CN202488153U - A grid-connected device for solar power generation - Google Patents

Abstract

The utility model discloses a grid-connected device for solar power generation, which is arranged on the output end of a solar photovoltaic array and comprises a direct-current bus capacitor, a three-phase inverting-bridge circuit, an alternating-current filtering circuit, a power-frequency isolating transformer and a controller. After the voltage of the direct current generated by the solar photovoltaic array is stabilized through a direct current bus capacitor and the harmonic components in the direct current are removed by filtering, the direct current is converted into the alternating current which has the same frequency and phase as a power grid by the three-phase inverting-bridge circuit, then the higher-order harmonics in the three-phase alternating current are removed by filtering by the alternating-current filtering circuit, and the alternating current is connected into the power grid. In the grid-connection process, the damage caused by heat dissipation can be reduced to the minimum extent so that the maximum power output is guaranteed and the electric energy input into the power grid contains the lowest harmonics. The grid-connected device for solar power generation is in a single-stage system structure, thus the cost of hardware is reduced greatly. The controller adopts the maximum power tracking algorithm, thus the maximum power is output by the solar photovoltaic array all the way.

Description

A grid-connected device for solar power generation

technical field

The utility model relates to a grid-connected technology for solar power generation, in particular to a grid-connected device for solar power generation.

Background technique

As a green and non-polluting renewable energy, solar energy has unique advantages compared with other energy sources. Solar energy has the huge advantage of "inexhaustible and inexhaustible", and is more and more favored by people. At present, there are mainly two modes of using solar energy for photovoltaic power generation: independent operation and grid-connected power generation. The independent operation mode requires a large-capacity battery as an energy storage system, and the stability is not high, while the grid-connected power generation mode is photovoltaic power generation. The mainstream direction, but the current grid-connected power generation devices have problems such as high cost and poor stability.

Utility model content

Aiming at the problems of high cost and poor stability of photovoltaic power generation grid-connected devices in the prior art, the purpose of this utility model is to provide a solar power generation grid-connected device.

In order to achieve the above object, the utility model adopts the following technical solutions:

A grid-connected device for solar power generation, set on the output side of a solar photovoltaic array, including a DC bus capacitor, a three-phase inverter bridge circuit, an AC filter circuit, a power frequency isolation transformer and a controller, the DC bus capacitor and the solar The photovoltaic arrays are connected in parallel; the input end of the three-phase inverter bridge circuit is connected to the two ends of the DC bus capacitor; the input end of the AC filter circuit is connected to the output end of the three-phase inverter bridge circuit; the power frequency isolation transformer The input end of the AC filter circuit is connected to the output end; the output end of the power frequency isolation transformer is connected to the power grid; the input end of the controller is connected to the input end of the AC filter circuit, the input end of the power frequency isolation transformer, the solar energy The photovoltaic array and the output terminals of the DC bus capacitor are connected, and the output terminal of the controller is connected with the three-phase inverter bridge circuit.

The controller includes a computing unit, a comparator, a PI regulator and a three-phase pulse modulator, the input terminal of the computing unit receives the output current and the output voltage of the solar photovoltaic array, and the input terminal of the comparator is connected to the The output terminal is connected; the input terminal of the PI regulator is connected with the output terminal of the comparator; the input terminal of the three-phase pulse modulator is connected with the output terminal of the PI regulator, and the output terminal of the three-phase pulse modulator is connected with the three-phase The inverter bridge circuit is connected.

The three-phase pulse modulator adopts a space vector pulse width modulation module.

