Chain power balancing device and control method and system therefor

Abstract

The application discloses a chain type power balancing device and a control method and system thereof, and belongs to the technical field of high-power power electronics. The application comprises an active stage, a module stage and a charging stage. The switching of active and reactive working modes is realized by controlling the on-off of the bypass circuit of the active stage, and the adjustment of active power or reactive power is realized by adjusting the module stage based on full-controlled devices. The application has three working states of active absorption, reactive absorption and reactive emission. The quick switching of different working states is realized by the input and output of the active stage, and the power size can be smoothly and quickly adjusted to realize the functions of power grid frequency modulation, power oscillation suppression, reactive power balancing, unbalanced load management and the like, so as to improve the power quality and improve the stability of the power system. The application uses full-controlled devices as main power devices, and has the advantages of quick adjustment, no harmonic, small occupation area and low investment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-power power electronics, and particularly relates to a chain type power balancing device and a control method and system thereof. BACKGROUND

[0002] Electricity is one of the most widely used energy forms in the current society and is an important way to achieve the double carbon goal. However, the power system cannot be stored on a large scale because of the instantaneous nature of electric energy, that is, instant production and instant consumption, so that the system needs to achieve real-time power balance, mainly reflected in active power balance and reactive power balance. The power system can be divided into strong grids and weak grids (including isolated grids or grids in remote areas) according to the short-circuit capacity. Since the power supply capacity of the weak grid is weak and the load fluctuation is large, the power balance problem is more prominent.

[0003] When the load reactive power suddenly changes: the load consumes a large amount of reactive power, the generator needs to provide additional reactive power, which reduces the power generation efficiency, and the system voltage is reduced, causing the load equipment to work abnormally or even unable to work, reducing the production efficiency; when the load generates a large amount of reactive or no load, the cable empty running generates a large amount of reactive, causing the system voltage to rise, affecting the safety of the equipment in the grid.

[0004] When the load active power suddenly changes: a large amount of active power originally consumed by the load suddenly disappears, that is, the active power suddenly decreases, and the power generation end needs to reduce the output of active power by adjusting the excitation, air valve, and machine end voltage. Once the amount of active change exceeds the adjustment capacity of the generator, it will cause power imbalance of the power generation system, resulting in frequency rise and voltage rise, and thus damaging the equipment in the power system. Therefore, when the power is unbalanced, the generator often chooses to be off-grid to protect the safety of the equipment. The off-grid of the generator may cause the entire grid to lose power supply, resulting in more serious consequences. Or the system has no load, and the power generation system starts the black start mode, which needs to gradually increase the active power to realize the black start in cooperation with the generator. SUMMARY

[0005] The application provides a chain type power balancing device, which can quickly adjust active power and reactive power, and is used to solve the power imbalance problem in the power system. Another object of the application is to provide a control method of the chain type power balancing device, which is used to simultaneously realize active and reactive power balance. Another object of the application is to provide a power balancing system comprising the chain type power balancing device.

[0006] Technical scheme: The chain type power balancing device of the application comprises:

[0007] An active stage, comprising at least one group of active stage sub-units connected in parallel with a power resistor and an active stage bypass circuit, the active stage bypass circuit being used to control the connection of the power resistor, for switching to any one of an active power absorption mode, a reactive power absorption mode or a sending mode;

[0008] A module stage, comprising at least one group of power modules, the power modules being used to adjust the size of the active power or the reactive power;

[0009] A charging stage, connected in series with the active stage and the module stage, the charging stage comprising a charging resistor and a charging stage bypass switch, the charging resistor and the charging stage bypass switch being connected in parallel, the charging stage bypass switch being used to control the connection of the charging resistor, for charging the module stage.

[0010] In some embodiments, further comprising:

[0011] A connection impedance;

[0012] The connection impedance is located between the active stage and the charging stage, and the connection impedance is connected in series with the active stage and the charging stage.

