Electric energy router and three-level flexible conversion method thereof

Abstract

The invention discloses an electric energy router and a three-level flexible conversion method thereof, and belongs to the technical field of electric energy conversion of electric energy routers, the electric energy router comprises a direct current bus and a plurality of parallel three-level ANPC converters, the direct current side of each three-level ANPC converter is connected with the direct current bus, and the direct current side of each three-level ANPC converter is connected with the direct current bus. The other side is connected to a flexible switch and then is used as an electric energy router port; by switching the flexible switch, the port of the electric energy router is controlled to be respectively connected with various source loads; when the flexible switches are switched to connect the ports of the electric energy router to an alternating current source, an alternating current load, a direct current source and a direct current load, any three, three, one and one three-level ANPC converters are called to operate respectively and controlled by adopting rectification, inversion, Boost and Buck control strategies respectively, so that conversion of various electric energy is realized. According to the invention, all ports of the electric energy router can be unified, multiple working modes can be realized at the same time, and the universality and reliability are high.

Description

Technical Field

[0001] The present invention belongs to the technical field of power conversion of power routers, and in particular relates to a power router and a three-level flexible conversion method thereof. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Building a new energy system is the only way to achieve carbon emission reduction, and its core is the large-scale development and utilization of new energy. New energy, mainly composed of solar energy, wind energy, and energy storage, is gradually becoming the main driving force of current energy. As its power generation continues to rise, improving the utilization rate of new energy and ensuring the stable operation of new power systems have become the main goals at present. With power conversion devices as the core, power routers integrate communication technology, power electronics conversion technology, intelligent control and management technology to achieve intelligent management of local power grid energy and efficient utilization and control of distributed energy. It has become the core equipment in new power systems.

[0004] Existing research on power routers mainly focuses on their own architecture, energy management and power control strategies. However, since power routers integrate multiple source-side input ports and load-side output ports, different ports require multiple types of converters to realize their functions. On the one hand, since the type of converter for each port is difficult to unify, this poses a severe challenge to the plug-and-play function of power routers; on the other hand, when a port fails, the lack of fault tolerance often causes the power router to lose some functions; in addition, multiple types of converters need to be developed separately, and the topology of power routers is difficult to unify. The cost remains high, which greatly limits the large-scale production and application of power routers. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention proposes an electric energy router and a three-level flexible conversion method thereof. The electric energy router is constructed based on multiple three-level ANPC (Active Neutral Point Clamped) converters, and the DC side of each three-level ANPC converter is connected to the DC bus of the electric energy router, and the other side is connected to a variety of sources and loads through a flexible switch. A variety of electric energy conversions are achieved by switching the flexible switches and control strategies. At the same time, the remaining three-level ANPC converters are used as redundant modules to make the electric energy router fault-tolerant, greatly increasing its versatility and reliability.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0007] In a first aspect, the present invention provides a power router.

[0008] A power router comprises a DC bus and a plurality of parallel three-level ANPC converters, wherein the DC side of each three-level ANPC converter is connected to the DC bus, and the other side is connected to a flexible switch to serve as a port of the power router; by switching the flexible switch, the ports of the power router are controlled to be connected to a plurality of sources and loads respectively; the plurality of sources and loads comprise an AC source, an AC load, a DC source and a DC load.

[0009] In a second aspect, the present invention provides a three-level flexible conversion method for an electric energy router.

[0010] A three-level flexible conversion method for an electric energy router, performing three-level flexible conversion on the electric energy router proposed in the first aspect, comprising:

[0011] When the power router port is connected to an AC source, any three three-level ANPC converters among a plurality of three-level ANPC converters are called to form a rectifier, the flexible switches of the three-level ANPC converters are switched to connect to the AC source, and the three three-level ANPC converters are operated and controlled simultaneously using a rectifier control strategy. At this time, the power router port operates in a three-phase three-level rectification mode, and the AC source supplies power to the DC bus of the power router.

[0012] A further technical solution is that the rectifier control strategy is:

[0013] The DC bus voltage is controlled by a first PI controller to output an active reference current;

[0014] The active reference current is used as the input of the current loop. The three-phase current of the current loop is phase-locked by a phase-locked loop and tracked by a second PI controller to output a three-phase initial modulation wave.

