A photovoltaic energy supply system based on hybrid transformer

Abstract

The present invention relates to a photovoltaic energy supply system based on a hybrid transformer, comprising a hybrid transformer, the hybrid transformer including a primary winding, a secondary winding, an auxiliary winding, and a three-phase iron core. The primary winding is connected to a grid circuit unit, the secondary winding is connected to an AC load, the auxiliary winding is connected to the output of a DC / AC inverter unit, the input of the DC / AC inverter unit is connected to the output of a DC / DC converter unit, the input of the DC / DC converter unit is connected to the power output of a photovoltaic array unit, and a filter unit is connected between the auxiliary winding of the hybrid transformer and the DC / AC inverter unit. The present invention achieves the purpose of supplying energy to the load side based on the auxiliary winding of the hybrid transformer; the present invention only needs to control the AC power output of the inverter unit to be the same amplitude, phase, and frequency as the induced voltage of the auxiliary winding of the specific hybrid transformer when it is unloaded to achieve the energy supply purpose; the present invention avoids adverse effects on the power grid of traditional centralized power supply systems, such as harmonic pollution and islanding effects.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic grid-connected hybrid transformers, and in particular to a photovoltaic energy supply system based on a hybrid transformer. Background Art

[0002] In recent years, photovoltaic power generation technology has continued to advance. Grid-connected photovoltaic power generation systems, including solar cell arrays, DC / DC converters, DC / AC inverters, and transformers, can convert the DC power output from the solar cell array into AC power with the same amplitude, frequency, and phase as the grid voltage, enabling connection to the grid and transmitting power to the grid. To meet the higher demands placed on power equipment by the development of smart grids, hybrid transformers based on traditional transformers and power electronics have been vigorously developed. These hybrid transformers not only possess the voltage conversion, power transmission, and isolation capabilities of traditional transformers, but also can regulate the output power quality and enable multi-source access, demonstrating a high degree of intelligence.

[0003] At present, traditional photovoltaic grid-connected power generation technology has the following defects: First, the direct current generated by the photovoltaic array units is inverted by the photovoltaic inverter and then connected to the grid side. It is not only necessary to ensure that the output power meets the grid's requirements for electrical performance indicators such as voltage and frequency, but it will also have adverse effects on the traditional centralized power supply system, such as harmonic pollution and islanding effects; Second, after the traditional photovoltaic system is connected to the grid, it will cause some power quality problems. For example, the direction of the current in the grid will change, resulting in increased line losses and the need to readjust the relay protection; Third, the randomness and volatility of the photovoltaic power generation system will cause grid voltage fluctuations; Fourth, a large number of power electronic devices are used in the photovoltaic system, which will cause harmonic pollution to the grid. Summary of the Invention

[0004] The purpose of the present invention is to provide a photovoltaic power supply system based on a hybrid transformer, which can supply energy to the load side through the auxiliary winding of the hybrid transformer, avoiding adverse effects on the power grid of the traditional centralized power supply system, such as harmonic pollution and islanding effect.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a photovoltaic energy supply system based on a hybrid transformer, comprising:

[0006] A grid circuit unit, used for supplying energy to AC loads;

[0007] Hybrid transformer for coupled energy transmission;

[0008] A filter unit is used to filter out harmonic components in the AC output after passing through the DC / AC inverter unit;

[0009] The DC / AC inverter unit is used to invert the DC power boosted by the DC / DC unit into the required AC power for input into the auxiliary winding of the hybrid transformer. The DC / AC inverter unit is provided with a control module for controlling the AC output of the DC / AC inverter unit to have the same amplitude, phase and frequency as the induced voltage of the auxiliary winding of the hybrid transformer when it is unloaded.

[0010] The DC / DC converter unit is used to boost the DC power generated by the photovoltaic array unit and provide energy to the DC side of the DC / AC inverter unit;

[0011] Photovoltaic array units for generating direct current electricity;

[0012] AC load, used to provide load;

[0013] The hybrid transformer includes a primary winding, a secondary winding, an auxiliary winding and a three-phase iron core. The primary winding is connected to the grid circuit unit, the secondary winding is connected to the AC load, the auxiliary winding is connected to the output end of the DC / AC inverter unit, the input end of the DC / AC inverter unit is connected to the output end of the DC / DC converter unit, the input end of the DC / DC converter unit is connected to the power output end of the photovoltaic array unit, and the filter unit is connected between the auxiliary winding of the hybrid transformer and the DC / AC inverter unit.

[0014] The secondary winding is wound on the three-phase iron core, the auxiliary winding is wound on the primary winding, and the primary winding is wound on the auxiliary winding.

[0015] The filtering unit adopts an LC second-order filtering circuit.

