Frequency converter performance detection method and frequency converter control device

Abstract

The invention discloses a frequency converter performance detection method and a frequency converter control device. The performance of a frequency converter can be quickly and accurately verified. The method comprises the following steps: acquiring an updated value of an influence factor of the output voltage of the frequency converter in the on-load operation process of the frequency converter; the output voltage of the frequency converter has a plurality of influence factors, and only one influence factor is updated at the same time; calculating a given value of the output voltage of the frequency converter according to the updated value; performing output voltage control on the frequency converter based on the given value; and obtaining the actual output power of the frequency converter to detect the performance of the frequency converter.

Description

[0001] This application claims the priority of the Chinese patent application filed with the China Patent Office on September 26, 2023, with application number 202311256512.X and invention name “A method for detecting inverter performance and inverter control device”, the entire contents of which are incorporated by reference in this application. Technical Field

[0002] The present invention relates to the field of frequency conversion technology, and more specifically, to a frequency converter performance detection method and a frequency converter control device. Background Art

[0003] Frequency conversion equipment (such as frequency conversion air conditioners, frequency conversion refrigerators, frequency conversion washing machines and other household appliances) is a device equipped with a frequency converter. The output end of the frequency converter is connected to the power supply end of the motor in the device; the frequency converter uses frequency conversion technology and microelectronics technology to control the operation of the motor by changing the power supply frequency of the motor.

[0004] The output power of the inverter needs to match the rated power of the motor load to ensure the performance of the inverter. Therefore, before the inverter leaves the factory, it is necessary to confirm the performance of the inverter by testing whether the output power of the inverter meets the requirements.

[0005] The traditional inverter performance testing solution is to install the inverter directly in the frequency conversion equipment and run it. During this period, the output power of the inverter is actually measured to confirm the performance of the inverter. However, this solution has the following disadvantages: the ambient temperature and humidity, the system refrigerant filling amount, etc. have an impact on the output power of the motor. Therefore, even at the same power supply frequency, the output power of the inverter will be different. When the deviation from the rated power is large, it takes a lot of time to confirm whether this is a problem with the inverter itself or caused by external factors. Summary of the invention

[0006] In view of this, the present invention provides a frequency converter performance detection method and a frequency converter control device, so as to realize fast and accurate verification of the performance of the frequency converter.

[0007] A method for detecting performance of a frequency converter comprises the following steps:

[0008] During the load operation of the inverter, an updated value of an influencing factor of the inverter output voltage is obtained; wherein the inverter output voltage has at least two influencing factors, and at least one of the influencing factors is updated at the same time;

[0009] Calculating a given value of the inverter output voltage at least according to the updated value;

[0010] Controlling the inverter output voltage based at least on the given value;

[0011] The actual output power of the inverter is obtained at least according to the output voltage of the inverter, and the performance of the inverter is detected at least according to the actual output power of the inverter.

[0012] A method for detecting performance of a frequency converter, characterized in that it comprises the following steps:

[0013] During the inverter load operation, the updated value of the influencing factor of the inverter output voltage is obtained; the inverter output voltage has multiple influencing factors, and only one influencing factor is updated at the same time;

[0014] Calculating a given value of the inverter output voltage according to the updated value;

[0015] Controlling the output voltage of the frequency converter based on the given value;

[0016] The actual output power of the inverter is obtained, and the performance of the inverter is tested accordingly.

[0017] A frequency converter control device comprises: a processor and a memory, wherein a program is stored in the memory, and the program can be called by the processor and used to execute the frequency converter performance detection method as described above.

