CN113067365A

CN113067365A - Direct-current coupling wind-solar complementary system and photovoltaic PID repair control method thereof

Info

Publication number: CN113067365A
Application number: CN202010001411.8A
Authority: CN
Inventors: 杨宗军; 邹绍琨; 张彦虎
Original assignee: Hefei Sungrow New Energy Technology Co Ltd
Current assignee: Hefei Sungrow New Energy Technology Co Ltd
Priority date: 2020-01-02
Filing date: 2020-01-02
Publication date: 2021-07-02

Abstract

The invention provides a direct-current coupling wind-solar complementary system and a photovoltaic PID repair control method thereof, wherein the system comprises: the system comprises a fan, a photovoltaic array, a PID (proportion integration differentiation) repair type DC/DC converter, a transformer, a machine side converter and a grid side converter; the PID repairing type DC/DC converter is used for switching from a normal power generation mode to a PID repairing mode when the electrical parameters of the photovoltaic array meet PID repairing conditions or a DC coupling wind-light complementary system receives a PID repairing instruction, and performing PID repairing on the photovoltaic array by using the voltage on the wind-power direct-current bus; the photovoltaic array and the fan photovoltaic complementary power generation are realized, meanwhile, the power generation influence of the PID effect on the photovoltaic array is reduced, and the neutral point voltage of the fan is prevented from being raised, so that the power generation capacity and the safety of the direct-current coupling wind-solar complementary system are improved.

Description

Direct-current coupling wind-solar complementary system and photovoltaic PID repair control method thereof

Technical Field

The invention belongs to the technical field of wind-solar hybrid construction, and particularly relates to a direct-current coupling wind-solar hybrid system and a photovoltaic PID (proportion integration differentiation) restoration control method thereof.

Background

Photovoltaic power generation and wind power generation are green electric energy which is mainly developed in China. China is a vast expanse, and in view of regional differences of wind energy and light energy, photovoltaic power stations and wind power generation fields are independently constructed and operated. However, due to the intermittent characteristics of wind energy and solar energy, when the night or cloudy day occurs, the solar energy cannot generate electricity or the generated energy is low, and at the moment, the wind speed may be very high, which is beneficial to wind power generation; when the weather is clear, the photovoltaic power generation is rapid, but the wind power generation is not necessarily strong; therefore, the wind energy and the solar energy have certain complementarity in the power generation angle, and the complementary application of the wind energy and the solar energy has value on the stability of a power grid. On the other hand, in order to fully exert wind and light resources, photovoltaic power stations and wind power plants in China are mostly built in northwest regions. The large-scale power station occupies more land resources, and because the fans are point land, gaps among the fans and peripheral areas are idle, if the fans are arranged above and the photovoltaic arrays are arranged below, and the fans and the photovoltaic arrays are combined together in space, more power generation units can be built in the same land area, and the land utilization rate is improved. Therefore, the wind power and photovoltaic space near complementary application has economic value.

Referring to fig. 1, a schematic diagram of a wind-solar hybrid system is shown, in which photovoltaic power and wind power are coupled on a direct current side, and a rear-stage device is shared, so that not only is the efficiency improved, but also the cost is lower. However, since the photovoltaic is coupled with the wind power system, some conventional photovoltaic problems cannot be handled according to conventional schemes, such as a typical PID (Potential Induced Degradation) repairing problem. The conventional PID repair scheme is an ac side virtual midpoint boost, or a dc side voltage boost. However, because the insulation grade of the fan is not matched with the insulation of the photovoltaic array, if the traditional scheme is used for carrying out voltage raising processing on the photovoltaic assembly in the scheme, the neutral point voltage of the fan is raised by more than half of the bus voltage; for a 1500V photovoltaic system, the neutral point voltage of a fan needs to be raised by more than 750V, the traditional fan cannot meet such a high voltage withstanding value at present, and the development and the use of the wind-solar hybrid system are limited.

Disclosure of Invention

In view of this, the present invention provides a dc-coupled wind-solar hybrid system and a photovoltaic PID repair control method thereof, so as to implement the photovoltaic array PID repair on the dc-coupled wind-solar hybrid system and avoid the increase of the neutral point voltage of the wind turbine.

The invention discloses a direct current coupling wind-solar complementary system in a first aspect, which comprises: the system comprises a fan, a photovoltaic array, a PID (proportion integration differentiation) repair type DC/DC converter, a transformer, a machine side converter and a grid side converter; wherein:

the alternating current side of the machine side converter is connected with the output end of the fan, and the direct current side of the machine side converter and the direct current side of the grid side converter are both connected with a wind power direct current bus;

the alternating current side of the grid-side converter is connected with a power grid through the transformer;

the input end of the PID repair type DC/DC converter is connected with the output end of the photovoltaic array, and the output end of the PID repair type DC/DC converter is connected with the wind power direct current bus;

the PID repairing type DC/DC converter is used for switching from a normal power generation mode to a PID repairing mode when the electrical parameters of the photovoltaic array meet PID repairing conditions or the direct current coupling wind-solar complementary system receives a PID repairing instruction, and performing PID repairing on the photovoltaic array by using the voltage on the wind power direct current bus.

Optionally, the PID repair type DC/DC converter includes: a DC/DC circuit;

the input end of the DC/DC circuit is used as the input end of the PID repairing type DC/DC converter, and the output end of the DC/DC circuit is used as the output end of the PID repairing type DC/DC converter;

the DC/DC circuit is a Buck circuit, a Boost circuit or a deformation circuit based on the Buck circuit or the Boost circuit.

Optionally, when the DC/DC circuit is a mirror image Boost circuit, if the electrical parameter of the photovoltaic array meets the PID repair condition, the mirror image Boost circuit disconnects the connection between itself and the negative electrode of the photovoltaic array by reversely stopping a diode arranged on the negative electrode branch of itself, and clamps the positive voltage of the photovoltaic array by the positive voltage on the wind power DC bus, so as to implement PID repair.

