Inverter power segment self-identification method, inverter and air conditioner

Abstract

The present invention discloses a method for self-adapting the power range of a frequency converter, a frequency converter, and an air conditioner. The method comprises: when the frequency converter is turned on, pre-charging the bus capacitor with current limiting via a charging resistor; calculating the charging time of the bus capacitor from the start to the end of charging; obtaining the power range of the frequency converter based on the charging time, and operating the control parameters under the current power range. Compared with the prior art, the present invention can automatically identify the power range of the frequency converter, eliminating the need for manual input of current parameters and models. The method can self-identify the power range and automatically adjust the control parameters of each functional part of the frequency converter, thereby improving the automated control effect and reducing the number of manual operation steps and the probability of human error.

Description

Technical Field

[0001] The present invention relates to the field of inverter control, and in particular to an inverter power segment self-identification method, an inverter and an air conditioner. Background Art

[0002] PV inverters for commercial air conditioners are designed and developed to match the power of their main units, covering a power range from a few kilowatts to one kilowatt. In the 100kW to 1000kW power range, inverter structures are similar, differing only in size, while the inverter controllers share essentially the same mounting location.

[0003] Current technical solutions only support one inverter control circuit for inverters in one power range. This results in the need to design multiple different controllers for inverters in various power ranges, significantly increasing product development and maintenance costs, product development time, and the price. Therefore, a universal controller is needed that can adapt to inverters of different power levels across the entire power range.

[0004] When designing a universal controller, the problem of automatic power segment identification may occur. The current common solution is to manually input control parameters, such as through interactive channels such as a host computer and key circuits. However, manual parameter input increases the number of manual operation steps and the probability of human error.

[0005] Therefore, how to design a frequency converter power segment self-identification method, frequency converter and air conditioner that can self-identify the power segment of the frequency converter operation is a technical problem that needs to be solved urgently in the industry. Summary of the Invention

[0006] In view of the problem that the current inverter power segment identification method in the prior art is to manually input control parameters, which increases the number of manual operation steps and the probability of human operation errors, the present invention proposes an inverter power segment self-identification method, an inverter and an air conditioner.

[0007] The technical solution of the present invention is to propose a method for self-identification of power range of an inverter, comprising:

[0008] When the inverter is turned on, the bus capacitor is pre-charged with current limiting through the charging resistor;

[0009] Detecting the charging time of the bus capacitor from the start to the end of charging;

[0010] The power range in which the inverter operates is obtained according to the charging time, and the control parameters under the current power range are operated.

[0011] Further, obtaining the power range of the inverter operation according to the charging time includes:

[0012] Calculate the capacitance value of the bus capacitor according to the charging time;

[0013] Obtain the power segment of the frequency converter operation corresponding to the capacitance value of the bus capacitor;

[0014] Set the correspondence between the power segment and the charging time, and obtain the power segment of the frequency converter operation according to the charging time.

[0015] Further, the charging time and the capacitance value of the bus capacitor satisfy the calculation model: t = -R * C * [-In(1 - V C / V DC )];

[0016] Where, C is the capacitance value of the bus capacitor, V C is the voltage across the bus capacitor, V DC is the charging voltage of the bus capacitor, R is the resistance value of the charging resistor, and t is the charging time.

[0017] Further, the correspondence satisfies:

[0018] When 0 < t ≤ 5RC1, determine that the power segment of the frequency converter operation is the first power segment;

[0019] When 5RC > t ≤ 5RC2, determine that the power segment of the frequency converter operation is the second power segment;

[0020] When t > 5RC2, determine that the power segment of the frequency converter operation is the third power segment;

[0021] Where, t is the charging time, C1 is the capacitance value of the bus capacitor when the power segment of the frequency converter operation is the first power segment, C2 is the capacitance value of the bus capacitor when the power segment of the frequency converter operation is the second power segment, C3 is the capacitance value of the bus capacitor when the power segment of the frequency converter operation is the first power segment, and R is the resistance value of the charging resistor.

