A high-frequency link type ac power grid flexible interconnection device

Abstract

The application discloses a high-frequency chain type alternating current grid flexible interconnection device, which is composed of A / B / C three-phase units with the same structure, each phase unit containing four interfaces T1, T2, T3 and T4. The positive electrode of the primary side three-phase input is connected with each phase T1 interface, and the negative electrode star connection node O is connected with the negative electrode; the positive electrode of the secondary side three-phase output is connected with each phase T3 interface, and the negative electrode star connection node N is connected with the negative electrode; each phase T2 interface star connection node is connected with the T4 interface star connection node. Each phase unit comprises four power units, a resonance capacitor C0, a resonance inductor L0 and a high-frequency transformer, wherein the first to fourth power units all contain a support capacitor, a fully controlled switching device and a diode network, and are interconnected through a capacitor-diode stack; the primary side of the high-frequency transformer is connected with the half-bridge midpoint of the first and second power units through the L0-C0 resonance network, and the secondary side is connected with the half-bridge midpoint of the third and fourth power units. The application reduces the capacitance value, and realizes high-efficiency and high-reliability grid interconnection.

Description

Technical Field

[0001] This invention belongs to the field of power, and specifically relates to a high-frequency chain-type AC power grid flexible interconnection device. Background Technology

[0002] To enhance the mutual support capability of power flow between different power supply nodes or power supply zones in an AC power grid without increasing the short-circuit capacity of the AC power grid, flexible interconnection technology based on power electronic converters has received widespread attention. Currently, the mainstream solutions for achieving flexible interconnection of AC power grids mostly adopt a back-to-back voltage source converter structure, realizing the transfer and control of electrical energy through dual conversion stages of AC / DC rectification and DC / AC inversion.

[0003] However, such traditional solutions have the following prominent problems: First, due to the use of power frequency transformers or multi-stage power conversion structures, the devices are large in size, heavy in weight, and costly; second, the power switching devices operate in a hard switching state, resulting in large switching losses and low efficiency, especially in high-voltage and high-capacity applications; in addition, in order to achieve bidirectional energy flow and voltage matching, a large number of energy storage capacitors are often required, which not only increases the system size but also reduces power density and reliability.

[0004] Existing solutions, such as CN117175592A, employ a combination of ANPC and DAB converters, which reduces the number of components but results in complex control, numerous conversion stages, and limited efficiency. CN110112927B utilizes an additive connection transformer to achieve multi-level output, but relies on a special power frequency transformer, leading to large size and high cost. CN114865634B achieves cross-voltage interconnection through idle windings in substations, offering flexibility but still not overcoming the inherent losses and capacitor size issues of back-to-back conversion. Overall, existing AC flexible interconnection devices generally suffer from numerous conversion stages, high switching losses, high required capacitor values, and low power density.

[0005] Therefore, there is an urgent need in the existing technology for a new type of flexible interconnection device that can take into account high efficiency, high reliability, compact structure and is suitable for direct interconnection of AC power grids, so as to overcome the shortcomings of traditional solutions in terms of conversion links, switching losses, capacitor values ​​and system complexity. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of traditional solutions in terms of switching stages, switching losses, capacitor values, and system complexity, and to propose a high-frequency chain-type flexible interconnect device. The specific technical solution is as follows:

[0007] A high-frequency chain-type AC power grid flexible interconnection device, comprising an A-phase high-frequency chain-type flexible interconnection device, a B-phase high-frequency chain-type flexible interconnection device, a C-phase high-frequency chain-type flexible interconnection device, primary-side three-phase AC power Ua, Ub, and Uc, and secondary-side three-phase AC power. , , Composition; the aforementioned A-phase high-frequency chain-type flexible interconnect device, B-phase high-frequency chain-type flexible interconnect device, and C-phase high-frequency chain-type flexible interconnect device, each phase has four interfaces, namely T 1a T 2a T 3a T 4a T 1b T 2b T 3b T 4b And T 1c T 2c T 3c T 4c The positive terminals of the primary side three-phase AC power Ua, Ub, and Uc are respectively connected to the T phase of the A-phase high-frequency chain-type flexible interconnect device. 1a Interface, B-phase high-frequency chain-type flexible interconnect device T 1b Interface and T-phase high-frequency chain-type flexible interconnect device 1c The interface connects the negative terminals of the primary side three-phase AC power supply Ua, Ub, and Uc in a star configuration to node O; the secondary side three-phase AC power supply... , , The positive terminals are respectively connected to the T phase of the high-frequency chain-type flexible interconnect device of phase A. 3a Interface, B-phase high-frequency chain-type flexible interconnect device T 3b Interface and C-phase high-frequency chain-type flexible interconnect device T 3c Interface, secondary side three-phase AC power , , The negative electrode is connected to node N in a star configuration; the interfaces T of the A-phase high-frequency chain flexible interconnect device, the B-phase high-frequency chain flexible interconnect device, and the C-phase high-frequency chain flexible interconnect device are... 2a T 2b T 2c Star connection to node Interface T 4a T 4b T 4c Star connection to node .

[0008] This invention offers the following advantages: By employing high-frequency chain resonant soft-switching technology and single-stage AC-AC direct conversion, switching losses and conduction losses are significantly reduced, achieving efficient power transmission; a high-frequency transformer is used for electrical isolation, replacing the traditional power frequency transformer; combined with an optimized capacitor-diode stacked interconnection structure, the capacitance value and device size are greatly reduced; through the stacked interconnection of power units and resonant network design, voltage stress balancing of power devices is achieved, enabling rapid blocking of relevant switching devices during grid faults, effectively interrupting fault current and protecting equipment safety; the main power switch adopts a strategy combining fixed duty cycle and phase-shift control, allowing smooth adjustment of transmission power with a single phase shift angle, resulting in a simple control system with fast dynamic response. Attached Figure Description

[0009] Figure 1 This is a circuit topology diagram of the three-phase high-frequency chain-type AC power grid flexible interconnection device of the present invention;

[0010] Figure 2 This is a circuit topology diagram of a one-phase high-frequency chain-type flexible interconnect device of the present invention;

[0011] Figure 3 For signal Q1, Q2 The switching timing signal diagram. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0013] like Figure 1 As shown, the high-frequency chain-type AC power grid flexible interconnection device provided in this embodiment of the invention consists of an A-phase high-frequency chain-type flexible interconnection device, a B-phase high-frequency chain-type flexible interconnection device, and a C-phase high-frequency chain-type flexible interconnection device with identical circuit structures. Each phase unit is provided with four standardized electrical interfaces: the A-phase unit interfaces are named T1a, T2a, T3a, and T4a; the B-phase unit interfaces are named T1b, T2b, T3b, and T4b; and the C-phase unit interfaces are named T1c, T2c, T3c, and T4c. The positive terminals of the three-phase AC input voltages Ua, Ub, and Uc on the primary side are respectively connected to the A-phase unit interface T1a, the B-phase unit interface T1b, and the C-phase unit interface T1c; the negative terminals of the three-phase AC input voltages Ua, Ub, and Uc on the primary side are connected in a star configuration to the common neutral point O. The secondary side three-phase AC output voltage... , , The positive terminals are respectively connected to the A-phase unit interface T3a, the B-phase unit interface T3b, and the C-phase unit interface T3c; the secondary side three-phase AC output voltage , , The negative terminals are connected in a star configuration to the common neutral point N. All phase elements' T2 interfaces (T2a, T2b, T2c) are connected in a star configuration to node O; all phase elements' T4 interfaces (T4a, T4b, T4c) are connected in a star configuration to node O. .

