High-inertia synchronous phase modifier adopting alternating current and direct current excitation

Abstract

The invention discloses a high-inertia synchronous phase modifier adopting alternating current and direct current excitation, and belongs to the field of power equipment.The synchronous phase modifier comprises a synchronous phase modifier body and an excitation system, and the excitation system is used for adjusting alternating current and direct current excitation current of the synchronous phase modifier body in real time according to the real-time condition of the voltage and frequency of a power grid. And then reactive power, active power and rotor speed of the motor are controlled. According to the synchronous phase modifier, on the premise that the reactive power supporting function of an existing synchronous phase modifier is completely reserved, the inertia / frequency instantaneous supporting function of a power grid is added through a special excitation control means, the problem that the phase modifier is disengaged from the network due to fault impact is effectively solved, and the stability of a new energy power system is better guaranteed. The scheme can be applied to function transformation of the existing synchronous phase modifier which is put into use, can also be applied to a scene where a new synchronous phase modifier is installed, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of electric power equipment, and more particularly, relates to a high-inertia synchronous phase regulator adopting AC and DC excitation. Background Art

[0002] As renewable energy sources gradually become the primary source of electricity supply, the proportion of traditional synchronous generators continues to decline. This leads to a loss of grid inertia and reduced damping properties, making it difficult to support safe and stable grid operation. Currently, the deployment of synchronous condensers is widely adopted to improve the grid's short-circuit ratio and enhance voltage support capabilities. However, existing synchronous condensers have weak inertia and active power transient support capabilities, and lack the ability to withstand grid frequency and power fluctuations and transient faults. During grid faults, especially frequency instability, they can be impacted and disconnected from the grid, making it difficult to ensure safe and stable grid operation.

[0003] As the proportion of new energy continues to increase, the inertia / frequency problem of new power systems will become more prominent, and there is an urgent need for new high-inertia synchronous phase regulators that can maintain their own stable operation and have the ability to support instantaneous faults. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a high-inertia synchronous phase regulator using AC and DC excitation, which aims to fully retain the reactive power support function of the existing synchronous phase regulator while adding an instantaneous strong support function for active power faults in the power grid. It can provide more stable fault support for the power grid while ensuring that the phase regulator itself is not disconnected from the grid due to fault impact, especially the ability to withstand and support instantaneous / short-term frequency instability faults.

[0005] To achieve the above object, according to a first aspect of the present invention, there is provided a high inertia synchronous condenser using AC and DC excitation, comprising: a synchronous condenser and an excitation system; The excitation system is connected in series with the single-phase excitation winding of the rotor of the synchronous condenser: When there is no disturbance or fault in the power grid, the excitation system provides a DC excitation current to the rotor, so that the synchronous condenser operates in the operating mode of a conventional synchronous condenser; When the grid is disturbed or impacted by a fault, resulting in an imbalance in grid voltage or power but no frequency fluctuation, the excitation system instantly increases the DC excitation current provided to the rotor to perform strong excitation regulation on the rotor, thereby achieving rapid support for the grid voltage or power; When the power grid is disturbed or impacted by a fault, causing the grid frequency to fluctuate, the excitation system provides AC excitation current to the rotor and quickly supports the grid frequency by quickly regulating the frequency, amplitude, and phase of the AC excitation current.

[0006] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art: 1. The high-inertia synchronous condenser using AC and DC excitation provided by the present invention has the following three operating modes: (1) When there is no disturbance or fault in the power grid, the motor can be operated and used as a traditional synchronous condenser and perform all the normal functions of a traditional synchronous condenser.

[0007] (2) When the power grid is disturbed or impacted by a fault, causing an imbalance in the voltage or power of the power system but not yet causing frequency fluctuations, the DC excitation of the motor is adjusted at this time. Through the rapid strong excitation adjustment of the DC excitation, strong compensation for the instantaneous rapid voltage or power of the power grid is achieved, which effectively supports the stability of the power grid and resists the impact of power grid disturbances or faults.

