Unbalanced voltage compensation device and control method thereof

Abstract

The invention discloses an unbalanced voltage compensation device and a control method thereof. The device comprises a power module which is connected in series between a new energy pooling station and an AC power grid. The power module comprises an A-phase compensation unit, and the A-phase compensation unit is connected in series in an A-phase power transmission line between the new energy collection station and the AC power grid. The B-phase compensation unit is connected in series in a B-phase power transmission line between the new energy collection station and the alternating current power grid; the C-phase compensation unit is connected in series in a C-phase power transmission line between the new energy collection station and the alternating current power grid; wherein each of the A-phase compensation unit, the B-phase compensation unit and the C-phase compensation unit comprises at least one full-bridge subunit which is connected in series, each full-bridge subunit comprises a capacitor, and each full-bridge subunit controls three-phase voltage balance by controlling the state of each capacitor. The three-phase unbalanced voltage regulation circuit has a good three-phase unbalanced voltage regulation effect.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality management, and in particular to an unbalanced voltage compensation device and a control method thereof. Background Art

[0002] The current renewable energy power generation has the problem of asymmetric impedance parameters of three-phase lines, which easily causes three-phase voltage imbalance at the renewable energy collection station. Excessive three-phase unbalanced voltage will cause serious harm to power equipment, easily cause large-scale disconnection of renewable energy converters, and threaten the safe and stable operation of the power system.

[0003] In the prior art, static var generator (SVG) technology is generally used to compensate for unbalanced voltage, or a power quality management device is configured in the circuit, and these methods have poor regulation effects. For example, the use of static var generator technology will inject unbalanced current into the power grid while compensating for the unbalanced voltage. In severe cases, it will cause the rotating motor to heat up and vibrate, affecting the power supply quality, thereby increasing line losses and reducing power supply reliability. Configuring a power quality management device requires connecting the transformer in series in the line to achieve voltage compensation, which has complex control logic, large power losses, and poor economy. Therefore, the prior art has a poor regulation effect on the three-phase unbalanced voltage. Summary of the invention

[0004] The present invention provides an unbalanced voltage compensation device and a control method thereof to improve the regulation effect of three-phase unbalanced voltage.

[0005] According to one aspect of the present invention, there is provided an unbalanced voltage compensation device, comprising a power module, wherein the power module is connected in series between a new energy collection station and an AC power grid; the power module comprises:

[0006] A phase compensation unit, the A phase compensation unit is connected in series in the A phase power transmission line between the new energy collection station and the AC power grid;

[0007] A B-phase compensation unit, the B-phase compensation unit is connected in series in a B-phase power transmission line between the new energy collection station and the AC power grid;

[0008] A C-phase compensation unit, the C-phase compensation unit is connected in series in a C-phase power transmission line between the new energy collection station and the AC power grid;

[0009] Among them, the A-phase compensation unit, the B-phase compensation unit and the C-phase compensation unit each include at least one full-bridge sub-unit connected in series, the full-bridge sub-unit includes a capacitor, and each of the full-bridge sub-units controls the three-phase voltage balance by controlling the state of each of the capacitors.

[0010] Optionally, the A-phase compensation unit further includes an A-phase bypass switch, wherein two ends of the A-phase bypass switch are respectively connected to two ends of the full-bridge subunits connected in series; the A-phase bypass switch is used to bypass the full-bridge subunits connected in series;

[0011] The B-phase compensation unit further includes a B-phase bypass switch, the two ends of which are respectively connected to the two ends of the series-connected full-bridge sub-units; the B-phase bypass switch is used to bypass the series-connected full-bridge sub-units;

[0012] The C-phase compensation unit also includes a C-phase bypass switch, the two ends of which are respectively connected to the two ends of the series-connected full-bridge sub-units; the C-phase bypass switch is used to bypass the series-connected full-bridge sub-units.

[0013] Optionally, the full-bridge subunit further includes a first bridge arm and a second bridge arm; the capacitor, the first bridge arm and the second bridge arm are connected in parallel;

[0014] The first bridge arm comprises: a first transistor and a second transistor, the first transistor and the second transistor are connected in series, and a connection point between the first transistor and the second transistor serves as an input end of the full-bridge sub-unit;

[0015] The second bridge arm comprises: a third transistor and a fourth transistor, the third transistor and the fourth transistor are connected in series, and a connection point between the third transistor and the fourth transistor serves as an output end of the full-bridge subunit;

[0016] The output end of the full-bridge sub-unit of the previous stage is connected to the input end of the full-bridge sub-unit of the next stage to form a series connection of the full-bridge sub-units.

[0017] Optionally, the unbalanced voltage compensation device further includes:

[0018] A line voltage acquisition module, used to acquire the voltage at the outlet of the power module;

[0019] A controller is used to receive the signal sent by the line voltage acquisition module, and control the full-bridge sub-units of the A-phase compensation unit, the B-phase compensation unit and the C-phase compensation unit to perform primary compensation for the unbalanced voltage.

