Novel photovoltaic grid-connected circuit topology with inversion and chopping multiplexing converter

Abstract

The invention belongs to the technical field of photovoltaic new energy grid-connected systems and power electronics, and discloses a novel photovoltaic grid-connected circuit topology with an inversion and chopping multiplexing converter, which comprises a high-frequency zigzag transformer, a photovoltaic cell, a three-phase grid-connected inversion and chopping multiplexing converter and a controller, the power grid is connected in series between the primary side and the secondary side of the high-frequency zigzag transformer; the alternating-current side of the three-phase grid-connected inversion and chopping multiplexing converter is connected with the secondary side through a power grid line equivalent resistor, and the direct-current side is externally connected with an energy storage battery through a direct-current bus; the photovoltaic battery is connected between the grounding end of the three-phase grid-connected inversion and chopping multiplexing converter and the grounding end of the energy storage battery; the three-phase grid-connected inversion and chopping multiplexing converter comprises a three-phase full-bridge circuit formed by IGBT (Insulated Gate Bipolar Translator) switching tubes Q1-Q6; and the controller is used for controlling the on-off of the IGBT switching tubes Q1-Q6, so that the three-phase full-bridge circuit is multiplexed as an inverter and a chopper circuit. According to the invention, the number of devices used by the photovoltaic grid-connected circuit topology can be reduced, and the cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic new energy grid-connected system and power electronics technology, and more specifically, relates to a novel photovoltaic grid-connected circuit topology with an inverter and a chopper multiplexed converter. Background Art

[0002] Photovoltaic grid-connected inverter circuit is used to invert the new energy electric energy generated by photovoltaic cells into AC electric energy that can be used for grid transmission.

[0003] The current mainstream three-port photovoltaic grid-connected inverter circuit topology on the market can basically be summarized as adding a DC / DC circuit as a chopper converter to the DC bus on the basis of the original photovoltaic and grid two-port circuit, forming a "three-port" parallel structure. In this structure, the photovoltaic is connected in parallel at the output end of the DC / DC circuit, the chopper converter transfers the power on the DC bus to the energy storage battery, and the grid-connected inverter connected between the photovoltaic and grid ports transfers the power on the DC bus to the grid. The circuit topology is clear and simple, the device pressure stability is uniform, and the switch error rate is low. However, this "three-port" parallel structure uses more devices and is more expensive. It is not friendly to the power quality of small users and is prone to problems such as harmonics and unbalanced power factors. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a new photovoltaic grid-connected circuit topology with an inverter and a chopper multiplexed converter, which aims to reduce the number of devices used in the photovoltaic grid-connected circuit topology and reduce costs.

[0005] To achieve the above object, according to a first aspect of the present invention, there is provided a novel photovoltaic grid-connected circuit topology with an inverter and chopper multiplexing converter, comprising: a high-frequency zigzag transformer, a photovoltaic cell, a three-phase grid-connected inverter and chopper multiplexing converter and a controller;

[0006] The high-frequency zigzag transformer includes a primary winding and a secondary winding connected in series; the power grid is connected in series between the primary winding and the secondary winding; the AC side of the three-phase grid-connected inverter and chopper multiplexing converter is connected to the secondary winding through the equivalent resistance of the grid line, and the DC side is connected to an external energy storage battery through a DC bus; the photovoltaic cell is connected between the ground terminal of the three-phase grid-connected inverter and chopper multiplexing converter and the ground terminal of the energy storage battery; and the three-phase grid-connected inverter and chopper multiplexing converter includes a three-phase full-bridge circuit composed of IGBT switch tubes Q1-Q6;

[0007] The controller is used to control the on and off of the IGBT switch tubes Q1-Q6, so that when the electric energy is transmitted between the power grid and the energy storage battery, the power grid, the secondary winding, the three-phase full-bridge circuit and the energy storage battery form an inverter circuit; wherein the three-phase full-bridge circuit is used as an inverter to realize the inverter function;

[0008] And / or, the controller is also used to control the on and off of the IGBT switch tubes Q1-Q6, so that when electric energy is transmitted from the photovoltaic cell to the energy storage battery, the photovoltaic cell, the high-frequency zigzag transformer, each phase arm of the three-phase full-bridge circuit and the energy storage battery constitute a chopper circuit; wherein each phase arm of the three-phase full-bridge circuit serves as a chopper circuit to perform chopping control on the current in the chopper circuit.

[0009] Furthermore, a voltage-stabilizing capacitor is connected in parallel at both ends of the photovoltaic cell; and a voltage-stabilizing capacitor is connected in parallel at both ends of the energy storage battery.

[0010] Furthermore, the high-frequency zigzag transformer also includes a magnetic column, and the corresponding phase coils of the primary side winding and the secondary side winding are reversely wound on the phase magnetic column, so that the primary side winding and the secondary side winding form a series zigzag connection.