[0015] The midpoint voltage is controlled by the third PI controller, and the output is injected into the three-phase initial modulation wave to generate the final modulation wave;

[0016] The final modulation wave is compared with the upper and lower carrier waves to output a PWM signal, completing the three-level rectification modulation.

[0017] Further technical solutions include:

[0018] When the power router port is connected to an AC load, any three three-level ANPC converters among a plurality of three-level ANPC converters are called to form an inverter, the flexible switches of the three-level ANPC converters are switched to connect to the AC load, and the three three-level ANPC converters are operated and controlled simultaneously using the inverter control strategy. At this time, the power router port operates in a three-phase three-level inverter mode, and the DC bus of the power router supplies power to the AC load.

[0019] A further technical solution is that the inverter control strategy is:

[0020] The three-phase current is tracked by the first PI controller, and the three-phase initial modulation wave is output;

[0021] The midpoint voltage is controlled by the second PI controller, and the output is injected into the three-phase initial modulation wave to generate the final modulation wave;

[0022] The final modulation wave is compared with the upper and lower carrier waves to output a PWM signal, completing the three-level inverter modulation.

[0023] Further technical solutions include:

[0024] When the power router port is connected to a DC source, any one of the multiple three-level ANPC converters is called to form a Boost converter, and the flexible switch of the three-level ANPC converter is switched to connect to the DC source. The three-level ANPC converter is operated and simultaneously controlled by the Boost conversion control strategy. At this time, the power router port operates in the three-level Boost mode, and the DC source supplies power to the DC bus of the power router.

[0025] A further technical solution is that the Boost conversion control strategy is:

[0026] The DC bus voltage is controlled by a first PI controller, and an inductor current reference value is output;

[0027] The inductor current reference value is tracked by the second PI controller and outputs the initial duty cycle;

[0028] The midpoint voltage is controlled by the third PI controller, and the compensation amount is output;

[0029] The compensation amount is injected into the initial duty cycle, and the final first and second duty cycles are obtained by addition and subtraction respectively. The final duty cycle is compared with the carrier to output a PWM signal to complete the three-level Boost conversion, that is, the three-level DC / DC boost conversion; wherein, the first duty cycle is compared with the carrier to control the opening and closing of the fifth switch tube in the three-level ANPC converter, the second duty cycle is compared with the carrier to control the opening and closing of the sixth switch tube in the three-level ANPC converter, the first and fifth switches are complementarily turned on, the fourth and sixth switches are complementarily turned on, the second switch tube is always turned on, and the third switch tube is always turned off.

[0030] Further technical solutions include:

[0031] When the power router port is connected to a DC load, any one of the multiple three-level ANPC converters is called to form a Buck converter, the flexible switch of the three-level ANPC converter is switched to connect to the DC load, and the three-level ANPC converter is operated and controlled by the Buck conversion control strategy at the same time. At this time, the power router port operates in the three-level Buck mode, and the DC bus of the power router supplies power to the DC load.

[0032] A further technical solution is that the Buck conversion control strategy is:

[0033] The DC bus voltage is controlled by a first PI controller, and an inductor current reference value is output;

[0034] The inductor current reference value is tracked by the second PI controller and outputs the initial duty cycle;

[0035] The midpoint voltage is controlled by the third PI controller, and the compensation amount is output;

[0036] The compensation amount is injected into the initial duty cycle, and the final first and second duty cycles are obtained by addition and subtraction respectively. The final duty cycle is compared with the carrier to output a PWM signal to complete the three-level Buck conversion, that is, the three-level DC / DC step-down conversion; wherein, the first duty cycle is compared with the carrier to control the opening and closing of the first switch tube in the three-level ANPC converter, the second duty cycle is compared with the carrier to control the opening and closing of the fourth switch tube in the three-level ANPC converter, the first and fifth switches are complementarily turned on, the fourth and sixth switches are complementarily turned on, the second switch tube is always turned on, and the third switch tube is always turned off.

[0037] A further technical solution is that during the operation of the power router, the non-operating three-level ANPC converter is used as a redundant module; when any operating three-level ANPC converter fails, the faulty converter is used as a faulty module, the flexible switch corresponding to the faulty module is switched to remove the faulty module, and the flexible switch of any redundant module is switched to connect the redundant module.

