Vienna rectifier, charging pile, control method, device and medium

Abstract

The invention discloses a Vienna rectifier, a charging pile, a control method, a device and a medium. The rectifier comprises a controller, a three-phase boost inductor, a three-phase uncontrolled rectification circuit and a three-phase neutral point clamping switch tube. The controller obtains a voltage difference value between the direct-current bus voltage and the reference voltage and a reactive power difference value between the reactive power and the reference reactive power, when the voltage difference value exceeds a first preset range or the reactive power difference value exceeds a second preset range, the power factor is controlled to be 1, and the direct-current bus voltage is adjusted according to the target voltage; the target voltage is updated reference voltage or reference voltage, the difference value between the adjusted direct current bus voltage and the target voltage is in a first preset range, the Vienna rectifier is controlled to output reactive power according to target reactive power, the target reactive power is updated reference reactive power or reference reactive power, and the reactive power can be output on the premise that hardware protection is not triggered.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, in particular to a Vienna rectifier, a charging pile, a control method and device, and a medium. BACKGROUND

[0002] The Vienna rectifier can adjust the output voltage to meet the demand of the voltage regulation range of the subsequent circuit.

[0003] The Vienna rectifier usually works at a power factor of 1, but in some application scenarios, it also needs to output reactive power to improve power quality. At present, the Vienna rectifier mainly uses the zero-sequence voltage injection method to control the output of reactive power, but this method easily causes current distortion on the grid side, and in severe cases, it will trigger hardware protection and shut down. SUMMARY

[0004] Therefore, the present application provides a Vienna rectifier, a charging pile, a control method and device, and a medium, which can output reactive power without triggering hardware protection.

[0005] The present application provides a Vienna rectifier, comprising: a controller, three-phase boost inductors, a three-phase uncontrolled rectification circuit, and three-phase neutral-point clamped switching tubes; the first ends of the three-phase boost inductors are respectively used to connect three-phase alternating current; the second ends of the three-phase boost inductors are respectively connected to the bridge arm midpoints of the three-phase uncontrolled rectification circuit; the three-phase neutral-point clamped switching tubes are respectively connected between the bridge arm midpoints of the three-phase uncontrolled rectification circuit and the DC bus midpoints; the controller is used to obtain the voltage difference between the DC bus voltage and the reference voltage and the reactive power difference between the reactive power and the reference reactive power, control the power factor to be 1 when the voltage difference exceeds a first preset range or the reactive power difference exceeds a second preset range, adjust the DC bus voltage according to a target voltage, the target voltage being an updated reference voltage or the reference voltage, so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range, and control the Vienna rectifier to output reactive power according to a target reactive power, the target reactive power being an updated reference reactive power or the reference reactive power.

[0006] In a possible implementation, the controller is specifically configured to keep the DC bus voltage unchanged, control the reactive power to be 0, and control the power factor to be 1.

[0007] In a possible implementation, the controller is specifically configured to keep the power factor to be 1, adjust the DC bus voltage according to the target voltage, and make the difference between the adjusted DC bus voltage and the target voltage be within the first preset range.

[0008] In a possible implementation, the controller controls the Vienna rectifier to output reactive power according to the target reactive power, and specifically includes: obtaining a power factor minimum value according to an input voltage of the Vienna rectifier and the DC bus voltage, obtaining active power according to an input voltage and an input current of the Vienna rectifier, and obtaining a reactive power allowable maximum value according to the power factor minimum value and the active power; and controlling the three-phase neutral point clamped switch tube to control the Vienna rectifier to output reactive power according to the reactive power allowable maximum value and the target reactive power.

[0009] In a possible implementation, the controller controls the Vienna rectifier to output reactive power according to the target reactive power, and specifically includes: obtaining a power factor minimum value according to an input voltage of the Vienna rectifier and the DC bus voltage, obtaining active power according to an input voltage and an input current of the Vienna rectifier, and obtaining a reactive power allowable maximum value according to the power factor minimum value and the active power; and controlling the three-phase neutral point clamped switch tube to control the Vienna rectifier to output reactive power according to the reactive power allowable maximum value and the target reactive power.

[0010] In a possible implementation, the controller specifically controls the power factor to be 1, adjusts the DC bus voltage according to the target voltage at a preset voltage step, and makes a difference between the adjusted DC bus voltage and the target voltage within the first preset range.

[0011] The application provides a charging pile, which includes a DC-DC circuit and the Vienna rectifier described above; an input end of the Vienna rectifier is used to connect alternating current; an input end of the DC-DC circuit is connected to an output end of the Vienna rectifier; and an output end of the DC-DC circuit is used to charge a battery.