[0022] Further, obtaining the power segment of the frequency converter operation corresponding to the capacitance value of the bus capacitor includes:

[0023] When the capacitance value of the bus capacitor is 12500uf, determine that the power segment of the frequency converter operation is the 250KW power segment;

[0024] When the capacitance value of the bus capacitor is 25000uf, determine that the power segment of the frequency converter operation is the 500KW power segment;

[0025] When the capacitance value of the bus capacitor is 37500uf, determine that the power segment of the frequency converter operation is the 750KW power segment.

[0026] Furthermore, before the bus capacitor is pre-charged with current limiting, the method further includes:

[0027] Detecting the grid-side voltage and determining whether the three-phase sequence of the grid-side voltage is normal;

[0028] If so, start current limiting precharging for the bus capacitor;

[0029] If not, an alarm is triggered and a power failure is indicated.

[0030] Furthermore, in all power sections in which the inverter operates, the resistance of the charging resistor is the same, and the resistance of the charging resistor is 100Ω.

[0031] Furthermore, when detecting the charging time, the method further includes:

[0032] detecting the voltage on the bus capacitor;

[0033] Determining whether the voltage on the bus capacitor reaches the charging voltage of the bus capacitor;

[0034] If so, it is determined that the bus capacitor is fully charged, and the charging time is calculated.

[0035] The present invention also provides a frequency converter, which adopts the above self-identification method.

[0036] The present invention also provides an air conditioner comprising the above-mentioned inverter.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] The present invention does not require the addition of additional components. By detecting and calculating the inverter, the power range of the inverter can be automatically identified, thereby achieving the effect of automatically adapting to inverters of different power ranges without the need for manual input of models and parameters through a host computer, key circuits, etc., thereby improving the automation control capability and reducing the number of manual operation steps and the probability of human operation errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 This is a control flow chart of the present invention as a whole;

[0041] Figure 2 This is a diagram of the inverter parameter setting architecture. DETAILED DESCRIPTION

[0042] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further 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 invention and are not intended to limit the present invention.

[0043] Thus, a feature indicated in this specification is intended to illustrate one of the features of one embodiment of the present invention, rather than to imply that every embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although certain features can be combined together to illustrate possible system designs, these features can also be used in other, not explicitly described, combinations. Thus, unless otherwise noted, the described combinations are not intended to be limiting.

[0044] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0045] When designing a universal controller, the problem of automatic power range identification arises. Currently, the common solution is to manually input control parameters, such as through interactive channels like a host computer or keypad circuits. However, manual parameter input increases the number of manual steps and the probability of human error. The present invention aims to determine the inverter's operating power range by detecting the charging time of the bus capacitor, thereby achieving self-identification.

[0046] The inverter power segment self-identification method proposed by the present invention includes:

[0047] When the inverter is turned on, the bus capacitor is pre-charged with current limiting through the charging resistor;

[0048] Detect the charging time of the bus capacitor from the start to the end of charging;

[0049] The power range of the inverter is obtained according to the charging time, and the control parameters under the current power range are operated.

[0050] The busbar capacitor value of each inverter is designed based on the power range in which the inverter operates. By detecting the busbar capacitor charging time, the present invention can determine the busbar capacitor value and, further, the inverter's operating power range, thereby achieving self-identification of the inverter's power range. All detection actions in the present invention can be implemented by the inverter controller, eliminating the need for additional components and reducing product development costs.

[0051] Specifically, the power range of the inverter operation is obtained according to the charging time, including:

[0052] Calculate the capacitance of the bus capacitor based on the charging time;

[0053] Get the power range of the inverter corresponding to the capacitance of the bus capacitor;

[0054] Set the relationship between the power range and the charging time, and obtain the power range of the inverter operation according to the charging time.

