Mmc energy router and control method thereof

Abstract

The application discloses an MMC energy router and a control method thereof, and comprises the following steps: a first AC circuit breaker is connected with an AC network and an AC side of a first MMC converter respectively, a second AC circuit breaker is connected with an AC side of a second MMC converter and a new energy station respectively, one end of a third AC circuit breaker is connected with a connection end of the first AC circuit breaker and the AC network, and the other end of the third AC circuit breaker is connected with a connection end of the second AC circuit breaker and the new energy station, an energy storage module is connected with a DC side of the first MMC converter and a DC side of the second MMC converter through a current bus, the first AC circuit breaker, the second AC circuit breaker and the third AC circuit breaker are electrically connected with a control module respectively, and control signals of the control module are received, and the control module switches the operation state of the MMC energy router through on-off of the third AC circuit breaker. Different operation modes are selected through internal transformation topological modes and port control modes, and the power grid transmission capacity and the power flow control capacity are improved.

Description

Technical Field

[0001] This invention relates to the field of power equipment technology, and in particular to an MMC energy router and its control method. Background Technology

[0002] The search for new renewable energy sources essential for sustainable economic development has become a global focus. Furthermore, the environmental pollution caused by traditional energy sources due to climate change is undeniable, serving as a stark warning that we must develop clean energy. Vigorously exploring and promoting clean, low-carbon, and renewable energy generation to replace traditional power generation is crucial for ensuring the safe and efficient operation of the future power grid. Supported by a large power grid and with renewable energy supply as the mainstay, a real-time coordinated balance between power generation, grid, load, and storage will be essential for building an energy internet that utilizes renewable energy and achieves both enhanced security and efficiency. This will become a form of future power grid.

[0003] Energy routers are a new type of power electronic equipment that can flexibly regulate power flow distribution in the power grid, dynamically improve the self-consumption capacity of renewable energy, and give the power grid greater controllability and flexibility. Energy routers have multiple flexible operating modes, including independent and networked operation. They enable bundled access of wind, solar, energy storage, and charging systems, improving overall system energy efficiency. This is of great significance for the utilization and grid-connected application of renewable energy. Currently, energy routers abroad are mainly small-capacity laboratory prototypes and have not yet been widely adopted. Domestic energy router demonstration projects in operation and under construction focus on research into the access of new energy generation and the application of DC power consumption, building AC / DC hybrid systems to achieve flexible AC / DC networking, reducing intermediate links in AC / DC conversion, and ensuring the economic efficiency and operational efficiency of power distribution.

[0004] Existing energy router technologies are all based on power electronics. With the decreasing cost of power electronic devices and the maturation of power electronic device technology, exemplified by energy routers, energy routers are finding increasing research applications, but mostly in small-capacity applications. Furthermore, energy routers are increasingly developing towards multi-port designs, resulting in relatively fixed internal structures and a single, non-switchable operating mode. Although they are multi-port devices, each port has a single control mode. Even products that allow switching between multiple modes must first stop operation and reselect the control mode. Ports cannot switch control modes during operation. These shortcomings significantly limit the application environment of energy routers. Summary of the Invention

[0005] The purpose of this invention is to provide an MMC energy router and its control method. By internally changing the topology and port control mode, different operating modes can be selected. The router can be flexibly switched without power outages, which solves the problem of power quality being affected by the connection of large wind and solar power plants to the power grid. This improves the local absorption of new energy sources, enhances the grid's transmission capacity and power flow control capabilities, and achieves power balance.

[0006] To address the aforementioned technical problems, a first aspect of this invention provides an MMC energy router, comprising: a first MMC converter, a second MMC converter, a first AC circuit breaker, a second AC circuit breaker, a third AC circuit breaker, an energy storage module, and a control module.

[0007] The first AC circuit breaker is connected to the AC grid and the AC side of the first MMC converter, respectively; the second AC circuit breaker is connected to the AC side of the second MMC converter and the new energy power station, respectively.

[0008] One end of the third AC circuit breaker is connected to the first AC circuit breaker and the AC grid connection terminal, and the other end is connected to the second AC circuit breaker and the new energy power station connection terminal.

[0009] The energy storage module is connected to the DC side of the first MMC converter and the DC side of the second MMC converter via a current bus.