[0038] One or more of the above technical solutions have the following beneficial effects:

[0039] 1. The present invention proposes an energy router and a three-level flexible conversion method thereof. An energy router is built based on multiple three-level ANPC (Active Neutral Point Clamped) converters. The DC side of each three-level ANPC converter is connected to the DC bus of the energy router, and the other side is connected to a variety of sources and loads through a flexible switch. A variety of energy conversions are achieved by switching the flexible switches and control strategies. The energy router is implemented based on the widely used three-level ANPC converter, does not require complex design, has high feasibility, and is easy to promote and use.

[0040] 2. The power router and its three-level flexible conversion method proposed in the present invention can unify all ports of the power router, laying a hardware foundation for the realization of the plug-and-play function of the power router; and can simultaneously realize multiple working modes on the basis of the unified port, including: three-phase three-level rectification, three-phase three-level inverter, three-level DC / DC buck-boost, realizing the universalization of the power router port topology, increasing the flexibility of the system, and greatly reducing its production and research and development costs. Moreover, each of the above working modes is three-level conversion, with excellent output power quality and small switch tube voltage stress, which can be applied to high-power working scenarios of the power router.

[0041] 3. The present invention uses the non-operating three-level ANPC converter as a redundant module and connects the redundant module to replace the faulty module, so that the redundant module has a certain fault tolerance capability, which greatly improves the versatility and reliability of the operation of the power router. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0043] Figure 1 It is a schematic diagram of the topological structure of a typical six-port single DC bus type power router;

[0044] Figure 2 A schematic diagram of the flexible conversion structure of the power router proposed in an embodiment of the present invention;

[0045] Figure 3 The topological structure and control block diagram of the power router in the rectification mode in an embodiment of the present invention;

[0046] Figure 4 The topological structure and control block diagram of the power router in the inverter mode in an embodiment of the present invention;

[0047] Figure 5 The topological structure and control block diagram of the power router in Boost mode in an embodiment of the present invention;

[0048] Figure 6 The topological structure and control block diagram of the power router in Buck mode in an embodiment of the present invention;

[0049] Figure 7 It is a waveform diagram of the simulation output of the rectification mode in an embodiment of the present invention;

[0050] Figure 8 is a waveform diagram of the inverter mode simulation output in an embodiment of the present invention;

[0051] Fig. 9 This is a waveform diagram of the simulation output of the three-level Boost mode in an embodiment of the present invention;

[0052] Fig.10 : This is a waveform diagram of the simulation output of the three-level Buck mode in an embodiment of the present invention;

[0053] Fig.11 It is a waveform diagram of the fault tolerance simulation output of the inverter mode in an embodiment of the present invention;

[0054] Fig.12 It is a waveform diagram of the fault tolerance simulation output of the three-level Buck mode in the embodiment of the present invention. DETAILED DESCRIPTION

[0055] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0056] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0057] Embodiment 1

[0058] like Figure 1The typical six-port single DC bus type power router shown in the figure, which integrates multiple source-side input ports and load-side output ports, and different ports require corresponding types of converters to realize their functions, including: grid port, which requires an AC / DC bidirectional converter; photovoltaic power generation port, which requires a Boost converter; wind power generation port, which requires a rectifier; energy storage port, which requires a DC / DC bidirectional converter; AC load port, which requires an inverter; DC load port, which requires a Buck converter. It can be seen that different ports of the power router require different types of converters, which greatly increases the difficulty and cost of power router research and development.

[0059] To this end, this embodiment proposes a power router, which includes: Figure 2 The flexible conversion structure shown in the figure specifically includes a DC bus and a plurality of parallel three-level ANPC converters. The three-level ANPC converter is used as a basic module. The DC side of each three-level ANPC converter (i.e., the basic module) is connected to the DC bus, and the other side is connected to a flexible switch as a port of the power router. The flexible switch and control strategy are switched according to the port requirements, so as to control each port of the power router to be connected to a variety of sources and loads, respectively, to achieve a variety of power conversion. Among them, the various sources and loads include AC source, AC load, DC source and DC load. The flexible switch has 1 to 4 switching ports, and each switching port corresponds to AC source, AC load, DC source and DC load in sequence.