Optionally, when the DC/DC circuit is a mirror Buck circuit, the PID repair type DC/DC converter further includes: a switching power supply for taking power from the photovoltaic array;

if the electrical parameters of the photovoltaic array meet PID repair conditions, the mirror-image Buck circuit controls a switching tube arranged on a negative branch of the mirror-image Buck circuit to be disconnected through power failure of the switching power supply, so that the connection between the mirror-image Buck circuit and the negative electrode of the photovoltaic array is disconnected; and simultaneously, clamping the positive voltage of the photovoltaic array through the positive voltage on the wind power direct current bus to realize PID repair.

Optionally, if the DC/DC circuit is the Buck circuit, the PID repair type DC/DC converter further includes: a first controllable switch;

if the electrical parameters of the photovoltaic array meet PID repair conditions or the direct-current coupling wind-solar complementary system receives a PID repair instruction, the Buck circuit controls the connection between the Buck circuit and the negative electrode of the photovoltaic array to be disconnected through the first controllable switch, and meanwhile, the positive voltage on the wind power direct-current bus clamps the positive electrode of the photovoltaic array through the switch tube on the positive branch of the Buck circuit to achieve PID repair.

Optionally, the first controllable switch is disposed between a negative electrode of an input capacitor in the Buck circuit and a negative electrode of the photovoltaic array;

or the first controllable switch is arranged between the negative electrode of the input capacitor in the Buck circuit and the anode of the diode in the Buck circuit;

or, the first controllable switch is arranged between the negative electrode of the output capacitor in the Buck circuit and the anode of the diode in the Buck circuit.

Optionally, if the DC/DC circuit is the Boost circuit, the PID repair type DC/DC converter further includes: a second controllable switch and a third controllable switch; wherein:

if the electrical parameters of the photovoltaic array meet PID repair conditions or the direct-current coupling wind-solar complementary system receives a PID repair instruction, the Boost circuit controls the connection between the Boost circuit and the negative electrode of the photovoltaic array to be disconnected through the third controllable switch, and controls the Boost circuit to be connected with the positive electrode of the photovoltaic array through the second controllable switch, so that the positive voltage on the wind-power direct-current bus clamps the positive electrode of the photovoltaic array, and the PID repair is realized.

Optionally, the third controllable switch is disposed between a negative electrode of an input capacitor in the Boost circuit and a negative electrode of the photovoltaic array, or between the negative electrode of the input capacitor in the Boost circuit and one end of a switching tube in the Boost circuit, or between a negative electrode of an output capacitor in the Boost circuit and one end of a switching tube in the Boost circuit;

the second controllable switch is connected in parallel with a diode in the Boost circuit, or one end of the second controllable switch is connected with the anode of an input capacitor in the Boost circuit, and the other end of the second controllable switch is connected with the anode of an output capacitor in the Boost circuit.

Optionally, the method further includes: a controller and an auxiliary power supply;

the input end of the controller is connected with the output end of an electrical parameter detection device in the direct-current coupling wind-solar hybrid system so as to detect the electrical parameters of the photovoltaic array through the electrical parameter detection device, and the output end of the controller is connected with the control end of the PID repair type DC/DC converter;

the input end of the auxiliary power supply is connected with the wind power direct current bus, and the output end of the auxiliary power supply is connected with the power supply end of the controller.

Optionally, the first controllable switch, the second controllable switch and the third controllable switch are mechanical switches or electronic switches.

Optionally, the method further includes: a PID power supply;

one end of the PID power supply is connected with the negative electrode of the photovoltaic array, and the other end of the PID power supply is grounded.

The second aspect of the present invention discloses a photovoltaic PID repair control method for a dc-coupled wind-solar hybrid system, which is characterized in that a controller applied to the dc-coupled wind-solar hybrid system according to the first aspect of the present invention, comprises:

judging whether the electrical parameters of the photovoltaic array meet PID repair conditions or whether the direct-current coupling wind-solar complementary system receives a PID repair instruction;

if the electrical parameters of the photovoltaic array meet PID repair conditions or the direct-current coupling wind-solar complementary system receives a PID repair instruction, controlling a negative branch of a PID repair type DC/DC converter in the direct-current coupling wind-solar complementary system to be disconnected, and controlling the positive pole of the photovoltaic array to be clamped by the positive pole on a wind-power direct-current bus in the direct-current coupling wind-solar complementary system through a positive branch of the PID repair type DC/DC converter so as to realize PID repair;

and if the electrical parameters of the photovoltaic array do not meet the PID repair conditions and the direct-current coupling wind-solar complementary system does not receive the PID repair instruction, controlling the PID repair type DC/DC converter to be in a normal power generation mode.

Optionally, before determining whether the electrical parameter of the photovoltaic array satisfies the PID repairing condition, the method further includes:

detecting an electrical parameter of the photovoltaic array.

Optionally, judging whether the electrical parameter of the photovoltaic array meets the PID repairing condition includes:

judging whether the electrical parameters of the photovoltaic array are smaller than corresponding threshold values;

and if the electrical parameter of the photovoltaic array is smaller than the corresponding threshold value, determining that the electrical parameter of the photovoltaic array meets the PID repair condition, and if the electrical parameter of the photovoltaic array is larger than or equal to the corresponding threshold value, determining that the electrical parameter of the photovoltaic array does not meet the PID repair condition.

