Input open-phase and unbalance detection method, frequency converter and frequency control device

Abstract

The application discloses an input open-phase and unbalance detection method, a frequency converter and a frequency conversion control device. The detection method comprises the following steps: obtaining a ripple period of a bus voltage and an output current; if the ripple period is consistent with an open-phase period, the frequency converter is operated to the maximum frequency, and then whether the output current is stable is detected; according to the detection result, whether the three-phase power supply input is open-phase or unbalanced is judged, and then the frequency of the frequency converter is reduced or a voltage stabilizing module is executed to stabilize the output current. The application accurately judges whether the three-phase power supply is input open-phase or unbalanced through the ripple period and the output current, then the output current is stabilized by reducing the frequency of the frequency converter first, if the output current is still unstable, the voltage stabilizing module is executed to stabilize the output current, so that the load continues to operate preferentially, the shutdown condition is avoided, and the needs of users are met.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, and in particular to a method for detecting input phase loss and imbalance, a frequency converter, and a frequency conversion control device. Background Technology

[0002] Traditional three-phase detection methods mostly determine phase loss or imbalance by directly analyzing the harmonics or phase difference of the AC side voltage. However, these methods have the following problems: they rely on AC side sensors, which increases system complexity; they require the detection of the bus voltage ripple period, but can only detect phase loss (such as the complete loss of a phase voltage), which may mistakenly identify an unbalanced state as a phase loss state and shut down the system.

[0003] However, in some harsh areas, the power quality is poor, and users require the system to continue operating even if a three-phase power supply is missing or unbalanced. However, existing detection methods directly shut down the system after detecting a three-phase power supply loss or imbalance, which does not meet user needs. Summary of the Invention

[0004] This invention provides a method for detecting input phase loss and imbalance, a frequency converter, and a frequency conversion control device, which solves the problem that the existing technology directly shuts down the machine after detecting a phase loss or imbalance in a three-phase power supply, which does not meet user needs.

[0005] The technical solution of this invention is a method for detecting input phase loss and imbalance, comprising:

[0006] The ripple period and output current of the bus voltage are obtained. If the ripple period matches the missing period, the frequency converter runs to the maximum frequency, and then the output current is checked to see if it is stable.

[0007] Based on the test results, it is determined that the three-phase power input is missing a phase or unbalanced. Then, the frequency of the inverter is reduced or the voltage regulation module is activated to stabilize the output current.

[0008] Further, detecting whether the output current is stable includes:

[0009] If the output current is unstable, the three-phase power supply input is missing a phase;

[0010] If the output current is stable, the three-phase power supply is unbalanced.

[0011] Furthermore, based on the unstable output current, the three-phase power supply input phase loss includes:

[0012] Check again whether the output current is stable;

[0013] If so, the frequency converter maintains the current frequency operation;

[0014] If not, the three-phase power supply is in an input phase loss state, and the frequency converter is in an abnormal operation state with an input phase loss. At this time, it is determined whether the frequency of the frequency converter is at the minimum frequency.

[0015] If so, the voltage regulator module is activated to stabilize the output current;

[0016] If not, continue to reduce the frequency of the inverter.

[0017] Furthermore, when the output current stabilizes, the inverter maintains operation at the current frequency, including:

[0018] Determine whether the current frequency is a preset frequency for the current temperature;

[0019] If so, the inverter maintains the current frequency, allowing the inverter to continue operating even when it is experiencing an input phase loss.

[0020] If not, reduce the frequency of the inverter to continue operation, so that the inverter continues to operate even when there is an input phase loss.

[0021] Furthermore, the inverter continues to operate even when it is experiencing an input phase loss, including:

[0022] Acquire and determine whether the ripple amplitude of the bus voltage exceeds a first threshold;

[0023] If so, the voltage regulator module is activated to stabilize the output current;

[0024] If not, the inverter continues to operate at the current frequency.

[0025] Further, based on the test results, the imbalance of the three-phase power supply can be determined, including:

[0026] Obtain and compare the temperature of the inverter module with the preset temperature threshold;

[0027] If the temperature of the inverter module exceeds the preset temperature threshold, the three-phase power supply is moderately unbalanced, and the operating frequency of the inverter is the preset frequency of the current temperature - Δf;

[0028] If the temperature of the inverter module does not exceed the preset temperature threshold, the three-phase power supply is slightly unbalanced, and the operating frequency of the inverter is the preset frequency for the current temperature.

[0029] Further, based on acquiring and comparing the inverter module's temperature with a preset temperature threshold, including:

[0030] Obtain the ripple amplitude of the bus voltage, and determine whether the ripple amplitude exceeds the first threshold based on the comparison result;

[0031] If so, the voltage regulator module is activated to stabilize the output current;

[0032] If not, the inverter maintains its current frequency operation.

