Phase sequence adjustment system and phase sequence adjustment method

Abstract

The present invention relates to a phase sequence adjustment system and a phase sequence adjustment method. The phase sequence adjustment system includes a power conversion circuit and a control circuit. The power conversion circuit is electrically connected to the mains power supply in a certain phase sequence. The control circuit applies a first excitation signal and a second excitation signal respectively to cause the power conversion circuit to form two short circuits with the mains power supply. The control circuit includes a current detection circuit and a control unit. The current detection circuit obtains two sets of current signals respectively during the two short circuit operations. The control unit calculates two sets of current angles respectively based on the two sets of current signals and determines whether the phase sequence is positive sequence or negative sequence accordingly. The control unit selects one of the two sets of current angles to correspond to calculating the voltage angle of the mains power supply, calculates the angle difference between the selected current angle and the voltage angle, and adjusts the feedback phase sequence according to the angle difference.

Description

Technical Field

[0001] The present disclosure relates to an adjustment method and an adjustment system for a power conversion circuit connected in parallel with a mains power grid, and particularly to a phase sequence adjustment method and a phase sequence adjustment system that can automatically detect and correct the phase sequence. Background Art

[0002] When a power conversion device is connected in parallel with a mains power grid, for the stability of the system operation, it is necessary to confirm the wiring sequence between the power conversion device and the mains power grid to ensure that the phase sequence received by the power conversion device is the same as the phase sequence output by the mains power grid, that is, to ensure the same phase sequence, so as to provide correct voltage and current feedback information to the controller of the power conversion device for subsequent operations.

[0003] If the phase sequence is incorrect, the information of voltage and current will not be correctly fed back, which may lead to system startup failure or abnormality. Therefore, how to simply and efficiently detect and correct the phase sequence without rewiring is one of the important topics in this field. Summary of the Invention

[0004] An embodiment of the present disclosure relates to a phase sequence adjustment system, including a power conversion circuit and a control circuit. The power conversion circuit is electrically connected to the mains power grid in a certain phase sequence. The control circuit is used to apply a first excitation signal and a second excitation signal to the switch of the power conversion circuit at different time points respectively, so as to form two short circuits between the power conversion circuit and the mains power grid. The control circuit includes a current detection circuit and a control unit. The current detection circuit is used to detect a first current signal corresponding to the first excitation signal and a second current signal corresponding to the second excitation signal when the power conversion circuit forms two short circuits. The control unit is used to calculate respectively according to the first current signal and the second current signal to obtain a first current angle and a second current angle, select one of the current angles from the first current angle or the second current angle and correspondingly calculate the voltage angle of the mains power grid. The control unit judges whether the phase sequence is positive sequence or negative sequence according to the first current angle and the second current angle, and calculates the angle difference between the selected current angle and the voltage angle, so as to adjust the feedback phase sequence of the power conversion circuit to the current detection circuit according to the angle difference.

[0005] Another embodiment of the present disclosure relates to a phase sequence adjustment method, comprising: applying a first excitation signal to form a short circuit between a power conversion circuit and the mains power, obtaining a first current signal of the power conversion circuit corresponding to the first excitation signal, wherein the power conversion circuit is electrically connected to the mains power in a certain phase sequence; after a time interval, applying a second excitation signal to form a short circuit between the power conversion circuit and the mains power again, obtaining a second current signal of the power conversion circuit corresponding to the second excitation signal; respectively calculating according to the first current signal and the second current signal to obtain a first current angle and a second current angle; judging whether the phase sequence is positive sequence or negative sequence based on the first current angle and the second current angle; calculating the voltage angle of the mains power obtained by the short - circuit operation time corresponding to one of the first current angle and the second current angle according to whether the phase sequence is positive sequence or negative sequence; calculating the angle difference between one of the first current angle and the second current angle and the voltage angle; and adjusting the feedback phase sequence of the power conversion circuit according to the angle difference.

[0006] In summary, the present disclosure can apply a first excitation signal to the power conversion circuit at any time for the first short - circuit operation, and apply a second excitation signal at an appropriate time interval for the second short - circuit operation. By obtaining two sets of corresponding voltage detection signals and two sets of current signals through the two short - circuit operations, the voltage angle of the mains power and the two current angles received by the power conversion circuit during the two short - circuit operations can be calculated. According to the angle difference between one of the two current angles and the voltage angle obtained by the corresponding short - circuit operation time, the current phase sequence can be judged, so that the phase sequence caused by the wrong connection of the three - phase lines of the power conversion circuit can be adjusted to be consistent with the phase sequence of the mains power through command feedback, so as to provide correct voltage and current feedback information. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 and Figure 2 FIG. is a schematic diagram showing a phase sequence adjustment system according to some embodiments of the present disclosure.

[0008] Figure 3 FIG. is a flowchart showing a phase sequence adjustment method according to some embodiments of the present disclosure.