[0010] The first AC circuit breaker, the second AC circuit breaker, and the third AC circuit breaker are electrically connected to the control module and receive control signals from the control module.

[0011] The control module switches the operating status of the MMC energy router by switching the third AC circuit breaker on and off.

[0012] Furthermore, the operating states of the MMC energy router include: a first operating state and a second operating state;

[0013] The first operating state is that the first AC circuit breaker and the second AC circuit breaker are in the closed position and the third AC circuit breaker is in the open position. The AC side of the first MMC converter is connected to the main grid and operates in DC voltage mode, rectifying a stable DC voltage. The AC side of the second MMC converter is connected to the wind and solar farm and operates in VF control mode, providing grid-connected AC voltage for wind turbines and photovoltaics.

[0014] The second operating state is that the first AC circuit breaker, the second AC circuit breaker, and the third AC circuit breaker are all in the closed position. The AC side of the first MMC converter is connected to the main power grid and operates in DC voltage mode, rectifying a stable DC voltage. The AC side of the second MMC converter is connected to the main power grid through the third AC circuit breaker and operates in active power mode, controlling the power flow of the MMC energy router.

[0015] Furthermore, the energy storage module is a lithium battery module or a lead-acid battery module.

[0016] Furthermore, the first MMC converter and the second MMC converter are modular flexible converter valves. Their passive mode AC side has AC side fixed frequency and fixed voltage or VF control functions. Their active mode active power control includes DC voltage control and active power control. Their reactive power control includes AC voltage control and reactive power control.

[0017] Accordingly, a second aspect of the present invention provides an MMC energy router control method for controlling any of the MMC energy routers described above, comprising the following steps:

[0018] Obtain and determine whether the real-time active power of the first MMC converter is greater than the preset power value and whether the duration is greater than the first preset determination time;

[0019] If so, send the same frequency and voltage regulation command to the second MMC converter; otherwise, maintain the current state.

[0020] Determine whether the AC voltages on both sides of the third AC circuit breaker are synchronized;

[0021] If so, the third AC circuit breaker is closed; otherwise, the state of the third AC circuit breaker is maintained.

[0022] The second MMC converter is switched from VF control to PQ control.

[0023] Furthermore, after controlling the third AC circuit breaker to close, the method further includes:

[0024] Determine whether the third AC circuit breaker completes closing within the second preset determination time;

[0025] If not, the third AC circuit breaker is determined to be in a fault state.

[0026] Accordingly, a third aspect of the present invention provides an MMC energy router control method for controlling any of the MMC energy routers described above, comprising the following steps:

[0027] Obtain and determine whether the real-time active power of the first MMC converter is less than the preset power value and whether the duration is greater than the first preset determination time;

[0028] If so, the third AC circuit breaker is controlled to trip; otherwise, the state of the third AC circuit breaker is maintained.

[0029] The second MMC converter is controlled to switch from PQ control to VF control.

[0030] Furthermore, after the control of the third AC circuit breaker to trip, the method further includes:

[0031] Determine whether the third AC circuit breaker has completed tripping within the second preset determination time;

[0032] If not, the third AC circuit breaker is determined to be in a fault state.

[0033] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0034] By selecting different operating modes through internal topology transformation and port control modes, it can flexibly switch without power outages, solving the problem of power quality issues caused by the connection of large wind and solar power plants to the power grid, improving the local consumption level of new energy, enhancing the grid's transmission capacity and power flow control capabilities, and achieving power balance. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structural principle of the MMC energy router provided in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the MMC energy router control method provided in an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0038] Please refer to Figure 1A first aspect of this invention provides an MMC energy router, comprising: a first MMC converter (VSC1), a second MMC converter (VSC2), a first AC circuit breaker (DL1), a second AC circuit breaker (DL2), a third AC circuit breaker (DL3), an energy storage module, and a control module; the first AC circuit breaker (DL1) is connected to the AC network and the AC side of the first MMC converter (VSC1), the second AC circuit breaker (DL2) is connected to the AC side of the second MMC converter (VSC2) and the new energy power station, and one end of the third AC circuit breaker (DL3) is connected to the AC side of the second MMC converter (VSC2) and the new energy power station. The first AC circuit breaker (DL1) is connected to the AC grid connection terminal, and its other end is connected to the second AC circuit breaker (DL2) and the new energy power station connection terminal. The energy storage module is connected to the DC side of the first MMC converter (VSC1) and the DC side of the second MMC converter (VSC2) through the current bus. The first AC circuit breaker (DL1), the second AC circuit breaker (DL2) and the third AC circuit breaker (DL3) are electrically connected to the control module and receive the control signals from the control module. The control module switches the operating status of the MMC energy router by opening and closing the third AC circuit breaker (DL3).