[0033] Further, according to the voltage regulator module, it includes:

[0034] Determine whether the output current is stable;

[0035] If so, the three-phase power supply is in a phase loss state, the frequency converter is at its minimum frequency and performs the normal operation of the voltage regulator module;

[0036] If not, the frequency converter operates at its minimum frequency and executes the abnormal operation state of the voltage regulator module until the frequency converter shuts down automatically.

[0037] Further, the ripple period of the bus voltage is obtained, and it is determined whether the ripple period conforms to the missing ripple period;

[0038] If not, the frequency converter is operating normally;

[0039] If so, the three-phase power supply is experiencing a phase loss or imbalance at the input.

[0040] Further, based on the three-phase power supply being in a state of input phase loss or imbalance, including:

[0041] The output current is monitored in real time to determine whether the output current changes from a continuous increase to a continuous decrease.

[0042] If not, the output current is stable;

[0043] If so, record the maximum value of the output current, and compare whether the maximum current difference between two adjacent cycles of the output current exceeds the second threshold.

[0044] If the comparison results for a preset number of consecutive times all meet the condition of exceeding the difference limit, the output current is unstable;

[0045] If the comparison results of a preset number of consecutive comparisons do not meet the condition of exceeding the difference limit, the output current will be stable.

[0046] The present invention also proposes a frequency converter, comprising:

[0047] The rectifier module connected to the three-phase power supply has its output side connected to the input side of the inverter module through a bus capacitor module. The output side of the inverter module is used to connect to a three-phase motor.

[0048] A voltage regulator module is connected in parallel with the bus capacitor module;

[0049] A ripple detection module connected to the bus capacitor module is used to detect the ripple period of the bus voltage of the bus capacitor module.

[0050] The motor is connected to a sampling module for detecting the output current in any two phases.

[0051] The control unit is connected to the voltage regulator module, ripple detection module, and sampling module respectively. The control unit is used to make the frequency converter run to the maximum frequency according to the ripple period matching the missing period, and then detect whether the output current is stable. Based on the detection result, it is determined that the three-phase power input is missing a phase or unbalanced, and then the frequency of the frequency converter is reduced or the voltage regulator module 20 is activated to stabilize the output current.

[0052] Furthermore, the voltage regulator module includes a transistor Q1, a relay K1, and a bus capacitor C2;

[0053] The base of transistor Q1 is used to connect to the output terminal of the control unit, the collector of transistor Q1 is connected to the first coil pin of relay K1, the second coil pin of relay K1 is used to connect to the power supply pin, the first contact pin of relay K1 is connected to the negative terminal of bus capacitor C2, and the positive terminal of bus capacitor C2 is used to connect to the positive terminal of bus capacitor module.

[0054] The emitter of the transistor Q1 and the second contact pin of the relay K1 are both grounded.

[0055] Furthermore, the ripple detection module includes resistor R1 and resistor R2;

[0056] The first end of resistor R1 and the first end of resistor R2 are both connected to the first sampling terminal of the control unit; the second end of resistor R1 is used to connect to the positive terminal of the bus capacitor module, and the second end of resistor R2 is grounded.

[0057] The present invention also proposes a frequency converter control device, which includes the frequency converter described above.

[0058] Compared with the prior art, the present invention has at least the following beneficial effects:

[0059] This invention uses ripple period and output current to accurately determine whether a three-phase power supply is experiencing a phase loss or imbalance. It then first reduces the frequency of the inverter to stabilize the output current. If the output current is still unstable, it activates the voltage regulation module to further stabilize the output current, thereby prioritizing the continued operation of the load and preventing shutdowns to meet user needs. Attached Figure Description

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings are used to distinguish different objects and not to describe a particular order.

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 This is a flowchart of the first method for detecting input phase loss and imbalance proposed in this invention;

[0063] Figure 2 This is a second flowchart of the input phase loss and imbalance detection method proposed in this invention;

[0064] Figure 3 The circuit diagram of the frequency converter proposed in this invention is shown below.

[0065] Figure 4 The waveform diagram of the output current of the frequency converter proposed in this invention when it is in a three-phase unbalanced state;

[0066] Figure 5 The waveform of the output current of the frequency converter proposed in this invention when the input phase is lost;

[0067] Figure 6 This is a waveform diagram of the output current of the frequency converter proposed in this invention when the input phase is lost and the voltage regulation module is started.

[0068] Figure label:

[0069] 10. Inverter module;

[0070] 20. Voltage regulator module;

[0071] 30. Rectifier module;

[0072] 40. Bus capacitor module;

[0073] 50. Electric motor;

[0074] 60. Detection module;

[0075] 70. Temperature detection module;

[0076] 80. Sampling module;

[0077] 90. Control unit. Detailed Implementation

[0078] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Therefore, a feature pointed out in this specification is used to illustrate one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0079] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0080] In some harsh areas, where power quality is poor, users require continued operation even after a three-phase power supply phase loss or imbalance. However, existing detection methods directly shut down the machine upon detecting a three-phase power supply phase loss, which does not meet user needs.