[0008] (3) If the power grid is disturbed or the power grid frequency fluctuates due to a fault, the fluctuation of the power grid frequency will cause the motor speed and the motor stator rotating magnetic field to slip. At this time, AC excitation will be applied to the rotor to compensate for the speed difference between the motor speed and the motor stator rotating magnetic field. By adjusting the frequency, amplitude and phase of the external AC excitation current, the motor can generate a stable and controllable synchronous electromagnetic torque while generating an asynchronous electromagnetic torque due to slip operation. By regulating the synchronous electromagnetic torque of the motor, the asynchronous and synchronous composite electromagnetic torque generated by the motor can be decelerated or accelerated according to the requirements of the stable support of the power system. The motor speed will run at a subsynchronous speed or supersynchronous speed condition with a very low slip rate with the rotating magnetic field speed on the motor stator side, realizing the output of active power to the power grid or the absorption of active power. At the same time, the motor excitation can be strengthened to achieve instantaneous strong frequency stabilization support for the power grid. In addition, when the power grid has a steady-state reactive power compensation demand (i.e., a demand to improve the power factor), and this demand is caused by a non-sudden disturbance or fault impact, at this time, the DC excitation current provided by the excitation system is adjusted to regulate the reactive power on the armature winding side of the motor, keeping the motor in a delayed or advanced state, thereby achieving steady-state reactive power compensation for the power grid.

[0009] 2. The high-inertia synchronous condenser with AC and DC dual excitation provided by the present invention releases or absorbs active power through instantaneous changes in speed while fully retaining the reactive power regulation capability of the synchronous condenser, giving full play to the efficiency of the high inertia of the unit, achieving rapid and short-term compensation of the active power of the power grid, strongly supporting the stability of the power grid frequency, resisting power grid disturbances and fault shocks, and achieving the purpose of power grid frequency stabilization. At the same time, it can effectively solve the problem of traditional synchronous condensers being disconnected from the grid due to fault shocks, ensuring the stability of the new energy power grid. The cost of the entire system is not much higher than that of the traditional synchronous condenser system, and it is easy to transform and implement.

[0010] 3. The high-inertia synchronous phase regulator with AC and DC excitation provided by the present invention is still directly connected to the power grid on the stator side without passing through any power electronic equipment. It has a higher instantaneous overload capacity, is more conducive to improving the short-circuit ratio of the power grid and the ability to quickly respond to instantaneous faults, and saves the cost of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is one of the topology diagrams of a high-inertia synchronous phase condenser system using AC and DC excitation provided by an embodiment of the present invention.

[0012] Figure 2 This is the second topology diagram of a high-inertia synchronous phase-converter system using AC and DC excitation provided by an embodiment of the present invention.

[0013] Figure 3 This is the third topology diagram of a high-inertia synchronous phase-converter system using AC and DC excitation provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is 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 for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0015] The embodiment of the present invention provides a high inertia synchronous condenser using AC and DC excitation, such as Figure 1 As shown, it includes: synchronous phase regulator and excitation system.

[0016] The synchronous condenser can be any existing traditional synchronous condenser, and its structure can be kept unchanged, and only its excitation system is modified or updated.

[0017] As an example, the synchronous condenser includes a stator structure and a rotor structure; The stator structure includes a stator core, an armature winding, and an optional rotor damping winding; the stator core is a laminated core, and the three-phase armature winding is evenly slotted in the core; The rotor structure includes a rotor core and an excitation winding, wherein the rotor topology presents a non-salient pole or salient pole characteristic; the rotor core is a solid structure or a laminated structure, and the rotor single-phase excitation winding is placed in the slots on the surface of the non-salient pole rotor or on the magnetic poles of the salient pole rotor.

[0018] To maintain high inertia, the rotor diameter or length of the motor can be appropriately increased.

[0019] In order to further increase the moment of inertia of the motor, preferably, the synchronous condenser further includes a flywheel; The flywheel is independent of the rotor body of the synchronous condenser and is coaxially connected to the rotor mechanical transmission; Alternatively, the flywheel is integrated with the rotor body of the synchronous condenser.

[0020] Specifically, the flywheel is designed and configured according to the amplitude of the grid frequency fluctuation and the phase-shifting capacity. It can be an explicit flywheel independent of the motor rotor body, coaxially connected to the motor rotor mechanical transmission, significantly improving the rotational inertia of the motor transmission system; or it can be an implicit flywheel integrated with the rotor body, which increases the rotational inertia by increasing the rotor volume. The system composition is simple and can further improve the overall reliability of the system.

