WO2022100123A1

WO2022100123A1 - Direct-current converter topology circuit and control method therefor, and inverter system

Info

Publication number: WO2022100123A1
Application number: PCT/CN2021/105760
Authority: WO
Inventors: 俞贤桥; 黄猛; 王京; 陈宁宁; 肖尊辉; 杨博
Original assignee: 珠海格力电器股份有限公司
Priority date: 2020-11-13
Filing date: 2021-07-12
Publication date: 2022-05-19
Also published as: CN112271925A

Abstract

A direct-current converter topology circuit and a control method therefor, and an inverter system. The direct-current converter topology circuit comprises a working circuit connected at two ends of a photovoltaic array, the working circuit having a Boost working mode and a Buck working mode, wherein when an input voltage of the photovoltaic array is less than or equal to a direct-current bus voltage, the working circuit enters the Boost working mode to increase the input voltage, and when the input voltage of the photovoltaic array is greater than the direct-current bus voltage, the working circuit enters the Buck mode to decrease the input voltage.

Description

DC converter topology circuit and its control method, inverter system

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on the CN application number 202011270674.5 and the filing date is Nov. 13, 2020, and claims its priority. The disclosure of the CN application is hereby incorporated into the present application as a whole.

technical field

The present disclosure relates to the field of photovoltaic power generation, in particular to a DC converter topology circuit, a control method thereof, and an inverter system.

Background technique

With the development of new energy technologies, inverters, as key power equipment, are increasingly used in photovoltaic power generation projects. Figure 1 is a topology diagram of an inverter system in the related art, which consists of a photovoltaic array, DC/DC, bus capacitor C1, DC/AC and a power grid, which can feed back photovoltaic power generation to the power grid or AC load. In order to utilize photovoltaic power with maximum efficiency, combined with the P-V curve of photovoltaic power generation, a DC/DC converter is generally used for maximum power point tracking (MPPT). For example, a topology diagram of a DC converter in the related art is shown in FIG. 2 , which belongs to a Boost circuit and works when the photovoltaic open-circuit voltage is lower than the DC bus voltage.

At present, the improved topological circuit diagram of the DC converter in the related art is shown in FIG. 3 , which can bypass the inductor L and the diode D1 to reduce the loss of the DC/DC converter and improve the DC/DC efficiency.

SUMMARY OF THE INVENTION

According to some embodiments of the present disclosure, a DC converter topology circuit is proposed, including a working circuit connected to both ends of a photovoltaic array, the working circuit has a Boost working mode and a Buck working mode; when the input voltage of the photovoltaic array is When it is less than or equal to the DC bus voltage, the working circuit enters the Boost working mode to increase the input voltage; when the input voltage of the photovoltaic array is greater than the DC bus voltage, the working circuit enters the Buck mode, reduce the input voltage.

In some embodiments, the working circuit includes: a switch S1, a switch S2, a switch S3, an inductor L1, an inductor L2, a capacitor C1, a diode D0, a switch S4, and a diode D4 disposed on the switch S4; One end of the switch S1 is connected to the output end of the photovoltaic array, the other end of the switch S1 is connected to one end of the switch S3, the other end of the switch S3 is connected to the anode of the diode D0, the cathode of the diode D0 is connected to one end of the capacitor C1, and the capacitor The other end of C1 is connected to the input end of the photovoltaic array; one end of the switch S2 is connected between the switch S1 and the output end of the photovoltaic array, the other end of the switch S2 is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the switch S1 and the switch S2 In between, one end of the inductor L2 is connected between the switch S1 and the switch S3, the other end of the inductor L2 is connected between the cathode of the diode D0 and the capacitor C1; the first end of the switch S4 is connected between the switch S1 and the switch S3, the switch The second terminal of the tube S4 is connected between the capacitor C1 and the input terminal of the photovoltaic array.

In some embodiments, when the switch S1 is turned off, the switch S2 and the switch S3 are turned on, and the switch tube S4 is in a high-frequency switching state, the working circuit enters the Boost working state.

In some embodiments, when the switch S1 is in a high-frequency switching state, the switch S2 and the switch S3 are turned off, and the switch S4 is turned off, the working circuit enters the Buck working mode.