[0012] The application provides a reactive power control method of a Vienna rectifier, which includes: obtaining a voltage difference between a DC bus voltage and a reference voltage and a reactive power difference between reactive power and reference reactive power; controlling the power factor to be 1 when the voltage difference is out of a first preset range or the reactive power difference is out of a second preset range; adjusting the DC bus voltage according to a target voltage, the target voltage being an updated reference voltage or the reference voltage, so that a difference between the adjusted DC bus voltage and the target voltage is within the first preset range; and controlling the Vienna rectifier to output reactive power according to a target reactive power, the target reactive power being an updated reference reactive power or the reference reactive power.

[0013] In a possible implementation, the controller controls the power factor to be 1, and specifically includes: keeping the DC bus voltage unchanged, controlling the reactive power to be 0, and making the power factor be 1.

[0014] In a possible implementation, the DC bus voltage is adjusted according to the target voltage, so that a difference between the adjusted DC bus voltage and the target voltage is within the first preset range, and the power factor is kept as 1.

[0015] In a possible implementation, the output reactive power of the Vienna rectifier is controlled according to the target reactive power, and the method specifically includes: obtaining a minimum power factor according to an input voltage of the Vienna rectifier and the DC bus voltage, and obtaining active power according to an input voltage and an input current of the Vienna rectifier; obtaining a maximum allowed reactive power according to the minimum power factor and the active power; and controlling the three-phase neutral-point-clamped switch tube to make the Vienna rectifier output the reactive power according to the maximum allowed reactive power and the target reactive power.

[0016] In a possible implementation, the minimum power factor is obtained according to the input voltage of the Vienna rectifier, the DC bus voltage, and a modulation degree of the Vienna rectifier, and the modulation degree is less than a preset value, and the preset value is obtained according to a phase difference between the input voltage and the input current of the Vienna rectifier.

[0017] In a possible implementation, the output reactive power of the Vienna rectifier is controlled according to the maximum allowed reactive power and the target reactive power, and the method specifically includes: when the maximum allowed reactive power is less than the target reactive power, controlling the reactive power output by the Vienna rectifier according to the maximum allowed reactive power; and when the maximum allowed reactive power is greater than or equal to the target reactive power, controlling the reactive power output by the Vienna rectifier according to the target reactive power.

[0018] The application further provides a control device, including a processor and a memory, the memory is used for storing programs, instructions or codes, and the processor is used for executing the programs, instructions or codes in the memory to complete the control method of the power converter.

[0019] The application further provides a computer readable storage medium, which stores a computer program, and the computer program is loaded by a processor to execute the control method of the power converter.

[0020] The Vienna rectifier provided by the embodiment of the application can output 0 reactive power first, that is, the power factor is 1, then adjust the DC bus voltage to reach a new reference voltage, and then adjust the output reactive power, so that current distortion is not caused, hardware protection shutdown is not caused, sustainability of battery charging is ensured, the reactive power scheduling of the power grid can be responded, and smooth transition of the reactive power is realized. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A schematic diagram of a Vienna rectifier provided by the embodiment of the application is provided.

[0022] Figure 2 A waveform diagram of current leading voltage provided by the embodiment of the application is provided.

[0023] Figure 3 A waveform diagram of current lagging voltage provided by the embodiment of the application is provided.

[0024] Figure 4 A relationship diagram of DC bus voltage and power factor provided by the embodiment of the application is provided.

[0025] Figure 5 A schematic diagram of adjusting reactive power provided by the embodiment of the application is provided.

[0026] Figure 6 A schematic diagram of adjusting reactive power provided by the embodiment of the application is provided.

[0027] Figure 7 A schematic diagram of adjusting reactive power provided by the embodiment of the application is provided.

[0028] Figure 8 A flowchart of a Vienna rectifier controlling reactive power output provided by the embodiment of the application is provided.

[0029] Figure 9 A waveform diagram of various parameters of a Vienna rectifier provided by the embodiment of the application is provided.

[0030] Figure 10 A schematic diagram of a charging pile provided by the embodiment of the application is provided.

[0031] Figure 11 A flowchart of a reactive power control method of a Vienna rectifier provided by the embodiment of the application is provided.

[0032] Figure 12 A schematic diagram of a control device provided by the embodiment of the application is provided. DETAILED DESCRIPTION

[0033] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the embodiments of the present application are further described in detail below with reference to the drawings and specific embodiments.

[0034] The Vienna rectifier provided by the embodiments of the present application can work in any scene requiring three-phase rectification, and the present application does not limit specific application scenes, for example, can be applied to a base station, and can also be applied to a charging pile and the like.

[0035] For the convenience of understanding, taking the application of the Vienna rectifier to the charging pile scene as an example, generally, the charging pile includes a Vienna rectifier and a DC-DC circuit, the input end of the Vienna rectifier is used for connecting three-phase alternating current, the output end of the Vienna rectifier is connected to the input end of the DC-DC circuit, and the Vienna rectifier is used for adjusting the input voltage of the DC-DC circuit, that is, the DC bus voltage, to meet the voltage regulation range requirement of the DC-DC circuit.