[0060] The topological structure of the three-level ANPC converter includes a bridge arm circuit, on which six switch tubes S are arranged in sequence from top to bottom and from right to left. x1 ~S x6 , where the first switch tube S x1 The first end of the first switch tube S is connected to the positive electrode of the DC bus. x1 The second end of the fifth switch tube S x5 The first end of the fifth switch tube S x5 The second end of the sixth switch tube S x6 The first end of the sixth switch tube S x6 The second end of the fourth switch tube S x4 The first end of the fourth switch tube S x4 The second end of the second switch tube S is connected to the negative electrode of the DC bus. x2 The first end of the first switch tube S x1 The second end of the second switch tube S x2 The second end of the third switch tube S x3 The first end of the third switch tube S x3 The second end of the sixth switch tube S x6The second end of the fifth switch tube S x5 The second end of the second switch tube S is connected to the midpoint of the DC bus. x2 The second end is the output end of the bridge arm circuit.

[0061] Furthermore, facing various sources and loads, the power router forms different types of converters by switching flexible switches, thereby realizing various power conversions, including:

[0062] Any three three-level ANPC converters among the multiple three-level ANPC converters form a rectifier, and the rectifier port serves as a three-phase AC port of the power router and is connected to the AC source through a flexible switch;

[0063] Any three three-level ANPC converters among the multiple three-level ANPC converters constitute an inverter, and the inverter port serves as a three-phase AC inverter port of the power router and is connected to the AC load through a flexible switch;

[0064] Any one of the multiple three-level ANPC converters forms a Boost converter, and a port of the Boost converter serves as a low-voltage DC port of the power router and is connected to a DC source through a flexible switch;

[0065] Any one of the multiple three-level ANPC converters forms a Buck converter, and a Buck converter port serves as a high-voltage DC port of an electric energy router and is connected to a DC load through a flexible switch.

[0066] Embodiment 2

[0067] This embodiment proposes a three-level flexible conversion method for a power router, and performs three-level flexible conversion on the power router proposed in the first embodiment. The method includes:

[0068] (1) When the port of the power router is connected to an AC source, an instruction is issued to make the port work in the rectification mode. First, any three three-level ANPC converters among multiple three-level ANPC converters are called to form a rectifier, and the flexible switches of the three-level ANPC converters are switched to "1", that is, connected to the AC source. The three three-level ANPC converters are operated and controlled by the rectifier control strategy at the same time. At this time, the power router port works in the three-phase three-level rectification mode, and the AC source supplies power to the DC bus of the power router.

[0069] The above rectifier control strategy is as follows Figure 3 As shown,

[0070] The DC bus voltage is controlled by the first PI controller, and the output active reference current i d *; Active reference current id * As the input of the current loop, the three-phase current of the current loop is phase-locked by the phase-locked loop and tracked by the second PI controller, outputting the three-phase initial modulation wave m x *; The three-phase initial modulation wave m x * Sort and add to m x *Inject zero sequence component into max *+m min *) / 2 to expand the modulation range, where m max * represents m x *Maximum value, m min * represents m x *, and the midpoint voltage (i.e. the midpoint voltage of the DC bus) is controlled by the third PI controller, and its output is injected into the three-phase initial modulation wave m x *, generate the final modulation wave m x ; The final modulation wave m x The PWM signal is output by comparing with the upper and lower carriers to complete the three-level rectification modulation.

[0071] (2) When the power router port is connected to an AC load, an instruction is issued to make the port work in the inverter mode. First, any three three-level ANPC converters among multiple three-level ANPC converters are called to form an inverter, and the flexible switches of the three-level ANPC converters are switched to "2", that is, connected to the AC load. The three three-level ANPC converters are operated and controlled by the inverter control strategy at the same time. At this time, the power router port works in the three-phase three-level inverter mode, and the DC bus of the power router supplies power to the AC load.