[0055] From the above introduction, it can be seen that the bus capacitor value set by the inverter is different when it is operating in different power segments. Therefore, the present invention can first calculate the capacitance of the bus capacitor based on the charging time, and then determine the power segment of the inverter based on the capacitance of the bus capacitor.

[0056] Among them, for the voltage across the bus capacitor, it satisfies the calculation formula: V C =V DC *(1-e^-t / T), where Vc is the voltage across the bus capacitor, V DC is the charging voltage of the bus capacitor, that is, the voltage provided by the power grid, t is the charging time, and T is the time constant.

[0057] After simplifying the above formula, we can get: e^-t / T=1-V C / V DC Since the charging voltage of the bus capacitor is a constant, it can be concluded from the above formula that as the charging time increases, the voltage on the bus capacitor will get closer and closer to the charging voltage, but it cannot be completely equal to the charging voltage. In the present invention, it is determined that when the voltage across the bus capacitor meets V C =99.326%V DC When the bus capacitor is fully charged.

[0058] In this regard, the present invention further includes the steps of detecting the charging time:

[0059] Detect the voltage on the bus capacitor;

[0060] Determine whether the voltage on the bus capacitor reaches the charging voltage of the bus capacitor;

[0061] If yes, it is determined that the bus capacitor charging is complete and the charging time is calculated.

[0062] Here, judging whether the voltage on the bus capacitor reaches the charging voltage of the bus capacitor is actually judging whether the voltage on the bus capacitor reaches 99.326% V DC If so, it can be determined that the bus capacitor is fully charged, otherwise it is necessary to continue charging the bus capacitor.

[0063] In order to obtain accurate charging time, it is necessary to ensure that the bus capacitance starts to increase from a voltage of 0. Therefore, in the present invention, the charging time action is designed to be when the inverter is turned on.

[0064] Among them, for the time constant T, it is related to the resistance value of the charging resistor and the capacitance value of the bus capacitor. Its calculation model is T = RC, where R is the resistance value of the charging resistor and C is the capacitance value of the bus capacitor. To exclude the influence caused by other unnecessary factors in the calculation process of the capacitance value of the bus capacitor, in this invention, the resistance values of the charging resistors in the relevant inverters are set to be the same, all set to 100 Ω, and aluminum shell resistors are used as the charging resistors. Therefore, when calculating the capacitance value of the bus capacitor through the charging time, the capacitance value of the bus capacitor is only related to the charging time, which can avoid misjudgment caused by other factors.

[0065] Here, substituting the time constant T = RC into the above formula, we can get: e^-t / (R*C) = 1 - V C / V DC ;

[0066] Taking the natural logarithm of both sides of this formula with base e, we can get: -t / (R*C) = In(1 - V C / V DC ). After simplification, we can obtain the calculation model satisfied between the charging time and the capacitance value of the bus capacitor: t = -R*C*[-In(1 - V C / V DC )];

[0067] Among them, C is the capacitance value of the bus capacitor, V C is the voltage across the bus capacitor, V DC is the charging voltage of the bus capacitor, R is the resistance value of the charging resistor, and t is the charging time.

[0068] Since the charging time of the bus capacitor in the inverter is different under different power segments, the corresponding relationship between the charging time and the power segment of the inverter operation can be set through the above relationship. After setting the corresponding relationship between the charging time and the power segment of the inverter operation, the power segment of the inverter operation can be obtained according to the charging time, and at the same time, in the subsequent detection of the power segment, this corresponding relationship can also be directly used.

[0069] Among them, in this invention, it is determined that when Vc = 99.326%V DC the bus capacitor is fully charged. Substituting this formula into the above calculation model, we can get t = 5RC. In a preferred embodiment of this invention, there are three power segments for the inverter operation. The capacitance value of the bus capacitor corresponding to the first power segment is C1, the capacitance value of the bus capacitor corresponding to the second power segment is C2, and the capacitance value of the bus capacitor corresponding to the third power segment is C3;

[0070] Therefore, according to the different charging times, the corresponding relationship can be obtained as follows:

[0071] When 0 < t ≤ 5RC1, it is determined that the power segment of the inverter operation is the first power segment;

[0072] When 5RC1 < t ≤ 5RC2, it is determined that the power segment in which the frequency converter operates is the second power segment;

[0073] When t > 5RC2, it is determined that the power segment in which the frequency converter operates is the third power segment.