[0009] Figure 4 is according to Figure 2 the embodiments of FIG. showing a waveform diagram of voltage and current.

[0010] Figure 5 FIG. is a waveform diagram of voltage and current showing according to some embodiments of the present disclosure.

[0011] Figures 6A to 6D FIG. is a waveform diagram of voltage and current showing according to some embodiments of the present disclosure.

[0012] Wherein, the reference numerals are explained as follows:

[0013] 100: Phase sequence adjustment system

[0014] 120: Output filter circuit

[0015] 140: Power conversion circuit

[0016] 160: Control circuit

[0017] 161: Current detection circuit

[0018] 162: Control unit

[0019] 163: Voltage detection circuit

[0020] AC: Mains electricity

[0021] A1: Area

[0022] Cdc, Cfa~Cfc: Capacitor

[0023] CS1: Drive control signal

[0024] CS2: Feedback control signal

[0025] Di1~Di3: Current detection signal

[0026] Di1_1~Di3_1, Di1_2~Di3_2: Current signal

[0027] Dva~Dvc: Voltage detection signal

[0028] ES1, ES2: Excitation signal

[0029] Lfa~Lfc, Lga~Lgc: Inductor

[0030] N1~N3, Na~Nc: Node

[0031] SW1~SW6: Switch

[0032] 300: Phase sequence adjustment method

[0033] S310~S370: Operation

[0034] T1, T2: Time point

[0035] t12: Time interval

[0036] p1: Half cycle

[0037] θ1, θ2: Current angle

[0038] θv, θvb: Voltage angle

[0039] Δθ: Angle difference Specific implementation manner

[0040] The following is a detailed description of embodiments in conjunction with the accompanying drawings. However, the specific embodiments described are only used to explain the present application and do not limit the present application. The description of the structure and operation is not used to limit the execution order. Any structure formed by recombining components and having an equivalent function is within the scope covered by the present disclosure.

[0041] Please refer to Figure 1 . As Figure 1 shown, the phase sequence adjustment system 100 includes an output filter circuit 120, a power conversion circuit 140, and a control circuit 160. The output filter circuit 120 is electrically connected between the mains AC and the power conversion circuit 140. Specifically, the input end of the output filter circuit 120 is electrically connected to the mains AC in parallel, and the power conversion circuit 140 is electrically connected to the output end of the output filter circuit 120 in a certain phase sequence. That is, the power conversion circuit 140 is electrically connected to the mains AC in this phase sequence. The control circuit 160 is connected to the power conversion circuit 140.

[0042] In some embodiments, the output filter circuit 120 may include a plurality of filter inductors Lfa to Lfc, Lga to Lgc and a plurality of filter capacitors Cfa to Cfc. The power conversion circuit 140 may be a three-phase six-arm conversion circuit, including a plurality of switches SW1 to SW6 and a capacitor Cdc. Structurally, the filter inductors Lfa and Lga are connected in series between the mains AC and the node Na. One end of the filter capacitor Cfa is connected between the filter inductors Lfa and Lga, and the other end of the filter capacitor Cfa is grounded. The switches SW1 and SW4 are connected to the node N1.

[0043] Similarly, the filter inductors Lfb and Lgb are connected in series between the mains AC and the node Nb. One end of the filter capacitor Cfb is connected between the filter inductors Lfb and Lgb, and the other end of the filter capacitor Cfb is grounded. The switches SW2 and SW5 are connected to the node N2. And the filter inductors Lfc and Lgc are connected in series between the mains AC and the node Nc. One end of the filter capacitor Cfc is connected between the filter inductors Lfc and Lgc, and the other end of the filter capacitor Cfc is grounded. The switches SW3 and SW6 are connected to the node N3. As Figure 1 shown, the phase sequence of the electrical connection between the output filter circuit 120 and the mains AC conforms to the output phase of the mains AC.

[0044] Operationally, the power conversion circuit 140 receives an AC power supply output by the output filter circuit 120 from the mains AC and performs AC-DC power conversion. The control circuit 160 is configured to receive three-phase voltage detection signals Dva to Dvc between the mains AC and the input terminal of the output filter circuit 120, and receive three-phase current detection signals Di1 to Di3 between the output terminal of the output filter circuit 120 and the power conversion circuit 140, and is configured to output a drive control signal CS1 to at least one of the plurality of switches SW1 to SW6 of the power conversion circuit 140 according to the voltage detection signals Dva to Dvc and the current detection signals Di1 to Di3 for drive control.