[0020] Optionally, the unbalanced voltage compensation device further includes:

[0021] A current collection module, used to collect the current of the power transmission line, including the current of the A-phase power transmission line, the B-phase power transmission line and the C-phase power transmission line;

[0022] A capacitor voltage acquisition module, used to acquire the capacitor voltage in each of the full-bridge sub-units;

[0023] Among them, the controller is used to receive signals sent by the current acquisition module, the capacitor voltage acquisition module and the line voltage acquisition module, and control the full-bridge sub-units of the A-phase compensation unit, the B-phase compensation unit and the C-phase compensation unit to perform secondary compensation for the unbalanced voltage.

[0024] Optionally, the controller is also electrically connected to the A-phase bypass switch of the A-phase compensation unit;

[0025] The controller is also electrically connected to the B-phase bypass switch of the B-phase compensation unit;

[0026] The controller is also electrically connected to the C-phase bypass switch of the C-phase compensation unit;

[0027] The controller is also used to control the actions of the A-phase bypass switch, the B-phase bypass switch and the C-phase bypass switch, and send a relay protection signal to the new energy collection station.

[0028] According to another aspect of the present invention, a control method for an unbalanced voltage compensation device is provided. The unbalanced voltage compensation device described in any embodiment of the present invention is adopted. The control method includes controlling the operating state of the full-bridge subunit to achieve unbalanced voltage compensation of the power transmission line.

[0029] Optionally, the control method of the unbalanced voltage compensation device includes primary compensation, and the primary compensation includes:

[0030] collecting the voltage at the outlet of the power module;

[0031] Determining an unbalanced voltage according to a voltage at an outlet of the power module;

[0032] determining a compensation voltage according to the unbalanced voltage;

[0033] A trigger pulse is generated according to the compensation voltage; wherein the trigger pulse is used to control the operating state of the full-bridge subunit.

[0034] Optionally, before determining the compensation voltage according to the unbalanced voltage, a secondary compensation is further included; the secondary compensation includes:

[0035] Acquiring the capacitor voltage of the full-bridge subunit and the current of the power transmission line;

[0036] The secondary compensation is used to determine the capacitor voltage balance control instruction for the power module according to the capacitor voltage of the full-bridge subunit and the current of the power transmission line; and to generate a trigger pulse using the capacitor voltage balance control instruction and the unbalanced voltage.

[0037] Optionally, while controlling the operating state of the full-bridge subunit, the method further includes:

[0038] The full-bridge subunit is provided with at least one of overcurrent protection, overvoltage protection, undervoltage protection and overheat protection.

[0039] The technical solution provided in the embodiment of the present invention realizes the regulation of the three-phase voltage balance by setting a power module. Specifically, the A-phase compensation unit, the B-phase compensation unit and the C-phase compensation unit are all connected in series in each phase power transmission line, and have a small equipment loss by directly compensating the unbalanced voltage. In the process of regulating the three-phase voltage, each compensation unit can be quickly put into use and generate a voltage equal to the unbalanced voltage and opposite in direction, thereby realizing a rapid balance of the three-phase voltage. At the same time, the unbalanced three-phase current is not transmitted to the power grid, thereby improving the power quality and the stability of the power system operation, and having a good regulation effect.

[0040] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 is a structural schematic diagram of an unbalanced voltage compensation device provided according to an embodiment of the present invention;

[0043] Figure 2 is a schematic structural diagram of a full-bridge subunit provided according to an embodiment of the present invention;

[0044] Figure 3 is a structural schematic diagram of another unbalanced voltage compensation device provided according to an embodiment of the present invention;

[0045] Figure 4 The present invention is a flowchart of a control method of an unbalanced voltage compensation device provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0048] An embodiment of the present invention provides an unbalanced voltage compensation device, which can adopt the control method of the unbalanced voltage compensation device provided by any embodiment of the present invention. Figure 1 This is a schematic diagram of the structure of an unbalanced voltage compensation device provided by an embodiment of the present invention. Figure 1 The unbalanced voltage compensation device includes a power module 1, which is connected in series between the new energy collection station 2 and the AC power grid 3; the power module 1 includes: an A-phase compensation unit 11, a B-phase compensation unit 12 and a C-phase compensation unit 13. The A-phase compensation unit 11 is connected in series in the A-phase power transmission line between the new energy collection station 2 and the AC power grid 3; the B-phase compensation unit 12 is connected in series in the B-phase power transmission line between the new energy collection station 2 and the AC power grid 3; the C-phase compensation unit 13 is connected in series in the C-phase power transmission line between the new energy collection station 2 and the AC power grid 3. Among them, the A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13 each include at least one full-bridge sub-unit 111 connected in series, the full-bridge sub-unit 111 includes a capacitor, and each full-bridge sub-unit 111 controls the state of each capacitor to control the three-phase voltage balance.