[0036] The Vienna rectifier is a three-phase three-level PWM rectifier, and can be regarded as a three-phase diode bridge cooperating with an integrated boost converter.

[0037] The Vienna rectifier generally works at a power factor of 1, but in some application scenarios, it also needs to work at a power factor that is not 1, that is, needs to output reactive power to improve power quality.

[0038] The method based on zero sequence voltage injection can control the Vienna rectifier to output reactive power, but the output of the Vienna rectifier is subject to the size of the DC bus voltage, and the Vienna rectifier cannot output the required reactive power at any value of the DC bus voltage. Since the modulation degree refers to the ratio of twice the grid phase voltage amplitude to the DC bus voltage, it can also be considered that the ability of the Vienna rectifier to output reactive power depends on the modulation degree.

[0039] For example, during the working process of the Vienna rectifier, the DC bus voltage may fluctuate with the load, and the reactive power scheduling of the grid may also change. Therefore, when the Vienna rectifier works, it does not take into account the DC bus voltage and directly controls the Vienna rectifier to respond to the reactive power scheduling at any time, which may cause current distortion on the grid side, and in severe cases, even trigger hardware protection and shut down. For example, when the Vienna rectifier does not work at a power factor of 1, opposite polarity pulses will be generated in the grid voltage and grid current in the opposite interval, resulting in current distortion on the grid side.

[0040] The Vienna rectifier provided by the embodiment of the present application does not output reactive power at first in order to avoid triggering hardware protection shutdown when the Vienna rectifier needs to adjust reactive power, that is, the DC bus voltage is adjusted at first in the state of power factor 1, so that the adjusted DC bus voltage supports the output of reactive power, and thus the Vienna rectifier does not trigger hardware protection shutdown.

[0041] The working principle of the Vienna rectifier will be introduced below in combination with the drawings.

[0042] Referring to Figure 1 The figure is a schematic diagram of a Vienna rectifier provided by the embodiment of the present application.

[0043] The Vienna rectifier provided by the embodiment of the present application comprises a controller (not shown in the figure), three-phase boost inductors L, a three-phase uncontrolled rectification circuit and three-phase neutral-point clamped switching tubes.

[0044] The three-phase uncontrolled rectification circuit refers to that each of the three-phase bridge arms comprises an uncontrolled diode, and the three-phase uncontrolled rectification circuit comprises the following six diodes: D1-D6, the A-phase bridge arm comprises D1 and D2 connected in series, the B-phase bridge arm comprises D3 and D4 connected in series, and the C-phase bridge arm comprises D5 and D6 connected in series. The three bridge arm midpoints of the three-phase uncontrolled rectification circuit are a, b and c respectively.

[0045] The first ends of the three-phase boost inductors are respectively used for connecting three-phase alternating currents; the second ends of the three-phase boost inductors are respectively connected to the bridge arm midpoints of the three-phase uncontrolled rectification circuit; that is, one boost inductor corresponds to each phase, and the second end of each boost inductor is connected to the corresponding bridge arm midpoint.

[0046] The three-phase neutral-point clamped switching tubes are respectively connected between the bridge arm midpoints of the three-phase uncontrolled rectification circuit and the DC bus midpoints. The three-phase neutral-point clamped switching tubes comprise two switching tubes connected in series to form a bidirectional switch corresponding to each phase, that is, the bidirectional switch corresponding to the A-phase comprises S1a and S2a, the bidirectional switch corresponding to the B-phase comprises S1b and S2b, and the bidirectional switch corresponding to the C-phase comprises S1c and S2c.

[0047] The DC side bus capacitor comprises C1 and C2 connected in series, and the common end of C1 and C2 is taken as the DC bus midpoint O. Generally, the capacitance value of C1 is equal to that of C2.

[0048] The working principle of the Vienna rectifier is as follows: assuming that the positive direction of the grid current is from the grid to the Vienna rectifier. Taking the A-phase as an example, when the grid current is positive, the current charges or discharges the DC side bus capacitor through the diode D1 or the bidirectional switches S1a and S2a; when the grid current is negative, the current charges or discharges the DC side bus capacitor through the diode D2 or the bidirectional switches S1a and S2a.

[0049] The controller is configured to obtain a voltage difference between the DC bus voltage and a reference voltage and a reactive power difference between the reactive power and a reference reactive power, and when the voltage difference exceeds a first preset range or the reactive power difference exceeds a second preset range, control the power factor to be 1, adjust the DC bus voltage according to a target voltage, the target voltage being the updated reference voltage or the reference voltage, so that a difference between the adjusted DC bus voltage and the target voltage is within the first preset range, and control the Vienna rectifier to output the reactive power according to a target reactive power. The target reactive power is the updated reference reactive power or the reference reactive power.

