Water-light power supply system based on power electronic transformer

Abstract

The invention discloses a water-light power supply system based on power electronic transformers, which comprises a water-light power generation system, a single-phase power electronic transformer A, a single-phase power electronic transformer B, a single-phase power electronic transformer C, an AC-DC converter and a DC-DC converter, each of the single-phase power electronic transformer A, the single-phase power electronic transformer B and the single-phase power electronic transformer C is a three-phase power electronic transformer with an input cascade structure formed by cascading n converter modules, the input side of each three-phase power electronic transformer is connected with a three-phase power grid in a grid-connected manner, and an output direct-current bus is converged with a direct-current bus of a water-light power generation system; the water-light power generation system is provided with output water-light power generation system ports W01-n and W1-n # charging ports; and switches W1-n # S are connected between the output ports W01-n and W1-n # charging ports of the water-light power generation system. The cost of the power supply system can be reduced, the electric energy conversion efficiency is improved through centralized power supply, and the electric energy quality problem caused by load imbalance is solved.

Description

Technical Field

[0001] The invention relates to the technical field of power supply systems for hydropower stations, and in particular to a hydro-photovoltaic power supply system based on a power electronic transformer. Background Art

[0002] At present, most large-scale power supply systems use power frequency transformers to step down the voltage output by the three-phase power grid and then output electrical energy. However, power frequency transformers have problems such as bulky structure, large energy consumption and high cost.

[0003] In order to solve the above problems, the present invention applies power electronic transformers to large power supply systems, and proposes a hydro-photovoltaic power supply system based on power electronic transformers and its energy control strategy that can maximize energy utilization according to the energy demand of the system in combination with the hydro-photovoltaic power generation system. The system can reduce the system volume and reduce the construction cost. The centralized power supply method can improve the efficiency of power conversion. The controllable voltage and current on the grid side can achieve the control of grid harmonics, improve power quality, and energy feedback, meeting the requirements of green environmental protection, energy saving and consumption reduction. Summary of the invention

[0004] The present invention provides a hydro-photovoltaic power supply system based on a power electronic transformer, which can flexibly dispatch the electric energy of the hydro-photovoltaic power generation system and the power grid according to the electric energy demand and effectively solve the power supply problem within the full load range of the power supply system based on the power electronic transformer, realize centralized multi-port fast charging and maximize the energy utilization rate and electric energy conversion efficiency.

[0005] The present invention solves the technical problem, and the technical solution adopted is: a hydro-photovoltaic power supply system based on a power electronic transformer, comprising a hydro-photovoltaic power generation system, a single-phase power electronic transformer A, a single-phase power electronic transformer B and a single-phase power electronic transformer C, an AC-DC converter, and a DC-DC converter. The single-phase power electronic transformer A, the single-phase power electronic transformer B and the single-phase power electronic transformer C are all three-phase power electronic transformers with an input cascade structure formed by cascading n converter modules, the input side of which is connected to the three-phase power grid, and the output DC bus is connected to the DC bus of the hydro-photovoltaic power generation system; the hydro-photovoltaic power generation system is provided with an output hydro-photovoltaic power generation system port WO1~n and a W1~n# charging port; a switch W1~n#S is connected between the output port WO1~n of the hydro-photovoltaic power generation system and the W1~n# charging port.

[0006] In particular, the water-solar power supply system is divided into power supply mode 1, power supply mode 2, and power supply mode 3 according to energy demand.

[0007] Specifically, the power supply mode 1 is as follows: when the water-light power generation system provides electrical energy to meet the charging energy demand of the electric vehicle, centralized power supply is provided by the water-light power generation system; the switches W1~n#S connected between the output ports WO1~n of the water-light power generation system and the W1~n# charging ports are all closed, the single-phase power electronic transformers A, B, and C do not transmit power, the switching signals of the isolated DC-DC converters in the single-phase power electronic transformers A, B, and C are all blocked, and the single-phase power electronic transformers A, B, and C are in the full no-load mode.