[0081] Therefore, in some embodiments, such as Figure 1 As shown, this invention proposes a method for detecting input phase loss and imbalance, comprising:

[0082] The ripple period and output current of the bus voltage are obtained. If the ripple period matches the missing period, the frequency converter is forced to run to the maximum frequency, and then the output current is checked to see if it is stable.

[0083] Based on the detection results, it is determined that the three-phase power input is missing a phase or unbalanced. Then, the frequency of the inverter is reduced or the voltage regulator module 20 is executed to stabilize the output current. At this time, the control unit 90 uploads the status information of the three-phase power input missing phase or unbalanced to the host computer and prompts an abnormality. When the voltage regulator module 20 is executed, the control unit 90 will also prompt the host computer that there may be a risk of shortened capacitor life.

[0084] It should be noted that the frequency reduction of the inverter proposed in this embodiment refers to reducing the inverter frequency to a preset frequency corresponding to the current temperature. The output current proposed in this embodiment refers to the current output by the inverter to the load (such as motor 50).

[0085] When the ripple period matches the missing period, the three-phase power supply has already experienced input phase loss or imbalance. However, it is not possible to accurately pinpoint whether it is input phase loss or imbalance at this time. Therefore, the frequency converter is forced to run at the maximum frequency, and then the output current is checked to determine whether it is stable, thereby accurately pinpointing whether it is input phase loss or imbalance.

[0086] In this way, the present invention can accurately determine whether the three-phase power supply is missing a phase or unbalanced by measuring the ripple period and the output current. Then, it first reduces the frequency of the inverter to stabilize the output current. If the output current is still unstable, it then executes the voltage regulation module 20 to stabilize the output current, thereby prioritizing the continued operation of the load and avoiding shutdown to meet the user's needs.

[0087] Among them, such as Figure 4 As shown, it can be seen that after the three-phase power supply becomes unbalanced, the output current is relatively stable; while as Figure 5 As shown, it can be seen that after a phase loss in a three-phase power supply, the output current becomes unstable, and the ripple becomes significantly larger; while as Figure 6 As shown, after a phase loss in the three-phase power supply, the voltage regulator module 20 is activated, and the output current becomes stable, with a noticeable reduction in ripple.

[0088] In some embodiments, such as Figure 1 As shown, the ripple period of the bus voltage is obtained, and it is determined whether the ripple period conforms to the missing ripple period.

[0089] If not, the inverter is operating normally, and the subsequent control unit 90 will continuously determine whether the ripple cycle matches the missing ripple cycle at intervals.

[0090] If so, the three-phase power supply is experiencing a phase loss or imbalance at the input.

[0091] In this way, the control unit 90 will continuously monitor the ripple period of the bus voltage. If the ripple period of the bus voltage is detected to match the characteristics of the missing ripple period, it indicates that there is a three-phase power input phase loss or imbalance. Then the control unit 90 will feed this information back to the host computer and indicate that the status is abnormal.

[0092] When the host computer receives the information that "three-phase power input is missing or unbalanced", it will continue to run by default. That is, the host computer will send a command to the control unit 90 to continue running. The inverter will be forced to run at the maximum frequency. Then the control unit 90 will monitor the stability of the output current to accurately determine whether the three-phase power input is missing or unbalanced.

[0093] Of course, if the user manually selects the stop command on the host computer, the frequency converter or the equipment with the frequency converter installed will enter the stop state.

[0094] In some embodiments, to accurately determine whether the output current is stable, such as Figure 2 As shown, the three-phase power supply being in a state of input phase loss or imbalance includes:

[0095] The output current is monitored in real time to determine whether the output current changes from a continuous increase to a continuous decrease.

[0096] If not, the output current is stable, and the frequency converter is operating normally;

[0097] If so, record the maximum value of the output current, and compare whether the maximum current difference between two adjacent cycles of the output current exceeds the second threshold.

[0098] If the comparison results for a preset number of consecutive times all meet the condition of exceeding the difference limit, the output current is unstable;

[0099] If the comparison results of a preset number of consecutive comparisons do not meet the condition of exceeding the difference limit, the output current will be stable.

[0100] It should be noted that the preset number of times proposed in this embodiment is 20 times as an example. Of course, other values ​​can be selected according to the actual situation, and this is not limited here. Moreover, the difference exceeding the limit condition proposed in this embodiment is that the maximum current difference between two adjacent cycles of the output current exceeds the second threshold.

[0101] In this way, if the maximum current difference between two cycles of the output current sampled 20 times exceeds the second threshold, the output current is determined to be unstable, thereby improving accuracy; and if the maximum current difference between two cycles of the output current does not exceed the second threshold once within 20 consecutive samples, the output current is determined to be stable.