In some embodiments, the working circuit includes: a switch S1, a switch S2, a switch S3, a switch S4, a diode D1 arranged on the switch S1, a diode D2 arranged on the switch S2, The diode D3 arranged on the switch tube S3, the diode D4 arranged on the switch tube S4, the diode D0, the inductor L1, the inductor L2, and the capacitor C1; the first end of the switch tube S1 is connected to the photovoltaic The output end of the array, the second end of the switch S1 is connected to the first end of the switch S3, the second end of the switch S3 is connected to the anode of the diode D0, the cathode of the diode D0 is connected to one end of the capacitor C1, the capacitor The other end of C1 is connected to the input end of the photovoltaic array; the first end of the switch S2 is connected between the first end of the switch S1 and the output end of the photovoltaic array, and the first end of the switch S2 The two ends are connected to one end of the inductor L1, and the other end of the inductor L1 is connected between the second end of the switch S1 and the first end of the switch S3; one end of the inductor L2 is connected to the second end of the switch S1 and the first end of the switch S3. Between the first end of the switch tube S3, the other end is connected between the cathode of the diode D0 and the capacitor C1; the first end of the switch tube S4 is connected between the second end of the switch tube S1 and the first end of the switch tube S3 , and the other end is connected between the input end of the photovoltaic array and the capacitor C1.

In some embodiments, when the switch S1 is turned off, the switch S2 and the switch S3 are turned on, and the switch S4 is in a high-frequency switching state, the working circuit enters the Boost working mode.

In some embodiments, when the switch S1 is in a high-frequency switching state, and the switch S2, the switch S3, and the switch S4 are turned off, the working circuit enters the Buck working mode.

In some embodiments, a detection unit is further included, and the detection unit is used to detect the photovoltaic input voltage in real time.

According to other embodiments of the present disclosure, a control method for a DC converter topology circuit is also provided, which includes detecting the input voltage of the photovoltaic array, comparing the input voltage with the DC bus voltage, and if the input voltage is greater than or equal to If the input voltage is lower than the DC bus voltage, the DC converter topology circuit enters the Buck working mode.

According to further embodiments of the present disclosure, an inverter system is also proposed, including a photovoltaic array, a DC converter connected to the photovoltaic array, a bidirectional converter connected to the DC converter, and a The power grid connected to the bidirectional converter further includes a DC load and a bus capacitor connected to the DC bus, and a compressor driver and a motor connected to the compressor driver, and the DC converter adopts the above-mentioned DC converter topology circuit.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present disclosure more clearly, the following briefly introduces the accompanying drawings required in the description of the embodiments or related technologies. Obviously, the accompanying drawings in the following description are only some of the present disclosure. In the embodiment, for those skilled in the art, other drawings can also be obtained according to these drawings without creative labor.

1 is a topology diagram of an inverter system in the related art;

2 is a topology circuit diagram of a DC converter in the related art;

Fig. 3 is the topological circuit diagram of the improved DC converter in the related art;

FIG. 4 is a topological circuit diagram of a DC converter according to some embodiments of the disclosure;

FIG. 5 is a topology circuit diagram of a DC converter according to other embodiments of the present disclosure;

FIG. 6 is a control logic diagram of a DC converter working mode according to some embodiments of the present disclosure;

FIG. 7 is a topology diagram of an improved inverter system according to some embodiments of the present disclosure.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present disclosure clearer, the present disclosure will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure, but not to limit the present disclosure.

Thus, a reference to a feature in this specification will be used to describe one of several embodiments of the present disclosure and not to imply that every embodiment of the present disclosure must have the described feature. Furthermore, it should be noted that this specification describes a number of features. Although certain features can be combined together to illustrate a system design, these features can also be used in other combinations not explicitly stated. Thus, unless otherwise stated, the combinations described are not intended to be limiting.

For the related technology in Figure 1, since the photovoltaic modules are easily affected by light, temperature and external obstructions, the open circuit voltage of the photovoltaic will fluctuate within a certain range; for the related technology in Figure 2, when the photovoltaic open circuit voltage is greater than the DC bus voltage, the In this circuit, only the inductor and diode D1 work, and the loss is large.

For the DC/DC converter solution in the above-mentioned related art, when the photovoltaic input open-circuit voltage is greater than the DC bus voltage, the photovoltaic array and the DC bus are directly connected, and the photovoltaic array charges the DC bus capacitor. Therefore, the PV DC bus voltage will rise synchronously. And in this state, DC/DC cannot perform maximum power point tracking (MPPT) of photovoltaic input. And in the photovoltaic (voltaic) storage and air-conditioning system, there are usually multiple DC loads, energy storage or air-conditioning equipment on the DC bus, and the DC bus voltage is required to remain relatively stable. error occured.