[0018] It can be seen from the above technical solution that the present invention detects the output power of the inverter when the inverter is running with load. During the detection, the embodiment of the present invention pre-sets various influencing factors of the inverter output voltage, and changes the inverter output power according to different test conditions by adjusting a certain influencing factor value, thereby verifying the performance of the inverter, and the verification result is fast and accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0020] Figure 1 A flow chart of a frequency converter performance detection method disclosed in an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of a frequency converter wiring disclosed in an embodiment of the present invention;

[0022] Figure 3a A schematic diagram of a dummy load circuit disclosed in an embodiment of the present invention;

[0023] Figure 3b A schematic diagram of another dummy load circuit disclosed in an embodiment of the present invention;

[0024] Figure 3c A schematic diagram of another dummy load circuit disclosed in an embodiment of the present invention;

[0025] Figure 3d A schematic diagram of another dummy load circuit disclosed in an embodiment of the present invention;

[0026] Figure 4a A frequency converter output voltage synthesis vector diagram disclosed in an embodiment of the present invention;

[0027] Figure 4b This is another inverter output voltage synthesis vector diagram disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1 The embodiment of the present invention discloses a method for detecting performance of a frequency converter, comprising:

[0030] Step S01: During the inverter's loaded operation, an updated value of an influencing factor of the inverter's output voltage is obtained, and then the process proceeds to step S02.

[0031] Among them, the parameters that affect the output voltage, that is, the influencing factors are readable and writable. They can be manually updated during operation or automatically updated according to the system, and then the updated value is read. Furthermore, the load carried by the inverter is a dummy load (dummy load is also called virtual load or simulated load; for example, Figure 2 As shown, the input end of the inverter is connected to the power supply, and the output end is connected to the dummy load); the output voltage of the inverter has multiple or at least two influencing factors, and only one influencing factor is updated at the same time or at least one of the influencing factors is updated at the same time. When the load is a dummy load instead of a real motor load, it can avoid the influence of environmental temperature and humidity, system refrigerant filling amount, etc. on the operation of the motor and thus affect the output power of the inverter. Only one influencing factor is updated at the same time, which means that only one influencing factor is changed each time, and the influencing factor is a single variable.

[0032] Specifically, when the impedance of the dummy load used in the inverter performance test is fixed, the factors affecting the inverter output voltage include: the power supply frequency F of the motor, the voltage-frequency ratio (that is, the ratio of the inverter output voltage Vout to the power supply frequency F of the motor) K, and the inverter output voltage Voffset corresponding to the motor when the motor is stationary.

[0033] When the dummy load impedance is fixed, the relationship between the inverter output voltage Vout, the motor power frequency F, the voltage-frequency ratio K, and the inverter output voltage Voffset corresponding to the motor being stationary can be simplified to the following relationship:

[0034] Vout=K*F+Voffset

[0035] In the formula, the units of Vout and Voffset are both V, the unit of F is Hz, and the unit of K is V / Hz. The maximum value of the inverter output voltage Vout is limited by the inverter bus voltage. times.

[0036] It should be noted that when the dummy load specification can cover the motor load power range actually corresponding to the inverter, there is no need to adjust the impedance of the dummy load, otherwise it needs to be adjusted.

[0037] Step S02: Calculate a given value of the inverter output voltage at least according to the updated value, and then proceed to step S03.

[0038] Step S03: Control the output voltage of the inverter at least based on the given value, that is, control the output voltage of the inverter at least based on the given value, and then enter step S04.

[0039] Step S04: Acquire the actual output power of the inverter and detect the performance of the inverter based on it, that is, obtain the actual output power of the inverter at least according to the output voltage of the inverter, and detect the performance of the inverter at least according to the actual output power of the inverter.

[0040] Specifically, it can be seen from the above formula that, when the dummy load impedance is fixed, adjusting the value of any one of the influencing factors among the power supply frequency F of the motor, the voltage-frequency ratio K, and the inverter output voltage Voffset corresponding to the motor when the motor is stationary can change the inverter output voltage Vout (Vout can be expressed as a voltage value). Therefore, when the inverter performance is tested in the embodiment of the present invention, the influencing factors of the inverter output voltage Vout are pre-set, and the given value of the inverter output voltage Vout is adjusted by adjusting the value of one of the influencing factors, and the inverter output voltage is controlled based on the given value (for example, the inverter output voltage is open-loop controlled based on the given value, and open-loop control is a basic control method, which refers to a control method that directly applies a control signal to the controlled object without a feedback control signal to achieve the expected effect), so that the inverter output voltage Vout changes, and the inverter output power changes with the inverter output voltage, so that the inverter output power changes under different detection conditions, and the performance of the inverter can be verified accordingly.