[0013] Alternatively,

[0014] The connection impedance is located between the charging stage and the module stage, and the connection impedance is connected in series with the charging stage and the module stage.

[0015] In some embodiments, the connection impedance comprises a reactor or a transformer.

[0016] In some embodiments, the power module comprises a full-controlled device and a diode connected in anti-parallel with the full-controlled device. The full-controlled device is used as a main power switching device, and can realize high-frequency on or off control, achieving millisecond-level fast regulation.

[0017] In some embodiments, the full-controlled device comprises an IGBT, a GTO or a power field effect transistor.

[0018] In some embodiments, the active stage sub-units are connected in series.

[0019] In some embodiments, the power modules are connected in series.

[0020] In some embodiments, the power module comprises a full-bridge or half-bridge structure.

[0021] In some embodiments, the power module adjusts the size of the active power or the reactive power by on or off control, and the on or off control of the power module specifically refers to the use of pulse width modulation technology or nearest level approximation technology for control.

[0022] In some embodiments, the active stage bypass circuit comprises an active stage bypass valve group or an active stage bypass switch.

[0023] In some embodiments, the active stage bypass valve group comprises a thyristor valve group; and the active stage bypass switch is selected from any one of a group consisting of a fully controlled solid-state switch, a fast switch, a normal switch and an isolation knife switch.

[0024] In some embodiments, the power resistance has a rated power greater than that of the charging resistance. The active stage power resistance has a variable resistance value, so as to realize online real-time adjustment of the size of the active power absorption range.

[0025] In some embodiments, the application further comprises a control method of the chain type power balancing device, which is applied to an active power absorption mode and comprises the following steps:

[0026] disconnecting the charging stage bypass switch;

[0027] disconnecting or locking the active stage bypass circuit;

[0028] adjusting the size of the active power absorption according to the active power demand.

[0029] In some embodiments, the control method of the chain type power balancing device is applied to a reactive power absorption mode or a reactive power emission mode and comprises the following steps:

[0030] disconnecting the charging stage bypass switch;

[0031] connecting or triggering the active stage bypass circuit;

[0032] adjusting the size of the active power absorption according to the reactive power demand.

[0033] In some embodiments, the application further comprises a chain type power balancing system, which comprises a chain type power balancing device, the chain type power balancing device comprising:

[0034] an active stage comprising at least one group of active stage sub-units connected in parallel with a power resistance and an active stage bypass circuit, the active stage bypass circuit being used to control the connection of the power resistance, so as to switch to any one of an active power absorption mode, a reactive power absorption or emission mode;

[0035] a module stage comprising at least one group of power modules, the power modules being used to adjust the size of the active power or the reactive power;

[0036] A charging stage connected in series with the active stage and the module stage, the charging stage comprising a charging resistor and a charging stage bypass switch, the charging resistor and the charging stage bypass switch being connected in parallel, the charging resistor being controlled by the charging stage bypass switch for charging the module stage.

[0037] In some embodiments, the chain type power balancing system further comprises a main switch and a bus, the chain type power balancing device being connected to the bus through the main switch.

[0038] In some embodiments, the chain type power balancing device in the chain type power balancing system can be connected in a star shape or an angle shape.

[0039] Advantages: Compared with the prior art, the chain type power balancing device of the present application comprises an active stage, at least one group of active stage sub-units connected in parallel by a power resistor and an active stage bypass circuit, the power resistor being controlled by the active stage bypass circuit for switching to any one of an active power absorption mode, a reactive power absorption mode or an output mode; a module stage comprising at least one group of power modules, the power modules being used for adjusting the size of active power or reactive power; a charging stage connected in series with the active stage and the module stage, the charging stage comprising a charging resistor and a charging stage bypass switch, the charging resistor and the charging stage bypass switch being connected in parallel, the charging resistor being controlled by the charging stage bypass switch for charging the module stage. The balancing device has three working states of active absorption, reactive absorption and reactive output, realizes rapid switching of different working states through the input and output of the active stage, and can smoothly and quickly adjust the power size, realizes functions of power grid frequency modulation, power oscillation suppression, balanced reactive, unbalanced load governance and the like, so as to achieve the purposes of improving power quality and improving power system stability.