[0014] like Figure 2 As shown, each phase high-frequency chain-type flexible interconnect device includes a first power unit, a second power unit, a third power unit, a fourth power unit, a resonant capacitor C0, a resonant inductor L0, and a high-frequency transformer. The first power unit corresponds to interface T1a and includes a support capacitor C1, a fully controlled switching device S11, a fully controlled switching device S12, a fully controlled switching device S1x, an anti-parallel diode D11 connected in anti-parallel across S11, an anti-parallel diode D12 connected in anti-parallel across S12, an anti-parallel diode D1x connected in anti-parallel across S1x, and an independent diode D1y. The specific connections are as follows: the collector of the fully controlled switching device S11 is electrically connected to the positive terminal of the supporting capacitor C1; the emitter of the fully controlled switching device S12 is electrically connected to the negative terminal of the supporting capacitor C1; the emitter of the fully controlled switching device S11 and the collector of the fully controlled switching device S12 are connected to form the midpoint of the half-bridge; the collector of the fully controlled switching device S1x is electrically connected to the positive terminal of the supporting capacitor C1; the emitter of the fully controlled switching device S1x is electrically connected to the cathode of the diode D1y; the anode of the diode D1y is electrically connected to the negative terminal of the supporting capacitor C1; the electrical interface T1a is electrically connected to the connection node between the emitter of the fully controlled switching device S1x and the cathode of the diode D1y. The circuit structure of the second power unit is the same as that of the first power unit, and its electrical interface T2a is electrically connected to the collector of the fully controlled switching device S2x. The circuit structure of the third power unit is the same as that of the first power unit, and its electrical interface T3a is electrically connected to the emitter of the fully controlled switching device S3x. The circuit structure of the fourth power unit is the same as that of the first power unit, and its electrical interface T4a is electrically connected to the collector of the fully controlled switching device S4x.

[0015] The power units adopt a stacked interconnection structure: the negative terminal of the supporting capacitor C1 of the first power unit is electrically connected to the positive terminal of the supporting capacitor C2 of the second power unit; the anode of the diode D1y of the first power unit is electrically connected to the cathode of the diode D2y of the second power unit; the emitter of the fully controllable switching device S12 of the first power unit is electrically connected to the collector of the fully controllable switching device S21 of the second power unit. The stacked connection method of the third and fourth power units is as follows: the negative terminal of the supporting capacitor C3 of the third power unit is electrically connected to the positive terminal of the supporting capacitor C4 of the fourth power unit; the anode of the diode D3y of the third power unit is electrically connected to the cathode of the diode D4y of the fourth power unit; the emitter of the fully controllable switching device S32 of the third power unit is electrically connected to the collector of the fully controllable switching device S41 of the fourth power unit. The primary winding of the high-frequency transformer is connected in series with a resonant capacitor C0 and a resonant inductor L0, and then electrically connected to the midpoint of the half-bridge of the first power unit, which is the connection node between the emitter of the fully controlled switching device S11 and the collector of the fully controlled switching device S12. The secondary winding of the high-frequency transformer is connected to the midpoint of the half-bridge of the second power unit, which is the connection node between the emitter of the fully controlled switching device S21 and the collector of the fully controlled switching device S22. The secondary winding of the high-frequency transformer is connected to the midpoint of the half-bridge of the third power unit, which is the connection node between the emitter of the fully controlled switching device S31 and the collector of the fully controlled switching device S32. The secondary winding of the high-frequency transformer is connected to the midpoint of the half-bridge of the fourth power unit, which is the connection node between the emitter of the fully controlled switching device S41 and the collector of the fully controlled switching device S42.