Optionally, the controlling the negative branch of the PID repair type DC/DC converter in the DC-coupled wind-solar hybrid system to be disconnected includes: controlling the switch on the negative branch to be switched off;

controlling the positive pole of the photovoltaic array to be clamped by the positive pole on the wind power direct current bus in the direct current coupling wind-solar complementary system through the positive pole branch of the PID repair type DC/DC converter, and the method comprises the following steps: controlling a switch on the positive branch to be closed, so that the positive voltage on the wind power direct current bus clamps the positive electrode of the photovoltaic array;

when the PID repair type DC/DC converter is a Boost circuit, the switch on the negative branch is a third controllable switch, and the switch on the positive branch is a second controllable switch; when the PID repair type DC/DC converter is a Buck circuit, the switch on the negative branch is a first controllable switch, and the switch on the positive branch is a switching tube in the Buck circuit.

From the above technical solution, the dc-coupled wind-solar hybrid system provided by the present invention includes: the system comprises a fan, a photovoltaic array, a PID (proportion integration differentiation) repair type DC/DC converter, a transformer, a machine side converter and a grid side converter; wherein: the wind power generation system comprises a machine side converter, a grid side converter, a PID (proportion integration differentiation) repair type DC/DC converter, a wind power direct current bus, a transformer, a PID (proportion integration differentiation) repair type wind-solar hybrid system and a wind power direct current bus, wherein the alternating current side of the machine side converter is connected with the output end of a fan, the direct current side of the machine side converter and the direct current side of the grid side converter are connected with the wind power direct current bus, the alternating current side of the grid side converter is connected with a power grid through the transformer, the input end of the PID repair type DC/DC converter is connected with the output end of a photovoltaic array, the output end of the PID repair type DC/DC converter is connected with the; the photovoltaic array and the fan photovoltaic complementary power generation are realized, meanwhile, the power generation influence of the PID effect on the photovoltaic array is reduced, and the neutral point voltage of the fan is prevented from being raised, so that the power generation capacity and the safety of the direct-current coupling wind-solar complementary system are improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic diagram of a wind-solar hybrid system provided by the prior art;

FIG. 2 is a schematic diagram of a DC-coupled wind-solar hybrid system provided by an embodiment of the invention;

FIG. 3 is a schematic diagram of another DC-coupled wind-solar hybrid system provided by an embodiment of the invention;

FIG. 4 is a schematic diagram of another DC-coupled wind-solar hybrid system provided by an embodiment of the invention;

FIG. 5 is a schematic diagram of another DC-coupled wind-solar hybrid system provided by an embodiment of the invention;

FIG. 6 is a schematic diagram of another DC-coupled wind-solar hybrid system provided by an embodiment of the invention;

FIG. 7 is a schematic diagram of another DC-coupled wind-solar hybrid system provided by an embodiment of the invention;

fig. 8 is a schematic diagram of a photovoltaic PID repair control method of a dc-coupled wind-solar hybrid system according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The embodiment of the invention provides a direct-current coupling wind-solar hybrid system, which aims to solve the problem that the development and the use of a wind-solar hybrid system are limited because a photovoltaic array cannot be subjected to PID (proportion integration differentiation) repair in the traditional wind-solar hybrid system.

The direct-current coupling wind-solar hybrid system, as shown in fig. 2, includes: a wind turbine, a photovoltaic array, a PID repair type DC/DC converter, a transformer, a machine side converter (such as AC/DC shown in figure 2) and a grid side converter (such as DC/AC shown in figure 2); wherein:

the alternating current side of the machine side converter is connected with the output end of the fan, and the direct current side of the machine side converter and the direct current side of the grid side converter are both connected with a wind power direct current bus; and the alternating current side of the grid-side converter is connected with a power grid through a transformer.

Specifically, the machine side converter comprises at least one rectifying module, and the rectifying module is used for rectifying alternating current output by the fan into direct current and outputting the rectified direct current to the wind power direct current bus. The grid-side converter comprises at least one inversion module, and is used for converting direct current on the wind power direct current bus into alternating current, namely converting the power generation electric energy of the fan, and outputting the converted alternating current to the transformer so as to enable the transformer to output the alternating current to a power grid after voltage rising/dropping.

The input end of the PID repairing type DC/DC converter is connected with the output end of the photovoltaic array, and the output end of the PID repairing type DC/DC converter is connected with the wind power direct current bus. Specifically, the PID repair type DC/DC converter may include a plurality of DC/DC conversion circuits therein, input ends of which are respectively connected to corresponding photovoltaic strings in the photovoltaic array, and output ends of which are connected in parallel.

The operation of the PID repair type DC/DC converter is divided into two modes: a normal power generation mode and a PID repair mode. The PID repairing type DC/DC converter is used for switching from a normal power generation mode to a PID repairing mode when the electrical parameters of the photovoltaic array meet PID repairing conditions or a direct current coupling wind-light complementary system receives a PID repairing instruction, and performing PID repairing on the photovoltaic array by using the voltage on the wind power direct current bus.

It should be noted that, at night/cloudy day, the photovoltaic array cannot generate electricity or the power generation amount is low, and as long as there is wind, the fan continues to generate electricity. Therefore, in general, when the photovoltaic power generation requirement is not satisfied but the wind power generation requirement is satisfied at night or on cloudy days, the fan continues to generate power, and the photovoltaic array stops generating power. That is to say, the wind power dc bus is kept in the powered state at night/cloudy day, the voltage of the conventional wind power dc bus is about 1050V, and the voltage of the anode of the conventional wind power dc bus is about +500V to the ground.

Specifically, when the PID repair type DC/DC converter is in a normal power generation mode, the PID repair type DC/DC converter converts the direct current of the photovoltaic array into a direct current having the same voltage as the wind power direct current bus, and outputs the converted direct current to the wind power direct current bus, so that the grid-side converter also converts the generated electric energy of the photovoltaic array, and the converted alternating current is output to the transformer, so that the transformer performs voltage conversion and outputs the converted alternating current to the power grid.