[0045] To ensure that the drive control signal CS1 generated according to the voltage and current detection signals is correctly fed back to the corresponding switch, it is necessary to determine that the phase sequence of the three-phase line formed by electrically connecting the power conversion circuit 140 to the output filter circuit 120 through wires matches the phase sequence of the three-phase line formed by electrically connecting the output filter circuit 120 to the mains AC through wires. However, the wire connection between the power conversion circuit 140 and the output filter circuit 120 is often installed manually, and the corresponding relationship of the three-phase lines is not completely reliable under manual installation and inspection. For example, as Figure 2 shown, area A1 is a general area for manual wiring. If the nodes N1, N2, and N3 at area A1 are not correctly connected to the nodes Na, Nb, and Nc, in the illustrated embodiment, the power conversion circuit 140 is electrically connected to the output filter circuit 120 in the phase sequence of b-phase, c-phase, a-phase, and the phase sequence of the output filter circuit 120 electrically connected to the mains AC is consistent, that is, the power conversion circuit 140 is substantially electrically connected to the mains AC in the phase sequence of b-phase, c-phase, a-phase. If it is not found during system operation that the power conversion circuit 140 is electrically connected to the mains AC in this incorrect wiring sequence, it will result in the power conversion circuit 140 being electrically connected to the mains AC in the wrong phase sequence during system operation, and this wrong phase sequence will cause errors in the feedback control of voltage and current.

[0046] To solve the above problems, the present application proposes a phase sequence adjustment method. Regardless of the wiring relationship at area A1, the phase sequence adjustment system 100 can determine the current phase sequence according to the voltage detection signals Dva to Dvc and the current detection signals Di1 to Di3, and redefine the feedback phase sequence control signal of the three-phase line according to the current phase sequence to ensure that the feedback phase sequence control signal is correctly matched to the corresponding switch and phase.

[0047] Specifically, as Figure 2As shown, the control circuit 160 includes a voltage detection circuit 163, a control unit 162, and a current detection circuit 161. The voltage detection circuit 163 is electrically connected between the mains AC and the input end of the output filter circuit 120. The current detection circuit 161 is electrically connected between the output end of the output filter circuit 120 and the power conversion circuit 140. The control unit 162 is electrically connected to the voltage detection circuit 163, the current detection circuit 161, and the power conversion circuit 140.

[0048] Operationally, the control unit 162 is configured to successively output a first excitation signal ES1 and a second excitation signal ES2 to the switches of the power conversion circuit 140 within a time interval to perform two short - circuit operations. The current detection circuit 161 is configured to receive two sets of current detection signals Di1 - Di3 obtained from the three - phase lines between the output filter circuit 120 and the power conversion circuit 140 corresponding to the two short - circuit operations performed in response to the first excitation signal ES1 and the second excitation signal ES2. The voltage detection circuit 163 is configured to receive two sets of voltage detection signals Dva - Dvc obtained from the three - phase lines between the mains AC and the output filter circuit 120 corresponding to the time of the two short - circuit operations. The control unit 162 is configured to determine the current phase sequence between the power conversion circuit 140 and the mains AC according to the two sets of voltage detection signals Dva - Dvc and the two sets of current detection signals Di1 - Di3, and adjust the definition of the three - phase lines according to the current phase sequence to send a corrected feedback control signal CS2 to the current detection circuit 161. The feedback control signal CS2 includes the adjusted definition of the three - phase line phase sequence. In one embodiment, the control unit 162 can be a signal generator, a processing circuit with specific digital logic (such as an executable application program), or a control circuit with a field - programmable gate array. The control unit 162 generates a feedback control signal CS2 to the current detection circuit 161 according to the determined current phase sequence. In this way, the current detection circuit 161 can determine the respective current phase sequences on the three paths of the three - phase line according to the feedback control signal CS2 and can correspond to the correct three - phase definition of the mains AC, that is, the three - phase definition of the actual wiring between the power conversion circuit 140 and the mains AC, avoiding the subsequent feedback control signal failing to be correctly matched due to different phase sequence definitions.

[0049] Please refer to Figure 3 . For convenience and clarity of description, the following phase - sequence adjustment method 300 is described in conjunction with Figure 2 、 Figure 4 and Figure 5 shown in the embodiments, but not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. As Figure 3 shown, the phase - sequence adjustment method 300 includes operations S310, S320, S330, S340, S345, S350, S360, and S370.

[0050] First, in operation S310, at any time, a first excitation signal ES1 is applied by the control unit 162 to a plurality of switches of the power conversion circuit 140, such as SW4, SW5, and SW6, and a first current signal corresponding to the first excitation signal ES1 is obtained. Specifically, the first excitation signal ES1 causes the lower-arm switches SW4, SW5, and SW6 of the three phases to conduct simultaneously. In other words, the control unit 162 of the control circuit 160 sends the first excitation signal ES1 to the power conversion circuit 140, so that short circuits are formed between the three-phase bridge arms of the power conversion circuit 140 and the mains AC, and the current detection circuit 161 obtains the current detection signals Di1 to Di3 corresponding to the short-circuit operation time and responsive to the first excitation signal ES1 as the first current signal. It should be noted that the foregoing short-circuit operation can also be achieved by applying the first excitation signal ES1 to cause the upper-arm switches SW1, SW2, and SW3 of the three phases of the power conversion circuit 140 to conduct simultaneously.

