A multi-port ac-dc hybrid power distribution network flexible interconnection topology and control method

Abstract

The application discloses a kind of multi-port AC / DC hybrid distribution network flexible interconnection topological structure and control method, belong to electric power system technical field;This multi-port AC / DC hybrid distribution network flexible interconnection topological structure is composed of DC side AC / DC converter, three-phase multiplexing circuit and three-phase alternating current side multi-port feeder branch;Three-phase alternating current side multi-port feeder branch includes n access AC feeder, and each AC feeder includes alternating current side filter inductance and voltage regulating circuit;N AC feeders converge to common AC bus and connect corresponding phase multiplexing circuit, and multiplexing circuit is connected with DC side AC / DC converter.The application changes the voltage amplitude and phase of alternating current side by adjusting the voltage of voltage regulating circuit on each port feeder, realizes the flexible interaction and power flow control of active / reactive power between multi-feeders;At the same time, the AC feeder voltage regulating circuit makes the topology have the ability of AC side ground fault ride-through.

Description

Technical Field

[0001] This invention relates to the technical field of power systems, specifically to a flexible interconnection topology and control method for a multi-port AC / DC distribution network. Background Technology

[0002] The uncertainty in power generation and demand of distributed energy sources and loads makes distribution networks prone to problems such as voltage exceeding limits and unbalanced feeder power, reducing the safety and reliability of the distribution system. On the other hand, the increasing number of DC power sources and loads such as photovoltaic power generation, energy storage batteries, and electric vehicles all require AC-DC converters to connect to the AC grid, resulting in significant power losses.

[0003] Therefore, to solve the above problems, some have proposed using distribution network reconfiguration based on tie switches, but this adjustment method has limited control speed and accuracy. Others have proposed using flexible interconnection switches based on power electronics technology, using fully controllable devices to replace traditional mechanical tie switches to achieve soft connections between AC distribution networks, offering advantages such as controllable power flow, flexible switching modes, and diverse control methods. Flexible controllers based on modular multilevel converters have advantages such as modularity, easy expansion, and active / reactive power decoupling, but they have disadvantages such as a large number of required modules, high cost, and large size. Patent CN202011197169.2 proposes a multi-port AC grid flexible interconnection device and its modulation method with active power flow control. This structure achieves multi-feeder access through a shared DC bus. However, when a single-phase ground fault occurs on any AC feeder, other feeders will feed power to the fault point of the faulty feeder, exacerbating the fault. Therefore, exploring flexible interconnection topologies and control methods for multi-feeder access to AC / DC hybrid distribution networks with advantages such as low cost and AC fault ride-through will strongly promote the large-scale utilization of distributed energy. Summary of the Invention

[0004] In view of the shortcomings mentioned in the above technical background, the purpose of this invention is to provide a flexible interconnection topology and control method for multi-port AC / DC distribution networks.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A flexible interconnected topology and control method for a multi-port AC / DC hybrid distribution network are disclosed. The topology consists of a DC-side AC / DC converter, a three-phase common circuit, and a three-phase AC-side multi-port feeder branch. The three-phase AC-side multi-port feeder branch includes n AC feeders, each of which includes an AC-side filter inductor and a voltage regulating circuit. The n AC feeders converge to a common AC bus and are connected to a corresponding phase multiplexing circuit, which is connected to the DC-side AC / DC converter.

[0007] The AC / DC converter is an AC / DC converter with bipolar output voltage.

[0008] Furthermore, the bipolar AC / DC converter can be a two-level converter, a three-level converter, or a multi-level converter.

[0009] Furthermore, the multilevel converter can be a modular multilevel converter or a modular multilevel converter with an optimized structure.

[0010] The modular multilevel converter is a three-phase six-bridge arm structure composed of sub-modules;

[0011] The optimized modular multilevel converter includes a three-phase six-arm bridge composed of sub-modules and an auxiliary switching circuit.

[0012] Furthermore, the submodule can be composed of half-bridge, full-bridge, or hybrid submodules;

[0013] Preferably, the auxiliary switch circuit can be a series connection of fully controlled power devices in the same direction, a series connection of fully controlled power devices in reverse direction, a series connection of semi-controlled power devices in reverse parallel, or a combination of fully controlled power devices and semi-controlled power devices.

[0014] Each phase of the three-phase multiplexing circuit is composed of a bipolar submodule;

[0015] Each phase of the three-phase AC side multi-port feeder branch is composed of a voltage regulating circuit and an AC side filter inductor connected in series.

