MODULE-SHARED FLEXIBLE LOOP CLOSING CONTROLLER TOPOLOGY FOR POWER GRID

Abstract

The invention discloses a power network flexible controller topology shared by modules. Each single-phase topology comprises an AC/AC converter including N.sub.1 CHB modules, and an AC/DC module including N−N.sub.1 full-bridge rectifiers; the AC input terminals of N.sub.1 CHB modules are connected in series to form an AC port on one side of the AC/AC converter, the AC output terminals of N.sub.1 CHB modules are connected in series to form the AC port on the other side of the AC/AC converter, the AC input terminals of N−N.sub.1 full-bridge rectifiers are connected in series to form the AC port of the AC/DC module, the AC port on one side of the AC/AC converter is connected in series with the AC side port of the AC/DC module and then connected to a first AC network nd the AC port on the other side of the AC/AC converter is connected in series with the DC side port of the AC/DC module.

Claims

1. A power network flexible closed-loop controller topology shared by modules, wherein each single-phase topology comprises: an AC/AC converter comprising N.sub.1 CHB modules, and an AC/DC module comprising N−N.sub.1 full-bridge rectifiers; AC input terminals of N.sub.1 CHB modules are connected in series to form an AC port on one side of the AC/AC converter, AC output terminals of N.sub.1 CHB modules are connected in series to form another AC port on the other side of the AC/AC converter, AC input terminals of N−N.sub.1 full-bridge rectifiers are connected in series to form an AC port of the AC/DC module, the AC port on one side of the AC/AC converter is connected in series with the AC side port of the AC/DC module and then connected to a first AC network, the AC port on the other side of the AC/AC converter is connected in series with the DC side port of the AC/DC module and then connected to a second AC network, and an AC incoming line and AC outgoing line of the three-phase topology are connected to the AC network in a star connection mode, where N and N.sub.1 are positive integers.

2. The power network flexible closed-loop controller topology shared by modules according to claim 1, wherein the CHB module is a dual active bridge DC/DC converter, and the dual active bridge DC/DC converter comprises a full-bridge rectifier, a high frequency isolation unit, and a full-bridge inverter connected in sequence.

3. The power network flexible closed-loop controller topology shared by modules according to claim 1, wherein the power network flexible closed-loop controller topology also comprises a power frequency transformer, the AC port on the other side of the AC/AC converter is connected in series with a primary coil of the power frequency transformer and then connected to the first AC network, and a secondary coil of the power frequency transformer is connected to the AC side port of the AC/DC module.

4. The power network flexible closed-loop controller topology shared by modules according to claim 1, wherein the value of N and N.sub.1 is selected with the aim of a DC voltage after maximizing a DC link voltage corresponding to the input voltage of the AC port on one side of the AC/AC converter and the DC link voltage corresponding to the output voltage of the AC port on the other side of the AC/AC converter, and converting the input voltage of the AC port of the AC/DC module;

5. The power network flexible closed-loop controller topology shared by modules according to claim 1, wherein the AC/AC module is a topology with one input port and multiple output ports, and each AC outgoing line of the AC/AC converter and a ground wire form an output port of the power network flexible closed-loop controller topology.

6. The power network flexible closed-loop controller topology shared by modules according to claim 1, wherein the AC incoming line of the AC/AC converter and the AC outgoing line of the AC/DC module are both connected with a filter inductance.

7. The power network flexible closed-loop controller topology shared by modules according to claim 2, wherein the high-frequency isolation unit comprises two full-bridge converters and a high-frequency isolation transformer connected between the two full-bridge converters.

8. The power network flexible closed-loop controller topology shared by modules according to claim 2, wherein both the port connecting the high-frequency isolation unit with the DC side of the full-bridge rectifier, and the port connecting the high-frequency isolation unit with the DC side of the full-bridge inverter are connected with a filter capacitor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is the single-phase structure diagram of a power network flexible controller topology shared by modules of the invention.

[0019] FIG. 2 is the single-phase structure diagram of the power network flexible controller topology shared by CHB-based modules of the invention.

[0020] FIG. 3 is the single-phase structure diagram of the power network flexible controller topology shared by modules based on a power frequency transformer of the invention.