[0008] Specifically, the power supply mode 2 is as follows: when the water-light power generation system provides electrical energy that does not meet the charging energy demand of the electric vehicle and the additional power grid energy demand is small, centralized power supply is provided by the water-light power generation system and some modules of the power electronic transformer; the switches W1~n#S connected between the output ports WO1~n of the water-light power generation system and the W1~n# charging ports are all closed, the single-phase power electronic transformers A, B, and C transmit a small amount of power, the switching signals of some isolated DC-DC converters in the single-phase power electronic transformers A, B, and C are blocked, and the single-phase power electronic transformers A, B, and C are in the partial no-load mode.

[0009] Specifically, the power supply mode 3 is as follows: when the water-light power generation system provides electrical energy that does not meet the charging energy demand of the electric vehicle and the additional power grid energy demand is large, centralized power supply is provided by the water-light power generation system and all modules of the power electronic transformer; the switches W1~n#S connected between the output ports WO1~n of the water-light power generation system and the W1~n# charging ports are all closed, the single-phase power electronic transformers A, B, and C transmit a large amount of power, the isolated DC-DC converters in the single-phase power electronic transformers A, B, and C operate normally, and the single-phase power electronic transformers A, B, and C are in the full load mode.

[0010] Specifically, the connection method of the three-phase power grid in parallel is as follows: the three-phase power electronic transformer is composed of the single-phase power electronic transformers A, B, and C connected in a star connection.

[0011] Specifically, the A-phase output of the three-phase power grid is connected to the positive input terminal AM11 of single-phase power electronic transformer A, the B-phase output is connected to the positive input terminal BM11 of single-phase power electronic transformer B, and the C-phase output is connected to the positive input terminal CM11 of single-phase power electronic transformer C. The negative input AMn2 of single-phase power electronic transformer A, the negative input terminal BMn2 of single-phase power electronic transformer B, and the negative input terminal CMn2 of single-phase power electronic transformer C are connected.

[0012] Specifically, the cascade connection method and characteristics of the converters are as follows: The left-end input wiring method of single-phase power electronic transformer A is that the positive input AM11 of single-module converter A1 is taken out, the negative input AM12 is connected to the positive input AM21 of A2, the negative input AM22 of A2 is connected to the positive input AM21 of A3, and so on. The negative input AM(n - 1)2 of An - 1 is connected to the positive input AMn1 of An, and the negative input AMn2 is taken out; similarly, n modules in single-phase power electronic transformer B and single-phase power electronic transformer C are connected in the same way as above.

[0013] Specifically, the specific quantity of the number n of the modules is related to the specific switching tubes and the adopted topological structure.

[0014] Specifically, the setting method of the specific quantity of the number n of the modules is as follows: When the withstand voltage level of the switching tubes is higher, the value of n is correspondingly smaller; when a multi-level topological structure is adopted, n is also correspondingly smaller, and vice versa, the number of modules is larger.

[0015] The object of the present invention is achieved through the following technical solutions: On the basis of three-phase power grid power supply, it is improved, passed through a three-phase power electronic converter device, and combined with a water-light power generation system to flexibly realize the conversion of electrical energy between alternating current and direct current. When the water-light power generation system provides electrical energy to meet the energy demand for electric vehicle charging, it is centrally powered by the water-light power generation system; when the electrical energy provided by the water-light power generation system does not meet the energy demand for electric vehicle charging and the additional power grid energy demand is small, it is powered by the water-light power generation system and some modules of the three-phase power electronic transformer at the same time. When the electrical energy provided by the water-light power generation system does not meet the energy demand for electric vehicle charging and the additional power grid energy demand is large, it is powered by the water-light power generation system and all modules of the three-phase power electronic transformer at the same time. This power supply system can maximize the energy utilization rate and the electrical energy conversion efficiency within the full load range, flexibly dispatch the electrical energy of the water-light power generation system and the power grid, and has the advantages of treating problems such as grid-side current harmonics, improving the power quality of the power grid, and reducing the construction cost. In summary, this power supply system is beneficial to the development of China's power supply system, the environment, and the conservation of electrical energy.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. The present invention replaces the power frequency transformer in a three-phase power grid power supply system with a multi-port power electronic transformer, which helps to reduce the volume of the power supply system and lower the system cost.