[0016] Furthermore, the voltage regulating circuit is composed of a bipolar submodule;

[0017] Furthermore, the AC-side filter inductor is connected to the AC system.

[0018] Preferably, the bipolar submodule can be a full-bridge submodule, a clamped bipolar submodule, a cross-type submodule, or a novel bipolar submodule.

[0019] Furthermore, when a single-phase ground fault occurs in any phase AC feeder of the three-phase AC side multi-port feeder branch, the bipolar submodule of the voltage regulation circuit on the non-faulty feeder and the faulty feeder can be blocked or modulated by statcom to achieve fault isolation.

[0020] Furthermore, the three-phase multiplexing circuit, in conjunction with the DC-side AC / DC converter, enables the multiplexing circuit to be reused by the AC / DC converter, thereby reducing the number of power devices and capacitors in the DC-side AC / DC converter.

[0021] The three-phase multiplexing circuit modulation method: control the upper and lower bridge arms of any phase of the DC-side AC / DC converter to work, and the phase multiplexing circuit cooperates with the upper and lower bridge arms to perform positive and negative half-cycle modulation.

[0022] Furthermore, any phase multiplexing bridge arm is multiplexed by the upper bridge arm, and the sum of the modulation voltages of the upper bridge arm and the multiplexing circuit is the difference between the positive voltage and the AC side common bus voltage, thus achieving half-cycle energy balance between the upper bridge arm and the multiplexing circuit; any phase multiplexing bridge arm is multiplexed by the lower bridge arm, and the sum of the modulation voltages of the lower bridge arm and the multiplexing circuit is the difference between the negative voltage and the AC side common bus voltage, thus achieving half-cycle energy balance between the lower bridge arm and the multiplexing circuit.

[0023] Furthermore, when the DC-side AC / DC converter is a modular multilevel converter, the multiplexing circuit can be omitted without affecting the normal modulation of the AC / DC converter.

[0024] The multi-port AC feeder modulation method: the voltage regulation circuit on each feeder can be equivalent to an AC voltage source, which can be used to realize flexible power flow control between feeders.

[0025] Furthermore, the grid-side voltage of any two AC feeders, the bridge arm inductor voltage, and the voltage regulation circuit voltage satisfy the following:

[0026]

[0027] in, and These are the grid-side voltage vectors for feeders 1, 2, and n of phase j, respectively; and These are the AC side filter inductor voltage vectors for feeders 1, 2, and n of phase j, respectively; and These are the AC side voltage vectors of the voltage regulation circuits for phase j feeders 1, 2, and n, respectively. Let J be the common bus voltage vector for phase j.

[0028] Furthermore, a reference power flow control feeder k is selected to determine the common bus voltage. satisfy:

[0029]

[0030] in, Let be the grid-side voltage vector of phase j feeder k; The voltage vector of the k-phase feeder inductor; The voltage vector of the j-phase feeder voltage regulation circuit;

[0031] The common bus voltage is controlled by adjusting the voltage regulation circuit of the reference power flow feeder k.

[0032] Furthermore, the voltage of the regulating circuit of any other feeder i and the voltage of the regulating circuit of the reference power flow control feeder k satisfy the following:

[0033]

[0034] Furthermore, the power flow control method for each feeder is as follows: the magnitude of active / reactive power flowing through the reference power flow feeder is indirectly controlled by the precise control of the total active power transmitted by the DC-side converter, the total reactive power, and the power of other feeders. The active power P transmitted by any other feeder i... i Reactive power Q i Determined as:

[0035]

[0036] in, Let i be the grid-side voltage vector of phase j feeder i; The voltage vector of inductor i in phase j feeder; X represents the vector difference between the voltage regulation circuits of phase j feeder k and feeder i; lji Let be the impedance of phase j feed line i.

[0037] pass This allows for flexible control of the active and reactive power transmitted by other feeders.

[0038] The energy balance method for the arbitrary feeder voltage regulation circuit is as follows: the control circuit modulates the voltage vector perpendicular to the feeder current vector to achieve periodic energy balance of the voltage regulation circuit.

[0039] Furthermore, the power control of the voltage regulation circuit satisfies:

[0040]

[0041] in, Power is transmitted to the j-phase voltage regulation circuit; The current flowing through phase j AC feeder i; The voltage vector of the i-phase feeder voltage regulator circuit; Let i be the conjugate of the i-phase AC feeder current; Re[] is the real part; Im[] is the imaginary part.

