DC/AC power converter with DC side double frequency pulsation suppression caused by AC side faults

• US 8,867,247 B2
• Filed: 03/15/2012
• Issued: 10/21/2014
• Est. Priority Date: 08/31/2009
• Status: Active Grant

• Current Assignee: Hitachi Industrial Products, Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Bando, Akira, Kiyofuji, Yasuhiro, Ichinose, Masaya, Sakai, Hiromitsu, Imazu, Yasuhiro
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US13/420,718
• Publication Number:
  US 20120170333A1
• Time in Patent Office: 950 Days
• Field of Search: 363/98
• US Class Current: 363/98
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 7/5395 by pulse-width modulation

Abstract

A commanded negative-sequence current is added to a commanded current so as to suppress double-frequency pulsation on the DC side. The commanded negative-sequence current is found from three values (i.e., the detected value of positive-sequence voltage vector on the power-supply side, the detected value of negative-sequence voltage vector, and a commanded positive-sequence current). Thus, the pulsations which occur on the DC side of a semiconductor power converter and which have a frequency double the power-supply frequency are suppressed even when the AC power supply is at fault while assuring stability of the current control system, thus permitting stable and continuous operation.

Claims

1. A semiconductor power converter comprising:

a power converter including arms constituting three-phase bridge connections having AC-side terminals which are connected with a three-phase AC system via an inductance, said arms having self-extinguishing semiconductor devices connected thereto, said self-extinguishing semiconductor devices being IGBTs or combinations of MOSFETs and free-wheeling diodes;

a voltage-measuring device for measuring an AC voltage developed across the three-phase AC system;

a current-measuring device for measuring an AC current flowing through the power converter;

a phase detector for detecting phase θ

of the AC voltage;

an AC current adjuster for outputting commanded pulses to the power converter based on a commanded active current value I_qref and a commanded reactive current value I_dref along two axes and on an output from the AC current-measuring device;

a two-phase voltage vector calculator for receiving a measured value of voltage developed across the three-phase AC system and calculating a positive-sequence voltage vector V_p and a negative-sequence voltage vector V_n; and

a phase calculator for calculating and outputting a positive-sequence voltage phase θ

_p from a reference phase θ

for the two-phase voltage vector calculator and from the positive-sequence voltage vector V_p;

wherein said AC current adjuster calculates a commanded positive-sequence current vector I_pref from the commanded two-axis current values I_qref and I_dref, calculates a commanded negative-sequence current vector I_nref using the relationship, I_nref=−

(V_n/V_p)×

I_pref, calculates commanded three-phase current vectors I_aref, I_bref, and I_cref from the commanded positive-sequence current vector I_pref and from the commanded negative-sequence current vector I_nef, calculates commanded three-phase current values from the commanded three-phase current vectors and from the positive-sequence voltage phase θ

_p, and outputs commanded pulses to bring the commanded three-phase current values into agreement with the measured values of AC current.

2. The semiconductor power converter of claim 1, wherein there are further provided a three-phase voltage vector calculator for receiving the measured value of voltage of the three-phase AC system and outputting three-phase voltage vectors (V_a, V_b, V_c) and a target voltage calculator for calculating a target voltage vector E1_aref of a first phase from the AC voltage vector V_a, the commanded current vector I_aref, and the impedance value of the inductance, calculating a target voltage value e1_aref from the target voltage vector E1_aref and from the reference phase θ

, and similarly calculating and outputting a target voltage value e1_bref of a second phase and a target voltage value e1_cref of a third phase, and wherein said AC current adjuster calculates and outputs correcting three-phase voltage values (e2_aref, e2_bref, e2_cref) to bring the commanded three-phase current values (i_aref, i_bref, i_cref) into agreement with the measured AC current values, adds the correcting three-phase voltage values (e2_aref, e2_bref, e2_cref) to the target three-phase voltage values (e1_aref, e1_bref, e1_cref), respectively, for each individual phase, takes the results as commanded three-phase voltage values, and outputs commanded pulses to bring the three-phase output voltages from the power converter into agreement with the commanded three-phase voltage values.

3. The semiconductor power converter of claim 1, further comprising a DC voltage-measuring device for measuring the DC output voltage from the power converter, a DC voltage adjuster for outputting a commanded first-axis current I_qref to bring the measured DC voltage value and the commanded DC voltage value into coincidence, a current vector calculator for receiving the measured value of AC current and calculating a positive-sequence current vector I_p, and a power factor adjuster for calculating a positive-sequence reactive power output Q_p from the positive-sequence current vector I_p and from the positive-sequence voltage vector V_p and outputting a commanded second-axis current value I_dref to bring the positive-sequence reactive power output Q_p and the commanded reactive power value into coincidence, and wherein said commanded positive-sequence current vector I_pref is calculated from the commanded two-axis current values I_qref and I_dref.