[0051] For example, as Figure 4 shown, at time point T1, the control unit 162 sends the first excitation signal ES1 to the power conversion circuit 140 for the first short-circuit operation, and the current detection circuit 161 correspondingly obtains the first current signals Di1_1 to Di3_1. In this embodiment, the time point T1 can be any time point, that is, regardless of the angle of the mains AC, the control unit 162 can apply the first excitation signal ES1 to the power conversion circuit 140 at any time for the first short-circuit operation. Accordingly, it is possible to effectively avoid the detection result being affected by specific non-ideal interference or harmonics in the mains AC voltage and resulting in an incorrect judgment.

[0052] Next, in operation S320, after a time interval, the control unit 162 applies a second excitation signal ES2 to the switches SW4, SW5, and SW6 of the power conversion circuit 140 to cause them to conduct simultaneously again, so that short circuits are formed again between the three-phase bridge arms of the power conversion circuit 140 and the mains AC, and the current detection circuit 161 obtains another set of current detection signals Di1 to Di3 corresponding to the short-circuit operation time and responsive to the second excitation signal ES2 as the second current signal. Specifically, operation S320 is similar to operation S310, and the form and function of the excitation signal ES2 are similar to those of the excitation signal ES1, and will not be elaborated here.

[0053] For example, as Figure 4As shown, at time point T2, the control unit 162 sends the second excitation signal ES2 to the power conversion circuit 140 for the second short - circuit operation, and the current detection circuit 161 correspondingly obtains the second current signals Di1_2~Di3_2. The time interval t12 between time points T1 and T2 is shorter than half of the cycle p1 of the mains AC output signal. In other words, within half of the cycle p1 of the mains AC output signal, the control unit 162 of the control circuit 160 respectively applies two excitation signals ES1 and ES2 to the power conversion circuit 140 for two short - circuit operations, and obtains two sets of current signals Di1_1~Di3_1 and Di1_2~Di3_2 corresponding to the two short - circuit operations via the current detection circuit 161.

[0054] Next, in operation S330, according to the first current signals Di1_1~Di3_1 of three phases at time point T1, the first current angle θ1 corresponding to the short - circuit operation time point T1 is calculated. Additionally, according to the second current signals Di1_2~Di3_2 of three phases at time point T2, the second current angle θ2 corresponding to the short - circuit operation time point T2 can be calculated. Specifically, for the calculation method of the current angle at any time point, please refer to the following derivation.

[0055]

[0056] Equation (1) is the voltage equation of the d - axis and q - axis in the stationary reference frame. Where p is the differential operator. Lf and Rf are the inductance value and resistance value of the output filter circuit 120. ω is the AC signal frequency of the mains power grid. Vg is the mains power grid voltage value.

[0057] When the power conversion circuit 140 receives the excitation signals ES1 and ES2 and performs the short - circuit operation, since the voltages of the d - axis and q - axis are both 0 during the short - circuit operation, that is Substituting the above - mentioned equation (1) can deduce equation (2), where Tsh is the time for maintaining the short - circuit operation.

[0058]

[0059] From the above equation (2), the current equations id(Tsh) and iq(Tsh) of the d - axis and q - axis during the short - circuit operation can be known, and based on this, the current angle at time t can be obtained as shown by θe(t) in equation (3).

[0060]

[0061] Accordingly, the former term in equation (3) of the current angle θe(t) can be obtained from the current transformation feedback to the stationary reference frame at present, and the latter term in equation (3) of the current angle θe(t) can be obtained from It can be obtained by substituting the mains frequency and related parameters into Equation (2). Substituting the parameters at time point T1 into Equation (3) can calculate the first current angle θ1 obtained by the first short-circuit operation at the corresponding time point T1. Additionally, substituting the parameters at time point T2 into Equation (3) can calculate the second current angle θ2 obtained by the second short-circuit operation at the corresponding time point T2.

[0062] In addition, the AC signal frequency ω of the mains power grid shown in Equation (2) can be calculated via the following Equation (4) based on the values of two sets of current angles, in addition to being determined according to the predetermined value of the mains power grid.

[0063]

[0064] Where τ12 in Equation (4) is the time interval between time point T1 and time point T2.