[0102] In some embodiments, to accurately determine whether a three-phase power supply is experiencing a phase loss or imbalance at the input, such as... Figure 1 As shown, detecting whether the output current is stable includes:

[0103] If the output current is unstable, the three-phase power input is missing a phase; in this way, the frequency of the inverter can be reduced first to stabilize the output current. If the output current is still unstable, the voltage regulator module 20 can be executed to stabilize the output current, thereby prioritizing the load to continue running and avoiding a shutdown.

[0104] If the output current is stable, the three-phase power supply is unbalanced. In this case, the frequency of the inverter can be reduced first to stabilize the output current. If the output current is still unstable, the voltage regulator module 20 can be executed to stabilize the output current, thereby prioritizing the load to continue running and avoiding a shutdown.

[0105] In some embodiments, such as Figure 1 As shown, based on the unstable output current, the three-phase power supply input is missing a phase, including:

[0106] Check again whether the output current is stable;

[0107] If so, the frequency converter maintains the current frequency operation to enable the frequency converter to operate;

[0108] If not, the three-phase power supply is in an input phase loss state, and the frequency converter is in an abnormal operation state with an input phase loss. At this time, it is determined whether the frequency of the frequency converter is at the minimum frequency.

[0109] If so, the voltage regulator module 20 is activated to stabilize the output current;

[0110] If not, continue to reduce the frequency of the inverter.

[0111] It should be noted that the abnormal operating state of the inverter in the three-phase power input phase loss mentioned in this embodiment refers to the inverter "running unstable", which is mainly manifested by the following characteristics: speed fluctuation, the loss of a phase causes the motor torque pulsation to increase, and the speed exhibits periodic fluctuations of more than ±5% (typical frequency is 100Hz), which is significantly different from the ±1% speed deviation during normal operation; current oscillation, in the two-phase operation state, the current amplitude of the remaining two phases will increase to 1.7-2 times the rated value, and is accompanied by high-frequency harmonic components.

[0112] In this way, when the frequency of the inverter decreases and the output current is still unstable, the control unit 90 will gradually reduce the frequency of the inverter until the output current reaches a stable state. If the output current is still unstable when the frequency of the inverter drops to the minimum frequency, the control unit 90 will directly start the voltage regulator module 20 to stabilize the output current.

[0113] In some embodiments, to ensure that the output current remains stable and the load can continue to operate when the frequency converter is in a state of input phase loss, such as... Figure 1 As shown, when the output current is stable, the frequency converter maintains operation at the current frequency, including:

[0114] Determine whether the current frequency is a preset frequency for the current temperature;

[0115] If so, the inverter maintains the current frequency, allowing the inverter, which is experiencing an input phase loss, to continue operating stably, thereby ensuring the load continues to operate;

[0116] If not, reduce the frequency of the inverter so that the inverter, which is experiencing an input phase loss, can continue to operate, thereby keeping the load running.

[0117] In some embodiments, to further ensure that the frequency converter can continue to operate even with a phase loss at input, such as Figure 1 As shown, the inverter continues to operate even when it is experiencing an input phase loss, including:

[0118] Acquire and determine whether the ripple amplitude of the bus voltage exceeds a first threshold;

[0119] If so, the voltage regulator module 20 is activated to stabilize the output current;

[0120] If not, the inverter continues to operate at the current frequency, and the control unit 90 will continuously determine whether the ripple amplitude of the bus voltage exceeds the first threshold during the interval.

[0121] Furthermore, each time the frequency of the inverter is adjusted, it will determine whether the ripple amplitude of the bus voltage exceeds the first threshold. If necessary, the voltage regulation module 20 will be activated and the corresponding status information will be fed back to the host computer.

[0122] In some embodiments, such as Figure 1 As shown, the three-phase power supply imbalance is determined based on the test results, including:

[0123] Acquire and compare the temperature of inverter module 10 with a preset temperature threshold;

[0124] If the temperature of the inverter module 10 does not exceed the preset temperature threshold, the three-phase power supply is only slightly unbalanced, and the operating frequency of the inverter is the preset frequency for the current temperature.

[0125] If the temperature of the inverter module 10 exceeds the preset temperature threshold, the three-phase power supply is only moderately unbalanced, and the operating frequency of the inverter is the preset frequency of the current temperature - Δf; if the temperature of the inverter module 10 still exceeds the preset temperature threshold after frequency reduction, the operating frequency of the inverter is further reduced to the minimum frequency.

[0126] It should be noted that the preferred Δf in this embodiment is 5Hz. Of course, other values ​​can be selected according to the actual situation, which are not limited here.