[0049] Among them, the new energy collection station 2 can be a new energy collection system including photovoltaic power generation, wind power generation, electrochemical energy storage, flywheel energy storage, etc., which is connected to the AC power grid through a converter. When an unbalanced voltage appears on the power transmission line, the power module 1 can adjust the unbalanced voltage of each phase of the power transmission line to balance the unbalanced voltage generated by each phase line. Each phase compensation unit can include multiple full-bridge sub-units 111, and the capacitor voltage generated by the capacitor in the full-bridge sub-unit 111 can be used to offset the unbalanced voltage generated in each phase line.

[0050] Specifically, the A-phase compensation unit 11 can generate a voltage equal to and opposite to the unbalanced voltage in the A-phase power transmission line through the capacitor in its full-bridge subunit 111, so as to offset the unbalanced voltage in the A-phase power transmission line. The B-phase compensation unit 12 can generate a voltage equal to and opposite to the unbalanced voltage in the B-phase power transmission line through the capacitor in its full-bridge subunit 111, so as to offset the unbalanced voltage in the B-phase power transmission line. The C-phase compensation unit 13 can generate a voltage equal to and opposite to the unbalanced voltage in the C-phase power transmission line through the capacitor in its full-bridge subunit 111, so as to offset the unbalanced voltage in the C-phase power transmission line. By controlling the A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13 respectively, the adjustment of the three-phase voltage balance can be achieved. Exemplarily, when the unbalanced voltage in the A-phase power transmission line is large, multiple full-bridge subunits 111 in the A-phase compensation unit 11 can be put into use, and the unbalanced voltage of the phase can be compensated by multiple capacitors together.

[0051] The technical solution provided in the embodiment of the present invention realizes the regulation of the three-phase voltage balance by setting the power module 1. Specifically, the A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13 are all connected in series in the power transmission lines of each phase, and have a small equipment loss by directly compensating the unbalanced voltage. In the process of regulating the three-phase voltage, each compensation unit can be quickly put into use and generate a voltage that is equal to the unbalanced voltage in magnitude and opposite in direction, thereby realizing a rapid balance of the three-phase voltage. At the same time, the unbalanced three-phase current is not transmitted to the power grid, thereby improving the power quality and the stability of the power system operation, and having a good regulation effect.

[0052] Continue to refer Figure 1On the basis of the above embodiments, optionally, the A-phase compensation unit 11 further includes an A-phase bypass switch K1, and the two ends of the A-phase bypass switch K1 are respectively connected to the two ends of the full-bridge subunits 111 connected in series; the A-phase bypass switch K1 is used to bypass the full-bridge subunits 111 connected in series. The B-phase compensation unit 12 further includes a B-phase bypass switch K2, and the two ends of the B-phase bypass switch K2 are respectively connected to the two ends of the full-bridge subunits 111 connected in series; the B-phase bypass switch K2 is used to bypass the full-bridge subunits 111 connected in series. The C-phase compensation unit 13 further includes a C-phase bypass switch K3, and the two ends of the C-phase bypass switch K3 are respectively connected to the two ends of the full-bridge subunits 111 connected in series; the C-phase bypass switch K3 is used to bypass the full-bridge subunits 111 connected in series.

[0053] Among them, the A-phase bypass switch K1, the B-phase bypass switch K2 and the C-phase bypass switch K3 are protection switches for the A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13, respectively. When the state of the A-phase compensation unit 11 is abnormal, such as abnormal current or abnormal voltage, the A-phase compensation unit 11 can be short-circuited by the A-phase bypass switch K1, so that the A-phase compensation unit 11 is removed from the power module 1. When the state of the B-phase compensation unit 12 is abnormal, the B-phase compensation unit 12 can be short-circuited by the B-phase bypass switch K2, so that the B-phase compensation unit 12 is removed from the power module 1. When the state of the C-phase compensation unit 13 is abnormal, the C-phase bypass switch K3 can be short-circuited by the C-phase bypass switch K3, so that the C-phase compensation unit 13 is removed from the power module 1. Through this setting, each phase compensation unit can be effectively protected, and each phase compensation unit can be prevented from outputting incorrect compensation voltages when a fault occurs, thereby aggravating the imbalance of the three-phase voltage.