[0041] Among them, different adjustment factors and adjustment values ​​correspond to different detection conditions, such as the following 1) to 3):

[0042] 1) To meet the inverter performance test under the constant torque working mode of the motor, the dummy load impedance, voltage-frequency ratio K and the inverter output voltage Voffset corresponding to the motor when it is stationary can be set to be fixed. By adjusting the power supply frequency F of the motor, the inverter can output different powers to verify the performance of the inverter.

[0043] 2) In order to meet the performance test of the inverter connected to different motors, the dummy load impedance, the power frequency F of the motor and the corresponding inverter output voltage Voffset when the motor is stationary can be set to be fixed. By adjusting the voltage-frequency ratio K, the purpose of the inverter outputting different powers can be achieved, thereby verifying the performance of the inverter.

[0044] Specifically, adjusting the voltage-frequency ratio K will change the voltage induced constant Ke of the motor; for an excitation motor, adjusting the voltage-frequency ratio K will affect its voltage induced constant Ke, and the output voltage and output power of the inverter will also change accordingly, so the performance of the inverter can be verified according to the change of the inverter output power; for a permanent magnet motor, the voltage induced constant Ke is a fixed value, so adjusting the voltage-frequency ratio K can correspond to permanent magnet motors with different voltage induced constants Ke. The larger the voltage induced constant Ke of the permanent magnet motor, the higher the output voltage and output power of the inverter, so the performance of the inverter can be verified according to the change of the inverter output power.

[0045] 3) In order to meet the inverter performance detection in the working mode where the motor load current changes, the dummy load impedance, voltage-frequency ratio K and motor power supply frequency F can be set to be fixed. By adjusting the inverter output voltage Voffset corresponding to the motor when it is stationary, the inverter outputs different powers to verify the performance of the inverter.

[0046] In summary, the embodiment of the present invention detects the output power of the inverter when the inverter is running with a load, and the load is a dummy load rather than a real motor load (that is, the embodiment of the present invention does not need to install the inverter in the frequency conversion equipment to drive the real motor load to run), thereby avoiding the influence of environmental temperature and humidity, system refrigerant filling amount, etc. on the operation of the motor and thus affecting the output power of the inverter. During the detection, the embodiment of the present invention pre-sets various influencing factors of the inverter output voltage, and changes the inverter output power by adjusting a certain influencing factor value according to different test conditions, thereby verifying the performance of the inverter, and the verification result is fast and accurate.

[0047] Moreover, different frequency converters need to be matched with different motors. The traditional frequency converter performance detection scheme needs to replace the motor according to the frequency converter during detection, which is not only troublesome in operation but also incompatible. However, from the above 2), it can be seen that the embodiment of the present invention does not need to replace the motor according to the frequency converter during detection, is compatible with a variety of frequency converters, and can confirm the performance of the frequency converter in a short time.

[0048] Optionally, in any of the above disclosed embodiments, the output power of the inverter can be obtained by actual measurement or by calculation based on the actual output voltage of the inverter and the impedance of the dummy load, and the calculation formula is P=V 2 / R. To save costs, the embodiment of the present invention recommends the latter.

[0049] In any of the above disclosed embodiments, in the dq coordinate system (the dq coordinate system is a synchronous rotating coordinate system, the d-axis is the direct axis, representing the excitation component; the q-axis is the quadrature axis, representing the torque component), the given value of the inverter output voltage is a voltage vector synthesized by the given values ​​of the d-axis and q-axis components according to the angle. Specifically: the given value Vq of the q-axis component of the inverter output voltage can be set to be constantly zero, and the given value Vd of the d-axis component can be calculated according to the formula (for example, the aforementioned formula Vout=K*F+Voffset), at this time Vd=Vout, for example Figure 4aAs shown; or, the given value Vd of the d-axis component of the inverter output voltage can be set to be constant at zero, and the given value Vq of the q voltage component can be calculated according to a formula (such as the aforementioned formula Vout = K*F + Voffset), in which case Vq = Vout; or, the given values ​​Vd and Vq of the d-axis and q-axis components can be set to be non-zero, and the given values ​​of the d-axis and q-axis components can be calculated respectively, and then the given value of the inverter output voltage can be synthesized according to the angle, for example Figure 4b To simplify the calculation, the embodiment of the present invention recommends using any one of the above two calculation methods.