[0072] The inverter control strategy mentioned above is as follows Figure 4 As shown,

[0073] The three-phase current is tracked by the first PI controller, and the three-phase initial modulation wave m is output. x *; To the three-phase initial modulation wave m x *Inject zero sequence component into max *+m min *) / 2 to expand the modulation range. At the same time, the midpoint voltage is controlled by the second PI controller, and its output is injected into the three-phase initial modulation wave m x *, generate the final modulation wave m x ; The final modulation wave m x The PWM signal is output by comparing with the upper and lower carriers to complete the three-level inverter modulation.

[0074] (3) When the port of the power router is connected to a DC source, an instruction is issued to make the port work in Boost mode. First, any one of the multiple three-level ANPC converters is called to form a Boost converter, and the flexible switch of the three-level ANPC converter is switched to "3", that is, connected to the DC source. The three-level ANPC converter is operated and controlled by the Boost conversion control strategy at the same time. At this time, the power router port works in the three-level Boost mode, and the DC source supplies power to the DC bus of the power router.

[0075] The above Boost conversion control strategy is as follows Figure 5 As shown,

[0076] The DC bus voltage is controlled by the first PI controller, and the inductor current reference value is output; the inductor current reference value is tracked by the second PI controller, and the initial duty cycle d is output; the midpoint voltage is controlled by the third PI controller, and the compensation amount Δd is output; the compensation amount Δd is injected into the initial duty cycle d, and the final first and second duty cycles are obtained by addition and subtraction, that is, the first duty cycle d is obtained. 1 =d-Δd and the second duty cycle d 2 =d+Δd; the final duty cycle is compared with the carrier to output a PWM signal, completing the three-level Boost conversion, that is, the three-level DC / DC boost conversion.

[0077] Furthermore, the first duty cycle d 1 The fifth switch S in the three-level ANPC converter is controlled by comparing with the carrier x5 The opening and closing of the second duty cycle d 2 The sixth switch S in the three-level ANPC converter is controlled by comparing with the carrier. x6 The first and fifth switch tubes (i.e. S x1 and S x5 ) are complementary turned on, the fourth and sixth switch tubes (i.e. S x4 and S x6 ) is complementary turned on, the second switch tube S x2 Always on and the third switch tube S x3 Always off.

[0078] (4) When the power router port is connected to a DC load, an instruction is issued to make the port work in Buck mode. First, any one of the multiple three-level ANPC converters is called to form a Buck converter, and the flexible switch of the three-level ANPC converter is switched to "4", that is, connected to the DC load. The three-level ANPC converter is operated and controlled by the Buck conversion control strategy at the same time. At this time, the power router port works in the three-level Buck mode, and the DC bus of the power router supplies power to the DC load.

[0079] The above Buck conversion control strategy is as follows Figure 6 As shown, its control process is the same as that of the Boost mode, including:

[0080] The DC bus voltage is controlled by the first PI controller, and the inductor current reference value is output; the inductor current reference value is tracked by the second PI controller, and the duty cycle d is output; the midpoint voltage is controlled by the third PI controller, and the compensation amount Δd is output; the compensation amount Δd is injected into the initial duty cycle d, and the final first and second duty cycles are obtained by addition and subtraction, that is, the first duty cycle d is obtained. 1 =d-Δd and the second duty cycle d 2 =d+Δd; the final duty cycle is compared with the carrier to output a PWM signal, completing the three-level Buck conversion, that is, the three-level DC / DC step-down conversion.

[0081] Furthermore, the first duty cycle d 1 The first switch S in the three-level ANPC converter is controlled by comparing with the carrier x1 The opening and closing of the second duty cycle d 2 Compared with the carrier, the fourth switch S in the three-level ANPC converter is controlled x4 The first and fifth switch tubes (i.e. S x1 and S x5 ) are complementary turned on, the fourth and sixth switch tubes (i.e. S x4 and S x6 ) is complementary turned on, the second switch tube S x2 Always on and the third switch tube S x3 Always off.

[0082] This embodiment innovatively proposes the modulation strategy in the DC / DC mode, and can implement three-level DC / DC step-down and step-up conversion based on a three-level ANPC converter.