[0065] Next, in operation S340, the control unit 162 determines whether the current phase sequence between the power conversion circuit 140 and the mains AC is positive or negative. Specifically, the control unit 162 of the control circuit 160 can determine whether the current phase sequence is positive or negative based on the calculated two sets of current angles θ1 and θ2. In a three-phase AC circuit, the positive phase sequence means that phase a leads phase b by 120 degrees, phase b leads phase c by 120 degrees, and phase c leads phase a by 120 degrees. The positive phase sequence can include a / b / c, b / c / a, and c / a / b according to its combination; conversely, the negative phase sequence means that phase a lags phase b by 120 degrees, phase b lags phase c by 120 degrees, and phase c lags phase a by 120 degrees. The negative phase sequence can include c / b / a, b / a / c, and a / c / b according to its combination; in this application Figure 1 or Figure 2For the schematic wiring method, assume that the phase sequence of the mains AC input to the output filter circuit 120 is positive sequence and the phase is a / b / c. Then, the phase sequence of the power supply received by the power conversion circuit 140 is still positive sequence, but the phase is incorrect b / c / a and needs to be adjusted. Specifically, when the control unit 162 confirms that the two successive current angles θ1 and θ2 are rotating incrementally from 0 degrees to 360 degrees, and when the angular change relationship of the second current angle θ2 minus the first current angle θ1 is incremental or the angular calculation difference is positive (i.e., the second current angle θ2 is greater than the first current angle θ1 and the angle increases with time), it is determined that the current phase sequence is positive sequence. For example, when the second current angle θ2 is 100 degrees and the first current angle θ1 is 40 degrees, the current angle is rotating incrementally from 0 degrees to 360 degrees, and the angular change relationship of the second current angle θ2 minus the first current angle θ1 is +60 degrees, then it can be determined that the current phase sequence is positive sequence. It should be noted that in another embodiment, during the incremental rotation of the current angle from 0 degrees to 360 degrees, if the aforementioned first current angle θ1 is 350 degrees and the second current angle θ2 is 40 degrees, actually the current angle is still increasing. It's just that the first current angle θ1 increases by 50 degrees (crossing 360 degrees) from 350 degrees to become the second current angle θ2 of 40 degrees in the next cycle. In the case of crossing 360 degrees, directly calculating the difference between the second current angle θ2 and the first current angle θ1 may be negative. Therefore, in terms of the priority of judgment, the rotation direction of the current angle should still be the main consideration, and it is determined that the current phase sequence is positive sequence from the increasing direction.

[0066] For example, as Figure 4 shown, this case is a positive sequence of wrongly connected three-phase wires with the phase sequence and phase combination of b / c / a. The second current angle θ2 obtained from the second current signals Di1_2~Di3_2 at time point T2 is greater than the first current angle θ1 obtained from the first current signals Di1_1~Di3_1 at time point T1. Since the angle from the first current angle θ1 to the second current angle θ2 increases during the period from time point T1 to time point T2, the control unit 162 can determine that the current phase sequence is positive sequence.

[0067] Conversely, when the control unit 162 confirms that the two sets of current angles θ1 and θ2 successively are in the process of decreasing rotation from 360 degrees to 0 degrees, and when the angular change relationship of subtracting the first current angle θ1 from the second current angle θ2 is decreasing or the calculated angular difference is negative (i.e., the second current angle θ2 is less than the first current angle θ1, and the angle decreases with time), it is determined that the current phase sequence is negative sequence. For example, when the second current angle θ2 is 120 degrees and the first current angle θ1 is 180 degrees, the angle rotates decreasingly from 360 degrees to 0 degrees, and the angular change relationship of subtracting the first current angle θ1 from the second current angle θ2 is -60 degrees, then it can be determined that the current phase sequence is negative sequence. It should be noted that in another embodiment, in the process of the current angle rotating decreasingly from 360 degrees to 0 degrees, if the aforementioned first current angle θ1 is 20 degrees and the second current angle θ2 is 320 degrees, actually the current angle is still in the decreasing process. It's just that the first current angle θ1 decreases by 60 degrees (crossing 360 degrees) from 20 degrees to become the second current angle θ2 of 320 degrees in the next circle. In the case of crossing 360 degrees, directly calculating the difference between the second current angle θ2 and the first current angle θ1 may be positive. Therefore, in terms of the priority of judgment, the rotation direction of the current angle should still be the main consideration, and it is determined that the current phase sequence is negative sequence at this time from the decreasing direction.

[0068] For example, as Figure 5 shown, this case is the negative sequence phase sequence of misconnected three-phase wires with the phase combination of a / c / b, and the second current angle θ2 obtained from the second current signals Di1_2~Di3_2 is less than the first current angle θ1 obtained from the first current signals Di1_1~Di3_1. And since the angle decreases during the rotation process, the control unit 162 can determine that the current phase sequence is negative sequence.

[0069] When the control unit 162 determines that the current phase sequence is positive sequence or negative sequence, operation S345 is performed to calculate the voltage angle of the mains AC as a reference signal, or operation S350 is performed to calculate the voltage angle of the mains AC as a reference signal.