Compared with the prior art, a grid-connected device for solar power generation of the present invention is installed on the output side of the solar photovoltaic array, including DC bus capacitors, three-phase inverter bridge circuits, AC filter circuits, power frequency isolation A transformer and a controller, the DC bus capacitor is connected in parallel with the solar photovoltaic array; the input end of the three-phase inverter bridge circuit is connected to both ends of the DC bus capacitor; the input end of the AC filter circuit is connected to the three-phase inverter bridge The output end of the circuit is connected; the input end of the power frequency isolation transformer is connected with the output end of the AC filter circuit; the output end of the power frequency isolation transformer is connected with the grid; the input ends of the controller are connected with the AC filter circuit The input end, the input end of the power frequency isolation transformer, the solar photovoltaic array and the output end of the DC bus capacitor are connected, and the output end of the controller is connected with the three-phase inverter bridge circuit. The DC power generated by the solar photovoltaic array is stabilized by the DC bus capacitor, and after filtering out the harmonic components in the DC power, the three-phase inverter bridge circuit converts the DC power into AC power with the same frequency and phase as the power grid, and the three-phase power is converted by the AC filter circuit. The high-order harmonics in the alternating current are filtered out, and finally merged into the power grid. In this way, during the grid connection process, the heat dissipation damage can be minimized to ensure the maximum power output, and the power input into the grid has the lowest harmonic content. The grid-connected device of the utility model adopts a single-stage system structure, so that the hardware cost will be greatly reduced. The controller adopts the maximum power tracking algorithm, referred to as MPPT, so that it can ensure that the output power of the solar photovoltaic array always reaches the maximum value. At the same time, for security reasons, island effect protection measures are added to the algorithm, which can make the system run safely and reliably.

Description of drawings

Fig. 1 is a schematic diagram of the principle of a grid-connected device for solar power generation of the present invention;

Fig. 2 is the circuit schematic diagram of DC bus capacitor, three-phase inverter bridge circuit, AC filter circuit and power frequency isolation of the utility model;

Fig. 3 is a schematic diagram of the control structure of the controller of the present invention.

Detailed ways

The technical scheme of the utility model is further described below in conjunction with the accompanying drawings and embodiments.

Please refer to Fig. 1 and Fig. 2 for a grid-connected device for solar power generation, which is located on the output side of the solar photovoltaic array 20, including a DC bus capacitor 11, a three-phase inverter bridge circuit 12, and an AC filter using LCL Circuit 13, power frequency isolation transformer 14 and controller 15, the DC bus capacitor 11 is connected in parallel with the solar photovoltaic array 20, the input end of the three-phase inverter bridge circuit 12 is connected to both ends of the DC bus capacitor 11, and the input of the AC filter circuit 13 end is connected with the output end of the three-phase inverter bridge circuit 12, the input end of the power frequency isolation transformer 14 is connected with the output end of the AC filter circuit 13, the output end of the power frequency isolation transformer 14 is connected with the grid 21, and the input end of the controller 15 The terminals are respectively connected to the input terminal of the AC filter circuit 13, the input terminal of the power frequency isolation transformer 14, the solar photovoltaic array 20 and the output terminal of the DC bus capacitor 11, and the output terminal of the controller 15 is connected to the three-phase inverter bridge circuit 12, The three-phase inverter bridge circuit 12 is mainly composed of six insulated gate bipolar transistors T1, T2, T3, T4, T5, T6. The controller 15 controls the six-way IGBTs whose outputs drive the three-phase inverter bridge circuit 12 to turn off. This topology is simple, and the maximum power point tracking control and grid-connected inverter can be realized with one power conversion link, so it has high conversion efficiency. Moreover, a power frequency isolation transformer 14 is added after the AC filter circuit 13, and the power frequency isolation transformer 14 can not only reduce the DC bus voltage, but also realize electrical isolation.