[0054] Figure 2 A schematic diagram of the structure of a full-bridge subunit provided by an embodiment of the present invention is shown in FIG. Figure 3 A schematic diagram of the structure of another unbalanced voltage compensation device provided by an embodiment of the present invention. Figure 2 and Figure 3On the basis of the above embodiments, optionally, the full-bridge subunit 111 further includes a first bridge arm 1111 and a second bridge arm 1112; the capacitor C, the first bridge arm 1111 and the second bridge arm 1112 are connected in parallel. The first bridge arm 1111 includes: a first transistor S1 and a second transistor S2, the first transistor S1 and the second transistor S2 are connected in series, and the connection point of the first transistor S1 and the second transistor S2 serves as the input end of the full-bridge subunit. The second bridge arm 1112 includes: a third transistor S3 and a fourth transistor S4, the third transistor S3 and the fourth transistor S4 are connected in series, and the connection point of the third transistor S3 and the fourth transistor S4 serves as the output end of the full-bridge subunit. The output end of the previous full-bridge subunit is connected to the input end of the next full-bridge subunit to form a series connection of each full-bridge subunit.

[0055] The voltage generated by the capacitor C can be adjusted by turning on or off each transistor in the first bridge arm 1111 and the second bridge arm 1112. For example, Table 1 is a relationship table between a full-bridge subunit and an output voltage provided by the present invention.

[0056] Table 1

[0057] S1 S2 S3 S4 Output voltage Activate Shutdown Activate Shutdown 0 Activate Shutdown Shutdown Activate <![CDATA[+U 电容 ]]> Shutdown Activate Activate Shutdown <![CDATA[-U 电容 ]]> Shutdown Activate Shutdown Activate 0

[0058] See Table 1, where the output voltage of the full-bridge subunit 111 can be adjusted by turning on or off different transistors in the full-bridge subunit 111, and the output voltage is the voltage generated by the capacitor C. By adjusting the output voltage of each full-bridge subunit 111, the output voltage of each phase compensation unit can be adjusted.

[0059] Exemplarily, when the first transistor S1 and the third transistor S3 are turned on, no voltage is generated on the capacitor C; when the first transistor S1 and the fourth transistor S4 are turned on, the capacitor C generates +U 电容 When the second transistor S2 and the third transistor S3 are turned on, the capacitor C generates -U 电容 voltage; when the second transistor S2 and the fourth transistor S4 are turned on, no voltage is generated on the capacitor C.

[0060] The technical solution adopted in the embodiment of the present invention realizes the control of the output voltage of each full-bridge sub-unit 111 by controlling multiple transistors. The transistor has high stability and reliability, reducing the maintenance cost and replacement frequency of the full-bridge sub-unit 111. At the same time, the transistor can quickly switch between on and off states, and the switching speed is fast, so that each transistor can quickly adjust the output voltage of the full-bridge sub-unit 111. The A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13 can directly compensate for the unbalanced voltage in real time, quickly and effectively.

[0061] Continue to refer Figure 3 On the basis of the above embodiments, optionally, the unbalanced voltage compensation device further includes: a line voltage acquisition module and a controller. The line voltage acquisition module is used to acquire the voltage at the outlet of the power module 1; the controller is used to receive the signal sent by the line voltage acquisition module, and control the full bridge subunit 111 of the A phase compensation unit 11, the B phase compensation unit 12 and the C phase compensation unit 13 to perform primary compensation for the unbalanced voltage.

[0062] Among them, the voltage at the outlet of the new energy collection station 2, the compensation voltage of the compensation unit and the voltage at the outlet of the power module 1 can be expressed by the following formula:

[0063] U A =U A补偿 +U a , U B =U B补偿 +U b , U C =U C补偿 +U c ;

[0064] U A is the voltage at the A phase outlet of the new energy collection station 2, U B is the voltage at the B phase outlet of the new energy collection station 2, U C is the voltage at the C phase outlet of the new energy collection station 2, U A补偿 is the compensation voltage of the A-phase compensation unit 11, U B补偿 is the compensation voltage of the B phase compensation unit 12, U C补偿 is the compensation voltage of the C-phase compensation unit 13, U a is the voltage of power module 1 at the outlet of phase A, U b is the voltage of power module 1 at the outlet of phase B, U c is the voltage of power module 1 at the outlet of phase C line.

[0065] Among them, U a Contains unbalanced voltage component U aimb and the balanced voltage component U a1 ,U b Contains unbalanced voltage component U bimb and the balanced voltage component U b1 ,U c Contains unbalanced voltage component U cimb and the balanced voltage component U c1 ,Right now:

[0066] U a =U a1 +U aimb , Ub =U b1 +U bimb , U c =U c1 +U cimb ;

[0067] By controlling the A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13 to generate the unbalanced voltage component U aimb , U bimb and U cimb Voltages of equal magnitude and opposite direction can make the voltage U at the outlet of the new energy collection station 2 A , U B and U C Equal to the balanced voltage component U a1 , U b1 and U c1 , reaching a three-phase equilibrium state. That is:

[0068] U A补偿 =-U aimb , U B补偿 =-U bimb , U C补偿 =-U cimb ;

[0069] U A =U A补偿 +U a1 +U aimb =-U aimb +U a1 +U aimb =U a1 ;

[0070] U B =U B补偿 +U b1 +U bimb =-U bimb +U b1 +U bimb =U b1 ;

[0071] U C =U C补偿 +U c1 +U cimb =-U bimb +U c1 +U cimb =U c1 ;

[0072] Therefore, by calculating the unbalanced voltage component U aimb , U bimb and U cimb , you can get U A补偿, U B补偿 and U C补偿 The A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13 can be respectively based on U A补偿 , U B补偿 and U C补偿 Voltage compensation is performed to achieve a three-phase balanced state.