[0039] Specifically, the operating states of the MMC energy router include: a first operating state and a second operating state. In the first operating state, the first AC circuit breaker (DL1) and the second AC circuit breaker (DL2) are closed, and the third AC circuit breaker (DL3) is open. The AC side of the first MMC converter (VSC1) is connected to the main grid and operates in DC voltage mode, rectifying a stable DC voltage. The AC side of the second MMC converter (VSC2) is connected to the wind and solar farm and operates in VF control mode, providing grid-connected AC voltage for the wind and solar turbines. In the second operating state, the first AC circuit breaker (DL1), the second AC circuit breaker (DL2), and the third AC circuit breaker (DL3) are all closed. The AC side of the first MMC converter (VSC1) is connected to the main grid and operates in DC voltage mode, rectifying a stable DC voltage. The AC side of the second MMC converter (VSC2) is connected to the main grid through the third AC circuit breaker (DL3) and operates in active power mode, controlling the power flow of the MMC energy router.

[0040] In one specific embodiment of the present invention, the energy storage module is a lithium battery module or a lead-acid battery module.

[0041] Furthermore, the first MMC converter (VSC1) and the second MMC converter (VSC2) are modular flexible converter valves. Their passive mode AC side has AC side constant frequency and constant voltage or VF control functions. Their active mode active control includes DC voltage control and active power control. Their reactive control includes AC voltage control and reactive power control.

[0042] The above technical solution selects different operating modes by internally changing the topology and port control modes, and can flexibly switch without power outages. This solves the problem of power quality being affected by the connection between large wind and solar power plants and the power grid, improves the local consumption level of new energy, enhances the grid's transmission capacity and power flow control capabilities, and achieves power balance.

[0043] Accordingly, please refer to Figure 2 A second aspect of the present invention provides an MMC energy router control method for controlling any of the aforementioned MMC energy routers, comprising the following steps:

[0044] S110, obtain and determine whether the real-time active power of the first MMC converter (VSC1) is greater than the preset power value and whether the duration is greater than the first preset determination time.

[0045] S120, if so, send the same frequency and voltage regulation command for the second MMC converter (VSC2); otherwise, maintain the current state.

[0046] S130, determine whether the AC voltages on both sides of the third AC circuit breaker (DL3) are synchronized.

[0047] S140, if so, control the third AC circuit breaker (DL3) to close; otherwise, maintain the state of the third AC circuit breaker (DL3).

[0048] S150 controls the second MMC converter (VSC2) to switch from VF control to PQ control.

[0049] Furthermore, after controlling the closing of the third AC circuit breaker (DL3), the following also includes:

[0050] S141, determine whether the third AC circuit breaker (DL3) has completed closing within the second preset judgment time.

[0051] S142, if not, then the third AC circuit breaker (DL3) is determined to be in a fault state.

[0052] Accordingly, please refer to Figure 2 A third aspect of the present invention provides an MMC energy router control method for controlling any of the aforementioned MMC energy routers, comprising the following steps:

[0053] S210, obtain and determine whether the real-time active power of the first MMC converter (VSC1) is less than the preset power value and whether the duration is greater than the first preset determination time.

[0054] S220, if so, controls the third AC circuit breaker (DL3) to open; otherwise, maintains the state of the third AC circuit breaker (DL3).

[0055] S230 controls the second MMC converter (VSC2) to switch from PQ control to VF control.

[0056] Furthermore, after controlling the tripping of the third AC circuit breaker (DL3), the following steps are also included:

[0057] S222, determine whether the third AC circuit breaker (DL3) has completed the tripping within the second preset judgment time.