[0016] It can be seen from the above technical solution that the beneficial effects of the present invention are: first, the present invention realizes the purpose of supplying energy to the load side based on the auxiliary winding of the hybrid transformer; second, compared with the traditional photovoltaic grid-connected functional system, which is a single method of inverting the direct current generated by the photovoltaic array unit through a photovoltaic inverter and then connecting it to the grid side, the present invention only needs to control the AC power output by the inverter unit to be the same amplitude, phase and frequency as the induced voltage of the auxiliary winding of the specific hybrid transformer when it is no-load to achieve the energy supply purpose; third, compared with the traditional photovoltaic grid-connected system, the present invention avoids the adverse effects on the power grid of the traditional centralized power supply system, such as harmonic pollution and islanding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The system structure of the present invention;

[0018] Figure 2 、 3 They are all structural schematic diagrams of the hybrid transformer in the present invention;

[0019] Figure 4It is a single-phase simulation electrical schematic diagram of the present invention;

[0020] Figure 5 This is the grid-side voltage waveform when the auxiliary winding is not connected to the photovoltaic inverter unit;

[0021] Figure 6 This is the grid-side current waveform when the auxiliary winding is not connected to the photovoltaic inverter unit;

[0022] Figure 7 This is the load-side voltage waveform when the auxiliary winding is not connected to the photovoltaic inverter unit;

[0023] Figure 8 This is the load-side current waveform when the auxiliary winding is not connected to the photovoltaic inverter unit;

[0024] Figure 9 This is the grid-side voltage waveform after the auxiliary winding is connected to the photovoltaic inverter unit;

[0025] Figure 10 This is the grid-side current waveform after the auxiliary winding is connected to the photovoltaic inverter unit;

[0026] Figure 11 This is the load-side voltage waveform after the auxiliary winding is connected to the photovoltaic inverter unit;

[0027] Figure 12 This is the load-side current waveform after the auxiliary winding is connected to the photovoltaic inverter unit. DETAILED DESCRIPTION

[0028] like Figure 1 As shown, a photovoltaic energy supply system based on a hybrid transformer 2 includes:

[0029] The grid circuit unit 1 is used to supply energy to the AC load 11;

[0030] Hybrid transformer 2, used for coupled transmission of energy;

[0031] The filter unit 3 is used to filter out harmonic components in the AC output after passing through the DC / AC inverter unit 4;

[0032] The DC / AC inverter unit 4 is used to invert the DC power boosted by the DC / DC unit into the required AC power and input it into the auxiliary winding 8 of the hybrid transformer 2. The DC / AC inverter unit 4 is provided with a control module for controlling the AC output of the DC / AC inverter unit 4 to have the same amplitude, phase and frequency as the induced voltage of the auxiliary winding 8 of the hybrid transformer 2 when it is unloaded.

[0033] The DC / DC converter unit 5 is used to boost the DC power generated by the photovoltaic array unit 6 and provide energy to the DC side of the DC / AC inverter unit 4;

[0034] Photovoltaic array unit 6, for generating direct current power;

[0035] The AC load 11 is used to provide a load.

[0036] like Figure 2 、 3 As shown, the hybrid transformer 2 includes a primary winding 9, a secondary winding 7, an auxiliary winding 8, and a three-phase iron core 10. The primary winding 9 is connected to the grid circuit unit 1, the secondary winding 7 is connected to the AC load 11, and the auxiliary winding 8 is connected to the output of the DC / AC inverter unit 4. The input of the DC / AC inverter unit 4 is connected to the output of the DC / DC converter unit 5, and the input of the DC / DC converter unit 5 is connected to the power output of the photovoltaic array unit 6. The filter unit 3 is connected between the auxiliary winding 8 of the hybrid transformer 2 and the DC / AC inverter unit 4. The secondary winding 7 is wound on the three-phase iron core 10, the auxiliary winding 8 is wound on the primary winding 9, and the primary winding 9 is wound on the auxiliary winding 8.

[0037] The control module primarily controls the output voltage amplitude and phase of the DC / AC inverter unit 4. The inverted output voltage is first calculated and its effective value is subtracted from a given value. This error, after passing through the PI regulator, is multiplied by a sine function to generate a modulation signal. This modulation signal is then compared with a set carrier, ultimately generating a control signal for the DC / AC inverter unit 4. When this control signal is input into the DC / AC inverter unit 4, the desired AC power is generated. This phase control is analogous to photovoltaic grid-connected technology. The present invention ensures that the output voltage of the DC / AC inverter unit 4 is in phase with the induced voltage of the auxiliary winding 8 of the hybrid transformer 2 when unloaded. This ensures that the AC power output from the inverter is fed into the auxiliary winding 8, avoiding oscillations caused by phase differences.

[0038] like Figure 4 As shown, the hybrid transformer 2 has a transformation ratio of 380:220:38 and a frequency of 50 Hz. The primary winding 9 is connected to an AC voltage source (380V / 50Hz) to simulate the grid-side voltage. The secondary winding 7 is directly connected to an AC load 11 (100Ω). The auxiliary winding 8 uses a DC voltage source (100V) to simulate the DC power generated by the photovoltaic array unit 6, providing energy for the DC side of the DC / AC inverter unit 4. The AC output of the DC / AC inverter unit 4 is filtered by the filter unit 3 to remove harmonic components and ultimately converted into 38V / 50Hz AC power, which is connected to the auxiliary winding 8. When the auxiliary winding 8 of the hybrid transformer 2 is connected to the photovoltaic inverter unit, the voltage and current on the AC load 11 connected to the secondary winding 7 remain unchanged. The voltage on the simulated grid side connected to the primary winding 9 remains unchanged, but the current decreases significantly. These simulation results verify the feasibility and rationality of the present invention.