[0050] It should be understood that, for the Vienna rectifier, the reference voltage and the reference reactive power are both obtained according to received instructions, for example, the output end of the Vienna rectifier is connected to a DC / DC circuit, and the reference voltage and the updated reference voltage can be voltage instructions received from the DC / DC circuit. The reference reactive power and the updated reference reactive power can be reactive power scheduling instructions received from the power grid. The Vienna rectifier provided in the embodiments of the present application obtains the voltage difference between the DC bus voltage and the reference voltage and the reactive power difference between the reactive power and the reference reactive power when it is necessary to update the operating point. For example, this can be when the controller receives new reactive power scheduling instructions or when the controller receives new voltage instructions.

[0051] The updated reference voltage is different from the reference voltage. The updated reference reactive power is different from the reference reactive power.

[0052] It should be understood that, during the operation of the Vienna rectifier, the reference reactive power or the reference voltage can change in real time. Therefore, when the Vienna rectifier is operating in a steady state, receives new reference reactive power or reference voltage, and the voltage difference exceeds the first preset range or the reactive power difference exceeds the second preset range, the following three steps of control need to be performed: first, pull the reactive power to 0, second, adjust the DC bus voltage, and third, adjust the reactive power. In this way, it can be ensured that the DC bus voltage supports the output of the reactive power, so as to avoid forced output of the reactive power and cause power grid current distortion and trigger hardware shutdown. However, when the three steps of control have already been started, that is, between the first step and the second step or between the second step and the third step, even if the updated reference voltage or the updated reference reactive power is received again, the first step will not be jumped to.

[0053] The Vienna rectifier provided in the embodiments of the present application needs to first control the reactive power to 0, then adjust the DC bus voltage according to the updated reference voltage, and then control the output of the reactive power according to the reference reactive power after the DC bus voltage is adjusted, so as to ensure that the power grid current is not distorted during the output of the reactive power. It should be understood that, the control according to the reference voltage or the control according to the updated reference voltage will not cause the power grid current to be distorted.

[0054] For the convenience of understanding the phase shift angle of the power grid voltage and the power grid current, please refer to Figure 2and Figure 3 . Figure 2 and Figure 3 The horizontal coordinate represents time, in s, and the vertical coordinate represents voltage and current.

[0055] Referring to Figure 2 , the figure is a waveform diagram of current leading voltage provided by the embodiment of the present application.

[0056] As can be seen from Figure 2 , when the grid voltage u has not reached 0, the grid current i has reached 0, that is, the phase of the grid current i leads the phase of the grid voltage u, and the angle of the leading is called the phase shift angle. That is, in the range of the two dotted lines shown in Figure 2 , the grid voltage u is negative and the grid current i is positive, that is, the signs of the grid voltage u and the grid current i are opposite, which easily causes the grid current distortion.

[0057] Referring to Figure 3 , the figure is a waveform diagram of current lagging voltage provided by the embodiment of the present application.

[0058] As can be seen from Figure 3 , when the grid current i has not reached 0, the grid voltage u has reached 0, that is, the phase of the grid current i lags the phase of the grid voltage u, and the angle of the lagging is called the phase shift angle. That is, in the range of the two dotted lines shown in Figure 3 , the grid voltage u is negative and the grid current i is positive, that is, the signs of the grid voltage u and the grid current i are opposite, which easily causes the grid current distortion.

[0059] In order to ensure that the Vienna rectifier does not produce current distortion when outputting reactive power, the regulation degree m should meet certain requirements, for example, the condition that the grid current does not produce distortion is m≤[1 / sqrt(3)] / [sin(π / 6+φ)], wherein φ represents the phase shift angle of the grid voltage and the grid current, and cosφ is the power factor. Assuming that the grid phase voltage amplitude is 311V, the power factor range corresponding to the DC bus voltage can be obtained according to the above inequality relationship, which will be described in detail below in combination with the accompanying drawings.

[0060] Referring to Figure 4 , the figure is a relationship diagram of the DC bus voltage and the power factor provided by the embodiment of the present application.

[0061] Figure 4 In the figure, the horizontal coordinate is the DC bus voltage Vbus, in V, and the vertical coordinate is the power factor PF. Figure 4 The figure includes the case that the current phase lags the voltage phase, that is, the region above OE; and the case that the current phase leads the voltage phase, that is, the region below OE.

[0062] Figure 4The gray area in the figure is the normal working range that does not cause power grid current distortion, i.e., the area enclosed by points O, M, E and N.

[0063] Figure 4 The white area in the figure is the forbidden zone. If the Vienna rectifier is forced to work in the forbidden zone, power grid current distortion will occur, and even hardware overcurrent protection will be triggered.

[0064] The following describes several processes of adjusting reactive power in the gray safe area.

[0065] Referring to Figure 5 , the figure is a schematic diagram of adjusting reactive power provided by an embodiment of the present application.

[0066] Referring to Figure 6 , the figure is another schematic diagram of adjusting reactive power provided by an embodiment of the present application.

[0067] Referring to Figure 7 , the figure is still another schematic diagram of adjusting reactive power provided by an embodiment of the present application.