[0070] Specifically, in operation S345, the voltage detection circuit 163 transmits the voltage detection signals Dva~Dvc to the control unit 162, and the control unit 162 calculates the voltage angle θv corresponding to the mains power grid at the short-circuit operation time of one of the first current angle θ1 or the second current angle θ2. As Figure 4 shown in the embodiment in, the control unit 162 selects to calculate the voltage angle θv at the time point T2 (the short-circuit operation time corresponding to the second current angle θ2) according to the voltage detection signals Dva~Dvc of the three phases. As Figure 4 shown, when the control unit 162 determines that the current phase sequence is positive sequence, the control unit 162 directly uses the calculated voltage angle θv as the reference angle adopted in the subsequent steps. In this case, as Figure 4As shown, the control unit 162 calculates the change curve VA of the voltage angle θv based on the voltage detection signal Dva of the a-phase. The change curve VA of the voltage angle θv gradually increases with time from the zero crossing point of 0 degrees until it reaches 360 degrees and then gradually increases again when it returns to zero, which is a periodic change. Similarly, the control unit 162 calculates the change curve CA of the current angle based on the current detection signal Di1 of the a-phase. Figure 4 It can be seen that there is a phase sequence difference between the two curves VA and CA due to the wrong wiring order, and this difference remains at a certain value.

[0071] On the other hand, when the control unit 162 determines that the current phase sequence is negative, it executes operation S350. The control unit 162 calculates the short-circuit operation time of the mains power grid corresponding to the voltage angle θv at either the first current angle θ1 or the second current angle θ2, and adjusts the aforementioned voltage angle θv according to the situation where the determined phase sequence is negative. Specifically, the control unit 162 calculates the voltage angle θv at the time point T2 (the short-circuit operation time corresponding to the second current angle θ2) based on the voltage detection signals Dva to Dvc of the three phases. As Figure 5 shown, the control unit 162 first subtracts 360 degrees from the originally calculated value of the voltage angle θv and then multiplies it by a negative sign to obtain a reference signal adjusted according to the negative sequence (i.e., Figure 5 the voltage angle θvb in ). For example, assume that the originally calculated voltage angle at the time point T2 based on the voltage detection signals Dva to Dvc of the three phases is 320. When it is determined that the current phase sequence is negative, the control unit 162 first subtracts 360 degrees from the originally calculated value of the voltage angle and then multiplies it by a negative sign according to the negative sequence to obtain the voltage angle θvb after negative sequence adjustment, that is, the adjusted voltage angle θvb = [-1 * (320 - 360)] = 40 degrees. As Figure 5 shown, the control unit 162 calculates the change curve VA of the voltage angle θvb after negative sequence adjustment based on the voltage detection signal Dva of the a-phase. The change curve VA of the voltage angle θvb after negative sequence adjustment gradually decreases with time from 360 degrees until it reaches the zero crossing point of 0 degrees, and then gradually decreases again from 360 degrees when the change curve VA of the voltage angle θvb after negative sequence adjustment reaches the zero crossing point of 0 degrees, which is a periodic change. Similarly, the control unit 162 calculates the change curve CA of the current angle based on the current detection signal Di1 of the a-phase. Figure 5 It can be seen that there is a phase sequence difference between the two curves VA and CA due to the wrong wiring order, and this difference remains at a certain value.

[0072] Next, in operation S360, an angle difference Δθ is calculated between one of the first current angle θ1 or the second current angle θ2 and the corresponding voltage angle according to whether the phase sequence is positive or negative. Specifically, the control unit 162 can calculate the angle difference Δθ between the first current angle θ1 or the second current angle θ2 calculated corresponding to the time point of one of the first and second short - circuit operations, and the voltage angle (voltage angle θv or the voltage angle θvb adjusted by negative sequence) obtained at the corresponding short - circuit operation time for the selected current angle, that is, calculate the angle difference between the selected current angle and the voltage angle obtained at the short - circuit operation time of this current angle. For example, if the current phase sequence is positive and the comparison current angle θ2 is selected, as Figure 4 shown, when it is determined that the phase sequence is positive, the angle difference Δθ is the voltage angle θv at the corresponding time point T2 minus the current angle θ2 at the corresponding time point T2. Another example, if the current phase sequence is negative and the comparison current angle θ2 is selected, as Figure 5 shown, the angle difference Δθ is the current angle θ2 at the corresponding time point T2 minus the voltage angle θvb at the corresponding time point T2 and adjusted by negative sequence.

[0073] In this way, two current angles θ1 and θ2 are obtained through two short - circuit operations. By comparing the second current angle θ2 obtained from the comparison of the second current signals Di1_2~Di3_2 with the first current angle θ1 obtained from the first current signals Di1_1~Di3_1, it is possible to determine whether the current phase sequence is positive or negative. According to whether the current phase sequence is positive or negative, one of the two current angles θ1 and θ2 is directly selected and compared with the voltage angle θv corresponding to the selected current angle or the voltage angle θvb adjusted by negative sequence and used as a reference signal, so as to obtain a stable and accurate angle difference Δθ between the current angle and the voltage angle.