[0050] In any of the above disclosed embodiments, the dummy load is a circuit having motor load characteristics formed by connecting three resistors and three inductors together in a preset connection mode. During detection, a dummy load with a certain impedance is used, and as long as the required impedance can be achieved, the resistance and inductance parameters and their connection modes are not limited. The following are only four optional connection modes:

[0051] 1) If Figure 3a As shown, the dummy load is composed of resistor R41, resistor R42, resistor R43, inductor L41, inductor L42 and inductor L43. The dummy load is a resistor and an inductor connected in series to simulate a single-phase load of a motor, and the three-phase simulated load is connected in a Y-shaped connection.

[0052] The three-phase simulated load is connected in a Y-connection method (ie, a star connection method), which means that one end of the three simulated loads is connected together, and three live wires U, V, and W are respectively led out from the other end.

[0053] 2) If Figure 3b As shown, the dummy load is composed of resistor R11, resistor R12, resistor R13, inductor L11, inductor L12 and inductor L13. The dummy load is a resistor and an inductor connected in series to simulate a single-phase load of a motor, and then the three-phase simulated load is connected in a delta connection.

[0054] The three-phase simulated load is connected in a △-shaped connection (ie, a triangle connection), which means that the three simulated loads are connected end to end in sequence to form a triangle, and the three vertices of the triangle lead out three live wires U, V, and W respectively.

[0055] 3) If Figure 3c As shown, the dummy load is composed of resistor R21, resistor R22, resistor R23, inductor L21, inductor L22 and inductor L23. The dummy load is to connect three inductors in a triangle shape, the three vertices of the triangle are respectively connected to one end of the three resistors, and the other ends of the three resistors are respectively connected to three live wires U, V, and W.

[0056] 4) If Figure 3d As shown, the dummy load is composed of a resistor R31, a resistor R32, a resistor R33, an inductor L31, an inductor L32 and an inductor L33. The dummy load is formed by connecting three resistors in a triangle shape, with the three vertices of the triangle connected to one end of the three inductors respectively, and the other ends of the three inductors lead out three live wires U, V and W respectively.

[0057] In the embodiment of the present invention, the parameter determination is related to power. For example: Figure 3a For example, assuming that the rated power of the motor load is 5KW~7KW and the rated current is 20Arms, then according to the formula P=I U 2 *R+I V 2 *R+I W 2 *R=3*I 2 *R, set the three resistors to 4.3Ω, set the three inductors to 2mh based on the actual motor inductance, and then confirm the inverter output voltage according to the initial output power of the inverter, for example, 4kW. F can be set to 60Hz, K to 2V / Hz, and Voffset to 11V. U ,I V ,I W , I, and R represent U-phase current, V-phase current, W-phase current, motor load rated current, and motor load impedance respectively.

[0058] In addition, corresponding to the above method embodiment, the embodiment of the present invention also discloses a frequency converter control device, including: a processor and a memory, wherein a program is stored on the memory, and when the program is executed by the processor, any frequency converter performance detection method disclosed above is implemented, that is, the program can be called by the processor and used to execute the frequency converter performance detection method disclosed in any of the above embodiments. .

[0059] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0060] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the embodiments of the present invention. Therefore, the embodiments of the present invention will not be limited to the embodiments shown herein, but rather to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting performance of a frequency converter, characterized in that: The following steps are involved: During the load operation of the inverter, an updated value of an influencing factor of the inverter output voltage is obtained; wherein the inverter output voltage has at least two influencing factors, and at least one of the influencing factors is updated at the same time; Calculating a given value of the inverter output voltage at least according to the updated value; Controlling the output voltage of the frequency converter based at least on the given value; The actual output power of the inverter is obtained at least according to the output voltage of the inverter, and the performance of the inverter is detected at least according to the actual output power of the inverter.

2. A method for detecting performance of a frequency converter, characterized in that: The following steps are involved: During the inverter's load operation, an updated value of the influencing factor of the inverter's output voltage is obtained; The inverter output voltage has multiple influencing factors, and only one influencing factor is updated at the same time; Calculating a given value of the inverter output voltage according to the updated value; Controlling the output voltage of the frequency converter based on the given value; The actual output power of the inverter is obtained, and the performance of the inverter is tested accordingly.