Therefore, how to design a DC converter topology circuit, its control method, and an inverter system that can still keep the bus voltage stable when the input voltage of the photovoltaic array is high is a technical problem to be solved urgently in the industry.

In the related art, when the photovoltaic input voltage is greater than the bus voltage, the photovoltaic array will charge the DC bus capacitor to increase the bus voltage, which will cause the system to become unstable or malfunction. The present disclosure proposes a DC converter topology circuit A control method therefor, and an inverter system.

Compared with the related art, the present disclosure has at least the following beneficial effects: 1. The DC converter of the present disclosure has a simple topology circuit structure and low cost; 2. The DC converter can still maintain the bus voltage when the input voltage of the photovoltaic array is higher than the DC bus. Stable; 3. The photovoltaic input voltage is within the voltage range that the system can withstand, the DC converter can work in the step-up/step-down mode within the full voltage range, and the photovoltaic input voltage is adjusted for MPPT optimization, which can maximize the photovoltaic input to work at Maximum power point to improve the efficiency of the DC converter.

The principle and structure of the present disclosure will be described in detail below with reference to the accompanying drawings and embodiments.

The present disclosure proposes a DC converter topology circuit, which includes a working circuit connected to both ends of a photovoltaic array, and has two working modes: Boost working mode and Buck working mode. When the input voltage of the photovoltaic array is less than or equal to the DC bus voltage , the working circuit enters the Boost working mode and increases the input voltage of the photovoltaic array. When the input voltage of the photovoltaic array is greater than the DC bus voltage, the working circuit enters the Buck working mode and reduces the input voltage of the photovoltaic array.

In some embodiments, please refer to the topological circuit diagram of the DC converter of some embodiments of the present disclosure shown in FIG. 4 , which includes a switch S1 , a switch S2 , a switch S3 , an inductor L1 , an inductor L2 , a capacitor C1 , a diode D0 and a switch tube S4, and the diode D4 arranged on the switch tube S4;

One end of switch S1 is connected to the output end of the photovoltaic array, the other end of switch S1 is connected to one end of switch S3, the other end of switch S3 is connected to the anode of diode D0, the cathode of diode D0 is connected to one end of capacitor C1, and the other end of capacitor C1 Connect to the input of the photovoltaic array;

One end of switch S2 is connected between switch S1 and the output end of the photovoltaic array, the other end of switch S2 is connected to one end of inductor L1, the other end of inductor L1 is connected between switch S1 and switch S2, and one end of inductor L2 is connected between switch S1 and switch Between S3, the other end of the inductor L2 is connected between the cathode of the diode D0 and the capacitor C1;

The first end of the switch S4 is connected between the switch S1 and the switch S3, and the second end of the switch S4 is connected between the capacitor C1 and the input end of the photovoltaic array.

Among them, when the switch S1 is turned off, the switch S2 and the switch S3 are turned on, and the switch S4 is in a high-frequency switching state, the working circuit enters the Boost working mode. In some embodiments, when the switch S4 is turned on, the current It flows out from the output end of the photovoltaic array, and returns to the input end of the photovoltaic array through the switch S2, the inductor L1, and the switch S4. At this time, the photovoltaic array charges the inductor L1. When the switch S4 is disconnected, the current flows from the photovoltaic array. The output terminal flows out, and returns to the input terminal of the photovoltaic array through switch S2, inductor L1, switch S3, diode D0, and capacitor C1. At this time, the inductor L1 discharges, and the energy is transferred from the inductor L1 to the capacitor C1. When the circuit is stable, the inductor L1's Charge and discharge balance. Assuming that the voltage at both ends of the photovoltaic array is E, and the turn-on and turn-off times of the switch S4 in one cycle are ton and toff respectively, then the output voltage Uo=E*(ton+toff)/ton, because the output voltage is higher than the input voltage, Therefore, the Boost circuit is a boost circuit. And because the input voltage in the photovoltaic array will change with the output voltage, that is, the input voltage is increased.