[0011] According to a second aspect of the present invention, a control method for a novel photovoltaic grid-connected circuit topology is provided, and the control method is applied to a controller in the novel photovoltaic grid-connected circuit topology according to any one of the first aspects, comprising:

[0012] Controlling the on and off of the IGBT switches Q1-Q6 so that when electric energy is transmitted between the power grid and the energy storage battery, the power grid, the secondary winding, the three-phase full-bridge circuit and the energy storage battery form an inverter circuit; wherein the three-phase full-bridge circuit works as an inverter in an inverter mode;

[0013] And / or, the on and off of the IGBT switch tubes Q1-Q6 are also controlled so that when electric energy is transmitted from the photovoltaic cell to the energy storage battery, the photovoltaic cell, the high-frequency zigzag transformer, each phase arm of the three-phase full-bridge circuit and the energy storage battery form a chopper circuit; wherein each phase arm of the three-phase full-bridge circuit works as a chopper circuit in a chopper conversion mode.

[0014] Furthermore, when the three-phase full-bridge circuit works as an inverter in the inverter mode, the direction of electric energy transmission between the power grid and the energy storage battery is determined in the following manner:

[0015] Based on the voltage and current equations satisfied by the equivalent circuit of the novel photovoltaic grid-connected circuit topology, the duty cycle of the control signal generated by the controller is adjusted to control the on and off of the IGBT switch tubes Q1-Q6, thereby changing the current moment i in the voltage and current equations. d 、i q and Ud , U q The size of d 、i q are the d-axis and q-axis components of the inverter AC side current after dq transformation, U d , U q are respectively the d-axis and q-axis components of the AC side voltage of the inverter after dq transformation;

[0016] Based on the current time i d 、i q and U d , U q The size of the line is used to calculate the active power transmitted by the line; the direction from the grid to the energy storage battery is set as i d 、i q In the positive direction, when the active power is positive, electric energy is transmitted from the grid to the energy storage battery, otherwise, electric energy is transmitted from the energy storage battery to the grid.

[0017] Furthermore, when the three-phase full-bridge circuit is used as a chopper circuit, the amount of electric energy transmitted from the photovoltaic cell to the energy storage battery is determined in the following manner:

[0018] The voltage transformation ratio K is adjusted to control the on and off of the IGBT switch tubes Q1-Q6 to change the loop current i of each chopper circuit. d2 , thereby changing the amount of electrical energy transmitted from the photovoltaic cell to the energy storage battery; wherein the voltage transformation ratio K satisfies:

[0019]

[0020] Where U PV is the output voltage of the photovoltaic cell, U dl is the output voltage of the energy storage battery, r eq2 is the equivalent resistance of the equivalent circuit of the novel photovoltaic grid-connected circuit topology.

[0021] Furthermore, when the three-phase full-bridge circuit is used as an inverter and a chopper circuit at the same time, the three-phase full-bridge circuit operates in an inverter and chopper mixed conversion mode; at this time, based on the voltage and current equations satisfied by the equivalent circuit of the novel photovoltaic grid-connected circuit topology, the duty cycle of the control signal generated by the controller is adjusted, and the size of the voltage transformation ratio K is adjusted to control the on and off of the IGBT switch tubes Q1-Q6, thereby changing the i in the voltage and current equations at the current moment. d 、i q and U d , U q The size of each chopper circuit and the loop current i d2 ;

[0022] Based on the current time id 、i q and U d , U q The size of the line is used to calculate the active power transmitted by the line; the direction from the grid to the energy storage battery is set as i d 、i q In the positive direction, when the active power is positive, electric energy is transmitted from the power grid to the energy storage battery, otherwise, electric energy is transmitted from the energy storage battery to the power grid;

[0023] According to the loop current i of each chopper circuit d2 , changing the amount of electrical energy transmitted from photovoltaic cells to energy storage batteries.

[0024] According to a third aspect of the present invention, there is provided a controller comprising a computer readable storage medium and a processor;

[0025] The computer-readable storage medium is used to store executable instructions;

[0026] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the control method described in any one of the second aspects.

[0027] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon, wherein the program, when executed by a processor, implements the control method as described in any one of the second aspects.

[0028] According to a fifth aspect of the present invention, there is provided a computer program product, comprising a computer program, which, when executed on a computer, enables the computer to execute the control method described in any one of the second aspects.