[0016] During normal operation of the device, the fully controlled switching devices S1x, S2x, S3x, and S4x are configured to remain continuously on. For example... Figure 3 As shown, the control method of the main power switch is as follows: Fully controlled switching devices S11 and S22 are applied with a square wave drive signal Q1 with a constant duty cycle of 50%; fully controlled switching devices S12 and S21 are applied with a square wave drive signal Q2 that is strictly complementary to the Q1 signal; fully controlled switching devices S31 and S42 are applied with a square wave drive signal that shifts the Q1 signal by an angle θ. The fully controlled switching devices S32 and S41 are applied with square wave drive signals that are strictly complementary to the Q1 signal. The switching frequency f of all drive signals sw The resonant frequency equation must be satisfied:

[0017] ;

[0018] Where L0 represents the resonant inductance parameter value and C0 represents the resonant capacitor parameter value. This frequency matching relationship ensures that the power switching device achieves zero-voltage turn-on characteristics. By adjusting the phase shift angle θ, continuous adjustment of the transmitted power is achieved. When a short-circuit fault is detected in the three-phase AC input Ua, Ub, and Uc on the primary side, the drive signals of the fully controlled switching devices S1x, S2x, S3x, and S4x are immediately shut off, cutting off the power transmission path within 10 microseconds to prevent damage to the power semiconductor devices from overcurrent or overvoltage.

Claims

1. A high-frequency chain-type AC power grid flexible interconnection device, characterized in that, The aforementioned high-frequency chain-type AC power grid flexible interconnection device comprises an A-phase high-frequency chain-type flexible interconnection device, a B-phase high-frequency chain-type flexible interconnection device, a C-phase high-frequency chain-type flexible interconnection device, primary-side three-phase AC power Ua, Ub, and Uc, and secondary-side three-phase AC power. , , Composition; the aforementioned A-phase high-frequency chain-type flexible interconnect device, B-phase high-frequency chain-type flexible interconnect device, and C-phase high-frequency chain-type flexible interconnect device, each phase has four interfaces, namely T 1a T 2a T 3a T 4a T 1b T 2b T 3b T 4b And T 1c T 2c T 3c T 4c The positive terminals of the primary side three-phase AC power Ua, Ub, and Uc are respectively connected to the T phase of the A-phase high-frequency chain-type flexible interconnect device. 1a Interface, B-phase high-frequency chain-type flexible interconnect device T 1b Interface and T-phase high-frequency chain-type flexible interconnect device 1c The interface connects the negative terminals of the primary side three-phase AC power supply Ua, Ub, and Uc in a star configuration to node O; the secondary side three-phase AC power supply... , , The positive terminals are respectively connected to the T phase of the high-frequency chain-type flexible interconnect device of phase A. 3a Interface, B-phase high-frequency chain-type flexible interconnect device T 3b Interface and T-phase high-frequency chain-type flexible interconnect device 3c Interface, secondary side three-phase AC power , , The negative electrode is connected to node N in a star configuration; the interfaces T of the A-phase high-frequency chain flexible interconnect device, the B-phase high-frequency chain flexible interconnect device, and the C-phase high-frequency chain flexible interconnect device are... 2a T 2b T 2c Star connection to node Interface T 4a T 4b T 4c Star connection to node .

2. The high-frequency chain-type AC power grid flexible interconnection device according to claim 1, characterized in that, The circuit topologies of the A-phase high-frequency chain flexible interconnect device, the B-phase high-frequency chain flexible interconnect device, and the C-phase high-frequency chain flexible interconnect device are completely identical.

3. The high-frequency chain-type AC power grid flexible interconnection device according to claim 1, characterized in that, Each phase of the high-frequency chain-type flexible interconnect device includes: a first power unit, a second power unit, a third power unit, a fourth power unit, a switching resonant capacitor C0, a resonant inductor L0, and a high-frequency transformer.