When the switch S1 is in the high-frequency switching state, the switch S2 and the switch S3 are turned off, and the switch S4 is turned off, the working band enters the Buck working mode. In some embodiments, when the switch S1 is turned on, the current flows from the photovoltaic array. The positive terminal flows through the switch S1, the inductor L2, and the capacitor C1 and returns to the negative terminal of the photovoltaic array. At this time, it is equivalent to the circuit magnetizing the inductor L2 and storing the energy in the inductor L2; when the switch S1 is turned off, the photovoltaic array and the inductor are at this time. L2 is disconnected, the inductor L2 releases the magnetic energy, and the current flows through the inductor L2, the capacitor C1, and the diode D4 back to the inductor L2, which is equivalent to the transfer of energy from the inductor L2 to the capacitor C1. When the circuit is stable, the magnetization and discharge of the inductor L2 are balanced. Assuming that the voltage across the photovoltaic array is E, and the switch S4 is turned on and off in one cycle, the turn-on and turn-off times are ton and toff respectively, then the output voltage Uo=E*ton /(ton+toff), because the output voltage is lower than the input voltage, the Buck circuit is a step-down circuit. Since the input voltage in the photovoltaic array changes with the output voltage, the input voltage is reduced.

Please refer to the topological circuit diagram of the DC converter of other embodiments of the present disclosure shown in FIG. 5 . The working circuit includes: a switch S1 , a switch S2 , a switch S3 , a switch S4 , and a diode D1 disposed on the switch S1 , the diode D2 set on the switch tube S2, the diode D3 set on the switch tube S3, the diode D4 set on the switch tube S4, the diode D0, the inductance L1, the inductance L2, and the capacitor C1;

The first end of the switch S1 is connected to the output end of the photovoltaic array, the second end of the switch S1 is connected to the first end of the switch S3, the second end of the switch S3 is connected to the anode of the diode D0, and the cathode of the diode D0 Connect to one end of the capacitor C1, and the other end of the capacitor C1 is connected to the input end of the photovoltaic array;

The first end of the switch S2 is connected between the first end of the switch S1 and the output end of the photovoltaic array, the second end of the switch S2 is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the first end of the switch S1. between the two ends and the first end of the switch tube S3;

One end of the inductor L2 is connected between the second end of the switch tube S1 and the first end of the switch tube S3, and the other end is connected between the cathode of the diode D0 and the capacitor C1;

The first end of the switch S4 is connected between the second end of the switch S1 and the first end of the switch S3, and the other end is connected between the input end of the photovoltaic array and the capacitor C1.

Wherein, when the switch tube S1 is turned off, the switch tube S2 and the switch tube S3 are turned on, and the switch tube S4 is in a high-frequency switching state, the working circuit enters the Boost working mode, and its working principle is the same as the Boost working mode in the first embodiment of the present disclosure. , which will not be repeated here.

When the switch S1 is in the high-frequency switching state, and the switch S2, the switch S3, and the switch S4 are turned off, the working circuit enters the Buck working mode, and its working principle is the same as the Buck working mode in the first embodiment of the present disclosure. Do repeat.

Wherein, the DC converter topology circuit of the present disclosure further includes a detection unit, and the detection unit is used to detect the working voltage of the photovoltaic array in real time.

The present disclosure also proposes a control method for a DC converter topology circuit, please refer to FIG. 6 , which includes: detecting the input voltage of the photovoltaic array, comparing the input voltage with the DC bus voltage, and if the input voltage is greater than or equal to If the input voltage is lower than the DC bus voltage, the DC converter topology circuit enters the Buck working mode.

Referring to FIG. 7 , the present disclosure also proposes an inverter system, which includes a photovoltaic array, a DC converter connected to the photovoltaic array, a bidirectional converter connected to the DC converter, and a power grid connected to the bidirectional converter , and also includes a DC load and a bus capacitor connected to the DC bus, and a compressor drive, a motor connected to the compressor drive, wherein the DC converter adopts the above-mentioned DC converter topology circuit.

Compared with the related art, the present disclosure realizes control through switches and switching tubes, has simple structure and low cost, and enables the DC converter to keep the bus voltage stable when the input voltage of the photovoltaic array is higher than the DC bus. And the photovoltaic input voltage is within the voltage range that the system can withstand, the DC converter can work in the step-up/step-down mode within the full voltage range, and the photovoltaic input voltage can be adjusted for MPPT optimization, which can maximize the photovoltaic input to work at the maximum power point. , to improve the efficiency of the DC converter.

The above descriptions are only preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present disclosure shall be included in the protection of the present disclosure. within the range.