[0083] like Figure 7 to Figure 10 As shown in FIG. 1 , the simulation waveforms of the method proposed in this embodiment under four working modes are shown, wherein: Figure 7 The three-phase current in the rectification mode, the phase voltage of phase A, the line voltage between phase A and phase B, the DC bus voltage and the two DC side capacitor voltages. It can be seen that the output current quality is good, the DC bus voltage is well controlled at the reference value, and the midpoint voltage is controlled to be balanced; Figure 8 The three-phase current in inverter mode, the phase voltage of phase A, the line voltage between phase A and phase B, and the two DC side capacitor voltages. It can be seen that the output current quality is good and the midpoint voltage is well controlled and balanced; Fig. 9The DC bus voltage, inductor current and two high-voltage DC side capacitor voltages in the three-level Boost mode show that the DC bus voltage is well controlled at the reference value and the midpoint voltage is balanced. Fig.10 It is the DC load side voltage, inductor current and two high-voltage DC side capacitor voltages in the three-level Buck mode, and also has a good output waveform.

[0084] As another implementation, during the operation of the power router, a non-operating three-level ANPC converter is used as a redundant module; when any operating three-level ANPC converter fails, the faulty converter is used as a faulty module, the flexible switch corresponding to the faulty module is switched to remove the faulty module, and the flexible switch of any redundant module is switched to connect the redundant module, so as to achieve replacement of the two, that is, in this way, the fault tolerance of the power router is achieved. Preferably, the above-mentioned faulty module can be determined by an existing fault diagnosis strategy.

[0085] like Figure 11-12 As shown, it is the simulation waveform of fault tolerance in the method proposed in this embodiment, where: Fig.11 The simulation waveform of fault tolerance in inverter mode. At 0.3s, the first three-level ANPC converter S a1 (i.e., the first switch tube of ANPC basic module a) has an open circuit fault. At this time, the three-phase current is severely distorted and the midpoint voltage begins to be unbalanced. At 0.35s, the faulty module is removed and a redundant module is connected. At this time, the three-phase current distortion is eliminated and the midpoint voltage is restored to balance; Fig.12 This is the simulation waveform of fault tolerance in the three-level Buck mode. At 0.3s, S a1 An open circuit fault occurs. At this time, the DC side capacitor voltage cannot be controlled at the reference value, and the midpoint voltage begins to be unbalanced. The faulty module is removed at 0.35s and a redundant module is connected. At this time, the port returns to normal operation.

[0086] The three-level flexible conversion method of the power router proposed in this embodiment realizes four modes of operation simultaneously based on the three-level ANPC module and has a certain fault tolerance capability. The effectiveness and reliability of the given topology are further verified by the above simulation results.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A power router, characterized in that: The invention comprises a DC bus and a plurality of parallel three-level ANPC converters, wherein the DC side of each three-level ANPC converter is connected to the DC bus, and the other side is connected to a flexible switch to serve as a power router port; by switching the flexible switch, the power router port is controlled to be connected to a plurality of sources and loads respectively; the plurality of sources and loads include an AC source, an AC load, a DC source and a DC load.

2. A three-level flexible conversion method for an electric energy router, performing three-level flexible conversion on the electric energy router as claimed in claim 1, characterized in that: include: When the power router port is connected to an AC source, any three three-level ANPC converters among a plurality of three-level ANPC converters are called to form a rectifier, the flexible switches of the three-level ANPC converters are switched to connect to the AC source, and the three three-level ANPC converters are operated and controlled simultaneously using a rectifier control strategy. At this time, the power router port operates in a three-phase three-level rectification mode, and the AC source supplies power to the DC bus of the power router.

3. A three-level flexible conversion method for an electric energy router as claimed in claim 2, characterized in that: The rectifier control strategy is: The DC bus voltage is controlled by a first PI controller, and an active reference current is output; The active reference current is used as the input of the current loop. The three-phase current of the current loop is phase-locked by a phase-locked loop and tracked by a second PI controller to output a three-phase initial modulation wave. The midpoint voltage is controlled by the third PI controller, and the output is injected into the three-phase initial modulation wave to generate the final modulation wave; The final modulation wave is compared with the upper and lower carrier waves to output a PWM signal, completing the three-level rectification modulation.