4. The high-frequency chain-type AC power grid flexible interconnection device according to claim 3, characterized in that, The first power unit circuit topology includes: a supporting capacitor C1, a fully controlled switching device S11, a fully controlled switching device S12, a fully controlled switching device S1x, diodes D1x, D11, D12, and D1y; diode D11 is connected in anti-parallel to the fully controlled switching device S11, and diode D12 is connected in anti-parallel to the fully controlled switching device S12; the collector of the fully controlled switching device S11 is connected to the positive terminal of the supporting capacitor C1, and the emitter of the fully controlled switching device S12... The emitter of the fully controlled switching device S11 is connected to the negative terminal of the supporting capacitor C1. The emitter of the fully controlled switching device S11 is connected to the collector of the fully controlled switching device S12 to form a half-bridge. The fully controlled switching device S1x is connected in anti-parallel with the diode D1x. The emitter of the fully controlled switching device S1x is connected to the cathode of the diode D1y. The collector of the fully controlled switching device S1x is connected to the positive terminal of the supporting capacitor C1. The anode of the diode D1y is connected to the negative terminal of the supporting capacitor C1. Interface T1a is connected to the emitter of S1x. The second... The power unit circuit topology includes: a supporting capacitor C2, fully controlled switching devices S21, S22, and S2x, diodes D2x, D21, and D22. All devices are connected in the same way as the first power unit circuit topology, with interface T2a connected to the collector of S2x. The third power unit circuit topology includes: a supporting capacitor C3, fully controlled switching devices S31, S32, and S3x, diodes D3x, D31, and D32. All devices are connected in the same way as the first power unit circuit topology, with interface T3a connected to the emitter of S3x. The fourth power unit circuit topology includes: a supporting capacitor C4, fully controlled switching devices S41, S42, and S4x, diodes D4x, D41, and D42. All devices are connected in the same way as the first power unit circuit topology, with interface T4a connected to the collector of S4x.

5. A high-frequency chain-type AC power grid flexible interconnection device according to claim 4, characterized in that, The first power unit and the second power unit are connected in a stacked manner, that is, the negative terminal of the supporting capacitor C1 is connected to the positive terminal of the supporting capacitor C2, the anode of the diode D1y is connected to the cathode of the diode D2y, and the emitter of the fully controlled switching device S12 is connected to the collector of the fully controlled switching device S21.

6. A high-frequency chain-type AC power grid flexible interconnection device according to claim 4, characterized in that, The third and fourth power units are connected in a stacked manner, that is, the negative terminal of the supporting capacitor C3 is connected to the positive terminal of the supporting capacitor C4, the anode of the diode D3y is connected to the cathode of the diode D4y, and the emitter of the fully controlled switching device S32 is connected to the collector of the fully controlled switching device S41.

7. A high-frequency chain-type AC power grid flexible interconnection device according to claim 4, characterized in that, The primary side of the high-frequency transformer, with the same name terminal connected in series with the resonant capacitor C0 and the resonant inductor L0, is connected to the emitter of the fully controlled switch S11 in the first power unit, and the opposite name terminal is connected to the emitter of the fully controlled switch S21 in the second power unit; the secondary side of the high-frequency transformer, with the same name terminal connected to the emitter of the fully controlled switch S31 in the third power unit, and the opposite name terminal connected to the emitter of the fully controlled switch S41 in the fourth power unit.

8. A high-frequency chain-type AC power grid flexible interconnection device according to claim 4, characterized in that, During normal operation, fully controlled switching devices S1x, S2x, S3x, and S4x remain continuously conducting. Fully controlled switching devices S11 and S22 are controlled by a square wave signal Q1 with a 50% duty cycle. Fully controlled switching devices S12 and S21 are controlled by a complementary square wave signal Q2. Fully controlled switching devices S31 and S42 employ a phase-shifted version of signal Q1. Square wave signal after angle Control; the fully controllable switching devices S31 and S42 employ phase shifting of signal Q1. Square wave signal after angle control.

9. A high-frequency chain-type AC power grid flexible interconnection device according to claim 8, characterized in that, The square wave signal Q1, square wave signal Q2, and square wave signal... and square wave signal The frequency is the resonant frequency f sw The resonant frequency f sw The relationship between the resonant capacitor C0 and the resonant inductance L0 is as follows: 。 10. A high-frequency chain-type AC power grid flexible interconnection device according to claim 4, characterized in that, When a short circuit fault occurs in the three-phase AC power Ua, Ub, and Uc on the primary side, the fully controlled switching devices S1x, S2x, S3x, and S4x are blocked.

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