[0042] The beneficial effects of this invention are:

[0043] The present invention discloses a flexible interconnection topology and modulation method for a multi-port AC / DC hybrid distribution network, which can achieve: (1) flexible access to different AC feeders with large voltage / phase ratios; (2) flexible adjustment of active and reactive power transmitted by feeders by adjusting the voltage difference between the voltage regulation circuits of each feeder; (3) reduction of converter cost by designing an energy balance modulation principle through reasonable control of the voltage modulation of the upper and lower arms and multiplexing circuits on the DC side; and (4) the voltage regulation circuits of each feeder enable any AC feeder to isolate single-phase ground faults. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a basic multi-port AC / DC hybrid distribution network flexible interconnection topology diagram of the present invention;

[0046] Figure 2 This is a flexible interconnection topology diagram of a multi-port AC / DC hybrid distribution network with a DC side consisting of a traditional modular multilevel converter, according to an embodiment of the present invention.

[0047] Figure 3 This describes the phase relationship of the multi-port AC feeder voltage and current in Embodiment 1 of the present invention.

[0048] Figure 4 This is a modulation control block diagram of the reference power flow control feeder voltage regulation circuit in embodiment one of the present invention;

[0049] Figure 5 This is a block diagram of the reference power flow feeder power flow control according to embodiment one of the present invention;

[0050] Figure 6 This is another feeder power flow control block diagram of embodiment one of the present invention;

[0051] Figure 7 This is a flexible interconnection topology diagram of a multi-port AC / DC hybrid distribution network with a bridge arm-selective modular multilevel converter on the DC side, as shown in Embodiment 2 of the present invention.

[0052] Figure 8 This is a block diagram of the DC-side bridge arm switch control according to embodiment two of the present invention;

[0053] Figure 9 This is a flexible interconnection topology diagram of a multi-port AC / DC hybrid distribution network using a bridge arm selection modular multilevel converter with eliminated multiplexing circuits according to Embodiment 3 of the present invention.

[0054] Figure 10 Here is the simulation waveform of embodiment three of the present invention: Figure 10 In the middle (a), the current of the shared AC bus is shown. Figure 10 In diagram (b), the current in AC feeder 1 is shown. Figure 10 In the middle (c), the current in feeder 2 is... Figure 10 In the middle (d), the currents of the upper and lower bridge arms on the DC side are represented. Figure 10 In the middle (e), the upper and lower bridge arm voltages on the DC side are represented. Figure 10 In the middle (f), the voltage of the feeder 2 voltage regulation circuit is... Figure 10 In the middle (g), the capacitor voltage of the DC-side bridge arm submodule is... Figure 10 The voltage at (h) represents the capacitor voltage of the feeder voltage regulation circuit submodule. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] The present invention proposes a flexible interconnection topology for a multi-port AC / DC hybrid distribution network. The topology consists of a three-phase DC side bridge arm, a DC side filter inductor, a three-phase multiplexing circuit, and a three-phase AC side multi-port feeder branch. The three-phase DC side bridge arm is composed of a sub-module bridge arm and a bridge arm switch connected in series.

[0057] Example 1 is as follows:

[0058] according to Figure 1 The aforementioned basic multi-port AC / DC hybrid distribution network flexible interconnection topology, when the DC-side AC / DC converter is a traditional modular multilevel converter (MMC), uses a half-bridge submodule (HBSM) for the DC-side bridge arm and a full-bridge submodule (FBSM) for each AC feeder. Figure 2 As shown. Taking phase A as an example, the working mode of this multi-port AC / DC hybrid distribution network flexible interconnection topology is analyzed. The upper arm ARM on the DC side... au It consists of k HBSMs connected in series, with each end connected to the positive electrode l. line and T au DC-side lower bridge arm ARM al It consists of k HBSMs connected in series, with each end connected to the negative terminal l. line and T alThe multiplexing circuit consists of m FBSMs, with both ends connected to the midpoint of the upper and lower DC-side bridge arms and the common AC bus, respectively. Each AC feeder includes a bridge arm filter inductor l. jn And a voltage regulation circuit, which consists of p FBSMs.

[0059] The DC-side modulation of this structure is consistent with the traditional MMC modulation method.

