# High Voltage Ride through Strategy of Wind Farm Considering Generator Terminal Voltage Distribution
## 1 Introduction  
With the massive consumption of primary energy, energy shortage has become a worldwide problem. Northwest China has a large amount of onshore wind resources, and the total wind power installations in these areas were over 50 GW at the end of 2019. However, the wind curtailment of Northwest China in 2019 was 9.3%, which was five percentage points higher than the national average. With the development of power electronics technology, high-voltage direct current (HVDC) technology is one of the most effective ways to reduce the wind curtailment [1; 2; 3; 4]. AC failure at the sending-end grid may cause the DC blocking of the HVDC transmission system, and further lead to voltage swell problem for wind farms. To improve the high-voltage ride-through (HVRT) success rate of doubly-fed induction generators (DFIG), some papers have studied the reactive power compensation capability of DFIGs and proposed corresponding wind turbine reactive power compensation control strategies [5; 6; 7; 8; 9]. Reference [6] put forward a reactive current assignment strategy for a grid-side convertor (GSC) and rotor-side convertor (VSC), for two different ride-through scenarios, which improves the ride-through capability of the wind turbine based on DFIGs. Reference [7] proposed a HVRT strategy based on the virtual resistance strategy by analyzing the transient process of the DFIG when facing the voltage swell problem. Other papers installed a reactive power compensation device at the grid-connection point to improve the wind farm's ride-through capability [10; 11; 12; 13]. References [11; 12; 13] compared the reactive power compensation capabilities of static synchronous compensators (STATCOM) and static varcompensators (SVC) during low voltage ride-through (LVRT) periods of wind farms. References [11; 13] revealed that STATCOMs can provide more reactive power during voltage sag periods, and have a better transient performance than SVC after a voltage sag fault. Reference [12] showed that STATCOM is more economical than SVC. Reference [14] adopted static var generators (SVG) as a reactive power compensation device for wind farms, and designed a capacity configuration method for SVG. However, in most existing research on HVRT strategies of DFIG with reactive power compensation devices involved, the wind farm is usually equivalent to a wind turbine, which means that the HVRT control strategies take the grid-connection point voltage as the control target, while ignoring the voltage distribution inside the wind farm. Since DFIGs have weak tolerance to high voltages, the above HVRT strategies of DFIGs may make wind turbines confront trip-off accidents at the end of the line, due to generator terminal voltage distribution caused by collection lines. Reference [15] analyzed the generator terminal voltage distribution inside a wind farm, and put forward a corresponding voltage coordinated control strategy, but the influence of DC blocking fault scenarios and the application of synchronous condensers were not considered in the paper. As synchronously rotating reactive power compensation equipment, the synchronous condenser presents good characteristics of strong voltage support capability, strong overload capacity, and long service life, compared with power electronic reactive power compensation equipment [16; 17]. At present, the synchronous condenser has been put into operation in many converter stations [18; 19; 20; 21]. Therefore, the installation of a synchronous condenser in wind farms can effectively improve the high and low voltage ride-through capabilities of the wind turbine by considering the voltage and reactive power distribution inside the wind farm. Reference [17] showed that the reactive power compensation capability of the synchronous condenser is better than STATCOM when facing the transient overvoltage problem caused by a DC blocking fault at the sending-end grid.