[0068] Figures 5-7 The figure shows the logic of switching three different working points, and point A represents the current working point of the Vienna rectifier, and point D represents the target working point.

[0069] The working point switching can include the following three cases:

[0070] The first case is that the DC bus voltage is unchanged, and the power factor changes;

[0071] The second case is that the power factor is unchanged, and the DC bus voltage changes;

[0072] The third case is that both the DC bus voltage and the power factor change.

[0073] Considering that the working point can be at the boundary of the safe area, slight changes in the DC bus voltage or the power factor can cause the working point to exceed the feasible range. Therefore, the technical solution provided by the embodiment of the present application immediately restores the power factor to 1 after determining that the working point changes, and the power factor of 1 corresponds to a reactive power of 0, for example Figures 5-7 switching from point A to point B; point B corresponds to a power factor of 1. Secondly, the bus voltage is adjusted according to a certain step size until the difference between the bus voltage and the voltage reference value does not exceed the first preset range (the reference value can also not change), and the power factor is maintained at 1 during the whole process, i.e., Figures 5-7 switching from point B to point C; finally, it is determined whether the new working point meets the reactive output capability corresponding to the current DC bus voltage, if not, the current maximum reactive output capability is output, if yes, the updated reference reactive output is output, i.e., Figures 5-7Switch from point C to point D.

[0074] In combination Figures 5-7 It can be seen that the Vienna rectifier control reactive power output provided by the embodiment of the application can include the following three stages:

[0075] The first stage: power factor to 1 stage (point A to point B); the process obtains the voltage difference between the DC bus voltage and the reference voltage and the reactive power difference between the reactive power and the reference reactive power, judges whether the voltage difference exceeds the first preset range or the reactive power difference exceeds the second preset range, and if so, controls the reactive power output to be 0, that is, the power factor is 1.

[0076] The second stage: DC bus voltage switching stage (point B to point C); this stage ensures that the power factor is 1, and controls the DC bus voltage to run to a new DC bus voltage. It should be understood that the DC bus voltage can be real-time changing, and after the power factor is 1, a new reference voltage, that is, an updated reference voltage, can be received, so that the DC bus voltage needs to be adjusted according to the updated reference voltage. It should be understood that the reference voltage can also not be updated, and the DC bus voltage is directly adjusted according to the reference voltage.

[0077] The third stage: reactive power climbing stage (point C to point D). After the new DC bus voltage is established, the minimum power factor PFmin corresponding to the current regulation degree (that is, the DC bus voltage) is calculated, and the active power Pout is calculated according to the current grid voltage and grid current, and finally the maximum allowed reactive power Qmax of the current working point is obtained. It should be understood that the maximum allowed reactive power Qmax is set in the embodiment of the application to ensure that the reactive power output by the Vienna rectifier needs to be less than or equal to the maximum allowed reactive power Qmax, so that the grid current can be ensured not to be distorted.

[0078] If the reference reactive power Qcommand received by the Vienna rectifier is greater than the maximum allowed reactive power Qmax, the reactive output instruction Qref is equal to Qmax; otherwise, Qref is equal to Qcommand. At the same time, it needs to be determined whether the output is inductive reactive power or capacitive reactive power, that is, the current leads the voltage or the current lags the voltage.

[0079] In order to facilitate understanding, the working principle of the Vienna rectifier provided by the embodiment of the application will be introduced in detail below in combination with the control flow chart.

[0080] Referring to Figure 8 The figure is a flow chart of the Vienna rectifier control reactive power output provided by the embodiment of the application.

[0081] S801: Obtain the voltage difference between the DC bus voltage and the reference voltage and the reactive power difference between the reactive power and the reference reactive power;

[0082] S802: Determine whether the voltage difference exceeds the first preset range or the reactive power difference exceeds the second preset range; if the voltage difference exceeds the first preset range or the reactive power difference exceeds the second preset range, execute S803. If the voltage difference is within the first preset range and the reactive power difference is within the second preset range, the output of the reactive power can be controlled according to the reference reactive power control in response to the reactive power dispatching instruction.

[0083] It should be understood that when the voltage difference does not exceed the first preset range and the reactive power difference does not exceed the second preset range, S802 is executed.

[0084] S803: Keep the DC bus voltage unchanged, control the reactive power to be 0, and make the power factor be 1.

[0085] S804: Keep the power factor to be 1, adjust the DC bus voltage according to the target voltage, so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range. The specific process of adjusting the DC bus voltage is not specifically limited in the embodiments of the application. For example, the DC bus voltage can be adjusted to the target value in one step; or the DC bus voltage can be adjusted according to a certain step size until the difference between the adjusted DC bus voltage and the updated reference voltage is within the first preset range. The target voltage is the reference voltage or the updated reference voltage.

[0086] S805: Obtain the minimum power factor according to the input voltage of the Vienna rectifier and the DC bus voltage.