[0060] For multi-port AC feeders 1-n connected to the shared AC bus of phase A, corresponding to the above, an analysis method for multi-port AC feeder access applicable to the present invention is proposed. Figure 3 This shows the phase relationship between the voltage and current for n AC feeders. Assuming the voltage and current of the AC system are in phase for each feeder, then the following holds:

[0061]

[0062] Because the voltage regulating circuit is connected in series on the AC branch, the AC feeder current must be perpendicular to the voltage vector of the voltage regulating circuit to achieve energy balance of the FBSM in the voltage regulating circuit during the power frequency cycle, and the voltage regulating circuit only performs reactive power regulation. It should also be clarified that since the maximum voltage regulation amplitude of the voltage regulating circuits connected in series on each feeder is the same, taking an extreme operating condition as an example, feeder 1 and feeder 2 have equal voltage amplitudes and a phase difference of 30°. Taking their respective vertices as centers and a radius equal to half the modulation voltage of the AC system, we obtain the intersection of two circles. It is clear that the voltage amplitude and phase of the other feeders must fall within this intersection.

[0063] Regarding the power regulation of each feeder, one feeder is selected as the reference power flow control feeder. For example, if feeder 1 is used as the reference power flow control feeder, and feeder 1 determines the shared AC bus voltage, then the following conditions are met:

[0064]

[0065] The overcurrent of any other AC feeder can be determined by the voltage regulation module of that feeder and the reference feeder:

[0066]

[0067] The power flow through AC feeder n can then be obtained as follows:

[0068]

[0069] in,() * For conjugate.

[0070] The power transfer of the AC voltage regulation circuits on each AC feeder is represented as follows:

[0071]

[0072] The voltage relationship between reference power flow feeder 1 and power flow feeder n in the time domain is as follows:

[0073]

[0074] The voltage modulation of the power flow feeder n-type voltage regulation circuit satisfies:

[0075] v arma1 -v arman =Δv a1n (7)

[0076] Based on the aforementioned modulation principle and power flow control method, the voltage regulation circuit on the reference power flow control feeder controls, as follows: Figure 4 The reference power flow control feeder control block diagram is as follows: Figure 5 Other feeder precision power flow control block diagrams are as follows: Figure 6 It should be noted that, under the premise that the power flow of other feeders is precisely controlled, the power flow of the reference feeder is precisely controlled under the total power control.

[0077] Furthermore, when a single-phase ground fault occurs on any AC feeder, to prevent non-faulty feeders from transmitting power to the faulty feeder and exacerbating the fault, an appropriate number of FBSMs (Full-Scale Isolation Screens) need to be configured to isolate the fault. This is considering that the maximum AC system voltage can be 1 / 2V. dc Therefore, each feeder voltage regulation circuit is equipped with a 0.25N FBSM. At this time, the number of FBSMs between non-faulty feeders and faulty feeders is 0.5N, which can ensure complete isolation of faulty feeders. At this time, the FBSMs in all feeder voltage regulation circuits can have two working modes: (1) All FBSMs are blocked, then the FBSM capacitor voltage will be reversed and fed into the AC circuit to block the increase of fault current. (2) All FBSMs on the power flow feeders are operating in STATCOM mode, then the voltage regulation circuits on all feeders only perform reactive power exchange.

[0078] Example 2 is as follows:

[0079] In this embodiment, the DC side is a bridge arm-selectable modular multilevel converter, such as... Figure 7 As shown, the DC bridge arm includes an HBSM valve string and a bridge arm selection switch. The multiplexing circuit consists of an FBSM, and each feeder voltage regulation circuit consists of an FBSM. The bridge arm selection switch is a fully controllable power device, such as an IGBT. The AC and DC side control methods for this structure are as follows:

[0080] When this structure is operating normally on the DC side, during the positive half-cycle, Tau is on and Tal is off, while ARM... au ARM com and v acom Commonly modulates 1 / 2Vdc; satisfies:

[0081]

[0082] Simultaneously, during the negative half-cycle, Tal is on, Tau is off, and ARMal, ARMcom, and vcom jointly modulate 1 / 2Vdc, satisfying:

[0083]

[0084] Analyzing the power balance of the upper bridge arm and the multiplexing circuit using the positive half-cycle of phase A, the following conditions are met:

[0085]

[0086] Similarly, the negative half-cycle also satisfies this balancing method. With a traditional MMC single-bridge arm having N sub-modules, this upper bridge arm and multiplexing circuit require a maximum of 0.82N sub-modules. If N is configured... ARMau =N ARMal =0.5N, then N ARMcom =0.32N, compared to traditional MMC, it can save 34% of sub-modules and 18% of power devices, reducing costs. Regarding switch T... au / T al When Tau is conducting, the pressure of Tal is V. dc -V armau -V armal =V Tal If the design satisfies the following during the Tau conduction period:

[0087]

[0088]

[0089] Therefore V Tal The value is 0, meaning only a very small number of switching devices are needed to meet the requirements. Furthermore, the bridge arm switch control meets... Figure 8 Control methods in [the context].

