Near-Five-Vector SVPWM Algorithm for Five-Phase Six-Leg Inverters under Unbalanced Load Conditions

Abstract

Multiphase machines are characterized by high power density, enhanced fault-tolerant capacity, and low torque pulsation. For a voltage source inverter supplied multiphase machine, the probability of load imbalances becomes greater and unwanted low-order stator voltage harmonics occur. This paper deals with the PWM control of multiphase inverters under unbalanced load conditions and it proposes a novel near-five-vector SVPWM algorithm based on the five-phase six-leg inverter. The proposed algorithm can output symmetrical phase voltages under unbalanced load conditions, which is not possible for the conventional SVPWM algorithms based on the five-phase five-leg inverters. The cause of extra harmonics in the phase voltages is analyzed, and an xy coordinate system orthogonal to the z ab coordinate system is introduced to eliminate low-order harmonics in the output phase voltages.Moreover, the digital implementation of the near-five-vector SVPWM algorithm is discussed, and the optimal approach with reduced complexity and low execution time is elaborated. A comparison of the proposed algorithm and other existing PWM algorithms is provided, and the pros and cons of the proposed algorithm are concluded. Simulation and experimental results are also given. It is shown that the proposed algorithm works well under unbalanced load conditions. However, its maximum modulation index is reduced by 5.15% in the linear modulation region, and its algorithm complexity and memory requirement increase. The basic principle in this paper can be easily extended to other inverters with different phase numbers.

A 3D Reduced Common Mode Voltage PWM Algorithm for a Five-Phase Six-Leg Inverter

“…where phase voltages are equal to V i0 = (2SW j − 1) V DC/2 and SW j (j ∈ [1 − 6]) equals 1 when the switch is active and 0 when the switch is inactive; V k (k ∈ α, β, x, y, γ) are the voltage vector components and C T is the Clarke transformation matrix given by [28]:…”

“…In [23], the wellknown near-state PWM (NS-PWM) modulation, first proposed for three-phase inverters in [27], is extended to three-phase four-leg inverters. Likewise, the only three-dimensional space-vector (3D SV-PWM) for a five-phase six-leg converter is proposed in [28].…”

Advances in Converter Control and Innovative Exploitation of Additional Degrees of Freedom for Multiphase Machines

“…A further recent interesting study includes development of a PWM technique for an unbalanced five-phase system supplied from a six-leg inverter, with the neutral point of the load connected to the sixth VSI leg [25]. Next, space vector based synchronized PWM schemes are reviewed for five-phase and six-phase drives in [26].…”

Random Harmonic Detection and Compensation Based on Synchronous Reference Frame

“…At present, the main methods for harmonic detection and compensation are classified as Filter method [13], Wavelet Transform method [14], Neural Network method [15,16], FFT method [17,18], PQ method [19], and SRF method [20]. The authors have deeply studied these methods by reading a large number of literatures [21][22][23][24][25][26][27] and evaluated them from computation, response speed, reliability, and compensation precision. As shown in Table 1, A to E stand for the grades from highest to lowest, and their abilities of random harmonic detection and compensation are also compared.…”