[0029] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0030] (1) The novel photovoltaic grid-connected circuit topology with an inverter and chopper multiplexing converter designed by the present invention adds a high-frequency zigzag transformer with a primary winding and a secondary winding connected in series, and sets the user-side photovoltaic cell between the grounding terminal of the three-phase grid and the three-phase grid-connected inverter and chopper multiplexing converter and the grounding terminal of the energy storage battery, and cooperates with the three-phase full-bridge circuit composed of IGBT switch tubes Q1-Q6, so that the three-phase full-bridge circuit has both the inverter and chopper multiplexing functions. Specifically, the three-phase full-bridge circuit composed of IGBT switch tubes Q1-Q6 is generally used as an inverter. If it is used as a chopper circuit, due to the presence of the DC current of the photovoltaic cell on the user side, the inductance existing in the three-phase grid will interact to produce a DC magnetization problem, and the zero-sequence current passing through the three phases will cause the three-phase voltage to fluctuate, causing the increase of grid harmonics, thereby reducing the power quality of the entire circuit system. Based on the above considerations, in order to enable the three-phase full-bridge circuit composed of IGBT switching tubes Q1-Q6 to be used as an inverter and a chopper circuit at the same time, the present invention considers introducing a high-frequency zigzag transformer with a primary winding and a secondary winding connected in series, and in particular connecting the user-side photovoltaic cell between the ground terminal of the three-phase power grid and the three-phase grid-connected inverter and chopper multiplexing converter, and the ground terminal of the energy storage battery. In this way, when the three-phase full-bridge circuit is used as a chopping circuit, the zero-sequence magnetic flux generated in the power grid can flow along the magnetic column of the high-frequency zigzag transformer instead of flowing along the leakage magnetic circuit, thereby suppressing the zero-sequence magnetic flux in the circuit, alleviating the DC magnetization problem, and improving the power quality on the power grid side; and, the secondary winding of the high-frequency zigzag transformer and the equivalent resistance of the power grid line constitute an RL filtering effect, further improving the power quality on the power grid side, therefore, the three-phase full-bridge circuit can be used as a chopping circuit, and when it realizes the chopping function, each phase arm of the three-phase full-bridge circuit can be independently used as a chopping circuit, and three independent chopping circuits jointly chop the DC current output by the photovoltaic cell on the user side. The present invention realizes that the three-phase full-bridge circuit has the functions of inverter and chopping multiplexing at the same time, reduces the number and cost of the devices used, and can improve the power quality, avoiding the problems of harmonics and power factor imbalance.

[0031] (2) In the topological structure of the present invention, since the secondary winding of the high-frequency zigzag transformer is connected to the AC side of the three-phase grid-connected inverter and chopper multiplexing converter through the equivalent resistance of the grid line, when the three-phase grid-connected inverter and chopper multiplexing converter are used as chopper circuits, the high-frequency zigzag transformer has a certain inhibitory effect on the current in the three chopper circuits, which can alleviate the problem of uneven heating of semiconductor devices caused by different on and off times of the switch tubes in a switching cycle. (3) As a preferred embodiment, a voltage stabilizing capacitor is connected in parallel at both ends of the photovoltaic cell and the energy storage battery, which can provide a stable photovoltaic voltage and energy storage battery voltage; the use of the voltage stabilizing capacitor in parallel with the photovoltaic cell can achieve more efficient and stable energy management, and has a buffering current function to prevent the photovoltaic cell on the user side from being damaged when the multiplexing circuit is working.

[0032] In summary, the photovoltaic grid-connected circuit topology designed by the present invention is a photovoltaic grid-connected circuit topology with an inverter and a chopper multiplexing converter. The converter has both inverter and chopper multiplexing functions, which can reduce the number of devices used in the photovoltaic grid-connected circuit topology and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The diagram is a schematic diagram of a novel photovoltaic grid-connected circuit topology structure with an inverter and chopper multiplexed converter in an embodiment of the present invention.

[0034] FIG2(a) is an equivalent circuit diagram of an inverter circuit formed when a three-phase grid-connected inverter and a chopper multiplexed converter are used as inverters.

[0035] FIG2( b ) is a diagram showing an equivalent circuit structure of a chopper circuit formed when a three-phase grid-connected inverter and a chopper multiplexing converter are used as a chopper circuit.

[0036] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0037] 1- High frequency zigzag transformer 1, 2- Photovoltaic cell, 3- Three-phase grid-connected inverter and chopper multiplexing converter. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] Example 1

[0040] like Figure 1As shown, an embodiment of the present invention provides a novel photovoltaic grid-connected circuit topology with an inverter and chopper multiplexing converter, which mainly includes: a high-frequency zigzag transformer 1, a photovoltaic cell 2, a three-phase grid-connected inverter and chopper multiplexing converter 3 and a controller.

[0041] The high-frequency zigzag transformer 1 includes a primary winding and a secondary winding connected in series; the three-phase power grid is connected in series between the primary winding and the secondary winding of the high-frequency zigzag transformer 1; the secondary winding of the high-frequency zigzag transformer 1 is connected to the AC side of the three-phase grid-connected inverter and chopper multiplexing converter 3 through the equivalent resistance of the grid line; the DC side of the three-phase grid-connected inverter and chopper multiplexing converter 3 is used to connect an external energy storage battery through a DC bus; a photovoltaic cell 2 is provided between the grounding terminal of the three-phase power grid and the three-phase grid-connected inverter and chopper multiplexing converter 3 and the grounding terminal of the energy storage battery.

