CN113922692A - Method for improving overall efficiency in two-stage bidirectional DCAC converter - Google Patents
Method for improving overall efficiency in two-stage bidirectional DCAC converter Download PDFInfo
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- 230000002457 bidirectional effect Effects 0.000 title claims abstract description 24
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- 230000008901 benefit Effects 0.000 abstract description 4
- 238000005516 engineering process Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
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- 238000006243 chemical reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1582—Buck-boost converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/20—Charging or discharging characterised by the power electronics converter
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a method for improving the efficiency of a whole machine in a two-stage bidirectional DCAC converter, which comprises the following steps: setting a voltage disturbance formula of the direct current bus voltage; starting from 0, increasing a preset disturbance value every time for the adjustment factor, and calculating and storing a direct current bus voltage set value and a complete machine efficiency value every time until the direct current bus voltage set value is larger than or equal to the maximum voltage in the range; and selecting the direct current bus voltage set value corresponding to the highest overall efficiency value from the stored direct current bus voltage set values, and taking the selected direct current bus voltage set value as the final direct current bus voltage set value. The invention continuously disturbs the direct current bus voltage set value according to the difference of the battery side voltage and selects the direct current bus voltage set value with the highest overall efficiency value, thereby ensuring the system to be in the best efficiency during the operation, reducing the loss, and improving the energy utilization rate and the economic benefit.
Description
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a method for improving the efficiency of a whole machine in a two-stage bidirectional DCAC converter.
Background
As shown in fig. 1, a front stage of an existing two-stage bidirectional DCAC converter system is a DCDC Buck Boost circuit, and a rear stage of the existing two-stage bidirectional DCAC converter system is a DCAC inverter circuit, and is suitable for PCS (energy storage converter), V2G (Vehicle-to-grid), a direct current source and the like, and is particularly widely used in a echelon battery. Specifically, the low-voltage side of the DCDC is connected to a battery or a direct-current load, the high-voltage side is a direct-current bus and is connected to the direct-current side of the DCAC, and the alternating-current side of the DCAC is connected to a power grid or an alternating-current load.
At present, the system completely decouples functions to respectively realize the functions of the system, and the control is relatively simple, but because two stages of power conversion exist, how to improve the system efficiency and the circuit reliability is a key problem in research. In the traditional control of the system, under the condition of grid connection, the direct current bus voltage is controlled by DCAC; in the case of no power grid, the dc bus voltage is controlled by the DCDC. Since the overall efficiency of the system varies with the voltage of the dc bus, the voltage value VbusSet of the dc bus needs to be adjusted continuously to achieve the purpose of ensuring the bidirectional flow of energy while optimizing the efficiency. When the hardware filter inductance, capacitance, and switching frequency are determined, the conventional method for adjusting the bus voltage generally directly gives the bus voltage a fixed value, or simply follows the battery voltage linearly through the dc-side battery voltage value Vbat (i.e., VbusSet ═ Vbat/k). However, neither of these approaches currently optimizes the overall efficiency of the system.
Therefore, there is a need for improvements in the prior art to improve the overall efficiency of the system.
The above information is given as background information only to aid in understanding the present disclosure, and no determination or admission is made as to whether any of the above is available as prior art against the present disclosure.
Disclosure of Invention
The invention provides a method for improving the efficiency of a whole machine in a two-stage bidirectional DCAC converter, which aims to overcome the defects of the prior art.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a method of improving overall efficiency in a two-stage bidirectional DCAC converter, the method comprising:
setting a voltage disturbance formula of the direct current bus voltage as Vbus set ═ Vbat/k + b according to the requirements that the battery side voltage, the duty ratio and the minimum voltage in the direct current bus voltage range need to be larger than the DCAC minimum bus voltage; wherein, VbausSet is a direct current bus voltage set value, Vbat is a battery side voltage, k is a fixed parameter, and b is an adjusting factor;
judging whether the operation is initial operation;
if not, increasing a preset disturbance value for each time by the regulating factor, and calculating and storing the set value of the direct current bus voltage and the efficiency value of the whole machine each time until the set value of the direct current bus voltage is greater than or equal to the maximum voltage in the range of the direct current bus voltage;
if so, assigning the adjusting factor to be 0, assigning the set value of the direct current bus voltage to be the minimum voltage operation in the range of the direct current bus voltage, then executing the step of adding a preset disturbance value to the adjusting factor each time, and calculating and storing the set value of the direct current bus voltage and the efficiency value of the whole machine each time until the set value of the direct current bus voltage is more than or equal to the maximum voltage in the range of the direct current bus voltage;
and selecting the direct current bus voltage set value corresponding to the highest overall efficiency value from the stored direct current bus voltage set values, and taking the selected direct current bus voltage set value as a final direct current bus voltage set value.