When the PID repairing type DC/DC converter is in a PID repairing mode, if the PID repairing type DC/DC converter is in a night/cloudy day, direct current conversion is not carried out, namely direct current is not output to a wind power direct current bus, a negative branch of the PID repairing type DC/DC converter is disconnected, a positive branch of the PID repairing type DC/DC converter is connected with the wind power direct current bus, at the moment, common-mode voltage of the positive pole of a photovoltaic assembly to the ground in the photovoltaic array can be automatically clamped to positive-pole voltage of the wind power direct current bus by the wind power direct current bus, namely the common-mode voltage of the positive pole of the photovoltaic assembly to the ground is larger than 0, and then PID repairing is carried out on the photovoltaic array by the voltage on the wind power direct current bus so.

That is, in the normal power generation mode, the power generation electric energy of the fan and the photovoltaic array is output to the power grid, so that economic benefit is realized; in the PID repairing mode, only the generated electric energy of the fan is output to the power grid, and part of the generated electric energy of the fan is used for performing PID repairing on the photovoltaic array.

In the embodiment, when photovoltaic complementary power generation of the photovoltaic array and the fan is realized, the influence of the PID effect on the power generation of the photovoltaic array can be reduced through the electric energy on the wind power direct current bus, and the rise of the neutral point voltage of the fan is avoided, so that the power generation amount and the safety of the direct current coupling wind-solar complementary system are improved.

It is also worth mentioning that a photovoltaic array repair method suitable for a photovoltaic system is proposed in the prior art. Specifically, a switch is added to the negative electrode of the direct current side of the inverter, and the switch is turned off when the inverter needs to be repaired, but in the scheme, the inverter needs to reversely provide extra direct current voltage when the inverter needs to be repaired, and the extra direct current voltage is generally obtained by alternating current rectification, so that the voltage is lower, and the repairing effect is poorer.

In the embodiment, a PID repair type DC/DC converter is arranged between the grid-side converter and the photovoltaic array, so that during a PID repair mode, voltage on the wind power direct current bus is used for PID repair, the voltage on the wind power direct current bus is higher, and the repair effect is better.

Optionally, in an embodiment of the present invention, the PID repair type DC/DC converter includes a DC/DC circuit.

The input end of the DC/DC circuit is used as the input end of the PID repair type DC/DC converter and is connected with the output end of the photovoltaic array, and the output end of the DC/DC circuit is used as the output end of the PID repair type DC/DC converter and is connected with the wind power direct current bus.

The DC/DC circuit is a Buck circuit or a Boost circuit, or a variant circuit based on the Buck circuit or the Boost circuit, such as a mirror Buck circuit and a mirror Boost circuit. The Buck circuit refers to a conventional Buck circuit which is formed by arranging an inductor on a positive branch, the Boost circuit refers to a conventional Boost circuit which is formed by arranging the inductor on the positive branch, the mirror image Buck circuit refers to a circuit which is formed by arranging the inductor on a negative branch and is in a mirror image structure with the conventional Buck circuit, and the mirror image Boost circuit refers to a circuit which is formed by arranging the inductor on the negative branch and is in a mirror image structure with the conventional Boost circuit. Here, the DC/DC circuits are respectively explained as a Buck circuit, a Boost circuit, a mirror Buck circuit, and a mirror Boost circuit one by one.

(1) Referring to fig. 3, the DC/DC circuit is a mirror Boost circuit including: first input capacitor Cin1, first output capacitor Cout1, first inductor L1, first diode D1 and first switch tube Q1, wherein:

the positive electrode and the negative electrode of the first input capacitor Cin1 are respectively used as the positive electrode and the negative electrode of the input end of the mirror image Boost circuit; the positive electrode and the negative electrode of the first output capacitor Cout1 are respectively used as the positive electrode and the negative electrode of the output end of the mirror Boost circuit; one end of the first inductor L1 is connected to the anode of the first input capacitor Cin1, and the other end is connected to the cathode of the first diode D1 and one end of the first switch Q1, respectively; the anode of the first diode D1 is connected to the cathode of the first output capacitor Cout 1; the other end of the first switch Q1 is connected to the anode of the first input capacitor Cin1 and the anode of the first output capacitor Cout1, respectively.

If the electrical parameters of the photovoltaic array meet the PID repair conditions, the mirror image Boost circuit cuts off the connection between the mirror image Boost circuit and the negative electrode of the photovoltaic array through the reverse cutoff of a first diode D1 arranged on the negative electrode branch of the mirror image Boost circuit, and clamps the positive voltage of the photovoltaic array through the positive voltage on the wind power direct current bus to realize PID repair; if the electrical parameters of the photovoltaic array do not meet the PID repair conditions, the mirror image Boost circuit is conducted in the forward direction through a first diode D1 arranged on a negative branch of the mirror image Boost circuit to enable the negative electrode of the wind power direct current bus to be connected with the negative electrode of the photovoltaic array, and therefore the power generation electric energy of the photovoltaic array is output to the wind power direct current bus.

That is to say, the photovoltaic array generates power automatically during the daytime, when the photovoltaic array cannot generate power at night, that is, the output end of the photovoltaic array is dead or the output voltage is low, the mirror image Boost circuit stops working due to the reverse cutoff of the first diode D1, and at this time, the positive electrode voltage on the wind power direct current bus is clamped to a level greater than 0 automatically because the positive electrode voltage on the wind power direct current bus is still connected to the wind power direct current bus.

In the embodiment, the characteristic of the mirror image Boost circuit is utilized, the PID repairing function can be automatically carried out, and the circuit cost is low.