[0018] 2. The use of the present invention can control the problems of grid current harmonics, thereby improving the power quality of the grid and meeting the requirements of green environmental protection.

[0019] 3. The present invention can automatically select different power supply modes according to the power demand, flexibly dispatch the water-light power generation system and the grid energy, and maximize the power conversion efficiency within the full load range in centralized power supply.

[0020] 4. The energy of the present invention flows bidirectionally. The connection between the DC bus of the three-phase power electronic transformer and the DC bus of the water-light power generation system realizes the energy feedback to the grid, meeting the requirements of energy conservation and increased income. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments.

[0022] Figure 1 It is the structure diagram of a single-module converter inside the single-phase power electronic transformer A of the present invention;

[0023] Figure 2 It is the structure diagram of the water-light power supply system based on the power electronic transformer of the present invention;

[0024] Figure 3 It is the circuit connection diagram of the specific implementation manner of power supply mode 1 of the water-light power supply system based on the power electronic transformer of the present invention.

[0025] Figure 4 It is the circuit connection diagram of the specific implementation manner of power supply mode 2 of the water-light power supply system based on the power electronic transformer of the present invention.

[0026] Figure 5 It is the circuit connection diagram of the specific implementation manner of power supply mode 3 of the water-light power supply system based on the power electronic transformer of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0029] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Figure 1 Shown is the internal single-module structure diagram of the single-phase power electronic transformer A of the present invention. The internal structures of the single-phase power electronic transformers B and C are the same as that of the single-phase power electronic transformer A. The input side adopts cascaded multi-module power electronic transformers, and the output DC sides are connected in parallel to form a multi-port power electronic transformer structure. Figure 2 Shown is the structure diagram of the water-light power supply system based on the power electronic transformer of the present invention. Figure 3 、 Figure 4 、 Figure 5 Shown are the circuit connection diagrams of the specific embodiments of power supply mode 1, power supply mode 2, and power supply mode 3 of the water-light power supply system based on the power electronic transformer of the present invention: A water-light power supply system and its energy regulation strategy, including a water-light power generation system, a single-phase power electronic transformer A, a single-phase power electronic transformer B, a single-phase power electronic transformer C, and an AC-DC converter and a DC-DC converter. It is applicable to a three-phase power grid power supply system. Each phase (A, B, C) of the three-phase power grid is connected out through cascaded n (n>1) converters (A1~An, B1~Bn, C1~Cn) to form a power supply device with an input cascaded structure. The power supply mode is divided into power supply mode 1, power supply mode 2, and power supply mode 3 according to the energy demand. Among them:

[0031] a. Power supply mode 1: When the water-light power generation system provides electrical energy to meet the charging energy demand of the electric vehicle, centralized power supply is provided by the water-light power generation system. The switches W1~n#S connected between the output ports WO1~n of the water-light power generation system and the W1~n# charging ports are all closed. The single-phase power electronic transformers A, B, and C do not transmit power, the switching signals of the isolated DC-DC converters in the single-phase power electronic transformers A, B, and C are all blocked, and the single-phase power electronic transformers A, B, and C are in the full no-load mode. Power supply mode 2: When the electrical energy provided by the water-light power generation system does not meet the charging energy demand of the electric vehicle and the additional grid energy demand is small, the switches W1~n#S connected between the output ports WO1~n of the water-light power generation system and the W1~n# charging ports are all closed. The single-phase power electronic transformers A, B, and C transmit a small amount of power, the switching signals of some of the isolated DC-DC converters in the single-phase power electronic transformers A, B, and C are blocked, and the single-phase power electronic transformers A, B, and C are in the partial no-load mode. Power supply mode 3: When the electrical energy provided by the water-light power generation system does not meet the charging energy demand of the electric vehicle and the additional grid energy demand is large, the switches W1~n#S connected between the output ports WO1~n of the water-light power generation system and the W1~n# charging ports are all closed. The single-phase power electronic transformers A, B, and C transmit a large amount of power, the isolated DC-DC converters in the single-phase power electronic transformers A, B, and C operate normally, and the single-phase power electronic transformers A, B, and C are in the full load mode.