[0073] Specifically, the line voltage acquisition module can acquire the voltage U at the outlet of the power module 1. a , U b and U c The controller can receive U a , U b and U c , and extract the power frequency (50Hz) component U through fast Fourier transform a工频 , U b工频 and U c工频 , and then to U a工频 , U b工频 and U c工频 By performing symmetrical component transformation, the compensation voltage of each phase can be obtained. The specific formula is as follows:

[0074]

[0075] Among them, j is the imaginary unit, N is the sequence length, k is the frequency index, which is 50 Hz, and n is the time index.

[0076] To U a工频 , U b工频 and U c工频 Perform a symmetric component transformation:

[0077]

[0078] Where a is the transformation factor e i2π / 3 , U1, U2, and U0 are positive, negative, and zero-sequence components, respectively.

[0079] The instantaneous value expression of the positive sequence component U1 is U1 = Usin (100πt + θ). Based on the instantaneous value expression of the positive sequence component U1, the balanced voltage component U can be obtained. a1 , U b1 and U c1 The instantaneous value expression of is:

[0080] U a1 =Usin(100πt+θ)

[0081] U b1 =Usin(100πt+θ-120°)

[0082] U c1=Usin(100πt+θ+120°)

[0083] From the above formula, we can see that through U a , U b and U c Respectively with the balanced voltage component U a1 , U b1 and U c1 By subtracting, we can get the unbalanced voltage component U aimb , U bimb and U cimb . aimb Take the inverse and you get U A补偿 , for U bimb Take the inverse and you get U B补偿 , for U cimb Take the inverse and you get U C补偿 The A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13 are respectively based on U A补偿 , U B补偿 and U C补偿 By performing compensation, balanced control of the three-phase voltage can be achieved.

[0084] Continue to refer Figure 3 On the basis of the above embodiments, optionally, the unbalanced voltage compensation device further includes: a current acquisition module, which is used to acquire the current of the power transmission line, including the current of the A-phase power transmission line, the B-phase power transmission line and the C-phase power transmission line. A capacitor voltage acquisition module, which is used to acquire the capacitor voltage in each full-bridge sub-unit 111; wherein the controller is used to receive signals sent by the current acquisition module, the capacitor voltage acquisition module and the line voltage acquisition module, and control the full-bridge sub-units 111 of the A-phase compensation unit 11, the B-phase compensation unit 12 and the C-phase compensation unit 13 to perform secondary compensation for the unbalanced voltage.

[0085] Among them, the current acquisition module and the capacitor voltage acquisition module can convert the strong electric analog signals of the three-phase current and the capacitor voltage into digital signals that can be recognized by the controller. When the full-bridge sub-unit 111 is put into use, the controller can selectively put into use different full-bridge sub-units 111 according to the capacitor voltage of each capacitor. Exemplarily, Table 2 is a state table of the charging and discharging of the full-bridge sub-unit capacitor provided according to the present invention.

[0086] Table 2

[0087] S1 S2 S3 S4 Output voltage Current direction Capacitor status Activate Shutdown Shutdown Activate <![CDATA[+U 电容 ]]> just Charge Activate Shutdown Shutdown Activate <![CDATA[+U 电容 ]]> burden Discharge Shutdown Activate Activate Shutdown <![CDATA[-U 电容 ]]> just Discharge Shutdown Activate Activate Shutdown <![CDATA[-U 电容 ]]> burden Charge Activate Shutdown Activate Shutdown 0 just bypass Activate Shutdown Activate Shutdown 0 burden bypass Shutdown Activate Shutdown Activate 0 just bypass Shutdown Activate Shutdown Activate 0 burden bypass

[0088] See Table 2 and combine Figure 2The controller can sort the capacitor voltages of the full-bridge sub-units 111 in the A-phase compensation unit 11 , the B-phase compensation unit 12 , and the C-phase compensation unit 13 according to the charge and discharge status of each full-bridge sub-unit 111 .

[0089] Exemplarily, when the compensation unit of a certain phase needs to compensate for the unbalanced voltage by discharging, a specified number of full-bridge subunits 111 are put into operation in the order of capacitor voltage from high to low. When the compensation unit of a certain phase needs to compensate for the unbalanced voltage by charging, a specified number of full-bridge subunits 111 are put into operation in the order of capacitor voltage from low to high. Through this setting, the balance control of the capacitor voltage can be achieved, and the charge and discharge state of each full-bridge subunit 111 can be better controlled, so that the capacitor voltage of the power module remains balanced and maintained at a certain voltage level to ensure the stable operation of the power module. This setting can also ensure that the power module can output a sufficiently large compensation voltage, with a better compensation effect.

