Control of grid-interfacing inverters with integrated voltage unbalance correction

Abstract

Abstract-This paper presents the control of a gridinterfacing inverter with integrated voltage unbalance correction. It is proposed to add an additional function to the inverter to decrease the negative-sequence voltage at the point of connection with the utility grid. Based on a symmetric sequence voltage decomposition and using an improved multi-variable filter, the grid-interfacing inverter intentionally absorbs a small amount of negative-sequence current from the grid, thereby helping to correct the negative-sequence voltage. Although the amplitude reduction contributed by each individual inverter system is small compared to the total negative-sequence component, gridinterfacing inverter modules can collectively achieve substantial results in the grid. The integrated function and proposed control has been verified in simulations and by experiments on a laboratory prototype.

Clustered PV inverters in LV networks: An overview of impacts and comparison of voltage control strategies

“…Borup is with Danfoss Solar Inverters A/S, Jyllandsgade 28 DK-6400 Sønderborg, Denmark (e-mail: uffe.borup@danfoss.com) its magnitude depends on available dc power and its phase is adjusted in such a way that unity power factor is achieved. Besides active power injection, additional functions can be added as ancillary services like low order selective harmonic compensation [9], anti-islanding detection [10], [11], lowvoltage ride-through [12] and voltage unbalance correction [12], [13] by improving grid interaction capabilities of inverters. But these multifunctional features are not enough to avoid voltage rise phenomena which is limited by utility standards [14], [15] at the point of common couplings.…”

Improved the ride-through capability of wind power plants using doubly-fed induction generator under unbalanced voltage conditions

“…Phương pháp này cũng được đề cập đến trong nhiều tài liệu nghiên cứu khác, chẳng hạn như trong [10,16,18]. Các biện pháp khắc phục lỗi lưới không đối xứng sử dụng bộ biến đổi với 4 nhánh van trong hệ thống ba pha 4 dây cũng được đề cập trong các tài liệu [17,31]. Bộ điều khiển dòng loại này cho phép điều khiển riêng rẽ các thành phần dòng điện thứ tự thuận, ngược và zero dẫn đến việc có thể loại bỏ được các nhiễu loạn của điện áp do tải không cân bằng gây ra.…”

High Performance Stationary Frame Filters for Symmetrical Sequences or Harmonics Separation Under a Variety of Grid Conditions

“…By utilizing a multi-state-variable structure, this cell can be easily implemented to achieve the function of a second-order band-pass filter in a stationary frame. To extend the application of this idea, an improved filter for fundamental positive and negative sequence voltage detection was described in [3], where detailed design formulas were given. Similarly, a generalized selective-harmonic bandpass filter cell can be derived.…”

“…Furthermore, in order to deal with power flow control or power quality improvement (like active power filtering, voltage dips compensation, etc. ), the detection of negative-sequence components or harmonics is also always needed [1]- [3]. Although in the utility grid the frequency is usually very stable, frequency fluctuations sometimes can be caused by transient faults on the grid, or frequently occur in weak small-scale networks.…”