(2) Referring to fig. 4 (the blower, the transformer, the machine-side converter, and the grid-side converter are not shown in fig. 4), when the DC/DC circuit is a mirror Buck circuit, the PID repair-type DC/DC converter further includes: follow switching power supply of getting electricity of photovoltaic array, mirror image Buck circuit includes: a second input capacitor Cin2, a second output capacitor Cout2, a second inductor L2, a second diode D2, and a second switch Q2, wherein:

the positive electrode and the negative electrode of the second input capacitor Cin2 are used as the positive electrode and the negative electrode of the input end of the mirror Buck circuit; the positive and negative electrodes of the second output capacitor Cout2 are used as the positive and negative electrodes of the output end of the mirror Buck circuit; one end of the second inductor L2 is connected to the negative electrode of the second output capacitor Cout2, and the other end of the second inductor L2 is connected to one end of the second switch Q2 and the anode of the second diode D2, respectively; the other end of the second switching tube Q2 is connected with the negative electrode of the second input capacitor Cin 2; the cathode of the second diode D2 is connected to the anode of the second input capacitor Cin2 and the anode of the second output capacitor Cout2, respectively.

One end of the switching power supply is connected with the output end of the photovoltaic array so as to take electricity from the photovoltaic array; the other end of the switching power supply is connected to the control end of the second switching tube Q2, and supplies power to the second switching tube Q2 to keep it in a closed state.

If the electrical parameters of the photovoltaic array meet the PID repair conditions, the mirror Buck circuit controls a second switching tube Q2 arranged on the negative branch of the mirror Buck circuit to be disconnected through the power failure of the switching power supply, so that the connection between the mirror Buck circuit and the negative electrode of the photovoltaic array is disconnected; meanwhile, the positive voltage of the photovoltaic array is clamped through the positive voltage on the wind power direct current bus so as to realize PID repair; if the electrical parameters of the photovoltaic array do not meet the PID repair conditions, the mirror-image Buck circuit controls a second switching tube Q2 arranged on a negative branch of the mirror-image Buck circuit to be closed through electrifying the switching power supply, so that the mirror-image Buck circuit is connected with the negative electrode of the photovoltaic array, and the generated electric energy of the photovoltaic array is output to a wind power direct current bus.

That is to say, when the photovoltaic array can generate electricity during the daytime, the switching power supply takes electricity from the photovoltaic array and drives the second switching tube Q2 to be conducted, and at the moment, the mirror-image Buck circuit keeps a normal power generation mode. At night, when the output voltage of the photovoltaic array is low, the switching power supply is automatically powered off, and the second switching tube Q2 is automatically switched off when power is lost, so that the mirror Buck circuit can automatically enter a PID repair mode. In the embodiment, the output voltage of the photovoltaic array is used as a driving signal to drive the second switching tube Q2, so that the circuit cost is reduced.

(3) Referring to fig. 5 (the blower, the transformer, the machine-side converter, and the grid-side converter are not shown in fig. 5), if the DC/DC circuit is a Buck circuit, the PID repair-type DC/DC converter further includes: a first controllable switch K1; the Buck circuit includes: a fourth input capacitor Cin4, a fourth output capacitor Cout4, a fourth inductor L4, a fourth diode D4, and a fourth switching tube Q4, wherein:

the positive electrode and the negative electrode of the fourth input capacitor Cin4 are used as the positive electrode and the negative electrode of the input end of the Buck circuit; the positive and negative electrodes of the fourth output capacitor Cout4 are used as the positive and negative electrodes of the output end of the Buck circuit; one end of a fourth inductor L4 is connected to the anode of the fourth output capacitor Cout4, and the other end of the fourth inductor L4 is connected to one end of a fourth switch Q4 and the cathode of the fourth diode D4, respectively; the other end of the fourth switching tube Q4 is connected with the negative electrode of the fourth input capacitor Cin 4; the anode of the fourth diode D4 is connected to the cathode of the fourth input capacitor Cin4 and the cathode of the fourth output capacitor Cout4, respectively.

In practical applications, the first controllable switch K1 has various connection relationships. One connection relationship is: the first controllable switch K1 is disposed between the cathode of the fourth input capacitor Cin4 and the cathode of the photovoltaic array in the Buck circuit, that is, one end of the first controllable switch K1 is connected to the cathode of the fourth input capacitor Cin4, and the other end of the first controllable switch K1 is connected to the cathode of the photovoltaic array (as shown in fig. 5). The other connection relation is as follows: the first controllable switch K1 is disposed between the cathode of the fourth input capacitor Cin4 in the Buck circuit and the anode of the fourth diode D4 in the Buck circuit, that is, one end of the first controllable switch K1 is connected to the cathode of the fourth input capacitor Cin4, and the other end of the first controllable switch K1 is connected to the anode of the fourth diode D4 (not shown). Another connection relationship is: the first controllable switch K1 is disposed between the cathode of the fourth output capacitor Cout4 in the Buck circuit and the anode of the fourth diode D4 in the Buck circuit, that is, one end of the first controllable switch K1 is connected to the cathode of the fourth output capacitor Cout4, and the other end of the first controllable switch K1 is connected to the anode of the fourth diode D4 (not shown).

If the electrical parameters of the photovoltaic array meet the PID repair conditions or the direct-current coupling wind-solar hybrid system receives a PID repair instruction, the Buck circuit is disconnected through the first controllable switch K1 to control the connection between the Buck circuit and the negative electrode of the photovoltaic array, and meanwhile, the fourth switch tube Q4 on the positive branch of the Buck circuit is closed to clamp the positive electrode voltage on the wind-power direct-current bus to the positive electrode of the photovoltaic array, so that the PID repair is achieved. However, if the electrical parameters of the photovoltaic array do not meet the PID repair conditions and the dc-coupled photovoltaic complementary system does not receive the PID repair instruction, the Buck circuit controls itself to be connected to the negative electrode of the photovoltaic array by closing the first controllable switch K1, and executes corresponding actions by the fourth switch Q4 on the positive branch of itself, so as to output the generated electrical energy of the photovoltaic array to the wind power dc bus.

