Abstract — Compensators and Proportional-Integral (PI) controllers have been designed and used for control of Zeta converters. However, frequent voltage variations in some applications such as maximum power point tracking of solar power require a high profile voltage tracking controller. In addition, load resistance and circuit parameter variations such as inductance, capacitance and their internal resistance influence the performance of conventional controllers. This paper illustrates the design and application of a complementary model reference adaptive controller for output voltage tracking control of zeta converters. The complementary controller structure will reduce the adaptive controller’s control effort to 2%-9% variation. The results demonstrate a close tracking profile with minimal control effort and elimination of the load resistance dependencies. Experimental results are provided to demonstrate the high performance of output voltage tracking profile. I. INTRODUCTION Zeta converters are non-inverting buck-boost circuits with applications in power quality improvement, power factor correction, and interfacing the renewable energy sources to the grid. Therefore, they have high potential for applications in microgrids and smart grids [1],[2]. These converters are also used in industrial applications such as: LED lamp drivers [3], electronic ballast (EB) for fluorescent lamps [2], power rating correction and power quality improvements (PFC) [1], DC/DC converter interfaces between photovoltaic systems and the grid [4], power electronic interface between storage devices (battery and ultra-capacitor) in hybrid electric vehicles [5], AC inverters [6], and DC converter used for permanent magnet synchronous machines (PMSM) to interface for applications such as air conditioning systems, refrigerators, washing machines and medical equipment [7- 10]. To achieve non-inverting, low harmonics, and high power factor, multiple resonant elements are used in their structure. These elements make the modeling and control of these converters complicated. Various techniques use peak and average of current and voltage values in a Proportional Integrator (PI), linear compensator, and feed-forward in single- or double-loop configurations [11]. These techniques generate high sensitivity to noise, exhibit error in averaged values, and require slope compensation [12]. Average current control techniques [7], [8], [13] are becoming the dominant approach in controlling these converters. The average current control loop is usually used inside a voltage A. Izadian is the founder and director of the Energy Systems and Power Electronics Laboratory at the Purdue School of Engineering and Technology, Indianapolis, IN. 46202. E-mail: aizadian@iupui.edu. P. Khayyer is with the Electrical and Computer Engineering Department at The Ohio State University, Columbus, OH, 43210. khayyer.1@osu.edu control loop where the error signal from the voltage loop is sent through a controller. The controller amplifies the current error and in comparison with a saw-tooth carrier waveform, it generates PWM pulses [13]. This controller has fixed gains for a voltage and current references, and needs tuning when circuit parameters or references change. Therefore, it has poor voltage tracking performance and generates overshoot and steady state error. Feed-forward control technique is also used specifically for grid-connected applications of zeta converter [14], [15]. In either single-loop or double- loop configurations, two major controllers are used which are the PI controller [5], [16], [17] and compensator designed based on pole placement techniques [8], [18-19]. While results obtained from pole placement have low error, this technique may not be useful in situations where variable reference voltage or current are the targets and when load and system parameters shift over time. In our previous work, we have introduced adaptive control of zeta converter [29]. To overcome this issue and to have a more accurate control for zeta converter, this paper focuses on application of a Model Reference Adaptive Controller to regulate the output voltage of zeta converters. The system operation, model, and transfer function will be obtained in section II, III, and IV. Closed loop control design and simulation results are in section V, and experimental results are provided in section VI. II. CIRCUIT OPERATION AND MODELING Power electronic converters have numerous applications and have important role in overall system efficiency and performance. Accurate control of power converters often guarantees the voltage and frequency stability of the power system. Dynamic modeling of converters is required to design controller for power electronic converters. Many linear or nonlinear modeling techniques are used for mathematical expression of power converters. Nonlinear techniques such as component connection modeling and signal flow graph (SFG) are used for complicated circuits and are generally more accurate. State space averaging technique represents a linear technique in power electronic circuit modeling [4], [5], [19], [21-24]. Shown in Figure 1, a non-inverting buck-boost zeta converter has higher number of resonant elements. This imposes a higher order system and higher modes of operation than a conventional converter. The two main operation modes are continuous current mode (CCM) and discontinuous inductor current mode (DCM). Afshin Izadian, Senior Member, IEEE, and Pardis Khayyer Complementary Adaptive Control of Zeta Converters 978-1-4673-4974-1/13/$31.00 ©2013 IEEE 1338