[0032] b. In the present invention, the three-phase power electronic transformer is composed of single-phase power electronic transformers A, B, and C connected in a star connection. The A-phase output of the three-phase power grid is connected to the positive input terminal point AM11 of the single-phase power electronic transformer A, the B-phase output is connected to the positive input terminal point BM11 of the single-phase power electronic transformer B, the C-phase output is connected to the positive input terminal point CM11 of the single-phase power electronic transformer C, and the negative input terminal points AMn2, BMn2, and CMn2 of the single-phase power electronic transformers A, B, and C are connected. The left-end input wiring method of the single-phase power electronic transformer A is that the positive input AM11 of the single-module converter A1 is taken out, the negative input AM12 is connected to the positive input AM21 of A2, the negative input AM22 of A2 is connected to the positive input AM21 of A3, and so on. The negative input AM(n - 1)2 of An - 1 is connected to the positive input AMn1 of An, and the negative input AMn2 of An is taken out; similarly, the n modules in the single-phase power electronic transformers B and C are also connected in the same way. The specific number of modules is determined according to the withstand voltage level of the specific switching tubes used, the topological structure, and the power supply requirements of the electric vehicle.

[0033] A water-light power supply system and its energy regulation strategy proposed by the present invention. In the three-phase power electronic transformer, A, B, and C are cascaded by n converter modules. The converter module is mainly composed of a rectifier circuit and a bidirectional DC-DC conversion circuit. From the perspective of modulation levels, the circuit can be a two-level, three-level or multi-level structure. From the perspective of bridge structures, the circuit can be a full-bridge or half-bridge structure. In addition, the bidirectional DC-DC conversion circuit can also have a resonant network or no resonant network. The structure can withstand high voltages and can be directly connected to the three-phase power grid. The subsequent DC-DC converter can customize charging modules with different voltage levels according to user needs and access the water-light power generation system to realize the integration of water-light power generation and grid power supply. On the basis of the existing power supply system, the present invention replaces the power frequency transformer with a multi-port power electronic transformer. The power supply system is divided into three power supply modes according to energy requirements to achieve centralized power supply within the full load range of the power supply system and ensure the maximization of power conversion efficiency.

[0034] On the basis of three-phase power grid power supply, it is improved. Through a three-phase power electronic converter device and combined with a water-light power generation system, the flexible conversion of AC and DC electrical energy can be realized. When the electrical energy provided by the water-light power generation system meets the energy demand for electric vehicle charging, the water-light power generation system provides centralized power supply. When the electrical energy provided by the water-light power generation system does not meet the energy demand for electric vehicle charging and the additional power grid energy demand is small, the water-light power generation system and some modules of the three-phase power electronic transformer supply power simultaneously. When the electrical energy provided by the water-light power generation system does not meet the energy demand for electric vehicle charging and the additional power grid energy demand is large, the water-light power generation system and all modules of the three-phase power electronic transformer supply power simultaneously. This power supply system can achieve the maximization of energy utilization rate and power conversion efficiency within the full load range, flexibly dispatch the electrical energy of the water-light power generation system and the power grid, and has the advantages of solving problems such as grid-side current harmonics, improving the power quality of the power grid, and reducing construction costs. In summary, this power supply system is beneficial to the development of China's power supply system, the environment, and the conservation of electrical energy.

[0035] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A water-light power supply system based on a power electronic transformer, characterized in that, It includes a hydro - photovoltaic power generation system, a single - phase power electronic transformer A, a single - phase power electronic transformer B, a single - phase power electronic transformer C, an AC - DC converter, and a DC - DC converter. The single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C are all three - phase power electronic transformers with an input - cascaded structure formed by cascading n converter modules. Their input sides are connected to the three - phase power grid in parallel, and the output DC buses are collected with the DC bus of the hydro - photovoltaic power generation system. The hydro - photovoltaic power generation system is provided with output ports WO1~n and W1~n# charging ports; a switch W1~n#S is connected between the output ports WO1~n and W1~n# charging ports of the hydro - photovoltaic power generation system.

