from short-circuiting.

[0034] The SVPWM signal generator controls three-phase output voltage, optimizes waveform quality, reduces harmonic content, improves bus voltage utilization, and further enhances system conversion efficiency.

[0035] The above-described embodiments are only descriptions of the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. An energy storage PCS device based on a two-stage three-level inverter topology, characterized in that, The utility model relates to a kind of energy storage battery, double active bridge converter, three-level inverter, SVPWM signal generator, AC contactor and AC filter;The energy storage battery, double active bridge converter, three-level inverter, SVPWM signal generator, AC contactor and AC filter are connected; The energy storage battery is connected with the input end of the double active bridge converter; The DC high-voltage output end of the double active bridge converter is connected with the three-level inverter; The input end of the AC contactor is connected with the AC output end of the three-level inverter; The input end of the AC filter is connected with the output end of the AC contactor; The SVPWM signal generator is connected with the three-level inverter; The double active bridge converter includes 2 full-bridge circuits and 1 high-frequency isolation transformer;The high-voltage side full-bridge circuit and the low-voltage side full-bridge circuit are connected through the high-frequency isolation transformer; The high-voltage side full-bridge circuit and the low-voltage side full-bridge circuit are symmetrically designed; The three-level inverter is composed of a first capacitor, a second capacitor and a plurality of clamping diodes; The three-level inverter adopts the structure of diode clamped inverter, and the first capacitor and the second capacitor are added on the DC side of each phase bridge arm, and one clamping diode is added on the AC side, thereby forming three levels. ​

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