[0127] When the current is stable and the temperature of the inverter module 10 does not exceed the preset temperature threshold, it indicates that the inverter has a slight acceptable three-phase imbalance. The inverter will adjust its frequency to the preset frequency at the current temperature. When the current is stable and the temperature of the inverter module 10 exceeds the preset temperature threshold, it indicates that the inverter has a moderate short-term acceptable three-phase imbalance (three-phase imbalance may cause a significant increase in the current of a certain phase. For example, if a certain phase is overloaded, even if the total current remains unchanged, the increase in local current will lead to an increase in the loss of the module in that phase, resulting in a higher temperature rise). The inverter will adjust its frequency to the preset frequency at the current temperature minus 5Hz. If the temperature of the inverter module 10 still exceeds the preset temperature threshold after frequency reduction, the frequency reduction will continue until the minimum frequency of the inverter is reached.

[0128] In some embodiments, such as Figure 1As shown, based on acquiring and comparing the temperature of inverter module 10 with a preset temperature threshold, including:

[0129] Obtain the ripple amplitude of the bus voltage, and determine whether the ripple amplitude exceeds the first threshold based on the comparison result;

[0130] If so, the voltage regulator module 20 is activated to stabilize the output current;

[0131] If not, the inverter continues to operate at the current frequency, and the control unit 90 will continuously determine whether the ripple amplitude of the bus voltage exceeds the first threshold during the interval.

[0132] In this way, when the frequency converter drops to the minimum frequency due to three-phase imbalance, it then checks whether the ripple amplitude of the bus voltage exceeds the first threshold. If it does, the control unit 90 executes the voltage regulation module 20 to stabilize the output current. Then, the control unit 90 sends status information to the host computer, indicating that there may be a risk of shortened capacitor life.

[0133] This ensures that the inverter can respond appropriately under various fault conditions, from slight acceptable three-phase imbalance to moderate short-term acceptable three-phase imbalance to severe input phase loss. The inverter can prioritize keeping the load running by adjusting the frequency and starting the voltage regulator module 20, while providing detailed fault information to the host computer so that maintenance measures can be taken in a timely manner.

[0134] In some embodiments, such as Figure 1 As shown, the voltage regulator module 20 includes:

[0135] Determine whether the output current is stable;

[0136] If so, the three-phase power supply is in a phase loss state, the frequency converter is at the minimum frequency and performs the normal operation of the voltage regulator module 20;

[0137] If not, the frequency converter operates at its minimum frequency and executes the abnormal operation state of the voltage regulator module 20 until the frequency converter shuts down automatically.

[0138] In this way, after the control unit 90 executes the voltage regulator module 20, it will determine whether the output current is stable. If the output current is stable, it indicates that the inverter is operating at the minimum frequency under the phase loss condition, and checks the ripple amplitude. If necessary, it will report the capacitor life risk to the host computer. If the output current is unstable, it indicates that the inverter cannot operate stably at the minimum frequency under the phase loss condition, even if the voltage regulator module 20 is started. Then, this status information is sent to the host computer. At this time, the inverter will not stop automatically, and the load will continue to run until the inverter automatically shuts down and the load stops.

[0139] In some embodiments, such as Figure 3 As shown, the present invention also proposes a frequency converter, comprising:

[0140] A rectifier module 30 is connected to a three-phase power supply. The output side of the rectifier module 30 is connected to the input side of the inverter module 10 through a bus capacitor module 40. The output side of the inverter module 10 is used to connect to a three-phase motor 50.

[0141] The voltage regulator module 20 is connected in parallel with the bus capacitor module 40;

[0142] The ripple detection module 60, which is connected to the bus capacitor module 40, is used to detect the ripple period of the bus voltage of the bus capacitor module 40.

[0143] The motor 50 is connected to a sampling module 80 for detecting the output current in any two phases.

[0144] The control unit 90 is connected to the voltage regulator module 20, the ripple detection module 60, the temperature detection module 70, and the sampling module 80 respectively. The control unit 90 is used to control the frequency converter to run at the maximum frequency according to the ripple period matching the missing ripple period, and then detect whether the output current is stable. Based on the detection result, it is determined that the three-phase power input is missing a phase or unbalanced, and then the frequency of the frequency converter is reduced or the voltage regulator module 20 is activated to stabilize the output current.

[0145] It should be noted that the ripple detection module 60 proposed in this embodiment can also be used to detect the ripple amplitude of the bus voltage of the bus capacitor module 40; this embodiment also proposes a temperature detection module 70 connected to the inverter module 10 and the control unit 90 respectively, which is used to detect the temperature of the inverter module 10. The control unit 90 proposed in this embodiment is preferably a DSP or FPGA.

[0146] In this way, the present invention can accurately determine whether the three-phase power input is missing a phase or unbalanced by measuring the output current and the temperature of the inverter module 10. Then, it first reduces the frequency of the inverter to stabilize the output current. If the output current is still unstable, it then executes the voltage stabilization module 20 to stabilize the output current, thereby enabling the load to continue to operate and avoiding shutdown, thus meeting the user's needs.