[0074] The principle of the present invention will be described below by taking the power segments of a frequency converter with three gears. The relationship between the capacitance value of the bus capacitor and the power segment in which the corresponding frequency converter operates is as follows:

[0075] Capacitance / uf 12500 25000 37500 Power range / KW 250 500 750

[0076] By multiplying the capacitance value of the bus capacitor by the charging resistor, the corresponding time interval can be obtained. Then, by judging the time interval in which the charging time is located, the corresponding power segment can be obtained.

[0077] Taking the resistance value of the charging resistor as 100 Ω as an example, for a frequency converter with a power segment of 250 KW, its charging time is t = RC = 100 * 12500 * 10^-6 = 1.25 s;

[0078] For a frequency converter with a power segment of 500 KW, its charging time is t = RC = 100 * 25000 * 10^-6 = 2.5 s;

[0079] For a frequency converter with a power segment of 750 KW, its charging time is t = 100 * 37500 * 10^-6 = 3.75;

[0080] Therefore, the comparison relationship can be set as: when 0 < t ≤ 1.25 s, it is determined that the power segment in which the frequency converter operates is 250 KW;

[0081] When 1.25 s < t ≤ 2.5 s, it is determined that the power segment in which the frequency converter operates is 500 KW;

[0082] When 2.5 s < t ≤ 3.75 s, it is determined that the power segment in which the frequency converter operates is 750 KW;

[0083] Then, obtain the charging time and judge which one of the above intervals the charging time is in, and the corresponding power segment can be determined.

[0084] It should be noted that the three power segments are only the design methods under a preferred embodiment of the present invention. In other embodiments of the present invention, multiple power segments can also be designed, and the charging time corresponding to different power segments can be determined by the above method.

[0085] Furthermore, before the current limiting pre-charging of the bus capacitor, it further includes:

[0086] Detect the grid-side voltage and determine whether the three-phase sequence of the grid-side voltage is normal;

[0087] If so, start the current-limiting pre-charging for the bus capacitor;

[0088] If not, trigger an alarm and prompt a power failure.

[0089] Since the abnormality of the grid-side voltage will affect the charging voltage and the operation of components in the subsequent circuit, it is necessary to detect whether the three-phase sequence of the grid-side is normal before charging the bus capacitor to avoid the occurrence of the above problems.

[0090] Please refer to Figure 1 , which is the overall working flowchart of the present invention:

[0091] First, define the parameters of each part, including the resistance value of the charging resistor, the ratio of the frequency converter, etc., and then start to detect the grid-side voltage and determine whether the three-phase phase sequence is normal;

[0092] If it is determined to be abnormal, a power failure needs to be reported to remind the user to perform maintenance;

[0093] If it is determined to be normal, start charging the bus capacitor and record the charging time t of the bus capacitor from the start of charging to the end of charging and disconnecting the contactor;

[0094] Then judge the interval where the charging time t is located. When the charging time t satisfies: 0 < t ≤ t1, it is determined that the operating frequency of the frequency converter is the first power segment, and the operating parameters in the first power segment are executed;

[0095] When the charging time t satisfies: t1 < t ≤ t2, it is determined that the operating frequency of the frequency converter is the second power segment, and the operating parameters in the second power segment are executed;

[0096] When the charging time t satisfies: t2 < t, it is determined that the operating frequency of the frequency converter is the third power segment, and the operating parameters in the third power segment are executed;