[0040] The power module of the present application comprises a full-controlled device and a diode connected in anti-parallel therewith, uses the full-controlled device as the main power device, and has the advantages of fast adjustment, no harmonic, small occupation area and low investment.

[0041] The control method of the chain type power balancing device of the present application comprises the following steps when applied to the active power absorption mode: opening the charging stage bypass switch, separating or locking the active stage bypass circuit, and adjusting the active power absorption size according to the active power demand; when applied to the reactive power absorption or output mode, the control method comprises the following steps: opening the charging stage bypass switch, closing or triggering the active stage bypass circuit, and adjusting the active power absorption size according to the reactive power demand. The control method of the device has the advantages of faster adjustment speed, no low-order harmonic, smooth non-polar output and no need to configure a filter branch compared with the method of adjusting the active power by a mechanical switch or a thyristor valve group series resistor.

[0042] The chain type power balance system of the application comprises a chain type power balance device, a main switch and a bus, the chain type power balance device is connected to the bus through the main switch, the chain type power balance device can be connected in a star shape or an angle shape, when connected in the angle shape, three-phase separate phases are controlled separately, each phase works in different active or reactive state, and has full-range smooth and fast adjustment capability from zero to rated value, so as to balance three-phase power and achieve the purpose of governing negative sequence voltage. BRIEF DESCRIPTION OF DRAWINGS

[0043] The technical scheme and other beneficial effects of the application will be apparent from the following detailed description of the specific embodiments of the application combined with the drawings.

[0044] Figure 1 is a star-shaped connection valve group bypass structure principle diagram of a chain type power balance device in the embodiment of the application;

[0045] Figure 2 is a star-shaped connection switch bypass structure principle diagram of another chain type power balance device in the embodiment of the application;

[0046] Figure 3 is a star-shaped connection without bypass principle diagram of a chain type power balance device in the embodiment of the application;

[0047] Figure 4 is a chain type power balance device containing a multi-stage active stage subunit structure principle diagram in the embodiment of the application;

[0048] Figure 5 is an angle-shaped connection structure principle diagram of a chain type power balance device in the embodiment of the application;

[0049] Figure 6 is a chain type power balance device module side connection impedance structure principle diagram in the embodiment of the application;

[0050] The reference signs, 1-bus, 2-main switch, 3-active stage bypass valve group, 4-power resistor, 5-connection impedance, 6-charging stage bypass switch, 7-charging resistor, 8-power module, 9-active stage bypass switch. DETAILED DESCRIPTION

[0051] The technical scheme in the embodiments of the application will be described clearly and completely in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0052] In the description of the present application, it is necessary to explain that, unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In the description of the present application, the meaning of "a plurality of" is two or more than two, unless otherwise explicitly specified and limited. In addition, the terms "first", "second" are for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included one or more of the features.

[0053] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and arrangements of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application.

[0054] The main circuit of the chain power balancing device of the present application includes an active stage, a charging stage, a module stage, a connecting impedance 5, etc.; the active stage is composed of a power resistor 4 and an active stage bypass circuit; the charging stage is composed of a charging resistor 7 and a charging stage bypass switch 6 in parallel; the module stage is composed of a chain of power modules 8, and each power module 8 is composed of a fully controlled device and its additional circuit. The active stage, the charging stage, the module stage, and the connecting impedance 5 are connected in series.

[0055] In some embodiments, the module stage is composed of power modules 8 connected in series. A single power module 8 can adopt a full-bridge or half-bridge structure, including fully controlled devices and anti-parallel diodes, and the fully controlled devices are controlled to be turned on or turned off quickly to change the size of active power or reactive power.