[0042] In an embodiment of the present invention, the three-phase grid-connected inverter and chopper multiplexing converter 3 includes a three-phase full-bridge circuit composed of IGBT switch tubes Q1-Q6, the DC side of the three-phase full-bridge circuit is the DC side of the three-phase grid-connected inverter and chopper multiplexing converter 3, and the AC side of the three-phase full-bridge circuit is the AC side of the three-phase grid-connected inverter and chopper multiplexing converter 3.

[0043] The controller is used to generate control signals to control the on and off of IGBT switch tubes Q1-Q6 under hybrid SPWM modulation, so that when energy flows between the power grid and the energy storage battery, the power grid, the secondary side of the high-frequency zigzag transformer, the three-phase full-bridge circuit and the energy storage battery on the DC bus side form an inverter circuit, and the three-phase full-bridge circuit acts as an inverter to realize the inverter function;

[0044] And / or, the controller is also used to generate a control signal to control the on and off of the IGBT switch tubes Q1-Q6 under hybrid SPWM modulation, so that when energy flows from the user-side photovoltaic cell to the energy storage battery, the user-side photovoltaic cell, the high-frequency zigzag transformer, each phase arm of the three-phase full-bridge circuit and the energy storage battery on the DC bus side constitute a chopper circuit, wherein each phase of the three-phase full-bridge circuit serves as an independent chopper circuit to perform chopping control on the current flowing into the chopper circuit, and the sum of the currents in the three chopper circuits is consistent with the output current of the user-side photovoltaic cell.

[0045] In an embodiment of the present invention, a high-frequency zigzag transformer 1 comprises: a magnetic column and a primary winding and a secondary winding wound on the magnetic column; wherein the corresponding phase coils of the primary winding and the secondary winding are reversely wound on the phase magnetic column, so that the primary winding and the secondary winding form a zigzag connection in series. Since the high-frequency zigzag transformer operates at a high frequency, its loss is relatively low, and its use can improve the conversion efficiency of the circuit topology, thereby improving the power quality, and the leakage inductance and distributed capacitance of the high-frequency zigzag transformer can be reduced by optimizing the design and winding process, and the voltage spike and current spike when the IGBT switch tube is switched can be reduced, thereby improving the stability and reliability of the entire system.

[0046] As a preferred implementation method, a voltage-stabilizing capacitor is connected in parallel at both ends of the photovoltaic cell on the user side, and a voltage-stabilizing capacitor Cd is connected in parallel at both ends of the energy storage battery. Specifically, the voltage-stabilizing capacitor and the photovoltaic cell are integrated into a system, which has the functions of buffering and filtering, and can provide a relatively stable photovoltaic voltage. The parallel use of photovoltaic cells and voltage-stabilizing capacitors can achieve more efficient and stable energy management, and has the function of buffering current to prevent damage to the photovoltaic cells on the user side when the reuse circuit is working. The capacitors connected in parallel with photovoltaic cells have the characteristics of high power density, fast charging and discharging capabilities, long cycle life and high safety. They can absorb or release electrical energy while maintaining voltage, and the photovoltaic cells provide electrical energy input. The mutual cooperation between the two subtly adjusts the energy flow structure in the system, making the power quality control more stable.

[0047] Specifically, after the novel photovoltaic grid-connected circuit with an inverter and chopper multiplexing converter in the embodiment of the present invention is connected to the power grid, there is energy flow and conversion of power grid electric energy, power of photovoltaic cells on the user side, and power on the DC bus side. The energy storage batteries on the grid side and the DC bus side and the photovoltaic cells on the user side constitute two circuits: an AC / DC power circuit and a DC / DC power circuit.

[0048] The conversion circuit, i.e., the AC / DC power circuit, composed of the power grid, the secondary side of the high-frequency zigzag transformer, the three-phase full-bridge circuit, and the energy storage battery on the DC bus side, is used to realize the energy exchange between the electric energy in the power grid and the energy storage battery on the DC bus side. At this time, the three-phase full-bridge circuit (three-phase grid-connected inverter and chopper multiplexing converter) serves as an inverter. By changing the duty cycle of the control signal generated by the controller, the energy flow between the grid side and the energy storage battery on the DC bus side is realized, and the three-phase grid-connected inverter and chopper multiplexing converter serves as an inverter to realize the energy inversion between the DC side of the energy storage battery and the AC side of the power grid.