Claims

A DC converter topology circuit, comprising:

A working circuit connected to both ends of the photovoltaic array, the working circuit has a Boost working mode and a Buck working mode,

When the input voltage of the photovoltaic array is less than or equal to the DC bus voltage, the working circuit enters the Boost working mode to increase the input voltage,

When the input voltage of the photovoltaic array is greater than the DC bus voltage, the working circuit enters the Buck mode to reduce the input voltage.
The DC converter topology circuit of claim 1, wherein the operating circuit comprises:

Switch S1, switch S2, switch S3, inductor L1, inductor L2, capacitor C1, diode D0 and switch S4,

One end of the switch S1 is connected to the output end of the photovoltaic array, the other end of the switch S1 is connected to one end of the switch S3, the other end of the switch S3 is connected to the anode of the diode D0, the cathode of the diode D0 is connected to one end of the capacitor C1, and the capacitor The other end of C1 is connected to the input of the photovoltaic array,

One end of the switch S2 is connected between the switch S1 and the output end of the photovoltaic array, the other end of the switch S2 is connected to one end of the inductor L1, the other end of the inductor L1 is connected between the switch S1 and the switch S2, and one end of the inductor L2 is connected to the switch S1 and switch S3, the other end of the inductor L2 is connected between the cathode of the diode D0 and the capacitor C1,

The first end of the switch S4 is connected between the switch S1 and the switch S3, and the second end of the switch S4 is connected between the capacitor C1 and the input end of the photovoltaic array.
The DC converter topology circuit of claim 2, wherein the operating circuit comprises:

The diode D4 is arranged on the switch tube S4.
The DC converter topology circuit of claim 2, wherein,

When the switch S1 is turned off, the switch S2 and the switch S3 are turned on, and the switch tube S4 is in a high-frequency switching state, the working circuit enters the Boost working state.
The DC converter topology circuit of claim 2, wherein,

When the switch S1 is in a high-frequency switching state, the switch S2 and the switch S3 are turned off, and the switch S4 is turned off, the working circuit enters the Buck working mode.
The DC converter topology circuit of claim 1, wherein,

The working circuit includes: a switch S1, a switch S2, a switch S3, a switch S4, a diode D1 arranged on the switch S1, a diode D2 arranged on the switch S2, a diode D2 arranged on the switch The diode D3 on S3, the diode D4, diode D0, inductance L1, inductance L2, and capacitor C1 disposed on the switch tube S4,

The first end of the switch S1 is connected to the output end of the photovoltaic array, the second end of the switch S1 is connected to the first end of the switch S3, and the second end of the switch S3 is connected to the diode D0. The anode, the cathode of the diode D0 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is connected to the input end of the photovoltaic array,

The first end of the switch S2 is connected between the first end of the switch S1 and the output end of the photovoltaic array, the second end of the switch S2 is connected to one end of the inductor L1, and the other end of the inductor L1. One end is connected between the second end of the switch S1 and the first end of the switch S3,

One end of the inductor L2 is connected between the second end of the switch S1 and the first end of the switch S3, and the other end is connected between the cathode of the diode D0 and the capacitor C1,

The first end of the switch S4 is connected between the second end of the switch S1 and the first end of the switch S3, and the other end is connected between the input end of the photovoltaic array and the capacitor C1.
The DC converter topology circuit of claim 6, wherein,

When the switch S1 is turned off, the switch S2 and the switch S3 are turned on, and the switch S4 is in a high-frequency switching state, the working circuit enters the Boost working mode.
The DC converter topology circuit of claim 6, wherein,

When the switch S1 is in a high-frequency switching state, and the switch S2, the switch S3, and the switch S4 are turned off, the working circuit enters the Buck working mode.
The DC converter topology circuit of claim 1, further comprising:

and a detection unit, which is used to detect the photovoltaic input voltage in real time.
A control method for a DC converter topology circuit, comprising:

The input voltage of the photovoltaic array is detected, and the input voltage is compared with the DC bus voltage. If the input voltage is greater than or equal to the DC bus voltage, the DC converter topology circuit enters the Boost working mode, and the DC converter topology circuit adopts the right The DC converter topology circuit described in any one of requirements 1 to 9;

If the input voltage is less than the DC bus voltage, the DC converter topology circuit enters the Buck working mode.
An inverter system includes:

a photovoltaic array, a DC converter connected to the photovoltaic array, a bidirectional converter connected to the DC converter, and a power grid connected to the bidirectional converter;

A DC load and a bus capacitor connected to the DC bus, a compressor drive, a motor connected to the compressor drive, the DC converter comprising the DC converter topology according to any one of claims 1 to 9 circuit.