4. A three-level flexible conversion method for an electric energy router as claimed in claim 2, characterized in that: Also includes: When the power router port is connected to an AC load, any three three-level ANPC converters among a plurality of three-level ANPC converters are called to form an inverter, the flexible switches of the three-level ANPC converters are switched to connect to the AC load, and the three three-level ANPC converters are operated and controlled simultaneously using the inverter control strategy. At this time, the power router port operates in a three-phase three-level inverter mode, and the DC bus of the power router supplies power to the AC load.

5. A three-level flexible conversion method for an electric energy router as claimed in claim 4, characterized in that: The inverter control strategy is: The three-phase current is tracked by the first PI controller, and the three-phase initial modulation wave is output; The midpoint voltage is controlled by the second PI controller, and the output is injected into the three-phase initial modulation wave to generate the final modulation wave; The final modulation wave is compared with the upper and lower carrier waves to output a PWM signal, completing the three-level inverter modulation.

6. A three-level flexible conversion method for an electric energy router as claimed in claim 2, characterized in that: Also includes: When the power router port is connected to a DC source, any one of the multiple three-level ANPC converters is called to form a Boost converter, and the flexible switch of the three-level ANPC converter is switched to connect to the DC source. The three-level ANPC converter is operated and simultaneously controlled by the Boost conversion control strategy. At this time, the power router port operates in the three-level Boost mode, and the DC source supplies power to the DC bus of the power router.

7. A three-level flexible conversion method for an electric energy router as claimed in claim 6, characterized in that: The Boost conversion control strategy is: The DC bus voltage is controlled by a first PI controller, and an inductor current reference value is output; The inductor current reference value is tracked by the second PI controller and outputs the initial duty cycle; The midpoint voltage is controlled by the third PI controller, and the compensation amount is output; The compensation amount is injected into the initial duty cycle, and the final first and second duty cycles are obtained by addition and subtraction respectively. The final duty cycle is compared with the carrier to output a PWM signal to complete the three-level Boost conversion, that is, the three-level DC / DC boost conversion; wherein, the first duty cycle is compared with the carrier to control the opening and closing of the fifth switch tube in the three-level ANPC converter, the second duty cycle is compared with the carrier to control the opening and closing of the sixth switch tube in the three-level ANPC converter, the first and fifth switches are complementarily turned on, the fourth and sixth switches are complementarily turned on, the second switch tube is always turned on, and the third switch tube is always turned off.

8. A three-level flexible conversion method for an electric energy router as claimed in claim 2, characterized in that: Also includes: When the power router port is connected to a DC load, any one of the multiple three-level ANPC converters is called to form a Buck converter, the flexible switch of the three-level ANPC converter is switched to connect to the DC load, and the three-level ANPC converter is operated and controlled by the Buck conversion control strategy at the same time. At this time, the power router port operates in the three-level Buck mode, and the DC bus of the power router supplies power to the DC load.

9. A three-level flexible conversion method for an electric energy router as claimed in claim 8, characterized in that: The Buck conversion control strategy is: The DC bus voltage is controlled by a first PI controller, and an inductor current reference value is output; The inductor current reference value is tracked by the second PI controller and outputs the initial duty cycle; The midpoint voltage is controlled by the third PI controller, and the compensation amount is output; The compensation amount is injected into the initial duty cycle, and the final first and second duty cycles are obtained by addition and subtraction respectively. The final duty cycle is compared with the carrier to output a PWM signal to complete the three-level Buck conversion, that is, the three-level DC / DC step-down conversion; wherein, the first duty cycle is compared with the carrier to control the opening and closing of the first switch tube in the three-level ANPC converter, the second duty cycle is compared with the carrier to control the opening and closing of the fourth switch tube in the three-level ANPC converter, the first and fifth switches are complementarily turned on, the fourth and sixth switches are complementarily turned on, the second switch tube is always turned on, and the third switch tube is always turned off.

10. A three-level flexible conversion method for an electric energy router as claimed in claim 5, characterized in that: During the operation of the power router, the non-operating three-level ANPC converter is used as a redundant module; when any operating three-level ANPC converter fails, the faulty converter is used as a faulty module, the flexible switch corresponding to the faulty module is switched to remove the faulty module, and the flexible switch of any redundant module is switched to connect the redundant module.

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