[0087] Obtaining the minimum power factor according to the input voltage of the Vienna rectifier and the DC bus voltage specifically includes: obtaining the minimum power factor according to the input voltage of the Vienna rectifier, the DC bus voltage, and the modulation degree of the Vienna rectifier, the modulation degree being less than a preset value; the preset value is obtained according to the phase difference between the input voltage and the input current of the Vienna rectifier. That is, the preset value can be obtained by the following formula: [1 / sqrt(3)] / [sin(π / 6+φ)].

[0088] S806: Obtain the active power according to the current grid voltage and the grid current.

[0089] S807: Obtain the maximum allowed reactive power according to the minimum power factor and the active power.

[0090] After the DC bus voltage is established, the condition that the grid current does not occur distortion is m≤[1 / sqrt(3)] / [sin(pi / 6+phi)], the modulation degree is obtained from the current DC bus voltage, the minimum power factor PFmin is obtained according to the above inequality satisfied by the modulation degree. The active power Pout is obtained according to the input voltage and the input current of the Vienna rectifier, and the maximum allowed reactive power Qmax at the current operating point is obtained according to the minimum power factor PFmin and the active power Pout. Qmax=Pout / PFmin*sqrt(1-PFmin*PFmin).

[0091] S808: When the maximum allowed reactive power is less than the target reactive power, the Vienna rectifier output reactive power is controlled according to the maximum allowed reactive power; when the maximum allowed reactive power is greater than or equal to the target reactive power, the Vienna rectifier output reactive power is controlled according to the target reactive power. The target reactive power is the reference reactive power or the updated reactive power.

[0092] Referring to Figure 9 , the figure is a waveform diagram of various parameters of the Vienna rectifier provided by the embodiment of the application.

[0093] Figure 9 The waveform diagram shown includes active power P, reactive power Q, DC bus voltage Vbus, grid voltage U and grid current I.

[0094] It should be understood that Figure 9 The parameters shown are only schematic, and the values of various parameters of the Vienna rectifier may be different in different application scenarios, which are not specifically limited here.

[0095] From Figure 9 It can be seen that, near 0.5s, the DC bus voltage reaches the rated value 840V, the reactive power slowly climbs to the maximum allowed reactive power corresponding to the DC bus voltage 840V, and the stable operation is maintained; at 0.8s, the reference voltage is suddenly switched from 840V to 680V, and the reactive power is immediately reduced to 0, ensuring that the power factor is 1; near 1.1s, the DC bus voltage basically reaches 680V, the reactive power slowly climbs to the maximum allowed reactive power corresponding to the DC bus voltage 680V, and the switching of the operating point is completed.

[0096] The Vienna rectifier provided by the embodiment of the application can stably find a new operating point in the process of outputting reactive power, that is, in the process of switching reactive power, the DC bus voltage can support the output of reactive power, thereby avoiding the distortion of the grid current and triggering the hardware protection shutdown, for example, when applied in the field of charging piles, the car can be charged all the time without interrupting the charging, thereby improving the charging efficiency and improving the satisfaction of users.

[0097] Based on the Vienna rectifier provided in the above embodiment, the embodiment of the present application further provides a charging pile, which will be described in detail below with reference to the drawings.

[0098] Referring to Figure 10 FIG. 2 is a schematic diagram of a charging pile provided by an embodiment of the present application.

[0099] The charging pile provided by the embodiment of the present application comprises a DC-DC circuit 602 and the Vienna rectifier 601 provided by the above embodiment.

[0100] The input end of the Vienna rectifier 601 is used to connect AC power.

[0101] The output end of the DC-DC circuit 602 is connected to the input end of the Vienna rectifier 601.

[0102] The output end of the DC-DC circuit 602 is used to charge a battery.

[0103] The charging pile provided by the embodiment of the present application, because the Vienna rectifier therein will first output 0 reactive power, i.e., the power factor is 1, when it is necessary to adjust the reactive power, and then adjust the DC bus voltage to reach a new reference voltage, and then adjust the output reactive power, so that it will not cause current distortion and will not cause hardware protection shutdown, thereby ensuring the sustainability of charging the battery, can respond to the reactive power scheduling of the power grid, and realize smooth transition of the reactive power.

[0104] Based on the Vienna rectifier and the charging pile provided in the above embodiment, the embodiment of the present application further provides a method for controlling the reactive power of the Vienna rectifier, which will be described in detail below with reference to the drawings.

[0105] Referring to Figure 11 FIG. 3 is a flowchart of a method for controlling the reactive power of the Vienna rectifier provided by an embodiment of the present application.

[0106] The method for controlling the reactive power of the Vienna rectifier provided by the embodiment of the present application comprises:

[0107] S1101: obtaining a voltage difference between a DC bus voltage and a reference voltage and a reactive power difference between a reactive power and a reference reactive power;

[0108] S1102: controlling the power factor to be 1 when the voltage difference exceeds a first preset range or the reactive power difference exceeds a second preset range.

