基于自适应下垂控制的风电场无功电压控制策略

Reactive power and voltage control strategy based on adaptive droop control for wind power plants

大规模风电场并网会对电网的稳定性产生负面影响,主要体现在电压、频率和次同步等方面。当系统无功功率不足时,仅靠风电机组自身的无功调节无法提供足够的无功支撑。对此提出一种风电场无功电压控制策略,变流器采用自适应下垂控制,按照各机组自身容量调整无功输出以支持并网点电压。具体策略为:通常情况下使用最大功率点跟踪(MPPT)控制,以实现有功功率输出的最大化;当并网点发生电压越限时,采用有功功率削减控制,实时计算风电机组的有功功率削减优先级,对高优先级风电机组的有功功率进行定量削减,以满足系统的无功需求。最后利用PSCAD/EMTDC平台进行验证,结果表明该控制策略能够有效控制并网点电压,防止电压越限。

The grid connecting of large-scale wind farms would exert negative impacts on the security and stability of power system,mainly in terms of voltage,frequency and sub-synchronization resonance. When the system reactive power is insufficient,the wind turbine itself cannot provide enough reactive power support.Therefore,a reactive power and voltage control strategy is proposed in which converters of wind turbines adopt adaptive droop control and adjust their reactive power outputs according to their own capacities in order to support the voltage at grid connection point. To be specific,the strategy adopts maximum power point tracking(MPPT)control mode under normal circumstances to maximize the active power output.In the event of voltage over-limit at grid connection point,the converters adopt active power curtailment and the active power curtailment priority of different wind turbine is calculated in real time. The active power of the wind turbines with high priority would be adjusted at first,to meet the reactive power requirement of the system. The PSCAD/EMTDC simulation results show that the proposed strategy is effective in controlling the voltage at grid connection point and preventing voltage over-limit.