Please refer to shown in Fig. 3 again, wherein controller 15 comprises operator 151, comparator 152, PI regulator 153 and adopts space vector pulse width modulation module to be called for short the three-phase pulse modulator 154 of SVPWM modulation module, the input of operator 151 terminal receives the output current and the output voltage of the solar photovoltaic array 20, the input terminal of the comparator 152 is connected with the output terminal of the arithmetic unit 151, the input terminal of the PI regulator 153 is connected with the output terminal of the comparator 152, and the three-phase pulse modulator 154 The input end of the PI regulator 153 is connected to the output end, and the output end of the three-phase pulse modulator 154 is connected to the three-phase inverter bridge circuit 12. In the figure, U _pv and I _pv are the output voltage and output current of the photovoltaic array respectively, U _a , U _b , and U _c are the voltages of the three-phase grid, and I _a , I _b , and I _c are the outputs of the three-phase inverter bridge circuit 12 current, U _dc is the DC bus voltage. By detecting the output voltage U _pv and the output current I _pv of the photovoltaic array, the voltage of the maximum output power is determined through the calculation of the operator 151, and the voltage is arithmetically operated by the comparator 152 and the DC bus voltage U _dc , and the output value is used as the current inner Command value of ring active axis. The output currents I _a , I _b , and I _c of the three-phase inverter bridge circuit 12 are transformed into active axis components I _q and reactive axis components I _d through coordinate transformation. The θ angle required for coordinate transformation is determined by the grid voltage phase-locked phase angle output. The current active axis component I _q and the current inner loop command value are calculated by the comparator, and then through the current active axis controller, the active axis control target vector U _cqref is output. Similarly, the reactive axis current control target vector U _cdref is obtained, two The target vectors are transformed into target vectors U _caref , U _cbref , and U _ccref in the three-phase coordinate system through coordinate transformation. The three target vectors output six pulses through the three-phase pulse regulator 154 to control the on-off of the IGBT.

In order to meet the requirement that the output power of the solar photovoltaic array 20 reaches the maximum value at any time, the maximum power tracking algorithm MPPT is adopted. At the same time, for safety reasons, island effect protection measures are added to the algorithm, which can make the system run safely and reliably.

The arithmetic unit 151 is controlled by an all-digital chip TMS320F2812, which has the advantages of high processing speed, stability and reliability. And the feasibility of the device is verified by simulation tools.

Before the grid-connected device of the utility model is connected to the grid, the power grid is firstly rectified to a DC of about 450V through an uncontrolled rectifier bridge to charge the DC bus capacitor 11 . After charging is completed, connect the solar photovoltaic array 20 into the main circuit. Then through the maximum power tracking control algorithm, determine the given value of the DC bus voltage. Finally, the grid-connected inverter is realized through digital chip control, so that the electric energy generated by the solar energy can be fed back to the grid.

Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the purpose of the utility model, rather than as a limitation of the utility model, as long as within the essential scope of the utility model, the above-mentioned The changes and modifications of the above embodiments will fall within the scope of the claims of the present utility model.

Claims (3)

1. A grid-connected device for solar power generation, located on the output side of the solar photovoltaic array, characterized in that: Including a DC bus capacitor, a three-phase inverter bridge circuit, an AC filter circuit, a power frequency isolation transformer and a controller, the DC bus capacitor is connected in parallel with the solar photovoltaic array; the input end of the three-phase inverter bridge circuit is connected to the DC bus capacitor The two ends of the AC filter circuit are connected; the input end of the AC filter circuit is connected with the output end of the three-phase inverter bridge circuit; the input end of the power frequency isolation transformer is connected with the output end of the AC filter circuit; The output end is connected to the power grid; the input end of the controller is connected to the input end of the AC filter circuit, the input end of the power frequency isolation transformer, the solar photovoltaic array and the output end of the DC bus capacitor, and the output end of the controller is connected to the output end of the DC bus capacitor. The three-phase inverter bridge circuit is connected. 2. The grid-connected device according to claim 1, characterized in that: The controller includes a computing unit, a comparator, a PI regulator and a three-phase pulse modulator, the input terminal of the computing unit receives the output current and the output voltage of the solar photovoltaic array, and the input terminal of the comparator is connected to the The output terminal is connected; the input terminal of the PI regulator is connected with the output terminal of the comparator; the input terminal of the three-phase pulse modulator is connected with the output terminal of the PI regulator, and the output terminal of the three-phase pulse modulator is connected with the three-phase The inverter bridge circuit is connected. 3. The grid-connected device according to claim 2, characterized in that: The three-phase pulse modulator adopts a space vector pulse width modulation module.

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