[0109] S1103: adjusting the DC bus voltage according to a target voltage, so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range; the target voltage is the reference voltage or an updated reference voltage.

[0110] S1104: output the reactive power of the Vienna rectifier according to the target reactive control, the target reactive being the reference reactive or the updated reference reactive.

[0111] The method for controlling the reactive power of the Vienna rectifier provided by the embodiments of the present application can output the reactive power as 0, i.e., the power factor is normalized, when the reactive power needs to be adjusted, then the DC bus voltage is adjusted to reach the new reference voltage, and then the output reactive power is adjusted, so that the current distortion is not caused, the hardware protection shutdown is not caused, the sustainability of the battery charging is ensured, the reactive power scheduling of the power grid can be responded, and the smooth transition of the reactive power is realized.

[0112] In a possible implementation, the power factor is controlled to be 1, and specifically, the DC bus voltage is kept unchanged, and the reactive power is controlled to be 0, so that the power factor is 1.

[0113] In a possible implementation, the DC bus voltage is adjusted according to the target voltage, so that the difference between the adjusted DC bus voltage and the target voltage is within a first preset range, and specifically, the power factor is kept to be 1, and the DC bus voltage is adjusted according to the target voltage, so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range. The target voltage is the reference voltage or the updated reference voltage, and it should be understood that the updated reference voltage is different from the reference voltage.

[0114] In a possible implementation, the Vienna rectifier outputs the reactive power according to the updated reference reactive, and specifically, the minimum power factor is obtained according to the input voltage and the DC bus voltage of the Vienna rectifier, the active power is obtained according to the input voltage and the input current of the Vienna rectifier, the maximum allowed reactive power is obtained according to the minimum power factor and the active power, and the Vienna rectifier outputs the reactive power by controlling the three-phase neutral point clamped switch tube according to the maximum allowed reactive power and the updated reference reactive.

[0115] In a possible implementation, the minimum power factor is obtained according to the input voltage and the DC bus voltage of the Vienna rectifier, and specifically, the minimum power factor is obtained according to the input voltage, the DC bus voltage of the Vienna rectifier, and the modulation degree of the Vienna rectifier, and the modulation degree is less than a preset value; the preset value is obtained according to the phase difference between the input voltage and the input current of the Vienna rectifier.

[0116] In a possible implementation, the Vienna rectifier outputs the reactive power according to the maximum allowed reactive power and the updated reference reactive, and specifically, when the maximum allowed reactive power is less than the updated reference reactive, the Vienna rectifier outputs the reactive power according to the maximum allowed reactive power; and when the maximum allowed reactive power is greater than or equal to the updated reference reactive, the Vienna rectifier outputs the reactive power according to the updated reference reactive.

[0117] In a possible implementation, referring to Figure 12 FIG. 1 is a schematic diagram of a control device according to an embodiment of the present application.

[0118] The control device can include a memory 1011 and a processor 1012. The processor 1012 can be connected with the power converter and can drive the switches in each power conversion circuit in the power converter. As shown in the figure, Figure 12 The memory can be a random access memory (RAM), a flash memory, a read only memory (ROM), an EPROM memory, an Electronic Programmable ROM (EPROM), a register, a hard disk, a removable disk, etc.

[0119] The memory 1011 can store computer instructions, and when the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be configured to perform the control method of the power converter. The memory 1011 can also store data, such as the reference reactive power, the reference voltage, etc. information involved in the above embodiments.

[0120] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or part of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions according to the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer readable storage medium or transferred from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center through wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) mode. The computer readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. integrated with one or more available media. The available media can be a magnetic medium (such as a floppy disk, a hard disk, a magnetic tape), or a semiconductor medium (such as a solid state disk (SSD)), etc.

[0121] The embodiments of the present application also provide a readable storage medium for storing the method provided by the above embodiments. For example, random access memory (RAM), flash memory, read only memory (ROM), EPROM memory, non-volatile read only memory (Electronic Programmable ROM, EPROM), register, hard disk, removable disk or any other form of storage medium in the art.

[0122] It should be noted that the various embodiments described in the specification are progressive, and each embodiment focuses on the differences from other embodiments. The same or similar parts of each embodiment can be referred to each other. For the method disclosed in the embodiments, since it corresponds to the product embodiments disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the product embodiments.

[0123] The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A Vienna rectifier, characterized in that, include: Controller, three-phase boost inductor, three-phase uncontrolled rectifier circuit and three-phase neutral point clamping switch; The first end of the three-phase boost inductor is used to connect to the three-phase AC power; the second end of the three-phase boost inductor is connected to the midpoint of the bridge arm of the three-phase uncontrolled rectifier circuit; the three-phase neutral point clamping switch is connected between the midpoint of the bridge arm of the three-phase uncontrolled rectifier circuit and the midpoint of the DC bus. The controller is used to obtain the voltage difference between the DC bus voltage and the reference voltage, and the reactive power difference between the reactive power and the reference reactive power. When the voltage difference exceeds a first preset range or the reactive power difference exceeds a second preset range, the controller controls the power factor to be 1, adjusts the DC bus voltage according to the target voltage (which is either the updated reference voltage or the reference voltage), so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range, and controls the Vienna rectifier to output reactive power according to the target reactive power (which is either the updated reference reactive power or the reference reactive power).