Further, in the method for improving overall efficiency in a two-stage bidirectional DCAC converter, before the step of setting the voltage disturbance formula of the dc bus voltage to VbusSet ═ Vbat/k + b according to the battery side voltage, the duty cycle and the requirement that the minimum voltage in the dc bus voltage range needs to be greater than the DCAC minimum bus voltage, the method further includes:
judging whether the variable quantity of the battery side voltage is larger than a preset voltage value or not;
if yes, updating a set value of the disturbed direct-current bus voltage, and executing the requirement that the minimum voltage in the range of the battery side voltage, the duty ratio and the direct-current bus voltage is greater than the DCAC minimum bus voltage, and setting a voltage disturbance formula of the direct-current bus voltage as Vbus set ═ Vbat/k + b;
if not, the set value of the disturbance direct-current bus voltage does not need to be updated.
Further, in the method for improving overall efficiency in the two-stage bidirectional DCAC converter, the step of calculating and storing the set value of the dc bus voltage and the overall efficiency value at each time includes:
calculating the voltage set value of the direct current bus every time according to VbausSet which is Vbat/k + b;
acquiring battery side voltage, battery side current, power grid voltage and power grid current, and calculating the overall efficiency value of each time;
and storing the set value of the voltage of the direct current bus and the efficiency value of the whole machine obtained by each calculation.
Further, in the method for improving overall efficiency in the two-stage bidirectional DCAC converter, the step of obtaining the battery side voltage, the battery side current, the grid voltage and the grid current, and calculating the overall efficiency value at each time includes:
acquiring a battery side voltage and a battery side current, and calculating a first power;
acquiring the voltage and current of the power grid, and calculating second power;
and calculating the efficiency value of the whole machine at each time through the first power and the second power.
Further, in the method for improving overall efficiency in the two-stage bidirectional DCAC converter, the step of obtaining a battery-side voltage and a battery-side current and calculating the first power includes:
acquiring battery side voltage and battery side current acquired by DCDC;
a first power is calculated from the battery side voltage and the battery side current.
Further, in the method for improving overall efficiency in the two-stage bidirectional DCAC converter, the step of obtaining the grid voltage and the grid current and calculating the second power includes:
acquiring power grid voltage and power grid current acquired by DCAC;
and calculating second power according to the power grid voltage and the power grid current.
Further, in the method for improving the overall efficiency of the two-stage bidirectional DCAC converter, k is 0.95.
Further, in the method for improving the overall efficiency of the two-stage bidirectional DCAC converter, the preset disturbance value is 5V.
Further, in the method for improving the overall efficiency of the two-stage bidirectional DCAC converter, the preset voltage value is 10V.
Compared with the prior art, the embodiment of the invention has the following beneficial effects:
according to the method for improving the overall efficiency of the two-stage bidirectional DCAC converter, provided by the embodiment of the invention, the direct-current bus voltage set value is disturbed continuously according to the difference of the voltage at the battery side, and the direct-current bus voltage set value with the highest overall efficiency value is selected, so that the optimal efficiency of the system in operation can be ensured, the loss is reduced, and the energy utilization rate and the economic benefit 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 described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a circuit topology diagram of a prior art two-stage bidirectional DCAC converter system;
fig. 2 is a schematic flowchart of a method for improving overall efficiency in a two-stage bidirectional DCAC converter according to an embodiment of the present invention.
Detailed Description
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. 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 the description of the present invention, it is to be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present.
Furthermore, the terms "long", "short", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing the present invention, but do not indicate or imply that the referred devices or elements must have the specific orientations, be configured to operate in the specific orientations, and thus are not to be construed as limitations of the present invention.
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
Example one
In view of the defects of the prior art, the inventor of the invention actively researches and innovates based on abundant practical experience and professional knowledge in many years of the industry and by matching with the application of theory, so as to create a feasible overall efficiency improving technology, thereby leading the technology to have more practicability. After continuous research, design and repeated trial and improvement, the invention with practical value is finally created.
Referring to fig. 1, fig. 1 is a schematic flowchart illustrating a method for improving overall efficiency in a two-stage bidirectional DCAC converter according to an embodiment of the present invention, where the method is suitable for a scenario where the overall efficiency is desired to be improved, and the method may be implemented by software and/or hardware. As shown in fig. 1, the method for improving overall efficiency in the two-stage bidirectional DCAC converter may include the following steps:
s101, setting a voltage disturbance formula of the direct current bus voltage as Vbus set ═ Vbat/k + b according to the battery side voltage, the duty ratio and the requirement that the minimum voltage in the direct current bus voltage range needs to be larger than the DCAC minimum bus voltage; wherein, VbusSet is a set value of the direct current bus voltage, Vbat is a battery side voltage, k is a fixed parameter, and b is an adjusting factor.