[0090] Power and voltage modulation methods for each feeder on the AC side:

[0091] The voltage / phase relationships of the reference power flow feeder and other feeders are as described in Example 1, satisfying formulas (1)-(2), (6)-(7), and also satisfying... Figure 3 The positional relationship. The power flow control magnitude of each feeder satisfies (4), and the power control of the voltage regulation circuit satisfies (5). The power control of each feeder also satisfies Figure 4 , Figure 5 and Figure 6 Control methods in China.

[0092] Example 3 is as follows:

[0093] To reduce control complexity, the control complexity can be reduced in Example 2. Figure 7 By removing the AC-side multiplexing circuit and superimposing all the submodules onto the upper and lower DC-side bridge arms, the following can be obtained: Figure 9 The topology is shown. Regarding the control of the DC-side bridge arm and its switches, as shown in Example 2, the number of upper and lower DC-side bridge arm submodules is 0.82N, which is approximately 18% less than the traditional MMC. The pressure on the bridge arm switches is also extremely low, requiring only a small number of switches to meet the requirements.

[0094] The voltage / phase relationships of the reference power flow feeder and other feeders are as described in Example 1, satisfying formulas (1)-(2), (6)-(7), and also satisfying... Figure 3 The positional relationship. The power flow control magnitude of each feeder satisfies (4), and the power control of the voltage regulation circuit satisfies (5). The power control of each feeder also satisfies Figure 4 , Figure 5 and Figure 6 Control methods in China.

[0095] Based on the above analysis, a two-port simulation analysis was conducted. The DC side voltage was ±10kV, the AC system voltage was 9kV, and power flow feeder 1 served as the reference power flow control feeder, transmitting 0.9MW. Feeder 2 transmitted 1.1MW. The two feeders had equal amplitudes and a phase difference of 30°. The simulation results are as follows: Figure 10 As shown. Figure 10 In the middle (a), the current of the shared AC bus is shown. Figure 10 In diagram (b), the current in AC feeder 1 is shown. Figure 10 In the middle (c), the current in feeder 2 is... Figure 10 In the middle (d), the currents of the upper and lower bridge arms on the DC side are represented. Figure 10 In the middle (e), the upper and lower bridge arm voltages on the DC side are represented. Figure 10 In the middle (f), the voltage of the feeder 2 voltage regulation circuit is... Figure 10 In the middle (g), the capacitor voltage of the DC-side bridge arm submodule is... Figure 10 In the figure (h), the capacitor voltage of the feeder voltage regulation circuit submodule is shown. Simulation results show that AC feeder 1 only transmits active power, the voltage regulation circuit of reference feeder 1 absorbs only 23.76 kVar of reactive power, and the voltage regulation circuit of feeder 2 outputs 28.74 kVar of reactive power.

[0096] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A control method for a flexible interconnected topology of a multi-port AC / DC hybrid distribution network, characterized in that, The topology consists of a DC-side AC / DC converter, a three-phase multiplexing circuit, and a three-phase AC-side multi-port feeder branch. The three-phase AC-side multi-port feeder branch includes n AC feeders, each of which includes an AC-side filter inductor and a voltage regulation circuit. The n AC feeders converge to a common AC bus and are connected to the corresponding three-phase multiplexing circuit, which is connected to the DC-side AC / DC converter. Each phase of the three-phase multiplexing circuit is composed of a bipolar submodule, and the voltage regulation circuit is composed of a bipolar submodule. When a single-phase ground fault occurs in any phase AC feeder of the three-phase AC side multi-port feeder branch, the bipolar submodule of the voltage regulation circuit on the non-faulty feeder and the faulty feeder can be blocked or modulated by statcom to achieve fault isolation. The three-phase multiplexing circuit, in conjunction with the DC-side AC / DC converter, enables the multiplexing circuit to be reused by the AC / DC converter, thereby reducing the number of power devices and capacitors in the DC-side AC / DC converter. The control method includes: Three-phase multiplexing circuit modulation method: control the upper and lower bridge arms of any phase of the DC-side AC / DC converter to work, and the multiplexing circuit of this phase works with the upper and lower bridge arms to perform positive and negative half-cycle modulation. Multi-port AC feeder modulation method: The voltage regulation circuit on each feeder can be equivalent to an AC voltage source, which can be used to realize flexible power flow control between feeders; Energy balance method for arbitrary feeder voltage regulation circuit: The control circuit modulates the voltage vector perpendicular to the feeder current vector to achieve periodic energy balance of the voltage regulation circuit.