[0049] The conversion circuit, i.e., the DC / DC power circuit, which is composed of the photovoltaic cell on the user side, the high-frequency zigzag transformer, the three-phase full-bridge circuit, and the energy storage battery on the DC bus side, is used to realize the energy exchange from the photovoltaic cell on the user side to the energy storage battery on the DC bus side. At this time, each phase arm of the three-phase full-bridge circuit (three-phase grid-connected inverter and chopper multiplexing converter) is used as a chopper circuit. By changing the duty cycle of the control signal generated by the controller, the energy flow from the user side to the DC bus side is realized, and the three-phase grid-connected inverter and chopper multiplexing converter is used as a chopper circuit to realize the chopping control of the user side and the DC bus side. Through different IGBT control methods, the three-phase grid-connected inverter and chopper multiplexing converter can be equivalent to three independent chopper converters, so that the electric energy on the user side can be transferred to the DC bus side while maintaining voltage stability. In this way, the circuit system can realize the transfer of electric energy from the user side to the grid side.

[0050] The novel photovoltaic grid-connected circuit topology with an inverter and chopper multiplexing converter designed by the present invention is realized by adding a high-frequency zigzag transformer 1 with a primary winding and a secondary winding connected in series, and arranging the user-side photovoltaic cell between the grounding terminal of the three-phase power grid and the three-phase grid-connected inverter and chopper multiplexing converter 3, and the grounding terminal of the energy storage battery, and cooperating with the three-phase full-bridge circuit composed of IGBT switch tubes Q1-Q6, so that the three-phase full-bridge circuit has both the inverter and chopper multiplexing functions. Specifically, the three-phase full-bridge circuit composed of IGBT switch tubes Q1-Q6 is generally used as an inverter. If it is used as a chopper circuit, due to the presence of the DC current of the photovoltaic cell on the user side, the inductance existing in the three-phase power grid will interact to produce a DC magnetization problem, and the zero-sequence current is passed into the three phases, which will cause the three-phase voltage to fluctuate, causing the increase of grid harmonics, thereby reducing the power quality of the entire circuit system. Based on the above considerations, in order to enable the three-phase full-bridge circuit composed of IGBT switching tubes Q1-Q6 to be used as an inverter and also as a chopper circuit, the present invention considers introducing a high-frequency zigzag transformer 1 with a primary winding and a secondary winding connected in series, and in particular connecting the user-side photovoltaic cell between the ground terminal of the three-phase power grid and the three-phase grid-connected inverter and chopper multiplexing converter 3, and the ground terminal of the energy storage battery. In this way, when the three-phase full-bridge circuit is used as a chopper circuit, the zero-sequence magnetic flux generated in the power grid can flow along the magnetic column of the high-frequency zigzag transformer 1 instead of flowing along the leakage magnetic path, thereby suppressing the zero-sequence magnetic flux in the circuit, alleviating the DC magnetization problem, and improving the power quality on the power grid side; and, the secondary winding of the high-frequency zigzag transformer 1 and the equivalent resistance of the power grid line constitute an RL filtering effect, further improving the power quality on the power grid side, therefore, the three-phase full-bridge circuit can be used as a chopper circuit, and when it realizes the chopping function, each phase arm of the three-phase full-bridge circuit can be independently used as a chopper circuit, and three independent chopper circuits jointly chop the DC current output by the photovoltaic cell on the user side. The present invention realizes that the three-phase full-bridge circuit has the functions of both inversion and chopping multiplexing, reduces the number and cost of the devices used, and can improve the power quality, avoiding the problems of harmonics and power factor imbalance.

[0051] Moreover, in the topological structure of the present invention, since the secondary winding of the high-frequency zigzag transformer 1 is connected to the AC side of the three-phase grid-connected inverter and chopper multiplexing converter 3 through the equivalent resistance of the grid line, when the three-phase grid-connected inverter and chopper multiplexing converter 3 is used as a chopper circuit, the high-frequency zigzag transformer 1 has a certain inhibitory effect on the current in the three chopper circuits, which can alleviate the problem of uneven heating of semiconductor devices caused by different turn-on and turn-off times of the switch tube in a switching cycle.

[0052] The topological structure of the present invention reduces the number of IGBT switch tubes and greatly reduces the cost. In the actual installation process, due to the reduction in the number of components, the space occupied by the circuit devices and packaging is reduced, and the redundancy of the circuit is reduced.

[0053] The high-frequency zigzag transformer series circuit is adopted to achieve high power density and current density. In combination with photovoltaic cells, three-phase grid-connected inverters and chopper multiplexing converters, the zero-sequence flux and zero-sequence impedance during circuit operation are reduced, ensuring the stability and reliability of the system during operation.