[0039] like Figure 4 As shown, the AC voltage source Uo simulates the grid-side voltage and is connected to the primary winding 9L0 of the hybrid transformer 2. The AC load 11R is directly connected to the secondary winding 7L1. The DC voltage source Vo simulates the DC power generated by the photovoltaic array unit 6, which is connected to the auxiliary winding 8L2 after passing through the full-bridge inverter circuit composed of MOSFETs and the LC filter circuit.

[0040] Figure 5 : is the grid-side voltage waveform diagram when the auxiliary winding 8 is not connected to the photovoltaic inverter unit. At this time, the voltage value is the voltage of the AC voltage source Uo.

[0041] Figure 6 This is the grid-side current waveform when the auxiliary winding 8 is not connected to the photovoltaic inverter unit. The AC current peak at this time is about 9.2A.

[0042] Figure 7 This is the load-side voltage waveform when the auxiliary winding 8 is not connected to the photovoltaic inverter unit. At this time, the voltage on the load is the induced voltage of the secondary winding 7, and its peak value is 311V.

[0043] Figure 8 This is the load-side current waveform when the auxiliary winding 8 is not connected to the photovoltaic inverter unit. At this time, the peak current on the load is 3.11A.

[0044] Figure 9 This is the grid-side voltage waveform after the auxiliary winding 8 is connected to the photovoltaic inverter unit. At this time, the voltage value is also the voltage of the AC voltage source Uo.

[0045] Figure 10 This is the grid-side current waveform after the auxiliary winding 8 is connected to the photovoltaic inverter unit. At this time, the peak value of the primary-side current is about 5.8A after stabilization, which is significantly lower than when the auxiliary winding 8 is not connected to the inverter unit.

[0046] Figure 11 This is the load-side voltage waveform after the auxiliary winding 8 is connected to the photovoltaic inverter unit. At this time, the voltage value on the load remains unchanged and is also an AC current with a peak value of 311V;

[0047] Figure 12 This is the load-side current waveform after the auxiliary winding 8 is connected to the photovoltaic inverter unit. At this time, the current value on the load remains unchanged and is also an AC current with a peak value of 3.11A.

[0048] In summary, the present invention achieves the purpose of supplying energy to the load side based on the auxiliary winding 8 of the hybrid transformer 2; compared with the traditional photovoltaic grid-connected functional system, which is a single system that inverts the direct current generated by the photovoltaic array unit 6 through a photovoltaic inverter and then connects it to the grid side, the present invention only needs to control the AC power output by the inverter unit and the induced voltage of the auxiliary winding 8 of the specific hybrid transformer 2 when it is no-loaded to achieve the energy supply purpose; compared with the traditional photovoltaic grid-connected system, the present invention avoids the adverse effects on the power grid of the traditional centralized power supply system, such as harmonic pollution and island effect.

Claims

1. A photovoltaic energy supply system based on a hybrid transformer, characterized by: include: A power grid circuit unit (1) for supplying energy to an AC load (11); A hybrid transformer (2) for coupled transmission of energy; A filter unit (3) is used to filter out harmonic components in the AC output after passing through the DC / AC inverter unit (4); The DC / AC inverter unit (4) is used to invert the DC power boosted by the DC / DC unit into the required AC power and input it into the auxiliary winding (8) of the hybrid transformer (2); a control module is provided in the DC / AC inverter unit (4) to control the AC output of the DC / AC inverter unit (4) and the induced voltage of the auxiliary winding (8) of the hybrid transformer (2) when unloaded to have the same amplitude, phase and frequency; A DC / DC converter unit (5) is used to boost the DC power generated by the photovoltaic array unit (6) and provide energy to the DC side of the DC / AC inverter unit (4); A photovoltaic array unit (6) for generating direct current power; AC load (11), used for providing load; The hybrid transformer (2) comprises a primary winding (9), a secondary winding (7), an auxiliary winding (8) and a three-phase iron core (10); the primary winding (9) is connected to the grid circuit unit (1); the secondary winding (7) is connected to the AC load (11); the auxiliary winding (8) is connected to the output end of the DC / AC inverter unit (4); the input end of the DC / AC inverter unit (4) is connected to the output end of the DC / DC converter unit (5); the input end of the DC / DC converter unit (5) is connected to the power output end of the photovoltaic array unit (6); and the filter unit (3) is connected between the auxiliary winding (8) of the hybrid transformer (2) and the DC / AC inverter unit (4).

2. The photovoltaic energy supply system based on the hybrid transformer (2) according to claim 1, characterized in that: The secondary winding (7) is wound on a three-phase iron core (10), the auxiliary winding (8) is wound on a primary winding (9), and the primary winding (9) is wound on an auxiliary winding (8).

3. The photovoltaic energy supply system based on the hybrid transformer (2) according to claim 1, characterized in that: The filtering unit (3) adopts an LC second-order filtering circuit.

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