[0021] The excitation system is connected in series with the single-phase excitation winding of the synchronous condenser rotor, and is used to adjust the AC and DC excitation currents of the synchronous condenser in real time according to the real-time conditions of the grid voltage and frequency; the adjustment includes: When there is no disturbance or fault in the power grid, the excitation system provides a DC excitation current to the rotor, so that the synchronous condenser operates in the operating mode of a conventional synchronous condenser; When the grid is disturbed or impacted by a fault, resulting in an imbalance in grid voltage or power but no frequency fluctuation, the excitation system instantly increases the DC excitation current provided to the rotor to perform strong excitation regulation on the rotor, thereby achieving rapid support for the grid voltage or power; When the grid is disturbed or impacted by a fault, causing the grid frequency to fluctuate, the excitation system is used to provide AC excitation current to the rotor and quickly adjust the frequency, amplitude, and phase of the AC excitation current to achieve rapid support for the grid frequency; When the power grid has a steady-state reactive power compensation demand, the reactive power on the motor armature winding side is regulated by adjusting the DC excitation current provided by the excitation system, keeping the motor in a delayed or advanced state, thereby achieving steady-state reactive power compensation for the power grid.

[0022] Specifically, the excitation system provides AC and DC excitation functions and is connected in series with the single-phase excitation winding of the phase regulator. This system is used to adjust the phase regulator's AC and DC excitation currents in real time based on the actual grid voltage and frequency, thereby controlling the motor's reactive power, active power, and rotor speed. The AC excitation function requires the ability to arbitrarily control the frequency, amplitude, and phase of the AC excitation current.

[0023] like Figure 2 As shown, as a preferred embodiment, the excitation system includes an excitation transformer and AC and DC adjustable excitation converters; The excitation transformer, AC and DC adjustable excitation converter, and single-phase excitation winding are connected in series.

[0024] The condenser is always connected to the grid for operation: (1) When there is no disturbance or fault in the power grid, the AC / DC adjustable excitation converter operates in the DC excitation mode, the phase-modulated motor rotor provides DC excitation current (or very low frequency near-DC AC excitation current), and the phase-modulated ...

[0025] (2) When the power grid is disturbed or experiences a sudden fault, but has not yet caused frequency fluctuations, the AC and DC adjustable excitation converters operate in the DC excitation mode. The synchronous phase regulator responds quickly at this time, and the AC and DC adjustable excitation converters quickly adjust the DC excitation current to achieve rapid strong excitation regulation of the DC excitation, thereby achieving rapid support for the grid voltage or power, suppressing the impact of grid disturbances or faults, and supporting grid stability.

[0026] (3) When the grid has a steady-state reactive power compensation demand, by adjusting (increasing or decreasing according to the needs of the grid power factor) the DC excitation current provided by the excitation system, the reactive power on the motor armature winding side can be controlled, the motor can be kept in a delayed or advanced phase state, and the grid can be compensated for the reactive power steady-state. When the grid frequency fluctuates due to disturbances or fault impacts, the motor speed will not change suddenly, and there is a certain slip between the motor speed and the grid frequency. At this time, the AC / DC adjustable excitation converter works in the AC excitation mode. By applying AC excitation and quickly adjusting the frequency, amplitude, and phase of the AC excitation current, the motor can generate a stable synchronous electromagnetic torque while naturally generating an asynchronous electromagnetic torque. By adjusting the frequency, amplitude, and phase of the AC excitation current, the motor synthetic electromagnetic torque can be guaranteed to be the negative or positive required to support the stability of the grid frequency, so that the motor rotor can be decelerated or accelerated, and active power can be sent to the grid or absorbed, so that the motor is in a generating or motoring state, so as to suppress the grid frequency fluctuation, strongly support the stability of the grid frequency, and effectively deal with the grid frequency fluctuation and grid oscillation.

[0027] like Figure 3 As shown in the figure, as another preferred embodiment, the excitation system includes an excitation transformer, a DC excitation converter, and an AC excitation converter. The two converters are connected in parallel and in series with the single-phase excitation winding of the phase modulator. This allows for real-time adjustment of the phase modulator's AC and DC excitation currents based on the actual grid voltage, frequency, and power, thereby controlling the motor's reactive power, active power, and rotor speed. The AC excitation converter must be able to arbitrarily adjust the frequency, amplitude, and phase of the AC excitation current.