[0054] Example 2

[0055] The embodiment of the present invention also provides a control method for a novel photovoltaic grid-connected circuit topology having an inverter and chopper multiplexing converter. The control method is applied to the controller in the novel photovoltaic grid-connected circuit topology having an inverter and chopper multiplexing converter in the above-mentioned embodiment 1, including: controlling the three-phase grid-connected inverter and chopper multiplexing converter 3 to operate in any of the following three modes:

[0056] 1) Three-phase grid-connected inverter mode:

[0057] Under hybrid SPWM modulation, the controller generates control signals to control the on and off of IGBT switches Q1-Q6, so that when energy flows between the power grid and the energy storage battery, the power grid, the secondary side of the high-frequency zigzag transformer, the three-phase full-bridge circuit and the energy storage battery on the DC bus side form an inverter circuit, and the three-phase full-bridge circuit acts as an inverter to achieve the inverter function. At this time, the electric energy output by the energy storage battery on the DC bus side is inverted into a three-phase symmetrical voltage and current with high power factor and low harmonic proportion through the regulation of IGBT, and then absorbed by the power grid; or, the AC power output by the power grid is converted into DC power through the regulation of IGBT and stored in the energy storage battery on the DC bus side.

[0058] In the embodiment of the present invention, the controller adopts power factor regulation and harmonic control regulation, and the IGBT switch tubes Q1-Q6 adopt the SPWM regulation mode.

[0059] Specifically, the energy flow between the energy storage battery on the grid side and the DC bus side is achieved by changing the duty cycle of the control signal generated by the controller.

[0060] When the three-phase grid-connected inverter and chopper multiplexing converter are used as the inverter, it is assumed that the equivalent voltage of the grid voltage after abc and dq transformation is E d 、E q The equivalent voltage of the three-phase grid-connected inverter and chopper multiplexing converter 3 after abc and dq transformation is U d , U qBased on the equivalent circuit topology Figure 2(a) at this time, the voltage and current equations of the three-phase grid-connected inverter and chopper multiplexing converter in the dq coordinate system can be listed:

[0061]

[0062] Where, L eq When the three-phase grid-connected inverter and chopper multiplexing converter are used as the inverter, the equivalent inductance of the high-frequency zigzag transformer and the grid transmission line in the photovoltaic grid-connected equivalent circuit, r eq When the three-phase grid-connected inverter and chopper multiplexing converter are used as the inverter, the equivalent resistance of the high-frequency zigzag transformer and the grid transmission line in the photovoltaic grid-connected equivalent circuit; i d 、i q When the three-phase grid-connected inverter and the chopper multiplexing converter are used as the inverter, the d-axis component and q-axis component of the AC side current of the three-phase grid-connected inverter and the chopper multiplexing converter after dq transformation; ω is the preset electrical angular velocity; t is the current moment; where L eq 、r eq That is Leq, Req in Figure 2(a).

[0063] Based on the above voltage and current equations, the duty cycle of the control signal is adjusted to change the current moment i d 、i q and U d , U q The size of i based on the current moment d 、i q and U d , U q Calculate the active power transmitted by the line, and determine the energy flow between the grid side and the energy storage battery on the DC bus side according to the positive and negative active power transmitted by the line. Specifically, assume that the power from the grid side to the DC bus side is i d 、i q In the positive direction, when the calculated active power transmitted by the line is positive, the electric energy is transmitted from the grid side to the energy storage battery on the DC bus side; when the active power transmitted by the line is negative, the electric energy is transmitted from the energy storage battery on the DC bus side to the grid side.

[0064] 2) User chopping mode:

[0065] Under hybrid SPWM modulation, the controller generates a control signal to control the on and off of the IGBT switch tubes Q1-Q6, so that when energy flows from the user-side photovoltaic cells to the energy storage battery, the user-side photovoltaic cells, the high-frequency zigzag transformer, the three-phase full-bridge circuit and the energy storage battery on the DC bus side form a chopper circuit, and the three-phase bridge arms of the three-phase full-bridge circuit are respectively used as three independent chopper circuits to realize chopper control.

[0066] In the three-phase grid-connected inverter mode, it is only assumed that the grid side and the DC bus side exchange electric energy. However, in the embodiment of the present invention, the circuit topology has a user-side photovoltaic cell, and the photovoltaic cell and the DC bus side realize the DC chopping function through a multiplexing converter. Different from the multiplexing converter as an inverter, the control strategy of the 6 IGBTs Q1-Q6 at this time is not to turn on each other in turn during three-phase inverter, but to control according to the DC voltage of the user-side photovoltaic cell.

[0067] When the three-phase grid-connected inverter and chopper multiplexing converter is used as a chopper circuit, based on the equivalent circuit topology diagram 2(b) at this time, the voltage and current equations of the three-phase grid-connected inverter and chopper multiplexing converter can be listed as follows:

[0068]

[0069] Where, L eq2 When the three-phase grid-connected inverter and chopper multiplexing converter is used as the chopper circuit, the equivalent series inductance in the photovoltaic grid-connected equivalent circuit, r eq2 is the equivalent resistance of the photovoltaic grid-connected equivalent circuit when the three-phase grid-connected inverter and chopper multiplexing converter are used as the chopper circuit; i d2 is the loop current of each chopper circuit. Ideally, the currents in the three chopper circuits are equal, and the sum of the currents in the three chopper circuits is consistent with the output current of the photovoltaic cell at the user side; U PV is the photovoltaic cell voltage; U2 is the output voltage of the AC side of the three-phase grid-connected inverter and chopper multiplexing converter when the three-phase grid-connected inverter and chopper multiplexing converter is used as a chopper circuit. eq2 、r eq2 That is Leq2, Req2 in Figure 2(b).