[0147] In this embodiment, the bus capacitor module 40 includes a bus capacitor C1, the positive and negative terminals of which are connected to the two ends of the output side of the rectifier module 30 and the two ends of the input side of the inverter module 10, respectively.

[0148] In some embodiments, to ensure that the voltage regulator module 20 can output a stable current, such as Figure 3 As shown, the voltage regulator module 20 includes a transistor Q1, a relay K1, and a bus capacitor C2;

[0149] The base of transistor Q1 is connected to the output terminal of control unit 90, the collector of transistor Q1 is connected to the first coil pin of relay K1, the second coil pin of relay K1 is connected to the power supply pin, the first contact pin of relay K1 is connected to the negative terminal of bus capacitor C2, and the positive terminal of bus capacitor C2 is connected to the positive terminal of bus capacitor C1.

[0150] The emitter of the transistor Q1 and the second contact pin of the relay K1 are both grounded.

[0151] Thus, when the voltage regulator module 20 is started, the control unit 90 will turn on the transistor Q1, activate the relay K1, and connect the parallel bus capacitor C2 to regulate the output current. Then, the control unit 90 will feed back this status to the host computer, indicating that although it can run at this time, there may be a problem of reduced capacitor life.

[0152] In some embodiments, to ensure that the control unit 90 can accurately or in real-time acquire the ripple period and ripple amplitude of the bus voltage, such as Figure 3 As shown, the ripple detection module 60 includes resistors R1 and R2;

[0153] The first end of resistor R1 and the first end of resistor R2 are both connected to the first sampling terminal of the control unit 90; the second end of resistor R1 is used to connect to the positive terminal of the bus capacitor C1, and the second end of resistor R2 is grounded.

[0154] In this embodiment, two sampling modules 80 are used as an example, that is, any two phases of the motor 50 are respectively connected to a sampling module 80. Specifically, this embodiment uses the first phase of the motor 50 as an example to illustrate the connection of a sampling module 80.

[0155] The sampling module 80 includes sampling resistors R3, R4, R5, R6, and R7, and operational amplifier U1;

[0156] Among them, the output side of the inverter module 10 is connected in series with the first phase of the motor 50, and the non-inverting terminal of the operational amplifier U1 is connected to the first terminal of the resistor R6 and the first terminal of the resistor R7. The second terminal of the resistor R6 is connected to the first terminal of the sampling resistor R3, and the second terminal of the resistor R7 is grounded.

[0157] The inverting input of operational amplifier U1 is connected to the first terminals of resistor R4 and resistor R5. The second terminal of resistor R4 is connected to the second terminal of sampling resistor R3. The second terminal of resistor R5 and the output terminal of operational amplifier U1 are both connected to the second sampling terminal of control unit 90.

[0158] Similarly, the circuit for connecting the second or third phase of motor 50 to a sampling module 80 is the same as that for the first phase, so we will not go into details here.

[0159] Furthermore, the principle that motor 50 only needs to sample the current of any two phases to calculate the current of the third phase is based on Kirchhoff's Current Law (KCL), that is, the vector sum of the three-phase currents is zero (I0). a +I b +I c =0), therefore the third phase current can be calculated from the first two phases: I c =-(I a +I b This allows for dual-resistance sampling; and by selecting the two phases with the largest duty cycle for sampling, the interference of switching noise on the phase current with the small duty cycle can be avoided, improving the calculation accuracy, thereby obtaining a more accurate output current based on the sampling of the three-phase current.

[0160] In some embodiments, the present invention also provides a frequency converter control device, which includes the frequency converter described above.

[0161] In this way, the present invention can accurately determine whether the three-phase power input is missing a phase or unbalanced by measuring the output current and the temperature of the inverter module 10. Then, it first reduces the frequency of the inverter to stabilize the output current. If the output current is still unstable, it then executes the voltage stabilization module 20 to stabilize the output current, thereby keeping the load running and avoiding the shutdown of the load or even the frequency converter control equipment, thus meeting the user's needs.

[0162] Specifically, the control flow of the present invention is as follows:

[0163] First, power on the device. The control unit 90 monitors the ripple period, ripple amplitude, and output current of the bus voltage in real time. After the motor 50 starts running, it checks whether the ripple period of the bus voltage matches the missing ripple period. If it matches the missing ripple period, it indicates that there is a phase loss or three-phase imbalance in the input, and this status is fed back to the host computer.

[0164] If the host computer commands continued operation, the inverter is forced to run at its maximum frequency. The control unit 90 determines whether the current is stable based on the detected output current. If the output current is stable, it indicates that there is only a three-phase imbalance. If the temperature of the inverter module 10 does not exceed the preset temperature, it indicates an acceptable, slight three-phase imbalance, and the inverter frequency is reduced to the preset frequency at the current temperature. Then, the control unit 90 determines whether the ripple amplitude of the bus voltage exceeds the first threshold. If it does, the control unit 90 drives transistor Q1, activates relay K1, and connects the parallel bus capacitor C2 for voltage regulation (equivalent to executing the voltage regulation module 20). This status is fed back to the host computer, indicating that although operation is possible, there may be a problem with reduced capacitor lifespan.