[0090] Continue to refer Figure 3 On the basis of the above embodiments, optionally, the controller is also electrically connected to the A-phase bypass switch K1 of the A-phase compensation unit; the controller is also electrically connected to the B-phase bypass switch K2 of the B-phase compensation unit; the controller is also electrically connected to the C-phase bypass switch K3 of the C-phase compensation unit; the controller is also used to control the operation of the A-phase bypass switch K1, the B-phase bypass switch K2 and the C-phase bypass switch K3, and send a relay protection signal to the new energy collection station 2.

[0091] The controller can detect the current of each power transmission line and the capacitor voltage of each full-bridge sub-unit 111 in real time according to the current acquisition module and the capacitor voltage acquisition module.

[0092] For example, when the current of any power transmission line exceeds the action protection threshold, the controller controls the bypass switches K1, K2 and K3 to close, and the entire power module is removed from the system. At the same time, the new energy collection station 2 can also receive the relay protection signal sent by the controller, and the new energy collection station 2 controls the relay protection action of the transmission line, disconnects the export circuit breaker, and removes the fault.

[0093] When the capacitor voltage in a full-bridge subunit 111 is greater than the overvoltage protection threshold or less than the undervoltage protection threshold, the controller bypasses the full-bridge subunit 111 by controlling the on and off of each transistor in the full-bridge subunit 111, and other full-bridge subunits 111 can still maintain normal operation. When the bypassed full-bridge subunit 111 in any compensation unit exceeds the threshold, the compensation unit may not be able to effectively compensate for the unbalanced voltage. Therefore, the bypass switch of the phase compensation unit can be closed to remove the entire compensation unit from the system.

[0094] It should be noted that, in the embodiment of the present invention, the compensation of three-phase unbalanced voltage is taken as an example for explanation, which is not a limitation of the present invention. In other implementations, it can also be applied to the compensation of other voltages such as harmonic voltages. As long as it can cause voltage imbalance, the unbalanced voltage compensation device provided in the embodiment of the present invention can be applied.

[0095] The embodiment of the present invention also provides a control method for an unbalanced voltage compensation device. The control method adopts the unbalanced voltage compensation device provided by any embodiment of the present invention, and the control method can be executed by a controller. The control method includes controlling the operating state of the full-bridge subunit to achieve unbalanced voltage compensation of the power transmission line. It has similar beneficial effects to the unbalanced voltage compensation device provided by any of the above embodiments, which will not be repeated here.

[0096] Figure 4 This is a flow chart of a control method of an unbalanced voltage compensation device provided by an embodiment of the present invention. Figure 4 Based on the above embodiments, optionally, the control method of the unbalanced voltage compensation device includes primary compensation, and the primary compensation includes:

[0097] S110 . Collecting the voltage at the outlet of the power module.

[0098] The voltage at the outlet of the power module includes: the voltage U of the power module at the outlet of the A-phase power transmission line a , the voltage U of the power module at the outlet of the B-phase power transmission line b , the voltage U of the power module at the outlet of the C-phase power transmission line c .

[0099] S120: Determine an unbalanced voltage according to a voltage at an outlet of the power module.

[0100] The controller calculates the unbalanced voltage through the voltage at the outlet of the power module.

[0101] S130: Determine a compensation voltage according to the unbalanced voltage.

[0102] The compensation voltage can be obtained by inverting the unbalanced voltage.

[0103] S140, generating a trigger pulse according to the compensation voltage; wherein the trigger pulse is used to control the operating state of the full-bridge sub-unit.

[0104] Among them, the trigger pulse is used to represent the unbalanced voltage that each phase compensation unit needs to compensate. The controller sends the trigger pulse to the full-bridge subunit in each phase compensation unit. The full-bridge subunit can generate a compensation voltage according to the trigger pulse to adjust the three-phase voltage balance.

[0105] Each compensation unit may have a plurality of full-bridge sub-units 111 connected in series, and the controller may calculate the number of full-bridge sub-units 111 invested in each compensation unit according to the capacitor voltage in each full-bridge sub-unit 111 and the compensation voltage of each phase.

[0106] Exemplarily, each full-bridge sub-unit 111 may use capacitors of the same capacity, that is, each capacitor may generate the same capacitor voltage when fully charged, and the number of full-bridge sub-units 111 invested in each phase compensation unit is:

[0107] N A =U A补偿 / U a电容 ; N B =U B补偿 / U b电容 ; N C =U C补偿 / U c电容 ;

[0108] Among them, N A The absolute value of is the number of full-bridge subunits 111 invested in the A-phase compensation unit, N B The absolute value of is the number of full-bridge subunits 111 invested in the B-phase compensation unit, N C The absolute value of is the number of full-bridge subunits 111 invested in the C-phase compensation unit, U a电容 is the capacitor voltage of the full bridge subunit 111 in phase A, U b电容 is the capacitor voltage of the full bridge subunit 111 in phase B, U c电容 is the capacitor voltage of the full bridge subunit 111 in the C phase.