[0056] In some embodiments, the fully controlled device uses pulse width modulation technology (PWM) or nearest level modulation technology (NLM) to achieve fast regulation. PWM technology can effectively suppress harmonics, improve the technical performance and reliability of the inverter circuit. NLM modulation method has the advantages of low harmonic distortion rate, low switching frequency and small loss, and is suitable for high-voltage and high-power occasions with a large number of sub-modules.

[0057] In some embodiments, the fully controlled device includes IGBT, GTO or power field effect transistor. The fully controlled device is a self-turn-off device, which means that the power electronic device can be controlled to be turned on and turned off by a control signal.

[0058] In some embodiments, the active level is formed by the power resistor 4 in parallel with the active level bypass circuit; the power resistor 4 can withstand large current for a long time, and the rated power is much larger than that of the charging resistor 7, and it works for a long time in the active power absorption mode; the resistance value of the power resistor 4 is different from that of the charging resistor, and the resistance value of the power resistor 4 needs to be determined according to the rated power and the working current flowing through it. The cooling method of the power resistor 4 can be natural cooling, forced air cooling, water cooling and other heat dissipation methods to transfer heat energy; the active level bypass circuit is long-term running in the active power absorption mode, and it is out of operation at other times.

[0059] In some embodiments, the active level bypass circuit includes an active level bypass valve group 3 or an active level bypass switch 9; the active level bypass valve group 3 can use a thyristor valve group, and the active level bypass switch 9 can use a fully controlled solid-state switch, a fast switch, a general switch or an isolation knife switch. The fast switch, the general switch, the fully controlled solid-state switch or the electric isolation knife switch achieve the purpose of bypass, but the working mode conversion time is shorter when using the thyristor valve group and the fully controlled solid-state switch as the bypass device, which can achieve millisecond-level response and no switching or number of times limit.

[0060] In some embodiments, the thyristor valve group refers to a valve group based on thyristor; when the thyristor valve group is used as the active level bypass circuit, the power resistor is switched by continuously conducting the thyristor valve group and bypassing the power switch; the response time of active mode and reactive mode switching is millisecond level, and there is no switching or number of times limit.

[0061] In some embodiments, the fully controlled solid-state switch refers to a solid-state switch based on a fully controlled device; when the fully controlled solid-state switch is used as the active level bypass circuit, the power resistor is switched by continuously conducting or continuously turning off the fully controlled solid-state switch; the response time of active mode and reactive mode switching is millisecond level, and there is no switching or number of times limit.

[0062] In some embodiments, when the fast switch is used as the active level bypass device, the power resistor is switched by closing or separating the fast switch; the response time of active mode and reactive mode switching is millisecond level, and there is a switching or number of times limit.

[0063] In some embodiments, when the general switch is used as the active level bypass device, the power resistor is switched by closing or separating the fast switch; the response time of active mode and reactive mode switching is tens of milliseconds level, and there is a switching or number of times limit.

[0064] In some embodiments, the isolation switch includes an electric isolation switch or a manual isolation switch. Using the electric isolation switch as a bypass device can achieve a response of tens of seconds and has a limit on the number of switching times. Using the manual isolation switch as a bypass device cannot switch the working mode online and needs to change the working state after power failure.

[0065] In some embodiments, the charging stage is composed of a charging resistor 7 and a charging stage bypass switch 6. The resistance value of the charging resistor 7 is determined by the system voltage level and the charging current size of the power module 8. The rated power of the charging resistor 7 is usually small, and natural heat dissipation can meet the demand. When the device starts, the charging stage bypass switch 6 is separated, and the charging resistor 7 is put into operation. At this time, the charging current flows, charging the module stage, and the charging current is much smaller than the rated current. After the module stage is charged, the charging stage bypass switch 6 is closed, and the charging resistor 7 exits operation.

[0066] In some embodiments, the connection impedance 5 can be a dry air-core reactor, a dry core reactor, or an oil-immersed reactor. The installation position of the connection impedance 5 is between the active stage and the charging stage, or between the charging stage and the module stage, and is connected in series. When the voltage level of the module stage is lower than that of the bus, the connection impedance can be replaced by a transformer.