[0070] Due to the modulation of the IGBT switch tube, the output voltage of the photovoltaic cell on the user side will maintain a ratio with the output voltage of the energy storage battery on the DC bus side, which is denoted as K. The voltage on the DC bus side is known to be U dl , then:

[0071] U2=KU dl (3)

[0072] From formula (2), we can get:

[0073]

[0074] It can be concluded that K can change the DC voltage and current, U PV with U dlThe ratio will affect the DC power regulation range. The IGBT regulation with multiplexing function can accurately control the size of K, so that the voltage at both ends of the multiplexing converter remains stable while realizing the flow of energy from the user side to the DC bus side. That is, by adjusting the size of the voltage transformation ratio K, the loop current i of each chopper circuit is changed. d2 , thereby changing the amount of power transmitted from the user side to the energy storage battery on the DC bus side; wherein the voltage transformation ratio K is used to reflect the change in the duty cycle of the control signal generated by the controller. d2 It is generally positive, so the energy is generally from the user's photovoltaic side to the DC bus to measure the energy storage battery.

[0075] 3) Inverter and chopper hybrid conversion mode

[0076] From the first two operating modes, we can know that the different regulation of the IGBT switch tube of the multiplexed converter can realize the inverter and chopping functions of the converter. When the modulation wave superposition of the inverter and chopping is adopted in the control circuit, it is reflected in the on-off state of the IGBT. Specifically, the simultaneous multiplexing of the inverter and chopping functions is realized by introducing the current control amount superposition operation in the control stage. That is, based on the voltage and current equation group shown in the above formula (1), the duty cycle of the control signal generated by the controller is adjusted to change the current moment i d 、i q and U d , U q The size of i based on the current moment d 、i q and U d , U q Calculate the active power transmitted by the line, and determine the energy flow between the grid side and the energy storage battery on the DC bus side according to the positive and negative active power transmitted by the line; at the same time, adjust the size of the voltage transformation ratio K to change the loop current i of each chopper circuit d2 , thereby changing the amount of electric energy transmitted from the user side to the energy storage battery on the DC bus side; in this way, the inverter and chopper hybrid conversion mode is realized at the same time.

[0077] Example 3

[0078] An embodiment of the present invention provides a controller, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the control method in the above-mentioned embodiment 2 when executing the computer program.

[0079] The relevant technical solutions are the same as above and will not be described again here.

[0080] Example 4

[0081] An embodiment of the present invention provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the control method in the above-mentioned embodiment 2 are implemented.

[0082] The relevant technical solutions are the same as above and will not be described again here.

[0083] Example 5

[0084] An embodiment of the present application provides a computer program product, including a computer program. When the computer program is run on a computer, the computer executes the steps of the control method in the above-mentioned embodiment 2.

[0085] The relevant technical solutions are the same as above and will not be described again here.

[0086] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A novel photovoltaic grid-connected circuit topology with an inverter and chopper multiplexed converter, characterized in that: include: High frequency zigzag transformers, photovoltaic cells, three-phase grid-connected inverters and chopper multiplexing converters and controllers; The high-frequency zigzag transformer includes a primary winding and a secondary winding connected in series; the power grid is connected in series between the primary winding and the secondary winding; the AC side of the three-phase grid-connected inverter and chopper multiplexing converter is connected to the secondary winding through the equivalent resistance of the grid line, and the DC side is connected to an external energy storage battery through a DC bus; the photovoltaic cell is connected between the ground terminal of the three-phase grid-connected inverter and chopper multiplexing converter and the ground terminal of the energy storage battery; and the three-phase grid-connected inverter and chopper multiplexing converter includes a three-phase full-bridge circuit composed of IGBT switch tubes Q1-Q6; The controller is used to control the on and off of the IGBT switch tubes Q1-Q6, so that when the electric energy is transmitted between the power grid and the energy storage battery, the power grid, the secondary winding, the three-phase full-bridge circuit and the energy storage battery form an inverter circuit; wherein the three-phase full-bridge circuit is used as an inverter to realize the inverter function; And / or, the controller is also used to control the on and off of the IGBT switch tubes Q1-Q6, so that when electric energy is transmitted from the photovoltaic cell to the energy storage battery, the photovoltaic cell, the high-frequency zigzag transformer, each phase arm of the three-phase full-bridge circuit and the energy storage battery constitute a chopper circuit; wherein each phase arm of the three-phase full-bridge circuit serves as a chopper circuit to perform chopping control on the current in the chopper circuit.