[0021] FIG. 4 is the three-phase star connection structure diagram of the power network flexible controller topology shared by modules of the invention.

[0022] FIG. 5 is the three-phase star connection structure diagram of the power network flexible controller topology shared by CHB-based modules of the invention.

[0023] FIG. 6 is the single-phase structure diagram of the power network flexible multi-port topology shared by modules of the invention.

[0024] FIG. 7 is the control block diagram of the cascaded H-bridge in embodiment 1 of the invention.

[0025] FIG. 8 is the control block diagram of the high frequency isolation level in embodiment 1 of the invention.

[0026] FIG. 9 is the waveform diagram of the output voltage and current in embodiment 1 of the invention.

[0027] FIG. 10 is the circuit vector diagram of embodiment 2 of the invention.

[0028] Description of the tag numbers in the drawings: 1. Full bridge rectifier, 2. High frequency isolation unit, 3. Full bridge inverter, and 4. Full bridge rectifier.

DETAILED EMBODIMENTS

[0029] According to the drawings, the technical scheme of the invention is described below in detail.

[0030] A power grid flexible controller topology shared by modules disclosed by the invention is shown in FIG. 4, and includes A phase, B phase, C phase. As shown in FIG. 1, each single-phase topology is a dual-port module connected between U.sub.g1 and U.sub.g2 networks, including the AC/AC converter of the non-shared module and the AC/DC module of the shared module. The AC port on one side of the AC/AC converter is connected in series with the AC side port of the AC/DC module and then connected to the AC network U.sub.g1, the AC port on the other side of the AC/AC converter is connected in series with the DC side port of the AC/DC module and then connected to the AC network U.sub.g2, and the AC incoming line and AC outgoing line of the AC/AC converter are connected with an inductance .sup.L. The incoming line or outgoing line of each port of the three-phase topology is connected to the AC network in a star connection mode, and the power network flexible controller topology is applicable to the connection of the distribution network where the voltage amplitude and phase angle difference between the two ports are small. The AC/AC converter can also be achieved by using the module with one input terminal and multiple output terminals as shown in FIG. 6; accordingly, the power network flexible controller topology also has multiple output terminals.

[0031] The single-phase structure of a power network flexible controller topology shared by CHB-based modules is shown in FIG. 2. The two ports of the single-phase structure are respectively connected to the AC network U.sub.g1 on side A and the AC network U.sub.g2 on side B, including a non-shared module composed of N.sub.1 CHB modules, and a shared module composed of N31 N.sub.1 full-bridge rectifiers 4, Each CHB module includes a full-bridge rectifier 1, a high-frequency isolation unit 2, and a full-bridge inverter 3 connected in sequence. The AC ports of N.sub.1 full-bridge rectifiers 1 are connected in series to form the input end of the non-shared module, the AC ports of N.sub.1 full-bridge inverters 3 are connected in series to form the output end of the non-shared module, the AC ports of N−N.sub.1 full-bridge rectifiers 4 are connected in series to form the input end of the shared module, the input end of the non-shared module is connected in series with the input end of the shared module and then connected to the AC network U.sub.g1 on side A, and the output end of the non-shared module is connected in series with the input end of the shared module and then connected to the AC network U.sub.g2 on side B. Denote the voltage at the input end and output end of the non-shared module as U.sub.1 and U.sub.2 respectively, and the voltage at the input end of the shared module as U.sub.3. U.sub.1+U.sub.3 is the voltage at the port where the single-phase topology is connected to the AC network on side A, and U.sub.2+U.sub.3 is the voltage at the port where the single-phase topology is connected to the AC network on side B. The high-frequency isolation unit 2 is a dual active bridge DC/DC converter, including two full-bridge converters and a high-frequency isolation transformer connected between the full-bridge converters; the two ports of the high-frequency isolation unit 2 are connected with a capacitor C in parallel. As shown in FIG. 5, the three-phase topology has 3N+9N.sub.1 full-bridge converters and 3N.sub.1 high frequency transformers in total. The three-phase topology cannot achieve delta connection and hybrid connection due to the same ground wire, so the topology is connected to the AC network in star connection mode.