[0067] In some embodiments, the chain-type power balancing device can work in three working states of active absorption, reactive absorption, and reactive emission. When the two working states of reactive absorption and reactive emission are converted, only the trigger instruction of the power module 8 needs to be adjusted to change the phase of the branch current to achieve the working state of reactive absorption or emission. When the chain-type power balancing device works in the state of reactive absorption or emission, the chain-type power balancing device can smoothly adjust the reactive power output within the rated power range by adjusting the trigger instruction of the power module 8. The chain-type power balancing device needs to operate the active stage bypass circuit when converting between the reactive power absorption or emission mode and the active power absorption mode.

[0068] In some embodiments, when the chain-type power balancing device is initially charged, the charging stage bypass switch 6 needs to be separated, and the charging resistor 7 is put into operation. At this time, a small charging current flows through the entire branch until the charging stage bypass switch 6 is closed after the module stage is charged, and the charging state is exited.

[0069] In some embodiments, the power resistor 4 of the active stage needs to flow through the working current, which is often composed of multiple resistance power supplies in series and parallel. The active stage can be composed of multiple active stage sub-units in series, and each active stage sub-unit is composed of a power resistor 4 and an active stage bypass circuit. The power resistor 4 can be connected in parallel with the active stage bypass valve group 3 or can be connected in parallel with the active stage bypass switch 9 to distinguish between them. By changing the resistance value of the power resistor 4 put into operation, the upper limit value of the active power absorption can be adjusted.

[0070] In some embodiments, when the chain type power balancing device works in the reactive power absorption or emission mode, the power resistor 4 needs to be bypassed closed or triggered, and the power resistor 4 does not flow through the current. At this time, the rated power size can be output, and it can be quickly and smoothly adjusted from the inductive to the capacitive interval, and the response time can reach milliseconds; when the chain type power balancing device works in the active power absorption mode, the power resistor 4 needs to be put in, and the power resistor 4 flows through the working current. At this time, the active power can be absorbed, and it can be smoothly adjusted within its rated power interval, and the response time can reach milliseconds, which is the fastest active regulation device.

[0071] In some embodiments, the module level of the chain type power balancing device can be controlled by PWM or NLM modulation to reduce the harmonic current injected into the power system. Compared with the traditional thyristor valve-based power balancing device, it does not generate low-order harmonic current, reduces the dependence on filter equipment, and thus achieves the purpose of saving land occupation and reducing investment.

[0072] In some embodiments, the chain type power balancing device, the main switch 2 and the bus 1 can also form a chain type power balancing system; the chain type power balancing device is connected to the bus 1 through the main switch 2.

[0073] In some embodiments, in the chain type power balancing system, the connection mode of the chain type power balancing device can be star-shaped or angular; when connected in an angular form, three-phase independent operation can be realized, and it can work in different working states. Each phase can smoothly and quickly output from zero to rated power, thereby achieving the purpose of balancing unbalanced load and governing negative sequence voltage.

[0074] Referring to Figure 1 A chain type power balancing device star connection valve group bypass structure is provided, which comprises a bus 1, a main switch 2, an active level bypass valve group 3, a power resistor 4, a connection impedance 5, a charging level bypass switch 6, a charging resistor 7 and a power module 8.

[0075] In some embodiments, the active level bypass valve group 3 and the power resistor 4 are connected in parallel across the active level; the charging level bypass switch 6 and the charging resistor 7 are connected in parallel to form a charging level; the connection impedance 5 is connected in series between the active level and the charging level; the active level is connected to the bus 1 through the main switch 2; and the charging level is connected to the module level formed by the power module 8.

[0076] In some embodiments, when the chain type power balancing device works in the active power absorption mode, the control method comprises the following steps:

[0077] Step one, disconnect the charging level bypass switch 6;

[0078] Step two, lock the active level bypass valve group 3;

[0079] Step three, the chain type power balancing device adjusts the active power absorption size according to the active power demand.