2. The novel photovoltaic grid-connected circuit topology according to claim 1 is characterized in that: A voltage-stabilizing capacitor is connected in parallel at both ends of the photovoltaic cell; and a voltage-stabilizing capacitor is connected in parallel at both ends of the energy storage battery.

3. The novel photovoltaic grid-connected circuit topology according to claim 1 or 2, characterized in that: The high frequency zigzag transformer also includes a magnetic column, and the corresponding phase coils of the primary side winding and the secondary side winding are reversely wound on the phase magnetic column so that the primary side winding and the secondary side winding form a series zigzag connection.

4. A novel control method for photovoltaic grid-connected circuit topology, characterized in that: The control method is applied to a controller in a novel photovoltaic grid-connected circuit topology according to any one of claims 1 to 3, comprising: Controlling the on and off of the IGBT switches Q1-Q6 so that when electric energy is transmitted between the power grid and the energy storage battery, the power grid, the secondary winding, the three-phase full-bridge circuit and the energy storage battery form an inverter circuit; wherein the three-phase full-bridge circuit works as an inverter in an inverter mode; And / or, the on and off of the IGBT switch tubes Q1-Q6 are also controlled so that when electric energy is transmitted from the photovoltaic cell to the energy storage battery, the photovoltaic cell, the high-frequency zigzag transformer, each phase arm of the three-phase full-bridge circuit and the energy storage battery form a chopper circuit; wherein each phase arm of the three-phase full-bridge circuit works as a chopper circuit in a chopper conversion mode.

5. The control method according to claim 4, characterized in that: When the three-phase full-bridge circuit works as an inverter in the inverter mode, the direction of electric energy transmission between the power grid and the energy storage battery is determined in the following manner: Based on the voltage and current equations satisfied by the equivalent circuit of the novel photovoltaic grid-connected circuit topology, the duty cycle of the control signal generated by the controller is adjusted to control the on and off of the IGBT switch tubes Q1-Q6, thereby changing the current moment i in the voltage and current equations. d 、i q and U d , U q The size of d 、i q are the d-axis and q-axis components of the inverter AC side current after dq transformation, U d , U q are respectively the d-axis and q-axis components of the AC side voltage of the inverter after dq transformation; Based on the current time i d 、i q and U d , U q The size of the line is used to calculate the active power transmitted by the line; the direction from the grid to the energy storage battery is set as i d 、i q In the positive direction, when the active power is positive, electric energy is transmitted from the grid to the energy storage battery, otherwise, electric energy is transmitted from the energy storage battery to the grid.

6. The control method according to claim 5, characterized in that: When the three-phase full-bridge circuit is used as a chopper circuit, the amount of electric energy transmitted from the photovoltaic cell to the energy storage battery is determined in the following manner: The voltage transformation ratio K is adjusted to control the on and off of the IGBT switch tubes Q1-Q6 to change the loop current i of each chopper circuit. d2 , thereby changing the amount of electrical energy transmitted from the photovoltaic cell to the energy storage battery; wherein the voltage transformation ratio K satisfies: Where U PV is the output voltage of the photovoltaic cell, U dl is the output voltage of the energy storage battery, r eq2 is the equivalent resistance of the equivalent circuit of the novel photovoltaic grid-connected circuit topology.

7. The control method according to claim 6, characterized in that: When the three-phase full-bridge circuit is used as an inverter and a chopper circuit at the same time, the three-phase full-bridge circuit operates in an inverter and chopper mixed conversion mode; at this time, based on the voltage and current equations satisfied by the equivalent circuit of the novel photovoltaic grid-connected circuit topology, the duty cycle of the control signal generated by the controller is adjusted, and the size of the voltage transformation ratio K is adjusted to control the on and off of the IGBT switch tubes Q1-Q6, thereby changing the i in the voltage and current equations at the current moment. d 、i q and U d , U q The size of each chopper circuit and the loop current i d2 ; Based on the current time i d 、i q and U d , U q The size of the line is used to calculate the active power transmitted by the line; the direction from the grid to the energy storage battery is set as i d 、i q In the positive direction, when the active power is positive, electric energy is transmitted from the power grid to the energy storage battery, otherwise, electric energy is transmitted from the energy storage battery to the power grid; According to the loop current i of each chopper circuit d2 , changing the amount of electrical energy transmitted from photovoltaic cells to energy storage batteries.

8. A controller, characterized in that: comprising a computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the control method described in any one of claims 4 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the control method according to any one of claims 4 to 7 is implemented.

10. A computer program product, characterized in that The invention comprises a computer program, which, when being executed on a computer, enables the computer to execute the control method according to any one of claims 4 to 7.

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