[0109] When N A 、N B or N C When N is a non-integer greater than 0, it is rounded down. A 、N B or N C When N is a non-integer less than 0, it is rounded up. The positive and negative signs of N represent the state of the full-bridge subunit 111. When N is a positive value, it means that the full-bridge subunit 111 is working at the output +U 电容 When N is negative, the full bridge subunit 111 of the input flag works at the output -U 电容 status.

[0110] The controller may control the A-phase compensation unit 11 , the B-phase compensation unit 12 , and the C-phase compensation unit 13 to input a specified number of full-bridge sub-units 111 according to the input number of the full-bridge sub-units 111 of each phase.

[0111] The technical solution provided by the embodiment of the present invention can determine the unbalanced voltage by collecting the voltage at the outlet of the power module. The controller can determine the compensation voltage according to the unbalanced voltage and generate a trigger pulse, thereby realizing the control of the operating state of each full-bridge sub-unit. In the process of regulating the three-phase voltage, each compensation unit can be quickly put into operation and generate a voltage equal to the unbalanced voltage and opposite to the direction, thereby realizing the rapid balance of the three-phase voltage and not transmitting the unbalanced three-phase current to the power grid, thereby improving the power quality and the stability of the power system operation and having a good regulation effect.

[0112] Based on the above embodiments, optionally, before determining the compensation voltage according to the unbalanced voltage, a secondary compensation is further included; the secondary compensation includes: obtaining the capacitor voltage of the full-bridge subunit and the current of the power transmission line. The secondary compensation is used to determine the instruction for the capacitor voltage balance control of the power module according to the capacitor voltage of the full-bridge subunit and the current of the power transmission line; and the trigger pulse is generated using the capacitor voltage balance control instruction and the unbalanced voltage.

[0113] Each phase compensation unit may include multiple full-bridge sub-units. When the capacitors of the full-bridge sub-units are charged or discharged, the voltage of the power module may be unbalanced, making it unable to effectively compensate for the unbalanced voltage. Therefore, it is necessary to control the balance of the voltages of each capacitor.

[0114] By using the instructions of capacitor voltage balance control and the trigger pulse generated by the unbalanced voltage, it is possible to select the appropriate full-bridge sub-unit to be put into operation while controlling the full-bridge sub-unit to be put into operation in a certain number. Exemplarily, by obtaining the capacitor voltage of the full-bridge sub-unit and the current of the power transmission line, the charge and discharge state of each full-bridge sub-unit can be determined, and the capacitor voltage of the full-bridge sub-units in each phase compensation unit can be sorted. When the full-bridge sub-unit put into operation is working in the charging state, the specified number is put into operation in sequence from low to high through the capacitor voltage; when the full-bridge sub-unit put into operation is working in the discharging state, the specified number is put into operation in sequence from high to low through the capacitor voltage. Through the instructions of capacitor voltage balance control, the capacitor voltage of the power module can be kept balanced and maintained at a certain voltage level, ensuring the stable operation of the unbalanced voltage compensation device.

[0115] On the basis of the above embodiments, optionally, while controlling the operating state of the full-bridge sub-unit, it also includes: performing at least one of overcurrent protection, overvoltage protection, undervoltage protection and overheat protection on the full-bridge sub-unit.

[0116] Among them, by monitoring the current, voltage, capacitor voltage, temperature and other data of the full-bridge sub-unit, the controller can identify various abnormal and fault conditions of the device. When an abnormality occurs, the controller can send a control signal in time to control the removal of each full-bridge sub-unit or the overall removal of the power module to protect the balanced voltage compensation device from damage.

[0117] For example, when the voltage at the outlet of the power module is abnormal, in order to prevent the power module from compensating for the fault voltage and affecting the normal operation of the relay protection of the new energy collection station's transmission line, it is necessary to put the A-phase bypass switch, the B-phase bypass switch and the C-phase bypass switch into operation to cut off the entire power module from the system. At the same time, the new energy collection station controls the relay protection of the transmission line, disconnects the outlet circuit breaker, and eliminates the fault.

[0118] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0119] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An unbalanced voltage compensation device, characterized in that: It includes a power module, which is connected in series between the new energy collection station and the AC power grid; the power module includes: A phase compensation unit, the A phase compensation unit is connected in series in the A phase power transmission line between the new energy collection station and the AC power grid; A B-phase compensation unit, the B-phase compensation unit is connected in series in a B-phase power transmission line between the new energy collection station and the AC power grid; A C-phase compensation unit, the C-phase compensation unit is connected in series in a C-phase power transmission line between the new energy collection station and the AC power grid; Among them, the A-phase compensation unit, the B-phase compensation unit and the C-phase compensation unit each include at least one full-bridge sub-unit connected in series, the full-bridge sub-unit includes a capacitor, and each of the full-bridge sub-units controls the three-phase voltage balance by controlling the state of each of the capacitors.