In practical applications, the PID repair type DC/DC converter may further include a fourth controllable switch (not shown); one end of the fourth controllable switch is connected to the positive electrode of the fourth input capacitor Cin4, and the other end is connected to the positive electrode of the fourth output capacitor Cout 4. When the electrical parameters of the photovoltaic array meet the PID repair condition or the direct-current coupling wind-solar complementary system receives a PID repair instruction, controlling the fourth controllable switch to be closed so that the positive voltage on the wind-power direct-current bus clamps the positive electrode of the photovoltaic array, and simultaneously reducing (under the condition that the fourth switch tube Q4 is also closed) or avoiding (under the condition that the fourth switch tube Q4 is disconnected) the loss on the fourth inductor L4; and when the electrical parameters of the photovoltaic array meet the PID repair conditions and the direct-current coupling wind-solar complementary system receives a PID repair instruction, controlling the fourth controllable switch to be switched off.

(4) Referring to fig. 6 (the wind turbine, the transformer, the machine-side converter, and the grid-side converter are not shown in fig. 6), if the DC/DC circuit is a Boost circuit, the PID repair-type DC/DC converter further includes: a second controllable switch K2 and a third controllable switch K3; a Boost circuit comprising: a third input capacitor Cin3, a third output capacitor Cout3, a third inductor L3, a third diode D3 and a third switching tube Q3; wherein:

two ends of the third input capacitor Cin3 are respectively used as the positive electrode and the negative electrode of the input end of the Boost circuit; the positive electrode and the negative electrode of the third output capacitor Cout3 are used as the positive electrode and the negative electrode of the output end of the Boost circuit; one end of the third inductor L3 is connected to the anode of the third input capacitor Cin3, and the other end is connected to the anode of the third diode D3 and one end of the third switching tube Q3, respectively; the cathode of the third diode D3 is connected to the anode of the third output capacitor Cout 3; the other end of the third switching tube Q3 is connected to the cathode of the third input capacitor Cin3 and the cathode of the third output capacitor Cout3, respectively.

In practical applications, the third controllable switch K3 has various connection relationships. Specifically, one connection relationship is: the third controllable switch K3 is disposed between the negative electrode of the third input capacitor Cin3 in the Boost circuit and the negative electrode of the photovoltaic array, that is, one end of the third controllable switch K3 is connected to the negative electrode of the third input capacitor Cin3, and the other end of the third controllable switch K3 is connected to the negative electrode of the photovoltaic array (as shown in fig. 6). The other connection relation is as follows: the third controllable switch K3 is disposed between a negative electrode of the third input capacitor Cin3 in the Boost circuit and one end of the third switching tube Q3 in the Boost circuit, that is, one end of the third controllable switch K3 is connected to the negative electrode of the third input capacitor Cin3, and the other end of the third controllable switch K3 is connected to one end of the third switching tube Q3 (not shown). Another connection relationship is: the third controllable switch K3 is disposed between a negative electrode of the third output capacitor Cout3 in the Boost circuit and one end of a third switching tube Q3 in the Boost circuit, that is, one end of the third controllable switch K3 is connected to the negative electrode of the third output capacitor Cout3, and the other end of the third controllable switch K3 is connected to one end of the third switching tube Q3 (not shown).

The second controllable switch K2 also has various connection relationships, such as the second controllable switch K2 is connected in parallel with the third diode D3 in the Boost circuit (not shown); alternatively, one end of the second controllable switch K2 is connected to the positive electrode of the third input capacitor Cin3 in the Boost circuit, and the other end of the second controllable switch K2 is connected to the positive electrode of the third output capacitor Cout3 in the Boost circuit (as shown in fig. 6).

If the electrical parameters of the photovoltaic array meet PID repair conditions or the direct-current coupling wind-solar complementary system receives a PID repair instruction, the Boost circuit controls the connection between the Boost circuit and the negative electrode of the photovoltaic array to be disconnected by disconnecting the third controllable switch K3, and controls the Boost circuit to be connected with the positive electrode of the photovoltaic array by closing the second controllable switch K2, so that the positive voltage on the wind-power direct-current bus clamps the positive electrode of the photovoltaic array, and the PID repair is realized. However, if the electrical parameters of the photovoltaic array do not meet the PID repair conditions and the dc-coupled photovoltaic complementary system does not receive the PID repair instruction, the Boost circuit is controlled to connect with the negative electrode of the photovoltaic array by closing the third controllable switch K3, and is also controlled to disconnect with the second controllable switch K2 on the positive branch of the Boost circuit, so as to output the generated electrical energy of the photovoltaic array to the wind power dc bus.

It should be further noted that, in the prior art scheme in which a switch is added to the negative electrode of the DC side of the inverter, the scheme is only applicable to a conventional single-stage inverter, and for an inverter with a DC/DC link, due to the existence of devices such as diodes, a common-mode voltage cannot be effectively established, and the inverter has limitations and cannot reliably operate to reduce the safety of a circuit.

In the embodiment, on the basis of a conventional DC/DC circuit, a parallel controllable switch is additionally provided for a diode branch on an anode branch of the DC/DC circuit, and the controllable switch is controlled to be closed to enable the diode to be in short circuit; or the diode is placed on the negative electrode branch circuit of the diode, so that the diode is cut off reversely and is automatically disconnected, the problem that the common-mode voltage cannot be effectively established and the limitation exists is solved, and the circuit can work safely and reliably.

In practical applications, the first controllable switch K1, the second controllable switch K2, the third controllable switch K3 and the fourth controllable switch are mechanical switches or electronic switches, and specifically, the first to fourth controllable switches may be Insulated Gate Bipolar Transistors (IGBTs) or relays. Preferably a mechanical switch with a smaller on-resistance and a larger off-resistance.

Optionally, referring to fig. 5 as well, the dc-coupled wind-solar hybrid system further includes: a controller and an auxiliary power supply.