In this embodiment, k is 0.95.
It should be noted that, in this embodiment, it is set that, after the variation of the battery-side voltage is greater than the preset voltage value, the set value of the dc bus voltage enters a new cycle of disturbance, and therefore, preferably, before the step S101, the method may further include:
judging whether the variable quantity of the battery side voltage is larger than a preset voltage value or not;
if yes, updating a set value of the disturbed direct current bus voltage, and executing the step S101;
if not, the set value of the disturbance direct-current bus voltage does not need to be updated.
In this embodiment, the preset voltage value is 10V.
S102, judging whether the operation is initial operation or not; if yes, go to step S103, then go to step S104; if not, step S104 is directly executed.
And S103, assigning the adjusting factor to be 0, and assigning the set value of the direct current bus voltage to be the minimum voltage operation in the direct current bus voltage range.
And S104, increasing a preset disturbance value for each time of the regulating factor, and calculating and storing the set value of the direct current bus voltage and the efficiency value of the whole machine each time until the set value of the direct current bus voltage is greater than or equal to the maximum voltage in the range of the direct current bus voltage.
In this embodiment, the preset disturbance value is 5V.
It should be noted that, the above-mentioned series of steps means that, in the initial operation of this embodiment, the adjustment factor b is assigned to 0, the dc bus voltage setting value is assigned to the minimum voltage operation in the dc bus voltage range, and then the dc bus voltage setting value is disturbed continuously, the dc bus voltage setting value is increased once every time by the preset disturbance value, that is, the adjustment factor b value is increased once every time by the preset disturbance value, after every disturbance, the disturbed dc bus voltage setting value and the current overall efficiency value need to be stored, and the disturbance is ended until the dc bus voltage setting value is greater than or equal to the maximum voltage in the dc bus voltage range.
Preferably, the step of calculating and storing the set value of the dc bus voltage and the efficiency value of the whole machine each time may further include:
calculating the voltage set value of the direct current bus every time according to VbausSet which is Vbat/k + b;
acquiring battery side voltage, battery side current, power grid voltage and power grid current, and calculating the overall efficiency value of each time;
and storing the set value of the voltage of the direct current bus and the efficiency value of the whole machine obtained by each calculation.
Preferably, the step of obtaining the battery side voltage, the battery side current, the grid voltage and the grid current, and calculating the overall efficiency value of each time may further include:
acquiring a battery side voltage and a battery side current, and calculating a first power;
acquiring the voltage and current of the power grid, and calculating second power;
and calculating the efficiency value of the whole machine at each time through the first power and the second power.
Preferably, the step of obtaining the battery side voltage and the battery side current and calculating the first power may further include:
acquiring battery side voltage and battery side current acquired by DCDC;
a first power is calculated from the battery side voltage and the battery side current.
Preferably, the step of obtaining the grid voltage and the grid current and calculating the second power may further include:
acquiring power grid voltage and power grid current acquired by DCAC;
and calculating second power according to the power grid voltage and the power grid current.
And S105, selecting a direct current bus voltage set value corresponding to the highest overall efficiency value from the stored direct current bus voltage set values, and taking the selected direct current bus voltage set value as a final direct current bus voltage set value.
It should be noted that, in this step, all the dc bus voltage set values stored during the disturbance period are compared, and the dc bus voltage set value corresponding to the highest overall efficiency value is selected from the dc bus voltage set values, so as to obtain the final most suitable dc bus voltage set value.
To prove the effectiveness of the present embodiment, the present embodiment is described with a specific example. In the system, the rated power of the selected two-stage system DCAC is 30kw, a preset disturbance value, namely 5V, is added to the set value of the DC bus voltage each time, and the load power on the DC side is 27kw for industrial control, then the test results are shown in the following table:
it can be seen that the actual operation result shows that the optimal direct current bus voltage set value is found out by continuously disturbing the direct current bus voltage set value, which is beneficial to improving the overall efficiency of the system.
According to the method for improving the overall efficiency of the two-stage bidirectional DCAC converter, provided by the embodiment of the invention, the direct-current bus voltage set value is disturbed continuously according to the difference of the voltage at the battery side, and the direct-current bus voltage set value with the highest overall efficiency value is selected, so that the optimal efficiency of the system in operation can be ensured, the loss is reduced, and the energy utilization rate and the economic benefit are improved.