[0074] Finally, in operation S370, the control unit 162 adjusts the feedback phase sequence of the power conversion circuit 140 according to the angle difference Δθ. Specifically, since there are six combinations of the connections of nodes N1, N2, and N3 to Na, Nb, and Nc, the angle difference Δθ will correspond to one of 0, 60, 120, 180, 240, and 300 degrees. Therefore, the control unit 162 can determine the current corresponding feedback phase sequence according to different angle differences Δθ and provide it to the current detection circuit 161 in the form of a feedback control signal CS2.

[0075] Taking the phase sequence of the mains AC electrically connected to the filter circuit 120 fixed as phase a, phase b, and phase c (three - phase AC power supply) as an example, the relationships between the six combinations of the phase sequences of the electrical connections between the output filter circuit 120 and the power conversion circuit 140 and the angle difference Δθ are respectively exemplified as follows. As Figure 4 shown, when the angle difference Δθ is 240 degrees, it can be known that the current phase sequence is phase b, phase c, and phase a, and as Figure 4In the illustrated embodiment, the angular relationship between the change VA of the voltage angle θv and the change curve CA of the current angle is fixed. That is, regardless of whether the angular difference Δθ is calculated between the first current angle θ1 or the second current angle θ2 and the corresponding voltage angle θv, it will always be fixed at 240 degrees. As Figure 5 shown, similar to the foregoing embodiment, in this embodiment, when the angular difference Δθ is fixed at 180 degrees, it can be known that the current phase sequence is negative and the phase combination is phase a, phase c, and phase b. As Figure 6A shown, when the angular difference Δθ is fixed at 0 degrees, it can be known that the current phase sequence is positive and the phase combination is the correct phase a, phase b, and phase c. As Figure 6B shown, when the angular difference Δθ is fixed at 120 degrees, it can be known that the current phase sequence is positive and the phase combination is phase c, phase a, and phase b. As Figure 6C shown, when the angular difference Δθ is fixed at 60 degrees, it can be known that the current phase sequence is negative and the phase combination is phase b, phase a, and phase c. As Figure 6D shown, when the angular difference Δθ is fixed at 300 degrees, it can be known that the current phase sequence is negative and the phase combination is phase c, phase b, and phase a. It should be noted that when the angular difference Δθ is 0 degrees, the positive and negative of the current phase sequence and the phase combination are the same as those of the mains AC input, and the feedback phase sequence does not need to be adjusted.

[0076] By judging the current feedback phase sequence through the angular difference Δθ, the control unit 162 can establish a corresponding relationship between the order of the current detection signals Di1~Di3 defined inside the control circuit 160 and the generated feedback control signal CS2, and adjust it to be consistent with the feedback phase sequence of the current mains AC input voltage. Without modifying the physical wiring order, redefining the phase sequence according to the feedback control signal CS2 can ensure the normal operation of the power conversion circuit 140.

[0077] For example, in the Figure 4 embodiment, based on the angular difference Δθ of 240 degrees, the control unit 162 knows that the current phase sequence is positive and the phase combination is phase b, phase c, and phase a (i.e., the wiring order shown in area A1 in Figure 2 ). Therefore, the control unit 162 generates feedback control signal CS2 information based on the current detection signal Di3 and the corresponding voltage detection signal Dva and outputs it to the corresponding switches SW3 and SW6, generates feedback control signal CS2 information based on the current detection signal Di1 and the corresponding voltage detection signal Dvb and outputs it to the corresponding switches SW1 and SW4, and generates feedback control signal CS2 information based on the current detection signal Di2 and the corresponding voltage detection signal Dvc and outputs it to the corresponding switches SW2 and SW5, enabling the power conversion circuit 140 to perform switch switching according to the correct and corresponding phase sequence of the mains AC without modifying the physical wiring order.

[0078] In summary, in the present application, by applying the above-described various embodiments, the power conversion circuit 140 is successively applied with the first excitation signal ES1 and the second excitation signal ES2 at a time interval to perform two short-circuit operations, so as to obtain two sets of voltage detection signals Dva to Dvc and two sets of current signals Di1_1 to Di3_1, Di1_2 to Di3_2 corresponding to the two short-circuit operation times, respectively. Then, the voltage angle θv of the mains AC and the two current angles θ1, θ2 received by the power conversion circuit 140 can be calculated. According to the angular changes of the two current angles θ1, θ2, it can be determined whether the current phase sequence is positive or negative; according to the angular difference Δθ between one of the two current angles θ1, θ2 and the voltage angle θv obtained by calculating the corresponding short-circuit operation time, the phase combination in the current phase sequence can be determined, so as to adjust the phase sequence of the three-phase lines of the power conversion circuit 140 to be consistent with the phase sequence of the mains AC, so as to provide correct voltage and current feedback information and make the operation accurate.

[0079] Although the present disclosure has been disclosed above in embodiments, it is not intended to limit the present disclosure. Those of ordinary skill in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to that defined by the appended claims.

