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CN-121984142-A - Mixed synchronous control method and system taking transient stability and network construction support into consideration

CN121984142ACN 121984142 ACN121984142 ACN 121984142ACN-121984142-A

Abstract

The invention belongs to the technical field related to control of a grid-built converter, and provides a mixed synchronous control method and a system which are compatible with transient stability and grid-built support, aiming at solving the problem that the conventional control strategy is difficult to compatible with transient synchronous stability and grid-built support, when the transient instability risk of the grid-built converter is detected, a grid-following control branch based on a first-order phase-locked loop is introduced in parallel on the basis of an original grid-built virtual synchronous machine control loop, an equivalent active power reference value is reduced to zero by setting a gain proportion coefficient at the initial stage of a fault, so that active power injection is blocked, the acceleration area is minimized, the current electromagnetic power is tracked in real time by dynamically adjusting the equivalent active power reference value after the preset initial period of time, and the grid support capacity of the converter is effectively restored while the stable angular oscillation is continued.

Inventors

  • Liu Pengyin
  • MA HONGWEI

Assignees

  • 山东大学

Dates

Publication Date
20260505
Application Date
20260408

Claims (10)

  1. 1. The hybrid synchronous control method taking account of transient stability and network construction support is characterized by comprising the following steps: When detecting that the grid-built converter has transient instability risk, on the basis of an original grid-built virtual synchronous machine control loop, parallelly introducing a grid-following control branch based on a first-order phase-locked loop, and determining a final output phase reference value of the grid-built converter by using angular frequency deviation signals output by the grid-built control branch and the grid-following control branch; And taking the instability detection moment as a reference, carrying out phased coordination control on gain proportion coefficients of the network construction control branch and the network following control branch, reducing the equivalent active power reference value to zero by setting the gain proportion coefficient in an initial time period after fault triggering, and dynamically adjusting the equivalent active power reference value to track the current electromagnetic power in real time after the preset initial time period.
  2. 2. The hybrid synchronous control method for combining transient stability and network support according to claim 1, wherein the final output phase reference value of the network converter is determined by angular frequency deviation signals output by the network control branch and the network following control branch, specifically: The method comprises the steps of enabling theta ref to be a final output phase reference value of a grid-built converter, enabling omega pll to be an angular frequency deviation signal output by a grid-built control branch, enabling omega vsg to be an angular frequency deviation signal output by the grid-built control branch, enabling omega 0 to be a rated angular frequency of a power grid, enabling k pll to be a gain of the grid-built branch, enabling k vsg to be a gain of the grid-built control branch, enabling V t and theta t to be voltage amplitude values and phases of grid-connected points of the converter respectively, enabling T p to be a virtual inertia time constant, enabling D p to be a damping coefficient, enabling P ref and P e to be active power reference values and electromagnetic power respectively, and enabling s to be complex frequency variables.
  3. 3. The hybrid synchronous control method for considering transient stability and grid support according to claim 1 is characterized in that an equivalent circuit of a grid-built converter and a power grid is constructed, and according to the power transmission relation of the equivalent circuit, the circuit relation between an angular frequency deviation signal under a hybrid synchronous control architecture of a grid-built control branch and a grid-connected point is substituted into a virtual rotor motion equation, an equivalent swing equation of the grid-built converter is deduced, and then an equivalent active power reference value is determined, wherein the equivalent active power reference value is smaller than an original reference active power value.
  4. 4. The hybrid synchronous control method for both transient stability and network support according to claim 1, wherein the determination of the gain of the network control branch during the fault period is specifically: when the transient instability risk is detected and the hybrid synchronous control is triggered, substituting the equivalent damping and the equivalent inertia into the power angle closed loop transfer function, and deducing the equivalent system damping ratio; Introducing a critical damping enhancement coefficient determined by the ratio of the transient damping ratio to the optimal damping ratio under steady-state design; and determining the gain of the network construction control branch circuit during the fault according to the equivalent system damping ratio and the critical damping enhancement coefficient.
  5. 5. The hybrid synchronous control method for combining transient stability and network support according to claim 1 or 4, wherein the gain of the network control branch during the fault period is specifically: Wherein D p is a damping coefficient, X eq is an equivalent output reactance of the converter, T p is a virtual inertia time constant, U g is a voltage amplitude of an infinite power grid, k vsg is a grid control branch gain, ζ th is a transient damping ratio, ζ op is an optimal damping ratio under steady-state design, and n is a critical damping enhancement coefficient; is the magnitude of the potential amplitude in the converter.
  6. 6. The hybrid synchronous control method for both transient stability and grid support of claim 1, wherein, during an initial period of time after a failure trigger, the equivalent active power reference value is reduced to zero by setting the gain scaling factor, where the gain scaling factor m stable is: Wherein P ref is an active power reference value, D p is a damping coefficient, V t is a voltage amplitude of a grid-connected point of the converter, delta t is a voltage phase deviation value of the grid-connected point, and delta is a phase deviation value generated by the converter.
  7. 7. The hybrid synchronous control method for both transient stability and network support according to claim 1, wherein after a preset initial period of time, the method dynamically adjusts the equivalent active power reference value to track the current electromagnetic power in real time, and the gain ratio coefficient value m GFM is: wherein, P ref and P e are respectively active power reference value and electromagnetic power, D p is damping coefficient, V t is voltage amplitude of grid-connected point of the converter, delta t is voltage phase deviation value of grid-connected point, delta is phase deviation value generated by the converter.
  8. 8. The hybrid synchronous control system taking account of transient stability and network construction support is characterized by comprising: The construction module is configured to introduce a net following type control branch based on a first-order phase-locked loop in parallel on the basis of an original net-structured virtual synchronous machine control loop when the transient instability risk of the net-structured converter is detected, and determine the final output phase reference value of the net-structured converter by the net-structured control branch and the angular frequency deviation signals output by the net following control branch; the control module is configured to perform phased coordination control on gain proportion coefficients of the network construction control branch and the network following control branch by taking instability detection time as a reference, reduce an equivalent active power reference value to zero by setting the gain proportion coefficient in an initial time period after fault triggering, and dynamically adjust the equivalent active power reference value to track current electromagnetic power in real time after a preset initial time period.
  9. 9. An electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the method of any one of claims 1-7.
  10. 10. A computer readable storage medium storing computer instructions which, when executed by a processor, perform the method of any of claims 1-7.