The foregoing description of the embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same elements or features may also vary in many respects. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those skilled in the art. Numerous details are set forth, such as examples of specific parts, devices, and methods, in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In certain example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises" and "comprising" are intended to be inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed and illustrated, unless explicitly indicated as an order of performance. It should also be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being "on" … … "," engaged with "… …", "connected to" or "coupled to" another element or layer, it can be directly on, engaged with, connected to or coupled to the other element or layer, or intervening elements or layers may also be present. In contrast, when an element or layer is referred to as being "directly on … …," "directly engaged with … …," "directly connected to" or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship of elements should be interpreted in a similar manner (e.g., "between … …" and "directly between … …", "adjacent" and "directly adjacent", etc.). As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region or section from another element, component, region or section. Unless clearly indicated by the context, use of terms such as the terms "first," "second," and other numerical values herein does not imply a sequence or order. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as "inner," "outer," "below," "… …," "lower," "above," "upper," and the like, may be used herein for ease of description to describe a relationship between one element or feature and one or more other elements or features as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below … …" can encompass both an orientation of facing upward and downward. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted.
Claims (9)
1. A method for improving the efficiency of the whole machine in a two-stage bidirectional DCAC converter is characterized by comprising the following steps:
setting a voltage disturbance formula of the direct current bus voltage as Vbus set ═ Vbat/k + b according to the requirements that the battery side voltage, the duty ratio and the minimum voltage in the direct current bus voltage range need to be larger than the DCAC minimum bus voltage; wherein, VbausSet is a direct current bus voltage set value, Vbat is a battery side voltage, k is a fixed parameter, and b is an adjusting factor;
judging whether the operation is initial operation;
if not, increasing a preset disturbance value for each time by the regulating factor, and calculating and storing the set value of the direct current bus voltage and the efficiency value of the whole machine each time until the set value of the direct current bus voltage is greater than or equal to the maximum voltage in the range of the direct current bus voltage;
if so, assigning the adjusting factor to be 0, assigning the set value of the direct current bus voltage to be the minimum voltage operation in the range of the direct current bus voltage, then executing the step of adding a preset disturbance value to the adjusting factor each time, and calculating and storing the set value of the direct current bus voltage and the efficiency value of the whole machine each time until the set value of the direct current bus voltage is more than or equal to the maximum voltage in the range of the direct current bus voltage;
and selecting the direct current bus voltage set value corresponding to the highest overall efficiency value from the stored direct current bus voltage set values, and taking the selected direct current bus voltage set value as a final direct current bus voltage set value.
2. The method of claim 1, wherein before the step of setting the dc bus voltage to VbusSet ═ Vbat/k + b according to the battery side voltage, duty cycle and the requirement that the minimum voltage in the dc bus voltage range needs to be greater than the DCAC minimum bus voltage, the method further comprises:
judging whether the variable quantity of the battery side voltage is larger than a preset voltage value or not;
if yes, updating a set value of the disturbed direct-current bus voltage, and executing the requirement that the minimum voltage in the range of the battery side voltage, the duty ratio and the direct-current bus voltage is greater than the DCAC minimum bus voltage, and setting a voltage disturbance formula of the direct-current bus voltage as Vbus set ═ Vbat/k + b;
if not, the set value of the disturbance direct-current bus voltage does not need to be updated.
3. The method of claim 1, wherein the step of calculating and storing the DC bus voltage setpoint and the overall efficiency value for each time comprises:
calculating the voltage set value of the direct current bus every time according to VbausSet which is Vbat/k + b;
acquiring battery side voltage, battery side current, power grid voltage and power grid current, and calculating the overall efficiency value of each time;
and storing the set value of the voltage of the direct current bus and the efficiency value of the whole machine obtained by each calculation.
4. The method of claim 3, wherein the step of obtaining the battery-side voltage, the battery-side current, the grid voltage and the grid current and calculating the total efficiency value for each time comprises:
acquiring a battery side voltage and a battery side current, and calculating a first power;
acquiring the voltage and current of the power grid, and calculating second power;
and calculating the efficiency value of the whole machine at each time through the first power and the second power.
5. The method of claim 4, wherein the step of obtaining the battery-side voltage and the battery-side current and calculating the first power comprises:
acquiring battery side voltage and battery side current acquired by DCDC;
a first power is calculated from the battery side voltage and the battery side current.
6. The method of claim 4, wherein the step of obtaining the grid voltage and the grid current and calculating the second power comprises:
acquiring power grid voltage and power grid current acquired by DCAC;
and calculating second power according to the power grid voltage and the power grid current.
7. The method of claim 1, wherein k is 0.95.
8. The method of claim 1, wherein the predetermined disturbance value is 5V.
9. The method of claim 2, wherein the predetermined voltage is 10V.
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