2. The water-light power supply system based on a power electronic transformer according to claim 1, characterized in that: The hydro - power supply system is divided into power supply mode 1, power supply mode 2, and power supply mode 3 according to energy requirements.

3. The water-light power supply system based on a power electronic transformer according to claim 2, wherein: Power supply mode 1 is: when the hydro - photovoltaic power generation system provides electrical energy to meet the energy demand for electric vehicle charging, centralized power supply is provided by the hydro - photovoltaic power generation system; the switches W1~n#S connected between the output ports WO1~n and W1~n# charging ports of the hydro - photovoltaic power generation system are all closed. The single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C do not transmit power. The switching signals of the isolated DC - DC converters in the single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C are all blocked, and the single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C are in a full no - load mode.

4. The water-light power supply system based on a power electronic transformer according to claim 2, wherein: Power supply mode 2 is: when the hydro - photovoltaic power generation system provides electrical energy that does not meet the energy demand for electric vehicle charging and the additional power grid energy demand is small, centralized power supply is provided by the hydro - photovoltaic power generation system and some modules of the power electronic transformer; the switches W1~n#S connected between the output ports WO1~n and W1~n# charging ports of the hydro - photovoltaic power generation system are all closed. The single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C transmit a small amount of power. The switching signals of some isolated DC - DC converters in the single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C are blocked, and the single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C are in a partial no - load mode.

5. The water-light power supply system based on a power electronic transformer according to claim 2, wherein: Power supply mode 3 is: when the hydro - photovoltaic power generation system provides electrical energy that does not meet the energy demand for electric vehicle charging and the additional power grid energy demand is large, centralized power supply is provided by the hydro - photovoltaic power generation system and all modules of the power electronic transformer; the switches W1~n#S connected between the output ports WO1~n and W1~n# charging ports of the hydro - photovoltaic power generation system are all closed. The single - phase power electronic transformers A, B, and C transmit a large amount of power. The isolated DC - DC converters in the single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C operate normally, and the single - phase power electronic transformer A, the single - phase power electronic transformer B, and the single - phase power electronic transformer C are in a full - load mode.

6. The water-light power supply system based on a power electronic transformer according to claim 1, wherein: The connection method of the three-phase power grid for grid connection is as follows: The three-phase power electronic transformer is composed of single-phase power electronic transformers A, B, and C connected in a star connection.

7. The water-light power supply system based on a power electronic transformer according to claim 1, wherein: The specific connection method of the three-phase power grid for grid connection is as follows: The A-phase output of the three-phase power grid is connected to the positive input terminal AM11 of the single-phase power electronic transformer A, the B-phase output is connected to the positive input terminal BM11 of the single-phase power electronic transformer B, and the C-phase output is connected to the positive input terminal CM11 of the single-phase power electronic transformer C. The negative input terminals AMn2 of the single-phase power electronic transformer A, BMn2 of the single-phase power electronic transformer B, and CMn2 of the single-phase power electronic transformer C are connected together.

8. A water-light power supply system based on a power electronic transformer according to claim 1, characterized in that: The cascade connection method and characteristics of the converters are as follows: For the single-phase power electronic transformer A, the left-end input wiring method is that the positive input AM11 of the single-module converter A1 is taken out, the negative input AM12 is connected to the positive input AM21 of A2, the negative input AM22 of A2 is connected to the positive input AM21 of A3, and so on. The negative input AM(n - 1)2 of An - 1 is connected to the positive input AMn1 of An, and the negative input AMn2 is taken out. Similarly, the n modules in the single-phase power electronic transformer B and the single-phase power electronic transformer C are connected in the same way as above.

9. A water-light power supply system based on a power electronic transformer according to claim 8, characterized in that: The specific number of the module number n is related to the specific switching tubes and the adopted topological structure.

10. A water-light power supply system based on a power electronic transformer according to claim 8, characterized in that: The setting method of the specific number of the module number n is as follows: When the breakdown voltage rating of the switching tubes is higher, the value of n is correspondingly smaller; when a multi-level topological structure is adopted, n is also correspondingly smaller. On the contrary, the number of modules is larger.

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