Description

Mixed synchronous control method and system taking transient stability and network construction support into consideration Technical Field The invention belongs to the technical field related to control of a grid-connected transformer, and particularly relates to a hybrid synchronous control method and system considering transient stability and grid support. Background The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art. Along with the continuous improvement of the permeability of new energy and the large-scale access of power electronic equipment, the novel power system increasingly presents obvious low inertia and weak power network characteristics, and brings serious challenges to the safe and stable operation of the system. To address this challenge, web-based control strategies are receiving widespread attention. The grid-structured converter operates as a voltage source, can simulate the operation characteristics of a traditional synchronous generator, and actively constructs and maintains the amplitude and the phase of terminal voltage, so that necessary voltage and frequency support is provided for a system, and the strength of a power grid is effectively enhanced. Although the grid-structured converter has remarkable advantages under a weak current network, the method still has challenges in ensuring the transient synchronous stability of the grid-structured converter when the grid is subjected to large disturbance. When the power grid has serious faults such as voltage drop or phase jump, the active power transmitted to the power grid by the converter is obviously reduced, so that serious unbalance is generated between the active power reference value and the actual output power. The unbalanced power may cause severe oscillations or monotonic divergence of the power angle inside the converter. In addition, under extremely weak power grid or serious fault working conditions, the stable balance point of the system can even disappear directly, and finally the converter is disconnected. Aiming at the transient instability problem under the large disturbance, the existing improved control strategy is mostly focused on maintaining the synchronous stability during the transient. For example, the power angle divergence is restrained by means of parameter optimization, transient damping is increased or a synchronous control mechanism is switched during faults, and the transient stability margin of the system is improved. However, the prior art ignores the need to maintain grid support performance during transients, often at the cost of severely limiting the active power output and fault current injection of the converter in maintaining transient stability. The method leads to the difficulty in considering transient synchronous stability and network construction supporting capability in the existing control strategy, and has obvious contradiction between the transient synchronous stability and the network construction supporting capability. Disclosure of Invention In order to overcome the defects in the prior art, the invention provides the hybrid synchronous control method and the system which give consideration to transient stability and network construction support, which not only effectively inhibit the divergence of a power angle and improve the transient stability of the system, but also obviously improve the power grid support capacity during faults, and realize the effective unification of the transient synchronous stability and the network construction support capacity. In order to achieve the above purpose, the present invention adopts the following technical scheme: in a first aspect, the present invention provides a hybrid synchronization control method that combines transient stability and network support, including: When detecting that the grid-built converter has transient instability risk, on the basis of an original grid-built virtual synchronous machine control loop, parallelly introducing a grid-following control branch based on a first-order phase-locked loop, and determining a final output phase reference value of the grid-built converter by using angular frequency deviation signals output by the grid-built control branch and the grid-following control branch; And taking the instability detection moment as a reference, carrying out phased coordination control on gain proportion coefficients of the network construction control branch and the network following control branch, reducing the equivalent active power reference value to zero by setting the gain proportion coefficient in an initial time period after fault triggering, and dynamically adjusting the equivalent active power reference value to track the current electromagnetic power in real time after the preset initial time period. In a second aspect, the present invention provides a hybrid synchronous control system that combines transie