Claims

1. A phase sequence adjustment system, comprising: A power conversion circuit electrically connected to a commercial power supply in a certain phase sequence; and A control circuit for applying a first excitation signal and a second excitation signal to a plurality of switches of the power conversion circuit at different time points respectively, so as to form two short circuits between the power conversion circuit and the commercial power supply. The control circuit includes: A current detection circuit for detecting a first current signal corresponding to the first excitation signal and a second current signal corresponding to the second excitation signal when two short circuits are formed between the power conversion circuit and the commercial power supply; and A control unit for respectively calculating to obtain a first current angle and a second current angle according to the first current signal and the second current signal, and selecting one of the current angles from the first current angle or the second current angle and calculating a voltage angle of the commercial power supply according to the short-circuit operation time corresponding to the current angle; Among them, The control unit judges whether the phase sequence is positive sequence or negative sequence according to the first current angle and the second current angle, and calculates an angle difference between the selected current angle and the voltage angle, so as to adjust a feedback phase sequence of the power conversion circuit according to the angle difference.

2. The phase sequence adjustment system according to claim 1, further comprising an output filter circuit including an input end and an output end. The output filter circuit is electrically connected between the commercial power supply and the power conversion circuit, wherein the power conversion circuit is electrically connected to the output end of the output filter circuit in the phase sequence.

3. The phase sequence adjustment system according to claim 2, wherein The control circuit further includes a voltage detection circuit. The voltage detection circuit is coupled between the input end of the output filter circuit and the commercial power supply to detect a voltage detection signal. The control unit calculates the voltage angle of the commercial power supply according to the voltage values of multiple phases of the voltage detection signal obtained according to the short-circuit operation time of the selected current angle.

4. The phase sequence adjustment system according to claim 1, wherein When the control unit judges that the phase sequence is positive sequence, the angle difference is calculated by subtracting the voltage angle from the selected current angle; And When the control unit judges that the phase sequence is negative sequence, the angle difference is calculated by subtracting the selected current angle from the voltage angle.

5. A phase sequence adjustment method, comprising: Applying a first excitation signal to form a short circuit between a power conversion circuit and a commercial power supply, and obtaining a first current signal of the power conversion circuit corresponding to the first excitation signal during its short-circuit operation time, wherein the power conversion circuit is electrically connected to the commercial power supply in a certain phase sequence; After a time interval, applying a second excitation signal to form a short circuit between the power conversion circuit and the commercial power supply again, and obtaining a second current signal of the power conversion circuit corresponding to the second excitation signal during its short-circuit operation time; Respectively calculating according to the first current signal and the second current signal to obtain a first current angle and a second current angle; Judging whether the phase sequence is positive sequence or negative sequence according to the first current angle and the second current angle; Calculating a voltage angle of the commercial power supply corresponding to one of the first current angle and the second current angle during the short-circuit operation time according to whether the phase sequence is positive sequence or negative sequence; Calculating an angle difference between one of the first current angle and the second current angle and the voltage angle; and Adjusting a feedback phase sequence of the power conversion circuit according to the angle difference.

6. The phase sequence adjustment method according to claim 5, wherein, The step of applying the first excitation signal to the power conversion circuit to form a short circuit can be performed at any time, and the time interval for applying the second excitation signal to the power conversion circuit to form a short circuit again is shorter than half a cycle of the mains output signal.

7. The phase sequence adjustment method according to claim 5, wherein, The step of determining whether the phase sequence is positive or negative further includes: During the process of confirming that the first current angle rotates from 0 degrees to 360 degrees to the second current angle, and when the angle change relationship is increasing, determining that the phase sequence is positive; and During the process of confirming that the first current angle rotates from 360 degrees to 0 degrees to the second current angle, and when the angle change relationship is decreasing, determining that the phase sequence is negative.

8. The phase sequence adjustment method according to claim 7 further includes: When it is determined that the phase sequence is positive, calculating the angle difference by subtracting the voltage angle from one of the first current angle and the second current angle.

9. The phase sequence adjustment method according to claim 7 further includes: when it is determined that the phase sequence is negative, performing negative sequence adjustment by subtracting 360 degrees from the calculated value of the voltage angle and then multiplying by a negative sign, and calculating the angle difference by subtracting one of the first current angle and the second current angle from the adjusted voltage angle.

10. The phase sequence adjustment method according to claim 5, wherein, The mains is a three-phase AC power supply with a / b / c phases, and the step of the control unit adjusting the feedback phase sequence of the power conversion circuit according to the angle difference includes: When the angle difference is 60, 120, 180, 240, or 300 degrees, determining that the phase combinations of the phase sequence are b / a / c, c / a / b, a / c / b, b / c / a, or c / b / a respectively, and adjusting the feedback phase sequence according to the phase combination of the phase sequence; and When the angle difference is 0 degrees, determining that the phase sequence is positive and consistent with the mains phase, and not adjusting the phase sequence.

Images