[0032] The single-phase structure of a power network flexible controller topology shared by modules based on a power frequency transformer is shown in FIG. 3. The AC ports of the full-bridge inverters in the non-shared module are connected in series and then connected in series with the input terminal of the non-shared module through a power frequency voltage transformer, and the rest of the circuit structure is the same as the single-phase structure of the power network flexible controller topology shared by CHB-based modules. The three-phase topology has 12N.sub.1+3N.sub.2 full-bridge converters, 3N.sub.1 high frequency transformers, and 1 power frequency transformer in total.

[0033] An example analysis is carried out taking the power network flexible controller topology shared by CHB-based modules as shown in FIG. 2 as an example.

[0034] Under normal operation, take a single phase as an example; according to FIG. 2, the relationship between KVL and KCL can be obtained from the analysis:

[00001]$\{\begin{array}{c}{U}_1+U_3=U_{g1}-L_1\frac{{\mathrm{dI}}_1}{\mathrm{dt}}\\ U_2+U_3=U_{g2}+L_2\frac{{\mathrm{dI}}_2}{\mathrm{dt}}\\ I_1=I_2+I_3\\ U_1=\underset{k=1}{\overset{N_1}{.Math.}}{s}_{1k}{U}_{\mathrm{dc}1}\\ U_2=\underset{k=1}{\overset{N_1}{.Math.}}{s}_{2k}{U}_{\mathrm{dc}2}\\ U_3=\underset{k=1}{\overset{N-N_1}{.Math.}}{s}_{3k}{U}_{\mathrm{dc}2}\end{array}\circ$

[0035] Where, most of the parameters are shown in FIG. 2, and s.sub.jk(j=1,2,3) is the switch function of each module.

[0036] According to the drawings, the technical scheme of the invention is described below in detail. The described embodiments are only a part of the embodiments of the invention, rather than all the embodiments.

Embodiment 1

[0037] The single-phase flexible controller topology is shown in FIG. 2. In this embodiment, it is assumed that the two ports of the topology are connected to two 3.6 kV AC networks with the same voltage amplitude and phase angle, and the connection function is verified through the simulation of the single-phase flexible controller topology. The main simulation parameters are shown in Table 1.

TABLE-US-00001 TABLE 1 Parameters of the flexible controller topology shared by modules in embodiment 1 Parameter Value Parameter Value Transmission power 100 Output side switching 10 P/kW frequency/kHz Input side voltage 3600 Filter inductance on both sides 10 U .sub.g1/V L/mH Input side phase angle 0 Capacitor voltage of side A 750 θ.sub.1/° module U.sub.dc/V Input side switching 10 Capacitor voltage of side B 750 frequency/kHz module U .sub.DC/V Output side load R/Ω 64.88 Number of full bridges of the 3 non-shared module N.sub.1 Output side phase 0 Number of full bridges of the 3 angle θ.sub.2/° shared module N-N.sub.1

[0038] In this simulation, side A is a single-phase AC power supply, and side B is an RLC load. As shown in FIG. 7, the modulation signals of the six full-bridge rectifiers 1 on side A are obtained from the dq voltage and current double closed-loop control. The average value of the single-phase DC side voltage is the outer loop, and the input AC current decoupled by dq is the inner loop. After a modulation wave is generated, the modulation signal of each full-bridge rectifier 1 is obtained by means of carrier phase-shifting.

[0039] As shown in FIG. 8, the DAB control in the middle is that one of the isolation units is connected to the DC voltage on side B, the phase shift angle of DAB is directly obtained through PI regulation, and all DAB modulation signals are generated. The control mode of DAB ensures the stability of DC voltage on side B. The modulation signal of the full-bridge inverter 3 in the 3 non-shared modules on side B is the same as the modulation signal of the full-bridge rectifier 1 in the 3 non-shared modules on side A; therefore, it can be ensured that the voltage amplitude and phase angle at the front and rear ends are the same.

[0040] The specific control block diagram of the CHB on side A is shown in FIG. 7, and the specific control block diagram of the middle high-frequency isolation unit is shown in FIG. 8. The simulated AC side output voltage and current are shown in FIG. 9.