[0028] The condenser is always connected to the grid for operation: (1) When there is no disturbance or fault in the power grid, the DC excitation converter provides adjustable DC excitation current to the motor rotor (the output current of the AC excitation converter is 0 or approximately 0), and the phase condenser operates in the traditional synchronous phase condenser working mode.

[0029] (2) When a disturbance or sudden fault occurs in the power grid but has not yet caused frequency fluctuations, the synchronous phase regulator responds quickly at this time, and realizes rapid strong excitation regulation of DC excitation by quickly adjusting the DC excitation converter, thereby achieving rapid support for the grid voltage or power, suppressing the impact of grid disturbance or fault, and supporting grid stability.

[0030] (3) When the grid has a steady-state reactive power compensation demand, the reactive power on the motor armature winding side can be regulated by adjusting the DC excitation converter, keeping the motor in a delayed or advanced phase state, thereby performing steady-state reactive power compensation for the grid. When the grid frequency fluctuates due to disturbances or fault impacts, the motor speed will not change suddenly, and there will be a certain slip between the motor speed and the grid frequency. At this time, the AC excitation converter quickly responds to the frequency fluctuation and provides an adjustable AC excitation current to the motor rotor (the output current of the DC excitation converter is 0 or approximately 0). By quickly regulating the frequency, amplitude, and phase of the AC excitation current, the motor can generate a stable synchronous electromagnetic torque while naturally generating an asynchronous electromagnetic torque. By adjusting the frequency, amplitude, and phase of the AC excitation current, the motor's synthetic electromagnetic torque can be guaranteed to be the negative or positive required to support the grid frequency stability, causing the motor rotor to slow down or accelerate, sending active power to the grid or absorbing active power, and putting the motor in a generating or motoring state to suppress the grid frequency fluctuation, strongly support the grid frequency stability, and effectively cope with the grid frequency fluctuation and fault stability support.

[0031] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high inertia synchronous condenser using AC and DC excitation, characterized in that: include: Synchronous condenser and excitation system; The excitation system is connected in series with the single-phase excitation winding of the rotor of the synchronous condenser: When there is no disturbance or fault in the power grid, the excitation system provides a DC excitation current to the rotor, so that the synchronous condenser operates in the operating mode of a conventional synchronous condenser; When the grid is disturbed or impacted by a fault, resulting in an imbalance in grid voltage or power but no frequency fluctuation, the excitation system instantly increases the DC excitation current provided to the rotor to perform strong excitation regulation on the rotor, thereby achieving rapid support for the grid voltage or power; When the power grid is disturbed or impacted by a fault, causing the grid frequency to fluctuate, the excitation system provides AC excitation current to the rotor and quickly supports the grid frequency by quickly regulating the frequency, amplitude, and phase of the AC excitation current.

2. The synchronous condenser according to claim 1, wherein: When the power grid has a steady-state reactive power compensation demand, the reactive power on the motor armature winding side is regulated by adjusting the DC excitation current provided by the excitation system, keeping the motor in a delayed or advanced state, thereby achieving steady-state reactive power compensation for the power grid.

3. The synchronous condenser according to claim 1, wherein: The excitation system includes an excitation transformer and an AC and DC adjustable excitation converter; The excitation transformer, AC and DC adjustable excitation converter, and single-phase excitation winding are connected in series.

4. The synchronous condenser according to claim 1, wherein: The excitation system includes an excitation transformer, a DC excitation converter and an AC excitation converter; The DC excitation converter and the AC excitation converter are connected in parallel and then in series with the single-phase excitation winding.

5. The synchronous condenser according to any one of claims 1 to 4, characterized in that: Also includes flywheel; The flywheel is independent of the rotor body of the synchronous condenser and is coaxially connected to the rotor mechanical transmission; Alternatively, the flywheel is integrated with the rotor body of the synchronous condenser.

6. The synchronous condenser according to claim 1, wherein: The synchronous condenser comprises a stator structure and a rotor structure; The stator structure includes a stator core and an armature winding; the stator core is a laminated core, and the three-phase armature winding is placed in the uniformly slotted core; The rotor structure includes a rotor core and an excitation winding, and the rotor topology presents a non-salient pole or salient pole characteristic; the rotor core is a solid structure or a laminated structure, and the rotor single-phase excitation winding is placed in the slots on the surface of the non-salient pole rotor or on the magnetic poles of the salient pole rotor.

7. The synchronous condenser according to claim 6, wherein: The stator structure also includes a rotor damping winding.

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