[0165] If the output current is stable, it indicates that there is only a three-phase imbalance. However, the temperature of inverter module 10 exceeds the threshold, indicating that the system has a moderate, short-term acceptable three-phase imbalance (three-phase imbalance may cause a significant increase in current in a certain phase; for example, if a phase is overloaded, even if the total current remains unchanged, the increase in local current will lead to increased losses in that phase module, resulting in a higher temperature rise). The inverter adjusts its frequency to the preset frequency at the current temperature minus 5Hz. If the temperature still exceeds the limit, the frequency continues to decrease until the minimum frequency is reached. Subsequently, the ripple amplitude of the bus voltage is checked. If it exceeds the first threshold, the voltage regulator module 20 is activated to regulate the voltage and transmits status information upwards, indicating a potential risk of shortened capacitor life.

[0166] If the inverter's output current remains unstable at its maximum frequency, or if a fault is reported, it indicates an input phase loss. First, the inverter's frequency is reduced to a preset frequency for the current temperature. If the output current stabilizes at this point, the inverter maintains the current frequency, reports the phase loss to the host computer, and continues operation (equivalent to stabilizing). Then, the control unit 90 determines whether the bus voltage ripple amplitude exceeds the first threshold. If it does, the voltage regulator module 20 is activated to regulate the voltage, and this status is reported back to the host computer, indicating that although operation is possible, there may be a reduction in capacitor lifespan. If the inverter's frequency is at the preset frequency for the current temperature, and the output current remains unstable, the frequency needs to be reduced further until the output current stabilizes. The host computer is then notified of the phase loss, frequency reduction, and stabilization. The control unit 90 then determines whether the bus voltage ripple amplitude exceeds the first threshold. If it does, the voltage regulator module 20 is activated to regulate the voltage, and this status is reported back to the host computer, indicating that although operation is possible, there may be a reduction in capacitor lifespan.

[0167] If the voltage regulator module 20 is activated and stabilizes the voltage, the control unit 90 then checks whether the output current is stable. If it is stable, it reports the minimum frequency operating condition of the inverter under phase loss conditions. Only after the voltage regulator module 20 is activated and stabilized will the inverter run stably. Then, the control unit 90 checks whether the ripple amplitude of the bus voltage exceeds the first threshold. If it does, it reports this status to the host computer, indicating that although the inverter can run at this time, there may be a problem with reduced capacitor life. If the inverter still cannot run stably at the minimum frequency under phase loss conditions even after activating the voltage regulator module 20, it sends this status information to the host computer. At this time, the inverter will not automatically shut down, and the load will continue to run (for as long as possible) until the inverter automatically shuts down, at which point the inverter control equipment or load will stop.

[0168] Obviously, the embodiments described above are merely some embodiments of the present invention, not all embodiments. The accompanying drawings show preferred embodiments of the present invention, but do not limit the patent scope of the present invention. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this invention.

Claims

1. A method for detecting input phase loss and imbalance, characterized in that, include: The ripple period and output current of the bus voltage are obtained. If the ripple period matches the missing period, the frequency converter runs to the maximum frequency, and then the output current is checked to see if it is stable. If the output current is unstable, it is determined that a phase of the three-phase power supply input is missing. If the output current is stable, it is determined that the three-phase power supply is unbalanced; Based on the detection results, it is determined that the three-phase power input is missing a phase or unbalanced, and then the frequency of the inverter is reduced or the voltage regulator module (20) is executed to stabilize the output current.

2. The input phase loss and imbalance detection method according to claim 1, characterized in that, If the output current is unstable, after determining that the three-phase power supply input is missing a phase, the following steps are also included: The frequency converter is reduced to a preset frequency at the current temperature; Check again whether the output current is stable; If so, the frequency converter maintains the current frequency operation; If not, the three-phase power supply is in an input phase loss state, and the frequency converter is in an abnormal operation state with an input phase loss. At this time, it is determined whether the frequency of the frequency converter is at the minimum frequency. If so, the voltage regulator module (20) is activated to stabilize the output current; If not, continue to reduce the frequency of the inverter.

3. The input phase loss and imbalance detection method according to claim 2, characterized in that, After the frequency converter maintains the current frequency operation, it also includes: Determine whether the current frequency is a preset frequency for the current temperature; If so, the inverter maintains the current frequency, allowing the inverter to continue operating even when it is experiencing an input phase loss. If not, reduce the frequency of the inverter to continue operation, so that the inverter continues to operate even when there is an input phase loss.