2. The Vienna rectifier according to claim 1, characterized in that, The controller is specifically used to keep the DC bus voltage constant, control the reactive power to be 0, and make the power factor 1.

3. The Vienna rectifier according to claim 1, characterized in that, The controller is specifically used to maintain the power factor at 1 and adjust the DC bus voltage according to the target voltage, so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range.

4. The Vienna rectifier according to any one of claims 1-3, characterized in that, The controller controls the output reactive power of the Vienna rectifier according to the target reactive power, specifically including: The minimum power factor is obtained based on the input voltage of the Vienna rectifier and the DC bus voltage. The active power is obtained based on the input voltage and input current of the Vienna rectifier. The maximum allowable reactive power is obtained based on the minimum power factor and the active power. Based on the maximum allowable reactive power and the target reactive power, the three-phase neutral point clamping switch is controlled to make the Vienna rectifier output reactive power.

5. The Vienna rectifier according to claim 4, characterized in that, The controller is configured to control the reactive power output of the Vienna rectifier according to the maximum allowable reactive power when the maximum allowable reactive power is less than the target reactive power; and to control the reactive power output of the Vienna rectifier according to the target reactive power when the maximum allowable reactive power is greater than or equal to the target reactive power.

6. The Vienna rectifier according to claim 3, characterized in that, The controller is specifically used to maintain the power factor at 1 and adjust the DC bus voltage according to the target voltage in a preset voltage step size, so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range.

7. A charging pile, characterized in that, Includes a DC-DC circuit and the Vienna rectifier as described in any one of claims 1-6; The input terminal of the Vienna rectifier is used to connect to alternating current. The input terminal of the DC-DC circuit is connected to the output terminal of the Vienna rectifier; The output of the DC-DC circuit is used to charge the battery.

8. A reactive power control method for a Vienna rectifier, characterized in that, include: Obtain the voltage difference between the DC bus voltage and the reference voltage, and the reactive power difference between the reactive power and the reference reactive power; When the voltage difference exceeds the first preset range or the reactive power difference exceeds the second preset range, the control power factor is 1. The DC bus voltage is adjusted according to the target voltage, which is either the updated reference voltage or the reference voltage, so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range. The Vienna rectifier outputs reactive power according to a target reactive power, which is either the updated reference reactive power or the reference reactive power.

9. The control method according to claim 8, characterized in that, The control power factor is 1, specifically including: Keep the DC bus voltage constant, control the reactive power to 0, and make the power factor 1.

10. The control method according to claim 8, characterized in that, The step of adjusting the DC bus voltage according to the target voltage, so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range, specifically includes: Keeping the power factor at 1, the DC bus voltage is adjusted according to the target voltage so that the difference between the adjusted DC bus voltage and the target voltage is within the first preset range.

11. The control method according to any one of claims 8-10, characterized in that, The reactive power output of the Vienna rectifier is controlled according to the target reactive power control, specifically including: The minimum power factor is obtained based on the input voltage of the Vienna rectifier and the DC bus voltage, and the active power is obtained based on the input voltage and input current of the Vienna rectifier. The maximum allowable reactive power is obtained based on the minimum power factor and the active power. Based on the maximum allowable reactive power and the target reactive power, the three-phase neutral point clamping switch is controlled to make the Vienna rectifier output reactive power.

12. The control method according to claim 11, characterized in that, The minimum power factor is obtained based on the input voltage of the Vienna rectifier and the DC bus voltage, specifically including: The minimum power factor is obtained based on the input voltage of the Vienna rectifier, the DC bus voltage, and the modulation index of the Vienna rectifier, wherein the modulation index is less than a preset value; the preset value is obtained based on the phase difference between the input voltage and the input current of the Vienna rectifier.

13. The control method according to claim 11, characterized in that, Based on the maximum allowable reactive power and the target reactive power, the three-phase neutral point clamping switch is controlled to cause the Vienna rectifier to output reactive power, specifically including: When the maximum allowable reactive power is less than the target reactive power, the reactive power output of the Vienna rectifier is controlled according to the maximum allowable reactive power; when the maximum allowable reactive power is greater than or equal to the target reactive power, the reactive power output of the Vienna rectifier is controlled according to the target reactive power.

14. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the control method of the power converter as described in any one of claims 8-13.

15. A computer-readable storage medium, characterized in that, The device contains a computer program that is loaded by a processor to execute the control method for the power converter as described in any one of claims 8-13.

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