AC voltage and current sensorless control method for three‐phase PWM converter

Abstract

SUMMARYWe present a three-phase PWM converter without AC voltage and AC current sensors. The phase angle used in the control system is adjusted by using a PLL controller without sensing AC voltage. To prevent overcurrent at startup, the initial phase angle of the source voltage is estimated from the shunt current using a novel strategy. Furthermore, the phase currents can be reconstructed from the shunt current without any modification of the PWM pattern. To reduce the effect of current ripple, the shunt current is sampled twice for every phase in one PWM period and the sample timings are carefully adjusted. All of the proposed control schemes can be implanted using a single chip microprocessor (SH7046, Renesas Tech.). Simulation and experimental results with a 5-kW prototype confirmed that the schemes worked well.

Sensorless control for a three-phase PWM rectifier-inverter system with single-chip micro-controller

“…To solve this problem, we have proposed a novel strategy to estimate the initial phase angle of the ac source from the detected shunt current [10]. In the proposed strategy, three on/off control signals shown in Fig.…”

“…The reference currents are also used when only one phase current can be detected [10]; therefore, the modification of the PWM pattern presented in [12] is not necessary, and the algorithm is simple. …”

Grid impedance estimation for islanding detection and adaptive control of converters

“…For grid‐connected converters, it is important to extract the synchronising angle even if the voltage at PCC is highly polluted due to the presence of a large grid impedance. To overcome this problem, a sensorless grid voltage detection‐based PLL is used [18]. The output voltage from the PI controller of the quadrature axis current control loop represents the reference quadrature axis component of the grid voltage and it can be used for synchronisation instead of a direct PCC voltage measurement.…”