[0041] Through simulation, it can be verified that the invention can realize the connection function when the voltage amplitude and phase angle at the two ports are the same, and that the invention can realize power transmission and power flow regulation.

Embodiment 2

[0042] The two ports are respectively connected to AC power network with voltage phase angles of 3.6 kV, 0° and 3.7 kV, 30°. The feasibility of the normal operation of the flexible controller topology is verified by means of a vector diagram when the power factor of the two ports of the flexible controller topology is 1. Assume that the specific parameters of the flexible controller topology are shown in Table 2. As shown in FIG. 10, assuming that the transmission power is determined and the voltage phase angle at the two ports is determined, the amplitude and phase angle of the AC currents I.sub.1 and I.sub.2 at the input and output ports can be calculated according to the transmission power, thereby calculating the amplitude and phase angle of U.sub.1+U.sub.3 and U.sub.2+U.sub.3.

[0043] The AC voltage corresponding to the H-bridge is smaller than the DC voltage corresponding to the H-bridge, so the maximum DC voltage amplitude U.sub.dc1,2 corresponding to U.sub.1 and U.sub.2 is the product N.sub.1×U.sub.dc of the number of unshared modules and the DC voltage of the capacitor. Similarly, the maximum DC voltage amplitude corresponding to side U.sub.3 is U.sub.dc3=(N−N.sub.1)×U.sub.dc. The number of non-shared modules and shared modules can be determined by estimation, so as to obtain the maximum DC voltage amplitude on U.sub.1, U.sub.2 and U.sub.3 sides. Draw a circle at the starting point of the vector U.sub.1+U.sub.3, U.sub.2+U.sub.3 with the maximum DC voltage amplitude U.sub.dc3 corresponding to side U.sub.3 as the radius, and then draw two circles at the end point of the vector U.sub.1+U.sub.3, U.sub.2+U.sub.3 with the maximum DC voltage amplitude U.sub.dc1,2 corresponding to sides U.sub.1 and U.sub.2 respectively as the radius. The shaded part U.sub.1, U.sub.2 and U.sub.3 where the three circles intersect is the area which can meet the operating conditions.

[0044] The shared module only sends reactive power, so the vector U.sub.3 is perpendicular to I.sub.3. The phase angle of U.sub.3 can be determined by this method. Based on the area that meets the operating conditions in the previous step, the value range of U.sub.3 can be obtained. The specific vector diagram is shown in FIG. 10.

[0045] The power transmitted by the non-shared module is P.sub.1=Re({dot over (U)}.sub.1I.sub.1*) and the power transmitted by the shared module is P.sub.2=Re({dot over (U)}.sub.3I.sub.2*). It can be seen that the larger the amplitude of U.sub.3 the smaller the power transmitted through the non-shared module, and the greater the power transmitted through the shared module. Therefore, by maximizing the number of shared modules, the transmission efficiency of the system can be improved.

TABLE-US-00002 TABLE 2 Parameters of the flexible controller topology shared by modules in embodiment 2 Parameter Value Parameter Value Transmission power 100 Filter inductance on both sides 10 P/kW L/mH Input side voltage 3600 Module capacitance 5 U .sub.g1/V C .sub.dc/mF Input side phase angle 0 Capacitor voltage of module 750 θ.sub.1/° U .sub.dc/V Output side voltage 3700 Number of non-shared modules 3 U .sub.g2/V N.sub.1 Output side phase 30 Number of shared modules 3 angle θ.sub.2/° N-N.sub.1

[0046] In this application scenario, the invention's feasibility of connecting two distribution networks differing to some extent in voltage and amplitude has been verified using the vector diagram method, and it has been proved that the invention can carry out power transmission in this case. In addition, it can be obtained from the vector diagram that for different voltages at both ends, different functions can be realized by setting the number and ratio of shared modules and non-shared modules, and the DC voltage value.

[0047] The above-mentioned embodiments are merely examples to clearly illustrate the invention, and are not intended to limit the implementation modes. As far as a person of ordinary skill in the art is concerned, the person can also make other changes or modifications in different forms on the basis of the above description. It is unnecessary and impossible to enumerate all embodiments here, and the obvious changes or modifications derived thereof are still within the protection scope of the invention.