2. The control method for a flexible interconnected topology of a multi-port AC / DC hybrid distribution network according to claim 1, wherein the DC-side AC / DC converter is a bipolar AC / DC converter with bipolar output voltage, and the bipolar AC / DC converter is one of a two-level converter, a three-level converter, or a multi-level converter.

3. The control method for a flexible interconnected topology of a multi-port AC / DC hybrid distribution network according to claim 2, characterized in that, The multilevel converter includes a modular multilevel converter and a modular multilevel converter with an optimized structure; The modular multilevel converter is a three-phase six-bridge arm structure composed of sub-modules; The optimized modular multilevel converter includes a three-phase six-arm bridge composed of sub-modules and an auxiliary switching circuit.

4. The control method for a flexible interconnected topology of a multi-port AC / DC hybrid distribution network according to claim 3, characterized in that, The submodule can be composed of half-bridge, full-bridge, or hybrid submodules; The auxiliary switch circuit can be composed of series-connected fully controlled power devices in the same direction, series-connected fully controlled power devices in reverse direction, series-connected semi-controlled power devices in reverse parallel, or a combination of fully controlled power devices and semi-controlled power devices.

5. The control method for a flexible interconnected topology of a multi-port AC / DC hybrid distribution network according to claim 1, characterized in that, Each phase of the three-phase AC side multi-port feeder branch is composed of a voltage regulating circuit and an AC side filter inductor connected in series. The AC-side filter inductor is connected to the AC system.

6. The control method for a flexible interconnected topology of a multi-port AC / DC hybrid distribution network according to claim 5, characterized in that, The bipolar submodule can be a full-bridge submodule, a clamped bipolar submodule, a cross-type submodule, or a novel bipolar submodule.

7. The control method for a flexible interconnected topology of a multi-port AC / DC hybrid distribution network according to claim 1, characterized in that, The number of the DC-side AC / DC converter bridge arm submodules and the number of the multiplexing circuit submodules can be flexibly matched, and the sum of the two numbers meets the maximum required modulation voltage requirement. The voltages on the grid side of any two AC feeders, the voltage of the bridge arm inductor, and the voltage of the voltage regulating circuit satisfy the following: in, , and These are the grid-side voltage vectors for feeders 1, 2, and n of phase j, respectively; , and These are the AC measured filter inductor voltage vectors for phase j feed lines 1, 2, and n, respectively; , and These are the AC side voltage vectors of the voltage regulation circuits for phase j feeders 1, 2, and n, respectively. The common bus voltage vector for phase j; A reference power flow control feeder k is selected to determine the common bus voltage. ,satisfy: in, Let be the grid-side voltage vector of phase j feeder k; The voltage vector of the k-phase feeder inductor; The voltage vector of the j-phase feeder voltage regulation circuit; The common bus voltage is controlled by adjusting the voltage regulation circuit of the reference power flow feeder k. The voltage regulation circuit voltage of any other feeder i satisfies the following relationship with the voltage regulation circuit voltage of the reference power flow control feeder k: Power flow control methods for each feeder: The active / reactive power flowing through the reference power flow feeder is indirectly controlled by the total active power transmitted by the DC-side converter, the total reactive power, and the power of other feeders; the active power P transmitted by any other feeder i is... i Reactive power Q i Determined as: in, Let i be the grid-side voltage vector of phase j feeder i; The voltage vector of inductor i in phase j feeder; The voltage vector difference between the voltage regulation circuits of phase j feeder k and feeder i; Let i be the impedance of phase j feeder; pass This allows for flexible control of the active and reactive power transmitted by other feeders; The voltage vector of any AC feeder i is 90° out of phase with the current vector of that feeder, achieving energy balance within the power frequency cycle. Its power transmission satisfies: in, Power is transmitted to the j-phase voltage regulation circuit; This refers to the current flowing through phase j AC feeder i. The voltage vector of the i-phase feeder voltage regulator circuit; Let i be the conjugate of the i-phase AC feeder current; Re[] is the real part; Im[] is the imaginary part.

Images