[0080] In some embodiments, when the chain type power balancing device works in the active power absorption mode, the control method comprises the following steps:

[0081] Step one, disconnect the charging stage bypass switch 6;

[0082] Step two, continuously trigger the active stage bypass valve group 3;

[0083] Step three, the chain type power balancing device adjusts the active power absorption size according to the active power demand.

[0084] In some embodiments, the active stage bypass valve group 3 adopts a thyristor valve group.

[0085] Referring to Figure 2 Another chain type power balancing device star connection valve group bypass structure composed of bus 1, main switch 2, active stage bypass switch 9, power resistance 4, connection impedance 5, charging stage bypass switch 6, charging resistance 7 and power module 8.

[0086] In some embodiments, the active stage bypass switch 9 and the power resistance 4 are connected in parallel across the two ends, forming an active stage; the charging stage bypass switch 6 and the charging resistance 7 are connected in parallel, forming a charging stage; the connection impedance 5 is connected in series between the active stage and the charging stage, and the active stage is connected to the bus 1 through the main switch 2, and the charging stage is connected to the module stage composed of the power module 8.

[0087] In some embodiments, when the chain type power balancing device works in the active power absorption mode, the control method comprises the following steps:

[0088] Step one, disconnect the charging stage bypass switch 6;

[0089] Step two, disconnect the active stage bypass switch 9;

[0090] Step three, the chain type power balancing device adjusts the active power absorption size according to the active power demand.

[0091] In some embodiments, when the chain type power balancing device works in the active power absorption mode, the control method comprises the following steps:

[0092] Step one, disconnect the charging stage bypass switch 6;

[0093] Step two, close the active stage bypass switch 9;

[0094] Step three, the chain type power balancing device adjusts the active power absorption size according to the active power demand.

[0095] In some embodiments, the active level bypass switch 9 employs a full-controlled solid-state switch, a fast switch, a common switch or an isolated knife switch.

[0096] Referring to Figure 3 Another star-connected valve group bypass structure of the chain-type power balancing device according to the application comprises a bus 1, a main switch 2, a power resistor 4, a connecting impedance 5, a charging level bypass switch 6, a charging resistor 7 and a power module 8.

[0097] In some embodiments, the power resistor 4 constitutes an active level, the charging level bypass switch 6 and the charging resistor 7 constitute a charging level, the connecting impedance is located between the active level and the charging level, the active level is connected to the bus 1 through the main switch 2, and the charging level is connected to a module level constituted by the power module 8.

[0098] In some embodiments, when the active level is not configured with an active level bypass circuit, the chain-type power balancing device has only one working mode, i.e. active power absorption.

[0099] In some embodiments, the chain-type power balancing device can only work in an active power absorption mode, and the control method comprises the following steps:

[0100] Step one, the charging level bypass switch 6 is turned off;

[0101] Step two, the chain-type power balancing device adjusts the size of active power absorption according to the active power demand.

[0102] Referring to Figure 4 A star-connected valve group bypass and power resistor adjustable structure of the chain-type power balancing device according to the application comprises a bus 1, a main switch 2, a plurality of active level bypass valve groups 3, a plurality of power resistors 4, a connecting impedance 5, a charging level bypass switch 6, a charging resistor 7 and a power module 8.

[0103] In some embodiments, the active level bypass valve group 3 and the power resistor 4 are connected in parallel to constitute an active level subunit, a plurality of active level subunits are connected in series to constitute an active level; the charging level bypass switch 6 and the charging resistor 7 constitute a charging level, the connecting impedance 5 is located between the active level and the charging level, the active level is connected to the bus 1 through the main switch 2, and the charging level is connected to a module level constituted by the power module 8.

[0104] In some embodiments, when the chain-type power balancing device works in an active power absorption mode, the control method comprises the following steps:

[0105] Step one, the charging level bypass switch 6 is turned off;

[0106] Step two, the active level bypass valve group 3 is locked out, and the power resistor 4 is connected;

[0107] Step three, chain power balancing device according to the active power demand range, adjust the number of active level bypass valve group 3, control access power resistance value, change the active regulation range, and adjust the active power absorption size;

[0108] Step four, chain power balancing device according to the active power demand size, adjust the active power absorption size.