3. The inverter performance detection method according to claim 1 or 2, characterized in that: The load carried by the frequency converter is a dummy load; the influencing factors include: the power frequency F of the motor, the voltage-frequency ratio K, and the frequency converter output voltage Voffset corresponding to the motor when it is stationary; The voltage-frequency ratio K refers to the ratio of the inverter output voltage Vout controlled based on the given value to the power frequency F of the motor.

4. The inverter performance detection method according to claim 3, characterized in that: When the dummy load impedance is fixed, the relationship between the inverter output voltage Vout, the power frequency F of the motor, the voltage-frequency ratio K and the inverter output voltage Voffset corresponding to the motor being stationary is: Vout=K*F+Voffset.

5. The inverter performance detection method according to claim 4, characterized in that: When it is necessary to detect the performance of the frequency converter in the constant torque working mode of the motor, the obtaining of the updated value of the influencing factor of the frequency converter output voltage under the condition that the dummy load impedance is fixed includes: obtaining the updated value of the power supply frequency F of the motor; When it is necessary to detect the performance of the frequency converter when connected to different motors, the updated value of the influencing factor of the frequency converter output voltage is obtained under the condition that the dummy load impedance is fixed, which is: obtaining the updated value of the voltage-frequency ratio K of the motor; When it is necessary to detect the performance of the inverter in the working mode where the motor load current changes, when the dummy load impedance is fixed, the updated value of the influencing factor of the inverter output voltage is obtained by: obtaining the updated value of the inverter output voltage Voffset corresponding to the motor when the motor is stationary.

6. The frequency converter performance detection method according to claim 1 or 2, characterized in that: The step of calculating a given value of the inverter output voltage according to the updated value comprises: In the dq coordinate system, the given value of the q-axis component of the inverter output voltage is set to be constant to zero, and the given value of the d-axis component is calculated at least according to the updated value, and the given value of the d-axis component is equal to the given value of the inverter output voltage; Alternatively, in the dq coordinate system, the given value of the d-axis component of the inverter output voltage is set to be constant at zero, and the given value of the q-axis component is calculated at least according to the updated value, and the given value of the q-axis component is equal to the given value of the inverter output voltage.

7. The inverter performance detection method according to claim 1 or 2, characterized in that: The controlling the output voltage of the frequency converter based on the given value comprises: performing open-loop control on the output voltage of the frequency converter based on at least the given value to obtain the output voltage of the frequency converter.

8. The inverter performance detection method according to claim 1 or 2, characterized in that: The obtaining of the actual output power of the inverter includes: calculating the actual output power of the inverter according to the output voltage of the inverter and the impedance of the load carried by the inverter.

9. The frequency converter performance detection method according to claim 1 or 2, characterized in that: The dummy load includes a circuit having motor load characteristics formed by connecting three resistors and three inductors together in a preset connection mode.

10. The frequency converter performance detection method according to claim 9, characterized in that: The dummy load uses a resistor and an inductor connected in series to simulate a single-phase load of a motor. The three-phase simulated load is connected in a star connection, and the three external connection terminals of the star lead out three live wires U, V, and W respectively; Alternatively, the dummy load uses a resistor and an inductor connected in series to simulate a single-phase load of a motor, and the three-phase simulated load is connected in a triangle connection, and the three vertices of the triangle lead out three live wires U, V, and W respectively; Alternatively, the dummy load connects three inductors in a triangle connection, the three vertices of the triangle are respectively connected to one end of three resistors, and the other ends of the three resistors are respectively connected to three live wires U, V, and W; Alternatively, the dummy load connects three resistors in a triangle connection, the three vertices of the triangle are respectively connected to one end of three inductors, and the other ends of the three inductors are respectively led out to three live wires U, V, and W.

11. A frequency converter control device, characterized in that: include: A processor and a memory, wherein a program is stored in the memory, and the program can be called by the processor and used to execute the inverter performance detection method according to any one of claims 1 to 10.

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