2. The unbalanced voltage compensation device according to claim 1, characterized in that: The A-phase compensation unit further includes an A-phase bypass switch, the two ends of which are respectively connected to the two ends of the full-bridge sub-units connected in series; the A-phase bypass switch is used to bypass the full-bridge sub-units connected in series; The B-phase compensation unit further includes a B-phase bypass switch, the two ends of which are respectively connected to the two ends of the series-connected full-bridge sub-units; the B-phase bypass switch is used to bypass the series-connected full-bridge sub-units; The C-phase compensation unit also includes a C-phase bypass switch, the two ends of which are respectively connected to the two ends of the series-connected full-bridge sub-units; the C-phase bypass switch is used to bypass the series-connected full-bridge sub-units.

3. The unbalanced voltage compensation device according to claim 1 or 2, characterized in that: The full bridge subunit further includes a first bridge arm and a second bridge arm; the capacitor, the first bridge arm and the second bridge arm are connected in parallel; The first bridge arm comprises: a first transistor and a second transistor, the first transistor and the second transistor are connected in series, and a connection point between the first transistor and the second transistor serves as an input end of the full-bridge sub-unit; The second bridge arm comprises: a third transistor and a fourth transistor, the third transistor and the fourth transistor are connected in series, and a connection point between the third transistor and the fourth transistor serves as an output end of the full-bridge subunit; The output end of the full-bridge sub-unit of the previous stage is connected to the input end of the full-bridge sub-unit of the next stage to form a series connection of the full-bridge sub-units.

4. The unbalanced voltage compensation device according to claim 1, characterized in that: Also includes: A line voltage acquisition module, used to acquire the voltage at the outlet of the power module; A controller is used to receive the signal sent by the line voltage acquisition module, and control the full-bridge sub-units of the A-phase compensation unit, the B-phase compensation unit and the C-phase compensation unit to perform primary compensation for the unbalanced voltage.

5. The unbalanced voltage compensation device according to claim 4, characterized in that: Also includes: A current collection module, used to collect the current of the power transmission line, including the current of the A-phase power transmission line, the B-phase power transmission line and the C-phase power transmission line; A capacitor voltage acquisition module, used to acquire the capacitor voltage in each of the full-bridge sub-units; Among them, the controller is used to receive signals sent by the current acquisition module, the capacitor voltage acquisition module and the line voltage acquisition module, and control the full-bridge sub-units of the A-phase compensation unit, the B-phase compensation unit and the C-phase compensation unit to perform secondary compensation for the unbalanced voltage.

6. The unbalanced voltage compensation device according to claim 4, characterized in that: The controller is also electrically connected to the A-phase bypass switch of the A-phase compensation unit; The controller is also electrically connected to the B-phase bypass switch of the B-phase compensation unit; The controller is also electrically connected to the C-phase bypass switch of the C-phase compensation unit; The controller is also used to control the actions of the A-phase bypass switch, the B-phase bypass switch and the C-phase bypass switch, and send a relay protection signal to the new energy collection station.

7. A control method for an unbalanced voltage compensation device, characterized in that: Using the unbalanced voltage compensation device as described in any one of claims 1 to 6, the control method includes controlling the operating state of the full-bridge subunit to achieve unbalanced voltage compensation of the power transmission line.

8. The control method of the unbalanced voltage compensation device according to claim 7, characterized in that: Comprising a primary compensation, the primary compensation comprising: collecting the voltage at the outlet of the power module; Determining an unbalanced voltage according to a voltage at an outlet of the power module; determining a compensation voltage according to the unbalanced voltage; A trigger pulse is generated according to the compensation voltage; wherein the trigger pulse is used to control the operating state of the full-bridge subunit.

9. The control method of the unbalanced voltage compensation device according to claim 8, characterized in that: Before determining the compensation voltage according to the unbalanced voltage, a secondary compensation is also included; the secondary compensation includes: Acquiring the capacitor voltage of the full-bridge subunit and the current of the power transmission line; The secondary compensation is used to determine the capacitor voltage balance control instruction for the power module according to the capacitor voltage of the full-bridge subunit and the current of the power transmission line; and to generate a trigger pulse using the capacitor voltage balance control instruction and the unbalanced voltage.

10. The control method of the unbalanced voltage compensation device according to claim 7, characterized in that: While controlling the operating state of the full-bridge subunit, the method further includes: The full-bridge subunit is provided with at least one of overcurrent protection, overvoltage protection, undervoltage protection and overheat protection.

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