[0109] In some embodiments, when the chain power balancing device works in the reactive power absorption or emission mode, the control method includes the following steps:

[0110] Step one, disconnect the charging level bypass switch 6;

[0111] Step two, continue to trigger all active level bypass valve group 3;

[0112] Step three, chain power balancing device according to the reactive power demand to adjust the active power absorption size.

[0113] Referring to Figure 5 A chain power balancing device angular connection valve group bypass structure is composed of bus 1, main switch 2, active level bypass valve group 3, power resistance 4, connection impedance 5, charging level bypass switch 6, charging resistance 7 and power module 8.

[0114] In some embodiments, the active level bypass valve group 3 and the power resistance 4 are connected in parallel to form an active level; the charging level bypass switch 6 and the charging resistance 7 are connected in parallel to form a charging level; the connection impedance 5 is located between the active level and the charging level, the active level is connected with the bus 1 through the main switch 2, the charging level is connected with the module level formed by the power module 8, and the whole branch is connected between two phases of the bus, forming an angular connection. In this connection form, the power balancing device can output asymmetric active and reactive currents to solve the asymmetric problem of the power grid.

[0115] In some embodiments, when the chain power balancing device works in the active power absorption mode, the control method includes the following steps:

[0116] Step one, disconnect the charging level bypass switch 6;

[0117] Step two, lock the active level bypass valve group 3;

[0118] Step three, chain power balancing device according to the active power demand to adjust the active power absorption size.

[0119] In some embodiments, when the chain power balancing device works in the reactive power absorption or emission mode, the control method includes the following steps:

[0120] Step one, disconnect the charging level bypass switch 6;

[0121] Step two, continuously trigger active level bypass valve group 3;

[0122] Step three, chain power balancing device adjusts the size of active power absorption according to reactive power demand.

[0123] In some embodiments, when the chain power balancing device works in unbalanced mode, the control method includes the following steps:

[0124] Step one, disconnect the charging level bypass switch 6;

[0125] Step two, chain power balancing device triggers the corresponding active level bypass valve group 3 according to the active demand of each phase;

[0126] Step three, chain power balancing device adjusts the size of each active power and reactive power according to the active and reactive power demand of negative sequence voltage or unbalanced load, respectively, to ultimately achieve the purpose of reducing or eliminating negative sequence voltage or balancing the total load of unbalanced load and power balancing device.

[0127] Referring to Figure 6 Another chain power balancing device star connection valve group bypass structure is composed of busbar 1, main switch 2, active level bypass valve group 3, power resistance 4, connection impedance 5, charging level bypass switch 6, charging resistance 7 and power module 8.

[0128] In some embodiments, the active level bypass valve group 3 and the power resistance 4 are connected in parallel across the active level; the charging level bypass switch 6 and the charging resistance 7 are connected in parallel to form the charging level, the connection impedance 5 is connected in series between the module level and the charging level, and the active level is connected through the main switch 2 between the busbar 1.

[0129] In some embodiments, when the chain power balancing device works in active power absorption mode, the control method includes the following steps:

[0130] Step one, disconnect the charging level bypass switch 6;

[0131] Step two, lock the active level bypass valve group 3;

[0132] Step three, chain power balancing device adjusts the size of active power absorption according to active power demand.

[0133] In some embodiments, when the chain power balancing device works in reactive power absorption or emission mode, the control method includes the following steps:

[0134] Step one, disconnect the charging level bypass switch 6;

[0135] Step two, continuously trigger active level bypass valve group 3;

[0136] Step three, the chain type power balancing device adjusts the active power absorption size according to the reactive power demand.