[0097] Here, t1 and t2 are the charging times calculated according to the first power segment and the second power segment respectively. Since there may be a deviation between the capacitance value of the capacitor and the actual capacitance value, and the charging time is also affected by other factors such as voltage fluctuations, the above judgment process is determined by a time interval. Figure 1 Although only the implementation manners of three power segments are pointed out in

[0098] Please refer to Figure 2The inverter on the left is a traditional design inverter. Since it requires manual input of parameters, a host computer needs to be set up inside it to interact with the manual input. However, after the present invention adopts the above-mentioned self-identification method, it does not require manual input. It can use its own controller to identify the power segment of the inverter operation and execute the corresponding control parameters. Therefore, it can cancel the setting of the host computer and reduce the hardware cost.

[0099] In this regard, the present invention further proposes a frequency converter which adopts the above-mentioned self-identification method.

[0100] The present invention also provides an air conditioner having the above-mentioned inverter.

[0101] Compared with the existing technology, the present invention does not require the addition of additional devices. By detecting and calculating the inverter, it can automatically identify the power range of the inverter operation, thereby achieving the effect of automatically adapting to inverters of different power ranges without the need for manual input of models and parameters through a host computer, key circuits, etc., thereby improving the automation control capability and reducing the manual operation steps and the probability of human operation errors.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. The inverter power segment self-identification method is characterized by: It includes: When the frequency converter is powered on, the charging resistor is used to limit the current for pre-charging the bus capacitor; Detect the charging time of the bus capacitor from the start of charging to the end of charging; Obtain the power segment in which the frequency converter operates according to the charging time, and operate the control parameters in the current power segment; Obtaining the power segment in which the frequency converter operates according to the charging time includes: Calculate the capacitance value of the bus bus capacitor according to the charging time; Obtain the power segment in which the frequency converter operates corresponding to the capacitance value of the bus capacitor; Set the correspondence between the power segment and the charging time, and obtain 2. The self-identification method according to claim 1, characterized in that The charging time and the capacitance of the bus capacitor satisfy the calculation model: t=-R*C*[-In(1-V C / V DC )]; Wherein, C is the capacitance of the busbar capacitor, V C is the voltage across the bus capacitor, V DC is the charging voltage of the bus capacitor, R is the resistance of the charging resistor, and t is the charging time.

3. The self-identification method according to claim 2, characterized in that: The power segment in which the frequency converter operates according to the charging time. The correspondence satisfies: When 0 < t ≤ 5RC1, it is determined that the power segment in which the frequency converter operates is the first power segment; When 5RC1 < t ≤ 5RC2, it is determined that the power segment in which the frequency converter operates is the second power segment; When t > 5RC2, it is determined that the power segment in which the frequency converter operates is the third power segment; Where, t is the charging time, C1 is the capacitance value of the bus 4. The self-identification method according to claim 1, characterized in that capacitor when the power segment in which the frequency converter operates is the first power segment, C2 is the capacitance value of the bus capacitor when the power segment in which the frequency converter operates is the second power segment, and R is the resistance value of the charging resistor. Before the current-limiting pre-charging of the bus capacitor, it further includes: Detect the grid-side voltage and judge whether the three-phase sequence of the grid-side voltage is normal; If so, start the current-limiting pre-charging for the bus capacitor; 5. The self-identification method according to claim 3, characterized in that: If not, trigger an alarm and prompt a power failure.

6. The self-identification method according to claim 1, characterized in that: In all power segments in which the frequency converter operates, the resistance value of the charging resistor is the same, and the resistance value of the charging resistor is 100Ω. When detecting the charging time, it further includes: Detect the voltage on the bus capacitor; 7. Frequency converter, characterized in that, Judge whether the voltage on the bus capacitor reaches the charging voltage of the bus capacitor; 8. Air conditioner, characterized in that If so, it is determined that the bus capacitor is fully charged, and calculate the charging time. The frequency converter adopts the self-identification method described in any one of claims 1 to 6. The air conditioner has a frequency converter as described in claim 7.

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