4. The input phase loss and imbalance detection method according to claim 3, characterized in that, After enabling the inverter to continue operating despite a phase loss at the input, the process further includes: Acquire and determine whether the ripple amplitude of the bus voltage exceeds a first threshold; If so, the voltage regulator module (20) is activated to stabilize the output current; If not, the inverter continues to operate at the current frequency.

5. The input phase loss and imbalance detection method according to claim 1, characterized in that, If the output current is stable, after determining that the three-phase power supply is unbalanced, the following steps are also included: Obtain and compare the temperature of the inverter module (10) with the preset temperature threshold; If the temperature of the inverter module (10) exceeds the preset temperature threshold, the three-phase power supply is moderately unbalanced, and the operating frequency of the inverter is the preset frequency of the current temperature - ∆f; If the temperature of the inverter module (10) does not exceed the preset temperature threshold, the three-phase power supply is slightly unbalanced, and the operating frequency of the inverter is the preset frequency of the current temperature.

6. The input phase loss and imbalance detection method according to claim 5, characterized in that, After the operating frequency of the inverter is adjusted, the following is also included: Obtain the ripple amplitude of the bus voltage, and determine whether the ripple amplitude exceeds the first threshold based on the comparison result; If so, the voltage regulator module (20) is activated to stabilize the output current; If not, the inverter maintains its current frequency operation.

7. The input phase loss and imbalance detection method according to any one of claims 1 to 6, characterized in that, The voltage regulator module (20) is executed, specifically including: Determine whether the output current is stable; If so, the frequency converter is at its minimum frequency and is operating normally as the voltage regulator module (20); If not, the inverter operates at its minimum frequency and performs an abnormal operation of the voltage regulator module (20) until the inverter shuts down automatically.

8. The input phase loss and imbalance detection method according to any one of claims 1 to 6, characterized in that, Obtain the ripple period of the bus voltage and determine whether the ripple period matches the missing period; If not, the frequency converter is operating normally; If so, the three-phase power supply is experiencing a phase loss or imbalance at the input.

9. The input phase loss and imbalance detection method according to claim 8, characterized in that, Detecting whether the output current is stable includes: The output current is monitored in real time to determine whether the output current changes from a continuous increase to a continuous decrease. If not, the output current is stable; If so, record the maximum value of the output current, and compare whether the maximum current difference between two adjacent cycles of the output current exceeds the second threshold. If the comparison results for a preset number of consecutive times all meet the condition of exceeding the difference limit, the output current is unstable; If the comparison results of a preset number of consecutive comparisons do not meet the condition of exceeding the difference limit, the output current is stable.

10. A frequency converter, characterized in that, include: The output side of the rectifier module (30) connected to the three-phase power supply is connected to the input side of the inverter module (10) through the bus capacitor module (40), and the output side of the inverter module (10) is used to connect the three-phase motor (50). A voltage regulator module (20) is connected in parallel with the bus capacitor module (40). A ripple detection module (60) connected to the bus capacitor module (40) is used to detect the ripple period of the bus voltage of the bus capacitor module (40). Any two phases of the motor (50) are respectively connected to a sampling module (80), which is used to detect the output current; The control unit (90) is connected to the voltage regulator module (20), the ripple detection module (60), and the sampling module (80) respectively. The control unit (90) is used to make the frequency converter run to the maximum frequency according to the ripple period matching the missing period, and then detect whether the output current is stable. According to the detection result, it is determined that the three-phase power input is missing or unbalanced, and then the frequency of the frequency converter is reduced or the voltage regulator module (20) is executed to stabilize the output current. If the output current is unstable, it is determined that the three-phase power input is missing. If the output current is stable, it is determined that the three-phase power is unbalanced.

11. The frequency converter according to claim 10, characterized in that, The voltage regulator module (20) includes a transistor Q1, a relay K1, and a bus capacitor C2; The base of the transistor Q1 is used to connect to the output terminal of the control unit (90), the collector of the transistor Q1 is connected to the first coil pin of the relay K1, the second coil pin of the relay K1 is used to connect to the power supply pin, the first contact pin of the relay K1 is connected to the negative terminal of the bus capacitor C2, and the positive terminal of the bus capacitor C2 is used to connect to the positive terminal of the bus capacitor module (40). The emitter of the transistor Q1 and the second contact pin of the relay K1 are both grounded.

12. The frequency converter according to claim 10, characterized in that, The ripple detection module (60) includes resistors R1 and R2; The first end of resistor R1 and the first end of resistor R2 are both connected to the first sampling terminal of the control unit (90); the second end of resistor R1 is used to connect to the positive terminal of the bus capacitor module (40), and the second end of resistor R2 is grounded.

13. A frequency converter control device, characterized in that, The frequency converter control device includes the frequency converter according to any one of claims 10 to 12.

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