A Flexible Maximum Power Point Tracking Control Strategy Considering Both Conversion Efficiency and Power Fluctuation for Large-inertia Wind Turbines

Abstract

Abstract:In wind turbine control, maximum power point tracking (MPPT) control is the main control mode for partial-load regimes. Efficiency potentiation of energy conversion and power smoothing are both two important control objectives in partial-load regime. However, on the one hand, low power fluctuation signifies inefficiency of energy conversion. On the other hand, enhancing efficiency may increase output power fluctuation as well. Thus the two objectives are contradictory and difficult to balance. This paper proposes a flexible MPPT control framework to improve the performance of both conversion efficiency and power smoothing, by adaptively compensating the torque reference value. The compensation was determined by a proposed model predictive control (MPC) method with dynamic weights in the cost function, which improved control performance. The computational burden of the MPC solver was reduced by transforming the cost function representation. Theoretical analysis proved the good stability and robustness. Simulation results showed that the proposed method not only kept efficiency at a high level, but also reduced power fluctuations as much as possible. Therefore, the proposed method could improve wind farm profits and power grid reliability.

Incorporating State-of-Charge Balancing into the Control of Energy Storage Systems for Smoothing Renewable Intermittency

“…Although SOC is typically calculated in terms of the current (with the unit of current), we apply the energy and power to calculate the SOC for energy feedback. Thus, we assume that the energy in ESS can be calculated from the integral form of the output power of ESS as shown in (5), and SOC in pu is divided by the amount of energy capacity of ESS (K E ) from (7). For the implementation of energy feedback, K p is added as a coefficient to connect the SOC and WT power in (6), which can be calculated as the minimum and maximum values of WT generation over the SOC range.…”

“…In other words, variations in the power generated by RES affect power system stability [1][2][3]. To resolve issues due to wind and PV power fluctuations, intermittent power-smoothing approaches are required to soften the fluctuations of wind power and PV power outputs, therefore various studies have been conducted to reduce the variability of wind power and PV [4][5][6][7][8][9].…”

“…Efforts to reduce the intermittent effects of RES can be classified into three categories: (i) using the internal energy of RES such as the kinetic energy of wind turbines; (ii) using the external energy of RES such as load control; and (iii) using energy storage system (ESS) and hybrid schemes that can compensate for a short time, such as a supercapacitor. Power-smoothing using the kinetic energy of wind turbines has been proposed in [7,[10][11][12]. Power-smoothing using the internal energy of wind…”

Mitigation of Short-Term Fluctuations in Wind Power Output in a Balancing Area on the Road Toward 100% Renewable Energy

“…To reduce the required reserves, we focused on mitigating short-term fluctuations (STFs), which have the same timescale with FRRs in Fig. 1, in wind power output, utilizing functions already incorporated in wind turbines: ramp rate limitation (RRL) and maximum power point tracking (MPPT) [15], [16], [17], [18], [19], [20], [21], [22], [23]. These functions are also required in IEC 61400-1, IEC 61400-3-1, and IEC TS 61400-3-2, in which design requirements for onshore (IEC 61400-1) and offshore wind turbines (IEC 61400-3-1 and IEC TS 61400-3-2) are described [24], [25], [26].…”

“…We propose five methods to mitigate STFs in the total wind power output in each BA, and compare the methods in terms of efficiency, which is indicated by the reduction in the absolute values of the STFs and the energy loss associated with application of the method. There are a number of studies on mitigation of the fluctuations in wind power output of single wind power plants (WPPs) and/or small systems consisting of several WPPs, and on the contribution of such mitigation to power systems [17], [18], [22], [23], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39]. In this study, we targeted the STFs in the total output of wind power in each BA and provide a framework for mitigating STFs.…”