The input end of the controller is connected with the output end of an electrical parameter detection device in the direct-current coupling wind-solar complementary system so as to detect the electrical parameters of the photovoltaic array through the electrical parameter detection device, and the output end of the controller is connected with the control end of the PID repair type DC/DC converter, namely the output end of the controller is respectively connected with the control ends of the first controllable switch K1 and the fourth switch Q4; in addition, the controller can be further provided with a communication terminal for receiving the PID repairing instruction. The input end of the auxiliary power supply is connected with the wind power direct current bus, the output end of the auxiliary power supply is connected with the power supply end of the controller, namely, the power taking mode of the auxiliary power supply is that power is taken from the wind power direct current bus, so that power cannot be cut off in night/cloudy days, and power supply of the controller is not influenced, namely, the power supply can be controlled at night.

The controller may be a controller in the PID repair type DC/DC converter, or may be a system controller, and is not particularly limited herein, and may be any controller as appropriate, and is within the scope of the present application. The electrical parameters may be output voltage, output power, output current, and the like of the photovoltaic array, and are not particularly limited herein and are within the scope of the present application.

Of course, on the basis of fig. 6, the dc-coupled wind-solar hybrid system may also include: the specific connection relationship between the controller and the auxiliary power supply is similar to that shown in fig. 5, and is not described in detail herein.

The operation principle is described as follows by taking fig. 6 as an example:

when the electrical parameter detected by the controller through the electrical parameter detection device is smaller than the corresponding threshold value or an external PID repair instruction is received, the third controllable switch K3 (or the first controllable switch K1 in fig. 5) is controlled to be switched off, and simultaneously the second controllable switch K2 (or the fourth switch tube Q4 in fig. 5) is controlled to be switched on, so that the positive electrode of the photovoltaic array is connected with the positive electrode of the wind power direct current bus, and PID repair is achieved.

If a fourth controllable switch is further included on the basis of fig. 5, when the electrical parameter detected by the controller through the electrical parameter detection device is smaller than the corresponding threshold value or an external PID repair command is received, the first controllable switch K1 is controlled to be opened, and the fourth controllable switch is controlled to be closed.

It should be noted that, the repair is performed through an external PID repair instruction to be an active repair, that is, the repair is actively switched between two modes, the repair is performed through an electrical parameter to be an automatic repair, and an active repair and/or a self-repair mode can be selected according to actual conditions, which is not specifically limited herein and is within the protection scope of the present application.

Optionally, on the basis of fig. 2 to fig. 6 in the embodiment of the present invention described above, referring to fig. 7 (shown as an example on the basis of fig. 6), the dc-coupled wind-solar hybrid system further includes: and a PID power supply.

In the embodiment, the common-mode voltage of the system can be further raised in a safe range by arranging the PID power supply at the negative electrode of the photovoltaic array, so that the PID repairing effect of the photovoltaic array is improved; the voltage of the PID power supply may be determined according to actual conditions, and is not specifically limited herein, and is within the scope of the present application.

In the implementation of the invention, various PID repair type DC/DC converters are provided, compared with an isolated DC/DC circuit, the cost is lower, even 0 hardware cost is increased, the influence on the conversion efficiency of a network side converter is reduced, the problem of PID repair of a photovoltaic array in a direct current coupling wind-solar complementary system is solved, and the PID repair type DC/DC converter is suitable for various types of DC/DC circuits and has wide adaptability.

The embodiment of the invention provides a photovoltaic PID repair control method of a direct-current coupling wind-solar complementary system, which is applied to a controller of the direct-current coupling wind-solar complementary system in any one of the embodiments of FIGS. 2 and 5 to 7, wherein the controller can be a system controller or a controller in a PID repair type DC/DC converter. For the specific structure of the direct-current coupling wind-solar hybrid system, reference is made to the above embodiments, and details are not repeated here.

The photovoltaic PID repair control method of the direct-current coupling wind-solar hybrid system, referring to fig. 8, includes:

s101, judging whether the electrical parameters of the photovoltaic array meet PID repair conditions or whether the direct-current coupling wind-solar hybrid system receives a PID repair instruction.

Before the step S101 of determining whether the electrical parameter of the photovoltaic array satisfies the PID repairing condition, the method further includes: an electrical parameter of the photovoltaic array is detected. The electrical parameter may be output voltage, output power and output current of the photovoltaic array, and the electrical parameter includes at least one of the output voltage, the output power and the output current.

In practical application, the specific process of judging whether the electrical parameters of the photovoltaic array meet the PID repairing conditions is as follows: and judging whether the electrical parameters of the photovoltaic array are smaller than corresponding threshold values.

Specifically, if the electrical parameter includes an output voltage, it is determined whether the output voltage of the photovoltaic array is less than a voltage threshold, such as 100V. If the electrical parameters comprise output voltage, output power and output current, whether the output voltage of the photovoltaic array is smaller than a voltage threshold value, whether the output power is smaller than a power threshold value and whether the output current is smaller than a current threshold value are judged. Certainly, when the electrical parameters include other parameters, the process of determining whether the electrical parameters of the photovoltaic array are smaller than the corresponding threshold values is similar to that described above, and is not repeated here one by one, and is all within the protection scope of the present application. The electrical parameters are not specifically limited, either, and are within the scope of the present application, as the case may be.

If the electrical parameters of the photovoltaic array are smaller than the corresponding threshold values, judging that the electrical parameters of the photovoltaic array meet the PID repair conditions, and executing the step S102; if the electrical parameter of the photovoltaic array is greater than or equal to the corresponding threshold value, it is determined that the electrical parameter of the photovoltaic array does not satisfy the PID repair condition, i.e., step S103 is executed.