[0058] S223, if not, then the third AC circuit breaker (DL3) is determined to be in a fault state.

[0059] The embodiments of the present invention aim to protect an MMC energy router and its control method, and have the following effects:

[0060] By selecting different operating modes through internal topology transformation and port control modes, flexible switching can be achieved without power outages. This solves the problem of power quality issues caused by the connection between large wind and solar power plants and the main power grid, improves the local absorption of new energy sources, enhances the grid's transmission capacity and power flow control capabilities, and achieves power balance.

[0061] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. An MMC energy router, characterized in that, include: The system comprises a first MMC converter, a second MMC converter, a first AC circuit breaker, a second AC circuit breaker, a third AC circuit breaker, an energy storage module, and a control module. The first AC circuit breaker is connected to the AC grid and the AC side of the first MMC converter, respectively; the second AC circuit breaker is connected to the AC side of the second MMC converter and the new energy power station, respectively. One end of the third AC circuit breaker is connected to the first AC circuit breaker and the AC grid connection terminal, and the other end is connected to the second AC circuit breaker and the new energy power station connection terminal. The energy storage module is connected to the DC side of the first MMC converter and the DC side of the second MMC converter via a current bus. The first AC circuit breaker, the second AC circuit breaker, and the third AC circuit breaker are electrically connected to the control module and receive control signals from the control module. The control module switches the operating status of the MMC energy router by opening and closing the third AC circuit breaker; The operating states of the MMC energy router include: a first operating state and a second operating state; The first operating state is that the first AC circuit breaker and the second AC circuit breaker are in the closed position and the third AC circuit breaker is in the open position. The AC side of the first MMC converter is connected to the main grid and operates in DC voltage mode, rectifying a stable DC voltage. The AC side of the second MMC converter is connected to the wind and solar farm and operates in VF control mode, providing grid-connected AC voltage for wind turbines and photovoltaics. The second operating state is that the first AC circuit breaker, the second AC circuit breaker, and the third AC circuit breaker are all in the closed position. The AC side of the first MMC converter is connected to the main power grid and operates in DC voltage mode, rectifying a stable DC voltage. The AC side of the second MMC converter is connected to the main power grid through the third AC circuit breaker and operates in active power mode, controlling the power flow of the MMC energy router.

2. The MMC energy router according to claim 1, characterized in that, The energy storage module is a lithium battery module or a lead-acid battery module.

3. The MMC energy router according to claim 1, characterized in that, The first MMC converter and the second MMC converter are modular flexible converter valves. Their passive mode AC side has AC side fixed frequency and fixed voltage or VF control functions. Their active mode active power control includes DC voltage control and active power control. Their reactive power control includes AC voltage control and reactive power control.

4. A control method for an MMC energy router, characterized in that, The method for controlling the MMC energy router as described in any one of claims 1-3 includes the following steps: Obtain and determine whether the real-time active power of the first MMC converter is greater than the preset power value and whether the duration is greater than the first preset determination time; If so, send the same frequency and voltage regulation command to the second MMC converter; otherwise, maintain the current state. Determine whether the AC voltages on both sides of the third AC circuit breaker are synchronized; If so, the third AC circuit breaker is closed; otherwise, the state of the third AC circuit breaker is maintained. The second MMC converter is switched from VF control to PQ control.

5. The MMC energy router control method according to claim 4, characterized in that, After controlling the third AC circuit breaker to close, the method further includes: Determine whether the third AC circuit breaker completes closing within the second preset determination time; If not, the third AC circuit breaker is determined to be in a fault state.

6. A control method for an MMC energy router, characterized in that, The method for controlling the MMC energy router as described in any one of claims 1-3 includes the following steps: Obtain and determine whether the real-time active power of the first MMC converter is less than the preset power value and whether the duration is greater than the first preset determination time; If so, the third AC circuit breaker is controlled to trip; otherwise, the state of the third AC circuit breaker is maintained. The second MMC converter is controlled to switch from PQ control to VF control.

7. The MMC energy router control method according to claim 6, characterized in that, After the control of the third AC circuit breaker to trip, the method further includes: Determine whether the third AC circuit breaker has completed tripping within the second preset determination time; If not, the third AC circuit breaker is determined to be in a fault state.

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