The grid-following (GFL) converter concept was proposed to connect renewable energy sources to the grid with two basic objectives: (i) easily implement the maximum power point tracking (MPPT) control and (ii) give robustness to semiconductor switches, as these converters behave as a current source. However, the high penetration of GFL converters in some grids is causing severe stability problems. In some cases, the problem is the lack of inertia or natural extra active power; in others, the problem is the lack of reactive power for voltage control. Due to these problems, many researchers propose using grid-forming (GFM) controlled converters to solve the issues related to inertia and reactive power control, as this converter behaves as a voltage source. However, with GFM control, the implementation of the MPPT algorithm is not as precise as in the case of GFL control. Therefore, the best solution would be to have a converter that operates simultaneously as GFL and GFM, where the GFL part functions as a GFL in a conventional wind turbine generator (WTG), and the GFM part ensures grid support. This control was proposed and named the Hybrid Control Converter (HCC) and was presented at the 2024 Wind and Solar Integration Workshop (WSIW). It is essential to note that this control does not require additional hardware. In principle, only a control system update would be enough.

Furthermore, it is essential to note that the HCC's GFL and GFM components operate simultaneously without any switching between these controllers. In the 2024 WSIW, it was shown that a converter with the HCC operates like a converter with two parallel converters, one GFL and one GFM. It was presented that the WTG with the HCC can operate normally with MPPT controlled by the GFL part, and the GFM part would give grid support. This grid support is natural, or in other words, without a specific control system to regulate the active power or reactive power, similarly to a synchronous generator. The active power support can be used temporarily as a synthetic inertia system if the GFL is operating at MPPT. If the WTG is operating derated, the active power support can last longer, provided that the MPPT is not reached. Since then, some changes have been implemented in the original HCC, which has been renamed to improved HCC.

The main objectives of this work are to present some essential characteristics of this new HCC: (i) the WTG can have black start capability, supplying power to a load or not; (ii) it can operate continuously isolated from the grid, allowing a 100% wind generation, provided there is enough wind; (iii) if there is not enough load, the WTG output power is automatically limited or reduced even if the GFL is controlled to operate at MPPT, this feature would limit the need for some compulsory curtailment due to lack of load and the headroom can be used when load is connected, again an essential feature in the case of 100% wind generation.

It was also demonstrated that the GFL part of the HCC can operate with or without a PLL circuit, which could be an advantage in cases highlighted in the literature where instability problems in the converter control system are attributed to excess voltage distortion, not allowing the correct operation of the PLL.

The final version will discuss simulation results of models developed in PSCAD, which validate the proposed theories.