S102, controlling a negative pole branch of a PID (proportion integration differentiation) repair type DC/DC converter in the direct-current coupling wind-solar complementary system to be disconnected, and controlling the positive pole of the photovoltaic array to be clamped by the positive pole of a wind power direct-current bus in the direct-current coupling wind-solar complementary system through the positive pole branch of the PID repair type DC/DC converter so as to realize PID repair.

In practical application, the specific process of controlling the negative branch of the PID repair type DC/DC converter in the DC-coupled wind-solar hybrid system to be disconnected in step S102 is as follows: and controlling the switch on the negative branch to be switched off. The specific process of controlling the positive pole of the photovoltaic array to be clamped by the positive pole on the wind power direct current bus in the direct current coupling wind-solar hybrid system through the positive pole branch of the PID repair type DC/DC converter related to the step S102 is as follows: and controlling the switch on the positive branch to be closed, so that the positive voltage on the wind power direct current bus clamps the positive electrode of the photovoltaic array.

Referring to fig. 6, when the PID repair type DC/DC converter is a Boost circuit, the switch on the negative branch is the third controllable switch K3, and the switch on the positive branch is the second controllable switch K2. Referring to fig. 5, when the PID repair type DC/DC converter is a Buck circuit, the switch on the negative branch is the first controllable switch K1, and the switch on the positive branch is the fourth switching tube Q4 in the Buck circuit. Or, when the PID repair type DC/DC converter includes a Buck circuit and a fourth controllable switch, the switch on the negative branch is the first controllable switch K1, and the switch on the positive branch is the fourth controllable switch.

And S103, controlling the PID repair type DC/DC converter to be in a normal power generation mode.

When the PID repair type DC/DC converter is in a normal power generation mode, the PID repair type DC/DC converter converts direct current of a photovoltaic array into high-voltage/low-voltage direct current, outputs the converted direct current to a wind power direct current bus in a direct current coupling wind-solar complementary system, so that a grid-side converter in the direct current coupling wind-solar complementary system converts power generation electric energy of the photovoltaic array and a fan, and outputs the converted alternating current to a transformer in the direct current coupling wind-solar complementary system for the transformer to perform voltage rising/falling and then output to a power grid.

In the embodiment, whether the PID repairing type DC/DC converter needs to enter the PID repairing mode is determined through the electrical parameters of the photovoltaic array and the PID repairing instruction, and the PID repairing type DC/DC converter is controlled to enter the PID repairing mode simply, so that the popularization and the use are facilitated.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A DC-coupled wind-solar hybrid system, comprising: the system comprises a fan, a photovoltaic array, a potential induced attenuation PID (proportion integration differentiation) repair type DC/DC converter, a transformer, a machine side converter and a network side converter; wherein:

2. The DC-coupled wind-solar hybrid system according to claim 1, wherein the PID repair type DC/DC converter comprises: a DC/DC circuit;

3. The direct-current coupling wind-solar hybrid system according to claim 2, wherein when the DC/DC circuit is a mirror-image Boost circuit, if the electrical parameter of the photovoltaic array meets the PID repair condition, the mirror-image Boost circuit disconnects the connection between itself and the negative electrode of the photovoltaic array by reverse blocking of a diode arranged on the negative electrode branch of itself, and clamps the positive voltage of the photovoltaic array by the positive voltage on the wind-power direct-current bus to realize PID repair.

4. The DC-coupled wind-solar hybrid system according to claim 2, wherein when the DC/DC circuit is a mirror Buck circuit, the PID repair type DC/DC converter further comprises: a switching power supply for taking power from the photovoltaic array;

5. The DC-coupled wind-solar hybrid system according to claim 2, wherein if the DC/DC circuit is the Buck circuit, the PID repair type DC/DC converter further comprises: a first controllable switch;

6. The DC-coupled wind-solar hybrid system according to claim 5, wherein the first controllable switch is arranged between the negative electrode of the input capacitor in the Buck circuit and the negative electrode of the photovoltaic array;

7. The direct-current coupling wind-solar hybrid system according to claim 2, wherein if the DC/DC circuit is the Boost circuit, the PID repair-type DC/DC converter further comprises: a second controllable switch and a third controllable switch; wherein:

8. The direct-current coupling wind-solar hybrid system according to claim 7, wherein the third controllable switch is arranged between a negative electrode of an input capacitor in the Boost circuit and a negative electrode of the photovoltaic array, or between a negative electrode of an input capacitor in the Boost circuit and one end of a switching tube in the Boost circuit, or between a negative electrode of an output capacitor in the Boost circuit and one end of a switching tube in the Boost circuit;

9. The DC-coupled wind-solar hybrid system according to any one of claims 5-8, further comprising: a controller and an auxiliary power supply;

10. The DC-coupled wind-solar hybrid system according to any one of claims 6-8, wherein the first controllable switch, the second controllable switch and the third controllable switch are mechanical switches or electronic switches.

11. The DC-coupled wind-solar hybrid system according to any one of claims 1-8, further comprising: a PID power supply;

12. A photovoltaic PID repair control method of a direct current coupling wind-solar complementary system is characterized in that a controller applied to the direct current coupling wind-solar complementary system as claimed in any one of claims 1, 2, 5-11 comprises the following steps:

13. The photovoltaic PID repair control method of the DC-coupled wind-solar hybrid system according to claim 12, further comprising, before determining whether the electrical parameter of the photovoltaic array satisfies the PID repair condition:

detecting an electrical parameter of the photovoltaic array.

14. The photovoltaic PID repair control method of the DC-coupled wind-solar hybrid system according to claim 12, wherein judging whether the electrical parameters of the photovoltaic array satisfy PID repair conditions comprises:

15. The photovoltaic PID repair control method of the DC-coupled wind-solar hybrid system according to any one of claims 12 to 14, wherein controlling the negative branch of the PID repair type DC/DC converter in the DC-coupled wind-solar hybrid system to be disconnected comprises: controlling the switch on the negative branch to be switched off;