[0137] The chain type power balancing device, the control method and the system thereof provided by the embodiments of the present application are described in detail above, and the principles and implementation manners of the present application are described by applying specific examples. The above embodiment descriptions are only used to help understand the technical solutions and the core ideas of the present application. Those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced equivalently, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A chain-type power balancing device, characterized in that, include: The active power level includes at least one set of active power level sub-units connected in parallel by a power resistor (4) and an active power level bypass circuit. The connection of the power resistor (4) is controlled by the active power level bypass circuit, which is used to switch to any one of the active power absorption mode, reactive power absorption mode or reactive power generation mode. The module level includes at least one set of power modules (8), each power module (8) including a fully controlled device and a diode connected in antiparallel to it; the power modules are controlled to turn on or off by pulse width modulation technology or nearest level approximation technology to adjust the magnitude of the active power or the reactive power; when switching between reactive power absorption mode and reactive power generation mode, the trigger command of the power module (8) is adjusted to change the phase of the branch current; when switching between reactive power absorption mode and reactive power generation mode, the trigger command of the power module (8) is adjusted to adjust the reactive power output within the rated power range; when switching between reactive power absorption mode and reactive power generation mode and active power absorption mode, the active power bypass circuit is operated. The charging stage is connected in series with the active stage and the module stage. The charging stage includes a charging resistor (7) and a charging stage bypass switch (6). The charging resistor (7) and the charging stage bypass switch (6) are connected in parallel. The charging resistor (7) is connected through the charging stage bypass switch (6) to control the connection of the charging resistor (7) for charging the module stage.

2. The chain-type power balancing device according to claim 1, characterized in that, Also includes: Connection impedance (5); The connection impedance (5) is located between the active stage and the charging stage, and the connection impedance (5) is connected in series with the active stage and the charging stage; Alternatively, the connection impedance (5) is located between the charging stage and the module stage, and the connection impedance (5) is connected in series with the charging stage and the module stage.

3. The chain-type power balancing device according to claim 2, characterized in that, The connection impedance (5) includes a reactor or a transformer.

4. The chain-type power balancing device according to claim 1, characterized in that, The fully controllable devices include IGBTs, GTOs, or power field-effect transistors.

5. The chain-type power balancing device according to claim 1, characterized in that, The active power level sub-units are connected in series.

6. The chain-type power balancing device according to claim 1, characterized in that, The power modules (8) are connected in series.

7. The chain-type power balancing device according to claim 6, characterized in that, The power module (8) includes a full-bridge or half-bridge structure.

8. The chain-type power balancing device according to claim 1, characterized in that, The active power bypass circuit includes an active power bypass valve group (3) or an active power bypass switch (9).

9. The chain-type power balancing device according to claim 8, characterized in that, The active power bypass valve group (3) includes a thyristor valve group; the active power bypass switch (9) is selected from any one of the following: fully controlled solid-state switch, fast switch, ordinary switch and isolating switch.

10. The chain-type power balancing device according to claim 1, characterized in that, The rated power of the power resistor (4) is greater than the rated power of the charging resistor (7).

11. The control method of the chain power balancing device according to any one of claims 1-10, applied to active power absorption mode, characterized in that, Includes the following steps: Disconnect the charging stage bypass switch (6); Separate or block the active power bypass circuit; Adjust the amount of active power absorbed according to the active power demand.

12. The control method of the chain power balancing device according to any one of claims 1-10, applied to reactive power absorption mode or reactive power generation mode, characterized in that, Includes the following steps: Disconnect the charging stage bypass switch (6); Close or trigger the active power bypass circuit; Adjust the amount of active power absorption according to the reactive power demand.

13. A chain-type power balancing system, characterized in that, Includes the chain power balancing device as described in any one of claims 1-10.

14. The chain-type power balancing system according to claim 13, characterized in that, Also includes: The main switch (2) and the bus (1) are connected to the chain power balancing device via the main switch (2).

15. The chain-type power balancing system according to claim 13, characterized in that, The chain-type power balancing devices are connected in a star or triangular shape.

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